MXPA00007754A - Rotary regenerative heat exchanger - Google Patents

Abstract

The heat exchange baskets (22) for a rotary regenerative air preheater are loaded radially into the rotor (14) rather than axially from the duct end. The rotor (14) is divided into sectors (20) by diaphragms (34), support gratings (40) are provided in each rotor section (20) with the baskets (22) being positioned and supported on the gratings (40). The baskets (22) are removed from the rotor (14) with a removal lug or tool (44) which includes a lever portion and a hook portion (46) with a beveled edge (50). The beveled edge (50) and then the entire hook portion (46) are inserted under the outer edge of a basket (22) and then rotated with the lever portion whereby the hook portion (46) engages the basket (22). The lug or tool (44) is then pulled outwardly to remove the basket (22).

Description

REGENERATIVE ROTATING HEAT EXCHANGER BACKGROUND OF THE INVENTION The present invention relates generally to rotary regenerative heat exchangers and, more specifically, to improved means for removing modular heat exchange baskets from the rotor. A rotary regenerative heat exchanger is used to transfer heat from a hot gas stream, such as a flue gas stream, to another cold gas stream, such as combustion air. The rotor contains a mass of heat-absorbing material that is first placed in a passage for the hot gas stream where the heat is absorbed by the heat-absorbing material. As the rotor rotates, the hot absorbent material enters the passage for the cold gas stream where the heat is transferred from the absorbent material to the cold gas stream. In a typical rotary heat exchanger, such as a rotary regenerative air preheater, the cylindrical rotor is disposed on a vertical central rotor post and divided into a plurality of sector-shaped compartments by a plurality of radial or diaphragm separations extending from the rotor post to the outer peripheral cover of the rotor. These sector-shaped compartments are loaded with modular heat exchange baskets containing the mass of heat absorbing material commonly of stacked plate-like elements. The rotor is surrounded by a housing and the ends of the rotor are partially covered by sector plates located between the gas inlet and outlet ducts which divide the housing into sides of hot gas and cold gas. In order to improve the efficiency of the operation, it is conventional to provide seals, referred to as radial seals, at the ends of the rotor in such a way that the seals will come in proximity with the sector plates and minimize the flow of gases. between the hot and cold sides at the ends of the rotor. These seals are usually fixed to the edges of the diaphragms. A type of modular heat exchange basket comprises an open frame and has no solid side walls. These baskets are mounted axially on the rotor from the upper end (duct end) and there are stop plates located between them and supporting radially adjacent baskets. To ensure that the baskets can be inserted freely, it is necessary that the baskets are smaller compared to the compartments formed by the diaphragms and stopping plates so that there is guard distance. Therefore, in order to provide the necessary heat exchange surface, it is necessary to have an excess of frontal area and consequently a large rotor. In addition, there are separations around each basket allowing the air and combustion gases to pass, thus reducing thermal efficiency. In another arrangement, the rotor is constructed to mount and remove the baskets in a radial direction on the rotor side instead of axially through the end of the duct. The baskets can be placed and supported in each sector so that they also act as a support between the diaphragms and serve to stiffen the structure of the rotor while reducing the separation of passage. The baskets are held on grids fixed between diaphragms at each end of the rotor and between layers of baskets. If the baskets also serve as support between the diaphragms, the angle of each rotor sector is less than the complementary angle of each basket so that the outer end of each basket can make contact with the diaphragms before the inner end makes contact. . The problem with laterally removable baskets, particularly those that make contact with the diaphragms, is that it can be difficult to remove the baskets for inspection or to be replaced with a new basket heat exchange surface. Removal requires that the baskets slide over the support grids and removal is complicated by limited access. Normally there is only 0.635 to 1.27 cm (one-quarter to one-half inch) of vertical guard distance. furtherIf baskets are pulled from any place other than the lower end edge, the baskets have a tendency to lean towards the bars of the support grids and hang. SUMMARY OF THE INVENTION The present invention relates to a novel method for removing heat exchange baskets in a radial direction through the sides of a rotary regenerative air preheater. The method involves inserting a bead device below the outer bottom edge of the baskets to lift the outer edge of the baskets a limited distance, rotate the bead device to hook the baskets, and then pull the bead device to remove the beakers. rotor baskets. BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a general perspective view of a rotary regenerative air preheater.

Figure 2 is a cross-sectional top view of a part of the rotor of the preheater of Figure 1 illustrating the support grids in position between the diaphragms. Figure 3 is a similar top view in cross section of a part of the preheater of Figure 1 illustrating the baskets in position. Figure 4 is a cross section of a part of the rotor with the baskets in position. Figure 5 is an isometric view of the removal heel of the present invention. Figures 6 and 7 are sectional views of a part of a rotor illustrating the use of the removal heel. DESCRIPTION OF THE PREFERRED EMBODIMENT Figure 1 of the drawings is a partially sectioned perspective view of a typical air heater showing a housing 12 in which the rotor 14 is mounted on a drive shaft or post 16 to rotate as indicated by arrow 18. The rotor is composed of a plurality of sectors 20 and each sector contains a number of basket modules 22 and with each sector defined by the diaphragms 34. The basket modules contain the heat exchange surface. The housing is divided by means of the sector plate impervious to flow 24 on one side of combustion gases and on one side of air. There is also a corresponding sector plate located at the bottom of the unit. The hot combustion gases enter the air heater through the gas inlet duct 26, flow through the rotor where heat is transferred to the rotor and then exit through the gas outlet duct 28. The air flow to Countercurrent enters through the air inlet duct 30, flows through the rotor where it collects heat and then exits through the air outlet duct 32. The basket modules 22 are mounted on the rotor 14 through an armature of the rotor 36 by removing the cover plates 38 and radially slipping the baskets towards each sector 20. Referring now to Figure 2 which shows a cross-sectional plan view of a part of the rotor, the diaphragms 34 are shown in section crossed and extending radially between the central portion 36 of the rotor and the armature of the rotor 38. This Figure 2 is a view before the basket modules are installed. The support grids 40 are held between and fixed to the diaphragms 34. These support grids are formed from the members 42 and are normally reinforced structures. Any desired set-up configuration can be used as long as it is structurally designed to hold the baskets. The grids are suitably fixed to the diaphragms 34, as for example using welding. As is conventional, there are a plurality of grid levels in each sector. The baskets of the present invention are placed in the rotor through the sides or the periphery of the rotor instead of the upper end of the rotor. When the baskets are mounted at the top, sufficient guard distance must be provided and stop plates are located between radially adjacent baskets to hold them in place. The guard distance around each basket means that the air preheater will require a larger front (end) area to accommodate a certain amount of heat exchange surface. When the baskets are mounted on the one hand, very little guard distance is needed and they can be placed snugly within the sections and between them so that most of the guard distances are eliminated. This eliminates the need for stop plates and reduces the front area required in the air preheater for a specific amount of heat exchange surface. Figure 3 shows a cross-sectional plan view of the same part of the rotor as in Figure 2 with the baskets 22 in position and resting on the racks 40 (not shown in Figure 3). Of course, as is conventional, there would normally be a plurality of layers of racks and basket modules in each sector as shown in Figure 4. Figure 3 illustrates the preferred embodiment in which the basket modules are tapered at an angle that is greater than the angle of tapering of sectors 20. Referring to this, see US Pat. No. 5,485,877. The baskets are installed laterally by pushing them in until the outer corners make contact with the diaphragms. The baskets can then be fixed, by properly securing with bolts at least the outer basket to the diaphragms. Figure 4 illustrates a cross section of a part of the rotor with the heat exchange baskets 22 in position. The baskets 2 are supported on the grids 40 which are fixed to the diaphragms 34, one of which is shown in this Figure 4. The removal bead 44 is also shown which is used in the method of the present invention to remove the baskets 22 of the rotor. The removal heel 44 and the removal method involving the use of the heel is illustrated more clearly in Figures 5 to 7. As shown in the isometric view of Figure 5, the removal heel 44 comprises a flat metal plate with a bent hook portion 46 at one end and a hole 48 at the other end for fixing a pull wire. The end of the hook portion 46 is beveled at 50 to form a relatively small and sharp edge for inserting the removal heel under the baskets 22 as shown in Figure 6. The removal heel 44 also has a notch 52 in it. the hook portion 46 which is adapted to fit over or straddle the typical retaining or joining bars of the baskets. These retaining bars are members that extend radially through the center of the bottom of each basket and which are attached to the inner and outer ends of the baskets. A retaining bar 54 is shown in Figures 6 and 7 which are cross sections of an outer bottom corner of the basket 22 on the trellis 40. The basket comprises the outer end portion 56 of the basket wrap and the side portion 58 of the basket wrapper. The holding bar 54 is fixed to the lower end edge of the outer end portion 56. In Figure 6, the removal bead 44 is shown in position so that the beveled edge 50 is inserted below the basket 22. This is usually it simply makes hammering on the removal heel. As can be seen in Figure 6, this begins to lift the outer edge of the basket 22 of the grids 40. Once the hook portion 46 of the removal lug 44 has been inserted sufficiently below the basket 22, the removal heel 44 is rotated to be positioned as shown in Figure 7. Although it can not be seen, the notch 52 in the removal heel 44 is straddling the retention bar 54. The removal heel 44 has its dimensions, particularly its thickness, that the distance that the basket 22 rises above the lattice 40 is less than the amount of free space available above the basket. This elevated distance is generally around 0.635 cm (one quarter of an inch). When the removal heel 44 is in the position shown in Figure 7, a cable or other pulling means is attached to the hole 48 and pulled out of the basket by the rotor.

Claims (2)

1. CLAIMS 1. A method for radially removing heat exchange baskets through one side of a rotor of a rotary regenerative air preheater where the baskets are supported on support grids within the rotor and where the baskets have a lower edge external and wherein the baskets include a member extending through at least the outer lower edge, characterized in that the method comprises the steps of: a) providing a removal tool comprising a lever portion and a hook portion, the removal tool includes a beveled edge on the hook portion; b) inserting the beveled edge into the hook portion between one of the baskets and the support grids; c) force the hook portion under the basket thus lifting the basket from the support grids; d) rotating the lever portion of the removal tool downwardly thereby engaging the hook portion of the member extending through the lower outer portion of the basket; and e) pull radially outwards with the removal tool and thus remove the basket from the rotor side.
2. 2. A method according to clause 1 characterized in that the removal tool includes a hole in the lever portion and where the pulling step includes the step of fixing a cable to the hole and pulling the cable.