US3625655A - Acid analyzer - Google Patents

Abstract

A SYSTEM THAT AUTOMATICALLY ANALYZES ACIDITY OR BASICITY OF A CHEMICAL PROCESS STREAM PERIODICALLY. THE SYSTEM CAN HANDLE A PETROLEUM PROCESS STEAM THAT CONTAINS AN ACID-HYDROCARBON OR BASE-HYDROCARBON EMULSION. AT LEAST SOME OF THE HYDROCARBONS ARE GASEOUS UNDER NORMAL AMBIENT CONDITIONS. THE ACID, UNDER SYSTEM PRESSURE, IS SETTLED IN A VERTICAL COLUMN AND SUBSEQUENTLY SAMPLED. THE ACID OR BASIC CONTENT OF THE SAMPLE IS DETERMINED BY A POTENTIOMETRIC TITRATION.

Description

Dec. 7, 1971 F2` A. CULP.. ETAL R. A. CULP., ET AL Dec. 7, 1971 ACID ANALYZER 4 Sheets-Sheet 2 wwm SM m.\ \QM\WWM.\NMWQ N-Qk Mmmm www L W s ,Nmm .wm I n @bmw m, u N win m. Y I www@ H E, Q MQW m @MM E w wwwwm b .NNKBQ \\\Nn 5 Q ww m mw Smw. T. Nv N* m NW m Nkmmw T. n N E, ESQ N. l P S@ T. ww wm nw Q E Smm m Q SNCMQ ntuv Dec. 7, 1971 R A, Cum ETA. 3,625,655

ACID ANALYZER Filed Dec. 2, 1969 4 Sheets-Sheet 5 Dec. 7, 1971 R. A CUL, mL 3,625,655

ACID ANALYZER Filed Dec. 2, 1969 /1 Sllootu-fhuot 4 United States -Patent O 3,625,655 ACID ANALYZER Robert A. Culp, Jr., Lafayette, Ind., and Robert E. Franke, Nederland, Tex., assgnors to Texaco Inc., New York, N.Y.

Filed Dec. 2, 1969, Ser. No. 881,359v Int. Cl. G01n 27/10;C07c 3/14 U.S. Cl. 23-253R 14 Claims ABSTRACT OF THE DISCLOSURE A system that automatically analyzes acidity or basicity of a chemical process stream periodically. The system can handle a petroleum process stream that contains an acid-hydrocarbon or base-hydrocarbon emulsion. At least some of the hydrocarbons are gaseous under normal ambient conditions. The acid, under system pressure, is settled in a vertical column and subsequently sampled. The acid or basic content of the sample is determined by a potentiometric titration.

BACKGROUND OF THE INVENTION Field of the invention This invention concerns a system for use in a petroleum process or other chemical process of like nature. More specifically, it concerns an analyzer that samples an emulsion of titratable material from a petroleum. process which exists under super-atmospheric pressure and where the titratable material is settled out while under pressure before sampling. The system is particularly applicable to the determination of the acidity of alkylation acid.

Description of the prior art While there have been various so-called acid analyzers available in the industry, none of those that are known have been particularly satisfactory in providing quick and accurate results that may be used in connection with the analysis and control of a petroleum process, e.g. the process known as alkylation. Such prior arrangements have not overcome a particular difficulty that relates to the fact that the acid for analysis is in the form of an emulsion under super atmospheric pressure with hydrocarbons mixed therewith and especially the fact that some of the hydrocarbons are gaseous at atmospheric pressure and ambient temperatures. Consequently, depressuring a sample of the process stream tends to cause foaming, cornposition changes, and other problems which have made it impossible to obtain a desirable degree of correlation between conditions in the process and titratable acidity.

SUMMARY OF THE :INVENTION Briefly, the invention relates to a combination for use in a chemical process wherein pH measurements of a constituent portion-of a product stream are desired, and wherein said stream is under super-atmospheric pressure with some of the other constituents being gaseous at atmospheric pressure. The combination includes means for settling a portion of said product stream in an upstanding column under super-atmospheric pressure, and means for sampling said rst-named constituent portion from said column. In the foregoing combination the last-named means comprises an auxiliary path of flow for said rstnamed constituent portion. The path goes from said means for settling back to said stream. The means for sampling said first-named constituent portion also comprises means for isolating and removing a sample from the said auxiliary path.

Once more, briefly, the invention comprises an acid analyzer for use with an alkylation process which includes a recirculation stream having therein a mixture of sulfuric acid with some hydrocarbons that are liquid under super-atmospheric pressure. The said stream is recirculated through a pump.

The invention comprises in combination an opstanding column or chamber for receiving a portion of the above stream, and a irst fluid passage from said stream on the outlet side of said pump to the bottom of said chamber. It also comprises a second fluid passage from the top of said chamber to said stream on the intake side of said pump, and a valve in said first fluid passage for periodically blocking flow of said stream portion to permit settling of said mixture in said chamber.

The invention also comprises an auxiliary iluid passage from the side of said chamber near the bottom of the column to said stream on the intake side of said pump, and a four-Way valve having two positions and being connected to said auxiliary passage. Furthermore, it comprises a bypass conduit for permitting flow in said auxiliary passage when the said four-way valve is in one position, and a sampling conduit for permitting flow in said auxiliary passage when said four-way valve is in the other position.

Additionally, the invention comprises a titration cell, a source of neutral fluid, and conduit means for connecting said source of neutral fluid to said four-way valve and said four-way valve to said titration cell for washing out a sample when said four-way valve is in said one position.

Finally, the invention comprises means for measuring the density of the fluid in said chamber near the bottom of the column when said mixture has settled.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects and benefits o-f the invention will be more fully set forth below in connection with the best mode contemplated by the inventors of carrying out the invention, and in connection with which there are illustrations provided in the drawings, wherein:

FIG. l is a block diagram illustrating the entire system according to the invention;

FIG. 2 is a function timing chart illustrating the actions that are carried out during one full cycle of the analyzer system;

FIG. 3 is a flow diagram illustrating the various fluid handling elements that are employed in a system according to the invention; and

FIG. 4 is a graph illustrating the form of electrical output signals from one potentiometric titration run.

DESCRIPTION OF fTHE PREFERRED EMBODIMENT Ever since the advent of the petroleum process known as alkylation, there has been a need for a precise onstream process analyzer to determine the titratable acidity of the alkylation acid. Heretofore various techniques that measure such physical properties as conductivity, specific gravity, and refractive index have been employed but these have not been successful because of the complex and varying nature of alkylation acid which made it impossible to obtain the required degree of correlation between such variables and titratable acidity. A system according to this invention has made it possible to obtain a reproducible sample and the density, and titration data required for an accurate and reliable determination of acidity.

The total system according to this invention is illustrated in FIG. 1. Also, many of the elements are schematically illustrated in FIG. 3. The process stream is a recycle ow in a sulfuric acid petroleum alkylation process consisting of an emulsion of acid and hydrocarbons.

The hydrocarbons are predominantly alkylate but some normally gaseous hydrocarbons are present. It will be observed in FIGS. 1 and 3 that the process stream flows through a pipe 11, to the suction side of anacid circulating pump 12. Then it is returned to the process from the discharge side of thepump 12 through anotherpipe 13.

It will be noted that the FIG. 1 illustration employs three different types of connecting lines. These are eX- plained by the appended legend.

The analyzer process lines, which are actually pipes for carrying fluid of one sort or another, `are illustrated by solid lines with arrow heads to indicate direction of ow. This is indicated by aline 14 in the legend, which is captioned analyzer process lines.

The electrical lines, which are actually various circuits that may include electronic elements (not shown) are illustrated by dashed lines. This is indicated yby adashed line 15 in the legend.

Finally, the pneumatic lines which are actually conventional pneumatic system pipes for carrying air under superatmospheric pressure, are illustrated by solid lines that are periodically crossed by two short sloping parallel lines. This is indicated by aline 19 in the legend, which is captioned instrument air lines.

It will be appreciated that in the actual system the required electrical power, and instrument air (pneumatic) pressure will be provided as needed. Of course, the air pressure needs to be only that required to operate the appropriate valves. In the case herein described, ninety pounds per square inch instrument air was required. Lower pressures might be satisfactory for other similar situations. Thus, input connections for pneumatic pressure will be made at various points, e.g. as indicated by the instrument air input arrows in FIG. l that are marked with thecaptions 90#1.A.

The illustrated embodiment of this invention may be described beginning with a fluid circuit for tapping off a portion of the recycled acid from an acid settler (not shown) on an alkylation unit (the process). Such a stream is being pumped through the pipes 11 and 13 (FIGS. 1 and 3). In describing the system, it will be noted that the block diagram of FIG. 1 may `be supplemented by reference to the timing diagram illustrated in FIG. 2 as well as by the flow diagram illustrated in FIG. 3. Also, it will be observed that the same reference numbers are employed for the same elements in all three of these gures.

A portion of the recycled acid stream will tend to ow from thehigher pressure pipe 13 through aow line 16 to a pneumatically actuatedvalve 17, that carries the designation V9 in FIG. 1. Fromvalve 17 this portion of the process stream will flow through anotherflow line 18 to asettler 21.

Settler 21 is a vertically mounted chamber having a relatively high length to diameter ratio. It may be made of glass or steel, but if made of steel preferably it should be lined with Teon or a similar material. It has been found that glass, Teflon and similar materials speed up the separation of acid and hydrocarbons.

The portion of the process stream that flows throughsettler 21 is introduced at the bottom of the settler and ows out at the top, as indicated in FIG. 3. From thesettler 21 this stream portion flows through aow line 22 and thence through another pneumatically actuatedvalve 23 into the main acid recycle stream, through aow line 24. As will appear more fully below, whenvalve 17 is closed, ow throughsettler 21 is stopped and acid and hydrocarbons separate.Valve 23 is left open to reduce the settler pressure and provide means of escape for the light hydrocarbons.

At a designated time a portion of the settled, yflat acid is routed from the lower portion ofsettler 21 through aflow line 28 to asampling device 29. From there it is returned through anotherflow line 30 which joins thetiow line 24 on the process stream side of valve 23 (designated V10 in FIG. 1) i.e. connects to the pipe 11. In this manner, under desired conditions (as will be described in more detail below) the at acid fromsettler 21 may be caused to ow through thesample device 29 and returned to the process stream. This is done while the sample is being maintained at essentially the pressure in pipe 11. It may be desirable `under some conditions to reduce the pressure insettler 21 below the pressure in pipe 11, in which case it will be necessary to discharge the flat acid to low pressure recovery facilities (not shown).

Thevalves 17 and 23 are pneumatically actuated. They are controlled by pneumatic pressure supplied through electrically actuated valves 33 (SV4) and 34 (SV6) respectively. It will be noted that there is anelectric line 35 connected to thevalve 33 and similarly anotherelectric line 36 that is connected to thevalve 34. Both of these electric control lines lead to a cam-type,sequence timer 39. This timer is conventional and may take the form of a plurality of cams, e.g. fteen in number, which are driven by a synchronous motor (not shown) and which actuate cam follower actuated, electric switches (not shown). Such switches carry out the desired electrical controls for timing of the different functions. One complete cycle is illustrated in the timing diagram of FIG. 2.

Thesampling device 29 may take various forms. Basically it is capable of segregating a predetermined volume of the titratable constituent and diverting it, along with the proper diluent, into the titration facility. In its simplest form the sampling device might consists of a four-way valve (not shown) and an outside loop (not shown) of specified volume. The valve arrangement would be such that the titratable constituent would flow normally through that loop on the way to pipe 11. Actuating that four-way valve would segregate the material contained in the loop while at the same time aligning it with a diluent supply for washing it out to the titration facility. The volume required in that loop would depend upon the strength of the titratable constituent. For alkylation acid of to 98% acidity, a volume of about 0.2 to 0.3 ml. is required. For acid contents of 40 to 80%, sample volumes of 0.5 to 0.7 ml. are desirable. Varying volumes would -be predetermined as required.

The required sample volume might be provided also by means of internal passages within the aforementioned four-way valve (not shown). In such case it would be necessary to provide a multiplicity of valves (not shown) with passages of different volumes to provide the flexibility desired.

A preferred form of thesampling device 29 is schematically indicated. It is adapted from a commercial valve such as that sold under the trade name Cheminert which is a dual four-way valve. That valve has a common inner slider (not shown) that may be shifted to cause simultaneous connections from two input ports (one for each fourway valve) to one of two output connections, alternatively, in each case. Each of these four-way valves has a fourth port which is connected to one of the alternative output ports, or is cut off.

The preferred arrangement of thesampling device 29 provides for completing a connection (when it is unactuated) to permit ow of acid from thesettler 21 through theow line 28 and through a sample loop 40 (FIG. 3) to theflow line 30 which carries the acid back to the process pipe 11, as described above. Then, when thesampling device 29 is actuated, its internal interport connections are shifted, as indicated above. Consequently, theflow line 28 is connected to theflow line 30 via a bypass loop 41 (FIG. 3). At the same time, thesample loop 40 has one end connected to alow line 44 with the other end connected to a ow line 4S that leads to atitration cell 46. There is a source of neutral wash uid 49 that is then connected so as to wash out the fluid in thesample loop 40, into thetitration cell 46. The neutral wash fluid may be any suitable fluid, such as the ion-exchanged steam condensate indicated in FIG. 1 or the acetone indicated in FIG. 3. Actuation of thesampling device 29 is controlled by a pneumatic valve 50 (SVS-FIG. 1) that is controlled electrically fromcam timer 39.

Titration cell 46 has conventional structure. It includes therewith anotherow line 52 that leads to the cell from an electrically controlled valve 53 (designated SV2 in FIG. 1). Thisvalve 53 controls the flow of a source ofwash water 54 through theline 52. This wash water should be a neutral fluid, and consequently it is indicated in FIG. 1 as being Ion-Exchanged Steam Condensate.

Valve 53 (SVZ) is controlled electrically. This includes an electric circuit that is indicated in FIG. 1 by an electrical line 57 which leads from thesequence timer 39. This permits introduction of wash water for flushing out thetitration cell 46 following each titration operation. The draining of the titration cell during such flushing procedure, is accomplished by means of a syphon arrangement. The syphon includesla flow line 58 that extends from near the bottom of thecell 46 for emptying the liquid. Theline 58 goes from thetitration cell 46 to avalve 59 that has connected to the other side thereof anotherflow line 62 which leads to a source ofvacuum 63. Thus, the fluid fromtitration cell 46 may be syphoned out and discarded through adrain 64.

The titration cell itself is conventional. It includes astirrer 67 for mixing the fluids in the cell during titration, and some means for determining the end point of a titration measurement.

While other means for determining the end point of a titration might be employed, it is preferred to use a potentiometric determination. This makes use of a pair ofelectrodes 68, one of which will be a reference electrode 69 (FIG. 3) while the other is a measuring (or indicator) electrode 70 (FIG. 3). It will be understood that theseelectrodes 69 and 70 together with the liquid solution in thecell 46, create an electric potential that is directly related in amplitude to the acidity pH of the fluid in the titration cell. In the system illustrated, the reference electrode is made of calomel while the measuring (or indicator) electrode is made of platinum-rhodium.

The electrical signal (potential) that is generated between theelectrodes 69 and 70, is carried over a circuit that is indicated by anelectrical line 73 to atitration controller 74. The latter includes an electronic amplifier 75 (FIG. 3) that has provision for amplifying the potential as developed at theelectrodes 68. This is done using a second `derivative circuit, in order to make accurate determination of the end point of the titration. This will be explained below in greater detail in connection with the FIG. 4 illustration.

The titration procedure, of course, involves introduction of a titrant (caustic) fluid 78 that is fed over afluid flow line 79 to a three-way pneumatically controlled valve 80 (V7).Valve 80 is pneumatically actuated by pneumatic pressure that is introduced over a pneumatic line 84 (FIG. l) which connects to an electrically controlled valve 85 (SVS). Whenvalve 80 is actuated, the titrant (caustic) uid 78 will flow throughvalve 80 to fill aburette 86 with titrant, which is preferably sodium hydroxide. Theburette 86 is driven by a synchronous electric motor (not shown) that is controlled by signals from thecam timer 39 and thetitration controller 74, viaelectrical lines 89 and 90 respectively, so as to start and stop a constant rate introduction of titrant from theburette 86 to the tit-ration cell 46.

There is aow line 93 that connectsvalve 80 to thetitration cell 46. This flow line carries the titrant from the burette to the titration cell. It is connected except when the burette is being filled from the supply of titrant (caustic)fluid 78. Thus, when the pneumatic control valve 85 (SVS) is actuated, it causes actuation of valve 80 (V7) and this shifts the connections of this three-way valve 80 to permit titrant (caustic) 78 to be drawn into theburette 86 for filling same.

In order to have desired accuracy in the titration, the appropriate physical elements are maintained at a given constant temperature which is somewhat higher than the maximum expected ambient temperature. This is carried out in any feasible manner, e.g. by havingappropriate housing 96 and 97 (FIG. l) for the various elements along with temperature controls (not shown) as required.

It will be understood that the titration stoichiometrically determines the amount of acid in the sample solution. This involves a conventional titration operation which includes the addition of caustic in a measured amount until the solution reaches a well defined end point.

In the titration operation employed in this invention, the measurement of the quantity of caustic that is added during a titration operation is determined by having the caustic solution introduced by means of a constant rate burette. The -time is then measured, from commencing to introduce the titrant until the end point (neutral condition) is reached. The beginning is easy to determine by means of a switch closure, and the exact end point is accurately determined by means of thepotentiometric electrodes 69 and 70. The potential, i.e. voltage, that is created between these electrodes is measured using a second derivative electronic circuit to note the change in the rate of change of the potential that is developed. The potential which is proportional to the acidity of the solution changes rapidly near the end point and consequently the second derivative provides an accurate indication of the end point.

The foregoing explanation concerning the end point of a titration will be more fully appreciated when it is considered that the solution potential changes relative to the volume of titrant. This potential follows a rising curve which has a slope that goes from zero to a maximum and back to zero as the potential changes. Thus the end point for acidity is at the mid-point of this rising curve where the slope, i.e. the rate of change of the potential, is maximum. In other words, the electrical potential rises as the acidity decreases, and the rate of Change in potential is maximum when the acidic species is depleted. Consequently, this maximum rate of change (slope) in potential marks the end point of the titration. It is most sharply defined by taking the second derivative of the potential since such derivative emphasizes the mid-point on the curve where it is a changeover from an increasing rate to a decreasing rate.

FIG. 4 illustrates a recording of the electrical signal that is obtained during a titration. Thus, in FIG. 4 there is a graph having time as the abscissa, and the second derivative of the voltage as the ordinate. Acurve 99 shows the second derivative of the voltage plotted against the titration time for an actual titration. The titration time is proportional to the quantity of titrant introduced, and such time is measured by first noting the starting point of titration. This is indicated by the caption, with anarrow 100.

The output signals from the electrodes 68 (FIGS. 1 and 3) are amplified using the second derivative amplifier-75 (FIG. 3) so that the output signals produced will clearly indicate the end point of the titration. This appears in FIG. 4 as amajor swing 101 on thecurve 99. This has a caption End Point indicating the middle of theswing 101.

One advantage of the sampling and analysis system according to this invention is its adaptability to computer monitoring and control. Consequently, as is indicated in FIG. l, there is a so-calledcomputer signal conditioner 104 that receives electrical signals from both thesequence cam timer 39 and the titration controller 75. This is illustrated by dashedlines 105 and dashedlines 106 respectively. The output signals from thisconditioner 104 are fed to a computer 110 as indicated.

An important feature of the invention is the combination with the sampling and analysis system of a density measurement made on the flat acid in thesettler 7 21 just -before sampling. This gives density data necessary to compute the titration results of acid concentration determinations since the density varies with acidity and with hydrocarbon content. Thus, there is a density gauge 114 (FIG. 1) that is incorporated physically with thesettler 21, as is indicated in FIG. 1. This gauge may be one like that manufactured by the Industrial Nucleonics Corporation and marketed under the trade name AccuRay. It makes a direct density determination, electronically, of the liuid in the lower portion ofsettler 21.

It is also advantageous to have a reading of the temperature of the fluid insettler 21. Consequently, there is a temperature sensing element 119 (FIG. 1). This is preferably a thermocouple (not shown) so that an electrical signal output is provided which is transmitted over anelectrical line 120 to the computer 110. This also is connected to atemperature section 121 of the recorder 118 over anotherline 122.

It may also be desirable to have a time printer 123 (FIG. 3) which is connected electrically to the titration controller via the output of the amplifier 75. This permits the time of titration to be printed for observation thereof as the cycles of operation are carried out. Also, as indicated only in FIG. 3, there may be aseparate recorder 124 for making a record of the titration output signals from the amplifier 75.

Other auxiliary elements in the system may include those schematically indicated only in FIG. 1, e.g. a manual overrideelectrical switch arrangement 127 and cycle-sequence indicators 128. These are electrically connected to thesequence cam timer 39, as indicated in FIG. l.

OPERATION OF THE SYSTEM In operation, the system goes through a repetitive cycle automatically. It is controlled electrically by a plurality of cams (not shown) that are part of the sequence timer 39 (FIG. l) and are driven at a speed so as to complete one whole cycle in a predetermined time. In the illustrated instance (see FIG. 2) the time period employed is twenty-four minutes. In the alkylation process with which the system of this invention is described, the period of twenty-four minutes is ample. Shorter or longer periods may be used if desired. However, the principles of the operation are the same in any event and consequently reference may be had to the following description relating to steps of a complete cycle.

FIG. 2 illustrates the actions for a complete cycle as carried out under the control of thesequence cam timer 39 which has fifteen active cams (not shown). This is indicated in the chart of FIG. 2 where the third column is headed Cam No. The control function is indicated under the second column headed Function And the valve or relay that controls the function (depending upon its actuation as determined by the cams) is listed under the first column titled Action Thus, the action during a cycle of twenty-four minutes, is illustrated in FIG. 2 in the manner indicated by the appended Notes At the beginning of a cycle two actions are shown, one already in progress. Cam number one controls actuation of the valve SV1 (valve S9) for approximately the first minute of the cycle. At the same time, cam number thirteen is continuing to control actuation of the valve SV6 (valve 34) which in turn actuates the valve 23 (V10), holding it open.

Valve SV1 (59) opens ow lines S8 and 62 and thus actuates thesyphon 63 and consequently drains thetitration cell 46. Shortly before the end of that syphoning time period, number two cam will cause actuation of the valve SV2 (53) to introduce wash fluid for a short time. Next, at the end of the first wash, cam number three will again actuate thesyphon 63 by opening valve SV1 (59) once more. This drains out the first wash fluid. Following a short delay, cam number four will cause actuation of valve SV2 (S3) again, and this will introduce another amount of wash fiuid from thesource 54CII 8 of neutral fluid. At about three minutes, cam number five will cause actuation of valve SV1 (59) once more. Therefore, thetitration cell 46 will be drained again. This time it is drained for a somewhat more extended period in order to 'be sure that it is completely empty prior to commencing a titration operation.

lBefore the last syphoning action just described is completed, i.e. at four minutes from the beginning of a cycle, theburette 86 is relled. This is controlled from the cam number seven which causes actuation of the electrical circuit controls to open the pneumatic valve SV3 (8S). Valve SV3 in turn causes actuation of the valve S0. Thus the 'burette 86 is refilled with titrant fromcontainer 78 prior to the beginning of a titration operation. It may be noted that there is a limit switch (not shown) to keep the burette from overfilling.

Before refilling of the burette is complete, cam number six causes actuation of valve SV2 (S3) once more, and a predetermined amount of neutral fluid, e.g. water-in this case ion-exchangedsteam condensate 54 is introduced intotitration cell 46. At about the same time, cam number eight followed by cam number nine, causes actuation of relays R-2 and R-3 (both not shown) for energizing the elapsed time printer, and for resetting same thereafter so as to be ready for the next timing period (elapsed time of titration).

As indicated above, cam number thirteen is continuing to cause actuation of the pneumatic valve SV6 (34) so that the valve 23 (V10) controlled thereby is held open 1n order to keep process suction pressure on the uid column in thesettler 21 all during the settling time. At the very end of the settling time, i.e. beginning at six minutes of the illustrated cycle, cam number ten causes actuation of a time delay relay TD-1 (not shown) for a short time. This provides a density reading at the end of the settling period. Consequently, this reading pertains to the fiat acid which is standing in thesettler column 21. The reading is determined by thedensity gauge 114.

Next, and right after the valve SV6 (34) which controls valve 23 (V10), is closed, i.e. de-energized (end of the shaded bar opposite cam number thirteen); cams number eleven and number twelve, in that order, cause actuation of valves SV4 (valve 33) and SVS (valve S0) respectively. lConsequently, right after settler column outlet lvalve 23 is closed, theinlet valve 17 is opened to apply pump discharge pressure from the process stream. This causessample loop 40 ofsampling device 29 to be filled with acid that has been settled insettler 21. Immediately thereafter samplingdevice 29 is actuated to cause wash flow throughsample loop 40.

As explained above, actuation of the sampling device 29 (controlled by valve SVS (50)) shifts thesample loop 40 into connection with thesource 49 of wash liuid, and thetitration cell 46. Therefore, the sample is washed into the cell during the time when cam number twelve causes that actuation. At the same time, in preparation for the next sample,settler 21 is flushed by the application of pressure from the pressure side of the process stream inpipe 13. 'Such pressure comes through valve 17 (V9) which is controlled by the pneumatic valve SV4 (33).

The flushing of thesettler 21, at first only goes through the bypass 41 of thesample valve 29 until at about seven and one half minutes in the `total cycle when the cam thirteen causes the valve SV6 (34) to be opened again, which in turn opens the valve 23 (V10). Thereafter, the flushing continues through the whole settler column in parallel with the sample valve, until at about nine minutes in the cycle when cam number eleven causes valve 17 (V9) under control of valve SV4 (33) to be closed again. This commences the next settling.

In the meantime, near the end of the time when the sample `valve 29 under control of valve SVS (S0) is shifted, cam number fourteen actuates a time delay relay (not shown) and another relay (not shown). This starts the introduction of titrant (start of titration) since the sample is fully washed into the titration cell and is being mixed continuously. Also, at the same instant that the introduction of titrant starts,titration controller 74 opera'tes a relay (not shown) that generates a titration started signal which is indicated in the next line below in the FIG. 2 diagram. This signal is sent to computer 110, as well as feeding a parallel signal to printer 1123. The titration runs its course under control of the separate titration controller 74 (FIG. 1) as has been described above. The signals from the operation are applied to the computer, as already indicated.

Although it has no direct relation to the determination of acidity, a cam number fifteen may be used to activate a reading of the density of the emulsion in thesettler column 21. It will be noted that this reading is taken near the end of the time when the inlet Valve 17 (V9) controlled by valve SV4 (33) for thesettler column 21, is open. This is when fresh emulsion from the process stream is owing through the settler in prparation for the next sampling to be titrated. This reading is useful to estimate the ratio of acid to hydrocarbon in the process stream.

As indicated on the last line of the FIG. 2 diagram, there is a titration complete signal that is generated in thetitration controller 74. This signal is sent to the computer 110, as well as feeding a parallel signal to theprinter 123.

An example of a given calculation for determining the acidity following the completion of a titration follows:

Weight percent H2SO4 Volume of Normality Milliequivalent caustic of caustic weight of H2SO4 Weight of acid sample X100 whe re Weight percent H2SO4 Time (sec.) 1/12 (mL/sec.)

0.200 (meq./ml.) X0.04904 (grams/meq.) 0.200 (ml.) XSpecific gravity (grams/ml.) 0.04904X100 Time inseconds 12 Specic gravity Sample calculation Where:

(l) Elapsed time of titration=40l.27 sec. (2) Specific gravity=1.7391

Therefore:

1It is to be noted particularly that the operation of a sampling system according to this invention, permits the periodic sampling of a at acid sample from an alkylation process stream, without running into any of the diiculties that in the past have prevented correlation of sampling variables with titratable acidity. Such difliculties relate to sampling of a stream of iluid that exists in the process under superatmospheric pressure, and that contains an emulsion of an acid with hydrocarbons, some of which are gaseous at atmospheric pressure and normal ambient temperature.

While the foregoing description has been made in considerable detail in accordance with the applicable statutes, it is not to be talken as in any way limiting the invention but merely as being descriptive thereof.

We claim:

1. Apparatus for use in a chemical process wherein acidity and basicity pH measurements of a constituent portion of a product stream are desired and wherein said stream is under super-atmospheric pressure with some of the other constituents being gaseous at atmospheric pressure, the combination of means for settling a portion of said product stream in an upstanding column under super-atmospheric pressure, and

means for sampling said rst-named constituent portion from said column,

wherein said last-named sampling means comprises an auxiliary path of flow for said .lirst-named constituent portion, from said means for settling back to said stream, and

means for isolating and removing a sample from said auxiliary path.

2. The invention according toclaim 1, wherein said means for isolating and removing includes alternative paths in said auxiliary path of How means for connecting a wash uid to one of said alterna-` tive paths, and

valve means for switching said auxiliary path of llow from one to the other of said alternative paths.

3. The invention according toclaim 2 further including a titration cell.

4. The invention according toclaim 2 wherein said product stream flows through a pump that increases the amount of pressure, and

further including a path of llow from said product stream on the discharge side of said pump to the bottom of said upstanding column.

5. The invention according toclaim 4 further including valve means in said last-named path of ow.

6. Apparatus for use in a chemical process wherein acidity or basicity pH measurements of a constituent portion of a product stream are desired and wherein said stream -ows through a pump that increases the amplitude of super-atmospheric pressure on said stream with at least some of the other constituent portions being gaseous at atmospheric pressure, the combination of an upstanding column or chamber having interior walls of material that is impervious to the constituents of said stream,

a rst path of How from the discharge side of said pump to the bottom of said chamber including a `first valve therein for periodically blocking said Ifirst path,

a second path of flow from the top of said chamber to the intake side of said pump including a second valve therein for periodically blocking said second path,

an auxiliary path of flow from in between the top and bottom of said chamber to the intake side of said pump including a sampling valve for periodically diverting a sample of said constituent following a settling thereof in said chamber, and

a titration cell for receiving the said constituent sample in order to make the desired pH measurement of acidity or basicity.

7. An acid analyzer for use with a petroleum process including a process stream having therein an emulsion of an acid with some hydrocarbons that are liquid under super-atmospheric pressure, comprising in combination means for passing a portion of said stream through an upstanding column under said super-atmospheric pressure,

means for periodically blocking flow of saidstream 1 1 portion in said column to permit said emulsion to separate in said column,

means for sampling and titrating some of the settled acid from said column, and

means for measuring the density of the settled acid in said column.

8. An acid analyzer according toclaim 7 wherein said petroleum process is an alkylation process and said stream is a recirculation of an acid hydrocarbon mixture through a pump.

9. An acid analyzer according toclaim 8 wherein said means for passing a portion of said stream, comprises a first fluid passage from the stream on the outlet side of said pump to the bottom of said upstanding column and a second uid passage from the top of said column to the stream on the intake side of said pump.

10. An acid analyzer according toclaim 9 wherein said means for periodically blocking flow, comprises a valve in said 'first lluid passage.

11. An acid analyzer according to claim 10 wherein said means for sampling and titrating, comprises an auxiliary uid passage from in between the top and bottom of said column to the stream on the intake side of said pump, and

means for diverting a sample of the settled acid into a titration cell.

:12. An acid analyzer according to claim 11 wherein said means for diverting a sample comprises valve means associated with said auxiliary fluid passage,

a bypass conduit for permitting flow in said auxiliary passage when said valve means is actuated to one position,

a sampling conduit for permitting flow in said auxiliary passage when said valve means is actuated to another position, and

means for depositing a sample from said sampling conduit into said titration cell.

13. An acid analyzer according to claim 12` wherein said valve means associated comprises a four-way valve, and

means for connecting said bypass conduit and said sampling conduit thereto, and

wherein said means for depositing comprises a source of neutral fluid, and

means for connecting said source to said titration cell via said four-way valve.

14. An acid analyzer for use with an alkylation process including a recirculation stream having a mixture of sulfuric acid with some hydrocarbons that are liquid under super-atmospheric pressure, said stream being recirculated through a pump, comprising in combination.

an upstanding column or chamber for receiving a portion of said stream,

a rst fluid passage from said stream on the outlet side of said pump to the bottom of said chamber,

a second fluid passage from the top of said chamber to said stream on the intake side of said pump,

a valve in said first fluid passage for periodically blocking flow of said stream portion to permit settling of said mixture in said chamber,

an auxiliary fluid passage from the side of said chamber near the bottom of the column to said stream on the intake side of said pump,

a four-way valve having two positions and being connected to said auxiliary passage,

a bypass conduit for permitting iiow in said auxiliary passage when said four-way valve is in one position,

a sampling conduit for permitting ow in said auxiliary passage when said four-way valve is in the other position,

a titration cell,

a source of neutral Huid,

conduit means for connecting said source of neutral uid to said four-way valve and said fourway valve to said titration cell for washing out a sample when said four-way valve is in said one position, and

means for measuring the density of the fluid in said chamber near the bottom of the column when said mixture has settled.

References Cited UNITED STATES PATENTS 2,592,063 4/l952 Persyn, Jr 23-253 2,977,199 3/1961 `Quittner 23-253 X 2,989,377 6/1961 Leisey 23-253 X 3,173,969 3/1965 Kap 23-253 X MORRIS O. WOLK, Primary Examiner R. E. SERWIN, Assistant Examiner U.S. Cl. X.R.

23-230 R, 230 A, 253A; 204-l95; 260-68358, 683.59; 324-30 R UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,625,655 Dated December "ii 1971 Inventar-(s) Robert A. Culp, Jr., and Robert E. Franke It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column lO,line 2?, (inClaim 2, third line) please cancel "means);

line 28, (at the beginning of the line) before "for" insert (with single Signe and sealed this 30th day of May 1972.

(SEAL) Attest:

EIDJARD BLFNCTCHERJR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents

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