Incinerating furnace

Abstract: This invention is an incinerating furnace utilizing mineral particles as a hearth bed. Hearth particles are supplied and automatically flow down by the gravity into the combustion chamber and onto the movable plane member (2), a rotary table for example disposed at the bottom of the furnace. A mixture of used hearth particles and the combustion remainder (b) is removed from the outlet (1) of the furnace as the movable plane member (2) moves and is introduced into a receiving tank (5). A supplement hearth particles (a) are supplied from the hopper into the combustion chamber forming an oblique hearth bed where the incineration takes place.

Description: The present invention relates to an improvement of an incinerating furnace utilizing mineral particles as a hearth bed, particularly to an improvement of taking out used hearth particles and a combustion remainder from the incinerating furnace. PRIOR ART It is known to use an incinerating furnace having a hearth bed consisting of mineral particles for incinerating plastic wastes which have a high calorific value and emit corrosive gases. There are two types of the incinerating furnaces having a hearth consisting of mineral particles, one is a fixed hearth and the other is a movable hearth. Among the movable hearths, the used hearth particles are taken out by a belt conveyer, by a rotating cylinder or by a rotating gear. Incinerating furnaces of this kind are disclosed in the Japanese Patent specification Sho 51-3139 (Kokoku 76-3139), Sho 52-21832 (Kokoku 77-21832), Sho 56-685(Kokoku 81-685) of which the hearths consisting of mineral particles are taken out by the belt conveyer disposed in the combustion chamber, Japanese laid open Sho 58-10831 (Kokai 83-108318) of which the hearth consisting of mineral particles is taken out by a rotary drum and Japanese laid open Sho 63-217127 (Kokai 88-217127) of which the hearth consisting of mineral particles is taken out by a rotary gear. Recently the need to incinerate used plastic equipments, such as plastic disposable injectors packed in a large plastic bag in an incinerating furnace of this kind is growing. After the incineration of materials to be incinerated, for example, plastic wastes, it often happens to remain a combustion remainder of large dimension in combustion chambers of the incinerating furnace but it is very difficult to take them out from the incinerating furnace because the size of the outlet of the combustion remainder is a fixed one and is not large enough for taking them out. GENERAL DESCRIPTION OF THE INVENTION This invention intends to solve the above mentioned problems and even materials to be incinerated emit corrosive gases, such as HCl, SOx, NOx, or bad smelling gases, the incinerating furnace according to this invention will prevent the emission of those harmfull gases to the surrounding environment. This invention also provides a complete combustion in the incinerating furnace, keeps the furnace hearth particle bed in a good condition, and prevents the wall and bed of the incinerating furnace from being damaged by the flame. It is easy according to this invention, to take out comparatively large sized combustion remainder from the incinerating furnace. BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 is a side view of the slag outlet of this invention. Fig.2 is a plane view of this invention. Fig.3 is another embodiment of this invention. Fig.4 and Fig.5 are schematic diagram indicating different types of the outlet structure. Fig.6 and Fig.7 are schematic diagram indicating the position of the outlet and the structure. Fig.8 is an embodiment of this invention indicating the sectional view of the incinerating furnace. Fig.9 is a plane view of the incinerating furnace shown in Fig.8 indicating the bottom of the outlet. Fig.10 is a front view of the incinerating furnace shown in Fig.8. Fig.11 is a back view of the incinerating furnace. Fig.12 is another embodiment of the invention. Fig.13 and Fig.14 are a side view and a front view of the outlet of the combustion remainder. DETAILED DESCRIPTION OF THE INVENTION Mineral particles applicable to the incinerating furnaces of this invention are natural stones, such as crushed stones, gravels and coarse sand, which must be durable to the high temperature and form sufficient gaps therebetween for supplying air to the combustion chamber when filled in the combustion chamber as to form a hearth bed, and the mean diameter of the hearth particles is from 5 mm to 3 cm. It is desirable to select crushed stones as hearth particles because the angle of rest of the crushed stones is quite large. Now the construction of the outlet of the incinerating furnace of this invention will be explained according to the attached drawings from Fig.1 to Fig.7 , Fig.13 and Fig.14. In Fig.1 and Fig.2, a mixture of a combustion remainder (b) of the materials to be incinerated and used hearth particles (a) (referred to as the mixed remainder hereinafter) slides or rolls down from the outlet 1 of the incinerating furnace and accumulates on the movable plane member 2 forming a slope of the particles. The movable plane member 2 is driven by the driving unit 3 mounted on the support 6. As the movable plane member 2 moves, the slope of the mixed remainder is taken out to the collecting guide 4 which extends laterally from the arm 7. Then the mixed remainder are introduced into the receiving tank 5 by the guide. The collecting guide 4 may also be secured to the incinerating furnace wall near the outlet 1 or to other parts if desired. The used hearth particles among the mixed remainder introduced in the receiving tank 5 are recovered by separating through a sieve, washing, and/or refining and then returned to the supply hopper 13 of the hearth particles for recycling. The outlet 1 is disposed preferably just above and within the area of the movable plane member 2 at a certain distance from the outlet, and the edge of the outlet 1 may be perpendicular to the movable plane member 2 or oblique thereto as illustrated in Fig.4. The cross section of the outlet 1 may be circular, square or any other appropriate section and a part of the section can be cut off as illustrated in Fig.5. The outlet 1 is not necessarily disposed just above the center of the movable plane member 2 but within the area of the movable plane member 2. The support 6 may be disposed on a lift 8 as illustrated in Fig.3, and the distance between the movable plane member 2 and the edge of the outlet 1 may be changeable by operating the lift 8. Fig.4 indicates an example in which the edge of the outlet 1 is oblique to the movable plane member 2. Fig.5 indicates an example in which the edge of circular outlet is partially cut off indicated as 10. Fig.6 indicates an example in which the auxiliary circular member is slidably mounted at the edge of the outlet which provides an adjustment of the distance between the outlet 1 and the movable plane member 2. Fig.7 indicates an example in which a shutter means is mounted at the cut off of the outlet letting the large sized combustion remainder going down by opening the shutter. The examples of the continuous slope of the mixed remainder formed at the part of the accumulation of the mixed remainder which flows down from the outlet after the incineration are shown in Fig.4, Fig.5, Fig.7, Fig.8, Fig.12 and Fig.13 and the examples of the continuous slope formed at the whole accumulation are shown in Fig.1, Fig.3 and Fig.6. Now in Fig.8 to Fig.11, an example of this invention applied to an incinerating furnace utilizing hearth particles which form an oblique hearth bed surface of which the angle of the bed is an angle of rest of the mineral particles therein. A cross section of the incinerating furnace is illustrated in Fig.8. Angles of the hearth inlet wall, of the incinerating furnace wall and of the walls of the incinerating furnace bottom, each of them contacts with hearth particles and is covered by the particles, are larger than the angle of rest of the hearth particles. Preferably the bottom opening of the inlet of the materials to be incinerated in the incinerating furnace is disposed upon the surface of the hearth bed 25 of the incinerating furnace. More preferably at least a single aperture is disposed at the wall of the incinerating furnace for auxiliary air supply into the incinerating furnace chamber for assisting the incineration in the combustion chamber 21. A combustion chamber 21 constructed with a hearth consisting of mineral particles and an upper wall, has a main air intake 22, a burner 23 and a combustion gas outlet 24. Further the incinerating furnace provides a laterally movable plane member 2 at its bottom which takes out continuously or periodically the used hearth particles together with combustion remainder of the burnt materials. The mixed remainder form a slope on the movable plane member of which an angle of rest is almost the same as the angle of rest of the hearth particles in the combustion chamber. The distance between the outlet 1 and the movable plane member 2 can be adjustable as described above by operation of the lift 8. As illustrated in Fig.8, an inlet of the hearth particles (A) consists of a hopper 13 and a passage 14, and an inlet of the materials to be incinerated consists of a hopper 15 and a passage 16. The incinerating furnace wall (B) extending from the inlet (A) consists of a front upper wall 17, a front lower wall 18, and a rear wall 19. The front upper wall 17 forms a combustion chamber 21 together with particle hearth bed 20. The combustion chamber 21 has an air intake 22, a burner 23, and a combustion gas outlet 24. The combustion chamber 21 is generally constructed with heat resistant bricks or heat resistant castables. The incinerating furnace wall (B) has one or more air inlet apertures 26 at the level of hearth bed slope surface 25 of the hearth 20 which assists the combustion of the materials to be incinerated in the combustion chamber 21. At the bottom of the incinerating furnace wall(B), there is the bottom part (C) which consists of a wall 27 which extends from the lower edge of the front lower wall 18 and of the rear wall 19 thereby forming a mixed remainder outlet 1. A movable plane member 2 is disposed under the outlet 1 which receives the mixed remainder flowing down from the combustion remainder outlet 1. The movable plane member contacts with the collecting guides 4, 4′ mounted on the wall 27 and moves laterally. The movable plane member is driven by the transmission mechanism 3 and mounted on the support 6. The support is mounted on the lift 8 and the distance between the movable plane member 2 and the outlet 1 is adjusted by operating the lift 8. The guides 4, 4′ can be mounted on the arm extending from the support 6. The outlet 1 has a cut off 10 as shown in Fig.9 letting the mixed remainder sliding down or rolling down onto the movable plane member 2 and the mixed remainder are moved to the receiving tank 5 as the movable plane member 2 moves and the guides 4, 4′ introduce the mixture mixed remainder into the tank 5. Fig.10 is front view of the outlet 1 and Fig.11 is a back view of the outlet 1 illustrated in Fig.8. Fig.12 is illustrating another example of this invention applied to an incinerating furnace constructed at a corner of a solid structure. In this type of the incinerating furnace, the hearth particle inlet 14, the inlet of the materials to be incinerated 16 and the combustion chamber could be much more compact than the conventional incinerating furnace and in addition, a downward oblique hearth bed is automatically formed by supplying hearth particles and crushed materials to be incinerated into the combustion chamber. 1 is an outlet of the mixture of the used hearth particles and the combustion remainders, 2 indicates a movable plane member disposed at the bottom of the furnace for taking out the used hearth particles and the combustion remainders from the incinerating furnace, and a guide 4 guides the mixture of used hearth particles and the combustion remainder to a receiving tank 5. The distance between the mixed remainder outlet and the movable plane member is adjustable as described in the above mentioned examples. Fig.13 and Fig.14 illustrate another embodiment of the outlet of the mixed remainder. Fig.13 is a side view of the outlet of the mixed remainder and Fig.14 is a front view of the mixed remainder. In fig.13 and Fig.14, the mixed remainder flows down or rolls down from the outlet 1 accumulating on a belt conveyer forms a continuous slope 9 at a part of or whole of the accumulation. The slope 9 extends between the outlet 1 and a surface of the belt conveyer 28 and the slope angle is the angle of rest ϑ₁ of the mixed remainder. It is possible to incinerate not only wastes from daily life, such as plastic wastes but also coal, and brown coal or lignite in the incinerating furnace according to this invention. After the incineration of the materials to be incinerated, the mixture of used hearth particles and the mixed remainder of the burnt materials slides down onto the movable plane member 2 and forms a slope 9 and the angle of the slope 9 is an angle of rest ϑ₁ of the mixed remainder. While the movable plane member 2 stops moving, the slope of the mixture remains still and the slope angle is the angle of rest ϑ₁ thereby the mixture of the hearth particles and the combustion remainders from the furnace does not flows down any further. When the movable plane member 2 starts moving continuously or periodically, the slope of the mixed remainder moves along the movable plane member 2 and reaches the guide 4 and falls down into the receiving tank 5 thereby the remaining mixed remainder in the furnace falls down onto the movable plane member 2 forming the slope. Therefore the slope angle remains the same as the angle of rest ϑ₁. In general, preferable angle value of the angle of rest is from 10 to 80 degree, more preferably from 30 to 80 degree, further more preferably from 40 to 70 degree. The dimension of the movable plane member is so determined depending on the angle of rest of the mixed remainder and the location of the outlet of the mixed remainder that the bottom edge of the slope would not go out of the movable plane member 2. As illustrated in Fig.13 and Fig.14, the mixed remainder flowing down from the outlet 1 and forming the slope 9 is transferred by the belt conveyer 28 which is an example of the movable plane member 2, to the other end 29 of the belt conveyer 28 and falls down into the receiving tank 5. The belt conveyer 28 is driven by a driving unit 3 and may be secured on a lift 8 disposed on a support 6 so as to change the distance between the remainder outlet 1 and the surface of the belt conveyer. We have disclosed herewith a rotary table and belt conveyer as the examples of the movable plane member, in the embodiment, the other examples of the movable plane member are a caterpillar like conveyer or other types of conveyer are applicable to this invention. The distance between the movable plane member 2 and the mixed remainder outlet could be bigger when the angle of rest of the mixed remainder is big. The hearth particles are supplied from the hopper 13 and fall down or roll down by the gravity through the inlet 14 and furnace wall (B), and accumulate at the bottom of the furnace (C). The bottom of the furnace is first filled with hearth particles then the furnace wall part (B) is filled, finally the rear wall part is also filled with hearth particles up to the inlet 14 therefore the surface of rear wall 19 is covered with hearth particles, thereby forming the oblique hearth 20. The inclined slope of the hearth particles, which is the surface of the particle hearth bed 25, is formed between the lower part of the inlet 14 and the front furnace wall 18 which forms an opening towards the combustion chamber 21, and the angle of the slope depending on the material of the particles, is the angle of rest of the particles ϑ₈. One of the features of this invention is the surface of the hearth is oblique as to the level, the angle value is preferably from 10 to 80 degree, more preferably from 30 to 80 degree, further more preferably from 40 to 70 degree. For instance, the angle of rest of the dried sand is 40 degree and that of the crushed stones having cleavage planes is bigger than 80 degree so it is possible to form a steep slope surface of the hearth. This improved furnace is so constructed that the incineration is conducted not only in the direction of oblique direction but also almost in the level direction. In case the interaction of the main air intake 22 and the auxiliary air inlet apertures 26 is expected, the flame of the combustion in the combustion chamber may goes up along the hearth bed 25 of the furnace. As the angles of all part of the passages of the hearth particles, for instance the angle of lower front wall 18 ϑ₂, of the rear wall 19 ϑ₃, of the front edge of the wall 27 ϑ₄, of the rear edge of the wall 27 ϑ₅, of the hearth particles hopper 13 ϑ₆, and the angle of the materials to be incinerated hopper 15 ϑ₇, are constructed larger than the angle of rest ϑ₈ ( the slope angle of the hearth bed 25), so that the hearth particles can slide down or roll down the slope of those passage parts and no clogging of the particles will occur. Materials to be incinerated are put into the furnace through the hopper 15 and the inlet of the materials to be incinerated 16 and fall down onto the hearth bed 25. The lower end of the inlet 16 is preferably disposed just above the hearth bed 25, the materials to be incinerated slide or roll down on the hearth bed 25 and will never go down outside the hearth bed 25. Therefore the materials to be incinerated are always incinerated completely and it is an advantage of this invention that the walls of the furnace never contacts with the incinerating materials which are in the state of high temperature because the walls are covered with hearth particles. Especially in case the air is introduced through the auxiliary air inlet apertures 26, combustion in the combustion chamber becomes strong, any not burnt remainings would never be observed in the furnace chamber. The auxiliary air inlet aperture 26 consists of pipes having holes thereto, and installation of these apertures to the furnace wall is very easy because there is no mechanical relation between the apertures and the surrounding parts of the furnace. A burner 23 is utilized as an auxiliary combustion in the chamber 21 spraying aero sol of combustible liquid and the combustion is conducted on the furnace bed 25. As the combustion in the combustion chamber starts, the movable plane member 2 starts moving continuously or periodically removing the hearth particles accumulated on the movable plane member 2 and the guide 4 introduces the mixed remainder down into the receiving tank 5. As the used hearth particles are taken out from the outlet 1 of the furnace, materials incinerated on the furnace bed 25 are dragged into the hearth particles and are mixed with said hearth particles forming a mixture and fall down, then the supplemental hearth particles come down from the hopper 13 forming the slope of the furnace bed 25 of which the angle remains the same as ϑ₁. The mixture of used hearth particles (a) and the combustion remainders (b) falls down the furnace wall part (B) and the bottom part (C) falling down from the outlet 1 and forms a slope 9 on the movable plane member 2, and the slope angle is ϑ₁. As the movable plane member 2 moves continuously or periodically the mixture is carried to the opposite side of the movable plane member where the guide 4 is disposed and the mixture is introduced down into the receiving tank 5 by the guide 4. It is one of the options to grade the mixtures through the sieve and to recyle the recovered hearth particles by refining. The angle of the slope ϑ₁ is constant depending on the material and the size of the particles, and is almost the same as the angle of the hearth bed slope angle ϑ₈. The bigger the angle of ϑ₁ is, the bigger the distance between the outlet 1 and the movable plane member 2 could take because the bottom area 9 of the mixed remainder will be smaller if the angle of rest is big. In case the edge of the outlet 1 has a cut off, the width of the cut off is preferably as big as possible within the diameter of the outlet. In case the forced draft system is equipped in the furnace exhaust system, the air is introduced through the hopper, when the hoppers 13, 15 are open, into the combustion chamber 21 which helps combustion in the chamber and the extra air will prevent the generation of bad smellings. When flue gas contains harmful components, such as HCl, SOx, and NOx, it would be recommended to attach gas removal system to the incinerating furnace, such as a wash tower to remove those harmful components. PREFERRED EMBODIMENT Using the furnace illustrated in Fig.8, in which the hearth particles are crushed stones of serpentinite produced in Chichibu area of Saitama Pref. Japan having mean diameter of 10 mm, the area of the furnace bed is 0.1m² ( 0.2m×0.5m ), and used disposable plastic injectors are crushed and incinerated in the furnace. The angles of the walls of the furnace are ϑ₂=75°, ϑ₃=90°, ϑ₄=90°, ϑ₅=80°, ϑ₆=80°, ϑ₇=80°. The area of the outlet of the mixed remainder 1 is 0.05m² and the distance between the outlet 1 and the rotary table 2 is 30cm. The fresh air mixed with combustion exhaust gas having a temperature about 300 °C is introduced from the auxiliary air inlet 26 at a rate 5 Nm³/min, supplying the crushed plastics to be incinerated at a rate 5kg/hr, the materials are all incinerated completely. The mixture of the used hearth particles and the inorganic combustion remainder contained in the materials to be incinerated is taken out at a rate of about 0.1kg/hr from the outlet 1. The angle of the furnace bed slope ϑ₈ is in the range of from 50° to 60° during the incineration. The angle of the pile slope ϑ₁ indicates the same angle of the furnace bed slope ϑ₈. The biggest combustion remainder of 10cm length is easily taken out from the outlet 1 and introduced into the receiving tank 5. 24 hour continuous operation is conducted using this furnace, no damages in the walls and the bottom are observed during the operation. The hearth particles of crushed stones of serpentinite having magnesium silicate as a main component show stable characteristic against the high temperature exposure at 1000°C and no change is observed in the used ones. ADVANTAGE OF THE INVENTION A mixed remainder is taken out through the outlet and the movable plane member which makes it possible to take out easily comparatively large sized combustion remainders and to prevent free downward flow of mixed remainder from the outlet. The furnace bed of this invention is renewed by the down flow of the hearth particles by the gravity, no special apparatus such as, a belt conveyer is necessary to transfer the hearth particles in the combustion chamber so the structure of the furnace can be simple and is easy to manufacture. The furnace bed of this invention is oblique as described before, the size of the furnace could be comparatively compact though the capacity of the material to be incinerated is large. Consequently the area of the furnace can be smaller when the angle of the hearth bed is large, that is the angle of rest of the particles is big. Though the materials to be incinerated have bad smelling components or emit harmful gases, such as HCl, SOx, or NOx, the incineration in this furnace is perfect as the air supply of this furnace is complete and in addition harmful gas removing apparatus can easily be attached thereto, emission of the harmful gases is prevented. Even materials to be incinerated containing plastics having high calorific value can be incinerated in this furnace without giving any damages caused by the flame to the walls and the bottom of the furnace.

Claims: An incinerating furnace containing hearth particles which must be durable to high temperature and form sufficient gaps therebetween for supplying air to the combustion chamber as to form a hearth bed as a fixed hearth bed or a movable hearth bed, comprising: a hopper (13) from which hearth particles can be supplied; a passage (14) extending from said hopper (13) to a combustion chamber (21) in which a hearth particle bed can be provided of which the surface is obliquely orientated, wherein the slope angle of said oblique hearth particle bed corresponds to the angle of rest (ϑ₈) of said hearth particles: a material hopper (15) for supplying materials to be incinerated into said combustion chamber (21), which is generally constructed with heat-resistant material and a passage (16) extending from the material hopper (15) and ending above the oblique surface of the hearth bed (25); an outlet (1) disposed at the bottom of the furnace and spaced a certain distance from said outlet for permitting a mixture of used hearth particles and combustion remainder to flow down or roll down, and a laterally movable plane member (2) for removing said mixed remainder disposed under said outlet (1) wherein said outlet and said laterally movable plane member (2) are arranged such that the whole of said mixture is able to form a continuous slope extending between said outlet (1) and the surface of the laterally movable plane member (2), said continuous slope being the angle of rest (ϑ₈) of said mixture; further comprising beans (3) for driving said movable plane member (2) continuously or discontinuously. An incinerating furnace according to claim 1 wherein the movable plane member is selected from a rotary table, a belt conveyor and a caterpillar conveyor. An incinerating furnace according to claim 1, further comprising a lift (8) for adjusting the distance between the outlet (1) and the movable plane member (2).

Inventors: SAITOH SHIGERU, SAITOH, SHIGERU
Applicants: SAITOH SHIGERU, SAITOH, SHIGERU
Application year: 1990
Main classification: F23G5
IPC codes: F23J1, F23G5