Production of Biogas - Fixed Dome Type Biogas Plant

Production of Biogas - Fixed Dome Type Biogas Plant

 

 Raw Materials Required

Forms of biomass listed below may be used along with water:

• Animal dung
• Poultry wastes
• Plant wastes ( Husk, grass, weeds etc.)
• Human excreta
• Industrial wastes(Saw dust, wastes from food processing industries)
• Domestic wastes (Vegetable peels, waste food materials)

Principle

Biogas is produced as a result of anaerobic fermentation of biomass in the presence of water.

Construction

The biogas plant is a brick and cement structure having the following five sections:

• Mixing tank present above the ground level
  
• Inlet chamber: The mixing tank opens underground into a sloping inlet chamber
  
• Digester: The inlet chamber opens from below into the digester which is a huge tank with a dome like ceiling. The ceiling of the digester has an outlet with a valve for the supply of biogas
  
• Outlet chamber: The digester opens from below into an outlet chamber
  
• Overflow tank: The outlet chamber opens from the top into a small over flow tank

• 

Working

• The various forms of biomass are mixed with an equal quantity of water in the mixing tank. This forms the slurry
  
• The slurry is fed into the digester through the inlet chamber. The temperature of the slurry must be maintained around 35 ^oC. Any drop in temperature will reduce the anaerobic activity and hence the yield of biogas
  
• When the digester is partially filled with the slurry, the introduction of slurry is stopped and the plant is left unused for about two months
  
• During these two months, anaerobic bacteria present in the slurry decompose or ferment the biomass in the presence of water
  
• As a result of anaerobic fermentation, biogas is formed, which starts collecting in the dome of the digester
  
• As more and more biogas starts collecting, the pressure exerted by the biogas forces the spent slurry into the outlet chamber
  
• From the outlet chamber, the spent slurry overflows into the overflow tank
  
• The spent slurry is manually removed from the overflow tank and used as manure for plants
  
• The gas valve connected to a system of pipelines is opened when a supply of biogas is required
  
• To obtain a continuous supply of biogas, a functioning plant can be fed continuously with the prepared slurry
• 
  

Advantages of Fixed Dome Type of Biogas Plant

• Requires only locally and easily available materials for construction
• Inexpensive
• Easy to construct
• Due to the above reasons, this plant is also called the Janata Gobar gas plant.

Advantages of Biogas as a Fuel

• As domestic fuel
• For street lighting
• For generation of electricity

• High calorific value
• Clean and excellent fuel containing upto 75% methane
• No residue produced
• No smoke produced
• Non - polluting
• The slurry is periodically removed and used as excellent manure which is rich in nitrogen and phosphorous
• Economical
• Can be supplied through pipe lines
• Burns readily - has a convenient ignition temperature Uses of Biogas
  
  • Biogas is used

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Biogas Plant Design

Introduction:
Biogas is based upon the use of dung to produce gas which is used as domestic fuel especially in rural areas. This technique is based on the decomposition of organic matter in the absence of air to yield gas consisting of methane (55%) and carbon dioxide (45%) which can be used as a source of energy.
Biogas is a gaseous fuel which may be directly burnt in a gas burner for the use as a cooking fuel or source of direct heat for thermal applications. It has a calorific value of 5871 kCal/m³.

Biogas Plant

The plant where biogas is produced is called biogas plant. The design of the plant is tailored to use cattle dung as feed stock. Cattle dung and water is mixed in the ratio of 1:1 and the resultant slurry containing 9% total solids is fed to the biogas plant by gravity. This slurry is retained in the digester for a period of 35-50 days. During this retention period, 35-40 liters of biogas is recovered per kg of dung fed.

Classification of Biogas Plants

Biogas generates from the disintegration of organic substrate and being lighter than air, rises upwards. This gas is collected in various types of drums. Therefore, according to the method of gas storage, biogas plants are of two types:

1. Floating dome biogas plants
2. Fixed dome biogas plants

Floating dome design: This design consists of a tank or a well with a partition wall to prevent shorting of influent fresh dung slurry with the outgoing spent slurry. The gas produced is trapped under a plastic or a metallic drum. With the continuous production more gas is trapped under this bell and the drum rises. This acts as a gas storage unit and when the tap above is released, the gas is discharged at more or less constant pressure.

Fixed dome design: This is designed to reduce the overall cost of the biogas plant. In this, the slurry is fed to a spherical masonry plant. When the gas is produced owing to the rigid nature of the masonry dome, the trapped gas exerts a pressure on the slurry surface and a corresponding amount of slurry is displaced into a wide outlet and inlet. As a result, the pressure of gas stored varies significantly.

 

RESOURCE :http://www.tutorvista.com

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DOWNLOAD PDF BIOGAS PLANT CONSTRUCTION, DESIGN

 DOWNLOAD PDF BIOGAS PLANT CONSTRUCTION, DESIGN

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Gobar Gas Plant construction [PPT]

[PDF] Biogas Notes

 

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Biogas, Gobar Gas Plant in India

Biogas Plant in India

Jo Lawbuary, HES

Contents

Introduction
Why biogas?
Methanogenesis
Evolution of biogas technology
Dissemination of biogas technology
Factors hindering spread of biogas
Conclusion
References

Tables and Figures

Tables:

1. Estimated potential of renewable technologies in India
2. Different biogas plants recognised by MNES
3. Daily dung requirements and dung fed

Figures:
Fig1. Process of methanogenesis
Fig2a. common biogas plants a: KVIC floating-drum model
Fig2b. Camartec fixed-dome model

Frontispiece:
Biogas promotion poster produced by the Khadi and Village Industry Commission
Introduction
Mahatma Gandhi, in his vision for India, envisaged a system of devolved, self-sufficient communities, sustaining their needs from the local environment, and organising income generating ventures around co-operative structures. Fifty years on, and Gandhi's vision of Swadeshi (self-sufficiency) for India, despite interpreted by some as a romantic and bucolic notion, is perhaps more urgent than ever. Diminishing forests, and a burgeoning, mainly rural biomass-dependent population of 984 million, necessitates a co-ordinated effort of rural India to supply itself with a dependable and sustained source of energy.
Biomass alone currently meets 57% of the national energy demand, (Tata, 1998) yet is rarely featured in any 'official' statistics of energy use, given perhaps its scattered nature, and its low status as fuel. Indeed, according to statistics, in 1995, 63.3% of India's energy production was from its reserves of low-grade coal, 18.6% from petroleum, while hydroelectricity, natural gas and nuclear accounted for 8.9%, 8.2%, and 1% respectively (EIA, 1998).
India's overall energy production in 1995 was approximately 8.8 quadrillion Btu (quads), while consumption was 10.5 quads. India's energy demand is increasing, and its inability to step up production to meet demand, has increased India's reliance on costly imports, the gap between consumption and production projected to widen into the next century, as demand for energy is projected to grow at an annual rate of 4.6% - one of the highest in the world (EIA, 1998). Energy for developing industries, transport, and a drive towards the electrification of India over the last three decades of an expanding residential sector, so that currently, a great percentage of villages in the subcontinent have access to the grid- as much as 90%, according to recent figures (EIA, 1998), have contributed to the energy production deficit.
However, as mentioned earlier, the conventional statistics do not take into account the informal and unorganised use of biomass, which is reputed to account for 57% of total energy, therefore, effectively energy from biomass more than equals the marketable energy production of 8.8 quads (However, given the inherent difficulty in estimating such a figure, there must be a wide margin of error, potentially). Fuelwood is the primary source of biomass, derived from natural forests, plantations, woodlots and trees around the homestead (Agarwal, 1998). Alarm regarding the state of India's forests, which were being lost at an estimated rate of 1.5 million hectares (Mha) in the early 1980's has kick started an intense afforestation and forest regeneration scheme that attempts to share management of forest resources between the forest department and local user communities. Afforestation appears to be showing up on satellite images on the subcontinent (Hall and Ravindranath, 1994), but whether ultimately, more fuelwood will be available to rural communities, will be more a political question.

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