JPS58134039A - Preparation of methanol - Google Patents

Abstract

PURPOSE:To obtain methanol form H2, CO, and CO2, by using the first reaction zone consisting of a heat insulating catalytic layer and the second reaction zone having a heat exchange type catalytic layer in series, using a process wherein a waste-heat boiler is set between the two reaction zones and a reaction heat is recovered efficiently. CONSTITUTION:In preparing methanol by bringing H2 and a gas such as CO and/or CO2 rich in a carbon oxide into contact with a high-temperature catalyst at high temperature under high pressure, a raw material gas is passed through the heat exchanger 24, preheated to 100-180 deg.C, 1/10-1/2 of the gas is preheated to 210-250 deg.C by a reaction heat generated by the second reaction zone 6, sent to a heat insulating catalytic zone of the uppermost flow of the first reaction zone 1, and the gas is reacted. While, the remaining raw material gas is separately sent to a mddle flow part of the first reaction zone 1, reacted, a methanole-containing gas is passed through the waste-heat boiler 21, cooled to 230-260 deg.C, and sent to the second reaction zone 6 to finish the reaction. Remaining heat is recovered from the methanol-containing gas flowing out from the reaction zone 6 by the waste-heat boiler 22 and the heat exchanger 23, and methanol is obtained from the pipe 42.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an improvement in a method for producing methanol by bringing hydrogen and a gas rich in carbon oxides such as carbon monoxide and/or carbon dioxide into contact with a high temperature catalyst under high temperature and high pressure. More specifically, a gas rich in hydrogen and carbon oxides (hereinafter simply referred to as raw material gas) under high pressure is transferred to a first reaction zone consisting of a high-temperature adiabatic catalyst layer and a heat transfer surface for indirect heat exchange. In the method of synthesizing methanol by passing it through the catalyst layer and the second reaction zone in this order, methanol is synthesized using a single-liquid reactor with a simple structure under the lowest possible pressure. The purpose is to recover the reaction heat as higher temperature steam.

As is well known, the contact thickness 1,6 for synthesizing methanol from the raw material gas is a violent exothermic reaction and, in terms of chemical equilibrium,
The higher the reaction conditions are, the higher the pressure and lower temperature, the higher the methanol concentration in the gas after the reaction, which is the preferred operating temperature range for a practical catalyst. 2Sθ~35θ℃, which is the pressure at which methanol can be easily produced within the temperature range 2Sθ~35θ℃.
．． 5θ to 3θθkV/ctAG are frequently used as conventional manufacturing conditions. Among such well-known methods, the use of the reactor is described, for example, in JP-A No. 3;'l-/! ;7
The preheated raw material gas is fed into a single reactor having a plurality of series adiabatic catalyst layers, such as 3/3, IN-I and turned to L6,
The temperature of the catalyst layer is controlled by supplying low-temperature raw material gas between each heat-insulating catalyst layer (hereinafter, the gas supplied in this manner is referred to as quench gas), and the reaction heat is used to preheat the raw material gas or heat water. As described in JP-A-4-3.27'1, a raw material gas is passed through a catalyst layer filled in a number of tubes placed in boiling water under high pressure, and then kept at a constant temperature. A method for reacting and recovering the reaction heat as high-pressure steam, and Hydrocarbon Processing Magazine/
973: A plurality of reactors with adiabatic catalyst layers described on page gθ of the July issue are used in series, and the reaction heat is converted into high-pressure steam by exchanging heat between the gas undergoing reaction and high-pressure water between each reactor. There is a method of recovering raw material gas as well as preventing an excessive rise in the temperature of each adiabatic catalyst layer, or by installing both an adiabatic catalyst layer and a heat exchange type catalyst layer in the same reactor as described in 11 of Japanese Patent Publication No. 9Q-Za967. There are methods such as first passing through an adiabatic catalyst layer and then a heat exchange type catalyst layer. All of these methods have drawbacks such as insufficient recovery of reaction heat, complicated reactor structure that is not suitable for dog-shaped reactors, or low methanol concentration at the reactor outlet. In other words, JP-A-9 Goo 737! Since method 3 uses only a plurality of adiabatic catalyst layers, the temperature of the catalyst and the gas during the reaction inevitably rises as methanol is produced. The amount of quench gas supplied between the layers needs to be adjusted to the temperature of the downstream adiabatic catalyst layer, and the supply of quench gas has the effect of diluting the generated methanol in addition to the effect of lowering the gas temperature. This causes a decrease in the methanol concentration in the outlet gas. Also, JP-A-116-3.2/1
In method 7, the pressure and temperature on the gas side of the reactor and the pressure and temperature on the steam side are different, so it is difficult to avoid large stresses caused by these pressure differences and differences in thermal expansion of the reactor materials in terms of design. A reactor with an incompatible structure is used as a dog-shaped reactor.

Furthermore, the method described in the aforementioned Hydrocarbon Processing magazine requires a large number of high-pressure reactors and waste heat boilers, making the entire device expensive. Even more Tokko Akira! ! The method of -g697 has the drawback that the reaction heat is insufficiently recovered during the reaction process, so the reactor outlet gas has a considerably high temperature, and the methanol concentration in the reactor outlet gas is low due to chemical equilibrium reasons.

The present invention is an alternative method for producing methanol that improves the drawbacks of the known methods as described above, in which a first reaction zone having an adiabatic catalyst layer has a temperature of 2/θ to 2! supplying 7 parts of the raw material gas preheated to a temperature between θ°C and the remaining raw material gas preheated to a temperature between 789 and 7g0°C as a quench gas;
The intermediate reaction gas flowing out from the first reaction zone, which does not have a sufficient methanol concentration, is cooled to a temperature between 23θ and 0°C while recovering the reaction heat using a waste heat boiler, and then this cooled gas is heat exchanged. The raw material gas is supplied to the second reaction zone having a type catalyst layer to increase the methanol concentration, and the entire amount of reaction heat at that time is supplied to the first reaction zone at a temperature between -70 and 00 °C. This method is used for preheating a portion of the reactor, and is a method in which the reaction heat is efficiently recovered as steam using two large-scale reactors with six reactors and/or waste heat boilers, each of which has a structure that is easy to manufacture.

This invention will be explained in detail using FIG. 7. 1st
The figure shows seven examples of the process according to the present invention. A first reaction zone having F, & and j, which reaction zone is designated as an independent reactor. 6 is a third reaction zone having a catalyst layer 7 and a heat exchanger tube g in contact with the catalyst layer, and is a heat exchange type independent reaction zone.
1.7, displayed as a vessel. The high-pressure new supply gas is supplied from pipe 3/, and after combining with the circulating gas from pipe
3 g of tubes from the second reaction zone 6, which still has residual heat after entering the heat exchanger 2 and recovering most of the heat there.
It is preheated by exchanging heat with the outflow gas. This preheated raw material gas is in one tube 33 and 3/l! 7? , , the flow in the tube 33 passes through the heat transfer tube of the second reaction zone B, and at that time, is further preheated by the reaction heat generated in the catalyst layer 7 and transferred to the tube 3S. It is fed to the most upstream catalyst layer in the first reaction zone, where the adiabatic methanol synthesis reaction is partially carried out. This gas, whose temperature has increased as a result of the progress of the methanol synthesis reaction, is mixed with a portion of the preheated branch stream 3 between the catalyst layer and 3 to lower the temperature and dilute the methanol concentration. . This mixed gas enters the catalyst layer 3 and the methanol synthesis reaction partially proceeds again, the temperature rises, and the catalyst layer 3
Similarly to the above, a part of the preheated raw material gas is supplied from the pipe 3 to lower the temperature. The same operation is repeated, and the gas whose methanol concentration has increased (not sufficient methanol concentration) from the most downstream catalyst layer S of the first reactor is made to flow into the waste heat boiler 2/ through the pipe 36, where it absorbs most of the reaction heat. is removed as steam. Most of the heat of reaction is removed: ·: The temperature of the octopus gas is 5. Once the operating temperature of the catalyst is met, it is then introduced into the catalyst bed 7 of the second reaction zone through a tube 37. In this catalyst layer 7, the methanol synthesis reaction further progresses, and the methanol concentration in the gas further increases, and the heat generated during the reaction is transferred to the raw material supplied to the first reaction zone through the pipe 33 as described above. It is used to preheat the gas flow to complete the Tsukunor synthesis reaction. The gas leaving the second reaction zone 6 passes through a pipe 3g to a second waste heat boiler, .
After the remaining heat is recovered by the heat exchanger 2 and further recovered by the heat exchanger as necessary, the remaining heat is used for preheating the 1BiI and feed gas by the heat exchanger and the 2 DA as described above. The reaction-completed gas flowing out from the heat exchanger 2 is cooled via pipe 32? ! The methanol vapor and by-product water vapor that were present in the gas flow into the i-needle 25 and are cooled by direct contact with water or indirect heat exchange, and become liquid.
The gas and liquid are then separated by the separator 2B via the pipe θ, and the unreacted gas passes through the pipe DA/, mixes with the new supply gas supplied from the pipe 3/, and is recycled as a raw material gas. :;1 compressor,! After being pressurized by 7, it is recycled to the inverse region as described above. The separated liquid is also sent to the purification process via tube &2.

The main advantages of the process of this invention are 11. For example, in the above process example, the second reaction zone 6 having an adiabatic catalyst layer and the second reaction zone B having a heat exchange type catalyst layer are used in series to generate gas after the reaction is completed. By increasing the methanol concentration in the reactor and interposing a waste heat boiler between these two reaction zones, it is possible to increase the amount of recovered steam and shift its temperature and pressure to higher levels compared to conventional methods. At the point. At this time, in order to maximize the residual heat that can be recovered as high-pressure steam, it is necessary to control the temperature or gas distribution during the process within a preferable range, which will be explained below.

As mentioned above, under equal pressure, the methanol synthesis reaction is advantageous because the lower the operating temperature of the catalyst, the higher the methanol concentration in the gas after the reaction, in terms of chemical equilibrium. To this end, many methanol synthesis catalysts have been developed and are well known. Among these many catalysts, those in practical use exhibit methanol synthesis ability at temperatures above 2/θ°C in the initial stage of catalyst use, but those at the end of their catalyst life exhibit methanol synthesis ability at 2'lO~, 2'
Demonstrates methanol synthesis ability at temperatures above 13°C.

Further, these catalysts have a heat resistance upper limit temperature of 330°C to 3qθ°C, and if the catalysts are overheated above this temperature, they lose their methanol synthesis ability. Therefore, the usable temperature range of such a catalyst is 170°C to 33θ when the catalyst is new in both the seventh reaction zone and the second reaction zone.
This indicates that the catalyst temperature, that is, the reaction temperature, needs to be controlled within the temperature range of 2g θ°C to 33θ°C as the temperature increases. The adiabatic catalyst layer used in the first reaction zone of this invention has a built-in reactor structure that is very simple, making it easy to handle, inexpensive, and easy to charge and discharge the catalyst. However, it is essential to introduce a quench gas in order to control the reaction temperature.

A large amount of this quench gas is required at the back of the adiabatic catalyst layer located downstream, and introducing a large amount of quench gas also has the effect of greatly reducing the concentration of methanol already produced in the gas. It is difficult to bring the methanol concentration in the gas very close to the chemical equilibrium concentration using only this type of reactor. This drawback is not a serious drawback when methanol synthesis is carried out at conventional pressures such as 300 H7 crho because the chemical equilibrium concentration of methanol is relatively high at q3 mol. However, in order to save the compression power of the raw material gas, which accounts for most of the energy required for methanol production, if the synthesis pressure is lowered to about /θθkan/ff1G, for example, to about θkg/aAG, methanol The above-mentioned drawback becomes a serious hindrance because the chemical equilibrium concentration of In order to overcome this drawback, the present invention introduces the gas flowing out of the first reaction zone into a waste heat boiler, cools it to a temperature of 3θ to 26θ℃ while recovering high-pressure steam, and then transfers it to the second reaction zone. to be introduced. , 23[theta] to -60[deg.] C. is the most preferable temperature in terms of the chemical equilibrium concentration and the reaction promoting effect of the catalyst when further proceeding with methanol synthesis in the second reaction zone. Therefore, it is preferable that the methanol synthesis reaction proceeds as homogeneously as possible in this reaction zone, and the reaction is carried out in approximately equal amounts within this temperature range while cooling the catalyst layer by dividing the raw material gas through the pipe 33. will be allowed to proceed. The heat of reaction in this second reaction zone is recovered as described above.

On the other hand, when the synthesis pressure is low, it is important to keep the temperature rise of the adiabatic catalyst layer in the first reaction zone smaller than in the conventional method 1) to proceed with the reaction in order to compensate for the low chemical equilibrium concentration. Become. As a result of the study by the inventors of this device, the amount of 27θ to 2% of the total raw material gas supplied to the first reaction zone is
It is essential to preheat to sθ℃ and supply it to the most upstream part of the adiabatic catalyst bed, and the remaining 709 to 7g is preheated to 9℃ and then distribute it to the midstream part of the adiabatic catalyst bed as a punch gas. These conditions are favorable for keeping the amount of catalyst relatively small, increasing the methanol concentration at the outlet of this reaction acid, and maximizing the amount of high-pressure steam recovered in the waste heat boiler 2/. If methanol synthesis is carried out under the above conditions, the log gas stream exiting the first reaction zone when the synthesis pressure is goH/crA G has a temperature of 27θ~290°C and a methanol content of q~S mole, and the waste heat is After cooling to the temperature in the boiler 2/2, the methanol concentration can be further increased in the first reaction zone to a range of 5 to 6 molar.

Another preferable thing is that when the synthesis pressure is low, the preferable ratio of the branched stream 3j to be supplied to the first adiabatic catalyst layer, whose temperature has already reached the operating temperature of the catalyst, to the total raw material gas is reduced. This divided flow is used to collect the reaction heat in the second reaction zone and most of the heat retained in the gas flowing out from the second reaction zone in the waste heat boiler J, 2. This makes it possible to preheat the catalyst to its operating temperature using low-temperature residual heat that is difficult to recover and utilize. As a result, the amount of recovered high-pressure steam increases. The retained preheating of the reaction gas flowing out of the waste heat boiler 2.2 is based on the above external quench gas in terms of quantity.
It is also possible to preheat the quench gas to 9° C., indicating a favorable agreement with the need to preheat the temperature of the quench gas fed to the first reaction zone to the desired temperature.

Taking all of the above into account, this invention
The conventional method using only the first reaction zone as described in 3/3 is
For example, when the synthesis pressure is 4/caO, the methanol concentration is 1.0% with the reaction completion gas of Sθmolti, and 11. S building/C→G saturated steam purified methanol/
/7θ, 2/θ, θ and λθθ per ton respectively
However, in this invention, a relatively small second
By installing a reaction zone, the methanol concentration in the gas after the reaction is completed is increased by about 1%, and 361. ! The saturated steam of S1 and gkg/aAO can be recovered by 3θ01.2/θ and 62θ of 1'7 methanol/ton, respectively.

The methanol synthesis catalyst used in this invention can be any of the well-known catalysts, such as chromium-based and copper-based catalysts, but those with low operating temperatures are particularly desirable. 11. Also, a suitable value for the quantitative ratio between each catalyst layer used adiabatically in the first reaction zone is to increase the amount of the adiabatic catalyst layer on the culm flow side where the synthesis pressure decreases by comparing it with the amount on the one upstream side. For example, the catalyst layer in FIG. 1 when the synthesis pressure is θt47crao! , 3, the catalyst amount ratio of Da and S is /
:, 2:3 Nige is good. Further, the amount of catalyst used in the second reaction zone may be about % of the total amount of catalyst used in the first reactor.

Furthermore, the first reaction zone, the waste heat boiler 2/2, and the second reaction zone do not need to be installed as independent reactors or boilers as shown in FIG.
It is also possible to design and manufacture such that all persons are housed in one pressure-resistant container. Note that although the first reaction zone in FIG. 1 has a quench gas mixing space in which catalyst particles are not present between each catalyst layer, this quench gas mixing space in which catalyst particles are not present is not necessarily necessary. For example, Tokuko Sho 113-76,
If a device capable of dispersing and mixing the catalyst particles as described in □1 of the catalyst particles is used in the catalyst layer, it is necessary to provide a mixing space that does not contain the catalyst particles. In addition, the space volume required for the first reaction zone can be saved.In addition, a heat exchanger for the final preheating of the branch stream 33 is provided in parallel with the waste heat boiler, and the outlet of the first reaction zone Diversion of part of the flow 33
There is also a method in which the reaction heat is recovered as high-pressure steam using the reactor described in JP-A-1-16-3.2/& as the reactor for the second reaction zone. Although the same effects as the present invention can be obtained, the structure of the reactor is more complicated. This invention can also be applied to the production of methanol, where the conventional synthetic pressure 3θθ is as high as 9/crAO.
The above advantages can be better exhibited in methanol synthesis under low pressures below Ao, and energy savings in methanol production can be realized.

EXAMPLE A methanol synthesis test was conducted using the apparatus shown in the process shown in Figure 1. However, at that time, heat exchange was not performed in the heat exchanger 23. The conditions for implementation are compliance with Table F.

The catalyst used was a copper-1lij lead based catalyst.

(to) Methanol synthesis pressure and θ are 9/crAO (
b) Catalyst amount in the first reaction zone 1st layer (k) '/2rt? First layer (J)
/ 9d 3rd layer (ll) r? i th layer (5), l19'rrlf now 3rd
Reaction zone catalyst amount 37- Gas in pipe 3S, 2g θ βθ1.5θθ θ3 pipe 3
Gu^'s gas /6! ;1. ．． 0 begda θθ Same as above tube 3
Gas in 6, 2'75 4t3 Gas in pipe 37, 2ss Gas in same tube 3g, 2Sθ 73/θθ S--, gas in pipe θ
New feedstock gas supply pressure from pipe 3/cf/clD 1 supply amount/3 7θθN-
4 o'clock, composition (7 books) hydrogen o de S - carbon oxide / 11,
3-chi, carbon dioxide 73-g, other J1 (to) tube lI, methanol obtained from 2! +', r,
! ;'0.7θθ House/hour Composition Methanol 7g 3% by weight, Water Co. x 3% by weight, Other θg Weight 17cm Waste heat boiler 2/36/mu θθθ Waste heat boiler 2/hour 23/643;θθ

[Brief explanation of the drawing]

FIG. 1 shows seven examples of the process of this invention. / 1st reaction zone 2 1st heat insulation - catalyst layer 3 2nd heat insulation catalyst layer q 3rd heat insulation catalyst layer d 9th heat insulation catalyst layer 6 1st reaction zone 7 Catalyst layer for the above g Heat exchanger tube for the above / Waste heat boiler 2,! Waste heat boiler, 23.2g Heat exchanger 2j Cooler 26 Gas-liquid separator 27 Gas circulation compressor 3/ New feedstock gas inlet 32~ll/ Connection pipe 11.2 Produced methanol liquid outlet 3 Purge gas outlet Applicant Toyo Engineering Co., Ltd. Agent Akira Ozu - 11゜Figure 7

Claims (1)

[Claims] (1) Gas rich in hydrogen and carbon oxide under high pressure is transferred to a first reaction zone consisting of a high-temperature adiabatic catalyst layer and a second reaction zone consisting of a high-temperature catalyst layer provided with a heat transfer surface for indirect heat exchange. In the methanol synthesis method in which the gas is passed in this order, (a) the total amount of the gas is preheated to 796-7g0°C, (1)) % to a given amount of the gas preheated in (a) above is used for the second reaction. Using the heat transfer area arranged in the second reaction zone, the reaction heat generated in the second reaction zone;
After being indirectly preheated to 3θ°C, it is introduced into the most upstream adiabatic catalyst layer of the first reaction zone to cause a methanol synthesis reaction.
)"--of the gas preheated according to (a) above)
The methanol synthesis reaction proceeds while distributing and supplying the remaining amount other than the amount used in the first reaction zone to the midstream part of the first reaction zone to prevent overheating of the catalyst, and (d) the methanol-containing gas that has flowed out of the first reactor is disposed of. The methanol synthesis reaction is completed by introducing the residual heat into the catalyst bed of the second reaction zone of the hind limb, which has been cooled to a temperature between 23θ and 2θ℃ by a heat boiler. A method for producing methanol, characterized in that after recovering the produced methanol, the produced methanol is separated, and the unreacted gas is recycled to the above (a).