Study On Pyrolysis Charcteristic And Pyrolysis Kinetics Analysis Of Spent Jew's-ear Substrate In Huangsongdian

The fungus chaff is the remaining culture medium after the edible fungus is picked in the plantation,which is mainly composed of sawdust and a small amount of wheat bran and soybean meal,and belongs to the category of biomass.With incomplete statistics,the annual amount of fungus chaff brought by edible fungus in China can reach 12.12 million tons.At present,most of the growers do not do harmless treatment to the bacterial chaff,and the treatment method is mainly accumulation in the field or direct combustion,which is not only serious pollution to the ecological environment,but also a waste of available resources.In this paper,the basic physicochemical characteristics,thermogravimetric infrared analysis,pyrolysis experiments and quality analysis of pyrolysis products of the spent Jew's-ear substrate(SJES)were analyzed to further study the pyrolysis behavior of fungus chaff,so as to lay the corresponding data foundation for the comprehensive and rational utilization of fungus chaff.Firstly,the basic characteristics of the sample was analyzed in detail based on the industrial analyzer,elemental analyzer,X-ray fluorescence spectrometer,Fourier transform infrared spectrometer,etc,and it was found that the SJES has the characteristics of volatilization,high fixed carbon,low ash and sulfur content,and its calorific value is 16159J/g,which has certain utilization value.The chemical composition is cellulose(43.7%)>hemicellulose(29.4%)>lignin(19.3%),and the sample itself may be composed of hydrocarbons,alcohols,aromatic compounds,oxygen-containing functional groups of acids,phenols and some aliphatic groups.Secondly,pyrolysis characteristics of sample at heating rates of 5,10,20,40 K/min were investigated applying a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer.The results show that the pyrolysis of SJES is roughly divided into four stages:drying,preheating,pyrolysis and carbonization.With the increase of heating rate,TG and DTG curves move to the high temperature region,the initial and final temperature of pyrolysis increase,the maximum peak value of DTG curve decreases gradually,and the corresponding maximum weight loss rate decreases.Typical pyrolysis products of SJES under the maximum weight loss rate are mainly small molecular gases such as H2O,CH4,CO2,CO,etc,and light tar components,such as acids,aromatic groups and alcohols.Compared with Coats-Redfern method,Flynn-Wall-Ozawa,Friedman-Reich-Levi and Kissinger three non-model calculation methods are used to calculate and analyze.It is found that the best reaction mechanism of the main pyrolysis section of SJES is random reaction nucleation and subsequent growth,and the reaction order n=4.At the same time,the apparent activation energy and pre-exponential factors corresponding to each heating rate in the main pyrolysis section were calculated respectively,and the pyrolysis kinetics models at different heating rates in the main pyrolysis stage were obtained.By fitting the values of kinetic parameters E and InA,it is proved that under different heating rates,E and InA conform to the kinetic compensation effect.Finally,a small pyrolysis device was built to test the samples to explore the influence of different conditions on their pyrolysis characteristics.At the same time,the pyrolysis products under different conditions were analyzed.The main conclusions are as follows:the higher final temperature bio oil contains more kinds of organics than the low temperature bio oil;The content of phenolic substances is the highest in all kinds of bio-oils,and the variety is the largest;The relative contents of glacial acetic acid,2,6-dimethoxyphenol,guaiacol,vanilic acid,catechol,methyl cyclopentenolone and hydroxyacetone were higher in the bio-oils under different working conditions;The types of functional groups on the surface of pyrolysis carbon in low temperature section are more abundant than that in high temperature section,and the strength of many functional groups is greatly affected by the final temperature.The type of adsorption isotherm of coke belongs to the type II adsorption isotherm,and the type of hysteresis ring is H4.Its specific surface area shows a positive correlation with the final temperature of pyrolysis.Under different final temperature conditions,the microstructure of the surface of the pyrolysis charcoal is more complicated,and the morphology of the coke in the low temperature section has changed less.The surface of high-temperature coke has no specific shape,and does not have a highly compact microporous structure similar to the surface of ordinary biomass pyrolysis carbon such as corn straw.