US3244602A - Method and apparatus for determining water content in gaseous media - Google Patents

Description

Aprll 5, 1966 J, ss ETAL 3,244,602

METHOD AND APPARATUS FOR DETERMINING WATER CONTENT IN GASEOUS MEDIA Filed Oct. 2, 1961 4 Sheets-Sheet 1 NE z E n O M Q 0: 2& 5 0 N n: Q- D Z I) Q Q INVENTORS.

JOHN R. GLASS a EDWARD J. MOORE BY @LQ/ ATTORNEYS SAMPLE SOURCE April 5, 1966 J. R. GLASS ETAL 3,244,602 METHOD AND APPARATUS FOR DETERMINING WATER CONTENT IN GASEOUS MEDIA 4 Sheets-Sheet 2 Filed Dot. 2, 1961 all mOmDOm EOPOE ll mwomoomm nimm ws vs INVENTORS. JOHN R. GLASS 8\ EDWARD J. MOORE flew $7 M ATTORNEYS Aprll 5, 1966 .1. R. GLASS ETAL 3,244,602

METHOD AND APPARATUS FOR DETERMINING WATER CONTENT IN GASEOUS MEDIA Filed Oct. 2, 1961 4 Sheets-Sheet 5 TIME MINUTES 0 IO 20 30 4 0 50 so I VALVES I5, 22 OPEN VALVES 3|, 31, 43 OPEN I so so Fla 3/! ELECTROLYSIS CURRENT I FLOWING I 410 6'0 RECORDER CHART I DRIVE RUNNING |43,4s-

RECORDER METER i Q INDICATING I 33,45}

TIME OF EVENT, MINUTES IO 20 310 40 5O 6O SWITCH PATTERNS I INVENTORS.

JOHN R. GLASS a F/G 35 BY EDWARD J. MOORE their ATTOR/VE Y5 April 5, 1966 J. R. GLASS ETAL METHOD AND APPARATUS FOR DETERMINING WATER? CONTENT IN GASEOUS MEDIA Filed Oct. 2, 1961 4 Sheets-Sheet 4.

ms POINT ON LEFT END OF RECORD (.27rno) INDICATES I WATER CONTENT x2 5 4:00 5 5=oo LL] 5 E e=oo l" l- 2 7 00 hi a: 8-00 8 .4 Lo

/ CURRENT, MILLIAMPERES WATER, PFM -O 0 IO 20 3O 4O 5O 6O 7O 8O 90 I00 IIO I20 I30 INVENTORS.

JOHN R. GLASS a EDWARD J. MOORE ATTORNEYS United States Patent 0 ice 3,244,602 MEIHGD AND APPARATUS FDR DETERMHNINS WATER CONTENT IN GASEGUS MEDIA John R. Glass, Glasshoro, and Edward J. Moore, Woodhury, NJ. Filed Oct. 2, 1961, Ser. No. 142,098 2 Claims. (Cl. 204-4) This invention relates to a method and apparatus for determining the Water content of a gaseous specimen and, more particularly, to a method and apparatus for semicontinuously measuring small concentrations of water in a gaseous stream, although it is not limited to such use.

In many chemical and other processes, the water content in a gaseous stream has a significant effect upon the process and efforts have been made heretofore to devise apparatus for continuously determining the water content in such streams so that appropriate corrective action may be taken, if necessary. In one form of device that has been developed for this purpose, the gaseous stream is passed through a special electrolytic cell in which all entering water is continuously and quantitatively absorbed and electrolyzed to hydrogen and oxygen. Since the quantity of electricity required to electrolyze water is known, the water content of the stream is determined by measuring the electrolysis current.

While apparatus of this general character is effective for some purposes, it has been found that the readings which it gives with certain gaseous streams, notably those containing hydrogen, are not accurate. The reason for this is believed to be that the oxygen released by the electrolysis tends to recombine with the hydrogen present in the stream to'form water which is again electrolyzed,

so that the water content readings obtained are high.

It is an object of the present invention, accordingly, to rovide an improved method and apparatus for measuring the water content of gaseous media which is free from the above-mentioned deficiencies of the prior art.

A further object of the invention is the provision of an electrolytic method and apparatus for semicontinuously determining the water content of a gaseous specimen stream in which no opportunity is afforded for the gasdetermining cell alternately to absorb moisture from a gaseous sample and to electrolyze moisture thus absorbed. in the case of a gaseous sample stream, the stream is caused to flow through the cell only during the moisture absorbing part of the operating cycle. During the part of the cycle devoted to electrolysis of the absorbed moisture, the sample stream is temporarily diverted from the cell so that there are no sample stream gas components present that might combine with the products of the electrolysis to form water. Preferably, an inert gas such as nitrogen is flowed through the cell during electrolysis to carry oh the hydrogen and oxygen thus produced. In this manner, it is possible to obtain highly accurate moisture-content determinations even with gaseous samples containing a gas such as hydrogen that might combine with the products of the electrolysis to form Water. By alternately absorbing moisture from a gaseous sample and electrolyzing it in this manner, determinations of Water content may be made semicontinuously.

' to control the'fiow through'the same.

3,244,5h2 Patented Apr. 5, 1966 Various other objects and advantages will appear from the following detailed description of a typical embodiment of the invention taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a simple flow diagram of a typical system according to the invention for determining the water content of a gaseous sample stream;

FIG. 2 is a schematic diagram of a simplified electrical control circuit for the water content determining system of FIG. 1;

FIGS. 3A and 3B are typical timing and switch pattern diagrams, respectively, for certain of-the operations carried out by the circuit of FIG. 2;

FIG. 4 is a typical water content record that might be produced by apparatus shown in'FIGS. l and 2; and

FIG. 5 is a representative calibration chart for a Water analyzer system of the type shown in FIGS. 1 and 2.

Referring first to FIG. 1, a gaseous sample stream, which may comprise,for example, gaseous hydrocarbon material in admixture with hydrogen from a petroleum refinery process stream, is supplied to the conduit'l'O of Water content determining apparatus embodying the invention. From the conduit 16, the sample stream passes through a valve 11, a conduit 12, a valve 13, aconduit 14, a solenoid operated valve 15, aconduit 16, a filter 17 and a conduit 18 to a water analysis cell 19'for determining the water content of the gaseous stream supplied thereto.

A pressure relief valve 24 may be connected to the conduit 12 between the valves 11 and 13 to prevent the pressure in the system from accidentally'rising to 'an unsafe value. The filter 17 may be of any known type and it serves to prevent solid particles suspended in the gaseous sample from reaching the cell 19.

The cell 19 is preferably of the type disclosed in prior Patent No. 2,830,945 to Keidel and further described in an article entitled Determination of Water by Direct AmperometricMeasurement by F. A. Keidel which appears at page 2043 of Analytical Chemistry, volume 13, No. 12, December 1959. In a cell of this character, a hygroscopic electrically conductive material absorbs moisture from any gas passing therethrough and'the cell can be energized electrically to electrolyze the moisture thus absorbed.

For proper operation of the water analysis cell 19, it is desirable that the sample flow therethrough be maintained at apredetermined arbitrary value. To this end, the output from the-cell 19 is fed through a conduit 21, a solenoid operated valve 22 and a conduit 23 to conventional flow regulating apparatus which may'comprise, for example, a pressure responsive flow regulator 24, a conduit 25, a conventional flow restrictor device'26, and conduit 27 for sensing the pressure at the output of the flow restrictor device and supplying it to'the regulator 24 The fiow regulator 24 functions automatically in the well known manner to maintain the pressure drop across the restrictor 26 at a value sufficient to preserve a predetermined sample fiow rate through the Water analysis cell 19. The rate of flow can be measured in any conventional manner as by a flow meter 28 connected by a-conduit 29 to receive the output of the restrictor 26.

In order to maintain a constant rate of sample flow through the system when the solenoid operated valves 15 and 22 are closed and the water sample collected by the water analysis cell 19 isbeing electrolyzed, a by-pass is provided which includes a conduit-30 connected to the conduit 14, a solenoid operated valve '31, a' flow restricting orifice 32, and a conduit 33 connected to the conduit 23. The flow restricting orifice 32 serves to restrict the sample flow through the by-pass so that the pressure of gas in the sample line will remain constant throughout the operating cycle.

As will be described in greater detail hereinafter, after a water sample has been collected by the water analysis cell 19 and the solenoid operated valves 15 and 22 have been closed, it is desirable to flush out the cell 19 with an inert gas and preferably to maintain the flow of inert gas through the cell 19 while the water sample collected thereby is being electrolyzed. For this purpose, inert gas is supplied from a suitable source through a conduit 34, a conventional gas dryer 35, a conduit 36, a solenoid operated valve 37 and a conduit 38 which is connected to the conduit 16. After passing through the cell 19, the inert gas is vented from the system over a path including a conduit 40 connected to the conduit 21, a conventional flow restrictor device 41 which may be a commercially available filter device or finely divided inert material packed in a housing, a conduit 42 and a solenoid operated valve 43.

In accordance with the invention, a sample stream from the source is passed through the cell 19 for a sutlicient period of time to permit any water contained therein to be absorbed by the hygroscopic material in the cell 19. The solenoid valves 15 and 22 are then closed, and the valves 31, 37 and 43 are opened. The opening of the valve 31 permits the sample stream to flow through the by-pass described above, thus maintaining the same rate of flow through the system, while the opening of the valves 37 and 43 permits inert gas to pass through the cell 19 and to flush out all traces of the sample stream previously flowed therethrough. Electric current is then passed through the cell 19 to electrolyze the water sample absorbed by the hygroscopic material therein and the electrolysis current is measured and taken as an indication of the water content present in the sample stream.

While the steps outline briefiy above may be carried out by hand, automatic operation is preferred, a control system of the type shown in FIG. 2 being employed for this purpose. Referring to FIG. 2, the several operations may be controlled in sequence by a conventional timer 44 driven by a synchronous motor 45 connected to the electrical power mains (not shown). The timer 44 may be of the type having a plurality of cams 46, 47, 48, 49 and 50 on a common shaft which are adapted to actuate the switches 51, 52, 53, 54 and 55, respectively, in predetermined sequence as outlined in greater detail below.

The switch 51 has a movable contact arm 56 which normally engages a fixed contact 57 and is adapted to be moved by the cam 46 into engagement with a second contact 58. The movable contact arm 56 is connected by a conductor 59 to one side of the power mains, the other side being connected by a conductor 60 to the solenoid 22' and through the conductors 61, 62, 63 and 64 to one side of each of the solenoids 43, 37', 31' and 15, for actuating the valves 22, 43, 37, 31 and 15, respectively. The other terminals of the solenoids 15' and 22 are connected by the conductors 65 and 66 to the fixed switch contact 57, while the other terminals of the solenoids 31', 37' and 43' are connected by the conductors 67, 68 and 69 to the fixed contact 58. It will be understood, therefore, that when the movable svdtch contact 56 is in engagement with the fixed contact 57, the solenoids 15' and 22' will be energized and the valves 15 and 22 (FIG. 1) will be opened, while the solenoids 31', 37' and 43' will not be energized so that the valves 31, 37 and 43 will be closed.

The switches 52 and 53 serve to control the supply of electric current to the cell 19 to electrolyze any water removed from the sample stream thereby. To this end, the switch 52 has a movable contact arm 70 which at the beginning of each cycle is normally in engagement with a fixed contact 71 but is adapted at the proper time to be moved by operation of the cam 47 into engagement with a fixed contact 72. The contact 72 is connected by a conductor 73 to one terminal 74 of the cell 19, the other terminal 75 of which is connected in series with a current limiting resistor 76 and a conductor 77 to one terminal 7 8 of a conventional low impedance electrical current source 79. The other terminal 80 of the current source 79 .is connected by a conductor 81 to the fixed contact 82 of the switch 54 which serves to connect a recorder for the electrolysis current in and out of the cell circuit during part of the operating cycle as described in detail below.

The switch 54 also has a movable contact 83 which, at the beginning of each cycle, engages a fixed contact 82 but is adapted to be moved by the cam 49 at the proper time into engagement with the fixed contact 84. The movable contact arm 83 of the switch 54 is connected by a conductor 85 to the movable contact arm 86 of the switch 53, which, at the beginning of an operating cycle, is normally in engagement with a fixed contact 87. The fixed contact 87 is connected by a conductor 88 to the movable contact arm 70 of the switch 52. The movable contact arm 86 of the switch 53 is adapted to be moved by operation of the cam 48 at the proper time in the cycle out of engagement with the contact 87 and into engagement with a fixed contact 89. t

The movable contact arms 83 and 86 of the switches 54 and 53, respectively, are also connected by a conductor 89a to one terminal 90 of a switch 91 having a movable con-tact arm 92 connected by a conductor 93 to one terminal of a conventional current recording device 95. The other terminal of the recorder 95 is connected by a conductor 96 to the movable contact arm 97 of a switch 98 which normally engages a fixed contact 99. The contact 99 is connected by a conductor 100 to the movable contact arm 101 of a switch 102 which normally engages a fixed contact 103 connected by the con ductor 104 to the conductor 81.

In order to provide a suitable reference reading, say zero, on the recorder 95 corresponding to dry gas, a circuit including an adjustable resistor 105, a fixed resistor 106 and a battery or other source of DC. voltage 107 may be connected between the fixed contact 99 and a second fixed contact 108 on the switch 98, the contact 108 also being connected to the conductor 89a. The fixed contact 99 on the switch 98 is also connected by a conductor 109 to a fixed contact 110 on the switch 91,;

so that the connections between. the recorder 95 and the reference voltage source can be reversed to enable the magnitude of the latter to be measured, if desired.

The switches 91, 98 and 102 are connected for ganged operation with a switch 111 having a movable contact arm 112 connected 'by a conductor 113 to one terminal of the drive motor circuit for the recorder 95. The switch 111 also has a fixed contact 114 connected by a conductor 115 to one side of the power mains, the other side of the power mains being connected by a conductor 116 to the other terminal of the recorder drive motor circuit.

The timer switch 55 serves to turn on the recorder 95 at the proper time in the operating cycle. To this end, it has a movable contact 117 which, at the beginning of each cycle, is in engagement with a fixed contact 118 but is adapted to be moved by the cam 50 at the appropriate time into engagement with a second fixed contact 119. The movable contact arm 117 is connected to the conductor 113 and the fixed contact 119 is connected to the conductor 115 so that when the two are in engagement, the drive motor for the recorder 95 is connectecl to the power mains.

In connection with the establishment of a reference reading (e.g., zero) on the recorder 95 for the condition when dry gas is passing through the cell 19, as mentioned above, provision should be made for drying the gaseous. sample stream before passing it through the cell 19. Thus, a conventional gas dryer 120 (FIG. 1) may be connected by conduits 121 and 122 and valves 123 and 124 on opposite sides of the valve 13 so that by closing the latter the sample stream may be'dried before it is fed to the water analysis cell 19.

In a typical operation, let it be assumed that the timer 44 is just beginning a cycle so that the valves 15 and 22 (FIG. 1) are open, while the valves 31, 37 and 43 are closed. Under'these conditions, with the valve 13 open and the valves 123 and 124 closed, the sample stream, which may be, for example, a gaseous hydrocarbon at a pressure of say lbs. per square inch and containing small amounts of moisture, will flow at a uniform rate through the water analysis cell 19. After'say twenty minutes of the cycle have elapsed, the contact arm 86 of the switch 53 is repositioned into engagement with the fixed contact 89 (FIG. 3B). When a further period, say 9.5 minutes has elapsed, the timer 44 (FIG. 2) will have driven the cam 46 to the point where it causes the movable contact arm 56 to disengagethe fixed contact 57 and to engage the fixed contact 58. This will cause the solenoids and 22' to be deenergized, closing the valves 15 and 22, respectively, (FIG. 1) and the solenoids 31, 37' and 43 to be energized, opening the valves 31, 37 and 43. These actions are shown graphically on the timing diagrams in FIGS. 3A and 3B.

Under these conditions, the fluid stream no longer flows through the cell 19 but is diverted through the bypass including the open solenoid valve 31. In its place, dry inert gas which may be, for example, nitrogen is flushed through the cell 19 at a rate of say 10 cubic centimeters per minute for a predetermined period which may be the remainder of the cycle.

A short time, say a half minute later, the movable contact 70 of the switch 52 is repositioned into engagement with the fixed contact 72 (FIGS. 2 and 3B).

After the cell 19 has been flushed with nitrogen for say, ten minutes, the timer 44 (FIG. 2) will have moved the cam 48 so that the movable contact arm 86 of the switch 53 is in engagement with the fixed contact 87. This in effect connects the conductor 81 to the conductor 73 so that the cell is now energized from the source '79 and electrolysis begins. This event is indicated on the timing chart of FIG. 3A. It will be noted, however, that the connection between the movable contact arm 83 and the fixed contact 82 of the switch 54 short circuits the recorder 95 so that it does not begin to record at this time.

After the electrolysis has proceeded for a predetermined period, say 2.5 minutes, the cam 49 causes the movable contact arm 83 of the switch 54 to disengage the fixed contact 82 and to engage the contact 84. This breaks the short circuit across the terminals of the recorder 95 so that it is now connected in series with the cell 19. Shortly thereafter, (e.g., at 43 minutes after the start of the cycle) the timer 44 will have moved the cam 50 to the position where the movable contact arm 117 of the switch 55 is in engagement with the contact 119. This connects the conductors 113 and 115 so that power is now supplied to the drive motor of the recorder 95 and a record strip therein (not shown) begins to move as a function of time (see FIGS. 3A and 3B).

Several minutes later (e.g., at 45.1 minutes after the beginning of the cycle), the timer 44 causes the cam 49 to move the contact arm 83 into engagement with the contact 82, again shorting out the recorder 95. This is followed (at say 46 minutes) by disengagement of the contact arm 117 and the contact 119, so that the recorder drive motor is deenergized. Then, just before the end of the cycle (at say 59 minutessee FIG. 3B) the contact arm 70 of the switch 52 (FIG. 2) is disengaged from the contact 72, so that the electrolysis current is cut off. The cycle then repeats so that a series of records of the electrolysis current at different times are made.

A typical graph, such as might be produced by the recorder 95 is shown in FIG. 4 in which the several discontinuous curves represent the records made'during successive times when the recorder is on.

If the electrolysis current is plotted against time, integ'fation of the area under'the curve will give a value proportional to coulombs consumed. However, it is simplierto take as ameasure of the Water content the current at a fixedtime, say five minutes, after electroly sis is initiated (i.e., the point on the-left end of each of the curves recorded on the graph in'FIG. 4).

FIG. 5 illustrates a typical calibration curve for the water detectingapparatusdescribed above in'wlhich the moisture in -a gaseous sample, in parts per million is plotted as a-function of theelect-rolysis' current If it is desired to establish a predetermined reference on therecorder 95 corresponding to" dry gas, the valve 13 "(FIG. 1) may be closed and the'valves 1-23 and 124 opened so that the; sample is passed through the gas dryer 120*and" driedbefore being supplied to the'cell 19.

With dry gas passing through the cell 19 for one or more cycles of operation as described above, the adjustable resistor 105 (FIG. 2) is adjusted to give a predetermined reference reading, say zero, on the record made by the recorder 95.

The ganged switches 11 1, 102, 98 and 911 which serve to start the recorder drive and to connect the recorder 95 to the bucking voltage appearing at the fixed contacts 99 and 108 of the switch 98 afford means for check ing the constancy of the bucking voltage prior to or after any fluid sample test.

While the flow rate through the water detection system described above is not critical, desirably it should be of the order of 100 cubic centimeters per minute. If it is solwer, less water will be picked up and, it faster, more Water will be picked up.

The timing cycle described above is typical for a flow rate of 100 cubic centimeters per minute and a pressure of approximately 10 lbs. per square inch gauge for the sample stream. With higher pressures for the sample stream, the sensitivity of the apparatus will be higher and the operating cycle may be made shorter.

The system will operate effectively at any temperature between the freezing and boiling points of water. However, the sample gas pressure, temperature and flow rate should preferably be maintained constant. Moreover, the apparatus may be used effectively for determining the water content of other gaseous streams such as oxygen streams, for example.

From the foregoing, it Will be understood that the invention provides a highly effective method and apparatus for accurately determining the presence of small quantifies of moisture in fluid streams. By virtue of the fact that absorption of moisture from a sample stream and electrolysis of such absorbed moisture are carried out sequentially, instead of simultaneously as in the prior art, there is no opportunity for oxygen generated during electrolysis to recombine with any hydrogen in the sample fluid stream passing through the cell to form water which might result in spurious readings.

While specific operations and operating cycles, as well as apparatus for carrying them out, have been described above by way of example, the invention is not intended to be limited thereto. On the contrary, it encompasses all modifications in form and detail falling Within the scope of the following claims.

We claim:

1. In a method for determining the water content of a specimen gas containing hydrogen, the steps of passing such gas at a predetermined rate through a confined space in the presence of a hygroscopic material, then blowing through said confined space a gas substantially dry and nonreactive with hydrogen to remove said specimen gas from said confined space while simultaneously bypassing succeeding portions of said specimen gas through an alternate route at the same rate of flow, said water being retained in said confined space by said hygroscopic material, then decomposing the water retained by said hygroscopic material by electrolysis for a predetermined period of time to indicate a function of said electrolysis.

2. In a method for determining the water content of a specimen gas containing oxygen, the steps of passing sue-h gas at a predetermined rate through a confined space in the presence of a hygroscopic material, then blowing through said con-fined space a gas substantially dry and nonreactive with oxygen to remove said speciment gas from said confined space while simultaneously bypassing succeeding portions of said specimen gas through an alternate route at the same rate of flow, said water being retained in said confined space by said hygroscopic material, then decomposing the water retained by said hygroscopic material by electrolysis for a predetermined period of time to indicate a function of said electrolysis.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES Keidel: Analytical Chemistry, December 1959, vol. 31, No. 12, pp. 2043-2048.

JOHN H. MACK, Primary Examiner.

JOSEPH R EBOL D, MURRAY TILLMAN, WINSTON A. DOUGLAS, Examiners.

Claims (1)

1. IN A METHOD FOR DETERMINING THE WATER CONTENT OF A SPECIMEN GAS CONTAINING HYDROGEN, THE STEPS OF PASSING SUCH GAS AT A PREDETERMINED RATE THROUGH A CONFINED SPACE IN THE PRESENCE OF A HYGROSCOPIC MATERIAL, THEN BLOWING THROUGH SAID CONFINED SPACE A GAS SUBSTANTIALLY DRY AND NONREACTIVE WITH HYDROGEN TO REMOVE SAID SPECIMEN GAS FROM SAID CONFINED SPACE WHILE SIMULTANEOUSLY BYPASSING SUCCEEDING PORTIONS OF SAID SPECIMEN GAS THROUGH AN ALTERNATE ROUTE AT THE SAME RATE OF FLOW, SAID WATER BEING RETAINED IN SAID CONFINED SPACE BY SAID HYGROSCOPIC MATERIAL, THEN DECOMPOSING THE WATER RETAINED BY SAID HYDROSCOPIC MATERIAL BY ELECTROLYSIS FOR A PREDETERMINED PERIOD OF TIME TO INDICATE A FUNCTION OF SAID ELECTROLYSIS.

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