A raw oil electric desalting method, device and application

Abstract

A raw oil electric desalting method, device and application, the raw oil electric desalting method, the electric desalting tank is used to the desalination of raw oil, the electric field intensity in the oil phase of electric desalting tank is gradually increased from bottom to top, and the deep electric desalting of inferior raw oil with high specific gravity, high viscosity, high salt content or high acid value is carried out.The present application improves the desalination efficiency of inferior crude oil.

Description

Technical Field

[0001] This invention relates to the field of crude oil pretreatment technology, specifically to a method, apparatus, and application for electro-desalting of feedstock oil. Background Technology

[0002] Electrostatic desalting is the first step in atmospheric and vacuum distillation, and it is widely used, especially in the processing of high-quality or light crude oil. Many mature electrostatic desalting technologies have been developed, such as AC electrostatic desalting, AC / DC electrostatic desalting, and high-speed electrostatic desalting.

[0003] However, with the increasing trend of crude oil deterioration, refineries are processing an increasing proportion of low-quality / heavy crude oil. Current electrostatic desalting technology has encountered problems such as low desalting and dehydration efficiency and substandard salt content in the desalted crude oil when applied to the desalting and dehydration of heavy / low-quality crude oil. Summary of the Invention

[0004] The present invention aims to provide a method, apparatus and application for desalting crude oil, which improves the desalting efficiency of inferior crude oil.

[0005] To solve the above technical problems, the specific solution adopted by the present invention is as follows: a method for desalting raw oil by electrostatic desalting, wherein the electric field strength in the oil phase of the electrostatic desalting tank is controlled to gradually increase from bottom to top.

[0006] Preferably, the circuit loops of two adjacent electrode plates in the oil-water emulsion layer are isolated within the electrostatic desalting tank.

[0007] The above-mentioned method for electro-desalting of feedstock oils enables deep electro-desalting of inferior feedstock oils with high specific gravity, high viscosity, high salt content, or high acid value.

[0008] An electric desalting device for raw oil includes an electric desalting tank with multiple positive electrode plates and multiple negative electrode plates. The positive and negative electrode plates are staggered in the electric desalting tank. Both the positive and negative electrode plates are irregularly shaped, so that the distance between the positive and negative electrode plates gradually decreases from bottom to top.

[0009] Preferably, the widths of the positive and negative electrode plates corresponding to their staggered distribution directions gradually increase from bottom to top.

[0010] Preferably, both the positive electrode plate and the negative electrode plate are Y-shaped.

[0011] Preferably, both the positive electrode plate and the negative electrode plate include inclined grids on the electrode plate that meet at the bottom and are distributed in a V-shape, and vertical grids on the electrode plate connected to the bottom of the inclined grids.

[0012] Preferably, both the positive electrode plate and the negative electrode plate are in the shape of a tuning fork.

[0013] Preferably, both the positive electrode plate and the negative electrode plate include vertical grids spaced apart on the electrode plate, horizontal connecting rods of the electrode plate connected to the bottom of the vertical grids on the electrode plate, and lower vertical grids of the electrode plate connected to the lower edge of the horizontal connecting rods of the electrode plate.

[0014] Preferably, an insulating partition is provided at the bottom of the electro-desalination tank at the position between any adjacent positive and negative electrode plates, with the upper edge of the insulating partition extending beyond the lower edge of the positive and negative electrode plates.

[0015] Preferably, the insulating partition is made of polytetrafluoroethylene or ceramic.

[0016] Preferably, the bottom of the electric desalting tank is provided with an oil inlet distributor for introducing raw material oil into the electric desalting tank and a drain outlet for draining water; the top of the electric desalting tank is provided with an overflow outlet.

[0017] Preferably, the electrostatic desalination tank is provided with a support frame for supporting all the insulating partitions at the middle position of the insulating partitions.

[0018] Preferably, all positive electrode plates are suspended from the positive electrode beam located at the top of the electro-desalination tank by insulating hangers; all negative electrode plates are suspended from the negative electrode beam located at the top of the electro-desalination tank by insulating hangers.

[0019] The above-mentioned feedstock desalting device enables deep desalting of inferior feedstocks with high specific gravity, high viscosity, high salt content, or high acid value.

[0020] Beneficial effects

[0021] In practical application, the feedstock oil electrostatic desalting method and apparatus of this invention delivers high-voltage electricity with both positive and negative responses simultaneously to specially designed positive and negative electrode plates via a high-voltage power supply unit. The positive and negative electrode plates are structurally designed to achieve different distances between them, allowing for a change in electric field strength from bottom to top under the same voltage. Because heavy crude oil contains a high content of polar components, these components readily interact with water, making dehydration and desalting difficult. During the upward flow of crude oil, water droplets first pass through a weak electric field, causing larger droplets to quickly coalesce and settle. Smaller droplets, due to their smaller diameter and slower movement, then pass through a strong electric field, accelerating their coalescence and thus improving the desalting and dehydration efficiency of heavy oil. This invention further enhances the collision and coalescence opportunities of water in crude oil within the electric field, improving desalting efficiency and achieving technical specifications of less than 3 mg / L salt content and no more than 0.3% water content after crude oil desalting.

[0022] In addition, conventional electrostatic desalting (ESD) units suffer from numerous problems during operation, including high current and susceptibility to shocks. This is because the entry of inferior crude oil into the refinery increases the difficulty of desalting and dehydration. This is mainly because these inferior crude oils, with their high specific gravity, high viscosity, high salt content, and high acid value, are prone to emulsification within the ESD tank, forming stable, difficult-to-demulsify oil-water emulsions at the oil-water interface. During the operation of the ESD equipment, the presence of the emulsion leads to a relatively high operating current. Moreover, once an oil-water emulsion layer forms, rapid current increases, short circuits, alarms, and equipment tripping can occur within a short period. In severe cases, power supply difficulties or high-voltage electric field short circuits can occur, affecting the stable operation of the ESD unit. Specifically, during normal operation of existing ESD equipment, the upper part of the ESD tank is the oil phase, and the high-voltage electric field is entirely designed within the oil phase; the lower part of the ESD tank is the water phase. Between the oil and water phases lies the oil-water emulsion layer and the oil-water interface. During the processing of heavy crude oil, a large amount of oil-water emulsion will accumulate at the oil-water emulsion layer, forming an oil-water emulsion layer. This emulsion layer contains a large amount of water, producing... Figure 5 The "turbulence" phenomenon shown indicates high conductivity. When the oil-water emulsion layer thickens, it will cause a sharp increase in the current during electro-desalination. In severe cases, it can cause a short circuit between the high-voltage electrode plates, leading to transformer tripping.

[0023] The applicant's research revealed that during actual operation, the operating current of the electro-desalination equipment is high when the oil-water emulsion layer is thick and the oil-water interface is unclear, and low when the oil-water emulsion layer is thin and the oil-water interface is low. This clearly indicates that the operating current of the electro-desalination equipment is actually the "conductive circuit" formed between the oil-water emulsion layer and the high-voltage electrode plate, rather than the current from the strong electric field in the upper oil phase. Therefore, it is necessary to isolate the conductive circuit between the oil-water emulsion layer and the electrode plate to prevent the formation of a circuit loop that would affect the current during the operation of the electro-desalination device. Therefore, in a preferred embodiment of the present invention, an insulating partition is added to the bottom of the electro-desalination tank, with its upper edge extending above the bottom of the positive and negative electrode plates. This isolates the circuit loop formed between the positive and negative electrode plates through the oil-water emulsion layer, reducing the current during the operation of the electro-desalination device. Specifically, this insulating partition can... Figure 4 The method shown reduces the "re-aggregation" of polar components in crude oil that easily cause emulsification at the bottom of the electrode during sedimentation, reduces the formation of emulsion and the "turbulence" of easily conductive substances at the bottom of the electrode, thereby reducing the current during the operation of the electro-desalting unit and preventing short circuits and tripping. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a feed oil electro-desalting device according to Embodiment 1 of the present invention;

[0025] Figure 2This is a schematic diagram of the positive electrode plate and the negative electrode plate in Example 1;

[0026] Figure 3 This is a schematic diagram of the positive electrode plate and the negative electrode plate in a structural schematic diagram of a raw oil electro-desalting device according to Embodiment 2 of the present invention;

[0027] Figure 4 This is a schematic diagram of how the insulating partition in Example 1 reduces the "turbulence" effect.

[0028] Figure 5 This is a schematic diagram of the "turbulence" at the oil-water interface in an existing electrostatic desalination tank.

[0029] Figure descriptions: 1. Electrodesalination tank; 2. Oil phase; 3. Negative electrode plate; 4. Positive electrode plate; 5. Oil-water emulsion layer; 6. Oil-water interface; 7. Insulating partition; 8. Aqueous phase; 9. Oil inlet distributor; 10. Insulating hanger; 11. Oil outlet; 12. Support frame; 13. Drain outlet; 14. Vertical grid on electrode plate; 15. Horizontal connecting rod of electrode plate; 16. Vertical grid below electrode plate; 17. Inclined grid on electrode plate. Detailed Implementation

[0030] The following describes the feed oil electro-desalting device of the present invention through Examples 1 and 2, and Example 1 specifically illustrates the feed oil electro-desalting method, application and effect of the present invention.

[0031] Example 1

[0032] like Figure 1 As shown, an electric desalting device for raw oil in this embodiment mainly includes an electric desalting tank 1 and a positive electrode plate 4, a negative electrode plate 3 and an insulating partition plate 7 disposed in the electric desalting tank 1.

[0033] The electrostatic desalting tank 1 is identical to existing electrostatic desalting technology, allowing this embodiment to retain the existing main electrostatic desalting equipment in practical implementation. Only modifications to the existing electrostatic desalting device are needed to meet the technical requirements for processing heavy, low-quality crude oil. The electrostatic desalting tank 1 is horizontal, with an oil inlet distributor 9 at the bottom for introducing raw oil and a drain outlet 13 at the bottom. An overflow outlet 11 is located at the top of the tank. Raw oil enters the tank through the oil inlet distributor 9, is desalted, and then discharged through the overflow outlet 11. Water is discharged through the drain outlet 13. All positive electrode plates 4 and negative electrode plates 3 are staggered along the longitudinal direction of the tank body within the electrostatic desalting tank 1. All positive electrode plates 4 are suspended by insulating hangers 10 from the positive electrode beam located at the top of the tank; all negative electrode plates 3 are suspended by insulating hangers 10 from the negative electrode beam located at the top of the tank. In this embodiment, the power supply unit outputs positive and negative high voltages, respectively, which are connected to the positive electrode plate 4 and the negative electrode plate 3 inside the electrostatic desalination tank 1. During operation, the upper part of the electrostatic desalination tank 1 contains the oil phase 2, and the lower part contains the water phase 8. Between the oil phase 2 and the water phase 8 are the oil-water emulsion layer 5 and the oil-water interface 6.

[0034] The main differences between this embodiment and existing electro-desalination technologies are as follows:

[0035] First, combined Figure 1 and Figure 2 As shown, in this embodiment, both the positive electrode plate 4 and the negative electrode plate 3 are tuning fork shaped, each including spaced vertical grids 14 on the electrode plate, horizontal connecting rods 15 connected to the bottom of the vertical grids 14 on the electrode plate, and lower vertical grids 16 connected to the lower edge of the horizontal connecting rods 15 on the electrode plate. This increases the distance between adjacent positive electrode plates 4 and negative electrode plates 3 from bottom to top, enabling an increase in the electric field strength between the plates from bottom to top under the same voltage. Based on this, in this embodiment, when processing crude oil, during the upward flow of crude oil, water droplets first pass through a weak electric field, causing large water droplets to quickly coalesce and settle. Small water droplets, due to their small diameter and slower movement, are then subjected to a strong electric field, which accelerates their coalescence, thereby improving the desalting and dehydration efficiency of heavy oil.

[0036] Secondly, as before Figure 1In this embodiment, insulating partitions 7 are provided at the bottom of the electrostatic desalination tank 1 and between adjacent positive electrode plates 4 and negative electrode plates 3. The insulating partitions 7 are made of ceramic (polytetrafluoroethylene can also be used in other embodiments), and the upper edge of the insulating partitions 7 extends beyond the bottom of the positive electrode plates 4 and negative electrode plates 3. This effectively isolates the circuit formed between the positive electrode plates 4 and negative electrode plates 3 through the oil-water emulsion layer 5, reducing the current during operation in this embodiment. To improve the stability of the insulating partitions 7, a support frame 12 is provided in the middle of the insulating partitions 7 in the electrostatic desalination tank 1 to support all the insulating partitions 7.

[0037] The electro-desalting device of this embodiment was tested in industrial trials at two companies processing different crude oils. The actual operating results are shown in Table 1 below.

[0038] Table 1. Technical Effects of Example 1

[0039]

[0040] Note: Crude oil density: g / cm³ 3 Salt content: mg NaCl / L, Current: A

[0041] As can be seen from Table 1, compared with conventional electro-desalination devices, the electro-desalination device provided in this embodiment can reduce the salt content after desalination by about 50% and the operating current by about 60%.

[0042] Example 2

[0043] The main structure of this embodiment is the same as that of embodiment 1, the difference being as follows: Figure 3 As shown, in this embodiment, both the positive electrode plate 4 and the negative electrode plate 3 are Y-shaped. Each positive electrode plate 4 and negative electrode plate 3 includes two inclined grids 17 arranged in a V-shape on the electrode plates and a lower vertical grid 16 connected to the bottom of the inclined grids. The technical principle and implementation method of this embodiment are the same as those of Embodiment 1, and will not be described again.

Claims

1. A method for electro-desalting raw oil, characterized in that: The feed oil is desalted using an electric desalting tank (1), and the current in the oil phase (2) of the electric desalting tank (1) is controlled to gradually increase from bottom to top; Isolate the circuit loop of two adjacent electrode plates in the oil-water emulsion layer (5) inside the electro-desalting tank (1); The electric desalination tank (1) has multiple positive electrode plates (4) and multiple negative electrode plates (3). The positive electrode plates (4) and negative electrode plates (3) are staggered in the electric desalination tank (1). Both the positive electrode plates (4) and negative electrode plates (3) are irregularly shaped, so that the distance between the positive electrode plates (4) and negative electrode plates (3) gradually decreases from bottom to top. An insulating partition (7) is provided at the bottom of the desalination tank (1) at the position between any adjacent positive electrode plate (4) and negative electrode plate (3). The upper edge of the insulating partition (7) extends beyond the lower edge of the positive electrode plate (4) and negative electrode plate (3).

2. The method for electro-desalting of raw oil as described in claim 1, characterized in that: Deep electro-desalting of inferior raw oils with high specific gravity, high viscosity, high salt content, or high acid value.

3. A feedstock oil electrostatic desalting device, comprising an electrostatic desalting tank (1), the electrostatic desalting tank (1) having a plurality of positive electrode plates (4) and a plurality of negative electrode plates (3), the positive electrode plates (4) and negative electrode plates (3) being alternately distributed in the electrostatic desalting tank (1), characterized in that: Both the positive electrode plate (4) and the negative electrode plate (3) are irregularly shaped parts, so that the distance between the positive electrode plate (4) and the negative electrode plate (3) gradually decreases from bottom to top; An insulating partition (7) is provided at the bottom of the desalination tank (1) at the position between any adjacent positive electrode plate (4) and negative electrode plate (3). The upper edge of the insulating partition (7) extends beyond the lower edge of the positive electrode plate (4) and negative electrode plate (3).

4. The feedstock oil electro-desalting device as described in claim 3, characterized in that: The widths of the positive electrode plate (4) and the negative electrode plate (3) corresponding to their staggered distribution directions gradually increase from bottom to top.

5. The feed oil electro-desalting device as described in claim 4, characterized in that: Both the positive electrode plate (4) and the negative electrode plate (3) are Y-shaped.

6. The feed oil electro-desalting device as described in claim 5, characterized in that: Both the positive electrode plate (4) and the negative electrode plate (3) include an inclined grid (17) on the electrode plate that intersects at the bottom and is distributed in a V-shape, and a vertical grid (16) on the electrode plate connected to the bottom of the inclined grid.

7. The feed oil electro-desalting device as described in claim 4, characterized in that: Both the positive electrode plate (4) and the negative electrode plate (3) are in the shape of a tuning fork.

8. The feed oil electro-desalting device as described in claim 7, characterized in that: Both the positive electrode plate (4) and the negative electrode plate (3) include vertical grids (14) on the electrode plate that are spaced apart, horizontal connecting rods (15) on the electrode plate that are connected to the bottom of the vertical grids (14) on the electrode plate, and vertical grids (16) on the lower edge of the horizontal connecting rods (15) on the electrode plate.

9. The feed oil electro-desalting device as described in claim 3, characterized in that: The insulating partition (7) is made of polytetrafluoroethylene or ceramic.

10. The feed oil electro-desalting device as described in claim 3, characterized in that: The bottom of the electric desalting tank (1) is provided with an oil inlet distributor (9) for introducing raw material oil into the electric desalting tank (1) and a drain outlet (13) for draining water; the top of the electric desalting tank (1) is provided with an overflow outlet (11).

11. The feedstock oil electro-desalting device as described in claim 3, characterized in that: The desalination tank (1) is provided with a support frame (12) in the middle of the insulating partition (7) for supporting all the insulating partitions (7).

12. The feedstock oil electro-desalting device as described in claim 3, characterized in that: All positive electrode plates (4) are suspended by insulating hangers (10) on the positive electrode beam located at the top of the desalination tank (1); all negative electrode plates (3) are suspended by insulating hangers (10) on the negative electrode beam located at the top of the desalination tank (1).

13. The application of the feedstock oil electro-desalting device according to any one of claims 3-12, characterized in that: Deep electro-desalting of inferior raw oils with high specific gravity, high viscosity, high salt content, or high acid value.

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