Solar-driven green hydrogen preparation and methanol conversion coupled hydrogen metallurgy integrated system and operation method

Abstract

The invention discloses a solar-driven green hydrogen preparation and methanol conversion coupled hydrogen metallurgy integrated system and an operation method. The system comprises a photovoltaic power generation system, a water electrolysis hydrogen production system, a reducing gas preparation system, a hydrogen metallurgy system, a top gas treatment system and a methanol conversion system. Photovoltaic power generation supplies power to hydrogen production through water electrolysis; when solar energy is sufficient, part of hydrogen generated by electrolyzing water enters the reducing gas preparation system, is mixed with circulating top gas, is heated and then is introduced into the hydrogen metallurgy system, and iron ore is reduced into direct reduction iron in the shaft furnace; treating the reacted furnace top gas, partially circulating, and partially combusting to heat the reducing gas; the captured carbon dioxide and hydrogen prepared by electrolyzed water are synthesized into methanol to be stored; when solar energy is insufficient, methanol is cracked to generate hydrogen and carbon monoxide as supplementary reducing gas to maintain stable operation of the system; according to the invention, the carbon emission of the metallurgical process can be greatly reduced, and the high-quality collaborative development of renewable energy sources and high-carbon industries is promoted.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of renewable energy utilization, and particularly relates to an integrated system and operation method of solar-driven green hydrogen preparation and methanol conversion coupled hydrogen metallurgy. BACKGROUND

[0002] The steel production of China accounts for more than 50% of the total global production. As a key field of high carbon emission, the steel industry is a research focus of reducing greenhouse gas emission. Hydrogen metallurgy, as a replacement scheme of traditional blast furnace technology, can significantly reduce carbon emission by replacing carbon monoxide with hydrogen to reduce iron ore. The MIDREX and HYL / Energiron processes are the current mainstream hydrogen metallurgy processes, but both mainly rely on methane reforming to prepare hydrogen-rich reducing gas, and still inevitably produce carbon dioxide emission. The use of green hydrogen obtained by electrolysis of water by renewable energy such as solar energy for metallurgy can greatly reduce the carbon emission of the metallurgical process. However, the renewable energy such as solar energy has volatility and randomness, resulting in unstable hydrogen production by electrolysis of water, which cannot guarantee the safe and stable operation of the metallurgical system. Green methanol is synthesized from green hydrogen and carbon dioxide, which can not only convert intermittent solar energy into stable chemical energy, but also can produce hydrogen by decomposition. However, how to realize the organic combination of green hydrogen production, methanol conversion and metallurgical production is still a difficult problem to be solved. Therefore, it is urgent to develop an integrated technology of green hydrogen production-methanol conversion-metallurgical production to greatly reduce the carbon emission of the metallurgical process and effectively guarantee the safe and stable operation of the metallurgical system. SUMMARY

[0003] To solve the problems in the prior art, the application aims to provide an integrated system and operation method of solar-driven green hydrogen preparation and methanol conversion coupled hydrogen metallurgy. The green hydrogen is obtained by electrolysis of water by photovoltaic power generation. Part of the green hydrogen is reacted with carbon dioxide to generate hydrogen-rich reducing gas through reverse water gas shift reaction, and the hydrogen-rich reducing gas is used to reduce iron ore in a gas-based direct reduction shaft furnace to generate direct reduced iron. The top gas after reaction is treated by a top gas treatment system and then recycled to the metallurgical furnace. The system integrates a methanol conversion module. When the solar energy is sufficient, the excess green hydrogen is reacted with the captured carbon dioxide to synthesize methanol, which not only converts unstable solar energy into stable chemical energy storage, but also realizes the resource utilization of carbon dioxide. When the solar energy is insufficient, the methanol can be cracked to generate hydrogen and carbon monoxide as reducing gas to meet the stable demand of the metallurgical furnace for reducing gas.

[0004] To achieve the above-mentioned purpose, the application adopts the following technical scheme: An integrated system of solar-driven green hydrogen preparation and methanol conversion coupled hydrogen metallurgy, characterized by comprising a photovoltaic power generation system, an electrolytic water hydrogen production system, a reducing gas preparation system, a hydrogen metallurgy system, a top gas treatment system and a methanol conversion system. The photovoltaic power generation system comprises a solar cell 2 and a DC / DC converter 3; the solar cell 2 absorbs solar radiation energy and converts solar energy into electric energy output; the DC / DC converter 3 converts the electric energy output by the solar cell 2 into stable direct current of different voltage levels to supply power to a subsequent system; The water electrolysis hydrogen production system comprises an alkaline electrolytic cell 4; an electric energy input end of the alkaline electrolytic cell 4 is connected with an output end of the DC / DC converter 3 to generate hydrogen and oxygen by electrolyzing water; a hydrogen outlet of the alkaline electrolytic cell 4 is divided into two paths, one of which is communicated with a reducing gas preparation system to deliver green hydrogen, and the other of which enters a methanol conversion system to provide raw materials for methanol synthesis; an oxygen outlet of the alkaline electrolytic cell 4 is communicated with the reducing gas preparation system to assist the reducing gas preparation process; The reducing gas preparation system comprises a hydrogen-carbon dioxide manifold 5, a reverse water gas shift heat exchanger 6, a reverse water gas shift reactor 7, a reducing gas water remover 8, a reducing gas manifold 9 and a reducing gas heating furnace 10; the oxygen outlet of the alkaline electrolytic cell 4 is connected with an oxygen inlet of the reducing gas heating furnace 10; a hydrogen outlet of the alkaline electrolytic cell 4 and an outlet of a carbon dioxide storage tank 16 are connected with two feed inlets of the hydrogen-carbon dioxide manifold 5 respectively; an outlet of the hydrogen-carbon dioxide manifold 5 is connected with a cold side inlet of the reverse water gas shift heat exchanger 6; a cold side outlet of the reverse water gas shift heat exchanger 6 is connected with an inlet of the reverse water gas shift reactor 7; an outlet of the reverse water gas shift reactor 7 is connected with a hot side inlet of the reverse water gas shift heat exchanger 6; a hot side outlet of the reverse water gas shift heat exchanger 6 is connected with an inlet of the reducing gas water remover 8; an outlet of the reducing gas water remover 8 is connected with a bottom inlet of the reducing gas manifold 9; an outlet of the reducing gas manifold 9 is connected with a heating side inlet of the reducing gas heating furnace 10; a heating side outlet of the reducing gas heating furnace 10 outputs high-temperature hydrogen-rich reducing gas for a hydrogen metallurgy system; The hydrogen metallurgy system comprises a gas-based direct reduction shaft furnace 11; the high-temperature hydrogen-rich reducing gas of the heating side outlet of the reducing gas heating furnace 10 enters from a furnace bottom inlet of the gas-based direct reduction shaft furnace 11, reacts with iron ore and generates direct reduced iron, and the reacted gas exits from a furnace top outlet of the gas-based direct reduction shaft furnace 11; The furnace top gas treatment system comprises a furnace top gas cooler 12, a furnace top gas water remover 13, a furnace top gas carbon dioxide absorption tower 14, a carbon dioxide stripping tower 15 and a carbon dioxide storage tank 16; the furnace top outlet of the gas-based direct reduction shaft furnace 11 is connected to the inlet of the furnace top gas cooler 12, the outlet of the furnace top gas cooler 12 is connected to the inlet of the furnace top gas water remover 13, and the outlet of the furnace top gas water remover 13 is connected to the inlet of the furnace top gas carbon dioxide absorption tower 14; the outlet of the furnace top gas carbon dioxide absorption tower 14 is divided into three paths, the first path is connected to the inlet of the carbon dioxide stripping tower 15, the second path is connected to the top inlet of the reducing gas collector 9, and the third path is connected to the combustion side inlet of the reducing gas heating furnace 10; the outlet of the carbon dioxide stripping tower 15 is divided into two paths, one path is connected to the carbon dioxide storage tank 16, and the other path enters the methanol conversion system; The methanol conversion system comprises a methanol synthesis raw material collector 17, a methanol synthesis raw material compressor 18, a methanol synthesis reactor 19, a methanol rectification tower 20, a methanol storage tank 21 and a methanol cracking reactor 22; the inlet of the methanol synthesis raw material collector 17 has two paths, one path is connected to the outlet of the carbon dioxide stripping tower 15, and the other path is connected to the hydrogen outlet of the alkaline electrolytic cell 4, the outlet of the methanol synthesis raw material collector 17 is connected to the inlet of the methanol synthesis raw material compressor 18, the outlet of the methanol synthesis raw material compressor 18 is connected to the inlet of the methanol synthesis reactor 19, the outlet of the methanol synthesis reactor 19 is connected to the inlet of the methanol rectification tower 20, and the outlet of the methanol rectification tower 20 is connected to the methanol storage tank 21; when the output power of the photovoltaic power generation system is insufficient and the green hydrogen supply amount of the alkaline electrolytic cell 4 cannot meet the hydrogen metallurgical demand, the outlet of the methanol storage tank 21 is connected to the inlet of the methanol cracking reactor 22, and the reducing gas at the outlet of the methanol cracking reactor 22 enters the middle inlet of the reducing gas collector 9.

[0005] Further, the photovoltaic power generation system and the water electrolysis hydrogen production system adopt an indirect coupling mode and are connected through a DC / DC converter 3.

[0006] Further, the water electrolysis hydrogen production system adopts an alkaline water electrolysis hydrogen production technology, and the working temperature of the alkaline electrolytic cell 4 is 70-80 °C.

[0007] Further, part of the hydrogen produced by the alkaline electrolytic cell 4 is used as reducing gas for reducing iron ore, and the other part is used as raw material for synthesizing methanol, and the oxygen produced is introduced into the combustion side of the reducing gas heating furnace 10 to provide combustion-supporting gas for the reducing gas heating process.

[0008] Further, the reverse water-gas shift heat exchanger 6 is a tubular heat exchanger, the hot fluid flows through the shell side, the cold fluid flows through the tube side, and the end difference between the hot fluid outlet and the cold fluid inlet is 25 °C.

[0009] Further, the reducing gas dehydrator 8 and the top gas dehydrator 13 both adopt flash evaporation type dehydrator, the working temperature is 25-30 °C, and the working pressure is 1-3 bar.

[0010] Further, the temperature of the reducing gas at the outlet of the reducing gas heater 10 is 900-1000 °C, and the volume fraction of hydrogen in the reducing gas is 50%-100%.

[0011] Further, the top gas carbon dioxide absorption tower 14 adopts 30%-35% (mass fraction) ethanolamine (MEA) solution as the absorption liquid, the carbon dioxide loading rate is 0.2-0.3 (mol CO2 / mol MEA), and the working pressure of the absorption tower is 1-2 bar.

[0012] Further, the methanol synthesis reactor 19 and the methanol cracking reactor 22 both adopt Cu / ZnO / Al2O3 as the catalyst, and the reaction temperature is 200-300 °C; wherein, the working pressure of the methanol synthesis reactor 19 is 50-110 bar, and the working pressure of the methanol cracking reactor 22 is 1-10 bar.

[0013] A running method of a solar-driven green hydrogen preparation-methanol conversion coupled hydrogen metallurgy integrated system is as follows: 1) When the solar energy is sufficient and the hydrogen production amount of the alkaline electrolytic cell 4 is greater than the hydrogen demand amount of the gas-based direct reduction shaft furnace 11, part of the hydrogen produced by the alkaline electrolytic cell 4 is combined with the carbon dioxide in the carbon dioxide storage tank 16, preheated by the reverse water-gas shift heat exchanger 6, and then introduced into the reverse water-gas shift reactor 7 to react, to generate carbon monoxide and water and form hydrogen-rich reducing gas, which is then combined with the circulating top gas output from the carbon dioxide absorption tower 14 at the reducing gas converging device 9 to meet the reducing gas demand of the gas-based direct reduction shaft furnace 11; the other part of the excess hydrogen is combined with the carbon dioxide resolved from the carbon dioxide resolution tower 15, compressed by the methanol synthesis raw material compressor 18, and then introduced into the methanol synthesis reactor 19 to react and synthesize methanol; 2) When the solar energy is sufficient and the hydrogen production amount of the alkaline electrolytic cell 4 is equal to the hydrogen demand amount of the gas-based direct reduction shaft furnace 11, the hydrogen produced by the alkaline electrolytic cell 4 is all introduced into the reverse water-gas shift reactor 7 to participate in the reaction to generate hydrogen-rich reducing gas, no hydrogen and carbon dioxide are introduced into the methanol synthesis reactor 19, and no methanol is produced; 3) When the solar energy is insufficient and the hydrogen production amount of the alkaline electrolytic cell 4 is less than the hydrogen demand amount of the gas-based direct reduction shaft furnace 11, the hydrogen produced by the alkaline electrolytic cell 4 is all supplied to the gas-based direct reduction shaft furnace 11; at the same time, the methanol stored in the methanol storage tank 21 is introduced into the methanol cracking reactor 22 to crack and generate hydrogen and carbon monoxide, which are combined with the reducing gas at the outlet of the reducing gas dehydrator 8 at the reducing gas converging device 9 to form reducing gas, which is heated and then introduced into the gas-based direct reduction shaft furnace 11. 4) When there is no solar energy at night, the alkaline electrolytic cell 4 stops working and no hydrogen is generated, and the reducing gas required by the gas-based direct reduction shaft furnace 11 is entirely provided by the methanol cracking reactor 22, and the methanol stored in the methanol storage tank 21 enters the methanol cracking reactor 22, and cracking produces hydrogen and carbon monoxide.

[0014] Compared with the prior art, the advantages of the present application are as follows: (1) By electrolyzing water through photovoltaic power generation, "green hydrogen" is prepared, and the "green hydrogen" is reacted with carbon dioxide through reverse water-gas shift reaction to prepare reducing gas required for metallurgy, which greatly reduces carbon emissions in the metallurgical production process.

[0015] (2) By the top gas treatment system, carbon dioxide in the top gas is captured for synthesizing methanol, and part of the top gas after carbon capture is recycled and mixed with fresh reducing gas and then re-enters the metallurgical furnace, i.e. the gas-based direct reduction shaft furnace, and the other part of the top gas is burned for heating the reducing gas, which reduces carbon emissions in the metallurgical process and reduces energy consumption.

[0016] (3) The methanol conversion system is integrated, when the solar energy is sufficient, the excess hydrogen prepared by electrolyzing water is synthesized with the captured carbon dioxide in the methanol synthesis reactor to synthesize methanol, which converts unstable solar energy into stable chemical energy storage and realizes resource utilization of carbon dioxide; when the solar energy is insufficient, the stored methanol is cracked in the methanol cracking reactor to produce hydrogen and carbon monoxide as a supplement of reducing gas, which effectively ensures the safe and stable operation of the metallurgical production process. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a schematic diagram of the system of the present application. DETAILED DESCRIPTION

[0018] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0019] As shown in Figure 1, a solar-driven green hydrogen preparation and methanol conversion coupled hydrogen metallurgy integrated system, comprising a photovoltaic power generation system, an electrolytic water hydrogen production system, a reducing gas preparation system, a hydrogen metallurgy system, a top gas treatment system and a methanol conversion system; The photovoltaic power generation system comprises a solar cell 2 and a DC / DC converter 3; the solar cell 2 absorbs solar radiation energy and converts solar energy into electrical energy output, and the DC / DC converter 3 converts the electrical energy output by the solar cell 2 into stable direct current of different voltage levels to supply power for the subsequent system; The electrolytic water hydrogen production system comprises an alkaline electrolytic cell 4; an electricity input end of the alkaline electrolytic cell 4 is connected with an output end of a DC / DC converter 3, hydrogen and oxygen are generated by electrolyzing water; a hydrogen outlet of the alkaline electrolytic cell 4 is divided into two paths, one path is communicated with a reducing gas preparation system to deliver green hydrogen, and the other path enters a methanol conversion system to provide raw materials for methanol synthesis; an oxygen outlet of the alkaline electrolytic cell 4 is communicated with the reducing gas preparation system and is used for assisting the reducing gas preparation process; The reducing gas preparation system comprises a hydrogen-carbon dioxide manifold 5, a reverse water gas shift heat exchanger 6, a reverse water gas shift reactor 7, a reducing gas water remover 8, a reducing gas manifold 9 and a reducing gas heating furnace 10; the oxygen outlet of the alkaline electrolytic cell 4 is connected with an oxygen inlet of the reducing gas heating furnace 10; a hydrogen outlet of the alkaline electrolytic cell 4 and an outlet of a carbon dioxide storage tank 16 are connected with two feeding inlets of the hydrogen-carbon dioxide manifold 5 respectively, a discharging outlet of the hydrogen-carbon dioxide manifold 5 is connected with a cold side inlet of the reverse water gas shift heat exchanger 6, a cold side outlet of the reverse water gas shift heat exchanger 6 is connected with an inlet of the reverse water gas shift reactor 7; an outlet of the reverse water gas shift reactor 7 is connected with a hot side inlet of the reverse water gas shift heat exchanger 6, a hot side outlet of the reverse water gas shift heat exchanger 6 is connected with an inlet of the reducing gas water remover 8, and an outlet of the reducing gas water remover 8 is connected with a bottom inlet of the reducing gas manifold 9; an outlet of the reducing gas manifold 9 is connected with a heating side inlet of the reducing gas heating furnace 10, and a heating side outlet of the reducing gas heating furnace 10 outputs high-temperature hydrogen-rich reducing gas for a hydrogen metallurgical system; The hydrogen metallurgical system comprises a gas-based direct reduction shaft furnace 11; the high-temperature hydrogen-rich reducing gas of the heating side outlet of the reducing gas heating furnace 10 enters from a furnace bottom inlet of the gas-based direct reduction shaft furnace 11, reacts with iron ore and generates direct reduced iron, and the reacted gas leaves from a furnace top outlet of the gas-based direct reduction shaft furnace 11; The furnace top gas treatment system comprises a furnace top gas cooler 12, a furnace top gas water remover 13, a furnace top gas carbon dioxide absorption tower 14, a carbon dioxide stripping tower 15 and a carbon dioxide storage tank 16; the furnace top outlet of the gas-based direct reduction shaft furnace 11 is connected with an inlet of the furnace top gas cooler 12, an outlet of the furnace top gas cooler 12 is connected with an inlet of the furnace top gas water remover 13, and an outlet of the furnace top gas water remover 13 is connected with an inlet of the furnace top gas carbon dioxide absorption tower 14; an outlet of the furnace top gas carbon dioxide absorption tower 14 is divided into three paths, a first path is connected with an inlet of the carbon dioxide stripping tower 15, a second path is connected with a top inlet of the reducing gas manifold 9, and a third path is connected with a combustion side inlet of the reducing gas heating furnace 10; an outlet of the carbon dioxide stripping tower 15 is divided into two paths, one path is connected with the carbon dioxide storage tank 16, and the other path enters the methanol conversion system; The methanol conversion system comprises a methanol synthesis raw material collector 17, a methanol synthesis raw material compressor 18, a methanol synthesis reactor 19, a methanol rectification tower 20, a methanol storage tank 21 and a methanol cracking reactor 22; the methanol synthesis raw material collector 17 has two inlets, one of which is connected with the outlet of the carbon dioxide stripping tower 15, and the other of which is connected with the hydrogen outlet of the alkaline electrolytic cell 4; the outlet of the methanol synthesis raw material collector 17 is connected with the inlet of the methanol synthesis raw material compressor 18; the outlet of the methanol synthesis raw material compressor 18 is connected with the inlet of the methanol synthesis reactor 19; the outlet of the methanol synthesis reactor 19 is connected with the inlet of the methanol rectification tower 20; the outlet of the methanol rectification tower 20 is connected with the methanol storage tank 21; when the photovoltaic power generation system outputs insufficient electric energy, and the green hydrogen supply amount of the alkaline electrolytic cell 4 cannot meet the hydrogen metallurgical demand, the outlet of the methanol storage tank 21 is connected with the inlet of the methanol cracking reactor 22, and the reducing gas at the outlet of the methanol cracking reactor 22 enters the middle inlet of the reducing gas collector 9.

[0020] As a preferred embodiment of the present application, the photovoltaic power generation system and the water electrolysis hydrogen production system adopt an indirect coupling mode, and are connected through a DC / DC converter 3, so that the output voltage of the solar cell can be adjusted to match the I-U characteristic of the electrolytic cell, thereby improving the hydrogen production efficiency.

[0021] As a preferred embodiment of the present application, the water electrolysis hydrogen production system adopts an alkaline water electrolysis hydrogen production technology, which is relatively mature, and has low cost and high durability; the working temperature of the alkaline electrolytic cell 4 is 70-80 °C, so that the hydrogen production efficiency can be maintained at a high level.

[0022] As a preferred embodiment of the present application, part of the hydrogen produced by the alkaline electrolytic cell 4 is used as reducing gas for reducing iron ore, and the other part is used as raw material for synthesizing methanol, so that unstable solar energy is converted into stable chemical energy storage; the oxygen produced is introduced into the combustion side of the reducing gas heating furnace 10 to provide combustion-supporting gas for the reducing gas heating process, thereby reducing the energy consumption of the metallurgical process.

[0023] As a preferred embodiment of the present application, the reverse water gas shift heat exchanger 6 is a tubular heat exchanger, in which the hot fluid flows through the shell side, and the cold fluid flows through the tube side; the end difference between the hot fluid outlet and the cold fluid inlet is 25 °C, so that the reactants are preheated, the heat of the reverse water gas reactor product is effectively recovered, and the efficiency of the system is improved.

[0024] As a preferred embodiment of the present application, the reducing gas dehydrator 8 and the furnace top gas dehydrator 13 both adopt flash evaporation type dehydrators, which have a working temperature of 25-30 °C and a working pressure of 1-3 bar; the water vapor in the reducing gas is removed, the purity of hydrogen and carbon monoxide is increased, and the utilization rate of the reducing gas is improved.

[0025] As a preferred embodiment of the present application, the temperature of the reducing gas at the outlet of the reducing gas heating furnace 10 is 900-1000°C, and the volume fraction of hydrogen in the reducing gas is 50%-100%, which not only ensures that the reducing gas and the iron ore can fully react and provide sufficient heat, but also reduces the carbon emission of the metallurgical furnace.

[0026] As a preferred embodiment of the present application, the absorption liquid used in the top gas carbon dioxide absorption tower 14 is a mass fraction of 30%-35% ethanolamine (MEA) solution, the carbon dioxide loading rate is 0.2-0.3 (mol CO2 / mol MEA), and the working pressure of the absorption tower is 1-2 bar, which can not only fully absorb the carbon dioxide in the top gas, but also reduce the energy consumption of the desorption tower.

[0027] As a preferred embodiment of the present application, Cu / ZnO / Al2O3 is used as the catalyst in the methanol synthesis reactor 19 and the methanol cracking reactor 22, and the reaction temperature is 200-300 °C, which ensures that the reactants have a high conversion rate during the methanol synthesis and cracking reaction process, and at the same time ensures that the catalyst has a high activity; wherein the working pressure of the methanol synthesis reactor 19 is 50-110 bar, and the working pressure of the methanol cracking reactor 22 is 1-10 bar, which can promote the conversion of the reactants during the methanol synthesis and cracking process.

[0028] As shown in FIG. 1, a method for operating a solar-driven green hydrogen production-methanol conversion coupled hydrogen metallurgy integrated system is as follows: 1) When the solar energy is sufficient and the hydrogen production amount of the alkaline electrolytic cell 4 is greater than the hydrogen demand of the gas-based direct reduction shaft furnace 11, part of the hydrogen produced by the alkaline electrolytic cell 4 is combined with the carbon dioxide in the carbon dioxide storage tank 16, preheated by the reverse water-gas shift heat exchanger 6, and then enters the reverse water-gas shift reactor 7 to react, generating carbon monoxide and water and forming hydrogen-rich reducing gas, which is then combined with the circulating top gas output by the carbon dioxide absorption tower 14 at the second outlet to meet the reducing gas demand of the gas-based direct reduction shaft furnace 11; the other part of the excess hydrogen is combined with the carbon dioxide desorbed by the carbon dioxide desorption tower 15, compressed by the methanol synthesis raw material compressor 18, and then enters the methanol synthesis reactor 19 to react and synthesize methanol; 2) When the solar energy is sufficient and the hydrogen production amount of the alkaline electrolytic cell 4 is equal to the hydrogen demand of the gas-based direct reduction shaft furnace 11, the hydrogen produced by the alkaline electrolytic cell 4 all enters the reverse water-gas shift reactor 7 to participate in the reaction to generate hydrogen-rich reducing gas, and no hydrogen and carbon dioxide enter the methanol synthesis reactor 19, so no methanol is produced; 3) When the solar energy is insufficient, and the hydrogen production of the alkaline electrolytic cell 4 is less than the hydrogen demand of the gas-based direct reduction shaft furnace 11, the hydrogen produced by the alkaline electrolytic cell 4 is all supplied to the gas-based direct reduction shaft furnace 11; at the same time, the methanol stored in the methanol storage tank 21 enters the methanol cracking reactor 22, and cracking produces hydrogen and carbon monoxide, which is combined with the reducing gas at the outlet of the reducing gas drier 8 in the reducing gas combiner 9 to form reducing gas, which is heated and then enters the gas-based direct reduction shaft furnace 11; 4) When there is no solar energy at night, the alkaline electrolytic cell 4 stops working and no hydrogen is generated, and the reducing gas required by the gas-based direct reduction shaft furnace 11 is all provided by the methanol cracking reactor 22, and the methanol stored in the methanol storage tank 21 enters the methanol cracking reactor 22, and cracking produces hydrogen and carbon monoxide.

[0029] The application provides a solar-driven integrated system and operation method for green hydrogen preparation-methanol conversion coupled hydrogen metallurgy, wherein green hydrogen is prepared by photovoltaic power generation and water electrolysis, part of the green hydrogen is reacted with carbon dioxide to generate hydrogen-rich reducing gas through a reverse water-gas shift reaction, iron ore is reduced in a gas-based direct reduction shaft furnace to generate direct reduced iron, and the top gas after the reaction is treated by a top gas treatment system and then recycled to the metallurgical furnace; a methanol conversion module is integrated in the system: when the solar energy is sufficient, the excess green hydrogen is reacted with captured carbon dioxide to synthesize methanol, which not only converts unstable solar energy into stable chemical energy storage, but also realizes resource utilization of carbon dioxide; when the solar energy is insufficient, the methanol can be cracked to generate hydrogen and carbon monoxide as reducing gas supplement to meet the stable demand of the metallurgical furnace for reducing gas. The application realizes organic integration of green hydrogen preparation-methanol conversion-metallurgical production, greatly reduces carbon emissions in the metallurgical process, converts unstable renewable energy into stable chemical energy, and effectively guarantees safe and stable operation of the metallurgical system.

Claims

1. An integrated system for solar-driven green hydrogen production and methanol conversion coupled with hydrogen metallurgy, characterized in that: This includes photovoltaic power generation systems, water electrolysis hydrogen production systems, reducing gas preparation systems, hydrogen metallurgy systems, furnace top gas treatment systems, and methanol conversion systems; The photovoltaic power generation system includes a solar cell (2) and a DC / DC converter (3); the solar cell (2) absorbs solar radiation energy (1) and converts solar energy into electrical energy output, and the DC / DC converter (3) converts the electrical energy output by the solar cell (2) into stable DC power of different voltage levels to power the subsequent system; The water electrolysis hydrogen production system includes an alkaline electrolyzer; the power input terminal of the alkaline electrolyzer (4) is connected to the output terminal of the DC / DC converter (3) to generate hydrogen and oxygen through water electrolysis; the hydrogen outlet of the alkaline electrolyzer (4) is divided into two paths, one path is connected to the reducing gas preparation system to transport green hydrogen, and the other path enters the methanol conversion system to provide raw materials for methanol synthesis; the oxygen outlet of the alkaline electrolyzer (4) is connected to the reducing gas preparation system to assist the reducing gas preparation process; The reducing gas preparation system includes a hydrogen-carbon dioxide manifold (5), a reverse water-gas shift heat exchanger (6), a reverse water-gas shift reactor (7), a reducing gas dehydrator (8), a reducing gas manifold (9), and a reducing gas heater (10); the oxygen outlet of the alkaline electrolyzer (4) is connected to the oxygen inlet of the reducing gas heater (10); the hydrogen outlet of the alkaline electrolyzer (4) and the outlet of the carbon dioxide storage tank (16) are respectively connected to the two feed ports of the hydrogen-carbon dioxide manifold (5), and the hydrogen... The outlet of the gas-carbon dioxide manifold (5) is connected to the cold side inlet of the reverse water-gas shift heat exchanger (6), and the cold side outlet of the reverse water-gas shift heat exchanger (6) is connected to the inlet of the reverse water-gas shift reactor (7); the outlet of the reverse water-gas shift reactor (7) is connected to the hot side inlet of the reverse water-gas shift heat exchanger (6), the hot side outlet of the reverse water-gas shift heat exchanger (6) is connected to the inlet of the reducing gas dehydrator (8), and the outlet of the reducing gas dehydrator (8) is connected to the bottom inlet of the reducing gas manifold (9). The outlet of the reducing gas manifold (9) is connected to the heating side inlet of the reducing gas heater (10), and the heating side outlet of the reducing gas heater (10) outputs high-temperature hydrogen-rich reducing gas for use in the hydrogen metallurgical system. The hydrogen metallurgical system includes a gas-based direct reduction shaft furnace (11); the high-temperature hydrogen-rich reducing gas from the heating side outlet of the reducing gas heating furnace (10) enters from the bottom inlet of the gas-based direct reduction shaft furnace (11), reacts with iron ore to generate direct reduced iron, and the gas after the reaction leaves from the top outlet of the gas-based direct reduction shaft furnace (11). The furnace top gas treatment system includes a furnace top gas cooler (12), a furnace top gas dehydrator (13), a furnace top gas carbon dioxide absorption tower (14), a carbon dioxide desorption tower (15), and a carbon dioxide storage tank (16). The furnace top outlet of the gas-based direct reduction vertical furnace (11) is connected to the inlet of the furnace top gas cooler (12), the outlet of the furnace top gas cooler (12) is connected to the inlet of the furnace top gas dehydrator (13), and the outlet of the furnace top gas dehydrator (13) is connected to the inlet of the furnace top gas carbon dioxide absorption tower (14). The outlet of the carbon dioxide absorption tower (14) is divided into three paths: the first path is connected to the inlet of the carbon dioxide desorption tower (15), the second path is connected to the top inlet of the reducing gas manifold (9), and the third path is connected to the combustion side inlet of the reducing gas heater (10). The outlet of the carbon dioxide desorption tower (15) is divided into two paths: one path is connected to the carbon dioxide storage tank (16), and the other path enters the methanol conversion system. The methanol conversion system includes a methanol synthesis feedstock manifold (17), a methanol synthesis feedstock compressor (18), a methanol synthesis reactor (19), a methanol distillation column (20), a methanol storage tank (21), and a methanol cracking reactor (22). The methanol synthesis feedstock manifold (17) has two inlets: one connected to the outlet of the carbon dioxide stripping column (15), and the other connected to the hydrogen outlet of the alkaline electrolyzer (4). The outlet of the methanol synthesis feedstock manifold (17) is connected to the inlet of the methanol synthesis feedstock compressor (18). The outlet of the feed compressor (18) is connected to the inlet of the methanol synthesis reactor (19), the outlet of the methanol synthesis reactor (19) is connected to the inlet of the methanol distillation column (20), and the outlet of the methanol distillation column (20) is connected to the methanol storage tank (21). When the output power of the photovoltaic power generation system is insufficient and the green hydrogen supply of the alkaline electrolyzer (4) cannot meet the hydrogen metallurgical demand, the outlet of the methanol storage tank (21) is connected to the inlet of the methanol cracking reactor (22), and the reducing gas from the outlet of the methanol cracking reactor (22) enters the intermediate inlet of the reducing gas manifold (9).

2. The integrated system for solar-driven green hydrogen production and methanol conversion coupled with hydrogen metallurgy according to claim 1, characterized in that: The photovoltaic power generation system and the water electrolysis hydrogen production system are indirectly coupled and connected by a DC / DC converter (3).

3. The integrated system for solar-driven green hydrogen production and methanol conversion coupled with hydrogen metallurgy according to claim 1, characterized in that: The water electrolysis hydrogen production system adopts alkaline water electrolysis hydrogen production technology, and the working temperature of the alkaline electrolyzer (4) is 70~80 °C.

4. The integrated system for solar-driven green hydrogen production and methanol conversion coupled with hydrogen metallurgy according to claim 1, characterized in that: The hydrogen produced by the alkaline electrolytic cell (4) is used partly as reducing gas for reducing iron ore and partly as raw material for synthesizing methanol. The oxygen produced is introduced into the combustion side of the reducing gas heating furnace (10) to provide combustion-supporting gas for the reducing gas heating process.

5. The integrated system for solar-driven green hydrogen production and methanol conversion coupled with hydrogen metallurgy according to claim 1, characterized in that: The reverse water-gas shift heat exchanger (6) is a shell-and-tube heat exchanger, with hot fluid flowing through the shell side and cold fluid flowing through the tube side. The temperature difference between the hot fluid outlet and the cold fluid inlet is 25 °C.

6. The integrated system for solar-driven green hydrogen production and methanol conversion coupled with hydrogen metallurgy according to claim 1, characterized in that: The reducing gas dehydrator (8) and the furnace top gas dehydrator (13) both adopt flash dehydration tanks with a working temperature of 25~30 °C and a working pressure of 1~3 bar.

7. The integrated system for solar-driven green hydrogen production and methanol conversion coupled with hydrogen metallurgy according to claim 1, characterized in that: The temperature of the reducing gas at the outlet of the reducing gas heater (10) is 900~1000 °C, and the volume fraction of hydrogen in the reducing gas is 50%~100%.

8. The integrated system for solar-driven green hydrogen production and methanol conversion coupled with hydrogen metallurgy according to claim 1, characterized in that: The absorbent used in the furnace top gas carbon dioxide absorption tower (14) is an ethanolamine MEA solution with a mass fraction of 30%~35%, a carbon dioxide loading rate of 0.2~0.3 (mol CO2 / mol MEA), and an operating pressure of 1~2 bar.

9. The integrated system for solar-driven green hydrogen production and methanol conversion coupled with hydrogen metallurgy according to claim 1, characterized in that: Both the methanol synthesis reactor (19) and the methanol cracking reactor (22) use Cu / ZnO / Al2O3 as catalysts, and the reaction temperature is 200~300 °C; the working pressure of the methanol synthesis reactor (19) is 50~110 bar, and the working pressure of the methanol cracking reactor (22) is 1~10 bar.

10. The method for operating an integrated system for solar-driven green hydrogen production and methanol conversion coupled with hydrogen metallurgy as described in any one of claims 1 to 9, characterized in that: 1) When solar energy is sufficient and the hydrogen production of the alkaline electrolyzer (4) is greater than the hydrogen demand of the gas-based direct reduction shaft furnace (11), part of the hydrogen produced by the alkaline electrolyzer (4) is combined with the carbon dioxide in the carbon dioxide storage tank (16), and after being preheated by the reverse water-gas shift heat exchanger (6), it enters the reverse water-gas shift reactor (7) to react, generating carbon monoxide and water and forming hydrogen-rich reducing gas. Then, it is combined with the circulating furnace top gas output from the second path of the carbon dioxide absorption tower (14) at the reducing gas manifold (9) to meet the reducing gas demand of the gas-based direct reduction shaft furnace (11); another part of the excess hydrogen is combined with the carbon dioxide desorbed by the carbon dioxide desorption tower (15), and after being compressed by the methanol synthesis raw material compressor (18), it enters the methanol synthesis reactor (19) to react and synthesize methanol. 2) When the solar energy is sufficient and the hydrogen production of the alkaline electrolyzer (4) is equal to the hydrogen demand of the gas-based direct reduction vertical furnace (11), all the hydrogen produced by the alkaline electrolyzer (4) enters the reverse water-gas shift reactor (7) to participate in the reaction to generate hydrogen-rich reducing gas. No hydrogen or carbon dioxide enters the methanol synthesis reactor (19), and no methanol is produced. 3) When solar energy is insufficient and the hydrogen production of the alkaline electrolyzer (4) is less than the hydrogen demand of the gas-based direct reduction shaft furnace (11), all the hydrogen produced by the alkaline electrolyzer (4) is supplied to the gas-based direct reduction shaft furnace (11); at the same time, the methanol stored in the methanol storage tank (21) enters the methanol cracking reactor (22), cracks to produce hydrogen and carbon monoxide, and merges with the reducing gas at the outlet of the reducing gas dehydrator (8) in the reducing gas manifold (9) to form reducing gas, which enters the gas-based direct reduction shaft furnace (11) after being heated. 4) When there is no solar energy at night, the alkaline electrolyzer (4) stops working and no hydrogen is generated. All the reducing gas required by the gas-based direct reduction shaft furnace (11) is provided by the methanol cracking reactor (22). The methanol stored in the methanol storage tank (21) enters the methanol cracking reactor (22) and cracks to produce hydrogen and carbon monoxide.

Images