US2385809A - Drying apparatus - Google Patents

Description

oct. 2, 1945. R HOOPER l 2,385,809

DRYING APPARATUS Filed Nov. 11, 1942 Imvcntor:

RayL.]oo/ver,

Cttorneg Patentedoct. 2,

assasco 4ori-ics DBYING APPARATUS RayL. Hooper, Brevard, N. C., assigner to Eousta Paper Corporation, a corporation of Delaware Application November 11, 1942, Serial No. 465,280

2 Claims.

:In the manufacture of pulp, it is necessary to determine the moisture content of the pulp at different stages of the process so that subsequent treatments ofthe pulp with chemicals can be regulated accordingly.v The dependency of the processing conditions upon this moisture content makes it important to carry out the moisture determination quickly as well as accurately.

Also, it is advantageous to test simultaneously two or more samples at each stage so as to check the accuracy of thev test. v The equipment used generally heretofore for moisture tests comprises, the conventional gas or electric drying oven, or. small, individualsample, driers. The usual drying oven has -the disadvantage of being too slow and requires about an hour or more to make the determination. The individual-sample driers are limited to testing one. sample at a time and in actual practice have not been found sufficiently stable or durable tigo withstand continuous use in pulp mill operaions.

One other prior arrangement comprises a heating coil and a suction fan adapted to draw heated air vertically througha series of trays, one arranged above the other for holding'material to be dried. This type of equipment has been known for many years for drying large amounts .of fruits, meat, etc. But it is not satisfactory for use where quick, accurate, moisture determination on following more detailed description taken in conjunction with the accompanying drawing, in which:

Fig. 1 is a-diagrammatic view, with parts broken away, of the drying system;

Fig. 2 is a sectional view taken along line 2-2 of. Fig. l:

Fig. 3 is a fragmentary sectional view taken along line 3-3 of Fig. 2;

Fig. 4 is an elevational perspective view of one Y of the sample boxes; and

Fig. 5 is a modification of the box oi' Fig. 4. 'Referring now to the several' iigures in the 'Y drawing, the system'shown in Fig. al comprises small, separate samples is required, yas in the I.

above mentioned pulp processes. The main reason is that the same drying air comes into contact successively' with the several trays and the material on the first trays dries more quickly than that on the subsequent trays. Consequently l p non-uniformity of drying results. ,l

In accordance with my invention, all of the limitations and disadvantages that characterize the previous driers have been overcome. The drier that I have developed and used satisfactorily on a commercial scale will dry quickly and uniformly a number of separate samples and can be used substantially continuously every day on a full twenty-four. hour day schedule, the same as the pulp processing equipment.

One of the features of the drier of my invena blower fan il, a heater |I,a duct l2 with dampers Il, and a series of horirpntally arranged, reticulated, sample boxes shown generally at Il. In a typical factory installation the heater and fan may be located near the ceiling line, as indicated in Fig. l, and the duct may be suitably curved, as indicated at I5, to provide an exhaust outlet ISA near the floor line.

The lair heating unit Il' may be of any suitable type adapted for continuous use. In actual practice I have obtained very satisfactory results with aconventional ,encasedv steam pipe form of heater through which air is passed and discharged therefrom in a heated condition andcommonly used for heating rooms of buildings. The fan i0, which is normally an associated part of the unit, is of rugged construction and has suillcient capacity to provide a relatively strong current of air downward through the duct in the direction of the arrows.

If the fan in is of a suitable type to operate in, an inverted position, the duct I2 need not be v curved as at IZA, but may assume a straight vertion is a horizontal arrangement of individual sample boxes so constructed and disposed with respect to a forced stream of drying air that the pulp samples placed in these boxes are simultaneously, rapidly, uniformly and separately dried.

The construction and mode of operation of this drier will be clearly understood from the tical form. Likewise, ifdesired, the fan may be a suction fan, instead of a blower, and arranged at the bottom near the section I5 todraw the air through the heating unit Il and downward through the sample boxes Il.

The sample boxes il are arranged cross-wise the duct I2 in substantially parallel, side by side position as shown in Figs. 1 and 2. They are located at a convenient height above the floor level to permit easy access by the operator. Each box comprises a metal or other suitable frame I6 and perforated sides, bottom and ends, which may be made of wire mesh as indicated at I1 in Fig. 4. No topl cover is necessary although a perforated top could be used if desired. The sides and ends need not be perforated but in practice it has been found expedient to make them of the same mesh material as the bottom of the box. v

Hinged doors I8 are shown in Fig. 1 for covering duct wall openings adjacent each of th individual boxes so as to prevent loss of the drying air during operation and to permit introduction and removal of the individual boxes to and from the drying system. When in operative position the boxesare supported, within the drying area, by metal brackets or other cross pieces I9 that extend transversely across the width of the duct I2, as indicated in Fig. 3. 'I'he boxes I4 may rest directly on the cross supports I9 or on rails 2E. Instead of the cross pieces I9, a coarse mesh wire or lath sheet may be usedfor supporting the boxes I4.

Joined to or integral with the rails 20 are vertical separators or partitions 2I. .These members 2i` serve to separate each box from the adjacent box. The partitions may be just high enough for that purpose or they may extend the full height up to the dampers I3 as indicated in Fig. 1 and by the dotted lines 22 in Fig. 3. In the latter case each box is maintained in substantially separate and independent position from the other boxes and .hereby prevents any eddy currents of mois air to flow from one box to the other.

In the modification shown in Fig. 5, the box I4 is the same as that of Fig. 4 except that it has a solid end 23, and a handle 24 to facilitate inserting and removing the box. When this type of box is used, the door or cover I 8 may be omitted and the solid front end23 of the boxes closely iitted to the opening in the duct I2, so as to avoid escape of the drying air.

A specific example of the operation or use of this apparatus for drying pulp comprises placing previously weighed moist samples of pulp in the boxes, the weight of which is also known, and

passing vertically through the samples and boxes a current of hot drying air supplied from the unit Ii. Duplicate samples are usually tested in two adjacent boxes to provide a check on the acr curacy of the test.

The other two boxes may or may not be used at this same time. However, they may advantageously be employed for testing another duplicate 'set of pulp samples of different characteristics. In the usual case I permit the above drying operation to continue for about l minutes as a precaution although a substantially shorter length of time may be used for the I normal moist pulp sample. 1

When the drying period has been completed l the dried samples are reweighed and the moisture content of the pulp calculated inthe same way. This moisture value thus determined is useful and in most cases essential for regulating the amount of chemicals to be used for subsequent treatment of the pulp, such as for example caustic or chlorine for digesting and bleaching of the pulp.

The dampers I3, shown in Fig. 1,'may be ,used for directing the current of heated drying air upon all or selected numbers of the samples in sample boxes I4. If, for example, only two pulp samples are being dried at one time, the dampers l, may be closed so as to shut oi the two end b oxes and to concentrate the air upon the two samples in the two center boxes,

For measuring the temperature of the drying air, thermometer wells indicated at 25 are supplied ior the insertion of thermometers into the current of air owing through the drying boxes I4. In a typical case, the temperature of the air` may be around 210 F. when the dampers I3 areopen and all four dryingv boxes are being used. When the dampers are closed and only the two center boxes are in use, the temperature of the drying air in the restricted area will be somewhat higher and` generally may be around 220 F. It is to be understood, however, that these temperatures may be varied substantially with different types of materials being dried and with v different constructions of the drying equipment.

It will vbe understood that the apparatus of my invention is not limited to the four sample boxes illustrated but may employ any desired lesser or greater number of boxes and such boxes may be of different shape and size from those` illustrated. A nd while the apparatus is especially adapted for drying pulp samples it may likewise be used for drying numerous other-materials. Various other modiiications and changes may be made within the scope of this invention, some of the novel features of which are defined in the appended claims.

l. An apparatus for use in determiningv the moisture content of pulp samples for quantitive calculations during the manufacture of pulp, comprising a vertical air duct of substantially uniform cross-section throughout its length, a heater and a cooperating fan arranged in said duct for creating and forcing a controlled stream of drying air downwardly through said duct and lengthwise thereof, a plurality of air-permeable boxes adapted to contain representative pulp samples selected from a batch in the course of processing, and partitioned means forming compartments for receiving and supporting said boxes individually in side by side arrangement transversely in said duct, and for positively dividing the stream of drying air in said duct and leading a constituent stream separately through each of said boxes, whereby the drying air is channeled a substantially equal distance to each of said boxes and the pulp samples contained therein are independently and uniformly dried, and

damper means associated with said partitioned means for selectively restricting the stream of drying air in said duct to particular compartments formed by said partition means.

2. An apparatus for use in determining the moisture content of pulp samples for quantitative calculations during the :manufacture of pulp, comprising a vertical air duct of substantially uniform cross-section throughout its length, a heater and a cooperating fan arranged in said duct for creating and forcing a controlled stream of drying air downwardly through said duct and lengthwise thereof, a plurality of air-permeable boxes adapted to contain representative pulp samples selectedl from a batch in the course of processing, and Ypartitioned means forming compartments for receiving and supporting said boxes individually in side by side arrangement transversely in said duct, and for positively dividing the stream of drying air in said duct and leading a constituent stream separately through each of said boxes, whereby the drying air is channeled a substantially equal distance to each of said boxes and the pulp samples contained therein are independently and uniformly dried, and means associated with said partitioned means for selectively restricting the stream of drying air in said duct to particularcompartments formed byv

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