FR2500716A2 - Modular digester to produce methane from pumpable waste - having open-topped cells opt. interconnected within common gas holder - Google Patents

Abstract

In the parent patent an installation for the prodn. of biomethane by digestion of pumpable, organic waste, e.g. liq. manure was described. The installation comprised a number of modular, digestion cells. The number of cells may be varied to suit the capacity of plant required. Provision was made for anaerobic prefermentation. A common pump and pipework system was installed for inter-cell transfer, cell charging and draining. The cells were temp.-controlled in a bain-marie type enclosure and provision was made for pH measurement and control. Methane gas is piped individually from each cell. In this addn. each cell is in the form of an open-topped, vertical cylindrical shell. The cells are gathered closely together on a common base pref. of regular geometrical form, e.g. square or circle. All cells are interconnected by a network of pipes, valves and common pump(s) so that fluid can be transferred any cell to any other cell. All the cells are enclosed within an expandable gas-holder made up of a flexible sheet, e.g. tarpaulin, cover with its lower edge dipping into the bain-marie to form a liq. seal. During the digestive process, the liq. can be advanced progressively from cell to cell, reaching the last cell as fermentation is almost complete. This ensures optimum rate of digestion which is never retarded by crust formation. Anaerobic conditions are enhanced by enclosing the cells in a single gas holder. Gas storage and withdrawal arrangements are simplified.

Description

 We filed on September 29, 1980, in Erance, an invention patent application which was registered under the NO 80-21 085.

Invention entitled: Modular displacement digester for the continuous production of biomethane from organic substances.

The present addition relates to this invention.

TECHNICAL AREAS TO WHICH THE ADDITION IS RM> POILTE
This addition relates to an apparatus intended for the continuous production of biomethane from organic substances contained in waste originating essentially from agriculture or industries derived therefrom.

It also relates to the purification systems of effluents heavily loaded with organic matter since methanogenic digestion is accompanied by a strong reduction in DB 0 5,
MEANS USED
The main patent application described a digester composed of a certain number of well-defined elements. The purpose of this addition is to describe another embodiment, which makes it possible to give birth to a whole family of devices with different characteristics from each other. For this, the modular displacement digester is composed of a central unit of the type modular com, stepped on by peripheral equipment, some compulsory, others optional; it is the presence or absence of 1 or more of these optional peripheral equipments which gives the digester these characteristics.

 The modular central unit is used to contain the products being digested. This unit is always designed in the same way, except that being modular it will include, according to each particular case, a number of variable digestion cells, proportional to the volume of digestion required in each installation.

Around the central digestion unit, there are a number of peripheral devices:
- The mandatory ones namely
- A pump to ensure product movements,
- Valves to direct fluids in places
desired,
- A device to control the temperature of the bath
Marie and keep it warm.

- The other optional ones to know
- Cells intended to ensure pre-fermentation.

Recall that pre-fermentation is an iron phase
aerobic indentation which precedes the fermentation phase
anaerobic.

- Heat exchangers intended to recover ca
lories on outgoing products to ensure pre
heating of incoming fresh produce.

- An automatic measurement and regulation device
of Ph.

 - An automatic valve control device.

The means used in this variant are essentially:
(We exclude from the description all the optional peripheral elements except the elements used for the measurement and the regulation of the Ph of which we will specify the position and the operating conditions)
- A set of cells "14" in variable number according to the vo
lume of digestion to ensure. These cells all seemed
bles, which gives a modular set. These cells are
preferably arranged for reasons of economy of buildings
according to a square, but not necessarily. Adaptation to the volu
digestion me desired is therefore done mainly by the va
the number of cells and secondarily in cases
particular by the variation in cell volume but
in all cases, the cells have, in the same device
same volume.

- The products in digestion are maintained at the temperature of
digestion (mesophilic or thermophilic) by heat transfer
through the cell wall, these plunging down to
lj3 of their height in a bain marie matenu at temperature
constant.

- A flexible cover "36" surrounds the upper part of the cells, the seal is ensured by a hydraulic seal "37" the edge of the cover immersed in the water bath. This flexible cover delimits an unmon space for recovering the gas common to all of the cells. The gas produced is evacuated through a pipe "409 which leaves vertically.

- The products before their introduction could be s
- Pre-fermented, that is to say having undergone a phase of fermen-
aerobic tation,
- Preheated by removing calories from the products
outgoing in a heat exchanger.

- The products before their introduction are necessarily brought to the digestion temperature so that the constancy of the temperature of the water bath is not disturbed by the introductions which would cause temperature variations for the products in digestion.

Circulation of products - All product movements are ensured by the po pue "23", - Fresh products (to be digested) pass through the pipeline "24" and their introduction is controlled by the opening of the valve "30", - The digested products circulate from "14" cells to "14" cells. They pass through all the cells and stay for an equal time in each cell, this residence time is substantially equal to the retention time in the digester divided by the number of digestion cells minus one (There is indeed a cell that remains empty inside the digester to allow transfers) .If the number of collages is too high, all the cells will be organized in autonomous units hydraulically so as to limit the number of transfers and allow sufficient residence time in each cell.

- The rejection of the digested products is controlled by the opening of the valve "31" the products passing through the pipe "25".

- At the start of digestion, incoming fresh products are threatened
- By mixing with 10, approximately of products at the end of di
management,
- These products intended for sowing are taken by
line "18" in the area above 1/4
bottom of the cell containing older products.

- When moving from one cell to another, the products 8 have seeds
- When switching from a cell of rank n to a cell of
rank (n + 1) around 10% of the cell's products (n + 1)
are used to seed the products from the cell
of rank n,
- These products intended for the seeding of the products of
the cell of rank n are taken via the line "18"
in the area above the lower 1/4 of the cell
the rank (n + 1),
- During digestion:
- If the digester is equipped with automatic regulation
of Ph it can be regulated.

- After digestion:
- If the digester is equipped with a heat exchanger,
calories will be recovered from the outgoing digested products
to preheat incoming fresh produce.

ADVANTAGES PROVIDED BY THE INVENTION AND MORE PARTICULARLY BY
THE BILL
- These are first of all the advantages indicated in the request
main patent to know in summary
- Homogeneity of digestion,
- Better anaerobic conditions,
- Solution of the problem of droppings and dense mud
which tend to settle at the bottom of the digester.

Possibility of reliable measurements of Ph and therefore possibilities
to correct Ph safely,
- Advantages due to modular construction with regard to
identifies the cost prices.

- Additional advantages provided by this addition:
- Possibility to build from a central unit
digestion always identical to her and team
peripheral elements in variable number (due to the teams
optional) digesters with different characteristics
performance annuities, parameter control
very digestion, degree of automatism. Digesters which
can best meet the requirements of each case
particular installation.

- Possibility with only 2 lines per cell 'as-
ensure the supply of each cell and its emptying å 2
different levels by the reversibility of product flows
in lines "18".

STATEMENT OF FIGURES - figure 1 plate 1:
- It is a vertical section passing through the axis of a row
cells. The cutting plane dA is shown in the fi
gure 2 plate 2.

- figure 2 plate 2
- This is a schematic plan view showing the layout
of the main elements.

- figure 3 plate 3
- It is a vertical section, the section plane passes through
the axis of symmetry of the pump "23".

- figure 4 plate 4
- This is the product circulation diagram.

- Note :
- The figures were represented with 9 cells, but
it is obvious that this is only a special case
since the number of cells is variable.

DETAILED DESCRIPTION - In Figure 1 Plate 1 which is a vertical section passing through the axis of a row of cells are shown
- The elements ensuring the general protection of one
tallation B namely, a slab "1" which supports the assembly
of the installation. this slab is poured on the ground. All
around this slab is a protective edge.

 The external side walls are formed by a joint "3". The upper part of the installation consisting essentially of the cover and the insulation of the upper part is supported by external pillars "4" and internal pillars "5". The roof is made up of beams "6", a waterproofing support "7" and an Ité waterproofing "8" (The installation can also be covered by any sloping roof) the presence of the pillars "5" allowing to have weak spans for frames.

- The elements ensuring thermal protection, namely an insulating layer "9" which is interposed between the slab "1" and the slab "26" where all the pipes are embedded an insulating layer "10" to insulate the walls side.

layers of insulation "11" and "12" to insulate the lateral pipes and valves, a layer of insulation "1Ç" to insulate the upper part.

- The elements used to contain the products being digested and which are constituted by cells "14" open upwards.

- The elements allowing the transport of products are as follows: from the lowest point of each cell, there is a drain line "17", in each cell a mixed drain supply line "18". All the pipes "18" are connected to the general supply manifold "19", all the pipes "17" and "18" are connected to the general drain manifold "20". All the pipes passing under the cells are embedded in a "26" slab. The valves are controlled by a device "39".

- The elements ensuring the maintenance of the digestion temperature are: the bath-nare which is contained by the wall "52"; a thermal probe "33" allowing the measurement of the temperature of the water bath which is maintained at a constant level "34".

- The elements making it possible to recover the biogas is:; u from anaerobic fermentation are the flexible recovery tarpaulin "35" which delimits a recovery space "55" as well as
all cells, sealing is ensured by a
hydraulic seal "37", the thrust on the tarpaulin due to the
slight suppression is contained by the bulkhead "38" against
which the tarpaulin rests on, the gas is evacuated by the con
pick "40".

- The space "41" is intended to receive the equipment
devices discussed above, except those
heating equipment which for safety reasons
are placed outside in a small annex room.

- In Figure 2 plate 2 which is a schematic view showing the arrangement of the main elements are shown the t
- Protection elements: "3" side cladding, feet
external support pillars "4", internal support pillars "5".

- Thermal protection elements: thermal insulation
lateral "10", the isolation of the valves "Il".

- Elements making it possible to contain the products: the cells
the digestion "14".

- Elements of product transport: Generated pipeline
supply line for "19" cells the main pipeline
drain line "20".

The general drain pipe
ge "Z0" and the general supply line "lgn
are connected to the single transfer pump n 23 n
- Also shown are the side wall "32" which
allows to contain the water bath and the pipe "40"
gas outlet.

- In Figure 3 plate 3, are shown
- The general "1 day" supply line for the cells,
the general drain line "20" for the cells, this
pipeline communicates via line "44" with the network
see "45". This tank is equipped with a level control
"47", it is connected to the suction of the pump "23" by the
line "46".

- The Pom2e "z" pumps back into the tank "49" through the
mediator of the "48" bend, this tank takes charge of the
general supply line "19" through one
diary of line "58".

- The tank "49" is equipped with a number of elements
mente: A level control "57" allows to stop the pump
eg "23" when the liquid reaches the tank "49"
the level "51" which is the filling level planned for
digestion cells. Line "56" connects
tion the tank "49" with the space "35" located above
digestion cells, levels at the end of filling
ge are therefore the same in tank "49" and in
digestion cells.

- The tank "49" is also equipped with a half chute
mobile cylindrical "52" which pivots around an axis "62",
the inclination of the chute "52" allows at will to say
manage or not the liquid leaving the line "48" on
a probe of Ph "53". The pH probe "53" is cleaned by
a jet of pressurized liquid brought in through the pipeline
"54". The Ph is corrected by a base which is introduced by
a pipe "55".

- Line "60" allows gas trapped in the ca
nal "20" to escape through the opening of a solenoid valve "61".

- In figure 4, plate 4 which is a general diagram showing the circulation of products are represented
- Digestion cells "14", from each cell leaves
a pipe "17" which is used only for emptying and
a mixed pipe "18" which is used for draining and a
food. All pipes "18" are connected to
the general line "19", all the lines
mixed "18" are connected to the general pipes "19"
and "20", transfers are made free of charge at the pump "23",
the supply of fresh products from outside
laughing is done by pipeline "24". rejection outside
The digested products are laughed at line "25".

 The valves "27" control the supply of each cell.

Claims (1)

 The valves "28" control the emptying of each cell at a  level located at the lower 1/4. The valves "29" control the  emptying of cells from the bottom. The 50 "valve controls  general admission of products. The valve "51" controls the  rejection outside of products. The general conduct "20" dice  mouth in the tank "45" which is connected to the suction  from pump "23" through line "46". General driving  feed line "19" is supplied by pump "23" by  through the reservoir "49".  CLAIMS Etevendication N 1  - Modular displacement digester for the continuous production of biomethane from organic substances characterized by  - In that the products inside the digester are contained in a variable number of cylindrical cells called digestion cells, so that the products during digestion pass from cell to cell,  - In that the digestion cells are arranged so that they can be inserted in a clad haggard whose surface on the ground is as close as possible to a square,  - In that the digestion cells are surrounded by a water bath maintained at constant temperature,  - In that a pipeline network makes it possible to connect any digestion cell to any other,  ~ In that a set of valves makes it possible from any digestion cell to pass the products into any other, to admit fresh products coming from the outside or to reject the products produced outside contained therein,  - In that the control of the filling level of the digestion cells is ensured by a single device which is common to all the digestion cells, and that the emptying control of the digestion cells is ensured by a single device which is common to all digestion cells.  - In that the biomethane is collected for all the cells by a flexible cover which determines above the digestion cells a single recovery space common to all the digestion cells. Claim 2  - Apparatus according to claim 1 comprising digestion cells "14" characterized  - In that they are all identical, they have in particular the same volume,  - In that they consist of a circular ferrule, the lower lateral edge of which is embedded a few centimeters in the concrete block which also serves to embed the supply and drain pipes,  - In that the bottom of the digestion cells formed by the concrete block which comes from another city is in the form of a truncated cone,  - In that the digestion cells are completely open at their upper part,  - In that the number of digestion cells is, with a determined type of digestion cell, a function of the maximum volume of the products being digested at the same time in the apparatus. Claim NO 3  - Apparatus according to claim 1 wherein the circulation of products from digestion cells to digestion cells is characterized:  - In that the residence time of the products in each digestion cell is roughly the same,  - In that if the number of digestion cells is greater than 9, the digestion cells are grouped into independent units, with regard to the circulation of products, each independent unit operates autonomously, it receives its fresh products directly from the outside, the products circulate from digestion cells to digestion cells in all the digestion cells of the unit, then they are discharged outside.  The autonomy of these sets is strictly limited to this. the number of digeation cells of an independent unit is between 5 and 8.  - In that the incoming fresh products are seeded with a certain percentage of the products whose digestion is finished 6  - In that during the passage of the products from a digestion cell of rank n to a digestion cell of rank (n + 1) the products coming from the digestion cell of rank n are seeded with a certain percentage of products originating the rank digestion cell (n + 1),  - In that, to all the digestion cells necessary to contain the total volume of products being digested inside the digester, an additional digestion cell is added in order to allow each transfer the complete emptying of a digestion cell in another digestion cell. Claim # 4  - Apparatus according to claim 1 comprising structures for protecting the digestion cells characterized:  - In that a vertical partition delimits two parallelipipedic volutes  - one which receives the digestion cells and which is isolated  continuously on all its faces,  - one that receives peripheral equipment except  of the heater which is placed outside the di  gestor,  - In that the part above the protection mainly consists of insulation and covering, is supported by pillars arranged laterally but also by pillars resting on the concrete block between the spaces remaining free between the digestion cells,  - In that the digestion cells rest on a base made up from bottom to top of a concrete slab resting on the ground, of a continuous layer of insulator, and of a concrete block in which are embedded all pipelines for transporting digested products, heat transfer fluid and biomethane evacuation. Claim NO 5  - Apparatus according to 1 comprising a heating system for the cells consisting of a characterized water bath  - In that all the digestion cells have their external lateral surface bathed by the water bath over a height equal to approximately 1/5 of the total height of the digestion cells,  - In that the water bath is contained inside a parallelipipedic tank whose four lateral faces surround all of the digestion cells, the bottom of this tank being formed by the concrete mass on which the cells rest . Claim NO 6  - Apparatus according to claim i comprising a network of Channels characterized:  - In that from the lowest point of each digestion cell, there is a drain pipe leading to a single general drain pipe,  - In that from each digestion cell leaves a mixed supply-drain pipe, in each digestion cell, the start of this pipe consists of a vertical tube drawn up in a zone tangent to the central zone, the length of the tube at 1 ' inside the digestion cell is approximately 1/4 of its height, at the other end this mixed pipe ends on the one hand on the single general drainage pipe and on the other hand on the only general supply line,  - In that the general supply pipe and the general drain pipe are each constituted by a parallelipiped pipe; these 2 pipes are placed side by side in the lower part of the space reserved for peripheral equipment, all the connections between the general supply and drain pipes and the pipes going to the cells are made through the underside of the pipes general supply and drainage,  - In that, from the upper face of the general drainage pipe, there is a pipe which, thanks to a solenoid valve situated above the maximum level reached by the products in the digestion cells, releases the gases possibly trapped in the general drainage pipe , by establishing communication with the space located above the digestion cells,  - In that the general drain pipe leads into a tank located entirely below the lowest point of this pipe,  - r.n that all product transfers are carried out by a single pump which is charged with respect to the general drainage pipe,  - In that the pump delivers to the upper part of a tank whose horizontal median plane coincides with the free surface of the products in digestion when the cells are full to the max.  - In that this tank communicates with the general supply pipe and puts it in charge and in that this tank communicates with the free space located above the digestion cells. Claim No. 7  - Apparatus according to claim i comprising a set of characterized valves  - In that at each junction between the drain pipes coming from each cell and the general drain pipe there is a valve,  - In that at each junction between a mixed drain supply line and the general drain line there is a valve and in that at each junction between a mixed drain supply line and the general drain line there is a valve,  - In that a valve is arranged in such a way that the pump can suck products either from the digestion cells or fresh products from the outside,  - In that a 3-way valve is placed immediately at the outlet of the pump discharge so that the pump discharges the products either at the top of the loading tank of the general supply line, or towards outside. Claim NO 8  - Apparatus according to claim i comprising a system for controlling the filling and emptying levels of the digestion cells characterized  - In that at the end of filling the level of the products in the tank for loading the general supply pipe is the same as in the cell being filled wDe and that this identical level is controlled by a single level control device located in the misc in tank of the general supply line,  - in that the lowest point of the bottom of each digestion cell is at a level higher than the tank for charging the pump and that this tank is equipped with a device for controlling the levels. Claim NO 9  - Apparatus according to claim 1 comprising a biomethane recovery system characterized  - In that the single flexible cover for recovering biomethans has the shape of a bell of parallelepipedic or cubic shape,  - In that the seal is ensured by a hydraulic seal the lower edge of the flexible recovery tank plunging into the water bath which surrounds the base of the digestion cells,  - In that the evacuation of the biomethane towards the outside is done by a pipe whose beginning is a vertical tube which leaves from the interior of the recovery space, this tube crosses the bain-marie then is embedded in the solid mass of concrete that supports the cells, it has no contact with the flexible recovery sheet. Claim NO 10  - Apparatus according to claim 6 comprising a tank for charging the general supply pipe which can optionally be equipped with a device for measuring and regulating the pH which is characterized - - In that a semi-cylindrical chute can by rotation around a horizontal axis divert on demand the products leaving the supply pipe in order to put them in contact or not with the Ph probe,  - In that a pipe opens near the Ph probe to allow its hydraulic cleaning,  - In that the Ph probe is fixed to the upper part of the tank so that it is still entirely above the free surface of the products in the tank when they reach their maximum level in said tank,  - In that a base supply line leads to the vicinity of the start of the tank drain line.