US2652591A - Method and apparatus for the treatment of pitch - Google Patents

Description

H. c. KUHN 2,652,591 METHOD AND APPARATUS FOR THE TREATMENT OF' FITCH sept. 22, 1953 Filed Jan. 5l, 1951 AII..

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INVENTOR Herman C. Kuhn BY l Wohuqyozwwzdm Magma ATTORNEY Patented Sept. 22, 17953 UNITED STATES PATENT GFFICE METHOD AND APPARATUS FOR THE TREATMENT F PITCH Application January 31, 1951, Serial No. 208,806

3 Claims.

My invention relates to methods and apparatus for use in the water quenching of hot molten petroleum pitch to produce a solid pitch conveniently adapted to conventional methods of storage and transportation. My invention is useful in the disposal of waste pitch produced in the conversion of heavy petroleum oils. More particularly, my invention iinds special utility in the pitching process, described in the applications for United States patents, Serial Nos. 136,069 and 135,427, filed on December 28, 1949, by Harry L. Pelzer and by Leroy K. Cheney, respectively, by providing a means for converting the pitch produced therein to a form compatible with commerical handling methods whereby the pitch may be transported to a point of use or storage.

The current production of heavy petroleum residual products vastly exceeds the natural demand for such residua in any form. The before noted copending applications describe a process of pitching which increases the recovery of more desirable hydrocarbons from such residua, but which is, itself, accompanied by a large production of petroleum pitch. The problem of the disposal of such pitch is enhanced by almost complete lack of utility as such in quantity, since it is obtained in the liquid state at temperatures usually in excess of 500 or 600 F. and ranging upwards to 900 F. or more. 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 pipe lines of any extended length without heavy nsulation and expensive reheating requirements in order to maintain it in iiuid condition. In addition, liquid pitch cannot be kept at temperatures necessary to maintain it in the liquid state for excessive lengths of time, as it is subject to coking and tar separation whereby the pipe lines and other vessels carrying such liquid pitch become plugged. As a consequence of these considerations, any means for solidifying the pitch, of necessity, must be located in the proximity of the pitching unit. Furthermore, the high softening point of the material prohibits conventional tank storage.

It has seemed necessary to dump the liquid pitch at some convenient location such as in a lake or on an open lield. But, as the material 2 cannot be dumped at one location continuously for any extended period of time, unless unlimited space is available, such procedure provides only a temporary solution. Ultimately, a new location must be found or the solid mass of pitch must be removed by blasting or other equally impractical means. Since extended pipe lines are not commercially feasible, eventually the pitching unit must be closed down for lack of space in which to dump pitch.

The desirable solution of the problem is obviously a means by which hot liquid pitch may be cooled, solidied and fragmented so 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.

By reason of the quantities of pitch which must be handled by any practical cooling means adaptable to commercial operation, water appears to be the most feasible coolant from an economic standpoint.

Several previous proposals have been made using Water as a coolant.

It has been proposed to use a water-cooled drum aking unit to produce a naked solid pitch. Such means are satisfactory in small scale operation, but are not practical when normal commercial production is contemplated, as equipment costs and size become prohibitive. For example, for such a unit to handle 10 barrels of fluid pitch per hour, a relatively small quantity in a commercial sense, would require a pair of drums 10 feet by 10 feet. Moreover, vast amounts of power are consumed in rotating the drums against the aking edge in order to overcome the strong adhesion of the solid pitch to the drums.

It has been proposed to effect cooling by water sprays directed against liquid pitch on a flexible steel conveyor belt. To operate such a system satisfactorily, even at the low pitch rate of 10 barrels per hour, would require a flexible steel belt conveyor of inches width. The largest such unit which appears tobe available at this date is only 72 inches wide. Again, the equipment size for commercial operation is excessive.

I have found that hot liquid pitch can be economically and practicably quenched with water on a commercial scale by introducing precooled liquid pitch to a fragmenting and di"- persing zone in which a rapidly revolving vortex of water slices the entering stream of pitch and simultaneously displaces the sliced fragments. The water stream carries the fragments through a cooling zone and then into a collecting zone in which the particles of pitch are caused to fall out of suspension by lowering the velocity of the moving water.

It has before been proposed to cool liquid pitch by direct contact with a body of water. Such methods to this time have been unsatisfactory because the product is friable and bulky with low apparent density, and has= a. multitude of. pores. Also, there is a large production of nes. 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; handlingv equipment.

Moreover, hot uidpitch is lighter than water and floats upon the surface forming a blanket. The underside ofthe 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 ineicient 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 solidies 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 has substantially even fragment size, high density, and is non-friable. The fragments formed are` smooth, hard, glass-like pellets which are particularly useful as a solid bituminous fuel, are easilyA 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 discharging liquid pitch through a restricted opening, such as a small bore pipe, directly into a rapidly rotating vortex of water coolant. The vortex is obtained by introducing water at high velocity in a direction substantially tangential to the inner surface of a cylindrical chamber. The rotating water stream, by reason of its velocity, simultaneously slices the pitch entering the chamber and displaces the sliced fragments. Proper slicing action is provided by introducing pitch in a line substantially radial to the chamber and at right angles with the axis thereof.

I have found that, because the pitch fragments tend to separate from the water vortex, itis important to provide prolonged contact vwith the water coolant to insure solidi'cation of the` fragments before they aggregate by centrifugal action. Proper dispersion is provided by causing the water vortex in the fragmenting and dispersing zone to gravitate downwardly in a helical path. The rotating water stream carries the sliced fragments of pitch in a dispersed state in its downward path. By placing the cylindrical chamber vertically, as ahead on'a larger vertical cylinder which is adapted to confine the water coolant as a body of water, I am also able to provide the necessary duration of coolant contact and at the same time to collect the solidified fragments. A baille, disposed in the upper end of the lower cylindrical chamber, just beneath the head, separates the body of water in the lower chamber from the vortex in the head. An outlet placed at the upper end of the lower chamber beneath the baille carries a fractional part of the circulated water. The purpose of this connection is to continuously draw off any particle of pitch which has not settled to the bottom of the pitch cooling and collecting zone.

It is also essential to the production of hard, pelleted pitch, as described above, that, prior or to introducing the liquid pitch into the water vortex, it be cooled to a temperature between the softening point temperature of the pitch and the temperature atwhich the density of the liquid pitch is equal to that of the coolant water. Failure so to pre-cool the liquid pitch results in a soft, porous product, produces a less even fragment size and causes a large production of nes and floaters.

Figure l is a conventional flow. diagram of the apparatus.

Figure 2 is an elevation view of an enclosed.

tank which is specifically adaptedl to carry out the process of my invention. Figure 2 is par an elongated cylindrical chamber 2 which isv tapered at its lower end to a small opening 3 adapted to the discharge of solid fragments of pitch admixed with water. The upper endA of chamber 2 likewise is tapered to a smaller diame ter having small. cylindrical headt surmounted thereon. Head 4 is capped at its upper end` 5. Head 4 is provided with a pitch inlet 6, which conveniently is a nozzle, and with awater inlet 1 which directs the path of. the entering water in a direction tangential to the interior surface of cylindrical head 4.

A cone 8 is mounted at the upper end of chamber 2 and centrally located therein. An outlet 9 provides egress from the upper end of cone- 8 to without tank i.

Figure 1 shows the use of such an apparatus in a typical pitching operation in which hot liquid pitch is produced in unit I charged with a heavyy petroleum residuum through linev Il. Lower boiling hydrocarbons are withdrawn as overhead through line I2 and the hot liquid pitch at typical temperatures of about 550 to 650 F. is withdrawn from the pitching unit through` line i3. Again, reference is made to the pitching opera.- tions described in the copendingY applications of Harry L. Pelzer and Leroy K. Cheney.. A centrifugal pump I4, or other suitable pumping means, directs the hot liquid pitch in line I3 through pre-cooling means l5.

Pre-cooling may be effected by several means. It is preferred that the step be carried out ina 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 asa direct contact coolant. The drop stack method is considered less desirable, primarily as it doesnot provide a good temperature control. Temperature control in the pre-cooling operation is quite critical as the pitch must' not be cooled so closeV to its softening point that it may clog line I3 'or the nozzle at inlet 6.

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 solidifieson 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 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 tank I. However, as liquid pitch is cooled, its density increases and equals and then exceeds that of water before the pitch hardens.

According to my invention the pitch is precooled in exchanger I5 to about 350-450" F. in the case of a pitch having a softening point of 282 F. and having a specific gravity of about 1.0 at 550 F. or about 425-550 F. in the case of a pitch having a softening point of 324 F. and having a specific gravity of about 1.0 at 650 F., 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 closer4 to the softening point.

The pre-cooled liquid pitch is delivered from exchanger I5 through line I3, without substantial loss of temperature, to water inlet 6. I have found it advantageous to provide van electrical resistance heating element in the nozzle at inlet 6 in order to prevent clogging of the nozzle due to contact with cold water in head 4 during starting and operation at partial capacity. By nozzle I refer to any conventional element used to discharge a fluid under pressure, a simple pipe will suffice.

Water is introduced by line I6 to unit I, through tangential inlet 1, under suficient head to impart a high velocity to the water discharged in head 4, thereby causing the water to flow in a rapidly rotating manner downwardly about the inner surface of head 4. The downwardly gravitating water in head 4 contacts hot pitch discharged by inlet 6, slices it into small fragments, and carries the fragments downwardly to chamber 2 of unit I. As a consequence of the larger diameter of chamber 2, the velocity of the downwardly rotating current of water is considerably reduced on entry into chamber 2 and the pitch which is in the water stream tends to fall out of suspension. The particles have, at such point, solidified by contact with the coolant. The solid particles of pitch sink and are collected at the bottom 3 of chamber 2.

slurry pump I8 withdraws water and pitch particles from chamber 2 through lines 9 and I1, respectively attached to cone 8 and to bottom 3. l

Pump I8 delivers the pitch particles with water necessary to suspend the particles through line I9 to dewatering hopper 20 which is located at a convenient point for use, storage, or disposal.

Water is withdrawn from hopper through 6 line 2| by pump 24 and recycled to unit I by line I6. A small quantity of water required to make up water losses of the system is introduced to line 2l by line 25.

Solid particles of pitch are withdrawn from the bottom of hopper 20 through valved line 22 through which the solid particles may be removed and dried, for example, on a continuous conveyor 23.

Alternatively, line I9 may deliver the pitch particles and water directly to the pitch storage area in which event pump 24 will withdraw water from the drainage basin at the pitch storage area and the dewatering hopper 20 will be eliminated.

My invention has several important advantages. It provides a simple means for pitch disposal. My invention provides an entirely closed system requiring a minimum of contact with air. No mechanical equipment other than conventional pumps is required, and cooling water serves the multiple function of fragmenting, cooling and transporting the solid pitch particles to a convenient point for storage, disposal or use. The water requirements of the system are not great, particularly as evaporation in hopper 20 will generally hold the Water temperature to about F. or lower which is entirely satisfactory; so make-up water is needed only to replace that evaporated and not to control the temperature of the coolant.

I claim:

1. In the process of cooling and solidifying hot molten petroleum pitch by contact with .a water coolant. the steps of rapidly revolving a stream of water coolant in a downwardly gravitating helical path by tangentially injecting water coolant on the inner surface of a vertically positioned cylinder, introducing liquid pitch at a temperature above the softening point temperature of the pitch but below that at which the specific gravity of the pitch is equal to that of the water coolant into said stream of water coolant in a direction substantially radial to `and at right angles with the vertical axis of the cylinder, whereby the liquid pitch is simultaneously sliced into small fragments and is displaced downwardly by the water stream, carrying the sliced fragments of pitch in contact with the water stream through a cooling zone, and collecting the solid fragments of pitch by reducing the velocity of the water in a collecting zone.

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 equal to that of the water coolant, rapidly revolving a stream of water coolant ina downwardly gravitating helical path by tangentially injecting water coolant on the inner surface of a vertically positioned cylinder, introducing the cooled liquid pitch into said stream of water coolant in a direction substantially radial to and at right angles with the vertical axis of the cylinder, whereby the liquid pitch is simultaneously sliced into small fragments an-d is displaced downwardly by the water stream, carrying the sliced fragments of pitch in contact with the water stream through a cooling zone, and collecting the solid fragments by reducing the velocity of the water in a collecting zone.

3. An apparatus of the type described which comprises a vertically positioned elongated cylindrical chamber, a vertically positioned cy1in mmm-n drcal head havng'a smaller `diameter thanthat. of the chamber andjoinec'ltheretok above the up` per end. thereof, a pitchinlet-mountedf in*` the head substantially radial to andA atrght angles with the vertical axis ofk the head; a Water discharge inlet mounted inthe; head substantially tangential tothe inner surfacel thereof; abafllef. disposed within the chamber atl ther upper' endl thereof and located to intercept the gravty'owof i Water kand. displacedl particles'of pitch` intcrsaid chamben an outlet at; the under surface. of the: baille, and anA outlet attheflower'endof thecy-f lindrcal chamber;

HERMAN C: KUHN;

References.l Cited irr the..v fileu of this. patent'.

UNITED S'llflTESv PATENTS Name Date Stevens Feb. 24; 1'91'4 Perry et al. Dec. 26', 1916 Walters May 1, 19'17' All'en July 4, 1'933 Hayes Mart 11', 1947 Me-'ghan etv al May 1'7`, 1949

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