Page 240 - Biomass Gasification, Pyrolysis And Torrefaction Practical Design and Theory

Chapter | 7 Gasification Theory 217

7.3.6.3 Entrained-Flow Reactor
Entrained-flow gasifiers are preferred for the integrated gasification com-

bined cycle plants. Reactors of this type typically operate at 1400 C and
20 70 bar pressure, where powdered fuel is entrained in the gasifying
medium. Figure 7.7 shows two entrained-flow gasifier types. In the first one,
oxygen, the most common gasifying medium, and the powdered fuel enter
from the side; in the second one, they enter from the top.
In entrained-flow gasifiers, the combustion reaction, R5 (Eq. (7.24)), may
take place right at the entry point of the oxygen, followed by reaction R4
(Eq. (7.25)) further downstream, where the excess oxygen is used up.
Powdered fuel (,75 μm) is injected into the reactor chamber along with
oxygen and steam (air is rarely used). To facilitate feeding into the reactor,
especially if it is pressurized, the fuel may be mixed with water to make a

(A) Gas

Gas
Biomass
Height
Gasification
Biomass
Combustion
Steam, air,
or oxygen 500 1000 1500
Temperature (°C)
Ash
(B) Biomass Steam, air,
or oxygen

Gas
Combustion
Biomass
Height
Gasification

500 1000 1500
Ash Gas Temperature (°C)
FIGURE 7.7 Two main types of entrained-flow gasifiers.