Combined H2S and CO2 removal process for upgrading biogas

ESR 4.1 : Keren Jenifer Rajavelu

Supervisor : Prof. Dr. Martin Denecke

Natural Gas

Heating value = 39

CH4 = 85 - 95 % (mol)

CO2 = 0.2 - 1.5 % (mol)

H20 = 0

H2S = 1.1 to 5.0 ppm

Biogas from AD

Heating value = 23

CH4 = 60 - 70 % (mol)

CO2 = 30 - 40 % (mol)

H20 = 1 - 5 % (mol)

H2S = 0 - 4000 ppm

Growth of biogas

industry 25% renewable

energy target

Upgrading biogas from AD – What makes the

difference?

Corrosion in engines and

pipelines, extremely toxic

Constant increase in

global average

concentration of CO2 in

earth's atmosphere !!

Research Aim

Basic concept Material and Methods Results

This presentation covers

Research aim and Structure of presentation

• Development of energy efficient,

scalable processes for hydrogen

sulphide H2S and CO2 removal

• Testing of individual lab scale reactor

for both processes

• Combination, optimization and

interaction of two process

The main reaction principle involved

H2S + ½ O2 Sº + H2O

Reference Bacterial

species

Source of

energy

Electron

acceptor

Process

of

removal

Kim and

Chang et al.,

1991

Chlorobium

limicola

light CO2 anaerobic

Alcantata et

al., 2004

Thiobacillus Sulphur CO2 aerobic

Lee et al.,

1993

Acidithiobacill

us thiooxidans

Sulphur CO2 aerobic

Ma et al.,

2006

Thiobacillus

denitrificans

Sulphur or

thiosulphide

nitrate aerobic

Gadekar et

al., 2006

Thiomicrospor

a sp.

Carbon

source

nitrate anaerobic

Cardoso et

al., 2010

Thiobacillus

denitrificans

Sulphur or

thiosulphide

nitrate anaerobic

Son et

al.,2005

Acidithiobacill

us

ferrooxidans

Sulphur iron aerobic

Biological desulphurization of biogas or

H2S removal

FISH analysis using alpha –

proteobacteria probe showed more

stable population of sulphur oxidizing

bacteria

Design of biotrickling filter system for H2S removal

Design of reactor

(scrubbing column)

Design of other

components parts

(aeration column, piping

and hosing etc)

Design of

alarm system

Monitoring of

parameters automated

and manually

Parameter Unit Current

design

Clean gas concentration mg/m3 <10

Raw gas concentration g/m3 1000

Height of carrier material h

Column ratio h:d

m 0.6 m

>3/1

Pressure loss Pa/m

Gas flow rate Q m3/h 0.02 to 0.08

Retention time S 12 s – 150 s

Volume of trickle bed m3 0.0007

Design according to guideline VDI 3478 part 2

Results

Experimental conditions

Experiment [H2S]

ppm

[H2S] LR

(g S- H2S m-3.h-

1)

EBRT

(s)

1 1000 14.285 250

2 1000 28.571 126

3 1000 57.428 62

4 1000 85.713 43

Effect of EBRT, RE and Dissolved oxygen

during initial operation

RE = [(Cin – Cout)] * 100

RE

Removal efficiency

V

Reactor bed volume m3

Cin

pollutant inlet

concentration

g pollutant. m-3

Cout

pollutant outlet

concentration

g pollutant. m-3

Results

LR = [(Q biogas + Q Air IN . CIN] / V

LR Loading Rate g pollutant .m-

3.h-1

Q biogas+Q

Air IN

Total gas flow

rate

CIN Pollutant inlet

concentration

g pollutant .m -3

V Reactor bed

volume

m3

EBRT = V / (Q biogas + Q Air IN)

EBRT empty bed

residence time

S

V Reactor bed

volume

m3

Q biogas

+ Q Air IN

Total gas flow

rate

g pollutant .m -3

EC and RE versus H2S loading rate (LR)

Design of CO2 absorption with bottom ash

Design of absorption

reactor (better the

width, lower is the

pressure drop)

Feed in of bottom

ash with different

size fractions

Study of absorption

capacity

Experimental set up for CO2 removal using bottom ash

Results

Experimental conditions

Test no 1 2 3 4 5 6 7

Grain size 0 – 1

mm

0 – 1

mm

0 – 1 mm 0 – 2

mm

0 –

2mm

0 – 2

mm

0 – 1

mm

Liquid /Solid

ratio

0.05 0.1 0.2 0.4 0.2 0.2 0.2

Bottom ash (g) 400 400 400 300 300 200 10

Flow rate

(ml/min)

10 10 10 500 90 500 60

Gas

composition

(v%)

99.8 99.8 99.8 99.8 99.8 99.8 99.8

Breakthrough

time (min)

60 60 40 - 10 - -

CO2 uptake

(g/kg of

Bottom ash)

10.96 14.56

12.63 - - - -

pH 9.2 9.1 9.2 - - - -

High absorption capacity

pH of noncarbonated

bottom ash showed

11.2

Results

Breathrough curve of CO2 with bottom

ash

Comparison of CO2 absorption with

different L/s ratio

high absorption of CO2

Test no 1 2 3

Initial bottom ash

mass (g of WS)

423.60 436.84 476.02

Final bottom ash

mass (g of WS)

428.12 442.07 479.95

CO2 fixation using

mass balance

(g/400g of BA)

4.52 5.23 3.93

CO2 fixation using

gas analysis and

flow (g/400g of BA)

5.05 5.825 4.386

CO2 uptake (g/kg

of BA)

10.96 14.56 12.63

Mass balance and CO2 uptake for test

1, 2 and 3

CO2 Absorption capacity as a function of

time

Significant increase in weight after CO2

absorption

Simultaneous removal of CO2 and H2S

Combination and optimization of both processes

Thanks for listening

This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement n. 316838

Project coordinated by the QUESTOR Centre at Queen’s University Belfast www.qub.ac.uk/questor