Limestone / gypsum desulphurization equipment detail:
Limestone / gypsum method is one of the most commonly used in wet desulfurization. But the limestone / gypsum method shortcoming is also obvious: the initial investment cost is too high, high operation cost, large area, complex operation and management system of wear corrosion phenomenon is more serious, a byproduct of gypsum very difficult (due to market issues could be piled up, more difficult to deal with waste water).
The difference between the technology and the discard method lies in the absorption tower of the slurry drum into the air, forced to make CaSO3 are oxidized to CaSO4 (gypsum), desulfurization by-product of gypsum. At the same time, the drum into the air produced a more uniform slurry, easy to achieve 90% of the desulfurization rate, and easy to control the scaling and clogging. Due to the low price of limestone, and easy to transport and preservation, since 80s since the limestone has become the main desulfurization agent. At home and abroad in the selection of thermal power plant flue gas desulfurization equipment, limestone / gypsum forced oxidation system to become a priority choice of wet flue gas desulfurization process.
Working principle of limestone / gypsum desulfurization:
The use of limestone or lime as absorbent, lime stone breaking and grinding into powder mixed with water into slurry, when using lime as absorbent, lime powder were made of water absorbent. In the absorption tower, flue gas and slurry mixed contact, the sulfur dioxide gas and slurry of calcium carbonate and drum into the air for chemical oxidation reactions to be removed, the final reaction product gypsum.
Limestone / gypsum desulfurization process:
Boiler / kiln - dust collector - draught fan - absorption tower - chimney
The flue gas from the boiler or furnace through the filter after the fan effect into the absorption tower, absorption tower for countercurrent spraying empty tower structure, including absorption, oxidation functions, upper absorption area, lower oxidation zone, after circulating slurry flue gas after dust removal and absorption tower reverse contact. The system is generally installed 3-5 stage slurry pump, each pump cycle is corresponding to a layer of spray coating. When only one unit is running or the load is relatively small, the system can stop the spraying layer of 1-2 layer, and the system still keeps a high liquid gas ratio, thus the required desulfurization effect can be achieved. The upper part of the absorption area is filled with two stage mist removing device, and the free water in the flue gas of the mist removing device is not more than 75mg/Nm3. After absorption of SO2, the slurry enters the circulating oxidation zone, in which the calcium sulfite is blown into a gypsum crystal. At the same time, the absorbent preparation system provides the fresh limestone slurry to the absorption oxidation system, which is used to supplement the consumed limestone, so that the absorption slurry can maintain a certain pH value. When the slurry of the reaction product reaches a certain density, it is discharged to the desulfurization by-product system.
Principle of limestone / gypsum desulphurization technology:
Desulfurization process
CaCO3+SO2+1/2H2O, CaSO3, 1/2H2O+CO2
Ca (OH) 2+SO2, CaSO3, 1/2H2O+1/2H2O,
1/2H2O+SO2+1/2H2O, Ca, CaSO3 (HSO3) 2
Oxidation process
1/2H2O+O2+3H2O, 2CaSO4, 2CaSO3, 2H2O
Ca (HSO3) 2+O2+2H2O, CaSO4, 2H2O+H2SO,