Analysis Of Hydrothermal Coke Characteristics Of Wood Fiber Biomass

Biomass hydrothermal carbonization technology,which is an effective biomass energy conversion technology,can transform biomass raw materials into hydrothermal coke at a certain temperature and pressure.Many scholars have shown that hydrothermal coke has the characteristics of high carbon content and high calorific value and so on.The application of hydrothermal coke as fuel and the preparation of high-value-added products as pyrolysis raw materials is promising,but the research on its related properties is not systematic enough.Therefore,based on Research on the mechanism of carbon transfer and retention in the residue of biomass wet digestion in wet digestion environment,the project of National Natural Science Foundation of China,three kinds of biomass,i.e.longan shell,bamboo shoot shell and corn straw,were used as raw materials to carry out the experimental research on the hydrothermal carbonization,and the evolution characteristics,thermodynamic characteristics and pyrolysis characteristics of hydrothermal coke were studied by combining the element analysis and thermogravimetric analysis The activation energy of kinetic parameters was calculated.The main work is as follows:?1?Hydrothermal chars were prepared from three kinds of biomass materials under different reaction intensities,and the evolution characteristics of hydrothermal chars were studied with element analysis.The results show that the yields and the mass fractions of C and O elements of the three kinds of biomass hydrothermal cokes all show a function reference relationship with the increase of the reaction intensity.According to the curve,they are divided into three stages:the first stage is relatively stable;the second stage changes dramatically;the third stage tends to be stable gradually.O/C atom ratio of longan shell hydrothermal coke and H/C and O/C atom ratio of bamboo shoot shell hydrothermal coke prepared under high reaction intensity are close to the standard coal,which shows that the hydrothermal carbonization process greatly promotes the coalification process of biomass and makes the prepared hydrothermal coke have good fuel characteristics.?2?Based on the element analysis,the formation enthalpy EF,chemical?exergy?CE,low calorific value LHV and high calorific value HHV of the hydrothermal coke from the shell of cinnamon and bamboo shoot were calculated.The results show that with the increase of reaction intensity,the thermodynamic parameters CE,HHV,LHV and EF of hydrothermal coke are increasing gradually,and they are similar to the changes of the evolution process of hydrothermal coke.They can also be divided into three stages:the first stage is stable;the second stage is sharp;the third stage is stable again.In addition,with the increase of reaction intensity,the thermodynamic parameters of hydrothermal Coke will gradually approach to the standard coal.The low calorific value of longan shell hydrothermal coke is 28.97 MJ/kg when the logR₀ is 7.10,and 28.87 MJ/kg when the logR₀ is 7.69,which are very close to the low calorific value of 29.27 MJ/kg of standard coal,indicating that it has good fuel characteristics.?3?The pyrolysis characteristics of bamboo shoot shell,corn straw hydrothermal coke and their raw materials prepared under different reaction intensities were analyzed by TGA.The TGA of corn straw hydrothermal coke and its raw materials prepared under 7.10?250?,480 min?reaction intensities were analyzed at different heating rates.The kinetic model was established to calculate the activation energy of reaction kinetic parameters.The results show that the pyrolysis process of hydrothermal coke and biomass can be roughly divided into three stages:dehydration,main pyrolysis and carbonization.In the dehydration stage,the free water precipitates out to about 125?;then it enters the main pyrolysis area,and the main components decompose gradually to about 565?;then it enters the carbonization stage,and the pyrolysis curve tends to be stable.In the pyrolysis process,the kinetic parameter activation energy of corn straw hydrothermal coke increases with the increase of conversion rate,while corn straw decreases with the increase of conversion rate.When the conversion rate exceeds 20%,the activation energy of hydrothermal coke has exceeded corn straw.When the final conversion rate reaches 75%,the activation energy of hydrothermal coke obtained by FWO and KAS has reached 260.88kJ/mol and 261.83 kJ/mol,far exceeding the corresponding activation energy of corn straw145.44 kJ/mol and 142.73 kJ/mol.