Study On Co-Pyrolysis Behavior And Kinetic Characteristics Of Biomass And Urea-Formaldehyde Resin

With the wide application of resin products in furniture,transportation,construction,automobile and other industries,a large amount of resin waste has been generated,which urgently needs to be treated reasonably and efficiently.The co-pyrolysis of biomass and waste urea-formaldehyde resin is proposed in view of the fact that landfill and incineration take up a lot of land and easily cause secondary pollution,in order to overcome the problems of secondary pollution caused by corrosive nitride produced by resin pyrolysis alone and improper treatment of halides produced by halogenation,the process of compression molding,pyrolysis,activation and so on,the conversion of waste resin to highly efficient resources and energy sources of combustible gas,fuel oil and biochar adsorbents was realized.In this study,biomass and urea-formaldehyde resin were co-pyrolyzed to realize the synergistic treatment of biomass and urea-formaldehyde resin.The problems existing in traditional landfiling,landfill and incineration of waste urea-formaldehyde resin were solved,which provided certain theoretical basis for the utilization of waste biomass and waste resin resources.Through pellet preparation experiments and strength analysis,the influence of pelletizing process and operating parameters on the mechanical strength of pellets was revealed,and the preparation method and strength control mechanism of high-strength pellets were mastered;thermogravimetric analysis and on-line product analysis were used to study the pyrolysis behavior and kinetics of single-component and blend pellets;the influencing factors on the distribution of pyrolytic products were investigated by means of pyrolysis equipment,and the variation law of product components was discussed;The microstructure and pore structure of activated pyrolytic carbon were characterized,and the adsorption properties of CO₂ on activated carbon were evaluated.The conclusions of this paper are as follows:（1）The heating temperature has a significant effect on the strength of the pellets,and the strength of the pellets decreased with the increase of temperature in the range of normal temperature to 800°C.Increasing the content of urea-formaldehyde resin reduced the compressive strength of pellets,and the mixing amount of urea-formaldehyde resin increases from 0%to 100%at 200°C pyrolysis temperature,and the strength of pellets decreases by 71.14%.When the mass ratio of biomass and urea-formaldehyde resin is1:0,the binder addition amount is 5%,the heating rate is 15°C/min,and the heating temperature is 200°C,the compressive strength of the pellets reaches the highest 511.43N.（2）When the pyrolysis conversion rate of pellets is less than 50%,the activation energy required for the pyrolysis of blended pellets is greater than that required for pyrolysis of single-component pellets,which reduces the reactivity activity.Kinetic analysis shows that biomass and urea-formaldehyde resin have mutual inhibition during pyrolysis.When the conversion rate of pellets is greater than 50%,the activation energy required for pyrolysis of blended pellets is between the activation energy of single-material pellets,indicating that co-pyrolysis improves pyrolysis reactivity and increases the activity with the increase of urea-formaldehyde resin content.（3）The distribution law and influencing factors of pyrolysis products of blended pellets are discussed,and it is found that with the increase of co-pyrolysis temperature,the yield of gas phase products increase gradually,and the yield of solid phase products decrease.Under the same pyrolysis temperature,with the increase of urea-formaldehyde resin content,the yield of pyrolysis gas phase and solid phase products shows a downward trend,and the yield of liquid phase products gradually increase.The nitrogenous compounds,CO₂ and NO in the gas phase increased with the increase of urea-formaldehyde resin mixing in the pellet.The mass spectra of liquid phase products shows that the interaction between biomass and urea-formaldehyde resin promoted the decomposition of macromolecular phenol derivatives,lipids and ketones,and produced more small molecule acids and alcohols.The content of urea-formaldehyde resin has a great influence on the micromorphology and pore structure of the solid phase product,and when the mass ratio of biomass to urea-formaldehyde resin is 5:1,the pore structure on the surface of pyrolytic carbon is developed.The amount of urea-formaldehyde resin added is further increased,the surface of pyrolytic carbon collapsed,and the pores are closed.（4）Taking the adsorption capacity of CO₂ as the evaluation index,the optimal preparation conditions of activated carbon are biomass:the mass ratio of urea-formaldehyde resin is 5:1,the alkali-carbon ratio is 1:1,the activation temperature is650°C,and the activation time is 2.5 h.Under this condition,the pore structure of activated carbon is developed,and the proportion of micropores is large,and the activated carbon prepared under this condition is used as an adsorbent,and the CO₂ adsorption capacity can reach 6 mmol/g at 25°C and 1 bar.