US1577853A - Apparatus for determining temperatures by co, content of combustion gases - Google Patents

Description

March 23., 1926.

' F. D..POTTER APPARATUS FOR DETERMINING TEMPERATURES BY 00: CONTENT OF COMBUSTION GASES Filed March 24 1919 I INVENTOR 5km w. 0 0w?- A TTORIVE Y 8 Patented Mar. 23, W26.

outrun stares F i Q E rarnuro FREDERICK D. POTTER, OF LINDEN, NEXV'JERSEZ, ASSIGNOB T0 COMBUSTION CON TROL COMPANY, INC, OF NEW YORK, N. Y.

APPARATUS FOR DETERMINING BY 00: CONTENT OF COMBUSTION GASES.

Application filed March '24, 1919. Serial No. 284,886.

To cZZ 207mm it may concern:

Be it known that I, FREDERlCK D. POTTER, a citizen of the United States, and a resident of Linden, county of Union, and State of New Jersey, have invented certain new and useful Improvements in Apparatus for Determining Temperatures by C0 Content of Combustion Gases, of which the following is a specification.

My invention relates to apparatus for determining temperatures from CO content of combustion gases produced by the combustion of fuel, as for example, from the burning of anthracite coal, coke or other fuels having a substantially high percentage of fixed carbon in boiler furnaces, furnaces for melting metal, reducing ores, etc.

Means are commercially available in the trade under the trade designation CC machines, for making periodic determinations of Ct) content of gaseous materials, and have been used heretofore as in connection with the uptake of boiler furnaces. In their use it is customary to attempt to run a fire in such manner as to give a substantially uniform production of CO at such percentage of total combustion gases produced as is found to give best results with the particular fuel which is being made use of, but without any particular or known relation or ratio to temperatures. The principle involved, so far as there is one, has been simply that combustion giving about a certain percentage of CO depending upon the fuel used, and other elements involved will secure best results in practice in the utilization of fuel and the production of heat therefrom.

The present invention depends upon an entirely diiferent principle. It is a known fact that perfect combustion of pure carbon uniting with the oxygen of atmospheric air produces a temperature of about 5000 F,

and to burn one pound of pure carbon, the

chemical equivalent of oxygen required is supplied by about thirteen pounds of air.

Such combustion produces about 21% CD and the balance of about 19% is principally nitrogen. If it were possible to carry on combustion practically in such man ner as to obtain a showing of about 20% to 21% of CO in the combustion gases, this would indicate therefore in burning practically pure carbon, that substantially perfect By means of a draft gauge used in connection with a furnace it may be determined which of these two conditions is present.

The draft gauge shows the difference in pressure above and below the tire bed or region of combustion. When there is a thick or close bed of coal, for example, or ash is present in considerable proportions, a considerable dilicrence in pressure is shown by the draft gauge. This serves to indicate that air is not being rapidly supplied in the region of combustion, but its passage is retarded, for example, by a very thick or close bed of fuel, or for other reasons, the indication being at all events that air in too small proportion is being supplied to the fuel which is being consumed. If the draft gauge shows a low difterence, this means that the air is passing through readily, and hat a plentiful supply of oxygen is available for combustion. If thcreforethere is a lowering of CO, content accompanied by low pressure draft gauge indication, it is apparent that reduction of temperature is due to too much air, in which case the air supply should be reduced or fuel added, and if there is a lowering of CO content accompanied by con'iparativel'y high indication on the draft gauge, this will mean that poor combustion is due to the fact that not enough air is being supplied, in which case additional air must be supplied, as for example, by means of a blower. By being given, therefore, the draft gauge indication and the CC indication, it becomes possible not only to obtain a knowledge of what is going on in the combustion chamber, but also to have the reasons therefor, thus enabling the fireman or other person in control, to vary the firing conditions to meet the situation.

Control of the combustion situation at least so far as to ensure that sufficient air is being supplied, may therefore readily be effected through the showing of the draft gauge and CO machine, and it is assumed in the following, that the furnace is being run in such manner that at least enough air for obtaining perfect combustion is being supplier according to the fuel in use. Part of this air may, of course, be supplied above the fuel bed. 7

With this assumption, and for such supply of air, the percentage of CO in the combustion gases varies inversely with the quan' tity of air supplied, and substantially directly with the temperatures obtained, for example, with perfect. combustion, and a maximum CO content only enough air is being supplied to support perfect combustion, and a. temperature of about 5000 F. is obtained, while with say about half of this percentage of CO substantially twice the air is being supplied that is required for perfect con bustion, and the temperature obtained is substantially half of 5000 F, or substantially 2500 F. It is readily possible therefore to construct a chart which can be calibrated to show from the CO content substantially the temperatures obtained, at least when the draft gauge indicates that enough air for perfect combustion or a greater amount of air is available. Such chart need only be calibrated to show temperatures of a given production of CO and same can be used to read temperatures directly, and one can disregard the fact that the use of a CC, machine is involved; the latter serving with a properly calibrated temperature chart, and within the limits set forth, as substantially a thermometer or temperature innicator.

Among numerous applications of the invention is its application to the blast fur- .naces for reducing ores, such as iron ore,

for example. The temperatures reached in such furnaces are of the highest importance because on them is dependent to a very great extent, the quality of the metal product obtained. In ordinary ore blast furnace practice, in which the escaping gases are used for consumption in gas engines or under boilers, the getting of perfect combustion in the furnace is of secondary importance, and furthermore would be productive of too high temperatures for the production of good quality yields of iron, or other metals. By the application of the process of the present invention to such blast furnaces, it readily becomes possible to obtain a fairly close indication of temperatures reached, and this can be done continuously, thus affording a guide for the controlling of the furnace to give the best results. This may be done, for example, by calibrating the GO, component of the gases to indicate corresponding temperatures, to which must be added of course, in the case where heat blast air is used, the temperature of the incoming air which enters the furnace. In this way unskilled or at least not highly skilled operatives may be used for running blast furnaces, it being only, necessary to control the combustion as by admission of additional air, or shutting off the air, or otherwise so that desired temperatures are obtained, which are shown directly on the chart, and for which no highly skilled observation is necessary, but the operator has only to ob serve his chart and carry on his operations accordingly.

i Vhere tight conduits are available, as for example, such conduits as lead from blast furnaces to gas engines for utilizing the waste gases, it is not material where the gases are taken off for the determination of the CO content to represent temperatures. They be taken directly from the furnaces or from any point of the conduit up to the gas engine, or from the means for consuming the unburnt gases as where the same are burnt, in a boiler or the like. In any part of such tight conduit, the composition of the gases will not vary materially, and in this way the temperature of the furnace may be obtained without the use of pyrometers or other instruments which would have to be so constructed as to stand very high temperatures, it being found impossible in practice to produce pyrometers, for example, which will show the temperatures reached in theinterior of a blast furnace, and will stand up in use.

Another of the many applications of the invention is to be found in boiler furnaces. It has been customary to make use of CO machines for determining CO content of gases which are taken from the 'uptake of each boiler. Boiler settings substantially always have more or less air leaks in various places therein, and it is impossible in practice to get correct CO content from uptake gases of boiler settings, because the CO content thereof is always different from what it is in the neighborhood of the combustion chamber.

In my prior Patent, No. 1,246,656, issued November 13th, 1917, I have shown how a small portion of the furnace gases may be short circuited through a short circuit passage such as an opening in the bridge wall or bai'i'le, and have disclosed means for indicating temperature changes in gases passing through such short circuit passage. In accordance with the present invention, a short circuit passage of this character may be utilized as a means for obtaining a representative supply of the gases of combustion, which are taken directly from such passage as by means of a lateral passage or conduit leading to a CG machine, which with a temperature chart calibrated as already explained, serves to give a direct indication of temperatures obtained in the combustion chamber.

The invention may also be applied to great advantage in the burning of powdered coal or other fuel in highly divided form, and containing substantially considerable proportions of fixed carbon, with an air or air and steam jet. In this case the proportions of fuel and of air or both can be readily controlled, and by determining the CO, content of the combustion gases, as with a CO, machine, calibrated to show temperatures, the control of the combustion obtained may be readily regulated and desired temperatures obtained within substantially narrow limits.

It is to be understood of course, that the present invention gives best results when applied to fuels high in percentage of fixed carbon, such as anthracite coal, coke and the like. Where considerable proportions of other combustible materials such as hydro gen, hydrocarbons and the like are present, the CO content cannot be depended on to give the results of combustion, and calibration to temperatures based thereon can similarly not be depended upon to give the temperatures obtained.

In the drawing Fig. l is a perspective view of a boiler in its setting and equipped with apparatus for indicating temperature by CO, content of furnace gases. Fig. 2 is an enlarged diagrammatic view of a chart calibrated to show temperatures from CO content of gases.

In said drawings represents a short circuit passage through the bridge wall 11 of a boiler furnace 12. 13 is a pipe or conduit leading from the passage 10 to a C0 machine 14 and gases are drawn through the conduit 13 to the CO, machine which acts to determine CO content in the usual well known manner. Instead of the usual inclication of CO content being made, however, the usual chart or record sheet of the CO,

machine is replaced by a chart or record sheet 15 calibrated to show temperatures as indicated in Fig. 2 and the record line 16 though actually made bv and corresponding to CO content givesan indication of te1nperatures obtained in the combustion chamber.

It will be seen that by my invention temperature indications may be obtained without exposure of any of the usual thermometric devices to furnace heat, and that there is none of the liability to errors or breakdown which may result from injury to pyrometer tubes or couples, for example, where same are exposed directly to a source of heat.

I claim:

l. The combination with means controlled in accordance with the CO content of combustion gases of a chart cooperating with said means for directly indicating temperatures corresponding to CO content of the gases.

2. The combination of a combustion apparatus producing combustion gases containing GO with indicator means controlled in accordance with the CO content for indicating corresponding temperatures, and means for supplying combustion gases thereto from the combustion apparatus.

3. The combination with a combustion chamber and a passage to which combustion gases pass indirectly, of a short circuit conduit between said combustion chamber and passage, means controlled in accordance with the CO content of' combustion gases and having a chart calibrated to show temperatures directly therefrom, and means for supplying gases thereto from said short circuit conduit.

In testimony that I claim the foregoing, I have hereto set my hand, this 13th day of February, 1919.

FREDERICK D. POTTER.

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