US2230833A - Method and apparatus for treating coarse materials - Google Patents

Description

Feb. 4, 1941. 1 A. E. DOUGLASS METHOD AND APPARATUSFOR TREATING COQRSE MATERIALS Filed April 3, 1940 4 Sheets-Sheet 1 Ha. I

INVENTOR Y A/fred f Davy/ass ATTORNEY5' Feb. 4, 1 941. A. E. DOUGLASS APPARATUS FOR TREATING COARSE MATERIALS METHOD AND Filed April 5, 1940 4 Sheets-Sheet 3 cf) 9 u L INVENTOR ATTORNEY5 Feb. 4, 1941-. DQUGLASS 2,230,833.

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Patented Feb. '4, 1941 UNITED STATES METHOD AND APPARATUS FOR TREATING COARSE MATERIALS Alfred E. Douglass, Catasauqua, Pa. Application April 3, 1940, Serial No. 327,609.

9 Claims.

This invention relates to the treatment. of coarse crushed or granular material in order to remove any moisture which might be retained therein and to raise the temperature of the material to an elevated degree. The invention comprehends the process and apparatus for extracting valuable heat units from hot gases used for this p and thereby effects savings in fuel. The invention may be used to advantage wherever coarse material is to be heated either by gases from a direct fired furnace or by waste gases carrying quantities of heat units from apparatus used in conjunction with the present invention for further treating the material. By way of exampleand not of limitation, the invention finds application in the treatment of limestone, phosphates, coal, ores, etc.

Various methods and apparatuses have been suggested in the prior art but have proved to be unsatisfactory due primarily to the lack of proper contact of the gases with the individual particles making up the material to be treated. -A lack of uniformity of the bed through which the gases pass causes some portions of the material to be heated while others are left more or less unchanged. The bed will occasionally have thin places or a portion made up of segregated large size material through which the gases readily pass so as to reach the grate member before losing any substantial amount of heat which has a tendency to burn out the grate members unless expensive heat-resisting metals are used. In those apparatuses where the material travels over the grate by gravity, the time and amount of material treated are unpredictable and result in a finished product of non-uniform character.

It is accordingly the purpose of this invention to raise the thermal efficiency of devices of this type and to deliver the finished product at a uniform'temperature or dryness.

The invention consists of a method and apparatus for removing any moisture present in coarse material, raising the temperature thereof to a uniform elevated point and usually both. To this end, the material is caused to form as a downwardly inclined bed of such slope or pitch that th'ecombined effect of agitation and gravity results in completely uniform resistance to air flow throughout thereby insuring uniform distribution of the gases. The slope is. however, made insufficient to cause the particles to move by gravity without agitation; The material to be treated is placed in a heating chamber having an entrance at one end and discharge at the other end. The material is supported on a downwardly inclined gas permeable support comprising a. series of overlapping vertically spaced grates with stationary gratesalternating with moveable ones, the moveable grates are reciprocated continuously to advance the material and constantly agitate the same while heated gases are to flow through the material to either dry or elevate the temperature or both. Due to the reciprocation of the moveable grates, the base of the bed is advanced which causes the bed to assume a definite cross-section withthe smaller particles at the bottom and the larger -ones at the top. This forming of a uniform cross-section results in several distinct advantages. The gases passing through the bed contact substantially the same surface area of material at all points along the bed so that when reaching the grate they have transferred-most of the heat to the bed and have no ill effects 30 upon the supporting structure. The grading of the bed from the large particles at the top to the smallest at the bottom has the advantage of bringing the hottest gases in contact with those particles which need the most heat in order to 25 penetrate to the core thereby to raise the temperature of the entire particle. It has been found in actual practice with one type of material when deliveringgases to the device at approximately 1500 F. that the exhaust gas temperature was about 300 F. and the material was uniformly heated to about 1150 F.

The invention is particularly adapted for use in connection with the treatment of material which is discharged into rotary kilns for further heat treatment such as in the burning of limestone. The heat developed in the rotary kiln is necessarily high for burning and the waste gases issuing from the kiln carry large quantities of heat. The gas discharge end of the kiln may be 40 directly connected with the present invention and the heated waste gases utilized to furnish all or part of the heat required. When used in connection with a rotary kiln of this type, a further advantage is noticed in that particles of partially treated material entrained in the gases are filtered out thereby increasing the efficiency of the process as a whole and obviating the use of separators in the conduits to the stack unless the material under treatment contains a substantial proportion of fines. Limestones treated by the present invention are found to. be uniformly heated and frequently have undergone a partial calcination before entering the kiln which results in the use of a shorter kiln or when used with existing structures a longer efiective length of kiln for heat treatment. The apparatus of the present invention may be attached with little or no change to existing kilns or the housings for these kilns.

Other objects and advantages of this invention will appear from the following detailed description taken in connection with the accompanying drawings, in which Fig. 1 is a sectional elevation of the device for pre-heating. 3

Fig. 2 is a vertical section of the device taken on line 2-2 of Fig. 1.

Fig. 3 is a side elevation, partly in section of a modified form of the device.

Fig. 4 is a fragmentary side elevation, partly in section of the upper portion of the grate mechanism.

Fig. 5 is a fragmentary plan elevation of a portion of the grate assembly.

Fig. 6 is a cross-sectional detail view of one of the supporting wheels.

Referring to the drawings and Figures 1 and 2 in particular, I designates an inclosed heating chamber having an inlet chute 2 connected to a material hopper 3 through slide valve 4 at one end, and a fluid inlet port 5 at the other end. Material entering the chamber is deposited upon a shelf 3 and after sufhcient material has 9.0-

cumulated upon the shelf to form a natural angle of repose, the descending particles are distributed by the pile thus formed and pass on to an inclined grate assembly 1 to form a flat bed. The slope or pitch of the grate assembly should be less than that which will permit the larger particles to roll downwardly freely. For the treatment of a relatively coarse material, such as crushed limestone of 1 /2 inch mesh, the pitch should preferablybe about 12. A steeper pitch may be used in the treatment of finer materials, but appears to have no advantage. The walls of the heating chamber above the grate assembly are constructed of ceramic or other heat resisting material with the exception of the end .wall 8 adjacent the inlet chute which is protected by the incoming material when the device is in operation. I

The grate assembly will now be described and it will be seen to comprise fixed grates 3 and moveable grates Hi, the fixed grates 9 are rigidly secured to a stationary frame and all of the moveable grates I are similarly secured to a moving frame, forming separate unitary structures. The stationery frame comprises inclined channel members II and I2 supported by members l3 and I4 welded or otherwise secured to upright supports l5, l6, l1 and I8 in turn supported on lower horizontal plate members I3 and I- beams 20 and 2|. The fixed grates 3 are bolted'as at 22 to angular brackets 23,'welded or otherwise secured to frame member eachbracket extending forward beyond the fixed grates to deflect the particles from the space between the side edges of the moving grates l0 and the frame member The moving frame comprises inclined side members 24 and 25 suitably braced by cross members 26, the side members carrying uprights 21 to which flanges, cast integrally at the side edges of the movable grates III, are secured as at 28. The members 24 and 25 are [secured to axles 29, supported by flanged wheels 3|], shown in detail in Fig. 6, provided with bronze bushings 3|, the wheels turning on the axles and running on rails 82. the rails being bolted to angle members 33 secured to and supported by uprights of the stationary frame by a horizontal I-beam 34. Plates 35 and 3B cooperate with seals 31 to pre- ,vent air from being drawn into the chamber below the grates.

The reciprocating motion of the moveable frame may be conveniently accomplished by two spaced eccentrics of the-conventional type comprising eccentric rod 38 pivotally connected to axle 29. Movement of the axle 29 is transmitted to the moveable frame by strap 39 rigidly connected to this frame by housing 40 and channel 4| as shown in Fig. 4. The rods 38 pass through slots inthe rear wall 42 of the chamber and terminate in the usual strap 43 surrounding each eccentric disc 44. A common crankshaft is provided with a sprocket 45 driven through a chain 46 by a variable speed motor, with speed reducer, indicated at 41. It will be seen .that grates l0 move in a horizontal plane between fixed grates 3 and that the extent of the movement or throw depends upon the eccentricity of discs 44 on the crankshaft. In Fig. 4 the moving grates are shown in their rearmost position and the maximum permissible advance as being one-half their width, at which point the rear edge of each moving grate is covered by the leading edge of the fixed grate above it, thereby avoiding the passage of material treated between the grates. lit will also be understood that the'rate of travel of the bed and consequently its thickness can be varied by changing the speed of the motor 41.

As shown in detail in Fig. 4, the fixed and moving grates are essentially similar and may be gray iron castings, the forward or leading edges of the fixed grates and the side edges of the moving grates preferably being chilled in casting to resist wear of any abrasive material which may be treated.

The adjacent grates are spaced a distance, usually it; inch,'to form horizontal gas passageways, each grate also contains rows of tapered holes 48 near the forward edge and similar rows of tapered holes 49 near the rearward edge forming additional passageways for the heated gases from the chamber Upon reciprocation of the movable grates it will be obvious from the construction shown that upon forward movement the openings in the rear portion of the movable grate as well as the opening in the forward edge will be exposed to the material and the rearward openings of the stationary grate will be closed by the forward portion of the movable grate, the opposite condition taking place upon rearward movement of the movable grates. The space below the grate assembly constitutes an air tight exhaust chamber having side walls 50, bottom 5| and rear wall 42, as shown constructed of metal plate, but obviously might be made of other materials. The forward or discharge end of the chamber below the grates is closed by a refractory wall 52 upon which the lowermost fixed grate rests. Attached to the wall 52 is a trough 53 into which the treated material is discharged, as shown in Fig. 1, the discharged material then passes to the rotary kiln 54. Below the grate assembly 1 and positioned in the bottom 5| as shown in Fig. 2 is a screvificonveyor 55 driven by a sprocket 58 and chain 51 from the motor 41, this conveyor advancing any material which might leak through the grates to the discharge trough 53. The heated exhaust gases from the kiln 54 are directed through the open- I ation of the device is not de motor 59 through belt having its intake connected through duct ii to the space below the grates causes a reduction in the pressure in this space sufllcient to cause the heated gases above the grate assembly to overcome the resistance presented by the grates and the thickness and density of the material bed to flow through the bed and into the duct 6|, the gases passing vertically downwardly into the .tapered openings in the grates and horizontally in a direction opposite to the travel or the bed into the openings between the alternating grates. In this'manner the heated gases from the kiln obtain the maximum surface contact with the particles making up the bed and consequently transfer most or their heat to the material, the gases entering the duct 6| being at a relatively cool temperature.

The exhaust of the fan ill is connected through duct 62 to stack 63 whereby the gases may issue to the atmosphere. The opening from the space below the grate assembly is controlled by louvers having adjustable controls 64 whereby the amount of heated gases passing through the bed and the speed thereof may be controlled.

When it be desired to pass any portion of the exhaust gases from the kiln over the material to heat the upper surface of the bed and then directlyto the stack 63 without going through the material bed, outlet connected to stack 63 by duct 66 is provided, the outlet 65 being controlled by louvershaving adjustable controls 61 as clearly shown in Fig.- 2.

By reference to Fig. 3 it will be seen that operndent, upon exhaust gases from a kiln, but may used with any type of heat generating device such as furnace 68. The treated material when using this type of heat generatingmeans may discharge to chamber 89 from which it is removed as by a drag chain It, the remainder of the device being the same as previously described.

The operation of this device is extremely simple and because of this simplicity is particularly adapted for use in its field. The material entering the inlet chute forms a fiat bed upon'the grates of a desired thickness which due to constant reciprocation of the moveable grates travels uniformly to the discharge port. During this travel the particles are constantly agitated, caused bytheir tumbling from one grate to the/next. The linear'speed of these grates being very slow cause no vibration or noise and consequently very little wear takes place on the moving parts. The heated gases are drawn through the bed in the desired quantities, these gases traveling through .the Bed in two directions to the vertical and hor-.

izontal openings in the grate assembly. The dispersion of the gases throughout the entire bed of material in this manner in connection with the constant tumbling of the panticles results in the maximum surface contact or gas and material, the gases exhausted from the device having the major portion of the heat extracted. Due to the efllcient transfer of the heat to the material the metal parts of the device need not be constructed of expensive heat-resisting material.

From the foregoing, the embodiments of my invention will be fully understood'but it is to be understood that the invention is not restricted to the present disclosure to any extent otherwise than restricted by the manner in which such in vention is claimed.

Reference is hereby made to my copending applications Serial Nos. 327,607 and 327,608, filed concurrently herewith.

I claim: 1. In a device for heat treating coarse or granu- 'lar. material which comprises an impervious chamber having a material inlet at the upper end with the stationary grates alternating with the rmvable grates, means to reciprocate the movable grates to advance intermittently and constantly to agitate the material, means to supply hot, gases to the upper compartment above the material, means to createa reduced pressure in the lower compartment rtocause the hot gases to flow downwardly through the material and support in that order, said suppo t being downwardly inclined at anangle less than the angle of repose of the material so that during advancement of the material along said grates it will be formed into and maintained in a bed of substantially uniform thicknms and the constant agitation thereof by said reciprocating means will cause the material of the bed to be graded according to particle size with the larger particles at the surface of the bed where they will be the first particles contacted :g'dthe hot gases passing downwardly through the and adjacent the uppermost grate to receive thematerial from the material inlet and direct the same to the support in a uniform manner and thickness, means to reciprocate the movable grates to advance intermittently and constantly to agitate the material, means to supply hot gases to the upper compartment above the bed of-material, means to create a reduced pressure in the lower compartment to cause the hot gases to how downwardly through the material bed and support in that order, said support being downwardly inclined at an angle less than the angle of repose of the material so that during advancement. of the material along said grates it will be formed into and maintained ina bed of substantially uniform thickness and the constant agitation thereof by said reciprocating means will cause 'thematerial of the bed to be graded according to particle size with the larger particles at the surface of the bed where they particles contacted by the downwardly through the bed.

3. In a device for heat treating coarse or granular material which comprises an impervious chamber having a material inlet at the upper end will be the first hot gases passing permeable support for the material to be treated dividing the chamber into upper and lower compartments. said support comprising a series of overlapping vertically spaced grates, stationary- .65 and a material outlet at the lower end, a gas terial, means to create a reduced pressure in the lower compartment to cause the hot gases to flow downwardly through the material bed and.

support in that order, means connecting the upper compartment to a reduced pressure area, and means controlling passage through said last named means to vary the portion of gases delivered to the upper compartment which passes through the bed, said support being downwardly inclined at an angle less than the angled repose of the material so that during advancement of the material along said grates it will be formed into and maintained in a bed of substantially uniform thickness and the constant agitation thereof by said reciprocating means will cause the material of the bed to be graded according .to particle size with the largerparticles at the surface of the bed where they will be the first particles contacted by the hot gases passing downwardly through the bed.

4. In a device for-heat treating coarse or granular material which comprises an impervious chamber having a material inlet at its upper end and a material outlet at its lower end, a wall upstanding from the bottom of the chamber extending laterally thereacross partially dividing the same, an opening through the wall, a gas permeable support for the material to be treated dividing the chamber into upper and lower compartments, said support comprising a series of overlapping vertically spaced grates, stationary grates alternating with movable grates for supporting a bed of material of substantial thickness, the lowermost grate having an air-tight connection with the laterally extending wall, means to reciprocate the movable grates to advance intermittently and constantly to agitate the bed, means to supply hot gases to the upper compartment above the bed of material, means to createa reduced pressure in the lower compartment to cause the hot gases to flow downwardly through the material bed and support in that order, a conveyor in the bottom of the lower compartment extending through the opening in the laterally extending wall to remove accumulated material passed through the support, and means to drive the conveyor, said support being downwardly inclined at an angle less than the angle of repose of the material so that dur-. ing advancement of the material along said grates it will be formed into and maintained in a bed of substantially uniform thickness and the constant agitation thereof by said reciprocating means will cause the material of the bed to be graded according to particle size with the larger particles at the surface of the bed where they will be the first particles contacted by the hot gases passing downwardly through the bed.

5. The method of heat treating coarse or granular material which comprises continually forming a bed of material particles on a support inclining downwardly at an angle less than the angle of repose of the material, applying mechanical pressureto the under portion of the bed to advance the same at a substantially uniform rate under conditions of continuous agitation to form a substantially uniform cross-section in the bed with the larger particles at the top and the smaller particles at the bottom, maintaining a source of heated gases above the bed, and maintaining a reduced pressure below the bed to cause a portion of the heated gases to flow through the material the remaining gas flowing thereover.

6. The method of heat treating coarse or granular material which comprises forming and continuously maintaining a bed of material of substantially uniform cross-section on a support inclined downwardly at an angle less than the angle of repose of the material, advancing said bed of material downwardly over said support in a direction substantially parallel to the support, under conditions of continuous agitation to cause relative movement of the particles thereof and to grade the particles as to size, with the larger particles at the top of the bed, directing heated gases above the bed, maintaining a flow of heated gases along the bed, maintaining a reduced.

at the top, supplying material to the upper end of the bed at the same rate as that at which it leaves the lower end of the bed, maintaining a source of heated gases above the bed, and maintaining a reduced pressure below the bed to cause the heated gases to flow uniformly through the bed and a multiplicity of vertically directed openings in the support.

8. The method of heat treating coarse or granular material which comprises forming and continuously maintaining a bed of material of substantially uniform cross-section on a support inclined downwardly at an angle less than the angle of repose of the material, advancing said bed of material downwardly over said support in a direction substantially parallel to the support, under conditions of continuous agitation to 'cause relative movement of the particles thereof and to grade the particles as to size, with the larger particles at the trip of the bed, directing heated gases above the bed, and maintaining a reduced pressure below the bed and causing the heated gases to flow uniformly through the bed in a multiplicity of vertically and horizontally directed streams.

, 9. The method of heat treating coarse or granular material which comprises continuously forming a substantially flat bed of material particles of uniform thickness on a support inclining downwardly at an angle less than the angle of repose of the material, advancing the bed downwardly parallel along the support at a substantially uniform rate under conditions of continuous agitation, maintaining a source of heated gases above the bed and in contact therewith, and maintaining a reduced'pressure below the bed to cause a portion only of the heated gases to flow uniformly through the material.

ALFRED E. DOUGLASS.

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