Method for preparing electronic grade phosphoric acid through liquid membrane crystallization

Abstract

The invention relates to a method for preparing electronic grade phosphoric acid through liquid membrane crystallization. The method comprises the following steps: slowly pouring seed crystals which are prepared in advance, in a column crystallizer, wherein the temperature of the wall of the column crystallizer is controlled to 10-20 DEG C; (2) adding liquid phosphoric acid in the column crystallizer form the top of the crystallizer while using cooling medium in the jacket of the column crystallizer to reduce the temperature of the column crystallizer to 5-10 DEG C, wherein raw material crystallizes and grows on the seed crystals to form a crystal film and uncrystallized liquid flows out from the bottom of the column crystallizer; stopping adding materials when the thickness of the crystal film is 1/4-1/3 of the diameter of the column crystallizer, keeping temperature for 15-30min to discharge feed liquid which does not form film; heating the column crystallizer to 15-29 DEG C and keeping temperature for 0.5-2h so as to melt the film layer, collecting the discharged liquid as a product; and (4) repeating the step (1), (2) and (3) by using the obtained product as raw material to perform secondary liquid film crystallization and obtaining the electronic grade phosphoric acid product. The method has simple operation, short production time, low energy consumption and high impurity removal rate, and the electronic grade phosphoric acid product with a concentration of 87-90% can be directly obtained.

Description

technical field [0001] The invention belongs to the technical field of crystallization, in particular to a method for preparing electronic grade phosphoric acid by liquid film crystallization. Background technique [0002] Phosphoric acid products can be divided into several grades such as industrial grade, food grade, and electronic grade according to their impurity content. The difficulty of preparation technology and market price increase sharply as the purity of phosphoric acid increases. [0003] Electronic-grade phosphoric acid is a high-purity chemical reagent used in the electronics industry. It is widely used in microelectronics industries such as ultra-large-scale integrated circuits and large-screen liquid crystal displays. It is mainly used for wet cleaning and wet etching of chips. In recent years, with the rapid development of the electronics industry, the types and quantities of electronic products have grown exponentially, and the market demand for electronic...

AI Technical Summary

Problems solved by technology

Since the 1990s, there have been many studies on the preparation of electronic-grade phosphoric acid by crystallization. Russian patent 2209178 purifies thermal phosphoric acid by cooling crystallization. 3193614, 3237009 and 2000026111 further purified electronic-grade phosphoric acid by cooling crystallization method and melt crystallization method to obtain higher-purity phosphoric acid, but this method has high requirements on the purity of raw acid, which has reached the level of electronic-grade phosphoric acid; Korean patent 2003042108 prepared electronic-grade phosphoric acid by cooling and crystallization, but the equipment was complicated, energy consumption was high, and production scale-up was difficult to realize; Chinese patent 200510013714.7 used solvent precipitation and extraction to pretreat the raw materials, and then prepared electronic-grade phosphoric acid by three times of cooling and crystallization

This method operates at extremely low temperature, consumes a lot of energy, and requires pretreatment of raw materials to remove arsenic. The operation time is long, the production cost is high, and the yield is low.

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