A method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid

Abstract

This invention provides a method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid, belonging to the technical field of calcium sulfate dihydrate preparation. The method includes the following steps: S1, purifying the anthraquinone waste sulfuric acid through an adsorption column, adding calcium sulfate, heating and stirring to dissolve, obtaining an acidic solution; S2, separately mixing calcium carbonate and water, stirring evenly, then adding a flocculant and stirring to obtain a mixture, adding the above acidic solution dropwise to the mixture, controlling the pH value of the reaction material, and continuing stirring until the reaction is complete; S3, filtering the material after the reaction to obtain large-particle-size calcium sulfate dihydrate. This invention provides a method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid, achieving the purpose of increasing the particle size of the calcium sulfate dihydrate product and reducing the attached water content of the calcium sulfate dihydrate product.

Description

Technical Field

[0001] This invention relates to the field of calcium sulfate dihydrate preparation technology, specifically to a method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid. Background Technology

[0002] Alkyl anthraquinones are important chemical raw materials in industrial production, widely used in the production of hydrogen peroxide, liquid crystals, dyes, pesticides, and pharmaceuticals. The phthalic anhydride process is currently the most widely used method for producing alkyl anthraquinones in China, offering advantages such as low cost and simple process. However, this process generates large quantities of waste sulfuric acid containing high concentrations of organic matter, which is highly corrosive and extremely harmful to the environment. Currently, there are relatively mature technologies for treating waste sulfuric acid, primarily focusing on its regeneration, purification, and utilization.

[0003] Calcium sulfate dihydrate is one of the main byproducts of anthraquinone waste sulfuric acid treatment. Calcium sulfate dihydrate (CaSO4·2H2O), commonly known as gypsum, is a white crystalline powder whose applications depend on the particle size of the crystals. Under current processes, the prepared calcium sulfate dihydrate particles are small and have a wide size distribution, resulting in high attached water content, slow filtration speed, and high impurity content. Therefore, it is often only treatable as industrial solid waste, increasing treatment costs. Summary of the Invention

[0004] In view of this, the present invention provides a method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid, thereby achieving the purpose of increasing the particle size of the calcium sulfate dihydrate product and reducing the attached water content of the calcium sulfate dihydrate product.

[0005] To achieve the above objectives, the present invention provides a method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid, comprising the following steps: S1. The anthraquinone waste sulfuric acid is purified by adsorption column, calcium sulfate is added, and the solution is heated and stirred to dissolve, thus obtaining an acidic solution. S2. Take calcium carbonate and water, mix them evenly, then add flocculant and stir to obtain a mixture. Add the above acidic solution dropwise to the mixture, control the pH value of the reactants, and keep stirring until the reaction is complete after the dropwise addition is finished. S3. After the reaction is complete, the material is filtered to obtain large-particle-size calcium sulfate dihydrate.

[0006] Optionally, the adsorbent in the adsorption column is one or a combination of two or more of macroporous adsorption resin, diatomaceous earth, and activated carbon.

[0007] Optionally, the mass ratio of calcium sulfate to anthraquinone waste sulfuric acid is 1:(100-250).

[0008] Optionally, the mass ratio of calcium sulfate to anthraquinone waste sulfuric acid is 1:(150-20).

[0009] Optionally, the mass ratio of calcium carbonate to water is 1:(5-16).

[0010] Optionally, the mass ratio of calcium carbonate to water is 1:(8-10).

[0011] Optionally, the flocculant is one or a combination of two or more of polyacrylamide, polyvinylamide, and polyoxyethylene.

[0012] Optionally, the flocculant is polyacrylamide.

[0013] Optionally, the mass ratio of the flocculant to calcium carbonate is 1:(500-1500).

[0014] Optionally, the pH value is 4 to 7.

[0015] To achieve the above objectives, the present invention provides a method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid.

[0016] The above-described technical solution of the present invention has at least the following beneficial effects: The preparation method provided by this invention is simple, and the proportion of 150-250 mesh particles in the obtained calcium sulfate dihydrate product is ≥75%, and the attached water content of the calcium sulfate dihydrate product is less than 15%. The reuse of anthraquinone waste sulfuric acid can effectively reduce production costs and realize the resource utilization of waste acid. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0018] The test method for the adhering water content in this application is as follows: the dry difference method is used according to GB / T 5484-2012 Chemical Analysis Methods for Gypsum.

[0019] The test method for the particle size of calcium sulfate dihydrate in this application is as follows: the particle size is determined by manual sieving according to the method specified in GB / T 17669.5-1999 "Determination of Physical Properties of Building Gypsum Powder".

[0020] Example 1 1000 kg of anthraquinone waste sulfuric acid (50% mass concentration) was pumped into a 2m... 3In the waste acid high-level tank, anthraquinone waste sulfuric acid flows from the top of the tank into the adsorption column. After adsorption by macroporous resin, the purified anthraquinone sulfuric acid flows from the bottom of the adsorption column into the sulfuric acid tank. The purified anthraquinone sulfuric acid is then pumped into the reaction vessel via a centrifugal pump. 10 kg of calcium sulfate is added to the reaction vessel, stirred and dissolved, and then pumped into the sulfuric acid high-level tank via a centrifugal pump.

[0021] 500 kg of calcium carbonate was added to a 15 m³ solution. 3 In the gypsum synthesis reactor, 8000 kg of water and 0.5 kg of polyacrylamide were added. After stirring for 30 minutes, anthraquinone sulfuric acid from the sulfuric acid high-level tank was added to the gypsum synthesis reactor through the regulating valve. The sulfuric acid dripping rate was adjusted to control the pH value between 4 and 7. After the dripping was completed, the reaction was stirred for another 30 minutes and then stopped.

[0022] After the reaction is complete, the solid-liquid mixture is filtered and separated, and the filter cake is calcium sulfate dihydrate product.

[0023] The attached water content and particle size of the calcium sulfate dihydrate product prepared in Example 1 were measured and the following results were obtained: the attached water content was 13.7%, the proportion of particles with a particle size of less than 150 mesh was 8.3%, the proportion of particles with a particle size of 150-250 mesh was 76.4%, and the proportion of particles with a particle size of more than 250 mesh was 15.3%.

[0024] Example 2 Compared with Example 1, the difference is that the 10 kg of calcium sulfate in Example 1 is replaced with 5 kg of calcium sulfate, and the 0.5 kg of polyacrylamide is replaced with 0.25 kg of polyethylene oxide. The remaining steps and raw materials are the same as in Example 1.

[0025] The attached water content and particle size of the calcium sulfate dihydrate product prepared in Example 2 were measured and the following results were obtained: the attached water content was 19.5%, the proportion of particles with a particle size of less than 150 mesh was 6.6%, the proportion of particles with a particle size of 150-250 mesh was 66.8%, and the proportion of particles with a particle size of more than 250 mesh was 26.6%.

[0026] Example 3 Compared with Example 1, the difference is that the macroporous adsorption resin in Example 1 is replaced with activated carbon, while the remaining steps and raw materials are the same as in Example 1.

[0027] The attached water content and particle size of the calcium sulfate dihydrate product prepared in Example 3 were measured and the following results were obtained: the attached water content was 16.9%, the proportion of particles with a particle size of less than 150 mesh was 16.6%, the proportion of particles with a particle size of 150-250 mesh was 69.9%, and the proportion of particles with a particle size of more than 250 mesh was 13.5%.

[0028] Example 4 Compared with Example 1, the difference is that the amount of calcium sulfate used in Example 1 is changed from 10 kg to 15 kg, while the rest of the steps and raw materials are the same as in Example 1.

[0029] The attached water content and particle size of the calcium sulfate dihydrate product prepared in Example 4 were measured and the following results were obtained: the attached water content was 15.7%, the proportion of particles with a particle size of less than 150 mesh was 10.5%, the proportion of particles with a particle size of 150-250 mesh was 71.7%, and the proportion of particles with a particle size of more than 250 mesh was 17.8%.

[0030] Comparative Example 1 Compared with Example 1, the difference is that the dropping rate of sulfuric acid in Example 1 is increased by 1 times, the pH value at the beginning of the reaction is ≤3, and the remaining steps and raw materials are the same as in Example 1.

[0031] The attached water content and particle size of the calcium sulfate dihydrate product prepared in Comparative Example 1 were determined as follows: the attached water content was 29.4%, the proportion of particles with a particle size of less than 150 mesh was 10.5%, the proportion of particles with a particle size of 150-250 mesh was 57.7%, and the proportion of particles with a particle size of more than 250 mesh was 31.8%.

[0032] Comparative Example 2 1000 kg of anthraquinone waste sulfuric acid (50% mass concentration) was pumped into a 2m... 3 In the waste acid high-level tank, anthraquinone waste sulfuric acid flows from the top of the tank into the adsorption column. After adsorption by macroporous resin, the purified anthraquinone sulfuric acid flows from the bottom of the adsorption column into the sulfuric acid tank. 4000 kg of water is added to the reactor, and the purified anthraquinone sulfuric acid is pumped into the reactor via a centrifugal pump, stirred evenly, and then pumped into the sulfuric acid high-level tank in batches via a centrifugal pump.

[0033] Next, 500 kg of calcium carbonate, 2000 kg of water, and 0.5 kg of polyacrylamide were added sequentially to the gypsum synthesis reactor. After stirring for 30 minutes, anthraquinone sulfuric acid from the sulfuric acid high-level tank was added to the gypsum synthesis reactor through a regulating valve. The sulfuric acid dripping rate was adjusted to control the pH value ≥ 4. After the dripping was completed, the reaction was stirred for another 30 minutes, and then the reaction was stopped. The solid-liquid mixture was filtered to separate the solids and liquids, and the filter cake was calcium sulfate dihydrate.

[0034] The attached water content and particle size of the calcium sulfate dihydrate product prepared in Comparative Example 2 were determined as follows: the attached water content was 28.9%, the proportion of particles with a particle size below 150 mesh was 4.2%, the proportion of particles with a particle size between 150 and 250 mesh was 59.8%, and the proportion of particles with a particle size above 250 mesh was 36.0%.

[0035] Comparative Example 3 Take 1000g of anthraquinone waste sulfuric acid and add it in batches to a 5L three-necked glass flask. Take 2L of water and 400g of calcium hydroxide, mix them evenly, and add them in batches to the three-necked flask. Stir for 30 minutes, filter the solid-liquid mixture, and the filter cake is calcium sulfate dihydrate product.

[0036] The attached water content and particle size of the calcium sulfate dihydrate product prepared in Comparative Example 3 were determined as follows: the attached water content was 48.4%, the proportion of particles with a particle size of less than 150 mesh was 11.3%, the proportion of particles with a particle size of 150-250 mesh was 14.8%, and the proportion of particles with a particle size of more than 250 mesh was 73.9%.

[0037] Comparative Example 4 Compared with Comparative Example 3, the difference is that the 1000g of anthraquinone waste sulfuric acid in Comparative Example 3 was replaced with 1000g of purified anthraquinone sulfuric acid, and the 380g of calcium hydroxide was replaced with 500g of calcium carbonate. The remaining steps and raw materials are the same as those in Comparative Example 3.

[0038] The attached water content and particle size of the calcium sulfate dihydrate product prepared in Comparative Example 4 were determined as follows: the attached water content was 39.6%, the proportion of particles with a particle size below 150 mesh was 17.7%, the proportion of particles with a particle size between 150 and 250 mesh was 40.8%, and the proportion of particles with a particle size above 250 mesh was 51.5%.

[0039] Comparative Example 5 Take 1000g of anthraquinone waste sulfuric acid and add it in batches to a 5L three-necked glass flask. Take 2L of water and 400g of calcium hydroxide and mix them evenly, then add them in batches to the three-necked flask. Stir for 30 minutes. Add 1g of polyacrylamide to the three-necked flask and continue stirring for 30 minutes. Filter the solid-liquid mixture to separate it. The filter cake is calcium sulfate dihydrate product.

[0040] The attached water content and particle size of the calcium sulfate dihydrate product prepared in Comparative Example 5 were determined as follows: the attached water content was 40.5%, the proportion of particles with a particle size of less than 150 mesh was 7.7%, the proportion of particles with a particle size of 150-250 mesh was 18.6%, and the proportion of particles with a particle size of more than 250 mesh was 73.7%.

[0041] As can be seen from Examples 1-4 and Comparative Examples 1-5 above, the calcium sulfate dihydrate product obtained by the preparation method provided by the present invention has a low content of attached water and a higher proportion of 150-250 mesh particles.

[0042] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid, characterized in that, Includes the following steps: S1. The anthraquinone waste sulfuric acid is purified by adsorption column, calcium sulfate is added, and the solution is heated and stirred to dissolve, thus obtaining an acidic solution. S2. Take calcium carbonate and water, mix them evenly, then add flocculant and stir to obtain a mixture. Add the above acidic solution dropwise to the mixture, control the pH value of the reactants, and keep stirring until the reaction is complete after the dropwise addition is finished. S3. After the reaction is complete, the material is filtered to obtain large-particle-size calcium sulfate dihydrate.

2. The method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid according to claim 1, characterized in that, The adsorbent in the adsorption column is one or a combination of two or more of macroporous adsorption resin, diatomaceous earth, and activated carbon.

3. The method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid according to claim 1, characterized in that, The mass ratio of calcium sulfate to anthraquinone waste sulfuric acid is 1:(65-250).

4. The method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid according to claim 1, characterized in that, The mass ratio of calcium carbonate to water is 1:(5-16).

5. The method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid according to claim 1, characterized in that, The flocculant is one or a combination of two or more of polyacrylamide, polyvinylamide, and polyoxyethylene.

6. The method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid according to claim 1, characterized in that, The mass ratio of the flocculant to calcium carbonate is 1:(500-2000).

7. The method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid according to claim 1, characterized in that, The pH value is 4 to 7.

8. A method for preparing large-particle-size calcium sulfate dihydrate from anthraquinone waste sulfuric acid as described in any one of claims 1-7.