CN1093798A

CN1093798A - Dryer

Info

Publication number: CN1093798A
Application number: CN93119924A
Authority: CN
Inventors: G·D·哈利; C·M·M·思韦茨; M·塔尔博特
Original assignee: WL Gore and Associates UK Ltd
Current assignee: WL Gore and Associates UK Ltd
Priority date: 1992-12-18
Filing date: 1993-12-18
Publication date: 1994-10-19
Also published as: GB9226394D0; AU5706494A; ZA939485B; WO1994015159A1

Abstract

A kind of equipment of drying material, the material of oven dry such as natural prodcuts comprise crop, cereal, vegetables, timber etc.This equipment comprises the chamber (2) of a sealing, puts material in the chamber (2) and chamber (2) also contains a gas compartment.The wall components (30) that the water vapour conversion equipment is installed on chamber is gone up or is provided in the mode of the unit (50) of a separation, and the water vapour conversion equipment comprises the barrier film of a selective penetrating power, this membrane permeate water vapour and impermeable gas.Gas in heater (20) heated chamber, gas absorbs water vapour from material.Optionally transferred out by the barrier film water vapour then, and the gas of heating is retained in the chamber.This drying course can effectively utilize energy.

Description

Dryer

The present invention relates to a kind of method of using the drying materials equipment and the oven dry material of energy effectively.Although this equipment designs (particularly cellulosic product) such as agricultural product (for example crop, cereal or vegetables) and Wood products in order to dry putrefactive natural products, the material that this equipment also is widely used in many kind needs dehydrations dewaters.

Its water content was about 15% of a weight when cereal (wheat, barley or other cereal) was sold usually.The product of the high-moisture of results was needing water content is reduced to this level before selling.In addition, because fungi growth, high water content impels cereal to degenerate.Typically, wet cereal is placed on its each limit to be had in the silo of perforation, utilizes air blast, and forced air is passed through cereal.The method of this oven dry cereal is lost time and the expense height of energy correspondingly.

In the torrid areas, the method for drying perishable natural prodcuts (as coffee bean, cocoa bean and other cereal, fish) usually is product to be placed under the sunlight shine.Unfortunately this weather also is the very high weather of rainfall, so the cereal that just needs when beginning to rain just to dry covers.Chronic as operculum, such danger is just arranged: the moisture content below the covering will increase, conk as a result, product has just degenerated.Also have is exactly labor cost height that covering is taken off and puts and the Physical Loss or Damage that can cause product itself.

Other technology just has many requirements, as machine with method on requirement, require to remove moisture content in the mode of effectively utilizing the energy.Usually, oven dry is finished by the circulation hot-air, because circulation hot air temperature height, it has reduced relative humidity and has impelled product drying.But the employed hot humid air of having drawn moisture content always is discharged in the air after use usually, so its contained heat has just lost.Water vapour can be separated from air, and for example the cooled surface condensation by a cooling is taken out, but this causes the lot of energy loss, and cost height in fact.

Our early stage European patent application EP 0525842(1993 is open February 3) disclosed a kind of water permeable steam and the purposes of the separator product of impermeable other gas, it is used to produce the container of storage cereal or other natural prodcuts.The impermeable oxygen of this barrier film, this barrier film descend (as dropping to 3%-7%) oxygen content in the atmospheric environment in the container, and this is because the metabolism use oxygen of the mould in insect, the cereal, cereal self causes.Insect can not survive under the so low condition of oxygen content.Therefore cereal does not use the chemical insecticide can insect protected yet.The character of the infiltration water steam of barrier film makes cereal to breathe and prevents atomizing that the mould in the product that is stored can not grow.

Have been found that if the air that contact with the cereal that is stored with the heating of heater, water vapour can be worn this barrier film and transfer out effectively, and the energy that hot simultaneously gas contains with it is retained among the container.This is a kind of drying mode that effectively utilizes energy.

Therefore, the invention provides a kind of equipment of drying material, this equipment comprises the chamber of storage material, and has in fact comprised a gas compartment in chamber; Also comprise a water vapour conversion equipment that forms the part of chamber and comprise a barrier film, this membrane permeate water vapour and impermeable described gas; Comprise that also an inside heat supply of giving chamber dries the heater of material, the water vapour in the gas described in the equipment is selectively seen through barrier film and gas has been left among the chamber basically.

Another object of the present invention provides a kind of method of corresponding oven dry material.

Chamber can be the suitable space of sealing basically of any size or shape.Chamber leaks gas slightly that yes and can allow, but the availability of equipment has just reduced.Chamber can have entrance and exit as required, particularly provides a material inlet port to be dried and the material of having dried to shift out mouth.In this case, the inside of chamber has transmits the suitable device of material by chamber, and this kind is to make gas carry out the mode of desirable oven dry to material by the mode of chamber.In the prior art, suitable conveyer belt is well-known as the belt conveyer belt of perforation, conical hopper with holes etc.In addition, chamber can use on the batch of material dish, and chamber is that the material of opening and need to dry is added into there, as is added on the charging tray, chamber sealing then, and material is dried and is moved out of.

Suitable device is provided so that the gas circulation in the chamber, thereby promotes water vapour evaporation and promote water vapour contained in the gas optionally to see through barrier film from the material of needs oven dry.Suitable fan is well-known in the prior art.

Firing equipment is provided to the heat supply of the inside of chamber so that help the oven dry material.It is necessary using firing equipment, so that obtain to dry fast and improve the gradient of the water vapour of the barrier film both sides between the chamber interior outside.Firing equipment make to force oven dry be performed and the content that reaches water far below not using the level of forcing heating to be reached.So the equipment that we early stage patent specification EP0525842 is disclosed is when preventing the atomization of liquid, it can not reach a desirable oven dry degree (this depends on the initial humidity and the external environment condition of the material that needs oven dry certainly).

Firing equipment can be any suitable equipment that the area of heating surface is provided, and for example, one by the surface of the heat exchanger that heats with combustion gas mode or electric heater mode.A preferred embodiment of using in sun-drenched environment is the surface that chamber has the absorption solar energy of blacking, or on the wall of chamber transparent component is arranged, and the surface of corresponding absorption solar energy is arranged in chamber, so just makes solar energy be used for heating.In addition, employing contains ultraviolet sunray and can be used for making that the fruit in maturity period has a good color.The characteristic that the ultraviolet ray that sodium carbonate glass can be used for providing suitable is passed through.

Need the material of oven dry to say in theory can be any solid (perhaps even can imagine it is a kind of liquid, the water in the liquid need be disposed), and generally exist with Granular forms.Powder such as milk powder also can be dried.The material of being dried also can be a natural material, and it can be mineral, can be plastics materials, can be drug powder, can be the material that crystal powder or the enough heated air of other energy are dried.

The water vapour switching equipment comprises a permselective barrier film, and this barrier film allows water vapor permeation, and the selected sexual intercourse between the heated air of chamber interior and atmosphere outside of the water vapour of infiltration is changed, and this depends on the difference of the inside and outside water vapor pressure of barrier film.

The selectivity barrier film can be any suitable barrier film well known in the prior art.Preferred specially suitable barrier film comprises porous distribution polytetrafluoroethylene (PTFE), and it can be according to U.S. Pat, 3,953,566 description production.This barrier film allows water vapour to pass through, but the gas handling capacity is also arranged.In fact, comparing limited gas with water vapour allows by characteristic.But the barrier film of airtight body can be used U.S. Pat 4,194,041 described method basically, obtains with the coating coated with PTFE barrier film of permeable steam.The PTFE barrier film can place on weaving or nonwoven, the artificial or natural pad material that is suitable for this purpose known in the state of the art, so that enough mechanical strength to be provided.

Other permeable steam in the prior art and the material of airtight body also can be used, for example polyurethane, polyester, polyolefin, polyacrylate and their mixture.

This barrier film is liquid-tight attitude water in general, and it prevents that entering of aqueous water and it are not subjected to climatic influences.

In a preferred construction, barrier film is layering, and it comprises the PTFE of the porous distribution that has the water vapor permeation coating, and another layer is bonded at the PTFE that the porous on the coating distributes by adhesive.This coating is airtight and energy permeate water steam.Adhesive phase preferably is made up of respirable compound, and this compound is permeable steam and airtight body, our U.S. Pat 4,532,316th, its suitable example.

The water vapor permeability that barrier film has usually (as the penetration speed of water vapour) is at least every square metre of 1500g every day, is preferably 3000-10000g as 1500g-35000g().Barrier film will be selected according to the moist degree of product and the surface area of chamber and the ratio of volume.Consider the energy loss that is allowed, the leakage rate of gas every day of assembling in the entire equipment preferably is less than 100% of the whole gas volume that closes, and be less than 50% preferential again every day, more preferably is less than 20% every day, most preferably is less than 10% every day.The permeability constant of oxygen is typically 3 * 10 ^-8-3 * 10 ^-6MS ^-1; The permeability constant of the nitrogen generally permeability constant than oxygen is little.Usually gas (for example oxygen) for the ratio of the permeability of water vapor permeation barrier film less than 1 * 10 ^-2, at regional area preferably less than 1 * 10 ^-4-1 * 10 ^-6, especially preferably less than 5 * 10 ^-5-2 * 10 ^-5The measuring method of these parameters will described subsequently.Between the water vapor permeation rate of usually specific diaphragm material and the gas permeability correlation is arranged, thus be necessary in the high water vapor permeation rate of the occasion of flash baking, and correspondingly higher gas permeability also allows.

Term " permeability " (with respect to " impermeability ") is used to describe the performance that barrier film sees through the material (or not seeing through the particular types material) that shifts particular types hereinafter; The material of particular types such as gas or water vapour.This term is described to be total effect that material passes through, and does not contain any specific science mechanism here.Because consider energy loss hereinafter described, this equipment seals basically.Like this, the present invention has an additional benefit: need the material of oven dry to comprise volatile component when (as being coffee bean, cocoa bean, pimiento, onion etc.), these components of easily scattering and disappearing have been enclosed in the inside of chamber, and this has just been avoided loss.For example, under normal conditions, the oven dry of coffee often causes the loss of volatile aroma ingredients, before selling, has to replenish aroma ingredients to these coffee.

It also is possible making oxygen (or being actually oxygen-atmosphere) in the chamber reduce, and this minimizing is to be made and used up by the independent process (as the growth of bacterium or insect) that takes place in the disclosed chamber of our European patent EP 0525842 by oxygen in the air.In addition, in chamber, charge into gas (for example: nitrogen, carbon dioxide, argon gas) and also can reduce oxygen content (for example less than 2%).Therefore, this equipment can be used for drying the material (as peanut) to the degree of oxidation sensitivity, and oxidation may influence the color and the taste (because generation of FFA) of these materials.So this equipment can be used for drying material, as flower, fruit (apricot, raisins, pears, peach etc.), spices (cardamom, cinnamon etc.), vanilla (parsley, Salvia japonica, thyme, rosemary, etc.).

Perhaps, other material during baking needs the existence of oxygen as tea and cocoa.But generally speaking, the characteristic that gas is sealed basically of this equipment make chamber inner sustain the gaseous environment of a selection, and allow water vapour to emit simultaneously.

Below in conjunction with the description of drawings embodiments of the invention:

Accompanying drawing 1 is the positive cross-sectional schematic that has comprised the dryer that specific material is dried of a unique conveyer belt;

Fig. 2 is to use the front elevational schematic of the dryer of three layers of conveyer belt;

Fig. 3 is to use the positive cross-sectional schematic of the dryer of a vertical feed system that is connected with the sieve aperture cone;

Fig. 4 is the front elevational schematic of drying plant with water vapour switch of separation.

Fig. 5 is the stereogram of crop dryer;

Fig. 6 is the cross-sectional schematic of crop dryer;

Fig. 7 is a preferred laminated sectional view used in the present invention;

Fig. 8 shows the moisture curve figure of characteristic of the present invention.

Shown in Figure 1 is the dryer of first embodiment of the invention, and it comprises a chamber 2, and chamber 2 has an inlet 4 that allows the funnel form that wet cereal enters, and also has one to make wet cereal enter the rotation inlet valve 6 of chamber with control mode.The outlet 8 that is rotated valve 10 control emits the cereal of having dried from chamber.The energy loss that the entrance and exit valve allows cereal to enter and emit to have limited simultaneously the hot-air that comes in chamber to produce.

Wet cereal is introduced in the upstream extremity of conveyer belt 14, and conveyer belt 14 is to be made by the screen cloth of perforation, and the air of heating can circulate by screen cloth.The two end supports of screen cloth conveyer belt on wheel 12,16, and transmitting at a slow speed cereal by dryer to outlet motion.

Because the effect of flabellum 18, air is circulation in chamber, and the flabellum agitation air enters in the manifold 22 by heat exchanger 20, and manifold 22 has a series of hot air outlet 24 below the screen cloth conveyer belt.Just by screen cloth conveyer belt and cereal and from that to conduit 26, the chilled air in the conduit 26 follows flabellum 18 places to hot-air again.

Chamber has comprised the lid 30 as its wall construction part, the lid 30 permselective barrier film materials that comprise as shown in Figure 7.The side of chamber has also comprised the plate that this permselective diaphragm material is made.

That shown in Figure 2 is second embodiment, and it is similar to first embodiment except having used three layers of conveyer structure.The similar identical numerical reference of partly annotating.

In this case, the air from flabellum 18 passes through heat exchanger 20, the cereal by transmitting then on conveyer belt 32,34 and 36.What conveyer belt can be that screen cloth makes also can be atresia.Cold air is recycled to the flabellum place by pipeline 26 then.

In Fig. 1, embodiment shown in Figure 2, hot-air by or pass wet cereal and taken away water vapour.The air that contains water vapour is then by permselective diaphragm 30, and barrier film 30 is retained in air in the chamber and allows water vapour by barrier film, and water vapour has just been removed from chamber like this.When reaching balance, the quantity of the dry moisture that falls equals the quantity of the moisture content lost by barrier film 30 from cereal.But do not have the loss from the hot-air of chamber interior basically, so the loss of energy is to have reduced to minimum.Certainly, also can isolated chamber with common mode and reduce thermal loss by the pipeline conduction.

Figure 3 shows that the 3rd embodiment, wet in this embodiment cereal is transmitted by moving both vertically of causing of gravity on the net at the conical screen of a series of vibration.Similarly part marks numeral the same as before.

Chamber 2 usefulness lightweight Aluminum Drums are made, and make with permselective diaphragm on the sidewall of chamber and top, and its end is hard.Heater is not provided here, but the outer surface of permselective diaphragm be black so that absorb solar rays to greatest extent, from wet product, remove the desired heat input of moisture content so provide.

6 controls of input valve are imported and be rotated to product like before from funnel.Wet cereal drops on the

taperer screen cloth

40,42 of vibration, and before the chamber lower end output, wet cereal is always on taperer and move downward at the product of oven dry.Taper screen cloth thing comprises a pair of towards last taperer 42 and a pair of prone taperer 40, and product slowly moves down by the zigzag passage in the chamber on taperer.

As preceding, the indoor air of acting chamber by flabellum 18 and recirculation conduit 26 is a circulation.

Shown in Figure 4 is a kind of drying plant, and the barrier film of removing water vapour in this equipment is to be among the water vapour conversion equipment 50 of a separation.

Drying plant comprises a chamber 52, and chamber 52 has the perforation plate 54 of a suspension.Above base plate, loaded the cereal that needs oven dry in the chamber, also stayed a headroom 58.There is the inlet 60 of an input hot-air below of the base plate of chamber, and chamber also has an outlet 62 that makes the air of water content from the headroom discharge.

Humid air goes out by outlet row 62, and it passes pipeline 64 and arrives water vapour conversion equipment 50.Conversion equipment comprises a housing 64, and there is the top board 66 of a porous below on housing top, and there is the base plate 68 of a porous top at the bottom of the housing.

The pipe 70 that the barrier film of a series of airtight and permeable steam is made is closed in this between porous top board and the base plate, and expands to top board and base plate.The barrier film pipeline has been formed the close access from the gas of chamber.

The effect (in figure do not draw flabellum) of air in the atmospheric environment by flabellum 72 has been conducted through housing to outlet 74 according to direction shown in the arrow from entering the mouth.Poor for the water vapor pressure that strengthens inside and outside the barrier film, if necessary, the air in the atmosphere has been dewatered by a dewaterer (not shown) when beginning most.

By before being sent back to chamber 52, from the drying of water vapour interchanger air be conducted through pipe 76 and arrive circulation flabellums 18, then by heater 20.

The advantage of this equipment is by the water vapour conversion equipment is set, and barrier film has just been kept apart with environment.In addition, the structure of chamber 52 can change, and forcibly not requiring has large-area barrier film on its wall.

Fig. 5 and shown in Figure 6 be another embodiment of the present invention, wherein the water vapor permeation barrier film is placed on the fluid-tight base plate in the slide fastener mode.

The wall of drying plant is made up of member 90, and member 90 is that it is supported under zinc-plated steel square framed bent and the necessary situation, can see that like this erects parts 92 and a horizontal part 94 that comes.Typical each parts are about one square metre.The waterproof rubber bottom plate 96 of Hypalon chlorosulfonated polyethylene (Du Pont's trade mark) has been formed the base plate and the side plate of equipment, and base plate 96 has flanging 98 along its side plate and blind end, is suitable for hiding the upper end of steel part.A pair of slide fastener stringer 100,102 is provided with by the top edge 104,108 along rubber bottom plate.

There are the barrier film of infiltration water steam of corresponding slide fastener stringer 101,103 and the very useful slide fastener of base plate top edge to couple together, so that form the chamber of a closure.Slide fastener has been connected to form airtight sealing.

One side of something 103 of slide fastener is stitched on the barrier film 110, and the PTFE sheet that sews with porous of stitching seals.Half of slide fastener 102 has been bonded on the edge of base plate.A TR thin rubber or the ribbon (not shown) is stitched or sticking be sewn to the following of barrier film 110 and go up with the protection slide fastener.Two slide fasteners are arranged, and each bar all begins to expand on the limit 104 of a correspondence of chamber from the mid point on base 108.

The front end 112 of chamber is open, the height forward end direction of limit wall be reduce so that the barrier film front portion drops to ground level.Similarly, the expansion of the front portion of base plate has exceeded the front portion of sidewall, so that it places the bottom of barrier film.The front end of the opening of enclosed cavity is closed by using weight to roll with base plate with the front portion that makes barrier film.

In installing with front chamber, barrier film 110 loaded onto the cereal (not shown).By opening the front end that can open and close, cereal can be output.

There are flabellum and conveyance conduit to assist the oven dry of cereal.The fresh air that is circulated once more and contain hyperoxia concentration from the air of chamber interior to avoid importing.As shown in Figure 6, recirculation is finished by fan 18, and fan 18 makes air be sucked out by outlet 114 and enter once more by inlet tube 112 that two pipes all are positioned at the rear portion of wall.Air was heated in heater 20 before entering chamber once more.For the first oven dry of cereal, can use barrier film 110, it has the performance (and high slightly permeability is correspondingly arranged) of high permeable steam.In case cereal has been finished after the first oven dry of avoiding fungus growth, barrier film can be from being replaced by the low other barrier film of water vapour air penetrability, and the airtight rate of this barrier film is lower, so that make oxygen content drop to desirable level (being typically 5-7%).

Figure 7 shows that and be suitable for the barrier film that the present invention uses.This film is the pliable and tough laminated composition by the

porous PTFE layer

80,82 of two-layer autgmentability, as W.L.Gore ﹠amp; The porous PTFE of the Gore-Tex trade mark that Associates company is sold.Applied the polyurethane coating 83 of a continuous infiltration water steam above the ground floor, as U.S. Pat 4,194,041 described polyurethane coating.Two-layer PTFE barrier film has been bonded to together by the adhesive layer 84 that uses between coat and the second layer PTFE film.Binding agent can be continuous one deck (it must be permeable steam in this case) or can be the adhesive spots of a series of spaces.Designed adhesive Q-11 is preferably according to U.S. Pat 4,532,316 description production.The porous PTFE layer also is an impenetrable liquid water, and its protection cereal is not caught in the rain.The penetration speed of the water vapour of this lamination is every day 4,000g/m ², be 351Sm to the resistance rate of water vapour ^-1, be 3.34 * 10 to the resistance rate of oxygen ⁷Sm ^-1; Its measuring method will be described subsequently.Is 1.05 * 10 to water vapour resistance rate with ratio to the resistance rate of oxygen ^-5

For barrier film is carried out physical protection, bonded some dot matrix of an anti-ultraviolet fibrous face (not shown) (for example: TP adhered on the face of barrier film ₃Binding agent can be from W.L.Gore ﹠amp; Associates company obtains).Bonding nylon wire has been adhered to the another side of barrier film with identical method.

Fig. 8 be moisture curve figure (not wishing that it is limited by any specific scientific theory) it our thinking has been described, the present invention is dried the material such as cereal according to this thinking.

Moisture curve figure has shown relation between relative humidity, air themperature and the absolute humidity (absolute humidity is the amount of water vapour in per unit volume or the per unit material, as the gram number of water vapour in the gram number of water vapour in every cubic metres of air or the every kg air).

Cereal and the air conditions of a typical embodiment are:

Initial water content 19%

Desirable water content 14%

Ambient air temperature 8%

Environment relative temperature 80%

Should be understood that: the material with specific water content correspondingly in air (under given temperature conditions) have specific water vapour pressure.For example the water vapour pressure of the balance of cereal is typically under 14 ℃ of situations:

Water content 19%(percentage by weight)=92% relative humidity; Water content 14%(percentage by weight)=65% relative humidity

These data depend on specific material.

Let us is observed 1,2,3 points on Fig. 8.Select 1-2: blown from the air that enters flabellum of cereal upper space and passing through heater, typically be enhanced 5-10 ℃ in the temperature of heater place air, relative humidity drops to 65% from 88%.These air advance along pipeline, enter cereal by the hole on the pipe (or cereal base plate etc.).Select 2-3: air passes the cereal motion, and air begins to heat and dry the cereal of close pipeline when doing like this.Because the cereal moisture content of the relative humidity of air corresponding about 14%, cereal will can not be dried and will be lower than this level.Cereal has just come up from cereal cooler and fogger.

Point 3-1: when air returns the road when headroom is got back to flabellum along it, water vapour enters in the atmosphere outside by barrier film.Some heats have also just lost simultaneously.

Barrier film transmission water vapour uses mechanical system to help the drying of cereal, and the water vapor concentration that needs only chamber interior is bigger than the concentration of chamber outside.Because the temperature of air is maintained at and is higher than atmospheric environment 5-10 ℃ in the headroom, even (see the point 4 among the figure, it represents surrounding air) water vapour also will transmit through barrier film in the time of outside wetting.In above-mentioned atmospheric environment, in the time of 14 ℃ relative humidity will drop to 55% or below so that the entering once more of water.At this moment corresponding one about 13% water content and when this water content the circulation of air will be stopped because oven dry is finished.The circulation that lacks air has seriously stoped the transmission of water vapour, so the wetting again possibility of cereal has been eliminated.The content difference of water vapour has determined that the speed-content difference of oven dry is big more between inside and outside, and the speed of oven dry is just fast more.So for the normal temperature condition of outside, when the relative humidity of external environment condition was hanged down, the speed of oven dry will be very fast.

Should also be noted that barrier film is the function of relative humidity to the Penetration Signature self of water vapour.In order to transmit water vapour to greatest extent by barrier film, the high relative humidity of chamber interior be pursue.The oxygen flow characteristic of barrier film also is the function of relative humidity, although the oxygen flow degree is lower.

Pay special attention to the specification of fan and heater, so that air sends cereal to accurate amount under correct temperature and relative humidity condition.

The operation of oven dry:

When having loaded cereal in the chamber, the relative humidity of headroom is corresponding to the water content of cereal.The cereal relative humidity of 20% moisture content is 89%.The switch closure of fan and heater, drying course has just directly begun.In the above-described embodiments, the air that comes from pipeline is during by cereal, only when the equilibrium relative humidity (ERH) of cereal be higher than air the time, air ability is taken away moisture content from cereal.By the relative humidity and control fan and the heater that monitor headroom, the process that makes oven dry cereal is when reaching with the desirable corresponding equilibrium relative humidity (ERH) of water content, and drying course has just stopped.The equilibrium relative humidity (ERH) of the cereal of 14% water content is 63%.If so be 65% from the relative humidity of the air of cereal.Cereal becomes and must do.Typically cereal was dried in six weeks.This is inaccessible not use heater.

Keep an anoxic environment space:

Before oven dry or when cereal is existed in the chamber in the drying course, cereal itself or relative bacterium will oxygen consumed, 21% decline that the contents level of oxygen is will be from air common.The existence of insect also has same oxygen consumption effect.Because the difference of the oxygen content that chamber is inside and outside, very a spot of oxygen may turn back to chamber from the outside.If the consumption of oxygen is higher, the hypoxgia that enters chamber just maintains in the chamber on the low-level oxygen content to improve oxygen concentration significantly.When the content of oxygen was low, the needed consumption of bacterium and insect had been limited.If therefore chamber interior exists active biology or insect activity, the level of low oxygen content can be kept, and this has limited the required consumption of cereal conversely.

The measurement of transmission of water vapor speed (WVTR)

Provide the description of the experiment that is used for measuring transmission of water vapor speed below.

In this process, about 70ml contains the potassium acetate of 35 weight portions and the solution of 15 weight portion distilled water has been placed in the polyacrylic cup of 133ml, and the internal diameter of rim of a cup is 6.5cm.Adopt a kind of minimum steam transmission speed, be approximately 85,000g/m ²The porous Teflon of/24h (PTFE) film, it is pressed the method for the U.S. Pat 4,862,730 of Crosby and tests, and can be from W.L Gore ﹠amp; Associates Inc.of Newark, the Delaware place obtains.This film is heated on the limit that is closed to a cup and forms a tension, sealing, microporous barrier, comprises solution.

A kind of similar porous PTFE barrier film has been arranged to the surface of a tank.Utilize a temperature-controlled chamber and a water circulating slot, water tank device is controlled in 23 ℃ ± 0.2 ℃.

Barrier film sample to be tested can be in temperature and is 23 ℃, relative humidity and be under 65% the condition before the beginning experimental arrangement.After sample was placed, the barrier film of many microporous polymers to be measured contacted with the porous Teflon barrier film that is placed in flume surface, and two membranes has at least 15 minutes and reaches balance before the cup device is introduced.

It is 1/1000g that the cup device is weighed into precision, and is reversed the center that is placed on test specimen.

The transmission of water is caused by driving force, oozes out current along the infiltration direction between water in the driving force tank and the saturated salt solution and produces.This sample was tested 20 minutes, then the cup device was removed, and was weighed into the accuracy of 1/1000g once more.

The transmission of water vapor speed (WVTR) of sample increases and calculates from the weight of cup device, and what restrained and represent with every per square meter of surface area sample transmission in per 24 hours.

The measurement of oxygen permeability

The measuring method of oxygen permeability (with resistance oxygen) below will provide.

The measurement of permeability is to use a kind of F738-85 experimental technique of the ASTM of meeting standard to carry out.The experiment material of experiment usefulness is divided into a upper chamber and a lower chamber with rustless steel container.The nitrogen of 100% content is passed through lower chamber, and the oxygen of 100% content is passed through upper chamber.Make the gas stream that flows through two chambers keep constant with flow controller.The content of oxygen is measured by gas chromatography.Permeability (P) obtains by following formula:

P＝C×F/A

Here C is the oxygen content of lower chamber

F is the throughput by lower chamber

A is the area of experiment thing

Because the characteristic of film, gas can not be completely enclosed within the permeability survey instrument.Now 100% nitrogen is passed through the upper and lower part chamber of permeability survey container, carry out " leak-testing ".Measure the oxygen concentration that is leaked in the lower chamber then, and calculate present permeability.

The oxygen permeability value of barrier film is used to the leakage rate of lower chamber and is revised, and can obtain, and its computational methods are to measure permeability to deduct the apparent permeability.

The permeability constant of interlayer is as follows:

K=2.99 * 10 ^-8MS ^-1(3.34 * 10 ⁷Sm ^-1The resistance rate) at this K=permeability/concentration gradients (gm ^-3).

Because it is too little that the content of lower chamber is compared with the content of upper chamber, the amplitude of concentration gradients can be for being the content of upper chamber.

The ratio of water vapor permeation constant and oxygen permeability

The permeability constant of transmission of water vapor can calculate (d=days) from a kind of transmission of water vapor speed of typical film.

Transmission of water vapor speed=4000gm ^-2d ^-1

＝0.0463gm ^-2S ^-1（/86400）

The permeability of equation that Here it is.The permeability constant K is

Permeability (Perm)=K * DELTAP or K=(Perm)/(DELTAP) gm ^-2S ^-1/ gm ^-3Here DELTAP is vapour content (20%) poor of vapour content (100%) and the fiber cloth outside of fiber cloth inside.DELTAP is the difference of the absolute humidity under 100% and 20% relative humidity (rh), and here absolute humidity ABSHUM is

ABSHUM＝（E×2170）/（273.15+T）gm ^-3

Here E is water vapor pressure Kpa

T is a temperature ℃

Water vapor pressure E is that saturated vapor pressure Es takes advantage of relative humidity when having provided relative humidity.

Es＝exp[16.6536-4030.183/（T+235）]Kpa?（6）

Test for the water transmission speed under 23 ℃ and 100% and 20% relative humidity condition

Es＝2.8087Kpa

DELTAP＝（1.0-0.2）×Es×2170/（273.15+23）gm ^-3

＝16.46gm ^-3

The permeability of water vapour is

K＝ 0.0463/16.46 gm ^-2S ^-1/gm ^-3＝2.8×10 ^-3ms ^-1

The ratio of the permeability of barrier film is

(KH ₂O)/(Ko ₂) = (2.8×10 ^-3)/(2.99×10 ^-8) =1×10 ⁵

So this typical barrier film is to oxygen permeability 100,000 times to the permeability of water vapour.

Claims

1, a kind of equipment of drying material, it comprises

The chamber of a dress material, and the chamber of dress material has kept a gas compartment basically;

Water vapour conversion equipment, water vapour conversion equipment are the parts of chamber, and it comprises infiltration water steam and the barrier film of impermeable described gas basically;

To the heater of chamber interior heat supply of oven dry material, the water vapour in the gas described in the equipment is selectively transferred out by barrier film and gas has been left in the chamber basically.

2, equipment as claimed in claim 1 is characterized in that chamber further comprises a closeable inlet and closeable outlet that the described material that will dry is transmitted by chamber.

3, equipment as claimed in claim 2 is characterized in that further comprising being in making the described material transmitting device by chamber continuously in the chamber.

4,, it is characterized in that further comprising the EGR of the gas recirculation that makes in the chamber as the described equipment of one of above-mentioned claim.

5,, it is characterized in that the part of the barrier film of water vapour conversion equipment as the wall of the integrated chamber of the described need oven dry of splendid attire material as the described equipment of one of above-mentioned claim.

6, as the described equipment of one of claim 1 to 4, it is characterized in that the water vapour conversion equipment is that first module by chamber constitutes, and be connected on Unit second of the chamber that the storage material uses, its tube connector guides to first module to the gas of the moisture vapor around the material of need oven dry, and the gas that vapour content has been reduced returns in described Unit second.

7, equipment as claimed in claim 6 is characterized in that the water vapour conversion equipment comprises a tubular barrier film at least.

8,, it is characterized in that further comprising the dehydration equipment that reduces the water vapour pressure in the barrier film ambient air outside as the described equipment of one of above-mentioned claim.

9,, it is characterized in that heater comprises the heater of a heated air as the described equipment of one of above-mentioned claim.

10,, it is characterized in that heating plant comprises a surface or an inner solar absorption surface at chamber wall, so that heat described gas as the described equipment of one of claim 1 to 8.

11, as the described equipment of one of claim, it is characterized in that described gas compartment oxygen content is less than 2%(weight).

12,, it is characterized in that barrier film comprises the porous Teflon (EPTFE) of infiltration water steam and a kind ofly is applied to the steam of infiltration water basically on the above-mentioned EPTFE and the coating of impermeable gas as the described equipment of one of above-mentioned claim.

13, equipment as claimed in claim 12 is characterized in that the adhesive linkage of infiltration water steam has been bonded at another EPTFE layer on the described coating.

14,, it is characterized in that barrier film has 1500g/m at least as the described equipment of one of above-mentioned claim ²It water vapor permeation rate.

15, as the described equipment of one of above-mentioned claim, the gas leakage that it is characterized in that chamber is that every day is less than 100% of volume of gas in the chamber.

16, as the described equipment of one of above-mentioned claim, it is characterized in that barrier film to the permeability of gas with to the ratio of the permeability of water vapour less than 1 * 10 ^-2

17,, it is characterized in that the water of the impermeable liquid state of barrier film as the described equipment of one of above-mentioned claim.

18, a kind of method of drying material, it comprises:

Provide one to hold material that needs oven dry and the chamber that contains a gas compartment basically;

Heated air;

Heated air is fed the content that contacts with material and improve water vapour in the gas; And

To increase the gas of vapour content with infiltration water steam basically and the barrier film of impermeable described gas contacts, like this, water vapour passes barrier film selectively and discharges.

19, method as claimed in claim 18 is characterized in that: need the material of oven dry to include volatile composition, barrier film is retained in volatile composition in the chamber basically.

20, as claim 18 or 19 described methods, it is characterized in that: needing the material of oven dry is coffee, cocoa, onion, pimiento.

21, as claim 18 or 19 described methods, it is characterized in that: needing the material of oven dry is cereal.

22, as the described method of one of claim 18 to 21, it is characterized in that: the oxygen content of the described gas compartment is less than 2% weight portion.

23, as the described method of one of claim 18 to 22, it is characterized in that: a kind of inert gas is introduced into the gas compartment.