CZ9804361A3 - Linear scanning system for detection of hot places - Google Patents

Abstract

The rotary air preheater (10) has a linear sensing system (38) for detecting hot spots. This linear sensing system (38) has a linear assembly for hot spot detection (44) rails generally extending from the center to the edges of the rotor space (14). The rail assembly (44) preferably carries two carriages assemblies (54) for linear movement of these carriage assemblies (54) after this rail assembly. On the outside wall of the preheater (10) a drive mechanism (58) disposed therein is provided moves back and forth trolleys between the center section and the rim part of the rotor space (14). Each carriage assembly (54) carries a single infrared sensor head assembly (66) detection of hot spots on the rotor (14) preheaters (10) air. The linear relative movement of the two carriages leads to complete coverage of rotary rotor (14) preheaters (10) air to detect hot spots.

Description

Linear sensing system for hot spot detection

Technical field

The invention relates to the detection of hot spots in rotary regenerative air preheaters. In particular, the invention relates to a sensing mechanism for improved hot spot detection.

BACKGROUND OF THE INVENTION

Rotary regenerative air preheaters are typically used to transfer heat from the flue gases present in the furnace to the incoming combustion air. In these air preheaters, a fire occurs, most often during cold start or during the following hot reserve. Fires ignite due to poor combustion of fuel resulting in unburned or partially burned fuel in the flue gas, which condenses or is deposited on the elements of the air preheater. If the temperatures entering the air preheater increase, the deposits are sintered to form hard lacquered materials. This sintering occurs at a temperature in the range of 205 to 260 ° C, and the deposits may ignite if the temperature rises to a temperature in the range of 315 to 370 ° C.

Ignition usually begins in small sediment areas, and the operator often has no idea that a fire has occurred. No external effects can be evident during the initial stages of ignition. Deposits typically limit the flow of gas or air so that some of the excess heat generated by the fire is dissipated. In addition, the subsequent mixing of fluids minimizes external effects and masks the existence of fire. Moreover, the heat generated is absorbed by the metal heat transfer elements located at the point of the fire. The actual temperature increase can be relatively slow. If hot spots can be detected early, hot spots may be detected. then the amount of water required to cool the air preheater elements having a temperature below the ignition temperature will not be excessive. However, in the absence of early detection of hot spots, the temperature rise of the surfaces of the air preheater elements will continue to rise until the metal itself can ignite. This can occur at a temperature of about 705 ° C, whereupon the temperatures can rise rapidly, ie within a few minutes, to 1650 ° C or more. The fire of the burning metal continues itself and large amounts of water are required to lower the temperature to a reasonable level. Other extinguishing agents other than water, such as carbon dioxide, are ineffective in these situations because they lack sufficient cooling effect.

In order to prevent the occurrence of fire, systems have been developed to detect overheated areas (hot spots) and trigger alarms. These detection systems preferably use infrared detectors or sensors due to their rapid response time and sensitivity to small changes in background temperature. The sensitivity of the infrared system is controllable, but can be set to trigger an alarm when hot spots are detected at a temperature higher than the flue gas inlet temperature, ie at a temperature in the range of 95-150 ° C.

Current hot spot detection systems typically include a plurality of infrared sensors to monitor hot spot on the air preheater rotor. These sensors are mounted to the sensor drive assembly for moving the sensors to measure temperature throughout the preheater rotor. The sensor drive assembly typically extends from the central portion of the air preheater to its outer edge. Most of the two to four equally spaced pivoting arms extend from said drive assembly. An infrared sensor is attached to each swivel arm for sensing hot spots. The desired number of swivel arms and sensors usually varies in proportion to the size of the preheater. Each swivel arm moves the transducer. • V - • tt · tt t · t · tt t · tttt ··Tttttttt ·· ·· along the appropriate arc path at 180 ° to completely cover the rotor radius. The sensor components and components of the sensor drive assembly, including the drive motor and passages of the sensor drive assembly, are typically mounted through the side of the cold end center section of the air preheater.

The desirable drive train, levers, joints, and swivel arms of the sensor drive assembly may occupy a considerable space within the air preheater. The space needed for conventional sensor drive assemblies can usually be hampered by various components, such as tubular reinforcement for air ducts. This interference results in a sensor offset from the air preheater elements less than the optimal offset. The closest distance between the sensors and the heating elements may be approximately 76.2 to 101.6 cm, depending on the height of the central portion to which the drive mechanism is attached.

In addition, the drive motor, the hoses and the passages for carrying and driving the sensors are arranged in the central section of the preheater. Placing these components in the middle section causes space-constrained operating conditions and associated problems in repairing the sensor drive assembly and sensor head.

Existing hot spot detection systems may have several operational drawbacks. Extensive arc movement of the sensors leads to unnecessary movement of the sensors across the rotor surface. In addition, a significant number of actuators, couplings, and rotary arms designed to move the sensors to provide complete rotor coverage can reduce the reliability of conventional hot spot detection systems.

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SUMMARY OF THE INVENTION The rail assembly is a linear movement of the rails. At on these air is

Briefly, the linear hot spot detection system has a linear rail assembly generally extending from the center to the edge of the rotor cavity. Preferably, the carriage assembly carries two drive assemblies for these carriage assemblies to the outer wall of the preheater, a drive mechanism that moves back and forth the carriages between the central portion and the peripheral portion of the rotor cavity. Each carriage assembly carries a mounting head with a single infrared sensor to detect hot spots on the air preheater rotor. The linear relative movement of the two carriages leads to complete coverage of the rotary rotor of the air preheater for hot spot detection.

The linear hot spot detection system of the invention requires only two sensor assemblies for hot spot detection in the full range of preheaters. Changing the length of the rail assembly allows the detection system to be used in preheaters of different sizes without the need for additional or different sensor assemblies or drive components. Said hot spot detection system simplifies the mechanical parts required and thus leads to a reduction in the cost of the detection system and an increase in the reliability of the detection system.

The drive motor, reduction gears, inlets for water, air and electrical connections and other components are located on the outside of the air preheater cover. This external arrangement of the components allows all maintenance of these components to be performed outside the air preheater, i.e. under better and safer working conditions. Thus, the maintenance and repair of the linear hot spot detection system is simplified.

Another advantage is that the sensor head ftft ftft ftft ftft ftft ftft ftft ftftftftft ftftftftftft ftftft closer to the preheater members due to the low profile of the drive assembly , which improves hot spot detection. The rail assembly and drive mechanism generally have a horizontal orientation within the preheater housing, causing a limited height for the hot spot detection system. Vertically oriented components, such as a drive assembly, are arranged outside the preheater housing.

Operationally, the reciprocal linear movement of the hot spot detection system limits the excessive movement of the sensor heads across the rotor surface as compared to conventional hot spot detection systems.

The present invention provides a hot spot detection system having improved hot spot detection.

Another object of the invention is a less complicated and more reliable hot spot detection system.

Yet another object of the invention is a hot spot detection system that can be maintained outside the air preheater.

Yet another object of the invention is a hot spot detection system that may be located closer to the air preheater members for improved hot spot detection.

Yet another object of the invention is a hot spot detection system requiring a reduced number of sensor heads to perform hot spot detection.

Yet another object of the invention is a hot spot detection system universally applicable to air preheaters of various diameters.

Overview of the drawings

The invention will be better understood by describing an exemplary example.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a cross-section of an air preheater using a linear hot spot detection system; Fig. 2 shows a top view of a linear hot spot detection system; Fig. 3 is a partial cross-sectional view of the linear hot spot detection system taken along line 3-3 of Fig. 2;

Giant. Fig. 4 is a side view of the linear hot spot detection system along line 4-4 of Fig. 2; Fig. 5 is a front view of the linear hot spot detection system along line 5-5 of Fig. 2; a view of the trolley, detector and rail along line 6-6 in Figure 2,

Giant. 7 is a top view of the gear assembly along line 7-7 of FIG. 5, and FIG. 8 is a top view of the inner end of the rail assembly of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, the rotary regenerative air preheater 10 includes a cylindrical housing 12 defining an internal space 13 of the preheater and an outer surface 21. Inside the housing 12 is rotatably mounted a rotor 14 that includes conventional heat exchange elements for heat transfer (see FIG. 1). This rotor 14 further has a shaft 18 for supporting and rotating the rotor 14. This shaft 18 extends through the hot end of the central section 31 and the cold end of the central section 33.

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444

Said housing further defines a flue gas inlet channel 20, a flue gas outlet channel 22, an air inlet channel 24, and an air outlet channel 26. Reinforcement 50 is provided across the inlet and outlet channels 20, 22, 24, 26 to reinforce the structural support of the housing 12 (see FIG. Fig. 2). Sector plates 28, 3.0 extend over the housing 12 and to the upper and lower sides of the rotor 14, which divide the preheater 10 into the air side 11 and the flue gas side 15. The arrows shown in FIG. 1 show the flow direction of the air and flue gas through the preheater 10. The hot flue gas flowing through the flue gas inlet passage 20 to the preheater 10 transfers heat to the air preheater members because the rotor 14 rotates continuously. These heated air preheater members are then rotated to the air side 11 of the preheater 10 in which heat is transferred to the combustion air stream entering the preheater through the air inlet duct 24.

A linear hot spot detection system 38 is located within the housing 12 at the air inlet duct 12 as shown in FIG. 1. This system 38 is preferably located below the rotor 14 at the air inlet duct 24 to detect hot spots on the air preheater rotor 14 . The hot spot detection system 38 generally extends between the center of the housing 12 and the edge of the housing. This system 38 comprises a linear rail assembly 44 extending generally radially and horizontally across the housing 12 at the air inlet duct 24. The inner end 46 of the rail assembly 44 is attached to the housing 12 generally near the center of the housing as seen in Figure 2. The outer end 48 of the rail assembly 44 is attached to the housing 12 at its edge. It should be noted that the hot spot detection system 38 may be located in any of the hot or hot spot input or output channels 20, 22, 24, 24.

Said rail assembly 44 has a pair of parallel and Φ Φ · Φ φ Φ φ φ φ Φ

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The spaced-apart linear rails 52 for supporting a pair of carriages 54 as shown in FIGS. 3 and 6. These rails 52 are secured to the housing 12 near the central section of the preheater. These rails 52 may further be supported by supports 49 attached to rails 52 and stiffeners 50. Each rail has a generally large I-shaped cross-section. Head 39 and foot 52 of each rail 52 define an outer rail gap 53 and an inner rail gap 55. On each rail 52 is a movable assembly of one carriage 54. The carriages 54 have carriage frames 36 whose cross-section has the shape of a large printing U, which frames extend along the entire length of the head 39 of the rail 52 and in front of the rail gaps 53, 55. pairs of flange wheel carriages 41 are rotatably mounted, the wheels in rolling engagement with the foot 40 of the rail 52 within the rail gaps 51, 55 of the rail 52. A pair of rollers 45 which are in rolling engagement with each other are also rotatably attached to each carriage frame 36. the inner surface of each foot 40 of the rail 52 to maintain the carriage of the frame 36 on the rail 52 for smooth rectilinear movement of the carriage frame on the rail. The rails 52 define a longitudinal axis A and a transverse axis B generally perpendicular to the longitudinal axis A. The hot spot detection system 38 is generally symmetrical along the longitudinal axis A.

The drive assembly 58 acts on the carriage 54 such that it carries out a linear reciprocating movement along the rail 52. The drive assembly 58 has one chain 57 extending along the inner gap 55 of each rail 52 and secured to each carriage frame 36 by a threaded adjustable chain connection 42/ both. This is evident from Fig. 6. In addition, a wire cable or rope 56 extending along the inner gap 55 of each rail 52 is attached to each carriage by a threaded adjustable cable connection 37 (see Fig. 6). Thus, the chain 57, the wire rope 56 and the carriages 54 define a continuous loop. A single chain 57, when driven, simultaneously acts on both carriages 54. 4 4 4 4 4 5 6 * Such that the carriages move on the rails 52 of the rail assembly 44 along the longitudinal axis A in opposite directions. 2a, in order to guide the wire rope 56 from the inner gap 55 of one rail 52 to the inner gap 55 of the other rail 52, a pair of pulley wheels 59 are rotatably mounted to the pulley 51 located at the inner end 46 of the rail assembly 44 as shown in FIG.

At the outer end 48 of the rail assembly 44, the chain 57 extends through the housing 12 and the drive assembly 58 generally attached to the outer surface 21 of the housing 12, before returning to the interior of the housing 12. Said drive assembly 58 has a pair of idler gears 61 for guiding the chain 57 in the internal gaps 55 of the rails 52. These idler gears are rotatably mounted to a sprocket housing 47 attached to the outer end 48 of the rail and housing assembly 44 as shown in Fig. 7. The tensioner 37 on the wire rope 56 is rotatably adjusted to maintain sufficient tension in the wire rope 56 and the chain 57, thus avoiding sagging and scrubbing the chain 57 and the wire rope 56 against the head 39 and the foot 40 of the rails 52 (see Fig. 6).

To move the chain 57 and hence the carriage 54 on the rail assembly 44, the chain 57 engages the rotary drive gear 63. The drive assembly 58 includes a reversing motor 60 that acts on the drive shaft 65 through the double reduction gear 62, which drives the drive gear 63 so that the gear performs an alternating rotary motion. Thus, the carriages 54 move in opposite straight directions, with one carriage 54 located at the inner end 46 of the rail assembly 44, the other carriage 54 being located at the outer end 48 of the rail assembly 44. Said drive gear 63 is disposed within a drive housing 69 attached to the outer portion of the housing 12. The drive shaft 65 extends through the drive housing to rotate the drive gear 63. The drive assembly 58 further comprises four end cam switches 64 which are: · · ♦ · ΒΒΒ · ♦

Β · · · ΒΒΒ Β ΒΒΒ ΒΒΒ ΒΒΒ ΒΒΒ Β

Manually adjusted based on the position of the carriage to control the reversing of the operation of the motor 60 to achieve a continuous opposite linear movement of the carriages 54 (see FIG. 5).

During operation of the drive assembly, the drive gear 63 by the motor 60 pulls one end of the chain 57, and thus pulls one of the carriages 54 toward the outer end 48 of the rail assembly 44. This tension in the chain 57 is transferred through the carriage 54 to a wire rope 56 which rotates the pulleys 59 and pulls the second carriage 54 towards the inner end 46 of the rail assembly 44. Reversing the direction of rotation of the drive gear extends the second end of the chain 57 and thus pulls the second carriage 54 towards the outer end 48 and the first carriage 54 towards the inner end 46 of the rail assembly 44.

A sensor assembly 66 is attached to each carriage. These sensor assemblies 66 preferably use infrared sensors to detect hot spots on the air preheater rotor 14. Said sensor assemblies 66 may optionally use thermoelectric cells, various thermistors, and ultraviolet detectors to detect thermal differences on the rotor 14. Each sensor assembly 66 is preferably centered relative to a respective rail 52 and disposed on a respective carriage frame 36 for improved balanced movement of the carriage 54 and the sensor of assembly 66 on rail 52.

Connected to each sensor assembly 66 is a water, air, and electrical cable assembly 67 that allows the transmission of signals from the sensor assembly 66 to the sensor display units (not shown). Each cable assembly 67 enters the air preheater 10 through a cable inlet 68 in the housing 12. The air, water, cable assemblies 67 extend through an obliquely rigid cable sleeve 70 disposed below the rail assembly 44. The rigid cable bushing 70 has approximately half the length of the rail assembly 44 and terminates at the cable fastening means 75, wherein the fefe fefe fefe fefe fefe f * fe f * fefe *

Fefefe fefe this means is fixed approximately in the middle of the length of the rail assembly 44. Each cable assembly 67 then proceeds separately, extending through a separate flexible segmental cable sleeve 72 attached at one end to the cable mounting means 75 and at the other end to one of the carriages 54. The flexible cable sleeves 72 define U-path travel between rails 52 as the carriages 54 move along the rail assembly 44. The generally U-shaped cable trays 73 arranged between the rails 52 and from each rail head 40 each vertically carry flexible cable sleeves 72. The cable tray 73 has longitudinal cable guides 73 to keep the flexible cable sleeves 72 parallel to the rails 52 because the carriages 54 perform movement along the rails 52 (see FIG. 3).

Access openings 74 are provided in housing 12 to provide access to each carriage 54 and sensor assembly 66 for maintenance and repair. Each access aperture 74 is generally located directly opposite the transport path of one of the carriage 54. During operation, the preheater 10 aperture covers 80 are sealed to each access aperture 74 to seal the cover 12. A flange 76 extends from each carriage 54 for sealing engagement. with a gasket 78 on the outside of each access aperture 74 when the carriage 54 is at the extreme limit of its travel at the outer end 48 of the rail assembly 44. When the carriage 54 is at the end of its travel, the sensor 66 on the carriage 54 extends into the access opening 74. The opening cover 80 thereafter may be removed for maintenance or repair of the sensor.

During operation, the reciprocal linear movement of the linear hot spot detection system 38 in combination with the rotary motion of the rotor 14 results in complete coverage of the air preheater rotor 14 with respect to hot spot sensing. The low profile of this system 38 allows this ftftft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft 38 rotor 14 and above the reinforcements 50 supporting the air inlet duct 24, which improves hot spot detection.

While the preferred embodiment of the invention has been described and illustrated in detail, it should be noted that other modifications and changes made to the invention will be apparent to those skilled in the art. Accordingly, the appended claims cover any and all such modifications that constitute the inventive idea and are within the scope of the invention.

Claims (17)

A rotary regenerative preheater, comprising a housing defining an inner housing space and an outer surface, the inner housing space having a central portion and an edge portion, a rotor means rotatably mounted in said housing for transferring heat from the flue gas stream to the air stream; means comprising a linear rail extending between said edge portion and said center portion, a carriage movably assembled on said rail means, a sensor means for detecting hot spots on said rotor means, said rotor means being attached to said carriage means, and a drive means associated with said carriage means said carriage means for moving said carriage means on said rail means between said central portion and said edge portion. 2. The rotary regenerative preheater of claim 1, wherein said drive means comprises a gear assembly and a chain that is attached to said carriage means and engages said gear assembly. • · · · * * * * * * * * · * * · · · · * * · 3. The rotary regenerative preheater of claim 1, further comprising a second carriage movably mounted on said rail means and coupled to said drive means for moving said second carriage means on said rail means between said central portion and said edge portion. parts. The rotary regenerative preheater of claim 3, wherein said chain and carriage means define a continuous loop, and said drive means further comprises a gear assembly with gear wheels attached to said outer surface to drive said chain. The rotary regenerative preheater according to claim 1, wherein the sensor means comprises an infrared sensor. 6. A rotary regenerative preheater according to claim 1, wherein said linear rail has an I-shaped cross section defining rail gaps, and said carriage means comprises wheels that are arranged in said rail gaps and are in rolling engagement with said rail. rail. 7. The rotary regenerative preheater of claim 1, further comprising cable means for delivering said sensor means, and a cable sheath means comprising a flexible sheath portion, said cable means within said flexible sheath means defining a variable path in the form of a sheath. aa ta aa aaa aa aa aa aa U 8. The rotary regenerative air preheater of claim 7 wherein said cable sheath means further comprises a fixed housing portion. 9. A rotary regenerative preheater comprising a housing defining an inner space and an outer surface, said outer space having a central portion and an edge portion, a rotor means rotatably mounted in said inner housing space to transfer heat from the flue gas to the air flow, rail means comprising a plurality of linear rails extending between said edge portion and said central portion, a plurality of carriage means each movably mounted on one of said rails, a sensor means mounted on each of said carriage means, said sensor means adapted to detect hot spots on said rotor means, and drive means for moving said carriage means on said rail means between said central portion and said edge portion, the drive means comprising a drive assembly attached to said outer surface. 10. A rotary regenerative preheater according to claim 9, further comprising a cable sheath means in said interior space, the cable sheath means having a fixed cable sheath portion and a flexible cable sheath. a housing part, said rigid cable housing part being attached to said housing and said flexible cable housing part attached to said trolley, and cable means extending from said outer surface through said cable housing to said trolley means. 11. A rotary regenerative preheater according to claim 9, wherein said linear rails have a generally I-shaped cross-section that defines channel gaps. 12. A rotary regenerative preheater according to claim 11, wherein said carriage means comprises wheels which are arranged in said rail gaps and are in rolling engagement with said linear rails. 13. The rotary regenerative preheater of claim 9, wherein said sensor means comprises an infrared sensor. A system for detecting hot spots in a regenerative preheater rotor, characterized in that it comprises rail means comprising a pair of adjoining heater. Parallel rails, a first carriage movably mounted on one of said rails, a second carriage movably mounted on the other of said rails, a detection means on each said carriage means for detecting hot spots, and driving means for reciprocating linear movements of the first and second carriage means on said respective rails. 15. The hot spot detection system of claim 7, wherein said drive means comprises a chain, means for attaching each of said carriage means to said chain, and geared drive means for driving said chain. 16. The hot spot detection system of claim 8, wherein said drive means further comprises a flexible rope attached to said first and second carriage means, said chain, said first carriage means, said second carriage means, and said rope forming a continuous loop. 17. The hot spot detection system of claim 7, further comprising cable sheath means for delivering said sensor means, the cable sheath means comprising a fixed cable sheath portion and a flexible cable sheath portion secured to said carriage means, and ft. ftftft The cable means extending through said rigid housing part and through said flexible housing part.