FI119802B - A method of operating a separator and a separator - Google Patents

Description

* 119802

METHOD FOR USING THE SEPARATOR AND THE SEPARATOR

The invention relates to a method for operating a centrifugal separator.

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The invention also relates to a centrifugal separator.

A centrifugal separator can separate two liquids of different densities. In addition, a centrifugal separator can separate slag and other solids from the liquid. The separator comprises a rotatable ball or rotor having a plate pack and a slag space for the liquid to be separated. As the ball rotates, the solid and / or heavier liquid, i.e. the higher density liquid, is transported to the outer part of the ball by a centrifugal force. slag from which they are removed. Separated, lighter or lower density fluid passes through the disc pack 15 into the inner portion of the ball, where it is led away from the separator.

For example, in the case of piston engines for ship and power plant operation, centrifugal separators are used to separate slag and water from lubricating oil and fuel oil. The oil-separated slag is discharged from the ball through outlet ports "1" for 20 periodic drainage periods. Before the start of the emptying cycle, a heavier fluid, or so-called liquid, is introduced into the ball * • displacement water, which fills the ball and • •:. · · freezes a lighter fluid, ie oil, and thus prevents the oil from leaving the ball. The problem with these types of separators is to optimize the amount of displacement water supplied to the ball. If too little displacement water is supplied, ··· · 1 ... · 1 25 separable oil is removed from the ball with the slag. Correspondingly, if too much displacement water is supplied, excess displacement water will flow into the already separated oil · · 1.

It is an object of the present invention to provide a solution for optimizing the amount of displacement fluid supplied to the centrifugal separator.

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The objects of the invention are achieved as set forth in claims 1 and 3. In the invention, the pressure of the displacement fluid supplied to the ball is measured, and the length of the displacement fluid supply cycle is adjusted based on the displacement fluid pressure.

The invention provides considerable advantages.

In the solution of the invention, the length of the displacement fluid supply cycle is varied as a function of the displacement fluid pressure. Because the amount of displacement fluid supplied to the ball per unit of time is substantially dependent on the displacement fluid pressure, changing the length of the 10 feeding cycles can always supply an optimum constant amount of displacement fluid and thereby prevent the already lighter fluid from being discharged

The invention will now be described, by way of example, with reference to the accompanying drawing, which shows in principle a cross-sectional view of a centrifugal separator according to the invention.

The drawing illustrates a centrifugal separator 1 used to separate two liquids of different densities and / or to separate slag and other solids from the liquid. There are two main types of centrifugal separators 1.

»·: One of these is the so-called. clarifier separator for separating solids and slag from • 1 ϊ · ί liquid. The second is the so-called. purifier separator for separating heavier liquid * · and solids / slag from lighter liquid. For example, in the large piston engines used in marine engines and power stations, the invention,. centrifugal separator 1 can be used to separate the water and / or slag and other solids contained in the fuel oil and lubricant.

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*: ** of high density oil. The centrifugal separator 1 can be of any of the types mentioned above.

30 • · • · · • • · «3 119802

The separator 1 comprises a rotor or ball 2 rotatable about an axis of rotation 3. The ball 2 comprises a body 4 containing a disc pack 13 and a slag space 6. The body 4 comprises two mutually arranged halves, a lower half 27 and an upper half 26. The lower half is pressed against the upper half 5 by means of the force exerted by the barrier fluid being fed along the line 25. The plate pack 13 and the slag space 6 surround the axis of rotation 3, whereby the slag and other solid and / or the higher density liquid are transported by the centrifugal force of the ball 2 in the radial direction to the outer part of the ball. slag 6. Similarly, the lower density fluid passes into the inner portion 7 of the separation-10 chamber 7. The ball 2 is surrounded by a stationary housing (not shown).

Separator 1 has a feed connection, i.e. a stationary feed tube 8 for supplying separable fluid to ball 2. Feed tube 8 has a pump 9 for pumping separating fluid into ball 2. The rotation speed of pump 9 is controlled by frequency converter 10. The ball 2 comprises a plate pack 13 / or the slag and other solid are separated from the lighter liquid. The feed tube 8 is disposed in the center of the ball 2 in a direction parallel to the axis of rotation 3 and has an orifice on the axis of rotation 3 whereby the liquid to be separated is introduced into the lower part of the ball 2 *: **: 20 below the distributor 28 Separator 1 also has an outlet * 11 · toy fitting or stationary outlet 11 for removing a separated or lighter or smaller fluid from the ball 2. The outlet of outlet 11 is located in the inner part of the ball of the separation chamber 7. The outlet 11 is equipped with: * · * pressure sensor 12, which measures the pressure of the separated or lighter fluid removed from the separator * ·· 25.

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The ball 2 has peripheral openings 14 which can be opened and closed, through which the slag and other solids are removed from the ball during the emptying cycle.

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The outlet openings 14 are opened by dissolving the lower half 27 downwards. The movement of the lower half 27 30 is accomplished along the control fluid conduit 16 by means of a control fluid Y supplied to the control chamber 17. The control chamber 17 has a discharge mechanism which, by the pressure of the control fluid, causes the pressure in the barrier chamber 24 to discharge through the nozzles 23 of the control chamber 17. In this case, the lower half 27 slides downwardly under pressure from the ball 5 and the outlet openings 14 open. The ball is closed by stopping the supply of control fluid to the control chamber 17 and by adding the blocking fluid to the closing chamber 24. The pressure of the closing fluid begins to act again on the closing chamber 24 and the lower half 27 slides back against the upper half 26 and covers the outlets 14.

The separator 1 is provided with a displacement fluid supply conduit 19 connected to a supply conduit 8 for supplying the displacement fluid to the ball 2 via the supply conduit 8. Supply of displacement fluid fills the ball with a heavier fluid and thus prevents lighter fluid from escaping from the ball through outlet ports 14 during the emptying period. The displacement fluid supply pipe 19 is provided with a shut-off valve 20, for example an electric solenoid valve, by means of which the flow of displacement fluid into the ball 2 15 can be prevented or allowed. The displacement fluid supply pipe 19 is provided with a pressure sensor 21 to measure the displacement fluid pressure. The sensor 21 is located in the flow direction of the displacement fluid upstream of the shut-off valve 20 in the displacement fluid supply pipe 19.

In addition, separator 1 comprises an electronic control system 22 arranged to collect information about different measuring objects, i.e. measuring signals of displacement fluid pressure sensor 21 and out-of-pipe pressure sensor 12. The control system 22 controls the shut-off valve 20 based on the displacement fluid pressure measurement 21. On the basis of measurement data from the pressure sensor 21, the control system 22 adjusts the opening time of the shut-off valve 20, i.e. the supply time of the displacement liquid to the ball 2. The supply volume of displacement fluid during the supply period is thus kept constant or approximately constant.

In addition, the control system 22 is provided with information on the control frequency or output frequency of the drive 10, which is at least approximately proportional to the rotation speed of the pump 9, and the outlet pipe. measurement signal of pressure sensor 12. Based on the speed of the pump 9: V: rotation, the control system 22 adjusts the alarm delay after the drain cycle. The alarm is triggered if, after the emptying period, after the start of the pumping operation, during the alarm delay, the pressure sensor 12 does not receive a sufficiently high pressure indicating signal, i.e. no liquid is flowing or too low.

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During operation of the centrifugal separator 1, the ball 2 is rotated about an axis of rotation 3. The fluid to be separated is pumped by pump 9 along supply line 8 to ball 2. Flow of liquid to be supplied to ball 2 is adjusted by changing the rotational speed of pump 9 by frequency converter 10. Control system 22 10 changes the output frequency of frequency converter 10 In the ball 2, a heavier or higher density liquid and / or slag and other solids pass into the outer part of the ball, i.e. slag 6. The lighter or lower density fluid passes through the disc pack 13 into the inner part 7. 15 In the Purifier . via Gravity Disc (not shown).

Separated or lighter fluid is discharged from the ball 2 along the outlet pipe 11. Heavier fluid and / or slag and solids are discharged from the ball slag space ·: * ·: 20 6 periodically through outlet ports 14. Prior to the start of the drainage section, the separation of the *: * conventional liquid through the supply channel 8 to the ball 2 is stopped. The shut-off valve 20 is then opened and the displacement fluid supply to the ball 2 is started. The displacement • φ · liquid has a higher density than the separated liquid. The displacement fluid is usually * ·: * ·· equal to the heavier fluid in the ball slag space 6, typically water. As a result of the displacement fluid supply, the amount of heavier fluid in the ball 2 is increased, whereby the interface between the lighter and heavier fluid 29 moves towards the separating chamber 7 · · * · * ♦ *.

··· • · ♦ ··· • ·:, * ·· If too little liquid is fed to the ball during the feeding cycle, the separated liquid will exit the ball through the outlet ports 14 during the discharge period.

: A: On the other hand, if the overflow liquid is fed to the ball 2 too much, the overflow • • 6 119802 liquid is transported to the separated liquid. The appropriate amount of displacement fluid may be determined, for example, experimentally or by the properties of the fluid to be separated. In order to optimize the displacement fluid supply amount, the length of the supply cycle is adjusted based on the displacement fluid pressure. The displacement fluid pressure mi-5 is measured in the displacement fluid supply pipe by the measuring device 21 and the measurement signal is supplied to the control system 22. The control system 22 determines the length of the displacement fluid supply period based on the displacement fluid pressure and controls the shut-off valve 20 accordingly. The object is to keep the amount of displacement fluid supplied to the ball 2 during the feeding cycle to be constant or substantially constant. For example, if the displacement fluid pressure is 6 bar, the feed cycle length is set to 4 s. Similarly, if the displacement fluid pressure is 2 bar, the feed cycle length is 7 s.

At the beginning of the emptying period or before commencement of the emptying period, the displacement fluid supply is stopped by closing the shut-off valve 20. housing. The aim is to minimize the loss of lighter, separated liquid, usually oil, during ball deflection. At the end of the drainage cycle: 20, the supply of control fluid is stopped and the existing hydraulic pressure in the control chamber 17 tt is released through the nozzles 23. Thereafter, the barrier fluid is fed to the barrier chamber 24 below the lower half of the ball 26, whereby the lower half bar 27 moves upwards and again covers the outlet openings 14 and the emptying period ends 1 ···. The length of the drain cycle is approximately one second or a few seconds if the supply of control fluid and • shut-off fluid is controlled by different solenoid valves. Often, however, in modern separators, the same control fluid both opens and closes the ball with internal loops, with channel arrangements of less than one second, even in fractions of a second. At the end of the emptying cycle ··· • · * ···, the supply of the liquid to be separated through the feed pipe 8 is started again: / ·; ball 2. In a purifier type separator, after completion of the drainage cycle, ball 2 • f1: 30 is fed through displacement fluid supply lines 19 and supply line 8 via a so-called. Concentrate · 1 · 1: Liquid before starting the supply of liquid to be separated.

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The adjustment of the length of the displacement fluid supply period can be implemented as a function of continuous measurement. For example, as the shut-off valve 20 opens, the pressure of the displacement fluid in the displacement fluid supply pipe 19 decreases. The displacement-5 fluid pressure in the feed pipe 19 is continuously measured during the feeding cycle and the control system 22 determines a new value for the length of the feeding cycle based on the average pressure during the feeding period. When the length of the displacement fluid supply period determined by the mean pressure is reached, the control system 22 closes the shut-off valve 20 and the displacement fluid supply to the ball 2 10 stops. Also in this embodiment, the amount of displacement fluid supply to the ball 2 is intended to be kept constant or substantially constant during the supply cycle regardless of pressure variations.

Adjustment of the length of the displacement fluid supply period can also be accomplished by calculating the volumetric flow of the 15 fluid displacements using the Bernoulli equation. Thereby, the displacement fluid supply pipe 19 has a throttle or other point having a different flow cross-section and a pressure sensor located therein. On the basis of the pressure measurements of the feed pipe 19 and the throttle, the volume flow rate of the fluid flowing in the blast feed pipe 19 can be calculated by the Bernoulli equation and the continuity equation, *: **: 20 when the pressure measuring points are at the same height.

·· ♦ »··· • ·: Bernoull’s Equation: · · · · · · # ··» · · · · · · 2 2 * V1 V2 O Α + γΡ = Λ + γΡ 25 ’; j · 8 continuity equation: · · · · · · · · V ·: Q - ν, −4 = v2A2 · · · · · · · 119192 From these, the displacement fluid volume flow is given by: Ö, = 4 1, l2 * (p2 -P1) / (p1 (l- (A1 / A2) 2)) where 5 Qt = volumetric flow rate in the displacement fluid delivery pipe, m3 / sv, = flow rate in the displacement fluid supply pipe, m / s v2 = flow rate at the displacement liquid throttle, m / s px = displacement fluid pressure in displacement fluid feed pipe, N / m2 p2 = displacement fluid pressure at throttle, N / m2 10 p = displacement fluid density, kg / m3

Ax = cross-sectional area of the displacement fluid inlet pipe, m2 A2 = cross-sectional area of the throttle, m2

From the flow rate, the volume flow rate of the displacement liquid can be determined by the flow cross-sectional area of the displacement liquid feed pipe.

The control system 22 defines a displacement fluid in the feed pipe 19 for filing water. based on equal throttling and pressure measurements of the feed pipe 19 and controls the shut-off valve «« «M *« so that the amount of water to be supplied to the separating chamber 5 during the displacement liquid supply period is desired. Also in this embodiment, the supply volume of displacement liquid • · · J * V to the separation chamber 5 is intended to be kept constant or substantially constant over the supply period of · · i ··], regardless of pressure variations. Using the Bemoull equation, calculate • »·. * ··. using the right flow rate, continuously calculate the correct opening time ***** for the displacement fluid valve 20.

The control system 22 also changes the length of the alarm delay used in the separator 1 as a function of the volume flow rate of the liquid to be fed into the separator.

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The desiccation delay begins when the separation is resumed at the end of the drain cycle.

• · .1. If the pressure of the separated liquid in the outlet pipe 11 is below a predetermined limit after a delay of 120 119802, an alarm is triggered. The pressure of the separated fluid is measured by the pressure sensor 12 and the control system 22 initiates an alarm if a signal from the pressure sensor 12 indicates that the pressure in the outlet pipe 11 is below a predetermined threshold after an alarm delay. Too low pressure in the outlet pipe 5 after the alarm delay may indicate a malfunction of the separator, for example the outlet ports 14 are not closed. For example, the pressure limit for the alarm is set to the same as the minimum pressure required for the application of the separated liquid. The rotation speed of the pump 9 influences the rate at which the pressure in the outlet pipe 11 returns to its normal level after the drain cycle 10 of the separation chamber 5. At a lower speed, the separator fills up and the pressure is restored more slowly than at a higher speed.

The length of the alarm delay is adjusted based on the volume flow rate of the liquid to be fed to the separator. The volume flow rate of the liquid to be separated may be determined, for example, by a gauging device suitable for forcing or by the speed of rotation of the pump 9 or by the output frequency or control frequency of the frequency converter 10. At lower flow rates, the alarm delay is longer than at higher flow rates. The control system 22 adjusts the length of the delay delay. For example, when pump 9 is rotating at 50 Hz output frequency of the frequency converter at no - *: · *: 20, the alarm delay length is 10 s. If the speed of pump 9 changes to 4t * i * drive frequency 15 Hz output, the control An alarm may be, for example, a message on the control panel display • · ·. · * And / or the control system 22 may interrupt the supply of liquid to the separator 1.

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After the emptying cycle, the length of the supply fluid (purifier ♦ ·! £! Fier separator) to the ball can be determined by measuring the pressure of the sealing fluid in the same manner as the length of the displacement fluid supply period determined above.

• · V ·: The same methods can also be used to determine the lengths of the control fluid and barrier fluid inlets.

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Claims (4)

A method of using a centrifugal separator (1), the centrifugal separator comprising a ball (2) for the liquid to be separated, in which method the liquid to be separated into the ball (2) is measured, the separated liquid is removed from the inner part of the ball ( 7), slag is removed from the outer part (6) of the ball periodically during emptying periods, and the displacement fluid is measured to the ball (2) during a displacement fluid feeding period before starting an emptying period, characterized in that the pressure of the tiling ball (2) is fed and adjusted the length of the displacement fluid feeding period on the basis of the pressure of the displacement fluid. Method according to claim 1, characterized in that the pressure of the displacement fluid supplied to the ball (2) is continuously measured during a feeding period, the average pressure of the displacement fluid is continuously determined during the feeding period and the length of the displacement fluid feeding period is adjusted on the basis of the average pressure liquid. * • · 20 Method according to claim 1 or 2, characterized in that the pressure is measured. at the tili ball (2) the displacement fluid is fed into two points with different ··· · •. *. flow area, the volume flow rate of the ball (2) supplied to the ball (2) is determined on the basis of the pressure measurements and adjusted during the emptying period: ***; length on the basis of the volume flow. · * 25: Y: A centrifugal separator (1) comprising a ball (2) for the liquid to be separated, a feeding channel (8) for conducting the liquid to be separated into the ball (2), an outlet channel (11) for removing the separated liquid • · ·: ··· from the inner part (7) of the ball, opening and closable outlet openings (14), v, 30 for removal of slag from the outer part (6) of the ball periodically during * · · • · • · In emptying periods and a displacement fluid supply channel (19) for supplying displacement fluid to the ball (2), which supply channel (19) is provided with a closure means (20) for controlling the supply of the displacement fluid, characterized by a connection fluid (19). provided a measuring device (21) for measuring the pressure of the displacement fluid and of a control system (22) arranged to control the closure means (20) on the basis of the pressure of the displacement fluid. 10 • · • Il I ··· • «• · t • · f Ml · • · · · · · I ··· f ·· • · · · · · · 1 * · M1 • · • · · · • · 1 i «1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1