Co-production method of calcium sulfate whisker and phosphoric acid

Abstract

The invention relates to a co-production method of calcium sulfate whisker and phosphoric acid. The method comprises the following technical steps of: (1) acid-hydrolyzing phosphate rock powder by hydrochloric acid with the mass concentration of 15 to 26% or nitric acid with the mass concentration of 20 to 90%, filtering the acid-hydrolyzed slurry into the acid hydrolysis solution containing Ca2<+>; (2) using the acid hydrolysis solution containing Ca2<+> and the sulfuric acid with the mass concentration of 20 to 90% as the raw materials, wherein the use level of the sulfuric acid is 100% of the needed theoretical amount of the sulfuric acid when the Ca2<+> in the acid hydrolysis solution and the sulfuric acid react completely, adding the sulfuric acid to the acid hydrolysis solution containing Ca<2+> under the stirring condition, reacting the sulfuric acid with the acid hydrolysis solution containing Ca2<+> at the normal pressure and at 50 to 90 DEG, filtering and separating the calcium sulfate whisker after the reaction is finished, and then washing and drying the calcium sulfate whisker; and (3) carrying out the counter-current extraction on the filtrate obtained in the step (2), wherein the extracted water phase is the phosphoric acid, and acid-hydrolyzing the phosphate rock powder by using the hydrochloric acid obtained by the counter-extraction of the soft water to the extracted organic phase which is separated in the counter-current extraction.

Description

technical field [0001] The invention belongs to the technical field of manufacturing calcium sulfate whiskers and wet-process phosphoric acid, and relates to a method for simultaneously producing calcium sulfate whiskers and phosphoric acid. Background technique [0002] Calcium sulfate whisker is a new material with great development potential, which has excellent properties such as high strength, good toughness, high temperature resistance and corrosion resistance. According to the length and diameter of calcium sulfate whiskers, it can be divided into three categories: short whiskers, medium-long whiskers and long whiskers. Short whiskers generally have a diameter of 0.1-4 μm and a length of 5-300 μm, and are mainly used in industries such as rubber, plastics, coatings, and adhesives; medium and long whiskers, with a length of 0.3-3.0 mm, are mainly used in papermaking and papermaking. Products industry; the length of long whiskers is greater than 3.0mm, mainly used in i...

AI Technical Summary

Problems solved by technology

[0003] At present, the main production method of calcium sulfate whiskers is the hydrothermal method, but the hydrothermal method has the following problems: production at high temperature or high pressure, high energy consumption, and high requirements for equipment; raw materials contain many impurities, which need to be purified and removed. Complicated, high production cost; the prepared calcium sulfate whiskers cannot meet the requirements of industries with high aspect ratio

This method has following deficiencies: 1, in CaO-P 2 o 5 -H 2 In the O system, the concentration of CaO≤5% (see "The Production and Application of Phosphate", edited by Chen Jiafu, Tan Guangxun, Chengdu University of Science and Technology Press, Figure 8-4 on page 116.), and when decomposing phosphate rock, the excess phosphoric acid and the Phosphoric acid leaching solution is gradually added to 30-35% sulfuric acid solution, which will also reduce the Ca in the suspension. 2+ The concentration of Ca 2+ The content is too low, which is not conducive to the growth of whiskers, thereby affecting the morphology of calcium sulfate whiskers, and it is difficult to obtain whiskers with relatively large major diameters (the whiskers prepared by the method described in this patent have a length of 30-200 μm, which belongs to short whiskers. The scope of application is limited); 2, the concentration of phosphoric acid is high, although it can increase the decomposition rate of phosphate rock, it will also increase the HPO 4 2- Substituting SO in the lattice 4 2- At the same time, the viscosity of the solution will increase accordingly, resulting in the deterioration of the crystallization conditions, and it will also increase the difficulty of subsequent filtration operations; 3. To achieve a high decomposition rate of phosphate rock, the amount of circulating phosphoric acid is large, and pumps are needed to transport it. Increased power consumption will also require larger reactors, increase equipment investment, and thus increase production costs

Although the addition of composite additive A can increase the decomposition rate of phosphate rock, although the addition of composite additive B can adjust the crystal form of calcium sulfate whiskers, the decomposition of phosphate rock is still CaO-P 2 o 5 -H 2 O system, the problems existing in the ZL 200410024348.0 patent cannot be solved fundamentally. The influence of compound additive B on calcium sulfate crystallization is multifaceted, and the composition of the reaction solution is different, and the amount of additives to be added is also different. Generally, the optimal amount It needs to be determined by experiments, and the phosphoric acid leach solution contains Mg 2+ 、Al 3+ , Fe 2+ The presence of these impurities also affects the amount of additives used, so the amount of additives used is not easy to control, and it is difficult to obtain the ideal whisker shape and size through additives

ZL 200710065806.9 does not disclose the shape and size of the prepared calcium sulfate whiskers, and cannot test the application effect of additives

In addition, adding additives will increase the cost and complicate the process

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