The acidic gases generated in garbage incineration include HCl, SO2, etc. The methods for removing acidic gases can be summarized into three types: wet method, semi dry method, and dry method. Their removal efficiency for HCl is 98%, 90%, and 80%, respectively, and their removal efficiency for SO2 is 95%, 80-90%, and 75%, respectively. The excess consumption coefficient for absorbent is 1, 2, and 3.
Obviously, the wet washing method has a better removal effect on acidic gases. However, due to the problem of sewage treatment in the wet washing method, the investment cost of its system is about 1.75 times that of the semi dry method system, and its operating and maintenance costs also increase accordingly.
The investment of dry deacidification method is similar to that of semi dry method, but its removal effect on acidic gases is poor.
The biggest feature of the semi dry method is to fully utilize the residual heat in the flue gas, evaporate the water in the absorbent, and purify the reaction products in the form of dry solids, avoiding the shortcomings of wet purification technology. The purification process involves reducing the flue gas from a higher temperature to a set temperature, injecting an alkaline absorbent to react with the acidic gas in the flue gas, and obtaining dry salt products, which are then recycled by a dust collector. By conducting sufficient mass and heat transfer between alkaline absorbents and acidic gases in flue gas, not only efficiency is improved, but also the reaction products can be dried, resulting in easily processed dry powder like products. The semi dry process is relatively mature, with simple equipment and low one-time investment. Its advantages are: high purification efficiency, simple process, and few equipment; The product is easy to handle and has no secondary pollution; Control the temperature and humidity of the system to avoid equipment corrosion; No scaling or blockage; Good adaptability to load fluctuations, and the amount of absorbent can be adjusted according to the concentration of pollutants in the flue gas; Easy to operate and minimal maintenance; Low water consumption and small footprint.
The semi dry deacidification method has good application practice, and the performance of incineration plants at home and abroad has shown its high reliability and good performance.