Sodium sulfite(SS) production technology

Sodium sulfite(SS) production technology

  1、Process features
  1.1Continuous and automatic production process.
  1.2The special design solves the tubes chocking problem during multi-stages of concentration.
  1.3The complete combustion of oxygen in the air greatly reduces the oxidation reaction in the synthesis process. It ensures that the product purity is always stable over 98% for a long time.
  1.4No dilute sulfuric acid wastewater is generated in the process of SO2 production.
  1.5Recovery of heat energy from sulfur burning and reduction of energy consumption.
  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 soda solution with water, and pump it to absorption tower, and react with SO2 gas coming from the bottom of tower, we obtain sodium bisulfite solution. Synthesis tail gas is sent to tail gas scrubber, washed by soda solution, purify SO2 in the tail gas. Absorption liquor is returned back to soda solution preparation tank. Tail gas meets discharge requirement (SO2 ≤ 30mg / Nm3).
  Na2CO3  +  SO2  +  H2O  =  2NaHSO3  +  CO2
  2.6Neutralization and concentration process: deliver sodium bisulfite solution and soda solution into the neutralization reactor, control temperature within 70-90℃, PH within 8-10, neutralize to get sodium sulfite, send sodium sulfite solution to the concentrator/evaporator, to get solid suspension. The steam condensate is recycled to the soda solution preparation process.
  2.6Centrifugal drying process: sodium sulfite suspension is sent to the centrifuge, through centrifugal separation, the liquid is returned to the concentrator, the solid is sodium sulfite containing 3-6% moisture, solid sodium sulfite is sent to the flash dryer, and the finished sodium sulfite is obtained by hot air drying.
  2.7Process flow chart
  3、Quality assurance and consumption list
  3.1 Sodium sulfite quality standard
Item Unit Index(guarantee)
Main purity(calculated by Na2SO3) % ≥98
Water insoluble % ≤0.05
  3.2consumption list
No. Item Unit Consumption quota
1 sulfur(reduce moisture) t 0.255
2 soda ash t 0.422
3 caustic soda(32%) t 1.00
4 power 380V kwh 120
5 steam 0.8MPa t -0.8t
  4、Ttreatment 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 the synthesis tail gas of absorption tower(scrubber) and dry tail gas. The main pollution factor of the absorber tail gas is SO2, and the main pollution factor of the drying tail gas is sodium sulfite dust. The contents of gas pollutants in each part are as follows:

synthesis tail gas drying tail gas
SO2 content(by volume) 0.50%
  2)Waste gas treatment measures: the waste gas enters into the washing tower(scrubber) and is absorbed by soda solution countercurrent. SO2 emission concentration in the absorbed tail gas is less than 30mg / Nm3. The dust is less than 10mg / Nm3. When the absorption solution is recycled to the soda solution preparation process, there is no loss of sulfur and sodium ions.
  4.3solid waste: no solid waste in this technology.
  4.4Summary of 3 wastes after treatment:
Discharge point Discharge flow Index
waste water no waste water 0
waste gas tail gas chimney 6000-8000Nm3/T
6000-8000Nm3/t SS
solid waste no solid waste 0



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