Desulfurization of coal
Lecture # 10
Desulfurization of coal
Lecture # 10
INTRODUCTION
• During coal combustion heat is
released to produce steam in boilers.
• Sulfur in the form of pyrite FeS
2
is
transformed into the gas phase as
SO
x
after combustion process.
• One of the cheaper method of
removing sulfur from coal is
biological process.
Microbial desulfarization
• Bioleaching support a use of bacteria
to remove of pyritic sulfur from coal.
• Acidithiobacillus ferrooxidans and
Sulfolobus acidocaldarius were well
known to be effective in removing
pyritic sulfur from coal.
Coal structure
H
H
H
H
H
H H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H H
H
H H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H H
2
H
H
2
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
C
C
H
2
C
C
C
C
C
C
C
C
O
S
S
C
S
H
NH
2
CH
3
S
OH
FeS
2
FeS
2
FeS
2
FeS
2
C
C
CH
3
C
C
C
Scanining electron micrograph of A.ferrooxidans
cells attached on the pyrite surface
Bioflotation of pyrite and
chalcopyrite
Pyrite bioleaching process
• 4FeS
2
+ 15O
2
+ 2 H
2
O =2Fe(SO
4
)
3
+2H
2
SO
4
• This oxidation reaction releases 24.2
MJ/kgS, requires 1.88 kgO
2
/kgS and
generate 0.76 kg H
2
SO
4
/kgS.
• Operation temperature at 35-40
o
C
• Operation pH in the range 1.6 – 1.8
Bioflotation and
bioflocculation
Surfactants
Surface tension of
surfactant solution
Surface tension of solution
with biosurfactant
Surface tension of mineral
suspension at the presence of
biosurfactant
0 . 0
5 0 . 0
1 0 0 . 0
1 5 0 . 0
2 0 0 . 0
2 5 0 . 0
T im e [h ]
2 0
3 0
4 0
5 0
6 0
7 0
S
ur
fa
ce
te
ns
io
n
[m
N
/m
]
w h ito u t m in e r a l p H = 6 . 9 - 7 . 2
h e m a tite p H = 6 . 1 - 6 . 4
k a o lin p H = 7 . 0 - 7 . 6
c h a lk p H = 7 . 6 - 8 . 0
d o lo m ite p H = 7 . 8 - 8 . 3
Critical micelle concentration
(cmc)
Micelle
Micelle
Flocculation
Bridging mechanism
Microflotation using Staphylococcus
carnosus as collector at pH=9
Selective flocculation of Illinois #6 coal
using M. phlei
Adhesion of M.phlei to two coals,
coal pyrite and mineral pyrite and
quartz
MEOR process
• Microbial Enhanced Oil Recovery (MEOR) is
the use of
down oil wells in order
to enhance the production of marginal oil
wells. Most conventional oil recovery
processes are only able to retrieve
approximately 50% of the available oil in
the area.
• The utilization of this process can extend
the life of the average well without
increasing excessive lifting costs.
MEOR process
Microbial Enhanced Oil
Recovery
1. Przepływ wody przez złoże roponośne
2. Dodanie surfaktanta do wody
3. Surfaktant zmniejsza
napięcie międzyfazowe
Microbial Enhanced Oil
Recovery
emulsja (w/o)
inoculum
woda
para wodna
powietrze