US3400984A - System for pumping slurries of high concentrations - Google Patents

Description

Sept. 10,1968 K. R. SHELLENE ETAL SYSTEM FOR FUMPING SLURRIES OF' HIGH CONCENTRATIONS Filed June 13, 1967 United States Patent Office v 3,400,984 Patented Sept. 10, 1968 3,400,984 SYSTEM FOR PUMPING SLURRIES F HIGH CONCENTRATIONS Kent R. Shellene, John P. Fraser, and Paul T. Chu, Houston, Tex., assignors to Shell Oil Company,

New York, N.Y., a corporation of Delaware Filed .lune 13, 1967, Ser. No. 646,420

8 Claims. (Cl. 302-14) ABSTRACT OF THE DISCLOSURE An apparatus for pum-ping a liquid-solids mixture with a high enough solids content to prevent stratification consisting of a liquid adder upstream from a pump and a liquid extractor downstream of the pump.

Background of the invention This invention relates to a method and-apparatus for continuously pumping a two-phase fluid through a pipeline. More specifically, this invention pertains to the continuous pumping of a highly viscous fluid flow stream that includes a solid such as wood chips, coal or potash as one phase of the flow stream.

It is generally known in the prior art that a' solid may be transported through a pipeline by admixing fragmentized particles of the solid with a fluid carrier that may be energized or moved by means of a pump. However, one difficulty arising out of the practical exploitation of such a concept is the stratification of the solid particles through the long laminar flowing portion ofthe pipeline. This stratification is due to a specific gravity differential existing between the solid particles and the fluid carrier and may result in particle movement to the top or bottom of the pipe depending on which phase is the heavier. As a consequence of such stratification, channels will form over, under or through the solid strata, and mainly the fluid carrier phase is actually transported which, `of course, defeats the primary objective.

It has been proposed that the stratification difficulty in transporting solid particles through pipelines may be overcome by admixing a slurry of the solid and fluid phases of such consistency and viscosity as to prohibit stratification by interparticle support. In other words, the solids concentration would be too great to permit further stratifcation under the differential specific gravity forces present, thereby presenting a uniform stratum of solid particles throughout the entire pipe cross-sectional area. f

Such an innovation would seemingly solve the stratification problem, but the exploitation Vof such a concept'is met with the practical inability of most commercially available pumps to handle a slurry of such consistency. It is, therefore, one object of this invention to provide means whereby solid and fluid slurry concentrations that` Pursuant to these and other objects, it is herein proposed that a thick, viscous slurry formed by the admixture of solid particles and a carrier fluid may be energized or moved as a fluid flow stream by first diluting the slurry with an excess of solid-free fluid and then pumping the dilute slurry with a conventional pu-mp. Immediately downstream of the pump the dilution fluid is extracted from the pressurized flow stream by filtering. In order to conserve power, the stream of filtered fluid is routed directly into the diluting apparatus where it is re-injected into the pump suction side of the flow stream under the driving pressure of the pump. The invention also includes a back-flushing system for periodically cleaning the downstream filter apparatus of solid particles which accumulate along the interior of the filters and tend to restrict the free extractionof the dilution fluid.

The invention will be understood from the following description when taken with reference to the drawing, which is a schematic representation of the proposed system.

Description of preferred embodiment Referring to the figure, there is shown an upstream portion 1 of a pipeline for carrying a concentrated slurry. The pipeline conducts the slurry into a diluter 2 having an internal conduit 3 with perforations 4. Around the perforated section of the conduit 3 there is provided a Water jacket 5. Perforations 4 in the conduit 3 are of such size as to allow fluid to pass therethrough but prevent passage of the majority of the solid particles. Connected to the water jacket 5 are diluent injector lines 6 which communicate with a. common diluent supply line 7.

Downstream of the diluter 2 and proximate with the main slurry flow line is a solids concentration indicator 9. This instrument may be a density measuring head which functions on gamma-ray absorption. Such devices are manufactured by the Industrial Nucleonics Corporation, Columbus, Ohio; Model DH-S, Product Data Sheet l2-40.1l365 and 12-43.01-3650, and the Ohmart Corporation. This function could also be handled by ultrasonics with the Solitrol instrument manufactured by the Powertron Ultrasonics Corporation. The solids concentration indicator 9 transmits a control signal to a diluent controller 10, which is an operational amplifier of the type manufactured by the Foxboro Company, Foxboro, Mass. Model M/64 with M/ 16, catalog No. 565, pp. A14-A17 (1964). The diluent controller 10 amplifies and transforms the solids concentration indicator signal into a control signal for the diluent control valve 11 which is of the ordinary air-operated or electro-hydraulic type as manufactured by the Foxboro Company, Model F-9 with 69TA-l, catalog No. 565, pp. Cl, C12 (1964). The diluent control valve 11 regulates the supply of solid-free diluent fluid from the de-watering line 26 described below. Relief valve 27 serves to dump an excess supply of diluent fluid from the cle-watering line 26 to the diluent storage tank 14. Diluent pump 13 provides additional diluent fluid through line 12 to diluent injector line 7 when the supply from line 26 is insuflicient to meet the immediate demands of the flow stream as measured by the concentration indicator.

After passing the solids concentration indicator 9, the diluted slurry is drawn into the suction 8 of the primary pipeline pumps 15. Here the sl-urry is highly energized for transport to the next pumping station.

Downstream of the pumps 1S and in the discharge line 16 thereof there are provided two concentrators 20 and 40, respectively. Both concentrators are in series communication with the main slurry discharge line 16 and vwith one another. Each concentrator, and 4l), respectively,- is provided with a perforated conduit 21 and 41 having perforations 22 and 42 of a size to allow the passage of solid-free uid but which prevent the passage of the slurry-included solids. Around the perforated conduit sections 21 and 41 there are provided water jackets 23 and 43, respectively. Connected to the respective water jackets are diluent discharge lines 24 and 44 having de- ' watering control valves 25 and 45, respectively. The dewatering control valves 25 and 45 are similar to the diluent control valve 11 and also may be of the air-operated type, preferably of the air-to-open type manufactured lby Masoneilan or Foxboro companies. Also connected tto the watei` jackets 23 and 43 are back-flushing iiuid lines34 and 54,'respectively. The back-flushing fluid lines '34 and. 54 are respectively controlled by back-flushing block valves 33 and 53. These are power-operated valves suchas the electro-hydraulic valve manufactured by the -General Control Company, Glendale, Calif.; Model V- 84.4/I-I10\, catalog No. 608-567, page 8. The de-watering control valves 25 andv 45 and back-flushing valves 33 and VV53 are automatically responsive to a control system which includes non-latching pressure differential switches 28 and 48 of the type manufactured by Static-O-Ring Switch Company, Kansas City, Mo., Model BR-KS. These switches measure the pressure differential existing across the water jacket in the main flow stream on the downstream side thereof. Pressure taps 29, 30, 49, and 50` are provided for this purpose. Connected to the pressure differential switches 28 and 48, by an electrical conduit, for example, Vare short-delay mechanisms 31 and 51. The short-delay mechanisms may be a time-delay relay of the type manufactured by the Elastic Stop Nut Corporation of America, Elizabeth, NJ., 2400 Series, catalog No. SR- 1, pp. l-14 (1965).

The short-delay mechanisms 31 and 51 transmit control impulses to both the de-Watering programmer 58 and the back- flush programmers 32 and 52, respectively.

The de-watering programmer 58 may be, for example,

Ytwo three-way solenoid valves plus a common two-position stepping switch of the type manufactured by the Automatic Electric Company. Each time the stepping switch is pulsed, the switch changes from a first position -t-o a second position or vice versa. The circuits of each position energize a respective one of the three-way solenoid valves. The particular three-way valve that is energized passes a control signal, pneumatic, for example, from the concentration controller `57 to the respective one of the de-watering control valves 25 and 45. The particular three-Way valve that is not energized blocks the pneumatic control sign-al from the concentration controller 57 and the residual pneumatic pressure on the `respective de-watering control valve diaphragm is ex hausted to the atmosphere. In summary, therefore, when the switch steps to one of the positions, the pneumatic control signal is passed to the respective control valve 25. or 45, and when the switch changes, the diaphragm pressure on that said valve is relieved.

- The short-delay mechanism 31 and 51 signal received by the back- flush programmers 32 and 52, respectively, serves to start the back-flush pump motor and open a respective one of said back-flushing valves 33 or 53, re-

spectively. The back-flushing programmers 32 and 52 are of a simple type designed to start the motor 37 and open the respective valve 33 and 57 for a short time period sufficient to clean the perforations 22 or 42 by reverse circulating diluent through the perforations into the main ow stream and close the respective back-flushing valve .33 or 53 when the reverse circulating cycle has completed.

It will be noted that when de-watering control valve 25 is open, the corresponding back-flush valve 33 is closed. Simultaneously, when de-watering control valve 25 is open, de-watering control valve 45 is closed and the corresponding back-flushing valve 53 is open. Since it is possible for de-watering control valVS .25 and 45 t0 both be closed the same time that both back-flushing " valves 33 and 53 are open, a safety alarm 38 is provided to give an indication of Such a condition. The circuit which energizes the safety alarm 38 is interrupted by two relays 39a, 39b `in series. When either of the backushing valves 33 or 53 is energized from. the respective back-flush programmers 32`or 52, respectively, a respective one of the alarm relays is closed. However, when both back-flushing valves are simultaneously energized, both alarm relays 'are also energized to actuate an audio or visual signal.

The concentration controller 57 may bea pneumatic controller of the type manufactured by the FoxboroCompany; IModel M/64, M/6l, 69TA-l, Catalog 565 pp. A14-A17, C12 (1964). The function of the concentration controller is to `receive continuously an output control signal from the concentration measuring instrument 56, which is similar to the solids concentration indicator 9, and compare it to a programmed standard or set-point. In response to the output signal of the concentration measuring instrument 5.6, the concentration controller 57 transmits a pneumatic, for example, control signal to the de-watering control valves via the de-watering programmer 58 that is proportional to the said concentration measuring instrument output signal.

Operation ofthe invention The system described hereinabove functions in the following manner. A highly concentrated slurry of fluid and solid is too thick to stratify or to pump is introduced to the system through the pipeline 1 where it is diluted by the injection of additional solid-free diluent fluid through perforations 4. Downstream of the perforated conduit section 3, the solids concentration indicator 9 evaluates the resultant slurry consistency to determine if additional diluent will be necessary to maintain a minimum pumping consistency. If the trend of the diluted slurry is to thicken beyond a minimum pumping consistency, a signal is transmitted to the diluent controller 10 which transforms the signal Iinto a form to which the diluent control valve 11 will respond and open to permit additional diluent to pass from the main diluent conduit 7 where it is introduced into the diluent water jacket 5 through diluent injection lines 6.

The diluted slurry is now of a consistency which may be drawn into the pump suction 8 and energized by the pump 15 where it is discharged at 16.

As the diluted slurry passes next through the concentrator 20, the excess solid-free diluent is drawn off through the perforatons 22 in theperforated conduit section 21,' thereby leaving the slurry in the reconcentrated condition as it was before entering the diluter 2.

The diluent is drawn off by virtue of the low pressure condition existing within the water jacket 23 provided by the diluent discharge line 24. The de-watering control valve 25 is normally open, thereby leaving diluent discharge line 24 and in open conduit relationship with the de-watering conduit 26 and diluent injection conduit 7. A pressure differential of a magnitude provided by pump 1S exists between'conduits 24 and 7. Hence, the diluent is induced to flow from the former to the latter.

As the diluent is continuously drawn off through the perforated conduit 21, the finer particles of the transported solid will tend to accumulate in the apertures of the perforations 22, thereby obstructing the continued extraction of the diluent. When this happens a pressure differential existing between the water jacket chamber and the main conduit line, as exists between the pressure taps 29 and 30, respectively, will grow. Pressure differential switch 28 continuously compares this pressure differential to a set point. When the pressure differential reaches the established standard a signal is sent to the short-delay mechanism 31 which delays operating on the signal for a desired time to allow for surges. If the signal from the pressure differential switch 28 persists throughout 4the anism 31, the de-watering programmer 58 transmits appropriate control pulses to the de-watering control valves 25`and 45 so as to close the former and open the latter. Simultaneous with the de-watering control valve pulses, the back-flush programmer 32 transmits a control pulse to the back-flushing lvalve 33` and to the back-flushing pump motor 37. The effect of these pulses from the back-flush programmer 32 is to open the back-flushing block |valve 33 and start the back-flushing pump 36 which draws diluent from the storage tank 14 and discharges it into the back-flush fluid manifold 35 where it is injected under pressure into the water jacket 23 through the back-flushing fluid lines 34. The pressure in the water jacket chamber being greater than that in the slurry flow stream, the diluent is injected through the perforations 22 to cleanse the accumulated solid particles therefrom.

Since it is unnecessary for the back-flushing cycle to be continuous, the lback-flush programmer 32 closes the valve 33 and stops the motor 37 after a predetermined period.

-It was noted that de-watering control valve 45 was opened simultaneously with the closing of de-watering control valve 25. The result thereof was to initiate the de-watering function of concentrator 40. Concentrator 40 functions in the same manner as that of concentrator so long as the pressure differential between the water jacket chamber 43 and the main slurry line remains within allowable limits as measured at pressure taps 49 and 50 by pressure differential switch 48. When the maximum allowable pressure differential across concentrator 40 is set by a pressure differential switch 48, a signal is transmitted to short-delay mechanism 51 which in turn transmits a control signal to the de-watering programmer 58 and to the `back-flush programmer 52. Upon receiving the signal from the short-delay mechanism 51, the dewatering programmer 58 transmits an appropriate signal to de-watering control valves and 45 to effectively reverse their condition, i.e., -de-watering control valve 25 is again opened and de-watering control val-ve 45 is closed. the back-flush programmer 52 opens the back-flush block valve 53 and starts the back-flushing pump motor 37 to initiate the back-flushing cycle for concentrator 40.

The purpose of the concentration measuring instrument 56 is to monitor continuously the resultant slurry concentration into the pipeline 55 and transmit an appropriate signal to the concentration controller 57. The concentration controller appropriately transforms `the signal from the concentration measuring instrument 56 where is is transmitted to and relayed yby the `de-watering programmer 58. The de-Watering programmer 58 relays the signal to the de-watering control valve that is presently open to effect a regulation of the watering function t'hen being performed by the respective concentrator.

The function of alarm 38 is to provide a signal in the event that both concentrators 20 and 40 are thrown into the back-flushing cycle at the same time.

When concentrator 20 or 40 is extracting more diluent than is requisitioned by the solids concentration indicator 9, the excess is released from the diluent recirculation circuit by the release valve 27 to the diluent storage tank 14.

It is also possible to arran-ge the concentrators 20 and 40 in parallel relationship to one another rather than in the series relationship as shown and preferred, but such a parallel arrangement would require additional valving `and control circuitry therefor. Furthermore, no appreciable advantage is to -be gained over the series circuit preferred.

We claim:

1. A method of continuously energizing a two-phase viscous fluid flow stream including a solid phase through a flow stream carrying conduit comprising the steps of:

(a) diluting said viscous fluidflow stream by injecting substantially solid-free fluid at a first point at said conduit;

(b) energizing said diluted flow stream at a pumping point in said conduit that is downstream of said first point; and

(c) extracting said solid-free fluid from said energized and diluted flow stream at a second point in said conduit that is downstream of said pumping point, said extraction fluid flow induced by the pressure differential existing across said pumping point and between said first and second points of said conduit and providing makeup fluid for said dilution.

2. A system for continuously pumping a two-phase fluid flow stream including a solid phase through a flow stream carrying conduit comprising:

(a) a pumping means for energizing said flow stream;

(b) a diluter means in said conduit upstream of said pumping means for injecting additional substantially Isolid-free fluid into said flow stream;

(c) a concentrator means in said conduit downstream of said pumping means for extracting said additional solidfree fluid from said flow stream; and

(d) first conduit means connecting said concentrator means to said diluter means whereby a pressure differential prevailing between the diluter means and said concentrator means causes said solid-free fluid flow from said concentrator to said diluter.

3. A two-phase fluid pumping system as described by claim 2 wherein said diluter means comprises a perforated conduit means for passage of said flow stream, said perforated conduit means being enclosed by a fluid-tight jacket means, said first conduit means connected to said jacket means whereby said substantially solid-free fluid may enter said flow stream via said jacket and said perforations.

4. A two-phase fluid pumping system described by claim 2 wherein said concentrator means comprises a perforated conduit means for passage of said flow stream, said perforated conduit means being enclosed by a fluidtight jacket means, said first conduit means connected to said jacket means whereby said substantially solid-free fluid may exit said flow stream via said perforation and said jacket means, said perforations being such size to prohibit the exit of solid phase particles from said flow stream.

5. A two-phase fluid pumping system as described by claim 4 wherein said concentrator means comprises at least two perforated conduit sections, each enclosed by a fluid-tight jacket means, said first conduit means connected t0 each said jacket means.

6. A two-phase fluid pumping system as described by claim 4 wherein said concentrator jacket means has second `conduit means connected thereto whereby substantially solid-free fluid .may be injected into said flow stream via said jacket .and said perforation for the purpose of cleaning accumulated particles of said solid phase from said perforations, said first conduit means having valve means `for blocking said flow through said first conduit means when fluid is flowing through said second conduit means.

7. A two-phase fluid pumping system as described by claim 5 wherein each said concentrator jacket means has second conduit means connected thereto whereby solidfree fluid may be injected into said flow stream via said jacket and said perforations for the pu'rpose of cleaning laccumulated particles of said solid phase from said perforations, said first and second conduit means having valve means whereby fluid flow through said first conduit means from one of said perforated conduit sections is blocked when said second conduitA means to said one perforated conduit section is opened and said first conduit means from the other of said perforated sections is open while said second conduit means to said other perforated conduit sections is blocked.

8. A two-phase fluid pumping system as described by claim 7 additionally comprising automatic control means for simultaneously and alternatively opening said rst conduit means vfrom said one perforated conduit section and said second conduit means to said other perforated conduit sections and closing said trst conduit means from Vsaid other perforated conduit sections and said second conduit means to said one perforated conduit section,

8 References Cited UNITED STATES PATENTS 3,038,760 6/1962 Crooke 302-14 3,212,822 10/1965 Payne et al. 2- 302--14 3,254,924 6/1966 Harrison et a1. 302-,14 3,328,089

V6/1967 Hodgson et al. 3D2- 1 4 ANDRES H. NIELSEN, Primary Examiner.y

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