STARTING UP A BIO GAS PLANT
POST NUMBER :08 Date : 02/05/2004
BIO GAS PLANT PROCESS
DESCRIPTION:
FLOW
CHART: CRUSHER(less than 7mm particle size)----thermophilic Aerobic
digester(Temp 55 degree C)---Mesophilic Anaerobic Digester(37 Degree C and pH at
7.5)---Manure Pit
Biotechnology process
stage one : hydrolysis by hydrolytic
bactaria, conversion of extracellular molecules
stage two : thermophilic
fermentation based on carbohydrates
stage three : synthesis of volatile
fatty acids by acetogenic bacteria
stage four : synthesis of methane by
methanogenic organisms
STARTING UP A BIO GAS PLANT:
OPERATION OF BIO GAS PLANT
FLOW CHART: CRUSHER(less than 7mm particle
size)----thermophilic Aerobic digester(Temp 55 degree C pH 5.5)---Mesophilic Anaerobic Digester(37
Degree C and pH at 7.5)---Manure Pit
Aspect
|
Bottlenecks
|
Remarks
|
CONTROLS
|
Check for Gas leaks
|
Check hood , pipe etc. Monthly checking of leakage by pressure system and
or with soap water
|
Cow dung slurry
|
Make slurry of cow dung and fresh
water in the ratio 2kg dung 15 liter water (thumb rule 10% dung of water
volume). Fill up the bio digester with the slurry.
|
Slurry fermentation
|
Wait for slurry to form gas. It
normally takes 3 to ten days.Gas formation can be seen by rising of floating
dome or pressure gauge in fixed dome.
|
Start of Feeding
|
Start fresh feeding after
formation of gas. Start with small quantity of feed material in 1:1 ratio.
After 15 days, start feeding full capacity.
|
Complete Release of first gas
produced
|
Gases
should be released to the atmosphere at least three times at
a gap of three days each.
It
may be needed to be released more till methane percentage of 60% reached .Do
a sample bio gas test to know exact position of gas produced.
|
Technical
|
Improper preparation of influent
solids
leading to blockage and scum
formation
|
Proper milling and other treatment
measures (pre-
soaking, adjustment of C/N ratio);
removal of inert
particles: sand and stone.
|
Temperature fluctuations
|
Careful regulation of temperature
through use of
incorporation of auxiliary solar
heating system.
|
Maintenance of pH for optimal
growth of
Methanogenic bacteria
C/N ratio
|
Appropriate choice of raw
material, regulation of
C/N ratio and dilution rate.
Appropriate mixing of N-rich and
N-poor
substrates with cellulosic
substrates.
|
Dilution ratio of influent solids
content
|
Appropriate treatment of raw
materials to avoid
stratification and scum formation.
|
Retention time of slurry
|
Dependent upon dilution ratio,
loading rate,
digestion temperature.
|
Loading rate
|
Dependent upon digester size,
dilution ratio,
digestion temperature.
|
Seeding of an appropriate
bacterial
Population for biogas generation
|
Development of specific and potent
cultures.
|
Corrosion of gas holder
|
Construction from cheap materials
(glass fibre,
clay, jute-fibre reinforced
plastic) and/or regular
cleaning and layering with
protective materials
(e.g., lubricating oil).
|
Pin-hole leakages (digester tank,
holder,
inlet, outlet)
|
Establishment of "no
leak" conditions, use of
external protective coating
materials (PVC,
creosotes
|
Occurrence of CO2 reducing
calorific
value of biogas
|
Reduction in CO2 content
through passage in
lime-water
|
Occurrence of water condensate in
gas
supply system (blockage, rusting)
|
Appropriate drainage system using
condensate
traps
|
Occurrence of H2S
leading to corrosion
|
On a village scale, H2S
removed by passing over
ferric oxide or iron filings
|
Improper combustion
|
Proper air gas mixing
appliances necessary
|
Maintenance of gas supply at
constant
pressure
|
Regulation of uniform distribution
and use of gas;
removal of water condensate from
piping systems;
appropriate choice of gas holder
in terms of weight
and capacity
|
Residue
utilization
|
Risks to health and plant crops
resulting
from residual accumulation of
toxic materials
and encysted pathogens
|
Avoid use of chemical industry
effluents; more
research on type, nature, and
die-off rates of
persisting organisms; minimize
long transportation
period of un-dried effluent
|
Health
|
Hazards to human health in
transporting
night soil and other wastes
(gray-water)
|
Linkage of latrine run-offs into
biogas reactors
promotes non-manual operations and
general
aesthetics
|
Safety
|
Improper handling and storage of
methane
|
Appropriate measures necessary for
plant
operation, handling, and storage
of biogas through
provision of extension and
servicing facilities
|
DO NOT USE
eggshells, Onion peels or left-over bones in this system as they will affect
the efficient functioning of the system
Hazards: Methane in a concentration of 6 to 15 percent with air
is an explosive mixture. Since it is lighter than air, it will collect in
rooftops and other enclosed areas. It is relatively odorless and detection may
be difficult. Extreme caution and special safety features are necessary in the
digester design and storage tank