CA1093822A - Treatment of coke oven gas - Google Patents
Treatment of coke oven gasInfo
- Publication number
- CA1093822A CA1093822A CA258,395A CA258395A CA1093822A CA 1093822 A CA1093822 A CA 1093822A CA 258395 A CA258395 A CA 258395A CA 1093822 A CA1093822 A CA 1093822A
- Authority
- CA
- Canada
- Prior art keywords
- gas
- carbon
- coke oven
- steam
- gas stream
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
- C10K3/00—Modifying the chemical composition of combustible gases containing carbon monoxide to produce an improved fuel, e.g. one of different calorific value, which may be free from carbon monoxide
- C10K3/02—Modifying the chemical composition of combustible gases containing carbon monoxide to produce an improved fuel, e.g. one of different calorific value, which may be free from carbon monoxide by catalytic treatment
- C10K3/04—Modifying the chemical composition of combustible gases containing carbon monoxide to produce an improved fuel, e.g. one of different calorific value, which may be free from carbon monoxide by catalytic treatment reducing the carbon monoxide content, e.g. water-gas shift [WGS]
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B13/00—Making spongy iron or liquid steel, by direct processes
- C21B13/0073—Selection or treatment of the reducing gases
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
- C21B2100/20—Increasing the gas reduction potential of recycled exhaust gases
- C21B2100/22—Increasing the gas reduction potential of recycled exhaust gases by reforming
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
- C21B2100/60—Process control or energy utilisation in the manufacture of iron or steel
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21B—MANUFACTURE OF IRON OR STEEL
- C21B2100/00—Handling of exhaust gases produced during the manufacture of iron or steel
- C21B2100/60—Process control or energy utilisation in the manufacture of iron or steel
- C21B2100/66—Heat exchange
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/10—Reduction of greenhouse gas [GHG] emissions
- Y02P10/134—Reduction of greenhouse gas [GHG] emissions by avoiding CO2, e.g. using hydrogen
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/10—Reduction of greenhouse gas [GHG] emissions
- Y02P10/143—Reduction of greenhouse gas [GHG] emissions of methane [CH4]
Abstract
TREATMENT OF COKE OVEN GAS
ABSTRACT OF THE DISCLOSURE
Coke oven gas does not find ready uses but is available in large quantities. It could be converted by steam reforming to a useful reducing gas, for example to reduce ferric oxide to iron, if carbon deposition during the steam reforming could be reduced. According to the invention this is achieved by reducing the carbon monoxide content of the coke oven gas either by converting carbon oxides to methane or by converting carbon monoxide to carbon-dioxide.
ABSTRACT OF THE DISCLOSURE
Coke oven gas does not find ready uses but is available in large quantities. It could be converted by steam reforming to a useful reducing gas, for example to reduce ferric oxide to iron, if carbon deposition during the steam reforming could be reduced. According to the invention this is achieved by reducing the carbon monoxide content of the coke oven gas either by converting carbon oxides to methane or by converting carbon monoxide to carbon-dioxide.
Description
3~32~
TREATMENT OF COKE OVEN GAS
This invention relates to the treatment of coke oven gases and in particular to reducing the propensity to carbon formation of such gases.
BACKGROUND OF THE INVENTION
-Coke oven gas has been used in the United Kingdom and in Europe as a town gas~ The gas is generally produced by heating rough coal to a temperature in the range 1000 to 1200C
to yield the coke oven gas together with coke. The ~as is sub-jected to several stages of cooling and purification to remove ;
impurities such as tar, naphthalene, ammonia and sulphur and the resulting gas is stable and easily transportable. Coke oven gases normally have a composition within the Eollowing ranges:
H2 ~---- 51 to 56%~
CO ......................................... 5 to 10%, C2 ~ ....................................... 2 to 5%, CH4 ....................................... 25 to 30%, ~ ;
C2H4 ........................................ 2 to 3%, N2 ~ 5 to 10%,
TREATMENT OF COKE OVEN GAS
This invention relates to the treatment of coke oven gases and in particular to reducing the propensity to carbon formation of such gases.
BACKGROUND OF THE INVENTION
-Coke oven gas has been used in the United Kingdom and in Europe as a town gas~ The gas is generally produced by heating rough coal to a temperature in the range 1000 to 1200C
to yield the coke oven gas together with coke. The ~as is sub-jected to several stages of cooling and purification to remove ;
impurities such as tar, naphthalene, ammonia and sulphur and the resulting gas is stable and easily transportable. Coke oven gases normally have a composition within the Eollowing ranges:
H2 ~---- 51 to 56%~
CO ......................................... 5 to 10%, C2 ~ ....................................... 2 to 5%, CH4 ....................................... 25 to 30%, ~ ;
C2H4 ........................................ 2 to 3%, N2 ~ 5 to 10%,
2 ~ ~ to 2.0%.
The extension of the use of natural gas has led to the gradual elimination of coke oven gas from domestic use.
Large volumes of coke oven gas are still produced, however, as a by~produc-t in the preparation of metallurgical coke. This gas has found few convenient outlets.
A recent development of a direct reduction process for the production of substitute scrap for electric arc furnaces has provided a possible opening for coke oven gas as a source of reducing gas. In this process a reducing gas is reacted with ferric oxide in a shaft furnace at a temperature in the range 500 to 900C to produce iron. The iron ln the form o-E
pellets may then be used in electric arc furnaces.
s~Q'~
",~
~ : ' ' .' . ' ~ 3~Z~
In the preparation of a suitable reducing gas, coke oven gas i.s preheated to a temperature in the range 400 to 530C
and .introduced into a steam reformer ~here it reacts with steam in the presence of a catalyst such as nickel on a refractory support, The hydrocarbons in the coke oven gas are converted to hydrogen and carbon dioxide and -the carbon monoxide to carbon dioxide. The disadvantage with this process however is that the preheating performed by conventional heaters is liable ~.
to cause carbon formation in accordance with the Boudouard a reaction:
2C0.~...._. _..:..> C + C02 since the equilibrium favours carbon formation at this .
temperature ranye. This carbon formation is highly undesirable.
It is an object of the present invention to treat coke oven gas to reduce this formation of carbon.
BRIEE' SUMMARY OF THE INVENTION ~
Therefore according to the invention there is ~:
provided a method of preparing a reducing gas suitable for use in the direct reduction of ferric oxide from a source gas stream, comprising from 5 to 12% by volume of carbon monoxide, 1.8 to 7% by volume of carbon dioxide and 50 to 65% by volume of hydrogen, in whi.ch the gas stream is treated to reduce its carbon monoxide content therein hy a process selected from (l) passing the gas stream at an initial temperature of 250 to 375C and a-t elevated pressure over a catalyst to convert car-bon oxides to methane, and (2) mixing the gas stream with steam and passing the mixture at an initial temperature of 200 to 270C over a low temperature shift catalyst to conver-t the carbon monoxide to carbon dioxide, and thereaEter subjecting the resulting gas to steam reforming in the presence of a cata-lyst to give the desired reducing gas.
--2~
~Jl The resulting gas has a low carbon formation propensity when subjected to the steam reforming step. Thus the gas may be reformed in a conventional steam reformer to produce a reducïng gas without undue carbon formation.
In one embodiment of the invention the carbon oxides in the coke oven gas are reacted with the hydrogen in the gas to form methane and water in the presence of a catalyst such as nickel on a refractory support. Suitable catalysts are well known in the art and are commercially available, for example, from Imperial Chemical Industries Limited or from C.C.E. The methanation reaction is favaured by a low temperature in the range 250 to 375C and elevated pressure, although the pressure effect is not very pronounced. The reaction however, is exothermic and the temperature rise must be moderated, for example, by inclusion of a relatively inert component. Generally it has been found that the total temperature rise for a single reactor should be limited to about 200C.
A reducing gas prepared from coke oven gas should have a reducing ratio defined at (H2 + C0)/(H20-~ C02) equal to about 9.0 if the gas is to be used for direct re-duction of iron ore. This means that in a steam reEormer for converting coke oven gas that the steam to hydrocarbon molar ratio should be in the range of 1.2 to 1.5. It is therefore convenient to use steam as an inert component to modify the temperature of the methanation reaction in the process of the invention since the resulting gaseous product may then be passed directly for steam reforming.
The extension of the use of natural gas has led to the gradual elimination of coke oven gas from domestic use.
Large volumes of coke oven gas are still produced, however, as a by~produc-t in the preparation of metallurgical coke. This gas has found few convenient outlets.
A recent development of a direct reduction process for the production of substitute scrap for electric arc furnaces has provided a possible opening for coke oven gas as a source of reducing gas. In this process a reducing gas is reacted with ferric oxide in a shaft furnace at a temperature in the range 500 to 900C to produce iron. The iron ln the form o-E
pellets may then be used in electric arc furnaces.
s~Q'~
",~
~ : ' ' .' . ' ~ 3~Z~
In the preparation of a suitable reducing gas, coke oven gas i.s preheated to a temperature in the range 400 to 530C
and .introduced into a steam reformer ~here it reacts with steam in the presence of a catalyst such as nickel on a refractory support, The hydrocarbons in the coke oven gas are converted to hydrogen and carbon dioxide and -the carbon monoxide to carbon dioxide. The disadvantage with this process however is that the preheating performed by conventional heaters is liable ~.
to cause carbon formation in accordance with the Boudouard a reaction:
2C0.~...._. _..:..> C + C02 since the equilibrium favours carbon formation at this .
temperature ranye. This carbon formation is highly undesirable.
It is an object of the present invention to treat coke oven gas to reduce this formation of carbon.
BRIEE' SUMMARY OF THE INVENTION ~
Therefore according to the invention there is ~:
provided a method of preparing a reducing gas suitable for use in the direct reduction of ferric oxide from a source gas stream, comprising from 5 to 12% by volume of carbon monoxide, 1.8 to 7% by volume of carbon dioxide and 50 to 65% by volume of hydrogen, in whi.ch the gas stream is treated to reduce its carbon monoxide content therein hy a process selected from (l) passing the gas stream at an initial temperature of 250 to 375C and a-t elevated pressure over a catalyst to convert car-bon oxides to methane, and (2) mixing the gas stream with steam and passing the mixture at an initial temperature of 200 to 270C over a low temperature shift catalyst to conver-t the carbon monoxide to carbon dioxide, and thereaEter subjecting the resulting gas to steam reforming in the presence of a cata-lyst to give the desired reducing gas.
--2~
~Jl The resulting gas has a low carbon formation propensity when subjected to the steam reforming step. Thus the gas may be reformed in a conventional steam reformer to produce a reducïng gas without undue carbon formation.
In one embodiment of the invention the carbon oxides in the coke oven gas are reacted with the hydrogen in the gas to form methane and water in the presence of a catalyst such as nickel on a refractory support. Suitable catalysts are well known in the art and are commercially available, for example, from Imperial Chemical Industries Limited or from C.C.E. The methanation reaction is favaured by a low temperature in the range 250 to 375C and elevated pressure, although the pressure effect is not very pronounced. The reaction however, is exothermic and the temperature rise must be moderated, for example, by inclusion of a relatively inert component. Generally it has been found that the total temperature rise for a single reactor should be limited to about 200C.
A reducing gas prepared from coke oven gas should have a reducing ratio defined at (H2 + C0)/(H20-~ C02) equal to about 9.0 if the gas is to be used for direct re-duction of iron ore. This means that in a steam reEormer for converting coke oven gas that the steam to hydrocarbon molar ratio should be in the range of 1.2 to 1.5. It is therefore convenient to use steam as an inert component to modify the temperature of the methanation reaction in the process of the invention since the resulting gaseous product may then be passed directly for steam reforming.
-3-~382~
In a preferred embodiment o-F the invention coke oven gas and steam are passed through a reactor having a plurality of react;on zones containing the catalyst in such a way that a portion of the coke oven gas to be reformed is mixed with at least a major portion oE the steam required for steam reforming and this mixture is passed through the firs-t reaction zone of the reac-tor. The mixture leaving the first reaction zone is mixed with a cold second portion of coke oven gas thereby lowering the temperature of the mixture and the gases passed through a second reaction zone. This quenching operation can be repeated several times. The resulting steam/treated coke oven gas mixture may be passed on to a steam reformer for subsequent conversion to a reducing gas with negligible carbon formation.
Other methods of controlling the temperature rise during the methanation reaction include recycling some of the product gas to increase the inert component content in the mixture and utilising the temperature rise to convert water to steam.
In a second method of reducing carbon formation from coke oven gas in accordance with the invention, coke oven gas is mixed with steam and reacted at a temperature in the range 200 to 270C in the presence of a low temperature shift catalyst to convert carbon monoxide to carbon dioxide.
This reaction is also exothermic and similar arrangements to those illustrated above in the conversion of carbon oxides to methane may be used to control the temperature rise. The resulting gaseous product may be used directly in a steam reforming reactor. Suïtable catalysts are similar to the ~, .
methanation catalysts and are commercially available from Imperial Chemical Industries Limited and C.C~E.
The process of the invention is not limi-ted to the treatment of coke oven gas and similar gas streams containing hydrogen and carbon oxides may also be trea-ted. Such gas streams include, for example, those having compositions within the ranges:
5 to 12% by volume carbon monoxide, 2 to 7% by volume of carbon dioxide, and 50 to 65% by volume hydrogen.
The process of the invention is however ideal for coke oven gas treatment and may be incorporated as a stage in the puriflcation and preparation of coke oven gas for use as a reducing gas. Thus suitable purification and processing stages would include in the following order de-tarring, ammonia removal, benzol removal, H2S removal, preheating organic sulphur removal, reduction of carbon monoxide content, preheating and direct reduction by steam reforming.
BRIEF DESCRIP _ON OF THE DRAWINGS
The invention will now be illustrated by the following Examples with reference to the accompanying drawings in which Figures 1, 2 and 3 represent flow diagrams of the reactions in Examples 1, 2 and 3, respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
-Example 1 100 Moles of coke oven gas to be steam reformed with 50.99 moles of steam, which is equivalen-t to a steam to hydro-carbon mole ratio of 1.~ were treated by the methanation process in accordance with the invention.
,~", ~, I
3~Z2 Figure 1 of the accompanying drawlngs represen~s a flow diagram of the system used. It includes a methanation reactor 2 having a nun~er of stages 2a to 2_.
The coke oven gas stream was divided such that one fifth was fed to the methanator reactor 2 at the inlet 4 with the major portion o~ process- steam. The amount of steam fed was 37.6 moles the remaining 13.39 moles required was produced in the methanator reactor and fed in as an additional moderator.
rrhe feed to the first stage 2a was:
moles mole ~ drymole ~ wet CO 1.02 5.1 1.77 H2 12.3 61.5 21~39 C~145.14 25.7 8.94 C2H60.52 2.6 0.90 C2 0.36 1.8 0.63 2 0.10 0.5 0.17 N2 0.56 2.8 0.97 ~;
H2O37.6 65.23.
The inlet temperature was 250C.
The outlet gas composition from the first stage was 2a was:
moles H2 7.6 CH4 6.52 C2H6 0.52 ~-N2 0.56 H2O 39.44.
The outlet temperature was 416C.
~, ~
3~
The gas leaving the first stage 2a of methanation was quenched with a further one fifth of the incoming co]ce oven gas added through an inlet 6 such that the mixture temperature was 319C and the gas composition was:
moles :
CO 1.02 H2 19.90 CH4 11.66 C2H6 1.04 CO2 0.36 2 0~50 :
N2 1.12 H2O 39~44 The gas was fed into a second stage 2b of methanation and the outlet gas from that stage had the following compositions:
moles H2 15.20 CH4 13.04 C2H6 1.04 N2 1.12 H2O 41.38.
The temperature of the gas at the outlet from the second stage 2b was 441C.
The gas leaving the second stage 2a was again quenched with a further one fifth of the feed coke oven gas introduced through inlet 8 and the temperature of the mixture was 362C and its composition was: .
.,,1 ,: ~
2~:
moles CO 1.02 ;.
H2 27.50 ~
CH4 18.18 ::
C2H6 1.56 C2 ~.36 2 0.10 :~
N2 1.68 H2O 41.38.
The gas mixture was fed into the third s-tage 2c of the methanation reactor and the resulting gas left it at 458C
and the gas composl-tion was as follows: -moles H2 22.80 ;
CH4 19.S6 C2H6 1.56 N2 1.68 H2O 43.32.
The gas was then again mixed with a further one fifth 20 of coke oven gas introd~ced through an .inlet 10 and the remaining process steam of 5.73 moles to give a mixture temperature of 371C. The gas was then fed into the fourth stage 2d o:E the methanation reactor to give a product gas of the following composition at 452C:
moles CH4 26.08 C2H6 2.08 .
N2 2.24 ~2 50 99 ~'.3~
This gas was then mixed with the remaining portion of coke oven gas feed passing along a line 11 and the resulting gas had the following composition:
moles mole % wet mole % dry CO 1.02 0.77 1026 H242.70 32O44 52.84 CH431.22 23.69 38.64 C2H62.60 1.97 3.22 C2 0.36 0.27 0.45 2 0.10 0.06 0.12 N2 2.80 2.12 3.47 H2O50.99 38.70 The resulting gas had a low carbon monoxide content and did not produce large carbon deposits when subjected to steam reforming to give a reducing gas.
Example 2 Figure 2 represents a flow diagram of the reaction system used in this Example. This Example describes the use of an isothermal reactor. ' Coke oven feed gas of composition shown below was fed into a multitube reactor 12 in which the tubes are packed with catalyst and the tubes were surrounded by water at its boiling point at a pressure of about 24 ky/cm absolute (220C).
The coke oven gas composition was:
moles CO10.20 ;
H256.20 CH426.20 C2H62.50 C2 3.20 N2 1.10 H2O44.84.
_g_ i i ~
r~
A portion of steam re~uired for the subsecluent steam reforming reaction was also fed into the reactor.
The heat of reaction was suEficient to produce 736 kg of steam at 24 kg/cm absolute.
The gas leaving the reactor had the following composition:
molesmole ~ wet mole % dry H2 11.80 10.05 12.00 CH4 39.60 33.72 72.00 C2H6 2.50 2.13 4.55 N2 1.10 0.94 2.00 ;
H2O 62.44 53.16 and were suitable for being subjected to steam reforming to give a reducing gas with large carbon deposition.
Example 3 This Example illustrates how gas treated by the present invention may be used as an inert COmpQnent to control the reaction temperature.
Figure 3 of the accompanying drawings represents a flow diagram of the system used.
Coke oven gas of composition as in Example 2 was mixed with product gas resulting from the methanation of coke oven gas and passed into a reactor 20. The product gas left the reactor at a temperature of 392C and was passed through at heat exchanger 22 in which it gives up some heat to recycled product gas. After the heat exchanger the product gas was cooled in a cooler 24 and the water content removed in a water separator 26. A portion of the resulting produGt gas~as then recycled via a compressor 28, heat exchanger 22 and heater 30 to provide an inert component to help to moderate the methanation of Eresh ,,.`,~
incoming coke oven gas.
The inlet gas mixture -to the reactor 20 was as follows:
moles CO 10.20 H2 127.00 CH4 263.80 C2H6 85.00 C2 3.20 lO 2 0-50 N2 7~70 ~-H2O 4.92.
The gas was heated to 250C by heat exchange with the product yases leaving the reactor 20. The produc-t gas left the reactor at 392C and had the following composition:
moles H2 82.60 CH4 277.20 C2H6 85.00 N2 7 70 ;
2 22.52.
Example 4 This Example illustrates carbon monoxide conversion to carbon dioxide and hydrogen to give a gas suitable for steam reforming to a reducing gas without significant carbon deposi-tion.
A portion of gas of composition as in Example l was preheated to 227C together with 48.06 moles of steam and was passed through the first stage oE the low temperature catalytic shift reactor.
The lnlet composition was:
~33~
moles CO 2.55 CH4 12.85 C2H6 1.30 2 0.25 N2 1.40 :
H2O 48.06.
The gas at the outlet from the reactor had the following composition at a temperature of 287C.
moles CO 0.15 H232.65 CH412.85 C2H61.30 N2 1.40 H2O46.16.
The yas was quenched with the remaining portion oE the coke oven feed gas and the temperature of the mixture was 207 C
and its composition was~
moles CO 2.70 H263.40 CH425.70 C2~62.60 C2 4.20 2 0.25 N2 2.80 H2O46.16.
The mixture was passed through the second stage of the 'low temperature shift' reactor and composition of the resulting gas a-t a temperature of 237C was:
moles CO 0.30 H265.30 CH425.70 C2H62.60 C2 6.60 N2 2.80 H2O44~26O
.:
3~2 The steam to hydrocarbon carbon ration was 1.43 and the ratio of oxidising components to hydrocarbon carbon i.e. H2O + 0.5 CO2 to carbon, was 1.54. The gas was suitable for steam reforming.
Example_5 Gas of eomposition as in Example 2 was preheated together with steam to 226C and passed through a tubular reaetor, in which the tubes were paeked with the 'low temperature shift' eatalyst and were surrounded by boiling water at approximately 15 kg/em2 absolute.
The gas was of the following composition:
moles CO 10.20 H2 56.20 CH4 26.20 C2H6 2.50 C2 3.20 2 0.50 N2 1.10 H2O 46.00.
The resulting gas has left the.reaetor at 226C and the gas eomposition was:
moles CO 0.30 H~ 65.10 CH4 26.20 C2H6 2.50 C2 13.10 N2 1.10 H2O 37.10.
~3B~
The heat of reaction evapora-ted 148 kg of water at 15 kg/cm2 absolute.
~ he ratio of oxidising components to hydrocarbon ~arbon tlle resulting g~s was 1~4 the gas was suitable for steam reforming.
A latitude of modification,change and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use oE other features. Accordingly it is appropriate that the appended claims be construed broadly and in a manner consistent wi-th the spirit and scope of the invention herein.
In a preferred embodiment o-F the invention coke oven gas and steam are passed through a reactor having a plurality of react;on zones containing the catalyst in such a way that a portion of the coke oven gas to be reformed is mixed with at least a major portion oE the steam required for steam reforming and this mixture is passed through the firs-t reaction zone of the reac-tor. The mixture leaving the first reaction zone is mixed with a cold second portion of coke oven gas thereby lowering the temperature of the mixture and the gases passed through a second reaction zone. This quenching operation can be repeated several times. The resulting steam/treated coke oven gas mixture may be passed on to a steam reformer for subsequent conversion to a reducing gas with negligible carbon formation.
Other methods of controlling the temperature rise during the methanation reaction include recycling some of the product gas to increase the inert component content in the mixture and utilising the temperature rise to convert water to steam.
In a second method of reducing carbon formation from coke oven gas in accordance with the invention, coke oven gas is mixed with steam and reacted at a temperature in the range 200 to 270C in the presence of a low temperature shift catalyst to convert carbon monoxide to carbon dioxide.
This reaction is also exothermic and similar arrangements to those illustrated above in the conversion of carbon oxides to methane may be used to control the temperature rise. The resulting gaseous product may be used directly in a steam reforming reactor. Suïtable catalysts are similar to the ~, .
methanation catalysts and are commercially available from Imperial Chemical Industries Limited and C.C~E.
The process of the invention is not limi-ted to the treatment of coke oven gas and similar gas streams containing hydrogen and carbon oxides may also be trea-ted. Such gas streams include, for example, those having compositions within the ranges:
5 to 12% by volume carbon monoxide, 2 to 7% by volume of carbon dioxide, and 50 to 65% by volume hydrogen.
The process of the invention is however ideal for coke oven gas treatment and may be incorporated as a stage in the puriflcation and preparation of coke oven gas for use as a reducing gas. Thus suitable purification and processing stages would include in the following order de-tarring, ammonia removal, benzol removal, H2S removal, preheating organic sulphur removal, reduction of carbon monoxide content, preheating and direct reduction by steam reforming.
BRIEF DESCRIP _ON OF THE DRAWINGS
The invention will now be illustrated by the following Examples with reference to the accompanying drawings in which Figures 1, 2 and 3 represent flow diagrams of the reactions in Examples 1, 2 and 3, respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
-Example 1 100 Moles of coke oven gas to be steam reformed with 50.99 moles of steam, which is equivalen-t to a steam to hydro-carbon mole ratio of 1.~ were treated by the methanation process in accordance with the invention.
,~", ~, I
3~Z2 Figure 1 of the accompanying drawlngs represen~s a flow diagram of the system used. It includes a methanation reactor 2 having a nun~er of stages 2a to 2_.
The coke oven gas stream was divided such that one fifth was fed to the methanator reactor 2 at the inlet 4 with the major portion o~ process- steam. The amount of steam fed was 37.6 moles the remaining 13.39 moles required was produced in the methanator reactor and fed in as an additional moderator.
rrhe feed to the first stage 2a was:
moles mole ~ drymole ~ wet CO 1.02 5.1 1.77 H2 12.3 61.5 21~39 C~145.14 25.7 8.94 C2H60.52 2.6 0.90 C2 0.36 1.8 0.63 2 0.10 0.5 0.17 N2 0.56 2.8 0.97 ~;
H2O37.6 65.23.
The inlet temperature was 250C.
The outlet gas composition from the first stage was 2a was:
moles H2 7.6 CH4 6.52 C2H6 0.52 ~-N2 0.56 H2O 39.44.
The outlet temperature was 416C.
~, ~
3~
The gas leaving the first stage 2a of methanation was quenched with a further one fifth of the incoming co]ce oven gas added through an inlet 6 such that the mixture temperature was 319C and the gas composition was:
moles :
CO 1.02 H2 19.90 CH4 11.66 C2H6 1.04 CO2 0.36 2 0~50 :
N2 1.12 H2O 39~44 The gas was fed into a second stage 2b of methanation and the outlet gas from that stage had the following compositions:
moles H2 15.20 CH4 13.04 C2H6 1.04 N2 1.12 H2O 41.38.
The temperature of the gas at the outlet from the second stage 2b was 441C.
The gas leaving the second stage 2a was again quenched with a further one fifth of the feed coke oven gas introduced through inlet 8 and the temperature of the mixture was 362C and its composition was: .
.,,1 ,: ~
2~:
moles CO 1.02 ;.
H2 27.50 ~
CH4 18.18 ::
C2H6 1.56 C2 ~.36 2 0.10 :~
N2 1.68 H2O 41.38.
The gas mixture was fed into the third s-tage 2c of the methanation reactor and the resulting gas left it at 458C
and the gas composl-tion was as follows: -moles H2 22.80 ;
CH4 19.S6 C2H6 1.56 N2 1.68 H2O 43.32.
The gas was then again mixed with a further one fifth 20 of coke oven gas introd~ced through an .inlet 10 and the remaining process steam of 5.73 moles to give a mixture temperature of 371C. The gas was then fed into the fourth stage 2d o:E the methanation reactor to give a product gas of the following composition at 452C:
moles CH4 26.08 C2H6 2.08 .
N2 2.24 ~2 50 99 ~'.3~
This gas was then mixed with the remaining portion of coke oven gas feed passing along a line 11 and the resulting gas had the following composition:
moles mole % wet mole % dry CO 1.02 0.77 1026 H242.70 32O44 52.84 CH431.22 23.69 38.64 C2H62.60 1.97 3.22 C2 0.36 0.27 0.45 2 0.10 0.06 0.12 N2 2.80 2.12 3.47 H2O50.99 38.70 The resulting gas had a low carbon monoxide content and did not produce large carbon deposits when subjected to steam reforming to give a reducing gas.
Example 2 Figure 2 represents a flow diagram of the reaction system used in this Example. This Example describes the use of an isothermal reactor. ' Coke oven feed gas of composition shown below was fed into a multitube reactor 12 in which the tubes are packed with catalyst and the tubes were surrounded by water at its boiling point at a pressure of about 24 ky/cm absolute (220C).
The coke oven gas composition was:
moles CO10.20 ;
H256.20 CH426.20 C2H62.50 C2 3.20 N2 1.10 H2O44.84.
_g_ i i ~
r~
A portion of steam re~uired for the subsecluent steam reforming reaction was also fed into the reactor.
The heat of reaction was suEficient to produce 736 kg of steam at 24 kg/cm absolute.
The gas leaving the reactor had the following composition:
molesmole ~ wet mole % dry H2 11.80 10.05 12.00 CH4 39.60 33.72 72.00 C2H6 2.50 2.13 4.55 N2 1.10 0.94 2.00 ;
H2O 62.44 53.16 and were suitable for being subjected to steam reforming to give a reducing gas with large carbon deposition.
Example 3 This Example illustrates how gas treated by the present invention may be used as an inert COmpQnent to control the reaction temperature.
Figure 3 of the accompanying drawings represents a flow diagram of the system used.
Coke oven gas of composition as in Example 2 was mixed with product gas resulting from the methanation of coke oven gas and passed into a reactor 20. The product gas left the reactor at a temperature of 392C and was passed through at heat exchanger 22 in which it gives up some heat to recycled product gas. After the heat exchanger the product gas was cooled in a cooler 24 and the water content removed in a water separator 26. A portion of the resulting produGt gas~as then recycled via a compressor 28, heat exchanger 22 and heater 30 to provide an inert component to help to moderate the methanation of Eresh ,,.`,~
incoming coke oven gas.
The inlet gas mixture -to the reactor 20 was as follows:
moles CO 10.20 H2 127.00 CH4 263.80 C2H6 85.00 C2 3.20 lO 2 0-50 N2 7~70 ~-H2O 4.92.
The gas was heated to 250C by heat exchange with the product yases leaving the reactor 20. The produc-t gas left the reactor at 392C and had the following composition:
moles H2 82.60 CH4 277.20 C2H6 85.00 N2 7 70 ;
2 22.52.
Example 4 This Example illustrates carbon monoxide conversion to carbon dioxide and hydrogen to give a gas suitable for steam reforming to a reducing gas without significant carbon deposi-tion.
A portion of gas of composition as in Example l was preheated to 227C together with 48.06 moles of steam and was passed through the first stage oE the low temperature catalytic shift reactor.
The lnlet composition was:
~33~
moles CO 2.55 CH4 12.85 C2H6 1.30 2 0.25 N2 1.40 :
H2O 48.06.
The gas at the outlet from the reactor had the following composition at a temperature of 287C.
moles CO 0.15 H232.65 CH412.85 C2H61.30 N2 1.40 H2O46.16.
The yas was quenched with the remaining portion oE the coke oven feed gas and the temperature of the mixture was 207 C
and its composition was~
moles CO 2.70 H263.40 CH425.70 C2~62.60 C2 4.20 2 0.25 N2 2.80 H2O46.16.
The mixture was passed through the second stage of the 'low temperature shift' reactor and composition of the resulting gas a-t a temperature of 237C was:
moles CO 0.30 H265.30 CH425.70 C2H62.60 C2 6.60 N2 2.80 H2O44~26O
.:
3~2 The steam to hydrocarbon carbon ration was 1.43 and the ratio of oxidising components to hydrocarbon carbon i.e. H2O + 0.5 CO2 to carbon, was 1.54. The gas was suitable for steam reforming.
Example_5 Gas of eomposition as in Example 2 was preheated together with steam to 226C and passed through a tubular reaetor, in which the tubes were paeked with the 'low temperature shift' eatalyst and were surrounded by boiling water at approximately 15 kg/em2 absolute.
The gas was of the following composition:
moles CO 10.20 H2 56.20 CH4 26.20 C2H6 2.50 C2 3.20 2 0.50 N2 1.10 H2O 46.00.
The resulting gas has left the.reaetor at 226C and the gas eomposition was:
moles CO 0.30 H~ 65.10 CH4 26.20 C2H6 2.50 C2 13.10 N2 1.10 H2O 37.10.
~3B~
The heat of reaction evapora-ted 148 kg of water at 15 kg/cm2 absolute.
~ he ratio of oxidising components to hydrocarbon ~arbon tlle resulting g~s was 1~4 the gas was suitable for steam reforming.
A latitude of modification,change and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use oE other features. Accordingly it is appropriate that the appended claims be construed broadly and in a manner consistent wi-th the spirit and scope of the invention herein.
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of preparing a reducing gas suitable for use in the direct reduction of ferric oxide from a source gas stream, said gas stream comprising:
5 to 12% by volume of carbon monoxide, 1.8 to 7% by volume of carbon dioxide, and 50 to 65% by volume of hydrogen, wherein the gas stream is treated to reduce the content of carbon monoxide therein by a process selected from:
(1) passing the gas stream at an initial temperature of 250° to 375° C. and at elevated pressure over a catalyst to convert carbon oxides to methane; and (2) mixing the gas stream with steam and passing the mixture at an initial temperature of 200° to 270°C. over a low temperatuare shift catalyst to convert the carbon monoxide to carbon dioxide, the resulting gas being subjected to steam reforming in the presence of a catalyst to give the desired reducing gas.
5 to 12% by volume of carbon monoxide, 1.8 to 7% by volume of carbon dioxide, and 50 to 65% by volume of hydrogen, wherein the gas stream is treated to reduce the content of carbon monoxide therein by a process selected from:
(1) passing the gas stream at an initial temperature of 250° to 375° C. and at elevated pressure over a catalyst to convert carbon oxides to methane; and (2) mixing the gas stream with steam and passing the mixture at an initial temperature of 200° to 270°C. over a low temperatuare shift catalyst to convert the carbon monoxide to carbon dioxide, the resulting gas being subjected to steam reforming in the presence of a catalyst to give the desired reducing gas.
2. The method of Claim 1 in which said gas stream is coke oven gas.
3. The method of Claim 1 in which said catalyst comprises nickel supported on a refractory support.
4. The method of Claim 1 further comprising adding an inert gas, inert to the reaction to convert carbon oxides to methane or to convert carbon monoxide to carbon dioxide, to said gas stream to moderate the temperature rise during the conversion of the carbon oxides to methane.
5. The method of Claim 4 in which said inert gas is steam.
6. The method of Claim 5 in which said inert gas is added in an amount to give a steam to hydrocarbon carbon molar ratio of from 1.2 to 1.5.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB36710/75A GB1566698A (en) | 1975-09-05 | 1975-09-05 | Treatment of gases containing hydrogen and carbon monoxide |
| GB36710/75 | 1975-09-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1093822A true CA1093822A (en) | 1981-01-20 |
Family
ID=10390561
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA258,395A Expired CA1093822A (en) | 1975-09-05 | 1976-08-04 | Treatment of coke oven gas |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS5241607A (en) |
| CA (1) | CA1093822A (en) |
| GB (1) | GB1566698A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140083252A1 (en) * | 2011-05-30 | 2014-03-27 | Siemens Vai Metals Technologies Gmbh | Reduction of metal oxides using gas stream containing both hydrocarbon and hydrogen |
| EP3663258A1 (en) * | 2018-12-04 | 2020-06-10 | Hyundai Motor Company | System and method for producing hydrogen using by product gas |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4253867A (en) * | 1979-10-15 | 1981-03-03 | Hylsa, S.A. | Method of using a methane-containing gas for reducing iron ore |
| DE3223702C2 (en) * | 1982-06-25 | 1984-06-28 | M.A.N. Maschinenfabrik Augsburg-Nürnberg AG, 4200 Oberhausen | Process for generating synthesis gas and reactor for carrying out the process |
| CN113845089B (en) * | 2021-08-13 | 2024-03-12 | 中国石油大学(北京) | Method for producing synthesis gas for reduced iron by using coke oven gas |
-
1975
- 1975-09-05 GB GB36710/75A patent/GB1566698A/en not_active Expired
-
1976
- 1976-08-04 CA CA258,395A patent/CA1093822A/en not_active Expired
- 1976-09-03 JP JP51105699A patent/JPS5241607A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140083252A1 (en) * | 2011-05-30 | 2014-03-27 | Siemens Vai Metals Technologies Gmbh | Reduction of metal oxides using gas stream containing both hydrocarbon and hydrogen |
| EP3663258A1 (en) * | 2018-12-04 | 2020-06-10 | Hyundai Motor Company | System and method for producing hydrogen using by product gas |
Also Published As
| Publication number | Publication date |
|---|---|
| GB1566698A (en) | 1980-05-08 |
| JPS5241607A (en) | 1977-03-31 |
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