FR2499542A1 - Digester vessel to make methane from liq. manure - has overflow with upstream vertical leg to build head pressure to shift blockage - Google Patents

Abstract

Digester vessel in which liq. manure is fermented to generate methane gas etc.. The vessel is of the type in which the level of liq. is automatically controlled by overflow discharge of surplus liq.. The overflow pipe extends downwards from its entry at the surface of the liq. for a distance equal to a substantial part of the total depth of the vessel. Pref. the lower end of the pipe is turned through a 180 deg. 'U'-bend to form a siphon trap leading to the discharge end of the pipe. Pref. an isolating valve is fitted at the discharge end of the overflow pipe. The vessel digests liq. manure to produce methane etc. and to convert the waste into a liq. fertiliser. The danger of blockage of the overflow pipe between additions of fresh manure is practically eliminated. Any crust formed in the 'U'-bend is probably shifted as overflowing liq. falls down the considerable height of pipe between the liq. surface and the 'U'-bend. If no the substantial head which builds up behind the blockage as the pipe fills with liq. will almost certainly clear the passage.

Description

In known slurry digesters, the slurry is emptied according to one of the following two types
- drain by overflow with plunger hose
- emptying by siphon type overflow.

 These two empties are said to be automatic because they evacuate the same quantity of slurry as that which was introduced by the intake manifold without any intervention.

They have the following drawbacks.

 The feeding of a digester is cyclical and is done once or several times a day. Between each injection, there is a more or less significant rest time. This time is sufficient to cause blockages inside the drain pipes. These blockages, which, at the beginning, only cause slowing of the flow, manage to completely block the pipes, opposing the emptying, which quickly leads to serious incidents.

 The invention intends to remedy this state of affairs by proposing a new arrangement of the evacuation duct.

 It therefore relates to a slurry digester, comprising a slurry treatment enclosure provided with a slurry supply to be treated and a slurry discharge conduit after treatment.

 This evacuation duct extends over a significant part of the height of the enclosure between the level of liquid manure in the treatment couic, situated at the upper part of the enclosure and I; lower part of the enclosure.

The following advantageous arrangements are, moreover, preferably adopted
- the lower part of the exhaust duct is shaped like a siphon
- an isolation valve is placed on the discharge pipe.

 The invention will be better understood, and secondary characteristics and their advantages will become apparent during the description of an embodiment given below by way of example.

 It is understood that the description and the drawing are given for information only and are not limiting.

 Reference will be made to the accompanying drawing, in which the single figure is an axial section of a digester according to the invention.

The slurry digester shown includes
- a generally cylindrical tank 1 with a vertical axis 2 of revolution
a duct 3 for admission into the tank 1 of the slurry to be treated there, a pipe which opens inside the tank, at its lower part,
a flange 4, which is integral with the upper bottom 5 of the tank and allows the connection of an exhaust duct (F) for the gas released by the slurry, and,
- a duct 6 for evacuating the treated slurry from the tank 1.

This conduit 6 itself has the following three parts
a section 7, which is rectilinear, vertical, and which extends between the upper level 8 of the free surface of the slurry inside the tank 1 and practically the lower part of the cylindrical body of this tank,
a bend 9 which extends the lower part of the section 7 and rises in a short vertical section 10, forming a drain siphon,
a horizontal rectilinear section 11, which is connected to the end of the vertical section 10, which passes through the wall of the tank 1, and, on which an isolation valve 12 is placed, outside the tank 1, provided with a device 13 for controlling its opening and closing.

 The isolation valve 12 is in principle open, its closing being controlled only exceptionally in order to be able to isolate the tank 1. In the present description of operation, it is assumed to be open.

In the idle state, the section 7 of the evacuation duct
tion is empty of slurry on the height H, which is filled by the
gas contained in the enclosure, in the upper volume 14 of
this one, located above level 8 of the slurry. The drop
h of slurry, which fills the elbow 9 and the section 10 and succeeds
the aforementioned height H of section 7, corresponds to the pressure of the gas in the digester, the slurry valve being open on
1 atmosphere.

During filling through the intake duct
3, the level of slurry rises in tank 1, and the slurry drains
cue then through the exhaust duct 6 without any problem.

But if you consider that after a period
rest, between two injections, the lower siphon is clogged,
two phenomena will combine to force anor resistance
male to evacuation thus established
- first of all, during feeding, the slurry
flows down the drain, and reaches the surface
free 15 of the siphon, after a significant fall H. This disposi
tion therefore substitutes for the regular flow of provisions
classic, a dynamic effect that can overcome a colmata
benign age
- if the clogging is more severe, the slurry will go up in the drain pipe, up to level 8 of the
free surface of the slurry in the tank 1, thus creating a
sensitive overpressure, corresponding to height H, on the siphon.

We thus perform a combined action of dynamic impact
that a kind of hunting effect, and overpressure favoring ~ evacuation considerably.

The invention is not limited to the embodiment which
has just been described, but on the contrary covers all the
variations that could be made to it without departing from its
frame, nor of his mind.

Claims (3)

R E V E N D I C A T I O N S  1. Slurry digester, comprising an enclosure (1) for treating slurry provided with a supply (3) of slurry to be treated and a conduit for evacuating slurry after treatment, characterized in that evacuation duct extends over a significant part (H) of the height of the enclosure between the level (8) of the slurry being treated, located at the upper part of the enclosure and the lower part of the pregnant.  2. Digester according to claim 1, characterized in that the lower part of the exhaust duct is shaped like a siphon (9).  3. Digester according to any one of claims 1 and 2, characterized in that an isolation valve (12) is arranged on the discharge pipe (6).