Study On The Thermal Transformation Characteristics And Pollutant Generation Of Domestic Waste In The Agricultural And Pastoral Areas Of Qinghai-Tibet Plateau

In recent years,solid waste production in the agricultural and pastoral areas of the Qinghai-Tibet Plateau has been increasing,and ecological security on the Qinghai-Tibet Plateau is facing serious challenges due to the lack of suitable disposal methods.Pyrolysis incineration process as a development direction of solid waste disposal in agricultural and pastoral areas is receiving wide attention.In this paper,we firstly investigated and sampled the agricultural and pastoral areas on the Qinghai-Tibet Plateau to understand the basic physicochemical properties of agricultural and pastoral solid waste;then we studied the pyrolytic weight loss of agricultural and pastoral solid waste and its combustible single-component samples as well as the co-pyrolytic properties of agricultural and pastoral solid waste and yak bone by using thermogravimetric analysis,and its thermodynamics is analyzed by combining the equal conversion rate method（FWO method）and the universal integration method.Finally,the distribution of pyrolysis products and the generation of pollutants from pyrolysis and incineration of solid waste in agricultural and pastoral areas were investigated.The research results are expected to provide theoretical basis and guidance for the disposal of solid waste pyrolysis and incineration in agricultural and pastoral areas,and the main findings are as follows:（1）The solid waste from agricultural and pastoral areas on the Qinghai-Tibet Plateau is mainly composed of food waste,paper and rubber and plastic waste in general,with the characteristics of low bulk weight,high volatile fraction and high calorific value,and high content of C,O,Cl,Cu,Cr,Mn and other elements.Its pyrolysis weight loss is mainly divided into 3 stages,and the pyrolysis is basically completed after 600℃.Increasing the pyrolysis heating rate can improve the performance of solid waste pyrolysis.The apparent activation energy of solid waste is 145-267 kJ/mol,and the apparent prefactor is 5.34×10⁹-2.14×10¹⁵ s^-1.The pyrolysis process is initially controlled by three-dimensional diffusion and then changes to random nucleation and subsequent growth control.（2）Co-pyrolysis of agro-pastoral solid waste and yak bone not only can make the pyrolysis reaction more concentrated,but also can improve the pyrolysis performance of yak bone,and there is a mutual promotion effect of co-pyrolysis when the blending ratio of yak bone is low.The apparent activation energy and prefactor of co-pyrolysis tended to decrease with the increase of yak bone blending ratio.The pyrolysis of yak bone is controlled by random nucleation and subsequent growth,and the addition of small amount of yak bone can slow down the nucleation of co-pyrolysis,but with the increase of blending amount,it will change the pyrolysis to random nucleation and subsequent growth control earlier.（3）The distribution of pyrolysis products at different pyrolysis temperatures showed that the optimum pyrolysis temperature for agro-pastoral solid waste was 700℃.The emission factors of SO₂,NO_X and heavy metals in the flue gas during the pyrolysis and incineration of agro-pastoral solid waste decreased with the increase of combustion temperature,and the emission factor of HCl showed a single-peak change and was the largest at 750℃.In different combustion atmospheres,the emission factors of SO₂,NO_X and HCl were the largest at 15%oxygen content,while the emission factor of heavy metals was the smallest at this time;with the increase of water content,the emission factors of SO₂,NO_X and HCl emission factors gradually decrease with increasing water content,but lead to an increase in the emission factors of heavy metals.