JP2002504034A - Apparatus and method for moisture control of granular material - Google Patents

Abstract

The moisture content of a material such as thermoplastic resin pellets (80) in a hopper (30) supplies dehumidified air from a desiccant bed (90) to the hopper (30) and the hopper (30). Conditioned by returning air from 30) to the desiccant bed (90). A dew point sensor (10) in the return air determines the moisture content of the material (80) in the hopper (30), and when the dew point drops to a preset level, the diverter (134) determines whether the return air flow is desiccant. Bypass the floor (90) and allow the hopper (30) to be re-fed without dehumidification. Two desiccant beds are provided, when one is on-process, the desiccant in the other is regenerated.

Description

DETAILED DESCRIPTION OF THE INVENTION Patent application title: Apparatus and method for adjusting moisture of granular material Cross-reference to related application   This application is based on U.S. Provisional Application No. 60 / 049,498, filed June 13, 1999. Claim a profit, which is entered here by reference. Background of the Invention   Field of the invention   This invention relates to moisture control in material handling systems, and more particularly to heat control. Plastic pellets used to make plastic molded and extruded parts Devices and methods used to regulate the water content of solid particulate materials, such as About.   Brief description of the prior art   For example, a typical system for adjusting the water content in a granular bed is the granular system. Supplying conditioned air to the granular bed and dehumidifying air returning from the granular bed Use a desiccant to   In this system, air with very low dew point humidity is supplied to the granular material layer. I have. If the material in the granular bed is some homopolymer, copolymer polyamide and When containing resins such as some polyesters (eg, nylon 6 and 6.6) The resin may be undesirably overdried. For final resin products A certain water content is required to maintain the desired impact resistance and flexibility. You.   Feeding granular beds as a traditional approach to overdrying problems Detects the amount of moisture in the compressed air and, if necessary, It was proposed to inject. However, this approach has some disadvantages There is.   Therefore, it is preferred from a granular bed without reducing the water content to an undesired level. By removing unwanted excess moisture, the moisture in the granular bed can be adjusted to the desired level. There has been a continuing need for methods and apparatus to ensure maintenance. Summary of the Invention   Therefore, an object of the present invention is to provide a material such as plastic pellets in a granular bed. To adjust the water content of the ingredients without reducing the water content to an undesirable level. It is to provide an apparatus and a method.   Further objects of the present invention will become clear from the description of the invention hereinafter.   According to one of the broader aspects of the present invention, the material handling system is conditioned for humidity. A supply gas flow path for supplying gas and gas removal from the material handling system; Return gas flow path, the first gas flow path including the dryer and the second gas flow without the dryer A dehumidification system having a flow path; and a second path between the supply and return gas paths. One of the gas flow path and the second gas flow path and both the first and second gas flow paths Alternatively connected to provide a closed loop circuit for humidity conditioned gas to reduce the moisture content of the material And a selector for adjustment.   According to another broad aspect of the invention, the inclusion of materials in a material handling system. Methods for adjusting the water flow include a first gas flow path containing a dryer, A dehumidification system having a second gas flow path without a layer is used. The method comprises Humidity control for material handling equipment Providing a supply gas flow path to supply a regulated gas; Providing a return gas flow path as desired; one of the first gas flow path and the second gas flow path; And the second gas flow path are connected alternatively between the supply and return gas flow paths to From providing a closed loop circuit of moisture conditioned gas to regulate the water content of the feed Become. BRIEF DESCRIPTION OF THE FIGURES   FIG. 1 shows the process air according to the invention when the air returning from the feed hopper is dehumidified. It is a schematic diagram which shows a flow.   FIG. 2 shows a process air according to the invention when the air returning from the feed hopper is not dehumidified. It is a schematic diagram which shows a flow.   FIG. 3 is an elevational view of the dehumidifier of the present invention as viewed from the front.   FIG. 4 shows an elevational view of the dehumidifier of the present invention as viewed from the back.   FIG. 5 shows a top view of the dehumidifier of the present invention.   FIG. 6 is an elevational view from the back of the dehumidifier of the present invention along line 6-6 in FIG. FIG. Detailed Description of the Preferred Embodiment   According to one aspect of the present invention, as shown in FIGS. An air stream of conditioned humidity from the floor 80 of the particulate material, eg, synthetic thermoplastic plus Feed hopper 30 or similar container containing And returned to the dehumidifier 100. The present invention relates to, for example, a thermoplastic molding machine. Alternatively, a supply hopper that is output through an outlet 40 to an extrusion device (not shown) 30 to adjust the water content of the thermoplastic synthetic resin pellets. Used.   The dehumidified air (process air) is typically supplied to a feed hopper 30 near the bottom. And through an air diffuser 50, such as a cone spreader, and Moisture is extracted from the granular material through a bed of the granular material 80. Then process air Is returned to the dehumidifier 100 where the water content is reduced to a drier, Reduced by passage through the floor. (As described below, the present invention relates to two desiccant beds. Are adopted alternately. ) The air passing through the dehumidifier is then supplied to the inlet air heater 70. Is supplied again to the supply hopper 30 and the air heater 70 is supplied from the dehumidifier. Heat the air to a temperature selected according to the type of particulate material. The air heater is Whether it is a gas-powered unit or an indirect gas-fired unit good.   The water content of the particulate material 80 in the feed hopper 30 depends on the humidity of the return air leaving the hopper. (Ie, dew point). Appropriate dew point or humidity A degree sensor 10 is provided at the outlet conduit (not shown) of the hopper, and the dehumidifier 100 To the control circuit in the control box 106 of FIG. control The control circuit may include a PLC processor. The moisture level in the granular material 80 As it decreases, the return air dew point from the supply hopper 30 also decreases. Return d A) the dew point decreases to a value corresponding to the lower acceptable limit of moisture in the particulate material 80 When the diverter is in the bypass position, the control circuit of the dehumidifier 100 Move the valve 134).   As shown in FIG. 2, the flow of process air then bypasses the desiccant bed 90. Is supplied to the supply hopper 30 again without being dehumidified. Process air is desiccant Because it does not pass through the floor, there is no dehumidification from the process air and the granular material 80 and Depending on the equilibrium between the process air and the process air, the process air Almost absorbed Does not absorb at all (or may even add moisture). The dew point of the process air is such that additional particulate material containing moisture is inserted at the top of the hopper. Displaced by the particulate material 80 that has entered and exited from the bottom outlet 40, and As ambient air enters the system, it increases.   The dew point of the return air corresponds to a preselected upper limit of the water content of the particulate material 80 When it increases to the value, the control circuit switches the diverter valve 134 and restarts the process. A stream of air is passed through the desiccant bed 90.   To achieve the optimal degree of drying for the granular material, the operator must diver The data valve can be set to the recommended dew point for proper operation. actually, For example, when the dew point sensor is in a predetermined dew point range (for example, 0 degrees F to -40 degrees F (-17. 8 degrees C to -40 degrees C)), and the operator has an appropriate Choose the right value. The operator also selects an appropriate drying temperature. Once appropriate When a proper drying temperature is selected, the air heater 70 is controlled to control the temperature sensor (illustrated in FIG. None), for example, the temperature can be adjusted using a thermocouple. Dew point sensor 60 is preferred Alternatively, it is provided between the outlet of the dehumidifier 100 and the air heater 70. However Therefore, the dew point sensor 60 can be provided anywhere in the supply air flow path.   The details of the dehumidifier 100 of the present invention will be described in detail below with reference to FIGS. . In the drawings, reference characters refer to the same elements throughout the figures. Business In the drawings, the drawings are for describing the main part of the present invention, and Will not be described in detail. Such structure The materials are shown in detail in the design drawings in the aforementioned provisional application 06 / 49,498. Have been.   The dehumidifier 100 of the present invention comprises two desiccant towers 102 and 104, of which Only one is used at a given time, ie, it is on-process. On process The desiccant bed is monitored and automatically when the desiccant approaches saturation. Reclaimed, and another floor that was previously reclaimed is turned on process .   The control box 106, which contains the control circuitry for the system, Between 2 and 104 and on the drying tower by a bracket 107 . The front panel of the control box 106 supports the display It then controls the operating parameters of the system. Display is preferred Temperature, dew point and other process parameters in a graphical schematic format. Shows the function of all key elements, including variables. The operating parameter values are also It can also be provided at an external communication port. The device also preferably has an elevated temperature A fail-safe function is provided for alarms for overrunning and shutdown control of the dryer. You.   In operation, return air enters dehumidifier 100 through inlet 158 and is More preferably, it passes through the process air cooler 154 provided in this embodiment.   The process air cooler 154 includes cooling coils, typically at the inlet and outlet. Cooling is achieved by circulating cooling water through connection 156. This return air This cooling coil in the line reduces the temperature of the humid return air to a desiccant Lower before entering to allow the desiccant to work effectively. However, the process The air cooler 154 ensures that the return air in the particular system is already sufficiently cooled. If they do, they need not be provided.   After passing through cooler 154, process air was contained in housing 112 Pass through the filter unit. The filter unit removes the contained dust particles A high efficiency air filter can be included to capture. In some cases, very Cycle that can capture particles with a diameter of about 1 micron Ronic filters can also be used. Process filter unit is monitor Can be provided need to clean or replace the filter cartridge A signal may be output at a certain time. After passing through the filter unit , Process air passes through an air conduit 114 and is driven by a motor 110. It reaches Seth air blower 108.   In a normal dehumidifying operation, the process air is supplied from the blower 108 to the upper four-way valve. 116, the four-way valve 116 directs air to one of the air conduits 122 or 120. Through the on-process drying of one of the desiccant columns 102 or 104, respectively. Turn to desiccant bed. The state of valve 116 is adjusted by actuator arm 124. It is. For clarity, actuator arms are shown on each side of the four-way valve. Have been. However, such an actuator arm is actually one of the valves It will be understood that this is only required on the side of   Process air passes through the on-process desiccant bed through air conduits 130 and It passes downward to the bottom of the floor, located near the height of 132. In the device shown The desiccant bed only fills the upper part of the desiccant towers 102 and 104; The lower part of the desiccant tower is provided for mechanical support members. Then the process air Through suitable conduits 130 or 132 to the lower four-way valve 118.   The state of the lower four-way valve 118 is determined by its actuator arm 126 (Two shown for clarity of illustration). Lower 4-way valve From 118, the dehumidified air passes through conduit 140 to diverter valve 134.   In a normal dehumidifying operation, the diverter valve 134 is connected to the operating air cylinder 1 for example. 36 directs the process air to outlet 142, where Process air is supplied to the feed hopper 30 containing, for example, pellets to be dried. Proceed to such a material supply device. After passing through and in the feed hopper 30 After absorbing moisture from the particulate matter, the process air is passed through a conventional return air conduit (not shown) And returns to the dehumidifier 100.   The humidity of the process air leaving the hopper 30, that is, the dew point is, as described above, a sensor. Measured by -10. The sensor 10 is preferably located in a hopper, It can also be located in the return air conduit or at the entrance to the dehumidifier 100.   The circuit in the control box 106 detects the dew point signal from the sensor 10 as described above. As such, when the water content of a particular material falls to a value corresponding to the desired lower limit, Put out. At this time, the circuit in the control box 106 is the air cylinder 136 To reposition the diverter valve to connect the conduit 130 or 132 to the lower Blocking the air coming from the desiccant bed via the four way valve 118 and Open air conduit 138 from process air blower 108 to diverter valve 134 Good. Separately, diverter valves should prevent air from entering the desiccant bed. Air may enter or exit the desiccant bed using two diverter valves Can be blocked.   Return air from hopper 30 is supplied to both desiccant towers 102 and 104. Bypassing the desiccant bed inside, and sent directly to the outlet 142 of the diverter valve 134 to Heated and re-fed to the hopper in another passage through the particulate material.   The dew point of the air leaving the hopper 30 indicates that the water content has reached a predetermined upper limit At this time, the control circuit switches the diverter valve 134 from its bypass state to the normal dehumidifying state. Working back, and process air is again removed in each passage through the dehumidifier 100. Wet. In this way, the water content of the process air (and, for example, the material in the hopper) Water content) is controlled by the operator at the front of control box 106 Maintained within a given range by simply setting the controls on the panel .   The dew point of the air entering the hopper indicates that the desiccant bed is saturated Bed, or more conveniently, on a timed cycle, 02 and 104 will fall out of the process air loop. And a new off-set in the other of the two desiccant beds 102 and 104 The process floor is turned on. This is done under the control of the control circuit. Control circuit operates a four-way valve actuator 162, which is a mechanical Connected to each other and to the valve actuator 162 by a dynamic link 164 Switching between four-way valves 116 and 118 via heater arms 124 and 126 You. The process air then flows from the blower 108 to the other of the desiccant towers 102 and 104. And the air is dehumidified and sent to the particulate material.   Regenerate desiccant in off-process desiccant tower 102 or 104 Or, to make it new, a regeneration cycle can be performed as follows.   First, during the heating period, moisture is released from the off-process desiccant bed. Surrounding Air enters the regeneration air filter housing 146 through the regeneration air filter. The regeneration filter unit cleans the filter cartridge or A monitor can be provided to generate a signal of the need for replacement. The air passing through the regeneration filter unit is driven by the motor 148 and Pass through regeneration air heater housing 150 by raw air blower 144 . The heater housing 150 is preferably provided externally for maintenance. It is designed to make it easy to access.   A heating element, such as a coil, in the motor housing 150 provides regeneration air. The water adsorbed by the desiccant bed can be released upon warming. Heated regeneration Air then passes from the heater housing 150 through conduit 152 to the lower four-way valve 1. 18, the four-way valve directs regeneration air through a suitable conduit 130 or 132 Point off-process into the floor. The heated regeneration air passes upward through the desiccant bed The adsorbed moisture therein is released by heat regeneration.   The moisture regenerating air then leaves the off-process floor and has a suitable upper conduit 120 or Through 122 to the upper four-way valve 116. Moisture regeneration air is the upper 4-way valve 1 It is exhausted to the surroundings via a regeneration air outlet 128 on the port below 16. Appropriate A sensor can be provided in the regeneration loop to control the temperature of the regeneration air.   After the heating period, the regeneration cycle preferably has a dynamic cooling period, During the cooling period, the heater is switched off and the blower 144 is kept on. It is. Finally, the blower 144 is turned off to provide static cooling and thus the Allow for a smooth transition between the floor and the process and off-process.   The method and apparatus of the present invention are defined as thermoplastic molding or extrusion resin pellets. Provides a convenient way to adjust the moisture content of such granular materials to a desired predetermined range. You.   While preferred embodiments of the present invention have been illustrated and described, it will be obvious to those skilled in the art. For example, changes may be made without departing from the principles and spirit of the claimed invention. It will be clear that this is possible.   For example, an element such as a process air blower moves the dryer away from the hopper. If applicable, attach it to a floor stand near the material handling hopper Can be.   Also, a single air drying unit functions as a central dehumidification system and One or more hoppers on one or more hoppers having a drying temperature set at Distribute unheated, regulated dew point air to a number of separate heaters / blowers. You can also make it. The dehumidifier of the present invention also uses air as a transport medium To serve as a source of dry air for an air transfer system It can also be used to distribute material to different molds or extruders.   Divertor valve is positioned by air cylinder in the above machine However, the diverter valve is operated by other means, such as a hydraulic cylinder or gearmotor. It can also be positioned. If, for example, a gear motor is used, a diverter valve Uses to regulate the supply of air from the desiccant bed and return air from the particulate material be able to. That is, the air dehumidified in the desiccant bed is supplied to the granular material. Wetness returning from the granular material in such a way as to more precisely adjust the moisture content of the generated air Can mix with air. In such systems (and other systems) From both sensors 10 and 60 The signal can be used for control.

Claims (1)

[Claims] 1. An apparatus for adjusting the water content of a material in a material handling system, Supply gas flow path for supplying humidity-regulated gas to the material handling system When,   A return gas flow path for venting gas from the material handling system;   Having a first gas flow path including a drier and a second gas flow path without a drier Dehumidification system and   One of the first gas flow path and the second gas flow path between the supply and return gas flow paths And the first and second gas flow paths are operated to selectively connect A closed loop circuit of humidified gas to regulate the water content of the material. A material handling system comprising a selector to be provided. Equipment for adjusting the water content of materials in 2. A sensor for outputting a signal based on the water content of the material, and the selector And a control circuit for operating based on the signal. The device according to claim 1, characterized in that: 3. 3. The sensor according to claim 2, wherein the sensor is provided in a return gas flow path. On-board equipment. 4. The dryer in the first gas flow path contains a desiccant. The apparatus of claim 1, wherein: 5. The selector selects the second gas between the supply and return gas flow paths; When connecting only the gas flow path, the selector blocks the gas flow through the dryer. 5. The device according to claim 4, wherein the device is activated. 6. The apparatus of claim 1, wherein said selector includes a valve. 7. An apparatus for adjusting the water content of a material in a material handling system,   Supply gas stream for supplying a humidified gas to the material handling system Road and   A return gas flow path for venting gas from the material handling system;   A first and a second method for removing moisture from gas withdrawn from the material handling system; A second desiccant tower;   A second one for admitting the vented gas to a selected one of the first and second desiccant columns. One valve,   Gas from the selected one of the first and second desiccant columns exits to a third valve. A second valve for powering, and   Supplying the evacuated gas to the third valve, whereby the first and second And a bypass gas flow path for bypassing the desiccant tower of A selected one or other of the bypass gas flow path and the output from the second valve; Alternately directs gas from the feed gas flow path to the bypass gas flow path and the Alternately block one or the other of the non-selected with the output from the second valve, Providing a humidity-regulated gas for regulating the water content of said material. In a material handling system characterized by the fact that Equipment for adjusting the water content of water. 8. It is provided in the return gas channel and outputs a signal based on the water content of the material. Sensors and   A control circuit for adjusting the third valve based on a signal from the sensor. The apparatus of claim 7, further comprising: 9. A signal is provided based on the dew point of the humidified gas provided in the supply gas flow path. And a control circuit provided in the supply gas flow path. Selecting the other of the first and second desiccant towers based on the signal from the sensor 9. The method according to claim 8, wherein the first and second valves are controlled to perform the control. apparatus. 10. Regulated by the circuit to regenerate the desiccant in the first and second columns 10. The apparatus of claim 9, further comprising a regenerative heater for. 11. A first gas flow path including a dryer and a second gas without a dryer Moisture of materials in a material handling system using a dehumidification system with flow channels A method for adjusting an amount, said method comprising:   Supply gas flow path for supplying a humidity controlled gas to the material handling system Providing,   Providing a return gas flow path for venting gas from the material handling system; and   One of the first gas flow path and the second gas flow path and the first and second gas flow paths; Alternatively, both of the channels are connected between the supply and return gas channels to reduce the water content of the material. Characterized by exhibiting a closed loop circuit of regulated humidity for regulating A method for adjusting the water content of a material in a handling system. 12. Detecting the water content of the material, said alternative connection being based on said detection The method of claim 11, further comprising: 13. 13. The method according to claim 12, wherein the detecting detects a water content of the gas in the return gas passage. Method. 14． The dryer in the first gas flow path contains a desiccant. The method according to claim 11, wherein: 15. When only the inside of the second gas passage is connected between the supply and return gas passages The gas flow flowing through the dryer is blocked. 15. The method according to 14.