FORM - 2
THE PATENTS ACT. 1970
&
The Patents Rules. 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION "A PROCESS FOR ENCHANING BIOGAS POTENTIAL BY PRESSURIZATION."
2. APPLICANT
a) NAME: Kirloskar Integrated Technologies Limited
b) NATIONALITY: An Indian Company registered under the provisions of the Companies
Act 1956.
e) ADDRESS: 13/A, Karve Road, Kothrud, Pune- 411038.M.S. India.
2.A. INVENTOR(S);
1.a) NAME: MATE NITANT VISHNU
b) NATIONALITY: An Indian national
c) ADDRESS: 9 'Shriman', 793 Bhandarkar Road.. Pune-411004, Maharashtra.. India.
2.a) NAME: GOYAL DEVENDRA JAYANT
b) NATIONALITY: An Indian national
c) ADDRESS: A7/I7, Vishnu Vihar, Bibvevadi Kondhwa Road, Bibvevadi, Pune 411037,
Maharashtra, India.
3.A) NAME: KHOT NIKH1L APPASAHEB

b) NATIONALITY: An Indian national
c) ADDRESS: Flat No.306, Dhruva Residency, 250B/28; Nagala Park.. Near Rajhans Press,
Kolhapur416003. Maharashtra, India.
4.A)NAME: PANDIT MAITREYE DEVASHISH
b) NATIONALITY: An Indian national
c) ADDRESS: 'Pandit Complex', Building No.3, Sitabardi, Nagpur- 440 012.
3. PREAMBLE TO THE DESCRIPTION
COMPLETE
The following specification describes the invention and the manner in which it is to be perfomed.

FIELD OF INVENTION:
The present invention illustrates biogas production by biomethanation process. More particularly, it illustrates effect of pressurized systems and / or pressure on biogas production by biomethanation process from fixed dome bioreactor.
BACKGROUND OF THE INVENTION:
Biogas is produced by means of anaerobic digestion in biogas plants. Two popular simple designs of biogas plants developed are the fixed dome type of biogas plant and the floating gas holder type of biogas plant. The digestion metabolism is same in both the process but the gas collection mechanism differs. In the fixed dome biogas plant, biomass is typically mixed with predetermined quantity of water in a mixing tank to form slurry. The slurry is fed into the digester through the inlet chamber. When the digester is partially filled with the slurry, the introduction of slurry is stopped and the plant is left unused for a couple of months. During this period, anaerobic bacteria present in the slurry decompose or ferments the biomass in the presence of water. As a result of anaerobic decomposition, biogas is evolved, which starts collecting in the dome of the digester. As more and more biogas is collected, 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, from where it is manually removed and taken for further processing or used as manure for plants. The gas valve connected to the system is opened when supply of biogas is required.
Though the fixed dome biogas plants are easy to construct, and are inexpensive, its (imitations exceed its advantages, and hence fixed dome construction is not very popular for energy generation projects, where large scale production of biogas is required. Its principle disadvantage lies in the fact that there is loss of useful microbes during gas production through the outlet tank of the digester. Due to biogas accumulation, i.e. pressure exerted by biogas, the slurry flows in the outlet tank, taking along with it the microbes that are useful for biogas production. It is direct loss of essential microbes. Gas pressure substantially drops depending on utilization and the volume of the stored biogas. Also, once the pressure inside the digester equals to that of the

atmosphere, no further gas can be utilized. Moreover, burners and other simple appliances cannot be set in an optimal way. If the gas is required at constant pressure, a gas pressure regulator is needed or a floating gas-holder is necessary.
Herein is a combined effort to overcome the above said limitations.
Some of the available patents and papers published relating to biogas production from fixed dome bioreactor are cited as follows:
PRIOR ART:
• Indian Patent Application No: 1697/MUM/2007itled 'A' fixed dome biogas plant.'
Abstract: A fixed dome biogas plant comprising a digester built with brick and cement concrete. The higags plant further comprises a dome integrally made of polyethylene and having atleast one gas outlet and a mounting flange at the base thereof adabted to be fitted at the mouth of the digester gas leak proof.
• US patent no: 6,375,838 titled "Scaled tanks for methane fermentation or storage in
a corrosive environment."
Abstract: A sealed tank includes a concrete footing, a steel or concrete shell ring and a sealed and corrosion-resistant dome having a double membrane There is an inner membrane delimiting, with the surface of the liquid effluent contained in the shell ring, a sealed chamber intended to receive biogas that results from the methane fermentation or from a corrosive environment. An outer membrane envelopes the inner membrane and which, when pressurized, applies a given pressure to the volume of biogas or of corrosive environment contained in the chamber.
• Patent Application No: WO/2005/113459 titled "Sell-pressurizing, self-purifying
system and method for methane production by anaerobicdigestion."

Abstract: Methane is produced using self-pressurizing, self-purifying system and method which converts biomass into a biogas using anaerobic digestion. The anaerobic digestion is conducted in a bioreactor that is maintained at a near constant pressure. The biogas that is generated is separated into a non-methane gas and a methane-containing gas. The purified methane-containing gas is stored and/or transported for use as a liquid fuel. The generated methane exhibits an energy density and purity that is equivalent to liquid fuels. The system requires little or no energy input, but is usable to produce methane that is equivalent to conventional liquid fuels in terms of energy density and purity.
LIMITATIONS OF PRIOR ART:
• Regulating and maintaining a pressure of 1000 psig is a difficult task, as also the construction of digester should be well engineered to withstand such a high pressure condition.(case : (WO/2005/113459)
BRIEF DESCRIPTION OF DRAWINGS:
The details of the present invention, both as to its structure and operation, may be gleaned in pari by study of the accompanying drawings, in which like reference numerals refer to like parts, and in which: Figure 1 is a process flow diagram of pressurized system for a fixed dome digester.
Part list:
1- Feed preparation tank
2- Transfer pump
3- Feed transfer line
4- Motor for stirrer
5- Digester
6- Stirrer
7- Gas collection transfer line
8- Pressure Indicator
9- Biogas collection and sampling

10- Biogas receiver unit 11-Water Drain
12- Pressure Regulating Device
13- Reaction chamber 14-Control Valve 15-Non Return Valve
Figure 2 is a graphical representation of results for biogas generation using Pennisetum purpureum as feed under pressurized system and inverted system
1 - Fresh Pennisetum purpureum Pressurized
2- Fresh Pennisetum purpureum Inverted
Figure 3 is a graphical representation of results for biogas generation using pure substrate as like cellulose as feed under pressurized system and inverted system
1- Fresh Cellulose Pressurized
2- Fresh Cellulose Inverted
OBJECT OF THE PRESENT INVENTION:
The main object of the present invention is to provide a method to create and sustain pressure on biogas by employing pressurized systems during biomethanation process.
An object of the present invention is to provide consistent flow of biogas at desired pressure say; 1.2 bar, from a fixed dome bioreactor without the aid of blower.
Another object of the present invention is to provide a fixed dome bioreactor.
Further object of the present invention is to increase biogas production by controlling pressure and to reduce the retention time of the biomethanation process using cellulosic feed as substrate.

Yet another object of the present invention is continuous biogas production from a fixed dome bioreactor and supply of the same at a consistent flow.
Yet another object of the present invention is to produce biogas at elevated pressures so that it can directly be fed further to processing units like hydrogen sulphide and carbon-dioxide scrubbers.
Yet another object of the present invention is maintaining the flow of biogas till the point of use.
Further object of the present invention is to reduce / eliminate the operating cost of the scrubber system.
Further object of the present invention is to increase biogas production by introducing pressurized systems to fixed dome bioreactor which may be as like but not restricted to any of the conventional biogas model.
Still further object of the present invention is to provide long distance consistent flow / supply of .biogas by connecting biogas channels / pipes from the source to the point of use, which may or may not be in close vicinity of the biogas plant.
SUMMARY OF THE PRESENT INVENTION:
The present invention describes a system of biogas production by allowing build up of pressure in a fixed dome bioreactor. The current invention describes biogas production under regulated pressure by means of pressure regulating device (12) mounted in the head region of the fixed dome bioreactor (5). The feed is introduced into the pressurized bioreactor (5) through the inlet chamber (1). The flow of the feed / slurry is regulated and maintained by the inlet control valve which is in immediate series connection with the feed inlet chamber (1). a control valve (13) and a non-return valve (14) both connected in series to the feed inlet chamber (1). A pump (3) is placed in series for forcing the feed into the pressurized digester (5). The feed, preferably cellulose rich feed, which is pre-mixed with specific bacterial cultures / microbes, is introduced

in the pressurized digester (5). The digestion may be enhanced by addition of specially developed microbial population capable of producing enzymes required to assist the biomethanation process. In digester (6), the conversion into biogas is brought by housing enriched microbial consortia and fresh cellulosic feed. The conversion into biogas is brought by addition of enriched microbial consortia, and with or without occasional stirring heating it to temperature between 35 Degree Centigrade and about 40 Degree Centigrade or as may be required by the consortia of microbes. The gas production takes place while the pressure is maintained over atmospheric pressures, preferably at 1.2 bar by means of a pressure regulating valve (12). Biogas production is directly proportional to the pressure maintained in the bioreactor (5) without the aid of any external pressure device. The pressure produced reduces the retention time of the biomethanation process by half as compared to the conventional biomethanation .equipment such as fixed-dome or floating dome bioreactors. Biogas produced is consistently supplied under increased pressure for further use such as electricity generation or as fuel gas for various applications. The process eliminates the need of a blower since flow of biogas is maintained by microbes. The rate of supply of biogas is maintained at the rate of gas generation under that particular pressure. The process reduces / eliminates electricity required to condition the gas for feeding into scrubbers.
The present invention encompasses an overall increase in biogas production with 50 percent decrease in retention time of conventional biomethanation process particularly for cellulosic substrate. The pressure produced and maintained is preferably of about 1.2 bar.
Other features, advantages, and objects of the present invention will become more apparent and be more readily understood from the following detailed description, which should be read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS:
The current invention relates to pressurized systems for biogas production by biomethanation process from fixed dome bioreactor. In a preferred embodiment, the feed, preferably cellulose rich feedstock and microbes specifically prepared for anaerobic digestion of the feed to produce

methane, is introduced into the pressurized digester (5) by means of a feed transfer Iine(3). The feed transfer line (3) is connected between the feed preparation unit (1) and the pressurized digester (5). The microbial consortium is specifically prepared for a particular target feed and is enriched from natural microbial mixtures such as cow-dung, sewage and the like, by a process of restricting its nutrition to the subject feed over a period of time. The reaction takes place in the digester (5). The flow of the feed/slurry is regulated and maintained by the inlet control valve (13). which is in immediate series connection to the feed inlet chamber (1), a control valve and non return valve (14) both connected in series to the feed inlet chamber (1). A pump (2) is placed in series for forcing the feed into the pressurized digester (2). The conversion into biogas is enhanced by heating it between temperature ranges of about 35 Degree Centigrade to about 40 Degree Centigrade or as may be required by the consortia of microbes, with or without occasional stirring by means of a stirrer (6) placed inside the reaction chamber of the pressurized digester (5). The pH of the reaction medium is maintained between 6 and 7.5. with the pressure inside the chamber reaching about 1 to 1.2 bar. A pressure regulating device (12) is mounted on the head region of the digester (5) by means of gas collection transfer line (7) which is connected to the head region of the digester (5) and the other end opening in the biogas receiver (10).
The biomethanation process is carried out in absence of any external pressure but solely in presence of pressure exerted by the biogas generated in the digester during the biomethanation process. This pressure varies depending on the biogas generation and consumption rates. The pressure created on the reaction mixture activates degradation of cellulose molecules and transports them into the cell and/or it enhances the degradation of cellulosic matter, thereby enhancing biogas production. In case of cellulose feed as substrate, 50 percent more biogas is generated per unit time in presence of gas pressure created on the culture / slurry. The rate of gas generation is proportional to the increase in the pressure. Increase in pressure also increases biogas potential. The pressure created enhances cellulose degradation which in turn reduces the retention time of the biomethanation process. The retention time is reduced to below half that of the conventional biogas production process. As the pressure reaches up to 1.2 bar. the gas generation is more in case of pressurized system than inverted batch system i.e. biogas production at atmospheric pressure. As the gas is produced, the pressure builds up to above atmospheric which is then is maintained at that desired level by means of a pressure regulating

device (12). The non-digesled sludge from the reactor is carried through the outlet control regulatory valve (15). The sludge directly goes to the manure yard for manure preparation, and may further be converted in value added fertilizer. Since the digester (5) has a fixed dome a pressure relief valve (12) is connected as safety device, to the fixed dome preceding the pressurized gas outlet. Biogas produced is supplied under pressure for cleaning and electricity generation or is used as fuel gas with or without cleaning for other applications.
The process eliminates the need of a blower since flow of biogas is maintained by continuous gas production by microbes. The process reduces / eliminates electricity required to condition the gas for feeding into the scrubbers. The system thereby produces biogas continuously at a pre-defined pressure (above atmospheric pressure) by regulating the pressure by means of a pressure regulating device (12). The biogas collected in the biogas receiver unit (10) can further be used for biogas sampling.
It is understood that many modifications and variations may be devised given the above description of the principles of the invention. The digester vessel can be constructed in a wide range of sizes, shapes and types and of different materials of construction / fabrication. The process parameters can vary depending on the composition of the input wastes / substrates / feeds, the processing rate or required volume, and / or output products desired. The intention, however, is not to limit the invention to the particular embodiment described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention.
The invention is further explained by the following non limiting illustrations.
Illustration 1:
In the following example pure protein substrate is taken as feed mixed with specific microbes to carry out biomethanation process under pressure and without pressure. 0.25 grams of protein is mixed with 70 ml slurry to produce the reaction mixture for biogas production. The pH of the mixture is 7.28 and pressure generated in the digester is of about 1.2 bar. Biogas potential

recovery obtained is 0.122 liters per grams T.S. under pressure with retention time of 15 days. The biogas potential recovery is 0.114 liters per kilograms T.S when the inverted system is used, where the process takes place at atmospheric pressure. The produced results do not show any considerable results for pressurized system. In case pure cellulose substrate is used as feed, biogas potential recovery is 0.159 liters pergrams T.S when the feed is 0.25 grams with pH of about 7.28 and pressure build up of about 1.2 bar. In case the inverted system, wherein the process takes place almost at atmospheric pressure, biogas potential recovery is 0.098. The potential recovery in case of inverted batch is in the range of 50-56 percent as compared to pressurized batch.
IIIustration 2:
The substrate used herein is Pennisetum purpureum. 2 grams of fresh weight of Pennisetum purpureum is mixed with 40 ml fresh water which makes 5 percent concentration of solids in total slurry. The total volume of slurry measured 42.94 ml. To this feed slurry 80 ml of culture slurry is added, thereby making the culture to feed volume ratio to 1:0.5. The potential biogas recovery obtained is 0.597 liters per grams T.S for pressurized system and 0.336 liters per grams T.S for the inverted (atmospheric pressure) system under neutral pH conditions and 15 days retention time.
ADVANTAGES OF THE PRESENT INVENTION:
• Biogas is consistently supplied to the end use situated at a long distance from the source biogas plant.
• The pressurized systems introduced for the biogas production eliminates the need of blower for feeding it into the scrubbers, thus reducing the energy requirement for the blower i.e. reducing electricity required for conditioning the biogas.
• Biogas is produced above atmospheric pressures by regulating pressure of the fixed dome digester plant.

• In case of cellulosic substrates, the retention time for biomethanation process is reduced by 50 percent than by conventional biomethanation process with increased biogas production.

CLAIMS:
We claim.
1) A process for biogas production under pressure preferably for cellulosic feed as substrate to increase biogas production, wherein the system comprises: a feed preparation tank for preparing the feed,
a transfer pump for transferring the slurry into the bioreactor under pressure, a stirrer for mixing the culture and slurry inside the bioreactor, a fixed dome digester for carrying out the biomethanation process, a pressure indicator for measuring pressure inside the bioreactor, a pressure regulating device for maintaining constant pressure, a pressure relief valve as safety device, a biogas collecting unit for biogas collection.
2) A process as claimed in claim 1, wherein the pressure in the bioreactor is above atmospheric pressure, preferably of about 1.2 atmospheric bar.
3) A process as claimed in claim 1, wherein biogas production increases while there is decrease in the retention time of the biomethanation process by about 50 percent as that required for the conventional biomethanation process at atmospheric pressure.
4) A process for biogas production which eliminates the need of blower to increase pressure and flow rate, thereby reducing the energy requirement of the blower i.e. reducing electricity required for conditioning the biogas for feeding into scrubbers.
5) A process to produce biogas at elevated pressures so that it can directly be fed further to processing units like hydrogen sulphide and carbon-dioxide scrubbers thereby reducing / eliminating the operating cost of the scrubber system.

6) A process to produce biogas at elevated pressure so that it can directly be fed further to the end use application even at considerable long distance from the point of biogas generation