Study On The Pressurized Pyrolysis Of Pine Sawdust And Products Characteristics

In recent years,biomass pyrolysis technology has received more and more attention,because of the combustion of fossil fuel has brought serious energy shortages and environmental pollution problems.Pressurized pyrolysis is undoubtedly an important way to solve the tar problem which is an obstacle to the widespread promotion of traditional pyrolysis technology.In this paper,the effects of temperature,pressure and feeding method on the product quality distribution and product characteristics during pyrolysis were studied by using self-made high temperature and high pressure reactor.The main research conclusions are as follows:?1?The results of thermo-gravimetric analysis showed that three stages existed in the pyrolysis process of pine sawdust.The detailed stages were the material drying stage,the primary pyrolysis stage and the secondary pyrolysis stage of the residue.The primary pyrolysis stage was the main pyrolysis reaction stage,and the mass loss was 63.10%.?2?In the experiment of pyrolysis of pine wood,tar was the main product of pyrolysis,and its yield was between 33.47% and 45.97%.In the pressurized pyrolysis,the pressure promoted the secondary cracking of the tar.When the pressure was 5 MPa at 600 °C,the tar yield was 14.24%.When feeding at high temperature,the yield of gas and tar increased obviously,and the yield of biochar and water decreased.The change of tar yield was the most significant,which was 11.26% higher than that at room temperature.?3?In the atmospheric pyrolysis,CO was the main gas component in the high temperature range,and the content of CO and H₂ was increased with the increasing of temperature and the content of CO₂ and CH4 was decreased.In the pressurized pyrolysis,the pressure promotes the decarboxylation of the tar,and the CO₂ content increased with the increase of pressure.When feeding at high temperature,the the secondary cracking reaction between tar and pyrolysis gas was weak,resulting in a significant decrease in the contents of H₂,CH4 and CO₂.?4?With the increase of pyrolysis pressure the oxygen content of the tar was significantly reduced.And the pressure promoted the secondary cracking of the tar to produce small molecules such as aldehydes,ketones and acids.The main components of the crushed oil pyrolysis oil at 600 °C and 3 MPa were oxygen compounds,and phenol and acetic acid were the main substances of pressurized pyrolysis tar.?5?The contents of volatile and H and O elements in biochar decreased with the increasing of pyrolysis temperature,and the contents of fixed carbon and ash were gradually increased.The FTIR analysis of biochar showed that the high temperature promoted the degradation of lignin and polysaccharide,and the high pressure did not inhibit the degradation of lignin,but promoted the degradation of aliphatic organic matter.For another,with the influence of pyrolysis pressure and temperature the combustion performance of biochar was improved significantly.The temperature range of thermal decomposition of biochar was 600 615 °C at 600 °C and 3 MPa,and the weight loss rate maintained at 6%·min-1 or more with in the range of 480 600 °C.In term of the microstructure of biochar,the pressure promoted the expansion of the internal carbon,and with the increase of the pyrolysis pressure,the surface of the biochar became rougher and the pore structure was more developed.