Vacuum heating tank and method for oil product dehydration and purification

Abstract

The vacuum heating tank comprises a vacuum tank upper shell and a vacuum tank lower shell, and further comprises an electric heating film inner barrel arranged in the vacuum tank lower shell, at least one layer of electric heating film is arranged on the electric heating film inner barrel in a winding mode, and the electric heating film inner barrel is arranged in the vacuum tank lower shell. A flow guide net is tightly wound on the oil liquid incoming flow side of the electric heating film, and the flow guide net and the electric heating film jointly form a detachable heating module; an extraction opening is formed in the top of the vacuum tank upper shell, and an oil inlet is formed in the side wall of the vacuum tank upper shell; oil enters from the oil inlet, is distributed by the flow dispersing device, enters from an oil inlet surface formed by the winding end surfaces of the electric heating film and the flow guide net, and sequentially flows through the surfaces of the flow guide net and the electric heating film from top to bottom. According to the invention, low-temperature, uniform and planar heating of the oil product is realized, so that the risk of cracking and deterioration of the oil product caused by local overheating is fundamentally eliminated, and meanwhile, the water evaporation efficiency and stability are greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a vacuum heating tank and method, in particular to a vacuum heating tank and method for oil dehydration and purification. BACKGROUND

[0002] Industrial oils such as insulating oil and lubricating oil are prone to mix water during storage, transportation and use, which seriously affects their insulation performance, lubrication performance and service life. Therefore, oil dehydration and purification is an indispensable key process in the fields of electric power and petrochemical industry. Vacuum heating dehydration is the current mainstream physical dehydration technology, which is based on the principle of reducing the viscosity of oil and increasing the kinetic energy of water molecules by heating, while reducing the boiling point of water in a vacuum environment, so that it is easy to evaporate and separate from oil.

[0003] However, the heating link in the existing vacuum dehydration device generally has significant technical bottlenecks, which restricts the dehydration efficiency and oil quality, mainly in the following two aspects: First, the traditional heating method is easy to cause local overheating and degradation of the oil. The widely used heater is a tubular electric heating element (electric heating tube), which is essentially a high-power density linear or point-like concentrated heat source. The surface working temperature of such a heater is extremely high, up to 300°C or more, with an average unit area power of hundreds of watts per square centimeter. Due to the poor thermal conductivity of oil, when the oil flow is too slow or the flow distribution is uneven, the thin layer of oil close to the surface of the high-temperature heating tube will be subjected to a temperature far exceeding its safety limit for a long time, causing a series of thermal degradation reactions such as thermal cracking, oxidation, carbonization and coking. This not only directly leads to changes in the chemical composition of the oil and a decrease in performance, but also produces impurities such as carbides that block the filter and pollute the system, seriously affecting the safety and service life of the equipment. Second, the traditional heating mode leads to uneven heating, resulting in unstable dehydration efficiency and effect. When using point or linear heat sources, the oil in the heating cavity is not evenly heated, with the oil temperature near the heat source being too high and the oil temperature far from the heat source being too low. This unevenness of the temperature field causes the oil to be unable to be heated synchronously and uniformly to the optimal dehydration temperature. As a result, part of the oil has already begun to degrade due to overheating, while another part of the oil has not yet reached the temperature required for water vaporization. This uneven heating makes it difficult for water to continuously and stably evaporate from the entire oil flow, resulting in large fluctuations in the dehydration process and ultimately insufficient dehydration depth, affecting the stability and reliability of subsequent filtration or use.

[0004] In summary, the local high-temperature degradation of oil caused by high-power density point / linear heating and the low dehydration efficiency caused by uneven heating in the existing technology are two core problems that restrict the development of vacuum dehydration technology in the direction of higher efficiency, gentler and more reliable. Therefore, a new heating technology and device that can achieve low-temperature, uniform and large-area heating is urgently needed to efficiently remove water while maximizing the protection of oil quality. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a vacuum heating tank and method for oil dehydration and purification.

[0006] In order to solve the above technical problems, the present application provides a vacuum heating tank and method for oil dehydration and purification. Further, the electric heating film and the flow guide net are co-wound and fixed on the outer peripheral wall of the electric heating film inner cylinder to form a multi-layer and three-dimensional heating layer structure. The upper shell of the vacuum tank is provided with an air outlet, and the side wall of the upper shell is provided with an oil inlet. The oil liquid enters from the oil inlet, is distributed by the flow distribution device, and then enters the oil inlet surface formed by the winding end surface of the electric heating film and the flow guide net, and flows sequentially from top to bottom through the surface of the flow guide net and the electric heating film.

[0007] Further, the electric heating film and the flow guide net are co-wound and fixed on the outer peripheral wall of the electric heating film inner cylinder to form a multi-layer and three-dimensional heating layer structure.

[0008] Further, the flow distribution device is a flow distribution device arranged above the electric heating film inner cylinder and located behind the oil inlet, and a plurality of through holes are formed in the flow distribution device for diffusing the concentrated oil flow into multiple thin streams.

[0009] A heating method for a vacuum heating tank for oil dehydration and purification, comprising the following steps: S1, the oil liquid to be treated enters from the oil inlet of the vacuum tank body, and is preliminarily dispersed by the flow distribution effect, and then flows downward under the action of gravity; the flow guide net arranged in the flow path further guides the oil liquid to form a uniform thin layer of liquid film on the surface of the electric heating film; S2, the thin layer of liquid film flows through the surface of the electric heating film with electricity, and the electric heating film provides a large-area, low-power-density surface heat source to uniformly and continuously heat the liquid film; S3, while maintaining the vacuum environment in the tank body, steps S1 and S2 are performed; the water in the heated oil liquid boils at a lower temperature in the vacuum environment, continuously vaporizes and escapes, and the vaporized water vapor is removed by the vacuum system, and the oil liquid from which the water has been removed continues to flow downward and collects.

[0010] Further, in step S2, the power of the electric heating film is controlled to maintain the surface working temperature between 50℃ and 120℃, so as to heat the oil liquid to avoid overheating and degradation of the oil product.

[0011] Further, in step S1, the flow guide net is arranged close to the surface of the electric heating film to force the oil to flow and be uniformly distributed.

[0012] Further, the oil and the water vapor generated in step S3 and drawn upward form a reverse flow, continuously breaking the gas-liquid balance of the oil-water interface to strengthen dehydration.

[0013] Further, by controlling the oil flow, the downward flow linear velocity of the thin liquid film is maintained within the range of 0.1-0.5 m / s.

[0014] Further, the absolute pressure in the vacuum tank is maintained between 0 Pa and -100000 Pa, so that the water boils at a temperature range of 40-60°C.

[0015] The present application discloses a vacuum heating tank and method for oil dehydration and purification. The present application uses a large-area electric heating film to replace the traditional tubular heater, and cooperates with a unique flow guide net and gas-liquid reverse flow design to realize low-temperature, uniform, and surface heating of the oil, thereby fundamentally eliminating the risk of oil cracking and degradation caused by local overheating, greatly improving the efficiency and stability of water evaporation, achieving the goal of energy saving, high efficiency, and deep dehydration under the premise of ensuring oil quality, and simplifying the maintenance process through modular design, providing a reliable and economical oil purification solution. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a perspective view of the present application.

[0017] Figure 2 It is a sectional view of the present application.

[0018] Figure 3 It is a schematic view of the setting of the gas cylinder and the reversing valve of the present application.

[0019] Figure 4 It is a structural schematic view of the core heating and flow guide module of the present application.

[0020] Figure 5 It is an expanded schematic view of the core heating and flow guide module of the present application.

[0021] In the figure: 1, upper shell of vacuum tank; 2, lower shell of vacuum tank; 3, inner cylinder of electric heating film; 4, electric heating film; 5, quick-mounting rubber pad; 6, quick-mounting clamp; 7, flow guide net; 8, dispersion plate; 9, oil inlet; 10, air outlet. DETAILED DESCRIPTION

[0022] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0023] As Figure 1 and2 The present invention provides a vacuum heating tank for oil dehydration and purification. The core design of this device is to achieve deep removal of water from oil under low temperature and uniform conditions through the synergistic effect of surface heating and gas-liquid countercurrent, fundamentally solving the technical bottlenecks of traditional tubular heaters, such as local overheating and deterioration of oil, uneven dehydration, and high energy consumption.

[0024] Specifically, the vacuum heating tank includes an upper shell 1 and a lower shell 2. The side wall of the upper shell 1 has an oil inlet 9, through which the water-containing oil to be treated is pumped into the tank. The upper shell 1 and the lower shell 2 are detachably and tightly connected by a quick-release sealing structure. This quick-release sealing structure typically includes a quick-release gasket 5 placed in a groove on the mating end face of the two shells, and a quick-release clamp 6 encircling the outside of the mating area. By tightening the quick-release clamp 6, a large clamping force is generated, deforming the gasket and thus achieving the reliable seal required for a high vacuum environment.

[0025] It also includes a core heating and flow guiding module integrated and installed inside the lower shell 2 of the vacuum tank. Its central component is an electrically heated inner cylinder 3, which is typically a cylindrical metal or high-temperature resistant composite material frame with open ends and a smooth outer wall. For example... Figure 3 As shown, its core lies in the shape and arrangement of the heating element, namely, at least one layer of electric heating film 4 is wound around the outer peripheral wall of the inner cylinder 3 of the electric heating film. Crucially, on the oil flow side (i.e., the side facing the oil flow direction) of each layer of electric heating film 4, a guide net 7 is also tightly wound around it. The guide net 7 is fixedly disposed on the surface of the electric heating film 4, and both are wound together and fixed to the inner cylinder 3 of the electric heating film, thus forming a stable multi-layer composite heating layer structure. Figure 4 and Figure 5 As shown, the electric heating film 4, the flow guiding net 7, and the inner cylinder of the electric heating film 3 together constitute an independent, detachable heating module. This modular design means that when the electric heating film or the flow guiding net needs maintenance or replacement, the entire module can be removed from the tank, simplifying the maintenance process.

[0026] To ensure the stability and alignment of the core heating module during operation, a positioning bracket is installed at the center of the lower housing 2 of the vacuum tank. This structure typically includes a fixed tube welded or fastened vertically to the bottom of the lower housing. During assembly, the inner cylinder 3 of the electric heating film is directly fitted onto the outside of this fixed tube.

[0027] To achieve uniform distribution of the oil before it enters the core heating zone, a flow diffuser is installed inside the upper shell 1 of the vacuum tank, located at the rear end of the oil inlet and directly above the opening of the inner cylinder 3 of the electric heating film. In this embodiment, the flow diffuser is specifically a dispersion plate 8. The dispersion plate 8 has a large number of regularly spaced through holes. When the concentrated oil flow falls from the oil inlet and impacts the dispersion plate 8, it is forcibly divided into countless fine streams, thus completing the first and crucial dispersion of the oil before it enters the heating zone.

[0028] During assembly, firstly, lay the electric heating film 4 and the guide net 7 flat, ensuring that the guide net 7 is above the electric heating film 4 (i.e., the side that the oil will contact first). Fix one end of both together to the outer wall of the inner cylinder 3 of the electric heating film, and then tightly wind them layer by layer along the outer circumference of the inner cylinder. After winding, fix the end to form a composite heating layer, with the end facing the diffuser forming the oil inlet surface. Smoothly place the assembled heating module (i.e., the inner cylinder 3 of the electric heating film covered with the electric heating film and guide net) into the lower shell 2 of the vacuum tank, ensuring that the bottom end of the inner cylinder fits into the fixing tube inside the lower shell, completing the positioning. Place the quick-release gasket 5 in the sealing groove of the upper flange of the lower shell 2 of the vacuum tank, then align and lower the upper shell 1 of the vacuum tank, and finally use the quick-release clamp 6 to tighten the upper and lower shells, completing the sealing assembly of the entire tank.

[0029] The working process of this device can be broken down into the following closely linked stages: First stage: Dispersion and thin-film formation. The aqueous oil to be treated is fed into the tank through the oil inlet on the side wall of the upper shell 1 of the vacuum tank. For example... Figure 2 and Figure 3 As shown, the oil first impacts the dispersion plate 8, where it is dispersed into numerous fine streams, completing the initial dispersion. These streams continue downwards under gravity, falling into the opening of the inner cylinder 3 of the electric heating film and beginning to contact the guide net 7. The mesh structure of the guide net breaks up the initially dispersed oil streams, further distributing and guiding them, forcing the oil to spread across the entire surface of the electric heating film 4 into an extremely uniform, stable, and very thin liquid film. This thin-film treatment is the physical basis for subsequent efficient heat and mass transfer.

[0030] The second stage: When the oil flows through the surface of the electric heating film 4 in a thin layer, the electric heating film is energized and operates. Traditional heaters use rod-shaped or U-shaped heating tubes, which are linear or point-based concentrated heat sources with extremely high surface temperatures, reaching over 300°C, and high power density, hundreds of watts per square centimeter. In stark contrast, the electric heating film 4 is a planar distributed heat source. Its heating element uniformly covers the entire film surface, with very low power per unit area, for example, about 5 watts per square centimeter. Therefore, its surface operating temperature can be stably and precisely maintained at a relatively low level, typically controlled between 50°C and 80°C depending on process requirements.

[0031] The advantages of planar heating are reflected in the following aspects. First, the heat source itself is a large-area, uniformly heated surface, directly avoiding localized high-temperature hotspots caused by concentrated heat sources. The thin layer of oil flows across the entire heated surface, receiving heating with a uniform heat flux density, resulting in minimal internal temperature differences and an extremely uniform temperature field. Second, because the heating surface temperature itself is not high, and the oil film is very thin and flows continuously, heat can be quickly absorbed and carried away by the oil. The temperature of the oil layer in close contact with the heating surface is only slightly higher than the mainstream oil temperature, completely avoiding the thermal degradation reactions such as cracking, carbonization, and coking that occur in the boundary layer oil adhering to the high-temperature pipe wall in traditional heaters due to prolonged exposure to temperatures of hundreds of degrees Celsius, thus greatly protecting oil quality. Finally, the planar heat source is in direct contact with the thin layer of oil, resulting in a large heat transfer area, a short heat transfer path, and low thermal resistance due to the thinness of the oil film. Heat energy is transferred from the heating film to the oil with almost no loss, resulting in high electrical energy conversion efficiency.

[0032] Importantly, the flowing oil moves downwards under gravity, and the contact time with the heating surface is determined by the flow rate and the height of the heating surface, making it easy to control and optimize. This flow pattern ensures that each batch of oil undergoes almost the same heating process, guaranteeing consistent treatment results.

[0033] The third stage: Throughout the heating and dehydration process, the vacuum system operates continuously, maintaining a high vacuum environment inside the tank, typically between 0 Pa and -100,000 Pa, preferably between 500 Pa and 5,000 Pa. According to physical laws, the boiling point of water decreases as pressure decreases; under this vacuum, the boiling point of water can drop to 40°C to 60°C. This means that, at the heating temperature of 50°C to 120°C provided by the electric heating film, the water in the oil has far exceeded its boiling point under this vacuum environment, thus obtaining a huge driving force for evaporation.

[0034] At this point, a subtle countercurrent flow of gas and liquid occurs within the device, forming a thin oil film that flows downwards under the influence of gravity. Under the suction of the vacuum pump, the water vapor generated by evaporation flows upwards and is rapidly drawn away from the extraction port 10 at the top of the tank.

[0035] Under static or co-current conditions, the water vapor concentration near the evaporation interface gradually increases, thus reducing the concentration gradient driving force for the evaporation of water from the liquid's interior. Under counter-current conditions, fresh oil enters through the inlet and encounters a relatively dry airflow rising from below. As the oil flows downwards, its water content continuously evaporates, decreasing, while it encounters a slightly more humid airflow from further below, where the water has just evaporated, but a concentration gradient always exists. This arrangement ensures that a water vapor concentration gradient, as large as possible, is maintained between the oil surface and the mainstream gas throughout the mass transfer path. This gradient is the direct driving force for water evaporation, enabling the dehydration process to proceed continuously and efficiently.

[0036] To achieve the aforementioned ideal working state, key process parameters need to be controlled collaboratively. By adjusting the input power of the electric heating film 4, its surface temperature is stabilized within a set range of 50-80℃. This temperature must be matched with the vacuum level to ensure efficient evaporation of water while remaining well below the thermal decomposition temperature of the oil. The vacuum system maintains the tank pressure at 500-5000Pa, corresponding to a water boiling point of 40-60℃, perfectly complementing the heating temperature to achieve low-temperature boiling. By adjusting the flow rate of the oil inlet pump, the linear velocity of the downward flow of the thin oil film is maintained within the range of 0.1-0.5 m / s. This flow rate range is optimized; too slow a flow rate may cause the oil to remain on the heating surface for too long, resulting in sufficient dehydration but a potential risk of overheating and low processing capacity; too fast a flow rate will result in insufficient contact time between the oil and the heating surface, leading to inadequate heating and dehydration, and the liquid film may become unstable, disrupting uniformity. A flow rate of 0.1-0.5 m / s ensures that the oil has sufficient time for heat and mass transfer, can be continuously renewed, forms a stable laminar flow, and establishes an effective countercurrent mass transfer interface with the rising steam.

[0037] In summary, the vacuum heating tank and its heating method provided by this invention achieve initial oil flow distribution through the dispersion plate 8, and realize thin-layer and uniform surface heating of the oil through the unique composite structure of the guide net 7 and the electric heating film 4. Combined with a precisely controlled vacuum environment and a gas-liquid two-phase countercurrent process, this invention synergistically solves the industry problems of uneven heating, localized overheating and deterioration, low dehydration efficiency, and high energy consumption during oil dehydration. The entire system is ingeniously conceived, with a modular design for easy maintenance and highly controllable process parameters, providing an efficient, reliable, and environmentally friendly solution for the deep purification and dehydration of insulating oils, lubricating oils, and other oil products.

[0038] The above embodiments are not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the technical solution of the present invention are also within the protection scope of the present invention.

Claims

1. A vacuum heating tank for oil dehydration and purification, comprising an upper shell (1) and a lower shell (2), characterized in that, It also includes an electric heating film inner cylinder (3) disposed inside the lower shell (2) of the vacuum tank. At least one layer of electric heating film (4) is wound on the electric heating film inner cylinder (3). A guide net (7) is also wound tightly on the oil flow side of the electric heating film (4). The guide net (7) and the electric heating film (4) together constitute a detachable heating module. The top of the upper shell (1) of the vacuum tank is provided with an air extraction port (10), and the side wall of the upper shell (1) of the vacuum tank is provided with an oil inlet (9). The oil enters from the oil inlet (9), and after being distributed by the dispersion plate (8), the oil enters from the oil inlet surface formed by the winding end face of the electric heating film (4) and the guide net (7), and flows sequentially from top to bottom across the surface of the guide net (7) and the electric heating film (4).

2. The vacuum heating tank for oil dehydration and purification according to claim 1, characterized in that: The electric heating film (4) and the guide net (7) are wound together and fixed to the outer peripheral wall of the inner cylinder (3) of the electric heating film to form a multi-layered and three-dimensional heating layer structure.

3. The vacuum heating tank for oil dehydration and purification according to claim 1, characterized in that: The diffuser is a diffuser plate (8) located at the rear end of the oil inlet (9) and directly above the inner cylinder (3) of the electric heating film. The diffuser plate (8) has multiple through holes for diffusing the concentrated oil flow entering the tank into multiple fine streams.

4. A heating method for a vacuum heating tank for oil dehydration and purification according to any one of claims 1-3, characterized in that, Includes the following steps: S1. The oil to be processed enters from the oil inlet of the vacuum tank and is initially dispersed by the diffusion effect, then flows downward under the action of gravity; the oil is further guided by the guide net set in the flow path, so that it forms a uniform thin liquid film on the surface of the electric heating film. S2. The thin liquid film flows over the surface of an electrically heated film, which provides a large-area, low-power-density surface heat source to uniformly and continuously heat the liquid film. S3. While maintaining the vacuum environment inside the tank, execute steps S1 and S2; the water in the heated oil has a lower boiling point under vacuum and continues to vaporize and escape. The vaporized water vapor is extracted by the vacuum system, while the dehydrated oil continues to flow downward and collect.

5. The heating method for vacuum dehydration of oil products according to claim 5, characterized in that, In step S2, the power of the electric heating film is controlled to maintain its surface working temperature between 50°C and 120°C, thereby heating the oil to prevent it from overheating and deteriorating.

6. The heating method for vacuum dehydration of oil products according to claim 5, characterized in that, In step S1, the guide net is closely attached to the surface of the electric heating film to force the oil to flow and distribute evenly.

7. The heating method for vacuum dehydration of oil products according to claim 5, characterized in that, The oil and the water vapor generated in step S3, which is drawn upwards, flow in opposite directions, continuously disrupting the gas-liquid balance at the oil-water interface to enhance dehydration.

8. The heating method for vacuum dehydration of oil products according to claim 8, characterized in that, By controlling the oil inlet flow rate, the downward linear velocity of the thin liquid film is maintained within the range of 0.1-0.5 m / s.

9. The heating method for vacuum dehydration of oil products according to claim 8, characterized in that, The absolute pressure inside the vacuum tank is maintained between 0 Pa and -100,000 Pa, so that the water boils in a temperature range of 40°C to 60°C.

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