Device and method for preparing sulfite

A method for preparing sodium sulfite by using a device, comprising the following steps wherein the device comprises:

• output ends of a mother liquor tank and an alkali storage A connected to a concentrated alkali tank, a liquid-phase output end of the concentrated alkali tank is connected to a first-stage reactor of a column reactor, one output end at the bottom of the first-stage reactor is connected to a first-stage gas-liquid mixer, the other output end is connected to an upper end of a bubbling reactor, a gas output end at the top of the bubbling reactor is connected to the first-stage gas-liquid mixer, the first-stage gas-liquid mixer is also connected to the top of the first-stage reactor, a gas output end at the top of the first-stage reactor and an output end at the bottom of a second-stage reactor are connected to a second-stage gas-liquid mixer, and the second-stage gas-liquid mixer is connected to the top of the second-stage reactor;
• a liquid-phase output end of the bubbling reactor is connected to a centrifuge or the concentrated alkali tank, a solid output end of the centrifuge is connected to a wet silo, and a liquid output end of the centrifuge is connected to the mother liquor tank;
• an output end of the wet silo is connected to a dryer, a gas-phase output end of the dryer is connected to a baghouse dust collector, and an output end at the bottom of the baghouse dust collector outputs a target product;
• and
• the bubbling reactor is configured with all or any one or more of a stirring paddle, a water cooling system, a heating system, and a vacuumizing system
• 1) preparation of main absorption liquid:
• preparing a thick slurry with a temperature of 45-57° C. and a relative density of 1.28-1.35 in the concentrated alkali tank from desalted water and sodium carbonate when the device runs for the first time or after a major repair;
• and preparing a thick slurry with a temperature of 42-57° C. and a relative density of 1.45-1.55 in the concentrated alkali tank by using a mother liquor of saturated sodium sulfite as a solvent and sodium carbonate as a solute in the normal production process;
• 2) preparation of auxiliary absorption liquid:
• dissolving sodium carbonate with desalted water and condensed water from a drying system to prepare a dilute lye with a temperature of 42-57° C. and a relative density of 1.25-1.33 in a dilute alkali tank;
• 3) production of intermediate slurry:
• transferring the prepared slurry in step 1) into the first-stage reactor of the column reactor by using a concentrated alkali pump to undergo counter-current contact reaction with SO2 raw material gas to produce an intermediate slurry of sodium sulfite and sodium bisulfite;
• 4) re-absorption of residual SO2 gas:
• transferring the dilute lye prepared in step 2) into the second-stage reactor of the column reactor by using a dilute alkali pump to react with residual gas from the first-stage reactor, reducing the volume concentration of SO2 in the residual gas from the first-stage reactor to 0.3% or less, transferring the absorption liquid in the second-stage reactor into the mother liquor tank by using a second-stage circulating pump when the pH value thereof is reduced to 6.8-7.8, and then turning on a dilute alkali pump and adding the same amount of absorption liquid into the second-stage reactor;
• 5) preparation of target product slurry:
• transferring the intermediate slurry obtained in step 3) into the mother liquor tank, preparing a sodium sulfite solution with a relative density of 1.32-1.62 and a pH value of 8-12 in the concentrated alkali tank from the slurry in the mother liquor tank, a lye in the alkali storage A, and fresh desalted water;
• and for the adjustment of pH, adjusting the pH value of the slurry to 6-8 with solid sodium carbonate or adjusting the pH value of the slurry to 6-8 with a concentrated sodium carbonate slurry with a mass concentration of 15-35%, and then adjusting the pH value to 8-12 with a sodium hydroxide solution with a mass concentration of 20-30%;
• 6) concentration and crystallization of target product:
• transferring the suspension obtained in step 5) into the bubbling reactor by using the concentrated alkali pump for cooking with a cooking temperature controlled to 50-75° C. or 98-105° C. and a gas-phase space pressure in the bubbling reactor controlled to an absolute pressure of 15-40 kPa or 100-120 kPa, until the relative density of the slurry in the bubbling reactor reaches 1.48-1.96 and the volume content of crystal particles larger than 150 mesh in the slurry reaches 20-50%;
• 7) separation of target product:
• transferring the suspension obtained in step 6) into the centrifuge to undergo separation by the centrifuge to obtain a wet product and a mother liquor of saturated sodium sulfite;
• and
• 8) drying and packaging:
• drying and packaging the wet product obtained in step 7) to obtain a sodium sulfite product.