Method and apparatus for monitoring energy management of plastic pellet dryer system and method and apparatus for drying plastic pellets

Abstract

The invention relates to a method and a device for monitoring the energy management of a plastic pellet dryer system and to a plastic pellet drying method and a device. According to the invention, the energy introduction and the energy demand are continuously determined, so that the operation of the corresponding system is optimized in terms of product quality and energy consumption.

Description

Technical Field

[0001] The invention relates to a device for monitoring the energy management of a plastic granulate dryer system.

[0002] Furthermore, the invention relates to a method for monitoring the energy management of a plastic granulate dryer system.

[0003] Furthermore, the invention relates to a plastic granulate drying system comprising at least one device for monitoring the energy management of a plastic granulate dryer system, in particular for preparing the plastic granules for a subsequent plasticizing process.

[0004] Furthermore, the invention relates to a method for drying plastic granules with energy management monitoring. Background Art

[0005] The corresponding devices and methods are used in particular for the production of plastic products, which are usually made from plastic granules. This applies in particular to hygroscopic granules which have to be dried before the plasticizing process in order to prevent the material from degrading during the plasticizing process. In addition, thermal energy can be fed into the material, which significantly supports the plasticizing process: since the plasticizing process has to provide less energy for melting the plastic material, the plasticizing process becomes more stable.

[0006] Today, the drying process of plastic granules is already very mature with appropriate methods and equipment. For example, in a plastic granule drying plant configured as a drying hopper where the material is ready for the plasticizing process, sufficiently dry process air is fed in countercurrent, which absorbs excess moisture in a controlled manner. The process air is then dried and recycled.

[0007] The simultaneous introduction of thermal energy into the plastic granules by means of the drying air is another problem in the prior art, as this process has not received sufficient attention. The reason for this is that measuring the energy introduced into the granules during continuous production is challenging and currently economically impossible, as the pellets of plastic granules are highly insulating and therefore the core temperature cannot be inferred from external temperature measurements. Although the temperature of the plastic granules can be monitored by thermal sensors, only the temperature of the process air is effectively measured, while the energy inside the individual granules remains unknown. However, this temperature display is overly important. For example, the typical temperature of polyethylene terephthalate (PET) during the drying process is 160°C-195°C, but it can also be lower or higher. If this material is saturated at the desired temperature due to its heat absorption capacity (material enthalpy), the production thermal management during processing is optimal and the best quality products can be produced. If the energy introduced into the plastic granules is too low, the subsequent injection molding machine requires significantly more energy to heat the material accordingly, and the material is subjected to very large loads due to the introduction of mechanical energy. In this way, the plasticizing screw often fails to fully homogenize the melt, or the screw torque increases or even exceeds the limit. This leads to undecomposed materials and bubbles in the product. In today's systems, in order to solve this problem, the plasticizing temperature curve is usually increased to reduce the torque or compensate for insufficient energy, or the screw itself reaches an uncontrollable high temperature due to excessive friction, resulting in the burning of the plastic material and / or its additives, which in turn manifests as black spots in the product.

[0008] It is not uncommon for operators of injection molding systems to lack detailed knowledge of the energy relationship between dryer and injection molding machine, since the dryer already fulfills its primary task of drying the material, which can easily be verified in the quality laboratory.

[0009] Today, there are still operators who suspect that the process air flow in the dryer is not sufficient to achieve energy saturation of the plastic granules and therefore recognize that this is associated with product defects. In this case, according to the prior art, the air volume flow in the dryer is increased so that energy saturation of the granules is achieved in order to ensure good production. In this case, it is not clear whether this process air will leave the drying system with excess energy. For example, when processing PET, the temperature of the outgoing process air flow can reach over 60°C, or even higher (e.g. 130°C). However, in order to effectively dry this air, it must be cooled to preferably about 60°C, which is done in a heat exchanger. In this case, the operator pays twice for the energy loss: after drying, the air must be reheated with the help of air drying equipment (e.g. silicate drying cylinders or drying wheels), while the heat exchanger conducts the excess energy, for example, into a cooler.

[0010] According to the prior art, due to the impossibility of measuring the energy content in the plastic pellets and the lack of up-to-date and precise information on the drying and energy saturation of the plastic pellets, the dryers are almost never operated at the optimum operating point. This is unacceptable under today’s conditions (such as the desire to save resources, rising energy costs and low available profits).

[0011] Today, dryer manufacturers help themselves by using load cells to determine the system throughput of plastic granules. Depending on the manufacturer, an air factor is used to adjust the air volume to the demand. In most cases, the air volume of the fan is theoretically determined from the power consumption of the fan or its speed. The current air temperature of the fan, which determines the air density, and the degree of clogging of the filters cannot be reliably displayed. In addition, the displayed air volume (usually in cubic meters) instead of the relevant mass can also mislead the operator. In addition, general process fluctuations, especially the inlet temperature of the plastic granules, are rarely taken into account. There are currently some drying hoppers on the market that reduce the air volume flow to a value selected by the operator when the process air temperature at the outlet is high, but the operator does not know whether the material has reached energy saturation or whether the heat exchanger is unknowingly removing excess energy from the process air. In addition, there is no system that rationally combines the energy consumption with the energy demand of the dryer. Therefore, it is not uncommon for the cooling water valve on the heat exchanger to get stuck and the air to be unnecessarily cooled to a temperature far below 60°C.

[0012] In summary, in currently known methods and plants for drying plastic granules, operators are almost unaware of the interrelationships of the heating of the plastic granules before the plasticizing process, the search for quality defects that often occur in the injection molding system, or the excess energy that disappears when cooling the process air after drying the granules, for example in the cooler, remains unnoticed in most cases.

[0013] Operators of known dryer systems often lack the information they need to assess the energy efficiency of their drying processes themselves. Today, many manufacturers of dryer systems claim that their dryer systems are optimally designed and that the quality of their work is correspondingly high. Unfortunately, this is rarely the case, as external influencing factors are too diverse or the dryers are too old to allow energy management during manufacture. For example:

[0014] - If the filter gradually becomes clogged, this is not taken into account;

[0015] - the inlet temperature of the pellets fluctuates over time, to which known dryers react only slightly;

[0016] - All dryers work on air volume and therefore do not adequately take into account air density when the temperature fluctuates;

[0017] - Air volume flow is almost always calculated through fan theory and rarely has actual values;

[0018] - It is often not possible to detect a defective heat exchanger. Summary of the invention

[0019] It is therefore an object of the present invention to provide a device for monitoring the energy management of a plastic granulate dryer system which at least partially solves the above-mentioned problems.

[0020] This object is achieved according to the invention by a device as claimed in claim 1 .

[0021] Another object of the present invention is to provide a plastic granule drying device which at least partially solves the above-mentioned problems.

[0022] This object is achieved according to the invention by a device as claimed in claim 9 .

[0023] Another object of the present invention is to provide a method for monitoring the energy management of a plastic granulate dryer system, which method at least partially solves the above-mentioned problems.

[0024] This object is achieved according to the invention by a method as claimed in claim 11 .

[0025] Another object of the present invention is to provide a method for drying plastic granules, which at least partially solves the above-mentioned problems.

[0026] This object is achieved according to the invention by a method as claimed in claim 23 .

[0027] Advantageous embodiments of the invention are set forth in the dependent patent claims.

[0028] All possible combinations of features of the device for monitoring the energy management of a plastic pellet dryer system, the plastic pellet drying device, the method for monitoring the energy management of a plastic pellet dryer system and the plastic pellet drying method disclosed below are part of the invention.

[0029] The basic idea of ​​the teaching of the invention is to determine the energy introduction into the plastic granules by means of the process air in order to achieve sufficient energy saturation of the plastic granules with the lowest possible losses in addition to drying.

[0030] Besides granular plastics, other forms of plastics can also be processed according to the invention, such as plastic flakes or plastic powder.

[0031] In some embodiments of the invention, the energy management of the dryer system may be continuously monitored or the energy management of the dryer system may be continuously monitored.

[0032] The plastic particle drying device according to the present invention at least comprises a drying chamber, a plastic particle supply device, a fan and a heater.

[0033] The plastic granules can be fed into the drying chamber via a supply device. With the aid of a fan, an air flow of dried process air can be passed through the process air line via the process air inlet and into the drying chamber. The process air in the area of ​​the process air line can be conditioned to a desired temperature by means of a heater, which in the case of drying PET granules is usually in the range of about 160° C. to about 195° C. In the drying chamber, the process air and the plastic granules come into contact with each other, wherein the process air absorbs moisture from the plastic granules and releases heat energy to the plastic granules.

[0034] In some preferred embodiments of the present invention, the drying chamber is thermally insulated, thereby greatly reducing the loss caused by unwanted heat loss.

[0035] The plastic granulate drying system according to the invention has at least one device for monitoring the energy management of the plastic granulate dryer system.

[0036] According to the invention, the device for monitoring the energy management of a plastic granule dryer system has at least one temperature sensor arranged or to be arranged in the process air inlet region for measuring the inlet temperature of the process air and at least one sensor arranged or to be arranged in the process air outlet region of the drying chamber for measuring the outlet temperature of the process air. Furthermore, the device for monitoring the energy management of a plastic granule dryer system has at least one temperature sensor for measuring the inlet temperature of the plastic granules.

[0037] Furthermore, the device according to the invention for monitoring the energy management of a plastic granulate dryer system has at least one evaluation unit.

[0038] In some embodiments of the invention, the inlet temperature of the plastic pellets can be determined by measuring the temperature at the storage location of the plastic pellets, provided that the plastic pellets remain in the storage location for a sufficiently long time so that the temperature there is uniformly transferred to the plastic pellets. In corresponding embodiments, the surface temperature of the plastic pellets in the region of the supply device of the plastic pellet drying device can also be additionally measured to check its plausibility.

[0039] If the quality of the process air passing through the drying chamber is known, the thermal energy released by the process air to the plastic granules (energy input) can be determined in addition to losses. To this end, the device according to the invention for monitoring the energy management of a plastic granule dryer system has a process air quality determination device.

[0040] In some embodiments of the present invention, the process air quality determination device is arranged or to be arranged in the process air pipeline area and includes an air volume measurement device. Considering that the density of the process air is related to the temperature (in some embodiments of the present invention, the density can be called from an electronic storage device), the quality of the process air fed into the drying chamber can be determined based on the measured air volume.

[0041] Since the density of air is closely related to temperature, in some advantageous embodiments of the invention at least one temperature sensor is arranged in the area of ​​the air volume measuring device so that the density of the process air in the area of ​​the air volume measuring device can be determined more accurately taking into account the temperature.

[0042] In some 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 accurately taking into account the air pressure.

[0043] In some 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 process air flow rate is integrated or integrable into a section of the process air supply line with a known cross-sectional area, so that the volume of process air introduced into the drying chamber within a determined time can also be determined.

[0044] The absolute energy input introduced by the process air can be determined by means of the evaluation unit from the difference between the inlet temperature and the outlet temperature and taking into account the mass of the process air supplied, from which the energy input per kilogram of process air (specific energy input) is obtained taking into account the heat capacity of the air. To simplify the calculation, in the embodiment of the invention, a value of 1 kJ / kg / K is assumed for the specific heat capacity of the air. Since the process air is dried air, this will not lead to significant errors.

[0045] In addition to determining the energy introduced into the process, it is important for the invention to also know the energy required for drying and energy saturation of the plastic granules. The energy requirement also depends on the mass (throughput) of the plastic granules fed into the dryer.

[0046] The evaluation unit is therefore designed to determine the throughput of the plastic granules.

[0047] In some embodiments of the invention, corresponding measuring devices are integrated or can be integrated into the supply of plastic granules in order to determine the mass of the plastic granules fed in. In other embodiments of the invention, the mass value of the plastic granules fed in can be retrieved by means of the evaluation unit, for example, if this is a predetermined process parameter, using which the supply unit can be controlled accordingly by means of the control unit. In a further embodiment, the material throughput of the dryer is synchronized with at least one downstream production unit (e.g. an injection molding machine) according to the material demand and the corresponding value can be retrieved by means of the evaluation unit.

[0048] In embodiments of the invention of a dryer system with a downstream injection molding system, the material throughput can be automatically derived from the corresponding values ​​taking into account the amount of plastic processed in the cycle of the injection molding system.

[0049] For example, the weight value of a single injection molded product (such as the weight of a preform), the number of mold cavities of the injection molding system, and the proportion of the material of the product (such as a preform) dried with the corresponding dryer can be input or called. Thus, the weight of material required for one cycle of the injection molding system can be determined with the aid of the device of the present invention. In some advantageous embodiments of the present invention, a signal synchronized with the cycle of the injection molding system, such as a signal of the start or end of the cycle, can be received with the aid of the device of the present invention, and the cycle time of the injection molding system can be determined thereby. In a corresponding embodiment, the material throughput required per unit time (for example, per hour) can be determined from the amount of plastic required for each cycle and the cycle time with the aid of the device of the present invention and can be used to calculate the energy demand associated with the throughput.

[0050] Depending on the type of plastic or plastic mixture being processed and the subsequent process, a target temperature for the plastic granules can be predetermined at which the plastic granules reach sufficient energy saturation. In PET and subsequent plasticization, the target temperature ranges from approximately 160° C. to 195° C. The device according to the invention for monitoring the energy management of a plastic granule dryer system has a corresponding input device for inputting the target temperature of the plastic granules.

[0051] The specific energy requirement can be determined by means of the evaluation unit from the difference between the target temperature and the inlet temperature of the plastic granules, taking into account the specific heat capacity of the respective plastic granules.

[0052] For this purpose, the corresponding specific heat value can be retrieved from the memory unit by means of the evaluation unit.

[0053] For example, the specific heat capacity of PET granules is 1.5 kJ / kg / K. Here, in the drying temperature range of -40°C to 230°C during the drying process, the PET material has an almost linear energy absorption (enthalpy), so it is relatively easy to determine the specific energy requirement of the material during the drying process.

[0054] By additionally taking into account the mass of the plastic granules fed into the drying chamber, the absolute energy requirement or the energy requirement related to the throughput required for this temperature increase can also be determined.

[0055] In some preferred embodiments of the present invention, in addition to the energy required for temperature increase, the energy required for actual drying of the plastic pellets is also taken into account when determining the total energy requirement. For example, the corresponding drying energy value of the corresponding material can be called up from a storage unit. For PET pellets, a common value of drying energy is about 12 kJ / kg.

[0056] The present invention therefore represents a solution for determining the optimum energy introduction into plastic granules without measuring the temperature of the granules after drying.

[0057] In some embodiments of the invention, the plastic granule drying device has an output device, which is in particular designed as a display, for outputting the determined specific energy requirement and / or absolute energy requirement and the determined specific energy input and / or absolute energy input. In some embodiments of the invention, energy requirement values ​​and energy input values ​​related to the throughput can be displayed.

[0058] In some preferred embodiments of the present invention, the output device is designed to output the respective energy requirement value and the energy input value in a comparative manner.

[0059] In some advantageous embodiments of the invention, the output device is designed for simultaneously outputting the values ​​graphically, for example a trend curve on a time axis. Based on the difference between the energy demand and the energy input, the operator of the drying system according to the invention can directly and clearly recognize whether the system settings are optimal with regard to the desired energy saturation and energy efficiency of the plastic granules or whether the settings need to be adjusted.

[0060] In some embodiments of the present invention, the device has a control unit, by which the fan and / or the heater can be controlled to adjust the process air quality and / or the process air inlet temperature fed into the drying chamber, so as to minimize the deviation between the energy introduction determined by means of the analysis unit and the energy demand, thereby achieving optimized automatic control of the energy introduction with respect to the actual energy demand.

[0061] In some embodiments of the present invention, the plastic pellet drying apparatus is designed to dry the plastic pellets in a countercurrent manner. Thus, heat energy can be optimally transferred from the process air to the plastic pellets.

[0062] In some embodiments of the present invention, the plastic granule drying device is designed as a drying hopper.

[0063] In some embodiments of the invention, the plastic granulate drying plant has a process air circuit in which the process air is reused.

[0064] After drying the plastic granules, the process air absorbs corresponding moisture and must itself be dried before it can be used again.

[0065] In order to dry the process air, in a corresponding embodiment the plastic granulate drying plant has a process air drying device.

[0066] For example, in some embodiments of the invention, a drying cartridge or drying wheel (eg, made of silicate) is used to dry the process air.

[0067] However, if the process air temperature is too high (generally above 60° C.), it cannot be dried sufficiently by means of known process air drying devices.

[0068] In order to cool down the process air accordingly after it leaves the drying chamber, in a corresponding embodiment the plastic granulate drying system has a heat exchanger which is arranged upstream of the process air drying device in the flow direction.

[0069] In some embodiments of the invention, the heat exchanger is coupled to a cooler. In corresponding embodiments, the higher the degree of cooling required for the drying process air, the higher the energy requirement required for operating the cooler.

[0070] It can be seen from this that in corresponding embodiments, an unnecessarily high set process air temperature or process air volume requires, on the one hand, an unnecessarily high energy consumption for providing the process air and, on the other hand, an unnecessarily high energy consumption for the subsequent cooling of the process air.

[0071] In some embodiments of the invention, this excess energy is shown in a third curve as specific losses per kg of plastic material.

[0072] In order to detect the energy required for cooling the process air, the device according to the invention for monitoring the energy management of a plastic granulate dryer system has, in a corresponding embodiment, at least one temperature sensor arranged in the process air line downstream of the heat exchanger in the flow direction. The specific energy loss can be determined from the difference between the outlet temperature measured in the process air outlet region and the temperature value of the cooled process air.

[0073] By adjusting the temperature and / or the volume flow of the process air so that the specific energy input curve and the specific energy demand curve approximately match each other and the loss curve is simultaneously minimized, the setting of the drying system can be optimized using the specific energy curve.

[0074] In a preferred embodiment of the device of the present invention with the function of determining energy loss, the process air quality determined by means of the process air quality determination device can be combined with the temperature difference between the cooled process air and the temperature at the process air outlet to determine the absolute energy loss while taking into account the quality of the cooled air.

[0075] The method of the invention for monitoring the energy management of a plastic granulate dryer system comprises at least the following method steps:

[0076] - Setting the target temperature of the plastic pellets;

[0077] -Measure the inlet temperature of the plastic pellets;

[0078] - determining the difference between the target temperature and the inlet temperature of the plastic pellets;

[0079] - Calculate the energy requirements for drying the plastic pellets and raising the temperature to the target temperature;

[0080] -Measure the process air inlet and outlet temperatures of the drying chamber;

[0081] - determining the difference between the inlet temperature and the outlet temperature of the process air;

[0082] - Determine the quality of the process air fed into the drying chamber;

[0083] - Calculate the energy introduced into the plastic granules by the process air;

[0084] - Values ​​of output energy demand and values ​​of imported energy.

[0085] In some embodiments of the methods of the present invention, the target temperature of the plastic particles is selected from the range between about 160°C and 195°C.

[0086] In some embodiments of the method of the present invention, the PET pellets are dried.

[0087] In some embodiments of the method according to the invention, the inlet temperature of the plastic granules is measured in the storage area of ​​the plastic granules and / or in the inlet area of ​​the dryer.

[0088] In some embodiments of the method of the present invention, to calculate the energy required to dry the plastic particles and raise the temperature to the target temperature, the temperature difference between the target temperature and the inlet temperature is multiplied by the specific heat capacity of the material to determine the specific energy requirement required per kilogram of plastic particles.

[0089] In some embodiments, the specific heat capacity is loaded or downloaded from an electronic storage unit depending on the material.

[0090] In some embodiments of the present invention, the energy required to dry a unit weight (eg, kilogram) of plastic particles (ie, drying consumption) is added to the energy required for heating to determine the specific total energy requirement for drying and heating the plastic particles.

[0091] In some embodiments of the method of the invention, a throughput-related energy requirement and / or a total energy requirement is determined.

[0092] In some embodiments of the method of the present invention, the mass of the process air supplied to the drying chamber is determined by measuring the volume flow rate of the supplied process air and multiplying by the density of the process air.

[0093] As an alternative to volume flow measurement, the flow velocity in a region with a known cross-sectional area can also be measured and integrated over a defined time.

[0094] In some advantageous embodiments of the method according to the invention, the temperature and / or the air pressure of the process air in the region of the process air quality determination device is measured and taken into account for determining the density of the process air.

[0095] In some embodiments of the method of the present invention, the air density table is stored in an electronic storage device and loaded or downloaded based on the measured values ​​of temperature and / or air pressure.

[0096] In some embodiments of the method of the present invention, the energy introduced into the plastic particles by the process air is calculated by multiplying the temperature difference of the process air by the specific heat capacity of the air.

[0097] In some embodiments of the method of the present invention, the output of the specific energy requirement value and / or the absolute energy requirement value and the output of the introduced specific energy value and / or the absolute energy value are performed by displaying a trend curve of the corresponding values ​​on a display.

[0098] In some embodiments of the method of the present invention, a value related to the throughput is output accordingly.

[0099] By outputting trend curves normalized for the plastic pellet throughput, the operator of the corresponding dryer or dryer system can easily set the optimal operating point by adapting the process air settings to the plastic pellet throughput and / or the inlet temperature by overlaying the curves.

[0100] When using the method of the invention to monitor the energy management of a plastic granulate dryer system with a circulating process air system, in some advantageous embodiments the method further comprises the following method steps:

[0101] -Measure the temperature of the process air after cooling for subsequent drying;

[0102] - Determine the difference between the outlet temperature of the process air of the drying chamber and the temperature of the air after cooling;

[0103] - Determine the quality of process air after cooling;

[0104] - Calculate the energy consumption (energy loss) required to cool the air;

[0105] - Output of calculated energy loss on the display.

[0106] In some embodiments of the invention, the calculated energy loss is output in the form of a trend curve, which is preferably displayed together with trend curves of the (total) energy demand and the energy import.

[0107] In some embodiments of the invention, the calculation of the energy loss takes into account the energy consumption of the cooling device used to cool the heat exchanger.

[0108] In some embodiments of the invention, the energy value is output in Wh, preferably normalized to the throughput of plastic pellets.

[0109] In some embodiments, the method of the present invention for monitoring energy management of a plastic pellet dryer system uses at least one device for monitoring energy management of a plastic pellet dryer system according to the present invention and / or a plastic pellet drying device according to the present invention.

[0110] The plastic granule drying method according to the invention comprises the method steps of the method according to the invention for monitoring the energy management of a plastic granule dryer system, wherein process air is heated by means of a heater and fed into and through a drying chamber of the plastic granule drying device by means of a fan and absorbs moisture in the drying chamber from the plastic granules also fed into the drying chamber and heats the plastic granules.

[0111] In some advantageous embodiments of the method, the process air is recirculated after leaving the drying chamber, wherein the process air is first cooled to a temperature of about 60° C. by means of a heat exchanger and then dried before it is fed again into the fan area and subsequently into the heater area.

[0112] In some embodiments, the plastic pellet drying method of the present invention uses at least one device for monitoring energy management of a plastic pellet dryer system according to the present invention and / or a plastic pellet drying device according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0113] Exemplary embodiments of the invention are shown in the drawings explained below. In the drawings:

[0114] Figure 1 : A schematic diagram showing a plastic granule drying device according to the present invention;

[0115] Figure 2 : shows a dryer system with two plastic granule drying devices according to the present invention;

[0116] Figure 3 : shows a two-stage dryer system with a dryer and a booster according to the present invention;

[0117] Figure 4 : Show Figure 2 and Figure 3 The combination of the dryer system shown; and

[0118] Figure 5 : A display output diagram showing an energy management monitoring device of a plastic pellet drying device or a plastic pellet dryer system according to the present invention. DETAILED DESCRIPTION

[0119] Figure 1 A dryer system (100) is shown, which comprises a plastic granule drying device (10) according to the invention, and which has a drying chamber (1) which is designed as a drying hopper. A plasticizing screw (2) is connected to the material outlet at the bottom of the drying hopper. It is not an essential component of the invention, but an example for further processing of the dried plastic granules. An extruder or other device for further processing of the dried plastic granules can also be connected.

[0120] The drying chamber (1) has a plastic granulate supply (3) on the upper side. The process air can be conducted from the process air outlet via a process air line to a heat exchanger (4), in which the process air is cooled.

[0121] The process air drying device (5) is next for drying the process air. The process air can be fed into the heater (7) through the process air line by means of a fan (6) and finally into the drying chamber (1) through the process air inlet.

[0122] To measure the required temperatures, a first temperature sensor T1 is arranged in the region of the plastic pellet supply (3), a second temperature sensor T3 is arranged in the region of the process air inlet, a third temperature sensor T4 is arranged in the region of the process air outlet, a fourth temperature sensor T5 is arranged between the heat exchanger (4) and the process air drying device (5), and a fifth temperature sensor T6 is arranged in the region of the process air quality determination device between the fan (6) and the heater (7). The mass volume flow m2 of the dried process air can be determined by means of the process air quality determination device.

[0123] The temperature value T2 represents a predefinable target temperature of the plastic granules.

[0124] Preferably, at least one air pressure sensor is additionally provided in the region of the process air quality determination device.

[0125] As mentioned above, the mass volume flow rate m1 of the plastic particles can be measured or otherwise determined in various ways.

[0126] The plastic granules and process air flow through the drying chamber in countercurrent.

[0127] The measured values ​​detected by means of the sensors, the target temperature T2 and the mass volume flow m1 can be detected by means of an evaluation unit and used to calculate the required energy.

[0128] Figure 2 A dryer system (100) is shown, which has two plastic granule drying devices (10), which are respectively labeled A and B. The individual components of the devices (10) are supplemented with "A" or "B" so that they are assigned to the respective devices (10). The plastic granules dried by the two dryers (10) are fed into a material meter and / or mixer (8).

[0129] Different materials can also be processed in the individual dryers, for example virgin plastic granules in dryer A and recycled material in dryer B.

[0130] Figure 3 A dryer system (100) is shown with a drying device (10) and a downstream booster (C). Figure 4 A dryer system (100) is shown with two dryers (A, B) and a downstream booster (C).

[0131] The booster (C) is a unit connected downstream of the drying device (10) and is used to further increase the temperature of the dried plastic particles. Figure 4 and Figure 5 The boosters (C) in the illustrated dryer system (100) are also equipped with an energy management monitoring device according to the present invention.

[0132] Figure 5 The output is shown on a display of the device according to the invention. The figure shows in comparative form the trend curves of the total energy requirement (I), the energy input (II) and the losses (III) normalized to the material throughput.

[0133] Individual curves can be selected or deselected for display. The time resolution of this display can be set to different levels.

[0134] If necessary, the loss curve can also be used to deduce whether the process air is being cooled too strongly than necessary, for example if a cooling valve is stuck or there are other faults in the cooling system.

Claims

1. A device for monitoring the energy management of a plastic pellet dryer system (100), wherein the dryer system (100) comprises at least one plastic pellet drying device (10), the plastic pellet drying device having at least one drying chamber (1), a plastic pellet supply (3), a fan (6) and a heater (7), characterized in that: The device for monitoring the energy management of a plastic granule dryer system (100) comprises at least one temperature sensor (T3) arranged or to be arranged in the process air inlet region of a drying chamber (1) for measuring the inlet temperature of the process air and at least one temperature sensor (T4) arranged or to be arranged in the process air outlet region of the drying chamber (1) for measuring the outlet temperature of the process air, at least one temperature sensor (T1) for measuring the inlet temperature of the plastic granules, at least one process air quality determination device and at least one analysis unit, wherein the difference between the inlet temperature and the outlet temperature of the process air can be determined by means of the analysis unit and the specific energy introduction can be determined based on the difference taking into account the heat capacity of the air and the absolute energy introduction introduced by the process air can be determined taking into account the quality of the supplied process air, wherein the throughput of the plastic granules can be determined or called up and the target temperature of the plastic granules can be called up and the difference between the target temperature of the plastic granules and the inlet temperature can be determined and the specific energy requirement can be determined based on the temperature difference taking into account the specific heat capacity of the corresponding plastic granules.

2. The device according to claim 1, characterized in that The process air quality determination device is arranged or is to be arranged in the region of the process air line and comprises an air volume measuring device.

3. The 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.

4. The 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.

5. The device according to any one of the preceding claims, characterized in that In order to determine the total energy requirement by means of the evaluation unit, in addition to the energy required for heating, the energy required for actually drying the plastic granules can also be taken into account.

6. The device according to any one of the preceding claims, characterized in that The device has an output device for outputting the ascertained specific energy requirement and / or absolute energy requirement and the ascertained specific energy input and / or absolute energy input.

7. The device according to any one of the preceding claims, characterized in that In order to detect the energy required for cooling the process air, the device has at least one temperature sensor (T5) which is arranged or is to be arranged downstream of the heat exchanger in the process air line of the dryer system in the flow direction, so that the specific energy loss can be determined by means of the analysis unit based on the difference between the outlet temperature measured in the area of ​​the process air outlet and the temperature measurement value of the cooled process air.

8. The device according to claim 7, characterized in that The process air quality determined by means of the process air quality determination device can be used in conjunction with the temperature difference between the cooled process air and the temperature at the process air outlet, so that the absolute energy loss can be determined taking into account the quality of the cooled air.

9. A plastic granule drying device (10), comprising at least one drying chamber (1), a plastic granule supply device (3), a fan (6) and a heater (7), characterized in that: The plastic granulate drying system comprises at least one device for monitoring the energy management of a plastic granulate dryer system according to one of the preceding claims, wherein functional elements of the device for monitoring the energy management of a plastic granulate dryer system are mounted at corresponding locations of the device (10).

10. The device (10) according to claim 9, characterized in that In order to adjust the process air quality and / or the process air inlet temperature supplied to the drying chamber (1), the fan (6) and / or the heater (7) can be controlled by means of a control unit so that the deviation between the energy introduction and the energy demand determined by means of an analysis unit is minimized, thereby achieving optimized automatic control of the energy introduction with respect to the actual energy demand.

11. A method for monitoring energy management of a plastic pellet dryer system, comprising at least the following method steps: - Setting the target temperature of the plastic pellets; -Measure the inlet temperature of the plastic pellets; - determining the difference between the target temperature and the inlet temperature of the plastic pellets; - Calculate the energy requirements needed to dry the plastic pellets and raise the temperature to the target temperature; - measuring the process air inlet and outlet temperatures of the drying chamber (1); - determining the difference between the inlet temperature and the outlet temperature of the process air; - Determine the quality of the process air supplied to the drying chamber; - Calculate the energy introduced into the plastic granules by the process air; - Output the value of the energy demand and the value of the energy introduced.

12. The method according to claim 11, characterized in that The target temperature of the plastic particles is selected from the range between approximately 160°C and 195°C.

13. The method according to any one of claims 11 and 12, characterized in that The inlet temperature of the plastic granules is measured in the storage area of ​​the plastic granules and / or in the inlet area of ​​the dryer.

14. The method according to any one of claims 11 to 13, characterized in that To calculate the energy requirement to dry the plastic pellets and raise the temperature to the target temperature, multiply the temperature difference between the target temperature and the inlet temperature by the specific heat capacity of the material to find the specific energy requirement per kilogram of plastic pellets.

15. The method according to any one of claims 11 to 14, characterized in that The energy required for drying and heating the plastic granules is determined by adding the energy required for drying per unit weight of the plastic granules, ie the drying consumption, to the energy required for heating.

16. The method according to any one of claims 11 to 15, characterized in that The energy requirement related to the throughput and / or the total energy requirement is determined.

17. The method according to any 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.

18. The method according to claim 17, characterized in that The temperature and / or the air pressure of the process air in the region of the process air quality determination device is measured and taken into account for determining the density of the process air.

19. The method according to any one of claims 11 to 18, characterized in that The energy introduced into the plastic granules by the process air is calculated by multiplying the temperature difference of the process air by the specific heat capacity of the air.

20. The method according to any one of claims 11 to 19, characterized in that The output of the specific energy requirement value and / or the absolute energy requirement value as well as the specific energy value and / or the absolute energy value introduced is performed by showing a trend curve of the corresponding values ​​on a display.

21. The method according to any one of claims 11 to 20, characterized in that The method further comprises the following method steps: -Measure the temperature of the cooled process air for subsequent drying; - Determine the difference between the outlet temperature of the process air of the drying chamber and the temperature of the air after cooling; - Determine the quality of process air after cooling; - Calculate the energy consumption (energy loss) required to cool the air; - Output of calculated energy loss on the display.

22. The method according to any one of claims 11 to 21, characterized in that At least one device for monitoring the energy management of a plastic granulate dryer system according to one of claims 1 to 8 and / or a plastic granulate drying system according to one of claims 9 and 10 is used.

23. A method for drying plastic particles, 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 fed into and through a drying chamber (1) of a plastic particle drying device (10) by means of a fan (6) and absorbs moisture from plastic particles also fed into the drying chamber (1) in the drying chamber (1) and heats the plastic particles.

Images