污泥粉燃烧的成灰行为及颗粒物生成特性

Behavior of Ash Formation and Characteristics of Particulate Matter Generation During the Combustion of Pulverized Sewage Sludge

污泥灰分含量高,燃烧过程中易造成锅炉的积灰结渣及颗粒物排放超标,为使污泥更好的燃烧并实现能源化利用,该文开展A、B两种污泥在沉降炉中900~1300℃的燃烧及热解实验,研究污泥粉燃烧的成灰行为、颗粒物生成特性和温度对两者的影响。结果表明,污泥粉燃烧生成灰颗粒和焦颗粒的尺寸向50~200μm内集中程度增大;1100℃以上时生成大量、熔融的焦和灰颗粒。燃烧时,石英、磷铝矿及铝硅酸盐的转化和产物间的反应生成Fe-Al-Si-P-Ca等物质和铝硅酸盐,在较高温度下更易形成熔融颗粒。污泥粉燃烧生成的PM_(10)(空气动力学直径<10μm颗粒物)呈三模态分布。温度升高,PM_(10)生成增加,PM1则显著增加。相同温度下,B污泥(简称BSS)的PM1生成量比A污泥(简称ASS)低得多,PM_(10)产量也低,前者主要因为其灰量多、Si O2含量高对碱金属捕集作用强;后者则是其成灰时高温熔聚作用强而破碎弱导致超微米颗粒生成少。因此,污泥在1100℃以上燃烧时,锅炉更易结渣;同时污泥种类影响颗粒物生成特性。

The ash content of sewage sludge is high,so it is easy to cause excessive boiler ash deposition and slagging and particulate matter discharge during the combustion process.In order to achieve a better burning effect of the sewage sludge and realize energy utilization,the combustion and devolatilization experiments of two types of sewage sludge at 900~1300℃in a drop tube furnace are carried out,and the ash formation behavior,particulate matter generation characteristics and the effects of temperature during the combustion of both types of pulverized sewage sludge are investigated.The results show that,the sizes of char and ash particles generated during the combustion of two kinds of sludge are more likely to concentrate in the range of 50~200μm,and when the temperature is above 1100℃,a large number of molten char and ash particles are generated.The transformation of major minerals including quartz,berlinite and aluminosilicates and reactions between products generates Fe-Al-Si-P-Ca minerals and aluminosilicates,which are easier to form molten particles at higher temperatures.PM_(10)(particulate matter with an aerodynamic diameter of<10μm)generated from the combustion of pulverized sludge presents a trimodal particle size distribution.With the increase of combustion temperature,both of the yield of PM_(10)and PM1 increases,however the yield of PM1 is much higher.Compared with A sewage sludge(abbreviation ASS),the yield of PM1 is much lower during the combustion of B sewage sludge(abbreviation BSS),while the yield of PM_(10)is the same.The former is mainly attributed to its higher ash and SiO2 contents and its stronger capability to capture alkali metals.The later is related to its stronger melting and weaker fragmentation at high temperatures during ash formation,which reduce the yield of super-micron particles.Therefore,when the sewage sludge is burned above 1100℃,the boiler is more likely to be slagged.At the same time,the types of sludge affect the characteristics of particulate matter formation.