US3002818A

US3002818A - Process control system

Info

Publication number: US3002818A
Application number: US624843A
Authority: US
Inventors: Donald E Berger
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1956-11-28
Filing date: 1956-11-28
Publication date: 1961-10-03
Anticipated expiration: 1978-10-03

Description

2 Sheets-Sheet 1 Oct. 3, 1961 D. E. BERGER PROCESS CONTROL SYSTEM Filed No?. 28. 1956 A TTORNEVS Oct. 3, 1961 D. E. BERGER PROCESS CONTROL SYSTEM 2 Sheets-Sheet 2 Filed Nov. 28. 1956 RECYCLE ISOBUTANE-l AIR AIR SUPPLY OUTPUT CONTROLLER SERVO AMPLIFIER FTI I |6 I l LI r lp COMPUTER ISOBUTANE ANALYZER OLEFI N PROPANE ISOBU TANE BUTANE PROPYLENE BUTYLEN E ISOBUTANE ANALYZER ISOBUTANE (Cles-Fles) (Cno- FI75) (Cm-Fm) TT INVENTOR.

D. E. BERGER HMM* (M SERVO AMPLIFIER I Lf (C le 7- F les) lISO P175 T L il lila A TTORNE V5 3,tll2,818 PRUCES CUNTRL SYSJI'EM Donald E. Berger, Bartlesville, Ghia., assigner to Phillips Petroleum Company, a corporation oi Delaware Filed Nov. 28, 11956, Ser. No. 624,843 i2 claims. (ci. zsuass) This invention relates to an improved control system for alkylation processes. ln another aspect, it relates to an improved control system for a fractionation column.

The demand for large volumes of high quality gasolines has brought about the development and commercialization of a number of processes for the conversion of nongasoline range hydrocarbons into high octane blending stocks. One of these processes, the alkylation of light olefins, such as propylene and butylenes, with isobutane, using liquid hydrotiuoric acid as the catalyst, has proved to be particularly effective in producing alkylates for aviation and motor fuel blending. As the result of considerable operational experience, this process has now been developed to such an extent that a commercial plant can be controlled by two men per shift to obtain desired product quality with safety. However, a substantial expenditure of laboratory and process engineering time still is required to coordinate the operations and to manipulate the process variables toward the economic optimum.

ln accordance with the present invention, an improved control system for such an alkylation porcess is provided. The combined feed stream to the reactor, which comprises parati-ln and ole'lin hydrocarbons, is analyzed to determine the ratio of isoparaftlns to olens. A ratio controller is provided to adjust the iiow of one or more of the feed streams in response to the analysis ratio so that the iso- 'parahins and olelins supplied to the reactor can be maintained at a desired ratio to obtain optimum economic operation. ln accordance with another aspect of this invention, an improved control system for a fractionation column is provided. This control is based upon analyses of sample streams removed from both the upper and lower regions of the column. The heat and material balances of the column are adjusted in response to these analyses so as to provide two output product streams of desired composition. The alkylation process is also controlled in accordance with this invention to limit the a-mount of non-reactive constituents, such as propane and normal butane in the system.

Accordingly, it is an object of this invention to provide an improved control system for an alkylation process.

Another object is to provide `a control system to adjust ratio of isoparadins to olelins supplied to an alkyln ation reactor.

A further object is to provide a control system for a fractionation column which operates to provide two product streams of desired compositions.

Dther objects, advantages, and features of this invention should become apparent from the following detailed de- United States Patent scription which is taken in conjunction with the accompanying drawing in which:

FIGURE l is a schematic representation of a hydroiluoric acid alkylation process having the control system of this invention incorporated therein.

FIGURE 2 is a schematic representation of an infrared analyzer which can be employed in the control system of FlGURE l.

FGURE 3 is a schematic representation of a second embodiment of the control system which regulates the ratio of isoparal'lins to olelins supplied to the alkylation reactor.

FIGURE Ll is a schematic representation of a computer `which can be employed in the control system of FIG- URE 3.

Referring to the drawing in detail and to FIGURE 1 icc in particular, there is shown an alkyla-tion reactor 10 which has an inlet conduit il. communicating therewith to supply liquid hydrouoric acid. A hydrocarbon feed stream is introduced into reactor lli) through -a conduit l2. An isobutane feed stream is supplied to inlet conduit l2 through a conduit lo. rllhe ilow through conduit 13 is regulated by a rate-of-ilow controller la which adjusts a valve l5. An olefin feed stream, which can be a mixture of propylene and butylenes, for example, is supplied to conduit l2 through a conduit lo. The flow through conduit la is regulated by a rate-of-ow controller .l' which adjusts a valve 18. The alkylation reaction is completed in reactor it) by intimately contacting the hydrocarbons with the hydroiuoric acid catalyst. The hydroilucric acid-hydrocarbon mixture is removed from reactor through a conduit 2l which communicates with a settler 23. The acid phase in settler 23 is withdrawn through a conduit 26 which communicates with an acid puriiication unit 27. All, or a part, of this acid is puriiied in unit 27 by distilling the acid from water and acid soluble oils. The ratio of acid to hydrocarbons supplied to reactor it) is generally controlled at a selected level between approximately 0.211 to 1:1, parts by weight.

The hydrocarbon phase, which contains some soluble hydrotluoric acid, is removed from settler 23 through a conduit 28 which communicates with the inlet of a fractionation column 33 that is operated as a deisobutanizer. Conduit 28 passes through a heat exchanger 29. A heating medium is circulated through exchanger 29 by means of a conduit 3d. The tlow of heating material through conduit 3d is regulated by a temperature controller di which adjusts valve 32 in response to a measurement of the temperature of the duid entering column 33. This insures that the feed stream is supplied to column 33 at substantially a constant temperature.

Column 33 is operated so as to separate the isobutane and lighter components from normal butano and the alkylate product. The normal butane and allrylate product are withdrawn as a kettle product `from column 33 through a conduit The rate of withdrawal of kettle product is regulated by a liquid level controller 36 which adjusts a valve 37 so as to maintain a constant liquid level in column Column 33 is provided with a reboiler 7d. A. heating medium is circulated through reboiler 7o by means of a conduit 'il which is provided with a rate-of-tlow controller 72 ti at adjusts a valve 73. The isobutane and lighter hydrocarbon components and soluble hydrotluoric acid are removed from the top of column 33 through a conduit itl which communicates with an accumulator l2 through a condenser dl. The flow through conduit dil is controlled by means of a pre sure controller t3 which adjusts a valve 44. A by-pass conduit is provided around condenser 4l. A pressure controller t7 adjusts a valve do in conduit l5 to regulate the amount `of material condensed and cooled in order to maintain a predetermined pressure in accumulator 4t2.

Hydroliuoric acid which settles out in accumulator 42 can be returned to the reactor system through a conduit 48 which communicates with a conduit Sil, the latter communicating with conduit Zt. Conduit 4S is provided with a valve d? so that the return of acid can be adjusted. The condensed hydrocarbons in accumulator 42 are withdrawn through a conduit 52. A portion of these condensed hydrocarbons is returned to column 33 as reflux through a conduit S3. The ilow through conduit 53 is regulated by a rate-of-low controller 50i which adjusts a valve S5. The remainder of the condensed hydrocarbons Withdrawn from accumulator 42 is directed through a conduit 5d. A portion of this material is directed through a conduit 59 to a second fractionation column SS which is operated as a depropanizer. The iiow through conduit 59 3 is regulated by a rateofow controller 6d which adjusts a valve 61. A heater 57 is provided in conduit 59. Heat is supplied to heater 57 by means of a conduit 63 yand at a rate which is regulated by a temperature controller 62V 'which adjusts a valve. 64. Temperature controller 62 responds to the temperature of the duid passed through conduit 59 so that the feed to column 58 is maintained at a constant temperature.

The major portion of the overhead product from column 33 is returned to reactor 16 through conduits 56, 75, and 12. The rate of liow through conduit d6 is adjusted by a liquid level controllereti which regulates a valve 67 to maintain a constant liquid level in accumulator 42.

Column S8 is operated so as to separate propane and any hydrouoric acid which remains in the system from the unreacted isobutane. A kettle product stream., which comprises principally the unreacted isobutane, is removed from column d through a conduit 75 which communicates with conduit i2. A cooler 76 is provided in conduit 75 to cool the isobutane that is recycled to reactor 1d. The liow through conduit 75 is adjusted by a liquid level controller 77 which adjusts a valve 7d in conduit 75 in response to the liquid level in column 58. Column 58 is providedV with a reboiler 80. A heating medium is circulated through reboiler 80 by a conduit 81 at a rate which is regulated by a temperature controller 82 which adjusts a valve S3 in response to the temperature in the lower region of column 53. The overhead stream from column 53 is removed through a conduit 55 which commnnica'tes with an accumulator S7 through a condenser Se. A pressure controller 93 regulates a valve 94 in conduit 85 so as' to maintain. a predetermined pressure in column 58. Coolant is circulated through condenser 86 by means of a conduit titl. The flow through conduit 9i) is' regulated by a pressure `controller 91 that adjusts a valve 92 to maintain a predetermined pressure in accumulator 37. Any acid which may settle out in accumulator S7 can be returned to the reactor system through conduit' 8S. A valve 3% is provided in conduit 33 to permit adjustment of the rate acid is returned to settler 23. The condensed hydrocarbon liquid in accumulator d'7 is removed through a conduit lill. A portion of this condensed liquid is' returned to column 53 as reflux through a conduit 9S. The tlow through conduit 9d is regulated by a rate-or-tlow controller 96 which adjusts a valve 97. The remainder of the liquid removed from accumulator 37 is directed through a conduit 93 to an acid stripper 95E. The rate of ilow through conduit 9, is adjusted by a liquid level controller ltlil which regulates a valve 106 in conduit 93 so as to maintain a constant liquid level in accumulstor 8'7.

Heat is supplied to the lower region of stripper @9 by means of a reboiler lili. A heating medium is circulated through reboiler 114 by means of a conduit 11;?. A temperature controller 116, which is responsive to the tema perature in the lower region of stripper 99, regulates a valve 117 in conduit 115. Any hydroiluoric acid which is introduced into stripper 99 is vaporized and removed through a `conduit 162 which communicates with accumulator 87. A predetgmined pressure is maintained in stripper 99 by means of a pressure controller 193 which adjusts a Valve 105 in conduit 162. Propane is withdrawn as the kettle product from stripper 99 through a conduit 11i) which has a cooler 111 therein. rlie rate of withdrawal of propane through conduit llo is adjusted 'oy a liquid lever controller 112 which regulates a valve 113 so as to maintain a constant liquid level in stripper 99.

Since the alkylation reaction is a chemical combination of one molecule of isobutane with each molecule of olefin fed into the system, sulcient fresh isobutane must be added to match this consumption and fractionation losses. Also, for the purpose of operatingY the unit so as to produce a maximum amount of high quality product, a

considerable volume of isobutane is recycled Within the unit so that at the reactor inlet' the Volume ratio of' isobutane -to total olens is maintained at a predetermined ratio. This ratio is of the order of 4-6 to l for the maximum economic production of motor fuel constituents, although this ratio Varies with different operations. The control system lof the present invention is provided. to maintain this ratio at a desired value, To this end, a sample of the feed stream l2 to reactor lil is removed through a sample conduit'12t') which communicates with an oletin analyzer 12l and an isobutane analyzer 122. Analyzer 121 provides a first output signal which is representative of the concentration of olefins supplied` to reactor 10. Analyzer 122 provides a second output signal which is representative of the concentration of isobutane supplied to reactor 10. These two output signals are applied as the respective inputs to a ratio controller 123. Ratio controller 123 provides an output signal which resets one of the

liow controllers

14 or 17. in this manner,4 the ratio of isobutane to oleiins supplied to reactor 1t) through conduit 12 is adjusted as necessary to maintain a predetermined ratio. This control can conveniently be made by regulating the isobutane iiow through conduit 13. Con.- troller 123 can be any conventional commercially available instrument which provides an output signal that isa function of the ratio of the two input signals applied thereto, such as, for example, the instrument described in Catalog 20-1 (l945) of the Brown instrument Com,- pany, Philadelphia, Pa. This controller can conveniently operate by pneumatic pressure, for example. By means of this control system the ratio of isobutane to totalV oleins supplied to reactor 1G is maintained at a desired value Jhich. results in the optimum economic production of motor fuel alkylates.

The operation of column' 33 is controlled in accordance with this invention in order to maintain the desired separation between normal butane and isobutane. To this end, a first sample stream is removed from the upper region of column 33 through a conduit 12S which cornmunicates with the inlet of a normal butane analyzer 126. A second sample stream is withdrawn from a lower region of column. 33 through a condut 127 which communicates with an isobutane analyzer 128. Analyzer 126 provides an output signal which is employed to reset rate-of-ow controller S4 on reflux conduit 53. Analyzer 128 provides an output signal which is employed to reset rate-offlow controller 72 which regulates the amount of heating medium supplied to reboiler 76. The concentration of normal butane in the sample stream removed through conduit 125 normally is quite small because column 33 is operated to remove the normal butane through conduit 34. Analyzer 126 provides an output signal which is representative of this concentration. lf normal butane concentration should exceed a predetermined value, for example, rate-of-llow controller 54 is reset so as to open valve v further to increase the redux rate. This serves to decrease the amount of normal butane in the upper region of column 33. Similarly, it is desired that the kettle product contain a minimum amount of isobutane. Analyzer 128 provides an output signal which is representative of the isobutane concentration of the lower region of column 33. If the measured isobutane concentration should increase above a preselected value, for example, analyzer 128 resets rate-of-tlow controller 72 so as to open valve 73 further. This increases the amount of heat supplied to reboiler so as to vaporize more of the iluid in column 33, which results in a greater amount of isobutane being removed as overhead product. It should thus be evident that the two

analyzers

126 and 128 cooperate with one another in a manner so as to accomplish an elcient separation between the normal butane and isobutane in column 33.

For satisfactory operation of the alkylation unit, propane must be removed from the system at the same rate it may be ted into the system by the inlet feed streams.

Vother non-absorbing gas or normal butane. -of cell 143 is to compensate for the radiation absorbed A sample conduit 130 communicates between conduit 56 and the inlet of a propane analyzer 131. This analyzer provides an output signal which is representative of the propane concentration in the stream directed through conduit 56. The output signal of analyzer 131 resets rateof-flow controller 69 so as to regulate the flow rate through conduit 59. If the measured propane concentration should increase, for example, rate-of-iiow controller 60 is reset to open valve 61 further. This allows additional propane and isobutane to be directed to

columns

58 and 99. The propane is eventually removed from the system ai the kettle product from stripper 99. In this manner, a build-up of propane in the alkylation unit is prevented.

The five analyzers employed in the control system of FIGURE 1 can advantageously be infrared analyzers. A suitable analyzer of this type is illustrated schematically in FIGURE 2. A iirst beam of radiation from an infrared source 141i is directed by means of a reflector 141 through a sample cell 145 and a filter cell 144 to impinge upon a first temperature sensitive electrical resistance element 145. A second beam of radiation from source 140 is directed by a reflector 146 through sample cell 143 and a filter cell 148 to impinge upon a second temperature sensitive electrical resistance element 1511.

Cells

143, 144, and 148 are provided with windows 151 that are transparent to the infrared radiation in the region of interest. These windows can be formed of quartz, for example. The sample stream to be' analyzed is in troduced into cell 143 by means of an inlet conduit 152 and is removed through a vent conduit 153. A voltage source 155 is connected across resistance elements 145 and d which are connected in series relationship. The

end terminals of a potentiometer 156 are connected to the respective terminals of voltage source 155. The junction between resistances 145 and 15G', and the contactor of potentiometer 156 are connected to the respective input terminals of a servo amplifier 157. The output of ampliiier 157 is connected to a reversible servo motor 158. The drive shaft of motor 158 is connected to the contactor of potentiometer 156 and to the input of a controller 160. Motor 155 can adjust a dapper valve in controller 160 to establish a pneumatic pressure representative of the motor rotation.

It should be evident that the illustrated electrical cir- -cuit comprises a modified form of alternating current URE 2 is to be employed to detect isobutane in

sample streams

120 and 127, cell 144 can be filled with a pure sample of isobutane. Cell 14S can be filled with air or The purpose by the windows of lter cell 144 and absorption due to other components. The wave lengths of radiation which are absorbed by isobutane are removed from the radiation beam which is directed through lter cell 144. The amount of radiation transmitted through cell 148 and vwhich impinges upon element 150 is a function of the isobutane concentration in sample cell 143. Any change in this concentration changes the ratio of the amounts of radiation impinging upon

elements

145 and 150. Such a change in the electrical resistances of these elements changes the electrical unbalance of the bridge network. The amount of rotation of motor 158 which is needed to restore a balancer-1 condition in the bridge is thus representative of the change in isobutane concentration in sample cell 143. The rotation of motor 15S is applied to controller 160. If controller 160 is a pneumatic instrument, for example, the drive shaft of motor 158 can be connected through suitable mechanical linkages to regulate a flapper valve in controller 160 to adjust the output air pressure. A telemetering potentiometer can d be employed if it is desired to utilize an electrical`con= troller. In any event, controller provides an output signal which is representative of the concentration of isobutane in the sample cell.

When the analyzer in FIGURE 2 is employed as ana# lyzer 126 of FIGURE l, normal butane is positioned in filter cell 144. Similarly, an olefin or a mixture of oleiins to be detected is positioned in filter cell 144 when the analyzer is employed as instrument 121 of FIGURE 1 to measure the concentration of oleins. Sample cell 144 can be filled with propane when the instrument of FIGURE 2 is employed at analyzer 131 of FIGURE 1.

In FIGURE 3 there is shown a second embodiment of the control system of this invention which is particularly useful if it is desired that the feed streams not be comf bined prior to their introduction into the alkylation reactor. In the system of FIGURE 3, the recycle isobutane conduit 654-75 Iand the fresh isobutane conduit 13" are connected to a common inlet conduit 163 of reactor 1li. The olens are introduced into reactor 1G through a conduit 1d.

Sample conduits

164 and 166 communicate between inlet conduit 16 and the inlets of an isobutane analyzer 165 and an olefin analyzer 167, respectively. A third sample conduit 169 communicates between conduit 1.63 and thepinlet of an isobutane analyzer 170i. Isobutane analyzer 165 is provided because there are moderate amounts of isobutane in the olefin feed stream. The output signals of

analyzers

165, 167, and 170, which represent the concentrations of isobutane, oleiins, and isobutane, respectively, are applied to the inputs of a computer network 173. A flow transmitter 158 provides a fourth input signal to computer 173 which is representative of the flow rate through conduit 16'.' A econd iiow transmitter 175 provides a fifth input signal to computer 173 which is representative of the iiow lrate through conduit 163. The computer 173, which can be an analogue or a digital computer, provides an output signal which is representative of the ratio by volume of the isobutane to total olens supplied to reactor 1t). This computer effectively solves the following equation and provides an output signal representative thereof:

Volume of isobutane: (CX65-F158) -l- (Cntr F115) Volume of olens (Gis1-Fmt) where C155 is the isobutane concentration measured by analyzer 165, C170 is the isobutane concentration measured by analyzer 170, C167 is the oleiins concentration measured by analyzer 167, F158 is the rate of flow through conduit 16', and F175 is the rate of flow through conduit 165. In this manner, the desired volumetric ratio between isobutane and olefins to reactor 1t) is maintained by controller 14' being reset by the output signal of computer 173.

A computer 173 which can be employed in the control system of FIGURE Sis illustrated schematically in FIG- URE 4.

Flow indicators

168 and 175 of FIGURE 3 provide electrical output signals representative of the respective measured flows. These input voltages F168 and F175 are applied to the illustrated input terminals. of FIGURE 4. The upper terminal F158 is connected to ground through a potentiometer 151i. The contactor of potentiometer 1S@ is connected through a high value isolating resistor 181 to the input of a summing ampliier 182. Terminal F175 is connected to ground through a potentiometer 153. he contactor of potentiometer 183 is connected through a high value isolating resistor 184 to the input of summing amplifier 182. The contactors of potentiometers 181i and 183 are adjusted by motors 158g and 15317, respectively, which represent the motors 153 of

analyzers

165 and 170, respectively. The motors are connected to the contactors of the potentiometers so as to move upwardly if the analyzer outputs increase and downwardly if the analyzer outputs decrease, thereby to perform the indicated multiplications. The output of amplifier 182 is connected to ground through a potentiometer 186. The second terminal Flea is con nected to ground through a potentiometer 187. The contactor of potentiometer 187 is connected to the input of a servo amplifier 188 which energizes a reversible servo motor 189. Amplifier 18S can be a conventional instrument which compares the input voltage with a reference voltage, converts the difference to a corresponding A.C. signal, and provides an output signal of phase represent-ative of the input signal being greater or less than a reference value. Such an amplifier is described in detail in Electronic Control Handbook, Batcher and Moulic, 1946, page 298. The contactor of potentiometer 187 is adjusted by a motor 158e which represents the output of analyzer 167. Motor 189 is set to move the contactor of potentiometer 186 in a direction to divide the voltage across the potentiometer by the input voltage to amplifier 188. Thus, if the input voltage to amplifier 188 increases, the contactor of potentiometer 186 is moved downwardly to decrease the quotient voltage at the contacter of potentiometer 186. The magnitudes ofthe vari ous voltages are calibrated to provide the indicated output signal. This signal, resets controller 14.

As a specific example of this invention, reactor 1t? is operated at 901 F. and at a sufficient pressure to maintain a liquid state. The ratio of is'obutane to olefins supplied to, reactor 10, based on parts by weight, is six to one. Hydouoric acid of 92 weight per cent purity is employed as the catalyst. This acid is supplied to reactor at a ratio of one-half to one, based on catalyst to hydrocarbon parts by weight. Column 33 is operated at 160 p.s.i.g., 165 F. top temperature, 280 F. bottom temperature, and a reux to feed ratio of two to. one. Column 58 is operated at 285 p.s.i.g., there being a pump, not shown, between

columns

33 and 58, 140 F. top temperature, and 220 F. bottom temperature. The compositions and flow rates through the several conduits are as follows:

Conduit 16 13' 2s at 5s 110 sts-Me Propy1ene.. 2, 021 v.... ...n Propane 9 54 l, 559 l, 569 1,025 544 Butylenes 2, Isobutane 1, 49h 3, 028 17, 536 120 17, 416 20 17, 396 NormalA B tane 2, 341 106 4, 007 2, 447 1, 550 1, 560 .Alkylate..- ....Y 7,460 ,460

The above gures are in barrels per day, based on condensed liquids From the foregoing it should be evidentv that there is provided in accordance with this invention an improved control system for an allrylation unit. By controlling the ratio of reactants fed to the alkylation reactor, it is possible to operate the unit in an automatic manner so as to provide a maximum amount of desired product. While the invention has been described in conjunction withl a particular reaction of isohutane with light olefins, it should be evident that it is not limited to this specific reaction. Also, the fractionation column control system is adaptable to any system wherein is is desired to separate a 'uid mixture into two or more product streams of desired composition.

While the invention has been described in conjunction with a present preferred embodiment, it should be evident that it is not limited thereto.

What is claimed is:

l. In an `allrylation unit wherein a mixture of olefins and isoparafins is contacted by a catalyst in a reactor; a control system to maintain a predetermined ratio of olens to isoparaffins in the hydrocarbon feed to the reactor comprising first conduit means communicating with said reactor to supply olefins, second conduit means `communicating with said reactor to supply isoparains, first `analyzing means to measure the flow of olefins by detecting the concentration of olefins supplied through said rst conduit mea-ns, second analyzing means to measure; the. fiow of isoparaliins by detecting the concentration of isoparafiins supplied through said second conduit means, and means responsive *o said first and second analyzing means toy adjust the fiow through at least one of said conduit means to maintain a predetermined ratio of olefins to isoparains in the hydrocarbon feed to the reactor.

2. In an alkylationl unit wherein a mixture of olefins and isoparafiins is contacted by a catalyst in a reactor; a control system to maintain a predetermined ratio of olefins to isoparafiins in the hydrocarbon feed to the reactor comprising a first conduit communicating with said reactor to introduce the hydrocarbon feed mixture, first conduit means communicating with said first conduit to supply oletins, second conduit means communicating with said first conduit to supply isoparafiins, rst analyzing means to measure the ow of olefins by detecting the concentration of oleins supplied through said iirst conduit, second analyzing means to measure the ow of isoparafiins by detecting the concentration of isoparaliins supplied through said rst conduit, and means responsive to said tirst and second analyzing means to adjust the fiow through at least one of said conduit means to maintain a predetermined ratio of oleiins to isoparains in the hydrocarbon feed to the reactor.

3. ln an alkylation unit wherein a mixture of olefins and isoparafiins is contacted by a catalyst in a reactor, and wherein at least a portion of the unreacted isoparaiiins is separated from the reactor efiluent and recycled to the. reactor;` a control. system to maintain a predetermined. ratio of oleiins to isoparafiins in the hydrocarbon feed to the reactor comprising an inlet conduit com municating with said reactor, first conduit means com.- municating with said inlet conduit to supply olefins, second conduitr means communicating with said inlet conduit to. supply fresh isoparatlins, third conduit means communicating with said inlet conduit to supply recycled isoparaflins, first analyzing means to measure the tiow of oleiins by detecting the concentration of olens supplied through said inlet conduit, second analyzing means to measure the flow of isoparahns by detecting the concentration of isoparafiins supplied through said inlet conduit, and means responsive tol said first and second analyzing means to adjust the flow through at least one of said conduit means to maintain a predetermined ratio of olefins to isoparafins in the hydrocarbon feed to the reactor.

4. In an allcylation unit wherein a mixture of olefins and isoparafiins is contacted by a catalyst in a reactor, and wherein at least a portion of the unreacted isoparafrins is separated from the reactor eiiiuent and recycled to the reactor; a control system to maintain a predetermined ratio of olefinsr to isoparafiins in the hydrocarbon eed to the reactor comprising first conduit means communicating'. with said reactor to supply olens, second conduit means communicating with said reactor, third conduit means. communicating with said second conduit means tol supply fresh isoparafiins, fourth conduit means communicating with said second conduit means to supply recycled isoparatiins, first analyzing means to measure the flow of olefins by detecting the concentration of olefins supplied through said first conduit means, second analyzing means to measure the flow of isoparaflins by detecting the concentration of isoparatlins supplied through said second conduit means, and means responsive to said first and second analyzing means to adjust the fiow through at least one of said conduit means to maintain a predetermined ratio of olefins to isoparains in the hydrocarbon feed to the reactor.

5. In an alkylation unit wherein a mixture of olefins and isoparafiins is contacted by a catalyst in a reactor, and wherein at least a portion of the unreacted isoparains is separated from the reactor eiiiuent and recycled to the reactor; a control system to maintain a predetermined ratio of oleiins to isoparafiins in the hydrocarbon feed to apuesta the reactor comprising tirst'conduit means communicating with said reactor to supply olefins, second conduit means communicating-with said reactor, third conduit means communicating with said second conduit means to supply fresh isoparafiins, fourth conduit means communicating with said second conduit means to supply recycled isoparafiins, rst analyzing means to measure the concentration of olefius in said iirst conduit means, second analyzing means to measure the concentration of isoparains in said second conduit means, first fiow measuring means to measure the ilow through said rst conduit means, second flow measuring means to measure the flow through said second conduit means, and means responsive to saidvrst and second analyzing means and said first and second ow measuring means to adjust the iiow through at least one of said conduit means to maintain a predetermined ratio of olefins to isoparafiins in the hydrocarbon feed to the reactor.

6. Apparatus for separating a fluid mixture of at least two components having different boiling points into tirst and second streams comprising a fractionation column, means to introduce the fluid mixture to be separated into said column, means to supply heat to said column, means to withdraw a kettle product stream from said column, an accumulator, a condenser, means to pass vapors from the upper region of said column through said condenser to said accumulator, means to pass iiuid Afrom said accumulator to said column as reflux, means to withdraw a rst sample stream from the upper region of said co1- umn, rst means to analyze said tirst stream to measure the concentration of the higher boiling component of the mixture being separated, means responsive to said rst means to analyze to adjust the reiiux fiow to maintain the measured concentration of said higher boiling component less than a predetermined value, means to withdraw a seco-nd sample stream from the lower region of said column, second means to analyze said second stream to measure the concentration of the lower boiling component of the mixture being separated, and means responsive to said second means to analyze to adjust the heat supplied to said column to maintain the measured concentration of the lower boiling component less than a predetermined value.

7. Apparatus for separating a iiuid mixture of at least two components having diierent boiling points into first and second streams comprising a fractionation column, means to introduce the iiuid mixture to be separated into said column, means to supply heat to said column, means to withdraw a kettle product stream from said column, an accumulator, a condenser, means to pass vapors from the upper region of said column through said condenser to said accumulator, means to pass fluid from said accumulator to said column as reiiux, means to remove iiuid from said accumulator as a second product, means responsive to the liquid level in said accumulator to regulate the rate of removal of said second product to maintain a predetermined liquid level in said accumulator, means responsive to the liquid level in said column to regulate the rate of withdrawal of said kettle product to maintain a predetermined liquid level in said column, means to withdraw a first sample stream from the upper region oi' said column, first means to analyze said rst stream to measure the concentration of the higher boiling component of the mixture being separated, means responsive to said iirst means to analyze to adjust the reiiux slow to maintain the measured concentration of said higher boiling component less than a predetermined value, means to withdraw a second sample stream from the lower region of said column, second means to analyze said second stream to measure the concentration of the lower boiling component of the mixture being separated, and means responsive to said second means to analyze to adjust the heat supplied to said column to maintain the measured concentration of the lower boiling cornponent less than a predetermined value.

8. An alkylation unit comprising a reactor; means to supply olefins and isoparafiins to said reactor; a iirst fractionation column adapted to separate normal butane and higher boiling constitutents from isobutane and lower boiling constituents; means to pass the reaction products from said reactor to said first fractionation column; a second fractionation column adapted to separate propane and lower boiling constituents from isobutane and higher boiling constituents; means to direct a first part of the overhead product from said first column to said second lcolumn as a rst stream; means to direct a second part of the overhead product from said first column to said reactor as a second stream; means to measure the propane concentrations of the overhead product of said first column; and means responsive to said means to measure to control the ratio of said rst and second streams to maintain the measured propane concentration less than a predetermined value.

9. An alkylation unit comprising a reactor; means to supply oleins and isoparaiiins to said reactor; a first fractionation column adapted to separate normal butane and higher boiling constituents from isobutane and lower boiling constituents; means to pass the reaction products from said reactor to said first fractionation column; means to remove a iirst part of the overhead product from said iirst column as a first stream; means to direct a second part of the overhead product from said iirst column to said reactor as a second stream; means to measure the propane concentration of the overhead product of said irst column; and means responsive to said means to measure to control the ratio of said first and second streams to maintain the measured propane con'- centration less than a predetermined value.

l0. An alkylation unit comprising a reactor; means to supply olefins and isoparafiins to said reactor; a first fractionation column adapted to separate normal butane and higher boiling constituents from isobutane and lower boiling constituents; means to pass the reaction products from said reactor to said first fractionation column; a condenser; a refiux accumulator; means to remove iiuid from the top of said first column and pass same through said condenser to said accumulator; means to return a portion of the liquid in said accumulator to said first column as reux; means to remove a second part of the liquid from said accumulator as a first stream; means todirect a third part of liquid from said accumulator to sa1d reactor at a rate to maintain a predetermined liquid level in said accumulator; means to measure the propane concentration in the liquid removed from said accumulator; and means responsive to said means to measure to control the fiow of said iirst stream to maintain the maelasured propane concentration less than a predetermined v ue.

11. lA11 alkylation unit comprising a reactor, an inlet conduit communicating with said reactor, rst conduit means communicating with said inlet conduit to supply olefins, second conduit means communicating with said inlet conduit to supply isoparaiiins, a fractionation column, means to pass the reaction products from said reactor to said fractionation column, means to supply heat to said column, means to Withdraw a kettle product stream from said column, an accumulator, a condenser, means to pass vapors from the upper region of said column through said condenser to said accumulator, means to pass Huid from said accumulator to said column as reflux, means to withdraw a iirst sample stream from the upper region of said column, first means to analyze said first stream to measure the concentration of the higher boiling component of the mixture being separated, means responsive to said iirst means to analyze to adjust the reflux fiow to maintain the measured concentration of said higher boiling component less than a predetermined value, means to withdraw a second sample stream from the lower region of said column, second means to analyze said, second stream to measure the concentration of the lower boiling component of. the mixture being separated, means responsive to said second means to analyze to ad` just the heat supplied to said column to maintain the measured concentration of the lower boiling' component less than a predetermined value, means to Withdraw a first product stream from said accumulator', means to pass lluid from said accumulator to said reactor, means to measure the propane concentration in the uid Withdrawn from said accumulator, and means responsive to said means to measure to control one of the fluid streams withdrawn from said accumulator to fmaintainthe measured propane concentration less than a predetermined value. l

12. An alltylation unit comprising a' reactor, an inlet conduit communicating with sa'id` reactor, rst conduit means communicating with said inlet conduit to supply olens, second conduit means communicating with said inlet conduit to supply soparainm a fractionation co1- umn, means to pass the reaction products froms'aid reactor to said fractionation column, means to supply heat to said column, means to withdraw a kettle product stream from said column, an accumulator, a condensen, means to pass vapors from the upper region of said column through said condenser to said accumulator, means to pass iiuid from said accumulator to said. column as. reflux, means to withdraw a rst sample stream from the, upper region of said column,l first means to analyze said first stream to measure the concentration of the, higher boiling component of the mixture being sepanated, meansr responsive to said rst means to analyze to adjust the reflux new to maintain the measured' concentration of said higher boiling component less than a predetermined Value, means to Withdraw a' second sample stream from the lower region of said column, second means to analyze said second stream to measure the concentration of the lower boiling component of the mixturev being separated, means responsive to said second means to analyze to adjust the heat supplied to said columnv to maintain the measured concentration of the lower boiling component less than a predetermined value, means to Withdraw a first product stream from said accumulator, means to pass fluid from said accumulator to said reactor, means to measure the propane concentration in the uid 'withdravtni from said accumulator, means responsivev to said means to measure to control one of the fluid streams withdrawn from said accumulator to maintain the -rneas'- ured propane concentration less than a predetermined value, third analyzing means to measurel the flow of olens by detecting the concentration of olens supplie' through said inlet conduit, fourth analyzingmeans to' measure the flow of isoparains by detecting the concentration of isoparains supplied through said inlet conduit, and means responsive to said third and fourth analyzing means to adjust the iow through at least one of said conduit means to maintain a predetermined ratio of olens to isoparans in the hydrocarbon feed to the reactor.

References Cttee in the are of this patent UNITED STATES" PATENTS;

2,518,307 Groebe Aug';l 8,- L95() 2,574,006 Allen e Nov.v 6, 1951 2,602,046 Podbielniak July i, 11952 2,666,691 Robinson'. Ian. 19, 1954 21,696,464 Mathis Dec. 7, 1954 2,726,936 Bornheim Dec. 13,- i955 2,759,032 Dixon Y Aug. 14, 1956 2,780,456 Berwaerts A Feb. 5, 195,7 2,868,216 Robertson Ian: 1-3, 1959 2,872,493 Hann Feb. s, 1959 2,881,235 Vanv Pool Apr. 7,4 1959 OTHER REFERENCES- Brattain: Cal- Oil World` and Petroleum lud, pages 9 17, January/'1943. A

Miller: Project Cyclone, Symposium-1I on REC Techniques, March 15-l6, 1951, N.Y.,v pages 117-123.

Claims

1. IN AN ALKYLATION UNIT WHEREIN A MIXTURE OF OLEFINS AND ISOPARAFFINS IS CONTACTED BY A CATALYST IN A REACTOR, A CONTROL SYSTEM TO MAINTAIN A PREDETERMIEND RATIO OF OLEFIN TO ISOPARAFFINS IN THE HYDROCARBONS FEED TO THE REACTOR COMPRISING FIRST CONDUIT MEANS COMMUNICATING WITH SAID REACTOR TO SUPPLY OLEFINS, SECOND CONDUIT MEANS COMMUNICATING WITH SAID REACTOR TO SUPPLY ISOPARFFINS, FIRST ANALYZING MEANS TO MEASURE THE FLOW OF OLEFINS BY DETECTING THE CONCENTRATION OF OLEFINS SUPPLIED THROUGH SAID FIRST CONDUIT MEANS, SECOND ANALYZING MEANS TO MEASURE THE FLOW OF ISOPARAFFINS BY DETECTING THE CONCENTRATION OF ISOPARAFFINS SUPPLIED THROUGH SAID SECOND CONDUIT MEANS, AND MEANS RESPONSIVE TO SAID FIRST AND SECOND ANALYZING MEANS TO ADJUST THE FLOW THROUGH AT LEAST ONE OF SAID CONDUIT MEANS TO MAINTAIN A PREDETERMINED RATIO OF OLEFINS TO ISOPARAFFINS IN THE HYDROCARBON FEED TO THE REACTOR.