US2587609A - Impact pulverizing apparatus having fluid jets firing toward a common point - Google Patents

Description

March 4, 1952 A. J. FISHER IMPACT PULVERIZING APPARATUS HAVING FLUID JETS FIRING TOWARD A COMMON POINT Filed Jun 5, 1947 2 SHEETSSHEET 1 March 4, 1952 FlsHER 2,587,609

IMPACT PULVERIZING APPARATUS HAVING FLUID JETS FIRING TOWARD A COMMQN POINT Filed June 5, 1947 2 SHEETSSHEET 2 Ilxl IiIII INVE NTOR fins re w Elsie/- Patented Mar. 4, 1952 IMPACT PU LVERIZING APPARATUS HAT ING FLUID JETS FIRING TOWARD A COMMON POINT Andrew J. Fisher, Sparrows Poin L Md.

Application June 5, 1947, Serial No. 752,694

4 Claims. (o1. 241 39) This invention relates to the grinding of material such as coal or the like to reduce it from lumps of intermediate size to a relatively fine state of subdivision for conveyance by a'fluid stream and, in particular, to an improved fluidjet impact pulverizin apparatus and method.

Fluid-jet impact grinders have been used for producing powdered soft or bituminous coal for combustion and less effectively for grinding hard or anthracite coal and coke breeze. It is the object of my invention, therefore, to provide a fluid-jet impact grinder having increased eificiency for pulverizing bituminou coal, and capable of efficiently pulverizing anthracite coal and coke breeze into particles having substantially the same range and distribution of size as those characteristic of bituminous coal when ground by fluid-jet impact apparatus. A further object is to provide an improved apparatus and method for pulverizing coal and the likewhereby greater economy in the use of the motive fluid is obtained.

In a preferred embodiment and practice of my invention, I provide a receptacle or tank having opposed ejectors located in the lower portion firing substantially horizontally and defining therebetween a grinding zone and a classifier in the upper portion. The classifier has an outlet;- for floating particles and includes a collector forreturning over-size particles to the grinding zone. Fresh material to be ground, i. e., coal of intermediate size, is fed into the collector through a duct which is maintained substantially full to. limit the induction of air along with coal. A

downwardly-firing injector in the bottom of the collector forcibly discharges the returned oversize particles and the fresh material into the grinding zone and also serves to cause re-circula-' tion through the classifier of a portion of the steam in the container. The downwardly-firinginjector further agitates a layer of partly ground material accumulating on the floor of the container to facilitate its injection into the grinding zone and maintains acrater in said layer by the scouring action of the particles discharged from the collector downwardly into and through the grinding zone. I also provide a novel form of ejector particularly adapted for delivering a jet of fluid entraining solid particles.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawings illustrating the preferred embodiment. In the drawings,

Figure 1 is a central verticalsection through the apparatus;

Figure 2 is a sectional view showing the down wardly-firing injector to enlarged scale; Figure 3 is a similar section through one of the horizontally-firing ejectors;

Figure 4 is a bottom plan view of an assembly of guide vanes at the inlet to the classifier;

Figure 5 is a partial radial section through said assembly;

Figure 6 is a perspective view of one of the vanes; and

Figure 7 is a view similar to Figure 1 showing a modified construction.

Referring in detail to the drawings, the apparatus of my invention comprises a container or tank It), conveniently a right circular cylinder fabricated from metal plate including a bottom II, a lateral wall l2 and a removable cover l3. A plurality of fluid-jet ejectors M are mounted substantially horizontally on the lateral wall ad-' j acent the bottom in opposed relation, there being,

four such ejectors uniformly spaced about the vertical axi of the tank. Each ejector includes a mounting plate l5 removably secured to a ring l6 positioned over a circular opening in the wall The details of the ejectors I4 are shown in Figure 3. As there illustrated, each ejector comprises a tubular body l8 having slots [9 opening thereinto.- A bushing-20 threaded into one end of the body I8 is provided with a nozzle 2! extending centrally through the body. A stuffingbox 20a seals the clearance between the bushing,

and injector body. A pipe 22 connected to the bushing extends to a suitable source of motive v fluid, such as superheated steam. j j A barrel 23 is seated in the forward end of the body 18. The barrel has a central bore therethrough which flares outwardly at the rear endas indicated at 24. The barrel has a removable.

liner sleeve 25 held in place by a spud 26 threaded on the outer end. The spud has an insert ring 21 bearing on the end of the sleeve.

The'nozzle 2! has a converging tip 28 at the forward end thereof with a central bore there through which has a constriction 29 therein adjacent the extreme end. The tip 28, asshow'n,

extends-into the outwardly flaring portion 24 ofthe bore through the barrel but is spaced from" the latter at all points. The sleeve 25, insert ring 27 and tip 28 are preferably composed ofa metalhaving good abrasion-resistant qualities.

The ejector 14 operates on well-known principles. That is to say, when a compressed fluid such as superheated steam is discharged fromthe nozzleZl, the gases surrounding the body l8 opposed jets of fiuid with solid particles entrained therein impinge on each other in a grinding zone around the axis of the tank and the impact of the solid particles on each other shatters them and increases the degree of subdivision thereof.

I have discovered that, for best results, the

nominal sectional area of thenozzle 2i, i. e., the sectional area of the constriction 29., should bear a predetermined ratio to the sectional area of the bore through the sleeve 25. Specifically,

the ratio should be 1:20 or greater. In a specific example, the constriction 29 had a diameter of %4" and the barrel an inside diameter of 1", giving a ratio of the sectional areas of 1:18. The length of the barrel 23 should be more than five times the diameter of the bore and preferably about ten times such diameter.

A classifier is disposed in the upper portion of the tank it coaxially therewith. It includes a. collector 3| in the form of an inverted conical frustum supported by web plates 32 spaced cir- 5 cumferentially of the tank and a ring 33 welded thereto. Tangential guide vanes 34 are spaced circumferentially about the upper end of the collector 3!, bein supported by a ring 35 having inner and outer flanges 35a and 36b welded there- 3 to, the ring '35 being welded to the cover l3. The vanes 34, as shown in Figure 6, have the shape of an air-foil, the leading and trailing edges being slotted as at 3'! and 38 to provide a T-head '39.

The ring 35 has a slot accommodating the 35 T-heads of the vanes 34. Bolts 40 positioned intermediate adjacent vanes 34 extend between the inner and outer flanges 35a and 35b and have washers 4i thereon which space the leading edge of one vane from the trailing edge of the ad- 40 jacent vane. The upper ends of the leading and trailing edges of the vanes engage shoulders 350 on the flanges 36a and 36b and are thereby held in the desired angular position as shownin Figure 5, the washers 4| serving to space the vanes apart circumferentially. The vanes 34 and bolts 40 are assembled between the flanges 35a and 36b before the latter are welded to the ring 35.

A bafile ring 42 extends around the upper end of the collector 3|, being welded thereto. The

axial height of the ring is such that it extends slightly above the lower ends of the vanes 34.

The cover 13 has a central turret 43 provided with a removable cover 44. An outlet pipe 45 extends downwardly through the cover 44 into the classifier coaxially thereof. As shown, the lower end of the pipe 45 extends below the top of the collector 3 i. An offtake 46 extends laterally from the pipe 45. A duct 4? connected to the ofitake conveys to a point of use the coal which has been 50 reduced to a state of subdivision sufiiciently fine that it floats in the on-going steam.

It will be apparent that the steam forming the jets from the ejectors expands in the grinding zone adjacent the axis of the tank and ascends toward the top of the tank carrying with it a portion of the entrained solids. The mixture passes over the upper edge of the bafile ring 42 and enters the classifier between the vanes 34. The

angular position of the latter imparts a tangential component of velocity and causes the mixture of steam and solids to traverse a helical path. Some separation of the larger particles from the smaller ones is effected as the mixture passes around the The larger particles upper edge of the ring 42.

entering the classifier tend to fall downwardly through the collector, being thrown outwardly therein by centrifugal force resulting from their tangential velocity component. The finest particles float in the steam passing upwardly through the outlet pipe 45. The larger particles thrown outwardly in the collector 3! slide down the inner surface thereof and are thus guided back to the grinding zone.

A downwardly-firing injector 48 generally similar to the ejectors I4 is suspended in the lower end of the collector 3| coaxially therewith. This injector has .a steam pipe 49 extending vertically up through the outlet pipe 45. The injector 48 may be adjusted vertically in the collector by means of nuts '50 turned on the threaded upper end of the pipe 49 and engaging a supporting yoke 5!. The yoke 5| is mounted on studs 52 extending upwardly from a cover plate 53 on the outlet pipe 45. A sleeve 54 extending upwardly from the body of the injector surrounds the pipe 49 for the greater portion of its length. The injector 48 is generally similar to the ejectors 14, the principal difference being that the barrel 23' thereof is somewhat longer than the barrel of the ejectors l4, and the bore is somewhat greater.

The injector 48 forcibly returns over-size particles falling downwardlythrough the collector 31 to the grinding zone between the ejectors 14. The solid particles delivered by the injector '48, after impinging on those delivered by the ejectors l4, exert a scouring action on solid particles accumulating on the bottom ll of the tank 10. A layer of such particles builds up somewhat as indicated by the chainline 55. The injector 48 causes the formation of a crater 56 centrally thereof and serves to agitate at least the solid particles on the surface of the accumulated layer, thus stirring them up for induction through the ejectors l4. The injector 48 also produces a recirculation of the steam in the space between the walls of the collector and tank, positively inducing an upward flow thereof with particles entrained thereby into the classifier.

A duct 51 extends radially through the wallsof the tank 10 and classifier 3|. The duct is secured in position by a flange 58 welded thereto which is removably attached to the tank wall. A helical-flight conveyor 59 is journaled in the duct and is adapted to be driven by any convenient source of power. An inlet 60 extending upwardly from the outer end of the duct and communicating therewith is connected to the discharge end of a coal hopper 6 I. An agitator disc 60a is mounted on a shaft journaled in the inlet 69 and has projections spaced circumferentially thereof adapted to be engaged by the flight of the conveyor. The disc is thus rotated by operation of the'conveyor and keeps the coal in the inlet 60 stirred up so that it will fiow readily into the duct. The fresh material to be ground is thus introduced first into the collector 31 and then forcibly delivered to the grinding zone by the injector 48 in the same manner as the over-size particles which sink from the steam flowing out of the classifier through pipe 45. The entering material is preferably maintained inthe hopper 6! at a level considerably above the top of the tank Hi. The inlet 60 and duct 51 are thus kept substantiallyfilled with material which acts as a seal between the pulverizer and the atmosphere. The conveyor 59, of course, should be driven at a speed appropriate to the rate at which material is ground fine enough for delivery to the point of consumption. As previously explained, a certain quantity of material'accumulates in the bottom of tank [0. The operation of the apparatus has been explained generally during the above description of its construction but will be briefly traced again. Coal is delivered to the hopper (it after being ground mechanically to an intermediate size such as lumps not exceeding in diameterwand is fed by the conveyor 59 through the duct 57 and discharged into the collector 3| at a predetermined rate. The entering material is drawn downwardly along with the over-size particles rejected by the classifier and discharged from the injector 48 into the grinding zone between the ejectors I l. The coal is thus broken up to a greater or less degree. Some of the larger particles may fall onto the accumulated layer 55. The finer particles float in the steam ascending from the grinding zone around the outside of the collector 3i. 1 The material in the layer 55 is agitated by the downwardly-firing injector 48 and the larger particles, being thus stirred up, are drawn into the inlet slots of the ejectors M and thereby subjected to impact and breakage in the grinding zone.

The ascending steam carrying the fine particles enters the classifier through the spaces between the vanes 34 and receives a tangential velocity component which throws the larger particles toward the outside where they strike the collector and are guided thereby downwardly into the injector 4B. The steam emerging through the outlet pipe 45 carries with it all the particles of sufficient fineness to float in the steam. The amount of steam delivered to the several ejectors should, of course, be correlated with the rate at which fresh coal is delivered through the duct 51 and the character of the coal, i. e., Whether anthracite, bituminous or coke breeze.

A modified form of apparatus is shown in Figure 7 generally similar to that of Figures 1 through 6 with the addition of a baflie ring 62 and a bowlshaped bafile 53. The ring 52 is spaced below the ring 33 and outwardly from the collector. The two rings define a circuitous path for the ascending gases and entrained solid particles, effecting a preliminary rejection of the larger particles. The baffle 63 also improves the selectivity of the classifier by preventing over-size particles from being carried up through the outlet pipe 45 with the escaping steam. V

The baiile is suspended below the bottom of the outlet on hanger bars 6 3. These bars are welded to the bafile and extend upwardly through the cover plate 44. The bars may be adjusted vertically by nuts turned on the threaded upper ends thereof. The bafile 63 has a, central opening and a fiange 65 depending therefrom. A disc 85 is secured to the sleeve 54 just below the top of the flange 65 and has a diameter slightly smaller than that of the flange. The baffle 63, flange 55 and disc 66 make it practically impossible for any over-size particles to be drawn upwardly through the outlet pipe.

The invention described above is characterized by numerous advantages over impact grindin apparatus known heretofore. In the first place, the invention is capable of grinding anthracite coal and coke breeze as well as bituminous coal. .The percentages of different sizes of particles are substantially the same in the case of any one kind of material, for various feeding rates from a minimum up to a maximum two and a half or three times as great as the minimum. For a given feeding rate, furthermore, the percentage distribution of the various sizes of particles is very closely parallel for the different kinds of material. The apparatus is characterized by high efiiciency, the steam consumption per pound of material pulverized decreasing with an increase in the rate of feeding material up to the maximum rate for which the apparatus was tested. At normal rates of -feed, the consumption of steam varied from about .6 lb. of steam per pound of bituminous coal' to .7 lb. of steam per pound of anthracite coal.

In addition to the foregoing, the apparatus is relatively simple and inexpensive. It requires but little attention in operation and practically no maintenance since the moving parts are few and the parts subject to abrasion by impingence of the 7 solid particles may be made from metal having high abrasion resistance. By arranging the feed duct so it delivers into the collector of the classifier, the entering material is immediately discharged into the grinding zone for rapid fragmentation. The downwardly-firing injector in the bottom of the classifier collector positively pulls the over-size particles downwardly along with the freshly-fed material. It also causes recirculation of the steam upwardly along the lateral wall of the tank and into the classifier. The nozzle and barrel of the ejectors are designed to produce ample suction to pull the solid particles into and through the latter from which they are discharged in a high-velocity jet.

Although I have illustrated and described but a preferred embodiment and practice of the invention, it will be recognized that changes in the details of the construction disclosed may be made without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. In combination, a pulverizer for impact grinding comprising a tank, a plurality of generally horizontal fluid-jet ejectors disposed adjacent the bottom of the tank, spaced about a common vertical axis and directed toward a common point to define a grinding zone therebetween, a classifier in the tank above said zone including a collector for funneling oversize particles to said zone, an outlet extending upwardly from the classifier, means for introducing fresh material to be ground into the body of the classifier and means for forcibly discharging material from the classifier into said zone generally toward said common point, said last-mentioned means including a fluid jet ejector.

2. In a fluid-jet impact pulverizer, in combination, a chamber having a grinding zone therein, a phu'ality of grinding injectors in substantially planar arrangement in said grinding zone substantially focused upon a common point, an outlet in said chamber for the escape of ground material, and a further injector in said chamber directed to said common point at an angle to the plane of said first-mentioned injectors, said further injector being adapted to feed material to be ground into said chamber.

3. In a fluid-jet impact pulverizer, in combination, a chamber having a grinding zone in the lower portion thereof, a plurality of grinding injectors in substantially horizontal planar arrangement in said grinding zone substantially focused upon a common point, an outlet in the upper portion of said chamber for the escape of ground material, and a substantially vertical injector in said chamber focused upon said common point, said further injector being adapted to feed material to be ground into said chamber.

4. In a fluid-jet impact pulverizer, in combination, a chamber having a grinding zone in the lower portion thereof, a plurality of generally horizontal grinding injectors in said grinding zone substantially focused upon a common point, a classifier in said chamber above said grinding zone, an outlet extending upwardly from said classifier for the escape of ground material, means for introducing material to be ground into said classifier, and a generally vertical injector substantially within said classifier focused upon said common point and adapted to forcibly discharge material from said classifier into said grinding zone.

ANDREW J. FISHER.

REFERENCES CITED UNITED STATES PATENTS Name Date Babcock "a- May 16, 1911 Number Number Number Name Date Luckenbach Apr. 8, 1913 MeKelvey Dec. 23, 1919 Newburger May 26, 1925 Murray et a1 J an. 11, 1927 Lykken Feb. 3, 1931 Lykken Dec. 29, 1931 Andrews et al Nov. 14, 1933 Andrews et al Feb. 27, 1934 Andrews Mar. 3, 1936 Sweeney Feb. 9., 1943 Hammond Sept. 25, 1945 Thomas Oct. 11, 1949 Andrews Nov. 8, 1949 FOREIGN PATENTS Country Date Germany Jan. 24,1931 Great Britain July 19, 1937

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