US2467174A - Method and apparatus for controlling fractionating columns - Google Patents

Description

April 1949- G. w. WILSON JR 2,467,174

METHOD AND APPARATUS FO R CONTROLLING FRACTIONATING COLUMNS Filed Dec. 12, 1944 2 Sheets-Sheet 1 pa m/@547,

ATTORNEY April 1949 G. w. WILSON, JR 2,467,174

' METHOD AND APPARATUS FOR CONTROLLING FRACTIONATING COLUMNS Filed Dec. 12, 1944 2 Sheets-Sheet 2 Tempura Rocordcr control lor gfmjay uwsmog,

my?Z Z ATTORNEY UNITED STATES PATENT OFFICE METHOD AND APPARATUS FOR CONTROL- LING FBACTIONATING COLUMNS Glenn W. Wilson, Jr., Goose Creek, Tex, assignmto Standard Oil Development Company, a corporation of Delaware Application December 12, 1944, Serial No. 587,849

Claims. (Cl. 202-160) I The present invention is-directed to a method and apparatus for controlling the operation or a iractionating column.

In order to obtain the maximum degree of the throttle valve and the temperature measured on the downstream side will beappreciably lower than the temperature inside the tower; By suitable adjustment of the throttle valve the 'diflerence between the temperature downstream ther can be made sufllciently large to permit the use of temperature-responsive actuating devices to fractionation in a given iractionating column, it 5 control or manipulate almost any kind of a do? is necessary to operate the column at themaxisired device for correcting the condition. mum allowable vapor rate, limited only by the The method of the present invention is practendency of some particular section of the tower ticed with conventional equipment. For examto flood. With the conventional methods of conple, the temperature-responsive device employed trol a designated vapor rate is set as the maximay be of any conventional type such as those mum to which the tower is controlled. .However, shown at pages 1688 and 1689 of the 1934 edition spilling rates will change from time to time, deof Chemical Engineers Handbook, by John H. pending on variations in feed stock composition, Perry, published by McGraw-Hill Company, Inc. operating conditions and the degree of tower These temperature-responsive control members fouling. It is desirable that the approach to can be used to ope te v ves e tly o may flooding ratesbe carefully controlled, as a short be used to control a compressed air supply, which period of upset operation may nullify the gains in turn may be connected to suitable recorders attributable to a marginal increase in vapor rate. and valve controls in the conventional manner. According to the present invention vapor rate The nature oi. the present invention may be is controlled by utilizing the increase in liquid better understood from the following detailed delevel on a selected plate, as flooding begins, either scription of the accompanying drawing, in which to operate a signal to warn the operator or to Fig. 1 is a front elevation partly in section and actuate control valves governing the feed rates partly in diagrammatic form of one type of appaof liquid feed stock and/or vapors from the reratus according to the present invention; and boiler and/or steam to the reboiler and/or fuel 2 i a Similar V f a yp which differs fed to the preheater for the feed stock. Briefly, in the control means. the presentinvention is based on the difference Referring to Fig. 1 0 the drawing in detail, between temperature drop due to the expansion numeral l designates a fractionating column havof vapors passing 'throughan orifice on the one ing plates 2. The liquid to be fractionated is m hand and the temperature drop resulting from a troduced into the column through line 3 after the partial vaporization of a liquid at its bubble passage through a pre r 4, into which the point when the pressure is reduced on the other feed stock-is introduced by way of line 5, pro-- hand. w vided with a control valve 6. The iuel for the In the practice of the present invention test D h is fed in by W y f lin Pr vi e work is conducted on. a given iractionating col- 3 With'a control valve I umh to locate the plate in the column on which The column I is provided with a bottom drawilooding occurs first. -A vapor line is connected of! line 9, 001111801586 reboiler i whi h i into the vapor space above the designated plate, a steam co H and an ov flow we l r conand this line is equipped with athrottle valve ducting ov t the oh sel to provide an adjustable orifice. Downstream upper P of the reboiler i provided with from the throttle valve is a temperature-respon- V line returning, Vapors t e colum sive element of the type nn employed to above the level of the bottoms. The feed line control other devices such as recording to the steam coil is provided with a control valve vice, a signal device,.or a valve. In the normal operation of the tower vapor will pass thrgugh 45 Above a selected plate, which has been deterthe throttle valve and the temperature measured mined to b the plate on which flooding b gins. or on the downstream side will be wlthih a few at leastaplate above that on which flooding begrees of the temperature inside the tower. If, S d adjacent thereto, is a draw-oil line I however, the vapor rate is increased to the point provided with a throttle valve ll. Downstream where flooding occurs, liquid will pass through from the throttle valve is a temperature-responsive element It of any conventional type, as hereinbefore mentioned, which is arranged to actuate a valve IS in a compressed airline 20- The compressed air in this line is used to actuate a temperature recorder 2|, which may be a conven- 24 and 21 the electric 'power may be used to cona 4 tion having been fully described, what I wish to claim as new and useful and to secure by Letters Patent is: a 1. In the operation of a fractionating column to prevent flooding thereof the steps of withdrawing from said column at a point above the location of the plate at which flooding begins, a sidestream of fluid whereby in the normal operation of said tower vapor will flow in said sidestream trol' electrically operated valve l5 in the feed line to heating coil II.

The vapors, after passing through throttle valve ll, may be led off by way of line 28 to a.

fuel burner. In the event a particular downstream pressure is desired rather than some convenient pressure, such as atmospheric or the while when flooding sets in liquid will flow in said sidestream, passing the fluid flowing in said sidestr'eam'through an orifice and utilizing the difference in temperature on the downstream side of said orifice between that prevailing when vapor flows in said sidestream and that prevailing when liquid flows'in said sidestream for setting pressure in a fuel system or the like, it will be desirable to provide an additional throttle valve in line 28. Adjustment of the two throttle valves will permit op ration at any flow rate and pressure differential desired. For example, a drop in pressure from 115 to 45 pounds per square inch gauge in a column for separating isobutane from butane will result in a 40 F. spread between downstream temperatures in branch line it for liquid and vapor,'while a drop from 110 pounds per square inch gauge to atmospheric pressure willincrease the spread to 95 F.

In Fig. 2 the parts corresponding to the same parts in Fig. I bear the same numerals. In this case a resistance thermometer 29 is placed ahead of the throttle valve l1 and a similar thermometer 30 is placed behind the throttle valve. These thermometers are connected in a known way to a differential temperature recorder controller 3| which may conveniently be the yp of instrument marketed by Leeds 8: Northrup. This instrument has a compressed air supply line 32 and a compressed air control line 33. In the latter line is a valve 34 which may be a two, three or four way valve. A line 35 connected with the valve supplies air for a horn 36. A second line 31 supplies air for an air operated valve 15 in steam line I l. .A third line 38 supplies compressed air for operation of air control valve 8 in fuel line 1. A fourth line 39 connected with valve 34 supplies compressed air to air control valve 6 in oil line 5. Thus it will be seen that this embodiment differs from the embodiment shown in Fig. 1 by the employment of air controlledvalves instead of electrically controlled valves. It may be mentioned that control valves of both types are well known onthe market and in common use in various industries. For this reason details of the construction of such valves are deemed unnecessary for this description.

The nature and objects of the present inveninto operation a corrective measure for at least one of the factors which contributes to flooding.

2. In a fractionating column having fractionating plates, in combination, an outlet line arranged between plates of said column above a plateat which flooding begins, means in said outlet for restricting the cross sectional area of the stream of fluid flowing therethrough, temperature responsive means on the downstream side of said restricting means and means actuated by said temperature responsive means for setting into operation at least one corrective measure for flooding in said fractionating column.

3. An apparatus according to claim 2 in which the means actuated by the temperature responsive means is a-signalfor warnin the operator that flooding has begun. 4. An apparatus according to claim 2 in which the fractionating column is provided with a reboiler including a line for conducting heating medium for said reboiler and the means set in operation by the temperature responsive element controls the flow of heatin medium in said line. 5. An apparatus according to claim 2, in which the means set in operation by the temperature responsive element controls the temperature of the material to be fractionated and fed to said fractionating column.

GLENN W. WILSON, JR.

REFERENCES CITED The following referencesare of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,930,166 Gard Oct. 10, 1933 2,081,601 Ridgway May 25, 1937 2,232,840 Clafley Feb. 25, 1941 2,286,864 Luhrs June 16, 1942 2,357,113 Houghland Aug. 29, 1944 2,386,778 Clafl'ey Oct. 16, 1945

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