Download - Biogas technology
BIOGAS PLANTS
FOR
RURAL AND INDUSTRIAL
WASTE WATER TREATMENT
1
BIOMETHANATION
Biogas Technology: Topics 2
Biogas Basics - Global Carbon Cycle -
Utility – Composition and Properties – Purify
for use as engine fuel- Rural Applications of
biogas - Feedstock for biogas: Aqueous
wastes containing bio-degradable organic
matter, animal residues.
Biogas Technology: Topics 3
Dry and wet fermentation.
Microbial and biochemical aspects.
Operating parameters for biogas production
by anaerobic digestion.
Kinetics and mechanism of biomethanation.
Biogas Technology: Topics 4
Digesters for rural application.
MNES Recognized Rural biogas-plant
models.
High rate digesters for industrial waste water
treatment.
Biogas Basics 5
• What is biogas?
• Biogas originates from bacteria by bio-
degradation of organic material under
anaerobic (without oxygen) conditions.
• The generation of biogas is an important
part of the biogeochemical carbon cycle.
Biogas Basics 6
• Methanogens (methane producing bacteria) are the last link in a chain of micro-organisms that degrade organic material and return the decomposition products to the environment, producing biogas.
Methane in atmosphere, from biogenic sources: 90 %
Methane in atmosphere, from petro-sources: 10%
UTILITY OF RURAL BIOGAS PLANTS 7
ENERGY RECOVERY:
FOR COOKING, LIGHTING, PUMPING, OR
POWER- - WITH BURNER, MANTLE LAMP,
ENGINE-PUMP AND GENERATOR
HYGIENIC DISPOSAL OF ANIMAL WASTE AS
MANURE
SUBSTITUTES FOR FUELWOOD &
KEROSENE
Anaerobic digestion process contributes to: 8
Energy recovery and reduction of greenhouse gas
[methane] emissions from open WWT ponds gives
environmental benefit also.
Substitutes for fossil fuels by utilizing methane
generated from the waste.
The energy generation from industrial wastewater, with
recycling of recovered water has double benefit in
India.
Biogas and the Global Carbon Cycle 9
Through microbial activity, 590-880 million
tons of methane are released into
atmosphere worldwide per annum.
In the northern hemisphere, the present
tropospheric methane concentration
amounts to about 1.65 ppm.
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Rural Applications of biogas plant
Compositon of Biogas 11
Composition:
60 to 70 per cent Methane,
30 to 40 per cent Carbon Dioxide,
traces of Hydrogen Sulfide, Ammonia
and Water Vapor
12
Properties of Biogas 13
It is about 20% lighter than air (density is
about 1.2 gm /liter).
Ignition temp is between 650 and 750 C.
Calorific value is 18.7 to 26 MJ/ m3 (500 to
700 Btu/ ft3.)
Calorific value without CO2: is between
33.5 to35.3 MJ/ m3
Explosion limit: 5 to 14 % in air.
Properties of Biogas continued
14
Air to Methane ratio for complete
combustion is 10 to 1 by volume.
One cubic meter of biogas is equivalent
to 1.613 liter kerosene or 2.309 kg of
LPG or 0.213 kw electricity.
Biogas Purification
15
Removal of CO2: Scrubbing with limewater or
ethanol amine solution.
Removal of H2S: Adsorption on a bed of iron
sponge and wood shavings.
Pressure & Temperature needed to liquefy:
Biogas needs 500 psi, at –83 C & LPG
Needs 160 psi, at ambient temperature.
Biogas Purification
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Biogas Purification
High Pressure Water Scrubbing 17
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The water scrubbing process contains two main waste
streams. The first waste stream is the exhaust of air which
was used to strip the regenerated water. This stream mainly
consists of air and a high percentage of CO2 but also
contains traces of H2S. Because H2S is rather poisonous
this stream needs to be treated. Also the stream contains
small amounts of CH4 Because CH4 is far more damaging to
the environmental than CO2 the CH4 in this stream should be
burned.
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Biogas as I.C. engine Fuel
20
Traces of H2S, NH3, water vapor to be removed by
absorption/adsorption.
With modified fuel injection system, in stationary
diesel or petrol engine biogas can be used.
In Diesel engine, dual fuel mode is needed.
After initial start up with petrol, engine can run on
biogas
Substrate and Material Balance of Biogas Production
21
Homogenous and liquid biodegradable
substrates are suitable for simple biogas
plants.
The maximum of gas-production
from a given amount of raw material
depends on the type of substrate.
WET BIODEGRADABLE WASTES:
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WASTE STARCH & SUGAR
SOLUTIONS:
Fruit processing, brewery, press_mud-from sugar factory etc
OTHER HIGH B O D EFFLUENTS:
Leather industry waste.
Pulp factory waste liquor
FEED FOR BIOGAS : WET
BIODEGRADABLE WASTE 23
DOMESTIC ANIMAL WASTES: Excreta of
cow, pig, chicken etc
MANURE, SLUDGE: Canteen and food
processing waste, sewage
MUNICIPAL SOLID WASTE: After
separation of non-degradable
WET FERMENTATION:
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FEED SUBSTRATE TOTAL SOLID CONCENTRATION,
(TSC) = 8 TO 9 % FOR COW DUNG,
RATIO OF DUNG TO WATER = 1:1
BIOGAS PRODUCED IS:
IN SUMMER AT 47 C, 0.06 M3 / KG DUNG ADDED
/ DAY
IN WINTER AT 8 C, 0.03 M3 / KG DUNG ADDED
/ DAY
DRY FERMENTATION OR
SOLID STATE FERMENTATION: 25
FEED SUBSTRATE TOTAL SOLID
CONCENTRATION, ( TSC) OF 20 TO 30 %,
A MIX OF COW DUNG AND A WIDE
VARIETY OF AGRO - RESIDUES.
DRY FERMENTATION OR SOLID STATE
FERMENTATION :
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FOR CATTLE DUNG AND MANY AGRO-
RESIDUES AT INITIAL CONCENTRATIONS
OF TSC BETWEEN 16 TO 25 % , BIOGAS
PRODUCTION HAS BEEN DEMONSTRATED
SATISFACTORILY IN SMALL BATCH TYPE
AND PLUG FLOW TYPE DIGESTERS.
Biology of Methanogenesis
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• This knowledge is necessary for planning,
building and operating biogas plants.
• Microbial Decomposition Occurs in Three
Stages: Hydrolysis, VFA Formation and
Methane formation.
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1. Hydrolysis of Biopolymers like
carbohydrates and proteins To Monomers
2. Convert sugars, amino acids, fatty acids
to H2, CO2, NH3, Acetic, Propionic And
Butyric Acids [VFA]
3. Convert [H2, Co2, Acetic Acid] To CH4
And CO2 Mixture
Biochemistry of Anaerobic Digestion 29
• Methanogenic bacteria take up acetic acid, methanol,H2, CO2 to produce methane
• O2,nitrites,nitrates etc. inhibit activity
• Acid formation and bicarbonate formation by two set of bacteria is balanced, the pH and biomethanation are stabilized.
Operating parameters affecting gas production:
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• Temperature: Optimum =35 C
• pH range: 6.8 to 7.8
• Favorable C/N ratio is 30:1
• Proportion of solids to water: 10 % for optimum operation
• Retention time: ratio of volume of slurry in digester to volume fed into/ removed from it per day=30 days for Temp. of 25-35 C
KINETICS OF DIGESTION 31
Refer: Chen and Hashimoto, Biotechnology
Bio-engineering Symposium 8, (1978) p
269-282 and
Biotechnology Bioengineering (1982) 24: 9-
23
KINETICS OF DIGESTION continued
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For a given loading rate, [So/HRT], daily
volume of methane per volume of digester
depends on
biodegradability of influent(Bo) and
kinetic parameters k & m
KINETICS OF DIGESTION continued
33
• Volumetric methane rate in cubic meter gas per
cubic meter of digester volume/day
• V = (Bo So / HRT)[1- K / (HRT*m-1+K)]
• Bo = Ultimate methane yield in cubic meters
methane / kgVS (Varies from 0.2 to 0.5)
• So = Influent volatile solids concentration
in kg VS /cubic m
KINETICS OF DIGESTION, CONTINUED
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(Loading rate range = 0.7 to 25 kg VS/m3 d)
HRT = Hydraulic retention time in days
K = Dimensionless kinetic parameter, for cattle
dung, K= 0.8+ 0.0016e0.06 So
m = Maximum specific growth rate of the
microorganism in day-1
TYPES OF RURAL BIOGAS PLANTS 35
FIXED DOME: JANATHA, DINABANDHU,
UTKAL / KONARK
FLOATING DRUM: K.V.I.C
COMBINED FEATURES: PRAGATI
FIXED DOME: JANATHA 36
DIGESTER WELL BELOW GROUND LEVEL
FIXED DOME GAS HOLDER BUILT WITH BRICK & CEMENT
BIOGAS FORMED RISES PUSHES SLURRY DOWN
DISPLACED SLURRY LEVEL PROVIDES PRESSURE-UPTO THE POINT OF ITS DISCHARGE/ USE
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K.V.I.C floating drum plant 38
MASONRY CYLINDRICAL TANK
ON ONE SIDE INLET FOR SLURRY
OTHER SIDE OUTLET FOR SPENT SLURRY
GAS COLLECTS IN INVERTED ‘DRUM’ GAS HOLDER OVER SLURRY
GAS HOLDER MOVES UP & DOWN DEPENDING ON ACCUMULATION OF GAS /DISCHARGE OF GAS, GUIDED BY CENTRAL GUIDE PIPE
K.V.I.C floating drum plant continued
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GAS HOLDER (MILD STEEL): PAINTED ONCE A YEAR.
K V I C Mumbai
MEDIUM FAMILY SIZE BIOGAS PLANT HAVING GAS DELIVERY OF 3 M3 /DAY REQUIRES 12 HEAD OF CATTLE AND CAN SERVE A FAMILY OF 12 PERSONS
Floating drum (rural) 40
K.V.I.C floating drum plant 41
Dinabandhu model
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Dinabandhu model
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Pragati rural biogas plant
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Pragati rural biogas plant 45
•COMBINES FEATURES OF KVIC &
DEENABANDU,DEVELOPED IN
MAHARASHSTRA
•LOWER PART: SEMI-SPHERICAL IN
SHAPE WITH A CONICAL BOTTOM
•UPPER PART: FLOATING GAS HOLDER
•POPULARIZED IN MAHARASHTRA,
UNDARP, PUNE
UTKAL / KONARK DIGESTER 46
SPHERICAL IN SHAPE WITH GAS STORAGE CAPACITY OF 50%
CONSTRUCTION COST IS REDUCED AS IT MINIMIZES SURFACE AREA
BRICK MASONRY OR FERROCEMENT TECHNOLOGY
A PERFORATED BAFFLE WALL AT THE INLET PREVENTS SHORT CIRCUITING PATH OF SLURRY (OPTIONAL)
UTKAL / KONARK DIGESTER
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FERROCEMENT, FRP DIGESTER: 48
CAST SECTIONS, MADE FROM A REINFORCED (MORTAR+WIRE MESH)- COATED WITH WATER PROOFING TAR
S E R I, ROORKEE
FIBER REINFORCED PLASTIC MADE BY CONTACT MOULDING PROCESS
FLEXIBLE PORTABLE NEOPRENE RUBBER MODEL
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FOR HILLY AREAS, MINIMIZES TRANSPORT COST OF MATERIALS
BALLOON TYPE, INSTALLED ABOVE GL, MADE OF NEOPRENE RUBBER
FOR FLOOD PRONE AREAS, UNDERGROUND MODELS NOT SUITABLE
SWASTHIK COMPANY OF PUNE DESIGN
HIGH RATE BIOGAS PLANTS FOR
INDUSTRIAL WASTE WATER TREATMENT 50
Brings down high BOD content to make it suitable
for aerobic biological treatment
Faster disposal of waste water with partial
recovery of energy as fuel [biogas]
Suitable for food processing waste water of high
BOD content
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• Industries Existing Bio- gas
plants units
• Distilleries 254 145
• Paper & Pulp 347 5
• Starch 13 1
INDUSTRIAL -WWT-BIOGAS PLANTS Present status in India
.
Indian Technology supplier –
Foreign collaborator 52
Degremont India Limited
Hindustan Dorr-Oliver
Sakthi Sugars Limited
UEM India (Private) Limited
Degremont, France
Dorr-Oliver, USA
SGN, France
ADI International, Canada
Indian Technology supplier -Foreign collaborator …
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Kaveri Engineering. Industries Limited
Western Paques India Limited
Western Bio Systems Limited
Vam Organic Chemicals Limited
Dewplane, UK
Paques, Netherlands
Sulzer Brothers, Switzerland
Biotim N V, Belgium
TYPES OF HIGH RATE BIOGAS PLANTS 54
ANAEROBIC CONTACT
ANAEROBIC FILTER:UPFLOW, DOWNFLOW
UPFLOW ANAEROBIC SLUG BLANKET
ANAEROBIC FLUIDISED/ EXPANDED BED
ANAEROBIC ROTATING CONTACTOR
Anaerobic contact digester 55
Anaerobic filter, downflow reactor
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Upflow Anaerobic Sludge Blanket Digestor 57
Fluidized/expanded bed reactor
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Applications of Biogas and Appliances needed:
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1. Cooking fuel- Stove / Burner.
2. Lighting Fuel- Mantle lamp.
3. Dual fuel stationary I. C. Engine –To run a
pump for drawing water
4. Dual fuel stationary I. C. Engine –To run a
generator for electricity.
Biogas burner & lamp 60
Both biogas burner and mantle lamp have some
structural similarity: each have inlet gas nozzle, air
inlet, & a mixing chamber.
Burner has fire-stove plate
Lamp has mantle that glows to emit light
Features of Biogas Stove 61
Operate at pressure:75-90 mm [3-3.5 inch] water
column; Air/Gas ratio is 10:1; Nozzle adjustment
necessary.
Temperature: About 800 C
For cooking, 0.28 to 0.42 m3 of biogas per person per
day is consumed.
Design different from those of LPG/Natural Gas stoves.
Features of biogas lamp: 62
Brightness depends on gas pressure, air to
gas ratio, extent of mixing etc. Proper nozzle
adjustment is necessary to achieve required
light intensity.
Lamps designed for 100 candle-power
consume 0.11 to 0.15 m3 biogas per hour.
Biogas for electricity Generation 63
One kwh can be generated from 0.7m3 of
biogas to light 15 bulbs [60watts] for one hour.
For lighting, power route is better than direct
burning
Economical for large sized plants, requires
high initial capital investment.
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TEXT BOOKS AND REFERENCES
1. Biotechnology Volume 8, H. J. Rehm and G. Reed, 1986, Chapter 5, “ Biomethanation Processes.‟ Pp 207-267 2. K. M. Mital, Non-conventional Energy Systems, (1997), A P H Wheeler Publishing, N. Delhi. 3. K. M. Mital, Biogas Systems: Principles and Applications, (1996) New Age International Publishers (p) Ltd, N. Delhi.
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References :
1. Effluent Treatment & Disposal: I Ch. E, U.K., Symposium Series No 96, 1986, P 137-147, Application of anaerobic biotechnology to waste treatment and energy production, Anderson & Saw. 2. “Anaerobic Rotating Biological Drum Contactor for the Treatment of Dairy Wastes‟, S. Satyanarayana, K. Thackar, S.N.Kaul, S.D.Badrinath and N.G. Swarnkar, Indian Chemical Engineer, vol 29, No 3, July-Sept, 1987