US1841587A

US1841587A - Combustion of pulverized or similar fuel

Info

Publication number: US1841587A
Application number: US237546A
Authority: US
Inventors: Stephen M Finn
Original assignee: DRAKE NON CLINKERING FURNACE B
Current assignee: DRAKE NON CLINKERING FURNACE B; DRAKE NON-CLINKERING FURNACE BLOCK COMPANY Inc
Priority date: 1927-12-03
Filing date: 1927-12-03
Publication date: 1932-01-19
Anticipated expiration: 1949-01-19

Description

Jan. 19, 1932. s. M. FINN 1,841,587

COMBUSTION OF PULVERI ZED OR SIMILAR FUEL Filed Dec. 3. 1927 4 Sheets-Sheet l INVENTOR:

J: 3% M. FM L BY I 5 09M, K MMH &W

80 f ATTORNEYS.

Jan. 19, 1932. s, M. HNN 1,841,587

COMBUSTION OF PULVERIZED OR SIMILAR FUEL Filed Dec. gs. 192'! 4 She ets-Sheet 2 IN VEN TOR.

M- Fv'wn,

BY I gw Kmwq away A TTORNEYS.

Jan. 19, 1932. s. M. FINN 1,841,587

coususnou orruLvsRIzEn on SIMILAR rum.

Filed Dec'. 3. 192'! 4 Sheets-Sheet 3 a? 24 a a 4 I Y 75 P WWW y (MW/1 A TTORNEY'.

Jan. 19, 1932. s, FlNN 1,841,587

COMBUSTION 0F PULVERIZED 0R SIMILAR FUEL Filed Dec. 3. 1927 Q 4 Sheets-Sheet 4 IN VEN TOR.

33414 M. Fm

BY PW,WMMZJ9 xfww A TTORNEYS Patented Jan. 19, 1932 UNlTED STATES PATENT OFFICE srnrnnn I. rim, or Jsnssr crrr, NEW messy, assrenoa Tb mam non-cnmxnnme rummcn :mocx comm, me, or new YORK, n. Y.

COMBUSTION OF P'UlIN'E-RIZED OR SIMILAR FUEL Application filed December This invention relates to combustion of pulverized or similar fuel, having particular reference to a system of burning pulverlzed coal or analogous'fuel in suspension in alr; andthe invention includes not merely the novel furnace hereindisclosed, the burner thereof, and other features of apparatus, but also the novel described method of combustion of such fuel, and features of operation and control. The present invention, although the disclosed embodiment is designed especially for use in boiler furnaces, is of wider utility, and availablefor various industrial or other combustion systems.

The general object of the present invention is to afiord apparatus for and method of combustion of pulverized or analogous fuel which will be of increased efliciency and durability, and more adaptable and convenient of control. A particular object is to afford a system, including apparatus and method, of fuel combustion wherein the fuel,

carriedin a stream of primary air, is supplied with' preheated secondary air at the combustion point in a practical and advantageous manner. Afurther object is to afford a combustion system for suspended fuel wherein the fuel laden primary. air and the secondary air are combined and delivered whirlingly into the furnace in such a manner as to produce the short,.wide-angled and turbulent type of flame which has been found to be very effective with steam boiler furnaces. A further object is to afford a burner having a driven fan orsuction means operating ina predeterminedcooperative manner upon both the fuel laden primary stream of air and the secondary air, so that the relation of the two and the type of flame ma be preserved when adjusting the rates of eed. A further particular object isv to afford an automatic control of combustion through the joint and several regulation of the primary andv secondary streams; for example through connections whereby the furnace conditions, such as boiler steam pressure and the CO content of the flue gas, may effect the desired regulation and thus maintain the combustion in harmony with the service and operation of the furnace or boiler. Other and furs, 1927. Serial No. beam.

ther objects and advantages of the present invention will be explained in the hereinafter following descriptlon of an illustrative embodiment thereof or will be understood to those conversant with the subject matter. To the attainment of the aforesaid objects and advantages the present invention consists. in the novel s stem of combustion and the novel features 0 apparatus, method, operation, arrangement, mechanism and structure herein described or illustrated.

In the accompany g drawings Fi 1 is a front elevation partly in diagram partly broken away, showing a furnace, burner and control mechanism embodying the present invention.

Fig. 2 is a central vertical section of the furnace and burner of Fig. 1.

' Fig. 3 is a central section of the burner on a larger scale. Fig. 4 is a front elevation of the burner shown in Fig. 3, partly broken away to show the interior.

Fig. 5 is a central vertical section of. a modified form of burner. Fig. 6 is a similar central vertical section showing another form of burner. Fig. 7 is a detail section view taken on the line 7-7 of Fig. 6.

Referring first to the embodiment shown in Figs. 1 to 4 a boiler furnace is indicated comprising a setting of any usual character, having for example a front wall 11, side walls 12, and a rear wall 13 which in some cases may be a bridge-wall, and below the enclosed combustion space or chamber a bottom or door 14. While the walls may be of 35 various construction they are indicated as built up of refractory blocks or fire brick, and having interior air ducts or passages as will be later described, and with convenient provision, for example by door or opening 15 for the removal and discharge of ash or soot accumulating on the floor or bottom.

The boiler is indicated as comprising a system .of water'tubes 16 which may be located directly over the combustion chamber and interconnected by the usual headers and communicating with the overhead drums 17 from which steam may be drawn through mains 18 for consumption. The present disclosure presupposes such usual details as bafile walls and the like. In Fig. l is shown I a conventional uptake 20 constituting the exit for the. spent gases and products of combustion, and leading to the usual stack.

The pulverized coal or similar suspended fuel may be brought to the furnace through a pipe 22 from any fuel supply, preferably directly from a pulverizing machine. This pipe is shown furnished with a damper 23 for restricting and regulating the fuel feed. The primary air and suspended pulverized fuel may be considered as the fuel stream, subsequently to be met and combined with the stream of secondary air at the place of combustion. The fuel pipe 22 terminates in an elbow 24 directly connected to the burner 25 which is shown arranged in a circular aperture in the furnace front wall 11 so as to geliver directly into the combustion cham- The burner 25 contains a centrally arranged fuel tube 26 which is coupled to the elbow 24 and shown supported from a Wall plate 27, which plate may be closed in cases where the secondary is drawn through wall ducts as herein illustrated. The fuel tube 26 separates the wall aperture into a central fuel passage 28 and a surrounding annular air passage 29, which, in the preferred embodiment of this invention, is intended to conduct preheated secondary air to the combustion point. The air passage 29 is shown surrounded by a cylindrical lining or sleeve 30 mounted directly in the refractory wall aperture and preferably connected with the outer wall plate 27. By this arrangement the fuel laden primary air is conducted centrally and directed into the combustion chamber, while surrounded by an annular stream of entering preheated secondary air.

According to one feature of this invention a rotary suction means or fan 32 is employed having the dual function of propelling, by separate portions of the fan, both the in coming primary or fuel stream and the surrounding secondary or air stream. This two-purpose fan or rotor is shown located directly at the mouth or exit of the burner, and its details of structure and operation will be described at a later point. The fan rotor is shown as having a flaring hub 33 mounted at the inner end of a driving shaft 34 which extends through a ball bearing 35 supported within the tube 26 and sealed to exclude fuel. Outwards of this bearing the shaft carries a screw blade or vane 36 arranged to propel the fuel through the tube.

.The outer end of the shaft is mounted in a bearing 37 in the elbow 2a and at its outer extremity is provided with suitable driving connections, such as a sprocket wheel 38 driven by a chain 39 from a sprocket wheel 40 on the shaft of a driving motor H, for example an electric or other controllable motor.

The dual suction fan 32, operating both on the primary current of air and fuel and upon the secondary air current, may be constructed in different ways, but preferably com prises, mounted on the hub 33 or shaft 34, a set of primary vanes, blades or portions 4; in line with the exit of the primary passage or fuel tube, and secondary blades or portions ll at the mouth or exit of the annular secondary or supplemental air passage 29.

Each set of blades or blade portions is preferably so designed as to produce both a propelling force, which draws the current through the passage and delivers it into the combustion chamber, and a rotary or whirling force tending to create, directly at the mouth of the passage, a fast whirling action and resulting centrifugal force. The blades or blade portions for the two passages are preferably designed especially each for its own function, and therefore operate separately to induce the correct relative supplies of fuel and air, although the two are shown mechanically connected together as an integral whole: The structure, for example maybe as illustrated in Figs. 3 and st wherein the primary blades 43 are mounted on the hub 33 and extend outwardly to a connecting ring or short cylinder 45 from theouter side of which spring the secondary blades 44, the extremities of which may in turn be connected and strengthened by an outer ring or short cylinder 46. As a result of this arrangement the inner and outer fans, for any given adjustment of the primary and secondary dampers, will operate to induce rates of flow through the primary and secondary passages which will preserve a substantially predetermined ratio or relation notwithstanding changes of fan speed as the latter may be adjusted to suit variations in the combustion rate or service of the furnace.

' As already stated, this invention preferably employs preheated secondary air of combustion, and for this purpose the secondary passage 29 may be connected with or piped to any suitable preheater or source of heated air, preferably'a preheater built with the furnace walls. With advantage the invention preferably employssecondary air preheated in the interior of the walls of the furnace, and to this end the following principles of construction may be employed. The cylindrical iron lining sleeve 30 is shown as formed with a number of air ports 49, ten of them being shown, and the refractory tiling 31 outside of the lining is similarly ported. In connection with this arrangement is shown a rotary damper or ring 50 having corresponding ports 51, shown in Figs. 3 and 4 as in a nearly full open position; adjustment therefore of the damper ring regulates the rate at which the fan may draw secondary air through the setting for combustion purposes.

' with recesses, passages or ducts for the'flow 'thercfrom is rcdelivered into the furnace of secondary combustion air.- Thus "surrounding the ports 49 are shown a number of wall recesses 52 extending outwardly and connecting by a series of lateral passages 53 with front wall air ducts 54. These front .wall ducts or channels may be substantially preferably in a manner to connect in series the ducts in the respective walls. At the upper part of the front wall 11 may be inlets 55 for the direct admission of atmospheric air to the duct 54 and controlled by dampers 56, thus cooling and utilizing the upper rtion of the front wall. Each furnace si e wall may be formed with ducts 58, indicated by dotted lines in Fig. 2, each of these being fed with atmospheric air through damper controlled inlets 59. The bottom wall 14 is shown formed with interior air ducts 61 having air inlets 62 at various points controllable by separate dampers 63. The bottom duct 61 is shown as discharging into the lower end of the front wall duct 54. The rear wall 13 is shown provided with a duct 64, fed by inlets 65, controlled by dampers 66; the air being admitted at the upper part of the rear wall and flowing downwardly to the foot thereof and thence into the bottom wall duct 61. In this way all five of the refra'ctory walls of the furnace are provided with air ducts through which atmospheric air travels eventually to the burner 32. Each of the walls is'thus interiorly swept with a constant stream of cooling air to the pro tection of the wall, while the heat extracted with the secondary air fed to the combustion point.

While in some cases it may be suflicient to have hand adjustment of the ring damper 50, it is one feature of this invention that said damper may beautomatically adjusted to regulate the supply of preheated secondary air in accordance with the combustion con-' dition and requirements. The connections for shifting the damper may be as follows. The ring 60 is shown with opposite lugs 69 which carry posts 70 extending outwardly through curved slots 71 to exterior points.

The outer ends of the posts are shown connected by links 72 to a damper operating lever 73 fulcrumed at 74. This lever is seen in Figs. 1 and 4 to extend leftward where its extremity may be swung upwardly and downwardly by means of a link 75 to adjust the damper. The linkconnects at its lower end with a bell crank lever 7 6' referably by means of an adjustable pivot 77 permitting the throw to be-varied. The bell crank is shown mounted on a bracket 78 upstanding.

from a box or frame 79 which carries a motor 80, preferably electric, through which the bell crank and connections are to be actuated for adjusting the damper 50. The connections from the motor to the bell crank may comprise a pinion 81 on the motor shaft engaging a gear 82 by which the speed is reduced, this gear being carried by a threaded shaft 83 taking its bearings in the bracket 78 and a bearing 84. Surrounding the screw shaft 83 is a threaded block or traveling nut 85 having a pin and slot connection 86 with the yoked lower end of the bell crank lever. By this arrangement when the motor is operated to turn in one direction or the other it will correspondingly throw the bell crank lever and thus effect the progressive opening or closing of the damper, and thus adjust the air supply to the requirements.

The damper adjusting motor 80 may itself be controlled automatically in various ways, for example from an indicator of the CO content of the flue gases, such as the pointer or index of a C0 meter; and Fig. 1 contains a diagrammatic illustration of the principlesof the arrangement. A pipe 89 is shown arranged to conduct flue gas from the stack or uptake 20 to a conventionally shown CO meter 90; this having a scale or dial 91, and an index or pointer 92 with which the control connections are intended to cooperate. The meter is shown with the pointer at 14.5 on the assumption that this is a fair or safe average CO reading for a furnace of the type to be regulated. The tip of the pointer or hand 92 is shown as provided with a light delicate contact or leaf spring 93 arranged to come in contact with one or another of two stationary but ad'ustable leaf contacts 94 and 95 when the C 2 percentage varies below or above the desired average. Fig. 1 shows diagrammatically an electric conductor or wire a from the index or finger 92, a wire I) from the contact 94, and a wire 0 from the contact 95, these three wires extending from the CO meter to the motor control means next to be described. The preferred plan of action is substantially as follows. When. for example, the CO content becomes deficient the contacts 93 and 94 will meet, thus closing the circuits through the conductors a and b, which will operate through the control motor 80 to close further the damper 50 and thus decrease the excessive rate of supply of preheated secondary air. This will have a substantially immediate effect on the com bustion, and a quick correction of the CO content, the meter responding with fair promptness, thus reversing the movement of damper. \Vhen the CO content becomes too high, indicating shortage of air and too hot combustion the reverse actions take place, the damper being shifted in a direction to increasethe rate of supply of secondary air. By the described automatic control the damper 50 may be in oscillating adjustment, synchronously with the shift of the CO meter between 14 and 15, and in a manner to maintain the CO content substantially be tween these percentages, or such other percentages as may be determined by the positions at which the contacts 94 and 95 are applied upon the dial 91.

The connecting means between the 00 meter 90 and the damper motor 80 may comprise a battery 96, first and

second solenoids

97 and 98, first and second switches 99 and 100, and wiring as follows. The battery 96 is interposed between the wire a and a wire at which is branched into wires e and f, the branch 6 extending to the solenoid 97 and the branch f to the solenoid 98, the other terminals of the solenoids being connected respectively with the conductors b and 0, so that when the CO content drops to 14% the circuit is connected through the wires a, d, e and b to energize the solenoid 97 which thereupon closes the switch 99, while when the CO content is excessive and rises to 15% the contacts will complete the circuit through wires a, d, f, and c to cause the energizing of solenoid f and the closing of switch 100.

The positive and negative line wires 9 and h for the motor 80 may extend from any source, preferably direct current, of electrical power. The wires 9 and it pass respectively to the two poles of each of the two switches 99 and 100. Assuming now the switch 99 to be closed, by undue lowering of CO content, the line current will be supplied to the motor as follows. The positive counter pole of the switch 99 is shown connected by wires 2' and branch wire j to one post or brush terminal 17 of the motor. while the negative counter pole of the switch 99 is connected by wire Z to a limit switch m, which in turn is connected by wire n and branch wire 0 to the other brushterminal p of the motor. In this way when the CO indicator indicates a low percentage the motor will be energized by positive current at the terminal 7c and negative current at the terminal 79 thereby to drive the motor in one direction, namely such as to operate the feed screw 83 to swing the bell crank 76 to the right and thus elevate the damper lever 73 to close further the ring damper 50, which decreases the supply of secondary air to the combustion point, and thus increases and restores the proper CO conditions.

in the opposite direction to the motor. The

positive counter pole of the switch 100 is shown connected by wires q and 0 with the terminal 1) of the motor. The negative counter pole of the switch is connected by wire 1' with a limit switch 8 which in turn is connected by wires 25 and with the other motor terminal 70. The motor is of such character that reversal of the current reverses the direction of rotation, so that in this case the bell crank lever 76 will be thrown to the left, and the damper lever 73 depressed to open further the ring damper 50 and increase the rate of supply of secondary air, thus tempering the combustion with additional excess air and lowering the CO content to the predetermined advantageous percentage.

The limit switches m and s are safety devices limiting the throw of the nut 85, bell crank 76, lever 73, and damper 50, namely, by breaking the circuit to the motor 80 by pressure of the nut 85 upon each of the limit switches, and the opening thereof, as the ad justment approaches the limit of movement.

Another cooperative feature of the present invention is the preferably automatic regulation of the operation or speed of rotation of the fan or fans which draw fuel laden air and preheated secondary air through the

passages

28 and 29 respectively and project them whirlingly into the combustion chamber. Such automatic control is herein illustrated by a system of regulating the speed of the fan shaft in accordance with changes of pres sure in the delivered steam, the speed being reduced when the pressure exceeds a predetermined amount, and vice versa. This part of the invention is shown diagrammatically in Fig. 1 and may be described as follows.

The speed of the fan driving motor 41 may be varied through a regulator or rheostat 104 having its terminals connected with the motor through wires 105. The rheostat is provided with a series of contact points 106 adapted to be successively contacted by a contact arm 107 to vary the resistance of the device and thereby control the current. passing to the motor and the speed of the latter. The rheostat arm 107 is shown connected by a pitmanor rod 108 with the cross head of a piston rod 109 operated by a piston 110 movable in a cylinder 111 having its ports controlled by a slide valve 112. The valve stem 113 is shifted by a bell crank lever 114 which in turn is connected by,.a link- 115 with a control lever 116 having a weight 117 tending to depress it, while a diaphragm 119 in a case 120 is arranged to lift the lever in opposition to'the weight. A steam pipe 121 conveys the pressure of the outgoing steam 1. the burner.

in pipe 18 to the diaphragm case, controlled by a cock 122. Thecasing of valve 112 and the cylinder 111 are supplied with steam, water or other fluid from any source of pressure through a pipe 124. The valve controls the admission of fluid to either end of the cylinder so as to operate the piston and adjust the rheostat, while the fluid from the other end of the cylinder escapes through exhaust pipes 125. When the steam pressure is excessive the diaphragm lifts lever 116, which throws valve 112 to the left, admitting fluid to the left end of cylinder 111, causing the piston and rheostat arm to shift to the right, thus increasing the resistance and reducing the current, to slow the motor 41, and so reduce the supply of both fuel and air, and slowing down the combustion. Cooperatively, a damper 127 in the uptake flue 20 maybe further closed with excess steam pressure by a rope or chain connection 128, passingover pulleys 129 and attached to the piston rod 109. v I

The features of the invention and their operation may be reviewed and explained further as follows. One feature is the induced and regulated supply of preheated secondary air to the combustion point, from any suitable source, specifically through air ducts in the combustion chamber walls, thus cooling the Walls. The supply of such preheated secondary air, being efl'ected by the force or suction induced by the rotary fan, obviates the usual forced draft created by a pressure blower, and avoids as well the necessity of relying upon an induced actlon from the primary stream supplied from a p'ulverizer or other source of fuel laden air.

While thereforethe streams of primary and secondary air are delivered cooperatively the are independently supplied and'controlle the primaryair supply being controlled by the action of the pulverizer or other fuel supply means supplemented by the restrictive control of the damper 23, while the preheated secondary air is, restrictively controlled by the ring damper 50,

The ingredients for combustlon are herein introduced in such a way as to produce advantageously the short flame, with whirllng action and turbulence, as stated. The WhlIl is produced by the fan, and this is located at the delivery point of the burner instead of at a point or points substantlally within By creating the whirling action directly at the mouth of the burner, where the combustion begins, it becomes highly effective for the purposes hereof. Both the central stream of fuel laden air and the annular stream of secondary air are whirled rapidly so that centrifugal force causes them to flare out fromthe axis of the burner into the chamber, producing a wide angle cone of flame, and intimately mixing the ingredients close to the burner so as to bring about quick cated by the arrowsin Fig. 3, the

and thorough combustion, which is completed in a quite brief space of time and travel. The resulting flame for example resembles that approximately illustrated in Fig. 2, combustion being completed before impingement upon any wall.

The dual acting burner fan is of substantial advantage for carryin out these operations. One set of fan bla es or portions 44 operates in the annular space conducting secondary air to the combustion point, while the other set 43 operates at the delivery of the fuel feeding tube, and these two sets of blades are connected to turn in unison, so that any variation of speed and action is caused to take place correspondingly'for the two streams. Conveniently the two blade sets are on the same operating shaft and constitute a single rotary member or rotor. It will be understood that initially the respective fan blades are to be designed so as to afford the desired predetermined ratios of suction or delivery action. The respective blades are shown as set at angles somewhere between 35 and but the angle may be considerably altered to suit the conditions at hand. For example the blades may be tilted to a very slight 'angle from the plane of rotation in which case a flame approaching the so-called long flame can be produced, consistin of a central stream of fuel laden air riven straight into the furnace in an suitable direction and enveloped by secon ary air, with progressive combustion continuing for a substantial period. If the blades are tilted nearly to the other extreme, that is, almost parallel to the axis, each entering stream will be given the maximum whirling action but minimum axial projectionfrom the burner. Ordinarily angles of blade and an action intermediate of these is the most desirable. A

differential arrangement is preferred as indiprimary stream receiving greater whirl an wider angle of spread, and the secondary stream less whirl'but more inward propulsion, resulting in an intersecting action. The combined arrangement sucks into the burner the respective components and whirls them while projecting them inwardly, as described, thus creating the short type of flame shown, with its extreme turbulence, quick mixing and rapid combustion.

The automatic adjustment of the speed of the burner fan is believed to be broadly new, especially with a dual acting fan as described, and especially under regulation of the degree of steam pressure in the boiler; This regulation of burner action is advantageousin improving the combustion action of the furnace. When higher service is required of a given boiler and furnace, calling for higher rates of combustion of fuel, and tendency to higher temperatures, the resulting lowered steam pressure will bring about the increase of speed of the burner fan. This higher speed not only cooperates in affording a higher rate of fuel feed through the central tube, but cooperatively supplies increased quantities of secondary air for the increased combustion, assisting greatly in preserving the required proportions; while such increased flow of secondary air through the furnace walls further affords a cooperative increased cooling action on the walls. The greater the tendency to overheat the walls the greater is the cooling action on the walls, which are thus kept within a comparatively steady range of safe temperature. On the other hand in times of low service, when the fuel and secondary air are supplied at lower rates, an advantage results in that the secondary air, traveling more slowly through the furnace walls, is caused to preheat to a relatively greater degree due to the greater time element in its travel, thus enhancing efficiency.

The regulating feature consisting of means for automatically adjusting the secondary air damper 50 is advantageous both in itself and in cooperation with the other described features. This automatic regulation is cooperative with the regulation of fan speed, the two together controlling the secondary air supply. The regulation is nevertheless independent and governed from a separate source, in this case illustrated by the CO meter. Assuming that the best efficiency of a given furnace is attained with a C0 content of 14% to 15%, then if the percentage of CO increases above this amount, the index or pointer of the CO meter will close the electrical circuits in a manner to cause an opening of the ring damper and thus afford a greater rate of supply of secondary air, bringing the combustion, the furnace temperature and the CO content back to the point desired. This regulation therefore controls the combustion efiiciency of the furnace in accordance with the rate of fuel supplied from the pulverizer or other source, making the secondary air supply in a manner self regulating to the fuel supply. The diaammatic illustration of a connection from the CO indicator to the secondary damper, for regulating the proportions or ratio of the primary and secondary streams, is merely exemplary of various connections; for example on account of the delicacy of movement of the pointer of the galvanometer of the CO meter it may be preferable to avoid me chanical contact therewith, and obviously a mirror may be provided to swing with the pointer and roject a beam of light along a system of se enium or other light cells, to generate currents which may be amplified or relayed to perform the damper shifting actions. In any case the damper readjustment may be slow and gradual so that the CO correction may be gradual and may b overtaken by the CO meter action, thus avoiding oscillation of the damper between extreme positions.

The regulation principles thus described may be employed in different ways from the analysis of the outgoing or flue gases; for example instead of operating the control from the CO percentage it may be operated from the percentage of some other ingredient of the flue gases such as hydrogen or CO.

The combined regulations greatly facilitate the control of a furnace by reducing the personal attention otherwise needed for maintaining economy. .VVhen at times of overload or high steam demand the steam pressure drops this will openfurther the uptake damper 127 and speed up the dual fan 32, expediting all factors of combustion, the fuel supply being supposed to be increased at the same time in any known manner. If now the speeded up fan fails to deliver the correct proportion of secondary air this will be manifested by an excess or deficiency of. CO content in the flue gases, which will act through the CO meter and damper motor to further open or close the secondary air damper until the correct supply is afforded. The fan therefore primarily regulates the secondary air while the dam-per supplemently adjusts it to the correct figure. Assuming, for example, a coal supply rate of 1000 lbs. per hour, and that the supplemental or secondary air should be between 3 and 3.3 pounds per pound of coal; if the fan should feed air only at the rate of 3 pounds per pound of coal, or 3000 lbs. of air per hour, this deficient rate would cause an increase of CO content, and when the CO indicator reaches 15 the ring damper will be opened further and increase the secondary air supply rate, but when the latter reaches 3300 the CO content becomes again reduced, the indicator shifting toward 1 1, and upon reaching 14 causing again the further closing of the damper; thus affording a continuous correction of combustion factors.

Referring next to the modification shown in Fig. 5, this embodies certain of the underlying features already described, including the supplying of preheated secondary air from the furnace walls to the combustion point, and the dual fan assisting the flow of both the primary and secondary streams; although the burner in this case, instead of delivering directly into the main combustion space, delivers into a preliminary space or ignition chamber wherein, with thorough mixing of all of the ingredients of combustion, a large part of the combustionwill take place, resulting in intense heat in this chamher, which thereupon delivers the flame whirlingly into the main combustion chamber. The wall 11 is apertured to form the ignition chamber 135, which is shown of Venturi-shape, tapered and flaring. Th

pulverized fuel may be supplied through a pipe 22 connecting by an elbow 24 with the burner 25 which is set outwardly as com pared with Fig. 3 so as to occupy no part of the ignition chamber 135. The burner comprises the central fuel tube 26 which may be cast integral with -the wall elements bounding the secondary passage, and this casting may be supported on a metallic wall plate 27 The fuel tube .26 encloses the fuel passage 28*, and surrounding it is the annular secondary air passage 29.

As in the first embodiment there is av dual acting fan 32 mounted on a shaft 34 driven by sprocket 38, the shaft being enclosed within a sleeve 136, with ball bearings between, the sleeve having a conical inner end 137 having substantially the same .flare as the mouth of the primary tube 26. The fan has the primary blades43 and secondary blades 44 delivering fuel and air into the chamber 135 in a manner to give a violent mixing action with high degree of combustion, the flame being projected into the main combustion chamber. The annular or secondary passage 29 is shown supplied with preheated air by curved pipes 52 leading from lateral passages 53". connecting with the wall ducts 54, so that, as before, the air preheated in' the furnace walls is supplied through the described passages to the combustion point.

The modification shown in Figs. 6 and 7 differs principally in the longitudinal enlargement of the ignition chamber 135", the

burner 32" being set out far beyond the'wall 11*. The pipe 22 and elbow 24" conduct the pgimary stream to the burner 25*, the elbow ing connected to the central fuel tube 26 containing the fuel passage 28 and surrounded by the secondary air passage 29". The fan 32' mounted on sprocket-driven shaft 34 comprises the primary and secondary blades 43 and 44 The shaft is surrounded by sleeve 136" flared at 137 Guides 52 conduct the secondary air to the annular assage from an annular passage 140 formed etween a large cylindrical casing 141 and a cylindrical wall 142 of tiles, the two being bonded and spaced by spacing elements 143.

The cylindrical wall 142 bounds the ignition chamber 135". The preheated air from the wall ducts 54 passes through lateral recesses 53* into the annular channel 140 and thence to the annular passage 29. As in the first described form the fan blades 43 and 44" may be designed to cause intersecting primary and secondary streams.

The forms of apparatus and method which are herein illustrated but not made the subject of specific claim are not intended to be disclaimed but are reserved for claim by divisional application or otherwise.

There has thus been described a system of combustion of pulverized or similar fuel embodying the principles and attaining the objects of the present invention; Since various matters of apparatus, method,'operation, arrangement, mechanism and structure may be modified without departing from the principles of the invention it is'not intended to limit the same to such matters except so far as set forth in the appended claims.

What is claimed is:

* .1. A burner for fluent fuel comprising a control passage for fuel laden air, a surrounding passage for secondary air, and rota means operating at the delivery ends of 0th passages for positively whirling and delivering both streams and causing. them to combine in a wide angle short flame.

2. Apparatus for combustion of fluent fuel, comprising an interior primary passage for a stream of primary fuel laden air-and a surrounding secondary passage for a stream of secondary air, rotary suction devices or blades at the delivery ends of said respective passages, and means for driving the respective suction devices in-unison to pull, whirl and deliver to the combustion point the primary and secondary streams in a predetermined relation.

.3. Apparatus asin claim 2 and wherein.

the drive means are adjustable to vary simultaneously and correspondingly theaction of the suction devices for controlling both streams adaptably to changes in combustion conditions.

4. Apparatus as in claim 2 and wherein the suction and delivery devices are such as to deliver both whirling streams at diverging angles but so that one impinges upon the other for rapid mixing and combustion, and a short turbulent flame.

i 5. Apparatus as in claim 2 and wherein the combustion space into which the flame is delivered is surrounded by walls having air passages connected to supply preheated air to the secondary passage to be drawn therethrough by the suction device at the mouth thereof. i

6. A burner asin claim 1 wherein the rotary whirling means for the two streams are interconnected to be driven in unison, a single driving means for both, and means for varying the speed thereof.

7 In a boiler furnace, a burner delivering a stream of fuel laden air and a stream'of secondary air to the combustion point, power means for positively drawing, whirling and injecting both said streams into the combustion space, a controller regulating the speed of said power means, and a steam pressure responsive device for regulating such controller.

8. Apparatus as in claim 2 and a boiler heated by the combustion, a' pressure responsive device operated by the boiler pressure, and a controller operated by said dewherein is vice for automatically regulating the means driving the suction devices.

9. Apparatus as in claim 2 and wherein is a boiler heated by the combustion, a pressure responsive device operated by the boiler pressure, and a controller operated by said device for automatically regulating the means driving the suction devices, and an uptake damper controlling the flow of outgoing gases, with means operated by the pressure responsive device for adjusting such damper.

10. The method of controlling a boiler furnace comprising jointly regulating the admission of fuel laden air and secondary air according to the steam pressure and separately regulatingthe proportions thereof according to the CO content of the flue gases.

11. In a furnace burning pulverized fuel separate passages conducting to the combustion point a stream of fuel laden primary air and a secondary air stream, a control means for adjusting the relative supply of the respective stream, a C0 measuring means, and connections therefrom for operating said control means to increase the proportion of secondary air upon increase of CO content and vice versa.

12. Apparatus for combustion of finely divided fuel in suspension in air comprising a fan sucking, whirling and delivering the ingredients into the combustion space, power means driving such fan, means for varying the action thereof, means controlled by the effect of combustion for automatically regulating such variation, and supplemental means, controlled by the CO content of the flue gases, for automatically regulating the proportions of air and fuel delivered to the combustion point. p

13. In a boiler furnace fired by fluent fuel means supplying a stream of fuel laden primary air. means supplying a stream of secondary air, regulating means operated by the steam pressure for jointly regulating both said'supply means, and se arate regulating means operated by the C 2 content of the flue gases for relatively regulating the operations of said supply means to vary the proportions of said streams.

14. Method of combustion of fluent fuel for steam generation comprising a supplying a central primary stream of fuel laden air and a surrounding stream of secondary air, positively drawing, whirling and delivering both streams with forward movement to combine in the combustion space, and automatically regulating the drawing, whirling and delivering of both such actions conjointly by increase of such action upon decrease of steam pressure and vice versa.

15. Apparatus for combustion of fluent fuel comprising concentric passages delivering the fuel and air, a fan occupying the delivery ends of both said passa es for sucking, whirling and delivering the respective ingredients into the combustion space, power means driving such fan, means for varying the speed thereof, and means controlled by the effect of combustion for automatically regulating such variation, and thereby the delivery of both fuel and air.

16. Method of combustion of fluent fuel comprising delivering a stream of fuel laden primary air and a stream of secondary air. to combine at the combustion point, restrictively adjusting the secondary air flow in relation to the primary air between the source and delivery point, and automatically regulating such adjustment by the combustion results.

17. In a fluent fuel combustion apparatus means supplying a stream of fuel and primary air, means supplying a stream of secondary air, a C9, meter, and means operated by the meter acting upon said supplying means for adjusting the relative proportions of such two streams.

18. Means for the combustion of fluent fuel comprising walls defining a central passage delivering under pressure a central stream of fuel laden air and outer walls defining an annular passage surrounding said central passage for delivering a stream of secondary air to the combustion point, and rotary means positively whirling in the same rotary direction at the delivery point both the fuel laden central and the secondary air annular streams, whereby they issue with both axial and spreading movement, thereby creating awide angle short flame with quick mixing and turbulent combustion.

19. Apparatus for the combustion of fluent fuel, comprising separate passages delivering fuel laden air and secondary air inwardly to the combustion point, the secondary air passage having an inlet damper controlling the flow, and a rotary device operating in the secondary air passage closely in advance of its delivery to the combustion point for forcing the flow of secondary air, said rotary device having power actuating means, and means for varying the forcing action there of to control the flow of secondary air.

In testimony whereof, I have affixed my signature hereto.

' STEPHEN M. FINN.