CA1094298A - Method and apparatus for handling heat-softenable batch material - Google Patents
Method and apparatus for handling heat-softenable batch materialInfo
- Publication number
- CA1094298A CA1094298A CA304,173A CA304173A CA1094298A CA 1094298 A CA1094298 A CA 1094298A CA 304173 A CA304173 A CA 304173A CA 1094298 A CA1094298 A CA 1094298A
- Authority
- CA
- Canada
- Prior art keywords
- batch material
- pellets
- depth
- liquid
- batch
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B3/00—Charging the melting furnaces
- C03B3/02—Charging the melting furnaces combined with preheating, premelting or pretreating the glass-making ingredients, pellets or cullet
- C03B3/023—Preheating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
- B01J2/14—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic in rotating dishes or pans
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B1/00—Preparing the batches
- C03B1/02—Compacting the glass batches, e.g. pelletising
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Feeding, Discharge, Calcimining, Fusing, And Gas-Generation Devices (AREA)
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
- Powder Metallurgy (AREA)
- Investigating Or Analyzing Materials Using Thermal Means (AREA)
- Glanulating (AREA)
- Glass Melting And Manufacturing (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method and apparatus are provided for handling heat-softenable batch material. The batch components are mixed together and then mixed with liquid and formed into pellets of substantially uniform size and shape. The pellets are preheated in a heat-exchange chamber through which hot gases are passed from a melting unit to which the preheated pellets are supplied, saving considerably on energy requirements. A physical characteristic such as the depth of a portion of the batch being formed into the pellets is sensed, the depth being related to moisture content. The ratio of the batch material and liquid is regulated in dependence upon this sensing to achieve uniformity in pellet size. Size uniformity is important in maintaining relatively free flow of the hot gases through the pellets in the heat-exchange chamber.
A method and apparatus are provided for handling heat-softenable batch material. The batch components are mixed together and then mixed with liquid and formed into pellets of substantially uniform size and shape. The pellets are preheated in a heat-exchange chamber through which hot gases are passed from a melting unit to which the preheated pellets are supplied, saving considerably on energy requirements. A physical characteristic such as the depth of a portion of the batch being formed into the pellets is sensed, the depth being related to moisture content. The ratio of the batch material and liquid is regulated in dependence upon this sensing to achieve uniformity in pellet size. Size uniformity is important in maintaining relatively free flow of the hot gases through the pellets in the heat-exchange chamber.
Description
~0~429~
This invention relates to a method and apparatus for handling batch of heat-softenable material.
It has been found to be advantageous to collect the products of combustion or hot gases over molten glass in a glass melting unit and to pass them in heat-exchange relationship with the batch material being supplied to the melting furnace. The batch can thus be preheated to elevated temperatures to save signifi-cant amounts of energy subsequently required to melt the batch.
The exhaust gases otherwise are simply expelled to the atmos-phere in many instances with a considerable waste of heatenergy.
Preferably, the heat-softenable batch material is in the form of pellets in the heat-exchange chamber through which the hot gases are passed. It has been discovered that the pellet size must be substantially uniform, because pellets of varying sizes tend to nest and provide excessive restriction to the flow of the gases past the pellets in the chamber. It has also been discovered that the actual pellet size is importan'. If the pellets are too small, again undue restriction to the flow of the hot gases results. If the pellets are too large, their surface area-to-weight ratio is reduced and the heat transferred to them is accordingly decreased. ~lso, trapped moisture in the larger pellets may turn to steam and cause the pellets to explode. Specifically, it has been found that pellets of half of an inch nominal diameter, with a range from three-eighths to five-eighths of an inch in diameter, are best for obtaining maximum heat transfer from the hot exhaust gases to the pellets.
The pellets of the heat-softenable batch material preferably are made in a modified commercially-available pelletizer. The components of the batch are mixed together and then supplied to ,~
, 10~?~298 the pelletizer. During transportation to the pelletizer, the batch components tend to segregate so that the actual batch supplied to the pelletizer varies, even though the final pellets produced and supplied to the melting unit average out so that the short-term variations are not material. However, the short-term variations in the batch components tend to affect the pellet-forming ability of the batch and the size of the pellets produced, other factors being constant. The feed rate of the batch to the pelletizer also varies and this also affects the pellet forming and pellet size. Liquid, and specifically water, is also supplied to the pelletizer near the batch supply. With the batch component or quantity variation, different size pellets will result when the water quantity is held constant.
An object of the present invention is to provide an improved method and apparatus for pelletizing batch material so that production of pellets of substantially uniform size and shape is facilitated.
According to one aspect of the present invention there is provided a method of pelletizing a batch of particulate material on a pelletizer so as to form pellets, which method comprises supplying said particulate material to a movable sur-face of said pelletizer, moving said surface, supplying liquid to the surface to aid in forming the batch material into pellets as the material moves on the surface, sensing the depth of the batch material on the surface, and changing the ratio of the liquid and the batch material in response to a change in the sensed depth.
According to another aspect of the present invention there is provided apparatus for pelletizing a batch of particulate material, comprising a movable surface, means for moving said 4 . -Dr ~ - 2 -surface, means for supplying particu:Late batch material to said surface, means for supplying liquid to said surface to cause the particulate material to form pellets as said surface moves, means for sensing the depth of the batch material on the surface, and means for changing the ratio of the liquid and the batch material in response to change in the depth sensed.
The invention arises from the finding that the liquid, e.g. water, quantity, or the ratio of the batch to the water, affects the pellet size, with more water resulting in larger pellets and less water resulting in smaller pellets, at least in most instances, together with the discovery that measurement of a physical characteristic of the batch on the pelletizer during the formation of the pellets enables a prediction to be made of pellet size. Consequently the batch to water ratio can be changed to avoid an undesired increase or decrease in pellet size. In particular, the depth of the batch material in the pelletizer at a portion thereof can be measured and the water flow changed accordingly. An increased depth of the nuclei or seeds of the batch material indicates that water content is higher, the water tending to cause the seeds to stick together more and thus build up higher. Consequently, the amount of water supplied to the pelletizer is reduced when the sensing device indicates that the batch depth has reached a predetermined value. The excess water would otherwise tend to make fewer but larger diameter pellets.
Similarly, if there is too little water, the depth of the nuclei or seeds of the batch decreases with the amount of water then being increased. The lesser amount of water otherwise would result in the individual final pellets thereby being smaller but in greater quantity.
The thus formed pellets of a substantially uniform size and shape facilitate the passage therethrough of hot exhaust gases from a melting unit, in heat-exchange relationship with the pellets.
The invention will be further understood from the following detailed description by way of example of an embodiment thereof with reference to the accompanying drawings, in which:
Fig. 1 is a somewhat schematic view in elevation of overall apparatus for handling heat-softenable batch material;
Fig. 2 is a front view in elevation of pelletizing apparatus shown in Fig. l;
Fig. 3 is a top, plan view of the apparatus of Fig. 2;
Fig. 4 is an enlarged, diagrammatic view of a portion of the pelletizing apparatus; and Fig. 5 is a diagrammatic view of controls for sensing batch material in the pelletizing apparatus and for controlling the flow of water to the apparatus.
Referring to Fig. 1, particulate~ heat-softenable batch mat-erial is transported to a supply hopper 10 and supplied to a pelletizer 12. The particulate batch material is formed into pellets which are discharged onto a trough 14 having openings 16 (Figs. 2 and 3) through which smaller or broken pellets are separated. The pellets are supplied to a horizontal conveyor 18 and then carried up to a vertical conveyor 20 to the top of a heat-exchange hopper 22 which forms a heat-exchange chamber. The pellets next move down a supply tube 24 to a feeder 26 which carries the pellets into a melting unit or furnace 28.
Hot exhaust gases or products of combustion from the furnace 28 are carried up an exhaust stack 30 to the bottom of the hopper 22. The exhaust gases are then drawn through the hopper 22 by a blower 32 and discharged. The heat-exchange hopper 22 is suf-ficiently large that the exhaust gases passing therethrough will be at a low velocity and not carry some of the pellets out through the blower 32. A substantial portion of the heat in the exhaust gases is transferred to the pellets in the heat-exchange hopper 22 so that the pellets are at an elevated temperature when they enter the furnace 28. A substantial increase in efficiency of the furnace 28 is thereby achieved.
The size uniformity of thepellets themselves is very impor-tant. If the pellet size varies too much, the pellets tend tonest together in the hopper 22 and excessively restrict the flow of the exhaust gases therethrough. However, if the pellets are of sufficiently uniform size, there will be sufficient voids among them that exhaust gases can pass through without exces-sive impediment. The nominal diameter of the pellets is also important because pellets which are too small provide excessive restriction to the flow of the exhaust gases. On the other hand, if the pellets are too large, their surface area-to-weight ratio is lower and the heat transferred to them is decreased.
Further, in the large pellets, moisture tends to be trapped therein and turned to steam by the exhaust gases, causing the pellets to explode. More specifically, by way of example, pellets having a nominal diameter of half of an inch, with a range of three-eighths of five~eighths of an inch, have been found to be best for obtaining maximum heat transfer from the exhaust gases to the pellets in the heat-exchange hopper 22.
The pelletizer 12 forms the particulate batch material into the half inch nominal diameter pellets. Unfortunately, the components of the batch material supplied to the pelletizer 12 and specifically to the supply hopper 10 tend to segregate during r~ .
10942~8 transportation. Such segregation is not deleterious to the operation of the furnace 28 because the components of the pel-lets supplied thereto average out over a period of time.
However, the short-term variations in the batch compone~ts do affect the pellet-forming ability of the batch material. In other words, variations in the components of the batch material supplied to the pelletizer 12 cause a change in pellet size, with other factors maintained constant. The feed rate of the batch to the pelletizer will also vary and change the pellet-forming ability and the pellet size with other factors beingconstant.
Liquid, and specifically water, is supplied to the pellet-izer 12 and it has been found that the water ~uantity or the ratio of the water to the batch material will affect the pellet size. An increase in the amount of water or an increase in the ratio of the water to batch material results in larger pellets being produced, while less water results in smaller pellets, at least with most batch materials. It has also been found that certain physical characteristics of the batch material on the pelletizer 12 can be sensed and used to control the flow of water and hence the ratio of water to batch material to maintain the pellet size in a desired range. In particular, the depth of the batch material or the pellets being formed at certain por-tions of the pelletizer can be measured,with the water flow then controlled accordingly. An increased depth of the nuclei or seeds of the batch material on which the pellets are formed indicates that the seeds are tending to stick together more and thus increase in depth. This occurs when the ratio of water to batch material increases. When the depth increases, the amount of water supplied to the pelletizer is then reduced because a -6~
109~29B
continued excess of water otherwise would cause fewer but larger pellets to be formed. Also, when the depth of the nuclei or seeds is less, they tend to stick together to a lesser extent, indicating that the water content has decreased and that the pellet size accordingly will be smaller. The amount of water is then increased to prevent this.
Referring to Figs. 2-4, the pelletizer 12 includes a movable surface 34 specifically formed by a rotatable member or disc, in this instance. The movable surface can also take other forms, however, such as a drum or a cone for producing the pellets. The disc 34 is rotatably carried on a bearing housing 36 (Fig. 1) which is pivotally mounted on arms 38 carried on an axle 40 which is mounted on a stand 42. The disc 34 is rotated by a suitable motor 44. An annular wall 46 surrounds the rotat-able member 34 with the pellets tumbling over this wall and down a spout 47 to the trough 14 when of the final size. An outer cleaning plow 48 (Figs. 2 and 3) and an inner cleaning plow 49 clean the surface of the rotatable member 34.
Batch from the supply hopper 10 is supplied to a lower central portion of the rotatable member 34, as indicated in Fig.
4, by a suitable feeder 50. In this instance, the feeder 50 is shown as having a belt conveyor 52 (Fiy. 2) driven by a motor 54;
however, other conveyors such as vibratory conveyors can be equally well employed. While the feeder is intended to supply a constant quantity of batch, as a practical matter, the feed rate of substantially any feeder is subject to some variation. This requires changes in the water supply even though the batch com-ponents do not vary. In addition, water is supplied to a lower central portion of the rotatable m~mber 34, at a portion thereof shown in Fig. 4, by a supply line or spout 56. With the rotatable j ~ ~
10~298 member 34 rotating in a clockwise direction, asshown in Fig.
4, the batch is carried in generally elliptical paths as it moves up the surface, the surface being maintained at a preset angle to the horizontal, such as 45, as determined by the position of the arms 38.
Actually, the wet batch moves in three rather dis-tinct streams or paths as it is carried up the moving surface and falls back. In the outer path are seeds or nuclei of the batch on which the pellets form. In the middle path are par-tially formed pellets having diameters in the range of onequarter to three-eighths of an inch when pellets having a nominal diameter of half of an inch are to be produced. In the inner path are finished pellets which roll in a tight elliptical path until they tumble over the annular wall 46.
As the seeds or nuclei form, the particulate batch material gathers thereon in continuous layers to gradually increase the diameters of the partially formed pellets until the desired size is attained. As moisture or water is introduced to the agitated mass of particulate material, the capillary force of the water and the mechanical force of the agitation of the particulate material against the moving surface causes packing and coalescing of the material into firm bodies.
The batch material in the outer stream and also, at least to some extent, in the middle stream, tends to stick together more when there is more moisture of water in the batch, with the depth of the stream correspondingly increasing. When this depth reaches a predetermined value, the water is cut back with the build-up of the batch material accordingly decreasing again. Otherwise, with the higher water content, the batch tends to agglomerate onto existing nuclei or seeds more readily, ~8~
109~29~ `
rather than forming new seeds, with fewer and larger pellets thereby resulting. Oppositely, with less moisture or water, the agglomeration tendency of the particulate batch material is decreased with more nuclei or seeds forming, which results in more but smaller pellets because there are more nuclei on which a given amount of batch can form, and there is a lesser tendency for the batch to agglomerate.
The water supply through the spout 56 to the moving surface 34 can be controlled by the system shown diagrammatically in Fig. 5. Accordingly, water is supplied to the spout 56 through a first passage or line 58 having a manually-controlled valve 60 therein. Water can also be supplied to the spout 56 through a second passage or line 62 having therein a solenoid-operated valve 64 and a manually-controlled valve 65 for adjustment. Water for both of the lines 58 and 62 is supplied through a suitable supply line 66. The flow of water through the line 58 to the spout 56 is such as to be less than the amount needed to produce the desired size of pellets on the pelletizer 12. However, the flow of water through both of the lines 58 and 62, when the valve 64 is open, is in excess of the amount needed for producing pellets of the desired size.
By way of example, with a typicalbatch material which is supplied to the pelletizer 12 at the predetermined rate of 2000 pounds per hour, for example, a water supply of forty gallons per hour may be required to produce pellets of a given nominal diameter. However, for short-term variations in the batch compon-ents, the amount of water may need to be varied between perhaps 35 and 45 gallons per hour in order to maintain the pellet size relatively constant. In that instance, the water flow through the first passage 58 can be set at 30 gallons per hour, below the minimum required. The supply of water through the second branch passage 62 can be set at 20 gallons per hour. The combined flow through both of the passages 58 and 62 is then 50 gallons per hour, which is in excess of the maximum quantity of water re-quired. Thus, liquid flow through the passage 58 is supplemented from time-to-time by flow through the passage 62 to obtain pellets of the desired nominal diameter.
The control of the water through the passages 58 and 62 is regulated by a suitable sensing device which senses a physical characteristic of the particulate bath material on the surface 34. The sensing device can sense the water content, as previously discussed, and can do this by sensing the depth of the nuclei or partially formed pellets moving in the outer or middle streams on the surface 34. In the specific example shown, the solenoid valve 64 is controlled by a timer 68 which, when energized, supplies power through contacts therein to the sole-noid of the valve 64 for a predetermined period of time, such as four seconds. Power to energize the timer, in turn, is controlled by a switch 70. The switch 70 has an actuating stem 72 connected with an arm 74 supporting a sensor or paddle 76 . The arm 74, in turn, is pivotally supported by an overhead bar 78 connected to a post 80 at one side of the pelletizer wall 46. The arm 74 is normally held against the stem 72 by a spring 82 to keep the switch 70 open.
The paddle 76 is located near the annular wall 46 above an upper, outer portion of the surface 34 of the pelletizer. It preferably is in a position to determine the depth of the seeds or nuclei in the outer path of the batch material on the moving surface 34 but can alternatively sense the depth of the partially formed pellets. When the depth of the batch material, whether --10"
~09~298 seeds or pellets, reaches a predetermined value, the paddle 76 is contacted and moved in a counterclockwise direction, as viewed in Fig. 5. The batch material, as discussed before, reaches the predetermined depth when the water content increases and causes it to stick together and build up. Consequently, when this condition occurs, it is desired to decrease the amount of water in the batch or decrease the ratio of the water to batch.
For this purpose, when the paddle 76 is moved, the actuating stem 72 of the switch 70 is moved outwardly to close the switch and energize the timer 68 for its predetermined period of time.
When the timer is energized, it closes the valve 64 and results in only the water from the line 58 being supplied to the spout 56. Each time the paddle 76 is moved, it resets the timer 68 so that the valve 64 remains closed until the paddle is no longer contacted by the batch material for a period of time exceeding the period set on the timer. With this arrangement, the water content can be maintained substantially constant in the batch so that the desired nominal size of the pellets will be produced.
If desired, the sensor or paddle 76 can instead be employed to control the flow of the batch material by the feeder 50. With the arrangement shown, the motor 54 can be a two-speed motor to drive the belt 52 at different speeds. If a vibrating feeder is employed, the rate of vibration can be controlled for the same purpose. Thus, instead of increasing the flow of water, the batch feed can be decreased, and vice versa.
Different types of sensors other than the paddle can also be employed. Thus, the depth of the pellets can be sensed by an electric eye. Also, ultrasonic waves or microwaves can be employed for this purpose.
~0!~298 Various modifications of the above-described embodi-ment of the invention will be apparent to those skilled in the art, and it is to be understood that such modifications can be made without departing from the scope of the invention as defined in the claims.
~12
This invention relates to a method and apparatus for handling batch of heat-softenable material.
It has been found to be advantageous to collect the products of combustion or hot gases over molten glass in a glass melting unit and to pass them in heat-exchange relationship with the batch material being supplied to the melting furnace. The batch can thus be preheated to elevated temperatures to save signifi-cant amounts of energy subsequently required to melt the batch.
The exhaust gases otherwise are simply expelled to the atmos-phere in many instances with a considerable waste of heatenergy.
Preferably, the heat-softenable batch material is in the form of pellets in the heat-exchange chamber through which the hot gases are passed. It has been discovered that the pellet size must be substantially uniform, because pellets of varying sizes tend to nest and provide excessive restriction to the flow of the gases past the pellets in the chamber. It has also been discovered that the actual pellet size is importan'. If the pellets are too small, again undue restriction to the flow of the hot gases results. If the pellets are too large, their surface area-to-weight ratio is reduced and the heat transferred to them is accordingly decreased. ~lso, trapped moisture in the larger pellets may turn to steam and cause the pellets to explode. Specifically, it has been found that pellets of half of an inch nominal diameter, with a range from three-eighths to five-eighths of an inch in diameter, are best for obtaining maximum heat transfer from the hot exhaust gases to the pellets.
The pellets of the heat-softenable batch material preferably are made in a modified commercially-available pelletizer. The components of the batch are mixed together and then supplied to ,~
, 10~?~298 the pelletizer. During transportation to the pelletizer, the batch components tend to segregate so that the actual batch supplied to the pelletizer varies, even though the final pellets produced and supplied to the melting unit average out so that the short-term variations are not material. However, the short-term variations in the batch components tend to affect the pellet-forming ability of the batch and the size of the pellets produced, other factors being constant. The feed rate of the batch to the pelletizer also varies and this also affects the pellet forming and pellet size. Liquid, and specifically water, is also supplied to the pelletizer near the batch supply. With the batch component or quantity variation, different size pellets will result when the water quantity is held constant.
An object of the present invention is to provide an improved method and apparatus for pelletizing batch material so that production of pellets of substantially uniform size and shape is facilitated.
According to one aspect of the present invention there is provided a method of pelletizing a batch of particulate material on a pelletizer so as to form pellets, which method comprises supplying said particulate material to a movable sur-face of said pelletizer, moving said surface, supplying liquid to the surface to aid in forming the batch material into pellets as the material moves on the surface, sensing the depth of the batch material on the surface, and changing the ratio of the liquid and the batch material in response to a change in the sensed depth.
According to another aspect of the present invention there is provided apparatus for pelletizing a batch of particulate material, comprising a movable surface, means for moving said 4 . -Dr ~ - 2 -surface, means for supplying particu:Late batch material to said surface, means for supplying liquid to said surface to cause the particulate material to form pellets as said surface moves, means for sensing the depth of the batch material on the surface, and means for changing the ratio of the liquid and the batch material in response to change in the depth sensed.
The invention arises from the finding that the liquid, e.g. water, quantity, or the ratio of the batch to the water, affects the pellet size, with more water resulting in larger pellets and less water resulting in smaller pellets, at least in most instances, together with the discovery that measurement of a physical characteristic of the batch on the pelletizer during the formation of the pellets enables a prediction to be made of pellet size. Consequently the batch to water ratio can be changed to avoid an undesired increase or decrease in pellet size. In particular, the depth of the batch material in the pelletizer at a portion thereof can be measured and the water flow changed accordingly. An increased depth of the nuclei or seeds of the batch material indicates that water content is higher, the water tending to cause the seeds to stick together more and thus build up higher. Consequently, the amount of water supplied to the pelletizer is reduced when the sensing device indicates that the batch depth has reached a predetermined value. The excess water would otherwise tend to make fewer but larger diameter pellets.
Similarly, if there is too little water, the depth of the nuclei or seeds of the batch decreases with the amount of water then being increased. The lesser amount of water otherwise would result in the individual final pellets thereby being smaller but in greater quantity.
The thus formed pellets of a substantially uniform size and shape facilitate the passage therethrough of hot exhaust gases from a melting unit, in heat-exchange relationship with the pellets.
The invention will be further understood from the following detailed description by way of example of an embodiment thereof with reference to the accompanying drawings, in which:
Fig. 1 is a somewhat schematic view in elevation of overall apparatus for handling heat-softenable batch material;
Fig. 2 is a front view in elevation of pelletizing apparatus shown in Fig. l;
Fig. 3 is a top, plan view of the apparatus of Fig. 2;
Fig. 4 is an enlarged, diagrammatic view of a portion of the pelletizing apparatus; and Fig. 5 is a diagrammatic view of controls for sensing batch material in the pelletizing apparatus and for controlling the flow of water to the apparatus.
Referring to Fig. 1, particulate~ heat-softenable batch mat-erial is transported to a supply hopper 10 and supplied to a pelletizer 12. The particulate batch material is formed into pellets which are discharged onto a trough 14 having openings 16 (Figs. 2 and 3) through which smaller or broken pellets are separated. The pellets are supplied to a horizontal conveyor 18 and then carried up to a vertical conveyor 20 to the top of a heat-exchange hopper 22 which forms a heat-exchange chamber. The pellets next move down a supply tube 24 to a feeder 26 which carries the pellets into a melting unit or furnace 28.
Hot exhaust gases or products of combustion from the furnace 28 are carried up an exhaust stack 30 to the bottom of the hopper 22. The exhaust gases are then drawn through the hopper 22 by a blower 32 and discharged. The heat-exchange hopper 22 is suf-ficiently large that the exhaust gases passing therethrough will be at a low velocity and not carry some of the pellets out through the blower 32. A substantial portion of the heat in the exhaust gases is transferred to the pellets in the heat-exchange hopper 22 so that the pellets are at an elevated temperature when they enter the furnace 28. A substantial increase in efficiency of the furnace 28 is thereby achieved.
The size uniformity of thepellets themselves is very impor-tant. If the pellet size varies too much, the pellets tend tonest together in the hopper 22 and excessively restrict the flow of the exhaust gases therethrough. However, if the pellets are of sufficiently uniform size, there will be sufficient voids among them that exhaust gases can pass through without exces-sive impediment. The nominal diameter of the pellets is also important because pellets which are too small provide excessive restriction to the flow of the exhaust gases. On the other hand, if the pellets are too large, their surface area-to-weight ratio is lower and the heat transferred to them is decreased.
Further, in the large pellets, moisture tends to be trapped therein and turned to steam by the exhaust gases, causing the pellets to explode. More specifically, by way of example, pellets having a nominal diameter of half of an inch, with a range of three-eighths of five~eighths of an inch, have been found to be best for obtaining maximum heat transfer from the exhaust gases to the pellets in the heat-exchange hopper 22.
The pelletizer 12 forms the particulate batch material into the half inch nominal diameter pellets. Unfortunately, the components of the batch material supplied to the pelletizer 12 and specifically to the supply hopper 10 tend to segregate during r~ .
10942~8 transportation. Such segregation is not deleterious to the operation of the furnace 28 because the components of the pel-lets supplied thereto average out over a period of time.
However, the short-term variations in the batch compone~ts do affect the pellet-forming ability of the batch material. In other words, variations in the components of the batch material supplied to the pelletizer 12 cause a change in pellet size, with other factors maintained constant. The feed rate of the batch to the pelletizer will also vary and change the pellet-forming ability and the pellet size with other factors beingconstant.
Liquid, and specifically water, is supplied to the pellet-izer 12 and it has been found that the water ~uantity or the ratio of the water to the batch material will affect the pellet size. An increase in the amount of water or an increase in the ratio of the water to batch material results in larger pellets being produced, while less water results in smaller pellets, at least with most batch materials. It has also been found that certain physical characteristics of the batch material on the pelletizer 12 can be sensed and used to control the flow of water and hence the ratio of water to batch material to maintain the pellet size in a desired range. In particular, the depth of the batch material or the pellets being formed at certain por-tions of the pelletizer can be measured,with the water flow then controlled accordingly. An increased depth of the nuclei or seeds of the batch material on which the pellets are formed indicates that the seeds are tending to stick together more and thus increase in depth. This occurs when the ratio of water to batch material increases. When the depth increases, the amount of water supplied to the pelletizer is then reduced because a -6~
109~29B
continued excess of water otherwise would cause fewer but larger pellets to be formed. Also, when the depth of the nuclei or seeds is less, they tend to stick together to a lesser extent, indicating that the water content has decreased and that the pellet size accordingly will be smaller. The amount of water is then increased to prevent this.
Referring to Figs. 2-4, the pelletizer 12 includes a movable surface 34 specifically formed by a rotatable member or disc, in this instance. The movable surface can also take other forms, however, such as a drum or a cone for producing the pellets. The disc 34 is rotatably carried on a bearing housing 36 (Fig. 1) which is pivotally mounted on arms 38 carried on an axle 40 which is mounted on a stand 42. The disc 34 is rotated by a suitable motor 44. An annular wall 46 surrounds the rotat-able member 34 with the pellets tumbling over this wall and down a spout 47 to the trough 14 when of the final size. An outer cleaning plow 48 (Figs. 2 and 3) and an inner cleaning plow 49 clean the surface of the rotatable member 34.
Batch from the supply hopper 10 is supplied to a lower central portion of the rotatable member 34, as indicated in Fig.
4, by a suitable feeder 50. In this instance, the feeder 50 is shown as having a belt conveyor 52 (Fiy. 2) driven by a motor 54;
however, other conveyors such as vibratory conveyors can be equally well employed. While the feeder is intended to supply a constant quantity of batch, as a practical matter, the feed rate of substantially any feeder is subject to some variation. This requires changes in the water supply even though the batch com-ponents do not vary. In addition, water is supplied to a lower central portion of the rotatable m~mber 34, at a portion thereof shown in Fig. 4, by a supply line or spout 56. With the rotatable j ~ ~
10~298 member 34 rotating in a clockwise direction, asshown in Fig.
4, the batch is carried in generally elliptical paths as it moves up the surface, the surface being maintained at a preset angle to the horizontal, such as 45, as determined by the position of the arms 38.
Actually, the wet batch moves in three rather dis-tinct streams or paths as it is carried up the moving surface and falls back. In the outer path are seeds or nuclei of the batch on which the pellets form. In the middle path are par-tially formed pellets having diameters in the range of onequarter to three-eighths of an inch when pellets having a nominal diameter of half of an inch are to be produced. In the inner path are finished pellets which roll in a tight elliptical path until they tumble over the annular wall 46.
As the seeds or nuclei form, the particulate batch material gathers thereon in continuous layers to gradually increase the diameters of the partially formed pellets until the desired size is attained. As moisture or water is introduced to the agitated mass of particulate material, the capillary force of the water and the mechanical force of the agitation of the particulate material against the moving surface causes packing and coalescing of the material into firm bodies.
The batch material in the outer stream and also, at least to some extent, in the middle stream, tends to stick together more when there is more moisture of water in the batch, with the depth of the stream correspondingly increasing. When this depth reaches a predetermined value, the water is cut back with the build-up of the batch material accordingly decreasing again. Otherwise, with the higher water content, the batch tends to agglomerate onto existing nuclei or seeds more readily, ~8~
109~29~ `
rather than forming new seeds, with fewer and larger pellets thereby resulting. Oppositely, with less moisture or water, the agglomeration tendency of the particulate batch material is decreased with more nuclei or seeds forming, which results in more but smaller pellets because there are more nuclei on which a given amount of batch can form, and there is a lesser tendency for the batch to agglomerate.
The water supply through the spout 56 to the moving surface 34 can be controlled by the system shown diagrammatically in Fig. 5. Accordingly, water is supplied to the spout 56 through a first passage or line 58 having a manually-controlled valve 60 therein. Water can also be supplied to the spout 56 through a second passage or line 62 having therein a solenoid-operated valve 64 and a manually-controlled valve 65 for adjustment. Water for both of the lines 58 and 62 is supplied through a suitable supply line 66. The flow of water through the line 58 to the spout 56 is such as to be less than the amount needed to produce the desired size of pellets on the pelletizer 12. However, the flow of water through both of the lines 58 and 62, when the valve 64 is open, is in excess of the amount needed for producing pellets of the desired size.
By way of example, with a typicalbatch material which is supplied to the pelletizer 12 at the predetermined rate of 2000 pounds per hour, for example, a water supply of forty gallons per hour may be required to produce pellets of a given nominal diameter. However, for short-term variations in the batch compon-ents, the amount of water may need to be varied between perhaps 35 and 45 gallons per hour in order to maintain the pellet size relatively constant. In that instance, the water flow through the first passage 58 can be set at 30 gallons per hour, below the minimum required. The supply of water through the second branch passage 62 can be set at 20 gallons per hour. The combined flow through both of the passages 58 and 62 is then 50 gallons per hour, which is in excess of the maximum quantity of water re-quired. Thus, liquid flow through the passage 58 is supplemented from time-to-time by flow through the passage 62 to obtain pellets of the desired nominal diameter.
The control of the water through the passages 58 and 62 is regulated by a suitable sensing device which senses a physical characteristic of the particulate bath material on the surface 34. The sensing device can sense the water content, as previously discussed, and can do this by sensing the depth of the nuclei or partially formed pellets moving in the outer or middle streams on the surface 34. In the specific example shown, the solenoid valve 64 is controlled by a timer 68 which, when energized, supplies power through contacts therein to the sole-noid of the valve 64 for a predetermined period of time, such as four seconds. Power to energize the timer, in turn, is controlled by a switch 70. The switch 70 has an actuating stem 72 connected with an arm 74 supporting a sensor or paddle 76 . The arm 74, in turn, is pivotally supported by an overhead bar 78 connected to a post 80 at one side of the pelletizer wall 46. The arm 74 is normally held against the stem 72 by a spring 82 to keep the switch 70 open.
The paddle 76 is located near the annular wall 46 above an upper, outer portion of the surface 34 of the pelletizer. It preferably is in a position to determine the depth of the seeds or nuclei in the outer path of the batch material on the moving surface 34 but can alternatively sense the depth of the partially formed pellets. When the depth of the batch material, whether --10"
~09~298 seeds or pellets, reaches a predetermined value, the paddle 76 is contacted and moved in a counterclockwise direction, as viewed in Fig. 5. The batch material, as discussed before, reaches the predetermined depth when the water content increases and causes it to stick together and build up. Consequently, when this condition occurs, it is desired to decrease the amount of water in the batch or decrease the ratio of the water to batch.
For this purpose, when the paddle 76 is moved, the actuating stem 72 of the switch 70 is moved outwardly to close the switch and energize the timer 68 for its predetermined period of time.
When the timer is energized, it closes the valve 64 and results in only the water from the line 58 being supplied to the spout 56. Each time the paddle 76 is moved, it resets the timer 68 so that the valve 64 remains closed until the paddle is no longer contacted by the batch material for a period of time exceeding the period set on the timer. With this arrangement, the water content can be maintained substantially constant in the batch so that the desired nominal size of the pellets will be produced.
If desired, the sensor or paddle 76 can instead be employed to control the flow of the batch material by the feeder 50. With the arrangement shown, the motor 54 can be a two-speed motor to drive the belt 52 at different speeds. If a vibrating feeder is employed, the rate of vibration can be controlled for the same purpose. Thus, instead of increasing the flow of water, the batch feed can be decreased, and vice versa.
Different types of sensors other than the paddle can also be employed. Thus, the depth of the pellets can be sensed by an electric eye. Also, ultrasonic waves or microwaves can be employed for this purpose.
~0!~298 Various modifications of the above-described embodi-ment of the invention will be apparent to those skilled in the art, and it is to be understood that such modifications can be made without departing from the scope of the invention as defined in the claims.
~12
Claims (22)
1. A method of pelletizing a batch of particulate material on a pelletizer so as to form pellets, which method comprises supplying said particulate material to a movable sur-face of said pelletizer, moving said surface, supplying liquid to the surface to aid in forming the batch material into pellets as the material moves on the surface, sensing the depth of the batch material on the surface, and changing the ratio of the liquid and the batch material in response to a change in the sensed depth.
2. A method according to claim 1 which further com-prises discharging the pellets from the movable surface, supply-ing the pellets to a chamber, passing hot gases from a melting unit through said chamber to preheat the pellets, and subse-quently supplying the preheated pellets from the chamber to the melting unit.
3. A method according to claim 1 wherein the movable surface is an inclined surface of a rotatable member, the batch material is supplied to a lower portion of said surface and the liquid is supplied to said surface near the batch material, and the surface is moved by rotating said rotatable member in a given direction to cause the batch material and pellets to move up along the surface and then to fall downwardly under the in-vluence of gravity so as to move in generally elliptical paths.
4. A method according to claim 1, 2, or 3 wherein said depth of the batch material is sensed on a predetermined portion of the movable surface.
5. A method according to claim 1, 2, or 3 wherein the ratio of the liquid and the batch material is changed by alter-ing the supply of liquid.
6. A method according to claim 1 or 2 wherein said movable surface comprises a rotatable member and said surface is moved by rotating said member.
7. A method according to claim 1, 2, or 3 wherein the depth is sensed by a pivotally supported sensor.
8. A method according to claim 1, 2, or 3 wherein the depth is sensed by a sensor which includes a pivotally supported arm and a paddle mounted thereon, said paddle being contacted by said batch material and moved when the depth of the batch material on an adjacent portion of the movable surface reaches a predetermined value.
9. A method according to claim 1, 2, or 3, wherein the depth is sensed by a sensor which is arranged to contact the batch material and to be forced thereby in an upward direction when the depth of the batch material on an adjacent portion of the movable surface reaches a predetermined value.
10. Apparatus for pelletizing a batch of particulate material, comprising a movable surface, means for moving said surface, means for supplying particulate batch material to said surface, means for supplying liquid to said surface to cause the particulate material to form pellets as said surface moves, means for sensing the depth of the batch material on the surface, and means for changing the ratio of the liquid and the batch material in response to change in the depth sensed.
11. Apparatus according to claim 10 wherein the depth of the batch material is sensed on a predetermined portion of the movable surface.
12. Apparatus according to claim 10 or 11 wherein said sensing means includes a pivotally supported sensor.
13. Apparatus according to claim 10 or 11 wherein said sensing means includes a pivotally supported arm and a paddle mounted thereon, said paddle being contacted by said batch material and moved when the depth of the batch material on an adjacent portion of the movable surface reaches a pre-determined value.
14. Apparatus according to claim 10 or 11 wherein said sensing means is arranged to contact the batch material and to be forced thereby in an upward direction when the depth of the batch material on an adjacent portion of the movable surface reaches a predetermined value.
15. Apparatus according to claim 10 or 11, and further comprising a heat-exchange chamber, means for supplying the pellets from the surface to the heat-exchange chamber, a melting unit, means for passing hot gases from said melting unit to said chamber to preheat the pellets, and means for supplying the pre-heated pellets from the chamber to the melting unit.
16. Apparatus according to claim 10 or 11 wherein said movable surface comprises a rotatable member and said means for moving said surface comprises means for rotating said rotatable member.
17. Apparatus according to claim 10 or 11 wherein said ratio changing means comprises means for changing the supply of liquid to said surface.
18. Apparatus according to claim 11 wherein said mov-able surface comprises an inclined rotatable member and said means for moving said surface comprises means for rotating said rotatable member whereby said batch material is carried up the inclined surface and moves down again in generally elliptical paths.
19. Apparatus according to claim 11 or 18 wherein said ratio changing means is adapted to cause the supply of liquid to said surface to decrease when the sensed depth of the batch material reaches a predetermined value.
20. Apparatus according to claim 10, 11 or 18 wherein said means for supplying liquid comprises a first passage for supplying liquid to said surface at a predetermined rate and a second passage for supplying additional liquid to said surface and wherein said ratio changing means comprises an electrically-operated valve located in said second passage and adapted to con-trol the flow of liquid therethrough.
21. Apparatus according to claim 18 wherein the means for supplying the batch material and the liquid are arranged to supply the batch material and the liquid to a lower portion of the inclined surface, the predetermined portion of the sur-face at which the depth of the batch material is sensed is at an upper portion of the inclined surface, the means for supplying liquid comprises a first passage for supplying liquid at a pre-determined rate which is less than that normally needed to form pellets of a desired size and a second passage for supplying additional liquid at a predetermined rate which in combination with the rate of liquid supplied by the first passage exceeds that normally needed to make pellets of the desired size, and wherein said ratio changing means comprises a valve in said second passage and means responsive to said sensing means for opening and closing said valve.
22. Apparatus according to claim 21 wherein said means responsive to said sensing means comprises time-delay means for closing said valve for a predetermined period of time in response to said sensing means sensing a predetermined depth of batch material.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US80959577A | 1977-06-24 | 1977-06-24 | |
| US809,595 | 1991-12-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1094298A true CA1094298A (en) | 1981-01-27 |
Family
ID=25201717
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA304,173A Expired CA1094298A (en) | 1977-06-24 | 1978-05-26 | Method and apparatus for handling heat-softenable batch material |
Country Status (15)
| Country | Link |
|---|---|
| JP (1) | JPS5411118A (en) |
| AU (1) | AU518153B2 (en) |
| BE (1) | BE868408A (en) |
| BR (1) | BR7803944A (en) |
| CA (1) | CA1094298A (en) |
| DE (1) | DE2827407C3 (en) |
| FI (1) | FI63004C (en) |
| FR (1) | FR2395479A1 (en) |
| GB (1) | GB1586358A (en) |
| IT (1) | IT1095922B (en) |
| NL (1) | NL176250C (en) |
| NO (1) | NO143739C (en) |
| NZ (1) | NZ187666A (en) |
| SE (1) | SE431291B (en) |
| ZA (1) | ZA783468B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4251475A (en) * | 1978-12-29 | 1981-02-17 | Owens-Corning Fiberglas Corporation | Method and apparatus for controlling the proportion of liquid and dry particulate matter added to a pelletizer |
| JPS6128312U (en) * | 1984-07-24 | 1986-02-20 | 八鹿鉄工株式会社 | Seed chemical coating machine |
| JPH0742521B2 (en) * | 1988-09-13 | 1995-05-10 | 日本鋼管株式会社 | Sintered raw material granulator |
| CN104086072A (en) * | 2014-07-24 | 2014-10-08 | 中国建材国际工程集团有限公司 | Energy-saving method of flue gas-emission glass melting furnace |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5037208A (en) * | 1973-08-02 | 1975-04-07 | ||
| US3883281A (en) * | 1974-06-21 | 1975-05-13 | Ferro Tech | Pelletizing disc assembly and control system |
| JPS51144379A (en) * | 1975-06-09 | 1976-12-11 | Showa Denko Kk | A method and apparatus for automatic granulating for tray type granula ting machines |
-
1978
- 1978-05-26 CA CA304,173A patent/CA1094298A/en not_active Expired
- 1978-05-31 SE SE7806313A patent/SE431291B/en unknown
- 1978-05-31 GB GB25928/78A patent/GB1586358A/en not_active Expired
- 1978-06-15 NL NLAANVRAGE7806474,A patent/NL176250C/en not_active IP Right Cessation
- 1978-06-16 AU AU37176/78A patent/AU518153B2/en not_active Expired
- 1978-06-16 ZA ZA00783468A patent/ZA783468B/en unknown
- 1978-06-22 DE DE2827407A patent/DE2827407C3/en not_active Expired
- 1978-06-22 JP JP7594578A patent/JPS5411118A/en active Pending
- 1978-06-22 BR BR787803944A patent/BR7803944A/en unknown
- 1978-06-22 FI FI782006A patent/FI63004C/en not_active IP Right Cessation
- 1978-06-23 NO NO782194A patent/NO143739C/en unknown
- 1978-06-23 IT IT24909/78A patent/IT1095922B/en active
- 1978-06-23 BE BE188807A patent/BE868408A/en not_active IP Right Cessation
- 1978-06-23 NZ NZ187666A patent/NZ187666A/en unknown
- 1978-06-23 FR FR7818912A patent/FR2395479A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| FR2395479A1 (en) | 1979-01-19 |
| JPS5411118A (en) | 1979-01-27 |
| FR2395479B1 (en) | 1984-02-10 |
| AU3717678A (en) | 1979-12-20 |
| NZ187666A (en) | 1981-05-15 |
| NO782194L (en) | 1978-12-28 |
| SE7806313L (en) | 1978-12-25 |
| DE2827407B2 (en) | 1981-07-09 |
| FI782006A (en) | 1978-12-25 |
| NL7806474A (en) | 1978-12-28 |
| DE2827407C3 (en) | 1982-03-11 |
| IT1095922B (en) | 1985-08-17 |
| SE431291B (en) | 1984-01-30 |
| AU518153B2 (en) | 1981-09-17 |
| FI63004B (en) | 1982-12-31 |
| NO143739B (en) | 1980-12-29 |
| BE868408A (en) | 1978-10-16 |
| IT7824909A0 (en) | 1978-06-23 |
| DE2827407A1 (en) | 1979-01-11 |
| FI63004C (en) | 1983-04-11 |
| BR7803944A (en) | 1979-01-16 |
| ZA783468B (en) | 1979-06-27 |
| NO143739C (en) | 1981-04-08 |
| GB1586358A (en) | 1981-03-18 |
| NL176250C (en) | 1985-03-18 |
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