Double alkali (sodium calcium) desulfurization technology
Chemical principle
1. Absorb
NaOH+SO2 → NaHSO3
Na2SO3+SO2+H2O → 2NaHSO3
The absorption solution containing sodium bisulfite is neutralized by liquid alkali to obtain sodium sulfite:
NaOH+NaHSO3 → Na2HSO3+H2O
2. Replacement of regeneration
the following reaction occurs When the absorption solution containing sodium sulfite meets and mixes with lime water, :
Ca(OH)2+Na2SO3→CaSO3↓+2NaOH
That is calcium sulfite precipitates, and sodium hydroxide is replaced again into the absorption tower to absorb sulfur dioxide.
3. Oxidation
the following reactions occur when dealing with flue gas containing oxygen or sulfur trioxide :
NaHSO3+O2→Na2SO4 +H2O
Na2SO3+O2→Na2SO4
NaOH+SO3→NaHSO4
Na2SO4+SO3+H2O→2NaHSO4
NaOH+NaHSO4→Na2SO4+H2O
Ca(OH)2+Na2SO4→CaSO4↓+2NaOH
Process flow diagram
Process principle introduction
Na2CO3 or NaOH solution as the first absorption solution and then limestone or lime solution used as the second alkaline solution for regeneration. the solution continues to be recycled after regeneration,. The SO2 obtained by this method still precipitates in the form of CaSO3 or CaSO4. the scaling and blockage are avoided due to the production process of its product is outside of the absorption tower .
The main function of equipment and process systems
1. Flue gas systems: flue pipeline , diverter damper and sealing devices etc .
2. Absorption System: reverse flow spray absorption tower to complete the absorption of SO2 and SO3.
3. The slurry preparation system: lime powder storehouse, gasification equipment,Dust removal device, metering and conveying device, lime milk tank, dosing pump etc ;
4. Circulating system: regeneration tank, sedimentation and concentration tank, circulating tank, oxidation system, various circulating pipelines and pumps etc ;
5. Control system: electrical control and thermal instrumentation etc.
Technical characteristics
1. Double alkali desulfurization system can be combined with dust removal , using an integrated dust removal and desulfurization device to simultaneously perform desulfurization and dust removal
2. Sodium alkali absorbent has High reactivity, fast absorption rate, and the liquid to gas ratio can reduce , and thus reducing operating costs can also decrease investments in water tanks, pumps, and pipelines.
3. there is no existed of fouling in the tower and slurry plugging problems since external circulation of the tower .
4. Sodium alkali recycling with minimal loss
5. Lime as regenerant (actual consumption of material), safe and reliable, widely sources, low price
6. Easy to operate, the system can be long-term stable operation