Process Options for Biomass Conversion

We then compare technologies that exploit different primary energy sources and secondary energy technologies. In the final section, we provide an overview of the different process options for biomass conversion. 

Figure 1.18 summarizes the different process options for biomass conversion. 

Figure 30.1 Process options for the catalytic conversion of biomass.

The data required for operation of the model consist of the resource availabilities of the various types of biomass feedstocks, the process economics of biomass conversion options, a framework of energy demands and market prices, and a set of three parameters that are used to describe the interaction of the biomass-derived products with the markets in which they compete. 

This chapter surveys different process options to convert terpenes, plant oils, carbohydrates and lignocellulosic materials into valuable chemicals and polymers. Three different strategies of conversion processes integrated in a biorefinery scheme are proposed from biomass to bioproducts via degraded molecules , from platform molecules to bioproducts , and from biomass to bioproducts via new synthesis routes . Selected examples representative of the three options are given. Attention is focused on conversions based on one-pot reactions involving one or several catalytic steps that could be used to replace conventional synthetic routes developed for hydrocarbons. 

Fast pyrolysis oil has almost the same elemental composition as the biomass itself hence it can be seen as a kind of liquid wood. It can be transported, can be pressurized and processed more easily than solid biomass. One of the major difficulties in the catalytic conversion of solid biomass is achieving effident con-tad between the heterogeneous catalyst (which is most of the times a solid) and the biomass itself. In this context, bio-oil provides more options for easier catalytic conversion. However, pyrolysis is a very complex and the oil is a difficult to handle chemical mixture. Complete vaporization, for instance, is not possible because part of the components start to decompose and polymerize upon heating... 

The chapters of this book have been selected to provide an introduction to the catalytic issues of biomass conversion processes. The introductory chapters make clear the political decisions, especially in the EU, that drive biomass conversion technology, its prospects compared with other options for renewable energy, and the main technological options for conversion of biomass into secondary energy carriers. 

These figures may appear to be daunting economic goals for biomass not to be restricted to essentially captive use within the present biomass industries. An opportunity cost of 3.84 /GJ coupled to a 40% efficient process constrains the capital cost to 1.5 k /TJ/annum output capacity. Only the densified biomass option coupled with gasifiers at the point of use can meet this cost criterion allowing that there will be prepared fuel transportation costs. If the liquid fuel opportunity cost of 5.49 is used then the capital cost for the conversion has to be less than 7.9 k /TJ/annum output capacity. Allowing that the usual scaling law of an exponent to the 0.7 power is likely to apply to methanol plants for example then a 4000 tpd plant would be feasible. 

Partial oxidation of methane (or hydrocarbons) is another option to produce syngas [4], This process, which runs without a catalyst, needs high temperatures for high CH4 conversion and to suppress soot formation. The process can handle other feedstocks, such as heavy oil factions and biomass, and yields syngas with a H2/CO ratio of about 2. The process is eminently suitable for large-scale production of syngas (e.g. for gas-to-liquids [GTL] plants). 

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