Vapor-liquid contact tray and downcomer assembly and method employing same

A mass transfer column comprising:

• an external shell defining an interior region open to the flow of vapor and liquid streams;
• a plurality of generally horizontally disposed and vertically spaced apart trays positioned in said open interior region to facilitate contact between the vapor and liquid streams when flowing in the interior region of the column, said trays having an upper surface along which the liquid stream can flow;
• at least one downcomer associated with each of said trays and extending downwardly toward an underlying tray to deliver liquid from the associated tray to the underlying tray, said downcomer having an inlet region through which liquid enters the downcomer and an outlet region through which liquid exits the downcomer, said outlet region of the downcomer being positioned above a liquid receiving area of the underlying tray, said liquid receiving area of the tray extending rearwardly from a forward end thereof at an angle .theta..sub.2 of between approximately 60.degree. and 90.degree. to the vertical;
• a bottom plate closing the outlet region of the downcomer and extending rearwardly from a forward end of the bottom plate at an angle .theta..sub.1 of between approximately 60.degree. and 150.degree. to the vertical, said bottom plate having a plurality of openings through which liquid may flow to exit the downcomer;
• a plurality of spaced apart ramps extending below said downcomer bottom plate in the path of said liquid exiting the downcomer, said ramps comprising a main wall inclined at an angle to a vertical axis of the column and positioned to redirect said liquid exiting the downcomer and impart an at least partially horizontal momentum to the redirected liquid, thereby reducing a vertically downward force with which the redirected liquid impacts the liquid receiving area of the underlying tray;
• a plurality of apertures in said trays through which ascending vapor may flow to interact with the liquid stream flowing across the upper surface of the trays;
• and
• a plurality of valves positioned on and extending above the liquid receiving area of the trays, each of said valves comprising:
• a second aperture distributed in and extending through the liquid receiving area of one of the trays;
• a frame extending above the liquid receiving area of the tray;
• a floating cap moveable within the frame in response to the upward force of vapor flow into the second aperture between a lower position covering said aperture to resist liquid entry therein and a raised position spaced above the tray to permit vapor flow through the second aperture;
• and
• a stationary cap positioned above the floating cap to deflect the downward flow of liquid away from the floating cap.

A vapor-liquid contact tray and downcomer assembly for placement within a mass transfer column to facilitate contact and interaction between ascending vapor and descending liquid, said assembly comprising:

• a plurality of vertically spaced apart trays, each of said trays having an upper surface along which liquid can flow and containing apertures through which vapor can ascend to interact with said liquid on the upper surface;
• at least one downcomer associated with each of said trays and extending downwardly toward an underlying tray to deliver liquid from the associated tray to the underlying tray, said downcomer having an inlet region through which liquid enters the downcomer and an outlet region through which liquid exits the downcomer, said outlet region of the downcomer being positioned above a liquid receiving area of the underlying tray;
• a bottom plate closing the outlet region of the downcomer and having a plurality of openings through which liquid may flow to exit the downcomer;
• a plurality of spaced apart ramps extending below said downcomer bottom plate in the path of said liquid exiting the downcomer, said ramps comprising a main wall inclined at an angle to a vertical axis of the column and positioned to redirect said liquid exiting the downcomer and impart an at least partially horizontal momentum to the redirected liquid, thereby reducing a vertically downward force with which the redirected liquid impacts the liquid receiving area of the underlying tray;
• a plurality of apertures in said trays through which ascending vapor may flow to interact with the liquid stream flowing across the upper surface of the trays;
• and
• a plurality of valves positioned on and extending above the liquid receiving area of the trays, each of said valves comprising:
• a second aperture distributed in and extending through the liquid receiving area of one of the trays;
• a frame extending above the liquid receiving area of the tray;
• a floating cap moveable within the frame in response to the upward force of vapor flow into the second aperture between a lower position covering said aperture to resist liquid entry therein and a raised position spaced above the tray to permit vapor flow through the second aperture;
• and
• a stationary cap positioned above the floating cap to deflect the downward flow of liquid away from the floating cap.

A method for interacting liquid and vapor streams on a vapor-liquid contact tray and downcomer assembly provided in an interior region of a mass transfer column, said assembly comprising a plurality of generally horizontally disposed and vertically spaced apart trays positioned in said open interior region, a plurality of apertures in said trays, at least one downcomer associated with each of said trays and extending downwardly toward an underlying tray, and a bottom plate closing an outlet region of the downcomer, said method comprising the steps:

• (1) directing a liquid stream to one of said trays;
• (2) flowing the liquid stream across said one tray in a first direction;
• (3) directing said liquid stream from said one tray into an inlet region of the associated downcomer and passing the liquid stream downwardly through said associated downcomer;
• (4) discharging the liquid stream in said associated downcomer onto a liquid receiving area of an underlying tray with an at least partially horizontal momentum to reduce the vertically downward force with which the liquid stream impacts the liquid receiving area by directing the liquid stream against a plurality of spaced apart and inclined ramps lying below the bottom plate, whereby said liquid stream is redirected by said ramps to have an at least partially horizontal momentum;
• (5) flowing said liquid stream across said underlying tray in said opposite direction;
• (6) repeating steps (3)-(5) on successive lower ones of said trays;
• (7) directing a portion of the vapor stream upwardly through said apertures in the trays to interact with said liquid stream flowing across the trays;
• and
• (8) directing another portion of the vapor stream upwardly through the liquid receiving area of the underlying tray and imparting an at least partially horizontal momentum to the vapor stream by passing the vapor stream through a plurality of spaced apart valves extending above the liquid receiving area of the trays and each comprising a second aperture distributed extending through the liquid receiving area of one of the trays and a floating cap moveable within a frame in response to the upward force of vapor flow into the second aperture between a lower position covering said aperture to resist liquid entry therein and a raised position spaced above the tray to permit vapor flow through the second aperture, whereby said vapor stream is redirected by said floating cap to impart said at least partially horizontal momentum.