US1504707A

US1504707A - Gas analysis

Info

Publication number: US1504707A
Application number: US684133A
Authority: US
Inventors: Jr Jacob C Peters
Original assignee: Leeds and Northrup Co
Current assignee: Leeds and Northrup Co
Priority date: 1924-01-03
Filing date: 1924-01-03
Publication date: 1924-08-12
Anticipated expiration: 1941-08-12

Description

J. c. PETERS, JR

GAS ANALYSIS Filed Jan. 5. 1924 Aug. 12 1924.

INVENTOR. 0. 0w) BY :4 6151/ Ak ATTORNEY.

Patented Aug. 12, 1924.

UNITED STATES,

"PATENTgermamcon c. mans, J'R., or STATE coLLEen, PmsYLvAm'assmNon r0 LEEDS a nommwr COMPANY, or rmmnnnrnm, rnnnsynvama, a CORPORATION or PENNSYLVANIA.

GAB manger s Application filed January 3,1924. Serial R o." 684,133{

My invention relates to analysis-of gases for determ ning, measuring, record1ng,'or

effectingacontrol in response to changes of the amount of one or'more particular gases in a gas mixture.

In practicing myinvention,there is utilized-theknown method of gas analysis depending upon changes 'in' thermal conductivity of the gaswith reference to the conductivity. of a standard gas, as measured or determined by changes'of resistance of a conductor disposed .in'a cell or chamber through which the gas to-be analyzed is passed, with-reference to the, simultaneous resistance of a. conductor similarly placed in another cell or chamber containing. the standard gasq' In accordance with my 'invention, particu-' 'larly for the continuous analysis of gases, a'

small fraction of the gas tobe analyzed is passed through the gas cellby convection effected by heat liberated from the conductor 7 in the cell, preferably from and back to the -main supply. or current of gas to be analyzed, and preferably from and'back to points located substantially in the same plane normal to the axis of flow of the main-supply of gas. Further in accordance with my invention, provided means for correctin or current which heats the conductors disposed in the gas cells.

Further-in accordance with my invention, means are provided for correcting or compensating for changes in temperature of the air surrounding the cells.

Furtherin accordance with my invention, means are provided for-correcting or compensating for permanent changes in the re- 'sistance of the conductors in the cells.

My invention resides in the method and features of structure and combination ofthe character hereinafter described and claimed.

For an illustration of one of the various forms my invention 'may take, reference is to be had to the accompanying drawing, in which: 1 I I Fig. 1 is a side elevational view of the cells and the connections of one of them to the gas conduit. V

Fig. 2 is-avertical'sectionalview, partly 1, taken on the line 2 2 of Fig. 3.

Fig. 3' is a'horizonta'l sectional view taken on the line 3-'3 of Fig. 1. I

Fig; a. is a diagrammatieview of a circuit arrangement 'in'accordance with my invention.

Referring to the draw'ing,.A is block of ,metal or other suitable material having therein the cells or chambers. B and C. Or

in elevation, of the structure shown in Fig.-

the cells B andC may be in separate blocks;

or members} Extending. longltudinally of the cells BandC are the resistance conductors R and B, respectively, of any suitable material having substantial temperature co- R arefine. platinum wires, which may have diameters ofjthe order of two mils. At their upper ends they are soldered ate and b, respectively, to the wires 0 and d, respecefiicient. "Preferably the conductors R and 7 5 tively, of gold'or other suitable material ex tending through the insulating members e and f, forming gas-tight end closures for the cells 'B and C,-re'spectively. At their lower ends the conductors R and R are 501 dered at g and h, respectively, to the metallic springs-i and j, respectively,=which are preferably of gold or other material chemically neutral with respect to'the gases involved. The springs c and 7' keep the conductors R and R taut, and are connected to the conductorsm and n, of gold orvother suitable material, sealed in the end closure members o'and p, respectively, for the cells B and C. The closure members 0 and 'p-may be of glass or other suitable insulating material, or the lower ends of the springs 11 and j may becon- *nected to metal end closures of the cells B and C when the block is of metal, as indicated. It will be understood that either a rrangement may be utilized, as ma be suitable or convenient. With the con uctors m and n connect conductors and r, for effecting connection of the resistance conductors R and R in a VVheatstone bridge or other suitable circuit arrangement. When the springs 2' and are connected to metallic end closures 0 an '72 as described, the external conductors g and 'r are not required, and the bridge connection may be made directly to the block A.

The gas to be analyzed flows through the conduit or pipe D in suitable direction, preferably in the direction of the arrow, Fig. 2. Connection is made from the conduit D to the lower end of the chamber B by the short tube a and from the upper end of the chamber B connection is made through the long tube t to the conduit D at a point longitudinally in the latter preferab y substantially identical with the location of the connection 8. The two points of connection of the cell or chamber B to the conduit D are preferably in the same plane normal to the longitudinal axis of the conduit D. It will be understood that the conduit D need not be parallel with either of the chambers B or C, but may extend at right angles to them or be in any other way suitably disposed or arranged.

The resistance wires R and R are connected in circuit as indicated in Fig. 4, which illustrates a Wheatstone bridge. In a conjugate conductor of the Wheatstone bridge are included the source of current- S, which may be of any suitable type, as a battery, the adjustable resistance or rheostat w and the ammeter E, the rheostat u serving to adjust and the ammeter E serving to indicate or measure the magnitude of the current passed from the source S through the bridge arms, in two of which are connected, respectively, the resistance wires R and R there being utilized in the arm with the resistance wire R an additional resistance 1:. The conductors r and g are connected together at a point of junction forming one end of the second conjugate conductor which includes the galvanometer G and whose other terminal is at the contact w movable along the resistance R divided by the contact to into portions disposed, respectively, in the other two arms of the bridge, in one of which are included the resistances R and m, and-in the other of which is connected the resistance R with the resistance y shunted by the variable resistance a.

While, as above stated the resistance wires R and R possess substantial temperature oo-efiicients, it is preferred that the resistances R R, R, v, y and a shall have substantially zero temperature coefficients, and to this end they may be made of manganin or equivalent material. The resistance w, however, has a temperature coefficient, and may be constructed of nickel wire.

The operation is as follows:

The as or gas mixture flows through the con uit D and a ortion of it circulates through the cell B y convection due to the heat liberated by the resistance R. The gas enters the cell B throu h the tube a, ascends through the cell E, and passes through the tube 13 back to the conduit D to a point therein similar to that from which the connection a is taken. By so relying upon convection for circulating the gas through the cell B, the amount of gas circulated through the cell is independent of the pressure of the gas within the conduit D and is also independent of the velocity of the gas through the conduit D. Accordingly, the apparatus is rendered free of error due to changes in quantity or rate of flow of gas through the cell B such as would be due either to changes in the pressure or velocity of the gas flowing through the conduit B. In accordance with my 1nve-ntion, therefore, the maintenance of a substantially constant rate of flow of the gas, for example, twenty-two cubic centimeters er minute, according to the Bureau of standards method, is dispensed with, nor is there need for recourse to a method involving a diffusion orifice for effecting continuous change of the gas within the cell B.

The current passing from the source S through the resistance wires R and R having been adjusted by rheostat u to a predetermined magnitude, indicated by the ammeter E, for which the apparatus is calibrated, the contact 10 is moved backward or forward over the resistance R to such position as will cause a mil deflection of the galvanometer G. Should the amount of a particular gas or particular mixture of gases in the mixture of gases passing through the conduit D change, the bridge will be unbalanced, because of the change in thermal conductivity of the gas circulating through the chamber or cell B, the efiect of change of thermal conductivity of the gas causing a change in the temperature and therefore in the resistance of wire R, since the amount of heat supplied to the wire by the electric current is substantially constant. There is a consequent unbalancing of the bridge, which may be rebalanced by moving the contact to to a. new and proper position upon the resistance R, with which may be associated a scale calibrated in terms of the amount of the particular gas or gases whose amount is to be determined.

It is practically impossible to construct the resistance wires of conductors R and R so that they shall be identical, and it is similarly practically impossible to construct the cells themselves so that they crate identically as regards radiation, heat conduction, etc., with the result that changes in value of the heating current passing through the conductors R and R introduce errors which diminish the accuracy of measurement. To correct for errors caused by changes in value of the heating current, there is introduced into'one of the bridge arms, as that including the conductor R, a resistance '0 of such magnitude that in combination with its associated resistance R the resistance in that arm of the bridge is one having in effect a different temperature coefficient from the resistance wire R itself. This is due to the fact that the temperature co-efficient of the resistance '0 is' different from that of the conductor R with which it is associated, and, accordingly, changes in resistance of the conductor R due to changes in its temperature have less effect on the change of the total resistance of the bridge arm than in case the resistance '0 were omitted. As stated, the resistance '0 preferably has very small or zero temperature co-efiicient, and therefore the effective or over-all temperature co-efficient of all the resistance in the bridge arm including R and 'v is in effect reduced, and therefore less affected by changes in magnitude of the heating current. It will be understood that the resistance '0 may be placed in the other bridge arm with the conductor R or resistances having the purpose of resistance *0 may be included in both adjacent bridge arms containing conductors R and B. By recourse to the resistance 0 as described, there results a combination with the resistance R, for example, having in effect a temperature coefficient different from that of the resistance R alone, and the total resistance in the bridge arm varies with change in heating current at the same rate that the resistance, as R, in the other bridge arm changes, whereby the errors due to changes in magnitude of heating current are reduced or eliminated. The magnitude of the resistance n is accordingly made such that the unbalance of the bridge due to deviations from the normal magnitude of heating current is a minimum, particularly with regard to the nature of the gas to be analyzed or the nature and amount of the particular gas whose quantity is to be determined.

In rior practice the cells correspondingto the ce ls B and C were placed in an air bath held with considerable difficulty at constant temperature, and it was necessary that that temperature should correspond substantially with the temperature at which the instrument as a whole was calibrated. To avoid the necessity for such air bath and its attendant disadvantages and difficulties, I introduce into a suitable arm of the bridge a shall opresistance on, of suitable magnitude and having a suitable temperature co-efiicient, as a positive temperature co-eflicient correspondmg, for example, with nickel. The reslstance is subjected to the temperature of the ambient atmosphere, and accordingly rises and falls in tem erature therewith, and in so rising and falling in temperature it increases and decreases the resistance in the bridge arm in which it is included in extent to correct or compensate for variations in atmospheric temperature. By use of the resistance w, the minimum unbalance of the bridge due to changes in atmospheric temperature is procured, as regards the particular gas and its amount as to which the analysis is to be effected. While the resist-,

ance m is indicated in Fig. 4 as present in a particular-bridge arm, it shall be understood that it may be placed in series with the resistance wire R which co-acts with the gas to be analyzed. Occasions might arise, however, that would require the inclusion of the resistance at in the bridge arm with the resistance R, or with the resistance R which latter is the resistance which co-acts with the standard gas, such as air or the like, sealed and maintained in the cell C.

Correction for errors due to permanent changes in the apparatus, such, for example, as permanent changes in either or both of the resistance wires R and R are compensated for by the resistance e shunted by the adjustable resistance a. The resistance y, with its variable shunt 2, may be placed in any arm of the bridge.

The corrections or compensations above described, particularly those effected by the resistances o, :0, 3 and 2, will in general be of advantage; and they are of great advantage for cases where the amount of a particular gas or gases in the mixture passing through the conduit D fluctuates Within a small range.

It will be understood that the galvanometer G may control a recorder or a control apparatus which may be utilized for effecting any suitable control, as, for example, for changing or controlling the mixture passing through the conduit D so as to maintain it substantially constant as regards the particular gas or gases whose amount it is desirable shall be maintained substantially constant. For example, the pointer or needle of the galvanometer G may control recorder mechanism of the character disclosed in Leeds Patent No. 1,125,699, in which case the relative movement between thecontact w and resistance R is effected by the recorder mechanism to effect rebalancing of the circuit, and the relative movement for such balancing is the movement which is transmitted to the recorder pen or marker.

The galvanometer G may be similarly utilized for controlling a control mechanism of any suitable character. For example, the galvanometer needle may control a mechanism of the character disclosed in said Leeds patent, in which case the contact w may be set to a desired position upon the resistance R corresponding with the desired amount of the particular gas or gases of the mixture traversing the conduit D, and the movement of the movable structure of the control mechanism will efiect change in the amount of the particular gas or gases in such direction as to cause a rebalance of the Wheatstone bridge.

By way of example merely, it ma be stated that it may be desirab e to fin the percentage or amount of S0,, 00,, H 0,, or other gas in mixture with air or other gas or gases, and for this purpose the meth 0d and apparatus herein escribed are useful. When a recorder is utilized as above described, it will draw a curve representative of the percentages or amounts of the particular gas or gases present in a current of a mixture containing it or them. Or it may be desirable that the amount of S0 for example, in mixture with air or other gas or gases, shall be maintained substantially constant, in which case the control mechanism will control the admission of SO at such rate or in such quantity as to maintain the percentage of this gas in the mixture constant or substantially constant. In those cases where the percentage or amount of the particular gas in a mixture does not vary over wide limits, but remains within a range of a few per cent, the corrections or compensations effected by the resistances o and m are substantially perfect, but less so when the percentage'of the particular gas varies within a wider range.

While I have hereinbefore referred to gas as undergoing test or analysis, it shall be understood, with respect to the appended claims, that the term gas includes gaseous fluid in general, as permanent gas or vapor, or mixtures of gas and vapor.

What I claim is:

1. In the art of gas analysis, the method of procuring a sample froman enclosed current of the gas to be analyzed, which comprises efi'ecting passage of the gas substantially solely by convection from and back to points in said current between which the pressure diflerence is substantially nil.

2. In the art of gas analysis, the method which comprises eflecting substantially solely by convection a current of a sample of the gas to be analyzed from and back to points in a moving mass of the gas between which the pressure difi'erence due to the gas velocity is substantially nil;

3. In the art of gas analysis, the method which comprises efiecting substantially solely by convection a current of a sample of the. as to be analyzed from and back to points ying substantiall in the same plane normal to the axis of ow of a stream of the s to be analyzed.

4. n the art of gas analysis, the method of procuring a sample from a current of the gas to be analyzed, which comprises heating a conductor by passing an electric current therethrough, an utilizing evolved heat for efi'ectm passage of the gas ast said conductor y convection from t e current of gas from and back to points in said current between which there is substantially no difference in pressure.

5. In the art of gas analysis, the method which comprises heating a conductor by passing an electric current therethrough, and utilizing evolved heat for producing a convection current of a sam le of the gas to be analyzed past said con uctor from and back to points in substantially the same plane normal to the axis of flow of a stream of the gas to be analyzed.

6. Apparatus for testing or analyzing gas comprising a conduit through which the gas to be tested or analyzed passes, a cell, means in said cell responsive to changes in thermal conductivity of the gas, and means producing by convection a current of gas from said conduit through said cell.

7. Apparatus for testing or analyzing gas comprising a conduit through which the gas to be tested or analyzed passes, a cell, means in said cell responsive to changes in thermal conductivity of the gas, and means producing by convection a current of gas from said conduit through said cell back to said conduit.

8. Apparatus for testing or analyzing gas comprising a conduit through which the gas to be tested or analyzed passes, a cell through which a sample of the gas is to be circulated, and means in said cell evolving heat to produce a convection current of gas from said conduit through said cell.

9. Apparatus for testing or analyzing gas comprising a conduit through which the gas to be tested or analyzed passes, a cell through which a sample of the as is to be circulated, and means in said cel responsive to changes in conductivity of the gas and evolving heat to produce by convection a current of gas from said conduit through said cell.

10. Apparatus for testing or anal zing gas comprising a conduit through whic the gas to be tested or analyzed passes, a cell, connections between points in said conduit substantially in the same plane normal to the longitudinal axis of said conduit and separated points in said cell, and means for heating the gas in said cell to effect a convection current therethrough.

11. Apparatus for testing or anal zing gas comprising a conduit through whic the gas to be tested or analyzed passes, a cell,

connections between points in said conduit substantially in the same plane normal to the longitudinal axis of'said conduit and points in said cell disposed at different altitudes, and means for heating the gas in said cell to effect a convection current therethrough.

12. Apparatus for testing or analyzing gas comprising a conduit through which the gas to be tested or analyzed passes, a cell, a conductor disposed therein, means for passing an electric current through said conductor, and connections between points in said conduit substantially in the same plane normal to the longitudinal axis of said conduit and separated points in said cell.

13. Apparatus for testing or analyzing gas comprising a conduit through which the gas to be tested or analyzed passes, a cell, a conductor disposed therein and having a substantial temperature co-efiicient, means for passing an electric current through said conductor, connections between points in said conduit substantially in the same plane normal to the longitudinal axis of said conduit and separated points in said cell, and means responsive to changes in resistance of said conductor.

14. Apparatus for testing or analyzing gas comprising a cell, a resistance conductor disposed therein, and a gold spring in circuit with said conductor in said cell holding said conductor taut.

15. Apparatus for testing or analyzing gas comprising a cell, a resistance conductor therein having a substantial temperature co-efiicient, a source of current in circuit with said conductor for passing heating current therethrough, and a resistance in circuit with said conductor for reducing error due to change in the magnitude of said current.

16. Apparatus for testing or analyzing gas comprising a plurality of cells, one of said cells containing a standard gas and another of said cells traversed by a current of the gas to be tested'or analyzed, resistance conductors disposed, respectively, in said cells and each having a substantial temperature co-efiicient, a Wheatstone bridge in different arms of which said conductors are connected, a source of current for de livering heating current through said conductors, and a resistance in series with one of said conductors in the same bridge arm therewith for minimizing the effects of change in magnitude of the current traversing said resistance conductors.

17. Apparatus for testing or analyzlng gas comprising a plurality of cells, one of said cells containing a standard gas and another of said cells traversed by a current of the gas to be tested or analyzed, resistance conductors disposed, respectively, in said cells and each having a substantial temperature co-efiicien't, a Wheatstone bridge in different arms of which said conductors are connected, a source of current for delivering heating current through said conductors, and a resistance having substantially zero temperature co-efiicient connected in series with one of said resistance conductors in the same bridge arm therewith for mini mizing the effects of change in magnitude of the current traversing said resistance conductors.

18. Apparatus for testing or analyzing gas comprising a plurality of cells, one of said cells containing astandard gas and another of said cellstraversed by a current of the gas to be tested or analyzed, resistance conductors disposed, respectively, in said cells and each havin a substantial temperature co-eflicient,a eatstone bridge in different arms of which said conductors are connected, a source of current for delivering heating current through said conductors, and a resistance connected in an arm of said bridge and having such magnitude and a temperature co-efiicient of such magnitude as to substantially compensate for changes in temperature of the atmosphere surrounding said cells.

19. Apparatus for testing or analyzing gas comprising a plurality of cells, one of said cells containing a standard gas and another of said cells traversed by a current of the gas to be tested or analyzed, resistance conductors disposed, respectively, in said cells and each having a substantial temperature co-eflicient, a Wheatstone bridge in different arms of which said conductors are connected, a source of current for delivering heating current through said conductors, and a resistance connected in an arm of said bridge and having a magnitude for substantially compensating for permanent changes in the resistance of one or more of said resistance conductors.

20. Apparatus for testing or analyzing gascomprising a plurality of cells, one of said cells containing a standard gas and' another of said cells traversed by a current of the gas to be tested or analyzed, resistance conductors disposed, respectively, in said cells and each having a substantial temperature co-eificient, a Wheatstone bridge in different arms of which said conductors are connected, a source of current for delivering heating current through said conductors, and a resistance connected in an arm of said bridge and having a magnitude for substantially compensating for permanent changes in the resistance of one or more of said resistance conductors, said resistance comprising a-resistance shunted by a variable resistance.

21. Apparatus for testing or analyzing gas comprising a conduit through which the gas tobe tested or analyzed passes,'a cell, means in said cell afi'ectedby changes inthermal conductivity of the gas, and; means for producing by convection a car- 5 rent of gas from said conduit through said cell comprising gas connections from said cell to points in said conduit between which thle difference in pressure is substantially n1 In testimony whereof'I have hereunto 1 aflixedmy signature this 31st day of December, 1923.

JACOB o. PETERS, JR.