FR2463808A1 - 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 (parallelepiped 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 or bucket elevator , 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 yolumes of the 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 demonstrable 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 but transportable. It thus makes it possible to combine a rigorously controlled quality with a relatively low short per useful cubic meter.

The apparatus object of the invention is composed of a horizontal cylindrical tank, manufactured according to the method used for oil tanks, formed of steel sheet ferrules, a reinforced and welded bottom and a door s 'opening along a vertical axis of rotation.

The cylindrical shape allows hydrostatic forces to be supported with the minimum admissible thickness of steel.

In a first solution, the opening of the door and the installation of a springboard, allow access to a handling machine such as an agricultural tractor or a belt or screw elevator for the supply of raw material or its removal.

In a second solution, a "basket" containing the fermentable materials, replaces the grating and enters after loading, inside the tank, and leaves it in the open air for unloading.

There is no longer any risk of explosion due to the presence of methane in an enclosed environment and work is much easier, one.

or tractors and their forks operating loading or unloading laterally.

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

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

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

This harrow is located in the upper part of the apparatus, and is welded to the ferrule.

- A grating in the lower part, placed on tubes drilled 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.

Each tank is associated with machinery, placed outside, intended for the transport of liquids and 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 ventilation 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 weakly exothermic, and the temperature having to be kept as close as possible to 37 during this reaction, a heat-insulating envelope completely surrounds the tank, door included.

The lower part of the tank rests on a shaped cradle, thermally insulating the shell from the ground.

We describe below a realization studied in detail.

As a first solution, it is the tank shown in Plate I.

Composed of ferrules I with diameters ranging from 2.50 m to 4 m, 3 m long, the total length of the tank is 3 to 18 m by all multiples of 3 m; automatic welds are competitively priced.

At the rear, the cylinder formed by a sheet 2 has the same diameter and is sealed. Vertical reinforcements in profiles make it possible to use only a flat sheet of the same thickness as that forming the ferrules.

At the front, a door 3 opens around a vertical plane of rotation. Once opened, it constitutes, with the stepping stones 4 set up manually, an entry valid for any handling machine.

Before the loading of the fermentable material tank is finished, a guard made of perforated sheet metal 5 is put in place to prevent the materials from moving outwards, hampering the closing of the door and creating leaks in the seal.

The door consists of a sheet 3 provided with internal reinforcements I6 and is applied once closed on a seal 6 fixed to the front part of the tank. It pivots on hinges 23 mounted on stops and needle bearings.

The entire metal assembly is protected from oxidation by a special zinc paint, inside and out.

The tightening of the seal 6 (Plate 11) is ensured by a series of conical locks I7, the number of which varies according to the diameter of the tank. The locks are actuated from a common point, located 1.50 m from the ground; a crutch key I8, removable after use, applies to a square secured to a double plate I9 forming an eccentric, which pushes or pulls by means of a connecting rod 20 and a yoke 21 adjustable in length, the latch I7 which engages or disengages from a fixed point 22 welded to the ferrule I.

The harrow, intended for watering and maintaining the height of the fermenting material, consists of a central collector 7 and smaller tubes 8 pierced with holes.

The whole is welded to the ferrules.

The grating 9, of trade, in galvanized steel, rests on IO tubes, having the same centers, drilled for the arrival of the necessary fluids, and supplied by a collector II.

The I2 machinery is placed on the ground in a thermally insulated enclosure at the rear of the tank.

It includes the organs necessary for the circulation of various fluids - circulation pump.

- supply fan.

 reheating system.

- isolation valves.

I3 cradles in number according to the length of the tank, are placed on the ground on level, horizontal surfaces and at the same height. The location that the open door will occupy is arranged, as well as that intended for the springboard and machinery before the tank arrives at its mounting location.

Unloaded from the truck by crane using 4 I4 welded rings to the ferrules, the tank is placed on its cradles.

The cradles I3 receive the tank through a sufficient thickness of thermally insulating synthetic foam.

After connecting the various fluid circuits, the tank will be covered on all its lateral and rear surfaces with the thickness of synthetic foam provided for the climate of the region, as well as the door.

This synthetic foam is not shown on Plate I.

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

To avoid the harmful influence of rains and winds, the tanks are buried at mid-height and the excavated soil is used to cover the synthetic foam. Only the bottom of the tank and the machinery on the one hand, the door on the other hand, need a rain or wind protection, easily executed in polythene or other fabrics.

In the second solution (plate III), the grating is eliminated and replaced by a dismountable assembly comprising - A bottom 26 composed of 2 spars and welded spacers on which is stretched a metal "Deployed", or similar, with fairly fine meshes, which allow the fluids coming from the collectors II to go up, distributed by IO tubes, through the fermentable material - A rear 27 and a front 28, always in metal "Deployed, removable from the bottom 26.

- Full side panels 29, made of thin sheet metal, made slightly deformable by stiffeners in sections, are joined together at the top by tie rods 30. During loading, all the front, rear and side panels are mounted and joined together ; the tractor loads the fermentable material over the forks in the intervals between tie rods 30. For unloading, the tie rods 30 are withdrawn, the panels 29 are removed in part and the tractor fork can collect the rest of the compost which has not slipped to the ground by gravity.

- A ring 31 is welded to the front of the chassis 26. Hitched to the tractor, it allows the "basket" to be pushed into the tank or taken out.

- Rails 24, fixed to the ground, guide the "basket" by means of flanged wheels, and are secured to the rails inside the tank by removable rails 25 which, once removed allow the door to close .

- The upper collector 7 and the harrow 8 remain identical to those of the first solution.

The whole assembly is hot dip galvanized.

In addition, in the case of the use of a battery of 3 large tanks, as recommended, a fourth basket can serve as a deposit for the fermentable material while waiting for its installation by a lateral transport carriage on rails in the one of the 3 tanks to be loaded.

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

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

It can 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 installation of gas compression stations in bottles, so as to use it as fuel for internal combustion engines (tractors, cars, vans, etc. ...)

Claims (1)

I - Methane fermentation tank from various plants, characterized by the fact that it consists of - a cylindrical metallic body. - an upper harrow, limiting the height of the fermentable materials, and allowing watering. Either a lower grating, galvanized steel or other. Or a mobile "basket" containing the fermentable materials, loaded and unloaded outside the tank. - a lower manifold, allowing the arrival or departure of fluids. - a set of pipes intended, on the one hand for the evacuation of the liquid, on the other hand, for the ventilation of materials in aerobic stage. - a door allowing the introduction of a handling machine. - a peripheral thermal insulation, made of synthetic foam or any other insulating material, allowing thermal equilibrium during the anaerobic methanogenic phase. - machinery comprising a pump, a fan, a heater and the necessary valves, pipes and fittings. - cradles-supports on the ground, forming thermal insulators. II - Fermentation tank according to claim I, made of a material other than metal: precast concrete, pre-stressed or not, wood, rigid plastic, reinforced plastic, masonry.