Method for manufacturing magnesium sulphate hepta hydrate fertilizer using boiler flue gas

Abstract

A method for producing magnesium sulfate heptahydrate fertilizer using boiler flue gas. The process is as follows: ①Magnesite ore is pulverized, and water is added to prepare absorbent slurry, which is sent to a desulfurization tower; HCl, HF, SO 3 ③ In the desulfurization tower, after absorption reaction, MgSO is generated 3 , ④ aeration oxidation, MgSO 3 Oxidize as much as possible into magnesium sulfate solution, ⑤precipitate to remove impurities, gravity settle impurities, ⑥flocculate and neutralize, add neutralizer and flocculant, add magnesium hydroxide solution, adjust the pH value of the solution to 7, add flocculation according to the monitoring data ⑦Filter and remove impurities to obtain a liquid without solid phase impurities, ⑧Concentrate and crystallize, keep the solution temperature at 40-45°C, vacuum dehydrate, and precipitate magnesium sulfate heptahydrate crystals in the solution, ⑨Separate and dehydrate to obtain wet state heptahydrate Magnesium sulfate crystal, ⑩ dry package. The positive effect of the present invention is that the magnesium sulfate heptahydrate product with a purity of 97% can be obtained. It is suitable for preparing magnesium sulfate heptahydrate fertilizer by using boiler flue gas.

Description

technical field [0001] The invention belongs to a preparation method of magnesium sulfate, in particular to a method for preparing magnesium sulfate heptahydrate fertilizer by using desulfurization waste liquid of boiler flue gas. Background technique [0002] Magnesium sulfate heptahydrate is an important agricultural fertilizer, and various raw materials can be used for its preparation. For many years, it is more common to use salt mud to produce magnesium sulfate heptahydrate, but the calcium sulfate slag produced by it accumulates in large quantities and is difficult to handle. There is also the use of salt lake brine to produce magnesium sulfate heptahydrate, which can only be applied in the salt lake area, and has relatively strong limitations. In recent years, in the field of flue gas desulfurization, the wet calcium method has taken the leading position, but due to the massive accumulation of its by-product gypsum, which constitutes serious secondary pollution to th...

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Problems solved by technology

[0003] There is an existing patent application "method for producing magnesium sulfate by using magnesium oxide desulfurization waste liquid". Since magnesium oxide is used as the raw material of desulfurization agent, the cost of magnesium oxide powder is relatively high, and the manufacturing process is to use magnesite ore at 800-900 °C Burning light-burned magnesia, and then grinding into magnesia powder, so it pollutes the environment and is not conducive to the popularization and application of magnesium desulfurization technology

Another disadvantage of this method is that the flue gas is not pretreated, and some of the smoke, HCl, HF, SO 3 Molecules are sent to the desulfurization tower at the same time for desulfurization and dust removal. As a result, after flue gas desulfurization, the waste liquid has more impurities. If the waste liquid is used to produce the by-product-magnesium sulfate, the purity of magnesium sulfate will be insufficient and the quality will not be high.

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