| During the smoking process of cigar,a series of complex thermal transformation reactions will take place in tobacco leaves under high temperature,anoxic environment,and limited conditions.The key to fully understand the release of flue gas components is to deeply study the combustion state of cigar and the pyrolysis and combustion process of tobacco leaves.In this study,the Great Wall Shengshi V cigar and 29 samples of cigar leaves were used as the research objects,and the characterization method of cigar combustion state was established.The basic composition and pyrolysis combustion characteristics of cigar leaves were investigated,and the release law of gaseous products during the pyrolysis combustion process of cigar leaves was analyzed.The main research contents and conclusions are as follows:1.According to the combustion characteristics of cigar,the suction pipe of single port smoking machine was modified,and the combustion state of cigar was characterized.(1)In the process of cigar smoking,the maximum temperature can reach 857.7?,the maximum volume of combustion cone can reach 4887.6 mm3,and the temperature of combustion cone is mostly concentrated in 200?600 ?.The volume of combustion cone increases rapidly within 8s after the end of suction.The temperature of cigarette decreases slowly and the volume of combustion cone decreases gradually in the process of static combustion.(2)According to the combustion state of tobacco,the combustion cone is divided into three regions:low temperature region,medium temperature region and high temperature region.Among them,the volume of low-temperature zone begins to decrease during suction,which decreases by about 350 mm3 in 2 seconds,and expands rapidly after suction,reaching a maximum of 2700 mm3 in 35 seconds,and then tends to be stable;the volume of medium temperature zone decreases by about 50 mm3 during suction,reaching a maximum of 1850 mm3 in 12 seconds,and then decreases slowly;the volume of high-temperature zone increases rapidly during suction,reaching a maximum of 1300 mm3 in 5 seconds And then the volume decreases rapidly.(3)The temperature distribution image of cigar combustion cone was constructed.The air inflow of cigar in the process of smoking would be hindered by soot,resulting in air flow to both sides.It was found that the fastest heating rate of tobacco in cigar was 170?·s-1,and it appeared in the middle of cigarette(4.5 mm).The highest temperature of the cigar during static combustion is in the center(9 mm),and the highest temperature during suction is in the middle(4.5 mm).2.The correlation between intrinsic components of cigar leaf and pyrolysis characteristic parameters was investigated,and the release of gaseous products during pyrolysis was analyzed.(1)The pyrolysis of cigar leaves in nitrogen atmosphere includes four weight loss stages.According to the reaction temperature from low to high,it corresponds to stage?-water evaporation,stage ?-pyrolysis of low boiling organic matter and hemicellulose,stage ?-pyrolysis of cellulose,stage ?-pyrolysis and carbonization of lignin.(2)The peak rate of the second stage(decomposition of low boiling point organic matter and hemicellulose)under pyrolysis conditions showed a significant positive correlation with C and H elements;the weight loss rate showed a significant positive correlation with volatile matter,and a significant negative correlation with moisture and ash content,indicating that volatile matter was mainly produced in this temperature range.The peak rate of pyrolysis stage III(cellulose decomposition)was significantly negatively correlated with volatile content,and significantly positively correlated with O content;the weight loss rate was significantly positively correlated with C and H content,indicating that this stage corresponds to the decomposition of a large amount of organic matter;the pyrolysis residue mass was significantly negatively correlated with C and H content,volatile content,and ash content There is a positive correlation between them.(3)The kinetic results of coats Redfem method showed that cigar leaves were controlled by one-dimensional diffusion in the pyrolysis temperature range of low boiling point organic matter and hemicellulose,while in the pyrolysis temperature range of cellulose,the reaction mechanism changed from one-dimensional diffusion to a more complex third-order chemical reaction.The results of FWO kinetics showed that the activation energy increased first,then decreased and then increased with the increase of conversion in the range of 0.1?0.9,and the activation energy of eggplant core was higher than that of eggplant shell during the whole pyrolysis process.(4)The gaseous products released during the pyrolysis process of cigar leaves can be divided into two types,one is small molecule gases such as H2O,CO2,CO and CH4,the other is organic components such as aldehydes,ketones,acids,alcohols,phenols and aromatic compounds.The results showed that the release of gaseous products was consistent with the differential thermal weight loss curve,and the release of H2O,alcohols,phenols and benzene compounds in the whole pyrolysis process of eggplant core tobacco was significantly higher than that of eggplant coated tobacco,while the release of CO2 from eggplant coated tobacco was higher than that of eggplant core tobacco.3.The correlation between intrinsic components of cigar leaf and combustion characteristic parameters was investigated,and the release of gaseous products during combustion was analyzed.(1)The combustion of cigar leaves in air atmosphere can also be divided into four stages,corresponding to stage ?-evaporation of water,stage ?-decomposition of biomass,accompanied by combustion of combustible volatiles,stage ?-combustion of coke and stage ?-decomposition of inorganic salts.(2)Under the combustion conditions,the peak velocity of stage ? has a significant positive correlation with the content of C,and a significant negative correlation with the content of O and S;the peak temperature of stage ? has a significant positive correlation with the content of H,and a significant negative correlation with the content of N;the peak velocity of stage ? has a significant negative correlation with the content of moisture and ash,and a significant negative correlation with the content of volatile matter.The results showed that there was a significant negative correlation between the peak temperature of stage ? and the content of O element;there was a significant positive correlation between the ignition temperature and the content of N element;there was no significant correlation between the burnout temperature and the content of tobacco components,but there was a significant negative correlation between the average combustion rate and the content of C and H element;there was a significant positive correlation between the comprehensive combustion characteristic index and the ash content,and there was a significant negative correlation between the average combustion rate and the content of C and H element.There was a significant negative correlation between carbon fixation and carbon content.(3)Coats Redfern kinetic results showed that the combustion process of cigar tobacco was controlled by two-stage chemical reaction.The results of FWO kinetics show that the activation energy of combustion reaction first increases,then decreases and then increases with the increase of conversion in the range of 0.1?0.9,and reaches the maximum after the conversion reaches 0.8.In the range of 0.1?0.5,the reaction activation energy of eggplant core leaf was higher than that of eggplant core leaf,and after 0.5,the reaction activation energy of eggplant core leaf was higher than that of eggplant core leaf.(4)The types of gaseous products produced in the combustion process of cigar leaf are similar to the pyrolysis reaction,and the gas release is mainly concentrated in the two temperature ranges of 200?300? and 400?500?.Due to the participation of oxygen,the release of H2O,CO2 and CO is higher in the combustion process.In the whole process,the release of gaseous products of eggplant core tobacco was higher than that of eggplant cover tobacco,corresponding to higher volatile content of eggplant core tobacco. |
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