Recovery method for iodine from wet-process phosphoric acid at low gas-liquid ratio

Abstract

The invention discloses a recovery method for iodine from wet-process phosphoric acid at a low gas-liquid ratio. The recovery method comprises the following steps: adding hydrogen peroxide into dilute phosphoric acid produced from phosphoric acid by a wet process and allowing hydrogen peroxide to react with dilute phosphoric acid; then blowing out molecular iodine by using air; absorbing molecular iodine by using an acidic solution; and finally adding hydrogen peroxide to allow iodine to be precipitated. The method is characterized in that molecular iodine is blown out by using normal temperature air and a volume ratio of blown air to liquid, i.e., a gas-liquid ratio, is low. The method has the following advantages: energy consumption is lowered down, layout of equipment is reduced, and investment cost is decreased; a gas-liquid ratio in blowing-out of molecular iodine by using a conventional extraction process for iodine from wet-process phosphoric acid is substantially decreased, fan delivery is reduced, investment cost for equipment is lowered down, and due to decrease of fan delivery, power consumption in the process of operation and operation cost are reduced; moreover, the low gas-liquid ratio enables the boundary dimension of an extraction tower to be effectively reduced and construction and maintenance cost for an apparatus to be substantially decreased.

Description

technical field [0001] The invention relates to a method for recovering iodine from wet process phosphoric acid with low gas-liquid ratio. Background technique [0002] With the development of industry and agriculture, iodine has been widely used in medicine and health, agriculture, industry, national defense and other aspects. At present, the extraction method of iodine mainly uses seaweed, brine and minerals (phosphate rock) as raw materials. The methods for extracting iodine mainly include dry distillation, leaching, ion exchange, solvent extraction, electrolysis, liquid membrane technology, and air blowing. Among them, the air blowing method is a relatively advanced production process. The air blowing method is initially applicable to the stock solution with high iodine content, mainly brine. The process is to first acidify the iodine-containing mother liquor with hydrochloric acid to a pH value of 1-2, and then introduce chlorine gas for oxidation to oxidize ion iodi...

AI Technical Summary

Problems solved by technology

But this method has some disadvantages

First of all, since iodine molecules are blown out by hot air at a temperature of 40-50°C during extraction, the air must be heated before it enters the extraction tower, and even heat exchange equipment is added, which leads to increased energy consumption and cost

Secondly, the gas-liquid ratio in the air blowing process of this method is 130-150:1, which is relatively large and requires a large amount of air, so it is necessary to use a fan with a large air volume and high motor power, resulting in increased cost investment, and Increased operating costs and reduced economic benefits

Thirdly, due to the relatively large gas-liquid ratio, the specification of the extraction tower is required to increase accordingly, resulting in an increase in the investment cost of the extraction equipment construction