Biomass thermochemical conversion processes

As biomaterials are structurally and chemically complex, biomass thermochemical conversion processes (1,2) produce complex fractions including a liquid fraction which, dep>ending on the process, can be obtained in large (liquefaction, pyrolysis) or small yields (gasification). These liquids have found little utility because of their large contents in oxygen which implies low heat values, instability and corrosive prop>erties. Two routes have been tested (3,4) in order to produce hydrocarbons from these liquids. The first one involves hydrotreatment with either H2 or H2 + CO over classical hydrotreatment catalysts. The second route is the simultaneous dehydration and decarboxylation over HZSM-5 zeolite catalyst in the absence of any reducing gas. 

Thermochemical conversion processes use heat in an oxygen controlled environment that produce chemical changes in the biomass. The process can produce electricity, gas, methanol and other products. Gasification, pyrolysis, and liquefaction are thermochemical methods for converting biomass into energy. 

Hydrogen can be produced from biorenewable feedstocks via thermochemical conversion processes such as pyrolysis, gasification, steam gasification, steam reforming of bio-oils, and supercritical water gasification (SWG) of biomass. 

Important biomass fuel properties for thermochemical conversion processes are reported as proximate and ultimate analyses. The proximate and ultimate analyses for selected biomass feedstocks are presented in Table 33.5. For comparison, the analyses from two selected coal samples are also presented. Biomass generally has a lower energy density than coal, oils, and natural gas it also has higher oxygen content. The higher volatiles and oxygen content of biomass translate into a higher reactivity compared to traditional fossil fuels. In terms of thermochemical conversions, this means that less severe process conditions (lower temperature and shorter residence time) are required for bio-... 

Biomass pyrolysis though is one of the fint process man developed, is being studied extensively since the last two decades to obtain liquid, gaseous and solid fuels and chemicals. It is well recognised that pyrolysis plays a key role in any of the thermochemical conversion process be it combustion, gasification, liquefaction, production of char or active carbon. In this context, selection of feedstock and optimal utilisation of the products can play a vital role [1], This paper suggests a criteria to select an appropriate biomass or find its relative suitability to the conversion processes. 

Fluidized bed application is fairly popular in biomass thermochemical conversions. The one of reason is due to the high efficient heat and mass transfers between particles and gases in the reactor. The initial and essential step of biomass thermochemical conversions such as combustion and gasification in a fluidized bed is pyrolysis. Directly experimental study on the pyrolytic process is limited. Numerical simulation can be an effective way for understanding of the first step of biomass combustion and gasification in applications. 

Thermochemical conversion processes employ elevated temperatures to convert biomass materials to more useful energy forms. Examples include ... 

Science Applications. Inc., "Biomass Based Methanol Processes", Presented at the Seventh Biomass Thermochemical Conversion Contractors Meeting, Roanoke. Va., April 24-25, 1979. 

Biomass can be converted into biofuels via two main types of processes thermochemical and biochemical/biological conversion (Huang and Yuan, 2015). The typical products of the thermochemical conversion process include syngas, bio-oil, and biochar and the products of the biochemical conversion process are bioalcohols, carbohydrates, and lignin. Our concern in this chapter is biochemical production of bioalcohols, or biorefinery process through the well-known sugar platform. ... 

Biorefineiy is the process of extracting valuable chemicals and polymers from biomass. The main technologies to produce cheiuicals from biomass are (a) biomass refining or pre-treatment, (b) thermochemical conversion (gasification, pyrolysis,... 

Demirbas, A. 1998. Yields of oil products from thermochemical biomass conversion processes. Energy Convers Manage 39 685-690. 

Fitzpatrick, S.W. 2004. Biofine Process A Biorefinery Concept Based on Thermochemical Conversion of Biomass. ACS National Meeting Book of Abstracts, 227, 173. 

Fig. 33.3. General schematic of a process for thermochemical conversion of biomass to fuels, heat, and power. ASU = Air Separation Unit, HRSG = Heat Recovery Steam Generator.

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