EP1580511B1 - Device for maintaining temperature of bulk material - Google Patents

Description

The invention relates to a device for controlling the temperature of bulk material.

Such tempering may consist of heating or cooling a bulk material. If there is a supply of heat to the bulk material, then it can - if this is still a carrier of moisture - take place simultaneously drying. The moisture is then removed by means of a supplied gas. For the purposes of this invention, bulk goods are understood to mean free-flowing bulk materials, such as, for example, bulk solids. As fertilizers, plastic granules, plastic powder or food but also such. B. granulated sugar.

The US 2,703,225 shows a bulk material heat exchanger using the example of a cooling device for sugar. The FR 538 935 shows heat exchanger assemblies with delivery pipes within a heat exchanger bed. The JP 04 115261 U shows pipes. The DE 38 23 166 A1 shows a vibrating apparatus for conveying bulk material. Another heat exchanger device for bulk material is from the US 2,519,148 known. The DE 900 333 C shows a cooler for bulk material. The WO 94/08193 shows a meandering guide of a heat transfer fluid within a heat exchanger device. The DE 31 33 467 A1 shows a preheating device for powdery material. The DE 25 52 891 A1 discloses a fluidized bed reactor having an inlet section, an intermediate section, and an outlet section. The NL 8 501 672 A describes a heat exchanger for hardening iron particles. The FR 2 222 131 and the US 893,812 each describe a bulk material heater.

The DE 35 16 062 A1 discloses a tube dryer for drying free-flowing goods.

When heating and cooling of bulk solids, the heat transfer from the bulk material to the heat transfer fluid or vice versa is limited by the low thermal conductivity of the bulk material. For tempering such bulk materials today shaft cooler are used, as for example in the form of a plate heat exchanger from the EP 0 444 338 B1 are known. The bulk material flows under the influence of gravity between at least two mutually parallel heat exchanger plates through. Channels for a suitable cooling medium are formed in the heat exchanger plates. The efficiency of such a plate heat exchanger is - based on the design effort - very bad. This also leads to a considerable height. Furthermore, the cleaning options in the area acted upon by the bulk material are not favorable. Such a plate heat exchanger requires that the inlet manifold and outlet header for the heat transfer fluid be present.

The invention is therefore an object of the invention to provide a device for controlling the temperature of bulk material, which allows a high heat transfer and easy cleaning with a simple structure.

This object is achieved by the features of claim 1. The fact that the bulk material is passed through the heat exchanger tubes, precisely defined and easy-to-clean, smooth-walled spaces are given by which the bulk material moves. This leads to a simple cleaning possibility of the heat exchange section. The heat exchanger tubes have - based on their cross-section - large area and high temperature gradients from the center of the pipe to the pipe wall, so that a correspondingly intense heat exchange can take place. As the heat transfer fluid suitable liquids, such as in particular water, but also gases or steam can be used. The design effort for the supply of the heat transfer fluid is low, since no inlet manifold or outlet collector for the heat transfer fluid is needed. Also, the cleaning on the side of the heat transfer fluid is easy to carry out. The bulk material is guided by gravity through the heat exchanger tubes. These are therefore usually arranged vertically, but can also be slightly inclined relative to the vertical, as long as it is ensured that the bulk material is passed by gravity through the heat exchanger tubes. So that the bulk material flows through the heat exchanger tubes without interference, the inner diameter of the heat exchanger tubes should be at least four to five times the particle size of the bulk material. As a result, a thorough emptying of the pipes is ensured. Instead of such a heat exchange section, a plurality of such sections may be provided in succession, so that in each case between two sections, a rearrangement of the bulk material takes place, whereby the temperature profile, which is adjusted from the pipe wall to the core of the bulk material, is made uniform. As a result, the temperature gradient is increased at the pipe wall in the subsequent heat exchange section and improves the temperature of the bulk material.

In one aspect of the device, at least one pressurized gas supply can open into a discharge section for the bulk material, which is arranged downstream of the lower end of the heat exchanger tubes. This ensures that a rearrangement of the bulk material takes place in the heat exchanger tubes and that in the discharge section, in the tubes in the Feed funnels and in the buffer section above the heat exchange section no bridging occurs.
In one aspect of the device according to claim 1, the heat exchanger tubes are held at their upper end in an inlet tube bottom, which has in the individual tubes opening, upwardly expanding inlet funnel. This ensures in a particularly simple manner that the bulk material is fed to the individual heat exchanger tubes by gravity without above the heat exchanger tubes dead spaces or dead areas remain in which remains bulk material that is not subjected to the heat exchange process. Due to the special shape of the inlet tube bottom, a complete emptying of the heat exchanger tubes during emptying of the heat exchange section is also achieved. Furthermore, bridging of the bulk material is avoided when entering the heat exchanger tubes through the funnel shape.

In the inlet tube bottom inlet openings for the heat exchanger tubes are formed, which are arranged on pitch circles about a central longitudinal axis of the housing. According to a first alternative of the invention, the ratio of the pitch of radially adjacent tubes to the outer diameter of the heat exchanger tubes is between 1.10 and 1.25. According to a second alternative of the invention, the ratio of the pitch of tangentially adjacent tubes to the outer diameter of the heat exchanger tubes is between 1.10 and 1.25. By this measure an optimal arrangement of the heat exchanger tubes and in particular a particularly thin configuration of the inlet tube bottom is achieved without the risk of a non-optimal bulk flow or even a non-optimal emptying of the buffer section would be given.

The heat exchange section, ie the actual tube bundle heat exchanger, according to claim 2 in a simple manner upstream of a buffer section for the bulk material and be subordinated according to claim 3, a discharge section. Advantageous ranges of an opening angle α of the inlet funnels are: 30 ° ≤ α ≤ 120 ° and preferably 40 ° ≤ α ≤ 100 °.

In the housing of the heat exchange section deflecting devices can be provided, which meander the heat transfer fluid along the heat exchanger tubes. This has the consequence that with particularly simple means a particularly effective heat exchange takes place in the cross-flow, preferably in the cross-countercurrent.

In the embodiment according to claim 3, at least one compressed gas supply can open into the discharge section. Through this development according to claim 4 it is achieved that a rearrangement of the bulk material takes place in the heat exchanger tubes and that no bridging occurs in the discharge section, in the tubes, in the inlet funnels and in the buffer section above the heat exchange section. If the compressed gas supply takes place in the form of gas pressure surges, the described effects are particularly effective. At the same time there is still a drying of the bulk material by the compressed gas, if necessary. Incidentally, the compressed gas can also be tempered and contribute to the tempering of the bulk material.

In the housing of the heat exchange section may be provided an enveloping the heat exchanger tubes bed. These measures lead to an improvement in the heat transfer on the side of the heat transfer fluid, ie on the outside of the heat exchanger tubes. This effect occurs in particular at low flow rates of the heat transfer fluid, since its flow velocity is increased.

At least the heat exchange section may have a circular cross section. By this measure, a particularly compact and easy to manufacture construction of the device according to the invention is achieved, which can be carried out in particular pressure-resistant for underpressure or overpressure.

Due to the embodiment according to claim 5, the heat transfer within the heat exchanger tubes is improved. The inner ribs can protrude freely towards the middle of the pipe. The inner ribs can be connected together in the middle of the tube. There may be two to twelve and preferably three to eight inner ribs. The inner ribs may be evenly distributed around the circumference of the tube.

Due to the advantageous development according to claim 6, the flow conditions can be improved for extremely poorly flowing bulk material.

The development according to claim 7 makes it possible, inter alia, to achieve a particularly good drying of the bulk material under reduced pressure.

Fig. 1

eine Vorrichtung nach der Erfindung im vertikalen Längsschnitt in schematischer Darstellung,

Fig. 2

einen Querschnitt durch ein Wärmetauscher-Rohr,

Fig. 3

einen Querschnitt durch eine weitere Ausführungsform eines Wärmetauscher-Rohres,

Fig. 4

eine nicht erfindungsgemäße Vorrichtung,

Fig. 5

eine Draufsicht auf einen Einlauf-Rohrboden einer erfindungsgemäßen Vorrichtung und

Fig. 6

den Einlauf-Rohrboden nach Fig. 5 in teilweise aufgebrochener Seitenansicht.

A ratio between an inner diameter of the heat exchanger tubes and a maximum diameter of particles of the bulk material can satisfy the following relation: 15 c ≦ d and preferably 10 c ≦ d. This ensures that, on the one hand, the bulk material flows without interference through the heat exchanger tubes, but on the other hand the most intensive possible contact with the heat exchanging surfaces of the tubes is achieved. Further features, advantages and details of the invention will become apparent from the following description of an embodiment with reference to the drawing. It shows:

Fig. 1

a device according to the invention in vertical longitudinal section in a schematic representation,

Fig. 2

a cross section through a heat exchanger tube,

Fig. 3

a cross section through a further embodiment of a heat exchanger tube,

Fig. 4

a device not according to the invention,

Fig. 5

a plan view of an inlet tube bottom of a device according to the invention and

Fig. 6

the inlet tube bottom after Fig. 5 in partially broken side view.

In the FIG. 1 illustrated device for controlling the temperature of bulk material has an upper buffer section 1, a central heat exchange section 2 and a lower discharge section 3. The sections 1, 2, 3 each have circular cross sections. The housing-like, substantially enclosed buffer section 1 is provided with an upper inlet nozzle 4 for supplying a bulk material to be tempered.
The heat exchange section 2 has a housing 5, in whose interior space 6 heat exchanger tubes 7 are arranged parallel to each other at a distance from each other. The interior 6 is therefore a heat exchange space.
Adjacent to the discharge section 3 opens into the interior 6 of the housing 5 of the heat exchange section 2, a supply nozzle 8 for heat transfer fluid. Adjacent to the buffer section 1 opens a discharge nozzle 9 from the interior 6 of the housing 5. In the interior 6 deflecting plates 10 are each transversely to the longitudinal direction of the tubes 7 at a distance from each other mounted such that a supplied via the supply nozzle 8 heat transfer fluid according to the flow directional arrow 11 meandering through the interior 6 each transverse to the longitudinal direction of the tubes gradually upward to the discharge nozzle 9 flows. The heat exchange section 2 is thus designed for a cross-countercurrent of the heat transfer fluid. The interior 6 can with a tube 7 enveloping bed 12 of glass balls, steel balls and Be filled plastic granules, which contributes to the improvement of the heat transfer between the heat transfer fluid and the tubes 7. The filling of this bed in the interior 6 via the discharge nozzle 9; a possible removal takes place via the supply nozzle 8. To secure the bed in the interior 6 removable retaining sieves 13 are arranged in the socket 8, 9. The size of the particles of the bed 12 should be such that they can be introduced into them after the heat exchange section 2 has been manufactured. The particles of the bed 12 must therefore in any case be smaller than the pitch of the tubes 7. The particles of the bed 12 are preferably spherical, lens or cylindrical shape.

The tubes 7 are connected at the top in an inlet tube plate 14 fixedly connected to the housing 5 and at the bottom with an outlet tube plate 15 in such a way that they are open towards the buffer section 1 and the discharge section 3. Between the buffer section 1 and the heat exchange section 2 on the one hand and the heat exchange section 2 and the discharge section 3 are flange connections 16 and 17. As the drawing is removed, the inlet tube plate 14 is configured in that each tube 7 has an inlet funnel 18 which widens toward the buffer section 1 and thus narrows towards the respective tube 7, with adjacent funnels 18 in turn being dimensioned so that they meet at the top in a relatively sharp edge 19. The inlet funnels 18 have an opening angle α which is at least 30 ° and at most 120 °, but is preferably in the range from 40 ° to 100 °. This avoids that in the inlet tube plate 14 between adjacent tubes 7 dead spaces or dead surfaces arise on which bulk material 20 remains lying, especially when emptying the heat exchange section 2 is not fed to a pipe 7 by gravity and therefore remains on the inlet tube sheet 14.

On the outside of the housing 5 vibrators 21 are mounted, by means of which the entire heat exchange section 2 and thus the tubes 7 are vibrated, whereby a heat transfer on the inside of the tubes 7, ie between them and the bulk material 20 is improved ,

The discharge section 3 is in the form of a downwardly tapered cone-shaped funnel. Such a shape causes the bulk material 20 flows in the discharge section 3 at all points of an arbitrarily selected cross section with almost the same speed, in this consideration, the immediate wall area is not taken into account, since there is always a delay due to wall friction. As a discharge device a rotary valve 22 is provided, the housing 23 is connected via a downpipe 24 with the discharge section 3. In the housing 23, a cellular wheel 25 is arranged, which is rotatably driven by a motor 26. The motor 26 is driven by a level detector 27, which in turn detects the level of the bulk material 20 in the buffer section.

Into the funnel-shaped discharge section 3 opens a supply line 28 for a gas. To this line 28, a small pressure vessel 29 is connected, upstream of a shut-off device 30 in the line 28 and a shut-off device 31 is arranged downstream. After opening the obturator 30, the pressure vessel 29 can be filled with compressed gas when the obturator 31 is closed. When the shut-off device 30 is closed by opening the obturator 31 with appropriate emptying of the pressure vessel 29 a compressed gas stream in the funnel-shaped discharge section 3 are given. The compressed gas rises and causes a rearrangement of the bulk material in the heat exchanger tubes 7 and thus improve the heat transfer. At the same time, the gas causes drying of the bulk material 20, if possible. Of course, both shut-off members 30 and 31 may be opened to allow a continuous supply of gas. So that the supplied gas can also escape from the device again, an exhaust nozzle 36 is provided on the upper side of the buffer section 1.

In the downpipe 24, a guide surface 33 is formed, which directs the bulk material 20 from the discharge section 3 to the revolving side of the rotationally driven in the direction of rotation 34 cell wheel 25. In other words, this means that the directed over the guide surface 33 bulk flow is already fully directed to a cell 35 of the cellular wheel 25 when the cell 35 is opened during rotation in the direction of rotation 34 to the downpipe 24 out. This ensures a uniform withdrawal of the bulk material 20 over the entire inlet cross section of the cellular wheel lock 22.

As FIG. 2 can be removed, the heat exchanger tubes 7 may have in the longitudinal direction continuous inner ribs 37, so that in each tube 7 itself again several channels 38 are formed, which are interconnected in the tube center. As Fig. 3 can be removed, inner ribs 37 'can also meet in the middle of the tube, so that a simple split tube 7 at two opposite inner ribs 37' or a star tube at three or more inner ribs 37 'is formed. The channels 38 'are completely separated from each other here. Of course, the tube 7 also inner ribs 37 ', which meet in the middle of the tube, and other inner ribs 37, which only project into the bulk material 20, have. The number of inner ribs 37, 37 'is 2 to 12 and in particular 3 to 8. The inner ribs 37, 37' are distributed at equal angular intervals on the circumference of the tube 7. The inner ribs 37 or 37 'may be rectilinear or else twist-shaped, ie helical.

Such tubes 7 with inner ribs 37, 37 'are usually made of aluminum and are produced by extrusion. Aluminum, but also Bundmetall, such. As copper, compared to stainless steel have the advantage of about 3 to 4 times higher thermal conductivity. By the inner ribs 37, 37 'and the heat transfer surfaces compared to a simple cylindrical tube 7 are greatly increased and at the same time the heat conduction routes for the supply or removal of heat from the tube 7 in the bulk material 20 greatly reduced.

The design after Fig. 4 is different from the after Fig. 1 in that the device can be operated with negative pressure. The entire device is therefore connected to a suction fan 39, which acts on the buffer section 1, the interior of the heat exchanger tubes 7 and the discharge section 3 with partial vacuum. So that this can be maintained, the supply of the bulk material 20 to the inlet nozzle 4 by means of a substantially vacuum-tight ZuführEinrichtung in the form of a cellular wheel lock 40. This lock 40 and the cellular wheel lock 22 close the entire device pressure-tight. A gas supply and an exhaust pipe are naturally not necessary here. In this embodiment, the inlet tube bottom 14 is simplified, namely flat, formed; he therefore does not have the inlet funnel 18. So that a complete emptying is still possible, For example, one or more air supply nozzles 41 are arranged in the buffer section 1, through which air can be injected for emptying or cleaning the inlet tube bottom 14 '. In addition, washing nozzles 42 are provided in the buffer section 1, through which a washing liquid, usually water, can be supplied to the buffer section 1, the heat exchanger tubes 7 and the discharge section 3 of adhering dusts clean. Incidentally, the comments on the Fig. 1 and 4 match.

As is clear from the FIGS. 5 and 6 results in a Fig. 1 only schematically illustrated tube sheet 14 circular inlet openings 43 for the tubes 7, which are arranged on dot-dash lines indicated partial circles 44, 45, 46 about the central longitudinal axis 47 of the housing 5. The inlet tube plate 14 is therefore circular in shape; Accordingly, the housing 5 is formed circular cylindrical. How vivid Fig. 5 shows that this arrangement of the inlet openings 43 on pitch circles 44, 45, 46 has the advantage that the inlet funnel 18 - even in the region of the outer edge 48 of the tube sheet 14 - areas of a greater distance to this edge 48 or to an adjacent Have inlet funnel. This has the consequence that, in compliance with the above-mentioned range for the opening angle α of the tube sheet 14 can be made relatively thin.

The diameter of the inlet openings substantially corresponds to the outer diameter d of the tubes 7. For the pitch of a radially adjacent openings 41 and thus tubes 7 is 1.1 D <a ≤ 1.25 D and preferably 1.15 D ≤ a ≤ 1 , 20 D. In the same way applies to the pitch b in the tangential direction between adjacent openings 43rd and thus tubes 7: 1.10 D ≤ b ≤ 1.25 D and preferably 1.15 D ≤ b ≤ 1.20 D.

For the inner diameter d of the tubes 7, in comparison to the maximum particle diameter c of the bulk material 20, i. to the maximum grain size c of the bulk material 20: double the distance 15 c ≤ d and preferably 10 c ≤ d.

Claims (9)

1. Device for maintaining a temperature of bulk material (20), comprising

   - a heat exchange section (2) having a housing (5),

   - heat exchanger pipes (7) arranged in the housing (5) in a direction of gravity,

   - a feed line (8), which leads into the housing (5), for a heat carrier fluid,

   - a discharge line (9), which leads out of the housing (5), for the heat carrier fluid,

   - a bulk material inlet arranged at the upper end of the pipes (7) for feeding the bulk material (20) into the pipes (7), and

   - an outlet for the bulk material (20) provided at the lower end of the pipes (7),

   - wherein access openings (43) for the heat exchanger pipes (7) are formed in an inlet pipe bottom (14), said access openings (43) being arranged on partial circles (44, 45, 46) about a longitudinal centre axis (47) of the housing (5),

   characterized in that
   the heat exchanger pipes (7) are held, at their upper ends, in the inlet pipe bottom (14), which has upwardly expanding inlet funnels (18) that lead into the individual pipes (7),
   the relationship of an outer diameter (D) of the heat exchanger pipes (7) to a mutual spacing (a) of radially adjacent pipes (7) is such that 1.10 D ≤ a ≤ 1.25 D
   and/or
   the relationship of the outer diameter (D) of the heat exchanger pipes (7) to the mutual spacing (b) of tangentially adjacent pipes (7) is such that 1.10 D ≤ b ≤ 1.25 D.
2. Device as claimed in claim 1, characterized in
   that a buffer section (1) for the bulk material (20) is arranged upstream of the upper end of the heat exchanger pipes (7).
3. Device as claimed in claim 1 or 2, characterized in
   that a discharge section (3) for the bulk material (20) is arranged downstream of the lower end of the heat exchanger pipes (7).
4. Device as claimed in claim 3, characterized in
   
   that at least one pressurized gas inlet leads into the discharge section (3).
5. Device as claimed in any one of claims 1 to 4, characterized in
   that the heat exchanger pipes (7) are provided with internal ribs (37, 37') running in the longitudinal direction thereof.
6. Device as claimed in any one of claims 1 to 5, characterized in
   that at least one vibrator (21) is arranged in the heat exchange section (2).
7. Device as claimed in any one of claims 1 to 6, characterized in
   that a partial vacuum can be applied to the device.
8. Device as claimed in any one of claims 1 to 7, characterized in
   that the following applies: 1.15 D ≤ a ≤ 1.20 D.
9. Device as claimed in any one of claims 1 to 8, characterized in
   that the following applies: 1.15 D ≤ b ≤ 1.20 D.

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