US1964544A - Method of firing furnaces - Google Patents

Description

June 26, 1934. w TRlNKs 1,964,544

METHOD OF FIRING FURNACES Filed April 5, 1928 2 Sheets-Sheet l gwvemtoz June 26, 1934. w. TRINKS METHOD OF FIRING FURNACES 2 Sheets-Sheet 2 Filed April 5. 1928 gwuwnto'o Ll/l Ill bO/d Trzn/(s 61 Momma Patented June 26, 1934 PATENT OFFICE METHOD OF FIRING FURNACES Willibald Trinks, Pittsburgh, Pa., assignor to Libbey-Owens-Ford Glass Company, Toledo, Ohio, a corporation of Ohio Application April 5, 1928, Serial No. 267,726

'20 Claims. (01. 158-1175) This invention relates to furnaces and method of firing the same.

One of the important objects of the invention is to provide a combustion type furnace and '5 method of firing the same whereby a highly luminous and radiant flame is obtained.

Another object of the invention is to provide a furnace and method of the aforesaid character wherein the fuel is practically burned and consumed before it leaves the furnace.

Still another object of the invention is to provide a furnace and method of this nature where- -in the length as well as the direction of the flame may be adequately and efliciently controlled.

16 Still another object of the invention is to provide such a furnace and method of firing the same wherein with the use of hydrocarbon fuels means is provided for decomposing or cracking 2O velocity through a port, in proximity to or in the presence of a heating agent, for instance, preheated air, also flowing at a low velocity, and then accelerating or facilitating complete combustion by introducing an elastic fluid by high velocity jets into the streams of slowly moving fuel and air near the mouth of the port.

Still another object of the invention is to provide a furnace and method of this nature wherein the hydrocarbon fuel is first preheated to a point just below its cracking temperature and then conducted to a port where it is subjected to heat above its cracking temperature to thus produce an energetic breaking up of the fuel gas.

Various other objects, advantages and novel details of construction of this invention will be made more apparent as this description proceeds, especially when considered in connection with the accompanying drawings, wherein:

Fig. 1 is a fragmentary vertical longitudinal sectional view through a glass furnace constructed in accordance with this invention.

Fig. 2 is a fragmentary horizontal longitudinal sectional view taken substantially on the plane.

indicated by line 2-'2 in Fig. 1.

Fig. 3 is a top plan view of the furnace.

Fig. 4 is a sectional elevational view of a reversing valve, and

Fig. 5 is a sectional View taken substantially on the plane indicated by line 5--5 in Fig. 4.

In glass melting furnaces and other combusemploy a. highly luminous and radiant flame. Likewise it is considered desirable and advantageous topractically burn the fuel before it leaves the furnace and also to control the length tion type furnaces it is generally expedient tov as well as the direction of the flame produced. Hydrocarbons, such for instance as tar, fuel oil, gasoline, acetylene and the like, which are rich in carbons, readily produce a flame of considerable luminosity. However, those hydrocarbons, such for instance .as methane or ethane which contains a considerable amount of hydrogen, have a tendency to produce a clear, blue heat which can scarcely be called a flame. If light hydrocarbons of this character are to be burned to produce a flame it is necessary to crack them, that is, by heating them in the absence of oxygen to break them up or decompose them into hydrogen and carbon. The extent of the decomposition is a function of the composition of the hydrocarbon, of the temperature to which it is heated and of the period of time during which it is maintained at a high temperathe fuel by flowing the same slowly or at a low ture in the absence of oxygen. For instance, hydrocarbon containing a relatively small amount 7 of carbon must be subjected to a higher temperature and maintained at that temperature for a longer period of time before there is any perceptible decomposition than a hydrocarbon containing a relatively greater amount of carbon.

In accordance with the present invention it is proposed to heat the hydrocarbon by the com-- bustion of a small portion of the fuel in a port of the furnace. This of itself, has been practiced before and is not claimed as new. However, in accordance with this invention the desired effect is obtained by admitting gas to the port of the furnace at a low velocity and permitting it to flow towards the furnace under a 0 layer or stratum of airalso flowing at a low velocity. Combustion occurs at the boundary between the two fluids and the gas lying under the flame of this combustion is heated and decomposed. The atoms of carbon thus formed coagulate and form flakes of soot.

The difficulty which has heretofore existed was not only that of burning the hydrogen quickly enough to produce a brilliant or luminous flame but also to burn the flakes of soot before they leave the furnace. The slower the flow of gas and of air, the greater is the breaking-up effect but at the same time the combustion is slower and less perfect. As a matter of fact the two actions, that is, breaking up and complete combustion are contrary and incompatible. While attempts have been made to obtain proper mixing by the shape of the port such attempts have generally been only partly successful beno cause they diminish one of the above actions by favoring the other.

In accordance with the present invention I propose first cracking the gas as above described and then introducing an elastic fluid by high velocity jets into the port near the mouth of the latter, the velocity of the jets being sufficient to produce a turbulent mixing and quick combustion. An elastic fluid such as compressed air can be used but I prefer to use gas as a mixing medium because it has no tendency to reduce flame temperature.

By reference to the drawings and in particular to Figs. 1 and 2 thereof one manner of carrying the present invention into execution will be described in detail.

In the drawings the reference character 10 indicates a heating device such as a regenerator connected at its upper end by means of a duct 11 to the furnace port 12. Preheated air is supplied by the regenerator 10 and passes through duct 11 to the port 12 and over bridge wall 13 and by reason of its buoyancy and its inertia it has a tendency to hug the roof or top portion 14 of the port. Viscous drag induces a secondary circulation in the otherwise dead space indicated by the reference character 15, somewhat in the manner indicated by the arrows 16. This circulation carries a small portion of the fuel gas which is admitted through fuel supply pipes 17 communicating with the port 12 at either side thereof. Extending longitudinally of the port and arranged between the fuel pipes 1'7 is a partition or monkey wall 18. g

The fuel supply pipes 1'7 are purposely of rather large diameter so that the fuel will not be forcibly ejected therefrom to thus prevent the same from. impinging against the wall 18. If the fuel did impinge against this wall it would probably spread into jets and flow into the air stream. On the contrary with the herein shown and described arrangement the greatest portion of the fuel introduced through the fuel pipes 17, because of the slight pressure produced by the incoming gas in the dead space 15, follows substantially the course or path indicated by arrow 19. While the gas is flowing through the port toward the outlet end or mouth 20 thereof the preheated air is likewise flowing therethrough toward the mouth 20, the preheated air clinging close to the roof 14 of the port while the gas flows in a substantially separate stream beneath the stream of air. At the boundary between the air and fuel gas an irregular fluttering combustion occurs in which only a small fraction of the air and fuel gas partake. The heat from this combustion, together with the heat coming from the walls of the port cracks or decomposes h h drocarbons. t rist experience has shown that the stratificaton of fuel and air persists in the furnace and that combustion is extremely slow, in fact too slow for useful purposes, unless a thorough mixing takes place at the mouth of the port. In accordance with my invention I propose to obtain this mixing by injecting a small amount of an elastic fluid such as fuel gas or air through. pipes 21 and nozzles 22. The jets of fuel gas or other fluid, under a pressure of, for instance one to flve pounds per square inch, is sufllcient to produce an excellent turbulence and mixing. In practice I have found that if fuel gas is injected, about fifteen per cent of the total fuel gas used should pass through the nozzles 22. However, obviously the percentage of gas entering the port through the nozzles 22 may be decreased or increased as found desirable, necessary or expedient. While as mentioned compressed air may be ejected through the nozzles 22 with the same mixing effect as fuel gas nevertheless compressed air results'in a slight lowering of the flame temperature and consequently is not as eilicient as fuel gas in this respect.

In order to'control the length and direction of the flame produced, the pipes 21 are preferably adjustably mounted by means (not shown) so that they may be swung in a horizontal plane or in a vertical plane as suggested by dot and dash lines in Figs. 1 and 2. If the pipes 21 are swung to the dot and dash position 21a (see Fig. 2) mixing occurs more rapidly. The ports are burned out at points just within the mouth thereof. If, on theother hand, the pipes 21 are moved to the position indicated by dot and dash lines 21b mixing occurs less'rapidly. Obviously the most satisfactory and efiicient adjustment for the pipes 21 may be determined upon full consideration of the conditions in existence and depends upon the length of the furnace, the direction of flame travel, composition of fuel, etc.

If, as shown in Fig. 1, the pipes 21 are adjusted to the position 210 indicated by dot and dash lines then the flame is shot down onto or in the direction of the'glass bath 23. ,On the other hand, if the pipes 21 are adjusted to the position 2112 indicated by dot and dash lines in Fig. 1 the flame is lifted. In glass furnaces such control is of extreme importance because it is frequently necessary to direct the flame close to the bath and yet not sufliciently close thereto to burn away certain fluxes and spoil the glass. It is also important that the pressure in pipes 21 be sumciently great to produce the momentum which is necessary to drag gas, air and the products of combustion into the wake of the jets. The lower the pressure in the pipes 21 the larger they must be and the more fluid must be passed through them in order to bring about this desirable condition and the greater is the fraction of uncracked fuel gas.

If the fuel gas is extremely lean, containing only methane, or even consisting of hydrogen with only a small admixture of hydrocarbons, it becomes necessary to preheat the fuel gas before it enters pipes 14 and 21. To this end independently flred heaters may be employed forthis preheating and the present invention contemplates the use of such heaters, although their use is not always necessary. However any external preheating of the fuel is not carried far enough to produce an energetic breaking-up of the fuel gas but yet far enough to cause an incipient breakingup, the final breaking-up and coagulation of the carbon atoms into soot flakes occuring in the port.

By reference particularly to Fig. 3 a method and means will be described wherein the waste heat of the furnace may be utilized for preheating the fuel gas. In this figure a conventional type of furnace is shown as comprising a glass containing receptacle 24 connected by ports 25 with the regenerators 10. The reference character 26 indicates a main fuel supply line which divides into two branch lines 27, these branch lines extending through the tunnels 28' of the regenerators 10. These branch lines are connected to a reversing valve 29 (see particularly Figures 4 and 5). Also connected to the reversing valve 29 are conduits 30 which act in the nature .one or the other of the conduits of headers to supply fuel to the plurality of fuel supply pipes 17. The reversing valve 29 is provided with a valve member 31 by means of which 30 may be put under pressure at one time, depending upon the direction of flame travel.

The tunnels under the regenerators are particularly well adapted for preheating the fuel gas because the temperature in them is not sumciently high to crack the fuel gas, which action would cause the pipes to clog with soot. At the same time the temperature is sufdciently high to require only a slight additional supply of heat for the purpose of starting the cracking operation as the fuel is introduced into the ports.

While an embodiment-of the invention has been described herein somewhat in detail it will be readily apparent to those skilled in this art that various modifications, rearrangements and changes may be resorted to without departing from the spiritand scope of this invention and to this end reservation is made to make such changes as may come within the purview of the accompanying claims.

I claim:

1. In the method of firing furnaces,. those steps which consist in flowing a hydrocarbon fuel andair in substantially separate but contacting streams at a low velocity through a furnace port so that there is no material intermingling thereof, and in then thoroughly mixing, these streams adjacent the mouth of the port by high velocity jets of an elastic fluid.

2. In the method of firing furnaces, those steps which consist in flowing a hydrocarbon fuel and preheated air in substantially separate but contacting streams at a low velocity through a furnace port so that there is no material intermingling thereof, causing the preheated air to crack or decompose the hydrocarbons while travcling at such low velocity, and in then thoroughly mixing these streams at the mouth of the port by high velocity jets of an elastic fluid.

3. In the method of firing furnaces, those steps which consist in flowing a hydrocarbon fuel and air in substantially separate but contacting streams at a low velocity through a furnace port so that there is'no material intermingling thereof, and in then thoroughly mixing these streams adjacent the mouth of the port by high velocity jets of fuel. s

4. In the method of firing furnaces, those steps which consist in passing a hydrocarbon fuel and air in substantially separate superimposed streams without a dividing wall through a furnace port at a low velocity so that there is no material intermingling thereof,. and in then thoroughly mixing these streams near the mouth of the port by high velocity jets of an elastic 5. In the method of firing furnaces, those steps which consist in passing hydrbcarbon fuel and preheated air in substantially separate superimposed but contacting streams through a furnace port at a low velocity so that there is no material intermingling thereof, causing the preheated air to crack or decompose the hydrocar-- bons while traveling at such low velocity, and in then thoroughly mixing these streams near the mouth of the port by high velocity jets of an elastic fluid.

6. In the method of firing furnaces, those steps which consist in flowing a hydrocarbon fuel at low velocity through a furnace port, heating the fuel partially by the heat of combustion of a which consist in fuel at low velocity through a furnace port, si-

combustion of a, fraction fraction thereof and-injecting additional fuel at high velocity near the mouth of the port.

7. In the method of firingfurnaces, those steps which consist in flowing a hydrocarbon fuel at low velocitythrough a furnace port, heating the fuel partially by the heat of combustion of a fraction thereof and injecting additional fuel at high velocity adjacent the mouth of the port through one or more nozzles in the direction of the desired flame travel.

' 8. In the method of firing furnaces, those steps which consist in flowing a stream of hydrocarbon fuel at low velocity through a furnace port, simultaneously flowing a stream of air at low velocity through said port, maintaining the stream of air'substantially separate from but in contact with the stream of hydrocarbon fuel so that there willbe no material intermingling thereof, heating the fuel by radiation from the furnace and port walls and also by the heat of combustion of a fraction of the fuel, and mixing the streams of fuel and air near the mouth of the port by high velocity jets of an elastic fluid.

9.- In the method of firing furnaces, those steps flowing a stream of hydrocarbon multaneously flowing a stream of preheated air at low velocity through said port, maintaining the stream of air substantially separate from but in contact with the stream of hydrocarbon fuel so that there will be no material intermingling thereof, heating the fuel by radiation from the furnace and port walls and also by the heat of of the fuel, and mixing the streams of fuel and air adjacent the mouth of the port by high velocity jets of relatively small proportions of fuel. I

10. In the method of firing furnaces, those steps which consist in flowing a stream of hydrocarbon fuel at relatively low velocity through a furnace port, flowing a stream of preheated air at a relatively low velocity through said port, in maintaining the streams substantially separate but in contact with one another so that there will be no material intermingling thereof, in causing combustion to occur at the boundary between said air and fuel in which only a small fraction of the air and fuel partake but which is suflicient to cause cracking of the hydrocarbons, and in then effecting a positive and turbulent mixing of the streams of air and fuel adjacent the mouth of the port to accelerate complete combustion.

11. In the method of firing furnaces, those steps which consist in flowing a stream of hydrocarbon fuel at a relatively low velocity through a furnace port and simultaneously flowing a preheatedv stream of air also at a low velocity through said port, in maintaining the streams substantially separate but in contact with one another so that there will be no material intermingling thereof,

in causing combustion to occur at the boundary between theair and fuel, and mixing the streams of fuel and air by high velocity jets of an elastic fluid adjacent the mouth of the port.

12. In the method of firing furnaces, those steps which consist in flowing a stream of hydrocarbon fuel through a furnace port at low velocity and heating the same, flowing preheated air through said port in a substantially separate stream and mixing the streams of fuel and air by high velocity jets of an elastic fluid adjacent the mouth of the port.

13. In the method of firing furnaces, those steps which consist in preheating a hydrocarbon fuel to a. point just below its cracking tempera.-

ture, flowing said fuel through a furnace port and heating it above its cracking temperature and mixing said fuel and air adjacent the mouth of the port by high velocity jets of an elastic fluid.

14. In the method of firing furnaces, those steps which consist in preheating a hydrocarbon fuel to a point slightly below its cracking temperature, flowing said fuel through a furnace port and heating it to a point above its cracking temperature by the combustion of a small fraction thereof and mixing said fuel and air adjacent the mouth of the port by jets or high velocity.

15. In the method of firing furnaces, those steps which com ist in preheating a hydrocarbon fuel to a point ust below its cracking temperature, flowing the same at a low velocity through a furnace port, flowing a stream of preheatedv air simultaneously through said port, heating the fuel in the port to a point above its cracking temperature by the combustion of a small fraction of the fuel and air at the boundary therebetween.

16. In the method of firing furnaces, those steps which consist in preheating a hydrocarbon fuel to a point just below its cracking temperature, flowing the same at a low velocity through a furnace port, flowing a stream of preheated air simultaneously through said port, heating the fuel in the port to a point above its cracking temperature by the combustion of a small fraction of the fuel and air at the boundary therebetween and mixing these streams at the mouth of the port I by high velocity jets of an elastic fluid.

17. In the method of firing furnaces, those steps which consist in flowing hydrocarbon fuel and air in substantially separate superposed but contacting streams at a low velocity through a furnace port so that there is no material intermingling of the two streams, causing a partial combustion to occur at the boundary between the streams of air and fuel in which only a small fraction of the air and fuel partake but which is sufficient to effect cracking of the hydrocarbons, flowing the streams at low velocity to the mouth of the port, and in then injecting into the streams high velocity jets of an elastic fluid to thoroughly mix the same and effect complete combustion.

18. In the method of firing furnaces, those steps which consist in flowing hydrocarbon fuel and air in substantially separate superposed but contacting streams at a low velocity through a furnace port so that there is no material intermingling of the two streams; causing a partial combustion to occur at the boundary between the streams of air and fuel in which only a small fraction of the air and fuel partake but which is sufficient to effect cracking of the hydrocarbons, flowing the streams at low velocity to the mouth of the port, in then injecting into the streams high velocity jets of an elastic fluid to thoroughly mix the same and effect complete combustion, and in controlling the length and direction of the flame produced by varying the angle of injection of the high velocity jets of elastic fluid into the said streams.

19. In the method of firing glass melting furnaces, those steps which consist in flowing a hydrocarbon fuel and air in substantially separate but contacting streams at a low velocity through a furnace port for a substantial distance sufficient to effect the cracking of the hydrocarbons without causing any material intermingling of the fuel and air, and in then thoroughly mixing these streams adjacent the mouth of the port by high velocity jets of an elastic fluid.

20. In the method of firing glass melting furnaces, those steps which consist in flowing a hydrocarbon fuel and preheated air in substantially separate superimposed contacting streams at a low velocity through a furnace port for a substantial distance sufficient to effect the cracking of the hydrocarbons without causing any material intermingling of the fuel and preheated air, and in then thoroughly mixing these streams adjacent the mouth of the port by high velocity jets of fuel.

WIILIBALD 'I'RINKS.

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