U.S. patent application number 13/820435 was filed with the patent office on 2013-08-29 for heat exchanger using non-pure water for steam generation.
The applicant listed for this patent is Greg Naterer, Edward Secnik, Zhaolin Wang. Invention is credited to Greg Naterer, Edward Secnik, Zhaolin Wang.
Application Number | 20130224104 13/820435 |
Document ID | / |
Family ID | 45772038 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130224104 |
Kind Code |
A1 |
Naterer; Greg ; et
al. |
August 29, 2013 |
Heat Exchanger Using Non-Pure Water for Steam Generation
Abstract
A process and a device are described for producing high purity
and high temperature steam from non-pure water which may be used in
a variety of industrial processes that involve high temperature
heat applications. The process and device may be used with
technologies that generate steam using a variety of heat sources,
such as, for example industrial furnaces, petrochemical plants, and
emissions from incinerators. Of particular interest is the
application in a thermochemical hydrogen production cycle such as
the Cu--Cl Cycle. Non-pure water is used as the feedstock in the
thermochemical hydrogen production cycle, with no need to adopt
additional and conventional water pre-treatment and purification
processes. The non-pure water may be selected from brackish water,
saline water, seawater, used water, effluent treated water,
tailings water, and other forms of water that is generally believed
to be unusable as a direct feedstock of industrial processes. The
direct usage of this water can significantly reduce water supply
costs.
Inventors: |
Naterer; Greg; (St. John's,
NL) ; Wang; Zhaolin; (Whitby, CA) ; Secnik;
Edward; (Pickering, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Naterer; Greg
Wang; Zhaolin
Secnik; Edward |
St. John's
Whitby
Pickering |
|
NL
CA
CA |
|
|
Family ID: |
45772038 |
Appl. No.: |
13/820435 |
Filed: |
March 30, 2011 |
PCT Filed: |
March 30, 2011 |
PCT NO: |
PCT/CA2011/000342 |
371 Date: |
May 17, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61379981 |
Sep 3, 2010 |
|
|
|
Current U.S.
Class: |
423/648.1 ;
122/367.1; 122/7R; 422/162 |
Current CPC
Class: |
C02F 1/16 20130101; Y02E
60/364 20130101; C01B 3/08 20130101; F22B 27/165 20130101; F28D
3/02 20130101; B01D 1/0047 20130101; F22B 37/265 20130101; C01B
13/0203 20130101; Y02W 10/37 20150501; B01D 1/0058 20130101; Y02E
60/36 20130101; F28D 7/106 20130101; C01B 3/045 20130101; C02F
1/001 20130101; F28D 21/0001 20130101; F22B 1/06 20130101 |
Class at
Publication: |
423/648.1 ;
122/7.R; 122/367.1; 422/162 |
International
Class: |
F22B 1/06 20060101
F22B001/06; C01B 3/04 20060101 C01B003/04; F22B 37/26 20060101
F22B037/26 |
Claims
1. In a high temperature industrial process where heat recovery is
desired, the improvement comprising transferring heat from a high
temperature molten or gaseous material obtained in the high
temperature industrial process, to generate high temperature steam
from non-pure water, with the impurities in the water being reduced
to a precipitate, a slurry or a concentrated aqueous solution,
which can be disposed of, or subjected to further processing.
2. The process as claimed in claim 1, comprising generating high
temperature steam in a heat exchange process, wherein heat from
molten material is supplied to non-pure water to produce high
temperature steam, with the impurities in the water being reduced
to a precipitate, a slurry or a concentrated aqueous solution,
which can be disposed of, or subjected to further processing.
3. The process as claimed in claim 1, comprising generating high
temperature steam in a heat exchange process, wherein the steam is
generated from a two-stage steam generation loop which comprises
two heat exchanges, a first-stage heat exchange comprising
transferring heat from molten material to a thermal fluid
circulating to a second-stage heat exchange, and back again to the
first-stage heat exchange; heat from the thermal fluid being
transferred to non-pure water in the second-stage heat exchange to
produce high temperature steam from which hydrogen gas is produced,
and impurities in the water are reduced to a precipitate, a slurry
or a concentrated aqueous solution, which can be disposed of, or
subjected to further processing.
4. The process as claimed in claim 1, wherein the industrial
process is a thermochemical Cu--Cl cycle for producing hydrogen gas
from water decomposition which comprises supplying heat to the
non-pure water from molten CuCl to produce high temperature steam
for the production of hydrogen gas, with the impurities in the
water being reduced to a precipitate, a slurry or a concentrated
aqueous solution, which can be disposed of, or subjected to further
processing.
5. The process as claimed in claim 1, wherein the industrial
process is a thermochemical Cu--Cl cycle for producing hydrogen gas
from water decomposition which comprises the generation of steam
from non-pure water using a two-stage steam generation loop which
comprises two heat exchanges, a first-stage heat exchange
comprising transferring heat from molten CuCl to a thermal fluid
circulating to a second-stage heat exchange, and back again to the
first-stage heat exchange; heat from the thermal fluid being
transferred to non-pure water in the second-stage heat exchange to
produce high temperature steam from which hydrogen gas is produced,
and impurities in the water are reduced to a precipitate, a slurry
or a concentrated aqueous solution, which can be disposed of, or
subjected to further processing.
6. A device for use in a high temperature industrial process where
heat recovery is required and high temperature steam is produced
which comprises using a tube and shell heat exchanger, the tube is
arranged to receive a high temperature molten or gaseous material
obtained from the high temperature industrial process and the shell
is arranged to receive non-pure water to which heat is transferred
from the high temperature molten or gaseous material in the tube,
which then generates high temperature steam from the non-pure
water, with the impurities in the non-pure water being reduced to a
precipitate, a slurry or a concentrated aqueous solution, which can
be disposed of, or subjected to further processing.
7. A device for use in a high temperature industrial process where
heat recovery is desired and high temperature steam is produced,
comprising a two-stage steam generation loop which comprises two
heat exchangers, each having a central tube and surrounding shell,
the first-stage heat exchanger arranged for high temperature molten
or gaseous material to pass through its central tube and the
surrounding shell is arranged to receive a secondary thermal fluid
to circulate in the surrounding shell to absorb heat from the high
temperature molten or gaseous material, the surrounding shell being
in fluid communication with the shell in the second-stage heat
exchanger to permit circulation of the heated thermal fluid from
one shell to the other and back again to the shell in the
first-stage heat exchanger; the central tube of the second stage
heat exchanger arranged to receive non-pure water which absorbs
heat from the thermal fluid to generate high temperature steam for
use in the high temperature industrial process, and impurities in
the water are reduced to a precipitate, a slurry or a concentrated
aqueous solution, which can be disposed of, or subjected to further
processing.
8. The device as claimed in claim 6, wherein the industrial process
is a thermochemical Cu--Cl cycle for the production of hydrogen
from water decomposition and the molten material is CuCl salt, and
the high temperature steam is used to produce the hydrogen gas from
decomposition of water in the thermochemical Cu--Cl cycle.
9. The device as claimed in claim 8, wherein the molten CuCl is
received in the tube of the heat exchanger and passes therethrough
with the assistance of at least one of gravity, a push-pull plate
or a helical screw.
10. The device as claimed in claim 8, wherein the molten CuCl
passes through the tube of the heat exchanger at a rate that allows
the production of high temperature steam at a temperature suitable
for the production of hydrogen gas from the decomposition of water
in the thermochemical Cu--Cl cycle.
11. The device as claimed in claim 8, wherein the tube wall is
treated with lubricant to assist passage of molten CuCl through the
tube of the heat exchanger, in at least one of the following ways:
in advance of the device being used, on a periodic basis and on a
continuous basis during use of the device.
12. The device as claimed in claim 8, wherein the shell walls are
washed with water or water containing cleaners or both to remove
any adhered impurities that foul the reactor, the washing taking
place either when the device is in use or when the device is not in
use.
13. The device as claimed in claim 9, wherein a helical screw is
used and assists the passage of molten CuCl through the tube as it
passes from a molten state to a solid state, as well as the
efficient heat transfer from the molten CuCl to the non-pure water.
Description
TECHNICAL FIELD
[0001] A process and a device are described for producing high
purity and high temperature steam from non-pure water which may be
used in a variety of industrial processes that involve high
temperature heat applications. The process and device may be used
with technologies that generate steam using a variety of heat
sources, such as, for example industrial furnaces, petrochemical
plants, and emissions from incinerators. Of particular interest is
the application in a thermochemical hydrogen production cycle.
Non-pure water is used as the feedstock in the thermochemical
hydrogen production cycle, with no need to adopt additional and
conventional water pre-treatment and purification processes. The
non-pure water may be selected from lake water, brackish water,
saline water, seawater, used water, effluent treated water,
tailings water, and other forms of water that are generally
believed to be unusable as a direct feedstock of industrial
processes. The direct usage of this water significantly reduces
water supply costs.
BACKGROUND
[0002] Hydrogen is widely believed to be one of the world's next
generation fuels, since its oxidation does not emit greenhouse
gases that contribute to climate change. Auto manufacturers are
investing significantly in hydrogen vehicles. Other transportation
vehicles, such as ships, trains and utility vehicles also represent
promising opportunities for use of hydrogen fuel. Hydrogen is also
a major necessity for the upgrading of heavy oils and fertilizer
production. Thus there is need for a reliable, safe, efficient and
economic process for the production of hydrogen gas for fuel, heavy
oil upgrading and fertilizer production.
[0003] Electrolysis is a proven, commercial technology that
separates water into hydrogen and oxygen using electricity. Net
electrolysis efficiencies are typically about 24%. In contrast,
thermochemical reactions to produce hydrogen using nuclear heat can
achieve heat-to-hydrogen efficiencies up to about 50% [See Schultz,
K., Herring, S., Lewis M., Summers, W., "The Hydrogen Reaction",
Nuclear Engineering International, vol. 50, pp. 10-19, 2005 and
Rosen, M. A., "Thermodynamic Comparison of Hydrogen Production
Processes", International Journal of Hydrogen Energy, vol. 21, no.
5, pp. 349-365, 1996.]
[0004] A copper-chlorine (Cu--Cl) cycle has been identified by
Atomic Energy of Canada Ltd. (AECL) [See Sadhankar, R. R., Li, J,
Li, H., Ryland, D. K., Suppiah, S. "Future Hydrogen Production
Using Nuclear Reactors", Engineering Institute of Canada--Climate
Change Technology Conference, Ottawa, May, 2006 and Sadhankar, R.
R., "Leveraging Nuclear Research to Support Hydrogen Economy", 2nd
Green Energy Conference, Oshawa, June, 2006.] at its Chalk River
Laboratories (CRL) as a highly promising thermochemical cycle for
hydrogen production. Water is decomposed into hydrogen and oxygen
through intermediate Cu and Cl compounds. Past studies at Argonne
National Laboratory (ANL) have developed enabling technologies for
the Cu--Cl thermochemical cycle, through an International Nuclear
Energy Research Initiative (INERI), as reported by Lewis et al.
[See 17. Lewis, M. A., Serban, M., Basco, J. K, "Hydrogen
Production at <550.degree. C. Using a Low Temperature
Thermochemical Cycle", ANS/ENS Exposition, New Orleans, November,
2003.] The Cu--Cl cycle is well matched to Canada's nuclear
reactors, since its heat requirement for high temperatures is
adaptable to the Super-Critical Water Reactor (SCWR), which is
being considered as Canada's Generation IV nuclear reactor.
[0005] Other countries (Japan, U.S. and France) are currently
advancing nuclear technology for thermochemical hydrogen production
[See Sakurai, M., Nakajima, H., Amir, R., Onuki, K., Shimizu, S.,
"Experimental Study on Side-Reaction Occurrence Condition in the
Iodine-Sulfur Thermochemical Hydrogen Production Process",
International Journal of Hydrogen Energy, vol. 23, pp. 613-619,
2000; Schultz, K., "Thermochemical Production of Hydrogen from
Solar and Nuclear Energy", Technical Report for the Stanford Global
Climate and Energy Project, General Atomics, San Diego, Calif.,
2003; and Doctor, R. D., Matonis, D. T., Wade, D. C, "Hydrogen
Generation Using a Calcium - Bromine Thermochemical Water-splitting
Cycle", Paper ANL/ES/CP-3-111623, OECD 2nd Information Exchange
Meeting on Nuclear Production of Hydrogen, Argonne, Ill., Oct. 2-3,
2003.]
[0006] The Sandia National Laboratory in the U.S. and CEA in France
are developing a hydrogen pilot plant with a sulphur-iodine (S--I)
cycle [See Pickard, P., Gelbard, F., Andazola, J., Naranjo, G.,
Besenbruch, G., Russ, B., Brown, L., Buckingham, R., Henderson, D.,
"Sulfur-Iodine Thermochemical Cycle", DOE Hydrogen Production
Report, U.S. Department of Energy, Washington, D.C., 2005 Fuel Cell
Vehicles: Race to a New Automotive Future, Office of Technology
Policy, US Department of Commerce, January, 2003.] The Korean KAERI
Institute is collaborating with Japan Atomic Energy Agency (JAEA)
aims to complete a large S--I plant to produce 60,000 m.sup.3/hr of
hydrogen by 2020, which will be sufficient for about 1 million fuel
cell vehicles [See Suppiah, S., Li, J., Sadhankar, R., Kutchcoskie,
K. J., Lewis, M., "Study of Hybrid CuCl Cycle for Nuclear Hydrogen
Production", Third Information Exchange Meeting on the Nuclear
Production of Hydrogen, Orai, Japan, October, 2005.] Several
countries, participating in the Generation IV International Forum
plan to develop the technologies for co-generation of hydrogen by
high-temperature thermochemical cycles and electrolysis, through
multilateral collaborations [See Rosen, M. A., "Thermodynamic
Analysis of Hydrogen Production by Thermochemical Water
Decomposition using the Ispra Mark-10 Cycle", In Hydrogen Energy
Prog. VIII: Proc. 8th World Hydrogen EnergyConference, ed. T. N.
Veziroglu and P. K. Takahashi, Pergamon, Toronto, pp. 701-710,
1990.]
[0007] When compared to other methods of hydrogen production, the
thermochemical Cu--Cl cycle has its own unique advantages,
challenges, risks and limitations. Technical challenges include the
transport of solids and electrochemical processes of copper
electrowinning, which are not needed by other cycles such as the
sulfur-iodine cycle. These processes are challenging due to solids
injection/removal, which can block equipment operation and generate
undesirable side reactions in downstream chemical reactors. Flow of
solid materials can lead to increased maintenance costs, due to
wear and increased downtime arising from blockage and unscheduled
equipment failure. A technological risk involves the potential use
of expensive new materials of construction that are needed to
prevent corrosion of equipment surfaces. These include surfaces
exposed to molten CuCl, spray drying of aqueous CuCl.sub.2 and high
temperature HCl and O.sub.2 gases. Additional operational
challenges entail the steps of chemical separation (which increases
complexity and costs) and phase separation (particles, gas, and
liquids must be separated from each other in fluid streams leaving
the reactors). As a result, the overall cycle efficiency becomes a
limitation, wherein the Cu--Cl cycle must compete economically
against other existing technologies of hydrogen production.
[0008] Despite these challenges and risks, the Cu--Cl cycle offers
a number of key advantages over other cycles of thermochemical
hydrogen production. The attractions include lower temperatures
compared to other cycles like the S--I cycle. Heat input at
temperatures less than 530.degree. C. make it suitable for coupling
to Canada's SCWR (Super-Critical Water Reactor; Generation IV
nuclear reactor) and reduced demands on materials of construction.
Other advantages are inexpensive raw materials and reactions that
proceed nearly to completion without significant side reactions.
Solids handling is required, but it is relatively minimal and it
can be reduced by combining thermochemical and electrochemical
steps together. Another key advantage is the cycle's ability to
utilize low-grade waste heat from power plants, for various thermal
processes within the cycle. US Patent Publication No. 2010/012987,
published May 27, 2010 describes a system utilizing a
thermochemical CuCl cycle in detail. The disclosures of this
application are incorporated herein in their entirety.
[0009] There is a need to improve the efficiency of the Cu--Cl
cycle for it to be competitive and all aspects of the cycle need to
be examined for such opportunities.
SUMMARY
[0010] This disclosure related to an improved high temperature
industrial process where heat recovery is desired, the improvement
comprising transferring heat from a high temperature molten or
gaseous material obtained in the high temperature industrial
process, to generate high temperature steam from non-pure water,
with the impurities in the water being reduced to a precipitate, a
slurry or a concentrated aqueous solution, which can be disposed
of, or subjected to further processing.
[0011] More specifically, high temperature steam is generated in a
heat exchange process, wherein heat from high temperature molten or
gaseous material is supplied to non-pure water to produce high
temperature steam, with the impurities in the water being reduced
to a precipitate, a slurry or a concentrated aqueous solution,
which can be disposed of, or subjected to further processing.
[0012] In another form of the process, where high temperature steam
is generated in a heat exchange process, the steam is generated
from a two-stage steam generation loop which comprises two heat
exchanges, a first-stage heat exchange comprising transferring heat
from molten material to a thermal fluid circulating to a
second-stage heat exchange, and back again to the first-stage heat
exchange; heat from the thermal fluid being transferred to non-pure
water in the second-stage heat exchange to produce high temperature
steam from which hydrogen gas is produced, and impurities in the
water are reduced to a precipitate, a slurry or a concentrated
aqueous solution, which can be disposed of, or subjected to further
processing.
[0013] In a particular form, the industrial process is a
thermochemical Cu--Cl cycle for producing hydrogen gas from water
decomposition which comprises supplying heat to the non-pure water
from molten CuCl to produce high temperature steam for the
production of hydrogen gas, with the impurities in the water being
reduced to a precipitate, a slurry or a concentrated aqueous
solution, which can be disposed of, or subjected to further
processing.
[0014] When the industrial process is a thermochemical Cu--Cl cycle
for producing hydrogen gas from water decomposition, it may
comprise the generation of steam from non-pure water using a
two-stage steam generation loop which comprises two heat exchanges,
a first-stage heat exchange comprising transferring heat from
molten CuCl to a thermal fluid circulating to a second-stage heat
exchange, and back again to the first-stage heat exchange; heat
from the thermal fluid being transferred to non-pure water in the
second-stage heat exchange to produce high temperature steam from
which hydrogen gas is produced, and impurities in the water are
reduced to a precipitate, a slurry or a concentrated aqueous
solution, which can be disposed of, or subjected to further
processing.
[0015] There is also disclosed a device for use in a high
temperature industrial process where heat recovery is required and
high temperature steam is produced which comprises using a tube and
shell heat exchanger, the tube is arranged to receive a high
temperature molten or gaseous material obtained from the high
temperature industrial process and the shell is arranged to receive
non-pure water to which heat is transferred from the high
temperature molten or gaseous material in the tube, which then
generates high temperature steam from the non-pure water, with the
impurities in the non-pure water being reduced to a precipitate, a
slurry or a concentrated aqueous solution, which can be disposed
of, or subjected to further processing.
[0016] In another form, the device is for use in a high temperature
industrial process where heat recovery is desired and high
temperature steam is produced, and comprises a two-stage steam
generation loop which comprises two heat exchangers, each having a
central tube and surrounding shell, the first-stage heat exchanger
arranged for high temperature molten or gaseous material to pass
through its central tube and the surrounding shell is arranged to
receive a secondary thermal fluid to circulate in the surrounding
shell to absorb heat from the high temperature molten or gaseous
material, the surrounding shell being in fluid communication with
the shell in the second-stage heat exchanger to permit circulation
of the heated thermal fluid from one shell to the other and back
again to the shell in the first-stage heat exchanger; the central
tube of the second stage heat exchanger arranged to receive
non-pure water which absorbs heat from the thermal fluid to
generate high temperature steam for use in the high temperature
industrial process, and impurities in the water are reduced to a
precipitate, a slurry or a concentrated aqueous solution which can
be disposed of or subjected to further processing.
[0017] When the industrial process is a thermochemical Cu--Cl cycle
for the production of hydrogen from water decomposition and the
molten material is CuCl salt, the high temperature steam is used to
produce hydrogen gas from decomposition of water in the
thermochemical CuCl cycle.
[0018] The molten CuCl may be received in the tube of the heat
exchanger and passes therethrough with the assistance of at least
one of gravity, a push-pull plate or a helical screw.
[0019] The molten CuCl may pass through the tube of the heat
exchanger at a rate that allows the production of high temperature
steam at a temperature suitable for the production of hydrogen gas
from the decomposition of water in the thermochemical CuCl cycle.
The tube wall may be treated with lubricant to assist passage of
molten CuCl through the tube of the heat exchanger, in at least one
of the following ways: in advance of the device being used, on a
periodic basis and on a continuous basis during use of the
device.
[0020] The shell walls may be washed with water or water containing
cleaners or both to remove any adhered impurities that foul the
apparatus, the washing taking place either when the device is in
use or when the device is not in use.
[0021] Finally, a helical screw is best used as it not only assists
the passage of molten CuCl through the tube, but also facilitates
passage as the salt passes from a molten state to a solid state, as
well as making the heat transfer from the molten CuCl to the
non-pure water most efficient.
[0022] A unique characteristic of the process and device disclosed
herein is that non-pure water is the feedstock used to produce high
purity, high temperature steam. Normally in the Cu--Cl cycle, the
water used is purified prior to use, a step which is costly and
usually eliminates the possibility of using water that contains
impurities or salts. Thermochemical hydrogen production is a
desirable technology for supplying hydrogen and oxygen at lower
cost and reducing environmental impact as compared with existing
technologies, for applications to refining, upgrading, and other
petrochemical plant operations. Water, heat and a minor amount of
electricity are used as inputs to produce hydrogen and oxygen,
without any internal consumption of materials, or external
emissions to the environment. It has now been found that the Cu--Cl
cycle is capable of utilizing non-pure water as feedstock and
various grades of waste heat from nuclear, solar, geothermal, and
petrochemical operations, such as, for example from upgraders,
gasifiers, and engines for equipment may be used to heat the
non-pure water to produce high temperature steam of high purity
with any impurities and salts present in the water being removed as
precipitates, or slurry or both, any valuable material being
recovered.
[0023] The non-pure water may be lake water, brackish water, saline
water, seawater, tailings water, effluent treated water, and used
water from drilling wells. The heat exchanger steam generator may
include a screw extruder, or a pull and push plate extruder, or a
casting extruder, which allows recovery of heat from molten CuCl,
high temperature O.sub.2, high temperature H.sub.2, high
temperature HCl, or other high temperature substances and
exothermic processes of the Cu--Cl cycle to a surrounding water
jacket. In the present application, the use of the heat
exchanger-steam generator is described with respect to the Cu--Cl
cycle and the heat is obtained from molten CuCl salt. A person
skilled in the art can readily adapt the equipment and process to
accommodate different heat sources. The steam generation may
alternatively comprise a two-stage heat exchanger which uses a
secondary thermal fluid other than water. In the first stage, the
secondary thermal fluid flows through the said jacket to extract
the heat from molten salt, and then in the second stage, steam is
generated from the secondary fluid using another heat
exchanger.
[0024] Any indirect contact between molten salt (or high
temperature gas as it occurs in the S--I cycle) and non-fresh water
can generate steam, so the steam generation is not limited to a
thermochemical cycle of hydrogen production, but may be utilized in
other high temperature heat recovery applications such as
industrial furnaces, petrochemical plants emissions, and
incinerators. For the example of the Cu--Cl cycle, the only
feedstock is non-pure water and the products are hydrogen and
oxygen, with no other waste streams flowing, except salts and other
impurities for the case of brackish water. The main energy input to
the Cu--Cl cycle is heat, significantly recycled internally or
low-grade heat. In the Cu--Cl cycle, steam reacts with auxiliary
compounds of Cu and Cl to form intermediates, then hydrogen and
oxygen are released from the intermediates, while the intermediates
are recycled internally without being consumed.
[0025] The non-pure water is directly fed into the Cu--Cl hydrogen
production cycle without using additional heat in the present
apparatus and processes. In comparison, other hydrogen production
cycles must utilize water that is treated and purified in a
separate process, and additional energy must be input for the
treatment and purification. The typical distribution of energy
requirements of the Cu--Cl cycle are shown in the accompanying
drawings.
[0026] When non-pure water is used as the direct feedstock of the
Cu--Cl cycle, the non-pure water is used directly without further
external thermal energy input for the processing. Other processes
of the Cu--Cl cycle still need further external thermal energy
input for the thermochemical hydrogen production.
[0027] Previously, if non-pure water was used, it was preferably
used after additional treatment and purification, but the treatment
and purification requirements set out herein are simpler than for
other traditional steam generators.
[0028] Non-pure water, before it can be used, preferably requires
additional water treatment and/or purification which involves
additional energy before it can be used in a Cu--Cl thermochemical
hydrogen production. The treatment and purification requirements of
the present disclosure are simpler and the additional energy
required thereof is much less than for other traditional steam
generators.
[0029] Cu--Cl cycles are known in the art and may comprise a number
of variants. For example, the Cu--Cl cycle may comprise a five step
process comprising the steps of [0030] 1) reacting Cu and dry HCl
gas at a temperature of about 450.degree. C. to obtain hydrogen gas
and molten CuCl salt; [0031] 2) subjecting solid CuCl and HCl to
electrolysis at a temperature of about 70 to about 90.degree. C. to
obtain Cu and an aqueous slurry containing HCl and CuCl.sub.2;
[0032] 3) heating the aqueous slurry obtained from step 2 at a
temperature of from about 375 to about 450.degree. C. to obtain
solid CuCl.sub.2 and H.sub.2O/HCl vapours; [0033] 4) heating the
solid CuCl.sub.2 and water/steam to obtain solid CuOCuCl.sub.2 and
gaseous HCl; and [0034] 5) heating the solid CuOCuCl.sub.2 obtained
in step 4) at a temperature of from about 500 to about 530.degree.
C. to obtain molten CuCl salt and oxygen gas.
[0035] Alternatively, the Cu--Cl cycle may comprise a four step
process comprising the steps of [0036] 1) reacting Cu and dry HCl
gas at a temperature of about 450.degree. C. to obtain hydrogen gas
and molten CuCl salt; [0037] 2) subjecting solid CuCl and HCl to
electrolysis at a temperature of about 70 to about 90.degree. C. to
obtain Cu and an aqueous slurry containing HCl and CuCl.sub.2;
[0038] 3) heating the aqueous slurry containing HCl and CuCl.sub.2
at a temperature of from about 375 to about 450.degree. C. to
obtain solid CuOCuCl.sub.2 and gaseous HCl; and [0039] 4) heating
the solid CuOCuCl.sub.2 at a temperature of from about 500 to about
530.degree. C. to obtain molten CuCl salt and oxygen gas.
[0040] A further alternative allows the use of a Cu--Cl cycle that
comprises a three step process comprising the steps of [0041] 1)
reacting Cu and dry HCl gas at a temperature of about 450.degree.
C. to obtain hydrogen gas and molten CuCl salt; [0042] 2)
subjecting solid CuCl and HCl to electrolysis at a temperature of
about 70 to about 90.degree. C. to obtain Cu and an aqueous slurry
containing HCl and CuCl.sub.2; [0043] 3) heating the aqueous slurry
containing HCl and CuCl.sub.2 at a temperature of from about 500 to
about 530.degree. C. to obtain molten CuCl salt and oxygen gas.
[0044] A further alternative allows the use of a Cu--Cl cycle that
comprises another three step process as follows: [0045] 1)
subjecting CuCl and HCl aqueous solution at a temperature of about
70 to 90.degree. C. to obtain H2 and an aqueous slurry containing
HCl and CuCl.sub.2; [0046] 2) heating the solid CuCl.sub.2 and
water to obtain solid CuOCuCl.sub.2 and gaseous HCl; [0047] 3)
heating the aqueous slurry containing HCl and CuCl.sub.2 at a
temperature from about 500 to 530.degree. C. to obtain molten CuCl
salt and oxygen gas.
DETAILED DESCRIPTION
BRIEF DESCRIPTION OF THE DRAWINGS
[0048] FIG. 1 illustrates a cross section of a screw extruder heat
exchanger for high temperature steam generation;
[0049] FIG. 1a illustrates the same cross section as shown in FIG.
1, but includes a closed loop whereby a water-steam chamber can be
flushed out and cleaned.
[0050] FIG. 2 illustrates the lower structure of the screw extruder
steam generator shown in FIG. 1, and is a top plan and perspective
view of a section along line 2-2 showing the arrangement of the
screw discharger for the precipitates or slurry or both from the
non-pure water, after the steam has been generated;
[0051] FIG. 3 illustrates a front cross-sectional view of a
pull/push plate in a molten salt heat exchanger for high
temperature steam generation;
[0052] FIG. 4 illustrates a front cross-sectional view of a
two-stage heat exchanger steam generator for high temperature steam
generation using impure water;
[0053] FIG. 5 illustrates a schematic representation of a two-stage
steam generation loop;
[0054] FIG. 6 illustrates the energy requirement distribution of
the Cu--Cl Cycle; and
[0055] FIG. 7 illustrates a simplified flow chart of a typical
Cu--Cl thermochemical cycle for the production of hydrogen gas from
the decomposition of water; and
[0056] FIG. 8 is a schematic representation of the benefits of
using the heat exchanger-steam generator apparatus and process
described herein in petrochemical operations.
STRUCTURE, DESIGN AND OPERATION OF THE HEAT EXCHANGER-STEAM
GENERATOR
[0057] One form of the apparatus of the present description is
illustrated in FIGS. 1 and 2 of the accompanying drawings. A
continuous production mode screw extruder-steam generator for steam
generation of this invention is shown generally at 10 in FIG. 1, it
consists of inner and outer annular tubes, 11 and 12, respectively.
The inner tube 11 contains a rotary screw 14 to agitate and push
molten salt to move downward through a central or core chamber 13,
surrounded by an outer chamber 25, both being formed by the outer
tube 12 and inner tube 11. The inner chamber has an inlet where a
feed 15 of molten CuCl at a temperature of from about 420 to about
900.degree. C., usually about 530.degree. C. is provided to the
inner chamber 13. The base of the reactor has an outlet for removal
of solidified CuCl shown at 24.
[0058] Non-pure water at a temperature ranging from about 0 to
about 100.degree. C., and typically at 20.degree. C. is fed at
inlet 16 into the outer chamber or jacket 25. The chamber 25 also
includes an inlet 19 at which a continuous water stream at a
temperature of about 0 to 100.degree. C., and typically from about
10 to about 40.degree. C., with 20.degree. C. being typical is fed
to chamber 25. Water is sprayed onto the outside wall of the inner
tube 11 to form a water film. When the film is flowing downward,
water accumulates, boils and vaporizes. The water can be introduced
also by a continuous flow stream via inlet 19. An outlet for the
steam is provided at 20 from the outer chamber. The temperature of
the steam generated is in the range of about 100 to about
500.degree. C. and the optimum range is about 300 to about
400.degree. C. The temperature of the molten salt entering the
inside tube is in the range of about 420 to about 900.degree. C.
and the optimum range is about 450 to about 530.degree. C. The
steam pressure can be in the range of about 0 to about 250 bar
(gauge) and the optimum range is about 0 to about 2 bar gauge so
that high temperature steam can be generated. The diameter of inner
tube 11A is in the range of about 5 to about 100 cm and the optimum
range is about 15 to about 45 cm. The space for the flights of the
screw, B is in the range of about 1 to about 10 cm and the optimum
range is about 2 to about 5 cm. The diameter of the screw root, C,
is in the range of about 1 to about 50 cm, and the optimum range is
about 5 to about 20 cm. It is noted that the outside tube could be
other than cylindrical in shape, for example, rectangular or
square. Between the two inlets 16 and 19, and between the inlet 16
and the outlet 20, within the chamber 25, the temperatures achieved
provide boiling water and high temperature steam, respectively.
[0059] The dimensions of the tubes 11 and 12, and the whole unit
are selected to ensure the most efficient heat transfer and the
generation of high temperature steam.
[0060] The molten salt can also be introduced from the top, by
either continuous melt stream or pouring in this form of the
apparatus. To avoid the attachment of the solidified salt onto the
wall of the inner chamber 13 during the downward travel of the
salt, a suitable lubricant such as grease (silicone) can be applied
onto the wall.
[0061] In operation, the process in this apparatus can be conducted
on a continuous basis. The molten salt is introduced into the
chamber 13 of the heat exchanger-steam generator and the water is
introduced as a spray and as a continuous flow stream into the
outer chamber 25. As the molten salt is pushed downwardly through
the central chamber via the turning of screw 14, heat is
transmitted to the water entering the outer chamber 25 and the
height of the apparatus is selected to ensure sufficient heat
transfer to generate high temperature steam from the water. Boiling
water Hb is produced in a lower portion of chamber 25 which rises
upwardly becoming high temperature steam Hs, which is removed via
outlet 20. As steam is formed from the non-pure water, impurities
and salts are deposited in the bottom of the chamber 25. These may
comprise a solid precipitate or slurry or both. Removal of these
materials is managed in a suitable manner known to those skilled in
the art and recovery of any valuable products can be undertaken
using known methods. An extruder 23 can be placed in the outlet
from chamber 25 to assist in removal of the impurities/minerals
etc. The molten CuCl solidifies as the heat is transferred from it
to the water. As the salt cools it solidifies. Removal of the salt
is undertaken in accordance with known methods for removing such
solids from industrial equipment.
[0062] In FIG. 3, there is illustrated an alternative structure for
the heat exchanger-steam generator. The rotary screw of FIG. 1 is
replaced with a push-pull plate arrangement shown generally at 40.
A top plate 41 and a bottom plate 42 are provided in an inner salt
chamber 43. The plates 41 and 42 may have the same diameter X,
which allows the plates to engage interior wall 45 of chamber 43.
The molten salt can be fed through a side inlet 15 and a top inlet
46. Removal of solid salt 21 can be achieved by removing the bottom
plate 42. Outer chamber 44 has the same inlets and outlets found in
the heat exchanger-steam generator shown in FIG. 1. However, in the
arrangement shown here, the process is generally conducted as a
batch or semi-batch process.
[0063] FIG. 4 illustrates a further alternative arrangement for the
heat exchanger-steam generator which employs a casting with a
mould: molten salt steam generator. The structure here is very
similar to the annular tube arrangement shown in FIG. 3. The
difference is that no device is used to assist passage of molten
salt through the central chamber. All other aspects of the
apparatus are the same as found in the apparatus of FIG. 3. To
approach a continuous operation, a surface coating such as a
lubricant, for example grease is usually needed to assist the CuCl
to move downwardly. When the molten CuCl is poured into the heat
exchanger, the lubricant, e.g. grease may be continuously applied,
e.g. by spraying onto the surface of the inside wall of the inner
tube 11, as indicated by element 15A in FIG. 4. Any other known
methods for distributing a lubricant such as grease onto the inside
wall at appropriate locations are suitable for this purpose.
[0064] FIG. 5 shows an alternative arrangement that comprises a
two-stage steam generation loop. Instead of directly generating the
steam by the heat of molten salt, secondary thermal fluids are
utilized to extract the heat from the molten salt, and then the
thermal fluid is allowed to transfer its heat to the non-pure water
to generate steam in a second stage heat exchanger. A big advantage
of using secondary thermal fluid is that the non-pure water can be
introduced to the tube route rather than the shell path so the
precipitates from the water can be more easily removed. Another
advantage is that any corrosion from the non-pure water on the
outside wall of the pipe that confines the molten salt is
eliminated. Typical secondary fluids include thermal oil, high
pressure gases such as nitrogen, helium, argon, and air.
[0065] The illustrated apparatus of FIG. 5 comprises two heat
exchangers 60 and 70, each having a shell 65, 75 and tube 64, 74
design. The heat exchangers 60 and 70 are connected so that the
secondary thermal fluid circulates from shell 65 to shell 75
through conduits 50, 51 and 52. In the first stage heat exchanger
60, molten salt enters tube 64 which may be provided with a
rotating screw 61 for pushing the molten salt through the tube 64.
Screw 61 can be replaced with an alternative device for pushing the
molten salt or no device may be used. Solidified salt exits at 24
and is removed in a suitable manner. Heat from the molten salt is
transferred to the thermal oil in shell 65 which circulates through
conduit 5 to a second stage heat exchanger 70 into shell 75.
Non-pure water is fed to the central tube 70 at inlet 16 and as it
passes through the heat exchanger 70, it picks up heat from the
circulating high temperature thermal oil and turns to super heated
steam, which is removed from outlet 20. Precipitates or slurry or
both collects in tube 74 and can be removed by a suitable device,
such as a rotating screw 71, and any valuable material can be
recovered in conventional ways.
Description of How the Molten Salt is Handled in the Heat
Exchanger
[0066] A portion of a pilot plant was constructed incorporating the
molten salt heat exchanger described herein. Referring to FIG. 1,
one can see how the heat exchanger 10 handles molten salt 15a,
which involves the salt being mixed and the dimensions of the tube
13 in the hear exchanger 10 being selected to ensure this mixing
takes place.
[0067] A feed of molten salt 15 is introduced to the tube 13 and is
then pushed downwardly by the axial pushing force of the flights
13b of the rotary screw 14. During the downward moving of the
molten salt 15, the salt 15 close to the inside wall of chamber 13
is cooled to a lower temperature than the molten salt 15 close to
the screw flights 13b and root 13a. At the same time, heat carried
by the molten salt 15 is transferred through the wall 11 of chamber
13 to the water or steam contained in the annulus (25). Due to the
radial agitating force of the flights 13b, the lower-temperature
molten salt 15 close to the inside wall of chamber 13 is agitated
until it is farther from the wall and closer to the screw root 13a
to mix with a portion of higher temperature molten salt 15. At the
same time, other portions of higher temperature molten salt 15 are
agitated until closer to the inside wall of chamber 13. Some
portions of molten salt 15 may solidify when the salt is agitated
closer to the inside wall of chamber 13 and is then agitated back
to closer to the root 13a to solidify more salt or it is melted
again. Through the mixing generated by the screw flights 13b, the
heat in various locations of the molten salt stream is transferred
to the wall of chamber 13 and hence to the water in the chamber
25.
[0068] During the downward movement of the molten salt 15, the
temperature of the salt becomes lower and lower. When the salt 15
moves near the bottom of chamber 13, all salt 15 has been
solidified. At this time, the rotary screw 14 also serves as a
granulator to avoid forming big chunks of solidified salt.
[0069] To achieve the functions as described above, e.g., the good
mixing and granulating, the dimensions of the screw 14 and chamber
13 and the rotary speed are selected and controlled to be in an
optimal range, which can be determined through routine
experimentation. The channel width B is usually in the range of
1-50 cm and the optimal width is 2-20 cm. The flight width (A-8) is
in the range of 0.2-10 cm and the optimal range is 1-4 cm. The
helix angle Ha may be selected from those in the range of 5-85
degrees and the optimal range is 15-45 degrees. The rotary speed
may be selected to be in the range of 0.5-5000 rpm and the optimal
range is 1-100 rpm. These parameters are based on the pilot design
and in practice can be readily adjusted to ensure maximum heat
transfer and steam production.
Handling of Water Impurities in Non-Pure Water
[0070] Safe operation of the heat exchanger 10 is necessary to
avoid cracking on the inside wall 17 of chamber 13. Cracking can be
avoided by enhancing the thickness of the chamber wall 17 and by
selecting suitable material for the inside wall of the tube 14,
along with regular checks and maintenance.
[0071] When the water is evaporated on the outside wall of chamber
13, impurities will be concentrated in the remaining unevaporated
water which flows downward along the wall. During the downward
movement on the wall, some impurities, such as salts, will
precipitate. The precipitates are entrained by the concentrated
water to accumulate in the chamber 25. Due to the density
difference of water and the precipitates, the precipitates settle
at the bottom of chamber 25. When the quantity of precipitates
exceeds the height of screw discharger 23 after some runtime, the
screw discharger will operate and remove the precipitates to
outside of chamber 25. The runtime depends on the steam generation
rate and scale, and the screw discharger 23 can then accordingly
operate intermittently or continuously.
[0072] To ensure the downward moving of the precipitated impurities
with concentrated water, preferably 1-10% of the water is not
evaporated so that the precipitated impurities can be entrained by
the downward flowing concentrated water on the outside wall of
chamber 13. Multiple water level gauges can be set to monitor the
evaporation extent. The water level gauges could be any known
gauges.
[0073] Referring now to FIG. 1a, after some runtime, for example, 6
months, the outside wall of chamber 14 may be covered by a layer of
precipitated impurities to foul the chamber and affect the
efficient operation of the heat exchanger 10. To remove the
precipitates on the wall, the process is slowed or stopped, and
simultaneously the water flow rate is increased at inlet 16 to a
higher value than normal, and the chamber 13 is filled with water
to reach the water level of inlet 16, and then the water is pumped
out through inlet 19 (now serving as an outlet) by pump 100 back to
inlet 16 to form a closed liquid water loop to dissolve the
precipitates and clean the outside wall of chamber 15. The speed of
the water flow is selected to be in the range of 5-30 m/s. After
cleaning, the closed water loop formed by inlets 16 and 19 is
disconnected, then the water flow rate of inlet 16, is restarted or
the molten salt processing is restarted or the molten salt
processing is speeded up. The connection or disconnection of inlets
16 and 19 is controlled by valve 99. Some cleaning acids, such as,
for example dilute HCl or HNO.sub.3, can also be used as additives
or agents, for the removal of water-insoluble impurities
precipitated on the wall.
[0074] The precipitates removed from chamber 25 may carry water or
be an aqueous slurry. The slurry can be conveyed to a filtration
system to extract water and the extracted water can be reused for
steam generation. The filtration can be conducted using any known
system.
[0075] The impurities do not have to be precipitated, as they can
also be produced in a highly concentrated aqueous solution which
accumulates at the bottom of chamber 25. The screw discharger 23
can remove the highly concentrated water, or the screw discharger
can be replaced by a simple pipe wherein the concentrated water can
be pumped out. In this case an extra loop may be required to
recover the water from the highly concentrated aqueous solution or
disposal of it may be needed.
[0076] The equipment and technology described herein are compatible
with most types of non-pure water and especially suitable for
geographical areas where fresh and high quality water are not as
plentiful as other areas, or where saline and brackish water are
richer than fresh, high quality water, e.g., industrial regions for
oil sands extraction and upgrading where the use of fresh and high
quality water is strictly limited and distributed.
[0077] Brackish water is water that has more salinity than fresh
water, but not as much as seawater. It may result from mixing of
seawater with fresh water, as in estuaries, or it may occur in
brackish fossil aquifers. Certain human activities can produce
brackish water, in particular certain civil engineering projects
such as dikes and the flooding of coastal marshland to produce
brackish water pools for freshwater prawn farming. Brackish water
is also the primary waste product of the salinity gradient power
process. Because brackish water is hostile to the growth of most
terrestrial plant species, without appropriate management it is
damaging to the environment. Technically, brackish water contains
between 0.5 and 30 grams of salt per litre--more often expressed as
0.5 to 30 parts per thousand (ppt or %.sub.o).
[0078] Pure water is a non-conductive substance that is toxic to
life, and corrosive of most metals. Impure water is water that has
impurities, such as salts, hardness, metal ions, and so on.
[0079] There are benefits to using the present technology in
conjunction with petrochemical processes and these are illustrated
in FIG. 8. Non-pure water, e.g. brackish water, can be used to
produce hydrogen that can be used for operations, such as oil sands
upgrading, refineries, enrichment of concentration of hydrogen in
syngas, among others. Also, oxygen can be used for gasification of
upgrading residuals or coal, improving combustion, reducing the use
of air heating, and lowering NOx emissions. This technology is
capable of using non-pure water to produce hydrogen and oxygen for
upstream and downstream units of petrochemical plant
operations.
[0080] FIG. 6 illustrates schematically the energy inputs and
outputs for a typical CuCl Cycle derived from incorporating the
present technology and equipment, which are considered to be
significant.
[0081] FIG. 7 is a simplified representation of a prior art Cu--Cl
Cycle, which is described in more detail in the previously
referenced US Patent Publication No. 2010/012987. Reference may be
had to the specific parts of this patent application which describe
the contents of FIG. 7 in detail, where it appears as FIG. 5. In
FIG. 7, an input of water is included. This represents an example
of how the present technology could be combined with the Cu--Cl
cycle.
[0082] The materials used to construct the apparatus of the present
technology may be selected in accordance with the operating
parameters of the equipment. The selection is within the common
knowledge of a person skilled in the art.
[0083] The above description is meant to be exemplary only, and one
skilled in the art will recognize that changes may be made to the
embodiments described without departing from the scope of the
invention disclosed. Modifications which fall within the scope of
the present invention will be apparent to those skilled in the art,
in light of a review of this disclosure, and such modifications are
intended to fall within the appended claims.
* * * * *