Structure and Characteristic of 150t/d Circulating Fluidized-bed Municipal Waste Incinerator

摘要

The incineration technology to dispose municipal solid waste (MSW) is now used more widely. In order to lower the emission of acidic gas pollutant (SO_2, NOx, HCl, HF etc.) and organic contaminant (PCDD/Fs etc.) released from MSW incineration with the flue gas, higher standards for the MSW incineration emission also has been established in many countries. For example, in China, corresponding emission standard was issued with the development and application of MSW incineration technology. The circulating fluidized-bed municipal waste incinerator with a capacity of 150t/d developed by Tsinghua University achieves lower pollutant emission capability and stable combustion. All the pollutant emission met the national environmental standards in China. The system and structure of the incinerator is introduced in this paper. And the technology of controlling the pollutant produced by the process of combustion is sufficiently analysed in this paper. The composition and heat value of MSW are varying along with seasons' alternation. When the MSW has almost high moisture (> 50% in mass) and low heat compositions (～4180kJ/kg), coal as the assistant fuel must be added to the incinerator to sustain the stable combustion in the incinerator. The ratio of MSW to coal wholly depends on the compositions, heat value of MSW and the thermal power of the incinerator. The air in MSW pool is drawn off to support the combustion by blower whose entry hole is on the top of MSW pool. So there is no odour could be leaked out. The incinerator can guarantee the flue gas to stay in the zone of temperature 850～950 more than three seconds. Because of high heavy metal content and organic contaminant, such as PCDD/Fs adsorption in fly ash collected by bag filter, it should not be discharged directly. So fly-ash secondary combustion device is designed and installed. All the flue gas should go through the ash separator, bag filter and cleaning tower before emission from the stack. Secondary pollution caused by MSW incineration can be avoided effectively. The monitoring data of routine gaseous pollutants (such as CO, SO_2, CO_2 etc.) satisfied with national standard. The PCDD/Fs emission is very lower than Chinese national standard, but higher than the European Economic Community Standard (EECS). The emission of heavy metal was far lower than national standard 1 to 2 order or even more. The test result expresses that organic pollutants emission met the EECS. Slag burn out rate of this furnace is only 0.49% lower than the national standard of 5%. The test data about radioactivity of slag also shows that the radioactivity met the safe emission standard.