GB2142407A

GB2142407A - Cleaning heat exchangers

Info

Publication number: GB2142407A
Application number: GB08416322A
Authority: GB
Inventors: Toshia Ogiwara
Original assignee: IHI Corp
Current assignee: IHI Corp
Priority date: 1983-06-30
Filing date: 1984-06-27
Publication date: 1985-01-16
Also published as: GB2142407B; DE3420117C2; NL8401607A; GB8416322D0; NL186273C; DE3420117A1; NL186273B

Abstract

A heat exchanger includes a housing 1 through which hot gas flows and through which a plurality of heat pipes 2 extend transverse to the direction of gas glow. In use, steel balls are allowed to drop from a supply 4 and to impinge against the heat pipes 2 to dislodge dust and the like adhering to them. The steel balls and the dislodged dust are then collected together and separated in a separator 9 whereafter the steel balls are recycled. Meshes or grids 5 are situated on the upstream and downstream sides of the heat pipes and prevent the steel balls from becoming scattered within the housing and deflect certain of the balls back towards the heat pipes thereby promoting the cleaning of the outer pipes. <IMAGE>

Description

SPECIFICATION Cleaning heat exchangers The present invention relates to heat exchangers for recovering heat from e.g. a boiler and relates more particularly to apparatus for cleaning a heat exchanger of the type in which cleaning materials, that is to say bodies such as steel balls, are dropped to impinge against the outer surface of a group of heat pipes in a gas passage, whereby dust and other deposits, e.g. condensates, on the outer surface of the pipes are removed.

Conventionally, rotary type heat exchangers have been used as gas-gas heaters in thermal power stations such as those used to heat outlet discharged gases by inlet discharged gases in desulphurizers or as gas-air heaters for heating combustion air by discharged gases from boilers. But the recent trend is to replace these with heat exchangers including heat pipes. Heat pipes are well known in the art and will thus not be described in this specification.

The gases discharged from boilers or the like include dust, mists and the like (referred to as "dust and the like" in this specification).

Referring now to Figures 1 and 2 which are diagrammatic views of a group of heat pipes in a heat exchanger and of the heat pipes only, respectively, when the exhaust gases discharged from a boiler or the like flow in the direction indicated by the arrow A relative to the group of heat pipes disposed in the main body of a heat exchanger as shown in Figure 1, dust and the like c adheres to the outer surfaces of the heat pipes as shown in Figure 2, thereby degrading the heat transfer efficiency of the heat pipes. Furthermore the dust and the like c progressively accumulates on the outer surfaces of the heat pipes so that the space between them becomes progressively clogged, resulting in failure of the heat exchanger.

In order to overcome the above problems, a cleaning method has been proposed in which, as shown in Figure 1, cleaning materials e, such as steel balls, are dropped from a supply device d disposed above the group of heat pipes b and are distributed by a distributer f.

The falling cleaning materials impinge on the heat pipes and knock the dust and the like from the heat pipes. The dropped cleaning materials e are collected together with the removed dust and the like and are removed.

The above method, however, has the following defects: When the cleaning materials e impinge on the heat pipes they are in part scattered outwardly and remain within the main body of the heat exchanger. As a result, it is difficult to recover all the cleaning materials. When the cleaning materials e impinge against the outer surfaces of the heat pipes, dust and the like adhering to the outer surfaces of the heat pipes are removed. However, the cleaning materials e tend not to impinge against the side surfaces of the heat pipes b' situated upstream and downstream of the heat exchanger main body, as shown in Figure 3, so that it is difficult to remove all the dust and the like adhering to them.In the case of a large-capacity heat exchanger, the height of the heat pipe group is relatively large so that as the cleaning materials, e.g. steel balls repeatedly collide with the heat pipes, they progressively lose their kinetic energy As a result, the lower the heat pipes are located, the lower is the kinetic energy posessed by the steel balls which impinge against them so that the efficiency of removal of dust and the like decreases.

In the case in which the heat pipes pass through two spaces through which high and low temperature gases respectively flow and in which the heat pipes are not disposed horizontally but are inclined at an angle such that the cooling part of each heat pipe is higher than the heating part thereof which is disposed in the flow of high temperature gases, the distribution of the dropped steel balls is not uniform in the direction of the length of the heatpipes because of the fins on the heat pipes and the steel balls tend to be concentrated at the lower portions of the heat pipes. Consequently the efficiency of cleaning of the heat pipes is decreased.Thus there is a tendency that at the heating parts of the heat pipes the steel balls impinge against the heat pipes at the portions adjacent to the cooling parts thereof while at the cooling parts of the heat pipes the steel balls impinge against the portions remote from the heating parts thereof.

It is an object of the present invention to provide apparatus for cleaning a heat-pipe type heat exchanger capable of preventing scattering of cleaning materials and removing even dust and the like which adheres to the outer surfaces of the heat pipes at the upstream and downstream sides of the gas flow.

It is a further object of the present invention to provide an apparatus for cleaning a heatpipe type heat exchanger capable of removing dust and the like which adheres to even the heat pipes at the bottom of the heat pipe group.

According to the present invention a heat exchanger includes a housing through which, in use, a fluid flows and through which a plurality of heat pipes extend, supply means disposed above the heat pipes for supplying cleaning materials and causing them to impinge against the heat pipes, collector means disposed below the heat pipes for collecting the cleaning materials supplied by the supply means after they have impinged against the heat pipes and also dust and the like dislodged from the heat pipes by the said impingement and constraining means disposed adjacent the heat pipes which, in use, contrain at least some of the cleaning materials to alter their direction of movement between the supply means and collector means. The heat pipes preferably extend transverse to the direction of fluid flow.

In one embodiment the constraining means constitutes confining means arranged to ensure that the cleaning materials, or at least a portion of them, are not scattered within the housing whereby the confining means is contacted, in use, by at least some of the cleaning materials and their direction of movement is then altered so that they travel back towards the heat pipes and impinge against them thereby dislodging further dust or the like. Thus in one embodiment the constraining means is situated both upstream and downstream of the heat pipes and extends over the substantially the entire area of the housing thereby effectively confining the cleaning material, in use, to the desired region of the housing, that is to say the region in which the heat pipes are situated.

In a further embodiment the heat pipes are divided into two or more vertically spaced subgroups, and in this event the constraining means may include one or more partitions so disposed in the or each space between the adjacent subgroups as substantially to prevent the flow of fluid through the or each space.

The space or spaces between adjacent subgroups thus constitute acceleration spaces in which the cleaning material which have slowed down by virtue of impingement against one or more heat pipes may accelerate to a higher speed and thus effectively dislodge dust and the like from the heat pipes of the adjacent but lower subgroup. A proportion of the cleaning materials will have a horizontal component of velocity in the or each space and these will then contact a partition and be constrained to move substantially vertically downwardly towards the next lower subgroup.

Alternatively or in addition, in the case in which the heat pipes are divided into subgroups the constraining means may include one or more partitions adjacent each side of the heat pipes and extending parallel thereto both above and below the heat pipes.

Certain of the heating materials will again engage these partitions and be confined by them, that is to say constrained to move substantially vertically downwardly.

The invention is particularly applicable to a heat exchanger in which the housing defines two spaces through which the heat pipes extend, through which spaces, in use, high and low temperature gases respectively flow.

In one embodiment of this type the heat pipes are provided with fins and are inclined whereby that portion of each heat pipe within the space through which high temperature gas flows is lower than that portion in the space through which low temperature gas flows and in which the heat pipes are divided into two or more vertically spaced subgroups, the constraining means including guides arranged between the or each adjacent pair of subgroups so that, in use, cleaning materials which leave a subgroup in a non-uniform distribution are caused to impinge on the adjacent subgroup below it in a substantially uniform distribution.Thus in the case in which the heat pipes are both inclined and provided with fins there is a tendency for the cleaning materials to be displaced along the length of the heat pipes and thus to leave them in a non-uniform manner which would result in a non-uniform and thus less effective cleaning of the next lower subgroup. The provision of guides, e.g. inclined guide vanes, permits this tendency to be corrected by directing the cleaning materials to flow in the opposite direction whereby they impinge against the next lower subgroup in a substantially uniform distribution.

Further features and details of the present invention will be apparent from the following description of certain specific embodiments which is given by way of example with reference to Figures 4 to 27 of the accompanying diagrammatic drawings, in which: Figure 4 is a sectional elevation of a first embodiment of apparatus for cleaning a heat exchanger in accordance with the present invention; Figure 5 is a partial view thereof on an enlarged scale Figure 6 is a sectional view on the line VI VI in Figure 4; Figures 7, 8 and 9 show different wire gauzes which may be used as the confining members in the present invention; Figures 10 to 1 5 show different perforated plates which may be used as the confining members; Figures 1 6 is a perspective view of a screen; ; Figures 17, 18 and 1 9 are fragmentary plan views of different forms of screen; Figure 20 shows a modified construction of the conffining members for use in the present invention; Figure 21 is a sectional elevation of a second embodiment of the present invention; Figure 22 is a sectional view on the line XXll-XXll in Figure 21; Figure 23 is a sectional elevation of a third embodiment of the present invention; Figure 24 is a sectional elevation of a fourth embodiment of the present invention; Figure 25 is a sectional view on the line XXV-XXV in Figure 24; Figure 26 is a perspective view on an enlarged scale of the guide vanes of Figure 25 and; Figure 27 is a perspective view on an enlarged scale of a modified construction of the guide vanes.

Referring first to Figure 4, the apparatus for cleaning a heat exchanger according to the present invention includes a supply device 4 for supplying cleaning materials 3, e.g. steel balls, disposed above a heat pipe group comprising a plurality of heat pipes extending horizontally transversely across a heat exchanger housing 1. Confining members 5 are disposed at the upstream and downstream sides of the heat pipe group 2 so that the cleaning materials 3 are prevented from falling outwardly of the heat pipe group 2, that is to say in the upstream and downstream directions. The cleaning materials 3 are dropped from the supply device 4 and are distributed by a distributor 4'. The heat exchanger housing includes a high temperature fluid casing 7 beside which is a low temperature fluid casing 8 which is visible in Figure 6 but not in Figure 4.The heat pipe group 2 extends through the high temperature gas casing 7 and the low temperature gas casing 8 and exhaust gases flow in through a gas passage 6. The cleaning materials 3 impinge on the heat pipes and knock off the adhering dust and the like 10 (see Figure 5). All these materials fall downwardly and are subsequently separated from each other by a separator 9. The separated dust and the like 10 is discharged through a discharge port 11 while the separated cleaning materials 3 are recycled through a recycling pipe line 12.

Various constructions of wire gauze may be used as the confining members illustrated in Figures 4 and 5, as shown in Figures 7 to 9.

Alternatively, various types of perforated plates, as shown in Figures 10 to 15, maybe used. Furthermore various types of welded screen maybe used, as shown in Figures 1 6 to 1 9 in which numeral 1 3 designates screen members carried by supporting members 14.

As a further alternative louvers may be used, as shown in Figure 20.

The cleaning materials 3 are generally steel balls, but it is to be understood that the present invention is not limited thereto. Thus balls of metal, such as aluminum, or of ceramic or plastics material may be used. The cleanihg materials 3 may also be in the form of particles, lumps or the like.

In use, the cleaning materials 3 are dropped from the supply device 4, as shown in Figure 4, over the distributor 4' and are scattered thereby and impinge against the outer surfaces of the heat pipes 2. As a result, dust and the like 10 on the outer surfaces of the heat pipes are removed and drop down with the cleaning materials 3. As shown in Figure 5, part of the cleaning materials 3 tend to fly outwardly and these then impinge on the confining members 5 disposed at the upstream and downstream sides of the heat pipe group 2 so that they rebound toward the heat pipe group 2 and impinge on the heat pipes again. Thus the cleaning materials 3 are prevented from being scattered outwardly of the heat pipe group 2.When the cleaning materials 3 rebound from the confining members 5, they impinge against the surfaces of the heat pipes 2 adjacent to the confining members 5 so that dust and the like 10 on such heat pipes is removed.

The cleaning materials 3 and dust and the like 10 which has been removed from the outer surfaces of the heat pipes 2 drop into the separator 9 and the separated dust and the like 10 is discharged through the discharge port 11 while the cleaning materials 3 are recycled through the recycling pipe line 1 2 to the supply device 4.

Referring now to the second embodiment of the present invention illustrated in Figures 21 and 22, a heat pipe group 2 is again disposed in the gas passage 6 of the main body 1 of a heat exchanger so that heat is exchanged between the fluid passing through the heat pipes 2 and the exhaust gases fiowing through the gas passage 6. A cleaning material supply device 4 is disposed above the heat pipe group 2 and a separator 9 is disposed below the heat pipe group 2. Partition walls 1 5 which constitute confining members are assembled like a box immediately above and below the uppermost and lowermost heat pipes 2 so that upper and lower box-like chambers are defined which are spaced above and below the gas passage 6.

The heat pipe group 2 is divided into upper and lower subgroups 2a and 2b which are spaced apart by a distance I which is more than five times the outer diameter d of the heat pipes 2 or two or three times the vertical pitch p of the heat pipes 2. An acceleration space 1 6 is thus defined between the upper and lower subgroups 2a and 2b.

Vertical partition walls 1 7 extending transverse to the gas passage 6 are disposed within the acceleration space 1 6 so that the exhaust gases can not directly flow through the acceleration space 16. The lower ends of the partition walls 1 5 of the lower box-like chamber are spaced from the walls of the main body 1 of the heat exchanger, as indicated at 18, so that cleaning materials 3 which are scattered outwardly of the lower heat pipe subgroup 2b can be collected.

In use, when the exhaust gases flow through the gas passage 6 and the heat pipe group 2, dust and the like 10 adheres to the outer surfaces of the heat pipes 2. When it is desired to clean the heat pipes, steel balls 3 are dropped from the supply device 4, which is disposed above the heat pipe group 2, onto the distributor 4' so that the steel balls 3 are scattered and drop uniformly on the upper heat pipe subgroup 2a. The steel balls impinge against the outer surfaces of the heat pipes 2 so that dust and the like which adhere to the outer surfaces of the heat pipes is removed and drops downwardly. Some of the steel balls 3 which fly outwardly of the upper heat pipe subgroup 2a collide against the partition walls 1 5 and 1 7 and rebound inwardly.

The further the steel balls 3 drop, the less is their kinetic energy due to the loss of energy which occurs on impingement with the heat pipes. However, due to the presence of the acceleration space 1 6 between the upper and lower heat pipe subgroups 2a and 2b, the steel balls 3 dropping from the upper heat pipe subgroup 2a are accelerated in the acceleration space 1 6 and impinge against the outer surfaces of the heat pipes of the lower subgroup 2b. Thus dust and the like on the outer surfaces of the lower heat pipes 2 is removed and collected in the lower box-like chamber and then the separator 9. The steel balls 3 separated by the separator 9 from the removed dust and the like are recycled through the recycling pipe line 1 2 to the supply device 4.

The third embodiment of the present invention illustrated in Figure 23 is substantially similar to the second embodiment described above with reference to Figures 21 and 22 except that two acceleration spaces 1 6 are defined between three adjacent heat pipe subgroups.

In the second and third embodiments, the heat pipes are divided into subgroups to define one or more acceleration spaces 16, but it is to be understood that the present invention is not limited thereto. For instance, a few heat pipes at the centre of a single heat pipe group may be removed to define an acceleration space. In this case, it is not necessary to provide the partition walls 1 7 so that an acceleration space can be provided in an existing heat pipe type heat exchanger only by removing a few heat pipes.

Figures 24, 25 and 26 show a fourth embodiment of the present invention. As best seen in Figure 25, the heat exchanger comprises a heating section 18 through which high temperature gases flow and a cooling section 1 9 through which low temperature gases flow. The heat pipe group is divided into three spaced subgroups and extend through the heating and cooling sections 18 and 1 9. Each heat pipe has fins 20 and is inclined such that the part of the heat pipe that is disposed in the cooling section is higher than the part of the heat pipe that is disposed in the heating section.

A plurality of guide vanes 21 are disposed between the adjacent heat pipe subgroups. As shown in Figure 26, the guide svanes 21 are connected together by a linkage 23 which in turn is connected to a drive shaft 22. As the drive shaft 22 is rotated, the angle 8 between the guide vanes and the vertical is adjusted.

In the construction shown in Figures 24 and 25, the cleaning materials 3, such as steel balls, are uniformly distributed by the distributor 4' over the upper heat pipe subgroup 2a. However, since the heat pipes 2 are inclined, the cleaning materials 3 tend to be directed by the fins of the heat pipes to the right, that is to say towards the cooling section 1 9 in the heating section 1 8 and away from the heating section 1 8 in the cooling section 1 9. However, the adjustable guide vanes 21 interposed between the heat pipe subgroups are angled to correct this tendency, that is to say to direct the steel balls to the left.In other words, in the upper heat pipe subgroup, the cleaning materials 3 tend to move to the right but when they drop from the upper heat pipe subgroup, they are redirected toward the left by the guide vanes 21 whose angle with respect to the vertical is H As a result, the cleaning materials 3 are uniformly distributed over the intermediate heat pipe subgroup. In like manner, the cleaning materials 3 which drop from the intermediate heat pipe subgroup are redirected by the guide vanes 21 so that they are uniformly distributed over the lower heat pipe subgroup.

The distribution of the cleaning materials 3 can be optimally controlled in the axial direction of each heat pipe by adjusting the angle o of the guide vanes 21.

The angle 8 of the guide vanes as shown in Figure 27 is fixed so that the construction of the guide vane assembly is simple. This angle is determined in dependence on the angle of inclination of the heat pipes 2.

The effects, features and advantages of the present invention can be summarised as follows: The cleaning materials, such as steel balls, are caused to collide with the outer suface of the heat pipes and some of them then tend to fly outwardly. These balls collide with confining members thereby preventing their being scattered and are redirected towards the heat pipes. Dust and the like which adheres to even the outermost heat pipes can thus be positively removed.

An acceleration space or spaces may be defined between vertically spaced subgroups of heat pipes so that the kinetic energy of the steel balls which is lost by impingement against the heat pipes of one subgroup can be recovered by the time they reach the next subgroup. As a result, the steel balls can remove dust and the like on the heat pipes in the lower subgroup or subgroups in the same manner and as effectively as they did in the upper subgroup. As a consequence, no clogging will occur.

One or more partition walls maybe disposed in the or each acceleration space to prevent the exhaust gases from directly flowing therethrough. As a result, the efficiency of the heat exchanger is not adversely affected. The length of the or each acceleration space can be freely chosen so that the removal of dust and the like maybe optimised in the lower heat pipe subgroup.

The guide vanes maybe interposed between the heat pipe subgroups so that cleaning materials which have been concentrated on one side of the upper heat pipe subgroup due to the fins on the heat pipes can be redirected by the guide vanes and uniformly distributed over the lower heat pipe subgroup. As a result, an incomplete removal of dust and the like due to the non-uniform distribution of the cleaning materails can be prevented.

It will be appreciated that numerous modifications maybe made to the specific embodiments described above and that the features of the various embodiments maybe combined in any of the many compatible combinations.

Claims

1. A heat exchanger including a housing through which, in use, a fluid flows and through which a plurality of heat pipes extend, supply means disposed above the heat pipes for supplying cleaning materials and causing them to impinge against the heat pipes, collector means disposed below the heat pipes for collecting the cleaning materials supplied by the supply means after they have impinged against the heat pipes and also dust and the like dislodged from the heat pipes by the said impingement and constraining means disposed adjacent the heat pipes which, in use, constrain at least some of the cleaning materials to alter their direction of movement between the supply means and the collector means.

2. A heat exchanger as claimed in claim 1 in which the heat pipes extend transverse to the direction of fluid flow.

3. A heat exchanger as claimed in claim 2 in which the constraining means is situated both upstream and downstream of the heat pipes and extends over substantially the entire area of the housing.

4. A heat exchanger as claimed in any one of the preceding claims in which the constraining means comprise wire gauzes.

5. A heat exchanger as claimed in any one of claims 1 to 3 in which the constraining means comprise perforated plates.

6. A heat exchanger as claimed in any one of claims 1 to 3 in which the contraining means comprise screens.

7. A heat exchanger as claimed in any one of the preceding claims in which the heat pipes are divided into two or more vertically spaced subgroups, the constraining means including one or more partitions so disposed in the or each space between adjacent subgroups as substantially to prevent the flow of fluid through the or each space.

8. A heat exchanger as claimed in any one of the preceding claims in which the heat pipes are divided into two or more vertically spaced subgroups, the constraining means including one or more partitions adjacent each side of the heat epipes and extending parallel thereto both above and below the heat pipes.

9. A heat exchanger as claimed in any one of the preceding claims in which the housing defines two spaces through which the heat pipes extend, through which spaces, in use, high and low temperature gases respectively flow.

10. A heat exchanger as claimed in claim 9 in which the heat pipes are provided with fins and are inclined whereby that portion of each heat pipe within the space through which high temperature gas flows is lower than that portion in the space through which low temperature gas flows and in which the heat pipes are divided into two or more vertically spaced subgroups, the constraining means including guides arranged between the or each adjacent pair of subgroups so that, in use, cleaning materials which leave a subgroup in a non-uniform distribution are constrained to impinge on the adjacent subgroup below it in a substantially uniform distribution.

11. A heat exchanger as claimed in claim 10 in which the guides comprise guide vanes which extend transverse to the length of the heat pipes and are inclined at an angle to the vertical and at an angle to the length of the heat pipes.

12. A heat exchanger as claimed in claim 11 in which the angle of each of the guide vanes is adjustable.

1 3. A heat exchanger substantially as specifically herein described with reference to Figures 4, 5 and 6 of the eaccompanying drawings in conjunction with any one of Figures 7 to 20 or Figures 21 and 22 or Figure 23 or Figures 24 and 25 in conjunction with Figure 26 or Figure 27.