US1912043A - Flame baffle for pulverized fuel furnaces - Google Patents

Description

W. K. SANDERS FLAME BAFFLE FOR PULVERIZED FUEL FURNACES May 30, 1933.

Filed June 6. 1931 4 Sheets-Sheet l May 30, 1933.

W. K. SANDERS FLAME BAFFLE FOR PULVERIZED FUEL FURNACES Filed June 6, 1951 4 Sheets-Sheet 2 INVENTOR. Wz'l/zdm fr. sanar BY fin g v ATTORNEYS.

30, 1 w. K. SANDERS 1,912,043

FLAME BAFFLE FOR PULVEHIZED FUEL FURNACES Filed June 6, 1951 4 Sheets-Sheet 3 nwnvrmw Wzf/zam K Sanders ATTORNEYS.

May 30, 1933. w. K. SANDERS FLAME BAFFLE FOR PULVERIZED FUEL FURNACES Filed June 6, 1931 4 Sheets-Sheet 4 IN V EN TOR. MZZzam if. 942 72 Jars BY m ATTORNEYS.

Patented May 30, 1933 UNITED STATE PATENT oFF'Icr-ii'f WILLIAM K. SANDERS, or McGILL, NEVADA, ASSIGN'OR on ONE-HALF TonnwA'nn'J.

' FRANKLIN, ors LT LAKE CITY, UTAH FLAME RAFFLE Fon- PULVE'RIZED FUEL FURNACES Application fi-led June 6, 1931. Serial No. 542,600.

This invention relates to animproved flame bafiie for pulverized fuelfurnaces. The invention is particularly intended and: adapted for use in connection with pulverized fuel '5' furnaces for heating water tube boilers,

The main object of the invention is to provide a means for preventing the flame andentrained particles of unburned or partly burned fuel from; passing directly into the front or first pass of a Water tube boiler when the fuelburner (pr-nozzle is located at or near the upper portion of a-furnace.

It. has been found, in the operationof a furnace, boiler and fuel burner combination such as abovereferred to that the draft pull maintained'in the furnace has a tendency to divert the flame from the burner directly into the first bank of boiler tubes over the top of,

the refractory baffling providedin the bank '29 of tubes, thus preventing the; flame from maintaining theU-shaped trajectory which is deemed desirable. This diversion, or shortening, of the flame trajectory causes a considerable decrease in the length of time that the fuel remains in the furnace, and hence prevents the complete combustion of all particles of fuel while iii-suspension in the combustion space of the furnace. The result is, that unburned or partly burned particles of fuel are drawn directly into the gaspassages betweentheboiler tubes causing a large loss in fuel and consequent clogging of the gas passages by reason of these fuel particiles congealing and adhering to the boiler tu esj Myinvention provides means whereby this difficulty is overcome and the flame from the burner is forced to passdownwardly into the 404 combustion chamber ofthe furnace before it passes. to the Water tube boiler. I

Another object of invention is. to: provide means which will increase the radiant; heat absorbent surface and also increase the evaporative ef'fcct'of the boiler.

Other objects of my invention will appear herein-after. I j

The accompanying drawings illustrate embodiments of my invention and referring thereto: x

Fig.v 1 is a vertical section of one type of water tube boiler and furnace therefor show; ing my invention applied thereto.

Fig. 2 is a section online 22 in Fig. 1.

Figs. 3, 4 and 5 arevertical sections of further modifications of the invention.-- I

In Figs. 1 and12 my invention is illustrated as applied in connection with. a boiler and. furnace construction comprising a water tube boiler 1,-

combustion chamber 2, and 00 a burner 3' adapted for combustion of pu1- verized fuel such as coal dustor atomized fuel oil. The boiler is shown as comprising three banks of water tubes 4, 5 and 6 with bafile walls '2, 8 and 9 at the rear of each bankof, water tubes, said baflie walls being staggered so as: to insure that the products of combustion will pass in tortuous-path and come into effective contact with substantially the entire area of each bank of water '70 tubes, a connection being provided to flue 14 for conducting the combustion gases after they have passed the last bank of boiler tubes toa stack or other outlet means for same. I

The water tubes are shown as connected at their lower ends to a Water drum 10 and at their upper ends to drums 11, 1'2 and 13, and suitable piping is provided for connect ing the upper and lower drums so as to provide for Water circulation; Such water circulating means may comprise a pipe 15 connected to the bottom water drum IO-and ex tending to the upper" front part of the fur nace where it is connected toa header pipe 16 ordinary practice such he'ader pipe 16 is connected. to-rone of the upper drums for the watertubes by pipes extending above the combustion chamber 2, leaving the space" between the burner 3 and the first bank of water tubes substantially unobstructed. With such an arrangement there is a tendency for the flames to pass from the burner directly to the passage 17 above the first baflle wall 7 aforesaid instead of passing in the desired U-shaped course indicated by the arrows in Fig. 1.

To provide for deflection of the gases in the desired course I provide a series or row of tubes 18 connected at one end to the header 16 and at the other end to the upper water tube drum 11, a portion of these tubes being bent downwardly in U-shape as indicated at 19, and a wall or baffle 20 of refractory material consisting, for example, of shapes or blocks of non-slagging refractory material, such as silicon carbide, is .mounted on the tubes 18 for example in such manner as to inclose the horizontal portion 19 of said tubes and the vertical portions 19" thereof which are nearest to the burner 3; The bottom 21 of the combustion chamber 2 may be of any desired shape or construction, either flat or inclined, and either water cooled or air cooled, as the construction of the furnace bottom and the means for disposing of ash therefrom forms no part of the present invention. 1 r

In operation,the fuel from the burner, with suitably regulated supply of air for combustion, produces a flame which is directed downwardly into the combustion chamber 2. The preferred path of the flame as shown by the arrows, describes a return bend, starting downwardly from the burner 3, to a point near the lower portion of the combustion space within chamber 2, thence turning upwardly, entering the boiler passes through the space 17 provided between the upper end of the front bafiie means 7 and the upperfront boiler drum 11. The hot gases then passv progressively through the boiler passes, under the centerbaflle 8,0ver the'rear baflle 9, and thence to the smoke flue 14. It is understood that the specific shape or disposition ofthe baffles 7, 8 and 9, Within the boiler passes forms no part ofthis invention, hence these baflles may be of any"de sired shape or form, the only condition being that the inlet space 17 between the top of the front baffle 7 and the boiler drum 11,be maintained. 5" l y In actual practice, it has been found that the flame does not always follow the preferred course above referred to, but on the contrary,.the suction or draft which-c'auses the hot gases to enter the boiler passes through the passage 17, has a tendency to divert the flamefrom the preferred path and cause it to follow a shorter path, depending upon the intensity of the draft or suction being maintained in the flue 14:, whether suchsuction be caused by a natural draft stack or by induced draft fans. a 1

: It is readily seen that such a diversion of the flame shortens materially the length of time that the burning fuel particles may re main in a state of free suspension. As it is Well known that every size of fuel particle requires a corresponding definite period of time in which to be consumed, it follows that, owing to the decrease in time during which such particles are in a state of free suspension, some of the relatively coarser particles of fuel will not be consumed completely, but will pass in an unburned or partially unburned state directly into the boiler passes.

This condition results in a variety of losses, such as loss of fuel due to unburned carbon, fouling of the boiler tubes by reason of the partially burned particles congealing thereon, incomplete combustion within the furnace combustion space, etc.

With the described construction the flames from the burner 3 are prevented from taking the shorter path above referred to and are forced to passfirst downwardly and then upwardly before they pass through the first bank of water tubes, thereby, insuring that the fuel particles will remain within the combustion chamber a sufficient time for effective combustion thereof and obviating the losses and difliculties above referred to. The deflection of the products of combustion in this manner also insures that they will be brought into more effective contact with the'first bank of water tubes, thereby increasing the evaporative effect. Additional evaporative effect is also secured by contact of the hot products of combustion with the downward bend 19- of' the return water tubes and by the heat absorbing and radiating action of the baflle wall 20 mounted thereon. r

In the operation of the boiler, relatively cool water from the lower or mud drum 10 of the boiler flows through the piping 15 to the roof tube header 16, thence through the roof tubes 18 and the return bends 19 to the boiler drum 11. The additional roof tube area, including the return bend 19, provides an increase in the area of heat absorbent evaporative surface exposed to the radiant heat of the flame. Furthermore, the refractory block covering on the front leg of the return bend 19 provides a reflecting surface which serves in conjunction with the upper portion of the refractoryfaced furnace wall 22 to maintain propagation of the flame in the incoming fuel, particularly during periods of light loading when only relatively small quantities of fuel are being fed to the furnace.

As an additional feature of this invention, and as shown in Fig. 3, a superheater element comprising tubes 67, with appropriate inlet header 68, supply pipe 69, outlet header 70, and discharge pipe 71 may conveniently be disposed within the space formed by the pre-' viously described return bend. A superheater located as above described,- will function partly as a radiant heat superheater and part- 1y as a convection type, due to the fact that some gases will sweep behind the tubes 67, while at the same time the superheater tubes are exposed to direct radiation from the incandescent gases before such gases enter the boiler gas passages through the opening above the first baffle as above described.

In some instances it may be found desirable to provide a means for regulating the amount of exposed tube surface over which hot gases may pass. For providing such a regulatory means, there is illustrated in Fig. 4, an adjustable shielding arrangement comprising the slidably disposed heat-resisting screen member 7 8 adjacent the tube members 7 4 and working through the slot-like opening 75 in the furnace roof covering 76. The

screen member 7 3 is connected by means of the rigid or flexible members 77 to the controlling or actuating means 78. The actuat ing means 78 may consist, for instance, of a hydraulic cylinder, power or hand actuated gearing, winches or any other common or well-known apparatus for attaining the purpose in View, namely, raising or lowering the screen member 73 any desired or required amount. With the screen member lowered to its fullest extent, the hot gases are prevented from passing behind the tube members 7 4, while should the screen member 73 be raised any distance, some of the hot gases will be allowed to pass behind and around the entire periphery of the tubes 74, thus exposing a greater total amount of evaporating or heat absorbing surface to the action of the hot gases.

In Fig. 5 is illustrated a further arrangement wherein the flame baflie water tube ele ments are connected for water circulation in conjunction with a boiler of the horizontal water tube type, and wherein the downwardly extending return bend tube elements are connected to headers instead of comprising a part of a continuous roof tube element.

In this form of the invention, the boiler 104 having drums 105, water legs 106 and 107, and tubes 108, cooperates with a furnace chamber 109, having a rear wall 110, front Wall 111 and a bottom or floor 112 of any shape. The furnace roof is composed of roof tubes 113 covered with any suitable material 114. The fuel burners or nozzles 115, fed by fuel pipe 116 are located in the furnace roof, passing through spaces provided between the several roof tubes 113, and is so disposed as todirect the fuel stream or flame downwardly into the combustion space 116 as indicated by the dart lines. The forward ends of the roof tubes 113 are fixed into the inlet header 118 while their rearward ends are fixed into the front return bend header 119. The return bend elements 120 have the end of one leg fixed into the header 119, while the end of the other leg is fixed into the header 121. The tubes 123. connect the header 12-1 with the water leg-106. of the boiler. It is understood that should itbe deemed desirable, the connection to, the boiler water circulation system may be made by connecting the header 121 to any portion of} the boiler drums 10-5 or water legs in any manner, rather than to the lowerpoi tion of the front water leg 106 asshown, said baffle means comprising water tubes bent and positioned in such mannerthat both. ends of said water tubes; are outof the path of the flame in the combustion chamber, said ends of the Water tube being in connection with the water tube boiler, to permit circulation of water through said tubes and refractory baffle means mounted on said tubes.

To supply relatively cooler water to the roof tube system previously described, tubes 12 1 are connected through header 128 and tubes 129 to the lower portion of the rear water legs 107 and at their outer ends these tubes are connected to the header 118. Water thus passes from the lowest portion of the boiler water system through tubes 124 to header 118, thence through roof tubes 113, header 119, return bend 120, header 121, returning through tubes 123 or other connections to the boiler water system again. On one of the legs of the return bend are provided the shapes 126 of suitable non-slagging refractory material, so applied as to form a virtually solid face, for the purpose of directing the flame from the burner nozzle 115 downwardly into the combustion chamber 116 and forcing it to follow the U-shaped path indicated by the dart lines.

Having described the objects to be attained by this invention, it should be understood that the accompanying illustrations cover only a few of the possible combinations of types of boilers, furnaces, fuel burners and flame baifle screens, and that such illustrations are not to be considered exclusive. It is the intention of this specification to include all combinations of these elements as Will fall within the spirit and objects of this invention.

I claim:

1. A water tube boiler and furnace construction comprising a combustion chamber having an outlet passage at the upper portion thereof, a Water tube boiler arranged to receive gases passing from said outlet means, a burner adapted to direct flame into the upper part of said combustion chamber and a baffle means extending downwardly from the top of the combustion chamber so as to prevent passage of flame from the burner directly to the said outward passage means, said baflle means comprising water tubes in connection with the water tube boiler so as to provide for circulation of water through said tubes and refractory baflie means mounted on said water tubes, said water tubes of the baffle means extending downwardly from the top of the combustion chamber and being bent downwardly and then upwardly form'- ing a return bend, so that each end of each of said tubes is outside of the path of the flame inthe combustion chamber.

2. A construction as' set forth in claim 1 in Which the refractory bafiie means are mounted on those legs ofsuch return bends which are nearer the burner.

In testimony whereof I have hereunto subscribed my name-this 30thday of May, 1931.

' WILLIAM K. SANDERS;

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