US2811953A

US2811953A - Slagging flyash

Info

Publication number: US2811953A
Application number: US380741A
Authority: US
Inventors: Jr Frank G Feeley
Original assignee: Riley Power Inc
Current assignee: Riley Power Inc
Priority date: 1953-09-17
Filing date: 1953-09-17
Publication date: 1957-11-05
Anticipated expiration: 1974-11-05

Description

Nov.. 5,` 1957 F. G. FEELEY, JR

SLAGGING FLYASH Filed Sept. 17, 1953 3 Sheets-Sheet 1 www INVENTOR M/VN G. FEELEm dR.

` ATTORNEY Nov. 5, 1957 Filed Sept. 17, 1953 F. G. FEELEY, JR 2,811,953

SLAGGING FLYASH 5 Sheets-Sheet 3 INVENTOR FRAN/r6. f1-En f/R.

ATTORNEY Unite States Patent O SLAGGING FLYASH Frank G. Feeley, Jr., Larchmont, N. Y., assiguor to Riley Stoker Corporation, Worcester, Mass., a corporation of Massachusetts Application September 17, 1953, Serial No. 380,741

3 Claims. (Cl. 122-240) This invention relates generally to melting dust-like materials and more particularly to a method and apparatus for performing such operations as reducing the fly ash collected in the back passes of a steam generating unit to a molten slag.

One of the outstanding problems encountered in the operation of large power plants is the disposal of the great quantities of ilyash which are collected in the back passes and other parts of the steam generating unit. This ilyash may be used for lling and reclaiming swamp areas and the like adjacent to the steam generating unit, but eventually these places for disposal become filled. If it then becomes necessary to cart the flyash away by truck, the cost of disposal goes up Very greatly. If, however, the flyash can be removed from the hoppers an-d collectors of the steam generating unit and converted to a slag, its bulk is materially reduced, and, furthermore, it becomes in many cases a commercially saleable product. If at the same time that the flyash is reduced to a slag the carbon remaining in the yash is converted to sensible heat, a very desirable situation exists. Slag in its hardened state has a Very hard glass-like quality that is useful as a road bed material and has been used as a base material for manufacturing fibrous insulating material. Attempts in the past to slag this yash have been unsuccessful for many reasons. First and foremost, it is not possible to reinject the iiyash into the high temperature portion of the conventional furnace because of the danger of carryover into the back passes; that is to say, reinjection of flyash brings about a substantial loading of the furnace gases. The danger exists also of the flyash slagging in the boiler passes, in which cases it sticks to the boiler tubes and forms an insulating coat around them. Furthermore, in some furnaces there is no area which reaches a temperature suiiiciently high to reduce the ilyash to a slag. Attempts in the past to slag liyash in conventional furnaces have resulted in failures. Similar difiiculties have been experienced in melting and agglomerating metallic dusts from mining operations and from metallurgical furnaces. The present invention obviates in a novel manner the difficulties experienced in the past in such operations as are set forth above.

It is therefore an outstanding object of the invention to provide a method and apparatus for melting dust-like materials.

Another object of the invention is the provision of a method to be used in conjunction with a conventional furnace for reducing flyash to a slag.

Still another object of the instant invention is the provision of an apparatus to be used in association with a conventional furnace for slagging flyash collected from the back passes of the steam generating unit with which it is to be used.

Still another object of the invention is the provision of a method for producing a zone of high temperature in association with a conventional furnace and introducing dusts therein for the slagging thereof.

A further object of the present invention is the provif. ICC

sion of an auxiliary furnace to be used in conjunction with a conventional furnace for producing a zone of high temperature and introducing llyash therein.

Another object of the invention is the provision of an auxiliary furnace for slagging flyash, making use of high heat release burners.

Another object of the invention is the provision of an auxiliary furnace to be mounted in operative association with a conventional furnace, having high heat release burners associated therewith for producing a zone of high temperature followed by an oxidizing zone, and having means for introducing flyash for reducing it to a slag.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation and manner of its organization may be better understood by referring to the following description taken in connection with the accompanying drawings forming a part thereof, in which:

Figure 1 is a vertical sectional View of a steam gener- Iating unit embodying the principles of the present invention,

Figure 2 is an elevational View partly in section of an apparatus for practicing the invention, and

Figure 3 is a plan View of the apparatus shown in Figure 2.

Like reference characters denote similar parts in the several figures of the drawings.

Referring first to Figure l, which best shows the general features of the invention, a steam generating unit indicated by the reference numeral 1t? is shown as comprising a furnace 11 and a boiler 12. The furnace 11 is of the water-cooled, slag-tap type and is made up of a forward wall 13, rear wall 14, and side walls 15, defining a combustion chamber lo. At the bottom of the combustion chamber 16 is situated a refractory slag bottom 17 of the usual type, having a means, not shown, for withdrawing molten slag from time to time. Mounted in the forward wall 13 of the furnace is a burner 18 for burning pulverized coal. The boiler 12 is made up in the usual manner of a steam-and-water drum 19 and a mud drum 20 joined by downcomer tubes 21. A large feeder tube 22 joins the mud drum 20 with a header 23 which overlies the top edge of the slag bottom 17 and which serves water wall tubes 24 which cover the inner `surfaces of the

Walls

13, 14, and 15 for cooling the combustion chamber 16 and forming steam. Also included in the boiler system is a superheater 25 of the convection type. In the lower part of the back pass of the boiler 12 is a hopper 26 in which is collected cinder and ilyash deposited therein. A cross-flow airheater 27 is mounted rearwardly and coextensive with the boiler 12 and is operatively connected in its lower portion with a cyclone type dust separator having a hopper 29 in which the dust is collected. Mounted rearwardly of the airheater 27 and generally coextensive therewith is an electrostatic precipitator 30 having a hopper 31 in the lower portion in which dust is collected. An induced draft fan 32 is mounted below the precipitator 3G and provides the draft for the entire furnace. An air duct 33 connects the airheater 27 to the burner 1S Vfor supplying secondary air for combustion.

Mounted to the rear of the furnace 11 and generally coextensive with the lower portion thereof is a flyash slagging apparatus 34 having a burner portion 35 anda barrel 36. The barrel 36 has an elongated tubular vertical portion 37 and a short horizontal portion 38. A lower plane surface 39 is provided in the bottom portion of the horizontal portion 38 and is inclined toward the furnace, the furnace end thereof being on the usual level of slag in the pool of slag 40 in the slag bottom 17. The upper horizontal surface 41 of the horizontal portion 38 "1s on a level considerably above any level of slag ever encountenedin thepool 40. *A

.Referring next to .Figures .2 .and 3 .wherein are .shown more detailed aspectsof .the -tlyashslagging apparatus .34, .itcan bezseen ythat .the burner .portion 35 `of .the .apparatus is formed-of Vrefractory .material so .as toform aportion 42 which is more or less an extension Aof .the .barrel .36 .and a `reduced tubular-portion 43 .of `considerable less a .diameter than the barrel 36. lherportions 42 -ancl 43 .arc .joined bya frusto-pyramidalportion 44 .andthe ,upperrend :of theportion 43 is closed byva generallypyramidal porition 45. The portions 42, V43,44, iand 45 have -axes that lie on the:axis.of.the,barrel.36. Throughithefapexof .the pyramidal portion 45 extends a nozzle 46 through which A passes a-.mixturefoffllyash and .-air. In .the eentral,portion :of .each .ofthe four .sides =of thepyramidal tportion `45 ris situated :a `high heat-release .burner 47 through `which passes ra mixture -of gas and air which originates -in .a manifold 4S ,serving -high heat-release burners. The .tubular portion43,1which isfof sguarecross section, land the pyramidalportionl45 -servefto define La small chamber 49. In the central portion of each of .the -four sides .of .the pyramidal portion 44 is situated an air nozzle 50 which surrounds the

portions

42 and 44. Situated on each of the four sides of the portion 42 are two high heat release burners 52. The burners are situated in close side-by-side relationship on opposite sides of the longitudinal center line of the respective side of the portion 42. These burners are of the same type as the burner'47 and may be of a special type wherein a high heat release is obtained by recirculating a portion of the combustion gases to adjacent the ignition point of the burner, whereby the ignition of incoming gases is facilitated and tremendous amounts of energy are released in a very small volume. These burners receive their gas from

gas manifolds

53 and 54 which entirely encircle the apparatus. .The burners 52 receive their air from-the vair plenum chamber 51. The burners 47 .are vinclined inwardly and downwardly and meet on the axis ofthe nozzle I46 at a portion thereof somewhat centrally 'of the `srnall vchamber v49. The `burners 50 are also inclined down- 'wardly and inwardly and meet on the axis at apoint somewhat downwardly of the burners 52. The airports 50 and the burners 52 re, of course, into the large-chamber 55 defined by the barrel 36, the portion 42, and' the pyramidal portion 44.

Returning to Figure 1 once more it is tobe notedthat 'a .forced draft fan 56 applies air to an-fejectorf'57 which discharges into a duct 58. The duct 58 is connected in series with the bottom portions ofthe

hoppers

31, 29, and 26 and connects finally with the nozzles 46. A gaspipe '59 `connects to the manifold 48 serving the burners 47 and tothe :gas manifolds'53 and 54 which serve :the burners :52. Also a duct.60 `branches off the main air duct 33 andfserves the burners 47 and the airplenum chamber 51.

The operation of the ;invention-will.now fbe understood in view of the above description. To begin with, the furnace 11 and the boiler 12 are operated in the usual manner'with the burner 18 discharging into the combus tion chamber 16 and the hot gases rising and passing over the superheater surfaces and the surfacesfof the downcomertubes 21 and transferring heat to the water and steam :contained therein. The water wall tubes v24, of course absorb heat by radiation. The hot gases, "after going through the back pass of the boiler, pass through the airheater where incoming air is heated before passage through the duct 33 to serve the burner 18. The gases after leaving theairheater27 enter-the cyclone separator 28'Where a certain amount'of'thel dust and cinders isremoved. The gases then enter 'the electrostatic precipitatol 30 Vandany'remaining dust and flyash is removedan'dde- `positedin the hopper 31. The induced 4draft fan '32, of course, projects the gases upwardly through the -precpitator 30 where they eventually travel into the stack, not shown. The extreme heat in the combustion chamber 16 causes a certain amount of the ash remaining after combustion to reach the slagging temperature in which vcase the slag passes downwardly through the chamber into the slag bottom 17 forming the pool 40. Slag is also deposited on the water walls and on the tubes over the chamber and drip and run downwardly into the pool 40. When the level of the slag pool 40 reaches a certain depth, some :of .the slag is removed. At the same time that the furnace is operating in the normal manner, hot gases and slag are received from the ilyash slagging apparatus 34. To begin with, air is supplied to the burners 47 `and the air plenum chamber 51 through the duct 60 which taps air from the duct 33. Gas from the pipe 59 mixes with the air in the burners 47 and with air in the burners 52 forming a combustion mixture which is burned in these burners with an extremely high heat release, as has ybeen explained. At the same time the fan 56 discharging .air .through the ejector 57 picks up yash, cinders and .dust from the

hoppers

31, 29, and 26. The air carrying -the yash along the duct 58 and permitting it `to be mixed .and.dis,charged through the nozzle 46 and into the small .chamber 49. In the chamber 49, then, exists a mixture oftheextremely hot gases ofcombustion .originating in .the burners 47 and the air and ilyash originating in the nozzle 46. Preferably, the gases'in the chamber 49 contain little or no excess air; this is accomplished by supply ing the bare minimum for combustion at the burners 47 and the minimum for carrying the flyash to the nozzle 46. In Ithis way, the temperature in the chamber 49 can be very high. Discharging into the larger chamber 56 are heated air from the nozzles 50 and very hot gases of combustion from the burners 52. By the time the llyash particles arrive in the barrel 36 they will have been raised .to a very high temperature. This high temperature along with the presence of excess air will cause the carbon to be `burned out of the particles and the particles to be melterl to slag. The slag will fall onto the surface 38 and will .run into the slag bottom 17 and the slag pool 40. The

`gases of combustion will also pass downwardly through .the barrel 56 into the short horizontal portion 38, will impinge Voirthe pool of slag, and will rise upwardly through the combustion chamber .'16, supplementing the 'flame and hot gases .originating inthe burner .18.

In a typical installation the ,burner 47 will use 177 pounds per hour of natural gas Vand ,2,970 .pounds .per hour .ofair at 670.degrees F. and 5 inches of water pressure. will .give 10% `excessair and a mixture pressure of approximately 4 .inches 4of water. The nozzle 46 willreceive a total of about 4,000 pounds per hour/of `flyash and 2,000-pounds per hour of air at670 degrees 'F.

A mixture'of flyash and air will be discharged through the nozzles at a velocity of about 38 feet persecond. This means that the mixture of hot combustion gases originating'in the burners 47 and yash and air originating in the nozzle 46 will leave'the small .chamber 49 at a velocity of about 40 feet per second, and a temperature 0f'2,'000 degrees F. The air ports 50 will receive in all approximately 12,860 pounds per hour of air at 670 degrees F. and 5 inches of water pressure and will leave the nozzles 50 at about 190 feet per second. The high heat release burners 52 will use 240 pounds per hour of natural gas and 3,760 pounds per hour of airat 607 degrees F. The maximum velocity of the mixtures of gases and yash traveling through the barrel 36 will be about 84 feet per second.

While certain novel features of the invention have been shown and described and are pointed out in the annexed claims, it will be understood that various omissions, vsubstitutions and changes in the forms and details ofthe device illustrated and inits operation may be made by those skilled in the art withoutgdeparting from'the yspirit f ofthe invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. Apparatus for use in slagging yash comprising a main combustion chamber having a gas off-take at its upper end and a slag bottom at its lower end, pulverized coal burners mounted adjacent the bottom to provide for most of the combustion which takes place in the chamber, an auxiliary chamber having an opening into the main combustion chamber adjacent the said bottom, the chamber being of vertically-elongated form, means for introducing a stream of fly-ash downwardly into the upper part of the auxiliary chamber, high-heat-release burners surrounding the auxiliary chamber and introducing hot gases into the stream of yash to produce turbulence, the mixture of gases and yash reaching a temperature above the fusion temperature of flyash within the auxiliary chamber.

2. Apparatus for use in slagging flyash comprising a main combustion chamber having a gas off-take at its upper-,end and a slag-tap bottom at its lower end, pulverized coal burners mounted adjacent the bottom to provide for the larger part of the combustion which takes place in the chamber, an auxiliary chamber having an opening into the main combustion chamber adjacent the said bottom, the chamber being of elongated tubular form with its centerline arranged vertically, means for introducing a stream of yash downwardly into the upper part of the auxiliary chamber, high heat-release burners surrounding the centerline of the auxiliary chamber and introducing hot gases into the stream of yash to produce turbulence, the mixture of gases and flyash reaching a temperature above the fushion temperature of flyash within the auxiliary chamber.

3. Apparatus for use in slagging yash comprising a main combustion chamber having a gas olf-take at its upper end and a slag-tap bottom at its lower end, pulverized coal burners mounted adjacent the bottom to provide for the larger part of the combustion which takes place in the chamber, yash collector means arranged to remove iyash from the combustion gases originating in the chamber, an auxiliary chamber having an opening into the main combustion chamber adjacent the said bottom, the chamber being of elongated tubular form with its centerline arranged vertically, means for introducing a stream of yash from the collector means downwardly into the upper part of the auxiliary chamber, high heat-release gas burners surrounding the centerline of the auxiliary chamber and introducing hot gases into the stream of flyash to produce turbulence, and means introducing sufficient air into the chamber to burn both the gas and the residual carbon in the yash, the mixture of gases and yash reaching a temperature above the fusion temperature of yash within the auxiliary chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,892,662 Kerr Dec. 27, 1932 1,942,687 Daniels Jan. 9, 1934 1,954,351 Dornbrook et al. Apr. 10, 1934 1,975,268 Grady Oct. 2, 1934 2,064,366 Bailey Dec. 15, 1936 FOREIGN PATENTS 384,877 Great Britain Dec. 15, 1932 627,287 Great Britain May 21, 1952