Apparatus for producing oligomers

Abstract

The present invention provides an apparatus for producing oligomers, the apparatus comprising: a reactor, having an upper gas region and a lower liquid region, for carrying out oligomerization reactions by receiving ethylene gas and a solvent into the liquid region; an overflow pipe, provided on the outer wall of the reactor and connected at the height corresponding to the boundary of the gas and liquid regions of the reactor, for discharging a liquid stream containing oligomer product; a gas-liquid separator, connected to the overflow pipe, for separating gas from the discharged liquid stream; a liquid-level measurement device provided in the gas-liquid separator; and a liquid discharge pipe, connected at the bottom of the gas-liquid separator, for discharging the gas-separated liquid stream.

Description

Oligomer manufacturing device

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0167898, filed November 28, 2023, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to an oligomer manufacturing device, and more particularly, to an oligomer manufacturing device capable of preventing pipe clogging by stably maintaining the liquid level of a reactor during oligomer manufacturing and minimizing bubbles in the liquid phase discharged from the reactor.

[0005] Alpha-olefins are widely used commercially as important substances used as comonomers, detergents, lubricants, and plasticizers. In particular, 1-hexene and 1-octene are widely used as comonomers to control the density of linear low-density polyethylene (LLDPE) during the production of polyethylene.

[0006] These alpha olefins can be produced 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 performed, for example, in a bubble column reactor.

[0007] In the bubble column reactor, the raw material gas is introduced into a liquid region containing a solvent, catalyst, etc. through a distribution device installed at the bottom thereof, and is dispersed while rising in the form of bubbles, and the dispersed gas is mixed within the liquid region while generating turbulence, thereby performing an oligomerization reaction.

[0008] At this time, the liquid level within the reactor must be maintained constant because it affects the control of reaction conditions such as pressure and temperature, the catalyst residence time, and the resulting ethylene conversion and calorific value. To this end, it is very important to indicate the liquid level within the reactor.

[0009] In the liquid region where the oligomerization reaction takes place in the above reactor, the composition of the liquid phase changes as the solvent, ethylene dissolved in the solvent, and the liquid substance (oligomer) generated by conversion from the ethylene coexist, so the density of the liquid phase after the reaction changes compared to the liquid phase before the reaction. In particular, the density within the entire liquid volume can be significantly reduced depending on the amount of gas bubbles (gas hole up) accompanying the liquid phase. In this way, the density is affected by the characteristics (temperature, pressure, composition, viscosity, etc.) of the liquid substance within the reactor.

[0010] In order to measure the liquid level within the reactor during the production of such oligomers, a differential pressure type level transmitter (LT) is typically used. However, depending on the degree of reaction, the density of the liquid phase may change, resulting in an incorrect liquid level indication. If the liquid level indication by the differential pressure type LT is significant, it is difficult to maintain a constant liquid level within the actual reactor.

[0011] In addition, if a large amount of bubbles are included in the liquid substance produced by the above oligomerization reaction and are transferred to the liquid discharge pipe connected to the lower part of the reactor, a serious blockage phenomenon may occur due to an increase in the two-phase in the pipe.

[0012] The present invention is intended to solve the problems mentioned in the background technology of the above invention, and provides an oligomer manufacturing device that prevents pipe clogging by stably maintaining the liquid level of a reactor during oligomer manufacturing and minimizing bubbles in the liquid phase discharged from the reactor.

[0013] According to one aspect of the present invention for solving the above problem, an oligomer production device is provided, comprising: a reactor including an upper gas phase region and a lower liquid phase region, wherein ethylene gas and a solvent are supplied to the liquid phase region to perform an oligomerization reaction; an overflow pipe provided on an outer side wall of the reactor and connected at a height corresponding to a boundary between the gas phase region and the liquid phase region of the reactor to discharge a liquid phase stream containing an oligomer product; a gas-liquid separator connected to the overflow pipe and separating a gas phase from the discharged liquid phase stream; a liquid level gauge provided in the gas-liquid separator; and a liquid discharge pipe connected to a lower portion of the gas-liquid separator and discharging the gas-separated liquid phase stream.

[0014] The oligomer manufacturing device according to the present invention can minimize changes in the density of the liquid phase by transporting a liquid stream that has risen above the boundary height from the reactor to the gas-liquid separator while maintaining the same pressure between the reactor and the gas-liquid separator through an overflow pipe provided at the boundary between the gas phase and the liquid phase of the reactor, thereby suppressing bubble entrainment. Thereafter, the height of the liquid phase in which the density change is minimized in the gas-liquid separator is measured to control the discharge amount of the liquid phase, thereby ultimately stably maintaining the liquid level of the reactor.

[0015] In addition, the amount of bubbles in the liquid stream discharged through the gas-liquid separator can be suppressed, thereby facilitating the flow of oligomer products in the liquid discharge pipe and preventing clogging, and reducing ethylene gas emission to the downstream stream.

[0016] Figure 1 schematically illustrates a process flow using an oligomer manufacturing device according to one embodiment of the present invention.

[0017] Figures 2 and 3 schematically illustrate the process flow using an oligomer manufacturing device according to a comparative example.

[0018] The terms or words used in the description and claims of the present invention should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0019] As used herein, the terms “include” or “contain” specify a particular characteristic, area, integer, step, operation, element, or component, but do not exclude the addition of other particular characteristics, areas, integers, steps, operations, elements, or components.

[0020] The term "stream" as used herein may refer to the flow of fluid within a process, or may refer to the fluid itself flowing within a pipe. Specifically, the stream may refer to both the fluid itself flowing within the pipe connecting each device and the flow of the fluid. Furthermore, the fluid may include one or more components of gas, liquid, and solid.

[0021] The term "upper" as used herein, unless otherwise specified, means a point 0 to 50% in height downward from the top of the device, and may specifically mean the top (top). In addition, the term "lower" means a point 50 to 100% in height downward from the top of the device, and may specifically mean the bottom (bottom).

[0022] The term 'side stream' as used herein may mean a stream discharged from the top of the device at a height of 25 to 80% or from 40 to 70% downwards, unless otherwise specified.

[0023] Additionally, the “pressure” referred to herein means gauge pressure measured relative to atmospheric pressure.

[0024]

[0025] Hereinafter, the present invention will be described in detail with reference to the attached drawings.

[0026] One embodiment of the present invention relates to an oligomer manufacturing device.

[0027] Referring to FIG. 1, the device according to the present invention may include a reactor (100) for performing an oligomer reaction; an overflow pipe (10) connected to the reactor for discharging 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 portion of the gas-liquid separator (200).

[0028] The above reactor (100) includes an upper gas phase region (110) and a lower liquid phase region (120), and in the liquid phase region (120), an oligomerization reaction of a monomer can be performed in a liquid state in which ethylene gas is dissolved in a solvent. The solvent can be supplied together with a catalyst through a solvent inlet pipe (121), and the ethylene gas can be supplied from a gas inlet pipe (122).

[0029] The above reactor may be a continuous stirred-tank reactor, a plug flow reactor, a bubble column reactor, etc.

[0030] For example, ethylene gas is introduced into a liquid region containing a solvent, catalyst, etc. through a distribution device installed at the bottom of a bubble column reactor, and is dispersed while rising in the form of bubbles, and the dispersed gas is mixed within the liquid region while generating turbulence, so that an oligomerization reaction can be performed.

[0031] The above oligomerization reaction may refer to a reaction in which monomers are oligomerized. Depending on the number of monomers polymerized, it is called trimerization or tetramerization, and these are collectively called multimerization. For example, alpha olefins such as 1-hexene and 1-octene can be produced through trimerization or tetramerization of ethylene.

[0032] The ethylene gas supplied to the above reactor (100) may be a stream containing ethylene (C2) separated from naphtha thermal cracking.

[0033] The solvent for dissolving the above ethylene gas may include at least one selected from the group consisting of 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, two types of the above solvents may be mixed and used. Through this, the ethylene gas can be liquefied at a higher temperature, and the dissolution rate of the ethylene gas in the solvent can be improved.

[0034] In the above ethylene oligomerization reaction, a compound containing a transition metal may be used as a catalyst to promote reaction activity. For example, the catalyst may be a compound containing at least one selected from the group consisting of chromium (III) acetylacetonate, chromium (III) chloride tetrahydrofuran, chromium (III) 2-ethylhexanoate, chromium (III) tris(2,2,6,6-tetramethyl-3,5-heptaneindionate), chromium (III) benzoylacetonate, chromium (III) hexafluoro-2,4-pentaneindionate, chromium (III) acetate hydroxide, chromium (III) acetate, chromium (III) butyrate, chromium (III) pentanoate, chromium (III) laurate, and chromium (III) stearate.

[0035] In addition, a cocatalyst may be additionally used to increase the activity of the catalyst, and for example, the cocatalyst may include at least one selected from the group consisting of trimethyl aluminum, triethyl aluminum, triisopropyl aluminum, triisobutyl aluminum, ethylaluminum sesquichloride, diethylaluminum chloride, ethyl aluminum dichloride, methylaluminoxane, modified methylaluminoxane, and borate.

[0036] The above oligomerization reaction can be operated under conditions commonly applied in the field, for example, 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.

[0037] When this oligomerization reaction is performed, a liquid stream containing ethylene polymerized oligomer products, by-products, solvent, unreacted gas dissolved in the solvent, etc. exists in the lower liquid region (120) of the reactor (100), and unreacted ethylene gas that is not dissolved in the solvent and thus does not participate in the oligomerization reaction can rise to the upper gaseous region (110).

[0038] The liquid stream present in the liquid region (120) of the above reactor may have a density that varies depending on the amount of liquid oligomer product generated by conversion from ethylene and the amount of bubbles derived from unreacted gas dissolved in the solvent. If an error occurs in the liquid level measurement due to such density change, it may be difficult to maintain the liquid level in the reactor stably.

[0039] To overcome these problems, in the present invention, an overflow pipe (10) is provided at a height corresponding to the boundary between a gas phase region (110) and a liquid phase region (120) on the outer side wall of the reactor, and is connected to a gas-liquid separator (200), so that a liquid stream containing an oligomer product obtained in the reactor (100) is transferred to the gas-liquid separator (200) through the overflow pipe (10), and then the liquid level of the gas-separated liquid stream is measured in the gas-liquid separator (200).

[0040] More specifically, the overflow pipe (10) enables movement of a liquid stream by overflow at the boundary between the gas phase and the liquid phase of the reactor (100), and at the same time, can promote pressure equilibrium between the reactor (100) and the gas-liquid separator (200). That is, the pressures of the reactor (100) and the gas-liquid separator (200) are maintained equal by the overflow pipe (10), so that the gas phase is equilibrated, and only the liquid phase that has risen above the boundary height can flow out from the reactor (100) to the gas-liquid separator (200).

[0041] If an overflow pipe is not provided, it is difficult to maintain the same pressure between the reactor and the gas-liquid separator. For example, if a pipe is connected to the lower liquid region of the reactor to transport the liquid stream to the gas-liquid separator, an additional pressure gauge and a pressure regulating valve will be required to control the pressure of the gas-liquid separator. In addition, when the upper gas stream of the gas-liquid separator is introduced into the upper gas region of the reactor, the mixing of the two streams may be restricted due to the pressure relationship between the two streams, and since the upper gas stream of the gas-liquid separator is a saturated gas, there is a possibility that condensation may occur.

[0042] The above overflow pipe (10) may have a sufficient size to enable effective movement of the liquid stream due to overflow and pressure balance of the gaseous stream, and there is no particular limitation on its inner diameter and length as long as the flow rate is not restricted when the liquid is discharged through the overflow pipe (10).

[0043] The liquid stream transferred from the reactor (100) to the gas-liquid separator (200) through the overflow pipe (10) can have bubble entrainment suppressed, thereby minimizing changes in the density of the liquid phase due to bubbles.

[0044] Additionally, the oligomer manufacturing device according to the present invention may further include a pressure maintenance pipe (11) connecting the gas phase region of the reactor (100) and the gas phase region of the gas-liquid separator (200) to each other.

[0045] The above pressure maintenance pipe (11) can be used to more effectively equalize the pressure of the reactor (100) and the gas-liquid separator (200), and can be designed in a manner conventional in the field.

[0046] The above gas-liquid separator (200) separates the gas contained in the liquid stream transferred 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 maintenance pipe (11), and the gas-separated liquid stream remains at the bottom of the gas-liquid separator (200).

[0047] The height of the liquid stream present in the above-mentioned gas-liquid separator (200) is measured by a liquid level gauge (20) provided in the gas-liquid separator (200).

[0048] The above liquid level gauge may be, but is not limited to, a differential pressure type level transmitter (LT) commonly used in the field.

[0049] The liquid phase transferred to the gas-liquid separator (200) is suppressed from bubbles, and since the composition of the liquid phase within the gas-liquid separator (200) does not change, there is little change in density. Therefore, unlike the reactor (100) where changes in the composition of the liquid phase occur, there is a low possibility of an error occurring when measuring the liquid level within the gas-liquid separator (200). For example, the liquid level measurement value may have an error of less than 5% compared to the actual liquid level within the gas-liquid separator.

[0050] Therefore, by measuring the height of the liquid phase with suppressed density change using the liquid level measuring device (20) provided in the gas-liquid separator (200), the liquid level of the reactor (100) can be stably maintained by discharging the liquid stream within the gas-liquid separator (200) according to the signal of the liquid level measuring device (20).

[0051] The liquid stream in the above-described gas-liquid separator (200) can be discharged through a liquid discharge pipe (30) connected to the lower portion of the above-described gas-liquid separator (200), and at this time, the discharge amount of the liquid stream can be controlled by controlling the opening and closing of a control valve (CV) provided in the liquid discharge pipe (30) according to a signal from a liquid level measuring device (20).

[0052] In addition, by minimizing the amount of bubbles in the liquid stream discharged through the gas-liquid separator, the flow of oligomer products in the liquid discharge pipe can be facilitated, clogging can be prevented, and ethylene gas emission to the downstream stream can be reduced.

[0053] Thereafter, the liquid stream discharged through the liquid discharge pipe (30) connected to the lower portion of the gas-liquid separator (200) can be supplied to a separation tower (not shown), and by further separating unreacted gas, solvent, etc. in the separation tower, a purified oligomer product can be obtained.

[0054] If necessary, the above oligomer manufacturing device may further include devices necessary for oligomer manufacturing, such as a condenser, a reboiler, a pump, a cooler, a filter, a stirrer, a compressor, and a mixer.

[0055] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present invention, and the scope of the present invention is not limited to these examples alone.

[0056]

[0057] Comparative Example 1:

[0058] A pilot system as shown in Fig. 2 was configured to measure the liquid level of the reactor (100) during oligomer production.

[0059] First, an oligomerization reaction was performed by supplying a solvent, a catalyst, and ethylene gas to the lower liquid region (120) of the reactor (100).

[0060] The height of the liquid stream containing the oligomer product obtained by the above reaction was measured using a differential pressure type level transmitter (LT) equipped in the reactor (100), and the liquid stream was discharged from the lower part of the reactor (100). Depending on the liquid level measurement value, the discharge amount of the liquid stream was controlled using a control valve (CV).

[0061]

[0062] Comparative Example 2:

[0063] A pilot system as shown in Fig. 3 was configured to measure the liquid level of the reactor (100) during oligomer production.

[0064] First, an oligomerization reaction was performed by supplying a solvent, a catalyst, and ethylene gas to the lower liquid region (120) of the reactor (100).

[0065] The liquid stream containing the oligomer product obtained by the above reaction was discharged through an overflow pipe (10) connected at a height corresponding to the boundary between the upper gas phase region (110) and the lower liquid phase region (120) of the reactor (100), thereby maintaining the liquid level of the reactor (100) by discharging the liquid stream higher than the boundary height.

[0066]

[0067] Example 1:

[0068] An oligomer was manufactured by configuring a pilot system as shown in Fig. 1, and the liquid level was measured in a gas-liquid separator (200) installed outside the reactor (100).

[0069] First, an oligomerization reaction was performed by supplying a solvent, a catalyst, and ethylene gas to the lower liquid region (120) of the reactor (100).

[0070] A liquid stream containing an oligomer product obtained through the above reaction was discharged to a gas-liquid separator (200) through an overflow pipe (10) connected at a height corresponding to the boundary between the upper gas phase region (110) and the lower liquid phase region (120) of the reactor (100) as a liquid stream rising higher than the boundary height. At this time, the pressures of the reactor (100) and the gas-liquid separator (200) were maintained the same.

[0071] The liquid level in the gas-liquid separator (200) was measured using the differential pressure LT equipped in the gas-liquid separator (200), and the liquid stream was discharged through the liquid discharge pipe (30) connected to the lower part of the gas-liquid separator (200). Based on the measured liquid level, the discharge amount of the liquid stream was controlled using the control valve (CV) equipped in the liquid discharge pipe (30).

[0072]

[0073] The results of liquid level measurement and liquid phase maintenance in the reactor according to the above examples and comparative examples are shown in Table 1 below.

[0074] Measurement of liquid level in the reactor Liquid level maintenance result Comparison example 1 Lower pipe reactor Liquid level rise in the reactor Comparison example 2 Overflow pipe - Maintaining reactor liquid level / Discharging a large amount of gas through the overflow pipe Example 1 Overflow pipe Gas-liquid separator Maintaining reactor liquid level / Maintaining gas-liquid separator liquid level

[0075] As can be seen in Table 1 above, in Example 1, the pressures of the reactor and the gas-liquid separator were maintained the same through an overflow pipe provided at the boundary between the gas phase and liquid phase regions of the reactor, and only the liquid phase that rose higher than the connection height of the overflow pipe was transferred to the gas-liquid separator to measure the liquid level. As a result, the liquid level of the reactor was stably maintained and there was almost no change in density due to bubbles in the liquid phase in the gas-liquid separator, so that the error of the differential pressure LT was minimized. Accordingly, the liquid level of the gas-liquid separator was maintained constant through the liquid level control valve (CV) connected to the differential pressure LT.

[0076] In addition, the amount of bubbles in the liquid stream discharged through the gas-liquid separator was minimized, thereby facilitating the flow of oligomer products in the liquid discharge pipe and preventing clogging, and reducing the emission of ethylene gas to the downstream stream.

[0077] In contrast, in Comparative Example 1, when the liquid phase of the reactor (100) was directly measured, an error occurred in which the LT indication decreased at the same liquid level. This is because the gas hold-up space distributed as bubbles, i.e. oligomers, are generated in the liquid phase inside the reactor increases, and the density of the liquid phase decreases. As a result, even when the liquid level exists at the same height, the differential pressure decreases, and the LT indication is displayed as a decrease in the liquid level. Due to this error, the control valve was closed to control the liquid level, and ultimately, the actual liquid level in the reactor increased. Due to this increase in the liquid level in the reactor, the catalyst residence time in the reactor increased, which limited the control of the amount of product and the calorific value, and a blockage phenomenon due to polymer occurred in the pipe through which the liquid stream was discharged, and the amount of ethylene to be recovered from the pipe increased.

[0078] Meanwhile, in Comparative Example 2, the liquid level of the reactor (100) was controlled by discharging a liquid phase that rose higher than the boundary height between the gas phase and the liquid phase through the overflow pipe (10) at the boundary without separately measuring the liquid level of the reactor, and as a result, a large amount of gas stream including unreacted ethylene was discharged together with the liquid stream through the overflow pipe (10). As a result, it was difficult to predict the amount of ethylene discharged through the overflow pipe, and a blockage phenomenon occurred due to an increase in the two-phase liquid-gas phase within the pipe.

[0079]

[0080] [Explanation of symbols]

[0081] 100: Reactor

[0082] 200: Gas-liquid separator

[0083] 10: Overflow pipe

[0084] 11: Pressure-retaining pipe

[0085] 20: Liquid level gauge

[0086] 210: Liquid discharge pipe

Claims

1. A reactor including an upper gas phase region and a lower liquid phase region, wherein ethylene gas and a solvent are supplied to the liquid phase region to perform an oligomerization reaction; An overflow pipe provided on the outer side wall of the reactor and connected to a height corresponding to the boundary between the gas phase region and the liquid phase region of the reactor to discharge a liquid stream containing an oligomer product; A vapor-liquid separator connected to the above overflow pipe and separating a vapor phase from the discharged liquid stream; A liquid level gauge provided in the above gas-liquid separator; and An oligomer manufacturing device including a liquid discharge pipe connected to the lower part of the above gas-liquid separator and discharging the gas-separated liquid stream.

2. In paragraph 1, The above overflow pipe is an oligomer manufacturing device that maintains the pressure of the reactor and the pressure of the gas-liquid separator to be the same.

3. In paragraph 1, An oligomer manufacturing device in which a liquid stream transferred from a reactor to a gas-liquid separator through the above overflow pipe is suppressed from entraining bubbles.

4. In paragraph 1, An oligomer manufacturing device further comprising a pressure maintaining pipe connecting a gaseous region of the reactor and a gaseous region of the gas-liquid separator.

5. In paragraph 1, The above liquid level gauge is an oligomer manufacturing device that measures the liquid level of a liquid stream separated from the vapor in a vapor-liquid separator.

6. In paragraph 5, An oligomer manufacturing device in which the above liquid level measurement value has an error of less than 5% compared to the actual liquid level in the gas-liquid separator.

7. In paragraph 1, An oligomer manufacturing device, wherein the liquid discharge pipe connected to the lower portion of the above-described gas-liquid separator includes a valve for controlling the amount of liquid discharged according to a signal from the above-described liquid level measuring device.

8. In paragraph 1, The above reactor is an oligomer manufacturing device including a bubble column reactor.

9. In paragraph 1, An oligomer manufacturing device, wherein the gaseous zone of the above reactor comprises an upper piping for discharging a gaseous stream containing unreacted ethylene gas.

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