CN116676672A - Method for preparing calcium sulfate whisker from mirabilite gypsum - Google Patents

Abstract

The invention discloses a method for preparing calcium sulfate whiskers from Glauber's salt gypsum, which relates to the technical field of preparing calcium sulfate whiskers, and includes the following steps: S1. Pretreatment of raw materials: adding water to dissolve and stir the raw material Glauber's salt gypsum at normal temperature, and exporting the upper layer Stir and hydrolyze the slurry, add calcium water, add dilute sulfuric acid to adjust the pH after fully stirring, wash with water for 2 to 3 times, filter to obtain a filter cake, add water to prepare a uniform gypsum slurry; S2, preparation of whiskers by hydrothermal method and modification: to step Add 2% to 10% magnesium salt or copper salt crystal growth promoter to the gypsum slurry obtained in S1, then add the gypsum slurry to the spherical reactor, use the pressure pump to pump the stabilizer and modifier, and the modification time for 0.5h to 2h, and then conduct solid-liquid separation of the reacted slurry to obtain a filter cake; S3, drying of the product. The technological process adopted in the present invention and the optimized technological operating conditions can make the finally obtained calcium sulfate whiskers have a uniform appearance, a suitable length-to-diameter ratio, and a high yield.

Description

A kind of method that prepares calcium sulfate whisker with Glauber's salt gypsum

technical field

The invention relates to the technical field of preparation of calcium sulfate whiskers, in particular to a method for preparing calcium sulfate whiskers from mirabilite gypsum.

Background technique

Gypsum whiskers are a new type of inorganic material with high comprehensive performance. The material has high strength, good toughness, high modulus, high dielectric strength, wear resistance, high temperature resistance, corrosion resistance, good infrared reflectivity, easy surface treatment, strong affinity with polymers, and good compatibility And smoothness, non-toxic and many other excellent physical and chemical properties. It can be used as reinforcement and toughening agent or functional filler in ceramics, metals, resins, plastics, rubber, coatings, paints, papermaking, asphalt, friction and sealing materials, and high insulation materials covering wires; it can also be used as insulation materials, Flame retardant materials, refractory heat insulation materials, infrared reflective materials; also can be used as filters, catalysts and carriers. The price of gypsum whiskers is only 1/200~1/300 of that of silicon carbide whiskers. It has an incomparable cost performance of other whiskers. It has a wide range of applications and strong market competitiveness.

According to the situation of using gypsum whiskers abroad, as an additive, the dosage of gypsum whiskers is 3-30% of the base material, generally 5-15%. If there are 10% paper plus gypsum whiskers, the demand is 50×6%=30,000 tons; if it is used in the plastic and rubber industry, the total domestic output is more than 8 million tons, if there are 10% of the products Adding gypsum whiskers requires 80×5%=40,000 tons. In addition, gypsum whiskers are used in friction materials, environmental engineering, lightweight building materials and other fields. It is estimated that the market prospect is expected to reach 2 million tons/year. Due to its wide application, large market demand, and low production cost of gypsum whiskers (the raw materials are usually low-cost industrial by-products or wastes), it has strong market competitiveness. Gypsum whiskers have been included in the catalog of high-tech industries encouraged by the state.

Domestic raw materials for preparing gypsum whiskers are very abundant, cheap and easy to obtain, and many raw materials can come from by-products and wastes in the production process. In Zigong area of my country alone, industrial wastes that can be used to prepare gypsum whiskers mainly include mirabilite gypsum3 thousand tons/year.

Glauber's salt gypsum is the milky white waste residue of sodium sulfate extracted from the symbiotic mine of Glauber's salt and gypsum, or Glauber's salt produced from Glauber's salt. In recent years, the annual output of thenardite in my country has remained at about 10 million tons, and the output of thenardite gypsum in 2020 will be about 4 million tons.

Due to the complexity of the components in Glauber's salt gypsum, in the current prior art method of preparing calcium sulfate whiskers using Glauber's salt gypsum, each component in Glauber's salt gypsum cannot be fully utilized, resulting in insufficient utilization of raw materials for preparation, affecting production efficiency .

For this reason, the present invention aims to provide a kind of new method that prepares calcium sulfate whisker with Glauber's salt gypsum, to solve the above problems.

Contents of the invention

The purpose of the present invention is in order to solve the problems referred to above, a kind of method of preparing calcium sulfate whisker with Glauber's salt gypsum is provided.

In order to achieve the above object, technical scheme of the present invention is as follows:

The invention provides a method for preparing calcium sulfate whiskers with Glauber's salt gypsum, comprising the following steps:

S1. Pretreatment of raw materials:

Dissolve and stir the raw material Glauber’s salt gypsum with water at room temperature, export the upper layer slurry, stir and hydrolyze it, add calcium water, add dilute sulfuric acid to adjust the pH after fully stirring, wash with water 2 to 3 times, filter to obtain a filter cake, add water to prepare a uniform gypsum slurry;

S2. Preparation of whiskers by hydrothermal method and modification:

Add 2% to 10% magnesium salt or copper salt crystal growth agent to the gypsum slurry obtained in step S1, then add the gypsum slurry into a spherical reactor, heat up to 120°C and start timing reaction for 3.5 hours, Use a pressure pump to pump in the stabilizer and modifier, the modification time is 0.5h to 2h, and then the reacted slurry is subjected to solid-liquid separation to obtain a filter cake;

S3. Drying of the product:

The filter cake obtained by the solid-liquid separation in step S2 is washed with cold water, and then dried by microwave at a power of 500-1000W for 20-60 minutes to obtain a calcium sulfate whisker product.

Further, the calcium water added in step S1 is 0.6-1.6 mol/L.

Further, dilute sulfuric acid is added in step S1 to adjust the pH to 2-6.

Further, the stabilizing and modifying agent described in step S2 includes stearate, stearic acid, silane coupling agent or titanate coupling agent, and the mass fraction of the described stabilizing and modifying agent in gypsum is 0.5% to 4%.

Further, the spherical tank reactor described in step S1 is a stirred, jacketed spherical tank reactor lined with a polytetrafluoroethylene-filled graphite anti-corrosion lining.

In the solution of the present invention, Glauber's salt gypsum is used as raw material, and in terms of raw material pretreatment, by adding water to dissolve and stir at room temperature, the upper layer slurry is derived and stirred for hydrolysis, so that the available components in Glauber's salt gypsum can be hydrolyzed as much as possible, and it is convenient to remove Glauber's salt The various components in gypsum are effectively used in the preparation; secondly, the use of hydrothermal method to produce gypsum whiskers can not only effectively utilize industrial by-products, solve the problem of environmental pollution caused by waste stacking, and achieve the purpose of green chemical industry, which is completely in line with the national industry Moreover, gypsum whiskers are high value-added environmental protection products with broad market demand prospects and obvious economic benefits. After being put into production, the region has sufficient and low-cost raw material resources, and the method is simple and easy to industrialize. Therefore, the study and final construction of this project in this area will definitely achieve huge economic and social benefits.

Compared with the prior art, the beneficial effect of this scheme:

1. The present invention adopts the hydrothermal method, which can not only effectively utilize industrial by-products, solve the problem of environmental pollution caused by waste stacking, and achieve the purpose of green chemical industry, which is fully in line with national industrial policies;

2, the whisker reactor that the present invention adopts is the spherical reactor of band jacket, and agitator is the propeller type; When the spherical reactor with stirring is stirring, it can make the fluid medium in the shell all can be in full capacity A more uniform flow field can be obtained in the middle, and it is easier to achieve completely uniform mass transfer without dead ends, while the shaft speed and shaft power can be relatively reduced; the propeller stirrer can make the fluid in the reactor not only have radial mixing, but also have Axial mixing, which can make the reaction system more uniform and make the aspect ratio of the final whiskers more uniform;

3, the lining material of the whisker reactor that the present invention adopts adopts the lining material of polytetrafluoroethylene filling graphite, adopts this lining material and can effectively satisfy the anticorrosion and heat transfer requirement of reactor;

4. The modified stabilizer (coupling agent, fatty acid or fatty acid salt) added in the present invention forms a hydrogen bond with the hydroxyl group on the CSW surface, and then a heating dehydration reaction occurs to form a partial covalent bond, so that the surface of the inorganic substance is covered by the coupling agent ; The modified stabilizer is not only easy to spread on the whisker surface, but also can change the surface state of the whisker and change the contact angle of its solid-liquid interface, thereby reducing the difference in interface properties between the whisker and the matrix;

5. The present invention adopts the microwave drying method, which can make the dehydration rate of the drying process reach about 98%, and the microwave drying time is only about 1/5 of the time of the ordinary drying method;

6, the technological process that the present invention adopts and the technological operation condition of optimization can make the finally obtained calcium sulfate whisker have uniform appearance, suitable aspect ratio (more than 50), yield can reach 84%, and whiteness ≥ 96%.

Description of drawings

Fig. 1 is the process flow chart of preparing calcium sulfate whisker in the embodiment of the present invention.

Detailed ways

In order to enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described in detail below in conjunction with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are only a part of the present invention Examples, but not all examples. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below in conjunction with examples.

Example:

The scheme that the embodiment of the present invention provides is: a kind of method for preparing calcium sulfate whisker with Glauber's salt gypsum, as shown in Figure 1, comprises the following steps:

1. Pretreatment of raw materials

The raw material Glauber's salt gypsum in the scheme of this embodiment contains 46% water, 40% hemihydrate gypsum, 10% Glauber's salt, 3% dihydrate gypsum, and 1% stone slag. The raw material Glauber's salt gypsum is dissolved in water at room temperature and stirred to export the upper layer of slurry for stirring For hydrolysis, add 0.6-1.6mol/L calcium water, stir well, add dilute sulfuric acid to adjust the pH to 2-6, wash with water 2-3 times, filter to obtain a filter cake, add water to prepare a uniform gypsum slurry.

2. Preparation and modification of whiskers by hydrothermal method

Add 2% to 10% magnesium salt or copper salt crystal growth agent to the slurry obtained in the previous step, and then add the slurry to a stirred and jacketed anti-corrosion lining material lined with polytetrafluoroethylene filled graphite Warm up to 120°C in the container and start timing reaction for 3.5 hours, then use a pressure pump to pump in stabilizing and modifying agents (stearate, stearic acid, silane coupling agent, titanate coupling agent, which account for gypsum The mass fraction is 0.5% to 4%), the modification time is 0.5h to 2h, and finally the solid-liquid separation of the reacted slurry is carried out).

3. Drying of the product

The filter cake obtained by solid-liquid separation is washed with cold water, and then dried by microwave under the power of 500-1000W for 20-60 minutes.

In the above-mentioned embodiments of the present invention, Glauber's salt gypsum is sodium sulfate extracted from a symbiotic ore of Glauber's salt and gypsum, or the milky white waste residue of Glauber's salt produced from Glauber's salt. In recent years, the annual output of thenardite in my country has remained at about 10 million tons, and the output of thenardite gypsum in 2020 will be about 4 million tons. Using mirabilite gypsum as raw material and adopting hydrothermal method to produce gypsum whiskers can not only effectively utilize industrial by-products, solve the problem of environmental pollution caused by waste piles, and achieve the purpose of green chemical industry, which is completely in line with national industrial policies; moreover, gypsum whiskers belong to high Value-added environmental protection products have broad market demand prospects and obvious economic benefits. After being put into production, there are sufficient and low-cost raw material resources in this area, and the method is simple and easy to industrialize. Therefore, the research and final construction of this project in this area will definitely achieve huge economic and social benefits

In addition, compared with the method for preparing calcium sulfate whiskers in the prior art, because the cost of Glauber's salt gypsum is very complicated (containing 46% water, 40% hemihydrate gypsum, 10% Glauber's salt, 3% dihydrate gypsum, 1% gravel etc.), the method of the prior art can not fully utilize the useful components in the Glauber's salt gypsum, in the method of the present invention, aspect the raw material pretreatment, has adopted the mode that the raw material is pre-hydrolyzed, the complex component in the raw material is pre-hydrolyzed After the preparation process, it is convenient to fully utilize the useful components in the thenardite gypsum, and compared with the prior art, it is convenient to improve the preparation efficiency. And, the technological process that the present invention adopts and the technological operation condition of optimization can make the finally obtained calcium sulfate whisker have uniform appearance, suitable length-to-diameter ratio (more than 50), yield can reach 84%, and whiteness ≥ 96%.

The above specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications to this embodiment without creative contribution according to needs after reading this specification, but as long as they are within the rights of the present invention All claims are protected by patent law.

Claims (5)

1. A method for preparing calcium sulfate whisker from mirabilite gypsum is characterized by comprising the following steps: the method comprises the following steps:

s1, pretreatment of raw materials:

dissolving and stirring the raw material mirabilite gypsum in water at normal temperature, leading out upper slurry, stirring and hydrolyzing, adding calcium water, fully stirring, adding dilute sulfuric acid to adjust the PH, washing for 2-3 times, filtering to obtain a filter cake, and adding water to prepare uniform gypsum slurry;

s2, preparing whiskers by a hydrothermal method and modifying:

adding 2% -10% of magnesium salt or copper salt crystal form growth promoter into the gypsum slurry obtained in the step S1, adding the gypsum slurry into a spherical kettle type reactor, heating to 120 ℃, starting timing reaction for 3.5 hours, pumping a stabilizing and modifying agent by using a pressure pump, modifying for 0.5-2 hours, and then carrying out solid-liquid separation on the reacted slurry to obtain a filter cake;

s3, drying a product:

washing the filter cake obtained by solid-liquid separation in the step S2 with cold water, and drying for 20-60 min under the power of 500-1000W by microwaves to obtain a calcium sulfate whisker product.

2. A method for preparing calcium sulfate whisker from mirabilite gypsum as claimed in claim 1, wherein: the calcium water added in the step S1 is 0.6-1.6 mol/L.

3. A method for preparing calcium sulfate whisker from mirabilite gypsum as claimed in claim 1, wherein: in the step S1, dilute sulfuric acid is added to adjust the PH to 2-6.

4. A method for preparing calcium sulfate whisker from mirabilite gypsum as claimed in claim 1, wherein: the stabilizing and modifying agent in the step S2 comprises stearate, stearic acid, a silane coupling agent or a titanate coupling agent, and the stabilizing and modifying agent accounts for 0.5-4% of the mass of the gypsum.

5. A method for preparing calcium sulfate whisker from mirabilite gypsum as claimed in claim 1, wherein: the spherical kettle reactor in the step S1 is a spherical kettle reactor with a stirring jacket and an anticorrosive lining material lined with polytetrafluoroethylene filled graphite.