biogas purification using water scrubbing systems - Indian Institute ...

BIOGAS PURIFICATION USING
WATER SCRUBBING SYSTEMS
Dr. Virendra K. Vijay
Centre for Rural Development & Technology
Coordinator‐ Biogas Development and Training Centre
Indian Institute of Technology, Delhi
Hauz Khas, New Delhi, India
E‐mail: vkvijay@rdat.iitd.ernet.in

INTRODUCTION
• Biogas is clean environment friendly fuel that can be
obtained by anaerobic digestion of animal residues and
domestic and farm wastes, abundantly available in the
countryside.
• Biogas is an important renewable energy resource for rural
areas in India
• Biogas generally comprise of 55-65 % methane, 35-45 %
carbon dioxide, 0.5-1.0 % hydrogen sulfide and traces of
water vapor.
• Average calorific value of biogas is 20 MJ/m 3 (4713
kcal/m 3 ).

INTRODUCTION
Biogas like Liquefied Petroleum Gas (LPG) cannot be
liquefied under normal temperature and pressure.
Critical temperature required for liquefaction of methane
is -82.1 o C at 4.71MPa pressure, therefore use of biogas is
limited nearby the biogas plant.
An estimate indicates that India has a potential of
generating 6.38 X 10 10 m 3 of biogas from 980 million
tones of cattle dung produced annually.
The heat value of this gas amounts to 1.3 X 10 12 MJ. In
addition, 350 million tones of manure would also produce
along with biogas.

ORGANIC WASTES & THEIR ESTIMATED
AVAILABILITY IN INDIA
Sr.
No.
Organic Wastes Estimated Quantity
1. Municipal Solid waste 30 million tons/year
2. Municipal liquid waste 12000 million litres/day
3. Distillery (243 units) 8057 kilolitres/day
4. Press mud 9 million tons/year
5. Food & fruit processing wastes 4.5 million tons/year
6. Willow dust 30000 tons/year
7. Dairy industry waste 50-60 million litres/day
8. Paper & pulp industry waste (300
mills)
1600 m 3 /day
9. Tannery (2000 units) 52500 m 3 waste water/day
Source: MNES Report, Renewable Energy in India and business opportunities, MNES. Govt. of India, New Delhi, 2001

BIOGAS PROGRAMMES
On-going Programmes:
• National Biogas and Manure Management
Programme (NBMMP).
• Biogas Based Distributed/ Grid Power Generation
Programme.
5

BIOGAS PRODUCTION PROCESS
Biogas production process (Anaerobic digestion) is a multiple-stage
process in which some main stages are:
Chemical reactions involved in biogas production:
C 6H 12O 6 → 3CO 2 + 3CH 4
CO 2 +4H 2 >CH 4 +2H 2O
CH 3COOH > CH 4 + CO 2

THE QUANTITY, RATE AND COMPOSITION OF BIOGAS
GENERATED DEPENDS ON
The nature and concentration of the substrate,
Feed rate,
pH value,
Bacterial population,
Temperature, and
Chemical inducers.

BIOGAS PRODUCTION POTENTIAL FROM
DIFFERENT WASTES

UTILIZATION OF BIOGAS
Cooking: Biogas can be used in a specially designed burner for cooking
purpose. A biogas plant of 2 cubic metres capacity is sufficient for providing
cooking fuel needs of a family of about five persons.
Lighting: Biogas is used in silk mantle lamps for lighting purpose. The
requirement of gas for powering a 100 candle lamp (60 W) is 0.13 cubic metre
per hour.
Power Generation: Biogas can be used to operate a dual fuel engine to
replace up to 80 % of diesel-oil. Diesel engines have been modified to run 100
per cent on biogas. Petrol and CNG engines can also be modified easily to use
biogas.
Transport Fuel: AfterremovalofCO2,H2Sand water vapor, biogas can be
converted to natural gas quality for use in vehicles.

BIOGAS DEVELOPMENT AND TRAINING CENTRES
(BDTCS)
For training and publicity purposes, Eleven Biogas
Development and Training Centres (BDTCs) are
functioning, one each in Assam, Himachal Pradesh,
Karnataka, Madhya Pradesh, Punjab; Rajasthan, Tamil
Nadu, Uttar Pradesh, West Bengal and Uttarakhand.
One BDTC has been started in IIT Delhi in 2008.
Central financial assistance is provided to these Centres
for staff and training courses.
BDTCs focus on the training of masons and
entrepreneurs to improve quality of construction of
biogas plants and to follow standard specifications &
approved construction techniques.

NEED FOR THE BIOGAS REFINING AND
BOTTLING
Potential of biogas is not fully utilized and commercialized so far.
For commercialization, its area of application may widen; from
cooking fuel to vehicle fuel.
For use as a vehicle fuel, it should be bottled like CNG.
Before bottling, it should enriched in methane content from 55 %
to 95 %; similar to CNG.

CO 2 & H 2S REMOVAL PROCESSES FROM BIOGAS
Process Advantage Disadvantage
PSA Economy in production with comparatively
high purity. Capital costs are moderate.
Relatively quick installation and start up.
Water
Scrubbing
Simple process, remove both H 2SandCO 2
using a water stream.
Not much scalability in production.
Equipment maintenance on the higher
side ,Chemical regeneration is required
High pressure, difficulty in recovery of
CO 2
Cryogenic High purity . Capital cost high. Requirement of
large sites. Longer start-up and shut
down process. Limited scalability in
production.
Membrane Fast installation and start up .Production of
Economically not viable. Not suitable
output is flexible .Purity and flow rate can for high purity needs. Consumes
vary.
relatively more electricity per unit of
gas produced.
Chemical
Absorption
The chemical absorbents are more efficient
in low pressure
Regeneration of the solvent requires a
relatively high energy input. Disposal
of by product formed due to chemical
reaction is a problem

THE DESIGNING OF THE PACKED BED SCRUBBER
INVOLVED THE FOLLOWING STEPS:
Assumptions of basic data
Solubility data generation
Material balance and determination of water flow rate
Selection of packing material
Determination of column diameter
Determination of the height of the packed bed column
Selection of packing support and water distributor

WORKING OF SCRUBBING SYSTEM
Water scrubbing method is found most suitable
for biogas enrichment in rural areas.
Water is good solvent for CO 2.
The solubility of CO 2 in water is governed by
variation in pressures and temperatures.

SYSTEM OPERATION
Raw biogas is compressed up to 1.0 MPa
pressure to enhance solubility of CO 2 in water.
Pressurized biogas is sent into bottom section of
the scrubber.
Packing material is used to enhance the contact
time (interfacial area) between gas and water.
Pressurized water is sprayed from top to absorb
the CO 2 from pressurized biogas.

COMPRESSION UNIT
Multi stage compressor : compression of
methane enriched biogas at 20 MPa Pressure
in cylinder.
Filters : for moisture removal.
Cylinders: High pressure, seamless, steel
cylinders that are already in being use for
CNG application.
Pipe fittings and accessories : G.I.

Water Tank
Pump
Biogas
Digester
Biogas (CH 4 CO 2) Moisture Removal
Flow Meter
Single Stage Compressor
Gas Storage Pressure Vessel
Water
Biogas Scrubber
Gas Storage Pressure Vessel
Moisture Filters
Pressure Reducers
Three Stage Gas
Compressor
Dissolved CO2 in
Water
Enriched Biogas
High Pressure Cylinders for Storage of Enriched
Gas

BIOGAS ENRICHMENT AND BOTTLING
SYSTEM
1-Biogas plant
11-Safety valve
2-Ball valve
12-Water sprayer
3-Water remover
13-Flange
4-Receiver mounted compressor 14-View glass
5-Pressure gauge
15-Water outlet
6-Gas Storage Vessel
16-Water pump
7-Rotameter
17-Gas filter
8-Supporting stand
18-Pressure reducer
9-Reshching rings
19-Three stage gas compressor
10-Scrubber
20-CNG Cylinder
1
2
3
5
4
6 7
Fig.1: Experimental setup for biogas purification and bottling
9
12
10
11
15
8
13
16
14
NOT TO SCALE
17
20
18
19

Water Out
Enriched Biogas
Water In
Raw Biogas
CO 2 SCRUBBING SYSTEM
Top Section
Middle Section
Bottom Section
500
mm
3500
mm
800
mm
150
mm
Not to scale
Enriched
Biogas
Water In
Packing
Supporting
Stand
Raw
Biogas
Water Out
Schematic Diagram of Packed Bed Column

SUCCESS CASE STUDIES OF BIOGAS AS AUTOMOTIVE
FUEL
•Rajasthan Go Sewa Sangh, Durgapura, Rajasthan:
•Plant started in 2007 and has been running successfully. A three
wheeler runs on biogas daily about 100 km. and approximate 4 kg
Bio-CNG is required.
•Shri Krishna Goshala, Ghaziabad:
•Plant started in 2009 and has been running successfully.
•
•Shri Madhav Go Vigyan Anusandhan Sansthan, Bhilwara,
Rajasthan:
•Plant started in 2009 and has been running successfully.

AUTOMOTIVE CAR AND THREE WHEELER
RUNNING ON ENRICHED BIOGAS

COST-ECONOMICS OF THE SYSTEM
The Cost of Biogas plant (1000 NM 3 /Day Capacity) is
approx. Rs. 60 lakhs
Biogas purification and bottling system is approx. Rs. 55
lakhs (excluding the cost of cylinder for gas storage)
slurry management and processing cost to produce dry
manure is Rs. 20 Lakhs
other costs like land preparation, civil work, high
pressure gas storage cylinders Taxes, logistic etc. is
appox. Rs.15 Lakhs.
total initial cost is Rs. 1.5 Crores of the whole system
with annual profit of approx. Rs. 34.125 Lakhs.

POSSIBLE ENTREPRENEURIAL AVENUES
Large Scale/ Community level Biogas Enterprises for
1. Cooking needs- Pipeline supply
2. Electricity Production and Supply
3. Rural sanitation & bio manure production
4. Cylindering of methane available from biogas plant for vehicles
and production of bio manure

CONCLUSIONS
India has second largest biogas programme in the world at rural and
as well as urban levels.
Many technologies/models have been successfully developed in
India for biogas programme.
There is need to develop a sustainable renewable energy programme
on biogas for replacing petroleum products by utilization of biogas
in the country.
This will help in green energy technology and reducing green house
gases emissions.

Biogas is a potential renewable energy source for rural India and
other developing countries.
Biogas generation and subsequent bottling will cater the energy
needs of villages, supply enriched manure and maintain village
sanitation.
The bottling system will work as a decentralize source of power
with uninterrupted supply using local resources, generate ample
opportunities for employment and income of the rural people.

THANK
YOU