US2788585A

US2788585A - Art of coal drying

Info

Publication number: US2788585A
Application number: US387742A
Authority: US
Inventors: Robert G Tucker
Original assignee: Combustion Engineering Inc
Current assignee: Combustion Engineering Inc
Priority date: 1953-10-22
Filing date: 1953-10-22
Publication date: 1957-04-16
Anticipated expiration: 1974-04-16

Description

2 Sheets-Sheet l Original Filed Nov 17, 1949 ATTORNEYS April 16, 1957 R. G. TUCKER 2,788,585

ART OF COAL DRYING original Filed Nov. 17, 1949 2 sheeis-sheei 2 INVENTOR @MJKM @n1/MPM ATTOR NEYS United States Patent O ART F COAL DRYING Robert G. Tucker, Chicago, Ill., assignor to Combustion Engineering, Inc., New York, N. Y., a corporation of Delaware Continuation of abandoned application Serial No.

127,897, November 17, 1949. This application 0ctober 22, 1953, Serial No. 387,742

This invention relates to comminuted coal drying and separating systems in which wet comminuted' coal is delivered into a stream of high velocity hot gases in which the coal particles are substantially instantaneously dried and the gases and coal particles carried thereby are delivered into a separator and collector, such as a cyclone, wherein the now moisture-laden gases are separated from the dried coal.

In such conventional systems, the wet comminuted coal is delivered laterally into the lower end of a tall upright drying column and the high velocity hot drying gas is delivered into the said end of the column closely adjacent to the point of coal admission. In consequence, the temperature of the drying gas is quickly reduced in the vicinity of the point of wet coal admission, with concomitant reduction in the volume and therefore of the velocity of the gas. In consequence, the pick-up of coal particles and the eiciency of the system are correspondingly lowered.` Particles of coal, not carried upwardly through the column, separate out by gravity and are removed, preferably periodically. For reasons above pointed out, the amount of coal so separating is unduly large because of the relative ineciency of the pickup.

The objective of the present invention is to render such systems more eicient by increasing the pick-up of coal particles by the incoming hot drying gases, thereby ensuring a maximum delivery of coal particles to the cyclone and diminishing the quantity of coal which separates out by gravity as aforesaid.

More specifically stated, the invention resides in providing the hot gas delivering parts with a high velocity pick-up section, so relatively constructed and arranged (a) as to be relatively unaffected by the sudden drop in temperature and therefore decrease in volume of the hot drying gases which occur at the region where the wet comminuted coal is delivered into the column, and (b) as to ensure adequate acceleration of upward movement of the heavier particles. In consequence, the coal particles have maximum momentum, ensuring greatly in creased pick-up and increased coal delivery to the cyclone. The parts are also arranged and constructed as to secure low pressure drop.

How the foregoing, together with such other objects and advantages as may hereinafter appear or are incident to the invention are realized, is illustrated in the accompanying drawings, wherein:

Fig. 1 is a diagrammatic side elevation of a drying system embodying my invention;

Fig. 2 is an enlarged cross sectional view illustrating certain details of the invention, and

Fig. 3 is a view somewhat corresponding to Fig. 2 but illustrating a modification of the invention.

Referring now to Fig. 1, the reference character A denotes a furnace for supplying hot drying gases, such, for example, as hot air; the reference character B denotes the drying tower or column; the reference character C, the cyclone separator; the reference character D, the

bin for comminuted coal; and the reference character E, the feeder for delivering the wet coal into inlet B 1ocated near the bottom of the column B.

The reference character F indicates a starting stack and the reference character G indicates, as a whole, a hot gas delivering and coal collecting chamber, for dclivering the hot gases to the open lower end of the column B and for collecting such particles of the coal as are not carried upwardly through the column by the hot gases and which fall out by gravity. The hot gases from furnace A are delivered to chamber G by means of the pipe or conduit 7.

The cyclone C has an outlet 8 for the moisture laden gases from which the coal has been separated in the separator, which outlet is provided with a fan 9 for drawing the gases through the system.

At the bottom the cyclone is provided with an outlet 1t? provided with a conventional air lock 11 below which there is a conveyor 12 for the dry coal. The wet coal is fed to the bin D by means of the conveyor 13.

Column B, chamber G, and conduit 7` are preferably circular in cross section.

Referring now to chamber G, this comprises a main portion 14- having a flanged inlet 15 adapted to be coupled to the conduit 7 in conventional manner.

At the upper end of the chamber G is a pick-up section 16 which has an internal diameter relatively substantially smaller than the internal diameter of the main portion 14 of the chamber. The pick-up section has a straight bore. The upper portion 17 of the main chamber 14 is tapered preferably at a 60 angle to merge with the pick-up reaction to reduce pressure drop. The lower end 18 of the main portion 14 is preferably tapered to a discharge opening 19.

The upper end of the pick-up section 16 registers with the lower open end of the column B and is secured thereto in any conventional manner.

The chamber G and the conduit 7 are desirably refractory lined so as to withstand the high temperatures of the hot gas discharging therethrough from the furnace A.

The internal diameter of the pick-up section 16 preferably approximates the internal diameter of the column B, and the internal diameter of the conduit 7 and the inlet 15 are preferably substantially the same as the internal diameter of the main portion 14 of the chamber G. In the embodiment illustrated, the internal diameter of the pick-up section 16 is 2 feet 8 inches, and the internal diameter of the outlet 19 of the chamber G is l foot. From these the proportions of the remaining parts of the particular installation can be readily ascertained.

It will Ibe observed that the vertical length of the piclcup section is substantial, roughly approximating the internal diameter of the pick-up section.

The operation is as follows:

The fan 9 has a capacity sufficient to draw the hot gases through the system at relatively high. veloci-ty. The gases leave the furnace A at relatively high temperature (of from about 1000D F. to about 1500 13.), and therefore in relatively greatly expanded condition. By reason of the relatively large size of the internal diameter of the conduit 7 and the chamber G, adequate volume of gases is provided for delivery therethrough with comparatively low pressure drop. The velocity of the gases is greatly increased in the pick-up `section because of its restricted size. In the particular installation shown, with coal particles (generally ranging downward from Vs" size), the velocity of the gases passing through the pick-up section is desirably in the neighborhood of 10,000 feet per minute. As pointed out, the pick-up section has substantial vertical length, that is to say, the bottom thereof is well below the bottom of the column B and Ihence well belowr` the feeder E.Ak whichv discharges the wet coal into the column.

By the introduction of the wet coal and the substantial instantaneous evaporation of moisture, the temperature of the gases at the point of wet fuel admission isquickly lowered, and in consequence Vthe volume of the gases is decreased and the velocity of the gases through the column is reduced, say to the neighborhood of 5500 feet per minute. However, because the pick-up section extends well ibelow the end of the column and therefore ybelow the point ol coal admission, there is a zone in whichv the high veloci-ty stream of gases is formed and well established before coal is delivered thereto, and the gases passing through the pick-up section are not appreci'a'bly cooled' and maintain their velocity. yto heavy particles of coal laterally introduced into the column, these, of course, accelerate slowly and normally tend to drop by gravity. Because of the depth of the pick-up section, it is ensured that any such heavy particles as tend to drop through the pick-up section have their downward movement arrested and have an upward movement imparted thereto sufliciently accelerated to give the impetus necessary to carry them through the system. Thus, the pick-up section is very effective and a maximum amount of coal is picked up and carried upwardly through the drying column to the cyclone separator.

The system will effectively handle comminuted coal in particle sizes ranging from about down to 'the lowest mesh coal produced.

The heavy particles which are not carried through the system are discharged through outlet 19 by means of a conventional double valve 2i) which permits ,the discharge thereof without introducing air into the -systemM A damper 21 may be provided for introducing tempering air into conduit 7. The bin D is provided with a conventional gate 22.

Referring now to the modification shown in Fig. 3, the chamber G has no tapered upper section bu-t has a straight bore. The pick-up section 16 in this instance is separate and consists of a tube llaring somewhat at the its bottom. Surrounding the lower end of the pick-up section 16 is an annular sealing device 23 carried by the top closure member 2.4 for the chamber G. The pick-up section 16 is free to slide with respect to the seal 23 and therefore can expand and contract. The pick-up section lo has a flanged coupling 25 which is complementary to the flanged coupling 26 at the lower end of theV inlet B for detachable connection, as lby nuts and bolts not shown. The length `of the pick-up section 16 may be adjusted by undoing the couplings and inserting a filler member therebetween.

The additional advantages of the modification are that standard kiln tile may be used as a liningv for the chamlber G; no difiiculties are encountered from expansionand contraction; and the pick-up section may be adjusted in length to aiford greater flexibility with respect to the kind of coai which may be handled.

This application is a continuation of Serial No. 127,897, filed NovemberV 17, 19,49, now abandoned.

I claim:

A method of flash drying coal to improve pickup eciency comprising the steps: forming a vertically rising stream yof hot gas moving at a predetermined velocity; increasing the velocity of the gas stream and substantially maintaining the velocity over a predetermined vertical distance; and feeding Wet coal into saidstrearn above the point where the velocity is initially increased, the point of said feeding 'being such that the high velocity gas stream operates to dry substantially all of any coal falling downwardly therethrough sufiicientlybefore the coal reaches the point where the velocity is initially increased so that the force yof the gas on the dried coal is ,sufficient to reverse its direction and move the same upwardly.

References Cited in the le of this patent UNITED STATES PATENTS .1,550,992 Trump Aug. 25, 1925 2,296,159 Gordon sept. 15, 1942 2,538,833 De Rycke 1an. 23, 1951