US2550390A - Method for treating fuel - Google Patents

Description

April 24,l 1951 `N. N. STEPHANQFF 2,550,390 METHOD FOR TREATING FUELi i Filed Aug. 25, .1944 3 Sheets-Sheet 1 N. N. STEPHANOFF METHOD FOR TREATING FUEL April 24, 1951 Fiied Aug. 25, 1944 3 Sheets-Sheet 2 m r M V W /Vz ao /s yep/m72 of BV /f Filed Aug. 25, 1944 PI 24, 1951 N. N. sTEPHANoFF I 2,550,390

METHOD F'OR TREATING `FUEL.

3 Sheets-Sheet 3 Patented Apr. 24, 1951 METHOD Fon TREATING FUEL Nicholas N. Stephanoff, Philadelphia, Pa., as-

signor, by mesne assignments, to C. H. Wheeler Manufacturing Company,

Pennsylvania a corporation of Application August 25, 1944, Serial No. 551,239

4 Claims. l

This invention relates to a method and apparatus for treating solid fuels and then burning the same, the invention relating primarily to the grinding or disintegration of solid fuels to a very fine dust, which dust, preferably without deposition from a suspension in elastic fluid in which it is ground, is fed to the point of combustion.

The broad object of the invention is to effect the fine grinding or disintegration just mentioned under proper conditions for delivery of the product to a burner.

Another object of the invention is the provision of a suitable burner arrangement for effecting complete combustion of such ne fuel.

These, and other objects of the invention, particularly relating to details of method and apparatus, will be apparent from the following description read in conjunction with the accompanying drawings, in which:

Figure 1 is a diagrammatic elevation partly in section showing a complete unit for the pulverizing andburning of fuel;

Figure 2 is an enlarged axial section showing details of the burner of Figure 1;

Figure 3 is a similar View of a modified form of burner;

Figure 4 is an end view of the burner of Figure 3, looking toward the delivery end thereof;

Figure 5 is a vertical section taken through an alternative form of apparatus for effecting the grinding and explosive disintegration of a solid fuel;

Figure 6 is a horizontal section through the same taken on the plane, the trace of which is indicated at 6 6 in Figure 5; and

Figure 7 is an enlarged fragmentary view on the same plane showing the construction of a nozzle.

'I'he invention is applicable to carbonaceous fuels of a great variety of types as, for example, anthracite and bituminous coals, anthracite and bituminous culm, river coal, lignite, brown coals,

peat, wood, bagasse, wood chips, tan bark, cokes of various types, or the like. It is further applicable to materials which are hard when cold but which soften when heated such as pitches, bitumens, and asphalts which in the cold state i may be treated as hereafter described. In special processing even materials of oxidizable nature not generally classified as fuels may be treated and for present purposes may be regarded as fuels. For example if the major end of a grinding and oxidizing step is to provide a metallic oxide inA fine state, the metal may be groundA lll toa fine state of subdivision and then oxidized (burnt) in a combustion chamber in order to make use of the generated heat. However, inasmuch as these materials are all handled similarly and the fuel of primary interest is coal, to simplify the following discussion, coal will be generally referred to with the understanding that the remarks are applicable to the other materials as well. In some specific particulars, as pointed out hereafter, certain of these substances may handle differently.

Referring first to Figure 1, there is illustrated at 2 a boiler in which the pulverized fuel is to be burned. This is, however, merely by way of illustration since the burning may be accomplished for a large variety of purposes, for eX- ample for the heating of stills or other chemical apparatus or even for the production of combustion gases for the operation of turbines or other engines. The invention is also adapted for the preparation of fuel for use in Diesel or other internal combustion engines.

A motor 4 is illustrated as driving both a blower 6 to provide a supply of combustion air and a crusher I0 adapted to reduce the fuel which may be contained, in lumps or large pieces, in the hopper 8 to a size suitable for introduction through the feed passage I2 into a grinding mill I4. The pieces so introduced need not be ne and, in fact, the mill is well adapted for the grinding of particles of fuel or sizes of the order of pea coal or stove coal.

The mill I4 is illustrated conventionally and may be of the type described in my Patents Nos. 2,237,091, dated April 1, 1941, or 2,325,080, dated July 27, 1943. As illustrated in these patents and, in particular, the latter which represents an improved form of this type of mill, the mill comprises an endless tube having a lower turn in which grinding is effected by the action of high velocity elastic fluid jets introduced through nozzles I6. The remaining portion of the mill serves for the purpose of recirculating large particles for further grinding, these being retained in the mill by centrifugal action, wherey as very fine ground particles are carried out from the boiler, as the elastic fluid, to effect the grinding. In other cases, however, steam from a separate source may be used, or, alternatively, air or even combustible gases under high pressure may be used for effecting the grinding.

Air from the blower passes through the connections '22 and 24, the latter controlled by a valve 2S, to a space 28 from which it is delivered about the burner indicated at 38. A branch 3% from the connection 22, controlled by a valve 32, serves to mix air with the suspension Aof the fuel to carry the same through the ,pipe 3d to the burner. This connection is desirable in the event that steam is used as a grinding -agent 'to insure that there is a substantial amount of air carrying the particles in their approach to the burner.

The burner itself is illustrated iin enlarged fashion in Figure 2. It comprises the tube 4 receiving the suspension of powdered fuel in steam and air, the tube 40 discharging the suspension through the annular space 42 inside an annular air chest 46 and outside a liquid fuel feeding assembly. A suspension of fuel of the type here considered and `as described in greater detail hereafter is not generally directly combustible unless projected into a space having a very high temperature. For the purpose, therefore, of initiating combustion or, `in vsome cases, for sustaining :the combustion, it is necessary to feed additional 'fuel which may be oil or combustible gas into the combustion zone. The burner illustrated in Figures l and 2 is designed for feeding in this Vfashion oil. This oil is 'fed through a pipe '52 into a space 54 between a sleeve 6@ and the walls of ajp'assage 55. For the adjustment of the flow of oil, 'the Vsleeve 60 is threaded into a fixed member 6| and is adapted to be rotated through gearing 62 vand 54 'by a shaft et. By the rotation ofthe sleeve 6@ it will be advanced or .retracted due to its Vthreaded mounting, thereby adjusting the clearance at the annular outlet 68. .'Io effect dispersion of the oil thus fed, nozzles '44 inthe inner wall of the chest l46 are vdirec'ted so as to project high velocity jets of air or steam into engagement with the issuing oil to enect'its atomization into condition for substantially instantaneous combustion. For Vthis -purpose, the nozzles 44 are preferably directed so as to cut across, more or less tangentially, the annular 'sheet of oil which'emerges from the nozzle, being 'directed in the `same direction about the axis so as to produce aviolent swirling action. At the same time it will be noted 'that these jets cut'across 'the suspension emerging at 42 `so as to pick up this dispersion and completely v-mix it with the oil in the process of atomization. Thus, the combustion of the oil will result in the production `of intense temperatures sufficient to cause Acombustion of Yeven relatively refractory (low grade) 'solid fuels which may be introduced. To further insure 4complete and rapid combustion, `auxiliary lair is introduced into the combustion zone through passage 5S, -being 4fed thereto through the connection 58, receiving air from a relatively low'pressu're source as, for example, the `connection 22. The flow of air or steam through the nozzles 44 maybecontro'lled by a valve '5e "in vvthe feeding connection i8 which connection is made `to asource of high pressure air 'which may, for example, consist of an auxiliary `compressor `osmall size'since the volume of Aair here needed is relatively small.

Alternatively, the jets issuing from nozzles '44 may/tbe Isteam `jets vin which 'case the chest 4S is supplied Vwith `steam 'at vhigh pressure from 'the boiler in which burning occurs, or from an auxiliary source. The major air for completion of the combustion proceeds from the plenum 28 through the annular space 10 between the burner and the boiler walls 12.

An alternative form of burner is illustrated in Figures 3 and 4. In this modification, the burner comprises a tube having a conical ldischarge and providing a passage 16 through which the suspension of powdered fuel is fed, the connection being to a passage such as 34 of the preceding modification. Within the passage i6 is located a tube 13 into which liquid or gaseous fuel is fed through the connection 80. The tube i8 terminates 'in a small opening 82 which may be adjustably restricted by a valve rod 84 threaded at '86 into a 'support ,-88 and arranged to be rotated by gearing indicated at connected to a hand wheel. By the rotation of the rod 84 it will be moved longitudinally to serve to adjust the opening.

About the discharge end of the passage 14 is located a chest 94 `for the reception of high pressure air or steam to be discharged through noz- 'zles e5 in jets having the directions which will -'be evident from the construction lines in Figures '3 Aand 4; i. e., the jets are directed forwardly in a skew direction about the axis of the tube 18 so that they will pick up both the suspension passing through 'the passage 76 and the liquid or Vgaseous fuel, creating intense 'turbulence and mixing these various constituents .to insure cornplete and rapid-combustion. In the case `of liquid fuel, the jets will serve for -'its Yfine atomization. As in the previous modification, -auxiliary air for supporting combustion will enter .about the passage 14.

Where liquid fuel is referred Lto Ain the foregoing, there is intended to `be Ameant fuel which is of generally liquid form but which may include, for example, oil carrying in suspension ne particles of -`coal -or other solid fuel, being of the so-called colloidal fuel ty-pe. This fuel may be provided, for example, by mixing a certain amount of the finely ground solid fuel with oil or any carbonaceous material which will flow when heated, thereby to reduce to a very substantial extent the *amount of -oil or other vfluent fuel which may be 4used for initiating or sustaining combustion.

The feeding "of liquid or gaseous fuel may be reduced 'or interrupted entirely after the furnace reaches a suiiicient temperature to insure combustion of the solid fuel in 'suspension without 'auxiliary aid. For example, in Astarting up a considerable amount vof liquid `or gaseous fuel may `'be used in order "to achieve rapid rise of vrthe temperature of 'the walls of the vcombustion Ychamber to a point Where, by radiation, they Iwill effect the ignition of the solid fuel suspension. There- '.after, the suspension, if proper air-to-fuel ratio is maintained, will continue to burn due to the high temperatures Sin the furnace. However, the flame -thus 'produced may, by vreason of delayed combustion, "be rather long `so that it may still be desirable 'to use a smallquantity of liquid or gaseous 'fuel 'to insure 'complete combustion in a small space "and with a quite Vshort flame. This last is, `in general, not 'a problem Which arises when `the'fuel 'is adequately ground and sufficient airi's ,provided for combustion. In fact tests have `showntha't anthracite may be ground'in accordan'celwith theinven'tionto such nneness that 40% is less than onemicroninsiz'e (theoretical 12,500 mesh). In such lcase theiiamemay be very short attacco fuels, including coal, there `'willhe an -aclsditio'rial very important type 'of `-dis'integration occurring due y'to the great ldrop "of pressure through `the nozzles occurring with great rapidity lso that the internal expansion Lof fiuid in thefpores will `reiiect explosive disintegration. The disintegration thus occasioned, however, ywill solely occur in materials of porous :nature and willxnot occur in general in Itherock materialwh-ich is relatively nonpor'ous. a result vof this action, there Ais a fselectivedegreeof grinding -Lor fcom-minution which occurs; i. Se., the'icarbonaceous porous fuel will 'bei-reduced to'veryiinef-particles as icomparedwith the rock or other adulterating material. kConsequently., it is possible to "effect separation :of the two materialsiso `that what passes to the point of combustion 'will 4contain ia diigher proportion of carbona'ceous "fuel than `the `-original material fed to the mill.

.The separation :is feiiected fby associ-'ating 'the A:regi'o'nllZt into which .the nozzles discharge :with a separator 'of -cyclone .type indicated 'as comprising a cylindrical section |28 axially =com municating with the yregion l2, a "conical section [30 forming a continuation oi the cylinder 128and areceiver conventionalized at l132.. ihe `high irate of rotation induced Aby the jets from the 'nozzles 12d 'w'll lserve to -e'ifect centrifugal separation `so that the relatively larger particles will be .centriugally thrown outwardly in the separator and will drop into the receiver T32. On the other hand, the finest particles will be carried by the issuing fluid through the opening |36 :of ythe "outlet lpassage i3d., 'which opening 136 projects `downwardly .into the separator .region 'as indicated. |34, Lthe suspension of fuel in the lelastic :fluid :will I:pass to the `cernbustion point yas in the previous modification.

1t will be evident, therefore, that 'b'.y 'a suit- `able Aselection of the `.amount Aof elastic 'fluid `introduced into the nozzles it, vthere may be avoided the ultra-:fine grinding of contammating incombustible material, with the result 4that a very low Agrade ufuel containing quite large proportions of rock vmay be transformed into :a relatively high `grade fuel passing to the point of combustion. While inevitably some yUf .the rock or the like will be ground to a `sufficiently iine degree to pass with the fuel, not Aonly will the proportion `of this loe less than the .proportion of rock in the original material, 'but the particles thereof will 'be so dine as to .pass out with .the iiue gases along with the fine ash which may result from the combustionfof the fuel itself. Thus,

the accumulation of .rock in the combustion'chamber will be greatly `reduced lover what would occur if a corresponding economy of Vgrinding were effected in the modification of Figure l. With the same fuel in Athe modification of Figure i, the grinding would have to be carried out to `an extent insuring that all of the contaminating material was reduced 'to a very ne .state of :subdivision along with the fue To secure effective lexplosive action in the fuel particles, the temperature and pressure condi tions in the first stage should .be desirably lsuoli as to maintain water in liquid form in the particles; i. e., the temperature should be below the boiling point of water at the existing pressure. Under such conditions, the dropping of pressure in the second stage results in an enormous increase in volume as the liquid water turns into steam, this taking place in the very short period of time oi passage through the nozzles 12B, with resulting great violence in explosive action. The

- suddenly lowering the pressure of said suspension,

75. by subjecting the materials tothe grinding action which is not so disintegrated, comprising the steps drop to centrifugal separating action to separate `circulation through the pressure drop step.

materials, -one of which is Vcapable of disintegraabove requirement fwill indicate that the lsteam existing in the fregion H2 should `:be Vsaturated or wet I.rather than superheated.

4It will be noted -that wet, las well as dry, iuei maybe satisfactorily handled in accordance with the invention, since 4actual drops of water will be disintegrated, if not vaporized, and will not impede `in lany way the burning action.

1The fuel particle :sizes achieved with the types of apparatusindica-ted 4are not critical, and ad- -justments may fbe readily :made to secure ranges of .particles of quite `difiere-nt sizes. However, as compared with ymecl-ianical ygrinding of coal -or the like, the particle's will, in general, be .quite small, average .sizes lof around 25 microns .being readily secured without uneconornical use` of grindingfluid. The attainment of much smaller particles of `the order of ,a :few microns in size necessarily involves the `use of greater vnumbers of jets for effecting grinding and the particle sizes involved depend, therefore, upon the ques- .tions of cost, considered in connection with the advantages resulting from small size particles. If the fuel is of high grade, i. e., low ashcontent, even relatively large size particles will Vg-ive rise to ash having very small particle sizes and, consequently, subject to very wide distribution from a stack. In general, ash particles of as large size as 20 .microns are tolerable from the standpoint of ldispersion over a large area from a stack. Under some conditions, however, where the fuel is to Ibe used to provide the gases for combustion engines or gas turbines, it is desirable that the ash particles be very small. This result is directly `related to the fine 'grinding of the .fuel `itself ,and with an ordinary average -grade fuel, Aa grinding .of the fuel to vparticles of the order oi lless than 20 microns will result in the production of ash particles of extremely small sizes.

What l claim is: l. The method of effecting separation of solid materials, one of which is capable of disintegration by sudden pressure drop and another of of producing a suspension of said materials in a vi'lne powder in an elastic fluid at high pressure,

and then subjecting the ksuspension after the pressure drop to centrifugal separating action to .separate the material disintegrated by the pressure drop from material not so disintegrated, the separation excluding the disintegrated material from recirculation throughthe pressure drop step.

2. The method of effecting separation of -solid materials, one `of which is capable of disintegration by sudden pressure drop and another of which is not so disintegrated, comprising the steps of producing a suspension of said materials in a ine powder in an 'elastic fluid at high pressure, suddenly lowering the pressure of said suspension by passing said .suspension through a nozzle, and then subjecting the suspension after the pressure the material disintegrated by the pressure drop from material not so disintegrated, the vseparation excluding the'disintegrated material from re- 3. The method `of eiiecting separation of .solid tion by sudden pressure drop Aand another of which is not so-fdisintegrated, vcomprising the steps vof producing a rsuspension 'of said materials in a fine powder in `an elastic fluid at high pressure solid material is readily carried from the combustion zone in the lue gases. In the case of It may be noted that in general no diculty will be encoun- It is, therefore, within the contemplation of the invention to effect the disintegration of the fuel in such fashion as to achieve from the ne particles of fuel which alone may To achieve this end, use is made of the fact that if an organi-c to temperatures .above the bo1l1ng point and socalled inherent water which is not ordinarily evaporable but which in this process contributes substantial and rapid pressure drop.

The apparatus of Figures 5, 6, and 7 is adapted to the carrying out of this procedure. A grinding mill comprises a tubular lower turn 98 in which grinding is effected, as in the mills of the patents referred to above, by the action of high velocity elastic uid jets issuing from nozzles |00 which are fed with steam or air under high pressure from a supply connection |02. In the of supply of the elastic fluid. Since there exists in the mill a quite high pressure as compared with the pressure in the mill of Figure 1, which cally by the provision of a closed hopper 04 subjected to the pressure in the line |02 through the connection |06, feed of the material being effected through a screw conveyor arrangement |08 driven by a motor H0. The hopper |00 will, of course, be of very substantial size to hold large showing in Figure 5 through the upwardly arranged stack ||2 and through a nozzle section ||4 substantially tangentially to a wall ||6 at the upper part of the mill, whence it may return through a passage ||8 to the grinding zone. The upper part of the mill has a form which will be clear from Figure 6, comprising an annular passage |20 communicating with the region adjacent the wall I6 and bounded inwardly by a cylindrical wall |22. As will be evident from Figure 6, the increase of velocity occasioned by the presence of the nozzle ||4 will serve to accelerate the particles of the material being ground to such high velocities that large particles will pass directly into the downwardly directed passage 8 without entering the annular passage |20, thereby to be recir- 9 of at least one high velocity elastic fluid jet, suddenly lowering the pressure of said suspension, and then subjecting; the suspension after the pressure drop to centrifugal separating action to separate the material disintegrated by the pressure drop from material not so disintegrated, the separation excluding the disintegrated material from recirculation through the pressure drop step.

4. The method of effecting separation of solid materials, one of which is Capable of disintegration by sudden pressure drop and another of which is not so disintegrated, comprising the steps of producing a suspension of said materials in a fine powder in an elastic fluid at high pressure by subjecting the materials to the grinding action of at least one high velocity elastic fluid jet, suddenly lowering the pressure of said suspension by passing said suspension through a nozzle, and then subjecting the suspension after the pressure drop to centrifugal separating action to separate the material disintegrated by the pressure drop from material not so disintegrated, the separation excluding the disintegrated material from recirculation through the pressure drop step.

NICHOLAS N. STEPHANOFF.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date Wood Apr. 4, 1916 Morgan Nov. 21, 1922 Dyson Sept. 18, 1923 Lykken July 14, 1931 Wohlenberg' Oct. 18, 1932 Tenney July 25, 1933 Andrews Mar. 3, 1936 Kennedy Sept. 8, 1936 Noack Sept. 22, 1936 Graemiger Dec. 28, 1937 Andrews Mar. 22, 1938 Noack Jan. 16, 1940 Hobbie Feb. 20, 1940 Kidwell et al. Oct. 20, 1940 Vogel-Jorgensen Oct. 21, 1941 Woolley June 2, 1942 Kennedy Nov. 23, 1943 Ladd Aug. l, 1944

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