US1876623A

US1876623A - Setts

Info

Publication number: US1876623A
Authority: US
Publication date: 1932-09-13
Anticipated expiration: 1949-09-13

Description

Sept. 13, 1932. F. H. DANiELs FURNACE Filed sept. 29. 1927 lll Illlllllllll Q Q32 "Nimh INVENTOR En h. MN/ELS ATTO EY WITNESS -g7. a if Patented Slept. 13, 1932 f UMTEDl sT-TEs .,RATENT orsi,clefl FRED H. DANIRLS, or. WORCESTER, MASSACHUSETTS, ASSIGNCR To RILEY STORER CORPORATION, or WORCESTER, MASSACHUSETTS, A CORPORATION 01j MASSACHUf SETTS Y l f FURNACE.l

vApplication filed September 29, 1927." SeralvN'o. 222,792.v

This invention relates to furnaces, and is particularly applicable'to a furnacev provided with an automatic Stoker mechanism arranged to transport fuel progressively therethrough for combustion. l

In furnaces of this type it is customaryl to introduce the fuel thru openings'in the front wall of the furnace, and the refuse resulting from the combustion is deposited in an ash dump adjacent to the rear wall ofthe furnace. Combustion conditions in the front part of such a furnace adj acentto the point of entrance of the fuel are very different from the conditions in the rear part of the furnace. The fuel on entering the `furnace gives olf its volatile matter, andthe fuel bed being relatively thick at this point there is likely to be a deficiency of air supplied therethrough, which resultsin the escape of a large amount-of rich gas from this part f the fuel bed. In the rear part of the furnace,.on the other hand, the fuel bed is relatively thin and consists largely vof ash and refuse, and in order to avoid the losses caused by the presence of combustible matter in this refuse it is necessary to supply air therethrough and this usually gives an excess of air in the furnaceat this point. It is obvious that this stratification of gasesv is the cause of material reduction in efficiency, as the rich and lean gases pass into the boiler'tubes unmiXed and arev there cooledv below the point of ignition so that further combustion becomes impossible.` j 'i It is, accordingly, one object ofthis invention to provide 'a stoker in whicha bed'of fuel is moved progressively toward' anash dump at the rear and in which the losses caused by stratication of the gases shall be reduced to the minimum.

In modern power 'plants'and particularlyr those engaged in supplyingpower to municipalities, the load demand on the furnaces varies considerably at Vcertain times ofthe day, and it is frequently necessary to operate the furnaces at extremely high ratings lwhen these so-called peak loads occur'. It has been found that with the usual type of automatic stoker the efficiency becomes very much lower when the machine is operated at'these eX- tremely highratings, andvthisrlowering of the efliciency causes the fuel consump-tionto be unnecessarily high and is obviously undesirable. f i

It isA accordingly a furtherl object of myzinvention tovprovide a furnace which can besuccessfully 'operated'at high rates of combustion without materiallylowering the vefli ciency. Y

With these' and other objects in view, as willY be apparent'to those skilled in the' art, my invention resides in the combination of parts set forthV in the specification andcovered by the claims appended hereto; f

In accordance with my invention' vide a-stoker constructed for transporting-a bed of fuel progressively from the front wall I proj of a furnace toward an ash dump Within' the furnace and vpreferably adjacent to the rear wall thereof. In order t0 make up for the deficiencyvin combustible gases adjacent the ash dumpI introduce fuel in pulveri'zed form into the combustion chamber and preferably directly thru the rearwall of the furnace.' It is desirable that this pulverized fuel' be introduced by a burner ofthe so-called turbu lent type which is adapted to produce a rapid and thorough mixture of gases inthefurnace,` ensuring the desired eHiciencyof combustion.

Referring to the drawing in 'which like reference' numerals indicate like parts,l

Fig. 1 is a longitudinal section thru a fur-V nace embodying my invention; i

Fig. 2 is a section on'the line 2-'-2 of Fig. 1, with certain parts broken away; and

Fig. 3 is a. section on the line 3 3 of Fig. 1, with parts .brokenv away. 2 I v The embodiment of my invention illu:- tlrated' in the drawing comprises a combustion chamber provided with affront wall lland a rear wall 12 formed of suitable re-z fractory material` A horizontal water tube boiler 15 of well-known construction may be mounted above the chamber -10 and arrangedto absorb heat from the gases issuing therefrom. In the drawing, I yhave illustrated' somewhat diagrammatically a Stoker of the multiple retort underfeed type. Such stok' ers are well-knownto those skilled in this art and are described,for example', in the U. S.

patents t0 Riley No. 1,322,822 and Riley et al No. 1,605,665. The stoker illustrated comprises a fuel hopper 16 mounted adjacent to retorts are trough shaped structures extending rearwardly in parallel relation to each other from the front wall 11. Each retort has a bottom 24 and side walls 25, the latter being surmounted by suitable tuyere blocks 27 arran-ged to Asupport the fuel bed and admit air thereto. In the rear of the retorts I ,have illustrated an overfeed grate section 30 and an overfeed rocker apron 31. The air to the overfeed grate and the rocker apron is controlled by suitable dampers 33. and 34 respectively.

In order to supply f-orced draft to the stoker, the space. beneath the retorts is enclosed to form :ain air chamber 38. The bottom 39 of this chamber is arranged toslope downwardly as illustrated so that the fine fuel which sifts thru the grate surface may be easily re-; moved by opening the slide gate 40. A suitable fan 42 is arranged to deliver air under pressure into the air chamber 38 thru an air duct 43 provided with a regulating damper 45.

As a suit-able means for disposing of the ash and refuse from the stoker, I have illustrated a double roll clinker grinder 48 extending transversely of the chamber 10 between the rocker apron 31 and the, rear wall 12. These rolls are preferably constructed as shown in the U. S.. patent to Riley No. 1.441,027, and are arranged to grind the ash against adjustable apron plates 50. Y The refv use after bein-g ground by the rolls falls into the ash pit 53 which may be ofany desired construction.

During operation the contour of the fuel bed in a Stoker of this type will be somewhat as shown by the dot and dash line 55. It is tol be noted that such a fuel bed is much thicker near the front of the furnace than it is towards the rear, and as the result of this dierence in thickness, and also because of the large amount of volatile matter which is given olf by the fuel near the front of the furnace, the gases arising at this point are usually somewhat deficient in oxygen. At the rear of the furnace the fuel bed is comparatively thin and is composed largely of coke and ash. While the dampers 33 and 34 permit a reduction in the air pressure at this part of the furnace, nevertheless it has been found difficult in practical operation to burn outY all the combustible matter in the refuse without at the same time bringing about a. large excess of air in the rear of the chamber. In furnaces as heretofore utilized, this lean gas from the rear of the stoker has passed into the boiler tubes Without becoming mixed with the rich gas from the fronty of the stoler. Such a method of operation has obviously resulted in great losses and inefficient combustion. Y This is particularly true in the case of an und'erfeed Stoker, in which the combustion chamber ordinarily` has Vvertical parallel walls and there are no arches or other previsions for causing the stratified gas columns to .mix before entering the tubes.

In order to eliminate to a large extent this stratification of gases in the furnace and to bringabout other advantages which will be apparent tovvthose skilled in the art, I introduce a stream of pulverized fuel and air into the furnace chamber 10 and preferably directly thru the rear wall 12 thereof. For thisV purpose the rear wall 12, as illustrated, is provided with an opening 60, circular in shape and preferably fla-ring to an increased diameter on the furnace side. vA horizontal cylindrical burner pipey 62 is mounted coaxiai-with the opening 60 and is provided with a substantially circular enlargement 63 at its outer end. 'Ihe circular chamber 63 is provided with a tangential inlet 65 as shown clearly in 2V- The pulverized V.fuel is brought to this inlet 65 from any suitable source and its tangential admission causes the fuel to whirl rapidlyin the chamber 63 and become evenly distributed around the circumference of thepipe 62.

The pulverized fuel may be brought to the burner from a storage bin if desired, but I pref-er to utilize a pulverizer 6'? of the socalled unit type. If desired this pulverizer maybe of the general type shown in the reissue ,patent to Blyth No. 16,229. .The machine as illustra-ted comprises a coal hopper 68 and a disch-arge pipe 69 leading to the inlet 65. A suitable spreading device 7 2 is mounted .adjacentto thedischarge end of the burner pipe 62 and comprises a series of substantially radial vanes, each bent at Van angle so as to whirl the issuing coal stream. and throw it outwardly into the combustion chamber 10.

In some cases the so-called primary air which is used to bring the pulverized fuel to the burner may be insufiicient for complete combustion and it may be desirable to introduce -additional orsecondary air thru the opening 60. I have therefore illustrated a series of guide vanes or louvers arranged concentric with the pipe 62 as shown in Fig. 3. These louvers are Aarranged to give the secondary air a pronounced whirling motion preferably in the direction opposite to the pulverized fuel. In case it is desired to supply air to the louvers 75 under pressure I have shown a casing 76 arranged to form an air chamber around them. A fan 8O of any desired construction may be connected to the air chamber by means of a duct 82 provided with a. damper 83. Y

Having thus described my invention, the operation and advantages thereof will be readily apparent to those skilled'in the art. The hopper 16 is kept filled with fuel and the underfeed Stoker is operated in substantially the same manner as it would be in an ordinary furnace except that somewhat more air may be introduced to the overfeed grate section 3() and rocker apron 3l near the rear of the furnace in order to ensure the complete burning` out of all the combustible matter in the refuse. rl`he hopper 68 is kept filled with fuel which passes into the pulverizer 67 where it is reduced to a fine powder. rI`he pulverized fuel is then delivered thru the pipe 69 tangentially into the chamber 63 where it whirls'around rapidly and is eventually discharged as a. turbulent blast into the chamber 10 thru the pipe 62, being whirled and thrown outwardly by the spreader 7 2 and thereby causing a thorough mixture of the stratified gases arising from the stoker bed. Secondary air, if desired, may be supplied by the fan 8O and is whirled rapidly around the issuing coal stream by the louvers 75. The turbulent action of the pulverized fuel flame in the combustion chamber 10 results in bringing about a thorough mixture of the rich gases from the front of the stoker with the lean gases from the rear thereof. In some cases it may be desirable to operate the pulverized fuel burner with awdeciency of air by regulating the damper 83 in a suitable manner and to depend upon the excess air issuing from the rear portion of the stoker to make up for this deficiency and to provide complete combustion. In case it is desired to operate thefurnace at an extremely high rating it is unnecessary to force the stoker beyond its eflicient capacity, for the pulverized fuel burner can be depended upon to supply the extra fuel necessary.

vA furnace operated in accordance with my invention will produce a great deal more heat in a given time than is possible with a furnace equipped with a stoker alone. This is due to the fact that the available combustion space is utilized in a much more efficient manner than has heretofore been possible. VThe extra cost of the pulverizer and burner is more thancompensated for by the increased efficiency and capacity obtainable. In an ordinary pulverized fuel furnace the disposal of the ash is a serious problem. It is usually in a light, flocculent condition so that it is easily blown away by the wind and hence it cannot be sold for filling material. In a furnace constructed in accordance with my invention, however, the ash from the pulverized fuel flame falls on top of the fuel bed and is transported therewith to the clinker grinders which easily dispose of it. 'KI-he pulverized fuel ash is so mixed with the ash from the underfeedstoker that no problem of disposal is presented. The pulverized fuel fiame may be operated alone if desired by first protecting the metal parts of the Stokery within the furnace by a bed of ashes.

- Having thus described' my invention, what I claim. as new and desire to secure ,by Letters Patent is Y v f v 1. A furnace comprising walls defining a combustion chamber, a stoker having means for feeding a bed of fuel progressively from thefront to the rear ywall cf the chamber and to an ash dump within the chamber and adjacent to the rear wall thereof, means for feeding a regulatable amount of air to the fuel bed and for providing an excess of air adjacent the, ash dump to burn all of the combustible material from the ash, a fuel pulverizer, a burner pipe Vconnected therewith and opening thru a Wall ofthe combustion chamber, and means for regulating the amount of air to said burner pipe so that the air will be insufficient in amount to burn the pulverized fuel and a portion of the latter will be free to combine with the excess 'air from the Stoker fuel bed, thereby equalizing the combustion throughoutk the combustion chamber and causing efficient burning of both types of fuel. 2. A furnace comprising walls defining a combustion chamber, an underfeed stoker in said chamber having retorts and tuyeres for admitting air adjacent to the top surface of the fuel bed, means for feeding fuel lengthwise of said retorts towards an ash dump adjacent to the rear wall of the furnace, means for regulating the air supply to said tuyres so that an excess of air is provided adjacent the ash dump to ensure complete combustion of the fuel as it is moved rearwardly, a source of supply of pulverized fuel, a burner pipe adjacent to the rear end of the combustion chamber, and means for supplying air to said pulverized fuel in insufficient amount to cause complete combustion, said parts being so constructed and arranged that the pulverized fuel issuing into the combustion chamber will combine with some of the excess'air passing through the fuel bed of the underfeed Stoker and thereby ensure efficient combustion of both types of fuel.

3. A furnace comprising walls defininga combustion chamber the rear wall'of which is provided with an opening, anunderfeed stoker therein having a plurality of parallel retorts extending rearwardly from the front wall of the chamber, an overfeed grate section in the rear of said retorts, an ash dump in the rear of the overfeed grate section'and adjacent the rear wall of the chamber, means for feeding a bed of fuel through said retorts and along said overfeed grate section to the ash dump, means for supplying air to the fuel in said retorts and on said overfeed grates, a pulverized fuel burner of the turbulent type mounted on said rear wall to deliver through said opening and means to supply air and pulverized fuel to said burner.

4. A furnace comprising walls defining a combustion chamber, yan underfeed stolzer in said chamber having a plurality of parallel retorts extending rearwardly from the front wall thereof, means within the combustion chamber forming an ash dump in the rear of the retorts, means for feeding fuel lengthwiseiof said retorts and towards the ash dump, means for supplying air to burn the fuel on the Stoker, and means including a burner pipe extending through a wall of said chamber for projecting a blast of pulverized fuel and air into th-e combustion chamber over the fuel bed, thereby mixing the air and the combustible gases arising from the fuel bed.

5. A furnace comprising walls defining a combustion chamber, an underfeed Stoker therein having a plurality of parallel retorts extending rearwardly from the front wall of the chamber, an ash dump in the rear of the retorts, means for feeding a bed of fuel through said retorts to the ash dump, means for supplying air to the fuel in said retorts, one wall of the chamber being provided with an opening, a pulverized fuel burner mounted on said wall and arranged to discharge through said opening, said burn- -er and opening being so located that the flame is over the ash dump, and means to supply air and pulverized fuel to said burner for combustion.

Signed at Worcester, Massachusetts, this 23rd day of September 1927.

FRED H. DANIELS.