An ethylene recovery system for reactors

Abstract

This utility model relates to the field of ethylene recovery technology, and more particularly to an ethylene recovery and utilization system for a reactor. It includes a reactor, characterized in that the reactor is provided with a process vent and a circulation port. The process vent is connected to a condenser, the outlet of the condenser is connected to a buffer tank, the outlet of the buffer tank is connected to a compressor, and the outlet of the compressor is connected to the circulation port. Through the combined structure of the reactor, condenser, buffer tank, compressor, and circulation pipeline, excess ethylene in the reactor is recovered, condensed to remove impurities, compressed, and then returned to the reactor to participate in the reaction. This changes the traditional method of directly venting ethylene, improving the utilization rate of ethylene feedstock, reducing the total production cost, and simultaneously reducing the environmental impact of ethylene emissions.

Description

Technical Field

[0001] This utility model relates to the field of ethylene recovery technology, and in particular to an ethylene recovery and utilization system for a reactor. Background Technology

[0002] Alkylation refers to the introduction of alkyl groups onto the carbon, nitrogen, and oxygen atoms of organic molecules to synthesize organic chemicals. The main alkylates are alkanes and their derivatives, aromatic hydrocarbons and their derivatives. The reactions are mainly classified into three types: C-alkylation, N-alkylation, and O-alkylation, and have wide applications in petrochemicals, fine chemicals, and other fields. Among these, DEA (2,6-diethylaniline) alkylation is an important process for preparing specific organic amine compounds. In this process, ethylene is the key alkylating agent; to ensure the reaction proceeds fully and to improve the yield of the target product, ethylene is usually introduced in excess during actual production.

[0003] Currently, DEA alkylation processes generally adopt a batch reaction mode. The operation process is roughly as follows: DEA and related catalysts are added into the reactor, and then ethylene is introduced to carry out the alkylation reaction. After the reaction is completed, the reaction products are first discharged from the reactor, and then the excess ethylene remaining in the reactor is directly discharged into the atmosphere or flare system through the process vent. Only after the ethylene has been vented can the next batch of raw materials be fed and a new reaction cycle be started.

[0004] This traditional operating method has many problems: First, if a large amount of unreacted ethylene is directly vented, it not only causes a serious waste of valuable chemical raw materials and increases the total production cost, but also poses a great safety hazard as ethylene is a flammable and explosive gas, and will also have a certain impact on the surrounding environment; Second, the ethylene venting process takes a certain amount of time, which leads to a longer idle period of the reactor, making it impossible to achieve continuous production and reducing the operating efficiency and capacity of the entire production unit; In addition, the unstable ethylene gas flow from direct venting may impact the venting system, increasing the difficulty and cost of equipment maintenance.

[0005] To address the problems of waste and low efficiency caused by the direct venting of excess ethylene from existing DEA alkylation reactors, this invention provides an ethylene recovery and recycling system for reactors, enabling the recovery and recycling of excess ethylene and reducing production costs. Utility Model Content

[0006] The purpose of this invention is to solve the problems existing in the prior art by proposing an ethylene recovery and utilization system for a reaction vessel.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: An ethylene recovery and utilization system for a reactor includes a reactor, characterized in that the reactor is provided with a process vent and a circulation port, the process vent is connected to a condenser, the outlet of the condenser is connected to a buffer tank, the outlet of the buffer tank is connected to a compressor, and the outlet of the compressor is connected to the circulation port.

[0008] Preferably, the buffer tank includes a primary buffer tank and a secondary buffer tank in sequence, with the outlet of the primary buffer tank connected to the inlet of the secondary buffer tank, and the outlet of the secondary buffer tank connected to the inlet of the compressor; the pressure inside the primary buffer tank is greater than the pressure inside the secondary buffer tank.

[0009] Preferably, a shut-off valve and a regulating valve are provided between the outlet of the primary buffer tank and the inlet of the secondary buffer tank.

[0010] Preferably, both the primary buffer tank and the secondary buffer tank are equipped with vent pipes with valves.

[0011] Preferably, the compressor outlet is connected to an ethylene buffer tank, and the outlet of the ethylene buffer tank is connected to a circulation port.

[0012] Preferably, the ethylene buffer tank is also connected to an external ethylene pipeline with a valve.

[0013] Preferably, the gas flows in one direction throughout the entire recovery system.

[0014] Preferably, the compressor is an ethylene diaphragm compressor.

[0015] Compared with the prior art, this utility model provides an ethylene recovery and utilization system for a reactor, which has the following beneficial effects: 1. This utility model, through the combined structure of a reactor, condenser, buffer tank, compressor and circulation pipeline, recovers, condenses and removes impurities from the reactor, compresses and sends the excess ethylene back into the reactor to participate in the reaction, changing the traditional method of directly venting ethylene, which can improve the utilization rate of ethylene raw materials, reduce the total production cost, and at the same time reduce the environmental impact of ethylene emissions.

[0016] 2. This utility model, through the pressure graded control of the two-stage buffer tank and the interlocking device between the pressure sensor and the valve, ensures that the pressure of the entire system remains stable within the set range, providing stable operating conditions for key equipment such as the compressor; the setting of the ethylene buffer tank further stabilizes the ethylene flow rate and pressure fed into the reactor, ensuring the stability of the DEA alkylation reaction.

[0017] 3. This utility model provides multiple safety guarantees through safety valves, vent pipes, and check valves on each level of buffer tank.

[0018] Other advantages, objectives and features of this invention will be set forth in part in the description which follows; and in part will be apparent to those skilled in the art upon examination of the following description; or may be taught from practice of this invention. Attached Figure Description

[0019] Figure 1 This is a simplified layout diagram of the ethylene recovery and utilization system of this utility model.

[0020] Figure 2 This is a partial schematic diagram of the reaction vessel in the recycling system of this utility model.

[0021] Figure 3 This is a partial schematic diagram of the dual-buffer tank system in the recycling system of this utility model.

[0022] Figure 4 This is a partial schematic diagram of the ethylene buffer tank in the recycling system of this utility model.

[0023] In the diagram: 1. Reactor; 2. Process vent; 3. Circulation port; 4. Condenser; 5. Primary buffer tank; 6. Secondary buffer tank; 7. Compressor; 8. Ethylene buffer tank; 9. External ethylene pipeline; 10. Return pipe; 11. Vent pipe. Detailed Implementation

[0024] The following will refer to the appendix in the embodiments of this utility model. Figure 1-4 The technical solutions in the embodiments of this utility model will be clearly and completely described. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments.

[0025] Example 1: To address the problem of waste of raw materials and environmental pollution caused by the direct venting of excess ethylene from the existing DEA alkylation reactor 1, this example provides a reactor ethylene recovery and utilization system to achieve preliminary recovery and utilization of ethylene.

[0026] The ethylene recovery and utilization system of the reactor 1 in this embodiment includes reactor 1, which is the core reaction equipment of the chemical reaction and also the emission starting point and circulation reflux endpoint of ethylene gas in this recovery and utilization system.

[0027] The top of reactor 1 is integrated with a material inlet, a material outlet, a nitrogen inlet, a safety vent valve, and a process vent port 2. Process vent port 2 is used to discharge excess ethylene remaining after the reaction. All these ports are equipped with corresponding valves. This is the basic structural equipment of reactor 1 and is existing technology, so it will not be described in detail here. The only modification in this design is the addition of a circulation port 3 on the side wall of reactor 1 to return the recovered ethylene to the reactor for recycling.

[0028] The process vent 2 is connected to a condenser 4 via a flange. The condenser 4 is a tubular structure with cooling water flowing inside to cool the vent gas containing ethylene, removing entrained vapors and some liquid impurities. Examples of condenser 4 produced by Sichuan Ruitong Machinery Equipment Co., Ltd. are examples of tubular condensers 4. The outlet of the condenser 4 is connected to a buffer tank via a pipeline. The buffer tank is a closed pressure vessel used to temporarily store the condensed ethylene gas, stabilizing gas flow and pressure to prevent damage to downstream equipment due to fluctuations in gas intake. The outlet of the buffer tank is connected to a compressor 7 via a pipeline, providing a stable power source for the entire recovery system. The outlet of the compressor 7 is sealed and connected to the circulation port 3 of the reactor 1 via a pipeline, forming a complete recovery circulation loop.

[0029] Using the aforementioned equipment, after the DEA alkylation reaction is completed, compressor 7 and process vent 2 are opened. Compressor 7 provides negative pressure absorption and extrusion, creating a unidirectional gas flow channel throughout the recovery pipeline. Under the action of compressor 7, excess ethylene remaining in reactor 1 is discharged from process vent 2. This gas first enters condenser 4 for cooling; then, the processed ethylene enters buffer tank for pressure and flow stabilization to prevent airflow from impacting compressor 7; finally, it is returned to reactor 1 via recirculation port 3 through compressor 7 to participate in the next batch of reaction.

[0030] This structure enables the recovery and reuse of excess ethylene, reduces waste caused by direct ethylene emissions, lowers safety hazards during venting, and initially improves the utilization rate of raw materials.

[0031] To address the issue of a single buffer tank's inability to stably regulate gas pressure, leading to large fluctuations in the inlet pressure of the subsequent compressor 7 and unstable equipment operation, the buffer system comprises a primary buffer tank 5 and a secondary buffer tank 6. The outlet of the primary buffer tank 5 is connected to the inlet of the secondary buffer tank 6, and the outlet of the secondary buffer tank 6 is connected to the inlet of the compressor 7. The design pressure within the primary buffer tank 5 is greater than the pressure within the secondary buffer tank 6. The set pressure within the primary buffer tank 5 does not exceed 1.0 MPa. After pressure reduction, the pressure in the secondary buffer tank 6 stabilizes between 0.2 and 0.4 MPa, forming a pressure gradient.

[0032] The primary buffer tank 5 first receives ethylene gas from the condenser 4, serving as a preliminary pressure stabilizer and buffer to prevent the gas from directly entering subsequent equipment and causing shock. Subsequently, the gas flows from the primary buffer tank 5 into the lower-pressure secondary buffer tank 6, further stabilizing the pressure and matching it with the inlet pressure of the compressor 7. This provides the compressor 7 with a stable inlet pressure, ensuring it always operates under rated conditions and reducing the frequency of equipment start-ups and shutdowns and the failure rate. Through this two-stage pressure control, the operational stability of the entire recovery system is significantly improved, and a foundation is laid for subsequent precise pressure regulation.

[0033] To ensure a stable pressure gradient between the primary buffer tank 5 and the secondary buffer tank 6, a buffer shut-off valve and a buffer regulating valve are installed between the outlet of the primary buffer tank 5 and the inlet of the secondary buffer tank 6, forming a pressure-reducing pipeline. Simultaneously, a pressure sensor is installed on the top of the primary buffer tank 5. This pressure sensor is wiredly connected to the controller of the shut-off valve at the process vent 2 of the reactor 1, achieving interlocked control: when the pressure inside the primary buffer tank 5 reaches the set upper limit, the process vent shut-off valve of the reactor 1 is interlocked and closed, stopping the gas supply to the primary buffer tank 5; the buffer shut-off valve and buffer regulating valve on the pipeline between the primary buffer tank 5 and the secondary buffer tank 6 are interlocked with the pressure sensor on the secondary buffer tank 6. When the pressure inside the secondary buffer tank 6 is below 0.2 MPa, the interlocked control valve opening increases, while ensuring the shut-off valve remains open, increasing the gas inflow; when the pressure inside the secondary buffer tank 6 is above 0.4 MPa, the interlocked control valve opening decreases, and if the pressure continues to rise, the shut-off valve closes, stopping the gas inflow.

[0034] In addition, both the primary buffer tank 5 and the secondary buffer tank 6 are equipped with safety valves. The safety valves are spring-loaded micro-opening safety valves. The safety valve set pressure of the primary buffer tank 5 is 1.0 MPa, and the safety valve set pressure of the secondary buffer tank 6 is 0.4 MPa. Together with the gas cut-off of the pressure sensor, they form a double safety guarantee.

[0035] Both the primary buffer tank 5 and the secondary buffer tank 6 have vent pipes 11 connected to their safety valve outlets, forming an emergency vent pipe 11. The two sets of vent pipes 11 eventually merge to discharge the overpressured ethylene gas.

[0036] To address the issue of fluctuating ethylene pressure at the compressor 7 outlet leading to unstable ethylene flow back to reactor 1 and affecting reaction efficiency, this embodiment incorporates an ethylene buffer tank 8 at the compressor 7 outlet. The compressor 7 outlet is connected to the ethylene buffer tank 8, and the outlet of the ethylene buffer tank 8 is connected to the circulation port 3 via a return pipe 10. The volumetric effect of the ethylene buffer tank 8 absorbs pressure fluctuations in the compressor 7 exhaust, maintaining stable ethylene pressure and flow at the outlet of the ethylene buffer tank 8. The stabilized ethylene is then fed into reactor 1 through the circulation port 3, providing a continuous and stable ethylene feedstock to reactor 1. This avoids problems such as incomplete reaction or unstable product quality caused by ethylene flow fluctuations, while also reducing the load impact on compressor 7 caused by exhaust pressure fluctuations, thus extending the service life of compressor 7.

[0037] The ethylene buffer tank 8 is also connected to an external ethylene pipeline 9, which is equipped with a shut-off valve to control the flow of external ethylene. A pressure sensor is also installed on the top of the ethylene buffer tank 8, and this pressure sensor is interlocked with the shut-off valve on the external ethylene pipeline 9: when the pressure inside the ethylene buffer tank 8 is lower than a set value, the pressure sensor sends a signal to the control system, which then controls the shut-off valve on the external ethylene pipeline 9 to open, allowing new ethylene to be supplied to the ethylene buffer tank 8 through the external ethylene pipeline 9; when the pressure inside the ethylene buffer tank 8 reaches the set upper limit, the pressure sensor sends a signal, and the control system controls the shut-off valve to close, stopping the supply of external ethylene. The external ethylene pipeline 9 can also be used directly as a pipeline for adding ethylene to the reactor 1.

[0038] In this scheme, the gas flow direction of the entire recovery system is set as follows: reactor 1 → condenser 4 → primary buffer tank 5 → secondary buffer tank 6 → compressor 7 → ethylene buffer tank 8 → reactor 1. To ensure that the gas flows unidirectionally in this direction, anti-backflow measures are set at key nodes. For example, a one-way valve structure is installed on the pipeline between the outlet of ethylene buffer tank 8 and the circulation port 3. The conduction direction of the one-way valve is consistent with the gas flow direction, allowing only ethylene to flow from ethylene buffer tank 8 to reactor 1, and prohibiting gas from flowing back from reactor 1 to ethylene buffer tank 8.

[0039] In this scheme, the compressor 7 is an ethylene diaphragm compressor 7. The compressor 7 adopts a diaphragm sealing structure, which has the characteristics of good sealing performance and high compression efficiency, and can effectively avoid the leakage of ethylene gas during the compression process.

[0040] In this design, a valve, such as a shut-off valve, is also installed between the ethylene buffer tank 8 and the circulation port 3. This is to control the gas inside the ethylene buffer tank 8, ensuring that the pipeline is opened to allow ethylene to be injected into the reactor 1 only when the next process requires it.

[0041] The overall operation process of this ethylene recovery and utilization system in reactor 1 is as follows: After the DEA alkylation reaction is completed and the product is discharged, the shut-off valve at the process vent 2 of reactor 1 is opened. Excess ethylene remaining in reactor 1 is discharged from process vent 2 and enters condenser 4 for condensation treatment to remove moisture and easily condensable impurities from the gas. The condensed ethylene gas enters the primary buffer tank 5 and the secondary buffer tank 6, and then enters the ethylene diaphragm compressor 7. After compression and pressurization, it is sent to the ethylene buffer tank 8. The ethylene in the ethylene buffer tank 8 is continuously fed back into reactor 1 through a pipeline via circulation port 3, providing raw materials for the next batch of reaction and realizing the recycling of ethylene. When the ethylene supply is insufficient, new ethylene is added through external ethylene pipeline 9.

[0042] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

[0043] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0044] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A reactor ethylene recovery system, comprising a reactor (1), characterized in that, The reactor (1) is provided with a process vent (2) and a circulation port (3). The process vent (2) is connected to a condenser (4). The outlet of the condenser (4) is connected to a buffer tank. The outlet of the buffer tank is connected to a compressor (7). The outlet of the compressor (7) is connected to the circulation port (3).

2. The ethylene recovery and utilization system for the reactor according to claim 1, characterized in that, The buffer tank includes a primary buffer tank (5) and a secondary buffer tank (6) in sequence. The outlet of the primary buffer tank (5) is connected to the inlet of the secondary buffer tank (6), and the outlet of the secondary buffer tank (6) is connected to the inlet of the compressor (7). The pressure inside the primary buffer tank (5) is greater than the pressure inside the secondary buffer tank (6).

3. The ethylene recovery and utilization system for the reactor according to claim 2, characterized in that, A shut-off valve and a regulating valve are provided between the outlet of the primary buffer tank (5) and the inlet of the secondary buffer tank (6).

4. The ethylene recovery and utilization system for the reactor according to claim 2, characterized in that, Both the primary buffer tank (5) and the secondary buffer tank (6) are equipped with vent pipes (11) with valves.

5. The reactor ethylene recovery system according to claim 1 or (2), characterized in that, The compressor (7) outlet is connected to an ethylene buffer tank (8), and the outlet of the ethylene buffer tank (8) is connected to the circulation port (3).

6. The ethylene recovery and utilization system for the reactor according to claim 5, characterized in that, The ethylene buffer tank (8) is also connected to an external ethylene pipeline (9) with a valve.

7. The ethylene recovery and utilization system for the reactor according to claim 6, characterized in that, The gas flows in one direction throughout the entire recovery system.

8. The ethylene recovery and utilization system for the reactor according to claim 1, characterized in that, The compressor (7) is an ethylene diaphragm compressor.

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