US3252769A - Nagelvoort coal treatment system - Google Patents

Description

May 24, 1966 A. NAGELVOORT COAL TREATMENT SYSTEM 5 Sheets-Sheet 1 Filed Jan. 10, 1963 UNCRUSHED COAL FLOTATION-SEPARATION M5 E 1 w 0 8 L6 A 1 @L E T M E A R WG NW E m W A ca L M E C Q RESIN INVENTOR ADRIAN NAGELVOORT BY ATTORNEYS May 1966 A. NAGELVOORT 3,252,769

COAL TREATMENT SYSTEM Filed Jan. 10 1963 3 Sheets-Sheet 2 ADRIAN NAGELVOORT w HQ 4 Y MMMM ATTORNEYS May 24, 1966 A. NAGELVOORT COAL TREATMENT SYSTEM 5 Sheets-Sheet 5 Filed Jan. 10 1963 FIG. 5

INVENTOR.

ADRIAN NAGELVOORT m MW.

ATTORNEYS United States Patent This invention relates generally to coal treatment and more particularly to the production of coal which is substantially free of materials, such as resins and ash.

Certain coals, such as Utah coal, contain substantial amounts of fossil resins and ash. Where relatively pure coal is desired, the resins and ash must be removed.

It is a general object of the present invention to provide an improved means for purifying coal.

It is another object of the invention to provide a method of preparing relatively pure coal by a combination of flotation-separation and leaching wherein the leaching agent serves as a flotation medium for the flotation-separation.

Still another object of the invention is to provide a substantially closed loop method and system for preparing relatively pure coal while recovering the resin therefrom.

These and other objects of the invention will be more clearly apparent from the following description when taken in conjunction with the accompanying drawings.

Referring to the drawings:

FEGURE 1 is a flow sheet according to the invention;

FIGURE 2 shows equipment according to the invention for following the method as presented by FIGURE 1, and

FIGURES 3, 4, and 5 are respectively a plan, side elevation, and front elevation view of recovery means for extracting dissolved material from the withdrawn solution in accordance with the invention.

In general, one form of the process of the present invention employs a reservoir containing a body of liquid as the flotation medium. Uncrushed coal is introduced into the medium. The specific gravity of the solvent is selected to be greater than that of coal and less than that of ash so that the coal fio ats on the surface while the ash sinks to the bottom. The liquid is selected to be a solvent for the resin whereby the coal is also leached during the separation of ash. According to the invention, the coal is further leached by passing it in counter-cur rent through a stream of the solvent.

Quantities of the solution (solute and solvent) are withdrawn from the body of liquid. The solute (resin) and the solvent are then separated. The solvent is then recirculated to serve as the leaching agent.

The method of the invention is more particularly illustrated in the flow sheet of FIGURE 1. Coal 10, such as Utah coal, is introduced into a reservoir for flotationseparation at 11. The flotation medium, for example, may consist essentially of hexane and carbon tetrachloride, taken on the order of equal parts of each. With the medium so comprised, the specific gravity will be on the order of 1.2. The specific gravity of the coal is on the order of 1.1 and, therefore, will float on the body of liquid, whereas the specific gravity of the ash 13 is on the order of 2.5 and will sink to the bottom. The ash is removed from the medium while the coal concentrate undergoes a leaching step 14. As will be presently described, solvent 15 is applied in counter-current to the flow of the coal concentrate to effect leaching. The pure coal product, therefore, is provided at 16, while a solution of resin and solvent empties from the leaching means into the body of liquid at 17. Quantities of the resin-solvent solution are also withdrawn for recovery at 18, the solute (resin) being rendered at 19 and the solvent 15 being recirculated for leaching. Thus, it is seen that the process comprises a substantially closed loop. Suitable apparatus is illustrated in FIGURE 2. Means are provided at one side of a reservoir 21 serving to introduce the coal at a slight angle to the surface of the body of liquid. The coal floats on the surface of the liquid because of its lower specific gravity. This coal carrying means is schematically represented by the endless belt conveyor 22 trained about rollers 23. The upper surface of belt 22 is disposed to deliver the ore at a slight angle to the surface of the body of liquid. The delivery end of belt 22 is somewhat submerged below the surface so that the untreated coal floats off belt 22. Drive means (not shown) are provided for operating belt 22 to move in the direction indicated by the arrows 25. p

Inasmuch \as the tailings of ash will sink to the bottom due to their relatively higher specific gravity, conveyor means are provided for removing the ash from reservoir 21. The tailing conveyor comprises a motor driven shaft 24 supporting a helical screw 25 for rotation in a tube 26. The tube 26 is open at the bottom so that tailings fall into the tube and are conveyed upwardly in the conveyor.

At a position in reservoir 21 remote from belt 22, another conveyor means is provided which serves to continuously remove the ash-free coal from a surface region of the liquid and transport it along a predetermined path. The last named conveyor means includes a motor driven screw conveyor 27 disposed at a slight angle to the surface of the medium. Conveyor 27 operates to entrain coal at the surface region of the liquid and carries it along the bore of the conveyor until it reaches an opening 28 where it falls out of the tube by gravity.

Means are provided for passing a solvent of the resin through the conveyor means 27 in counter-current to the coal being carried upwardly toward opening 28. Thus, a pipe line 30 is disposed to pass the leaching agent, i.e., solvent, into the housing 29 at a point in the upper region of the conveyor means but downstream of opening 28. Conduit means comprised of suction piping 31, pump unit 32 and exhaust piping 33 are provided to connect the reservoir to recovery means 34 for withdrawing a quantity of the body of liquid from a subsurface region thereof. Recovery means 34 is'interp'osed between the conduit means and the leaching means thereby serving torecover solvent from the withdrawn quantity and recirculate the recovered solvent through the leaching means.

A recovery means and method for extracting the dissolved material (resin) from the withdrawn solution is illustrated in detail in FIGURES 3-5.

The apparatus consists of an enclosed vessel or tank 35 which has an upper section 36 serving to collect the solvent vapors and direct the same upwardly along the inclined top to the vapor outlet 37. In order to minimize condensation of the solvents along the top wall of the vessel, there may be provided a plurality of pipes 38 which include spray heads (not shown) to continuously spray the wall with hot liquid to maintain the temperature of the surfaces above the condensation temperature of the solvent. All of the solvent is conveyed away and none forms droplets which could fall ontothe separated material fioating in the liquid bath, to be presently described. The solvent vapors are directed to a condenser (not shown) and the liquid solvent then pumped to the surge or storage tank where it is available for use.

The bottom of the vessel 35 includes a plurality of adjacent ridges and troughs 40 and 41, respectively, as shown more clearly in FIGURE 5. The bottom wall serves as the bottom of the vessel which serves to hold the bath liquid. A plurality of spaced inclined troughs 44, as shown in the figure, are spaced from the bottom and coincide generally with the troughs formed in the bottom.

The troughs are relatively deep at one end 46 and become shallower towards the other end 47 whereby liquid which spills over into the troughs flows downwardly along the troughs into the outlet 48 and into the receiver 50. Liquid is continuously supplied to the vessel through jets 42 in the pipes 43. It overflows into the troughs and is collected in the receiver.

The solution from which the material is to be separated is introduced into the liquid bath. Referring now to the figure, there is shown a plurality of spaced solution pipes 55 located below the ridges 40 and spaced therefrom. Each of these pipes is provided with a plurality of jets 56 extending upwardly and providing means for injecting the solution into the liquid bath. It is to be noted that the main supply pipe 55 is spaced from the walls of the vessel whereby its temperature may be maintained below the temperature of the liquid within the vessel. As will become presently apparent, this will prevent evaporation of the solvent prior to the injection of the solution into the liquid bath.

When the solution comes into contact with the heated liquid in the bath, the solvent evaporates and forms bubbles which rise towards the surface. As the bubbles increase in size, the rate of evaporation increases. The bubbles rise to the surface. When the bubbles reach the surface, they burst. During this process, the solute collects on the surface of the bubbles in a highly comminuted form. When the bubbles burst, the material floats on the surface of the liquid and spills into the troughs 47 where it flows with the overflow liquid into the receiver. Skimming means 67 are associated with the receiver 50 for skimming off the separated material. In order to minimize the loss of solvent which may be retained on the surface of the separated material, there is provided means 70 for injecting hot steam into the pipe 68 in countercurrent to the material liquid mixture as it flows to the receiver. The steam serves to vaporize any solvent which may be entrained in the material being separated. In essence, the steam serves as a one-way trap recovering by vaporizing almost the entire amount of retained solvent.

The recovery process above has been described in general terms since it is applicable to the recovery from solution of many types of materials. It is to be observed that the essential feature is that the liquid in the bath be selected so that the solvent and material are not miscible therewith.

When my process is used for recovering resin from coal, it includes the step of leaching the coal by using, for example, as a solvent a solution having a high proportion of hexane. This solution has a boiling point of about 73 C. Both the solution and the resin are hydrophobic. The water bath is maintained near its boiling point. Sufficient temperature difference is present to cause the vaporization of the solvent and recovery of the resin in fine particles in the manner described above.

Although the specific example given above employs as a liquid bath, water, and as solvent for the resin a solution having a high proportion of hexane, it is known that other sol-vents exist. For example, for the recovery of resin, the following solvents and baths may be used: toluol, benzene, pentane, hexane and other low boiling petroleums, all with hot water baths, as well as others. When the boiling point of the solvent is near that of water, it is desirable to raise the boiling point of water by adding salts such as sodium chloride, sodium acetate, aluminum chloride, iron sulfate and others well known in the art.

Thus, it is seen that there is described a continuous process and apparatus for use therein for the purification of coal and the recovery of resin. The process is economical, safe and simple. The process provides a highly comminuted resin material useful directly in many applications without further processing and serves to recover solvent for recirculation through the leaching means thereby minimizing costs. The resulting coal is relatively pure and can be used for metallurgical purposes and for coking.

I claim:

1. The method of preparing substantially resin-free coal comprising the steps of floating uncrushed coal upon a flotation medium to form a coal concentrate by separating ash therefrom, said medium having a specific gravity greater than said coal and less than said ash, conveying the coal concentrate from the surface region of the medium in a given direction, passing a solvent of the resin in said coal through the concentrate in an opposite direction to remove the resin therefrom and form a resinsolvent solution, collecting the resin-solvent solution to provide the flotation medium, continuously withdrawing said medium and recovering solvent from said withdrawn medium for recirculation, and reintroducing the recovered solvent to pass through the concentrate in said opposite direction.

2. A system for removing resin from coal comprising a reservoir for holding a body of liquid, means disposed with respect to said reservoir for introducing the coal at a slight angle to the surface of said body to float said coal upon same thereby serving to separate ash thereof and form a coal concentrate, conveyor means disposed at a location remote from the last named means and adapted with respect to said reservoir to remove the concentrate from a surface region of a body of liquid in said reservoir and transport said concentrate along a predetermined path, leaching means for passing a leaching agent to said reservoir in an opposite direction along said path through the concentrate being conveyed therealong, conduit means connected to said reservoir means and adapted to withdraw a quantity of liquid from a subsurface region of the body of liquid, and recovery means interposed between said conduit means and said leaching means serving to recover the leaching agent from the withdrawn quantity of liquid and recirculate same through said leaching means.

References Cited by the Examiner UNITED STATES PATENTS Behavior of Bituminous Coals Towards Solvents, by Dryden, Fuel, September 1950, vol. 29, No. 9, pp.

Solvent Extraction of Lignites and Bituminous Coals, by Crick, Fuel, August 1951, vol. 30, No. 8, pp. 187-190.

DANIEL E. WYMAN, Primary Examiner.

C. F. DEES, Assistant Examiner.

Claims (1)

1. THE METHOD OF PREPARING SUBSTANTIALLY RESIN-FREE COAL COMPRISING THE STEPS OF FLOATING UNCRUSHED COAL UPON A FLOTATION MEDIUM TO FORM A COAL CONCENTRATE BY SEPARATING ASH THEREFROM, SAID MEDIUM HAVING A SPECIFIC GRAVITY GREATER THAN SAID COAL AND LESS THAN SAID ASH, CONVEYING THE COAL CONCENTRATE FROM TEH SURFACE REGION OF THE MEDIUM IN A GIVEN DIRECTION, PASSING A SOLVENT OF THE RESIN IN SAID COAL THROUGH THE CONCENTRATE IN AN OPPOSITE DIRECTION TO REMOVE THE RESIN THEREFROM AND FORM RESINSOLVENT SOLUTION, COLLECTION THE RESIN-SOLVENT SOLUTION TO PROVIDE THE FLOTATION MEDIUM, CONTINUOUSLY WITHDRAWING SAID MEDIUM AND RECOVERING SOLVENT FROM SAID WITHDRAWN MEDIUM FOR RECIRCULATION, AND REINTRODUCING THE RECOVERED SOLVENT TO PASS THROUGH THE CONCENTRATE IN SAID OPPOSITE DIRECTION.

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