Method and apparatus for controlling the dew point temperature of the supply air in a rotary dehumidifier

Abstract

The present invention provides a control method and apparatus for a rotary dehumidifier that consistently ensures the supply air dew point temperature is below a desired temperature while minimizing fluctuations, and that contributes to energy saving. [Solution] If the measured supply air dew point temperature is higher than the set supply air dew point temperature, the regenerative heater output is immediately increased. If the measured supply air dew point temperature is lower than the set supply air dew point temperature, a decision is made to increase, decrease, or maintain the regenerative heater output depending on the degree of the decrease; the increase is implemented immediately, and the decrease is implemented after a predetermined time interval. If the measured supply air dew point temperature is lower than the set supply air dew point temperature, the regenerative heater output may be increased immediately, and then the decision may be postponed for a first time, or the regenerative heater output may be decreased if the degree of the decrease is maintained for a second time. The device may also include a temperature sensor and a controller, with the controller executing the above means.

Description

Technical Field

[0001] The present invention relates to a method for controlling the supply air dew point temperature in a rotary dehumidifier using an adsorbent rotor. In particular, it relates to a control method and device that can ensure the supply air dew point temperature in an ultra-low dew point range and achieve energy savings at the same time.

Background Art

[0002] The general configuration of a rotary dehumidifier using an adsorbent rotor is schematically shown in FIG. 1. The adsorbent rotor 2 in the rotary dehumidifier 1 is generally formed by accommodating an adsorbent in a honeycomb structure formed in a cylindrical shape, and includes a treatment area 3 (the adsorbent adsorbs moisture to dehumidify the passing air) and a regeneration area 4 (heat is applied to the adsorbent to remove moisture to restore the adsorption capacity of the rotor). In addition, the air introduced into the regeneration area is heated by a regeneration heater 5 before introduction. The adsorbent rotor 2 may be provided with a circulation purge area (pre-cooling / pre-heating area) as required (not shown). As the adsorbent, for example, an optimal one is selected and used from chemical substances such as silica gel, zeolite composite, and lithium chloride according to the temperature and humidity environment and air quality environment. The adsorbent rotor 2 rotates by a driving device composed of a driving force transmission belt 6, a motor 7, etc. The rotation passage area of the adsorbent rotor 2 (the area through which each adsorbent part passes as the adsorbent rotor 2 rotates) is partitioned into two airtight areas of the treatment area 3 and the regeneration area 4 for dehumidifying the outside air OA by a casing or the like (not shown) that rotatably accommodates the adsorbent rotor 2. Each adsorbent part 3, 4 in the adsorbent rotor 2 passes through the above two areas in sequence as the adsorbent rotor 2 rotates.

[0003] A processing air passage 8 is connected to the processing area 3 while maintaining an airtight seal. The processing air passage 8 supplies outside air OA to the processing area 3 via the processing fan 9 and flows the processed air SA that has passed through the processing area 3 into a desired space such as a drying chamber. A regeneration air passage 10 is connected to the regeneration area 4 while maintaining an airtight seal. The regeneration air passage 10 is an air passage that allows air to pass through the regeneration area 4 by the action of the regeneration fan 11, making the adsorbent of the adsorbent rotor 2 reusable.

[0004] In rotary dehumidifiers using adsorbent rotors, it is necessary to heat the adsorbent rotor to a high temperature to remove moisture from the adsorbent rotor after it has absorbed moisture, and it is common to install a regenerative heater in the aforementioned position. Since the humidity of the atmosphere differs greatly between summer and winter, the temperature (energy) of the regenerative heater required to stably obtain the desired dehumidified air from the rotary dehumidifier using an adsorbent rotor differs between summer and winter. Conventionally, it has been standard practice to operate the rated system based on the highest humidity in summer. In such a case, for example, if the supply air dew point temperature is set to -50°C and the regenerative heater temperature is set to 140°C for rated operation, the supply air dew point temperature may drop to -70°C in winter. In other words, if the system is operated at rated operation throughout the year, extra energy will be continuously consumed in winter, which is undesirable from an energy-saving perspective.

[0005] On the other hand, as illustrated in Figure 2, the supply air dew point temperature fluctuates even when the regeneration heater's set temperature is constant (Figure 2 shows a range of several tens of minutes across the entire horizontal axis, and the vertical axis is marked in 1°C increments over a certain temperature range below freezing). This is thought to be due to factors such as (1) in large rotary devices, the rotor is divided into several components, resulting in localized variations in performance, (2) in the low dew point region, even slight differences in moisture content can cause dew point fluctuations, and (3) other factors such as the condition of the processing air (outside air) introduced into the adsorbent rotor. Furthermore, while some periodicity is observed in the fluctuation pattern, as shown in Figure 2, it is not constant. Therefore, when controlling the set temperature of the regeneration heater, the fluctuation of the supply air dew point temperature exhibits even more complex behavior.

[0006] In PID control (PID; Controller; Proportional-Integral-Differential Controller) used to control the set temperature of a regenerative heater in a rotary dehumidifier, control is generally performed by measuring the supply air dew point temperature and determining the output of the regenerative heater according to the deviation between the measured value and the set value. In conventional PID control, as illustrated in Figure 3(1), the actual measured supply air dew point temperature fluctuates as shown by the solid line relative to the set value of the supply air dew point temperature.

[0007] Referring to Figures 3(1) and (2) together, first, if the measured supply air dew point temperature exceeds the supply air dew point setpoint, the regenerative heater output is set to 100%, promoting a rapid decrease in the supply air dew point temperature. As the temperature decreases, the supply air dew point temperature continues to decline monotonically, and the regenerative heater output decreases steadily due to PID control. Eventually, the supply air dew point temperature falls below the supply air dew point setpoint, and after some time, the regenerative heater output reaches 0%. As long as the supply air dew point temperature is sufficiently low compared to the supply air dew point setpoint, the regenerative heater output remains at 0%. If the regenerative heater output remains at 0% for an extended period, the supply air dew point temperature begins to rise, and to suppress this rise, the regenerative heater output is turned ON by PID control. The regenerative heater output is digitally increased to 100%, as shown in Figure (2), but because it follows the rise in the supply air dew point temperature, the supply air dew point temperature eventually exceeds the supply air dew point set value again, returning to the initial state. In other words, the delay in changing the regenerative heater output setting in response to the rise and fall of the supply air dew point temperature induces a delay in controlling the supply air dew point temperature, causing the supply air dew point temperature to continuously fluctuate above and below the set value. Note that Figure 3(1) is a schematic representation of Figure 2, meaning that the scale of the horizontal and vertical axes in Figure 3 is approximately the same as in Figure 2.

[0008] Furthermore, the rotation of the rotor is one of the factors contributing to the delay in controlling the intake air dew point temperature. In other words, because the rotor rotates at a low speed of about one revolution every few minutes, there is a time lag between the time a setting is changed and the effect of that change becoming apparent.

[0009] Thus, appropriately controlling the supply air dew point temperature in a rotary dehumidifier is extremely difficult because multiple factors interact in a complex manner, and furthermore, due to the nature of PID control, while it is possible to reduce the fluctuation range of the supply air dew point temperature, it is not possible to make it perfectly constant.

[0010] On the other hand, in the ultra-low humidity environments required in battery manufacturing lines and other applications, the amount of moisture in the air (dew point temperature) directly impacts quality, thus requiring quality assurance to ensure that the supply air dew point temperature is always below the desired temperature. However, as mentioned above, it is difficult to precisely control the supply air dew point temperature with rotary dehumidifiers, and from a quality assurance standpoint, it has become common practice to operate the regenerative heater at its rated capacity, even at the expense of energy efficiency. In particular, the ultra-low dew point range requires considerable precision (a difference of 1°C at -20°C DP (dew point) is 0.06 g / kg, and at -60°C DP it is 0.0008 g / kg), making control extremely difficult.

[0011] Several control methods have been proposed to address the aforementioned problems, but these involve selecting adsorbents or adjusting the airflow of the regeneration fan or the rotation speed of the adsorbent rotor. However, these methods cannot cope with rotor degradation or unexpected situations, and there is room for improvement from the perspective of quality assurance mentioned above. Furthermore, using many sensors to control many targets requires complex calculations, making the device configuration complex and expensive unavoidable. Moreover, even when aiming for a configuration that minimizes the range of temperature fluctuations, products that contribute to quality assurance have not been realized. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 06-63344 [Patent Document 2] Japanese Patent Publication No. 2007-260506 [Patent Document 3] Japanese Patent Publication No. 2011-85270 [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] The present invention was made to solve the technical problems described above. Specifically, the objective is to provide a method for controlling the supply air dew point temperature in a rotary dehumidifier using an adsorbent rotor, which ensures that the supply air dew point temperature is always below a desired temperature while minimizing fluctuations, and which contributes to energy saving, and a rotary dehumidifier equipped with such a supply air dew point temperature control method. [Means for solving the problem]

[0014] To solve the above problems, the present invention provides a method for controlling the dew point temperature of a rotary dehumidifier, in which the output of a regenerative heater is set based on the measured temperature of the supply air dew point temperature. The method involves immediately increasing the output of the regenerative heater when the measured temperature of the supply air dew point temperature is higher than the set temperature of the supply air dew point temperature, and determining whether to increase, decrease, or maintain the output of the regenerative heater according to the degree of the decrease when the measured temperature of the supply air dew point temperature is lower than the set temperature of the supply air dew point temperature, with the increase being performed immediately and the decrease being performed after a predetermined time.

[0015] Furthermore, the present invention provides a rotary dehumidifier equipped with a temperature sensor and a controller, which executes the above-described supply air dew point temperature control method via the controller.

[0016] If the measured supply air dew point temperature is lower than the set supply air dew point temperature, the regenerative heater output may be immediately increased, and then the decision may be postponed for a first time.

[0017] When the measured temperature of the supply air dew point temperature is lower than the set temperature of the supply air dew point temperature, if the measured temperature (1) exceeds the first threshold value, immediately enhance the regeneration heater output and then hold the decision for the first time. If the measured temperature (2) is lower than the second threshold value which is lower than the first threshold value, (i) if the measured temperature exceeds the second threshold value before the elapse of the second time, do not execute the relaxation of the regeneration heater output. (ii) If the measured temperature is still lower than the second threshold value even at the elapse of the second time, the relaxation of the regeneration heater output may be executed at that time.

[0018] In this specification, the "temperature sensor" refers to all devices that can measure the temperature of an object, convert the measured temperature into an electrical signal, and output it. The "controller" will be described later.

[0019] In this specification, "immediately" is used in the sense of "immediately after the controller recognizes that the measured temperature of the supply air dew point temperature and the set temperature of the supply air dew point temperature have reached a predetermined high-low relationship based on the signal from the temperature sensor".

Advantages of the Invention

[0020] According to the supply air dew point temperature control method or device of the present invention, since the intensity of the regeneration heater output can be controlled within an appropriate range, energy saving can be realized. In addition, the supply air dew point temperature can be arbitrarily set and has versatility. Furthermore, since the supply air dew point temperature is the control target, even if the adsorbent of the rotary dehumidifier deteriorates, control according to the deterioration is possible.

[0021] In addition, in order to perform fine control of the supply air dew point temperature, conventionally, complex calculations were required together with many measurement points (types and numbers of sensors), but in the present invention, such procedures are unnecessary, and a simple control method, and thus an inexpensive rotary dehumidifier can be realized.

Brief Description of the Drawings

[0022] [Figure 1] Explanatory drawing of a rotary dehumidifier using a general adsorbent rotor [Figure 2]Graph showing the variation of the supply air dew point temperature under a constant set temperature of the regeneration heater [Figure 3] Graph showing the variation of the supply air dew point temperature in the PID control of a conventional rotary dehumidifier [Figure 4] Schematic diagram of the PID control of a rotary dehumidifier (1) Conventional configuration (2) Embodiment of the present invention [Figure 5] Flowchart according to an embodiment of the present invention [Figure 6] Graph showing an example of the variation of the supply air dew point temperature according to an embodiment of the present invention

Mode for Carrying Out the Invention

[0023] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0024] Fig. 4 schematically shows a comparison of the configuration of (1) the PID control of a conventional rotary dehumidifier and (2) the PID control in the present invention with respect to the adjustment of the supply air dew point temperature and the setting of the regeneration heater temperature in a rotary dehumidifier.

[0025] Conventionally, by the PID control of the right box (DPIC) that controls the supply air dew point temperature setting, a signal that eliminates the deviation between the measured value of the supply air dew point temperature obtained from the signal of the temperature sensor and the set value of the supply air dew point temperature is transmitted to the left box (TIC) that controls the regeneration heater output setting. The box (TIC) that receives the signal uses PID control that incorporates the measured value of the regeneration heater temperature obtained from the signal of the temperature sensor and the set value of the regeneration heater temperature, and transmits a signal that determines the output of the heater in a form based on the above deviation to the heater (see Fig. (1) above).

[0026] In contrast, the present invention is characterized by the provision of a controller that performs calculations and decisions between the left and right boxes described above. The right box (DPIC), which is in charge of setting the supply air dew point temperature, only determines whether the measured value of the supply air dew point temperature obtained from the signal from the temperature sensor exceeds the set value of the supply air dew point temperature and several separately set thresholds, and transmits the result of this determination as a signal to the controller. The controller that receives the signal performs calculations and decisions, which will be described in detail later, and transmits a signal to the left box (TIC), which is in charge of setting the regeneration heater output. The box (TIC) that receives the signal uses PID control that incorporates the measured value of the regeneration heater temperature obtained from the signal from the temperature sensor and the set value of the regeneration heater temperature, and transmits a signal to the heater at the appropriate timing, taking into account the above-mentioned deviation (see Figure (2) above).

[0027] In the embodiments of the present invention, PID control is used as an example for controlling the regenerative heater output by the controller. However, the control means itself is not essential to the present invention, and other control methods may be adopted within the scope of the present invention's concept. Furthermore, in implementing the present invention, the controller that performs signal input / output and calculations is assumed to be a combination of a general temperature controller, timer, and signal converter, but it is not necessarily limited to this configuration. For example, a PLC (Programmable Logic Controller) may be used, or it may be configured as, for example, SCADA (Supervisory Control And Data Acquisition), BMS (Building Management System), or EMS (Energy Management System).

[0028] The above flow will be explained in detail below, primarily from the perspective of the controller's calculation decision and execution timing, with reference to Figure 5.

[0029] For the purpose of this explanation, we will introduce the following values. (i) Let the set temperature of the supply air dew point temperature be T0. Also, let two threshold values that are less than T0 be T1 and T2 (T1 > T2). T1 and T2 can be specified as arbitrary values. Let the measured value measured by a temperature sensor or the like be T as the actual supply air dew point temperature. (ii) Let two variation ratios (unit: %) of the regeneration heater output be d1 and d2. Both d1 and d2 are values less than 100%, and there is no limitation on the magnitude relationship between d1 and d2, but in the main case, it is set as d1 > d2. d1 is used when strengthening the regeneration heater output to relatively quickly lower T when T is within the range of T1 < T < T0 where T approaches T0, and can be set to an arbitrary ratio. On the other hand, d2 is used when relaxing the regeneration heater output because there is no need to lead T to a lower temperature when T is within the range of T < T2 where T is sufficiently lower than T0, and can be set to an arbitrary ratio. (iii) Let two times be τ1 and τ2 as the maintenance times. There is no limitation on the magnitude relationship between τ1 and τ2, but in the main case, it is set as τ1 < τ2. τ1 is used when T is within the range of T1 < T < T0 where T approaches T0, and it is necessary to immediately strengthen the heater output by d1 to surely avoid the situation where T exceeds T0, and then require the arithmetic judgment of the controller after a relatively short maintenance time, and can be set to an arbitrary value. On the other hand, τ2 is used when T is within the range of T < T2 where T is sufficiently lower than T0, and when requiring the arithmetic judgment of the controller after a relatively long maintenance time (since T is sufficiently lower than T0, even if a relatively long maintenance time is provided, it will not affect the stable operation of the device), and can be set to an arbitrary value.

[0030] Hereinafter, the flow (Fig. 5) will be described in order. (1) The controller monitors the deviation e (= T0 - T). Here, T0 is a set value (fixed value), and T is a measured value (variable value) by a temperature sensor. (2) When e < 0: T exceeds T0. Since it is necessary to quickly lower T below T0, the controller sets the regeneration heater output to 100% maximum and continues monitoring (returns to (1)). (3) When 0 < e < T0 - T1: T is lower than T0 but higher than T1 and approaching T0. To ensure that T does not exceed T0, the controller immediately increases the output of the regeneration heater by d1% and maintains this state for τ1 hours, then continues monitoring (returns to (1)). (4) When T0 - T1 < e < T0 - T2: T is lower than T1 and higher than T2. This is a state where the performance of the dehumidifying device is maintained and there is less waste of energy consumption. To maintain this state, the controller continues monitoring without changing the intensity of the regeneration heater output (returns to (1)). (5) When T0 - T2 < e: T is lower than T2. This is a state where the performance of the dehumidifying device is maintained while there is more waste of energy consumption. The controller continues monitoring (returns to (1)) and determines whether this state (T < T2) persists for τ2 hours. That is, (6) If it does not persist for τ2 hours, when the persistence is interrupted, the controller's command switches to the route of (4). On the other hand, (7) If it persists for τ2 hours, the controller relaxes the regeneration heater output by d2% (to suppress energy consumption) and continues monitoring (returns to (1)). By performing the relaxation of d2% one or more times, T increases. When the persistence of T < T2 is interrupted, the controller's command switches to the route of (6) and then to the route of (4). Needless to say, when the heater output is 100% of the upper limit, the increase of d1% is not executed (not shown). The same applies to the relaxation of d2% when the heater output is 0% of the lower limit.

[0031] Qualitatively summarizing the above explanation, the greatest feature of the present invention is that, when it is necessary to lower the supply air dew point temperature, the regeneration heater output is immediately increased, while the decision to reduce the regeneration heater output is withheld for a predetermined time, that is, the timing of the processing can be arbitrarily set. In this case, if the measured supply air dew point temperature is higher than the set supply air dew point temperature, the regeneration heater output is immediately increased, and if the measured supply air dew point temperature is lower than the set supply air dew point temperature, the decision to increase or reduce the regeneration heater output is made according to the deviation, with the increase being carried out immediately and the decision to reduce being withheld for a predetermined time. Furthermore, when the measured supply air dew point temperature is lower than the set supply air dew point temperature, the first time decision may be withheld after the regeneration heater output is increased. Furthermore, if the measured supply air dew point temperature is lower than the set supply air dew point temperature, (1) if the measured temperature exceeds the first threshold, the regenerative heater output may be immediately increased and the first time decision may be postponed; (2) if the measured temperature falls below the second threshold which is lower than the first threshold, (i) if the measured temperature exceeds the second threshold before the second time has elapsed, the regenerative heater output may not be reduced; and (ii) if the measured temperature remains below the second threshold even after the second time has elapsed, the regenerative heater output may be reduced at that time.

[0032] With this in mind, please refer to Figure 5 again for further explanation. If the actual supply air dew point temperature T is significantly lower than the set temperature T0, the loop (1)-(5)-(7)-(1) causes the regenerative heater output to relax (d2) every τ2 hours, gradually increasing the supply air dew point temperature T, and eventually the state in (7) transitions to the state in (6). Conversely, if the supply air dew point temperature T is higher than the set temperature T0, the loop (1)-(2)-(1) immediately operates the regenerative heater output at a maximum of 100%, causing the supply air dew point temperature T to drop rapidly, resulting in state (2) eventually transitioning to state (3), (4), or (5). Furthermore, if the actual supply air dew point temperature T approaches the set temperature T0, the system follows the route (1)-(3)-(1) and immediately increases the regenerative heater output (d1). However, it sets a grace period of τ1 hours (generally shorter than τ2 hours) before the next decision ((1)), rather than immediately or after τ2 hours, to prevent extreme fluctuations in the supply air dew point temperature T.

[0033] Figure 6 is a schematic graph showing an example of the actual fluctuation of the supply air dew point temperature due to the supply air dew point temperature control of the present invention (the entire horizontal axis is approximately 120 to 180 minutes, and there are differences of several degrees Celsius between T0, T1, and T2 on the vertical axis). Understanding the present invention will be facilitated by referring to this graph together with the flowchart in Figure 5. The key points of Figure 6 will be explained below in chronological order.

[0034] Section A: Near time 0, the measured value T was above T0 (rated operation zone: Z0), and T rapidly decreased monotonically due to the regenerative heater output being 100% (corresponding to (2) in Figure 5). Eventually, T reached T2. Section B:T continued to decline and fell below T2 (set relaxation zone: Z3), and since the Z3 state lasted for τ2 hours, the regenerative heater output was reduced by d2% after τ2 hours (corresponding to (5) and (7) in Figure 5). Since the condition in section C:Z3 persisted for another τ2 hours, the regenerative heater output was further reduced by d2% after τ2 hours (corresponding to (5) and (7) in Figure 5). Section D:T began to rise, eventually surpassing T2 (setting maintenance zone: Z2), and reaching T1. Section E:T continued to rise and surpassed T1 (enhanced setting zone: Z1). At this time, the regeneration heater output was increased by d1%, and left for τ1 hours (corresponding to (3) in Figure 5). During τ1, T fluctuated between Z1 and Z2, and after τ1 hours, it was back in Z1 (enhanced setting zone), so the regeneration heater output was increased by another d1%. The interval F:T remained stable within Z2, fluctuating until it temporarily dropped to Z3. However, since its duration τ2' was less than τ2, the regenerative heater output was maintained (corresponding to (5) and (6) in Figure 5). Subsequently, T gradually increased within Z2. Section G:T reached T1, the regenerative heater output was increased by d1%, and left for τ1 hours (corresponding to (3) in Figure 5). During τ1, T fluctuated between Z1 and Z2, and since it was in Z2 (the setting maintenance zone) after τ1 hours, the regenerative heater output was maintained (corresponding to (5) and (6) in Figure 5).

[0035] By adopting the above configuration, it is possible to achieve supply air dew point temperature control that reliably guarantees the supply air dew point temperature in the ultra-low dew point region while simultaneously saving energy.

[0036] Although embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the configuration of the above embodiments, and can be modified in any way within the scope of the spirit of the present invention as can be understood by those skilled in the art. [Explanation of symbols]

[0037] OA outside air SA treated air 1. Rotary dehumidifier using an adsorbent rotor 2 Adsorbent Rotor 3. Processing area 4 Play area 5. Regenerative heater 6. Drive force transmission belt 7 Motor 8. Processed air flow path 9 Processing Fans 10 Regeneration air channel 11 Replay Fan

Claims

1. In a rotary dehumidifier's method for controlling the supply air dew point temperature, which determines whether to strengthen or reduce the regenerative heater output based on the measured supply air dew point temperature, A set temperature for the supply air dew point temperature and a first threshold temperature that is lower than the set temperature are defined. The measured temperature is, (1) If the temperature is higher than the set temperature, perform the enhancement described above. (2) If the temperature is lower than the set temperature and higher than the first threshold, the determination will not be made after the enhancement has been performed until the first state maintenance time has elapsed from the time the enhancement was performed. A method for controlling the dew point temperature of the supply air.

2. A second threshold temperature, which is lower than the first threshold, is further determined. The measured temperature is, (3) If the temperature is lower than the second threshold, the relaxation will be performed when the second state maintenance time has elapsed since the time the measured temperature fell below the second threshold and the temperature remains below the second threshold. The method for controlling the dew point temperature of the supply air according to claim 1.

3. A rotary dehumidifier that makes a determination regarding the strengthening or weakening of the regenerative heater output based on the measured supply air dew point temperature, A temperature sensor for measuring the dew point temperature of the supply air, and The system includes a controller that adjusts the timing of the execution of the aforementioned determination. The set temperature of the supply air dew point temperature and the first threshold temperature which is lower than the set temperature are defined. The controller, when the measured temperature is (1) If the temperature is higher than the set temperature, perform the enhancement described above. (2) If the temperature is lower than the set temperature and higher than the first threshold, the determination will not be made after the enhancement has been performed until the first state maintenance time has elapsed from the time the enhancement was performed. Rotary dehumidifier.

4. The aforementioned controller, It further has a second threshold temperature which is lower than the first threshold temperature, The measured temperature is, (3) If the temperature is lower than the second threshold, the relaxation will be performed when the second state maintenance time has elapsed since the time the measured temperature fell below the second threshold and the temperature remains below the second threshold. The rotary dehumidifier according to claim 3.

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