Agitating – Having interrelated feed and discharge means – Including means to monitor or control operation
Reexamination Certificate
2001-08-28
2003-07-15
Cooley, Charles E. (Department: 1723)
Agitating
Having interrelated feed and discharge means
Including means to monitor or control operation
C366S136000, C366S153100, C366S160200, C366S183100
Reexamination Certificate
active
06592246
ABSTRACT:
FIELD OF THE INVENTION
THIS INVENTION relates to slurries. More particularly, the invention relates to a method and to an installation for forming and maintaining, for consumption, a stock of slurry.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a method of forming and maintaining for consumption a stock of slurry derived from a liquid and from a particulate solid material, the method including the steps of:
withdrawing a slurry of the liquid and the solid material from a stock of the slurry in a reservoir;
directing a stream of the liquid or of the withdrawn slurry at a bulk supply of the solid material in the form of a heap of the solid material, and on to the solid material of the heap;
allowing the stream directed at the heap to drain under gravity from the heap into the reservoir, the stream, while draining from the heap, entraining therein solid material from the heap to increase the specific gravity of the stream and to carry solid material from the heap into the stock of slurry in the reservoir to increase the specific gravity thereof; and
feeding liquid to the reservoir to maintain the volume of the slurry in the reservoir, the method including controlling both the volume of slurry in the reservoir and the specific gravity of the slurry in the reservoir, the feeding of the liquid into the reservoir being initiated, or having its feed rate increased, in response to decreases in the volume of the slurry in the reservoir associated with withdrawal of slurry from the reservoir for consumption thereof, and the directing of the stream at the heap of solid material being initiated, or having its flow rate increased, in response to decreases in the specific gravity of the slurry in the reservoir associated with feeding the liquid to the reservoir, thereby both to maintain the volume of slurry in the reservoir at a desired value, and to maintain the specific gravity of the slurry in the reservoir at a desired value, the feeding of liquid to the reservoir being reduced in rate or discontinued when the desired slurry volume is regained, and the directing of the stream at the heap being reduced in rate or discontinued when the desired specific gravity value is regained.
It will be appreciated that increases and decreases to the specific gravity of the slurry are associated respectively with increases and decreases to the solids content thereof.
While it is in principle possible to carry out the method by directing a stream of the liquid at and on to the solid material of the heap, to form a slurry having a solids content and specific gravity greater than the solids content and specific gravity respectively of the slurry in the reservoir, to permit drainage of a slurry from the heap into the reservoir which increases the solids content and specific gravity of the slurry in the reservoir, it is preferable to employ slurry withdrawn from the reservoir for this purpose. The stream directed at the heap may thus be a stream of the slurry withdrawn from the reservoir.
The method of the invention contemplates that withdrawal of slurry from the reservoir for consumption thereof may be continuous or intermittent, and that the liquid feed to the reservoir, which may be continuous or intermittent, will be at a rate such that the volume of slurry in the reservoir is maintained at the desired value when slurry is withdrawn for consumption at any rate up to the maximum intended rate. Similarly, the withdrawal of the stream of slurry from the reservoir to direct at the heap, which withdrawal may also be continuous or intermittent, will in turn be at a rate such that the specific gravity of the slurry in the reservoir is maintained at the desired value when the slurry is withdrawn for consumption at any rate up to the maximum intended withdrawal rate for consumption. Thus, the desired volume of the slurry, at least on average and with no more than acceptable departures from the desired value, can be maintained in the reservoir while the specific gravity, ie the density or solids content, of the slurry is likewise maintained, at least on average and with no more than acceptable departures from the desired value. In a particular embodiment of the invention, when the stream directed at the heap is a stream of slurry withdrawn from the reservoir, the liquid feed to the reservoir may be intermittent, being at a fixed rate no less than the maximum rate at which the slurry is withdrawn from the reservoir for consumption, the stream directed at the heap being withdrawn from the reservoir intermittently and at a fixed rate.
In a further particular embodiment of the invention the liquid may be water, the solid material being particulate or powdered limestone, or possibly dolomite. In other words, the liquid may be water, the solid material being selected from the group consisting of limestone, dolomite and mixtures thereof.
The controlling of the volume of slurry in the reservoir may be automatic, being by controlling the depth of slurry in the reservoir by means of a valve, the valve being selected from the group consisting of ultra-violet (UV)-controlled valves and, preferably, float-controlled valves and the valve controlling the liquid feed to the reservoir. Similarly, controlling the specific gravity of the slurry in the reservoir may be automatic, for example by using one or more load cells on which the reservoir is supported, to measure the mass of the reservoir, or by using one or more pressure cells in the interior of the reservoir to measure the static pressure in the reservoir, said cell or cells controlling the withdrawal of the stream of liquid from the reservoir which is directed at the heap. In other words, the controlling of the specific gravity of the slurry in the reservoir may be automatic, being by using a cell selected from load cells which measure the mass of the reservoir and pressure cells which measure static pressure in the reservoir, to control the directing of the stream at the heap. The liquid feed to the reservoir or the slurry stream withdrawal from the reservoir may be provided with on/off flow control, and/or they may incorporate variation of their flow rates in response to the magnitude of any departure of the slurry volume or specific gravity from the respective desired values thereof.
Indeed, instead of using load cells or pressure cells, the reservoir can in principle float in a body of water, the depth at which the reservoir floats in the body of water being related to the mass of the reservoir and hence to the specific gravity of the slurry therein, changes in this depth being used to control the directing of the stream at the heap, although it is expected that use of load cells or pressure cells will be preferred.
The method may involve agitation of the slurry in the reservoir to promote maintenance of the solid material in suspension in the liquid and to resist its settling out from the liquid, and the method may include replenishing the bulk supply of particulate material in the heap, as and when required, e.g. intermittently by means of vehicles loaded therewith Withdrawal of slurry from the reservoir, either as a stream to be directed at the heap, or for consumption thereof, may be by pumping it, and directing the stream of slurry at the heap may be by spraying it, e.g. from one or more spray nozzles at the ends of respective hoses, which may be hand-held. In particular, the method may include the step of agitating the slurry to promote maintenance of the solid in suspension in the liquid, withdrawal of slurry from the reservoir being by pumping, directing the stream at the heap being by spraying it from one or more hand-held nozzles, and feeding the liquid to the reservoir being by directing it at the heap.
If desired, the method may make provision for the removal of stones and/or grit from the slurry, between the reservoir and the hose or hoses, e.g. by passing the slurry upwardly through an inverted-conical tank, the slurry from the reservoir being fed into the tank at a low level where its diameter is small, and the slur
Cooley Charles E.
CSIR
Klarquist & Sparkman, LLP
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