One-step method dihydrate-semi-hydrated wet production process for phosphoric acid

Abstract

The invention relates to a one-step method dihydrate-semi-hydrated wet production process for phosphoric acid. The one-step method dihydrate-semi-hydrated wet production process comprises the following steps: carrying out leaching reaction and dehydrate-semi-hydrated conversion; growing grains; separating, filtering and washing; by controlling technological indicators of all the steps, finished product phosphoric acid filtrate with high concentration and by-product phosphogypsum with high quality are obtained. The finished product phosphoric acid filtrate obtained by production of the one-stepmethod dihydrate-semi-hydrated wet production process disclosed by the invention has the advantages that the concentration of P2O5 is about 35 percent, concentration input of the phosphoric acid canbe avoided and an energy-saving effect is good. In addition, the phosphorus conversion rate and the washing rate are high; the final by-product phosphogypsum has the characteristics that the total content of the P2O5 is smaller than or equal to 0.5 percent, the content of water-soluble P2O5 is smaller than or equal to 0.15 percent and the yield of the P2O5 reaches 98 percent. The one-step method dihydrate-semi-hydrated wet production process disclosed by the invention retains the characteristics of good energy-saving effect, high phosphorus yield and high quality of byproduct alpha-semi-hydrated gypsum of a traditional two-step method dehydrate-semi-hydrated technology; meanwhile, a dihydrate filtration procedure is omitted, the process flow is shortened and the operation rate of a deviceis improved, so that the problem that water balance of a system cannot be realized due to overhigh content of wash water for filter cloth is solved.

Description

technical field [0001] The invention belongs to the technical field of phosphoric acid production, and in particular relates to a one-step dihydrate-semihydrate wet-process phosphoric acid production process. Background technique [0002] The industrial production methods of phosphoric acid can be divided into two categories: thermal phosphoric acid and wet phosphoric acid. my country is a big producer of thermal phosphoric acid, and its technology is mature. However, due to the huge energy consumption of thermal phosphoric acid and serious environmental pollution, P 2 o 5 The yield is low, and its production capacity is gradually being replaced by wet-process phosphoric acid due to industrial policy restrictions. Phosphoric acid produced by decomposing phosphate rock with strong acids such as sulfuric acid, hydrochloric acid, nitric acid, and fluosilicic acid is collectively called wet-process phosphoric acid. The wet-process phosphoric acid production method is usually ...

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Problems solved by technology

[0007] With the continuous increase of national environmental protection and the increasingly fierce competition in the industry, energy saving, environmental governance and comprehensive utilization of resources have been paid more and more attention by enterprises. The traditional dihydrate phosphoric acid process has high energy consumption, resource loss, and environmental pollution of phosphogypsum. and other issues have become a huge obstacle to the survival and development of enterprises

At present, the concentration of phosphoric acid in domestic dihydrate phosphoric acid production enterprises is 20-25%P 2 o 5 , high consumption of condensed steam

Total P of gypsum by-product of dihydrate phosphoric acid 2 o 5 The content is about 1%, which not only leads to the loss of phosphorus resources, but also easily produces a large amount of acid sewage during the discharge and storage of phosphogypsum, which increases the risk of environmental pollution and increases the operating costs of enterprises

In general, wet-process phosphoric acid produces 1t P 2 o 5 About 5 tons of phosphogypsum should be produced as a by-product. Due to the high impurity content of phosphogypsum in the dihydrate phosphoric acid process in my country, it is difficult to comprehensively utilize it, resulting in a large amount of phosphogypsum piled up

According to incomplete statistics, as of 2016, the cumulative discharge of phosphogypsum in my country has reached 350 million tons, and the stockpiles have exceeded 250 million tons. At present, about 80 million tons of phosphogypsum are newly added every year. By the end of 2016, the comprehensive utilization rate of phosphogypsum in my country will be less than 30%.

However, due to the long process flow, the equipment investment increases, and the operating rate decreases; at the same time, because the process adopts secondary filtration, the filter cloth of the filter has a large amount of washing water, and it is difficult to solve the water balance of the phosphate slurry production system (Used by Plyon Company) Phosphate rock powder for production), at present, this process is still in the research and development stage in China

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