FR2499545A1 - Digester vessel to make methane from heated liq. manure - employs external heating jacket circulating water from boiler - Google Patents

Abstract

The vessel is equipped with a heating system to warm the liq. manure. The heating system comprises an external source of heated fluid which is circulated through an external heat transfer jacket on the vessel. Pref. the jacket encircles a zone in the lower half of the vessel pref. the exterior of the jacket is encased in a thicker layer of thermal insulation than the remainder of the exterior surface of the vessel. The vessel is used for digesting liq. manure to produce methane gas etc. as it converts the waste into liq. fertiliser. The liq. manure is heated to about 37 deg.C to assist fermentation. The heat transfer jacket offers efficient heating from a high area of heat exchange surface. The heating system is entirely outside the vessel space so that no projections can obstruct rotary agitators.

Description

Slurry digester with heating wall.

 The slurry of a digester is heated, according to the known prior art, either by passing hot water, coming from a boiler, through a coil disposed inside the slurry treatment tank, or on the contrary, by passing the slurry through a coil arranged inside a hot water tank separate from the treatment tank.

These arrangements have the following disadvantages
- difficulty in achieving large exchange surfaces which then require considerable and expensive coil lengths
- in the second hypothesis, there are significant risks of clogging, and an additional energy expenditure due to the presence of the slurry circulation pump.

 The invention intends to remedy this state of affairs by proposing a new slurry digester and therefore having as its object a slurry digester comprising a slurry treatment enclosure provided with a slurry heating device.

 This reheating device comprises a double wall constituting at least part of the wall delimiting the enclosure, and, a source of heat transfer fluid to which said double wall is connected.

The following advantageous arrangements are, moreover, preferably adopted
- the double wall is located in the lower half of the main body of the enclosure;
- in line with the double wall, the thermal insulation of the enclosure is reinforced.

 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 drawings are given for information only and are not limiting.

Reference will be made to the accompanying drawings, in which
- Figure 1 is an axial section of a slurry digester according to the invention
- Figure 2 is an enlarged view of detail D of Figure 1.

The slurry digester shown includes
- A tank 1 in which the slurry is treated, delimited by a cylindrical wall 2, and provided with a domed upper bottom 3, and a tronconioue bottom bottom 4
- a flange 5, which is integral with the upper bottom 3 and allows the connection of a gas evacuation pipe released by the slurry,
- a ferrule 6, which is of generally cylindrical shape, and is fixed to the external face 7 of the lower part of the wall 2 by welding (8) of its upper and lower edges 9, which are slightly offset relative to the body of this shell, so that a double wall is produced in cooperation with the wall 2 and delimits a sealed enclosure 10 all around the lower part of this wall 2,
a boiler 11, external to the tank 1,
- two conduits for circulation of the heat transfer fluid (generally water) between the boiler 11 and enclosure 10 the conduit 12 for admitting hot water into the enclosure 10 and the conduit 13 for returning water to the boiler after cooling by heat exchange with the slurry,
a thermal insulating coating 14 with a thickness E14 over the entire external face of the tank (wall 2, upper bottom 3, lower bottom 4), except on the part covered by the ferrule 6,
- a # .ent thermal insulating coating 15 of thickness
E15 on ferrule 6 and on conduits 12 and 13.

 In the example shown, E15 = (r14) x 2.

 In addition, it should be noted that the insulation material is the same for the coating 14 and for the coating 15. In fact, in the digester considered, the temperature of the slurry of the tank 1 is of the order of 370C, while the temperature of the heating water admitted into the enclosure 10 is of the order of 700C, which explains the doubling of the thickness of thermal insulating material.

Furthermore, if we designate by
- Fol2, the height of the cylindrical part of the tank 1, which coincides with the wall 2,
h, the height of the lower part of this wall 2, which, in this case, corresponds substantially to the lower third of the wall 2, and,
- H6, the height of the ferrule 6, we see that the ferrule 6 is located at the lower part of the wall 2, and, in fact, is contained in the height h. Note also, the presence in the tank 1 of the slurry, which fills this tank up to level 16, at the upper part of the wall 2.

The layout shown has the following advantages
- simplicity of implementation,
- very large exchange area,
- no internal relief preventing the mixing of the slurry.

 The invention is not limited to the embodiment shown, but on the contrary covers all the variants which could be made to it without departing from its scope or its spirit.

Claims (3)

 1. Slurry digester comprising an enclosure (1) for treating slurry provided with a device (11-10) for reheating slurry, characterized in that this reheating device comprises a double wall (10) constituting at least one part of the wall (2) delimiting the enclosure (1), and, a source (11) of heat transfer fluid to which said double wall is connected (12 -13).  2. Digester according to claim 1, characterized in that the double wall (10) is located in the lower half (h) of the main body (2) of the enclosure (1).  3. Dig # esteur according to any one of claims 1 and 2, characterized in that in line with the double wall (10), the thermal insulation (15) of the enclosure is reinforced (E15).