Common correct media sump and wing tank design

Details Common correct media sump and wing tank design Common correct media sump and wing tank design

2002-03-12

2004-06-01

Walsh, Donald P. (Department: 3749)

Classifying, separating, and assorting solids

Special applications

C209S017000

Reexamination Certificate

active

06742656

ABSTRACT:

FIELD OF THE INVENTION
The present invention is directed generally toward coal preparation plants and, more particularly, toward a new common correct media sump and wing tank apparatus for processing raw coal particles with a slurry of media and water.
BACKGROUND OF THE INVENTION
Coal preparation plants separate organic and non-organic solid particles by their specific gravities. The coal preparation plant receives a feed of raw mined coal, and separates the raw mined coal into clean coal and refuse. Coal preparation plants typically utilize two basic processing methods for separating raw coal from rock and varying proportions of striated rock and coal from the higher quality coal. These two processing methods include heavy media and water based separation methods. Heavy media separation, utilizing a slurry of media, e.g., magnetite or ferrosilicon and water, to separate the coal from the refuse according to their specific gravity of dry solids, is the most common separation process for larger size (Plus 1 mm-0.5 mm) particles. Whereas, water based separation processes are more commonly used for the “cleaning” of the finer sized particles, as that term is commonly understood in the coal processing art.
Coal preparation plants may incorporate one or two heavy medium circuits for processing coal with a bottom size ranging from 0.5 mm to 2.0 mm. Often two separate processing methods, or circuits, are employed, namely, heavy media vessel and heavy media cyclone circuits for cleaning the coarser and finer coal size fractions, respectively.
Plants using heavy media processing require a pre-sized (removal of undersized and/or oversized particles) circuit feed. Raw coal screens are generally used to pre-size the correct media feed, whereas deslime screens are used to pre-size the heavy media cyclone feed, although a single screen may be used to pre-size the feed for both unit operations.
The raw coal screen receives the raw coal feed particles and separates them into coarse and undersized raw coal. The coarse or larger sized particles discharged from the raw coal screen surface are directed by gravity to the heavy media vessel. The deslime screen receives the undersized raw coal from the raw coal screen and separates it into intermediate and finer sized fractions. The raw coal particles discharged from the screen surface of the deslime screen are directed to the heavy media cyclone feed circuit, while the finer sized particles passing through the deslime screen are fed to the fine coal section of the coal preparation plant.
Traditionally, each heavy media feed circuit retains its own medium for recirculation, and thus requires separate medium storage sumps. These separate storage sumps increase the overall size of the plant area requirements, and add to the cost of building the coal preparation plant.
The present invention is directed toward overcoming one or more of the above-mentioned problems.
SUMMARY OF THE INVENTION
In a coal preparation plant which receives a raw coal feed and separates the raw coal into clean coal and refuse, an apparatus is provided for use therein. The inventive apparatus is a combined sump common to the heavy media vessel and heavy media cyclone circuits used for storage of the recirculating medium for the heavy media vessel circuit and a mixing device, referred to as a wing tank, to proportionally combine intermediate sized raw coal feed particles with a slurry of media and water for feeding the heavy media cyclone circuit. The advantage of this combined system is the ability to use a common recirculating media for use in both the heavy media vessel and heavy media cyclone circuits, without sacrificing the ability to have different recirculating gravities for each separating circuit.
The commonality between the two chambers of the combined apparatus is connecting the overflow of the wing tank to the correct media feed sump. The inventive apparatus includes a wing tank with an inlet receiving the intermediate sized raw coal directly from a deslime screen and a slurry of media and water from the drain portion of an underpan of at least one media recovery screen (refuse screen and clean coal screen) and an outlet by which the mixture of intermediate sized raw coal and slurry exits the column. The wing tank mixes the intermediate sized raw coal and the slurry of media and water according to a select proportion, and it is then pumped to a heavy media cyclone separation circuit, or section, of the coal preparation plant.
The inventive apparatus also includes a storage and feeding device, i.e, correct media sump, for retaining and distributing, via a pump, the recirculating medium used for the correct media circuit. The correct media feed sump includes a open top inlet for collection of the slurry of media and water from the drain portion of an underpan of at least one media recovery screen (refuse screen and clean coal screen) and an outlet by which the medium exits the sump.
In one form of the inventive apparatus, the wing tank is located adjacent to, or integrally formed with, the correct media feed sump, such that an overflow from the wing tank discharges into the correct media feed sump. The overflow is created when wetted intermediate raw coal particles discharged from the deslime screen are fed into the wing tank displacing an equivalent volume of media contained within the wing tank.
First and second nuclear density gauges may be provided for measuring the specific gravities of both the mixture output by the wing tank and the medium output by the correct media feed sump. The signals generated by the nuclear density gauges are received by control circuitry that adjusts the addition of water to the outputs of both chambers. Specifically, a water source is connected to the outputs of the wing tank and correct media feed sump via at least two control valves. The control circuitry adjusts the control valves to add water from the water source to the output mixtures based upon the measured specific gravity value of each mixture contained within the respective discharge pipes.
In another form, the inventive apparatus includes first and second pumps for discharging the mixture of raw coal and medium from the wing tank and medium only from the correct media feed sump. Each of the pumps has a suction connected to the respective storage device and an output connected to an input of the respective heavy media separating device, namely, vessel and cyclone separating devices. The water source is preferably connected between the respective storage device and each of the pump suctions, while the nuclear density gauges are preferably provided between the pump output and the respective heavy media separating device input.
In a further form, the inventive apparatus may include an over dense media splitter box, at least one bleed box, and a common medium distribution box. Over dense media from a magnetic separator, which is used to recover magnetite from the effluent streams from both of the heavy media separating circuits, is collected and distributed to the two chambers of the common correct sump/wing tank via the over dense media splitter box. The over dense media splitter box preferably contains a pneumatically controlled actuator driven by a signal generated from the plant control circuitry.
The common medium distribution box receives the slurry of media and water from the drain portion of the underpan of at least one media recovery screen. The bleed box is used to remove extraneous amounts of non-magnetics and water from the recirculating medium in the common medium distribution box. A quantity of the recirculating medium is bled from the system proportional to the feed contaminants. The bleed box device preferably contains a pneumatically controlled actuator driven by a signal generated from the plant control circuitry.
In an alternate form, the common medium distribution box may be removed and the return media proportionally fed directly to the wing tank and the common correct media sump. In this alternate form, the bleed box can be fed by any other means containing c

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