U.S. patent application number 14/293612 was filed with the patent office on 2014-09-25 for water purification using energy from a steam-hydrocarbon reforming process.
This patent application is currently assigned to Air Products and Chemicals, Inc.. The applicant listed for this patent is Air Products and Chemicals, Inc.. Invention is credited to Bryan Clair Hoke, JR., Xiang-Dong Peng.
Application Number | 20140284199 14/293612 |
Document ID | / |
Family ID | 50024402 |
Filed Date | 2014-09-25 |
United States Patent
Application |
20140284199 |
Kind Code |
A1 |
Peng; Xiang-Dong ; et
al. |
September 25, 2014 |
Water Purification Using Energy from a Steam-Hydrocarbon Reforming
Process
Abstract
A process and system for producing a H.sub.2-containing product
gas and purified water from an integrated catalytic
steam-hydrocarbon reforming and thermal water purification process.
Raw water, such as salt water, is heated by indirect heat transfer
with reformate from the catalytic steam reforming process for
purifying raw water in one of a multiple effect distillation
process and a multi-stage flash process.
Inventors: |
Peng; Xiang-Dong; (Orefield,
PA) ; Hoke, JR.; Bryan Clair; (Bethlehem,
PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Air Products and Chemicals, Inc. |
Allentown |
PA |
US |
|
|
Assignee: |
Air Products and Chemicals,
Inc.
Allentown
PA
|
Family ID: |
50024402 |
Appl. No.: |
14/293612 |
Filed: |
June 2, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14061157 |
Oct 23, 2013 |
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14293612 |
|
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13858363 |
Apr 8, 2013 |
8709287 |
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14061157 |
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61648662 |
May 18, 2012 |
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Current U.S.
Class: |
202/174 |
Current CPC
Class: |
C01B 3/384 20130101;
C01B 2203/0233 20130101; C02F 1/048 20130101; C02F 1/06 20130101;
C01B 2203/0283 20130101; C02F 1/16 20130101; Y02W 10/37 20150501;
C01B 2203/0816 20130101; C01B 2203/0827 20130101; Y02A 20/128
20180101; B01D 3/065 20130101; C02F 2103/08 20130101; C01B
2203/0495 20130101; C01B 2203/0883 20130101; Y02P 20/129 20151101;
C02F 2103/007 20130101; C01B 2203/043 20130101; C02F 2103/06
20130101; B01D 3/146 20130101 |
Class at
Publication: |
202/174 |
International
Class: |
B01D 3/06 20060101
B01D003/06; C02F 1/16 20060101 C02F001/16 |
Claims
1. A system for producing a H.sub.2-containing product gas and for
producing purified water from a raw water stream containing
contaminants, the system comprising: a thermal water purification
system comprising a plurality of evaporators, wherein at least a
first evaporator of the plurality of evaporators comprises a first
heat transfer coil operatively connected to a source of a reformate
comprising H.sub.2, CO, CH.sub.4, and H.sub.2O to receive reformate
from the source of the reformate and a second heat transfer coil
operatively connected to a steam source to receive steam from the
steam source; and a gas separator operatively connected to the
first heat transfer coil to receive reformate from the first heat
transfer coil.
2. The system of claim 1 wherein the steam source is a second
evaporator of the plurality of evaporators, and the source of the
reformate is a steam-hydrocarbon reforming system.
3. The system of claim 2 wherein the first heat transfer coil is
operatively connected to a third heat transfer coil contained in
the second evaporator to receive the reformate from the third heat
transfer coil, and the third heat transfer coil is operatively
connected to the source of the reformate to receive the reformate
from the source of the reformate.
4. The system of claim 1 wherein at least a second evaporator of
the plurality of evaporators comprises a heat transfer coil
operatively connected to the source of the reformate to receive the
reformate from the source of the reformate.
5. The system of claim 1 wherein the gas separator is a pressure
swing adsorber.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application is a divisional of U.S. patent
application Ser. No. 14/061,157, filed Oct. 23, 2013, which is a
continuation-in-part of U.S. patent application Ser. No.
13/858,363, filed Apr. 8, 2013, now U.S. Pat. No. 8,709,287, which
claims the benefit of Provisional Application Ser. No. 61/648,662,
filed on May 18, 2012, the contents of each of which are hereby
incorporated by reference as if fully set forth.
BACKGROUND
[0002] Thermal water purification processes, such as thermal
desalination of salt water using multi-stage flash (MSF) or
multiple effect distillation (MED), use heat from a low-pressure,
high-quality steam energy source to effect the water purification
process. Low pressure steam is generated using common boiler
technology (cf. U.S. Pat. Nos. 4,338,199 and 5,441,548).
[0003] It is known to use other forms of energy for desalination.
For example, U.S. Pat. No. 5,421,962 utilizes solar energy for
desalination processes, U.S. Pat. Pub. 2011/0162952 utilizes energy
from a gasification process, and U.S. Pat. Pub. 2011/0147195 uses
waste heat from a power generation plant for the desalination
process.
[0004] Industry desires to utilize waste heat from catalytic
steam-hydrocarbon reforming processes. Catalytic steam-hydrocarbon
reforming processes release a large amount of waste heat under
various circumstances. One circumstance is when the energy cost is
low and less capital is spent on heat recovery. Another
circumstance is when the process does not produce a large amount of
high pressure export steam due to the lack of demand for export
steam. Low or zero export steam production reduces the heat sink
for the process, resulting in a large amount of waste heat.
[0005] Industry desires to produce purified water in water-stressed
regions. The water can be used as make-up water in the catalytic
steam-hydrocarbon reforming process, making the process
self-sufficient with regard to water. Water can also be sold as a
product for industrial and municipal use.
[0006] Industry desires to reduce or eliminate water treatment cost
in a catalytic steam-hydrocarbon reforming plant. Currently,
make-up water needs to be treated in a catalytic steam-hydrocarbon
reforming plant so that it meets the requirements for the boiler
feed water. These treatments include filtration to remove
particulates, demineralization to remove dissolved minerals, and
deaeration to remove soluble gases such as O.sub.2 and
CO.sub.2.
[0007] Industry desires to reduce the capital and energy cost of
the catalytic steam-hydrocarbon reforming process. The thermal
efficiency of catalytic steam-hydrocarbon reforming processes
depends on the utilization of low level heat. When the energy cost
is high, more low level heat is recovered for better thermal
efficiency or lower energy cost. However, recovering more heat
means using more and/or larger heat exchangers, resulting in higher
capital cost. In contrast, when the energy cost is low, the capital
cost for heat exchangers is minimized with the sacrifice of thermal
efficiency or energy cost.
[0008] There exists a need in the art for systems and processes for
producing H.sub.2-containing product gas and purified water that
are cost-effective and provide greater heat utilization of waste
heat from catalytic steam-hydrocarbon reforming processes.
BRIEF SUMMARY
[0009] Embodiments of the present invention satisfy the need in the
art by providing systems and processes for producing a
H.sub.2-containing product gas and purified water from an
integrated catalytic steam-hydrocarbon reforming and thermal water
purification process. Embodiments of the present invention better
utilize waste heat from catalytic steam-hydrocarbon reforming by
using heat from the reformate in each effect or stage of the
thermal water purification process. Embodiments of the present
invention can reduce or eliminate costs associated with dissipating
excess waste heat and can also provide flexibility to balance heat
load and other operating conditions across the thermal water
purification process.
[0010] There are several specific aspects of the systems and
processes outlined below. The reference numbers and expressions set
in parentheses are referring to an example embodiment explained
further below with reference to the figures. The reference numbers
and expressions are, however, only illustrative and for the
convenience of the reader, and do not limit the aspect to any
specific component or feature of the example embodiment. The
aspects can be formulated as claims in which the reference numbers
and expressions set in parentheses are omitted or replaced by
others as appropriate.
[0011] Aspect 1. A process for producing a H.sub.2-containing
product gas (200) and for producing purified water (42) from a raw
water stream (53) containing contaminants, the process comprising:
[0012] (i) withdrawing a reformate (60) comprising H.sub.2, CO,
CH.sub.4, and H.sub.2O from a reformer furnace (100); [0013] (ii)
passing at least a portion (62) of the reformate (60) from step (i)
to a first evaporator (58) of a plurality of evaporators of a
thermal water purification system (16); [0014] (iii) passing at
least a portion (63) of the raw water stream (53) to the first
evaporator (58); [0015] (iv) introducing a first steam stream (41)
into the first evaporator (58), the first steam stream (41) formed
in a second evaporator (52) of the plurality of evaporators of the
thermal water purification system (16); [0016] (v) heating the at
least a portion (63) of the raw water stream (53) passed to the
first evaporator (58) in step (iii) in the first evaporator (58) by
indirect heat transfer with the at least a portion (62) of the
reformate (60) from step (ii) and separately by indirect heat
transfer with the first steam stream (41) from step (iv) to form a
second steam stream (43) by evaporating a portion of the at least a
portion (63) of the raw water stream (53), thereby cooling the at
least a portion (62) of the reformate (60), forming a first
condensate stream (71) from the first steam stream (41), and
concentrating the contaminants in the at least a portion (63) of
the raw water stream (53); [0017] (vi) withdrawing the second steam
stream (43) from the first evaporator (58); [0018] (vii)
withdrawing the at least a portion (62) of the reformate (60) from
the first evaporator (58); [0019] (viii) withdrawing the first
condensate stream (71) from the first evaporator (58), wherein the
purified water (42) comprises the first condensate stream (71),
[0020] (ix) withdrawing the at least a portion (63) of the raw
water stream (53) from the first evaporator (58), the at least a
portion (63) of the raw water stream (53) having a higher
concentration of the contaminants than when it was introduced into
the first evaporator (58); and [0021] (x) passing the at least a
portion (62) of the reformate (60) withdrawn in step (vii) to a gas
separator (210) and separating the at least a portion (62) of the
reformate (60) in the gas separator (210) to produce at least a
portion of the H.sub.2-containing product gas stream (200) and at
least a portion of a by-product gas stream (250).
[0022] The at least a portion (63) of the raw water stream (53) in
which the contaminants are concentrated in step (v), and that is
withdrawn from the first evaporator (58) in step (ix), is the
remainder of the at least a portion (63) of the raw water stream
(53) introduced into the first evaporator (58) that is not
evaporated in step (v) to form the second steam stream (43).
[0023] Aspect 2. The process of Aspect 1, wherein the first steam
stream (41) is formed by indirect heat exchange with at least one
of (a) a second portion (68) or all of the reformate (60) and (b) a
steam stream (46) formed in a third evaporator (83).
[0024] Aspect 3. The process of Aspect 1 or Aspect 2, wherein the
at least a portion (62) of the reformate (60) is cooled to a
temperature ranging from 25.degree. C. to 65.degree. C. in the
first evaporator (58).
[0025] Aspect 4. The process of any one of Aspects 1 through 3,
wherein all of the reformate (60) is passed to the first evaporator
(58).
[0026] Aspect 5. The process of any one of Aspects 1 through 4,
wherein the at least a portion (62) of the reformate (60) in step
(ii) is all of the reformate (60).
[0027] Aspect 6. The process of any one of Aspects 1 through 5,
further comprising passing at least a portion of the purified water
(42) as make-up water (95) to a steam-hydrocarbon reforming system
comprising the reformer furnace (100).
[0028] Aspect 7. The process of any one of Aspects 1 through 6,
wherein the reformate (60) or portions thereof heat the raw water
stream (53) or portions thereof in each of the plurality of
evaporators.
[0029] Aspect 8. The process of any one of Aspects 1 through 7,
wherein the raw water comprises at least one of salt water, river
water, stream water, lake water, municipal recycled water,
industrial recycled water, groundwater, and process condensate from
a steam methane reforming process.
[0030] Aspect 9. The process of any one of Aspects 1 through 8
wherein the gas separator (210) is a pressure swing adsorber and
the at least a portion (62) of the reformate (60) is separated by
pressure swing adsorption to produce the at least a portion of the
H.sub.2-containing product gas stream (200) and the at least a
portion of a by-product gas stream (250).
[0031] Aspect 10. The process of any one of Aspects 1 through 9,
wherein the at least a portion (62) or a second portion (68) of the
reformate (60) transfers heat to the at least a portion (63) or a
second portion (69) of the raw water stream (53) by indirect heat
transfer in the second evaporator (52).
[0032] Aspect 11. The process of Aspect 10, wherein the at least a
portion (62) of the reformate (60) transfers heat to the second
portion (69) of the raw water stream (53) by indirect heat transfer
in the second evaporator (52) by: [0033] passing the at least a
portion (62) of the reformate (60) to the second evaporator (52);
[0034] passing the second portion (69) of the raw water stream (53)
to the second evaporator (52); and [0035] heating the second
portion (69) of the raw water stream (53) in the second evaporator
(52) by indirect heat transfer with the at least a portion (62) of
the reformate (60) thereby forming the first steam stream (41) by
evaporating a portion of the second portion (69) of the raw water
stream (53), thereby cooling the at least a portion (62) of the
reformate (60), and concentrating the contaminants in the second
portion (69) of the raw water stream (53).
[0036] The second portion (69) of the raw water stream (53) in
which the contaminants are concentrated is the remainder of the
second portion (69) of the raw water stream (53) introduced into
the second evaporator (52) that has not been evaporated to form the
first steam stream (41).
[0037] Aspect 12. The process of Aspect 11, further comprising:
[0038] withdrawing the first steam stream (41) from the second
evaporator (52); [0039] withdrawing the at least a portion (62) of
the reformate (60) from the second evaporator (52); and [0040]
withdrawing the second portion (69) of the raw water stream (53)
from the second evaporator (52), the second portion (69) of the raw
water stream (53) having a higher concentration of the contaminants
than when it was introduced into the second evaporator (52).
[0041] Aspect 13. The process of Aspect 10, wherein the second
portion (68) of the reformate (60) transfers heat to the second
portion (69) of the raw water stream (53) by indirect heat transfer
in the second evaporator (52) by: [0042] passing the second portion
(68) of the reformate (60) to the second evaporator (52), [0043]
passing the second portion (69) of the raw water stream (53) to the
second evaporator (52); and [0044] heating the second portion (69)
of the raw water stream (53) in the second evaporator (52) by
indirect heat transfer with the second portion (68) of the
reformate (60) thereby forming the first steam stream (41) by
evaporating a portion of the second portion (69) of the raw water
stream (53), thereby cooling the second portion (68) of the
reformate (60), and concentrating the contaminants in the second
portion (69) of the raw water stream (53).
[0045] The second portion (69) of the raw water stream (53) in
which the contaminants are concentrated is the remainder of the
second portion (69) of the raw water stream (53) introduced into
the second evaporator (52) that has not been evaporated to form the
first steam stream (41).
[0046] Aspect 14. The process of Aspect 13, further comprising:
[0047] withdrawing the first steam stream (41) from the second
evaporator (52); [0048] withdrawing the second portion (68) of the
reformate (60) from the second evaporator (52); [0049] withdrawing
the second portion (69) of the raw water stream (53) from the
second evaporator (52), the second portion (69) of the raw water
stream (53) having a higher concentration of the contaminants than
when it was introduced into the second evaporator (52); and [0050]
passing the second portion (68) of the reformate (60) withdrawn
from the second evaporator (52) to the gas separator (210) and
separating the second portion (68) of the reformate (60) in the gas
separator (210) to produce at least a portion of the
H.sub.2-containing product gas stream (200) and at least a portion
of a by-product gas stream (250).
[0051] Aspect 15. The process of any one of Aspects 1 through 9,
wherein the at least a portion (62) or a third portion (86) of the
reformate (60) transfers heat to a third portion (65) of the raw
water stream (53) by indirect heat transfer in a third evaporator
(83) of the plurality of evaporators.
[0052] Aspect 16. The process of Aspect 15, wherein the at least a
portion (62) of the reformate (60) transfers heat to the third
portion (65) of the raw water stream (53) by indirect heat transfer
in the third evaporator (83) by: [0053] passing the at least a
portion (62) of the reformate (60) to the third evaporator (83),
[0054] passing the third portion (65) of the raw water stream (53)
to the third evaporator (83); and [0055] heating the third portion
(65) of the raw water stream (53) in the third evaporator (83) by
indirect heat transfer with the at least a portion (62) of the
reformate (60) thereby forming a third steam stream (46) by
evaporating a portion of the third portion (65) of the raw water
stream (53), thereby cooling the at least a portion (62) of the
reformate (60), and concentrating the contaminants in the third
portion (65) of the raw water stream (53).
[0056] The third portion (65) of the raw water stream (53) in which
the contaminants are concentrated is the remainder of the third
portion (65) of the raw water stream (53) introduced into the third
evaporator (83) that has not been evaporated to form the third
steam stream (46).
[0057] Aspect 17. The process of Aspect 16, further comprising:
[0058] withdrawing the third steam stream (46) from the third
evaporator (83); [0059] withdrawing the at least a portion (62) of
the reformate (60) from the third evaporator (83); and [0060]
withdrawing the third portion (65) of the raw water stream (53)
from the third evaporator (83), the third portion (65) of the raw
water stream (53) having a higher concentration of the contaminants
than when it was introduced into the third evaporator (83).
[0061] Aspect 18. The process of Aspect 15, wherein the third
portion (86) of the reformate (60) transfers heat to the third
portion (65) of the raw water stream (53) by indirect heat transfer
in the third evaporator (83) by: [0062] passing the third portion
(86) of the reformate (60) to the third evaporator (83); [0063]
passing the third portion (65) of the raw water stream (53) to the
third evaporator (83); and [0064] heating the third portion (65) of
the raw water stream (53) in the third evaporator (83) by indirect
heat transfer with the third portion (86) of the reformate (60)
thereby forming a third steam stream (46) by evaporating a portion
of the third portion (65) of the raw water stream (53), thereby
cooling the third portion (86) of the reformate (60), and
concentrating the contaminants in the third portion (65) of the raw
water stream (53).
[0065] The third portion (65) of the raw water stream (53) in which
the contaminants are concentrated is the remainder of the third
portion (65) of the raw water stream (53) introduced into the third
evaporator (83) that has not been evaporated to form the third
steam stream (46).
[0066] Aspect 19. The process of Aspect 18, further comprising:
[0067] withdrawing the third steam stream (46) from the third
evaporator (83); [0068] withdrawing the third portion (86) of the
reformate (60) from the third evaporator (83), [0069] withdrawing
the third portion (65) of the raw water stream (53) from the third
evaporator (83), the third portion (65) of the raw water stream
(53) having a higher concentration of the contaminants than when it
was introduced into the third evaporator (83); and [0070] passing
the third portion (86) of the reformate (60) withdrawn from the
third evaporator (83) to the gas separator (210) and separating the
third portion (86) of the reformate (60) in the gas separator (210)
to produce at least a portion of the H.sub.2-containing product gas
stream (200) and at least a portion of a by-product gas stream
(250).
[0071] Aspect 20. A system for producing a H.sub.2-containing
product gas (200) and for producing purified water (42) from a raw
water stream (53) containing contaminants, the system comprising:
[0072] a thermal water purification system (16) comprising a
plurality of evaporators (51, 52, 58, 83), wherein at least a first
evaporator (58) of the plurality of evaporators comprises a first
heat transfer coil (81) operatively connected to a source (100) of
a reformate comprising H.sub.2, CO, CH.sub.4, and H.sub.2O to
receive reformate from the source of the reformate, and wherein
each evaporator (83, 52, 58) of the plurality of evaporators except
for a second evaporator (51) of the plurality of evaporators
comprises a heat transfer coil operatively connected to a
respective steam source (51, 83, 52) to receive steam from the
respective steam source; and [0073] a gas separator (210)
operatively connected to the thermal water purification system (16)
to receive reformate from the thermal water purification
system.
[0074] Aspect 21. The system of Aspect 20, wherein each of the
plurality of evaporators (51, 52, 58, 83) comprises a heat transfer
coil operatively connected to the source of the reformate (100) to
receive reformate from the source of the reformate.
[0075] Aspect 22. The process of Aspect 10, wherein the at least a
portion (62) of the reformate (60) transfers heat to the at least a
portion (63) of the raw water stream (53) by indirect heat transfer
in the second evaporator (52) by: [0076] passing the at least a
portion (62) of the reformate (60) to the second evaporator (52),
[0077] passing the at least a portion (63) of the raw water stream
(53) to the second evaporator (52); [0078] heating the at least a
portion (63) of the raw water stream (53) in the second evaporator
(52) by indirect heat transfer with the at least a portion (62) of
the reformate (60) thereby forming the first steam stream (41) by
evaporating a portion of the at least a portion (63) of the raw
water stream (53), thereby cooling the at least a portion (62) of
the reformate (60), and concentrating the contaminants in the at
least a portion (63) of the raw water stream (53).
[0079] The at least a portion (63) of the raw water stream (53) in
which the contaminants are concentrated is the remainder of the at
least a portion (63) of the raw water stream (53) introduced into
the second evaporator (52) that has not been evaporated to form the
first steam stream (41).
[0080] Aspect 23. The process of Aspect 22, further comprising:
[0081] withdrawing the first steam stream (41) from the second
evaporator (52); [0082] withdrawing the at least a portion (62) of
the reformate (60) from the second evaporator (52); and [0083]
withdrawing the at least a portion (63) of the raw water stream
(53) from the second evaporator (52), the at least a portion (63)
of the raw water stream (53) having a higher concentration of the
contaminants than when it was introduced into the second evaporator
(52).
[0084] Aspect 24. The process of Aspect 10, wherein the second
portion (68) of the reformate (60) transfers heat to the at least a
portion (63) of the raw water stream (53) by indirect heat transfer
in the second evaporator (52) by: [0085] passing the second portion
(68) of the reformate (60) to the second evaporator (52), [0086]
passing the at least a portion (63) of the raw water stream (53) to
the second evaporator (52); [0087] heating the at least a portion
(63) of the raw water stream (53) in the second evaporator (52) by
indirect heat transfer with the second portion (68) of the
reformate (60) thereby forming the first steam stream (41) by
evaporating a portion of the at least a portion (63) of the raw
water stream (53), thereby cooling the second portion (68) of the
reformate (60), and concentrating the contaminants in the at least
a portion (63) of the raw water stream (53).
[0088] The at least a portion (63) of the raw water stream (53) in
which the contaminants are concentrated is the remainder of the at
least a portion (63) of the raw water stream (53) introduced into
the second evaporator (52) that has not been evaporated to form the
first steam stream (41).
[0089] Aspect 25. The process of Aspect 24, further comprising:
[0090] withdrawing the first steam stream (41) from the second
evaporator (52); [0091] withdrawing the second portion (68) of the
reformate (60) from the second evaporator (52); [0092] withdrawing
the at least a portion (63) of the raw water stream (53) from the
second evaporator (52), the at least a portion (63) of the raw
water stream (53) having a higher concentration of the contaminants
than when it was introduced into the second evaporator (52); and
[0093] passing the second portion (68) of the reformate (60)
withdrawn from the second evaporator (52) to the gas separator
(210) and separating the second portion (68) of the reformate (60)
in the gas separator (210) to produce at least a portion of the
H.sub.2-containing product gas stream (200) and at least a portion
of a by-product gas stream (250).
[0094] Aspect 26. The process of any one of Aspects 1 through 9,
wherein the at least a portion (62) or a third portion (86) of the
reformate (60) transfers heat to the at least a portion (63) or a
second portion (69) of the raw water stream (53) by indirect heat
transfer in a third evaporator (83) of the plurality of
evaporators.
[0095] Aspect 27. The process of Aspect 26, wherein the at least a
portion (62) of the reformate (60) transfers heat to the at least a
portion (63) of the raw water stream (53) by indirect heat transfer
in the third evaporator (83) by: [0096] passing the at least a
portion (62) of the reformate (60) to the third evaporator (83);
[0097] passing the at least a portion (63) of the raw water stream
(53) to the third evaporator (83); and [0098] heating the at least
a portion (63) of the raw water stream (53) in the third evaporator
(83) by indirect heat transfer with the at least a portion (62) of
the reformate (60) thereby forming a third steam stream (46) by
evaporating a portion of the at least a portion (63) of the raw
water stream (53), thereby cooling the at least a portion (62) of
the reformate (60) and concentrating the contaminants in the at
least a portion (63) of the raw water stream (53).
[0099] The at least a portion (63) of the raw water stream (53) in
which the contaminants are concentrated is the remainder of the at
least a portion (63) of the raw water stream (53) introduced into
the third evaporator (83) that has not been evaporated to form the
third steam stream (46).
[0100] Aspect 28. The process of Aspect 27, further comprising:
[0101] withdrawing the third steam stream (46) from the second
evaporator (52); [0102] withdrawing the at least a portion (62) of
the reformate (60) from the third evaporator (83); and [0103]
withdrawing the at least a portion (63) of the raw water stream
(53) from the third evaporator (83), the at least a portion (63) of
the raw water stream (53) having a higher concentration of the
contaminants than when it was introduced into the third evaporator
(83).
[0104] Aspect 29. The process of Aspect 26, wherein the third
portion (86) of the reformate (60) transfers heat to the at least a
portion (63) of the raw water stream (53) by indirect heat transfer
in the third evaporator (83) by: [0105] passing the third portion
(86) of the reformate (60) to the third evaporator (83); [0106]
passing the at least a portion (63) of the raw water stream (53) to
the third evaporator (83); and [0107] heating the at least a
portion (63) of the raw water stream (53) in the third evaporator
(83) by indirect heat transfer with the third portion (86) of the
reformate (60) thereby forming a third steam stream (46) by
evaporating a portion of the at least a portion (63) of the raw
water stream (53), thereby cooling the third portion (86) of the
reformate (60), and concentrating the contaminants in the at least
a portion (63) of the raw water stream (53).
[0108] The at least a portion (63) of the raw water stream (53) in
which the contaminants are concentrated is the remainder of the at
least a portion (63) of the raw water stream (53) introduced into
the third evaporator (83) that has not been evaporated to form the
third steam stream (46).
[0109] Aspect 30. The process of Aspect 29, further comprising:
[0110] withdrawing the third steam stream (46) from the third
evaporator (83); [0111] withdrawing the third portion (86) of the
reformate (60) from the third evaporator (83), [0112] withdrawing
the at least a portion (63) of the raw water stream (53) from the
third evaporator (83), the at least a portion (63) of the raw water
stream (53) having a higher concentration of the contaminants than
when it was introduced into the third evaporator (83); and [0113]
passing the third portion (86) of the reformate (60) withdrawn from
the third evaporator (83) to the gas separator (210) and separating
the third portion (86) of the reformate (60) in the gas separator
(210) to produce at least a portion of the H.sub.2-containing
product gas stream (200) and at least a portion of a by-product gas
stream (250).
[0114] Aspect 31. The process of any one of Aspects 1 through 19
and 22 through 30, further comprising: [0115] passing the second
steam stream (43) to a condenser (134) for condensation thereof
thereby forming a second condensate stream from the second steam
stream (43); and [0116] withdrawing the second condensate stream
from the condenser (134), wherein the purified water (42) also
comprises the second condensate stream.
[0117] Aspect 32. The process of Aspect 31, wherein heat is
transferred by indirect heat exchange from the second steam stream
(43) to the raw water stream (53) in the condenser (134).
[0118] Aspect 33. A system for producing a H.sub.2-containing
product gas (200) and for producing purified water (42) from a raw
water stream (53) containing contaminants, the system comprising:
[0119] a thermal water purification system (16) comprising a
plurality of evaporators (52, 58), wherein at least a first
evaporator (58) of the plurality of evaporators comprises a first
heat transfer coil (81) operatively connected to a source (100) of
a reformate comprising H.sub.2, CO, CH.sub.4, and H.sub.2O to
receive reformate from the source of the reformate and a second
heat transfer coil (57) operatively connected to a steam source to
receive steam from the steam source; and [0120] a gas separator
(210) operatively connected to the first heat transfer coil (81) to
receive reformate from the first heat transfer coil.
[0121] Aspect 34. The system of Aspect 33, wherein the steam source
is a second evaporator (52) of the plurality of evaporators and the
source of the reformate is a steam-hydrocarbon reforming system
comprising a reformer furnace (100).
[0122] Aspect 35. The system of Aspect 33 or Aspect 34 wherein the
gas separator (210) is a pressure swing adsorber.
[0123] Aspect 36. The system of any one of Aspects 33 through 35,
wherein the first heat transfer coil (81) is operatively connected
to a third heat transfer coil (59) contained in the second
evaporator (52) to receive the reformate from the third heat
transfer coil (59), and the third heat transfer coil (59) is
operatively connected to the source (100) of the reformate to
receive the reformate from the source of the reformate.
[0124] Aspect 37. The system of any one of Aspects 33 through 35,
wherein at least a second evaporator (52) of the plurality of
evaporators comprises a heat transfer coil (59) operatively
connected to the source of the reformate (100) to receive the
reformate from the source of the reformate.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0125] FIG. 1 is a process flow diagram of an integrated
steam-hydrocarbon reforming process and multi-stage flash process
where raw water is heated by indirect heat transfer with reformate
without using a working fluid.
[0126] FIG. 2 is a process flow diagram of an integrated
steam-hydrocarbon reforming process and multiple effect
distillation process where raw water is heated by indirect heat
transfer with reformate without using a working fluid.
[0127] FIG. 3 is a process flow diagram of an integrated
steam-hydrocarbon reforming process and multi-stage flash process
where raw water is heated by indirect heat transfer with reformate
using a working fluid.
[0128] FIG. 4 is a process flow diagram of an integrated
steam-hydrocarbon reforming process and multiple effect
distillation process where raw water is heated by indirect heat
transfer with reformate using a working fluid.
[0129] FIG. 5 is a process flow diagram of an integrated
steam-hydrocarbon reforming process and multiple effect
distillation process with two stages where raw water is heated by
indirect heat transfer with reformate without using a working
fluid.
[0130] FIG. 6 is a process flow diagram of an integrated
steam-hydrocarbon reforming process and multiple effect
distillation process with two stages where raw water is heated by
indirect heat transfer with reformate without using a working
fluid.
[0131] FIG. 7 is a process flow diagram of an integrated
steam-hydrocarbon reforming process and multiple effect
distillation process with four stages where raw water is heated by
indirect heat transfer with reformate without using a working
fluid.
[0132] FIG. 8 is a process flow diagram of an integrated
steam-hydrocarbon reforming process and multiple effect
distillation process with four stages where raw water is heated by
indirect heat transfer with reformate without using a working
fluid.
[0133] FIG. 9 is a process flow diagram of an integrated
steam-hydrocarbon reforming process and multiple effect
distillation process with two pairs of stages where raw water is
heated by indirect heat transfer with reformate without using a
working fluid.
DETAILED DESCRIPTION
[0134] The articles "a" and "an" as used herein mean one or more
when applied to any feature in embodiments of the present invention
described in the specification and claims. The use of "a" and "an"
does not limit the meaning to a single feature unless such a limit
is specifically stated. The article "the" preceding singular or
plural nouns or noun phrases denotes a particular specified feature
or particular specified features and may have a singular or plural
connotation depending upon the context in which it is used. The
adjective "any" means one, some, or all indiscriminately of
whatever quantity. The term "and/or" placed between a first entity
and a second entity means one of (1) the first entity, (2) the
second entity, and (3) the first entity and the second entity. The
term "and/or" placed between the last two entities of a list of 3
or more entities means at least one of the entities in the
list.
[0135] The phrase "at least a portion" means "a portion or all."
The at least a portion of a stream may have the same composition as
the stream from which it is derived. The at least a portion of a
stream may have a different composition to that of the stream from
which it is derived. The at least a portion of a stream may include
specific components of the stream from which it is derived.
[0136] As used herein, "first," "second," "third," etc. are used to
distinguish from among a plurality of features and/or steps and
does not indicate the relative position in time or space.
[0137] As used herein, the term "catalyst" refers to a support,
catalytic material, and any other additives which may be present on
the support.
[0138] As used herein a "divided portion" of a stream is a portion
having the same chemical composition as the stream from which it
was taken.
[0139] The term "depleted" means having a lesser mole %
concentration of the indicated component than the original stream
from which it was formed. "Depleted" does not mean that the stream
is completely lacking the indicated component.
[0140] As used herein, "heat" and "heating" may include both
sensible and latent heat and heating.
[0141] As used herein, "raw water" is any impure water, for
example, one or more of salt water (ocean water, seawater, brackish
water), surface water such as a stream, river, or lake,
groundwater, municipal/industrial reuse or recycled water, or waste
water from an industrial process, such as rejected water from a
steam methane reforming process such as the process condensate. The
process condensate is the water condensed from the reformate stream
of the SMR process. Raw water is generally less pure than
conventional industrial feed water, such as potable water.
[0142] As used herein, "purified water" means any distilled water
(i.e. distillate or condensed water) from a thermal water
purification process.
[0143] As used herein, "reformate" or "a reformate stream" is any
stream comprising hydrogen and carbon monoxide formed from the
reforming reaction of a hydrocarbon and steam.
[0144] As used herein, "indirect heat transfer" is heat transfer
from one stream to another stream where the streams are not mixed
together. Indirect heat transfer includes, for example, transfer of
heat from a first fluid to a second fluid in a heat exchanger where
the fluids are separated by plates or tubes. Indirect heat transfer
includes transfer of heat from a first fluid to a second fluid
where an intermediate working fluid is used to carry the heat from
the first fluid to the second fluid. The first fluid may evaporate
a working fluid, e.g. steam, in an evaporator, the working fluid
passed to another heat exchanger or condenser, where the working
fluid transfers heat to the second fluid. Indirect heat transfer
from the first fluid to a second fluid using a working fluid may be
accommodated using a heat pipe, thermosyphon or the like.
[0145] As used herein, "direct heat transfer" is heat transfer from
one stream to another stream where the streams are intimately mixed
together. Direct heat transfer includes, for example,
humidification where water is sprayed directly into a hot air
stream and the heat from the air evaporates the water.
[0146] In the figures, conduits are depicted as lines with arrows
connecting one or more other components of the system. Each such
conduit is operatively connected to an outlet of a component (i.e.,
the component from which the line originates) and an inlet of
another component (i.e., the component at which the arrow
terminates) such that a gas and/or liquid can be carried
therebetween. In addition, components of the system can be
operatively connected to each other via other components of the
system that may separate them (e.g., evaporators, heating coils,
etc.). Operatively connecting two or more components such that a
gas and/or liquid can be carried therebetween can involve any
suitable methods known in the art, including the use of flanged
conduits, gaskets, and bolts.
[0147] In the claims, letters (e.g., (a), (b), (c), (d), etc.) or
roman numerals (e.g., (i), (ii), (iii), (iv), etc.) may be used to
identify claimed process steps. These letters or roman numerals are
used to aid in referring to the process steps and are not intended
to indicate the order in which claimed steps are performed, unless
and only to the extent that such order is specifically recited in
the claims.
[0148] The present invention relates to a system and process for
producing a H.sub.2-containing product and for producing purified
water. The H.sub.2-containing product may be a purified H.sub.2
product gas or a synthesis gas having a desired H.sub.2:CO molar
ratio. The purified water may be desalinated water, i.e. purified
water from salt water. For the purposes of the present disclosure,
"desalinated water" means water from which 99-100 wt % of salt
originally present has been removed.
[0149] The present invention relates to heat integration between a
catalytic steam-hydrocarbon reforming process and thermal water
purification process. The catalytic steam-hydrocarbon reforming
process uses a large amount of water for reaction (e.g.
CH.sub.4+2H.sub.2O.fwdarw.4H.sub.2+CO.sub.2) and production of high
pressure steam as a co-product. The process also produces a large
amount of low level heat. Thermal water purification produces
purified water from raw water, and its energy source is low level
heat. These two processes complement each other in that catalytic
steam-hydrocarbon reforming consumes water and generates low level
heat, whereas thermal water purification consumes low level heat
and generates water. The present invention exploits this good match
and achieves reduction in the total capital and energy cost of the
integrated process.
[0150] A thermal water purification process as used herein is any
process that uses a heat source to evaporate raw water and
condenses the evaporated water vapor into a condensate or
distillate (i.e. the purified water). The thermal water
purification process may be, for example, a known commercial
thermal desalination process such as multi-stage flash (MSF) or
multiple effect distillation (MED).
[0151] Catalytic steam-hydrocarbon reforming has heretofore not
been integrated with thermal water purification, even though
catalytic steam-hydrocarbon reforming produces a large amount of
low level heat. No specific integration schemes have been disclosed
up to now.
[0152] Referring now to the drawings, wherein like reference
numbers refer to like elements throughout the several views, FIGS.
1 and 3 show process flow diagrams for various arrangements whereby
a steam-hydrocarbon reforming process is integrated with a
Multi-Stage Flash (MSF) thermal water purification process for
producing a H.sub.2-containing product 200 and purified water 42.
FIGS. 2 and 4 show process flow diagrams for various arrangements
whereby a steam-hydrocarbon reforming process is integrated with a
Multiple Effect Distillation (MED) thermal water purification
process for producing a H.sub.2-containing product 200 and purified
water 42. FIGS. 5 and 6 show process flow diagrams for embodiments
of the present invention comprising an integrated steam-hydrocarbon
reforming process and MED process with two stages where raw water
is heated by indirect heat transfer with reformate without using a
working fluid. FIGS. 7 and 8 show process flow diagrams for
embodiments of the present invention comprising an integrated
steam-hydrocarbon reforming process and MED process with four
stages where raw water is heated by indirect heat transfer with
reformate without using a working fluid. FIG. 9 shows a process
flow diagram for an embodiment of the present invention comprising
an integrated steam-hydrocarbon reforming process and hybrid MED
process with two pairs of stages where raw water is heated by
indirect heat transfer with reformate without using a working
fluid.
[0153] It should be noted that the embodiments of FIGS. 1 through 4
have been included in this application to provide context for the
present invention, but are not within the scope of the claims of
the present invention.
[0154] The steam-hydrocarbon reforming process of embodiments of
the present invention utilizes catalytic steam-hydrocarbon
reforming. Catalytic steam-hydrocarbon reforming, also called steam
methane reforming (SMR), catalytic steam reforming, or steam
reforming, is defined as any process used to convert reformer
feedstock into synthesis gas by reaction with steam over a
catalyst. Synthesis gas, commonly called syngas, is any mixture
comprising hydrogen and carbon monoxide. The reforming reaction is
an endothermic reaction and may be described generally as
C.sub.nH.sub.m+n H.sub.2O.fwdarw.n CO+(m/2+n) H.sub.2. Hydrogen is
generated when synthesis gas is generated.
[0155] The multiple effect distillation process 16 of the
embodiments of FIGS. 5-9 utilizes a reformate 60 that is withdrawn
from the steam-hydrocarbon reforming process. The reformate 60 may
be produced by introducing a reformer feed gas mixture 15 into a
plurality of catalyst-containing reformer tubes 20 in the reformer
furnace 100, reacting the reformer feed gas mixture 15 in a
reforming reaction under reaction conditions effective to form a
reformate 60 comprising H.sub.2, CO, CH.sub.4, and H.sub.2O. The
reformate 60 may then be withdrawn from the catalyst-containing
reformer tubes 20 of the reformer furnace 100.
[0156] The reformer feed gas mixture 15 may comprise a hydrocarbon
feedstock and steam, or a mixture of prereformed hydrocarbon
feedstock and steam. Feedstock may be natural gas, methane,
naphtha, propane, refinery fuel gas, refinery off-gas, or other
suitable reformer feedstock known in the art.
[0157] The reforming reaction may take place in the plurality of
catalyst-containing reformer tubes 20 in reformer furnace 100. A
reformer furnace, also called a catalytic steam reformer, steam
methane reformer, and steam-hydrocarbon reformer, is defined herein
as any fired furnace used to convert feedstock containing elemental
hydrogen and carbon to synthesis gas by a reaction with steam over
a catalyst with heat provided by combustion of a fuel.
[0158] Reformer furnaces with a plurality of catalyst-containing
reformer tubes, i.e. tubular reformers, are well known in the art.
Any suitable number of catalyst-containing reformer tubes may be
used. Suitable materials and methods of construction are known.
Catalyst in the catalyst-containing reformer tubes may be any
suitable catalyst known in the art, for example, a supported
catalyst comprising nickel.
[0159] The reaction conditions effective to form the reformate 60
in the plurality of catalyst-containing reformer tubes may comprise
a first temperature ranging from 500.degree. C. to 1000.degree. C.
and a first pressure ranging from 203 kPa to 5,066 kPa
(absolute).
[0160] Saturated boiler feed water 106 from steam drum 160 may be
heated by indirect heat transfer with the reformate 60 withdrawn
from the plurality of catalyst-containing reformer tubes 20 in a
first heat exchanger 110 thereby forming high pressure steam 165
having a pressure ranging from 1.5 to 12.5 MPa (absolute). The
reformer feed gas mixture 15 may include the high pressure steam
165.
[0161] As shown in the figures, saturated boiler feed water 106 may
be withdrawn from steam drum 160 and passed to heat exchanger 110
where the saturated boiler feed water 106 may be heated by indirect
heat exchange with the reformate 60 in heat exchanger 110. The
heated boiler feed water may be returned to steam drum 160 where
steam and water are separated. High pressure steam 165 may be
withdrawn from the steam drum and saturated boiler feed water may
be passed to various heat exchangers to be heated.
[0162] Boiler feed water 105 may be heated in a second heat
exchanger 170 by indirect heat transfer with reformate 60 from the
first heat exchanger 110. As shown in the figures, the boiler feed
water 105 may be heated in the second heat exchanger 170 before
being heated in the first heat exchanger 110.
[0163] Boiler feed water is water that meets certain purity
requirements for use in boilers and stream drums.
[0164] As shown in the figures, the reformate 60 may be passed from
the second heat exchanger 170 to shift reactor 70. The process may
comprise reacting the reformate 60 from the second heat exchanger
170 in the presence of a shift catalyst 75 under reaction
conditions effective to form additional hydrogen in the reformate
60. Additional hydrogen gas may be obtained by the catalytic
reaction of carbon monoxide and steam. This reaction is exothermic
and is commonly referred to as the water-gas shift reaction or
shift reaction: CO+H.sub.2O.fwdarw.CO.sub.2+H.sub.2. The reaction
is effected by passing carbon monoxide and water through a bed of a
suitable catalyst. The reaction conditions effective to form
additional hydrogen in the reformate 60 may comprise a second
temperature ranging from 190.degree. C. to 500.degree. C. and a
second pressure ranging from 203 kPa to 5,066 kPa (absolute).
[0165] Any suitable shift catalyst may be used. The shift reactor
may be a so-called high temperature shift (HTS), low temperature
shift (LTS), medium temperature shift (MTS), or combination. Since
the article "a" means "one or more," one or more shift reactors may
be used in the process.
[0166] For high temperature shift, an inlet temperature in the
range 310.degree. C. to 370.degree. C., and an outlet temperature
in the range 400.degree. C. to 500.degree. C. are typical. Usually
an iron oxide/chromia catalyst is used for high temperature
shift.
[0167] For low temperature shift, an inlet temperature in the range
190.degree. C. to 230.degree. C., and an outlet temperature in the
range 220.degree. C. to 250.degree. C. are typical. Usually a
catalyst comprising metallic copper, zinc oxide, and one or more
other difficultly reducible oxides such as alumina or chromia is
used for low temperature shift
[0168] For medium temperature shift, an inlet temperature in the
range 190.degree. C. to 230.degree. C. and an outlet temperature of
up to 350.degree. C. are typical. A suitably formulated supported
copper catalyst can be used for medium temperature shift. Medium
temperature shift may be preferred for the present process.
[0169] A combination may include a sequence of high temperature
shift, cooling by indirect heat exchange, and low temperature
shift. If desired, either shift stage can be subdivided with
interbed cooling.
[0170] As shown in the figures, the process may further comprise
heating the boiler feed water 105 by indirect heat transfer with
the reformate 60 from the shift reactor 70 in optional heat
exchanger 180 prior to heating the raw water 53 by indirect heat
transfer with the reformate 60 from shift reactor 70 wherein the
boiler feed water 105 is heated by the reformate from shift reactor
70 before being heated in heat exchanger 170.
[0171] In various embodiments, boiler feed water 105 is not heated
by reformate 60 leaving the shift reactor 70 and before the
reformate 60 is used to heat raw water 53. In conventional
catalytic hydrocarbon-reforming processes, omission of heat
exchanger 180 will result in increased loss of low level heat to
the environment (waste heat) and poor energy efficiency for the
system. In the present case, in the embodiments of FIGS. 1 through
4, omission of heat exchanger 180 results in more low level heat
being transferred from the reformate 60 to the raw water 53 through
heat transfer coil 21, evaporator 51, or heat exchanger 190. In the
embodiments of FIGS. 5 through 9, omission of heat exchanger 180
results in more low level heat being transferred from the reformate
60 to the raw water 53 through one or more evaporators of the
multiple effect distillation process 16 (e.g., evaporators 52, 83,
51, and 58) and does not result in increased waste heat losses. As
a result, in the embodiments of FIGS. 1 through 4, the temperature
of the reformate 60 leaving the heat recovery system (e.g. heat
exchanger 90) ranges from about 25.degree. C. to 65.degree. C.,
which is similar to the temperature leaving a deep heat recovery
system in a conventional catalytic steam-hydrocarbon reforming
process that includes heat exchanger 180. Similarly, in the
embodiments of FIGS. 5 through 9, the multiple effect distillation
process 16 can be operated such that temperature of the reformate
60 returned from the multiple effect distillation process 16 ranges
from about 25.degree. C. to 65.degree. C. These embodiments are
advantageous when the value of the water is much greater than the
value of energy and/or when the demand for high pressure export
steam is low or zero.
[0172] As shown in FIGS. 1 through 9, raw water 53 is heated by
indirect heat transfer with a first steam stream 196 or the
reformate 60 (after the reformate 60 undergoes the optional shift
reaction), thereby heating the raw water 53 for purification of the
raw water in a multi-stage flash process 2 as shown in FIGS. 1 and
3, or a multiple effect distillation process 16 as shown in FIGS. 2
and 4 through 9, to produce purified water 42. As the first steam
stream 196 or reformate 60 gives up heat to the raw water 53, the
first steam stream 196 or reformate 60 is cooled. The amount of
heat transferred from the first steam stream 196 or reformate 60 to
the raw water 53 may range between 115 to 2784 kJ per kg of make-up
water 95.
[0173] The make-up water 95 may be further heated by indirect heat
transfer with the reformate 60 in heat exchanger 90 prior to
separating the reformate 60. In the embodiments of FIGS. 1 through
4, the temperature of the reformate 60 leaving heat exchanger 90
ranges from about 25.degree. C. to about 65.degree. C. or from
about 35.degree. C. to about 55.degree. C.
[0174] "Make-up water" is water introduced into the catalytic
steam-hydrocarbon reforming process as a feedstock stream. Make-up
water can be boiler feed water quality or may need to be further
treated to become boiler feed water quality. The amount of make-up
water added to the system is the amount required for reaction in
the catalytic steam-hydrocarbon reforming process plus the amount
required for export steam production. In case excess steam in the
reformate 60, which is condensed in knock-out drum 220 as process
condensate 224, is not recycled to the catalytic steam-hydrocarbon
reforming process, the amount of make-up water required is
increased by the amount of process condensate.
[0175] The make-up water 95 may comprise purified water 42. The
make-up water 95 may consist of purified water 42. A portion or all
of the purified water 42 produced may be used as make-up water for
the reforming process.
[0176] The purified water from thermal water purification processes
can be boiler feed water quality. Direct use of the purified water
will save on water treatment costs at the catalytic
steam-hydrocarbon reforming plant. Use of purified water 42 as
boiler feed water 105 can pay for itself if the total cost of the
purified water 42 is less than the sum of raw water 53 cost plus
the capital and operating cost of water treatment and deaeration in
the catalytic steam-hydrocarbon reforming plant.
[0177] In case the purified water 42 is not boiler feed water
quality, the purified water 42 may be treated by methods used for
conventional make-up water treatment.
[0178] FIG. 1 shows reformate 60 passed to heating chamber 10 of a
representative multi-stage flash process 2. Reformate 60 passes
over metallic heat transfer coil 21, disposed internally of heating
chamber 10 through which raw water 53 flows and is heated and
subsequently enters first stage flash tank 12.
[0179] Raw water 53 enters heat transfer coil 14 of flash tank 28.
Raw water inside coil 14 is heated by heat transfer as water vapor
condenses against the heat transfer coil 14. Optionally, for
distillation to occur at lower temperatures, either a vacuum pump
or steam ejector 130 is connected to any or all of the flash tanks
12, 24, 26, or 28, lowering the internal tank pressure to below
atmospheric pressure. The pressure is successively reduced at each
stage from flash tank 12 through to flash tank 28.
[0180] Purified water condensate produced by this condensation
process is collected in collector 18 of flash tank 28 and exits the
tank as a stream of purified water 42.
[0181] The incoming raw water 53 is heated further as it passes
through the heat transfer coils 14 of flash tanks 28, 26, 24, and
then 12. Heated raw water exits flash tank 12 and enters the heat
transfer coil 21 of heating chamber 10. Reformate 60 enters heating
chamber 10 and contacts the heat transfer coil 21 to effect heat
transfer to further heat raw water 53 passing internally through
the heat transfer coil 21. Cooled reformate 60 produced as a result
of this heat transfer exits the heating chamber 10.
[0182] Water vapor which condenses upon contact with coil 14 forms
a purified water condensate 17 which drips from the coil 14 into
collector 18 of each flash tank and is collected as purified water
42. Evaporation of the raw water causes the low quality reject
water 22 in the bottom of the flash tanks to become increasingly
concentrated in impurities. In the case of desalination of salt
water, the low quality reject water 22 is brine and the brine in
the bottom of the flash tanks becomes increasingly concentrated
with salt. Low quality reject water 22 passes to flash tanks 24,
26, and 28, respectively, where the thermal water purification
process repeats at progressively lower pressures. Low quality
reject water which is concentrated in impurities exits flash tank
28 in low quality reject water 77 and is typically discharged.
[0183] Alternatively (not shown in the figures), a portion of the
low quality reject is withdrawn and joins the raw water 53 as a
portion of the feed water to the thermal water purification
process. This low quality reject water recycle increases the
conversion rate of the raw water into the purified water, also
known as the recovery of the raw water. The higher the amount of
recycled low quality reject water, the higher the impurity in the
feed water to the thermal water purification process. The amount of
recycled low quality reject water depends on the allowable impurity
level of the feed water to the thermal water purification
process.
[0184] In the embodiments shown in FIGS. 1 and 2 the cooled
reformate 60 may be optionally further cooled by passing through
optional heat exchanger 80 to heat hydrocarbon feedstock 85 by
indirect heat transfer with the cooled reformate 60. In the
embodiments of FIGS. 3 and 4, hydrocarbon feedstock 85 is not
heated by heat exchange with reformate from shift reactor 70 or by
heat exchange with cooled reformate after the reformate has heated
raw water 53. In conventional catalytic steam-hydrocarbon reforming
processes, omission of optional heat exchanger 80 results in
increased loss of low level heat to the environment (waste heat)
and poor energy efficiency. In the present case, omission of
optional heat exchanger 80 results in more low level heat being
transferred from the reformate 60 to the raw water 53, and does not
result in increased waste heat. Even with the omission of optional
heat exchanger 80, the temperature of the reformate 60 leaving heat
exchanger 90 ranges from 25.degree. C. to 65.degree. C., similar to
that of a conventional catalytic steam-hydrocarbon reforming
process with a deep heat recovery system that normally contains
optional heat exchanger 80.
[0185] In the embodiment shown in FIG. 1, the cooled reformate 60
returned from the multi-stage flash process 2 is further cooled by
passing through heat exchanger 90 where make-up water 95 is heated.
Make-up water 95 is heated in heat exchanger 90 before being heated
in either of optional heat exchanger 180 or heat exchanger 170.
[0186] FIG. 2 illustrates an embodiment utilizing a representative
multiple effect distillation process 16. FIG. 2 shows reformate 60
passed to heat transfer coil 59 of evaporator 51. Reformate 60 is
cooled in heat transfer coil 59 as a result of heat transfer with
raw water 53 brought into contact with the exterior of the coil 59,
typically by spraying the raw water through spray bar 55. Cooled
reformate is withdrawn from coil 59 and may be optionally further
cooled by passing through optional heat exchanger 80 to heat
hydrocarbon feedstock 85.
[0187] In the embodiment shown in FIG. 2, the reformate returned
from the multiple effect distillation process 16 is further cooled
by passing through heat exchanger 90 where make-up water 95 is
heated. Make-up water 95 is heated in heat exchanger 90 for use as
boiler feed water 105, which is then heated in either of optional
heat exchanger 180 by the reformate from the shift reactor or heat
exchanger 170.
[0188] The raw water 53 which is sprayed through spray bar 55 onto
the exterior of the coil 59 of evaporator 51 undergoes evaporation
to form water vapor due to heat transfer between the coil 59 heated
by the reformate 60 passing internally therethrough. The water
vapor so produced passes from evaporator 51 into heat transfer coil
57 disposed internally of another evaporator 54. Raw water 53 is
sprayed onto the exterior of heat transfer coil 57 through spray
bar 102, and the water vapor inside the coil 57 condenses within
the heat transfer coil 57, exits evaporator 54 and is collected as
water condensate in purified water 42. Water vapor produced by heat
transfer in evaporator 54 is passed into evaporator 56 where the
process is repeated, and so on for as many evaporators as are
present in the system. Water vapor exiting the last evaporator in
the series (evaporator 56 in FIG. 2) is condensed in condenser 134
by contact with heat transfer coil 136 through which cold raw water
53 is passed. Purified water condensate so produced is combined
with that produced in the previous evaporators and collected as
purified water 42. Low quality reject water 22 collected at the
bottom of evaporator 51 is combined with low quality reject water
22 from the other evaporators 54 and 56 in low quality reject water
77, where the thermal water purification process continues
optionally at progressively lower pressure operating conditions,
and is later discharged.
[0189] The cooled reformate 60, after cooling in heat exchanger 90
is passed to knock-out drum 220 to remove water formed by
condensation of steam, typically called process condensate. Process
condensate 224 may be purified and reused, or alternatively
discharged. Purified process condensate may be combined with
make-up water 95 and heated in heat exchanger 90, optional heat
exchanger 180, and/or heat exchanger 170.
[0190] The process condensate 224, along with the raw water 53, may
be fed to the thermal water purification unit to purify the process
condensate for reuse.
[0191] The cooled reformate 60 is separated after the reformate 60
heats the raw water 53 to produce the H.sub.2-containing product
200 and a by-product gas 250. The reformate 60 may be separated by
any known means for separating reformate. As shown in the figures,
the reformate 60 may be separated by pressure swing adsorption in
gas separator 210 to produce the H.sub.2-containing product 200 and
the by-product gas 250. The by-product gas 250 from a pressure
swing adsorber is commonly called a tail gas. Alternatively, the
reformate 60 may be cryogenically separated into synthesis gas
products in a cold box (not shown).
[0192] As shown in the figures, a fuel 35 may be combusted with an
oxidant gas 120 in the reformer furnace 100 external to the
plurality of catalyst-containing reformer tubes 20 under conditions
effective to combust the fuel 35 to form a combustion product gas
40 and generate heat to supply energy for reacting the reformer
feed gas mixture 15 inside the plurality of catalyst-containing
reformer tubes 20. The combustion product gas 40 may be withdrawn
from the reformer furnace 100. Conditions effective to combust the
fuel may comprise a temperature ranging from 600.degree. C. to
1500.degree. C. and a pressure ranging from 99 kPa to 101.3 kPa
(absolute).
[0193] The fuel 35 may comprise by-product gas 250 from the means
for separating the reformate 60, i.e. the gas separator 210. The
fuel 35 may comprise supplemental fuel 150. The supplemental fuel
is often called trim fuel. The supplemental fuel may be natural gas
or other suitable fuel.
[0194] The fuel 35 and oxidant gas 120 are combusted external to
the plurality of catalyst-containing reformer tubes 20 in the
combustion section 30, (also called radiant section) of the
reformer furnace 100. The combustion product gas 40 is passed from
the combustion section 30 to the convection section 50 of the
reformer furnace 100. In the convection section 50 of the reformer
furnace 100, various streams are heated by the combustion product
gas 40. The combustion product gas 40 may be withdrawn from the
convection section through exhaust fan 140.
[0195] As shown in the figures, oxidant gas 120 may be compressed
in compressor 135 and may be heated in a heat exchanger in the
convection section 50 before being introduced for combustion.
Boiler feed water may be withdrawn from steam drum 160, heated in a
heat exchanger in the convection section 50 of the reformer furnace
100, and passed back to the steam drum 160 to make steam. Pressure
swing adsorber tail gas may be heated in a heat exchanger (not
shown) in the convection section 50 before being introduced for
combustion.
[0196] High pressure steam 165 from the steam drum 160 may be
superheated in a heat exchanger in the convection section 50 of the
reformer furnace 100. At least a portion of the superheated steam
(commonly called process steam) is blended with a hydrocarbon
feedstock 85 to form the reformer feed gas mixture 15. A portion of
the superheated steam may be exported as export steam 230.
[0197] The reformer feed gas mixture 15 may be further heated in a
heat exchanger in the convection section 50 of the reformer furnace
100 before being passed to the plurality of catalyst-containing
reformer tubes 20.
[0198] The superheated steam may be blended with a hydrocarbon
feed, heated and passed to a prereformer to reform a portion of the
blend. The prereformer may be an adiabatic prereformer. The mixture
from the prereformer may be heated in the convection section 50 of
the reformer furnace 100 before being passed to the plurality of
catalyst-containing reformer tubes as the reformer feed gas mixture
15.
[0199] FIGS. 1 and 2, as well as FIGS. 5 through 9, illustrate
processes wherein the step of heating raw water 53 does not include
heating of an intermediate working fluid. Embodiments where no
intermediate working fluid is used provide the advantage of not
requiring a low pressure steam and/or medium pressure steam boiler.
Eliminating one stage of heat exchange between the reformate 60 and
the raw water 53 also increases the heat exchange temperature
differences in the remaining heat exchangers, thereby providing
advantages in capital cost and improved thermal efficiency.
[0200] FIG. 3 is an alternative embodiment of FIG. 1 where like
numerals designate like components. FIG. 3 is an embodiment wherein
the step of heating raw water includes heating of an intermediate
working fluid. The embodiment shown in FIG. 3 operates similarly to
the embodiment shown in FIG. 1. Differences are described
below.
[0201] FIG. 4 is an alternative embodiment of FIG. 2 where like
numerals designate like components. FIG. 4 is an embodiment wherein
the step of heating raw water includes heating of an intermediate
working fluid. The embodiment shown in FIG. 4 operates similarly to
the embodiment shown in FIG. 2. Differences are described
below.
[0202] In the embodiments shown in FIGS. 3 and 4, the step of
heating raw water 53 by indirect heat transfer may comprise heating
a working fluid 185 by indirect heat transfer with the reformate 60
in heat exchanger 190, and heating the raw water 53 by indirect
heat transfer with the working fluid 185. The working fluid may be
water. Water may be evaporated to form a first stream 196 of steam
having a pressure ranging from 15.2 kPa to 304 kPa (absolute) or
ranging from 20.3 kPa to 132 kPa, when heated by the reformate 60
in heat exchanger 190. The first stream 196 of steam is condensed
to form condensate 23 when heating the raw water 53 and returned to
heat exchanger 190 be re-evaporated.
[0203] The ratio of the mass flow rate of the first stream 196 of
steam to the mass flow rate of the make-up water 95 may be greater
than 0.05 and less than 1.2. This is a new operating condition that
a conventional steam methane reformer has not used and would not
use.
[0204] In the embodiments of FIGS. 3 and 4, steam may be optionally
generated and expanded in a steam turbine to generate shaft work.
In one option, working fluid water is evaporated to form a second
stream 197 of steam having a pressure ranging from 280 kPa to 608
kPa or ranging from 304 kPa to 405 kPa. The reformate 60 from the
shift reactor 70 heats the second stream 197 of steam prior to
heating the first stream 196 of steam. The second stream 197 of
steam is expanded to generate shaft work in steam turbine 205 prior
to heating the raw water 53. The shaft work may be used in either
or both of the reforming process and the thermal water purification
process. The expanded steam is condensed to form condensate 29 when
heating the raw water 53. In this option, the ratio of the sum of
mass flow rates of the first stream 196 and the second stream 197
of steam to the mass flow rate of the make-up water 95 may be
greater than 0.05 and less than 1.2. These embodiments are
advantageous when the value of the water is much greater than the
value of energy and/or when the demand for high pressure export
steam is low or zero.
[0205] In the embodiments of FIGS. 3 and 4, another option for
generating shaft work comprises expanding a portion of the high
pressure steam 165 to generate shaft work in steam turbine 215. The
shaft work may be used in the reforming process for pumping and
compression and/or to generate electric power. Raw water may be
heated by indirect heat transfer with the expanded steam thereby
heating the raw water 53 for purification thereof in the multiple
effect distillation process 16 or the multi-stage flash process 2.
Generating shaft work from high pressure steam is not commonly
practiced in conventional catalytic steam-hydrocarbon reforming
processes because there is often no end use for the expanded steam.
Capturing the value of the expanded steam requires using a
condensing turbine, at the expense of a large capital expenditure.
In the integrated process, the value of the expanded steam is
captured as the energy source for thermal water purification
without incurring additional capital expense. The integration
synergy makes it an attractive practice to generate power in the
catalytic steam-hydrocarbon reforming process when the value of
electricity is high.
[0206] FIGS. 5 through 9 illustrate process flow diagrams for four
embodiments of a steam-hydrocarbon reforming process integrated
with an MED thermal water purification process for producing an
H.sub.2-containing product 200 and purified water 42. In each of
these embodiments, the reformate 60 is used as a heat source in
multiple evaporators, which can provide greater utilization of the
heat from the reformate 60, lessen or eliminate the release of
waste heat from the reformer furnace 100, and reduce or eliminate
cost associated with equipment and utilities that otherwise may be
needed to dissipate waste heat from the reformate 60 to the
atmosphere. Many components of the steam-hydrocarbon reforming
process shown in FIGS. 5 through 9 are the same as those in the
embodiments shown in FIGS. 1 through 4 and, therefore, are
identified with the same reference numerals as used in FIGS. 1
through 4 and will not be discussed in detail below.
[0207] In the exemplary embodiment shown in FIG. 5, all of the
reformate 60 is passed to heat transfer coil 59 of evaporator 52.
Reformate 60 is cooled in heat transfer coil 59 as a result of heat
transfer with a portion 69 of raw water stream 53 brought into
contact with the exterior of the coil 59, typically by spraying the
raw water through spray bar 55. Cooled reformate is withdrawn from
coil 59 and passed to a heat transfer coil 81 in another evaporator
58.
[0208] The raw water which is sprayed through spray bar 55 onto the
exterior of the coil 59 of evaporator 52 undergoes evaporation to
form water vapor due to heat transfer between the coil 59 heated by
the reformate 60 passing internally therethrough. The steam stream
41 produced by the evaporation passes from evaporator 52 into heat
transfer coil 57, which is located inside of evaporator 58. A
portion 63 of raw water stream 53 is sprayed onto the exterior of
heat transfer coil 57 and heat transfer coil 81 through spray bar
102, and the steam stream inside the coil 57 condenses within the
heat transfer coil 57, exits evaporator 58 and is collected as
water condensate stream 71. Steam stream 43 produced by heat
transfer in evaporator 58 by contact with heat transfer coils 57
and 81 is withdrawn from evaporator 58 and condensed in condenser
134 by contact with heat transfer coil 136, through which cold raw
water stream 53 is passed.
[0209] The purified water condensate produced is combined with the
condensate produced in the evaporators and is collected in purified
water 42. Low quality reject water 22 collected at the bottom of
evaporator 52 is combined with low quality reject water 22 from
evaporator 58 in low quality reject water 77, where it can later be
utilized in another process or it can be discharged. In addition,
valves 91 through 93 can be opened and closed such that the low
quality reject water 22 is provided to each evaporator in series.
More specifically, with valves 91 and 93 open and valve 92 closed,
the raw water 53 and low quality reject water 22 will flow as
previously discussed, However, with valves 91 and 93 closed and
valve 92 open, the low quality reject water 22 from evaporator 58
will be provided to spray bar 55 of evaporator 52 instead of, or in
addition to, a portion of raw water 53.
[0210] As shown in FIG. 5, unlike the embodiments of FIGS. 1
through 4, the reformate 60 returned from the multiple effect
distillation process 16 is not passed through heat exchangers
(e.g., optional heat exchanger 80 and heat exchanger 90) prior to
being passed to knock-out drum 220 (also known as a knock-out pot).
Knock-out drum 220 separates process condensate 224 from reformate
stream 226. As previously discussed, process condensate 224 may be
purified and reused, or alternatively discharged from the process.
Reformate stream 226 is passed to a gas separator 210 (e.g. a
pressure swing adsorber) to produce a hydrogen-containing product
gas stream 200 and a by-product gas 250 (e.g., comprising carbon
monoxide), the latter of which is recycled to the reformer furnace
100 as a portion of the fuel 35.
[0211] Turning now to FIG. 6, in this exemplary embodiment, the
reformate 60 is divided into separate streams before being
introduced into each of the evaporators. A portion 62 of reformate
60 is passed to evaporator 58. Another portion 68 of reformate 60
is passed to evaporator 52. As previously discussed with regard to
FIG. 5, the portion 68 of reformate 60 is cooled in heat transfer
coil 59 as a result of heat transfer with a portion 69 of raw water
stream 53 brought into contact with the exterior of the coil 59 by
spraying the raw water through spray bar 55. However, in this
embodiment, the cooled portion 68 of the reformate 60 withdrawn
from coil 59 is not passed to evaporator 58; instead, the cooled
portion 68 of the reformate 60 is collected and combined with the
cooled portion 62 of the reformate 60 from evaporator 58, as
discussed below.
[0212] The raw water which is sprayed through spray bar 55 onto the
exterior of the coil 59 of evaporator 52 produces steam stream 41,
which is passed from evaporator 52 into heat transfer coil 57
disposed internally of evaporator 58. A portion 63 of raw water
stream 53 is sprayed onto the exterior of heat transfer coil 57 and
heat transfer coil 81 through spray bar 102, and the steam stream
inside the coil 57 condenses within the heat transfer coil 57,
exits evaporator 58 and is collected as water condensate stream 71.
Steam stream 43 produced by heat transfer in evaporator 58 by
contact with heat transfer coils 57 and 81 is condensed in
condenser 134 by contact with heat transfer coil 136, through which
cold raw water stream 53 is passed. Purified water condensate from
condenser 134 is combined with water condensate stream 71 produced
in evaporator 58 and is collected as purified water 42. Low quality
reject water 22 collected at the bottom of evaporator 52 is
combined with low quality reject water 22 from evaporator 58 as low
quality reject water 77, where it can later be utilized in another
process or it can be discharged. In addition, like the embodiment
of FIG. 5, valves 91 through 93 can be opened and closed such that
the low quality reject water 22 is provided to each evaporator in
series. More specifically, with valves 91 and 93 open and valve 92
closed, the raw water 53 and low quality reject water 22 will flow
as previously discussed, However, with valves 91 and 93 closed and
valve 92 open, the low quality reject water 22 from evaporator 58
will be provided to spray bar 55 of evaporator 52 instead of, or in
addition to, a portion of raw water 53.
[0213] The cooled portion 62 of reformate 60 from heat transfer
coil 81 is combined with the cooled portion 68 of reformate 60 from
heat transfer coil 59. Again, the reformate 60 returned from the
multiple effect distillation process 16 is not passed through heat
exchangers (e.g., optional heat exchanger 80 and heat exchanger 90)
prior to being passed to knock-out drum 220. Knock-out drum 220
separates process condensate 224 from reformate stream 226. As
previously discussed, process condensate 224 may be purified and
reused, or alternatively discharged from the process. Reformate
stream 226 is passed to gas separator 210 (e.g., a pressure swing
adsorber) to produce a hydrogen-containing product gas stream 200
and a by-product gas 250 (e.g., comprising carbon monoxide), the
latter of which is recycled to the reformer furnace 100.
[0214] Turning now to FIG. 7, shown is an embodiment in which all
of the reformate 60 is passed through each of the evaporators 51,
83, 52, and 58, beginning with evaporator 51. Reformate 60 is
cooled in heat transfer coil 59 of evaporator 51 as a result of
heat transfer with a portion 64 of raw water stream 53 brought into
contact with the exterior of the coil 59 by spraying the raw water
through spray bar 55. The cooled reformate 60 is withdrawn from
coil 59 and passed to a heat transfer coil 82 in another evaporator
83.
[0215] The raw water which is sprayed through spray bar 55 onto the
exterior of the coil 59 of evaporator 51 undergoes evaporation to
form water vapor due to heat transfer between the coil 59 heated by
the reformate passing internally therethrough. The steam stream 45
produced by the evaporation passes from evaporator 51 into heat
transfer coil 84, which is located inside evaporator 83. A portion
65 of raw water stream 53 is sprayed onto the exterior of heat
transfer coil 84 and heat transfer coil 82 through spray bar 103,
and the steam stream inside the heat transfer coil 84 condenses
within the heat transfer coil 84, exits evaporator 83 and is
collected in purified water 42. Steam stream 46 produced by heat
transfer in evaporator 83 is passed into evaporator 52 where the
process is repeated, and so on for as many evaporators as are
present in the system. The steam stream exiting the last evaporator
in the series (in FIG. 7, steam stream 43 from evaporator 58) is
condensed in condenser 134 by contact with heat transfer coil 136
through which cold raw water stream 53 is passed, as previously
discussed. Purified water condensate from condenser 134 is combined
with condensate produced in the evaporators and is collected in
purified water 42.
[0216] The reformate 60 in heat transfer coil 82 is further cooled
upon heat transfer with the a portion 65 of raw water stream 53 to
produce the steam stream 46. The reformate 60 is then passed to
evaporator 52, where the process is repeated, and so on for as many
evaporators as are present in the system. The reformate 60 exiting
the last evaporator in the series (in FIG. 7, evaporator 58) is
returned to knock-out drum 220. Low quality reject water 22
collected at the bottom of evaporator 51 is combined with low
quality reject water 22 from evaporators 83, 52, and 58, where it
can later be utilized in another process or it can be
discharged.
[0217] Again, the reformate 60 returned from the multiple effect
distillation process 16 is not passed through heat exchangers
(e.g., optional heat exchanger 80 and heat exchanger 90) prior to
being passed to knock-out drum 220. Knock-out drum 220 separates
process condensate 224 from reformate stream 226. Process
condensate 224 may be purified and reused, or alternatively
discharged from the process. Reformate stream 226 is passed to a
gas separator 210 (e.g., a pressure swing adsorber) to produce a
hydrogen-containing product gas stream 200 and a by-product gas 250
(e.g., comprising carbon monoxide), the latter of which is recycled
to the reformer furnace 100.
[0218] Turning now to FIG. 8, in this exemplary embodiment, the
reformate 60 is divided into separate streams before being
introduced into each of the evaporators. Specifically, in this
embodiment, a portion 62 of reformate 60 is passed to evaporator
58; another portion 68 of reformate 60 is passed to evaporator 52;
another portion 86 of reformate 60 is passed to evaporator 83; and
another portion 87 of reformate 60 is passed to evaporator 51.
Alternatively, heat transfer coils that receive portions of
reformate 60 could be omitted from one or more evaporators. For
example, the heat transfer coils of evaporators 52 and 83 which
receive portions 68 and 86 of the reformate 60 could be omitted,
which is represented in FIG. 8 by showing these features in dashed
lines.
[0219] The portion 87 of reformate 60 is cooled in heat transfer
coil 59 of evaporator 51 as a result of heat transfer with a
portion 64 of raw water stream 53 brought into contact with the
exterior of the coil 59 by spraying the raw water through spray bar
55. The cooled portion 87 of reformate 60 is withdrawn from coil 59
but is not passed to evaporator 83; instead, the cooled portion 87
of reformate 60 is combined with cooled portions 62, 68, and 86 of
the reformate 60 from evaporators 58, 52, and 83, respectively, as
discussed below.
[0220] The raw water which is sprayed through spray bar 55 onto the
exterior of the coil 59 of evaporator 51 undergoes evaporation to
form water vapor due to heat transfer between the coil 59 heated by
the reformate passing internally therethrough. The steam stream 45
produced by evaporation passes from evaporator 51 into heat
transfer coil 84, which is located inside evaporator 83. A portion
65 of raw water stream 53 is sprayed onto the exterior of heat
transfer coil 84 and heat transfer coil 82 through spray bar 103,
and the steam stream inside the heat transfer coil 84 condenses
within the heat transfer coil 84, exits evaporator 83 and is
collected in purified water 42. Steam stream 46 produced by heat
transfer in evaporator 83 is passed into evaporator 52 where the
process is repeated, and so on for as many evaporators as are
present in the system. The steam stream exiting the last evaporator
in the series (in FIG. 8, steam stream 43 from evaporator 58) is
condensed in condenser 134 by contact with heat transfer coil 136
through which cold raw water stream 53 is passed, as previously
discussed. Purified water condensate from condenser 134 is combined
the condensate produced in the evaporators and is collected in
purified water 42. Low quality reject water 22 collected at the
bottom of evaporator 51 is combined with low quality reject water
22 from evaporators 83, 52, and 58 in low quality reject water 77
where it can later be utilized in another process or it can be
discharged.
[0221] The portion 86 of the reformate 60 in heat transfer coil 82
of evaporator 83 is further cooled upon heat transfer with a
portion 65 of raw water stream 53 to produce the steam stream 46,
the portion 68 of the reformate 60 in heat transfer coil in the
next evaporator (evaporator 52) is further cooled upon heat
transfer with a portion 69 of raw water stream 53 to produce steam
stream 41, and so on for as many evaporators as are present in the
system. The portion of the reformate 60 exiting the last evaporator
in the series (in FIG. 8, portion 62 exiting evaporator 58) is
combined with the cooled reformate 60 from the other heat transfer
coils in the system. Again, the reformate 60 is then returned from
the multiple effect distillation process 16 but is not passed
through heat exchangers (e.g., optional heat exchanger 80 and heat
exchanger 90) prior to being passed to knock-out drum 220.
Knock-out drum 220 separates process condensate 224 from reformate
stream 226. Process condensate 224 may be purified and reused, or
alternatively discharged from the process. Reformate stream 226 is
passed to gas separator 210 (e.g., a pressure swing adsorber) to
produce a hydrogen-containing product gas stream 200 and a
by-product gas 250 (e.g., comprising carbon monoxide), the latter
of which is recycled to the reformer furnace 100.
[0222] Turning now to FIG. 9, shown is an exemplary embodiment that
is a hybrid of the embodiments of FIGS. 7 and 8. In this
embodiment, the reformate 60 is divided into separate streams
before being introduced into each of two pairs of evaporators. A
portion 62 of reformate 60 is passed to evaporator 52, and another
portion 87 of reformate 60 is passed to evaporator 51.
[0223] The portion 87 of reformate 60 is cooled in heat transfer
coil 59 of evaporator 51 as a result of heat transfer with a
portion 64 of raw water 53 brought into contact with the exterior
of the coil 59 by spraying the raw water through spray bar 55. The
cooled portion 87 of reformate 60 is withdrawn from coil 59 and
passed to a heat transfer coil 82 in another evaporator 83 (i.e.,
evaporator 51 and evaporator 83 are a pair).
[0224] The raw water which is sprayed through spray bar 55 onto the
exterior of the coil 59 of evaporator 51 undergoes evaporation to
form water vapor due to heat transfer between the coil 59 heated by
the reformate passing internally therethrough. The steam stream 45
produced by the evaporation passes from evaporator 51 into heat
transfer coil 84, which is located inside evaporator 83. A portion
65 of raw water 53 is sprayed onto the exterior of heat transfer
coil 84 and heat transfer coil 82 through spray bar 103, and the
steam stream inside the heat transfer coil 84 condenses within the
heat transfer coil 84, exits evaporator 83 and is collected in
purified water 42. Steam stream 46 produced by heat transfer in
evaporator 83 is passed into evaporator 52 where the process is
repeated, and so on for as many evaporators as are present in the
system. The steam stream exiting the last evaporator in the series
(in FIG. 7, steam stream 43 from evaporator 58) is condensed in
condenser 134 by contact with heat transfer coil 136 through which
cold raw water 53 is passed, as previously discussed. Purified
water condensate from condenser 134 is combined with condensate
produced in the evaporators and is collected in purified water
42.
[0225] The cooled portion 87 of the reformate 60 in heat transfer
coil 82 is further cooled upon heat transfer with the a portion 65
of raw water 53 to produce the steam stream 46, however the cooled
portion 87 of the reformate 60 is not then passed to another
evaporator; instead, the cooled portion 87 of the reformate 60 is
collected and combined with the cooled portion 62 of the reformate
60 from evaporator 58 of the other pair of evaporators, where the
process is repeated for as many pairs of evaporators (or larger
groups of evaporators) as are present in the system. The cooled
portion of the reformate 60 exiting the last evaporator of the
series (in FIG. 9, cooled portion 62 exiting evaporator 58 of the
pair of evaporators 52 and 58) is combined with cooled portion 87
and cooled portions from any other pairs of evaporators in the
system.
[0226] Again, the reformate 60 is then returned from the multiple
effect distillation process 16 but is not passed through heat
exchangers (e.g., optional heat exchanger 80 and heat exchanger 90)
prior to being passed to knock-out drum 220. Knock-out drum 220
separates process condensate 224 from reformate stream 226. Process
condensate 224 may be purified and reused, or alternatively
discharged from the process. Reformate stream 226 is passed to gas
separator 210 (e.g., a pressure swing adsorber) to produce a
hydrogen-containing product gas stream 200 and a by-product gas 250
(e.g., comprising carbon monoxide), the latter of which is recycled
to the reformer furnace 100.
[0227] Other embodiments of the multiple effect distillation
process 16 include different hybrids of the embodiments discussed
in FIGS. 1 through 9. For example, another embodiment involves a
hybrid between the embodiments of FIGS. 2 and 7, where the
plurality of evaporators (e.g., six evaporators) in the multiple
effect distillation process 16 alternate between those that include
a single coil for heat transfer with steam from a preceding
evaporator (e.g., evaporator 54 in FIG. 2), and those that include
both a coil for heat transfer with steam from a preceding
evaporator and a coil for heat transfer with reformate (e.g.,
evaporator 83 in FIG. 7).
[0228] Accordingly, in the embodiments of FIGS. 5 through 9, one or
more additional evaporators are utilized to cool the reformate 60.
Stated differently, one or more additional evaporators have two
heat exchange coils: one coil for reformate 60, and another for a
steam stream generated in a preceding evaporator. Preferably, all
evaporators in the multiple effect distillation process 16 include
a heat transfer coil for heat transfer with steam from a preceding
evaporator except for an evaporator that is not preceded by another
evaporator in a series of evaporators (e.g., evaporator 52 in FIGS.
5 and 6, and evaporator 51 in FIGS. 7 through 9), and at least one
evaporator in the series of evaporators includes both a coil for
heat transfer with steam from a preceding evaporator and a coil for
heat transfer with reformate (e.g., evaporator 58). More
preferably, all evaporators in the multiple effect distillation
process 16, except for an evaporator that is not preceded by
another evaporator in a series of evaporators, include both a coil
for heat transfer with steam from a preceding evaporator and a coil
for heat transfer with reformate. By utilizing both the heat of the
reformate 60 and the heat of the steam stream from each preceding
evaporator, the multiple effect distillation process 16 of these
embodiments provides greater utilization of the heat from the
reformate 60, lessens or eliminates the release of waste heat from
the reformer furnace 100, and lessens or eliminates costs
associated with equipment and utilities that otherwise may be
needed to dissipate waste heat from the reformate 60 to the
atmosphere or further cool the reformate 60 prior to being passed
to a knock-out drum 220 or gas separator 210.
[0229] In addition, the embodiments of FIGS. 5 through 9 provide
the flexibility to balance heat load and other operating conditions
across the evaporators of the multiple effect distillation process
16 during design and operation. For example, the multiple effect
distillation process 16 can be configured with a combination of
temperature controllers (not shown) within each evaporator and
valves (not shown) on each conduit carrying reformate 60. A control
logic can monitor operating temperatures of each evaporator with
the temperature controllers and adjust those temperatures by
controlling the valves to modify the amount of reformate 60 being
passed to each evaporator for heat transfer. By doing so, the
control logic may mitigate unwanted temperature gradients across
the evaporators of the multiple effect distillation process 16 and
also control with greater precision the temperature of the
reformate 60 stream ultimately being returned for processing in a
gas separator or other piece of equipment having specific
temperature requirements. In this respect, the embodiments of FIGS.
6, 8, and 9 afford more control in balancing heat load across the
multiple effect distillation process 16 by providing the
flexibility to individually regulate how much of the reformate 60
is provided to each evaporator. One disadvantage of such
embodiments, however, is that the temperature of the combined
portions of the reformate 60 returned from the multiple effect
distillation process 16 will be greater than that of embodiments in
which all of the reformate 60 is passed through each evaporator in
series (e.g., FIGS. 5 and 7).
Example
[0230] The following is an example showing the heat utilization of
the embodiment of FIG. 2 as compared to the embodiment of FIG. 7.
Certain simulation parameters and simulated data have been excluded
from the following discussion for clarity.
[0231] Example 1 is based on the embodiment shown in FIG. 2. The
reformate is withdrawn from the SMR unit upstream of a heat
exchanger (e.g., heat exchanger 90) for preheating SMR make-up
water with reformate, and optionally, another heat exchanger (e.g.,
optional heat exchanger 80) for preheating the hydrocarbon feed
with reformate. The reformate is fed to a first evaporator of a
series of evaporators of the MED unit at 159 C and returns to the
SMR unit at 144 C after providing the heat for water evaporation in
the first evaporator of the MED unit. The amount of the reformate
heat utilized in the MED unit for producing purified water is 47.9
GJ/hr. The return reformate is used in the SMR unit to heat the
make-up water. The reformate is then cooled in an air cooler to
37.8 C and fed to a hydrogen PSA unit for separating hydrogen from
the reformate and producing the hydrogen product. The heat
dissipated from the reformate to atmosphere via the air cooler is
19.5 GJ/hr.
TABLE-US-00001 TABLE 1 Feed Return Reformate reformate reformate
Reformate cooling load in temperature temperature heat load the SMR
unit (.degree. C.) (.degree. C.) (GJ/hr) (GJ/hr) Example 1 159 144
47.9 19.5 Example 2 106 38 67.5 0
[0232] Example 2 is based on the embodiment shown in FIG. 7. The
reformate is withdrawn from the SMR unit after its heat has been
fully recovered by the heat sources in the SMR unit (e.g.,
downstream of heat exchanger 90). The reformate is fed to a first
evaporator of a series of evaporators of the MED unit at a lower
temperature 106 C. After providing heat for water evaporation in
the first evaporator, the reformate is fed to three more
evaporators to evaporate water and to be cooled to a desired
temperature. The reformate returns to the SMR unit at 37.8 C and is
fed to a hydrogen PSA unit for separating hydrogen from the
reformate and producing product hydrogen. The reformate heat
utilized in the MED unit is 67.5 GJ/hr, which is 19.6 GJ/hr greater
than that in Example 1. In addition to better utilizing the heat of
the reformate, this integration also does not release any waste
heat to atmosphere and does not need any cooling equipment in the
SMR unit.
* * * * *