C6-C8 recovery system of the aromatics hydrogenation unit in an ethylene plant
Patent Information
- Application Number
- CN202522044602.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-22
- Publication Date
- 2026-09-01
- Estimated Expiration
- 2035-09-22
AI Technical Summary
[0003]但上述的乙烯装置裂解芳烃加氢系统在实际运行时还存在一定的不足：经污油污水泵送至碳十粗芳烃罐的C6～C8物料，很难进行回收，只能通过装车外送，处理成本增加造成很大的经济损失
[0013]与现有技术相比，本实用新型的优点：本实用新型的乙烯装置裂解芳烃加氢单元的C6～C8回收系统通过设置回收管线及三通控制阀，将污油污水泵原泵送下游的含C6～C8组分的凝液重新引至脱碳九塔的进料管线，实现了对轻组分的循环回收，减少了物料损失，同时降低了后续污油处理系统的负荷，尤其是避免了将轻组分作为废油装车外送所产生的运输、处置费用，直接将废物转化为产品，经济效益提升显著。仅通过管线与阀门的优化增设实现功能，无需改动核心设备，投资成本低，且操作灵活，易于集成到现有装置中稳定运行。
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Figure CN224700174U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the technical field of aromatic hydrocarbon hydrogenation systems for ethylene plants, and in particular to a C6-C8 recovery system for an aromatic hydrocarbon hydrogenation unit in an ethylene plant. Background Technology
[0002] In the existing ethylene plant cracking aromatics hydrogenation system, after the feed from the bottom of the decarbonization tower 5 is sent to the decarbonization tower 9, the top gas phase is C6-C8 fraction. After being condensed by the top condenser, the condensate enters the decarbonization tower 9 reflux tank. The gas phase in the reflux tank is cooled by the tail gas condenser of the decarbonization tower 9, and the condensate returns to the reflux tank. The non-condensable gas is sent to the wet flare network through the vacuum system. The condensed condensate goes to the flare tank. When the liquid level in the flare tank rises, it is sent to the sludge tank through the static pressure difference, and then pumped to the C10 crude aromatics tank by the sludge pump.
[0003] However, the aforementioned ethylene plant's cracked aromatics hydrogenation system still has certain shortcomings in actual operation: the C6 to C8 materials pumped to the C10 crude aromatics tank via sludge pumps are difficult to recover and can only be transported by truck, which increases processing costs and causes significant economic losses.
[0004] Therefore, the C6-C8 recovery system of the existing ethylene plant's aromatic hydrocarbon hydrogenation unit needs further improvement. Utility Model Content
[0005] The technical problem to be solved by this utility model is to provide a C6-C8 recovery system for the cracking aromatics hydrogenation unit of an ethylene plant that can effectively recover C6-C8 materials and reduce processing costs, in light of the current state of the technology.
[0006] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows: a C6-C8 recovery system for an aromatic hydrocarbon hydrogenation unit in an ethylene plant, comprising a decarbonization tower 9, which is connected to a feed pipeline from the bottom of the decarbonization tower 5 and a top vapor phase output pipeline for outputting C6-C8 fractions. The outlet of the top vapor phase output pipeline is connected to a reflux tank, and a top condenser is provided on the top vapor phase output pipeline. The top of the reflux tank is connected to a tail gas condenser through a reflux vapor phase output pipeline, and the tail gas condenser is connected to a non-condensable gas delivery pipeline. The system is connected to a vacuum treatment device, which is connected to a flare network via a flare gas delivery pipeline. A flare tank is installed on the flare gas delivery pipeline. The bottom outlet of the flare tank is connected to a sludge tank via a condensate delivery pipeline. The outlet of the sludge tank is connected to a C10 crude aromatics tank via a sludge tank pipeline. A sludge pump is installed on the sludge tank pipeline. The system also includes a recovery pipeline. The inlet of the recovery pipeline is connected to a position on the sludge tank pipeline downstream of the sludge pump via a three-way control valve. The outlet of the recovery pipeline is connected to the feed pipeline.
[0007] Flare networks refer to the pipeline systems in chemical plants used to collect and burn flammable gases emitted from them, ensuring safe production and compliance with environmental protection standards.
[0008] As an improvement, the three-way control valve is connected to the outlet drain of the sludge pump. By installing the three-way control valve at the existing outlet drain of the sludge pump, no additional pipeline joints are needed, reducing modification costs.
[0009] The aforementioned "drainage outlet" generally refers to a drain port located at the lowest point of a pipeline or equipment, used to discharge accumulated liquid or clean residues, and is usually equipped with a valve to control the discharge. For example, a pump outlet drainage outlet can be used to discharge residual liquid inside the pump to prevent blockage or corrosion.
[0010] As an improvement, the outlet of the recycling pipeline is connected to the lowest point of the inlet pipeline. Similarly, connecting the outlet of the recycling pipeline to the lowest point of the inlet pipeline eliminates the need for additional pipeline joints, reducing modification costs.
[0011] As an improvement, the condensate from the flare tank is delivered to the sludge tank under the action of hydrostatic pressure differential. The condensate transport from the flare tank to the sludge tank is achieved through hydrostatic pressure differential, eliminating the need for additional power equipment, reducing system energy consumption and maintenance costs, and simplifying the process flow.
[0012] The aforementioned "hydrostatic pressure difference" can be understood as the flow of fluid driven by the pressure difference generated by the liquid's own gravity, without the need for external power input. For example, liquid in a high-level tank flows naturally to a low-level tank due to the difference in liquid level.
[0013] Compared with existing technologies, the advantages of this invention are as follows: The C6-C8 recovery system of the aromatic hydrocarbon hydrogenation unit in the ethylene plant of this invention, by setting up recovery pipelines and three-way control valves, redirects the condensate containing C6-C8 components originally pumped downstream by the waste oil and wastewater pump back to the feed pipeline of the decarbonization tower, realizing the recycling and recovery of light components, reducing material loss, and lowering the load on the subsequent waste oil treatment system. In particular, it avoids the transportation and disposal costs incurred by loading and transporting light components as waste oil, directly converting waste into products, resulting in significant economic benefits. The functionality is achieved only through the optimization and addition of pipelines and valves, without modifying core equipment, resulting in low investment costs, flexible operation, and easy integration into existing plants for stable operation. Attached Figure Description
[0014] Figure 1 This is a three-dimensional structural diagram of an embodiment of the present utility model. Detailed Implementation
[0015] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.
[0016] In the specification and claims of this utility model, terms indicating direction, such as "front," "rear," "upper," "lower," "left," "right," "side," "top," and "bottom," are used to describe various exemplary structural parts and elements of this utility model. However, the use of these terms is merely for the purpose of explanation and is based on the exemplary orientations shown in the accompanying drawings. Since the embodiments disclosed in this utility model can be arranged in different orientations, these terms indicating direction are for illustrative purposes only and should not be regarded as limitations. For example, "upper" and "lower" are not necessarily limited to directions opposite to or consistent with the direction of gravity.
[0017] Figure 1 This invention illustrates a preferred embodiment of a C6-C8 recovery system for an aromatic hydrocarbon hydrogenation unit in an ethylene plant. The C6-C8 recovery system for this ethylene plant's aromatic hydrocarbon hydrogenation unit is an optimized improvement upon existing equipment structures, aiming to solve the problems of difficult recovery of C6-C8 components and the increased costs resulting from the need for external processing.
[0018] The C6-C8 recovery system of the aromatics hydrogenation unit in the ethylene plant cracking process includes a decarbonization tower 1 (tower 9). Tower 1 has a feed line 11 to receive material from the bottom of the upstream decarbonization tower (tower 5). Tower 1 has a top vapor output line 12 for outputting the C6-C8 fractions. A top condenser 120 is installed on the top vapor output line 12 to condense the vapor into a liquid phase. The condensed material is temporarily stored in a reflux tank 10.
[0019] The top of the reflux tank 10 is equipped with a reflux gas phase output pipeline 101, which is connected to the tail gas condenser 13. The tail gas condenser 13 further cools the uncondensed gas phase components. The condensate returns to the reflux tank 10, while the non-condensable gas enters the vacuum treatment device 14 through the non-condensable gas delivery pipeline 131. After processing the non-condensable gas, the vacuum treatment device 14 delivers it to the wet flare network via the flare gas delivery pipeline 15. The flare gas delivery pipeline 15 is equipped with a flare tank 16 for temporarily storing the condensed droplets. The bottom of the flare tank 16 is equipped with a condensate outlet, which delivers the condensate to the sludge tank 17 through the condensate delivery pipeline 161 under the action of hydrostatic pressure difference. The above-mentioned hollow treatment device generally uses a steam ejector or a liquid ring vacuum pump to create and maintain the vacuum required by the system, while simultaneously removing and processing non-condensable gases from the condenser. Its specific structure and working process are existing technologies and will not be described in detail.
[0020] The outlet of the sludge tank 17 is connected to the sludge pipeline 171, and the pipeline is equipped with a sludge pump 172, which is used to pump the accumulated liquid in the tank to the C10 crude aromatics tank 18.
[0021] The improvement to this system lies in the addition of a recovery pipeline 19 and a three-way control valve. The inlet of the recovery pipeline 19 is connected to the sludge pipeline 171 downstream of the sludge pump 172 via the three-way control valve, preferably at the drain valve at the outlet of the sludge pump 172. After the three-way control valve is installed at the pump outlet drain, one path can discharge normally, while the other path is connected to the low-point drain of the feed pipeline 11 of the decarbonization tower 1. The three-way control valve has three ports, which can switch the fluid flow direction. In the normal operation mode, the valve position controls the material at the outlet of the sludge pump 172 to flow entirely to the C10 crude aromatics tank 18. When it is necessary to recover C6 to C8 components, the operator switches the valve position of the three-way control valve, causing some or all of the material to enter the recovery pipeline 19 and flow back to the feed pipeline 11 of the decarbonization tower 1. After mixing with the fresh feed, it re-enters the decarbonization tower 1 for fractionation. The return flow can be flexibly controlled by adjusting the valve opening.
[0022] The system's workflow is as follows: During normal operation, the C6-C8 fractions generated at the top of Decarbonization Tower 1 are condensed, and the non-condensable gases eventually enter the flare system. The condensate is collected in flare tank 16 and flows by gravity to the waste oil and wastewater tank 17 based on static pressure difference. In traditional operation, the material in waste oil and wastewater tank 17 is considered waste oil and is entirely sent to C10 crude aromatics tank 18 by waste oil and wastewater pump 172, awaiting loading and transportation. The abundant C6-C8 light components are thus lost. With this system, operators can switch the three-way control valve based on analytical data (such as the light component content of the material in waste oil and wastewater tank 17) or a periodic recovery strategy. The material rich in C6-C8 is directly returned to the feed of Decarbonization Tower 1 via recovery pipeline 19. These light components re-enter the distillation system, are separated again in Decarbonization Tower 1, and are thus recovered and incorporated into the main product stream, turning waste into treasure.
[0023] In some embodiments, the three-way control valve is not limited to being installed at the pump outlet drain. Instead, the same flow path switching function can be achieved by adding a three-way fitting to the main pipeline downstream of the sludge pump 172. The outlet of the recovery pipeline 19 can also be directly connected to the main pipeline of the feed pipeline 11 by means of a clamp or welding, rather than being limited to the low-point drain, as long as the pressure at the connection point is matched and the material can be transported smoothly. This provides flexibility for on-site pipeline configuration.
[0024] In some embodiments, a flow meter and regulating valve may be further added to the recovery pipeline 19, interlocked with the DCS control system. The system can automatically calculate the optimal reflux flow rate based on the rate of increase of the liquid level in the sludge tank 17 or the concentration of light components detected by an online analyzer (such as a chromatograph), and automatically control the opening of the three-way control valve through the regulating valve to achieve accurate and automatic recovery of C6 to C8 materials, reduce manual intervention, improve recovery efficiency and system intelligence.
Claims
1. A C6-C8 recovery system for an aromatics hydrogenation unit in an ethylene plant, characterized in that: The system includes a decarbonization tower (1), which is connected to a feed line (11) from the bottom of the decarbonization tower (5) and a top vapor output line (12) for outputting C6-C8 fractions. The outlet of the top vapor output line (12) is connected to a reflux tank (10), and a top condenser (120) is provided on the top vapor output line (12). The top of the reflux tank (10) is connected to a tail gas condenser (13) through a reflux vapor output line (101), and the tail gas condenser (13) is connected to a non-condensable gas delivery pipe. Line (131) is connected to vacuum treatment device (14), which is connected to flare network through flare gas delivery pipeline (15). Flare tank (16) is provided on flare gas delivery pipeline (15). The bottom outlet of flare tank (16) is connected to sludge tank (17) through condensate delivery pipeline (161). The outlet of sludge tank (17) is connected to C10 crude aromatics tank (18) through sludge pipeline (171). Sludge pump (172) is provided on sludge pipeline (171). It also includes a recovery pipeline (19), the inlet of which is connected to the oily wastewater pipeline (171) downstream of the oily wastewater pump (172) via a three-way control valve, and the outlet of the recovery pipeline (19) is connected to the feed pipeline (11).
2. The C6-C8 recovery system of the aromatic hydrocarbon hydrogenation unit in an ethylene plant according to claim 1, characterized in that: The three-way control valve is connected to the outlet drain of the sludge pump (172).
3. The C6-C8 recovery system of the aromatic hydrocarbon hydrogenation unit in an ethylene plant according to claim 1, characterized in that: The outlet of the recovery pipeline (19) is connected to the low point of the feed pipeline (11).
4. The C6-C8 recovery system of the aromatic hydrocarbon hydrogenation unit in an ethylene plant according to claim 1, characterized in that: The flare gas condensate in the flare tank (16) is sent to the sludge oil and wastewater tank (17) under the action of hydrostatic pressure differential.