Method and device for monitoring the energy management of dryer systems for plastic granulate, and method and device for drying plastic granulate

Abstract

The invention relates to a method and a device for monitoring the energy management of dryer systems for plastic granulate and to a method and a device for drying plastic granulate. According to the invention, both the energy input as well as the energy requirement are continuously determined so that the operation of the corresponding systems can be optimized both with respect to the product quality as well as to the energy consumption.

Description

[0001] Method and device for monitoring energy management in dryer systems for plastic granulate and method and device for drying plastic granulate

[0002] The invention relates to a device for monitoring energy management in dryer systems for plastic granulate.

[0003] Furthermore, the invention relates to a method for monitoring energy management in dryer systems for plastic granulate.

[0004] The invention further relates to a device for drying plastic granules comprising at least one device for monitoring the energy management in dryer systems for plastic granules, in particular for preparing plastic granules for a subsequent plasticizing process.

[0005] The invention also relates to a method for drying plastic granulate with monitoring of energy management.

[0006] Corresponding devices and processes are used particularly in the manufacture of plastic products, which are usually made from plastic granules. This applies in particular to hygroscopic granules that must be dried prior to the plasticizing process to prevent degradation of the material during the plasticizing process. In this process, thermal energy is also supplied to the material, which significantly supports the plasticizing process: the plasticizing process becomes more stable because the plasticizing process requires less energy to melt the plastic material. The drying process for plastic granules, realized with corresponding devices and processes, is already highly sophisticated today.In devices designed, for example, as drying hoppers for drying plastic granules, in which the material is prepared for the plasticizing process, sufficient dry process air is fed in countercurrent, which absorbs the excess moisture in a controlled manner. The process air is then dried and recycled.

[0007] The situation regarding the simultaneous introduction of heat energy into the plastic granules by the dry air is different in the current state of the art, as this process is not given sufficient attention. The reason for this is that measuring the energy introduced into the granules is challenging and economically impossible during ongoing production processes. The granules of the plastic granules are highly insulating, meaning that an external temperature measurement cannot be used to determine the core temperature. While a thermal sensor monitors the temperature of the plastic granules, it effectively only measures the temperature of the process air – the energetic state of a single granule remains unknown. Nevertheless, too much importance is attached to this temperature indicator.Typical drying temperatures for polyethylene terephthalate (PET), for example, are 160°C - 195°C, but can also be lower or higher. If this material is saturated at the desired temperature due to its heat absorption capacity (enthalpy of the material), the processing is optimal in terms of thermal control during production, and the product can be manufactured with the highest quality. If the energy input into the plastic granulate is too low, a downstream injection molding machine requires significantly more energy to heat the material accordingly, and the material is subjected to considerable stress due to the mechanical energy input. The plasticizing screw is then often unable to sufficiently homogenize the melt, or the screw torque increases or even exceeds its limit. This leads to undigested material and bubbles in the product.To solve the problem in today's systems, the plasticizing process is often raised in its temperature profile in order to reduce the torque or to compensate for the lack of energy - or it reaches uncontrolled high temperatures due to high friction, which causes the plastic material and / or its additives to burn, resulting in black spots in the product.

[0008] It is not uncommon for operators of injection molding systems to lack detailed knowledge of the energetic relationship between dryers and injection molding units, since the dryer has fulfilled its main task of drying the material, which can easily be verified in the quality laboratory. Even today, there are operators who suspect that the process air flow in the dryer is insufficient to energetically saturate the plastic granules and thus recognize the connection to the defects in their product. In these cases, according to the state of the art, the air flow rate in the dryer is increased, thus achieving energetic saturation of the granules in order to ensure good production. In these cases, it remains unclear whether this process air then exits the drying device with an energy surplus. This escaping process air flow can, for example, reach temperatures of over 60°C during the processing of PET and significantly higher (e.g.130°C). However, to dry this air efficiently, it ideally needs to be cooled to approximately 60°C, which is done in a heat exchanger. Here, the operator pays for the energy loss twice: After drying, the air must be reheated using an air drying device, such as a silicate drying cartridge or a drying wheel, while the heat exchanger channels the excess energy into a cooling unit, for example.

[0009] According to the current state of the art, dryers are almost never operated at their optimal operating point due to a lack of accurate, up-to-date information regarding the drying and energy saturation of the plastic granules, as the energy content of the granules is not measurable. This situation is unacceptable under current conditions, such as the desired conservation of resources, rising energy costs, and the low achievable margins.

[0010] Dryer manufacturers today help themselves by using load cells to determine the system throughput of plastic granulate. Depending on the manufacturer, an air factor is used to adjust the air volume to demand. In most cases, the air volume is theoretically determined at the blower using the blower's power consumption or speed. The current air temperature at the blower, which determines the air density, and the degree of filter clogging are not reliably displayed. It is also misleading for the operator that the air is displayed in volume (usually in m3) and not in its more relevant mass. Furthermore, general process fluctuations, in particular the inlet temperature of the plastic granulate, are given little consideration.There are drying hoppers on the market today that regulate the air flow to a value selected by the operator when the process air temperature at the outlet is high. However, the operator is not aware of whether the material is then energetically saturated and the heat exchanger is unnoticed disposing of the excess energy from the process air. There are also no systems that plausibly correlate energy consumption with the dryer's energy requirements. It is therefore not uncommon for the cooling water valve on the heat exchanger to jam, unnecessarily cooling the air well below 60°C.

[0011] In summary, in the currently known processes and devices for drying plastic granules, the relationships between the heating of the plastic granules before the plasticizing process are almost unknown to the operators, the search for problems in the case of quality defects is more likely to take place in the injection molding system, or the excess energy that disappears when the process air is cooled down after the granules have been dried, for example in a cooling machine, goes unnoticed in most cases.

[0012] Operators of conventional drying systems generally lack the information they need to assess the energy efficiency of the drying process themselves. Today, drying systems are offered whose manufacturers claim to be optimally designed and operate to a correspondingly high standard. Unfortunately, this is rarely the case in reality, as external influences are too diverse, or the drying machines are of an age where energy management was hardly relevant during their manufacture. Examples of this include:

[0013] If filters become clogged gradually, this is not taken into account

[0014] The inlet temperature of the granulate varies depending on the season, to which known dryers react little

[0015] All dryers work with air volume and therefore the density of the air is not sufficiently taken into account when temperature fluctuates

[0016] The air flow is almost always calculated theoretically on the fan, there is rarely a real value

[0017] A defective heat exchanger is usually not detected

[0018] It is therefore an object of the invention to provide a device for monitoring energy management in dryer systems for plastic granulate, which at least partially eliminates the aforementioned problems.

[0019] This object is achieved according to the invention by a device according to claim 1.

[0020] It is a further object of the invention to provide a device for drying plastic granulate which at least partially eliminates the aforementioned problems.

[0021] This object is achieved according to the invention by a device according to claim 9. It is a further object of the invention to provide a method for monitoring energy management in dryer systems for plastic granulate, which at least partially eliminates the aforementioned problems.

[0022] This object is achieved according to the invention by a method according to patent claim 11.

[0023] It is a further object of the invention to provide a method for drying plastic granulate which at least partially eliminates the aforementioned problems.

[0024] This object is achieved according to the invention by a method according to patent claim 23.

[0025] Advantageous embodiments of the invention are claimed in the dependent claims.

[0026] The features disclosed below of a device for monitoring energy management in dryer systems for plastic granulate, a device for drying plastic granulate, a method for monitoring energy management in dryer systems for plastic granulate and a method for drying plastic granulate are part of the invention in all executable combinations.

[0027] The basic idea of ​​the teaching according to the invention is to determine the energy input into the plastic granulate realized with the help of the process air, so that in addition to drying, sufficient energetic saturation of the plastic granulate is possible with the lowest possible losses.

[0028] In addition to the granular form of plastic, other forms of plastic, such as plastic flakes or plastic powder, can also be processed according to the invention.

[0029] In embodiments of the invention, the energy management of dryer systems can be continuously monitored or the energy management of dryer systems is continuously monitored.

[0030] A device according to the invention for drying plastic granules has at least one drying chamber, a feed device for plastic granules, a blower, and a heater. Plastic granules can be fed into the drying chamber via the feed device. With the help of the blower, a flow of dried process air can be realized through a process air line via a process air inlet into and through the drying chamber. With the heater, the process air in the region of the process air line can be adjusted to a desired temperature, in applications for drying PET granules generally in a range between approximately 160°C and approximately 195°C. In the drying chamber, the process air and plastic granules come into contact with each other, with the process air absorbing moisture from the plastic granules and transferring thermal energy to the plastic granules.

[0031] In preferred embodiments of the invention, the drying chamber is thermally insulated so that losses due to unwanted escape of heat are significantly reduced.

[0032] A device according to the invention for drying plastic granules has at least one device for monitoring the energy management of dryer systems for plastic granules.

[0033] According to the invention, the device for monitoring energy management in dryer systems for plastic granules comprises at least one temperature sensor for measuring the inlet temperature of the process air, arranged or to be arranged in the region of the process air inlet, and at least one temperature sensor for measuring the outlet temperature of the process air, arranged or to be arranged in the region of a process air outlet from the drying chamber. Furthermore, the device for monitoring energy management in dryer systems for plastic granules comprises at least one temperature sensor for measuring the inlet temperature of the plastic granules.

[0034] Furthermore, a device according to the invention for monitoring the energy management in dryer systems for plastic granules has at least one evaluation unit.

[0035] In embodiments of the invention, the inlet temperature of the plastic granulate can be determined by measuring the temperature at a storage location for the plastic granulate, provided that the plastic granulate remains at this storage location long enough for the temperature prevailing there to be homogeneously absorbed throughout the plastic granulate. In corresponding embodiments, an additional measurement of the surface temperature of the plastic granulate in the area of ​​the feed device of the device for drying plastic granulate can be carried out for plausibility purposes. The thermal energy (energy input) transferred by the process air to the plastic granulate, apart from losses, can be determined if the mass of the process air passed through the drying chamber is known. For this purpose, the device according to the invention for monitoring energy management in dryer systems for plastic granulate has a process air mass determination device.

[0036] In embodiments of the invention, the process air mass determination device is arranged or to be arranged in the region of the process air line and comprises an air volume measuring device. Taking into account the temperature-dependent density of the process air, which in embodiments of the invention can be retrieved from an electronic storage device, the mass of the process air supplied to the drying chamber can be determined from the measured air volume.

[0037] Due to the strongly temperature-dependent density of air, in advantageous embodiments of the invention at least one temperature sensor is arranged in the region of the air volume measuring device, so that the density of the process air in the region of the air volume measuring device can be determined more precisely taking the temperature into account.

[0038] In embodiments of the invention, at least one pressure sensor for determining the air pressure is additionally arranged in the region of the air volume measuring device, so that the density of the process air in the region of the air volume measuring device can be determined even more precisely, taking the air pressure into account.

[0039] In embodiments of the invention, the air volume measuring device is designed as a volume flow measuring device. In other embodiments, a velocity meter for measuring the flow velocity of the process air is integrated or can be integrated into a section of the process air supply line with a known cross-section, so that the volume of process air introduced into the drying chamber in a specific time can also be determined.

[0040] Using the evaluation unit, the difference between the inlet temperature and the outlet temperature can be calculated, which, taking into account the heat capacity of air, yields the energy input per kg of process air (specific energy input), and the absolute energy input by the process air, taking into account the mass of the supplied process air. To simplify the calculation, the value of the specific heat capacity of air is assumed to be 1 kJ / kg / K in embodiments of the invention. This is possible without significant errors, especially since the process air is dried.

[0041] In addition to determining the energy input into the process, it is essential for the invention to know the energy required for drying and the energy saturation of the plastic granules. The energy requirement also depends on the mass of plastic granules fed into the dryer (throughput).

[0042] The evaluation unit is therefore designed to determine the throughput of plastic granulate.

[0043] To determine the mass of the supplied plastic granulate, in embodiments of the invention, a corresponding measuring device is integrated or can be integrated into the feed device for the plastic granulate. In other embodiments of the invention, the value for the mass of the supplied plastic granulate can be retrieved using the evaluation unit, for example if it is a predetermined process parameter based on which the feed device can be controlled accordingly using a control unit. In further embodiments, the material throughput of the dryer is synchronized with at least one downstream production unit, for example an injection molding machine, based on the material requirement, and the corresponding value can be retrieved using the evaluation unit.

[0044] In embodiments of the invention for a dryer system with a downstream injection molding system, the material throughput can be automatically derived from corresponding values, taking into account the amount of plastic processed in one cycle of the injection molding system.

[0045] For example, values ​​for the weight of an individual injection-molded product (e.g. preform weight), the number of mold cavities of the injection molding system, and the proportion of material dried with the respective dryer in the product (e.g. preform) can be entered or retrieved. From this, the weight of the material required for a cycle of the injection molding system can be determined using the device according to the invention. In advantageous embodiments of the invention, a signal synchronized with the cycle of the injection molding system, which signals, for example, the start or end of a cycle, can be received using the device according to the invention, and from this the cycle time of the injection molding system can be determined. From the required plastic quantity per cycle and the cycle time, the required material throughput per unit of time (e.g.per hour) and can be used to calculate the throughput-dependent energy requirement.

[0046] Depending on the plastic or plastic mixture being processed and the type of subsequent process, a target temperature for the plastic granules can be specified at which sufficient energy saturation of the plastic granules is achieved. For PET and subsequent plasticization, the target temperature range is between approximately 160°C and 195°C. A device according to the invention for monitoring energy management in dryer systems for plastic granules has corresponding input means for entering the target temperature for the plastic granules.

[0047] From the difference between the target temperature and the inlet temperature of the plastic granulate, the specific energy requirement can be determined using the evaluation unit, taking into account the specific heat capacity of the respective plastic granulate.

[0048] For this purpose, the value of the respective specific heat capacity can be retrieved from a storage unit using the evaluation unit.

[0049] PET granulate, for example, has a specific heat capacity of 1.5 kJ / kg / K. In the drying temperature range of -40°C to 230°C, PET material has an almost linear energy absorption (enthalpy), which makes it relatively easy to determine the specific energy requirement of the material during drying.

[0050] By additionally taking into account the mass of plastic granulate fed into the drying chamber, the absolute energy requirement or the throughput-dependent energy requirement for this temperature increase can also be determined.

[0051] In preferred embodiments of the invention, when determining the total energy requirement, the energy required for the actual drying of the plastic granulate is taken into account in addition to the energy required for the temperature increase. For example, the corresponding drying energy value for the respective material can be retrieved from a storage unit. For PET granulate, a value of approximately 12 kJ / kg is a typical value for the drying effort.

[0052] The invention thus presents a solution for determining the optimal energy input into the plastic granulate without requiring a temperature measurement of the dried granulate. In embodiments of the invention, the device for drying plastic granulate comprises an output device, in particular designed as a display, for outputting the determined specific and / or absolute energy requirement and the determined specific and / or absolute energy input. In embodiments of the invention, the throughput-dependent values ​​for the energy requirement and the energy input can be displayed.

[0053] In preferred embodiments of the invention, the output device is designed to comparatively output the respective values ​​for the energy demand and the energy input.

[0054] In advantageous embodiments of the invention, the output device is designed to simultaneously output the values ​​graphically, for example, as curves plotted against a time axis. From the difference between energy demand and energy input, an operator of the drying device according to the invention can immediately and clearly determine whether the system is optimally configured with regard to the desired energy saturation of the plastic granules and energy efficiency, or whether the settings need to be adjusted.

[0055] In embodiments of the invention, the device comprises a control unit with which the fan and / or the heater can be controlled to adjust the mass fed into the drying chamber and / or the inlet temperature of the process air to minimize the deviation of the energy input from the energy requirement determined by the evaluation unit, so that an optimized automatic control of the energy input with regard to the actual energy requirement is realized.

[0056] In embodiments of the invention, the device for drying plastic granules is designed for countercurrent drying of the plastic granules. This allows for optimal transfer of heat energy from the process air to the plastic granules.

[0057] In embodiments of the invention, the device for drying plastic granulate is designed as a drying hopper.

[0058] In embodiments of the invention, the device for drying plastic granulate has a process air circuit in which the process air is reused.

[0059] After drying the plastic granulate, the process air has absorbed the corresponding moisture and must be dried before reuse. To dry the process air, the device for drying plastic granulate, in appropriate embodiments, includes a process air drying device.

[0060] In embodiments of the invention, a drying cartridge or a drying wheel, e.g. made of silicate, is used to dry the process air.

[0061] However, if the process air is too hot (usually over 60°C), it cannot be sufficiently dried using the known process air drying devices.

[0062] In order to cool the process air after it leaves the drying chamber, the device for drying plastic granulate in corresponding embodiments has a heat exchanger arranged in the flow direction upstream of the process air drying device.

[0063] In embodiments of the invention, the heat exchanger is coupled to a cooling machine. The more the process air needs to be cooled for drying, the higher the energy requirement for operating the cooling machine in corresponding embodiments.

[0064] It is thus clear that in corresponding embodiments, an unnecessarily high set process air temperature or process air quantity firstly requires an unnecessarily high energy expenditure for the provision of the process air and secondly requires an unnecessarily high energy expenditure for the subsequent cooling of the process air.

[0065] In embodiments of the invention, this excess energy is specifically represented as a loss per kg of plastic material in a third curve.

[0066] To measure the energy required to cool the process air, the device according to the invention for monitoring energy management in dryer systems for plastic granules, in corresponding embodiments, comprises at least one temperature sensor arranged or to be arranged in the process air line downstream of the heat exchanger in the direction of flow. The specific energy loss can be determined from the difference between the initial temperature measured in the area of ​​the process air outlet and the temperature measurement of the cooled process air.

[0067] The setting of the drying device can be optimized based on the specific energy curves by adjusting the temperature and / or the volume flow of the process air in such a way that the curves of the specific energy input and the specific energy demand are approximately on top of each other and at the same time the loss curve is minimized.

[0068] In preferred embodiments of the device according to the invention with a determination of the loss energy, the process air mass determined by means of the process air mass determination device can be used in conjunction with the temperature difference between the cooled process air and the temperature at the process air outlet in such a way that the absolute loss energy can be determined taking into account the mass of the cooled air.

[0069] A method according to the invention for monitoring energy management in dryer systems for plastic granules comprises at least the following method steps:

[0070] Setting a target temperature for the plastic granulate

[0071] Measurement of the inlet temperature of the plastic granulate

[0072] Determination of the difference between target and inlet temperature of the plastic granulate

[0073] Calculation of the energy requirement for drying the plastic granulate and increasing the temperature to the target temperature

[0074] Measuring the inlet and outlet temperature of the process air at the drying chamber

[0075] Determination of the difference between the inlet and outlet temperatures of the process air Determination of the mass of the air supplied to the drying chamber

[0076] Calculation of the energy introduced into the plastic granulate by the process air

[0077] - Output of the values ​​for energy demand and entered energy.

[0078] In embodiments of the method according to the invention, the target temperature for the plastic granulate is selected from a range between approximately 160 °C and 195 °C.

[0079] In embodiments of the process according to the invention, PET granules are dried.

[0080] In embodiments of the method according to the invention, the inlet temperature of the plastic granulate is measured in the area of ​​a storage area for the plastic granulate and / or in the inlet area of ​​the dryer.

[0081] In embodiments of the method according to the invention, in order to calculate the energy requirement for drying the plastic granulate and increasing the temperature to the target temperature, the difference in temperature between the target temperature and the inlet temperature is multiplied by the specific heat capacity of the material in order to determine the specific energy requirement per kg of plastic granulate.

[0082] In some embodiments, the specific heat capacity is loaded from an electronic storage unit depending on the material.

[0083] In embodiments of the invention, the energy required for drying the plastic granulate per unit of weight (e.g. kg), the drying effort, is summed with the energy required for increasing the temperature and thus the specific total energy requirement for drying and heating the plastic granulate is determined.

[0084] In embodiments of the method according to the invention, the throughput-dependent energy requirement and / or total energy requirement is determined.

[0085] In embodiments of the method according to the invention, the mass of the process air supplied into the drying chamber is determined by measuring the volume flow of the supplied process air and multiplying it by the density of the process air.

[0086] As an alternative to a volume flow measurement, the flow velocity can also be measured in an area with a known cross-section and integrated over a defined time.

[0087] In advantageous embodiments of the method according to the invention, the temperature and / or the air pressure of the process air are measured in the region of the process air mass determination device and taken into account to determine the density of the process air.

[0088] In embodiments of the invention, a density table for air is stored in an electronic storage device and is loaded according to the measured value of temperature and / or air pressure.

[0089] In embodiments of the method according to the invention, the energy introduced into the plastic granulate by the process air is calculated by multiplying the temperature difference of the process air by the specific heat capacity of air.

[0090] In embodiments of the method according to the invention, the values ​​for the specific and / or absolute energy requirement and the entered specific and / or absolute energy are output by displaying curves of the respective values ​​on a display.

[0091] In embodiments of the method according to the invention, the throughput-dependent values ​​are output accordingly.

[0092] The output of the curves standardized to the plastic granulate throughput enables the operator of a corresponding dryer or dryer system to easily set the optimal operating point by adjusting the process air setting to the throughput and / or the inlet temperature of the plastic granulate in such a way that the curves overlap.

[0093] When applying the method according to the invention for monitoring energy management in dryer systems for plastic granules on dryers with a circulating process air system, this additionally comprises the following method steps in advantageous embodiments:

[0094] Measurement of the temperature of the process air after cooling for subsequent drying

[0095] Determination of the difference between the outlet temperature of the process air from the drying chamber and the cooled air

[0096] Determination of the cooled process air mass

[0097] Calculation of the energy required to cool the air (lost energy)

[0098] - Output of the calculated energy loss on the display

[0099] In embodiments of the invention, the calculated energy loss is output as a curve, which is preferably displayed together with the curves for the total energy demand and the energy input.

[0100] In embodiments of the invention, the energy consumption of a cooling machine used to cool the heat exchanger is taken into account for calculating the energy loss.

[0101] In embodiments of the invention, the energy values ​​are output in Wh, preferably standardized to the throughput of plastic granules. The method according to the invention for monitoring energy management in dryer systems for plastic granules uses, in embodiments, at least one device according to the invention for monitoring energy management in dryer systems for plastic granules and / or one device according to the invention for drying plastic granules.

[0102] A method according to the invention for drying plastic granulate comprises the method steps of a method according to the invention for monitoring the energy management in dryer systems for plastic granulate, wherein process air is heated by means of a heater and is introduced into and passed through the drying chamber of a device for drying plastic granulate by means of a fan and absorbs moisture in the drying chamber from a plastic granulate also introduced into the drying chamber and heats the plastic granulate.

[0103] In advantageous embodiments of the method, the process air is recirculated after leaving the drying chamber, first being cooled to a temperature of approximately 60°C using a heat exchanger and then dried before being fed back into the area of ​​the fan and subsequently the heater.

[0104] The method according to the invention for drying plastic granules uses, in embodiments, at least one device according to the invention for monitoring the energy management in dryer systems for plastic granules and / or a device according to the invention for drying plastic granules.

[0105] The following figures illustrate exemplary embodiments of the invention. They show:

[0106] Figure 1: A schematic representation of a device according to the invention for

[0107] Drying of plastic granulate,

[0108] Figure 2: A dryer system with two devices according to the invention for drying plastic granulate,

[0109] Figure 3: A two-stage dryer system with a dryer according to the invention and a booster,

[0110] Figure 4: A combination of the dryer systems shown in Figures 2 and 3 and Figure 5: A representation of the display output of a device according to the invention for drying plastic granulate or a device for monitoring the energy management of dryer systems for plastic granulate.

[0111] Figure 1 shows a drying system (100) comprising a device according to the invention for drying plastic granules (10) having a drying chamber (1) designed as a drying hopper. A plasticizing screw (2) is connected to the drying hopper at the bottom of the material outlet. This screw is not a necessary component of the invention, but serves as an example for further processing the dried plastic granules. An extruder or other devices for further processing the dried plastic granules can also be connected.

[0112] At the top, the drying chamber (1) has a feed device (3) for plastic granulate. The process air is guided via a process air line from the process air outlet to a heat exchanger (4), where the process air can be cooled.

[0113] E is followed by a process air drying device (5) for drying the process air. The process air is fed by a fan (6) through the process air line to a heater (7) and finally into the drying chamber (1) via a process air inlet.

[0114] To measure the required temperatures, a first temperature sensor T1 is located near the plastic granulate feed (3), a second temperature sensor T3 near the process air inlet, a third temperature sensor T4 near the process air outlet, a fourth temperature sensor T5 between the heat exchanger (4) and the process air drying device (5), and a fifth temperature sensor T6 near the process air mass determination device between the blower (6) and the heater (7). The mass flow m2 of the dried process air can be determined using the process air mass determination device.

[0115] The temperature value T2 represents the preset target temperature of the plastic granulate.

[0116] Preferably, at least one air pressure sensor is additionally provided in the region of the process air mass determination device(s).

[0117] The mass flow m1 of the plastic granules can be measured or determined in various ways, as explained above. The plastic granules and the process air flow countercurrently through the drying chamber.

[0118] The measured values ​​recorded by the sensors, the target temperature T2 and the mass flow m1, can be recorded by an evaluation unit and used to calculate the required energy.

[0119] Figure 2 shows a drying system (100) with two devices for drying plastic granules (10), designated A and B. The individual components of the devices (10) are each labeled "A" or "B" to identify them with the respective device (10). The plastic granules dried by both dryers (10) are fed to a material dosing device and / or mixer (8).

[0120] Different materials can also be processed in the individual dryers, e.g. new plastic granulate in dryer A and recycled material in dryer B.

[0121] Figure 3 shows a drying system (100) with a drying device (10) and a downstream booster (C) and Figure 4 shows a drying system (100) with two dryers (A, B) and a downstream booster (C).

[0122] A booster (5) serves as a unit downstream of a drying device (10) for further increasing the temperature of the dried plastic granulate. The boosters (5) in the drying systems (100) shown in Figures 4 and 5 are also each equipped with a device according to the invention for monitoring energy management.

[0123] Figure 5 shows the output on a display of a device according to the invention. It shows comparative curves for the total energy demand (I), the energy input (II), and the losses (III), normalized to the material throughput.

[0124] The individual curves can be selected or deselected for display. The temporal resolution of the display can be adjusted to various levels.

[0125] The loss curve can also be used to determine whether the process air is being cooled unnecessarily, for example if the cooling valve is stuck or there is another malfunction in the cooling system.

Claims

Patent claims Device for monitoring the energy management in dryer systems (100) for plastic granulate, wherein a dryer system (100) comprises at least one device for drying plastic granulate (10), which has at least one drying chamber (1), a feed device for plastic granulate (3), a blower (6) and a heater (7), characterized in that the device for monitoring the energy management in dryer systems (100) for plastic granulate has at least one temperature sensor (T3) for measuring the inlet temperature of the process air arranged or to be arranged in the region of the process air inlet of the drying chamber (1) and at least one temperature sensor (T4) for measuring the outlet temperature of the process air arranged or to be arranged in the region of a process air outlet of the drying chamber (1), at least one temperature sensor (T1) for measuring the inlet temperature of the plastic granulate,at least one process air mass determination device and at least one evaluation unit, wherein the evaluation unit can be used to determine the difference between the inlet temperature and the outlet temperature of the process air and from this, taking into account the heat capacity of air, the specific energy input and, taking into account the mass of the supplied process air, the absolute energy input by the process air, and wherein the evaluation unit can be used to determine or retrieve the throughput of the plastic granulate and the target temperature for the plastic granulate and the difference between the target temperature and the inlet temperature of the plastic granulate and, from this temperature difference, the specific energy requirement, Taking into account the specific heat capacity of the respective plastic granulate. Device according to claim 1, characterized in that the process air mass determination device is or is to be arranged in the region of the process air line and comprises an air volume measuring device. Device according to claim 2, characterized in that at least one temperature sensor (T6) is arranged in the region of the air volume measuring device, so that the density of the process air in the region of the air volume measuring device can be determined taking into account the temperature. Device according to claim 3, characterized in that at least one pressure sensor for determining the air pressure is arranged in the region of the air volume measuring device, so that the density of the process air in the region of the air volume measuring device can be determined taking into account the air pressure.Device according to one of the preceding claims, characterized in that, in order to determine the total energy requirement with the aid of the evaluation unit, the energy required for the actual drying of the plastic granulate can also be taken into account in addition to the energy required for the temperature increase. Device according to one of the preceding claims, characterized in that it has an output device for outputting the determined specific and / or absolute energy requirement and the determined specific and / or absolute energy input. Device according to one of the preceding claims, characterized in that, in order to record the energy required for cooling the process air, it has at least one heat exchanger arranged or connected in the process air line of the dryer system in the direction of flow downstream of a heat exchanger.to be arranged temperature sensor (T5), so that with the help of the evaluation unit the specific loss energy can be determined from the difference between the output temperature measured in the area of ​​the process air outlet and the temperature measurement value of the cooled process air. Device according to claim 7, characterized in that the process air mass determined with the aid of the process air mass determination device can be used in conjunction with the temperature difference between the cooled process air and the temperature at the process air outlet in such a way that the absolute energy loss can be determined taking into account the mass of the cooled air. Device for drying plastic granulate (10), comprising at least one drying chamber (1), a feed device for plastic granulate (3), a blower (6), and a heater (7), characterized in that it has at least one device for monitoring the energy management of dryer systems for plastic granulate according to one of the preceding claims, wherein the functional elements of the device for monitoring the energy management of dryer systems for plastic granulate are installed at the corresponding locations on the device (10).Device (10) according to claim 9, characterized in that the blower (6) and / or the heater (7) can be controlled by means of the control unit to adjust the mass fed into the drying chamber (1) and / or the inlet temperature of the process air in order to minimize the deviation of the energy input from the energy requirement determined by the evaluation unit, so that optimized automatic control of the energy input with regard to the actual energy requirement is realized. A method for monitoring energy management in dryer systems for plastic granulate, comprising at least the following method steps: Setting a target temperature for the plastic granulate, Measurement of the inlet temperature of the plastic granulate, Determination of the difference between target and inlet temperature of the plastic granulate, Calculation of the energy requirement for drying the plastic granulate and increasing the temperature to the target temperature, Measuring the inlet and outlet temperature of the process air at the drying chamber (1), Determination of the difference between the inlet and outlet temperature of the process air, Determination of the mass of the process air supplied to the drying chamber, calculation of the energy introduced into the plastic granulate by the process air, Output of the values ​​for energy demand and entered energy. Method according to claim 11, characterized in that the target temperature for the Plastic granules are selected from a range between approximately 160°C and 195°C. The method according to one of claims 11 and 12, characterized in that the inlet temperature of the plastic granules is measured in the area of ​​a storage area for the plastic granules and / or in the inlet area of ​​the dryer. The method according to one of claims 11 to 13, characterized in that, to calculate the energy requirement for drying the plastic granules and raising the temperature to the target temperature, the temperature difference between the target and inlet temperatures is multiplied by the specific heat capacity of the material in order to determine the specific energy requirement per kg of plastic granules.Method according to one of claims 11 to 14, characterized in that the energy required for drying the plastic granulate per unit weight, the drying effort, is added to the energy required for increasing the temperature, and thus the specific total energy requirement for drying and heating the plastic granulate is determined. Method according to one of claims 11 to 15, characterized in that the throughput-dependent energy requirement and / or total energy requirement is determined. Method according to one of claims 11 to 16, characterized in that the mass of the process air supplied to the drying chamber (1) is determined by measuring the volume flow of the supplied process air and multiplying it by the density of the process air.Method according to claim 17, characterized in that the temperature and / or air pressure of the process air is measured in the region of the process air mass determination device and is taken into account to determine the density of the process air. Method according to one of claims 11 to 18, characterized in that the energy introduced into the plastic granulate by the process air is calculated by multiplying the temperature difference of the process air by the specific heat capacity of air. Method according to one of claims 11 to 19, characterized in that the values ​​for the specific and / or absolute energy requirement and the entered specific and / or absolute energy are output by displaying curves of the respective values ​​on a display. Method according to one of claims 11 to 20, characterized in that it additionally comprises the following method steps: Measuring the temperature of the process air after cooling for subsequent drying, Determination of the difference between the initial temperature of the process air from the drying chamber and the cooled air, determination of the cooled process air mass, Calculation of the energy required to cool the air (lost energy), Output of the calculated energy loss on the display. Method according to one of claims 11 to 21, characterized in that at least one device for monitoring the energy management on dryer systems for plastic granules according to one of claims 1 to 8 and / or a device for drying plastic granules according to one of claims 9 and 10 is used. Method for drying plastic granules comprising the method steps of the method according to one of claims 11 to 22, wherein process air is heated by means of a heater (7) and is introduced into and passed through the drying chamber (1) of a device for drying plastic granules (10) by means of a fan (6), and in the drying chamber (1) absorbs moisture from plastic granules also introduced into the drying chamber (1), and heats the plastic granules.

Images