JPH0563392B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and apparatus for draining an oil storage tank, and can be used in an oil refinery or the like equipped with an oil storage tank.

[Prior Art] In oil refineries and the like, products stored in oil storage tanks (tanks) and their intermediate products usually contain water. When some of that water separates and accumulates at the bottom of the oil storage tank, water-soluble corrosive substances dissolved in the water, such as chlorine, cyanide, and phenol, can corrode the bottom and side panels of the oil storage tank.
This poses the problem of contamination in products. Therefore, in conventional oil storage tanks, water is drained by disposing a water drain valve near the bottom of the oil storage tank. but,
With this configuration, there are problems in that accidents may occur in which oil leaks out together with the water to be discharged, and it is difficult to completely drain the water accumulated at the bottom of the oil storage tank.

In order to solve these problems, an oil-containing water outlet pipe is installed on the side wall near the bottom of the oil storage tank located at a higher position than the box where oil and water separation is performed, and the oil-containing water outlet pipe is installed in the middle of the box. At the top of this box, there is an oil drain pipe that communicates with the oil layer of the oil storage tank, and at the bottom of this box, there is an automatic pipe that is controlled by an interface meter attached to this box. Alternatively, a tank draining device equipped with a drain pipe with a manual control valve has been proposed (Utility Model Publication Act 1983-
(See Publication No. 23734).

[Problems to be Solved by the Invention] As described above, an oil-containing water outlet pipe is provided on the side wall of the tank, and the oil-containing water collected at the bottom of the tank is passed through the outlet pipe to a box located at a lower position due to the difference in specific gravity. In the case of a structure in which water is continuously introduced to the middle part of the body, there is a problem in that water accumulated at the bottom of the oil storage tank cannot be completely drained out. Furthermore, if water remained in the outlet pipe after the oil removal process was completed, there was a risk that the water in the pipe would freeze and burst in the winter, causing an accident.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for draining water from an oil storage tank that can completely drain water from the oil storage tank.

[Means for Solving the Problems] A method for draining water from an oil storage tank according to the present invention is to drain oil-containing water accumulated at the bottom of the oil storage tank from the side wall of the oil storage tank into a non-open type oil-water separator tank through a lead-out pipe. When forcibly draining with a pump, the angle between the outlet pipe and the drain pipe in the oil-water separation tank is set to 30 degrees or more, and the interface level in the oil-water separation tank is detected by an interface detector installed in the oil-water separation tank. The apparatus is characterized in that the drive and stop of the pump and the opening and closing of a drainage pipe provided in the oil-water separation tank are automatically controlled in accordance with the detection signal obtained.

In addition, the water draining device for the oil storage tank for this purpose includes a non-open type oil-water separation tank that communicates with the oil storage tank through a lead-out pipe provided on the side wall of the oil storage tank, and an oil-containing water separation tank that is collected at the bottom of the oil storage tank. a pump that forcibly introduces water into the oil-water separation tank; an interface detector provided in the oil-water separation tank; a drain pipe having opening/closing means for discharging water from the oil-water separation tank; an oil return pipe that returns the oil to the oil storage tank, and means for automatically controlling driving and stopping of the pump and opening and closing of the pump according to a detection signal obtained by the interface detector, and It is characterized in that the angle between the outlet pipe and the drain pipe is set to 30 degrees or more.

[Operation] The interface detector provided in the oil-water separation tank detects that the oil-water interface level is at a low level, and supplies the obtained detection signal to the control means. This drives the pump, forcibly introduces oil-containing water from the side wall of the oil storage tank into the oil-water separation tank, drains the water in the separation tank, and returns the oil to the oil storage tank. Also, when the interface level reaches a high level, the interface detector detects this level and supplies the obtained signal to the control means.
This stops the pump and drains the separated water from the oil-water separation tank through the drain pipe until the interface detector in the oil-water separation tank detects a low level.

[Embodiment] An embodiment of the present invention applied to a method and apparatus for draining an oil storage tank in an oil refinery will be described with reference to the drawings.

First, the configuration of the water draining device for the oil storage tank will be explained.

The oil storage tank 1 is disposed on the foundation 2, in which oil 5A is stored, and separated water 5B is collected at the bottom. On a side wall near the bottom of this oil storage tank 1, there is disposed a lead-out pipe 3 whose open end 3A is bent downward to near the bottom. By extending this lead-out pipe 3 to the oil-water separation tank 4, the oil storage tank 1 and the oil-water separation tank 4 are communicated with each other. This outlet pipe 3 has
Bent parts 3B bent downward in order from the oil storage tank 1 side
A bent part 3C is formed which is continuous with this bent part 3B and bent upward. Note that the topmost portion 3C ₁ of the upper bent portion 3C is set at a higher position than the lowest position of the interface 9 between the oil 5A and water 5B of the oil-containing water 5 in the oil-water separation tank 4. In addition, the bent portion 3C is connected to the pump 1.
Considering the backflow from the oil return pipes 12A and 12B of No. 1, it is necessary to have a capacity sufficient to prevent the oil 5A in the bent portion 3C from being replaced with water due to backflow.
Further, in order to prevent backflow from the oil storage tank 1, it is preferable to provide a check valve 18 on the pump discharge side. An on-off valve 6A is provided in the outlet pipe 3 near the oil storage tank 1.

The oil/water separation tank 4 is a non-open type container. Water 5B from which the oil-containing water 5 has been separated is placed on the side of the oil-water separation tank 4.
A drain pipe 10 is provided for discharging water, and a diaphragm type on-off valve 6B is provided in the middle of the drain pipe 10. Note that, as shown in FIG. 2, the angle α between the drain pipe 10 and the outlet pipe 3 needs to be set to 30 degrees or more. This is because just before the end of water removal, only the oil 5A is introduced into the separation tank 4 through the outlet pipe 3, but at this time, the opening 3D of the outlet pipe 3 provided in the separation tank 4
If the opening 10A of the drain pipe 10 is nearby, the oil 5
This is because there is a risk that A may directly leak outside.
In this way, instead of adjusting the angle α between the drain pipe 10 and the outlet pipe 3, a partition plate 21 may be provided at the bottom. When this partition plate 21 is provided, a communication hole (not shown) is formed in the lower part of the partition plate 21, and the drain pipe 10 is installed on the opposite side of the outlet pipe 3 with the partition plate 21 in between. Further, the discharge port 10A of the discharge pipe 10 is provided at approximately the same height as the mouth portion 3D of the outlet pipe 3, or at a slightly lower position. Also, connect the diameter of the outlet pipe 3 to the drain pipe 1.
It is preferable to set the diameter to be larger than the diameter of 0.

A first interface detector 7 having a float and arranged vertically is provided on the upper surface side of the oil-water separation tank 4, and a second interface detector 8 having a sensor is provided on the side surface side. This first interface detector 7 stops the pump 11 when the interface 9 reaches a high level;
When the low level is reached, it is detected when to start the pump 11, which will be described later. This high level setting is
Since there is a possibility that the interface may shake when the oil-containing water 5 is introduced or drained, it is necessary to make the total volume 90%, preferably 80%, in order to extract only the oil 5A. In addition, a low level setting value may cause the interface to shake when introducing or draining oil-containing water, so in order to extract only water 5B,
% preferably 50%. Second
The interface detector 8 detects when the interface 9 is below a certain level and the oil 5A is about to flow out through the drain pipe 10. Therefore, the sensor can detect the level. The detector 8 is installed at approximately the same height as or slightly above the mouth 10A of the drain pipe 10 provided in the separation tank 4. The sensor of the second interface detector 8 is a capacitive sensor that detects the level by using the capacitance difference between the oil 5A and the water 5B, and a capacitive sensor that detects the level by using the difference in the refractive index of the interface 9. An ultrasonic sensor or the like can be used.

The air-driven pump 11 is installed so as to communicate with the separation layer 4 through an oil return pipe 12A connected to the top surface of the oil-water separation tank 4, and an on-off valve 6 is installed in the middle of the pipe 12A.
Provide C. Furthermore, from this pump 11, the oil storage tank 1
By connecting the oil return pipe 12B to the upper part of the tank, the separation tank 4 and the oil storage tank 1 are communicated with each other. This air-driven pump 11 is provided with a pipe 13A for supplying driving air, and the supply pipe 13A is connected to an air source 14 provided in the refinery via a diaphragm type on-off valve 6D. Connect to. Note that this pump 11 is driven by an air pressure of 5 to 8 kg/cm ² .

Next, the specific configuration of the means for automatically controlling the drive and stop of the pump 11 and the opening and closing of the on-off valves 6B and 6D in accordance with the detection signals obtained by the first and second interface detectors 7 and 8 will be explained. explain.

Pipes 13B and 13C are provided for supplying control air to the on-off valve 6B of the drain pipe 10 and the on-off valve 6D of the air supply pipe 13A of the pump 11, respectively,
These air supply pipes 13B and 13C are connected to the air source 14.
Connect to. A first air pressure control section 15A is provided in the middle of one air supply pipe 13B, and a second air pressure control section 15B is provided in the middle of the other air supply pipe 13C. Circuit 16A that supplies the interface level signal obtained by the first interface detector 7
is connected to the first air pressure control section 15A and also to the second air pressure control section 15B. Further, a circuit 16B that supplies an interface level signal obtained by the second interface detector 8 is connected to the first air pressure controller 15A. Note that these diaphragm-type on-off valves 6B and 6D are configured to operate in reverse by springs. The valve 6D is interlocked with the pump 11, and when the valve 6D is closed, the pump 11 is
When the pump 11 stops and the valve 6D opens, the pump 11 starts. When high pressure is supplied, for example 1.0 Kg/cm ² , valve 6B is fully open and valve 6D is closed.
Further, when a low pressure, for example 0.2 kg/cm ² is supplied, the valve 6B is closed and the valve 6D is fully open. This predetermined pressure is controlled by air pressure controllers 15A and 15B to supply air to each on-off valve 6B and 6D.

Next, the water removal method of this embodiment will be explained.

At the start of the water removal process, the oil-water separation tank 4 is filled with oil-impregnated water 5. First interface detector 7
detects that the oil-impregnated water 5 is separated into an upper layer of oil 5A and a lower layer of water 5B, and that the interface 9 is 50%, and supplies this signal to the second air pressure control section 15B. Based on this detection signal, the second air pressure control section 15B controls the air pressure to 0.2 kg/cm ² , supplies this air to the on-off valve 6D through the air supply pipe 13C, and opens the valve 6D. By supplying air of 5 to 8 kg/cm ² from the air source 14 to the air-driven pump 11 through the air supply pipe 13A, the pump 11
is driven. As a result, oil return pipes 12A, 12B
The oil 5A in the oil-water separation tank 4 is forcibly returned to the oil storage tank 1 through the outlet pipe 3, and the water 5B accumulated at the bottom of the oil storage tank 1 is forcibly returned to the oil separation tank 4 through the outlet pipe 3.
to be introduced within.

When the interface 9 rises, the first interface detector 7 detects the interface level and increases the supplied air pressure according to the interface level. As a result, valve 6
The open and closed states of B and 6D change. The interface level
When the air pressure reaches 80%, the air pressure supplied from the air pressure control parts 15A and 15B is controlled to 1.0Kg/ ^cm2 , and the valve 6
B is fully opened and water 5B is discharged from the drain pipe 10. In addition, the valve 6D is closed in the opposite direction, and the pump 11
stops.

When the interface level is between 50 and 80%, valve 6
Both B and 6D are in an open state, and the oil-impregnated water 5 is introduced and drained at the same time.

As the drainage progresses, water 5B in the oil-water separation tank 4
The level of the interface 9 begins to decrease as the amount of . The first interface detector 7 detects that this level is 50%.
When it is detected that the detection signal has reached the
Send the air pressure to the air pressure control section 15A, and adjust the air pressure to 0.2Kg/
Control to ^cm2 . This air is transferred to the on-off valve 6 of the drain pipe 10.
B and closes the on-off valve 6B. Further, the signal obtained by the first interface detector 7 is simultaneously transmitted to the second interface detector 7.
The air pressure is also sent to the air pressure control unit 15B, where the air pressure is controlled to 0.2 kg/cm ² . This air is supplied to the on-off valve 6D of the air supply pipe 13A, the on-off valve 6D is fully opened, the pump 11 is driven, and the oil-containing water 5 is introduced into the oil-water separation tank 4.

When introducing this oil-containing water 5, water 5B in the oil storage tank 1
When most of it is gone, it gradually becomes a mixture of oil and water,
At the end, only 5A of oil is left. The vicinity of the mouth 3D of the outlet pipe 3 connected to the separation tank 4 is a layer of water 5B with a heavy specific gravity, so after the water draining process is completed, the oil 5A in the outlet pipe 3 does not move downward. oil 5a
remains filled in the outlet pipe 3. After confirming that there is no more water 5B in the oil storage tank 1 to be drained, the pump 11 is stopped to complete the draining process.

When the level at the interface 9 reaches a low level (50%), the on-off valve 6B of the drain pipe 10 is automatically closed, so it should not drop any further, but if it does not operate normally, the interface 9 is the drain pipe 10
There is a risk that the oil 5A in the separation tank 4 below the mouth 10A of the tank 4 may flow out through the drain pipe 10.
Therefore, when the second interface detector 8 detects that the interface level has fallen too much, the detection signal is sent to the first air pressure control section 15A. Here, the air pressure is controlled to 0.2 kg/cm ² and this air is sent to the on-off valve 6B of the drain pipe 3 through the air supply pipe 13B. This closes the valve 6B and prevents the oil 5A from flowing out.

Next, the effects of this embodiment will be explained.

Since the oil-containing water 5 is forcibly led out from the oil storage tank 1 to the oil-water separation tank 4 using the pump 11, even if the lead-out pipe 3 is provided on the side wall of the oil storage tank 1, its open end 3A is located near the bottom. By bending it until
Complete drainage is possible. Therefore, corrosion of the oil storage tank 1 can be completely prevented. In addition, since the interface level signal detected by the interface detector 7 is sent to the air pressure controllers 15A and 15B to control the drive and stop of the pump 11 and the opening and closing of the on-off valve 6B of the drain pipe 10, complete Automation is possible. After the oil removal process is completed, the outlet pipe 3 is filled with oil 5A, so there is no risk of rupture even in winter. In addition, a second interface detector 8
As a result, the level when the interface 9 starts to fall abnormally is detected, and the on-off valve 6B of the drain pipe 10 is automatically closed, so there is no risk of an accident in which the oil 5A leaks outside. . Furthermore, the drain pipe 10
Since the angle between the tank and the outlet pipe 3 is set to 30 degrees or more, when only the oil 5A is introduced into the separation tank 4 immediately before the end of draining, the oil 5A will not directly flow out to the outside.

The present invention is not limited to the above-mentioned embodiments, and various modifications can be made to the configuration.

For example, the air for controlling the opening and closing of the on-off valves 6B and 6D and the driving air for the pump 11 are supplied from the same air source 1.
Although air supplied from No. 4 was used, air supplied from different air sources can be used. That is, dehumidified air may be used as the control air, and non-dehumidified air may be used as the drive air.

Furthermore, although air was used for control and driving purposes in consideration of explosion protection, electricity may also be used as long as safety is ensured. That is, an electrically driven pump may be used instead of the air driven pump 11.

Furthermore, although diaphragm type on-off valves are used as the on-off valves 6B and 6D, any other type of on-off valve may be used as desired.

Further, although two control units 15A and 15B are provided for supplying air to the valves 6B and 6D, a configuration may be provided in which only one control unit is provided.

[Effects of the Invention] According to the present invention, it is possible to completely drain water from an oil storage tank, and since automation is performed, the efficiency of the water draining process can be improved.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a water draining device according to an embodiment of the present invention, and FIG. 2 is a plan view showing the piping configuration of FIG. 1. 1...Oil storage tank, 3...Outlet pipe, 4...Oil-water separation layer, 5...Oil-containing water, 5A...Oil, 5B...Water, 6
A to 6E... Opening/closing valve as opening/closing means, 7... First interface detector, 8... Second interface detector, 9...
... Interface, 10 ... Drain pipe, 11 ... Air drive pump, 12A, 12B ... Oil return pipe, 14 ... Air source, 15A, 15B ... Air pressure control section.

Claims (1)

[Scope of Claims] 1. When the oil-containing water accumulated at the bottom of the oil storage tank is forcibly led out from the side wall of the oil storage tank to the non-open type oil-water separation tank by a pump, the water in the oil-water separation tank is The angle between the outlet pipe and the drain pipe is set to 30 degrees or more, and the interface level in the oil-water separation tank is detected by an interface detector installed in the oil-water separation tank,
A method for draining water from an oil storage tank, characterized in that the driving and stopping of the pump and the opening and closing of a drain pipe opening/closing means provided in the oil/water separation tank are automatically controlled in accordance with the obtained detection signal. 2. A non-open oil-water separation tank that communicates with the oil storage tank through a lead-out pipe provided on the side wall of the oil storage tank, and a pump that forcibly introduces the oil-containing water accumulated at the bottom of the oil storage tank into the oil-water separation tank. an interface detector provided in the oil-water separation tank; a drain pipe having an opening/closing means for discharging water from the oil-water separation tank; an oil return pipe for returning oil from the oil-water separation tank to the oil storage tank; means for automatically controlling driving and stopping of the pump and opening/closing of the opening/closing means according to a detection signal obtained by an interface detector, and an angle between the outlet pipe and the drain pipe in the oil/water separation tank. A water draining device for an oil storage tank characterized by setting the temperature to 30 degrees or higher.