Method of controlling a device for maintenance operation of a recovery boiler and device for maintenance operation

Description

1 / 18 METHOD FOR CONTROLLING AN APPARATUS FOR MAINTENANCE OPERATION OF A RECOVERY BOILER AND APPARATUS FOR MAINTENANCE OPERATION FIELD OF THE INVENTION

[0001] The invention relates to a method of controlling an apparatus for operating and maintaining a recovery boiler and to an apparatus for operating and maintaining it. BACKGROUND OF THE INVENTION

[0002] The primary fuel burned in a recovery boiler is black liquor. Secondary fuels, such as oil, natural gas, or some renewable fuels like tar or resin oil, are used during start-up and shutdown. In normal operation, only black liquor is burned, using specialized nozzles designed to atomize the liquid fuel for optimal combustion. The purpose of atomization is to allow for the rapid drying and volatilization of organic material in the fuel, which consists mainly of lignin and hemicellulose separated from the wood fibers in the pulp manufacturing process.

[0003] In addition to organic material, black liquor contains chemicals used in the Kraft pulp process. These inorganic materials, mainly sodium sulfate and sodium carbonate, melt with the heat of combustion of the organic material. The molten salt (molten material) flows out of the boiler through molten material spouts at the bottom of the boiler furnace to a dissolving tank.

[0004] Black liquor combustion is a delicate process in which it is necessary to maintain a balance between burning temperature and pressure, nozzle angle and type, and liquor quality. The effects of inadequate liquor combustion include the accumulation of deposits on heating surfaces, inefficient reactions in the charcoal melt bed, and increased flue gas pollutants. To avoid Petition 870250085824, dated 09 / 23 / 2025, page 8 / 45 2 / 18 To prevent improper combustion and ensure proper functioning, the burner must be kept free of molten metal and carbon deposits. These deposits tend to accumulate and cause clogging in boiler furnace elements that exhibit irregularities, such as molten material spouts, liquor gun openings, and cleaning and inspection hatches. Therefore, regular cleaning of these items is unavoidable to maintain optimal and uninterrupted process performance. Traditionally, these maintenance operations were performed manually using appropriate hand tools, but due to the high safety risks of working in the area with potential splashes of hot molten material, automated and / or robotic maintenance equipment for these tasks has been increasingly used in recent decades.

[0005] Known automated maintenance systems and devices, as described, for example, in publications WO 2018 / 229334, EP1914477 B1, EP 2024559 B1 or US 555425650 B, have recently been used, for example, in reducing the aforementioned safety risks for employees. However, in some respects, further improvements are still needed for these arrangements. For example, a disadvantage of known automated solutions currently being applied is related to their position control methods. This is because known maintenance operation devices are not adapted to compensate for large temperature variations and thermal expansion, which normally occur in the walls of the recovery boiler when the combustion process is switched between its different operational phases, i.e., from start-up to normal operation and from normal operation to shutdown.The effects of this thermal expansion are, in most cases, unpredictable, partly due to the non-linearities caused by the structural complexity of the boiler. Petition 870250085824, dated 09 / 23 / 2025, page 9 / 45 3 / 18 Thus, for example, mere predetermined compensations based on simple linear calculation models may not adequately solve these problems. SUMMARY OF THE INVENTION

[0006] The object of the present invention is to provide an improved method for controlling an apparatus for operating maintenance on a recovery boiler, whereby the maintenance operations performed by the apparatus can be controlled by considering the maintenance of the displacements of objects caused by thermal expansions that occur in the wall of the recovery boiler due to temperature transitions during the different operational phases of the recovery boiler. Furthermore, the object of the invention is to provide an apparatus for performing maintenance operations that is controlled according to the method of the invention.

[0007] The disadvantages described above are corrected by the method of the invention, because in the method an initial base coordinate system, which coincides with an object to be maintained in a fixed universal coordinate system and in which the apparatus for maintenance operation performs the maintenance operation, is determined in such a way that the initial base coordinate system is transferred from its initial position and orientation to its actual position and orientation, that is, where it is actually located after the occurrence of displacements caused by thermal expansion, which occurs in a recovery boiler during its operation. To be more precise, the method according to the invention is characterized by what is described in independent claim 1 and the apparatus by what is described in independent claim 16.Dependent claims 2-15 describe advantageous embodiments of the method, as do dependent claims 17 and 18, which describe advantageous embodiments of the apparatus.

[0008] One advantage of the method according to the invention is that, Petition 870250085824, dated 09 / 23 / 2025, p. 10 / 45 4 / 18 By means of it, the maintenance apparatus control system can compensate for misalignments and displacements of objects held in the boiler caused by thermal expansion. Therefore, by means of the method according to the invention, maintenance operations performed on objects to be held in a recovery boiler are carried out safely and reliably, regardless of the displacements of the objects caused by temperature transitions occurring in the recovery boiler. In practice, this means that the maintenance apparatus is always automatically adapted to operate according to the prevailing temperature of the recovery boiler.Thus, for example, in the case of cleaning a molten material nozzle, the molten material nozzle cleaning tool, moved by a molten material nozzle cleaning device, always remains precisely aligned in the desired position on the molten material nozzle to be cleaned, regardless of the operational phase of the recovery boiler. This ensures smooth and effective cleaning cycles and avoids the uncertainty of control and potential damage to the molten material nozzles and / or cleaning tools related to known control methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The invention will now be described in more detail with reference to the accompanying drawings, in which:

[0010] Figure 1 shows a diagram representing the determination of a temperature-corrected basis coordinate system from an initial basis coordinate system in a universal coordinate system.

[0011] Figure 2 shows an embodiment of the apparatus for maintenance operation, which is a cleaning apparatus for the spout of molten material from a recovery boiler and which is controlled according to the method of the invention, viewed obliquely from above. Petition 870250085824, dated 09 / 23 / 2025, page 11 / 45 5 / 18

[0012] Figure 3 shows an enlarged view of a molten material nozzle from the recovery boiler, viewed obliquely from above and showing how an initial basis coordinate system is arranged in the molten material nozzle, in the case of the molten material nozzle cleaning apparatus of Figure 2.

[0013] Figure 4 shows a systematic drawing, which represents the location of the universal coordinate system and the locations of the initial base coordinate systems in relation to the molten material spouts, in the method for controlling the apparatus for maintenance operation applied in the embodiment shown in Figures 2 and 3.

[0014] Figure 5 shows a top view of the apparatus for maintenance operation, and how the measuring sensors, for determining the positions of the molten material spouts, are positioned in relation to the molten material spouts and the recovery boiler.

[0015] Figure 6 shows a top view of the apparatus embodiment for maintenance operation, as shown in Figures 25, and a drawing represented in the same showing the displacements caused by the rotation of the recovery boiler wall in relation to the Y axis due to thermal expansion.

[0016] Figure 7 shows a front view of the embodiment of the device for maintenance operation shown in Figures 2-6, and a drawing shown therein showing the displacements caused by the rotation of the recovery boiler wall about the X-axis due to thermal expansion. DETAILED DESCRIPTION OF SOME ADVANTAGEOUS IMPROVEMENTS

[0017] The method according to the present invention can be applied to various different maintenance operations of a recovery boiler, for example, tasks such as cleaning the nozzle of material in Petition 870250085824, dated 09 / 23 / 2025, p. 12 / 45 6 / 18 Fusion, cleaning of the liquor gun opening or cleaning of the inspection hatch opening. Thus, in this respect, the control of maintenance operations performed by a maintenance operation device is generally discussed, which refers to any operation that is performed regularly or occasionally for the recovery boiler.

[0018] The apparatus for maintenance operation means, in the present patent application, an apparatus comprising a control unit, by means of which the physical (moving) parts of the apparatus can be automatically controlled according to a control program executed in the control unit. Thus, the control unit comprises, for example, a computer or other data processing device, in which said control program can be programmed and / or installed, as well as consequently executed. The control unit is further equipped with control hardware suitable for controlling electrically, pneumatically and / or hydraulically operated actuators, arranged to move the physical parts of the apparatus for maintenance operation, herein referred to as the tool moving device.Typically, the tool handling device for maintenance operations may consist of, for example, an articulated industrial robot with an appropriate number of degrees of freedom. A maintenance operation device may include one or more tool handling devices.

[0019] Maintenance tools, which are used in maintenance operations, can be chosen according to the maintenance operation. For example, in cleaning the nozzle of molten material, molten material nozzle cleaning tools are used. Therefore, a maintenance tool can also be a multi-functional tool, suitable for several different maintenance operations, or any specifically designed maintenance tool. Petition 870250085824, dated 09 / 23 / 2025, page 13 / 45 7 / 18 for the intended purpose. The maintenance operation apparatus may comprise several maintenance tools. Preferably, it has at least one maintenance tool for each tool handling device.

[0020] Generally, the method for controlling a maintenance operation includes at least the following steps: a) define a position of a fixed universal coordinate system in the recovery boiler; b) define a position of an initial base coordinate system of at least one maintenance object, which is at a selected point of at least one maintenance object determined in the fixed universal coordinate system, at an initial temperature of the recovery boiler; c) define a position of a corrected base coordinate system of at least one maintenance object in the fixed universal coordinate system, which is located at the position of the selected point in the fixed universal coordinate system, at a transition temperature of the recovery boiler; and d) control a device to move tools to perform the maintenance operation on at least one maintenance object in the corrected base coordinate system.

[0021] Defining a corrected base coordinate system position can be done, for example, so that the tool moving device is controlled to move the maintenance tool to the position of the selected point on at least one maintenance object, at the transition temperature, and records the coordinates of the selected point in the universal coordinate system. This control can be done manually or automatically. Manual definition can be done by controlling the tool moving device to move the tool in a Petition 870250085824, dated 09 / 23 / 2025, page 14 / 45 8 / 18 predetermined reference position. Automatic definition can be performed, for example, with the help of a suitable location device (such as an RFID tag) on ​​the object, which would indicate the reference position of an object to be maintained to the control unit.

[0022] In one embodiment of the method, the position of the corrected basis coordinate system is determined, at least in part, by calculating the displacement of the initial basis coordinate system, caused by the thermal expansion of the recovery boiler wall due to the temperature transition.

[0023] In one embodiment of the method, at least the universal coordinate system is a three-dimensional Cartesian coordinate system, and the determination of the position coordinates (i.e., position coordinates of the origin) of the corrected basis coordinate system is calculated using the following equations: X' = X + ΔΧ (1) Y ' = Y + ΔY (2) Z' = Z + ΔZ (3) where: The coordinates X', Y', Z' are position coordinates of the base coordinate system corrected to the fixed universal coordinate system; The coordinates X, Y, Z are position coordinates of the initial base coordinate system in the fixed universal coordinate system; and ΔΧ, ΔΥ, ΔΖ are displacements of the position coordinates of the initial base coordinate system, due to thermal expansion, in the fixed universal coordinate system.

[0024] In the case where the method comprises controlling the maintenance operation of at least two maintenance objects, arranged adjacent to each other in the recovery boiler, the Y-axis denotes the direction along a line between the at least two Petition 870250085824, dated 09 / 23 / 2025, page 15 / 45 9 / 18 adjacent maintenance objects, the X-axis denotes the direction perpendicular to the Y-axis, being in the same plane as the X-axis, and the Z-axis denotes the direction perpendicular to the plane defined by the X and Y axes.

[0025] Typically, an initial base coordinate system and a corrected base coordinate system are determined for each of at least two maintenance objects. Thus, the tool handling device is controlled to perform the maintenance operation for each of at least two maintenance objects in its respective corrected base coordinate system. Furthermore, in addition to these embodiments, for the displacements of the position coordinates ΔΧ, ΔΥ, and ΔΖ, the correction includes the rotation of the coordinate axes of the initial base coordinate system due to the rotation of the recovery boiler wall caused by thermal expansion. Thermal expansions of other parts of the recovery boiler, other than the recovery boiler wall, may also be considered, but in most cases these are considered insignificant.The rotation angles A and C of the coordinate axes of the initial basis coordinate system, as shown in Figure 1, are determined by the equations: A = arctan (ΔΧ2-ΔΧι) / (Υ2-Υι) (4) C = arctan (ΔΖ2-ΔΖι / (Υ2-Υι), (5) where:. A is the angle of rotation of the Y-axis relative to the X-axis; C is the angle of rotation of the Y-axis relative to the Z-axis; Y 1 is a first Y position; Y 2 is a second Y position; ΔΧι is the displacement in the X direction that occurs at positionYi; ΔH2 is the displacement in the X direction that occurs at position Y2; ΔZ1 is the displacement in the Z direction that occurs at positionYi; and ΔZ2 is the displacement in the Z direction that occurs at position Y2. Petition 870250085824, dated 09 / 23 / 2025, page 16 / 45 10 / 18

[0026] In one embodiment, the deformation of the recovery boiler wall, caused by the temperature transition, is measured by at least one displacement sensor placed at a known position in the recovery boiler. The measurement results from at least one displacement sensor are used to determine the initial displacement of the base coordinate system to determine the position of the corrected base coordinate system. If there are at least two displacement sensors placed at at least two different positions, they can be used to determine the displacements that occur at at least two different positions in the recovery boiler.This allows the rotation angles of the corrected base coordinate systems to be determined, where the rotation of the initial base coordinate system, due to the displacement variation that occurs at different positions in the recovery boiler, is calculated based on displacements measured at at least two different positions. Example

[0027] In this example, whose configuration is shown in Figure 2, the maintenance operation apparatus 10 is responsible for cleaning the molten material chutes S1-S14 of a recovery boiler 11, applying the method according to the invention. It includes five tool handling devices R1-R5 which, in this example, are articulated industrial robots. As can be seen in the figure, the recovery boiler 11 has, in this case, fourteen molten material chutes S1-S14. Thus, each robot R1-R5 needs to clean a maximum of three molten material chutes, which ensures that the response time of the cleaning process remains short compared, for example, to a case where only one tool handling device is used for all of them. The molten material chutes S1-S14 were divided among each robot R1-R5 as described in Table 1. Petition 870250085824, dated 09 / 23 / 2025, page 17 / 45 11 / 18 below. Table 1. Division of molten material nozzles between robots R1-R5 Melting material spouts S1-S3 Robot R1 Melting material spouts S4-S6 Robot R2 Melting material spouts S7-S8 Robot R3 Melting material spouts S9-S11 Robot R4 Melting material spouts S12-S14 Robot R5 Universal coordinate system

[0028] The displacements of the molten material nozzles S1-S14, which occur due to thermal expansion, are determined in a universal coordinate system 20, which is located at a fixed position. In the case of a single robot, the attachment point of the robot structure and the universal coordinate system are normally placed in the same position. In the case of multiple robots, as in this case, the universal coordinate system 20 for each robot R1-R5 is positioned at a predetermined point, which is the same for each robot. In this example, the universal coordinate system 20 was placed between the two most central molten material nozzles S7 and S8. Initial basis coordinate systems

[0029] Cleaning movements of spouts of molten material S1-S14 are executed in a corrected basis coordinate system (also called the “operational coordinate system”) 22. In this example, the initial basis coordinate systems 21 and the corrected basis coordinate systems 22 are positioned as shown in Figure 3 (i.e., at the lower end of the molten material spouts S1-S14). Alternatively, they can be positioned at any suitable location, for example, on a plate with a hole, provided, however, that the positions are considered in the calculations. In any case, the positions and orientations of the initial basis coordinate systems 21 are corrected by applying the principles Petition 870250085824, dated 09 / 23 / 2025, page 18 / 45 12 / 18 described above to form corrected base coordinate systems 22, which then compensate for the effects of thermal expansion in controlling the cleaning operations of the molten material spouts.

[0030] Figure 4 shows how the initial basis coordinate systems 21 were selected in this example. The origins of the initial basis coordinate systems 21 are defined in the universal coordinate system 20. In practice, they can be determined, for example, by a real robot and a molten material nozzle cleaning tool, applying the following procedure: The molten material nozzle cleaning tool 13 is moved close to the respective molten material nozzle S1-S14 by means of the regular control program of the respective robot R1-R5; From its nearby position, the S1-S14 molten material spout cleaning tool is moved to a desired point via manual control by the corresponding R1-R5 robot; At the desired position, the coordinates are defined as an origin of the respective initial base coordinate system 21 in a universal coordinate system 20; and The coordinates are saved in the control unit's memory for maintenance operation 10 as an origin of the respective initial coordinate system 21. Displacements and corrected base coordinate systems

[0031] The displacements that occur in the recovery boiler (which occur mainly in the recovery boiler wall 12) due to thermal expansion are, in this case, measured by using three measuring sensors M1-M3 in three dimensions (X, Y and Z). The measuring sensors M1-M3 can be any suitable measuring sensors capable of measuring or determining position directly (e.g., optical sensors or cameras) or indirectly (e.g., strain gauges or other type of displacement sensors). Petition 870250085824, dated 09 / 23 / 2025, page 19 / 45 13 / 18 Due to the displacement, the positions of the molten material chutes S1-S14 also change. These changes are compensated for by controlling the movements of the respective cleaning tools of the molten material chutes 13 in corrected base coordinate systems 22, in which displacements are taken into account.

[0032] The positions of the measuring sensors M1, M2, and M3 are shown in Figure 5. As can be seen in Figure 5, in this example, the Y direction denotes the horizontal direction transverse to the longitudinal direction of the molten material nozzles S1-S14. Thus, the thermal expansion, which causes displacement in the Y direction, alters the distances between the adjacent nozzles S1-S14, as well as between the measuring sensors M1, M2, and M3, which, in this example, are as shown in Figure 5. It should also be noted that changes in the distances between the measuring sensors in the Y direction (i.e., ΔY1, ΔY2, ΔY3) also affect the calculation of displacements in the X and Z directions, since these distances are also used in the calculation of rotation with respect to the Z and X axes.

[0033] The altered distances between the measuring sensors in the Y direction can be calculated for nozzles S1-S7 as follows: where: M1'(Y) is the altered Y coordinate of sensor M1; M2'(Y) is the altered Y coordinate of the measuring sensor M2; M1(Y) is the original Y coordinate of the measuring sensor M1; M2(Y) is the original Y coordinate of the measuring sensor M2; ΔY is the displacement of the measuring sensor M1 in the Y direction; ΔY2 is the displacement of the measuring sensor M2 in the Y direction; and M12'dist is the distance changed between the measuring sensors M1 and M2,

[0034] and for the molten material spouts S8-S14: M1'(Y) = M1(Y) + ΔΥ1 (9) M2'(Y) = M1(Y) + ΔΥ2 (10) Petition 870250085824, dated 09 / 23 / 2025, p. 20 / 45 14 / 18 M23'dist = ABS(M1'(Y) - M2'(Y)) (11) where: M3'(Y) is the altered Y coordinate of the measuring sensor M3; M3(Y) is the original Y coordinate of the measuring sensor M3; ΔY3 is the displacement of sensor M3 in the Y direction; and M23'dist is the distance changed between the measuring sensors M2 and M3.

[0035] Thus, if the thermal expansion is considered to be uniform in the Y direction, the displacements of the molten material spouts S1-S14 in the Y direction can be calculated from the equations: Kçj . _ . ..... Y'sí = M12dist(y)X M12dÍSt(Y^, 1 = 1-7(11) K'sí =M23di^(y)X M23'dist(Y), i = 8...14 (12) ΔΥ& = Y'si-Ysi, i = 1 ... 14(13) where: Y'si is the Y coordinate of the spout of molten material Si after thermal expansion has occurred; and Ysi is the Y coordinate of the molten material spout Si before thermal expansion occurs.

[0036] The wall of recovery boiler 12 can also twist about the Z-axis, which causes the degree of displacement that occurs in the adjacent molten material nozzles in the X direction to vary. Figure 6 shows a situation in which the displacements in the X direction, ΔΧ1, ΔΧ2 and ΔΧ3, of the measuring sensors M1, M2 and M3 in Figure 6 are not equal. In this case, the wall has twisted about the Z-axis and the displacement due to thermal expansion for each molten material nozzle S1-S14 must be calculated separately.

[0037] In the region of nozzles S1-S7, the wall rotation angle A1 can be calculated from the equation: A1 = arctan (ΔΧ1-ΔΧ2') M12 ' dist(Y) (14) where: Petition 870250085824, dated 09 / 23 / 2025, page 21 / 45 15 / 18 ΔΧ1 is the displacement of the measuring sensor M1 in the X direction; ΔΧ2 is the displacement of the measuring sensor M2 in the X direction; and M12'dist(Y) is the distance between the sensors in the Y direction after the displacement occurs.

[0038] Respectively, in the region of the spouts of molten material S8-S14, the rotation angle A2 can be calculated from the equation: A2 = arctan (ΔΧ2-ΔΧ3) M23fdist(Y') (15) where: ΔΧ3 is the displacement of the measuring sensor M3 in the X direction; and M23'dist(Y) is the distance between the sensors in the Y direction after the thermal expansion occurs.

[0039] When the rotation angles A1 and A2 are known, the displacements of each nozzle S1...S14 in the X direction can be calculated from the equations: ΔXsi = ΔX2 + tan A1 · Ysi (i = 1.7) (16) ΔXsi = ΔX2 + tan A2 · Ysi (i = 8 .14) (17) where: ΔXsi is the displacement of the molten material spout Si caused by the rotation of the recovery boiler wall 12 with respect to the X-axis; and Ysi is the distance of the molten material spout Si in the Y direction from the origin of the universal coordinate system 20.

[0040] The wall of recovery boiler 12 may also twist about the X-axis, which causes the degree of displacement that occurs in the adjacent spouts in the Z direction to vary. Figure 7 shows a situation where the displacements in the Z direction, ΔZ1, ΔZ2 and ΔZ3, of the measuring sensors M1, M2 and M3 in Figure 7 are not equal. In this case, the wall has twisted about the X-axis, and the displacement in the Z direction for each molten material spout S1-S14 must be calculated separately. Petition 870250085824, dated 09 / 23 / 2025, page 22 / 45 16 / 18

[0041] In the region of the spouts of molten material S1-S7, the angle of rotation C1 of the wall with respect to the X axis can be calculated from the equation: C1 = arctan (ΔZ1-ΔZ2) M12rdist(Y') (18) where: ΔΧ1 is the displacement of the measuring sensor M1 in the X direction; ΔΧ2 is the displacement of the measuring sensor M2 in the X direction; and M12'dist(Y) is the distance between the sensors in the Y direction after thermal expansion has occurred.

[0042] Respectively, in the region of the spouts of molten material S8-S14, the rotation angle A2 can be calculated from the equation: C2 = arctan (ΔZ1-ΔZ2} M23rdist(Y') (19) where: ΔZ3 is the displacement of the measuring sensor M3 in the X direction; and M23'dist(Y) is the distance between the sensors in the Y direction.

[0043] When the rotation angles C1 and C2 are known, the displacements in the Z direction of each molten material spout S1...S14 can be calculated from the equations: ΔZsi = ΔΖ2 + tan C1 · Ysi, when i = 1 .7 (20) ΔZsi = ΔZ2 + tan C2 · Ysi, when i = 8 .14 (21) where: ΔZsi is the displacement of a spout of molten material Si in the Z direction caused by the rotation of the wall about the X axis; and Ysi is the distance of a spout of molten material Si in the Y direction from the origin of the universal coordinate system 20.

[0044] Thus, using these equations, the displacements ΔXSi, ΔYSi, and ΔZSi of each molten material spout S1-S14 can be calculated in the directions of the three coordinate axes X, Y, and Z. In this way, the positions and orientation of the corrected base coordinate systems 22 (i.e., coordinate systems of Petition 870250085824, dated 09 / 23 / 2025, page 23 / 45 17 / 18 work), which, in this example, coincide with the spouts of molten material Si, can be determined in the universal coordinate system 20, by adding to the coordinates of the respective initial base coordinate systems 21 the respective displacement in each direction (i.e., ΔXSi, ΔYSi and ΔZSi) and considering the angles of the coordinate axes (i.e., the angles A1, A2, C1 and C2).

[0045] Therefore, by applying the corrected base coordinate systems 22 determined in the manner described above, the robots R1 .,.R5 can be controlled to perform the cleaning movements of the cleaning tools of the molten material spouts 13 in such a way that all the effects of thermal expansion are compensated and the uncertainty of the control caused by thermal expansion can be avoided.

[0046] Undoubtedly, the method of controlling a device for maintenance operation, according to the invention, can be performed in several different ways, differing from the example described above. For example, the positions of each initial base coordinate system can be selected differently, which also has an effect on the corrected base coordinate systems. In the case of different maintenance objects to be maintained, the control method can be adapted according to their characteristics.For example, in the case of inspecting a hatch, the initial base coordinate system can be positioned at one of its corners or another suitable position, preferably in a position where its determination using the respective device for moving maintenance tools (e.g., a robot) can be done reproducibly (i.e., including some physical point of discontinuity against which the maintenance tool can be moved using the device for moving tools).

[0047] Consequently, the invention is not limited to Petition 870250085824, dated 09 / 23 / 2025, page 24 / 45 18 / 18 implementations described above, but may vary within the scope of the attached claims. Petition 870250085824, dated 09 / 23 / 2025, page 25 / 45

Claims

1 / 6 CLAIMS 1. A method for controlling an apparatus for maintenance operation (10) of a recovery boiler (11) to conduct the maintenance operation of at least one maintenance object (S1-S14) in a recovery boiler (11), wherein the apparatus for maintenance operation (10) comprises a maintenance tool (13) and a tool moving device (R1-R5) to move the maintenance tool (13) to perform the maintenance operation, characterized in that it comprises the method steps of: a) defining a position of a fixed universal coordinate system (20) in the recovery boiler (11); b) defining a position of an initial base coordinate system (21) of at least one maintenance object (S1-S14), which is located at a selected point of at least one maintenance object (S1-S14), determined in the fixed universal coordinate system (20) at an initial temperature of the recovery boiler (11);c) define a position of a corrected base coordinate system (22) of at least one maintenance object (S1-S14) that is located at the selected point of at least one maintenance object (S1-S14), determined in the fixed universal coordinate system (20), at a transition temperature of the recovery boiler (11); and d) control the tool moving device (R1R5) to conduct the maintenance operation of at least one maintenance object (S1-S14) in the corrected base coordinate system (22).

2. Method according to claim 1, characterized in that the position of the corrected base coordinate system (22) is determined by the tool moving device (R1 Petition 870250085824, dated 09 / 23 / 2025, page 26 / 45 2 / 6 R5) by controlling the tool moving device (R1-R5), to move the maintenance tool (13) to the position of the selected point on at least one maintenance object (S1-S14), at a transition temperature, and by recording the coordinates of the selected point in the fixed universal coordinate system (20).

3. Method, according to claim 1 or 2, characterized in that the position of the corrected basis coordinate system (22) is determined, at least in part, by calculating the displacement of the initial basis coordinate system (21), caused by the thermal expansion of a wall of the recovery boiler (12) due to the temperature transition.

4. Method, according to any of the preceding claims, characterized in that at least the fixed universal coordinate system (20) is a three-dimensional Cartesian coordinate system, and the determination of the position coordinates of the corrected basis coordinate system is calculated using the following equations: X' = X + ΔΧ Y' = Y + ΔΥ Z' = Z + ΔΖ wherein: the coordinates X', Y', Z' are position coordinates of the corrected basis coordinate system (22) in the fixed universal coordinate system (20); the coordinates X, Y, Z are position coordinates of the initial basis coordinate system (21) in the fixed universal coordinate system (20); and ΔΧ, ΔΥ, ΔΖ are displacements of the position coordinates of the initial basis coordinate system (21), due to thermal expansion, in the fixed universal coordinate system (20). Petition 870250085824, dated 09 / 23 / 2025, page 27 / 45 3 / 6 5. Method according to claim 4, characterized in that it comprises controlling the maintenance operation of at least two maintenance objects (S1-S14), arranged adjacent to each other in the recovery boiler (11).

6. Method, according to claim 5, characterized in that the Y-axis denotes the direction along a line between at least two adjacent maintenance objects (S1-S14), the X-axis denotes the direction perpendicular to the Y-axis, which is in the same plane as the X-axis, and the Z-axis denotes the direction perpendicular to the plane defined by the X and Y axes.

7. Method, according to any one of claims 4 to 6, characterized in that the displacements of the position coordinates ΔΧ, ΔΥ, ΔΖ include the rotation of the coordinate axes of the initial base coordinate system (21) due to the rotation of the recovery boiler wall (12), caused by thermal expansion.

8. Method according to claim 7, characterized in that the rotation angles A and C of the coordinate axes of the initial basis coordinate system (21), due to the rotation of the recovery boiler wall (12) caused by thermal expansion, are determined by the equations: A = arctan (ΔΧ2-ΔΧι) / (Υ2-Υι) C = arctan (ΔΖ2-ΔΖ1 / (Υ2-Υι), wherein: A is a rotation angle of the Y-axis with respect to the X-axis; C is the rotation angle of the Y-axis with respect to the Z-axis; Yi is a first Y-position; Y2 is a second Y-position; ΔΧ1 is the displacement in the X-direction that occurs at position Y1; Petition 870250085824, dated 23 / 09 / 2025, page 28 / 45 4 / 6 ΔΧ2 is the displacement in the X-direction that occurs at position Y2; ΔZ1 is the displacement in the Z direction that occurs at position Y1; and ΔZ2 is the displacement in the Z direction that occurs at position Y2.

9. Method, according to any one of claims 5 to 8, characterized in that an initial basis coordinate system (21) and a corrected basis coordinate system (22), for each of at least two maintenance objects (S1-S14), are determined.

10. Method, according to any one of claims 5 to 9, characterized in that the tool moving device (R1-R5) is controlled to conduct the maintenance operation for each of at least two maintenance objects (S1-S14), in their respective corrected base coordinate system (22).

11. Method, according to any of the preceding claims, characterized in that the displacement that occurs in the recovery boiler (11), caused by the temperature transition, is measured by at least one displacement measuring sensor (M1-M3), placed in a known position in the recovery boiler (11).

12. Method according to claim 11, characterized in that the measurement results of at least one displacement measurement sensor (M1-M3) are used in determining the displacement of the initial base coordinate system position (21) to determine the corrected base coordinate system position (22).

13. Method according to claim 11 or 12, characterized in that at least two displacement sensors Petition 870250085824, dated 09 / 23 / 2025, page 29 / 45 5 / 6 (M1-M3), placed in at least two different positions, are used to determine the displacements that occur in at least two different positions in the recovery boiler (11).

14. Method, according to claim 13, characterized in that the rotation of the initial base coordinate system (21), due to the variation of the displacement at different positions in the recovery boiler (11), is determined based on the displacements measured at at least two different positions.

15. Method, according to any of the preceding claims, characterized in that the maintenance operation is at least one of the following operations: cleaning of molten material nozzle; cleaning of liquor gun opening or cleaning of inspection hatch opening, and wherein the maintenance tool is, respectively, one of the following tools: molten material nozzle cleaning tool (13); cleaning tool for liquor gun opening or cleaning tool for inspection hatch opening.

16. Maintenance operation apparatus (10) for conducting at least one maintenance operation for at least one maintenance object (S1-S14) on the recovery boiler wall (12), characterized in that the apparatus comprises a maintenance tool (13) and a tool moving device (R1-R5) for moving the maintenance tool (13) to perform the maintenance operation, and in that the maintenance operation apparatus (10) comprises a control device for controlling the maintenance operation apparatus (10), according to the method as defined in any one of claims 1 to 15.

17. Maintenance operation apparatus (10), according to claim 16, characterized in that the tool-moving device (R1-R5) is an articulated industrial robot. Petition 870250085824, dated 23 / 09 / 2025, p. 30 / 45 6 / 6 18. Maintenance operation apparatus (10), according to any one of claims 16 or 17, characterized in that the maintenance operation apparatus (10) comprises at least one displacement measuring sensor (M1-M3), for measuring the displacement that occurs in the recovery boiler (11). Petition 870250085824, dated 23 / 09 / 2025, pp. 31 / 45

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