Gasifying consumption

In operating a fluidized bed reactor such as a fluidized bed coal gasifier, fine particles tend to be elutriated from the fluidized bed. The elutriated fines, if not recovered, represent a significant carbon loss and thus a significant loss of reactor efficiency. In actual industrial practice, the fines are recycled back to the fluidized bed for further consumption. The location of the fines reinjection point into the fluidized bed reactor is important in order to maximize the consumption of fines in each pass. Otherwise, the fines will build up in the recycle loop and increase the heat load of the reactor operation. The fines reinjection location is selected to maximize the fines residence time in the bed and to provide an conducive environment for consumption, such as high temperature and an oxidizing atmosphere. 

A 1,000 ton/day methanol plant, using a Winkler type gasifier adapted to burn wood chips and to use the ICI process for synthesis, requires the following consumption of ingredients per ton of methanol ... 

If ones utilizes conventional gasifiers operating at atmospheric pressure, such as the Davy or Lacotte type, raw material consumption goes up. This also applies if charcoal is used as a raw material. The main reasons are that much of the tars is lost and more energy is needed to compress the gases. 

To develop and build a wood gasifier using experience from the present pilot plant. This will be a fixed bed unit, with recirculation of wood volatiles the reaction heat will be obtained partly from electric power and partly through oxygen injection which permits good reaction control and avoids excessive consumption of electricity. 

Figure 10 shows the flows of exergy between the major groups of equipment in the Synthane process. Also shown is the consumption in each group and its efficiency. Furthermore, unit costs of exergy are shown in parentheses. A notable feature of the SYNTHANE process is that more electric power is produced from the gasifier by-product char than is consumed by the process itself hence the excess is available for "export" from the plant. 

The atmospheric-pressure gasification is a considerable disadvantage of this process route, which substantially increases equipment dimensions and costs, as well as the power required for synthesis gas compression. An energy input of 51.5 GJ/t NIL, (LHV) has been reported. According to [563], the atmospheric ACGP gasifier (Section 4.1.2.3) could lower the consumption to 44 GJ/t NH( (HHV). 

Due to the dry feeding of the Shell gasifier, the 02 consumption is reduced, and the efficiency is increased by -2% compared with the CWS feeding system. However, the maximum gasification pressure is limited to about 5 MPa due to the dry-feeding system, as opposed to 8 MPa for some CWS feeding systems. 

Typical temperatures of Shell gasifiers are in the range of 1440-1600 °C. The typical 02 consumption rate of Shell gasifiers is 0.9 kg 02/kg of coal (on a dry, ashfree basis). The ratio of steam consumption to 02 consumption ratio is 0.14. The cold syngas efficiency is -82% and the carbon conversion can reach >99%. The wet syngas compositions (mol %) from the gasification of a Cerrejon coal from Columbia are... 

In 2004, a 0.5t/day pilot gasifier was completed to verify this gasifier concept. The result showed that the 02 consumption was lower, the thermal efficiency was 1% higher, and the outlet syngas temperature was 200 °C lower than that of a one-... 

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