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(11) Patent Number: KE 67
(45) Date of grant: 10/12/1996
(12) PATENT
 
(51) Int.C1.7: E 03B 3/06, E 03F 5/02, F 16L 9/22
(21) Application Number: 1996/ 000196
(22) Filing Date: 10/12/1996
 
(73) Owner: Kentainers Limited of, P.O. Box 42168 Nairobi, Kenya
(72) Inventor: Nikhil Shah
 
(54) Title: AN APPARATUS FOR PRODUCTION OF BIOGAS AND THE METHOD FOR MANUFACTURING AND/OR ASSEMBLING THIS APPARATUS AND THE METHOD OF MANUFACTURING THE BIOGAS HOLDER AND/OR USE OF SUCH BIOGAS HOLDER IN CONNECTION WITH A STATIONARY DIGESTER MADE OF METAL AND/OR CONSTRUCTED BY USING BRICK OR STONE, OR CONCRETE BLOCKS AND SAND AND CEMENT.
(57) Abstract:
A apparatus for production of biogas from biological waste comprising a lower portion (being the digester) of a substantially cylindrical shape and integrally formed with the bottom portion with an inlet tube entering the cylindrical outer wall of the lower portion and outlet tube near the top of the lower portion for discharging the fermentation products form biogas apparatus and an upper portion (being the biogas holder), of a substantially cylindrical shape, to collect and hold biogas, the said upper portion being formed with a lid portion including a valve means for taking gas from the upper portion for connecting to a biogas discharging pipe. Both the said lower portion and the upper portion are made from polyethylene or other suitable polymer material by rotational moulding or other suitable plastic moulding process. The said upper portion is inserted in the lower portion and it moves slidingly in a vertical direction in accordance with the volume of biogas produced. Alternatively, a biogas holder apparatus, being the upper portion, of a substantially cylindrical shape , to collect and hold biogas, the said upper portion being formed with a lid portion including a valve means for taking gas from the upper portion for connection to a biogas discharging pipe; the said upper portion in such case being made from polyethylene or other suitable polymer material by rotational moulding process or other suitable plastic moulding process and the said lower portion being made of any other suitable material such as brick or stone or concrete blocks and sand and cement.
 
AN APPARATUS FOR PRODUCTION OF BIOGAS AND THE METHOD FOR MANUFACTURING AND/OR ASSEMBLING THIS APPARATUS AND THE METHOD OF MANUFACTURING THE BIOGAS HOLDER AND/OR USE OF SUCH BIOGAS HOLDER IN CONNECTION WITH A STATIONARY DIGESTER MADE OF METAL AND/OR CONSTRUCTED BY USING BRICK OR STONE, OR CONCRETE BLOCKS AND SAND AND CEMENT
This invention relates to an apparatus for production of biogas and the method for manufacturing and/or assembling this apparatus and the method of manufacturing the biogas holder and/or use of such biogas holder in connection with a stationary digester made of metal and/or constructed by using brick or stone or concrete blocks and sand and cement.
Biogas, containing flammable gases notably methane, is a by-product of the decomposition of human, animal or vegetable waste. If biogas is collected, it can be used as an energy source, for example, for cooking and lighting and serves as an environmental friendly alternative to wood fuel. We have designed and manufactured simple biogas apparatus. All its parts (except a few small items) are made from polymer raw materials. The two main parts, the digester and the gasholder, are made using the rotational moulding process. Rotational Moulding is a very versatile process and allows the use of several different alternative polymer raw materials including, but not limited to, polyethylene, nylon and polycarbonate. In rotational moulding, a metal mould containing the raw material is rotated through one or more axes in a heated environment. The raw material adheres to the inner surface of the mould, forming its shape through heating and subsequent cooling. The raw material used to manufacture the digester and the gasholder, the two main parts of the biogas apparatus, is a polymer.
 
The waste is collected in a rotationally moulded container called "the digester" as shown in Figure 1 being the lower portion (of the said Biogas Apparatus) indicated as (A) and in Figure 3 indicated as (A) and an alternative design of the Digester is shown in Figure 2 also indicated as (A) and in Figure 4 also indicated as (A). However, this digester (A) can be made of varying dimensions and shapes according to the volume of gas required and the type of waste used. The waste is normally mixed with water and its concentration varies with the type of waste being used. No catalysts are required to be added to the waste to produce biogas although fresh waste should be added periodically. The waste is normally fed into the digester through an inlet pipe as shown in all the Figures 1, 2, 3 and 4 indicated as (D) connected to the digester near the base of the digester although the waste can also be fed into the digester frosts the top end of the digester in the gap between the digester and the gasholder.
The upper portion being the gasholder is also a rotationally moulded container as shown in all four Figures 1, 2, 3 and 4 indicated as (G). In these two designs of the Biogas Apparatus, (design of one type is being shown in Figures 1 and 3 and design of the second type being shown in Figures 2 and 4, we have used the floating drum concept. The waste and water mixture in the digester, termed as slurry, ferments and this leads to the formation of gas. This gas rises and collects inside the gasholder which in turn rises from its nearly submerged position within the digester as shown in Figure 3 and in Figure 4 upwardly as shown in Figure 1 and Figure 2. The gasholder is normally weighted down so that pressure is artificially created, The concave design of the top of the gasholder indicated as (K) in all the four Figures 1, 2, 3 and 4 allows for the placement of sand or gravel in this concave area the lid portion of the upper portion (G), at the top of the gasholder, for use as a weight. The concavity ensures that most weight is in the center. The gas collected in the gasholder is extracted through a small hole near or on the top of the gasholder indicated as (P) in all the four Figures 1, 2, 3 and 4 which, using a suitable nipple, can be connected to a pipe and open/close valve so that the gas can be utilized elsewhere as and when needed. This floating drum concept eliminates the need for a pressure release valve in the digester as well as the need for a super strong digester able to withstand high pressure. In Figures 2 and 4 gases pressure is equalized using a connecting pipe indicated as (I). Pipe (I) is welded by a plastic welding process to a plastic plate indicated as (M) in figure 2 and 4 which in turn is also welded by the same plastic welding process to the inwardly bent inside wall of the biogas holder via the upper portion (C). As waste is 54 from the inlet into the digester, more solid particles settle to the bottom of the digester and this displaces the watery slurry at a higher level in the digester from an outlet as shown in all the four Figures 1, 2, 3 and 4 indicated as (L). This watery slurry can be used as an organic fertilizer.
A number of the embodiments of the biogas apparatus according to the invention are its characteristics which are as follows. The two designs of the biogas apparatus and the apparatus    itself are extremely simple and use minimum parts. This apparatus is a new product. Rotational
moulding is a low pressure process which imparts high impact strength and low stress properties
to products made by this process and the main parts of this biogas apparatus viz the digester and
the gasholder retain a degree of flexibility and shock resistance and are suitable for long distance
 transport with minimal or no damage. This Biogas apparatus and, in particular the digester and
the gasholder, have been so designed as to allow the gasholder to nest inside the digester, for the
purpose of transportation to the site where the Biogas apparatus is to be installed and thereby
saving space and reducing cost of transportation. The whole apparatus is comparatively thin, very light in weight, easy to load and offload. It contains very few parts and can be assembled by an unskilled worker at the site. It is, therefore, also easy to dismantle the whole apparatus and re-assemble it elsewhere thus making it a movable biogas apparatus. This biogas apparatus, made from polymer raw material, does not absorb water or waste and is, therefore, easy to clean and very hygienic. Because all parts of this Biogas apparatus are made of plastic, the corrosive nature
of the slurry and especially the biogas does not affect this Biogas apparatus or any of its parts.  Neither the digester nor the gasholder nor any of the fittings used in this apparatus get rusted. If,
however, a metal gasholder were to be used, it would rust very quickly because of the corrosive
nature of both the slurry and the biogas and once it rusts, the holes made by rusting allow the
biogas to escape rendering the biogas plant made with metal gasholder useless. The polymer used to manufacture this biogas apparatus is also stabilized against ultra violet rays of the sun and, therefore, this biogas apparatus is suitable for outdoor use. The polymer used also remains stabling extreme temperatures ranging from + 60 degree centigrade to - 40 degree Celsius. Overall this apparatus is user friendly and long lasting.
Alternatively, the digester (A) can be made of any other material such as brick or stone or concrete blocks and sand and cement and our gasholder (G) made of polymer by rotational moulding process or any other suitable plastic moulding process can be used with such digester.
Although in the present invention, the biogas apparatus is made of a single layer of polyethylene or other suitable polymer, it can also be made of two layers, the outer layer of the biogas apparatus (that is the outer layer of the lower portion (A) and the outer layer of the upper portion (G) ) being made of normal (untreated) polyethylene or other suitable polymer and the inner layer of the lower portion (A) and the inner layer of the upper portion (G) being made of foamed polyethylene (i.e. treated polyethylene) or any other suitable foamed polymer. Foamed polymer (such as polyethylene) incorporates an active agent that, once all the polymer (such as polyethylene) has melted, decomposes and releases inert gases. These gases create small bubbles in the polymer (such as polyethylene) layer increasing its thickness. This is the foaming process. This second foamed layer provides the necessary strength and rigidity to the walls of the upper portion (G) and the lower portion (A) and the foamed polymer also has, in addition, insulation properties which enables it to more efficiently retain the heat generated during the process of fermentation of the biological waste in the lower portion (A), the digester, and thereby slightly accelerating this fermentation process and biogas production.
Currently, alternative binges apparatuses exist in the market. The most common one in use is a digester made mainly of brick, concrete blocks or stone often, but not always, using a metal gasholder. These alternatives have several drawbacks. Firstly, a skilled mason is required to build the digester and a skilled worker is required to fabricate the metal gasholder. Secondly, once set in the ground, it cannot be moved to a new site, 'thirdly, it takes a much longer time to build it. Fourthly, the slurry and the biogas will, as stated above, corrode the metal gasholder causing holes and leaks and loss of Biogas. Our biogas apparatus made of polymer is simple to install, long lasting and because it has nanny any moving parts, it does not require any maintenance and it can be easily be dismantled and re-assembled at a different site as and when desired.
It is the object of the present invention to provide a biogas apparatus made from a suitable    polymer which is consisting of very few parts and is easy to assemble and to disassemble, which is also a user-friendly, long-lasting and almost maintenance-free apparatus and which constitutes a more economic alternative to less flexible stationary binges plants and also to provide a biogas
holder made of a suitable polymer by rotational moulding process as a user friendly, long lasting, almost maintenance-free gasholder and which is a more economic alternative to all other alternative forms of gas holder such as those made of metal and which can be used with a digester made of any other material such as brick or stone or concrete blocks and sand and cement.

ABSTRACT
An apparatus for production of biogas from biological waste comprising a lower portion (A) (being the digester) of a substantially cylindrical shape and integrally formed with the bottom portion (X) with an inlet tube (D) entering the cylindrical outer wall of the lower portion (A) and outlet tube (L) near the top of the lower portion (A) for discharging the fermentation products from Binges Apparatus and an upper portion (G) (being the biogas holder), of a substantially cylindrical shape, to collect and hold binges, the said upper portion (G) being formed with a lid portion (K) including a valve means (P) for taking gas from the upper portion (G) for connection to a binges discharging pipe. Both the said lower portion (A) and the upper portion (G) are made from polyethylene or other suitable polymer material by rotational moulding process or other suitable plastic moulding process. The said upper portion (G) is inserted in the lower portion (A) and it moves slidingly in a vertical direction in accordance with the volume of Biogas produced. Alternatively, a biogas holder apparatus, being the upper portion (G), of a substantially cylindrical shape, to collect and hold binges, the said upper portion being formed with a lid portion (K) including a valve means (P) for taking gas from the upper portion (G) for connection to a biogas discharging pipe; the said upper portion (G) in such case being made from polyethylene or other suitable polymer material by rotational moulding process or other suitable plastic moulding process and the said lower portion (A) being made of any other suitable material such as brick or stone or concrete blocks and sand and cement.
 
CLAIMS
(1) Biogas Apparatus for producing biogas from biological waste, comprising:-
 a lower portion (A) (being the digester) of a substantially cylindrical shape and integrally formed with a bottom portion (X) and an inlet tube (1)) entering the cylindrical outer walls of the lower portion (A); and An upper portion (G) (being the biogas holder) of a substantially cylindrical shape for collecting and holding biogas, having a diameter smaller in size than that of the lower portion (A), the said upper portion (G) being formed with a lid portion (K) including a valve means (P) for taking gas from the upper portion (G). the said apparatus being characterized in that:-  the said upper portion (G) (the biogas holder is inserted in that lower portion (the digester) and is slidingly guided to be movable in a vertical up and down direction, in accordance with the volume of biogas produced; and the said tipper portion (G) and the said lower portion (A) are made of plastic material.
(2) Biogas Apparatus according to Claim 1, characterized in that the lid portion (K) of the upper portion (G) comprises a concave inwardly recessed portion for accommodating specific load which can be varied from the outside to obtain a desired pressure of the biogas by appropriately varying the additional load.

(3) Biogas Apparatus according to Claims 1 and/or 2, characterized in that the said lower
portion (A) includes at the top and of the cylindrical side wall an inwardly bent side wall
portion defining a ring-shaped space for collecting biogas.
 
(4) Biogas Apparatus according to Claim 3, characterized in that a connecting pipe (J) is
provided between the ring-shaped space of the lower portion (A) and the upper portion (G) to allow a gas exchange between the ring-shaped space and the space covered by the upper portion (G).
(5) Biogas Apparatus according to each and/or any of the Claims 3 to 4, characterized in that   the said inwardly bent side wall portion of the lower portion (A) reinforces the lower portion (A) and is designed to guide the upper portico when moving upwardly or downwardly, respectively.

(6)  Biogas Apparatus according to each and/or any of the Claims 1 to 5, characterized in that the said lower portion (A) is provided with an outlet tube (L) near the top end of the lower portion (A) for discharging fermentation products from the biogas apparatus.
(7) Biogas Apparatus according to each and/or any of the Claims 1 to 6, characterized in that said valve means (P) is an ON/OFF-valve and is provided with means for connection to a biogas discharging pipe.
(8) Biogas Apparatus according to each and/or any of the Claims 1 to 7, characterized in that
the upper ends of the discharging tube (L) and the inlet tube (D) outside the lower portion (A) are located above the highest possible level of the biological waste.

9) Biogas Apparatus according to each and/or any of the Claims 1 to 8, characterized in that both the lower portion (A) and the upper portion (G) are so designed as to allow the biogas apparatus to be transported with the upper portion (G) accommodated (or nested) in the lower portico (A) to reduce transportation space and cost.
(10) Biogas Apparatus for producing biogas from biological waste, comprising:-
 • a lower portion (A) of substantially cylindrical shape and integrally formed with a bottom portion (X) and an inlet tube (1)) entering the cylindrical outer walls of the lower portion (A), and
• An upper portion (G) of a substantially cylindrical shape for collecting and holding biogas, having a diameter smaller in size than that of the lower portion (A), the said upper portion (G) being formed with a lid portion (K) including a valve means (P) fiir taking gas from the upper portion (G)
characterized in that:-
the said upper portion (0) is inserted in the said lower portion and is slidingly guided to be movable in a vertical up and down direction in accordance with the volume of biogas produced; and the said tipper portion (0) is made of plastic material and said lower portion (A) is made of any suitable material such as brick or stone or concrete blocks and sand and cement.
(11) A Biogas Holder Device for collecting and holding biogas from biological waste,    15
comprising an upper portion (G) of a substantially cylindrical shape for collecting and holding biogas, having a diameter smaller in size than that of the lower portion (A), the said upper portion (G) being formed with a lid portion (K) including a valve means (P) for taking gas Born the upper portion (G)
characterized in that:-
• the said upper portion (G) is inserted in the said lower portion and is slidingly guided to be movable in a vertical up and down direction in accordance with the volume of biogas produced;
• the said upper portion (G) is made of plastic material; and the said lower portion (A) is made of any suitable material such as brick or stone or concrete blocks and sand and cement.
(12) A method of manufacturing the Biogas Apparatus and/or the said lower portion (A) and/or the said upper portion (G) of any dimensions and shapes in accordance with each and/or any of Claims 1 to 11 using the rotational moulding process or any other suitable plastic process.
(13) A method of manufacturing the Biogas Apparatus and/or the said lower portion (A) and/or the said upper portion (G) of any dimensions and shapes in accordance with each and/or . any of Claims I to 11 using the rotational moulding process or any other suitable plastic process wherein polyethylene or other suitable polymer is used in the manufacture of such apparatus and/or the said lower portion (A) and/or the said upper portion (G)
(14) A method of manufacturing the Biogas Apparatus and/or the said lower portion (A) and/or the said upper portion (G) of any dimensions and shapes in accordance with each and/or any of Claims 1 to 11 using the rotational moulding process or any other suitable plastic process wherein treated polymer (that is, a polymer with an active agent for foaming) such as polyethylene is used in the manufacture of such apparatus or the said lower portion.(A) and/or the said upper portion (G) for increasing rigidity of the said apparatus and/or the said lower portion (A) and for the said upper portion (G).
(15) A method of manufacturing the Biogas Apparatus and/or the said lower portion (A) and/or
the said upper portion (G) of any dimensions and shapes in accordance with each and/or any of Claims 1 to 11 and Claim 14 using the rotational moulding process or any other suitable plastic process wherein treated polymer (that is, a polymer with an active agent for foaming) such as polyethylene is used in the manufacture of such apparatus and/or the said lower portion (A) and/or the said upper portion (G) for increasing insulation properties of the polymer material and the said apparatus and/or the said portions (A) and (G) and/or either of them and thereby retaining the heat generated in the fermentation process in the Biogas Apparatus, particularly in the lower portion (A) and thereby accelerating the process of fermentation of the biogas waste and biogas production.

(16)  A Biogas Apparatus in accordance with to Claims 1 to 15 and for any of them where any
polymer material (other than polyethylene or treated polyethylene) is used to manufacture
the biogas apparatus and/or the said lower portion (A) and/or the said portion(G) by rotational moulding process or any other plastic process.
(17) A design in accordance with each of the Claims 1 to 16 above shown in each of the Figures 1 and 3 and any design or designs derived there from to allow for a complete biogas apparatus and/or the said lower portion (A) and/or the said upper portion (0) of any dimensions and/or shapes.

        (18) A design it accordance with each of the Claims 1 to 16 above shown in each of the Figures 2 and 4 and any design or designs derived there from to allow for a complete biogas apparatus and/or the said lower portion (A) and/or the said upper portion (G) of any dimensions and/or shapes.

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