The synthetic method of sodium metabisulfite

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2022-05-23 15:13:39.681

1. Send crushed sulfur into the combustion furnace, add compressed air about twice the theoretical amount, and spontaneously ignite at 600-800 °C. After cooling, dust removal and washing, it is sent to a multi-stage reactor for reverse absorption with sodium carbonate solution; the temperature of the absorption liquid is controlled at about 45 ° C, the crystal slurry flowing out of the multi-stage reaction is centrifugally separated, and dried below 160 ° C is the finished product.

2. Add a certain amount of soda ash to the sodium bisulfite solution to form a sodium sulfite suspension. Sulfur dioxide is added to generate sodium metabisulfite crystals, which are obtained by centrifugal separation and drying.

3. Put glass wool on the lower part of the ordinary glass drying tower, then fill it with the mixture of NaHCO3 and broken glass pieces, and pass SO2 gas from the lower part of the tower under negative pressure until no more carbon dioxide escapes. The water formed in the reaction is concentrated at the bottom of the column, and the resulting salt is practically dry. Sieve out the broken glass pieces and place in an airtight bottle. Then the anhydrous salt is calcined in a large porcelain crucible at 500-600° C. for 2-3 hours, and the calcination is carried out until the precipitate formed by the reaction between the aqueous solution of the preparation sample and AgNO3 is pure white.

4. At a temperature of about 30°C, pass SO2 gas into the 30% sodium carbonate solution until there is a strong SO2 smell. Put this solution into a desiccator with concentrated sulfuric acid as a desiccant, keep the temperature above 25°C, and let stand until the crystals are precipitated.

5. Use the absorption method. The food-grade soda ash solution is used to absorb sulfur dioxide to generate sodium pyrosulfite, which is refined to remove impurities, filtered and dried to obtain food-grade sodium pyrosulfite.