Research On PM_2.5 Emission Characteristic Of Industrial Fluidized Bed Boilers

The PM2.5which can be enter into the lung and cause haze is one of the mostsignificant pollutants, more and more haze days have a serious impact on thehealth of residents. The coal combustion is a major proportion in the source ofPM2.5, and more than98%of boilers in China are industrial boilers. Theproportion of the fluidized bed boiler in the industrial boilers is increasingbecause the fluidized bed boilers have many advantages such as the wideapplicability of fuel and the high efficiency. The PM2.5emission of the industrialfluidized bed boilers is researched poorly, so this topic is important to carry out.This paper selects seven circulating fluidized bed boilers and a bubbling bedboilers in accordance with the boiler capacity20t~35t,35t~50t and50t greaterrange and different dust removers. The number and mass concentrations of PM2.5from the outlet of boilers and different dust removers are mearsued by ElectricalLow Pressure Impactor (ELPI) after a secondary dilutes. Using the TH-880F tomonitor the gas components and collect PM2.5particles with Polycarbonate,quartz and Teflon for the physical and chemical analysis.The curves of particles number size distributions of PM2.5which generatedby the industrial fluidized bed boilers presented double peaks, which appeared inthe size at0.2and0.76μm, the curves of particles mass distributions presentedone single peak which appeared in the size at0.12μm. The concentration ofsubmicron particles formed is low due to the lower combustion temperature andthe violent mixing and violent of furnace particles in the fluidized bed. Theformer number concentration peak of PM2.5after the dust removals appeared inthe size at0.12~0.3μm and the secondary peak appeared in the size at0.76μm in parts of boilers, the mass size distributions presented one single peak whichappeared in the size at0.12~0.3μm. The number and mass concentrations ofPM2.5are decreased significantly from the outlet of differernt types removers, theremoval efficiencs of dust removers are different, the efficiency of bag filter ishigh and the wet srcubber is low. The results of PM2.5on physical and chemicalcharacteristics show that a major proportion of irregular particles and a smallamount of solid spherical particles in single particle morphology, the number ofparticle aggregates is larger due to the collisions of particles. The desulfurizationis applied in the fluidized bed boilers, the mass concentration of SO42-is highand the Ca2+have a big range due to the adding limestone adsorbent proportionof Ca/S is differernt. The elements mass concentration of samples, the highest isSi and the second is Al in the major elements, the highest is Cd and the lowest isHg which contains only several ppm in the trace elements.