33 results about "Calcium sulfide" patented technology

The invention discloses a green roasting method for recycling desulfurized gypsum, and belongs to the technical field of solid waste recycling. According to the process disclosed by the invention, the desulfurized gypsum solid waste rich in calcium sulfate is used for replacing part or all of sulfate to be mixed with lepidolite for roasting reaction, and components such as calcium carbonate and calcium sulfite contained in the desulfurized gypsum are utilized by controlling the step-by-step heating rate and the roasting temperature; under specific roasting process conditions, calcium oxide and calcium sulfide generated through self-reaction serve as purifying agents and react with fluorine and thallium to form stable calcium fluoride and thallium sulfide precipitates, fluorine and thallium are fixed in the high-temperature roasting stage, the pressure of follow-up flue gas treatment and wastewater treatment is effectively reduced through self-purification, and environmental pollution is reduced.

The application discloses a hydrogen fuel engine oil composite additive composition, which comprises 3.0-5.0% high-alkali-value magnesium sulfonate, 12.0-20.0% low-alkali-value calcium sulfonate, 3.0-4.0% high-alkali-value calcium sulfide alkyl phenol, 2.0-5.0% amine type antioxidant, 2.0-5.0% phenol type antioxidant, 2.0-5.0% alpha-naphthylamine, 1.5-3.0% dibutyl dithiocarbamic acid ester, 1.5-3.0% anti-wear agent, 0.2-0.5% fatty amide, and the rest is ashless dispersant. The application further discloses a hydrogen fuel engine oil composition, which comprises 14.4-15.5% composite additive composition, 7.0-9.0% tackifier, 0.2-0.5% pour point depressant, and the rest is base oil. The composite additive improves the demulsification performance of the hydrogen fuel engine oil under high-temperature and high-pressure conditions, and further improves the water separation property and other comprehensive use performances of the oil product.

The invention provides an ex-situ chemical reduction stabilization remediation method for hexavalent chromium contaminated soil, which comprises the following steps: collecting soil from a contaminated land parcel, airing, crushing, screening and uniformly mixing to obtain pretreated contaminated soil; testing the content of hexavalent chromium in the polluted soil, then adding solid calcium polysulfide into the polluted soil according to the molar ratio of the solid calcium polysulfide to the hexavalent chromium of (12-16): 1, and uniformly mixing; and after uniform mixing, spraying water into the polluted soil according to 15-20% of the total solid mass, and carrying out static maintenance. According to the stable remediation method, the remediation target value (the hexavalent chromium in the soil is lower than 5.7 mg / kg) is achieved on the third day of maintenance, the remediation effect is continuous and good, and rebounding does not occur.

The invention provides application of water-soluble inorganic sulfide in improvement of plant salt stress resistance and / or improvement of saline-alkali soil, relates to the technical field of agriculture, and provides application of water-soluble inorganic sulfide in improvement of plant salt stress resistance and / or improvement of saline-alkali soil. The water-soluble inorganic sulfide is selected from at least one of potassium sulfide, ammonium sulfide and calcium polysulfide, the potassium sulfide, the ammonium sulfide and the calcium polysulfide can effectively improve the germination ability of plant seeds under salt stress, and the calcium polysulfide can effectively improve the plant antioxidant system activity and the plant photosynthesis efficiency; the survival rate and the growth performance of the plants under salt stress are effectively improved; the water-soluble inorganic sulfide solution can effectively reduce the EC value of the saline-alkali soil, so that the germination rate of plant seeds in the saline-alkali soil is effectively increased, and the saline-alkali soil is effectively improved. Therefore, the application provided by the invention is of great significance in fully utilizing saline-alkali land resources and improving the crop yield.

The invention relates to the technical field of ceramic materials, in particular to calcium lanthanum sulfide transparent ceramic powder and a preparation method and application thereof.The preparation method comprises the following steps that CaS powder and La2S3 powder are placed in a sealed quartz container, the raw materials are mixed to be uniform in an ultrasonic rotation mode, high-temperature swing sintering is conducted in a vacuum state, then slow cooling is conducted to the room temperature, and the calcium lanthanum sulfide transparent ceramic powder is obtained. And grinding to obtain the CaLa2S4 powder. According to the preparation method of the CaLa2S4 powder, the problem of sulfur loss can be avoided in a limited mode, toxic and dangerous gas of hydrogen sulfide or carbon disulfide is not used, the preparation method is safe, efficient, easy to operate, low in raw material cost and suitable for industrial batch production, and further development of the infrared transparent ceramic application technology is expected to be promoted.

The application pertains to processes for producing components such as an alkali hydroxide and a carboxylic acid. The processes generally comprise reacting a component comprising calcium carbonate, or calcium sulfide, or calcium hydroxide, or calcium oxide, or calcium weak acid, or any combination thereof with a component comprising a carboxylic acid to form a component comprising a calcium carboxylate and a component comprising carbon dioxide, or hydrogen sulfide, or water, or any combination thereof. At least a portion of the formed calcium carboxylate is reacted with a component comprising an alkali sulfate to form a component comprising an alkali carboxylate and a component comprising calcium sulfate. At least a portion of the formed alkali carboxylate is electrochemically reacted to form a component comprising an alkali hydroxide and a component comprising a carboxylic acid.

This invention provides a method for preparing hydrogen and sulfur from solid waste gypsum through reduction and acidification in a cement kiln, relating to the field of solid waste disposal technology. The method involves targeted local modifications to a novel dry-process cement clinker rotary kiln production system. Using desulfurized gypsum, phosphogypsum, and other solid waste gypsum as raw materials, the gypsum is crushed, ground, preheated, and dehydrated. Then, it is calcined in a modified three-lobe gravity semi-suspended rotary kiln at 800–1100℃ in a reducing atmosphere to generate high-purity calcium sulfide. After sealed cooling, the calcium sulfide reacts with byproduct hydrochloric acid to produce high-purity hydrogen sulfide. The hydrogen sulfide is then used to co-produce hydrogen and sulfur via a medium-assisted electrochemical decomposition method, or high-purity sulfur can be directly prepared using the Claus process. This invention achieves full resource utilization of solid waste gypsum using existing cement kiln equipment, requires minimal modification, has low investment costs, and enables the cascade utilization of CO waste gas and kiln waste heat, reducing overall energy consumption by more than 30% compared to traditional processes.

The application relates to the field of calcium sulfide, in particular to a kind of calcium sulfide prepared from biomass waste and reduced gypsum solid waste, a preparation method and application.The method comprises the following steps: raw material pretreatment, batching and mixing: the gypsum powder and biomass powder are mechanically mixed according to the mass ratio 10:(10-50) to obtain a reaction precursor; one-step reduction reaction: the reaction precursor is placed in a reactor in an inert atmosphere or a closed environment, heated to 800-1050 DEG C at a heating rate of 5-20 DEG C / min, and kept at the temperature for 0.5-2 hours; product treatment: after the reaction is completed, the reaction product is taken out and crushed and ground to obtain the final product under inert atmosphere cooling to room temperature.The product has a porous loose structure, a high specific surface area (actually up to 50-200 m 2 / g), and can simultaneously remove heavy metals (such as Pb 2+ , Cd 2+ ) in wastewater treatment, soil remediation and other scenarios, realizing the synergistic effect of "adsorption-precipitation".

The application provides a method for preparing metallic arsenic and sulfur fixation by calcium oxide assisted carbothermic reduction of arsenic sulfide residue, comprising: providing a reaction container with a high-temperature zone and a low-temperature zone in communication; reacting arsenic sulfide residue, calcium oxide and a carbon source in the high-temperature zone; the molar ratio of the calcium oxide to arsenic sulfide in the arsenic sulfide residue is not less than 2; the molar ratio of carbon in the carbon source to arsenic sulfide in the arsenic sulfide residue is not less than 2; the temperature of the high-temperature zone is 750-900 DEG C, the temperature of the low-temperature zone is 650-750 DEG C, and the temperature of the high-temperature zone is higher than that of the low-temperature zone; during the reaction, the generated metallic arsenic transfers to the low-temperature zone, and the generated calcium sulfide stays in the high-temperature zone. The application recovers metallic arsenic and fixes sulfur from arsenic sulfide residue through one-step smelting, avoids the generation of sulfur-containing gas, and improves the recovery rate of the metallic arsenic product.

This invention discloses a method for producing calcium oxide by reducing the decomposition temperature of phosphogypsum under hydrogen and steam conditions. In this method, after removing silica impurities from the phosphogypsum by acid washing with sulfuric acid solution, the phosphogypsum is reduced and decomposed under a hydrogen atmosphere to obtain calcium sulfide solid product. Subsequently, the hydrogen is turned off and steam is introduced, and the reaction continues under these conditions to produce high-purity calcium oxide. The exhaust gas generated during this process can be dried and used as feed gas for acid production. This method uses pretreated phosphogypsum as raw material to prepare high-purity calcium oxide, simultaneously achieving phosphogypsum reduction and sulfur resource recycling. It lowers the temperature for producing calcium oxide from phosphogypsum, significantly reducing energy consumption and eliminating carbon dioxide emissions compared to existing processes. This is a key technology for the green and sustainable development of phosphogypsum. Under these process conditions, phosphogypsum can be decomposed at a low temperature of 800℃ to obtain high-purity calcium oxide, achieving a calcium hydroxide yield of over 97.22%.

The utility model relates to the technical field of gas extraction, in particular to a gas extraction pipe with a concentration detection function, which comprises an extraction pipe body and a deacidification assembly, and the deacidification assembly comprises a gas inlet pipe, a connector, a treatment box and a deacidification plate. The gas inlet pipe, the connector and the treatment box are all made of stainless steel materials, gas and hydrogen sulfide are guided into the treatment box through the gas inlet pipe, the hydrogen sulfide is treated through quicklime on the deacidification plate to generate calcium sulfide and water, and therefore the hydrogen sulfide accompanying in the gas is removed, the gas is introduced into the extraction pipe body through the treatment box, and the gas is extracted from the extraction pipe body. Water generated by deacidification drips into the water collecting tank at the bottom of the treatment box to be collected, after a period of time, a worker takes down the water collecting tank to pour out water in the water collecting tank and takes out the deacidification plate to replace quick lime in the deacidification plate, operation is convenient and fast, the deacidification assembly is used for pretreating extracted gas, removing accompanying hydrogen sulfide in the gas, and the gas treatment efficiency is improved. And the extraction pipe body is protected from being eroded.

This invention discloses a sulfide solid electrolyte, its preparation method, and a battery, belonging to the field of battery material technology. The preparation of the sulfide solid electrolyte includes: thermally reacting the raw materials for the preparation of the sulfide solid electrolyte; tangentially filtering the material obtained after the thermal reaction; and spray-drying the solid obtained from the tangential flow filtration. The raw materials include a first precursor, a second precursor, and a solvent. The first precursor includes lithium sulfide, and the second precursor includes at least one selected from phosphorus pentasulfide, silicon sulfide, germanium sulfide, tin sulfide, sodium sulfide, potassium sulfide, ammonium sulfide, calcium sulfide, and arsenic sulfide. This method has a relatively simple process flow and operation, low energy consumption and cost, and high production efficiency, making it suitable for industrial production. The sulfide solid electrolyte obtained in this way is relatively soft, making it easier to contact the positive and negative electrodes under extrusion conditions during the further preparation of the battery, improving density, thereby facilitating electron transport and reducing losses.

The invention belongs to the technical field of water treatment, and particularly relates to a biochar wetland desulfurization and denitrification system based on a rotary reactor. The system comprises a rotary sulfate reduction unit and a charcoal-based artificial wetland unit which are connected in series, a rotary filler device, a Ca-charcoal complex layer and a granular calcium sulfide solid layer are arranged in the rotary unit, the concentration of SO4 < 2-> / S2 <-> is monitored in real time through an ion selective electrode, and filler lifting and wastewater backflow are linked; and the wetland unit adopts a charcoal-sand mixed matrix layer to plant reeds. And adsorbing and reducing SO4 < 2-> by the wastewater through the rotating unit to generate CaSO4 precipitate, and releasing S < 2-> to enter the wetland to drive sulfur autotrophic denitrification. The removal rate of SO4 < 2-> in high-sulfate and low-carbon-nitrogen-ratio wastewater is greater than 84%, the removal rate of NO3 <-> is greater than 66%, the COD effluent is less than 20mg / L, and the problems of high water mineralization degree and nitrogen removal inhibition are solved.

The application relates to a system for preparing valuable products by sectional fluid roasting of gypsum and a method thereof, and belongs to the field of comprehensive utilization of gypsum. The system comprises a feeding-dedusting system, a first roasting system, a second roasting system and a gas-solid separation-treatment system; the feeding-dedusting system, the first roasting system, the second roasting system and the gas-solid separation-treatment system are sequentially connected. The system is suitable for three different processes of gypsum -> beta-hemihydrate gypsum -> anhydrite, gypsum -> anhydrite -> calcium oxide + sulfur dioxide and gypsum -> anhydrite -> calcium sulfide by roasting different gases. Compared with traditional rotary kiln and shaft furnace roasting, the system realizes efficient mass and heat transfer of gas and solid. In the roasting process, sectional roasting technology is adopted, the roasting atmosphere (air, coal gas and hydrogen), the gas amount and the roasting temperature of the second roasting system are finely controlled, and the phase transformation of gypsum is accurately controlled. Compared with other roasting furnaces, the system has the advantages of low energy consumption, small floor area and high running rate.

The invention belongs to the technical field of agricultural light conversion materials, and discloses a modified calcium europium sulfide light conversion material, a preparation method thereof and an agricultural light conversion composite film containing the modified calcium europium sulfide light conversion material. The preparation method of the modified calcium-europium sulfide light conversion material comprises the following steps: dispersing CaS: Eu < 2 + > in a first alcohol solvent, then adding water, tetrafunctional alkoxy silane and a pH regulator, and carrying out a primary reaction; after the reaction is finished, centrifuging to obtain a light conversion material coated with a silicon dioxide layer; dispersing the light conversion material coated with the silicon dioxide layer in a second alcohol solvent, adding a silane coupling agent with a long-chain hydrophobic group, carrying out a secondary reaction, and centrifuging and washing after the reaction is finished, so as to obtain the modified calcium europium sulfide light conversion material. The modified calcium-europium sulfide light conversion material provided by the invention is high in chemical stability, the water and oxygen permeability can be remarkably reduced, and the stability of an agricultural light conversion composite film prepared from the modified calcium-europium sulfide light conversion material is remarkably improved in a damp-heat aging test.

This invention belongs to the field of solid waste resource utilization technology, and discloses a method for preparing composite porous carbon materials using biomass waste residue and phosphogypsum, and its application. The biomass waste residue is washed, dried, crushed, and carbonized to obtain biochar. The biochar is then uniformly mixed with phosphogypsum to obtain a biochar-phosphogypsum composite porous carbon material. The composite porous carbon material is then subjected to a gasification reaction under a carbon dioxide atmosphere to generate high-calorific-value combustible carbon monoxide and high-value-added calcium sulfide. This invention features a simple process and achieves the synergistic high-value utilization of two typical solid wastes: biomass waste residue and phosphogypsum. It not only provides an effective way to utilize organic solid waste and phosphogypsum, but also efficiently converts them into clean energy and high-value by-products, resulting in significant environmental and economic benefits.

A method of producing cement clinker from a raw material (3) comprising a source of calcium sulfate, comprising - a first step of reducing a first portion of the calcium sulfate in the presence of a reducing agent (6) in a reduction reactor (1) to obtain calcium sulfide, wherein the reducing agent comprises hydrogen, and subsequently - a second step of introducing the calcium sulfide and a second portion of the calcium sulfate into a clinkerization reactor (2), reacting them with each other to obtain calcium oxide and sulfur dioxide, and calcining the calcium oxide in the presence of silica, alumina, and iron oxide containing materials to obtain cement clinker.

The invention relates to a method for measuring the conversion rate of reducing calcium sulfate into calcium sulfide, and belongs to the technical field of analysis and detection. Adding calcium sulfate with the mass of m1 and a roasted product of a carbon reduction reaction into a sealed reactor; adding deionized water into the sealed reactor, and continuously introducing nitrogen; excessive phosphoric acid is added into the dropping funnel, and the overall mass is m2; phosphoric acid is slowly dropwise added into the sealed reaction container, and after the reaction is completed, the overall mass is m3; and calculating the conversion rate of reducing calcium sulfate into calcium sulfide through a formula. The method has the advantages of being high in operability, accurate in analysis and rapid in detection.

The application discloses a method for preparing a denitrification denitrogenation and dephosphorization agent by carbon reduction of waste gypsum and an application method thereof, and belongs to the technical field of wastewater treatment. The method comprises the following steps: carrying out a high-temperature reduction reaction on waste gypsum and coke to obtain a calcium sulfide product; dissolving the calcium sulfide with water and filtering to remove insoluble substances; and mixing the liquid with a waste incineration fly ash washing liquid to obtain the denitrification denitrogenation and dephosphorization agent. The denitrification denitrogenation and dephosphorization agent is added into water in a denitrification denitrogenation reactor by using a metering pump, the calcium sulfide serves as an electron donor for sulfur autotrophic denitrification and a pH neutralizer, and the calcium ions serve as a precipitant for dephosphorization, so that denitrogenation of wastewater or simultaneous denitrogenation and dephosphorization is realized.

The present invention discloses a composite biomass carbon source and sulfur source denitrifying agent, as well as its preparation and application. The denitrifying agent comprises a biomass carbon source composed of crude glycerol and growth factors with a COD of 1.1 million to 1.2 million mg / L, and calcium polysulfide, prepared by boiling quicklime, sulfur, and water in a mass ratio of 1:(2-4):(10-12) and a COD of 600,000 to 700,000 mg / L. This denitrifying agent couples heterotrophic denitrification with autotrophic denitrification, combining their respective advantages to achieve efficient denitrification in water pollution control. Under a COD / TN ratio of 1, both the nitrate reduction rate and total nitrogen removal efficiency can reach over 90%. Furthermore, no ammonium nitrogen and nitrite accumulation is observed in the treated water, and sulfate generation is approximately 70 mg / L, both meeting national surface water discharge standards. The composite biomass carbon source and sulfur source denitrifying agent of the present invention is a biodenitrifying material that is non-secondary-pollution, environmentally friendly, low-cost, and easy to prepare.

This invention discloses a low-temperature decomposition method for phosphogypsum that requires no carbon reducing agent or additives and produces pure products. This method eliminates the need for pretreatment of the phosphogypsum. By introducing a hydrogen-containing gas at 700-800°C with a molar ratio of 0.45-10.69:1 to calcium sulfate dihydrate in the phosphogypsum for 45-60 minutes, 100% decomposition of calcium sulfate in the phosphogypsum can be achieved without mechanical vibration. The solid product, except for silica impurities, consists mainly of high-purity calcium sulfide. This method enables highly efficient decomposition of phosphogypsum without the introduction of carbon reducing agents or the addition of accelerators. The pure products are easy to separate and produce zero carbon emissions. This method has positive significance for the high-value conversion of bulk phosphogypsum solid waste and the coupled development of hydrogen metallurgy technology.

The application pertains to processes for producing components such as an alkali hydroxide and a carboxylic acid. The processes generally comprise reacting a component comprising calcium carbonate, or calcium sulfide, or calcium hydroxide, or calcium oxide, or calcium weak acid, or any combination thereof with a component comprising a carboxylic acid to form a component comprising a calcium carboxylate and a component comprising carbon dioxide, or hydrogen sulfide, or water, or any combination thereof. At least a portion of the formed calcium carboxylate is reacted with a component comprising an alkali sulfate to form a component comprising an alkali carboxylate and a component comprising calcium sulfate. At least a portion of the formed alkali carboxylate is electrochemically reacted to form a component comprising an alkali hydroxide and a component comprising a carboxylic acid.

The present application relates to the technical field of lubricating oil, and provides a marine propeller shaft oil composition, a preparation method and application thereof.The marine propeller shaft oil composition comprises 1-5 parts by weight of a detergent, 1-5 parts by weight of a dispersant, 1-5 parts by weight of an antioxidant, 0.01-1 parts by weight of a pour point depressant, 0.01-0.5 parts by weight of an antifoaming agent and 83.5-96.98 parts by weight of a base oil; the detergent comprises high-alkaline value synthetic calcium sulfonate and high-alkaline value calcium sulfide alkyl phenol.The marine propeller shaft oil composition provided by the present application has excellent water separation and anti-emulsification performance, and still has good comprehensive performance in a water-containing environment, and fully meets the working condition requirements of a marine propeller shaft.

The invention provides a combined chemical removal agent and application. The combined chemical removal agent is composed of sodium sulfide, sodium hydrosulfide, calcium sulfide and activated carbon particles. According to the method, efficient separation flotation of the copper-molybdenum ore is achieved, the influence of reagents in the copper-molybdenum bulk flotation stage on rear-end copper-molybdenum separation is effectively avoided, and losses of copper and molybdenum resources are reduced; by the adoption of the combined reagent, the molybdenum grade can be improved by 4-6%, and the molybdenum recovery rate can be improved by 6-8% or above.

The present application belongs to the technical field of water treatment, and particularly relates to a biochar wetland desulfurization and denitrification system based on a rotating reactor. The system comprises a rotating sulfate-reducing unit and a biochar-based artificial wetland unit connected in series. The rotating unit is internally provided with rotatable filler devices, Ca-bacteria charcoal composite layers and granular calcium sulfide solid layers. The concentration of SO4 2‑ / is monitored in real time by an ion selective electrode, and the filler lifting and wastewater backflow are linked. 2‑ The wetland unit is provided with a biochar-sand mixed substrate layer for planting reeds. The wastewater is subjected to adsorption and reduction of SO4 2‑ by the rotating unit to generate CaSO4 precipitates and release S 2‑ into the wetland to drive sulfur autotrophic denitrification. The system can achieve a SO4 2‑ removal rate of more than 84%, a NO3 ‑ removal rate of more than 66%, and a COD effluent of less than 20 mg / L, thereby solving the problems of high water quality mineralization and inhibited denitrification.

The application provides a lime causticization regeneration process of printing and dyeing wastewater deodorization absorption liquid, which comprises the following steps: pretreating the printing and dyeing wastewater deodorization absorption liquid to be regenerated, removing suspended solids and mechanical impurities, and obtaining clear waste lye; reacting the pretreated clear waste lye with calcium hydroxide in a causticization reactor, converting sodium carbonate into calcium carbonate precipitate, and converting sulfide into calcium sulfide; performing solid-liquid separation on the mixed liquid after the reaction is completed; the solid phase obtained by the separation is mainly calcium carbonate and contains calcium sulfide, and the solid phase is used for elemental sulfur recovery or as a building material raw material; the liquid phase obtained by the separation is sodium hydroxide regeneration liquid, which is reused in a printing and dyeing wastewater deodorization system or reused after being adjusted in concentration. The application regenerates NaOH by causticization reaction of waste lye, reduces the cost of reagents and energy consumption, and converts Na2CO3 and Na2S in the waste lye into reusable CaS precipitate, which creates conditions for sulfur resource recovery.

The invention discloses a high-temperature profile control plugging agent for a steam injection well. The high-temperature profile control plugging agent for the steam injection well comprises the following components in percentage by mass: 5-10% of aluminum sulfate; 10%-15% of calcium sulfide; 5%-10% of bentonite; and the balance water. The preparation method comprises the following steps: injecting water into a batching tank, starting a stirrer, sequentially adding aluminum sulfate, calcium sulfide and bentonite, and stirring at room temperature, so that the bentonite is fully hydrated and dispersed, and the aluminum sulfate and calcium sulfide powder is uniformly dispersed in the water. The high-temperature plugging control plugging agent for the steam injection well is an inorganic cementing material, has relatively long gelation time, good construction safety, pumping performance, proper structural strength, relatively good high temperature resistance and other properties, has the properties required by high-temperature plugging control and channeling sealing materials, and has good adaptability in plugging control and channeling sealing of heavy oil thermal recovery and steam injection wells.

The invention discloses a preparation method of homogeneous up-conversion self-excitation infrared light-emitting particles. The light-emitting particles comprise microcrystal particles with calcium sulfide as a core matrix material and up-conversion light-emitting nanoparticles with calcium sulfide as a matrix material, the homogeneous calcium sulfide microcrystal particles and nano-particles form up-conversion self-excited infrared light-emitting particles with core-shell structures through a potassium silicate solution; after drying, a fluidized bed chemical vapor deposition technology is used, and the surfaces of the up-conversion self-excitation infrared light-emitting particles are coated with aluminum oxide moisture-proof layers, so that the up-conversion self-excitation infrared light-emitting particles have good moisture resistance; near-infrared light is used for irradiating the nano-particles, and the continuously luminous up-conversion nano-particles excite the microcrystal particles to emit light at the same time, so that the luminescence attenuation of the microcrystal particles which excite luminescence is made up, and the continuous luminescence and sensitivity of the infrared luminous particles are improved.

This invention provides a method for producing calcium hydroxide by low-temperature decomposition of phosphogypsum coupled with hydrolysis. In this method, phosphogypsum is used as raw material. After simple drying and sieving pretreatment, it is reduced with hydrogen to obtain a solid product mainly composed of calcium sulfide. This product is then used as raw material in a next stage for hydrolysis in a reactor to obtain high-purity calcium hydroxide. This method uses pretreated phosphogypsum as raw material, hydrogen as the reducing gas, and a low-temperature hydrolysis reaction (60~150 °C). Both stages lower the temperature for producing calcium hydroxide from phosphogypsum, significantly reducing the reaction temperature and energy consumption. This process produces no carbon dioxide emissions and further reduces energy consumption, enabling energy conservation and emission reduction in the phosphogypsum decomposition process. Under these conditions, phosphogypsum can be decomposed below 800 °C and then hydrolyzed at 150 °C, achieving a calcium hydroxide yield of over 98%.

The application provides a method for preparing metallic arsenic and sulfur fixation by calcium oxide assisted carbothermic reduction of arsenic sulfide residue, comprising: providing a reaction container with a high-temperature zone and a low-temperature zone in communication; reacting arsenic sulfide residue, calcium oxide and a carbon source in the high-temperature zone; the molar ratio of the calcium oxide to arsenic sulfide in the arsenic sulfide residue is not less than 2; the molar ratio of carbon in the carbon source to arsenic sulfide in the arsenic sulfide residue is not less than 2; the temperature of the high-temperature zone is 750-900 DEG C, the temperature of the low-temperature zone is 650-750 DEG C, and the temperature of the high-temperature zone is higher than that of the low-temperature zone; during the reaction, the generated metallic arsenic transfers to the low-temperature zone, and the generated calcium sulfide stays in the high-temperature zone. The application recovers metallic arsenic and fixes sulfur from arsenic sulfide residue through one-step smelting, avoids the generation of sulfur-containing gas, and improves the recovery rate of the metallic arsenic product.