FR2754883A1 - Furnace for thermolysis and energy upgrading of waste materials - Google Patents

Abstract

The furnace for treating waste products with an organic content, consists of a loader (1), and a thermolysis reactor (13) for thermal separation at low pressure and high temperature. There is an air lock (5, 50) on each side of the reactor to ensure that thermolysis takes place in an atmosphere with a very low oxygen content. It has a recuperator (15, 16) at the top of the reactor for the organic gas fraction formed during thermolysis and to feed the gas fraction to a combustion chamber (20) connected to a steam generator (22). A second recuperator (51) at the bottom of the reactor collects the solid carbon products formed during thermolysis and feeds them to a combustion chamber connected to a second steam generator or an outlet system. The gases from the combustion chamber and the steam from the generator are used to dry the waste prior to thermolysis. The waste material is shredded to a controlled size before thermolysis, which takes place in an atmosphere virtually devoid of oxygen at a temperature of 400 - 1000 deg C and a pressure of 5000 - 40000 Pa below atmospheric.

Description

PLANT FOR THE THERMOLYSIS DESTRUCTION OF
MEAT FLOUR AND ENERGY RECOVERY OF
THESE FLOURS.

Technical area
The invention relates to an installation for the destruction by thermolysis of meat flours and simultaneously the energy recovery of these flours.

Previous techniques
As we know, the problem of the destruction of meat meal unfit for animal consumption is becoming a concern, particularly with the risk of the presence of prions in this meal.

 Essentially, several incineration techniques have been proposed to date.

 The first technique consists of mixing these flours with urban waste, then pyrolyzing everything in urban incinerators, which we know are already saturated. Furthermore, the small particle size of these flours entails risks of soaring, disrupting the operation of incinerators. This technique is so expensive that it has not seen any development.

 It has also been proposed to incinerate these flours in inclined rotary ovens. Again, the small particle size of these flours leads to a risk of soaring and the flow in the ovens is often poorly performed. Finally, the fumes produced must be treated by special equipment which prohibitively burdens the cost of the installation.

 The invention overcomes these drawbacks. It is aimed at an installation of the type in question in which not only are the said flours successfully destroyed, but where the energy produced during this destruction is recovered in order to make the unit which itself produces these flours function independently. .

Brief description of the invention
The invention relates to an installation for the destruction by thermolysis of meat-and-bone meal and simultaneously the energy recovery of this meal, which is characterized in that it comprises:
a unit for the production of meat-and-bone meal from carcasses
animals;
a thermolysis reactor for the flours thus produced;
means to recover the gaseous fraction at the top of the reactor
organic formed during thermolysis and to bring this fraction
gas with a first combustion chamber supplying a first
steam generator;
means to recover carbonaceous solid residues at the bottom of the reactor
formed during thermolysis and to bring these solid residues to a
second combustion chamber, in turn supplying a second
steam generator,
and in that the two steam generators in turn supply
energy the meat meal production unit.

 As is known, thermolysis designates an operation which consists in heating a product to dissociate it into two essential phases, gaseous and solid respectively; preferably, this operation is carried out in the absence of oxygen, but at reduced pressure, or even under an atmosphere of neutral gas. In practice, this thermolysis is carried out at a temperature between 400 and 1000 "C, and in particular in the vicinity of 5000C, with a vacuum in the reactor of the order of five thousand to forty thousand (5000 to 40,000), preferably ten thousand (10,000), Pascals below atmospheric pressure; the duration of stay of the flours in this reactor is of the order of several tens of minutes, in particular around thirty (30) minutes.

Advantageously, in practice:
- the thermolysis reactor is preceded by a continuous supply airlock
and a gravity hopper for feeding the flours produced in
unity;
- the thermolysis reactor operates at reduced pressure;
- the thermolysis reactor operates in the absence of oxygen at a
temperature between 400 and l0000C, preferably around
500 "C and the pressure in the reactor is maintained at five thousand to forty
thousand (5000 to 40,000), preferably ten thousand (10,000) Pascals below
of atmospheric pressure.

the means for recovering the organic gaseous fraction comprise a
fan intended to bring this gaseous fraction to the first chamber of
combustion.
the means for recovering the solid residues comprise a screw without
end supplying two storage tanks, respectively the first of
loading under reduced pressure, the second in which solid residues
stored are brought to atmospheric pressure;
- the solid carbonaceous residues formed are sieved before being brought to the
second combustion chamber, the rejected residues then being reinjected
in feed hopper;
- the second steam generator includes a unit for processing
fumes;
- the pollutants recovered in the smoke treatment unit and the
ash recovered in the second combustion boiler, are put in
discharge of ultimate residue
Brief description of the figures
The single attached figure illustrates an installation according to the invention.

This installation includes a meat-and-bone meal production unit symbolized by the reference (1). This unit produces dry flour (2) intended to be destroyed because it is unfit for animal consumption. These flours (2) are brought to a hopper (3) where they flow by gravity into an airlock (4), for example with helical compression screw. This airlock (4) is connected to a thermolysis reactor, of the type described in patent application WO-96/11742 of
Applicant, in particular in Figures 6, 9 and 10 of this document. This electrically heated reactor (5) can also be produced in another way, for example by a set of endless belts and drive bars connected to a conveyor. As already said, this reactor (5) operates in oxygen deficiency.

 The reactor (5) is heated to a temperature in the region of 500 "C with a vacuum of the order of ten thousand (10,000) Pascals below atmospheric pressure and the residence time of the flours in this reactor (5) is thermolysis causes the formation of two products, respectively an organic gas fraction recovered upwards (6), and a fraction of carbonaceous solid residues recovered downwards (11).

 According to a first characteristic of the invention, the installation comprises means (6-10) for recovering at the top (6) of the reactor (5) the organic gaseous fraction formed during thermolysis. The gaseous fraction is brought by a pipe to a fan (7) in turn connected to a first combustion chamber (8), for example of the horizontal cylindrical type. This chamber (8) in turn feeds a first steam generator (9), for example of the dual-circulation boiler type, connected by a tube (10) to the unit (1) for producing flour.

 According to a second characteristic of the invention, the solid carbonaceous residues formed during thermolysis are recovered by the pipe (11) such as an endless screw placed at the bottom of the reactor (5), to bring these residues to a storage area. (12) formed of two reservoirs, respectively (13) and (14), one loading at reduced pressure, the other for bringing the residues to atmospheric pressure and alternately.

 The solid carbonaceous residues obtained are rich in carbon, but also in polluting products, such as chlorine, sulfur or phosphorus.

 These residues are in the form of a very fine powdery powder which is sieved in (15), for example by passing over screens making it possible to refuse all residues having a predetermined dimension greater than a few micrometers, such as for example fully thermolysed bone residues, carbonized during the treatment in the reactor (5). The accepted powder is injected through the tubing (16) into the second combustion chamber (17). On the other hand, the siftings (15) are through a tubing (18) reinjected into the hopper (3), then from there into the reactor (5) to better retain pollutants.

 The second combustion chamber (17) essentially comprises a specific burner (19) for powdered coal. This chamber (17) in turn feeds a second steam generator (20) similar to (9). The ashes (21) obtained in the second combustion chamber (17) are discharged from ultimate residues.

 The second steam generator (20) is associated with a smoke treatment unit (22) intended to recover the polluting agents (25) to also put them in discharge of ultimate residues.

 The steam produced by the second generator (20) is supplied by a pipe (23) similar to (10) to the unit (1) for producing meat-and-bone meal, in particular in the assembly for drying the carcasses of meat or in the assembly intended to dry the flours produced.

 In this way, the installation only releases outside fumes reputed to be clean and ultimate residues, since all the energy produced transformed into vapor is reinjected into the installation, therefore is recovered.

 The gaseous fraction brought into the first combustion chamber (8) and the solid residues brought into the second combustion chamber (17) are burned at a temperature in the region of 850 "C for at least two seconds. The thermal destruction is then complete and optimizes the recovery of the energy content of the flours, in the form of steam used on the site, or even partially outside this site.

 The installation according to the invention therefore makes it possible to successfully destroy meat-and-bone meal, in particular beef meat unfit for animal consumption. It also allows and above all an energy recovery from this destruction by thermolysis by allowing the recovery of two phases produced, respectively gaseous and solid, and the combustion of these two phases to produce steam intended to supply the flour production unit. .

 During operation, the installation is almost energy self-sufficient, which makes it very attractive in terms of investment and operation.

Claims (9)

 1 / Installation for the thermolysis destruction of meat flours (2) and the energy recovery of these flours, characterized in that it comprises:  a production unit (1) of meat-and-bone meal from animal carcasses  a thermolysis reactor (5) of the flours thus produced;  means (6,7) for recovering the fraction at the top of the reactor (5)  organic gas formed during thermolysis and to bring this  gas fraction with a first combustion chamber (8) supplying  a first steam generator (9);  means (11,14,16) for recovering residues at the bottom of the reactor (5)  carbonaceous solids formed during thermolysis and to bring these residues  solids to a second combustion chamber, in turn feeding a  second steam generator (20);  and in that the two steam generators (9,20) in turn supply  in energy the production unit (1) of meat-and-bone meal.  2 / Installation according to claim 1, characterized in that the thermolysis reactor (5) is preceded by a continuous airlock (4) and -a gravity hopper (3) for feeding the flours produced in unity.  3 / Installation according to claim 2, characterized in that the thermolysis reactor (5) operates at reduced pressure.  4 / Installation according to claim 3, characterized in that the thermolysis reactor (5) operates in oxygen deficiency, at a temperature between 400 and 1000 "C, preferably around 500oC and the pressure in the reactor is maintained between five thousand and forty thousand (5000 and 40,000) Pascals below atmospheric pressure.  5 / Installation according to claim 1, characterized in that the means for recovering the organic gas fraction comprises a fan (7) intended to bring the gas fraction to the first combustion chamber (8).  6 / Installation according to claim 1, characterized in that the means for recovering solid residues comprise an endless screw (11) supplying two storage tanks (13,14), respectively the first loading under reduced pressure, the second in which the stored solid residues are brought to atmospheric pressure.  7 / Installation according to one of claims 1 and 6, characterized in that the solid carbonaceous residues formed are screened (15) before being brought to the second combustion chamber (17), the rejected residues then being reinfected in the feed hopper (3).  8 / Installation according to claim 1, characterized in that the second steam generator (20) comprises a smoke treatment unit (22).  9 / Installation according to claim 8, characterized in that the pollutants (25) recovered in the smoke treatment unit (22) and the ashes (21) recovered in the second combustion boiler (17), are landfilled ultimate residue.