JPH05163180A - Methanol synthesis using hydrocarbon gas as raw material - Google Patents

Abstract

(57) [Abstract] [Purpose] To make effective use of surplus hydrogen generated by the reforming of methane during methanol synthesis. [Structure] Methane CH ₄ is steam reformed by the reformer 1,
This produces CO + 3H ₂ . The generated hydrogen is supplied as fuel gas to the anode 9 of the molten carbonate fuel cell 6 and used for power generation. Thereafter, the gas discharged from the anode 9 is cooled by the cooler 10, compressed by the compressor 3 and sent to the methanol synthesizer 4. The methanol synthesizer 4 synthesizes the carbon monoxide CO, carbon dioxide CO _2, and hydrogen 3H ₂ to produce methanol CH ₃ OH. Since hydrogen generated by reforming methane is used for power generation, it can be effectively used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for synthesizing methanol used in a methanol production plant using a gas containing natural gas or a gas accompanied by petroleum as a main component.

[0002]

2. Description of the Related Art Conventionally, as a method for synthesizing methanol using natural gas or the like as a raw material, as shown in FIG. 3, methane CH ₄ in natural gas is reformed by CH ₄ + H ₂ O → CO + 3H in a reformer 1. ₂ , steam reforming is carried out, and the gas containing carbon monoxide and hydrogen obtained by this reforming and carbon dioxide gas generated by the shift reaction is cooled by the cooler 2 and then compressed by the compressor 3; In the methanol synthesizer 4, carbon monoxide CO, carbon dioxide gas CO ₂ and hydrogen 3H ₂ are subjected to high pressure contact reaction to synthesize C,
It is set to methanol of H ₃ OH.

In the above-mentioned methanol synthesis method, the amount of hydrogen generated by reforming natural gas or the like in the reformer 1 is more than the amount required for the production of methanol. Therefore, conventionally, the above-mentioned excess hydrogen is generally released as a purge gas from the methanol separator 5, but if the released hydrogen is not effectively used, the utilization rate of the raw material is deteriorated, so that the purge gas is discharged. As shown in Fig. 3, it can be used as fuel for the reforming reaction in the reformer 1, can be purified and recovered as hydrogen gas, or can be introduced as carbon dioxide gas corresponding to excess hydrogen from the outside to produce methanol. It is being appreciated.

[0004]

However, the excess hydrogen of the hydrogen produced in the reforming reaction during the synthesis of methanol is conventionally purified as described above and recovered as hydrogen, or carbon dioxide gas is discharged to the outside. They are brought in more as methanol, or they are released together with the purge gas and used as fuel for the reforming reaction. In either case, it cannot be said that the surplus hydrogen can be used effectively. It was

In view of the above, the present invention intends to effectively utilize the excess hydrogen contained in the reformed gas in the methanol synthesis to reduce the purge gas and increase the utilization rate of the raw material.

[0006]

In order to solve the above-mentioned problems, the present invention steam-reforms a hydrocarbon gas in a reformer,
The reformed gas is used as a fuel gas for the anode of the fuel cell, cooled, compressed, and then subjected to methanol synthesis in a methanol synthesizer. As the fuel cell, a molten carbonate fuel cell or a solid oxide fuel cell is used. When a molten carbonate fuel cell is used, the fuel exhaust gas used for reforming in the reformer can be used as a part of the oxidizing gas supplied to the cathode side.

[0007]

[Function] When the gas reformed by the reformer is supplied to the anode of the fuel cell as the fuel gas, excess hydrogen can be utilized in the fuel cell, so that the loss of hydrogen due to the purge gas can be reduced, The utilization rate of raw materials can be increased.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. Like the conventional methanol synthesis method used in a methanol production plant using natural gas as a raw material shown in FIG. 3, a reformer 1,
A cooler 2, a compressor 3, a methanol synthesizer 4, and a methanol separator 5 are provided in this order in the line direction, and methanol is produced from carbon monoxide and hydrogen obtained by reforming methane CH ₄ in a raw material gas. In such a method, between the cooler 2 on the outlet side of the reformer 1 and the compressor 3, as a fuel cell, an electrolyte plate 7 impregnated with molten carbonate as an electrolyte is used as a cathode 8 and an anode 9. A molten carbonate fuel cell 6 which is sandwiched by both electrodes from both sides to supply an oxidizing gas to the cathode side and a fuel gas to the anode 9 side in a multi-tiered stack to form a stack and cooling. Is installed so that the gas reformed by the reformer 1 can be supplied to the anode 9 as a fuel gas, and the anode outlet gas discharged from the anode 9 is cooled and then compressed to perform methanol synthesis. To Migihitsuji.

When methane is steam-reformed in the reformer 1, the reaction of CH ₄ + H ₂ O → CO + 3H ₂ is performed in the reformer 1 as described above, and the gas reformed by the reformer is converted into gas. After cooling with the cooler 2, the anode 9 of the molten carbonate fuel cell 6
As fuel gas. In the anode 9, resulting carbonate ion CO ₃ was reached through the electrolyte plate 7 to the anode 9 side at the cathode 8 side ^{- _{by, CO 3 - + H 2 →}} H 2 O + CO 2 + 2e - reaction is performed is hydrogen The steam H ₂ O and the carbon dioxide gas CO ₂ in an amount equal to the consumed and reacted hydrogen amount are increased to the reformed gas, and power generation is performed. The gas discharged from the anode 9 is cooled by the cooler 10 and then the compressor 3
And is supplied to the methanol synthesizer 4, where
Carbon monoxide, carbon dioxide gas and hydrogen in the reformed gas are synthesized to produce methanol of CO ₃ OH. The gas leaving the methanol synthesizer 4 is cooled in a cooler 11 and then separated in a methanol separator 5 into a liquid L containing methanol as a main component and an unreacted gas G, and most of the unreacted gas G is recycled. It is recycled to the methanol synthesizer 4 in the line 12, and a part thereof is introduced into the combustion chamber of the reformer 1 by the line 13 and used. The unreacted gas (purge gas) introduced into the reformer 1 is burned in the combustion chamber of the reformer 1, reformed by the combustion heat, and then taken out as combustion exhaust gas. Since this combustion exhaust gas contains CO ₂ ,
The combustion exhaust gas is used as the cathode 8 of the molten carbonate fuel cell 6.
Line 13 is supplied to the inlet side. The liquid L separated by the methanol separator 5 is further introduced as crude methanol to the methanol purifying device to be highly pure methanol.

In the embodiment shown in FIG. 1, of hydrogen gas contained in the gas reformed by the reformer 1, 1 / m
When 5 equivalents of hydrogen was used in a molten carbonate fuel cell to generate electricity and the gas discharged from the anode 9 was used for methanol synthesis, 0.83 kg · mol / hr of methanol was obtained per 1 kg · mol / hr of methane. The generated electric power of 8 KW could be extracted from the fuel cell 6. The amount of methanol produced could be increased by about 15% as compared with the case where the molten carbonate fuel cell was not used.

Next, FIG. 2 shows another embodiment of the present invention. Instead of the molten carbonate fuel cell 6 shown in FIG. 1, for example, an electrolyte in which an electrolyte of nickel and yttria-stabilized zirconia is applied. Plate 16 as cathode 17 and anode 1
The solid oxide fuel cell 15 sandwiched by 8 is used to supply reformed gas to the anode 18 and use hydrogen contained in the reformed gas as fuel gas for power generation.

When the solid oxide fuel cell 15 is used as the fuel cell as in the embodiment of FIG. 2, since it operates at a high temperature, the gas reformed by the reformer 1 remains at a high temperature without being cooled. The gas discharged from the anode 18 is supplied to the anode 18 as it is, and the gas discharged from the anode 18 is cooled by the cooler 10 and then compressed and sent to the methanol synthesizer 4, where it is composed of carbon monoxide, carbon dioxide gas and hydrogen. The gas as the synthesis gas, which has exited the methanol synthesizer 4, is cooled by the cooler 11 and sent to the methanol separator 5, and the liquid L containing methanol as the main component and the unreacted gas G are used as in the case of FIG. To be separated.

As shown in FIG. 2, when a solid oxide fuel cell 15 is used as the fuel cell, 1 kg of methane
When hydrogen of 0.38 kg · mol / Hr is used for power generation per mol / Hr, 15 kW of electric power is obtained, and methanol is 0.7
2 kg · mol / Hr was produced. This amount of methanol was almost equivalent to that obtained without using the fuel cell.

[0015]

As described above, according to the methanol synthesis method of the present invention, excess hydrogen contained in the gas obtained by reforming methane in the reformer is supplied to the anode of the fuel cell for use in power generation. Since the gas discharged from the anode is synthesized by the methanol synthesizer with methanol, surplus hydrogen of the hydrogen generated by the reforming of methane can be effectively used and the purge gas can be reduced to use the raw material. Rate, and by using a molten carbonate fuel cell as the fuel cell, the carbon dioxide gas generated by the reaction at the cathode can be sent to the methanol synthesizer, and the carbon dioxide in the methanol synthesizer can be increased. Since the amount of gas can be increased, the excellent effect that the amount of synthetic methanol can be increased can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

FIG. 2 is a schematic view showing another embodiment of the present invention.

FIG. 3 is a schematic diagram of a conventional methanol synthesis method.

[Explanation of symbols]

 1 Reformer 4 Methanol Synthesizer 5 Methanol Separator 6 Molten Carbonate Fuel Cell 7 Electrolyte Plate 8 Cathode 9 Anode 15 Solid Electrolyte Fuel Cell 16 Electrolyte Plate 17 Cathode 18 Anode

Claims (3)

[Claims] 1. A hydrocarbon gas is steam-reformed by a reformer,
Methanol synthesis using hydrocarbon gas as a raw material, characterized in that reformed gas is supplied to the anode of a fuel cell, hydrogen in the reformed gas is used for power generation, and then sent to a methanol synthesizer for methanol synthesis. Law. 2. The molten carbonate fuel cell is used as the fuel cell, the reformed gas is supplied to the anode of the molten carbonate fuel cell, and the flue gas discharged from the reformer is supplied to the cathode. The method for synthesizing methanol using the above hydrocarbon gas as a raw material. 3. The methanol synthesis method using a hydrocarbon gas as a raw material according to claim 1, wherein a solid oxide fuel cell is used as the fuel cell, and the reformed gas is supplied to the anode of the solid oxide fuel cell at a high temperature.