Furnaces – Process – Incinerating refuse
Patent
1997-01-17
1998-09-15
Bennett, Henry A.
Furnaces
Process
Incinerating refuse
110348, 110245, 110224, F23G 1500
Patent
active
058064443
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the technical field of treating waste, and it relates, more particularly but not exclusively, to the treatment of waste that is moist, and more specifically sludges of various origins.
By way of example, mention may be made of sludges from foodstuffs, papermaking, iron and steel making, dying, treating waste water, etc. . . .
Various difficulties need to be overcome when it is desired to treat and make inert moist waste, and in particular sludges. These difficulties include the following, without the order of enumeration being considered to be of any importance:
The first difficulty relates to the water content that must necessarily be removed so that appropriate treatment can succeed in "inerting" the residual dry matter. The neologism "inerting" should be understood as any means suitable for ensuring that, after treatment, such waste is unsuitable for giving rise to pollution of itself or by leaching. This first difficulty is associated with the need to control energy expenditure so as to ensure that the cost of treatment is acceptable.
The second difficulty is associated with the sludgy or pasty form of the waste which gives rise to a problem that is difficult to solve concerning transfer within an installation, due to the risk of clogging, setting, and bridging that can occur within transfer circuits, in particular.
The third difficulty relates to setting up, running, and monitoring a treatment method capable of reliably and completely eliminating all of the waste components capable of being destroyed by incineration. This is an objective that must necessarily be achieved in order to satisfy the requirements of regulations and legislation seeking to eliminate, in due course if not immediately, the depositing or tipping of waste in dumping grounds, whether regulated or otherwise.
PRIOR ART
Various methods have been proposed in the prior art to attempt to inert waste. Those methods can be classified into two major categories referred to as a "cold" process and as a "hot" process.
Cold processes consist in coating the waste in a matrix that may be bitumen, cement, or an appropriate plastics material. Such processes can be seen immediately to be inappropriate for moist waste, and in particular sludges.
Hot processes include the process which consists in vitrifying waste included in a mixture of silica or of alumina. Vitrification takes place at a very high temperature generated by technical means that are expensive, complex, and fragile, which cannot be envisaged for treating all waste, and above all are unsuitable for moist waste.
The prior art proposes a processing method that is more specifically intended for such waste. That method as taught by U.S. Pat. No. 3,677,404 consists in creating a fluidized bed in an incineration furnace, the fluidized bed being made up of solid inert mineral particles, e.g. constituted by grains of sand, with such a bed being heated to an appropriate temperature, e.g. close to 750.degree. C.
The particles flow from the bottom of the bed up towards the top level from which they are recycled to be incorporated in waste. The resulting mixture is received in a filter tower for removing at least a portion of the moisture.
A bottom take-off device is provided to extract the mixture from the filter tower and direct it to the input of a feed system which delivers the mixture of hot articles to the furnace, at the base of the fluidized bed.
In this way, it is expected that the waste-and-particle mixture will possess the property of being put into circulation and, by feeding the furnace continuously, will follow an upward path in the fluidized bed with it being possible for burnable components to be incinerated therein.
That technique which was put forward in 1970 does not appear to be capable, in fact, of genuine industrial application to moist waste, and in particular to sludges, because it suffers from various drawbacks.
The first stems from the desire to pass the mixture through the filter tower. This proposition is easily under
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patent: 5049361 (1991-09-01), Harandi et al.
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patent: 5394811 (1995-03-01), Weiss
Baudequin Fran.cedilla.ois
Figueras Michel
Bennett Henry A.
Electricite de France
Figueras Michel
FM Industrie
Tinker Susanne C.
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