Environmental Engineering Reference
In-Depth Information
2.00
PM 1 PM 2.5
PM 10
1.80
1.60
1.40
1.20
1.00
0.80
0.60
0.40
01234567
8
9
10
11
12
13
14
15
16
Particle size, (
ยต
m)
As
Cr
Mn
Ni
Pb
Zn
Fig. 3.11 Size distribution of bottom ash in a fluidised bed coal-fired thermal power plant
Under the circumstances, aerosol formation during combustion was studied in a
fluidised bed 800 MW
t
h boiler, during combustion of finely divided wood, with and
without coal or flying ash as alkaline capture additive.
Both the physico-chemical characteristics and the PMmorphology of the aerosol
samples were analysed. Sub-micrometre sizes were determined with the electron
microscope (SEM/EDS and Met/EDS). Sub-micrometre particles (PM
1
) with a
concentration of 44-47 mg/Nm
3
were identified.
The Gaussian distribution of nanoparticles highlighted a characteristic maxi-
mum peak at about 200 nm. This peak consisted mainly of ultrafine aggregates
(
100 nm) of particles rich in K, Cl and S formed through the homogeneous and
heterogeneous vaporisation of solutions containing chloride, potassium, sodium
and sulphate ions from the gaseous state.
In an experimental variant based on ash tree wood flour with the addition of
alkaline flying ash, for a 1:2 or 1:4 mass ratio, the Gaussian distribution of
sub-micrometre particles indicated sizes larger than those in the experiments
without coal flying ash. The PM
1
concentration diminished from the above-
mentioned value to 11-19 mg/Nm
3
.
In this case, ultrafine particles (
<
60 nm) had a more regular, almost spherical
shape, and the composition changed from the Na-K-Cl-S quaternary system to the
<
