TREA

Rotary calcining kiln

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Information

  • Patent Grant
  • 4834648
  • Patent Number
    4,834,648
  • Date Filed
    Thursday, September 17, 1987
    37 years ago
  • Date Issued
    Tuesday, May 30, 1989
    35 years ago
Information
Abstract
A calcining kiln for decontaminating and detoxifying materials, such as earth, contaminated by hazardous chemicals and substantially incapable of autogenous combustion, consisting of an elongated kiln body through which the material to be treated is conveyed in the form of a tumbling bed, and apparatus for directing flame jets of high temperature against and into the tumbling bed at closely spaced intervals along the length of the kiln body to stir and agitate the material. The tumbling and the stirring and agitation reduce the material to a pulverized form of fine particle size so that all of the contaminating chemicals may be reached and destroyed by the high temperature flame jets. Various fuel gases may be used depending on the heat producing capacity required under any particular circumstances, and the heat produced in successive longitudinally spaced zones of the kiln body may be independently controlled according to the heat requirements in each zone.
Description
Claims
  • 1. A calcining kiln for decontaminating earth or other feedstock material incapable of autogeneous combustion to remove hazardous chemicals therefrom, said kiln comprising:
  • a. a holllow, axially rotatable elongated kiln body,
  • b. means operable to introduce said feedstock material into one end of said kiln body,
  • c. means operable to cause said feedstock material to move through the length of said kiln body in the form of a tumbling bed,
  • d. means operable to direct jets of flame toward and into said tumbling body of material at closely spaced intervals along the length of the kiln body, whereby to stir and agitate the bed material to assist in the reduction of said bed material to a pulverized form of fine particle size in a calcining process, including a series of jet nozzles disposed in closely spaced relation along the length of the kiln body, and directed downwardly toward said bed and means operable to deliver fuel gas and combustion and air to each of said nozzles, said fuel gas and combustion air delivering means comprising:
  • 1. a pipe system for delivering fuel gas to each of said nozzles,
  • 2. an air deck system for delivering combustion air to each of said nozzles, said fuel pipe and air deck systems extending longitudinally through said kiln body,
  • 3. a plenum chamber surrounding the portions of said fuel pipe and air duct systems within said kiln body, and
  • 4. means operable to circulate a flow of cooling gas through said plenum chamber, whereby to protect said fuel pipe and air duct systems against the extreme heat of the calcining process occurring within said kiln body; and
  • e. means operable to remove the residue of said clacining process from the opposite end of the kiln body.
  • 2. A calcining kiln as recited in claim 1 with the addition of means operable to deliver any of a plurality of cooling gases selectively to said plenum chamber, the gas being selected according to the cooling capacity required.
  • 3. A calcining kiln as recited in claim 1 with the addition of means operable to deliver any of a plurality of fuel gases selectively to said flame jets, the gas being selected according to the heat producing capacity required in the calcining process occurring within the kiln body.
  • 4. A calcining kiln as recited in claim 1 wherein said means for delivering fuel gas and combustion air to said nozzle is additionally operable to deliver independently regulated and controlled quantities of gas and air to the nozzles disposed within each of a series of longitudinally successive zones of said kiln body, whereby to produce only the amount of heat required for the calcining process in each of said zones.
  • 5. A calcining kiln as recited in claim 4 wherein said fuel gas and combustion air delivery means is additionally operable to deliver any of a plurality of fuel gases selectively and in independently controlled and regulated amounts to each of the longitudinally successive zones of said kiln body.
  • 6. A calcining kiln as recited in claim 1 with the addition of a series of data-collection devices, such as thermocouples and gassampling tubes, mounted within said plenum chamber and distributed along the length of the kiln, said devices being protected from the extreme heat of the remainder of the kiln by the cooling gas circulating through said plenum chamber.
BACKGROUND OF THE INVENTION

This invention relates to new and useful improvements in kilns, and has particular reference to a kiln for use in the detoxification of soil or earth containing toxic and hazardous chemicals The contamination of soil or earth with various toxic and hazardous chemicals is becoming more and more common. The use of such materials as PCB, TNT, and solvents such as toluene, xylene, and trichloroethane in agricultural and industrial applications, is becoming more and more common, and often leads to the contamination thereby of soil or earth, which must then be classified as extremely hazardous material. The decontamination and detoxification of such material presents certain problems. While the chemicals themselves may be combustible, or capable of being destroyed or rendered harmless by extreme heat, the soil is not. The soil is largely inorganic material, and is not capable of autogenous combustion, so that it cannot be burned, and as a result will often protect the chemicals intermixed therein from combustion, or from the heat necessary to render them harmless, if attempts are made to "burn" the earth or otherwise to subject it to high degrees of heat. A device which will perform this decontamination and detoxification efficiently and reliably would obviously be a substantial and valuable contribution to the art. The principal object of the present invention is the provision of a kiln in which the feedstock, earth or the like, is moved continuously through the kiln in the form of a tumbling bed, adn is subjected for the whole time it remains in the kiln to flame jets provided by an external fuel such as natural gas, oxygen or propane The flame jets not only raise the feedstock temperature to the very high level required for calcining, perhaps 2500-3000 deg. Fahr., but also stir or agitate the material in the bed to insure that the substantially incombustible material will be very thoroughly pulverized to fine particle size, which in turn insures that all of the contaminating chemicals mixed with the earth are thoroughly exposed to maximum heat for the combustion or thermal destruction thereof. I have elected to denote the process as calcination, which is believed to be accurate. Another object is the provision of a calcining kiln of the character described into longitudinally successive zones of which fuel gas and combustion air may be introduced in independently regulatable amounts. In this manner the heat requirements dictated by the stage to which the calcination has advanced in each kiln zone may be accomodated. A further object is the provision of a calcining kiln of the character described having means operable to direct cooling gases, such as air or nitrogen, into the kiln to cool the fuel gas and combustion air supply means, in order to protect the structural integrity of these elements against the extreme heat of calcination, without at the same time preventing the application of the calcining heat to the feedstock. A still further object is the provision of a kiln of the character described which may alternatively be used to treat combustible material capable of augtogeneous flame, the extreme heat being useful in guaranteeing a complete burnout of the carbon of such materials. Other objects are simplicity and economy of construction, and efficiency and dependability of operation.

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