US2510372A - Process for drying hops - Google Patents

Description

June 6, 1950 v. BLQXHAM 2,510,372

PROCESS FOR DRYING HOPS Filed March 29, 1948 IYIIIIIIII I III/III I IIIIIIIIIIII 1 gi Z INVENTOR.

Var/in A. B/OX/767/77 ATTORNE Patented June 6, 1950 PROCESS FOR DRYING HOPS Verlin A. Bloxham, Berkeley, Calif.

Application March 29, 1948, Serial No. 17,655

6 Claims. (Cl. 3410) 1 This invention relates to a process for drying hops.

The process commonly employed in drying hops involves the use of apparatus including a houselike structure having a reticulated floor upon which the hops are loaded. This floor may be some 20 feet above the ground. Beneath the floor is disposed a heater burning fuel of one sort or another. The products of combustion from the heater usually pass through a zig-zag or similar arrangement of pipes, located perhaps 8 feet beneath the floor on the way to the chimney. Forced draft of air is not provided, but the house is built tall enough, compared to its section, to provide a stack eflect. p

In order to dry a quantity of hops, the hops are first loaded on the fioor to a limit depth of about 24 inches. The heater is then fired up and maintained hot for a sufiicient period of time to allow the hops to dry.

There are a great number of objections to this manner of drying, and to the hop drier itself. One of the main objections is the variable quality of the dried product. This variable quality is due to several factors inherent in the process and apparatus. One of the main ones is that drying is more efilcient in the lower portion of the bed, due largely to the slow passage of air through the bed. The result of this is that if the bed is not turned one or more times during the 2 tremely sensitive to excessive temperature. Furthermore, this radiant heat raises the temperature of portions of the enclosure which are seen by the pipes to excessive levels. This results in the successive drying, charring and perhaps final combustion of the combustible material, generally wood, employed in construction of the drier. At least the loss of the driers by fire is a common drying process, the product will not be uniformly. a

dried.

The turning of the hops, in order to overcome lack of uniformity in drying, has its own drawbacks. Afer the hops dry, they become very fragile and brittle and are easily broken, and when the bed is turned, in order to reverse positions of the upper and lower layers, many of the cones which have reached the brittle stage will be broken, and the product taken finally from the drier will have an excessively high proportion of fines. The labor involved in these extra operations is also objectionable.

occurrence.

A further serious objection to the apparatus is encountered in the fact that fines fall from the hops through the fioor 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.

Since the driers are so tall, the difiiculty, and labor involved in loading, turning, and unloading is considerable. Floor loading is limited to about 24 inches, since heavier loading unduly restricts flow of air. The heater is inemcient, as much as 50% of the heat going out of the stack. It is an object of my invention to provide a new and improved process for drying hops, which process avoids the enumerated disadvantages of the present process.

A further object of my invention is to provide a hop drying apparatus for carrying out my new process, the apparatus being very eflicient and effective in operation.

A further object of the invention is to provide a process resulting in a greatly superior product.

Other objects will become apparent in the following description.

The apparatus is shown in the drawing Figure 1 of which is a plan, the enclosure being sectioned below the hop floor.

Figure 2 is an elevation with parts in section.

In the drawing, the reference numeral I 0 refers generally to the enclosure or drying house. This house has four walls, as shown, a gable roof II, a reticulated drying floor l2, and in the apex of the roof an air outlet l3. An air inlet I l is provided above the level of the hops, for reasons which will be presently described.

The apparatus for applying drying gas to the house is indicated generally by the numeral 20. This includes a burner 2|, 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 house there is provided an outlet valve 25. Dampers 26 may be so operated as to close of! the conduit. Within the plenum under the drying floor I2 is a plurality of outlets 21 so located and arranged as to secure a maximum of uniformity of distribution of the drying gas to the bottom of the floor l2.

A diffuser indicated at 28 is used between the burner and the plenum to secure efiicient mixture of the incoming air with the products of combustion. Suflicient 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 started up 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 atmosphere.

The opening l4 may be provided at any point under the roof and over the level of the hop bed, but ordinarily on the side of the house from which come the prevailing winds. The purpose of this opening I4 is to allow ingress of atmospheric air to the space above the hops. The air passing through the hop bed evaporates and thus contains a considerable amount of moisture, and in certain stages of the drying, the relative humidity of the air passing from the bed and out the opening 13 may be well up toward 100%. If such conditions obtain for any length of time, moisture may condense on the roof and other exposed and perhaps cool portions of the enclosure. To prevent this, the outside air dilutes the humid air. To this end, the openings l3 are of sufficient size relative to the quantity of air passing therethrough that additional air may be easily forced in by even a slight breeze from the direction which applies pressure to the opening I4.

I have contemplated that a slight aspirating effect may be obtained by the air passing through the bed and through the openings l3 so that openings or louvers l4 need not be in any particular position with relation to the prevailing wind.

On the other hand, the dilution of the humid gas by means of outside air is not vital to the process and may be omitted.

In performing the process of this invention, the green hops are first loaded upon the reticulated floor. This may be in conformity with present practice with the exception that the load may be much deeper, due to the increased eificiency of the process. This, of courseyprovides a larger output from a given floor. The hops will be arranged as uniformly as possible with regard to density and to depth of the bed, which may generally be in the neighborhood of 45 inches.

Drying is accomplished by blowing mixed air and products of combustion of the fuel through the bed of hops from beneath under the carefully controlled conditions which will be described hereinafter. Important among these conditions are the velocity of gas flow, the moisture content, and the temperature of the gas.

With regard to velocity, I prefer to pass the drying gas through the hops at a velocity of between 25 and 70 feet per minute, since I have found that velocities within this range secure a substantial benefit in avoidance of crushing of the hops in the lower portions of the bed, which is accomplished by the lifting of the hops in the upper portions. With respect to this action, the upper limit of the velocity is that at which the -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 the slower the air travel, the more likely it is to be saturated before it reaches the upper layers, in which event the upper layers will not be properly dried but might even have water deposited upon them.

With regard to temperature, the temperature may not be above about 145 F., otherwise the hops will be charred or drying may be too rapid. I prefer that the air be at a temperature between and F.

Obviously, the drier the air, the more effectively it will dry the first hops with which it comes in contact; however, if the drying gas be too dry, I have found that it is not possible to dry a substantial bed with a satisfactory degree of uniformity; therefore, I prefer that the air used have a relative humidity of between about 10% and about 17%.

'With the above conditions all met, I am able to dry a bed 45 inches thick, and even thicker, in 15 hours, turning being unnecessary and uniformity of the drying being such that the greatest difierences between samples are in the neighborhood of from 3-8%. with present processes, a difierence of 20% is common.

A surprising thing about my process is the suitability of the mixture of combustion gases and air for drying hops, which are notoriously sensitive and delicate. Those skilled in this art have been very difficult to convince that hops may be satisfactorily dried with such a mixture. However, a considerable amount of experience has proved that premium hops may be prepared by the use of my apparatus and the performance of the process.

Sometimes herein I have referred to the drying gases broadly as air. It is to be understood that the combustion products of hydrocarbon fuels are included. Such fuels as coal, natural or producer gas, oil, petroleum derived bottled gases, and gasoline are to be used.

The disclosure contained in my application, Serial No. 8,757 filed February 16, 1948, is incorporated herein by reference.

Iclaim:

1. A process for drying hops comprising disposing a quantity of green hops in a substantially horizontal bed, burning a hydrocarbon fuel with air to provide a hot gas stream mixing the hot gas stream with a stream of atmospheric air to provide an inert gas stream having a relative humidity of between 10% and 17% and a temperature between about 125 F. and 140 F., and blowing said inert gas stream upwardly through the green hop bed at a velocity relative to the bed of between about 25 and 70 feet per minute until the moisture content of the hops is less than about 10% by weight, the depth of the bed and the gas velocity each being such that (1) the inert gas is in contact with the hops in the bed for from about 3 to about 7 seconds, and (2) there is secured a partial and substantial lifting of the weight of the bed of hops.

2. A process for drying hops comprising disposing a quantity of green hops in a substantially horizontal bed, burning a hydrocarbon fuel with air to provide a hot gas stream mixing the hot gas stream with a stream of atmospheric air to provide an inert gas stream having a relative humidity of about 14% and a temperature of about 135 F., and blowing said inert gas stream upwardly through the green hop bed at a velocity relative to the bed of about 40 feet per minute until the moisture content of the hops is less than about by weight, the depth of the bed and the gas velocity each being such that (1) the inert gas is in contact with the hops in the bed for about 5 seconds, and (2) there is secured a partial and substantial lifting of the weight of the bed of hops.

3. A process for drying hops comprisingdisposing a quantity of green hops in a substantially horizontal bed about 45 inches deep, burning a hydrocarbon fuel with air to provide a hot.,gas stream mixing the hot gas stream with a stream of atmospheric air to provide an inert gas stream having a relative humidity of about 14% and a temperature of about 135 F., and blowing said inert gas stream upwardly through the green hop bed at a velocity relative to the bed of about 40 feet per minute and in contact with the hops in the bed for about 5 seconds until the moisture content of the hops is less than about 10% by weight, the depth of the bed-and the gas velocity being such that there is secured a partial and substantial lifting of the weight of the bed of hops. 4

4. A process for drying hops comprising disposing a quantity of green hops in a substantially horizontal bed, and blowing an inert gas upwardly through the green hop bed at a velocity relative to the bed of between about 25 and '10 feet per minute, until the moisture content of the hops is less than about 10% by weight, the depth of the bed and the gas velocity each being such that (1) the inert gas is in contact with the hops in the bed for from about 3 to about 7 seconds and (2) there is secured a partial and substantial lifting of the weight of the bed of hops, the air initially having arelative humidity of between 10% and 17% and a temperature between about 125 F, and 140 F.

5. A process for drying hops comprising disposing a quantity of green hops in a substantially horizontal bed, and blowing an inert gas upwardly through the green hop bed at a velocity relative to the-bed of about 40 feet per minute until the moisture content of the hops is less than about 10% by weight, the depth of the bed and the gas velocity each being such that (1) the inert gas is in contact with the hops in the bed for about 5 seconds and (2) there is secured a partial and substantial lifting of the weight of the bed of hops, the air initially having a relative humidity of about 14% and a temperature of about 135 F. i

6. A process for drying hops comprising disposing a quantity of green hops in a, substantially horizontal bed about inches deep, and blowing an inert gas upwardly through the green hop bed at a velocity relative to the bed of about 40 feet per minute and in contact with the hops in the bed for about 5 seconds, until the moisture content of the hops is less than about 10% by weight, the air initially having a relative humidity of about 14% and a temperature of about F., and the depth of the bed and the gas velocity being such that there is secured a partial and Zubstantial lifting of the. weight of the bed of ops.

VERIJN A. BLOXHAM.

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

UNITED STATES PATENTS Number Name Date 37,403 Marsh Jan. 13, 1863 198,875 Edgerton Jan. 1, 1878 655,330 Dowdeli Aug. 7, 1900 1,224,560 Needham et a1. May 1, 1917 1,226,052 Benjamin May 15, 191'! 1,713,619 Owen May 21, 1929 2,231,445 Grapp Feb. 11, 1941 2,422,987 Roberts June 24, 1947 OTHER REFERENCES Fan Engineering published by Buffalo Forge C0,, Copyright 1925, pages 219-22.

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