FR2785366A1 - DEVICE FOR THE THERMAL OXIDATION TREATMENT OF SOLID, LIQUID OR GASEOUS RESIDUES PRODUCED BY SLAUGHTERHOUSES AND EQUARRISSING UNITS - 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

-1 The technical field of the invention is that of heat treatment

produced residues

  in industrial slaughterhouses and rendering plants.

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

  - Flours unfit for animal consumption.

  - Fats and greasy sludge from the effluent treatment of the plant.

  - The dehydration and cooking vapors.

  From the dead body of a cattle, for example, that it is a question of treating in the rules imposed by the regulation, the products to be eliminated, mentioned above, are obtained in a chain of treatment which includes schematically the stages following - Grinding - Dehydration in a steam-heated cooker - Pressing and packaging flours Dehydration and conditioning of flours produce fumes which are, in fact, the aqueous part of the load collected in the form of more or less charged steam. carbonated fats and volatile compounds that are highly malodorous. This vapor phase represents approximately

  % of initial weight and must be oxidized at high temperature.

  Part of the fat is recovered at the outlet of the cooker and another part after

  pressing extraction of the solid residue.

  The solid phase, partially dehydrated and degreased, represents 30 to 40% of the incoming charge. In so far as it comes from animals that are contaminated and declared unfit for

  recycling in the food chain for livestock, it must be incinerated.

  Greases with a high calorific value can be used as auxiliary fuel

  in the device of the heat treatment.

  Of course, the combustion of the products considered above must be carried out in

  compliance with the legal provisions, more and more restrictive.

  The subject of the present invention relates precisely to the optimization of the conditions of

  combustion of all the residues involved.

  As regards the prior art, various processes can be used to incinerate the products in question, by means of furnaces of various designs, such as rotary hearth furnaces,

  mechanical grids, fluidized bed, pyrolysis, rotary, open flame.

  Among all possible technologies, that of the rotary kiln slightly inclined on

the horizontal prevails.

  It is a furnace presenting itself as an elongate cylinder, arranged between a fixed facade on the inlet side and a fixed chamber of ash removal on the outlet side for recovering the slag constituted by the incombustible parts. The interior of the oven is lined with refractory products, bricks or -2beton, to insulate the walls and withstand high temperatures. The fireplace is rotated

  by means of rollers or by chain and toothed wheel.

  Solid waste is introduced at the façade by screw or push. It's in

  facade also that are injected liquid and gaseous effluents, as well as combustion air.

  The regular and continuous rotation of the furnace causes the mass of solid waste as soon as it is introduced and during combustion in a permanent reversal movement, accompanied by a mixing and splitting of the mass which makes it possible to expose the waste, renewed in permanence, the radiation of the refractory lining and the combustion air

  depends on the activation of the 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 regard to the admission into the oven of the air necessary for combustion. According to the techniques applied to date, the air is injected by means of tubing distributed at different points of the facade. According to this way of proceeding, a large part of the air thus introduced flows axially through the furnace without participating in the combustion. This results in poor use in particular of the first zone of the furnace and the production of unburnt gas, which must then be burned in a second fixed chamber, called post-combustion, whose performance may also be

  insufficient, the standards of imposed discharges becoming difficult to satisfy.

  Similarly, the rate of unburnt carbonaceous solids in slag is generally higher

  to the accepted limits, which requires expensive reprocessing of solid waste.

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

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

random combustion air.

  In application of the invention, the combustion is complete at the exit of the rotary kiln and the

  Negligible unburnt content, both in gases and in slag.

  Correlatively, the optimization of the combustion as soon as it enters the oven results in a homogenization of the temperatures, a better use of the volume of the furnace and thus a

rational dimensioning.

  The device used consists of a multifluid member, hereinafter referred to as a combustor, whose geometrical and energetic characteristics as well as the positioning on

  the facade of the furnace constitute the material of the invention.

  The combustor is presented as a multiple-input and parallel-flow injection pipe, of the tubes-in-tubes type, which receives separately all the fluids admitted to the furnace, namely: liquid or gaseous support fuel, liquid effluents, gaseous effluents, air -3 - atomization and combustion air, to inject them in a single jet, a strictly axial flow in the oven. The geometric characteristics of the combustor are dependent on those of the

  rotary kiln, as will be specified below.

  According to the device of the invention, the axis of the combustor is offset relative to the axis of the rotary kiln by a distance depending on the diameter of the furnace and an angle related to the speed of rotation. The device associates a succession of elements whose conjunction realizes the setting

  process, as shown 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 a on the horizontal and with an inside diameter D, is supplied in front with solids to be incinerated by the screw (2) and with active fluids by the combustor (3). It opens at the other end in the fixed post-combustion (4). Upstream solid residues (5) are fed into a storage (6), and then distributed by a screw recovery under hopper (7) to the screw (2). The liquid effluents (8) are stored in the tank (9) and then pumped to the combustor (3). The combustor (3) also receives the compressible fluids, such as: atomizing air (10),

  gaseous or fumes (11), combustion air (12).

  The slag (13) is collected under the post-combustion chamber (4) and the combustion gases

  combustion (14) escape to the upper part to the flue gas treatment.

  Figure 2 shows a front view, front side of the rotary kiln (1). It specifies the

  position of the combustor (3) and the solids screw (2), as well as the direction of rotation of the oven (1).

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

H = 0.3. D

  o: H is the difference in height between the horizontal axes of the oven (1) and the

  combustor (3), as shown in FIGS. 1 and 2.

  According to the invention, the radial axis of the combustor (3) makes an angle P3 relative to the vertical, a function of the speed of rotation of the furnace (1). For the rotational 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 [t = 20, the 20 being counted in the forward direction, defined by the direction of rotation of the

  oven (1), as specified in Figure 2.

  Still according to the invention, all the fluids admitted into the rotary kiln (1) is injected via the single combustor (3), in pure axial flow, ie without rotating any of the fluids. in question and so that the axial pulse G of the entire jet from the combustor (3), verifies the condition:

G> 60. W

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

  G is the axial momentum or thrust flow rate of the reaction or pulse of the

combustor, expressed in Newton.

  This latter relation actually defines the dimensions of the combustor (3) to be used to satisfy the invention, the feed rates and pressures of each fluid being fixed or known. For example, the device according to the invention is implemented for the removal of organic residues from slaughterhouses and squares. The residues in question consist of:

  - 950 kg / h of animal meal, collected in public service or produced partly in situ.

  - 2500 Kg / h of dehydration vapors from steam cookers.

  - 400 kg / h of miscellaneous solid waste, such as pig bristles, sawdust and soiled packaging,

greasy sewage sludge.

  The auxiliary fuel consists of animal fat with a 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 FIG. 2, with H = 630 mm and

= 20 C.

  The flow rate and the pressure of the active fluids are:

  - For combustion air (12): 9000 Nnm3 / h to 600 min.

  - For atomizing air (10): 1500 Nm3 / h to 700 mbar.

  - For fogging (11): 2000 Nm3 / h to 100 minCE.

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

  According to the requirements of the invention, the condition G> 60 W must be fulfilled, ie:

G> 410 Newton.

  The calculation of G gives G = 435 N. The provisions adopted are therefore in accordance

those required by the invention.

  The device can be used for other applications that are not outside the scope of the invention. Thus it is possible, according to the provisions of the invention, to proceed to the incineration of various solids and crushed and continuously introduced into a rotary kiln. For example,

  hospital waste, compost refusals, dewatered sludge, packaging, etc.

  It should be noted that the device makes it possible to simultaneously incinerate gaseous and liquid effluents, some of these effluents with appreciable calorific value being able to serve as an energy supply of support. Application of the device to the restrictive treatment of exclusively gaseous and / or liquid products leads to the simplified implementation of a combustor (3) associated with a fixed and non-rotary kiln (1) without departing from the scope of the invention. the invention, since the condition G> 60 W is satisfied. In this

  particular case and with reference to Figures 1 and 2, the quantities H, P and a are equal to zero.

-6-

Claims (4)

  1) Rotary or fixed oven-type incinerator device (1) for the destruction of residues of the animal meal, grease and dehydration fog type, characterized by: a combustor (3) which receives all the active fluids, such as: atomizing air (10), combustion air (12), possible support fuel, residual fumes (11), greases and residual liquids (8) and transfer into the rotary or stationary furnace (1) in a single jet with strictly axial flow, parallel to the axis of the furnace (1)   - A screw (2) for the continuous supply of the oven (1) crushed solid residues (5).   2) 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 oven (1) of inner diameter D, which satisfies the condition H = 0.3 D.   3) Device according to claims 1 and 2, characterized in that the radial axis of the   combustor (3) makes an angle [B = 20 with the vertical axis, the said axes passing through the center of the front of the oven (1).   4) Device according to claims 1, 2 and 3, characterized by the axial pulse G of   combustor (3), expressed in Newton, which is connected to the thermal power W of the furnace (1), expressed in MW, by the condition G> 60 W.