Method for preparing industrial-grade phosphoric acid by decomposing mid-low-grade phosphorite with nitric acid

Abstract

The invention relates to a method for preparing industrial-grade phosphoric acid by decomposing mid-low-grade phosphorite with nitric acid. The method comprises the following processing steps: (1) decomposing phosphorite with nitric acid; (2) separating calcium nitrate through freezing crystallization; (3) carrying out deep deliming with sulfuric acid; (4) conducting countercurrent or cross current extraction of filtrate obtained in the step (3) by using a first mixed extractant to obtain raffinate which is coarse phosphoric acid; (5) conducting countercurrent or cross current extraction of the coarse phosphoric acid obtained in the step (4) by using a second mixed extractant, carrying out countercurrent washing on the load organic phase obtained by the countercurrent or cross current extraction by using dilute phosphoric acid for at least two times, and then conducting countercurrent reverse extraction by using deionized water to obtain strip liquor which is purified dilute phosphoric acid after removing impurities such as iron, magnesium, aluminum, calcium and fluorine; and (6) sequentially conducting evaporation concentration, dearsenification, heavy metal removal, decoloring, filtration and concentration adjustment on the purified dilute phosphoric acid obtained in the step (5) to obtain industrial-grade phosphoric acid.

Description

technical field [0001] The invention belongs to the field of phosphoric acid production, and relates to a method for preparing industrial-grade phosphoric acid by decomposing medium and low-grade phosphorous rocks with nitric acid. Background technique [0002] The existing methods for preparing industrial-grade phosphoric acid using wet-process phosphoric acid as raw materials generally use high-grade phosphate rock, and most of them use sulfuric acid to decompose phosphate rock. my country is a country severely deficient in sulfur. In 2010, the import of sulfur exceeded 10 million tons, and the dependence on foreign countries reached 60%, resulting in a geometric increase in the price of sulfur. In contrast, the production capacity of nitric acid in my country is seriously overcapacitated, and the price of nitric acid has been declining year by year. In addition, every ton of industrial-grade phosphoric acid produced by the sulfuric acid method will produce 4.5 to 5.5 tons...

AI Technical Summary

Problems solved by technology

The disadvantage of this method is that the evaporation energy consumption is too large, and the purification treatment of iron, magnesium, aluminum and other impurities is not disclosed

There are literatures (Process development for the production of pure phosphoric acid and its salts - N 235 Extraction and separation of nitric acid to produce pure phosphoric acid and KH 2 PO 4 "Chemical Fertilizer Industry" No. 04, 1987, author: Zhu Xiaoda, Li Daochun) reported using nitric acid, potassium nitrate and phosphoric acid as raw materials, using N 235 (a mixture of tertiary amines) is used as the extractant to extract and separate nitric acid, and the raffinate is concentrated and crystallized to precipitate potassium dihydrogen phosphate to obtain relatively pure phosphoric acid. However, the raw materials used in this process are all chemically pure, and nitric acid is not considered to decompose phosphate rock. The obtained acid solution contains a large amount of impurities such as calcium, magnesium, aluminum, iron, fluorine, and N 235 The extraction rate of phosphoric acid is also large, which is not conducive to improving the yield of phosphoric acid

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