GB2484335A

GB2484335A - Rotary heat exchanger

Info

Publication number: GB2484335A
Application number: GB1016933.2A
Authority: GB
Inventors: Ronald Gloudie Sherwen
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-10-07
Filing date: 2010-10-07
Publication date: 2012-04-11
Also published as: GB201016933D0

Abstract

A rotary heat exchanger comprises a rocking cradle 1 mounted on a support structure 3 for back and forth rotary motion relative to the support structure, and at least one container mounted on the cradle and constrained to rotate with the cradle. The container defines a heat exchange chamber having entry and exit openings. The support structure comprises rollers 2 moving in steel channel guides 3. The cradle is rocked through 45 degrees in either direction using a reversing electric motor 4 and chain 5, which is attached to the cradle by eyebolts (14, fig 2). The container may be kidney shaped and comprise of a lobed floor 6 and arched roof 7 joined together at flanges 8. A plurality of containers / chambers may be mounted on the cradle with the exit of one connecting with the entry opening of an adjacent. Each container may be tilted downwards by 1 to 2 degrees so that particles tumble form one chamber to the next. The heat exchanger may be modular, may be a kiln for drying particulates, combustion of material and/or the manufacture of burned or fired materials, or used in cooling.

Description

HEAT EXCHANGERS

Field of Invention

The invention relates to heat exchangers and in particular rotary heat exchangers in which particulate material, e.g. powder, granules, pellets or larger masses, is agitated or turned over by rotation or rocking of a heating or cooling chamber of the heat exchanger.

The term heat exchanger is intended herein to include apparatus in which heat transfer is effected by radiant and/or conductive heating. The term heat exchanger is also intended herein to include apparatus that functions to cool material by exposing it to a cooler gas stream (where the heat exchange is from the material to the gas stream).

The term rotary heat exchanger is intended herein to include apparatus where a heating chamber rocks back and forth with a rotary motion without necessarily being driven through complete revolutions.

Backqround The use of rotary heat exchangers to heat particulate material is well known.

Conventional rotary heat exchangers (e.g. kilns) typically comprise a cylindrical container defining a heating chamber within. The container is supported by riding rings that are in turn supported by rollers mounted on a support framework. Rotary motion is imparted to the container by a rotary drive such as a chain drive that operatively links a drive motor to a cog or cogs attached to the exterior of the container.

Rotary heat exchangers for high temperature processes have traditionally had an inner refractory brick lining. This results in a very heavy structure requiring massive supports and high-power ddve motors. Such rotary heat exchangers or kilns are costly to maintain and repairs and periodic replacement of the brick lining Jead to considerable loss of production efficiency given the very long periods of time that are required to cool the kiln down and to subsequently return it at a controlled rate to its operating temperature. It is also difficult, if not impossible, to adapt these kilns to cope with a variety of materials to be fired; they tend to be commissioned for a specific purpose and very time consuming and costly modifications required if they are to be adapted for an alternate purpose.

In my earlier UK patent no. GB 1 600 373, I describe a much improved rotary heat exchanger in which the heat exchange chamber has a non-circular internal cross-section with three equi-spaced lobes, having a trefoil shape. The walls of the heat exchange chamber have a relatively light weight, sandwich construction, having an inner heat-resisting lining, an outer casing and a thermal insulation layer in the space between the lining and casing. This lobed form of heat exchanger has been shown to have a relatively high heating efficiency, due to the continual intensive turnover of the particulate material as the chamber rotates, meaning that the chambers can be much shorter than a more conventional plain cylindrical chamber. The wall construction means that the kiln can be rapidly cooled for repair and maintenance and brought back to operating temperatures much quicker than a brick-lined kiln (hours instead of days). This weight reduction compared with conventional kilns also greatly assists the transportability of the kiln. However, this improved kiln still suffers from the drawback that it can be difficult to adapt for changing purposes; as with the conventional kiln they tend to be commissioned for a specific purpose.

It would be advantageous, therefore, to provide a rotary heat exchanger (e.g. kiln) that can be readily and inexpensively adapted for different purposes.

Sumrnaiof invention A general proposition of a first aspect of the present invention is for a rotary heat exchanger (e.g. kiln) that can be quickly and cheaply configured on site from a number of standard components to meet whatever process demands may be made upon at any given time. Such a kiln, that can be provided in "kit form" offers very significant advantages over conventional kilns and my own earlier kiln referred to above, as it can be very rapidly deployed and adapted as process demands change over time.

In a first aspect the present invention provides a rotary heat exchanger comprising a support structure, a rocking cradle mounted on the support structure for back and forth rotary motion relative to the support structure, and at least one container mounted on the cradle and constrained to rotate with the cradle, the container defining a heat exchange chamber within having entry and exit openings at opposite ends along its rotary axis.

As the container for the heat exchange chamber is a separate component from the cradle and support structure, a very versatile, modular construction is possible. With this configuration, the cradle in effect serves as a table' upon which one or more containers can be placed. A rotary rocking motion can be imparted to the container(s) by driving the cradle to rock back and forth, with a drive means such as a reversing electric motor, for example, with a chain drive or other suitable mechanism linking the motor to the cradle.

A variety of different, standard containers can be provided, with different configurations (for example different heat exchange properties and/or different ancillaries), so that for any given installation, one or more appropriate containers can be selected, mounted on the cradle and connected together, with the exit opening of one chamber connecting to the entry opening of an adjacent chamber, so that material can pass from one chamber to the next. A typical installation will have at least two containers and more typically three or four or five or six or more containers, as required to satisfy the specific process demands. In some installations there may be as many as eight or even more containers.

Two or more of the containers may be of the same configuration as one another. For instance, where the installation comprises a number of processing zones in series, one or more of the zones may each comprise multiple containers of the same configuration.

At the inlet end of the installation, material to be processed may be introduced to the first heat exchange chamber either through the entry opening of the chamber or, more preferably, through an opening in the top wall of the chamber for a more reliable gravity feed of new material into the chamber. In the latter case, the entry opening of this first chamber is preferably closed, for example with a blanking plate or alternatively a sight glass that enables an operator to visually inspect the chamber.

To feed of material through the rotary heat exchanger, from one heat exchange chamber to the next may be a simple gravity feed, with each chamber being tilted slightly downwards from, for example by about I to 2 degrees, towards the exit end, so that the particles tumble from one chamber to the next, through their joined exit and entry openings, as the chamber rocks.

The entry and exit openings in end walls of the chambers are preferably spaced from the base of the chamber. In this way, a portion if the end wall below the exit opening acts as a baffle to retain a minimum amount of material within the chamber, controlling the flow of material from one chamber to the next.

Although each container is constrained to rotate with the cradle, they need not be similarly constrained in their longitudinal direction. Indeed, they may be free to slide on their axial direction away from an end stop, e.g. to allow for thermal expansion.

The cradle and the support structure that the cradle is mounted on may themselves be modular, assembled from standard segments, differing numbers of which can be connected together to achieve the desired length of cradle to support the configuration of containers that it is determined are required for a given process. In some embodiments, each cradle segment may be designed to support only a single container, in a complete installation, the number of cradle segments being equal to the number of containers.

Alternatively, the cradle segments may be sized to each hold two or more containers.

Preferably, the containers, cradle and support are sized to be readily transportable.

They may, for instance, be designed to be transported within limits set by a standard shipping container frame (e.g. approx B x B x 32 ft).

The heat exchange chamber within the container preferably has a non-circular internal cross-section transverse to its axis of rotation, comprising a plurality of lobes. As in my earlier GB 1 600 373, these lobes are shaped so that material within the chamber is alternately restrained to co-rotate with the chamber and then allowed to slip under gravity during continued rotation of the chamber. As the chamber rotates back and forth with a rocking motion, this lobed configuration causes the material to tumble from one lobe to another and back to obtain substantially uniform heating of the material.

The lobes preferably have a curved profile and are so shaped as to retain the material therein against slippage until they have undergone a substantial angular displacement from their lowest position, e.g. preferably at least 20 degrees, when a critical slope is reached. The material then begins to slip and a the complete mass of particles is turned over in to the adjacent lobe relatively rapidly to come to rest again until the critical angle is again passed as the chamber rocks back in the opposite direction.

In a preferred form, a base of the chamber has two lobes symmetrically arranged with respect to the chamber axis. The roof of the chamber is preferably curved but need not have lobes. In a preferred embodiment, the chamber is kidney' shaped, with two lobes in the base and a roof with a curved profile with a radius twice that of the radius of each lobe.

The containers are themselves preferably of a modular construction, so that different configurations of container can be assembled from a set of standard container components. The container is preferably in two, separable parts, a base and a roof.

Each of these parts preferably has a sandwich wall construction the same or similar to that described in my earlier GB 1 600 373, with an inner lining, and outer casing and a thermal insulation layer in between. For high-temperature operations, the inner lining of at least the base part is a heat-resistant material such as a ceramic. For lower temperature operations, for instance drying, the inner lining may be a less expensive material such as steel. In some cases it may also be desirable to have an inner wall in the base that is configured as an air distribution plate to introduce combustion air from below the bed of material in the chamber. These different forms of inner lining can be assembled with an outer casing and insulation layer common to all of them.

Similarly, alternative roof parts may be provided. For instance, one form of roof part may have a relatively large opening through which material may be introduced. Another form of roof part may have a relatively smaller opening for the introduction of a burner and/or instrumentation for example. Another form of roof part may have no opening.

Embodiments of the rotary heat exchanger of the first aspect above can be used for relatively low temperature heating processes, such as drying of particulate materials in a heated gas stream, as well as for the combustion of material and/or the manufacture of burned or fired materials that may require to be subjected to temperatures as high as 1500°C. Embodiments of the rotary heat exchanger can also be used for other heat exchange processes, such as cooling. Advantageously, given the modular nature of the heat exchanger, sections with different configurations can be assembled in-line to provide an apparatus with having a number of zones with different heat exchange properties that the particulate material can pass through in series as it is processed. For instance, material may be introduced to a drying zone, pass to a firing zone and then on to a cooling zone before discharging from the apparatus.

One exemplary use for embodiments of this first aspect of the invention is the production of artificial aggregates from argillaceous material (e.g. clay or shale). Furthermore, if waste material is mixed with the argillaceous material, this mixture can be fired to produce an artificial or synthetic aggregate; a particularly effective way of disposing of waste, especially given the shortage of landfill sites and the rising cost of waste disposal, that also results in a useful, benign end product.

For any given installation, appropriate component parts can be selected to assemble the required containers needed to meet the process demands, the assembled containers and associated cradle and support segments can be readily transported to the site and quickly assembled. The assembly may be provided on a temporary basis to deal with a specific one off waste disposal requirement or a more permanent basis, for instance at a waste disposal site, but can be easily modified as and when the waste disposal requirements change.

f Desçjption of Drawinq An embodiment of the invention is described below, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view through a rotary rocking heat exchanger assembly in accordance with an embodiment of the present invention; Figure 2 shows a side elevational view and end view of an assembled cradle and support structure of the heat exchanger assembly of fig. 1, along with a perspective view of a cradle segment; Figure 3 shows, in a perspective view, examples of standard components that can be used to assemble containers for the heat exchanger assembly of fig. 1; Figure 4 shows, in a perspective view, a roof part of a container and an insulated cowl for use in combination with the roof part; Figure 5 illustrates schematically the rotary rocking operation of the heat exchanger assembly in a container having the roof part and cowl of fig. 4, along with views of end covers for the containers; and Figure 6 shows a schematic side view of a complete installation configured for disposal of waste such as sewage sludge.

Description of an Embodiment

Figure 1 illustrates a rotary (rocking) heat exchanger in accordance with an embodiment of the invention. The heat exchanger comprises a cradle I that is supported through rollers 2 in steel channel guides 3 (that serve as a support structure for the cradle 1) and a container sat within the cradle I. The cradle I can be rocked back and forth in a rotary fashion relative to the guides 3.

The container is constrained to rock with the cradle 1, In this example, the cradle I can be rocked through 45°, in either direction, indicated by the arrows, by use of a reversing electric motor drive 4 and chain 5. Opposite ends of the chain 5 can be attached to the cradle I using eyebolts 14 (see fig. 2), which supplement or take the place of the rollers 2 in some sections of the cradle I. The container, shown diagrammatically in cross section in fig. 1, is in two parts; a lobed floor 6 and a roof 7, which when assembled define a heat exchange chamber within the container. These two parts are joined (e.g. bolted) together at flanges 8 to either side of the container. The floor part 6 has brackets 9 to opposite sides which rest upon respective ledges 10 formed on the cradle I (e.g. welded to the cradle segment).

The preferred heat exchange chamber profile, as illustrated, is kidney shaped with the roof radius twice that of the lobe radius.

Fig. 2 shows a side elevation and end view of an assembled cradle and in perspective a segment 11 to which a roller 13 may be attached or an eyebolt 14 if the segment is to be used also as a support segment as indicated at 12 or a drive segment as indicated at 15. The support segments 12 mount the cradle support structure (i.e. the guides 3) on a base 16 that, as with the cradle I and guides 3, may be composed of standard segments bolted together.

Fig.3 shows in perspective some of the standard components that can be selectively assembled to form containers of differing configuration. The part at the top of the figure, labeled 17, is an internally insulated roof section fitted with ports 18, 19 through which a burner, instrumentation or other process requirement may be introduced.

Below this is shown a floor furnishing suitable for processing at 1500°C. This floor section comprises cast refractory blocks 20, one at each end, with fixing bolts 21 for fixing the floor section to an outer framework 30 and cover plate 25. The inner faces of the block 20 (i.e. those surfaces facing one another) have grooves 22 formed therein in which respective ends of a plurality of ceramic rods 23 are received. These rods are forced against the upper surface of the grooves by compressing ceramic fibre blanket 24 onto them using outside cover plate 25. This method of assembly allows for thermal expansion of the rods, which may for example be silicon carbide, and provides a spring or cushioning effect to dampen any inadvertent impact loading from the bed of material being processed.

Below this again is an alternative floor furnishing in the form of an air distribution plate 26 having a series of apertures fitted with mushroom caps 27 for introducing combustion air to the bed. Air is supplied to this plate 26 through air boxes 28 attached externally to each lobe. A fan may be attached to pipes 29 and electrically controlled so as only to provide air when the mushroom caps are covered.

Operated in reverse this furnishing can draw cold air through a fired bed to provide cooling as shown in Fig 6. This furnishing is also insulated on the outside using ceramic fibre blanket 24. The steel framework 30 into which either of the two types of floor furniture may be fitted is provided with cover plates 25.

Fig. 4 shows in perspective an internally insulated roof section 31 through which material to be processed may be introduced at any point along the kiln or gases extracted. It is provided with an insulated cowl 32 that extends over the roof section 31 of the container, adjacent the opening but does not rock with the container. The cowl may, for example, be mounted on the cradle support.

The cooperation between the opening in the roof section 31 and the cowl 32 is seen in fig. 5, which shows how the combination of the feed roof section 31 and the cowl 32 enables material 33 to be introduced and gas 34 extracted throughout the rocking cycle without the need to have a material feed or gas exhaust that moves with the rocking container.

Also in Fig. 5 there is shown an end cover for the kiln 35 that can be fitted with a sight glass at the feed end and through which processed material can be discharged at the exit end. Bolted back to back as indicated at 36 these components can provide dividers to separate one zone from the other as shown in Fig.6.

An exemplary assembly configured for a waste disposal operation is seen in fig. 6. In the configuration shown the feed may, for example, be p.f.a. (pulverized fuel ash) recovered from an old tip and having a significant carbon content, mixed with sewage sludge provided for disposal and pelletized. At the inlet / feed end of the assembly there is a drying zone, which is supplied with warm air from the cooling zone. In the burn-out zone the bed temperature is regulated by variable speed fans drawing in atmospheric air for combustion and passing this through the bed. The hot gases from the burn-out zone pass through a heat exchanger in which steam may be raised for heating purposes. In the sinter zone the pellets are raised to the desired temperature using roof mounted burners following which they enter the cooling zone before discharge.

As the skilled person will appreciate, the invention has been illustrated above with a specific embodiment by way of example only. Various modifications to that which has been specifically described are possible within the scope of the invention. In particular, the number and configuration of the heat exchange chambers can be selected to satisfy the demands of a given process.

Claims

Claims: 1. A rotary heat exchanger comprising a support structure, a rocking cradle mounted on the support structure for back and forth rotary motion relative to the support structure, and at least one container mounted on the cradle and constrained to rotate with the cradle, the container defining a heat exchange chamber within having entry and exit openings at opposite ends along its rotary axis.
2. A rotary heat exchanger according to claim 1, comprising a plurality of containers mounted on the cradle for rotation therewith, the exit opening of one chamber connecting to the entry opening of an adjacent chamber, so that material can pass from one chamber to the next.
3. A rotary heat exchanger according to claim 2, comprising at least three or more containers.
4. A rotary heat exchanger according to claim 2 or claim 3, wherein at least one of the containers has a chamber with different heat exchange properties to the chamber of at least one other of the containers.
5. A rotary heat exchanger according to any one of claims 2 to 4, wherein at least one of the containers has a chamber with the same heat exchange properties as the chamber of at least one other of the containers.
6. A rotary heat exchanger according to any one claims 2 to 5, wherein each container is tilted downwards towards the exit end, so that the particles tumble from one chamber to the next through their joined exit and entry openings as the containers rock.
7. A rotary heat exchanger according to claim 6, wherein each container is tilted downwards by about I to 2 degrees.
8. A rotary heat exchanger according to claim 6 or claim 7, wherein the entry and exit openings in end walls of the chambers are spaced from the base of the chamber so that a portion of the end wall below the exit opening acts as a baffle to retain a minimum amount of material within the chamber, controlling the flow of material from one chamber to the next.
9. A rotary heat exchanger according to any one of the preceding claims, wherein the cradle and/or the support structure that the cradle is mounted on are modular constructions assembled from standard segments.
10. A rotary heat exchanger according to any one of the preceding claims, wherein the heat exchange chamber within the or each container has a non-circular internal cross-section transverse to its axis of rotation, comprising a plurality of lobes.
11. A rotary heat exchanger according to claim 10, wherein the lobes have a curved profile and are so shaped as to retain the material therein against slippage until they have undergone a substantial angular displacement from their lowest position.
12. A rotary heat exchanger according to claim 10 or claim 11, wherein a base of the chamber has two lobes symmetrically arranged with respect to the chamber axis.
13. A rotary heat exchanger according to claim 12, wherein the roof of the chamber is curved with a radius twice that of the radius of each lobe such that the chamber is kidney' shaped.
14. A rotary heat exchanger according to any one of the preceding claims, wherein the container is of a modular construction, so that different configurations of container can be assembled from a set of standard container components.
15. A rotary heat exchanger as described herein with reference to and as illustrated in figures Ito 5 and 6 of the accompanying drawings.Amendments to the claims have been filed as follows C1ms: 1. A rotary heat exchanger comprising a support structure, a rocking cradle mounted on the support structure for back and forth rotary motion relative to the support structure, and a plurality of containers mounted on the cradle and constrained to rotate with the cradle, the container defining a heat exchange chamber within having entry and exit openings at opposite ends along its rotary axis, and wherein the exit opening of one chamber connects to the entry opening of an adjacent chamber, so that material can pass from one chamber to the next.2. A rotary heat exchanger according to claim 1, comprising at least three or more containers.3. A rotary heat exchanger according to claim 1 or claim 2, wherein at least one of the containers has a chamber with different heat exchange properties to the chamber of at least one other of the containers.4. A rotary heat exchanger according to any one of claims 1 to 3, wherein at least one of the containers has a chamber with the same heat exchange properties as the chamber of at least one other of the containers.5. A rotary heat exchanger according to any one claims I to 4, wherein each container is tilted downwards towards the exit end, so that the particles tumble from one S.....* chamber to the next through their joined exit and entry openings as the containers rock.* us*.. * .6. A rotary heat exchanger according to claim 5, wherein each container is tilted * fl' downwards by about ito 2 degrees.7. A rotary heat exchanger according to claim 5 or claim 6, wherein the entry and :. exit openings in end walls of the chambers are spaced from the base of the chamber so * that a portion of the end wall below the exit opening acts as a baffle to retain a minimum amount of material within the chamber, controlling the flow of material from one chamber to the next.8. A rotary heat exchanger according to any one of the preceding claims, wherein the cradle and/or the support structure that the cradle is mounted on are modular constructions assembled from standard segments.9. A rotary heat exchanger according to any one of the preceding claims, wherein the heat exchange chamber within the or each container has a non-circular internal cross-section transverse to its axis of rotation, comprising a plurality of lobes.10. A rotary heat exchanger according to claim 9, wherein the lobes have a curved profile and are so shaped as to retain the material therein against slippage until they have undergone a substantial angular displacement from their lowest position.11. A rotary heat exchanger according to claim 9 or claim 10, wherein a base of the chamber has two lobes symmetrically arranged with respect to the chamber axis.12. A rotary heat exchanger according to claim 11, wherein the roof of the chamber is curved with a radius twice that of the radius of each lobe such that the chamber is kidney' shaped.13. A rotary heat exchanger according to any one of the preceding claims, wherein the container is of a modular construction, so that different configurations of container can be assembled from a set of standard container components.S* S....* : 14. A rotary heat exchanger as described herein with reference to and as illustrated * * in figures 1 to 5 and 6 of the accompanying drawings. * . * *54 I s*e * S S. * * *4 S 5"