Experimental Study On Pyrolysis Characteristics Of Typical Solid Waste

A large number of solid wastes will be output during the operation and maintenance of the nuclear power plant,which possess very low radioactive fraction and large volume.Therefore,volume reduction treatment is required before landfilling.Pyrolysis is available techniques to achieve a better reduction volume.The current work is to address the pyrolysis characteristics of the uncontaminated radioactive element typical solid wastes of nuclear power plants in the thermogravimetric analyzer and fixed-bed pyrolysis system.The product characteristics of fixed-bed pyrolysis were also evaluated.The non-isothermal pyrolysis characteristics of several typical solid wastes?PE,glove,paper towel,cloth and wood?in N2 atmosphere were examined by a thermogravimetric analyzer,the effects of heating rate on the pyrolysis characteristics and non-isothermal kinetic characteristics of typical solid wastes was obtained.As the heating rate increased from 10 to 25 ? min-1,the average reaction rate of solid waste increased by about 1.5 times respectively,and the pyrolysis index of PE,glove,paper towel,cloth and wood are enhanced by about 3,4,3.7,3.4 and 4.6 times,respectively.The main reaction temperature range of polyethylene was 440-500 ?,and pyrolysis of other cellulosic solid wastes finished before 400 ?.The average activation energies of polyethylene,glove,paper towel,clothe and wood were 268.34 kJ mol^-1,220.31 kJ mol^-1,235.33 kJ mol^-1,209.62 kJ mol^-1 and 222.37 kJ mol"1,respectively.Isothermal pyrolysis characteristics of typical solid wastes in nuclear power plants were carried out in a fixed bed pyrolysis furnace under the temperatures between 475 ? and 550 ?.The influence of the temperature and mixing ratio on the pyrolysis index,kinetic parameters and pyrolysis products was addressed.The results showed that the pyrolysis index of polyethylene,glove,paper towel,clothe and wood increased by about 78,6,1,2,and 2 times,respectively,with the rising temperature from 475 ? to 550 ?,and the isothermal pyrolysis activation energies were 116.64 kJ mol^-1,52.79 kJ mol^-1,24.19 kJ mol^-1,23.69 kJ mol^-1,21.70 kJ mol^-1,respectively.HZSM-5 had a good catalytic effect on the pyrolysis of polyethylene.While HZSM-5 were prone to be deactivated for the carbon deposition from the pyrolysis of cellulosic solid waste.The co-pyrolysis of polyethylene with cellulosic solid wastes suggested that there was certain interaction existed between its components during the mixture pyrolysis,which could accelerate the reaction,and the activation energy of the mixed samples was lower than the activation energy of the individual pyrolysis of the polyethylene.The liquid yield of pyrolysis of typical solid waste were arranged from larger to small:polyethylene,glove,paper towel,clothe and wood,and solid yield were arranged from larger to small:wood,glove,clothe,paper towel and polyethylene.The co-pyrolysis of polyethylene and cellulose solid wastes could adjust the C/H ratio of samples,promote the production of liquid products.And the co-pyrolysis also increased the solid yield.The main liquid components of the polyethylene are alkanes and alkenes,while the liquid products of cellulose solid waste are mainly oxygenated substances such as aldehydes,ketones and phenols.The co-pyrolysis of polyethylene and cellulose solid waste promoted the hydrocarbon production,and inhibited the production of ketones and phenols.The components in the polyethylene gas product were alkanes and alkenes,while the components of the cellulosic solid waste were primarily CO,CO₂ and a portion of hydrocarbon gases.The research results can provide some basic data for the pyrolysis treatment of solid waste in the nuclear power plants.