CN-118184191-B - Method for preparing desulfurization gypsum into alpha-type high-strength gypsum

CN118184191BCN 118184191 BCN118184191 BCN 118184191BCN-118184191-B

Abstract

The invention belongs to the technical field of material preparation, and particularly relates to a method for preparing desulfurization gypsum into alpha-type high-strength gypsum. The method improves the utilization rate and the utilization value of the desulfurization gypsum, and relieves the resource waste and the environmental pollution caused by accumulation and landfill of the desulfurization gypsum. The method comprises the steps of carrying out water washing pretreatment on desulfurized gypsum for 3 times, drying, adding lime accounting for 1% of the mass of the desulfurized gypsum in the pretreatment for 3 times, adding a solution containing a crystal conversion agent into the pretreated desulfurized gypsum, uniformly mixing, wherein the mass of crystal conversion agent aluminum sulfate and water is respectively 0.08-0.12 wt% and 10-15 wt% of the dry basis weight of the desulfurized gypsum, pressing the obtained mixture on two sides under the pressure of 20 Mpa by a pressing machine, putting the pressed mixture into an autoclave, steaming and pressing 8-10 h under the conditions of 150 ℃ and 1.4 Mpa, immediately drying at 100 ℃, and grinding to obtain high-quality alpha-type high-strength gypsum with whiteness reaching 70% and strength reaching alpha 30.

Inventors

HUANG WEI
CAO YONGGANG
ZHANG ZILONG
Xue kui
WANG JIALIANG

Assignees

福州大学

Dates

Publication Date: 20260505
Application Date: 20240511

Claims (2)

1. A method for preparing desulfurization gypsum into alpha-type high-strength gypsum is characterized in that after pretreatment of desulfurization gypsum, adding a solution containing a crystal transformation agent, uniformly mixing, pressing the mixture into blocks by a pressing machine, putting the blocks into an autoclave for steaming, immediately drying the blocks, and grinding to obtain alpha-type high-strength gypsum; The pretreatment comprises the steps of immersing the desulfurized gypsum in tap water, wherein the mass ratio of the desulfurized gypsum to the tap water is 1:3, stirring the desulfurized gypsum and the tap water once every 20min, filtering the water every 60min, repeating the water change for 3 times, and drying the water, wherein lime accounting for 1% of the mass of the desulfurized gypsum is additionally added in the third pretreatment; the solution containing the crystal transformation agent is an aluminum sulfate aqueous solution, wherein the addition amounts of aluminum sulfate and water are respectively 0.08-0.12wt% and 10-15wt% of the weight of the pretreated desulfurized gypsum dry basis; The pressing method of the pressing machine comprises the steps of placing the mixture into a static pressure machine die, and adopting double-sided two-section pressing, wherein the pressing pressure of the first section is 20MPa, the loading is stopped after the loading is carried out for 30 seconds, and the pressing of the second section is carried out after waiting for 1 minute, the pressing pressure of the second section is 20MPa, and the loading time is 30 seconds; The autoclaved condition of the autoclave is that desulfurized gypsum blocks are put into the autoclave and autoclaved for 8-10h under the conditions of 150 ℃ and 1.4 MPa; The drying condition is that the autoclaved desulfurized gypsum blocks are immediately dried at 100 ℃; The grinding condition is that the grinding is carried out until the screen allowance of the square hole screen with the diameter of 0.125mm is not more than 5 percent.
2. The alpha-form high-strength gypsum prepared by the method of claim 1.

Description

Method for preparing desulfurization gypsum into alpha-type high-strength gypsum Technical Field The invention belongs to the technical field of material preparation, and particularly relates to a method for preparing desulfurization gypsum into alpha-type high-strength gypsum. Background With the rapid development of industry, the discharge amount of the desulfurized gypsum is increased rapidly, at present, the accumulated accumulation amount of the desulfurized gypsum in China exceeds 360 Mt, the discharge amount is increased up to 120 Mt year by year, and the annual trend still exists. So that a large amount of desulfurized gypsum is piled up and buried, and resource waste and environmental pollution are brought. At present, the utilization rate of the desulfurization gypsum in China is only 70%, and the desulfurization gypsum is generally used as building auxiliary materials, such as cement retarder, filler and the like, so that the utilization benefit is low. Desulfurized gypsum generally contains K, na, P, F or other impurities, and in order to reduce the damage of the impurities to products, the desulfurized gypsum is usually pretreated by a calcination method, a water washing method, an acid treatment method and the like to reduce the impurities. However, the calcination method generally has the disadvantages of high energy consumption and low treatment efficiency, the water washing method has high water consumption, and the acid treatment method can reduce the product quality due to the addition of acidic substances and has the risk of equipment corrosion. The conventional autoclaved method is only suitable for natural gypsum, is not suitable for powdery industrial byproduct gypsum, and can not change crystal morphology by adding a crystal transformation agent, the obtained alpha-type high-strength gypsum has poor quality, and the pressurized water solution method, the normal pressure salt solution method, the normal pressure acidification method, the normal pressure alcohol water method and the like have complex processes, can only be realized in a laboratory at present, are difficult to realize industrial production, can generate a large amount of wastewater containing chlorine and acid, and still need to solve the problem of wastewater treatment. In the prior art, the utilization rate and the added value of the desulfurized gypsum are low, the prior method for preparing the alpha-type high-strength gypsum is difficult to realize the recycling utilization of the desulfurized gypsum, and the technical problem to be solved is how to realize the industrialized preparation of the desulfurized gypsum into the alpha-type high-strength gypsum. Disclosure of Invention In view of the above, the present invention aims to provide a method for preparing desulfurized gypsum into alpha-type high-strength gypsum. The method has the advantages of simple process, low running cost and investment cost, realization of industrial production, environmental friendliness and remarkable economic benefit. In order to achieve the above purpose, the invention adopts the following technical scheme: a process for preparing alpha-type high-strength gypsum from desulfurized gypsum includes such steps as pretreating desulfurized gypsum, adding solution containing crystal transfer agent, mixing, pressing to become blocks, steaming, baking, and grinding. Further, the desulfurization gypsum pretreatment method is that the desulfurization gypsum is soaked in tap water, wherein the mass ratio of the gypsum to the water is 1:3, the water is stirred every 20 min, the water is filtered every 60 min, the water is repeatedly changed for 3 times, and lime accounting for 1% of the mass of the desulfurization gypsum is additionally added in the third pretreatment. Further, the solution containing the crystal transformation agent is an aluminum sulfate aqueous solution, wherein the addition amounts of aluminum sulfate and water are respectively 0.08-0.12 wt% and 10-15% of the weight of the pretreated desulfurized gypsum dry basis. Further, the pressing method of the pressing machine comprises the steps of placing the mixture into a static pressure machine die, and pressing the mixture into a block shape with 240mm multiplied by 115mm multiplied by (30-50) mm by adopting double-sided two-stage pressing, wherein the pressing pressure of the first stage is 20 MPa, the loading is stopped after the load is 30S, the pressing of the second stage is carried out after waiting for 1 min, the pressing pressure of the second stage is 20 MPa, the loading time is 30S. Further, the autoclave has an autoclave condition of 150 ℃ and 1.4 Mpa, and the autoclave is autoclaved for 8-10 h. Further, the drying condition is 100 ℃; Further, the grinding condition is that the grinding is carried out until the screen allowance of the square hole screen is not more than 5 percent at 0.125 mm percent. The alpha-type high-strength gypsum prepared by the method has whitene