US1624754A - Drying system - Google Patents

Description

' 'il 12 1927. M. MUELLER" DRYING SYSTEM FiledNov. 4. .1926 s'sheets-sheetl 1 Apnl 12 1927- L. MUIELLER DRYING SYSTEM Filed Nov 4. 192,5

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uNiTEo Y STATES PATENT OFFICE.

IO BTTZ 1' MU ELLEB, OI SEATTLE, WASHINGTON, ASSIGNOR TO NORTHWEST BLOWER KILN OF PORTLAND, OREGON, A CORPORATION OF WASHINGTON.

name SYSTEM.

"hrplication med November 4, 1926. Serial No. 146,135.

This invention relates to drying systems and it has for its object to so correlate a plurality of drying agenciesthat their complemental operation will present marked ad- 6 vantages and economiespver what wpuld be secured by their operation, smgly.

In a great manytypes of driers, both for. lumber and other materials, a series or battery of driers are located in adjacent POSI- ltl difl'erent atmospheric conditions in various driers at the same time. As for instance, the product being dried will be just starting in one chamber or several,- more progressed in others and nearly finished in still others of the same battery.

Inasmuch as in all driers wherein the drying process is accomplished at atmospheric pressure, there are waste vapors escaping at certain stages of the drymg, a considerable amount of hot moist air is being I thrown off. from some chambers of a bat tery of driersat practically all times. These vapors result from the water in'the' product being evaporated and the -necessity of removing-such vapor to prevent. the development; of. internal pressure inside the chamber or the a'tm'osphe're becoming saturatedas the Y liquid water in the products: is: turned into a gaseous vapor-by evaporation.

inclu in'g lumber, tl1ere are several stages to the drying process", these stages being'necessary .tofdr'y the --lproduct without -1n ury.

. These stages or periods any one chamber are usually of the following nature when considered in relation to the balance of the ad- .joining driers. v H

(a) The starting stage, when 'the cold product to be dried is warmed up to the center of its bulk at which time a large volume of heat isrequired to heat up the product and also a large volume of atmospheric moisture is required to prevent surface drying taking place before the product is heated throughout its bulk. At-this stage, the drier [can use to advantage the hot moist' exhaust- "apors thrown off by adjoining driers as 5 these exhaust vapors will permit the prodvery rapidly with a minimum consumption of a plied heat of any kind (such, for ex-" 'tions and the product being dried is under.

udri'ers to pour In. raetically .every product thatis dried,

products in other chambers.

net of the drie'rsin question to be heated up pipes) and will also supply the necessary moisture to the air with the minimum use of live steam or other usual humidifying moisture.

(b) The intermediate drying stage, where it is necessary to have a higher humidity in one driertha'n in other driers in order to protect the product being dried from injury.

The usual way of producing such' higher humidity condition is by the use of live steam sprayed into the atmosphere, or some similar humidifying device. This can better be'acccmplished by .allowing the exhaust vapors from adjoinin driers to pour into the drier in question because a more penetrating moisture will be secured and the use of live steam will be avoided or reduced.

(0) The final conditioning stage, where many products when dry require a softening treatment td relieve the drying strains produced by the removal of water from their structure. At this stage, the product requires its surrounding atmosphere to be very moist for a period of time. This condition is usually produced by flooding the drier with live steam but could better be accomplished by permitting the nearly saturated exhaust vapors from the adjoining into the drier in question. Where products of a. different nature are being dried ina battery of driers, the products in some chambers will require lower temperatures and higher humidities than sible. because of this condition to use what will constitute exhaust vapor fronri certain' driers for the drying of the roduct in-other chambers and even of taking the exhaust vapors j from a drier using exhaust vapor from other driers and use it again for still others requiring lower temperatures and higher humidities than this second class.

This low temperature drying being now accomplis hed by live steam of high value, I

could be accomplished at a considerable saving by using the. exhaust vapors now being wasted to the atmosphere.

Further, where a'series of driers are drying products requiring diflerent atmospheric temperatures and humidities and each ex.- hausting vapors of consequently varying temperatures and humidities the aggregate accumulated exhaust vapors of all the driers vapors, thereby removing the necessity as a whole or in part of supplying heat from -other sources such as live steam, for example.

Further, inasmuch as it is necessary in the drying of all products at atmospheric pressure to exhaust definite amounts of evaporated water at certain stages to make drying possible, it is advisable to prepare means for withdrawing such vapors from the prod ucts being dried, to accelerate their drying. I have chosen to illustrate the invention applied to a battery of kilns in which lumber is dried. However, it will be clear as this description proceeds that the basic principles involved are applicable to driers, kilns, ovens and the like adapted to handle all sorts of material.

In the drawings- Fig. 1 is a diagrammatic plan view of a battery of kilns having the invention applied thereto.

Fig. 2 is a partial side elevation thereof. Fig. 3 is a diagrammatic end elevation. Fig. 4 is a longitudinal sectional view illustrating the invention applied to an external fan-type drier.

Fig. 5 is a diagrammatic cross sectional view of the drier of. Fig. 4. I

Fig. 6 is a view similar to Fig. 5 but illustrating a natural draft drier.

- tween a plurality of kilns,

Fig. 7 is a view similar to Fig. 6 but illustrating an internal fan drier, and

Fig. 8 is a partial longitudinal section through the drier of Fig. 7.

Like numerals designate corresponding parts in all of the figures of the drawing.

In the diagrammatic view, Fig. 1, the dotted lines 5 represent the division walls be ovens or other drying chambers. I have chosen to illustrate the invention in conjunction with kilns of the general character of those shown in Patent #1,437,385, issued to me on November 28, 1922. Fig. 3 of that patent illustrates the pressure conduit as being centrally disposed and the suction conduits as being disposed at the sides of the kiln, the heated air being discharged upwardly into an opening left in a stack of flat iled lumber, passing outwardly through t e pile of lumber and then downwardly along the sides of the pile of lumber to the suction conduits. Fig. 4 of the patent referred to discloses the reverse of this in that the suction is in the center and the pressure conduits are at the sides, this arrangement being particularly useful in connection with edge piled lumber. The diagrammatic sectional views 5, 6 and 7 make it clear that the present invention is applicable to both types of kilns referred to and in addition is applicable to many types of driers and ovensother than those intended for the conditioning of lumber.

From the foregoing it will be understood that each kiln is provided with means for setting up a circulation of air therein, under either natural or forced draft and these means may be varied within wide-ranges without affecting the applicability of the present invention, which is in addition to or supplementary to, said circulatory systems. A suction conduit 6 extends across and is common to all of the battery of kilns 5. Suetion laterals 7 extend longitudinally along the tops of the kilns from the suction conduit and have communication with the tops of the kilns, at intervals, through ports 8. This suction conduit is connected at one end with the casing 10 of,a fan, driven by a motor or other suitable means indicated at 11. The pressure side of the fan casing is connected to a pressure conduit- 12, which extends across and is common to all of the battery of kilns. Cross connection duct 13 is preferably employed and connects pressure duct 12' with the suction duct 6. This cross connection is provided with a damper 14 which permits or prevents a circulation of the air through the suction and ressure ducts according to the degree to which said damper is opened. Permitting the air to recirculate decreases the suction effect of the fan effective into the various driers and preventing recirculation increases said suction effect. Conditioning means 15 may be disposed at any suitable point in either the suction or pressure duct. The conditioning equipment may consist of means for cooling, humidifying or dehumidifying the air passed therethrough. The pressure duct is provided with an exhaust vent 17, having a damper 18' therein, which is arranged to open when a predetermined pressure has been built up in the pressure.

conduit to permit the escape of vapor beyond that point. No specific illustration showin the damper employed, has, been given,.smce automatic pressure relief valves are common to-many o thearts. The pressure duct 12, which extends across all of the kilns, communicates with the main suction conduits 19 of the several kilns through ports 19, which are controlled by hapd or automatic-dampers' 20. .The points of commuthe art and are available upon the. public market. It is a matter of choiceto select the the. circulated vapors.

proper dampers for use in these locations.

lVliile I have stated that a fan is employed, it may be possible to omit this fan where differences in pressure in the two conduits exist with sufiicient force to'make the use of the fan unnecessary.

In the form of the invention illustrated in Figs. 4 and 5, the main circulatory system of the individual kiln there shown comprises an externally located fan 25 which draws vapor through the main suction con'- duit 19, past a suitable heating unit (in this case a bank of steam pipes 26) and discharges the vapors. from the pressure side of the fan "er'tically into the body of the kiln as indicated by the arrows ((1). Thus it will be seen that any air (vapors, etc.) delivered into the main suction conduit 19 from auxiliary pressure conduit 12 will partake of any treatment, such as heatin by the coils 26, that is given to -the main liody of vapor travelling in the conduit 19. Thus when the vapor is delivered into the drying chamber of the kiln it will be uniform throughout as to humidity, temperature, etc.

In the form of the invention illustrated in Fig. 6, steam coils 27 are disposed horizontally and extend longitudinally of the kiln. In Figs. 7 and 8, the main circulating fan 20 is internally located with respect to the kiln and draws the vapors downwardly from the drying chamber of the kiln and forces them upwardly into the drying chamber of the kiln as indicated by the arrows, steam pipes 29 being disposed horizontally and longitudinally in the path of In this latter form of the invention the pressure conduit 12 of my economizer system is in communication with longitudinally extending pressure ducts 30 having ports 31 at intervals which communicate with the main circulatory sys .tem of the kiln to deliver. auxiliary vapor to the main body of vapor. being circnlatedin the kiln.

The operation is as follows:

"The fan 10 would be operated at a con stant .or variable speed with the pressure relief exhaust damper 18 set to maintain a constant ressure in the pressure conduit, also the amper 14 in the cross connection set to maintam a constant negative pressure in the suction conduit.

This would produce a drawing effect'on all the laterals of the suction conduit and thence into all driers, where the suction conduit damper21 was open; resulting in exhaust vapors from such driers being drawn to the fan. An acceleration in the drying rate of the product in such driers would be thus efiected by the more rapid removal of the moisture they were losing.

The accumulation of hot moist vapors in the suction conduit, being an average of exhaust vapors from all the driers, would be vapors.

This accumulated exhaust vapor of high temperature and humidity (ordinarily If insutficieutly hot,

wasted) would now be available as primary or auxiliary heating, and humidifying means for use in certain driers operating at stages below average and consequently requiring heat and humidity. The dampers to the pressure conduit on such driers would be opened suflicie'ntly to allow the most advantageous use of this heat and vapor in the drying of their products. Such driers as are filled with a cold prod uct, whose heating, moistening and drying was to be started, would have the damper from the pressure conduitopened wide allowing the hot, humid vapor to pour into them in large volumes. The corresponding suction conduit dampers would be open pcrmitting the cold air in the drier to be rapidly withdrawn. As a result a quick heat and a high humidity would be produced either entirely by the use ofthese exhaust vapor; or in combination with live steam in heating radiation, the result being to decrease 1natcrially the amount of steam required to heat the material and condition it for drying.

Such driers ot' the battery whose enclosed product was being dried under a condition where additional heat was required to raise the temperature or where an, even heat beduced, making necessary a final condition ing treatment, would have all live steam turned off and the pressure conduit dampers opened. The very moist air pouring into the drier would give a superior conditioning treatment to that usually accomplished by floodinglthe drier with live. steam and in addition, save such live steam.

The driers containing material requiring vexce tionally low temperatures and high humldities would have the pressure conduit dampers opened permitting the exhaust The exhaust damper in the pressure'conduit being adjustable would prevent the continuous reclrculation of exhaust vapors and hence prevent these vapors reaching saturation and make such vapors always capable of further drying for this reason. Obviously this use would make a material saving of live steam now used to dry such products.

Under existing practice with most types of driers, from 2 pounds to 7 pounds of live steam are used to evaporate 1 pound of water from a product being dried. Of this 2 to '7 pounds of steam, a percentage varying from 25% to is permitted to escape to the atmosphere in an efi'ort to dry the product rapidly. The saving of as large as possible an amount of this 'now wasted steam and heat is of course very desirablel While the suction and pressure conduits, which are common. to a plurality of kilns, have as their prime function the delivery of -waste vapors from one kiln to another kiln,

as described, it is a fact thatan important auxiliary advantage and effect arises from the fact that the increased circulation set up, acts to markedly accelerate the action of the drier or kiln, with a. corresponding in" crease in efliciency.

The dampers 20 and 21 may serve to render the pressure and suction conduits 6 and 12' inoperative with respect to any particular kiln. Further I contemplate discharging vapors'directly from any given kiln, into the atmosphere. It is common to provide means for discharging kiln vapors from any given kiln, into the atmosphere, at will. As

one means for accomplishing that result I have indicated vents 8 in Fig. 7, which may be closed by closures 8". However, with vents 8 of any given kiln, open, and the damper 21 of the said kiln closed, the waste vapors discharged into the kiln would not be recirculated through the auxiliary suction duct 6 but would be discharged through vents 8. In suchcase the hot, moist, waste vapors entering the kiln from the auxiliary pressure conduit 12 and main pressure con-.

duit 19, would speedily warm up the lumber or other product being dried and force out the cold air from said product. dislodged cold air and the waste vapors delivered into the kiln, (by this time largely deprived of their heat) would pass out ofvents 8* into the atmosphere, it follows that the lowering of the average temperature in conduit 6 would be avoided. The waste vapors which accomplish the foregoing useful result, might well be those which would otherwise be discharged through exhaust vent 17 and wholly wasted. I am awareof the fact that the patent to Duryea 887,317,

Since this.

discloses a plurality of kilnshaving common suction and pressure ducts. However, the inventive thought in the Duryea patent resides in periodically reversing the current fl'ow in any given kiln. The delivery of air from one kiln to another, designedly and in such controllable way as to insure the delivery of any definite proportion of air of any definite temperature or moisture content, is neither contemplated nor possible in the Duryea structure. The delivery'of air from one kiln to another is possible but is not aisured in Duryea. Thereforeit is to be understood that the recitation in the appended elairns of the steps of delivering the air controllably at will from one kiln to another, means a designed and predetermined control of the air in such way that the particular kiln from which air is to be delivered and the particular kiln to-which air is to be delivered, will be under selection of the operator,-and the duration of the delivery of air from one kiln to the other, independently of the duration of delivery to any other kiln, will be at the will of the operator.

It is to be understood that the.invention is not limited to the precise construction set forthbut that it includes within its purview whatever changes fairly come within either the terms or the spirit of the appended claims.

Having described my invention what I claim is:

1. The combination with a battery of driers having their, usual main circulatory systems, of connecting ducts between all of said driers which are in addition to and auxilia'ry to said main circulatory systems and are arranged to controllably deliver at will .waste vapors from the drying chambers of some of said driers to others of said driers.

. 2. The combination with a battery of driers having their usual main circulatory systems, of asuction duct common to all of said driers, individual and independent controlling dampers for the several driers leading into said suction duct and means for deliveringvapors from said suction duct into another of the driers, said suction'ducts and vapor delivering means being in addition to and auxiliary to the said main circulatory systems.- Y

3. The combination with a battery of driers and their usual main circulatory; systems of 'a suction duct common to all ofsaid driers, individual and independentcontrolling dampers for each of said driers into said suction duct, a pressure duct to which the suction duct is connected, said pressure duct be ng common to all of said driers and 1ndividual and independent controlling dampers in the pressure duct for each of the driers.

4. A structure as recited in claim 3 incomtrolling dampers for and an automatic relief element in said line adapted to discharge the vapors therefrom when the pressure in said line reaches a predetermined degree. 1

6. The combination with a battery of driers, each of said driers having its longitudinally extending main pressure and suction ducts and main heating means therein,-of an auxiliary suction duct common to all of said driers, an auxiliary pressure duct common to all of said driers and having ports communicating withthe suction ducts of the respective driers, individual and independent consaid ports. individual and independent controlling dampers between the several driers and the auxiliary suction ducts, connections between the auxiliary suction duct and the auxiliary pres sure duct to cause these ducts to constitute a closed path, a fan disposed in said closed path, an automatic vent permitting'the escapeof pressure from said path when the pressure therein has reached a predetermined. degree.

7. A structure as recited in claim 6 in combination with a damperin said path for determining the degree of recirculation of the air therethrough.

8. A structure as recited in claim 6 in combination with conditioning means disposed in said path.

, between each of nections between 9. The combination with a battery of driers, each of said driers comprising a drying chamber having longitudinally extending main pressure and suction ducts associated therewith and having main air circulating means and main heating means associated with said pressure and suction ducts, --the whole constituting a main circulatory system for each of the driers, of an auxiliary suction duct common to all of said driers and individual suction laterals 7 extending along each of thedrying chambers and connected to the last named suction duct, individual controlling dampers said laterals and the'suction duct with which they are connected, an auxiliary pressure duct common to all of said driers and having port's communicating with the, circulatory systems of the.

respective driers, individual and independent controlling dampers for said ports, conthe auxiliary suction duct and the auxiliary pressure 'duct to cause these ducts to constitute a closed path, and means for setting up a circulation of air in said closed path.

10. A structure as recited in claim 9 in combination with an automatic vent permitting the escape of pressure from said path when the pressure therein has reached a predetermined degree.

11. A structure as recited claim 9 in combination with a damper in said path for the air therein. I

12. A structure as recited in claim 9 in combinationwith air conditioning means disposed in said path.

13. The herein described method of controllingconditions in a battery of driers of a nature wherein the whole drying operation is effected by the circulation of heated air and wherein the material being dried has a determining the degree of recirculation of cpnsiderable moisture content at the,beginning of the drying operation, which con- SlSl'S of setting up a main circulation of heated air through each of said driers and controllably withdrawing, at will, some of said heated air and the vapors of the moisture drivenoif'thereby, from any kiln and controllably delivering the same at will to any other kiln.

14. The herein described method of controlling conditions in a battery of driers of a nature wherein the whole drying operation is effected by the circulation of heated air and wherein the material being dried has a considerable moisture content at the beginning of the drying operation, which consists of setting up a main circulation of heated air through. each of said driers and controllably WithdraWing at will, some of said heated air and the vapors of the moisture driven ofl' thereby, from any kiln in an advanced stage of drying, delivering the same atwill to any other kiln in a less advanced stage of drying.

15. In combination, a battery of kilns, a main circulating system for each of said kilns, each main circulating system comprising pressure anchsuction air ducts, means for heating the air therein and means for setting up a circulation of air therein and an auxiliary circulating system having individually. controllable connections with the drying chambers of each of said kilns and individually controllable connection with the main suction ducts of the several main circulating systems of the various kilns.

In testimony whereof I atfix my signature.

MORITZ L. MUELLER.

and controllably

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