A structure for solving coking and clogging in slurry bed pre-flash distillation tower systems

Abstract

This invention discloses a structure for solving coking and blockage in a slurry bed pre-flash tower system, relating to the technical field of slurry bed residue oil hydrotreating units. It includes a pre-flash tower, a feed cyclone separator, a spray distribution pipe, a conical head, a slurry valve, a basket filter, a centrifugal pump, and multiple pipelines. By removing part of the bottom tray of the pre-flash tower and installing a spray distribution pipe, adding a feed cyclone separator at the feed inlet, changing the bottom head to a conical head, optimizing the pipeline layout and adding a basket filter, and simultaneously reducing the diameter of related valves and pipelines, this invention addresses the problem of coking and blockage in the pre-flash tower from four aspects: feed distribution, reducing coking space, increasing pipeline flow rate, and increasing active coking removal. This fundamentally solves the coking and blockage problem in the pre-flash tower, extends the unit's operating cycle, improves operational stability and economy, and reduces safety risks. It is applicable to heavy oil medium towers in various "bottom-in, top-out" slurry bed residue oil hydrotreating units.

Description

Technical Field

[0001] This invention relates to the technical field of slurry bed residue oil hydrogenation equipment, specifically to a structure for solving coking and blockage in slurry bed pre-flash distillation tower systems. Background Technology

[0002] Slurry-bed residue hydrotreating technology is a core component in modern integrated refining and chemical enterprises for processing low-quality heavy oil and achieving efficient resource conversion. Its operational stability directly affects the overall plant material balance and economic benefits. However, during actual high-load, long-cycle operation, the pre-flash distillation tower system is prone to coking and blockage, becoming a bottleneck restricting the long-term operation of the unit and the improvement of overall economic benefits.

[0003] In existing technologies, slurry-bed residue hydrotreating units commonly used in petrochemical enterprises experience a series of frequent problems from the first operating cycle as the unit load increases: coking debris falls off the bottom of the pre-flash tower and the bottom outlet pipeline, causing blockages in valves and pipelines, which in turn triggers a chain reaction of system disturbances such as interruption of the external wax oil pipeline, fluctuations in the feed to the vacuum distillation tower, and flooding of the pre-flash tower; frequent blockages in the intermediate reflux filter cause insufficient or even interrupted reflux flow, significantly increasing the risk of coking on the trays and upward movement of heavy components; the top product carries heavy components such as slurry, directly affecting product quality and increasing the load and blockage risk of the downstream atmospheric fractionation system. These problems become particularly pronounced after the unit operates at 85%-100% load for 6-8 months. Disruptions in the pre-flash tower system force the unit to reduce its output to gain time for unblocking. However, the aftereffects of the disruption, such as coking of the tower trays caused by bottom blockage, can lead to a forced reduction in the unit's processing load by 5%-15% at best, and a significant reduction in output to maintain operation at worst. If the blockage cannot be cleared and the system cannot be restored, the unit must be shut down for treatment, which drastically shortens the operating cycle and seriously affects the economic efficiency of the unit.

[0004] After in-depth investigation and analysis, the fundamental mechanism of coking in the pre-flash tower in existing technology mainly includes three aspects: Firstly, the uneven distribution of feed and the entrainment of slurry components: the two feeds from the bottom slurry stripping tower and the hot low-temperature separation tank do not have secondary distribution. Due to the uneven distribution of the heavy slurry components, the uneven mass transfer and washing in the middle section cause the heavy slurry components to move upward and gradually form coking on the tray. In addition, the heavy slurry components washed down adhere to, deposit and coke on the bottom elliptical head. Secondly, coke lumps and coke powder blockage occurs. Heavy components of the slurry deposit, adhere to the walls, coke, and thicken in areas where the flow rate slows down, such as the bottom of the pre-flash tower, horizontal pipes and bends, pump inlet filters, and regulating valves. During the start-up and shutdown of the unit, production fluctuations, or normal pressure / temperature changes, coke lumps can easily fall off and cause blockages in the downstream path and pump cavitation. Third, a vicious cycle occurs: coking and detachment at the bottom of the tower and in the pipelines cause blockages in the downstream transport, and the remaining space in the tower bottom can easily lead to flooding and slurry overflow. The heavy components of the slurry have an adverse effect on the mid-section reflux and the top reflux, which in turn exacerbates the risk of coking and blockage, thus forming a vicious cycle.

[0005] Currently, due to the limitations of the process characteristics, there is a lack of effective countermeasures in existing technologies. Once the conveying system of the pre-flash tower becomes blocked and disordered, the only way to buy time for reverse flushing and unblocking is to reduce the flow rate. However, the time and difficulty of unblocking are affected by the degree of coke blockage, and the degree of contamination of the tower trays is difficult to estimate. The impact on the tower separation effect is irreversible. The only way to maintain operation is through the above-mentioned means, which cannot fundamentally solve the problem. Summary of the Invention

[0006] The purpose of this invention is to provide a structure that solves the problem of coking and clogging in slurry bed pre-flash tower systems. This structure can fundamentally solve the problems of poor separation of heavy components such as slurry in pre-flash towers and easy coking and clogging at the bottom. It also solves the problems of low flow rate coking on the pipeline system and cleaning of coking deposits.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention provides a structure for solving coking and blockage in a slurry bed pre-flash tower system, comprising a pre-flash tower, a feed vortex separator, a spray distribution pipe, a slurry valve, a first double-basket filter, a first pipeline, and a second pipeline. The spray distribution pipe is connected to the intermediate reflux spray pipeline via the first pipeline, and is installed inside the pre-flash tower at the position corresponding to the original tray. The bottom of the pre-flash tower has two feed inlets, each equipped with a feed vortex separator. The bottom end cap of the pre-flash tower is a conical end cap. The outlet of the conical end cap is connected to the inlet of the slurry valve via the second pipeline. The outlet of the slurry valve is divided into two branches: one branch connects to a pressure reducing tower, and the other branch connects to the inlet of the first double-basket filter. The first double-basket filter is connected to a wax oil delivery line, which is sequentially connected to a centrifugal pump and a second double-basket filter.

[0008] Preferably, the intermediate reflux spray pipeline is divided into pipeline No. 3 and pipeline No. 4. Pipeline No. 3 is connected to the pre-flash tower and is equipped with a transfer pump and a No. 3 double basket filter. Pipeline No. 4 is connected to the pre-flash tower to form a circulation pipeline between pipelines No. 3 and No. 4.

[0009] Preferably, the inlet pipe diameter of the three-way slurry valve is set to 8 inches, outlet 1 is 6 inches, and outlet 2 is 4 inches; the first double basket filter is set to 6 inches, and the pipe diameter of the second double basket filter is set to 4 inches.

[0010] Preferably, the spray distribution pipe is a 6-inch main pipe connected to 10 2-inch branch pipes, and each pipe is evenly provided with a number of spray heads. The orifice diameter of the spray head is 3-5mm, and the distance between adjacent spray heads is 90-100cm.

[0011] Preferably, the number of spray distribution pipes is 1 main pipe and 10 branch pipes. The multiple spray distribution pipes are evenly distributed along the circular cross-section of the pre-flash tower, and the multiple spray distribution pipes are connected to the main pipe and then connected to the No. 1 pipeline.

[0012] Preferably, the feed vortex separator adopts a streamlined structure, the inlet of the feed vortex separator is welded and fixed to the external feed pipe, and the outlet of the feed vortex separator extends to 120° and 220° positions respectively along the tower wall.

[0013] Preferably, the cone angle of the conical head is 60°, the large end of the conical head is welded and fixed to the tower body of the pre-flash tower, and the small end of the conical head is connected to the flange of the second pipeline.

[0014] Preferably, a regulating valve is provided between the No. 1 pipeline and the intermediate return spray pipeline, and a flow regulating valve is provided on the branch connecting the pressure reducing tower, which can be used for flow regulation.

[0015] Preferably, both the No. 1 double basket filter and the No. 2 double basket filter adopt a detachable filter basket structure, and the filtration accuracy of the filter basket is 40 mesh.

[0016] Preferably, the inlet of the centrifugal pump is connected to the flange of the branch pipeline, and a pressure transmitter, flow regulating valve, etc. are installed on the wax oil delivery line.

[0017] Beneficial effects: Through structural design, this invention can achieve four functions: feed distribution, reduction of coking space, increase of pipeline flow rate, and increase of active coking removal measures. It effectively ensures the separation of light and heavy components, controls the generation of sediment and wall-mounted coking, and completely solves the problem of blockage in the pre-flash tower system from the root cause. This effectively curbs the vicious cycle of coking in the pre-flash tower system, achieving the goal of long-term operation of the unit. It is expected that the operating cycle can be extended from the current 6 months to more than 12 months. This significantly enhances the unit's ability to cope with production fluctuations, reduces the risk of unit load reduction and unplanned shutdowns, and ensures stable production. It solves the core problems that cause the equipment to reduce load and operate on a short cycle, improves the wax oil extraction rate, reduces the energy consumption of secondary processing of products, and has a very high return on investment; at the same time, the newly added wax oil delivery process can deliver 80% pure wax oil to the downstream wax oil refining unit, further realizing energy saving, consumption reduction, production increase and efficiency improvement. Through structural and system design, the safety risks caused by blockage in the pre-flash tower system are reduced, while ensuring operational stability and compliance with environmental standards. It can be widely used in heavy oil medium towers, containers and other equipment in various slurry bed residue hydrotreating units (such as suspension bed and slurry bed hydrocracking units) that adopt the "bottom in, top out" slurry bed hydrotreating system, and has broad application prospects. Attached Figure Description

[0018] Figure 1 This is a block diagram illustrating the structural principle of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of the invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] The purpose of this invention is to provide a proactive and preventative structural modification that addresses the problems of poor separation of heavy components such as slurry and easy coking and blockage at the bottom of the pre-flash tower system by modifying the structure. It also solves the problems of low-flow-rate coking on the pipe system and the cleaning of coking material, ensuring stable operation of the device under long-term and high-load conditions and improving overall economic efficiency.

[0022] Invention content / principle: (I) Core Technology Solution This invention includes a pre-flash tower 11, a feed vortex separator 4, a spray distribution pipe 3, a slurry valve 6, a first double basket filter 7, a first pipeline, and a second pipeline. The spray distribution pipe 3 is connected to the intermediate reflux spray pipeline 2 through the first pipeline, and the spray distribution pipe 3 is installed inside the pre-flash tower 11 corresponding to the original tray position. The bottom of the pre-flash tower 11 has two feed inlets, and a feed vortex separator 4 is installed at each feed inlet. The bottom end cap of the pre-flash tower 11 is a conical end cap 5. The outlet of the conical end cap 5 is connected to the inlet of the slurry valve 6 through the second pipeline. The outlet of the slurry valve 6 is divided into two branches, one of which is connected to the pressure reducing tower, and the other branch is connected to the inlet of the first double basket filter 7. The first double basket filter 7 is connected to the wax oil delivery line, and a centrifugal pump 8 and a second double basket filter 9 are connected in sequence on the wax oil delivery line. The intermediate reflux spray pipeline 2 is divided into pipeline 3 and pipeline 4. Pipeline 3 connects to the pre-flash tower 11 and is connected to a transfer pump 10 and a double basket filter 1. Pipeline 4 connects to the pre-flash tower 11 to form a circulation pipeline between pipelines 3 and 4. The slurry valve 6 has a diameter of 4 inches, and the double basket filters 7 and 9 both have a diameter of 6 inches. Several spray heads are evenly distributed on the spray distribution pipe 3, with an orifice diameter of 3-5 mm and a spacing of 90-100 cm between adjacent spray heads. There are 10 spray distribution pipes 3, which are evenly distributed along the circular cross-section of the pre-flash tower 11 and are all connected to the main pipe, which in turn connects to pipeline 1. The feed cyclone separator 4 adopts a streamlined structure. Its inlet is welded to the external feed pipe, and its outlet extends along the tower wall to positions 120° and 220° inside the pre-flash tower 11. The conical head 5 has a cone angle of 60°. Its large end is welded to the tower body of the pre-flash tower 11, and its small end is connected to the flange of pipeline number two. A regulating valve is installed between pipeline number one and the intermediate return spray pipeline 2, and a flow regulating valve is installed on the branch connecting to the pressure reducing tower. Both the first double basket filter 7 and the second double basket filter 9 adopt a detachable basket structure, with a filtration accuracy of 40 mesh. The inlet of the centrifugal pump 8 is connected to the branch pipeline flange, and a pressure transmitter and regulating valve are installed on the wax oil delivery line.

[0023] (II) Technical Concept The core innovation of this invention lies in the functional reengineering of the existing process flow and equipment internal structure, comprehensively solving the pre-flash tower blockage problem from four aspects: improving feed distribution, reducing coking space, increasing pipeline flow rate, and adding active coking removal measures.

[0024] Specifically: By installing feed vortex separators 4 at the two feed inlets at the bottom of the pre-flash tower 11, uniform feed distribution is achieved; the bottom end cap of the pre-flash tower 11 is changed to a conical end cap 5 to reduce the space for sedimentation and coking; the slurry valve 6 and related pipelines are reduced in diameter to increase the flow rate of the medium in the pipeline and avoid the deposition of heavy components; the trays of the traditional pre-flash tower are removed and spray distribution pipes 3 are installed, as well as structures with No. 1 double basket filter 7 and No. 2 double basket filter 9, etc., to achieve washing of heavy components and targeted interception and removal of coking materials, ultimately preventing coking on the walls of upstream equipment and pipelines and ensuring smooth system operation.

[0025] Example 1: The present invention will be further described in detail below with reference to specific examples.

[0026] (a) Structural assembly The structure for solving coking and blockage in the slurry bed pre-flash tower system in this embodiment includes a pre-flash tower 11, a feed vortex separator 4, a spray distribution pipe 3, a slurry valve 6, a first double basket filter 7, a first pipeline, and a second pipeline. The spray distribution pipe 3 is connected to the intermediate return spray pipeline 2 through the first pipeline. A regulating valve is installed between the first pipeline and the intermediate return spray pipeline 2 to control the on / off of the intermediate return oil and adjust the spray volume.

[0027] Ten spray distribution pipes 3 are installed inside the pre-flash tower 11, corresponding to the original tray positions. These ten pipes are evenly distributed along the circular cross-section of the pre-flash tower 11 and connected to the main pipe, which in turn connects to the first pipeline. Several spray heads are evenly distributed on each spray distribution pipe 3, with an orifice diameter of 3-5 mm and a spacing of 90-100 cm between adjacent spray holes. This ensures that the intermediate return oil is evenly sprayed, achieving thorough washing of the feed's heavy components.

[0028] The pre-flash tower 11 has two feed inlets at its bottom: a hot low-temperature fraction feed inlet and a slurry stripping tower feed inlet. Each feed inlet is equipped with a feed cyclone separator 4. The feed cyclone separator 4 has a streamlined structure. Its inlet is welded to the corresponding hot low-temperature fraction feed line and slurry stripping tower feed line. Its outlet extends along the tower wall to positions 120° and 220° inside the pre-flash tower 11, respectively, ensuring uniform distribution of the two feed streams after entering the pre-flash tower 11.

[0029] The bottom end cap of the pre-flash tower 11 is replaced with a conical end cap 5. The cone angle of the conical end cap 5 is 60°. The large end of the conical end cap 5 is welded and fixed to the tower body of the pre-flash tower 11, and the small end of the conical end cap 5 is connected to the flange of pipeline No. 2 to reduce the space for deposition and coking of heavy components at the end cap. The discharge port of the conical end cap 5 is connected to the inlet of the slurry valve 6 through pipeline No. 2. The two outlet pipe diameters of the slurry valve 6 are set to 6 inches and 4 inches, which is a reduction in diameter compared to the traditional 8-inch pipe diameter to increase the flow rate of the medium in the pipeline.

[0030] The outlet of the slurry valve 6 is divided into two branches. One branch is connected to the pressure reducing tower and is equipped with a flow regulating valve to regulate the flow rate of the medium entering the pressure reducing tower. The other branch is connected to the inlet of the No. 1 double basket filter 7. The No. 1 double basket filter 7 is connected to the wax oil delivery line. The wax oil delivery line is connected in sequence to the centrifugal pump 8 and the No. 2 double basket filter 9.

[0031] Both the No. 1 double basket filter 7 and the No. 2 double basket filter 9 have a pipe diameter of 6 inches, which is a reduction compared to the traditional 8-inch pipe diameter. They also adopt a detachable filter basket structure with a filtration accuracy of 40 mesh, which makes it easy to regularly disassemble and clean the coking material.

[0032] The inlet of centrifugal pump 8 is connected to the branch pipeline flange. Pressure transmitters, regulating valves, etc. are installed on the wax oil delivery line to monitor pressure changes in real time during the wax oil delivery process.

[0033] The middle section reflux spray pipeline 2 is equipped with pipeline No. 3 and pipeline No. 4. Pipeline No. 3 is connected to the pre-flash tower 11, and a transfer pump 10 and a double basket filter No. 3 are connected to pipeline No. 3. Pipeline No. 4 is connected to the pre-flash tower 11 to form a circulation pipeline between pipelines No. 3 and No. 4, which further improves the washing effect of the middle section reflux and facilitates the cleaning and recombinant component interception of the middle section reflux pipeline.

[0034] (II) Work Process During the operation of the slurry bed residue hydrotreating unit, the hot low-density feed and the slurry stripping tower feed are respectively transported to the two feed inlets at the bottom of the pre-flash tower 11 through corresponding external feed pipelines. After being evenly distributed by the feed cyclone separator 4, they enter the interior of the pre-flash tower 11. At the same time, the mid-section reflux oil is transported to the spray distribution pipe 3 through the mid-section reflux spray pipeline 2 and the No. 1 pipeline. The spray distribution pipe 3 is evenly sprayed by the spray heads to wash the feed entering the pre-flash tower 11 and initially separate the heavy components in the feed.

[0035] After washing and separation, the medium is further separated in the pre-flash tower 11. The heavy components flow to the bottom under gravity and enter the conical head 5. Due to the structural design of the conical head 5, the sedimentation space of the heavy components is reduced. The heavy components enter the slurry valve 6 through the second pipeline. After passing through the slurry valve 6, the flow is divided into two branches (the two branches are backups for each other): one branch enters the pressure reducing tower for further processing after the flow rate is regulated by the flow regulating valve; the other branch enters the first double basket filter 7, where the coking material is initially intercepted and filtered. The filtered wax oil (purity of about 80%) is transported through the wax oil delivery line, and is then pressurized by the centrifugal pump 8 and filtered again by the second basket filter 9 before being sent to the downstream wax oil refining unit.

[0036] During operation, the pressure changes of the wax oil delivery line can be monitored in real time via a pressure transmitter. When the pressure rises abnormally, it indicates that the filter baskets of either the No. 1 double basket filter 7 or the No. 2 double basket filter 9 may be clogged. In this case, the system can be switched to the standby filter to disassemble and clean the filter basket. The No. 3 and No. 4 pipelines, which are separate from the intermediate return spray pipeline 2, form a circulation pipeline. The No. 3 line stabilizes the tower and ensures the tower effect, while the No. 4 line sprays to ensure the washing of heavy components. While the intermediate return oil flows in the circulation pipeline, the pressure difference of the No. 3 double basket filter 1 is monitored. If necessary, the system can be switched to the standby basket filter or the auxiliary line to clean the intermediate return pipeline and ensure the smooth flow of the intermediate return system. Through the above structure and operation process, the coking and clogging problem of the pre-flash tower system is effectively solved, ensuring the stable operation of the unit under long-term, high-load conditions.

[0037] Finally, it should be noted that the present invention is not limited to the above embodiments, and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A structure for solving coking and plugging of a slurry bed pre- flash tower system, characterized by, The system includes a pre-flash tower (11), a feed vortex separator (4), a spray distribution pipe (3), a slurry valve (6), a basket filter (7), a pipeline (1), and a pipeline (2). The spray distribution pipe (3) is connected to the intermediate reflux spray pipeline (2) through the pipeline (1), and the spray distribution pipe (3) is installed inside the pre-flash tower (11) at the position corresponding to the original tray. The pre-flash tower (11) has two feed inlets at the bottom, and the feed vortex separator is installed at both feed inlets. (4) The bottom end cap of the pre-flash tower (11) is set as a conical end cap (5); the outlet of the conical end cap (5) is connected to the inlet of the slurry valve (6) through the No. 2 pipeline. The outlet of the slurry valve (6) is divided into two branches. One branch is connected to the pressure reducing tower, and the other branch is connected to the inlet of the No. 1 basket filter (7). The No. 1 basket filter (7) is connected to the wax oil delivery line. The wax oil delivery line is connected in sequence to the centrifugal pump (8) and the No. 2 basket filter (9).

2. The structure for solving the coking and plugging of the slurry bed pre- flash tower system according to claim 1, characterized in that, The middle section reflux spray pipeline (2) is divided into pipeline No. 3 and pipeline No.

4. Pipeline No. 3 is connected to the pre-flash tower (11), and a transfer pump (10) and a No. 3 double basket filter (1) are connected to pipeline No.

3. Pipeline No. 4 is connected to the pre-flash tower (11) to form a circulation pipeline between pipeline No. 3 and pipeline No.

4.

3. The structure for solving the coking and plugging of the slurry bed pre- flash tower system according to claim 1, characterized in that, The inlet pipe diameter of the slurry valve (6) is set to 8 inches, outlet 1 is 6 inches, and outlet 2 is 4 inches. The first double basket filter (7) is set to 6 inches, and the pipe diameter of the second double basket filter (9) is set to 4 inches.

4. The structure for solving the coking and plugging of the slurry bed pre- flash tower system according to claim 1, characterized in that, The spray distribution pipe (3) is evenly provided with several spray heads, the orifice diameter of the spray head is 3-5mm, and the distance between adjacent spray heads is 90-100cm.

5. The structure for solving the coking and plugging of the slurry bed pre- flash tower system according to claim 1 or 4, characterized in that, The number of spray distribution pipes (3) is 10. Multiple spray distribution pipes (3) are evenly distributed along the cross-sectional direction of the pre-flash tower (11), and multiple spray distribution pipes (3) are connected to the main pipe and connected to the No. 1 pipeline by the main pipe.

6. The structure for solving the coking and plugging of the slurry bed pre- flash tower system according to claim 1, characterized in that, The inlet of the feed vortex separator (4) is welded and fixed to the external feed pipe, and the outlet of the feed vortex separator (4) extends along the tower wall to the 120° and 220° positions of the pre-flash tower (11).

7. The structure for solving the coking and plugging of the slurry bed pre- flash tower system according to claim 1, characterized in that, The cone angle of the cone head (5) is 60°. The large end of the cone head (5) is welded and fixed to the tower body of the pre-flash tower (11). The small end of the cone head (5) is connected to the No. 2 pipeline flange.

8. The structure for solving the coking and plugging of the slurry bed pre- flash tower system according to claim 1, characterized in that, A regulating valve is provided between the No. 1 pipeline and the middle section return spray pipeline (2), and a flow regulating valve is provided on the branch connecting the pressure reducing tower.

9. The structure for solving the coking and plugging of the slurry bed pre- flash tower system according to claim 1 or 3, characterized in that, Both the No. 1 double basket filter (7) and the No. 2 double basket filter (9) adopt a detachable filter basket structure and the filters can be switched online. The filtration accuracy of the filter basket is 40 mesh.

10. The structure for solving coking and blockage in a slurry bed pre-flash distillation tower system according to claim 2, characterized in that, The inlet of the centrifugal pump (8) is connected to the flange of the branch pipeline, and a pressure transmitter is installed on the wax oil delivery line.

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