US1467306A

US1467306A - Method of and apparatus for drying and conditioning materials

Info

Publication number: US1467306A
Application number: US507670A
Authority: US
Inventors: Willis H Carrier
Original assignee: Carrier Engineering Corp
Current assignee: Carrier Engineering Corp
Priority date: 1921-10-14
Filing date: 1921-10-14
Publication date: 1923-09-11
Anticipated expiration: 1940-09-11

Description

Sept. ll, 1923.

W. H. CARRIER METHOD OF AND APPARATUS FOR DRYING AND CONDITIONING MATERIALS Filed Oct. 14, 1921 6 Sheets-Sheet 1 Sept. 11, 1923. 1,467,306

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Sept. 11, 1923. 1,467,306,

l w. H. CARRIER METHOD OF AND APPARATUS FOR DRYING AND CONDITIONING MATERIALS File oct. 14, 1921 6 sheets-smet 2)) l k w N a X Sept. '11, 1923. 1,467,306

w. H. CARRIER l METHOD OF AND APPARATUS FIOR DRYING AND CONDITIONING MATERIALS Sept. 1l. 1923.

lW. H. CARRIER METHOD OF AND APPARATUS FOR DRYING AND CONDITIONING MATERIAIS 6 Sheets-Sheet 5 lFiled Oct. 14 1921 Sept. 11,` 1923.

Filed Oct. l14 1921 W. H. CARRIER f METHOD OF AND APPARATUS FOR DRYING AND CONDITIONING MATERIALS 6 Sheets-Sheet 6 -l ,4 Treffs/5K5.

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it TUS FUR DEYIING; AND CONDITIONING In? n, n JERSEY, .assieme 'ro cana-:ae nul aerienne f: aan, any".

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' To all 'wlw/m it mayconoem:

Be it known that I, WILLIS H. C Aniurm, a citizen of the United States, residing at Essex Fells, in the county of Essex and State of New Jersey, have invented anew and useful Improvement `in Methods of and A paratus for Drying and Conditioning aterials, of which the following is a specification.

This invention relates to methods of and apparatus for drying materials. in the drying of materials, it is desirable in order to attain the'best results, to use diderent rates or schedules of drying eects for the different materials, 'dependin upon their different .characteristics or t e final results required. It is also an advantage to be able to tion is to produce a definite predetermined schedule o the rate of drying, the rate of drying being more rapid at the beginning and decreasing slowly or gradually as the material dries. conspicuous novel feature of the system is that the drying' capaci-ty is definitely predetermined and fixed by introducin a relatively small but constant amount o air having a constant temperature and a definite degree of dryness, .that is a definite moisture content or a definite wet bulb temperature with respect to the dry bulb temperature. An important advantage of this process is that the schedule can be varied to suit particular individual requirements of materials'by simply reducing the air quantity and raising its temperature, or increasing the air quantity and reducing its temperature, giving the same total rate of drying with the saine wet bulb temperature. In ,the first case, the rate of drying will be more evenly sustained, that is it will be more nearly uniform througout the drying process until the material is completely dried. In the second case, the rate of drying will fall oil' more rapidly as the drying progresses and may becomeexceedingly slow at the last part of the drying, whic is a necessary requirement 1n drying certain products.v

By this system the amount of drying can be definitely measured and controlled from a 50 source independent of conditions in the room itself. The difference between controlling'this way and controlling in the room is that in the room control one gets a constant condition of tem rature and relative humidity whileI by this system one gets a progressively increasing temperature and correspondingly progressive, decreasing relative humidity. If this same result were to be obtained by controlling the conditions in the room, it would be necessary either to make frequent adjustments of the control instruments by hand or have an automatically adjusting or changing instrument located in .the room to give the required schedule. As disclosed in this case, the control is edected b independently regulating the wet bulb an dry bulb temperatures or the air supplied, but it could also be accomplished by other means which would fix the 3@ inisture content of the entering air, as for instance, by controlling the dew point of the entering air or controlling the relative humidity of the entering air by means of a Q5 hyrostat.

ther objects of the invention are to accomplish such results by a method and apparatus in which a relatively large volume of air is circulated for the treatment of the material, but in which it is only necessary W to conditionl a relatively much smaller volume of air so that .large quantities of 'material can be properly dried with definite results, .by means of a comparatively small and inexpensive ap small quantity of air; also to improve and simplify drying systems in the other respects hereinafter described and set forth in the claims.

It is known that the absorption of one 1G@ from the material by each cubic foot of air l@ will be equal to the drop in temperature between the air entering-and leaving the material divided by 8%. ln the method and apparatus of this application, this principle is employed and the rate of drying of the 1l@ ratus handling only a. @5

material is detinitel predetermined as required by fixing or etermining the volume and the moisture content of the air supplied to the drying chamber so as to ve the required drop in thetemperature tween the air entering and leavin the material. Ac-

cording to this metho the drying is effected and the rate of drying definitely controlled as required, depending upon the characteristicsof the material being dried, by supplying to the dryin chamber a relatively small volume of air w ich is caused to mix with a relatively much larger volume of air in the drying chamber, circulating the mixed air through the material and regulating the volume and condition of this relatively small volume 4of air supplied to the drying chamber so as to maintain a predetermined wet bulb temperature in the drying chamber and give a predetermined, definite drop 1n temperature between the air supplied to the drying chamiber and the air leaving the ma'- terial. The required temperature and hu- 'midity of the air supplied to the chamber can be obtained by various means but preterably by mixing outside air and return air from the chamber and adding moisture and heat as may be necessary to give such required temperature and humidity to the air su lied.

y improved methodl of drying is explained in detail in connection with the description of the o eration of the apparatus lfor carrying out t e method.

In the accompanying drawings, apparatus of three slightly dii'erent arrangements are illustrated for carrying out the method.

Fig. 1 is a partly diagrammatic longitudinal sectiona elevation lof an apparatus embodying the invention and adapted for carrying out my improved method.

Fig. 2 is a sectional plan view thereof, on line 2-2, Fig. 1.

Fi 3 is a sectional plan view thereof, on a redilced scale, on line 3 3, Fig. 1.

Fig. 4 is a view similar to Fig. 1 of an apparatus of slightly modified arrangement.

Fig. 5 is a sectional plan view thereof on line 5 5, Fig. 4.-

Fig. 6 is a view similar to Fig. 1 of still another arrangement of apparatus embodyin the invention.

lrig. 7 is a sectional plan view thereof on line 7 7, Fig. 6.

Referring first to Figs. 1 to 3, A repre-4 sents a drying chamber in which the material B is preferably arranged on trucks,

racks, trays or otherwise, as may be most suitable, depending upon the nature of the material, so as to leave unobstructed spaces in the chamber at three adjoining sides of the material, that is, for instance, at opposite ends of and above the material, and provide flow passages for the air through the material, preferably arranged so that the air Merece can circulate horizontally through the material from one end of the chamber or the other, as indicated by the arrows.

10 represents a supply duct for delivering air, conditioned as to temperature and humidity, to the drying chamber. ln the `arrangement shown in Figs. 1 to 3, this supply duct 10 is provided with a discharge head 11 equipped with a plurality ot nozzles 1l and extending horizontally across the chamber in a space 13 between one end of the material .and a plurality of air circulating fans 14 arranged in openings in a partition 15 extending across the drying chamber. These fans,'the number of which depends upon the width ot the drying chamber, and which may be driven by any suitable drive mechanism, draw the air in the chamber through the material and force it up into the near -end of the unobstructed space above the material and also draw in airthrough the supply duct 10, causing `it to mix with the larger volume of circulating air in the chamber and causing the mixed air to circulate in the chamber and repeatedly pass through the material, as indicated by the arrows. Preferably a false ceiling 15 extends from the partition 15 lengthwise in the drying chamber above the material, forming a space through which the air discharged by the fans 14 flows to the opposite end of the material.

16y represents a return air duct leading from the end of the chamber at which the fans are located tothe air supply duct 10, and the latter is provided with an open, outer end 17 for the admission of outside or fresh air. The

ducts

10 and 16 are controlled by fresh and return air dampers 18 and 19 of any suitable sort connected by suitable mechanism 20 whereby the opening ot one damper will cause the closing of the other damper, thus enabling any desired proortion of outside or fresh air and return air rom the chamber to be supplied to the chamber. 21 represents a steam radiator or heater for heating the air supplied to the drying chamber and 22 represents means, prefer ably consisting of one or more steam disdrying chamber and controls the heater 21 through any `suitable or usual instrumentalities, such as a diaphragm valve24 in the steam supply pipe 25 for the heater and actuated by compressed air supplied by a *pipe 26 under the control of the thermostat 23. The wet bulb tem erature ot the air supplied tothe-drying c amber is controlled preferably by a wet bulb thermostat 27 f Menem ,A

the wet bulbtemperature of the 'air'su plied to the drying chamber, and contro the steam nozzle 22 and the fresh and return air dampers 18 and 19 through any suitable or Vusua instrumentalitiessuch as a diaphra valve 28 in the steam supply pipe -for t e nozzle 22, anda damper actuating motor 29, the diaphragm valve 28 and motor 29 being actuated by compressed air supplied by a pipe 30 under the control of the wet bulb thermostat 27. The dry bulb and wet bulb thermostats 23 and 27' are ada ted to regulate respectively the dry and wet ulb tempe-ratures of the air Supplied by the duct 10 to the drying chamber so that the air will be delivered to the chamber with a'v definite dry bulb temperature of, for ex ample 152 F. and a denite Wet` bulb temperature of for example 100 F. rlhe dry bulb thermostat is adapted to regulate the supply of steam to the'heater 21 so as to maintain this dry bulb temperature and the wet bulb thermostat 27 is adapted to regulate the dischar e of steam from the nozzle 22 and change t e position of the fresh air andreturn air dampers 18 and 19 so as to maintain this predetermined Wet bulb tem-` perature.

31 represents a duct for the relief of air from the drying chamber, the duct prefer: ably leading from the space 13 in the chamber between the air circulating fans 14 and the adjacent end of the material B.

in the slightly ydierent arrangement of the apparatus shown in Figs. 4 and 5, the disposition of the material in the drying chamber and the means for regulating the dry bulb and f/wet bulb temperatures of the air supplied to the drying chamber are the same as explained above, but the arrangement of the air supply means is di'erent.

'In this Fig. 1-5 arrangement, the conditioned air is supplied to the chamber by a fan 35 located in the air supply duct 10 and the discharge head 36 of thel supply duct extends across the dryin chamber in the lower portion of the space 3 between the adjacent end oi the drying chamber and the partition in which the circulating fans 14 are located. ln other words,vthe air supplied by the supply duct 10 is delivered by the fan 35 into the dryin chamber at the pressure side of the circu ating` fans and is mixed with the larger volume of the air in the drying chamber and circulated throu h the drying chamber and material by the fgans 14. therwise, the control and operation of the system is the same as above described.

ln the apparatus as shown in Figs. 6 and 7 the air supply duct 10 leads to a fan 40 which is disposed in the dryin chamber in thev space between one end o the chamber and the adjacent end of the material andthis fan 4is provided with a discharge du'ct41 conlair from the supply duct 10 with the other .naar wat @a menage-haare which @2X- tends across thev drying chammr in the upper portion thereof and is provided with a .series of nozzles 43 disposed so as to discharge the air into the unobstructed-space above the material toward the far end of the f chamber. The fan 40 is adapted to draw in the airfrom the supply duct and also to draw the larger volume of air in the drying' chamber through the material and mix the air in the chamber and discharge. the 'mixed air into the space in the chamber above the material. The discharge of the air'at a reli V `atively high velocity from the vnozzles 43, and

the suction of the fan Ointimatel the conditioned incoming air with t e other air in the drying` chamber and induces a circulation of the 'whole volume of air in the chamber through the material. In this arrangement, as in the others described, the

-control of the wet and dry bulb temperatures of the air supplied tothe drying chamber isthe same as above described and the o eration of the system and maintenance of t e conditionsk in thedrying chamber are th same. v

ln each of the three dierent apparatus illustrated a relatively small volume of conditioned air is supplied to the drying cham` ber and is intimately mixed with the other air in the drying chamber and the entire volumeof this mixed air. which is many times' greater than that of the conditioned air supplied, is circulated so as to ow through or over and dry the material in the chamber. The relief duct permits the escape from the chamber ot an amount of air equal to the amount supplied by the duct 10, so that a substantially constant volume of air acts on the material at all times.

In drying material-by the apparatus and in accordance with, the method of this in vention, the ratio of the volume ofv condi.- tioned air entering the drying chamber to the entire volume of air circulated throu h proportional to the ratio of the drop in temlperture of the respective volumes of air.

For' example, if the Iair is supplied by the duct 10 with a dry bulb temperature of 152 and leaves the chamber at 106, and the entire circulating body of air in the chamber enters and leaves the material at temperatures of 108 and 106 respectively, then the volume of conditioned air supplied to the chamber should be approximately 1/22 of the entire volume of air circulatezl in the drying chamber. -If the heat transmission Ythrough the walls of the drying chamber is negligible, which is readily possible in a properly constructed drying chamber. the wet bulb temerature of the air circulating in and leavlng the drying chamber will remain the same as that of the air suppliedto the chamber in mixes accordance with the psychrometrical principle governing the evaporation of moisture. The dry' bulb temperature of the drying chamber and material will increase, however, and produce a graduali increasing Wet bulb depression and decreasing relativehumidity in the drying chamber as the drying proceeds and the moisture in the material lessens. The rate of drying is determined by the diiierence in temperature of the conditioned air entering and leaving the drying chamber, and any desired constant or decreasing rate of drying can be obtained by fixing the volumel 4and temperature of the conditioned air supplied to the drying chamber to suit the-drying conditions required. The volume of the air supplied can be regulated by any suitable means such asy an ordinary hand actuated damper in the air supply duct 10. When the appropriate volume and temperature for the entering air have been determined, the `volume and temperature thereof remain constant throughout the drying process or a desired period thereof. pSince the drying tendency is proportional to the wet bulb depression for a given quantity of moisture in the material, a more rapid drying at the end of the drying period can be secured by supplying a comparatively small volume of air at 'a high temperature. While a larger volume of air with a lower temperature will give a less rapid drying at the finish.

claim as my invention :A

1. The hereindescribed method of drying material which consists in circulating a body of air through the material in a dryingchamber, supplying to and mixing with said circulating body of air a relatively much smaller volume of air, maintaining a redetermiiied wet bulb temperature o said smaller volume of supplied air previous to its supply to the chamber, and causing said smaller volume of supplied air to enter the drying chamber with a predetermined dry bulb temperature higher than the temperature of the circulating mixed air entering and leaving the material, whereby a predetermined weight of-moisture is evaporated per unit quantity of the smaller volume of air supplied.

2. The hereindescribed method of drying material which consists in circulating a body of air through the material in a drying chamber, supplying vto and mixing with said circulating body of air a relatively milch smaller substantially constant volume of air, maintaining a constant wet bulb temperature of said smaller volume of supplied air previous to its supply to the chamber, and regulating the dry bulb temperature of said smaller volume of supplied air so that said air enters the drying chamber with a substantially constant dry bulb temperature higher than the temperature of the circulatgemene its supply to the chamber, and regulating the dry bulb temperature of saidsmaller volume of air so that said supplied air enters the drying chamber with a dry bulb temperature higher than the temperature of the circulating air entering and leaving the material and such as to maintain a predetermined drop in temperature between the air entering vand leaving the material.

4. The hereindescribed method of drying material which consists in circulating a body of air through the material in a drying chamber, suppl ing to-and mixing with said circulating bo y of air a relatively much smaller volume of air, maintaining a predetermined wet bulb temperature of said smaller volume of supplied air previous to its supply to the chamber, and predeterniining the volume andtemperatui'e of said smaller volume of supplied 4air so that the.

ratio of the volume of conditioned air entering the drying chamber to the entire vc-lumc vof air circulating through the material will be approximately inversely proportional to the ratio of the drop in temperature of the respective volumes of air.

5. The hereindescribed method oi drying material which consists in circulating a body -of air through the material in a drying chamber, supplying to and mixing with said circulating body of air a relatively much smaller volume of air, maintaining a predetermined Wet bulb temperature of said smaller volume of suppliedlair previous to its supply to the chamber. by mixing fresh air and return air from the drying chamber and regulating its humidity under the control of the wet bulb temperature of said air supplied to the drying chamber, and regulating the dry bulb temperature of said smaller volume of supplied air, so that said supplied air enters the drying chamber with a predetermined .dry bulb temperature ing mixed air entering and leaving the material, whereby a predeterminedweight of moistureis evaporated per unit quantity or the smaller volume of air supplied.

' 6. In an Lapparatus for drying material, the combination of a drying Vchamber in which the material is located, means for circulating the air in said chamber through the material, means for supply to and mixing higher than thel temperature of the circulatmiY and maintaining the same at a dry bulb temperature higher than the temperature ofthe circulating mixed air entering and leerling the material.

7. In an apparatus or drying material, the combination of a drying chamber in which the material is located, means for circulating the air in said chamber through the material, means for supplying'to and mix'- ing with said circulating body of air a relatively much smaller volume of conditioned air, means for the relieiE ot air from the drying chamber, means for regulating the humidity of said smaller volume of supplied air previous to its supply to the chamber, a heater for heating1 said supplied air previous to its supply to the chamber, a wet bulb thermostat induenced by said supplied air and controlling said humidity regulating means, and a dry bulb thermostat influenced by the temperature or said supplied air and regulating said heater.

8. ln an apparatus for drying material, the combination of a drying chamber in which the material is located,.means ,for circulating the air in said chamber through the material., a duct for supplying to and mix'- ingl with said circulatin body of air a relatively much smaller vo nine of conditioned airn said duct having a fresh air inlet, means for the relief of air from said drying chamber, a return air duct leading from said drying chamber to said supply duct, dampers controlling said fresh air inlet and return air duct, moisture supply means in said supply duct, a heater in said supply duct, a Wet bulb thermostat in said supply duct controlling said dempers and said moisture supply' means, and a drybulb thermostat in said supply duct controlling said heater, whereby said supplied air is maintained at a vpre-A and circulate 'with theother air in the cham.-

ber, said duct having a fresh air inlet, means for the relief of air from the drying chamber, a return air duct leading from the drying chamber to said supply duct, meansior regulating the wet bulb temperature of the air supplied to the dryingr chamber pre- I vious to its admission to the chamber includinr means for controlling the propor.

tions of fresh air and return air supplied to the chamber,-and means for regulating the dry' bulb temperatureof the air supplied to the drying chamber previousto its admission to the chamber, whereby said supplied air is maintained at a predetermined Wet bulb temperature and ata dry bulb vtemperature higher than the temperature of the air enterinu and leaningb the materia-l.

10. The hereindescribed method of drying material Which consists in circulating a body of air through the material in a drying chamber, supplying to and mixing with said circulating body of air a relatively much smaller volume oi air, regulating the moisture content of said smaller volume of supplied. air previous to its admission to the chamber so that said supplied air enters the chamber with a predetermined moisture content, and regulating the dry bulb temperature of said smaller volume of supplied air so that the dry bulb temperature of said supplied air entering the chamber is higher than the temperature of the circulating air entering,r and learingthe material and such as to maintain a predetermined drop in temperature between the air entering and leer ing the material. v

WlLLlS H. CARRER,