US1562087A

US1562087A - Method of and apparatus for controlling combustion

Info

Publication number: US1562087A
Application number: US358018A
Authority: US
Inventors: Griswold John William
Original assignee: Henry L Doherty & Co
Current assignee: Henry L Doherty & Co
Priority date: 1920-02-12
Filing date: 1920-02-12
Publication date: 1925-11-17
Anticipated expiration: 1942-11-17

Description

Nov. 17, 1925 -1 ,562,0s7

I J. w. GRISWOLD METHOD OF AND APPARATUS FOR CONTROLLING COMBUSTION Filed Feb, '12, 1920 Patented Nov. 17, 1925.

UNITED STATES JOHN WILLIAM GRISWOLD, OF WARREN,

1,562,087 ENT OFFICE.

PENNSYLVANIA, ASSIGNOR TO HENRY I4.

PAT

YORK, N. Y.

DOHERTY & COMPANY, A COPARTNERSHIP COMPOSED OF HENRY L. DOHERTY I AND FRANK W. FRUEAUFF, OF NEW METHOD OF AND APPARATUS FOR CONTROLLING COMBUSTION. I

Application filed February- To all whom it may concern:

Be it known that I, J OHN WVILLIAM GiuswoLn, a citizen of the United States of America, residing at Warren, in the county of \Varren, State of Pennsylvania, have invented certain new and useful Improvements in Methods of and Apparatus.forCYmtrolling Combustion; and I do" hereby declare the following tojbe .a'ful'lfclear, and exact descriptien o 1e lnven ion, lTus'Wil'heIk' able others skilled in the art to whiEh it ap- JJ JlQjLliQ-TSEO make and use the same.

i the oxygen necessaryf'for burning all of the\ This invention relates to a method of and an apparatus for controlling the combustion of fuel in a furnace, and more particu larly to a method and apparatus for controlling the combustion of-fuel in accordance with the composition of the flue gases leaving the furnace. To obtain perfect combustion of fuel, it is essential that sufficient air or other source of oxygen be supplied to a furnace to provide fuel. In utilizing the heat of combustion of fuel in a commercial furnace, it is very desirable that all of the products tion shallbe burned before passgg outof' contact with a heat transferring surffie and \ghihat unburned combustible gases shall not 10 carried out of the furnace with the exu might insure a complete 0 haust product though the use of a large excess of air for combusmgz in a furnace o bustion of the fuel, such an excess is not desirablebecause it tends to cool the flame temperature and the combustion zones and acts to carry a large quantity of unabsorbed heat out of the furnace with the e xhaus t products. The 1deal onditions for combustion, accordingly,

may beobtained when the minimum of air necessary to effect complete combustion of the fuel is supplied to t-hefilrnace. In the practical operation of a furnac however. in order to insure that there shall be an adequate supply of air, it is advisab' to provide a slight excess of air over tha necessary for complete combustion, as indlcated by the existence in the flue gases of a small percentage only of free oxygen. V

The presence of free oxygen or uncons'umed combustible gases in the products of combustion may, in certain cases, be indirectly detected by a determination of the amount of carbon dioxide in the flue gases and a \tion of the flue g. ses.

12, 1920. Serial] No. 358,018.

knowledge of the empirical relation between the percentage of carbon dioxide and the quantity of unconsumed combustion gases. For instance, in the combustion of a fuel which is with the carbon to form carbon dioxide and practically pure carbon, nearly /o, of th oxyg n of'the air would combine 6 the percentage of carbon dioxide in the flue portion of carbon and hydrogen is used the A rough con regulation of combfitiom wvigcentage of carbon dioxide in the flue gas ul accordingly be rendered unreliable. The primary object of the present invention is to provide a process of regulating the; combustion of fuel in a furnace in which the vide an apparatus fol; regulating the oo1nbustion of fuel in a furnace bytwhich the supply to said furnace of air for supporting combustion is controlled directly by the of combussupply of air to said furnace is controlled so quantity of free oxygeninthe products of .7 r

combustion from said furnace.

A further "object of the invention is to i provide a method OfreguIating the combustion of fuel-in a boiler furnace, in which the r rate of combustion of the fuel is controlled by the boiler pressure, and the character c; E

combustion is controlled by the amount of free oxygen or combustible gases in the products of combustion in the furnace.

A further object of the invention is to plgvide an apparatusin whichthe supply of air forsupporting combustion is con-.1. tinuouslv under the control of the composi- 1 With these and o ratus described in the following specification and defined in the claims.

then-objects in view, the invention consists in the process and .appa- H The various features of the invention-are unconsumed oxygen in the products of combustion leaving the furnace. To this end, a primary draftof air is admitted beneath and forced upwardlythroughthe fuel bed wastes":

electric circuit is arrangedto control a draft regulating damper to decrease the supply of secondary air to the furnace when the quantity of tree oxygen in the flue gases rises above a maximum amount.

If liquid or gaseous fuel is used, the supply of fuel, and accordingly therate of combustion, may be controlled directly by the steam pressure of the boiler. and the entire quantity of air supplied to the furnace, and accordingly the character of rgmbustion, may be controlled by the oxygen content of thefuel gases.

A combustion regulator applied to an ordinary coal fired steam boiler. is shonlg in arid the rate ofcombustion is regulatedby l ig l. In this arrangement, air for support- M,

increasing or decreasing the draft. To, insure tlfiwmpleteutilization of this primary ing ombustig is forced through an air spgp ly pipelO authegters a furnace 12 un- W of air, a comparat'rveljwthiclrbed o't der a'tuel" grate '14fiLl quantit-y. pi i fuel 1 w which acts similarly to a gas.;lla,sgi ng through the p e-wTethegpace un 5 producer to tornLcarbon monoxide in the upwardly pass ing gases. The priinary-air as it leaves the tuel bed, therefore, carries with it a considerable amount of unburned combustible gases. To complete the coml tion of the unburned gases, a sec ary supply of air slightly in exc of that sufiicient to insure com 1 combustion is introduce 1e combustiop c haniber above 'Wfuel bed.

'lhe quantity 'oi' secondary air supplied to the furhace' is controlled directly by the 5 thrgggh a second gas meter. If there is no sp,eedflan the meter through I passes to the absorption chain er. The two (,0 d to a differential sample of flue gas flows through an absorpj ifierentspeeds due to absorption of through a lever 24 denihe grate 14 controls the rate offlin amp ed by the steam pressure of the a pressure diaphragm 18 which communicates through a connecting conduit LO ii it T a steam drum 22 of the boiler. The movement of the diaphragm 18 with variations in -steam pressure of the boiler is transmitted and a connecting rod 26 quantity of free oxygen in the products of t,o,the./dainper 16? Asthe pressurein"the combustion passing from the furnacer Td steam drum 22 of the boiler increases, the

this end a small portion of the products of combustion 1S continuously withdrawn from the furnace finefthrougl-iei'gas meteifivhfidiring\rod 26 to mov "*Which is filled with an oxygen absorbing substance to completely remove any free oxygen contained 111 the products of combustion, and from the absorbing chamber passes free gxygenin' the products of con'ibiistion, there will be no change in the volume of gas passing through the absorption chamberand the twoineters placed at opposite sides of saidgabs'orption chamber will be rotated at substantially the samelrate of speed. When the flue gas contains free oxygen, the volume of the gas passing through the absorp tionchainber'willbe decreased by the absorption of the oxygen gndothe second gas tion is withdrawn meter will be mtatedilt a slower rate'o' e gas speed of rotation of the gas meters is'equal,

but which is refitted to close an electric draft regulating circuit when the meters rotate at free oxygen in the absorption chamber. The

diaphragm movement through the lever 24 and connectmperddtoward closed'p'b'sitibn Conversely. when the steam pressure in the drum 22 falls, the diaphragm 18 is depressed and transmits its 18 rises and the damper 16 is iWL (spar position.

The combustlon ot tlfe'unburned combustible gases leaying the fuel bed is completed by mean'sdf a secondary airsupply introduced by a branch pipe 28 leading from the pipe 10 to a combustion chamber- EEO above the grate 14; From the cgnib'ustioiflamber 30 'the products ot/cgmbustfdn pass back and forth in contact with' a bank of Water tubes 32 and leave the furnace through a flue 34:. a

In testing the products of combustion p g r ugh the flue 34Yfor free oxygen, 1 Small P rtion of the products of combusfrom the flue 34 through b11108 36 and passed through a wet gas meter 38 to determine the rate at which the gas is witlidrawn. From the gas meter 38, the

which is-filled with phosphorous or other material capable of selectively absorbing free oxygen without affecting the other constituents of the flue gas. An alkaline solution of pyrogallol may be used, butin that case it will be necessary to tion chamber 40 er 16, the position of wliih intermittent energizing of the solenoid 88, the switch 124 is closed for definite intervals and a lifting force exerted on the-rod 134 through the energizing of the solenoid 130. In this manner a series'of lifting impulses is exerted on the lever 138 to close the damper 116. If this closing action does not suffice to bring the free oxygen content of the flue gases back to the desired maxi-. mum limit, the contact 50 will continue to move downwardly and to connect the plate 68 successively with the branch circuits 80, 82'and '84 and to thereby lengthen the periods of time during which current is sent through the solenoid 88. The effect of increasing the length of time during which the solenoid 88 is energized is to increase the length of time during which the switch 124 is closed and the current is sent through the solenoid 130. In this manner, a more prolonged lifting action is exerted on the rod 134 until the damper 116 is closed sufficiently to bring the oxygen content of the gases in the flue 34 below the desired maxi- .mum limit. When this point is reached, the

volume ofthe sample of flue gases is substantially undiminished in passing through the absorption chamber 40 and the meter shaft 48 is rotated at a slightly greater rate of speed than the shaft 46 and the contact 50 is thereby lifted into its uppermost po: sition. I

When the contact 50 is in its uppermost position, the switch 124 is continually held open by the spring 126 and the circuit through the solenoid 130 is continually open. The weight of the damper operating lever mechanism acts on the link 118 to slowly open the damper 116 until the oxygen content of the ases in the flue 34 rises to the point at which the contact 50 is operated in the manner described above. The action of the dash pot 142 and the .iston 140- retards the movement of the amper operating mechanism to such an extent that a slightchange in the position of the damper 116 will affect the draft regulating device before the damper 116 will have moved into extreme positions.

While. the invention has been described as applied to a steam boiler in connection with a device by which the rate of combustion is independently regulated, the apparatus described above may be used in other --cases without an independent device for regulating the rate of combustion. For example, in brass melting and similar metallurgical furnaces, the rate of combustion is regulated by hand and combustion is controlled to give a maximum temperature. For this purpose, the supply of air must be so regulated that there will be very little if any excess of air supplied and accordingly little or no free oxygen in the prodnets of combustion, since the addition of air manner that the amount of free oxygen in the combustion-products is reduced to the minimum amount necessary toinsure complete combustion of the fuel. y

The method and apparatus of this invention are similar in certain of their broader aspects to the method and apparatus for controlling the combustion of fuel in a furnace, disclosed in my co-pending application, Serial No. 358,016, filed Feb. 12, 1920. The subject matter common to this application and application, Serial No. 358,016 is claimed in the latter application.

Having described the invention, what is claimed as new is:

1.A combustion regulator for furnaces,

comprising means continuously acting to increase the draft-to a furnace, means governed by an electric current for intermittent- 1y decreasingsaid draft, a gas absorption chamber, means for drawing a portion of the products of combustion from said furnace through the gas absorption chamber, and means governed by thedecrease in volume of the gas in passing through said absorption chamber for controlling said electric current. a

2. A combustion regulator for furnaces, comprising means continuously acting to increase the draft to a furnace, means gov-. erned by an electric current for intermittently decreasing said draft, means for retard ing the speed of said draft increasing and decreasing means, a gas absorption chamber, means for drawing a portion of the prodnets of combustion from said furnace through the gas absorption chamber, and

means governed byv the decrease in volume of the gases in passing through said absorption chamber for controlling said electric current. 3. A combustion regulator for furnaces, comprising adamper for controlling the draft to a furnace, a lever mechanism acted upon by gravity to move said damper into open position, an electromagnetic means acting on said lever mechanism to close said damper upon passage of current thru said electromagnetic means, a. gas absorption chamber, means for-drawing a portion of the products of combustion. from said furnace thru the gas absorption chamber,and means governed by the decrease in volume of the gas in; passing through said absorption chamber for opening and closing said electric current through said electromagnetic damper operating mechanism. p

4. combustion regulator for furnaces,

comprising a damper for controlling the draft to a furnace, a lever mechanism acted upon by'gravity to move said damper into open position, an electroi'nagnetic means acting on said lever mechanism to close said damper upon passage of current thru said electromagnetic means, a dash pot device acting on said lever mechanism to retard the movement of said damper, a gas absorption chamber, means for drawing a portion of the products of combustion from said furnace through the gas absorption chamber, and means governed by the decrease in volume ,of the gas in passingthrougli said absorption chamber for opening and closing said electric current through said electromagnetic damper operating mechanism.

A combustion regulator for furnaces, comprising means for controlling the supply of air for supporting combustion to said furnace, a gas measuring means, an absorption chamber, a second gas. measuring means, means for drawing a portion of the products of combustion from said furnace thru'said first measuring means, said absorption chamber and second measuring, means, and means controlled by said gas measuring means for operating the means for controlling the air supply to the furnace.

6. A combustion regulator for furnaces, which comprises means continuously acting to increase the draft to a furnace, means acted upon by the passageof an electric current to decrease said draft. means for directing said current thru one of a series of parallel branch electric circuits, a make and break device arranged. to intermittently open and close said branch electric circuits for varying lengths of time, and means governed by the amount of free oxygen in the products of con'ibustion passing from said furnace for connecting said current through the branch electric circuit having the longest period of closing the oxygen contained in the said products of eon'ibustionincreases.

7. A combustion regulator for furnaces, comprising a gas meter, a gas absorption chamber, a second gas meter, means for drawing a portion of the gas passing from said furnace "successively through said first gas meter, said absorption" chamber and said second gas meter, a differential gear driven in opposite directions by the differ.

ences in speed of rotation of said meters, a contact moved by said difierential gear, a

series of'parallel branch electric circuits po- 1 sitioned to be separately and singly closed by said contact, means-for intermittently opening said separatebranch circuits for different lengths of time, a magnetic switch connecting the said branch circuits, 2. second circuit closed by said magnetic switch, a solenoid in said-second circuit and a draft controlling damper operated by said solenoid.

8. A combustion regulator for furnaces, com 'n'ising a gas meter, a gas absorption cl'iamber, a second gas meter, means for drawing a portion of the gas from said furnace successively through said" first gas an electric circuit for different intervals of time and increasing the time of each closure as the difference in flow of gas through said meters increases, a solenoid excited by said current in said circuit, a draft controlling damper urged toward open position by a constantly acting force and toward closed position by said solenoid, and means for retarding the motion of said damper.

10. A combustion regulator for furnaces, coi'nprising a gas meter, at gas absorption chamber, a secondgas meter, means for drawing a portion of the gas passing through said furnace successively through said first gas meter. said absorption chamber and said second gas meter, a series of parallel branch electric circuits, a contact operated by the difference in volume of gas passing through said meters to separately and singly close said branch electric circuits, means-for intermittently opening and closing said branch electric circuits for different lengths of time, a magnetic switch arranged to be closed during the passage of intermittent currents through. said branch electric circuits, and means controlled by said second circuit for operating the draft cont-rolling damper'of said furnace.

11. A combustion regulator for furnaces, comprising means constantly acting to increase the draft to a furnace, means for constantly testing the quantity of free oxygen in the products of combustion from said furnace, and means acting intermittently for increasingly longer periods of time, as the quantity of free oxygen'increases beyond a certain percentage, to decrease said draft. a I

12. The method of regulating combustion in furances, which comprises continuously removing a sample of the flue gases from a furnace, continuously testing sald sam' ple of flue gases for free oxygen, continu- 1 is below a certain percentage, and decreasintermittent energizing of the solenoid 88, the switch 124 is closed for definite intervals and a lifting force exerted on the rod 134 through the energizing of the solenoid 130. In this manner a seriesof lifting impulses is exerted on the lever 138 to close the damper 116. If this closing action does not suffice to bring the free oxygen content of the flue gases back to the desired maxi: mum limit, the contact 50 will continue to move downwardly and to connect the plate 68 successively with the branch circuits 80, 82'and 84 and to thereby lengthen the periods of time during which current is sent through the solenoid 88. The effect of increasing the length of time during which the solenoid 88 is energized is to increase the length of time during which the switch 124 is closed and the current is sent through the solenoid 130. In this manner, a more prolonged lifting action is exertedon the rod 134 until the damper 116 is closed sufliciently to bring the oxygen content of the gases in the flue 34 below the desired maximum limit. When this point is reached, the volume ofthe sample of flue gases is substantially undiminished in passing through the absorption chamber 40 and the meter shaft 48 is rotated at a slightly greater rate fore the damp with a device by which of speed than the shaft 46 and'the contact 50 is thereby lifted into its uppermost position.

When the contact 50 is in its uppermost position, the switch 124 is continually held open by the spring 126 and the circuit through the solenoid 130 is continually open. The weight of the damper operating lever mechanism acts on the link 118 to slowly open the damper 116 until the oxygen content of the gases in the flue 34 risesto the point at which the contact 50 is operated in the manner described above. The action of the dash pot 142 and the iston 140 retards the movement of the amper operating mechanism to such an extent that a slight change in the position of the damper 116 will affect the draft regulating device beer 116 will have moved into extreme positions.

While the invention has been, described as applied to a steam boiler in connection the rate of combustion is independently regulated, the apparatus described above may be used in other cases without an independent device for regulating the rate of combustion. For example, in brass melting and similar metallurgical furnaces, the rate of combustion 1s regulated by hand and combustion is controlled to give a maximum temperature. For this purpose, the supply of air must be so regulated that there will be very little if any excess of air supplied and accordingly little or no free oxygen in the prod since the addltlon of air nets of combustion,

above that necessary for complete combustion reduces the temperature obtained because of the cooling action of the excess air. In this case, therefore, the above described combustion control device is used, without an automatic device for controlling the rate of combustion, to control the total amount of air supplied to the furnace in such a manner that the amount of free oxygen in the combustion products is reduced to the minimum amount necessary to insure complete combustion of the fuel.

Having described the invention, what is I crease the draft to a furnace, means governed by an electric current for intermittentlydecreasing said draft, means for retard ing the speed of said draft increasing and decreasing means, a gas absorption chamber, means for drawing a portion of the products of combustion from said furnace through the gas absorption chamber, and means governed by the decrease in volume of the gases inpassing through said absorption chamber for controlling said electric current.

3. A combustion regulator for furnaces, comprising a damper for controlling the draft to a furnace, a lever mechanism acted upon by gravity to move said damper into open position, an. electromagnetic means acting on said lever mechanism to close said comprising a damper for controlling the draft to a furnace, a lever mechanism acted upon by'gravity to move said damper into open position, an electron'iagnetic means acting on said lever mechanism to close said damper upon passage of current thru said electromagnetic means, a dash pot device acting on said lever mechanism to retard the movement of said damper, a gas absorption chamber, means for drawing a portion of the products of combustion from said furnace through the gas absorption chamber, and means governed by the decrease in volume of.the gas in passing through said absorption chamber for opening and closing said electric current through said electromagnetic damper operating mechanism.

A. combustion regulator for furnaces, comprising means for controlling the supply of air for supporting combustion to said furnace, a gas measuring means, an absorption chamber, a second gas measuring means, means for drawing a portion of the products of combustion from said furnace thru said first gas measuring means, said absorption chamber and second measuring. means, and means controlled by said gas measuring means for operating the means for controlling theair supply to the furnace.

6. A combustion regulator for furnaces, which comprises means continuously acting to increase the draft to a furnace, means acted upon by the passage-of an electric current to decrease said draft. means for directing said current thru one of a series of parallel branch electric circuits, a make and break device arrangedv to intermittently open and close said branch electric circuits for varying lengths of time, and means governed by the amount of free oxygen in the products of combustion passing from said furnace for connecting said current through the branch electric circuit having the longest period of closing as the oxygen contained in the said products of combustion increases.

7 A-combustion regulator for furnaces, comprising a gasmeter, a gas absorption chamber, a second gas meter, means for drawing a portion of the gas passing from said furnace successively through said first gas meter, said absorption" chamber and said second gas meter, a differential gear driven in opposite directions by the differ-.

ences in speed of rotation of said meters, a contact moved by said differential gear, a

series of parallel branch'electriccircuits po- 1 sitioned to be separately and singly closed by said contact, means-for intermittently opening said separatebranch circuits for different lengths of time, a magnetic switch connecting the said branch circuits, a second circuit closed by said magnetic switch, a solenoid in saidsecond circuit and a draft controlling damper operated by said solenoid.

8. A combustion regulator for furnaces, comprising a gas meter, a gas absorption chamber, a second gas meter, means for drawing a portion of the gas from said furnace successively through said first gas meter, said absorption chamber and second gas meter, and means controlled by the dif fcrence in speed of rotation of said meters for controlling the draft to said furnace.

9. A combustion regulator for a furnace, comprising means for measuring the rate of {low of gas, an absorption chamber,'a sec' ond means for measuring the rate of flow of gas, means for drawing a portion of the products of combustion from said furnace successively through said first measuring means, said absorption chamber and said second measuring means, means controlled by said gas measuring .means for closing an electric circuit for different intervals of time and increasing the time of each closure as the difference in flow of gas through said meters increases, a solenoid excited by said current in said circuit, a draft controlling damper urged toward open position by a constantly acting force and toward closed position by said solenoid, and means for retarding the motion of said damper.

,10. A combustion regulator for furnaces, comprising a gas meter, a gas absorption chamber, a secondgas meter, means for drawing a portion of the gas passing through said furnace successively through said first gas meter. said absorption chamher and said second gas meter, a series of parallel branch electric-circuits, a contact operated by the difference in volume of gas passing through said meters to separately and singly close said branch electric circuits, means for intermittently opening and clos ing said branch electric circuits for different lengths of time, a magnetic switch arranged to be closed during the passage of intermittent currentsthrough said branch electric circuits, and means controlled by said second circuit for operating the draft cont-rolling damper of said furnace.

11. A combustion regulator for furnaces, comprising means constantly acting to increase the draft to a furnace, means for constantly testing the quantity of free oxygen in the products of combustion from said furnace, and means acting intermittently for increasingly longer periods of time, as the quantity of free oxygen'increases beyond a certain percentage, to de- 1 crease said draft.

12. The method, of regulating combustionin furances, whlch comprises contlnuously removing a sample of the flue gases from when the content of oxygen in the flue gases is below a certain percentage, and decreasing the draft when the quantity of free oxygen increases abovesaid fixed percenta e.

13. The method of regulating combustion in furnaces whlch comprises continuously removing a sample of the flue gases from a furnace, continuously testing said sample of flue gases for free oxygen, continuously increasing the draft to the furnace when the content of oxygen in the flue gases is below a certain percentage, and intermittently decreasing the draft when the percentage of oxygen increases beyond a fixed q naces which comprises means governed by the steam pressure in said boiler for controlling the rate of combustion in said furnace, an air supply for completing the combustion of fuel in said furnace, means continuously acting to increase said air supply to said furnace, means governed by an electrio, current-for intermittently decreasing said draft, a gas absorption chamber, means for drawing a portion of the products of combustion from said furnace through said gas absorption chamber, and means governed by the decrease in volume of gas in passing through said absorption chamber for controlling said electric current. 16. A combustion regulator for boiler furnaces which comprises means governed by the steam pressure in said boiler for controlling the rate of combustion in said furnace, an air supply for completing combus-f tion in said furnace, a gas meter an ab'sorption chamber, a second gas meter, means for drawing a portion of the products of combustion successively through said first gas meter, said absorption chamber and said sec ond gas meter andmeans governed by the difference in speed of rotation of said meters for controlling said air supply to said furnace.

17. A combustion regulator for furnaces c'om rising a primary air supply for control mg the rate of combustionof fuel in said furnace, means igoverned by the steam pressure .in said boi er fox-controlling the rate of suppl of said primary air, a second air supply or completing combustion of fuel in said furnace, a gas meter, an absorpgases rises beyond a fixed pertion chamber, a second gas meter, means for drawing-a portion of tie products of combustion successively through said first meter, said absorption chamber and said second meter and means governed by the difference in the speed of rotation of said metersfor controlling the supply of secondary air to said furnace.

18. In a furnace having primary and secondary air supplies, a combustion regi'ilator for furnaces comprising an absorption cham-. ber, means for passing a portion of the flue gases from the furnace continuously through the absorption chamber, andmeans for au-' tomatically controlling the supply. of secondary air to the furnace in accordance withthe amount of gas absorbed in said chamber.

.19. A combustion regulator for furnaces comprising an absorption chamber adapted to absorb oxygen only from the furnace gases, means for passing a portion of the gases from said furnace through the absorption chamber, and means for controlling the supply of air to the furnace in accordance with the extent-to which the volume of the furnace gases is reduced by-the' absorption of oxygen from them.

20. A'combustion regulator for furnaces comprising means for removing the free oxygen from a portion of the flue gases and means'for controlling :the' six pl of air to the furnace in accordance with t e ratio of the volume of gasesiibefore' and after the removalof the oxygen.

21. Th in-furnaces which comprises continuously removing a sample stream of the flue gases e method of regulating combustion from a furnace, effecting a continuous analy-- sis of the chemical composition of said sample, metering the volume ofthegasesbefore and after the analysis and automatically governing the draft on said furnace in ac-,

cordance with the volume change of the sam ple effected by the analysis.

' 22, The method of regulating comfbustion' in furnaces which comprises continuously removing asample stream of flue gases from a furnace, efiectmg-awontinuous chemical combination of the free oxygen in said sample, measuring the volume change in said sample produced by said combination and regulating the amount of draft'on the furnace inaccordance with said volume change.

23 ."The methodof regulating combustion in furnaces which comprises continuously removing a sample stream of the flue gases from a furnace, continuously absorbing the free oxygen content of said'sample' and re lating the draft to the furnace by a mec anism responsive to the volume change in said sample before and after the absorption. In testmron whereof I aflix m signature. J OHN WILLIAM GRI WULD.