A Study On The Effect Of Reaction Parameter Coupling Volatile-Char Interactions On Biomass Pyrolysis

Biomass energy is a widely distributed,abundant and renewable energy,which plays an indispensable role on the road to achieving the dual carbon targets.Biomass pyrolysis refers to the process of transforming biomass into biochar,bio-oil and pyrolysis gas through thermochemical conversion.Volatile-char interactions and different reaction parameters exist in the process of pyrolysis will bring complex changes to pyrolysis.Therefore,it is of great significance to explore the influence of reaction parameter coupling volatile-char interactions on pyrolysis.In this paper,poplar wood was used as the main experimental material.A two-layer quartz reactor was designed to regulate the volatile-char interactions,and the effects of volatile-char interactions coupled with reaction activity,reaction temperature and reaction duration on pyrolysis were studied.Specific research contents are as follows:(1)The AAEMs of poplar wood were removed by acid-washing pretreatment to change the reactivity,and the degree of volatile-char interactions was changed by replacing the inner tube of the two-layer quartz reactor.The influence of reactive coupled volatile-char interactions on pyrolysis was studied at 600°C.The results showed that after the removal of AAEMs,the activity of the reaction decreased,the yield of bio-oil increased,and the yield of biochar and non-condensable gas decreased.The decrease of reactivity and the decrease of volatile-char interactions led to the increase of C content and the decrease of O content in biochar.In addition,the decrease of reactivity also resulted in the decrease of the contents of acids and carbonyl compounds,and the increase of the content of dehydrated sugars.A highest bio-oil yield of 63.37%with 34.38%of anhydrosugars could be obtained even for a packed fixed-bed reactor by regulating the reaction activity and volatile-char interactions.(2)The reaction temperatures were set at 400°C,600°C and 800°C,and experiments were conducted under different degrees of volatile-char interactions to study the influence of reaction temperature coupling volatile-char interactions on pyrolysis.The results showed that the yield of biochar decreased and the yield of non-condensable gas increased with the increase of reaction temperature.Under the condition of 800°C and strong volatile-char interactions,the yield of non-condensable gas reached 29.75%.Increasing reaction temperature and weakening volatile-char interactions could increase the C content of biochar,while decreasing O content and increasing HHV of biochar.The increase of reaction temperature and the increase of volatile-char interactions led to the increase of specific surface area of biochar.Under the condition of 800°C and strong volatile-char interactions,the specific surface area of biochar reached 367 m~2/g.Increasing the reaction temperature will decrease the content of acids in bio-oil and increase the content of dehydrated sugars.When the reaction temperature was increased from 400°C to 800°C and volatile-char interactions were weakened,the acid content decreased from 24.48%to 8.06%,and the dehydrated carbohydrate content reached the highest 13.29%.(3)Under the temperature of 600°C,the same mass of volatile was controlled to interact with activated carbon of different mass,and the influence of reaction duration coupled volatile-char interactions on pyrolysis was studied.The results showed that increasing the duration of volatile-char interactions led to the increase of activated carbon mass,the increase of volatile matter content in activated carbon,the decrease of fixed carbon content,the decrease of ash content,and the decrease of specific surface area.With the increase of the duration of volatile-char interactions,the yield of bio-oil decreased,and the content of dehydrated sugars in bio-oil decreased to a lower value.In addition,under the same conditions,the yield of non-condensable gas increased,the content of carbon dioxide and hydrogen increased,and the content of carbon monoxide decreased.When the duration of volatile-char interactions is long,the highest carbon dioxide content could reach 55.39%,and the lowest carbon monoxide content was 24.77%.In this paper,by changing reaction parameters and regulating volatile-char interactions,the influence of different reaction parameters coupling volatile-char interactions on biomass pyrolysis was studied,which made it possible to selectively produce pyrolysis products,provided a scientific basis for accurately regulating the distribution and quality of pyrolysis products,and was of great significance for realizing accurate control of the pyrolysis process to generate value-added products.