Method for producing sodium hypophosphite

Abstract

The invention is a method for producing sodium hypophosphite, which is characterized in that the process steps include batching, reaction, filtration, first concentration, adjustment, second concentration, cooling and crystallization, and centrifugal packaging. Advantages: Put the measured liquid caustic soda into the lime milk tank, mix it with water and quicklime, and pump it into the reaction kettle together. In this way, it is not necessary to disassemble the liquid alkali pipeline frequently, thereby reducing the unfavorable factors affecting normal production; the reactor is emptied with nitrogen, which should be evacuated with steam, which is easy to operate and does not require additional equipment; replace the old-fashioned plate with a diaphragm press filter Frame filter. The water content of the filter cake is reduced from 45-50% to 35-40%, and the filter cake content of 1-1.5% sodium hypophosphite is reduced to 0.4-0.8%. The reduction of the water content of the filter cake not only improves the recovery rate of sodium hypophosphite, but also improves the operating conditions of slag unloading; the ratio of yellow phosphorus per kettle is changed from 90 to 100kg to 150kg, which greatly increases the output of a single device.

Description

technical field [0001] The invention relates to a method for producing sodium hypophosphite, which belongs to the technical field of inorganic chemical additives. Background technique [0002] Sodium Hypophosphite, also known as Sodium Hypophosphite: SHPP / HYPO for short. Molecular formula: NaH 2 PO 2 ·H 2 O, molecular weight: 105.99. Appearance: pearly crystal or white crystalline powder. Odorless, salty, strong water absorption, easy to deliquescence, soluble in water and glycerin. The aqueous solution is neutral, and it will decompose rapidly when heated above 200°C, releasing phosphine gas which may be naturally poisonous. It is an inorganic hypophosphite with strong reducibility and can explode when in contact with strong oxidants. The existing production method is to first make lime emulsion with quicklime and water in a weight ratio of 1:16 and pump it into the reactor, put the measured liquid alkali into the reactor by using the liquid level difference, and the...

AI Technical Summary

Problems solved by technology

Because the reaction kettle is easy to scale, it is easy to block the liquid caustic nozzle installed on the reaction kettle, which often leads to dismantling and dredging of the liquid caustic pipeline, which seriously affects the production progress; during the reaction of sodium hypophosphite, air is strictly prohibited in the kettle , Phosphine gas will explode when it encounters air, so the air must be driven out before the reaction is fed, and the cost of exhausting the air with nitrogen is relatively large, and the operation is inconvenient; the reaction filtrate is filtered with a plate and frame filter press, and the filter The moisture content of the cake is generally 45-50%. No matter how the filter cake is washed, it always contains 1-1.5% sodium hypophosphite and is transported away with the waste residue.

The waste residue with high moisture content is viscous when disassembled, and the operation is inconvenient; the proportion of yellow phosphorus per kettle is 90-100KG, and the output is low