JP5987605B2 - Coke oven wall diagnosis method and coke oven wall repair method - Google Patents

Description

  The present invention relates to a coke oven furnace wall diagnosis method and a coke oven furnace wall repair method for quantitatively evaluating the deformation state of a carbonization chamber furnace wall in an aged coke oven.

  In the iron and steel industry, coke ovens are used to produce coke from coal, but in recent years, coke ovens have become increasingly aging furnaces that have passed 40 years since construction.

  The coke oven has a structure in which bricks are stacked while being bonded with a thin mortar layer and tightened from the front, rear, left and right to maintain the shape (furnace tightening). This brick structure has a heat storage chamber on the foundation, a cavity called a carbonization chamber having a height of about 7 m, a width of about 400 mm, and a depth of about 16 m on the upper side, and a combustion chamber of about 900 mm in width for burning fuel gas. Are arranged side by side in the width direction, with a brick ceiling on top.

  Then, heat from burning the fuel in the combustion chamber is passed through the wall bricks of the combustion chamber, the carbonization chamber is set to 1000 ° C. or more, coal is introduced from the charging hole at the upper portion of the carbonization chamber, and the coal is dry-distilled to produce coke. To manufacture.

  The finished coke is inserted with an extrusion ram from one of the kiln ports having a height of about 7 m at both ends of the coking chamber and having a width of about 400 mm, and the coke inside the coking chamber is discharged from the other kiln port.

  After the completion of construction, the coke oven burns fuel inside, gradually raises the brick temperature to 1000 ° C. or higher, and then keeps the temperature until the furnace is stopped.

  The brick wall that separates the combustion chamber and the carbonization chamber is called the furnace wall and shields the combustion gas from flowing into the carbonization chamber, and also plays an important role in transmitting the combustion heat to the carbonization chamber and supporting the ceiling.

  A ceiling load and a furnace tightening force always act on the furnace wall, and an extrusion ram load and an extrusion frictional force are temporarily applied during extrusion.

  The ceiling load and the furnace tightening force have the role of stabilizing the furnace wall structure, but as aging progresses, there are gaps in the joints, gaps in the joints, defects that cause one or more bricks to come off, wide If an aggression where the brick wears and thins on the surface, or an overhang occurs when the brick collapses on the wide surface and protrudes to the carbonization chamber side, damage will occur if furnace tightening force or extrusion force acts on the furnace wall in such a state Progresses and, in some cases, bricks collapse.

  In addition, if unevenness occurs on the wall surface due to such brick aegle, chipping, overhang, etc., the distance between the left and right furnace wall surfaces (kiln width) of the carbonization chamber will change from the design dimensions, and the coke Extrudability deteriorates.

  Therefore, if the furnace wall is further damaged or deformed, repairs such as transshipment in large-scale cases such as replacement of bricks and overhanging are carried out for spraying of irregularly shaped materials and overfilling and chipping of Aegle. Trying to restore a healthy state.

  At that time, the shape of the furnace wall changes slowly, and the amount of deformation occurs in the order of several centimeters. However, it is difficult to measure the shape of the furnace wall that maintains a temperature close to 1000 ° C. Until now, it has relied on visual inspection. I came.

  On the other hand, recently, several methods for assuming the shape of the furnace wall of the carbonization chamber have been proposed.

  For example, Patent Documents 1 to 3 propose a method of measuring a change in shape at a certain height by attaching a laser distance meter to an extrusion ram and moving the furnace back and forth.

  Patent Document 4 proposes a method of measuring a shape by placing a shape measuring device using a laser on a dedicated lance and moving the furnace back and forth.

International Publication No. WO2004 / 090071 JP 2004-168958 A JP 2004-245688 A JP 2007-127672 A

  However, the methods described in Patent Documents 1 to 4 have the following problems because the apparatus is measured through the inside of a high-temperature carbonization chamber near a high-temperature furnace wall of about 1000 ° C.

  (A) A heat insulation measure becomes large-scale and a measuring apparatus becomes large-scale.

  (B) Poor workability when attaching / detaching during measurement.

  (C) In order to measure the entire furnace wall, it is necessary to arrange a large number of devices.

  (D) Since the device itself moves and travels, meandering of the entire device and vibration of the device occur, resulting in disturbance of measurement data, and the measurement accuracy deteriorates. Measurement of the generated meander and vibration is difficult and correction is difficult.

  In response to these problems, the heat received by the measuring device from the coke oven includes heat transfer from a high temperature atmosphere (air temperature) and radiant heat from the wall, but it is measured from the bottom of the carbonization chamber outside the carbonization chamber. In this case, since the air convection flows upward, a high-temperature air flow can be avoided.

  The present invention has been made in view of the circumstances as described above, and measures the deformation state of the wall of the coking chamber in the aging coke oven (the unevenness of the wall surface, changes in the kiln width) in the inside of the coking chamber. An object of the present invention is to provide a method for diagnosing a coke oven wall and a method for repairing a coke oven wall that can be easily and accurately measured from the outside of the coking chamber without introducing any other material.

  In recent years, an apparatus called a laser three-dimensional measuring apparatus or a laser scanner has been used in civil engineering surveys.

  This laser three-dimensional measuring device is a distance meter that emits laser light and measures the time it takes for reflected light to return, and irradiates the laser radially in a vertical plane. Rotate 180 degrees horizontally as an axis, measure the polar coordinate system by three angles of horizontal rotation angle, laser beam elevation angle and laser measurement distance, convert this to XYZ orthogonal coordinate system, and measure the position where the laser hit To do.

  At that time, by dividing the horizontal rotation angle and the launch elevation angle finely and measuring a number of positions, a point cloud is obtained, and by displaying this, a 3D shape can be measured, and a laser 3D shape can be measured. It can be used as a measuring device.

  Therefore, when this laser type three-dimensional shape measuring apparatus is used, the inside of the carbonization chamber can be measured from the outside of the carbonization chamber.

  Therefore, in the present invention, this laser type three-dimensional shape measuring apparatus is used to measure and diagnose the deformation state of the wall surface of the carbonization chamber (the unevenness of the wall surface and the change in the kiln width).

  Based on the above concept, the present invention has the following features.

  [1] A method of diagnosing the furnace wall shape of a coking chamber of a coke oven, wherein a laser type three-dimensional shape measuring device is arranged outside the carbonizing chamber with a lid, and the carbon type three-dimensional shape measuring device is used for carbonization. The process of measuring the shape of the wall surface as a point cloud by irradiating a laser beam obliquely from the kiln entrance of the chamber was performed independently on the left and right wall surfaces of the carbonization chamber, and then the left and right sides were measured independently. The shape of the wall (point cloud) is synthesized based on the reference material around the carbonization chamber, and is combined into one shape data to obtain the left and right synthetic furnace wall shape (point cloud). The left and right synthetic furnace wall shape (point cloud) A furnace wall shape diagnosis method for a coke oven, wherein the distance between the left and right wall surfaces (kiln width) is calculated to diagnose the furnace wall shape.

  [2] Based on the design shape of the furnace wall based on the left and right composite furnace wall shape (point group), the amount of deviation of each measurement point is calculated, and the amount of deviation is used as the unevenness of the wall surface to diagnose the furnace wall shape. The method for diagnosing a furnace wall shape of a coke oven according to the above [1], wherein:

  [3] When calculating the deviation amount of each measurement point from the left and right synthetic furnace wall shape (point group) on the basis of the design shape of the furnace wall, the left and right synthetic furnace wall shape on the basis of the furnace frame hardware ( Point cloud) and the position of the design shape, the depth direction of the left and right composite furnace wall shape (point cloud) is adjusted to the design shape by rotational movement, and the amount of deviation of each measurement point is calculated. The method for diagnosing a furnace wall shape of a coke oven according to [2].

  [4] A coke oven characterized in that a furnace wall is repaired by determining a repair amount of the furnace wall from the unevenness of the wall surface obtained by the method of diagnosing the furnace wall shape of the coke oven as described in [2] or [3] Furnace wall repair method.

  In the present invention, the deformation state of the wall of the carbonization chamber in the aging coke oven (the unevenness of the wall surface, the change in the kiln width) can be easily and accurately performed from the outside of the carbonization chamber without inserting a measuring device inside the carbonization chamber. Can be measured.

It is a perspective view which shows the measurement state in one Embodiment of this invention. It is a top view which shows the fundamental view of the measuring method in one Embodiment of this invention. It is a figure which shows an example of the measurement result (whole furnace wall shape) in one Embodiment of this invention. It is a figure which shows an example of the measurement result (unevenness | corrugation of a furnace wall surface) in one Embodiment of this invention.

    An embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view showing a measurement state in one embodiment of the present invention, and FIG. 2 is a top view showing a basic concept of a measurement method in one embodiment of the present invention.

  As shown in FIGS. 1 and 2, in one embodiment of the present invention, a laser type three-dimensional shape measuring device 20 is disposed outside the carbonization chamber 10 when diagnosing the shape of the carbonization chamber 10 of the coke oven. Then, the step of measuring the shape of the furnace wall (wall surface) 13 as a point cloud by irradiating the laser 21 obliquely from the kiln opening 11 with the lid 12 taken by the laser type three-dimensional shape measuring apparatus 20 is performed. After carrying out independently with respect to the left and right wall surface 13a, 13b of the chamber 10 (FIG. 2 (a), (b)), the shape of the wall surface measured independently on the left and right is referred to as a reference object around the carbonization chamber 10 ( For example, a spherical body 22) having a known radius is synthesized based on one shape data (point group) to form a left and right synthetic furnace wall shape (FIG. 2 (c)). The distance between the wall surfaces (kiln width) is calculated, and the furnace wall shape (wall surface irregularities) And to perform the diagnosis of changes in the kiln width).

  That is, the carbonization chamber 10 has a height of about 7 m in height, a width of about 400 mm, and a depth of about 16 m, and the kiln 11 has a long and narrow structure with a width of about 400 mm and a height of about 7 m. When 21 is irradiated, the optical axis of the laser 21 enters the wall surface 13 at a shallow angle. An attempt to measure the left and right furnace walls 13a and 13b at a time is disadvantageous because the incident angle of the laser 21 becomes very shallow. Further, when the light is incident at a shallow angle, if the wall surface 13 is overhanging, the back of the wall 13 is shaded, the laser 21 does not reach, and measurement cannot be performed. For this reason, the furnace walls 13a and 13b are measured one by one.

  In addition, since the kiln opening 11 can completely open one side surface of the carbonization chamber 10 in the width / height direction, there is nothing to block the laser 21 other than the furnace wall 13 and a wide measurement range can be taken.

  The measured data is left and right as it is, but can be evaluated independently. Although the wall surface 13 has unevenness, it forms a flat surface as a whole. Therefore, by calculating the average plane from the measured point group and calculating the distance of each point from the average plane, the local unevenness state is numerically calculated. It is possible to The distance may be calculated by calculating a normal direction distance between each point and the average plane, or by calculating the distance in the width direction of the kiln (carbonization chamber) 10. In addition, with a high-resolution laser type three-dimensional shape measuring apparatus, the interval between measurement points is very small, and a large number of points can be obtained. It is possible to reduce the amount and reduce the measurement error by averaging. Further, evaluation may be performed by creating a small triangular element (polygon) from the point group and expressing the whole with a combination of small surfaces, and reducing and averaging the data amount.

  However, when extruding coke from the carbonization chamber 10, an extrusion ram having a width of about 350 mm is inserted into the carbonization chamber 10 having a width of about 400 mm. Therefore, whether the extrusion ram can pass smoothly is determined by the distance between the left and right wall surfaces. (Kiln width) is important information.

  When calculating the width of the kiln, the left and right furnace walls 13a and 13b may be evaluated independently. In this embodiment, as described above, the left and right furnace walls 13a obtained independently. , 13b are combined into a single data (point group) to calculate the kiln width.

  That is, the data (point group) of the left and right furnace walls 13a and 13b are combined into one data (point group) as follows.

  First, a plurality of (for example, four) dedicated reference bodies (for example, spherical bodies with known radii) 22 are arranged around the kiln 11 and the spherical bodies 22 are measured on the left and right furnace walls 13a and 13b. Measure at the same time. Next, the center position of the spherical body 22 in each measurement data is calculated. And since the positional relationship between the spherical bodies 22 does not change, a one-to-one correspondence between the center positions of the spherical bodies 22 in the left and right measurement data is found, and one point group is moved so that they overlap. Then, the independent point cloud is put together.

  Note that a dedicated reference body may be used, and if there is an object whose position can be easily identified, it may be used.

  Thereby, the relative positional relationship between the left and right wall surfaces 13a and 13b becomes clear, and the kiln width can be evaluated.

  Then, by using the data obtained by combining the left and right wall surfaces, it becomes possible to evaluate the difference between the original design shape of the furnace wall and the current shape of the furnace wall.

  By the way, in the coke oven, when the coke is extruded, the width of the kiln on the side where the coke goes out is adjusted by pushing the extrusion ram so that the coke cake (which indicates the entire structure in which the finished coke lumps are stacked) is not easily rubbed against the wall surface. It has a tapered shape that is about 30 mm wider than the width of the kiln on the insertion side. That is, a taper of about 30 mm with respect to a depth of 16 m is present on both sides, and there is a possibility that deviation occurs in the average plane calculated from the individual measurement point groups as described above.

  On the other hand, if the point group is a combination of the left and right wall surfaces, the degree of expansion of the kiln width will be clarified, and the unevenness of the wall surfaces can be evaluated by calculating the distance between the design shape and the point group. At that time, some kind of reference is required for positioning the composite point group and the design shape.

  In this embodiment, since the incidental equipment outside the kiln 10 can be measured simultaneously, these can be used as a reference. However, the incidental equipment used for a long time is significantly deformed and does not necessarily retain its original shape, so it is necessary to select appropriate incidental equipment.

  There are several iron members in the vicinity of the kiln opening 11, but the member called the furnace frame in it is attached on the basis of the furnace wall 13 to be replaced and repaired as damage progresses, Since the positional relationship with the furnace wall 13 is the clearest, it is appropriate as a reference.

  Since the center position from the left and right of the upper corner of the lower short side of the furnace frame is close to the laser type three-dimensional shape measuring apparatus 20 and the shape is clear, it is easy to specify the position.

  Specifically, the center position of the upper corner of the lower short side of the furnace frame is specified by the following procedure.

  First, an average plane is calculated from a point group of two orthogonal faces of one vertical column. Next, a straight line is calculated from the intersection of the two surfaces. Next, the straight line is similarly calculated for the other vertical column. Then, the average plane is calculated from the point group on the upper surface of the furnace frame lower short side.

  Next, a point (one point each) where the previous two straight lines intersect with the average plane is defined. On the straight line connecting the two points, the center point is an exactly middle point where the distances from both are equal. The point group is moved and matched so that the center position and the corresponding position of the coking chamber plane shape data created from the design drawing coincide.

  Next, the depth direction (longitudinal direction) of the kiln is adjusted by rotating the point group around the vertical direction.

  Since there is no optimum standard for this, the point group of the wall and the design standard shape are optimally matched or visually matched. At this time, it is better to select a part with less deformation from the point cloud and match it with the design shape.

  If there is a deviation in the vertical direction, the coking chamber floor surface is preferably aligned with the floor surface of the design shape.

  Incidentally, there may be an error in the synthesis of the left and right wall surfaces. The error includes a parallel error in which the left and right widths are constant and a rotation angle error caused by rotation about the axis. In particular, the rotation angle error increases as the distance from the reference increases. If an error occurs, it becomes impossible to accurately represent the taper of the left and right wall surfaces, and it may be necessary to perform correction. In such a case, an error can be corrected by finding a normal part of the wall surface and moving the right or left point group individually or simultaneously so that the part matches the design shape. Such an operation can be easily performed by extracting the data of the vertical cross section or horizontal cross section of the left and right point groups, and making corrections while displaying them two-dimensionally together with the line of the design shape.

  A laser type three-dimensional shape measuring apparatus (hereinafter referred to as a measuring apparatus) is generally mounted on a solid tripod for measurement.

  At that time, measurement can be performed by a measurement unit comprising a measurement device, a tripod, and a display PC, and the portability is good, a dedicated lance and a drive device are not required, and mobility is high.

  Moreover, since it is possible to measure a wide range with one measuring unit and it is easy to move, it is possible to divide the measurement into two measurements with one measuring unit, and it is not necessary to prepare a plurality of measuring units.

  In addition, all necessary ranges can be measured with the measurement unit fixed, disturbances such as vibration and meandering can be eliminated, and the accuracy and correction of measurement results can be minimized.

  In addition, it is basic to measure in the fixed state with the vertical direction of the measuring device aligned with the direction of gravity (vertical direction), but high accuracy cannot be expected by using a bubble type level, and correction data is obtained. Because it can not be done, it can not be corrected. Therefore, it is possible to correct the point group with a vertical direction sensor built in the measuring apparatus. When this is used, it is not necessary to match the vertical direction in alignment with the design shape.

  The measured data can be stored and the measurement data of any date and time of the same kiln can be compared. For comparison, the two data needs to be well matched to the design shape. However, in many cases, the matching is not completely performed in the synthesis process or the work for matching with the design shape. In general, the deformation of the furnace wall does not change greatly as a whole and often occurs partially. Since the measurement method according to the present invention is measured from a fixed place, it was found that there was little disturbance and the shapes themselves matched well even with data measured at different dates. For this reason, when there are two pieces of data of different date and time, the amount of change of the changing portion can be accurately calculated by precisely matching the portions where both data are not changing. To match precisely, as in the above-mentioned composition correction processing, a vertical section at the same depth position or a horizontal section at the same height position is extracted from the left and right point cloud data at different dates and displayed two-dimensionally on the same graph. However, it is preferable to correct so that the point clouds of the portions without change overlap. At this time, it is more preferable to divide the left and right furnace walls of either one of the furnace wall data, and perform different corrections for each wall so as to match the other shape well. In this way, by taking the difference between two or more fixed periods of data, the progress of damage can be managed quantitatively, or the repair finish can be evaluated by comparing the data before and after the repair. It becomes possible.

  In addition, since the measuring device can be fixed below the kiln, high-temperature air flowing upwards does not directly hit the measuring device, and only a heat-resistant equipment to block radiant heat is required, so the measuring device is large. Never become.

  It is also possible to place a heat shielding material on the carbonizing chamber side of the measuring device arranged outside the carbonizing chamber, shield the radiant heat from the inside of the furnace, and move the heat shielding material only during measurement.

  And the synthetic | combination data of the right-and-left wall surface obtained by measuring an actual coke oven using said measuring method is shown in FIG. Moreover, the data which show the uneven | corrugated state of a wall surface are shown in FIG. In FIG. 4, a positive value portion is a concave state (a shaved portion), and a negative value portion is a convex state (a protruding portion).

  Based on the deformation state of the wall of the carbonization chamber calculated as described above (irregularity of the furnace wall surface, changes in the kiln width), the dimension where the wall surface protrudes from the reference surface or is scraped is measured and measured. Follow the procedure below to determine the amount of repair.

  By the way, in the overhanging part, when the finished coke is pushed out, it gets caught and resistance increases, so this part is repaired by scraping.

  Moreover, since the protrusion is generated in the coke at the shaved portion (eggle or missing portion), mortar spray coating or thermal spray repair is performed to fill the portion.

  At this time, based on the shape data, the repair range and the repair thickness can be instructed to the builder in advance, and the repair accuracy can be increased. In other words, in the past, the repair range and repair thickness were determined empirically by the difference from the surrounding conditions in a relatively narrow range of several meters, but here, the optimal repair amount is determined from the shape of the entire furnace wall. (Repair range, repair thickness) can be specified.

  Furthermore, the amount of the repair material used can be specified in advance from the shape data and used as a guide. For example, the volume to be filled in the thermal spray repair is calculated, converted to the weight of the thermal spray material, and the amount used is determined from the repair yield (rough value can be specified by the ratio of the material fixed on the wall to the total amount sprayed). It can be identified and set as one of the check items for repair completion.

  In addition, it is possible to measure again after the repair and evaluate the repair result. In addition, the shape before and after the repair can be combined with the parts that have not been repaired, and by comparing changes in the repaired parts, it is possible to check the repair amount and to evaluate and educate the level of proficiency of the workers. Since it can be based on the above-mentioned standard (for example, ancillary equipment outside the kiln), two separate measurements can be matched with the same standard, so that the comparison can be performed with high accuracy. On the other hand, since there is no reference object near the furnace top, it is difficult to perform the matching operation.

  Since electronic data can be obtained, automatic repair by a robot or a dedicated machine is also possible. Although it is desirable to make the repair surface flat as much as possible in line with the reference surface, in general, repair is often performed over a wide area thinly, and it is difficult to finely adjust the repair amount by manual spraying repair. High-precision repair is possible with precise movement.

  The laser type three-dimensional shape measuring apparatus used in this embodiment has a characteristic that the number of measurement data (number of point groups) decreases as the object to be measured is farther away. However, it is known that most of the damage to the furnace wall occurs in the vicinity of the kiln, and in this embodiment, since measurement is from the kiln, it is possible to obtain a highly accurate measurement result of the necessary part. It is.

  In addition, the coke oven has two facing sides on the extruder side and the coke discharge side. Select the range so that the center part overlaps slightly from both sides, and the data measured from both sides is the reference information (the length of the kiln). It is also possible to obtain the shape data of the entire furnace wall without reducing the amount of information as much as possible in the central part by matching the overlapping part of the data.

  In this embodiment, a film (referred to as furnace wall carbon) in which carbon adhering to the ceiling or wall is fixed can also be measured. Although it is difficult to distinguish the furnace wall and furnace wall carbon from the data, it is possible to identify the furnace wall carbon attachment position visually during measurement, and the vicinity of the ceiling, etc. should be attached with a thickness of several tens of mm. And can be easily determined. Furnace wall carbon is effective in reducing friction during extrusion if it is attached in an appropriate amount, but if the thickness increases too much, it leads to increased friction, and the furnace wall carbon must be controlled by properly controlling the thickness by incineration. Is desirable. It is also possible to optimize the incineration of the furnace wall carbon by visually identifying the adhesion position, estimating the thickness from the shape data.

  Thus, in this embodiment, the deformation state of the wall surface of the carbonization chamber in the aged coke oven (the unevenness of the wall surface, the change in the kiln width) can be measured without putting a measuring device in the carbonization chamber. It can be easily and accurately measured from the outside.

  That is, since a mechanism for driving the measuring device is not required, the measuring device can be easily transported and inspected. In addition, by measuring from outside the furnace, the thermal protection means of the measuring device is simplified, and the preparation and measurement work is facilitated in a short time. Moreover, it becomes possible to reduce the area which cannot be measured by measuring the left and right wall surfaces one by one. Furthermore, the shape of both wall surfaces can be obtained by combining the left and right wall surface data. Since the measuring device does not move, it is possible to accurately measure the absolute shape of the wall surface and the width of the kiln (interval between the left and right wall surfaces) without being affected by vibration and meandering.

10 Carbonization room (kiln)
11 Kiln entrance 12 Lid 13 Furnace wall (wall surface)
13a Left furnace wall (wall surface)
13b Furnace wall (wall surface) on the right
20 Laser type three-dimensional shape measuring device 21 Laser 22 Reference body (spherical body)

Claims (4)

  A method for diagnosing a furnace wall shape of a coking chamber of a coke oven, wherein a laser type three-dimensional shape measuring device is arranged outside the carbonizing chamber having a lid, and the laser type three-dimensional shape measuring device is used to set the kiln of the carbonizing chamber. After performing the process of measuring the shape of the wall surface as a point cloud by irradiating the laser beam obliquely from the mouth, the shape of the wall surface measured independently on the left and right sides of the carbonization chamber (Point group) is synthesized based on the reference material around the carbonization chamber, and is combined into one shape data to form the left and right synthetic furnace wall shape (point group). A method for diagnosing a furnace wall shape of a coke oven, wherein the distance between the wall surfaces (kiln width) is calculated to diagnose the furnace wall shape.   Calculate the deviation of each measurement point from the left and right synthetic furnace wall shape (point cloud) based on the design shape of the furnace wall, and perform the diagnosis of the furnace wall shape using the deviation as the unevenness of the wall surface. The method for diagnosing a furnace wall shape of a coke oven according to claim 1.   When calculating the deviation of each measurement point from the left and right composite furnace wall shape (point group) based on the design shape of the furnace wall, the left and right composite furnace wall shape (point group) based on the furnace frame hardware The shift amount of each measurement point is calculated by matching the position of the design shape with the design shape, and adjusting the depth direction of the left and right composite furnace wall shape (point group) to the design shape by rotational movement. The method for diagnosing the shape of a coke oven wall as described.   A furnace wall repair method for a coke oven, wherein the repair amount of the furnace wall is determined by determining the repair amount of the furnace wall from the unevenness of the wall surface obtained by the method for diagnosing the furnace wall shape of the coke oven according to claim 2 or 3.

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