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

microbes

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