JP2000233918A - Production of carbon monoxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method of CO capable of increasing the production of CO by converting CO2 usually wasted as a waste gas to CO to recover without necessitating the remarkable remodeling of an existing device and equipment. SOLUTION: In the producing method of CO for recovering CO from a reformed gas 4 produced by reforming a hydrocarbon 1, CO is separated and recovered from the reformed gas 4 by a PSA method, CO2 contained in the off-gas is catalytically reduced with H2 in the presence of a reverse CO shift catalyst at 500-850 deg.C to produce CO and steam, the produced gas is cooled to separate steam as condensed water and CO in the produced gas is separated and recovered by the PSA method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing CO, and more particularly to a method for producing CO from off-gas in a process for producing CO from hydrocarbon reformed gas.
And a method for producing the same.

[0002]

2. Description of the Related Art Carbon monoxide (CO) is useful as plastics such as polycarbonate and polyurethane or as a raw material for acetic acid and the like. If the amount of produced CO can be improved and the amount of emitted CO ₂ can be reduced, it will be an effective technique for suppressing the generation of carbon dioxide (CO ₂ ), a substance causing global warming.

[0003] Conventionally, CO is a hydrocarbon such as naphtha or methane.
To the raw material by steam reforming, etc.
Manufactured by a method of liquefying and separating the reformed gas at low temperature
Was. The reformed gas obtained by reforming hydrocarbons is H_Two, CO, CO
_TwoAnd methane (CH_Four) And is generally equivalent to CO
About half of the CO_TwoIs included. And CO _Two
Is a valuable carbon resource, but is conventionally disposed of as exhaust gas
It had been.

In recent years, CO ₂ contained in the residual gas obtained by separating CO from the reformed gas is recovered and recycled as a reforming raw material to increase the concentration of CO in the reformed gas to separate and purify CO. A method has been proposed for reducing the burden on the raw materials and increasing the utilization efficiency of Carbon in the raw material (JP-A-59-116114, JP-A-63-29720).
No. 9, JP-A-02-124710, etc.).

FIG. 4 shows an apparatus system showing such a prior art.
It is a diagram. In FIG. 4, the device includes a hydrocarbon source.
Steam reformer 41 for reforming and C from reformed gas
And a PSA device 42 for separating and recovering O.
And a hydrocarbon source, such as naphtha 43,
Introduced to Steam Reformer 41 with Team 44
And reformed at 850 ° C. in the presence of a reforming catalyst to form H
_Two, CO_Two, CO, CH _Four, H_TwoIncluding O (steam)
It becomes the reformed gas 45. The reformed gas 45 is cooled by a cooler 46, for example.
For example, it is cooled to 30 ° C.
After being separated, it flows into the PSA unit 42, where CO is
Separated and collected. CO emitted at this time _TwoRich gas
50 is recycled as a reforming raw material, and H_TwoIncluding off
The gas 49 is used, for example, as a fuel for the reformer.
You.

Further, as a method of producing a synthesis gas having a small H ₂ / CO ratio and producing CO from the gas by a cryogenic separation method, reforming of CH ₄ as a raw material gas with CO ₂ has also been proposed. (Japanese Patent Laid-Open No. 63-29
7209). However, these methods do not
_In order to recycle ( ₂₎ to the upstream side of the reformer, it is necessary to design a reformer (reactor), heating furnace, etc. corresponding to the amount including the recycled gas from the beginning with sufficient planning from the beginning. In order to increase CO production in the above facilities, there was a problem that the capacity of the main equipment, the reactor and the heating furnace, was insufficient, and the equipment had to be greatly remodeled, such as the addition of reaction tubes and reactors. .

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and does not require a large-scale modification of existing equipment such as a steam reformer and equipment. It is an object of the present invention to provide a CO production method capable of converting and recovering CO ₂ that has been used and recovering CO as a result, thereby increasing CO production.

[0008]

Means for Solving the Problems To solve the above problems,
Therefore, the present inventor has proposed that PS from reformed gas obtained by reforming hydrocarbons
CO in off-gas from which CO was separated by method A_Twoand
H_TwoThe offgas is aqueous based
CO is generated by gas denaturation (reverse CO shift reaction)
Gas that is convenient for
O_TwoTo 500-850 ° C. in the presence of a reverse CO shift catalyst
Heated, and H contained in the off-gas _TwoContact by
CO and steam (H_TwoO)
The product gas was cooled and the water vapor was separated as condensed water
Later, CO is increased by separating and recovering CO.
And found the present invention.

That is, the invention claimed in the present application is as follows. (1) From a reformed gas obtained by reforming a hydrocarbon, carbon monoxide (C
In the method of producing CO for recovering O), CO is separated and recovered from the reformed gas, and CO ₂ contained in the residual gas is converted into hydrogen (H ₂ ) at 500 ° C. to 850 ° C. in the presence of a reverse CO shift catalyst. To reduce CO and steam (H
_A method for producing CO, comprising producing ₂ O), cooling the produced gas and separating the water vapor as condensed water, and then separating and recovering CO.

(2) The residual gas obtained by separating CO from the reformed gas is an off-gas when CO is separated from the reformed gas by a pressure swing adsorption (PSA) method. 2. The method for producing CO according to 1. (3) The above (1), wherein a catalyst containing Fe and Cr as an active component or a catalyst containing active alumina (Al ₂ O ₃ ) as an active component is used as the reverse CO shift catalyst.
Or the method for producing CO according to (2).

(4) The method for producing CO according to any one of (1) to (3), wherein the reaction of catalytically reducing CO ₂ with H ₂ is carried out at a pressure of 1 atm to 20 atm. . (5) The method of separating and recovering CO from a product gas after separating the steam as condensed water is performed by pressure fluctuation adsorption (PS).
A) The method for producing CO according to any one of the above (1) to (4), which is a method.

In the present invention, examples of the hydrocarbon reforming method include steam reforming.
Steam reforming is a process in which a hydrocarbon source is supplied to a reaction tube having a heating means, and the hydrocarbon is brought into contact with steam in the presence of a reforming catalyst to convert the hydrocarbon into H ₂ , CO, and C.
Reforming into a mixed gas (reformed gas) containing O ₂ , CH _4, etc. As the hydrocarbon source, for example, naphtha, raffinate, LPG, natural gas and the like are used.

In the present invention, as a method for separating CO from the reformed gas, there is, for example, a pressure swing adsorption (PSA) method. The PSA method is a method in which a mixed gas is introduced into a plurality of adsorption towers filled with an adsorbent such as activated carbon, and, for example, an adsorption step, a depressurization step, a purge step, a pressurization step, and the like are repeated according to a time sequence. A gas separation method for separating components that are easily adsorbed by an adsorbent from components that are hardly adsorbed. In the present invention, CO is separated from the reformed gas that is a source gas for increasing the production of CO, and as a residual gas that is recovered, the CO is separated and recovered by the PSA method from the reformed gas, and H ₂ is discharged. It is preferable to use an off gas containing CO ₂ .

In the present invention, the reverse CO shift catalyst is
A catalyst for promoting a reverse CO shift reaction represented by the following formula (1). _{CO 2 + H 2 → CO +} H 2 O ΔH 0 298K = 9.6kcal / mol ... (1) where, [Delta] H ⁰ _298K is the standard heat of formation at 25 ° C..

That is, the present invention provides a water-based gas represented by the following formula (2), wherein a water-containing gas or other CO-containing gas is reacted with water vapor to convert CO in the gas into H ₂ and CO _2. By utilizing the denaturation, by promoting the reaction (reverse CO shift reaction) from the right side to the left side in the equation (2), CO ₂ contained in the off gas from which CO is separated from the reformed gas by, for example, the PSA method is removed. It is changed to CO and separated and recovered. In the present invention, the reaction from left to right in equation (2) is called a CO shift reaction, and the reaction from right to left is called an inverse CO shift reaction.

CO + H ₂ O = H ₂ + CO ₂ (2) The reverse CO shift reaction is an endothermic reaction, but the reaction heat is small, and the necessary endothermic amount is 1 in comparison with the steam reforming or CO ₂ reforming reaction. / 3 to 1/4. Therefore, the reactor does not require a large heating furnace unlike a reformer, and a normal catalyst packed bed reactor can be used. The reverse CO shift reaction is a reversible reaction and requires a temperature of 500 ° C. or higher to generate sufficient CO. Therefore, in the present invention, the reaction temperature of the reverse CO shift reaction is 500 to 850 ° C, preferably 500 to 700 ° C.
It is.

In the present invention, the reverse CO shift reaction is
It is preferable to use a catalyst to reach equilibrium fast enough.
Good. Examples of the reverse CO shift catalyst include Fe and
Catalyst containing Cr as an active component or activated alumina (Al_Two
O_Three) Can be used as the active component. Reverse
As a method for producing a CO shift catalyst, for example, Fe_TwoO _Three
Cr in fine powder_TwoO_Three5-20 wt% of fine powder
Combined and wet, for example, pellets of 2mmφ × 10mm
And baking at 800 ° C. or more for 6 hours.
It is.

In the presence of such a reverse CO shift catalyst,
CO in fugas_TwoAnd H_TwoThe reaction of_Two
Is converted to only CO and CH_FourGenerates very little.
Therefore, at relatively low temperatures of 500 ° C. to 700 ° C., CO 2_Two
Can be converted to CO.
The burden on the O purification step is reduced. Also, CH _Four
Since almost no gas is generated, the unreacted gas is recovered and
It is easier to cycle.

In the present invention, the reverse CO shift reaction comprises 1
It is preferably performed in an atmosphere of 20 to 20 atm, more preferably 3 to 7 atm. If the reaction pressure is too low, the reactor becomes large, and if the reaction pressure is too high, the production amount of CH ₄ increases. In the present invention, as a method of recovering CO by separating unreacted CO ₂ and CH ₄ from the product gas of the reverse CO shift reaction, pressure fluctuation adsorption (PSA) for separating and concentrating gas components having an intermediate adsorption power is used. Preferably, the method is used.

[0020]

Next, the present invention will be described in more detail by way of examples. FIG. 1 is an apparatus system diagram showing one embodiment of a CO production method according to the present invention. In FIG. 1, this apparatus is installed in an existing CO production apparatus having a steam reformer 3 for reforming a hydrocarbon source and a PSA apparatus 7 for separating and recovering CO from the reformed gas.
A reverse CO shift reactor 12 for reforming CO ₂ contained in the off-gas separated into CO into CO and an accompanying facility therefor are provided. That is, the apparatus of FIG. 1 is a hydrocarbon source,
For example, a reforming furnace (steam reformer) 3 for reforming the naphtha 1 by contacting and reacting with the steam 2, a cooler 5 for the reformed gas 4 generated by the steam reformer 3,
PS for separating and recovering CO6 from cooled reformed gas 4
A device 7 and off-gas 9 discharged from the PSA device 7
And CO in the off-gas 9 after heating.
A reverse CO shift reactor 12 for reducing ₂ to H ₂ and shifting it to CO, a circulating pipe 13 for circulating an outlet product gas 16 of the reverse CO shift reactor 12 to the PSA device 7, and a circulating pipe 13. The generated gas 16 and the PS
It mainly comprises a heat exchanger 10 for exchanging heat with the A-device 7 outlet off-gas 9. 8 is condensed water, 15 is
This is a circulation pipe for the CO ₂ rich gas 14 discharged from the PSA device 7.

In such a configuration, the naphtha 1, which is a hydrocarbon source, is introduced into the steam reformer 3 together with the steam 2, and is supplied to a reforming catalyst such as alumina based on N 2.
In the presence of a catalyst supporting i, for example, the reaction is carried out at 860 ° C. to form a reformed gas 4 comprising a mixture of H ₂ , CO ₂ , CO, CH _{4 and the} like. The reformed gas 4 is supplied to the cooler 5
For example, after being cooled to 30 ° C. to separate water vapor as condensed water 8, it flows into the downstream PSA device 7. The H ₂ and CO in the reformed gas 4 flowing into the PSA device 7 pass through a packed tower, not shown, for example, filled with an activated carbon-based adsorbent, and are recovered as CO 6 containing a small amount of H ₂ (adsorption). Process).

Next, the packed tower after the adsorption step is decompressed in the direction opposite to the flow direction of the reformed gas to discharge the CO ₂ rich gas 14 (decompression step), and circulates through the circulation pipe 15 to the inlet of the steam reformer 3. Is done. The packed tower after the pressure reduction step is purged by using a part of H ₂ separated from the H ₂ -containing CO gas 6 recovered in the adsorption step as a purge gas, and the off gas 9 in which CO ₂ and H ₂ are mixed is discharged. Is done. The off-gas 9 is, for example, at 30 ° C.
After heat exchange with the generated gas 16 at the outlet of the reverse CO shift reactor 12 described later, the temperature is raised to, for example, 350 ° C., and then flows into the heater 11 installed in the convection heat transfer section of the steam reformer 3, for example. And a high temperature gas such as 74
The temperature is raised to 0 ° C. The heated off-gas 9 flows into, for example, a reverse CO shift reactor 12 filled with a reverse CO shift catalyst containing Fe and Cr as main components, where CO ₂ is removed.
There the product gas 16 containing CO and H ₂ O is reduced with H _2. Product gas 1 flowing out of the reverse CO shift reactor 12
6 is, for example, 600 ° C., and then flows into the heat exchanger 10 where it exchanges heat with the PSA unit 7 outlet off-gas 9 and is rapidly cooled to, for example, 30 ° C. The cooled product gas 16 merges with the reformed gas 4, water is separated as condensed water 8, flows into the downstream PSA device 7, and CO is recovered in the same manner as described above.

The packed tower of the PSA device 7 after the purging step is pressurized by a part of the separated H ₂ (pressurizing step), and proceeds to the next adsorbing step, where the adsorbing step, the depressurizing step, and the purging step are performed. By repeating the step and the pressure increasing step, CO is separated and recovered from the reformed gas 4 and the product gas 16 of the reverse CO shift reaction 12.

According to the present embodiment, conventionally, for example, the CO ₂ in the mixed off-gas 9 in CO ₂ and H ₂ which in reformer or the like had been consumed as auxiliary fuel, at a relatively low temperature of for example 600 ° C., the CH ₄ Since it can be converted into CO and recovered without generation, CO can be increased. Further, according to the present embodiment, since the amount of heat required for the reverse CO shift reaction is relatively small, the reverse CO shift reaction can proceed with the heat amount of the reactant itself.

According to the present embodiment, the PSA apparatus for recovering CO from the reformed gas 4 and the PSA apparatus for recovering CO from the generated gas 16 of the reverse CO shift reactor 12 are used together, thereby reducing the equipment cost. In addition, it is possible to efficiently increase CO production.

The PSA device 7 of the present embodiment uses the C gas contained in the reformed gas 4 and the reaction product gas 16 of the reverse CO shift reaction.
The O ₂ by adsorption separation is intended to recover the CO containing H _2, H ₂ is used as a purge gas at the time of regenerating the adsorbent by desorbing the CO ₂ adsorbed. Therefore, the off-gas 9 of the PSA device 7 is a gas in which CO ₂ and H ₂ are appropriately mixed, and can be suitably used as a source gas for the reverse CO shift reaction.

In the present embodiment, when it is desired to produce a high purity CO is of H ₂ containing CO gas 6 was recovered in the PSA system, the type of PSA system for purifying CO (CO-P
(SA device) to separate the H ₂ . The separated H ₂ can be used as a purge gas for the PSA device 7 in FIG.

In this embodiment, if the processing capacity of the PSA device 7 is at a limit, it is preferable to add a small PSA device. This makes it possible to increase the production of CO. In this embodiment, the heating source of the heater 11 is as follows.
The combustion gas of the steam reformer 3 or the high-temperature process gas can be used, but the exhaust gas of a large boiler or the exhaust gas of a heating furnace of another process can also be used.

[0029]

Next, specific examples of the present invention will be described. Example 1 FIG. 2 is a diagram showing a process for converting CO from naphtha reformed gas using the apparatus shown in FIG.
1 shows the carbon balance at the time of the production of. In the figure
132.5 (kg · m
ol / Hr) Naphtha with steam
Into Nitrogen 3 and loaded Ni on alumina base
After reforming at 860 ° C in the presence of a reforming catalyst,
123.8 (kg-mol / Hr)
Of CO _TwoAnd a reformed gas containing CO. this
The reformed gas is cooled to 30 ° C. by the cooler 5 to separate condensed water.
After that, it is introduced into the downstream PSA device 7 to remove the activated carbon adsorbent.
When flowing into the packed packed tower, it is equivalent to carbon atoms
100 (kg · mol / Hr) of H_TwoContained CO
Was recovered (adsorption step).

Next, when the packed tower after the adsorption step was decompressed in the direction opposite to the flow direction of the reformed gas, 62.5 (kg · mol / Hr) of CO and C in molar equivalent to carbon atoms was obtained.
An O ₂ -containing mixed gas was obtained (decompression step). This mixed gas was circulated through the circulation pipe 15 to the inlet of the steam reformer 3.

When a part of H ₂ separated from the H ₂ -containing CO gas recovered in the adsorption step was introduced as a purge gas into the packed tower after the pressure reduction step, 7 moles of carbon atoms equivalent to 7 moles were obtained.
1.2 (kg · mol / Hr) of CO ₂ and CO containing offgas 9 was obtained. This off-gas 9 is transferred to the heat exchanger 1
0, the temperature was raised to 350 ° C.,
Was heated to 0 ° C., where reverse CO shift catalyst composed mainly of Fe and Cr were reversely CO shift reaction is introduced into the reverse CO shift reactor 12 which is filled, 60 of CO ₂ contained in the off-gas 9 A product gas (600 ° C.) with% shifted to CO was obtained. At this time, CH ₄ was hardly generated.

Next, the resulting product gas was introduced into the heat exchanger 10, quenched to 30 ° C. to separate water as condensed water, and then introduced into the PSA unit 7, where it was 32.5 moles equivalent to carbon atoms. (Kg · mol / Hr) of CO can be recovered, and together with the CO recovered from the reformed gas 4, 132.5 (kg · mol / Hr) equivalent to a carbon atom is obtained.
Of CO could be recovered.

According to this embodiment, CO is set to 100 (kg ·
mol / Hr) in a CO production apparatus mainly composed of a steam reformer 3 and a PSA apparatus 7,
A reverse CO shift reactor 12 filled with a high-temperature reverse CO shift catalyst mainly containing Cr and Cr, a heater 11 installed in a convection heat transfer section of the reformer 3, a heat exchanger 10, and the like are provided. The CO production was 132.5 (kg · m) without major modification of the reformer 3.
ol / Hr). Therefore, according to this embodiment, C
O production could be increased by 32.5%.

Example 2 FIG. 3 shows a small P for separating and recovering CO in product gas in the reverse CO shift reactor 12 by using the apparatus shown in FIG.
This shows the carbon balance when the SA device 17 is added and CO is produced in the same manner as in the first embodiment. In FIG. 3, the CO-containing product gas generated when the off-gas of the PSA device 7 is subjected to the reverse CO shift reaction in the reverse CO shift reactor 12 is introduced into the small PSA device 17 to separate and recover CO, thereby implementing the method. 32.5 (kg ·
mol / Hr) CO could be increased.

[0035]

According to the first aspect of the present invention, CO ₂ contained in the residual gas obtained by separating CO from the reformed gas is converted into H ₂ at 500 ° C. to 850 ° C. in the presence of a reverse CO shift catalyst.
To produce CO and water vapor (H ₂ O), and to separate and recover CO in the produced gas,
CO production can be increased simply by adding a simple heat exchanger and a reactor filled with a catalyst.

According to the invention of claim 2 of the present application, off-gas generated when CO is separated and recovered from the reformed gas by the pressure swing adsorption (PSA) method is used as the residual gas obtained by separating CO from the reformed gas. By using this, the efficiency of separating CO in the reformed gas is improved, in addition to the effects of the above invention.

According to the invention of claim 3 of the present application, the inverse C
By using a catalyst containing Fe and Cr as an active component or a catalyst containing activated alumina (Al ₂ O ₃ ) as an active component as an O shift catalyst, CH ₄
Can be suppressed and the reverse CO shift reaction can be promoted.

According to the invention of claim 4 of the present application, CO
By performing the reverse CO shift reaction of catalytically reducing ₂ with H ₂ at a pressure of 1 atm to 20 atm, in addition to the effects of the above invention, separation and recovery of generated CO becomes easy,
CO can be increased more efficiently.

According to the invention described in claim 4 of the present application, the inverse C
The method of separating and recovering CO from the reaction product gas of the O shift reaction is a pressure fluctuation adsorption (PSA) method. In addition to the effect of the above invention, the excess H ₂ is effectively used, and the CO is efficiently used. Can increase production well.

[Brief description of the drawings]

FIG. 1 is an apparatus system diagram of a CO production method according to an embodiment of the present invention.

FIG. 2 is an explanatory view of a specific embodiment of the present invention.

FIG. 3 is an explanatory diagram of another specific embodiment of the present invention.

FIG. 4 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

1: Naphtha, 2: Steam, 3: Steam reformer, 4: Reformed gas, 5: Cooler, 6: CO, 7: PSA
Equipment, 8: condensed water, 9: off-gas, 10: heat exchanger, 1
1 ... heater, 12 ... inverse CO shift reactor, 13 ... circulating pipe, 14 ... CO ₂ rich gas, 15 ... circulating pipe, 16 ...
Generated gas, 17: small PSA device, 41: steam reformer, 42: PSA device.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Susumu Shishikura No. 1 Yawata Kaigandori, Ichihara City, Chiba Prefecture Mitsui Engineering & Shipbuilding Co., Ltd. F term (reference) 4D012 CA03 CB16 CD07 CH05 CJ02 CJ06 4G046 JA02 JA04 JB01 JB07 JB12

Claims (5)

[Claims] 1. A method for producing CO for recovering carbon monoxide (CO) from a reformed gas obtained by reforming a hydrocarbon, wherein CO is separated and recovered from the reformed gas, and carbon dioxide (CO) contained in a residual gas is recovered. CO ₂ ) in the presence of a reverse CO shift catalyst,
The catalyst is catalytically reduced with hydrogen (H ₂ ) at 00 ° C. to 850 ° C. to generate CO and water vapor (H ₂ O). The produced gas is cooled and the water vapor is separated as condensed water. A method for producing CO, comprising recovering. 2. The residual gas obtained by separating CO from the reformed gas is an off-gas when CO is separated and recovered from the reformed gas by a pressure swing adsorption (PSA) method. 2. The method for producing CO according to 1. 3. A catalyst containing Fe and Cr as an active component or activated alumina (Al ₂
The method for producing CO according to claim 1 or 2, wherein a catalyst containing O ₃ ) as an active component is used. 4. The method for producing CO according to claim 1, wherein the reaction of catalytically reducing CO ₂ with H ₂ is performed at a pressure of 1 atm to 20 atm. 5. The method according to claim 1, wherein the method of separating and recovering CO from a product gas after separating the steam as condensed water is a pressure swing adsorption (PSA) method.
The method for producing CO according to any one of the above.