GB2127517A

GB2127517A - Cleaning heat exchangers

Info

Publication number: GB2127517A
Application number: GB08325224A
Authority: GB
Inventors: Adolf Margraf
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-09-21
Filing date: 1983-09-21
Publication date: 1984-04-11
Also published as: GB2127517B; GB8325224D0; DE3331484A1; AU1930883A

Abstract

Flattened cooling pipes 2 comprising plane vertical lateral surfaces are installed horizontally in vertical rows within a housing 1. The plane lateral surfaces are swept over by scrapers 3, 4 jointedly secured on pendularly suspended supports 5 under contact with the lateral surfaces, and these lateral surfaces are cleared of adhering dust whilst doing so. The supports are suspended on chains or ropes 10 in the upper part of the housing 1 and are placed in pendular reciprocating motion by a drive 13, 14 separate from the suspension. To prevent jamming of the scrapers between the rows of pipes which may warp under particular circumstances, the rows of pipes 2 are kept at a precise spacing by a spacing element 9 or by several spacing elements 9 installed at identical intervals. To this end, the scraper supports are rigidly interconnected, so that a single drive only is needed for the coupled supports. <IMAGE>

Description

SPECIFICATION Heat exchangers for hot flue gases The present invention relates to heat exchangers for hot flue gases of the kind in which flattened cooling pipes which are horizontal and provided with plane sidewalls at right angles are installed one above another in vertical parallel rows in a housing provided with a bottom dust collector space, said pipes being traversed in longitudinal direction by a flow of coolant and laved by the hot flue gases in vertical direction.

Hereinafter such heat exchangers will be referred to as "of the kind described".

Heat exchangers comprising cooling pipes laved by hot flue gases which are to be cooled and traversed by a flow of coolant have the disadvantage that in particular adhesive dust particles of the flue gases remain stuck to the outer surfaces of the cooling pipes in an increasingly thicker layer and impede the heat exchange. Consequently, to assure an economic heat transfer, the adhering dust particles are frequently removed by hand despite cleaning mechanisms which may possibly be present, to remove adhering dust layers as far as possible. It has also been attempted to remove the dust layers by means of lances by blasting off by compressed air or pressure jet, a part only of the heat exchange surfaces being affected in each case, however.

The cleaning operation has moreover been performed by dropping a shower of steel balls. All the known methods require high expenditure upon purchase and primarily during operation.

It is an object of the invention to provide a heat exchanger of the kind described in performing the cleaning of the plane lateral surfaces determinant for the heat exchange -- of flattened cooling pipes, in such manner as to clear these periodically or constantly of adhering dust at low expense and extremely effectively, and consists in that at least one rigid horizontal pendularly suspended support is installed in the upper part of the housing transversely to and above the rows of pipes so that it is movable back and forth along the length of said pipes and is provided with suspended scrapers in contact with the plane surfaces of both sides of the cooling pipes.

If desired, a plurality of the supports is provided and these are movable back and forth along part lengths of the pipes.

Each support provided with suspended scrapers is advantageously suspended pendularly on the upper part of the housing by means of chains or ropes and may be moved back and forth pendularly by means of a reversible independent drive acting thereon.

The scrapers may be link chains loaded or ballasted by weights at the bottom to keep them taut, but are advantageously rigid round bars or flat irons loaded by bottom weights, which bear along their length or with a longitudinal edge on the plane lateral surfaces of the cooling pipes and are scraped alongside these lateral surfaces and thereby remove even strongly adhering dust which drops to the bottom where it may be withdrawn.

Since the cooling pipes may warp by being acted upon by the hot flue gases, which may lead to jamming of the scrapers, the heat exchanger may be so constructed that two adjacent vertical rows of pipes are in each case held at a precise mutual spacing by at least one spacing element supported in the housing, e.g. a pipe, and that scrapers reciprocatingly movable at either side of each spacing element are in each case suspended on a support displaceable in the longitudinal direction of the pipe. The spacing between two adjacent vertical rows of pipes is thereby positively established.

It is then necessary however to provide supports pendularly suspended at either side of the spacing element and provided with scrapers, which are then advantageously joined together by rigid tie rods acting on the supports, whereby a single drive may be brought into use for two or more supports as will hereinafter be described, and the drive is no longer loaded with considerable weights.

In order that the invention may be more clearly understood reference will now be made to the accompanying drawings, which show certain embodiments thereof diagrammatically by way of example and in which: Figure 1 shows a vertical cross-section through a first embodiment of a heat-exchanger, Figure 2 shows a vertical longitudinal crosssection through a second embodiment of a heat exchanger, Figure 3 shows a cross-section along the line Ill-Ill of Figure 2, Figure 4 shows a cross-section along the line IV--IV of Figure 2.

Identical reference symbols are allocated to sequentially identical parts in the figures.

Referring now to the drawings, a heat exchanger in accordance with the invention comprises a housing 1 which is advantageously traversed downwards from above by hot flowing flue gases which are to be cooled. In the housing 1 which has a bottom dust collector space 1 a and a dust outlet, are installed one above another in vertical parallel rows, horizontal cooling pipes 2, which have a flattened outline with plane lateral surfaces at right angles. Sections which proved to be advantageous, had a ratio of pipe height to pipe width of 2 :1 to 4:1 the width being in the range 10 to 30 mm.

During the heat exchange, dust is deposited from the flue gas on the plane lateral surfaces of the cooling pipes, which adheres particularly stubbornly in the case of adhesive dusts. The cleaning of the plane lateral surfaces of the cooling pipes is performed, according to Figure 1, by the fact that scrapers in the form of metal chains 3 and 4 are suspended on a support 5 above the cooling pipes 2 of each vertical row of pipes, said scrapers being combined in pairs at the upper extremity and pendularly touch the plane lateral surfaces of the two sides of the cooling pipes and the link width of which should if possible be no greater than half the spacing between two rows of pipes in each case.

The chains 3, 4 are individually or jointly loaded or ballasted at the bottom extremity by weights 6, thereby promoting the contact of the chains on the plane lateral surfaces of the pipes.

During a cleaning operation on the plane cooling pipe surfaces, the support 5 on which the chains 3, 4 are suspended is displaced along the length of the pipes 2 by a drive, the chains 3, 4 scraping along the plane lateral surfaces and freeing the adhering dust layers.

According to Figure 1, the support 5 is rigidly coupled by tie rods 7 to a shaft 8 reciprocatingly rotatable by means of a drive, that is in such manner that the support sweeps over the whole length of the cooling pipes during its oscillatory reciprocal displacement.

In order that distortion or buckling of the cooling pipes 2, possibly caused by the temperature difference, may be averted in any event, and that precise mutual spacings may be established between two vertical rows of pipes in each case, and thereby prevent jamming of the scrapers, a spacing element 9 which assures a constant mutual spacing between the rows of pipes is installed as shown in Figures 2 to 4 between two adjacent rows of pipes in each case on the longitudinal centre of the pipes, e.g.

supported at the top and bottom in the housing 1.

It is also possible however to install several spacing elements 9 between two rows of pipes in each case, at identical longitudinal intervals, e.g.

of 1 metre.

In the case of Figures 2 to 4, the supports 5 are pendularly suspended on the ceiling of the housing 1 by means of chains 10 or ropes, in such manner that the lateral surfaces of the cooling pipes 2 are swept by the scrapers throughout their length or part length at either side of a spacing element 9, the scrapers advantageously comprising round bars or flat irons 11 which may in the latter case move so that the one longitudinal edge scrapes along the lateral surfaces of the pipes and thereby frees adhering dust in any event.

According to Figures 2 to 4, a pendularly suspended support 5 with its suspended scrapers 11, is placed in oscillatory motion by a separate drive, e.g. a crank drive, which is not weightloaded in view of the pendular suspension of the supports 5, as is the case according to Figure 1. If use is made of one spacing element 9 or of several spacing elements 9, the supports 5 are interconnected by rigid tie rods 12 coupled to the supports 5. A single drive is then sufficient for the oscillating supports 5.

A drive utilised'in Figures 2 and 4 is particularly uncomplicated. This comprises a shaft 14 rotatable back and forth in the housing 1 above the cooling pipes 2 by means of a reversing motor 13. A chain 1 5, a rope or the like, is wound once or more times around this shaft 14 and firmly connected to the shaft 14 at an appropriate point, said shaft being situated above a spacing element 9. The extremities of the chain 1 5 act on the two adjacent supports 5. As soon as the shaft 14 is turned in the one direction, the one chain extremity is unwound from the shaft and the other chain extremity is wound on to the shaft, under pendular entrainment of the rigidly coupled supports 5, so that the scrapers 11 clear the lateral surfaces of the pipes 2 of adhering dust.

The direction of rotation of the shaft 14 is reversed automatically as soon as the outward pendular displacement has been completed, thereby causing the pendular return displacement of the supports 5 with the scrapers 11. These operations are performed intermittently or continuously.

Claims

1. A heat exchanger for hot flue gases of the kind described, wherein at least one rigid horizontal pendularly suspended support is installed in the upper part of the housing transversely to and above the rows of pipes so that it is movable back and forth along the length of said pipes and is provided with suspended scrapers in contact with the plane surfaces of both sides of the cooling pipes.

2. A heat exchanger as claimed in claim 1, wherein are provided a plurality of rigid horizontal pendularly suspended supports which supports are movable back and forth along part lengths of said pipes.

3. A heat exchanger as claimed in claim 1 or 2, wherein the or each support is suspended pendularly on suspension members such as chains or ropes on the upper part of the housing and is movable back and forth pendularly by means of an independent reversible drive acting thereon.

4. A heat exchanger as claimed in claim 3, wherein the scrapers each comprise link chains suspended and joined together in pairs on the support above the uppermost of the pipes of each vertical row of pipes, said chains being loaded or ballasted at the lower extremity below the rows of pipes by means of weights.

5. A heat exchanger as claimed in claim 3, wherein the scrapers are held singly or jointly in a vertical position at the lower extremity by means of weight under contact with the plane pipe sides.

6. A heat exchanger as claimed in any of the preceding claims, wherein two adjacent vertical rows of pipes are in each case held at a precise mutual spacing by at least one vertical spacing element supported in the housing and the scrapers movable back and forth at either side of the spacing element are each suspended on a support movable back and forth in the longitudinal direction of the pipe.

7. A heat exchanger as claimed in claim 6, wherein, if several said spacing elements are situated between two vertical rows of pipes in each case, the suspended supports comprising scrapers are connected by means of rigid tie rods joined in articulated manner to the supports, and a reversible drive is provided for the pendular reciprocating displacement of the supports.

8. A heat exchanger as claimed in claim 6, wherein the drive comprises a shaft which is turnable back and forth by motor means, installed transversely to the cooling pipes and above a spacing element which has wound around it once or more times a chain or rope fixedly connected to the shaft at one point, the extremities of which are joined to said supports suspended at either side of said shaft.

9. A heat exchanger substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

10. A heat exchanger substantially as hereinbefore described with reference to Figures 2, 3 and 4 of the accompanying drawings.