Research On Pyrolysis And Smoke Components Of Paper-making Reconsitituted Tobacco Based On Electrodialysis

Reconstituted tobacco sheet (RTS) has now gained increasing world-wide acceptance by tobacco industry and played an important role in cigarettes due to its advantageous economic impact on the manufacturing cost as well as its superiority in structural strength, combustion performance and tar delivery. It has been well believed that the pyrolysis and combustion of tobacco, mainstream smoke of cigarettes, burning characteristics and sensory evaluation are closely related to its chemical components, especially salts content. The existence and interaction of various kinds of mineral ions can complex the mechanism of single ion. However, the usual way of acid and water demineralization on biomass may yield unreliable results because of chemical degradation. Electrodialysis (ED) is a novel separation technology with the advantages of high efficiency, low energy consumption, continuously running and no introduction of other ions, and is now widely employed to remove the main ions in concentrated tobacco extract to reduce the interference of endogenous ions themselves. In this dissertation, the thermal behavior and smoke components of RTS were investigated by adding back different potassium salts and various content of alkali and alkaline earth metals into tobacco extract on the basis of ED technology.ED has a high efficacy and fast speed of demineralization. It had been found that the main ions in tobacco extract could be removed efficiently and quickly with the removal rate over 90% under the conditions at the current of 2A, double-diluted concentration and original pH value.Typical thermal degradation process of RTS could be divided into five stages: water evaporation, simple sugars pyrolysis, carbohydrates degradation, residual char combustion and calcium carbonate decomposition. ED-modified RTS improved the peak temperature, corresponding maximum weight loss rate (WLRmax) and total heat release on the pyrolytic oxidation stage, yet accelerating the thermal degradation of carbohydrates. On the process of char oxidation, ED increased the peak temperature but decreased corresponding WLRmax and heat release, resulting in the inhibition of residual char combustion. Also, RTS smoke components could be modified by ED due to the reduction of NH3, TSNA and carbonyl compounds though the release of CO was increased.Organic and inorganic potassium had a great effect on the thermal behavior, gaseous product distribution and smoke components of RTS. The whole stage of carbohydrates degradation moved towards lower temperature by decreasing the apparent activation energy with the addition of potassium. On the stage of char oxidation, inorganic potassium could affect the characteristic parameters and promote the formation of stable char whereas the organic ones totally changed the char oxidation process. A new strong peak appeared at high temperature and organic potassium reduced the specific surface area and enhanced the stability of residual char. Moreover, potassium affected the gaseous product and mainstream smoke firmly depending on its chemical state. The release of CO, HCN, NNK and crotonaldehyde was all decreased while CO2 increased with the incorporation of potassium.Alkali metal played an important role in the thermal behavior and mainstream smoke composition of RTS and the content mattered extraordinary. The whole stage turned to hypothermia direction and the apparent activation energy got decreased on the pyrolysis of carbohydrates. Also, the temperature of main peak dropped and the addition amount was negatively correlated as well. Moreover, alkali metal changed the char oxidation process into several peaks at higher dose (≥0.8mmol/g). The main weight loss and heat release moved to higher temperature. The firecone temperature also decreased due to the heat release in wider temperature range resulted from multiple peaks. What’s more, the emission of CO in mainstream declined in alkali metal modified RTS. As for alkaline earth metal, it had less significant effect on RTS degradation compared with alkali metal, but still it could lower the apparent activation energy of carbohydrates, and have an impact on the mechanism of char-forming, characteristics and amount of residual char, thus enhancing the yield of stable char.