FR2470161A1 - Continuous anaerobic fermentation of heterogeneous mass - in closed fermentation chamber with hydraulic air-locks fitted with mechanical devices for feeding and discharging mass - Google Patents

Abstract

Appts. for continuous anaerobic fermentation of a solid or liq. heterogeneous mass contg. more than 10% of dry materials comprises a closed fermentation chamber fitted with a device with a seal for taking off gas, a device for feeding the mass to be treated, a device for drawing off the fermented mass and a heating device. The appts. incorporates first and second hydraulic air-locks. The first air-lock for the feed is constituted by a vessel contg. liq. into which dips a partition which does not touch the bottom. One of the walls of the vessel is constituted by the wall of the fermentation chamber. The partition is constituted by a part of the top of the fermentation chamber The air-lock is fitted with a mechanical feed device and a level controller. The second hydraulic air-lock, for the discharge, is also constituted by a vessel into which dips a partition which does not touch the bottom. One wall and the partition of the air-lock are constituted by the lower walls of the fermentation chamber. The second air-lock is fitted with a mechanical discharging device. Appts. is applicable to fermentable masses of urban or agricultural origin e.g. household refuse, manure contg. litter, beetroot pulp, sea-weed. The invention resolves the problem of providing an anaerobic fermentation appts. operating continuously and fluid-tight to the gas obtd. by fermentation.

Description

The present invention relates to a device for anaerobic continuous fermentation of a heterogeneous solid or liquid mass containing more than 10% of dry matter.

This device applies in particular to methane fermentation. This fermentation is a complex process which takes place in an anaerobic environment thanks to complementary populations of microorganisms and which gives rise to the formation of a gas containing methane and carbon dioxide (C02). This fermentation is slightly exothermic and to obtain a good yield the fermented mass must have a temperature of 35 to 370. In temperate climates it is therefore generally necessary to heat the mass to be fermented.

The device of the present invention makes it possible to treat heterogeneous solid or liquid masses containing more than 10% of dry matter. It applies to fermentable masses of urban or agricultural origin such as household waste, livestock manure containing the elements of the litter, for example straw, beet pulp, or seaweed.

 Hitherto it has been known to treat these heterogeneous masses batch by batch. But in this case it is necessary to inoculate each new mass to be treated and to restart after each unloading or loading operation the fermentation process leading to methanogenesis.

 On the other hand, it is known to treat liquid substrates by pumping systems. These methods are difficult to apply to the treatment of heterogeneous substances because it is necessary to carry out grinding to remove the heterogeneous solids which would clog and block the installations. The grinding costs necessary to obtain a fluid product are very high.

 The problem to be solved was therefore to find an anaerobic fermentation device of a heterogeneous mass which functions continuously and which is impermeable to the gas obtained by fermentation.

The present invention relates to a device which makes it possible to solve this problem.

The present invention relates to a device for anaerobic continuous fermentation of a heterogeneous solid or liquid mass containing more than 10% of dry matter comprising a closed fermentation chamber provided with a device for evacuating gas, a device for introduction of the mass to be treated and of a device for withdrawing the fermented mass and possibly a heating device characterized in that it comprises a first hydraulic airlock consisting of a tank containing liquid in which dives a partition not touching the bottom of the tank, one of the walls of the tank being constituted by the wall of the fermentation chamber and the partition by a part of the roof of the fermentation chamber, the airlock being provided with a device for mechanical power supply and a level controller, and a second hydraulic airlock also consisting of a tank containing liquid in which plunges a partition not touching the bottom, a wall and the partition being formed by the lower walls of the fermentation chamber, the second airlock being provided with a mechanical withdrawal device.

 The presence of the hydraulic locks prevents the escape of the fermentation gas, the gas pressure that one wishes to obtain being controlled by the height of the liquid in the hydraulic lock. On the other hand, it is possible to introduce through the lower part of the airlock, under a partition separating the airlock into two compartments, heterogeneous substances without there being any blockage.

 According to the present invention the material to be treated is fed into the first airlock, enters the fermentation chamber and after a stay in it emerges through the second airlock. It is most often necessary that the levels of liquid in the two airlocks are controlled. In fact, the raw material introduced will, depending on its dry matter content and its retention power, absorb a greater or lesser amount of the liquid contained in the first airlock. In addition, often the mechanical introduction device will, by pumping effect or as a result of projections, introduce a part of the airlock liquid into the fermentation chamber. The liquid level in the first airlock therefore tends to drop, so it is necessary to control it and reintroduce liquid to bring back or maintain the desired level in the airlock.

A fraction of the liquid from the first airlock is absorbed by the fermenting material, but most often the other part is collected at the bottom of the fermentation chamber and completes the liquid mass of the racking airlock. On the other hand when the fermenting mass is heated using a heat transfer liquid, a fraction of this liquid also completes the level of the liquid in the airlock.

Therefore the level of this liquid rarely tends to decrease. However, it may be preferable to also introduce a level controller in cases where the quantity of liquid withdrawn with the fermented substance is high or when there is a large evaporation.

 Depending on the nature of the raw material treated, the liquid added to maintain the level in the airlocks will consist of clear water or any other solution compatible with the treated material. It may be preferable to introduce a solution containing an inoculum into the first airlock to facilitate fermentation.

 In the case where the fermenting mass is heated using a heat transfer liquid, the level can also be supplemented with a fraction of this heat transfer liquid. In this case the level controller of the supply airlock is connected to a bypass of the coolant supply line.

 The level controller can be of any known type such as float, bubbling or echo controller.

The mechanical supply devices contained in the supply and withdrawal airlocks must on the one hand be adapted to the geometric shape of the airlock, on the other hand to the physical form of the mass treated.

These devices can be either chains or dredgers with scraper, buckets or fork fingers, or a drum system provided with blades, fork fingers or lugs, or a system of force-feeding Archimedes or jack shield, or a plow type blade system.

 The geometric shape of the fermentation chamber can be arbitrary. The fermentation chamber preferably has an inclined side wall so as to facilitate the flow of the fermentation mass. It also includes a roof, a part of which is inclined or vertical so as to form the partition of the first hydraulic airlock. The roof is also provided with a gas-tight closing device comprising a pipe for drawing off the fermentation gas. The lower parts of the side walls respectively form a wall and the partition of the airlock.

 According to a particular embodiment of the invention, the fermentation chamber has an elongated shape, the airlock and the airlock having a channel shape and being connected to the long sides of the fermentation chamber. In this case it is preferable, to balance the supply of raw material and the racking of fermented material, that the loading or unloading devices are mobile and can move along the fermentation chamber. For this purpose, the loading and unloading devices are, for example, mounted on carriages with manual or motorized translation.

 According to a particular embodiment of the invention, the mobile loading and / or unloading device circulates in an airlock filled with clear water and it is in a closed enclosure isolated from the airlock. For this purpose, the mobile loading device also includes a hydraulic lock whose level is controlled. An on-board siphon allows for example to take the quantity of liquid required in the airlock filled with clear water.

 The description given below without implied limitation will allow a better understanding of the invention.

 Figure 1 shows in vertical section a fermentation device according to the invention.

 Figures 2 to 4 schematically represent different types of mechanical devices for introducing the mass to be fermented.

 Figures 5 and 6 schematically represent a particular embodiment of a mobile power supply device.

The fermentation device according to the invention shown in FIG. 1 comprises a first hydraulic airlock for supplying the mass to be treated (1), a fermentation chamber (2) and a second airlock for withdrawing the fermented mass (3). The first airlock consists of a tank comprising a lateral retaining wall (4) and a wall (6) common with the fermentation chamber (2). The airlock partition consists of a part of the roof (5). In the embodiment shown in FIG. 1, the mass to be treated is loaded using a fork finger chain (12). Other loading devices are possible: drum fitted with lugs ( Fig. 2), set of two drums rotating in the same direction and located in each compartment of the airlock (Fig. 4), Archimedes screw (Fig. 3>
The fermentation chamber (2) is closed by a watertight cover in which pipe feeders are provided to a gas storage gasometer. According to the embodiment shown in Figure 1 the seal is obtained by hydraulic seals (10). In the fermentation chamber (2), part of the wall (6) is inclined so as to facilitate the flow of the treated mass towards the lower part of the fermentation chamber and the hydraulic airlock (3). This wall (6) also constitutes one of the walls of the hydraulic airlock (3). The wall (7) of the fermentation chamber which is vertical in the embodiment shown in FIG. 1, constitutes the internal partition of the hydraulic airlock (3 ). The mechanical extraction device shown in FIG. 1 consists of a fork dredger (8). The drip area (9) of the fermented mass is slightly inclined so as to facilitate the recycling of drips.

 Figures 5 and 6 schematically show a hydraulic airlock (1) containing a mobile loading device. Figure 5 is a side view and Figure 6 a vertical sectional view.

The mobile loading device consists of a siphon-shaped tank (11) which can move laterally in the airlock (1). In the embodiment shown the introduction device (12) consists of a drum provided with lugs. An on-board siphon (13) makes it possible to maintain the balance of the levels between the airlock (1) and the mobile tank (11).

According to the embodiment shown diagrammatically in FIG. 5, the level of liquid in the airlock (1) is controlled by a float ((14).

 The fermentation device can be constructed of concrete, masonry, sheet metal boilermaking or rigid or flexible plastic. it suffices that the material used provides sealing.

Claims (4)

1 / Device for anaerobic continuous fermentation of a heterogeneous mass  solid or liquid containing more than 10% dry matter with a  closed fermentation chamber provided with a gas evacuation device  formed, a device for feeding the mass to be treated, a device  tif of withdrawal of the fermented mass, and possibly a device  heating characterized in that it includes a first hydrau airlock feed line consisting of a container containing liquid in which  plunges a partition not touching the bottom of the tank, one of the walls of the tank being constituted by the wall of the fermentation chamber and the partition  by a part of the roof of the fermentation chamber, this first airlock being fitted with a mechanical supply device and a level controller, and a second hydraulic airlock also consisting of a tank containing liquid into which a partition does not touch the bottom, a wall and the bulkhead of the airlock being constituted by the lower walls  of the fermentation chamber, this second airlock being provided with a device for  mechanical racking. 2 / Anaerobic fermentation device according to claimlcomportant a  heating system using heat transfer liquid, characterized in that the hydraulic airlock level controller is connected to a dice  rivation of the coolant supply line. 3 / Anaerobic fermentation device according to claims 1 or 2 charac  terrified by the fact that the fermentation chamber has an elongated shape, that  the supply and withdrawal airlocks have a channel shape and are connected  along the long sides of the fermentation chamber and that the  loading and unloading are mobile along the farm chamber  tation.  veal. strategically a hydraulic airlock containing a ni control device a closed enclosure isolated from the airlock and / or racking and compor by the fact that the loading and / or unloading devices are in  4 / Anaerobic fermentation device according to claim 3 characterized