DE2809223A1 - ROTATING HEAT EXCHANGER - Google Patents

Description

f'afenfsnwSfte

Rosentfia! 7 / II. "5543

Munich 2

March 3, 1978

SHERWBN ENGINEERING- COMPANY LIMITED, Mile End Green, Dartford, Kent, England

Rotating heat exchanger

The invention relates to rotating heat exchangers in which particulate material, e.g. powder, granules, Pellets or larger masses that move or circulate when the chamber rotates. The term heat exchanger is intended to include a device in which heat is transferred by radiation and / or conduction heating.

While the invention is applicable to heating processes at relatively low temperatures, e.g. It is particularly concerned with drying particulate materials in a heated gas stream such a device when burning material and / or producing burned or burned materials, namely those that are subjected to temperatures of perhaps e.g. t300 ° C or more during their processing have to. For example, the burning of lime, the production of dead-burned magnesia or cement and in particular the production of artificial aggregates from material

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lien like clay or clay or slate are mentioned ^ wherein the material is machined to obtain larger aggregate pieces within a desired size range.

The use of cylindrical rotating chambers for heating particulate material is well known. By turning the chamber around its cylinder axis is the material by the opposing forces of friction with the Drum surface and gravity are moving continuously, and fresh surfaces are continuously moving exposed to the heating influence of a flame or a stream of hot gas.

The amount of material that can be easily heated in the chamber at any time is, however, severely limited with regard to the chamber size, as it increases with the depth of the Bed of material becomes harder to ensure that all particles are exposed sequentially to the heat source. Uneven heating of the material can, and at times, require a longer heating time difficult to obtain a sufficiently uniform end product. Furthermore, if the entire mass is within the Chamber is not moved continuously, individual particles can grow together even while they are moved, and the physical and / or chemical changes intended by the heating process cannot occur. This effect can occur under high temperature conditions, such as when burning loam or clay containing materials cause large masses of material to melt together and form masses of slag or clinker which are discarded and may actually be difficult to remove from the chamber.

It is known to have inwardly extending projections such as axially arranged rods to be provided on the chamber walls,

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to increase material circulation, and they can too the effect of increasing the depth of the material bed adhere. The cylindrical shape of the furnace is retained, not least because the circular cross-section is necessary for strength and also the most effective Form under the aspect of heat loss through the walls. Limit for high temperature applications also the harsh physical conditions are used Such steps: In the Danish patent application 128 218, a brick-lined furnace turns different bricks Strength to form inwardly protruding projections, but these must be kept flat and against Abrasion and impact on the part of the furnace contents are protected by metal reinforcements, which in turn cause damage and hardly change the conventional circular cross-section.

It should be noted that the known cylindrical rotary chambers Due to the small thickness of the material of the chamber, a considerable proportion of the heat input during the cooling effect the chamber walls can lose on the material, which reduces the operating performance. With high temperature processes A high-temperature-resistant brick lining is provided, which results in a very heavy furnace structure leads and requires massive support structures and energy-consuming drive motors. Such ovens are because of The need for frequent repair and replacement of the liner is costly in maintenance. this leads to also to a considerable loss of production and efficiency, since the furnace cools down at every opportunity must be able to and must then be brought back to operating temperature at a controlled speed. Because Due to the high heat mass, these processes can take several days.

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According to the invention, a rotatable heat exchanger is provided which has a chamber through which a particulate Material for heating or cooling can be guided in the chamber by means of a device, the Chamber has a non-circular internal cross-section with a large number of arcs at right angles to its axis of rotation, whereby the material in the chamber can alternately be prevented from rotating together with the chamber, and then again during continued rotation of the chamber under the influence of gravity to slide can be arranged «

In an advantageous manner, the cross section is formed by an arrangement with three spatially evenly arranged arcs of a clover-leaf shape. It can have a larger number of such arcs, but not in such a way that their depth is inappropriately restricted, since they should be relatively deep radially to the axis of rotation of the chamber, for example between 20 and 60, preferably about 40 and 55 % of the maximum radius of the chamber » The arches are suitably curved and are designed to prevent the material from slipping off until they have undergone significant angular displacement from their lowest position, e.g., preferably at least 20 from the position at which a critical slope angle is reached . Then the material begins to slide, and the entire particle mass is turned relatively quickly in order to come to rest again until the critical angle is exceeded again due to the progressive rotation of the furnace.

If the material is heated by one or more burners, it can be achieved that between each slip, direct Radiant energy from the burner acts on the top layers of the material for a relatively long time, and the Burner can be provided with reflective devices

be to increase the release of radiant heat to the material, while heat also passes through conduction from one Hot gas flow can be transmitted over the material. The cross-sectional profile of the chamber can also be designed so that from the uppermost sheet or sheets from which the material has already fallen, preferably radiating heat directed towards the bulk of the material in an ascending arc.

With the repeated occurrence with each revolution of the chamber by completely circulating the material, it is possible to achieve practically uniform heating of the material, learner the material bed can be kept relatively deep in the chamber by the retention effect of the arches, so that a smaller surface is in contact with the chamber walls for a given volume of material and the cooling effect of the Walls is reduced.

A rotary chamber according to the invention can be used for high-temperature operation a furnace structure with a heat-resistant inner lining and outer load-bearing supports for comprising the liner and the chamber contents with the supporting means extending longitudinally across the furnace, but is thermally insulated from the inner lining. The inner lining naturally has the aforementioned cross-section with arcs to increase the direct radiant heating from one or more burners in the furnace onto the one to be processed Material.

The heat-resistant inner lining of the furnace can form the inner layer of a sandwich construction, with a thermal insulation layer lies in the tree between the heat-resistant inner lining and an outer lining. the Inner liner can be a one-piece perimeter construction which either extends over the entire length of the chamber or consists of a series of shorter lengths with overlapping

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penden connecting parts, or they can be a number similar segments welded together, and in Each EaIl it is supported by the outer housing segments directly through the insulating layer, which is made by a mold which can transfer the load bearing load from the inner lining directly to the outer lining.

If the inner lining is a single peripheral unit, it can however, it suffices to focus solely on the spacer effect the insulating layer to leave the inner lining in relation to the outer lining in place to keep.

The invention is explained below by way of example with reference to the schematic figures; show it

Pig. 1 and 2 are a side view and a cross-sectional view, respectively, of a high temperature heating rotary chamber or a furnace according to the invention,

Fig. 3 is a detailed sectional view of the sandwich construction of the Walls of the chamber according to Figures 1 and 2,

FIG. 4 is a schematic plan view of that shown in FIG. 2 Burner,

5 and 6 show the fuel supply system of the burner in the Figures 4 and 5 and

7 and 8 are a side view and a cross-sectional view of a further rotary heat exchange chamber according to the invention for operation at a lower temperature than in the previous examples.

According to FIGS. 1 and 2, the furnace has a rotating container which is mounted on a fixed support frame 14. Of the Container is carried by rollers 16 on the fixed frame and on it are seated end rings 18 which are fastened to the container are. The end rings act as circular guideways for the rotation of the container by a or

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several hydraulic motors 20 mounted on the fixed frame and also with the end rings are engaged. The container has a heating chamber 22 with a clover leaf shape, that is, with three deep arches 24 provided inner cross-section, the arches each showing a curve profile. The vertices or transition areas 26 between the arcs are flattened to prevent overheating. With this particular one Example the arcs are circular, with a diameter equal to the chamber radius in the center of the arcs, and their circle points all intersect on the central longitudinal axis of the chamber.

The furnace walls have a sandwich construction with a 6 mm thick outer support jacket 32 made of weldable steel, a 100 mm thick main insulating lining 34, the cooler outer layers of which are mineral wool and the inner layers are hotter Layers of ceramic fiber, a permanent inner liner 36 of a high temperature alloy, e.g. 3 mm Incoloy 800H, a heat-resistant alloy rich in Ni and Cr. Preferably lies within these layers also a thin 12 mm thick layer 38 made of ceramic fiber insulation and one entirely inside High temperature alloy liner 40, also made from 3mm Incoloy 800H, which forms the inner surface of the furnace.

All layers of this construction have similarly curved profiles with flattened transition zones between the arches. The outer shell wall 32 can be made first with the end rings close to each other Ends of the container rest on rollers 16 for carrying. Spacers 44 attached to the inner surface of the shell wall lay the inner liner 36 fixed, which is manufactured as a one-piece circumferential unit, e.g. from welded sheet metal (however, it can also be used as a a series of short axial pieces are made, which then

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overlapping with each other within the shell wall Circumferential connections are put together). The spacers 44 place the liner 36 evenly apart from the outer shell wall, and the insulation 34 is then wrapped and optionally acts as a Spacers. The insulation 38 is then placed over the liner 36, and finally partial sheets of the innermost lining 40 placed over the second insulating layer and welded together to form a continuous inner wall

The plies or layers of sandwich construction will not positively attached to each other to allow differential thermal expansion. Nevertheless, due to the non-circular cross-section, they are circumferentially defined without to shift. The inner layers or layers are covered over their entire circumferential surface by the outer housing wall and also the weight of the material in the oven is similarly applied directly to the outer shell wall transfer. The inner metal linings are thus practically stress-free, and the loads are from the relatively cold outer shell walls are caught and transferred to the rollers 16 via the end rings 18.

Nevertheless, it is to be expected that under very high temperatures and with abrasion from the furnace contents, the innermost lining 40 can wear out during operation. The inner liner 38 acts as an indication _for that a hole in the liner 40 will appear, and this can then be repaired. Normal abrasion or wear and tear can therefore be repaired without impairing the intermediate lining 34, the service life of which is further extended due to the insulating effect of the layer or ply 38.

At the material entry end of the chamber there is a cylindrical

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drical port set 52 of a slightly smaller diameter than the minimum diameter in the transition areas between the arches. In the entry end of the chamber extension there is an entry container 54 into which the material to be burned is entered through an upper opening 55. The material falls on a cascade of Blades 56, which deflect it towards the cylindrical extension, but ensure that a free one for the furnace exhaust gases Passage for outflow from an outlet opening 58 remains, such as a rear outlet as shown. More details of the way in which this entry and Outlet connections are used are in the

(simultaneously filed) patent application P ...

specified. The cylindrical extension has a cruciform, axially extending barrier 60 dividing the interior into a series of smaller passages forming a passageway to form the main arched area of the furnace where more intense agitation occurs.

At the discharge end of the furnace, the burned particles pass through a chute 62 which leads to a discharge line 64 which is connected to a compressed air blower 66 . Cold air from the fan hits the material, which it suddenly cools and also takes with it in the manner of a jet pump, so that it is carried away in the air stream.

The furnace heat source may be a radiant liquid fuel burner such as a heat lance 68 which is coaxial protrudes into the chamber from a fixed attachment 69 at the end of the material aus. Since the oven is mainly relies on radiant heat, the arcuate cross-section offers an advantage by reducing the radiant energy significantly is better focused on the material than in a conventional rotary kiln. In other words, with one given burner length is the radiant heat flux density on the surface of the material bed considerably

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increases, and the heat flux density can be up to 2.5 times a conventional design. This fact along with the upheaval that the whole Continuously exposing material to radiant heat allows a much shorter furnace to be used than one Great cylindrical furnace with the same output.

The burner can use its radiant heat energy will be operated under essentially stoichiometric conditions and it is minimal Gas flow through the furnace is necessary. This lowers the need for dust removal from the exhaust gases, but what about processes is of greater importance where there is an excess of oxygen can have an adverse influence, as in the burning of clay or clay materials, it is easier to put in to maintain a non-oxidizing atmosphere in the chamber.

Figures 4 to 6 show further details of the burner 100 der! Ig. 2 and its control devices. The burner has a housing 102 that extends over the entire or extending a substantial part of the entire length of the furnace and at both ends of stub shafts is held. The housing has a focal surface 106, from where from the burner flames hit the material to be processed, to it through direct flame contact as well as through To heat radiant heat. The burning surface is inclined to the horizontal so that it is in an arc of the furnace held material is opposite, at the stage at which the material slips into the subsequent arc starts when the furnace rotates, with the burner housing itself normally remains stationary, but on its stub shafts up to an optimum angle for a chosen furnace rotation speed is tiltable.

The burner housing may have an inner liner 108 have stainless steel, covered with a layer of

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ceramic fiber insulation 110 and clad with a outer cover made of Incoloy 112 or a ceramic or cermet material. In particular, the focal surface must have good heat resistance properties, but the opposite surfaces of the burner housing will not used as radiant heating surfaces and are only subject to external heat influences. They are therefore much lower Exposed to maximum temperatures and require less protection.

A large number of burner nozzles 114 are useful on top of that entire extent of the focal surface arranged. The nozzles are grouped to common fuel supply lines 116 with groups of e.g. 6 nozzles over a short distance, e.g. 15 cm, of the length of the burner housing. Control valves 118 in the supply lines to the respective groups of nozzles are regulated by pyrometers 120, which are also arranged in the focal surface, each close to its own group of nozzles, so that the temperature profile along the burner housing as well as the maximum temperature at the combustion surface can be controlled.

The burner is operated with oil firing (but gas firing can also be provided) and the nozzles 114 are conventional feather pressure nozzles, such as those used in household heating systems are known, wherein a common pump 122 supplies a divider circuit 124 from which all burner nozzles are supplied. A compressed air fan 126 supplies combustion air with a slight excess pressure through a conduit 127, the interior 128 of the burner housing 102 acting as a conduit for the air flow and at the same time is cooled by this.

The shape of the focal surface, in particular the concave shape shown in FIG. 3, is chosen to reduce its radiant heat emission to concentrate on the material to be processed

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trier, but the rear surfaces of the housing can have any appropriate shape. Since the burner housing offers the possibility of direct most of the heat dissipation To aim at a relatively deep bed of material “is that Temperature of the furnace interior walls lower, and it can also be possible to lead a flow of cooling gas through the space behind the burner. It can therefore turn out to be possible prove to be economically advantageous for both the high-temperature protection of the housing and its thermal insulation to design.

The embodiment of the invention shown in FIGS. 7 and 8 is not intended for the very high temperatures of the preceding examples and acts as a low-temperature dryer in the patent application mentioned. In this further construction, the cross-sectional shape of the chamber is as already described, but the heat source is a hot gas stream, e.g. the combustion gases for the purpose of heating and / or drying particulate material in the chamber. The internal metal walls of the chamber are at a sufficiently low temperature to form part of a load-bearing structure, and it is simple enough to surround this internal housing with an outer layer of heat-insulating material (not shown) to avoid undue heat losses. The heating gases are generated in a burner in an air flow generated by a compressed air blower 82, the flow being conveyed through the chamber by a suction air blower 84 at the discharge end. The gases enter the chamber through a central-axial tube 86 with exit slots 88 which run in the longitudinal direction of the chamber an ascending arc ₉ is directed analogously to the burner shown in FIG. Transverse baffles 90 are

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spaced the length of the chamber to ensure that a minimum amount of material is retained will. Material is introduced through a fixed entry chamber and an exhaust chimney 92 is with the outlet of the fan 84 connected.

The dryer rotary chamber is in a static support frame 93 mounted by end mounting rings 94 attached to the Chamber lining are attached, and is carried by rollers 95, with a drive device 96 as in FIG the example of the Pig. 1 works. In this pail they are End rings attached to the chamber by pairs of attachment rods 97 located between circumferentially Splash 98 of the fairing and blocks 99 protruding inwardly onto the mounting rings.

In each example of a chamber described, the material is gradually advanced through the chamber as it rotates, because the chamber is inclined slightly downwards by about 1 to the end of the material discharge. Because of the arch-shaped Cross-section of the chamber, the material in the floor arch is raised to the point as it rotates at which its angle of repose is exceeded. Then a thicker top layer slips off and falls into the next one deeper arch, which is quickly followed by the rest of the material that had previously formed the lower layers, but that now falls on the first part of the material. This process repeats itself continuously, when each arc is from a deepest one Position ascends. [In fact, the material is continuously circulated when it is in free flow into a certain area of the cross-section of the chamber falls, so that the entire material of the heat source three times with each revolution is exposed to the chamber at a concentration similar to that of a plied bed.

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The migration rate of the material through the chamber _S can be controlled by varying the downward inclination of the longitudinal axis of the chamber from the material entry end, for example, characterized in that the support rollers are vertically adjustable against one end of the chamber.

Due to the relatively high heating output of the described, arched heat exchangers as a result of the continuous intensive circulation of their contents can these Chambers are much shorter than a full cylinder tower Chamber, especially as regards a high temperature or kiln. The oven described with its light weight Insulation can be cooled for repair in a few hours and brought back to operating temperatures, and the weight reduction also greatly promotes transportability in comparison with a conventional furnace with a brick lining or a refractory, pourable cement lining, although it is possible to have the arcuate cross-sectional shape with conventional materials to use.

Of course, the terms used herein include heat exchangers and heating chamber all heat exchange chambers including those that have a cooling effect on the material, by exposing it to a cooler gas flow, since in this case the gas is heated. One example is that Cooling chamber for burned pellets, which is described in the mentioned (simultaneous) patent application.

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Claims (16)

Claims 1.j Rotatable heat exchanger with a chamber through which a particulate material can be fed for heating or cooling, characterized in that the chamber has a non-circular inner cross-section transverse to the axis of rotation with a number of arcs (24), whereby the material within the chamber are alternately prevented from rotating with the chamber and then can slip under the influence of gravity during the further rotation of the chamber. 2. Heat exchanger according to claim 1, characterized in that the cross section three spatially uniformly designed Has arches (24). 3. Heat exchanger according to claim 2, characterized in that the arches have a radial depth between 20 and 60 % of the maximum radius of the chamber cross-section. 4. Heat exchanger according to claim 3, characterized in that the radial depth is between 40 and 55 % of the maximum radius. 5. Heat exchanger according to one of the preceding claims, characterized in that at least one in the chamber circumferential baffle member (90) for retaining a minimal amount of migration through the chamber Material is present in the area behind the impact member. 6. Heat exchanger according to one of the preceding claims, characterized in that it is a generally cylindrical Entry section (52) has been fed through the material to the arcuate cross-section and the one radius is not greater than the inner radius of the arcs (24) nat. 0830 2809 ?? 3 7. Heat exchanger according to one of the claims related to the gate, characterized in that heating devices (68 or 100) extend axially through the central region of the chamber over at least a major part of it Extend length. 8. Heat exchanger according to one of the preceding claims, characterized in that it is used as a high-temperature heating rotary chamber or oven and a sandwich wall construction with a heat-resistant Metal inner lining (36), a heat-insulating intermediate jacket (34) and an outer metal housing (32), through which the weight of the inner lining and the contents of the furnace is taken up. 9. Heat exchanger according to claim 8, characterized in that a further heat-resistant lining (40) provided within the first liner (36) and from the first liner by an insulating layer (38), which is thinner than the first insulating layer (34), is separated. 10, heat exchanger according to claim 8 or 9 »characterized in that that it is designed as a rotary kiln whose inner lining (s) (36, 40) relative to the outer Housing (32) by contact pressure from the adjacent insulating layer (34, 38) of the sandwich wall construction between the lining and the housing fixed locally and otherwise to adapt to the thermal expansion is or are freely movable. 11. Heat exchanger according to one of the preceding claims, which is equipped with a liquid fuel burner Has heating devices, characterized in that the burner (100) has one for directing heat that of an ascending arch (24) of the chamber cross-section held during the rotation of the chamber BQ9836 / 0339 materially arranged focal surface (106) has " 12. Heat exchanger according to claim 11, characterized in that that the burner (100) around the axis of rotation of the furnace to adjust the direction of heat emission is tiltable. 13 · Heat exchanger according to claim 11 or 12, characterized in that that the focal surface (106) of the burner has a cross-section of concave shape for compression which has radiant heat energy on the material. 14. Heat exchanger according to one of claims 1ΐ to 13, characterized in that devices (118, 120) intended to control the variable heat emission of the burner over the length in the axial direction of the furnace are. 15. Heat exchanger according to claim 14 »characterized in that that the burner has a plurality of fuel nozzles combined into groups (114) on which the combustion in each case by temperature sensors (120) is controllable, each of which is arranged in or near the area of the respective nozzle groups. 16. Heat exchanger according to one of the preceding claims, characterized in that at the furnace discharge end a cooling gas flow (64) for porting the heated material is arranged as a jet pump by a discharge line with cooling. BG3S36 / 0838