US2763894A - Cooling and solidifying molten asphalt - Google Patents

Description

pi. 25, 1956 w. L. BULKLEY EI'AL v 2,763,894

COOLING AND SOLIDIFYING MOLTEN ASPHALT Filed June 21, 1955 2 Sheets-Sheet l A Liquid Coo/am Level i William L. Bulkley John R. Krebs Lawrence 71 Wrig/lf INVEIVTORS.

Q W (/W A TTOHWEY Sept. 25, 1956 Filed June 21, 1955 W. L. BULKLEY H COOLING AND SOLIDIFYING MOLTEN ASPHALT 2 Sheets-Sheet '2 William L. Bulk/6y John E. Krebs Lawrence 7. M rifigf INVENTO 5 e on [4W A 7' TORNEY United States Patent COOLING AND SOLIDIFY IN G MOLTEN ASPHALT William L. Bulkley, Munster, and John R. Krebs, Indianapolis, Ind, and Lawrence T. Wright, Homewood, IlL, assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana Application June 21, 1955, Serial No. 517,032

7 Claims. (Cl. 18--15) This invention relates to a method and apparatus for handling asphalt and preparing it for packaging. More particularly, it relates to a method and apparatus for cooling and solidifying asphalt in the form of a film by contact with the surface of a moving stream of water.

The preparation, handling and packaging of asphalts have presented great difiiculties in the past. It has been customary in preparing asphalts for packaging, to transfer hot asphalt from a preceding treatingstep or separation to an intermediate holding or filling tank so that it may cool to a temperature where it can be handled further. It is then generally pumped to a pouring station where relatively expensive clay-coated fibre-board cartons are filled with the molten material and allowed to cool for a period of one to two days before shipping. There are several aspects to this method which are undesirable; these are excessive cooling and handling time, costly removal of leakage and spillage, and rigorous safety precautions necessary when handling molten asphalts. Asphaltic type materials commonly have a very low thermal conductivity which makes them extremely difficult to cool from the liquid to the solid phase in bulk form. The one to two day cooling period mentioned above is necessary to assure that the asphalt container packages are chilled sufficiently throughout to permit stacking them on top of one another for economical shipping.

Various methods have been suggested to overcome the difiiculties enumerated above. Some of these have been to insert cooling means in the containers to reduce the cooling time, drum chilling techniques have also been proposed, but, for one reason or another, these methods have either proven inoperative or economically unfeasible.

It is, accordingly, a primary object of this invention to provide a method of cooling and solidifying molten asphalt material so that it may be readily handled. It is a further object to provide an apparatus to carry out this method.

It has already been proposed to continuously cool and solidify molten asphalt by distributing a layer of the molten material on a moving belt submerged in water. This general method has many drawbacks, however, in that the equipment is rather complicated and expensive and the solidified material is not in a form which may be readily packaged. It has also been found, when using a device of this type, that the asphaltic type material tends to adhere to the conveyor belt and ultimately causes the process to be interrupted.

Methods of cooling and solidifying Various molten thermoplastic materials by contact with a moving stream of liquid coolant have been suggested. None of these methods, however, have proven applicable for cooling and solidifying molten asphalt. Physical properties such as surface tension make the problem of cooling molten asphalt very diflicult. For instance, when molten asphalt is spread on a stream of liquid coolant, surface tension effects cause gross irregularities and complete ruptures if any flaws are present in the edge of a sheet formed in this manner. When forming slabs of wax by such. a process, difficulties of this type are not encountered. Of

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2 the many incentives for developing a continuous method for cooling and solidifying molten asphalt, one of the most important is the elimination of any preceding cooling or holding step before the solidification step. To be economically feasible, such a process must be able to accept molten asphalt at a temperature in the range of 400 to 500 F. The methods proposed by the art for cooling plastic materials, such as wax, on a moving stream of liquid coolant do notsuggest a solution for this problem.

It is an object of this invention to provide a method for forming a continuous sheet or film of asphaltic type material on a moving stream of water without the use of belts or other complicating equipment to support the sheet or film of asphalt.

Another object is to provide a method of cooling and solidifying molten asphalt by forming a continuous sheet or film on a relatively rapid flowing stream of water whereby the asphalt, of substantially the same density as the water, does not sink, but floats on the surface of the water. Still another object is to provide an apparatus to carry out the above method.

A further object is to provide a spout for forming a sheet or film of molten asphalt of substantially uniform thickness whereby the sheet or film so produced may be distributed on a stream of flowing water in a continuous fashion in which the film'is not subject to irregularities in width. Additional objects will become apparent to those skilled in the art as the description of the invention proceeds.

A method whereby the above objects are accomplished comprises forming a sheet or film of molten asphalt of substantially uniform width and thickness, which thickness is less than 4; inch and preferably about & of an inch. This sheet or film is then flowed from a distance of from about /2 to about 3 inches, and preferably about one inch, above a stream of Water which has a lineal velocity of from about /2 to 6 feet per second, and preferably about 2 feet per second, and which stream of Water is at least about three times as deep as the thickness 'of the sheet or film, and has a temperature of from about 45 to F., and preferably about 65 F. The sheet or film then flows concurrently with and on the surface vof the moving stream of water until it has been substantially cooled and solidified. The film and water are then separated by conveying the solidified film above and away from the water stream. Traces of surface moisture are removed by air jets, or other suitable means, before passing the film on to a collecting roller or into an extruder.

An apparatus to carry out the objects, as hereinbefore pointed out, comprises a sluice or trough and necessary auxiliary equipment for maintaining a stream of water moving at a lineal velocity of from about /1 to 6 feet per second at a temperature from about 45 to 100 F., and means to form a sheet or film of molten asphalt of substantially uniform width and thickness disposed above one end of the sluice or trough. The thickness of the film should not be more than about A; of an inch. The sheet or film forming means maybe a receptacle having one edge substantially the same length as the desired Width of the film, this edge being horizontal and plarallel to a plane transverse to the direction of flow of the stream of water, with a bafile disposed in a plane panallel to and directly above the edge whereby surface irregularities in the sheet or film of molten Iasphalt passing over the weir are removed. An inclined surface is disposed below this edge and is provided with lateral retaining means whereby the molten film of asphalt is confined on the surface. Flow distributing and straightening vanes substan. tially parallel to the lateral retaining means are also provided on the surface disposed logarithmically from the: center to the lateral retaining means whereby the flow velocity of the sheet or film moving on the surface is substantially equ alized. The lip of'this surface is positioned at a distance of from about /2 to 3 inches, and preferably about one inch, above the stream of water whereby the sheet or film of molten asphalt is distn'buted onto the surface of the stream of water. Means for separating the water and the substantially cooled and solidified sheet or film are provided and means for collecting the film in an appropriate manner such as rolling on a mandrel to form a cylinder or feeding to an extnider to obtain a desired shape or form are also provided.

In the accompanying dnawing, the process of the invention is depicted and a preferred form of apparatus to carry out the process is shown.

Figure 1 depicts, in diagrammatic form, the overall process of forming a continuous sheet or film of asphaltic material :and shows one apparatus which may be used to carry out the process.

Figure 2a is a side view section drawing illustrating a preferred embodiment of the spout used to form the sheet or film. Figure 2b is an isometric drawing of this embodiment.

Figure 3a is a front viewof another embodiment of the spout. Figure 3b is a side view of this embodiment.

The process and apparatus depicted in the drawing will be particularly described with respect to forming a continuous film of roofing asphalt prepared by air blowing a reduced mid-continent crude to the specifications shown in Table I.

Table I Softening point 180 Penetration, ASTM at 77 F 35 Specific gravity 0.995 Flash point, F. (Cleveland Open Cup) 525 It is understood that with various modifications apparent to those skilled in the art, the process and apparatus are also applicable for preparing continuous sheets or films of any asphaltic material.

Referring to the drawings, in Figure 1, asphalt is supplied from a suitable source 1 to the spout 2; the sounce 1 may be a preceding process step, a holding tank or the like. The spout will be described in greater detail hereinafter. A thin film of molten asphalt flows from the spout 2 and onto the surface of a moving stream of water 3. The water stream is confined in a flume 4 and the water is fed to the flume from a reservoir 5 over a weir which distributes water uniformly across the width of the flume and reduces turbulence. Said reservoir is maintained at a predetermined level by recycling from container 6 through line 7 by means of a pump 8. A heat exchanger 9 is provided to cool the water. Make up water is supplied through line 10 as required. The asphalt film then tnavelsconourrently with the stream of water and on its surface for a distance necessary to effect substantial cooling and solidification. For instance, in handling an asphalt of the type commonly designated as a roofing asphalt and having physical inspections as shown in Table I, it was found convenient to make the length of the flume about 55 feet. After traveling in contact with the water for this distance at a speed of about 2 ft./sec., or a total contact time of slightly less than thirty seconds, the temperature of the film was about 100 F. as compared to a temperature of about 450 F. when it first contacted the stream of water.

At the end of the flume, the asphalt film and stream of water are separated. The water stream is collected in a reservoir 6 and recycled fas hereinbefore described. The film of substantially cooled, dried and solidified asphalt is freed from surface moisture by lair jets 21 and rolled to form a cylindrical shape by means of a mandrel 11. Of course, other means could be used to collect the asphalt film; for instance, the film of asphalt could be fed to a hopper and then into an extruder, or, if desired, the film could be formed into sheets of desired thickness by various means.

In Figure 2, a preferredembodiment of the spout is shown. Molten asphalt is admitted to the receptacle 12 and passes over the weir formed by edge 13. An adjustable oveiflow baflle 14 is provided to reduce surface waves and turbulence effects and thereby produce a film of morenearly uniform thickness. The inclined member 15 is essential to the formation of a film of substantially uniform thickness. Although the film flowing from the weir 13 is initially of uniform thickness, it immediately becomes non-uniform due in part to the higher velocity of asphalt at the center of the weir. The inclined member 15 causes the flow velocity :across the width of the film to approach a constant value thus resulting in a film of 1016 uniform thickness. Flow straightener vanes 16, consisting of parallel longitudinal baflles spaced logarithmically from the edges to the center of the member, are provided to further insure uniform film thickness. The distance A from the lip of member 15 to the water bed 3, and the angle B of the member 15 with the horizontal, are dependent upon the physical properties of the material being handled. Fora typical roofing asphalt, as hereinbefore described, the distance A is approximately one inch and the angle B is between 20 and 60. The distarrce between, and the number of, the flow straightener vanes is not critical and depends upon the type of material being lt andled. The use of these flow straightener vanes is to ofier the greatest resistance to the flow of the film where the velocity would be the highest without such vanes, i. e., the flow velocity of a film moving on a surface with edges would be greater at a point intermediate the edges due to the friction between the material and the edges. This would tend to cause the film to be of somewhat greater thickness in the center than at the edges if the flow straightener vanes were not used.

Another embodiment of the spout is shown in Figure 3. Molten asphalt is admitted to conduit 17 through line 18. A slit type orifice 19 is provided along the length of conduit 17 of substantially the same length as the desired Width of the film to be formed. The molten asphalt is emitted from conduit 17 through the slit orifice 19 and flows upon the inclined member 20 and is directed to a point above the surface of the flowing stream of coolant as pointed out with respect to the embodiment shown in Figure 2. Flow straightener vanes may also be provided on member 20 as described in connection with the embodiment shown in Figure 2 depending upon the degree of uniformity of thicknesses desired in the finished film of aspha1t..

Although not shown in the drawings, heating elements may be provided on the pouring spout to aid in preheating the unit before starting up or for supplying heat in the event the apparatus is used only intermittently and does not have time to reach equilibrium operating conditions.

Table II is given as a typical illustration of our process and the use of the preferred form of our apparatus as shown in Figure 1. In this example, the asphaltic material is a roofing asphalt as described in Table I.

Table 11 Water bed depth inches A Flume width do 18 Flume length ft 55 Water flow rate lb./min 200 Water speed F. P. M 140 Water temperature (hot) F Water temperature (cold) F 65 Asphalt temperature (hot) F 450 Asphalt temperature (cold) F -100 Sheet dimensions (average) inches 12 /2 X Asphalt flow rate lb./min 24 Speed of the moving water stream 3 is dependent mainly upon the slope of the sluice 4; while the quantity of water supplied to the reservoir will fix'flie depth of the water bed. The values for speed and depth of water quoted in Table I are average values and may be varied depending upon the properties of the material being chilled and the amount of heat to be removed. It is an essential feature of the process that the stream of water moves at a relatively fast rate, i. e., from about /2 to 6 feet per second. Moving the water stream at such a rate draws the film away from the lip of the spout at a correspondingly fast rate and reduces the tendency for excessive boilingand steaming at this point and also keeps the film from dipping below the surface of the water and causing it to sink thereby contacting the sluice and upsetting the operation. If velocities lower than about /2 ft. per second are employed,'and even though the asphalt flow rate is reduced, the film tends to submerge in the water and excessive steaming and boiling is encountered which results in non-uniformity in the film. At water flow rates of greater than about 6 feet per second, excessive turbulence of the water stream is encountered causing irregularities in the film surface, and the length of the flume to obtain adequate contact time becomes economically unattractive. For instance, at a water flow rate of 10 feet per second, to obtain the necessary cooling of the asphalt film, the sluice would have to be about 300 feet long.

The bed depth should be at least three times the thickness of the film in order that any slight submergence of the film as it enters upon the moving water stream will not permit the film to contact the sluice itself and thereby cause operational difliculties. Since the slip velocity between the asphalt sheet and the transporting cooling medium is negligible, additional bed depth will tend to cause the terminal asphalt temperature to approach more closely the initial coolant temperature.

The dimensions of the flume 4 will depend primarily upon the properties of the material being chilled and the sheet width which can be economically handled.

Large variations in the temperature of the asphalt at the pouring spout have only a minor influence on the time required to chill the asphalt sheet to a specified handling temperature. The same is true of small variations in coolant temperature. Sheet thickness, however, is instrumental in fixing the time variable as the cooling rate is almost entirely dependent upon the thermal conductivity of the material. Inasmuch as the cooling time increases at a much greater rate than the rate of increasing thickness of the film, it is obvious that, if a sheet of appreciably greater thickness than /8 inch is produced, the cooling time and, consequently, the length of the flume necessary to afford this contact time would be economically unfeasible.

It has been found that the asphalt may be handled in a shorter fiume by supplying additional cooling water to the top side of the moving film. However, such additional water should be applied downstream from the pouring station a suitable distance so that the film surface does not pockmark excessively when the water strikes it. Fog or spray nozzles have also been found to be useful in this application and tend to give a smoother surface finish to the film than the use of running water. If surface finish is not an important criterion, applying cooling water to both sides of the film will result in de creased fluid length at the expense of complicating the equipment. It is essential that, if water is applied to the top side of the film, the application be uniform across the film to prevent wrinkling due to uneven thermal contraction.

In addition to detracting from the appearance of the asphalt surface, excessive pockmarking from overhead water sprays may result in occluding water which cannot be removed by air jets or other simple means but which will produce foaming when the asphalt is melted for use. Asphalt cooled by the process herein described with no water supplied to the top surface, or with such water supplied so as to minimize pockmarking, has been found to contain no occluded water as measured by the standard ASTM Test D-46.

The advantage of the particular spout which has been described hereinbefore becomes quite apparent when compared to other methods of forming sheets or films of asphaltic material. For instance, when a simple slit type orifice is used to form the film directly above a moving stream of water, a film is formed which varies in thickness and is generally substantially thicker in the center than at the edges. The edges of a film so formed have a pronounced tendency to tear and quite often this results in a complete rupture and consequent discontinuity in the film. It is impossible to form a uniform cylinder by rolling such a film due to its non-uniformity in thickness, such a cylinder would be much thicker at its center than at its ends. Discontinuities in the film would, of course, interfere with the continuous operation of the process as hereintofore described.

As pointed out previously, this process and apparatus is applicable for cooling and solidifying any asphaltic material by forming a continuous sheet or film on a relatively rapidly moving stream of Water wherein a film of substantially uniform thickness not subject to tearing or rupture at its edges is desired.

It is contemplated that those skilled in the art may make various changes without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawings or described in the specification but only as limited in the appended claims.

We claim:

1. The process for handling asphalt which comprises forming a film of molten asphalt of substantially uniform width and thickness which thickness is less than about A; inch, flowing said film from a distance of from about /2 to 3 inches above a stream of water, which stream has a lineal velocity of from about /2 to 6 feet per second and which stream is at least three times as deep as the thickness of said film, flowing said film on said stream, separating said film and said stream after said film has been substantially cooled and solidified, removing excess water from the surface of said film, and collecting said film.

2. The method of claim 1 wherein said film is formed by passing molten asphalt over a weir onto an inclined surface, and obstructing the flow of said film on said surface whereby the resultant fiow velocity profile of said film is substantially uniform.

3. The process of claim 1 wherein said substantially cooled and solidified film is collected on a mandrel whereby it is formed into a generally cylindrical shape.

4. The method of claim 1 wherein said substantially cooled and solidified film is collected in an extruder and formed into a generally cylindrical shape.

5. A device for handling asphalts which comprises means for maintaining a stream of water moving at a lineal velocity of from about /2 to 6 feet per second at a temperature of from about 45 to F., means to form a film of molten asphalt of substantially uniform width and thickness, which thickness is not more than about /8 of an inch, means for flowing said film on said stream of water from a distance of about /2 to 3 inches above said stream of water, means for separating said film and said water after said film has been cooled and solidified by contact with said stream of water, means for removing excess water from the surface of said film, and means for collecting said film.

6. The device of claim 5 wherein said means for forming said film of molten asphalt comprises a receptacle having one edge substantially the same length as the width of said film, which edge is horizontal and parallel to a plane transverse to the direction of flow of said stream of water, a baffle disposed in a plane parallel to and directly above said edge whereby surface irregularities in the stream of molten asphalt passing over the Weir are removed, an inclined surface disposed below said edge, lateral retaining means on said surface whereby the molten film of asphalt is confined on said surface, and flow distributing and straightening vanes substantially parallel to said lateral retaining means on said surface, which vanes are logarithmically spaced from the lateral retaining means to the center of said surface.

7. In a device for handling asphalt by passing said asphalt in a molten state through a spout and onto the surface of a moving stream of water, the improvement of a spout which comprises a receptacle having one edge substantially the same length as the width of said film, which edge is horizontal and parallel to a plane transverse to the direction of fiow of said stream of water, a baffle disposed in a plane parallel to and directly above said edge whereby surface irregularities in the stream of molten asphalt passing over the weir are removed, an inclined surface disposed below said edge, lateral retaining means on said surface whereby the molten film of asphalt is confined on said surface and flow distributing and straightening vanes substantially parallel to said lateral retaining means on said surface, which vanes are logarithmically spaced from said lateral retaining means to the center of said surface.

References Cited in the file of this patent UNITED STATES PATENTS 103,852 Dietz June 7, 1870 1,003,406 Ottrnann Sept. 12, 1918 1,327,354 Perry Jan. 6, 1920 1,920,118 Walsh et al. July 25, 1953

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