Study On The Generation Of Fine Particles And The Occurrence Of Heavy Metals In Sludge Incineration

Sludge is an inevitable product of sewage treatment.With the increasing production of sewage,a topic of the sludge treatment and disposal has become an increasing concern.Due to its advantages of harmlessness,resource utilization and reduction,the sludge incineration has become one of the mainstream methods of sludge treatment and disposal.However,the composition of sludge is complicated.During the incineration process,the formation of fine particle matters and the volatilization of heavy metals attached to it are inevitable,and it is also one of the current research hotspots.In this paper,the characteristics of the generated fine particles were analyzed by changing the incineration temperature,particle size and CaO addition ratio,and the four occurrence forms of fine particles obtained from sludge incineration were analyzed by BCR continuous extraction method.The FactSage chemical thermodynamic simulation software was used to simulate the migration and transformation of heavy metals in sludge incineration process under different working conditions,so as to figure out the influence of incineration temperature on the formation characteristics of sludge incineration fine particles and the occurrence of heavy metals.Studies have shown that the fine particulate matter(PM₁₀)produced by sludge incineration has a bimodal distribution with two peaks located around 0.5μm and 5μm,respectively.The amount of fine particles increased with the increase of incineration temperature.Compared with the increase of fine particulate matter PM_0.5 by 12.88 mg/g,the incineration temperature has a greater influence on the mass concentration of coarse mode particulate matter PM₅ that increased up to 57.79 mg/g.The smaller the particle size of the sludge,the larger the amount of fine particles produced.The increase of the CaO addition ratio can inhibit the generation of fine particles during sludge incineration.When 3%CaO,6%CaO and 9%CaO are added to the sludge,the mass concentration of PM_0.3 decreases by53.7%,63.5%and 86.1%,while the mass concentration of PM₃ decreased by 43.9%,74.7%and 91.7%,which give a fully responds to that the addition of CaO has a greater influence on the coarse mode particulate matter.The occurrence of five heavy metals such as Cd,Cr,Cu,Pb and Zn in fine particles is characterized by an increase in the particle size and an increase in the proportion of additive CaO added as the incineration temperature increases,and the acid-soluble and reduced states.The percentage of the oxidized state decreases and the percentage of the residual state increases.