JPH03200734A - Synthesis of methanol - Google Patents

Abstract

PURPOSE:To economically obtain methanol by using H2 generated from a water or steam electrolyzing device and CO2 obtained from CO2-rich gas derived from a fossil fuel burner, etc., by a CO2-separating and recovering device as raw materials. CONSTITUTION:Fossil fuel is charged in a burner 041 or a fuel improver 042 and gas containing CO2 is obtained from an exit port, then separated, thus the CO2 component is stored in a gas holder 051. On the other hand, electric power, water and thermal energy are supplied into a water electrolyzing device from outside of the device system and H2 gas and O2 gas are stored in respective holders. Next, resultant CO2 gas and H2 gas are sent to a methanol synthesizing device 001 and reacted in the presence of Cu/ZnO/Al2O3 catalyst, etc., to afford CH3OH. The above-mentioned O2 gas may be used in a burner 041 or a fuel improver 042 and resultant CH3OH may be used as a raw fuel in a burner, etc., thus reducing of CO2-discharging amount is possible in a global scale.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for synthesizing methanol, particularly from hydrogen (H2) produced by water or steam electrolysis and carbon dioxide (CD2) obtained by carbon dioxide separation and recovery. This invention relates to a method for synthesizing methanol.

[Conventional technology]

The method of synthesizing methanol from H2 gas and CD or CO2 gas is a well-known method, but the raw material gas used for this method is fossil fuels such as coal, naphtha, and natural gas.

The reaction formula for methanol synthesis is from ■ to ■ where the main reaction is CD +282- CH30H+ 21.7 Kcal
/mol・■ CO2+ 3H2→CH30H+H20+11.8 K
cal/mol■ Therefore, Co: H2= 1 : 2 or CO2: H
It is necessary to adjust the ratio of the mixed gas in the raw material so that the mixture ratio (volume ratio) is , = l:3 before supplying it to the converter. FIG. 6 shows the methanol conversion rate under various temperatures and pressures in the methanol synthesis reaction shown in equation (2) above. In terms of equilibrium, lower temperatures and higher pressures are preferable, but from the viewpoint of the activation of the synthesis catalyst, such as Cu-based synthesis catalyst, built in the converter and the energy required to boost the gas pressure, in practical plants it is recommended to
Values of ˜300° C. and 40-150 kg/cdG have been chosen.

Furthermore, Figure 7 is a schematic diagram of a conventional methanol synthesis reactor that synthesizes methanol from CO and H2, and 003 is a reformer that converts natural gas into H, CD rich gas;
34 is a heat exchanger, 004 is a compressor, 005 is a gas recirculator, 002 is a converter, and refoamer 00
3. Each converter 002 has a built-in catalyst.

With the above device, raw natural gas is mixed with steam and introduced into a reforming tube containing a catalyst of Reformer 003, and when heated from the outside, becomes H2-rich gas through the reaction of the following formula (1).

CH, + LO→ CO+ 382・■ In reality, excessive water vapor is often added to prevent caulking. l(,/C from Refoma 003
After the D mixed scum is cooled by a heat exchanger 034, the pressure is increased by a compressor 004, and the mixture is led to a converter 002 containing a methanol synthesis catalyst, where methanol is synthesized mainly by the formula (2). Note that the unreacted raw material gas is guided to the converter 002 again by the gas recirculator 005.

In addition, the water electrolysis method is generally established as a method for obtaining 02 gas, and alkaline water electrolysis devices have been put into practical use as water electrolysis devices, and ion exchange membrane water electrolysis devices and steam electrolysis devices have also been developed. Among them, some of them have been put into practical use.

To explain the principle of a general alkaline water electrolysis device, an aqueous alkaline solution is filled in a tank whose interior is divided by partition plates and diaphragms, and an anode and an anode are alternately placed in each compartment.
When the cathode is suspended and direct current power is supplied to the electrodes (anode and cathode) from the outside in such a device, the alkaline aqueous solution is electrolyzed to generate oxygen from the anode and hydrogen from the cathode. The reaction formulas are shown in (1) to (2), but since water is consumed, it is necessary to supply pure water to the cathode side.

(Anode> 20H-→H20+ 2e-10'A 02
1 ■ (Cathode) 2H20+2B--2DH-
＋ h ↑ ■(Overall) 2H20→ H2↑＋'A 02 T +)IJ ■
Note that asbestos or porous Teflon is used for the diaphragm, and steel is used for the electrodes. Also, as an alkaline aqueous solution, 20% NaOH
or 30% KO)l, etc. are used.

[Problem to be solved by the invention]

1. Conventional methanol synthesis technology produces methanol CH3
The starting material for the hydrogen atoms in DH is fossil fuels (including CO+H produced in the reforming reaction of coal), and as methanol production increases, large amounts of fossil fuels are consumed, and the increase in CO2s in the atmosphere increases. This was a contributing factor.

2. In conventional water electrolysis equipment, the H2 produced was used as is for various industrial purposes, but there was a limit to demand due to economic reasons, as storage and transportation costs accounted for a large proportion of sales costs. .

In view of the above-mentioned state of the art, the present invention uses hydrogen obtained by methanol solution, and uses fossil fuels produced at thermal power plants, steel plants, chemical complexes, etc. as starting materials of carbon atoms to produce various products (including electric power). The aim is to provide a method for producing methanol more economically using the entire plant, using carbon dioxide CO3, which is the waste gas from the production equipment.

[Means to solve the problem]

The present invention provides: (1) H2 and CO2 generated from water or steam electrolysis equipment;
A method for synthesizing methanol, which comprises synthesizing methanol in a methanol synthesis device using CO2 obtained from a separation and recovery device as a raw material.

(2) CO2 from fossil fuel combustors or fossil fuel reformers
The rich gas is supplied to the C[12 separation and recovery device (1)
) Method for synthesizing methanol as described.

(3) The methanol synthesis method according to (1) above, in which CO2'J putsch from an underground gas processing device such as a geothermal steam turbine is supplied to a CO2 separation and recovery device.

(4) The methanol synthesis method according to (2) above, in which water or by-product oxygen from the steam electrolysis device is supplied to a fossil fuel combustor or a fossil fuel reformer.

(5) Either H2 from the water or steam electrolyzer or CO2 from the CO2 separation and recovery device is obtained at a high pressure compared to the methanol synthesis pressure, and the pressure of the other raw material is increased by the pressure energy of the high-pressure raw material. Then, both raw materials are mixed/supplied to the tanol synthesis equipment (1) to (4) above.
) The method for synthesizing methanol according to any one of the above.

(6) The method for synthesizing methanol according to (2) above, wherein methanol synthesized in a methanol synthesis device is used as a raw material for a fossil fuel combustor or a fossil fuel reformer.

[Effect]

A water or steam electrolysis device and a CO2 separation and recovery device are combined, and raw materials from both, i.e., 02 from the former,
By introducing the raw material mixed with CO2 from the latter to the methanol synthesis device, it is possible to reduce CO2 emissions without significantly impairing economic activity on a global scale.

Typically, surplus electricity from power plants at night is used to operate water or steam electrolyzers, and CO2 emitted from thermal power plants is separated and recovered during the daytime when demand for electricity is high. H2 from the former and CO from the latter at night
2 in the presence of a catalyst to synthesize methanol.

If methanol is repeatedly used as raw fuel for thermal power plants, the total amount of CD2 released into the earth's atmosphere from thermal power plants will be drastically reduced.

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

[Embodiment 1] Fig. 1 shows the first embodiment of the present invention, in which when fossil fuel is input into the combustor 041 or the fuel reformer 042, gas containing CO□ is discharged from the outlet thereof. . The gas is then separated into two components, a component mainly other than CO2 and a component mainly CO2, in a CO2 separation and recovery device 031, of which the latter gas is stored in a CO2 gas holder 051.

- In the power water electrolyzer 021, electricity and water are supplied from outside the system, or in case 1
As a result, thermal energy is supplied, and as a result, H2 gas and 0□ gas are released outside the system. Electrolytic gas is H2 gas holder 061 and 02 gas holder 06 respectively.
It can be stored in 2.

After that, the stored CO2 gas and H2 gas are sent to the methanol synthesis equipment 001, and after being mixed briefly, Cu/ZnO
Methanol CH3DH is produced by the reaction of the above-mentioned formula (2) under a methanol synthesis catalyst such as /A1zOs system.

The synthesized methanol is stored in a methanol tank 006 and shipped when necessary.

There are several methods for separating and recovering CO2 from CO2 mixed gas, such as absorption method, adsorption method, and membrane separation method, and the most suitable method is selected depending on the properties of CD□ mixed gas, operating pressure, temperature, etc. This article describes the MEA method, which is a type of absorption method. The method is carried out by absorbing carbon dioxide with an aqueous solution of monoethanolamine and releasing carbon dioxide by heating the absorption liquid. For example, when a gas containing carbon dioxide (e.g. exhaust gas from a combustor) supplied to the bottom of an absorption tower comes into contact with a cold ethanolamine aqueous solution flowing down inside the absorption tower, the reaction of the following formula (■) proceeds to the right and carbon dioxide is absorbed. Ru. The liquid that has absorbed carbon dioxide is heated and sent to the upper part of the stripping tower, heated by the repoiler at the lower end, and releases carbon dioxide from the upper part of the stripping tower. Absorption towers generally have a capacity of 10 to 20 kg/c.
It is operated under a pressure of 100 ft, but can also be operated under atmospheric pressure.

CO2+ H3O+ RNH2#RNH3・HCO3■
In addition, hot potassium carbonate is also used as the absorption liquid in place of the monoethanolamine mentioned above, and carbon dioxide is separated and recovered by the reaction of the following formula (1).

The basic system is the same as that for monomethanolamine described above, but the operating pressure in the absorption tower is 15-20 kg/c [111] and the operating temperature is 120-160°C.

Note that if the raw material gas contains sulfur oxides (5Ox), it is necessary to remove them in advance.

The above explained the separation and recovery method of CO□ using a wet method.
may be separated and recovered.

[Embodiment 2] FIG. 2 shows a second embodiment of the present invention. The difference from the first embodiment is the method for producing carbon dioxide-rich gas.
Then, material from underground, such as geothermal gas, is passed through a steam turbine generator 043 that acts as a -tanium expander, and further through a condenser 044 to become CO2-rich gas.
The point is that it is guided to the CD3 separation and recovery device 031.

Furthermore, this example shows an example in which there is a large amount of geothermal hot water as a substance from underground, and an example in which a flasher 045 that decompresses the hot water and generates steam is installed upstream of the steam turbine generator 043. .

Note that instead of the geothermal gas in this example, this flow can also be applied to the case where a mixed gas of CH and CO2 from a natural gas field is guided to the CO2 separation and recovery device 031.

[Embodiment 3] FIG. 3 shows a third embodiment of the present invention. This embodiment differs from the first embodiment in the following points.

By-produced oxygen is provided between the oxygen gas holder 062 and the combustor 041 or the fuel reformer 042 so that the oxygen produced by the water electrolysis device 021 can be used as the oxidant gas required by the combustor 041 or the fuel reformer 042. For example, in the combustor 041, LNG or methanol is combusted with oxygen instead of air, so no N2 gas is generated in the exhaust gas, so it is a non-condensing separation type. The CO□ separation and recovery device 031 can economically condense CO□ by n minutes.

[Embodiment 4] FIG. 4 shows a fourth embodiment of the present invention. This embodiment differs from the first embodiment in the following points.

The gas pressure from the combustor 041 or fuel reformer 042 to the CO□ gas holder 051 is a low pressure of 1 kg/crIG or less, and the operating pressure of the hydroelectric electrolysis device 021 is 50 kg/c.
II! If the pressure exceeds G, the high pressure N2 gas stored in the N2 gas holder 061 is introduced into the expander 043, and the compressor 004 of the same Tsumugi produces 1kg/caf.
The point is that the pressure of CO2 gas below G is increased to the pressure required for the methanol platform.

[Embodiment 5] FIG. 5 shows a fifth embodiment. This example differs from the fourth example described above in the following points.

As a means of increasing the pressure of the mixed raw material gas to the pressure required for the methanol table bottom, CO2 concentrated in the CO2 separation and recovery device 031 is guided to the CO2 liquefaction device 053.
Change the phase of □ from gas to liquid and store it in the liquefied CO2 storage tank 052. Then, during methanol synthesis, C
After pressurizing to 50 kg/cafG or more with the loss pump 054, it is made into high-pressure CL gas in the liquefied CO2 evaporator 055, and with the pressure energy, the pressure of h gas of 10 kg/cafG or less is boosted in the compressor 044, and the reduced pressure is converted into CL gas.
The point is that it is introduced into the methanol synthesis apparatus 001 after being combined with O2.

In addition, in the fourth and fifth embodiments, the expander 043 and the compressor 004 are shown or the same parts are omitted. SPE
The solid oxide electrolyte method can also be used as well as the alkaline method.

〔Effect of the invention〕

(1) It becomes possible to suppress the amount of emissions from C port without significantly reducing the total energy generation.

(2) It becomes possible to recover and fix CO, which was unnecessarily thrown away.

(3) Since the pressurization energy, which accounts for most of the power unit for methanol synthesis, can be reduced, the economic value increases and practical application becomes possible.

[Brief explanation of drawings]

Figures 1 to 5 are schematic diagrams for explaining the first to fifth embodiments of the present invention, Figure 6 is a characteristic diagram showing the conversion rate of methanol synthesis reaction, and Figure 7 is a conventional methanol synthesis reaction. FIG. 2 is a schematic diagram for explaining one aspect of the invention.

Claims (6)

[Claims] (1) H_2 and CO generated from water or steam electrolysis equipment
_2 A method for synthesizing methanol, which comprises synthesizing methanol in a methanol synthesis device using CO_2 obtained from a separation and recovery device as a raw material. (2) CO_ from fossil fuel combustors or fossil fuel reformers
2. The method for synthesizing methanol according to claim 1, characterized in that the 2-rich gas is supplied to a CO_2 separation and recovery device. (3) The methanol synthesis method according to claim (1), characterized in that CO_2-rich gas from an underground gas processing device such as a geothermal steam turbine is supplied to a CO_2 separation and recovery device. (4) The method for synthesizing methanol according to claim (2), characterized in that water or by-product oxygen from the steam electrolysis device is supplied to a fossil fuel combustor or a fossil fuel reformer. (5) H_2 and CO_2 from water or steam electrolysis equipment
One of the CO_2 from the separation and recovery equipment is obtained at a high pressure compared to the methanol synthesis pressure, the pressure energy of the high-pressure raw material is used to boost the pressure of the other raw material, and then both raw materials are mixed and supplied to the methanol synthesis equipment. The method for synthesizing methanol according to any one of claims (1) to (4), characterized in that: (6) The methanol synthesis method according to claim (2), wherein the methanol synthesized in the methanol synthesis device is used as a raw material for a fossil fuel combustor or a fossil fuel reformer.