US3559597A

US3559597A - Incinerator

Info

Publication number: US3559597A
Application number: US795126*A
Authority: US
Inventors: Bernhard Heiny
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 1968-01-30
Filing date: 1969-01-29
Publication date: 1971-02-02
Anticipated expiration: 1988-02-02
Also published as: FR2000985A1; BE727638A; SE351713B; GB1215792A; CH493791A; FR2000985B1

Abstract

Incinerator furnace is gravity fed and includes a secondary combustion chamber beneath the primary chamber. The fire pot of the latter and the outer wall of the furnace stack are rotated. Auxiliary burners in the second chamber ensure complete burning of the refuse. An exhauster draws the combustion gases through a boiler, and through a preheater for combustion air, and keeps the furnace at a negative pressure.

Description

0 United States Patent 1111 3,559,597

[72) Inventor Bernhard l-leiny [56] References Cited Wolfsburg, Germany UNITED STATES PATENTS P 2,797,668 7/1957 Seidl 122/336 [221 PM 291 3,344,758 10/1967 Wotschke 1 10/18 [45] Patented Feb. 2, W71 [73] Assignee Volkswagenwerk A. G, Pnmary Examiner-Kenneth W. Sprague wolfsburg, Ge man Attorney-Burns, Doane, Benedict, Swecker & Mathis a corporation of Germany [32] Priority Jan. 30, 1968, Feb. 16, I968 [33] Germany [31] 1,601,294 and 1,601,295

[54] INCINERATOR 26 Claims, 5 Drawing Figs.

52 11.5.0 110/10, 122/2 51 Int.Cl F23g5/l2 s0 FieldofSearch...: 11o/7,s,

ABSTRACT: Incinerator furnace is gravity fed and includes a secondary combustion chamber beneath the primary chamber. The fire pot of the latter and the outer wall of the furnace stack are rotated. Auxiliary burners in the second chamber ensure complete burning of the refuse. An exhauster draws the combustion gases through a boiler, and through a preheater for combustion air, and keeps the furnace at a negative pressure.

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ATTORNEYS INCINERATOR BACKGROUND OF THE INVENTION the refuse. This isparticularly true with industrial waste that has a high proportion of synthetic plastic. The complete burning of such waste is a problem that till now has not been satisfactorily solved.

SUMMARY OF THE INVENTION The chief object of the invention is to produce an incinerator of the aforesaid kind and which ensures the continuous and complete burning of any kind of refuse, including industrial waste, even where the refuse is partly solid and partly fluid, or, indeed, where it is entirely composed of synthetic plastics.

Another object of the invention is an incinerator of which those parts subject to great thermal and mechanical stress have a long service life and require attention only after prolonged intervals ofuse, thereby reducing maintenance costs. The discharge opening in the primary combustion chamber, in

- particular, has a long, trouble-free life.

A further object of the invention is an incinerator in which the refuse slides continuously from the stack into the primary "combustion chamber, from which latter it moves continuously, partly as a fluid ash and partly as an incompletely burned pasty or lumpy mass, into the secondary combustion chamber, and then, after it is completely burned, it is continuously removed in a fluid state and treated in a known manner, such as granulation in the water bath of an ash remover.

. A still another object-of the invention is an incinerator that completely burns refuse with a minimum amount of heat and which enables the economical burning of refuse with very high moisture contents.

3 r The invention, in its novel essentials, is characterized bya the bottom and the ash discharge openingof the secondary combustion chamber; and by an exhauster connected to the combustion-gas outlet of the secondary combustion chamber.

An incinerator so constructed enables the continuous and complete burning of refuse of any kind, with only aminimum amount of maintenance of the installation. When the inventor constructed an incinerator having a daily capacity of 60 tonsv (2,000 pounds/ton)v of industrial waste, it became apparent that the construction of the primary and secondary combustion chambers was of crucial importance.

It is advantageous, with an incinerator constructed in accordance with the essentials listed previously, to increase the time that the refuse remains in the primary. combustion chamber. To this end, the primary combustion chamber is enclosed by the lower part of a stationary cylindrical refractory wall, and the roof of this chamber is conical and incorporates a plurality of nozzles for introducing air for combustion into the chamber, the nozzles being angled with respect to the axis of the chamber so as to create a cyclonelike flow of air and of h c s the height of the refuse charged into the primary combustion chamber.

For trouble-free continuous operation, it is advantageous to arrange a series of water-cooled refuse deflectors on the lower part of the cylindrical refractory wall for forcing the refuse radially towards the center of the tire pot when the latter turns. These deflectors are expediently so constructed that their deflecting angle is adjustable and that they can be easily replaced. The water-cooled refuse deflectors. together with the inclined fire pot, ensure a trouble-free movement of the refuse out of the stack and onto the tire pot, and the movement of the partly burned refuse down the inclined surface of the fire pot towards the central opening that leads to the secondary combustion chamber. The refuse charged into the annular stack is further encouraged to slide down the latter by providing an outer metal wall, rotatable about the stack axis, and positioned above the cylindrical refractory wall.

Those parts of the incinerator that are subject to great thermal and mechanical stress-particularly the roof of the primary combustion chamber, the central opening in the tire pot, the walls and ash discharge opening of the secondary combustion chamber, as well as the gas deflecting surfaceare advantageously provided with suitable cooling pipe arrangements.

In order to prevent flames and combustion gases from escaping to the outside, in accordance with the invention, the incinerator, is operated at a pressure below the atmospheric. Water seals are advantageously used to provide seals between the rotating and stationary parts of the furnace.

In accordance with the invention, the complete burning of the refuse in the secondary combustion chamber is obtained by laterally shifting the ash discharge opening, with respect to the central opening, in the direction of flow of the combustion gases, and by arranging a gas-deflecting surface in the secondary combustion chamber for causing at a least part of the combustion gases to blow against the bottom and the ash discharge opening of the secondary combustion chamber. These measures prolong the time that the partly burned refuse remains in the secondary combustion chamber. For the purpose of ensuring the continuous advance of the refuse and the ash through the secondary combustion chamber, it has proven most effective to incline the chamber bottom at an angle of about 20 towards the ash discharge opening, and to tip the auxiliary burners at about the same angle above the bottom. With this construction of the secondary combustion chamber, the gas-deflecting surface is arranged so that it projects downwardly from the top of the chamber and its lower edge lies approximately vertically above the end of the chamber bottom where it borders on the ash discharge opening. These measures reduce the cross section of the secondary combustion chamber in front of the ash discharge opening, thereby increasing the velocity of the combustion gases above the ash discharge opening, and causing the hot combustion gasesin part because of the angular position of the gasdeflecting surface and in part because of the flame direction of the auxiliary bumerto blow on the sloping chamber bottom and in particular on the funnel-shaped ash discharge opening.

With a view to raising the buming efficiency of the furnace and to preparing refuse with a high moisture content for burning, the air for combustion that is blown into the primary com- If the incinerator must bum refuse having very high moisture contents, a plurality of nozzles for introducing hot air into the primary combustion chamber are arranged in the 1 upper part of the cylindrical refractory wall at a height below bustion chamber and/or the hot air that is blown into the refuse-loaded primary combustion chamber is advantageously heated by a preheater, which is arranged after a waste-heat boiler and through which the combustion gases pass. Downstream of the ash discharge opening the secondary combustion chamber is constructed to form a combustion-gas duct that rises at an angle of about 20 towards the waste-heat boiler. Advantageously, the cross-sectional area through which'the gases are free to flow in the latter is such that the combustion gases lose most of their speed, whereby the fly ash settles out of the gases and can be collected at the floor of the boiler.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described, with reference to the FIGS. of the accompanying drawings, wherein:

FIG. 1 is a simplified lateral elevation of the incinerator of the invention; the waste-heat boiler is removed;

FIG. 2 is a side view in cross section ofthe fire pot of the primary combustion chamber;

FIG. 3 is a top view of the structure seen in FIG. 2; and

FIG. 4a, 4b is a side view, in cross section, of the complete installation, in including the waste-heat boiler and the air preheater.

DESCRIPTION OF THE PREFERRED EMBODIMENT with reference to the FIGS., the incinerator illustrated is essentially composed of a pair of charging hoppers I, an annular furnace stack 3, and a primary combustion chamber 6. The latter incorporates a fire pot 5 that rotates about the axis of the furnace, the pot 5 embodying a central opening 7. The partly burned refuse, or waste, passes through this opening and into a secondary combustion chamber 20, where the refuse is completely burned with the aid of several oil burners 26a. The fluid ash falls through an opening 25 and is granulated in an ash remover having a water bath 30. The combustion gases flow from the secondary combustion chamber 20 through the duct 20:: to a waste-heat boiler (not shown in FIG. 1).

The incinerator in accordance with the invention will be described in detail with reference to FIG. 4a, 4b. The refuse is loaded into two charging hoppers I, from where conveyor rollers 2 move it down into the annular stack 3, of which the outer wall 4 is arranged to rotate, whereby to ensure that the refuse is evenly distributed throughout the stack 3. The outer wall 4 is mounted on rollers 4a. Laterally arranged rollers 4b keep the wall in its circular path. The refuse slides down the furnace stack 3 and into the fire pot 5 of the primary combustion chamber 6. The fire pot is rotatably mounted on rollers 5a and laterally guided in its circular path by rollers 5b. The fire pot embodies an upper surface, in the shape of an inverted cone, made of a suitable refractory material. This surface slopes towards the opening 7 at an angle of about 30. The downwardly expanding discharge opening 7 is located in the center of this upper surface, and is designed and shaped to diffuse the matter and gases passing through it. For the purpose of reducing wear and carrying off heat, the opening is provided with a water-cooled, metal-clad circular shell 8 made of a suitable high-temperature steel, and the inner wall of which shell serves as the wall of the opening.

The water for cooling the opening 7 is moved by a pump 81; from a reservoir 812 into the hollow of the shell 8 and then back into the reservoir. The outer wall of the shell 8 is provided with a water seal 9, which makes a gastight seal between the rotatable fire pot 5, or the shell 8, and the base of the furnace, since the installation operates at a pressure below atmospheric. The water seal 9 also acts to conduct away heat from the greatly heated opening 7 and the shell 8.

The refuse continuously slides down the stack 3 and distributes itself over the rotating fire pot 5, where the slope and rotation of the latter, as well as the stationary water-cooled, replaceable deflectors 10, cause the refuse to slide towards the discharge opening 7. The angular position of the refuse deflectots can be adjusted by a handcrank (not shown) to correspond to the desired rate of feed towards the center of the fire pot 5. The furnace is filled with refuse up to the lower edge of the stack inner wall II, which latter can be made of steel plate. When at this height, the refuse begins to burn at a rate that depends on its composition and its moisture content. A burner 26 in the roof of the primary combustion chamber 6 begins the combustion. The refuse spread over the rotating fire pot 5 burns throughout its entire height, the burning temperature increasing from the outside of the refuse towards the center of it. The primary combustion chamber is covered by a cone-shaped roof 12. That part of the roof which is touched by the flames is composed of a pipe-on-pipe construction, which is filled with cooling water or steam. This pipe construction is made gastight by plugs and packing. The space I3 above the roof I2 is used as a distribution chamber for the combustion air heated by an air preheater l4 in the waste-heat boiler IS. The injection nozzles 16 for the preheated combustion air extend from within the distribution chamber I3 to the primary combustion chamber6. The nozzles are so angled with respect to the chamber axis that the combustion air injected into the chamber 6 causes a cyclonelike propagation of the combustion, thereby ensuring that the combustion gases remain longer in the chamber 6 to obtain a more intensive combustion of the refuse.

Acylindrical refractory wall 17, which is not rotatable, encloses the primary combustion chamber 6. If the refuse has a very high moisture content, hot air, from the preheater l4, predrying the refuse can be introduced by an annular conduit 18 and nozzles I9, which latter are angled in the wall 17 so that the hot air is introduced at a suitably acute angle with respect to the surface of the wall 17.

The unburned part of the refuse, because of the high temperature in the central zone of the rotating fire pot 5, moves as a fluid or pasty mass, together with the combustion-gas current, through the diffusing discharge opening 7 and into the secondary combustion chamber 20. The higher temperature in this space completes the combustion.

In contrast to a known incinerator, the incinerator of the invention operates at a negative pressure. To this end, an exhaust fan 21 is arranged after the waste-heat boiler 15 and the preheater 14. Water seals are arranged between the rotating and stationary parts of the furnace to prevent air from being sucked into the furnace. Thus, a water seal 23a is located on the outer wall 4 of the stack 3; another, 22, between the stationary refractory wall 17 and the rotating fire pot 5-of the chamber 6; and the previously mentioned waterf seal 9 between the discharge opening 7 and shell 8, on the-one hand, and the furnace base, on the other. Closable flaps 24, arranged below the conveyors 2, prevent air from entering the furnace when the hoppers l are empty. I

The secondary combustion chamber 20, including the opening 25, has hot-cooled walls composed of a pipe-on-pipe construction, and the chamber opens, through the duct 20a, into the waste-heat boiler 15. In accordance with the invention, the ash discharge opening 25 of the chamber 20 is laterally displaced, with respect to the opening 7, in the direction of the combustion gas current. The bottom 27 of the chamber 20 slopes downwards at an angle of a about 20 towards the opening 25. The auxiliary oil burners 26a, mounted in oneend of the chamber 20, are tilted at approximately the same angle. A deflecting surface 28 for the combustion gases slants downwards from the roof of the chamber 20 so that its lower edge is positioned approximately vertically above the end of the sloping bottom 27, where the latter borders on the opening 25. The surface 28 is advantageously formed by cooling pipes.

The mutual arrangement ofthe bottom 27 and the surface 28 reduces the cross section of the chamber 20 in front of the opening 25. This construction of the chamber 20 causes the ash and the still incompletely burned part of the refuse to remain longer in the chamber. The unburned refuseand the ash slide down the bottom 27 towards the discharge opening 25. The increased temperature, produced by the burners 26a, helps to burn the refuse completely. The flow of ashes down the floor 27 is encouraged, because the flames of the oil burners 26a act in a direction parallel to the floor and are directed towards the opening 25. The arrangement of the surface 28 and the manner in which it reduces the cross sectionof the chamber 20 in front of the opening 25 are such that the combustion gases move at an increased velocity over the floor 27 and the opening 25. This causes a complete burning of the refuse and a continuous flow of ashes towards the ash discharge opening 25. The ashes are continuously kept in the desired fluid state by the lateral displacement of the opening 25 with respect to the opening 7, by the slope of the floor 27, and by the surface 28. i

The fluid ashes fall out of the opening 25. through a discharge container 29, and into an ash remover having a water bath 30, from which latter an endless conveyor 3] removes them in the form of granules. The discharge container 29 is partly submerged into the water bath 30 in order to provide an air seal between the furnace and the ash remover.

Behind the opening 25 the chamber 20 forms a duct 20a for the combustion gases. This duct slopes upwardly towards the waste-heat boiler 15 at an angle of about 20. so that the ash particles, carried along by the gaseous current, can fall back into the opening 25.

The combustion gases move from the secondary combustion chamber 20, through the duct 20a, and into the first chamber 15a of the waste-heat boiler 15. This chamber, which is designed as a radiation space has its walls formed by pipes. It is sufficiently large so that the speed of the gases is reduced from about 15 meters/second in the secondary combustion chamber 20 to about 2 to 3 meters/second. As a consequence, some of the fiy ash carried by the gases settles and falls through a funnel 32 into an ash remover having a water bath and an endless conveyor 33. The tube of the funnel 32 dips into the water bath. The combustion gases move out of the first chamber 15a through a very coarse grid of pipes into a second chamber 15b. The walls of this chamber can also be built of pipes, for the purpose of extracting heat from the gases, or the walls can be used as a preheater, as is the third chamber 15c, for the combustion air. Funnels mounted underneath the second and third chambers catch the falling fly ash and lead it into the water bath of the the aforesaid ash remover.

A cyclone filter, mounted between the boiler 15 and the exhaust fan 21, cleans the combustion gases of all particulate matter larger than ;.t.

The steel frame and body 35 of the incinerator serves to mount and support various parts of the furnace and the boiler. Several circular platforms 36, located at various heights of the furnace, are also mounted on the incinerator frame and body 35.

The preheater c is advantageously located at a position in the boiler 15, and has a cross section for the gases of such a size, so that the temperature of the combustion gases lies below the softening point of the ash.

The word refractory in the specification and claims is intended to cover metallic as well as nonmetallic materials.

Although the preferred embodiment of the invention has been described, the scope of, and the breadth of protection af forded to, the invention are limited solely by the appended claims.

I claim:

1. An incinerator comprising:

a primary combustion chamber having a central refuse burning chamber, a refuse inlet and outlet, and burner means for producing combustion gases within said central refuse burning chamber for burning refuse within said primary combustion chamber; and

a secondary combustion chamber having a refuse inlet and outlet, a sloping base, and an auxiliary burner means for producing combustion gases within said secondary combustion chamber for burning refuse within said secondary combustion chamber, said secondary combustion chamber inlet being positioned below said primary combustion chamber outlet and said secondary combustion chamber outlet being laterally offset with respect to said primary combustion chamber outlet in the direction of flow of the combustion gases in said secondary combustion chamber.

2. An incinerator as defined in claim I and further comprising a gas deflecting surface arranged in said secondary combustion chamber to cause at least a portion of the combustion gases in said secondary combustion chamber to blow against said sloping base and outlet in said secondary combustion chamber.

3. An'incinerator as defined in claim 1 wherein said primary combustion chamber outlet being shaped to diffuse gases and refuse passing therethrough.

4. An incinerator as defined in claim 1 wherein said primary and secondary combustion chambers are provided with sloping base portions, the slope of the base portion of said primary combustion chamber being greater than the slope of the base portion of said secondary combustion chamber.

5. An incinerator as defined in claim 1 wherein said auxiliary burner means positioned within said secondary combustion chamber being directed generally parallel to said base portion of said secondary combustion chamber and toward said secondary combustion chamber outlet opening whereby the flow of material within said secondary combustion chamber toward said outlet opening is facilitated.

6. An incinerator, including a furnace, said furnace having an annular stack for receiving refuse, a primary combustion chamber connected to said annular stack to receive refuse sliding down the latter, a fire pot comprised by said primary combustion chamber including a burner means for producing combustion gases within said fire pot, a central opening in said fire pot, a secondary combustion chamber fed burned and unburned refuse through said opening, auxiliary burner means for the latter said chamber for producing auxiliary combustion gases within said secondary combustion chamber, and an ash discharge opening in said secondary combustion chamber, and wherein the improvement comprises:

means for mounting and rotating said fire pot about the axis of said annular stack, said fire pot having an upper refractory surface, said surface being conical and sloping downwardly toward said central opening;

said ash discharge opening is laterally shifted, with respect to said central opening, in the direction of flow of the combustion gases in said secondary combustion chamber;

a bottom for said secondary combustion chamber;

a gas deflecting surface arranged in said secondary combustion chamber to cause at least a part of the combustion gases to blow against said bottom and ash discharge opening; and

an outlet for combustion gases connected to said secondary combustion chamber, and an exhauster connected to said outlet.

7. An incinerator as defined in claim 6, wherein said conical upper refractory surface slopes downwardly at an angle of about 30.

8. The incinerator as defined in claim 6, wherein said exhauster ensures that the incinerator operates at a negative pressure.

9. The incinerator as defined in claim 6, including an outer cylindrical wall for said annular stack positioned above said stationary cylindrical refractory wall, and means for mounting and rotating said stack outer wall about the axis of said stack.

10. The incinerator as defined in claim 6, wherein said central opening is shaped to diffuse the gases and refuse passing therethrough, and a cooling arrangement provided for the wall of said central opening.

1 l. The incinerator as defined in claim 10, wherein the wall of said central opening is a refractory pipe arrangement for carrying a circulating cooling medium.

12. The incinerator as defined in claim 6, including a stationary cylindrical refractory wall that at its lower part encloses said primary combustion chamber, a conical roof for the latter said chamber, and a plurality of combustion-air nozzles in said roof for introducing air for combustion into said primary combustion chamber.

13. The incinerator as defined in claim 12, wherein said nozzles are so angled as to create a cyclonelike flow of air and gases in said primary combustion chamber.

14. The incinerator as defined in claim 12, including a plurality of drying-air nozzles for introducing hot air into said primary combustion chamber to dry refuse having a high moisture content, said nozzles being located in the upper part of said cylindrical wall at a height below the height of the refuse charged into said primary combustion chamber.

15. The incinerator as defined in claim l2. including a plurality of water-cooled refuse deflectors provided at the lower part of said cylindrical wall for forcing the refuse radially towards the center of said firc pot when the latter rotates.

16. The incinerator as defined in claim 15. wherein said refuse deflectors are spaced along the inner circumference of said cylindrical wall.

17. The incinerator as defined in claim 15, including means for adjusting the angular position and therefore the deflecting angle of said refuse deflectors.

18. The incinerator as defined in claim 17, wherein said refuse deflectors are replaceable 19. The incinerator as defined in claim 12, wherein said conical roof is composed at least in part of piping for carrying a circulating cooling fluid.

20. The incinerator as defined in claim 12. including an outer cylindrical wall for said annular stack p'ositioned about said stationary cylindrical refractory wall, and means for mounting and rotating said stack outer wall about the axis of said stack, and water seals arranged between said stationary cylindrical wall and said outer cylindrical wall, between said fire pot and said stationary cylindrical wall, and between said central opening and the immediately neighboring stationary part of said furnace.

21. The incinerator as defined in claim 6, wherein said bottom of the secondary combustion chamber and said auxiliary burner means are inclined downwards at an angle of about towards said ash discharge opening.

22. The incinerator as defined in claim 21, wherein said gas deflecting surface projects downwardly from the top of said secondary combustion chamber and defines a lower edge that lies approximately vertically about the lower end of said secondary combustion chamber, whereby said surface reduces the cross section of the latter said chamber upstream, as defined by the direction gas flow, of said ash discharge openmg.

23. The incinerator as defined in claim 22, including a waste-heat boiler and a duct for the combustion gases, said duct connecting said secondary combustion chamber, at a point downstream, as defined by the direction of gas flow, of said ash discharge opening, to said boilerand rising at an angle of about 20" towards said boiler.

24. The incinerator as defined in claim 23, including cooling pipes for composing the walls of said secondary combustion chamber and said ash discharge opening.

25. The incinerator as defined in claim 23. wherein said boiler includes a plurality of chambers and is provided with a preheater for the air for combustion, the cross section, through which the combustion gases are free to flow, of said boiler chambers being sufficiently great to cause a considerable reduction in the speed at which the gases move, and means for collecting and removing the fly ash in said boiler.

26. The incinerator as defined in claim 25, wherein said preheater is arranged at a position in said boiler, and has a sufficiently large cross section through which the combustion gases are free to flow, so that the temperature of the gases in the preheater lies below the softening point of the ash.

Claims

1. An incinerator comprising: a primary combustion chamber having a central refuse burning chamber, a refuse inlet and outlet, and burner means for producing combustion gases within said central refuse burning chamber for burning refuse within said primary combustion chamber; and a secondary combustion chamber having a refuse inlet and outlet, a sloping base, and an auxiliary burner means for producing combustion gases within said secondary combustion chamber for burning refuse within said secondary combustion chamber, said secondary combustion chamber inlet being positioned below said primary combustion chamber outlet and said secondary combustion chamber outlet being laterally offset with respect to said primary combustion chamber outlet in the direction of flow of the combustion gases in said secondary combustion chamber.

2. An incinerator as defined in claim 1 and further comprising a gas deflecting surface arranged in said secondary combustion chamber to cause at least a portion of the combustion gases in said secondary combustion chamber to blow against said sloping base and outlet in said secondary combustion chamber.

3. An incinerator as defined in claim 1 wherein said primary combustion chamber outlet being shaped to diffuse gases and refuse passing therethrough.

6. An incinerator, including a furnace, said furnace having an annular stack for receiving refuse, a primary combustion chamber connected to said annular stack to receive refuse sliding down the latter, a fire pot comprised by said primary combustion chamber including a burner means for producing combustion gases within said fire pot, a central opening in said fire pot, a secondary combustion chamber fed burned and unburned refuse through said opening, auxiliary burner means for the latter said chamber for producing auxiliary combustion gases within said secondary combustion chamber, and an ash discharge opening in said secondary combustion chamber, and wherein the improvement comprises: means for mounting and rotating said fire pot about the axis of said annular stack, said fire pot having an upper refractory surface, said surface being conical and sloping downwardly toward said central opening; said ash discharge opening is laterally shifted, with respect to said central opening, in the direction of flow of the combustion gases in said secondary combustion chamber; a bottom for said secondary combustion chamber; a gas deflecting surface arranged in said secondary combustion chamber to cause at least a part of the combustion gases to blow against said bottom and ash discharge opening; and an outlet for combustion gases connected to said secondary combustion chamber, and an exhauster connected to said outlet.

7. An incinerator as defined in claim 6, wherein said conical upper refractory surface slopes downwardly at an angle of about 30*.

11. The incinerator as defined in claim 10, wherein the wall of said central opening is a refractory pipe arrangement for carrying a circulating cooling medium.

15. The incinerator as defined in claim 12, including a plurality of water-cooled refuse deflectors provided at the lower part of said cylindrical wall for forcing the refuse radially towards the center of said fire pot when the latter rotates.

16. The incinerator as defined in claim 15, wherein said refuse deflectors are spaced along the inner circumference of said cylindrical wall.

18. The incinerator as defined in claim 17, wherein said refuse deflectors are replaceable.

19. The incinerator as defined in claim 12, wherein said conical roof is composed at least in part of piping for carrying a circulating cooling fluid.

20. The incinerator as defined in claim 12, including an outer cylindrical wall for said annular stack positioned about said stationary cylindrical refractory wall, and means for mounting and rotating said stack outer wall about the axis of said stack, and water seals arranged between said stationary cylindrical wall and said outer cylindrical wall, between said fire pot and said stationary cylindrical wall, and between said central opening and the immediately neighboring stationary part of said furnace.

21. The incinerator as defined in claim 6, wherein said bottom of the secondary combustion chamber and said auxiliary burner means are inclined downwards at an angle of about 20* towards said ash discharge opening.

22. The incinerator as defined in claim 21, wherein said gas deflecting surface projects downwardly from the top of said secondary combustion chamber and defines a lower edge that lies approximately vertically about the lower end of said secondary combustion chamber, whereby said surface reduces the cross section of the latter said chamber upstream, as defined by the direction gas flow, of said ash discharge opening.

23. The incinerator as defined in claim 22, including a waste-heat boiler and a duct for the combustion gases, said duct connecting said secondary combustion chamber, at a point downstream, as defined by the direction of gas flow, of said ash discharge opening, to said boiler and rising at an angle of about 20* towards said boiler.

25. The incinerator as defined in claim 23, wherein said boiler includes a plurality of chambers and is provided with a preheater for the air for combustion, the cross section, through which the combustion gases are free to flow, of said boiler chambers being sufficiently great to cause a considerable reduction in the speed at which the gases move, and means for collecting and removing the fly ash in said boiler.