RU2394754C1 - Method of obtaining hydrogen from hydrocarbon material - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: invention can be used to obtain hydrogen from gaseous hydrocarbon material - natural gas, associated petroleum gas, as well as hydrocarbon gas obtained by evaporating liquid fuel. The material is fed into a desulphurisation unit 1 and divided into two streams after purification from sulphur compounds. One of the streams is mixed with water vapour and undergoes catalytic conversion at 800-1050C in a radial-spiral type reactor 2. The obtained converted gas is fed as heating medium into a waste-heat boiler 4 for partial cooling. Catalytic steam conversion of carbon oxide takes place in a radial-spiral type reactor 5 at 190-230C. The obtained hydrogen-containing gas is cooled and separated from moisture in gas drier-cooler 6 and then fed into a separation unit 7 in which hydrogen is separated and blowout gas is tapped and mixed with the second stream of hydrocarbon gas purified from sulphur. The obtained mixture is fed as fuel gas into a burner 3 of catalytic reactor 2, where before feeding into the burner, this mixture and air required for combustion are heated in the heat recuperation unit 8 through partial cooling of flue gases coming from reactor 2. The flue gases are cooled in a drier-cooler 9 in order to separate moisture and are taken out of the installation. The condensate released in the drier-coolers 6 and 9 undergo purification in a water treatment unit 10 and fed into a waste-heat boiler to produce steam which is required for steam conversion of hydrocarbons. ^ EFFECT: use of the invention increases efficiency of the process. ^ 4 cl, 2 dwg

Description

The invention relates to methods for producing pure hydrogen from gaseous and liquid hydrocarbon raw materials and can be used in chemical, metallurgical and other industries, as well as in hydrogen energy, in particular for stationary and mobile power plants with electrochemical generators based on fuel cells.

In various sectors of the economy, hydrogen is increasingly used. Hydrogen production is possible by various methods:

- catalytic conversion of hydrocarbons;

- electrolysis of water;

- thermochemical decomposition of water using chemically active compounds of iodine or bromine and others.

The basis of modern industrial methods for the production of hydrogen is the process of steam conversion of hydrocarbon gases, which consists in the decomposition of the starting products into a mixture of hydrogen and carbon monoxide on nickel catalysts at a temperature of 800-1050 ° C and the subsequent release of pure hydrogen from a hydrogen-containing gas. Moreover, both gaseous and liquid hydrocarbons can be used as feedstock.

A known method of producing highly pure hydrogen (patent RU No. 2085476, M. class. С01В 3/32, 3/56, publ. 07/27/97, Bull. No. 21), including sequentially desulfurization of natural gas (GHG), mixing purified GHG with steam in a ratio of 1: 1.75 to 1: 2.1, steam conversion of the obtained gas-vapor mixture in a catalytic reactor to produce a mixture of hydrogen and carbon monoxide and steam conversion of carbon monoxide in the converter at a pressure of 0.105-0.110 MPa, compression of the gas mixture to pressure of 1.0-5.0 MPa, the release of carbon dioxide and water from it by freezing and diffusion of hydrogen and through a palladium membrane at a temperature of 773-900K with the release of very pure hydrogen.

The disadvantages of this method are as follows:

- provides for the compression of the gas mixture before the final stages of the process to a pressure of 1.0-5.0 MPa using a compressor, which leads to an increase in investment, as well as operating costs for the drive and maintenance of the compressor;

- the compressor is installed after the CO converter, and all previous processes proceed at low pressure (0.105-0.110 MPa), which results in increased dimensions and mass of the catalytic reactor for converting the gas-vapor mixture and the CO converter;

- due to the fact that the hydrogen-containing gas after separation of water and carbon dioxide by freezing has a low temperature, and the diffusion evolution of hydrogen on the palladium membrane must be carried out at a temperature of 773-900 ° K, for this process it is necessary to supply heat from an external source to heat the incoming gas, which increases energy costs for hydrogen production.

- the method does not provide heat recovery of the streams for heating the feedstock supplied to the steam reforming catalytic reactor, as well as fuel gases burned in the burner of the steam reforming catalytic reactor, which results in increased fuel consumption, i.e. a decrease in the amount of hydrogen produced from a unit of feedstock.

The closest in technical essence and the achieved result to the proposed invention is a method for producing hydrogen from hydrocarbon gas according to patent RU No. 2078518, M. cl. СВВ 3/32, 3/56, publ. 08/27/97, Bull. Number 24. The method involves steam conversion of a hydrocarbon gas to produce a gas containing hydrogen and CO, supplying the obtained gas to CO conversion, cooling the converted gas to separate water condensate from it, extracting carbon dioxide from the converted gas, purifying the resulting hydrogen-containing gas from impurities by the short-cycle adsorption method with the production of hydrogen, regeneration of the adsorbent by blowing part of the obtained hydrogen to produce regeneration gases that return to the stage of CO conversion moreover, the conversion stages are carried out at a pressure close to atmospheric, and the adsorption ones at a pressure of 1.5-3.0 MPa, for which the gas in front of the short-cycle adsorption apparatus is compressed to the specified pressure using a compressor. Before being fed to the steam reforming, the hydrocarbon gas is saturated with condensate by saturation.

This method has the following disadvantages:

- the consequence of the conversion stages of the process at low atmospheric pressure is the increased overall dimensions and metal consumption of the equipment used at these stages (catalytic reactor for the conversion of feedstock, catalytic reactor for the conversion of carbon monoxide, heat exchangers, condenser), which leads to an increase in capital costs when implementing the proposed method;

- to increase the pressure of the gas mixture before the final stages of the process to a pressure of 1.5-3.0 MPa, the installation must contain a compressor, which leads to an increase in investment, as well as operating costs for the drive and maintenance of the compressor;

- provides for the allocation of carbon dioxide from a gas mixture in a separate adsorber, which complicates and increases the cost of installation when implementing the method in question;

- the method does not provide for the recovery of heat of the exhaust flue gases and the use of the water contained in them, as a result of which the consumption of feedstock used as fuel increases, and an external source of water vapor is required to conduct steam catalytic conversion of hydrocarbon gas with a corresponding additional fuel consumption for steam generation .

The task of the invention is to increase the efficiency of hydrogen production.

The objective of the invention is also to increase the yield of the final product - salable hydrogen from a unit of input feedstock.

The objective of the invention is also to provide the possibility of carrying out all stages of the process at one pressure and thereby excluding from the compressor installation for intermediate compression of a hydrogen-containing gas.

The objective of the invention is the elimination of the need to use water vapor from an external source for conducting steam conversion of hydrocarbons.

The tasks are solved as follows.

In the known method for producing hydrogen from gaseous hydrocarbon feedstocks (natural gas, associated petroleum gas, as well as hydrocarbon gas obtained by evaporation of liquid fuel), including purification of the supplied gas from sulfur compounds, mixing purified hydrocarbon gas with water vapor, catalytic steam conversion of a gas-vapor mixture with by supplying high-temperature heat and obtaining converted gas, catalytic steam conversion of carbon monoxide with the removal of low-temperature heat by evaporative cooling by the deposition and evolution of commercial hydrogen from a hydrogen-containing converted gas, the following is proposed:

gaseous hydrocarbon feed is brought to the desulfurization unit with a pressure of at least 0.5 MPa, after which the hydrocarbon gas purified from sulfur compounds is divided into two streams; one gas stream is mixed with water vapor and subjected to steam conversion at a temperature of 800-1050 ° C in a radial-spiral type steam conversion catalytic reactor, the resulting converted gas is fed as a heating medium to a steam recovery boiler, partially cooled in it and then at a temperature 190-220 ° C are subjected to steam conversion of carbon monoxide in a radial-spiral type catalytic reactor; then, the stream of the obtained hydrogen-containing gas is additionally cooled to a temperature of 20–40 ° C with an external coolant and separated from moisture in a gas cooler-dryer, after which it is fed to a hydrogen-containing gas separation unit, in which the final product, commodity hydrogen, is isolated, and the purge gas is removed from it and mixed with a second stream of sulfur-free hydrocarbon gas; the resulting mixture is fed as fuel gas to the burner of a catalytic reactor for steam reforming of hydrocarbons, and before being fed to the burner, this mixture and the air required for combustion are heated in the heat recovery unit due to partial cooling of the flue gases leaving the catalytic reactor for steam reforming of hydrocarbons, followed by moisture separation gases are additionally cooled with an external coolant in a flue gas cooler-dryer and removed from the installation; the condensate generated in the coolers-dehydrators of hydrogen-containing gas and flue gases is subjected to purification in the water treatment unit and sent to produce steam necessary for steam conversion of the initial hydrocarbons to a steam recovery boiler, in which the condensate is heated and evaporated due to the heat of the converted gas obtained in a catalytic reactor for steam conversion of hydrocarbons.

The separation of the hydrogen-containing gas into pure hydrogen and the purge gas is carried out by the method of short-cycle adsorption or other known method.

In addition, the water vapor generated by the evaporative cooling of the carbon monoxide steam reforming catalytic reactor is mixed with the steam obtained in a steam recovery boiler, after which the resulting steam mixture is divided into two streams, one of which is sent to mix with the first stream purified from compounds sulfur of hydrocarbon gas for conducting steam conversion of hydrocarbons, and the second stream is directed for external consumption and / or used to produce electricity needed to drive pumps, valves Yator and other mains powered equipment installation.

In addition, the processes of heat recovery of technological and energy flows of working fluids and heat removal from working fluids by external refrigerants are carried out mainly in radial-spiral type apparatuses.

Below the invention is illustrated by specific examples of its implementation and the accompanying drawings, in which:

figure 1 depicts a schematic flow diagram of the production of hydrogen from gaseous hydrocarbon feedstocks;

figure 2 is a fragment of a schematic flow diagram of the production of hydrogen from liquid hydrocarbon feedstocks.

The following elements are indicated on the diagrams:

1 - desulfurization unit;

2 - catalytic reactor for steam conversion of hydrocarbons;

3 - burner;

4 - steam recovery boiler;

5 - catalytic reactor for steam conversion of carbon monoxide;

6 - a cooler-dryer of hydrogen-containing gas;

7 - node separation of hydrogen-containing gas;

8 - flue gas heat recovery unit;

9 - cooler-dryer of flue gases;

10 - site water treatment;

11 - a water pump;

11 - a reservoir of liquid hydrocarbons;

12 - liquid hydrocarbon pump;

13 - evaporator;

14-39 - lines of supply and removal of working environments.

Schematic diagram of the production of hydrogen from gaseous hydrocarbon raw materials (natural gas, associated petroleum gas, etc.) is shown in figure 1. The implementation of such a scheme is possible provided that gaseous hydrocarbon feeds are received for processing with a pressure of at least 0.5 MPa, at which the entire process for producing hydrogen by the proposed method is carried out. At lower pressure, the initial product should be pre-compressed to a pressure not lower than the specified value.

The feed gas is supplied through line 14 to the desulfurization unit 1, after which the hydrocarbon gas purified from sulfur compounds is divided into two streams. The first hydrocarbon gas stream through line 15 is directed to the steam conversion of hydrocarbons into a radial-spiral type catalytic reactor 2, equipped with a burner 3, and before entering the catalytic reactor 2, the hydrocarbon gas is mixed with the steam required for steam conversion via line 16. Conversion carried out at a pressure equal to the pressure of the hydrocarbon gas supplied to the processing, and a temperature of 800-1050 ° C.

The converted gas obtained through line 17 enters the steam recovery boiler 4 as a heating medium, where it is partially cooled, and then fed through line 18 to a radial-spiral type catalytic reactor 5 for conversion of carbon monoxide, which is carried out at a temperature of 190- 230 ° C.

Next, the obtained hydrogen-containing gas is sent through line 19 to a cooler-dryer 6, where it is additionally cooled by an external coolant (for example, water or air) to a temperature of 20-40 ° C and separated from moisture, after which it is fed through line 20 to a hydrogen-containing gas separation unit 7 , in which the final target product - hydrogen is cleaned of impurities and removed from the installation, and the purge gas from the separation unit of the hydrogen containing gas 7 is discharged along line 21, and mixed with the second hydrocarbon gas stream supplied from the unit desulfurization 1 through line 22, after which the resulting mixture through line 23 is fed to the flue gas heat recovery unit 8, heated in it, and then fed through line 24 to burner 3, where it is burned at a temperature not exceeding 1150 ° C. The air necessary for combustion is also heated in the flue gas heat recovery unit 8, and then it is supplied to the burner 3 via line 25. Due to the purge gas being burned in the burner, the inert gases coming into the cycle together with the flue gases entering the composition of the feedstock, and thereby excludes their accumulation in the cycle.

Flue gases are discharged from the catalytic reactor 2, through line 26 they are fed to the flue gas heat recovery unit 8, where they are partially cooled, after which they are sent through line 27 to a cooler-dryer 9, in which they are additionally cooled with an external coolant (for example, water or air) and separated from moisture. Cooled and drained flue gases through line 28 are discharged into the atmosphere.

The condensate extracted from the gas flows in coolers-dehumidifiers 6 and 9 is supplied via lines 29 and 30 to the water treatment unit 10, from which it is taken by pump 11 via line 31 and pumped through line 32 to the waste heat boiler 4, respectively, and line 33 - into the evaporative cooling cavity of the catalytic reactor 5. Water vapor generated in the steam recovery boiler 4 is discharged along line 34 and mixed with water vapor coming through line 35 from the evaporative cooling cavity of the catalytic reactor 5. The resulting mixture water vapor through line 16 is mixed with the first stream of hydrocarbon gas, purified from sulfur compounds and fed to the catalytic reactor 2 for steam reforming of hydrocarbons. Excess water vapor can be routed through line 36 for external consumption and / or used to generate the electric power needed to drive pumps, fans, and other power-consuming equipment of the installation. For the initial filling and, if necessary, replenishment of the system, it is possible to supply water from an external source via line 37.

In the presented scheme, the use of catalytic reactors 2 and 5 of a radial-spiral type is provided. Other heat and mass transfer apparatuses of the installation, including a steam recovery boiler, a flue gas heat recovery unit, coolers, dehumidifiers, can also be performed predominantly of this type, which will significantly reduce the metal consumption and dimensions of the apparatus and the installation as a whole.

If the feed gas does not contain sulfur compounds, the desulfurization unit may be excluded from the installation.

Figure 2 presents a fragment of a schematic technological diagram of the production of hydrogen from liquid hydrocarbon feedstocks.

The initial liquid hydrocarbon raw material (gasoline, kerosene, diesel fuel, naphtha, synthetic liquid fuel) is taken from the tank 11 by a pump 12 and fed through line 38 to the evaporator 13. The hydrocarbon gas formed in the evaporator 13 via line 39 enters the desulfurization unit 1. The further process hydrogen production is completely similar to that shown in the scheme of figure 1. The pressure of the pump 12 must be sufficient so that at the outlet of the evaporator 11 the gas pressure is at least 0.5 MPa.

If the initial liquid hydrocarbon feed does not contain sulfur compounds, the desulfurization unit may be excluded from the installation. In particular, this concerns the production of hydrogen from their synthetic liquid fuels, in which the absence of sulfur compounds is ensured during its production.

The proposed method for producing hydrogen from hydrocarbons has the following advantages:

- the supply of the source gas with a pressure of at least 0.5 MPa allows the entire process of producing hydrogen at a single pressure, so that the compressor is excluded from the circuit; in addition, the overall dimensions and mass of catalytic reactors and heat exchange equipment are reduced;

- carrying out steam conversion of hydrocarbon gas in a radial-spiral type reactor ensures the maintenance of a uniform temperature field and high selectivity of the process; due to this, the upper limit of the reaction temperature can be increased to 1050 ° C with a corresponding decrease in the size and metal content of the reactor, as well as an increase in productivity, which leads to a shift in the equilibrium of the catalytic reaction in the direction of obtaining the target reaction products.

- conducting steam reforming of carbon monoxide in a radial-spiral type catalytic reactor ensures that the temperature in the reaction zone is kept within rather narrow limits, that is, a mode close to isothermal is maintained and efficient heat removal of the exothermic reaction is realized due to evaporative cooling;

- due to the recovery of flue gas heat, fuel consumption is significantly reduced and thereby the yield of the final target product from a unit of feedstock is increased;

- the use of a source of hydrocarbon gas purified from sulfur compounds as fuel provides the emission of flue gases not containing sulfur dioxide and allows to obtain pure gas condensate, which can be used to generate water vapor;

- burning the purge gas discharged from the hydrogen gas separation unit also reduces the consumption of the source gas to the burner;

- steam generation in the recovery boiler due to the heat recovery of the converted gas not only provides steam with the steam reforming process of hydrocarbon gas and eliminates the consumption of steam from an external source, but also allows you to get an excess amount of steam that can be sent for external consumption and / or used for the production of electricity necessary for their own needs;

- the allocation of condensate from hydrogen-containing gas and flue gases in cooler-driers and its use for steam generation eliminates or at least substantially reduces the need for water supply from an external source.

Claims (4)

1. A method of producing hydrogen from gaseous hydrocarbon feedstocks - natural gas, associated petroleum gas, as well as hydrocarbon gas obtained by evaporation of liquid fuel, including purification of the supplied gas from sulfur compounds, mixing purified gas with water vapor, catalytic steam conversion of hydrocarbons with the supply of high-temperature heat and obtaining converted gas, catalytic steam conversion of carbon monoxide with the removal of low-temperature heat by evaporative cooling and the release of marketable hydrogen from a hydrogen-containing gas, characterized in that the gaseous hydrocarbon feed is brought to the desulfurization unit with a pressure of at least 0.5 MPa and, after purification from sulfur compounds, is divided into two streams, one of the streams being mixed with water vapor, which is then subjected to catalytic steam conversion at a temperature of 800-1050 ° C in a radial-spiral type reactor, the resulting converted gas is fed as a heating medium to a steam recovery boiler for partial cooling, catalytic steam conversion carbon monoxide is carried out in a radial-spiral type reactor at a temperature of 190-230 ° C, then the resulting hydrogen-containing gas is additionally cooled to a temperature of 20-40 ° C by an external coolant and separated from moisture in a gas cooler-dryer, and then fed to a hydrogen-containing gas separation unit , in which the final product, commercial hydrogen, is isolated, and the purge gas is removed from the separation unit of the hydrogen-containing gas and mixed with a second stream of sulfur-free hydrocarbon gas, the resulting mixture is served as the top gas to the burner of a catalytic hydrocarbon conversion reactor, and before feeding to the burner this mixture and the air required for combustion are heated in the heat recovery unit by partially cooling the flue gases leaving the catalytic hydrocarbon conversion reactor, after which the flue gases are additionally cooled by external coolant in the flue gas cooler-dryer and is removed from the installation, and the condensate generated in the cooler-dryer of hydrogen-containing gas and flue gas, jected purified water treatment unit and is directed to the production of steam required for steam reforming of hydrocarbons in the vapor recovery boiler. 2. The method according to claim 1, characterized in that the separation of the hydrogen-containing gas into components - salable hydrogen and purge gas is carried out in a short-cycle adsorption unit. 3. The method according to claim 1, characterized in that the steam generated during the evaporative cooling of the catalytic conversion reactor of carbon monoxide is mixed with the steam obtained in a steam recovery boiler, after which the resulting steam mixture is divided into two streams, one of which is used for steam conversion of hydrocarbons, and the second stream is directed for external consumption and / or used to produce electricity needed for power-consuming equipment, such as pump and fan drives. 4. The method according to claim 1, characterized in that the processes of heat recovery of technological and energy flows of the working media, as well as heat removal from the working media by external refrigerants, are carried out mainly in radial-spiral type apparatuses.

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