A method for decomposing phosphogypsum to prepare porous block and sulfuric acid

Abstract

The invention relates to a method of preparing porous building blocks and sulphuric acid by decomposing phosphogypsum. According to the technical scheme, the method comprises the steps of taking 60-90 wt% of phosphogypsum and 10-40 wt% of carbonized rice husk as raw materials, adding water-reducing admixture of 0.5-2.0 wt% of the raw materials and water of 50-100 wt% of the raw materials, mixing and forming pug, and then adding foams prepared by foaming agents, of 0.5-1.0 wt% of the raw materials, stirring, adding gel of 1.0-2.5%wt of the raw materials, stirring, casting, molding, naturally drying and demoulding; drying at 110 DEG C for 5 to 10h, and baking at 170 DEG C for 5 to 10h to produce porous precast blocks; finally enabling the porous precast blocks to be subjected to catalytic decomposing reaction in a nitrogen atmosphere at the temperature of 800 to 1000 DEG C to obtain porous building blocks and sulfur dioxide gas; oxidizing and absorbing the sulfur dioxide gas to produce sulphuric acid. The method of preparing porous building blocks and sulphuric acid by decomposing phosphogypsum is low in cost and energy consumption, high in sulfur convertion rate, and capable of efficiently utilizing reaction tailings to prepare porous building blocks while producing sulphuric acid. Besides, the prepared porous building block has low volume density and thermal conductivity.

Description

technical field [0001] The invention belongs to the technical field of phosphogypsum treatment. Specifically relates to a method for decomposing phosphogypsum to prepare porous block and sulfuric acid. Background technique [0002] Phosphogypsum is the main solid waste in the phosphating industry, and its main component is dihydrate gypsum (CaSO 4 2H 2 O) and hemihydrate gypsum (CaSO 4 0.5H 2 o). According to incomplete statistics, the total annual discharge of phosphogypsum in my country exceeds 55 million tons (on a dry basis), and the cumulative stockpiles exceed 250 million tons. With the development of high-concentration phosphate fertilizers in China, the discharge of phosphogypsum will increase. At present, phosphogypsum is mainly treated by stacking, which not only occupies a large amount of land, wastes precious sulfur and calcium resources, but also causes serious environmental pollution, restricting the development of the phosphorus chemical industry to a ce...

AI Technical Summary

Problems solved by technology

The industrial method of producing sulfuric acid from phosphogypsum is mainly to reduce phosphogypsum with coke, and the reaction principle is mainly C and CaSO 4 However, due to the relatively low reactivity of coke and the small contact surface with phosphogypsum, the decomposition temperature of phosphogypsum is high and the reaction energy consumption is large

In addition, there are also about reducing gases (such as CH 4 , CO, H 2 ) and sulfur-reduced phosphogypsum, but the process is complicated, the production cost is high, and the decomposition temperature of phosphogypsum is not significantly lowered (above 1100°C), so it has not been widely used so far.

There is also research on the production of sulfuric acid from sulfur phosphogypsum. For example, Sichuan University, on the basis of the comprehensive utilization of phosphogypsum, first proposed the method of sulfuric acid reduction from phosphogypsum. However, this method uses sulfur as a reducing agent, which not only improves production The cost is also not in line with the shortage of sulfur resources in my country

In addition, the current technical method of producing sulfuric acid from phosphogypsum mainly uses its tailings for co-production of cement, but the serious overcapacity problem faced by the cement industry also greatly hinders the effective promotion of the above-mentioned technology

[0004] The patented technology of "A Production of Sulfuric Acid Using Biomass Reduction and Decomposition of Phosphogypsum" (CN201110097225.X) proposes to use biomass raw materials as a reducing agent to decompose phosphogypsum to produce sulfuric acid, but this method only utilizes the reductivity produced by incomplete oxidation of biomass Gas is used as the reducing agent, the catalyst content in the ash is small, the catalytic effect is not obvious, and there is still high energy consumption

The patented technology of "a method for catalytically decomposing phosphogypsum" (CN201410095622.7) proposes to use carbonized rice husk as a reducing agent to decompose phosphogypsum. The problem of low utilization rate of tailings