Research On Activation And Utilization Of Biochar From Biomass Catalytic Pyrolysis

Biomass is a kind of clean and renewable energy and has large quantities throughout the world. Recently, the utilization and conversion technology of biomass has received more and more attention. Biomass fast pyrolysis is a very promising technology with the aim of maximizing the yield of bio-oil. However, the utilization of crude bio-oil is still limited due to some disadvantages, such as high oxygen content, poor stability and corrosion. Catalytic pyrolysis with zeolites can improve the quality of the resulting bio-oil. Because, in the presence of zeolites, the volatiles released from biomass pyrolysis can be transformed into hydrocarbons through dehydration and deoxygenation reactions. Among all the zeolites, many researchers found ZSM-5was outstanding. However, there is very limited research on the effect of ZSM-5on the characteristics of the biochar from biomass pyrolysis. Meanwhile, as a by-product of biomass catalytic pyrolysis, catalytic biochar has not been effectively utilized although it accounts for15-25wt%of raw biomass. Supported by relevant research programs, an integrated research on the effect of ZSM-5on the characteristics of biochar from catalytic pyrolysis of biomass in a fluidize bed is presented in this thesis. And some utilization methods of catalytic biochar are explored.Non-catalytic biochar and catalytic biochar were produced from the fast pyrolysis of lauan in a fluidized bed with silicon sand and ZSM-5as bed material respectively. The proximate and ultimate analysis, scanning electron microscope (SEM) analysis, N2physisorption, X-Ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) have been performed to investigate the texture and structure of the non-catalytic biochar and catalytic biochar. Results indicated that ZSM-5can facilitate the proceeding of the pyrolysis reaction. Compared with non-catalytic biochar, catalytic biochar has lower content of volatiles and higher content of fixed carbon, carbon element and ash content. Meanwhile, catalytic biochar has lower content of amorphous carbon and organics. The pore diameters of both biochars are in the range of middle-pore with little BET surface area.Chemical (KOH) activation of non-catalytic biochar and catalytic biochar were carried out in a tubular furnace reactor in nitrogen atmosphere. Effect of temperature on the product yield and the texture of non-catalytic biochar and catalytic biochar after activation were investigated. With the rising of temperature, the product yield and the content of volatiles decreased while the content of fixed carbon and element carbon increased. Meanwhile, the surface functions of non-catalytic biochar and catalytic biochar decreased sharply. What’s more, the activation process contributed to the improvement of the degree of graphitization. Compared with non-catalytic biochar, catalytic biochar has higher activation yield but lower BET surface area. After chemical activation at700℃, the BET surface area of non-catalytic biochar and catalytic biochar reached1101m2/g and733.6m2/g respectively which can be used as activated carbon.Steam gasification of non-catalytic biochar and catalytic biochar before and after activation were studied in a fixed bed reactor at atmospheric pressure. Results showed that the conversion efficiency of non-catalytic steam gasification was higher in comparison with that of catalytic biochar. The product gas species from steam gasification of both biochars was same, but with different concentration. For both biochars, higher temperature promoted the production of gases, especially the hydrogen. The maximum concentration of hydrogen from steam gasification of non-catalytic biochar and catalytic biochar reached at83%and88%at800℃respectively. The conversion efficiency of the non-catalytic biochar and catalytic biochar after activation decreased. Meanwhile, the conversion efficiency decreased with the rising of activation temperature. The hydrocarbon content from steam gasification of both biochars after activation decreased sharply which improves the purity of product gas. In addition, the total gas yield from steam gasification of both biochars after activation also decreased.