EP0997686A1 - Device for thermal oxidation of solid, gaseous or liquid residues of slaughterhouses - Google Patents

Abstract

The burner (3) receives all active flows, including atomization air (10), combustion air (12), possible secondary fuel, condensibles (11), fats and residual liquids (8) and transfers them into a rotary or fixed furnace (1), as a single jet with axial discharge. A screw conveyor (2) feeds in crushed solids (5) continuously. Preferred Features: The height (H) of the burner axis above the furnace axis satisfies H = 0.3 D, where D is the furnace internal diameter. The burner radial axis makes the angle beta = 20 degrees with the vertical axis, these axes passing through the center of the furnace end face. Axial thrust exerted by the burner, expressed as G Newtons, which is related to furnace thermal loading, expressed as W Megawatts, satisfies G is greater than or equal to 60 W.

Description

The technical sector of the invention is that of the thermal treatment of the residues produced in industrial slaughterhouses and rendering units.

• Les farines impropres à la consommation animale.
• Les graisses et les boues grasses du traitement des effluents de l'usine.
• Les buées de déshydratation et de cuisson.

The residues in question mainly concern the products resulting from the processing of animal carcasses or various by-products into flour, such as pig bristles, viscera, bones, feathers, etc., namely :

• Flours unfit for animal consumption.
• Fats and oily sludge from the treatment of plant effluents.
• Dehydration and cooking fumes.

• Broyage
• Déshydratation dans un cuiseur chauffé à la vapeur
• Pressage et conditionnement des farines

From the carcass of a bovine, for example, which is to be treated in the rules imposed by the regulations, the products to be eliminated, mentioned above, are obtained in a processing chain which schematically includes the stages following:

• Grinding
• Dehydration in a steam heated cooker
• Pressing and packaging of flour

The dehydration and conditioning of the flours produces fumes which are, in fact, the aqueous part of the charge collected in the form of vapor more or less charged with grease carbonated and in highly smelly volatile compounds. This vapor phase represents approximately 40% of the initial weight and must be oxidized at high temperature.

Part of the fat is collected at the outlet of the cooker and another part, after extraction by pressing of the solid residue.

The solid phase, partially dehydrated and degreased, represents from 30 to 40% of the incoming charge. Insofar as it comes from contaminated animals declared unfit for recycling in the cattle food chain, it must be incinerated.

High calorific fats can be used as an auxiliary fuel in the heat treatment device.

Of course, the combustion of the products considered above must be carried out in compliance with the increasingly restrictive legal provisions.

The object of the present invention relates precisely to the optimization of the conditions of combustion of all the residues in question.

With regard to the prior art, different methods can be used to incinerate the products in issue, using ovens of various designs, such as rotary hearth ovens, mechanical grids, fluidized bed, pyrolysis, rotary, open flame.

Among all the possible technologies, that of the rotary oven slightly inclined on the horizontal prevails.

It is an oven appearing as an elongated cylinder, arranged between a fixed facade on the inlet side and a fixed ash removal chamber on the outlet side for recovery of the formed slag by non-combustible parts. The interior of the oven is lined with refractory products, bricks or concrete, to insulate the walls and resist high temperatures. The hearth is rotated by means of rollers or by chain and toothed wheel.

Solid waste is introduced at the facade by screw or pusher. It's in also facade which are injected the liquid and gaseous effluents, as well as the combustion air.

The regular and continuous rotation of the furnace causes the mass of solid waste as soon as it introduction and during combustion in a permanent reversal movement, accompanied by mixing and fractionation of the mass which makes it possible to expose the waste, permanently renewed, to the radiation of the refractory lining and to the combustion air of which depends on the activation of combustion.

According to the state of the art, the provisions concerning the mechanics of the rotary kiln and the introduction of residues are known and well controlled. It is not the same with what concerns the admission into the furnace of the air necessary for combustion. According to the techniques in application to date, air is injected by means of tubes distributed at different points of the facade. According to this procedure, a large part of the air thus introduced flows axially through the furnace without participating in combustion. This results in misuse in particular of the first zone of the oven and the production of unburnt gas, which must then be re-burned in a second fixed chamber, called post-combustion chamber, whose performance may also be insufficient, the imposed discharge standards becoming difficult to meet.

Likewise, the rate of carbonaceous solid unburnt in slag is generally higher with the accepted limits, which obliges an expensive reprocessing of solid discharges.

The advantages of the invention will be better understood in the light of the details below.

The present invention relates to a device for injecting combustion air, as well as other fluids, which leads to perfect control of the internal aerodynamics of the oven, allows a distribution of the oxygen in the air at the level of the solids load and thereby overcomes the drawbacks and defects of the known devices, linked, as indicated above, to a distribution random combustion air.

In application of the invention, combustion is complete at the outlet of the rotary kiln and the negligible unburnt content, both in gases and in slag.

Correlatively, the optimization of combustion upon entering the furnace results in homogenization of temperatures, better use of the oven volume and therefore rational sizing.

The device used consists of a multifluid member, hereinafter designated combustor, whose geometric and energetic characteristics as well as the positioning on the front of the oven constitute the material of the invention.

The combustor is presented as a multiple inlet and flow injection nozzle parallel, of the tube-in-tube type, which receives all the fluids admitted into the furnace separately, know: liquid or gaseous support fuel, liquid effluents, gaseous effluents, air atomization and combustion air, to inject them in a single jet, strictly flowing axial in the furnace. The geometric characteristics of the combustor are dependent on those of the Rotary kiln; as will be explained below.

According to the device of the invention, the axis of the combustor is offset from the axis of the rotary oven with a distance depending on the diameter of the oven and an angle related to the speed of rotation.

La figure 1 schématise le dispositif de l'invention en coupe longitudinale. Le four rotatif (1), incliné d'un angle α sur l'horizontale et de diamètre intérieur D, est alimenté en façade en solides à incinérer par la vis (2) et en fluides actifs par le combusteur (3). Il débouche à l'autre extrémité dans la pot-combustion fixe (4). A l'amont les résidus solides (5) sont amenés dans un stockage (6), puis distribués par une vis de reprise sous trémie (7) vers la vis (2). Les effluents liquides (8) sont stockés dans la cuve (9), puis admis par pompage au combusteur (3). Le combusteur (3) reçoit également les fluides compressibles, tels que : air d'atomisation (10), effluents gazeux ou buées (11), air de combustion (12). Les scories (13) sont recueillies sous la chambre de post-combustion (4) et les gaz de combustion (14) s'échappent à la partie supérieure vers le traitement des fumées.

La figure 2 schématise une vue de face, côté façade, du four rotatif(1). Elle précise la position du combusteur (3) et de la vis à solides (2), ainsi que le sens de rotation du four (1).

The device combines a succession of elements, the conjunction of which carries out the implementation of the method, as indicated in Figures 1 and 2 attached.

Figure 1 shows schematically the device of the invention in longitudinal section. The rotary kiln (1), inclined at an angle α to the horizontal and of internal diameter D, is supplied on the front with solids to be incinerated by the screw (2) and with active fluids by the combustor (3). It ends at the other end in the fixed burn pot (4). Upstream, the solid residues (5) are brought into a storage (6), then distributed by a hopper recovery screw (7) to the screw (2). The liquid effluents (8) are stored in the tank (9), then admitted by pumping to the fuel (3). The combustor (3) also receives compressible fluids, such as: atomizing air (10), gaseous or mist effluents (11), combustion air (12). The slag (13) is collected under the post-combustion chamber (4) and the combustion gases (14) escape at the top towards the treatment of the fumes.

Figure 2 shows schematically a front view, facade side, of the rotary kiln (1). It specifies the position of the combustor (3) and the solid screw (2), as well as the direction of rotation of the furnace (1).

H est la différence de hauteur entre les axes horizontaux du four (1) et du combusteur (3), comme indiqué sur les figures 1 et 2.

According to the provisions of the invention, there is a geometric relationship between the position of the combustor (3) and the internal diameter D of the rotary kiln (1), which is expressed by: H = 0.3. D or :

H is the difference in height between the horizontal axes of the furnace (1) and the combustor (3), as shown in Figures 1 and 2.

According to the invention, the radial axis of the combustor (3) makes an angle β relative to the vertical, depending on the oven rotation speed (1). For the rotation speeds usually used, this angle is close to 20 °. One of the characteristics of the device of the invention is therefore constituted by an angle β = 20 °, the 20 ° being counted in the direct direction, defined by the direction of rotation of the oven (1), as shown in Figure 2.

W est la puissance thermique du four (1), exprimée en MW (mégawatts).

G est le débit de quantité de mouvement axial ou poussée de réaction ou impulsion du combusteur, exprimé en Newton.

Still according to the invention, all of the fluids admitted into the rotary kiln (1) are injected via the only combustor (3), in pure axial flow, that is to say without any rotation of any of the fluids we cause and in such a way that the axial pulse G of the whole of the jet coming from the combustor (3), checks the condition: G ≥ 60. W or :

W is the thermal power of the furnace (1), expressed in MW (megawatts).

G is the flow rate of the amount of axial movement or thrust of reaction or pulse of the combustor, expressed in Newton.

This last relation defines the dimensions of the combustor (3) to be used. to satisfy the invention, the flow rates and supply pressures of each fluid being fixed or known.

• 950 Kg/h de farines animales, collectées en service public ou produites pour partie in situ.
• 2500 Kg/h de buées de déshydratation provenant de cuiseurs à vapeur.
• 400 Kg/h de déchets solides divers, tels que soies de porcs, sciures et emballages souillés, boues grasses d'épuration.

By way of example, the device according to the invention is used for the elimination of organic residues originating from slaughterhouses and rendering. The residues in question consist of:

• 950 Kg / h of animal meal, collected in public service or partly produced in situ.
• 2500 Kg / h of dehydration mist from steam cookers.
• 400 Kg / h of various solid waste, such as pig bristles, sawdust and soiled packaging, fatty sewage sludge.

The auxiliary fuel consists of animal fats with high calorific value, extracted during the flour making process.

Thermal calculations lead to a power developed in the rotary kiln (1) of 6.8 MW and with a useful diameter of 2100 mm.

The combustor (3) is then positioned as shown in Figure 2, with H = 630 mm and β = 20 ° C.

- Pour l'air de combustion (12) :

9000 Nm³/h à 600 mmCE.

- Pour l'air d'atomisation (10) :

1500 Nm³/h à 700 mbars.

- Pour les buées (11) :

2000 Nm³/h à 100 mmCE.

The flow and pressure of the active fluids are:

- For combustion air (12):

9000 Nm ³ / h at 600 mm EC.

- For atomizing air (10):

1500 Nm ³ / h at 700 mbar.

- For fogging (11):

2000 Nm ³ / h at 100 mmCE.

The dimensions of the combustor (3) are defined accordingly.

According to the requirements of the invention, the condition G ≥ 60 W must be fulfilled, that is: G ≥ 410 Newton.

The calculation of G gives G = 435 N. The provisions adopted are therefore consistent to those required by the invention.

The device can be used for other applications which are not outside the scope of the invention. Thus it is possible, according to the provisions of the invention, to incinerate various solids and ground and introduced continuously into a rotary kiln. We can cite, for example, hospital waste, compost rejects, dehydrated sludge, packaging, etc.

Note that the device makes it possible to incinerate gaseous and liquid effluents simultaneously, some of these effluents with appreciable calorific value being able to be used as energy supply of support.

The application of the device to the restrictive treatment of exclusively gaseous products and / or liquids led to the simplified implementation of a combustor (3) associated with a stationary furnace (1) and not rotating without departing from the scope of the invention, provided that the condition G ≥ 60 W is satisfied. In this particular case and with reference to Figures 1 and 2, the quantities H, β and α are equal to zero.

Claims (4)

Device of the rotary or stationary oven incinerator type (1) for the destruction of animal meal, fat and dehydration mist residues, characterized by: A combustor (3) which receives all of the active fluids, such as: atomizing air (10), combustion air (12), any supporting fuel, residual fumes (11), residual fats and liquids (8) and transfer to the rotary or stationary oven (1), there is a single jet with strictly axial flow, parallel to the axis of the oven (1) A screw (2) for the continuous supply of the furnace (1) with crushed solid residues (5). Device according to claim 1, characterized by the position of the combustor (3), defined by the height H of its horizontal axis above the horizontal axis of the diameter furnace (1) interior D, which satisfies the condition H = 0.3 D. Device according to claims 1 and 2, characterized in that the radial axis of the combustor (3) makes an angle β = 20 ° with the vertical axis, the said axes passing through the center of the oven front (1). Device according to claims 1, 2 and 3, characterized by the axial pulse G of the combustor (3), expressed in Newton, which is related to the thermal power W of the furnace (1), expressed in MW, by the condition G ≥ 60 W.

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