FR2461750A1 - Fermentation chamber to produce methane from organic waste - has extra large doorway for fast batch loading and discharging - Google Patents

Abstract

In appts. for the aerobic or anaerobic fermentation of vegetable waste, manure, stable litter etc. in which a batch of waste is loaded into a chamber, the chamber now has a doorway in one side which is big enough to allow the vehicle loading of a new batch into the chamber. The chamber can be of rectangular cross-section made up of flat, prefabricated units, e.g. of concrete, lined with a gas-impermeable membrane of rubber or flexible patrick. Alternatively, the chamber can be of horizontal, cylindrical form, made of rigid metal or plastic sections which are factory made and assembled on site. The chamber can be loaded in stages by a tractor driving in and out. Alternatively, a complete batch can be wheeled into the chamber in a cage which stays inside until fermentation is complete.. Loading and unloading of the chamber is speeded up considerably. Manhandling is eliminated. Inexpensive factory units can be assembled for high output generators of methane.

Description

The present invention relates to methane fermentation tanks, intended to produce methane from manure, straw or any other fermentable plant. It is particularly suitable for the DUCELLIER-ISMAN process, which consists in preceding the methanogenic phase of anaerobic fermentation, with an aerobic pre-fermentation phase, in fermenters with discontinuous operation, by successive vatting.

The tanks currently used have various shapes (parallel or cylindrical) and are made of reinforced concrete, metal, or rigid plastic, such as PVC, or polyester reinforced with fiberglass.

They are loaded with fermentable material either by pumping effluents containing solid particles (which obviously considerably limits the load in fermentable material), or by handling equipment such as a farm tractor fork, belt elevator or buckets, worm, etc.

 (which requires the presence of a cover and a door).

The technical requirements imposed by the very nature of the fermentation (resistance to corrosion, tightness to liquids and gases), lead to manufacturing in the factory, subject to strict controls, of monoblock assemblies.

We are then limited, in size, by the sizes imposed on road or rail transport.

However, the economic benefit of methane fermentation is all the greater as the volumes of fermenters are greater
We are therefore faced with a choice between two solutions - Factory construction of satisfactory quality fermenters, but of necessarily limited dimensions, therefore of a high cost price per cubic meter.

- On-site construction of large capacity fermenters, but of questionable technical quality in terms of sealing and corrosion resistance.

The fermenter object of the invention allows to get out of this alternative, by making in the factory a tank of large dimensions, very easily assembled at the place of operation. It thus makes it possible to combine a rigorously controlled quality at a relatively low cost per useful cubic meter.

The device object of the invention consists of a pocket of flexible material, easily foldable for transport, waterproof to water and gas, mounted on the place of operation in an assemblable cradle, intended to give it the desired shape (parallel lepiped, -or other) and to support the hydrostatic forces generated by the mass contained in the pocket.

The cradle is therefore easily transported, in disassembled elements, to the place of assembly. It is assembled by any fixing system, such as bolting or the like, so as to produce the cradle intended to receive the flexible bag.

This is mounted on the cradle, and constitutes a 5-sided parallelepiped.

Indeed, to allow access from the pocket to a handling machine such as an agricultural tractor or a belt or screw elevator, one of the side faces of the parallelepiped is removed, and replaced by a door.

Other devices complete this tank: - A manhole in the flexible pocket to allow ventilation of the fermenter in the aerobic phase, and after fermentation, before the penetration of handling equipment into the fermenter.

(Forced ventilation intended to lower the methane level below the explosion limit).

- A harrow, made of tubes pierced with holes, allowing floating materials to be kept at a limit level, and also ensuring watering of the material.

This harrow is located in the upper part of the device, and rests on battens also serving as protection against shocks.

- A grating in the lower part, placed on tubes with holes. The grating is used for the circulation of a machine in the tank; the drilled tubes are used for evacuating the liquid after the anaerobic phase, and for blowing air in the aerobic phase.

- A hole in the upper part, for collecting the methane produced.

To each tank is associated a machinery, placed outside, | intended for the transport of liquids and for ventilation.

It includes - A pump, suitable for pumped liquids, allowing filling, emptying and recycling of loaded liquids.

- A heating device mounted on the recycling circuit allowing the mass inside the tank to be kept at constant temperature.

- A ventilation device (pressurized air - booster fan) ensuring the aeration of fermentable materials during the aerobic phase.

- The valves necessary for the various operations.

- The temperature and level control and regulation devices necessary for conducting fermentation operations.

Finally, the anaerobic methanogenic reaction being very slightly exothermic, and the temperature having to be kept as close as possible to 370 during this reaction, a heat-insulating envelope completely surrounds the tank, door included.

The lower part of the tank rests on a base of insulating material capable of supporting the load of the fermenter: polyurethane, for example.

We describe below a realization studied in detail by mentioning the different possible variants. It is the tank shown in Plate I.

A cradle is made by assembling frames made of metal profiles I, made in the factory, on site. These frames are coated internally with a plywood 2 "exterior" quality glued to the uprights of the frame with a polymerizing adhesive. All of the metal parts are protected by hot-dip galvanizing or zinc painting.

This cradle being mounted, the flexible waterproof pocket is applied to its walls, and held by fixing ears. This pocket 3 can be made of natural or synthetic rubber
or similar plastic product, coated. It is completely airtight, made in the factory using the well-known technique of inflatable boats.

Details 4 & 5 of plate no. III show how, in this airtight enclosure, the fitting of the upper harrow 4 and the sealing of the door 5 are carried out.
The door 7 opens forward, around a horizontal axis at its base; once opened, it is a springboard for entry.

It consists of a square tube frame, covered with a smooth sheet metal which serves as a support for the seal; two ribbed sheets prevent skidding on the open door.

It is calculated to support the weight of an agricultural tractor.

The closing and opening of the door is controlled by a screw. end and a system of nuts 8 with trapezoidal threads, maneuverable using a crankshaft.

It is blocked naturally, at the end of the race. The tightening on the joint, to make it watertight, is obtained by a series of captive screws, operated with the same tools as the approach screw.

The harrow is made up of a central collector in square tube, longitudinal, and of transverse square tubes of smaller section 4 drilled for watering.

The grating 9, of trade, in galvanized steel rests on the 2 longitudinal collectors IO placed on the ground, and on the lateral wooden wedges II.

To protect the flexible casing against possible shocks during loading and unloading, I2 fir battens are placed horizontally against the side walls, up to harrow height. They are interconnected by vertical battens applied against the flexible covering, and supporting the harrow.

I The I3 machine is placed in a thermally insulated enclosure at the rear of the fermenter. (plate NO II)
It includes the organs necessary for the circulation of various fluids
- I circulation pump 16
- I supply fan 17 - I heating system I8
- isolation valves 19
I4 insulation is provided by a high thickness of polyurea
thane (thickness depending on the climate of the region) on all
the faces, door included. The insulation is permanently fixed, for example by gluing.

the whole is covered with earth on the 3 side faces,
so as to best isolate it from the outside environment. The door
is placed in the best possible orientation, sheltered from the winds (in the South, in principle in our renions).

An I5 manhole allows venting or venting
forced lation before entering the tank, at the end of
cycle.

The apparatus which is the subject of the invention allows large-scale industrial production of large-scale fermenters intended for equipping all types of agricultural holdings.

Its modular design allows the production of tanks of different lengths, from standard frames, by assembling an adequate number of these frames together.

Its low cost price, its perfect seal, its very good resistance to corrosion, its easy transport and assembly, will allow its wide distribution.

It could also be used, in large dimensions, on the scale of agricultural cooperatives processing maize or wheat for example.

Such installations, by the importance of the quantities of methane produced, would justify the establishment of compressor stations
gas in bottles, so that it can be used as a car
fuel for internal combustion engines (tractors, cars, trucks
sharp, etc

Claims (1)

I - Methane fermentation tank from various plants, characterized by the fact that it consists of a rigid metal cradle assembled on site. - rigid panels made of rot-proof material such as plywood. "Outside. - a flexible pouch, waterproof and gas-tight, made in the factory, made of coated flexible material, such as natural or artificial rubber, or an appropriate plastic. - an upper harrow, limiting the height of the fermentable materials, and allowing watering. - a lower grating, in galvanized steel or other. - a set of lower piping intended, on the one hand for the evacuation of the liquid, on the other hand, for the ventilation of materials in aerobic stage. -a drop-down door allowing the introduction of a handling machine. - a peripheral thermal insulation, in polyurethane foam, or any other insulating material, allowing thermal balance during the anaerobic methanogenic phase. - machinery comprising a pump, a fan, a heater and the necessary valves, pipes and fittings.  II - Fermentation tank according to claim I, characterized in that the frames constituting the cradle are made of material other than metal: precast concrete, (pre-stressed or not) wood, rigid plastic, masonry.