FI128199B - Arrangement in a rotary kiln and method for guiding air to a rotary kiln - Google Patents

Abstract

The present invention relates to an arrangement in a rotary kiln (20) as well as to a method of supplying air to such a rotary kiln. The rotary furnace comprises a circular cylindrical structure having a combustion chamber (22) surrounded by a sheath (23), which sheath is provided with nozzles (34) which convey combustion air to the combustion chamber. Said combustion space is arranged to be substantially conical expanding from a first end (28) of the rotary furnace (20) to its second end (31). Hereby, each of the nozzles (34) is connected to trachea (26), which are arranged in the conically expanding sheath and are arranged to be parallel to both the longitudinal axis of the rotary kiln and the surface (27) of its sheath. Thus, combustion air can be supplied in air openings (33) exhibited by the first end face and connected to the trachea, to be transported to the combustion space via the nozzles (34).

Description

The present invention relates to an arrangement in a drum furnace according to the preamble of claim 1 and a method for introducing air into the drum furnace according to the preamble of claim 13.

Combustion plants are used for the production of heat and other energy. Solid fuel combustion plants and power plants, in particular biofuels, are playing an increasingly important role in meeting the ever-increasing demand for energy in an economically and environmentally sustainable way.

From the economic and ecological point of view, it is advantageous to maintain reasonable availability of fuel for the equipment and transport distance. This can most safely be achieved by using combustion equipment which can utilize various fuels found in the vicinity, such as wood bark, wood chips, 15 chips, peat, sewage sludge, etc., manure, municipal waste and the like.

In combustion plants using a so-called drum furnace, it is often a challenge to obtain sufficient combustion air to maintain the combustion process in the furnace. Conventional 20 or moving grate solutions for the combustion air that direct the combustion air into the furnace and their air vents or nozzles are often prone to clogging. Particularly in the combustion of a wide variety of materials, there is the problem of liquid liquefied ash, chemical compounds, etc., penetrating into the open air holes in their fires during the combustion process. In addition, these resulting ingredients can also lead to the mixing of the slag with the combustion medium and similar problems. Decreased airflow through its fires is also likely to interfere with the combustion process. Interference with the combustion process is particularly harmful when using different fuels of different quality in the same combustion plant. This kind of disturbance can create additional impurities, such as fine particles, which are embarrassing to the environment, up to 30 harmful.

Brief Description of the Invention

It is therefore an object of the present invention to provide a method and apparatus implementing the method so as to provide a completely new solution to the above-mentioned problems of prior art 35.

20155263 prh 25 -09-20199

This object is achieved in that the arrangement in the drum furnace and the method for supplying air to the drum furnace in accordance with the present invention have the features defined in the claims. In particular, the present problems can be solved by combining the features in a manner similar to that of claims 15 and 13.

Preferred embodiments of the invention are claimed in the dependent claims.

The invention provides considerable advantages. Thus, the air ducts supplying combustion air to the drum furnace are protected by an insulating layer. Salo rack The mouth openings of these pipes and the air jets flowing from the air pipes are substantially unobstructed in the direction of the combustion process in the combustion chamber. Thus, in a rotating drum furnace, the fuel rolling from the inlet to the outlet and its combustion event do not enter the air pipes but pass through their orifices without being caught.

The non-rotatable baffle is positioned against the end of the drum furnace and is provided with one or more air inlets. By controlling this aperture, the air supply to the drum furnace combustion chamber can be directed to the desired air pipes at any given time.

The inner surface of the drum furnace and the air pipes formed in the drum furnace casing are protected by casting. In addition, the inner surface of the jacket, which acts as a fire support, is protected by a glass-resistant and sinter-resistant refractory coating. This allows the drum oven to clean itself while it is rotating.

By casting the casing and blowing the air through the air tubes, the surface temperature of the drum's outside circumference can be maintained. In this case, the bearings of the rollers supporting the rum25 wood furnace also do not overheat.

By continuously ensuring sufficient supply of combustion air with its fires, the present invention achieves all the benefits and safety of cylindrical combustion. At the same time, it can be ensured that the maximum energy content of the combustible material from the combustible material to be treated can be utilized in the combustion process. As a result, this thermal power plant with the present drum furnace and the so-called afterburner provides not only the thermal energy generated from the fuel itself, but also the same advantages and safety in the combustion of hazardous waste as the previously known cylindrical combustion plants specifically designed for hazardous waste. For example, liquids discharged from hazardous waste or the like 35 will not cause harm to any part of the combustion chamber but will be controlled from the drum furnace end to the ash compartment.

20155263 prh 25 -09-20199

The stepwise expansion of the inner surface of the drum furnace towards the outlet creates a natural rolling surface which is inclined to the drum furnace. As a result, as is known in the art, it is not necessary to install the drum furnace in an inclined position to scroll the fuel in the direction of the outlet port 5, but to install the furnace substantially horizontally.

Other advantages of the invention are set forth below when specific embodiments of the invention have been described in more detail.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, some preferred embodiments of the invention will be described in more detail with reference to the accompanying drawing, in which: Fig. 1 is a schematic diagram of a prior art drum; Figure 4 is a detail view of the casing structure of Figure 4, AA, Figure 6 is a detail view of the casing structure of Figure 4, B, Figure 7 is a schematic sectional view of the drum a fire blower25 coming from the first end of the furnace and the control damper therein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present figures, the arrangement in the drum furnace and the method for controlling the air in the drum furnace are not shown in scale, but Figures 30 are schematic, illustrating the basic structure and operation of preferred embodiments. In this case, the components designated by the reference numerals in the accompanying figures correspond to the components designated by the reference numerals in this specification.

Figure 1 shows a solution known per se, in which the drum furnace 1 is utilized as part of a heating plant. Drum ovens are also used 35 in, inter alia, the manufacture of cement clinkers and waste incineration.

20155263 prh 25 -09-20199 also suitable for burning solid, liquid, paste and gaseous materials. Such a furnace is a straight cylindrical cylinder of combustion and heat resistance, in which the material to be processed is burned in a drum rotating about its longitudinal axis. However, in order to maintain combustion, the furnace 5 has had to be supplied with combustion energy externally, for example oil or gas, since it has not previously been possible to obtain the harmless air supply required for the independent combustion of the material to be burned.

The drum furnace 1 is normally associated with a separate afterburner space 2 in which the gases formed in the furnace are completely burned. The drum oven is usually 10 slightly inclined. It then has an upper end 3 provided with a special inlet 4 for directing the fuel 5 to its circumferentially spaced pieces 6. The combustion air is typically fed to the drum furnace through channels 8 piercing the shell 7 substantially in the radial direction of the circumferential cylinder.

During the fire, the drum furnace 1 rotates slowly, for example 5-40 revolutions per hour depending on the quality of the fuel 5. Due to the rotation and the oblique position of the drum, the fuel rolls forward in the circular cylinder towards the outlet 10 at its lower end 9, thereby effectively mixing the fuel, improving the contact of the combustion air with the fuel and allowing the fuel to burn throughout.

Since the fire takes place against the casing 7 of the drum furnace 1, it must be constantly cooled. This is done in such known technology either with air circulating the outer surface 11 of the circular cylinder or with water.

The combustion gases and ash generated during the fire exit from the outlet 10 at the lower end 9 of the drum furnace 25 to the afterburn space 2.

Contrary to known solutions, the present drum furnace 20, shown in Fig. 2, for example, is supplied with combustion air 21, in particular, through the inner surface 24 of the mantle 23 surrounding the combustion chamber 22, underneath the combustible material. For this purpose, special longitudinal air tubes 26 of the drum furnace are provided in a circular cylinder rotating about its central axis 25, i.e. the drum 30.

It is advantageous to arrange these air tubes throughout the circumference of the drum furnace. The structure of such a drum furnace can be seen in more detail in the cross-section of the jacket 23 of Figure 5. Thus, the outer surface 27 of the jacket is preferably formed by a circular cylinder made of steel. The rim of a circular cylinder is rotated by two rim rings in a known manner. The rim rings form the drum rails of the drum oven.

On these, the oven is supported by a bearing. If desired, also a drum

20155263 prh 25 -09-20199 rotation of the furnace can be achieved from said circumference. This structure, known per se, and its operation have not been discussed in detail in this context.

Although tubes 26 are referred to herein as air tubes, they do not limit their use to supplying air only. Thus, these tubes can also be utilized to supply other gases or other fire promoting compounds with their burns 22.

The drum furnace 20 has a first end 28, as described above, having an inlet 29 for guiding fuel through the drum furnace chunks 22 by means known per se. This first end is preferably made of sheet steel 30 which is tightly and rigidly connected to the outer surface 27 of the jacket. At the opposite end 31 of the drum furnace, there is an outlet 32, from which the waste debris is discharged in a known manner and as described above to a post-combustion space and further to post-treatment.

The first end 28 is provided with air openings 33 surrounding the inlet 29, whereby they are substantially concentric with the inlet. The air vents are connected to the air tubes 26 in the sheath, which are substantially parallel to the central axis 25 of the drum furnace and parallel to the outer surface 27 of the sheath. The function of these air tubes is thus to direct the fire ground from the first end of the drum furnace to the drum furnace pieces. The air vents and the associated air ducts are then preferably provided on the end and the sheath in a plurality of concentric annular layers. The air vents may be arranged radially in the queue as shown in Figure 2, but such radial organization is by no means necessary for the operation of the drum furnace.

The manufacture of the jacket 23 proceeds in the first preferred embodiment of the drum furnace, as shown in Figure 5, as follows. The first cylinder layer is cast on the steel cylinder forming the outer surface 27 of the jacket. After this has sufficiently cured, air tubes 26 substantially parallel to the center axis 25 of the drum and parallel to the outer surface 27 of the jacket are provided with the pieces thereof against the barrier layer 30. from its inner end near the drum furnace outlet 32 32. Next, these first layer air tubes are clad with a second die casting, on which again slightly shorter il6

20155263 prh 25 -09-20199 Map tubes 26. Installation of the air pipes and the dripping of the insulation layers is continued until the desired amount of combustion air with its fires 22 conducting air pipes has been achieved. At the same time, a somewhat conical expansion from the inlet 29 designed for the combustion chamber to the outlet 32 is provided, cf. Figure 2. After completion of the last 5 insulating molding, it is preferable to finish the interior of the combustion chamber with refractory surface molding or surface treatment.

The inner surface 24 of the drum furnace 20 manufactured in this way, for example, as shown in Fig. 2, shows a cross-section of a staircase having a long step but a small step pitch. When viewed from the inlet, the insert looks like a descending step. In turn, viewed from the direction of the outlet, the openings 35 of the air tubes 26 at the base of the stair head surface 34 and arranged in several nested layers on the sheath can also be distinguished. The air tubes are preferably arranged substantially evenly spaced along the periphery.

The staggered conical expansion of the combustion chamber 22 may be realized in the same spiral-expanding manner as in the present embodiment with segmental staggering of different lengths. The latter is simpler to implement technically.

The drum oven 20 can also be made from prefabricated elements20. In this case, the drum furnace is formed, for example, by successive cylindrical cylinders of the same outer diameter. The parts are made so that their inner diameter increases one by one. When the parts are joined together, the stepwise expanding conical combustion chamber 22 described above is formed into the cylinders, during manufacture, the necessary air tubes 26 are installed. 25 When assembling the drum furnace, these air tubes are aligned with each other to provide uniform pipelines. The finished drum furnace is preferably finished with a refractory surface casting or surface treatment covering the inside of the combustion chamber

The drum oven can also be assembled from shrink and cross-sectional cylinder elements. Thus, the outer surface of the cylinder elements to be installed inside the outermost element 30 is preferably provided with the necessary air ducts or grooves forming such. This leaves each layer of air duct under the protective structural layer. It is also advantageous to finish such a finished drum oven by surface casting or finishing.

By arranging the orifice 35 of the air tube 26 to orient toward the 35 orifice 32, for example, as shown in Figure 6, the fuel 22, which is fed by the drum furnace chips 22, and

20155263 prh 25 -09-20199 fire event can enter air vents. In the present arrangement, the fuel and combustion event continuously scrolled away from the orifice, being driven by an air jet from the air pipes. Thus, the air pipe is thus arranged to open with its fires at the front surface 34 formed by the staggering in the combustion chamber in the direction of the flow of rolling fuel and hot gases. In this way, the problem inherent in known solutions whereby the orifices accumulate around the air nozzles and are blocked by fuel and slag can be effectively avoided. The structure can also ensure that hazardous waste incineration is safe as well, since the effluents, ash and other slags generated during the incineration are directed to the ash space in the afterburner.

Due to the construction of the air conduits 26 of the present drum furnace, the flow of fuel and of effluent, ash and other slags during combustion can be effectively controlled. By adjusting the velocity of the gas flowing through the air pipe, etc., the flow of the components surrounding the outlet can be affected.

In order to direct air to the air tubes 26 parallel to the longitudinal axis 25 of the drum furnace 20, special means 36 are provided at the first end 28 of the drum furnace for the air openings 33 connected to the outer end of the air tubes. a baffle to be placed against the end and preferably arranged to be non-rotatable. This baffle has at least one air inlet 37 for directing the air to the respective openings 33 of the air tubes 26 at the inlet. Since the drum stove against the baffle is in continuous circulation, the air should therefore be directed only to a portion of the tubes. at the baffle air inlet. Thus, it is particularly advantageous to position the baffle in such a position that the at least one air inlet therein directs the combustion air only to those air pipes whose mouth 35 at any given time is in the combustion space beneath and on the sides of the rolling fuel.

Thus, to control the flow of air, the air inlet 37 in the baffle 36 is shaped as a sector of a circle or circle. The air inlet is preferably arranged to be adjustable in size. The adjustment can be effected, for example, by a structural solution according to a kind of harp control principle. The inlet size is then preferably adjustable automatically by furnace control logic to control the combustion process.

In order to provide the required flow of air with its chunks 22, a pipe fitting 38 is arranged schematically in the baffle 36 which can be arranged on the baffle 36 and can be provided with a separate fan

Preferably, the tube assembly may also comprise means 39 for directing air to the outermost air tube assembly of the drum furnace, thereby reducing the diameter of the baffle so that the outermost vents are released. In this way, air can advantageously be directed to the outermost air ducts around the periphery of the entire drum furnace. By directing air to these outermost air tubes, too, the entire drum 10 on the periphery of the furnace, and not only at the above-mentioned air inlet, can cool the drum furnace casing 23 in a controlled manner. This air flow to the outside air ducts can also be arranged to be individually controlled by a fan installed for this purpose.

By aligning the baffle plate 36 flat against the flat first end 28 of the drum furnace 20 with a light elastic load, a sufficient seal is obtained to direct the required air flow to the air pipes. Thus, there is no need for a complete air leakage barrier between the end of the rotating drum oven and the fixed baffle plate rubbing against it. The air mattress that penetrates between the panels acts as a friction reducing device and also as a cooling end.

It is to be understood that the foregoing description and the accompanying figures are merely intended to illustrate the present solution. Thus, the solution is not limited to the embodiment set forth above or as defined in the claims, but many variations and modifications thereof will be apparent to those skilled in the art, within the spirit of the appended claims.

Claims (16)

An arrangement in a rotary kiln (20), the rotary kiln comprising a circular cylindrical structure having A combustion space (22) surrounded by a sheath (23), which sheath is provided with nozzles (34) for conveying combustion air to the combustion space, and the combustion space (22) is arranged to be substantially conically expanding from that of the rotary furnace (20). the first end wall (28) against its second end end (31), said first end end having a feed opening (29) for conveying fuel to the combustion space, and said second end end being arranged to form a substantially open outlet (32), The rotary furnace is arranged to rotate about its center axis (25), characterized in that each and every one of the nozzles (34) is connected to an air pipe (26), which air pipes are arranged in the conically expanding manifold (23), and the trachea is joined to an air aperture (33) shown by the first end 20 (28) of the rotary kiln (20), such that the trachea is oriented substantially in the direction of the rotary kiln's center axis (25) as well as parallel to a surface (27) shown by the male. the air openings as well as the air pipes arranged thereto are arranged to the gable (28) and to the male ends (23) in several concentric annular layers 25 2. Arrangement according to claim 1, characterized in that the manifold (23) exhibits air tubes (26) arranged therein in several concentric layers. Arrangement according to Claim 1 or 2, characterized in that the men (23) have trachea (26) around their entire circuit. 4. Arrangement according to some previous claim, characterized in that the conical expansion of the combustion chamber (22) is arranged to be terraced. 20155263 prh 25 -09-2019 5. Arrangement according to claim 4, characterized in that said terracing is arranged to be helically expanding. 6. Arrangement according to claim 4, characterized in that said terracing is realized with various long terrace segments. Arrangement according to any one of claims 4 to 6, characterized in that the trachea (26) is arranged to open to the combustion space (22) in the direction of flow of hot gases and rolling fuel in one of the tees. 10, the end surface (35) is formed. Arrangement according to any preceding claim, characterized in that the first end (28) of the combustion chamber (22) is provided with means (36) arranged to actuate air to the air pipes (26), which The means comprises an unrotating guide disc arranged against the end of the rotary furnace, which guide at least one flow opening (37) for operating air in air openings (33) located at the flow opening, respectively, which air is further directed to the air pipes (26). 9. Arrangement according to claim 8, characterized in that the flow opening (37) has the shape of a circle sector. Arrangement according to claim 8, characterized in that the flow opening (37) has the shape of a sector of a circular ring. Arrangement according to any of claims 8 to 10, characterized in that the guide plate (36) comprises a fixed pipe sleeve (38) arranged on top of the flow opening (37). Arrangement according to any of claims 8 to 11, characterized in that the guide plate (36) is arranged planarly against the flat first end (28) of the rotary kiln (20) with a light spring load. 20155263 prh 25 -09-2019 13. A method of supplying air to a rotary kiln (20), providing a circular cylindrical structure rotating about its center axis (25), which forms a combustion space (22) in the rotary kiln (20), which is Substantially conical expanding from a first end (28) shown by the rotary furnace (20) to its second end (31), nozzles (34) are formed in the conically expanding manifold (23) by passing combustion air to the combustion space, whereby a feed opening ( 29) is formed in the first end wall (28) through In which the fuel is conveyed to the combustion space, a substantially open drain opening (32) is formed in the second gable (31), through which combustion residues are removed from the rotary furnace, characterized in that each nozzle (34) is arranged in air pipes (26). in And the trachea is connected to an air opening (33) exhibited by the first end of the combustion furnace (28), the trachea (26) being arranged to be unobstructed substantially in the direction of the rotary kiln's center axis (25) as well as parallel to one of the men (23) has a surface (27), and the air openings as well as the air pipes arranged thereto are arranged to the gable (28) and to the male ends (23) in several concentric annular bearings, as well, that air is supplied in air openings (33) exhibited by the first gable and provided with the trachea, to be transported to the combustion compartment via the nozzles (34). 14. A method according to claim 13, characterized in that the first end (28) of the combustion chamber (22) is provided with means (36) arranged to Actuating air to the air openings (33) of the air pipes (26), which comprise an unrotating guide disk arranged against the end of the rotary furnace, which is provided with at least one flow opening (37) for operating air in the air pipes (33) of the air pipes (26). each moment is located at the flow opening. Method according to Claim 14, characterized in that air is drawn to the trachea (26) via a fixed pipe sleeve (38) arranged on top of the flow opening (37) of the guide plate (36). Method according to any one of claims 13 to 15, characterized in that the trachea (26) is molded concentrically to the surface (27) of the rotary kiln (20) casing (23).