Background of the invention

The invention relates to a rotary cooler intended for simultaneous conveyance and cooling of hot bulk mate rial .

The invention further relates to a method of uti lizing the rotary cooler when handling hot bulk material.

The field of the invention is defined more specif ically in the preambles of the independent claims.

Different cooling solutions are widely applied in a process industry. Main driver for cooling is that the solid material exiting a high temperature process cannot be treated in the subsequent process stages because of the high temperature of the material. Furthermore, cooling is often for practical and lay-out reasons combined with conveying. Most typical equipment for combined cooling and conveying are cooling drums, cooling screws and cooled drag chain conveyors. The cooling screws or rotary coolers are widely used in industrial cooling applications because of their compact structure. However, the present rotary coolers con tain some disadvantages, and especially regarding their in sufficient cooling capacity. When desired cooling cannot be reached by the rotary cooler itself, there is need to com plete the cooling by using multiple cooling devices, which is expensive and difficult. Some prior art solutions have been disclosed in documents JP-2004012061-A, DE- 102016007221 -A1 , JP-5167100 -B2 , US-3800865-A and CN- 109315813-A.

Brief description of the invention

An object of the invention is to provide a novel and improved rotary cooler and a novel and improved method for simultaneous cooling and conveyance of hot bulk mate rial . The rotary cooler according to the invention is characterized by the characterizing features of the inde pendent apparatus claim.

The method according to the invention is character- ized by the characterizing features of the independent method claim.

An idea of the disclosed solution is that the rotary cooler is intended for simultaneous cooling and transpor tation of very hot bulk materials. The rotary cooler is an elongated device comprising a stator having an inner surface with first diameter and a rotor arranged inside the stator and having an outer surface with second diameter. Bulk ma terial is fed through a feed port inside an annular cooling space limited by the mentioned first and second diameters. On the outer surface of the rotor are several separate blades forming together a screw surface for feeding the bulk material inside the cooling space. The blades not only transport the bulk material but also mix it. Further, sur faces of the rotor and the stator are cooled by means of a cooling system.

An advantage of the disclosed solution is that higher cooling efficiency can be achieved compared to the known apparatuses. There is no longer need for additional supplementary or secondary cooling devices and phases. Since the disclosed rotary cooler alone is sufficient to cool the material, the system may be simpler and less expensive. Further, thanks to the increased cooling capacity, dimen sions of the rotary cooler may be reasonable. When the device is smaller in size and no secondary cooling devices is needed, then layout of the production plant is easier to design .

The disclosed solutions provides improvements for the entire material handling system of the production plant. Very hot bulk material may be fed to the rotary cooler and after being treated, temperature of the bulk material is lowered to temperature level which allows safe further transportation of the bulk material by means of conventional transport means. Further, the enhanced cooling properties allow handling of materials with higher temperature than before .

The increased cooling rate is based on enhanced heat convection, which is mainly improved by the design of the rotor and its blades. The blades cause mixing of the bulk material thereby improving significantly the heat convec tion.

According to an embodiment, the mentioned several separate blades form together a discontinuous screw surface on the rotor. Thus, the rotor is provided with an imaginary thread, screw or spiral element.

According to an embodiment, the mentioned several successive blades of the rotor are not in physical contact with each other. In other words, there are openings, slots or gaps between two neighboring blades. The discontinuous structure allows flows of bulk material through the gaps.

According to an embodiment, circumferential length of the blades is 50 - 150 mm.

According to an embodiment, the blades are formed of steel plate material. The blades may be mounted on the rotor by weld joints. Thus, the structure is simple, durable and easy to manufacture with conventional manufacturing techniques.

According to an embodiment, number of the separate blades of the rotor is at least 25. Great number of the blades means that there is also a great number of the gaps ensuring proper mixing.

According to an embodiment, each blade of the rotor has elongated plate-shaped configuration. The blades have also angular orientation relative to the axial direction of the rotor. Then the angular orientation defines pitch for the imaginary screw of the feed means.

According to an embodiment, the cooling system is based on circulating cooled fluid inside structures of the stator and rotor. The cooling is applied by absorbing the heat into the structures of the rotor and stator and further to the flowing cooling fluid or media.

According to an embodiment, the cooling system com- prises separate cooling circuits for the stator and rotor. The cooling system further comprises control means for in dependent control of the separate cooling circuits.

According to an embodiment, the cooling system com prises several separately controllable cooling circuits for the stator. Periphery of the stator may comprise two or more stator elements and their cooling can be controlled sepa rately. Then it is possible to enhance cooling of stator elements on the bottom side of the device in relation to the stator elements on the top side.

According to an embodiment, the cooling system may be controlled by means of a control unit according to a pre determined control program. The cooling system is also pro vided with several sensors, such as temperature and flow sensors in order to monitor the stator elements. The control unit may control temperature and flow of the coolant agent, or cooling media, circulating in the stator elements. The control unit may also control a coolant circuit of the rotor. Thus, the rotary cooler comprises several control lable cooling circuits.

According to an embodiment, the cooling system is a liquid cooling system. Liquids have typically good heat transfer properties, whereby liquid cooling systems are ef fective. The cooling liquid may be water or oil, for exam ple. Predominant coolant in industrial applications is wa- ter, because it is safe, sustainable, advantageously priced, versatile to use, and furthermore, it has relatively high specific heat capacity.

According to an embodiment, the cooling system may utilize any other cooling fluid. The cooling fluid may be liquid or gas. The fluid fed to the system may be precooled by means of a cooler device. According to an embodiment, the rotary cooler may comprise two feeds ports allowing thereby feeding the bulk material from two sources. Thus, the rotary cooler provided with two feed ports may serve two energy boilers, or when the energy boiler has two discharge openings, one rotary cooler may serve them both.

According to an embodiment, the rotor comprises sev eral successive blades. Between the blades are axial gaps though which the handled bulk material can penetrate. When the bulk material flows through the gaps, it becomes sim ultaneously well mixed. The mixing improves heat convection and the cooling significantly.

According to an embodiment, no uniform plug of the bulk material occurs inside the cooling space. Plug flow is typical in conventional rotary coolers. Instead of the plug flow the bulk material is mixed inside the annular cooling space in the present solution. When the plug flow is formed, then only the outer and inner layers are in contact with the cooled surfaces of the rotary conveyor resulting in less effective cooling.

According to an embodiment, because of the above mentioned gaps, the bulk material has axial flow rate lower than theoretical axial flow rate defined by the blade pitch and the rotation speed of the rotor. In other words, the bulk material stays longer inside the cooling space as it should theoretically. Thereby, the material has more time to be affected by the cooled surfaces limiting the cooling space. In other words, axial movement of the bulk material is delayed and there is more time for cooling. However, despite of the axial delaying, intense continuous movement of the material occurs because of the mixing. The mixing makes the material moving locally and in relation to itself.

According to an embodiment, radial distance between the inner diameter D _sta tor of the stator and the outer diam- eter D _rot0 r of the rotor is less than 180 mm. Then, maximum thickness of material layer of the bulk material inside the rotary cooler is 180 mm. Thanks to the relatively thin material layer, heat convection is enhanced and cooling capacity is improved.

According to an embodiment, the maximum radial dis- tance of the diameters and the maximum thickness of the material layer are 100 mm. In this embodiment thickness of the material layer is very thin and cooling is thereby further intensified.

According to an embodiment, ratio D _st ator/D _ro tor be- tween the inner diameter D _sta tor of the stator and the outer diameter D _rot0 r of the rotor is 1.1 - 2.2.

According to an embodiment, the D _sta tor is 600 mm and the D _rotor is 400 mm. Then the thickness of the bulk material layer is 100 mm and the ratio D _sta tor/D _ro tor is 1.5.

According to an embodiment, the D _sta tor is 800 mm and the D _rotor is 600 mm. Then the thickness of the bulk material layer is 100 mm and the ratio D _sta tor/D _ro tor is 1.3.

According to an embodiment, the D _sta tor is 800 mm and the D _rotor is 500 mm. Then the thickness of the bulk material layer is 150 mm and the ratio is 1.6.

According to an embodiment, the D _sta tor is 400 mm and the D _rotor is 200 mm. Then the thickness of the bulk material layer is 100 mm and the ratio is 2.0.

According to an embodiment, degree of filling of the cooling space is 80 - 85%. In other words, the volume between the stator and rotor is 80 - 85% full of the bulk material during the normal operation. At the top part of the annular cooling space there may be some free volume, whereas the other parts are fully loaded with the bulk material.

According to an embodiment, input temperature Ti _n of the fed bulk material may be up to 950 °C and output tem perature T _out of the discharged bulk material may be 160 - 250 °C. In conventional rotary coolers the output tempera- ture is 300 - 450 °C. In some cases the output temperature may be nearly 100 % lower than in conventional devices. The solution allows proper handling of extremely hot materials.

According to an embodiment, the final temperature of the discharged bulk material is below 100 °C, whereby long distance transportation of the bulk material from the production plant to target positions can be done by means of road transportation. When regulations concerning the road transportations can be fulfilled the long distance trans portation is facilitated.

According to an embodiment, the separate blades of the rotor have angular orientations relative to the axial direction of the rotor. The blades form together a discon tinuous screw on the rotor. The discontinuous screw has pitch defined by the angular orientations of the separate blades.

According to an embodiment, the mentioned pitch of the discontinuous screw formed of the several separate blades is 100 - 350 mm at the feed area.

According to an embodiment, the mentioned pitch of the discontinuous screw formed of several separate blades is 100 - 350 mm at the discharge area.

According to an embodiment, the pitch is constant through the axial length of the rotor. Thereby all sections of the rotor have the same pitch. However, number of the blades varies at different portions of the rotor. Then the ability to generate axially forwarding movement may be var ied by the number of the blades instead of the pitch.

According to an embodiment, the rotor has at least two longitudinal sections wherein magnitudes of pitches of the discontinuous screw are different. Cooling and convey ing properties of the device can be adjusted by the magni tude of the pitch.

According to an embodiment, number of the separate blades on the rotor per axial distance is configured to change from the feed port end of the rotor towards the discharge port end of the rotor. Thereby the rotor provided with a discontinuous screw formed of the several separate and successive blades has at least two different blade rates. Then the ability to generate axially forwarding move ment component may be varied by the number of the blades. The amount of blades per axial length may be arranged to change gradually.

According to an embodiment, the number of the blades i.e. the blade rate discussed in the previous embodiment is greatest at the inlet area. Thanks to this, faster axial movement for the very hot bulk material fed through the feed port occurs at the feed area. After the critical inlet section the blade rate is lower. In the sections following the feed area minor amount of blades allow more enhanced mixing feature. At first the very hot bulk material needs to be moved relatively quickly onwards, and when the tem perature has become lower, then the material may be conveyed forwards with slower speed and may be mixed more inten sively. Rapid initial axial movement of the bulk material inside the cooling space reduces wear of the components at the inlet area. Further, when the inlet section is provided with greater number of the blades, then it can be ensured that the fed bulk material moves away from the inlet area and plugging of the device may be prevented.

According to an embodiment, realized axial advance of the handled bulk material inside the annular space per one revolution of the rotor is minor than nominal axial advance per revolution. The mentioned nominal advance is determined by the pitch defined by the blades.

According to an embodiment, the realized axial ad- vance is smaller than the nominal advance because of the mixing feature existing especially after the inlet area. When part of the bulk material inside the cooling space may pass through the gaps between the blades, axial moving com ponent is not fully utilized for causing the axial advance for the material. According to an embodiment, length of the rotary cooler is at least 3 m. Further, diameter of the annular cooling space is at least the 400 mm.

According to an embodiment, the rotary cooler com- prises two or more successive modules. Then rotary coolers with desired total length may be formed by multiplying sev eral similar modules with the same or different lengths. The modular structure provides structural flexibility and reduces costs.

According to an embodiment, total length of the rotary cooler is at least 6 m. The rotary cooler may be formed of two axially successive modules with 3 m length or alternatively three modules with 2 m length.

According to an embodiment, rotation speed of the rotor is 0.30 - 50 rpm (revolutions per minute) .

According to an embodiment, the disclosed rotary cooler is designed for serving as a removal device for hot ash in a power plant.

According to an embodiment, the disclosed rotary cooler is a bottom ash removal device mounted in connection with an energy boiler.

According to an embodiment, the disclosed rotary cooler is a fly ash removal device mounted in connection with an energy boiler.

According to an embodiment, the disclosed rotary cooler is a removal device mounted in connection with a roaster for transporting and cooling calcine material.

According to an embodiment, the disclosed rotary cooler is a removal device mounted in connection with a calcining drum for transporting and cooling calcine mate rial .

According to an embodiment, the solution relates to a method of transporting and cooling hot bulk material. The method comprises feeding hot bulk material to an annular space between a stator and a rotor of a rotary cooler. The rotor is rotated relative to the stator and the bulk mate rial inside the cooling space is moved axially towards a discharge end of the rotary cooler. The structure of the rotary cooler is cooled during the operation so that the bulk material becomes in contact with cooled surfaces lim iting the cooling space. The cooled bulk material is dis charged finally at the discharge end of the device. The fed bulk material inside the annular cooling space is moved and mixed by means of several separate blades, which protrude from the outer surface of the rotor and form discontinuous screw surfaces inside the cooling space. Simultaneous mix ing and axial movement of the bulk material occurs and there is no uniform plug flow inside the annular cooling space.

According to an embodiment, the method comprises allowing the fed bulk material to pass partly through gaps between the successive blades. Part of the bulk material moves in smaller batches axially forward. The mixing pre vents the bulk material from moving forward as a plug flow inside the annular cooling space.

According to an embodiment, the method comprises delaying axial movement of the fed bulk material inside the cooling space relative to nominal axial advance defined by rotation rate and blade pitch of the rotor. The method further comprises mixing the fed bulk material by means of the several separate rotating blades during the delayed stay inside the cooling space. The delaying and the mixing are both based on gaps between the successive blades.

According to an embodiment, the method comprises intensifying the above mentioned delaying and mixing after the inlet section of the rotary cooler. Then the very hot bulk material fed to the inlet section is at fist conveyed with greater axial velocity forwards, and is in the follow ing sections delayed and mixed more intensively. Since the temperature of the bulk material is at the inlet section at its highest, it is advantageous to move it relatively quickly onwards so that the thermal stress and wearing di rected to the components remain in an acceptable level. The temperature of the bulk material decreases at the inlet area and when the bulk material continues its movement to fol- lowing sections, its temperature level is at a lower level thereby allowing the axial movement and mixing to be inten sified in order to enhance the cooling. In the following sections the temperature of the bulk material no longer causes problems to durability of the components of the de- vice. In other words, increased mixing and delaying are utilized at sections downstream from the inlet section.

According to an embodiment, the method comprises limiting thickness of the fed bulk material layer inside the annular cooling space to be less than 180 mm. This intensifies cooling since heat convection between cooled inner and outer surfaces of the annular cooling space is increased. Also the mixing effect is intensified in the relatively thin material layer.

According to an embodiment, the rotary cooler dis- closed in this document can be retrofitted to existing in dustrial systems and plants. In other words, the existing power plants may be modernized by replacing their conven tional ash conveying devices with the disclosed rotary cool ers. The disclosed rotary cooler requires only very limited changes in layout. Further, it is possible to double the power output of the bottom ash cooling simply by substitut ing the existing conventional cooling screws with the dis closed rotary cooler. Since the cooling capacity of the disclosed device may be double or even greater compared to the existing screw conveyors, it may be possible in some production plants to substitute two traditional conveyors with one device, which is in accordance with this document. The disclosed rotary cooler can do the job of two conven tional cooling screws.

According to an embodiment, the discharge port has a discharge direction, which is directed laterally relative to the longitudinal direction of the rotary cooler. This way the discharge port is located at a vertical distance from a bottom part of the cooling space. In other words, there is no bottom discharge in the present solution. Then the handled bulk material is prevented from flowing out of the cooling space passively under influence of gravity only. This embodiment is especially suitable for some fluidized bulk materials which cause problems to bottom discharge systems .

The discharge port may be configured to form a bar rier or border preventing free flow of the bulk material out of the cooling space. Compared to conventional arrange ments wherein the discharge port is facing downwards from the bottom of the cooling space, the present discharge port provides more controllable discharge flow.

According to an embodiment, discharge direction of the discharge port is adjustable. Then orientation of the discharge port may be selected case by case. The orientation angle may be selected in accordance with the type of the handled bulk material, for example. The discharge port may comprise a turnable element, which may be turned relative to longitudinal axis of the rotary cooler. Height of the discharge connection is adjustable. The adjusting may be executed manually for example during operational brakes and service operations. Alternatively, the discharge module may be provided with an actuator for turning the discharging connection into desired position. Then a control system of the rotary cooler may control the orientation of the dis charging connection automatically or under control on input control commands. The discharge angle may be one control parameter of the rotary cooler.

According to an embodiment, the rotary cooler com prises a discharge module provided with the adjustable dis charge port. Axial length of the discharge module is ad- justable or alternatively there is a set of modules with different axial lengths allowing suitably dimensioned dis charge module to be selected. Thanks to this embodiment length of the rotary cooler may be fine adjusted between the feed and discharge stations of different plants.

The above disclosed discharge module has an im portant role in preventing the hot and fluidized material from escaping the rotary cooler in an uncontrolled manner. To further control the material level and flow inside the rotary cooler the special adjustable discharge connection is created. There is an adjustable opening at the discharge connection which allows to adjust the filling degree of the rotary cooler. This has many benefits related to the cooling performance and operability of the rotary cooler. By means of the adjustable discharge connection it is also possible to affect positively for performance and operation of the preceding process equipment.

The discharge connection is located at a vertical distance from the bottom of cooling space. Then there is vertical barrier or wall preventing the handled bulk mate- rial from escaping from the discharge opening in uncon trolled manner. Then the rotating rotor and its blades con trol the discharging process.

According to an embodiment, regarding wear control the rotary cooler comprises hard coating at least on inner surfaces of the stator of the feed module. Very hot and abrasive bulk material causes wearing problems for the inner parts of the rotary cooler. Problems arise especially at the front most part of the rotary cooler wherein temperature is at its highest. In order to improve wear resistance, inner surfaces of the stator may be treated by means of thermally sprayed coating material. It possible to provide the coating also for the rotor and the blades at least at the feed area of the device.

According to an embodiment, the rotary cooler has a modular structure comprising two or more successive cooling modules. The basic structure of the rotary cooler may be composed of a feed or inlet module, one or more middle modules and at the end of the device there is a discharge module. Length of the middle modules may be the same, or alternatively, modules with different lengths may be com- bined in order to vary total length of the device. In other words, length of the device may be selected by the number of the modules and by selecting modules with different lengths. A further advantage of the embodiment is that mounting, transporting and servicing of the rotary cooler is easier when it is composed of several shorter modules instead of one single piece. Failed module may be replaced if needed.

According to an embodiment, the stator of the rotary cooler may be of modular construction comprising a basic frame and several removable cooling elements mounted on the frame. The cooling elements may be elongated panels having curved profiles. Each cooling element is also provided with a cooling fluid circulation system. Failed or worn cooling elements may be removed and substituted with new or recon- ditioned elements. The cooling elements can be removed and replaced within hours. The disclosed modular structure also ensures quick access inside the rotary cooler to remove possible impurities and to make preventive maintenance in spections .

According to an embodiment, the above mentioned cooling elements may be interchangeable. Because of uneven wearing subjected to the stator some of the cooling elements wear more than the others. Then it is possible to balance the wearing of the stator by changing positions of the interchangeable cooling elements. Cooling elements which are subjected to heavier wearing may be moved to positions of lighter wearing, and correspondingly cooling elements which are located at positions with lighter wearing are moved to positions where more intensified wearing occurs. When device comprises two or more cooling modules with sim ilar lengths then the changes of the cooling elements may occur also between the modules.

According to an embodiment, the above disclosed cooling elements of the stator may be turned 180°. This embodiment relates to the fact that the wearing of the elements may be axially uneven. Then first end portions of the elements may wear more than second end portions. By turning the elements it is possible to balance the axially uneven wearing.

According to an embodiment, the above disclosed changes in positions and the turning of the cooling elements may both be implemented when servicing the rotary cooler.

According to an embodiment, the rotary cooler com- prises a skeleton frame and several cooling elements or panels mounted removably on the frame. The skeleton frame may be formed of steel bars welded together and provided with support surfaces against which the elements may be removably fastened by means of screw mounting, for example.

According to an embodiment, the cooling elements are provided with several conduits or other flow paths for circulating cooling fluid inside their structure. The cool ing element may comprise a curved inner panel and a curved outer panel. Between the panels may be a tubing connectable to the cooling circuit. At the longitudinal end portions of the cooling elements is a coolant feed port and a coolant discharge port. The cooling elements may be connected to each other for forming two or more cooling sub-circuits. It is possible to cross-connect the cooling elements of the successive cooling modules so that a cooling element which is located at a bottom part of a module is connected to a cooling element which is located at a top part of another module. By means of the cross-connection cooling need of the sub-circuits may be balanced. The above disclosed embodiments may be combined in order to form suitable solutions having those of the above features that are needed.

Brief description of the figures

Some embodiments are described in more detail in the accompanying drawings, in which

Figure 1 is a schematic side view of a production plant comprising a rotary cooler,

Figure 2 is a schematic view of a rotary cooler, Figure 3 is a schematic and highly simplified view of a principle of a prior art rotary cooler,

Figure 4 is a schematic and highly simplified view of a principle of a novel rotary cooler,

Figure 5 is a schematic end view of a rotary cooler and its cooling space between a stator and a rotor,

Figure 6 is a schematic side view of a rotor of a rotary cooler, wherein the rotor is provided with several radial blades,

Figure 7 is a schematic detail of an outer surface of a rotor of a rotary cooler,

Figure 8 is a schematic view of a rotary cooler having a modular structure,

Figure 9 is a schematic view of a frame structure of a cooling module of a rotary cooler,

Figures 10 - 13 illustrate some possible combina tions of cooling modules and differently dimensioned rotary coolers ,

Figure 14 is a schematic view of a discharge module of a rotary cooler, and

Figure 15 is a schematic end view of a discharge end section of a rotary cooler.

For the sake of clarity, the figures show some em bodiments of the disclosed solution in a simplified manner. In the figures, like reference numerals identify like ele- ments. Detailed description of some embodiments

Figure 1 shows a production plant or power plant PP provided with at least one process device PD. The process device PD may be an energy boiler, for example. High tem- perature bulk material is discharged from the process device PD as a continuous process. The discharged bulk material may be received by one or more rotary coolers RC by means of which the bulk material can be moved away. Thus, the rotary cooler RC serves as a device for short distance transport SDT. The rotary cooler RC has a feed section 1 at its first end and a discharge section 2 at its opposite second end. Between the feed and discharge ends there may be one or several cooling sections 3. The rotary cooler RC is an elongated device and comprises a stator S and a rotor R. The rotor R is rotated around its longitudinal axis by means of a rotating device 4. The stator S and rotor R are both connected to cooling system CS. The cooling system CS may be configured to circulate coolant fluid or agent inside the structures of the stator S and rotor R. The rotor R comprises feed means on its outer surface whereby the re volving rotor R moves A the bulk material from the feed section 1 through the cooling sections 3 to the discharge section 2 wherein the bulk material is discharged from the device. After being cooled during the short distance transport SDT executed by means of the rotary cooler RC, the bulk material may be transported further by means of long distance transport LDT means. The discharged bulk ma terial may be transported further by means of road or rail transportation means, for example.

Figure 2 discloses a rotary cooler RC which may be an elongated modular structure comprising several succes sive cooling modules 5. At a feed end 1 there is a feed module 5a provided with a feed opening or feed port 6. The feed opening 6 may be facing upwards. At an opposite dis- charge end 2 there is a discharge module 5b provided with a discharge opening or discharge port, which is shown in Figures 5, 14 and 15, for example. Between the feed module 5a and the discharge module 5b is a cooling section 3 pro vided with several successive cooling modules 5c - 5e. Num ber of the cooling modules 5c - 5e may be greater or minor as shown in Figure 2, and they are all, in addition to the feed module 5a, connected to a cooling system. A rotating device 4 for rotating a rotor inside the structure is pref erably located at the discharge end 2, where temperature is lower. The rotating device 4 may comprise a rotation motor 4a and a transmission unit 4b.

Figure 3 discloses a principle of a prior art rotary cooler RC wherein a rotor R is provided with a uniform screw 7 on its outer surface 8. Then bulk material fed to an annular cooling space 9 between an inner surface 10 of a stator S and the outer surface 8 of the rotor R moves A as a butt flow towards a discharge end when the rotor R is rotated T around a central axis B.

A rotary cooler RC disclosed in Figure 4 differs from the one shown in Figure 3 in that the rotor R is provided with a discontinuous screw element on its outer surface 8. Several successive blades 11 are configured to form feed means for moving A the bulk material axially inside the annular cooling space 9. Between the successive blades 11 are gaps 12 through which part of the bulk mate- rial may penetrate 13 during the operation. Thereby not only axial transfer but also mixing occurs. It is further indi cated that the blades 11 are orientated at an angle C rel ative to axial direction.

Further, in prior art solutions, such as in Figure 3, thickness E of material layer inside the cooling space

9 is significantly greater compared to the one in the pre sent solution. An example of the lower thickness E is shown in Figure 4.

Figure 5 is a highly simplified end view of a rotary cooler RC . For clarity reasons the blades are not shown. The stator S has an inner diameter D _sta tor and the rotor R has an outer diameter D _rot0 r· Ratio between the diameters Dgtator and D _rot0 r has been discussed already above in this document as well as the thickness E of material layer inside the cooling space 9. Figure 5 further discloses that the bulk material is fed vertically through the feed port 6 and is discharged laterally through a discharge port 14.

Figure 6 discloses a rotor R of a rotary cooler. The rotor R is provided with several radial blades 11 and gaps 12 or openings between them. As can be noted, number of blades 11 is greater at a feed end 1 compared to discharge end 2 and middle section 3. Advantages of such uneven dis tribution of the blades 11 are discussed already above in this document. At the ends of the rotor R may be bearing and rotation transmission surfaces 15, 16.

Figure 7 shows in a more detailed manner the outer structure of the rotor R. The blades 11 may be made of plate material and their shape may substantially resemble letter S. The blades 11 may be mounted by means of weld joints on the outer surface 8 of the rotor R.

Figure 8 discloses a rotary cooler RC comprising six successive modules 5a - 5f. Thus, the rotary cooler RC has modular construction. Figure 8 further discloses that each of the modules 5, except the discharge module 5b, may comprise a frame 17 and several removable cooling elements 18. The frame 17 may have skeleton-like configuration and it may receive the cooling elements 18. The cooling elements 18 may be interchangeable whereby their position is freely selectable, as it is illustrated by an arrow G. Further, the cooling elements 18 may be turned H in case being sub- jected to uneven wearing in axial direction. Advantages and possibilities offered by the modular structure have already been discussed above in this document.

Figure 9 discloses an example of a skeleton-type frame 17 of a cooling module. The frame 17 may comprise two transverse flanges 19 and several longitudinal support bars 20 between them. The support bars 20 comprise support sur faces against which the cooling modules 18 can be mounted removably .

Figures 10 - 13 disclose some possible combinations of the above mentioned cooling modules. As can be noted, rotary coolers RC with different diameters and lengths can be formed of some standard modules.

Figure 14 discloses a discharge module 5b comprising a laterally directed discharge port 14. Orientation of the discharge port 14 may be adjusted 21. On top of the dis charge module 5b may be an inspection hatch 22. The dis charge module 5b may be a substantially tubular element having mounting flanges 23 at its ends.

Figure 15 discloses that the rotary cooler RC is without a bottom discharge. Instead, the discharge port 14 is directed side wards and may also be provided with an adjusting feature 21. Then there is a vertical barrier 24 between the inner surface 10 of the stator S and a lowermost part of the discharge port 14.

The drawings and the related description are only intended to illustrate the idea of the invention. In its details, the invention may vary within the scope of the claims .