JPH0782185A - Method for producing methanol - Google Patents

Abstract

PURPOSE:To provide a method for producing methanol by preliminarily reacting a synthetic gas containing hydrogen, carbon monoxide and carbon dioxide in a solid catalyst reactor, separating the produced crude methanol and subsequently reacting the remaining gas in a fluidized catalyst reactor. CONSTITUTION:A synthetic gas containing hydrogen, carbon monoxide and carbon dioxide gas is preliminarily subjected to a methanol synthesis reaction in a solid catalyst reactor. The obtained reaction gas is cooled to separate the produced crude methanol, and the remaining gas is circulated together with a circulation gas and subjected to a methanol synthesis reaction in a fluidized catalyst reactor. Since the employment of the solid catalyst reactor before the use of the fluidized catalyst reaction system enables an increase in the production of the methanol and a decrease in the amount of the circulation gas, the size of the reactor can be reduced, and the whole installation for the synthesis of the methanol can be enlarged. Since components lowering the synthetic gas in slight amounts, such as sulfur, can almost be removed during their passage in the catalyst layer of the solid catalyst reactor, the life of the catalyst in the fluidized catalyst reactor can be elongated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing methanol from synthesis gas suitable for upsizing, and more particularly to a method for producing methanol using a fluid catalytic reactor.

[0002]

2. Description of the Related Art Methanol is attracting attention as an alternative fuel for petroleum that is low in pollution and easy to transport, and can be supplied in large quantities.
Also, in order to reduce construction costs due to economies of scale, the development of ultra-large equipment with a capacity of 5000T / D or 10000T / D or more is required. Conventionally, a fixed bed catalyst is used in a methanol synthesis apparatus, and an adiabatic reactor is generally used as a reactor. Although this adiabatic reactor has a simple structure, the temperature of the catalyst layer rises due to the heat generated by the methanol synthesis reaction, so the method of dividing the catalyst layer into several parts and introducing cooling gas between the catalyst layers is adopted. Has been. Since the heat generation amount of the methanol synthesis reaction is large, it is difficult to increase the methanol concentration at the reactor outlet in such an adiabatic quench type reactor, and the reaction gas must be cooled in order to increase the reaction yield of the synthesis gas. After separating the methanol,
It is necessary to return a large amount of unreacted gas to the methanol synthesis reactor. As described above, in the adiabatic quench type reactor, since the amount of circulating gas is large, the amount of circulating gas compression power increases and the reactor becomes large, and the production limit thereof is reached. Also, most of the reaction heat generated in the adiabatic quench reactor is used to heat the feed gas, and only a low level of heat is recovered from the reactor outlet gas, so that the reaction heat can be recovered efficiently. I can't.

Further, in the methanol synthesizer, a tubular reactor as an isothermal reactor using a fixed bed catalyst is also used. The tubular reactor is a reactor in which a large number of reaction tubes installed inside the reactor are filled with a catalyst to carry out a methanol synthesis reaction, and boiler water is introduced outside the reaction tube to recover steam. Since the filling rate of the catalyst with respect to the cross section of the reactor is limited, the volume of the reactor becomes large. In addition, it is difficult to manufacture a large-sized reactor because there are structural problems such as manufacturing of a tube sheet. Therefore, the tubular reactor is also not suitable for a very large device.

On the other hand, the fluid catalytic reactor has good heat transfer in the catalyst layer and a uniform temperature distribution, so that side reaction products can be suppressed to be low and high conversion and high selectivity can be obtained. The characteristics are that the heat of reaction can be recovered at a high level. In recent years, such a fluid catalytic reactor has been developed as a response to an ultra-large apparatus for producing methanol for fuel. For example, JP-A-60-84142, JP-A-60-122040, and JP-A-60-106534 describe a method for producing a fluidized catalyst for methanol synthesis.
-211246 describes the catalyst and reaction conditions when carrying out methanol synthesis using a fluidized bed catalyst. Further, JP-A-4-28230 describes a method in which a plurality of fluid catalytic reactors are continuously arranged and methanol is separated from the reaction product gas between each stage.

[0005]

Since the fluidized catalytic reactor has the characteristics as described above, it is considered to be suitable for use in a large-scale apparatus. However, when the fluidized catalytic reactor is incorporated into a methanol synthesis process, it is as follows. There is a problem. That is, the fluid catalytic reactor is a reactor having a large number of heat transfer tubes for fluidizing the catalyst to carry out a methanol synthesis reaction. However, in the production or maintenance, the supply gas to the reactor is introduced and dispersed. There is a part (adiabatic zone) where a heat transfer tube cannot be installed above the plate, and a high concentration reaction rate-controlling component (where the supply gas is usually in excess of hydrogen, carbon monoxide and carbon dioxide gas become the reaction rate-controlling component). By introducing the gas having the formula (1) to this adiabatic zone, the temperature locally rises, and the amount of side reaction produced increases or the catalyst is likely to deteriorate in that part. In particular, when the synthesis raw material gas having a high concentration of the reaction rate-determining component is directly introduced into the fluid catalytic reactor as in the method of the above-mentioned JP-A-4-28230, this local temperature increase becomes large.

As one of the countermeasures for this, a method of increasing the amount of circulating gas to reduce the concentration of the reaction rate-determining component in the gas supplied to the reactor can be considered. Because the power to circulate is increased,
It is not the preferred method for increasing the size. As another measure, it is possible to lower the reaction temperature by lowering the steam pressure generated in the fluid catalytic reactor. However, the generated steam must be heated to generate medium-pressure steam of about 20 to 40 atm in order to effectively use it as process steam in power recovery and synthesis source gas manufacturing equipment, so to avoid local temperature rise. It is not a good idea to lower the generated steam pressure to lower the reaction temperature.

On the other hand, in the fixed catalyst reactor, most of the catalyst is free from poisoning because the components such as sulfur that become the catalyst poison are adsorbed in the catalyst layer portion near the gas inlet, but the fluid catalytic reactor. In, the gas and the catalyst particles are uniformly mixed, so that the catalyst is uniformly poisoned. For this reason, when a fluidized catalytic reactor is used, a higher degree of purification of the synthetic raw material gas is required.

[0008]

Means for Solving the Problems The inventors of the present invention have made earnest studies on a methanol production apparatus using a fluidized catalytic reactor having the above-mentioned problems, and as a result, have found that a fixed catalyst layer is provided in front of a methanol synthesis apparatus having a fluidized catalytic reactor. If the reaction rate-determining component concentration in the synthesis gas is reduced by installing the reactor, the amount of circulating gas in the methanol synthesizer having the fluidized catalyst reactor can be reduced, and the activity of the fluidized catalyst can be prevented from lowering. The present invention has been completed, and it has been found that it is possible to increase the size, and the present invention has been achieved.

That is, according to the present invention, a synthetic raw material gas containing hydrogen, carbon monoxide and carbon dioxide gas is previously subjected to a methanol synthesis reaction in a fixed catalyst reactor, and the obtained reaction gas is cooled to separate crude methanol. The method for producing methanol is characterized in that it is introduced into a methanol synthesizer using a fluidized catalytic reactor together with a circulating gas.

The methanol synthesis reaction from hydrogen, carbon monoxide and carbon dioxide of the present invention is carried out according to the following reaction formula. CO + 2H ₂ → CH ₃ OH + 21.6 kcal / mol CO ₂ + H ₂ → CO + H ₂ O − 9.8 kcal /
mol CO ₂ + 3H ₂ → CH ₃ OH + H ₂ O + 11.
8 kcal / mol

A copper catalyst is usually used in the methanol synthesis reaction, and the reaction is carried out at a temperature of 200 to 300 ° C. and a pressure of 50 to 150 atm. As a fluidized catalyst for a methanol synthesis reaction, a catalyst in which a catalyst component is supported on a strong carrier such as silica, alumina or zirconium is usually used, and the particle size of the catalyst is
It is 1 to 250 μm.

The fixed catalyst reactor installed in advance in the present invention may be either a conventional adiabatic quench type reactor or an isothermal type reactor such as a tubular reactor, but circulation in a methanol synthesis apparatus using a fluid catalytic reactor In order to reduce the amount of gas, it is desirable that the reaction amount in the fixed catalyst reactor is as large as possible, and for this purpose, it is preferable to use an isothermal type reactor. As the isothermal reactor, a tube reactor or a system in which a heat transfer tube is installed in a fixed catalyst layer is used, and boiler water is heated in the reactor to recover steam.

In order to enhance the effect of the present invention, it is desirable to increase the outlet methanol concentration in the fixed catalyst reactor installed beforehand. Since the methanol synthesis reaction is an exothermic reaction, it is advantageous in terms of reaction equilibrium to use a reactor having a structure in which the reaction temperature is lowered at the outlet side of the reactor as in JP-A-60-225632. The reaction gas from the fixed catalyst reactor is usually heat-exchanged with the feed gas of the fixed catalyst reactor, and further heat recovery is performed if necessary, followed by cooling to separate condensed crude methanol. It is sent to a methanol synthesizer with a fluid catalytic reactor.

In the methanol synthesizing apparatus using the fluidized catalytic reactor according to the present invention, the reaction gas from the fixed catalyst reactor is cooled to separate crude methanol, and the gas is a circulating gas as in the conventional methanol synthesizing apparatus. It is mixed with and introduced into a fluid catalytic reactor. In a fluid catalytic reactor, it is necessary to generate medium pressure steam of about 20-40 atm in order to effectively use the generated steam for power recovery and process steam in the synthetic raw material gas production equipment, and the reaction temperature is 250-280 ° C. To a degree, the methanol synthesis reaction is performed.

In the method of the present invention, the synthesis raw material gas is previously subjected to the methanol synthesis reaction in the fixed catalyst reactor, so that the local temperature rise in the gas supply section from the dispersion plate of the fluid catalytic reactor is avoided, and The amount of circulating gas can be reduced and the power required for the circulator can be reduced. The amount of circulating gas in a methanol synthesizer with a fluid catalytic reactor varies depending on the composition of the synthetic gas, etc., but the amount of gas is reduced and fixed by cooling the reaction gas from the fixed catalytic reactor to separate crude methanol. Since the reaction rate-determining component concentration in the synthesis gas decreases due to the reaction in the catalytic reactor, the circulating gas amount can be significantly reduced. That is, the ratio of the circulating gas amount to the raw material synthesis gas is about 4 to 6 in the conventional apparatus, but in the method of the present application, this ratio is 3 or less, preferably 1.5.
Since it can be set to about 2.5, and the amount of circulating gas is significantly reduced compared to the conventional device, the circulation power is reduced and the reactor can be made smaller, which is more advantageous in increasing the size. Becomes

As another effect of the present invention, a component that reduces the activity of a methanol synthesis catalyst such as sulfur contained in a small amount in the synthesis raw material gas by reacting the synthesis raw material gas in advance in the fixed catalyst reactor is a fixed catalyst. Almost all of it is adsorbed and removed while passing through the catalyst layer near the inlet of the reactor, which reduces the decrease in the activity of the catalyst in the fluid catalytic reactor.
It is possible to prolong the catalyst life. Since the activity of a copper-based catalyst usually used for a methanol synthesis catalyst is easily influenced by sulfur and the like, there is a great merit that the life of an expensive fluidized catalyst is extended.

Next, the present invention will be specifically described with reference to the drawings. FIG. 1 shows an example of a system diagram of a methanol synthesizer according to the method of the present invention. A synthesis raw material gas containing hydrogen, carbon monoxide and carbon dioxide is introduced from a flow path 1, preheated by a synthesis gas raw material preheater 2, and then introduced into a fixed catalyst reactor 3. The fixed catalyst reactor 3 is an isothermal reactor, and water vapor is recovered from the flow path 4. Fixed catalytic reactor 3
The reaction gas from the methanol condenser after the heat recovery such as preheating of the synthetic raw material gas is performed between the channel 5 and the channel 6.
The crude methanol that has been cooled and condensed in (I) 7 is separated in the methanol separator (I) 8 and is sent from the flow path 9 to the distillation and purification step.

On the other hand, the unreacted gas separated in the methanol separator (I) 8 is sent to the methanol synthesizer having a fluid catalytic reactor through the flow path 10 and is synthesized from the flow path 11 together with the circulating gas of the apparatus. Introduced into the gas circulator 12, after boosting pressure,
After being preheated by the syngas preheater 13, it is supplied to the fluid catalytic reactor 14. A dispersion plate 15, a heat transfer tube 16 and a cyclone 17 are installed inside the fluid catalytic reactor 14, and the supply gas to the fluid catalytic reactor is uniformly introduced into the fluid catalytic layer 18 by the dispersion plate 15. In the fluidized catalytic reactor 14, a heat transfer tube is installed in the fluidized catalyst layer, and water vapor is recovered from the flow path 19. The upper part of the fluid catalytic reactor is a freeboard section 20, and the fluid catalyst in the reaction gas is the freeboard section and the cyclone 17.
Separated by. The reaction gas from the fluid catalytic reactor 14 is subjected to heat recovery such as preheating of the synthesis gas between the flow paths 21 and 22 and then cooled by the methanol condenser (II) 23, and the condensed crude methanol is It is separated in the methanol separator (II) 24 and sent to the distillation purification step from the flow path 25. On the other hand, the unreacted gas from which the crude methanol has been separated is partially purged from the flow path 26 in order to suppress the accumulation of the inert gas component, and the remaining unreacted gas is returned to the synthesis gas circulator through the flow path 11. Be done.

[0019]

EXAMPLE In FIG. 1, first, a double-tube reactor with a fixed catalyst layer (reactor inner diameter 1.6 m, as disclosed in JP-A-60-225632) was used.
, Reaction tube outer tube inner diameter 75mm, inner tube outer diameter 19mm, reaction tube length 1
2m, 200 reaction tubes) 4133.6 kg-mol / h
Was introduced at a pressure of 85 kg / cm ² G and 160 ° C to carry out a methanol synthesis reaction, and after cooling the reaction gas to separate condensed crude methanol, a fluid catalytic reactor (reactor inner diameter 2.27 m, height 20 m , 90-inch 4-inch heat transfer tubes were installed) to carry out the methanol synthesis reaction.

The fluidized catalytic reactor contains Cu with an average particle size of 60 μm.
-Filled with Zn-Zr fluidized catalyst and gas circulation rate of 7608.0 kg-m
The methanol synthesis reaction was carried out by introducing the feed gas 10425.8 kg-mol / h at a pressure of 80 kg / cm ² G and 200 ° C. as ol / h (circulation ratio to the synthetic raw material gas = 1.85). The maximum temperature of the fluidized catalyst bed is 269 ° C, and the required power of the gas circulator is 70
It was 0 kw. In addition, saturated steam with a pressure of 33 kg / cm ² G was applied to the fixed catalyst reactor and the fluidized catalyst reactor at 13.0 T each.
/ H, 11.6 T / H, a total of 24.6 T / H were collected. Table 1 shows the gas flow rate, temperature, and pressure in the main flow paths of FIG. The total amount of crude methanol produced by both reactors is 972.6 kg-mol /
It was h (747.1 T / D). Therefore, the steam recovery amount per methanol production amount is 0.79 T / T-methanol, and the gas circulation power is 22.5 KWH / T-methanol. In the crude methanol, approximately 380 ppm of higher alcohols with C ₂ or more,
About 42 ppm of paraffins of ₅ or more was contained. The total flow rate and the flow rate of each component in the table are kg-mol / h, the temperature is ° C,
The pressure is kg / cm ² G, and CH ₃ OH is a value including these by-products. Under these conditions, the methanol synthesis operation was continued for 3 months, but the catalyst activity was hardly reduced.
The sulfur content in the catalyst extracted from the fluid catalytic reactor was 18 ppm, which was almost the same value as before use.

[0021]

[Table 1] Flow path 1 5 9 10 11 21 25 26 27 Total flow rate 4133.6 3308.0 490.2 2817.8 7608.0 9298.1 881.9 808.2 10425.8 CO ₂ 403.0 355.6 14.6 341.0 364.5 408.8 5.6 38.7 705.5 CO 651.3 286.5 1.9 284.6 160.2 177.7 0.5 17.0 444.8 H ₂ 2953.5 2080.4 3.3 2077.1 6107.9 6760.5 3.7 648.9 8185.0 CH ₄ 102.1 102.1 0.9 101.2 931.9 1033.1 2.2 99.0 1033.1 N ₂ 1.2 1.2 0.0 1.2 11.5 12.7 0.0 1.2 12.7 H ₂ O 21.9 70.0 69.4 0.6 3.3 301.1 297.4 0.4 3.9 CH ₃ OH 0.0 412.2 400.1 12.1 28.7 604.2 572.5 3.0 40.8 Temperature 40.0 231.6 40.0 40.0 40.0 267.2 40.0 40.0 47.6 Pressure 86.5 82.0 79.5 79.5 77.5 80.0 77.5 77.5 83.0

Comparative Example 1 Fixed catalyst reactor loop (equipment and flow in FIG. 1
No. 2 to 9) was used, and a synthesis gas having the same composition as in Example 1 was directly introduced into the intake side of the synthesis gas circulator 12 from the flow path 10 to obtain a fluid catalytic reactor similar to that in Example 1. Was used to carry out a methanol synthesis reaction. The reaction conditions of the fluid catalytic reactor were the same as in Example 1 except that the pressure was 80 kg / cm ² G and the temperature was 200 ° C.
Saturated steam of 3 kg / cm ² G was generated. Syngas was introduced at 2817.8 kg-mol / h as in the fluidized bed reactor in Example 1, and the gas circulation rate was 7608.0 kg-mol / h (gas circulation ratio = 2.
In the case of 7), a temperature rising part up to 285 ° C was observed at the bottom of the fluidized catalyst bed, side reaction products increased, and 830 ppm of higher alcohols with C ₂ or more and 88 ppm of paraffins with C ₅ or more.
Became. Therefore, in order to avoid a local temperature rise in the adiabatic zone below the fluidized catalyst bed and to obtain a catalyst bed temperature distribution (maximum temperature 269 ° C.) similar to that in Example 1, the synthesis tower inlet gas amount was 10425.8 kg-mol. / h, the synthesis raw material gas amount is changed to 217
It was reduced to 2kg-mol / h and the gas circulation ratio was set to 3.8. As a result, the methanol production was 533.1 kg-mol / h (410 T / D), the gas circulation power was 702 kw, and the amount of saturated steam generated at a pressure of 33 kg / cm ² G was 12 T / H. Therefore, the steam recovery amount per methanol production amount is 0.70 T / T-methanol and the gas circulation power is 41.1 KWH / T-methanol.
Table 2 shows the gas flow rate, temperature and pressure in the main flow paths. The amount of side reaction products in this case was about the same as in Example, but the sulfur content contained in the catalyst extracted after continuing the operation for 3 months was 104 ppm. This is because a trace amount of catalyst poison components such as sulfur in the syngas were introduced into the fluid catalytic reactor.

[0023]

[Table 2] Flow path 10 11 21 25 26 27 Total flow rate (kg-mol / h) 2172.0 8253.8 9855.8 753.8 348.2 10425.8 CO ₂ 211.8 230.1 248.2 3.4 9.7 441.9 CO 342.5 142.5 148.8 0.3 6.0 485.0 H ₂ 1551.9 6628.3 6911.4 3.5 279.6 8180.2 CH ₄ 53.6 1201.8 1255.4 2.9 50.7 1255.4 N ₂ 0.7 15.1 15.8 0.0 0.7 15.8 H ₂ O 11.5 3.2 213.7 210.6 0.1 14.7 CH ₃ OH 0.0 32.8 567.3 533.1 1.4 32.8 Temperature 40.0 40.0 265.2 40.0 40.0 46.9 Pressure 79.5 77.5 80.0 77.5 77.5 83.0

In the above embodiment, by installing the fixed catalytic reactor in front of the fluid catalytic reaction system in the method of the present invention, the methanol production amount is increased by 82% (747/410 = 1.82), and Gas circulation power is about 45% per methanol production
(22.5 / 41.1 = 0.547) decreased, and the amount of water vapor recovered was 13% (0.79 / 0.
70 = 1.13) It is increasing. Therefore, it can be seen that the methanol production method of the present invention is extremely advantageous for increasing the size and significantly improves the energy efficiency. That is, in the method of the present invention, the amount of the circulating gas in the methanol synthesizer can be reduced, so that the diameter of the reactor can be reduced, the manufacturing cost of the reactor and the power cost of the circulating gas can be reduced, and the energy efficiency can be improved. In addition, the methanol synthesizer can be made larger.

Further, according to the method of the present invention, the concentration of the reaction components (CO, CO ₂ ) in the feed gas of the fluid catalytic reactor is lowered, so that the local temperature rise in the fluid catalytic reactor is avoided and the side reaction is avoided. It is possible to prevent an increase in production amount and catalyst deterioration. Further, according to the method of the present invention, components that reduce the activity of the methanol synthesis catalyst, such as sulfur, which are contained in a small amount in the synthesis gas, are almost removed while passing through the catalyst layer of the fixed catalyst reactor.
Decreased catalyst activity reduction in fluidized catalytic reactors and increased catalyst life. Therefore, the present invention is a very useful method in a large-scale methanol production apparatus using a fluid catalytic reactor.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a system diagram of a methanol synthesis apparatus according to the present invention.

[Explanation of symbols]

 1 Synthetic raw material gas 2 Synthetic raw material gas preheater 3 Fixed catalytic reactor 7 Methanol condenser (I) 8 Methanol separator (I) 12 Synthetic gas circulator 13 Syngas preheater 14 Flow catalytic reactor 23 Methanol condenser (II ) 24 Methanol separator (II)

Claims (2)

[Claims] 1. A synthesis gas containing hydrogen, carbon monoxide and carbon dioxide is previously subjected to a methanol synthesis reaction in a fixed catalyst reactor, and the obtained reaction gas is cooled to separate crude methanol, and then the reaction gas is mixed with a circulating gas. A method for producing methanol, which is characterized in that it is introduced into a methanol synthesizer using a fluidized catalytic reactor. 2. The method for producing methanol according to claim 1, wherein the ratio of the amount of circulating gas supplied to the fluidized catalytic reactor to the amount of synthetic raw material gas supplied to the fixed catalytic reactor is 3.0 or less.