CH648646A5 - PROCESS OVEN WITH A FLUID BED. - Google Patents

Description

The invention relates to a process furnace with a fluidized bed. This process furnace including the fluidized bed can be used to burn household waste, rubbish and the like, or to decompose it using heat.

Destroying rubbish becomes a serious problem

because this rubbish takes up large volumes and increases from year to year.

Burning the rubbish and waste is one of the many ways you can get rid of it.

In conventional incineration plants or waste incineration plants that have a fire grate, serious problems and difficulties occur, which are summarized below.

(1) The plastics present in household rubbish melt and move through the grate and are burned in an area around the grate or below the grate, the grate being exposed to flames at high temperatures and therefore it is possible that the grate is damaged at an early stage which results in high maintenance costs. This difficulty is very serious because the proportion of plastics in the rubbish is relatively high and is increasing more and more.

(2) Household rubbish contains different types of material, which are not uniformly mixed with each other and therefore the respective parts of the rubbish have different burning properties, which can generate localized areas of extremely high temperature during combustion and therefore cause damage to the wall of the combustion chamber can. Furthermore, such a high local temperature can easily generate NOx and thus cause an environmental pollution problem.

(3) When burning solids, it is generally the case that combustion takes place during combustion, which requires heat absorption and the speed of heat transfer is relatively low, such that a fire grate with a large surface area is generally necessary.

Because of its associated members or components, for example means for moving it, a fire grate is generally costly and if a large fire grate is used, a large combustion system or combustion chamber must therefore be present, and accordingly the expenditure required to build the waste incineration system becomes necessary are higher.

To solve the problems mentioned above, a fluidized bed incinerator has been used in which inert, i.e. chemically inert particulates can be used to create a fluidized bed. The chemically inert solid particles normally used for this purpose are usually grains of sand and therefore the term “grains of sand” and / or “sand” is used in the present text in the sense that it is not restricted to “sand” only, but also includes any particles or grains which are useful for forming the fluidized bed. The incinerator with a fluidized bed is advantageous in the following points.

a) The liquefied plastics and similar substances are heat-decomposed in the fluidized bed and burned therein, and therefore the possibility that a gas distribution plate or gas diffusion plate, which corresponds to the rust in the device referred to above, is damaged, because such a plate is not exposed to the flame of the burning plastics.

b) Because the temperature in the fluidized bed is always approximately the same, there are no difficulties due to the locally high temperatures inside the kiln.

c) The heat transfer mass between the grains of sand and the substances to be burned is extremely high, so

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that it is possible to use a base plate with a relatively small surface area in the combustion chamber, so that it is possible to use a combustion furnace of limited dimensions, so that the production costs of the plant are reduced.

Therefore, the conventional incinerator which has a fluidized bed for burning household garbage and the like can be used well. However, with such systems it is necessary or important that the substances that are to be burned do not migrate down to the bottom of the fluidized bed. The reason for this is that if the substances that are to be burned migrate to the bottom of the fluidized bed, the perforations in the perforated plate (diffusion plate) are blocked, so that the vertebrae, i.e. suspended in suspension above the closed section would be prevented and the grains of sand in these sections would cake to a mass, with the result that in-suspension is insufficient or even the formation of the fluidized bed is impossible.

Consequently, it is necessary to pulverize the substances that should be burned in a fluidized bed incinerator so that a certain largest grain size is formed, usually in the range of 50 mm to 70 mm. However, the garbage and corresponding household waste contains different types of substances, each of which offers a different resistance to grinding. For example, brittle, brittle materials, for example glass, earthenware, pottery, ceramic materials and concrete, can be ground or broken very easily,

whereas, on the other hand, tough materials, for example rubber and plastics, cannot simply be converted into a powder form if they are not exposed to a shearing action by using sharp cutting edges or the like. It is therefore desirable to grind household garbage, which is a mixture of different types of garbage, into grains whose dimensions are below a predetermined, preferred value, by using only a single device, the device which can be used for this purpose must be able to grind as well as shear. However, the cutting edges, which are necessary for shearing, are worn out very easily and quickly by the brittle or brittle materials such as glass, earthenware, pottery, ceramics, concrete etc. or materials such as metals that offer great resistance to the shearing action damaged. Accordingly, it is difficult to pulverize or grind household rubbish by means of a single device, so that it is suitable for burning in a conventional waste incinerator with a fluidized bed.

Therefore, due to the above-mentioned conditions, or in the above-mentioned conditions, the garbage is first ground in practice by using a device which is mainly designed for grinding. Then the ground or brittle materials are sorted out using a sieve, etc. and the iron-containing materials are magnetically removed. The remaining portion of the rubbish is then torn apart by means of a further device, which has sharp edges and, above all, is designed to exert a shearing and / or tearing effect. Accordingly, the process steps that have to be carried out before the actual combustion are more or less complex.

As has been explained above, the step of reducing or controlling the dimensions has so far been one of the most serious difficulties that have been considered which have to be solved if the waste is incinerated in a conventional waste incinerator a fluidized bed is to be performed.

It is therefore desirable to simplify or completely eliminate the time-consuming preparation or preparation that is necessary to burn the combustible parts of the refuse.

Accordingly, it is an object of the present invention to provide a process furnace which does not have the disadvantages mentioned above.

It is also an object of the present invention to provide a process furnace with a fluidized bed in which substances are prevented from reaching the bottom of the fluidized bed.

It is a further object of the present invention to provide a process furnace with a fluidized bed in which non-combustible residues are effectively conveyed outward from the furnace.

The process furnace according to the invention is characterized by the features of claim 1.

Thus, it can now be possible to burn materials with the process furnace with a fluidized bed, in particular household rubbish and the like, without it having to be necessary to use the difficult pretreatment stage to control the dimensions which were previously necessary in conventional process furnaces with a fluidized bed is.

The combustion process in the fluidized bed combustion chamber can include ashing, partially oxidizing, gasifying, roasting, calcining or splitting (catalyzing).

The process furnace advantageously has a feed opening, which leads to a means for producing a fluidized bed for conveying, which can be arranged directly above the bottom surface of the furnace, with a plurality of parallel hollow cylindrical rotors being provided, which form the means for forming the fluidized bed and for Conveying can form, and which can be arranged above the bottom surface, there being a distance between the respective rotors, these rotors being arranged in such a way that they go in the same direction in order to be able to release residues, each rotor having a plurality of Introducing gas-serving perforations, wherein air is advantageously introduced, with which a fluidized bed can be produced.

The reason of the distance, i.e. of the space is that it is prevented that substances can fall through the space between the respective rotors. The bottom plate of a process furnace is usually designed to be a diffusion plate, i.e. a gas introduction plate which has a plurality of introduction holes or perforations, which perforations are arranged in such a way that a gas or air flow is introduced with a vector component which points parallel to the base plate in a direction against the outlet opening, such that the residues pass through it can be released and which gas flows also help to support the formation of the fluidized bed.

In some embodiments of the present invention, a locking bar is arranged in each of the spaces between adjacent rotors, which effectively prevents substances from falling down through the gap or space between adjacent rotors. In such a case, the perforations in the base plate can be omitted.

The subject matter of the invention is explained in more detail below with reference to the drawings, for example.

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It shows

1 is a simplified representation of a cross section through a preferred embodiment of the present invention,

2 shows a part of the device shown in FIG. 1, drawn on an enlarged scale, the design of an embodiment of rotors being shown,

3 shows a representation similar to that of FIG. 3 of a further embodiment of the base plate in the combustion chamber,

4 shows a part of an alternatively designed combustion chamber, in which blocking strips are arranged between the rotors,

Fig. 5 shows another alternative of the arrangement shown in Fig. 4, and

Fig. 6 is a plan view of the part shown in Fig. 5, showing in simplified form the drive which is useful for the rotors shown in Fig. 5.

1 shows in simplified form and in cross section a preferred exemplary embodiment of a process furnace 10 designed according to the invention, which has a combustion chamber 11. The interior of the combustion chamber 11 is generally divided into an upper section and a lower section, the upper section being referred to as the free section 12 and the lower section hereinafter being referred to as the fluidized bed 13. The fluidized bed 13 is formed by chemically inert solid particles, or grains of sand, which are kept in suspension by gas introduced upwards or air introduced upwards. In order to introduce the gas or the air so that the grains of sand are kept in suspension, a plurality of hollow cylindrical rotors 14 are arranged parallel to one another above a base plate 15 of the chamber 11, which base plate 15 is advantageously inclined and to an outlet opening 16 leads. Each rotor 14 is spaced from the respective adjacent rotors, and is designed such that each rotor rotates in the same direction as indicated by the arrow, which is carried out by a suitable drive, each rotor having a plurality of through holes 17 ( Fig. 2), which are formed in its cylindrical wall, through which through holes 17 gas or air is introduced into the sand, which gas, or which air is supplied from a supply source through appropriately sealed connection arrangements to the rotating, hollow cylindrical rotors 14 . The introduction of the gas, or air, into the sand creates the fluidized bed 13, while the rotation of the rotors 14 causes the residues to move against the outlet opening 16, the rotors forming the means for producing the fluidized bed and for transporting them inside the process furnace 10 . A plurality of through holes 18 are also formed in the base plate 15, through which gas or air is introduced upwards, so that the suspension or whirling and the combustion are supported.

The group of rotors 14 ends next to the outlet opening 16, the cross-sectional area of the outlet opening 16 gradually being reduced downwards, and which is connected to an outlet pipe 19, to which outlet pipe 19 an injection pipe 20 is connected.

Gas or air is introduced through the blow-in pipe 20 into the outlet pipe 19 with a flow rate which is useful for keeping the sand grains in suspension in the outlet opening 16 and in the outlet pipe 19. Below the

A double gate valve 21 is arranged in the outlet pipe 19 to connect the pipe 19 to the pipe 20, so that two passages 21a and 21b can be opened or closed alternately, so that the unmistakable residues which pass through the outlet opening 16 and the outlet pipe 19 have been funded, can ultimately be led away. The sand present in the outlet pipe 19 can be conveyed out together with the residues through the double gate valve 21 and the sand, which is subsequently separated from the residues, can be brought back into the combustion chamber in the combustion chamber 11.

A feed device 22, which serves to feed the substances to be burned to the process furnace 10, has a hopper 23, a gate valve 24 and a tappet device 25, the feed device 22 being connected to the free section 12 of the combustion chamber 11 . In addition, a ventilation opening 26 is arranged at the uppermost point of the combustion chamber 11, which serves to discharge the fuel gases to the outside through a dust collector 27, by means of which dust collectors 27 ashes that are present in the exhaust gas are captured.

In the process furnace 10 described as above, household garbage can now be fed through the feeder 22 into the process furnace 10 in a state as it has been collected without any pretreatment, or with only opening or tearing the rubbish bags. That part of the rubbish, which consists of relatively light substances and small dimensions, hovers within the fluidized bed 13 and is burned, and that part of the rubbish, which consists of relatively heavy substances, drops to the bottom of the fluidized bed 13. The combustible materials, which sink to the bottom, are also exposed to the swirling action of the sand which is moved at a relatively high speed and are thus effectively burned, so that the possibility that the through holes 17 are closed by caked, melted or melted plastics or the like are largely impossible, in contrast to the case in which a grate is used for burning, the surface dimension of the base plate being relatively small compared to that which is necessary in process furnaces with grate. The heavy substances which sink to the bottom of the fluidized bed 13 are subsequently conveyed against the outlet opening 16 due to the rotating cylindrical rotors 14 and during this slow movement of the substances their combustible parts are completely burned by the action of the fluidized bed 13 and they become exclusive the non-combustible residues are discharged to the outside through the outlet opening 16, the outlet pipe 19 and the double gate valve 21.

The flow of the gas or air, which is directed through the through holes 17 of the rotors 14 during their downward rotation, impinges on the base plate and has the effect that the sand which is in the slider is held or swirled again has fallen down between the rotors and conveys this sand upward when the gas or air is blown up through the space that prevails between the rotors 14. This gas or air flow also effectively prevents the sand of the fluidized bed 13 from falling down and accumulating on the base plate 15.

It can be seen from FIG. 2 that the base plate 15 has a plurality of through holes 18, as was the case above

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has been explained, through which through holes 18 gas or air is introduced from a shaft 28 upwards in order to support the swirling or in the suspension and conveys the sand that has fallen under the rotors 14 upwards and into it Bed 13.

Each axis, i.e. Longitudinal axis, the through holes 18 is arranged inclined such that the air introduced through the through holes 18 has a vector component which is directed parallel to the bottom plate against the outlet opening 16, so that the transfer of the sand and the non-combustible residues on the bottom plate in the direction against the Outlet opening 16 is supported and ensured.

The distance “a” between the respective adjacent rotors 14 and the distance “b” between the rotors 14 and the base plate 15 are preferably chosen such that “b” is greater than “a”, so that the possibility that the space “ b »is blocked, reduced or completely avoided by substances which have passed through room« a ».

3 shows part of a further exemplary embodiment of the present invention. In this exemplary embodiment, the base plate 15a is made from a plurality of flat strips 29 which partially overlap one another such that passages 18a are formed between adjacent strips 29, which passages 18a produce the same effect as is the case with the passages 18 which are shown in Fig. 2.

Although the bottom plates 15 or 15a shown in FIGS. 1, 2 and 3 are drawn as inclined, they can also be arranged horizontally, provided that the movement of the non-combustible residues and the sand causes against the outlet opening becomes.

The process furnaces shown in Figs. 1, 2 and 3 work satisfactorily; however, some other designs or modifications may be preferred to improve the properties of the process ovens for the following reasons.

i) Incombustible residues, which may or may not have been caked into a mass, and which residues are moved over the rotors, can be caught in the gaps that are present between the respective rotors, so that difficulties arise, for example large load changes, which act on the drive means, which serve to rotate the rotors, or that the drive means are overloaded. In such conditions, an additional process step to pulverize, i.e., grind the garbage can solve such difficulties, but such an additional process step is obviously not preferable in light of the objectives of the present invention.

ii) The introduced gas or the introduced air can cause sand to hit the cylindrical surface of the rotating rotors and this can result in erosion of the rotor and / or a further refinement of the sand, so that an increase in the The sand is consumed and more dust is generated which exits the process furnace, so that operating costs are increased and an environmental pollution problem arises.

iii) If the supply of the gas or air which serves to keep the sand in suspension and to maintain the fluidized bed is prevented, sand can enter and accumulate in the hollow cylindrical rotor or the through holes which are formed in the rotors, so that differences in the gas flow or the air flow that is introduced are generated. Accordingly, the creation of a satisfactory floating or a satisfactory fluidized bed is hindered, so that the operability of the process furnace is reduced and that it is possible that clinker, i.e. Slag is generated.

These disadvantages and difficulties are eliminated in the further exemplary embodiments of the present invention.

FIG. 4 shows a side view of a section of a further exemplary embodiment of the process furnace, which is designed in accordance with the present invention. In this exemplary embodiment, a locking bar 30 is arranged parallel to the axes of the rotors 14 and above each of the spaces or spaces (a) between adjacent rotors 14. The bar 30 is designed such that it has a cross-sectional shape which corresponds to the shape of the upper one Section of the intermediate space corresponds, for example, approximately to the same as a trapezoid standing on the apex and runs parallel to the rotor axes and extends along the rotor 14 and has approximately the same length. The locking bar 30 can only be arranged in the gap between adjacent rotors or can be connected at its two opposite ends to the wall of the chamber 11. Alternatively, the locking bar 30 can be carried by bolts (not shown) which are connected to the base plate 15. These blocking strips 30 effectively prevent non-combustible residues (which can be baked into a mass) from entering the gaps between the rotors 14. The gas or air that is used to form the fluidized bed, and since it is introduced into the space below the locking bars 30 around the rotors 14, flows upward through the gaps between the rotors 14 and the locking bars 30. Because the gaps or spaces between these barrier strips 30 have become narrower or are even completely closed, in the case when the barrier strips 30 are not supported on the walls and are merely placed on the rotors, the flow rate of the gas or air can be reduced which flows through these columns become too large.

By arranging an appropriate number of perforations 30a which run approximately perpendicularly through the strips 30, this difficult condition can be eliminated by the flow which flows upwards through these gaps. Also, the through holes 18 or 18a in the bottom plate 15 or 15a (Figs. 2 and 3) can be omitted if the through holes 30a are present because the presence of the through holes 18 or 18a in the bottom plate 15 or 15a is not absolutely necessary.

The blocking strips 30 described above effectively prevent incombustible residues (which may or may not have caked to a mass) from being caught or pinched in the gaps between the rotors 14.

5 shows a further modified embodiment of the rotors 14a. This rotor 14a also has a plurality of through holes 17a, which are formed in the cylindrical jacket of the rotor, so that the gas or air can be blown outward from the interior of the rotor, so that the fluidized bed is formed. However, the passage holes 17a are now arranged on the cylindrical outer surface of each rotor 14a in such a way that they are limited to a predetermined area, which area is limited between two lines running parallel to the axis on this outer surface. In other words, these two lines running in the axial direction delimit a rectangular area in the viewing direction transverse to the two in the axial direction

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Seen in the direction of the running lines. The two lines enclose an angle “a” relative to the central axis of the rotor 14a according to the view shown in FIG. 5. Furthermore, a drive device (DM) which serves to rotate the rotors 14a and which has already been mentioned is shown in simplified form in FIG. 6. If the rotors 14a according to FIG. 5 are used, it is preferable to have the limited areas, in which the through holes 17a are arranged, in the same angular position in each case, from the explanations given below. As shown in simplified form in FIG. 6, in this case the drive device (DM) is coupled to all rotors 14a in such a way that the respective rotors have the same speed and the through-holes have the same angular position at all times. Such a drive device usually has an endless chain which extends over chain number edges which are connected to the respective shafts 14b of the rotors 14a, although other designs of drive device are applicable, and therefore the drive device according to the present invention is not such Combination consisting of endless chain and sprockets limited. The drive device can also be used in other process ovens, such as those shown in FIGS. 1 to 4.

With the arrangement in which the through holes 17a are arranged in the limited areas of the respective cylinder walls of the hollow rotors 14a and the angular position of each of these limited areas is controlled, it is possible to eliminate or reduce the disadvantages which are produced as a result. that sand enters the hollow rotors, that sand appears on the rotors, that the sand is refined more, etc. For example, if the rotors are driven gradually, the possibility that the surfaces of the rotors are eroded is reduced. In this case, the limited areas of the respective rotors are arranged in such a way that they point upwards during the period during which the rotors are temporarily deactivated, so that the gas or air that is introduced continues without interruption is introduced and the direction of flow is such that the fluidized bed is maintained. Such a gradual stopping of the rotors also reduces the possibility that the sand, which is brought into suspension by the introduced gas or the introduced air from one rotor, impinges on the adjacent rotor, so that eroding and / or or wear of the rotor surfaces and finer grinding of the sand is prevented, so that the operating costs are reduced.

On the other hand, when the process furnace is not in operation, i.e. no gas or air is introduced, the limited areas are arranged so that they face downwards, so that the sand cannot enter the hollow rotors.

Although a locking bar 30 is shown in FIG. 5,

it can be omitted, as is the case with the exemplary embodiments drawn in FIGS. 1 to 3.

The angle “a” in FIG. 4 is preferably 120 °,

however, such an angle should be chosen appropriately, depending on the factors that occur, for example the substances to be burned, the type of destruction (ashing, burning, partial oxidation, gasification, burning, roasting (calcining), splitting (catalysis) ,) from the gaps between the rotors and also from the sand grains used.

With a process furnace which is designed in accordance with the present invention and is manufactured in accordance with the above-mentioned embodiments, pretreatment of the waste is largely no longer necessary in the event that household waste or the like is to be eliminated by incineration.

However, grinding and sorting of the rubbish can be carried out before burning in order to recover reusable parts of the rubbish. Such pretreatment is advantageously carried out by means of suitable pulverizing or grinding devices, as described in US Pat. No. 3,941,089; 3,973,735 and 4,076,177. During such a pretreatment in such a pulverizing device as indicated above, paper is sorted out from waste containers or paper and food waste etc. present in rubbish, the remaining portion then usually containing plastics, metals, fabrics, textiles, the proportion by volume of thin plastic films being proportional is high. Also, metals are usually separated in operation carried out by the pulverizer referred to above. Gemäss According to tests that have been carried out, it has been recognized that the light substances do not necessarily have to be ground, because substances, such as thin plastic films, paper and fabric, float within the fluidized bed and are simply burned without sinking to the bottom of the fluidized bed . Further, the burning rate with respect to the above-mentioned light substances mainly depends on the thickness of the light substances to be burned, and thus grinding these above-mentioned light substances does not necessarily have to increase the burning speed of these substances. If it is desired to burn the waste or food and the paper after grinding using the above-mentioned grinding device, they are also burned very easily in the process furnace according to the present invention because their dimensions have already been reduced. Therefore, the effectiveness of the process furnace is improved after such a pretreatment because the ratio of the heavy substances that sink to the bottom of the fluidized bed is relatively or noticeably reduced.

While the present invention has been explained in detail above and various embodiments have been described, the present invention is not limited to these embodiments, and changes and modifications of the present invention will be readily apparent to those skilled in the art. Changes in the spirit and scope of the present invention are possible within the preceding claims.

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Claims (10)

648 646 PATENT CLAIMS 1. Process furnace with a fluidized bed, characterized by a fluidized bed combustion chamber (11), including a base plate (15, 15a) with an outlet opening (16); by means of a plurality of hollow cylindrical rotors (14, 14a) which are arranged above the base plate and run parallel to it, with a distance between the rotors in each case, each rotor has a plurality of perforations (17, 17a) serving for introducing gas, which in its cylindrical wall are arranged and the interior of each rotor is connected to a gas source, and wherein all rotors are arranged such that they are rotatable in the same direction; and by a feed device (22) which serves to introduce substances into the fluidized bed combustion chamber. 2. Process furnace according to claim 1, characterized in that the base plate has a plurality of perforations (18, 18a) intended for introducing gas. 3. Process furnace according to claim 2, characterized in that the perforations present in the base plate are arranged such that the flow of the gas introduced therewith has a vector component directed parallel to the base plate (15, 15a) against the outlet opening. 4. Process furnace according to one of claims 1 to 3, characterized in that the base plate is inclined downwards towards the outlet opening. 5. Process furnace according to one of claims 1 to 4, characterized in that the distance (b) between the base plate and the rotors is greater than the distance (a) between the rotors. 6. Process furnace according to one of claims 1 to 5, characterized by a locking bar (30) which is arranged in each case in the upper space delimiting by the rotor distance and the rotors. 7. Process furnace according to claim 6, characterized in that the perforations are arranged in the cylindrical wall of each rotor at a point which corresponds to a region which is delimited by two lines running in the axial direction on the cylindrical outer jacket, all the rotors are arranged in such a way that the respective regions have the same angular position both during the rotation and also when the rotors are at a standstill. 8. Process furnace according to claim 7, characterized in that the rotors can be rotated step by step, the limited regions pointing upwards during the period during which the rotors are temporarily at a standstill. 9. Process furnace according to claim 7, characterized in that the limited areas are arranged such that if no penetration of gas through the perforations is caused, they point downwards. 10. Process furnace according to one of claims 6 to 9, characterized in that a useful number of perforations is formed in the locking strips, which perforations run approximately perpendicularly through the strips.