Furnaces – Process – Incinerating refuse
Reexamination Certificate
2000-07-27
2002-10-29
Lazarus, Ira S. (Department: 3749)
Furnaces
Process
Incinerating refuse
C110S203000, C110S204000, C110S226000, C110S233000, C110S246000, C110S255000, C432S106000
Reexamination Certificate
active
06470812
ABSTRACT:
BACKGROUND OF INVENTION
This invention discloses and claims an improved method and equipment to recover energy from wastes by combustion of same in industrial furnaces.
This invention allows an efficient use of the heating power of volatile components in waste materials, preferably solids whether in bulk or crushed, such as vehicle tires, bags, bales, bulk material that may be contained in tanks, barrels, etc. to dramatically reduce fuel consumption expenses in large capacity industrial furnaces, particularly of the rotary kiln type, used in the cement or similar industries.
In the past, the need to diminish as much as possible the amount of solid, gas or liquid primary fuel that needs to be burned in large capacity industrial furnaces, in order to achieve a more efficient and productive operation of the same at a lower cost, has been recognized.
On the other hand, it has been found, that all industrial processes in general produce waste that can be burned. Many such wastes, because of their special inflammability and/or toxicity features, have been classified as hazardous waste that need to be handled with great care and deposited in distant locations, away from populated urban centers, where a degree of certainty can be achieved that they will not produce pollution to harm the environment. The above situation has promoted building the so-called garbage and waste cemeteries, as well as the famous “sanitary land fills”, where the aforementioned toxic waste is buried and covered by large amounts of soil, to avoid any contact with the atmosphere or the people.
In the cement industry all over the world, rotary furnaces requiring large amounts of fuel, particularly of the liquid and gas types to achieve the high temperatures needed, in the range of 1200° C. to 1900° C., have been used. These temperatures are capable of burning or incinerating all sorts of materials that may be fed to such furnaces. Thus, obviously, a means to diminish the amount of traditional higher-cost fuel required to operate a cement furnace would be to feed into the furnace other fuel in the form of waste materials that will contribute to reducing fuel costs for such equipment.
Also evident, is the fact that the rotary furnaces mentioned above, are in themselves highly effective and efficient devices for elimination of hazardous waste through full and absolute combustion, due to the high temperatures they reach. They are capable of disintegrating hazardous waste into their more basic components, such as carbon dioxide, nitrogen gases, etc. which are no longer hazardous either to the environment nor to people. Also combustion residues from many waste materials classified as hazardous may be safely incorporated in the cement clinker product as an environmentally safe use.
Attempts have been made in industrialized countries, since the end of the past century, to reduce fuel costs for the cement industry in general and for rotary furnaces in particular; to try to optimize the combustion conditions of such fuels, and in place of traditional fuels to substitute organic fuel material having a very low cost. Among the latter, all sorts of organic waste and even “garbage” can be found. In some cases these could have a minimal cost, which is generally represented only by the cost of handling and transportation to the plant site where they will be burned, and thus they are extremely useful.
In the United States of America and other industrial countries, many efforts have been made to develop methods and equipment that will benefit from burning combustible materials in industrial furnaces at high temperatures, in order to reduce fuel costs and to eliminate industrial waste.
Examples of the somewhat more relevant prior art are EPO patent number 0 582 394 A1 and the more pertinent of the patents cited therein and therewith;
namely, U.S. Pat. No. 4,295,823; French patent number 2,548,660; and U.S. Pat. No. 4,645,452 (which latter is equivalent to the French language EPO patent number 0 140 771). The contents of the foregoing and other patents cited in this application are incorporated herein by reference.
The Jul. 14, 1993, European patent application number 0 582 394 A1 discloses a modification of a conventional cement kiln plant with a rotary kiln for producing cement clinker having a downstream cooler and an upstream calciner and preheater (the preheater being a typical cascade of cyclone separators). A tertiary air duct conventionally conveys hot air from the clinker cooler to the intake to the calciner. Added to this conventional structure is a separate decomposition chamber for converting waste material into combustible gas by means of heat derived from injection of a portion of the preheated and calcined cement raw meal particles into the decomposition chamber.
There is no teaching of injection of the waste materials simply directly into the tertiary air duct. The EPO publication instead teaches a significantly more complex apparatus requiring not only significant added capital cost, but also more complicated control variables. The decomposition chamber is taught to be optionally formed as a spouted bed, a fluidized bed, or a rotatable drum.
The aforementioned European patent application characterizes the Oct. 20, 1981, U.S. Pat. No. 4,295,823 as utilizing the exhaust gases from the rotary kiln for the decomposition of waste and notes that such a method makes it difficult for the kiln gases to move up through the decomposition chamber in a controlled flow due to the high temperature and further that such utilization of the kiln gases for decomposition of the waste materials will have a disturbing effect on the draft conditions of the kiln system.
This U.S. Pat. No. 4,295,823 shows six different embodiments, one in each of the six drawings, all of which have the common feature of utilizing the exhaust gas from the rotary kiln in the upstream decomposition of the waste material. In
FIG. 1
no tertiary air duct is shown at all. In
FIGS. 2 and 3
, there is no flow of the tertiary air from duct (
61
) through the decomposition chamber (
18
or
73
). In none of the six figures is there a direct feeding of the waste material into the tertiary air duct itself. Also none of the disclosed embodiments teach any decomposition of the waste material by means of the tertiary air alone. In
FIGS. 4
,
5
and
6
, tertiary air is discharged from the tertiary air duct and mixed in a separate chamber with exhaust gas from the kiln and the resulting mixture is used to decompose the waste materials. All of these six variations have the common disadvantage emphasized at the top of page two of the aforementioned European patent.
Included in the aforementioned European publication is a search report listing six references, four being related only to technology background, but two being indicated to be relevant in combination. The latter two are the aforementioned French patent 2,548,660 and the European equivalent of U.S. Pat. No. 4,645,452. The French patent teaches injection of the waste materials in very small sized particles into a fluidized bed reactor which serves as the calciner (
5
) and utilizes the tertiary air (
8
&
9
) from the clinker cooler (
16
&
18
) as the fluidizing medium. Again there is absolutely no teaching of direct injection of waste materials into the tertiary air duct (the decomposition in the patent's apparatus instead taking place in an entirely separate vessel structure).
The same is true of the U.S. Pat. No. 4,645,452 where a portion of the tertiary air from the clinker cooler is fed to a rather complex fluidized bed separate decomposition chamber
10
which thereafter feeds the calciner and ultimately one of two sets of parallel preheaters.
The following patents give a further historical background showing the long felt need and slow development in this field, and more particularly are directed to the mechanisms for feeding waste to rotary furnaces.
In U.S. Pat. No. 2,813,822 issued on Nov. 19, 1957, Mr. Robert T. Collier discloses equipment and methods for burning petroleum coke, coal, and simil
Arroyave-Garcia Jose Luis
Berrun-Castanon Jorge
Diosdado Juan Manuel
Farias Luis
Garcia Armando J.
Cemex, S.A. de C.V.
Frommer & Lawrence & Haug LLP
Lazarus Ira S.
Rinehart K. B.
Safford A. Thomas
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