Бурение грунтовых зондов, установка энергетических колодцев

The major drawback of biomass is that the energy density is an order of magnitude lower than that of crude oil (Table 4-17). When it is further considered that biomass for fuel is a difficult to handle solid (grain is an exception in that it almost flows like water), this implies that fuel biomass can never be shipped economically over long intercontinental distances.

Therefore, when contemplating really large biomass production, the first conver­sion that has to take place is to convert the biomass into a transportable product. The best way to accomplish this is by flash pyrolysis, which is a fast pyrolysis at a high temperature of 450^-75 °С. In this way the solid biomass is converted into a transport­able liquid with an energy density of about 20GJ/m3 (see Table 4-17), which is similar to that of methanol. The pyrolysis plants can be located anywhere, because they can be economically built on a reasonably small scale. A stand-alone gasifier is only likely to be economic for world-scale plants, and hence they always depend on biomass from a variety of sources. The energy conversion of flash pyrolysis is now 75% but could well increase to 80% in the future. The bio-oil product is a transportable material that has as its only disadvantage that it is corrosive due to the presence of organic acids. A big advantage is that it can be gasified with oxygen in the same commercial gasifiers that can process heavy oil fractions. An added advantage of bio-oil is that it is easily homogenized. Holt and van der Burgt (1997) proposed such a concept of decentralized flash pyrolysis plants feeding a single large gasification installation. Research on details of actual implementation is continuing (Henrich, Dinjus, and Meier 2002).

Table 4-18 lists some of the most important properties of bio-oils. Additional data, in particular of some important organic compounds in bio-oil, is contained in Henrich, Dijus, and Meier (2002). In terms of its suitability for gasification in a standard oil gasifier, the most important aspects are the pH (material selection of the feed train) and the alkaline ash content. This latter may favor the use of a radiation screen instead of simple refractory lining.

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