| As one of the cutting-edge technologies of biomass thermochemical conversion,pyrolytic poly-generation can convert raw biomass materials into solid（biochar）,liquid（bio-oil）and gaseous（pyrolysis gas）products,which has attracted wide attention.However,the bio-oil produced by conventional pyrolysis has complex composition,low calorific value and poor quality.The heavy component（heavy bio-oil）of bio-oil contains pyrolytic lignin,phenolic substances and other components,which has high viscosity,poor stability and easy coking when heated,which is an important factor restricting the high value utilization of bio-oil.In addition,ash and alkali/alkaline earth metal elements in raw materials are also important reasons for the difficult utilization of biomass pyrolysis products,while the light component of bio-oil（light bio-oil）contains a lot of water and organic acids,which has the potential to remove ash by washing biomass.Based on this,this paper proposed a method of washing the raw bamboo using light bio-oil,and then co-pyrolysis with heavy bio-oil to improve the quality of products.The response surface methodology was used to conduct a basic study on the co-pyrolysis of heavy bio-oil and washed bamboo.The effects of washing pretreatment on the distribution and properties of the three-phase products during the co-pyrolysis of bamboo and heavy bio-oil were analyzed.The synergistic effect of the co-pyrolysis of bamboo and heavy bio-oil was explored,and the fitting model between the yield and properties of products and the pyrolysis conditions（mass ratio,pyrolysis temperature and residence time）was established.The optimum experimental conditions for co-pyrolysis of biochar,bio-oil and pyrolysis gas were obtained,which provided data and theoretical basis for the development of biomass pyrolysis poly-generation technology and effective utilization of heavy bio-oil.（1）Researching on biochar produced by co-pyrolysis of heavy bio-oil and light bio-oil washed bambooFirstly,the co-pyrolysis of heavy bio-oil and apricot shell was carried out in a tube furnace,and the feasibility of co-pyrolysis of heavy bio-oil and biomass was analyzed.The results showed that the co-pyrolysis of heavy bio-oil and apricot shell had a synergistic effect,which increased the yield and higher heating value（HHV）of biochar.Based on this,light bio-oil（LB）was used as a leaching and deashing agent for biomass.A series of studies were carried out on the preparation of three phase products by co-pyrolysis of heavy bio-oil and bamboo before and after washing pretreatment.The effects of mass ratio（0:1～1:0）,pyrolysis temperature（400～700°C）and residence time（5～30 min）on the pyrolysis products were studied by response surface methodology.After washing pretreatment,the contents of ash,hemicellulose and extractives decreased,while the contents of cellulose and lignin increased.Co-pyrolysis of heavy bio-oil and raw bamboo also improved the yield and HHV of biochar,and the synergistic effect was more significant after washing pretreatment.At a mass ratio of 1:1,550°C and 17.5 minutes,the yield（25.97 wt.%）and HHV（29.43 MJ/kg）of biochar from co-pyrolysis of bamboo and heavy bio-oil were 1.61 wt.%and 1.01 MJ/kg higher than the theoretical values,respectively,while the yield（24.63 wt.%）and HHV（30.62 MJ/kg）of biochar from co-pyrolysis of LB washed bamboo and heavy bio-oil were2.40 wt.%and 1.57 MJ/kg higher than the theoretical values,respectively.Washing pretreatment had a negative effect on biochar yield,but reduced the ash content and improved the HHV of biochar.The fitting models for the yield and HHV of biochar were quadratic equations.The optimization results showed that the highest yield and HHV of biochar derived from co-pyrolysis of heavy bio-oil and raw bamboo were 33.98 wt.%and 31.6 MJ/kg,respectively,and that from co-pyrolysis of heavy bio-oil and washed bamboo were 34.75 wt.%and 32.3 MJ/kg,respectively.（2）Researching on bio-oil produced by co-pyrolysis of heavy bio-oil and light bio-oil washed bambooIn this work,light bio-oil leached bamboo（LB-MB）and heavy bio-oil were used as raw materials to produce bio-oil in a vertical tube furnace,and the raw bamboo（MB）was co-pyrolyzed with heavy bio-oil for comparison.Results showed that co-pyrolysis had a negative effect on the mass yield of bio-oil,but it improved the HHV of bio-oil.Co-pyrolysis was beneficial to reducing the relative contents of acids,aldehydes,ketones,and N-containing compounds in bio-oil,thus improving the quality of bio-oil.The ash in bamboo was significantly removed by washing pretreatment,which improves the mass yield and HHV of bio-oil,and reduces the water content.Washing pretreatment promoted the formation of phenols,hydrocarbons,and anhydrosugars,and inhibited the formation of acids and aldehydes in bio-oils.Among the three experimental variables,the mass ratio and pyrolysis temperature had great effects on the yield,water content and HHV of bio-oil.Meanwhile,the fitting models for the yield of bio-oil were quadratic equations.For the co-pyrolysis of heavy bio-oil and raw bamboo,the highest yield of bio-oil was 61.84 wt.%,and the bio-oil had the lowest water content（15.78 wt.%）and a higher HHV（27.75 MJ/kg）.For the co-pyrolysis of heavy bio-oil and washed bamboo,the highest yield of bio-oil was 62.08 wt.%,and the bio-oil had the lowest water content（14.02 wt.%）and highest HHV（28.43 MJ/kg）.（3）Researching on pyrolysis gas produced by co-pyrolysis of heavy bio-oil and light bio-oil washed bambooIn this work,light bio-oil leached bamboo（LB-MB）and heavy bio-oil were used as raw materials to produce pyrolysis gas,and the raw bamboo（MB）was co-pyrolyzed with heavy bio-oil for comparison.Results showed that co-pyrolysis increased the yield of pyrolysis gas,but reduced the HHV of pyrolysis gas.Washing pretreatment was beneficial to improving the mass yield and HHV of pyrolysis gas.Meanwhile,it can increase the content of CO and CH4 in pyrolysis gas and reduce the content of CO2.Among the three experimental variables,the mass ratio had an important effect on the CH4 content,CnHm content,and HHV of the pyrolysis gas,and these parameters increased with the increase in mass ratio.Pyrolysis temperature had the greatest influence on the yield,CO content,H2 content,and CO2 content of pyrolysis gas.With the increase in pyrolysis temperature,the yield,CO content,and H2 content of pyrolysis gas increased,while the CO2 content decreased.The best fitting models for the yield and HHV of pyrolysis gas were quadratic equations.Optimization analysis showed that the highest yield of pyrolysis gas from co-pyrolysis of heavy bio-oil and raw bamboo was 39.28 wt.%with a HHV of 16.44 MJ/Nm3,and that from co-pyrolysis of heavy bio-oil and washed bamboo was 42.92 wt.%with a HHV of 19.26MJ/Nm3.The energy yield analysis showed that co-pyrolysis was beneficial to increase the energy yield of biochar and pyrolysis gas,while leaching pretreatment was beneficial to increase the energy yield of bio-oil and pyrolysis gas.Co-pyrolysis poly-generation gives full play to the respective characteristics of light and heavy bio-oils and provides a potential way for classification and utilization of bio-oils.Meanwhile,it also has theoretical and practical significance for the high-value comprehensive utilization of biomass resources. |
