1 Desulfurization efficiency
In the case of high flue gas temperature, when the SO2 concentration in the flue gas is less than 2000mg/Nm3, the spray drying desulfurization technology can achieve a desulfurization efficiency of 80%. If the SO2 concentration is less than 1000mg/Nm3, the spray drying desulfurization technology can reach nearly 90% % desulfurization efficiency. The lower the SO2 concentration, the higher the desulfurization efficiency, and the higher the SO2 concentration, the lower the desulfurization efficiency. When the SO2 concentration in the flue gas is greater than 2500mg/Nm3, and the flue gas temperature is greater than 200°C, it is not suitable to use spray drying desulfurization technology. It is difficult to meet the emission requirement of 400mg/Nm3 under such working conditions. When the inlet flue gas temperature is 120~160°C and the SO2 concentration is 2500mg/Nm3, the spray drying method can achieve a desulfurization efficiency of up to 95%. Under this working condition, the requirements for the desulfurization tower and the control system are very high.
The circulating fluidized bed technology can achieve high desulfurization efficiency, and the desulfurization efficiency can reach 95% when the outlet temperature of the desulfurization tower is controlled to about 80°C. Such a high desulfurization efficiency fully meets the flue gas desulfurization requirements of all glass kilns. When the glass kiln is refired, the temperature of the flue gas fluctuates greatly, and sometimes it can reach 40°C. The desulfurization system generally adjusts the water injection rate slowly. When the temperature is controlled to 90°C or higher, the desulfurization efficiency is relatively low, and Ca/S will exceed 1.5.
2 Dust removal efficiency No matter it is the spray drying method or the circulating fluidized bed desulfurization method, high-efficiency dust collectors such as electric dust collectors or bag dust collectors must be equipped behind, and these dust collectors can meet the emission requirements of 50mg/Nm3.
3 Flue gas temperature The spray drying method has no special requirements for the inlet temperature of the system. As long as the system design is reasonable, the inlet temperature can fluctuate from 120°C to 500°C, and the flue gas temperature has a wide range of adaptations. However, if the flue gas temperature is too high, the flue gas temperature at the outlet of the desulfurization tower cannot be too low. If the inlet temperature exceeds 200°C, the desulfurization efficiency will be difficult to reach more than 90%. The circulating fluidized bed desulfurization method requires that the inlet temperature of the desulfurization tower should not exceed 200°C, otherwise the desulfurization efficiency cannot be guaranteed. If the flue gas temperature entering the desulfurization system exceeds 200°C, a cooling tower must be installed in front of the desulfurization tower to reduce the flue gas temperature to below 200°C. The nozzle of the cooling tower is easy to be corroded, and the cooling tower is prone to local over-humidity and corrosion of the cooling tower. When designing the cooling tower, attention should be paid to the protection of the nozzle and the prevention of local over-humidity.
4 Absorbent Utilization Rate Both the spray-drying method and the circulating fluidized bed method require some excess of absorbent, and the utilization rate of absorbent is lower compared with the wet method. Using the spray drying method, when the inlet flue gas SO2 concentration is lower than 1000mg/Nm3, if the bag filter is used to remove dust, the utilization rate of the absorbent can reach more than 98%. When the inlet flue gas SO2 concentration is 2000mg/Nm3, if the electrostatic precipitator is used to remove dust, the utilization rate of the absorbent is lower than 80%.
The absorbent utilization rate of circulating fluidized bed desulfurization has a great relationship with the flue gas temperature at the outlet of the desulfurization tower. If the outlet temperature of the desulfurization tower can be controlled at about 10°C near the adiabatic saturation temperature, when the desulfurization efficiency is 95%, the Ca/S The ratio can reach 1.2. The higher the outlet temperature of the desulfurization tower, the higher the Ca/S at the same desulfurization efficiency.
5 operating costs If the spray drying method uses NaOH and Na2CO3 as absorbents, the price of these two substances is high, and the operating cost is relatively high. If Ca(OH)2 is used as the absorbent, the nozzle needs to be replaced regularly due to the wear of the nozzle by the lime. Circulating fluidized bed uses Ca(OH)2 or CaO as absorbent, slaked lime or lime is cheap, and the operating cost is lower than that of the spray drying method. The higher the SO2 concentration at the system inlet, the lower the unit SO2 removal cost.
6 Desulfurization by-products If NaOH and Na2CO3 are used as the spray drying method of the absorbent, the by-products of desulfurization are mainly Na2SO3 and Na2SO4, which can be used as clarifiers for glass production. When the bag filter is used as the dust collector, the by-products are mainly Na2SO4. No problem, no waste from the desulfurization system. The main components of circulating fluidized bed desulfurization ash are CaSO3·1/2H2O, CaSO4·1/2H2O, unreacted Ca(OH)2, and impurities. This desulfurization ash can be used for waste mine landfill, highway roadbeds, sound-absorbing materials, cement admixture, etc. But in fact, the utilization rate of desulfurization by-products of the circulating fluidized bed method in my country is low, and they are generally discarded directly as industrial waste.