A Study On The Characteristics And Mechanism Of The Co-pyrolysis Of Municipal Solid Waste And Paper Sludge

The rapid process of urbanization and industrialization has led to a substantial increase in the production of municipal solid waste and sludge,and inadvertent treatment will have adverse effects on the environment and spread diseases.Exploring disposal technologies of capacity reduction,harmlessness and resource utilization is an important subject related to ecological civilization and environmental protection.Therefore,this paper took municipal solid waste?MSW?and paper sludge?PS?as the research object,and discussed in depth the weight loss characteristics,kinetic parameters,infrared evolution characteristics of gas products,pyrolysis product components and reaction mechanism of the co-pyrolysis of MSW and PS,catalytic co-pyrolysis and ultrasonic pretreatment driven by catalytic co-pyrolysis,so as to provide a new technical route and theoretical guidance for the heat treatment of combustible solid waste.Firstly,the influence of mixing ratio of MSW and PS on the weight loss characteristics of mixed samples was studied by Mettler automatic thermogravimetric analyzer.The pyrolysis characteristic parameters and comprehensive pyrolysis characteristic index of mixed samples were obtained.The pyrolysis kinetics reaction model was established,and the interaction law between MSW and PS in pyrolysis process was analyzed.The results showed that the pyrolysis weightlessness characteristic parameters of mixed samples were between the single parameters of MSW and PS.With the increase of sludge proportion,the comprehensive pyrolysis characteristic index decreased and the descending trend showed a linear relationship:y=-1.46082x+113.75415.There was interaction between MSW and PS in the process of mixed pyrolysis,which was mainly manifested as inhibition,especially in the low temperature stage.When the sludge mixing ratio was 50%,the average activation energy of the mixtures reached the minimum,111.56 kJ/mol?FWO?and 95.70 kJ/mol?KAS?.The mixing ratio of MSW and PS was 50%was each,which was an ideal mixing ratio for co-pyrolysis.Secondly,the characteristics of pyrolysis products at different mixing ratios were analyzed by TG-FTIR and Py-GC/MS techniques.The characteristics of gas products,the evolution behavior of main functional groups,the components of pyrolysis products and reaction pathways were discussed.The results showed that the presence of a small amount of sludge could promote co-pyrolysis and fixed sulfur and nitrogen,and the total amount of pollutant gas emissions was the lowest when the sludge mixing ratio was 50%.With the addition of sludge,the proportion of oxygen-containing substances in the products increased from 56.28%to 76.39%.When the sludge mixing ratio was 10%,the hydrocarbon substances reached the highest value of 28.53%,and the benzene substances reached the minimum value of 10.39%.Therefore,50%and 10%could be used as sludge mixing ratios of low pollution gas emissions and high quality liquid products,respectively.Then,additives were added to the co-pyrolysis reaction of MSW and PS to obtain pyrolysis characteristic parameters,pollutant gas yield and pyrolysis product components under different kinds/proportions of additives.Kinetic reaction model was established,and the influence rule and mechanism of additives on catalytic co-pyrolysis were revealed.The results showed that the initial temperature and average activation energy of the samples could be reduced by adding 5%MgO,ZnO and Al₂O₃,and only MgO could reduce the residual mass of the samples.At the same time,the effect of MgO and activated carbon on co-pyrolysis showed that the addition ratio of 5%was slightly better than 10%,and additives could promote the reaction at high temperature.The addition of MgO could reduce the content of pollutants?CO,SO₂,NO,HCl?and oxycompounds,increase the content of aliphatic compounds,and reduce the average activation energy of the mixture.The activation energy distribution function curves at 30%sludge mixing ratio showed that the activation energy ranged from 200-550 kJ/mol to 100-260 kJ/mol before and after adding MgO.Therefore,70%MSW+30%PS+MgO?5%?was an ideal combination.Finally,the effects of multi-factor and multi-level conditions on the pyrolysis and catalytic pyrolysis of mixed samples were studied by orthogonal experiment with ultrasonic pretreatment instrument.The changes of physical and chemical characteristics,co-pyrolysis and catalytic pyrolysis characteristic parameters,kinetic parameters and product components before and after pretreatment were obtained,and the effects of ultrasonic factors on pyrolysis behavior were revealed.The results showed that the working conditions with the highest H/C after pretreatment were:frequency 80 kHz,power 400 W,mixing ratio 50M50P and 2 h action time.The order of influence of four factors was action time>mixing ratio>power>frequency.The working conditions with the lowest residual mass before and after adding MgO were 40 kHz,300 W,90M10P and 3 h and 100 kHz,200 W,90M10P and 2 h,respectively.The order of influence of factors was mixing ratio>power>frequency>action time.Ultrasound pretreatment could accelerate the pyrolysis reaction and precipitate volatiles in time;the longer the reaction time and the higher frequency were beneficial to reduce the oxygen content in the products;MgO could improve the pyrolysis index of samples only at 45kHz;the average activation energy of pre-treated samples increased slightly,and MgO could reduce the average activation energy of mixed samples,80 kHz,200 W,50M50P,1 h was the most significant condition for the catalytic effect.