Furnaces – Process – Incinerating refuse
Patent
1995-07-27
1997-08-12
Bennett, Henry A.
Furnaces
Process
Incinerating refuse
110236, 110257, 110258, 110229, F23G 500
Patent
active
056554656
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the treatment of toxic wastes. The invention is particular by suitable for, but not limited to, the thermal desorption of hydrocarbon contaminants from soils.
The contaminants may include, but are not limited to, petroleum products (e.g. petrol, oils, greases); phenols; coal tars; cyanides; pesticides; PCB's and HCB's .
2. Prior Art
The treatment of contaminated soils is a world-wide problem. Often the soils are simply removed and transferred to a toxic waste dump. This does no more than move the problem.
Where thermal treatment of the wastes is effected, the traditional method is by direct heating in a rotary kiln. Indirect treatment methods include (a) the externally heated rotary kilns (where the heat is transferred through the kiln wall to the soil) and (b) auger-type heaters, where heat is applied to the soil through the heater casing and/or the flyte(s), of the auger e.g. by the circulation of hot oil. With such methods, the soil may only be heated to approximately 150.degree.-450.degree. C. and many contaminants may not be treated at those relatively low temperatures.
For contaminants such as PCB's , the Environmental Protection Authorities around the world specify strict conditions for their disposal in very high temperature incinerators, e.g. found on the vessel "VULCANUS".
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for the treatment of soils to remove hydrocarbon and other contaminants.
It is an object of the present invention to provide a method which meets, and exceeds, Environmental Protection Authorities specifications.
It is a further object of the present invention to provide a method which can be carried out on the site of the contamination.
It is still a further object of the present invention to provide an apparatus to effect the method of the present invention.
One aspect the present invention resides in a method of treating toxic wastes or other contaminants in soils, the method of one embodiment of the present invention including the steps of: above 500.degree. C.; cause the waste or contaminants to be given off from the soil and gases; and
Preferably the retort is heated by the external gases from a combustion cheer, where the combustion chamber may surround the retort.
The soil may be ground to a powder or granular form and may be preheated and/or dried before being fed to the retort.
Preferably a screw Conveyor or the like agitates the soil to generate rapid circulation of the soil in the retort for improved heat transfer from the walls of the retort and better mixing of the soil to ensure all of the soil is treated.
The gases may be transferred to the combustion chamber to be burnt with air and optionally fuel to generate the heat to heat the retort; may be burnt in a secondary burner to preheat the soil fixed or be condensed and stored for later destruction.
A second aspect the present invention resides in an apparatus for the treatment of toxic wastes, including hydrocarbon contaminants, including: into contact with the heated walls of the retort to cause the contaminants to be given off as gases; at least a portion of the retort to heat the retort.
The combustion chamber may at least partially surround the retort; or the retort may be at least partially surrounded by a heat chamber and the heat transfer means includes means to transfer the heat from the combustion chamber to the heating chamber to heat the retort.
Preferably the retort is substantially or wholly enclosed by the heating chamber, and has stainless or alloy steel walls capable of withstanding >1000.degree. C., while allowing effective heat transfer from the heating chamber to the soil in the retort.
Preferably the soil is crushed or ground and is fed through a hollow shaft or tube of a rotatable helical spiral, the latter being rotated to agitate the soil in the retort. Alternatively, the soil is fed into the retort (e.g. by a screw conveyor) and is agitated by a vertical auger or spira
REFERENCES:
patent: 4821653 (1989-04-01), Jones
patent: 5072674 (1991-12-01), Noland et al.
patent: 5117771 (1992-06-01), Summers
patent: 5220873 (1993-06-01), Milsap, III
patent: 5337684 (1994-08-01), Summers
patent: 5405579 (1995-04-01), Melzer et al.
Bennett Henry A.
Tinker Susanne C.
Tox Free Limited
Tox Free Systems, Inc.
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