Liquid distributor for heat and material exchange column

Abstract

Title of the invention: Liquid distributor for heat and mass exchange column. A liquid distributor (1) comprises a lower plate (P) provided with orifices through which a liquid leaves the distributor to irrigate a lower element, parallel parallelepiped chimneys (C) dedicated to the passage of the ascending gas, thus delimiting liquid channels above the lower plate, these chimneys being provided with closing means on the upper part allowing the liquid to be diverted, the chimneys are distributed over a central circular section of the lower plate, creating a peripheral channel on the perimeter of the lower plate fluidly connected to the channels, a plurality of plates (R1, R2), each plate having an elongated rectangular shape with two ends, with two plates per channel,the plates being oriented at an acute or zero angle to the horizontal characterized in that the total length of the two plates present in a channel is less than 85% of the length of the channel, so that the plates of each channel are spaced apart from each other. [FIG.2]

Description

Title of the invention: Liquid dispenser for heat and matter exchange column

[0001] The present invention relates to a liquid distributor for a heat and mass exchange column, particularly a packed column. It further relates to a column equipped with such a distributor and at least one structured packing module. It also relates to a distillation process for separating a mixture of at least two components, in which the mass and heat exchange between a liquid and a gas is carried out using a distributor according to the invention or a column according to the invention.

[0002] For difficult distillation in a packed column—that is, the distillation of a mixture whose components have similar boiling points—it is common practice to regularly redistribute the liquid after a certain number of theoretical stages, typically every 10 to 25 theoretical stages. This is typically the case for argon-oxygen distillation, but also for isotope separation columns where the relative volatilities are sometimes less than 1.005.

[0003] Redistribution, which involves collecting the liquid and redistributing it, provides greater robustness against distribution defects that naturally develop in a section and optimal performance of the seals. To best homogenize the liquid content, mixing devices are also used within the distributor, either by means of channels when using a separate manifold, as illustrated in US8118284 B2 and US4689183, or by means of baffles within the re-distributor itself, as illustrated in US5132055, US2014 / 0374927 A1 and US5752538. The re-distributor is in fact a distributor that incorporates the function of collecting the liquid from the upper section.

[0004] However, these devices, with their numerous parts, involve many manufacturing steps, often manual. Furthermore, they do not directly contribute to the transfer, although they occupy a significant portion of the height of a distillation column. Due to their complexity, efforts are generally made to limit their number, even though they are essential for optimal column operation.

[0005] Solutions with separate collector and distributor are bulky and complex. They have multiple disadvantages.

[0006] [Fig. 1] represents a known solution that is the most compact while integrating numerous functions: collector, distributor supporting the packing sections, and mixer. This last function is produced by the combination of a peripheral angle bracket approximately halfway up the distributor, which collects the liquid The dispenser consists of a wall-mounted unit and a set of inclined plate pairs in each trough. The liquid collected by the angle bracket flows onto the plates, which also collect a fraction of the liquid that falls vertically.

[0007] To control the liquid distribution, slots are cut into the angle brackets in front of each plate. A wider slot allows for feeding a longer channel. Gravity flow requires a vertical sequence of the different elements: at the top, the lateral angle bracket, then the plate inclined towards the center, and finally the distributor.

[0008] In the diagram shown, there are 22 plates, but there may be more for wider columns. The angle bracket is also composed of several elements. At a minimum, a flat base welded to the wall of the dispenser and vertical plates to form the various slots for distributing the liquid onto the plates.

[0009] According to one object of the invention, a gravity-fed liquid dispenser is provided comprising: • a lower plate equipped with orifices through which a liquid leaves the dispenser to irrigate a lower element, • parallel parallelepiped chimneys dedicated to the passage of the ascending gas, thus defining liquid channels above the lower plate, these chimneys being equipped with means of closure on the upper part allowing the liquid to be diverted, • The chimneys are distributed across a central, circular section of the lower plate, creating a peripheral channel around the perimeter of the lower plate which is fluidly connected to the chutes, • a plurality of plates, each plate having an elongated rectangular shape with two ends, with two plates per channel, • the plates being oriented at an acute or zero angle to the horizontal characterized in that the total length of the two plates present in a channel is less than 85% of the length of the channel, so that the plates of each channel are spaced apart from each other.

[0010] The invention will be described in more detail with reference to the figures where:

[0011] [Fig.2] represents a distributor according to the invention.

[0012] [Fig.3] represents a distributor according to the invention.

[0013] [Fig.4] represents a distributor according to the invention.

[0014] [Fig.2] represents a gravity-fed liquid dispenser according to the invention which is arranged in a distillation column and comprising a lower plate P with orifices through which a liquid leaves the distributor to irrigate a lower element, for example a section of packing present in the column. It also includes parallel parallelepiped chimneys C dedicated to the passage of gas The system is arranged in an ascending fashion, thus defining liquid channels G above the lower plate. These channels are equipped with shut-off devices on their upper portion to divert the liquid. These channels are distributed across a central, circular section of the lower plate, creating a peripheral channel around the perimeter of the lower plate that is fluidly connected to the channels. The distributor comprises a plurality of plates, each plate having an elongated rectangular shape with two ends, with two plates per channel. These plates RI, R2 are oriented at an acute or zero angle to the horizontal. The total length of the two plates RI, R2 present in a channel G is less than 85% of the channel length, so the plates in each channel are spaced apart. Preferably, the free ends of the plates are aligned to form an open rectangular space E.

[0015] Furthermore, the liquid velocity field in the lower distribution zone is likely to disrupt the homogeneity of the liquid jets and therefore the distribution. The design must carefully limit, in particular, the horizontal velocity of the liquid in this zone. To achieve this, we aim for taller inserts when the liquid level is high, i.e., at high speeds. This provides a large passage area for the liquid in the distributor's chutes.

[0016] Conversely, when the liquid height is low, at low load, the liquid level is low and the liquid collected by the plates is likely, upon falling, to disturb the flatness of the free surface of the liquid and thus to generate a maldistribution due to a variation in height of the level above each hole.

[0017] We seek to simplify the mixing function of the mixing re-distributor. For this, we can integrate the angle bracket and the plurality of plates into a single piece, cut for example by laser.

[0018] This is possible because the slope of the plates only serves to direct the liquid towards the center of the channels. However, if the plates are fixed to the angle bracket, the liquid will not find a passage between the two. Furthermore, the fine distribution of the liquid collected by the angle bracket between the different channels is unnecessary since the peripheral channel of the distributor already allows for the equalization of liquid levels between the different channels.

[0019] To fix the assembly, localized folds will be used on excess material, welded to the side walls or to those of the gas chimneys C.

[0020] [Fig.3] shows that play between the angle-plate system and the distributor can be tolerated because the re-mixing function does not need to be perfect to be effective.

[0021] Beyond reducing the number of parts and assemblies, the integration of the angle bracket and the R1,R2 plates also helps to limit the constraints of dimensioning in the vertical succession of elements, the angle and the plates then being at the same level.

[0022] Today, a spacing is fixed between the inserts RI, R2 for all the channels G of a device. It is more optimal to adapt this spacing to the length of the channel G and the total flow rate passing through each channel, in order to limit the liquid velocity under each insert. Care is taken to limit the liquid velocity under the channels G to less than 0.2 m / s, preferably 0.1 m / s. The total length of the two inserts RI, R2 present in a channel is less than 85% of the length of the channel G, so that the inserts in each channel are spaced apart.

[0023] Conversely, at low speeds, the aim is to limit the effect of the falling liquid on the homogeneity of the liquid level above the holes. One solution allows for limiting both the jet's velocity and its impact point: optimizing the shape of the insert edges. Rather than a straight edge, it is given a slanted or beveled cut to increase its overall width, which then acts as a weir for a jet with a locally lower flow rate.

[0024] Furthermore, the shape also helps direct the jet. The flow rate is maximum where the insert is shortest, because it falls there sooner. Thus, if the holes in the dispenser are on one side of a chute, it is advantageous to have a diagonal edge, longer on the side without holes. If the holes are in the center of the chute, a V-shaped edge with a longer insert in the center is preferred. Finally, if the holes are on both sides of the chute, a V-shaped edge is also preferred, but this time with a shorter insert in the center.

[0025] [Fig.3] shows a distributor whose plates RI, R2 each have an end with a V-shaped cut edge.

Claims

[Claim 1] Demands Gravity-fed liquid dispenser (1) comprising: • a lower plate (P) equipped with orifices through which a liquid leaves the dispenser to irrigate a lower element, • parallel parallelepiped chimneys (C) dedicated to the passage of the ascending gas, thus delimiting liquid channels (G) above the lower plate, these chimneys being equipped with closing means on the upper part allowing the liquid to be diverted, • The chimneys are distributed across a central, circular section of the lower plate, creating a peripheral channel around the perimeter of the lower plate which is fluidly connected to the chutes, • a plurality of plates (RI, R2) each plate having an elongated rectangular shape with two ends, with two plates per channel, • the plates being oriented at an acute angle or zero to the horizontal characterized in that the total length of the two plates present in a channel is less than 85% of the length of the channel, so that the plates of each channel are spaced (E) apart from each other.

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