Patent Description:
In downflow reactors, such as downflow reactors, a layer of filtering material is often placed on top of the first catalyst bed to catch particles such as fines and scales. Typically, this layer may be <NUM> to <NUM> (<NUM> to <NUM> inches) thick and reduces the space available for the catalyst to take up. In addition, the filtering material has to be removed and replaced within an operating cycle when solids accumulates within the layer of filtering material or between the filtering material and catalyst bed causing a high pressure drop. In commercial operation,
the feed rates may vary widely (e.g. <NUM> to <NUM>% of design). The challenge is to design a scale collection device that can effectively remove solids from reactor feed streams without reducing catalyst loading and can be easily cleaned and maintained during turnaround.

<CIT> relates to a filtering distributor plate for supplying a fixed bed reactor having a co-current downflow of gas and liquid for the treatment of heavy clogging feeds.

<CIT> relates to a filtering and distribution device for a catalytic reactor.

<CIT> relates to a scale collection and predistribution tray for vessel with downwards two-phase flow.

<CIT> relates to an apparatus for contacting a gas and a liquid.

The invention is in accordance with the appended claims. The invention involves a reactor comprising an upper portion and a lower portion wherein the upper portion contains a scale collection device. The scale collection device is composed of a filtering zone located above a rough liquid distribution tray and wherein a vapor-liquid distribution tray is located below said rough liquid distribution tray and wherein the lower portion contains a catalyst bed. The filtering zone may comprise a single layer or multiple layers of filtering materials having the same or different physical and chemical properties. The filtering zone contains porous ceramic pellets or other materials that achieve a similar function. The filtering materials are enclosed by a cylindrical side wall attached to the bottom plate of the rough liquid distribution tray. The diameter of the cylindrical wall is smaller than that of rough liquid distribution tray. The filtering zone is spaced above the bottom perforated plate of the rough liquid distribution tray by a plurality of spacers or of grating materials so that the holes on the bottom plate of the rough liquid distribution tray is not plugged by the filtering materials. The spacers or gratings sit directly on the perforated plate of the rough liquid distribution tray within the cylindrical side wall. A layer of wire mesh may be placed above spacers or gratings and at bottom of the filtering bed so that the filtering materials will not fall onto the perforated plate of the rough liquid distribution tray. A plurality of chimneys with caps attached to the bottom of the perforated plate of the rough liquid distribution tray for liquid overflow such that the tray can be operated in a wide range of liquid flows while maintaining full of liquid in the filtering zone during operation for maximizing solid removal efficiency. The addition of the caps to the chimneys is for making sure that the overflow liquid must enter the chimneys from a clearance at bottom of the caps close to the tray floor such that it will not bypass the filtering materials for solid removal material.

<FIG> shows the upper portion of a reactor showing a scale collection device located above the distribution trays.

It has now been found that a different arrangement is preferred to filter particles from a feed stream in a downflow reactor. More particularly, a scale collection device is located within an upper portion of a downflow reactor or reactor head for removing solids from feed streams and to increase reactor operating cycle time without any impact on the amount of effective reactor space for catalyst loading. It has also been found that the solid removal efficiency and the effective use of the filtering material for solid removal can be greatly improved by maintaining a certain liquid level within the device to improve uniformity of liquid flow distribution and to reduce liquid flow velocity through the filtering zone. This is achieved by a specially designed scale collection device located within a reactor head. As shown in <FIG>, the scale collection device is constructed with a cylindrical side wall <NUM> and one or multiple layers of filtering materials <NUM> sitting above a rough liquid distribution tray <NUM>. A layer of grating and wire mesh <NUM> may be placed between the perforated plate <NUM> of the RLDT and the filtering bed so that the filtering materials will not fall onto the perforated plate causing the perforations being plugged. Multiple chimneys with caps <NUM> are attached to the perforated plate <NUM> within the cylindrical wall <NUM> for liquid overflow at high feed rates. The filter bed <NUM> contains one or more layers of filtering materials with the same or different physical and chemical properties. There may be a holddown grid at top of the filtering material to keep the filtering material from moving around. The top of cylindrical side wall is notched for controlling liquid overflow around the top of the wall when the filter bed is plugged. The chimneys with caps are extended above top of the filter bed and overflow liquid needs to pass the filter bed before entering into chimneys. The height of the chimneys are designed to maintain a certain liquid level in the scale collection device before liquid overflows through the chimneys. The liquid from the perforated bottom plate and the overflow liquid from the chimneys falls onto a vapor-liquid distribution tray below for redistribution. The chimneys are sized and positioned such that the overflow liquid will not fall onto top of the plurality of distributors on the vapor-liquid distribution tray if the distributors do not have caps above top of the openings for vapor entry.

Gas and liquid enter into the reactor through an inlet distributor <NUM>. The inlet flow stream may be straightened vertically downwards by an orifice plate at top of the distributor. The liquid is distributed across the top of the scale collection device. Gas is separated from liquid in the space between the inlet distributor <NUM> and top of the scale collection device <NUM>. The liquid flows downward through the scale collection device while the gas through an open annular area between the cylindrical side wall <NUM> and reactor head <NUM>. With gas bypassing the filtering material, the pressure drop will not increase even with the filtering material filled with solids.

With this design, the reactor cycle time can be increased by the additional filter bed within top reactor head <NUM> or catalyst loading increased by reducing the filter material on top of the catalyst bed.

The liquid out of the filtering zone is redistributed by the rough liquid distribution tray <NUM> below. Gas and liquid are then distributed through a vapor-liquid distribution tray <NUM> in fluid communication with the rough liquid distribution tray to the catalyst bed. The rough distribution tray <NUM> includes an upper liquid retention baffle <NUM>.

As shown in <FIG>, according to one or more embodiments of the present invention, in order to remove the scales and fines in a liquid stream from within reactor <NUM> is shown an outer reactor shell having a rounded upper portion <NUM>. The lower portion of reactor <NUM> contains a catalyst bed <NUM>. A scale collection device <NUM> is located above a rough liquid distribution tray <NUM> and a vapor-liquid distribution tray <NUM>. In the scale collection device <NUM>, a filtering zone <NUM> is located a small distance above the bottom plate <NUM> that has a series of openings <NUM>. Sections of the grating are placed within the cylindrical side wall <NUM> on the bottom perforated plate <NUM> for supporting the filtering material in filtering zone <NUM>. The grating is mostly open (over <NUM>%) for not restricting liquid flow through the scale collection device to the rough liquid distribution tray <NUM>. The total open area of the perforations <NUM> on bottom plate <NUM> is designed such that a certain liquid level is maintained within the scale collection device at the minimum operating liquid load. The top of cylindrical side wall <NUM> of the scale collection device <NUM> has notches or openings, such as triangular or rectangular openings for liquid overflow in case that the filtering zone is plugged by solids. To prevent the overflow liquid from bypassing the filtering zone without filtration, one or more chimneys with caps <NUM> are attached to the rough liquid distribution tray <NUM>. The chimneys are extended up above the rough liquid distribution tray <NUM> for maintaining a certain liquid level on tray before liquid overflow through the chimneys. The caps on top of the chimneys are spaced a small distance above the perforated plate of the rough liquid distribution tray for liquid entry so that the overflow liquid will not bypass the filtering materials. The chimneys and caps can be designed in various shapes and sizes and it is preferred that the overflow liquid will not fall on the top of the distributors <NUM>. In the example illustrated in <FIG>, there are a total of <NUM> rectangular chimneys and caps <NUM>. Circular or square shape of chimneys and caps may also be used. The liquid from the scale collection device then passes down to the rough liquid distribution tray <NUM> for redistribution to a vapor-liquid distribution tray <NUM>. The gas and liquid from the vapor-liquid distribution tray <NUM> are then pass the catalyst bed <NUM> below. The vapor-liquid distribution tray <NUM> has numerous distributors <NUM> for uniformly distributing gas and liquid across the top of the catalyst bed <NUM>.

The scale collection device <NUM>, the rough liquid distribution tray <NUM> and the vapor-liquid distribution tray <NUM> can be supported by a set of double-truss beams on one support ring attached to the reactor shell <NUM>.

The filter material <NUM> used in the filtering zone <NUM> may comprise pellets, sheets or other configuration of a porous material as known in the art. Preferred materials for the filtering zone are ceramic pellets which have a high internal porosity, such as the products available from Crystaphase Technologies, Inc. , located in Houston, Texas USA. One or more layers of the filtering materials <NUM> with the same or different physical and chemical properties may be used in the filtering zone <NUM>. Other filtering materials may be used. The grating or grating with a wire mesh sheet <NUM> above, upon which the filtering material <NUM> is supported has openings that are smaller than the size of the filter material <NUM>.

With respect to the collection of the solid materials from the liquid, the configuration also reduces the tendency of rough liquid distribution tray <NUM>, and vapor-liquid distribution tray <NUM> being plugged by solids. The quality of liquid distribution through the rough liquid distribution tray <NUM> and vapor-liquid distribution tray <NUM> was also found improved due to the reduced disturbance of liquid on the rough liquid distribution tray <NUM> by the scale collection device <NUM> above.

The filtering materials can be loaded into the scale collection device with various methods such as socket or bucket and removed by vacuum. The device is easy to clean and maintain after the filtering materials are removed during turn-around.

As the entire scale collection device is filled with filtering materials <NUM> and the total void fraction of the filtering materials can be as high as <NUM>%, the device has a high solid removal capacity. The solid removal efficiency is also high due to the special design of the scale collection device with the filtering material mostly submerged in the liquid pool and no liquid bypassing the device without filtration before the device reaches the full capacity of solid removal.

Claim 1:
A reactor comprising an upper portion and a lower portion, wherein the upper portion contains:
a scale collection device (<NUM>);
a rough liquid distribution tray (<NUM>) comprising a bottom plate (<NUM>) having a plurality of perforations (<NUM>);
a vapor-liquid distribution tray (<NUM>);
wherein the scale collection device (<NUM>) is composed of a filtering zone with a filter bed containing filtering materials and is located above the rough liquid distribution tray (<NUM>),
wherein the vapor-liquid distribution tray (<NUM>) is located below the rough liquid distribution tray (<NUM>);
wherein the filtering zone is spaced above the bottom plate (<NUM>) of the rough liquid distribution tray (<NUM>) by a plurality of spacers or of grating materials so that the holes on said bottom plate (<NUM>) are not plugged by the filtering materials of the filter bed;
wherein the scale collection device (<NUM>) comprises a cylindrical side wall (<NUM>) attached to the bottom plate (<NUM>) of the rough liquid distribution tray (<NUM>), and wherein filtering materials (<NUM>) are enclosed by the cylindrical side wall (<NUM>);
wherein the liquid out of the filtering zone is redistributed by the rough liquid distribution tray (<NUM>) to the vapor-liquid distribution tray (<NUM>);
wherein a series of chimneys with caps (<NUM>) are affixed to the rough liquid distribution tray (<NUM>),
wherein the chimneys with caps (<NUM>) are extended above the top of the filter bed (<NUM>);
and the caps (<NUM>) on top of the chimneys are spaced a small distance above the perforated bottom plate (<NUM>) such that overflow liquid in case that the filtering zone is plugged does not bypass the filtering materials (<NUM>).