The Dalian project has a capacity of 1500T/D for domestic waste treatment, with 3 sets of 20.83T/H incinerators. Each incinerator is individually equipped with one set of flue gas purification treatment device, lime slurry production system and activated carbon injection system shared by the three furnaces. The project adopts semi-dry flue gas purification process, i.e. spray reaction tower acid removal + activated carbon injection adsorption + pulse bag type dust removal for treatment.   1、Characteristics of flue gas of waste incineration power plant The amount of HCL generated in Dalian project is about 2352.77T/A, and the emission is about 89.63T/A after flue gas purification treatment; the amount of SO2 generated is about 1232.4T/A, and the emission is about 336.11T/A after flue gas purification treatment; the amount of flue gas dust generated is about 5108.88T/A, and the large particles of the flue gas dust are removed after the purification of semi-dry tower and baghouse dust collector, and the emission is about 56.02T/A; after activated carbon adsorption and bag filter treatment, the emission concentration of heavy metals can reach mercury, cadmium, thallium and their compounds ≤ 0.05M VG/M3, antimony, arsenic, lead, chromium, cobalt, copper, manganese, nickel, vanadium and their compounds ≤ 1MG/M3; after SNCR system off, the emission concentration of NOX is controlled at 200MG/NM3.The flue gas produced by waste incineration Has the following characteristics. 1.1 The flue gas contains large amount of moisture. The water content of the garbage is high, and some hydrocarbons also generate water vapor in the combustion, and the moisture content of the flue gas is generally 23%-30%.   1.2 Complex composition of garbage. The burning of garbage will produce toxic and harmful components, including some trace heavy metals.   1.3 Complex composition of flue gas. Flue gas not only contains O2, SOX, CO2, NOX, etc., but also HCL, HF and other acidic gases, water vapor, total hydrocarbons (THC).   1.4 Combustion may also produce dioxins and furans and other carcinogenic substances, extremely harmful to the human body.   1.5 The dust in the flue gas is fine in particle size and high in viscosity.   2、Fume purification treatment process 2.1 Process flow Waste incinerator flue gas from the waste heat boiler outlet first into the spray reaction acid removal tower, where the acidic gas and the lime slurry sprayed in the middle of the top of the tower for neutralization reaction, and then by the start of the reaction tower outlet sprayed into the activated carbon, the flue gas in the heavy metals and dioxin adsorption into the baghouse dust collector. The bag filter captures and purifies the particulate pollutants, neutralization reactants, activated carbon and adsorbed pollutants in the flue gas, and the clean flue gas is discharged from the outlet pipe of the dust collector through the induced draft fan and from the chimney to the outside.   2.2 Activated carbon injection device The total amount of activated carbon consumed in the Dalian project (3 waste treatment production lines) is 27.9KG/H (100% MCR) (purity of 90%), which is transported to the activated carbon site of the flue gas purification system of the plant by special trucks under the responsibility of the supplier. The whole plant is equipped with a 25M3 activated carbon silo, and then the activated carbon is loaded into the silo by loading hoist crane. The activated carbon silo is equipped with high and low material level meters, silo top dust collector, vacuum pressure release valve, silo wall vibrator and manhole and other ancillary facilities. The volume of the activated carbon silo ensures the usage of the whole plant for more than 7 days. The activated carbon feeding is a continuous operation, and the activated carbon is conveyed by air, with 4 sets of blowers (3 running and 1 standby).   2.3 Bag filter A low-pressure blowing pulse bag filter with bypass is used to collect the soot in the flue gas. The dust catcher consists of bracket, ash hopper and accompanying heat, box and bypass flue, circulating heated air system, filter bag, blowing cleaning device, ash discharge valve and pulse controller and other parts, for the unit combination structure. The filter bag is made of PTFE-coated filter material, which is characterized by good acid and alkali resistance, strong regeneration ability, high filtration efficiency, long-lasting operation, low resistance and good water repellency, etc. The service life is more than 3 years, and the keel is made of stainless steel. In order to avoid flue gas condensation and affect the normal work of the bag filter, the dust collector is equipped with perfect overall thermal insulation measures Measures.   3、System design points 3.1 Semi-dry reaction tower diameter of 9524MM, tower straight height of 11020MM, flue gas volume of 100250NM3 / H, tower flue gas flow rate of 0.656M / S, calculated tower flue gas residence time of 21 seconds, the guaranteed value of 20 seconds.   3.2 Semi-dry reaction tower ash hopper should be set outside the tracer, tracer must make the ash hopper inside the fly ash temperature of 140 ℃ or more, tracer power is not less than 300W/M2;.   3.3 Rotary sprayer installed in the center of the reaction tower center channel at the top of the snail shell center, the system can be replaced on-line spare sprayer operation;   3.4 Bag filter bag material selection. Waste incineration flue gas filter material needs to be considered comprehensively temperature resistance, acid resistance, alkali resistance, oxidation resistance, resistance to hydrolysis, price and other factors, the use of different filter media temperature, dust removal efficiency, dust removal performance, cost and the degree of corrosion resistance to different chemical components in the flue gas are not the same. Dalian project filter bag material selection of 100% PTFE needle punched felt coated filter bag (filter material requirements of Europe and the United States imported products); PTFE acid, alkali, temperature and hydrolysis resistance and other properties, is dedicated to high temperature, high corrosion places of high-grade filter media.   3.5 To pay attention to the acid dew point of flue gas. Waste incineration supporting the filter media, in addition to the nature of the soot itself will affect its service life and reliability, and the acid dew point of the flue gas will also have a certain impact, when the flue gas temperature is lower than the acid dew point, the acid produced by condensation will corrode the equipment and in the formation of soot adhesion on the filter media. Dalian project has a bypass channel in the middle of the dust collector, once the temperature of the flue gas entering the dust collector is higher or lower than the set temperature, the control system sends out a signal, the valve is switched, and the flue gas passes through the bypass, which effectively protects the filter bag.   3.6 Control system requirements:Pre-formulated lime slurry, together with water, respectively, into the rotary sprayer, sprayed from the nozzle. Rotary spray semi-dry desulfurization reactor tower made of wear-resistant alloy mechanical rotary nozzles, each spray lime slurry (12%) amount of up to 1194KG / H (110% MCR), slurry particle size of 30-40MM rotary sprayer cooling fan, desulfurization reactor tower body, lime slurry system and the related control system components.   4、 conclusion In view of China's current status of development of waste incineration flue gas treatment technology and the affordability of most cities, the use of semi-dry purification process based on the flue gas treatment process is appropriate.