US2689047A - Pebble flow control for a pebble heat exchanger - Google Patents

Description

Sept. 14, 1954 PEBBLE FLOW CONTROL FOR A PEBBLE HEAT EXCHANGER L. C. BEARER 2 Sheets-Sheet l ATTORNEYS I.. C. BEARER Sept. 14, 1954 PEBBLE FLOW CONTROL FOR A PEBBLE HEAT EXCHANGER 2 Sheets-Sheet 2 Filed July 15, 1949 I'll INVENTOR. L.C. BEARER A TTORNEVS Patented Sept. 14, 1954 PEBBLE FLOW CONTROL FOR A PEBBLE HEAT EXCHANGER Louis C. Bearer, Bartlesville, Okla., assignor to Phillips Petroleum Company, a. corporation of Delaware Application July 15, 1949, serial No. 104,964

9 Claims.

yThis invention relates to a solid material feeder. In one ofits more specific aspects, it relatesto a pebble feeder in pebble heater apparatus. In another of its more specific aspects, it relates to an improved means and method for controlling the speed and volume of pebble flow through pebble heat exchange apparatus.

Thermal treating and conversion processes which are carried out in so-called'pebble heater apparatus utilize a fluent mass of solid heat exchange material, which mass is heated to a high temperature in a first heat exchange chamber and is then caused to contact reactant materials in a second heat exchange chamber furnishing heat to the reactant materials for the thermal treating or conversion thereof. pebble heater apparatus generally comprises two chambers which may be disposed in substantially vertical alignment. The solid heat exchange material is introduced into the upper portion of the first or upper chamber. That material forms a moving or fluent bed of solid heat exchange material which flows downwardly as a contiguous mass through the chamber in direct heat exchange with a first iiuid heat exchange material. The solid heat exchange material is heated to a relatively high temperature in the heat exchange and is then passed to a second chamber in which the hot solid heat exchange material is caused to contact a second gaseous material in av second direct heat exchange relation, furnishing heat for the treatment or conversion of the gaseous material.

. Flow of solid heat exchange material through pebble heat exchange apparatus is in many instances quite difficult to control. When the apparatus is utilized for the purpose of converting hydrocarbons, the flow rate of pebbles through the pebble heater apparatus is very critical to the efficient conversion of the hydrocarbons. It is only by the closest control of the pebble flow rate that it is possible to prevent the over-conversion of the gaseous hydrocarbons by reason of excessive temperatures Within the conversion chamber or to prevent insufficient conversion of the hydrocarbons by reason of insufficient temperatures Within the conversion chamber. The flow rate of solid material has heretofore been partially controlled. by the utilization of many types of flow controllers. Conventional star valves, slide valves, rotating tables, screen conveyors, conveyor belts, and the like have been used for the purpose of controlling the flow of solid materials through heat exchangers. Star valves have proved to be rather impractical in The conventional' pebble heater apparatus for the reason that considerable crushing of pebbles is caused thereby. Insuliicient direct control of solid material ow is obtained when using conventional slide or gate valves. The slide or gate valves also tend to cause bridging of pebbles when nearly closed. All of these, but especially the screw conveyor, give prohibitive abrasion losses because of having sliding contact with the extremely hard pebbles. Also, all of these devices have moving parts which are exposed to the atmosphere within the pebble apparatus. The temperature of the pebbles at the feeder may run as high as 1000 to 1200 F. which makes proper lubrication exceedingly difficult, even with Water-cooled bearings. Pebble dust from this atmosphere gets into the bearings and causes very excessive wear. Moving parts also make diflicult the problem of sealing against gas leaks when super-atmospheric pressures are used, as is becoming more and more common, because some, and usually all, of the moving parts have connections with the outside atmosphere.

Generally speaking, this invention comprises the improvement of pebble heat exchange apparatus by the utilization of an improved vibratory pebble feeder Which avoids all of the above diiiiculties and yet provides for accurate, automatic control of the pebble flow. The feeder is vibrated in such a manner as to make lateral iiow of pebbles possible and improvements are provided so as to overcome any inherent fluctuations and inaccuracies.

An object of this invention is to provide an improved method for controlling the flow of solid materials through a solid'material system. Another object of the invention is to provide an improved means for controlling the rate of flow of solid materials through a solid material system. Another object of the invention is to provide a means for controlling the rate of `flow of pebbles through pebble heat exchange apparatus.

Another object of the invention is to provide an from one pebble heat exchange chamber through `a gas heating or conversion chamber without rapid deterioration or substantial breakage. Pebbles conventionally used in pebble heater ap- 1 paratus are substantially spherical and range from about 1/8 inch to about 1 inch in diameter. 3 In a high temperature process, pebbles having a diameter between 1A; inch and inch are preferred. The pebbles must be formed of a refractory material which will withstand tempera'-` tures at least as high as the highest temperature attained in the pebble heat eichange chambers;

`The pebbles must also be capable of withstanding temperature changes within the apparatus. Refractory materials, such as metal alloys;

' ceramics, or other material having the properties above described may be utilized to form such pebbles. Silicon carbide, alumina, periclase,

i beryllia, stellite, thoria, zirconia,` and mullite may be satisfactorily used t form such pebbles or may be used in admixture with each other or with other materials. Pebbles formed of such lm ateri'als, particularly of alumina and mullite,

when properly iired, serve very well in high tem; peratu're operations, some withstanding tem= peatures upto about 3500" F. Pebbles which are used may be either inert or catalytic when 1 use in any selected process.

Understanding of this invention will be facilitated upon reference to the diagrammatic drawis -a side view of a section of a pebble conduit showing ainea'suring device therein.

In Figure 1 'of the drawing, first pebble chamber I I is provided in its upper end with pebble in= let oolidliit I2 and ''iilelt -Outlet Cond'llt I3. A ffluid heat exchange material inlet conduit I4 i's provided in the lower portion of the first pebble chamben Although the drawing shows l conduit I4 as communicating with the lower portion of irst pebble chamber II at a single peint, it is within the scope of this disclosure that conduit I 4 may eominunicate with the lower por'- tin 'off ehamber II byv'r'riean's of 'a header encir cling the lower portion of chamber I l and com-l inuniating with chamber II through a'plurality of inlets; Second pebble chamber I5 is provided l below chamber I I and is provided in its upper end portion with effluent 'utl'et 'Conduit I6. Pebble conduit I'I is provided 's'o as to communicate between first pebble chamber I I and second -pebble chamber I5. Pebble conduit II extends between the lower portion of chamber II and the upper portion of chamber I5. Pebble outlet conduit I8 provided the lower portion of second pebble chamber I5. Fluid heat exchange material inlet conduit I9 is provided in the lower portion of sec'- ond pebble chamber I5. Fluid conduit I9, like fluid conduit I4, may be connected with the cham# ber with which it communicates by means of a header member and a plurality of inlets from the header into the lower portion of chamber I5.

` Magnetic vibrator 2l is supported from some base,

suoh as second pebble chamber I5 by means of support member v22. Pebble feeder 23 communi- Cates with pebble `outlet I8. Feeder 23 and pebble outlet l2 may be structurally unconnected for opL 4 eration at atmospheric pressure or they maybe non-rigidly connected, for instance by means of bellows Z4, for operation at superatmospheric pressures. The outlet end of pebble feeder 23 likewise communicates with pebble conduit 25 and may be connected thereto by means of bellows member L16. Pebble conduit llcorhihi-inicates with the lower end portion of elevator 7ZI and pebble conduit 2S extends between the upper portion of elevator 27 and pebble inlet conduit I2 in the upper portion of first pebble chamber II. Pebble'feeder 23 is provided in its lower side portion with a hopper which forms a pebble fines collection chamber.r Outlet conduit 29 is provided in the lower portion of the hopper and provides outlet for pebble lines from the pebble heat exchange system. A gate 3l is provided in pebble ure 2 of the drawing, and actuating member 35' is threaded interior-ly so as to cooperate withthe threads of connecting rod 34 and move connecting rod 34 in response to controller 3G. Actuating member 35 can be rotated by any means, not

shown, in response to pebble now through con-l duit25. e

In one modification of the invention, yautomatic control is provided by a source of light 3'I in one side of pebble conduit 25 and photoelectric cell 38 in the other side-of yconduit 25'in the direct rays of a beam thrown by lightfsource 37. Photo.L electric cell 38 is operatively connected to ycon-'- troller 3B. Controller 36 in turn controls the actuation of member 35 for positioning gate 3|.- In another modincation of the invention, as shown in -F-igure 3, a pressure sensitive device 39 supports, at least partly, the downstream end of screen member 30 and is sensitive to the weight 4of pebbles flowing across the rupper surface of lscreen member 3l),l Variations in the weight of pebbles on screen 30 are sensed by device 9 and'transmitted electrically, hydraulically, or mechanically to controller 36 for the positioning of gate 3 I-. In yet another though less desirable modication of the invention, as schematically shown in Figure 5 of theorawings, a continuous belt'tl is mounted on pulley members 42 and 43 in the lower portion of pebble conduit 25 and extends to a point adja cent elevator 2'I-. Scale 44 is provided'adja'ce'nt the upper belt section and is actuated by the weightof `pebbles upon the upper su-rface ofthe belt. Scale d4 also is operatively "connectedto controller 3 6.. y

rRod 45 oi vibrator -2I, as is show-n in Figure l3 of the drawing extends upwardly and generally in a directiontoward the downstream end jof .pebble feeder 23 and is rigidly aflixed to pebble )feeder 23 so as te permit spring-loaded connection, by means of a spring, such as forexample coilspring 4'I,of vibrator ZI to feeder 23. Vibrator 2`I and spring 4'I cooperate by means of opposite forces so that a substantially elliptical path, in a vere tical plane parallel-to the feeder, is described by feeder a3. It is this ellipticalfmotion of feeder the inlet' end thereof so that the pebbles employed will not -substantially continue entering the feeder and flow therethrough after the vibrator has been halted. The angle of repose of pebbles is generally in the neighborhood of 30 fromy the horizontal. More positive control of pebble ilow is obtained when the angle at which the pebble feeder is disposed is considerably less than the angle of repose.

In the operation of the device shown as Figure of the drawings, pebbles are passed into the upper portion of chamber II through pebble inlet conduit I2 and ilow downwardly therethrough as a fluent, gas-pervious, contiguous mass. A first fluid heat exchange material is passed into the lower portion of chamber II and upwardly through the fluent mass of pebbles. Gaseous effluent material is removed from the upper portion of chamber I I through effluent outlet conduit I3. When the pebble heat exchange apparatus is a pebble heater apparatus, the fluid heat exchange material which is supplied to the lower portion of first pebble chamber I I is a hot heat exchange gas or a fuel which is burned on the surface of the downflowing pebbles, imparting heat thereto. The hot gas may be a hot combustion gas formed by the combustion of fuel outside of chamber I I. At times it is desirable to utilize a combustion chamber in the lower portion of the pebble heater chamber and a separate combustion chamber is formed below the pebble mass in chamber Hot combustion gases formed by the combustion of fuel within such a combustion chamber are passed into the lower portion of the pebble bed through perforations in a separation member in the lower portion of the chamber.

Pebbles from chamber are passed into the upper portion of second pebble chamber I5 through pebble conduit Il. The pebbles form a fluent, gas-pervious, contiguous mass within chamber |5 and ilow downwardly therethrough. A second iluid heat exchange material is passed into the lower portion of chamber I5 through fluid heat exchange material inlet conduit I9. The pebbles in chamber I5 act in the heat exchange with the fluid heat exchange material in a manner contra to that in which it acted in the heat exchange in chamber II, i. e., if the pebbles take up heat in the first heat exchange in chamber |I they give up heat in the heat exchange in chamber I5. When the pebbles are heated in cham- 'ber II, the pebbles carry heat into chamber I5 for the purpose of providing heat of conversion to materials which are supplied to chamber through conduit I9.

Pebbles from chamber I5 gravitate through pebble outlet conduit I8 into the inlet end of pebble feeder 23. Pebbles which are passed into a chamber or open space through an inlet in its upper end tend to flow downwardly `and outwardly from the inlet and form a cone of pebbles. After the pebbles have formed this cone, the slope of which is the angle of repose of the pebbles, it apparently is impossible to cause them to move any further laterally merely by applying pressure to the pebbles from above. The same is true for the pebbles entering pebble feeder 23 so that no pebble flow across screen 30 is possible when feeder 23 is still. In this invention, vibratory motion is supplied to pebble feeder 23 by means of vibrator 2|. Pebble feeder 23 is vibrated so that the pebbles are caused to move laterally along the surface of screen 30. Positive movement of the pebbles and some control of 6. their flow is therefore -obtained by controlling the amplitude of vibration of the pebble feeder. However, it has been found that exact control of pebble flow therethrough, especially in the case of large-capacity feeders, can be obtained only through the help of this invention which modifies the passageway through the pebbley feeder by means of gate 3|. Gate 3| is moved in response to controller 36 by actuating means 35. Controller 36 acts in'response to impulses received from a pebble flow measuring devicev such as one of the three measuring devices described above.

The combination of the photoelectric cell and the light source is utilized in the preferred modi.

iication of this invention. Use of this type of measuring device is preferred because it eliminates all moving parts which would be contained in the hot, dust-laden atmosphere of the pebble apparatus. vAt slowrates of flow through pebble feeder 23 the individual pebbles can be counted by a counter connected with the photoelectric cell. At faster rates of flow, however, the flow rate is measured in terms ofthe intensity of light passing through the stream of pebbles and striking the photoelectric cell. Impulses from photoelectric cell 38 are supplied to controller 36 which actuates Aa motor, not shown, which operates member 35 and baille' 3| so as to maintain a, predetermined flow of pebbles through pebble conduit 25.

In a sec-ond modification of the invention, the weight of pebbles flowing across the screen member in the floor of pebble feeder23 makes an impression 4upon the pressureor weight-sensitive member 3S so as to supply animpulse to controller member 36 which causes baille 3| ,to be positioned. A curved weir may be used at the downstream end of screen 30 so that4 the depth of pebbles, and therefore their weight, on the screen will vary directly with the rate of flow.

In the third modification of the invention, a continuous belt is rotated in the lowerportion of pebble conduit 25 so as to catch pebbles from the outlet of pebble feeder 23 and to convey them to the lower portion of elevator 2l. The weight of the pebbles carried on belt 4| is measured by scale 44 which actuates controller 36 to position baille member 3| in response thereto.

Each of the above modications makes possible very close control of the flow of pebbles through a pebble heat exchanger. By this new method of control, variation in pebble flow are automatically and continuously smoothed out. Variations in flow commonly occur from temporary bridging of pebbles in the pebble outlet I 8, from oversensitivity of the feeder device, and from ordinary uctuations in the amount of power supplied to the feeder by the prime mover employed. Pebble feeder 23 also acts to separate pebble fines, which result from breakage `and attrition within the pebble heat exchanger system, from pebbles of desired size. The pebble nes Iare separated by screen member 30 and are removed from the lower portion of pebble feeder 23 through fines outlet 29.

Although screen member 30 is shown in Figure 3 of the drawing as a regular interwoven screen, -that portrayal is entirely schematic. A grizzly or-other type of screen may be used, depending chieily on which type is most practical for the size of pebbles employed. Vibrator 2| could be positioned within pebble feeder 23 so as to vibrate only screen member 30, if desired. However, it is advantageous to maintain the vibrator outside of feeder 23, as shown, so that `dust-"laden atmosphere. struction of the feeder housing is kept smal-ler andsimpler with the vibrator outside.

tuted for the diaphragm motor. `may be arranged to supply the airfhydraulic `die vibrator is not subjected to 'the not, dust- `ber 3U in the lower portion of the pebble feeder and thus eliminate all moving parts within the In addition the con- Altho-ugh `gate member 3| has been described only as a hinged member, it may be a slide-type gate, as shown in Figure i of the drawings. In

Figure 4 mem-ber 3| is shown to be actuated directly by a diaphragm motor instead of a threaded member 35. as shown in Figure 2. It is evident that a pneumatic piston,- Va hydraulic piston, or other suitable follower device may be substi- Cont'roller 36 fluid, electrical current, or other power-supplying medium directly to the motor chosen to operate gate 3| and in the quantities which should secure the desired positioning of the gate. -On the other hand, a positioner may be connected to gate 3| or rod 34 to receive the impulse from controller 36. This positioner checks `on the actual position of the gate and permits force to be applied `until the gate 3| is at the position called for by controller 36. The details and choice of the `cont-roller and follower mechanisms are not part Q of this invention but these are mentioned to indicate how adaptable this invention is to means l already known to the art.

Although gate 3| has been shown as extending across feeder 23 from Athe side, it is within the scope of this disclosure that gate 3| may extend upwardly through the bottom of the feeder or `be pivotally affixed intermediate its ends to the l walls of the feeder. Par-tial control of solid material flow may also be obtained by varying the elevation of one end of the pebble feeder in lesponse to solid material flow therethrough.-

As will be evident to those lskilled in the art, various modifications of this invention can be made or followed in the light of the foregoing disclosure and discussion without departing from the spirit or scope of the disclosure or of the within and supported by the walls of said conduit, said baille being adapted to variably modify a pebble passageway through said conduit; means `to adjust said baffle; and a vibrator extending upwardly and generally toward the downstream l end of said conduit operatively connected to the upstream end portion of said conduit, said vibrator Abeing adapted to supply elliptical motion j to said conduit so as to move pebbles through said conduit.

2. The pebble heat exchanger of claim 7, wherein said adjustable baffle is pivo-ted to a wall of said pebble conduit; an actuating member ex- 1 tending outside of said pebble conduit and operar tively attached to said baille member; and said controller operatively connecting said actuating member and said measuring device.

3. The pebble heat exchanger of claim 7, wherein said measuring device comprises a photoelectric counter in one side of said outlet pebble conduit and a cooperating light source in the 8 side of said outlet conduit opposite said photoelectric counter, said light source being disposed so that light therefrom is spotted on said photoelectric counter across the passage formed by the walls of said outlet pebble conduit.

4.- The pebble heat exchanger of claim 6, wherein a screen is positioned in the bottom side portion of said pebble conduit forming a floor therein; and a fines collection chamber below said screen and having an outlet vin its lower portion.

5. The pebble heat exchanger of claim 6, wherein said vibrator is an electromagnetic type vibrator. y

6. A pebble feeder comprising a laterally and downwardly disposed pebble conduit having an inlet conduit in its upper end and an outlet conduit in its lower end, said outlet being' disposed no lower than 30 from said inlet; lan adjustable baille member within and supported by said conduit and adapted to variably modify a'pebble passageway through said feeder; a vibrator operatively connected to said pebble feeder so asv Ato supply elliptical motion thereto; and a controller operatively connected to and adapted to variably move said adjustable balde member.

'7. A pebble feed-er comprising a laterally and downwardly disposed pebble conduit having an inlet conduit in its upper end and an outlet conduit in its lower end, said outlet being disposed no lower than 30 from said inlet; an adjustable baille member within said conduit and adaptable to variably modify the opening through a pebble passageway through said feeder; `a vibrator extending upwardly a-nd generally toward the downstream end of said conduit operatively connected to the upstream end portion of said pebble feeder; a controller operatively connected to and adapted to variably move said Iadjustable baille member; and solids flow measuring means operatively connected to said o-utlet conduit and said controller. Y

8. A pebble feeder comprising a laterally and downwardly disposed pebble conduit having an inlet conduit in its upper end and an `outlet conduit in its lower end, said outlet being disposed no lower than V30" from said inlet; an adjustable baille member within and supported by said conduit and adapted to variably modify a pebble passageway through said feeder; a vibratork extending upwardly and generally toward the downstream end of said conduit voperatively connected to said pebble feeder; a controller operatively connected to and adapted to variably move said adjustable baffle member; a screen positioned in the bottom side of said laterally and downwardly disposed conduit, forming a licor therein upstreamr and downstream of said baille; a fines collection chamber below said screen and having an outlet in its lower portion; and a solids flow measuring means comprising a weight sensitive means operatively communicating between said screen and said controller.

9. The pebble feeder of claim 6, wherein a rotatable, laterally extending continuous belt is provided in the lower portion yof said outlet oonduit; and solids flow measuring means comprising a scale operatively communicating between the top length of said belt and said controller.

(References on following page) References Cited in the flle of this patent UNITED STATES PATENTS Number Re. 23,087

Name Date Bailey et al Mar. 8, 1949 5 Hufhines May 22, 1906 Marquardt Nov. 19, 1912 Mattingly Mar. 10, 1914 Black Sept. 18, 1917 Schaffer Dec. 16, 1919 Alwart June 5, 1923 Pereda Jan. 11, 1927 Carl-son July 12, 1927 Fckel Apr. 6, 1937 Douglass Aug. 3, 1937 Rapp Dec. 7, 1937 Bird July 4, 1939 Number OTHER REFERENCES Catalogue 650, Jeirey-Traylor Division, Jeffrey Mfg. Co.,

Columbus, 10 pages 32, 37, 38, 39. Copy in Div, 25.

Ohio. Copyright 1937;

Catalogue 63, W. S. Tyler Co., Cleveland, Ohio. Copyright 1940. Copy in Div. 25.

Kramer: Electronics With Special Reference to Measurement and.v Control, Instruments Pub- 15 lishing Co., Pittsburgh, 1945, pp. 140, 141.

in Div. 25.

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