US1957808A - Fluid analyzing method and apparatus - Google Patents

Description

May 8, 1934. c. z. ROSECRANS FLUID ANALYZING METHOD AND APPARATUS 2 Sheets-Sheet 1 Filed Oct. 9, 1929 May 8, 1934. c. z. ROSECRANS FLUID ANALYZING METHOD AND APPARATUS Filed Oct. 9, 1929 2 Sheets-Sheet 2 00 E: nun noun M16270 bATTORA/EY.

Patented May. 8, I934 FLUID ANALYZING METHOD AND APPARATUS Application October 9,

Claims.

This invention relates to improvements in fluidanalyzing method and apparatus.

In apparatus for handling fluids, it is fre quently desirable to analyze the fluid as it passes 5 "through the apparatus for the purpose of ascertaining as to the manner of operation thereof and providing for control of the same to regulate or control the proportion of the fluid constituents. For example, in apparatus for mak ng sulphur dioxide gas, the combustion chamber of the apparatus is provided'with an air inlet valve or damper which is regulated in such wise as to pro vide for supply of the proper amount of air to carry on the process, for which purpose suitable gas-analyzing apparatus is connected to the outlet connection. from the combustion chamber and through suitable relay apparatus imparts opening or closing movement to the damper in accordance with varia ion in the sulphur dioxide content. In such apparatus, difiiculties have been experienced heretofore in the way of errors and corrosion in parts comprising the gas-analyzing apparatus due to the presence of particles of H2504 mist. This gas, accordingly, was caused to pass through a diatomaceous earth filter which filtered out the particles of H2504 and permitted only S02 and O2 and N2 to find its way to the gas-analyzing apparatus. Such filters, however, had to be renewed at frequent intervals because of clogging and permitted of gas-flow to the analyzer at only a very low velocity such that response of the latter to variations in the S02 content at the point in the system from which the sample gas was taken was greatly retarded. This inherent time lag in the systems used heretofore which increased as the clogging progressed with more erratic control action, rendered the same practically inoperative for the purpose of properly controlling the air damper to control the S02 content, for the reason that opening or closing movement of the damper did not follow within a reasonably short period of time from an occurring variation in the S02 content and the hunting or overshooting of the control became worse and worse until the filter was renewed.

One of the objects of the present invention, therefore, is to provide an improved system or apparatus of the character referred to wherein an undesirable constituent of a fluid may be filtered or removed therefrom before the same reaches the fluid-analyzing apparatus, the arrangement being such that the rate of flow of the fluid sample to the analyzing apparatus is increased substantially over the rate permissible heretofore, such that the analyzing apparatus 1929, Serial No. 393,351

is effective to render the air damper or other control member more sensitive and responsive to variations in the gas content than has been possible in the systems proposed heretofore.

Other objects and advantages will hereinafter appear.

For the purpose of illustrating the invention, one embodiment thereof is shown in the drawings, wherein A Figure l is a diagrammatic view, partly in section, of a system embodying the present improvements, one of the pieces of apparatus in the system being shown on an enlarged scale;

Fig. 2 is a diagrammatic View, partly in section, illustrating the automatic control arrangement in Fig. 1; and

Fig. 3 is an enlarged fragmentary perspective View of relay apparatus forming part of the system in Fig. 2.

Referring to Fig. l, the sulphur fumes from the sulphur burner 10 pass in the direction indicated by the arrow into the combustion chamber 11 where further oxidation takes place to form S02 and a quantity of S03;

The gas passes by way of connection 15 to the coke box 16 of suitable construction and thence to a suitable catalyst chamber 17, and is withdrawn by way of connection 18.

Suitable gas-analyzing apparatus or means, designatedgenerally by reference numeral 19 and shown as being of the general type illustrated and described in Patent No. 1,504,707 of August 12, 1924, to Peters, is connected in the system at the points 20 and 21 or" difierent pressure, such that a sample of the gas flows continuously from point 21 into apparatus 19 in thedirection of the arrow shown and from the apparatus by way of connection 22 to point 20 in discharge connection 18.

As the gas passes through the section 23 of apparatus 19, a representative sample of such gas fills chamber 24 containing the resistance conductor 25 which has a substantial temperature coefficient and which forms one arm of the Wheatstone bridge shown. The chamber 26 is sealed as shown and contains a standard gas and the resistance Wire 27 which also has a substantial temperature coefficient and forms another arm of the Wheatstone bridge. The resistances 28 and 29 form the other arms of the bridge and are connected at their respective adjacent ends by the resistance wire 30 with which is associated contact 31.

iThe galvanometer needle 33 in the bridge forms part of suitable relay or control mechanism designated generally by the reference numeral 32 and shown as being of the general type described in Patent No. 1,125,699 of January 19, 1915, to Leeds.

The system shown generally in Fig. 2 is the same as that described in detail in co-pending application of Schofield, Jr., et al., Serial No. 697,484, filed March '7, 1924.

The operation of the system or apparatus thus far described is as follows. As the gas passes through connection 15 a continuous sample is taken from the point 21 due to the greater pressure at this point as compared with the pressure at point 20. Upon occurrence of variation in the S02 content, therepresentative sample of the gas in chamber 24 will vary accordingly to cause corresponding unbalance of. the bridge and accompanying deflection of the'galvanometer needle 33 in the proper direction to effect opening or closing movement of damper 12, depending upon whether such variation is a decrease or an increase in the S02 content. For example, assuming that the connection or arrangement is such that upon increase in the S02 content above normal the bridge will be unbalanced to cause clockwise movement of the galvanometer needle, such movement of the needle will be accompanied in the well known manner by clockwise movement of the rotary switch 34 to eflect excitation of relay 35 to cause operation of motor 14 in the proper direction to open damper 12 further. The supply of air to combustion chamber 11 is, therefore, increased by such amount as to bring the S02 content back to normal. As the S02 content returns to normal, the bridge and associated galvanometer will operate in the well known manner to effect return movement of switch 34 to the position shown to open the energizing circuit for relay 35. Upon decrease in the S02 content below normal, the action is reversed, that is, the bridge will become unbalanced in such wise as to cause counter-clockwise movement of galvanometer needle 33 and similar movement of switch 34 to cause excitation of relay 36 and rotation of motor 14 in the other direction to impart closing movement to damper 12 in amount corresponding to this variation in the S02 content. The action, therefore, is such that the gasanalyzing apparatus 19 is responsive to variations in the S02 content, and operates through the control mechanism 32, motor 14 and associated parts to operate damper 12 in the proper direction upon such variations, whereby the air supply to combustion chamber 11 is controlled in such wise as to cause the process to proceed properly.

For a more detailed explanation of the manner of operation of the automatic control system shown in Fig. 2, reference might be made to the co-pending application of Schofield, Jr., et al., referred to hereinbefore. In Fig. 2, reference numerals 30, 31, 3'7 and 38 designate parts or connections corresponding to the parts or connections in said application designated therein by the reference characters or numerals R3, w, 36, and 72, respectively.

The apparatus for removing the particles of H2s04 mist content from the sample of gas to prevent the same from traversing the gasanalyzing apparatus 19, will now be described. In the connections between point 21 and the gas-analyzing apparatus is disposed the tubular member 39 which forms part of such connections. Disposed upon the exterior of the tube between trap being open to atmosphere.

the inlet and outlet ends thereof is an electrode 40, preferably of metal foil or other conductive coating to insure intimate contact between the adjacent faces of the electrode and tube. An inner electrode 41 of fine wire of platinum, or other suitable material, is supported at the upper end of the tube by the plug 42 of suitable insulating material such as glass, the wire being secured at its lower end to an electrically conductive supporting member 43 projecting inwardly from a collecting chamber 44 which may be of metal, such as iron.

The open upper end of chamber 44 is threaded to receive the plug 45 through which the open lower end of tube 39 extends, suitable packing means 46 providing a seal between the plug and tube. A suitable trap 46 is connected as shown to the bottom of chamber 44, the end 47 of the The electrodes 40 and 41 are connected, respectively, to the opposite phases '48 and 49 of a suitable source of alternating current designated generally by reference numeral 50. The inner electrode 41 may be grounded through support 43, chamber 44 and connection 51. The apparatus just described might properly be called a precipitator, the construction and manner of operation being such that the charged mist particles of S03 are deflected from the gas stream under the influence of the electrostatic field and caused to travel across the stream into contact with a collecting surface, such as electrode 41 or the inner surface of tube 39, before reversal of polarity of the electrodes. In the specific type of apparatus shown, the distance between electrodes 40 and 41 is so small that the charged particles of S03 in the gas stream traverse the distance between their original position to a collecting surface, that is, either to wire 41 or the inner surface of tube 39, during the time of one-half cycle. Use of a tube about three-quarters inch inside diameter and a source of alternating current having a frequency of 60 cycles and a potential of about 15,000 volts has been found to provide for satisfactory precipitation. The length of electrode 40 and consequently of the region in which the gas stream is subjected to the action of the electrostatic field is sufiiciently great to insure substantially complete precipitation, for example, to within .1 percent. The tube 39 is preferably of lead glass or other material of relatively good conductivity to obtain large potential drop between the electrode 41 and the inner surface of the tube. In fact, that portion of tube 39 ad.- jacent the metal foil 40 is itself an electrode, the glass conducting appreciable current at the high potentials involved. To avoid excessive losses, the length of tube 39 from the edges of the outer electrode 40 to the nearest conductor of opposite polarity is suitably great.

As the gas stream passes upwardly through tube 39, the S03 in the form of sulphuric acid mist particles collects on electrode 41 and the inner surface of tube 39 and runs down into chamber 44. The acid drain leg or trap 46 is so dimensioned that a liquid seal is maintained, as well as the desired sub-atmospheric pressure within the chamber 44. For example, the pressure in chamber 44 may be 25" of water below atmospheric. During operation, the precipitate drips from the open end 47 of the trap at a rate corresponding to the rate of precipitation in tube 39. As the separated particles are removed from the path of flow of the gas, the resistance to gas flow by the precipitator is sub stanti'ally constant and low. For the purpose of ascertaining as to the proportion of sulphuric acid mist, a definite volume of the gas is passed through the precipitator, the precipitate washed and a titration made. For the purpose of increasing the precipitating capacity, particularly for purposes other than analysis which require larger volumes or quantities of gas, a suitable number of precipitators may be arranged in multiple or parallel relation.

While the apparatus just described provides for practically complete separation of the S03 content from the gas sample during its passage to the gas-analyzing apparatus 19, a diatomaceous earth filter 52 may be employed and connected as shown between the precipitator and apparatus 19. The diatomaceous earth filter may be of the usual construction used heretofore, but due to the fact that it is called upon to filter out only a very small and negligible quantity of S03 mist, such as might find its way through the precipitator, this filter difiers from those used heretofore in that the same permits more freely of fiow of the gas through itself, the rate of flow being suificiently great to eliminate the undesirable time lag referred to above and which has been inherent in the systems constructed heretofore. Furthermore, due to the fact that very little if any S03 gas will be permitted to pass through the precipitator to the filter, renewal of the latter will be necessary only after long periods of service. Where it appears that the precipitator operates to remove all the S03 gas, the filter 52 or equivalent mechanical filter may be omitted, in which case there will be a free passage for the gas from the point 21 to apparatus 19, and, accordingly, practically no time lag, or otherwise stated, the S02 content of gas entering at 21 is the same as the S02 content of gas in the analyzer 19.

The specific construction disclosed of the precipitator has been found to provide for satisfactory results, and forms the subject matter of my co-pending application, Serial No. 373,806, filed June 26, 1929. Any other equivalent construction may, of course, be substituted for the particular construction disclosed.

The Wheatstone bridge and associated control mechanism 32 may be mounted as a single unit in the casing 53, while the relays 35 and 36 and associated parts or connections may be mounted as a unit in the casing 54.

The details of construction and manner of operation of control mechanism 82 are fully set forth in Patent No. 1,125,699 of January 19, 1925, to Leeds.

While the present invention has been disclosed as embodied in a system for handling S02 gas, it will be appreciated that the invention is of much broader adaptation, and may be embodied in other systems such, for example, as those wherein the constituent to be removed is in the form of a finely divided solid. Furthermore, it will be appreciated that various changes might be made such as in the size, shape and arrangement of the parts without departing from the spirit of the invention or the scope of the claims.

The invention claimed is:

1. A system comprising gas analysis apparatus, means affording a path for flow of gas to said apparatus, a mechanical filter in said path, means for maintaining substantially constant the resistance offered by said filter to the flow of gas comprising an electrical precipitator in advance of said filter for freeing the gas substantially completely from suspended particles, and means controlled by said apparatus for controlling the composition of said gas flowing thereto.

2. A system comprising gas-analysis apparatus, means affording a path for flow of gas to said apparatus, a mechanical filter in said path, mechanism operated by said apparatus to control the composition or" said gas, and means for maintaining substantially constant and low the resistance offered by said filter to the flow of gas comprising an electrical precipitator in advance of said filter in said path.

3. A sulfur-dioxide producing system comprising a combustion chamber, structure for varying the admission of air to said chamber to vary the sulfur-dioxide content of gas produced in said chamber, gas-analysis apparatus for controlling said structure, means for affording a path for fiow of a sample of gas from said chamber to said apparatus, and means for ensuring accurate and rapid analysis of the gas sample for correct and prompt control of said structure to maintain the sulfur-dioxide content of the gas substantially constant, comprising an electrical precipitator in said path offering low and constant resistance to the flow of the gas sample and for removing the sulfuric acid mist therefrom.

1. In the control of the composition of a gas containing entrained particles, the method which comprises effecting continuous flow of the gas at high and substantially constant velocity through a path offering low resistance to the fiow, continuously determining the composition of the gas flowing at said high and constant velocity at the end of said path, and immediately controlling the proportions of the gas components in accordance with said determination entering said path, and producing an electric field at a region in said path before said determination to remove said particles and so increase the accuracy thereof without reduction in the velocity or constancy of velocity of the gas flow.

5. A system comprising structure adjustable to vary the composition of a gas containing entrained particles, gas analysis apparatus for controlling the composition of said gas by control of said structure, means providing a path of fiow of a sample of said gas to said gas-analysis apparatus, and an electrical precipitator in said path for removal of the entrained particles offering low and constant impedance to the flow of said sample to ensure accurate and rapid analysis of the gas sample for proper and prompt control of said structure.

CRANDALL Z. ROSECRANS.

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