JPH04135602A - Electrolytic desalter - Google Patents

Abstract

PURPOSE:To desalt oil with a one-stage desalting bath in an electrode structure by connecting plural sheets at regular intervals by providing plural protrusions on both sides of the electrode sheet. CONSTITUTION:An mineral oil is desalted in the presence of water in this electrolytic desalter. In this case, plural electrode sheets 111(a) and 111(b) are connected at regular intervals to form a structure. Plural protrusions 113 are provided on both sides of the electrode sheet. Namely, fine water droplets in the oil are agglomerated close to the protrusion in the nonuniform electric field generated by charging the electrode sheet, and the water droplet in oil and the salt dissolved in the water droplet are efficiently removed. Consequently, oil is desalted with this one-stage desalting bath.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to mineral oils, such as crude oil, heavy oil, fuel oil, petroleum refinery residue oil, coal liquefied oil, oil sand oil, shale oil, and other synthetic crude oils. Regarding dehydration and desalination equipment.

[Conventional technology]

The principle of a conventional electrical desalination device will be explained with reference to FIG. 5, and the device configuration is shown in FIGS. 6 to 9. Conventional electrical desalination equipment injects fresh water or salt water with a low salinity concentration of several percent to ten-odd percent of crude oil as dilution water, mixes and stirs the crude oil, transfers the salt in the crude oil into the dilution water, and reduces the diameter of water droplets. By applying a high voltage electric field to a water-in-oil emulsion with an increased number of water droplets, the aggregation of saline water particles is promoted. The flocculated salt water is separated from the crude oil by settling due to the difference in specific gravity between it and the crude oil.

FIG. 5 shows the charged state of salt-containing water particles in an electric field. In Figure 5, 1 is a positive electrode, 2 is a negative electrode, 3
indicates the charged particles, 4 indicates the direction of the electric field, and 5 indicates the attractive force acting between the charged particles.

The force acting between charged saline water particles in an electric field is expressed by the following equation.

[F: Attraction force between salt water particles, E: Potential gradient, a: Radius of salt water particles, d: Distance between salt water particles, K: Constant]

As shown by this equation, the suction force acting between particles of salt water in crude oil is proportional to the sixth power of the particle size and inversely proportional to the fourth power of the center-to-center distance. For this reason, by injecting several percent to several ten percent of dilution water into the crude oil and stirring it, the number of salt-containing water particles in the crude oil is increased and aggregation is further promoted.

FIG. 6 shows a system diagram of the conventional electrical desalination method.

Crude oil 11 and dilution water 12 are generally heated, then mixed and stirred in a mixing valve 13, and enter a desalination tank 15 via a line 14. A high-voltage electric field is applied to the desalination tank 15, and the salt water particles coagulate, are separated from the crude oil due to the difference in specific gravity, and are discharged outside the system as salt-containing waste water 17, and the desalted crude oil 16 is transferred to the desalination tank 15.
sent outside the system.

A conventional electrical desalination apparatus will be specifically explained with reference to FIGS. 7 and 8. Figure 7 is a longitudinal section of the electric desalination tank, and Figure 8 is the 7th section.
It is a sectional view taken along line 1-1' in the figure.

In FIGS. 7 and 8, 201 is a desalination tank, 202 is a treated oil supply pipe, 203 is a distribution pipe, and 204 is an oil collection pipe. Further, inside this desalination tank 201, a medium electrode 205 and a high voltage electrode 206 provided below and opposite to this medium electrode 205 are provided.
A high voltage is applied to 6 from a power supply 207. In addition, 20
8 is an insulator that supports the high voltage electrode 206. Impurities such as minute water droplets and impurities contained in the oil to be treated that is supplied from the oil to be treated supply pipe 202 to the desalination tank 201 via the distribution pipe 203 are removed from the ground electrode 205 and the high voltage electrode 201.
The minute water droplets repeatedly coalesce with each other in the electric field generated between the two water droplets, the diameter of these water droplets gradually increases, and they settle and separate due to gravity. The decomposed water in the lower part of the desalination tank 201 is discharged from the drain 209, and the oil to be treated from which minute water droplets have been removed is discharged from the oil collecting pipe 204.

Note that 210 is an interface meter that monitors an interface 212 between the oil to be treated and decomposed water.

Conventional electric field-based desalting tanks for mineral oil, etc., called Deitzruter, apply a high-voltage electric field to condense the salty water contained in crude oil, making the water droplets larger and increasing the separation speed due to the difference in gravity. However, as the water droplets coagulate and separate from the large ones, the size of the water droplets remaining in the oil becomes smaller as time passes, and the amount of water droplets decreases. The distance between them increases.

The force that acts between charged water droplets in an electric field is as shown in equation (1) above, and a decrease in the diameter of the water droplets and an increase in the distance between the water droplets both cause a rapid decrease in the force that acts between the water droplets, resulting in a substantial Therefore, it becomes impossible to expect a cohesive effect within the electric field. One possible solution to this problem is to increase the cohesive force that raises the voltage, but excessive voltage increases can cause problems such as short circuits and increased equipment costs due to the introduction of high voltage equipment. The upper limit of the practical voltage is 20.000V.

Another solution is to install Daysulters in series, and mix dilution water into each Daysulter again to reduce the salt concentration in the water droplets in the oil, and increase the water droplet diameter and number of water droplets to increase the desalination rate. efforts are being made to improve the An example is shown in FIG.

FIG. 9 shows an example in which two demineralization tanks, which are Deutsulters, are installed in a series. are stirred and mixed in the first mixer 22, and the line 24
The water is then sent to the first desalination tank 25. In the first desalination tank 25, water droplets in the oil coalesce between the electrodes and are taken out of the system as a drain 27, and the dehydrated and desalted oil is sent to the second mixer 28 via a line 26.

In the second mixer 28, the petroleum separated in the first desalination tank 25 is stirred and mixed with dilution water 29, and sent to the second desalination tank 31 via a line 30. 25, the dehydrated and desalinated petroleum is sent to the outside of the system via line 32, and dilution water 23 separated by this is sent to circulation pump 34.
is sent to the first mixer 22 and used as dilution water.

In this method, it is possible to increase the desired desalination effect by installing multiple desalination tanks, but an increase in the number of desalination tanks causes an increase in costs, and there are costs such as securing dilution water. There is a problem in that the cause of the increase is a large one, and it has been desired to develop a high-performance desalination tank that functions in the -stage.

[Problem to be solved by the invention]

The present invention has been made in view of the above-mentioned technical level and in response to the above-mentioned demands.
The present invention aims to provide a device that enables desalination in oil using stage desalination tanks.

[Means to solve the problem]

The present inventors have investigated various methods of coagulating micro water droplets in oil, and have found that by devising the electrode structure of the desalination tank, it is possible to coagulate micro water droplets that could not be achieved with conventional desalination tanks. We have confirmed that this is the case, and have completed the present invention. That is, the present invention provides an electric desalination apparatus for desalinating mineral oil in the presence of water, and an electrode plate attached to the apparatus is a structure in which a plurality of thin flat plates are connected at equal intervals, The electrode structure is an electrical desalination device characterized in that it is constituted by an electrode plate having a plurality of protrusions on both sides of the electrode plate.

The present invention provides a plurality of protrusions on an electrode plate, forms an uneven electric field in a region near the protrusions, and collects the water droplets in the direction of the protrusions by the dielectrophoretic force acting on the water droplets in the uneven electric field. The distance between each water droplet, that is, d in the above formula (1) is reduced, and the suction force acting between each water droplet is increased to promote aggregation of the water droplets.

By this means, the minute water droplets in the oil phase coalesce and enlarge,
Substantially the water in the oil phase is removed, and thus the salts dissolved in the water are removed simultaneously with the water removal.

[Effect]

Hereinafter, the function of the electrodes of the device of the present invention will be explained with reference to FIG.

FIG. 4(a) is an explanatory view showing the protrusion 42 of the electrode plate 41 of the present invention and its vicinity. By charging the electrode plate 41, an unequal electric field is formed near the protrusion 42. In the figure, the fact that the lines of electric force 44 are not parallel indicates unequal electric field properties. Figure 4(b) shows the force acting on the water drop 43 placed in an unbalanced electric field.
Due to the electric charge induced on the water droplet 4, the attraction force is stronger in the direction where the electric field strength is stronger, that is, in the direction where the electric lines of force are denser, and the water droplet 4
3 moves along the zoelectric lines of force 44 in the direction of the protrusion 42 .

As shown in FIG. 4(C), due to this movement, the distance between each water droplet 43 decreases, and therefore the suction force between each water droplet also increases rapidly. (According to the above formula (1)) Therefore, the minute water droplets in the oil phase aggregate and coalesce and are separated from the oil phase.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1, 2, and 3. FIG. 1 is a longitudinal sectional view of an embodiment of the device, FIG. 2 is a sectional view taken along line IT' in FIG. FIG.

In the figure, 101 is a desalination tank, 102 is a treated oil supply pipe, and 10
3 is a distribution pipe, 104 is an oil collecting pipe, and the oil to be treated is sent from the oil to be treated pipe 102 to the desalination tank 10 via the distribution pipe 103.
1 and is discharged through the oil collection pipe 104. In this desalination tank 101, two pairs of electrodes, a first upper electrode 105, a first lower electrode 106, and a second electrode pair 111 having unequal electrical polarity, are arranged one above the other. Further, a high voltage is applied to the first upper electrode 105, the first lower electrode 106, and the second electrode pair group 111 from a power source 107. Furthermore, 10B is an insulator for supporting the electrode, 109 is a drain for discharging separated water, and 11
0 is an interface meter that monitors the interface 112 between the oil to be treated and water.

In the apparatus according to the embodiment of the present invention configured as described above, the oil to be treated is supplied into the demineralization tank 101 from the oil to be treated supply pipe 102 via the distribution pipe 103. Then, the minute water droplets in the oil to be treated are transferred to the first lower electrode 106 and the first upper electrode 105.
In the electric field generated between them, they coalesce with each other, settle downward, and are discharged from the drain 109. In other words, most of the minute water droplets are removed when passing through the electrode, but 10μ
Most of the micro water droplets with a size of about m or less do not coalesce between the electrodes, but flow upwards in the oil to be treated, and are transferred to the first upper electrode 10.
5 and is supplied to the second electrode group 111.

FIG. 3 shows the second electrode group 111 in more detail, in which the electrodes are provided with protrusions 113 on thin flat plates 111(a), 111, etc.) and arranged in parallel for the purpose of forming an uneven electric field. It is installed. The minute water droplets in the oil to be treated aggregate and enlarge in the second electrode group 111, and settle in the oil phase. Therefore, the dehydration (desalination) of the oil to be treated is completed efficiently.

The oil to be treated that has passed through the second electrode group 111 contains almost no water, and is sent out of the system from the desalination tank 101 via the oil collecting pipe 104.

Note that the second electrode group 111 is not limited to that shown in FIG. 3, but may have any shape as long as it forms an uneven electric field by protrusions on a flat plate.

As described above, the present invention provides a demineralization tank for storing oil to be treated containing impurities, and also provides a demineralization tank above the electrodes of a normal demineralization tank.
By providing a second electrode group, impurities can be separated efficiently and in a short time by the electric field generated between these multiple electrodes, and there is no need to increase the voltage applied between the electrodes, so spark discharge The effects are great, as there is no danger of this happening.

Further, the second electrode group 111 is not limited to being installed in the desalination tank 101, and the second electrode group may be installed in a desalination tank installed in series with the desalination tank.

The present invention will be explained below using experimental examples.

An example of measuring the residual moisture concentration of an electrode made of two thin flat plates and an electrode made of a thin flat plate having protrusions on the surface will be shown. The electrodes are separated by about 50 mm, and the oil is kerosene, liquid paraffin for viscosity adjustment, saline, and surfactant for emulsion stabilization at 4.3 wt%, 1.0 wt%, and 0.0 wt%.
A mixture containing 5 wt% was used. Salt water and salt concentration approximately 6
It was wt%. The feed electrode was charged with alternating current so that the electric field strength was IKV/Cm, and the oil was caused to flow at a rate of about 1 mm/sec. The results are shown in the table.

Table: Residual moisture concentration at each electrode The flat plate with protrusions has a residual moisture concentration of about 4
0%, indicating that the provision of the protrusions makes water removal more efficient.

[Effects of the Invention] According to the device of the present invention, in an uneven electric field formed by charging an electrode plate having a large number of protrusions on a thin electric plate, minute water droplets in the oil phase are Water droplets in the oil phase that aggregate and enlarge near the protrusions and salt dissolved in the water droplets can be efficiently removed.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of an apparatus according to an embodiment of the present invention, in which FIG. 1 is a longitudinal sectional view thereof, FIG. 2 is a sectional view taken along line II' in FIG. 1, and FIG. The figure is a detailed view of one embodiment of an electrode that forms an unequal electric field, which is a feature of the present invention, and FIG. 4(a).
(3) and (C) are detailed explanatory diagrams of the present invention, Fig. 5 is an explanatory diagram of the principle of the electrodesalination apparatus, Fig. 6 is a system diagram of the conventional electrodesalination method, Figs. 7 and 8. is an explanatory diagram of a conventional electrical desalination equipment,
FIG. 9 is a system diagram of another conventional electrodesalination method.

Claims (1)

[Claims] In an electric desalination apparatus for desalinating mineral oil in the presence of water, an electrode plate attached to the apparatus is a structure formed by connecting a plurality of thin flat plates at equal intervals, and the electrode structure is An electrical desalination device comprising an electrode plate having a plurality of protrusions on both sides of the electrode plate.