US2686085A - Method of conveying or transporting small-size solids - Google Patents

Description

Ag. l10, 1,954 w. w.'oDE| L 2,686,085. SMALL-SIZE soLIbs METHOD OF CONVEYING OR TRANSPORTING '2 Sheets-Sheet 2 Filed July 15. 1950 Mh Nh Nimm uw wv. E@ @n O \v lllll Il' mw -ILL QN .WN QM. .3%

QQLM 94064@ nvenil Patented Aug. 10, 1954 METHOD OF CONVE YIN G OR TRANSPORT- ING SMALL-SIZE SOLIDS William W. Odell, New York, 'N. Y.

Application July 15,

16 Claims.

This invention relates to a method of conveying or transporting small-size solids through a tubular transmission system. In particular it has to do with the transmission of small solids through a pipe line while they are suspended in a liquid in which they are preferably insoluble. Specically the invention deals with the transportation of crushed mineral matter through a pipe line While said crushed matter is immersed in water or other suitable liquid.

In the mining and marketing of minerals, of which coal is an example,v it is sometimes found that water is available at the mine and rail or other usual transportation facilities are not at hand and that a pipe line can be provided that will afford cheaper transportation of the coal than can be obtained by building and using a railroad. Crushed coal lAr-inch and less in diameter can very readily be suspended in a liquid, Water for example, and p shed through a pipe just about as conveniently as one can pump Water. Larger sizes have a greater tendency to settle and it is necessary in transporting them submerged, to maintain a turbulent iiow or such a high flow rate that settling does not occur.

Because it is highly undesirable to attempt to pass the mixture of solids and liquid through a pump or the equivalent to maintain the suspended therein and propel it some distance but this is not always the case. Other objects will become evident from the following disclosures.

1950, Serial No. 174,050

2 the discharge end of the line and separating the gas from the liquid and solids.

Referring to Figure l, crushed solids hereinafter referred to as coal is continuously introduced through conduit l to the conical member 2 in which the level of water is maintained at LW by the continuous supply of Water through conduit I5, valve i6, bustle pipe il and the nozzles I8 which nozzles cause the Water to enter tangentially. The coal concentration in the water is controlled by regulating the relative rates of supply of each (coal and water) to element 2. The suspension passes down through downcomer 3 under its own head and is thus supplied to the head li of pipe line 5 which is part of the transmission pipe line having valve 6.

under the latter pressure through valve 9, conduit li, valve i3 and adjustable nozzle i2 having adjustment control handle Ill. A suitable pressure is maintained in reservoir 'l by controlling the temperature, which usually requires that heat be supplied; to accomplish this a temperature or other Huid for heating and Water for cooling, is supplied-through valve i9, conduit 2S, coil 2i, oftake conduit 22 and valve 23. A constriction or throat 8 is provided adjacent nozzle l2 outlet to promote the ejector eii'ect in propelling the coal suspension in l down stream through 5 under superatmospheric pressure. Gage 24 indicates the pressure in line 5. Conduit 3G with propane owing liquid state. When it passes through valve i3 into and through nozzle l2 the pressure is released, that is, it is lowered sufficient for the propane to vaporize and increase in volume considerably. One gallon of propane (03H8) yields 36 cu. ft. of vapor at 60 F. and atmospheric pressure, or 1 cu. ft. of propane yields 270 cu. ft. of vapor at atmospheric pressure. However, when the initial pressure in line 5 is say 100 pounds gage the vapor volume of 1 cu. ft. of propane approximates 35.2 cu. ft. The boiling point of propane at 100 pounds pressure is approximately F., or expressed diierently, the vapor pressure of propane is pounds gage when its temperature approximates 65 F. It is essential for a clear understanding of this invention to note the change in vapor pressure with temperature changes for the different hydrocarbons of low molecular weight; this relationship is shown in the following table.

Vapor pressure, pounds per sq. in. gage L ,.-r-f- Temperature, F. N

Iso- Propyl- Butane Propmle Butane ene 3. G3. 3 l2. 2 83 6. 9 77 l. 17. 8 97 1l. 6 92. 4 24. 0 117 16. 9 109. 3 31. 1 136 22. 9 12B. 1 39. 2 158 29. 8 149. 0 48. 6 185 37. 5 172. 0 59. 0 213 46. 1 197. 0 70. 4 245 56. 1 225. 0 83.3 275 56. 7 257.3 97. 3 315 140 77. 9 290. 3 112. l Critical temperature, F- 273 6 273 198 Critical Pressure, lbs.

gge 544 602. 3 515 647 In order to inject propane into the suspension when said suspension is under pressure of say 185 pounds gage, the temperature of the propane liquid in the reservoir should normally be about 120 F. or higher. At 120 F. the pressure difference (225-185)==40 pounds which is the head due to the vapor pressure of the propane in excess of the pressure of the suspension.

Referring to Figure 2, in which the numerals all refer to different parts than those of Figure 1 except 5 which is the transmission line, the latter line discharges the mixture of gas, water and powdered coal through dip pipe 2l under water in reservoir 26 in which the liquid level is at LR. The gas liberated at the relatively low pressure in 26, which pressure may be say 2 to 25 pounds, passes through oitake conduit 28 to seal box 29 and then through oitake 30 and valve 3l to a suitable system for handling the gas; a low pressure holder is a convenient means of storing the gas but when it is to be distributed at high pressure or liqueed, suitable equipment for compressing and liquefying are required. Valve 33 in offtake 32 adjacent the bottom of reservoir 26 is used to remove the suspension substantially free of gas; it is conducted through 34 to suitable known settling and separating means for the recovery of the coal. The depth of liquid in 26 is deep relative to the depth in 29 to facilitate rapid and complete separation of the gas. The liquid level in 29 is at LS.

EXAMPLE Conveying coal in suspension in water Coking coal is crushed to sizes 1/4-inch and finer and is conveyed through conduit l (referring to Figure 1) to conical element 2 which is kept full of water at the level LW. Water is through the conduit I5, valve i6, bustle pipe l1 and nozzles I8. Propane is supplied from reservoir I to the head 4 of pipe 5 by opening valve 9 and by opening valve i3 suicient to maintain the desired pressure in 5 as indicated by gage 24 which pressure in this example is 60.0 pounds. The temperature of the liquid propane is 90 F. and the water temperature is 70 F. Under these conditions the propane vaporizes by absorbing heat from the water. 1t is desirable that before the propane reaches the throat 3 or end of the nozzle l2. The table shows that the vapor pressure of the propane at the given temperature (90 F.) is ample to force the propane into the system, and it also shows that the propane is in the vapor phase at the temperature of the water, 70 F. The heat oi vaporization of propane lowers the water temperature. The water in head 4 which is in continuous movement gives up heat to the propane, to supply the latent heat of vaporization. In this example, supplying sufficient propane to decrease the temperature of the water 10 F., the approximate proportions of propane and water may be computed as follows, taking the heat of vaporization of propane as 150 B. t. u. per lb. and 1 gallon of propane weighing 5.2 pounds: (150) (5.2) :785 B. t. u. latent heat per gallon. Now 785-:-l0 Fir-78.5 pounds of water which must pass and give up heat to the propane and itself become cooled from 70 to 60 F. The proportions thus used in this instance are 1 gallon of propane to l8.5-:-62.5=1.25 cubic feet of water. This is equivalent to about 54 cu. ft. of propane vapor at 60 pounds gage pressure to 1.25 cubic feet of water. This is a higher ratio of propane to water than may be desired for the transportation of the propane but not necessarily higher than may be desired for supplying motive power, the latter varies with the distance transported. Obviously the heat of vaporization of the propane may be supplied by other means than as shown in Figure 1. A separate extraneous vaporizer may be used and the heat may be taken from the water before it mixes with coal or the downcomer pipe 3 of Figure 1 may be the inner tube of a vaporizer and the propane would thus be fed to valve I3 as a vapor. This invention is not concerned with this particular means of vaporzation which is not new. The amount of coal used in this example is 10 per cent of the total water and coal, in other words for every gallons of water transported r200 pounds of coal are also transported. This is not a limit but merely an example.

The velocity of nuid through the pipe line 5, still referring to Figure 1, must be greater than the settling rate of the suspended solids under the conditions of transportation. Settling rates are much lower for small-size solids than for relatively large solids of a given substance, coal in this example. When settling begins in the line the back pressure will build up indicating that the fluid flow rate is not high enough to keep the coal in suspension. By increasing the flow rate the deposited matter will again be entrained and the pressure differential per unit of line will be more uniform. In starting the operation it is preferred that the location of the inlet end of line 5 be at a greater elevation than the discharge end of the line so that pressure loss due to friction, viscosity, etc. are largely or completely neutralized by the increased head differential due to a difference in elevation. Under these conditions much less motive force or propellant is required at the mine. With very fine-size coal, particles say 100 mesh in size, the flow-pressure conditions are substantially the same as calculated results for a liquid having a specic gravity of 1.05 to 1.10, when the suspension is say 10% coal. Increasing the concentration of the coal in the water does not increase settling rates, rather the contrary is true under certain conditions. However, it does increase the density of the uid (mixture) and also increases the viscosity and friction factor. At a velocity oi now of 2 feet per second the quantity of materials flowing through a 16v-inch diameter pipe will be approximately 2.8 cu. ft. per second which amounts to 177 pounds of water and 20.0 pounds of coal per second or 36.0 tons of coal per hour.

ow the critical velocity in a 16-inc`h, for water at 68 F. is about 0.01 ft. per second, which is, the velocity where the ilow changes from straight line to turbulent flow as the velocity is increased, hence a llow rate of 2 feet per second is above critical for watervalone and for most coal suspensions. The calculated pressure drop for miles of pipe is about 58 pounds at the given velocity of 2 feet per second. Similarly at 3 feet per second velocity of flow the approximate 54 pounds per sq. inch over the 10 miles and the coal carried at the concentration in this example will be 81 tons per hour. To accomplish this it is necessary to introduce sufcient propane into the line at 4 to maintain a pressure at gage 24 of the stated pressure or at a higher pressure.

It is recognized that this is normally an ineilicient way of supplying power for transportation and it is also recognized that the quantity of propane required for the continuous transportation of coal is not always desired at the discharge end of the line and further, the required amount is not always available at the intake end of the line. However, the novelty and usefulness of this invention will become clearer when it is realized that in the pipe-line transmission of natural gas it is necessary to remove the pentane, almost all of the butane and a large portion of the propane from the gas before pumping it at high pressure through the pipe lines, even though it is desirous to leave them in the gas particularly in the winter months. This is true because at the usual high pressures prevailing in the latter lines condensation occurs at the prevailing ground temperatures, 30 to 50 F. It is possible to transport propane in natural gas under the conditions described and the B. t. u. and composition may vary over a wide range; the normally bothersome hydrates (hydrocarbon hydrates) are not bothersome under these conditions. Thus with natural gas as the major gasiform propellant, propane may be simultaneously introduced in any desired proportion and mixture collected at the discharge end of the line and blended with other gas or separated into various fractions by known methods. It so happens that many coal seams in West Virginia for example, are located at an elevation more than 500 feet above sea level, hence in the transportation of the suspended coal under such conditions less power is requiredper unit of suspension passed per hour because of the increase in head progressively along the line. In some cases the costs will be very low, for transporting both the solids, and the gasiform medium. Still referring to Figure 1, the natural gas is introduced in the gaseous state through conduit 36 and valve 37 under controlled pressure and chosen amounts.

Now it is known that expensive tank cars are required for the haulage of propane and butane and these must be returned empty for rell. The time required for a round trip is frequently as long as 30 days, and this is one of the reasons for high transportation costs; with the present proposed method these costs are reduced. Again, when methane is synthesized from Water gas, made at the mine, it is usually associated with unreacted CO and H2, yielding a gas which may be as low as 700 B. t. u. It is not possible to inject sumcient propane and butane in it to raise the B.`t. u. to 1000 when the resulting gas is to be transmitted through the usual lines at high pressure; such enriched gas can be transported along with water and coal as described. The latter is pressure drop will believed-to be an important future use-of this invention.

Now by referring to the table it will be noted that at 40 F., a common ground temperature in the winter months the vapor pressures of N-butane, propane and iso-butane are respectively 3.0, `63.3 and 12.2 lbs. per sq. inch, and it follows that when the pressure in the system, namely in the inlet end of line 5 of Figure 1 is high and the temperature is say 40 F. these hydrocarbons will remain in the liquid phase substantially entirely whenV they are introduced into the system as de-i scribed, through line H and valve I3 without the simultaneous admission of gas through 36 and 31. Very little propelling force is supplied in this instance but the operation can be performed under a particular set of conditions. The pressure at the gage 24 say is 200 pounds, the effective head of the suspension 200 pounds and the temperature in reservoir 1 is maintained at a level whereby the vapor pressure therein is somewhat above 200 pounds. Under these conditions the hydrocarbons can be transported as a liquid and will not vaporize until the pressure in the system has decreased below that corresponding to the stated 40 F. They can be removed from the water when they arrive at the discharge end of 5 as liquid by simple settling or by reducing the pressure and removing them in the vapor phase.

I believe it is new in the art to transport coal in water in the presence of a hydrocarbon, and I also believe it is new to employ the hydrocarbon as a propellant supplying at least a portion of the power required to propel the suspension through the transmission line. It is also believed to be new to employ a hydrocarbon which, under pressure, is a wetting agent for coal andwhich retards its oxidation both in transit and in temporary or short term storage. Propane does not remain on the surface of coal after pressure is released, other than in adsorbed amounts but some of the higher hydrocarbons remain on the surface in larger amounts and they thus retard oxidation of the coal and preserve its coking qualities. The higher hydrocarbons may be added with the propane and they may have a higher molecular weight than butane. When small amounts of oil are used the coal separates from the water at the discharge end of 5, .upon settling and draining, quicker and more completely than when no oil is added. Thus the oil wetted coal is preserved from oxidation and it packs to greater density in coke ovens than the unwetted coal.

Because of the abrasive effect of some of the mineral matter normally associated with coal as ash, bone and the like it is preferable to treat the crushed coal by a suitable deashing process which removes free mineral matter including pyrite before the coal is transported through the line. Liquid sedimentation processes or dry separation processes may be used.

Referring to Figure 1, the ordinary method of propelling a liquid through draw it by pump fit from valve 42 to pipe-head 4, valve 43 being closed. Now, this procedure or the equivalent may be employed in the practice of this invention along with the introduction of propane and/or combustible gas as described. Air is not a desirable gas for three important reasons, i. e. it has no value at the discharge end of the line, it tends to oxidize coking coal and it promotes oxidation of the line. Combustible reducing gases do not have supplied to 4 through 3 is about these effects. Again, it is preferable to so size the coal before attempting to transport it, that very large lumps are not presen Before presenting my claims it is desirable to call attention to the fact that, even though it is desired to convey or transport the propane, butane, propylene or butylene and the like in the liquid form, it is advantageous to introduce it in the vapor phase from the injection nozzle l2 (referring to Figure 1) in order to obtain the maximum injector effect. For example when propane vapor at 290 pounds gage pressure is supplied to valve i3 by opening valve 9, while the temperature of the water-solids mixture supplied to 4 from conduit 3 is 60 F. and the pressure as indicated by gage 24 is say 19'? pounds, the propane thus introduced will largely condense as injected into the system. f normal butane is substituted for propane at the same pressure and the water temperature is 60 F. it also will largely condense immediately and will exert a vapor pressure in the pipe line of not more than 11.6 lbs. gage pressure which is approximately 5.9 per cent of the total pressure in said line. The temperature 4 feet underground is normally 40 to 50 F. hence at these temperatures butane exerts a vapor pressure (over butane) of only 3 to '7 pounds gage, hence it is possible to recover such products partly as a liquid at the discharge end of the pipe line when the discharge pressure is appreciably greater than the vapor pressure of the butane or the like at the discharge temperature. Referring to Figure 2 this may be done as follows: The mixture transported through 5 is discharged into receiver 26 through dip pipe 21. The water and solids settle out and are removed at the rate of accumulation in 2S and are removed through 32 and 33 and pass through 34 to a suitable settling means where the solids and water are separated by the force of gravity or other known means; the solids having a greater density than 1.0. The gas passes out of 26 through 28 to sealpot 29 out through 30 and 3l to a gas collecting means of known design. The liquid hydrocarbons collect as a top layer in the liquid in 26, with a level at LR and are removed therefrom through valve 45 to 29 where the liquid is maintained at the level LS. The liquid thus collected in 29 is removed as it accumulates through valve 3E r and conduit 41 to settling chamber 48 where the remaining water and fine-size particles of solids are settled and removed through 5l and 52 whereas the hydrocarbon liquid is withdrawn through 49 and 5U substantially at the rate of accumulation. The liquid in reservoir 48 is at LO.

Having described my invention so that one skilled in the art can readily practice it, I claim:

1. The method of transporting crushed solids and combustible fluids in a transmission pipe, comprising, suspending insoluble solids in a nonstabilized form in a liquid comprising water, supplying the mixture to said pipe under superatmospheric pressure substantially continuously at substantially the inlet end of said pipe at such an initially high velocity greater than the settling velocity of said solids in said liquid that the suspension is maintained in said liquid, introducing a non-oxidizing, normally gasiform combustible fluid into said mixture in said pipe as an additional propellant at substantially the inlet end thereof under superatmospheric pressure, thereby causing the whole final mixture to pass through said pipe without the settling of said solids therein by virtue of said velocity meanwhile maintaining a non-oxidizing condition in said pipe throughout its length, and separating the latter mixture at the discharge end of said pipe into its three component parts, water, solids and combustible uid; said solids being initially of a size that will readily settle out of said suspension on standing for a short period.

2. The method described in claim 1 in which said combustible iiuid as fed to said pipe is a liquid but is a non-oxidizing gas at normal temperature and pressure and the quantity of it is such that it supplies a major portion of the propelling force required for the transmission of said suspension through said pipe.

3. The method described in claim 1 in which said liquid is water and in which said combustible fluid is a reducing gas at normal temperature and pressure.

4. The method described in claim 1 in which said fluid is a reducing gas at normal temperature and pressure but is liquid as introduced into said pipe under said superatmospheric pressure and is at least in part vaporized during the transmission of said solids therethrough.

5. In the process of transporting crushed mineral matter solids through a transmission pipe while they are suspended in an unstabilized state under superatmospheric pressure in a liquid in which they are insoluble and recovering said solids separate from said liquid at the discharge end of said pipe, the steps comprising, introducing the said liquid and solids under superatmospheric pressure at a high velocity into substantially the inlet end of said pipe, introducing also into said inlet end as a propellant a combustible, non-oxidizing gasiform fluid under superatmospheric pressure at a high velocity which iiuid is substantially insoluble in said liquid at normal temperature and pressure, maintaining a nonoxidizing condition in said pipe throughout its length, and separating all three components, said liquid, solids and said fluid at the discharge end of said pipe.

6. In the process of transporting small-size minera-l solids through a transmission pipe while they are suspended in a non-stabilized form under superatmospheric pressure in a liquid of lower density in which they are insoluble and recovering said solids separate from said liquid at the discharge end of said pipe, the steps comprising, introducing a suspension of said solids in said liquid at a high velocity and high superatmospheric pressure into substantially the inlet end oi said pipe only, simultaneously introducing into the latter end only as a propellant a combustible, non-oxidizing gasiform fluid that is substantially insoluble in said liquid at normal temperature and pressure but which has a greater vapor pressure than said liquid, separating and recovering said uid from the mixture at the discharge end of said pipe by virtue of a difierence in its vapor pressure from that of said liquid and separately recovering said solids from said liquid at the discharge end of said pipe by virtue of their greater density than that of said liquid.

7. In the process of transporting crushed mineral solids through a transmission pipe while they are suspended under superatmospheric pressure unstabilized in a liquid in which they are insoluble and recovering said solids separate from said liquid at the discharge end of said pipe, the steps comprising, employing `both water and a water insoluble combustible, normally gaseous non-oxidizing uid as the transporting agents for said solids in said pipe, introducing said combustible fluid at least in part in the liquid state into said pipe under superatmospheric pressure at substantially the inlet end thereof as a propellant, vaporizing the liquid fuel thus introduced to a larger volume in said pipe, separating the said iiuid and suspended solids from said water at said discharge end of said pipe and separately recovering them; the relative amount of said fluid thus introduced being suflicient to maintain a non-oxidizing condition in said pipe throughout its length.

8. In the process oi transporting small-size crushed mineral solids through a transmission pipe while said solids are suspended under superatmospheric pressure in a non-stabilized form in a liquid carrying agent comprised of water and separating said solids from said agent at the discharge end of said pipe and recovering them, the steps comprising, introducing said agent substantially free of oxidizing gas along with said solids into said pipe at substantially the inlet end thereof under superatmospheric pressure, simultaneously introducing a non-oxidizing combustible fluid containing considerable propane into the ysuspension in said carrying agent substantially at the inlet end of said pipe only, mospheric pressure, conducting the non-stabilized mixture through said pipe under pressure under non-settling velocity conditions by virtue of the propelling force of said agent and of said combustible fluid thus introduced into the pipe inlet, separating said combustible fluid from said mixture as a gas at the discharge end of said pipe at a lower pressure than inlet pressure and separately recovering the said solids at the latter end of said pipe.

9. The method of transporting small-size mineral matter solids through a pipe to distant points under superatform in a liquid, which pipe has a considerably greater altitude at the inlet end than at the discharge end thereof, comprising, feeding water, a combustible fluid which is non-oxidizing and gaseous at ordinary temperature and pressure, and said solids into said pipe at substantially the inlet end thereof only under superatmospheric pressure of the order of 50 to 700 pounds gage, conducting the mixture through said pipe under non-settling conditions partly by virtue of the impelling force of said water and said fluid and partly by virtue of the increase in head due to altitude variation, and separately recovering the said combustible uid and said solids at the discharge end of said pipe; the relative amount of said combustible liuid thus introduced into said pipe being at least suicient to maintain nonoxidizing conditions in said pipe throughout its length; said solids being initially of such size that they will readily settle out of said mixture upon standing for a short time.

10. The method of transporting crushed coal and combustible fluids through a transmission pipe, comprising, introducing substantially continuously into a transmission pipe adjacent the inlet end thereof under superatmospheric prescent said inlet end as a propellant and as a reducing agent a reducing combustible gas mixture containing a readily liquiable hydrocarbon under superatmospheric pressure, maintaining a reducing condition throughout the pipe by virtue of the presence of said gas mixture, maintaining a high linear velocity of the coal, water and gas in said pipe chieiiy by virtue of the kinetic energy of the fluids introduced adjacent said pipe inlet, thereby causing the coal to be suspended in said water in a non-stabilized form, discharging the whole mixture at a pressure lower than inlet pressure from the outlet end of said pipe as a stream and separately recovering therefrom said coal and said combustible gas mixture, said crushed coal initially being of such size that it normally settles readily in water.

1l. The method dened in claim 10 in which the size of the crushed coal particles is of the order of 1ML-inch in diameter.

l2. The method dened in claim 10 in which said combustible gas mixture is comprised of C3 and C4 hydrocarbons.

13. The method defined in claim 10 in which the crushed coal is in the size range about 1A,- inch and somewhat smaller in diameter and in which said coal is largely deashed prior to its introduction into said pipe.

14. The method defined in claim 10 in which said combustible gas mixture is largely natural gas containing appreciable amounts of condensable hydrate-forming hydrocarbons.

15. The method deiined in claim 10 in which the said combustible gas mixture is comprised of at least one of the hydrocarbons from the group consisting of propane, propylene, butane and butylene, and in which the said hydrocarbons are introduced into said pipe at a temperature considerably above 60 F.

16. The method of transporting crushed coal and combustible iiuids to a distant point through a transmission pipe, comprising, continuously introducing into said pipe adjacent the inlet end thereof under considerable superatmospheric pressure a non-stabilized suspension of crushed coal in water, simultaneously continuously introducing into said pipe adjacent said inlet as a liquid under still higher pressure a fluid that is gaseous under normal temperature and pressure conditions which Huid is non-oxidizing and combustible, vaporizing at least a portion of said uid in said pipe, so proportioning the amounts of said suspension and said iluid that said fluid is at least in part the propelling force which initiates high stream velocity in said pipe greater than the coal settling velocity therein, thereby transporting said suspension and said uid to the non-oxidizing condition throughout said pipe, discharging the whole at said discharge end and separately recovering said coal and said fluid; the initial size of said coal being such that it readily settles in water upon standing a short period of time.,

References Cited in the file of this patent UNITED STATES PATENTS

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