US2683288A - Treatment of pitch - Google Patents

Description

July 13, 1954 F. J. FONTANA 2,683,288

TREATMENT OF PITCH Filed March 10, 1951 2 Sheets-Sheet 1 FIG FRANK J. FONTANA INVENTOR aim/M 61 0%(Sw ATTORNEYS y 1954 F. J. FONTANA 2,683,288

TREATMENT OF PITCH Filed March 10, 1951 2 Sheets-Sheet 2 FRANK J. 'FONTANA INVENTOR da/Zhmc/MmZ ATTORNEYS Patented July 13, 1954 UNITED TREATMENT OF PITCH Frank}; Font'ana, Long Beach, Califgassi'gnorto': Richfi'eld Oil Corporation,- Los:Angeles,.. Galif:,, a corporationaof: Delaware Aipplicatibn March 10, 1951', SerialNo. 2114;909

cial utility in the pitching process, described intheapplications for United States Patents; Serial Nos; 1236;069 and 135-327, noWPatent No. 2,633,449; filed on December 28, 1949", by Harry'lii. Pelzer and byLeroy K. Cheney, respectively; by'providing a means for converting the pitch produced therein to" a form compatible with commercial" handling methods whereby the pitch may be transported toa point of use-or'storage.

The current production of heavy" petroleum residual products vastlyexce'eds the natural demand for such residua inany form". The" before noted copending applications describe a process of pitching which increases'the recovery'of more desirable hydrocarbons from suchresi'dua, but which is, itself, accompanied by a; largeprod'umtion of petroleum-pitch. The problem of the dis-- posal of such pitch is enhanced by almost complete lack of utility as such in quantity; since-it"is obtainedin the liquid state at'temperatures usually in' excess of 500* or-600 Fj and-ranging=upwards to 900 F: ormore. Moreover; petroleum pitch has a softening-point (R. & B-.)- which is of the order" of 200 to 400 F; and, consequently, cannot be conveniently transported by pipelines or" any exten'dedlength without heavy insulation and expensive reheating requirements in order to: maintain it in fluid condition. In addition, liquid pitch cannot be kept at temperatures necessary to maintain it inthe liquid state for excessive lengths oftime, as it is subject'to coking" and tar separation whereby the pipe lines and other vessels carrying such liquid pitch becomeplugged. As a consequence of these-considerations, any means for solidifying" the pitch, of necessity, mustbe located the proximity of the pitching unit. Furthermore, the, high softening point of the'material prohibits conventional tank l storage.

'It has seemed necessary to" dump the liquid pitch at some convenient; location such' as in a lake or on an open fieldz. But, asv the material cannot: be dumped at" one location continuously for any extended p'eri'odof time, unless unlimited space is. available, such procedure provides only a temporary solution. Ultimately, .a; new-location must be found or the solid mass ofJpitch must be removed by blasting or other equally impractical Also; there a large prod'uctienof fines;

means. Since extended pipe linesare not commercially feasible, eventually the pitchingunitmust be closed clown for lack. of space in which todump pitch. V

The desirable-solution of the problem is obvi ousl'y a means by which hot liquid pitch may be cooled, solidified and fragmentedso that it may easily be handled by conventional conveyors, elevators and other methods of transportation.

. It is even more desirable that the fragmented pitch should have some utility of" itself, for example; as a fuel: It is to these ends that my invention is specifically: directed.

. Byreasonof the quantities of pitch-which mustbehandlec-l by anypractica-l coolingmea-ns adapt ableto commercial operation, Water appears to be the most feasible coolantfrom an economic standpoint;

I havefound that hot liquid pitch can be economically and practically quenched with water on a commercial scale by pouring pre-cooled liquid pitch onto-the surface of a body of waterperhour; a relatively small quantity in a comm'ercial sense", would require a pairof drums 1O feet'by 10 feet. Moreover, vast amounts of power are-consumed in rotating the drums against the flaking edge in order to overcome the strong adhesion'ofithe solidpitch to the drums.

It has been proposed to eitect cooling by water sprays directed against liquid pitch on a flexiblesteel conveyor belt. To operate such a system satisfactorily; even at the low pitch rateof 10' barrels per hour, would require a flexible The largestv such unit which appears. to. be. available Again, the equipment size" for commercial operation is ex steel belt conveyor of I29 inches" Width.

at this. time is only'72 inches wide;

cessiye.

Itj'has before been proposed to cool liquid pitch by direct contact with" a" body of water; Such methods to" thistime have been unsatisfactory because the product" is friable, bulky with low apparent density, and has a multitude'of pores: Such solid fragments as are produced quickly crumble when handled by conventional equipment such as conveyors and elevators. The fine particles are extremely difficult to dry and tend to clog standard mechanical handling equipment.

Moreover, hot fluid pitch is lighter than water and floats upon the surface forming a blanket. The underside of the blanket, which is in immediate contact with the water, as it cools and solidifies, becomes a thin, tenacious, rubber-like, flexible sheet which is an ineificient conductor of heat. The molten pitch above builds up and tends to spread over the surface of the water. Such heat as is transmitted through the blanket to the water generates steam which bubbles up through the molten pitch causing it to froth.- Ultimately, the pitch solidifies in a sponge-like mass.

It is indeed surprising in view of these considerations to find that pitch may be quenched by direct contact with the water, yet I have found it possible to do so without excessive equipment cost or size. Moreover, the pitch produced when using my method and apparatus hassubstantially even fragment size, high density, and is nonfriable. The fragments formed are smooth, hard and glassy-like from about S-niesh size to 2 in size. They are particularly useful as a solid bituminous fuel, are easily dried and do not crumble when subjected to the rough handling of a screw conveyor.

I have been able to obtain such satisfactory results by pouring liquid pitch onto the surface of a body of water, :by confining the blanket of pitch formed within a small area of such surface and by forcibly submerging the blanket beneath the surface as soon as it is formed.

It is also essential to the production of hard, fragmented pitch, as described above, that, prior to pouring the hot liquid pitch onto the surface of the water, it be cooled to a temperature between the softening point temperature of the pitch and the temperature at which the density of the liquid pitch is equal to that of the coolant water. Failure so to pre-cool the hot liquid pitch results in a soft, porous product, produces a less even fragment size and causes a large production of fines and floaters.

The drawings illustrate an apparatus which is specifically adapted to carrying out the process of my invention and which is itself part of my invention.

Figures 1, 2 and 3 show the entire apparatus, respectively, in elevation, plan and cross-sectional views. The cross-sectional view in Figure 3 is taken from line 33 in Figure 1.

Figures 4, 5 and 6, are, respectively, elevation, plan and cross-sectional views of a particular portion of the same apparatus, enlarged to show the important details. Figure 6 is taken at line 6-6 of Figure 4.

The reference numeral I designates a tank adapted to confine a body of water, open at its top and tapered inwardly and upwardly at one end. Thus bottom 2 of tank 1 inclines upwardly toward the tapered end. A launder 3 is provided to maintain the level of water surface 4 in tank I.

At a central point of the water surface 4, cross planks 5 and 6 and longitudinal planks I and 8 are positioned to form an open-ended box which confines a small portion of water surface 4. The planks 5, 6, I and 8 are positioned to extend a short distance above and below the level of water surface 4.

I An inclined catch pan 9 is mounted above the tank in a position to direct the pitch poured thereon to fall into the center of the area of surface 4 enclosed by the box formed of planks 5, 6, I and 8. Catch pan 9 is conveniently provided with sides In and II, and its lower edge is advantageously provided with an upwardly inclined serrated weir I2.

A continuous chain belt I3 is mounted on Wheel and axle assemblies I4, I5 and It which are mounted to the sides of tank I.

The belt I3 comprises two continuous chains I1 and I8, which advantageously are of roller chain construction and which are adapted to pass over wheels I9, 20 and 2| of assemblies I l, I5 and I 8, respectively. Wheels i9, 28 and 2| advantageously are of the sprocket type adapted to receive the links of chains I1 and I8. Cross bar 22 with drag bars '23 mounted thereon are spaced at intervals between chains I1 and I8. Chain belt I3 is conveniently driven by a motor 24 mounted at one of the wheel and axle assemblies, for example, the assembly It as shown in Figures 1 and 2.

Chain I3 is so positioned by assemblies It, I5 and I6 that it passes downwardly through the area of surface t confined by planks t 6, l and 8 to wheel and axle assembly is located at the lower end of bottom 2 within tank i. Chain I3 then passes upwardly along inclined bottom 2 to wheel and axle assembly IE located at the outer tip of the tapered end of tank I. From assembly IE, chain I3 nearly reverses the direction of its path to return above tank I to assembly I5 and thereby complete its path. Chain guards 27 are provided intermediate assemblies I l and IE to prevent the formation of pitch on chains ii and I8 as chain belt I3 passes downwardly into tank I.

Conveniently, tank I is provided with a hopper 25 mounted as a continuation of bottom 2 directly beneath assembly I6. Solid pitch dragged by chain belt I3 from the bottom of tank I is thereby discharged into hopper 25 where it may be collected. Hopper 25 conventionally may be adapted to discharge onto a continuous conveyor '25, for example, for transfer to a zone of storage,

use or disposal.

In carrying out my process, hot molten pitch, which typically is withdrawn from a pitching unit such as is described in the before noted copending applications of Harry L. Pelzer and Leroy K. Cheney, is first subjected to a pre-cooling operation.

Pre-cooling may be effected by several means. It is preferred that the step be carried out in a conventional shell and tube heat exchanger using high pressure steam or hot oil as the coolant. It is, however, practicable to cool the pitch in a drop stack using air, steam or a water fog as a direct contact coolant. The drop stack method is considered less desirable, primarily as it does not provide a good temperature control. Temperature control in the pre-cooling operation is quite critical as the pitch must not be cooled so close to its softening point that it may clog the equipment used to distribute it onto the water surface.

If a heat exchanger is employed, as in the preferred form, almost any coolant, consistent with the economics involved, will be satisfactory if it is capable of being maintained at a temperature above the softening point of the pitch. Water is not satisfactory. The temperature of cooling water without pressure is too low so that a film of pitch solidifies on the inner surface of the tubes, thereby resulting in poor heat transfer and eventual clogging of the tubes. High pressure steam may be used but advantageously fresh feed to the pitching unit is employed. The pitcher feed will normally arrive at the unit hot or will receive preheat by exchange in the usual manner prior to the exchange with the hot pitch. Also, additional preheat is provided for the feed, assisting the thermal balance of the unit.

The hot liquid pitch, at the temperatures at which it is withdrawn-from the pitching unit, has a density which is less than that of the water in the quench tank. However, as liquid pitch is cooled, its density increases, and equals and then exceeds that of water before the pitch hardens.

The table illustrates the relationship between specific gravity and temperature of two pitches which are typical.

Specific Gravity B A is a pitch with an R. and B. melting point of 282 F. B is a pitch with an R. and B. melting point of 354 F.

Such pitches are drawn from a pitching unit at typical temperatures of about 550 F. to 650 F. According to my invention the hot pitch is precooled to about 400 F. in the case of pitch A or about 450 F. in the case of pitch B at which temperatures the pitch has a specific gravity greater than that of water, but is in a free and running condition and not thick and viscous as it would be at temperatures closer to the softening point.

The pre-cooled pitch is delivered without substantial temperature loss to the apparatus pictured in the drawings where it is poured onto catch pan 9, for example, through a nozzle. Catch pan 9 is suitably warmed prior to the initiation of operation to prevent its clogging during warm-up. Chain belt I3 is moving in a counter-clockwise manner as illustrated in the drawings and water is placed in the tank to the level indicated so that planks 5, 6, I and 8 extend above and below the level of water surface 4 to a depth suflicient to confine the floating blanket of pitch.

As the liquid pitch falls off catch pan 9 into the open-ended box formed by planks 5, 6, I and 8 it is somewhat broken u and separated by serrated weir IZ. Drag bars 23 which are continuously passing downwardly through the box pull the pitch under water surface 4. Any blanket of pitch forming on water surface 4 is confined be tween planks 5, 6, i and 8 and so is readily submerged by drag bars 23.

Once under water the pitch solidifies in fragments and sinks to the bottom of tank I.

As the size of tank I is necessarily limited, cold water make-up must be added continuously or intermittently to prevent excessive rise of temperature in the water in tank I. The temperature of such water is not critical except that of course the cooler the water, the quicker the pitch solidifies. I have found it quite practical to maintain a water temperature in the range of about F. or less. However, higher temperatures may be employed. A great part of the heat removed from the pitch is absorbed by the generation of steam from the water in immediate contact with the molten pitch with the result that the control of the average temperature of water in tank I is not difficult.

I have found it quite convenient to add makeup cold water by spraying it on chain belt I3, particularly on cross bars 22 and drag bars 23 just prior to their entry into the box formed by planks 5, 6, i and 8. Such point of addition serves a second useful result inasmuch as liquid pitch exhibits a minimum adhesive effect to wet metal. It is not quite as convenient to add make-up water by wetting the surface of catch pan 9 as such practice may cause excessive cooling of catch pan 9 and result in the partial solidification of pitch thereon with the eventual clogging of catch pan 9 and interruption of operation. The solidified pitch fragments sink to the bottom 2 of tank I where they are removed by the chain belt I3 as it moves upwardly across bottom 2, and are discharged into hopper 25, from which they may conveniently be removed on conveyor 25.

A possible alternative process would involve the removal of catch pan 9 and introduction of precooled liquid pitch directly into the area of water surface & enclosed between open-ended box formed by planks 5, 6, I and *8. However, I prefer the means illustrated by the apparatus shown in the drawings.

I claim:

1. In the process of cooling and solidifying hot molten petroleum pitch by contact with a water coolant, the steps of pouring hot molten pitch, at a temperature above the softening point temperature of the pitch but below the temperature at which the specific gravity of the pitch is less than that of the water coolant, onto a surface of a body of water coolant, and mechanically pulling the pitch beneath the said surface of the body of water.

2. In the process of cooling and solidifying hot molten petroleum pitch by contact with a water coolant, the steps of cooling the hot molten pitch to a temperature above the softening point temperature of the pitch but below the temperature at which the specific gravity of the pitch is less than that of the water coolant, pouring the cooled liquid pitch onto a surface of a body of water coolant, and mechanically pulling the pitch beneath the said surface of the body of water.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,088,635 Stevens Feb. 24, 1914 1,638,669 Wachtel Aug. 9, 1927 1,780,201 Martin Nov. 4, 1930 2,446,784 Daley et a1 Aug. 10, 1948 2,471,559 Dolezal May 31, 1949 2,464,187 Seaton Mar. 8, 1949 2,510,574 Greenhalgh June 6, 1950

Claims (1)

1. IN THE PROCESS OF COOLING AND SOLIDIFYING HOT MOLTEN PETROLEUM PITCH BY CONTACT WITH A WATER COOLANT, THE STEPS OF POURING HOT MOLTEN PITCH, AT A TEMPERATURE ABOVE THE SOFTENING POINT TEMPERATURE OF THE PITCH BUT BELOW THE TEMPERATURE AT WHICH THE SPECIFIC GRAVITY OF THE PITCH IS LESS THAN THAT OF THE WATER COOLANT, ONTO A SURFACE OF A BODY OF WATER COOLANT, AND MECHANICALLY PULLING THE PITCH BENEATH THE SAID SURFACE OF THE BODY OF WATER.

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