US3670667A

US3670667A - Incinerator for the combustion of waste products, particularly plastic materials

Info

Publication number: US3670667A
Application number: US31507A
Authority: US
Inventors: Bent Faurholdt
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-04-24
Filing date: 1970-04-24
Publication date: 1972-06-20
Anticipated expiration: 1989-06-20

Abstract

In an incinerator comprising two combustion chambers, the primary combustion chamber comprising refractory ceramic elements located adjacent to one another so as to form inclined continuous guide surfaces and means for supplying primary combustion air to said primary combustion chamber opening into said chamber at different levels above the bottom thereof.

Description

United States Patent Faurholdt [451 June 20, 1972 s41 INCINERATOR FOR THE 1 3,495,555 2/1970 Boyd et al ..1 10/8 3,190,244 6/1965 HOSkl son. ....110/1s COMBUSTION 0F WASTE PRODUCTS 2,961,977 11/1960 colerr i an ..1 10/8 PARTICULARLY PLASTIC MATERIALS Primary Examiner-Kenneth W. Sprague 72 l t Be t F holdt T 134, 2730 .1 ne'l' levy gznm omemseve] Attorney-Watson, Cole, Grmdle & Watson [22] Filed: April 24, 1970 21 Appl. No.: 31,507 [571 ABSTMCT In an incinerator comprising two combustion chambers, the primary combustion chamber comprising refractory ceramic [52] U.S.Cl ..110/8 A, 110/8 C, ll0/l8C elements located adjacent to one another so as to form [51] Int. CLm... "F238 5/12 inclined continuous guide Surfaces and means for supplying [58] Field of Search ..1 10/7, 8, 8 A, 8 C, 18, 18 C primary combustion air to i primary combustion Chamber opening into said chamber at different levels above the bottom [56] References Cited thereof. 1

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INVENTOR 77412 G za BY af dzzw (5P4 yfi'mm/ Y a ATTORNEYS PATENTEDmzo I972 SHEET t 0F 7 INVENTOR ATTORNEYS SHEET 60F 7 6 14; K -15 o o o o o o o l8 v INVENTOR ATTORNEY-S s/ I 5 BY f (M r PATENT Emma [s12 INCINERATOR FOR THE COMBUSTION OF WASTE PRODUCTS, PARTICULARLY PLASTIC MATERIALS BACKGROUND OF THE INVENTION This invention relates to an incinerator for the combustion of waste products and particularly plastic materials comprising a primary combustion chamber, means for supplying primary combustion air to said primary combustion chamber and a secondary combustion chamber which is thermally isolated from the primary combustion chamber and has means for initiating a secondary combustion.

The still increasing use of articles made from plastic materials and particularly disposable plastic materials presents problems with respect to the disposal of such articles. In order to reduce the risk of infection and to eliminate the cleaning of used articles it is important, particularly in hospitals and laboratories in which disposable plastic materials find widespread use that these plastic articles can be quickly and easily destructed by incineration.

Also in industries in which plastic materials are produced or utilized, serious problems are encountered when waste products made from plastic materials have to be destroyed because said plastic materials cannot be decomposed as ordinary refuse when stored in refuse dumps, compost heaps, etc.

In the prior art incinerators the destruction of plastic materials presents serious problems because these plastic materials burn in a manner which is very different from that of household refuse.

The problems which are encountered during the incineration of plastic materials in prior art incinerators comprising a grate supporting the plastic materials are due to the fact that the grate quickly stops functioning in the normal manner because the holes in said grate through which the air is supplied beeome clogged. This clogging has the effect of initiating a destruction of the grate if it is made from commonly used materials, such as cast steel alloys.

Other problems are due to the high soot content in the flue gases leaving incinerators in which plastic materials are incinerated. This soot content which is due to an incomplete combustion strongly contaminates the atmosphere and is a nuisance in the area surrounding such incinerators.

The reason forthese difficulties is that plastic materials possess the property of becoming soft and melting before they are ignited and burn. If refuse containing plastic materials is introduced into and ignited in an incinerator in which the grate consists of perforated grate elements of cast iron or grate lamellae separated by passages for supplying air, the openings or passages in the grate become clogged whether it is constructed as a step grate, a plane grate, or as an inclined grate because of the melting of said plastic materials. During the combustion which takes place on the basis of the combustion air which is supplied to the refuse without passing through the grate, very high temperatures are developed on the upper surface of the grate. Because of the clogging of the passages in the grate the latter is not subjected to the cooling which nor mally takes place during the passage of the cool combustion air through the grate passages. Thus, the grate, e.g., made from cast iron is heated to very. high temperatures and said heating causes an irreversible increase of volume.

Furthermore, the plastic materials possess the property that even when heated to a moderate temperature large amounts of gases are developed and the amount of said gases increases exponentially with increasing heating temperatures. Thus, if refuse containingplastic materials is introduced into and ignited in the above mentioned incinerators, large amounts of gases containing carbon particles are quickly formed in the zone above the refuse layer and said carbon particles escape from the combustion chamber together with the flue gases. If it is attempted to avoid the formation of these carbon particles by introducing more combustion air in the combustion chamber, the increased amount of heat resulting from the secondary combustion causes a generation of still greater amounts of gases and sooty carbon particles. Thus, the

problems are progressively increased until the gases and carbon particles have been completely burned away. At this time the supply of a large amount of secondary air effects a strong cooling of the combustion chamber, thus decreasing the combustion temperature of the material which has not been completely burned out. This temperature decrease also leads to the fonnation of soot which leaves the incinerator together with the flue gases.

As mentioned above the rate at which the generation of volatile gases and soot particles takes place within the primary combustion chamber depends on the generation of heat and consequently the temperature within the primary combustion chamber. However, by effecting the combustion in two thermally separated chambers it can be prevented that the generation of heat and the increase of temperature resulting from the secondary combustion influence the combustion process in the primary combustion chamber and the generation of gases and sooty particles within said chamber.

The object of the present invention is to provide an incinerator which is suitable for the combustion of articles made from plastic materials and other organic materials having similar combustion properties and which eliminates the drawbacks of the prior art incinerators.

SUMMARY .OF THE INVENTION According to the invention there is provided an incinerator having a primary combustion chamber which comprises inclined continuous guide. surfaces consisting of guide elements made from a refractory ceramic material and in which the means for supplying primary combustion air to said primary combustion chamber open into said chamber at different levels above the bottom thereof.

I When incinerating plastic materials in the incinerator according to the invention, the plastic material while melting flows down along the inclined guide surfaces and during said movement the temperature is increased to a value such that a gasification takes place. Due to the fact that the primary com bustion air is supplied at different levels above the bottom of the chamber, there is effected an intimate mixing of the primary combustion air and the compounds formed during said gasification which compounds subsequently burn.

In a preferred embodiment of the incinerator according to the invention guide surfaces are located in the form of steps at different levels above the bottom of the chamber and the means for supplying primary combustion air open into the primary combustion chamber in zones between the guide surfaces or between the lowermost guide surface and the bottom of said chamber.

The introduction of primary combustion air in the zones between the guide surfaces mounted in the form of steps has the effect of cooling the underside of the guide elements so as to avoid an excessive heating of said elements.

The guide elements preferably consist of small plate elements which are mounted adjacent to one another inrows extending transversely of the incinerator. In another preferred embodiment of the incinerator according to the invention the guide elements are supported by hollow metal pipes which serve as means for introducing primary combustion air. By supplying primary combustion air through said supporting pipes, the latter are cooled so that a deflection thereof can be avoided. Furthermore, the use of such supporting pipes permits in a simple manner a selective introduction of combustion air at diflerent levels within the combustion zone. In a still further embodiment of the incinerator according to the invention the hollow metal pipes are provided with discharge openings located so as to direct streams of gas against the upper surface of the underlying guide surface. Thus, the air flowing out from said openings causes said guide elements to be cooled. The incinerator according to the invention is preferably constructed in such a manner that a relatively large amount of combustion air can be supplied at the lowermost guide surfaces in order to ensure that plastic material which without burning completely out has reached the bottom of the incinerator is caused to burn at this place.

In a further preferred embodiment of the incinerator according to the invention the lowermost portion of the walls of the primary combustion chamber form said guide surfaces and the means for introducing primary air consist of downwardly inclined ducts provided in the walls of the primary combustion chamber.

The secondary combustion chamber may be separated into a number of adjacent and interconnected combustion chambers lined with refractory ceramic materials or other materials capable of resisting high temperatures.

The secondary combustion chamber or chambers are preferably constructed in such a manner that the first part thereof is in connection with the primary combustion chamber through an intermediate chamber or passage in which the direction of the flow of gases is turned I80The shape of the secondary combustion chamber or chambers is not critical but in order to reduce the production costs it is preferred to use a secondary combustion chamber having a rectangular cross section. The secondary combustion chamber preferably comprises restrictions at the inlet and outlet ends for the flue gases. The means for initiating a secondary combustion preferably consist of one or more oil burners, gas burners or spark igniters provided in the wall of the secondary combustion chamber. There is preferably provided means for supplying air to the combustion in the secondary combustion chamber. The air supply means can be nozzles located at different locations relative to the flow direction of the flue gases. Nozzles located at opposite sides of the flow channel are preferably offset relative to one another.

In order to reduce the loss of draught which is caused by the flow of flue gases through the secondary combustion chamber, it is preferred to mount the air supply nozzles in such a manner so as to direct the streams of air generated therein in the direction of movement of the flue gases. Due to the fact that the secondary combustion is effected in a zone which is thermally separated from the primary combustion zone, it is possi ble by adjusting the amount of air supplied through the air nozzles to effect a combustion which at any time is adjusted to the amount of gases and soot particles which is fed to the secondary combustion chamber. If air was introduced in an amount so as to ensure a complete combustion at any given time too much air would be introduced over long periods and consequently, the combustion chamber would be cooled. Thus, an incomplete combustion would take place and this would lead to high contents of soot in the gases leaving the secondary combustion chamber.

Instead of using air nozzles having separate feeding means it is preferred to feed the air through a pipe which is closed at one end and which comprises a wall having a large number of perforations, which pipe is located centrally within the secondary combustion chamber. By using a pipe comprising perforations which are of different sizes within the different zones of the combustion chamber, the air may be introduced in a pre-determined pattern.

The openings connected to the air supply means can also be openings in the walls of the secondary combustion chamber. These openings are connected with a head box on the exterior side of said walls, and air is supplied to said head box from the atmosphere by means of a pump connected to said head box.

A preferred embodiment of the incinerator according to the invention comprises means for automatically controlling the ratio of air supplied to the primary combustion chamber to air supplied to the secondary combustion chamber. These means are controlled by the heat generation and consequently the temperature within the secondary combustion chamber. This may be effected by providing within the secondary combustion chamber a thermo couple which is connected to a regulator on which the maximum temperature permitted within the secondary combustion chamber can be set. The regulator is connected to a regulating damper which controls the supply of air to the primary combustion chamber and the secondary combustion chamber, respectively. By means of a servo-control system it is possible in the manner described above to effect a continuous regulation of the supply of air to the primary combustion chamber and the secondary combustion chamber, respectively. In the incinerator according to the invention the combustion air may also be supplied to the combustion chambers in an amount which depends on the temperature within the primary combustion chamber.

Finally, the incinerator according to the invention may be constructed in such a manner that the supply of air is controlled by a soot detector mounted close to the secondary combustion chamber at the downstream side thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a vertical sectional view of an embodiment of the incinerator according to the invention,

FIG. 2 illustrates a vertical sectional view of a second embodiment of the incinerator according to the invention,

FIG. 3 illustrates a horizontal sectional view of the incinerator shown in FIG. 2 along the line IIIllI,

FIG. 4 illustrates a vertical sectional view of a third embodiment of the incinerator according to the invention,

FIG. 5 illustrates a vertical sectional view of the secondary combustion chamber in a further embodiment of the incinerator according to the invention,

FIG. 6 illustrates a vertical sectional view of the secondary combustion chamber in a still further embodiment of the incinerator according to the invention,

FIG. 7 illustrates a vertical sectional view of the primary combustion chamber in a further embodiment of the incinerator according to the invention, and

FIG. 8 illustrates a vertical sectional view of the primary combustion chamber shown in FIG. 7 along the line VII-VII.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings 1 is a primary combustion chamber containing inclined guide elements 2 of a refractory ceramic material. These guide elements 2 are supported by hollow metal pipes 3 provided with holes and connected to means for supplying primary combustion air to the combustion chamber. The primary combustion chamber is connected to a secondary combustion chamber 6 through a duct 4 and a flow-tuming chamber 5. In an opening in the wall of the secondary combustion chamber 6 there is provided an oil burner 7 and a large number of air supply nozzles 8.

The secondary combustions chamber shown in FIGS. 2 and 3 also comprises a large number of air supply nozzles 8. These air supply nozzles 8 are connected through ducts 9 with air supply compartments 10 mounted at opposite sides of the secondary combustion chamber. Air is supplied to said compartments 10 through pipes 11. Temperature sensors 22 and 24 are respectively mounted in secondary combustion chamber 6 and primary combustion chamber 1 and provide signals to air delivery controller 23 for the purpose of varying the supply of air to combustion chamber 1 in accordance with either the temperature of the first or secondary combustion chamber. As mentioned previously, another means of controlling the supply of air to combustion chamber 1 is to sense the amount of soot emanating from the second combustion chamber, and for such a control, the temperature sensor 22 may be replaced by a soot sensor which is mounted close to the secondary combustion chamber at the downstream side thereof. In the incinerator illustrated in FIG. 4 central guide elements 12 supported by air supply pipes are provided within the primary combustion chamber. These central guide elements 12 permit a satisfactory supply of air to that portion of the plastic material which during the incineration is located at the center of the primary combustion chamber.

In the secondary combustion chamber shown in FIG. 5 there is provided a central air supply pipe 13 which is closed at its lowermost end and which is provided with horizontal rows of holes 14. The distance between the rows is less in the restricted area at the outlet of the secondary combustion chamber 6 than at the center thereof. This pipe 13 permits the supply of different amounts of air to different portions of the secondary combustion chamber.

The secondary combustion chamber shown in FIG. 6 consists of two cylindrical concentrically mounted

pipes

15 and 16, of which the innermost one 16 is made from stainless steel. The space between the two pipes forms an air supply compartment 17 to which air is supplied through a pipe 18. The innermost pipe 16 is provided with horizontal rows of holes 14 through which the air supplied is introduced into the secondary combustion chamber. In the incinerators disclosed an oil burner (not shown) is mounted in the side wall of the primary combustion chamber. This oil burner serves to initiate the combustion within the primary combustion chamber.

In the incinerator illustrated in FIGS. 7 and 8 the side walls of the primary combustion chamber 1 form inclined guide surfaces 19 of a refractory ceramic material. Downwardly directed ducts 20 for the introduction of primary combustion air are provided in said side walls.

The incinerator shown in FIGS. 7 and 8 is preferably connected to a secondary combustion chamber of the type shown in FIG. 6. a

I claim:

1. An incinerator for the combustion of waste products and particularly plastic materials comprising a primary combustion chamber, means for supplying combustion air to said primary combustion chamber, a secondary combustion chamber thermally isolated from the primary combustion chamber, means for initiating a secondary combustion and means for supplying combustion air within said secondary combustion chamber, the primary combustion chamber comprises inclined continuous guide surfaces consisting of guide elements made from a refractory ceramic material, said guide surfaces are mounted at difi'erent levels within said primary combustion chamber, and said means for supplying primary combustion air to said primary combustion chamber open into said chamber between said inclined guide surfaces.

2. An incinerator according to claim 1, wherein said guide surfaces are in the form of steps at difierent levels above the bottom of the primary combustion chamber, and said means for supplying primary combustion air open into the combustion chamber in zones between the guide surfaces and between the lowermost guide surface and the bottom of the primary combustion chamber.

3. An incinerator according to claim 2, further comprising hollow pipes for supporting said guide elements and for introducing primary combustion air into the primary com bustion chamber.

4. An incinerator according to claim 3, wherein said hollow pipes include discharge openings located so as to direct streams of gas generated therein against the upper surface of the underlying guide elements.

5. An incinerator according to claim 1, wherein the lowermost portion of the walls of the primary combustion chamber form said guide surfaces and that the means for supplying primary combustion air to the primary combustion chamber consist of downwardly inclined ducts provided in the walls of said primary combustion chamber.

6. An incinerator according to claim 1, further comprising means for controlling the amount of air supplied to the prima ry combustion chamber dependent on the generation ofheat within the secondary combustion chamber.

7. An incinerator according to claim 1, further comprising means for controlling the supply of air to the primary combustion chamber dependent on the generation of heat in the primary combustion chamber.

8. An incinerator according to claim 1, further comprising means for controlling the supply of air to the primary combustion chamber dependent on the contents of soot in the flue gases leaving the secondary combustion chamber.

Claims

1. An incinerator for the combustion of waste products and particularly plastic materials comprising a primary combustion chamber, means for supplying combustion air to said primary combustion chamber, a secondary combustion chamber thermally isolated from the primary combustion chamber, means for initiating a secondary combustion and means for supplying combustion air within said secondary combustion chamber, the primary combustion chamber comprises inclined continuous guide surfaces consisting of guide elements made from a refractory ceramic material, said guide surfaces are mounted at different levels within said primary combustion chamber, and said means for supplying primary combustion air to said primary combustion chamber open into said chamber between said inclined guide surfaces.

2. An incinerator according to claim 1, wherein said guide surfaces are in the form of steps at different levels above the bottom of the primary combustion chamber, and said means for supplying primary combustion air open into the combustion chamber in zones between the guide surfaces and between the lowermost guide surface and the bottom of the primary combustion chamber.

3. An incinerator according to claim 2, further comprising hollow pipes for supporting said guide elements and for introducing primary combustion air into the primary combustion chamber.

6. An incinerator according to claim 1, further comprising means for controlling the amount of air supplied to the primary combustion chamber dependent on the generation of heat within the secondary combustion chamber.