US1709042A - Combustion apparatus - Google Patents

Description

April 16, 1929.

H. c. SIEBE RT COMBUSTION APPARATUS Filed May 20, 1924 2 Sheets-Sheet l INVENTOR 6i Swfieri ATTORNEY April 16, 1929. H. c. SIEBERT COMBUSTION APPARATUS Filed May 20, 1924 2 Sheets-Sheet iiitt t? INVENTOR a 49 wwfi,

ATTORNEY ,Patente'd I Apr. I 16,

- STATES 1,709,042 PATENT OFFICE.

s rnnr. comraur.

commission API'ARATUS.

Application filed May 20,1924. Serial No. 714,530.

My invention relates to combustion apparatus and it has for an object to prov de means in connection therewith for keeping the combustible gases in the products of combustion at a minimum. V

More particularly, my invention has for an object to provide combustible gas detectlng apparatus in connection with a furnace which detecting apparatus serves to regulate combustion. v

y A further object of my invention is to provide, in connection with a metallurgical furnace, or in connection with any furnace where the presence of combustible gas is undesira- 1 ble owing to its chemical reaction on materlal being treated, and which furnace or apparatus is maintained at predetermined temperatures, means for detecting the presence of combustible gas in the products of combustion, which means operates in conjunction with suitable pyrometric apparatus to provide for combustion to maintain a desired temperature with the presence of combustible gas in the products of combustion at a minimum.

An excess of air in the furnace means an excess of oxy en and therefore the atmosphere is oxi izing. On the other hand, should there be an excess of combustible gas, the atmosphere is reducing.

It is, therefore, an object of my invention to so control the relative amounts of air and fuel admitted that, not only are desired and predetermined temperatures maintained, but also the character of the furnace atmosphere may be varied to suit different requirements. In melting furnaces, such as an open hearth furnace, the atmosphere may be oxidizing or reducing; and in heat treatment furnaces, such as heating, annealing, tempering, and tinning and galvanizing furnaces, the atmosphcre may be neutral or slightly reduc ing, but should not be oxidizing.

These and other objects are accomplished by my invention as will be apparent from'the following description taken in connection with the accompanying drawings, forming a part of this application, in which: a Fig. 1 is a diagrammatic viewof a furnace 50 showing my improved regulating apparatus applied thereto; a

Fig. 2 is a diagrammatic view showing my improved regulating apparatus applied to a furnace of the steam boiler type; and,

Fig. 3 is a diagrammatic view of a metallurgical furnace showing my improved combustion regulating apparatus applied thereto.

Referring now .to the drawings for a better understanding of my invention, in Fig. 1, I show a furnace, at 10, having a-fuel sup ly line 11 and air supply line 12, the latter being provided with a suitable control valve 13. The position of the valve 13 is regulated in accordance with the amount of combustible gas in the 1products of combustion; and, to this end, I s ow a combustible gas detecter, at 14, which is sensitive to-combustible gas in the products of combustion and which operates, through a suitable relay, at 15, to control reversible operating means, at 16, for example, an electric motor mechanically connected to the valve 13.

The combustible gas detecter is preferably of the Wheatstone bridge type. The bridge comprises resistance arms 17 and 18 and arms 19 and 20 connected in a parallel between the leads 21 and 22, which are connected to any suitable source of current supply, the lead 22 preferably including a rheostat 23 whereby the current passing through the arms of the bridge may be regulated. A conductor 24 is connected to the junction at 25 between the arms 17 and 18 and a conductor 26 is connected between the arms 19 and 20, the conductors 24 and 26 leading to a switch, at 28, of the galvanometer type which will be more particularly described.

The arms 19 and 20 include platinum wires extending through chambers 30 and 31 and the current passing thercthrough' is regulated to maintain a temperature of substantially 800 F. in such wires. The chamber 31 is arranged to receive products of combustion by way of the conduit 32, which extends into the furnace, at 10. 1 A current of such products of vcombustion through the chamber 31 is assured, as indicated by the arrows, by a suit-ableejector 33 which is connected at the end of the chamber 31-opposite to the connection of the conduit 32 therewith. If the products of 100 combustion contain any combustible gases, such as carbon monoxide or hydrogen, when they come into contact with the heated platinum wire in the chamber 31, catalytic action ensues, that is, combustion of the combustible 105 constituents takes place and the temperature of the arm 20 is increased, with the result that the electric resistance of such arm is also increased. Ordinarily there would be sufficient oxygen in the products of combustion 110 to provide for combustion of any combustible gases as might pass through the chamber 31; however, in order to provide for any doficiency in the supply of oxygen, I show an air supply conduit 34 connected to tlieconduit 32, the inner end of the conduit 34 being connected to a scrubbing chamber 35 which, in turn, communicates with the atmosphere through a port 36.

From the structure described, it will be apparent that a rise in temperature of the wire in the chamber 31 results in an increase in resistance thereof and consequently an unbalancing of the bridge with the result that current flows through the conductors 24 and 26 to secure actuation of the coils of the galvanometer switch, at 28.

The galvanometer switch, at 28, includes any suitable movable coil element in series with the conductors 24 and 26 or equivalent devices and such element carries a contact member 37 which is arranged to contact, with segments 38 and 39 separated by appropriate insulating material, at 40. The arm 37 is connectedto a conductor 42, which is connected to any suitable source of electric current supply, as a battery 43. The segments 38 and 39 are connected by the conductors 44 and 45, respectively, to the solenoids 46 and 47, respectively, and the other terminals of the solenoids are joined together and are connected, by the conductor 48, to the other terminal of the battery 43. The solenoids 46 and 47 are spaced apart a suitable distance and are in substantial alignment. A switch arm 50 is pivotally mounted at 51 and it has an arma- -ture element 52 disposed between opposing ends of the solenoids 46 and 47. It will be apparent, therefore, that the armature 52 and the arm 50 will be attracted either to the solenoid 46 or to the solenoid 47 depending upon which of the contacts 38 and 39 is engaged by the contact arm 37.

The arm 50 of the relay is connected to current supply lead 53 from any suitable source and, at its upper end, it carries a con-- tact element 54 for engagement with either of the contacts 55 and 56, connected, respectively, to the conductors 57 and 58 leading to the reversible motor, at 16. The other current supply lead 59 is connected directly to the reversible motor. It will be apparent, therefore, that the relay, at 15, is operative in opposite directions in respect to the combustible gas content in the products of combustion in the furnace, at 10, to control the direction of rotation of the motor, at 16, to move the valve 13 either in an opening or in a closing direction.

In operation, assuming, that fuel in gaseous or liquid form is supplied through the conduit 11 to the furnace and that the combustible gas content of the products of combustion should increase, this would result in unbalancing the detecter bridge, at 14, and the galvanometer switch, at 28, would be operated to move the arm 54 in a direction to so close a circuit for the motor, at 16, resulting in operation of the latter to open the valve 13 wider so as to increase the air supply and reduce the combustible gas. In operation, too much air may be supplied, in which case, the apparatus would operate to move the valve 13 in a closing direction. To this end, the resistance arms 17 and 18 and 19 and 20 are so arranged that the bridge is unbalanced when the wire 20 is heated to a predetermined minimum extent above its normal temperature due to the presence of combustible gases drawn from the furnace. \Vhen the bridge is in equilibrium, the contact arm 37 will occupy a position over the insulated separator 40 between the contacts 38 and 39 so that the valve 13 is held in a fixed position so long as the quantity and qualit of fuel supply shall remain constant. ombustible gas in an amount in excess of the predetermined minimum therefore, results in actuation of the apparatus to move the valve 13 in an opening direction to supply more air for combustion. On the other hand, when the combustible gas tends to drop below the predetermined minimum, the bridge operates to secure movement of the galvanometer switch in the other direction and movement of the reversible motor 16 in the opposite direction to move the valve 13 in a closing direction to cut down the supply of air.

The apparatus shown and described in connection with Fig. 1 is particularly applicable to a furnace using gaseous or liquid fuels. In so far as my invention is concerned, however, the principles are equally applicable to furnaces of other types, two of which will now be described.

In Fig. 2, I show a furnace, at 61, of the ordinary steam generating type which includes a stoker 62 having an air supply conduit 63 provided with a control valve 64, the latter being mechanically connected to a rc- Versible motor, at 16. such as heretofore described. A combustible gas detecter, at 14, is in communication with the combustion space or any place through which products of combustion pass; and, such detecter operates in the manner already described to secure opening or closing motion of the valve 64 in accordance with the combustible gas The valve 70 is therefore regulated by a pyrgmetric device. A reducing atmosphere is maintained at a desired value by apparatus already described which functions to control the degree of openness of the valve 68 in the air supply. A desirable state of combustion is, therefore, maintained in the furnace, at 66a substantially constant temperature is maintained by pyrometric regulation of the fuel valve 70; and, at the same time, for the given predetermined temperature the reducing gas component of the products of combustion is maintained at a desired value by proper regulation of the air supply in the Fanner already described in connection with 1g. 1. Referring now to the pyrometric apparatus for controlling the fuel valve 70, I show a pyrometer 71' of a well-known type and which is suitably'located in the furnace, at 66. The leads 72 and 73 of the thermo-couple of the pyrometer are connected to voltmeter type of apparatus 74 having an arm 7 5 adapted to engage with contacts 76 and 77 connected, respectively, to the conductors 78 and 79 leading to a reversible relay, at 80, which serves to move the valve 70 in opening and closing directions to regulate the quantity of fuel supplied to the furnace for the purpose of maintaining a substantially constant temperature. A drop in temperature indicates a deficiency in fuel and the pyrometer responds to open the valve 70 wider to supply more fuel. An increase in temperature in the furnace has the contrary effect.

With the maintenance of a substantially constant temperature in the manner just referred to, the combustible gas detecting apparatus operates to maintain the combustible atmosphere in the furnace at any desired value by proper regulation of the air supply, thereby making it possible to give proper heat treatment to any suitable material, such as metal, at a predetermined temperature, without the danger of affecting the chemical constituents of the material undergoing treatment in the furnace to any deleterious extent. As shown in Fig. 3, the conduit 32 for supplying a portion of the products of combustion to the detecting apparatus, at 14, has its lower end 81 arranged contiguously to the pyrometer so that each of these instruments shall be affected by products of combustion having substantially constant characteristics.

From the foregoing, it will be apparent, that I have devised combustion apparatus in which a closer regulation is maintained by properly controlling the air supply in accordance with the combustible gas in the products of combustion. It will also be seen that my improved combustible gas air regulating apparatus is particularly useful in connection with a heat treatment furnace of any type wherein it is desirable to maintain a substantially constant temperature While at the same time avoiding the generation of an oxidizing or an excessively reducing atmosphere in quantities suflicient to affect chemically material being treated.

It is to be understood that, in so far as my invention is concerned, any suitable character of fuel, solid, liquid or gaseous, may be used.

While 'I have shown my invention in a plurality of forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed there upon as are imposed by the prior art or as are specifically set forth in the appended claim.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

In a metallurgical furnace, the combination of a conduit for supplying air to the furnace, a conduit for supplying fuel to the furnace, valves in the conduits, a'pyrometer in the furnace for controlling the position of the fuel valve, and means responsive to the combustible gas content of the products of combustion to control the air valve.

In testimony whereof I hereunto affix my signature this 12th day of May, 1924.

HERMAN C. SIEBERT.

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