Furnaces – Process – Incinerating refuse
Reexamination Certificate
1999-03-26
2001-06-12
Ferensic, Denise L. (Department: 3749)
Furnaces
Process
Incinerating refuse
C110S234000, C110S218000, C110S219000, C110S224000, C110S342000, C110S345000, C201S013000, C202S113000, 42
Reexamination Certificate
active
06244199
ABSTRACT:
TECHNICAL FIELD
The invention relates to a plant for the treatment by thermolysis and simultaneously for the upgrading with regard to energy of waste comprising an organic fraction.
PRIOR ART
The treatment of waste comprising an organic fraction is well known, in particular in the treatment of waste as diverse as automobile shredder residues (ASR), hospital waste, also known as healthcare activity waste, old tyres, green waste or waste resulting from biomasses, municipal and domestic waste, or meat meal, but also treatment plant sludges and the sludges from various petroleum products. The treatment of waste of these types is becoming increasingly worrying as a result of the increasingly large amounts to be treated and of the increase in the cost of these treatments.
The thermal dissociation of waste comprising an organic fraction under reduced pressure and at high material temperature is well known (see in particular document U.S. Pat. No. 4,077,868, U.S. Pat. No. 4,833,021 and CA-A-1,163,595).
In essence, a plant for the thermal dissociation at reduced pressure of waste comprising an organic fraction essentially comprises:
a unit for loading and for introducing the waste to be treated;
and a reactor for thermal dissociation under reduced pressure and at high temperature, for example at a temperature of between 400 and 1000° C., in particular in the region of 500° C., under a pressure of between 0.1 and 1 atmosphere.
In the document WO-96/11742, the Applicant Company described a plant of the type in question in which two chambers, placed in parallel, are positioned between the introduction means and the reactor, each of these chambers being connected to the introduction means of the reactor, thus allowing one of the two chambers to be loaded at atmospheric pressure while the other is being discharged at reduced pressure into the reactor. This batchwise/continuous plant, well suited to the treatment of large amounts, exhibits the disadvantage, however, of requiring significant investment.
Furthermore, the production of oils by condensation during the treatment is, on a practical level, difficult to manage industrially.
In addition, and as said above, the destruction of meat meal unfit for animal consumption is becoming worrying, in particular with the risk of the presence of prions in this meal, so that several techniques have been provided to date for the incineration of meal.
The first technique consists in mixing this meal with municipal waste and in then pyrolysing the combined mixture in municipal incinerators, which are known to be already overloaded. Furthermore, the small particle size of this meal leads to the risk of it being swept away into the air, interfering with the operation of the incinerators. This technique is so expensive that it has not experienced any development.
Provision has also been made to incinerate this meal in inclined rotary kilns. Here again, the small particle size of this meal leads to the risk of it being swept away into the air and the flow in the kilns is often not very good. Finally, the flue gases produced have to be treated with special equipment which places a crippling burden on the cost of the plant.
The invention overcomes these disadvantages. It is targeted at a plant for the treatment by thermolysis of waste and for the upgrading with regard to energy of this waste which is well suited to the treatment of waste of the most varied kinds, in small and medium volumes, with a good ratio between investment and operation. It is more particularly targeted at a plant of the type in question which is reliable and robust and which has operating conditions which scrupulously respect the environment.
Another object of the invention is to provide a plant which can carry out a complete treatment of the thermolysis by-products until the final waste is obtained, that is to say waste which cannot be upgraded under current economic conditions.
The invention is targeted at a plant of the type in question in which the energy produced during the treatment is recovered in order to operate, in part and autonomously, the plant itself and part of the unit which can produce this waste.
SUMMARY OF THE INVENTION
The invention relates to a plant for the treatment by thermolysis of waste comprising an organic fraction and simultaneously for the upgrading with regard to energy of this waste of the type essentially comprising:
a unit for loading and for introducing the waste to be treated;
a reactor for thermal dissociation thermolysis under reduced pressure at high temperature,
characterized
in that it comprises:
upstream and downstream of the reactor, an isolation means intended to maintain a partial vacuum in the reactor in order to ensure thermolysis in an atmosphere with a very low oxygen content;
first means for recovering, in the upper part of the reactor, the gaseous organic fraction formed during the thermolysis and for introducing this gaseous fraction into a combustion chamber feeding a steam generator;
second means for recovering, at the bottom of the reactor, the solid carbonaceous products formed during the thermolysis and for introducing these solid products into a combustion chamber feeding a steam generator or a discharge system;
and in that the gases from the combustion chamber and the steam produced by the steam generator in their turn feed the unit in which the waste is produced and/or a means for predrying the waste positioned immediately upstream of the reactor.
In other words, the invention consists in heating the waste exhibiting a controlled particle size under conditions suitable for dissociating this waste essentially into two phases, respectively a gas phase and a solid phase, this being carried out in the virtual absence of oxygen but under reduced pressure, indeed even under a gaseous atmosphere.
The invention consists in recovering the gas phase and the solid phase in order to upgrade them by producing energy in a combustion chamber intended to heat steam which in its turn feeds the unit in which waste is produced and/or is targeted at predrying the waste before it arrives at the reactor.
In practice, the thermolysis, also denoted under the term of “pyrolysis”, is carried out at a temperature of between 400 and 1000° C., in particular in the region of 500° C., with a pressure in the reactor of 5000 to 40,000, preferably 10,000, pascals below atmospheric pressure. The residence time of the waste in this reactor is of the order of several tens of minutes, for example of the order of thirty minutes.
As already said, depending on the nature of the waste to be treated, the latter is advantageously premilled in order to exhibit a controlled, indeed even homogeneous, particle size and physical consistency.
In practice, a particle size is defined of between 1 and 10 centimetres, these limits being in no way limiting.
Likewise, the waste can advantageously be subjected to a predrying intended to lower the water content in this waste. This heating, carried out in an appropriate chamber, can, depending on the nature of the waste to be treated, be carried out in two ways, namely directly or indirectly. In the direct drying, the mass of the waste is heated by circulation of hot air or of steam recycled from the generator characteristic of the invention or of hot air recycled from the combustion chamber. This method of predrying is particularly appropriate for waste with a low volatile solid fraction (dust), such as ASR. When treatment plant sludges are treated, it is preferable to carry out indirect heating, that is to say to heat the chamber externally, while providing a degree of mixing intended to break up the product in order to increase the contact surface with the air.
In an advantageous embodiment, a means for adding an agent for the neutralization of the aggressive components, such as, for example, halogens or sulphur, which makes it possible to avoid the subsequent presence of harmful compounds (SO
2
, HCl, HF) in atmospheric discharges, is positioned in the path of the waste between the introduction device and the reactor. This neutra
Chambe Eric
Chambe Maurice
Haxaire Pascal
Ferensic Denise L.
Rinehart K. B.
Traidec S.A.
Wall Marjama & Bilinski
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