Changes of pollutant emission from co-combustion of coal and paper mill sludge in pulverized coal boiler
The co-combustion of paper mill sludge in coal-fired boilers presents an economically viable sludge disposal method.The pa-per mill sludge contains a lot of organic matter.Based on the reason,the coal-fired heating boiler that built in the paper mill to burn the paper sludge was used in the experiment.The co-combustion can reduce sludge treatment costs and utilize the thermal energy present in the sludge.Co-firing paper mill sludge in the boiler has the potential to alter the composition of pollutants in solid wastes like flue gas,fur-nace slag,fly ash.A co-firing test was conducted using a 2×300 MW unit boiler in a paper mill.A total of 755 tons of paper mill sludge was blended with a coal-to-sludge ratio of 22∶1.The calorific value of the mixed fuel showed a slight reduction compared to coal.The blending test lasted for 3 d.Samples of flue gas,dried sludge,slag and fly ash were collected.3 flue gas samples and 3 dried sludge sam-ples were collected before blending,1 blank sample of slag and fly ash was collected,and 6 flue gas samples,16 slag samples and 50 fly ash samples were collected after blending.The results indicate that conventional gaseous pollutants in the flue gas such as NOx increases by 1.5 times,SO2 concentration increases slightly,and heavy metals Ni,Zn,Ba,Se,Cr,Mn,Sb,Pb,Cu are detected.The most prevalent heavy metals are Ba and Zn.PCDD/Fs are not detected in the blank flue gas samples,with an average concentration of 1.2 pg/m3(in TEQ)in the co-firing group.Following co-firing,the furnace slag exhibits a notable increase in Pb concentration by 2.5 times,while concentrations of Cu,Ni,Co,Ba,and Mn decreases by 1.5 to 2.5 times.PCDD/Fs concentrations remain within permissible limits in both groups.The concentration of heavy metal elements in fly ash shows significant variations,with elements such as Ba,Mn,and As increasing by 1.5 to 2.0 times,while others decreases compared to the blank group.PCDD/Fs are not detected in the coal fly ash of the blank group,and the concentration of dioxins in the fly ash of the mixed-burning group is 2 pg/g.All pollutants generated during this co-firing test remains within the prescribed limits set by Chinese national standards.
paper sludgepulverized coal furnaceco-combustionheavy metalsdioxin
万方数据
维普
