US1893857A

US1893857A - Pulverized fuel feeder

Info

Publication number: US1893857A
Application number: US503169A
Authority: US
Inventors: Charles M Buck
Original assignee: Individual
Current assignee: Individual
Priority date: 1930-12-18
Filing date: 1930-12-18
Publication date: 1933-01-10
Anticipated expiration: 1950-01-10

Description

Jan. W, 1933. c. M. BUCK PULVERIZED FUEL FEEDER Filed Dad. 18, 1930 ATTORNEY- tion of a modification of the invention, and

Patented Jan. 10, 1933 UNITED STATES CHARLES; H. BUCK, OF BROOKLYN, NEW YORK PULVERIZED FUEL FEEDER Application filed December 18, 1930. Serial No. 503,169.

This invention relates to devices for feeding pulverized material such as coal, and it is especially useful in feeding a mixture of.

air and coal to a burner.

One of the primary objects of the invention is to make it possible to feed the pulapproximately the same velocity throughout the stream.

When feeding a mixture of coal and air to a burner, the rate of feed must, of course, be varied according to the rate at which it is desired to fire the furnace. It will be apparent that there will be a wide variation in conditions between minimum and maximum rates of operation. It is one of the primary objects of the invention to secure uniformity and evenness of mixture and stream flow for all rates of firing. 1 w A More particularly it is an object to secure the above advantages in connection with a relatively low pressure feeder.

l accomplish the foregoing,'together with such other objects and. advantages as may hereinafter appear, or are incident to the invention, by means of a construction which I have illustrated in the preferred form in the accompanying drawing, wherein Fig. l is an end elevation of my improvedfeeder with portions thereof broken away to more clearly show details of the construction; Fig. 2 is a vertical section through Fig. 1. Fig. 3 is a partial side elevation and sec- Fig. 4 illustrates a detail of the modification of Fig. 3.

Referring now to the drawing the reference numeral 7 indicates a hopper or bin for the pulverized coal or similar material. This hopper has a discharge throat 8 which has a long but narrow discharge orifice 9 through which a Wide thin stream of coalis delivered. In the throat immediately above the discharge orifice 9 is an agitating roll" 10 provided with toothed projections which serve to stir up the coal in the throat. In order to prevent packing and resultant arching of the coal in the hopper I provide the

screens

11 and 12, each of which supports a portion of the Weight of the coal in the hopper whereby the total head of coal in the hopper is not effective to produce packing. These screens are described, illustrated andclaimed in my copending application Serial No. 495,006, filed November 12th, 1930, for pulverized fuel feeder. In addition, I provide an aerating device 13, also shown in said application, and which is in the form of a pipe or pipes which communicate at their lower ends with the interior or bottom portion 14 resting upon the screen 11, and which communicate at their upper ends with the interior of the hopper at a point above the normal level of the coal. As coal is fed a quantity of air is drawn downwardly into the region of the upper end of the throat which serves to aerate the coal and thus assist in preventing packing and arching. Immediately below the dis- 7 charge orifice is a fan casing or housing 15 which has an opening 16 directly below and in line with the discharge orifice 9, such opening being of the same width as the discharge orifice. The fan casing or housing is somewhat like a volute and the fan 17 is mounted in the casing so that its periphery is closely adjacentthe portion of the housing indicated at 18. The air inlet to the housing is indicated at '19 and the outlet 20 from the housing is in the form of a fiat wide conduit, the width of which corresponds approximately to the length of the slot, as does the length of the fan.

The fan and the roll 10 are rotated by any preferred means such as 1 the gearing diagrammatically indicated at 21.

The operation of the device is as follows: When the fan is rotated centrifugal force tends to throw the air between the blades outwardly and since the wall 15 of the fan casing progressively approaches the periphery of the fan so that it is fairly close to the periphery thereof at the point indicated at 22 and quite closeto the part 18, a current of air is set up in the conduit 20 for the full width thereof, this current being uniform across the entire section of the conduit. The current is discharged into the conduit with substantial velocity, practically that of the 199 velocity of the blade tips, because of the volute. In consequence of this there is a tendency to create a vacuum in the housing above the fan, particularly in the neighborhood of the inlet 19, so that a current of air is drawn through the inlet into the housing. This current flows across the discharge orifice and the coal drops thereinto, in part by gravity and in part by the suction of the current. The compartments between the blades of the fan are comparatively empty in the re gion opposite the wall 18, but as they travel upwardly from that region, air admitted from the inlet 19 enters, as well as some of the coal, but is shortly thereafter discharged, producing eddies in the volute, which, in turn, secure intimate admixture of the coal and air in the volute. Since the volute decreases in cross section this intimate and uniform admixture of the coal and air is maintained to the point of discharge into the conduit 20. Thus the fan delivers a stream across the full width of the conduit in which there is a uniform admixture of coal and air throughout, with all portions of the stream moving substantially uniformly, except immediately adjacent the inner faces of the conduit where eddying again occurs because of frictional contact. It will be apparent that the continuing discharge of the contents of the compartments between the blades will maintain the coal in suspension in the volute. Also that uniformity of feed through the discharge orifice and along its full length are also obtained. The uniformity of the flow of the current across the orifice and the instrumentalities which prevent the packing and secure aerating of the coal in the hopper cooperate toward this result.

The device will operate with relatively low pressure and still secure the desired results. If a blower fan of the axial inlet type were provided, it would not be possible to obtain the uniformity desired except with a relatively narrow conduit andthe fan would have to operate at higher pressures. I am enabled by the arrangement described to deliver a stream of great breadth, for the full width of the furnace if desired.

It might here be noted that certain features of'the fan or blower arrangement herein disclosed are not a part of the present invention per se but are described and claimed in my copending application Serial No. 646,882 filed December 12, 1932.

In the modification shown in Figs. 3 and 4 I provide a rotating heater or agitator 23 immediately below the discharge orifice to aid in maintaining admixture. This agitator may be rotated in any preferred manner as, for example, by the gearing 23a shown in Figure 4. As illustrated in this figure, furthermore, the beater 23 includes a plurality of heater or agitator rods 23?) extended lengthwise for the full length of the fuel discharge orifice. In the arrangement of Fig. 2 some air may be admitted, preferably through the openings. 24 controlled by a disk shutter or the like.

' In'the preferred practice of my invention I thermolize crushed coal by heating it, preferably in inert gases, from a temperature substantially above about 220 F. to approximately 450 F. The coal is subjected to this heat treatment until the particles are brought to this temperature throughout. This drives ofi the lighter volatiles, satisfies the chemical affinities which produce autogenous combustion and renders the coal non-explosive. This temperature, however, is insufficient to produce thermal decomposition. The thermolized coal is then pulverized.

With the coal in this condition I am enabled to deliver it to the combustion chamber with substantially all the air required for combustion, at low pressure and at low velocity, by means of an apparatus such as shown and described.

lVith ordinary raw pulverized coal it has been found commercially impractical to deliver the coal admixed with all of the air required for combustion, for the reason that coal in such condition must be introduced by a high pressure blast involving the use of a high pressure fan. It is expensive to produce such high pressure air. Thermolized coal, either because of low rate of flame propagation, or for some other reason, can be introduced in a state of admixture with practically all the air required for combustion and at velocity so low as to permit of the use of a low pressure fan-such as described. This makes a very economical process for burning coal, besides having other advantages.-

The treated coal and process of treating the same, per se, herein referred to, are part of the subject matter of my copending application Serial No. 265,303, filed March 28th, 1928.

The method of burning pulverized coal herein referred to is described and claimed in my copending application Serial No. 629,063, filed August 16th, 1932.

I claim 1. In a pulverized coal feeder, a substantially volute-like fan casin terminating in an inlet opening at its larger end, a fan in said casing including a ring of fan blades mounted for rotation in a path extended from the large end of the volute to the small end thereof, a discharge passage extended from the smaller end of the volute casing, I

and means for feeding powdered coal into the casing at a point adjacent its inlet end.

2. A pulverized coal feeder including a rotary fan, a generally volute-like fan casing wall substantially surrounding the fan "with one portion thereof disposed closely adjacent to the path of movement of the fan from which point the wall progressively diverges, a relatively large area air inlet in said Wall in the re 'on thereof spaced the maximum distance rom the path of movement of the fan, a discharge opening in said wall in its region of. minimum spacing from the path of movement of the fan, said discharge opening being of relatively small cross sectional area as compared to the inlet opening, and

means for feeding pulverized coal into the fan casing at a point in the region'of the air inlet opening.

3. A. ulverizedcoal feeder including a rotary an, a generally volute-like fan casing wall substantially surrounding the fan i with one portion thereof disposed closely adv jacent to the path of movement of the fan 7 from which point the wall progressively diverges, a relatively large area air inlet in said wall in the region thereof spaced the maximum distance from the path of movement of the fan, a discharge opening in said wall in its region of minimum spacing from the path of movement of the fan, said discharge opening being of relatively small cross sectional area as compared to the inlet opening, and means for feeding pulverized coal into the fan casing at a point in the region of the air inlet opening, there being a casing part of relatively small. dimension circumferentially of the fan disposed closely adj acent to the ath of movement of the fan and interposed; etween the inlet and the discharge openings.

4. A pulverized coal feeder including a rotary fan, a generally volute-like fan casing wall substantially surrounding the fan with one portion thereof disposed closely adjacent to the path of movement of the fan from which point the wall progressively diverges, a relatively large area air inlet in said wall in the region thereof spaced the maximum distance from the path of movement of the fan, a discharge opening in said wall in its region of minimum spacing from the path of movement of the fan, said discharge opening being of relatively small cross sectional area as compared to the inlet opening, and means for feeding pulverized coal into the fan.casing at a point in the region of the air inlet opening, there being a casing part of relatively small'dimension circumferentially of the. fan interposed between the inlet and the discharge openings and disposed closer to the path of movement of the fan than the casing wall at the opposite side of said discharge opening.

5. In pulverized coal feeding apparatus,

a fan including a ring of generally radially disposed fan blades, a fan casing wall spaced avconsiderable distance from the periphery of the fan atone point and rogressively approaching the periphery of the fan, means for feeding pulverized coal into the casing adjacent said point, a peripheral air inlet opening in said casing adjacent said point, a peripheral discharge opening in said casing in a region in which the casing wall is relatively close to the periphery of the fan, and a casing part between said openings disposed closely adjacent to the fan periphery, the area of said discharge opening and the area and disposition of said casing part being so relatively arranged and proportioned that upon discharge of the coal and air from the fan under the influence of centrifugal force, the resultant reduced pressure between the fan blades is maintained until the blades have passed said closely spaced casing part, whereby a negative pressure is produced in the region of the air inlet.

6. A pulverized coal feeder including a fan having a ring of blades mounted for movement in a generally circular path, a generally volute-like casing wall surrounding the periphery of the fan and closely spaced with respect thereto at one side of the fan ascompared \to another side thereof, a discharge conduit extended from the fan casing generally tangentially from a point in the region where the casing wall is relatively close to the periphery of the fan, an air inlet passage extended generally tangentially of the fan in a region in which the casing wall is relatively widely spaced from the fan periphery, and means for feeding pulverized coal to the fan through the casing wall at a point intermediate the air inlet and the said discharge conduit.

7. A pulverized coal feeder including a fan having a ring of blades mounted for rotation in a circular path, a generally volutelike casing for the fan with its wall spaced a substantial distance from the periphery of the fan in one portion thereof as compared to another portionthereof, means for introducing pulverized coal through the casing wall to the fan in a region in which the said wall is relatively widely spaced from the periphery of the fan, a peripheral air inlet passage to said fan extended into the casing toward the coal inlet, the casing being substantially unobstructed between the air inlet and the point of coal; admission, and a peripheral discharge opening'in said casing in the region in which the casing wall is relatively closely spaced with respect to the periphery of the fan.

8. A pulverized coal feeder including a rotary fan having a ring of fanblades mounted for movement in a generally circular path, the blades being considerably elongated axially of the fan, a generally volute-like fan casing wall substantially surrounding the fan with one portion thereof disposed closely adjacent to the path of movement of the fan from which point the wall progressively diverges, a peripheral air inlet to said fan formed through the casing wall in a region thereof which is spaced a relatively great distance from the path of movement of the fan, the length of the inlet opening being substantially equal to the axial length of the fan, a peripheral discharge opening formed in the casing wall in a region in which it is positioned relatively close to the path of movement of the fan, the length of the discharge opening also being substantially equal to t e length of the fan, and means for feeding a relatively thin but wide sheet of pulverized coal into the fan casing at a point in the neighborhood of the air inlet, the length of the sheet also being substantially equal to the length of the fan.

9. A pulverized coal feeder including a rotary fan having a ring of fan blades mounted for movement in a generally circular path, the blades being considerably elongated axially of the fan, a generally volute-like fan casing wall substantially surrounding the fan with one portion thereof disposed closely adjacent to the path of movement of the fan from which point the Wall progressively diverges, a peripheral air inlet to said fan formed through the casing wall in a region thereof which is spaced a relatively great distance from the path of movement of the fan, the length of the inlet opening being substantially equal to the axial length of the fan, a peripheral discharge opening formed in the casing wall in a region in which it is positioned relatively close to the path of movement of the fan, the length of the discharge opening also being substantially equal to the length of the fan, the air inlet and the discharge openings in said casing being arranged close to each other toward one side of the fan, there being a fan casing wall part interposed between the air inlet and the discharge openings of relatively small circumferential dimension disposed inclose proximity to the path of movement of the fan blades, and means for feeding a relatively thin but wide sheet of pulverized coal into the fan casing at a point in the neighborhood of the air inlet, the length of the sheet also lpeing substantially equal to the length of the In testimony whereof I have hereunto signed my name.

CHARLES M. BUCK.