Gasification heat supply, type

The different gasification processes can be characterized 1) by the type of coal used and 2) by the coal s physical and chemical properties. On the other hand, the processes differ in the technology involved. For example the heat supply can be allothermal (i.e., external heating) or autothermal (i.e selfheating) and the reactor can be fixed-bed, fluidized-bed or entrained-bed. Furthermore, the actual gasification reaction and the gas composition are determined by46 ... 

PTGL-processes (table Ia,b,c) can be characterized by their operating principle (pyrolysis, gasification or liquefaction) and reaction conditions, their type of reactor and method of heat supply and the possible presence of auxiliary systems. The selection of a particular process will ultimately be based on its proven reliability on one hand and on the quality of the process output on the other [ ]. ... 

The important factors in coal conversion are the physical and chemical properties of the coal, heat supply (autothermal or allothermal), reactor type (fixed bed, moving bed, fluidized bed, or entrained bed), gasification agent (air, oxygen, steam, or a combination thereof), and process conditions. Typically, coal conversion is carried out at high temperatures (900—1000 C) be-... 

The gasification techniques can be distinguished related to different criteria such as reactor type (fixed bed or fluidized bed), gasifying agent (air, oxygen, or steam), heat supply into the reactor (directly or indirectly heated) and reactor... 

To achieve temperatures in a reactor above 700 °C to maintain the reaction of gasification agent and feedstock, heat can be either added externally or generated internally. Based on heat supply to the process, allothermal, autothermal, and hydrogenating processes are distinguished. The main characteristics of the different types of heat supply are shown in Table 4.1. 

Typical of an installation for re-gasification of LNG is that it includes a vaporiser and one or more LNG storage tanks - either vertical or horizontal type. The vaporiser receives heat as required to evaporate the LNG either from the surrounding air or from hot water. In the latter case, hot water is usually supplied via a gas-fired burner that consumes about 2% of the corresponding LNG stream to be vaporised [12]. Hot-water-based evaporation is more expensive than the ambient-based evaporation, but is less dependent on the ambient conditions. The re-gasification installation will furthermore include gas controllers and an odoriser. Since natural gas does not smell odour should be injected to the gas flow for safety reasons. Except for the filling of the LNG tanks from time to time - and also the unloading LNG carriers - such facilities could be unmanned. 

Low BTU gasification technology is commercially available for most types of biomass feedstocks and can be expected to have an impact on energy supplies by 1985. Many of these commercial processes are based on low BTU coal gasification technologies and the gas produced can best be used as fuel for supplying process heat, process steam or for electrical power generation. 

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