1. Advantages of high temperature incineration of waste
High temperature incineration method is an effective method to deal with all kinds of garbage, hazardous waste, sludge, waste liquid and other substances in daily life and industrial production. Through full combustion under oxygen-rich conditions ~ 1000℃, it can completely eliminate pathogenic organisms and organic matter, eliminate flammability, toxicity and corrosion, and realize harmless; The heat energy generated after incineration can be used for heating and power generation to achieve energy conservation and emission reduction. After incineration, the volume can be reduced by more than 90%, and the weight can be reduced by more than 80%, effectively reducing the landfill land and realizing the reduction. Incineration residue has the potential to be used to recover metals, produce building materials, and achieve comprehensive utilization of resources.
In recent years, with the rapid development of China’s economy and the requirement of continuous improvement of the environment, the construction and operation of waste incineration power generation projects are springing up all over the country, and the latest technology and standards for deep purification treatment of incineration flue gas have been constantly applied.
2. Emission standards and purification conditions of incineration flue gas
Our waste incineration power generation industry started in the late 1980s. Through introducing foreign advanced incineration equipment and technology, digestion and absorption optimization, it has gone through the stages of industrialization research and development, equipment localization and so on. Since the large-scale promotion of BOT mode in waste incineration industry in 2005, the industry has ushered in a wave of rapid development. From 2011 to 2018, the harmless treatment capacity of domestic waste incineration in China increased year by year, reaching 370,000 tons/day in 2018, with a year-on-year growth of 24.1%.
The pollutants produced in the process of waste incineration are:
（1）Soot, particulate matter and drifting dust;
（2）Acid gas: SO2, HCI, HF, NOx, etc.
（3）Toxic heavy metals: Pb, Cd, Hg, As, Cr, etc.
（4）Halogenated compounds such as dioxins: PCDDs (dioxins), PCDFs (furans).
The main purification methods are:
（1） Particulate matter: Rely on cloth bag dusters
（2） Acid gas: neutralize by alkaline substances such as lime, caustic soda and baking soda, and remove NOx by reduction of SNCR and SCR
（3） Heavy metals and dioxins are removed by PAC activated carbon spray or catalytic filter bags
The current national standard is: GB18485-2014 “Domestic Waste incineration Pollution Control Standard” :
According to the discharge standard, the flue gas purification process adopted by most household waste incinerators is as follows: SNCR+ lime milk rotating spray deacidification + slaked lime dry deacidification + activated carbon jet + cloth bag dust collector + induced draft fan + chimney. A few units adopt the process of lime circulating fluidized bed deacidification. The overall emission standards are relatively loose, but they have been gradually tightened. For example, Hainan and other places have implemented stricter emission standards, mainly restricting the emission limits of acid gas:
3. The rapid development of waste incineration power generation project
With the rapid development of society and economy, residents’ requirements for living environment are also increasing. It is urgent to solve the problem of the disposal of household garbage. Landfills are already overwhelmed, making it almost impossible to build new ones.Due to the advanced technology of waste incineration power generation, it has outstanding advantages. At the same time, most areas have been able to withstand the high investment and operating costs of waste incineration power generation projects. Therefore, domestic waste incineration power generation projects are blooming everywhere, and the central and eastern regions are basically close to the level of one project per county.For example, the Medium and Long Term Special Plan for Domestic Waste Incineration and Power Generation in Sichuan Province contains 62 projects;The Medium and Long Term Special Plan for Household Waste Incineration and Power Generation in Hebei Province (2018-2030) will establish 65 waste incineration and power generation projects by 2020;The medium and long-term plan for waste incineration and Power generation in Henan Province (2018-2030) requires that 75 new household waste incineration and power generation projects be planned throughout the province in accordance with the principle of “overall planning at the provincial level, with cities and counties taking the main role”;The Medium and Long Term Special Plan of Fujian Province for Household Waste Incineration and Power Generation (2019-2030) (Draft for Comments) plans to build 17 new (expanded) household waste incineration power plants throughout the province;Hainan Province plans to build 9 domestic waste incineration power plants in the Medium and Long Term (2018-2030). As more and more waste incineration power generation projects are built, how to reduce the total amount of air pollutants as much as possible and eliminate the “NIMby effect” will become one of the important goals in the next stage.
4. Application analysis of dry deacidification of baking soda
By comparing GB18485-2014 Domestic Waste Incineration Pollution Control Standards with local standards of Hainan Province, it can be seen that the main differences in acid gas emission standards are as follows:
The concentration of SO2 and HCl in the flue gas of household waste incineration is generally not more than 500mg/m3, and the efficiency of removing SO2 and HCl can easily reach 85% and 95% with the mainstream rotary spray semi-dry method, which can stably meet the requirements of national standards. When the emission concentration is further reduced, the pursuit of higher deacidification efficiency often brings about a series of technical and economic problems, such as increased consumption of desulfurizer, increased yield of fly ash, and risk of clotting bag. The reduction of nox emission standards also makes SCR denitrification technology an inevitable choice, while SCR catalysts have strict requirements on SOx concentration, which decreases significantly with the decrease of operating temperature. At this time, the efficiency of SO2 and HCl removal can reach 95% and 99% by using baking soda dry deacidification process with higher activity. As a fine removal method, combined with slaked lime semi-dry process, the dosage of slaked lime and baking soda can reach a lower value, and the best overall technical and economic effects can be achieved. Baking soda dry deacidification as a key tail control technology, the use rate will continue to improve.
As a professional company in the field of air pollution control in China, Aier environmental protection has worked for many years in the field of dust removal, VOCs, flue gas management and other professional fields, with a large number of high-tech products, can provide customers with the best environmental technology product solutions.
