1. Low nitrogen combustion technology.Low nitrogen combustion technology belongs to controlled combustion technology, by regulating the oxygen content in the combustion air, reduce the generation of nitrogen oxides, all low nitrogen combustion technology must be able to let the boiler have a stable combustion process, otherwise there will be no obvious transformation effect or combustion instability.For biomass boilers, flue gas recirculation technology is commonly used.Flue gas recirculation technology has two processes:
The smoke after the induced draft fan is directly led to the inlet of the primary fan.The scheme does not need to change the primary fan, the recyculating flue gas does not need to exhaust fan, energy saving, simple transformation, nitrogen oxide concentration can be reduced by 20% ~ 40%;
The flue gas after the induced draft fan is directly led to the primary air chamber and the secondary air chamber in the furnace.In this scheme, the primary fan needs to run at reduced load, and the recirculated flue gas also needs to be equipped with a high-temperature exhaust fan, and the air pressure is equivalent to that of the primary fan.This scheme increases the operation power consumption, the transformation is relatively complicated, and the mass fraction of nitrogen oxides can be reduced by 25% ~ 50%.The flue gas recirculation technology also increases the concentration of sulfur dioxide and water content in the flue gas, but reduces the total emission of flue gas.
2. SNCR technology.SNCR belongs to selective non-catalytic reduction technology. SNCR technology is suitable for the boiler whose furnace outlet smoke temperature meets 800 ~ 1100℃. When the temperature is lower than this, the denitration efficiency is low, and the mixing effect of ammonia and flue gas has a great influence on the denitration efficiency (such as the mixing effect of cyclone inlet area is better).If the mixing is not sufficient and the reaction time is not enough, the same denitration efficiency will be achieved, which will increase the operation cost. At the same time, the exhaust ammonia escape also has the problem of exceeding the standard.In addition, the content of SO3 in the flue gas of biomass boiler is often high, and there are problems such as sulfate blockage and corrosion in the low temperature area of equipment below 280℃.SNCR denitration efficiency is also related to the initial concentration of nitrogen oxides in the smoke. SNCR denitration efficiency of biomass boiler is 20% ~ 50%.
3. O3 oxidation technology.NO% oxidation is the use of strong oxidant oxidation eventually converted to nitric acid or nitrate, commonly used oxidants are hydroxyl radicals Ho, O3, H2O2, MnO4, C1O2, Cl2;Among them, O3 is a commonly used oxidant with a fast reaction rate. Under the condition of full mixing with flue gas, the oxidation rate reaches more than 90%, and the operation is stable, and the industrial application performance is many.The suitable temperature of O3 oxidation denitration is 50 ~ 180℃, and there is NO requirement for the concentration of SO2. It can be installed in the low-temperature flue gas section. After NO% oxidation, alkaline substance absorption system should be added to absorb the oxidized nitrogen oxides.