US2944531A - Fire-boxes operating on atomized fuel - Google Patents

Description

F. J- MARY FIRE-BOXES OPERATING ON ATOMIZED FUEL [Jul 12, 1960 2 Sheets-Sheet 1 Filed Sept. 1, 1954 INVENTOR MAI/m JOSEPH MARY ATTORNEYS July;l2, 1960 F. J. MARY FIRE-BOXES OPERATING 0N momzao FUEL 2 Sheets-Sheet 2 Filed Sept. '1; 1954 INVENTOR FRANCIS JOSEPH MARY M a v B ITTORIYEY United StatesPatent FIRE-BOXES OPERATING N ATOMIZED Font.

My invention has for its object improvements in fireboxes operating on atomized fuel and chiefly to those fire-boxes which are lined over the major part of their inner surface with Water-tube screens and whichare generally known as cold combustion chambers and produce pulverulent ashes.

Fire-boxes of this type lead in particular to certain the more marked when the fuel used has. lower contents of volatile material.

The starting of said fire-boxes generally requires the use of auxiliary burners which consume more or less considerable amounts of a liquid'or gasiform starting fuel. On the other hand, such fire-boxes do not allow, in general, lowering the speed of combustion underneath a predetermined value without this leading to a risk of extinction unless an auxiliary fuel is again resorted to. 7

Furthermore, the gases passing out of the combustion chamber, carry along with them the major part of the pulverulent ashes and they must consequently be freed of such solid particles, this freeing being all the more thorough when the coal used has large ash contents. The removal of the residual material collected in the devices used for such purposes leads generally to difiicult problems and it is mostly necessary to convey this material towards sewage farms at a distance from the point at which the ashes are produced.

Lastly, these loose ashes contain amounts of unburnt carbon which amounts are greater when the rate of operation of the fire-box diflfers from optimum conditions to a greater extent.

According to my invention, it has been attempted to I reduce the above mentioned drawbacks to within the range of practical possibilities and I have imagined to this end to suspend, inside the combustion chamber of these fire-boxes burning atomised fuel, at least one member which is cooled internally. by a flow of a suitable fluid and which is fitted outwardly over at least part of its height with a refractory cover.

The. cooling of this member may advantageously be executed by air pulses tapped if required, from the output of an air-heating device such as that generally. located at the end of the path followed by the combustion gases of .boilers burning atomised coal. cooling may be provided also by any other suitable fluid.

The memberor members considered may be suspended to the actual framework of the boiler-room or to the boiler body through the agency, if required, of loadhandling or hoisting means, such as winches or the like or of members which serve for checking or adjusting the rate of combustion such as scales or the like. The internally cooled members may thus expand freely under This changer;

' of the internally cooled-membensuspended inside the 2 of example and by nomeans in a limiting sense, various embodiments of the object of my invention. In the said drawings:

Fig. 1 is a vertical sectional view of a fire-box provided with horizontal burners having a single heat ex- Fig. 2 shows on alarger scale a modified embodiment combustion chamber: Fig. 3 is a horizontal sectional view of a square firebox provided with burnersin its corners;

obligations when working and these obligations are all 7 Fig. 4 illustrates an arrangementfor the suspension of an internally cooled member; Fig. 5 illustrates an arrangement for suspending a internally cooled member to a weighing means;

Fig. 6 is a vertical cross-section of a modification which includes an arrangement for imparting to' an internally cooled membera rotary movement round a vertical axis.

Turning to Fig. l, 1 designates a fire-box incorporating horizontal burners 2 of which some are fed with atomised fuel and others are fed with the auxiliary fuel usedfor the starting of the fire-box and possibly for operation. at a reduced rate; In the drawing, only one burner 2 has been shown.

A designates an internally cooled heat exchanger member which is suspended vertically to a beam B rigid with the framework of the boiler room. The said member A is constituted by a heatjexchanger including two coaxialtubes 3 and 4, of which the outer tube 4 is provided with an outer refractory cover 5. The tubes 3 the action of heat without exerting any strain on the rest axis. v

I have illustrated in accompanying drawings byway and 4' may be made of stainless ferritic steel or even of austenitic steel while the cover 5 may be made of refractory cement such as that known under the trade name chromeore.

The cooling air entering through the tube 6 flows downwardlyinside the annular space provided between the tubes 3 and 4 and rises again through the inner tube 3 so as to enter the tube 7 forming a continuation of the latter .and to be injected into the combustion chamber at 8 round the burner or burners 2.

As apparent from inspection of Fig. 1, the lower end of the member A is more or less exposed to the impact of the jets passing out of the burners 2.

V The cooling air' arriving through the tube 6 may, according to a slight modification, be caused'to flow first downwardly through the inner tube 3 and to rise thereafter into the annular gap defined between the said tube 3 and the outer tube 4, 'the said gap communicating in this case with the tube 7.

In Fig. 2, the internally cooled suspended heat exchanger member A is constituted by a system of tubes 99 of smaller diameter arranged in a vertical plane and looped into hair pin formation at their lower ends. The cooling fluid admitted through the tube 6 enters a first box 10 and progresses then downwardly inside the two inner tube sections 9so as to rise again inside the outer tube sections 9 at the upper end of which. it enters a second box 11 arranged coaxially with reference to the box 10, the two boxes being separated by par.- titions 12.. From the box 11, the cooling fluid passes into the tube 7 as in the previously described example.

In said Fig. 2, the refractory cover 5 is shown by way of example as covering only the lower part of the member '4. The upper part of the latter requires then generally a periodical cleaning of its outer surface by means of soot-removing blowers. Whatever arrangement is adopt ed in the execution of the member A, its outer surface 7 Instead of being injected round the burner orbnrners 2 as illustrated in Fig. 1, theair passing out of the in- Patented July 12 1960 ternally cooled member A may be introduced into the fire-box 1 through independent nozzles located in the immediate vicinity of the said burners. It may also be distributed uniformly bet-ween the diiferent burners of the fire-box or else itmay be directed by way of preference to one or more burners, specially intended for starting purposes and for operation at a reduced rate.

Turning again to Fig. l, the operation ofthe arrangement according to my invention is as follows: during the periods corresponding to the starting and to the operation of the fire-box under reduced load, the refractory cover of the internally cooled suspended .heat exchanger member A, located in the path of the flame passing out' of the burners 2, is speedily brought to a high temperature. The calorific inertia of the member A furthers then the stabilization of the firing through radiation and through convection. Furthermore, the air passing through the heat exchanger forming the central part of the member A is also heated to a considerable extent before it is injected round the nose of the burner 2 and it cooperates thus in improving the conditions of ignition of the atomized fuel. It is, moreover, easy to obtain for said air the highest temperature consistent with the preservation of the material in contact with it: it is suflicient to this end to reduce its rate of delivery as desired.

The present apparatus thus provides: an easier ignition of the atomised fuel and a reduced consumption of auxiliary fuel; a lowering of the minimum rate of combustion which may be ensured by burners burning only coal without being assisted by burners burning auxiliary fuel.

Now, if the load on the fire-box is gradually increased, the general temperature conditions in the combustion chamber rise and, from a given moment onwards, the temperature of the lower end of the internally cooled suspended heat exchanger member A rises above the temperature of softening of the ashes. This lower end is thus finally covered by a more or less thick film of molten ashes which flows through gravity towards the tip of the member from which it drops through the slag hopper into a sump 13 filled with Water (Fig. l). The molten ashes in contact with the water burst so as to produce a granular material applicable for use in various fields such as the building industry and public works.

The more or less liquid layer of ashes covering the surface of the lower end of the member A permits arresting and holding of a fraction of the particles of ignited fuel passing out of the burners 2. The particles then finish burning and the non-combustible residual matter thus formed melts in its turn and flows into the ash pit 13.

My invention permits both a reduction of the loss of solid unburnt particles and a relative increase of the amount of ashes collected in a molten state.

It is of advantage, consequently, to associate my invention with the known method of injection of soot into the fire-box since the main drawback of last mentioned method, which consists in an exaggerated enrichment of pulverulent products in the gases formed, is thus cut out to a considerable extent, as disclosed, through the application of my invention.

Fig. 3 illustrates a fire-box 1 including four corner burners 2 while the heat exchanger member A is suspended at the center of the said fire box which is the hottest point thereof. This arrangement furthers the melting of a fraction of the ashes on the surface of the member A, as disclosed hereinabove, and this melting is still furthered by providing burners 2 with a variable angular setting around vertical axes so as to distribute the jet of ignited gases passing out of the burners onto an adjustable area of the refractory end 5 of the member A and to modify thus the temperature of the latter and thereby the amount of molten ashes deposited on said surface.

It is of interest in all cases to insert above each member A a load-handlingor hoisting member such for instance as a. stationary winch located outside theboiler as illusof coal is expected.

The presence of such a control member allows reducing or cutting out completely'the erection of large scafloldings inside the combustion chamber.

In contradistinction, during normal operation, it may be preferable to use for the member A suspension means including a rudimentary weighing machine, constituted, as illustrated in Fig. 5, by an arm 17 pivotally secured at 16 and the outer free end of Which carries'an indicator pointer hand while the member A is suspended at 18 to said arm, the weight of the said member A being normally balanced by a spring 19. The shifting of the hand 17 permits the easy ascertaining of the weight of ashes attached to the suspended member A and. adjusting the rate of combustion correspondingly with a view to increasing or to reducing the ash-melting capacity of the member A.

The same Fig. 5 illustrates a which allows measuring the temperature of the member A inside the ash-rnelting area, which provides furthermeans for checking and controlling the rate of combustion. allows measuring the temperature of the hot air passing out of the heat exchanger. his instrument may advantagecusly be used as input means for a regulating system controlling the iiow of cooling air to be introduced into the tube 6.

In Fig. 6 is illustrated an arrangement for imparting to the internally cooled member a rotary movement round a vertical axis. Here the above described tubes 3 and i are again shown; the tube 3 is carried by a stationary cylindrical body 22 surrounding the said tube 3 and to which is connected the pipe 6 feeding the cooling fluid while the tube 3 opens into the exhaust tube 7 for the fluid. The second tube 4 is revolubly mounted round the lower end of the said cylindrical body 22 and it is fitted at its lower end with an outer refractory cover which is not illustrated in Fig. 6. The tube 4 is provided with an outer annular reinforcing collar 23 carrying eyebolts 24 through which it may be secured rigidly with the cylindrical body 22 for dismantling and handling purposes; said collar 23 forms an abutment for a carrier 25 constituted by two parts assembled with each other along a diametrical plane and clamped over the tube 4. At its periphery, the carrier 25 is rigid on one hand with a rail 2r: forming an annulus running over rollers 29 rigid with a ring 28 secured to the framework of the generator system, said carrier being rigid on the other hand with a toothed annulus 27 driven by the motor 31 with the interposition of a speed-reducing gear 30. These coaxial annuli 26--.27 revolve thus in unison with the tube 4 forming the outer section of the internally cooled member A.

What I claim is:

In a firebox for use with pulverized fuel including a combustion chamber having inlet and outlet openings in the top and bottom thereof respectively, and at least one burner horizontally directed into said chamber, a combustion aid comprising a closed hollow member, a weighing machine connected to said member for lowering said member through said chamber inlet opening'while supporting the same in a vertical position and presenting a portion thereof to the flames from said burner and indicating the increase in weight due to the addition of ash thereto as a signal to the operator of conditions in said fire-box, refractory cover means enveloping said hollow member for the portion thereof exposed to said burner flames and means for internally cooling said 1101- radiation pyrometer 2i)- Furthcrrnore, 21 designates a thermometer whichlow member by circulating a cooling medium .therethrough.

References Cited in the file of this patent UNITED STATES PATENTS 731,300 Holland June 16, 1903 905,644 Brown Dec. 1, 1908 2,295,115 Keller Sept. 8, 1942

Images