2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
Table II
The results of coal magnetic separation after the microwave
radiation
Grain Magnetic Mass yield of Recovery of
size induction magnetic S pyr in mag.
[mm] [T] product [%] prod. [%]
0.13 4.32 39.6
0.24 4.72 43.2
0.05–0.2 0.42 10.80 44.7
0.51 11.54 45.5
Fig. 1. The influence of ratio of NaOH and coal on the total
sulphur content in coal sample (Cígeľ) after RMCL process, Socontent
of sulphur basic sample
From the obtained results, it is possible to state, that
80 % of the total sulphur content is possible to remove by
ratio of naOH : coal = 3 : 1.
Effect of reaction time
The time dependence of microwave heating on decrease
of the total sulphur content in coal from the Cígeľ locality
by ratio of naOH : coal = 1 : 1 is displayed in Fig. 2. The sulfur
removal increased to 76 % within 5 minutes and reached
85 % at 10 minutes, but after 10 minutes, the change was not
significant.
The total sulphur content decreased from 2.27 % to 1.0 %
(56 %) in the mufle oven at the temperature 380 °C (within
reaction time 40 minutes). The main difference between the
Fig. 2. The change of total sulphur content of the coal samples
with time
s532
thermal and microwave heating was the extremely short time
for desulphurization in the case of microwave experiments.
Effect of the coal deposits
The dependence of sulphur content in the coal samples
from the localities Cígeľ, Handlová, nováky in RMCL proces
is displayed in Fig. 3. The conditions of the microwave
heating were following: temperature 380–400 °C, time 3
minutes, the ratio of naOH : coal = 1 : 1.
It can be seen, that the effect of microwave pretreatment
on reduction of the total sulfur content in samples from
nováky and Cígeľ (52–56 %) is higher than in sample from
Handlová (28 %).
Fig. 3. RMCL for coal samples from Handlová, Nováky, Cígeľ
Effect of the particle size
The influence of particle size on chemical desulfurization
process was also studied. The representative samples
were divided in fractions of 1–3, 0.5–1, 0.07–0.5, < 0.07 mm
and microwave heating of samples from Donbas (500 W and
6 minutes) and Sokolov (750 W and 3 minutes) was realized.
The results are given in Figs. 4. and 5.
The decrease about 25 % of the total sulphur content
was in the sample from Sokolov eminent. The influence of
graine size was negligible.
The decrease about 35 % of the total sulphur content in
black coal from Donbas locality for graine size 1–3 mm was
observed.
Fig. 4. The decrease of the total sulphur content in sample from
Sokolov versus different size fraction in RMCL process