RU2254322C1 - Method for preparing methanol from gas in gaseous and gas-condensate deposit - Google Patents

Abstract

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to the improved method for preparing methanol. Method involves the successive feeding hydrocarbon-containing gas, injection of chemically purified water, carrying out the preliminary steam reforming for preparing synthesis gas and carrying out the final reforming if formed gas with addition of oxygen under pressure for carrying out synthesis of methanol, heating reactor for preliminary reforming by flow of obtained synthesis gas going out from reactor for the final reforming that is fed to intertubular space of reactor for preliminary reforming followed by cooling synthesis gas obtained as result of reforming by vapor-gas mixture and carrying out synthesis of methanol in 2-step reactor. Cooling the reaction mixture for carrying out isothermal reaction for synthesis of methanol in intermediate external heat exchanger of two-step reactor is carried out with vapor-gas mixture and cooling flow going out from reactor for synthesis of methanol is carried out with vapor-gas mixture and chemically purified water. Also, invention relates to unit for preparing methanol including the source of hydrocarbon-containing gas and unit for complex preparing gas, reactor for preliminary vapor reforming heated with flow going out from reactor for final reforming, two-step reactor for synthesis of methanol, heat exchangers for cooling synthesis gas, heat exchangers for cooling flow going out from reactor for synthesis of methanol, separator for separation of reaction products and exhausting gases and crude methanol. The unit for preparing methanol is assembled with unit for complex gas preparing including block for preparing chemically purified water, block for preparing raw, additional manufacture involving torch making, cleansing constructions, sources of electric energy, air of control and measuring instruments and automatic equipment, chemical laboratory and operating block. Two-step reactor for synthesis of methanol joined with heat exchanger for cooling synthesis gas with vapor-gas mixture, intermediate external heat exchanger for cooling the reaction mixture with vapor-gas mixture is joined in-line with heat exchanger for cooling flow obtained in reactor with vapor gas mixture, heat exchanger for cooling of chemically purified water and separator for separation of reaction products. Ignition device is assembled in reactor for final reforming that promotes to carry out the start of unit without trigger furnace. Water is injected in flow hydrocarbon gas directly before heat exchanger for the reaction mixture that provides excluding boiler-utilizer and trigger boiler from schedule and to solve the problem for cooling the reaction mixture in reactor for synthesis of methanol also. Based on integration of the device for preparing methanol in technological schedule with unit for complex preparing gas and significant change of the conventional schedule for preparing methanol method provides 3-fold reducing capital investment.

EFFECT: improved method for preparing methanol.

2 cl, 1 dwg

Description

The present invention relates to the field of organic chemistry, and in particular to a technology for the production of methanol through synthesis gas.

The main gas and gas condensate fields are located in remote areas of the Far North of the Yamal-Nenets Autonomous District, Krasnoyarsk Territory and Yakutia. Today, up to 85% of gas is produced in the North of the Tyumen Region at large fields: such as Urengoyskoye, Yamburgskoye, Zapolyarnoye, which have entered the declining production regime. Further growth and maintenance of achieved gas production volumes will mainly be carried out at the expense of numerous small fields. The cost-effectiveness of hydrate inhibitors (up to 2.5 kg per 1000 m ^{3 of} gas for gas condensate fields), which use methanol, mainly affects the profitability of such deposits. The delivery of methanol to remote fields is a huge cost, several times higher than the price for the purchase of methanol from petrochemical plants.

The creation of small-tonnage methanol production plants under field conditions as part of integrated gas treatment plants (GTP) would solve the above problems for gas and gas condensate producers.

A number of methods are known for converting methane to methanol. The following technologies have wide industrial application:

- steam reforming of methanol into synthesis gas (a mixture of CO, CO ₂ , H ₂ ) for large-capacity methanol production, more than 1000 tons per day, followed by catalytic conversion to methanol (they are licensed for the production of Davy Progress Tegnology United Kingdom, AG Lurgi, AG "Linda", GIAP RF, etc.);

- autoforming of methane into synthesis gas with a preliminary methane steam reforming unit and additional oxidation in an autoforming reactor with oxygen supply, and then catalytic conversion to methanol (licensed by AG Lurgi), which can be used for medium (from 500 t / day) and large-scale production of methanol;

- the Tandem process was developed by Russian developers of GIAP, the license for which was sold to AG Linda, the process is based on the production of synthesis gas in 2 reactors, the heat of the methane oxidation reaction with oxygen is used in a tubular steam reforming reactor, the process is used for medium (500 t / day) and larger industries.

These technologies are described in many publications and presentation materials of the above companies. To implement these processes, it is necessary to have sophisticated equipment, high requirements for gas purity, high energy costs for producing synthesis gas and its purification, the use of expensive gas compressors, unprofitability of small plants with a capacity of less than 500 t / day.

Currently, the most interesting is the direct, bypassing the stage of synthesis gas production, gas-phase oxidation of methane to methanol at high pressures. The process is carried out at pressures of up to 10 MPa and temperatures of 400-500 ° C in tubular reactors at relatively low initial oxygen concentrations, followed by cooling of the gas-liquid mixture and separation of liquid products, from which methanol is isolated by distillation (Arutyunov VS, Krylov OV “Oxidative transformations methane ", Moscow," Nauka ", 1998, RU A, 2049086; GB 2196335; SU A1, 1469788; RU A, 2162460, 2203261). The above known methods of partial direct oxidation allow you to create small-scale production of methanol. The main disadvantages of this production are: obtaining raw methanol of low concentration, obtaining a large number of by-products, such as formaldehyde, acetic acid and others, which, in turn, are not used in commercial conditions, and when disposed of, they worsen the environmental situation and have a harmful effect on equipment , lowering its corrosion resistance, which in turn makes this method of producing methanol uncompetitive.

Closest to the proposed method is the production of methanol by the technology of GIAP RF (patent 803191, 784148).

The synthesis gas required for the synthesis of methanol is obtained by the steam conversion method using a combined scheme of a tubular reactor and a shaft reactor. The name of the natural gas reforming system is “Tandem”.

In a tubular reactor, a preliminary conversion of methane and other hydrocarbons of natural gas is carried out by using the heat of the converted gas after the shaft reactor.

The technological scheme of methanol production includes the following main stages of the process:

- block for the preparation of raw materials, hydrotreating raw materials for cleaning from sulfur compounds;

- steam conversion of natural gas at a pressure of 2-3.5 MPa and at a temperature of 510-600 ° C in a tubular reactor, 700-850 ° C in a shaft reactor with a heat recovery system for converted gas;

- compression and circulation of the converted gas by a synthesis gas compressor driven by a steam turbine or electric motor;

- synthesis of crude methanol at a pressure of 6.0-8.0 MPa and at a temperature of 220-280 ° C in a radial type reactor using the heat of synthesis reaction in external heat exchangers to heat with feed water or generate steam; rectification of crude methanol in two columns using the heat of the converted gas to obtain rectified methanol of a given quality;

- auxiliary production (deaeration of demineralized water to produce feed water, waste-heat boilers, start-up boiler, pump feed water, installation of preparation of feed water additives, stripping of process condensate under pressure using stripping gas for the process, start-up furnace, treatment facilities, etc. .d.).

The use of this set of equipment makes the process expensive and unprofitable for small-tonnage installations.

Given the above factors, it can be stated that there are no competitive small-tonnage methanol production plants on the methanol production market.

Let us consider as an example the composition of the GIAP medium-tonnage installation, which consists of blocks for the preparation of raw materials (purification from sulfur compounds), the Tandem process for producing synthesis gas (a mixture of CO, CO ₂ , H ₂ ), a methanol synthesis reactor, and a chemical purification preparation unit water, an oxygen-enriched air compression unit, a methanol distillation unit, heat exchangers, air-cooling units, a start-up boiler for producing steam, a recovery boiler for receiving steam, a tank farm, auxiliary production.

Methanol production can be conditionally divided into the following blocks for capital investments:

- gas treatment unit - 13-17%;

- synthesis gas production unit - 25-30%;

- methanol synthesis unit - 10-12%;

- methanol distillation unit - 15-20%;

- unit for the preparation of chemically purified water - 4-6%;

- compressor installation for compression and circulation of synthesis gas - 4-8%;

- heat recovery unit to produce steam - 8-10%;

- oxygen preparation unit - 6-8%;

- starting boiler and starting furnace - 6-8%;

- auxiliary production - 10-15%.

The task of creating a small-tonnage plant for the production of methanol through synthesis gas (a mixture of CO, CO ₂ , H ₂ ) is solved by integration with a complex gas treatment unit (UKPG), where methanol is used as an inhibitor of hydrate formation in the gas collection, preparation and long-distance transport system. The integration scheme of the methanol production unit with the gas treatment unit allows to reduce capital investments in the creation of a methanol production unit several times in comparison with traditional methods and significantly reduces the cost of methanol production.

The problem is solved at the expense of:

- exceptions block preparation of raw materials, because gas produced at the gas treatment facility of the Far North and East of the Russian Federation does not contain sulfur compounds that poison the synthesis gas and methanol synthesis catalysts (reporting materials of TyumenNIIgiprogaz LLC, VNIIgaz LLC, Gazprom OJSC and reference materials for the fields);

- exclusion of the recovery boiler for generating steam by injecting water into the gas stream through the nozzle directly in front of the heat exchanger for cooling the products of the methanol synthesis reactor, as well as for using this vapor-gas mixture with a temperature of 120-150 ° C to cool the intermediate reaction mixture of the methanol synthesis reactor;

- exceptions of the starting boiler for steam production, as water is injected directly into the gas stream;

- exclusion of the starting furnace for heating the gas mixture to the temperature of the beginning of the synthesis gas production process by installing a special igniter in the shaft reactor;

- exclusion of the compressor installation for compression and circulation of synthesis gas due to the process of producing synthesis gas at a pressure equal to the pressure of the synthesis of methanol;

- exceptions to the rectification unit of crude methanol, because a high concentration of crude methanol up to 78-84% allows the use of raw methanol as an inhibitor of hydrate formation;

- exceptions of the unit for the preparation of chemically purified water, because a unit for the preparation of chemically purified water is available at the gas treatment facility;

- exceptions of auxiliary production (flare, treatment facilities, sources of electrical energy, instrumentation air, control room, chemical laboratory, etc.), because these facilities are part of the gas treatment plant.

Thus, due to the integration of a small-tonnage methanol production unit into the gas treatment plant and due to a significant change in the traditional methanol production scheme (except for a recovery boiler, start-up boiler, start-up furnace, compressor installation, etc.), an almost 3-fold decrease in capital investments is achieved, which in turn makes this methanol production process a very competitive offer. At the same time, the conditions for the ratio of the capacities of the gas treatment plant and the methanol production unit remain unchanged, because the specific consumption of methanol per 1000 m ^{3 of} gas for almost all fields is approximately the same.

The problem is also solved by the fact that hydrocarbon gas with a gas treatment plant at a temperature of 20 ° C, cooling the reaction mixture of methanol synthesis in a gas-gas heat exchanger, where chemically purified water is injected into the stream directly in front of the heat exchanger through the nozzle, to the extent necessary for the preliminary process steam reforming in a tubular reactor, then the gas-vapor mixture enters the intermediate heat exchanger of the methanol synthesis reactor to maintain the temperature of the methanol synthesis in isothermal Mode. The gas-vapor mixture after cooling the methanol synthesis products is sent to the gas-gas heat exchanger for quenching (overheating) and for cooling the synthesis gas products in front of the methanol synthesis reactor. After quenching, the gas-vapor mixture with a temperature of 380-430 ° C enters the tube space of the tubular preliminary steam reforming reactor, the tubes of which are filled with the K-905 GIAP-16 nickel-containing catalyst. The gas resulting from the reforming proceeds to the next reforming stage, where the final synthesis gas is produced by adding oxygen, and then this hot gas is used to heat the tubes with the catalyst in the initial reforming stage. The process of formation of synthesis gas in a shaft reactor proceeds at a temperature of 600-950 ° C and at a pressure equal to the pressure of the synthesis of methanol. During the process, approximately the following main reactions occur:

CH ₄ + H ₂ O = CO + 3H ₂

CH ₄ + 2O ₂ = CO ₂ + 2H ₂ O

CO + H ₂ O = CO ₂ + H ₂

and etc.

The resulting synthesis gas, after cooling in a heat exchanger of quenching the feedstock with a temperature of 250-280 ° C, enters a 2-stage isothermal methanol synthesis reactor.

To carry out the methanol synthesis process (СО + 2Н ₂ = СН ₃ ОН + heat, СО ₂ + 3H ₂ = СН ₃ ОН + Н ₂ O + heat), the reactor is filled with a copper-containing catalyst SNM-3С. The methanol synthesis reaction proceeds with the formation of heat, and for carrying out the isothermal process, the reactor is carried out in 2 stages with an external heat exchanger for intermediate cooling of the reaction mixture. The reaction of methanol synthesis occurs at a temperature of 220-280 ° C. The resulting reaction mixture is sent for cooling to a gas-gas heat exchanger and then for final gas-liquid cooling, where chemically purified water is used as a cooling agent, which is then sent for injection into the gas stream for the purpose of preliminary reforming. The cooled reaction mixture with a temperature of 20-35 ° C enters the separator to separate the crude methanol from the unreacted synthesis gas products. Raw methanol with a concentration of 78-84% is sent to the methanol storage park, and gases from the separator, mainly containing CH ₄ , H ₂ and CO ₂ , are sent for use for own needs of the gas treatment plant (boiler house, power plant and other heaters) or mixed with gas treatment plant, and due to the small volumes of unreacted gas, the gas treatment process does not affect the quality of the produced commercial gas.

The main difference between this method and traditional methods for producing methanol through synthesis gas (steam reforming, combined reforming, the Tandem process) is that by integrating the methanol production unit into the gas treatment plant, an almost 3-fold reduction in the set of equipment and capital investments is achieved to obtain methanol as an inhibitor of hydrate formation, as well as a significant reduction in operating costs by reducing energy consumption (compressor and compression circuits are excluded synthesis gas, start-up boiler and start-up furnace, waste-heat boiler, installation for the preparation of chemically purified water).

Due to the absence of harmful emissions, the process is an environmentally friendly production.

In the future, the invention is illustrated by specific examples of its implementation and the attached drawing, which shows a General view of the installation for producing methanol.

The methanol production plant comprises a 2-stage reactor 7 for carrying out a methanol synthesis reaction with an external heat exchanger 3 for cooling the reaction mixture in order to carry out an isothermal reaction, which is connected through a gas-gas heat exchanger 4 to the preliminary steam reforming reactor 5 in the form of a tubular reactor where the tubes are filled with catalyst, the annulus is separated by the tube plate, where hot synthesis gas is supplied from the final reforming reactor. To carry out the final reforming, the reactor 6 has a mixing device for mixing preliminary reforming gases with oxygen, equipped with a pilot light to start the installation, and the reactor 6 is filled with a catalyst, the upper catalyst layer is protected by ceramic tiles (balls) from catalyst baking. Oxygen is supplied from the oxygen production unit, which is supplied as a unit. The reaction mixture from the reactor 7 for cooling is fed into the pipe space of the gas-gas heat exchanger 2, into the annular space of which hydrocarbon gas is supplied from the complex gas treatment unit, into the stream of which chemically purified water is injected directed from the gas-liquid heat exchanger 8, the cooled reaction mixture to a temperature of 20-35 ° C enters the separator 9 for the separation of crude methanol, the crude methanol is sent to the storage park for further use, and the unreacted synthesis gas is returned to GPP for use for own needs or for mixing with commercial gas.

An example confirming the feasibility of the proposed method for producing methanol.

Cold hydrocarbon-containing gas with UKPG 1 with a flow rate of 906.8 kg / h at a pressure of P = 8.0 MPa passes through heat exchangers 2, 3, 4, where it is heated to 380-430 ° C, into the flow of which before the heat exchanger 2 in an amount of 1150 kg chemically purified water is injected per hour, the mixture enters the pre-steam reforming reactor 5 into the pipe space, then the pre-reforming gas is sent for final reforming to the reactor 6, where oxygen is supplied in the amount of 743.5 kg / h, then the reaction mixture with a temperature of 750 -900 ° C through reactor 5, heat exchanger 4, with a temperature of 220-280 ° C enters the methanol synthesis reactor 7, the methanol synthesis process proceeds at a temperature of 230-280 ° C and a pressure of up to 8.0 MPa. Next, the reaction mixture through heat exchangers 2, 8 enters the separator 9, unreacted gas in the amount of 1356.5 kg / h is sent to the gas treatment plant for own needs, raw methanol 78-84% concentration in the amount of 1439.3 kg / h is sent to the park.

Claims (2)

1. A method of producing methanol, comprising sequentially supplying a hydrocarbon-containing gas, injecting chemically purified water, conducting preliminary steam reforming of the synthesis gas, carrying out the final reforming of the resulting gas with the addition of oxygen at a pressure equal to the pressure of the methanol synthesis, by heating the preliminary reforming reactor with the obtained synthesis stream -gas exiting the final reforming reactor, which is fed into the annulus of the pre-reactor reforming, then cooling the synthesis gas obtained by reforming with a gas-vapor mixture and carrying out methanol synthesis in a 2-stage reactor, characterized in that the reaction mixture is cooled for conducting an isothermal reaction of methanol synthesis in an intermediate external heat exchanger of a two-stage reactor with a gas-vapor mixture, and cooling the stream leaving the methanol synthesis reactor is carried out with a gas-vapor mixture and chemically purified water. 2. A methanol production unit containing a source of hydrocarbon-containing gas from a complex gas treatment unit, a preliminary steam reforming reactor heated by a stream leaving the final reforming reactor, a two-stage methanol synthesis reactor, synthesis gas cooling heat exchangers, and cooling heat exchangers for the stream leaving the methanol synthesis reactor , a separator for separating the reaction products into exhaust gases and raw methanol, characterized in that the installation for the production of methanol integra with a complex gas treatment unit (CCGT) containing a unit for the preparation of chemically purified water, a unit for the preparation of raw materials, auxiliary production, including flare production, treatment facilities, electric energy sources, instrumentation and control air, a chemical laboratory, a control room, and a two-stage methanol synthesis reactor connected with a heat exchanger for synthesis gas cooling with a gas-vapor mixture, equipped with an intermediate remote heat exchanger for cooling the reaction mixture with a gas-vapor mixture and connected in series n with heat exchanger cooling the resulting vapor mixture to flow reactor, a cooling heat exchanger and chemically purified water separator for separating the reaction products.