BASKET FOR HEAT TRANSFER ELEMENTS FOR A ROTARY AIR PREHEATER
A basket for an air preheater includes two metallic frames each having two corner pieces and two connector pieces. For each frame, one of the connector pieces is secured to one end of each of the corner pieces and another of the connector pieces is secured to an opposite end of each of the corner pieces thereby forming a rectangular opening in each frame. The basket includes two heavy gauge metallic sheets that are secured to the corner pieces, thereby spacing the frames equally apart from and parallel to one another thereby forming a channel between two of the sheets.
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The present invention relates generally to a basket for receiving heat transfer elements for a rotary air preheater in which high temperature flue gases and air flow though, and more specifically to a light weight metallic basket that includes one or more heavy gauge side structural support and wear resistant walls that help contain air and gas flows laterally within the basket.
BACKGROUND OF THE INVENTIONRotary air preheaters typically have a plurality of pie shaped sectors, each of which have several baskets containing heat transfer elements therein. The heat transfer elements are typically manufactured from corrugated metallic plates. Each basket contains a plurality of the heat transfer elements. The baskets are constructed to orient the heat transfer elements in a flow direction of flue gas and air through the air preheater. Since the heat transfer elements are of a substantive weight, the baskets have a structure sufficient to support the weight of the heat transfer elements. The overall weight of the baskets and the heat transfer elements are supported by a spindle mounted on bearings that enable rotation of the sectors. High weight baskets can cause the bearings to become overloaded. In addition, high weight baskets are expensive to manufacture.
It is known that the heat transfer elements can become fouled with ash deposits thereby reducing the effectiveness of the air preheater. Soot blowing arrangements have been employed to clean the ash deposits off of the heat transfer elements. However, the soot blowing operations can erode or crack portions of the basket.
In addition, some prior art baskets do not keep air and gas flows laterally contained within the basket, but instead allow a portion of the air and gas flow to bypass the heat transfer elements in the basket and to flow through empty gaps between the basket of heat transfer elements and the rotor structure. Such lack of lateral containment and bypass flow reduces heat transfer and air preheater effectiveness.
Thus, there is a need for an improved lighter weight basket for heat transfer elements that is resistant to erosion and other effects of soot blowing and that has improved heat transfer and that results in an improved heat transfer effectiveness of the air preheater.
SUMMARYIn one aspect, the present invention resides in a basket for receiving heat transfer elements for a rotary air preheater. The basket includes two metallic frames each having two elongate corner pieces and two elongate connector pieces. Each of the corner pieces has a two leg angled cross section and each of the connector pieces are substantially flat. For each frame, one of the connector pieces is secured to one end of each of the corner pieces and another of the connector pieces is secured to an opposite end of each of the corner pieces such that the corner pieces are spaced apart from and parallel to one another and the connector pieces are spaced apart from and parallel to one another thereby forming a rectangular opening in each frame. The basket includes two heavy gauge metallic sheets (e.g., 12 gauge). Each sheet has opposite edges secured longitudinally along one of the corner pieces, thereby spacing the frames equally apart from and parallel to one another, thereby forming a channel between the two sheets. The channel has a longitudinal axis that is parallel to and bounded by the corner pieces. The channel is configured to receive heat transfer elements having a flow direction coaxial with the channel.
In one embodiment, the basket includes a metallic closure grid secured, at each opposing end of the channel, to two of the connector pieces and two of the sheets. The closure grid has a plurality of openings therein. The openings are configured to convey a flow of a fluid therethrough. The closure grid is configured to secure the heat transfer elements in the channel between the two closure grids.
In another aspect, the present invention resides in a method of retrofitting a basket for receiving heat transfer elements for a rotary air preheater. The method includes at least partially disassembling the basket, removing worn, inefficient or antiquated heat transfer elements from the basket, positioning new or refurbished heat transfer elements in the basket; and reassembling the basket.
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While the welds WW1, WW2, WW3 and WW4 are shown and described, the present invention is not limited in this regard as other locations of welds and/or fasteners may be employed without departing from the broader aspects of the present invention.
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Each of the three closure strips 52A′, 52B′ and 52C′ have one end thereof secured to an inside facing surface of the connector piece 24B and an opposing end thereof secured to an inside facing surface of the connector piece 24B′, for example by welding. The closure grid 50′ includes one cross piece 54′ extending through and secured to the closure strips 52A′, 52B′ and 52C′, for example by welding. One end of the cross piece 54′ is secured to the sheet 30 and an opposite end of the cross piece 54′ is secured to the sheet 30′, for example by welding. The closure grid 50′ has a plurality of openings 55′ therein. The openings 55′ are configured to convey a flow of a fluid therethrough and into the channel 40. The closure grids 50 and 50′ are configured to secure the stack 80 of heat transfer elements 88 in the channel 40 between the two closure grids 50 and 50′. The closure grids 50 and 50′ also provide lateral support between and prevent bowing of the sheets 30 and 30′. The closure grids 50 and 50′ further provide lateral support between and prevent bowing of the respective pairs of connector pieces 24A, 24A′ and 24B, 24B′.
While the closure grids 50 and 50′ are shown having three closure strips 52A′, 52B′ and 52C′ and one cross piece 54′, the present invention is not limited in this regard as more or less than three closure strips and/or more than one cross piece may be employed, depending upon the size of the basket 10.
In one embodiment, corner pieces 22A, 22B and 22A′, 22B′ and connector pieces 24A, 24B and 24A′, 24B′ each have a width W1 that is less than 5 percent of an overall width W or W′ of the frame 20, 20′.
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While the present disclosure has been described with reference to various exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims
1. A basket for receiving heat transfer elements for a rotary air preheater, the basket comprising:
- two metallic frames each having two elongate corner pieces and two elongate connector pieces, each of the corner pieces having a two leg angled cross section, for each frame one of the connector pieces is secured to one end of each of the corner pieces and another of the connector pieces is secured to an opposite end of each of the corner pieces such that the corner pieces are spaced apart from and parallel to one another and the connector pieces are spaced apart from and parallel to one another thereby forming a rectangular opening in each frame; and
- two heavy gauge metallic sheets, each sheet having opposite edges secured longitudinally along one of the corner pieces, thereby spacing the frames equally apart from and parallel to one another thereby forming a channel between two of the sheets, the channel having a longitudinal axis that is parallel to and bounded by the corner pieces, the channel being configured to receive heat transfer elements having a flow direction coaxial with the channel.
2. The basket of claim 1, wherein the heavy gauge sheets are 12 gauge.
3. The basket of claim 1, further comprising:
- a metallic closure grid secured, at each opposing end of the channel, to two of the connector pieces and two of the sheets, the closure grid having a plurality of openings therein, the openings being configured to convey a flow of a fluid therethrough.
4. The basket of claim 1, wherein each of the connector pieces is substantially flat.
5. The basket of claim 1, wherein, the corner pieces each having two elongate sections, each elongate section extending outwardly from a bend at an angle from one another and wherein the angle is obtuse for two of the corner pieces and the angle is acute for two of the corner pieces.
6. The basket of claim 1, wherein at least one of the securing:
- of opposite edges of each sheet longitudinally along of each of two of the corner pieces,
- of one of the connector pieces to one end of each of the corner pieces and the securing of another of the connector pieces to an opposite end of each of the corner pieces, and
- of the opposite edges of the sheets longitudinally along one of the corner pieces;
- is by welding.
7. The basket of claim 4, wherein the opposite edges each of the sheets is secured to an outside surface of the each of the respective elongate section of each of two of the corner pieces.
8. The basket of claim 1, wherein outside surfaces of the connector pieces of each frame are coplanar with outside surfaces of one of the elongate sections of the corner pieces of the respective frame.
9. The basket of claim 1, wherein two of the connector pieces of one of the frames are longer than two of the connector pieces of the other frame.
10. The basket of claim 2, wherein the closure grid comprises:
- at least one closure strip secured to opposing ones of the connector pieces; and
- at least one cross piece extending through and secured to the at least one closure strips and opposing ends of the at least one cross piece being secured to opposing ones of the sheets.
11. The basket of claim 1, wherein the connector pieces and the corner pieces each have a width that is less than 5 percent of an overall width of the frame.
12. The basket of claim 1, wherein the connector pieces and the corner pieces are positioned at a perimeter of the frame.
13. The basket of claim 1, further comprising a plurality of heat transfer elements stacked upon one another and disposed therein.
14. The basket of claim 13, wherein said heavy gauge metallic sheets form a barrier to prevent gas and air flow bypass around edges of the heat transfer elements in contact therewith to improve effectiveness of the plurality of heat transfer elements in the basket installed in the air preheater as compared to heat transfer elements in baskets with open lateral sides.
Type: Application
Filed: Jul 26, 2016
Publication Date: Feb 1, 2018
Applicant: ARVOS, Inc. (Wellsville, NY)
Inventors: Lawrence Gilbert Cowburn (Ulysses, PA), Scott Richard Duffney (Little Genesee, NY), James Leslie Bice (Ulysses, PA)
Application Number: 15/219,800