FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
PROVISIONAL SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A fixed dome biogas plant
APPLICANTS
Reliance Industries Limited, Maker Chambers IV, Nariman Point, Mumbai - 400 021, Maharashtra, India, an Indian Company
INVENTORS
Mallia Vinod Kumar Rajarathana and Samantapudi Venkatarama Raju, both of Reliance Industries Limited, Swastik Mills Compound, Sion-Trombay Road, VN Purav Marg, Chembur, Mumbai - 400 071, Maharashtra, India, both Indian Nationals
PREAMBLE TO THE DESCRIPTION
The following specification describes the invention:

This invention relates to a fixed dome biogas plant.
Biogas plants are used for producing biogas or biofuel and are generally floating dome type and fixed dome type. A biogas plant mainly comprises a digester with a floating or fixed dome. In the case of a fixed dome biogas plant, the dome is fixed on the digester. Biogas is produced in the digester by digestion or fermentation of biodegradable organic matter including manure, sewage sludge, municipal solid waste or biodegradable feed stock like biodegradable waste under anaerobic conditions. Biogas comprises primarily methane and carbon dioxide and is used as a fuel in vehicles and for utilitarian purposes like generation of electricity, cooking, heating, lighting or refrigeration.
The invention provides a fixed dome biogas plant comprising an integrally formed polyethylene dome having a mounting flange or collar at the base thereof adapted to be fitted at the mouth of a digester built with brick and cement concrete in a gas leak proof manner.
The following is a description of the invention with reference to the accompanying drawings, in which:
Fig 1 is a crossectional view of a fixed dome biogas plant according to an embodiment of the invention;
Fig 2 is an elevation of the dome of the biogas plant of Fig 1;
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Fig 3 is an enlarged view of the flange of the dome of Fig 2;
Fig 4 is an enlarged view at X in Fig 1;
Figs 5 and 6 are enlarged views of the flanges of a dome according to different embodiments of the invention;
Fig 7 is a gas outlet of the dome of the invention according to another embodiment thereof;
Figs 8 and 9 are gas outlets of the dome of the invention according to different embodiments thereof fitted with inserts; and
Figs 10, 11 and 12 are elevations of the dome of the invention according to different embodiments thereof.
The biogas plant 1 as illustrated in Figs 1 to 4 of the accompanying drawings comprises a digester 2 constructed with bricks and cement concrete. 3 is a mixing tank connected to the digester by pipe 4. 5 is an outlet tank connected to the digester and provided with an outlet valve 6 and cover 7. 8 is a dome of the biogas plant provided with a U-shaped mounting flange (collar) 9 at the base thereof and a gas outlet 10. The mounting flange is provided with bolt holes 11 and the dome is fitted at the mouth of the digester by bolts 12 passing through the bolt holes in the flange and tightened at the mouth side wall of the digester against the flange. 13 represents cement concrete filling at the joint between the
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dome and the digester so as to render the joint therebetween gas tight. Instead of cement concrete other binding or sealant materials like epoxy resins or polyurethanes may be used to cover the joining between the dome and the digester in a gas tight manner. 14 represents sand and earth loading (filling) over the biogas plant. Biodegradable organic matter (not shown) is mixed with water (not shown) in tank 3 to form a slurry (not shown) which is fed into the digester via pipe 4 and is subjected to anaerobic digestion in the digester. Biogas (not shown) generated in the digester is collected via outlet pipe. The spent slurry flows out through the outlet valve 6.
The flanges 15 and 16 of the dome 8 as illustrated in Figs 5 and 6 of the accompanying drawings are C-shaped and plain, respectively. The gas outlet 17 as illustrated in Fig 7 of the accompanying drawings is a through hole. The gas outlets 18 and 19 as illustrated in Figs 8 and 9 of the accompanying drawings, respectively are fitted with a threaded metal insert 20. The metal insert may be made of metals like brass, stainless steel or mild steel and may be inserted in the gas outlets at the time of making the dome. Preferably, the metal insert is made of brass. A gas out tube provided with corresponding threads (not shown) can be advantageously fitted in the gas outlets in thread engagement therewith. The dome 21 as illustrated in Fig 10 of the accompanying drawings is provided with stiffening (reinforcing) ribs 22 circumferentially and the dome 23 as illustrated in Fig 11 of the accompanying drawings is provided with stiffening ribs 24 radially and the dome 25 as illustrated in Fig 12 of the accompanying drawings is provided with stiffening ribs 22 circumferentially and stiffening ribs 24 radially.
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The dome is elliptical or spherical shaped and may be provided with more than one gas outlet which may be formed at the time of making the dome. Alternatively the gas outlet may be drilled in the dome after it is made. The mounting flange may be provided with mounting holes during making of the dome or alternatively the mounting holes may be drilled in the mounting flange after it is made. The flange geometry may vary and the flange may be adapted to be fitted at the mouth of the digester made with bricks and cement concrete in any other manner. The reinforcing or stiffening ribs are essentially to increase the mechanical strength of the dome and may be of different geometries. The dome is made with polyethylene which is weather resistant including UV, formable, thermally insulating, impervious and durable and which has excellent mechanical strength and stiffness. Preferably the polyethylene has a density in the range of 0.924 to 0.960 gm/cc measured as per ASTM D 792 and a melt flow index (MFI) in the range of 1.5 to 50.0 gm/10 min measured as per ASTM D 1238 @ 2.16Kg, 190°C. The polyethylene may be linear low density polyethylene (LLDPE) or high density polyethylene (HDPE) or blends thereof. The polyethylene used for making the dome is UV stabilized with UV stabilizers like hindered amine light stabilizers (HALS) or alternatively with carbon black. The polyethylene dome may be formed by rotomoulding or thermoforming, preferably by rotomoulding. The polyethylene used for rotomoulding is, preferably rotomoulding grade. The dome may be made of single layer or multiple layers of polyethylene. In the case of multilayer construction, the inner layers of the dome may polyethylene foamed layers for improving the mechanical strength thereof. The dome of the invention is integrally formed with polyethylene having excellent mechanical strength and stiffness, thermal insulation and weathering properties including UV resistance. It is monolithic and seamless in construction and ready for installation or
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capping at the mouth of the digester. It has sufficient mechanical strength and stiffness to withstand the gas pressure from inside and the sand and earth loading from outside. It is not prone to cracks and corrosion and is impervious and gas leak proof. It is light weight and is easy to transport and handle. It can be easily fitted at the mouth of the digester even by unskilled persons and is maintenance free. Making time and installation time of the dome are considerably reduced. It has long life and is highly economical. It does not affect the temperature in the digester for the anaerobic digestion of the organic matter therein. Therefore, there is no delay in the generation of biogas after installation of the dome.



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