Method for decomposing phosphogypsum to produce sulphuric acid and cement with suspended state

Abstract

The invention discloses a method for preparing sulfuric acid with co-production lime by decomposing ardealite in a suspended state, the method comprises the following steps: a) crushing and drying; b)decomposing in a suspended state: the hot air flow at 850-1200 DEG C and minus 0.8KPa in the upper part pipe of a decomposing furnace (16) exchanges heat with gas-solid biphase of the ardealite, theardealite flows through the upper part pipe of the decomposing furnace (16) with the hot air flow and enters a cyclone material and gas separator (14), the materials separated by the cyclone materialand gas separator (14) enter the bottom of the furnace body for cyclic decomposition via an air lock feeder B (15) arranged at the lower part of the cyclone material and gas separator (14); a fluidized fan (17) at the bottom of the decomposing furnace produces a fluidized decomposition effect, a necking in the middle of the decomposing furnace produces a spayed decomposition effect; the high-concentration SO2 separated by the cyclone material and gas separator (14) and the lime are led to the upper part with the hot air flow at 850 DEG C and minus 1.8KPa for cyclone separation; and c) cycloneseparation. The method is characterized by short ardealite decomposition time, high decomposition efficiency, high-concentration SO2, energy saving and consumption reduction.

Description

technical field [0001] The invention belongs to the technical field of chemical industry, and in particular relates to a method for decomposing phosphogypsum. Background technique [0002] Phosphogypsum is the solid industrial waste produced during the production of wet-process phosphoric acid. About 4-5 tons of phosphogypsum are produced for every ton of phosphoric acid produced. In 2004, the world's phosphogypsum emissions reached 295 million tons. At present, the annual emission of phosphogypsum in my country is about 50 million tons. The rapid development of the phosphate and compound fertilizer industry will inevitably bring about two major problems: the treatment of phosphogypsum waste residue and the increase in demand for sulfuric acid. CaSO in phosphogypsum 4 2H 2 The O content is generally as high as 90%, and it is an important renewable resource. However, phosphogypsum contains many harmful impurities such as phosphorus, fluorine and organic matter, so that it...

AI Technical Summary

Problems solved by technology

However, the existing technology is to prepare raw meal by phosphogypsum, clay, iron powder, and coke, and then calcined to obtain cement clinker. Since the decomposition of phosphogypsum and the firing of cement clinker are completed in one device in the rotary kiln, this system The main technical problems are as follows: (1) The decomposition temperature of phosphogypsum is high (1100°C-1200°C), and the decomposition time is long, while the cement clinker starts to appear liquid phase at 1250°C-1280°C.

Therefore, when the phosphogypsum has not been completely decomposed, the liquid phase has begun to appear in the kiln, covering the phosphogypsum and preventing its decomposition; (2) The full combustion of coal and the formation of high-quality clinker require an oxidizing atmosphere, and the decomposition of phosphogypsum requires Reduction atmosphere is required, which is a pair of contradictions that are difficult to reconcile, production control is difficult, clinker quality is poor and fluctuates greatly

(3) The cement firing temperature is high (1450°C), and the amount of gas required is large, resulting in SO in the tail gas 2 The concentration is low, and the dust content in the tail gas is high, so the sulfuric acid production, purification, drying, conversion, absorption and other acid production processes are complicated and the equipment investment is large

Therefore, the existing ones have the problems of large investment, poor product quality, small scale of production, and difficulty in popularization.

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