Incinerator and method for incineration

Abstract

 Substances to be incinerated such as municipal and industrial wastes are pre-burned in a rotative stoker (3), and unburned matters, i.e., some portions of the substances the combustion of which has not been completed in the stoker, are completely combusted in a fluidized bed incinerator (4) which is maintained at a high temperature.

Description

[0001] This invention relates to an incinerator which is utilized for incinerating municipal and industrial wastes and a method for incinerating such substances. More specifical­ly, it is concerned with an incinerator the structure of which with regard to after-burning is improved, and a method for incineration to be conducted in such an inci­nerator.

[0002] Heretofore, typical mechanical incinerators have structures shown in figures 2 and 3.

[0003] Figure 3 illustrates one example of a known mechanical in­cinerator. As depicted in figure 2, substances to be in­cinerated, such as municipal and industrial wastes which are supplied into a hopper chute b of the mechanical inci­nerator a are introduced into a main stoker c and undergo a primary combustion while the main stoker c rotates. The substances burned in the main stoker c are then introduced into an after-burning substoker d which is connected to the downstream end of the main stoker c so as to undergo a se­condary combustion therein. Following the secondary com­bustion in the substoker d, ashes together with unburned materials and incombustible matters are water-cooled and discharged through a discharging port e connected to the downstream end of the substoker d. Numeral f designates a space where firing takes place by firing means, such as burners.

[0004] Figure 3 illustrates another example of the prior art. As shown in figure 3, a main stoker c where a main or primary combustion takes place and a substoker d where after-­ or secondary combustion takes place are inclined downwardly in sequence.

[0005] Due to their dead load, the substances fed to a hopper chute b move through the stokers c and d and are burned in the main stoker c (primary combustion) and in the sub­stoker d (secondary combustion). Ashes produced upon the secondary combustion in the substoker d, together with the unburned and incombustible matters, are cooled by water and discharged from an exhaust port e. In figure 3, numeral f denotes a space where burning by means for burning, such as burners, takes place.

[0006] A mechanical incinerator a of the above-mentioned type has the following disadvantages.

[0007] Without intensive care and observation during operation, the unburned matters from the main stoker c cannot undergo the secondary combustion in the substoker d so that the amount of unburned matters among the substances to be dis­charged from the substoker d to the discharging port e in­creases, thus deteriorating the incinceration performance.

[0008] It is a further disadvantage of the mechanical incinerator a in comparison with fluidized bed incinerators that the volume of the substances to be discharged is large.

[0009] Furthermore, since water is supplied to the substances which include ashes and unburned and incombustible materials dis­charged from the substoker d to the exhaust port e, the sub­stances contain moisture so that dehydration is necessary in order to more easily handle the substances.

[0010] Yet another problem is that such a mechanical incinerator may require a processing equipment for cleansing the dis­charged matters.

[0011] The object of this invention is to provide an incinerator which is capable of realizing a desired combustion per­formance without care on operation or special controlling equipments.

[0012] Another object is to provide an incinerator from which ashes are discharged in dried state, and a method therefor.

[0013] Still another object is to provide an incinerator which does not require special preparations or preprocessings such as breaking and crushing of the substances to be incinerated, and which is capable of simplifying a manipu­lation concerned with combustion.

[0014] The invention solves these objects by the features of claim 1 or claim 3, respectively. Claim 2 describes a pre­ferred further development of the incinerator of claim 1.

[0015] A preferred embodiment of the incinerator of this invention will be described with reference to the accompanying dra­wings.

Figure 1 is a schematic view of a preferred embodiment of an incinerator of this invention.

Figures 2 and 3 are schematic views of mechanical incinera­tors according to the prior art.

[0016] As depicted in figure 1, there is provided a hopper chute 2 at one end of an incinerator 1, said hopper chute being apt for receiving substances to be incinerated, such as municipal and industrial wastes. This hopper chute 2 is formed in such manner that its opening is directed upward­ly and its lateral view is L-shaped. A stoker 3 is connec­ted to the hopper chute 2 in which the substances to be in­cinerated and introduced from the hopper chute 2 are rota­ted and pre-combusted. This stoker 3 corresponds to the main stoker of the mechanical incinerator as mentioned in the description of the prior art, and it contains water tubes which rotate along its inner side wall. To the down­stream end of this combustion stoker 3 there is connected a fluidized bed incinerator 4 where unburned matters which are already pre-burned in the stoker 3 and carried down­stream thereof undergo after-burning. In other words, the stoker 3 is connected to penetrate the side wall of the fluidized bed incinerator 4 which surrounds and defines the firing space formed in its upper section.

[0017] Said hopper chute 2 and the stoker 3 connected thereto are both inclined downwardly toward the fluidized bed incine­rator 4.

[0018] Numeral 6 designates air diffuser tubes for supplying air into the fluidized bed incinerator 4, numeral 7 a dischar­ging mechanism for carrying sand or the like out of the in­cinerator, and numeral 8 an exhaust port for discharging substances including ashes, incombustible materials and sand.

[0019] A method for incineration by use of the above-described incinerator will now be explained.

[0020] After being fed into the hopper chute 2 of the incinerator 1, substances to be incinerated such as municipal and industrial wastes are introduced into the stoker 3. Through rotation and agitation by means of the rotating water tubes inside the stoker 3, those substances are ignited at its entire surface and undergo a mechanical pre-combustion. Among the substances which were pre-combusted in the stoker 3, ashes are removed through gaps between the water tubes which are separated from each other. On the other hand, the unburned substances are agitated and introduced into the fluidized bed incinerator 4 because the stoker 3 is inclined downwardly. Since the inlet opening of the incinerator 4 is located at a high level, the manipulation of combustion is simplified and drawbacks of the conventional incinerator are eliminated. Unlike conven­tional incinerators this equipment does not require a crane for handling the substances to be incinerated. Furthermore, preparation or pretreatment such as breaking and crushing the substances is not necessary.

[0021] Moreover, since the materials which are still unburned in spite of pre-combustion are fluidized and after-burned in the fluidized bed incinerator 4, a complete combustion is obtained without care on operation and special control.

[0022] Therefore, in an incinerator in which the handling of the substances to be burned is easy and preparation and pre­treatment is not necessary, the volume of the discharged sub­stances is small.

[0023] Furthermore, because of the characteristics of the fluidized bed incinerator, the ash can be discharged in dried state from the incinerator.

[0024] The incinerator of this invention combines the advantages of both mechanical incinerators and fluidized bed incinera­tors.

Claims

1. An incinerator including:
a hopper chute (2) for receiving substances to be incinerated such as municipal and industrial refuses;
a stoker (3) for pre-burning said substances introduced through said hopper chute (2); and
a fluidized bed incinerator (4) for after-burning sub­stances which are still unburned after said pre-burning at said stoker (3), the downstream end of said stoker (3) being connected to said fluidized bed incinerator (4).

2. An incinerator of claim 1, wherein a rotative stoker (3) is provided.

3. A method for incineration, comprising the following steps:
supplying substances to be incinerated such as municipal and industrial refuses into a stoker (3);
pre-burning said substances in said stoker (3), so that a portion of said substances is burned therein; and
fluidizing and after-burning the remaining, unburned portions of said substances in a fluidized bed incinera­tor (4).

4. The method of claim 3, wherein said substances are agitated in said stoker (3).

5. The method of claim 3 or 4, wherein the preburned substances are introduced by gravity into an upper section of said fluidized bed incinerator (4).

6. The method of any one of claims 3 to 5, wherein incombus­tible materials are carried out of said fluidized bed in­cinerator in dried state by means of a discharging mecha­nism (7) provided at the lower end of said fluidized bed incinerator (4).

Drawing