An argon fractional displacement method for n-butyllithium synthesis

Abstract

This invention relates to the field of argon staged displacement technology, specifically to an argon staged displacement method for the synthesis of n-butyllithium. The method includes the following steps: a gas-filling chamber is set between adjacent reactors, and this chamber is controllably connected to the outlet of the preceding reactor and the inlet pipeline of the following reactor via a control valve group; argon gas is first introduced into the pretreatment equipment (branch pipe) of a single reactor to purge the mixed gas in the pipeline blind zone, and then the timing and flow rate of argon gas at the upstream, downstream, and midstream inlets are controlled to form a stable pressure gradient, directionally pushing the mixed gas in the reactor to the gas-filling chamber; the mixed gas in the preceding gas-filling chamber is introduced into the following reactor for repeated displacement, and finally discharged from the end; this invention enhances blind zone purification, improves displacement efficiency, reduces argon consumption, reduces inert gas waste, contributes to carbon emission reduction, and assists in air pollution prevention and control.

Description

Technical Field

[0001] This invention relates to the field of argon gas fractionation technology, and more specifically, to an argon gas fractionation method for the synthesis of n-butyllithium. Background Technology

[0002] n-Butyllithium (n-BuLi) is a widely used polymerization initiator in the production of lithium-based polymers. Industrially, it is mainly used in the production processes of thermoplastic elastomers such as SBS, SIS, SEBS, low-cis polybutadiene rubber, solution-polymerized styrene-butadiene rubber, and K-resin. In addition, n-Butyllithium is also widely used in the fine chemical and pharmaceutical industries. Currently, my country's polymer production capacity using n-Butyllithium as an initiator exceeds 210,000 tons per year.

[0003] Currently, the production equipment for n-butyllithium involves heating metallic lithium in white oil to above its melting point under the protection of an inert gas to completely melt it. Then, it is dispersed at high speed by stirring to form highly active fine lithium sand. Subsequently, it is reacted with chlorobutane in a solvent system of cyclohexane or n-hexane to obtain a n-butyllithium solution. The solution is then filtered to separate the n-butyllithium.

[0004] In a multi-reactor series system used for continuous production of n-butyllithium, creating and maintaining a pure, oxygen-free, and anhydrous environment presents a significant challenge due to the system's inherent structure. To meet the demands of multiple processes such as lithium melting, dispersion, reaction, and filtration, the system inevitably integrates various branch pipes, instrument interfaces, sampling ports, and connecting elbows, forming a complex network of pipes. This complex structure creates numerous inaccessible geometric dead zones outside the main system. Traditional displacement techniques, whether simple one-end blowing and one-end extraction or vacuuming followed by inert gas filling, are inadequate for this structure. The former naturally draws airflow towards the main channel of least resistance, failing to effectively sweep away and remove residual gases in the dead zones, making these areas a potential source of continuous contamination of the reaction system; the latter has limited effectiveness in removing the molecular adsorption layer adhering to the large inner wall surface and the static gases within the dead zones.

[0005] In continuous production scenarios with multiple reactors connected in series, replacing each reactor independently and sequentially is not only inefficient and consumes a huge amount of inert gas, but the connecting pipelines between the reactors themselves can also become blind spots for replacement. If not handled properly, residual impurities will diffuse between the reactors, causing a chain reaction of cross-contamination and endangering the quality of n-butyllithium products. Summary of the Invention

[0006] This invention provides an argon staged displacement method for the synthesis of n-butyllithium. By setting up gas-filling chambers between adjacent reactors in a multi-reactor series system and coordinating the timing and flow rate of the downstream, midstream, and upstream gas inlets of each reactor, a stable directional pressure gradient is formed inside the reactor. This allows the original gas and the mixed gas formed during the displacement process to be sequentially and directionally pushed into the gas-filling chambers for temporary storage, serving as the gas source for the next reactor displacement. Ultimately, this effectively sweeps away the geometric dead zones in the entire complex piping system, fundamentally avoiding cross-contamination problems under multi-reactor series conditions. Simultaneously, it improves displacement efficiency and significantly reduces inert gas consumption, thereby solving the problems mentioned in the background art.

[0007] Existing technologies cannot overcome the inherent problems of displacement dead zones and cross-contamination in the complex structure of multi-reactor series systems, resulting in low efficiency and incomplete effect of inert gas displacement.

[0008] To achieve the above objectives, the argon staged displacement method for the synthesis of n-butyllithium includes the following steps:

[0009] S1. System construction: A gas-filling chamber is set between two adjacent reactors to be replaced, and the gas-filling chamber is controllably connected to the gas outlet of the upstream reactor and the gas inlet pipeline of the downstream reactor through a control valve group.

[0010] S2. Pressure gradient formation and displacement: For a reactor, firstly, at least one branch pipe of the reactor is opened and argon gas is introduced to clear the pipeline blind zone; then, by coordinating the timing and flow rate of argon gas introduction into its downstream, midstream and upstream inlets, a stable pressure gradient decreasing from upstream to downstream is formed inside the reactor, thereby directionally pushing the gas inside the reactor to the gas-filling chamber connected to it;

[0011] S3. Gas pushing and sweeping: The mixed gas temporarily stored in the pre-stage gas chamber is introduced into the upstream gas inlet of the downstream reactor, and step S2 is repeated for the downstream reactor. In this way, the original gas in the system and the mixed gas formed during the replacement process are used as gas sources to push and sweep in a step-by-step manner, so as to effectively sweep the complex pipeline and finally discharge it from the end of the system.

[0012] S4. Combined purging: After all the mixed gas has been discharged, keep the gas inlets of all reactors open and simultaneously introduce argon gas to purge the entire system for 3-10 minutes.

[0013] It should be added that the above method is applied to a production system consisting of at least two reactors connected in series via pipelines, and a gas-filling chamber is provided between adjacent reactors.

[0014] In the above technical solution, in S1, the gas-holding chamber is set between adjacent reactors. Its core function is firstly to serve as a dynamic buffer and temporary storage container to receive and contain the gas mixture discharged from the upstream reactor under the pressure gradient drive. The gas-holding chamber transforms the unavoidable instantaneous impact gas flow in traditional direct series displacement into a controllable and phased gas transfer, effectively preventing the displacement blind zone formed in the dead corner due to the sudden reduction of kinetic energy when the gas flow directly rushes into the complex pipeline system of the downstream reactor.

[0015] Meanwhile, by controlling the valve group, the inlet of the gas chamber is controllably connected to the outlet of the pre-stage reactor and the outlet is controllably connected to the inlet pipeline of the post-stage reactor, thus constructing a programmable gas flow path. This not only ensures the timing and order of the gas replacement process and avoids cross-contamination and disordered back-mixing of gas streams of different purities, but more importantly, it enables the mixed gas of the previous stage replacement process to serve as the scavenging gas source for the subsequent stage replacement process, thereby forming a step-by-step gas scavenging. Finally, the initial air and intermediate replacement products are systematically driven from the beginning of the system to the end exhaust port for discharge, achieving efficient and thorough scavenging of the entire complex pipeline system and the geometric dead zone inside the reactor, and significantly reducing the total consumption of high-purity inert gas.

[0016] In step S2, for a reactor, branch pipes one and two are first opened to purge the dead zones in the pipeline. It should be noted that if there are other dead zones in the reactor, additional purge branch pipes are required for each dead zone. Then, the downstream and midstream inlets are opened sequentially to establish a main airflow from bottom to top. Finally, the upstream inlet is opened, and the timing and relative flow rate of argon gas introduced into the downstream, midstream, and upstream inlets are precisely controlled to construct and maintain a stable pressure field that decreases from upstream to downstream inside the first reactor. This pressure gradient drives the original mixed gas in the reactor to be pushed in a directional and orderly manner as a whole and to be temporarily stored in the first gas chamber. This not only removes residual gas in the reactor and related pipeline dead zones, but also provides a preliminarily purified gas source for the subsequent recursive replacement of the second reactor.

[0017] The timing and relative flow rate of argon gas introduction are further explained here. First, in terms of timing, the downstream and midstream gas inlets are opened preferentially or simultaneously to establish an initial main gas flow from the bottom of the reactor upward. The main function of this gas flow is to initially replace the volume of the reactor body and form a basic flow field.

[0018] Then, the upstream inlet is opened, and the relative flow rates of the three inlets are precisely adjusted so that the upstream inlet supplies argon gas at a relatively high flow rate, thereby creating a local high-pressure zone at the top of the reactor. Meanwhile, the midstream and downstream inlets operate at decreasing flow rates, thus precisely creating a pre-defined pressure stratification in the vertical space of the reactor. This pressure difference from top to bottom generates a powerful directional driving force. This driving force does not rely on simple overall gas turbulent mixing, but rather on a laminar flow displacement action of "piston pushing," continuously and directionally pushing the original gas in the reactor, as well as the low-purity mixed gas generated by the displacement, from the higher-pressure upstream area to the outlet connected to the gas chamber. This ensures that all spaces inside the reactor, including geometric dead zones and gas stagnation zones that are difficult to effectively displace using traditional methods, can be systematically swept and displaced by this directional airflow, ultimately achieving efficiency and thoroughness far exceeding that of traditional single-point inlet gas displacement methods.

[0019] Step S3 is a further extension of the multi-stage reactor replacement step. It involves placing the mixed gas in the gas chamber of the preceding reactor as the gas source for the upstream gas inlet of the next reactor when the mixed gas in the preceding reactor is placed in the gas chamber. Then, by repeating step S2, the gas to be replaced and the gas source gas in all reactors in the replacement system are pushed out step by step and finally discharged from the end exhaust port of the entire replacement system.

[0020] In S4, after the staged replacement of the reactors is completed, the replacement system enters the final joint purging stage. At this time, the upstream, midstream and downstream gas inlets of all reactors are kept open and high-purity argon gas is introduced simultaneously. By coordinating the flow rate of each gas inlet, a stable purging gas flow field covering the entire multi-reactor series system and related pipelines is established. This gas flow field, with a continuous purging time of 3 to 10 minutes, performs a final thorough cleaning and replacement of all potential residual gas molecules, pipeline connections and structural dead zones in the replacement system, thereby ensuring that the entire system reaches and maintains the high purity standard required by the process, and providing a highly inert and homogenized reliable environment for subsequent sensitive chemical processes.

[0021] Based on this, the pressure gradient is specifically as follows: upstream pressure is 16-20 kPa, midstream pressure is 13-17 kPa, and downstream pressure is 10-14 kPa. This pressure gradient utilizes a pressure difference of at least 3 kPa between adjacent regions as the driving force for gas flow, ensuring that the airflow from the upstream inlet can overcome flow resistance and directionally penetrate the entire reactor cavity in a stable piston flow form. Its function is to provide sufficient kinetic energy for the mixed gas to achieve substantial and complete replacement from upstream to downstream, effectively sweep and remove residual gas in the dead zones of the pipeline and reactor internal structure, and prevent gas flow instability and turbulence or back mixing by avoiding pressure changes or excessively high flow rates. Thus, while efficiently completing the replacement process, it ensures the stability of operation and the safety of the system.

[0022] Preferably, in step S2, for any reactor, the specific steps for forming the pressure gradient include:

[0023] S2.1. Open at least one branch pipe of the reactor and introduce argon gas to eliminate the pipeline blind zone;

[0024] S2.2 Open the downstream and midstream air inlets of the reactor to establish an upward main airflow at the bottom of the reactor;

[0025] S2.3. Open the upstream air inlet of the reactor, and coordinate the flow rates of the downstream air inlet, the midstream air inlet and the upstream air inlet to form and maintain the stable pressure gradient.

[0026] It should be noted that in S2.1, the branch pipe includes branch pipe two and branch pipe one set on one side of the discharge pipe and the discharge pipe valve body. In addition to branch pipe one and branch pipe two, it also includes branch pipes located in other pipeline blind areas in the reactor. The operation of introducing argon gas to clear the pipeline blind areas lasts for 1-3 minutes.

[0027] Preferably, the volume of the gas-filling chamber is 5%-15% of the volume of the connected reaction vessel.

[0028] Preferably, in step S2, the duration for forming a pressure gradient and displacing a single reactor is 5-15 minutes.

[0029] Preferably, the downstream air inlet, the midstream air inlet, and the upstream air inlet are located at the bottom, middle, and top of the reactor, respectively.

[0030] More preferably, an oxygen content sensor is installed at the inlet or outlet pipe of the gas chamber; when the detected oxygen content is higher than a preset threshold, the replacement time of the previous reactor forming the pressure gradient is automatically extended; the preset threshold is 100 ppm; when the oxygen content sensor detects a value higher than this threshold, the replacement system extends the replacement time of the previous reactor by 20%-50%.

[0031] Furthermore, during the combined purging process in S4, the entire replacement system maintains a positive pressure of 5-10 kPa. This positive pressure is intended to create a stable and moderate pressure barrier within the system. The core principle is to maintain the internal system pressure consistently higher than the external atmospheric pressure, thereby physically preventing external oxygen-containing air or other impurity gases from penetrating into the system through any potential weak points in the seal due to the pressure difference.

[0032] Its function is to ensure that the high-purity argon purge gas flow can always occupy an absolute dominant position and maintain a unidirectional outward flow trend throughout the entire combined purging process. This not only ensures the high purity and thoroughness of the purging process itself, but also provides a continuously controlled and pollution-free inert environment for the entire multi-reactor system during the purging operation, fundamentally eliminating the risk of reverse contamination from external gases, and ultimately ensuring that the system can achieve and maintain the purity required by the process after purging.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] By setting up gas chambers between adjacent reactors and coordinating the timing and relative flow rate of argon gas introduced into the downstream, midstream and upstream gas inlets of each reactor, this system can actively construct and precisely maintain a stable, directional pressure gradient from top to bottom within a single reactor.

[0035] Precise timing control ensures the orderly initiation of the airflow purging action, avoiding disorderly collisions and back-mixing of airflows from different sources. Fine-tuning, by setting a flow ratio that decreases sequentially from upstream to downstream, substantially shapes and stabilizes the required pressure stratification from an energy perspective. The most directional pressure gradient transforms the aforementioned timing and flow parameters into a powerful, directional pneumatic piston, achieving a fundamental shift from random displacement relying on turbulent diffusion to directional displacement relying on laminar purging. The original gas in the displacement system and the mixed gas formed during the displacement process are irreversibly and directionally pushed into the downstream gas storage chamber by this gradient force for temporary storage, serving as the intake gas source for the next reactor displacement. This process is interconnected, avoiding the problem of cross-contamination between multiple reactors caused by airflow turbulence or dead zone residue. At the same time, it realizes the recycling and reuse of inert gas at the system level, thereby achieving ultra-low residual oxygen levels while significantly improving displacement efficiency and greatly reducing inert gas consumption. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the equipment structure applicable to the replacement method of the present invention;

[0037] Figure 2 This is a schematic diagram of the applicable device structure in Embodiment 1 of the present invention;

[0038] Figure 3This is a schematic diagram of the steps in the argon gas staged replacement method of the present invention.

[0039] The meanings of the labels in the diagram are as follows:

[0040] 100a, downstream air inlet; 100b, downstream air inlet of reactor 2; 100c, downstream air inlet of reactor 3;

[0041] 101a, midstream air inlet; 101b, midstream air inlet of reactor 2; 101c, midstream air inlet of reactor 3;

[0042] 102a, upstream air inlet; 102b, upstream air inlet of reactor 2; 102c, upstream air inlet of reactor 3;

[0043] 103. Branch pipe one; 104. Discharge pipe; 105. Branch pipe two; 106. Air outlet; 107a. First air chamber; 107b. Second air chamber; 108. End exhaust port. Detailed Implementation

[0044] 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.

[0045] Current technologies suffer from low efficiency and incomplete inert gas replacement due to the inherent problems of displacement dead zones and cross-contamination in the complex structure of multi-reactor series systems. This invention provides an argon gas staged displacement method for the synthesis of n-butyllithium, comprising the following steps:

[0046] S1. System construction: A gas-filling chamber is set between two adjacent reactors to be replaced, and the gas-filling chamber is controllably connected to the gas outlet of the upstream reactor and the gas inlet pipeline of the downstream reactor through a control valve group.

[0047] S2. Pressure gradient formation and displacement: For a reactor, firstly, at least one branch pipe of the reactor is opened and argon gas is introduced to clear the pipeline blind zone; then, by coordinating the timing and flow rate of argon gas introduction at its downstream inlet 100a, midstream inlet 101a and upstream inlet 102a, a stable pressure gradient decreasing from upstream to downstream is formed inside the reactor, thereby directionally pushing the gas inside the reactor to the gas-filling chamber connected to it;

[0048] S3. Gas push and sweep: The mixed gas temporarily stored in the pre-stage gas chamber is introduced into the upstream inlet of the downstream reactor, and step S2 is repeated for the downstream reactor. In this way, the original gas in the system and the mixed gas formed during the replacement process are used as gas sources to push and sweep in a step-by-step manner, so as to effectively sweep the geometric dead zone inside the pipeline and reactor, and finally discharge from the end exhaust port.

[0049] S4. Combined purging: After all the mixed gas has been discharged, keep the gas inlets of all reactors open and simultaneously introduce argon gas to purge the entire system for 3-10 minutes.

[0050] Example 1:

[0051] This embodiment provides an argon staged replacement method for a three-reactor series n-butyllithium production system. The replacement system is as follows: Figures 1-2 As shown, it mainly includes a first reactor (R1), a second reactor (R2), and a third reactor (R3) connected in series by pipelines.

[0052] A first gas-filling chamber 107a is provided between the first reactor (R1) and the second reactor (R2). The inlet of the first gas-filling chamber 107a is connected to the gas outlet 106 of the first reactor (R1) via a pipeline, and the outlet of the first gas-filling chamber 107a is connected to the upstream gas inlet 102b of the second reactor (R2) via a control valve. A second gas-filling chamber 107b is provided between the second reactor (R2) and the third reactor (R3). The inlet of the second gas-filling chamber 107b is connected to the gas outlet of the second reactor (R2), and the outlet of the second gas-filling chamber 107b is connected to the upstream gas inlet 102c of the third reactor (R3) via a control valve. Each reactor is independently equipped with upstream, midstream, downstream, and branch pipe gas inlets, and is equipped with corresponding flow and pressure control valves. The volume of each reactor is 2.0 m³. 3 The built-in solvent is hexane. The replacement medium is argon gas with a purity of 99.999%.

[0053] The replacement process is automatically executed by the PLC system, such as Figure 3 As shown, the specific steps are as follows:

[0054] S1, First Reactor (R1) Replacement and Gas Temporary Storage Stage:

[0055] At time T0, the downstream air inlet 100a and the midstream air inlet 101a of the first reactor (R1) are opened, respectively, with a flow rate of 12 Nm. 3 / h and 8Nm 3 Argon gas is introduced at a flow rate of / h for 2 minutes, driving the gas at the bottom of the vessel to move upward.

[0056] At time T0+2 minutes, branch pipe 103 and branch pipe 105 of the first reactor (R1) are opened at a rate of 5 Nm. 3 Argon gas is introduced at a flow rate of / h to clear the blind spots in the pipeline using the main gas flow; branch pipe 2 105 is located on the side of the discharge pipe (104).

[0057] At time T0+4 minutes, the upstream air inlet 102a of the first reactor (R1) is opened. Through PLC regulation, a stable pressure gradient is established inside the first reactor (R1) with upstream (18 kPa), midstream (15 kPa), and downstream (12 kPa). Under this gradient, the mixed gas inside the first reactor (R1) is smoothly pushed into the first gas-holding chamber 107a for temporary storage. This step lasts for 6 minutes.

[0058] At time T0+10 minutes, all inlet valves of the first reactor (R1) are closed. The first reactor (R1) has completed the purging process, and the purged gas has been temporarily stored in the first gas storage chamber 107a.

[0059] S2, Replace the second reactor (R2), and temporarily store the gas in the second gas chamber 107b:

[0060] At time T0+10, perform the following operations simultaneously:

[0061] 1. Open the downstream air inlet 100b and the midstream air inlet 101b of the second reactor (R2), respectively, with a flow rate of 12 Nm. 3 / h and 8Nm 3 Argon gas is introduced at a flow rate of / h to begin establishing the main gas flow for R2.

[0062] 2. Open the outlet valve of the first gas chamber 107a and the upstream gas inlet 102b of the second reactor (R2) (argon flow rate 10 Nm). 3 / h).

[0063] Through this coordinated operation, the mixed gas temporarily stored in the first gas chamber 107a from the first reactor (R1) is pushed into the upstream gas inlet 102b of the second reactor (R2) as the initial gas inlet for the second reactor (R2).

[0064] The replacement process in the second reactor (R2) repeats the operation of step S1, driving all the mixed gas inside the second reactor (R2) into and temporarily storing it in the second gas placement chamber 107b. The total replacement time for the second reactor (R2) is 10 minutes.

[0065] S3, Third Reactor (R3) Replacement and Final System Purification Stage:

[0066] At time T0+20 minutes, the downstream air inlet 100c and the midstream air inlet 101c of the third reactor (R3) are opened; and the outlet valve of the second gas chamber 107b and the upstream air inlet 102c of the third reactor (R3) are opened, so that all the gas in the second gas chamber 107b is introduced into the third reactor R3.

[0067] After the third reactor R3 completes its own deep replacement, all gases are discharged from the end exhaust port 108; then, keep the inlet valves of all reactors open and perform a joint purging of the entire system for 5 minutes.

[0068] Testing revealed that the oxygen content at the end exhaust port 108 dropped to 2 ppm and the dew point dropped to -70°C, indicating that the system has met the requirements for a high-purity inert environment.

[0069] Example 2:

[0070] This embodiment provides an argon staged replacement method for a five-reactor series n-butyllithium production system. The aim is to demonstrate the effectiveness and scalability of this method in multi-reactor series systems.

[0071] System configuration: Five reactors (R1 to R5) are connected in series. There are independent gas-filling chambers between R1 and R2, R2 and R3, R3 and R4, and R4 and R5.

[0072] Replacement method: The replacement process is exactly the same as in Example 1, following a cyclical pattern of replacement, temporary storage, and import to re-replacement, executed sequentially from R1 to R5.

[0073] Each gas chamber acts as an independent buffer and temporary storage unit, ensuring that the replacement gas from the previous batch is completely collected and accurately introduced when the next batch of replacement begins.

[0074] Replacement effect: This embodiment successfully applied the staged replacement method with gas chamber in Embodiment 1 to a more complex five-reactor series system. Practical results show that the core logic of this scheme, the cyclic mode of replacement, temporary storage, and propulsion to re-replacement, has excellent scalability and versatility.

[0075] By sequentially setting independent gas-filling chambers between each vessel as buffer and transfer units, the system also achieves the cascade and recycling of argon resources. Compared with existing technologies such as traditional parallel purging, while ensuring that the system end reaches a high-purity inert environment equivalent to that of Example 1 (i.e., oxygen content ≤ 5 ppm, dew point ≤ -65℃), it also significantly saves the total consumption of inert gas and greatly shortens the overall replacement time of the system. This fully demonstrates the application potential and significant technical and economic value of the method of the present invention in series systems of different scales.

[0076] Comparative Example 1:

[0077] This comparative example simulates a commonly used inert gas replacement method in current industrial production, which involves simultaneously purging all reactors in parallel, to highlight the advantages of this invention.

[0078] System: The same three-reactor series n-butyllithium production system (R1, R2, R3) as in Example 1.

[0079] Replacement method:

[0080] S1. Simultaneously open the upstream, midstream, and downstream intake valves of R1, R2, and R3 respectively.

[0081] S2, Apply the same, larger initial flow rate (20 Nm) to all reactors. 3 The system is purged by blowing through the / h / pipe port to quickly dilute the air in the system, and then continuously discharged through the terminal exhaust port 108.

[0082] S3. Once the oxygen content begins to decrease, gradually adjust each intake valve to maintain a low purge flow rate (8 Nm). 3 / h / pipe inlet), until the oxygen content at the end of the system is ≤5ppm and the dew point is ≤-65°C.

[0083] Experimental Example 1:

[0084] Experimental objective: To compare and verify the performance differences between the staged replacement method provided by this invention and the traditional parallel purging method in terms of inert gas consumption, replacement efficiency, and final system purity.

[0085] Experimental subjects and conditions:

[0086] Test group: The three-reactor series system and replacement method described in Example 1 were used.

[0087] Control group: The traditional parallel purging method described in Comparative Example 1 was used.

[0088] Initial conditions: Both sets of experiments used the same three-reactor series system. Each reactor was initially filled with air, and the volume and connecting pipelines were kept consistent to ensure the fairness of the comparison.

[0089] Termination condition: The replacement process continues until the oxygen content and dew point reading at the end exhaust port 108 remain stable, at which point the replacement is considered complete.

[0090] Test items: Record the total argon consumption, total replacement time, final oxygen content and final dew point at the end of the replacement for both sets of experiments. Specific data are shown in Table 1.

[0091] Experimental results:

[0092] Table 1: Performance Test Results

[0093]

[0094] Experimental Results: As shown in Table 1, the performance test data demonstrates that, compared with Comparative Example 1, which represents the traditional replacement process, the staged replacement method with a gas chamber provided in Example 1 of this invention exhibits significant comprehensive advantages. Specifically, the total argon consumption is reduced from 68.0 Nm³. 3 Significantly reduced to 25.5 Nm 3 The efficiency was reduced by approximately 62.5%, and the total replacement time was shortened from 50 minutes to 25 minutes, doubling the efficiency. This not only means a reduction in the production preparation cycle and a significant saving in operating costs, but also that the final system environment is superior in terms of purity and dryness, with an oxygen content stable at 2 ppm and a dew point as low as -70°C, both of which are better than the 4 ppm and -66°C of Comparative Example 1. Thus, a higher standard of system inerting effect was achieved with less resource consumption and shorter operation time. This fully demonstrates that the present invention's scheme of achieving gas recursion and pressure gradient coordinated control through the gas chamber solves the technical bias of serious resource waste and low efficiency in traditional methods, and achieves technological progress.

[0095] Comparative Example 2: Improved Parallel Purging (for complex pipelines)

[0096] System configuration: This comparative example uses the same three-reactor series n-butyllithium production system as Example 1, including the same reactors (R1, R2, R3), the same complex piping layout (such as the presence of branch pipes for adding catalysts, long inter-reactor connecting pipes), and the same upstream, midstream, downstream, and branch pipe inlet configurations.

[0097] Replacement method: This comparative example simulates a traditional parallel purging method optimized for complex piping systems. The specific steps are as follows:

[0098] S1. At time T0, only the branch pipe intake valves of R1, R2, and R3 are opened simultaneously, with a flow rate of 15 Nm. 3 Argon gas is introduced into each branch pipe at a flow rate of / h and purged continuously for 3 minutes to prioritize the removal of residual air in the blind areas of each reactor pipeline.

[0099] S2. At T0+3 minutes, simultaneously open the upstream, midstream, and downstream air inlet valves of all three reactors (R1, R2, R3), and close branch pipe 103 and branch pipe 205.

[0100] S3, all air intakes are at 20Nm 3 A large initial flow rate of / h is used for powerful purging, and the air is continuously discharged through the terminal exhaust port 108 to quickly dilute the air in the main circuit of the system.

[0101] S4. When the oxygen content sensor at the end of the system detects a drop in reading to 50 ppm (approximately at T0+18 minutes), adjust the flow rate of all air inlets to 8 Nm. 3 The maintenance flow rate is maintained at / h; finally, purging continues until the oxygen content at the end exhaust port 108 stabilizes at ≤5ppm and the dew point is ≤-65°C, at which point the replacement is considered complete.

[0102] Replacement effect: Although this method pre-treats the blind area of ​​the branch pipe, the lack of directional pressure control and gas push mechanism in the whole main purging stage leads to mutual interference of gases in each vessel and chaotic flow field, resulting in low replacement efficiency. Moreover, the replacement effect is not good in the deep part of the main loop and the dead corner of the connection between vessels.

[0103] Example 3: Optimized hierarchical replacement for complex pipeline structures

[0104] System Configuration: The basic system configuration in this embodiment is the same as that in Embodiment 1. It is particularly important to emphasize that this system contains a complex internal structure: each reactor is connected to branch pipes for the addition of different raw materials, not just branch pipes 103 and 105 shown in the figure. These branch pipes form potential displacement blind zones; simultaneously, the connecting pipelines between reactors are long and have U-shaped bends, making it easy for residual gas to accumulate.

[0105] Replacement Method: This embodiment further optimizes and clarifies the design logic and operational details for complex pipelines based on the graded replacement method provided in Embodiment 1. The replacement process is also automatically executed by the PLC system, and the specific steps are as follows:

[0106] S1, Deep replacement and temporary gas storage in the first reactor (R1):

[0107] Establishing the main airflow and clearing blind spots:

[0108] 1. At time T0, open the downstream air inlet 100a (flow rate 12 Nm³) of the first reactor (R1). 3 / h) and midstream air inlet 101a (flow rate 8Nm 3 / h). This operation aims to establish a bottom-up main airflow within the vessel, driving the gas at the bottom of the vessel and in the main circuit upwards.

[0109] 2. At time T0+2 minutes, specifically, to clear the blind zone of the branch pipes, open branch pipe 103 and branch pipe 105 of the first reactor (R1) at a flow rate of 5 Nm. 3 Argon gas is introduced at a flow rate of / h. At this time, the main gas flow already established in the first reactor (R1) is used as a gas curtain to accurately carry out the mixed gas from the branch pipe, which may contain residual air, and merge it into the main gas flow, ensuring that the complex local structure is effectively purified.

[0110] Establishing pressure gradients and targeted delivery:

[0111] 1. At time T0+4 minutes, open the upstream air inlet 102a of the first reactor (R1). Precisely adjust each air inlet valve using a PLC to create and maintain a stable pressure gradient within the first reactor (R1) at the upstream (18 kPa), midstream (15 kPa), and downstream (12 kPa) levels. This gradient ensures directional and stable gas flow within the complex pipeline system, effectively preventing flow field disturbances and reverse diffusion of gas to branch pipes or upstream pipelines due to pressure differential runaway.

[0112] 2. Under this precisely controlled pressure gradient, all the displaced mixed gas in the first reactor (R1) is smoothly pushed into the first gas-holding chamber 107a for temporary storage. This step lasts for 6 minutes.

[0113] In the above steps, it should be noted that an oxygen content sensor can be installed at the inlet pipe of the first gas chamber 107a. When the oxygen content of the discharged gas is detected to be higher than the set threshold at T0+8 minutes, the PLC can automatically extend the replacement pressure gradient maintenance time of the first reactor (R1) by 2 minutes, thereby achieving adaptive optimization control for different complex working conditions.

[0114] S2, Replacement and Temporary Gas Storage in the Second Reactor (R2):

[0115] The method is exactly the same as step S2 in Example 1, demonstrating the repeatability and reliability of this method in a series system. Finally, all the replacement gas in the second reactor (R2) is driven into and temporarily stored in the second gas-holding chamber 107b.

[0116] S3, Third Reactor (R3) Replacement and Final System Purification:

[0117] The method is exactly the same as step S3 of Example 1.

[0118] Experiment Example 2: Comparison of displacement effects under complex structures

[0119] Experimental objective: To compare and verify the performance difference between the optimized hierarchical replacement method (Example 3) provided by this invention and the traditional parallel purging method (Comparative Example 2) for optimizing complex pipelines in a system with complex piping.

[0120] Experimental subjects and conditions:

[0121] Test group: The system and replacement method described in Example 3 were used.

[0122] Comparative group: The system and substitution method described in Comparative Example 2 were used.

[0123] Initial conditions: Both sets of experiments used the same three-reactor series system with a complex piping structure. Each reactor and branch pipe was initially filled with air to ensure the fairness of the comparison.

[0124] Termination condition: The replacement process continues until the oxygen content and dew point reading at the end exhaust port 108 remain stable. After the replacement is completed, a portable high-precision oxygen analyzer is used to directly measure the oxygen content at the end of the blind zone of the branch pipe of the second reactor (R2) through the preset sampling port.

[0125] Test items and results: Record the total argon consumption, total replacement time, final oxygen content at the end of the system, and oxygen content in the blind zone of the branch pipe for both sets of experiments.

[0126] Table 2: Performance Test Results of Complex Structure Systems

[0127]

[0128] Experimental conclusions: According to the experimental results in Table 2, for series reaction systems with complex internal pipelines, even with targeted optimization of the traditional parallel purging method (comparative example 2 prioritizes purging blind areas), the total argon consumption and replacement time are still much higher than in example 3.

[0129] More importantly, regarding the key indicator of the branch pipe blind zone, which represents the complexity of the structure, the oxygen content in the branch pipe blind zone of Comparative Example 2 still reached 35 ppm after gas replacement, while the oxygen content in the branch pipe blind zone of Example 3 was only 3 ppm after gas replacement. This strongly demonstrates that the hierarchical recursive replacement method based on the coordinated control of gas chamber buffer and directional pressure gradient provided by this invention can achieve full-area, deep, and efficient replacement of complex pipeline systems, fundamentally eliminating replacement dead zones and meeting the requirements of high-purity production processes.

[0130] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. An argon-stage displacement method for the synthesis of n-butyllithium, characterized in that, Includes the following steps: S1. System construction: A gas-filling chamber is set between two adjacent reactors to be replaced, and the gas-filling chamber is controllably connected to the gas outlet of the upstream reactor and the gas inlet pipeline of the downstream reactor through a control valve group. S2. Pressure gradient formation and displacement: For a reactor, firstly, at least one branch pipe of the reactor is opened and argon gas is introduced to clear the pipeline blind zone; then, by coordinating the timing and flow rate of argon gas introduction into its downstream inlet (100a), midstream inlet (101a) and upstream inlet (102a), a stable pressure gradient decreasing from upstream to downstream is formed inside the reactor, thereby directionally pushing the gas inside the reactor to the gas-filling chamber connected to it; S3. Gas pushing and sweeping: The mixed gas temporarily stored in the pre-stage gas chamber is introduced into the upstream inlet of the downstream reactor, and step S2 is repeated for the downstream reactor. In this way, the original gas in the system and the mixed gas formed during the replacement process are used as gas sources to push and sweep in a step-by-step manner, so as to effectively sweep the geometric dead zone inside the pipeline and reactor, and finally discharge from the end exhaust port. S4. Combined purging: After all the mixed gas has been discharged, keep the gas inlets of all reactors open and simultaneously introduce argon gas to purge the entire system for 3-10 minutes. The pressure gradient is specifically as follows: upstream pressure is 16-20 kPa, midstream pressure is 13-17 kPa, and downstream pressure is 10-14 kPa. In step S2, for any reactor, the specific steps for forming the pressure gradient include: S2.

1. Open at least one branch pipe of the reactor and introduce argon gas to clear the pipeline blind spots; S2.2 Open the downstream air inlet (100a) and the midstream air inlet (101a) of the reactor to establish an upward main airflow at the bottom of the reactor; S2.3 Open the upstream air inlet (102a) of the reactor, and coordinate the flow rates of the downstream air inlet (100a), the midstream air inlet (101a) and the upstream air inlet (102a) to form and maintain the stable pressure gradient. The downstream air inlet (100a), the midstream air inlet (101a), and the upstream air inlet (102a) are located at the bottom, middle, and top of the reactor, respectively.

2. The argon staged displacement method for the synthesis of n-butyllithium according to claim 1, characterized in that: The volume of the gas-filling chamber is 5%-15% of the volume of the connected reaction vessel.

3. The argon staged displacement method for the synthesis of n-butyllithium according to claim 1, characterized in that: In S2, the duration for forming a pressure gradient and performing displacement on a single reactor is 5-15 minutes.

4. The argon staged displacement method for the synthesis of n-butyllithium according to claim 1, characterized in that: An oxygen content sensor is installed at the inlet or outlet pipeline of the gas chamber; when the detected oxygen content is higher than a preset threshold, the displacement time for the pressure gradient to be formed in the previous reactor is automatically extended.

5. The argon staged displacement method for the synthesis of n-butyllithium according to claim 1, characterized in that: In S2.1, the branch pipe includes a discharge pipe (104) and a second branch pipe (105) and a first branch pipe (103) provided on one side of the discharge pipe valve body. The operation of introducing argon gas to clear the blind area of ​​the pipeline lasts for 1-3 minutes.

6. The argon staged displacement method for the synthesis of n-butyllithium according to claim 1, characterized in that: In S4, during the combined purging, the entire replacement system maintains a positive pressure of 5-10 kPa.

7. The argon staged displacement method for the synthesis of n-butyllithium according to claim 4, characterized in that: The preset threshold is 100 ppm; when the oxygen content sensor detects a value higher than this threshold, the replacement system will extend the replacement time of the previous reactor by 20%-50%.

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