CN102012148B - Vacuum drying control method - Google Patents
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- CN102012148B CN102012148B CN 201010550715 CN201010550715A CN102012148B CN 102012148 B CN102012148 B CN 102012148B CN 201010550715 CN201010550715 CN 201010550715 CN 201010550715 A CN201010550715 A CN 201010550715A CN 102012148 B CN102012148 B CN 102012148B
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Abstract
The invention discloses a vacuum drying control method. The control method comprises the following steps: placing the materials to be dried in a sealed drying chamber, and heating the drying chamber; starting a vacuum pump communicated with the drying chamber, and pumping the air in the drying chamber; monitoring the air pressure in the drying chamber continuously with a pressure meter, and transmitting the air pressure signal to a micro processor with the pressure meter; and judging whether the materials to be dried are dry by the micro processor according to the variation of the air pressure in the drying chamber. By adopting the technical proposal provided by the invention, drying of the materials to be dried can be finished accurately, and the cost can be reduced.
Description
Technical field
The present invention relates to the vacuum drying technique field, relate in particular to a kind of vacuum drying control method.
Background technology
The characteristic that vacuum drying utilizes liquid (water, chemistry or biological solvent) boiling point under the low pressure state to reduce, can be under room temperature or low-temperature condition dry thing to be dried.Vacuum drying does not destroy physics, the biological and chemical characteristic of thing to be dried, all is widely used in all trades and professions.In the process of vacuum drying, thereby how the drying regime of perception thing to be dried control dry run is a key factor.The method of present modal control dry run is regularly, namely rule of thumb sets the needed time of thing dry run to be dried.The method shortcoming is bad timing, if regularly too short, dry run stops too early, and thing to be dried also contains moisture, if regularly long, dry run stops too late, can lose time and the energy.
Another kind method is to install humidity sensor in vacuum drying cabinet, and for example infrared sensor utilizes airborne moisture the absorption of infrared ray specific wavelength to be come the humidity of perception thing to be dried.But the humidity sensor temperature influence is larger, and the temperature of thing to be dried can affect the precision of humidity sensor, and humidity sensor can increase the cost of Minton dryer.
The method that also has another kind of decision drying regime is to measure the indoor pressure of vacuum drying.When pressure is lower than a people for the particular value set, think that thing to be dried has reached drying regime.The starting point of the method is to think after thing to be dried reaches drying regime, no longer includes liquid evaporation, and the indoor pressure of vacuum drying will reduce.But the method has been ignored the very important point, and namely the evaporating state of thing to be dried not only depends on the content of the liquid (water, chemistry or biological solvent) that needs are dry, and depends on the evaporating temperature of thing to be dried.When the temperature reduction of thing to be dried, when making liquid (water, chemistry or biological solvent) steam pressure (vapor pressure) reduction of its contained needs drying, evaporation can slow down greatly, thereby causes the indoor pressure decreased of vacuum drying.If be that the particular value of setting judges that thing to be dried has reached drying regime be lower than a people when pressure this moment only, will cause erroneous judgement disconnected, evaporation process is stopped too early.Another shortcoming of the method is that object to be dried and class of liquids are a lot, if set a single particular pressure value for all drying objects and liquid, usually make many objects can not reach abundant drying, thereby or overdrying destroy physics, the biological and chemical characteristic of object to be dried.If set respectively a particular pressure value for each drying objects and liquid, will be so that the manufacturing of vacuum drying system and maintenance be very complicated.In addition, the operating characteristic of vacuum drying system changed along with service time, for example, the leakage of vacuum system and pollution, the variation of vavuum pump operating characteristic all can be so that the particular value that begins to set be no longer applicable.
Summary of the invention
The object of the invention is to propose a kind of vacuum drying control method, can finish exactly the drying to thing to be dried, and cost.The present invention proposes vacuum dryer and control method is applicable to any dry liquid that needs, and below the explanation supposition need to dry liquid be water.
For reaching this purpose, the present invention by the following technical solutions:
A kind of vacuum dryer, comprise hothouse, condenser, vavuum pump, pressure sensor, signal amplifier and microprocessor, wherein, hothouse, condenser is connected air duct with vavuum pump and connects successively, pressure sensor one end is communicated with hothouse by air duct, the other end of pressure sensor is connected with signal amplifier, signal amplifier also is connected with microprocessor, hothouse is airtight, be used for placing thing to be dried, vavuum pump is used for extracting the air of hothouse and condenser, condenser is used for the airborne moisture that the deposition hothouse transports, pressure sensor is used for converting the air pressure in the hothouse to the signal of telecommunication and sends to signal amplifier, signal amplifier is used for amplification signal and is transmitted to microprocessor, and microprocessor is used for the signal of telecommunication control dry run of sending according to signal amplifier and judges whether thing to be dried reaches drying regime.
Pressure sensor comprises temperature compensation means.
Also comprise heater, heater is used for heating to hothouse.
Also comprise differential pressure transducer and vacuum valve, one end of differential pressure transducer with and the air duct connection that is communicated with of pressure sensor, the other end of differential pressure transducer by vacuum valve with and the air duct connection that is communicated with of condenser, differential pressure transducer also is connected with signal amplifier.
Microprocessor comprises analog-digital commutator, and the signal of telecommunication that analog-digital commutator is used for signal amplifier is sent converts data signal to.
A kind of vacuum drying control method may further comprise the steps:
A, thing to be dried is put into airtight hothouse, and dry kiln;
The vavuum pump that B, unlatching are communicated with hothouse extracts the air in the hothouse;
C, pressure gauge continue to monitor the air pressure of hothouse, and air pressure signal is sent to microprocessor;
D, microprocessor judge according to the air pressure change of hothouse whether thing to be dried reaches drying regime.
Step C further may further comprise the steps:
At first adopts pressure sensor is monitored the air pressure of hothouse, and air pressure signal is sent to microprocessor;
When the air pressure of hothouse is not more than 40 millimetres of mercury, adopts the air pressure of differential pressure transducer monitoring hothouse, and air pressure signal is sent to microprocessor.
Step D further may further comprise the steps:
In the thing dry run to be dried, microprocessor is to the continual real-time sampling of pressure sensor, the air pressure in the timing acquisition hothouse.Per 0.1 second of sample frequency is (10HZ) once.After per 100 samplings, microprocessor calculates average A (i)=∑ [0.01*y (i)] to 100 force value, and y (i) is the per 0.1 second sampled value of pressure sensor.Calculate last air pressure and the difference of working as time air pressure, it is the slope that pressure changes, (original difference is only the time dependent slope of air pressure in the hothouse divided by time of timing microprocessor sampling air pressure to B (j)=A (i-1)-A (i), but the time because of the air pressure in the microprocessor samples hothouse is fixed, so can be equivalent to slope with difference.If the time of the air pressure in the microprocessor samples hothouse is revocable, then need to replace difference with slope).
And in the memory cell of microprocessor, preserve nearest five times difference.
Phase I if difference shows that greater than zero (B (j)＞0) pressure descends, at this moment, even force value may be very low, can not stop dry run, and pressure drop is that the moisture evaporation reduces because the vapour pressure of moisture reduces in the thing to be dried.If the amplitude of variation of nearest five times difference greater than the predetermined quantity millimetres of mercury (such as 5 millimetress of mercury, this numerical value is looked concrete thing to be dried and difference), when the difference fast-descending and reach and be not more than 1 millimetres of mercury, heat to hothouse, when heating, microprocessor continues to monitor four kinds of situations that pressure changes:
If the absolute value of 1 difference keeps being not more than 1 millimetres of mercury, judge that then thing to be dried has reached drying regime, stops dry run.
If 2 differences become less than zero (B (j)＜0), show that pressure rises, judge that thing to be dried does not reach drying regime, moisture evaporates in the thing to be dried, and no matter force value just can not stop dry run, keep thing temperature to be dried, enter second stage.
If 3 differences are greater than zero, difference descends slowly and greater than 1 millimetres of mercury, judges that then thing to be dried does not reach drying regime, enters second stage.
If 4 differences are less than zero (B (j)＜0), but the absolute value of difference is excessive, the vapour pressure that shows moisture in the thing to be dried rises very large, so that the moisture evaporation is too fast, the very large temperature of thing to be dried that then shows of the vapour pressure of moisture rising raises too much in the thing to be dried, for some thermally sensitive things to be dried, destroys thing to be dried in order to prevent high temperature, should slow down the heating to thing to be dried this moment, enters second stage.
Second stage, the absolute value of difference is not more than 1 millimetres of mercury, judges that then moisture evaporation and the vacuum pumping speed of thing to be dried reaches balance, and thing to be dried does not reach drying regime, continues dry run, enters the phase III;
Phase III, through after the second stage, if current difference and nearest five times difference continue greater than zero, and the difference amplitude of variation less than the predetermined quantity millimetres of mercury (such as 5 millimetress of mercury, this numerical value is looked concrete thing to be dried and difference), heat to hothouse, if difference keeps being not more than 1 millimetres of mercury greater than the absolute value of zero or difference, judge that then thing to be dried has reached drying regime.
When coming to object intensification to be dried by dry kiln, stop as required vavuum pump.
Adopted technical scheme of the present invention, can finish exactly the drying to thing to be dried, avoid making many objects can not reach abundant drying, or thereby overdrying destroys physics, the biological and chemical characteristic of object to be dried, and pressure sensor is of many uses, and use amount is large, batch production, unit price is low, and selectable model is many, can reduce cost with respect to controlling dry run with other sensor.
Description of drawings
Fig. 1 is the structural representation of vacuum dryer in the specific embodiment of the invention.
Fig. 2 is the flow chart of vacuum drying control in the specific embodiment of the invention.
Fig. 3 is the drying curve figure of thing to be dried in the specific embodiment of the invention.
The specific embodiment
Further specify technical scheme of the present invention below in conjunction with accompanying drawing and by the specific embodiment.
The main thought of technical scheme of the present invention is to utilize the variation of measuring the indoor pressure of vacuum drying to come perception thing drying regime to be dried, rather than one the people judge drying regime for the particular value of setting, the indoor pressure of vacuum drying is that the pressure that produces during the moisture evaporation in the thing to be dried changes and the dynamic equilibrium of vacuum pumping speed.When thing to be dried was not yet finished drying, the moisture evaporation in the thing to be dried became gaseous state, and the indoor pressure of vacuum drying is raise, and after thing drying to be dried, water no longer evaporates, and the indoor pressure of vacuum drying reduces rapidly.So, by measure pressure in the hothouse change can perception thing to be dried drying regime, thereby the control dry run.
Fig. 1 is the structural representation of vacuum dryer in the specific embodiment of the invention.As shown in Figure 1, this vacuum dryer comprises hothouse 101, heater 109, condenser 104, vavuum pump 105, pressure sensor 103, differential pressure transducer 111, vacuum valve 112, signal amplifier 110 and microprocessor 108, wherein, hothouse, condenser is connected air duct 106 and connects successively with vavuum pump, the air duct internal diameter is 6 millimeters, pressure sensor one end is communicated with hothouse by air duct, the other end of pressure sensor is connected with signal amplifier by wire 107, signal amplifier also is connected with microprocessor, one end of differential pressure transducer with and air duct 106 connections that are communicated with of pressure sensor, the other end of differential pressure transducer by vacuum valve with and the air duct 106 that is communicated with of condenser be communicated with, differential pressure transducer is also passed through wire 107 and is connected with signal amplifier.
Hothouse is airtight, is used for placing thing 102 to be dried.
Heater is selected 300 watts PULSE HEATING device, can heat to hothouse.
Vavuum pump power is 3/4 horsepower (560 watts), and 220 liters of gas pumping speed per minutes, end vacuum are used for extracting the air in hothouse and the condenser less than 2000Pa.
The airborne moisture that condenser deposition hothouse transports.
The pressure sensor model is MPX2100DP, and range 0-0.1MPa has demarcated and has temperature compensation means, and it converts the air pressure in the hothouse to the signal of telecommunication and sends to signal amplifier.
Signal amplifier can amplification signal and is transmitted to microprocessor.
Microprocessor adopts the PIC18F452 processor, comprise analog-digital commutator, the signal of telecommunication that analog-digital commutator can be sent signal amplifier converts data signal to, and the signal of telecommunication that microprocessor is also sent according to signal amplifier is controlled dry run and judged whether thing to be dried reaches drying regime.
High ten times of the pressure measurement accuracy specific pressure sensors of differential pressure transducer, but little ten times of the pressure range specific pressure sensors of differential pressure transducer.One end of differential pressure transducer links to each other with air duct by a vacuum valve, and the other end directly links to each other with the air duct of pressure sensor, and the output electrical signals of differential pressure transducer also links to each other with microprocessor by signal amplifier.When the vacuum valve was opened, the pressure at differential pressure transducer two ends equated that the signal of differential pressure transducer is output as zero.When the measured force value of pressure sensor reaches or during less than 40 millimetres of mercury, vacuum valve is closed.Close the end that rear differential pressure transducer links to each other with vacuum valve, pressure remains on a steady state value, and the pressure of the differential pressure transducer other end is along with the change in pressure in the hothouse.Like this, just cause a pressure differential at the two ends of differential pressure transducer, it is measured by microprocessor that its pressure differential converts the signal of telecommunication to.The certainty of measurement specific pressure sensor of differential pressure transducer is wanted high ten times, can change by the interior pressure of more accurate measurement hothouse.
The evaporation capacity of moisture depends on the pressure the when steam pressure (vapor pressure) of moisture is the thermodynamical equilibrium of steam and condensed state water (liquid state) in the thing to be dried.When reaching thermodynamic equilibrium state, aqueous water has tendency to flash to gaseous form, and vaporous water also has tendency to be condensed into liquid state from gas form.The speed that two states changes equates.In process of vacuum drying, the steam that produces during evaporation constantly shifts out outside the drying device by vavuum pump, so that the moisture in the thing to be dried can only unidirectionally evaporate, and can not condense like this.
The boiling point of liquid is the temperature of vapour pressure and the ambient pressure of liquid when equating, when boiling temperature, makes the water in the thing to be dried become gaseous state from liquid state thereby the vapour pressure of liquid can overcome environmental pressure.The vapour pressure of moisture is directly connected to the evaporation rate of liquid, and under same environmental pressure, higher steam pressure energy produces larger evaporation rate.The vapour pressure of water is along with the relation between the variations in temperature of water can be described with the Clausius-Capeyron formula.
When with the dry thing to be dried of vacuum dryer, the evaporation rate linear correlation of liquid in the instantaneous pressure value in the hothouse and the thing to be dried.For example, when the liquid in the thing to be dried was water, the evaporation rate of moisture depended on two factors in the thing to be dried: the content of the vapour pressure of water and water in the thing to be dried.The not only variation of the content of water in the thing to be dried, the variation of the vapour pressure of water also can affect the variation of air pressure in the device in the thing to be dried.When the vapour pressure of water in the thing to be dried lowered, evaporation rate can reduce, and the pressure in the hothouse can reduce.But this does not show that thing to be dried has reached drying regime.Thing to be dried probably also contains moisture, and just evaporation rate has reduced.Iff the drying regime of indicating thing to be dried with the atmospheric pressure value in the hothouse, usually can judge by accident disconnectedly, it is too early to stop dry run, so that thing to be dried bone dry not yet.
The vapour pressure of water changes along with the variations in temperature of thing to be dried in the thing to be dried.In the actual drying process, water is being converted in the gaseous process by liquid state, takes away amount of heat (2260 joule/gram), so that the instantaneous reduction of thing temperature to be dried, cause that vapour pressure lowers, thereby so that evaporation rate reduces, cause the minimizing of hothouse internal gas pressure.Later effect along with the hothouse external heating device, thing absorbing heat to be dried, thing temperature recovery to be dried, the vapour pressure of moisture rises thereupon in the thing to be dried, thus evaporation rate rises, and the pressure in the hothouse also rises.So vapour pressure is a fast-changing process on the impact of air pressure in the device.
Otherwise moisture then is a slow procedure on the impact of hothouse internal pressure in the thing to be dried.Moisture evaporation in the thing to be dried needs a time course.The time of thing bone dry to be dried is depended on and many factors, the pumping speed of vavuum pump, the power of heater, the size of thing to be dried, what of moisture in the thing to be dried, but the pressure in the hothouse is a relatively level and smooth time course when not considering the variation of vapour pressure along with the variation of the water content of thing to be dried.
When the force value in using hothouse was controlled the dry run of thing to be dried, the variation of the vapour pressure of moisture was noise on the impact of hothouse internal pressure in the thing to be dried, disturbs the observation to dry run.But the variation of vapour pressure is a Fast Process, and impact then is a process that changes at a slow speed to moisture on the hothouse internal pressure in the thing to be dried.Calculate the time dependent slope of hothouse internal pressure by microprocessor and can remove the vapour pressure variation to the interference of force value, correctly judge the drying regime of thing to be dried.
Fig. 2 is the flow chart of vacuum drying control in the specific embodiment of the invention.As shown in Figure 2, the flow process of vacuum drying control may further comprise the steps:
The vavuum pump that step 202, unlatching are communicated with hothouse extracts the air in the hothouse.
In this process, in order to take into account pressure range and accuracy, pressure gauge adopts two kinds, and a kind of is pressure sensor, and another kind is differential pressure transducer.At first adopts pressure sensor is monitored the air pressure of hothouse, and air pressure signal is sent to microprocessor, when the air pressure of hothouse is not more than 40 millimetres of mercury, adopts the air pressure of differential pressure transducer monitoring hothouse, and air pressure signal is sent to microprocessor.
In the thing dry run to be dried, microprocessor is to the continual real-time sampling of pressure sensor, the air pressure in the timing acquisition hothouse.Per 0.1 second of sample frequency is (10HZ) once.After per 100 samplings, microprocessor calculates average A (i)=∑ [0.01*y (i)] to 100 force value, and y (i) is the per 0.1 second sampled value of pressure sensor.
Calculate last air pressure and the difference of working as time air pressure, it is the slope that pressure changes, (original difference is only the time dependent slope of air pressure in the hothouse divided by time of timing microprocessor sampling air pressure to B (j)=A (i-1)-A (i), but the time because of the air pressure in the microprocessor samples hothouse is fixed, so can be equivalent to slope with difference.If the time of the air pressure in the microprocessor samples hothouse is revocable, then need to replace difference with slope).
And in the memory cell of microprocessor, preserve nearest five times difference.
If 1 difference is sometimes greater than zero, sometimes less than zero, and the absolute value of difference keeps being not more than 1 millimetres of mercury, judges that then thing to be dried has reached drying regime.
If 2 differences become less than zero (B (j)＜0), show that pressure rises, judge that thing to be dried does not reach drying regime, moisture evaporates in the thing to be dried, and no matter force value just can not stop dry run, keep thing temperature to be dried, enter second stage.
If 3 differences are greater than zero (B (j)＞0), difference descends slowly and greater than 1 millimetres of mercury, shows that then pressure descends, but the evaporation of the moisture of thing to be dried and vacuum pumping speed not yet reach balance, judge that thing to be dried does not reach drying regime, enters second stage.
If 4 differences are less than zero (B (j)＜0), but the absolute value of difference is excessive, the vapour pressure that shows moisture in the thing to be dried rises very large, so that the moisture evaporation is too fast, the very large temperature of thing to be dried that then shows of the vapour pressure of moisture rising raises too much in the thing to be dried, for some thermally sensitive things to be dried, destroys thing to be dried in order to prevent high temperature, should slow down the heating to thing to be dried this moment, enters second stage.
When coming to object intensification to be dried by the heating, vacuum hothouse, faster in order to heat up, can optionally stop vavuum pump.When vavuum pump stopped extracting vacuum, the pressure rise that vacuum drying is indoor cause vapour pressure and the poor of environmental pressure of the liquid of the needs drying in the thing to be dried to increase, thereby evaporation process was slowed down.Because evaporation process is slowed down, the heat that evaporation is taken away reduces, thereby it is faster that object to be dried is heated up.Extracting vacuum again after object to be dried heats up is carried out above Four processes.
Fig. 3 is the drying curve figure of thing to be dried in the specific embodiment of the invention.As shown in Figure 3, the A section of curve is initial stage of drying, and thing temperature to be dried is low, and the vapour pressure of moisture is less than the pressure of thing surrounding environment to be dried in the hothouse in the thing to be dried, and evaporation slows down or evaporates almost and stops.At this moment, the time dependent curve of pressure in the hothouse shows very large negative slope, and the force value in the hothouse is very little.Will think drying of thing to be dried by mistake if only judge by the numerical value of pressure this moment, clearly, this and actual state are not inconsistent.
The vapour pressure of the B section of the curve thing temperature to be dried that is thing to be dried behind the hothouse external heat parts absorbing heat and moisture raises gradually, evaporation recovers or accelerates, at this moment, the pressure rise that heating in vacuum is indoor, when the pumping speed of thing evaporation rate to be dried and vavuum pump reached dynamic equilibrium, the pressure in the hothouse kept relatively stably value.
The C section of curve is that thing to be dried approaches drying, because the minimizing of moisture, evaporation capacity reduces, pressure in the hothouse begins to descend, the D section of curve is to evaporate to stop behind thing bone dry to be dried, and the pressure in the hothouse tends to be steady again, but remains on a lower force value.
So drying regime that the force value in the hothouse and the time dependent slope of force value can be used for judging thing to be dried jointly.This method can avoid the impact of the vapour pressure variation of moisture in the thing to be dried, thereby it is disconnected to reduce erroneous judgement than the drying regime of only judging thing to be dried with force value.
The time dependent other feature of force value also can help to judge the degree of drying of thing to be dried.When the moist thing to be dried of drying, force value is slow decreasing in time; When not having thing to be dried in the hothouse, then the force value fast-descending keeps constant, no longer temporal evolution; When dry low moisture thing to be dried, force value begins fast-descending, then rising.Its ascensional range depends on water content and the evaporation rate of thing to be dried.
Use the variation of the measured pressure value that the differential pressure meter can be sensitiveer.At this moment, because differential pressure instrumentation amount is the relative pressure value, so the variation of force value is opposite with the timing of use absolute pressure.The rising of differential pressure instrumentation amount is equivalent to the decline of absolute pressure timing, and vice versa.
In addition, utilize amplitude of variation, rate of change or the change histories etc. of pressure slope, can judge the degree of drying of thing to be dried.
The above; only for the better specific embodiment of the present invention, but protection scope of the present invention is not limited to this, anyly is familiar with the people of this technology in the disclosed technical scope of the present invention; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claim.
Claims (3)
1. a vacuum drying control method is characterized in that, may further comprise the steps:
A, thing to be dried is put into airtight hothouse, and dry kiln;
The vavuum pump that B, unlatching are communicated with hothouse extracts the air in the hothouse;
C, pressure gauge continue to monitor the air pressure of hothouse, and air pressure signal is sent to microprocessor;
D, microprocessor judge according to the air pressure change of hothouse whether thing to be dried reaches drying regime,
Wherein, step C further may further comprise the steps:
Adopt the air pressure of two kinds of pressure gauge monitoring hothouses, a kind of is pressure sensor, and another kind is differential pressure transducer, and at first adopts pressure sensor is monitored the air pressure of hothouse, and air pressure signal is sent to microprocessor;
When the air pressure of hothouse is not more than 40 millimetres of mercury, adopt the air pressure of differential pressure transducer monitoring hothouse, and air pressure signal is sent to microprocessor,
Step D further may further comprise the steps:
Timing microprocessor obtains the air pressure in the hothouse, calculates last air pressure and the difference of working as time air pressure, and preserves nearest five times difference in the memory cell of microprocessor;
Phase I, if difference is greater than zero, and difference reaches greater than 1 millimetres of mercury, show that pressure is just at fast-descending, at this moment, even force value is very low, also continue dry, if the amplitude of variation of nearest five times difference is greater than the predetermined quantity millimetres of mercury, when the difference fast-descending and reach when being not more than 1 millimetres of mercury, heat to hothouse, and when heating, microprocessor continues to monitor following four kinds of situations that pressure changes: (1) if difference sometimes greater than zero, sometimes less than zero, and absolute difference keeps being not more than 1 millimetres of mercury, judge that then thing to be dried has reached drying regime, (2) if difference becomes less than zero, judge that then thing to be dried does not reach drying regime, keep thing temperature to be dried, enter second stage, (3) if difference greater than zero, difference descends slowly and greater than 1 millimetres of mercury, judges that then thing to be dried does not reach drying regime, enter second stage (4) if difference less than zero, but the absolute value of difference is excessive, judges that then the moisture evaporation is too fast in the thing to be dried, slows down the heating to hothouse this moment;
Second stage, the absolute value of difference is not more than 1 millimetres of mercury, judges that then moisture evaporation and the vacuum pumping speed of thing to be dried reaches balance, and thing to be dried does not reach drying regime, continues dry run, enters the phase III;
Phase III, through after the second stage, if current difference and nearest five times difference continue greater than zero, and the difference amplitude of variation is less than the predetermined quantity millimetres of mercury, heat to hothouse, if after after a while difference keep greater than zero or the absolute value of difference be not more than 1 millimetres of mercury, judge that then thing to be dried has reached drying regime.
2. a kind of vacuum drying control method according to claim 1, it is characterized in that microprocessor once obtained manometric air pressure signal in per 0.1 second, after per 100 samplings, microprocessor is to 100 atmospheric pressure value calculating mean values, as the current air pressure of hothouse.
3. a kind of vacuum drying control method according to claim 1 when coming to object intensification to be dried by dry kiln, stops vavuum pump as required.
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| CN102628639A (en) * | 2012-05-09 | 2012-08-08 | 常州广为仪器科技有限公司 | Vacuum drying device and vacuum drying control method |
| CN102914484A (en) * | 2012-10-16 | 2013-02-06 | 绥中正国新能源科技有限公司 | Testing method for dryness of pole piece or cell of lithium ion battery |
| CN104396946B (en) * | 2014-11-30 | 2016-02-10 | 河北省农林科学院旱作农业研究所 | Zasiokaurin is from the active dehumidifying device of disturbance normal temperature transformation and the method with its dehumidification |
| KR102203851B1 (en) | 2018-11-12 | 2021-01-15 | 주식회사 케이티앤지 | Aerosol generating device and method of controlling same |
| FR3090835B1 (en) * | 2018-12-19 | 2023-01-13 | Ways | [Process for thermal drying of wood under CO2 atmosphere, drying installation for the implementation of said process and product obtained] |
| TWI687630B (en) * | 2019-04-16 | 2020-03-11 | 亞台富士精機股份有限公司 | Drying system and control method thereof |
| CN114659341B (en) * | 2022-03-02 | 2023-07-07 | 上海兰钧新能源科技有限公司 | Control method for baking lithium ion battery |
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| CN101529189A (en) * | 2006-09-19 | 2009-09-09 | 泰事达技术有限公司 | Method and system for controlling a freeze drying process |
| CN101726447A (en) * | 2009-12-29 | 2010-06-09 | 常州广为仪器科技有限公司 | Method and device for measuring moisture absorptivity of aggregates |
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