Experimental Study On Characteristics Of Different Kinds Of Fly Ash

Fly ash is the main by-product of power plants in China which has a high utilization value of resources.One of the main factors which affect the utilization of fly ash is the high carbon content in fly ash.As a dry and low cost method,the decarbonization method applied to fly ash has been widely concerned and researched at home and abroad.Jiangsu Electric Power Design Institute proposed the technology of online fly ash separation by conducting inductive charge,the technology solve the problem which is difficult to integrate into the power plant dust removal system by the current fly ash carbon sorting technology,thus achieve fly ash online sorting and reduce the cost of fly ash treatment.Due to the different types of fuel and combustion methods,the characteristics of different kinds of fly ash is distinct,and the properties of fly ash collected from different parts is also different.Therefore,in order to realize the application of online separation of fly ash by conducting inductive charge,it is necessary to study on the different characteristics of different fly ash and fly ash collecting location,which provide theoretical support for electrical separation of fly ash decarburization and the further development and utilization of carbon rich products.In this thesis,a large number of pulverized coal fly ash,fluidized bed fly ash and biomass ash were collected.The chemical composition of different fly ash samples was analyzed by X-ray fluorescence spectrometer.It was found that the chemical composition of different kinds of fly ash was different due to the different fuel properties;The mineral composition of different types of fly ash samples was analyzed by X-ray diffractometer.And the result show that the fuel type and combustion temperature have a great influence on the composition of fly ash minerals.,the mineral composition of SiO2 as the main component has the highest content in mineral.The analysis of carbon content of fly ash from different types and different parts shows that the carbon content of coal ash obtained by pulverized coal combustion is generally lower than that of biomass ash and fluidized bed fly ash;For the fly ash from electrostatic precipitated parts and bags of dust,the coal ash carbon content of electric parts is higher than the coal ash carbon content of bag dust removal parts in pulverized coal furnace while the result in fluidized bed boiler is opposite.The particle size and unburned carbon distribution of different kinds of fly ash were analyzed by sieving method and burnout method.It show that for the coal ash of pulverized coal furnace combustion,with the increase of particle size the coal ash carbon content increase.However,for the coal ash from fluidized bed boiler and biomass ash,when the particle size of fly ash is lesser carbon content is higher.The samples of typical fly ash samples were washed and pickled to obtain samples which has more than 85%carbon content.The unburned carbon particles were observed by scanning electron microscopy.And it was found that the fluidized bed unburned carbon in fly ash is irregular particles,more compact surface while the most unburned carbon in coal ash of pulverized coal furnace is the honeycomb,pore structure is more clear.In the experimental study on the electrical characteristics of fly ash,the influence factors of fly ash specific resistance were studied by using high pressure dust resistance test bench.The results show that:In the temperature range of 90?-200? and the voltage is 1kV,the specific resistance of fly ash increases rapidly with the increase of temperature,the resistance of fly ash reaches the maximum at about 150?,and then begins to decrease.The overall value of coal ash resistivity between 105?1013,and the specific resistance of fly ash decreases sharply with the increase of carbon content of fly ash.In addition,when the temperature is 150?,the specific resistance of fly ash decreases slowly with the increase of voltage and particle size.The self-made experimental device was used to study the charging characteristics of fly ash conduction It shows that:charge-to-mass ratio of coal ash first increases and then drops rapidly with the increase of voltage in 8kV-20kV voltage range,the charged capacity enhanced with the increase of particle size of fly ash.The trajectories of fly ash particles in electrostatic field are quite different under different voltage and field strength.