US2770052A - Method and apparatus for drying treatment of solids in the fluidized or gas entrained state - Google Patents

Description

Nov. 13, 1956 R. MORRISON 2,770,052

METHOD AND. APPARATUS FOR DRYING TREATMENT OF SOLIDS IN THE FLUIDIZED OR GAS ENTRAINED STATE Filed July 29, 1952 4 Sheets-Sheet 1 ow N I I! O INVENTOR. L N Roberr L.Morrison BY 0Z4 ATTORNEY 4 Sheets-Sheet 2 m d-u m 1956 R. L. MORRISON METHOD AND APPARATUS FOR DRYING TREATMENT OF SOLIDS IN THE FLUIDIZED 0R GAS ENTRAINED STATE Filed July 29. 1952 INVENTOR. Robert L. Morrison ATTORN EY 2,770,052 ENT OF SOLIDS Nov. 13, 1956 R. L. MORRISON METHOD AND APPARATUS FOR DRYING TREATM IN THE FLUIDIZED OR GAS ENTRAINED STATE Filed July 29, 1952 4 Sheets-Sheet 5 INVENTOR. Robert L. Morrison fifa 7 Zw ATTO R N E r' Nov. 13, 1956 R. L. MORRISON 2,770,052

METHOD AND APPARATUS RYING TREATMENT OF souns IN THE FLUIDIZ GAS ENTRAINED STATE Filed July 29, 1952 4 Sheets-Sheet 4 ATTORNEY United States Patent Robert Laurance Morrison, Blairrnore, Alberta, Canada, assignor to Silver Engineering Works, Inc., a division of the Silver Corporation, a corporation of Colorado Application July 29, 1952, Serial No. 301,494

8 Claims. (Cl. 34-10) This invention relates to fluidized or gas-entrained drying of solid materials, and is particularly suited for a drying treatment of coal having a relatively high percentage of surface or inherent moisture. I

Treatments for the drying of coal in the fluidized state have been the subject of considerable study by the U. S. Bureau of Mines and the results of these studies have been disclosed in the patent application of Vernon F. Parry, Serial No. 111,752, filed August 22, 1949, for Continuous Process for Devolatilization of Carbonaceous Materials, etc., now U. S. Patent No. 2,666,269, issued January 19, 1954. Such treatments have involved the reduction of the coal or other fuel to finely divided condition, after which it is fed into a heating chamber where it is entrained in a rising column of heated gas and is moved at a controlled rate to bring the temperature of the solids to a predetermined point, thus limiting the heating interval and effecting a maximum removal of moisture without destructive distillation of the coal.

The present invention represents improvements over prior practice in the method of introducing the fuel and entraining the materials being processed and in the control of combustion. While the invention will be described with particular reference to treatments involving the removal of surface or inherent moisture from fine coal, it should be understood that it is generally applicable to the treatment of any kind of subdivided material, such as coal, vermiculite, ore concentrates, sludges, beet pulp or the like.

It is an object of the present invention to provide a simple, economical and efficient process for the removal of surface or inherent moisture from materials in finely divided condition.

Another object of the present invention is to provide a method of control of the entrainment stage by which coal or the like is conducted through a drying treatment in a fluidized or gas-entrained state.

A further object of the invention is to provide a simple, durable and efficient mechanism for the entrainment of coal or the like in a fluidized or gas-entrained state preparatory to drying.

Still another object of the invention is to provide a simple, economical and efficient mechanism for classifying solids in the drying column.

Another object of this invention is to provide a novel control of the combustion stage of the operation.

Other objects reside in novel details of construction and novel combinations and arrangements of parts, all of which will be set forth in the following description.

The practice of the invention will be best understood by reference to the accompanying drawings. In the drawings, in the several views of which like parts have been designated similarly,

Fig. 1 is a schematic representation in front elevation of a typical plant installation embodying features of the present invention;

Fig. 2 is a fragmentary front elevation, partially broken to show interior parts, ofthe furnace and mixing zone "ice of the plant assembly shown in Fig. 1, and drawn to an enlarged scale;

Fig. 3 is a section taken along the line 33, Fig. 2;

Fig. 4 is a fragmentary section of the extractor unit for removal of coal from the pressurized mixing zone shown in Fig. 2;

Fig. 5 is a fragmentary front elevation, partially broken to show interior parts, of the drying column and fuel feeding mechanism of the plant assembly shown in Fig. 1, and drawn to an enlarged scale;

Fig. 6 is a section taken along the line 66, Fig. 5;

Fig. 7 is a section taken along the line 77, Fig. 5;

Fig. 8 is a section taken along the line 88, Fig. 5;

Fig. 9 is a section taken along the line 9-9, Fig. 8;

Fig. 10 is a vertical central section through a pressure valve or feeding device of the type shown in Fig. 1; and Fig. 11 is a section taken along the line 11-11, Fig. 10.

The plant assembly shown in Fig. 1 comprises a storage bin or receptacle 20, from which the stored material such as coal, is moved by an agitator unit 21 into a feeding device 22, both of which are driven by a motor 23 through the intermediary of transmission systems 24 and 25. The material is discharged by the feeding device 22 into a. drying column 26 intermediate the limits of its vertical extent. The base of the column is supported on a mixing chamber 27 forming an extension of the furnace unit 28 and having a sump portion 29 for the removal of oversize material, as will be set forth in the following description.

The vertical column 26 terminates at its upper end in an extension conduit 31, which delivers the fluidized material and associated gases and vapors into a primary separator unit 32, preferably of the cyclone separator type, from which gases and suspended solids travel through a top outlet 33 to a point of division 34, with one stream of the gas with suspended material passing into a dust separator 35, whilethe remainder is drawnby a fan 36 through another duct or conduit 37 to constitute the supply for a recirculating gas main duct 38 discharging into the lower portion of furnace 28 for mixing in chamber 27.

A suitable damper or valve 39 directs a portion of the flow in duct 38 upwardly through a conduit 41 having a damper control 40 supplying a header 42 mounted on the top of furnace 28, and a series of downwardly directed ports or outlets 43 discharge the recirculated gases along the inner walls of the furnace to insulate them from excessive heating, thus retarding the formation of slag. A blower or fan 44 supplies air through a line 45 into the top entrance of furnace 28 and a second line 46 extending from the blower receives the solids discharge of dust separator 35 through a feeder or valve 47 and the resulting mixture constitutes one of the fuel supplies of furnace 28. Additional fuel, which may be oil, gas or added pulverized fuel, is delivered through a header or line 48 into the top entrance of furnace 28.

The separated solids of primary separator 32 descend into an outlet line 49 and are discharged therefrom by a pressure valve or feeder 51 onto a conveyor 52 which conducts them to storage or point of use. This discharge represents the dried coal or material recovery of the system and is in condition for use as a dried product at the time of discharge.

With this understanding of the general plant arrangement and operation, various novel details and operations of the present invention will be described. The mixing chamber 27 of this invention is preferably supported on suitable structure such as a series of beams 53 (Fig. 2) and has an insulated bottom 54 separated by a ventilation space from the foundationSS. The main duct 38 enters the furnace 28 adjacent its bottom and extends into an inspirator unit 56 so arranged as to provide a venturi passage for products of combustion travelling from furnace 28 to mixing chamber 27. A baffle 57 positioned forwardly from the discharge end of duct 38 imparts an upward component of movement to the resulting mixture of products of combustion and recirculating gas in mixing chamber 27 and accelerates the flow of the mixture into entrance 58 at the bottom of column 26. This bafile also provides a quiescent zone for collection of oversize material.

Solids which are too heavy to entrain in the rising gases descend from column 26 into sump 29, as do other solids from furnace 28 which are swept over baffle 57 but are not entrained in the vertically rising gases. A screw conveyor 59 or other conveying means moves these collected solids through the sump to a discharge outlet 60 (Fig. 4) controlled by a pressure valve 61. A thermocouple 62 is provided at the bottom of column 26 for controlling the mixed gas temperature by controlling the damper 39 and therefore controlling the quantity of recycled gases entering the mixing chamber 27.

Referring next to Figs. 5 through 9, a material such as bituminous coking coal having from 5% to 25% surface moisture is stored in bin 28, and the agitator 21 at the bottom of the bin breaks up consolidated masses and delivers the coal in loose condition into the screw conveyor or feeding device 22. Suitable manholes or service openings 63 may be provided in this device.

The screw discharges the conveyed coal onto a suspended screen'64 and a series of agitator blades 65 are disposed above screen 64 within column 26 to facilitate the discharge through the screen openings and over the sides and end of the screen. Part of the coal is entrained immediately above the screen by gases passing upwardly through the screen holes. This action produces a reasonably uniform distribution of the product throughout the area of the column, and entrained solids will rise readily through and around the screen and agitator blades in their ascent through the column.

The mixed gases entering column 26 through entrance 58 are first subjected to a swirling effect by a vane assembly 67. In order to getthe desired swirling eifect with the least loss of pressure, the individual vanes (Fig. 9) have a vertical portion 68, a curved intermediate portion 69, and an upper inclined portion 70. A series of baffles 72 in radial arrangement are positioned above the vane assembly 67 to break up the swirling effect. This arrangement of vanes and baffles establishes a pressure or velocity equalization across the area of the drying column which facilitates entrainment. In this way proper control of the entraining action can be maintained. The individual particles are so thoroughly dispersed in the gaseous portion that all their surfaces are brought into repeated and intimate contact with the rising gases.

The swirling vanes can be arranged at a suitable angle to give a classifying effect on the material to be dried, with the oversize particles descending into sump 29, while lighter solids are readily entrained and pass upwardly in column 26.

Solids falling as agglomerated masses on the vane structure are broken up on such vane structure and there-. after are subjected to the aforesaid entraining or classifying effects.

The fluidized or gas-entrained fuel has attained the desired reduction in moisture content by the time it reaches the primary separator 32 and is subjected to a gas-solids separation therein. The separated gases passing out through outlet 33 carry minor quantities of. fine dust. Since fuel is a requirement of the treatment, these solids are separated in dust separator 35 and delivered into the furnace 28 as part of the fuel supply thereto.

The dried coal settling in dust separator 35 descends through its conical bottom portion to enter an outlet passage 50, the discharge of which is controlled by the pressure valve or feeder device 47 (valve 47 is structurally similar to valve 51 and both are similarly operated), the details and functioning of which will now be described. This valve comprises an intermediate cylindrical body portion 75 and a flanged, tubular inlet 76 and a flanged tubularoutlet 77. The inner-cylindrical portion comprises an inner and outer annulus 78 and 79 respectively, both of which are stationary and an intermediate annulus 81 which is rotary.

The outer annulus has an entrance opening 82 which aligns with inlet76, and an outlet passage 83 at 180 from opening 82. The rotary annulus 81 is provided with a series'ofopenings: 84 which move in register with entrance opening 82 toreceive coal from inlet 76. The side walls of cylindrical portion 75 'are journalled as shown at 85a and 85b for reception of a shaft 86 which imparts the rotation toannulus 81 through a hub 90 adapted to be held on shaft 86, and a plate 91 connects annulus 81 and hub 98. An opening 87 is provided for admission of a pressure fluid into the interior of annulus 78, which fluid flowing through opening 88 forces the descending coal through opening 83 whenever one of the openings 84 aligns therewith and the companion opening 77 of the outlet passage.

This arrangement maintains sufficient pressure in the interior of annulus 78 to provide a positive discharge of the solids against the pressure flow in line 46, while permitting a combined gravity-mechanical feeding to insure an adequate supply of solids within the enclosure. After discharge from valve 47, the solids descend into line 46 and pass to furnace 28.

In a typical operation, the mixture of coal and gas usually reaches a final temperature of from 250 F. to 350 F. before discharging into primary separator 32. The volume of the passage from the furnace outlet to the primary separator is a factor of residence time and where materials of relatively high moisture content are being treated, a preferred arrangement is to enlarge the,

vertical column .as indicated by dotted lines 26x in Fig. l to provide a longer residence time.

It is towbe understood that the practices and plant ar:

' rangement previously described are intended to teach the practice of the present invention, but not to limit same, and changes and modifications may-be availed of within the spirit and scope of this invention.

I claim: 1

1. In apparatus for-drying subdivided materials in a fluidized or gas-entrained state, an upright drying column, means for introducing heated gases into the lower end of said column, means for introducing subdivided material intosaid column above its bottom, a swirl-imparting means in the column intermediate said points of introduction having surfaces arranged to impart a centrifugal movement to the entering gases, and vertical 'bafile meansin said column intermediate said points of introduction and above and spacedfrom said swirl-imparting means to retard the centrifugal movement.

2. Iii-apparatus for drying subdivided materials in a fluidized or gas-entrained state, an upright drying column, means for introducing heated gases into the lower end of said column, meansforiintroducing material in subdivided condition into said column above its bottom, a series of spaced vanes in the column intermediate said points of introduction having surfaces arranged to impart'a centrifugal movement to the entering gases, and a series of vertical baffles in the column intermediate said points of introduction andabove'and spaced from said vanes for retarding the centrifugalmovement.

3. In apparatus for drying materials in a fluidized or gas-entrained state, an upright drying column, means for introducing-'heatedgases into the lower end of said column, means for introducing material in subdivided condition into said column above its bottom, a swirlimparting means in thecolurnn-intermediate said points of introduction to impart a centrifugal movement to the entering gases and arranged to impart a classifying effect in the material, and baflle means in the column intermediate said points of introduction and above said vanes for arresting the centrifugal movement and resulting material classifying action.

4. In apparatus for drying subdivided materials in a fluidized or gas-entrained state, an upright drying column, means for introducing heated gases into the lower end of said column, and a feeding device for introducing subdivided material into said column intermediate its ends, including a screen member of curved section having an open top and an open end extending substantially across the interior of the column, and agitators for breaking up lumps and moving the subdivided material through the screen openings and over the top and end so as to discharge the material over a substantial area of the column.

5. In apparatus for drying subdivided materials in a fluidized or gas-entrained state, an upright drying column, means for introducing heated gases into the lower end of said column, and a feeding device for introducing subdivided material into said column intermediate its ends, including a material supporting surface having an open top and an open end extending into said column and an agitator mechanism for breaking up lumps and discharging the feed over the edges of said surface and over a substantial area of the column.

6. The process of drying sub-divided coal or the like, which comprises directing heated gases upwardly through a closed vertical drying zone, feeding such coal in subdivided condition into said drying zone intermediate its ends, subjecting the heated gases to a swirling action at the lower end of said drying zone and below the level of feed introduction, subjecting the swirling gases to a swirl-retarding action at a point below the level of feed introduction to the drying zone whereby the coal is suspended in the non-swirling gas, and separating the dried coal from heated gases after its passage from said drying zone.

7. In apparatus for drying subdivided materials in a fluidized or gas-entrained state, a furnace having walls defining a combustion zone and provided with a fuel inlet at one end and a discharge for heated gases at an opposite end, conductive means for returning cooled, circulated gases of the drying treatment to the furnace and a series of spaced ports at the inlet end of the furnace arranged to receive and discharge the recirculated gases adjacent to and along the interior walls of the furnace in the direction of the discharge end, whereby to insulate said walls from excessive heating and slag formation.

8. In apparatus for drying subdivided materials in a fluidized or gas-entrained state, a furnace having walls defining a combustion zone, conductive means for returning cooled circulated gases of the drying treatment to the furnace, and a series of laterally spaced conduits arranged to receive the recirculated gases and having downwardly directed outlets adjacent to and along the inner upright walls of the furnace, whereby to insulate said walls from excessive heating and slag formation.

References Cited in the file of this patent UNITED STATES PATENTS 748,894 Trump Ian. 5, 1904 1,013,379 Dunn Jan. 2, 1912 1,200,028 Roberts Oct. 3, 1916 1,550,992 Trump Aug. 25, 1925 1,576,547 Reader Mar. 16, 1926 1,742,716 Meyer Ian. 7, 1930 1,789,692 Rosencrants Jan. 20, 1931 1,937,040 Vogel-Iorgensen Nov. 28, 1933 1,992,669 Labus Feb. 26, 1935 2,032,402 Colby et a1. Mar. 3, 1936 2,033,757 Crites Mar. 10, 1936 2,066,418 OMara Ian. 5, 1937 2,100,907 McGehee et al. Nov. 30, 1937 2,132,656 Smith Oct. 11, 1938 2,148,981 Dundas et al. Feb. 28, 1939 2,250,864 Gordon July 29, 1941 2,513,370 Shaw July 4, 1950 2,607,537 Shaw Aug. 19, 1952 2,666,269 Parry Ian. 19, 1954

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