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DEVICES AND METHODS OF EXTRACTING AND ACCUMULATION OF HYDROGEN AND OXYGEN
INVENTION
Patent of the Russian Federation RU2274600

METHOD OF MULTI-STAGE RECEPTION OF SYNTHETIC GAS

METHOD OF MULTI-STAGE RECEPTION OF SYNTHETIC GAS

The name of the inventor: Stolyarevsky Anatoly Yakovlevich
The name of the patent holder: LLC "Center KORTES"
Address for correspondence: 123098, Moscow, ul. Maksimova, 4, LLC "Center KORTES"
Date of commencement of the patent: 2004.09.03

The invention relates to a process for the production of synthesis gas containing mainly H 2 and CO for the production of hydrogen, alcohols, ammonia, dimethyl ether, ethylene, for Fischer-Tropsch processes, and can be used in the chemical industry for processing hydrocarbon gases, Chemothermal systems of accumulation and energy transport and methane-methanol thermochemical cycles of water decomposition. According to the invention, in a multistage synthetic gas production process, at least two successive steps are carried out, in each of which a stream containing lower alkanes having about one to four carbon atoms is passed through a heating heat exchanger and then through an adiabatic reactor filled with a catalyst packing . After the last stage water vapor is removed from the stream. Prior to the first stage and between the stages, the stream is mixed with steam and / or carbon dioxide and cooling is carried out at the end of each stage. The invention makes it possible to increase the conversion rate of lower alkanes and to reduce the H 2 / CO ratio in the production synthesis gas.

DESCRIPTION OF THE INVENTION

The invention relates to a process for the production of synthesis gas containing mainly H 2 and CO, for the production of hydrogen, alcohols, ammonia, dimethyl ether, ethylene, for Fischer-Tropsch processes and can be used in the chemical industry for processing hydrocarbon gases, Chemothermal systems of accumulation and energy transport and methane-methanol thermochemical cycles of water decomposition.

It is known to produce a synthesis gas containing mainly H 2 and CO for the production of alcohols, ammonia, dimethyl ether, ethylene, for Fischer-Tropsch processes described in RF patent No. 2228901, date of publication. 2004.05.20, IPC From 01 to 3/38. A known method for producing a synthesis gas with a predetermined ratio H 2 / CO in the range of 1.0 to 2.0 comprises two steps: a) partial oxidation step and step B) conversion of the residual methane to the products of step A) on the catalyst. Step A) of the partial oxidation is carried out in two stages: a) noncatalytic partial oxidation of the natural gas with oxygen, producing in the reaction products a nonequilibrium content of H 2 O and CH 4 at a molar ratio of oxygen and methane of about 0.76-0.84, b) Conversion of reaction products of step a) with correction additives CO 2 and H 2 O or H 2 O and CH 4 to produce a gas mixture that undergoes the conversion of residual methane by steam on the catalyst. The method makes it possible to produce a synthesis gas with a composition that corresponds to a predetermined CO / H 2 ratio. The method can be used to prepare the feedstock for further processes of synthesis of alcohols, dimethyl ether, ammonia or other large-scale chemical products.

However, the described method has a number of drawbacks, which can include functional and economic limitations of the application of the method, associated with the need to supply large amounts of oxygen (exceeding the mass flow of convertible natural gas), the production of which requires large energy (up to 1000 kWh / t) and Capital expenditures (up to 1500 USD / kg.h -1 ). A serious problem is the soot formation, which sharply reduces the activity of the catalysts.

There is a known method for producing synthesis gas containing mainly H 2 and CO, described in the monograph "Nuclear-technological complexes based on high-temperature reactors", A.Ya. Stolyarevsky-Moscow: "Energoatomizdat", 1988. - 152 p. (ISBN 5-283-03750-9), p.107-109. This process for the technological conversion of a hydrocarbon feedstock involves a multistage synthesis gas synthesis comprising mainly H 2 and CO, in which at least two successive steps are carried out, in each of which a stream containing lower alkanes having about one to four carbon atoms is passed through Through a heat exchanger, and then through an adiabatic reactor filled with a catalyst packing, and after the last stage water vapor, a prototype, is removed from the stream. The disadvantages of this solution are a relatively low alkane conversion rate (up to 90%) and a relatively high H 2 / CO ratio in the synthesis gas as the product of the process, which worsens the conditions for the subsequent synthesis of the derivatives from the synthesis gas.

It is an object of the present invention to provide a novel method for increasing the conversion rate of lower alkanes and to provide technological opportunities to reduce the H 2 / CO ratio in the produced synthesis gas.

The task is solved by the fact that:

In a multi-step synthesis gas synthesis in which at least two successive steps are carried out, in each of which a stream containing lower alkanes having about one to four carbon atoms is passed through a heating heat exchanger and then through an adiabatic reactor filled with a catalyst packing , And after the last stage water vapor is removed from the stream, the stream containing the lower alkanes in front of the first stage and between the stages is mixed with steam and / or carbon dioxide and at the end of each stage the flow is cooled. The alkane conversion ratio in this method is increased by more than 90%, and the H 2 / CO ratio can vary from 2 to 4 depending on the desired final product;

- cooling of the flow is carried out with heat recovery for heating and evaporation of water;

- after removing steam from the stream, carbon dioxide and / or hydrogen are removed from the stream, at least a portion of which is sent to mix with the stream before and / or between the stages;

- before the stages, the stream is purified from the sulfur compounds;

- in the heating exchanger, the heating of the stream is due to the convective cooling of the coolant through the hermetic heat exchange surfaces;

- heating of the flow by the heat carrier at each stage is conducted parallel to the other stage along the coolant cooling path;

- in the adiabatic reactor, a temperature in the range of about 600 ° C to 900 ° C is maintained;

The catalyst contains, as active components, a metal selected from the group of rhodium, nickel, platinum, iridium, palladium, iron, cobalt, rhenium, ruthenium, copper, zinc, iron, mixtures or compounds thereof;

- the lower alkane is methane;

- the flow pressure is selected in the range of about 2.0 to 9.0 MPa;

- the volume content of carbon dioxide before the first stage is maintained in the range of about 10 to 30% of the volumetric content of alkanes;

- the volume content of water vapor before the first stage is maintained in the range of about 4 to 12 times greater than the volume content of alkanes;

- helium, heated in a nuclear reactor, is used as the heat carrier.

An example of implementing the invention is a multi-stage synthesis gas synthesis process described below.

In the exemplary embodiment of the invention, methane is used as the lower alkane, which makes it possible to characterize the features of implementing the invention as applied to natural and associated gas processing processes.

Methane with a pressure of more than 4.0 MPa is mixed with a recycle gas containing hydrogen, carbon monoxide and carbon dioxide compressed to methane pressure, heated to a temperature of about 400 ° C, and the resulting gas stream is fed to the purification stage of sulfur compounds (if they are contained as impurities in methane ), Which is carried out in two steps: first, for example, on an aluminocobalt-molybdenum catalyst, hydrogenation of organic sulfur compounds, for example mercaptans, to hydrogen sulfide is carried out, and then the stream is directed to the absorption of the formed hydrogen sulfide with activated zinc oxide in the absorption reactors included in the operation in series or in parallel. The gas flow, purified (in terms of sulfur) to a mass concentration of sulfur of less than 0.5 mg / Nm 3 , is mixed with a superheated steam stream to a steam / gas ratio, for example, equal to 5.0. In order to increase the conversion of methane, the volume content of water vapor before the first stage is maintained in a range of about 4 to 12 times greater than the volume content of the alkanes. If the steam / gas ratio falls below 4, the efficiency of the process decreases and the capital costs increase, which is connected either with the need to increase the flow of gas recirculation due to a low degree of conversion at the below mentioned flow heating temperature or with the need to increase the heating temperature of the stream above 1000-1200 ° C , Which will force to use more expensive materials for the heat exchanger. Increasing the steam-gas ratio above 12 and causing a decrease in the efficiency of the process due to the need to produce excess water vapor.

The resulting stream is sent to the first section of the heating heat exchanger, where it is heated, for example, to a temperature of about 650 ° C and sent to the first adiabatic reactor filled with a catalyst packing, for example, which is preferably a nickel catalyst such as GIAP-16. Other catalysts based on other active metals selected from the group of rhodium, platinum, iridium, palladium, iron, cobalt, rhenium, ruthenium, copper, zinc, iron, mixtures or compounds thereof can also be used. The composition of the catalyst with a change in the content of platinoids as well as metals that affect the kinetics of oxidation of carbon monoxide by water vapor (shear reaction) will allow controlling the hydrogen content in the final product.

In an adiabatic reactor without heat input, partial conversion of methane to a volume fraction of methane is not more than 33%, after which a stream with a temperature of about 600 ° C is sent for cooling in a waste heat boiler to produce water vapor. Cooling the flow allows improving the operation of the heating coil by increasing the average log heat head. Before the next stage of the process, which repeats the first stage in the composition of the actions, water vapor is dosed into the stream.

The stream enriched in the components is sent to the second section of the heating heat exchanger where the flow temperature is raised to 750 ° C. and then sent to a second adiabatic reactor, in a design repeating the first adiabatic reactor filled with a catalyst packing in which further conversion of methane occurs with a reduction in its content to 17% at a flow outlet temperature of about 660 ° C. Then the stream is again cooled in a recovery boiler, mixed with additional water vapor and sent to the final preconversion of methane to the third stage, in which the order and content of the operations do not differ from the first two stages, and the heating temperature is about 870 ° C. The choice of the heating temperature is determined, first of all, by the temperature potential of the heat source, for example, helium heated in the nuclear reactor, and by the possibilities of creating heat exchangers with relatively inexpensive heat-resistant heat exchange surfaces based on steels and alloys with low content of expensive components (nickel, cobalt, chromium, Molybdenum, etc.), which predetermines the preferred level of the upper possible temperature of 900 ° C. On the other hand, the equilibrium degree and rate of conversion of methane below 600 ° C, even at relatively high water vapor / gas ratios, is practically unacceptable.

After leaving the third stage with an outlet temperature of over 750 ° C, a stream with a methane content of about 3% is sent sequentially to the superheater, the recovery boiler, the feedwater heater, and then to the heat exchanger in the heating water, in which the stream is cooled to 170 ° C, after Which is finally cooled to 40 ° C in water heat exchangers for heating of non-aerated water. The degree of conversion of methane in the described process is about 80%, and the ratio H 2 / (CO + CO 2 ) is about 2.9.

The resulting synthesis gas can then be used to produce commercial hydrogen, for which CO 2 is removed from the stream in absorption purification, for example with an aqueous solution of activated mono- and diethanolamine, and then hydrogen is finally released by short-cycle adsorption on activated carbon or zeolite, during which Desorption products are obtained which are directed in part to combustion and used as a recycle gas.

In the second example, methanol and / or dimethyl ether production options, after desulfurization, methane is mixed with carbon dioxide compressed to the pressure of the stream, the source of which can be flue gases, technological processes, including fermentation, decarbonization or, as in the Orenburg field, a composite Part of underground natural gas, as well as the recycling of the streams of production itself. The resulting stream is sent to the first section of the heating heat exchanger, which is heated, for example, to a temperature of about 650 ° C, and sent to the first adiabatic reactor filled with a catalyst packing, for example, which is preferably a nickel catalyst. Catalysts based on other active metals can also be used. The composition of the catalyst affects the kinetics of processes involving carbon dioxide, which will allow controlling the hydrogen content in the final product.

In an adiabatic reactor without heat input, partial conversion of methane to a volume fraction of methane is not more than 40%, after which a stream with a temperature of about 600 ° C is sent for cooling in a heat recovery boiler. Prior to the next stage of the process, which repeats the first stage in the composition of the actions, an additional amount of carbon dioxide is dosed into the stream, thereby shifting the thermodynamic equilibrium of the process toward greater conversion of methane to synthesis gas.

The stream enriched in the components is sent to the second section of the heating heat exchanger where the flow temperature is raised to 750 ° C. and then sent to a second adiabatic reactor repeating the first adiabatic reactor filled with a catalyst packing in which further conversion of methane occurs with a decrease in its content below 20% at a flow outlet temperature of about 650 ° C. Then the stream is again cooled in a recovery boiler, mixed with an additional amount of carbon dioxide and sent to the final preconversion of methane to the third stage, in which the order and content of the operations do not differ from the first two stages, and the heating temperature is about 860 ° C. The choice of the heating temperature is determined primarily by the temperature potential of the heat source, for example, the products of combustion of process gases or helium heated in the nuclear reactor, and the possibilities of creating heat exchangers with relatively inexpensive heat-resistant heat exchange surfaces based on steels and alloys with a low content of expensive components (nickel , Cobalt, chromium, molybdenum, etc.), which predetermines the preferred level of the upper possible temperature of 900 ° C. On the other hand, the equilibrium degree and rate of methane conversion below 600 ° C, even at relatively high water vapor / gas ratios, is practically unacceptable.

After exiting from the third stage with an outlet temperature of over 750 ° C, a stream with a methane content of about 3% is sent sequentially to the recovery boiler and then to the heat exchanger in the heating water, where the stream is cooled to 170 ° C, after which it is finally cooled to 40 ° C C in water heat exchangers for the heating of non-aerated water.

A third embodiment of the process is also possible, in which instead of three stages of heating, the flow is passed through a double heating-cooling cycle. Such an option is possible with an increase in the heating temperature of the flow in the first and second stages to 900 ° C, with a simultaneous increase in the vapor-gas ratio above 8. In this case, it is possible to obtain the required methane conversion rates (about 90%) or other lower alkanes with simultaneous reduction Costs of metal on the heat exchanger, but with increased metal costs for the generation of water vapor. If carbon dioxide is used to convert methane for a two-stage process, it will be necessary to increase the CO 2 content, which will increase energy costs and power to release excess CO 2 and recycle it.

A fourth embodiment of the process is possible in which steam is used as the main methane conversion agent, but, simultaneously, in this example, in order to reduce the H 2 / (CO + CO 2 ) ratio in the final synthesis gas, the carbon dioxide content before the first stage is maintained in the range Approximately 10 to 30% of the volumetric content of alkanes. In this case, all the steps are carried out in a manner similar to the first described example, but the H 2 / (CO + CO 2 ) ratio is approximately 2.1, i.e. lower than in the first example, which is favorable for the production of certain products. In particular, in the case of using the obtained dried synthesis gas for the subsequent synthesis of methanol or dimethyl ether, the stream can be directly sent to the catalytic synthesis columns without purification from CO 2 and hydrogen evolution, where unreacted gas exiting the synthesis compartment is directed.

Taking into account the need to reduce the work of compression, the process is carried out at a pressure that is at least slightly different from the synthesis pressure of the subsequent marketable product, which is in various technologies from 6 to 10 MPa, or the pressure given for subsequent use of hydrogen or converted gas (2 to 9 MPa) As is the case in the nuclear chemothermal systems described in the source cited above. Similarly, pressure is selected in the production of alcohols, ammonia, dimethyl ether, ethylene, for Fischer-Tropsch processes and other technologies where the method according to the invention can be effectively applied.

Processes for the production of synthesis gas from streams containing other lower alkanes (ethane, propane, butane), for example, based on associated gas from oil production, are carried out in a manner analogous to the examples set forth above.

CLAIM

A method for synthesizing a synthesis gas in a multi-step process, wherein at least two successive steps are carried out, in each of which a stream containing lower alkanes having about one to four carbon atoms is passed through a heat exchanger and then through an adiabatic reactor filled with And after the last stage water vapor is removed from the stream, characterized in that the stream containing the lower alkanes is mixed with water vapor and / or carbon dioxide before the first stage and between the stages and cooling is carried out at the end of each stage.

2. A method according to claim 1, characterized in that the cooling of the flow is carried out with heat recovery for heating and evaporation of water.

3. A method according to claim 1 or 2, characterized in that, after removal from the steam stream, carbon dioxide and / or hydrogen is removed from the stream, at least some of which are directed to be mixed with the stream before and / or between the stages.

4. A method according to claim 1 or 2, characterized in that the streams from the sulfur compounds are purified before the steps.

5. A method according to claim 1 or 2, characterized in that in the heating heat exchanger, the heating of the flow is carried out by convective cooling of the heat transfer medium through hermetic heat exchange surfaces.

6. A method according to claim 1 or 2, characterized in that the heating in the heat exchanger of the flow by the heat carrier at each stage is conducted parallel to the other stage during the cooling of the coolant.

7. A method according to claim 1 or 2, characterized in that the adiabatic reactor is maintained at a temperature in the range of about 600 to 900 ° C.

8. The process of claim 1 or 2, wherein the lower alkane is methane.

9. A method according to claim 1 or 2, characterized in that the flow pressure is selected in the range of about 2.0 to 9.0 MPa.

10. A method according to claim 1 or 2, characterized in that the volume content of carbon dioxide before the first stage is maintained in the range of about 10 to 30% of the volumetric content of the alkanes.

11. A method according to claim 1 or 2, characterized in that the volume content of water vapor before the first stage is maintained in a range of about 4 to 12 times greater than the volumetric content of alkanes.

12. A method according to claim 1 or 2, characterized in that helium heated in a nuclear reactor is used as the heat carrier.

print version
Date of publication 02.03.2007гг