US2909133A - Apparatus for drying comminuted coal containing fine particles and dust - Google Patents

Description

Oct. 20, 1959 c. w. GORDON 2,909,133

APPARATUS FOR DRYING COMMINUTED COAL CONTAINING FINE PARTICLES AND DUST Filed Nov. 23, 1956 Starting Fig. l.

Start-Up Burner 24 Stock 5 Sheets-Sheet 1 Main Veni Fan f you \AATAAAA'A vvvvvvvv Charles W. Gordon ATTORNEY Oct. 20, 1959 c. w. GORDON 2,999,133

APPARATUS FOR DRYING COMMINUTED COAL CONTAINING FINE PARTICLES AND DUST Filed Nov. 23, 1956 5 Sheets-Sheet 2 A F Q I 1 l Q 6 I, J /2 so .a0 I5 I l3 I (i I I as 1 2 i i D l9 y I 28 Auxilior Fuel y i n Furnace H, 5 tr; 24 1] Charles W. Gordon c. w. GORDON APPARATUS FOR DRYING COMMINUTED COAL Oct. 20, 1959 CONTAINING FINE PARTICLES AND DUST Filed NOV. 23, 1956 5 Sheets-Sheet 3 INVENTOR Charles W. Gordon flaw TTORN Oct. 20, 1959 c. w. GORDON 2,909,133

APPARATUS FOR DRYING COMMINUTED com. cormmmc FINE PARTICLES AND DUST 5- Sheets-Sheet 4 Filed Nov. 23, 1956' Fig. 4.

INLVENTOR Charles W. Gordon Fig. 5.

Oct. 20, 1959 c. w. GORDON 2,909,133

APPARATUS FOR DRYING COMMINUTED COAL CONTAINING FINE PARTICLES AND DUST Filed Nov. 23, 1956 5 Sheets-Sheet 5 I I 40 so I ,2 F H V I ll g u I n Fig. 7.

INVENTOR Charles W. Gordon I fififi i 46 ATTORNEY United States Patent APPARATUS FOR DRYING COMlVHNUTED COAL CONTAINING FINE PARTICLES AND DUST Charles W. Gordon, Glen Ellyn, Ill., assignor to Combustion Engineering, Inc, New York, N.Y., a corporation of Delaware Application November 23, 1956, Serial No. 624,002 '1 Claim. 01. 110-104 This invention relates to new and useful improvements in drying apparatus and is particularly directed to apparatus for drying screened coal upon its removal from the mine. Coal of this variety is not in pulverized condition but consists of particles of different sizes and weights from about down to thelowest mesh or fineness.

Such coal carries with it moisture that must be removed before it can be satisfactorily handled and used; moreover it contains a small dust fraction, mostly below 325 mesh, which is very troublesome in the handling of the finished product due to the dust nuisance and which is normally high in ash and therefore a. low grade product.

In coal drying and separating systems as used heretofore the moist or wet comminuted coal together with its content of troublesome fines and dust is delivered into a stream of high velocity hot gases wherein both the larger coal particles and the fines are substantially instantaneously dried; the gases and the coal carried thereby then are delivered to a cyclone separator wherein the now moisture-laden gases are separated from the dried coal which is thereupon withdrawn from the system; and said hot gases for drying the comminuted coal typically originate in a furnace fired by auxiliary fuel that in the past has been supplied from a source other than the comminuted coal passing through the drying system.

Broadly stated, the object of my invention is to lower the cost of operating such coal drying apparatus and at the same time improve the quality of the dried coal that is withdrawn from the drying system.

A more specific object is to accomplish the foregoing in a new and unique way which drastically reduces auxiliary fuel requirements and at the same time makes the dried comminuted coal more suitable for handling and use.

Another object is to provide novel and highly practical means for firing the heating furnace of such a drying system by small coal particles and dust that are taken out of the comminuted coal after it has been dried by the hot gases but before it leaves the separating cyclone of the system.

Other objects and advantages will become apparent as the disclosure and description hereof proceeds.

An illustrative embodiment of the invention is shown by the accompanying drawings wherein:

Fig. 1 is a diagrammatic elevation view showing typical drying apparatus assembled into a system which incorporates my inventive improvements as novelly organized to extract fine coal dust in quantity sufficient to provide all of the heat for :drying.

Fig. 2 repeats certain portions of the diagrammatic Fig. 1 representation and shows those repeated portions in greater mechanical detail.

Fig. 3 is a sectional view of the Fig. 2. drying and separating apparatus taken along line 3-3 of Fig. 2.

Fig. 4 is a top plan view of the cyclone'and furnace and cooperating devices taken along line 44 of Fig, 2.

Fig. 5 is an enlarged sectional View of thetop portion ice of the separating cyclone taken along line 5-5 of Fig. 3.

Fig. 6 is a similarly enlarged sectional view of the cyclone separator, with portions cut away, which is taken along line 6-6 of Fig. 2 and which shows how the adjustable finescollector tube is installed inside the main cyclone casing.

Fig. 7 is a view on line 77 of Fig. 6 showing how the fines collector tube appears when viewed from the bottom.

In the drawing views hereof like reference characters are used throughout to designate like elements.

Illustrative system to be benefited Referring to the drawings, the drying apparatus there illustrated utilizes a furnace A for supplying the hot drying gases, which satisfactorily may be hot air; a drying tower or column B through Which said hot gases from the furnace rise upwardly; a cyclone collector or separator C into which said upwardly rising gases discharge and by which coal carried thereby is separated from those gases; a bin D for holding a quantity of the comminuted coal that is to be dried; a feeder E for receiving wet coal from the bin and for delivering it into the stream of upwardly rising hot gases in the drying column; a starting stack F for the furnace A; and a main vent fan G communicating with the top outlet 12 of cyclone C and serving to draw hot drying gases from furnace A first through conduit 14 and chamber 16 and next into and through the drying tower B and finally into and through cyclone separator C, withv the gases being discharge from the system via conduit I Thewet comminuted coal. to be driedis released into thefeederE from bin D via the customary feed gate 18; and in the arrangement shown said wet coal is supplied to that bin. via the usual conveyor belt 10. If desired a supplemental conveyor belt 11 further may be provided for also delivering Wet coal directly into the feeder E, in the way indicated by Fig. 1. Said feeder E is of course provided with suitable drive means 28.

The cyclone separator C is provided with a lower outlet .20 having a conventional air lock 21 below which thereruns a conveyor belt 22 that is adapted to receive the coal as discharged: from the system after having been dried. This belt 22 carries the dried coal to some de sired point (not shown) where it may be loaded into a railroad car (not shown): or the like brought to the dryer location on rails such as are indicated at 23 in Figs. 3 and 4.

Drying column or tower B, chamber 16 and conduit 14 are: preferably circular in cross section. Said chamber 16 may satisfactorily be organized as disclosed and claimed in copending application Serial No. 387,742 which was filed October 22, 1953, now Patent No. 2,788,585, in the: name of R. G. Tucker and assigned to the same assignee as is this application which issued on April 16, 1957?, as-U.S. Patent 2,788,585. A rotary air valve 17 isprovided at the bottom of this chamber 16 so that any large pieces of coal'which'may occasionally drop through the chamber from feeder E can be taken out of the chamber bottom without admitting outside air into the chamber..

The furnace A may be any desired type of heater, the overall details of which are relatively unimportant. Past practicehas been to fire such a furnace with auxiliary fuel such as may be introduced therein via pulverized coal burner 24, with such fuel being supplied to the burner from apulverizing mill (not shown) that is fed withthe needed coal; or alternatively the furnace maybe equipped with a grate (not shown) to which unpulverized fuel is supplied as by a stoker (also not shown). Such furnace serves to heattheair or other gases leaving it to a relatively high temperature, as from about 1000 F. to about 3 1500 F. The air to be heated may be admitted into the furnace in part through the burner 24 and in remaining part at other points such as wing blower 25 or the like.

The system components thus far described are relatively conventional and they operate as follows: The main vent fan G is provided with suitable drive means 29 and has a capacity ample to draw the hot gases from furnace A through the system at relatively high velocity. These high temperature gases (1000 to 1500 F.) in greatly expanded condition pass through the large conduit 14 into the chamber 16 in adequate volume to provide for delivery upwardly through the chamber with comparatively low pressure drop. In the reduced diameter pick up section 19 (which constitutes the lower end of drying tower B) the velocity of these gases is greatly increased.

In the particular installation shown, with coal particles ranging downward from. in size, the velocity of the hot gases passing through pick-up section 19 from chamber 16 and into the lower end of drying column B may desirably be in the neighborhood of 10,000 feet per minute; and this pick-up section 19 (see Figs. 1 and 2) has the substantial vertical length indicated (see Figs. 1 and 2) with the bottom thereof being well below the feeder E which introduces the wet coal into the column B.

Such introduction of the wet coal is accompanied by a substantially instantaneous evaporation of the moisture therefrom. This quickly lowers the temperature of the gases at the point of said wet fuel admission with resultant decrease in the volume of those gases and some accompanying reduction in their speed of upward travel into and through the drying column B. However, the stream of gases so passing feeder E still has a relatively high velocity (of the order of 5500 feet per minute) and such stream is formed and well established before reaching the top of pick-up section 19 where coal is delivered thereinto; moreover these drying gases maintain their said relatively high velocity during further upward travel through the remaining length of drying column B and into the tangential opening 13 of cyclone separator C.

Coal fines and dust particles, being relatively light, drop little if any below the level of feeder E, and these quickly acquire the upward speed of the moving column of drying gas. Heavier particles of coal laterally introduced into the column accelerate slowly and may initially tend to drop by gravity. But the aforementioned depth of pickup section 19 insures that any such heavy particles as do start to drop through the section will have their downward movement arrested and will have imparted thereto an upward movement suificiently accelerated to give the impetus necessary to carry them through the system. In this way substantially all of the comminuted coal introduced into the system by feeder E is picked up and carried upwardly through the drying column B to the cyclone separator C.

The drying system just described will effectively handle comminuted coal particle sizes ranging from about /8" down to the lowest mesh coal produced. Any especially heavy lumps of coal as are not carried through the system are released from the bottom of chamber 16 by means of the aforementioned double valve 17 which permits the discharge thereof without admitting air into the system.

To facilitate start up of the unit, automatic dampers 26 and 27 customarily are provided in the hot gas conduit 14 and in the furnace stack F in the way shown by Figs. 1 and 2. At the beginning of such start up damper 26 will be closed while damper 27 will be open; and as the desired temperature in furnace A is approached damper 27 will gradually close while damper 26 will at the same time open to divert the hot furnace gases from starting stack F to the conduit 14 which leads to chamber 16 and drying column B.

The improvements of this invention In accordance with my invention the drying system elements and organization just described are supplemented .4 by novel additional facilities which during normal operation of the systemmake unnecessary the supply of auxiliary fuel to furnace A (from any suitable source generally designated 35 in Fig. 2) and instead provide for the firing of the furnace by coal dust and ultrafine particles which are withdrawn from the interior of cyclone C and which have heretofore been a nuisance when permitted to remain in the dried coal as discharged upon conveyor belt 22 from the cyclone outlet 20.

Such new facilities are represented in the form of an adjustable collector tube K that is positioned centrally inside the casing of main cyclone C and that communicates with a duct or conduit 30 which leads out of the cyclone top in the manner shown; a fan 32 which draws the collected coal fines and dust through conduit 30 and passes them by way of a dust burner 34 into furnace A where they are ignited and burned for the purpose of heating the air that is needed to operate the drying system; and means for vertically adjusting collector tube K in cyclone C to the position which is most effective for collecting the fine coal particles and dust and which otherwise results in the best operation of furnace A when fired by those small particles of collected coal. Structural members for supporting fan 32 have been omitted in order to simplify the drawings; and for the same reason the fan drive means are not fully shown.

From Fig. 6 and other drawing views it will be seen that collector tube K is provided with an outwardly flared lower fitting 36 having vertical vanes 37 radially disposed within the interior thereof. Purpose of these vanes is to increase the effectiveness of said fitting 36 in picking up coal fines and dust from the currents of drying air which swirl through the lower interior of cyclone casing C above the bottom outlet 21-20 (see Figs. 1-2-3) for the dried coal; it being understood that a major portion of the hot gas which enters the cyclone from drying column B leaves that casing through the top central outlet 12. In said cyclone C as here illustrated the upper casing portion has the usual parallel walls While the lower casing portion has the usual conical shape that tapers downwardly and inwardly to the aforesaid bottom outlet 2120.

In operation, this represented cyclone C receives tangentially near its top the current of drying gases and entrained coal from the column B via the earlier mentioned cyclone inlet shown at 13 in Figs. 2, 3 and 4; the larger particles of this entrained and dried coal are thrown by centrifugal force close to the cyclone casing wall and they spiral downwardly in close proximity to that wall towards the bottom outlet 20 where rotary valve 21 passes them through that outlet and onto dry coal belt 22, with the drying gases thus freed of said larger coal particles leaving the cyclone 'via the central top outlet '12; and the coal fines and dust particles being lighter tend to stay closer to the center of the cyclone casing and many of them in approaching the casing bottom are found to concentrate towards the cyclone center a short distance above said casing bottom.

This characteristic of behavior is taken advantage of by my novel collector tube K; and in order to insure maximum effectiveness in collecting the dust and fines from the cyclone I have mounted this tube K so that its vertical position can readily be adjusted to the level where optimum operating efliciency is achieved.

In the mounting arrangement illustrated the upper portion of tube K is slidably fitted into the interior of a surrounding stationary tube 38 which constitutes the lower portion of the earlier described conduit 30 through which the collected coal fines and dust are conveyed out of the cyclone to the fan 32 and thence into furnace A. Supporting the weight of adjustable tube K is a cable 40 the upper end of which is fixed to and wrapped around a pulley 41 that is carried by a horizontal shaft 42. This shaft 42 receives rotative movement from a gear wheel 43 which meshes with a worm gear 44 carried by the upper end of a vertical shaft 45 which extends downwardly along one side of cyclone C and has a hand wheel 46 mounted on the lower end thereof.

This hand wheel 46 can be turned by the operator of the drying system. Rotation in one direction serves to raise the position of collector tube K inside cyclone C; while rotation in the opposite direction serves to lower the collector tube position. In order that the operator may know at all timeswhat position the collector tube is occupying the lower portion of the aforesaid shaft 45 is provided with an indicator 48 which registers with a scale 49 and which upon rotation of the hand wheel is arranged to move up and down along said scale in a way which tells the operator what position within cyclone C is occupied by the lower pick up fitting '36 of collector tube K.

During operation of the complete system as improved by this invention it is of course necessary that furnace A initially be fired by auxiliary fuel from some suitable source (indicated at 35 in Fig. 2) either introduced through the pulverized coal burner 24 or otherwise made available in the furnace. Once the discharge gases from the furnace have acquired a sufiiciently high temperature the wet coal to be dried as brought into the system by conveyor belts and L1 (and including fine particles and dust) is introduced by feeder E into the vertical drying column or tower B above pick up section 19 and chamber 16. The column of hot drying gases rapidly rising through B dries this introduced wet coal and carries it upwardly into cyclone separator C. There the hot drying gases are separated from the dried coal and carried out of the system by main vent fan G. The dried coal falls by gravity to the lower portion of cyclone casing from which it is withdrawn via rotary valve 21 and discharged at outlet on to the dry coal belt 22.

The ultrafine particle and dust constituents (such as below 200 mesh) of this dried coal are by collector tube K withdrawn from the cyclone and passed by fan 32 and burner 34 into furnace A where they are ignited and burned for the purpose of heating the drying gases. Once this burning has been gotten under way the heat released from combustion of these collected coal fines is adequate to continue operation of the system without any need for burning auxiliary furnace fuel; and from this point on the drying system will be self-sustaining and supply of all auxiliary fuel to furnace A can be cut olf.

Most effective collection of the coal fines and dust and optimum performance of the drying system when furnace A is fired thereby is assured by adjusting hand wheel 46 so as to position collector tube K at the elevation within cyclone C which yields the best results. If any further adjustment should be needed, it can be made by changing the position of damper 33 in the dust conduit 30.

If desired the fines burner shown at 34 in Figs. 1 and 2 can be combined with the start up burner 24 earlier described; however use of such a pulverized fuel burner 34 (either alone or combined with start up burner 24) assumes that a major portion of the coal fines picked up by collector tube K and supplied to the burner have a smallness below about 200 mesh.

Should it be desired to adjust the position of tube K so that it also will collect coal particles of substantially larger size, such larger particles likewise can be employed to provide the needed drying heat in furnace A. For example, this can be done by directly substituting them for the auxiliary start-up fuel which is fed to the furnace from source 35 (see Fig. 2) either through the start up burner 24 or by the aid of the earlier mentioned stoker (not shown) by which such larger collected coal particles can successfully be burned in the furnace; and if the installation does use a start-up burner 24 that is supplied by a coal pulverizer (not shown) those larger collected coal particles can first be passed through the pulverizer and then blown into the furnace after their size has been suitably reduced by the pulverizer,

Summary From the foregoing it will be apparent that the drying system improvements herein disclosed have practical utility of a high order and that the specific functions described therefor are accordingly to be interpreted in an illustrative rather than in a restrictive sense.

It will thus be seen that my invention lowers the cost of operating coal drying apparatus and at the same time improves the quality of the coal which is withdrawn from the system; that it accomplishes the foregoing in a new and unique way which drastically reduces auxiliary fuel requirements and at the same time makes the dried comminuted coal more suitable for handling and use; and that it provides novel and highly practical means for firing the heating furnace of the drying system by small coal particles and dust which are taken out of the comminuted coal after the coal has been dried by the hot gases but before the coal leaves the separating cyclone of the system.

My inventive improvements are therefore extensive in their adaption and hence are not to be restricted to the specific form here disclosed by way of illustration.

What I claim is:

In a system for drying comminuted coal that contains fine particles and dust and for utilizing the said fines and dust content of the coal as the source of drying heat, the combination of a furnace provided with a fines burner and also with start up means effective to bring in and burn auxiliary fuel from which hot combustion gases initially are produced, a drying column receiving the hot combustion gases from said furnace and passing same upwardly through the column, a feeder for introducing the wet comminuted coal with its aforesaid fines and dust content into the lower portion of said drying column, a cyclone separator having an upper casing portion with central top outlet for discharge of gas plus a tangential side inlet connected to receive the hot gas and coal mixture from the upper end of the drying column and having a lower casing portion of conical shape that tapers from the upper casing portion downwardly and inwardly to a bottom outlet via which the collected dried coal leaves the cyclone, means for causing hot combustion gases from said furnace to flow through the system, a vertically disposed fines collector tube arranged within and concentric to said upper and lower portions of the cyclone separator and having an open lower end positionable to collect the aforesaid coal fines and dust from the lower interior of said tapered lower casing, means for adjusting said collector tubes lower end vertically inside of the surrounding cyclone separator casing into that position above the cyclones said bottom outlet where maximum pick up of fines and dust occurs, and means effective to withdraw from the said cyclone separator the coal fines and dust as picked up by said collector tube and to introduce them via said fines burner into said furnace where they are usefully burned with resultant production of the drying heat that is required to operate the system, said heat production from such burning of the coal fines and dust serving to permit shut off of said auxiliary start up fuel once a given level of coal drying operation has been attained by the system.

References Cited in the file of this patent UNITED STATES PATENTS 1,843,167 Lucke Feb. 2, 1932 FOREIGN PATENTS 627,759 Germany Sept. 15, 1933 729,086 Great Britain May 4, 1955 96,899 Sweden Sept. 19, 1939

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