JPH0240601B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing liquid hydrogen using alcohol, which is easy to handle and has excellent storage stability, as a raw material. Conventionally, high-purity hydrogen gas for liquid hydrogen production has been produced using the following gases as raw materials. a Off-gas from petroleum refineries, etc. b Off-gas from salt electrolyzers (caustic soda production, etc.) c Synthetic gas obtained by distillation reforming of natural gas, petroleum, etc. d Synthetic gas obtained by partial oxidation of natural gas, petroleum, etc. Obtained Synthesis Gas The general flow of producing high-purity hydrogen gas for producing liquid hydrogen using these gases as raw materials will be explained. The above off-gas (a) contains hydrogen, carbon monoxide, and light hydrocarbons as main components, and its composition varies depending on the equipment configuration of the petroleum refinery and the like. To produce the above-mentioned high-purity hydrogen gas from this off-gas,
Basically, it is produced by the same process as the production process from synthesis gas (described later) in c or d above. Since the hydrogen purity of the above-mentioned off-gas (b) is usually about 99.8 mol%, it is used as is for producing liquid hydrogen. The process for producing the above-mentioned high-purity hydrogen gas from the synthesis gas in c is as follows, including the process for synthesizing the synthesis gas in c. The raw material (in this case, natural gas) desulfurized in the desulfurization equipment is mixed with superheated steam and fed into a reaction tube filled with a catalyst placed in a reformer, where the pressure is 7 to 7.
Heated by combustion of fuel under 30 atmospheres (approximately 900℃)
The gas is then converted into crude synthesis gas, whose main components are CO and _H2 . This crude synthesis gas is heat-recovered using water in a heat recovery device, and then undergoes a CO conversion process and a decarboxylation process to become purified hydrogen gas with a hydrogen purity of approximately 98 mol%.
Remaining CO ₂ , CH ₄ , and CO are removed by a low-temperature purification process, resulting in a purified gas with a hydrogen purity of about 99.99 mol % or higher, which is sent to a liquefaction process. The process for producing the above-mentioned high-purity hydrogen gas from the synthesis gas in d above, including the step of synthesizing the synthesis gas in d, is as follows. The raw material (in this case, heavy oil) is mixed with steam and is injected into the reactor through a burner together with oxygen obtained, for example, by cryogenic separation of air.
Through a partial oxidation reaction, it is converted into crude synthesis gas whose main components are CO and _H2 . The reaction temperature at this time is 1200~
The temperature is 1500℃ and the pressure is 20-150 atm. After this crude synthesis gas is heat-recovered using water in a heat recovery device, it is further cooled with water in a cooling/dedusting device to remove carbon and at the same time replenish the water necessary for CO conversion. The gas is then fed to a CO conversion process, where the CO in the gas is converted into CO ₂ and H ₂ . After that, acidic gases such as H ₂ S and CO ₂ are absorbed and removed by an alkaline solution, etc., and the gas becomes purified hydrogen gas with a hydrogen purity of about 98 mol%.The remaining CO ₂ , CH ₄ , and CO are removed during the low-temperature purification process. Hydrogen purity removed by approximately 99.99
It becomes a purified gas of mol% or more and is sent to the liquefaction process. Note that the acidic gases such as H ₂ S and CO 2 removed by the above-mentioned alkaline solution etc. are converted into S ₂ , CO _{2 etc.} in a sulfur plant. The above conventional method has the following drawbacks. In the case of methods a and b above, which use off-gas as a raw material, (1) high-purity hydrogen gas production equipment and liquefaction equipment are attached to oil refineries, caustic soda factories, etc., so there are restrictions on the installation location; (2) off-gas There is a difference in the pattern of the amount of hydrogen generated and the amount of liquid hydrogen produced, and off-gas may have to be stored and used. However, off-gas has drawbacks such as poor storability and inconvenience in handling. In addition, in the case of methods c and d above that use synthesis gas as a raw material, (1) a special high-temperature heat-resistant alloy is required in terms of equipment materials, and depending on the process, pure oxygen production equipment is required, which requires large-scale equipment. (2) Since both are high-temperature processes of over 1000℃, it takes a considerable amount of time to start up and shut down the plant, making it difficult to start up and shut down the plant at any time or even on a daily basis. (3) The ability to follow load fluctuations and the range of fluctuations are insufficient. The present invention has been made with the object of eliminating the above drawbacks and providing a simple and economical method for producing liquid hydrogen using alcohol such as methanol, which is liquid at room temperature and pressure, as a raw material. That is, the present invention applies pressures of 10 to 45 atmospheres and 200
Alcohol is reformed in the presence of water vapor at a temperature of ~400°C, and the high-pressure crude synthesis gas obtained by reforming is converted to hydrogen with a purity of 99.99 mol% or more using a pressure swing method using an adsorbent. At the same time as obtaining high-pressure hydrogen gas, the by-product flammable gas is used as a heat source for the reforming reaction, and when high-pressure, high-purity hydrogen gas is liquefied in the liquefaction process, the self-pressure of the gas is used to drive an expansion turbine. This is a method for producing liquid hydrogen, characterized in that the hydrogen is used as power for a liquefaction process. The new ideas of the present invention are listed below. (1) Use methanol, ethanol, propyl alcohol, butanol, and other alcohols as raw materials for liquid hydrogen. (2) For example, use the following methanol reforming reaction for the purpose of producing liquid hydrogen. Endothermic reaction CH ₃ OH + H ₂ O Endothermic reaction ----→ CO ₂ + 3H _2The reaction temperature is low (200-400℃), and the reaction pressure is at the optimal level (10-45 atm) for the subsequent liquefaction process. will be held. Moreover, a low heat source of about 400 to 600°C can be used for the amount of heat required for the reaction. Therefore, high temperature operation over 1000℃ is not required,
This allows the plant to be started and stopped easily and in a short time. (3) Because the raw material is methanol, etc., which is liquid at room temperature and pressure, it is easy to store the raw material. (4) A method for producing liquid water from alcohol that combines alcohol reforming, separation and purification of hydrogen gas from crude synthesis gas using an adsorbent, and cryogenic liquefaction of hydrogen gas using an expansion turbine. thing. From the above (1) to (4), it can be seen that the present invention has the following advantages. (1) Since there are no particular restrictions on the installation location of a plant that implements the method of the present invention, the method can be easily implemented even in remote areas such as remote islands and non-industrial areas. (2) Since the operating temperature is low, a simple and inexpensive heat supply system and a simple and inexpensive reaction apparatus can be used. (3) Since the plant can be easily started and stopped, it can be operated intermittently on a daily or weekly basis depending on the demand for liquid hydrogen. In addition to general liquid hydrogen production, the method of the present invention also
It can also be applied to the production of hydrogen for fuel cells, hydrogen for hydrogenation for the oil and fat and food industries, and hydrogen for reduction for the metal refining and semiconductor industries. Hereinafter, the method of the present invention will be explained in detail with reference to the accompanying drawings and the like. FIG. 1 is a diagram showing the basic flow of the method of the present invention. In FIG. 1, a mixture of alcohol 5 and water or steam or circulating water 8 (described below) pressurized to 10 to 45 atmospheres is heated to 200 to 400°C and becomes gaseous.
By passing through a catalyst layer in the reforming step 1, it is converted into crude synthesis gas 6 mainly consisting of H ₂ , CO ₂ and H ₂ O. The above catalyst may be copper-zinc based, for example, CuO-ZuO (Zn/Cu weight ratio = 2), or 80 wt% of the CuO-ZnO and 20% of γ-Al ₂ O _3.
Those loaded with wt% are used. For example, in the case of methanol, the main reaction in the reforming step 1 is represented by the following formula. CH ₃ OH→CO+2H ₂ ...(1) CO+H ₂ O→CO ₂ +H ₂ ...(2) Overall, by adding the above two equations, the following equation is obtained. CH ₃ OH + H ₂ O → CO ₂ + 3H ₂ ...(3) Crude synthesis gas 6 is cooled and condensed water is separated in step 2
The synthesis gas 9 is supplied to the purification step 3. Further, the separated condensed water is circulated to the reforming step 1 as circulating water 8. In the purification step 3, CO ₂ which is an impurity other than hydrogen,
The purpose is to remove CH ₄ , CO, etc., and there are various removal methods, but first CO ₂ is removed by a decarboxylation process such as the hot potassium carbonate method, the monoethanolamine method, and the lectisol method, and then the remaining impurities are removed.
It is particularly preferable from the economic point of view to remove CH ₄ , CO, etc. by the PSA (pressure swing adsorption) method, or to remove all impurities by the PSA method alone. In addition,
Synthetic zeolite or the like is used as an adsorbent in the PSA method. The off-gas 11 released from the refining process 3 is
Since it contains CH ₄ , CO, H _{2 ,} etc. and has value as a fuel, it is used as a heat source in the reforming process 1. The purified gas 10 from the purification step 3 is at approximately room temperature, 10~
The hydrogen is supplied to the liquefaction step 4 under a pressure of 45 atm and a hydrogen purity of approximately 99.99 mol% or higher. Note that by setting the hydrogen purity of the purified gas 10 to about 99.99 mol % or more, low-temperature purification in the liquefaction step 4 is basically unnecessary. In the liquefaction process 4, the self-pressure of the purified gas 10 is used to drive an expansion turbine, and this is used as compression power for liquefaction to achieve self-cooling (heat exchange with hydrogen gas at the same temperature level as liquid hydrogen). ), indirect cooling using a refrigerant such as nitrogen or helium, or a combination thereof, to produce liquid hydrogen 12. Note that 7 in FIG. 1 indicates fuel used as a heat source in the reforming step 1. According to the method of the present invention described in detail above, the following effects can be achieved. (1) The plant can only be operated at temperatures below 400°C, which simplifies equipment, materials, and operations, making it easy to start and stop the plant, and allowing flexible operation to meet the demand for liquid hydrogen. (2) Off gas 11 from purification process 3 is transferred to reforming process 1
It can be used as a heat source for synthesis gas at its own pressure (10~
45 atm) can be used to reduce the power of the liquefaction process 4, which is efficient and economical. (3) Basically, a plant can be located as long as there is alcohol that is easy to handle, and it is especially useful for on-site (local production) plants in non-industrial areas, remote areas such as remote islands. FIG. 2 is a diagram showing a specific embodiment of the method of the present invention when methanol is used as a raw material. In FIG. 2, liquid methanol 105 is mixed with make-up water 121 for reforming and circulating water 108 separated from crude synthesis gas 106 at the outlet of reforming reactor 134, and then used to heat heat medium oil 118. The heated air exhaust gas, the outlet crude synthesis gas 106 (approximately 250°C) of the reforming reactor 134, and the heat medium oil 118 of approximately 400°C are transferred to the heat exchangers 131, 132, 133.
The fuel is sequentially indirectly heated through the reactor 134 and then supplied to the reforming reactor 134. In the reforming reactor 134, methanol is reformed under conditions of about 250° C. and about 30 atmospheres, and converted into crude synthesis gas 106 mainly containing hydrogen and carbon dioxide. The heat required for this reaction is about 400℃ heat transfer oil 1
18. The heat medium oil 118 is used as fuel 1 in the hot air generating furnace 137.
07 and off gas 11 from PSA device 139
1 and the air 114 to generate hot air, which is heated in the heat exchanger 135. The above-mentioned reforming reactor 134 is a shell and tube heat exchanger, and the inside of the tube is filled with a commercially available copper-zinc catalyst, into which methanol gas is supplied. As a heating method for the reforming reactor 134, other heat carriers such as molten salt may be used instead of the heat carrier oil 118, or reaction heat may be provided within the combustor or by combustion gas. Crude synthesis gas 106 is transferred to heat exchangers 132 and 1
After the heat is recovered and cooled by 36 and the condensed water is separated, it is supplied to the decarboxylation device 138 at approximately room temperature.
There are various types of decarboxylation equipment 138, but here we use a wet method using a monoethanolamine aqueous solution to remove carbon dioxide gas and achieve a hydrogen purity of approximately 98%.
Synthesis gas 151, which has become mol%, is transferred to PSA device 13.
9, where the hydrogen purity is approximately 99.99 mol%
It is refined to a higher level. If this purified gas 110 contains impurities such as CO and CH ₄ of approximately 0.01 mol% or more, they will freeze during the liquefaction process and adhere to the equipment, causing trouble such as blockage. If impurities are not removed by such methods, low-temperature purification is required, but by employing the PSA device 139, low-temperature purification is not necessary. An example of the PSA device 139 is schematically shown in FIG. Figure 3 shows four adsorption towers 1 filled with adsorbent.
56 are used. In FIG. 3, synthesis gas 151 at about room temperature and about 10 to 45 atm hydrogen purity of about 98 mol% is transferred to an adsorption column 156.
Components other than hydrogen are adsorbed by the adsorbent. Before the adsorbent is saturated with impurities, the supply of synthesis gas 151 is stopped and the pressure is reduced, and then purified gas 151 is
10 is poured into the adsorbent to release impurities adsorbed on the adsorbent and regenerate the adsorbent. The purified gas required for this regeneration is stored as an off-gas 111 in an off-gas tank 158 and used as fuel for a reforming heat source. Note that FIG. 3 shows a state in which three towers are refining the synthesis gas 151 and one tower is regenerating the adsorbent using a part of the purified gas 110. By cyclically performing adsorption, depressurization, and regeneration operations in each tower in this way, hydrogen purity of approximately 99.99 mol% is achieved.
The above purified gas 110 is obtained. In this case, the hydrogen recovery rate is approximately 75%. Purified gas 110 exiting the above PSA device 139
enters the liquefaction process at approximately 40°C and approximately 29 atm. In the liquefaction process, it first enters the expansion turbine 140, where it is depressurized to near normal pressure, enters the cold boxes 143 and 144, and indirectly exchanges heat with the deep-chilled helium 116, becoming approximately 20㎓ of liquid hydrogen. The product liquid hydrogen 11 is stored in a tank 146.
2 is used from time to time. The above-mentioned refrigerant, helium 116, has a pressure of about 1.2 atmospheres and about 15㎓ at the outlet of the expansion turbine 142, and the cold box (aluminum plate heat exchanger) 1
After indirectly liquefying the entire amount of hydrogen in step 44, it is branched into two streams: one helium stream precools the hydrogen gas in a cold box (heat exchanger) 143, and the other helium stream flows through a cold box (heat exchanger) 143. 1
45 pre-cools the helium gas from the compressor 141 at a pressure of about 300㎓ and about 15 atm. These branched helium gases are combined again and sent to the compressor 141.
Helium thus forms a completely closed cycle. Note that the expansion turbines 140 and 142 are recovered as power for the compressor 141 in the liquefaction process, and the insufficient efficiency is compensated for by the electric motor 147. Table 1 shows an overview of the logistics in the main lines mentioned above. 【table】

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic flow of the method of the present invention, FIG. 2 is a diagram showing an example of an embodiment of the method of the present invention, and FIG.
The figure shows a specific example of the PSA device 139 used in FIG. 2.

Claims (1)

[Claims] 1 Alcohol is reformed in the presence of water vapor at a pressure of 10 to 45 atm and a temperature of 200 to 400°C, and the high-pressure crude synthesis gas obtained by reforming is subjected to pressure swing using an adsorbent. Hydrogen purity 99.99 by method
At the same time as obtaining high-pressure hydrogen gas of more than mol%, the combustible gas by-product is used as a heat source for the reforming reaction,
A method for producing liquid hydrogen, characterized in that when high-pressure, high-purity hydrogen gas is liquefied in a liquefaction process, the self-pressure of the gas is used to drive an expansion turbine and used as power for the liquefaction process.