阅读说明：本技术 一种蒸氨废液水热法制备半水硫酸钙晶须的方法 (Method for preparing calcium sulfate hemihydrate crystal whisker by ammonia distillation waste liquid hydrothermal method ) 是由 罗仙平 宋学文 曹雨微 刘辉 翁存建 逯登琴 宋磊 贾发云 周贺鹏 于 2021-01-14 设计创作，主要内容包括：本发明公开了一种蒸氨废液水热法制备半水硫酸钙晶须的方法,按以下步骤进行：将蒸氨废液过滤,硫酸铵加水完全溶解；将过滤后的蒸氨废液和溶解的硫酸铵移入高温高压反应釜中,设置一定的温度、转速和时间生成白色沉淀；将反应所得产物进行过滤、洗涤、干燥得到半水硫酸钙晶须。本发明以蒸氨废液为钙源,其工艺流程简单、生产成本低,在高效回收利用蒸氨废液的同时实现了半水硫酸钙晶须的制备,使得蒸氨废液得到了回收利用,具有良好的环境效益；采用本方案制备的半水硫酸钙晶须产品长径比大,可以用作増强组元、摩擦材料、造纸材料等,具有极大的应用价值和市场价值。(The invention discloses a method for preparing calcium sulfate hemihydrate crystal whiskers by ammonia distillation waste liquid hydrothermal method, which comprises the following steps: filtering the ammonia distillation waste liquid, and adding water into ammonium sulfate for complete dissolution; transferring the filtered ammonia evaporation waste liquid and the dissolved ammonium sulfate into a high-temperature high-pressure reaction kettle, and setting certain temperature, rotation speed and time to generate white precipitate; and filtering, washing and drying the product obtained by the reaction to obtain the calcium sulfate hemihydrate crystal whisker. The method takes the ammonia evaporation waste liquid as a calcium source, has simple process flow and low production cost, realizes the preparation of the calcium sulfate hemihydrate crystal whisker while efficiently recycling the ammonia evaporation waste liquid, ensures that the ammonia evaporation waste liquid is recycled, and has good environmental benefit; the semi-hydrated calcium sulfate whisker product prepared by the scheme has large length-diameter ratio, can be used as a reinforcing component, a friction material, a paper making material and the like, and has great application value and market value.)

1. A method for preparing calcium sulfate hemihydrate whiskers by an ammonia evaporation waste liquid hydrothermal method is characterized by comprising the following steps: the method comprises the following steps of (1),

A. filtering the ammonia distillation waste liquid to completely remove solid impurities;

B. weighing ammonium sulfate, adding water to dissolve completely, and rapidly transferring the filtered ammonia distillation waste liquid and the dissolved ammonium sulfate into a reaction kettle with set parameters for reaction so as to obtain Ca in the ammonia distillation waste liquid²⁺And SO₄ ^2-Fully contacting to generate calcium sulfate precipitate under hydrothermal condition;

C. and filtering a product obtained by the reaction, washing and drying a filter cake to obtain the calcium sulfate hemihydrate crystal whisker.

The chemical equation for the reaction is as follows:

CaCl₂+(NH₄)₂SO₄→CaSO₄·0.5H₂O+NH₄Cl。

2. the method for preparing the calcium sulfate hemihydrate whiskers by the ammonia evaporation waste liquid hydrothermal method according to claim 1, characterized by comprising the following steps: in step B, Ca is maintained before the filtered ammonia distillation waste liquid is transferred to the dissolved ammonium carbonate²⁺And SO₄ ^2-The concentration is 1.2mol/L, Ca in the reaction system is obtained after the filtered ammonia distillation waste liquid and the dissolved ammonium sulfate are transferred into a reaction kettle²⁺And CO₃ ^2-Is 1: 1.

3. The method for preparing the calcium sulfate hemihydrate whiskers by the ammonia evaporation waste liquid hydrothermal method according to claim 2, characterized by comprising the following steps: in the step B, the initial pH of the ammonia evaporation waste liquid filtrate is 11.2, the pH of the calcium sulfate solution is not adjusted, and the initial pH of the reaction is not adjusted.

4. The method for preparing the calcium sulfate hemihydrate whiskers by the ammonia evaporation waste liquid hydrothermal method according to claim 2, characterized by comprising the following steps: in the step B, the filtered ammonia distillation waste liquid and the dissolved ammonium sulfate are placed at the rotation speed of 500r/min and the initial temperature of normal temperature, when the temperature of the reaction kettle rises to between 115 ℃ and 145 ℃, the temperature is kept unchanged, and the reaction is finished after 60min under the condition.

5. The method for preparing calcium sulfate dihydrate whiskers by the ammonia evaporation waste liquid hydrothermal method according to claim 2, characterized by comprising the following steps: in the step B, the ratio of the total volume of the ammonia evaporation waste liquid and the ammonium sulfate solution to the total volume of the reaction kettle is 72%.

6. The method for preparing the calcium sulfate hemihydrate whiskers by the ammonia evaporation waste liquid hydrothermal method according to claim 1, characterized by comprising the following steps: in the step A, the ammonia evaporation waste liquid is filtered for three times.

Technical Field

The invention relates to the technical field of calcium sulfate whisker preparation, in particular to a method for preparing calcium sulfate hemihydrate whiskers by an ammonia evaporation waste liquid hydrothermal method.

Background

The calcium sulfate whisker has the advantages of good thermal stability, chemical corrosion resistance, nearly perfect structure, high strength and rigidity and the like. The crystal morphology and crystal size of the calcium sulfate hemihydrate whiskers have a decisive influence on the application properties thereof. The calcium sulfate hemihydrate crystal whisker with lower aspect ratio has excellent mechanical performance and good fluidity and is suitable for being used as a cement framework. The calcium sulfate whisker with high length-diameter ratio is widely applied to industries such as plastics, ceramics, rubber, papermaking and the like as a reinforcing material due to excellent thermal stability, chemical resistance and good compatibility.

From the economic and environmental aspects, the preparation of the calcium sulfate whisker by using the industrial byproduct has great economic effect and environmental effect, the research and application of the calcium sulfate whisker in foreign countries and the like relate to the fields of electronics, instruments, machinery and the like, and the research and application of the calcium sulfate whisker in China is relatively late, but has great market demand. At present, the annual output of calcium sulfate whiskers in China is about ten thousand tons, and most of calcium sulfate whiskers are exported; the future development trend of industry is to replace the existing whisker products with calcium sulfate whiskers, and the calcium sulfate whiskers are applied to the industries of engineering plastics, rubber, papermaking and the like. According to the use conditions at home and abroad, the dosage of the calcium sulfate whisker used as the additive is usually the base material, and the annual demand is about ten thousand tons; if the automobile, coating, electronic, building material and other industries can be continuously developed, the annual demand is expected to exceed ten thousand tons, and the output value can break through hundred million yuan. The introduction of the calcium sulfate whisker reduces the production cost for each industry and effectively improves the profit margin. Therefore, the application research of the calcium sulfate whisker by using the ammonia distillation waste liquid has great economic value and environmental effect.

Disclosure of Invention

The invention aims to solve the technical problem of the prior art, provides a method which has the characteristics of simpler process flow, convenient operation and environmental friendliness, realizes the preparation method of calcium sulfate hemihydrate whiskers while efficiently recycling ammonia evaporation waste liquid, and provides a method for preparing calcium sulfate hemihydrate whiskers by using an ammonia evaporation waste liquid hydrothermal method.

In order to solve the technical problems, the invention adopts the following technical scheme: a method for preparing calcium sulfate hemihydrate whiskers by an ammonia evaporation waste liquid hydrothermal method is characterized by comprising the following steps: the method comprises the following steps of (1),

A. filtering the ammonia evaporation waste liquid for three times;

B. weighing ammonium sulfate, and adding water to completely dissolve;

C. transferring the filtered ammonia distillation waste liquid and ammonium sulfate into a reaction kettle, stirring and reacting at the same time, adjusting the rotating speed to 500r/min, regulating and controlling the temperature to 145 ℃ of 115-;

D. and (3) quickly filtering a product obtained by the reaction, and washing and drying a filter cake to obtain the calcium sulfate dihydrate crystal whisker.

The chemical equation for the reaction is as follows:

CaCl₂+(NH₄)₂SO₄→CaSO₄·0.5H₂O+NH₄Cl

in step B, Ca is maintained before the filtered ammonia distillation waste liquid is transferred to the dissolved ammonium carbonate²⁺And CO₃ ^2-The concentration is 1.2mol/L, Ca in the reaction system is obtained after the filtered ammonia distillation waste liquid and ammonium sulfate are transferred into a reaction kettle²⁺And CO₃ ^2-In a molar ratio of 1: 1; the initial pH of the ammonia evaporation waste liquid filtrate is 11.2; the ammonia evaporation waste liquid and the dissolved ammonium sulfate solution are put into the reaction at any temperature between the rotating speed of 500r/min and the reaction temperature of 115-145 ℃, the reaction time is 60min, and the ammonia evaporation waste liquid and the dissolved ammonium sulfate solution are quickly filtered and immediately dried after the reaction is finished.

The method takes the ammonia evaporation waste liquid as the raw material, the filtrate of the ammonia evaporation waste liquid and the ammonium sulfate solution are added into the reaction kettle, and the calcium sulfate hemihydrate crystal whisker prepared by a hydrothermal method has the advantages of simple process flow and low production cost, and not only can the raw material not generate obvious environmental pollution, but also the ammonia evaporation waste liquid is recycled, so that the problem of difficult preparation of the calcium sulfate hemihydrate crystal whisker is solved while the ammonia evaporation waste liquid is efficiently recycled, the ammonia evaporation waste liquid is recycled, and certain environmental benefits are achieved.

Drawings

FIG. 1 shows the X-ray diffraction analysis (XRD spectrum) of calcium sulfate hemihydrate whiskers;

FIG. 2 is a scanning electron micrograph of calcium sulfate hemihydrate whiskers.

Detailed Description

The following is further described in conjunction with the detailed description:

example 1, preparation of the reaction starting materials: filtering the ammonia distillation waste liquid for three times, and taking the filtrate, wherein Ca is contained in the filtrate²⁺The concentration is 1.20 mol.L^-1. 14.271g of ammonium sulfate is weighed and placed in a conical flask, 90ml of water is added, and the mixture is fully shaken until the ammonium sulfate is completely dissolved;

secondly, preparing calcium sulfate hemihydrate whiskers: and (3) putting 90mL of ammonia evaporation waste liquid filtrate into a measuring cylinder, putting 90mL of completely dissolved ammonium sulfate solution into a high-temperature high-pressure mechanical stirring reaction kettle, adjusting the rotating speed to 500r/min, regulating and controlling the temperature to 115 ℃, quickly adding the measured ammonia evaporation waste liquid filtrate and ammonium sulfate solution into the reaction kettle after the solution is ready, keeping the temperature unchanged after the temperature of the reaction kettle is increased to 115 ℃, and reacting for 120min under the condition of 500 r/min. The product is filtered, quickly washed and immediately dried to obtain the calcium sulfate dihydrate crystal whisker.

Example 2, preparation of the reaction starting materials: filtering the ammonia distillation waste liquid for three times, and taking the filtrate, wherein Ca is contained in the filtrate²⁺The concentration is 1.20 mol.L^-1. 14.271g of ammonium sulfate is weighed and placed in a conical flask, 90ml of water is added, and the mixture is fully shaken until the ammonium sulfate is completely dissolved;

secondly, preparing calcium sulfate hemihydrate whiskers: and (3) putting 90mL of ammonia evaporation waste liquid filtrate into a measuring cylinder, putting 90mL of completely dissolved ammonium sulfate solution into a high-temperature high-pressure mechanical stirring reaction kettle, adjusting the rotating speed to 500r/min, regulating and controlling the temperature to 130 ℃, quickly adding the measured ammonia evaporation waste liquid filtrate and ammonium sulfate solution into the reaction kettle after the ammonia evaporation waste liquid filtrate and the ammonium sulfate solution are ready, keeping the temperature unchanged after the temperature of the reaction kettle is raised to 130 ℃, and reacting for 120min under the condition of 500 r/min. The product is filtered, quickly washed and immediately dried to obtain the calcium sulfate dihydrate crystal whisker.

Example 3, preparation of the reaction starting materials: filtering the ammonia distillation waste liquid for three times, and taking the filtrate, wherein Ca is contained in the filtrate²⁺The concentration is 1.20 mol.L^-1. 14.271g of ammonium sulfate is weighed and placed in a conical flask, 90ml of water is added, and the mixture is fully shaken until the ammonium sulfate is completely dissolved;

secondly, preparing calcium sulfate hemihydrate whiskers: and (3) putting 90mL of ammonia distillation waste liquid filtrate into a measuring cylinder, putting 90mL of ammonium sulfate solution which is completely dissolved into a high-temperature high-pressure mechanical stirring reaction kettle, adjusting the rotating speed to 500r/min, regulating and controlling the temperature to 145 ℃, quickly adding the measured ammonia distillation waste liquid filtrate and ammonium sulfate solution into the reaction kettle after the solution is ready, keeping the temperature unchanged after the temperature of the reaction kettle is increased to 145 ℃, and reacting for 120min under the condition of 500 r/min. The product is filtered, quickly washed and immediately dried to obtain the calcium sulfate dihydrate crystal whisker.

Example 4, preparation of the reaction starting materials: filtering the ammonia distillation waste liquid for three times, and taking the filtrate, wherein Ca is contained in the filtrate²⁺The concentration is 1.20 mol.L^-1. 14.271g of ammonium sulfate is weighed and placed in a conical flask, 90ml of water is added, and the mixture is fully shaken until the ammonium sulfate is completely dissolved;

secondly, preparing calcium sulfate hemihydrate whiskers: and (3) putting 90mL of ammonia evaporation waste liquid filtrate into a measuring cylinder, putting 90mL of completely dissolved ammonium sulfate solution into a high-temperature high-pressure mechanical stirring reaction kettle, adjusting the rotating speed to 500r/min, regulating and controlling the temperature to 130 ℃, quickly adding the measured ammonia evaporation waste liquid filtrate and ammonium sulfate solution into the reaction kettle after the solution is ready, keeping the temperature unchanged after the temperature of the reaction kettle is raised to 130 ℃, and reacting for 80min under the condition of 500 r/min. The product is filtered, quickly washed and immediately dried to obtain the calcium sulfate dihydrate crystal whisker.

Example 5, preparation of the reaction starting materials: filtering the ammonia distillation waste liquid for three times, and taking the filtrate, wherein Ca is contained in the filtrate²⁺The concentration is 1.20 mol.L^-1. 14.271g of ammonium sulfate is weighed and placed in a conical flask, 90ml of water is added, and the mixture is fully shaken until the ammonium sulfate is completely dissolved;

secondly, preparing calcium sulfate hemihydrate whiskers: and (3) putting 90mL of ammonia evaporation waste liquid filtrate into a measuring cylinder, putting 90mL of completely dissolved ammonium sulfate solution into a high-temperature high-pressure mechanical stirring reaction kettle, adjusting the rotating speed to 500r/min, regulating and controlling the temperature to 130 ℃, quickly adding the measured ammonia evaporation waste liquid filtrate and ammonium sulfate solution into the reaction kettle after the solution is ready, keeping the temperature unchanged after the temperature of the reaction kettle is raised to 130 ℃, and reacting for 100min under the condition of 500 r/min. The product is filtered, quickly washed and immediately dried to obtain the calcium sulfate dihydrate crystal whisker.

The present invention has been described in detail, and it should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.