Fine grinding device and method for coarse fly ash

Abstract

The invention discloses a fine grinding device and method for coarse fly ash, and relates to the technical field of industrial engineering and environmental protection. The coarse fly ash grinding device comprises pretreatment mechanisms, material conveying mechanisms, a grinding mechanism and a material receiving mechanism, and is characterized in that the material conveying mechanisms are located on the two sides of the grinding mechanism, the pretreatment mechanisms are located at inlets of the material conveying mechanisms, the material receiving mechanism is located at outlets of the material conveying mechanisms, the pretreatment mechanisms comprise feeding boxes, and the feeding boxes are connected with the conveying mechanisms. Crushing rollers are movably mounted on the two sides of an inner cavity of the feeding box correspondingly. According to the coarse fly ash grinding device and method, through the arrangement of the pretreatment mechanism, the problem that large particle caking possibly exists in coarse fly ash is solved, fly ash enters the whole system from the feeding box, crushing rollers are located on the two sides of an inner cavity of the feeding box, and crisscrossed friction blocks are arranged on the surfaces of the crushing rollers on the two sides; and large fly ash blocks can be crushed through rotary motion.

Description

Technical Field

[0001] The invention relates to the technical field of industrial engineering and environmental protection, and in particular to a fly ash coarse ash grinding device and method. Background Art

[0002] Fly ash is the fine ash discharged from coal-fired power plants. It is an industrial solid waste. However, through proper treatment, fly ash can be reused as building materials, soil conditioners, etc. In order to improve the application value of fly ash and broaden its application range, grinding the coarse ash is an important processing step.

[0003] However, the existing grinding devices usually grind the coarse ash directly by means of spiral blade crushing or ball friction crushing, lack of fly ash pretreatment process, and the processing process is relatively rough. Some coarse fly ash may contain large particle lumps with high hardness, which may cause damage to the blade body when directly colliding with the spiral blade, thereby affecting the service life of the entire device. On the other hand, the ground fly ash is prone to cause a lot of dust when discharged, which is easy to cause damage to the lungs of workers after a long time. The existing grinding devices lack effective dust prevention capabilities and have certain usage defects. Summary of the invention

[0004] In view of the deficiencies of the prior art, the present invention provides a fly ash coarse ash grinding device and method, which solves the problem of lack of fly ash pretreatment process and dust prevention ability in the prior art.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: a fly ash coarse ash grinding device and method, comprising a pretreatment mechanism, a feeding mechanism, a grinding mechanism and a receiving mechanism, characterized in that: the feeding mechanism is located on both sides of the grinding mechanism, the pretreatment mechanism is at the entrance of the feeding mechanism, and the receiving mechanism is at the exit of the feeding mechanism, the pretreatment mechanism comprises a feeding box, both sides of the inner cavity of the feeding box are movably mounted with crushing rollers, the outer side of one side of the crushing roller is movably connected with a first drive motor, the first drive motor is fixedly connected to the feeding box, and the other end of the crushing roller is fixedly mounted with a transmission gear; the receiving mechanism comprises a feeding pipe, a sealing box is fixedly mounted at the bottom of the feeding pipe, a vacuum pump is fixedly mounted on the back of the sealing box, a storage draw plate is movably mounted on the inner side of the sealing box, a textile filter plate is fixedly mounted on the inner side of the storage draw plate corresponding to the vacuum pump output port, a limit plate is fixedly mounted on the outer side of the storage draw plate, and a handle is fixedly mounted on the outer side of the limit plate.

[0006] Furthermore, the material transmission mechanism includes a feed transmission pipe and a discharge transmission pipe, and the inner sides of the feed transmission pipe and the discharge transmission pipe are both provided with Jiaolong transmission rods, and the Jiaolong transmission rods are driven by a built-in motor.

[0007] Furthermore, the feed transfer pipe is fixedly connected to the bottom of the feed box, and a discharge pipe is fixedly installed on the bottom surface of the discharge transfer pipe, and the discharge pipe is bolted to the feed pipe.

[0008] Furthermore, the grinding mechanism includes a processing cylinder, side guard plates are bolted on both sides of the processing cylinder, grinding steel balls are arranged in the inner cavity of the processing cylinder, a material receiving pipe is fixedly installed on the outer side of the side guard plate, and a gear ring is fixedly installed on the surface of the processing cylinder.

[0009] Furthermore, a driving wheel is meshingly connected to one side of the gear ring, a second driving motor is movably connected to the outer side of the driving wheel, and a bottom plate is fixedly installed at the bottom of the second driving motor.

[0010] Furthermore, a bearing sealing ring is provided at the connection between the material receiving pipe and the material transmission mechanism, a support plate is fixedly installed on the outer side of the bearing sealing ring, and the support plate is fixedly connected to the bottom plate.

[0011] Furthermore, a control panel is fixedly mounted on the surface of the bottom plate and located on one side of the second driving motor, and operation buttons are arranged on the surface of the control panel.

[0012] Furthermore, a support frame is fixedly installed at the bottom of the pretreatment mechanism, and a balancing pad is fixedly installed at the bottom of the support frame.

[0013] Furthermore, fixing plates are fixedly installed on both sides of the bottom of the support plate, and limiting holes are provided on the surfaces of the fixing plates.

[0014] S1: Start the pretreatment mechanism, press the corresponding operation button on the control panel, start the first drive motor, make the crushing roller start to rotate, add the fly ash coarse ash to be processed into the system through the feed box, at this time, the crushing roller will initially crush the larger particles.

[0015] S2: Start the material conveying mechanism, start the built-in motors in the feed pipe and the discharge pipe respectively, and drive the Jiaolong transmission rod to operate, so as to realize the smooth transportation of materials from the pretreatment mechanism to the grinding mechanism. According to actual needs, appropriately adjust the speed of the Jiaolong transmission rod to ensure that the material can enter the grinding mechanism evenly and continuously.

[0016] S3: Start the grinding mechanism, press the corresponding button on the control panel, start the second drive motor, and through the meshing transmission of the driving wheel and the gear ring, the grinding steel balls in the processing cylinder begin to grind the fly ash efficiently. Use the control panel to monitor the working status of the grinding mechanism in real time, including parameters such as temperature and speed, to ensure stable operation and achieve the expected grinding effect.

[0017] S4: Start the material collecting mechanism. After the grinding is completed, turn on the vacuum pump to maintain the negative pressure environment in the sealed box to prevent dust leakage. The clean air filtered by the textile filter plate is discharged, and the ground fly ash is stored in the storage drawer. When the storage drawer is full, it can be drawn out through the handle for subsequent processing or packaging.

[0018] The present invention has the following beneficial effects: 1. The fly ash coarse ash grinding device and method, through the setting of the pretreatment mechanism, is intended to solve the problem of large particle agglomeration that may exist in the coarse fly ash. The fly ash enters the whole system from the feed box, and the crushing rollers are located on both sides of the inner cavity of the feed box. The surfaces of the crushing rollers on both sides are provided with criss-cross friction blocks, which can crush large pieces of fly ash through rotational motion. The transmission gear is installed at one end of the crushing roller and is connected to the first drive motor to transmit power and ensure the synchronous operation between the two crushing rollers. In summary, the pretreatment mechanism can effectively pre-treat the fly ash before it enters the main grinding process, thereby reducing the potential damage of hard particles to subsequent equipment.

[0019] 2. The fly ash coarse ash grinding device and method can be specially designed to solve the problem of dust easily generated when the ground fly ash is discharged through the setting of the collecting mechanism. The feed pipe is connected to the material flow coming out of the grinding mechanism to guide the ground fly ash into a sealed box. The sealed box is a closed space to prevent the material from leaking into the external environment during the collection process. The vacuum pump maintains an internal negative pressure state through suction to further prevent dust from escaping. The storage drawer plate is used to temporarily store the ground fly ash. It can be drawn out or inserted as needed to facilitate the operator to clean or replace it. The textile filter plate is fixed on the inner side of the storage drawer plate and corresponds to the vacuum pump output port to filter the suspended particles in the air to ensure that only clean air is discharged out of the system. In summary, the collecting mechanism effectively solves the dust problem when the ground fly ash is discharged by adopting measures such as sealing, negative pressure and high-efficiency filtration, and provides safer and more environmentally friendly working conditions.

[0020] 3. The fly ash coarse ash grinding device and method, through the setting of the material conveying mechanism, is responsible for transferring the pretreated fly ash from the feed box to the grinding mechanism, and after the grinding is completed, the finished fly ash is sent to the receiving mechanism, which ensures the smooth transition of materials between different processes and avoids dust leakage.

[0021] 4. The fly ash coarse ash grinding device and method can further grind the fly ash through the setting of the grinding mechanism. It uses the mechanical force generated by the grinding steel balls falling up and down in the processing cylinder and the friction between each other to finely grind the fly ash until the required particle size is reached. This process determines the quality of the final product.

[0022] 5. The fly ash coarse ash grinding device and method integrates all necessary operation buttons through the setting of the control panel, allowing the user to easily start, stop and adjust the working status of each part. At the same time, it can also display important operating parameters such as temperature, pressure, etc., to help operators understand the equipment status in a timely manner.

[0023] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a front view stereoscopic schematic diagram of the overall structure of the present invention; Figure 2 It is a back perspective schematic diagram of the overall structure of the present invention; Figure 3 It is a partially enlarged three-dimensional schematic diagram of the pretreatment mechanism and the feed transfer pipe structure of the present invention; Figure 4 It is a partially enlarged three-dimensional schematic diagram of the connection between the grinding mechanism and the second driving motor structure of the present invention; Figure 5 It is a partially enlarged stereoscopic schematic diagram of the bearing sealing ring structure of the present invention; Figure 6 It is a partially enlarged three-dimensional schematic diagram of the cross-section of the grinding mechanism structure of the present invention; Figure 7 It is a partially enlarged three-dimensional schematic diagram of the material discharging transfer pipe and the material receiving mechanism structure of the present invention; Figure 8 It is a partially enlarged three-dimensional schematic diagram of the crushing roller structure of the present invention; Fig. 9 It is a partially enlarged three-dimensional schematic diagram of the material receiving mechanism structure of the present invention.

[0025] In the figure, 1, pre-treatment mechanism; 101, feed box; 102, crushing roller; 103, first driving motor; 104, transmission gear; 2, material transmission mechanism; 201, feed transmission pipe; 202, discharge transmission pipe; 203, Jiaolong transmission rod; 204, feed pipe; 3, grinding mechanism; 301, processing cylinder; 302, side guard plate; 303, grinding steel ball; 304, receiving pipe; 305, gear ring; 4, receiving Feeding mechanism; 401, feeding pipe; 402, sealing box; 403, vacuum pump; 404, material storage drawer plate; 405, spinning filter plate; 406, limit plate; 407, handle; 5, driving wheel; 6, second driving motor; 7, bottom plate; 8, bearing sealing ring; 9, support plate; 10, control panel; 11, operation button; 12, support frame; 13, balance pad; 14, fixing plate; 15, limit hole. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In the description of the present invention, it should be understood that the terms "opening", "upper", "lower", "thickness", "top", "middle", "length", "inside", "all around" and the like indicating orientation or positional relationship are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the components or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0028] See also Figure 1-Figure 9 The embodiment of the present invention provides a technical solution: a fly ash coarse ash grinding device and method, comprising a pretreatment mechanism 1, a feeding mechanism 2, a grinding mechanism 3 and a receiving mechanism 4, characterized in that: the feeding mechanism 2 is located on both sides of the grinding mechanism 3, the pretreatment mechanism 1 is at the entrance of the feeding mechanism 2, and the receiving mechanism 4 is at the exit of the feeding mechanism 2, the pretreatment mechanism 1 includes a feed box 101, both sides of the inner cavity of the feed box 101 are movably installed with crushing rollers 102, the outer side of one side of the crushing roller 102 is movably connected with a first drive motor 103, and the first drive motor 103 is connected to the The feed box 101 is fixedly connected, and the other end of the crushing roller 102 is fixedly installed with a transmission gear 104; the material receiving mechanism 4 includes a feed pipe 401, a sealing box 402 is fixedly installed at the bottom of the feed pipe 401, a vacuum pump 403 is fixedly installed on the back of the sealing box 402, a storage drawer 404 is movably installed on the inner side of the sealing box 402, a textile filter plate 405 is fixedly installed on the inner side of the storage drawer 404 at a position corresponding to the output port of the vacuum pump 403, a limit plate 406 is fixedly installed on the outer side of the storage drawer 404, and a handle 407 is fixedly installed on the outer side of the limit plate 406.

[0029] Specifically, the material transfer mechanism 2 includes a feed transfer pipe 201 and a discharge transfer pipe 202. The inner sides of the feed transfer pipe 201 and the discharge transfer pipe 202 are both provided with a Jiaolong transfer rod 203, and the Jiaolong transfer rod 203 is driven by a built-in motor.

[0030] In this embodiment, through the setting of the discharge transfer pipe 202, the finished fly ash can be sent to the receiving mechanism 4 after the grinding is completed to ensure the smooth discharge of the material. Through the setting of the dragon transmission rod 203, the material can be pushed forward by the rotation movement, and the material transmission rate can be flexibly adjusted according to actual needs.

[0031] Specifically, the feed transfer pipe 201 is fixedly connected to the bottom of the feed box 101 , and a discharge pipe 204 is fixedly installed on the bottom surface of the discharge transfer pipe 202 , and the discharge pipe 204 is bolted to the feed pipe 401 .

[0032] In this embodiment, the feeding pipe 204 can be bolted to the feeding pipe 401 of the material receiving mechanism 4 to form a closed material channel to prevent dust.

[0033] Specifically, the grinding mechanism 3 includes a processing cylinder 301, side guard plates 302 are bolted on both sides of the processing cylinder 301, the inner cavity of the processing cylinder 301 is provided with grinding steel balls 303, the outer side of the side guard plate 302 is fixedly installed with a material receiving pipe 304, and the surface of the processing cylinder 301 is fixedly installed with a gear ring 305.

[0034] In this embodiment, by setting the grinding steel balls 303, steel balls of suitable size and material can be selected to ensure the best grinding effect. By setting the material receiving pipe 304, the material discharged from the processing cylinder 301 can be received and guided to the material transmission mechanism 2. By setting the gear ring 305, it can engage with the driving wheel 5 to transmit the power from the second drive motor 6 to rotate the processing cylinder 301.

[0035] Specifically, a driving wheel 5 is meshedly connected to one side of the gear ring 305 , a second driving motor 6 is movably connected to the outer side of the driving wheel 5 , and a bottom plate 7 is fixedly installed at the bottom of the second driving motor 6 .

[0036] In this embodiment, the driving wheel 5 is configured to mesh with the gear ring 305 to transmit power from the second drive motor 6 to rotate the processing cylinder 301. The base plate 7 is configured to provide a stable installation foundation for the second drive motor 6 and other related components.

[0037] Specifically, a bearing sealing ring 8 is provided at the connection between the material receiving pipe 304 and the material transmission mechanism 2 , and a support plate 9 is fixedly installed on the outer side of the bearing sealing ring 8 , and the support plate 9 is fixedly connected to the bottom plate 7 .

[0038] In this embodiment, by setting the bearing sealing ring 8, good sealing performance can be provided at the connection between the material receiving pipe 304 and the material transmission mechanism 2, effectively preventing dust from leaking into the external environment. By setting the support plate 9, additional support can be provided for the bearing sealing ring 8 and other key components.

[0039] Specifically, a control panel 10 is fixedly mounted on the surface of the bottom plate 7 and located on one side of the second driving motor 6 , and an operation button 11 is disposed on the surface of the control panel 10 .

[0040] In this embodiment, through the setting of the control panel 10, all necessary operation buttons 11 can be integrated, allowing the user to easily start, stop and adjust the working status of each part.

[0041] Specifically, a support frame 12 is fixedly installed at the bottom of the pretreatment mechanism 1 , and a balancing pad 13 is fixedly installed at the bottom of the support frame 12 .

[0042] In this embodiment, by providing the support frame 12 and the balancing pad 13, a stable foundation can be provided for the pretreatment mechanism 1, vibration can be reduced, and the service life of the equipment can be extended.

[0043] Specifically, fixing plates 14 are fixedly installed on both sides of the bottom of the support plate 9 , and limiting holes 15 are provided on the surface of the fixing plates 14 .

[0044] In this embodiment, by providing the fixing plate 14 and the limiting holes 15 , key components in the grinding mechanism 3 , such as the supporting plate 9 , can be fixed and supported, thereby ensuring structural stability and safety.

[0045] When in use (working), first, start the pretreatment mechanism 1, press the corresponding operation button 11 on the control panel 10, start the first drive motor 103, make the crushing roller 102 start to rotate, and add the fly ash coarse ash to be processed into the system through the feed box 101. At this time, the crushing roller 102 will preliminarily crush the larger particles. Secondly, start the conveying mechanism 2, and start the built-in motors in the feed conveying pipe 201 and the discharge conveying pipe 202 respectively to drive the dragon conveying rod 203 to operate, so as to realize the smooth transportation of materials from the pretreatment mechanism 1 to the grinding mechanism 3. According to actual needs, the speed of the dragon conveying rod 203 is appropriately adjusted to ensure that the materials can enter the grinding mechanism 3 evenly and continuously. Then, start the grinding mechanism 3, press the control panel 10, start the second drive motor 6, through the meshing transmission of the driving wheel 5 and the gear ring 305, the grinding steel ball 303 in the processing cylinder 301 starts to grind the fly ash efficiently, and use the control panel 10 to monitor the working status of the grinding mechanism 3 in real time, including parameters such as temperature and speed, to ensure stable operation and achieve the expected grinding effect. Finally, start the collecting mechanism 4. After the grinding is completed, turn on the vacuum pump 403 to maintain the negative pressure environment in the sealing box 402 to prevent dust leakage. The clean air filtered by the spinning filter plate 405 is discharged, and the ground fly ash is stored in the storage drawer 404. When the storage drawer 404 is full, it can be drawn out through the handle 407 for subsequent processing or packaging.

[0046] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0047] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A fly ash coarse ash grinding device and method, comprising a pretreatment mechanism (1), a material conveying mechanism (2), a grinding mechanism (3) and a material receiving mechanism (4), characterized in that: The material conveying mechanism (2) is located on both sides of the grinding mechanism (3), the pretreatment mechanism (1) is located at the entrance of the material conveying mechanism (2), and the material receiving mechanism (4) is located at the exit of the material conveying mechanism (2). The pretreatment mechanism (1) comprises a feed box (101), and crushing rollers (102) are movably installed on both sides of the inner cavity of the feed box (101), and the outer side of one side of the crushing roller (102) is movably connected to a first drive motor (103), and the first drive motor (103) is fixedly connected to the feed box (101). The other end of the crushing roller (102) is fixedly installed with a transmission gear (104); The material receiving mechanism (4) comprises a feeding pipe (401), a sealing box (402) is fixedly installed at the bottom of the feeding pipe (401), a vacuum pump (403) is fixedly installed on the back of the sealing box (402), a material storage drawer (404) is movably installed on the inner side of the sealing box (402), a spinning filter plate (405) is fixedly installed on the inner side of the material storage drawer (404) at a position corresponding to the output port of the vacuum pump (403), a limiting plate (406) is fixedly installed on the outer side of the material storage drawer (404), and a handle (407) is fixedly installed on the outer side of the limiting plate (406).

2. A fly ash coarse ash grinding device and method according to claim 1, characterized in that: The material transfer mechanism (2) comprises a feed transfer pipe (201) and a discharge transfer pipe (202), and a Jiaolong transmission rod (203) is arranged inside the feed transfer pipe (201) and the discharge transfer pipe (202), and the Jiaolong transmission rod (203) is driven by a built-in motor.

3. A fly ash coarse ash grinding device and method according to claim 2, characterized in that: The feed transfer pipe (201) is fixedly connected to the bottom of the feed box (101), and a discharge pipe (204) is fixedly installed on the bottom surface of the discharge transfer pipe (202), and the discharge pipe (204) is bolted to the feed pipe (401).

4. The fly ash coarse ash grinding device and method according to claim 1, characterized in that: The grinding mechanism (3) comprises a processing cylinder (301), side guard plates (302) are bolted on both sides of the processing cylinder (301), a grinding steel ball (303) is arranged in the inner cavity of the processing cylinder (301), a material receiving pipe (304) is fixedly installed on the outer side of the side guard plate (302), and a gear ring (305) is fixedly installed on the surface of the processing cylinder (301).

5. A fly ash coarse ash grinding device and method according to claim 4, characterized in that: A driving wheel (5) is meshingly connected to one side of the gear ring (305), a second driving motor (6) is movably connected to the outer side of the driving wheel (5), and a bottom plate (7) is fixedly mounted on the bottom of the second driving motor (6).

6. A fly ash coarse ash grinding device and method according to claim 4, characterized in that: A bearing sealing ring (8) is provided at the connection between the material receiving pipe (304) and the material transmission mechanism (2), a support plate (9) is fixedly installed on the outer side of the bearing sealing ring (8), and the support plate (9) is fixedly connected to the bottom plate (7).

7. The fly ash coarse ash grinding device and method according to claim 5, characterized in that: A control panel (10) is fixedly mounted on the surface of the bottom plate (7) and located on one side of the second drive motor (6), and an operating button (11) is arranged on the surface of the control panel (10).

8. The fly ash coarse ash grinding device and method according to claim 1, characterized in that: A support frame (12) is fixedly mounted on the bottom of the pretreatment mechanism (1), and a balancing pad (13) is fixedly mounted on the bottom of the support frame (12).

9. The fly ash coarse ash grinding device and method according to claim 6, characterized in that: Fixed plates (14) are fixedly mounted on both sides of the bottom of the support plate (9), and limiting holes (15) are provided on the surface of the fixed plates (14).

10. S1: Start the pre-treatment mechanism (1), press the corresponding operation button (11) on the control panel (10), start the first drive motor (103), make the crushing roller (102) start to rotate, add the fly ash coarse ash to be processed into the system through the feed box (101), at this time, the crushing roller (102) will initially crush the larger particles; S2: starting the material conveying mechanism (2), respectively starting the built-in motors in the feed conveying pipe (201) and the discharge conveying pipe (202), driving the Jiaolong conveying rod (203) to operate, so as to realize the smooth conveyance of the material from the pretreatment mechanism (1) to the grinding mechanism (3), and appropriately adjusting the speed of the Jiaolong conveying rod (203) according to actual needs, so as to ensure that the material can enter the grinding mechanism (3) evenly and continuously; S3: starting the grinding mechanism (3), pressing the corresponding button on the control panel (10), starting the second driving motor (6), and through the meshing transmission of the driving wheel (5) and the gear ring (305), the grinding steel balls (303) in the processing cylinder (301) begin to grind the fly ash efficiently, and using the control panel (10) to monitor the working state of the grinding mechanism (3) in real time, including parameters such as temperature and rotation speed, to ensure stable operation and achieve the expected grinding effect; S4: Start the material collecting mechanism (4). After the grinding is completed, turn on the vacuum pump (403) to maintain the negative pressure environment in the sealed box (402) to prevent dust leakage. The clean air filtered by the textile filter plate (405) is discharged, and the ground fly ash is stored in the storage drawer (404). When the storage drawer (404) is full, it can be drawn out through the handle (407) for subsequent processing or packaging.

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