Agriculture Reference
In-Depth Information
C
ONCLUSION
Fluidized bed tests have been performed with sugar industry biomass including vinasse,
raffinate and PP when co-firing with coal. The results show that raffinate and vinasse are
problematic fuels and cause agglomeration fairly quickly. Calcium in coal ash extends
defludidisation time which indicates that lime can be used as a bed material to increase
operational times while firing these troublesome fuels. However, no signs of agglomeration
were observed during prolonged tests with coal and pulp. Therefore, PP can be used as fuel in
fluidized bed without the use of alkali getters as long as operational parameters are properly
controlled. But, vinasse and raffinate can‟t be used without adapting measures such as
addition of alkali getters to reduce agglomeration.
The results show that blending pulp with coal considerably reduces emissions of NO
x
and
SO
x
due to lower sulphur and nitrogen content of pulp. The reduction in emissions is
observed to be higher with increased biomass content in the blends. It is observed that ratio of
volatiles to fixed carbon plays a key role in reducing NO
x
emissions. There was no
considerable effect of moisture content on NO
x
emissions. However, NO
x
emissions found to
be increased with increase in excess air and decreased with increase in bed temperature.
Emissions of SO
2
found to be decreased with increase in biomass proportion due to
increase in Ca/S ratio. Higher moisture content of fuel reduces SO
2
emissions by possibly
converting them to H
2
SO
4
. Emissions of SO
2
found to be decreased with increase in excess
air and decrease in bed temperature with more pronounced effects with higher moisture
content fuels. The emissions of CO are found to be decreased first and then increased with
increase in excess air. Emissions of CO are found to be increasing with increase in coal
proportion in the blend when high moisture biomass was co-fired with coal. Emissions of CO
found to be decreased with increase in pulp proportion in the blend despite increase in
moisture content, possibly due to delayed ignition and longer residence time in the bed.
The results presented and discussed in this chapter show that it is possible to recover
energy from sugar industry by-products by employing a suitable technology. Pressed pulp is
relatively easy fuel and can be used to recover energy and to reduce coal and oil consumption
costs. However, in order to devise suitable energy recovery systems for vinasse and raffinate,
more research is needed to fully understand the behaviour of potassium during combusion in
fluidized beds.
R
EFERENCES
[1]
Aho, M.J., Hamalainen, J.P. &Tummavuori, J. L. (1993). “Importance of solid fuel
properties to nitrogen oxide formation through HCN and NH3 in small particle
combustion”,
Combustion and Flame
,
95
, 22-30.
[2]
Akram, M. (2012).Optimisation of Co-Firing of High Moisture Biomass with Coal in a
Bubbling Fluidized Bed Combustor”, PhD Thesis, University of Glamorgan, UK.
[3]
Alzueta M.U., Glarborg, P. & Dam-Johansen, K. (1997). “Low temperature interactions
between hydrocarbons and nitric oxide: An experimental study”,
Flame and
Combustion
,
109
, 25-36.
