JP2005187322A - Gypsum decomposition method - Google Patents

Abstract

An object of the present invention is to contribute to the construction of a recycling system for gypsum by efficiently decomposing waste gypsum board into useful materials without being bothered by its difficult separation from a completely new viewpoint. It is another object of the present invention to provide a composite waste treatment system that can treat not only waste gypsum board but also waste plastic, waste rubber, or non-ferrous metal smelting exhaust gas at the same time.
Gypsum is reacted with a plastic decomposition gas or a hydrocarbon-containing gas under heating to decompose and recover hydrogen sulfide and calcium carbonate and / or calcium sulfide.
Further, the obtained hydrogen sulfide is reacted with sulfur dioxide-containing gas or oxygen to be converted into elemental sulfur and recovered.
[Selection figure] None

Description

  The present invention relates to a method for treating waste gypsum. More specifically, the present invention relates to recycling waste gypsum by separating and collecting it into sulfur and calcium carbonate and / or calcium chloride and calcium fluoride using a carbide-containing waste.

With the growing need for global environmental protection, the effective use of plastic waste (waste plastic, waste tires, waste wires, waste printed circuit boards, etc., hereinafter simply referred to as plastic waste) is becoming increasingly important.
In recent years, waste gypsum board has been regarded as a problem in terms of environmental pollution. Gypsum is calcium sulfate, which was previously considered a chemically stable substance, but hydrogen sulfide may be generated at waste disposal sites. It has been pointed out that wastes containing such sulfates generate hydrogen sulfide by the action of sulfate-reducing bacteria in an anaerobic environment.

The action of sulfate-reducing bacteria requires organic matter that is a carbon source, which is supplied by organic waste mixed in the waste.
For this reason, the “Construction Recycling Law” calls for the construction of a gypsum recycling system.
Most of gypsum is used as a building material as a gypsum boat, and according to a calculation by the Japan Gypsum Board Industry Association, the amount of gypsum board discarded is estimated to reach 1.4 million tons in 2010.

On the other hand, limestone is the largest mineral resource in Japan, and it goes without saying that it is desirable to recycle it if possible, considering the energy and landscape conservation involved in mining.
From this point of view, there is a study by Okumura et al. (“Regeneration of Lime by Reductive Decomposition of Gypsum Waste”: Proceedings of the Symposium of the Energy Division of the Chemical Engineering Society 2002). In this method, waste gypsum is reduced using hydrogen or carbon monoxide, and the calcium content is recovered as lime (CaO), but sulfur recovery in the gypsum is not taken into consideration.
In addition, foreign materials such as paper and vinyl cloth are mixed in the gypsum board, and separation and development of foreign material removal technology are important issues for recycling.

  On the other hand, as described later, the present invention uses hydrocarbon-containing waste as a reducing agent and not only recycles calcium, but also sulfur, and is included in hydrocarbon-containing waste. At the same time, halogen elements such as chlorine and fluorine are also recycled, and the problem of separation and removal of the foreign matters is solved.

By the way, a large amount of hydrogen sulfide gas is generated from petroleum refining and acid natural gas refining processes. This gas oxidizes part of it,
2H ₂ S + SO ₂ = 3S + 2H ₂ O
Elemental sulfur is produced by this reaction. This process is known as the “Klaus reaction” and is in operation around the world.
There is also a proposal to produce elemental sulfur using this Claus reaction after partially converting sulfur dioxide in non-ferrous metal smelting exhaust gas to hydrogen sulfide to form a mixed gas of sulfur dioxide and hydrogen sulfide. (Patent Document 1 JP 2003-95623 A). However, no attempt has been made to recover sulfur from gypsum, which has the same sulfur content.

On the other hand, there is another problem, such as plastic waste disposal, for environmental protection. Plastic waste is currently incinerated or treated by landfill because it contains hydrocarbons and is flammable, so-called 3R (reuse, reduce, recycle) is not sufficient, More effective utilization is desired.
JP 2003-95623 A "Regeneration of lime by reductive decomposition of gypsum waste": Symposium 2002

  In such a situation, the present invention contributes to the construction of a gypsum recycling system by efficiently decomposing the waste gypsum board into useful materials without being troubled by the difficult separation from a completely new viewpoint. To provide a composite waste treatment system that can treat not only waste gypsum board but also waste plastic, waste rubber or nonferrous metal smelting exhaust gas at the same time. It is intended.

As a result of intensive studies, the present inventor has conceived that gypsum that is chemically very stable is reduced and decomposed and recovered and recycled as elemental sulfur and calcium compounds. Further, the gypsum reducing material and the fuel source ( The idea was to use plastic waste as a heating source), and further studies were made to arrive at the present invention.
That is, the present invention

(1) A method for decomposing gypsum, comprising reacting gypsum with a hydrocarbon-containing plastic decomposition gas or hydrocarbon gas under heating to decompose it into hydrogen sulfide and calcium carbonate and / or calcium sulfide.
(2) A method for decomposing gypsum characterized by reacting gypsum with a chlorine-containing plastic decomposition gas under heating to decompose it into hydrogen sulfide and calcium sulfide and / or calcium chloride.
(3) A method for decomposing gypsum, comprising reacting gypsum with fluorine-containing plastic decomposition gas under heating to decompose it into sulfur dioxide and calcium fluoride.
(4) The gypsum decomposition according to (2) or (3), wherein the decomposition gas is a decomposition gas obtained directly from a plastic waste during a decomposition reaction of gypsum, or a decomposition gas obtained by dry distillation of plastic waste. Processing method.
(5) The gypsum decomposition treatment method according to (1), wherein the hydrocarbon gas is LPG.
(6) The method for decomposing gypsum according to (1), wherein the hydrocarbon gas is a gas generated by decomposing biomass into microorganisms.
(7) React gypsum with plastic decomposition gas or hydrocarbon gas under heating to decompose it into hydrogen sulfide and calcium carbonate and / or calcium sulfide, and further react hydrogen sulfide with sulfur dioxide-containing gas or oxygen. A method for decomposing gypsum characterized by being converted to sulfur.
(8) React gypsum with chlorine-containing plastic decomposition gas under heating to decompose it into hydrogen sulfide and calcium sulfide and / or calcium chloride, and further react hydrogen sulfide with sulfur dioxide-containing gas or oxygen to form sulfur. A method for decomposing gypsum, characterized by converting.
(9) A gypsum characterized by reacting gypsum with fluorine-containing plastic decomposition gas under heating to decompose it into sulfur dioxide and calcium fluoride, and further converting sulfur dioxide into sulfur by reacting with hydrogen sulfide. Decomposition method.
(10) The method for decomposing gypsum according to (7) or (8), wherein the sulfur dioxide-containing gas is a smelting exhaust gas accompanying the production of nonferrous metals.
(11) The method for decomposing gypsum according to (7), (8), or (9), wherein the hydrogen sulfide used in the reaction contains hydrogen sulfide obtained by a reaction between calcium sulfide and water vapor or high-temperature water.
(12) The method for decomposing gypsum according to any one of (1) to (11), wherein the gypsum is a waste gypsum board.
About.

  Gypsum is considered as a stable substance, and its waste is currently mainly used for landfill. Even if it is recycled, it is only reused in the form of gypsum after complicated separation. However, there was a concern about the environmental pollution described above when the waste gypsum was stored. According to the present invention, waste gypsum can be recovered and reused as safe calcium carbonate, calcium sulfide, or sulfur by eliminating such concerns. In particular, the recycling to sulfur facilitates the conversion to sulfuric acid through this, so the options for recycling can be expanded. Furthermore, according to the present invention, sulfur dioxide-containing gas from plastic waste, non-ferrous metal smelting gas, etc. is used for the treatment of waste gypsum, and these treatments can be performed all at once, thereby solving environmental problems. Can greatly contribute.

As the gypsum used in the present invention, waste gypsum board is preferably used from the viewpoint of treatment of the waste, but it goes without saying that gypsum itself can also be used.
When the waste gypsum board is used, it is not particularly necessary to separate paper or vinyl cloth contained therein. Paper, vinyl cloth, and the like can be used as they are as a hydrocarbon-containing waste as a hydrocarbon-containing gas source. Also, waste containing chlorine and fluorine can be used.

The waste used in the present invention is not limited as long as it generates hydrocarbons which are reactants when gypsum is decomposed and also serves as a heat source for promoting the reaction. What is necessary is just to include as the component. For example, polyolefins such as polyethylene and polypropylene, polyesters such as polystyrene and PET, hydrocarbon-containing plastics such as polyamide, chlorine-containing plastics such as polyvinyl chloride and polyvinylidene chloride, fluorine-containing plastics such as fluororesin General plastic waste, plastic waste shredder dust, waste tires, waste wire, waste wire skin (
Nugget scrap), waste printed circuit boards, etc.

  These wastes may be used as they are for the gypsum treatment reaction, or may be supplied to the reactor with a hydrocarbon-containing gas generated by treating the waste by another process, for example, dry distillation. Of course, as the hydrocarbon-containing gas, ordinary hydrocarbon-containing gases other than those obtained from waste as a raw material, that is, city gas, LPG can be used, and biomass can also be used and these are used in combination. You can also.

In the present invention, hydrogen sulfide is generated when gypsum is decomposed, which can be further reacted with sulfur dioxide to be converted into elemental sulfur and recovered. This reaction is shown below and is a prominent reaction as the Claus reaction.
H ₂ S + 1 / 2SO ₂ → 3 / 2S + H ₂ O
As the sulfur dioxide necessary for this reaction, air or nonferrous metal smelting exhaust gas (for example, flash furnace exhaust gas) containing sulfur dioxide can be used. In addition to sulfur dioxide, oxygen, carbon dioxide, nitrogen and water vapor are usually contained in the flash furnace exhaust gas. The concentration of sulfur dioxide is approximately 5 to 90 vol%, the concentration of oxygen is approximately 5 to 20 vol%, the concentration of carbon dioxide is approximately 1 to 5 vol%, and the remainder is nitrogen or water vapor.

The first stage reaction of the present invention is a reaction between gypsum and a hydrocarbon-containing gas. This reaction generates calcium carbonate and / or calcium sulfide and hydrogen sulfide. In this reaction, calcium carbonate or calcium sulfide is mainly produced depending on temperature conditions, and the production amount of hydrogen sulfide is changed accordingly.
The state of the reaction can be inferred by thermodynamic stoichiometry. In the thermodynamic stoichiometric calculation described below, methylene is mainly used as a model as a hydrocarbon-containing gas, but basically the same applies to other hydrocarbon-containing gases.

FIG. 1 shows the basic reaction 1 of the present invention shown below.
CaSO ₄ + 4 / 3CH ₂ →
CaCO ₃ + H ₂ S + 1 / 3H ₂ O + 1 / 3CO ₂
Shows the abundance of reactants and products in an equilibrium state in a temperature range of 400 to 750 K when CaSO ₄ is 1 mol. Thus, it can be seen that the reaction proceeds almost 100% up to about 630K. When the temperature exceeds 630 K, S in CaSO ₄ is fixed as CaS, and as a result, the amount of H ₂ S generated decreases.

FIG. 2 shows that the reaction between gypsum and CH ₂ has priority over the CaS generation reaction at 700 K or higher. This reaction is the basic reaction 2 of the present invention.
CaSO ₄ + 4 / 3CH ₂ →
CaS + 4 / 3H ₂ O + 4 / 3CO ₂
Indicated by

FIG. 3 shows the abundance of the reaction product when the addition amount of CH ₂ which is the reaction gas is changed at 600 K for 1 mole of CaSO ₄ for the basic reaction 1. From FIG. 3, as the amount of CH ₂ added increases, unreacted CaSO ₄ decreases, and CaCO ₃ and H ₂ S increase. It can be seen that when the stoichiometric ratio is reached, unreacted CaSO ₄ disappears and the above reaction proceeds almost 100%. It can also be seen that excessive addition of CH ₂ does not significantly affect the amount of H ₂ S generated.

FIG. 4 shows basic reaction 2 of the present invention.
CaSO ₄ + 4 / 3CH ₂ →
CaS + 4 / 3H ₂ O + 4 / 3CO ₂
About the abundance of the reaction product when the addition amount of CH ₂ which is the reaction gas at 1 mol of CaSO ₄ and 900 K is changed. From FIG. 4, as the amount of CH ₂ added increases, unreacted CaSO ₄ decreases and CaS increases. It can be seen that when the stoichiometric ratio is reached, unreacted CaSO ₄ disappears and the above reaction proceeds almost 100%. It can also be seen that excessive addition of CH ₂ does not significantly affect the amount of CaS generated.

FIG. 5 shows a state in which a combustion reaction of CH ₂ is added to the basic reaction 1, and the calculation is based on a 2/3 molar excess of CH ₂ with respect to the stoichiometric amount of the basic reaction 1. The oxygen necessary for the combustion was added and supplied in terms of air (oxygen: nitrogen = 1: 4), and the relationship between the amount of oxygen at 650 K and the reaction product was examined.
As a result, it was found that if the amount of oxygen was 1 mol or less, all S in CaSO ₄ was converted to H ₂ S. In addition, the amount of oxygen necessary for completely burning the CH ₂ 2/3 mol excess addition amount is 1 mol assuming the following reaction.
2/3 CH ₂ + O ₂ → 2/3 H ₂ O + 2 / 3CO ₂
In addition, the actual gypsum is assumed here, and calculation is performed with a dihydrate containing two molecules of crystal water.

FIG. 6 shows the result of thermal calculation under the condition in which a CH ₂ combustion reaction is added to the basic reactions 1 and ₂ described above. As a result, it was found that the basic reaction itself is an exothermic reaction, and the exothermic amount increases as the amount of oxygen increases.

FIG. 7 shows that the above basic reactions 1 and ₂ were added in excess of 2/3 mol of CH ₂ , and 0.5 mol corresponding to 1/2 of the amount required for complete combustion was added as air. The temperature change of the reaction product was calculated under the conditions. As a result, it was found that basic reaction 1 preferentially occurred up to around 700 K, and sulfur in the gypsum was almost converted to H ₂ S and Ca was converted to CaCO ₃ . In addition, it was found that basic reaction 2 was prioritized at 700 K or more, and sulfur and Ca content in gypsum were almost converted to CaS.

  FIG. 8 assumes that the addition of woody waste as an auxiliary heat source, and the calculation was performed by adding 5% of the amount of gypsum to the conditions of FIG. As a result, it was found that the addition of wooden waste did not affect the previous basic reactions 1 and 2.

FIG. 9 shows the gas composition (nitrogen: 59.3% CO ₂ : 13.4%, oxygen: 0.6%, hydrogen: 10.15) generated in the car shredder dust carbonization test conducted by the Japan Automobile Manufacturers Association. %, CO: 4.55%, HCl: 12.0% Estimated using “Research and development of volume reduction, solidification, and carbonization gasification technology for used automobiles” 5.3.1 page 25) It was. As a result, it was found that all S in the gypsum was converted to H ₂ S up to around 700K.

FIG. 10 is a trial calculation assuming methane gas generated in methane fermentation.
As a result, it was found that all S in the gypsum was converted to H ₂ S up to around 670K.
FIG. 11 shows a trial calculation using LPG, assuming a large amount of industrial processing. As a result, it was found that all S in the gypsum was converted to H ₂ S up to around 680K.

FIG. 12 shows the result of trial calculation of gypsum reduction when polyvinyl chloride (C ₂ H ₃ Cl) is used as the reducing agent and fuel as the chlorine-containing waste. In this case, the following basic reaction 3 proceeds almost 100% in the temperature range of 400 to 800K.
CaSO ₄ + 2C ₂ H ₃ Cl + 3O ₂ = CaCl ₂ + H ₂ S + 4CO ₂ + 2H ₂ O
As a result, calcium chloride and hydrogen sulfide are generated. The calcium chloride produced here is used as a desiccant, a snow melting agent for roads, and the like, and can be effectively used as a recycled resource.

FIG. 13 shows the result of trial calculation of gypsum reduction when fluorine resin ((C ₂ F ₄ ) n) is used as a reducing agent and fuel as fluorine-containing waste. the ₂ F ₄ was assumed. In this case, it can be seen that the following basic reaction 4 proceeds almost 100% in the temperature range of 800 K or higher. .
CaSO ₄ + 1 / 2C ₂ F ₄ → CaF ₂ + CO ₂ + SO ₂
As a result, calcium fluoride and sulfur dioxide are generated. Calcium fluoride can be used as an auxiliary material in the steel industry. Single sulfur can be recovered from sulfur dioxide by the Claus reaction.

FIG. 14 shows that the desulfurization reaction of CaS occurs at 650 K or less in the presence of H ₂ O and CO ₂ to generate H ₂ S and the Ca content becomes CaCO ₃ .
CaS + 2H ₂ O (gas) + CO ₂ → CaCO ₃ + H ₂ S
FIG. 15 shows that when CaS generated at a high temperature is added to liquid water, all of the S content becomes H ₂ S, and the Ca content is adjusted by adjusting the amount of CO ₂ to be added to Ca (OH) ₂ and CaCO _3. Shows that it can be made separately.
CaS + 2H ₂ O (liquid) → Ca (OH) ₂ + H ₂ S
CaS + H ₂ O (liquid) + C 0 ₂ → CaCO ₃ + H ₂ S

FIG. 16 shows the temperature dependence of the reaction product when the flue gas (SO ₂ : 35%, oxygen 10%, nitrogen: 53%, CO ₂ : 3%) is mixed with the product gas at 600K in FIG. It is a trial calculation. As a result, it was found that the amount of S generated peaked around 470K.

  As is clear from the above, according to the present invention, gypsum can be decomposed into hydrogen sulfide and calcium carbonate and / or calcium sulfide by reacting with a hydrocarbon-containing plastic decomposition gas or hydrocarbon gas. Further, according to the present invention, gypsum can be decomposed into calcium sulfide and calcium chloride by reacting with chlorine-containing plastic decomposition gas. Furthermore, according to the present invention, gypsum can be decomposed into calcium fluoride and sulfur dioxide by reacting with fluorine-containing plastic decomposition gas.

These reactions can be performed using a reactor generally used for solid-gas reactions. Any reaction furnace may be used as long as it has a function of continuously discharging reaction product gas and solid matter such as an external heat kiln, an internal heat kiln, a fluidized bed furnace, and a stoker furnace.
In the hydrogen sulfide generation type, the sulfur content in gypsum is separated as hydrogen sulfide gas in a reaction furnace, dust and trace impurity gases contained in the reaction product gas are removed by dry or wet methods, and sulfur dioxide is then removed in a Claus reactor. Alternatively, it reacts with oxygen to recover simple sulfur. Examples of the sulfur dioxide gas include a gas generated by non-ferrous metal smelting, a gas generated by a reaction between fluorine-containing waste and gypsum, a pyrolysis gas of sulfuric acid, and an oxidation product gas of hydrogen sulfide.
Solids generated from the reactor are calcium carbonate when using hydrocarbon-containing waste other than chlorine-containing waste and fluorine-containing waste as a reducing agent for gypsum, and calcium chloride when using chlorine-containing waste as a reducing agent. When fluorine-containing waste is used as a reducing agent, calcium fluoride is the product.

  In the calcium sulfide generation type, the sulfur content in the gypsum is fixed as solid calcium sulfide in the reaction furnace. Calcium sulfide is reacted with water vapor and carbon dioxide gas in a dry hydrogen sulfide generator to generate hydrogen sulfide and obtain calcium carbonate. It is also possible to react with high-temperature water in a wet hydrogen sulfide generator to obtain hydrogen sulfide. At that time, calcium can be recovered as calcium hydroxide, but it can also be recovered as calcium carbonate by reacting with carbon dioxide gas. It is. Hydrogen sulfide generated in the hydrogen sulfide generator recovers sulfur in the above-mentioned Claus reactor.

When hydrogen sulfide generated by the above-described decomposition treatment method is further converted to elemental sulfur, a reaction with oxygen or sulfur dioxide is used, but a Claus reaction with sulfur dioxide is preferably used. In this case, the treatment of nonferrous metal smelting exhaust gas can be performed at the same time. This conversion reaction of hydrogen sulfide to elemental sulfur may be carried out by introducing the hydrogen sulfide gas obtained by the above solid-gas reaction to another reactor and supplying non-ferrous metal smelting exhaust gas to the reactor. preferable.
The Claus reaction is preferably performed at H ₂ S: SO ₂ = 1 to 3: 1 (molar ratio), particularly 2: 1 (molar ratio), and therefore, it is preferable to adjust so as to obtain a mixture in this range.

  This conversion of hydrogen sulfide to elemental sulfur is preferably installed in a place where a sulfur dioxide-containing gas can be easily obtained, for example, near a non-ferrous metal smelter, when using the Claus reaction. Therefore, it can be said that it is preferable to use the reaction equipment installed near the nonferrous metal smelter in the method for decomposing gypsum of the present invention.

Examples of the present invention are shown below. Example 1 Confirmation Experimental Formula of Calcium Sulfide Formation Basic Reaction Formula 2: CaSO ₄ + 4 / 3CH ₂ = CaS + 4 / 3H ₂ O + 4 / 3CO ₂

Test apparatus The test apparatus shown in FIG. 19 was used.
A reaction tube with a diameter of 3 cm and a length of 50 cm is placed in a heating furnace composed of a heating element and ceramic, and an alumina crucible is placed inside it.
The upper end of the reaction tube is sealed with a gas inlet, an exhaust port, a polyethylene inlet, and silicon rubber penetrating a thermocouple.

Test Procedure In the crucible, about 1 g of an anhydrous gypsum made by heating and holding the reagent hemihydrate gypsum (powder) manufactured by Kanto Chemical Co., Ltd. at a high temperature in advance to volatilize the crystal water.
After plugging the upper end, the temperature is raised while introducing gas. Air was used as the gas. After the inside of the crucible reached a predetermined temperature, polyethylene particles were continuously fed into the crucible while flowing air. A predetermined amount of polyethylene was continuously supplied from an inlet provided to drop into the crucible. The polyethylene particles to be charged are spherical and have a particle size of about 3 mm and a weight of about 0.025 g.
After the test was completed, the reaction tube was taken out of the heating furnace and allowed to cool, and then the sample was analyzed.

Test conditions ・ Set temperature: 900 ℃
・ Reaction time: 4 hours ・ Air flow rate: 200ml / min
・ Anhydrous gypsum amount: 0.9775 g
・ Polyethylene content: 5.63 g
・ Molar ratio of gypsum and input polyethylene (CH ₂ conversion) 1: 54.7

Test Results and Discussion About 41 times the amount of polyethylene required for basic reaction formula 2 (CH ₂ conversion) was added. After completion of the reaction, there were reaction products and carbon-containing material (char) in the crucible. As estimated from the air flow rate, it is considered that about 50% of polyethylene burned, and most of the remainder remained as unburned or vaporized or char.
The reaction product excluding char was analyzed by an X-ray diffractometer. As a result, the X-ray diffraction peak of gypsum that existed before the test disappeared after the test, and it was found that gypsum was not present in the reaction product. Moreover, the X-ray diffraction peak of the reaction product was consistent with the CaS peak predicted by the reaction formula.
From this, it was confirmed that the basic reaction formula 2 proceeds.

Example 2 Confirmation of basic reaction formula 3 for the formation of calcium chloride Experimental reaction formula: CaSO ₄ + 2C ₂ H ₃ Cl + 3O ₂ = CaCl ₂ + H ₂ S + 4CO ₂ + 2H ₂ O

Test apparatus The test apparatus shown in FIG. 19 was used.
A reaction tube with a diameter of 3 cm and a length of 50 cm is placed in a heating furnace composed of a heating element and ceramic, and an alumina crucible is placed inside it.
The upper end of the reaction tube is sealed with a gas inlet, an exhaust port, a polyethylene inlet, and silicon rubber penetrating a thermocouple.

Test Procedure In the crucible, about 1 g of an anhydrous gypsum made by heating and holding the reagent hemihydrate gypsum (powder) manufactured by Kanto Chemical Co., Ltd. at a high temperature in advance to volatilize the crystal water.
After plugging the upper end, the temperature is raised while introducing gas. Air was used as the gas. After the inside of the crucible reached a predetermined temperature, the particles in which the vinyl chloride resin powder was compacted continuously were put into the crucible while flowing air. A predetermined amount of vinyl chloride was continuously supplied from an insertion port installed so as to drop into the crucible. The vinyl chloride resin particles to be charged are spherical and have a particle size of about 3 mm and a weight of about 0.025 g.
After the test was completed, the reaction tube was taken out of the heating furnace and allowed to cool, and then the sample was analyzed.

Test conditions ・ Set temperature: 1200 ℃
・ Reaction time: 10 minutes ・ Air flow rate: 100 ml / min
・ Anhydrous gypsum amount: 1.003 g
-Input vinyl chloride resin amount: 4.136g
・ Molar ratio of gypsum and input vinyl chloride (C ₂ H ₃ Cl conversion) 1: 9

Test results and discussion About 9 times the amount of vinyl chloride necessary for basic reaction formula 3 (converted to C ₂ H ₃ Cl) was added. The reaction product showed deliquescence after completion of the reaction. The dried portion of the reaction product was analyzed with an X-ray diffractometer. As a result, the X-ray diffraction peak of gypsum that existed before the test disappeared after the test, and it was found that gypsum was not present in the reaction product. The first peak of the reaction product coincided with the CaCl ₂ peak predicted by the reaction formula.
The product sample removed from the X-ray diffractometer was subsequently deliquescent. Of the compounds that can be produced by the reagents used in the test, only CaCl ₂ exhibits deliquescence. It is considered that the deliquescence after the completion of the reaction was due to H ₂ O generated in the basic reaction formula 3. Therefore, it was confirmed that the basic reaction formula 3 proceeds.

Example 3 Confirmation Experimental Reaction Formula of Calcium Fluoride Formation Basic Reaction Formula 4: CaSO ₄ + 1 / 2C ₂ F ₄ = CaF ₂ + SO ₂ + CO ₂

Test apparatus The test apparatus shown in FIG. 22 was used.
A reaction tube with a diameter of 3 cm and a length of 50 cm is placed in a heating furnace composed of a heating element and ceramic, and an alumina crucible is placed inside it. The crucible was covered with a lid having a small diameter vent.
The upper end of the reaction tube is sealed with a silicone rubber penetrating the exhaust port and thermocouple.

Test Procedure In a crucible, a finely cut Teflon (registered trademark) tube as hydrated gypsum and fluororesin has a molar ratio of gypsum (CaSO ₄ · 1 / 2H ₂ O) and fluororesin (C ₂ F ₄ ). The mixture was put in a ratio of about 1: 2, stirred well, and then the crucible was covered. After the crucible was placed in the reaction tube, the temperature was raised by closing the silicon stopper. After the test was completed, the reaction tube was taken out of the heating furnace and allowed to cool, and then the sample was analyzed.

Test conditions ・ Set temperature: 700 ℃
・ Reaction time: 1 hour ・ Hydrohydrate amount: 1.0181 g
・ Fluororesin amount: 1.3795 g

Test results and discussion The set temperature was reached within a few minutes after the start of temperature increase. When the reaction product was visually observed after completion of the reaction, no carbon-containing material such as char was found. The reaction product was analyzed with an X-ray diffractometer. The reaction product had peaks other than the X-ray diffraction peak of gypsum, and these peaks were consistent with the CaF ₂ peak predicted by the reaction formula. From this, it was confirmed that the basic reaction formula 4 proceeds.

CaSO ₄ graph 1 mol ₊ CH 2 4/3 moles of temperature dependence of the amount of reaction products of (cold side). The graph which shows the same as the above (high temperature side). Graph showing relationship (low temperature side) of the CH ₂ amount and amount of reaction products. The graph which shows the same as the above (high temperature side). Graph showing the abundance of the reaction product in the case of the CH ₂ gas partial combustion with air (low temperature side). Oxygenation reaction temperature when the CH ₂ gas was partially burned with air, the graph showing the calorific value of the relationship (low temperature side). Graph showing the temperature dependence of the reaction product in the case of a CH ₂ gas partial combustion with air. CaSO ₄ 1 mol + 5 mass% cellulose graph showing the temperature dependence of the amount of reaction products when using _{(C 6 H} 10 _{O 5)} is added to CH ₂ gas in desulfurization and a heat source. CaSO 4 ₁ mol + graph showing the temperature dependence of the amount of reaction products when the shredder dust carbonization gas was used for desulfurization and the heat source. Graph showing the temperature dependence of the amount of reaction products when using CaSO 4 ₁ mol + methane gas desulfurization and the heat source. Graph showing the temperature dependence of the amount of reaction products when using CaSO ₄ 1 mol + LPG desulfurization and a heat source. CaSO ₄ 1 mol ₊ C ₂ H 3 Cl ₂ moles graph showing the temperature dependence of the amount of reaction products of. Graph showing the temperature dependence of CaSO ₄ 1 mol ₊ C ₂ F 4 1/2 mol reaction product. Graph showing the temperature dependence of the _{H 2} S generation reaction from CaS (reaction with water vapor). Graph showing the temperature dependence of the _{H 2} S generation reaction from CaS (reaction with water). The graph which shows the temperature dependence of the amount of reaction products at the time of mixing a flash furnace exhaust gas on the conditions of FIG. An explanatory view of an apparatus for carrying out the present invention. Explanatory drawing of another apparatus for implementing this invention. FIG. 3 is an explanatory diagram of a test apparatus used in Examples 1 and 2. The X-ray diffraction charts of the pre-test gypsum used in Example 1, the reaction product of Example 1, and the CaS reagent, respectively. X-ray diffraction chart of the pre-test gypsum used in Example 2, the reaction product of Example 2, and the CaCl ₂ reagent. FIG. 5 is an explanatory diagram of a test apparatus used in Example 3. The X-ray diffraction charts of the pre-test gypsum used in Example 3, the reaction product of Example 3, and the CaF ₂ reagent, respectively.

Claims (12)

A method for decomposing gypsum, comprising reacting gypsum with a hydrocarbon-containing plastic decomposition gas or hydrocarbon gas under heating to decompose it into hydrogen sulfide and calcium carbonate and / or calcium sulfide. A method for decomposing gypsum, comprising reacting gypsum with a decomposition gas of chlorine-containing plastic under heating to decompose it into hydrogen sulfide and calcium sulfide and / or calcium chloride. A method for decomposing gypsum, comprising reacting gypsum with fluorine-containing plastic decomposition gas under heating to decompose it into sulfur dioxide and calcium fluoride. The gypsum decomposition treatment method according to claim 1, 2 or 3, wherein the decomposition gas is a decomposition gas obtained directly from a plastic waste during a decomposition reaction of gypsum, or a decomposition gas obtained by dry distillation of plastic waste. The gypsum decomposition treatment method according to claim 1, wherein the hydrocarbon gas is LPG. The method for decomposing gypsum according to claim 1, wherein the hydrocarbon gas is a gas generated by decomposing biomass into microorganisms. Gypsum is reacted with plastic cracking gas or hydrocarbon gas under heating to decompose into hydrogen sulfide and calcium carbonate and / or calcium sulfide, and hydrogen sulfide is further reacted with sulfur dioxide containing gas or oxygen to convert to sulfur. A method for decomposing gypsum, comprising: Reacting gypsum with chlorine-containing plastic decomposition gas under heating to decompose it into hydrogen sulfide and calcium sulfide and / or calcium chloride, and further converting hydrogen sulfide into sulfur dioxide-containing gas or oxygen to convert to sulfur A method for decomposing gypsum characterized by the above. A method for decomposing gypsum characterized by reacting gypsum with fluorine-containing plastic decomposition gas under heating to decompose it into sulfur dioxide and calcium fluoride, and further converting sulfur dioxide into sulfur by reacting with hydrogen sulfide. . The method for decomposing gypsum according to claim 7 or 8, wherein the sulfur dioxide-containing gas is a smelting exhaust gas accompanying the production of non-ferrous metals. The method for decomposing gypsum according to claim 7, 8 or 9, wherein the hydrogen sulfide used for the reaction contains hydrogen sulfide obtained by a reaction between calcium sulfide and water vapor or high-temperature water. The gypsum decomposition treatment method according to any one of claims 1 to 11, wherein the gypsum is a waste gypsum board.

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