US1024678A - Process for increasing the temperature of combustion in gas-fired furnaces. - Google Patents

Description

H. L. DOHERTY. PROCESS FOR INCREASING THE TEMPERATURE OF COMBUSTION LN GAS FIRED FURNACES.

APPLICATION FILED MAR. 31, 1909.

Patented Apr. 30; 1912.

2 SHEETS-SHEET 1.

INVENTOR HenryLDOAerf] f BY 7 4 %0RNEY WITNESSES H. L. DOHERTY. v PROCESS FOR INCREASING THE TEMPERATURE OF COMBUSTION IN GAS FIRED FURNACES.

APPLICATION FILED MAR. 31, 1909.

Patented Apr. 30, 1912.

2 SEEETS-SHEET 2.

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INVENTOR WITNESS iw Henry L 'DoEerfy W M WEB/v now: runs. 04: Limo ushmrnon. hi 4:.

HENRY L. DOHERTY, OF NEW YORK, N, Y.

PROCESS FOR INCREASING lI-IE TEMPERATURE OF COMBUSTION IN GAS-FIRED FURNACES.

To all whom it may concern: 7

Be it known that I, HENRY I1. DOHER'TY, a citizen of the United States, residing at New York city,-in the countyof New York and State of New York, have invented new and useful Improvements in Processes for Increasing the Temperature of Combustion in Gas-Fired Furnaces, of which the following is a specification.

My invention relates to a process forincreasing the temperature of combustion in gas-fired furnaces, and it relates particularly, to thattype of such processes in which the control and regulation of the temperature in the producer is secured by the in- ,troduction of some endothermic agent.

The objects of the invention are. the increase in efliciency of heat utilization due to the increased temperature secured in the furnace, and the increased economy in fuel dueto a more 'perfect recuperation of the heat of the flue gases, than is secured by the various processes in present use.

My invention-can be applied to any gasproducingrand-consuming apparatus, in which the waste gases of combustion are at a higher temperature than the producer gas leaving the gas producer.

My invention can be used equallywell in connection with, either the'type of producer wherein the temperature control thereof is effected by the introduction of water vapor, or wherein, the temperature control is effected by the introduction of a regulated proportion of combustion gases into the air current supplied to the producer.

The particular application of my invention which I have selected for purposes of illustration, is that to a furnace for manufacturing illuminating gas by the destructive distillation of coal. Inthe usual type of these furnaces, the coal is" distilled'or carbonized in retorts, which are heated by the combustion 'of producer gas, generated in a producer placed below the retort oven. The namecommonly applied to this appa ratus is gas bench. These are usually built back to back, forming twin settings, a number of these being erected side by side,

Specification of Letters Patent.

PatentedApr. 30, 1912.

Application filed March 31, 1909. Serial No, 486,888.

forming what is known as a battery, or stack of benches My invention may be applied to any combined gas-producing and gas-consuming ap paratus in which the products of combustion leave the gas-consuming apparatus", or

furnace, at a higher temperature than that v at which the producer gas enters it, the relation of the two parts of the apparatus be;

ing such, that the products of combustion may be passedinto recuperators for heatmg the producer gas at, substantially, the

temperature at which they leave the furnace. For instance, my invention may be applied to zinc furnaces or open-hearth steel furnaces, and to many other similar types of furnaces. ings, I show a single gas bench to illustrate the application of my invention to such ap-" paratus. The bench shown in Figures 1', 2 and 3, is of the general type that is, at present, used and which is well adapted for use in the practical working of my process of gas-producer control. My invention can be applied equally well tothe ordinary type of gas bench, wherein the temperature control'of the producer is efiectedby the introduction of water or water vapor into the fuel bed.

In the drawings l shows a single bench partly in section and partly in elevation. Fig. 2 is a lon'giutdinal section on In the accompanying draw:

the line AB of Fig. 1. Fig. 3 is a section through a recuperator on the line CD of Fig. 1. y

In the application of my invention which I herein claim, the recuperator portion of the bench is in duplicate, the construction 3 is a pipe through which air underpres sure is supplied to the injector; 4 is the grate of the producer; are fiues conveying producer gas to the producer gas recuperators 6.; 7 are equalizing fines; 8 the producer gas flue through the recuperator.

9, and 10 are passages for conducting the producer gas from the producer gas recuperators to the retort oven.

11 are the retorts containing the coal. .to be carbonized. v

12 is a series of ports or orifices in a flue 13, (one for each recuperator), through which the, waste gases of combustion pass to the recuperator.

. 14- and 15 are lines affording passage for the waste gases through the recuperator to the flue 16 leading to the stack. 17 the air recuperators having air-inlet flues 18, and series of return-bend tlues 19. 20, horizontal partitions dividing the air recuperators into a series of returirbend lines.

21 are ports, one for each recuperator, providing entrance for air into the equal izing fines 22.

23 are ports connecting fines 22 with par allel flues 24.

25 are movable tiles which can be used to regulate the area of the openings in the port 23, so as to secure a uniform flow of air from 22 to 24 along the entire length of the flues.

26 are two series of fiues (one series for each side of the recuperator) connecting 24- with another parallel flue 27, from which the air. discharges through the ports or nostrils 28 into the stream of producer gas entering the retort oven through the port 10.

29 are flues, one for each side of the bench, conducting part of the Waste gases, after their passage through the retort oven, to the induction chamber 30 of the inductor 2.

31 is the nozzle of the inductor.

52 are vertical partitions in recuperators 6; 53 is a. chute through which the fuel is charged into the producer 1.

The method of operating my invention is as follows: The bench being in operation,

the main portion of the Waste combustion gases is taken oil from the retort oven through the ports 12 into the fines 13, from which the gases pass into the fines 1 1, back and forth through 1.41; and 15 in a serpentine course through the recuperators 6 and 17, and thence to the stack through the dues 16.

The air, for the primary combustion in the producer, is brought under pressure to the injector 2, through the pipe 3. For compressing the air any satisfactory type of positive blower may be used. The air discharges -into the inductor or injector 2 through the nozzle 31, creating a reduced pressure in the chamber 30. This, in turn, inducesa flow of waste combustion gases through the flue 29, from the retort oven, the current of combustible gases mingling with the air discharged-through the nozzle 81, the mixture forced under the grate of the producer, and thence passes up into the.

fuel bed. Here, in the manner. described in my Letters Patent No. 829,105, the free oxygen of the air and one-half of the combined oxygen of the car'bon-dioxid of the flue gases, combines with the carbon of the incandescent bed of fuel in the producer, to form the combustible gas, carbon monoxid, which constitutes the chief combustible ingredient of my producer-gas.

Although the product of the reaction in each case is the same, viz. carbon monoxid, I, by bu ning part of the fuel by the available 0 of the CO secure certain very important results. the oxygen of the air and the carbon-of the fuel, viz.

a very large amount of heat,-about 4 150 B. T. U. per pound of carbon so consumed,-is liberated. This, if no provision is made for absorbing and removing it from the fuel bed, would raise the latter to a very high temperature, more or less completely fluxing the ash, with the result that the latter would form large aggregations in the fuel bed, known as clinker-s. This action would, in time, almost completely prevent the passage of the gaseous current into the producer. By the second reaction, however, which I make use of in my producer, this excess heat is absorbed. and made latent in the shape of carbon-inonoxid. This second reaction is 2CO +C :4.-CO.

In this reaction, for every pound of the carbon of the fuel so consumed, about 10,000 B. T; U. are absorbed and rendered latent. It is apparent that by properly regulating the proportion of combustion gases to air, I may maintain any desired temperature in my producer.

' The producer gas rising from the fuel bed of the producer is taken off from the producer through the fines 5 and passes therethrough to the equalizing tlues 7 of the recuperators 6. These lines 7 are simply open passages running the length of the recuperators G, and serving to distribute the pro ducer gas. uniformly throughout the length of the recuperators' These producer-gas recuperators have vertical partitions 52, which serve to support the flues 14, and,-in effect, divide the main producer-gas flues into groups of sub-fines. The producer-gas rising through the fines 8, passes around the horizontal flues 14:, receiving heat froni the By the reaction betweensame and having its temperature correspondingly increased.

The heatedproducer gas-leaves the re ducer gas meets the. secondary air and burns.

- The secondary air enters the recuperators,

.- 17,1 through the air inlet flues 18, thence passes throughth'e series of return-bend 'flues 1 9,- backs-and forth through the recuperators in. a direction contrary to the flow ofdconibustion gas'es throughthe smaller.return-bend'flues,15, and 14. "The high conductivity-while the upper flues, 14, v are of material such as fire clay, possessingv lower-fines, 15, are of metalof relatively a. high degree of refractoriness. The use of material of relatively high conductivity for the. lower flues of the recuperator enables Ine-to secure practically as high a tempera ture in my secondary air as I could secure in older-type of recuperator such. as shown in'Letter's Patent above referred. to, although in my present invention I am entering the flue gases into'the secondary'air recuperat'or at a; somewhat lower tempera- The highly heated secondary air leaves the uppermost hub, 19, through the port, 2LT and passes into the equalizing flue, 22;

Along this flue, as shown, are small orifices .or ports, 23., having movable tiles, 25, which may be adjusted by means of a metal rod or hoe workedthrough a suitable handhole at the end of 'theflue, so as to regulate the free areaof the ports, 23(- By this means I flowofthe secondaryair into the flue, 24, i

am able to secure a practically uniform V alongits wholelengtlzg; Fi'om 24 the sec- 26, into a flue 27'. From 2'1 t-he airis dis tributedto thenostrils, 28, from. which it' ondaryfair passes upward through the flues,

discharges into the combustion chamber of the retort oven burning the producer gas entering through 10'.- a The products of this combustion pass upand around the retorts,

imparting-to the latter' -part of their sensible heat, thence to the upper flue's,-13,' of, therecuperators and part to the injectors Thepart going to the injector is passed into the fuel bedin the manner-already explained.

The main current of combustion gases passes fr'om the' disvhargeflues of there'- cuperat'orsfthrough. the flues, 16,"t.o the sta'clgi whence the gases V-di'scharge into the atmosphere.-

In theiparticular application of my "in vent-ion, which Ihave selected'for purposes of iillustrationpyia, that to a furnace for heating re'tor'ts for the manufacture of illuofcoal or o 'lherbitumlnous substances, the heat which doesusefulwork i's, only, tha

.niinatinggas by'the' destructive distillation portion of theto-tal heat developed in the furnace which is absorbed by the coal or other bituminous matterin the'lflto'rts;

effect this destructive fdistillation of coal in a manner which is commercially profit able, it is necessary to keep the 'retorts a comparatively high tem era-turf say, at

least 200091 Althoug in practice the temperature is more usually nearer "2300 F. It is easily seen that this temperature of, the retorts fixes the temperature at which the waste gases mustbe allowed to leave-the furnace, since,'anyfurther cooling of them,

would involve a corresponding giro in the temperatiu-e of the retorts with which they were latest in contact: For thisreilson, it

is not possible'to, increaset-he economy of heatutilizat-ionot the furnace by reducing the temperature at which the, products," of combustion are discharged, On th .ogh

hand, any increase in the maximum temper ature of the combustion gases in the oombustion chamber of the furnace; increases, correspondmgly, the amount of heat that may beutilized in the retorts. This is due, 7

to the fact that the'amountof heat trans mitted by conduction ,fromlone fluid to an- I other through a partition se 'iarating the two flui cls is directly proportional-to the temperature difference between the two. For-example if, in the customary methodv of-operating a bench, the retorts are kept. at

a temperature of 2000" F., wh.ile the high- I,

est temperature of the combustion gases is- 2500 F., and the temperature at which they I make their exit from the furnace is 2000" F., we would get a certain amount of heat transmitted from the combustion" gases through the walls of the retort, to the or other material therein. Now it. through preheating the producer gas and the air supplied to the combustion chamber,'wc are enabled to raise the temperature of the 'com-' bustion gases to, say, 2700 F wewould,

theoretically? multiply-the amount of heat transmitted conduction by the ratio of the corresponding difference in temperature between the "combustion chamber and. the

retorts. Thatds, assuming. that the same weights of producer gas and air are sup plied in the two cases, with'the higher telnperature in the retorhoven, we would in crease the qua-ntity of heat passlng into the retorts inthe ratio'YOO/SOO, or an increase pera-tura -In additioirto' the heat transof forty per cent;.-.over the quantity of heat "passinginto' theiretorts at the lower teni- 1 mitted by conduction weha've to consider I that. transmitted by radiation. '-A;ccordi-ng to a well knownlaw the radiation from a ret'orts themselves. heat passing into the retort goes to hasten the process of distillation, or c-rbonization as it is, usually, termed, and not, to any great extent, to raisii'lg the temperature of the coal. This true as long as the coal .F., (2, from 2959" absolute to 3159" absolute), we would increase tlwradiation at 2500 in the ratio W:- L?) (about It should be noted, in this connection, that the average temperature of the mass of coal or other material in' the ,retorts, is much lower than the temperature of the Any increase in the unc'zirbonized; and, since it is the aim to remove from the retorts the residual coke as soon as most of the volatile matter of the cealhas been driven off, the above statement is, substantially, true in the practical operation of gas benches.

I is used in the preheating of the air and producer gas isfrecuperated from the sensible heat of the Waste flue gases, the increased utilization of heat that I get in my retort even is clear gain. I am, simply, taking "heat from the, otherwise, wasted heat of the flue gases and adding it to the heat utilized,

.using the producer and the air for combustion as the mediuinof transference. By

my invention, I am, therefore, able to carbonize a considerably greater we1ght of coal for the same expenditure of fuel in the producer.

The method of operating the gas producer 0f the combined gas producer and gasfired furnace in this case a gas benchithmy present invention applied thereto,

in not, essentially, different from that described in my Letters Patent No. 829,105, when the application of the invention is to 1 the typeof combined gas producer and fur -nace therein described. The principal difference is that the flue leaving the re- .tort oven are first passed througl'i recuperators for heating the producer They then pass into the recuperators, for heating e seconc a'r air. 11 o:-

th l y Dun g their pa sage through the producer gas recuperators the flue gases, of course, fall in temperature by heat which they give up to the producer gas.

an amount corresponding to the quantity of They, therefore, do not enter the air recuperators at so high a temperature as m the rosters type of bench described in my Letters Pat out No. 829,105. In this present type of bench, therefore, in order to secure the same degree of preheating of the air, I cause the air current, instead of flowing in a direct vertical direction through the recuperators to flow back and forth in the recuperator in a direction contrary to the direction of flow of the line gases passing through the smaller fines located within the air fines. Likewise, as described and claimed in the same application, I make the lowertlues of the recuperator of metal of a relatively high heat con ductivity.- In thus causing the air to traverse a. comparatively long path through a line of relatively small cross-section, I. gain an important increase in the ethciency of heat transference from the flue to the air. The transn'iission of heat from one fluid to another through a separating diaphragm depends, not only on the difference in the temperature between the two fluids, and the time during which they are in contact with the heaotransmitting diaphragm, but, also, upon Whatis, of equal importance, the velocities of the two fluids along the surfz-ices of the transmitting diaphragins. The quantity of heat taken up from or given out to a hcattransmitting surface by a fluid is proportional to the square root of the ve locity of flow of the flu id along -the surface. This factor is of even greater importance when the heat-transmitting diaphragm is-- as in part of the recuperator we are now con sideringof a rough porous surface. The combination of this type of recuperator with the recuperator for heating the producer gas is, therefore, a point of great importance, and it is this combination which gives my invention, as a whole, great practical utility.

, This invention is, particularly applicable to producers in which bituminous coal, lignite, or any other fuel containing a large amountof volatile matter is used in the producer. In this-case, the rapid evolution of volatile matter immediately after charging greatly reduces thetenu'ierature of the gas leaving the producer. This, in turn, results in a lower temperature in the retort oven,.0r

furnace, and in consequence subjects the retorts with their contents to a decided chilling effect. By my invention this irregularity of heating the air to be used for burning said gas, burning the so-heated gas and air in the retort oven of said gas bench, and introducing another portion of the waste combustion gases into the gas-producer of said gas bench for the purpose of regulating the temperature thereof, substantially as 'described. j

2. In the operation of .a gas-bench the process which consists in dividing the products of combustion leaving the retort-oven of said gas bench into two portions, introducing one portion, at substantially the-temperature at which it leaves the retort-oven of said gas bench, into the gas producer of said gas bench for the purpose of regulating the temperature thereof, and passing the other portion of said products of combustion first through a recuperator for raising the temperature of the roducer gas leaving the 20 said gas producenfgtndthen through a refisterslov a or 'said'gas heath, substantially 25 as described.

Signed at New York city, in the county of New York and State of NeW' York this 30th day of March 1909.

' ig'HEN RY L. DUHERTY;

Witnesses:

LOUIS F- Mam, FRED I. srfirn,

Copies of thispatent may be obtained for five cents each, by addressing the Commissioner of Patents.

Washington, D. O.

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