US2559107A - Drying hops - Google Patents

Description

July 3, 195] Y. A. BLoxHAM DRYING HOPS 2 Sheets-Sheet 1 Filed May 19, 195o NWN INVENTOR. Verl/f7 A. Blox/1am TTOENE m 2 l t 9 e 8 Y 5 a. mw E 5 Wx N 2 w 5 P M Q h ///U N5 m w L. U 1A.. ,.T a. m w y ...n V x O H I.. L G E.. f B m Am H V.

w//Tlw I.. I 6 F/d/r//r/ n ,2a. 2 0 M 5 f Q 4 1 0 .h i l v. d w .m m .J F 2 Patented July 3, 1951 UNITED STATES PATENT i GFFICE DRYING HOPS Verlin A. Bloxham, Berkeley, Calif.

Application May 19, 1950, Serial No. 162,911

13 Claims. 1

This is a continuation-in-part of my application Serial No. 141,001, iiled January 28, 1950.

This invention relates to an improved process for the drying of hops.

The common process employed, in lowering the moisture content of hops from 75% to 80% to 7 to 11%, involves the use of apparatus including a house-like structure having a reticulated oor upon which the hops are loaded. Beneath the floor there is disposed a heater, commonly direct fired, and the products of combustion from which usually pass through a zigzag or like arrangement of large pipes, located beneath the hop oor, on the way to the stack. Forced draft of air through the hops is not provided, the house being tall compared to its section so as to provide a stack eiiect, the hop-floor being some twenty feet above ground level. There are a great number of objections to this manner of drying, the major one probably .being the variable quality of the dried product. This variable quality is clue to several factors inherent in the process employed, one of the main ones of which is that the drying is more eicient in the lower portion of the bed, with the result that if the bed is not turned one or more times during the drying process, the drying will not -be uni,- form and hops in one portion of the bed will be of a different moisture content from those in another portion.

The turning of the hops, to ensure uniformity in drying, has its own drawbacks. After the hops dry, they become very fragile and brittle and easily broken, and when the bed is turned to reverse the position of the upper and lower layers, many of the cones which have reached the brittle state will be broken, and the product taken from the dryer will have an excessively high proportion of fines. The labor involved in lthis operation is, of course, objectionable in addition.

As will be apparent from the above description of the apparatus, the hops are subjected not only to heat by convection from the pipes, but also to radiant heat. For this reason, though ordinary dry bulb thermometers are customarily used in order to control the temperature Within the bed, the lower layers of hops to which heat is radiated will be at temperatures higher than that indicated by the thermometer. This consideration, of course, renders the control by thermometer inadequate and misleading and constitutes one of the reasons for lack of uniformity in the product, since the hop is extremely sensitive to excessive temperature. Further, action of this radiant heat is to raise the temperature to excessive levels of those portions of the enclosure which are seen by the pipes. This results in the successive drying, charring and perhaps iinal combustion of the combustible material, generally wood, employed in constructionrof the driers; the loss of the driers by fire is a common occurrence.

A still further serious objection is encountered due to the fact that fines fall from hops through the floor and onto the hot pipes where they become charred and give rise to vapors which in turn pass through the hops and may be condensed on or absorbed by them.

The driers are tall, as referred to above, which increases the difficulty and labor involved in loading, turning and unloading. Floor loading is limited to a depth of about twenty-four inches. The heating system is ineflicient, wasting as much as 50% of the heat.

The present invention contemplates the continuous drying of hops, thus avoiding any delay between the harvesting of the hops and the drying operation. This facilitates the harvesting operation inasmuch as it is not necessary to assemble a kiln charge prior to the drying operation for loading into the kihi. Thus, the drying operation and the harvesting operation can be coordinated and carried on simultaneously and continuously.

Of late, a practice has developed of pressing fresh hops and holding the hops under refrigeration (see Patent 2,473,395) until their use is desired, following which the hops are dried. The process and apparatus of the present invention are' particularly suitable for the processing of these as well as hops taken directly from the field; in either case, the hops are green and undried.

It is an object of my invention to provide an improved process for the drying of hops.

A further object of the invention is to provide a process resulting in a vastly superior product from the drying floor, due to uniformity of drying, adequacy of control and the avoidance of crushing the lower layers.

While I have developed a novel and satisfactory apparatus, many other forms of apparatus may be used, and the process which is the subject of this application is not dependent upon the particular apparatus disclosed, even though this is novel, as will be apparent from the description following.

The practice of the invention will become further apparent upon consideration of the following, particularly in connection with the drawing showing a typical apparatus set-up and wherein Figure 1 is a side elevation partly in section presently appear.

l 3 y through a form of continuous hop-dryer embodying this invention.

Figure 2 is a section in Figure 1.

Figure 3` is a side elevation partly in section showing the seal utilized.

Figure 4 is a plan view showing the arrangement of the drying system.

Figure 5 is a plan view with portions of the apparatus in section showing a modified form of drying system.

Figure 6 is a sectional view taken along the line 6-6 in Figure 5.

To carry on a continuous drying of hops, I have found that the hops should be subject to drying under conditions suited to the moisture content of the hops. Thus, I preferably employ a process wherein the hops are first dried at a relatively high temperature and thereafter at a lower temperature. I have found that if one attempts to dry the hops under substantially uniform conditions, adequate reduction of the moisture content of the hops is not attained if the temperature during the process be sufficiently low as not to harm the hops at any time, while if the drying of the hops is attempted under relatively elevated temperature conditions, the length of time of drying being reduced, the hops are over-cured, the volatile oils, which largely determine the quality of the hop, being lost or burned. Thus, I have found that green hops, either from the field or from storage refrigeration, as outlined in the aforementioned patent, can be dried at an elevated temperature of the order of 160 to 200 F. until the moisture content is reduced to the order of about half that originally present whereupon the temperature should be reduced to the order of 120 F. to 160 F. and preferably in the range of 135 to 150 F. The practice of the invention will become further apparent upon a consideration of typical taken along the line 2-2 equipment which can be employed and its operation.

' Referring to Figures 1-4 in the drawings, a

vfeed hopper 6 is provided into which the hops to be dried are introduced. The hopper is shown as provided with drums 1 and 8 having teeth III thereon which operate to pick the hops apart, particularly when a block of frozen hops is placed in the hopper 6. A vibrating screen 9 is provided across a lower portion of the hopper while a vaned feed wheel II rotates in a clockwise direction to move hops onto shelf I2, from which the hops are transferred to between the conveyors generally indicated at I4 and I6.

Conveyor I4 includes a porous flexible metal belt I1 passing about suitable drums I8 and I9 at each end of the conveyor. A horizontal extending member 2| is provided between the upper and lower runs of the conveyor, this having a plurality of spaced rollers 22 mounted thereon across the belt and adjacent the underside thereof to support the lower side of the conveyor belt I1 and prevent it from moving upwardly, as Will Other rollers 22 are provided upon theupper side of the horizontal member 2I to support the upper run of the conveyor belt. Housing 23 is provided over the shelf I2 and feed wheel II, the housing including an arcuate portion 24 fitting snugly about the belt as it passes about the drum I8, as appears in Figure 3. The lower conveyor I6 includes a porous flexible metal belt 3I extended about drums 32 and 33. A plurality of rollers 34 are provided on either `side of the lower run of the belt to hold it in position while rollers 36 are provided to support the upper run of the belt. The porous metal belts are well-known in the conveyor art; the openings therein pass the air freely while retaining the hops.

Shelf I2 feeds the hops to between the conveyor belts which move to the right in Figure 1, that is, the-lower run of belt I4 and the upper run of belt I6 move to the right in Figure 1 at the same rate to confine the hops between them and carry them toward the opposite end of the conveyor structure whereat the hops pass downwardly between confining walls 4I and 42 and through a vaned discharge wheel 43.

The conveyors I4 and I6 are preferably conned to receive warm, dry air and pass this over hops placed between them. Thus, as appears in Figures 1 and 4, the initial portion 'of the run of the conveyors I4 and I6 is confined between vertical side Walls generally indicated at 5I and by end walls 1I and 12; these provide a first drying zone or drying` chamber generally indicated at 52 and which opens directly into the atmosphere.

The remaining portion of the conveyors I4 and` I6 is confined by side Walls 5I and end walls 12 and 13 to provide a second drying zone or chamber generally indicated at 54, this chamber including a return duct 56 leading info a furnace or heat tunnel 5'I wherein oil, natural gas or the like is burned with air by burner 66 to supply a stream of hot, dry gas when mixed with the return gas from the second drying chamber. Each conveyor belt runs closely adjacent to a longitudinal seal member 53 extending along the belt to prevent the air from passing between the belt and the housing instead of through the belts and the hops. Heated air and products of combustion are mixed directly and discharged through outlets 58 into a blower 59 and thence into chamber 54 through duct 6I, while another portion of the hot air is taken through duct 62 into blower 63 and thence through duct 64 into drying charnber 52.

The operation of the apparatus will become further apparent upon the following description of an operation, for example, upon the handling of frozen hops. These are solid and are at approximately 32 F. as they are taken from a refrigeration chamber. The blocks, usually about sixteen inches square and having a density of about 25.5 pounds per cubic foot, are fed into the hopper 6 from which they are picked apart by rolls 1 and 8 and pass through vane feeder I I to between the conveyors I4 and I6, The belts can be spaced apart a distance of about 5" to 10 and the blocks of hops are fed into the hopper at a rate such that this bed depth is maintained. The conveyors are moved at a rate such that the hops are in each of the separate drying zones for a period of about thirty minutes.

In the first drying zone, the hops are subject to hot, dry air at a temperature which should not exceed 200 F. and which is preferably of the order of 175 F., the air having a relative humidity of between 1% and 8%. A lower temperature can be utilized, but in this case the length of time the hops are in contact with the air must be increased; the lower temperature limity in any case, is about 160 F. In the second zone, the air is at a temperature of preferably about 145 F.; of the order of 30 F. less than that in the first zone, the temperature should not be less than F. in any case. In determining when the hops are dried, I have found that one should observe the dry bulb temperature ci.' the air leaving the hops as this is the only trustworthy indi-- cation of the condition of the hops inasmuch as it is desired to leave the hops with from 7% to 11% oi' free moisture. Generally, the dry bulb temperature of the air issuing from the hops should be at least F. less than that of the air entering the hops. As soon as the dry bulb temperature difference between the entering air and the issuing air approaches 5 F., the operation should be closely observed and should be concluded rapidly. In any given apparatus, the actual differential to be maintained can be readily ascertained and coordinated with the hop quality desired in the product; generally, it is of the order of 5 F., but it can vary between about 15.

F. and 0 F., depending on the hop quality desired and the particular operating conditions, including the depth of the bed.

The air is forced through the hops at the rate of from 150 to 500 feet per minute. If the hops have been under refrigeration, they become defrosted within about 30 seconds after entering between the conveyor belts. When operating upon field hops, the bed depth can be increased to 30, rolls 1 and 8 being omitted. From the above, it will be observed that the air is in contact with the hops for from about 0.05 to 1.0 seconds, depending on the bed depth and the air velocity. In any case, the air velocity is such that the conveyor belts tend to move upwardly and it is for this reason that the rollers 22 are provided upon the underside of the upper run of conveyor belt l1 to hold the belt in place and prevent the hops from being displaced by Jthe air velocity. The air velocity in any case is such that the Weight of the bed is entirely supported by the air and crushing` of the fragile hops is thus avoided, as

' will now he explained.

Drying is accomplished by blowing conditioned air through the bed of hops from beneath under certain carefully controlled conditions. One of the most important of these is the velocity of air flow, this being particularly important because it serves two separate and distinct purposes to have this velocity at a proper value. 'I'he first reason is to secure a complete and sustained lifting of the Weight of the bed of hops. This is important, particularly in the latter stages of the drying as the hops become more fragile, because the weight of the upper layers is taken in large degree from the lower layers, and the crushing of these lower layers is thus-substantially avoided; the air velocity should be such that the bed is supported by the upward air thrust and the fragile hop petals are not crushed, broken or compressed by the gravitational force acting on the bed.

Another advantage of moving the air through the bed at a relatively high velocity is that less harm is done the hops if the temperature is elevated; for example, I have found that air at 200 F. could be passed through green hops at 400 per minute without damage whereas at 90' per minute, the hops were severely damaged, the hops in each instance having initially free moisture present in substantially the same amount; free moisture is considered to be all water which is not chemically combined and which can be removed under the recited conditions of drying. A sufficiently high velocity is further important because it assures that the air in the upper portion of the bed will still be able, due to its low relative humidity, to abstract water from the hops in the upper layers. It will be apparent that if the air at the given conditions has abstracted from the lower layer of hops all the moisture it can hold, in other words, is saturated, the upper layers will not be dried but might even have water deposited upon them. I have found that these velocities for both purposes should be between 150 and 500 feet per minute. 'Ihe lower velocity value is determined largely by the consideration of drying the upper layers, while the upper value is that at which economical opera tion can be obtained in the light of the lnower and heat required. The resident time of the hops in the nrst or high temperature zone should be such that the moisture content of the hops is reduced to approximately half of that present in the green hops, and in any case, between 30% and 60%; prior to drying, hops contain from 65% to moisture. When this is reduced to the order of 371/2%40%, the conditions should be altered so that the hops are subject to a temperature about 30 lower than that utilized in the first zone, preferably to a temperature in the range of -160 F. This change of conditions can be eiected by actual physical movement of the hops to a second zone, as has been disclosed in connection with Figures 1-4, or it can be achieved by actual alterations of the operating conditions, as will be described subsequently in connection with the apparatus disclosed in Figures 5 and 6. Under the conditions discussed, about one-half hours time is required in each zone; that is, utilizing air between 120 and 200 F. at the velocity specified, about one-half hours drying time is required to lower the free moisture content of the hops to less than half of what it was initially. Thereafter, about another half hour is required to lcwer the free moisture content of the hops to a point whereat the hops can be considered dry, for purposes of commerce. The use of two zones is of advantage inasmuch as it permits a heat economy for the relative humidity of the air removed from the second zone will be such that additional heat can be saved by re-heating the air, preferably in a mixture with free air, and passing it through the hops in the first zone.

Typical operations on frozen hops, employing conveyor belts 30" wide, are set forth in the following table, and wherein the hops were present in each zone an equal length of time, being moved continuously:

Sample l Sample 2 Total drying time Maximum temperature Minimum temperature Maximum velocity l hour, 5 minutes.

While I have mentioned the preferred use of a plurality of zones, this is not an absolute essential, and one can achieve good results by using a single zone but altering the drying conditions. It is to be remembered that a hop is a very fragile and delicate natural product. The petals containing moisture are very thin and, under drying conditions, give up their moisture readily. Where free moisture is present, as in hops taken from refrigeration, the initial drying temperature can be relatively elevated "without damage to the product, thus speeding up the overall drying rate. As drying progresses, the free moisture disappears and, if the product is not to be harmed, I have determined that the temperature should be lowered. Thus, if one utilizes a single drying zone and air at a relatively high temperature, one must be content with a product of inferior quality or else reduce the temperature, accept a lower throughput rate, but achieve a Aquality product.

In outlining a process utilizing two zones, I

have provided a practicalcompromise between a one-zone, one-.condition operation and a plural-zone operation; for example, utilizing. say,

ve zones, the drying of the hops would` be improved for this would enable the zones to be maintained at temperature gradients of 200,

Y blowing the air upwardly through the hop bed. 'I the hops are maintained in a loose. gas-penetrating bed whereby substantially uniform drying takes place throughout the bed and the hops issue from the operation with a substantially uniform moisture content, between 7% and 11%.

While the preferred operation includes movement of the hops from one zone to a second zone,

actual movement of the hops from one zone to a second zone is not essential and the hops can remain in one location. However, in this mode of operation, the temperature of the gas must be lowered when, in effect, the hops would be moved to the second zone in a continuous process. For example, I have successfully dried green field hops by passing air at 160 F. and having a relative humidity .of at 200 feet per minute through a bed 30" deep for thirty minutes until the moisture content of the hops was reduced from '75% to 38%. The air temperature was then lowered F. to 140 F., the operation being continued otherwise under the same conditions. The temperature of the air in the bed was continuously observed by a pyrometer in an intermediate portion of the bed. An apparatus for carrying on this operation will now be described.

In Figures 5 and 6, the reference numeral ||5 refers generally to the movable hop drying basket.

This includes four walls, a reticulated drying floor ||2 and a removable reticulated top portion |14; both the floor and the top are covered with a cover'of a porous covering material such as wire mesh so that adequate support is provided to the hops and yet the hops cannot escape. At the same time, a free egress of air is permitted. The basket is removably positioned upon a vertically extending support |0 to which dry air is supplied, as will be explained. A plurality ofbaskets can be employed, one being lled while one is drying and While a third is being unloaded. In this manner, maximum and continuous use is made of the air supply provided to support ||0.

The apparatus for supplying dry gas is indicatedv generally by the numeral |20. f This includes a burner |2 I, in this instance a gas burner, and a blower |22 with its motor |23. Near the burner |2| is an air inlet |24 which admits air to support combustion of the gas, and also additional air to be mixed with the products of combustion.

Between the blower |22 and support I0 is provided an outlet valve |25; dampers |26 may be so operated as to close off the conduit. Within the support ||0 and |20 under the basket IIB a plurality of outlets |21 are so located and arranged as to secure a maximum of uniformity of distribution of the drying gas to the bottom of the basket. A diffuser indicated at |28 is placed below the basket ||5 to ensure upward flow through the hops. Sufllcient air is taken in through the inlet |24 to mix with the products of combustion and the hot gases so that the temperature of the mixture is within a suitable range.

The dampers |26 are used mainly to cut off the flow into the drier whenever this is desirable as, for example, when the apparatus is just being startedup and the products of combustion may include smoke or the like which should not be sent through the hops. With the dampers |26 closed and the valve |25 open, the gases may be by-passed to the atmosphere.

In operating the unit shown in Figures 5 and 6, a removable basket is filled with hops and the cover ||4 is placed thereon to secure the hops in place. The basket is then lowered into position on support l0 and the hot, dry conditioned air is forced through the hops. The air moves at a velocity and is at a temperature between 160 F. and 200 F.; this is continued until the moisture content of the hops has been reduced by less than one-half. This usually requires about one-half hours time. When the hops have about onehalf their initial moisture content, the temperature of the air is decreased by suitable control of the fuel and the air admitted to the unit to lower the temperature about 30 F. and into therange of F.160 F. Such operation is continued until the dry bulb temperature of the air issuing from the hops is approximately only 5 F. less than that of the entering air whereupon the operation is discontinued. The removable basket of dry hops is lifted off and a freshly loaded basket is lowered into place for drying.

In place of burning a fuel to supply the heat, mixing the products of combustion with the admitted air, one can heat the admitted air indirectly as by passing it over a heat exchange.

Air is used in a broad sense herein and in the claims to include air per se or mixed with products of combustion.

I claim:

l. A process for continuously drying green hops comprising first passing a first stream of hot dry 'air having a relative humidity between 1% 'and 8% and at a temperature of 160 F. to 200 F. upwardly through the hops at a velocity of Iabout -500 feet per minute until the free moisture content of the hops, as herein deilned,

is reduced by about 30% to 60%, the depth of the bed and the rst air stream velocity each being such that the air in the ilrst stream requires from 0.05 second to 1.0 second .to traverse the bed, and then passing a second stream of hot dry air having a relative humidity of between 1% and 8% and a temperature in the range of 120 F. to 160 F. upwardly through the hops at a velocity of about 15G-500 feet per minute until the free moisture content of the hops, as herein defined, is between 7% and 11%, the depth of the bed and the second air stream velocity each being such that the air in the second stream requires from 0.05 to 1.0 second to traverse the bed.

2. A process as in claim 1 whereinthe first air stream is passed through the bed for about thirty minutes and the temperature of the second air stream is about 30 F. less than that of the mst airstream.

3. A process for continuously drying green hops comprising passing n, first stream of hot dry air having a relative humidity between 1% and 8% and at a temperature of 160 F. to 200 F. upwardly through a bed of hops at a velocity of about 150-500 feet per minuto and suiiicient to support said bed substantially against its own weight until thc free moisture content of the hops. herein defined. is reduced to about 30% to 60% of that originally present, the depth ot" the bed and the air velocity each being such that the first air stream requires from 0.05 second to 1.0 second. and then passing a second stream of hot dryair having a. relative humidity of between 1% and 8% and at a temperature about 30 F. less than that of the first stream upwardly through the hops` in the bed .it a velocity of about 15o-500 feet per minute and suflicient to support said bed substantially against its own weight until the moisture content of the hops. as herein defined. is substantially uniform and between 7% and 11%, the depth of the bed and the velocity of the second air stream each being such that the air requires from 0.05 second to 1.0 second to traverse the hops in said bed.

4. A process forrcontinuously drying green hops comprising passing a first stream of hot dry air having a relative humidity between 1% and 8% and at a temperature of 160 F. to 200 F. upwardly through a bed of the hops at a Velocity suiiicient to support said bed completely yagainst its own weight until the free moisture content of the hops. as herein defined, is reduced to about 30% to 60% that originally present, the depth of the bed and the velocity of the iirst air stream each being such that the air requires from 0.05 second to 1.0 second to traverse the hops in the bed, passing a. second stream of hot dry air having a relative humidity of between 1% and 8% and at a temperature in the range of 120 F. to 160 F. upwardly' through the hops in the bed at a velocity suiiicient to support said bed completely against its own weight until the moisture content of the hops, as herein defined, is substantially uniform and between 7% and 11%, the depth of the bed and the velocity of the second air stream each being such that the air requires from 0.05 second to 1.0 second to traverse the bed.

5. A process as in claim 4 wherein the first air stream is passed through the hops for about thirty minutes and the temperature of the second air stream is about 30 F. less than that of the first air stream.

6. A process for continuously drying green hops comprising passing a rst stream of hot dry air having a relative humidity between 1% and 8% and at a temperature of 160 F. to 200 F. upwardly through a bed of the hops at a velocity sufcient to support said bed completely against its own weight until the free moisture content of the hops, as herein defined, is reduced to about 30% to 60% that originally present, the depth of the bed and the velocity of the first air stream each being such that the air requires from 0.05 second to 1.0 second to traverse the hops in the bed, passing a second stream of hot dry air having a relative humidity of between 1% and 8% and at a temperature in the range of 120 F. to 160 F. upwardly through the hops in the bed at a velocity Sufficient to support said bed completely against its own weight until the dry bulb temperature of the second air stream issuing from the bulb is only about F. less than that of the second air stream entering the bed, the

- l0 depth of the bed and the velocity of the second air stream each being such that the air 4requires from 0.05 second to 1.0 second to traverse the bed.

7. A process for continuously drying green hops comprising first passing a first stream of hot dry air having a relative humidity between 1% and 8% and at a temperature of 160 F. to 200 F. upwardly through the hops in a fixed bed at a velocity of about 150-500 feet per minute until the free moisture content of the hops, as herein dened, is reduced by about 30% to 60%, the depth of the bed and the air velocity each being such that the first air stream is in contact with the hops in the bed in the first zone for from 0.05 second to 1.0 second, and then passing a second stream of hot dry air having a relative humidity of between 1% and 8% and a temperature in the range of F. to 160 F. upwardly through the hops in said fixed bed at a velocity of about 150-500 feet per minute until the free moisture content of the hops, as herein defined, is between 7% and 11%, the depth of the bed and the second air stream velocity each being such that the air in the second stream requires from 0.05 second to 1.0 second to traverse the bed.

8. A process for continuously drying green hops comprising first passing a iirst stream of hot dry air having a relative humidity between 7% and 8% and at a temperature of 160 F. to 200 F. upwardly through the hops in a fixed bed at a velocity of about 150-500 feet per minute until the free moisture content of the hops, as herein defined, is reduced by about 30% to 60%, the depth of the bed and the air velocity each being such that the first air stream is in contact with the hops in the bed in the rst zone for from 0.05 second to 1.0 second, and then passing a second stream of hot dry air` having a relative humidity of between 7% and 8% and a temperature in the range of 120 F. to 160 F. upwardly through the hops in said fixed bed at a velocity of about 150-500 feet per minute until the free moisture content of the hops, as herein defined, is between 7% and 11%, the depth of the bed and the second air stream velocity each being such that the air in the second stream requires from 0.05 second to 1.0 second to traverse the bed.

9. A process for continuously drying green hops comprising rst passing a rst stream of hot dry air having a relative humidity between 1% and 8% and at a temperature of 160 F. to 200 F. upwardly through the hops in a fixed bed at a velocity of about 15G-500 feet per minute for about thirty minutes and until the free moisture content of the hops, as herein defined, is reduced by about 30% to 60%, the depth of the bed and the air velocity each being such that the first air stream requires from 0.05 second to 1.0 second to traverse the bed and then passing a second stream of hot dry air having a relative humidity of between 1% and 8% and a temperature in the range of F. to 150 F. upwardly through the hops in said fixed bed at a velocity of about -500 feet per minute until the free moisture content of the hops, as herein dened, is between 7% and 11%, the depth of the bed and the velocity of the second air stream each being such that the air in the second stream requires from 0.05 second to 1.0 second to traverse the bed.

10. A process for continuously drying green hops comprising moving the hops continuously through a first drying zone and a second drying zone; passing hot dry air having a relative humidity between 1% and 8% and at a temperature of 160 F.to 200 F. upwardly through the hops in the ilrst zone at a velocity oi' about being such that the air requires from 0.05 second to 1.0 second to traversevthe hops in the bed in.

the rst zone; passing hot dry air having a relative humidity of between 1% and 8% and at a temperature of 120 F. to 160 F. upwardly through the hops in the second zone at avelocity oi about 150-500 feet per minute until the free moisture content of the hops, as herein defined, is substantially uniform and -between 7% and 11%, the depth of the bed and the air velocity in the second zone each being such that the air requires from '.05,second to 1.0 second to traverse the hops in the bed in the second zone; and removing the hops from the second zone.

11. A process for continuously drying green hops comprising moving the hops continuously through a first drying zone and a second drying zone; passing hot dry air having a relative humidity between 1% and 8% and at a temperature of about 175 F. upwardly through the hops in the rst zone at a velocity of about 150-500 feet per minute and sufcient to support said bed substantially against its own weight until the free moisture content of the hops, as herein defined, is reduced toabout 30% to 60% of that originally present, the depth of the bed and the air velocity each being such that the air requires from 0.05 second to 1.0 second to traverse the hops in the bed in the first zone, passing hot dry air having a relative humidity of between 1% and 8% and at a temperature about 30 F. less than that of the rst stream and in the range of about 135 F. to

-150 F. upwardly through the hops in the second zone at a velocity of about 150-500 feet per minute and sufficient to support said bed substantially against its own weight until the moisture content of the hops, as herein defined, is substantially uniform and between 7% and 11%, the depth of the bed and the air velocity each being such that the air requires from 0.05 second to 1.0 second to traverse the hops in the bed in the lseco nd zone.

12. A process for continuously drying green hops comprising moving the hops continuously through a iirstldrying zone and a second drying zone; Passing hot dry air having a. relative humidity between 1% and 8% and at a temperature of 160 F. to 200 F. upwardly through the hops in the rst zone at a velocityv of about 150-500 feet per minute for about thirty minutes, the depth of the bed and the air velocity each being such that the air requires from 0.05 second to 1.0 second to traverse the hops in the bed in the iirst 12 zone; passing hot dry air having a relative humidity between 1% and 8% end at a temperature -of 120 F. to 160 F. upwardly'through the hops f zones; and removing the hops from the second each being such that the air requires from 0.05

second to 1.0 second to traverse the hops in the bed in the first zone; passing hot dry air having a relative humidity between 1% and 8% and at a temperature about 30 F. less than that of the irst air stream upwardly through the hops in the second zone at a velocity of about -500 feet per minute until the free moisture content of the hops, as herein defined, is substantially uniform and between 7% and 11%., the depth of the bed and the air velocity each being such that the air requires from 0.05 second to 1.0 second to traverse the hops in the second zone; releasing the air from iirst zone to the atmosphere; collecting air from the second zone, mixing the collected air with fresh dry air, heating the mixture and returning the heated mixture to at least one of said zones.

VERLIN A. BLOXHAM.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 271,184 Altenbrand Jan. 23, 1883 655,330 Dowdell i Aug. 7, 1.900

1,226,052 Beniamin May 15, 1917 1,408,457 Harrison Mar. 7, 1922 l 2,032,628 Nelson et al Mar. 3, 1936 2,473,395 Segal June 14,1949 2,510,372 Bloxham June 6, 1950

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