WO2012031597A1

WO2012031597A1 - Method and apparatus for treating a bed of particulated material

Info

Publication number: WO2012031597A1
Application number: PCT/DK2011/050332
Authority: WO
Inventors: Mogens Juhl FØNS
Original assignee: Fons Cos Aps
Current assignee: Fons Cos Aps
Priority date: 2010-09-10
Filing date: 2011-09-05
Publication date: 2012-03-15
Anticipated expiration: 2013-03-10
Also published as: EP2614328A1; CN103124888B; EP2614328B8; CN103124888A; EP2614328B1

Abstract

Device for use in a bottom construction of a bed for cooling particulate material, where said device comprises a frame comprising means for fastening said device to the bottom construction, and where inside the frame a primary and a secondary opening is provided, where said primary and secondary openings allows cooling air to pass through the frame and thereby through the bottom and through the bed of particulate material, and where a pendulum plate is pivotably arranged on an axle, such that the pendulum plate may pivot and thereby block off more or less of the primary opening, and where said pendulum plate is biased towards a position allowing the primary opening to be as open as possible.

Description

Method and Apparatus for Treating a Bed of Particulated Material

Field of the Invention

The present invention relates to a method for cooling a bed of particulate material supported on an air distribution bottom using air which via ducts is conducted in sec- tionalised manner to and directed up through the air distribution bottom and the bed of material from one or several underlying compartments, while the particulate material is transported horizontally or slightly tilted from the inlet end to the outlet end of the distribution bottom.

The invention also relates to a device and an apparatus for carrying out the method according to the invention.

Background of the Invention

An example of an apparatus which comprises an air distribution bottom is a cooler for cooling, for example cement clinker. In such a cooler the primary aim is to achieve a favourable degree of heat exchange between the clinker and the cooling air so that essentially all the thermal energy contained in the hot clinker can be returned to the kiln system in the cooling air, while at the same time the clinker is discharged from the cooler at a temperature which is close to the ambient temperature. It is a precondition for achieving a favourable degree of heat exchange that the cooling air flow through the clinker is well-defined and quite homogenous.

In connection with the cooling of cement clinker which is discharged from the kiln installed ahead of the cooler it has, however, emerged that the clinker is not always uniformly distributed across the width of the cooler. Instead, there is a tendency towards the clinker being distributed so that the larger clinker lumps are predominantly located at the one side of the cooler, whereas the fine clinker lumps are located at the other side. Also, the thickness of the clinker bed may exhibit variations both longitu- dinally and transversely through the cooler. Since it is easier for the cooling air to penetrate a bed of larger clinker lumps and/or a thinner bed as compared to penetrating a bed of finer clinker lumps and/or a thicker bed, and since, quite naturally, the cooling air will always follow the route of least resistance, any such uneven distribu- tion of clinker often entails that the finer clinker material is not sufficiently cooled, hence causing hot zones, so-called "red rivers", to be formed in the cooler. Such uneven distribution of the clinker will also entail that the cooling air in the areas where it encounters least resistance will simply cool the clinker more, due to the higher air flow through the clinker bed in the area. The heat exchange efficiency of the cooler is essential for having the highest possible air temperature returning to the process, after heat exchanging with the clinker.

When an area has a thinner clinker bed as described above it becomes an attractive way for the air to flow through, as the pressure difference through the clinker bed is less. To achieve the uniformed airflow also in this area, it is essential to ad extra flow resistance in a flow regulator device under the grate plate. The extra flow resistance in the device should be the same as the loss in flow resistance through the clinker layer. Hereby the total flow resistance through the device and clinker bed becomes constant, and the flow will be constant.

In revoked patent EP0848646 / WO1997007881 a mechanical flow regulator was patented, where a continuous regulation of each flow regulator is automatically moveable in direct response to the air flow condition. From time to time the kiln operation becomes unstable, and the kiln discharge larger quantities of clinker. The operator would prefer to add more cooling air in this situation, to still achieve relatively cold clinker discharging the cooler.

In EP0848646 the pressure loss over the device will become very high, as now the orifice area in the device is small and the fan supplying the cooling air will have to overcome this pressure loss. In reality the designed sizing of fans becomes too large, if handling this upside operation should be possible. At all normal operation times it is essential to have a substantially constant relationship between production rate (kg clinker per minute) and air rate (kg air per minute). Hereby the flow setting (kg of air per square meter per minute) should be changed when the production rate is changed.

Object of the Invention

The present invention will obtain a desired cooling of clinker for upside conditions that was not achievable before with EP0848646, without having too big fan design. The present invention will obtain easy adjustment of the flow rate without changing any parts of the device, hereby being able to obtain optimal heat exchange for different production rates etc.

Description of the Invention

The present invention addresses these issues by providing a device for use in a bottom construction of a bed for cooling particulate material, where said device comprises a frame comprising means for fastening said device to the bottom construction, and where inside the frame a primary and a secondary opening is provided, where said primary and secondary openings allow cooling air to pass through the frame and thereby through the bottom and through the bed of particulate material, and where a pendulum plate is pivotably arranged on an axle, such that the pendulum plate may pivot and thereby block off more or less of the secondary opening, and where said pendulum plate is biased towards a position allowing the secondary opening to be as open as possible.

With this device is achieved that the drop in air-pressure in the clinker bed will cause the pendulum plate to pivot and thereby adjust the amount of air which is allowed through the device. By furthermore providing a section of the device which is not influenced by the pendulum plate a basic air flow is ensured at all times. The biasing of the pendulum plate towards the maximum opening will ensure a relatively quick response to changes in the thickness of the clinker bed layer and as such an automatic adjustment mechanism of the air flow such that optimum cooling is achieved at all times.

In a further advantageous embodiment a shutter plate is provided in the frame, where said shutter plate steplessly may be adjusted between positions where the shutter is not blocking or substantially completely blocking said primary and/or secondary openings. The shutter serves to adjust the airflow both of the open section which the pendulum plate does not influence and the section in which the pendulum plate adapts the airflow area by pivoting from its non-blocking position to any position suitable, until substantially blocking the opening, such that depending on the size of the production going on in the cooler and the device's position in the cooler, preset airflows may be adjusted by altering the position of the shutter plate.

In a still further advantageous embodiment of the invention a section of the shutter plate corresponding to the secondary opening is curved, where the curve substantially corresponds to the radius described by the end of the pendulum plate.

In this manner it is achieved that the pendulum plate will provide a more or less linear change in airflow depending on the pressure drop across the bed of clinker and at the same time the space which the entire device occupies is reduced.

The invention is furthermore directed to an apparatus for cooling a bed of particulate material where the apparatus comprises an air distribution bottom utilizing air from one or more compartments, which in sectionalised manner direct the air up through the particulate material, the flow of the air through each section is regulated by means of a device. The distribution bottom is typically constructed in such a manner that clinker will not fall through the bottom and into the compartments, but will still allow the cooling air to be directed through the particular material. Each compartment may comprise one or more devices according to the invention depending on the size of the compartment and the desired airflow through the bed of particulate material, especially clinker, in that particular position in the cooler. It is to be understood that the number/density of devices per area unit may vary through the cooling installation such that the most optimum cooling of the particulate material is achieved before the particulate material is expelled from the cooling device.

In a further advantageous embodiment the shutter plate can be repositioned in the di- rection defined by the centre line of the shaft, hereby increase or decrease the primary and/or secondary openings, and supply a new flow rate for each new position.

This repositioning is especially interesting in cases where the cooling installation is to be treating more or less material or be treating a different kind of material such that the whole airflow into the compartments and thereby also through the bottom of the cooler may be readjusted to that particular purpose. By providing the shutter plate such that it may be displaced along a line parallel to the shaft around which the pendulum plate pivots it is relatively easy without any reconstruction of the device to readjust the airflow openings in the device per se.

The invention is also directed to a method for cooling a bed of particulate material which is supported by an air distribution bottom, utilizing air from one or more compartments, which in sectionalised manner direct the air up through the particulate material; the flow of the air through each section is regulated by means of a device, where a pendulum plate swings around a shaft; where the device comprises primary and secondary openings, and where the area of the primary opening is adjusted by a shutter plate member, and where the secondary opening has a dual adjustment mechanism comprising a biased pendulum plate, and a shutter plate for adjusting the open area of the secondary opening.

Naturally, this method utilizes all the advantages of the invention as already explained above.

In a further advantageous embodiment of the method the pendulum plate can swing above the upper edge of the shutter plate and create a larger area for airflow. In this situation the airflow does not follow the normal flow/resistance for a fixed orifice opening, which normally would be a function including the square root of the air flow. The airflow will in this position of the pendulum plate be substantially linear and having a greater increase.

This is an important feature in that as already explained in the introductory part of the description it is sometimes necessary to introduce a lot of air into the cooler which hitherto has been achieved by having very large fans providing this extra airflow. However, this extra airflow or volume of air is only necessary in very few situations, and as such the over-capacity of the fans relative to the normal situation is an expensive way of providing this facility, and thus the fan during normal operation has a poorer efficiency as compared to the normal efficiency range. By being able to pivot the pendulum plate free of the shutter and thereby substantially allowing an unrestricted airflow through the device the invention provides this added function in a very simple and reliable manner without the necessity for extra fans capacity, but simply by increasing the airflow area through the device, allowing more cooling air to be passed through the cooling bottom.

This aspect is further elaborated in a further advantageous embodiment of the invention where the bias of the pendulum plate is selected such that during normal operation of the cooling bed, the pendulum plate will not pivot past the shutter plate for adjusting the open area of the secondary opening. By adjusting the biasing means such that the situation where the pendulum plate swings above the upper edge of the shutter plate the device will during normal operation be within the range of airflow which it initially has been set at, namely by displacing the shutter plate relative to the shaft in such a manner that the airflow openings in the device are within the desired range and biasing the pendulum plate such that it will be able to adjust the airflow relative to the expected thickness of the bed of particulate material which is to be cooled.

Description of the Drawing

The invention will now be explained with reference to the accompanying drawings wherein

Figure 1 illustrates a cooler with an inlet and an outlet

Figure 2 illustrates a cross section through a device illustrates a 3D isometric view of a device

illustrates a cross-section through a device

illustrates air flow curves for different shutter settings Detailed Description of the Invention

In figure 1 is shown a cooler 1 which comprises an inlet end 2 and an outlet end 3. The cooler is connected to a rotary kiln 4 from which it receives hot material which is to be cooled. The material from the rotary kiln 4 drops onto a distribution bottom 5 provided in the cooler 1 and it is conveyed as a material layer 6 on the distribution bottom 5 from the inlet end 2 to the outlet end 3 of the cooler 1 by means of transport - not shown. The means of transport could (but not limited to) be: reciprocating grates, reciprocating bars or a walking floor principle. Under the distribution bottom 5 the cooler 1 comprises of one or more compartments 7, where each is supplied with cooling air from a fan installation 8. The compartment 7 may both in the longitudinal direction of the cooler and transversely hereof, be divided into a number of smaller compartments, not shown, and, if so, cooling air is supplied to each single compartment. The distribution bottom 5 is sectionalised in a number of smaller distribution areas 9 - called grate plates. Each grate plate or group of grate plates is equipped with a flow device 10. The flow device 10 consist of a pendulum plate 11 that rotates at a shaft 12, and the pendulum plate 11 is forced open by a spring 13. The pressure loss over the device 10 results in a force (area multiplied by pressure) at the pendulum plate 11. The force at the centre point of the pendulum plate 11, results in a torque in relation to shaft 12. In a static condition the "pressure" torque equals to the torque from the spring 13, but the pendulum plate 11 will be more and more closed as the pressure loss over the device 10 increases. When the pressure loss over the device 10 increases the active part of orifice area 14 will reduce. The orifice area 14 consists of:

• a secondary area 14a where the pendulum plate 11 can activate more or less of this area when the pendulum plate 11 change position.

• a primary area 14b which the pendulum plate 11 never covers.

The shutter plate 15 can be repositioned by an operator traversing the shutter plate 15 in the direction defined by the centre line of the shaft 12, hereby the orifice area 14 (both secondary 14a and primary 14b) can be changed. By calculations and experience it has been proved that the flow characteristic value can be changed linear (by repositioning the shutter plate 15) throughout the whole area of operation, where the delta pressure over the device 10 is different. In upside kiln operation condition, where a larger air amount is required, the pendulum plate 11 can swing past the top point 16 of the shutter plate 15. Hereby the total orifice area is increased by a slotted opening, and larger quantities of air can pass without much extra pressure loss over the device.

In figure 4 is illustrated a cross-section through a device corresponding to the device described above with reference to figure 2. In this situation, however, the pendulum plate 11 has pivoted free of the top edge 16 of the shutter plate 15 such that airflow is not restricted by the pendulum plate through the device 10. By shortly turning to figure 5 the figure illustrates the airflow through the device depending on the pressure drop across the bed of particulate material. Please note that the curves are only illustrative and many other airflows may be achieved with various sizes of the device and capacity of the ventilators. The four different lines illustrate four different positions of the shutter plate 15 relative to the openings in the device, i.e. corresponding to different opening areas 14a, see figure 3. As the kiln becomes unstable as explained above, the bed of particulate material may vary dramatically, and as such instead of providing large ventilators which may provide extra air through the device the pendulum plate 11 may pivot as illustrated with reference to figure 4 into a position where it is free of the shutter plate 15 at the top edge 16, thereby allowing a radical increase in the airflow which is illustrated by the right-hand end of the four lines 20, 21, 22, 23. Where the lines end upwards from the substantially linear section between 50 and 300 millimetre H₂0 to the upwards inclined line sections for pressures above 300 millimetres H₂0 is the situation where the pendulum plate 11 is in a position past the top edge 16, as illustrated in figure 4, whereas the linear sections between 50 and 300 millimetre H₂0 corresponds to various positions of the pendulum plate superposed the shutter for example as illustrated with reference to figure 2.

Claims

1. Device for use in a bottom construction of a bed for cooling particulate material, where said device comprises a frame comprising means for fastening said device to the bottom construction, and where inside the frame a primary and a secondary opening is provided, where said primary and secondary openings allows cooling air to pass through the frame and thereby through the bottom and through the bed of particulate material, and where a pendulum plate is pivotably arranged on an axle, such that the pendulum plate may pivot and thereby block off more or less of the secondary open- ing, and where said pendulum plate is biased towards a position allowing the secondary opening to be as open as possible.

2. Device according to claim 1, where a shutter plate is provided in the frame, where said shutter plate steplessly may be adjusted between positions where the shutter plate is not blocking or substantially completely blocking said primary and/or secondary openings.

3. Device according to any of claims 1 or 2, wherein a section of the shutter plate corresponding to the secondary opening, is curved, where the curve substantially corre- sponds to the radius described by the end of the pendulum plate.

4. Device according to any preceding claim where the pendulum plate can pivot past the secondary opening.

5. An apparatus for cooling a bed of particulate material 6, characterised in that the apparatus is comprised of an air distribution bottom 5 utilizing air from one or more compartments 7, which in sectionalised manner 9 direct the air up through the particulate material 6, the flow of the air through each section 9 is regulated by means of one or more devices 10 according to any of claims 1 to 4.

6. An apparatus for cooling a bed of particulate material according to claim 5, characterized in that the shutter plate 15 can be repositioned in the direction defined by the centre line of the shaft 12, hereby increase or decrease the primary and/or secondary openings 14, and supply a new flow rate for each new position.

7. An apparatus according to claim 5, wherein area 14 consist of an area 14a defined by the position of pendulum plate 11 and an area 14b disregarding the position of the pendulum plate 11.

8. A method for cooling a bed of particulate material 6 which is supported by an air distribution bottom 5, utilizing air from one or more compartments 7, which in sec- tionalised manner 9 direct the air up through the particulate material 6; the flow of the air through each section 9 is regulated by means of a device 10, where a pendulum plate 11 swings around a shaft 12; characterized in that the device comprises primary and secondary openings, and where the area of the primary opening is adjusted by a shutter plate, and where the secondary opening has a dual adjustment mechanism comprising a biased pendulum plate, and a shutter plate, both adjusting the open area of the secondary opening.

9. A method according to claim 8 wherein the pendulum plate 11 can swing above the upper edge 16 of plate 15 and create a larger area for airflow.

10. A method according to claim 8 or 9 where the bias of the pendulum plate is selected such that during normal operation of the cooling bed, the pendulum plate will not pivot past the plate for adjusting the open area of the secondary opening.