Study On Copyrolysis Characteristics Of Biomass And Polylactic Acid Plastic Blends

Great consumption of fossil fuels and increasing concern over the environmental pollution have been promoting an urgent search for new and cleaner energy.Biomass has received much attention in recent years,due to the lower contents of sulfur and nitrogen in the biomass.Thermochemical processes are thought to have great promise as a means for convening biomass into higher value fuels.Pyrolysis lies at the heart of all the themochemical fuel conversion processes and is assumed to become a thermocbemical conversion technology for the production of chars,liquids or gases.Pyrolytic oil has strategic value because,as a liquid with high calorific value,its handling,storage,transportation,and utilization are similar to that of oil.It can be upgraded to obtain light hydrocarbons for transport fuel.Bio-oil can be used in fuel applications or upgraded to refined fuels and chemical products.The solid char can be used as a fuel or it can be upgraded to activated carbon and used in purification processes.The gases generated have a low to medium heating value,but may contain sufficient energy to supply the energy requirements of a pyrolysis plant.The fast pyrolysis of biomass inherently results in the production of pyrolyic water, which is one of the major drawbacks of the hie-oil produced.The reduction of the water content and the augment of the heating value are essential upgrading steps in order to increase the applicability of bio-oil and to make the production of bio-oil competitive.The use of copyrolytic techniques on biomass/plastic ratios has already been investigated on based-petroleum plastics.Biopolymers(such as PLA),which are a special kind of platic,will be widely applied in the future.Despite their biodegradability,however,most biopolymers still have to be considered as waste,since it would be ecologically unacceptable to dispose of them in the environment.The copyrolysis and polylatic acid plastic is aimed to increase the production of bio-oil,reduce the content of pyrolytic water and increase the heating value of bio-oil.The technique offers an alternative waste treatment option and may act as an upgrading step during the pyrolysis of biomass.The following works are carried main experimental results and conclusions are as follows in this dissertation:(1) Thermal decomposition of polylactic acid(PLA) was studied in the presence of pine wood sawdust(PS),walnut shell(WS),corncob(CC) in order to understand the pyrolytic behavior of these components occurring in waste.A thermogravimetric analyzer(TGA) was applied for monitoring the weight loss profiles under heating rate of 10℃/min.Results obtained from this comprehensive investigation indicated that PLA was decomposed in the temperature range 300～372℃,whereas the thermal degradation temperature of hiomass was 220～400℃.The difference of weight loss(ΔW) between experimental and theoretical ones, calculated as algebraic sums of those from each separated component,was about 17～46%at 300～400℃.These experimental results indicated a significant synergistic effect during PLA and biomass copyrolysis.Moreover,a kinetic analysis was performed to fit thermogravimetric data,the global processes being considered as one to two consecutive reactions.A reasonable fit to the experimental data was obtained for all materials and their blends.(2) Gas release and products distribution in corncob pyrolysis was investigated by simultaneous TGA/FTIR(Thermogravimetry-Fourier Transform Infrared) and Py-GC/MS (Pyrolysis-Gas chromatography/Mass spectrometry) techniques.The results showed that the mainly prolytic reaction occurs in the range of 220～400℃,and DTG(Differential Thermogravimetry) curves reached the maximum at 339℃.The real-time gas evolution was detected by FTIR and the evolutions of CH₄,CO₂,CO and organics were qualitatively analyzed.FTIR data was compared with TGA/DTG curves and an agreement between DTG and FTIR results was observed.Py-GC/MS was used for studying products distribution of corncob pyrolysis.Results indicated that the oxygenated organic compounds such as phenol, furan,ketone etc.were the main components.(3) Gas release and products distribution in PLA pyrolysis was investigated by simultaneous TGA/FTIR and Py-GC/MS techniques.The results showed that the mainly prolytic reaction occurs in the range of 320～372℃,and DTG curves reached the maximum at 359℃.The real-time gas evolution was detected by FTIR and the evolutions of CH₄,CO₂, CO and organics were qualitatively analyzed.FTIR data was compared with TGA/DTG curves and an agreement between DTG and FTIR results was observed.Py-GC/MS was used for studying products distribution of PLA pyrolysis.Results indicated the organic compounds such as acetaldehyde,ketone,esters,oligomers etc.were the main components.(4) Pyrolytic process has a promising potential for the environmentally friendly upgrading of biomass and other materials such as plastic,coal.The thermal degradation of corncob,PLA and their blends under nitrogen were studied using TGA/FTIA as a function of temperature.The gases evolved during degradation were inspected by in situ FTIR.The results showed that obvious synergies between corncob/PLA during copyrolysis were observed.Furthermore,the influence of a polylactic acid(PLA) plastic on the pyrolysis of corncob was investigated using a fast pyrolysis fixed-bed reactor.The results indicated that the coprocessing of PLA with corncob increased liquefaction yields and a lower water content as a function of the corncob/PLA ratios were obtained.(5) Studies on a batch sorption process using activated carbon derived from biomass were investigated to remove Ni²⁺ ions from aqueous solutions.The influence of operational conditions such as contact time,solution initial pH,Ni²⁺ initial concentration,sorbent mass and temperature on the sorption were studied.The kinetic data was fitted to pseudo-first order model and pseudo-second order model for different initial concentration to evaluate the model parameters.Pseudo-second order model was better to represent the adsorption process.