US3545683A - Explosive shattering method - Google Patents

Description

United States Patent Inventor Elwood V. Schulte Pittsburgh, Pennsylvania Appl. No. 748,759 Filed July 30, 1968 Patented Dec. 8, 1970 Assignee Koppers Company, Inc.

a corporation of Delaware EXPLOSIVE SHATTERING METHOD 8 Claims, 2 Drawing Figs.

U.S. Cl. 241/1, 24l/5 Int. Cl. ..B02c 19/06,

8020 19/1 8 Field ofSeareh 24l/l,5, 1 38, 39

References Cited UNITED STATES PATENTS 10/1945 Joyce l2/l953 Dickinson 2/1954 Skelly ll/l967 Schulte Primary Examiner-Theron E. Condon Assistant Examiner-Donald G. Kelly Attorneys-Sherman H. Barber and Oline E. Williams ABSTRACT: The improved method for explosive shattering of particulate material includes adjusting the moisture content of the material in a first pressure vessel; heating and pressurizing the material to a range of 500-3000 p.s.i.g. and then flowing the material at this pressure through a system including a velocity increasing section and into a vessel wherein conditions are such that all of the moisture in the pores and crevices of the particulate material instantly becomes gaseous and effects explosive shattering of the material.

PATENIEBBEI: 8l97fl 35451683 SHEET 1 OF 2 DISCHARGING ORE INTO RECEIVING HOPPER WETTING THE ORE AS NECESSARY;

CHARGING A FIRST PRESSURE VESSEL WITH THE ORE;

HEATING AND PRESSURIZING ORE TO PRESSURE IN RANGE OF 500-3,000 PSIG AND TO TEMPERATURES IN RANGE I OF IOO 750F MAINTAINING PRESSURE WHILE FLOWING ORE IN A SYSTEM OF PRESSURE VESSELS;

FLOWING ORE THROUGH A VELOCITY INCREASING SECTION;

FLOWING ORE INTO VESSEL AT SUBSTANTIALLY LOWER PRESSURE WHEREIN EXPLOSIVE SHATTERING OCCURS; AND

REMOVING SHATTERED ORE FROM SUCH VESSEL INVENTOR. [1 W000 I/. SCHULTE BY JWm 1 EXPLOSIVE SHATTERING METHOD BACKGROUND OF THE INVENTION This invention relates to comminution and, more particularly, to improvement in the method and apparatus for continuously comminuting materials,.such as ores, by explosive shattering,

US. Pat. No. 3,352,498 which issued Nov. 14, 1967 discloses a method and apparatus for continuously com-minuting particulate material, such as ores, by what is termed explosive shattering" What actually causes particulate matter to experience explosive shattering is not entirely understood, but

- it is believed that liquid becomes trapped in the pores of particulate material and when the liquid is pressurized and then allowed to expand very rapidly, it becomes gaseous and the ore is subjected to forces exerted by the expanding gases and disintegrate along natural cleavage lines, or otherwise. Further, it is believed that, when the particulate material is heated and then cooled suddenly, that thermal shock forces the particles to disintegrate.

In any event, the effect of the explosive shattering upon particulate material is devastating, and the present invention is an improvement in. the method described in US. Pat. No.

3,352,498 which is assigned to the assignee of this invention.

SUMMARY OF THE INVENTION The method for continuously comminuting friable material comprises the steps of discharging a first quantity of friable material into a vessel and wetting the friable material as necessary to insure adequate surface moisture on the particles of friable material. The material is thereafter discharged into a first pressure vessel wherein it is pressurized to a pressure in the range of 500-3000 p.s.i.g. and is also heated to a temperature in the range of 100-750 F. Thereafter, the quantity of friable material discharges into a second pressurized vessel; passes through a velocity-increasing section; and flows into a receptacle wherein the pressure is less than the pressure in the second pressurized vessel. The pressure and temperature in the receptacle are maintained so that all of the moisture in the pores, crevices and cleavage planes of the friable material flashes into gaseous fluid, as such friable material enterssaid receptacle.

For a further understandingof the invention and for features and advantages thereof, reference may be made to the following description taken in conjunction with the drawings which shows for the purposes of exempliflcation apparatus suitable for carrying into practice the method of the invention, and a flow chart delineating the steps of the method of the invention.

BRIEF DESCRIiTION OF THE DRAWING In the drawing:

FIG. 1 is a schematic diagram illustrating the method steps of the invention; and

FIG. 2 is a schematic diagram illustrating apparatus suitable for carrying into practice the method of the invention.

DE AIL D DESCRIPTION The method of FIG. 1 includes a series of steps, performed sequentially, wherein ore particles or other friable material are treated and explosively shattered intosmalldiscrete particles. The friable material to be so treated is at first subjected to a preliminary crushingin order to reduce-it to particles having a size that is convenient for explosive shattering. Theparticle size will be determined to some extent by the type of material, but, generally, the largest pieces to be fed to the receiving hopper will be in the size range of %-%inch de' pending on the comminution rate. The larger the installation, the larger the pieces to be comminuted.

As carried into practice, the method illustrated in FIG. 1 is exemplified by using the apparatus 11 illustrated in FIG. 2 and comprises several steps commencing initially with the step of discharging ore 13 carried on the continuous belt 15 into a receiving hopper 17. While a continuous belt 15 has been selected for the purpose of'exemplification, it is to be understood that other suitable ore delivering apparatus, such as a skip hoist, screw conveyor, or the like, may be preferred.

Receiving hopper 17 is provided with both high 19 and low 21 level alarm devices and controllers that detect the level of ore 13 in the hopper 17. They also start the belt conveyor 15 when more ore is needed, and stop belt conveyor belt conveyor 15 when a preselected level in the hopper 17 is reached.

Receiving hopper 17 is also provided with a fluidadding means 23:: that is connected to a conduit 23 that conveys fluid carried in a storage vessel 25, to theore in the receiving hopper 17. A suitable pump 27 is installed in the conduit 23 for moving the fluid from the storage vessel 25 to the receiving hopper 17. Suitable controls to actuate and deactuate the pump 27 are, of course, included, but are not shown in the drawing.

Receiving hopper 17 discharges material through a suitable valve mechanism, such as a rotary vane feeder 29 or rotary plug valve, into a pressure vessel 31, which serves as a primary hopper. This pressure vessel or primary hopper 31 is fitted also with high 33 and low 35 level alarm or control devices like those installed in the receiving hopper 17 Pressure vessel or primary hopper 31 is also provided both with a pressurizing conduit 37 in which there is a solenoid control valve 39, and with an exhaust conduit 41 in which there is a solenoid valve 43. The pressure vessel or primary hopper 31 is also fitted with a flow control device 45 that is similar to the rotary vane feeder 29, or plug valve mentioned previously. 7

Material in the primary hopper 31 discharges into a second pressure vessel or feed tank 47 which also is provided with high 49 and low 51 level control devices, like those provided in the primary hopper 31 and the receiving hopper 17. The pressure vessel or feed tank 47 is also provided with a pressurizing conduit 46, valve 48, exhaust conduit 50, and valve 52 like those provided with the primary hopper 31.

Material in the second pressure vessel or feed tank '47 discharges through a flow control device 53 that is, or may be, similar to the flow control devices 29, 45. The discharge end of the flow control device 53 is connected to a downwardly sloping conduit 55, which communicates with a branch con- 1 duit 57 located about where shown in FIG. 2. Branch conduit 57 includes a solenoid or pressure control valve 59. Preferably, the conduit 55 slopes at an angle A, measured from the horizontal, which may be in the range of 30 80.

Conduit 55 connects axially to a venturi section 61 which, in

turn, discharges into another vessel or receptacle 63 that is maintained at pressures below the pressure in conduit 55. The venturi section 61 may be of any type of velocity-increasing, pressure-reducing and cooling section desired, but preferably not a fixed plate, orifice member.

The vessel 63 has an exhaust conduit 65 in which there is a control valve 67, and a flow control device 69 at the bottom which may be similar to the flow control devices 29, 45, 53, or any other preferred type.

In carrying the method into practice, the moisture content ofthe ore 13 that discharges from the conveyor belt 15 into the receiving hopper 17 is controlled to the extent that, whenthe ore is thereafter pressurized in the primary hopper 31, suf-,

ficient moisture is present to completely fill the pores,

crevices, cleavage lines, in the ore particles, If the moisture content of the ore is insufficient, then-additional moisture may be added to the ore by flowing water or other suitable liquid in conduit 23; drawing such liquid from the source of supply 25 with the aid of the pump 27. The moistened ore will then be heated with hot inert gases, steam coils, or other indirect heating means after it has become pressurized in the primary hopper 31. If sufficient moisture is present on the ore as it enters the receiving hopper'17, it will not be necessary to add additional moisture through conduit 23. The ore then, as before, may be heated by hot inert gases, steam coils, or other indirect heating means after it has become pressurized in the primary hopper 31. If sufficient moisture is present on the ore as it enters the receiving hopper 17, it will not be necessary to add additional moisture through conduit 23. The ore then, as before, may be heated by hot inert gases, steam coils, or other indirect heating means after it has become pressurized in the primary hopper 31.

1f sufficient moisture is present on the ore as it enters receiving hopper 17 it may also be heated by direct contact with high pressure steam while the ore is being pressurized in primary hopper 31 except in this case, because of condensation of some of the steam on the ore particles, more moisture will have been added than is needed to fill the pores, crevices and cleavage lines in the ore particles with liquid water.

If the moisture content of the ore is insufficient, then additional moisture may be added also by use of steam or a mixture of steam and another inert noncondensible gas added directly to primary hopper 31 to pressurize the ore in this hopper, which, after some condensation, will be sufficient to fill the pores, crevices and cleavage lines of the ore at the higher pressure and at the pressure prevailing in feed tank 47 and line 55.

From the receiving hopper 17, the ore gravitates through the flow control device 29 into the primary hopper 31. Then, the flow control device 29 closes (the flow control device 45 having been closed previously), and the belt conveyor starts to discharge ore again into the receiving hopper 17.

The ore material in the primary hopper 31 is now treated in the following manner. A gaseous fluid, such as steam that is under pressure, flows in conduit 37 and into the primary hopper 31; valve 43 being closed. The gaseous fluid both heats and pressurizes the ore to such an-extent that the moisture on the ore is forced into the pores crevices, and cleavage lines. The pressure within the primary hopper 31 is in the range of 500-3000 p.s.i.g., and the temperature is above 100 F. and preferably below 750 F. Actually, the heating may occur before and during pressurization, or during and immediately after pressurization. While the gaseousfluid may be steam, those skilled in the art will recognize that a number of other gaseous fluid may be used; one such other gaseous fluid being ammonia.

Desirably, the temperature of the moisture on the ore should not exceed the boiling temperature of the liquid at the pressure prevailing in the receiving hopper l7.

Enough ore is charged into the primary hopper 31 until the level therein reaches the high level controller 33, which actuates the flow control 29 so that no more ore enters the primary hopper 31. The conveyor belt 15, however, continues to operate until the ore in the receiving hopper 17 reaches the high level controller 19. Thereafter, the conveyor belt stops until actuated again, and the ore in the receiving hopper drops to the lower level 21.

Then, the pressure and temperature prevailing in the primary hopper 31 are maintained during the time the ore flows from the primary hoppers 31 into the feed tank 47, and in the sloping conduit 55.

After the ore leaves the primary hopper 31, the flow control device 45 is closed; the valve 43 is opened to release the pressure of the primary hopper; and then, with the valve 43 open, the flow control device- 29 is opened to release ore material from the receiving hopper 17 into the primary hopper 31. Thereafter, valve 29 is closed and this ore material is then treated in the manner described hereinbefore.

As the ore leaves the feed tank 47 it flows in the inclined conduit 55 toward the venturi or velocity-increasing section 61. The pressure in the receptacle 63 is considerably lower than the pressure in the feed tank 47 and in the inclined conduit 55. In fact, the pressure in the receptacle 63 should be such that, when the ore reaches the receptacle 63 and cools due to expansion, the liquid in the pores, cavities, and crevices, and around the particles, flashes into a gas. The gas in the pores, crevices and cleavage lines expands forcefully, it is believed, to produce explosive shattering of each ore particle.

Of course, when the ore level in the feed tank 47 reaches the lower limit 51, the flow control device 45 opens to admit more ore under pressure from the primary hopper 31. Thus, the ore is continuously flowing through the venturi or velocity increasing section and is continuously undergoing explosive shattering in the receptacle 63. Flow of shattered ore from the receptacle 63 may be regulated by the flow control device 69, as desired. 7

In order to ensure that practically all of the liquid in the pores, crevices, and cleavage lines of the ore flashes into a gas as soon as the ore passes into the receptacle 63, the ore must not be allowed to cool to a temperature below the flashing point of the liquid. In the case of water, the temperature must not be allowed to cool below 212 F. when the pressure downstream of the venturi or velocity-increasing section 61 and receptacle 63 is at atmospheric pressure, which is the boiling point of water at ambient atmospheric pressure.

In the event the temperature of the ore entering the receptacle 63 is only slightly above freezing point of the liquid in the pores, crevices, and cleavage lines, then the absolute pressure in the receptacle must be maintained at such a level that the liquid will flash into a gas. If the liquid is water and the ore cools to slightly above 32 F., then the pressure in the receptacle must be about 4.6 mm of mercury, so that practically all the water will flash to steam and forcibly shatter the ore particles.

The method of the invention may be carried into practice regardless of the moisture content of the ore as it is discharged into the receiving hopper 17. The ore in the primary hopper 31 may be pressurized by a gaseous fluid containing at least 50 percent by volume of steam in sufficient quantity to raise the temperature of the ore to always ensure that there is liquid in the pores, crevices, and cleavage lines of the particulate matter. The temperature is such that, at atmospheric pressure, liquid in the pores, crevices, and cleavage lines will flash to gaseous steam, and yet the temperature of the ore will be above the freezing temperature of water, 32 F.

Pressurizing the ore initially by means of a gaseous fluid containing at least 50 percent by volume of steam is accomplished in less than 5 seconds time, and before the steam heats the ore to the temperature of saturated steam at the prevailing pressure. Thereafter, the gaseous fluid, containing at least 50 percent by volume of steam, is replaced by either air, or other suitable inert gas under pressure. Such air or inert gas includes enough steam to maintain the desired lower temperature, or such gaseous mixture is replaced by air or inert gas that has been preheated only enough to maintain the ore at the temperature desired.

Thus, instead of using steam exclusively, the use of air or other inert gas, as a pressurizing medium after the ore has been initially heated to the desired temperature, affords considerable economy in carrying out the method of the invention.

The comminuted material in receptacle 63 may, of course, be continually removed through the flow control device 69 and conduits attached thereto.

Conduit 65 and valve 67 are connected to suitable apparatus to maintain the pressure and temperature within the receptacle 63 at the desired values.

A feature of the invention is that the pores, crevices, and cleavage lines of the ore particles are filled with moisture derived from the gas used to pressurize the ore particles, and it is not necessary to add substantial moisture, such as steam, during pressurizing in the primary hopper and feed tank.

A feature of the invention is that high-pressure steam is not required to maintain the pressure in the feed tank, since the desired moisture in the pores, crevices, and cleavage planes is obtained from the surface moisture plus heat applied to the ore after the ore is pressurized in the primary hopper.

A feature of the invention is that air under pressure or other pressurized inert gas may be economically used to maintain the ore at desired physical conditions while it is in the feed tank and as it flows downward and through the velocity increasing section.

A feature of the invention is that the gas initially used to pressurize the primary hopper has a greater tendency to condense in the pores, crevices,- and cleavage planes of the ore particles than the gas used for maintaining the pressure in the feed tank and in the sloping conduit.

A feature of the invention is that the method of explosive shattering is continuous, and, being continuous, smaller pieces of apparatus may be used to accomplish the same or better results than using batch type comminuting apparatus available in the prior art.

A feature of the invention is that the apparatus used to practice the method of the invention requires only a very few moving parts, wherefore the cost of maintenance and repair to the apparatus is minimal.

Although theinvention has been described herein with a certain degree of particularity, it is understood that the present disclosure has been made only as an example and that the scope of the invention is defined by what is hereinafter claimed.

lclaim:

l. The method for continuously comminuting friable particulate material comprising the steps of:

a. discharging a first quantity of such friable material into a first vessel;

b. wetting the first quantity of friable material in said first vessel to ensure adequate surface moisture on the particles of said friable material;

. flowing said first quantity of friable material into a first pressure vessel; increasing, pressure reducing and cooling section and thence into a receptacle whereby the pressure downstream of said velocity increasing, pressure reducing and cooling section including said receptacle is lessthan in the second pressure vessel and conduit, said friable material being subjected to the effect of explosive shattering forces downstream of said velocity increasing, pressure reducing and cooling section and in said d. pressurizing and heating said friable material in said first pressure vessel and effecting the filling of pores, crevices and cleavage planes of said friable material with moisture; discharging said first quantity of material into a second pressure vessel previously pressurized and heated to the conditions in said first pressure vessel;

f. discharging a second quantity of friable material into said first vessel after said first quantity of friable material has been discharged into said first pressure vessel;

g. thereafter discharging said second quantity of friable material into said first pressure vessel after said first quantity of friable material has been discharged into said second pressure vessel;

h. discharging said first quantity of friable material from said second pressure vessel into a first conduit;

. flowing said first quantity of friable material through a velocity increasing section and thence through a second conduit into a receptacle wherein the pressure is less than in the second pressure vessel and the first conduit, said friable material being subjected to the effect of explosive shattering forces in said receptacle; and

j. flowing additional quantities of friable material into the several vessels of the system to insure substantial continuity of flow of material into said receptacle wherein continuous explosive shattering occurs.

2. The method of claim 1 wherein heating and pressurizing of the friable material is carried out at temperatures in the range of l00--750F. and pressures in the range of 500- -3000 p.s.i.g.

3. The method of claim 1 including maintaining said friable material under said preselected pressure and temperature conditions until said material passes through said velocity increasing section.

4. The invention of claim 1 including heating and pressurizing said friable material with a gaseous fluid containing at least 50 percent by volume of steam.

5. The invention of claim 1 including maintaining the pressure in said receptacleat such a ressure that all of the moisture in the pores, crevices, and c eavage planes of said friable material flashes into agaseous fluid and effects explosive shattering as said friable material leaves said velocity-increasing section and enters receptacle.

6; The invention of claim 4 including replacing the gaseous fluid containing steam with inert gas at the same pressure and temperature conditions after pressurizing and heating said friable material for a period of time of less than 5 seconds.

7. The invention of claim 4 including replacing the gaseous fluid containing steamwith inert gas at the same pressure and temperature conditions after pressurizing and thereafter heating said friable material for a period of time of less than 5 seconds.

8. The invention of claim 7 wherein said pressurizing and heating occur simultaneously.

Patent No. v3 545 683 December 8 1970 Dated Elwood V. Schulte Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the cover sheet, H. Barber and 01in E. Williams Columns 5 and 6:

the attorneys should read Shermar after Column 4, insert A feature of the intention is that the pas initially used to g. thereafter diseharpiiu. said second quantity of plesstltllc the primary lu|| "i has :ltJ-tltt tendency to eon material into said first pressure vessel after said firs dense in the pores. err-vices. and eleava-re planes of the ore tity of friable material has been discharged int particles than the pas u ed lor maintaining the pressure in the second pressure vessel; feed tank and in the sloping conduit 5 h. discharging said first quantity of friable material A feature of the invention is that the method of explosive said second pressure vessel intoa first conduit; shatterinpis LUlillttttfltlmitllth being continuous,sniallerpieees i. flowing said first quantity of friable material thr of apparatus may he used to accomplish the same or better velocity increasing section and thence through :1 results than Using: batch type comniinuting apparatus available conduit into a receptacle wherein the pressure is le in the prior art. l() in the second pressure vessel and tlte first condu A feature ofthe invention is that the ap aratus used to pmcfriable material being subjected to the effect ol'ex tiee the method of theinvention requires only a very few inovshattering forces in said receptacle; and in parts wherefore the cost of maintenance and repair to the j. flowing additional quantities of friable material it apparatus is minimal. several vessels of the system to insure sul stanti Although the invention has been described herein with a l tinuity f flow 0f n utfil'ifll into Said rCCCpltlCle certain degree of particularity, it is understood that the COHliIIU U CXPIOS C fil llul' ng CCutS.

present disclosure has been made only as an example and that 2. The method of Claim I wherein heating and pres the scope of the invention is defined by what is hereinafter of the friable material is carried out at temperatures claimed. range of l00 750li and pressures in the range I claim: 3000 p.s.i.g,-

I. The method for continuously cmnminuting friable par- 3. The method of claim 1 including maintaining said ticulate materialcomprising the steps of: material under said preselected pressure and temp a. discharging a first quantity of such friable material into a Condiiions lllllil Said milicl'illl P115565 t oug S Wit! first vessel; creasing section.

b. wetting the first quantity of friable material in said first 4- T invention ll fl 1 i cluding heating an pt" vessel to ensure adequate surface moisture on the parting i f ll m ri il gH O fl i Con aining cles ofsaid friable material; 50 percent by volume ofstcamt c. flowing said first quantity of friable material into a first The n n i n f Cl im 1 including maintaining tl pressure vessel;increasing pressure reducing and cooling Sure in said receptacle at such a rcssurc that all section and thence into a receptacle whereby the pressu re mo'swm "l and c cfwugc planes downstream of said velocity increasing, pressure reducing able mfncmll i mm mud n and cooling section including said receptacle is less than hancnflg as Smd mmmal leaves in the second pressure vessel and conduit. said friable mg and f l material being subjected to the effect ofexplosive shatter- The l 'f' of f' f mcludmg "P the l ing forces downstream of said velocity increasing, prcs cmmmmg F l the same W sure reducing and Cooling Scam" and in Said temperature conditions aftcr pressurlzmg and heating d4 pressurizing and heating said friable material in said first able mmclrml P f t 9 than S cc0nd5 pressure vessel and effecting the filling of pores, crevices The f 'f of l mcludmg rcplacmg met and cleavage planes ofsaid friable material with moisture; cunmmmg Fi wnh f'l same 6. discharging said first quantity of material into a second 40 r condmmlsilflcr press-9mm"; P thcrcilrl pressure vessel previously pressurized and heated to the mg fnablc mammal for a pcnod or of [U conditions in said first pressure vessel; seconds I f. discharging a second quantity of friable material into said 1 '.",""P" of Chum 7 Prcm'm first vessel after said lirst quantity of friable material has 5 hcamg Occur s'mulmnewsly' been discharged into said first pressure vessel;

UNITED STATES PATENT OFFICE Y CERTIFICATE OF CORRECTION 3,545 ,683 Dated December 8 1970 Elwood V. Schulte PAGE 2 Patent No.

Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Signed and sealed this 7th day of March 1972 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patent:

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