阅读说明：本技术 一种利用蒸氨废液生产二水硫酸钙晶须的方法 (Method for producing calcium sulfate dihydrate whisker by using ammonia distillation waste liquid ) 是由 李克非 张瑞 孙雷 张强 万莲 道如娜 于 2018-06-04 设计创作，主要内容包括：一种利用蒸氨废液生产二水硫酸钙晶须的方法,涉及硫酸钙晶须生产领域。本发明针对蒸氨废液的回收再利用的问题,提供了一种利用蒸氨废液生产二水硫酸钙晶须的方法:将蒸氨废液冷却后过滤,获得含固量＜100mg/L的待处理液,向其中通入CO<Sub>2</Sub>窑气,反应获得含有碳酸钙的盐溶液；然后经提浓处理,将获得的含固量小于100mg/L的清液与硫酸钠饱和溶液混合,在90-95℃条件下保温4-6小时,得到的悬浊液经冷却、过滤,洗涤,烘干获得二水硫酸钙晶须。本发明适用于蒸氨废液的回收再利用,并拓展了硫酸钙晶须的生产方式。(2 The invention provides a method for producing calcium sulfate dihydrate whiskers by using ammonia evaporation waste liquid, which relates to the field of calcium sulfate whisker production and aims at the problem of recycling of ammonia evaporation waste liquid.)

1. a method for producing calcium sulfate dihydrate whisker by using ammonia evaporation waste liquid is characterized by comprising the following steps of:

1) Cooling and separating the ammonia evaporation waste liquid to obtain a liquid to be treated with the solid content of less than 5 g/L;

2) Precipitating and filtering the solution to be treated in the step 1), and concentrating the obtained filtrate to obtain clear liquid with the solid content of less than 100 mg/L;

3) Introducing CO ₂ kiln gas into the clear liquid obtained in the step 2), adjusting the pH value to 6-9, and carrying out carbonization reaction to obtain a salt solution containing calcium carbonate;

4) concentrating the salt solution containing calcium carbonate prepared in the step 3) to obtain clear liquid with solid content less than 100mg/L, and heating the clear liquid to 94-100 ℃;

5) heating the saturated solution of sodium sulfate to 80-94 ℃;

6) Mixing the heated clear liquid in the step 4) with the heated sodium sulfate saturated solution in the step 5), preserving the heat for 4-6 hours at the temperature of 90-95 ℃ and the stirring speed of 150rpm to obtain a suspension, cooling to 60-70 ℃, and filtering;

7) And 6) washing and drying a filter cake obtained after filtering to obtain calcium sulfate dihydrate crystal whiskers, wherein the length-diameter ratio of the calcium sulfate dihydrate crystal whiskers is 30-50.

2. The method for producing calcium sulfate dihydrate whiskers by using the ammonia evaporation waste liquid according to claim 1, wherein the mass ratio of the ammonia evaporation waste liquid to the thenardite is as follows: anhydrous mirabilite 50: 7.

3. The method for producing calcium sulfate dihydrate whiskers by using the ammonia evaporation waste liquid as claimed in claim 1, wherein the ammonia evaporation waste liquid in the step 1) is cooled to 40 ℃.

4. the method for producing calcium sulfate dihydrate whiskers by using ammonia still waste liquid as claimed in claim 1, wherein in step 3), the volume concentration of CO ₂ in the CO ₂ kiln gas is 40%, the volume ratio of CO ₂ to ammonia still waste liquid is (1.1-1.2): 1, and the carbonization reaction time is 1 h.

5. The method for producing calcium sulfate dihydrate whiskers by using ammonia distillation waste liquor as claimed in claim 1, wherein the clear liquor in step 4) is heated to 94 ℃ and the saturated solution of sodium sulfate in step 5) is heated to 80 ℃.

6. The method for producing calcium sulfate dihydrate whiskers by using ammonia still waste liquid as claimed in claim 1, wherein the saturated sodium sulfate in step 5) is prepared by dissolving anhydrous sodium sulfate with a purity of 90% per 200kg of water per 410kg of water and filtering.

7. The method for producing calcium sulfate dihydrate whiskers by using ammonia distillation waste liquor as claimed in claim 1, wherein the water washing method in step 7) is to use a water washing method in which the water washing temperature is 80 ℃, and the mass ratio of the water washing temperature to the filter cake is 1:1 is washed by clean water.

8. the method for producing calcium sulfate dihydrate whiskers by using ammonia still waste liquor as claimed in claim 1, wherein the drying in step 7) is performed at 80 ℃ for 12 h.

9. The method for producing calcium sulfate dihydrate whiskers by using ammonia still waste liquid according to claim 1, characterized in that the filter cake in step 7) is washed with water to remove sodium chloride residues on the filter cake, so as to obtain washing water containing sodium chloride, and then the washing water is mixed with the clear liquid containing the residual calcium sulfate dihydrate whiskers obtained after filtration in step 6) and then concentrated, so as to obtain the clear liquid which is a salt solution with the sodium chloride mass concentration of 5% -6%.

Technical Field

the invention relates to the field of calcium sulfate whisker production, in particular to a method for producing calcium sulfate dihydrate whisker by using ammonia distillation waste liquid.

Background

The whisker is an important reinforcing component in the composite material, and the whisker reinforced composite material with excellent performance can be prepared by adding the whisker into materials taking metal, ceramic, rubber, plastic, resin and the like as matrixes. The whisker shows excellent physical and chemical properties and excellent mechanical properties when used as a modified reinforcing material.

Calcium sulfate whiskers generally refer to a fibrous (whisker-like) single crystal that is grown in a single crystal form by artificial control from gypsum, and has a uniform cross section, a complete shape, and a perfect internal structure. The calcium sulfate dihydrate crystal whisker, the calcium sulfate hemihydrate crystal whisker and the calcium sulfate anhydrite crystal whisker are all white fluffy solids in appearance.

the ammonia-soda process has the characteristics of long history, mature technology, high product purity, good quality and the like. Has great advantages for coastal and salt lake areas in China, but the ammonia-soda process for producing soda ash can produce huge amounts of waste liquid, waste residue and carbon dioxide waste gas. The ammonia evaporation waste liquid contains a large amount of calcium chloride and sodium chloride, ammonia nitrogen and calcium hydroxide, has pH of more than 11, has strong basicity and corrosivity, causes hardening of saline-alkali soil, soil hardening and threatens the surrounding environment. A large amount of solid slag is precipitated at the front end of the waste liquid reservoir, the quantity is huge, the reservoir capacity of the waste liquid reservoir is reduced, the liquid level of the tail reservoir is continuously improved, the lake discharge capacity is reduced, the safety warning line is continuously reduced, the potential threat to the surrounding ecological environment is caused, and the waste of mineral resources is caused. For the treatment in the ammonia distillation waste liquid, the existing treatment method in coastal areas is to mix a large amount of seawater after natural precipitation so as to dilute the pH value in the waste liquid and reduce the temperature of the waste liquid for direct discharge; the method for treating inland salt lake production area is characterized by that a large-scale waste liquor storage pool is built to store waste liquor, and the waste liquor is reduced by means of natural evaporation. The ammonia evaporation waste liquid contains alkalinity in residual solid residues, sodium chloride, calcium chloride and other salts after natural drying and evaporation, so that the soil is alkalized. Therefore, the recycling of the ammonia distillation waste liquid has important value for environmental protection.

Disclosure of Invention

The invention provides a method for producing calcium sulfate dihydrate crystal whisker by using ammonia evaporation waste liquid, aiming at the problem of recycling the ammonia evaporation waste liquid, and the method adopts the ammonia evaporation waste liquid and gypsum produced by thenardite as raw materials and comprises the following steps:

1) Cooling and separating the ammonia evaporation waste liquid to obtain liquid to be treated with solid content less than 5 g/L;

2) Precipitating and filtering the solution to be treated in the step 1), and concentrating the obtained filtrate to obtain clear liquid with the solid content of less than 100 mg/L;

3) Introducing CO ₂ kiln gas into the clear liquid obtained in the step 2), adjusting the pH value to 6-9, and carrying out carbonization reaction to obtain a salt solution containing calcium carbonate;

4) Concentrating the salt solution containing calcium carbonate prepared in the step 3) to obtain clear liquid with solid content less than 100mg/L, and heating the clear liquid to 94-100 ℃;

5) heating the saturated solution of sodium sulfate to 80-94 ℃;

6) Mixing the heated clear liquid in the step 4) with the heated sodium sulfate saturated solution in the step 5), preserving the heat for 4-6 hours at the temperature of 90-95 ℃ and the stirring speed of 150rpm to obtain a suspension, cooling to 60-70 ℃, and filtering;

7) And 6) washing and drying a filter cake obtained after filtering to obtain calcium sulfate dihydrate crystal whiskers, wherein the length-diameter ratio of the calcium sulfate dihydrate crystal whiskers is 30-50.

preferably, the mass ratio of the ammonia distillation waste liquid to the thenardite is that of the ammonia distillation waste liquid: anhydrous mirabilite 50: 7.

Preferably, the ammonia distillation waste liquid in the step 1) is cooled to 40 ℃.

Preferably, the volume concentration of CO ₂ in the CO ₂ kiln gas in the step 3) is 40%, the volume ratio of CO ₂ to the ammonia distillation waste liquid is (1.1-1.2): 1, and the carbonization reaction time is 1 h.

Preferably, the clear solution of step 4) is heated to 94 ℃ and the saturated solution of sodium sulfate of step 5) is heated to 80 ℃.

Preferably, the saturated sodium sulfate of step 5) is prepared by dissolving anhydrous sodium sulfate having a purity of 90% per 200kg of water per 410kg of water and filtering.

Preferably, the water washing method in the step 7) is to use a water washing method with the mass ratio of 80 ℃ to the filter cake of 1:1 is washed by clean water.

Preferably, the drying in step 7) is drying at 80 ℃ for 12 h.

Preferably, the filter cake in the step 7) is washed by water, sodium chloride residues on the filter cake are removed, washing water containing sodium chloride is obtained, and then the washing water is mixed with the clear liquid containing the residual calcium sulfate dihydrate crystal whiskers obtained after filtration in the step 6) and concentrated, so that the obtained clear liquid is a salt solution with the sodium chloride mass concentration of 5% -6%.

Advantageous effects

In the aspect of production of calcium sulfate whiskers: the existing gypsum fiber preparation technology uses natural gypsum as a raw material, and belongs to a mineral conversion method. The purity of the gypsum fiber product produced by the method depends on production raw materials, the whiteness of the product is obviously influenced by the production raw materials and the configuration of equipment, and different mineral sources need to be selected according to market requirements. The calcium chloride in the ammonia distillation waste liquid reacts with the sodium sulfate to obtain the gypsum, and the gypsum whisker with high purity and good whiteness can be produced by a chemical conversion method. Meanwhile, the emission of ammonia distillation waste liquid and the recycling of salt water are reduced.

the invention utilizes the carbon dioxide waste gas generated in the production process of soda ash to treat ammonia distillation waste liquid and purchase excessive anhydrous sodium sulfate in inland production areas. Through working sections such as pretreatment, carbonization, calcium sulfate whisker reaction and the like, the calcium sulfate dihydrate whisker is obtained, sodium chloride is recycled, and carbon dioxide waste gas is also utilized, so that a large amount of carbon dioxide is reduced. The method achieves the aims of treating the ammonia distillation waste liquid pollution, improving the water resource utilization and increasing new products.

finally, the method realizes the complete resource utilization of the waste ammonia evaporation waste liquid, the carbon dioxide waste gas and other effective components in the process of producing the soda ash by the ammonia-soda process, achieves the purposes of utilizing waste to prepare waste and changing waste into valuable, and develops the production approach of the calcium sulfate whisker. Improves the economic benefit and converts the gypsum with low added value into the calcium sulfate dihydrate whisker product with high added value. Emission reduction of carbon dioxide in industrial waste gas, and the emission reduction of carbon can be reduced by 12g for each ton of waste water.

Detailed Description

The water quality indexes of the ammonia distillation waste liquid in the invention are shown in the following table 1:

TABLE 1 Ammonia distillation effluent quality

the method for producing calcium sulfate whiskers by using the ammonia still waste liquor of soda ash according to the present invention is specifically described below.