Method and application of preparing calcium polysulfide using desulfurization intermediates from power plants

Abstract

The present invention relates to the field of post-processing and purification of sulfur oxides, and discloses a method and application for preparing calcium polysulfide using a desulfurization intermediate product from a power plant. The method comprises the following steps: (1) adjusting the pH of the desulfurization intermediate product from the power plant, and then mixing the adjusted product with a reducing agent, a catalyst, an auxiliary agent, and a stabilizer to obtain a slurry; (2) subjecting the slurry to a catalytic reduction reaction to obtain a powder product; (3) boiling and crystallizing the powder product to obtain calcium polysulfide; wherein the desulfurization intermediate product from the power plant contains calcium sulfite. The method provided by the present invention has the characteristics of a short process flow, a small amount of raw materials, a low reaction temperature, and a fast reaction rate. It can also reduce desulfurization costs and reduce solid waste in power plants, and is therefore of great practical value. Moreover, the calcium polysulfide product prepared by the method provided by the present invention has a high recovery rate.

Description

Technical Field

[0001] The present invention relates to the field of post-processing and purification of sulfur oxides, and in particular to a method and application of preparing calcium polysulfide by utilizing desulfurization intermediates from power plants. Background Art

[0002] The large amount of desulfurization gypsum, a byproduct of flue gas desulfurization in coal-fired power plants, is easily discharged and causes secondary pollution. Therefore, there is an urgent need to provide a method for the comprehensive utilization of flue gas desulfurization byproducts, especially desulfurization gypsum.

[0003] CN111233020A discloses a system for preparing calcium oxide and sulfur using gypsum, an industrial byproduct. The system includes a feed unit, a reaction unit, and a discharge unit. The feed unit includes a solid feed unit and a gas feed unit, each independently connected to the reaction unit's feed port. The discharge unit includes a calcium oxide discharge unit and a sulfur discharge unit, each independently connected to the reaction unit's discharge port. The core process of the system provided by this invention is that superheated steam reacts with gypsum, an industrial byproduct, to produce calcium oxide, hydrogen sulfide, and sulfur dioxide. The hydrogen sulfide and sulfur dioxide further react to produce sulfur. The prepared sulfur can be directly used as a raw material for sulfur-based acid production. The calcium oxide is filtered to obtain an active calcium oxide product, thus realizing the resource utilization of the industrial byproduct gypsum. This process utilizes industrial byproduct gypsum to prepare sulfur and calcium oxide, which can realize the resource utilization of industrial byproduct gypsum and provide a new direction for the comprehensive utilization of gypsum. However, this process requires dehydration and oxidation of gypsum, and the temperature of the reduction and calcination process is as high as 850°C, so the reaction process has high energy consumption; in addition, the process will produce harmful gas hydrogen sulfide, which has high requirements for equipment; on the other hand, the target product of this invention is sulfur, which has no obvious effect on power plants. Summary of the Invention

[0004] The present invention aims to overcome the problems of large amounts of desulfurization gypsum accumulation and high operating costs of power plant desulfurization in the prior art by providing a method and application for preparing calcium polysulfide using desulfurization intermediates from power plants. The calcium polysulfide product produced using the method provided by the present invention has a high recovery rate, a short process flow, low raw material usage, low reaction temperature, and a fast reaction rate. This method can also reduce desulfurization costs and solid waste in power plants, thus being highly practical.

[0005] In order to achieve the above object, the first aspect of the present invention provides a method for preparing calcium polysulfide using desulfurization intermediates from a power plant, comprising the following steps:

[0006] (1) adjusting the pH of a desulfurization intermediate product from a power plant, and then mixing the resulting adjusted product with a reducing agent, a catalyst, an auxiliary agent, and a stabilizer to obtain a slurry;

[0007] (2) subjecting the slurry to a catalytic reduction reaction to obtain a powder product;

[0008] (3) boiling and crystallizing the powder product to obtain calcium polysulfide;

[0009] Wherein, the desulfurization intermediate product of the power plant contains calcium sulfite.

[0010] The second aspect of the present invention provides calcium polysulfide prepared by the method described in the first aspect.

[0011] The third aspect of the present invention provides a use of the calcium polysulfide described in the second aspect as a heavy metal scavenger for desulfurization wastewater in power plants, a soil additive, and a pesticide.

[0012] Through the above technical solution, the present invention can achieve the following beneficial effects:

[0013] (1) The method of the present invention uses the desulfurization intermediate product as a raw material, eliminating the oxidation reaction and the concentrated gypsum production system (or concentration system) in the desulfurization process, thereby saving the desulfurization operation cost of the power plant;

[0014] (2) The calcium polysulfide product prepared by the method provided by the present invention can be used as a heavy metal scavenger for desulfurization wastewater (mine wastewater) in power plants, which not only solves the problem of desulfurization gypsum accumulation but also saves the cost of desulfurization wastewater treatment;

[0015] (3) The method of the present invention effectively reduces the reaction temperature during the reduction process by utilizing catalytic reduction technology, thereby saving energy consumption;

[0016] (4) The method of the present invention reduces the desulfurization intermediates of the power plant instead of oxidizing them. Since the solubility of calcium sulfite is lower than that of calcium sulfate, the calcium sulfite removal rate is higher, the sulfur and calcium contents in the filtered water are lower, the water quality is better, and it is more conducive to the treatment of desulfurization wastewater;

[0017] (5) The calcium polysulfide product prepared by the method provided by the present invention has a wide range of uses and can be used as a water treatment agent, a soil additive, and an insecticide. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention provides a schematic flow diagram of the process for preparing calcium polysulfide from desulfurization intermediates in power plants. DETAILED DESCRIPTION

[0019] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0020] The first aspect of the present invention provides a method for preparing calcium polysulfide using desulfurization intermediates from power plants, such as Figure 1 As shown, the following steps are included:

[0021] (1) adjusting the pH of a desulfurization intermediate product from a power plant, and then mixing the resulting adjusted product with a reducing agent, a catalyst, an auxiliary agent, and a stabilizer to obtain a slurry;

[0022] (2) subjecting the slurry to a catalytic reduction reaction to obtain a powder product;

[0023] (3) boiling and crystallizing the powder product to obtain calcium polysulfide;

[0024] Wherein, the desulfurization intermediate product of the power plant contains calcium sulfite.

[0025] The present invention can reduce calcium sulfite in the desulfurization intermediate product of a power plant into calcium sulfide through a catalytic reduction reaction, convert the calcium sulfide into a calcium polysulfide solution through water boiling, and further obtain a calcium polysulfide solid product through crystallization.

[0026] In some embodiments of the present invention, the power plant desulfurization intermediate product is the slurry discharged from the desulfurization tower, that is, the slurry before entering the oxidation pond during the desulfurization process. The main component of the power plant desulfurization intermediate product is calcium sulfite, and it also includes small amounts of calcium sulfate, sulfurous acid, and water.

[0027] In some embodiments of the present invention, to prevent the hydrolysis of calcium sulfite and to convert some of the dissolved SO₂ in the slurry discharged from the desulfurization tower into calcium sulfite, the pH of the power plant desulfurization intermediate product is adjusted to a weak alkaline state. Preferably, the pH of the adjusted product is 7-9.5, more preferably 8-9.5. To ensure that the pH of the adjusted product meets the above conditions, the pH can be adjusted using a pH adjuster known in the art. Preferably, the pH adjuster is selected from at least one of calcium carbonate, calcium oxide, and calcium hydroxide, with calcium carbonate being preferred.

[0028] The present invention does not particularly limit the mixing conditions in step (1), as long as they can facilitate uniform mixing of the product with the reducing agent, catalyst, auxiliary agent, and stabilizer. Preferably, the mixing conditions include: a stirring time of 10-40 minutes and a stirring speed of 350-500 rpm.

[0029] In some embodiments of the present invention, preferably, the reducing agent is selected from at least one of clean coal powder, high-sulfur coal powder and high-carbon powder, preferably clean coal powder.

[0030] In some embodiments of the present invention, in order to avoid the influence of impurities in the reducing agent on the preparation process and the properties of the obtained calcium polysulfide product, the ash content of the reducing agent is as low as possible. Preferably, the ash content of the reducing agent is less than 10 wt%.

[0031] In some embodiments of the present invention, preferably, the catalyst is selected from at least one of iron oxide, nickel oxide, zinc oxide, palladium oxide and cobalt oxide, preferably iron oxide and / or nickel oxide.

[0032] The inventors of the present invention have found in their research that, since iron and nickel oxides are variable valence oxides and have the ability to donate and accept electrons, they have a highly active catalytic effect, thereby reducing the reduction calcination temperature.

[0033] In some embodiments of the present invention, the mixture of iron oxide and nickel oxide has a mass ratio of iron oxide calculated as iron to nickel oxide calculated as nickel of 1:1 to 10:1, preferably 1:1 to 5:1. When the mass ratio of iron oxide to nickel oxide meets the above conditions, the catalytic effect of the catalyst is promoted, and the catalytic efficiency is high.

[0034] In some embodiments of the present invention, preferably, the auxiliary agent is selected from aluminum oxide, because aluminum oxide has a strong electron transfer ability and thus helps the catalytic reaction proceed.

[0035] In some embodiments of the present invention, preferably, the stabilizer is selected from titanium dioxide and / or silicon oxide.

[0036] In some embodiments of the present invention, preferably, based on the solid content of the power plant desulfurization intermediate product, the amount of the reducing agent is 15-40wt%, preferably 20-40wt%, the amount of the catalyst is 1-5wt%, preferably 1-3wt%, the amount of the auxiliary agent is 1-3wt%, and the amount of the stabilizer is 1-3wt%. This preferred method can effectively promote the catalytic reduction reaction of the power plant desulfurization intermediate product, achieving a good reduction effect.

[0037] In some embodiments of the present invention, Figure 1 As shown, the process of the catalytic reduction reaction includes: dehydrating the slurry, drying the obtained filter cake, grinding the dried material into powder, and calcining it to reduce calcium sulfite to calcium sulfide.

[0038] The inventors of the present invention have discovered that after a catalytic reduction reaction, calcium sulfite and calcium sulfate in the desulfurization intermediate products of a power plant are reduced to calcium sulfide, while calcium oxide is generated as a by-product. The reaction equation for the catalytic reduction reaction is:

[0039]

[0040] 2C+O2→2CO

[0041]

[0042]

[0043] CaSO3 / CaSO4+C→CaO+CO2↑+SO2↑(side reaction)

[0044] In some embodiments of the present invention, preferably, the drying conditions include: a temperature of 90-120° C., preferably 90-105° C., and a moisture content of the dried material of 10-20 wt %, preferably 10-15 wt %. In the present invention, the moisture content of the dried material is measured using a moisture meter.

[0045] The inventors of the present invention have found in their research that when the dried material contains a small amount of water, it is beneficial for the reduction reaction to proceed.

[0046] In some embodiments of the present invention, the drying process is carried out in conventional drying equipment in the art, for example, the drying process is carried out in a forced air drying oven.

[0047] In some embodiments of the present invention, to ensure sufficient reaction between calcium sulfite and the reducing agent in the power plant desulfurization intermediate product, preferably, the calcination conditions include: a calcination temperature of 450-750°C, preferably 600-750°C, and a calcination time of 1-5 hours, preferably 1-3 hours. The calcination process is carried out in conventional calcination equipment in the art, for example, in a muffle furnace.

[0048] In some embodiments of the present invention, the boiling and crystallization process includes: boiling water, adding the powder product and sulfur for a boiling reaction, filtering the resulting product; adjusting the pH of the filtered filtrate, and then subjecting it to a hydrothermal crystallization reaction with an anionic surfactant; and allowing the resulting hydrothermal crystallization product to stand, separate, and dry. After the boiling reaction, calcium sulfide is converted into calcium polysulfide. The boiling reaction equation is:

[0049]

[0050] In some embodiments of the present invention, in order to ensure that the powder product and sulfur react sufficiently, the conditions of the water boiling reaction include: a temperature of 40-90°C, preferably 50-80°C; a time of 10-60 min, preferably 20-50 min, and the water boiling reaction is carried out under stirring conditions at a stirring speed of 30-100 rpm.

[0051] In some embodiments of the present invention, preferably, the mass ratio of water to powder product is 2:1-5:1, and the mass ratio of sulfur to powder product is 1:2-1:10, preferably 1:2-1:6. This preferred method can ensure that calcium sulfide and calcium oxide are fully reacted and converted into calcium polysulfide.

[0052] In the present invention, in order to promote the vulcanization reaction and reduce the foaming of the surfactant during the stirring process, stearic acid is also added during the boiling reaction.

[0053] In some embodiments of the present invention, the mass ratio of stearic acid to water is 0.01-0.25: 100. When the amount of stearic acid and water meets the above range, the recovery rate of the prepared calcium polysulfide product is high.

[0054] In some embodiments of the present invention, the pH of the filtrate is preferably between 8.0 and 9.5. To ensure that the pH of the filtrate meets the aforementioned conditions, the pH may be adjusted using a pH regulator known in the art. Preferably, the pH regulator is selected from at least one of calcium carbonate, calcium oxide, and calcium hydroxide.

[0055] In some embodiments of the present invention, preferably, the conditions of the hydrothermal crystallization reaction include: a temperature of 50-80° C., a time of 20-40 min, and the hydrothermal crystallization reaction is carried out under stirring conditions at a stirring speed of 30-100 rpm.

[0056] In some embodiments of the present invention, preferably, the anionic surfactant is selected from anionic polyacrylamide and / or alkylbenzene sulfonate; the alkylbenzene sulfonate can be various alkylbenzene sulfonates commonly used in the art, preferably sodium dodecylbenzene sulfonate.

[0057] In some embodiments of the present invention, the mass ratio of the anionic surfactant to water is 0.02-0.2:100, preferably 0.02-0.1:100.

[0058] In some embodiments of the present invention, the standing time is 3-14 hours, preferably 9-12 hours.

[0059] In some embodiments of the present invention, in order to prevent the prepared calcium polysulfide from being oxidized, the drying is performed under an inert atmosphere selected from nitrogen and / or argon.

[0060] The second aspect of the present invention provides a calcium polysulfide obtained by the method described in the first aspect. The calcium polysulfide obtained by the method provided by the present invention has a high recovery rate.

[0061] A third aspect of the present invention provides the use of the calcium polysulfide described in the second aspect as a heavy metal scavenger for power plant desulfurization wastewater, a soil additive, and a pesticide. The calcium polysulfide product produced using the method provided by the present invention can be used as a heavy metal scavenger for power plant desulfurization wastewater (or mining wastewater), thereby solving the problem of desulfurization gypsum accumulation and reducing desulfurization wastewater treatment costs. Furthermore, the calcium polysulfide product produced using the method provided by the present invention can also be used as a soil additive and pesticide.

[0062] The present invention will be described in detail below through examples. In the following examples and comparative examples, all raw materials involved are commercially available unless otherwise specified.

[0063] In the following examples and comparative examples, the properties of the prepared calcium polysulfide products were tested according to the following methods, including product recovery, total sulfur content and polysulfide sulfur content, wherein:

[0064] The total sulfur content is tested by the gravimetric method: the product is fully oxidized to form sulfate, and the resulting barium sulfate is titrated with soluble barium chloride and determined by the gravimetric method.

[0065] The polysulfide content is tested using the iodine titration method: under boiling conditions, hydrogen sulfide is collected by acidification and blowing to separate sulfide (monosulfide) from polysulfide. The hydrogen sulfide in the absorption liquid is tested using the iodine titration method, and the polysulfide is obtained by subtracting the monosulfide content from the total sulfur content.

[0066] The product recovery rate is calculated according to the following formula:

[0067]

[0068] Where m 产品 、m 原料 are the quality of products and raw materials, ΣS 产品 and ΣS 原料 are the total sulfur content of the product and raw materials respectively.

[0069] Example 1

[0070] Preparation of calcium polysulfide:

[0071] (1) The slurry from the absorption tower of a power plant affiliated to the State Energy Group (before entering the oxidation tank) was used as raw material. The solid content was tested to be 50%. 50 g of the slurry was taken into a beaker, 0.2 g of calcium carbonate was added, and the pH was tested to be 8.356 after stirring evenly. 7.5 g of clean coal powder (ash content less than 8%), 0.5 g of Fe2O3, 0.2 g of NiO, 0.5 g of Al2O3 and 0.4 g of TiO2 were added in sequence. The mixture was stirred by electromagnetic stirring for 30 min at a stirring speed of 350 rpm to obtain a slurry.

[0072] (2) The slurry was centrifuged at 12,000 rpm for 3 minutes. The filter cake was dried in a forced-air drying oven at 90°C for 2 hours. The moisture content was tested to be 15%. After grinding, the cake was placed in a crucible and sealed with a lid. The crucible was then placed in a muffle furnace for reduction calcination at 600°C for 1 hour at a heating rate of 5°C / min. The cake was then cooled naturally to obtain a powder product.

[0073] (3) Add 60 g of water to a polytetrafluoroethylene-lined reactor, heat to boiling, add 18 g of the powder product and 7.5 g of sulfur, and add 0.09 g of stearic acid, put it into a homogeneous reactor, and carry out water boiling reaction. The reaction temperature is 50 ° C, the reaction time is 30 min, and the rotation speed is 30 rpm.

[0074] (4) The product obtained from the water boiling reaction was filtered and the filter cake was retained. The pH of the filtrate was adjusted to 9.235 using calcium carbonate. 0.05 g of anionic surfactant was added, and then the mixture was sealed and placed in a homogeneous reactor. The reaction temperature was 60°C, the reaction time was 30 min, and the rotation speed was 30 rpm. After the reaction was completed, the mixture was allowed to stand for 12 h. The anionic surfactant used was sodium dodecylbenzenesulfonate.

[0075] (5) The material after the above reaction is filtered and separated, and dried under nitrogen protection to obtain crystalline calcium polysulfide (solid lime sulfur mixture). The filtrate is reused.

[0076] The performance of the prepared calcium polysulfide product was tested, and the test results are shown in Table 1.

[0077] Example 2

[0078] Calcium polysulfide was prepared according to the method of Example 1, except that in step (1), the catalysts Fe2O3 and NiO were replaced by 0.5 g Fe2O3, and the stabilizer TiO2 was replaced by a mixture of 0.25 g TiO2 and 0.25 g SiO2. In step (2), the calcination temperature was 650°C.

[0079] The performance of the prepared calcium polysulfide product was tested, and the test results are shown in Table 1.

[0080] Example 3

[0081] Calcium polysulfide was prepared according to the method of Example 1, except that in step (3), the amount of stearic acid added was 0.01 g; and in step (4), the standing time was 9 h.

[0082] The performance of the prepared calcium polysulfide product was tested, and the test results are shown in Table 1.

[0083] Example 4

[0084] Calcium polysulfide was prepared according to the method of Example 1, except that in step (3), the amount of sulfur added was 3 g, the reaction temperature was 60° C., and the reaction time was 40 min.

[0085] The performance of the prepared calcium polysulfide product was tested, and the test results are shown in Table 1.

[0086] Example 5

[0087] Calcium polysulfide was prepared according to the method of Example 1, except that in step (3), the amount of stearic acid added was 0.01 g.

[0088] The performance of the prepared calcium polysulfide product was tested, and the test results are shown in Table 1.

[0089] Example 6

[0090] Calcium polysulfide was prepared according to the method of Example 1, except that in step (1), the amount of the additive Al2O3 added was 0.4 g, the amount of the reducing agent clean coal powder added was 8 g, and in step (2), the calcination temperature was 700°C.

[0091] The performance of the prepared calcium polysulfide product was tested, and the test results are shown in Table 1.

[0092] Comparative Example 1

[0093] Calcium polysulfide was prepared according to the method of Example 1, except that in step (1), no catalyst and reducing agent were added.

[0094] The performance of the product prepared above was tested, and the test results are shown in Table 1.

[0095] Table 1

[0096] project Recovery rate / % <![CDATA[∑S 产品 / %]]> Polysulfide sulfur content / % Example 1 79 45 29 Example 2 76 48 31 Example 3 72 50 33 Example 4 73 45 31 Example 5 75 47 30 Example 6 79 46 32 Comparative Example 1 10 23 —

[0097] It can be seen from the results in Table 1 that the calcium polysulfide product prepared by the method provided by the present invention has a high recovery rate and a high content of polysulfide sulfur in the product, which is significantly better than the comparative example.

[0098] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing calcium polysulfide using desulfurization intermediates from power plants, characterized in that: The following steps are involved: (1) adjusting the pH of a desulfurization intermediate product of a power plant, and then mixing the obtained adjusted product with a reducing agent, a catalyst, an auxiliary agent, and a stabilizer to obtain a slurry; the catalyst is iron oxide and nickel oxide, the auxiliary agent is aluminum oxide, and the stabilizer is titanium oxide; Based on the solid content of the desulfurization intermediate product of the power plant, the amount of the reducing agent is 15-40wt%, the amount of the catalyst is 1-5wt%, the amount of the auxiliary agent is 1-3wt%; the amount of the stabilizer is 1-3wt%; (2) subjecting the slurry to a catalytic reduction reaction to obtain a powder product; The catalytic reduction reaction process includes: dehydrating the slurry, drying the obtained filter cake, grinding the dried material into powder, and calcining to reduce the calcium sulfite to calcium sulfide; (3) boiling and crystallizing the powder product to obtain calcium polysulfide; The boiling process includes: boiling water, adding the powder product and sulfur to carry out boiling reaction; stearic acid is also added during the boiling reaction, and the mass ratio of stearic acid to water is: 0.15-0.25:100; The boiling conditions include: a temperature of 40-90°C and a time of 10-60 minutes; The crystallization conditions include: temperature of 50-80°C and time of 20-40 minutes; Wherein, the desulfurization intermediate product of the power plant contains calcium sulfite.

2. The method according to claim 1, wherein The pH value of the adjusted product is 7-9.

5.

3. The method according to claim 1, wherein The reducing agent is selected from at least one of clean coal powder, high-sulfur coal powder and high-carbon powder.

4. The method according to claim 3, wherein: The ash content of the reducing agent is less than 10 wt %.

5. The method according to claim 1, wherein Based on the solid content of the desulfurization intermediate product of the power plant, the amount of the reducing agent is 20-40wt%; the amount of the catalyst is 1-3wt%.

6. The method according to claim 1, wherein The mass ratio of iron oxide calculated as iron to nickel oxide calculated as nickel is 1:1-10:

1.

7. The method according to claim 6, wherein: The mass ratio of iron oxide calculated as iron to nickel oxide calculated as nickel is 1:1-5:

1.

8. The method according to claim 1, wherein During the catalytic reduction reaction, the drying conditions include: a temperature of 90-120° C., and a moisture content of the dried material of 10-20 wt %.

9. The method according to claim 8, wherein During the catalytic reduction reaction, the drying conditions include: a temperature of 90-105° C., and a moisture content of the dried material of 10-15 wt %.

10. The method according to claim 1, wherein During the catalytic reduction reaction, the calcination conditions include: a calcination temperature of 450-750° C. and a calcination time of 1-5 hours.

11. The method according to claim 10, wherein: During the catalytic reduction reaction, the calcination conditions include: a calcination temperature of 600-750° C. and a calcination time of 1-3 hours.

12. The method according to claim 1, wherein The boiling and crystallization process includes: boiling water, adding the powder product and sulfur to perform a boiling reaction, filtering the product obtained by the boiling reaction; adjusting the pH value of the filtrate obtained by filtration, and then performing a hydrothermal crystallization reaction with an anionic surfactant, and standing, separating, and drying the obtained hydrothermal crystallization reaction product.

13. The method according to claim 12, wherein: The conditions for the water boiling reaction include: a temperature of 50-80° C. and a time of 20-50 min.

14. The method according to claim 12, wherein: The mass ratio of water to powder product is 2:1-5:1, and the mass ratio of sulfur to powder product is 1:2-1:

10.

15. The method according to claim 14, wherein The mass ratio of sulfur to powder product is 1:2-1:

6.

16. The method according to claim 12, wherein The pH value is 8-9.

5.

17. The method according to claim 12, wherein: The anionic surfactant is selected from anionic polyacrylamide and / or alkylbenzene sulfonate.

18. The method according to claim 17, wherein The alkylbenzene sulfonate is sodium dodecylbenzene sulfonate.

19. The method according to claim 12, wherein: The standing time is 3-14 hours.

20. The method according to claim 19, wherein The standing time is 9-12 hours.

21. The method according to claim 12, wherein The drying is performed under an inert atmosphere selected from nitrogen and / or argon.

22. Calcium polysulfide obtained by the method according to any one of claims 1 to 21.

23. Use of the calcium polysulfide according to claim 22 in heavy metal scavengers for desulfurization wastewater in power plants, soil additives and pesticides.

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