Preparation And Application Of Biomass Stalk Granular Material By Microwave Method

Biomass tobacco stem,as a byproduct of cigarette industry,was mainly used to prepare expanded stem and reconstituted tobacco sheet,which played an important role in reducing tar and harmful components of cigarettes.However,a large amount of tobacco stem was disposed of as rubbish every year in China due to difficulties in the comprehensive utilization technologies of them.It has resulted in enormous waste of natural plant resource and serious environmental pollution.Development of prepared biomass stem granules from tobacco stems with microwave radiation method was an emerging process,which has opened up a new application direction for the comprehensive utilization of tobacco stem resources.The key to the technology is tobacco stem expanded via microwave,but the current process of medium solid preheating-tunnel microwave equipment for expanding tobacco stem has some shortcomings,such as high energy consumption,low yield,low purity of products,and so on.In addition,there is no the development of efficient microwave reactor for expanding tobacco stem.They have constrained the industrialization development and application of biomass stem granules.Therefore,a new technology of medium gas preheating-drum microwave equipment for expanding tobacco stem was put forward through thchnology transfer of drum reactor for microwave metallurgy.Based on research of fundamental features of tobacco stem,development of key equipment,parameter optimization of major production process and application evaluation of biomass stem granules in cigarettes,their relative theories and key technologies were studied systematically for preparation of stem granules with microwave radiation method.Through researches on expansion characteristics and dielectric properties of biomass tobacco stems under microwave electric field,the differences of microwave expansion characteristics between tobacco stem from typical tobacco-growing areas in Yunnan were explained,and the function relationships of moisture content,temperature with dielectric constant and dielectric loss were established.Based on the dielectric properties,theoretical calculation and principle of non-coherent power synthesis,the microwave continuous drum equipment with power of 84kW for expanding tobacco stems was developed through data modeling and physical modeling by using Finite Difference Time Domain(FDTD)in electromagnetic field,which was composed of fifty-six water-cooled magnetrons with 2450 MHz frequency and 1.5 kW power.It has made up the defects of medium solid preheating-tunnel microwave equipment,and successfully applied to the industrialization line on the preparation of biomass stem granules with capacity of 1200t one year.It also has filled the gaps of high-power drum microwave continuous equipment applied to tobacco industry for expanding tobacco stem.Through parameters optimization of main processes on preparation of biomass stem granules via microwave method,polynomial regression equations were established to analyze and predict the processes of microwave expanding tobacco stem and drying stem granules,and explained the influences of main factors on them and their changed rules.Moreover,determined the optimal conditions for expanding tobacco stem of 84kW microwave equipment were steam pressure 0.8MPa,microwave power 56kW and drum rotation frequency 25Hz.The proper aging time of microwave expanded stem was 7?14d.The optimal conditions for microwave drying of stem granules were microwave power 35kW,moisture content 30%,materials thickness 30mm and drying time 150s.Under the optimum conditions,the filling power and yield of stem granule material could reached 7.58cm3/g and 61.82%.The analysis results of continuous flow analyzer,SEM,GC-MS and nitrogen-adsorption showed that the total sugar and reducing sugar content in the expanded tobacco stems were significantly decreased.The prepared stem granule was mesoporous materials.The average pore size and total volatile components after microwave dried increased from 45.426 nm to 62.246nm,from 94.15 ?g/g to 109.80 ?g/g,respectively.They indicated the preparation of biomass stem granules via microwave method is benificial to improve the quality and filling power of the products.Through studies on pyrolysis characteristic of biomass stem granules and its effect on burning temperature of cigarettes and harmful components of mainstream smoke,the results showed that the pyrolysis process of stem granules was similar with reconstituted tobacco and cut tobacco.The contents and types of thermal cracking products include benzene series compounds and polycyclic aromatic compounds,increase with rising temperature of thermal cracking.Within the range studied,the burning temperature of cigarettes,the deliveries of harmful components in mainstream smoke such as tar,nicotine,TPM,CO,HCN,NNK,NH3,B[a]P,phenol,crotonaldehyde,Cr,Ni,Cd,Pb,etc.,and the hazard evaluation index(H)were obviously reduced with the mix proportion increasement of stem granules,and had good linear negative correlation.When mixed 6%and 8%stem granules,the hazard evaluation index(H)were reduced 25.46%,38.53%,respectively.It revealed that addition a certain amount of stem granules into cigarette could reduce the dangers of smoking to the human body.In a word,the study of this paper has formed the basic theories and key technologies of the preparation biomass stem granules via microwave method.It has provided the theoretical basis and references to selecting raw material of tobacco stem,developing of microwave equipment and setting process parameters.Meanwhile,the drum microwave equipment with high-power has successfully applied to the industrialization line for the large-scale production of biomass stem granules,and the prepared products has made a good effect on reducing harmful components and tar of mainstream cigarettes smoke.It also has improved the utilization values of tobacco stem resource effectively.