Apparatus For Unloading Pulverized Material In Tank

Abstract

A device for creating a slurry of pulverized material in a tank including a rotating cylindrical body having an adjustable nozzle therein for jetting the high-pressure water against the material in the tank. A sump is provided adjacent the bottom of the tank around the rotary cylindrical body and means is provided for injecting water into the sump to control the fluidity of the pulverized material falling into the sump. Detection rods are provided to detect the total amount of material in the tank and to detect the amount of pulverized material which is compacted against the sides of the tank. Controls are provided to regulate the flow and orientation of flow of water through the two nozzles and the orientation of the rotating nozzle to break down the caking of the pulverized material and to effect efficient discharge of the slurry of material from the tank.

Description

The present invention relates to an unloading apparatus of pulverized material by slurrifing.

Generally, pulverized material such as pulverized ore is transported to the tank of a tanker in the form of slurry, and the material remains in a dewatered condition when stored in the tank. However when the material is discharged for unloading from the tanker, it is usually again reduced into the form of slurry. The present invention is to provide an apparatus which may unload continuously in the uniform condition.

The present invention will be understood from the following description and the accompanying drawings in which:

FIG. 1 is a diagrammatical illustration of a conventional unloading system of pulverized material;

FIG. 2 is a diagrammatical illustration of an embodiment of the present invention;

FIG. 3 is an enlarged view of the sump section in FIG. 2;

FIG. 4 is a sectional view of the water jetting section;

FIG. 5 is a sectional view taken on line A--A of FIG. 4; and

FIG. 6 is a chart illustrating the process of the discharging operation according to the present invention.

The discussion will first be made on a conventional discharging device shown in FIG. 1. In this device, as will be noted, a sump 2 is provided centrally at the funnel-shaped bottom of the tank 1, and a cylinder 3 is rotatably provided extending through the sump. At the upper end of the cylinder 3 is provided a nozzle 4 from which high pressure water is jetted against the mass of pulverized material 5, while the cylinder 3 is rotated. Upon receiving water impingement, the mass of pulverized material is reduced into slurry and flows down into the sump 2 from which the slurry is discharged through a pipe 7 along with low pressure water introduced from an inlet 6 and is finally discharged by the action of a slurry pump 8.

In this apparatus: 1. the angle .theta. formed by the jetting direction of the nozzle 4 with respect to the horizontal plane is constant; 2. the rotational frequency .omega. of the vertical cylinder 3 is constant or uncontrolled; 3. the amount of high pressure water jetted from the nozzle and the amount of low pressure water are not controlled; 4. no control of the slurry surface level in the sump is made.

On the other hand, the condition of the pulverized material in the tank greatly varies as the discharging process advances, thereby the angle .epsilon. of the direction of high pressure water to the surface of rupture of the pulverized material mass, the velocity u at which injected water sweeps the ruptured surface of the material mass, and the distance between the nozzle and the ruptured surface are greatly varied, which results in wide variation in the slurry concentration. Such variation of concentration is excessively great when .epsilon. and u are improper. The excessively increased concentration may result in blockade or stuffing of the sump 2 or the pipe 7 between the sump and the slurry pump 8 with pulverized material, which will cause retardation of discharge of water injected into the tank and idle rotation of the slurry pump. In order to avoid such difficulties, there is no alternative but to carry on the operation by reducing the average concentration of the slurry. But this requires a great amount of water and a large power consumption as well as a large-capacity tank for receiving the slurry.

The present invention is intended to provide a novel apparatus which can solve all of the problems and with which it is possible to enhance the average concentration by maintaining constant and uniformalizing the slurry concentration and which can also be operated automatically.

Now, the invention, will be described in detail with reference to the drawings. In FIG. 2, the same reference numerals as those in FIG. 1 to indicate similar parts to those in FIG. 1, but the high pressure water jetting device 10 is a specific and novel device constructed according to the present invention. Referring now to FIG. 4 in particular, it will be seen that a sleeve 11 is mounted extending through the bottom of the sump 2, and rotatably fitted in said sleeve is a rotary cylinder 12 which is kept watertight by means of seal rings 13. The lower end of said rotary cylinder 12 is connected to a rotary shaft 15 supported by thrust bearings 14. At the upper part of said rotary cylinder is rotatably supported a cylindrical shaft 16 of the nozzle 4. A pinion 17 fixed to the cylindrical shaft is meshed with a rack 18 vertically slidably mounted within the rotary cylinder 12. Also, at the top of the rotary cylinder 12 a cap 20 is fixed for protecting the nozzle 4. The nozzle 4 projects from a slit 21 of the cap in such a manner the nozzle can swivel.

A rod 22 coupled to the rack 18 extends slidably and rotatably through the rotary shaft 15 and is coupled to a piston 25 in a hydraulic cylinder 24 through a thrust coupling 23. Thus, vertical movement of the piston 25 urges corresponding movement of the rod 22 and the rack 18, which causes the nozzle 4 to swivel vertically through the angular space .theta. within the range of .+-. 90.degree. about the cylindrical shaft 16. It will also be noted that a pulley 26 is fixed to the rotary shaft 15 and connected through a belt 27 to a pulley 29 of a motor 28, so that motive force produced by the motor 28 is transmitted through the rotary shaft 15 and the rotary cylinder 12 to the nozzle 4 to let it rotate in the holizontal plane.

High pressure water is pumped out from a tank 31 by a pump 30 and introduced through valves 32 and 33 into an annular chamber 35 in the sleeve 11 from its inlet 34, from which the water is entered into the rotary cylinder 12 through the apertures 36 formed in the cylinder and injected from the nozzle 4. On the other hand, low pressure water is pumped out by a pump 37, a part of which is passed through a pipe 40 into the sump 2 from its inlet 6, while the other part of the low pressure water is passed through a valve 38 and a pipe 41 and flown into the sump 2 from small openings or apertures 42 formed along the entire upper periphery of the sump 2 to prevent deposition of the pulverized material on the sump wall surface. Low pressure water is also injected from a nozzle 43 directed toward a discharge pipe 7 provided in the sump to expedite discharge of the slurry in the sump toward the discharge pipe.

Atop the tank 1 is provided a first detection rod 45 for detecting the amount of pulverized material 5 in the tank. The detection rod is pivoted at 46 and a mid portion thereof is coupled to a vertically movable rod 47, the vertical position of the rod 47 being detected by a potentiometer 48. There is also provided a second detection rod 50 adapted to be vertically movable, with its vertical position being detected by a potentiometer 51. The both potentiometers 48 and 51 transmit signals to a speed governor 52 of the motor 28 and to a servo valve 53 of the hydraulic cylinder 24. Upon receiving the signal, the speed governor 52 controls the motor 28 to a desired rotational frequency. While the servo valve 53 controls pressure oil to the cylinder 24 correspondingly to the received signal to fix the piston 25 and the rod 22 in the suitable position or to move them through a fixed range centering that fixed position to swivel the nozzle 4.

Now, the process of the unloading operation will be described hereinafter.

For starting the unloading operation, first the valve 54 is opened and the low pressure water pump 37 and the slurry pump 8 are actuated. Then the servo valve 53 is manually operated to move the piston 25 to its uppermost position so that the angle of the nozzle 4 is at -90.degree., and then the high pressure water pump 30 is operated. Both high pressure water and low pressure water are fed in full capacity gradually varying the nozzle angle .theta. from -90.degree. to 0.degree., thereby the pulverized material in the sump 2 is completely discharged.

Then, the nozzle angle .theta. is increased to +90.degree. where the nozzle is directed uprightly, and high pressure water is jetted out therefrom, thereby a narrow conical opening or hollow portion is formed above the nozzle extending to the surface of the pulverized material mass. The condition of the mass at this stage is shown by chain lines in FIG. 2. The free end of the detector rod 45 is in contact with the middle part of the surface 5a of the pulverized material mass, and when the opening is formed at this part, the detector rod is swayed to cause change of the signal. According to this change of signal the speed governor 52 and the servo valve 53 are operated to control the nozzle motion. It will be understood that the pulverized material mass is gradually broken down or scraped while forming a substantially conical ruptured face by the action of high pressure water. It is to be noted that the nozzle is controlled in such that it forms an angle 5.degree. to 20.degree. smaller than the ruptured angle .phi. of the mass, that is, a value of .phi. -(5.degree. to 20.degree.). When the surface of the pulverized material mass descends below a certain level, it becomes no longer possible to detect the surface level with the detector rod 45. Thus, thereafter the detector rod 50 is used in combination with the potentiometer 51 for the same purpose to perform the similar control. In such a way the angle .phi. of the ruptured face is gradually reduced, and at last it reaches the angle .phi.f of the tank bottom. The amount of high pressure water Wh is adjusted by an adjusting valve 32 according to the slurry concentration detected by a slurry densitometer 55 disposed in the discharge side pipeline of the slurry pump 8. More specifically, the amount of water is decreased when the detected concentration is higher than a set value, but increased when the concentration is lower than the set value.

The flow rates of high pressure water and low pressure water are detected by a high pressure water flow meter 56 and a low pressure water flow meter 57, respectively, and the flow rate low pressure water is controlled by a flow rate controlling valve 33 in such that the sum W of Wh and Wl will be substantially constant. If the slurry concentration in the sump 2 or in the pipe between the sump and the slurry pump 8 is excessively increased so that flow resistance of the slurry is increased, the slurry surface in the sump is raised, and when it exceeds a certain predetermined level, it is detected by a level gauge 58. According to the detection the feed of high pressure water is stopped temporarily by closing the valve 33. Thereby, the low pressure water reaches to the maximum flow rate and flows away the blocking material and when the surface level in the sump declines thereafter, the high pressure water system is again put to normal operation.

The rotational frequency .omega. of the vertical rotary cylinder is controlled through the speed governer 52 according to the ruptured face angle .phi. detected by the detector rod 45 or 50 in such that the sweeping velocity U of the high pressure jet on the rupture face will become substantially constant. In the final stage of the unloading operation, the ruptured face angle .phi. of the pulverized material mass is approximated to the angle .phi.f of the tank bottom face and the flow of the produced slurry down to the sump becomes more and more stagnant. Therefore, it needs to make the arrangement in such a design that the angle .phi.f of the tank bottom face to the horizontal plane is larger than the angle determined by the critical tractive force corresponding to the type of the pulverized material (in the case of iron sand or pulverized iron ores such angle is about 17.degree.).

Now, the control of each parameter will be discussed with reference to FIG. 6 where the tendencies of variation of various types of parameters during the unloading operation are shown.

The operation for reducing the pulverized material in the tank into slurry and discharging it outside of the tank may be divided into the following three steps: A. the steps of breaking down the mass of pulverized material. B. the steps of carrying the broken down material to the sump. These steps can be accomplished through combination of the following two actions: a. Dropping the material down to the sump by gravitation; and b. Riding the material in the flow of jet water returning to the sump. C. the steps of carrying the material from the sump to the pump suction by adjusting the concentration with low pressure water. Considering the operations divided in the above manner, it is found that the following conditions must be met to obtain a constant and uniform concentration: 1. That the slurrification proceeds with the above-said three steps A, B and C being conducted in a well-balanced manner.

The value of .phi. varies from 90.degree. to .phi.f . In the early stage where the value of .phi. is large, the actions of A and B are brisk and therefore the action of C lags behind, resulting in increase of slurry concentration and blockade or stuffing of the sump and/or other pipe lines. In this stage, therefore, Wh is kept low while Wl is enlarged as seen in FIG. 6 so as to obtain good balance between the actions of A and C. On the other hand, in the terminal stage where .phi. .apprxeq. .phi.f , the actions of A and B are decreased to cause reduction of the concentration, so that in the step C, the amount of high pressure water Wh is increased while the amount of low pressure water is limited and no control of concentration is conducted. However, increase of Wh does not invite proportional increase of the flow velocity itself which is related to the tractive force, so that it needs to keep the angle .phi.f of the bottom face greater than the angle which corresponds to the critical tractive force. 2. That the moment-by-moment variation of the amount of break-down or scraping is limited in small amount during the pulverized material mass breaking down or scraping operation.

If the amount of scraping fluctuates widely from moment to moment, there is a danger of causing blockade particularly when such amount reaches the maximum. In order to limit the fluctuation, it needs to keep the value of .phi. - .theta. within the range of about 5.degree. to 20.degree. . If the value of .phi. - .theta. is too great, the angle of the scraped face may become negative intermittently, causing a repetition of crumbling rather than scraping, resulting in wide variation of the amount of pulverized material broken down. It is also necessary to keep substantially constant the sweeping velocity U of the high pressure water jet on the surface of rupture of the pulverized material mass during the unloading operation. If the velocity U is too slow, perforation may be made on the rupture surface by water jet, which causes excessive enlargement of the actual value of .phi. - .theta. to invite a crumbling or fall-in phenomenon, resulting in wide variation of the slurry concentration.

As will be apparent from the foregoing discussion, the present invention has the following advantages: 1. There is no fear of causing blockade or stuffing with slurry or pulverized material. 2. The variations of concentration and flow rate are limited in a small range, so that variation of loading is small, thus allowing minimization of the size of instruments used and piping capacity. 3. The average concentration can be elevated, obtaining reduction of the water amount for slurrification and the capacities of the slurry receiving equipments. 4. The operation for slurrification is simplified and also the unloading operation is automated, thus realizing enormous saving of labor. 5. The time required for the unloading operation is shortened.

Claims

What is claimed is:

1. An apparatus for unloading pulverized material in a tank by turning said material into slurry comprising a rotary cylindrical body rotatably provided extending through a sump at the bottom of the tank, a nozzle provided rotatably in the vertical plane at the top of said rotary cylindrical body, means for rotating said rotary cylindrical body, means for transmitting the rotating motion to said nozzle to rotate it, means for adjusting the nozzle angle in accordance with the angle of the surface of rupture of the pulverized material mass in the tank, means for controlling the rotating velocity of said rotary cylindrical body, pump and piping systems for feeding high pressure water into said rotary cylindrical body, and means for controlling the amount of high pressure water in accordance with the slurry concentration, said high pressure water being passed through said rotary cylindrical body and jetted out through said nozzle.

2. Apparatus according to claim 1 including an auxiliary nozzle in the sump at the bottom of the tank and means for projecting low pressure water through said nozzle to control the slurry concentration in the sump.

3. Apparatus according to claim 1 including a detector rod for sensing the amount of material in the tank.

4. Apparatus according to claim 1 including a detector rod for sensing the angle of the surface of rupture of the pulverized material mass in the tank.