CN112645283B - System and method for producing hydrogen - Google Patents
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Abstract
The present invention relates to a system and method for producing hydrogen. The method comprises the steps of firstly carrying out hydrogenation reaction and desulfurization on a hydrocarbon raw material, carrying out pre-conversion reaction on the hydrocarbon raw material and steam, carrying out self-heating reaction on the pre-conversion reaction, oxygen and steam contained in the pre-conversion reaction, carrying out conversion reaction after the self-heating reaction, carrying out pressure swing adsorption on mixed gas after the conversion reaction to obtain mixed gas of first product hydrogen and tail gas, carrying out fine desulfurization on the mixed gas of the first product hydrogen, and carrying out methanation reaction to obtain final product hydrogen. The conversion rate, yield and purity of hydrogen produced by using hydrocarbons as raw materials are improved, and the national standard requirements of hydrogen fuel cells are met.
Description
Technical Field
The invention belongs to the technical field of hydrogen preparation by hydrocarbon compounds, and particularly relates to a system and a method for producing hydrogen.
Background
The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.
The national standards of the people's republic of china, GB 50177-2005 "design specifications for hydrogen stations" and GB 50516-2010 "technical specifications for hydrogen stations", list the specifications of hydrogen gas applied to hydrogen fuel cells, wherein as regards the production of hydrogen gas, processes that can be used are: water electrolysis, natural gas conversion, methanol conversion, coke oven gas, water gas shift and the like. In view of the field environment and the miniaturization of the apparatus, water electrolysis, natural gas reforming, and methanol reforming are preferable.
At present, natural gas resources in China are in shortage, various hydrocarbon-containing gases or hydrocarbon raw materials generated in the oil refining chemical process are fully utilized, and the method is one of the ways for obtaining cheap hydrogen at the present stage.
For oil refining chemical enterprises, the method for industrially utilizing hydrocarbon compounds, such as natural gas, refinery gas, liquefied petroleum gas and naphtha, to produce hydrogen mainly is a hydrocarbon steam reforming method, a tubular reformer and a nickel-based catalyst are used for carrying out reforming reaction in a steam atmosphere, the reaction temperature is usually 480-910 ℃, the water-carbon ratio is more than or equal to 3.0, and the methane content of a process gas at the outlet of the reformer is 4.5-7%; then the process gas passes through a CO shift reactor, PSA separation is carried out to obtain 99.99 percent of high-purity hydrogen, and the obtained hydrogen usually contains CO and CO 2 And 2, the total amount of the hydrogen is 10-15ppm, so that the strict requirements of hydrogen fuel cells on hydrogen cannot be met (GB T37244-2018 fuel hydrogen for proton exchange membrane fuel cell automobiles).
Disclosure of Invention
In view of the above problems in the prior art, it is an object of the present invention to provide a system and method for producing hydrogen.
In order to solve the technical problems, the technical scheme of the invention is as follows:
a method for producing hydrogen comprises the following specific steps:
the method comprises the steps of firstly carrying out hydrogenation reaction and desulfurization on a hydrocarbon raw material, carrying out pre-reforming reaction on the hydrocarbon raw material and steam, carrying out self-heating reaction on the pre-reforming reaction, oxygen and steam contained in the pre-reforming reaction, wherein the oxygen-carbon ratio is 0.1-0.2mol/mol, carrying out conversion reaction after the self-heating reaction, carrying out pressure swing adsorption on mixed gas after the conversion reaction to obtain mixed gas and tail gas of first product hydrogen, and carrying out methanation reaction on the mixed gas of the first product hydrogen after fine desulfurization to obtain final product hydrogen.
Compared with the prior art, the method for producing hydrogen by using hydrocarbon raw materials does not add water vapor in the autothermal reaction process, but uses the water vapor contained in the mixed gas after the pre-reforming reaction to react with hydrocarbon to obtain CO and hydrogen, and the hydrocarbon and the water vapor in the pre-reforming process gas react with the added oxygen to generate carbon monoxide, carbon dioxide, hydrogen and water vapor.
The steam in the autothermal reactor comes from the slight excess steam left after pre-reforming (the pre-reforming water-carbon ratio is usually between 1.5 and 2.0), which is much lower than the usual 2.5 to 3.5 of the autothermal process, so as to achieve the effect of saving energy.
The prior art method can only reduce the PSA yield, generally to about 70%, to make the poison content in the obtained hydrogen meet the standard requirements, thereby causing the cost to be increased and the carbon dioxide emission to be increased. In the present invention, CO and CO are subjected to methanation reaction 2 The content is reduced, the purity of the hydrogen in the product is improved, and the PSA can be operated in a parameter interval with high hydrogen extraction rate. The invention improves PSA (pressure swing adsorption) extraction rate, and then reduces CO and CO through methanation process 2 The content of the hydrogen gas is increased while the PSA extraction rate is increased.
By the method, the yield of the obtained product hydrogen is more than 90%, the purity of the hydrogen is high-purity hydrogen with the purity of more than 99.98%, and CO in the obtained hydrogen 2 The content is less than 10ppb. Can be directly used as hydrogen raw material in fuel cell.
In some embodiments, the catalyst for the hydrogenation reaction is one or more of a nickel molybdenum or cobalt molybdenum nickel catalyst. The hydrogenation process hydrogenates sulfides and chlorides into hydrogen sulfide and hydrogen chloride.
In some embodiments, the reactor inlet temperature for the pre-reforming reaction is 440-630 ℃ and the water to carbon ratio is 1.5-2.0.
In some embodiments, the catalyst of the pre-reforming reaction is a nickel-based catalyst. In some embodiments, the pressure of the pre-reforming reaction is between 1.5 and 2.6MPa. The pressure range is beneficial for increasing the hydrogen yield of the PSA. In some embodiments, the process gas at the reactor outlet of the pre-reforming reaction is mainly composed of methane, carbon monoxide, carbon dioxide, hydrogen. The pre-conversion process is beneficial to the heat of the process gas after the autothermal reactor on one hand, and the purpose of energy conservation is achieved.On the one hand, the higher hydrocarbon in the hydrocarbon raw material is completely converted into carbon one (the composition is CH) 4 、CO、CO 2 、H 2 ) So as to simplify the hydrocarbon steam reforming reaction in the subsequent reactor (the natural gas reforming has low requirement on the catalyst and is not easy to form carbon in the reaction process).
In some embodiments, the oxygen in the process of autothermal reaction is air, oxygen-enriched air, or pure oxygen. In some embodiments, the reactor inlet temperature for the autothermal reaction is typically 1250 to 1480 ℃ and the outlet temperature is 910 to 960 ℃, the pressure for the autothermal reaction is 1.5 to 2.5MPa, and the methane content of the outlet process gas is 0.5% by volume or less. In some embodiments, the process gas after autothermal reaction is comprised primarily of methane, carbon monoxide, carbon dioxide, hydrogen.
The amount of heat required to effect the steam reaction per mole of hydrocarbon is fixed. Compared with the conventional hydrocarbon steam reforming process, the conventional reforming furnace is adopted, and fuel is used for supplying reaction heat; the self-heating is to generate a combustion reaction by means of oxygen and part of hydrocarbons, CO and hydrogen to generate a large amount of heat for supplying heat for subsequent reactions.
The reaction temperature of the autothermal reaction depends on the amount of oxygen and the water-carbon ratio. The conversion rate of hydrocarbons in autothermal reaction depends on temperature, water-carbon ratio and pressure. The water-to-carbon ratio of the present invention is lower than the conventional autothermal process parameters, resulting in a hydrocarbon conversion that is also lower than the conventional autothermal process, so the exit methane content is slightly higher (near 0.5% at the end).
In some embodiments, the reactor outlet carbon monoxide volume content of the shift reaction is 2% or less.
In some embodiments, the catalyst for fine desulfurization is a copper-based desulfurization catalyst. Copper-based catalysts have the ability to desulfurize and dechlorinate. The content of sulfur and chlorine after fine desulfurization is less than or equal to 4ppb. In some embodiments, the catalyst of the methanation process is a nickel-based methane catalyst. In some embodiments, the inlet temperature for the methanation reaction is 310-350 ℃.
A system for producing hydrogen comprises a hydrogenation reactor, a desulfurization tank, a pre-reforming reactor, an autothermal reactor, a shift reactor, a pressure swing adsorption device, a fine desulfurization device and a methanation reactor, wherein hydrocarbon raw materials enter the hydrogenation reactor, the hydrogenation reactor is sequentially connected with the desulfurization tank, the pre-reforming reactor, the autothermal reactor, the shift reactor, the pressure swing adsorption device, the fine desulfurization device and the methanation reactor, water vapor is introduced into the pre-reforming reactor, and oxygen is introduced into the autothermal reactor.
The hydrocarbon raw material comprises natural gas, refinery gas, liquefied petroleum gas or naphtha, and compared with the existing hydrocarbon steam conversion system, the purity of the hydrogen is improved, and CO in the product hydrogen are 2 The content is reduced, and the fuel meets GB T37244-2018, and can be used for hydrogen fuel cells.
Compared with the existing system for preparing hydrogen, the system for producing hydrogen has the advantages that the autothermal reactor is additionally arranged in front of the shift reactor, and the fine desulfurization and methanation reactors are additionally arranged behind the pressure swing adsorption device.
Most of hydrocarbons in the autothermal reactor are converted into CO and CO 2 And H 2 Compared with the existing system for preparing hydrogen, the autothermal reactor does not reintroduce the water vapor raw material, and only introduces oxygen as the raw material of the autothermal reaction.
In some embodiments, the upper section of the hydrogenation reactor uses a nickel molybdenum or cobalt molybdenum nickel catalyst and the lower section uses a cobalt molybdenum catalyst. The hydrocarbon raw material is hydrogenated by the hydrogenation reactor through the upper section and the lower section respectively, so that the hydrogenation precision is improved.
In some embodiments, the desulfurization tank is divided into a first desulfurization tank and a second desulfurization tank, and the hydrogenation reactor is sequentially connected with the first desulfurization tank and the second desulfurization tank. Preferably, the first desulfurization tank is filled with a dechlorinating agent and a zinc oxide desulfurizer, and the filling volume ratio of the dechlorinating agent to the zinc oxide desulfurizer is 1:3-5. The second desulfurization tank is filled with zinc oxide desulfurizer. The hydrocarbon raw material is hydrogenated, and then dechlorinated and desulfurized to remove sulfur and chlorine in the hydrocarbon raw material.
In some embodiments, the pre-reforming reaction is conducted at an inlet temperature of 380-630 ℃ and an outlet temperature of 520 ℃ or less. The purpose of controlling the inlet temperature of the pre-conversion reactor is to ensure the pre-conversion efficiency and improve the conversion rate of the hydrocarbons.
The inlet temperature control of the pre-conversion reactor is related to the raw material, and when the raw material is natural gas, the inlet temperature can be controlled to be less than or equal to 630 ℃; when the raw material is high-grade hydrocarbon such as refinery gas and naphtha, the inlet temperature can be controlled at 380-450 ℃. The outlet temperature is controlled by the reaction. For natural gas feeds, the exit temperature is typically between 420 and 450 ℃; for higher hydrocarbons such as refinery gas, naphtha, etc., the exit temperature is typically between 460-500 ℃.
In some embodiments, the outlet temperature of the autothermal reactor is 910-960 ℃. The reaction in the autothermal reactor is a process in which the hydrocarbon compound reacts with oxygen and steam, unlike the prior art (tubular reformer) in which the hydrocarbon compound simply reacts with steam. Controlling the reaction temperature to be different, and controlling the outlet temperature in this range in the present invention, can contribute to the reaction efficiency of the autothermal reaction process.
The invention has the beneficial effects that:
the invention provides a hydrogen production method, which expands the range of converted raw materials by means of a combined mode of pre-conversion and self-heating conversion, improves the conversion rate of methane and reduces the production cost of hydrogen under the condition of lower water-carbon ratio; by means of the combination of pressure swing adsorption, fine desulfurization and methanation, high-quality hydrogen meeting the requirements of the hydrogen fuel cell is obtained in a relatively low-cost mode.
The hydrogen production method removes higher hydrocarbons, carbon monoxide and carbon dioxide, so that the final impurity content is reduced to meet the national standard requirement of hydrogen of the hydrogen fuel cell; firstly, removing a part of higher hydrocarbon, then utilizing oxygen and water vapor to simultaneously carry out autothermal reforming reaction with the hydrocarbon, improving the conversion rate of the hydrocarbon, and then carrying out fine desulfurization and methanation to remove the toxic substances harmful to the hydrogen fuel cell.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the invention and not to limit the invention.
FIG. 1 is a schematic diagram of a principal system for producing hydrogen;
1. the device comprises a hydrogenation reactor, 2, a first desulfurization tank, 3, a second desulfurization tank, 4, a pre-conversion reactor, 5, an autothermal reactor, 6, a shift reactor, 7, a pressure swing adsorption device, 8, a fine desulfurization device, 9 and a methanation reactor.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The hydrocarbon steam conversion is a common process for preparing hydrogen by utilizing gaseous hydrocarbon and liquid hydrocarbon, and the common processes are hydrogenation, desulfurization, ppb-level desulfurization (optional), pre-conversion (optional), conversion, transformation and PSA purification. By using the process flow, 99.99 percent of high-purity hydrogen can be obtained, the hydrogen yield can be more than 90 percent, but CO and CO in the obtained hydrogen are obtained at the moment 2 The content exceeds the regulation range of GB T37244-2018, and the fuel cell can not be directly used for a hydrogen fuel cell. If hydrogen with the poison content meeting GB T37244-2018 is directly obtained through the process, the PSA yield needs to be reduced, the hydrogen yield of the PSA is reduced to about 70% through measurement and laboratory verification, and the poison content of the obtained hydrogen can meet the standard requirement. This results in increased hydrogen acquisition costs and increased carbon dioxide emissions.
By utilizing the process, the hydrogen yield of PSA can be kept above 90% and the purity of the hydrogen produced by PSA is 99.99% when the hydrogen is produced daily. By means of the copper-based desulfurizing agent in the step (5), poison in hydrogen can be subjected toRemoving CO and CO in the hydrogen by virtue of methanation reaction 2 And the methane is converted into methane, so that the effect of purifying hydrogen is achieved, the hydrogen yield of the device can be kept to be more than 90%, and the hydrogen cost is effectively reduced.
The invention is further illustrated by the following examples:
example 1
A useful hydrocarbon feedstock is natural gas.
The upper section of the hydrogenation reactor uses a cobalt-molybdenum-nickel catalyst, and the lower section uses a cobalt-molybdenum catalyst. The first desulfurization tank is filled with a dechlorinating agent and a zinc oxide desulfurizer, the filling proportion is 1. The pre-reforming reactor is filled with a nickel-based pre-reforming catalyst. The autothermal reactor is loaded with a nickel-based autothermal reforming catalyst. The shift reactor is filled with iron-chromium carbon monoxide shift catalyst. The fine desulfurization tank is filled with a copper-based final desulfurizing agent. The methanation reactor is filled with a nickel-based methanation catalyst.
The pre-conversion reactor controls the inlet temperature of the reactor to be 480 ℃ and the outlet temperature to be about 430 ℃ according to different raw materials; the water-carbon ratio is controlled to be 2.0; the inlet pressure is 2.60MPa, and the outlet pressure is 2.55MPa; the pre-conversion process gas comprises the following components: 76.69% of methane, 0.05% of carbon monoxide, 3.81% of carbon dioxide and the balance of hydrogen.
The oxygen used in the autothermal reactor is pure oxygen; the oxygen-carbon ratio is controlled to be 0.15mol/mol, a steam distribution line is not arranged in front of the reactor, and the autothermal reactor completely utilizes the residual steam of the pre-reforming reactor to carry out reforming reaction; the outlet temperature of the autothermal reactor is 920 ℃, the inlet pressure is 2.48MPa, the outlet pressure is 2.39MPa, and the outlet process gas composition is as follows: 0.21% of methane, 21.47% of carbon monoxide, 4.50% of carbon dioxide and the balance of hydrogen.
The carbon monoxide content at the outlet of the shift reactor is less than or equal to 2 percent.
The purity of PSA hydrogen production is 99.99%, the hydrogen yield is 91%, and PSA tail gas enters a gas pipe network to be used as fuel.
And the hydrogen produced by PSA is purified again in a fine desulfurization tank, and the content of sulfur and chlorine after purification is less than or equal to 4ppb. After passing through the methanation reactor, the total amount of carbon monoxide and carbon dioxide in the hydrogen is less than or equal to 10ppb, and the purity of the hydrogen is more than or equal to 99.98 percent.
Example 2
As shown in fig. 1, a hydrogen production system in which methane is used as a hydrocarbon raw material in example 1 includes a hydrogenation reactor 1, which is connected in sequence to a desulfurization tank, a pre-reforming reactor 4, an autothermal reactor 5, a shift reactor 6, a pressure swing adsorption device 7, a fine desulfurization device 8, and a methanation reactor 9.
The hydrocarbon raw material purification unit comprises a hydrogenation reactor and a desulfurization tank, and olefin saturation and fine desulfurization in the raw material are completed.
The pre-reaction unit is mainly a pre-conversion reactor (adiabatic reactor) filled with a pre-conversion catalyst. The purified hydrocarbon raw material and water vapor are mixed and enter a pre-conversion reactor to remove or reduce the content of higher hydrocarbon, and pre-conversion process gas is methane, carbon monoxide, carbon dioxide, hydrogen and trace higher hydrocarbon.
And the main reaction unit is used for introducing the pre-converted process gas and oxygen into an autothermal reactor to generate the autothermal reforming reactor, wherein the process gas is methane, carbon monoxide, carbon dioxide and hydrogen.
And the conversion unit generates water gas conversion reaction on the self-heated process gas by using an iron-chromium-based carbon monoxide conversion catalyst by means of an adiabatic reactor, thereby increasing the yield of hydrogen.
The hydrogen separation and purification unit consists of Pressure Swing Adsorption (PSA), fine desulfurization and methanation. In the unit, hydrogen in the shift process gas is purified by PSA, and the hydrogen purity can reach 99.99 percent; then, after further purification by a fine desulfurization and methanation reactor, the quality of the obtained hydrogen can meet the index of the hydrogen fuel cell.
The upper section of the pre-conversion reactor uses nickel-molybdenum or cobalt-molybdenum-nickel catalyst, and the lower section uses cobalt-molybdenum catalyst.
The desulfurizing tank is divided into a first desulfurizing tank 2 and a second desulfurizing tank 3, and the hydrogenation reactor 1 is sequentially connected with the first desulfurizing tank 2 and the second desulfurizing tank 3. Preferably, the first desulfurization tank 2 is filled with a dechlorinating agent and a zinc oxide desulfurizer, and the filling volume ratio of the dechlorinating agent to the zinc oxide desulfurizer is 1:3-5.
According to the agent loading conditions of the first desulfurization tank and the second desulfurization tank, the operation condition of the first desulfurization tank only needs to be detected during daily production, when the purification effect of the first desulfurization tank does not reach the standard, the agent is replaced, and the second desulfurization tank can be utilized to continuously maintain production during the agent replacement.
The inlet temperature of the pre-conversion reaction is 380-630 ℃, and the outlet temperature is controlled to be less than or equal to 520 ℃.
The outlet temperature of the autothermal reactor is 910-960 ℃.
Example 3
A useful hydrocarbon feedstock is liquefied petroleum gas.
The upper section of the hydrogenation reactor uses a cobalt-molybdenum-nickel catalyst, and the lower section uses a cobalt-molybdenum catalyst. The first desulfurization tank is filled with a dechlorinating agent and a zinc oxide desulfurizing agent according to the filling proportion of 1. The pre-reforming reactor is filled with a nickel-based pre-reforming catalyst. The autothermal reactor is loaded with a nickel-based autothermal reforming catalyst. The shift reactor is packed with an iron-chromium-based carbon monoxide shift catalyst. The fine desulfurization tank is filled with a copper-based final desulfurizing agent. The methanation reactor is filled with a nickel-based methanation catalyst.
The pre-conversion reactor controls the inlet temperature of the reactor to be 420 ℃ and the outlet temperature to be 480 ℃; the water-carbon ratio is controlled to be 2.0; the inlet pressure is 2.6MPa, and the outlet pressure is 2.55MPa; the pre-conversion process gas comprises the following components: 68.00 percent of methane, 0.18 percent of carbon monoxide, 5.52 percent of carbon dioxide and the balance of hydrogen.
The oxygen used in the autothermal reactor is pure oxygen; the oxygen-carbon ratio is controlled to be 0.15mol/mol, a steam distribution line is not arranged in front of the reactor, and the autothermal reactor completely utilizes the residual steam of the pre-reforming reactor to carry out reforming reaction; the outlet temperature of the autothermal reactor is 920 ℃, the inlet pressure is 2.48MPa, the outlet pressure is 2.39MPa, and the outlet process gas composition is as follows: 0.29% of methane, 22.38% of carbon monoxide, 3.38% of carbon dioxide and the balance of hydrogen.
The carbon monoxide content at the outlet of the shift reactor is less than or equal to 2 percent.
The purity of PSA hydrogen production is 99.99%, the hydrogen yield is 91%, and PSA tail gas enters a gas pipe network to be used as fuel.
And the hydrogen produced by PSA is purified again in a fine desulfurization tank, and the content of sulfur and chlorine after purification is less than or equal to 4ppb. After passing through the methanation reactor, the total amount of carbon monoxide and carbon dioxide in the hydrogen is less than or equal to 10ppb, and the purity of the hydrogen is more than or equal to 99.98 percent.
Comparative example 1
A useful hydrocarbon feedstock is natural gas.
The upper section of the hydrogenation reactor uses cobalt-molybdenum-nickel catalyst, and the lower section uses cobalt-molybdenum catalyst. The first desulfurization tank is filled with a dechlorinating agent and a zinc oxide desulfurizing agent according to the filling proportion of 1. The pre-reforming reactor is filled with a nickel-based pre-reforming catalyst. The autothermal reactor is loaded with a nickel-based autothermal reforming catalyst. The shift reactor is filled with iron-chromium carbon monoxide shift catalyst. The fine desulfurization tank is filled with a copper-based final desulfurizing agent. The methanation reactor is filled with a nickel-based methanation catalyst.
The inlet temperature of the pre-conversion reactor is controlled to be 480 ℃, and the outlet temperature of the pre-conversion reactor is controlled to be 430 ℃; the water-carbon ratio is controlled to be 2.0; the inlet pressure is 2.6MPa, and the outlet pressure is 2.55MPa; the pre-conversion process gas comprises the following components: 76.69% of methane, 0.05% of carbon monoxide, 3.81% of carbon dioxide and the balance of hydrogen.
The outlet temperature of the autothermal reactor is 920 ℃, the inlet pressure is 2.48MPa, the outlet pressure is 2.39MPa, and the outlet process gas composition is as follows: 0.21% of methane, 21.47% of carbon monoxide, 4.50% of carbon dioxide and the balance of hydrogen.
The reactor was equipped with a steam feed line, the amount of steam fed corresponds to the difference between 3.0 and 2.0 of the total water to carbon ratio (total water to carbon ratio = (molar amount of steam pre-reforming + autothermal)/molar amount of total carbon), i.e. the total water to carbon ratio for example 1 was 2.0 and the total water to carbon ratio for comparative example 1 was 3.0; the outlet temperature of the autothermal reactor is 920 ℃, the inlet pressure is 2.48MPa, the outlet pressure is 2.39MPa, and the outlet process gas composition is as follows: 0.01% of methane, 20.01% of carbon monoxide, 5.26% of carbon dioxide and the balance of hydrogen.
The carbon monoxide content at the outlet of the shift reactor is less than or equal to 2 percent.
The PSA hydrogen production purity is 99.99%, the hydrogen yield is 91%, and the PSA tail gas enters a gas pipe network to be used as fuel.
And the hydrogen produced by PSA is purified again in a fine desulfurization tank, and the content of sulfur and chlorine after purification is less than or equal to 4ppb. After passing through the methanation reactor, the total amount of carbon monoxide and carbon dioxide in the hydrogen is less than or equal to 10ppb, and the purity of the hydrogen is more than or equal to 99.98 percent.
The specific quantity of water and carbon is increased, the hydrogen content of the process gas from the hot outlet is increased by 0.91 percent, namely the hydrogen yield is increased by 1.23 percent, the cost is that the water quantity is increased by 50 percent, subsequent cooling and recovery equipment is enlarged, the investment is increased, the cost of environment-friendly water treatment is also increased, and the cost is not cost-effective.
Comparative example 2
A useful hydrocarbon feedstock is natural gas.
The upper section of the hydrogenation reactor uses cobalt-molybdenum-nickel catalyst, and the lower section uses cobalt-molybdenum catalyst. The first desulfurization tank is filled with a dechlorinating agent and a zinc oxide desulfurizing agent according to the filling proportion of 1. The pre-reforming reactor is filled with a nickel-based pre-reforming catalyst. The autothermal reactor is loaded with a nickel-based autothermal reforming catalyst. The shift reactor is packed with an iron-chromium-based carbon monoxide shift catalyst. The fine desulfurization tank is filled with a copper-based final desulfurizing agent. The methanation reactor is filled with a nickel-based methanation catalyst.
The pre-conversion reactor controls the inlet temperature of the reactor to be 440 ℃ and the outlet temperature to be 450 ℃ according to different raw materials; the water-carbon ratio is controlled to be 2.0; the inlet pressure is 2.6MPa, and the outlet pressure is 2.55MPa; the pre-conversion process gas comprises the following components: 74.01% of methane, 0.09% of carbon monoxide, 4.34% of carbon dioxide and the balance of hydrogen.
The oxygen used in the autothermal reactor is pure oxygen; the oxygen-carbon ratio is controlled to be 0.3mol/mol, a steam distribution line is not arranged in front of the reactor, and the autothermal reactor completely utilizes the residual steam of the pre-reforming reactor to carry out the reforming reaction; the outlet temperature of the autothermal reactor is 920 ℃, the inlet pressure is 2.48MPa, the outlet pressure is 2.39MPa, and the outlet process gas composition is as follows: 0.02% of methane, 22.97% of carbon monoxide, 4.67% of carbon dioxide and the balance of hydrogen.
The carbon monoxide content at the outlet of the shift reactor is less than or equal to 2 percent.
The purity of PSA hydrogen production is 99.99%, the hydrogen yield is 91%, and PSA tail gas enters a gas pipe network to be used as fuel.
And the hydrogen produced by PSA is purified again in a fine desulfurization tank, and the content of sulfur and chlorine after purification is less than or equal to 4ppb. After passing through the methanation reactor, the total amount of carbon monoxide and carbon dioxide in the hydrogen is less than or equal to 10ppb, and the purity of the hydrogen is more than or equal to 99.98 percent.
By comparing example 1 with comparative example 2, it is understood that the present invention can improve the conversion of hydrocarbons by setting the oxygen to carbon ratio, which would result in an economically disadvantageous ratio if the oxygen to carbon ratio is too high.
The oxygen-carbon ratio is too high, so that the amount of oxygen has influence on the cost, the oxygen is more, and the cost is increased; the oxygen distribution is more, the hydrogen of the process gas is reduced by 1.86%, and compared with the comparative example 1, 2.5% of hydrogen is lost.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A method of producing hydrogen, characterized by: the method comprises the following specific steps:
the method comprises the following steps of firstly carrying out hydrogenation reaction and desulfurization on a hydrocarbon raw material, carrying out pre-reforming reaction on the hydrocarbon raw material and steam, carrying out self-heating reaction on the pre-reforming reaction, oxygen and steam contained in the pre-reforming reaction, wherein the oxygen-carbon ratio is 0.1-0.2mol/mol, carrying out conversion reaction after the self-heating reaction, carrying out pressure swing adsorption on a mixed gas after the conversion reaction to obtain a mixed gas of a first product hydrogen and a tail gas, and carrying out methanation reaction on the mixed gas of the first product hydrogen after fine desulfurization to obtain a final product hydrogen;
wherein the temperature of the reactor inlet of the pre-conversion reaction is 440-630 ℃, and the water-carbon ratio is 1.5-2.0.
2. The method for producing hydrogen according to claim 1, characterized in that: the catalyst for hydrogenation reaction is one or mixture of nickel and molybdenum or cobalt, molybdenum and nickel catalyst in any proportion.
3. The method of producing hydrogen as claimed in claim 1, wherein: the catalyst for the pre-reforming reaction is a nickel-based catalyst.
4. The method of producing hydrogen as claimed in claim 1, wherein: the pressure of the pre-conversion reaction is 1.5-2.6MPa.
5. The method for producing hydrogen according to claim 1, characterized in that: the process gas at the outlet of the pre-conversion reactor comprises hydrocarbon compounds, carbon monoxide, carbon dioxide and hydrogen.
6. The method of producing hydrogen as claimed in claim 1, wherein: the oxygen in the autothermal reaction process is air, oxygen-enriched air or pure oxygen.
7. The method for producing hydrogen according to claim 1, characterized in that: the temperature of the inlet of the reactor of the self-heating reaction is 1250-1480 ℃, the temperature of the outlet is 910-960 ℃, the pressure of the self-heating reaction is 1.5-2.5MPa, and the volume content of methane in the process gas at the outlet is less than or equal to 0.5 percent.
8. The method of producing hydrogen as claimed in claim 7, wherein: the volume content of carbon monoxide at the outlet of the shift reactor is less than or equal to 2 percent.
9. A system for producing hydrogen, comprising: the system comprises a hydrogenation reactor, a desulfurization tank, a pre-reforming reactor, an autothermal reactor, a shift reactor, a pressure swing adsorption device, a fine desulfurization device and a methanation reactor, wherein a hydrocarbon raw material enters the hydrogenation reactor, the hydrogenation reactor is sequentially connected with the desulfurization tank, the pre-reforming reactor, the autothermal reactor, the shift reactor, the pressure swing adsorption device, the fine desulfurization device and the methanation reactor, water vapor is introduced into the pre-reforming reactor, and oxygen is introduced into the autothermal reactor.
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