US1453750A - Apparatus for drying granular products - Google Patents

Description

May 1, 1923. A 1,453,750

N. C. CHRISTENSEN APPARATUS FOR DRYING GRANULAR PRODUCTS Filed Ma rch 8 1921 2 Sheets-Sheet [NYE/VTUH 7M 6. W

- May 1, 1923.

1,453, 750 N. c. CHRISTENSE'N APPARATUS FOR DRYING GRANULAR PRODUCTS Filed- March 8, 1921 2 Sheets-Sheet 2 .F2 .15. j Z

' INVENTOR M C? Mir/)2 ATTORNEY .To allwhom it may comer n.-

Patented May 1, 1923.

UNITED, srATas ass st PATENT orsica.

- NIELS C. CHRISTEI Q'SEN, OESAL'J. LAKE (iITY, UTAH.

"LIP PARA?US F63 DRYING GBANULAR PRODUCTS.

Application filed March 8, 1921. Serial No. 450,679.

Be it known that I, NmLs C. CHRIsrnN- SEN, a citizen of the United States, residing at Salt Lake Cit in the county of Salt Lake and State 'Utah, have invented certain new and useful Improvements in Ap-- paratus for Drying Granular Products, of which the following is a specification.

- This invention relates'toiinprovements in methods and apparatus for drying gran-"- ular products such aslwheat and other grains or granular mineral products. It is. particularly adaptable to the drying of sized products, i. e., products in which the grams or particles are of approximately the samesize, but is useful for the treatment of all products which are granular in their. nature. It. is not applicable to the treatment of fine material or to the treatment of a mixture of coarse and fine in which the fine is in such proportion as to fill the voids between the coaser or, granular products.

The method of drying now' most com. monly used consists in dropping the material to be dried throu h'a current of air which is either cold as in some wheat driers now used or hot as is used in different forms of ore and coal driers, etc. The dro ping of the material to be dried, thr0ugh t e air current is accomplishedinitwo general ways,

either by dropping-the material down a shaft supplied with baflie's or deflectors against an upward current of air as exempli,

fied in, some wheat driers, or by passing the material through a revolving substantially horizontal c linder supplied with lifting de' vices which ift the material as the drum revolves and drops it through the currentof hot air or furnace gases. In some forms of driers the drying gases are merely passed over the surface 0 g which is stirred to bring different portions of the mass i'r'itocontact with the ases In all these forms ofz'apparatus t e material to if dried dccupies a relatively small part of. he space in-the machines and is in intimate contact or mixture with the (1 ing glases must be used, as in drying wheat or 0t er. grains in tower driers in which case avery large and very high apparatus-and an extremely large volume of jat ordinary the mas of material mg gases but a small part. of the time and t ese. machines; therefore have-.a relatively smallcapacity in relation to'g their size. This is particularly true wheti' 'relatively coldfdry il speratur s ust 11 y c011 siderable drying efiect. .In the case of such as wheat the dryin thus secured is only superficial and is submit to the changes in moisture content of the air used in drying which may have practically no drying effect at all durin rainstorms or periodsof high humidity. n all these forms of' apparatus the material is subjected to considerable abrasion and bruising which. is detrimental to many products and also results in the, formation of fines which are blown away in the drying gases. i

Th's invention aims to overcome all these objections and disadvantages by'the use of a new method of drying by which the capacity f. the apparatus per unit volume is very greatly increased, greater efiiciency of drying b the gases is secured and practiv cally all ruising and abrasion of the material prevented and the temperature'of drying may be easil regulated and controlled. This new met od consists in passin a current of drying granular materia 1. e., forcing the drying gas under sufficient pressure throu h the voids between the particles and thus v ringing the gas through a bed of the s into intnnate-contactuw'ith-thejm dividua grains. This maybe done in a method of drying should preferably be carried out in counter-current fashion.-

Myx preferred manner of utilizing this new method consists therefore in passin the granular product to be dried downwar as a mass through a vertical shaft and at the same time forcing the-d 'ngg'ases up throu h the mass in the voidz between the granu ar products. In this way ra'cticall the entire drying apparatus is lled wit material to bedried and this material is in the most intimate contact with the drying gases during the entire "time of passage through the apparatus. The apparatus has therefore a very large capacity per unit of volume: Due to the. intimate mixture of the sees and solids and their counter-current ow the drying efliciency of the gases s no. I

would be practical with the methods of dry now in common use, due to the low capacity of the apparatus using these methods.

To secure the'greatest eiliciency in using my method it is necessary'that the flow of material downward through the dryin shaft and the flow of drying gases upwar through the mass of material be practically the form an continuous and uniform over the entire hori- -zonta1= cross section of the mass of material in the shaft. To secure these conditions the material to be dried should be fed practis cally continuously onto the upper part of the chargeand should be dischar ed from the lower part of the charge at t e same rate, and the discharge from the bottom of the charge should be substantially uniform over the whole bottom and the depth of Y the charge should be substantially the same in all parts. The finer the granular particles,- the more exactly must these conditions be met to secure good results. With coarser material the depth ofthe charge need not be so exactly the same in all parts.

To secure these conditions in my method of drying, I use the type of apparatus shown in the drawings which consists in general of av'vertical'shaft, to contain the material to be dried with means for feeding the material substantially continuously and at 'a uniform rate, into the top of the shaft and distributing it over the whole area of the shaft, and means for substantially continuously discharging the material at auniform rate at the bottom and/uniformly over the entire bottom of the char e, and means for forcing d ing'gases u t rough the charge from the ttom to t e top. means for heating the ases to the desired temperature will be use in most cases as the volume of drying gas is so very much less when it is 'warmas compared with cold gases that the cost of warming the gases is much 'less than the cost of forcing the much larger v gases are intr volume of colder gases through the charge.

It'will be ap arent that many variations details of construction will be possiblein an apparatus of this type.

The drawings show some of the forms of my apparatus which may be used for this 11 a on:

p 1is a verticalsection on "a fiameter Extraneous of a circular form of theap aratus, Fig. 2 a

.plan'view of the same an using no mechanical discharge device. 1g.

Fig. 3 a horizontal section of the same just above the 7 shows a vertical section of a type of the apparatus of which Fig. 8 is a partial plan View. Figs: 9 and 10 are enlarged sections of the discharge device or feeder which may be used in the form of apparatus shown in Figs. 1 and 3,.and Figs. 11 and 12 enlarged sections of the discharge. device or feeder which ma be used in the form of apparatus shown in igs. 4 and 5. Fig. 13 is a vertical ,section on line A-A of the plan views shown in Figs. 14 and 15 of m preferred form of a paratus. Figs. 16 an 17 show a form of istributing device which me. be used with the form shown in Fig. 15, 16 beinga plan view and 17 a vertical sectionona-diameter-of 1g. 16. Fig. 18 is a vertical section of the simple apparatus for intermittent drying.

As previously stated the preferred apparatus consists in general of a vertical shaft (1) which may be square or rectangular or circular in cross-section. The length of the 'shaft will depend on the depth of the char used which willin turn depend on the time of drying and the nature of the charge. 'lhe'i lofiger the time required,

the longer. the 'shaft, and the-coarser the the charge is a discharge device or discharge and a suitable distributing device orrake (3) or feed hopper (11) to keep the top of the charge level. At the bottom offeeder (4) which maybe constructed in a number. of difierent ways. The function of this feeder is to substantially continuously discharge the dried material uniformly over a the whole bottom of the charger The means used to cause the current of drying gas to flow up through the charge may also be of difierent forms; In my preferred form the bottom of the shaft beneath the discharge feeder (4) is closed by a suitable hopper (5) or plate or housing (40) and hopper 5) as ownin Fi 1, 4; 13 and 15 and the or closed space (7 under pressure throu h a'presshrepipe (8) and pass u throu h t e discharge "coder (4) and up throng the uced into this hopper' (5) j char e. The dischargehizpper (5) has a suite le-discharge spoutat its lower oint through which the dried roduct is discharged. This spout should be ept filled in a portion of its length in-order to prevent touch the plates (23).

escape of the drying gases through it. Another method of passing the gases up through the charge consists in the use of stationary perforated pipes (10) in the lower part of the shaft as shown in Figs. 6 and 7. These pipes are connected with the main pressure pipe (58) outside of the shaft and are so arranged that the dried product may flow downward around them and be discharged at sufiicient distance beneath the pipes to secure a uniform flow and discharge.

As noted the feeding device may consist of spouts (2) alone or a spout and rotary feeder hopper (11) or a' spout (2) and suitable leveling devices (3). The spouts alone may be used with coarse granularmaterial and the feeding (2) and leveling devices (3) with finer. material. The exact form of this part of the apparatus will depend on the nature of the product and the shape of the shaft. With the circular forms as shown in Figs. 1, 6 and a rotating feed hopper (11') or spouts (2) and a rotatingrake or levelling device (3) may be used. If desired the necessary'levelling may be done by hand at suitable intervals. The form of the discharge device may vary with the shape of the shaft. In the circular forms as shown in Figs. 1, 2, 3 and 9 it may consistof two sets of concentric circular plates, one set slightly above the other, both the upper set (13) and the lower set (14) being stationary and staggered so that the dried product cannot pass down throu h the annular openings (15) and (16).1nto the hopper. As shown the lower rings of the feeder (14) are beneath'the annular opening (15) between the upper rings so that the dried product may flow through the upper openings (15) onto the lower rings (14). The material on these lower rings (14) is continuously removed bythe plows (17) which project up through the annular rings (16). The plows are attached to the radial arms (18) which are attached to the rotating shaft (19') to which the feed hopper (11) is also attached. Fig. 10 shows a rotary feederwhich is similar to the foregoing except that the plows (7 are attached to the .upperrings.

(13) and the lower rings rotate being supported by a suitable spider (20) which is attached to the central shaft (19). In the square form of any apparatus a reciprocating discharge feeder'ofthe type shown in Figs. 4, 5, and 11 may be used. This c0nsists of an upper set of stationary parallel plates (21) separated byopenings (22). Beneath the upper set is a similar set of parallel plates (23) with openings (24) so arranged that the plates (23) are beneaththe openings (22) so that no dried product can flow into the hopper (5) beneath. In the middle of each opening (22) is a'stationary vertical'plate extending down so as to almost The plates'(23) are supported by the. beams (25) and moved backward and forward by the rod (26) and eccentric (27) (or other reciprocating device) so that the material on the plates (23) is pushed off through the openings (24).

The discharge feeder shown.in Fig. 12 is forth on the lower plates by the reciprocating device (26 and 27). As will be readily seen by the use of these feeders a substantially uniform discharge from the whole area of the bottomof the charge is' secured and that the rate of downward flow of the charge may be accurately regulated by the speed of the feeder mechanism.

If it is necessary or desirable to secure a very uniform feed intothe top of the shaft (1) over the whole area of the shaft this may be secured byfeeding the material into the top of the shaft through a feeder similar to those described and shown in the foregoing and shown in Figs. 1, 3, 4 and 5, instead of by means of. leveling devices as previously described. I

Another type of discharge feeder, which is my preferred type for many purposes, is shown in Figs. 7, 8 and 13, 14 and 15. This type of feeder consists ofan endless belt which is held in place on the two pulleys (30) and supported by the plate (31) beneath the charge. The part of the belt on which the charge rests, which is supported by the plate (31), is pulled forward toward the discharge side or hopper by turning one (or both) of the pulleys, preferably the one near the discharge, by applying powerto the pulley(or gear or sheave) (32). In order to secure a uniform discharge over the whole.

bottom the transverse vertical distributing plates (33) are used. These extend across the charge above the belt and are arranged preferably at equal distances apart and the lower edges in a sloping plane, extending from the rear edge (34) of the shaft at the level of the belt to the edge (35) of the d scharge opening in the front of the shaft.

In this way a layer of equal thickness is removed from each of the spaces (36) between the vertical plates (33), thus securing a similar discharge from the entire bottomof the charge. As shown in Fig. 15 this type of discharge feeder may be used with a shaft of circular cross section. In this case the lower edges of the portions (37) of the side of the shaft between two adjacent plates 'should slope upward from lower edge of the tions (38) of the rear distributing plates (33) which extend beyond the next plates to the rear, should be at the same level as the next plate to the rear, in order to secure a uniform downward flow over the entire cross-section of the char e. This type ofdischarge feec er may be enclosed in a housing (40) as shown in Figs. 13 and 14 into which the drying gases are forced through the inlet pressure pipe (8). In thiscase a perforated supporting plate (61) is used and the endless belt (59) is also perforated so that the drying gasesmay pass up through the supporting plate (61) and belt (59) and upward through the charge. The belt may be made of any suitable chain or link or screen construction with small enough openings so that'the dried material will notrun through or blind the openings. This type of discharge feeder may also be used without the enclosing housing as shown in Fig. 7 In this case the belt (33) is'supported on the bottom (41) of theshaft and enters beneath the charge through a slot (42) at the rear of the bottom of the shaft.

The sides (43) and top (44) of the discharge passage (45) are extended so as to prevent excessive leakage of the drying gases through the discharge opening (46). The drying gases are introduced into the charge through the perforated pipes (10) connected with the pressure pipes (8) as previously described. v

Fig. 6 shows a vertical section of a form of my apparatus in which no discharge feeder is used the discharge being regulated at the end of the discharge spout (9). This form is not my preferred type as a uniform downward flow of the charge cannot be secured except in small machines. The drying gases in this form are introduced through the perforated pipes 10) from the pressure pipe (8). This form may be either circular or-square in cross-section.

For intermittent drying the. simple apparatus shown in Fig. 18 may be used. This consists of a vertical shaft or box (1) of any desired shape in cross-section with a closed bottom (47) and a grating (48) above the bottom, and a ressure (or vacuum) pipe (8) connected wit the open space (5) beneath the grating. The charge is filled into the upper part of the shaft and levelled and air is then forced through the charge from the pressure pipe (5.). (Or may be drawn down through the char e by application of suction to the pipe (8). When the charge has been dried it is removed from the grating by any suitable means, such as dropping the grating and a new charge supplied.

From the foregoing description the operation of my apparatus will be apparent so that an extended description will not be necessary. To secure the best results a substan tially continuous feed should be supplied to esa-rec the to of the charge which should preferably l? maintained at ap roximately the same level at all times and a substantially continuous discharge at a uniform rate should be maintained. The drying gases should also preferably be supplied at a uniform rate and pressure. Good results may also be securedby intermittent. continuous operation, i. e.,by feeding and discharging at short intervals with no movement of the charge between providing the intervals are not too long. r The depth of bed and amount of drying gases and the required pressure and temperature of these will vary with each materia to be dried agpording to the nature of the material, the size of the grains, the moisture content, the dificulty of dryin and the desired drying effect. As previous y noted, the invention is especially. applicable to the drying of material which are dried with difficulty and which must be dried with relatively low temperature drying air or gas, such as wheat and other grains.

Having described my invention, what I claim and desire to patent is:

1. The apparatus for drying grains and granular products which consists of a vertical shaft for containing a bed of such above said material, a discharging-device arranged to-support a such said bed and arranged to discharge such above said material from the bottom of a such above said bed in such amanner as to secure a substantially uniform downward movement of the material in all parts of said bed, means for forcing a current of a gaseous medium upward through such above said bed in said shaft.

2. The apparatus for drying grains and granular products which consists of a vertical shaft for containing a bed of such above said material, means for feeding such above said material onto the top of such above said bed in said shaft and means for maintaining the top of a such said bed substantially level; a discharging device arranged to support a such saidbed and arranged to discharge such above said material from the bottom of a such above said bed in such a manner as to secure a substantially uniform downward movement of the material in all parts of said bed, means for forcing a current of a gaseous medium upward through such above said bed in said shaft.

3. The apparatus for continuously drying grains and granular products which consists of a vertical shaft for containing a bed of such above said material, means for continuously feeding such above said material onto the top of such above said bed in said shaft and means for maintaining the top of a such said bed substantially level; a dischargin device arranged to support a such said be and arranged to continuously discharge such above said material from the bottom of a such above said bed in such a manner as to secure a substantially continuously uniform downward movement of the material in all parts of said bed, means for continuously cal shaft, for containing a bed of such above said material, which is closed at thebottom and has adischargin device therein above said bottom arran e to support a such above said bed an arranged to allow the passage of a current of gaseous medium up through said device in such a manner that said current of gaseous medium will be substantially uniformly distributed over the entire horizontal section of said bed and arranged to discharge such above said material from the bottom of such above said bed in such a manner as to secure a substantially uniform downward movement of the material in all partsof said bed, means for introducing a current of gaseous medium under pressure into the closed space beneath said discharge device, and means for removing the such above said. material removed from the bottom of such above said bed from the lower part of said apparatus.

5. The apparatus for drying grains and anular material which consists of a vertical shaft for containing a bed of such above said material, said shaft being closed at the bottom, means for feeding such above said material onto such above said bed in said shaft and means for maintaining the top of'a such said bed substantially level,

a discharging device in said shaft abovesaid closed bottom arranged to support a such above said bed and arranged to allow the passage of a currentof gaseous medium up through said device in such a manner that said current of gaseous medium will be substantially uniformly distributed over the entire horizontal section of said bed and arranged to discharge such above said ma terial from the bottom' 'of such above said bed in such a manner as to secure a substantially uniform downward movement of the material in all parts of said bed, means for introducing a current of gaseous medium under pressure into the closed space beneath said discharge device, and means for removing the such above said material removed from the bottom of such above said bed from the lower part of said apparatus.

6. The apparatus for continuously drying grains and granular material which consists of a vertical shaft for containing a bed of such above said material, said shaft being closed at the bottom, means for continuously feeding such above said material front of said shaft.

onto such above said bed in said shaft and means for maintaining the top of a such said bed substantially level, a discharging device in said shaft above said closed bottom arranged to support a such above said bed and arranged to allow the passage of a current of gaseous medium up through said device in such a manner that said current of gaseous medium will be substantially uniformly distributed over the entire horizontal' section of said bed and arranged to continuously discharge such above said material from. the bottom of such above said bed in such a manner; as to secure a s'ub-' stantially continuously uniform downward movement of the material in all parts of said bed, means for continuously introducing a current of gaseous medium under pressure into the closed space beneath said discharge device, and means for continuously removing the such above said material removed from the bottom ofsuch above said bed from the lower part of said apparatus.

7. The apparatus for securing a substantially uniform downward movement of the material in all parts of a bed of material in a vertical shaft which consists of an endless belt feeder beneath said shaft, and arranged to support the material in said shaft, with transverse vertical plates above said belt and extending across said shaft and spaced at substantially equal distances apart from the back of said shaft to the discharge opening in the front of said shaft and having their lower edges in a sloping plane extending from the lower edge of the back of the shaft at the belt to the upper ed e of the discharge opening in the front of t e shaft.

8. The apparatus for securing a substantially uniform downward movement of the material in all parts of a bed of material in a vertical shaft which consists of an endless belt-feeder beneath said shaft, and arranged to support the material in said shaft with transverse vertical plates above said belt and extending across said shaft and spaced at substantially equal distances apart from the back of said shaft to the discharge opening in the front of said shaft and aving their lower edges in a sloping plane extending from the lower edge of the back of the shaft at the belt to the '11 per edge of the discharge opening in the rout of the shaft, with means for causing the movement of the upper art of said belt from the back of said sha to the discharge In testimony whereof I' have signed my name to this specification.

Y NIELS C. CHRISTENSEN.

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