feeding problems, and inadequate information about combustion
and emissions characteristics [11].
Using different air-staging strategy in FB combustion of forest
residue had no influence on the NO emissions [12]. The combustion
of pre-dried bagasse was studied in a stationary conical FB
[13]. The axial temperature profiles were uniform and weakly affected
by operating conditions, especially in the bottom (bed) region.
These profiles, as well as the NOx and CO emissions from
the combustor, were apparently affected by both the excess air
and combustor load. However, the minimized NOx emissions could
be achieved at EA = 1.5–1.6.
The SO2 and CO emissions from circulating FB combustion of
bagasse were under the German standard limits but the NOx
emissions were above these limits [14]. By increasing the primary
air ratio (primary air to total air ratio) from 0.3 to 0.5, the temperature
and the NOx emissions decreased but still the NOx emissions
were above the limits. The German limits used for comparison in
that study were that of coal combustion in a pilot-scale fluidized
bed: CO < 250 mg/Nm3
, NOx < 300 mg/Nm3
, and SOx < 400 mg/
Nm3
.
The combustion characteristics of cattle manure and wood
(sawdust) in a 100 kWth circulating FB were studied in [15,16]. It
was found that the excess air ratio had slight effect on the nitrogen
oxides. When burning Egyptian biomass (manure and bagasse) in a
stationary FB, it was noticed that the excess air ratio had unclear
influence on the gas emission [10].
The previous investigations showed that the effect of some
parameters as excess air and staged combustion on the emissions
was unclear and indefinite. It was found also that there are insuf-
ficient investigations for Egyptian biomass, which varies widely
in calorific value and analysis. In this paper, an attempt was made
to study the combustion characteristics of four different kinds of