U.S. patent application number 12/435488 was filed with the patent office on 2009-09-03 for electric reaction technology for fuels processing.
This patent application is currently assigned to EGT ENTERPRISES, INC.. Invention is credited to Bernard P. Ennis.
Application Number | 20090220412 12/435488 |
Document ID | / |
Family ID | 38366856 |
Filed Date | 2009-09-03 |
United States Patent
Application |
20090220412 |
Kind Code |
A1 |
Ennis; Bernard P. |
September 3, 2009 |
ELECTRIC REACTION TECHNOLOGY FOR FUELS PROCESSING
Abstract
A method and apparatus for producing hydrogen is disclosed
wherein a hydrocarbon gas is fed into an electric reaction
technology system to decompose the hydrocarbon gas to hydrogen gas
and carbon solids. The electric reaction technology system
comprises one or more heating zones, wherein each heating zone
comprises one or more heating stations and each heating station
comprises one or more heating screens followed by a final
near-equilibrium attainment zone without additional heat input.
After passing the hydrogen gas through the electric reaction
technology system the hydrogen gas and any remaining carbon solids
and hydrocarbon gas are cooled. The hydrogen gas and any remaining
carbon solids and hydrocarbon gas flow through a scrubber, filter,
drier or other phase separation system to remove substantially all
of the carbon, leaving hydrogen product. The electric reaction
technology system can also be used to pyrolyze hydrocarbons.
Inventors: |
Ennis; Bernard P.; (Cedar
Grove, NJ) |
Correspondence
Address: |
SCHNADER HARRISON SEGAL & LEWIS, LLP
1600 MARKET STREET, SUITE 3600
PHILADELPHIA
PA
19103
US
|
Assignee: |
EGT ENTERPRISES, INC.
Cedar Grove
NJ
|
Family ID: |
38366856 |
Appl. No.: |
12/435488 |
Filed: |
May 5, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11674250 |
Feb 13, 2007 |
7563525 |
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12435488 |
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11674250 |
Feb 13, 2007 |
7563525 |
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11674250 |
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60773613 |
Feb 15, 2006 |
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Current U.S.
Class: |
423/650 ;
422/187; 422/199 |
Current CPC
Class: |
C10G 2400/24 20130101;
H01M 8/0612 20130101; H01M 8/04022 20130101; C10G 2300/1044
20130101; C10G 2300/1081 20130101; C01B 3/24 20130101; C10G 9/24
20130101; C10G 2300/1025 20130101; C10G 2300/4081 20130101; Y02E
60/50 20130101; Y02P 20/133 20151101; H01M 2008/1293 20130101; H01M
2008/147 20130101; C10G 2400/20 20130101; Y02E 60/526 20130101;
C01B 2203/0272 20130101; C10G 2300/1059 20130101 |
Class at
Publication: |
423/650 ;
422/199; 422/187 |
International
Class: |
C01B 3/24 20060101
C01B003/24; B01J 7/00 20060101 B01J007/00 |
Claims
1. A hydrogen production system comprising: an electric reaction
technology system having electric resistance heaters having one or
more heating zones, wherein each heating zone comprises two or more
selectably-spaced heating stations in series and each heating
station comprises one or more heating screens through which process
gases can flow, followed by a final near-equilibrium attainment
zone without additional heat input; a selectable heat input into
the heating stations; an inlet into a first of the one or more
heating zones configured for input of a gas from which hydrogen gas
will be formed; a finishing station for cooling and removal of
carbon solids; and an outlet configured for output of the hydrogen
gas.
2. The system of claim 1 further comprising: a heat exchanger
disposed after the heating zones configured to utilize heat from
the electric reaction technology system to heat the incoming
gas.
3. The system of claim 1 further comprising a carbon solid removal
component after each heating zone configured to remove some or all
of the carbon solids.
4. The system of claim 1 further comprising a pre-heater disposed
after the inlet and before the first heating zone.
5. The system of claim 1 further comprising a recycling mechanism
configured to recycle at least a portion of the heated hydrogen gas
and any remaining carbon solids and hydrocarbon gas exiting the
heat exchanger into the hydrocarbon gas flow.
6. The system of claim 5 further comprising a recycle compressor
disposed within the system such that recycled hydrogen passes
through it prior to mixing with the input gas.
7. The system of claim 1 further comprising a wind-generated
electricity source.
8. The system of claim 1 wherein one or more heating stations is
configured to deliver a different heating duty to the system.
9. The system of claim 1 comprising four heating zones.
10. The system of claim 1 comprising four heating stations for at
least one heating zone.
11. The system of claim 1 wherein the electric reaction technology
system is disposed in a substantially vertical position with
respect to the level ground.
12. The system of claim 1 wherein the spacing between heating
stations increases in the gas flow direction.
13. The system of claim 1 wherein the heat duty delivered by each
heating station is substantially equal.
14. The system of claim 1 wherein the heat delivered by each
heating station is substantially constant within each zone.
15. The system of claim 1 wherein the heat duty delivered by each
subsequent zone decreases.
16. The system of claim 1 wherein the heating station spacing
varies continuously after the first zone to maintain substantially
isothermal conditions by controlling reaction rates and
volumes.
17. The system of claim 1 configured so the temperature can be
varied between heating zones.
18. The system of claim 1 comprising a second inlet configured to
introduce a second gas into the first gas stream prior to entering
the first heating zone.
19. A pyrolysis method comprising: feeding a hydrocarbon gas into
an electric reaction technology system having electric resistance
heaters to pyrolyze the hydrocarbon gas to produce cracked gas
products, the electric reaction technology system comprising one or
more heating zones, wherein each heating zone comprises two or more
heating stations in series and each heating station comprises one
or more heating screens through which process gases flow; selecting
heat input into heating stations and spacing between heating
stations to optimize hydrocarbon gas conversion to cracked gas
products; quenching the cracked gas products; and separating the
cracked gas products.
20. The method of claim 19 wherein ethylene is separated from the
cracked products.
21. The method of claim 19 wherein acetylene is separated from the
cracked products.
22. The method of claim 19 wherein propylene is separated from the
cracked gas products.
23. The method of claim 19 wherein, after separation of the cracked
gas products, hydrogen is recycled into the process.
24. The method of claim 19 wherein the hydrocarbon feed gas
comprises one or more hydrocarbons that can be vaporized.
25. The method of claim 19 wherein the hydrocarbon feed gas is
selected from the group consisting of ethane, propane, butane,
naphthas, gas oils and C.sub.2, C.sub.3, C.sub.4, and C.sub.5
hydrocarbons.
26. The method of claim 19 wherein steam is added to the feedstock
before it enters the electric reaction technology system.
27. A pyrolysis system producing cracked gas products comprising:
an electric reaction technology system having electric resistance
heaters having one or more heating zones, wherein each heating zone
comprises two or more selectably-spaced heating stations in series
and each heating station comprises one or more heating screens
through which process gases can flow; a selectable heat input into
the heating stations; an inlet into a first of the one or more
heating zones configured for input of a gas from which cracked gas
products will be formed; a finishing station for cooling and
removal of carbon solids; and an outlet configured for output of
the cracked gas products.
28. The system of claim 27 further comprising: a heat exchanger
disposed after the heating zones configured to utilize heat from
the electric reaction technology system to heat the incoming
gas.
29. The system of claim 27 further comprising a pre-heater disposed
after the inlet and before the first heating zone.
30. The system of claim 27 further comprising a recycling mechanism
configured to recycle at least a portion of the heated cracked gas
products exiting the heat exchanger into the hydrocarbon gas
flow.
31. The system of claim 29 further comprising a recycle compressor
disposed within the system such that at least some of the recycled
cracked gas products pass through it prior to mixing with the input
gas.
32. The system of claim 27 further comprising a wind-generated
electricity source.
33. The system of claim 27 wherein one or more heating stations is
configured to deliver a different heating duty to the system.
34. The system of claim 27 comprising four heating zones.
35. The system of claim 27 comprising four heating stations for at
least one heating zone.
36. The system of claim 27 wherein the electric reaction technology
system is disposed in a substantially vertical position with
respect to the level ground.
37. The system of claim 27 wherein the spacing between heating
stations increases in the gas flow direction.
38. The system of claim 27 wherein the heat duty delivered by each
heating station is substantially equal.
39. The system of claim 27 wherein the heat delivered by each
heating station is substantially constant within each zone.
40. The system of claim 27 wherein the heat duty delivered by each
subsequent zone decreases.
41. The system of claim 27 wherein the heating station spacing
varies continuously after the first zone to maintain substantially
isothermal conditions by controlling reaction rates and
volumes.
42. The system of claim 27 configured so the temperature can be
varied between heating zones.
43. The system of claim 27 comprising a second inlet configured to
introduce a second gas into the first gas stream prior to entering
the first heating zone.
Description
[0001] This application is a divisional application and
continuation application of U.S. patent application Ser. No.
11/674,250, having a filing date of Feb. 13, 2007, and entitled
"Electric Reaction Technology for Fuels Processing," which claims
priority to U.S. provisional application having Ser. No.
60/773,613, having a filing date of Feb. 15, 2006, entitled
Electric Reaction Technology for Pollution-Free Fuels
Decarbonization.
BACKGROUND OF THE INVENTION
[0002] Carbon dioxide is produced when burning any hydrocarbon
fuel. Additional carbon dioxide is produced by the chemical
industry when hydrocarbons are used as feedstocks for catalytic
steam reforming, partial oxidation and water gas shift reaction
processes to manufacture hydrogen-containing synthesis gas. Little
has changed in the last 50 years and almost all this carbon dioxide
finds its way into the atmosphere. In recent years, carbon dioxide
has been identified as a contributor to global climate change.
Governments and corporations have proposed many methods to reduce
or manage atmospheric carbon dioxide emissions. Furthermore, major
efforts have been mounted to produce hydrogen more economically,
since it burns cleanly, producing only water (as steam) and heat as
combustion products. All approaches to move toward environmentally
friendly fuels entail great complexity and expense.
[0003] The only way to completely eliminate the production of
carbon dioxide when combusting hydrocarbons would be to: [0004] 1.
Apply heat to hydrocarbons to cause decomposition to elemental
carbon and molecular hydrogen; [0005] 2. Separate the hydrogen and
carbon; and [0006] 3. Either burn the hydrogen with air or oxygen
forming high temperature steam as a useful source of heat or
electrochemically convert the hydrogen into water and electricity
in a fuel cell.
[0007] In such processes, the heating value of carbon combustion
would be unrealized as useful heat. This loss of carbon heating
value would nominally require twice the fuel to produce a given
amount of hydrogen or process heat. However, carbon solids
recovered in the process could be marketed or stored (sequestered)
much more economically than by `end-of-the-process` capture and
sequestration of carbon dioxide.
[0008] Accordingly, a need exists for a method and apparatus to
produce hydrogen in an efficient manner with limited carbon dioxide
emission.
SUMMARY OF THE INVENTION
[0009] Embodiments of the invention provide a method and apparatus
for producing hydrogen wherein a hydrocarbon gas is fed into an
electric reaction technology system to decompose the hydrocarbon
gas to hydrogen gas and carbon solids. The electric reaction
technology system comprises one or more heating zones, wherein each
heating zone comprises one or more heating stations and each
heating station comprises one or more heating screens. (The term
"screen" as used herein means a meshed wire component.) Preferably,
a final near-equilibrium attainment zone without additional heat
input follows either the complete ERT heating phase or one or more
stages of the ERT heating phase. In an illustrative embodiment of
the invention, the attainment zone comprises a carbon reaction
chamber. Preferably, the temperature of the hydrogen and any
remaining carbon and hydrocarbons leaving the electric reaction
technology system is in the range of about 2000.degree. F. to about
2700.degree. F. After passing the hydrogen gas through the electric
reaction technology system, the hydrogen gas and any remaining
carbon solids and hydrocarbon gas are cooled. The hydrogen gas and
any remaining carbon solids and hydrocarbon gas then flow through a
phase separation system, such as a scrubber, filtration or drying
system for example, to remove substantially all of the carbon,
leaving hydrogen product.
[0010] In an illustrative embodiment of the invention, heat
generated from the electric reaction technology system is used to
heat the incoming hydrocarbon gas feed. Preferably, the hydrocarbon
gas feed is heated by the heat generated from the electric reaction
technology system to a temperature in the range of about
400.degree. F. to about 1200.degree. F. This can be accomplished by
flowing the hydrocarbon gas into a heat exchanger, and flowing the
heated hydrogen gas and any remaining carbon solids and hydrocarbon
gas through the heat exchanger to heat additional incoming
hydrocarbon gas. The hydrocarbon gas flow may also be preheated
prior to feeding it into the electric reaction technology system or
heat exchanger. In an exemplary embodiment of the invention, the
temperature increase of the hydrocarbon gas flow from the
pre-heating step is in the range of about 250.degree. F. to about
600.degree. F.
[0011] In an illustrative embodiment of the invention, the heated
hydrogen gas and carbon solids exiting each heating zone in the
electric reaction technology system flow through a carbon removal
component to remove some or all of the carbon solids.
[0012] The heated hydrogen gas and any remaining carbon solids and
hydrocarbon gas may be passed through a quench system after exiting
the electric reaction technology system and prior to entering the
phase separation system. Water may be added to the hydrogen gas and
any remaining carbon solids and hydrocarbon gas in the phase
separation system to create a slurry containing substantially all
of the carbon.
[0013] In a further embodiment of the invention, at least a portion
of the heated hydrogen gas and any remaining carbon solids and
hydrocarbon gas exiting the heat exchanger is recycled into the
hydrocarbon gas flow. Preferably the ratio of recycled hydrogen to
non-recycled hydrogen is in the range of about 2:1 to about 4:1,
and more preferably in the range of about 2.5:1 to about 3.5:1. The
hydrogen gas that will be recycled is passed through a recycle
compressor to compensate for pressure losses through the system.
Hydrogen gas from the phase separation system may also be recycled
into the hydrocarbon gas flow. This can be done either instead of
recycling hydrogen gas from the heat exchanger or in addition to
it.
[0014] The spacing of screens in the ERT system and the residence
times are important factors in optimizing the process. In a
particular embodiment of the invention, the spacing between heating
screen stations increases in the gas flow direction. In a further
embodiment of the invention, the spacing between heating screen
station varies continuously after the first zone to maintain
substantially isothermal conditions. Illustrative embodiments of
the invention provide residence times that increase for each
heating station; and residence times that decrease with each
heating screen station.
[0015] The heat duty delivered by each heating screen station may
be substantially equal or may vary from station to station. In
further embodiments, the heat duty delivered by each subsequent
zone decreases, or the heat duty delivered by all zones is
constant. Additionally, in an illustrative embodiment of the
invention the heat delivered by each heating screen station is
substantially constant within each zone.
[0016] The temperature may vary between heating zones. In a
particular embodiment of the invention, the difference between the
temperature of the flow entering a heating screen station and the
temperature of the flow exiting the heating station is in the range
of about 125.degree. F. to about 175.degree. F.; in other
embodiments the heating input may cause a temperature rise of
400.degree. F. or more
[0017] The electric reaction technology system can also be used to
pyrolyze hydrocarbons.
DESCRIPTION OF THE DRAWINGS
[0018] The invention is best understood from the following detailed
description when read with the accompanying drawings.
[0019] FIG. 1 depicts a stagewise hydrogen production system
according to an illustrative embodiment of the invention.
[0020] FIG. 2 is a graph showing equilibrium and operating curves
for a stagewise hydrogen production system according to an
illustrative embodiment of the invention.
[0021] FIG. 3 depicts a hydrogen production system having a recycle
configuration according to an illustrative embodiment of the
invention.
[0022] FIG. 4 is a graph showing equilibrium and operating curves
for a hydrogen production system having a recycle configuration
according to an illustrative embodiment of the invention.
[0023] FIG. 5 depicts a single pass hydrogen production system
according to an illustrative embodiment of the invention.
[0024] FIG. 6 is a graph showing equilibrium and operating curves
for a hydrogen production system having a single pass configuration
according to an illustrative embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Disclosed is an Electric Reaction Technology (ERT) process
and apparatus directed to the production of hydrogen and carbon
solids by decomposition of methane or natural gas. The ERT
apparatus may also be used for pyrolysis processes. When used for
the former, the ERT process may also be called a fuel
decarbonization process. The process employs electric resistance
heaters capable of adaptation to the selective decomposition of
hydrocarbons and filtration/separation equipment capable of
effective filtration/separation under very high carbon loading.
[0026] As the source of electricity may be an environmental
concern, such a plant could be situated near an economical and
eco-friendly wind farm to provide the necessary electricity. There
would be little or no resulting carbon dioxide or other greenhouse
gas emissions from either one of these processes, as compared to
conventional fossil fuel technologies.
[0027] Hydrocarbon decomposition, also known as fuels
decarbonization, has been neglected as a potential route for
commercial hydrogen and carbon solids manufacture and as a process
to mitigate global warming. Methane, the largest constituent in
natural gas, is also the hydrocarbon with the highest hydrogen to
carbon ratio. It therefore has the potential to produce relatively
more hydrogen than any other hydrocarbon. Methane decomposition has
simple one-step chemistry; and superior thermodynamics in that the
chemical reaction requires only 11.3 Kcal/mol of hydrogen, the
lowest known process energy consumption per unit of hydrogen
produced.
[0028] Methane Decomposition by Heating: (One Non-Catalytic
Step)
TABLE-US-00001 Methane Decomposition CH.sub.4 .fwdarw. C + 2H.sub.2
Process Energy/Unit of Hydrogen +11.3 Kcal/mol hydrogen
[0029] This compares favorably with methane reforming by steam
comprising a two-step, two-catalyst process that requires 18.8
Kcal/mol of hydrogen.
[0030] Methane Reforming by Steam: (Two Catalytic Process
Steps)
TABLE-US-00002 Steam Reforming CH.sub.4 + H.sub.2O .fwdarw. CO +
3H.sub.2 Water-Gas Shift CO + H.sub.2O .fwdarw. CO.sub.2 + H.sub.2
Overall Reaction CH.sub.4 + 2H.sub.2O.fwdarw. CO.sub.2 + 4H.sub.2
Process Energy/Unit of Hydrogen +18.8 Kcal/mol hydrogen
[0031] The first reaction (steam reforming) is highly endothermic
and the mols of products exceed the mols of reactants, therefore,
the reaction proceeds to completion at high temperature and low
pressure. The second reaction (water-gas shift) is mildly
exothermic and favors low temperature but is unaffected by
pressure. The composition of the products depend upon the process
conditions, including temperature, pressure, and excess steam,
which determine equilibrium, as well as velocity through the
catalyst bed, which determines the approach to equilibrium. All
other proposed processes have far-inferior thermodynamics, e.g.
electrolysis processes require approximately +106 Kcal/mol of
hydrogen.
[0032] Methane decomposition schemes proposed and implemented by
others either have very high capital costs arising from the
complexity of high temperature equipment designs or have failed to
perform reliably at commercial scale. Thus, it is apparent why
industry deploys steam methane reforming for the majority of
`on-purpose` hydrogen production.
[0033] Hydrogen has long been an important gaseous raw material for
the chemical and petroleum industries. Steam methane reformers are
the basis of over 90% of the world's on-purpose hydrogen
production. Presently such plants cost approximately $100 million
to produce 100 mM SCFD of hydrogen. Particular embodiments of the
disclosed methane decomposition plant are much simpler in concept
and would be expected to cost substantially less. Operating margin
analysis for feed and fuel and carbon solids at $4.50/Million Btu
shows that the disclosed process could breakeven with electricity
priced as high as $95.50 per Megawatt-hour. Conversely, with feed
and fuel remaining at $4.50/Million Btu and electricity available
at $40 per Megawatt-hour, hydrogen could be produced at breakeven
for as little as $5.78 per Million Btu.
[0034] Carbon black is used primarily by the tire industry for the
production of vulcanized rubber; however, it is also used as a
black pigment for inks and paints. The worldwide demand for carbon
black is predicted to increase 4% per annum through 2008. With
respect to a hypothetical project to produce 50,000 mtpa of carbon
black, the following estimates apply:
TABLE-US-00003 Natural Gas Feedstock 10.5 million standard cubic
feet per day Electricity Consumption 18.3 megawatts 97.3 mol %
Hydrogen Product 5,575 pounds per hour Specific Electricity 2.91
kWh per kilogram of carbon black; or Consumption 20.8 kWh per
thousand SCF of hydrogen
Advantageously, particular embodiments of the disclosed invention
may provide: [0035] Lower capital cost; [0036] Simplicity of
design, operations and maintenance; and [0037] Margins between
market and breakeven costs for electricity, hydrogen and carbon
black; [0038] Analogous advantages that would apply for production
from other hydrocarbons.
[0039] The basic principle of the ERT process will now be
described. When methane (or natural gas or other hydrocarbons) is
heated above a certain temperature, it will decompose to hydrogen
gas and carbon solids and absorb the heat of reaction as shown in
the chemical equation above. The rate of decomposition increases
with temperature. However, the extent of decomposition will reach
an equilibrium level dependent on the temperature level. After the
electrically heated screens within the ERT heat the gas,
decomposition will follow which will tend to cool down the
gas/carbon mixture. Since the time for heating is very short
relative to the decomposition time, a space is allowed for reaction
to take place after each heating stage. The ERT process is
preferably constructed with multiple stages of heating and reaction
steps.
[0040] Following are illustrative configurations designed with
different design constraints. Each description only highlights the
main differences between the various configurations of the
equipment required for each. The illustrative configurations
discussed herein feature an optional quench cooling of the product
carbon/gas mixture. Several of the configurations feature an
optional pre-heater in order to heat the natural gas feed to a
higher temperature to speed up the reaction, and accordingly the
production of carbon and hydrogen; preheating also serves to
minimize the electrical requirements that provide the heat that
drives the chemical reactions. Due to concerns over the settling
out of carbon particles within the ERT unit cross sectional flow
area and flow rate have been selected to maintain fluid velocity
well within the acceptable safe area of design.
[0041] The illustrative embodiments depicted in FIGS. 1, 3 and 5
show an ERT unit disposed vertically. The unit can also be disposed
horizontally or at an angle to the normal.
[0042] In an illustrative embodiment of the invention, the ERT unit
is set at approximately 200 KW input to the ERT. In a preferred
embodiment, the ERT is a plug flow reactor and consists of four (4)
separate heating zones, each zone containing four (4) screen heater
stations. This will be referred to as the Full Conventional
configuration and will be discussed in more detail below.
[0043] FIG. 1 depicts an illustrative embodiment of the invention
referred to as "Stagewise Configuration". This Stagewise Carbon
Removal configuration features a single ERT unit 102 at its core as
well as several finalizing reaction chambers 104, 106, 108, 110,
112. The ERT unit is a single pass arrangement, meaning that the
products are not recycled back into the process. This configuration
is based upon running the reaction adiabatically while utilizing
the product to heat the fresh natural gas feed 114. A hydrogen
purity of 95.1 mol % is potentially attainable with this particular
design. The main design constraint that was taken into
consideration while creating this configuration dealt with the
temperature of the carbon/gas mix exiting each heating screen
station. The goal was to find a design in which the temperature of
the carbon/gas mix leaving each heating zone maintained
approximately a 50.degree. F. approach to the equilibrium
temperature, meaning that each of the reaction chambers was
designed in such a way that the exit temperature was at least
greater than about 50.degree. F. than the equilibrium temperature
at the corresponding exit concentration of hydrogen. Calculated
data is provided in Table 1 at nominal 300 pounds per square inch
system pressure. This data is common to all the illustrative
embodiments described herein. The methods and systems described
herein are applicable at higher and lower pressures to be selected
for each instance of use by designers skilled in the art.
TABLE-US-00004 TABLE 1 DATA FOR EQUILIBRIUM CURVES Equilibrium Data
50 F Approach Mol Mol Temperature Fraction Temperature Fraction
(.degree. F.) Hydrogen (.degree. F.) Hydrogen 2800 0.98169 2850
0.98169 2700 0.98169 2750 0.98169 2600 0.98169 2650 0.98169 2500
0.98169 2550 0.98169 2400 0.97710 2450 0.97710 2300 0.97098 2350
0.97098 2200 0.96275 2250 0.96275 2100 0.95153 2150 0.95153 2000
0.93614 2050 0.93614 1900 0.91496 1950 0.91496 1800 0.88593 1850
0.88593 1700 0.84638 1750 0.84638 1600 0.79423 1650 0.79423 1500
0.72679 1550 0.72679 1400 0.64405 1450 0.64405 1300 0.54767 1350
0.54767 1200 0.44276 1250 0.44276 1100 0.33940 1150 0.33940 1000
0.23741 1050 0.23741 900 0.15248 950 0.15248 800 0.06995 850
0.06995 700 0.03854 750 0.03854 600 0.01879 650 0.01879 500 0.00789
550 0.00789 400 0.00273 450 0.00273 300 0.00073 350 0.00073 200
0.00013 250 0.00013 100 0.00001 150 0.00001
[0044] The natural gas feed enters a pre-heater 116, preferably at
a temperature of about 90.degree. F. and exits the pre-heater,
preferably at a temperature of about 400.degree. F. The natural gas
feed then passes through a feed/product exchanger 118. This is a
head to tail heater that utilizes the heat of the product
carbon/gas mixture to heat the natural gas feed, preferably to a
temperature of about 1000.degree. F. The natural gas feed proceeds
into the first heating screen station 120 of the ERT unit. A screen
station may include one or more screens. The term "zone" will also
be used herein. A zone includes one or more screen stations and is
characterized by an individual power source. Upon leaving the first
heating zone 120, the carbon/gas mixture has preferably increased
to a temperature over about 2250.degree. F. After passing through
each heating zone 120, 122, 124, 126, 128, the carbon/gas mixture
passes through reaction and carbon removal chambers 104, 106, 108,
110, 112, respectively. These carbon product removal chambers will
allow for easy sampling of the carbon formed throughout the ERT
unit. Each subsequent heating zone gradually heats the remaining
carbon/gas mixture in order to increase the reaction rate, and thus
the rate at which carbon and hydrogen are produced. The flow
through the ERT unit can be said to be once through, meaning that
the products are not recycled back into the system after leaving
the ERT unit. After passing through the fifth heating screen
station 128, the carbon/gas mixture preferably exits the ERT unit
at a temperature of approximately 2250.degree. F. and passes
through final chamber 112 where it auto-cools to about 2160.degree.
F. The carbon/gas mixture then passes through several additional
pieces of equipment, or the finalizing stage 130.
[0045] In this illustrative embodiment, the flow channel of each
ERT unit is about 5 feet in length and is comprised of five heating
zones 120, 122, 124, 126, 128 delivering a total heat input of
about 200 kW. The Stagewise Carbon Removal configuration will
preferably be fabricated in such a way that each individual heating
zone is immediately followed by a large carbon removal chamber 104,
106, 108, 110, 112. Each of the five ERT units preferably consists
of a single heating screen station, each delivering a different
heat duty to the system. Since each ERT zone is a separate unit,
this simplifies electrical design and controls. Immediately
following each ERT unit 120, 122, 124, 126, 128 is a carbon removal
chamber 104, 106, 108, 110, 112 that provides both a reaction
volume and a settling location for the carbon produced. Each
removal chamber is refractory-lined and water-jacketed and features
continuous carbon cooling and removal. Removing the carbon from the
heating duty of the system shortly after it is produced reduces
energy input. Each of the heating zones in the respective ERT units
will deliver varying amounts of heat to the system. Once again,
this value is determined based upon the design constraint.
[0046] The finalizing stage is where the carbon/gas mixture is
cooled and separated. In an illustrative embodiment of the
invention, first, the carbon/gas mixture is cooled as it passes
through a head to tail heat exchanger. The products will exit the
exchanger, preferably at a temperature of about 500.degree. F. Then
the products go through a phase separator 134, such as a Venturi
scrubber, where water 136 is added, thus cooling the products and
creating slurry. The carbon settles on the bottom of the apparatus
and exits as slurry 138. Samples can then be taken before sending
the product carbon slurry on for drying and final carbon product
production. The remaining gas leaving the top of the phase
separation apparatus comprises the hydrogen product.
[0047] Calculated volume flow, heat duty, residence time, reaction
chamber outlet temperature and outlet gas composition are shown in
Table 2 for a five-section Stagewise carbon removal configuration.
The associated equilibrium and operating curves are shown in FIG.
2.
TABLE-US-00005 TABLE 2 STAGEWISE CARBON REMOVAL CONFIGURATION
Volumetric Volumetric Outlet Outlet Mol Volume Flow In Flow Out
Heat Duty Time Temperature Fraction Section (ft.sup.3)
(ft.sup.3/hr) (ft.sup.3/hr) (kW) (sec) (.degree. F.) Hydrogen ERT
Section 1 15.037 4603 8258 83.0 8.418 1436 0.568 2 8.590 6431 8813
51.7 4.057 1662 0.790 3 4.712 7622 8957 35.2 2.046 1882 0.889 4
2.827 8290 8968 21.3 1.180 2048 0.933 5 1.445 8629 8916 11.5 0.593
2160 0.951
There are several potential advantages to the Stagewise Carbon
Removal configuration: [0048] High hydrogen purity can be achieved.
[0049] Carbon is removed after each individual heating screen
station, thus decreasing the required heat inputs to each ERT
unit.
[0050] This particular configuration only consists of five heating
screen stations; this configuration can be expanded to include six
or more heating screen stations. Fewer heating screens can also be
used but will generally result in lower purity hydrogen.
Calculations show 95% hydrogen purity is potentially attainable
with five stations as shown in FIG. 2.
[0051] The next illustrative embodiment is referred to as a
"Recycle Configuration" and is shown in FIG. 3. The Recycle
configuration 300 is based upon recycling a portion of the reactor
effluent back to the feed end of the ERT unit. This will enable the
use of a single heating zone to be operated as the "final stage of
ERT process." A simple ERT design may be used to obtain desired
results. The Recycle configuration consists of an ERT unit 302,
reaction chamber 304, and a recycle system 306. A hydrogen purity
of 95.5 mol % is potentially attainable with this design. The main
design constraint dealt with controlling the temperature of the
carbon/gas mixture exiting each heating screen station.
[0052] Following is a description of a recycle configuration
according to an illustrative embodiment of the invention. The
Recycle configuration features a loop design. The natural gas feed
308 enters the system, preferably at a temperature of about
90.degree. F. and is injected into the recycle stream at the feed
side inlet 312 of a feed/product exchanger 314. The exchanger 314
utilizes the heat of the recycle gas mixture to heat the natural
gas feed and the recycle gas/recycle mix, preferably to a
temperature of about 1000.degree. F. The mixed feed proceeds into
the first heating screen station 316 of the ERT unit. Upon leaving
the first station 316, the carbon/gas mixture has preferably
increased to a temperature over 1600.degree. F. Each subsequent
heating screen station 318, 320, 322 gradually heats the carbon/gas
mixture to a higher temperature in order to increase the reaction
rate. After passing through the fourth heating screen station 322,
the carbon/gas mixture exits the ERT unit 302 at a temperature of
preferably nearly 2700.degree. F. and flows to the reaction chamber
where it auto-cools to about 2200.degree. F.
[0053] In this illustrative embodiment, the ERT unit 302 itself is
12 feet in length and is comprised of four heating screen stations
316, 318, 320, 322, preferably delivering a total heat input of
about 80 kW. The Recycle ERT unit is preferably substantially
vertical to allow the gas flow through the ERT unit 302 to carry
the carbon with it, preventing or minimizing build up of carbon on
the screens or on the walls of the ERT unit 302. The ERT unit 302
preferably has a first heating screen station 316 where preheating
takes place, three additional heating screen stations 318, 320, 322
where the reaction takes place. The primary function of the first
heating screen station 316 is to heat the mixed gas feed in order
to increase the rate of reaction. Minimal amounts of carbon and
hydrogen are produced during this stage due to the slow rate of
reaction. Therefore, the spacing between the first screen station
316 and the second screen station 318 does not need to be very
large, however, due to design constraints, as well as trying to
maximize the hydrogen purity, the spacing between the first and
second screen stations 316, 318 is preferably moderately large.
Once the carbon/gas mixture reaches temperatures over 1500.degree.
F., noticeable amounts of carbon and hydrogen are produced:
consequently, the remaining heating screen stations 318, 320, 322
preferably have larger spacing between them. Preferably, the heat
delivered by each heating screen station does not vary; each
heating screen station in both the pre-heating area and reaction
area ideally delivers 20 kW to the system in this particular
embodiment. By varying the spacing between each heating screen
station throughout the entire ERT unit 302, higher hydrogen purity
will likely be achieved.
[0054] The reaction mix from the ERT 302 unit flows to the reaction
chamber 304. The chamber 304 adds the residence time needed for
high hydrogen purity to be achieved. By the time the gas leaves the
reaction chamber 304, the temperature of the carbon/gas mixture has
preferably dropped to approximately 2200.degree. F. The carbon/gas
mixture then proceeds to go through a splitter (not diagrammed, but
indicated at 324) where the product stream is separated. In an
illustrative embodiment of the invention, approximately 40% of the
products and the mixture is then sent through a quench cooling
system 326 where they are cooled, preferably to about 500.degree.
F. with quench water. The products then go through a phase
separator 328, such as a Venturi scrubber, where the carbon/gas
mixture is cooled further by contacting with a circulating slurry
of water and carbon. Make up water 330 is added to the phase
separation system 328, thus cooling the products and creating
slurry. Other compatible cooling and separation systems, are within
the spirit and scope of the invention. The product carbon settles
on the bottom of the apparatus and exits as slurry at outlet area
332. Samples can then be taken before sending the product carbon
slurry on for drying and final carbon product production. The
remaining `cleaned gas` leaving the top of the phase separation
apparatus substantially carbon-free, containing a mixture of
methane and hydrogen comprises the hydrogen product.
[0055] The remaining 60% of the reaction chamber effluent is the
recycle gas. It passes through the feed/product exchanger 314 where
it is cooled by the feed and recycle mix stream preferably to about
900.degree. F. The huge drop in temperature is due to the fact that
the heat of the product stream is used to heat the feed stream,
which is much cooler (about 200.degree. F.). The recycle mixture is
then passed through an air cooler 334 where it is preferably cooled
to about 200.degree. F. before it passes through a compressor 336,
which compresses the recycle stream to the required feed inlet
pressure. The carbon/gas recycle mixture is then injected with
fresh natural gas after passing through the compressor 336.
[0056] Table 3 shows calculated volumes, heat duties, residence
times, outlet temperatures and compositions for a four-section
Recycle Configuration system. The associated equilibrium and
operating curves are shown in FIG. 4.
TABLE-US-00006 TABLE 3 RECYCLE CONFIGURATION Volumetric Volumetric
Outlet Outlet Mol Volume Flow In Flow Out Heat Duty Time
Temperature Fraction Section (ft.sup.3) (ft.sup.3/hr) (ft.sup.3/hr)
kW (sec) (.degree. F.) Hydrogen ERT Section 1 0.380 4700 4724 20.0
0.291 1600 0.704 2 0.380 4712 4927 20.0 0.284 2014 0.732 3 0.543
4820 5515 20.0 0.379 2240 0.818 4 2.365 5167 6305 20.0 1.484 2198
0.955
[0057] The Recycle configuration has several potential advantages:
[0058] Very high hydrogen purity can be achieved due to the gas
mixture entering the ERT unit at a very high temperature and
already containing hydrogen. The finishing reaction chamber at the
end of the ERT unit also contributes to the high hydrogen purity
that can potentially be achieved. The large finishing reaction
chamber adds residence time to the system, meaning that the
reaction has a longer time to progress, thus resulting in more
conversion. [0059] The ERT unit itself can be moderately sized and
priced. [0060] Uniform heat delivered by each heating screen
station can help to simplify the electrical controls and thereby
may reduce costs compared to variable heat input configurations.
[0061] The Recycle configuration can operate over a wide range of
desired outlet conditions by varying the recycle ratio and overall
heat input.
[0062] FIG. 5 depicts an illustrative embodiment of a system
referred to as a "Full Conventional Configuration." The Full
Conventional configuration features a single, large ERT unit 502
and the flow or reactant or reaction mix is once through, meaning
that the products are not recycled back into the process. This
configuration is based upon the concept of minimizing reaction
time, and consequently reaction volume, by reaching a high reaction
temperature (over 2500.degree. F.) quickly and running most of the
reaction as close to isothermal conditions as possible. A hydrogen
purity of 97.2 mol % is potentially attainable with this particular
design. The main design constraint dealt with temperature of the
carbon/gas mixture exiting each heating screen station. Preferably,
the range of the temperature of the carbon/gas mixture leaving each
heating screen station is within a small range of the temperature
of the carbon/gas mixture entering that heating screen station
(approximately 150.degree. F.). By maintaining high temperature,
the rate of reaction is maximized and the residence time
minimized.
[0063] The overall system design can be relatively simple. Natural
gas feed 504 enters a small pre-heater 506, preferably at a
temperature of about 90.degree. F. and is preferably heated to a
temperature of about 400.degree. F. The natural gas feed proceeds
into the ERT unit 502. Upon leaving a first screen station within
heating zone 508, the carbon/gas mixture has preferably increased
to a temperature over 1000.degree. F. Each subsequent heating
screen station in zone 508, gradually heats the carbon/gas mixture
to the target isothermal zone temperature range of 2200.degree. F.
to 2500.degree. F. in order to increase the reaction rate, and thus
the rate at which carbon and hydrogen are produced. After passing
through the last heating screen station, the carbon/gas mixture
preferably exits the ERT unit 502 at a temperature of about
2600.degree. F. and flows to the finalizing stage. Appropriate
near-equilibrium attainment time is provided in the ERT outlet and
interconnecting piping.
[0064] The ERT unit 502 is approximately 40 feet in length and
consists of sixteen heating screen stations (not shown) delivering
a total heat input of about 260 kW. The Full Conventional ERT unit
502 is preferably vertical, to allow the gas flowing through the
ERT to pneumatically convey the carbon with it, preventing or
minimizing build up of carbon on the screens or on the walls of the
ERT. The ERT unit preferably has four zones 508, 510, 512, 514 with
four heating screen stations in each (not shown). The primary
function of the first zone 508 is to heat the natural gas feed 504
in order to increase the rate of reaction. Due to the slow reaction
rate at lower temperatures, minimal amounts of carbon and hydrogen
are produced during this stage; therefore, the spacing between each
heating screen station does not need to be very large and does not
need to vary over the course of the zone. Once the carbon/gas
mixture reaches temperatures over 1500.degree. F., the reaction
rate increases and noticeable amounts of carbon and hydrogen are
produced: consequently, the remaining three zones 510, 512, 514
have larger spacing between each heating screen station than does
the first zone. Preferably, the heat delivered by each heating
screen station remains constant within each zone, which allows for
some simplification in the design of the ERT unit 502. The heat
delivered by each heating screen station in the first zone is
preferably 30 kW. The total heat duties delivered by each
subsequent zone preferably decreases. The heat delivered by each
heating screen station in the second zone 510 is 22.5 kW, while the
heat duty delivered in the third zone 512 is 9.5 kW. The heat duty
delivered by each heating screen station in the final zone 514 is
only 2.4 kW. The reaction rates and residence times necessary to
achieve the desired conversion to hydrogen and carbon depend, at
least in part, on the heating screen station spacing. Preferably,
the heating screen station spacing varies continuously after the
first zone 508 in order to maintain near isothermal conditions.
[0065] The finalizing stage is where the carbon/gas mixture is
cooled and separated. First, the carbon/gas mixture passes through
a quench cooling system 516 where quenching water 518 is injected.
The products will exit the quench cooling system, preferably at a
temperature of about 500.degree. F. The products then go through a
phase separator 520, such as a Venturi scrubber, where the
carbon/gas mixture is cooled further by contacting with a
circulating slurry of water and carbon. Make up water 522 is added
to the phase separation system 524, thus cooling the products and
creating slurry. The carbon settles on the bottom of the apparatus
and exits as slurry. Samples can then be taken before sending the
product carbon slurry on for drying and final carbon product
production. The remaining `cleaned gas` leaving the top of the
phase separation apparatus substantially carbon-free, containing a
mixture of methane and hydrogen comprises the hydrogen product.
[0066] Table 4 provides calculated volumes, flow rates, heat
duties, residence times, outlet temperatures and outlet
compositions for a sixteen section, single pass configuration. The
associated equilibrium and operating curves are shown in FIG.
6.
TABLE-US-00007 TABLE 4 FULL CONVENTIONAL CONFIGURATION Volumetric
Volumetric Outlet Outlet Mol Volume Flow In Flow Out Heat Duty Time
Temperature Fraction Section (ft.sup.3) (ft.sup.3/hr) (ft.sup.3/hr)
kW (sec) (.degree. F.) Hydrogen ERT Section 1 0.054 4600 4600 30.0
0.043 1033 0.000 2 0.054 4600 4610 30.0 0.042 1527 0.002 3 0.054
4600 4680 30.0 0.042 1947 0.017 4 0.054 4640 4930 30.0 0.041 2294
0.075 5 0.380 4784 6650 22.5 0.240 2218 0.389 6 0.380 5714 7020
22.5 0.215 2256 0.554 7 0.380 6370 7710 22.5 0.195 2288 0.692 8
0.380 704 8000 22.5 0.315 2408 0.776 9 0.489 7520 8300 9.5 0.223
2372 0.836 10 0.489 7910 8380 9.5 0.216 2411 0.869 11 0.489 8140
8570 9.5 0.211 2462 0.898 12 0.489 8350 8740 9.5 0.206 2524 0.923
13 0.163 8550 8550 2.4 0.069 2564 0.923 14 0.163 8550 8690 2.4
0.068 2569 0.931 15 0.163 8612 8740 2.4 0.068 2578 0.939 16 1.537
8680 9180 2.4 0.620 2411 0.972
[0067] The Full Conventional configuration has several potential
advantages. [0068] Very high hydrogen purity may be achievable with
this particular design. [0069] The kinetics of this particular
system favors both high temperatures and a long residence time in
order to achieve high hydrogen purity. [0070] The Full Conventional
configuration can use near isothermal high temperatures to minimize
residence time. [0071] A minimal amount of equipment is required
for particular embodiments of this configuration. [0072] The quench
cooling system that is used to cool the carbon/gas product is
relatively inexpensive in comparison to a more complex and costly
recycle system. [0073] Embodiments of this particular configuration
may be highly efficient in terms of energy input per amount of
product produced for a full-scale industrial process.
[0074] The invention may be embodied in a variety of ways, for
example, a system, method, device, etc.
[0075] The high-level heat energy capable of being produced by
embodiments of the invention can be integrated into other
electrical or chemical processes. Accordingly, the invention is not
limited to the uses described above. As an example, the effluent
can be used as a heat source for a solid oxide fuel cell.
[0076] Still further, the carbon produced can be used for various
applications. For example, it can be used for molten carbonate fuel
cells (MCFC). MCFCs use an electrolyte composed of a molten
carbonate salt formed by mixing carbon or a carbon precursor with a
salt.
[0077] As noted above, the ERT apparatus can be used for pyrolysis
of hydrocarbons, such as ethane, propane, butane, naphtha, or any
hydrocarbon feedstock that can be vaporized. In an illustrative
example, an ERT apparatus analogous to that depicted in FIG. 5 is
used to pyrolyze hydrocarbon gas. The hydrocarbon feedstock is
preferably preheated to approximately 400.degree. F. and then is
fed through the ERT system. The heat produced by the ERT system
pyrolyzes the hydrocarbon feedstock. The pyrolyzed gas is then
passed through a quenching system, preferably immediately after
exiting the ERT apparatus. The resulting cracked gas products then
undergo separation using conventional separation methods. Hydrogen,
methane, and various C.sub.2, C.sub.3, C.sub.4, C.sub.5 and heavier
components can be separated and heat recovered. The separated
hydrogen can be recycled in the system. In a preferred embodiment,
the pyrolysis system is designed for lesser pressure and lesser
residence times than the systems used for decarbonization and the
quenching of the gases exiting the ERT is designed for minimum
residence time to stop free-radical chemical reactions rather than
to allow additional time for the gases to approach equilibrium as
in the decarbonization systems. Further, the gas processing
time-temperature relationship can be managed in pyrolysis modes to
optimize economically the cracked gas product spectrum. In
pyrolysis operations, steam may be added to the feedstock as it
serves to reduce hydrocarbon partial pressure thereby enhancing
yield spectra and it may reduce any tendency for carbon formation.
A minimal amount of carbon monoxide and carbon dioxide will form
but the short residence time will tend to preclude much steam
reforming of the hydrocarbon feedstock.
[0078] An illustrative ERT apparatus is approximately six feet
long, having approximately sixteen screens, each separated by
approximately four inches.
[0079] While the invention has been described by illustrative
embodiments, additional advantages and modifications will occur to
those skilled in the art. Therefore, the invention in its broader
aspects is not limited to specific details shown and described
herein. Modifications, for example, to particular pressure and
temperatures used; number, size and configurations of screens and
ERT units; and types of cooling, phase separation, scrubbing,
filtration, and drying systems used may be made without departing
from the spirit and scope of the invention. Accordingly, it is
intended that the invention not be limited to the specific
illustrative embodiments, but be interpreted within the full spirit
and scope of the described inventions it equivalents. It is further
noted that the description of each of the three illustrative
configurations, are themselves illustrative embodiments of the
particular configuration.
* * * * *