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.

10

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

16

Biogas Purification

High Pressure Water Scrubbing 17

18

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.

19

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:

22

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:

24

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 :

26

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

27

• This knowledge is necessary for planning,

building and operating biogas plants.

• Microbial Decomposition Occurs in Three

Stages: Hydrolysis, VFA Formation and

Methane formation.

28

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:

30

• 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

32

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

34

(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

37

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

39

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

42

Dinabandhu model

43

Pragati rural biogas plant

44

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

47

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

49

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

51

• 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 …

53

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

56

Upflow Anaerobic Sludge Blanket Digestor 57

Fluidized/expanded bed reactor

58

Applications of Biogas and Appliances needed:

59

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