Sodium metabisulfite(SMBS) production technology

Sodium metabisulfite(SMBS) production technology

  1、Process features
  1.1Continuous and automatic production process.
  1.2The complete combustion of oxygen in the air greatly reduces the oxidation reaction in the synthesis process. This ensures that the product purity is always stable over 98%.
  1.3Chemical sulfur removal is adopted, gas purification is complete, and product impurity is low.
  1.4No dilute sulfuric acid wastewater will be generated.
  1.5Recover the heat energy of sulfur burning, and can send out steam.
  2、Process description
  SO2 gas can come from sulfur burning, other material containing sulfur burning or other tail gas. Now take sulfur as an example:
  2.1Sulfur melting process: put solid sulfur into the sulfur melting tank, put steam into the jacket and coil to melt sulfur into liquid, get pure liquid sulfur through clarification and purification, and store it in the liquid sulfur storage tank. Liquid sulfur can also be used directly.
  2.2Air compression process: air compressor increases air pressure, after drying, it is going to the burner, and reacts with the filled liquid sulfur, then, we can obtain SO2 gas.
  2.3Sulfur burning process: liquid sulfur is added into the burner through a pump and reacts with the dry air to obtain SO2 gas. At the same time, the heat is released, which is taken out by the high-temperature gas and go into the waste heat boiler. The gas in the waste heat boiler is cooled to 240-280 ℃ and by-product steam is obtained (the steam pressure can be designed according to the actual requirements). SO2 gas enters the 2nd stage of cooler and cools to 140 ℃.
  S  +  O2  =  SO2  +  Q
  2.4Gas purification process: cooled gas enters into the sulfur removal reactor, using SO3 to remove sulfur, sulfur carried in the gas will react with SO3. The sulfur is oxidized to SO2, and the sulfur carried in the gas is removed. Pure SO2 gas is sent to the SMBS synthesis reactor. This technology is designed with a small SO3 generating device.
  SO2  +  O2  =  SO3
  S   +  2SO3  =  3SO2
  2.5Soda solution preparation and synthesis process: put solid soda ash into the soda solution preparation tank, make suspension with mother liquor from centrifuge, then pump it into the synthesis reactor, and soda solution reacts with SO2 gas through 3rd stage of reactor, 2nd stage of reactor, and 1st stage of reactor in turn. Then, we obtain SMBS suspension. SO2 gas passes through the 1st, 2nd and 3rd stage of reactors in turn, and the synthesis tail gas goes into the tail gas scrubber, washed by soda ash solution to absorb SO2 in the tail gas. The absorption liquid is recycled to the soda solution preparation tank. Tail gas meets discharge requirement (SO2 ≤ 30mg / Nm3).
  Na2CO3  +  SO2  =  Na2S2O5  +  CO2
  2.6Centrifugal drying process: SMBS suspension is sent to the centrifuge, and the centrifugal mother liquor is collected to the mother liquor tank through centrifugal separation, and the mother liquor is recycled to the soda solution preparation process. The centrifuged solid is SMBS contains 3-6% moisture. The solid is sent into the flash dryer through the spiral conveyor, and finished SMBS is obtained by hot air drying.
  2.7Process flow chart:
  3、Product standard and consumption list
  3.1SMBS quality standard
Item Unit Index(guarantee)
Main purity(calculated by Na2S2O5)
% ≥98.0
moisture % ≤0.5
Water insoluble % ≤0.02
sodium sulphate % 1.50%
  3.2SMBS consumption list
No. Item Unit Consumption quota
1 sulfur(reduce moisture) t 0.335
2 soda ash(reduce moisture) t 0.575
3 ower 380V kwh 150
4 steam 0.5MPa t 0.7t
5 tap water t 2.0
  4、treatment for “3 wastes”
  4.1waste water: no waste water in this technology.
  4.2waste gas
  1)Source and composition of waste gas: the waste gas mainly comes from synthesis tail gas, drying tail gas and negative pressure induced draft gas. The main pollution factor is SO2, and the content of SO2 in the tail gas of each part is as follows:

Synthesis tail gas Drying tail gas Induced draft tail gas
content (by volume)
0.50% 0.50% 0.30%
  2)Waste gas treatment measures: adopt 2-stages of soda solution countercurrent absorption, and the SO2 emission concentration in the absorbed tail gas is less than 30ppm. It is superior to the Chinese 1st level emission standard. There is no loss of sulfur and sodium ions when the absorption liquid is reused to the soda solution preparation process.
  4.3 solid waste: no solid waste in the technology.
  4.4Summary of 3 wastes after treatment:

Discharge point Discharge flow Index
waste water no waste water 0
waste gas tail gas chimney 6000-10000Nm3/T
6000-10000Nm3/t SMBS
solid waste no solid waste 0



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