Download - Biogas Power Point Final
BiogasThe Anaerobic Digestion Process
Andrew Gabriel and Tidasate Success
What exactly is biogas (composition)? What is the biological process by which it is
created? What type of substance is used in this
process? What are the three stages of the biogas
production process?
Things you should learn from this presentation
Biogas is a gas composed of methane and carbon dioxide
It is desired for its highmethane content foruse as a fuel
What is biogas?
The commercial recovery of biogas hasn’t been a main concern in industry until the mid 1970’s the fuel’s potential was realized. Today, farm based anaerobic digestion facilities are the most common in biogas production industry. Most of these facilities use the biogas as an energy source for their own usage.
History
The process by which biogas is produced Uses carbonaceous organic matter In the absence of oxygen
C6H12O6 → 3CO2 + 3CH4. (Organic Material) (Carbon Dioxide) (Methane)
Anaerobic Digestion
sewage sludge solids refuse food waste biomass including plants Crops plant and crop wastes industrial liquids and solids anything else organic
Anaerobic Digestion:Carbonaceous Organic Matter
The three main stages are: Hydrolysis/fermentation Acid phase digestion Acetogenesis Methane phase digestion
Anaerobic Digestion
Legend 1. Feeding header
2. Gas header3. Gas collecting system
Methanisation stage
Hydrolyse
stage
Methanisation stage
Feeding piping
Evacuated into the
substrate storage
Anaerobic Digestion
Bioreactor type: fixed dome and floating drum◦ Other types include balloon, horizontal, earth-pit
ferrocement plant
Bioreactor Design Parameters
Parts of the plant:◦ Mixing pit ◦ Digester◦ Strirring system◦ Gas holder◦ Slurry storage◦ Heating system◦ Pumps◦ Rings
Bioreactor Design Parameters
Solids content◦ High or low◦ Wet or dry
Temperature:◦ Psychrophilic◦ Mesophilic◦ Thermophilic
Operating Parameters
C:N ratio 15:1-25:1 Excess Carbon
◦ organic acids: lower pH Excess Nitrogen
◦ Ammonia: higher pH
Operating Parameters
Acidity: Carbon Nitrogen ratio
◦ 30:1◦ Excess Carbon
organic acids: lower pH◦ Excess Nitrogen
Ammonia: higher pH
Operating Parameters
Daily◦ Gas pressure, substrate temperature, gas
production, strong sludge odor Weekly
◦ Clean gas appliances, lubricate movable parts, control gas appliances
Monthly◦ Maintenance of slurry agitator
Annually◦ Check for corrosion
Maintenance
Main producers of biogas come from: Farm based facilities Waste water treatment plants Sewage treatment plants
Biogas Producers
In 1977 Pacific Gas and Electric Co. and Southern California Gas Co. contracted Bio Gas of Colorado
Project used waste from 30,000 head of cattle
Two 21,300 gallon digesters 1.5 million standard cubic feet per day of
biogas (60% methane composition) average-year gas cost was $3.44/million Btu Average retail cost that year was $10.99
Imperial Valley Biogas Project
contribute to a number of health hazards to humans.
These emissions are regulated by The United States Clean Air Act and Title 40 Part 59 of the Code of Federal Regulations (CFR).
volatile organic compounds (VOCs)
For employers to ensure employee safety dealing with flammable or explosive materials:◦ Dangerous substances◦ Control measures to remove risks.◦ Controls to reduce the effects of any incidents.◦ Plans and procedures to deal with accidents,
incidents and emergencies.◦ Employees are trained to deal with the risks.◦ Classify areas where explosive atmospheres may
occur and avoid ignition sources in those areas.
DSEAR Guidelines
Number of Reactors Single Stage
◦ Entire process in one step the two main phases can conflict with each other
Multi-Stage◦ hydrolysis and acid phase steps are combined,
and the methane phase digestion proceeds separately. Better pH regulation
Other Considerations
The size of the digester◦ Vd = Sd x RT [cubic meter/days x number of days]
Daily gas production◦ Based on volatile solids content G = VS x Gy◦ Weight of the moist mass B: G = B x Gy◦ STD gas yield values per livestock unit
Digester loading◦ Daily total solids input
The size of the gas holder◦ depends on the relative rates of gas
generation/consumptions
Calculations
Biogas is made up of methane and carbon dioxide
Biogas is produced through the process of anaerobic digestion
The substance used in this process is carbonaceous organic matter
The three stages of biogas production are ◦ Hydrolysis/fermentation◦ Acid phase digestion◦ Methane phase digestion
Conclusion
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Questions