Effect Of Hydrothermal Pretreatment On The Pyrolysis Characteristics Of Tobacco Stem And Its Mixture With Microalgae

In the context of the new round of energy revolution,the development and utilization of renewable energy has become an important way to solve the problem of depletion of fossil energy.Biomass energy is one of the renewable energy with great development potential.According to the characteristics of high oxygen content,low heating value,poor stability,and high acidity of bio-oil,hydrothermal pretreatment technology is used to improve the quality of pyrolysis oil by improving the fuel characteristics of biomass.In this study,the effect of hydrothermal pretreatment on the pyrolysis characteristics of tobacco stems and its mixture with microalgae was studied in order to effectively use biomass resources.The research content is as follows:?1?Study on the effects of hydrothermal pretreatment on the physical and chemical characteristics of tobacco stems:Use high-pressure reactors,elemental analyzers,¹³C superconducting nuclear magnetic resonance spectrometer and other instruments to study the physical and chemical characteristics of raw materials and hydrochar.After hydrothermal pretreatment,the maximum increase in carbon content of tobacco stems reached 61.31%,the maximum decrease in oxygen content was 36.67%,HHV,fixed carbon,H/C_eff,fuel ratio and energy densification continued to rise,the crystallinity index first increased and then decreased,and the aromaticity continued to increase.?2?Study on the effects of hydrothermal pretreatment on the pyrolysis characteristics of tobacco stems:The fast pyrolysis analyzer coupled to gas chromatography/mass spectrometer,thermogravimetric analyzer coupled to infrared spectrometer were used to study the pyrolysis characteristics of tobacco stem and hydrochar.With the increase of hydrothermal temperature,the maximum weight loss rate DTG_max and the comprehensive pyrolysis index increased first and then decreased.Hydrothermal pretreatment with a hydrothermal temperature below 240°C reduced the average apparent activation energy of the pyrolysis of tobacco stems.With the increase of hydrothermal temperature and residence time,the content of aliphatic hydrocarbons in pyrolysis products increased,the content of ketones and acids decreased,and the quality of bio-oil was improved.The combined effect of hydrothermal pretreatment and catalyst HZSM-5 can increased the total peak area of hydrocarbons?aliphatic and aromatic?up to 8.19 times the total peak area of raw tobacco stems without catalyst.?3?Study on the pyrolysis characteristics of tobacco stems and microalgae after co-hydrothermal pretreatment:Using the above experimental facilities,the synergistic effect of co-hydrothermal pretreatment of tobacco stem and microalgae and the pyrolysis characteristics of co-hydrochar were studied.With the increase of the proportion of microalgae,the carbon and hydrogen content of the co-hydrochar increased,the oxygen content decreased,and the H/C_effand HHV continued to increase;as the proportion of tobacco stems increased,the fixed carbon content increased,and the nitrogen and sulfur content decreased.The synergistic effect of co-hydrothermal pretreatment increased the mass yield,carbon yield,and energy yield of co-hydrochar.The advantages and disadvantages of hydrochar generated from a single raw material are relatively prominent,and co-hydrochar can achieve complementary advantages.The ratio of tobacco stem and microalgae can be flexibly adjusted according to the target product to obtain the optimal bio-oil.