Embedded vacuum overhead condenser

Abstract

The invention provides an embedded vacuum overhead condenser, and belongs to the technical field of chemical engineering. Comprising a rectifying tower shell, and a condenser is arranged in the top of the rectifying tower shell; a condenser sleeve is arranged outside the condenser, a long-strip-shaped hole is formed in the condenser sleeve in the axis direction and serves as a condenser gas phase inlet, and a gas phase outlet is formed in the top of the condenser. A liquid collecting tray is arranged in the rectifying tower shell and located below the condenser, a gas raising cylinder is arranged on the liquid collecting tray, and a liquid phase outlet is formed in the position, located on the liquid collecting tray, of the side wall of the rectifying tower shell. The occupied area is reduced while the heat exchange efficiency is improved; a large-diameter gas phase pipeline does not need to be configured, for some systems which are prone to crystallization or high in melting point, a gas phase medium can exchange heat with external heat to be liquefied and solidified in the flowing process of the gas phase pipeline, the situation can be avoided, a heat tracing device does not need to be additionally arranged, and the investment cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to an embedded vacuum tower top condenser. Background Technology

[0002] Distillation columns and overhead condensers are a typical combination of process equipment in product refining and separation, widely used in petrochemical, pharmaceutical, and seawater desalination industries. The overhead condenser absorbs heat from the overhead gas, condensing it into a liquid state and discharging the non-condensable gases. Cooling water indirectly removes the heat.

[0003] Existing distillation column systems typically employ external vacuum condensers, with a vapor phase pipe leading from the top of the column serving as the condenser inlet. These systems also include a reflux tank, reflux pump, and other related equipment. Furthermore, external vacuum condensers require relatively long additional vacuum piping, resulting in pressure drops and necessitating additional vacuum system capacity. For media with high freezing points (above 50°C), this vacuum piping also requires additional heat tracing (e.g., external coils, external tracing pipes, jacketed pipe heat tracing), increasing the estimated cost of additional heat tracing facilities and overall investment. Summary of the Invention

[0004] The purpose of this invention is to solve the problems existing in the prior art and provide an embedded vacuum tower top condenser.

[0005] This invention is achieved through the following technical solution:

[0006] This invention provides an embedded vacuum column top condenser, comprising a distillation column shell, wherein a condenser is disposed inside the top of the distillation column shell;

[0007] A condenser sleeve is provided outside the condenser. An elongated hole is opened on the condenser sleeve along the axial direction as the condenser gas phase inlet. A gas phase outlet is provided at the top of the condenser.

[0008] A liquid collection tray is provided inside the distillation column shell below the condenser, and a gas riser is provided on the liquid collection tray. A liquid phase outlet is provided on the side wall of the distillation column shell at the location of the liquid collection tray.

[0009] A further improvement of the present invention is that:

[0010] The width of the elongated hole is set according to the central angle of the chord length of the condenser sleeve cross section, which is 70° to 120°, preferably 70° to 90°.

[0011] A further improvement of the present invention is that:

[0012] The condenser is provided with a first baffle and a second baffle from top to bottom;

[0013] The first baffle is positioned near the gas phase outlet, and two baffles are arranged sequentially from top to bottom;

[0014] The second baffle is located below the first baffle, and multiple baffles are arranged sequentially from top to bottom.

[0015] A further improvement of the present invention is that:

[0016] The first baffle is a single-arch baffle.

[0017] A further improvement of the present invention is that:

[0018] The second baffle is a double-arched baffle; and / or,

[0019] The distance between two adjacent second baffles is 600-1100 mm.

[0020] A further improvement of the present invention is that:

[0021] The liquid collection tray is fixed inside the distillation column shell and located below the condenser. The liquid collection tray is provided with multiple through holes, and the gas riser is provided on the through holes.

[0022] A further improvement of the present invention is that:

[0023] The height of the air lift cylinder is between 600 and 1500 mm.

[0024] A further improvement of the present invention is that:

[0025] The top of the air cylinder is equipped with an air-lifting cap.

[0026] A further improvement of the present invention is that:

[0027] The condenser uses a U-tube heat exchanger, which is fixed to the top of the distillation column shell by a flange.

[0028] A further improvement of the present invention is that:

[0029] The gas phase outlet is connected to a vacuum system to enable vacuum operation.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] This invention saves space compared to the original external condenser and reflux tank by placing the condenser inside the top of the distillation column shell, thus improving heat exchange efficiency while reducing the footprint. It also eliminates the need for large-diameter gas phase pipelines. For some systems that are prone to crystallization or have high melting points, the gaseous medium may liquefy and solidify during flow through the gas phase pipeline due to external heat exchange. This invention's built-in vacuum condenser avoids this situation and eliminates the need for additional heating devices, reducing investment costs.

[0032] In this invention, by placing the liquid phase outlet below the condenser, the condensed liquid falls into the collection tray under gravity and then flows out through the liquid phase outlet, which can reduce the head of the reflux pump. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of an embedded vacuum tower top condenser;

[0034] Figure 2 This is a schematic diagram of the first baffle plate;

[0035] Figure 3 This is a schematic diagram of the second baffle plate;

[0036] Figure 4 This is a schematic diagram of the liquid collection tray.

[0037] In the diagram, 1 is the distillation column shell, 2 is the condenser sleeve, 3 is the elongated orifice, 4 is the gas phase outlet, 5 is the U-tube heat exchanger, 6 is the first baffle plate, 7 is the second baffle plate, 8 is the liquid collection tray, 9 is the gas riser, 10 is the gas riser cap, and 11 is the liquid phase outlet. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings:

[0039]

Example 1

[0040] This invention provides an embedded vacuum tower top condenser, such as... Figure 1 As shown, it includes a distillation column shell 1, and a condenser is installed inside the top of the distillation column shell 1;

[0041] A condenser sleeve 2 is provided outside the condenser. A long hole 3 is opened on the condenser sleeve 2 along the axial direction as the condenser gas phase inlet. A gas phase outlet 4 is provided at the top of the condenser. The gas phase outlet 4 is connected to the vacuum system to realize vacuum operation.

[0042] A liquid collection tray 8 is provided inside the distillation column shell 1 below the condenser. A gas riser 9 is provided on the liquid collection tray 8. A liquid outlet 11 is provided on the side wall of the distillation column shell 1 at the position of the liquid collection tray 8.

[0043] The gas phase inside the distillation column shell 1 enters the condenser for heat exchange through the gas riser 9 on the liquid collection plate 8 and the elongated hole 3 on the condenser sleeve 2. After heat exchange, the gas phase is discharged through the gas phase outlet 4 at the top of the condenser, and the liquid phase falls onto the liquid collection plate 8 under the action of gravity and then flows out through the liquid phase outlet 11 provided on the side wall of the distillation column shell 1.

[0044] This invention saves space compared to the original external condenser and reflux tank by placing the condenser inside the top of the distillation column shell 1, thereby improving heat exchange efficiency while reducing the footprint. It also eliminates the need for large-diameter gas phase pipelines. For some systems that are prone to crystallization or have high melting points, the gas phase medium may liquefy and solidify during the flow of gas phase media and external heat exchange. The built-in vacuum condenser of this invention can avoid this situation and eliminates the need for additional heat tracing devices, thus reducing investment costs.

[0045] In this invention, by setting the liquid phase outlet 11 below the condenser, the condensed liquid falls into the liquid collection tray 8 under the action of gravity and then flows out through the liquid phase outlet 11, which can reduce the head of the reflux pump.

[0046]

Example 2

[0047] The upper part of the distillation column shell 1 is a constricted section, and the condenser is set in the constricted section. On the one hand, the steel plate material required for the constricted section is much less than that of the original size, which reduces investment costs. On the other hand, it can effectively avoid short circuits in the gas phase, which would reduce the heat exchange effect.

[0048] The condenser adopts a U-tube heat exchanger 5, which is fixed to the top of the distillation column shell 1 by a flange. The condenser sleeve 2 is welded inside the distillation column shell 1 and located on the periphery of the condenser, which plays a stabilizing role. A long hole 2 is opened on the condenser sleeve 2 along the axial direction as the gas phase inlet of the condenser. The gas phase in the distillation column passes through the gas riser 9 on the liquid collection plate 8, the annular gap between the condenser sleeve 2 and the distillation column shell 1 in sequence, and finally enters the condenser through the long hole 3 for heat exchange, which can reduce the leakage between the tube bundle and the shell and improve the heat transfer efficiency.

[0049] A small portion of the vapor phase in the distillation column directly exchanges heat with the U-bend of the condenser, which increases the heat exchange area and is beneficial to the heat exchange effect. Another portion enters through the notch of the baffle plate, but due to the pressure drop balance, this part is relatively small and has little impact on the heat exchange.

[0050] The top of the U-tube heat exchanger 5 is equipped with a head tube box, which has a medium inlet and a medium outlet.

[0051]

Example 3

[0052] like Figure 1 As shown, a first baffle plate 6 and a second baffle plate 7 are arranged sequentially from top to bottom inside the condenser. The first baffle plate 6 is positioned near the gas phase outlet 4, and two first baffle plates 6 are arranged alternately from top to bottom. Figure 2As shown, the first baffle 6 is a single-arch baffle, mainly used to prevent short circuit of the gas phase in the condenser, and to condense the uncondensed gas phase in the heat exchange area supported by the second baffle 7, which can further reduce the tail gas temperature and improve the heat exchange effect.

[0053] The second baffle 7 is disposed below the first baffle 6, and multiple baffles are arranged sequentially from top to bottom. Preferably, the distance between two adjacent second baffles 7 is 600-1100 mm. The second baffle 7 is a double-arched baffle. Figure 3 As shown. In order to both maximize the tube area to reduce the condenser size and ensure sufficient gas rising channels to reduce operating pressure drop, the embodiment of the present invention is further preferred in that the second baffle 7 is formed by cutting 9-15% on both opposite sides of the disc-shaped baffle, wherein the angle between the cutting point and the center of the disc-shaped baffle is close to 90°, so that the area on one side between the condenser sleeve and the heat exchange tube bundle accounts for 9.5% of the area of ​​the condenser sleeve.

[0054] The second baffle plate 7 serves to distribute gas and support the heat exchange tubes. Most of the gas phase entering the condenser through the elongated hole 3 is condensed in the heat exchange area supported by the second baffle plate 7. The remaining small amount of uncondensed gas phase flows upward along the gap between the second baffle plate 7 and the condenser sleeve 2 and is condensed in the heat exchange area supported by the first baffle plate 6, further reducing the gas phase temperature. The condensed liquid phase flows downward and falls onto the liquid collection plate and flows out through the liquid phase outlet.

[0055] One of the cut sides of the second baffle plate 7 is positioned directly opposite the elongated hole 3, so that most of the gas phase entering the condenser through the elongated hole 3 is condensed in the heat exchange area supported by the second baffle plate 7, and the remaining small amount of uncondensed gas phase flows upward along the gap between the second baffle plate 7 and the condenser sleeve 2 and is condensed in the heat exchange area supported by the first baffle plate 6.

[0056]

Example 4

[0057] The area of ​​the elongated orifice 3 is calculated based on the gas phase cross-sectional flow velocity, specifically as follows:

[0058] Based on the different pressures of the vacuum system, set the gas phase flow rate (e.g., 50 m / s for the gas phase flow rate through the elongated orifice), and then determine the inlet volume flow rate of the condenser based on the design (1.06 × 10⁻⁶ m / s). 6 m 3 Calculate the corresponding area S using / h):

[0059]

[0060] The width of the elongated hole 3 is set according to the central angle of the chord length of the condenser sleeve cross section, which is 70° to 120°, preferably 70° to 90°.

[0061] The width of the elongated orifice 3 is set approximately at 90° based on the central angle corresponding to the chord length of the condenser sleeve cross-section, corresponding to a 15% cut-off rate for the double-baffle (second baffle). Alternatively, the width of the elongated orifice can be set at 70° based on the central angle corresponding to the chord length of the condenser sleeve cross-section, corresponding to a 9% cut-off rate for the double-baffle. A cut-off rate less than 9% for the double-baffle reduces the rising gas phase space for non-condensable gases and the descending liquid phase space, increasing pressure drop. The maximum opening angle of the elongated orifice is recommended not to exceed 120°, corresponding to a 25% cut-off rate for the double-baffle. Increasing this angle further reduces the heat exchange area, requiring increased heat exchange tube length to compensate, which increases equipment investment. Furthermore, a larger notch increases the proportion of process gas directly entering the notch area of ​​the baffle, reducing heat exchange efficiency.

[0062] In this invention, an elongated hole 3 is opened along the axial direction on the condenser sleeve 2 as the gas phase inlet of the condenser, instead of a circumferential opening. On the one hand, the axial opening is not much different from the structure without a condenser sleeve, and both will cause large leakage and short circuit, reducing the heat exchange effect. On the other hand, by opening an elongated hole on one side of the condenser sleeve, it is convenient to collect non-condensable gas on the other side and send it to the first baffle for heat exchange.

[0063]

Example 5

[0064] like Figure 4 As shown, the liquid collection tray 8 is fixed inside the distillation column shell 1 and located below the condenser. The liquid collection tray 8 is provided with multiple through holes, and the gas lifting cylinder 9 is provided on the through holes. Preferably, the multiple gas lifting cylinders 9 are evenly arranged on the liquid collection tray 8 to facilitate the uniform distribution of gas.

[0065] The shape of the air lifter 9 is not fixed; it can be round or square, as long as the cross-sectional area of ​​the air lifter meets the design requirements.

[0066] The height of the air lifting cylinder 9 is designed according to the process dwell time requirements. Preferably, the height of the air lifting cylinder 9 is between 600-1500mm.

[0067] Preferably, a gas lift cap 10 is provided at the top of the gas lift cylinder 9 to prevent the condensed liquid phase from directly entering the gas lift cylinder 9. The size of the gas lift cap 10 is larger than the size of the gas lift cylinder 9, so that the gas phase can rise through the gap between the gas lift cylinder 9 and the gas lift cap 10 to the annular gap between the condenser sleeve 2 and the distillation column shell 1, and then enter the condenser through the elongated hole 3 for condensation and heat exchange.

[0068] Preferably, a groove is provided on the side of the liquid collection tray 8 near the distillation column shell 1, and the liquid phase outlet 11 is located at the position corresponding to the groove on the side wall of the distillation column shell 1. The liquid phase after being condensed by the condenser falls into the liquid collection tray 8, is collected by the groove, and finally flows out through the liquid phase outlet 11.

[0069]

Example 6

[0070] This invention uses Aspen Plus V12 to obtain the heat transfer curves of the overhead condenser in a ketone distillation column under operating conditions. The thermodynamic method chosen is the non-stochastic two-liquid model (NTRL) equation, and the structural calculations of the embedded vacuum overhead condenser in a 200,000-ton / year cyclohexanone esterification plant are performed using the heat exchanger calculation software HTRI 9.1. The operating pressure of the cyclohexanone column is 6 kPaA, the overhead operating temperature is 71.2℃, and the condenser outlet temperature is controlled at approximately 50℃. The condenser feed composition is shown in Table 1.

[0071] Table 1. Feed composition to the top condenser of the ketone tower

[0072]

[0073] Because the openings, pipe fittings, and flange connections in a vacuum system are not completely sealed, outside air can leak into the vacuum system due to pressure exceeding the system operating pressure. Therefore, the feed composition takes into account a certain amount of air.

[0074] This invention takes the operating parameters of a ketone tower (diameter DN5800) in a 200,000-ton / year esterification cyclohexanone unit as an example, and compares the heat exchange using a conventional external horizontal condenser and the embedded vacuum tower top condenser of this invention.

[0075] The vapor phase composition of the distillation column is mainly cyclohexanone, which is relatively clean and not prone to scaling. Assume its process medium fouling thermal resistance is 0.00017m. 2 .K / W, and flowed through the shell side; the selected cold source is circulating cooling water, assuming its fouling thermal resistance is 0.000344m. 2 The circulating water supply temperature is 33℃, the maximum return water temperature is 43℃, and the allowable pressure drop on the circulating water side is set at 50 kPa. In this embodiment, the allowable pressure drop on the process side of the vacuum tower top condenser is 1 kPa.

[0076] Table 2 shows the simulation results of the structural parameters of the two condensers.

[0077] Table 2 Simulation Results

[0078]

[0079] As shown in Table 2, with condenser structural dimensions generally between 2.8m and 3.1m in diameter, heat exchange tube lengths between 4.5m and 5.5m, and a design margin controlled at around 50%, horizontal condensers have a relatively large number of heat exchange tubes but a smaller heat exchange area, as well as smaller temperature differences and pressure drops. This is mainly because the condenser is limited by the opening of the gas phase inlet on the shell side, requiring the shell diameter to be increased to 3100mm, which allows for the arrangement of more heat exchange tubes in the original 2800mm tube bundle area.

[0080] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0081] In the description of this invention, unless otherwise stated, the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0082] The above technical solution is only one embodiment of the present invention. For those skilled in the art, based on the principles disclosed in the present invention, it is easy to make various types of improvements or modifications, and not limited to the technical solutions described in the specific embodiments of the present invention. Therefore, the foregoing description is only a preferred option and is not restrictive.

Claims

1. An inline vacuum overhead condenser characterized by, The rectifying tower shell is internally provided with a condenser at the top; The condenser is externally provided with a condenser sleeve, the condenser sleeve is provided with a long hole as a gas phase inlet along the axial direction, and the condenser is provided with a gas phase outlet at the top; The rectifying tower shell is internally provided with a liquid collecting tray at a position below the condenser, the liquid collecting tray is provided with a gas lifting cylinder, and the sidewall of the rectifying tower shell is provided with a liquid phase outlet at the position of the liquid collecting tray.

2. The inline vacuum overhead condenser of claim 1, wherein, The width of the long hole is set according to the chord length of the condenser sleeve section corresponding to the central angle of 70°-120°, preferably 70°-90°.

3. The inline vacuum overhead condenser of claim 1, wherein, The condenser is sequentially provided with a first baffle and a second baffle from top to bottom; The first baffle is provided at a position close to the gas phase outlet and is sequentially provided with two pieces from top to bottom; The second baffle is provided below the first baffle and is sequentially provided with multiple pieces from top to bottom.

4. The inline vacuum overhead condenser of claim 3, wherein, The first baffle is a single-arch baffle.

5. The inline vacuum overhead condenser of claim 3, wherein, The second baffle is a double-arch baffle; and / or, The distance between adjacent two second baffles is 600-1100 mm.

6. The inline vacuum overhead condenser of claim 1, wherein, The liquid collecting tray is fixed on the inner wall of the rectifying tower shell; The liquid collecting tray is provided with multiple through holes, and the through holes are provided with the gas lifting cylinder.

7. The inline vacuum overhead condenser of claim 6, wherein, The height of the gas lifting cylinder is 600-1500 mm.

8. The inline vacuum overhead condenser of claim 7, wherein, The top end of the gas lifting cylinder is provided with a gas lifting cap.

9. The inline vacuum overhead condenser of claim 1, wherein, The condenser adopts a U-shaped tube heat exchanger, which is fixed on the top of the rectifying tower shell through a flange.

10. The inline vacuum overhead condenser of claim 1, wherein, The gas phase outlet is connected with a vacuum system to realize vacuum operation.

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