CA1077427A - Fractionating process control system - Google Patents

Abstract

METHOD AND APPARATUS FOR MONITORING LIQUID LOADING
WITHIN A FRACTIONATING PROCESS SYSTEM FOR THE
PURPOSE OF PROVIDING NOVEL CONTROL CHARACTERISTICS
USEFUL THEREIN

ABSTRACT OF THE DISCLOSURE
In accordance with the present invention, liquid load-ings on one or more trays of a fractionating column is monitored to provide a surprisingly useful control characteristic related to the efficiency (or lack thereof) of not only the fractionating column itself but also associated processes linked to the column.
Accurately monitoring the liquid loading within the column is provided by a liquid loading meter means of the present invention positioned within a channel connecting two adjacent trays of the column. In accordance with one aspect of the present invention, the liquid loading meter means includes cooperative baffle means mounted interior of the channel (i) for reducing channel cross sectional flow area and (ii) in conjunction with an upright measuring weir attached at the downstream end of the cooperative baffle means, to provide a repository interior of the channel by which a reservoir of liquid condensate interior of the column can be first collected and then allowed to overflow relative to the measuring weir in a manner that provides useful information as to the liquid loading of the trays within the column. Differential pressure measuring means is also provided with a sensing means in the vicinity of the measuring weir. In turn, the differential pressure measuring means is connected in series to a recording means located external of the column. Result: As overlimit swings in liquid loading occur, corrective action, say via separate process controller means, can be quickly implemented to bring the system back to stable operations.

Description

`' 1~77427 FIELD OF THE INVENTION
____________~______ ~` 2 The present invention relates to an apparatus and 3 method for monitoring liquid condensate flow w;thin a fractiona-4 ting process system, and more particularly, to a method and means ` 5 which utilize the flow rate of liquid condensate between adjacent 6 trays of a fractionating column as a control characteristic of .~ .
7 not only the fractionating column itself but also of associated 8 processes linked thereto.
t' ' 9 BACI~GROUND_OF_THE_INVE~TION
Today's petroleum refinery processes include ~any . ~
11 complex operations, one or more which may require control regu-~i` 12 lation of process streams as a function of measured system 13 parameters.
14 For example, in a hydrocarbon flash distillation ~` 15 process, an intermediate liquid side stream drawn from liguid 16 condensate within a distillation column say, at a withdra~al 17 zone, may be used for a multiplicity of purposes, inter alia, (i) 18 to produce subsequent distillate product with or without 19 downstream liquid-vapor stripping, (ii) to control flow and , 20 hence efficiency of side stream gas recovery column, reboilers 21 and the like, and (iii) to control intermediate recycle 22 circulation of the distillation column itself. Remaining 23 excess liguid condensate within the column is free to cascade 24 down to lower fractionation trays of the column below the withdrawal zone. In providing items (i~-(iii), above, the flow ~ 26 rates of the side streams have been found to be valuable - 27 parameters to be monitorea for control purposes. Ho~ever, 28 experiences also show that as the established withdra~al rate 29 becomes unbalanced vis-a-vis the flow rate of the excess condensate belo~ the withdrawal zone, i.e., "overflash", there 31 can be upsets in the associated processes linked to the with-32 drawal line as ~ell as a reduction in fractionation efficiency .~
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` 1077427 .
::, within the distillation column~ See Schenski, F.G., "The Yalue of Process Control", Oil and Gas Journal, February 18, 1974, and articles cited therein.
In another example, related to operation of crude - distillation columns, optimum operations often require accurate measurement of the liquid condensate flow from fractionating tray to adjacent fractionating tray in the area of the feed entry of each column. Such liquid condensate is commonly termed "overflash" and the entry feed section in this region is called the "flash zone". If the overflash rate is excessive, valuable products (diesel, fuel oil, catalytic cracking unit feed, hydrocracker feed, etc.) can be lost, that is, they can fall to the column bottom and become part of the less valuable residuum.
Excessive overflash can also result in nonsalable residuum if the overhead products are detrimental to the residuum quality. If the overflash rate is too low, on the other hand, then the overhead product can be unsalable due to insufficient fractiona-tion. Insufficient overflash could also result in unacceptable dry trays within the column which, in addition to being inef-ficient for fractionation purposes, also result in a formation of coke particles on the trays. Coke formation impairs-column operation and may require premature column shutdown for coke cleanout.
While instrumentation is available for measuring process parameters adjacent to as well as within the column, response time for such equipment is often inadequate to properly control processing systems tied to the column, at least in the situation where deviation from selected set point limits occurs at a rather rapid rate.

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iO77~z7 OB~ECT OF THE INYENT~ON
An object of the invention is the provision of a novel - system for controlling a fractionation system by which a sur-prisingly useful control characteristic associated with internal condensate liquid loading on one or more trays of the column can be generated by monitoring liquid condensate flow rates between adjacent trays of the column. Once a deviation from acceptable set point limits is detected, control operators can be genera-ted which aid in reestablishing acceptable process control parameters.
SUMMARY OF THE INVENTION
In accordance with the present invention, conventional control parameters within a fractionating system can be augmented to a surprising degree through generation of a liquid loading parameter associated with condensate flow between adjacent trays of a fractionating col D . Such a control parameter is generated by a metering means comprising cooperative baffle means unted interior of a channel connected between adjacent column trays under observation. Purpose of the cooperative baffle means: (i) to reduce the cross sectional flow area of the channel and (ii) in conjunction with upright weir means attached to a remote end - of the baffle means, to provide a repository interior of the channel by which a reservoir of liquid condensate can be first collected and then its rate of overflow relative to the measuring weir monitored whereby liquid loading of the adjacent trays can be determined. The liquid loading parameter is determined, of ;~ course, from nitoring the rate of flow of liquid condensate (from the reservoir) over the measuring weir as determined by , differential pressure measuring means provided in the vicinity of the measuring weir. In turn, differential pressure measuring means is connected in series to a recording means positioned external of the column.

:-~` ~077~27 ~`

Thus this invention provides an article of manufacture for use . within a fractionation column to measure liquid condensate flow interior of said column between adjacent or linked trays connected via channel means, : comprising cooperative frame baffle means connected to upright measuring weir means, mountable within said channel means at a position intermediate said .~ linked trays so as to provide a repository for said condensate in the vicini~y of said measuring weir means, said measuring weir means having a selected height so that flow of said condensate during column operations can be metered as a function of liquid head over a range of rates associated with efficient column operations; said cooperative baffle means being providedwith a hat member mountable above a portion of said cooperative means adjacent to said measuring weir means forming said respository, so as to prevent cascading liquid from falling in the vicinity of said weir means after said article is mounted within said channel means; and said cooperative means being also provided with upright smoothing vanes attached between said portion of said cooperative means adjacent to said measuring weir means and said hat member.
. Preferably, said portion of said cooperative baffle means is a flat, plate me=ber attachable to the side wall of eaid colun~.

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--` 10'779~27 1 In accordance with more detailed apparatus aspects of

2 the present invention, the cooperative baffle means preferably

3 includes a planar floor member mounted across the channel onto

4 which the measuring weir is mounted (preferably at the downstream edge of the latter). The height of the measuring ~eir above the ; 6 floor member is selected so that the rate of flow of a liquid 7 condensate over the measuring ~eir can be calibrated in terms of 8 liquid head on the measuring weir itself. The latter, in turn, 9 is indicated by differential pressure measuring means mounted in the vicinity of the measuring weir. In that way, condensate 11 released over the measuring weir and falling down~ard by gravity 12 to the next ad~acent tray can be easily indicated, such 13 characteristics being accurately indicative of liguid loading on ; 14 the trays as a function of time.
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In accordance ~ith more detailed aspects in the present 16 invention, the downward cascading liquid condensate between 17 ad~acent trays of the column proride valuable processing control 18 parameters when used in association ~ith fractionating control ;, 19 systems, that parameter being useful in controlling not only the flash distillation process interior of the column but also 21 processes exterior of the column. Since the liquid head above 22 the measuring weir is directly proportional to the flow of the 23 condensate over the measuring weir, measurement of the latter can 24 be carried out by differential pressure means including sensor means located in the liquid condensate repository formed within ~,, 26 the channel by introducing the cooperative baffle means across 27 the interior of the latter. The pressure measuring means 28 generates pneumatic signals indicative of liguid head, those 29 signals being recordea by recorder means external of the column.
Thereafter the flow rate is interpreted in terms of liguid 31 loading on the trays. Result: As overlimit trends related to the 32 liquid loading on the trays are noted, corrective action can then 1 be initiated to stabilize system operations, if reguired.
.` 2 FURTHER OBJE_TS_OF_TE3E_INVENTION
3 Further objects and features of the present invention 4 will become readily apparent to those skilled in the art from the following description of improved emboaiments thereof.
6 BRIE~-D~scRIpT2oN-oF-THE-DRAwIN-7 FIG. l is a schematic diagram of a fractioDatinq 8 process system utilizing a liquid loading measuring means of the 9 present invention;
10 FIG. 2 is a top elevation of a distillation column of 11 the system of FIG. l, partially cut away, to illustrate con-: 12 structural features of the liquia loaaing measuring means of the ; 13 present invention;
i 14 FIG. 3 is a section taken along line 3-3 of FIG. 2;
. 15 FIGS. 4 ana 5 are sections taken along lines 4-4 and 16 5-S, respecti~ely, of FIG. 3.
17 FIG. 6 is a side elevation of a crude distillation 18 column, partially cut away, to illustrate a modified liquia 19 loading measuring means of the present invention;
~' 20 FIG. 7 is a section taken along line 7-7 of FIG. 6; and 21 FIG. 8 is a response curve of the modified liquid 22 measuring means of FIGS. 6 and 7.

.~ 24 EMBODIMENTS_QF_THE INVENTION____ Reference should no~ be had to the figures, with 26 particular reference to fractionation system l0 of FIG. l.
27 As shown, fractionation system l0 includes a distil-28 lation column ll. A complex controller means 12 operatively , 29 connects to column ll, ana includes a separate regulation means 13 associated ~ith control of withdra~al zo~e 14 of the column 31 ll. Purpose of the controller 12 and regulations means 13: To 32 optimize and stabilize process variables ~ithin fractionation .~, - : :
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~, ` 10'~74Z7 1 system lO as a functlon of various process parameters as 2 explained in detail below.
3 In describing the operation of distillation column ll, 4 consider the flow of feed, recycle, intermediate, and product streams at various inlet and outlet lines of the column ll, e.g., 6 (i) Feed and recycle streams are seen in FIG. l to he 7 associatea with the lines 17-23 described as shown, while 8 (ii) Intermeaiate and products streams are seen to exit 9 from the column ll at overhead line 24, at medium gasoline draw line 25, at reboiler outlet 26, at bottoms line 27 as well as at 11 side stream draw line 28.
12 As to flow in line 28~ note the usage of a positive 13 flow pump 29 adjacent to the connection of the line 28 to sump 30 14 of the withdrawal zone 14 as well as the employment of a T-junction 31 at the aischarge side of the pump 29 which provide 16 hot oil draw flows in two parallel lines.
17 Junction line 31a carries the hot oil to vapor-liquid 18 stripping system 32, and associated line 31b carries a parallel 19 stream to hot oil circulation system 33. Stripper 32a of the stripping system 32 provides a bottoms stream which becomes jet 21 product via line 34 and passes through a recorder analyzer 35.
22 Circulation system 33 performs two separate functions:
23 (i) aids in the recovery of gas in the associated gas 24 stream process connected to line 31b in the direction of arro~
37; and 2~ (ii) controls the cooling by steam generation of the 27 recycled hot oil draw stream within the secondary circulation 28 networks 38a ana 38b under control of regulation means 13.
29 As a result, the recycled oil reentering the column ll via line 23 can, under normal process conditions, be kept within 31 acceptable process temperature setpoint limits.
32 However, e~perience shows that even with the use of '~ , " 1(~774'~7 1 complex control equipment, such as controller linkages 39 2 connected to controller means 12, the fractionation system lO of 3 FIG. l can still become unbalanced. For example if the . .
4 witharawal rate of hot oil via line 28 is too low (or too high) l 5 efficiency within the column ll can suffer. For example, if the - 6 internal flow of condensate below withdrawal line 28 in the 7 vicinity of feed line 17 (i.e., "flash zone 40") is excessive, 8 overhead, medium gasoline draw and/or hot draw product can be 9 lost. Also, if the "overflash" flo~ becomes insufficient, draw trays of the column can go dry resulting not only in the lo~ering 11 of fractionation efficiency within the column but also leading to 12 the formation of coke particles on the trays, such coke formation 13 further impairing column efficiency.
- 14 In accordance with the present invention, process ~ .:
control parametsrs associated ~ith conventional fractionation 16 system lO of FIG. l can be enhanced to a surprising degree by the 17 generation of liquid loading parameters related to liguid 18 condensate flow from adjacent trays within the fractionation 19 column ll, such as within flash zone 40 adjacent to feed stream line 17 of PIG. l.
21 Such a cont~ol parameter can be accurately generated by 22 liquid loading measuring means 46 of the present invention 23 operationally attached to the column ll ~ithin flash zone 40 as . ., 24 shown in FIG. l.
Briefly, measuring means 46 provides a series of 26 signals: These signals indicate liguid loading on trays 47 by 27 measuring liquid flow therebet~een say via central channel 49 28 depending from tray 47. The signals can also be recorded as a 29 function of time to form histograms at indicating and recording system 44 exterior of the column ll ~hich can be interpreted, and 31 corrective action there dictated taken by human intervention.

32 Noreover the signals developed at system 44 can also be passed _ g _ ' : . -- ' ~ ' ' ' ' ~

~0'~74'~7 .,i .;
1 directly to complex controller means 12 say via complex linkage 2 41 to effect direct changes in the associated process variables, 3 say via selected sets of the linkages 39 connected from the 4 controller 12 to various system lines as well as to separate regulation means 13 say via linkages 39b-39f.
6 FIGS. 2, 3, 4 and 5 illustrate, in more aetail, the 7 liquid loading measuring means 46 of the present invention.
8 In FIGS. 2 and 3, the measuring means 46 is seen to be 9 centrally mounted within channel 49 of the column ll. It ``, 10 includes cooperative but segregated baffle means generally .. `
11 indicated at 50. Cooperative baffle means 50 includes a "hat"
.,, 12 member 52 mountea above planar floor member 53 (FIG. 3).
13 Attached to the planar floor member 53 is a series of parallel 14 smoothing vanes 54. Ad~acent to the smoothing vanes 54 is an upright measuring weir 5S.
16 In PIG. 3 note that channel 49 comprising parallel side 17 walls 56a and 56b is attached to central edges of bifurcated .
i~ 18 fractionation tray 47, each side wall 56a, 56b being fitted 19 within and permanently attached by velding.
Also note that the side walls 56a and 56b have j 21 elongated lips 57 which extend above the tray 47; lower edges 58 22 terminate above the adjacent fractionating tray 48.
; 23 During operations, liquid and vapor traffic passes 24 relative to the trays 47 and 48 of the column ll in the following manner.
26 Vapor traffic from the fractionation tray 48 passes 27 upward to and then through the fractionating tray 47. Of course 28 the liquid traffic is countercurrent to the vapor flo~. It 29 passes downward from the fractionating tray 47 of PIG. l via j 30 metering means 46 and channel 49 in a manner which provides 31 loading data as well as uninterrupted flow between the trays.
32 The flow pattern of the liquid traffic is shown in 1~:)774Z7 1 detail in FIGS. 3 and 4.
2 It should also be noted that substantially all of the 3 liquid between the trays 47 and 48 pass via channel 49 since 4 remaining do~ncomers extending from the tray 47 have been closed to liquid flow as by welding. ~ote also that the liguid on tray 6 47 first passes over lips 57 of channel 49 and then cascades 7 downwardly until contacting broad surface 61 of hat member 52 or 8 if falling in the region B (~IGS. 2 and 4) adjacent the projected 9 intersection of hat member 52 and the side wall of the column ll directly upon upper surface 62 of the floor member 53. The 11 condensate collects on hat member 52; but because of upright wall 12 63 at the far edge of the hat member 52 ~FIG. 4), the liquid 13 ultimately flows toward region B and then onto surface 62 of the 14 floor member 53.
In FIG. 2, it should also be noted that in the region 16 B, floor member 53 is attached not only to channel 49 but also by 17 its end edges to the column ll sar by welding. Result: As shown 18 in FIG. 4, a repository 64 for the liquid condensate can be 19 formed in the vicinity of measuring weir 55 during operations, such repository 64 being formed of (i) segments of the side walls 21 56a and 56b of the channel 49 (FIG. 3), coplanar pro~ections of 22 the side surface of the column ll (FIG. 2) as well as (ii) the 23 measuring weir 55 (FIG. 4).
24 As the reservoir o~ liguia forms, liquid condensate flows over the measuring weir 55. The flow rate of the liquid in 26 the vicinity of the weir 55 -- and hence the loading of the trays 27 -- can be determinea by measuring the liquid head on the weir 55.
28 For the purpose of monitoring head, indicating and 29 measuring system 44 is provided in FIG. 4 to translate different pressures due to the head on the Reir 55 to recordable pneumatic 31 signals. Internally of the column ll, it includes sensing 32 nozzles 66a and 66b positioned at preselected positions in the , .

1~774Z7 1 vicinity of weir 55 and connected via piping 67a, 67b to the 2 exterior of column ll.
3 External elements of indicating and measuring means 44 4 are only functionally illustrated in FIG. 4 since they are readily available from several commercial sources.
6 Briefly, in one embodiment, a pair of fle~ible 7 diaphragms (not shown) is used for sensing elements. These 8 diaphragms are welded to opposite siaes of a rigid steel disc to 9 form a force of balance principle of operation of a dif-ferential cell 65 external of the column, the cell 65 allowing 11 for measuring differential pressures in a range betueen 0 to 5 12 and 0 to 25 inches of water differential existing at the 13 measuring weir 55. ~he output pneumatic signals are generated by 14 a pneumatic translation means within differential cell 65 generally indicated 68, and a purge gas source 69. ~he generated 16 signal proportional to the differentlal pressure, say arranged 17 from 3 to 50 psi is then transmitted to the recording means 70.
18 At the recording means 70 there is generated a histogram of 19 signal amplitude versus time, calibrated to provide flow data of the liquid condensate -- and hence liquid loading on the trays --21 as to be explained below.
22 Note that the sensing nozzles 66a and 66b are 23 positionea to provide an indication of a head height on the weir 24 55. For example, nozzle 66a can be located near the top of the measuring weir 55 ~ithin the repository 64, ~hile second nozzle 26 66b can be located in the vapor zone of the column thus avoiding 27 being submerged within any backup liquid into the vicinity of the 28 weir 55. Note also that nozzle 66a is located do~nstream of 29 smoothing vanes 54. Hence the resulting indication of aifferential pressure at recorder 70 avoids shortcomings caused 31 by turbulence and end effects as the liguid flo~s over the ~eir 32 55.

1(~77427 .
1 FIG. 5 illustrates liquid smoothing occurring in the 2 vicinity of measuring weir 55.
3 In this regard, note that the smoothing vanes 54 are 4 attached on edge, between floor member 53 and hat member 52 in parallel relationship to each other above tray 48 so as to 6 minimize turbulence in the vicinity of measuring pipe 67a ana the 7 weir 55. Thus, not only is turbulence minimizea, but also ; 8 reduced are end effects. Although only three such smoothing 9 vanes 54 are indicatea in ~IG. 5, the number can be increased if -~ 10 process conditions so dictate.
11 Pabrication of the measuring means 46 of the present 12 invention and its implementation in existing ~or new) distil-13 lation columns within petroleum refineries poses no unusual 14 engineering problems except to note that cross sectional flow area of the channel 49 (~hich houses the metering means 46) j 16 directly available to gravity flo~ is reduced by the amount egual ~! 17 to area of the floor member 53. Hence, care must be taken that 18 such reduction does not adversely effect column flo~
19 characteristics.
Usually the metering means 46 of the present invention 21 is fabricated as a subassembly and then attached to channel 49 22 auring shutdown of tbe column. The subassembly uses floor member 23 53 as a founaation to which (i) measuring weir 55 can ~e first 24 attached as by welding follo~ed by mounting of the upright vanes 54 to a more centralized section of its broad surface 62 and then ',1 26 (ii) "free" ends of the vanes 54 can be attached to the 27 undersurface of hat member 52. Result: After being positioned 28 interior of the channel 49, the subassembly is spot~elded, say 29 along contacting surfaces of the column, floor member 53 and hat member 52, as reguired to secure the resulting measuring meter 31 relative to the channel 49 (ana the column ll).
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` 1~774Z7 ~;`
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2 PIGS. 6 and 7 illustrate a modification of the metering 3 means of the present invention useful in monitoring liguid 4 loading of crude distillation units which may have relatively low liguid conaensate flow rates.
6 ~s sho~n in FIG. 6, modified metering means 73 is 7 located interior of truncated channel 74 ~ithin a crude unit 75.
8 Note that channel 74 has been shortened and is no longer of 9 constant cross sectional flow area; instead it is provided with a j 10 larger mean cross sectional flow area at its upper end adjacent 11 to fractionating tray 76, and with a smaller draw pipe 78 (of 12 reduced cross sectional flow area) at its lo~er end.
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13 Cooperative baffle means 80 of the modified means 73 is 14 of similar design and construction as that previously described with reference to PIGS. 2 to 5 except that floor member 81 16 extends fully across the full extent of the crude column 75. For 17 its attachment to pipe 78, it is also provided with an opening 1B 79. Smoothing of the liguid condensate within the metering means 19 is provided by vanes 82. In that way, tur~ulence and end effects at the measuring weir 83, downstream of the smoothing vanes 82 21 are minimized. The l'umbrella effect" provided by hat member 84 22 (FIG. 7) including end wall 84a above the smoothing vanes 82 also 23 aids in this regard.
24 As shown best in FIG. 7, the liquid head of the conden-sate in resulting repository 85 and hence flow rate over 26 measuring weir 83, is provided by measuring and indicating means 27 86. Means 86 includes associated nozzles 87a and 87b interior of 28 the column connected to differential cell 87c exterior of the 29 column. As shown in FIG. 7, the differential cell 87c is connected parallel between recorder 88 and purge gas supply 89.
31 In that wa~, a generated histogram at the recorder 88 (amplitude 32 versus time) can he calibrated to indicate flow rate and hence 1~774Z7 1 liquia loads on the trays.
2 FIG. 8 illustrates a response curve 90 generated by the 3 modified metering means 73 of FIGS. 6 and 7.
4 Note that response curve 90 is nearly linear over a S selected operational flo~ range of interest, 1500-5500 BPD, 6 deviating only slightly from theoretical linear response curve 9l 7 sho~n in phantom line.
~ 8 Such response characteristics seem to be due, at least `~ g in part, to the smoothing of the liquid condensate flow within the repository 85 of FIG. 7 by smoothing vanes 82 prior to 11 overflowing the measuring weir 83; such smoothing of liquid flow 12 also seems to settle into a steady state rather rapidly, allowing 13 for successful implementation via various control parameters of 14 the system as deviations occur. Result: ~igh guality of fractionation within the column, reauced operating costs, as ~ell 16 as good product quality within associated processes.
17 Experience has shown that for a crude aistillation 18 column of a type illustratea in FIGS. 6 and 7, modified metering 19 means 73 of the present invention having the following dimensions and specifications, can provide useful indications by which 21 control parameters can be easily associated.
; 22 Metering means 73 23 Cooperative baffle means 80 `j 24 ~at member 84 5-l/2' x l-l/2' Upright ~all 84a 8" x l-l/2' 26 Floor member 81 lO~ x l-l/2' 27 Smoothing vanes 82 (Number 3) . 28 8" x 2-l/4' x 3/16"
29 Measuring weir 83 3/l6" x 5" x l-l/2' Indicating and Measuring Means 86 31 Differential cell means 87c 32 Pressure differential ranges 0-5 and .

1~779~

:` 1 0-25" of water; static pressures max. 500 psi, 2 Output signal: 3-15 psi . 3 Manufacturer: Foxboro Corporation ' 4 Model lS
Purge Gas Supply 89 6 Pressure Rating: 20 psi .~ 7 Flow Recorder 88 -~ 8 Type: Pneumatic 9 Rhile specified preferred embodiments of the present invention have been hereinbefore described, it should be under-11 stood that the invention is not limited thereto as many varia-12 tions will be readily apparent to those skilled in the art and 13 thus the invention is to be given the broadest possible inter-14 pretation within the terms of the following claims.

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Claims (2)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An article of manufacture for use within a fractionation column to measure liquid condensate flow interior of said column between adjacent or linked trays connected via channel means, comprising cooperative frame baffle means connected to upright measuring weir means, mountable within said channel means at a position intermediate said linked trays so as to provide a repository for said condensate in the vicinity of said measuring weir means, said measuring weir means having a selected height so that flow of said condensate during column operations can be metered as a function of liquid head over a range of rates associated with efficient column operations;
said cooperative baffle means being provided with a hat member mountable above a portion of said cooperative means adjacent to said measuring weir means forming said repository, so as to prevent cascading liquid from falling in the vicinity of said weir means after said article is mounted within said channel means; and said cooperative means being also provided with upright smoothing vanes attached between said portion of said cooperative means adjacent to said measuring weir means and said hat member.

2. The article of Claim 1 in which said portion of said cooperative baffle means is a flat, plate member attachable to the side wall of said column.