'Back to Biogas Portal
If you want to learn more, please visit our website Underground Biogas Plant.
Introduction
Construction of the digester neck with steel reinforcement[1]
Choosing a right biogas digester is a very important while constructing a biogas plant. From the standpoint of fluid dynamics and structural strength, an egg-shaped vessel is about the best possible solution. This type of construction, however, is comparatively expensive, therefore, its use is usually restricted to large-scale sewage treatment plants. The Chinese fixed-dome designs are of similar shape, but less expensive. The hemispherical CAMARTEC design is optimized in structural strength, but does not make optimal use of the excavation required.
Simplified versions of such digester designs include cylinders with conical covers and bottoms. They are much easier to build and are sometimes available on the market as prefabricated units. Their disadvantage lies in their less favorable surface-volume ratio. The cylinder should have a height equal to its diameter. Prone cylinders have become quite popular on farms, since they are frequently the more favorable solution for small-scale bio-methanation. Cuboid digesters are often employed in batch-fed systems used primarily for fermenting solid material, so that fluid dynamics are of little interest.
Types of Small-Scale Digesters
Fixed Dome Biogas Plants
A fixed-dome plant comprises of a closed, dome-shaped digester with an immovable, rigid gas-holder and a displacement pit, also named 'compensation tank'. The gas is stored in the upper part of the digester. When gas production commences, the slurry is displaced into the compensating tank. Gas pressure increases with the volume of gas stored, i.e. with the height difference between the two slurry levels. If there is little gas in the gas-holder, the gas pressure is low.
'Read more here...
Floating Drum Plants
Floating-drum plants consist of an underground digester and a moving gas-holder. The gas-holder floats either directly on the fermentation slurry or in a water jacket of its own. The gas is collected in the gas drum, which rises or moves down, according to the amount of gas stored.
'Read more here...
Low-Cost Polyethylene Tube Digester
The Low-Cost Polyethylene Tube Digester model consist of tubular polyethylene film (two coats of 300 microns) bent at each end around a 6 inch PVC drainpipe and is wound with rubber strap of recycled tire-tubes.
'Read more here....
Balloon Plants
A balloon plant consists of a heat-sealed plastic or rubber bag (balloon), combining digester and gas-holder. The gas is stored in the upper part of the balloon. The inlet and outlet are attached directly to the skin of the balloon.
'Read more here...
Horizontal Plants
Disadvantages: Problems with gas-space leakage, difficult elimination of scum.
'Go to Top
Earth-pit Plants
Masonry digesters are not necessary in stable soil (e.g. laterite). It is sufficient to line the pit with a thin layer of cement (wire-mesh fixed to the pit wall and plastered) in order to prevent seepage. The edge of the pit is reinforced with a ring of masonry that also serves as anchorage for the gas-holder. The gas-holder can be made of metal or plastic sheeting. If plastic sheeting is used, it must be attached to a quadratic wooden frame that extends down into the slurry and is anchored in place to counter its buoyancy. The requisite gas pressure is achieved by placing weights on the gas-holder. An overflow point in the peripheral wall serves as the slurry outlet.
Advantages
Disadvantages
'Go to Top
Ferro-cement Plants
The ferro-cement type of construction can be applied either as a self-supporting shell or an earth-pit lining. The vessel is usually cylindrical. Very small plants (Volume under 6 m3) can be prefabricated. As in the case of a fixed-dome plant, the ferrocement gasholder requires special sealing measures (proven reliability with cemented-on aluminium foil).
Disadvantages
'Go to Top
Industrial Digester Types
Control glasses for an industrial digester for solid organic waste, Germany[2]To give an overview, some fictitious designs have been chosen as they could be found in, for example, Europe. The designs are selected in a way that all the typical elements of modern biogas technology appear at least once. All designs are above-ground, which is common in Europe. Underground structures, however, do exist.
Mixing pit varies in size and shape according to the nature of substrate. It is equipped with propellers for mixing and/or chopping the substrate and often with a pump to transport the substrate into the digester. At times, the substrate is also pre-heated in the mixing pit in order to avoid a temperature shock inside the digester.
Fermenter or digester is insulated and made of concrete or steel. To optimize the flow of substrate, large digesters have a longish channel form. Large digesters are almost always agitated by slow rotating paddles or rotors or by injected biogas. Co-fermenters have two or more separated fermenters. The gas can be collected inside the digester, then usually with a flexible cover. The digester can also be filled completely and the gas stored in a separate gas-holder.
Gas-holder is usually of flexible material, therefore to be protected against weather. It can be placed either directly above the substrate, then it acts like a balloon plant, or in a separate 'gas-bag'.
Slurry store for storage of slurry during winter. The store can be open (like conventional open liquid manure storage) or closed and connected to the gas-holder to capture remaining gas production. Normally, the store is not heated and only agitated before the slurry is spread on the field.
Gas use element is in Europe in 95% of the cases a thermo-power unit which produces electricity for the farm, the grid and heat for the house, greenhouses and other uses. The thermo-power unit has the advantage, that the required energy can be produced in any mixture of gas and fossil energy. It can, therefore, react to periods of low gas production and high energy requirements or vice versa.
Concrete digester with two chambers (one heated, one unheated for storage)[2]
Concrete digester with integrated plastic gas-holder[2]
Steelvessel fermenter with seperate ballon gas-holder[2]
'Go to Top
Batch plants
Batch plants are filled and then emptied completely after a fixed retention time. Each design and each fermentation material is suitable for batch filling, but batch plants require high labor input. As a major disadvantage, their gas-output is not steady.
'Go to Top
Continuous plants
Continuous plants are fed and emptied continuously. They empty automatically through the overflow whenever new material is filled in. Therefore, the substrate must be fluid and homogeneous. Continuous plants are suitable for rural households as the necessary work fits well into the daily routine. Gas production is constant, and higher than in batch plants. Today, nearly all biogas plants are operating on a continuous mode.
'Go to Top
Semi-batch basis
If straw and dung are to be digested together, a biogas plant can be operated on a semi-batch basis. The slowly digested straw-type material is fed in about twice a year as a batch load. The dung is added and removed regularly.
'Go to Top
Dry Fermentation Plants
Dry fermentation is an anaerobic process in which micro-organism break down biodegradable material. Renewable organic feedstocks are used as a the source of energy for the process. The nutrient-rich solids resulting from the digestion can be used as a fertiliser subsequently.
Almost any organic material can be processed with dry fermentation. This includes biodegradable waste materials such as waste paper, grass clippings, leftover food, sewage and animal waste.
Process
'Go to Top
Further Information
English
Articles on energypedia
'Go to Top
References
This article is based on the following publication:
GTZ: Biogas Digest Volume II: Biogas - Application and Product Development
OBOR ASTM HDPE Geomembrane Pond Liners for Biogas Digester
Basic Details
OBOR Geomembrane; pond liner
Thickness
0.5mm,0.75mm,1.0mm,1.5mm,2.0mm,3.0mm
Width
Within 1-12m
Length
50m-200m/ roll
or as required
Color
B
lack,
W
hite
, Blue, Green
Material
HDPE, LDPE, LLDPE
Surface
Textured or Smooth
Payment
T/T, L/C, D/P D/A, MoneyGram, Credit Card
Certification
CE, ISO, ISO
HDPE Geomembrane is a new material that can be waterproof and barrier-proof. It mainly uses high-density polyethylene resin and is added carbon black, antioxidant, anti-aging and UV-resistance component to have excellent environmental stress crack resistance, low temperature resistance, aging resistance, corrosion resistance and large service temperature and long service life. It is widely used in biogas digester,domestic landfills, solid waste landfill, sewage treatment plant, artificial lake and water containment applications.
Biogas geomembrane roof
The Double Membrane Gas storage cover is engineered and designed to meet all relevant European building standards. All Double Membrane Gas Storage Covers supplied with static calculations specific to the site location ensuring suitability for the desired application.
The static calculations take into account the wind- and snow-loads for the area and are based on the full system including the centre column, the tensioning belts and clamps and both the inner and outer membranes.
Biogas silo liners
A membrane liner in the biogas silo forms a watertight seal that separates the contents from the base and the wall. A liner is not only used in new situations, but also for the renovation of existing silos.
The type of membrane to be used is determined by the chemical properties of the silo's contents, but usually the high-quality HDPE Geomembrane.
Characteristics:
1. Good flexibility
2. For service temperature range:-70°C~110°C
3. Corrosion resistance, aging resistance
4. Excellent environmental stress cracking resistance property
5. High tensile strength and elongation
HDPE Geomembrane pond liner TechnicalParameter
ASTM Standard geomembrane
Spec
Properties
Test method
ASTM
GMS0.5
GMS0.75
GMS1.0
GMS1.25
GMS1.5
GMS2.0
GMS2.5
Thickness
D
0.5mm
0.75mm
1.00mm
1.25mm
1.50mm
2.00mm
2.50mm
Density (' g/cc)
D
0.940
0.940
0.940
0.940
0.940
0.940
0.940
Tensile Properties
(Each direction) (')
' yield strength
' break strength
' yield elongation
' break elongation
D
Type IV
8
kN/m
14
kN/m
12%
Are you interested in learning more about jaw crusher components? Contact us today to secure an expert consultation!
700%
11 kN/m
20kN/m
12%
700%
15 kN/m
27 kN/m
12%
700%
18 kN/m
33 kN/m
12%
700%
22 kN/m
40 kN/m
12%
700%
29 kN/m
53 kN/m
12%
700%
37kN/m
67kN/m
12%
700%
Tear Resistance (')
D
64
N
93 N
125 N
156 N
187 N
249 N
311 N
Puncture Resistance (')
D
16
0 N
240 N
320 N
400 N
480 N
640 N
800 N
Stress Crack Resistance (')
D
500 hr.
500 hr.
500 hr.
500 hr.
500 hr.
500 hr.
500 hr.
Carbon Black Content
D
2.0-3.0%
2.0-3.0%
2.0-3.0%
2.0-3.0%
2.0-3.0%
2.0-3.0%
2.0-3.0%
Carbon Black Dispersion
D
Note(1)
Note(1)
Note(1)
Note(1)
Note(1)
Note(1)
Note(1)
Oxidative Induction Time (OIT) (')
(a)Standard OIT
- or -
(b)High Pressure OIT
D
D
100 min.
400 min.
100 min.
400 min.
100 min.
400 min.
100 min.
400 min.
100 min.
400 min.
100 min.
400 min.
100 min.
400 min.
Geomembrane production
OBOR HDPE geomembrane is made by 100% virgin materials
OBOR geomembrane adopted the first class automatic production equipment and three-layer pressing technology. All geomembrane quality is meeting with GB, GRI and ASTM test standard.
Packing and Shipping
1.Packing: PP woven geotextile bags or PE film. Or according to customers requirements.
2.Delivery: Within 7-10 days after receiving your deposit.
Samples are free for your review.
Good quality and good services:
(1)Service:
A. OEM/ODM orders are warmly welcome
B. All of our products have proceeded testing before shipment and we guaranteed the good quality.
(2) Quality Control:
We have established a national-standard laboratory for in-house quality control and built a strict quality control system in all aspects from raw materials testing and production processes to final product quality testing.
Not only is stringent internal quality control carried out at OBOR, but regular testing and analyzing of our product performance is implemented by authoritative testing organizations in Europe and the United States.
Related Products---Geomembrane welder
Company Information
OBOR is a professional geosynthetic products manufacturing company
with registered capital more than $ 5 million, covers an area of 100,000 square meters. The main products are HDPE / LDPE Geomembrane,Plastic Grass Grids, Woven/nonwoven Geotextile, Drainage Board, Composite Membrane and Textile,Plastic netting, 3D Planting Geomat, and other geosynthetic products.
OBOR Company has altogether 26 production liners including HDPE/LDPE Geomembrane liners, Plastic Grass Grids liners, Nonwoven Geotextile liners, Woven Geotextile liners, Drainage Board liners, PlasticNetting liners from Germany, and variety testing machines.
We are specialized in providing professional geosynthetics solutions for Road, Highway, Railway, Airport, Tunnel, Mine Supporting and Protecting, Hydro, Reinforced Steep Slopes, Reinforced Retaining Wall, Reinforced Embankments, Landfill, Containment, water conservancy facilities, soft foundation treatment and other related projects.
Contact Us
Shandong Obor New Materials Co., Ltd
----a professional geosynthetic products manufacturer in China
Customers Visiting
Want more information on ballistic seperator? Feel free to contact us.