FI119975B - Method of using a separator and a separator - Google Patents

Description

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 in ship and power plant, centrifugal separators are used to separate slag and water from lubricating oil and fuel oil. The oil-separated slag is removed from the ball through the outlet ports 20 periodically during the drainage periods. Before the start of the emptying cycle, a heavier fluid, i.e. so-called liquid, is fed to the ball. displacement water to fill the ball and displace a lighter fluid, thus preventing the oil from escaping with the slag. After the emptying cycle, when the separation begins again, the pressure of the separated liquid to be removed from the separator is measured. If the pressure does not rise to a predetermined value during the 25 alarm delays, the separator may malfunction and the separator control system will trigger an alarm. If the volume flow rate of the liquid to be separated is small, filling the separator and raising the pressure to a sufficient level after the emptying period may cause an alarm delay for a longer period, in which case the control system will trigger the alarm unnecessarily.

It is an object of the present invention to provide a solution for optimizing the length of the alarm delay of the separator.

The objects of the invention are achieved by the methods set forth in claims 1 and 4. The invention determines the volume flow rate of the liquid to be supplied to the ball and adjusts the length of the alarm delay based on the volume flow rate of the liquid to be separated.

The invention provides considerable advantages.

With the solution of the invention, the length of the alarm delay can be optimized according to the volume flow rate of the liquid to be separated, which reduces the number of false alarms when the volume flow rate of the liquid to be separated is small. Similarly, in the event of a disturbance, the alarm can be triggered earlier when the volume flow rate of the liquid to be separated is high.

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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 a liquid. There are two main types of centrifugal separators 1. One is the so-called. clarifier separator for separating solids and slag from liquid. The second is the so-called. purifier separator for separating heavier liquid 25 and solids / slag lighter liquid. For example, in large reciprocating piston engines, which are used as main engines and power plants for ships, the centrifugal separator 1 according to the invention can be used to separate water and / or slag and other solids between fuel oil and lubricating oil and oil of lower density. The centrifugal separator 1 can be either of the 30 types mentioned above.

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The separator 1 comprises a rotor, or ball 2, pivotable about a rotation axis 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, lower half 27 and upper 5 halves 26. 24 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. 10 The slag space 6. Correspondingly, the lower density fluid passes into the inner part 7 of the separation chamber. 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 liquid 15 to ball 2. Feed tube 8 has a pump 9 for pumping the liquid to be separated 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 the direction of the axis of rotation 3 and has an orifice 20 on the axis of rotation 3, whereby the liquid to be separated is introduced into the lower part of the ball 2 below the distributor 28. Separator 1 also has a drain plug or stationary outlet 11 for removing the separated or lighter or lower density fluid from the ball 2. The outlet of the outlet 11 is located inside the separation chamber ball 7. The outlet 11 is provided with 25 pressure sensors 12 for is measured.

The ball 2 has peripheral openings 14 which can be opened and closed, through which slag and other solids are removed from the ball during the emptying period. The outlet openings 14 are opened by dissolving the lower half 27 downwards. The movement of the lower half 27 is accomplished by the control fluid 4 being fed into the control chamber 17 along the control fluid channel 16. The control chamber 17 has a discharge mechanism which causes the pressure in the control chamber 17 to discharge through the nozzles 23 of the control chamber 17 as a result of the pressure of the control fluid. In this case, the lower half 27 slides downwardly under pressure from the ball 5 and the outlet openings 14 open.

5 The ball is closed by stopping the supply of control fluid to the control chamber 17 and adding the blocking fluid to the blocking chamber 24. The pressure of the blocking fluid begins to act again on the blocking 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 pipe 19 which is connected to the supply pipe 8 for supplying the displacement fluid to the ball 2 via the supply pipe 8. The injection of sputtering fluid fills the ball with a heavier fluid and thus prevents the lighter fluid from escaping from the ball through the outlet ports 14 during the emptying period. The displacement fluid supply pipe 19 is provided with a shut-off valve 20, 15, for example an electric solenoid valve, by means of which the flow of displacement fluid to the ball 2 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.

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Further, the separator 1 comprises an electrical control system 22 arranged to collect information about the various measuring objects, i.e. the measurement signals of the displacement fluid pressure sensor 21 and the outlet pipe pressure sensor 12. The control system 22 controls the shut-off valve 20 based on the displacement fluid pressure measurement 21. Based on the measurement data 25 from the pressure sensor 21, the control system 22 adjusts the opening time of the shut-off valve 20, i.e., the supply fluid displacement time to the ball 2. Thus, the displacement fluid supply volume during the supply period is held constant or approximately constant.

Further, 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 measurement signal of the discharge pressure sensor 12. Based on the speed of rotation of the pump 9 5, the control system 22 adjusts the length of 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 5 or too low pressure in the outlet pipe 11.

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. The flow rate of fluid to be supplied to the ball 2 is adjusted to the desired 10 rpm of pump 9 by frequency converter 10. The control system 22 changes the output frequency of frequency converter 10. In ball 2, a heavier or higher density liquid and / or slag and other solids pass into the outer part of the ball or slag space 6. The lighter or less-15 lower density fluid passes through the plate pack 13 into the inner part 7. In the purifier type separator 6 continuously the so-called. 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 slag space 6 of the ball periodically through outlet ports 14. Before the discharge section begins, the supply of the liquid to be separated 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 liquid has a higher density than the separated liquid. The displacement fluid is usually the same as 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 lighter and heavier fluid interface 29 moves towards the inner part 7 of the separation chamber.

If too little of the displacement liquid is fed to the ball during the feeding cycle, the separated liquid is discharged from the ball through the outlet ports 14 during the discharge period.

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On the other hand, if the displacement liquid is supplied to the ball 2 too much, the displacement liquid enters into 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 supply volume of the displacement fluid, the lengths of the supply cycle are adjusted based on the pressure of the displacement fluid. The displacement fluid pressure in the displacement fluid supply pipe is measured by a 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 cycle based on the displacement fluid pressure and controls the shut-off valve 20 accordingly. The aim is to maintain a constant or substantially constant amount of displacement fluid to be delivered to the ball during the feeding cycle. 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 commencement of the emptying period or before commencement of the emptying period, the supply of displacement fluid 15 is stopped by closing the shut-off valve 20. The control fluid is fed through housing. The goal is to minimize the loss of lighter, se-20 paraffinic liquid, usually oil, during ball ball emptying. At the end of the drainage period, the supply of control fluid is stopped and the hydraulic pressure in the control chamber 17 is released through the nozzles 23. Subsequently, the barrier fluid is fed below the lower half of the ball 26 into the barrier chamber 24, whereby the lower half 27 moves upward and again covers the outlet ports 14 and the emptying cycle ends. The drainage period is approximately one second or a few seconds if the control fluid and barrier fluid supply is controlled by different solenoid valves. Often, however, in modern separators, the same control fluid both opens and closes the ball with internal channel arrangements in less than a second, even in fractions of a second. At the end of the purge period, the supply of separable liquid through supply line 8 to ball 2 is started again. In the purifier type separator, after the discharge period, ball 2 7 is supplied via displacement fluid supply lines 19 and supply line 8 so-called. sealing liquid prior to starting the supply of liquid to be separated.

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 pressure of the displacement fluid in the feed pipe 19 is continuously measured during the feed cycle and the control system 22 determines a new value for the length of the feed cycle based on the average pressure during the feed cycle. When the length of the displacement fluid supply period determined on the basis of the mean pressure 10 is reached, the control system 22 closes the shut-off valve 20 and the displacement fluid supply to the ball 2 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.

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Adjustment of the length of the displacement fluid supply period can also be accomplished by calculating the displacement fluid flow rate using the Bernoulli equation. The displacement fluid supply pipe 19 then has a throttle or other point having a different flow cross-sectional area in which a pressure sensor is disposed. From the feed pipe 19 and the throttle pressure measurement 20, it is possible to calculate the volumetric flow rate of the fluid in the displacement fluid feed pipe 19 using the Bernoulli equation and the continuity equation when the pressure measurement points are at the same height.

Bernoulli's equation: 25 2 2 V, V, Ρι + γΡ = Ρι + γΡ continuity equation: 8 Q = Vj4 = v2A2 From these, the displacement fluid flow rate is: 5 ii = A * λ / 2 * <> 2 - Pi) Kp * (1- (4 IA?)) Where <2, = volumetric flow in displacement fluid inlet, m3 / sv, = flow rate in displacement fluid inlet, m / s v2 = flow rate at displacement fluid throttle, m / s 10 px = displacement fluid pressure in displacement fluid inlet pipe, displacement fluid pressure at throttle, N / m2 p = displacement fluid density, kg / m3

At = flow cross sectional area of displacement fluid inlet pipe, m2 A2 = flow cross section at throttle, m2 15

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

The control system 22 determines the amount of water 20 in the displacement fluid feed pipe 19 based on the throttling and the pressure measurements of the feed pipe 19 and controls the shut-off valve so that the amount of water to be fed to the separation chamber 5 during the displacement fluid supply period. Also in this embodiment, the supply volume of displacement liquid to the separation chamber 5 is intended to be kept constant or substantially constant during the supply period, irrespective of pressure variations. Using the calculated flow rate using the Bernoulli equation, the correct opening time for the displacement fluid valve 20 is continuously calculated.

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 supplied to the separator.

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The desiccation delay begins when the separation is resumed at the end of the drain cycle. If the pressure of the separated liquid in the outlet pipe 11 is below a predetermined threshold after a delay delay, 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 11 after the alarm delay may indicate a malfunction of the separator, for example the outlet 14 is 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 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 volumetric flow rate of the liquid to be fed to the ball is determined, for example, after the emptying period, once the separation has started. The volume flow rate of the liquid to be separated can be determined, for example, by a gauge suitable for the ram or by the speed of rotation of the pump 9 or the output frequency or control frequency of the frequency converter 20. At a lower flow rate, the alarm delay is longer than at a higher flow rate. The control system 22 adjusts the length of the delay delay. For example, when pump 9 is rotating at 50 Hz output frequency, the alarm delay length is 10 s. / or the control system 22 may interrupt the supply of the liquid to be separated to the separator 1.

After the drain cycle, the length of the balloon sealing fluid supply cycle (Puri-30 fier separator) can be determined by measuring the sealant fluid pressure in similar ways as the length of the displacement fluid supply cycle defined above.

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The same methods can also be used to determine the lengths of the control fluid and barrier fluid supply cycles.

Claims (6)

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, the pressure of the separated liquid (2) removed from the ball is measured and alarm is triggered if the pressure of the separated ball (2) removed the separated liquid after an alarm delay after an emptying period. below a predetermined limit value, characterized in that the volume flow is determined for the liquid to be fed to the ball (2) and adjusted the length of the alarm delay on the basis of the volume flow for the liquid to be separated. 15 Method according to claim 1, characterized in that the liquid to be separated is measured to the ball with a pump (9) whose rotational speed can be changed and the volume flow of the liquid to be separated is determined on the basis of the rotational speed of the pump (9). 20 Method according to claim 1 or 2, characterized in that the rotational speed of the pump (9) is changed by a frequency converter (10) and the volume flow of the liquid to be separated is determined on the basis of the frequency or output frequency of the frequency converter (1). A centrifugal separator (1) comprising a ball (2) for the liquid to be separated, a supply channel (8) for conducting the liquid to be separated into the ball (2), an outlet channel (11) for removing the separated liquid from the interior of the ball part (7), said outlet channel (11) being provided with a measuring device (12) for measuring the pressure of the separated liquid, opening and closable outlet openings (14) for removing slag from the outer part (6) periodically during emptying periods and a control system (22) arranged to trigger alarms if the pressure of the separated liquid in the outlet channel (11) after an alarm delay after an emptying period falls below a predetermined limit value, characterized in that the control system (22) is adapted to adjust the alarm delay length. of the volume flow of the liquid supplied to the separator to be separated. Separator according to claim 4, characterized in that the separator comprises a pump (9) whose rotational speed can be changed and the control system (22) is arranged to adjust the length of the alarm delay on the basis of the rotational speed of the pump (9). Separator according to claim 4 or 5, characterized in that the separator comprises a frequency converter (10) for changing the rotational speed of the pump (9) and the control system (22) is arranged to adjust the length of the alarm delay on the basis of the frequency or output frequency of the frequency converter (10).