A crude oil two-component pre-separation method and device

Abstract

The present application belongs to the field of petroleum processing, in particular to the field of crude oil distillation technology, and provides a method for pre-separating two components of crude oil. After desalination and dehydration, the crude oil is preheated in a heating furnace or heat exchange equipment, and then enters a pressurized separation tower. The low-boiling-point component is gasified and separated into a gaseous component and a high-boiling-point liquid component, so that the crude oil is separated into low-boiling-point and high-boiling-point components under pressurized conditions without side-line heat exchange. The low-boiling-point component is sent out in a gaseous state, and the separation ratio can be adjusted by controlling the pressure of the separation tower. The present application provides a pressurized flash evaporation device without a side-line extraction system, a tower-top condensation separation system, and a side-line rectification tower, which can separate crude oil into light distillate and heavy distillate. A small amount of supporting facilities can achieve the precise fractionation of two components of crude oil. The two components of crude oil are separated by pressurized flash evaporation, and the system pressure of the downstream device is connected.

Description

Technical Field

[0001] This invention belongs to the field of petroleum processing, particularly the field of crude oil distillation technology. Specifically, it relates to a method and apparatus for the pre-separation of two components in crude oil. Background Technology

[0002] Existing crude oil fractionation methods include flash distillation, atmospheric distillation, and vacuum distillation;

[0003] Crude oil flash evaporation: Crude oil flash evaporation is achieved under atmospheric pressure as an atmospheric pressure pre-separation method. It is mainly used to remove gaseous components and light naphtha components from crude oil, improve the heating furnace and transportation conditions, and there is a lot of component overlap. The low-boiling-point components flashed out are generally fed into the atmospheric pressure tower for further processing.

[0004] Atmospheric distillation of crude oil is an essential process in all crude oil distillation. Atmospheric distillation typically involves drawing liquid from multiple stages within the distillation column, cooling it through a heat exchange system, and then returning the cooled oil back into the column. This staged heat extraction and reflux method achieves fractionation of crude oil according to its true boiling point or boiling range. Therefore, it requires heat exchangers, reflux pumps, and in-column liquid collectors for convenient side-stream extraction. Atmospheric distillation columns also include a top product condensation section, where the gaseous products from the rectification section are condensed into a liquid phase using cooling water and air coolers before oil-water separation. Vapors with a high latent heat of condensation are also condensed, resulting in a high load on the top condenser. The investment in the side-stream cooling and heat exchange system for atmospheric distillation is far higher than that of the fractionation column itself. In addition, top condensers, oil-water separators, pumps, and other equipment are required, leading to significant equipment investment. Furthermore, the separated water is oily wastewater that needs to be purified by a wastewater treatment plant, increasing wastewater treatment costs.

[0005] Crude oil vacuum distillation: In addition to having the process characteristics of atmospheric distillation, crude oil vacuum distillation achieves component separation by drawing a vacuum or applying negative pressure.

[0006] Both atmospheric and vacuum distillation achieve partial vaporization separation under low pressure. Therefore, the rising mixed gas and bottom liquid phase in the rectification section cannot be directly used as feedstock for downstream units and cannot be directly coupled with catalytic cracking units. Conventional "flash distillation" technology cannot achieve the required crude oil separation after pressurization, such as failing to separate diesel components. Moreover, the separated product components overlap significantly, affecting the selectivity of subsequent reactions. Summary of the Invention

[0007] Petrochemicals are a large-scale chemical industry with low profit margins per unit of output, making it crucial to reduce equipment investment and operating energy consumption. This invention aims to provide a method for pre-separating crude oil into two components without relying on side-stream heat exchange. Furthermore, the separation ratio and precision can be adjusted as needed during operation, and pressurized separation can be achieved through downstream equipment. This method achieves pre-separation of crude oil into two components with low investment and low energy consumption. This invention also provides an apparatus for implementing the above method.

[0008] The crude oil two-component pre-separation method of the present invention is characterized by:

[0009] After desalting and dehydration, the crude oil is preheated in a heating furnace or heat exchanger and then enters a pressurized separation tower. The low-boiling-point components are vaporized and separated into a gaseous phase component and a high-boiling-point liquid phase component. The specific process is as follows:

[0010] (1) After desalting and dehydration, crude oil is pressurized and preheated, and part or all of it forms crude oil flow into the separation tower. The pressure is reduced in the separation tower, and the low-boiling-point components in the crude oil are vaporized in the separation tower. After vaporization, the gas flow flows upward, and the unvaporized high-boiling-point components settle to the bottom of the separation tower.

[0011] (2) The cold reflux stream enters at the top of the separation tower. The cold reflux stream is a liquid stream with a temperature not exceeding 250°C.

[0012] The cold reflux stream is a portion of crude oil, water, or cooled stream from the liquid component at the bottom of the separator; preferably, a portion is diverted from the crude oil before heating as a cold reflux stream and enters the separator from the top; or, a portion is drawn from the high-boiling-point component at the bottom of the separator, cooled, and enters the separator from the top region; or / and, water is used as a cold reflux stream and enters the separator from the top.

[0013] In the top region of the separation tower, the cold reflux stream mixes with the rising gas stream vaporized from the crude oil entering the tower and cools it down. This causes the high-boiling-point components in the vaporized gas stream of the crude oil entering the tower to liquefy again. The liquefied portion flows downward together with the high-boiling-point components in the cold reflux stream and continues to mix with the rising gas below, reducing the content of high-boiling-point components in the gas components. The liquid portion returns to the high-boiling-point components at the bottom of the separation tower. The low-boiling-point gas phase component at the top of the separation tower, i.e., the top component, flows out of the separation tower, and the high-boiling-point liquid phase component, i.e., the bottom component, flows out of the bottom of the separation tower.

[0014] By changing the temperature of the crude oil feed stream, the operating pressure of the separation tower, or the flow rate of the cold reflux stream, the composition and flow rate ratio of the separated top and bottom components can be controlled. Prioritizing the adjustment of the separation ratio, composition, or separation accuracy by regulating the operating pressure of the separation tower and the flow rate of the cold reflux stream; in practice, the cold reflux stream is divided into several streams that enter the separation tower at different heights.

[0015] The aforementioned crude oil two-component pre-separation method further involves injecting steam or water before or after the crude oil enters the separation tower, or injecting steam or water into the lower liquid phase component within the separation tower. This reduces the partial pressure of oil and gas within the separation tower, causing the low-boiling-point components in the bottom liquid phase to vaporize into the gas phase, thereby improving the fractionation accuracy of the two components separated by the separation tower, i.e., improving product quality. The injected water or stripping steam should not exceed 15% (by mass) of the crude oil.

[0016] In this invention, crude oil, water, and steam entering the separation tower are dispersed across the cross-section of the separation tower by a distributor; the distributor is well known to those skilled in the art.

[0017] The aforementioned crude oil two-component pre-separation method further utilizes water as the cold reflux stream for the separation tower. The cold reflux water enters the separation tower from the top region and / or middle section, mixes with the rising gas from the vaporized crude oil stream, and cools it, thereby liquefying the high-boiling-point components in the vaporized components. The cold reflux water flow rate is no more than 10% (by mass) of the crude oil, and the water is preferably wastewater from the catalytic cracking unit's stripping process.

[0018] In the above-mentioned crude oil two-component pre-separation method, the crude oil is further preheated to 200°C to 380°C and pressure is 250 kPa (absolute) to 1.3 MPa (absolute) when it enters the separation tower; the pressure at the top of the separation tower is 230 kPa (absolute) to 460 kPa (absolute).

[0019] This invention also provides a crude oil two-component pre-separation device, which includes crude oil heat exchange or heating equipment and a separation tower; the separation tower is vertical, with a bottom component liquid outlet at the bottom, a top component gas outlet at the top, an inlet for crude oil flow at the lower outer side, a steam or water inlet below the crude oil flow inlet, and a cold reflux flow inlet at the top and / or middle.

[0020] The pipeline connecting the crude oil inlet to the heat exchange or heating equipment and the separation tower;

[0021] The cold reflux inlet is connected to the upstream pipeline of the heat exchange or heating equipment so that the crude oil enters the top of the separation tower from the cold reflux inlet before entering the heat exchange or heating equipment; a pressure regulating valve is installed on the component gas phase pipeline at the top of the fractionation tower to control the operating pressure at the top of the separation tower.

[0022] The aforementioned crude oil bicomponent pre-separation device further includes a water inlet in the middle and / or upper part of the separation tower to introduce cold reflux water.

[0023] In the aforementioned crude oil two-component pre-separation device, the separation tower is further provided with a tray or packing 30 below the inlet of the cold reflux stream.

[0024] The aforementioned crude oil two-component pre-separation device further includes a packing material, tray, or liquid coalescing device installed below the top outlet of the separation tower or above the inlet of the cold reflux stream. The coalescing device, also known as a coalescer, is well-known and can be filamentous, corrugated plate, or similar.

[0025] The crude oil two-component pre-separation method of the present invention is specifically implemented as follows:

[0026] 1. Crude oil two-component pre-separation, including crude oil feed section, crude oil separation tower and product separation control section;

[0027] The crude oil is usually pressurized crude oil from the desalting and dehydration unit (or crude oil from the storage tank after being pressurized by a pump);

[0028] The crude oil feed section includes a crude oil heat exchange or heating system before separation, pumps, feed flow meters, etc.; the product separation control section includes a tower top reflux control section, a water or steam injection control section, and a separation tower top pressure control section.

[0029] In practice, crude oil feed is connected to heat exchange or heating equipment such as a furnace or heat exchanger via pipeline. The furnace or heat exchanger is connected to the crude oil inlet of the separation tower via pipeline. A control system consisting of a feed flow meter and a regulating valve is installed on the pipeline before the furnace or heat exchanger, and a temperature transmitter is installed on the pipeline between the furnace and the separation tower. The cold reflux stream is transported via pipeline to the cold reflux stream inlet. When the cold reflux stream is crude oil, a cold reflux crude oil quantity control system is installed on the above pipeline. Both the cold reflux flow rate and the crude oil feed temperature can be adjusted, thereby adjusting the separation quality of the two-component separation products.

[0030] 2. When the cold reflux stream at the top of the tower is part of the crude oil after desalting and dehydration, the crude oil is divided into two streams. One stream is heated and becomes the feed material of the separation tower, i.e., the crude oil stream entering the tower. The other stream is used as the cold reflux stream at the top of the tower. At this time, the composition of the cold reflux stream at the top of the tower is the same as that of the crude oil in the feed section. The amount of cold reflux crude oil is not greater than 15% (mass ratio) of the crude oil.

[0031] When the cold reflux stream consists of a portion of crude oil and water, the crude oil and water are preferentially separated and enter the separation tower separately, with the crude oil entering from the bottom and the water entering from the top; the water enters the separation tower from the top area of ​​the tower, or above the tray or packing.

[0032] The flow rate of crude oil refluxed from the top of the tower is adjusted according to the quality requirements of downstream units for the light oil product at the top of the tower and the heavy oil product at the bottom of the tower.

[0033] 3. The stripping steam enters the separation tower through pipelines or first enters the crude oil, is heated, and then mixed with the crude oil before entering the separation tower. The stripping steam pipeline is equipped with a loop control system consisting of a flow meter and a regulating valve. The flow rate of the stripping steam is adjusted according to the quality requirements of the downstream unit for the light oil product at the top of the tower and the heavy oil product at the bottom of the tower.

[0034] 4. The control section of the separation tower includes tower top pressure control, flash temperature control, tower liquid level control, and equipment insulation measures.

[0035] The pressure control at the top of the tower is achieved through a control system consisting of a regulating valve installed on the gas product pipeline at the top of the tower and a pressure transmitter at the top of the tower.

[0036] Although the gaseous components separated by the separation tower are a mixture containing light oil fractions and vapor, they are all output as the feed gas in the downstream unit.

[0037] The liquid level inside the tower and the regulating valves and flow meters installed on the product pipeline at the bottom of the tower constitute a liquid level-flow cascade control system.

[0038] Beneficial effects:

[0039] This invention relates to a pressure flash distillation device that can separate crude oil into light and heavy fractions without a side-stream extraction system, a top-of-tower condensation separation system, or a side-stream distillation column. It achieves high-precision fractionation of crude oil using minimal auxiliary equipment. The pressure flash distillation method separates the two components of crude oil, a broad-boiling-range medium, and connects them to the downstream system pressure. This invention breaks through the conventional atmospheric and vacuum distillation column processes, employing a simpler process flow, requiring fewer auxiliary equipment, and significantly reducing investment costs. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the process in Embodiment 1 of the present invention;

[0041] Figure 2 This is a schematic diagram of the process in Embodiment 2 of the present invention;

[0042] The numbering labels in the diagram are as follows:

[0043] F0 crude oil, T0 separation tower, 20 crude oil heating or heat exchange equipment, 30 tower tray or packing; R catalytic cracking reactor, R2 second catalytic cracking reactor; 11 crude oil feed stream (i.e., the stream formed after crude oil heating and entering the separation tower); 12 steam or water, 13 cold reflux stream, 14 bottom component, 15 top component or gas stream flowing out of the top of the tower, 16 pressure or flow regulating valve, 17 cold reflux water, FRC flow recording control signal, LC level control signal, PIC pressure indication control signal. Detailed Implementation

[0044] The technical solution of the present invention will be described below with specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0045] Example 1:

[0046] like Figure 1 As shown, using crude oil F0 from Daqing Oilfield, at a rate of 300 t / h, the requirement is that 95% TBP (tributyl phosphate) of the petroleum hydrocarbon fraction in the top gas of the tower be at 200℃; the implementation is as follows:

[0047] The flash pressure of the separation tower T0 is 0.26 MPa(a), the diameter is 2600 mm, and it is equipped with 6 layers of floating valve trays 30.

[0048] Crude oil F0 from the desalting and dehydration unit enters the unit at a pressure of 0.3 MPa(a) and a temperature of 120°C. It is heated to 200°C in the crude oil heating or heat exchange equipment 20 and enters the separation tower T0 as crude oil feed stream 11. Superheated steam 12 at 250°C is injected at the bottom of the separation tower at a rate of 6 t / h. At the same time, catalytic cracking gas wastewater, i.e., cold reflux water 17, and crude oil before heating are used as cold reflux feed stream 13. 4.5 t / h of cold reflux wastewater enters the separation tower T0 from the top of the tray, and 10 t / h of crude oil at 120°C enters the separation tower T0 from the bottom of the second tray from the top.

[0049] Top component 15, i.e., the gas stream flowing out of the top of the tower, is 29.5 t / h and is sent out of the unit, of which 19 t / h is petroleum hydrocarbons; bottom component 14, i.e., the liquid petroleum hydrocarbons at the bottom of the tower, is sent out of the unit, with a flow rate of 281 t / h.

[0050] Example 2:

[0051] like Figure 2 As shown, naphtha components were separated from Daqing crude oil at a rate of 300 t / h. The process was as follows:

[0052] Crude oil F0 is heated to 270℃ in crude oil heating or heat exchange equipment 20 and then enters separation tower T0 as crude oil feed stream 11. The separation tower has 6 layers of floating valve trays 30, and the top pressure of the separation tower is 0.26MPa(a). 250℃ superheated steam 12 enters separation tower T0 from the bottom liquid zone at a rate of 6t / h. 120℃ crude oil is used as cold reflux feed stream 13. The cold reflux feed stream enters the separation tower in two layers: 4.5t of crude oil enters the separation tower from above the top tray, and 10.5t / h of crude oil enters the separation tower from below the second tray from the top. The top component 15, i.e., the top gas phase flow rate, is 42t / h, and the low-boiling-point component of the crude oil, petroleum hydrocarbons, is 36t / h. The bottom component 14, liquid, is 264t / h. The liquid bottom component 14 enters the catalytic cracking reactor R via pipeline; the low-boiling-point top component 15, in gaseous state, enters the second catalytic cracking reactor R2 via pipeline.

[0053] Everything else is the same as in Example 1.

Claims

1. A method for pre-separation of two components in crude oil, characterized in that, After desalting and dehydration, the crude oil is preheated in a heating furnace or heat exchanger and then enters a pressurized separation tower. The low-boiling-point components are vaporized and separated into a gaseous phase component and a high-boiling-point liquid phase component. The specific process is as follows: (1) After desalting and dehydrating, crude oil (F0) is pressurized and preheated, and part or all of it forms crude oil stream (11) which enters the separation tower (T0). The low-boiling-point components in the crude oil are vaporized in the separation tower (T0). After vaporization, the gas stream flows upward, and the unvaporized high-boiling-point components settle to the bottom of the separation tower. (2) A portion of the crude oil (F0) before heating is diverted as a cold reflux stream (13) and enters the separation tower (T0) from the top; or, a portion of the high-boiling-point component at the bottom of the tower is cooled and becomes a cold reflux stream and enters the separation tower (T0) from the top region; or / and, water is used as a cold reflux stream and enters the separation tower (T0) from the top. The cold reflux stream (13) mixes with the rising gas stream vaporized in the crude oil stream (11) entering the tower in the top region of the separation tower (T0) and cools it down, causing the high-boiling-point components in the gas stream vaporized in the crude oil stream (11) entering the tower to liquefy again. The liquefied part flows downward together with the high-boiling-point components in the cold reflux stream (13) and continues to mix with the rising gas below to reduce the content of high-boiling-point components in the gas components. The liquid part returns to the high-boiling-point components at the bottom of the separation tower. The low-boiling-point gas phase component at the top of the separation tower, i.e., the top component (15), flows out of the separation tower (T0), and the high-boiling-point liquid phase component, i.e., the bottom component (14), flows out of the bottom of the separation tower. By changing the temperature of the crude oil stream entering the tower, the operating pressure of the separation tower, or the flow rate of the cold reflux stream, the composition and flow rate ratio of the top component (15) and the bottom component (14) separated from the tower can be controlled. The absolute pressure at the top of the separation tower is between 230 kPa and 460 kPa.

2. The crude oil two-component pre-separation method as described in claim 1, characterized in that: Steam or water is injected before or after the crude oil enters the separation tower, or steam or water is injected into the lower liquid phase component of the separation tower.

3. The crude oil two-component pre-separation method as described in claim 1, characterized in that: Water is used as the cold reflux stream for the separation tower (T0). The cold reflux water (17) enters the separation tower (T0) from the top area of ​​the separation tower. The cold reflux water (17) mixes with the rising gas after vaporization in the crude oil stream (11) entering the tower and cools it down, so that the high boiling point components in the vaporized components are liquefied.

4. The crude oil two-component pre-separation method as described in claim 1, characterized in that: The crude oil (F0) is preheated to 200°C to 380°C and subjected to an absolute pressure of 250 kPa to 1.3 MPa when it enters the separation tower (T0).

5. A crude oil two-component pre-separation device, characterized in that: The unit is equipped with crude oil heat exchange or heating equipment (20) and separation tower (T0); the separation tower (T0) is vertical, with a bottom component liquid outlet at the bottom, a top component gas outlet at the top, an inlet for crude oil flow at the lower outer side, a steam or water inlet below the crude oil flow inlet, and a cold reflux flow inlet at the top and / or middle. The pipeline connecting the crude oil inlet to the heat exchange or heating equipment (20) and the separation tower (T0); The cold reflux feed inlet is connected to the upstream pipeline of the heat exchange or heating equipment (20) so that the crude oil enters the top of the separation tower from the cold reflux feed inlet before entering the heat exchange or heating equipment; a pressure regulating valve is installed on the component gas pipeline at the top of the fractionation tower to control the operating pressure at the top of the separation tower.

6. The crude oil two-component pre-separation device as described in claim 5, characterized in that: The separation tower (T0) has a tray or packing material below the inlet of the cold reflux material.

7. The crude oil two-component pre-separation device as described in claim 5, characterized in that: The separation tower (T0) is equipped with packing, trays, or liquid coalescing equipment below the top outlet or above the inlet of the cold reflux stream.

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