JPS5929504B2 - Sludge accumulation prevention device for crude oil tanks - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for preventing sludge accumulation in a tank.

Currently, crude oil extracted from underground is generally collected at the base of the mountain.
After sufficiently removing mud water using a surfactant or the like, the mud is transported by large tanker to a receiving site, first received and stored in a large crude oil storage tank, and then discharged as needed.

Crude oil contains various components, among which paraffin, asphaltene, water, etc. change over time during transportation in tankers, storage in tanks, and precipitate and separate or combine from crude oil. Sludge forms and settles at the bottom of the tank.

This sludge cannot be completely removed using the normal removal method, and as a result it sticks to the bottom of the tank.

Recently, open inspections have been carried out regularly for the safety of tanks, but in tanks with a capacity of 100,000 to 150,000 km, the cumulative accumulation of sludge can reach several thousand km in about 5 years.
Removal of this sludge requires a lot of effort and several months of time and effort, so various methods have been tried in the industry to prevent sludge build-up. From this point of view, as the sludge in storage tanks has come to be discharged together with crude oil and sent to refineries to be turned into products, measures to prevent sludge accumulation in storage tanks have become more important. A conventional method for preventing sludge accumulation in crude oil storage tanks is to attach a side-entering mixer to the inner wall of the tank side plate to agitate the stored crude oil in the tank, as shown in Figure 1. The crude oil tank has a diameter of 8
In order to effectively and economically agitate the crude oil in the tank, which measures 0 to 100 meters and is 22 meters high, it is necessary to place several side-entering mixers along specific lines, but with this method. It has the disadvantage that vortices are generated at specific locations and sludge is deposited there.

For this reason, the tank is of a swing type, and the flow of crude oil inside the tank is switched sequentially from right to center to left to prevent sludge buildup. However, in the case of the center above, 80 to 10 of the tank diameter
In order to make the jet stream from the propeller of a side-entering mixer reach a distance of 0 meters, a side mixer with a large capacity is required, and the required power is 100 meters per tank.
~150KW, and continuous operation is uneconomical, so
The disadvantage is that the vehicle must be operated for about 5 to 10 hours per day in order to save money. There is also dinit stirring shown in FIG. 2, but it has not been implemented because it is inappropriate for large tanks. Also, it has been proposed that a riser pipe 20 is provided from a branch pipe 19 of the piping 18 arranged at the bottom of the tank shown in FIGS. 3 and 4, and a rotary nozzle 21 shown in FIG. 5 is provided at the top. It is difficult to check whether the rotating nozzle is operating smoothly, it is necessary to empty the tank for maintenance and inspection, and a rotating nozzle is required, and the rotating nozzle is located at the top of the riser pipe 20. Therefore, a pump for pumping oil was required to have a large lift, which had drawbacks such as increased equipment and operating costs. SUMMARY OF THE INVENTION The object of the present invention is to provide a sludge deposition prevention device for a crude oil tank, which eliminates the above-mentioned drawbacks.

The structure of the sludge accumulation prevention device for a tank according to the present invention will be explained in detail based on an embodiment shown in FIG. along the inner wall of the opening 10', 1V
A suction nozzle 10 for the tank contents and a side wall side discharge nozzle 11 for the tank contents are provided, which do not face each other but face in opposite directions.
A tank contents central discharge nozzle 13 is provided facing the bottom plate 2 and opening at a slight distance m from the bottom plate 2.
A rotary vane pump 9 for circulating the contents of the tank is provided outside, and the suction nozzle 10 is connected to the circulation pump 9 through the piping 3 and the valve 6.
The side wall side discharge nozzle 11 is connected to the circulation pump 9 through the piping 4 and the valve 7, and the central discharge nozzle 13 is connected to the tank internal piping 12, the tank external piping 5, and the valve 8 to the suction side of the circulation pump 9. It has a structure in which it communicates with a pipe 9' that continues on the discharge side.

In addition, the above-mentioned interval m assumes that the diameter of the pipe 12 is D (1 to 1/
2) A grade of D is good. Since this embodiment has the above-mentioned configuration, when the valves 6 and 7 are opened and the valve 8 is closed to drive the circulation pump 9, the contents of the tank are sucked through the opening 10' of the suction nozzle 10 and the contents are sucked into the side wall of the gourd. Opening 11' of side discharge nozzle 11
Liquid pressure acts on the liquid at the bottom of the tank in the direction of arrow 14, causing the liquid at the bottom of the tank to initially swirl mainly around the circumference, but due to liquid layer friction, the liquid at the entire bottom as well as the upper part in contact with it swirls. will also begin to rotate.

The velocity of the swirling flow of the liquid at this time is 0 along the vertical center axis of the tank.
The −0 section is O, the circumferential portion is the maximum, and the intermediate portion has an intermediate speed proportional to the distance from the vertical center axis 0-0. Next, open valves 6 and 8, close valve 7, and use circulation pump 9.
When driven, the liquid is sucked from the suction nozzle 10 and discharged from the central discharge nozzle 13.The discharged liquid collides with the upper surface of the tank bottom plate 2 as shown in FIGS.
The liquid flows radially from the center 01 along the top surface of the bottom plate as shown by arrows 15 in FIG. 7 and reaches the side wall of the tank.

At this time, the speed of the content liquid on the upper surface of the tank bottom plate is fastest at the center 0, and decreases as it approaches the side wall of the tank around the circumference, and becomes slower approximately in inverse proportion to the distance from the center 01. Next, valves 6 and 7
, 8 are opened and the circulation pump 9 is driven, the liquid is sucked through the suction nozzle 10 and discharged from the side wall side discharge nozzle 11 and the center discharge nozzle 13. At this time, the liquid on the top surface of the tank bottom plate is discharged from the side wall side discharge nozzle 11. It rotates due to the discharged liquid, but on the other hand, it is located slightly above the center 01 of the bottom plate 2.
The liquid is ejected from the central discharge nozzle 13 toward the center 01, so as shown by the arrow 17 in FIG. A flow occurs in the direction.

That is, when using the apparatus of this embodiment, the layer above the nozzle in the tank is generally in a stationary state, so when the sludge component generated at room temperature slowly descends to the bottom due to gravitational sedimentation, it will drop below the nozzle. In the lower layer of the tank, near the center 01 of the bottom plate 2 of the tank, a quiet swirling flow occurs radially, and near the tank side wall, a quiet swirling flow is generated circumferentially around the center 01, so the descending sludge components are collected around the tank. This concentrated sludge component is sucked through a suction nozzle 10 on the tank side plate by a circulation pump installed outside the tank, and is crushed and stirred by the rotary blades of the pump. After that, the sludge is returned to the bottom of the tank through the discharge nozzle and is constantly circulated, which prevents sludge from accumulating.

Since this invention is a device for preventing sludge accumulation in a crude oil tank as described above, it has the following particularly remarkable effects.

That is, I. If the circumferential velocity of the liquid near the side wall is V1, the linear velocity at 1/2 of the radius r of the tank is 1/2, and the liquid discharged from the central discharge nozzle 13 and flowing along the bottom plate, If the speed at the center 01 of the tank bottom plate is 2, then
The speed at 1/2 of the radius r of the tank is approximately 2/2.

Therefore, the resultant velocity V near r/2 is -V(-21
)2+(-V!)2.

Therefore, it is possible to adjust the valves 7 and 8 appropriately so that 1=V2.

In other words, the slowest speed is V1- at 1/2 of the radius of the tank.
V2 can be approximately 70% of the tank bottom plate, so the liquid flow on the top of the tank bottom plate can be made to flow over the entire top of the tank bottom plate in the range of 1-2 to 0.7V1. It can prevent it from sticking to the surface.

i1 The sludge in a crude oil tank is slightly heavier than crude oil, so if it does not move up and down within the crude oil tank, it will settle over time, accumulate sludge particles on the tank bottom plate, and become attached to each other. , so-called sludge solidifies.

However, in the device of this invention, from the suction nozzle 10,
The thickest slurry with the highest specific gravity swirling around the bottom of the tank is sucked by the circulation pump 9, and when it passes through the pump's impeller, the slurry is crushed, so the sludge in the slurry sticks to each other and becomes sludge. It is possible to prevent it from forming into lumps. 111 There are no moving parts inside the tank, there are only three nozzles and the tank internal piping 12, and the driving machine is the circulation pump 9 installed outside the tank 1, so the oscillating side entering mixer As there are no seals for moving parts like in the first example, there is no need to worry about oil leakage, and by closing valves 6, 7, and 8, the circulation pump can be easily dismantled and repaired, ensuring safety and maintenance of large storage tanks. It is also extremely advantageous.

The circulation of crude oil at the bottom of the 1V tank is done by a circulation pump, but since it is sucked in from the suction nozzle 10 at the bottom of the tank and discharged from the discharge nozzle 11 at approximately the same level, the circulation pump is an axial flow pump with an extremely low head. This means that the length of the piping can be extremely short, and the flow rate of the contents of the tank discharged from the discharge nozzle can be low, so the power required for the pump can be extremely small.

The amount and nature of the sludge produced in V1 crude oil varies depending on the extraction location and handling, and therefore the minimum flow or circulation required to keep the produced sludge in a slurry with the crude oil during storage. However, when using an axial flow pump, the flow rate can be easily adjusted by varying the angle of the impeller, and the most economical operation is possible depending on the region of crude oil production.

The contents of the tank passing through the V1 circulation pump are the thickest slurry in the tank, so if you place a sample so that it can be taken out from an appropriate location on the piping outside the tank, you will be able to see the state of sludge formation in the crude oil. can be investigated. Vl
l The discharge amount of the discharge nozzles 11 and 13 is adjusted by adjusting the opening degree of the valves 7 and 8, and the discharge amount is determined by adjusting the opening degree of the valves 7 and 8. The ratio to the discharge amount for dissipation can be freely changed, and therefore the required power of the circulation pump can be used effectively.

VIII One of the methods for preventing sludge accumulation in crude oil is to chemically prevent the formation of sludge by mixing a chemical solution, or to dissolve the generated sludge. However, when the chemical solution is injected through the piping outside the tank, the chemical solution can be mixed and circulated to the part of the tank where the sludge is the thickest, and the chemical solution can be effectively used sparingly.

IX Even if sludge has already accumulated in an existing large tank, etc., with the device according to this invention, the suction nozzle, discharge nozzle, etc. can be installed using the manhole provided on the side plate of the tank. Therefore, when mixing chemicals and circulating crude oil as described above, it is possible to dissolve sludge and prevent sludge accumulation in an extremely economical and labor-saving manner.

[Brief explanation of drawings]

Figures 1, 2, and 3 are explanatory diagrams of various conventional sludge accumulation prevention devices, and Figure 4 is a front view of the one shown in Figure 3.
Fig. 5 is a front view of the rotating nozzle used in the one shown in Fig. 3, Fig. 6 is a plan view of an embodiment of the crude oil tank sludge accumulation prevention device according to the present invention, and Fig. 7 is a central discharge nozzle. FIG. 8 is a front view of FIG. 7; FIG. 9 is a plan view showing the quiet flow of tank contents in a radial and swirling manner according to the present invention;
FIG. 10 shows their perspective views, where 1 is a cylindrical crude oil tank, 2 is a bottom plate, 6, 7, and 8 are valves, 9 is a tank contents circulation pump, 10 is a suction nozzle, and 11 is a discharge nozzle on the side wall of the tank. , 13 indicates the central discharge nozzle, 0-0 indicates the vertical central axis of the tank, and 01 indicates the center of the tank bottom plate, respectively.

Claims (1)

[Claims] 1 Along the inner wall of the side plate near the bottom plate 2 of the crude oil tank 1, a suction nozzle 10 and a tank inner wall side discharge nozzle 11 are provided whose openings 10' and 11' do not face each other but face in opposite directions. A central discharge nozzle 13 in the tank that faces the bottom plate 2 and is open is provided near the center, a rotary vane pump 9 for circulating tank contents is provided outside the tank 1, and the suction nozzle 10 is connected to the suction side of the circulation pump 9. Moreover, the sludge accumulation prevention device for a crude oil tank is characterized in that the side wall side discharge nozzle 11 and the central discharge nozzle 13 are communicated with the discharge side of the circulation pump.