Fluidized Bed Combustion of Coal, Renewable Fuels, and Waste: Current Status and Developments - Novel Combustion Concepts for Sustainable Energy Development - page 228

signi cantly. The in situ SO 2 capture ef ciency from the fl fluidized bed is highest at

bed operating temperature of 850 C.

Potential disadvantages are that a somewhat higher power demand is necessary
for the operation of a

°

fluidized bed and that the fuel preparation is very important.
There should not be too large and heavy objects in the feeding lines because those
are not

fl

fluidized in the combustor. Another issue is that low melting mixtures have
to be avoided because this may lead to agglomeration and consequently to de-
fl

fl

fluidization of the bed.
Basically there are two different types of fl fluidized bed combustors (FBC), the

stationary or bubbling fl fluidized bed and the circulating fl fluidized bed. In a bubbling

fl fluidized bed (BFBC), the fl fluidized bed stays stationary but fl fluidized in the com-

bustion chamber, whereas in the case of the circulating fl fluidized bed combustor

(CFBC), the fluidized bed is circulating between the combustion chamber which is

in form of a riser then separated usually by a cyclone from the gas and fed back via
the return leg into the riser, that is, the

fl

fluidized bed is circulating.
Usually in smaller scale, BFBCs are in operation, whereas CFBCs operate up to
very large scales. Currently the largest scale in operation of

fl

fl fluidized bed tech-

nology is the 600 MWe coal- red CFBC in Baima, Neijiang City, China.

The CFBC can also handle a somewhat wider range of fuels. In terms of their
calori c value, fuels from as low as about 7 MJ/kg up to about 40 MJ/kg can be

utilized. In BFBC, typical fuels with calorific values from as low as about 3 MJ/kg
up to about 20 MJ/kg are utilized.

3 Current Developments

There are several major developments of fl fluidized bed technology on-going

worldwide.

3.1 One Is the Signi cant Progress in Scale-up

FBC, that is CFBC, are continuously further developed to increase their capacity
(refer to Fig. 1 ). They operate at high ef

ciencies and use supercritical steam cycles.
In 2014, the largest CFBC worldwide has successfully reached its 600 MWe. It is
based on coal and located in Baima, Neijiang City, China (refer to Fig. 2 ).
In China, there are more than 3,000 units of CFBCs in operation and more than
100 units in the size range of 300 MWe (Yang 2012 ).
Another signi cant project of a similar size class is on-going in Korea. In

Samcheok, Korea, 4

×

550 MWe CFBCs are in construction (refer to Fig. 3 ). They
are located at the coast location and based on coal with the option of biomass
addition. Their full operation is considered in 2016.