US2654218A - Ash handling system for high-pressure combustion of pulverized solid fuels - Google Patents

Description

Oct. 6; 1953 J. YELLOTT ASH HANDLING SYSTEM FOR HIGH-PRESSURE COMBUSTION 0F PULVERIZED soun FUELS 2 Sheets-Sheet 1 Filed June 5, 1948 T INVENTOR. JZJHNZXELLUTT ATTUHZSZEY Oct. 6, 1953 J. YELLOTT ASH HANDLING SYSTEM FOR HIGH-PRESSURE COMBUSTION OF PULVERIZED SOLID FUELS 2 Sheets-Shed 2 Filed June 3, 1948 m 5 6 2 2 W 4 6 a w 0 v 4 w 5 z 4 w 4. M

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000000 GOO0,0 m 7 2 m I 2 07 z w 7 E m 2 r0 7 O 4 4 W m 7 m z a z y a m .2 7 6 I 0 0 2 2 I 1 4 I 1 1 1 I 'llIllIlIIIlIIIIIIIl/IlIIIIIIIIIIIIII v, nunnnul Patented Oct. 6, 1953 ASH HANDLING SYSTEM FOR HIGH-PRES- SURE COMBUSTION OF PULVERIZED SOLID FUELS John I. Yellott, Cockeysville, Md., assignor to Bituminous Coal Research, Inc., Washington, D. 0., a corporation of Delaware Application June 3, 1948, Serial No. 30,816 Claims. (01. (so-39.46)

This invention relates to improvements in the pressurized combustion of pulverulent solid fuels, and, more particularly to a novel system and apparatus for cooling and conveying hot fly-ash separated from the gaseous products of combustion of pulverulent fuel.

In my Patent No. 2,583,921 of January 29, 1952, I have shown and claimed a special pressurized combustion system, including novel means for separating fly-ash from the gaseous products of combustion of pulverulent fuel.

I have now found that the fiy-ash derived from the pressurized combustion of pulverulent fuel should be cooled as rapidly as possible to a temperature below the ignition temperature of any uncombusted oversize fuel particles and of the unburned carbon which is commonly contained in fly-ash.

It is, therefore, among the features of novelty and advantage of the present invention to provide a fiy-ash cooling and treating system which will permit the continuous removal of superheated fly-ash from a fly-ash separator and discharge of the same in a pressurized stream of relatively cool air into a container, the coolant air with the heat units derived from the now cooled fly-ash being returned to the system as added motive gases, or discharged to the atmosphere, while the stored fiy-ash, being relatively cool, is not subject to burning or clinkering.

The features of novelty and advantage of the present invention which have been indicated hereinabove, will be more readily comprehended by reference to the following specification and accompanying drawings, wherein there is disclosed a generating electric power plant embody ing a pulverized coal-fired gas turbine installation incorporating a novel fiy-ash separator, and in which like numerals refer to similar parts throughout the several views, of which Fig. l is a perspective view of a generating electric power plant embodying a gas turbine, a fly-ash separator, coal-fired combustor, and a fly-ash cooling device;

Fig. 2 is a detail view, partlyin vertical section and partly in elevation, of the fly-ash separator and cooler showing the inter-connections therebetween;

Fig. 3 is a vertical section taken on line 33 of Fig. 2, showing the fly-ash discharge means from the bottom of the fly-ash separator, and

Fig. 4 is a horizontal section taken on lines 4-4 of Fig. 2, showing the inlet into the fly-ash cooler and separator.

In the gas turbine-generating electric power unit shown in Fig. l, and more particularly claimed in my application Serial No. 746,818, filed May 8, 1947, now Patent No. 2,583,921, issued January 29, 1952, the power plant comprises a bed or base it! of spaced parallel everted channels I l, secured by interposed cross-bracing members, designated generally by the numeral l2. When used in a locomotive, the bed may be integral with the locomotive frame. The power unit comprises a gas turbine 20, an air compressor 60, and a generator coupled to the turbine shaft through gear box 10. Gas turbine 20 has an exhaust stack 2| in which is mounted a combustor 3B and two banks of regenerator tubes 49 on either side of the combustor unit. A pair of inlet ducts 22, 23 connect the turbine to a fly-ash separator I00. Separator m0 is secured between the frame members H in any suitable manner. An air compressor 60 is mounted on the turbine shaft and discharges moderate pressure air of the order of 60 to 100 p. s. 1. through ducts 5| into the combustor and regenerator tubes, as will be described more in detail hereinafter. Gear box 10 serves to couple the turbo-compressor shaft to generator unit 80, mounting auxiliary generators 8|, 82 thereon. The auxiliary generator 8! serves to power auxiliary equipment, including a field generator or exciter 83 for the main generator 80. Auxiliary generator 82 is D. C. Wound and the same shaft powers the high pressure booster compressor 84. This booster compressor, or auxiliary air pump, is connected through line 85 to the pressure or discharge side of compressor 60, as shown in Fig. 1. Booster compressor 84 discharges through line 86 and a T connection to an auxiliary high pressure air tank 81, and a separate high pressure air line 88. The pressure tank 81 can also serve as a reservoir for air-brake air, and for other equipment, such as bell ringers, sanders, control equipment, and the like.

The coal utilized for combustion is fed from supply means, not shown, by high pressure air line 88, the streaming entrainment of fluidized solid particles being delivered through line 89 and coal atomizer 90 to feed line 9| of combustor 30. A by-pass for the air-borne coal from feed line 89 back to the storage hopper, not shown, is provided by line 92, which is connected to the atomizer 90 through'two-way valve 93. This arrangement permits the discontinuance of the coal feed and, conversely, the initiation of the coal feed, as when the turbine is first being started, after being initially supplied with gaseous or liquid fuel.

An aspirator 95 having a relatively large open chamber 96 is connected to the tip or discharge end 91 of dump line 92, the discharge end being preferably reduced, aligned with, and discharging into line 98 through the aspirator 95, the other end of the line 98 discharging into the crushed coal hopper, not shown. When; as in the case of an emergency stop, or when shutting down the engine at the end of a run, or for any other reason (as indicated above), the fluidized solid fuel supply in high pressure line 89 is diverted. through the atomizer into line 92 by operating valve lever 94, any excess temperature possessed by the coal contained therein is reduced by contact with an striction 91 into line 08. This operation effectu-..

.. is secured to the cover by machine screws, not

ally cools the heated pressurized, fluidized .pul-. verulent fuel mass which has been previously heated by contact with the high pressure atomizing air. This discharged-pressure air, now reduced in pressure and effectively cooled to atemperature below the dangerpointof spontaneous combustion, with its "pulverulent coal, which forms a very fine powden'is discharged into the hopper (not shown) and prevented from discharging directly into the atmosphere.

Because of this novel safety feature, fire or explosion hazards in the operation of the novel pressurized combustion system herein; are reduced below any danger point, even under conditions of shock such as can obtain in train wrecks and the like.

The combustor in its combination with' the compressor 60, turbine 20, exhaust stack 2|, re-

generator tube banks 40, and the fly-ash sep'ara' tor I00, is more particularly shown and claimed.

in my said Patent No. 2,583,921 andwill be described herein only insuflicient detail to point out the novel elements of the system forming the supply pipe 9!, which introduces'pulverized fuel into the flame tube in a pressurized, air-borne.

stream. The cap 36 is'provided further with a fluid fuel inlet tube 31 for introducing liquid? or gaseous fuel for starting the turbine, and a. second fuel pipe 3 8 is provided for the introduction of a liquid or gaseous fuel to serve as. a pilot. light or.

igniter for the system. A sight tube 39 is also provided adjacent tothe flame carrier, so as to. permit inspection thereof; For remote inspece tion and control, the sight tube may be provided with a suitable alarm system. A photoelectric cell, or other flame-and heat-responsivedevice may be connected thereto, suitable connections. to the instrument board of the system beingprovided.

The fuel delivered through coal atomizer 90 and feed pipe 9| to the. combustor 30, will becom busted therein and the products of. combustion will be diluted in theupper mixing chamber of fly-ash separator I00 by the extra, relatively cool air delivered through ducts of the combustor-case ing and the air delivered through the tube sheets of the regenerator banks 40. The detailsof the novel fly-ash separator will be described.

As shown in Fig. 2, the fly-ash separator. comprises a generally cylindrical, laminated pressure vessel I00, having an outer steel wall, an inner stainless steel heat-resistant lining, and any intermediate or internal insulation filler between the At the fuel inlet'end the com-.

H0 in sliding bearing engagement.

-of" the same material as the bottom cover and 1-0- the wall of the container. The cover H0 is centrally apertured to. receive shaft I Id of piston I I5, which, as shown, is mounted for reciprocation in cylinder H6 having a closed bottom with a central'boss centrally apertured to receive the shaft The outer portion of the central boss is received in a confer-med aperture in the cover I i0, and the cylinder shown, passing through the flanged base and into the top cover section. The upper end of the piston cylinder is closed by a removable plate I20,

secured in place by thev usual bolts and nuts, not.

shown. The piston H5 divides the pistoncylinder into an upper chamber and a lower chamber, which are severally connected to suitable sources of fluid supply by pipes I25,- I-26, respectively. A closure disc IZI, having a beveled seat is fixedly mounted on shaft H4. The disc I2? is adapted- .to be lifted up by the shaft IM when piston H5 is urged upwardly by fluid pressure in the chamher 120. The function of the closure disc I27 will be described more in detail hereinafter in connection with the particular description of the separator tube assembly.

An inlet chamber I30 connects the upper per-- tion of the cylinder I00 with the combustor discharge and the regenerator discharge outlets.-

The inlet duct or passageway I30 is provided with ....parallel top and bottom walls I3I, I32 and outwardly flaring side walls, formed as a unit with in'the wall of the container immediately below the duct I30 and are disposed somewhat-below the middle of the vessel.

turbine byflexible. coupling members I31, I38.

Internally, the chamber or vessel I00 is divided into three sections: "an'upper' plenum chamber I50, a bottom fly-ash receiving chamber MI, and

an intermediate cleaned gas-receiving chamber IA'Lwhich discharges into the outlets I35; I 30;

The plenum chamber and intermediate clean gas, receiving chamber, together with the fly-ash Claimed in my abovesaid Patent No; 2,583,921.

In the instantaneous burning of coal dust, a maximum rise of 3000? F. can occur. Since the normal operating temperature of the air in the.

inner chamber I41 will be about1300 F., or l760 abs, a rise in temperature of 3000" F. would pro.-

duce a total absolute temperature of 47.60 F. This is a three. to one increase in absolute tem-' perature, and, in a closed vessel, wouldresult in a pressure rise of three to' one. Because of the .unusually large venting area provided by the cyclone separators and the adjacent chambers the These ducts are severally connected to the inlets 22', '23 of the gas inner chamber 5 M is instantaneously enlarged to include the upper chamber I40, the annular V trough immediately below it, as well as the throat I30 leading from the combustor unit to the flyash separator, and the annular chamber I42, ducts I35, I36, and gas turbine 20. In other words, the quantity of intensely heated air developed in the cylinder and resulting from the explosion, can be allowed to flow into a relatively large volume and certainly at least three times greater than that of the chamber, so that the force of the explosion can be dissipated without resulting in harm to the equipment.

In a series of exhaustive studies on dust explosions the Bureau of Mines has found that a venting area of 5 sq. ft. per hundred cubic feet of explosion volume affords an ample safety factor in closed chambers where explosion hazards exist. Because of the lack of venting space, such conditions indicate positive explosion hazards. As the vent area increases up to 2 sq. ft. per hundred cubic feet of explosion volume, it will be seen that the pressure developed, expressed in pounds per square foot, decreases, arriving asymptotically at a minimum value between 5 and sq. ft. of venting area per 100 cubic feet of explosion volume.

Considering these controlling factors with respect to the invention herein, the inherent safety factor will be apparent. The fiy-ash chamber I4! is in open communication with the upper plenum chamber I40 andithe ducts 22, 23 leading to the turbine as well with the chambers formed by the separator units I50 and their supporting structures. The separator units I50 provide free, substantially unimpeded paths between all chambers so that thefiy-ash chamber I4I has a vent area equal to substantially 70% of its surface which aifords a positive assurance of safety from explosions due to delayed combustion of solid combustive materials in the fiy-ash chamber under high pressure conditions.

In the pressurized combustion system herein this type of safety factor is of maximum importance, as well as from the operating efilciency as from the primary and controlling factor of safe-guarding human life. Because of the relatively enormous vent area provided, the pressures utilized can be greatly increased without increasing explosion dangers in a comparable manner. With any explosion in the fly-ash chamber, the

gase are vented immediately, in opposed directionsj through the turbine on one side, and back through the plenum chamber and combustor on the other side, 'softhat, the volume of discharge space available in the turbine and its inlet ducts and outlet exhaust stack,"as well as in the plenum and mixing chamber of the combustor, and the combustor itself together with the regenerator tubes, is extremely large as compared with the restricted volume of the fly-ash chamber.

The special fly-ash disposal system for pressurized combustion systems of the type shown in my said Patent No. 2,583,921, issued January 29, 1952, for Multiple Element Vortical Whirl Ash Separator, and as shown generally in Figs. 1 and 2, comprises a second, combination fiy-ash separator and storage tank 200, feed line 2I0, cleaned air discharge system 220, and high pressure ejector feed line 230. To integrate the fly-ash separator of my above said application with the present system, the fly-ash receiving chamber MI is provided with a V-trough 24I, discharging through elbow 242 of ash dump line 243 into feed line 2l0. A worm 244 is mounted for constant rotation in the V-trough MI and is driven by motor 245, as shown in Fig. 2.

The second, combination fly-ash separator and storage tank 200 comprises a generally cylindrical tank having a bodyportion 20I with a truncated conical bottom 202 closed by a large dump valve, designated generally by the numeral 203. In place of the dump valve, the tank may discharge through a depressurizer, permitting the ash to be stored at atmospheric pressure. The top of the tank is closed by annular plate 204 having an axial discharge opening 205, and mounting a depending cylinder 206. A tangentia1 inlet 201 is formed in the upper cylinder wall immediately below the cover plate 204.

The air feed line 2I0 is tapped into the discharge duct 6| of the main compressor 60, and is brought to tank 200 after picking up fly-ash discharged through dump line 243. Immediately upstream of the dump line 243 the line 2"! is fitted with a reducing nozzle 2 II which serves to increase the velocity of the pickup and coolant air flowing past the discharge opening of dump line 243, and to equalize the pressure in the discharge line. A valve M2 is mounted in the line 2I0 upstream of the nozzle to control the fiow of air therethrough. Normally, the flow through line 2! will be less than 1% of the total air flow. Downstream of dump line 243 the air line 2I0 is directed upwardly, to form an ash delivery line 2 I3, then horizontally to form tangential delivery line 224, whose outlet is secured to, and is coextensive with inlet 20?, in the tank 200. A valve 2 I 5 is fitted in line 2 I 3 upstream of the outlet.

The cleaned air discharge system 220 comprises a vertical line 22i secured to discharg opening 225 of tank 20L The line 22I is directed horizontally, as indicated at 222 to the inlet 223 of airoperated ejector 224. The ejector 224 discharges downwardly into line 225 fitted with valve 220, the line being directed horizontally, below the valve as indicated at 221, into the plenum or mixing chamber I40 of the fiy-ash separator I00.

The high pressure ejector feed line 230, is supplied with air from auxiliary compressor 84, and isconnected at 23! to the inlet 223 of ejector nozzle 224. A valve 232 is fitted in line 230 and desirably adjacent the discharge 23!. A twoway valve 228 and discharge pipe 229 are provided in line 220 to vent the clean air from the tank 200 tothe atmosphere or to auxiliary heating services, when it is not desired to recycle it to the fly-ash chamber.

The operation of the combination ash cooling and auxiliary motive gas generating system, de scribed immediately above, will be considered with respecttir'tiieg nprovement in overall operation and efficiency ofcoal-burning gas-turbine power plants, and particularlytiof such power plants as incorporated in locomotives, aiidmarine installations.

Motive gases are delivered from fly-ash separator I00 to gas turbine 20 at maximum operating temperatures of 1300 F., to 1350 F. At these temperatures, the separated fly-ash, which is discharged and collected in fiy-ash receiving chamber I4I, retains significant quantities of heat. The ash, having a low heat conductivity, is essentially a good insulating material. Because of the poor heat transfer characteristics of the ash, the problem of cooling superheated (1300 F.) masses of the same, in restricted spaces, as in locomotives and marine installations, where space is always at a premium, assumes major engineering importance. This problem is complicated further by the fact that the system must be maintained pressurized, and, in the instant system, desirably at an operating pressure of 4-5 atmospheres at the turbine inlets. The novel ashcooling system herein solves this problem by cooling the hot (1300 F.) ash in an, ejector stream of coolant gaseous fluid (air, steam, etc), and discharging it into a cyclone separator where it undergoes further cooling and separation from the gaseous entraining stream.

What is claimed is:

1. In a plant for the pressurized combustion of pulverized fuel, a combustion chamber, a discharge line for the products of combustion, means in said discharge line effective to remove the flyash from the products of combustion comprising a first ash separator, a second ash separator, pneumatic conduit means connecting the ash discharge of the first said separato to the inlet of the second said separator, means for discharging ash from the first separator into the said pneumatic conduit, and means for delivering pneumatic coolant through said conduit to the second said separator, whereby entrained ash from the first separator is cooled and delivered to the second separator and the cooled ash is separated from the entraining fluid.

2. System according to claim 1 in which the second said separator incorporates a storage chamber.

3. In a power plant for the pressurized combustion of pulverized fuel, in combination, a combustion chamber, a discharge line for the products of combustion, a first ash separator in said discharge line to remove the ash from the products of combustion, means for cooling said separated ash to remove the heat energy therefrom, means to return to the system the heat energy derived from the-separated ash, said means including a second separator incorporating ash storage means and a cleaned air return line to the system.

4. System according to claim 3 in which the clean gas discharge line from the second separator is connected to the input side of the first said ash separator.

5. In an apparatus for the pressurized burning of pulverized fuel having a combustion chamber, a discharge line for the products of combustion, a fly-ash separator, and a fiy-ash receiving chamber in the separator, the improvements comprising fly-ash discharge means in the said chamber, and efferent pneumatic conduit means connected to the said chamber discharge means, whereby the discharged hot ash from the separator isentrained and cooled in said pneumatic conduit.

JOHN I. YELLOTT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 730,782 Morrison June 9, 1903 1,814,560 Kreisinger July 14, 1931 2,055,385 Noack Sept. 22, 1936 2,187,627 Noack Jan. 16, 1940 2,192,885 Avery Mar. 12, 1940 2,288,734 Noack July 7, 1942 2,375,436 Noack May 8, 1945 2,399,884 Noack May '7, 1946 2,401,285 Woodward May 28, 1946 2,445,388 Ramseyer Aug. 3, 1948 2,509,246 Ramsey May 30, 1950 FOREIGN PATENTS Number Country Date 168,406 Great Britain Aug. 31, 1921

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