US1573144A - Method and apparatus for drying - Google Patents

Description

Feb. 16 1926.

J. CREDO METHOD AND APPARATUS FZOR DRYING Filed May 24, 1924 INVENTOR tn cm, M

T ORNEY Patented Feb. 16, 1926.

UNITED STATES PATENT OFFICE.

JULIUS CREDO, OF LOUISVILLE, KENTUCKY, ASSIGNOR TO LOUISVILLE DRYING MA- CHINERY CO. INC., OF LOUISVILLE, KENTUCKY, A CORPORATION OF KENTUCKY.

METHOD AND APPARATUS FOR DRYING.

Application filed May 24, 1924. Serial No. 715,503.

. act description.

My invention relates to a method and apparatus for drying and has reference more particularly to drying in rotary dryers.

An object of the invention is to be able to dry at a temperature below that at which the Substance to be dried is injured, and with an economy of air and at a reduced air velocity to decrease the loss of the finer par- .ticles of the dried substance.

Another object of the invention is to reg,- ulate the temperature of evaporation by the volume of air supplied.

A further object of the invention is to control the rate of evaporation by a supply of additional air.

Another object of the invention is to provide a rotary dryer suitable for carrying out my method of drying.

In the appended drawing I illustrate a form of an apparatus suitable for carrying out my method and in which Figure 1 is a longitudinal section on line 1-1, Figure 2,

Figure 2 is a cross-section on line 22, Figure 1, showing the rear head, and

Figure 3 is a cross-section 'on line 33, Figure 1, of the head only.

In methods of drying in rotary cylinders hitherto employed, the wet material in entering the dryer is forced to a temperature which is injurious to the substance to be dried. As for example, pomace when first introduced into a dryer is subjected to air having a temperature of about 17 5 degrees F., saturated with water vapor, thus being subjected to a high vapor pressure. As heat from the tubes is being constantly supplied to the material, and it cannot, because of the vapor pressure give up any moisture until it first assumes a temperature higher than 175 degrees F., it is rapidly heated far above that dew point temperature. Of course, as the wet material .progresses through the dryer and meets air of constantly lowering temperature, and lowering vapor pressure as well, the evaporation of water from it proceeds moreand more rapidly and the material cools in proportion. The damage to the material, however, has already been done at the beginning of the process, because firstly, its temperature has been forced to rise above 160 degrees -F., which is injurious to the pomaces and the color has deepened, and secondly, because the temperature was high while the material contained the maximum of free water, a hydrolization of the pectin resulted, with a lowering of quality and marketability.

To cure this condition requires the passing of a much larger than usual volume of air through the dryer in a given time, so that the air exhausted from the dryer will be at a lower temperature and a much lower saturation than at present. Tests indicate that three times as much air as is now employed will suflice for pomace. This, however, would have the effect of tripling the velocity of the air through the cylinder and would carry out of the dryer a prohibitive percentage of the finer particles of the material to be dried.

To overcome this, I propose to introduce air from both ends of the dryer, taking it out between the ends. This arrangement permits meto introduce the necessary volume of air but the velocity is increased only fifty per cent over the original. By this proposed change I will be able to discharge the dried materal from the dryer with a residual moisture content of about ten per cent and at a temperature of 140 degrees F., or even less. This temperature is below 160 degrees F., for pomace, and. the improvement in the quality of the dried material is very striking. The color of the dried product is lighter and it contains more water soluble pectin, and therefore it commands a higher price. Such results are obtainable also with other substances of a similar nature that are now dried in rotary dryers of this type.

To carry out my method of drying I employ a rotary cylinder 5 terminating at the ends with hollow heads 6 and 6 secured to the cylinder. The cylinder is supported on rollers 7 preferably near each end of the cylinder, in amanner thatit is maintained in a slightly inclined position, the high point being the inlet end for the material and the lower end the discharge end for the material to be dried. Rotary motion is transmitted to the cylinder through a connected by tubes 14 extending through the cylinder 5. The said tubes 14 are suit ably disposed in the cylinder to supply the maximum amount of radiant and transmitted heat when steam is supplied to the tubes. The housing 10 has also an air inlet 15 through which air may be supplied to the cylinder at the raised end. The air supphed at this end is controlled by a damper 15' and will travel in the same direction as the material which is fed through the cylinder. The head 6 at the hollow of the head 6.

lower end of the cylinder fits into the stationary housing 16. The said housing 16 has a. central passage 17 leading into the A steam conduit 18 is connected to the central passage to supply the steam to' the head 6 from where it passes to the head 6 through the tubes 14.

The housing 16 has also an air inlet 19 through which air is introduced to pass into the cylinder through the apertures 13 of the head 6. The air entering the head 6' is controlled by a damper 19 and will flow in a direction opposite to the travel of the material in the cylinder. The housing 16 has a suitable conveyor 20 for discharging the dried material which is delivered to thehousing 16 through the openings 13 of the head 6.

Somewhere along the length of the cyhnder between the heads 6 and 6, I provide a stationary housin 21 which encompasses the cylinder and whlch is in communication with the interior of the cylinder through a series of air outlets 22 carried by the cylinder. The outlets 22 extend from the periphery of the cylinder to a point above the level of the material to be dried which is maintained in the cylinder, and the apertures 23of the outlets 22 are so formed that the material to be dried cannot enter the said apertures 23 while the cylinder is rotated and the material is caused to rise and fall by the motion of the members and the tubes provided in the cylinder. The air laden with moisture escapes through the apertures 23 into the outlets 22, thence into the housing 21, from where it may be carried off either by a high stack or an exhaust fan.

The material as it travels from the higher to the lower end of the cylinder, is subjected to the radiant and transmitted heat supplied to the tubes The air to carry off the,

the maximum temperatures to which the.

material is heated initially, and then the rate of evaporation of moisture caused by the heat supplied by the tubes.

The temperature is controlled in the dryer by the manual setting gjfibf the dampers and this is dependent upon the temperature desired and the location of the air outlet.

I claim 1. In a method of "drying, steps which consist in feeding substance to be dried in one direction, supplying air from opposite directions to the substance to be dried, heating the'substance and the air and removing the products ofevaporation and the air supplied.

2. In-a method of drying, steps which consist in feeding and heating the substance to be dried, supplying air from opposite directions to the substance so that the air meets, and removing the air supplied and 3. In a method of dr ing in a rotary dryer, steps which consist in feeding the substance to be dried from the inlet to the outlet end of the dryer, introducing air from both ends of the dryer, heating the substance and air in the dryer, and removing the air and products of evaporation at a place between the ends of the dryer.

4. In a method of drying, steps' which consist in causing a progression of the material to be dried, subjecting the material while it is being progressed first to an air current moving into the same direction with the material and then to an air current moving in a direction opposite to that of the material, heating the progressing material and the oppositely moving air currents and regulating the air volume moving in opposite directions. v

5 In a method of drying, steps which consist in causing a progression of the material to be dried, subjecting the material to egulate currents of air flowing in opposite irections and heating the material and air currents,

' heating the pomace while. it is being fed,-

In a method of drying, steps whicli, consist in causing a pro on of? the ma terial to be dried, -heatingthe material while it progresses, regulatingthe temperature of eva ration by the volume'o atmos'pheric a1r caused to flow in a direction with that of the materialbutin a difieren't' path, and controlling the. rate of eva oration by a supply of additional atmosp eric air which flows insa direction opposite to that of the material but in aidifierent ath ofsaid material. I q

7 A method of drying pomace in-a' rotary dryer, which consists in feeding thepomace from one end to the other of the dryer,

andremoving. the air and the products of evaporation substantially from the middle part of the cylinder. I a y Y I '9. In a method of drying pomac'e, steps which consist. in feedingthe pomace theinlet to the outlet end of rotary dryer,

introducing air' from the inlet and the outlet end of the dryer, heating the pomace' and the air and removing theair'and the prod not of evaporation between theends of the 10L Inc-a method" of drying pomace, etc 5 1 which. consist in supplying air all over t eration from above of the pomace.

'pomace,-heating the omace and the air and removingthe air an the'product of evapothe air at places between {the ends of the 11. In a' dryer, a cylinder having lets at each end and an air outlet between the-ends;v

12."In a dryer, a revoluble" cylinder thro h which a substance to be dried may and heated, said cylinder having an air inlet at each end and an air outlet be-' tween the ends.

13. In 1 a (1 er, a" revoluble 0 means whereby eat may be supplie means of the cylinder to discharge the "substance linder,

vat one end of the cylinder to,.feed-the sub i r I stance to be dried, means at the other end dried, said cylinder having an air inlet at each end, a housing associated with the from the cylinder,

cylinder between the ends thereof, means establishing communication between the cylinder and the housing for delivering the clip and the product of evaporation to said 1 ousi '14. n' a dryer, an inclineiii revoluble cylinder having air inlets at eaclig'e'nd, means for supplying heat to the cylinder, means at the higher end for receiving material to 'be dried and feedingit. into the cylinder,

means at the lower end for discharging the dried material, a. housin encom assing the.

cylinder between'the en s of Said cylinder,

said cylinder'having outlets forthe air and product of evaporation leading into the housi in one direction, supplying air to" the substance from opposite directions, so that the of evaporation from 'the substance, substan iiifamahtdhf drying, steps which consist in feeding the substance to be dried air currents meet, heating the substance and I air, and removingtheair and the products my, tially as the meeting point of the air cur- "rents Y n a and substantially midway I

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