Equipment for preparing oligomer

Abstract

The present disclosure provides an apparatus for preparing an oligomer, comprising: a reactor comprising an upper gas zone and a lower liquid zone, and performing an oligomerization reaction by receiving ethylene gas and a solvent into the liquid zone; the overflow pipe is arranged on the outer side wall of the reactor and is connected at a height corresponding to the boundary between the gas phase region and the liquid phase region of the reactor so as to discharge a liquid flow containing an oligomer product; the gas-liquid separator is connected with the overflow pipe and is used for separating gas from the discharged liquid flow; the liquid level meter is arranged in the gas-liquid separator; and a liquid discharge pipe which is connected to the lower part of the gas-liquid separator and discharges the liquid stream from which the gas has been separated.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims priority and the benefit of Korean Patent Application No. 10-2023-0167898, filed on November 28, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to an apparatus for preparing oligomers, and more particularly, to an apparatus for preparing oligomers that can prevent pipeline blockage by stably maintaining the liquid level of a reactor during oligomer preparation and minimizing gas hold-up (bubbles) in the liquid discharged from the reactor. Background Art

[0004] α-olefins are important materials for comonomers, detergents, lubricants, plasticizers, etc., and are widely used commercially. Among them, 1-hexene and 1-octene are widely used as comonomers for controlling the density of polyethylene when preparing linear low-density polyethylene (LLDPE).

[0005] These α-olefins can be prepared by performing an oligomerization reaction in a state where ethylene is dissolved in a solvent in the presence of a catalyst, and the oligomerization reaction can be carried out, for example, in a bubble column reactor.

[0006] The bubble column reactor allows a raw material gas to flow into a liquid zone containing a solvent, a catalyst, etc. through a distribution device installed at its lower part, and is dispersed while rising in the form of bubbles, and an oligomerization reaction is carried out by mixing the dispersed gas in the liquid zone while generating turbulence.

[0007] At this time, since the liquid level in the reactor affects the control of reaction conditions such as pressure, temperature, catalyst residence time, the amount of ethylene conversion obtained, calorific value, etc., the liquid level in the reactor should be kept constant. For this purpose, it is very important to indicate the liquid height in the reactor.

[0008] Since in the liquid zone where the oligomerization reaction occurs in the reactor, a solvent, ethylene dissolved in the solvent, and liquid substances (oligomers) generated by ethylene conversion coexist, the composition of the liquid changes, so the density of the liquid after the reaction is different from that of the liquid before the reaction. In particular, the density within the overall liquid volume is greatly reduced due to the amount of gas hold-up in the liquid. Thus, the density is affected by the characteristics (temperature, pressure, composition, viscosity, etc.) of the liquid substances in the reactor.

[0009] To measure the liquid level in the reactor during the preparation of oligomers, a differential pressure type liquid level transmitter (LT) is usually used. However, the liquid density changes with the reaction degree, so there may be an error in the liquid level indication. When the situation of incorrect liquid level indication by the differential pressure type LT occurs significantly, it is difficult to keep the actual liquid level in the reactor constant.

[0010] In addition, when a large amount of gas is retained in the liquid substance generated by the oligomerization reaction and is transported to the liquid discharge pipe connected to the lower part of the reactor, due to the increase in two phases in the pipe, a serious blockage phenomenon may occur. Summary of the Invention

[0011] Technical Problem

[0012] The present disclosure aims to solve the problems mentioned in the background art and provides an apparatus for preparing oligomers, which can prevent pipeline blockage by stably maintaining the liquid level of the reactor during the preparation of oligomers and minimizing the gas retention accompanied in the liquid discharged from the reactor.

[0013] Technical Solution

[0014] In a general aspect, an apparatus for preparing oligomers includes: a reactor including an upper gas zone and a lower liquid zone, and performing an oligomerization reaction by receiving ethylene gas and a solvent into the liquid zone; an overflow pipe provided on an outer sidewall of the reactor and connected to a height corresponding to a boundary between the gas zone and the liquid zone of the reactor to discharge a liquid flow containing an oligomer product; a gas-liquid separator connected to the overflow pipe and separating gas from the discharged liquid flow; a liquid level gauge provided in the gas-liquid separator; and a liquid discharge pipe connected to a lower part of the gas-liquid separator and discharging the liquid flow from which gas has been separated.

[0015] Advantageous Effects

[0016] According to the apparatus for preparing oligomers of the present disclosure, the liquid flow rising above the boundary height is transported from the reactor to the gas-liquid separator through the overflow pipe provided at the boundary between the gas zone and the liquid zone in the reactor, while keeping the pressures of the reactor and the gas-liquid separator the same, thereby suppressing the accompanying gas retention and minimizing the change in the liquid density. Thereafter, by measuring the height of the liquid with minimized density change in the gas-liquid separator to control the discharged liquid amount, the liquid level in the reactor can be stably maintained.

[0017] In addition, by suppressing the amount of gas retention in the liquid flow discharged from the gas-liquid separator, the flow of the oligomer product in the liquid discharge pipe can be made smooth, preventing blockage phenomena and reducing the emission of ethylene gas to the downstream flow. Brief Description of the Drawings

[0018] Figure 1It is a diagram schematically showing the process flow of an apparatus for preparing oligomers according to an embodiment of the present disclosure.

[0019] Figure 2 and Figure 3 It is a diagram schematically showing the process flow of an apparatus for preparing oligomers according to a comparative example. Detailed Embodiments

[0020] The terms and words used in this specification and claims should not be construed as having a general meaning or a dictionary meaning, but should be understood as meanings and concepts conforming to the technical spirit of the present disclosure based on the principle that the inventor can appropriately define the terms in order to describe his own invention in the best way.

[0021] The term "comprising" or "containing" used herein specifically indicates a specific property, region, integer, step, operation, element or component, and does not exclude the existence or addition of other specific properties, regions, integers, steps, operations, elements, components or their combinations.

[0022] The term "flow" used herein may refer to the flow of a fluid in a process or the fluid itself flowing in a pipeline. Specifically, the flow can refer to both the fluid itself and the flow of the fluid flowing in the pipeline connecting each device. In addition, the fluid may include at least one component of gas, liquid or solid.

[0023] Unless otherwise specified, the term "upper part" used herein refers to a point at a height of 0 to 50% from the top of the device, and specifically may refer to the top (top of the tower). In addition, the term "lower part" refers to a point at a height of 50 to 100% from the top of the device, and specifically may refer to the bottom (bottom of the tower).

[0024] Unless otherwise specified, the term "side stream" used herein may refer to a stream discharged at a height of 25% to 80% or 40% to 70% from the top of the device.

[0025] In addition, the "pressure" mentioned herein refers to the gauge pressure measured based on the atmospheric pressure.

[0026] The present disclosure will be described in detail below with reference to the accompanying drawings.

[0027] An embodiment of the present disclosure relates to an apparatus for preparing oligomers.

[0028] See Figure 1 , the apparatus according to the present disclosure includes a reactor 100 for carrying out an oligomerization reaction; an overflow pipe 10 connected to the reactor to discharge a liquid stream containing an oligomer product; a gas-liquid separator 200 connected to the overflow pipe; a liquid level gauge 20 provided in the gas-liquid separator 200; and a liquid discharge pipe 30 connected to the lower part of the gas-liquid separator 200.

[0029] The reactor 100 includes an upper gas zone 110 and a lower liquid zone 120. In the liquid zone 120, the oligomerization reaction of monomers can be carried out in a liquid state where ethylene gas is dissolved in a solvent. The solvent can be supplied together with a catalyst through a solvent inlet pipe 121, and ethylene gas can be supplied from a gas inlet pipe 122.

[0030] A continuous stirred tank reactor, a plug flow reactor, a bubble column reactor, etc. can be used as the reactor.

[0031] For example, the feed gas flows into the liquid zone containing a solvent, a catalyst, etc. through a distribution device installed at the lower part of the bubble column reactor, and is dispersed while rising in the form of bubbles. The dispersed gas can be mixed in the liquid zone while generating turbulence, thereby carrying out the oligomerization reaction.

[0032] The oligomerization reaction refers to a reaction in which monomers oligomerize. Depending on the number of polymerized monomers, the oligomerization reaction is called trimerization or tetramerization, and is collectively referred to as oligomerization. For example, α-olefins such as 1-hexene and 1-octene can be prepared by the trimerization or tetramerization of ethylene.

[0033] The ethylene gas supplied to the reactor 100 can be a stream containing ethylene (C2) separated from naphtha thermal cracking.

[0034] The solvent for dissolving ethylene gas can include one or more selected from n-pentane, n-hexane, n-heptane, cyclohexane, methylcyclohexane, octane, cyclooctane, decane, dodecane, benzene, xylene, 1,3,5-trimethylbenzene, toluene, ethylbenzene, chlorobenzene, dichlorobenzene, and trichlorobenzene. In some cases, a mixture of two or more of the above can be used as the solvent. Therefore, ethylene gas can be liquefied at a higher temperature, and the dissolution rate of ethylene gas dissolved in the solvent can be increased.

[0035] In the oligomerization reaction of ethylene, a compound containing a transition metal can be used as a catalyst to improve the reaction activity. For example, the catalyst can be a compound containing one or more selected from the following: chromium(III) acetylacetonate, chromium(III) chloride tetrahydrofuran, chromium(III) 2-ethylhexanoate, chromium(III) tris(2,2,6,6-tetramethyl-3,5-heptanedionate), chromium(III) benzoylpyruvate, chromium(III) hexafluoro-2,4-pentanedionate, chromium(III) acetate hydroxide, chromium(III) acetate, chromium(III) butyrate, chromium(III) valerate, chromium(III) laurate, and chromium(III) stearate.

[0036] In addition, a cocatalyst can be additionally used to improve the activity of the above catalyst. The cocatalyst may include one or more selected from, for example, trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, ethyl sesquichloride, diethylaluminum chloride, ethylaluminum dichloride, methylaluminoxane, modified methylaluminoxane, and borate.

[0037] The oligomerization reaction can be carried out under conditions commonly used in the relevant art. For example, it can be carried out at a temperature of 30°C to 150°C or 50°C to 120°C and a pressure of 20 bar to 65 bar or 20 bar to 40 bar.

[0038] When carrying out this oligomerization reaction, a liquid stream containing oligomer products polymerized from ethylene, by-products, solvents, unreacted gases dissolved in the solvent, etc. will exist in the lower liquid zone 120 of the reactor 100, and the unreacted ethylene gas that is not dissolved in the solvent and thus does not participate in the oligomerization reaction can rise to the upper gas zone 110.

[0039] The density of the liquid stream existing in the liquid zone 120 of the reactor can vary according to the amount of liquid oligomer products generated by the conversion of ethylene and the amount of gas retention from the unreacted gases dissolved in the solvent. When an incorrect indication occurs during the liquid level measurement due to the density change, it may be difficult to stably maintain the liquid level in the reactor.

[0040] To solve the above problems, in the present disclosure, an overflow pipe 10 is provided at a height corresponding to the boundary between the gas zone 110 and the liquid zone 120 on the outer side wall of the reactor and is connected to a gas-liquid separator 200, so that the liquid stream containing oligomer products obtained in the reactor 100 is transported to the gas-liquid separator 200 through the overflow pipe 10, and then the liquid level of the liquid stream from which the gas has been separated in the gas-liquid separator 200 is measured.

[0041] More specifically, the overflow pipe 10 allows the liquid stream to move by overflowing at the boundary between the gas zone and the liquid zone of the reactor 100. At the same time, pressure balance between the reactor 100 and the gas-liquid separator 200 can be achieved. That is, the pressures of the reactor 100 and the gas-liquid separator 200 are kept the same through the overflow pipe 10, so that the gas is in an equilibrium state, and only the liquid rising above the boundary height can flow out of the reactor 100 into the gas-liquid separator 200.

[0042] When the overflow pipe is not provided, it is difficult to keep the pressures of the reactor and the gas-liquid separator the same. For example, when a pipe is connected to the lower liquid zone of the reactor to transfer the liquid flow to the gas-liquid separator, additional pressure gauges and pressure control valves are required to control the pressure of the gas-liquid separator. In addition, when the upper gas flow of the gas-liquid separator is injected into the upper gas zone of the reactor, the mixing of the two flows may be restricted by their respective pressure relationships, and since the upper gas flow of the gas-liquid separator is a saturated gas, there is a possibility of condensation.

[0043] The overflow pipe 10 can have a sufficient size to effectively achieve the movement caused by the overflow of the liquid flow and the pressure balance of the gas flow, and there are no particular restrictions on its inner diameter and length as long as the flow rate of the liquid discharged through the overflow pipe 10 is not restricted.

[0044] The liquid flow conveyed from the reactor 100 to the gas-liquid separator 200 through the overflow pipe 10 can suppress the accompanying gas retention, thereby minimizing the liquid density change caused by gas retention.

[0045] In addition, the apparatus for preparing oligomers according to the present disclosure may further include a pressure maintaining pipe 11 that connects the gas zone of the reactor 100 and the gas zone of the gas-liquid separator 200 to each other.

[0046] The pressure maintaining pipe 11 can be used to more effectively equalize the pressures of the reactor 100 and the gas-liquid separator 200, and can be designed in a conventional manner in the relevant field.

[0047] The gas-liquid separator 200 separates the gas contained in the liquid flow conveyed through the overflow pipe 10, and the separated gas can be mixed with the gas present in the reactor 100 through the overflow pipe 10 or the pressure maintaining pipe 11, and the liquid flow from which the gas has been separated remains in the lower part of the gas-liquid separator 200.

[0048] The height of the liquid flow present in the gas-liquid separator 200 is measured by a liquid level gauge 20 provided in the gas-liquid separator 200.

[0049] The above liquid level gauge can be a differential pressure type liquid level transmitter (LT) commonly used in the relevant field, but is not limited thereto.

[0050] In the liquid conveyed to the gas-liquid separator 200, the accompanying gas retention is suppressed, and the composition of the liquid in the gas-liquid separator 200 does not change, so the density change is small. Therefore, different from the reactor 100 where the liquid composition changes, when measuring the liquid level in the gas-liquid separator 200, the possibility of false indication is low. For example, the error between the liquid level measurement value and the actual liquid level in the gas-liquid separator can be less than 5%.

[0051] Therefore, by measuring the height of the liquid with suppressed density change using the liquid level gauge 20 provided in the gas-liquid separator 200, and discharging the liquid flow in the gas-liquid separator 200 according to the signal of the liquid level gauge 20, the liquid level in the reactor 100 can be stably maintained.

[0052] The liquid flow in the gas-liquid separator 200 can be discharged through the liquid discharge pipe 30 connected to the lower part of the gas-liquid separator 200. At this time, the opening and closing of the control valve CV provided in the liquid discharge pipe 30 can be controlled according to the signal of the liquid level gauge 20, thereby controlling the amount of the discharged liquid flow.

[0053] In addition, by minimizing the amount of gas retention in the liquid flow discharged from the gas-liquid separator, the oligomer product flow in the liquid discharge pipe can be made smooth, blockage can be prevented, and the discharge of ethylene gas to the downstream flow can be reduced.

[0054] Thereafter, the liquid flow discharged through the liquid discharge pipe 30 connected to the lower part of the gas-liquid separator 200 can be supplied to a separation column (not shown), and unreacted gas, solvent, etc. can be further separated in the separation column to obtain a purified oligomer product.

[0055] If necessary, the apparatus for preparing oligomers may further include devices necessary for preparing oligomers, such as condensers, reboilers, pumps, coolers, filters, stirrers, compressors, and mixers.

[0056] Examples

[0057] The present disclosure will be described in more detail below through examples. However, the following examples are provided only for illustrative purposes of the present disclosure, and those skilled in the art can obviously make various modifications and changes without departing from the scope and spirit of the present disclosure, and the scope of the present disclosure is not limited to these examples.

[0058] Comparative Example 1:

[0059] As Figure 2 The pilot plant system shown was configured to measure the liquid level in the reactor 100 during oligomer preparation.

[0060] First, a solvent, a catalyst, and ethylene gas were supplied from the lower liquid zone 120 of the reactor 100 to carry out an oligomerization reaction.

[0061] The height of the liquid flow containing the oligomer product obtained by the reaction was measured using a differential pressure type liquid level transmitter (LT) provided in the reactor 100, and the liquid flow was discharged from the lower part of the reactor 100. According to the liquid level measurement value, the amount of the discharged liquid flow was controlled using the control valve CV.

[0062] Comparative Example 2:

[0063] AsFigure 3 The pilot system shown is configured to measure the liquid level in the oligomer preparation device in reactor 100.

[0064] First, a solvent, a catalyst, and ethylene gas are supplied from the lower liquid region 120 of reactor 100 to carry out an oligomerization reaction.

[0065] The liquid flow containing the oligomer product obtained by the reaction and rising above the boundary height is discharged through an overflow pipe 10 connected to the height corresponding to the boundary between the upper gas region 110 and the lower liquid region 120 of reactor 100, thereby maintaining the liquid level in reactor 100.

[0066] Example 1:

[0067] As Figure 1 The pilot system shown is configured to manufacture oligomers and measure the liquid level in a gas-liquid separator 200 installed outside reactor 100.

[0068] First, a solvent, a catalyst, and ethylene gas are supplied from the lower liquid region 120 of reactor 100 to carry out an oligomerization reaction.

[0069] The liquid flow containing the oligomer product obtained by the reaction and rising above the boundary height is discharged through an overflow pipe 10 connected to the height corresponding to the boundary between the upper gas region 110 and the lower liquid region 120 of reactor 100 to the gas-liquid separator 200. At this time, the pressures of reactor 100 and gas-liquid separator 200 are kept the same.

[0070] The differential pressure type LT provided in the gas-liquid separator 200 is used to measure the liquid level in the gas-liquid separator 200, and the liquid flow is discharged through a liquid discharge pipe 30 connected to the lower part of the gas-liquid separator 200. According to the liquid level measurement value, a control valve CV provided in the liquid discharge pipe 30 is used to control the amount of the discharged liquid flow.

[0071] The results of the liquid level measurement and liquid maintenance of the reactors in the above examples and comparative examples are shown in Table 1 below.

[0072] [Table 1]

[0073]

[0074] As can be seen from Table 1 above, in Example 1, by means of an overflow pipe provided at the boundary between the gas zone and the liquid zone of the reactor, while maintaining the same pressure in the reactor and the gas-liquid separator, only the liquid rising above the connection height of the overflow pipe is conveyed to the gas-liquid separator to measure the liquid level. As a result, the liquid level in the reactor remains stable, and there is almost no change in the density of the liquid in the gas-liquid separator due to gas retention. Therefore, the false indication of the differential pressure type LT is minimized. Thus, through the level control valve CV connected to the differential pressure type LT, the liquid level of the gas-liquid separator remains constant.

[0075] Furthermore, by minimizing the amount of gas retention in the liquid flow discharged from the gas-liquid separator, the flow of the oligomer product in the liquid discharge pipe can be made smooth, preventing clogging phenomena and reducing the discharge of ethylene gas to the downstream flow.

[0076] On the other hand, in Comparative Example 1, the liquid in the reactor 100 was directly measured, so false indications of a decrease in the LT indication occurred at the same height. Since the gas retention (i.e., the gas retention space distributed with the generation of oligomers) accompanying the liquid in the reactor increased, the liquid level was measured in a state where the liquid density decreased. As a result, even though the liquid level was at the same height, the pressure difference decreased, so the LT indication value showed a decrease in the liquid level. Due to this false indication, the control valve was closed to control the liquid level, so the actual liquid level in the reactor rose. Due to this increase in the liquid level in the reactor, the residence time of the catalyst in the reactor became longer, the control of the product quantity and calorific value was restricted, a clogging phenomenon caused by polymers occurred in the pipe for discharging the liquid flow, and the amount of ethylene recovered from the pipe increased.

[0077] Meanwhile, in Comparative Example 2, the liquid level in the reactor was controlled by discharging the liquid rising above the boundary height through an overflow pipe 10 located at the boundary between the gas zone and the liquid zone, without separately measuring the liquid level in the reactor 100. As a result, a large amount of gas flow containing unreacted ethylene was discharged through the overflow pipe 10 together with the liquid flow. As a result, it was difficult to predict the content of ethylene discharged through the overflow pipe, and a clogging phenomenon occurred due to the increase in the liquid-gas two-phase in the pipeline.

[0078] Reference Numerals

[0079] 100: Reactor

[0080] 200: Gas-Liquid Separator

[0081] 10: Overflow Pipe

[0082] 11: Pressure Maintenance Pipe

[0083] 20: Level Gauge

[0084] 210: Liquid Discharge Pipe

Claims

1. An apparatus for preparing oligomers, comprising: A reactor, which includes an upper gas zone and a lower liquid zone, and performs an oligomerization reaction by receiving ethylene gas and a solvent into the liquid zone; An overflow pipe, which is arranged on the outer sidewall of the reactor and is connected at a height corresponding to the boundary between the gas phase zone and the liquid phase zone of the reactor to discharge a liquid stream containing an oligomer product; A gas-liquid separator, which is connected to the overflow pipe and separates gas from the discharged liquid stream; A liquid level gauge, which is arranged inside the gas-liquid separator; and A liquid discharge pipe, which is connected to the lower part of the gas-liquid separator and discharges the liquid stream from which gas has been separated.

2. The device according to claim 1, wherein The overflow pipe maintains the same pressure in the reactor and the gas-liquid separator.

3. The device according to claim 1, wherein, The liquid stream transported from the reactor to the gas-liquid separator through the overflow pipe is inhibited from being accompanied by gas retention.

4. The apparatus according to claim 1, further comprising a pressure maintaining pipe connecting the gas zone of the reactor and the gas zone of the gas-liquid separator.

5. The device according to claim 1, wherein, The liquid level gauge measures the liquid level of the liquid stream from which gas has been separated in the gas-liquid separator.

6. The device according to claim 5, wherein, The error between the measured value of the liquid level and the actual liquid level in the gas-liquid separator is less than 5%.

7. The apparatus according to claim 1, wherein The liquid discharge pipe connected to the lower part of the gas-liquid separator includes a valve for controlling the discharged liquid amount according to the signal of the liquid level gauge.

8. The device according to claim 1, wherein, The reactor includes a bubble column reactor.

9. The device according to claim 1, wherein The gas zone of the reactor includes an upper pipe for discharging a gas stream containing unreacted ethylene gas.

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