APPARATUS FOR DISTRIBUTING FLUID IN DOWNFLOW REACTORS

The present subject matter relates an apparatus (120) for distributing polyphasic fluid mixture to a catalyst bed in a downflow reactor (100). The apparatus (120) comprises a distributor tray (140) comprising a plurality of distributor units (150). The distributor unit (150) comprises an inner tube (210), an outer tube (220) disposed outside and concentric to the inner tube (210), a cover (346), a cap plate (350), and a gas inlet (358). The inner tube comprises a first aperture (314) to allow liquid to enter the inner tube (210) and a solid insert (326). The solid insert (326) forms a narrow passage (330). The outer tube (220) comprises a slot (338) to allow liquid from the distributor tray (140) to enter an annular portion (342).

TECHNICAL FIELD

The present subject matter relates in general to downflow reactors and in particular to an apparatus for distributing a polyphase fluid mixture to a catalyst bed in downflow reactors.

BACKGROUND

Reactors used in chemical, petroleum refining, and other industries generally have a fluid passing through a catalyst bed for performing various types of processes such as cracking, hydrotreating, etc. The fluid may be a polyphasic mixture of gas and liquid. In a downflow reactor, the gas and liquid flow in a concurrent manner from the top of the reactor to the bottom of the reactor. To ensure complete and efficient utilization of the catalyst, it is necessary for the gas and liquid mixture to be distributed throughout the catalyst bed. Generally, distribution of fluid in the reactor is achieved by using distributor plates or distributor trays. These distributors may be a plate with orifices with the distributor plate placed above the catalyst bed so that the fluid passes through the distributor plate before entering the catalyst bed.

DETAILED DESCRIPTION

The present subject matter relates in general to downflow reactors and in particular to an apparatus for distributing a polyphase fluid mixture to a catalyst bed in downflow reactors.

In a downflow reactor, fluid having reactants enters from the top of the reactor and products are removed from the bottom of the reactor. The fluid may be polyphasic, comprising at least one liquid phase reactant and one gas phase reactant. Gas and liquid reactants are mixed and passed over a catalyst bed for performing several processes such as hydrotreating, cracking, desulfurization, etc. When the mixture is passed over the catalyst, it is important that the gas-liquid mixture is distributed uniformly over the catalyst bed to ensure efficient utilization of the catalyst. Efficient utilization of the catalyst is important for ensuring a uniform rate of reaction, increasing productivity, and yield. This may also allow increased use of catalyst before regeneration or replenishment. Furthermore, in hydroprocessing reactors involving exothermic reactions, uneven distribution of liquid or gas can lead to excess release of heat in certain regions compared to other regions. The high temperatures further accelerate the reaction rate, resulting in development of hot spots in the reactor, reducing the overall catalyst life.

Generally, distribution of gas and liquid over the catalyst bed is achieved using a distributor plate or distributor tray. Typically, a sieve plate distributor plate and a chimney distributor is used to distribute the gas and liquid reactants over the catalyst bed. The sieve tray distributor plate may be a plate with orifices that is placed over the catalyst bed horizontally. Conventional sieve tray distributor plates have orifices on a plate through which liquid and gas flows. Gas and liquid pass through the orifices and enter the catalyst bed. Since the orifices are spread throughout the plate, it helps with distribution of the gas-liquid mixture. However, the distribution of fluid through these plates is even if the plate is not completely level. The plate may go out of level over time, i.e., the plate may get inclined such that one side of the plate may be at a slightly lower level than another side. In such cases, more fluid flows through the portion of the plate that is at a lower level than the portion of the plate that is at a higher level. In other words, the plate is very sensitive to out-of-levelness. Conventional chimney distributors include pipes (called downpipes), which pass through orifices on the distributor plate. The gas enters the downpipes from near the top end of the downpipes and flows downwards through the pipes. The liquid collects over the tray and enters the downpipes through smaller apertures on the side of the downpipe and then flows downwards with the gas. The minimum size of these apertures on the side of the downpipe is about 6 mm. The apertures are susceptible to clogging when the liquid is sludgy, turbid, or has scales, requiring that the distributor plate be removed and cleaned. This increases reactor downtime and increases operational costs.

In addition, conventional distributors require a large number of orifices and specific designs to ensure uniform distribution. If the distributor plate becomes out-of-level, it results in some regions of the catalyst bed receiving more of the gas-liquid mixture than in other regions, making for non-uniform distribution of the fluid over the catalyst bed. In exothermic reactions, if the distributor plate does not provide uniform distribution of fluid to the catalyst bed, for example because of the distributor plate being not level, there is poor heat exchange, which leads to the formation of hot spots in the catalyst bed. This reduces reaction rate and reduces product yield.

The present subject matter overcomes these, and other problems associated with current distributors in downflow reactors. The present subject matter relates to an apparatus for distributing a polyphase fluid mixture over a catalyst bed in a downflow reactor. The apparatus comprises a distributor tray comprising a plurality of distributor units.

In one implementation, a distributor unit comprises an inner tube disposed on an orifice in the distributor tray. The inner tube comprises a first aperture disposed on a side portion of the inner tube to allow liquid to enter the inner tube. A solid insert is disposed in a top portion of the inner tube, the outer diameter of the solid insert being smaller than the inner diameter of the inner tube. The solid insert results in formation of a narrow passage around it in the top portion of the inner tube to allow gas to pass through. An outer tube is disposed concentric to the inner tube forming an annular portion between the inner tube and the outer tube. The outer tube comprises a slot disposed on a bottom portion of the outer tube. The slot allows liquid from the distributor tray to enter the annular portion between the inner tube and the outer tube. A ring-like cover is disposed on a top portion of the inner tube inside the outer tube to enclose the annular portion on the top while leaving the top end of the inner tube open to allow entry of gas. A support structure is disposed on the outer tube at its top portion to extend over the outer tube and a gas inlet is disposed on the support structure to allow gas to enter the distributor unit. The top end of the support structure is covered by a cap plate disposed on the support structure. The gas thus enters the inner tube through the support structure and mixes with the liquid that enters the inner tube through the first aperture. In an example, a venturi insert may be disposed within the inner tube and below the first aperture to further facilitate mixing of liquid and gas.

The apparatus of the present subject matter allows improved distribution of the liquid-gas mixture to the catalyst bed compared to conventional distributor trays. During operation, gas flows via the narrow passage in the inner tube at high velocity causing reduced pressure. This allows liquid entering via the slots in the outer tube to rise in the annular region. Thus, because the liquid flow is dependent on gas flow, the apparatus of the present subject matter has low sensitivity to out-of-levelness of the distributor tray. Hence, even if the distributor tray is not level, fluid flow to the catalyst bed is uniform. The apparatus can be used over a wide range of fluid flow regimes by changing the size of the solid insert in the inner tube. For example, in low gas flow conditions, the narrow passage may be made narrower than in a high gas flow condition, increasing gas velocity and thus providing a greater pressure drop, which increases the amount of liquid entering via slots in the outer tube and the height to which the liquid rises in the annular portion. This increases the dependence of liquid flow on gas flow, even in low gas flow conditions. This is advantageous in low gas flow conditions, as the low pressure can be created in the annular portion using the solid insert, resulting in lower sensitivity to out of levelness. As will be understood, low gas flow conditions and high gas flow conditions may correspond to different gas flow rates used in the reactor, which may depend on reactor configuration and processing parameters.

As the liquid travels first into the slot in the outer tube and then into the first aperture or a second aperture disposed above the first aperture in the inner tube, where the apertures are placed 90° away on a circumference of the inner tube from the slot, solid particles present in the liquid will deposit on the distributor tray. This prevents clogging of the apertures leading to longer use of the distributor tray between maintenance compared to conventional distributors. This reduces reactor downtime and leads to reduced operating costs. The venturi insert disposed in the inner tube allows greater mixing of gas and liquid before the mixture enters the catalyst bed. In an example, there may be a static mixer disposed near the exit of the inner tube, which improves mixing further. The enhanced mixing improves reaction rate and thus the product yield. Furthermore, the apparatus allows even liquid flow exiting the inner pipe even if the liquid flow to the distributor plate is uneven or is pulsed.

In another embodiment, the distributor unit comprises a tube disposed on the distributor tray. A first aperture is disposed on a lower portion of the tube near the distributor tray to allow liquid to enter the distributor unit. A solid insert is disposed within the tube so that a lower portion of thesoliinsert is adjacent to the first aperture. The lower portion of the solid insert has corrugated edges and an upper portion of the solid insert has rounded edges. A cap plate is disposed on a support structure disposed on the tube and a gas inlet is disposed on the support structure to allow gas to enter the distributor unit.

Aspects of the present subject matter are further described in conjunction with the appended figures. It should be noted that the description and figures merely illustrate the principles of the present subject matter. It will thus be appreciated that various arrangements that embody the principles of the present subject matter, although not explicitly described or shown herein, can be devised from the description and are included within its scope. Moreover, all statements herein reciting principles, aspects, and implementations of the present subject matter, as well as specific examples thereof, are intended to encompass equivalents thereof.

FIG.1illustrates an example downflow reactor comprising an example apparatus for distributing a polyphasic liquid mixture, in accordance with an embodiment of the present subject matter. The downflow reactor100comprises a fluid inlet110. The fluid may comprise a mixture of gas and liquid. The fluid passes through an apparatus120for distributing the mixture and enters the catalyst bed130, where catalytic hydroprocessing reactions, such as hydrotreating, cracking, etc., occur. The apparatus120may be a distributor tray140comprising a plurality of distributor units150. In an example, after the reactions are complete, the resulting products may pass through a second apparatus160for distributing the product mixture to a second catalyst bed170. The second apparatus160may be the same as the apparatus120or may be a conventional distributor. The product gas and liquid may be removed from the bottom of the reactor from a gas outlet180and a liquid outlet190.

FIG.2illustrates a top view of a section of an example distributor tray comprising a plurality of distributor units, in accordance with an embodiment of the present subject matter. The distributor tray140comprises a plurality of distributor units150, referred to singly as distributor unit150. The plurality of distributor units150may be disposed in any arrangement on the distributor tray depending on the required flow characteristics. In an example, the plurality of distributor units150may be arranged in a triangular pitch. The distributor unit150comprises an inner tube210and an outer tube220concentric to the inner tube.

FIG.3(a)illustrates a cross-section of an example distributor unit, in accordance with an embodiment of the present subject matter. The distributor unit150comprises an inner tube210disposed vertically on an orifice310of the distributor tray140. The inner tube210comprises a first aperture314disposed on a side portion of the inner tube210at a height above the distributor tray140to allow liquid to enter the inner tube210. In another example, the inner tube210may comprise two first apertures314, with the two first apertures314disposed 180° from each other on a circumference on the inner tube210at the same height. In an example, a second aperture318may be disposed on a side portion of the inner tube210above the first aperture314. In another example, the inner tube210may comprise two second apertures318disposed 180° from each other on the circumference on the inner tube210. In various examples, the first aperture314and the second aperture318may have a circular cross-section or cross-section of other shapes. The apertures314and318may be sized to offer required resistance to liquid flow, depending on the operational characteristics of the reactor100.

A venturi insert322may be disposed within the inner tube210below the first aperture314. In another example, a static mixer (not shown in the figure) may be disposed below the venturi insert322. The static mixer may comprise twisted ribbons, in an example. The inlet to the venturi insert322is placed such that the liquid entering the inner tube210from the first aperture314enters the venturi insert322and further mixes with the incoming gas that comes in from the top of the inner tube210.

A solid insert326may be disposed coaxially on a top portion of the inner tube210. In an example, the solid insert326may be cylindrical in shape with a hemispherical top portion and smooth edges on the bottom portion. The solid insert326forms a narrow passage330around it in the inner tube210, where gas flows with a high velocity and thus creates reduced pressure. The solid insert326may be held in position using support rod328that attaches the solid insert326to the top end of the inner tube210. The support rod328may pass through the inner tube210and the solid insert326to hold the solid insert326firmly. In an example, several support rods328may be disposed at multiple positions around the solid insert326with spacing provided between them to allow inflow of gas. The solid insert326may be disposed so that it is adjacent to an inner slot334on the inner tube210. The inner slot334may be fluidically connected to the narrow passage330. In an example, there may be two inner slots334diametrically opposite to each other. The size of the inner slot334is such that it offers low resistance to fluid flow.

An outer tube220may be disposed on the distributor tray140concentric to the inner tube210forming an annular portion342therebetween. The outer tube220comprises slot338disposed on a bottom portion of the outer tube220and in contact with the distributor tray140. The slot338allows liquid from the distributor tray140to enter the annular portion342between the outer tube220and the inner tube210. In an example, two slots338may be disposed 180° from each other on a circumference of the outer tube210. In another example, the slot338may be disposed at 90° from the first aperture314and the second aperture318. As the liquid travels upward in the annular portion342and horizontally, for example, at 90°, around the circumference of the inner tube210in the annular region, most of the undesired particles or scales get settled on the distributor tray140. This prevents clogging of the first aperture314or the second aperture318. The sizes of the slot338and the diameter of the outer pipe220may be sized to provide calculated resistance for the liquid flow through the annular portion342, depending on the capacity of the reactor100.

A cover346may be disposed on top of the inner tube210inside outer tube220to cover the annular portion342while leaving the top end of the inner tube210open. The cover346may be for example of ring shape. In an example, the solid insert326may be attached to the cover346. A cap plate350may be disposed on a support structure354disposed on the outer tube220. The cap plate350covers the distributor unit150on the top. In an example, the support structure354may be metal rods or bars welded for holding the cap plate350in position above the outer tube220. A gas inlet358may be disposed on the support structure354to allow gas to enter the distributor unit as shown by arrow358.

During operation, liquid accumulates on the distributor tray140forming a liquid level362. Gas enters the distributor unit150via the gas inlet358and enters the inner tube210via the narrow passage330(shown by dotted arrows inFIG.3(a)). As the density of gas is low, the gas path volume is to be reduced to create a pressure drop that can lift the liquid in the annular portion342. The use of solid insert326in the upper region of the inner pipe accomplishes this by creating the narrow passage330. As a result, there is increase in liquid level inside the annular portion342compared to the liquid level on the distributor tray140. Since the inner slot334is fluidically connected to the annular portion342and the narrow passage330, the low pressure is transmitted to the annular portion342and causes a rise in the liquid in the annular portion342to an annular liquid level366, because gas will not flow into the annular portion342as the high velocity in the narrow passage330causes low pressure in the narrow passage330. The liquid in the annular portion342enters the inner tube210via the first aperture314(liquid flow is shown by solid arrows inFIG.3(a)). The presence of the venturi insert322increases the mixing between the gas and liquid. In an example, if the annular liquid level366is high, the liquid may also enter the inner tube210via the second aperture318. If the annular liquid level366rises further, the liquid may enter the inner tube210via a third aperture (not shown in the figure). Any number of apertures of any shape may be disposed on inner tube210to allow liquid to enter. It is preferred that the apertures are immersed in the liquid, otherwise the lower pressure in the annular portion342compared to the pressure in the inner tube210, may not be maintained. For higher liquid flow rates, it is preferred that the liquid passes through the lower end of the inner slot334. However, at the lower end of the inner slot334, because they are close to the narrow passage330, the low pressure in the annular portion342is not affected much even if they are not immersed in liquid. The location of the solid insert326allows for the low pressure region to be created just at the inner slot334and into the annular portion342. This assures low pressure is directly delegated to the annular portion342, without reducing the gas path too much. This is especially advantageous for relatively low gas flow rates.

For low liquid flow rates, the size of an aperture in conventional distributors is very small, which results in clogging of the liquid aperture for sludgy liquids. However, in the present subject matter, since the first aperture314is disposed on the inner pipe210, which is located inside the outer pipe220, the chances of clogging of the aperture is reduced as the particles settle on the tray rather than entering the inner pipe210.

In an example, a pipe-piece structure370may be disposed below the first aperture314and the venturi insert322. The pipe-piece is held in place by means of orifice plate371. The pipe-piece structure370may be disposed on a bottom portion of the inner tube210above the orifice310. The pipe-piece structure370also reduces a cross-sectional area of fluid flow. The shape of the pipe-piece structure370may be any shape that provides a constriction in the fluid flow path in the inner tube210. The pipe-piece structure370is sized to provide calculated resistance to flow and shaped to provide a constriction in the path of fluid flow. The presence of this resistance to flow increases the liquid level in the annular portion342of the distributor unit150. This resistance to liquid flow acts in series to the resistance caused by the first aperture314through which the liquid flows. The outlet of the pipe-piece structure370is shaped to splash the gas-liquid mixture onto the portion below. In a conventional distributor downpipe, for example in a chimney distributor, the minimum size of the aperture for liquid flow is about 6 mm. Further reduction in aperture size to increase resistance to liquid flow in case of low liquid flows is not recommended as it results in clogging of the aperture. The required resistance to flow in the present subject matter is provided by using resistance to flow in the inner tube210by sizing the pipe-piece structure370appropriately without clogging due to the reasons discussed above. In addition, some resistance to liquid flow may also be given by slot338.

The level of liquid in the annular portion342is more stable compared to the liquid level outside the outer pipe220as it is controlled by the gas flow rate. Hence, the amount of liquid entering the inner tube210is more even, without much pulsing, or uneven flow, as the outer pipe220helps in dampening the liquid waves on the tray plate. This results in even flow of liquid into the inner tube210through the first aperture314.

The liquid flow from the annular portion342to the inner tube210is only due to the liquid head in the annular portion342and not because of the low pressure within the inner tube210, as there is no pressure difference within the inner tube210and the annular portion342because there is no or minimal flow of gas through the inner slot334As a result, the liquid flow is only due to the liquid head, which reduces the liquid flow through the second aperture318placed above the first aperture314. This increases the operating range of distributor unit150, as the apparatus120can operate either only through the first aperture314or through both the first aperture314and second aperture318, without much deviation when liquid level passes above the first or second apertures314and318.

As the liquid level depends on the gas flow through the narrow passage330and the resistance offered by the pipe-piece structure370, when the distributor tray140is out of level, an increase in the liquid flow through a distributor unit150that is lower than another distributor unit150, causes lower gas flow through the narrow passage330, as the pressure drop across the plurality of distributor units150is same on a distributor tray140. Because of the presence of the flow resistance due to the pipe-piece structure370, when the distributor tray140is out of level, the distributor units150that are lower send more liquid, resulting in lower gas flow, as the overall pressure drop across the plurality of distributor units150is equal. This leads to less gas flow into the lower distributor unit150, which causes less liquid level to be built up in the annular portion342resulting in lesser liquid flow. Hence, the distributor tray140has lower sensitivity to out-of-levelness.

FIG.3(b)illustrates a top view of a section along the line A-A of the example distributor unit illustrated inFIG.3(a), in accordance with an embodiment of the present subject matter. The outer tube220is disposed concentric to and outside the inner tube210forming the annular region342. The solid insert326is disposed in the inner tube210forming the narrow passage330in the inner tube210. The inner tube210has two inner slots334that open into the annular region342.

FIG.3(c)illustrates a top view of a section along the line B-B of the example distributor unit illustrated inFIG.3(a), in accordance with an embodiment of the present subject matter. The first aperture314is disposed on the inner tube210. Two slots338are disposed on the outer tube220such that the slots338are disposed 180° from each other on the circumference of the outer tube220and at 90° from the first aperture314.

FIG.3(d)illustrates an enlarged cross-sectional view of an example dispersion section374, in accordance with an embodiment of the present subject matter. In an example, a dispersion section374may be disposed below the exit of the inner tube210. The dispersion section374allows the exiting gas-liquid mixture to be spread out before entering the catalyst bed. The dispersion section374may comprise dispersion slots378. The dispersion slots378may be placed at the exit of the inner tube210. In one example, the width of the dispersion slots378may be such that it is equal to the space between them. An upper sieve plate382may be attached below the dispersion slots378, such that there is a height h between the upper sieve plate382and the dispersion slots378. A splash plate384may be placed on the upper sieve plate382, such that the top of the splash plate384is at the same height h, above the top of the upper sieve plate382.

The pipe-piece structure370may be shaped to direct fluids on the splash plate384. The pipe-piece structure370is intended to be used along with splash plate384. As the fluid mixture is directed by the pipe-piece structure370, fluid hits the splash plate384dispersing liquid through the dispersion slots378. A part of the liquid is dispersed and passes through the dispersion slots378. Another part of the liquid passes through the upper sieve plate382and is dispersed on a lower sieve plate320of larger diameter, where it is spread more widely. The lower sieve plate320has sieve plate wall323on the edges with sieve plate slots324. This allows a certain amount of liquid to be held on the lower sieve plate320, allowing uninterrupted flow of liquid

FIG.3(e)illustrates a top view of a section along the line C-C of the example distributor unit illustrated inFIG.3(d), in accordance with an embodiment of the present subject matter. The splash plate384is disposed on the upper sieve plate382comprising sieve orifices325.

FIG.3(f)illustrates the top view of a section along the line D-D of the example distributor unit illustrated inFIG.3(d), in accordance with an embodiment of the present subject matter. The lower sieve plate320comprises sieve plate slots324and lower sieve orifices321. The lower sieve plate320allows the fluid to spread more before it enters the catalyst bed

FIG.4(a)illustrates another example distributor unit comprising the solid insert attached to the cap plate, in accordance with an embodiment of the present subject matter. The solid insert326bis disposed within the inner tube210. The top of the solid insert326bmay be removably attached to the cap plate350, for example using bolts. This allows for replacing the solid insert as required, for processes or reactors that require varying gas flows. For example, for low gas flows, a sold insert326bwith a larger diameter may be used. The dispersion section374may be disposed below the exit of the inner tube210.

FIG.4(b)illustrates a top view of a section along the line A-A of the example distributor unit illustrated inFIG.4(a), andFIG.4(c)illustrates a top view of a section along the line B-B of the example distributor unit illustrated inFIG.4(a), in accordance with an embodiment of the present subject matter. Referring toFIG.4(b), the solid insert326bmay be disposed within the inner tube210. The inner tube210has two inner slots334. The outer tube220is disposed concentric to and outside the inner tube210. Referring toFIG.4(c), the first aperture314is disposed on the inner tube210. Two slots338are disposed on the outer tube220such that the slots338are disposed 180° from each other on the circumference of the outer tube220and at 90° from the first aperture314.

FIG.4(d)illustrates another example distributor unit comprising a static mixer, in accordance with an embodiment of the present subject matter. In another example, the pipe-piece structure370may be disposed below the first aperture314and a static mixer322b. In an example, the static mixer322bmay comprise twisted ribbons. Any other static mixers known in the art may be used. The inlet to the static mixer322bis placed such that the liquid from the first aperture314enters in each of the openings of the static mixer322and mixes with the incoming gas in a series of rotations. The thickness of the ribbon of the static mixer322bmay be varied so that there is no significant pressure loss because of the static mixer322b. The static mixer322bmay be placed near an exit of the inner tube210to create a swirling motion of the gas-liquid mixture exiting the inner tube210.

The pipe-piece structure370may be disposed on a bottom portion of the inner tube210above the orifice310. The pipe-piece structure370reduces a cross-sectional area of fluid flow. The shape of the pipe-piece structure370may be any shape that provides a constriction in the fluid flow path in the inner tube210. The pipe-piece structure370is sized to provide calculated resistance to flow and shaped to provide a constriction in the path of fluid flow. The presence of this resistance to flow increases the liquid level in the annular portion342of the distributor unit150. This resistance to liquid flow acts in series to the resistance caused by the first aperture314through which the liquid flows. The outlet of the pipe-piece structure370is shaped to splash the gas-liquid mixture onto the portion below. In a conventional distributor downpipe, for example in a chimney distributor, the minimum size of the aperture for liquid flow is about 6 mm. Further reduction in aperture size to increase resistance to liquid flow in case of low liquid flows is not recommended as it results in clogging of the aperture. The required resistance to flow in the present subject matter is provided by using resistance to flow in the inner tube210by sizing the pipe-piece structure370appropriately. In addition, the required resistance to liquid flow may also be given by slot338.

FIG.5(a)illustrates a cross-sectional view of another embodiment of the distributor unit comprising one tube, in accordance with an embodiment of the present subject matter. In another embodiment, the distributor unit500comprises a tube510disposed on an orifice514on a distributor tray140. A first aperture518may be disposed on a lower portion of the tube510near the distributor tray140to allow liquid to enter the distributor unit500. In an example, there may be two first apertures518disposed at 180° from each other on a circumference of the tube510at the same height. A solid insert522may be disposed within the tube510so that a lower portion of the solid insert522is adjacent to the first aperture518. The lower portion of the solid insert522may have corrugated edges526and an upper portion of the solid insert522may be hemispherical or may have rounded edges530. The solid insert522may be held in position using support rod528that attaches the insert to the tube510. The support rod528may pass through the tube510and solid insert522to hold the insert522firmly. The support rod528may be present at multiple positions around the solid insert522while leaving sufficient space for allowing flow of gas and liquid. A cap plate534may be disposed on a support structure538, the support structure538being disposed on the tube510. A gas inlet542may be disposed on the support structure538to allow gas to enter the distributor unit500. The distributor unit500may comprise a second aperture546disposed on a portion of the tube510above the first aperture518. The second aperture546allows liquid to enter the tube510. A top slot550may be disposed near a top portion of the tube510to allow liquid to enter the tube in cases where the liquid level554on the distributor tray140becomes high or increased flow conditions.

In an example, the first aperture518may be disposed 1 to 4 inches above the distributor tray140. The first and second apertures518and546may be sized as to offer required resistance to liquid flow, depending on the operational characteristics of the reactor. The solid insert522effectively reduces the flow path, creating a passage562between the solid insert522and the tube510. The feed gas passes through the passage562at high velocity creating low pressure in the region. Liquid from the distributor tray140is pulled to this low pressure region and the corrugated edges526result in increased mixing with the gas.

An orifice insert558may be disposed at the exit of the tube510, which reduces the flow area, thereby enhancing mixing of gas and liquid. In an example, the orifice insert558may be disposed 1 to 3 inches below the solid insert522. In an example, the orifice514may be part of the orifice insert558, and in this case the orifice514may be disposed higher or lower in the tube510and may be different from a tray orifice where the tube510is attached to the tray140. In another example, a venturi insert may be disposed below the first aperture518. In an example, the dispersion section374as discussed above may be disposed below the exit of the tube510. The distributor tray140comprising a plurality of distributor units500may used to distribute a gas-fluid mixture in a reactor.

FIG.5(b)illustrates a top view of a section along line A-A of the example distributor unit shown inFIG.5(a), in accordance with an embodiment of the present subject matter. The solid insert522is adjacent to the two first apertures518, the two first apertures518disposed at 180° from each other on the circumference of the tube510.

During operation, the low pressure in the passage562causes liquid to be pulled into the tube510via the first aperture518. As a result, the driving force for liquid flow is increasing gas velocity compared to liquid head above the tray140. This can help in providing a lower requirement of the height of the distributor unit500for the same sensitivity to out-of-levelness.

The volumetric flow rate of liquid is given by

Where, H=liquid height above the lowest aperture,
QL=is volumetric liquid flow rate
QG=volumetric gas flow rate
f(H0.5) is a function of h0.5
g(QL) is an another function of QL

When the tray140is out-of-level, the lower distributor unit passes more liquid due to the increased height. This causes less gas to flow through that particular distributor unit, which in turn lowers the amount of liquid passing through the distributor unit as the pressure drop is reduced due to lower gas flow. Thus, as the liquid flow depends on increasing gas velocity, the distributor apparatus has lower sensitivity to out of levelness.

EXAMPLES

The disclosure will now be illustrated with working examples, which are intended to illustrate the working of disclosure and not intended to take restrictively to imply any limitations on the scope of the present disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice of the disclosed methods and compositions, the exemplary methods, devices and materials are described herein. It is to be understood that this disclosure is not limited to particular methods, and experimental conditions described, as such methods and conditions may apply.

The following is to illustrate the advantage of using the solid insert326in the distributor unit150comprising the inner tube210and the outer tube220. This was compared to a conventional distributor tray without a chimney distributor unit. The distributor trays are subject to be out-of-level with the horizontal, such that the higher distributor is 1 cm above the lower distributor. The sensitivity due to 1 cm out of levelness is defined as:

where, Qlowis volumetric liquid flow through lower distributor unit, and Qhighis volumetric liquid flow rate through higher distributor unit.

Table 1 shows a comparison of the sensitivity to out of levelness of the distributor apparatus of the present subject matter and conventional apparatus. The sensitivity to out of levelness at high flow rate and low flow rate is the least with the distributor unit of the present subject matter. The addition of the solid insert326and the additional resistances, such as venturi insert370, reduces the sensitivity further.

TABLE 1Comparison of sensitivity to out of levelnessof different distributor apparatus.Sensitivity at 0.8Sensitivity at 0.4cm/s (%)cm/s (%)Distributor unit without solid insert6.920and venturi insertDistributor unit with solid insert at4.515upper regionDistributor unit with solid insert at3.18upper region and orifice or otherpressure resistances in inner tubebelow liquid inlet.

The following is to illustrate the different benefits of the distributor unit150with an inner tube210and outer tube220, is compared with a conventional chimney distributor. The distributor trays are subjected to be out of level with the horizontal, such that the higher distributor is 1 cm above the lower distributor. The sensitivity due to 1 cm out of levelness is defined as

where, Qlowis volumetric liquid flow through lower distributor unit, and Qhighis volumetric liquid flow rate through higher distributor unit. Low value of sensitivity indicated better performance in uneven conditions of liquid depth on the tray.

FIG.6illustrates the variation in sensitivity with superficial velocity for example 2, in accordance with an embodiment of the present subject matter. The operational superficial velocity of liquid in typical hydroprocessing reactors ranges between 0.3 to 1.2 cm/s. The solid line610is for the distributor unit150of the present subject matter, the dotted line620is for a standard chimney distributor with a slot opening. The dashed line630shows sensitivity for a conventional chimney distributor with two apertures. The figure shows limit of less than 20% above flow of 0.3 cm/s for the distributor unit150, which is better than the acceptable limit of 20%. This is achieved, due to combined effect of using the solid insert326and additional inserts, such as the venturi insert322and the pipe-piece structure370to give calculated resistance to flow in the inner tube210. In contrast, the conventional distributor does not achieve a sensitivity below 20% for any flow rate and the distributor with two apertures achieves it only at high flow rates above about 0.7 cm/s

Two distributors were compared to illustrate the advantage of having liquid flow depend on gas velocity in addition to the static liquid head. Table 2 shows the values of sensitivity and liquid height for a conventional chimney distributor compared to the distributor unit500comprising tube510. Equalizing the sensitivity, it can be seen that the distributor unit500of the present disclosure has liquid height of 3 cm compared to the conventional chimney distributor. The additional height can be utilized for catalyst bed.

TABLE 2Comparison of sensitivity to out of levelness of a conventional distributorand a distributor of the present disclosure with one tube.Sensitivity at 0.5Liquid height for 0.5cm/s (%)cm/s distributor (cm)Chimney distributor58 cmDistributor with one tube4.93 cmof present disclosure

Although embodiments of the present subject matter are described in language specific to structural features, it is to be understood that the specific features and methods are disclosed as example embodiments for implementing the claimed subject matter.