Agriculture Reference
In-Depth Information
self defined thermal-technical efficiency was higher than 70% and the emissions of NO
x
(corrected to 11% O
2
) were around 180 mg/Nm
3
.
Hrdlicka and Dlouhy (2002) co-fired lignite and sugar beet pulp having 79.7% moisture,
1.21% ash and with energy value of 1.45 MJ/kg. Combustion of pulp alone was possible
when moisture content of the pulp was reduced to 45%, its energy value increased to 8.5
MJ/kg. They co-fired lignite and pulp blends in 2MW fluidized bed boiler with lignite to pulp
ratios of 3:1 and 1:1. The test data is shown in Table 8. The data shows that at higher
proportion of pulp in the blend CO emissions are higher but NO
x
emissions are lower. They
stated that burning of pulp can cover 30 - 50% of heat and power requirements of sugar mill.
Moreover, co-firing reduces emissions of NO
x
and SO
2
.
Apart from Jevic et al. (2007) described above, there is no authentic open literature on the
combustion of pressed pulp primarily due to the reason that so far the pulp has been used as a
feedstock for animals. The pressed pulp is dried for use as cattle feed primarily using a coal
fired fluidized bed to produce hot combustion products which are subsequently fed into a
rotary drier. Consequently there is an interest in co-firing pressed pulp with coal to reduce
coal imports and thus saving money. There is a lack of published data on co-firing of these
by-products therefore the main aim of the rest of this chapter is the discussion of combustion
of these in a fluidized bed for energy recovery.
Table 7. Characteristics of wheat straw and 15% sugar beet pulp briquettes(wt/wt)
Wheat straw and 15% SBP*
Sugar Beet Pulp
Total Moisture (%)
6.34
71
Volatile matter (%)
72.15
12.9
Fixed Carbon (%)
-
14.1
Ash (%)
6.42
2
Carbon (%)
42.61
14.1
Hydrogen (%)
5.41
1.8
Nitrogen (%)
0.53
0.14
Sulphur (%)
0.05
0.14
Oxygen (%)
37.22
10.9
Sodium (%)
-
0.1
Potassium (%)
-
0.75
Calcium (%)
-
1.2
Gross CV (MJ/kg)
16.62
5.2
Net CV (MJ/kg)
15.03
3.2
*Jevic et al. (2007)
Table 8. Measurements on FK 2MW boiler Co-Firing Lignite and Sugar Beet Pulp
Blending ratio (lignite/pulp)
3:1
1:1
Output (kW)
1100
1200
O
2
(%)
9.2
8.6
CO (mg/Nm
3
) corrected to 6% O
2
111
196
Excess air
1.78
1.7
NO
x
(mg/Nm
3
) corrected to 6% O
2
616
570
Bed temperature(BT),(°C)
835
845
