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Sunday, December 17, 2017

HOW TO START UP AND RUN A BIO GAS PLANT

HOW TO START UP AND RUN A BIO GAS PLANT

FOR MORE DETAILS
www.envoprojects.com     9899300371 9810004529


SUNDAY, MAY 02, 2004


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.
pH control
If required then only Lime should be added in the Mesophilic anaerobic digester to maintain pH at 7.5  for optimum gas production. 

Avoid dozing of lime in Methanogenic digester if proper mixing arrangement is not provided
Negative pressure
No Negative pressure inside anaerobic digester. Watch pressure gauge.
RECYCLE OF LEACHATE
Recycle leachate to Mesophilic Anaerobic Digester to increase bactaria count.
Recycle of H2S
Recycle  H2S  to Mesophilic Anaerobic Digester for short mixing period.
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

SOME LITERATURE STUDY FOR PROBLEM SOLVING :
When bio gas digester start producing gas
https://www.researchgate.net/post/When_do_biogas_digesters_start_to_produce_biogas
https://www.researchgate.net/post/How_do_you_prepare_inoculum_for_the_biogas_digester_in_the_absence_of_animal_manure
https://www.researchgate.net/post/What_is_the_expected_biogas_production_from_1_kg_of_kitchen_waste

Anaerobic digestion process depends on substrate composition, load, digester type, mixing of substrate, quality of methanogens and other parameters, but also to a great extent on temperature. You didn't specify at what temperature your process has been carried out. For example, thermophilic digestion operates in temperatures above 50°C and can be much (up to ten times) faster than mesophilic process, for which optimum temperature is in range 35-40°C.



It can be explained in several ways. First, several factors including substrate type (biodegradability), organic loading, source of inoculum, temperature, pH, mixing, physical parameters of the reactor (geometry) and the activity of methanogens predominantly determine the biogas potential of an anaerobic digester. If you think all these parameters are quite normal to previous works, then, source of inoculum or the activity of methanogens could play a major role during the start up of this digester. For example, if you take seed sludge from a similar bioreactor with high methanogenic activity, then you should see a quicker adaptation than the normal. To understand it clearly, perform a SMA test (specific methanogenic activity test) with acetate or acetate + propionic+butyric as a substrates. Most importantly, did you check the composition of the biogas? During start up, you can even observe hydrogen (during acetogenesis step) and also carbon dioxide.

3 years ago
Sjoerd Nienhuys
Added an answer


The reactor will start producing biogas almost instantly, but before you can use it you need to empty the first batch of gas completely (from fixed containers or domes), otherwise the gas contains oxigen from the air; this is an explosive mix.



Not enough information on the system. But I know when I did pilot tests long ago on   continuous stirred tank reactor (CSTR) anaerobic digesters under mesophilic conditions with different types of domestic sludge from wastewater plants, and freshly started up, gas did get produced within 7 days. Depend on the waste, conditions and reactor type and so on as others have also pointed out. See some links below:



















Also came across this innovative renewable biogas system marketed from Kenya - claims  biogas production in 7-10 days. See link below:











Effect of initial pH on anaerobic co-digestion of kitchen waste and cow manure

Abstract https://www.sciencedirect.com/science/article/pii/S0956053X15000082

Highlights

Five different initial pHs were controlled in co-digestion of kitchen waste with cow manure.
The modified Gompertz equation was used to predict the potential of methane production.
The highest CH4 yield was achieved at initial pH of 7.5.
This study investigated the effects of different initial pH (6.0, 6.5, 7.0, 7.5 and 8.0) and uncontrolled initial pH (CK) on the lab-scale anaerobic co-digestion of kitchen waste (KW) with cow manure (CM). The variations of pH, alkalinity, volatile fatty acids (VFAs) and total ammonia nitrogen (NH4+–N) were analyzed. The modified Gompertz equation was used for selecting the optimal initial pH through comprehensive evaluation of methane production potential, degradation of volatile solids (VS), and lag-phase time. The results showed that CK and the fermentation with initial pH of 6.0 failed. The pH values of the rest treatments reached 7.7–7.9 with significantly increased methane production. The predicted lag-phase times of treatments with initial pH of 6.5 and 7.5 were 21 and 22 days, which were 10 days shorter than the treatments with initial pH of 7.0 and 8.0, respectively. The maximum methane production potential (8579 mL) and VS degradation rate (179.8 mL/g VS) were obtained when the initial pH was 7.5, which is recommended for co-digestion of KW and CM.


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