Wet Limestone-gypsum Desulfurization Technology

Introduction

 

  After dust removal in the electrostatic precipitator, flue  gas will enter the absorption tower through booster fan. In the absorption tower flue gas moves upwards and is sufficiently contacted and washed by circulating slurry spraying downwards to remove SO2, SO3, HCL and HF in the flue gas. Meanwhile, side products generated in “forced oxidation process" are oxidized to be CaSO4 by the imported air with absorbent limestone being consumed. In the slurry of the absorption tower, CaSO4.2H2O is generated through CaSO4 crystallization and is discharged by gypsum slurry pump into gypsum dewatering system to form desulfurized gypsum after primary and secondary dehydration processing.

 

System flow chart of Tuna's wet limestone-gypsum desulfurization technology:

 

 

 Reaction mechanism：

 

1、 Absorption reaction: SO₂+H₂O H₂SO₃H＋ + HSO₃－

2、Oxidation reaction:  H＋+ HSO₃－+ 1/2O₂2H₂O +SO₄2－

3、 Dissolution reaction:CaCO₃+ 2H＋Ca₂＋ + H₂O +CO₂

4、 Neutralization reaction:CO2＋+   SO₄2－+ 2H₂O CaSO₄·2H₂O

 

Process description：

 

  Process water is mixed with limestone powder as desulfurizer at a certain proportion and then fed evenly into the pulp chest at the bottom of the absorption tower.Flue gas flows into absorption tower from the middle of the absorption section and goes upward to the spray section, where it is cooled by the pulp. Part of the pulp water is evaporated, cooling the flue smoke. The pollutants in the flue gas are absorbed by the pulp, which then falls into the reaction tank. The oxidization air blowers blows the humidified air into the blender to be blended and then into the reaction tank, where oxidization and precipitation happens and gypsum appears.

 

 

 

 

Technical features of Tuna's wet limestone-gypsum desulfurization technology:

 

The use of the empty spray tower is used without any grid or trays can ensure low resistance, and effectively avoid scales during operation.

 

Backwashing ensures the full contact of flue gas and reactants.

 

Unit design: spray unit- air/ liquid contact washing; defogging unit- the separation of air and liquid; pulp chest unit- oxidization, dissolution and crystallization.

 

The advanced flow field simulation technology achieves the even spread of flue gas to prevent flue gas escape because of the uneven spread of flue gas in the tower and thus ensures the efficiency of desulfuration.

 

 

Flow chart of the process：