System and method for producing sulfur from hydrogen-reduced desulfurized gypsum

Abstract

The application discloses a system and method for preparing sulfur from hydrogen-reduced desulfurization gypsum, and relates to the technical field of sulfur resource recovery. The system comprises an electrolytic water unit, a gypsum pretreatment and reduction unit, a hydrolysis and oxidation unit and a sulfur preparation unit. The electrolytic water unit is used for preparing hydrogen and oxygen. The gypsum pretreatment and reduction unit, the hydrolysis and oxidation unit and the sulfur preparation unit all take electric heating as the main heat source and take high-temperature steam generated by hydrogen and oxygen combustion as the auxiliary heat source. The reduction process of the gypsum pretreatment and reduction unit takes hydrogen as the reducing agent. The oxidation process of the hydrolysis and oxidation unit takes oxygen as the oxidizing agent. The application only needs to consume electricity and water, takes electric heating or hydrogen-oxygen combustion to generate heat as the main and auxiliary heat sources, and takes hydrogen and oxygen as the reducing agent and the oxidizing agent, so that high-quality sulfur and calcium-based products are obtained, and the whole process realizes zero pollutant emission and zero carbon emission.

Description

Technical Field

[0001] This invention relates to the field of sulfur resource recovery technology, specifically to a system and method for producing sulfur from hydrogen-reduced desulfurized gypsum. Background Technology

[0002] The wet flue gas desulfurization process generates a large amount of desulfurization gypsum, which is usually composed mainly of calcium sulfate dihydrate. If desulfurization gypsum is stored for a long time, it will not only occupy land resources, but may also bring secondary environmental risks due to the migration of soluble salts, acidic components or impurities. Therefore, it is necessary to utilize the calcium and sulfur elements in it as resources.

[0003] To achieve sulfur resource recovery, traditional gypsum-based sulfur production or gypsum reduction technologies often employ carbon-containing reducing agents such as pulverized coal, coke, coal gas, natural gas, or carbon monoxide, and typically require external fuel or electric heating to maintain the high-temperature reaction. However, this approach has the following drawbacks: on the one hand, it involves carbon dioxide emissions or the pressure of treating carbon-containing tail gas; on the other hand, sulfur resources often need to undergo multiple intermediate conversions, such as sulfur dioxide, calcium sulfide, and hydrogen sulfide, before sulfur can be obtained.

[0004] To address the carbon emissions associated with carbothermic reduction, the industry has begun exploring hydrogen reduction routes that replace carbon-containing reducing agents. Existing hydrogen reduction processes typically rely on coal-to-hydrogen or natural gas reforming for hydrogen supply, and usually employ electric heating to maintain the high-temperature environment of the reduction furnace at 900–1000°C. However, this presents several problems: First, both coal-to-hydrogen and natural gas reforming are inherently high-carbon emission processes, contradicting the green principles of gypsum resource utilization. Second, electric heating schemes are extremely energy-intensive; direct grid connection would be costly and difficult to adapt to fluctuating renewable energy sources such as wind and solar power curtailment. Furthermore, relying solely on electric heating results in slow reactor temperature response, leading to lag in temperature control when hydrogen flow fluctuates, impacting the reduction conversion rate of calcium sulfate. In addition, existing processes often limit the utilization of calcium to the production of low-value-added building gypsum or disposal as waste, failing to achieve calcium recovery and utilization.

[0005] The aforementioned existing hydrogen reduction processes typically rely on coal-to-hydrogen or natural gas reforming for hydrogen supply, but do not utilize water electrolysis. This is because water electrolysis is energy-intensive; if operated solely for reducing agent production, the high electricity costs would make sulfur production costs far exceed market prices, lacking economic competitiveness. Furthermore, while combining water electrolysis with sulfur production allows the generated hydrogen to be used as a reducing agent, the byproduct oxygen lacks effective utilization in a pure hydrogen reduction process. Direct discharge would be a waste of resources, while mandatory use would require additional complex facilities. Moreover, the start-stop response characteristics of water electrolysis are difficult to match with the continuous and stable operation requirements of gypsum reduction and the Claus reaction, easily causing production fluctuations. Therefore, applying water electrolysis to sulfur production faces economic barriers, system complexity, and poor process compatibility. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a system and method for producing sulfur from hydrogen-reduced desulfurized gypsum. It only requires electricity and water, using electric heating or heat generated by hydrogen-oxygen combustion as the main / auxiliary heat source, and hydrogen and oxygen as the reducing agent and oxidizing agent, respectively, to obtain high-quality sulfur and calcium-based products. The entire process achieves zero pollutant emissions and zero carbon emissions.

[0007] The technical solution of the present invention is as follows: In a first aspect of the present invention, a system for producing sulfur from hydrogen-reduced desulfurized gypsum is provided, comprising an electrolysis water unit, a gypsum pretreatment and reduction unit, a hydrolysis and oxidation unit, and a sulfur production unit. The water electrolysis unit is used to produce hydrogen and oxygen; The gypsum pretreatment and reduction unit is used to dry and reduce gypsum, wherein hydrogen is used as a reducing agent in the reduction process; The hydrolysis and oxidation unit is used to hydrolyze and oxidize the reduction products, wherein oxygen is used as the oxidant in the oxidation process; The sulfur production unit includes a Claus reactor for performing a Claus reaction on some hydrolysis products and oxidation products to produce sulfur. The drying and reduction processes of the gypsum pretreatment and reduction unit, the hydrolysis and oxidation processes of the hydrolysis and oxidation unit, and the Claus reaction process all use electric heating as the main heat source and high-temperature steam generated by the combustion of hydrogen and oxygen as the auxiliary heat source.

[0008] In some embodiments of the present invention, the water electrolysis unit includes a water electrolysis device, wherein the hydrogen outlet of the water electrolysis device is connected to a hydrogen storage tank, the oxygen outlet is connected to an oxygen storage tank, both the hydrogen storage tank and the oxygen storage tank are connected to a hydrogen-oxygen burner, and the steam outlet of the hydrogen-oxygen burner is connected to a steam distributor.

[0009] In some embodiments of the present invention, the gypsum pretreatment and reduction unit includes a heat exchange dryer and a reduction reactor connected in sequence. The reduction reactor is connected to the hydrogen storage tank, and the reduction product outlet of the reduction reactor is connected to the hydrolysis and oxidation unit. Both the heat exchange dryer and the reduction reactor are provided with a high-temperature steam indirect heat exchange structure and an electric heating component. The high-temperature steam indirect heat exchange structure is connected to a steam distributor.

[0010] In some embodiments of the present invention, the hydrolysis and oxidation unit includes a hydrolysis reactor and an oxidation reactor. The hydrolysis product outlet of the hydrolysis reactor is connected to the oxidation reactor and the Claus reactor, respectively. The oxidation product outlet of the oxidation reactor is connected to the Claus reactor. The hydrolysis reactor, the oxidation reactor, and the Claus reactor are all equipped with a high-temperature steam indirect heat exchange structure and an electric heating component. The high-temperature steam indirect heat exchange structure is connected to a steam distributor.

[0011] In some embodiments of the present invention, the calcium-based product outlet of the hydrolysis reactor is connected to a calcining furnace, the carbon dioxide outlet of the calcining furnace is connected to the hydrolysis reactor, and the calcining furnace is provided with a high-temperature steam indirect heat exchange structure and an electric heating component, the high-temperature steam indirect heat exchange structure being connected to a steam distributor.

[0012] In some embodiments of the present invention, the electricity for the water electrolysis unit and the electric heating is derived from electricity generated by wind and solar power curtailment, off-peak electricity, or renewable energy sources.

[0013] In a second aspect of the invention, a method for producing sulfur from hydrogen-reduced desulfurized gypsum is provided, which is implemented using the system described in the first aspect, comprising: Electricity generated from abandoned wind and solar power, off-peak electricity, or renewable energy sources is used to electrolyze water to produce high-purity hydrogen and high-purity oxygen, which are then stored separately. Electric heating is used as the main heat source to directly heat each reaction device; or some hydrogen and oxygen are burned to generate high-temperature steam, and the high-temperature steam flows through the heat exchange structure outside each reaction device for non-contact indirect heat exchange. After drying and sieving, the desulfurized gypsum is reduced with hydrogen at high temperature to produce calcium sulfide. Calcium sulfide is mixed with water and carbon dioxide to undergo hydrolysis and carbonation reactions, producing calcium carbonate and hydrogen sulfide gas. Hydrogen sulfide is divided into two parts. The first part is oxidized to produce sulfur dioxide. The second part is mixed with sulfur dioxide in a specific ratio and then subjected to a Claus reaction under the action of a catalyst to produce sulfur, which is then condensed and recovered.

[0014] In some embodiments of the present invention, the temperature of the reduction reaction is 900–1000°C and the reaction time is 45–90 min; the temperature of the hydrolysis and carbonation reaction is 50–80°C and the reaction time is 60–120 min; the first stage temperature of the Claus reaction is 300–350°C and the second stage temperature is 220–250°C.

[0015] In some embodiments of the present invention, the calcium carbonate is calcined to produce carbon dioxide, which participates in the hydrolysis and carbonation reactions; the calcination temperature is 700-850°C, the pressure is -0.01--0.05 MPa, and the calcination residence time is 30-60 min.

[0016] In some embodiments of the present invention, the hydrogen sulfide is divided into a first portion of 1 / 3 and a second portion of 2 / 3 according to the volume flow rate, and the second portion of hydrogen sulfide is subjected to a Claus reaction with sulfur dioxide at a volume ratio of 2:1.

[0017] One or more technical solutions of the present invention have the following beneficial effects: (1) The system provided by this invention only requires electricity and water to produce hydrogen and oxygen through water electrolysis, which are used as reducing agents and oxidizing agents, respectively. It is coupled with hydrogen-oxygen combustion as an auxiliary heat source to directionally convert desulfurized gypsum into high-value sulfur and calcium-based products. Compared with the gypsum resource utilization route that uses carbon-containing reducing agents, this invention does not introduce carbon-containing reducing agents such as coal powder, coke, coal gas or carbon monoxide. Compared with the route that uses hydrogen-oxygen combustion as the main heat source, this invention uses electric heating as the main heat source for drying, high-temperature reduction, hydrolysis, hydrogen sulfide oxidation, Claus reaction and optional calcination, which can reduce the efficiency loss and hydrogen consumption caused by first converting electrical energy into hydrogen and then burning it for heating.

[0018] (2) In this invention, the oxygen generated from water electrolysis is not only used as an oxidant for the partial oxidation of hydrogen sulfide to sulfur dioxide, but more importantly, the remaining hydrogen and oxygen are burned together in a hydrogen-oxygen burner to produce high-quality high-temperature steam at 1000-1100°C as an auxiliary heat source. This setup achieves hydrogen-oxygen co-processing, greatly simplifies the system process, and reduces equipment investment and floor space. By utilizing the energy of the by-product oxygen, waste is turned into treasure, significantly improving the system's energy density and self-sufficiency.

[0019] (3) The dual-layer heating architecture proposed in this invention, consisting of electric heating as the main heat source and high-temperature steam as an auxiliary indirect heat source, balances the contradiction between energy consumption and reaction efficiency. Electric heating is used as the main heat source, ensuring the stability and controllability of the base temperature; at the same time, the high-temperature steam generated by hydrogen-oxygen combustion is used for indirect heat exchange through non-contact structures such as jackets and coils, strictly prohibiting steam from directly entering the reactant or gas space. It utilizes the advantages of rapid heating and supplemental heating from hydrogen-oxygen combustion, while completely avoiding additional water vapor that could increase the partial pressure of the products, dilute the reaction gas, or reduce the driving force of the reaction. The entire process achieves zero pollutant emissions and zero carbon emissions.

[0020] (4) This invention further calcines the calcium carbonate produced in the hydrolysis section into calcium oxide and high-purity carbon dioxide by setting up a selectively accessible calcium carbonate calcination and carbon dioxide circulation unit. Among them, the carbon dioxide is returned to the hydrolysis reactor to participate in the reaction, forming an internal circulation of carbon elements and reducing the cost of purchasing CO2; the calcium oxide can be returned to the flue gas desulfurization process as an absorbent for reuse, or sold directly as a high value-added product. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall process of producing sulfur from hydrogen-reduced desulfurized gypsum according to the present invention.

[0022] In the diagram: 1. Water electrolysis device; 2. Oxygen storage tank; 3. Hydrogen storage tank; 4. Hydrogen-oxygen burner; 5. Steam distributor; 6. Heat exchange dryer; 7. Reduction reactor; 8. Hydrolysis reactor; 9. Oxidation reactor; 10. Claus reactor; 11. Calcination furnace. Detailed Implementation

[0023] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is intended to include the plural form as well. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] Example 1 In a typical embodiment of the present invention, a system for producing sulfur from hydrogen-reduced desulfurized gypsum is provided, such as... Figure 1 As shown, it includes a water electrolysis unit, a gypsum pretreatment and reduction unit, a hydrolysis and oxidation unit, and a sulfur production unit; The water electrolysis unit is used to produce hydrogen and oxygen; The gypsum pretreatment and reduction unit is used to dry and reduce gypsum, wherein hydrogen is used as a reducing agent in the reduction process; The hydrolysis and oxidation unit is used to hydrolyze and oxidize the reduction products, wherein oxygen is used as the oxidant in the oxidation process; The sulfur production unit includes a Claus reactor 10, which is used to perform a Claus reaction on some hydrolysis products and oxidation products to produce sulfur. The drying and reduction processes of the gypsum pretreatment and reduction unit, the hydrolysis and oxidation processes of the hydrolysis and oxidation unit, and the Claus reaction process all use electric heating as the main heat source and high-temperature steam generated by the combustion of hydrogen and oxygen as the auxiliary heat source.

[0026] In this embodiment, the water electrolysis unit includes a water electrolysis device 1. The hydrogen outlet of the water electrolysis device 1 is connected to a hydrogen storage tank 3, and the oxygen outlet is connected to an oxygen storage tank 2. Both the hydrogen storage tank 3 and the oxygen storage tank 2 are connected to a hydrogen-oxygen burner 4, and the steam outlet of the hydrogen-oxygen burner 4 is connected to a steam distributor 5. The water electrolysis device 1 electrolyzes water at 25–50°C and 0.5–3.0 MPa to obtain hydrogen and oxygen, respectively. The generated hydrogen and oxygen are stored in the hydrogen storage tank 3 and the oxygen storage tank 2, respectively. The electricity used by the water electrolysis device 1 comes from wind and solar power curtailment, off-peak electricity, or electricity generated from renewable energy sources. The hydrogen storage tank 3 and the oxygen storage tank 2 ensure the stability of the entire system operation even when the power output fluctuates. The hydrogen-oxygen burner 4 receives hydrogen and oxygen in a volume ratio of 2:1 and burns them to produce high-temperature steam. The steam distributor 5 can be a steam distribution cylinder, which is used to receive the high-temperature steam produced by the hydrogen-oxygen burner 4. The steam distributor 5 distributes the steam evenly and stably to the gypsum pretreatment and reduction unit, the hydrolysis and oxidation unit and the sulfur production unit through an internal pressure equalization structure.

[0027] Furthermore, the gypsum pretreatment and reduction unit includes a heat exchange dryer 6 and a reduction reactor 7 connected in sequence. The reduction product outlet of the reduction reactor 7 is connected to the hydrolysis and oxidation unit. Both the heat exchange dryer 6 and the reduction reactor 7 are equipped with a high-temperature steam indirect heat exchange structure and an electric heating component. The high-temperature steam indirect heat exchange structure is connected to the steam distributor 5. The heat exchange dryer 6 is connected to a feeder, which transports gypsum into the dryer for heat exchange. The dryer 6 uses electric heating as the main heat source and high-temperature steam as an auxiliary heat source. The high-temperature steam indirect heat exchange structure within the dryer 6 ensures that the high-temperature steam does not directly contact the gypsum, thus avoiding the introduction of additional water vapor into the drying space and reducing the dehydration driving force. The reduction reactor 7 is connected to a hydrogen storage tank 3. The desulfurized gypsum undergoes a reduction reaction using hydrogen supplied by the tank 3 as a reducing agent. The reduction reactor 7 uses electric heating as the main heat source and high-temperature steam as an auxiliary heat source. The specific reduction reactor 7 can be a fluidized bed reduction reactor, in which desulfurized gypsum reacts with hydrogen at 900-1000℃ to generate calcium sulfide.

[0028] In this embodiment, the hydrolysis and oxidation unit includes a hydrolysis reactor 8 and an oxidation reactor 9. The hydrolysis product outlet of the hydrolysis reactor 8 is connected to the oxidation reactor 9 and the Claus reactor 10, respectively. The oxidation product outlet of the oxidation reactor 9 is connected to the Claus reactor 10. The hydrolysis reactor 8, the oxidation reactor 9 and the Claus reactor 10 are all equipped with a high-temperature steam indirect heat exchange structure and an electric heating component. The high-temperature steam indirect heat exchange structure is connected to the steam distributor 5.

[0029] Among them, the hydrolysis reactor 8 adopts a hydrolysis reactor, which is equipped with a calcium sulfide inlet, a water inlet and a carbon dioxide inlet. The hydrolysis reactor receives calcium sulfide, water and carbon dioxide, and converts calcium into calcium carbonate solid and sulfur into hydrogen sulfide gas. The hydrolysis reactor uses electric heating as the main heat source and high-temperature steam as the auxiliary heat source. The high-temperature steam is used to assist in regulating the hydrolysis and carbonation temperatures, and the heat carrier in the high-temperature steam indirect heat exchange structure does not enter the hydrolysis reactor as reaction water.

[0030] A gas-liquid separator and a gas splitter are sequentially arranged between the hydrolysis reactor 8 and the oxidation reactor 9. The gas-liquid separator is used to dehydrate the hydrogen sulfide gas, and the gas splitter divides the hydrogen sulfide gas into a first part and a second part. The first part of hydrogen sulfide reacts with oxygen in the oxidation reactor 9 to generate sulfur dioxide. The oxidation reactor 9 can be a high-temperature oxidation reactor. The high-temperature oxidation reactor uses electric heating as the main heat source and high-temperature steam as the auxiliary heat source. The high-temperature steam indirectly heats the high-temperature oxidation reactor and does not directly contact the first part of hydrogen sulfide and oxygen.

[0031] Furthermore, the calcium-based product outlet of the hydrolysis reactor 8 is connected to the calcining furnace 11, and the carbon dioxide outlet of the calcining furnace 11 is connected to the hydrolysis reactor 8. A high-temperature steam indirect heat exchange structure and electric heating components are provided, and the high-temperature steam indirect heat exchange structure is connected to the steam distributor 5. The calcining furnace 11 is an optional unit and can be a rotary kiln, vertical furnace, or fluidized bed calcining furnace with resistance heating, induction heating, microwave heating, or electromagnetic heating. When the calcining furnace 11 is in operation, it uses electric heating as the main heat source and high-temperature steam as the auxiliary heat source. The carbon dioxide generated from the calcination of calcium carbonate is returned to the hydrolysis reactor 8 through the carbon dioxide inlet. When the calcining furnace 11 is not in operation, the calcium carbonate generated by the hydrolysis reactor 8 is output as a calcium-based product or returned to the flue gas desulfurization process.

[0032] In this embodiment, the power for the electric heating components comes from wind and solar power curtailment, off-peak electricity, or renewable energy. When the power fluctuates, high-temperature steam is used for auxiliary heating, which effectively compensates for the heat gap caused by insufficient or interrupted power supply, maintains the thermal balance required by each reaction unit, and ensures that the entire process system can still operate continuously and stably under unstable power input conditions.

[0033] In this embodiment, the electric heating unit serves as the main heat source, including an electric heating power supply bus, an electric heating controller, and electric heating components respectively installed on the heat exchange dryer 6, reduction reactor 7, hydrolysis reactor 8, oxidation reactor 9, Claus reactor 10, and calcining furnace 11. These electric heating components act as the main heat source for the heat exchange dryer 6, reduction reactor 7, hydrolysis reactor 8, oxidation reactor 9, Claus reactor 10, and calcining furnace 11. High-temperature steam generated by the combustion of hydrogen and oxygen serves as an auxiliary heat source. The auxiliary heat source unit includes a hydrogen-oxygen burner 4, a steam distributor 5, and a high-temperature steam indirect heat exchange structure installed on the heat exchange dryer 6, reduction reactor 7, hydrolysis reactor 8, oxidation reactor 9, Claus reactor 10, and calcining furnace 11. The high-temperature steam indirect heat exchange structure can be a jacket, coil, tube, or external heat exchanger. The high-temperature steam does not directly enter the reactant or reaction gas space. The high-temperature steam is only used as an auxiliary heat source for start-up reheating, waste heat utilization, or temperature regulation.

[0034] The working principle of the hydrogen reduction desulfurization gypsum sulfur production system provided in this embodiment is as follows: The system is powered by electricity, which is output in two ways: one to the water electrolysis unit 1 and the other to the electric heating power supply bus. When the water electrolysis unit 1 operates, it produces hydrogen and oxygen. The hydrogen is delivered to the hydrogen storage tank 3, and the oxygen to the oxygen storage tank 2. Both the hydrogen and oxygen storage tanks 3 and 2 release gases, with a portion of the hydrogen and oxygen being proportionally delivered to the hydrogen-oxygen burner 4. The burner 4 ignites and generates high-temperature steam, which enters the steam distributor 5. The steam distributor 5 is connected via pipelines to the inlets of the high-temperature steam indirect heat exchange structures of the heat exchange dryer 6, reduction reactor 7, hydrolysis reactor 8, oxidation reactor 9, Claus reactor 10, and optional calcining furnace 11. The high-temperature steam is discharged after heat exchange within these structures. The electric heating power supply bus is connected to the electric heating components inside the heat exchange dryer 6, reduction reactor 7, hydrolysis reactor 8, oxidation reactor 9, Claus reactor 10, and optional calcining furnace 11, providing them with electrical energy.

[0035] The desulfurized gypsum is fed into heat exchange dryer 6. Heat exchange dryer 6 uses internal electric heating components and a high-temperature steam indirect heat exchange structure to remove moisture from the gypsum. The dried gypsum is discharged and sent to a screening machine. The screening machine filters the gypsum particles to a set particle size and then sends them to reduction reactor 7. At the same time, hydrogen from hydrogen storage tank 3 is transported to reduction reactor 7. The hydrogen and gypsum come into contact in the furnace and undergo a reduction reaction to produce calcium sulfide. The calcium sulfide is discharged and sent to hydrolysis reactor 8.

[0036] Hydrolysis reactor 8 receives solid calcium sulfide, along with externally supplied process water and carbon dioxide gas. Calcium sulfide, water, and carbon dioxide mix within reactor 8, generating a solid-liquid mixture containing calcium carbonate and hydrogen sulfide gas. The solid-liquid mixture is discharged, and the hydrogen sulfide gas is discharged. The hydrogen sulfide gas is then transported to a gas splitter, which divides it into two parts. The first part is transported to oxidation reactor 9, and the second part is transported to Claus reactor 10. Oxidation reactor 9 simultaneously receives oxygen from oxygen storage tank 2. The first part of hydrogen sulfide reacts with oxygen within oxidation reactor 9 to generate sulfur dioxide. This sulfur dioxide gas is discharged and mixed with the second stream of hydrogen sulfide from the splitter, forming a mixed gas that is then transported to Claus reactor 10. Claus reactor 10 contains a catalyst bed. The mixed gas flows through the catalyst bed and reacts to generate a gaseous mixture containing sulfur. This mixture is then transported to a sulfur condenser. The sulfur condenser condenses the sulfur in the gaseous phase into a liquid or solid state, completing sulfur recovery.

[0037] The solid-liquid mixture containing calcium carbonate discharged from hydrolysis reactor 8 is transported to a solid-liquid separation device, where it is separated to obtain calcium carbonate solid filter cake and process wastewater. The calcium carbonate filter cake can be selectively transported to calcination furnace 11, which simultaneously receives high-temperature steam from steam distributor 5. Electric heating elements and a high-temperature steam indirect heat exchange structure heat the filter cake, causing it to decompose into calcium oxide solid and carbon dioxide gas. The calcium oxide solid is discharged and collected, while the carbon dioxide gas is purified and returned to hydrolysis reactor 8 for recycling. If calcination furnace 11 is not used, the calcium carbonate solid filter cake is directly discharged as a product.

[0038] When there are power fluctuations caused by wind and solar power curtailment, off-peak electricity, or renewable energy sources, high-temperature steam is used for auxiliary heating to effectively compensate for the heat gap caused by insufficient or interrupted power supply, maintain the thermal balance required by each reaction unit, and ensure that the entire process system can still operate continuously and stably under unstable power input conditions.

[0039] Example 2 In a typical embodiment of the present invention, a method for producing sulfur from hydrogen-reduced desulfurized gypsum is provided, comprising: High-purity hydrogen and high-purity oxygen are produced by electrolyzing water using electricity generated from abandoned wind and solar power, off-peak electricity, or renewable energy sources, and stored separately. The hydrogen produced by water electrolysis has a purity of 99.99 vol% and the oxygen has a purity of 99.95 vol%. The hydrogen and oxygen are compressed and stored in corresponding storage tanks with a pressure of 2.0–10.0 MPa.

[0040] Electric heating is used as the main heat source to directly heat each reaction device; at the same time, some hydrogen and oxygen are burned to generate high-temperature steam, which is then passed through the heat exchange structure outside each reaction device for non-contact indirect heat exchange; specifically, the hydrogen-oxygen combustion temperature is 1200-1500℃, and the high-temperature steam generated by combustion has a temperature of 1000-1100℃ and a pressure of 0.8-2.0MPa; After drying and sieving, the desulfurized gypsum is reduced with hydrogen at high temperature to produce calcium sulfide. The temperature of the reduction reaction is 900-1000℃ and the reaction time is 45-90 min. Calcium sulfide is mixed with water and carbon dioxide to undergo hydrolysis and carbonation reactions, producing calcium carbonate and hydrogen sulfide gas. During the hydrolysis and carbonation reactions, the calcium sulfide is cooled to below 100°C and then prepared into a suspension slurry with a solid content of 15–25 wt%. The stirring speed is 100–300 rpm, the reaction pressure is atmospheric pressure or 0.1–0.15 MPa, the carbon dioxide introduced has a purity of 95 vol%, the temperature of the hydrolysis and carbonation reactions is 50–80°C, and the reaction time is 60–120 min.

[0041] Hydrogen sulfide is divided into two parts. The first part is oxidized to produce sulfur dioxide. The second part is mixed with sulfur dioxide in a specific ratio and then subjected to a Claus reaction under the action of a catalyst to produce sulfur, which is then condensed and recovered. Specifically, the hydrogen sulfide is divided into a first part (1 / 3 by volume flow rate) and a second part (2 / 3 by volume flow rate). The second part of hydrogen sulfide and sulfur dioxide undergo a Claus reaction at a volume ratio of 2:1. The Claus reaction uses vanadium pentoxide catalyst, TiO2, or other catalysts suitable for the reaction of hydrogen sulfide and sulfur dioxide. The volume ratio of H2S:SO2 in the mixed gas entering the Claus reactor is detected by an infrared gas analyzer. The first stage temperature of the Claus reaction is 300–350°C, and the second stage temperature is 220–250°C.

[0042] In this embodiment, a calcium carbonate calcination process is also included, in which the calcium carbonate is calcined to produce carbon dioxide, which participates in the hydrolysis and carbonation reactions. The calcination temperature is 700–850°C, the pressure is -0.01–-0.05 MPa, and the calcination residence time is 30–60 min. When the calcium carbonate calcination and carbon dioxide recycling are not selected, the calcium carbonate is output as a calcium-based product or returned to the flue gas desulfurization process.

[0043] In this embodiment, the electric heating unit is directly connected to the power of abandoned wind and solar power, off-peak electricity, or renewable energy sources and serves as the main heat source. High-temperature steam is only used as an auxiliary heat source for start-up heating, waste heat utilization, or temperature regulation. The high-temperature steam only flows within the heat exchange tubes, heat exchange jackets, coils, tubes, or external heat exchangers of each reactor and does not come into direct contact with hydrogen and calcium sulfate in the high-temperature hydrogen reduction process, calcium sulfide slurry in the hydrolysis and carbonation process, H2S / O2 reaction gas in the partial oxidation of hydrogen sulfide, H2S / SO2 mixed gas in the Claus reaction process, or calcium carbonate or calcium oxide in the optional calcium carbonate calcination process.

[0044] The desulfurized gypsum in the method of this embodiment can also be replaced with phosphogypsum, fluorogypsum or natural gypsum.

[0045] In some exemplary embodiments, desulfurized gypsum, a byproduct of coal-fired power plants, is used as raw material. Water electrolysis is performed at 35°C and 1.5 MPa, while hydrogen and oxygen are stored in a 5.0 MPa tank. The desulfurized gypsum is dried with waste heat steam at 100°C for 45 minutes and then sieved to obtain 100-mesh particles. The reduction reactor temperature is 950°C, and the reaction time is 60 minutes. The hydrolysis temperature is 65°C, and the carbon dioxide reaction time is 90 minutes. The first stage temperature of the Claus reaction is 325°C, and the second stage temperature is 235°C, resulting in a final sulfur purity of 99.8%.

[0046] In some exemplary embodiments, the CaCO3 obtained from hydrolysis and carbonation is not put into the calcination step, but is reused as a calcium-based material in the flue gas desulfurization process; this scheme is used to illustrate that the calcium resources in this invention can be further recycled back to the desulfurization system in addition to sulfur production.

[0047] In some exemplary embodiments, phosphogypsum is used as raw material and a relatively low temperature operating condition is adopted: water electrolysis is carried out at 25°C and 0.5MPa, phosphogypsum is dried by waste heat steam at 80°C for 60 minutes and sieved to obtain 80-mesh particles; the high-temperature hydrogen reduction temperature is 900°C and the reaction time is 90 minutes; the hydrolysis temperature is 50°C and the reaction time is 120 minutes; the final sulfur purity is 99.5%.

[0048] In some exemplary embodiments, natural gypsum ore powder is used as raw material, and a relatively high temperature condition is adopted: water electrolysis is carried out at 50°C and 3.0 MPa, natural gypsum is dried by steam at 120°C for 30 minutes, and 200-mesh particles are sieved; the reduction temperature is 1000°C and the reaction time is 45 minutes; the residence time of the oxidation process is 2 seconds; and the sulfur purity is 99.9%.

[0049] In some exemplary embodiments, fluorogypsum is used as raw material. The electric heating power supply bus directly supplies the reduction reactor, oxidation reactor, Claus reactor, dryer, and optional CaCO3 calcining furnace as the main heat source by using the abandoned wind and solar power or off-peak electricity. The 1050°C high-temperature steam generated by hydrogen-oxygen combustion is used as an auxiliary heat carrier. It is first used for start-up heating or temperature fine-tuning of the reduction reactor and oxidation reactor, and then cooled and supplied to the Claus reactor through a jacket or tube. Finally, the 110°C tail steam is used for gypsum drying through an indirect dryer, thereby verifying the energy utilization network that combines the electric heating main heat source with the high-temperature steam auxiliary heat source.

[0050] In some exemplary embodiments, a high-precision gas mass flow meter is used to strictly split H2S into 33.3% and 66.7% streams, and an infrared gas analyzer is used to confirm that the actual volume ratio of H2S:SO2 in the mixed gas is stable at 2.02:1; the Claus reactor is loaded with TiO2 catalyst, and the final collected sulfur purity reaches 99.85%.

[0051] In some exemplary embodiments, CaS is prepared with deionized water to form a high solids content suspension slurry of 25 wt%, and the stirring speed is increased to 300 rpm; carbon dioxide at a pressure of 0.15 MPa is introduced from the calcination process to shorten the reaction time to 60 minutes, and the final sulfur purity is 99.7%.

[0052] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A system for producing sulfur from hydrogen-reduced desulfurized gypsum, characterized in that, It includes a water electrolysis unit, a gypsum pretreatment and reduction unit, a hydrolysis and oxidation unit, and a sulfur production unit; The water electrolysis unit is used to produce hydrogen and oxygen; The gypsum pretreatment and reduction unit is used to dry and reduce gypsum, wherein hydrogen is used as a reducing agent in the reduction process; The hydrolysis and oxidation unit is used to hydrolyze and oxidize the reduction products, wherein oxygen is used as the oxidant in the oxidation process; The sulfur production unit includes a Claus reactor for performing a Claus reaction on some hydrolysis products and oxidation products to produce sulfur. The drying and reduction processes of the gypsum pretreatment and reduction unit, the hydrolysis and oxidation processes of the hydrolysis and oxidation unit, and the Claus reaction process all use electric heating as the main heat source and high-temperature steam generated by the combustion of hydrogen and oxygen as the auxiliary heat source.

2. The system for producing sulfur from hydrogen-reduced desulfurized gypsum as described in claim 1, characterized in that, The water electrolysis unit includes a water electrolysis device. The hydrogen outlet of the water electrolysis device is connected to a hydrogen storage tank, and the oxygen outlet is connected to an oxygen storage tank. Both the hydrogen storage tank and the oxygen storage tank are connected to a hydrogen-oxygen burner. The steam outlet of the hydrogen-oxygen burner is connected to a steam distributor.

3. The system for producing sulfur from hydrogen-reduced desulfurized gypsum as described in claim 2, characterized in that, The gypsum pretreatment and reduction unit includes a heat exchange dryer and a reduction reactor connected in sequence. The reduction reactor is connected to the hydrogen storage tank, and the reduction product outlet of the reduction reactor is connected to the hydrolysis and oxidation unit. Both the heat exchange dryer and the reduction reactor are equipped with a high-temperature steam indirect heat exchange structure and an electric heating component. The high-temperature steam indirect heat exchange structure is connected to a steam distributor.

4. The system for producing sulfur from hydrogen-reduced desulfurized gypsum as described in claim 2, characterized in that, The hydrolysis and oxidation unit includes a hydrolysis reactor and an oxidation reactor. The hydrolysis product outlet of the hydrolysis reactor is connected to the oxidation reactor and the Claus reactor, respectively. The oxidation product outlet of the oxidation reactor is connected to the Claus reactor. The hydrolysis reactor, the oxidation reactor, and the Claus reactor are all equipped with a high-temperature steam indirect heat exchange structure and an electric heating component. The high-temperature steam indirect heat exchange structure is connected to a steam distributor.

5. The system for producing sulfur from hydrogen-reduced desulfurized gypsum as described in claim 4, characterized in that, The calcium-based product outlet of the hydrolysis reactor is connected to the calcining furnace, and the carbon dioxide outlet of the calcining furnace is connected to the hydrolysis reactor. The calcining furnace is equipped with a high-temperature steam indirect heat exchange structure and an electric heating component. The high-temperature steam indirect heat exchange structure is connected to a steam distributor.

6. The system for producing sulfur from hydrogen-reduced desulfurized gypsum as described in claim 1, characterized in that, The electricity for both the water electrolysis unit and the electric heating comes from abandoned wind and solar power, off-peak electricity, or electricity generated from renewable energy sources.

7. A method for producing sulfur from hydrogen-reduced desulfurized gypsum, implemented using the system described in any one of claims 1-6, characterized in that, include: Electricity generated from abandoned wind and solar power, off-peak electricity, or renewable energy sources is used to electrolyze water to produce high-purity hydrogen and high-purity oxygen, which are then stored separately. Electric heating is used as the main heat source to directly heat each reaction device; or some hydrogen and oxygen are burned to generate high-temperature steam, and the high-temperature steam flows through the heat exchange structure outside each reaction device for non-contact indirect heat exchange. After drying and sieving, the desulfurized gypsum is reduced with hydrogen at high temperature to produce calcium sulfide. Calcium sulfide is mixed with water and carbon dioxide to undergo hydrolysis and carbonation reactions, producing calcium carbonate and hydrogen sulfide gas. Hydrogen sulfide is divided into two parts. The first part is oxidized to produce sulfur dioxide. The second part is mixed with sulfur dioxide in a specific ratio and then subjected to a Claus reaction under the action of a catalyst to produce sulfur, which is then condensed and recovered.

8. The method for producing sulfur from hydrogen-reduced desulfurized gypsum as described in claim 7, characterized in that, The reduction reaction is carried out at a temperature of 900–1000℃ for a reaction time of 45–90 min; the hydrolysis and carbonation reactions are carried out at a temperature of 50–80℃ for a reaction time of 60–120 min; the first stage of the Claus reaction is carried out at a temperature of 300–350℃ and the second stage at a temperature of 220–250℃.

9. The method for producing sulfur from hydrogen-reduced desulfurized gypsum as described in claim 7, characterized in that, The calcium carbonate is calcined to produce carbon dioxide, which participates in the hydrolysis and carbonation reactions. The calcination temperature is 700-850℃, the pressure is -0.01--0.05MPa, and the calcination residence time is 30-60min.

10. The method for producing sulfur from hydrogen-reduced desulfurized gypsum as described in claim 7, characterized in that, The hydrogen sulfide is divided into a first part (1 / 3) and a second part (2 / 3) according to volume flow rate. The second part of hydrogen sulfide is reacted with sulfur dioxide at a volume ratio of 2:1 using a Claus reaction.

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