Method for preparing hydrogen from gypsum

Abstract

The invention relates to the technical field of solid waste resource utilization, in particular to a method for preparing hydrogen from gypsum, which comprises the following steps: S1, mixing gypsum with a reducing agent to prepare balls, and carrying out negative pressure roasting reaction to produce calcium sulfide and carbon monoxide; s2, calcium sulfide is subjected to a hydrolysis reaction, and hydrogen sulfide gas and calcium hydroxide are produced; and S3, carrying out direct electrolytic reaction or indirect conversion reaction on the hydrogen sulfide gas to obtain elemental sulfur and hydrogen. In the step S1, when the reducing agent is carbon powder, carbon monoxide is directionally generated by controlling the reaction temperature of negative-pressure roasting, and then the carbon monoxide is used as a heat source of the negative-pressure roasting reaction; or in the step S1, when the reducing agent is carbon monoxide, carbon dioxide is obtained through the negative-pressure roasting reaction, the carbon dioxide generated through negative-pressure roasting in the step S1 is captured through calcium hydroxide generated through the calcium sulfide hydrolysis reaction in the step S2, the light calcium carbonate product is prepared, energy consumption is reduced, and high-value utilization of gypsum is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste resource utilization, and in particular to a method for preparing hydrogen from gypsum. Background Art

[0002] Gypsum, a major component of industrial byproducts such as phosphogypsum and desulfurized gypsum, contains significant amounts of CaSO₄. As an industrial byproduct, it is emitted in excess of 100 million tons annually. This massive amount of gypsum is not effectively utilized and must be stored in piles. This not only wastes land resources but also restricts regional development planning and spatial layout. Furthermore, long-term storage of gypsum can pollute the air, soil, and water resources due to factors such as rain and strong winds.

[0003] Chinese patent publication number CN119505931A discloses a phosphogypsum-based saline-alkali soil conditioner, preparation and application method. The conditioner comprises the following raw materials by weight: 235-330 parts of phosphogypsum, 40-100 parts of sepiolite, 20-70 parts of lignocellulose, 15-30 parts of epichlorohydrin, and 8-20 parts of urea. This solution uses sepiolite and phosphogypsum to hydrate and dissolve Ca 2+ Replacement of Na in soil + Sepiolite fixes Na in soil through magnesium ion exchange. + The magnesium ions react with the water-soluble phosphorus in the phosphogypsum to reduce the effect of soluble phosphorus on the hydration of the phosphogypsum and dissolve Ca 2+ It can further promote the hydration of phosphogypsum, thereby improving the improvement and management effect of phosphogypsum on saline-alkali land.

[0004] Chinese patent publication number CN119285323A discloses a fluidized fill material and its preparation method, belonging to the field of building materials technology. The fluidized fill material comprises the following raw material components, by weight: 85-95 parts of recycled redundant soil slurry from construction waste, 5-15 parts of slurry from water plant tailings, 40-90 parts of low-quality recycled aggregate from construction waste, 5-10 parts of granulated blast furnace slag powder, 3-6 parts of asbestos-free mineral fiber, 1-4 parts of cement, 1-2 parts of industrial by-product gypsum, 0.3-1 part of bentonite, and 0.5-1.5 parts of a water reducer. This fluidized fill material has excellent and stable performance, achieving green resource utilization of construction waste and water plant tailings, and addressing the high treatment costs and environmental pollution caused by these waste and water plant tailings. It can be seen that the treatment methods of gypsum in the above two patents, whether it is to promote the hydration of phosphogypsum or to prepare fluid filling materials, although they belong to the recycling of gypsum, they are more focused on low value-added products, that is, the efficiency of gypsum recycling is low, and it is difficult to achieve large-scale high-value utilization.

[0005] To this end, the present invention provides a method for preparing hydrogen from gypsum. Summary of the Invention

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for preparing hydrogen from gypsum, thereby solving the problem of gypsum recycling. However, the method focuses more on low added value, the efficiency of gypsum recycling is low, and it is difficult to achieve large-scale high-value utilization.

[0007] In order to achieve the above object, the present invention provides a method for preparing hydrogen from gypsum, comprising:

[0008] Step S1: Gypsum and a reducing agent are mixed to form balls, and then subjected to negative pressure roasting reaction to produce calcium sulfide and carbon monoxide;

[0009] Reducing agents include carbon powder or carbon monoxide;

[0010] The carbon powder includes any one of coal, coke, petroleum coke or biomass.

[0011] When the reducing agent is carbon monoxide, the ventilation rate of carbon monoxide is 0.5L / min to 50L / min.

[0012] The conditions for mixing gypsum and reducing agent to make pellets are as follows: gypsum and reducing agent are mixed in a mass ratio of 3:1 to 10:1 to prepare pellets of 6 mm to 15 mm; the pellet drying temperature is 60° C. to 200° C.; and the pellet drying time is 2 hours to 24 hours.

[0013] The conditions for negative pressure roasting are: roasting pressure of 0.01 to 1 atmosphere; roasting temperature of 600° C. to 1000° C.; roasting time of 10 minutes to 180 minutes;

[0014] Gypsum includes one or more combinations of desulfurized gypsum, phosphogypsum, and fluorinated gypsum.

[0015] Step S2: Calcium sulfide undergoes hydrolysis reaction to produce hydrogen sulfide and calcium hydroxide;

[0016] The reaction conditions for the hydrolysis of calcium sulfide are as follows: the volume ratio of water to the mass ratio of calcium sulfide is 0.5 mL to 10 mL: 1 g; the hydrolysis temperature is 20° C. to 95° C.; and the hydrolysis time is 1 min to 120 min.

[0017] The carbon dioxide generated by the negative pressure roasting in step S1 is captured by the calcium hydroxide produced by the calcium sulfide hydrolysis reaction in step S2 to prepare a light calcium carbonate product.

[0018] Step S3: hydrogen sulfide gas undergoes direct electrolysis reaction or indirect conversion reaction to obtain elemental sulfur and hydrogen;

[0019] The indirect conversion reaction of hydrogen sulfide gas is to first react hydrogen sulfide gas with ferric chloride to obtain ferrous chloride, hydrochloric acid and elemental sulfur, and then use electrolysis method to prepare ferric chloride and hydrogen with hydrochloric acid aqueous solution, and the ferric chloride is recycled.

[0020] The catalyst for the direct electrolysis of hydrogen sulfide gas is any one or more of transition metal sulfides: MoS2, WS, FeS, CoS, Pt / C or Pd / C;

[0021] The reaction conditions of the direct electrolysis reaction are: electrolysis temperature of 50° C. to 80° C., electrolysis voltage of 0.5V to 6V, and current efficiency greater than 90%.

[0022] In step S3, the indirect conversion reaction of hydrogen sulfide gas includes:

[0023] Step S31: H2S gas reacts with FeCl3 to produce ferrous chloride, hydrochloric acid and elemental sulfur;

[0024] Step S32: ferrous chloride and hydrochloric acid aqueous solution are subjected to electrolysis reaction to produce ferric chloride and hydrogen;

[0025] Wherein, the reaction conditions of step S31 are:

[0026] The reaction temperature is 25°C to 90°C, the H2S gas introduction rate is 0.5L / min to 20L / min, the FeCl3 concentration is 0.5mol / L to 10.0mol / L, the solution pH is 1.0 to 6.0, the reaction time is 30min to 90min, and the H2S gas absorption efficiency reaches more than 99%;

[0027] The electrolysis reaction conditions of step S32 are: electrolysis voltage of 1.5V to 8.0V, electrolysis time of 1h to 6h, electrolysis temperature of 25°C to 640°C, pH value of 1.0 to 3.0, Cl- concentration of 2.0mol / L to 10.0mol / L, and current efficiency greater than 90%.

[0028] The method for preparing hydrogen from gypsum is carried out in a gypsum hydrogen preparation system, which includes:

[0029] The negative pressure roasting furnace comprises a furnace body; a feed port is provided on the upper part of the furnace body, a discharge port is provided on the lower part of the furnace body, and a plurality of temperature measuring thermocouples are inserted in the furnace body to detect the temperature inside the furnace body; the furnace body is gradually inclined downward from the direction of feed to discharge; a vacuum pump is provided on the side wall of the furnace body;

[0030] The hydrolysis device includes a hydrolysis furnace; the hydrolysis furnace is connected to the discharge port of the negative pressure roasting furnace; a spray nozzle is arranged on the top wall of the hydrolysis furnace; a conveyor belt is arranged on the bottom wall of the hydrolysis furnace and corresponds to the position of the spray nozzle; a heating element is arranged inside the conveyor belt; and a hydrogen sulfide gas outlet is arranged on the side wall of the hydrolysis furnace and near the end of the conveyor belt.

[0031] The direct electrolysis device or the indirect conversion device is arranged on the side of the hydrolysis furnace and is connected to the hydrogen sulfide gas outlet.

[0032] Optionally, the indirect conversion device includes: a tank body, the solution inlet and the mixed liquid overflow port are both arranged on the side wall of the tank body, and the position of the solution inlet is lower than the mixed liquid overflow port; a zeolite filler is arranged on the bottom layer inside the tank body; an air inlet is arranged below the tank body and connected to the zeolite filler; and a stirring paddle is inserted inside the tank body.

[0033] The beneficial effects of the present invention are:

[0034] The present invention provides a method for preparing hydrogen from gypsum. By performing negative pressure roasting, the roasting reaction temperature is reduced. Compared with conventional roasting or calcining, the negative pressure roasting temperature of the present invention is reduced by 0°C to 400°C, and the roasting time is reduced by 0min to 170min, thereby significantly saving energy consumption for heating.

[0035] Furthermore, in step S1, when the reducing agent is carbon monoxide, a negative pressure roasting reaction is performed to produce carbon dioxide, which is used to prepare light calcium carbonate with calcium hydroxide, the product of the hydrolysis reaction in step S2. This recycling process realizes the first carbon cycle in the present method for preparing hydrogen; the carbon monoxide produced in the process of preparing light calcium carbonate from calcium hydroxide is used as fuel gas for negative pressure roasting, and this recycling process realizes the second carbon cycle in the present method for preparing hydrogen. Through the above two carbon cycles, efficient carbon recycling is achieved, energy consumption costs are saved, and carbon emissions are reduced.

[0036] Furthermore, in step S1, when the reducing agent is carbon powder, carbon monoxide is generated in a direction by controlling the reaction temperature of the negative pressure roasting, and then the carbon monoxide is used as a heat source for the negative pressure roasting reaction, thereby further realizing efficient carbon recycling, saving energy consumption costs, and reducing carbon emissions.

[0037] Furthermore, in step S2, the amount and speed of water addition are strictly controlled to form calcium hydroxide solid rather than calcium hydroxide aqueous solution, thereby avoiding the problem that the calcium hydroxide solution is difficult to separate.

[0038] Furthermore, hydrogen sulfide gas is converted into elemental sulfur and hydrogen through direct electrolysis or indirect conversion reaction, and the heat source for electrolysis adopts a green and environmentally friendly heat source, thus realizing high-value and clean utilization of gypsum.

[0039] Furthermore, the gypsum hydrogen production system utilizes porous zeolite to disperse hydrogen sulfide gas. The stirring paddle further disperses the hydrogen sulfide gas, reducing the bubble size. During the direct electrolysis reaction, the hydrogen sulfide bubbles are evenly distributed, improving hydrogen sulfide utilization efficiency. Compared to existing electrolysis devices, the present invention achieves a hydrogen sulfide utilization rate of over 98%. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the process flow of the method for preparing hydrogen from gypsum of the present invention;

[0041] Figure 2 This is a schematic structural diagram of a negative pressure roasting furnace for preparing hydrogen from gypsum according to the present invention;

[0042] Figure 3 This is a schematic structural diagram of a hydrolysis device in a gypsum hydrogen production system according to the present invention;

[0043] Figure 4 This is a schematic structural diagram of the indirect conversion device of the gypsum hydrogen production system of the present invention.

[0044] Description of reference numerals:

[0045] 1. Negative pressure roasting furnace; 2. Furnace body; 3. Feed port; 4. Discharge port; 5. Thermocouple; 6. Vacuum pump; 7. Hydrolysis device; 71. Feed bin; 72. Discharge bin; 8. Hydrolysis furnace; 9. Spray nozzle; 10. Conveyor belt; 11. Heating element; 12. Hydrogen sulfide gas outlet; 13. Indirect conversion device; 14. Tank body; 15. Zeolite filler; 16. Air inlet; 17. Stirring paddle. DETAILED DESCRIPTION

[0046] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Instead, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0047] The present invention uses gypsum and carbon to produce calcium sulfide and carbon monoxide by roasting under negative pressure. The calcium sulfide is then hydrolyzed with water to produce hydrogen sulfide and calcium hydroxide. The hydrogen sulfide is electrolyzed to produce elemental sulfur and hydrogen. The reaction formula involved in the reaction process includes:

[0048] Calcium sulfate and carbon negative pressure roasting reaction:

[0049] CaSO4+4C=CaS+4CO↑

[0050] Calcium sulfide hydrolysis reaction:

[0051] CaS+2H2O=H2S↑+Ca(OH)2

[0052] Direct electrolysis reaction of hydrogen sulfide:

[0053] 2H2S=2S+2H2↑

[0054] Indirect conversion reaction of hydrogen sulfide:

[0055] H2S+2FeCl3=2FeCl2+2HCl+S↓

[0056] 2FeCl2+2HCl=2FeCl3+H2↑

[0057] Example 1

[0058] In this embodiment, the gypsum particle size is 2 mm, and the carbon powder is selected from pulverized coal, with the pulverized coal added in an amount equal to 1 times the chemical reaction stoichiometry. Gypsum and a reducing agent are mixed in a mass ratio of 3:1 to form pellets. The gypsum and pulverized coal are then dried at 60°C for 24 hours to reduce the moisture content of the pellets to less than 0.5 wt%. This removes bound water from the pellets and gypsum crystallization water, preventing sulfur from escaping from the vacuum roasting furnace 1 as hydrogen sulfide during the vacuum roasting process, thereby reducing sulfur loss.

[0059] The negative pressure roasting reaction conditions of gypsum and coal powder are as follows: roasting pressure of 1 atmosphere, roasting temperature of 1000°C, and roasting time of 180 minutes. In Example 1, the gypsum conversion rate is 70%. The carbon monoxide gas in the roasting product is used as the roasting fuel gas.

[0060] The reaction conditions for the hydrolysis of calcium sulfide are as follows: the ratio of the volume of water to the mass of calcium sulfide is 0.5 mL:1 g, the hydrolysis temperature is 25° C., the hydrolysis time is 120 min, and the hydrolysis rate of calcium sulfide reaches 98%.

[0061] Hydrogen sulfide undergoes electrolysis reaction with the catalyst being MoS2, the reaction temperature being 50°C, the reaction voltage being 0.5V, and the current efficiency being 90%.

[0062] Example 2

[0063] In this embodiment, the gypsum particle size is 1 mm, and the carbon powder is coking coal, with the coking coal added in an amount of 4 times the chemical reaction stoichiometry. Gypsum and a reducing agent are mixed in a mass ratio of 5:1 to form pellets. Gypsum and coal powder are then dried at 200°C for 2 hours to reduce the moisture content of the pellets to less than 0.5 wt%. This removes bound water from the pellets and gypsum crystallization water, preventing sulfur from escaping from the negative pressure roasting furnace 1 as hydrogen sulfide during the roasting process, thereby reducing sulfur loss.

[0064] The negative pressure roasting reaction conditions for gypsum and coke are: a roasting pressure of 0.01 atmospheres, a roasting temperature of 1000°C, and a roasting time of 10 minutes. The negative pressure roasting process shortens the roasting time by 170 minutes, reduces energy consumption by 30%, and increases the gypsum decomposition efficiency by 30%. The gypsum conversion rate in Example 2 reaches 82%. The carbon monoxide gas in the negative pressure roasting product is used as fuel for the negative pressure roasting.

[0065] The reaction conditions for the hydrolysis of calcium sulfide are as follows: the ratio of the volume of water to the mass of calcium sulfide is 2 mL:1 g, the hydrolysis temperature is 95° C., the hydrolysis time is 20 min, and the hydrolysis rate of calcium sulfide reaches 99%.

[0066] The reaction conditions of H2S and FeCl3 are as follows: reaction temperature of 25°C, H2S introduction rate of 2 L / min, FeCl3 concentration of 2.0 mol / L, solution pH of 2.0, reaction time of 90 min, and H2S absorption efficiency of 99%.

[0067] The reaction conditions of the electrolysis method of ferrous chloride and hydrochloric acid aqueous solution are: electrolysis voltage 1.5V, current density 50mA / cm 2 , electrolysis time was 1 h, electrolysis temperature was 25°C, pH value was 1.0, Cl- concentration was 2.0 mol / L, and current efficiency was 90%.

[0068] Example 3

[0069] In this embodiment, the gypsum particle size is 1 mm, and the carbon powder is petroleum coke, with the added amount of carbon powder being twice the chemical reaction stoichiometry. Gypsum and a reducing agent are mixed in a mass ratio of 7:1 to form pellets. Gypsum and coal powder are then mixed to form pellets 10 mm to 12 mm in diameter. The pellets are then dried at 170°C for 5 hours to reduce the moisture content to less than 0.5 wt%. This removes bound water from the pellets and gypsum crystallization water, preventing sulfur from escaping from the negative pressure roasting furnace 1 as hydrogen sulfide during the roasting process, thereby reducing sulfur loss.

[0070] The reaction conditions for the negative pressure roasting of gypsum and petroleum coke are: a roasting pressure of 0.3 atmospheres, a roasting temperature of 600°C, and a roasting time of 100 minutes. The negative pressure roasting process reduces the roasting temperature by 400°C, shortens the roasting time by 80 minutes, reduces energy consumption by 30%, and increases the gypsum decomposition efficiency by 30%. The gypsum conversion rate in Example 3 reaches 85%. The carbon monoxide gas in the negative pressure roasting product is used as fuel for the negative pressure roasting.

[0071] The reaction conditions for the hydrolysis of calcium sulfide are as follows: the ratio of the volume of water to the mass of calcium sulfide is 4 mL:1 g, the hydrolysis temperature is 90° C., the hydrolysis time is 90 min, and the hydrolysis rate of calcium sulfide reaches 99%.

[0072] The reaction conditions of H2S and FeCl3 are as follows: reaction temperature of 60°C, H2S introduction rate of 20 L / min, FeCl3 concentration of 10.0 mol / L, solution pH of 6.0, reaction time of 90 min, and H2S absorption efficiency of 99%.

[0073] The electrolysis reaction conditions are as follows: electrolysis voltage of 8.0 V, electrolysis time of 6 h, electrolysis temperature of 40° C., pH value of 3.0, Cl − concentration of 10.0 mol / L, and current efficiency of 90%.

[0074] Example 4

[0075] In this embodiment, the gypsum particle size is 0.5 mm, and the carbon powder is biomass, with the biomass added in an amount equal to 1 times the chemical reaction stoichiometry. Gypsum and a reducing agent are mixed in a mass ratio of 9:1 to form pellets. Gypsum and coal powder are then mixed to form pellets 12 mm to 15 mm in diameter. The pellets are then dried at 100°C for 6 hours to reduce the moisture content to less than 0.5 wt%. This removes bound water from the pellets and gypsum crystallization water, preventing sulfur from escaping from the negative pressure roasting furnace 1 as hydrogen sulfide during the roasting process, thereby reducing sulfur loss.

[0076] The negative pressure roasting reaction conditions for gypsum and biomass were: a roasting pressure of 0.1 atmosphere, a roasting temperature of 700°C, and a roasting time of 80 minutes. The negative pressure roasting process reduced the roasting temperature by 300°C, shortened the roasting time by 100 minutes, reduced energy consumption by 30%, and increased the gypsum decomposition efficiency by 30%. The gypsum conversion rate in Example 4 reached 85%. The carbon monoxide gas in the negative pressure roasting product was used as fuel for the negative pressure roasting.

[0077] The reaction conditions for the hydrolysis of calcium sulfide are as follows: the ratio of the volume of water to the mass of calcium sulfide is 10 mL:1 g, the hydrolysis temperature is 95° C., the hydrolysis time is 1 min, and the hydrolysis rate of calcium sulfide reaches 98%.

[0078] The hydrogen sulfide catalytic electrolysis reaction uses Pt / C (platinum carbon) as the catalyst, the electrolysis temperature is 80°C, the electrolysis voltage is 6V, and the current efficiency is 90%.

[0079] Example 5

[0080] In this embodiment, the gypsum particle size is 0.1 mm, and the carbon powder is coking coal, with the coking coal added in an amount of four times the chemical reaction stoichiometry. Gypsum and a reducing agent are mixed in a mass ratio of 10:1 to form pellets. Gypsum and coal powder are then mixed to form pellets 12 mm to 15 mm in diameter. The pellets are then dried at 120°C for 6 hours to reduce the moisture content to less than 0.5 wt%. This removes bound water from the pellets and gypsum crystallization water, preventing sulfur from escaping from the negative pressure roasting furnace 1 as hydrogen sulfide during the roasting process, thereby reducing sulfur loss.

[0081] The reaction conditions for the vacuum roasting of gypsum and coke were: a roasting pressure of 0.8 atmospheres, a roasting temperature of 900°C, and a roasting time of 120 minutes. This vacuum roasting process reduced the roasting temperature by 100°C, shortened the roasting time by 60 minutes, reduced energy consumption by 30%, and increased the gypsum decomposition efficiency by 30%. The gypsum conversion rate in Example 5 reached 80%. The carbon monoxide gas in the vacuum roasting product was used as fuel for the vacuum roasting.

[0082] The reaction conditions for the hydrolysis of calcium sulfide are as follows: the ratio of the volume of water to the mass of calcium sulfide is 1 mL:1 g, the hydrolysis temperature is 45° C., the hydrolysis time is 30 min, and the hydrolysis rate of calcium sulfide reaches 98%.

[0083] The reaction conditions of H2S and FeCl3 are as follows: reaction temperature of 30°C, H2S introduction rate of 0.5 L / min, FeCl3 concentration of 0.5 mol / L, solution pH of 2.0, reaction time of 90 min, and H2S absorption efficiency of 99%.

[0084] The electrolysis reaction conditions are: electrolysis voltage 2.0 V, current density 10 mA / cm 2 , electrolysis time was 4h, electrolysis temperature was 30℃, pH value was 2.0, Cl- concentration was 2.0mol / L, and current efficiency was 95%.

[0085] Example 6

[0086] In this embodiment, the gypsum particle size is 0.1 mm, carbon monoxide is used as the reducing agent, the carbon monoxide feed rate is 5 L / min, the roasting pressure is 0.8 atmospheres, the roasting temperature is 800°C, and the roasting time is 90 minutes. Through the treatment of the negative pressure roasting process, the roasting temperature is reduced by 200°C, the roasting time is shortened by 90 minutes, the energy consumption is reduced by 30%, the gypsum decomposition efficiency is increased by 30%, and the gypsum conversion rate of Example 6 reaches 85%. The calcium hydroxide produced by the calcium sulfide hydrolysis reaction in step S2 captures the carbon dioxide generated by the negative pressure roasting in step S1 to produce a light calcium carbonate product.

[0087] The reaction conditions for the hydrolysis of calcium sulfide are as follows: the ratio of the volume of water to the mass of calcium sulfide is 1 mL:1 g, the hydrolysis temperature is 40° C., the hydrolysis time is 40 min, and the hydrolysis rate of calcium sulfide reaches 98%.

[0088] The reaction conditions of H2S and FeCl3 are: reaction temperature of 30°C, H2S gas introduction rate of 0.5L / min, FeCl3 concentration of 0.5mol / L, solution pH of 2.0, reaction time of 90min, and H2S gas absorption efficiency of 99%.

[0089] The electrolysis reaction conditions are: electrolysis voltage 2.0 V, current density 10 mA / cm2 , electrolysis time was 4h, electrolysis temperature was 30℃, pH value was 2.0, Cl- concentration was 2.0mol / L, and current efficiency was 95%.

[0090] Example 7

[0091] In this embodiment, the gypsum particle size is 0.1 mm, carbon monoxide is used as the reducing agent, the carbon monoxide feed rate is 45 L / min, the roasting pressure is 0.6 atmospheres, the roasting temperature is 800°C, and the roasting time is 120 minutes. Through the treatment of the negative pressure roasting process, the roasting temperature is reduced by 200°C, the roasting time is shortened by 60 minutes, the energy consumption is reduced by 30%, the gypsum decomposition efficiency is increased by 30%, and the gypsum conversion rate of Example 6 reaches 85%. The calcium hydroxide produced by the calcium sulfide hydrolysis reaction in step S2 captures the carbon dioxide generated by the negative pressure roasting in step S1 to produce a light calcium carbonate product.

[0092] The reaction conditions for the hydrolysis of calcium sulfide are as follows: the ratio of the volume of water to the mass of calcium sulfide is 2 mL:1 g, the hydrolysis temperature is 60° C., the hydrolysis time is 30 min, and the hydrolysis rate of calcium sulfide reaches 98%.

[0093] The reaction conditions of H2S and FeCl3 are: reaction temperature of 50°C, H2S gas introduction rate of 3L / min, FeCl3 concentration of 0.5mol / L, solution pH of 2.0, reaction time of 80min, and H2S gas absorption efficiency of 99%.

[0094] The electrolysis reaction conditions are: electrolysis voltage 2.0 V, current density 10 mA / cm 2 , electrolysis time was 4h, electrolysis temperature was 30℃, pH value was 2.0, Cl- concentration was 2.0mol / L, and current efficiency was 95%.

[0095] The system for preparing hydrogen from gypsum in this embodiment is as follows: Figure 2 and Figure 3 As shown, the system includes:

[0096] The negative pressure roasting furnace 1 includes a furnace body 2; a feed port 3 is provided on the upper side of the furnace body 2, and a discharge port 4 is provided on the lower side. A plurality of temperature measuring thermocouples 5 are also inserted into the furnace body 2 to detect the temperature inside the furnace body 2; the furnace body 2 gradually tilts downward from the direction of feeding to discharging; a vacuum pump 6 is provided on the side wall of the furnace body 2;

[0097] The hydrolysis device 7 includes a hydrolysis furnace 8; the hydrolysis furnace 8 is connected to the discharge port 4 of the negative pressure roasting furnace 1; a spray nozzle 9 is arranged on the top wall of the hydrolysis furnace 8; a conveyor belt 10 is arranged on the bottom wall of the hydrolysis furnace 8 and corresponds to the position of the spray nozzle 9; a heating element 11 is arranged inside the conveyor belt 10; and a hydrogen sulfide gas outlet 12 is arranged on the side wall of the hydrolysis furnace 8 and near the end of the conveyor belt 10.

[0098] The direct electrolysis device or the indirect conversion device 13 is disposed on the side of the hydrolysis furnace 8 and is connected to the hydrogen sulfide gas outlet 12 .

[0099] Exemplarily, the direct electrolysis device can be an existing electrolysis device, which belongs to the existing technology and is not specifically limited here.

[0100] For example, the furnace body 2 gradually tilts downward from the feed to the discharge at an angle of 3% to 3.5%. The rotation of the furnace body 2 stirs the pellets within the body, causing a chemical reaction. The inclination of the furnace body 2 allows the pellets to be discharged through the discharge air lock and into the discharge port 4, completing the roasting process. The furnace body 2 is equipped with multiple thermocouples 5 for temperature measurement. These thermocouples ensure precise temperature control. A vacuum pump 6 maintains the pressure within the furnace body 2 at 0.2 to 0.8 atmospheres.

[0101] Exemplarily, blowers are respectively provided at the feed port 3 and the discharge port 4 of the furnace body 2 , thereby facilitating the feeding and discharging of the furnace body 2 .

[0102] For example, the hydrolysis furnace 8 of this embodiment is a sealed crawler-type reactor, and the conveyor belt 10 is a crawler belt. The heating element 11 is located inside the conveyor belt 10 at the bottom of the hydrolysis furnace 8. A spray nozzle 9 is installed at the top of the hydrolysis furnace 8 to spray atomized water droplets during the calcium sulfide conveying process, and the amount and speed of water added to the hydrolysis furnace 8 are precisely controlled. Calcium sulfide is added from one side of the hydrolysis furnace 8 and spread flat on the conveyor belt 10, with the material layer thickness not exceeding 10 cm. In the hydrolysis furnace 8, calcium hydroxide generated by the reaction of calcium sulfide and water is carried out of the reaction area by the conveyor belt 10, and the generated hydrogen sulfide is discharged through the hydrogen sulfide gas outlet 12 at the top of the hydrolysis furnace 8. The advantages of the gypsum hydrogen production system of this embodiment are high reaction efficiency, water utilization rate exceeding 90%, and hydrogen sulfide capture efficiency exceeding 95%.

[0103] For example, a conveyor belt 10, driven by a motor, transports calcium sulfide into the hydrolysis furnace 8 at a speed set to ensure that the time required for the calcium sulfide hydrolysis reaction is equal to the time required for the calcium sulfide to be transported from the entrance of the furnace 2 to the discharge port 4. Hydrogen sulfide, a gaseous product produced by hydrolysis, exits the hydrolysis unit 7 through a hydrogen sulfide gas outlet 12. A heating element 11 is installed within the conveyor belt 10 to maintain the required temperature for the calcium sulfide hydrolysis reaction.

[0104] Exemplarily, a feed bin 71 and a discharge bin 72 are respectively provided at both ends of the hydrolysis furnace 8. The feed bin 71 is arranged above the hydrolysis furnace 8 near the starting end of the conveyor belt 10, and the discharge bin 72 is arranged below the hydrolysis furnace 8 near the ending end of the conveyor belt 10, thereby providing feed and discharge for the hydrolysis reaction on the conveyor belt 10.

[0105] In one possible embodiment, Figure 4 As shown, the indirect conversion device 13 includes: a tank body 14, the solution inlet and the mixed liquid overflow port are both arranged on the side wall of the tank body 14, and the position of the solution inlet is lower than the mixed liquid overflow port; a zeolite filler 15, which is arranged at the bottom layer inside the tank body 14; an air inlet 16, which is arranged below the tank body 14 and connected to the zeolite filler 15; and a stirring paddle 17, which is inserted into the tank body 14.

[0106] For example, hydrogen sulfide gas is dispersed into the ferric chloride solution within tank 14 through zeolite filler 15. A stirring paddle 17 is installed at the top of tank 14, with a stirring speed set at 300 to 500 rpm. Zeolite filler 15 disperses the hydrogen sulfide gas, and the stirring paddle 17 further disperses and reduces the particle size of the hydrogen sulfide bubbles, evenly distributing them within the absorption chamber. This improves hydrogen sulfide gas utilization efficiency. Compared to conventional electrolytic absorption chambers, this embodiment achieves a hydrogen sulfide gas utilization rate exceeding 98%.

[0107] Illustratively, hydrogen sulfide gas generated by the hydrolysis reaction enters the tank body 14 through the hydrogen sulfide inlet 16 and first passes through the zeolite filler 15. After being dispersed by the zeolite filler 15, the hydrogen sulfide gas enters the tank body 14 and reacts with ferric chloride entering from the ferric chloride solution inlet under the action of the stirring paddle 17 to produce ferrous chloride and sulfur. The resulting mixed solution flows out of the tank body 14 through the mixed solution overflow port, and the solution obtained after solid-liquid separation is fed into the direct electrolysis device or the indirect conversion device 13.

[0108] For example, the iron sulfide solution obtained by the indirect conversion device 13 is returned to the tank body 14 through the solution inlet for recycling.

[0109] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0110] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0111] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may alter, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing hydrogen from gypsum, characterized in that: include: Step S1: Gypsum and a reducing agent are mixed to form balls, and then subjected to negative pressure roasting reaction to produce calcium sulfide and carbon monoxide; Step S2: Calcium sulfide undergoes hydrolysis reaction to produce hydrogen sulfide gas and calcium hydroxide; Step S3: hydrogen sulfide gas undergoes direct electrolysis reaction or indirect conversion reaction to obtain elemental sulfur and hydrogen; In step S1, when the reducing agent is carbon powder, the reaction temperature of the negative pressure roasting is controlled to directionally generate carbon monoxide, and then the carbon monoxide is used as a heat source for the negative pressure roasting reaction; Alternatively, in step S1, when the reducing agent is carbon monoxide, carbon dioxide is produced by the negative pressure roasting reaction, and the carbon dioxide produced by the negative pressure roasting in step S1 is captured by the calcium hydroxide produced by the calcium sulfide hydrolysis reaction in step S2 to prepare a light calcium carbonate product; The method for preparing hydrogen from gypsum is carried out in a gypsum hydrogen preparation system.

2. The method for preparing hydrogen from gypsum according to claim 1, wherein: In step S1, the reducing agent includes carbon powder or carbon monoxide; Wherein, the carbon powder includes any one of coal, coke, petroleum coke or biomass; In step S1, the gypsum includes one or more combinations of desulfurized gypsum, phosphogypsum or fluorinated gypsum; When the reducing agent is carbon monoxide, the ventilation rate of carbon monoxide is 0.5L / min to 50L / min.

3. The method for preparing hydrogen from gypsum according to claim 1, wherein: In step S1, the conditions for mixing gypsum and reducing agent to make balls are: Gypsum and reducing agent are mixed in a mass ratio of 3:1 to 10:1 to prepare pellets of 6 mm to 15 mm; The pellet drying temperature is 60℃~200℃; The pellet drying time is 2h to 24h.

4. The method for preparing hydrogen from gypsum according to claim 1, wherein: In step S1, the conditions for negative pressure roasting are: The roasting pressure is 0.01 to 1 atmosphere; The calcination temperature is 600℃~1000℃; The roasting time is 10 minutes to 180 minutes.

5. The method for preparing hydrogen from gypsum according to claim 1, wherein: In step S2, the calcium sulfide hydrolysis reaction conditions are: The ratio of the volume of water to the mass of calcium sulfide is 0.5mL~10mL:1g; The hydrolysis temperature is 20℃~95℃; The hydrolysis time is 1 min to 120 min.

6. The method for preparing hydrogen from gypsum according to claim 1, wherein: In step S3, the catalyst for the direct electrolysis reaction of hydrogen sulfide gas is any one or more of transition metal sulfides: MoS2, WS, FeS, CoS, Pt / C or Pd / C; The reaction conditions of the direct electrolysis reaction are: electrolysis temperature of 50° C. to 80° C., electrolysis voltage of 0.5V to 6V, and current efficiency greater than 90%.

7. The method for preparing hydrogen from gypsum according to claim 1, wherein: In step S3, the indirect conversion reaction of hydrogen sulfide gas includes: Step S31: H2S gas reacts with FeCl3 to produce ferrous chloride, hydrochloric acid and elemental sulfur; Step S32: ferrous chloride and hydrochloric acid aqueous solution are subjected to electrolysis reaction to produce ferric chloride and hydrogen; Wherein, the reaction conditions of step S31 are: The reaction temperature is 25°C to 90°C, the H2S gas introduction rate is 0.5L / min to 20L / min, the FeCl3 concentration is 0.5mol / L to 10.0mol / L, the solution pH is 1.0 to 6.0, the reaction time is 30min to 90min, and the H2S gas absorption efficiency reaches more than 99%; The electrolysis reaction conditions of step S32 are: electrolysis voltage of 1.5V to 8.0V, electrolysis time of 1h to 6h, electrolysis temperature of 25°C to 640°C, pH value of 1.0 to 3.0, Cl- concentration of 2.0mol / L to 10.0mol / L, and current efficiency greater than 90%.

8. The method for preparing hydrogen from gypsum according to claim 1, wherein: The gypsum hydrogen preparation system includes: A negative pressure roasting furnace, comprising a furnace body; The furnace body is provided with a feed inlet on the top and a discharge outlet on the bottom. The furnace body is also provided with a plurality of thermocouples to detect the temperature inside the furnace body. The furnace body gradually tilts downward from the direction of feeding to the direction of discharging; a vacuum pump, arranged on a side wall of the furnace body; A hydrolysis unit, including a hydrolysis furnace; The hydrolysis furnace is connected to the discharge port of the negative pressure roasting furnace; A spray nozzle is provided on the top wall of the hydrolysis furnace; A conveyor belt is arranged on the bottom wall of the hydrolysis furnace and corresponds to the position of the spray nozzle; A heating element is arranged inside the conveyor belt; a hydrogen sulfide gas outlet, arranged on the side wall of the hydrolysis furnace and close to the end of the conveyor belt; A direct electrolysis device or an indirect conversion device is arranged on the side of the hydrolysis furnace and is connected to the hydrogen sulfide gas outlet.

9. The method for preparing hydrogen from gypsum according to claim 8, wherein: The indirect conversion device comprises: The tank body, the solution inlet and the mixed liquid overflow port are both arranged on the side wall of the tank body, and the position of the solution inlet is lower than the mixed liquid overflow port; Zeolite filler, arranged at the bottom layer inside the tank; an air inlet, disposed below the tank body and connected to the zeolite filler; A stirring paddle is inserted into the tank body.

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