| With the development of China’s social economy and the process of urbanization,garbage generated in the process of production and living is also on the increase,countless garbage occupied the arable land and industrial land,and cities are gradually surrounded by garbage.In the face of the increasingly severe "garbage siege" problem,garbage incineration is a kind of harmless and complete,fast treatment speed,good reduction effect,project land use saving quality treatment method.The waste treated by incineration will produce bottom ash and fly ash,in which the fly ash enriches a lot of permeable harmful heavy metals,which is a kind of hazardous waste.Whether it is for transportation or for other purposes,it needs to be pre-treated in the producing area to meet the requirements of the specification.At the same time,due to the source of domestic garbage,fly ash often contains a large amount of chlorine salt,so it is necessary to remove chlorine salt in the processing of fly ash.Therefore,it is of great significance for the treatment and engineering application of fly ash to find the removal method of chlorine salts and appropriate measures for solidification and migration of heavy metals.In this paper,the fly ash was firstly washed to remove chlorine salts,and then the heavy metals were solidified by physical and chemical combination measures.This paper has done exploratory and innovative work in the following aspects:(1)Study on the elution performance of chlorinated salt by fly ash powder waterThe results show that after single washing,the residual chlorine content of fly ash decreases with the increase of liquid-cement ratio,showing an overall inverse proportional trend.When the liquid-cement ratio is greater than 7,the removal rate of chlorine has little change.Fly ash quality loss and the ratio of liquid a ln in the form of change,to wash the main material from soluble salts;The water consumption can be greatly saved by using three graded water washing measures.(2)Study on desalination performance of fly ash granulationThe test results show that,from the perspective of the effect of granulation dechlorination,the use of single cement is the worst,the slag cement mixture is in the middle,the effect of single slag is the best,the content of mineral admixture has little influence on the chlorine removal rate.Moreover,the content of sodium silicate has no obvious effect on the removal rate of chlorine salt.The fully consolidated slag based fly ash cement raw material balls can meet the requirements of full immersion after 24 hours,and the removal of chlorine salt can reach 99% compared with the powder fly ash.(3)Study on curing properties of transportable heavy metals in physically cured fly ashThe results show that the cement hardener has a good curing effect on most heavy metals,but not enough curing effect on Pb.At the same time,when BA was solidified,the leaching test results showed that the dissolution of heavy metals increased instead,which may be the result of the integration of part of BA contained in cement.The slag curing agent has a good curing effect on most heavy metals such as Pb,but it can not cure for Se,but increases the dissolution of heavy metals.(4)Curing properties of chemical hardeners for transportable heavy metals in fly ashBy changing the dosage of chemical curing agent,the curing effect of heavy metal under different dosage was compared.The research results show that,after the screening of chemical curing agent in the early stage,sodium sulfide is selected As the experimental material of this part.The surface of the test results shows that the curing effect of mineral admixtures is better than that of sodium sulfide for Be,Ni and As,and that the curing effect of sodium sulfide is better than that of mineral admixtures for Cu,Zn,Cd and Pb.Mineral admixture curing and chemical curing methods have their advantages and disadvantages.Single use cannot guarantee the safe use or landfill of fly ash after disposal,so it needs to be used in coordination.(5)Research on solidification mechanism of transportable heavy metals in fly ashThe results show that mineral admixtures and chemical hardeners play different roles in the solidification of heavy metals in fly ash.After adding slag fly ash,fly ash than infrared curve,Si-O-M asymmetric stretching vibration blue shift,to 1013 cm-1 absorption peak and presents the trend of wide,main reason is because after adding slag,slag forming a polymer of heavy metals in fly ash physical closed makes Al-O form around complex cation layers,make the absorption peak of Si-O-M wide,shows that after the introduction of slag,has influenced the structure of the fly ash.At the same time,the shift of the vibration frequency of the absorption peak shows that the chemical bond vibration frequency is affected by the chemical combination of fly ash and slag.(6)Research on composition design of fly ash granulation solidified bodyThe tests show that the more mineral admixtures are added in the process of making fly ash balls,the higher the compressive strength of the solidified body is.In the whole process of making fly ash ball,changing the content of sodium silicate has little effect on the strength.In the comparison test of fly ash ball and fly ash sand with the same ratio as the test,it is found that the compressive strength of fly ash ball group is higher than that of fly ash sand group,and the longer the curing age,the greater the difference.There are 54 figures,24 tables and 98 references in this thesis. |
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