Method for preparing high-concentration phosphoric acid by direct-reduction of phosphate ore

Abstract

The invention relates to a high concentration phosphoric acid producing method by directly deoxidized phosphorite. The process that the stock produced by phosphorus ore, diatomite, coke or coal accomplishes a reduction-oxidation to produce phosphoric acid consists of a preheating zone, a reducing zone and an oxidation combustion zone which are composed of different equipment modules. The preheating zone is under 1150 DEG C to 1200 DEG C; the reducing zone is under 1250 DEG C to 1450 DEG C, the coke or the coal in the stock performs a reduction reaction with phosphorite; phosphorus vapor that is P4 and carbon monoxide gas which are produced enter into the oxidation combustion zone again; air is added into the oxidation combustion zone, thus the phosphorus vapor that is P4 and the carbon monoxide gas are oxidized to produce a mixed kiln gas which is composed of P2O5 and CO2; the mixed kiln gas with high temperature is sucked out and led into a hydration absorption tower after dust abatement, and the phosphoric acid is produced by recycle acid absorption. The stock after the reduction reaction is exported from the reducing zone, and is formed into cement clinker or building materials after cooling and heat transfer. The invention has the innovative points that the processes of preheating, deoxidizing and oxidizing of reducing gas of the stock are separated, and the reactions are not mutually interfered. The control of the action process is simple, in addition, the percent reduction of the phosphorite is high, and the high yield of total phosphorus can be gained.

Description

technical field [0001] The invention relates to the technical field of phosphoric acid preparation, in particular to a method for preparing high-concentration phosphoric acid (and by-product cement and building material products) by direct reduction of medium and low-grade phosphate rocks. Background technique [0002] The main methods of industrialized production of phosphoric acid are as follows: (1) take yellow phosphorus as raw material, produce phosphoric acid through oxidative combustion, hydration absorption; the product quality that this method makes is good, concentration is high but its raw material production needs to consume a large amount of electric energy and Medium and high-grade phosphate rock has high energy consumption and high cost, and is conventionally called thermal phosphoric acid. (2) Decompose phosphate rock with sulfuric acid to produce phosphoric acid; the production cost of this method is relatively low, but it needs to consume a large amount of ...

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Problems solved by technology

[0002] The main methods of industrialized production of phosphoric acid are as follows: (1) take yellow phosphorus as raw material, produce phosphoric acid through oxidative combustion, hydration absorption; the product quality that this method makes is good, concentration is high but its raw material production needs to consume a large amount of electric energy and Medium and high-grade phosphate rock has high energy consumption and high cost, and is commonly called thermal phosphoric acid

(2) Decompose phosphate rock with sulfuric acid to produce phosphoric acid; the production cost of this method is relatively low, but it needs to consume a large amount of sulfuric acid and high-quality phosphate rock, the product quality is poor, and the acid concentration is low. Acid Requirements for Phosphate Production

Moreover, the above two production methods all have a large amount of solid waste discharge, which causes great pressure on the environment.

(3) The new kiln-based phosphoric acid production process. At present, domestic reports have built two sets of production devices. This method uses carbon as a reducing agent and silicon dioxide as an auxiliary agent to directly reduce phosphate rock to produce phosphoric acid; Reduced carbon early combustion and phosphorus pentoxide back absorption, in the process of making blanks, one-time molding and two to three wrapping methods are often used. The blank production process is complicated, the workload is heavy, the energy consumption is high, and a large amount of high-value raw materials are consumed. Wrapping agent increases the production cost of kiln-process phosphoric acid and reduces the market competitiveness of kiln-process phosphoric acid

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