Method for the continuous heat treatment of plant bulk material
The method addresses the challenge of varying bulk plant material properties by using a conveying system with adjustable heating zones and sensors to dynamically adjust energy input, ensuring precise and reproducible heat treatment outcomes.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- AUGUST TOEPFER & CO (GMBH & CO) KG
- Filing Date
- 2025-10-17
- Publication Date
- 2026-05-28
AI Technical Summary
Existing heat treatment methods for bulk plant materials face challenges in achieving precise control of energy input to prevent unwanted structural or sensory changes, particularly in roasting and drying processes, due to varying properties within a single batch, such as moisture content and particle size, which traditional power settings cannot account for.
A method involving a conveying system with multiple heating zones, each with adjustable heat sources, where the bulk material is divided into virtual subunits, and temperature and moisture content are monitored to adjust energy input dynamically, using sensors and averaging techniques to maintain target temperatures and prevent overheating.
Ensures precise and reproducible heat treatment results by adapting energy input to varying material properties, preventing burning or charring while achieving consistent aroma and moisture levels.
Abstract
Description
[0001] PATENT ATTORNEY
[0002] August Töpfer & Co. (GmbH & Co.) KG
[0003] Bullenhuser Damm 41
[0004] D-20359 Hamburg
[0005] 2868PA122W0
[0006] Method for the continuous heat treatment of bulk plant material
[0007] The present invention relates to a method for the continuous heat treatment of bulk plant material, in particular seeds, nuts, nut kernels and coffee beans, in a conveying system and by means of direct heating of the bulk plant material.
[0008] It is known to subject bulk plant materials to heat treatment to achieve a desired result. For example, seeds or nuts, as well as other plant products processed in bulk, are heat-treated to kill germs. This can be, for example, pasteurization. This can be done dry, with a specific moisture content, or even with the addition of water. Another application of heat treatment is roasting the raw materials to create roasted aromas or to release aromas in the first place. For example, coffee is roasted in such processes to generate the typical coffee aroma from the initially green beans.
[0009] In such heat treatments, it is crucial that the energy input into the plant material is highly targeted and controlled. For example, when killing germs through heat treatment, it must be ensured that a sufficient amount of energy is introduced to...
[0010] Raffay & Fleck • Stepha nsplatz 2 -6 • D-20354 Ha mbu rg
[0011] Tel.: +49 (0) 40 47 80 23 • Fax: +49 (0) 40 480 25 02 • info@raffay-fleck.de The goal is to kill germs while simultaneously avoiding excessive energy input into the product being treated, thus preventing unwanted structural or sensory changes. For example, roasting the product is generally undesirable when using heat treatment alone to kill germs.
[0012] If, however, the bulk plant material is to be roasted as part of the heat treatment, precise control of the roasting process and the energy input is also necessary. The primary goal is to prevent the material from burning or charring. Furthermore, the change in aromas caused by roasting is highly dependent on the energy input required to achieve a specific degree of roast. Generally, the aim of the roasting process is to achieve a particular aroma composition, i.e., a specific degree of roast. Maintaining this consistently requires precise control of the energy input into the material during the roasting process. In addition, it is often crucial not to exceed a maximum energy density during treatment.
[0013] Heat treatments are also used to dry bulk plant material. Especially when the bulk plant material is temperature-sensitive, such drying can place high demands on the accuracy of the process control.
[0014] Since the bulk plant material undergoing heat treatment is typically a natural product, it exhibits varying properties depending on several factors during its production, storage, and transport, often even within a single batch. These varying properties can particularly affect the moisture content of the bulk material, i.e., the individual particles. Because a portion of the energy applied during heat treatment is always initially used to evaporate moisture and thus reduce the moisture content, and because the moisture content, as mentioned, varies, often even within a single batch, a fixed preset power setting for the heat sources (e.g., heat pumps) is not feasible, especially when very precise control of the energy input is required.It is not possible to operate the heat-generating infrared radiators directly, but rather a control system is required that depends on a recognized result of the heat treatment.
[0015] This is where the invention comes in, which aims to create an improved way of controlling the energy input into the bulk plant material to be subjected to heat treatment, so that more precise control and adjustment of the result of the heat treatment can be achieved.
[0016] According to the invention, this is achieved by the measures and method specified in claim 1. Advantageous embodiments are specified in claims 2 to 24.
[0017] The solution to the above problem consists accordingly of a method for the continuous heat treatment of bulk plant material, in particular seeds, nuts, nut kernels and coffee beans, in a conveying system and by means of direct heating of the bulk plant material by a heat source, in particular by means of infrared radiation. In this method, bulk plant material is continuously fed into the conveying system at an inlet in a predetermined mass flow and conveyed in a controlled manner through at least two sequentially arranged heating zones, each equipped with its own heat source, which covers the entire length of the respective heating zone and whose output power is adjustable separately in each zone, but collectively for each zone.The temperature of the bulk plant material is recorded with a temperature sensor as it leaves a first heating zone located upstream and before entering a second heating zone that follows the first heating zone downstream.
[0018] The special feature of the method according to the invention is that, for monitoring and controlling the heat treatment process, the mass flow of the bulk plant material is seamlessly divided into virtual subunits, and that for each of these virtual subunits, the temperature of the bulk plant material at the end of the first heating zone is recorded by means of a temperature sensor. From the temperature of the bulk plant material of each virtual subunit, an actual temperature value is derived according to the invention, and this actual value is compared with a target temperature value planned for the heat treatment at the end of the first heating zone. If a deviation of the actual value from the target value is detected, the power output of at least the heat source located in the second heating zone is then adjusted.
[0019] An expected target temperature can be determined based on assumed or previously determined properties of the plant material, particularly its moisture content and particle size, as well as on the power setting of the heat sources (e.g., infrared heaters), the mass flow rate, and / or the residence time of the plant material in the first heating zone. The target value can be defined during process planning. However, it can also be adjusted or redefined during the ongoing process based on process results and feedback obtained.
[0020] In the context of the invention, a first and a second heating zone are defined as a pair of two heating zones arranged in the conveying system at any position whatsoever, with the second heating zone immediately following the first heating zone in the conveying direction. Therefore, if, as is usually the case, more than two heating zones are provided in the conveying system, the first heating zone is not necessarily the foremost heating zone into which the bulk material to be treated first enters the conveying system. The terms "first heating zone" and "second heating zone" thus only denote the sequence of two consecutive heating zones within a pair of heating zones selected arbitrarily from a sequence of heating zones in the conveying system. If, when comparing the actual temperature value with the target value, a deviation of the actual temperature from the target value is detected, this can, for example,This can be attributed to a moisture content of the virtual subunit under consideration that deviates from the assumption or from the result of a measurement based on a sample. If higher moisture content is present, the actual temperature will be below the expected target temperature because some of the heating power introduced directly into the material being heated by the heat sources does not result in a temperature increase, but rather in the expulsion of moisture from the bulk plant material. Conversely, if the actual temperature is higher than the target temperature, a lower residual moisture content can be assumed, meaning that less power was required for the expulsion of moisture, thus making more power available for heating the bulk material.
[0021] Since, as already mentioned, the properties, especially the residual moisture, can vary even within a single batch being treated, it is advantageous to have close and, in particular, virtually seamless monitoring and corresponding control, i.e., adjustment of the heat source output and thus the amount of energy input. This is made possible by dividing the process into virtual subunits, which comprise a fraction of the product quantity being treated within a heating zone. Virtual data sheets are attached to these virtual subunits, displaying the temperatures measured for these subunits by the aforementioned temperature sensors, as well as the values derived from the set heat source output(s) and the dwell time in the heating zone (or...).The energy acting on the virtual subunit (derived from the conveying speed through the heating zone) is recorded and stored. This allows for adjustments to the power settings of the heat sources, or alternatively, the conveying speed of the bulk material, for each individual virtual subunit if a deviation is detected. This adjustment ensures that the energy input is fine-tuned to achieve the desired heat treatment result, precisely and reproducibly despite variations in the properties of the raw material being supplied.
[0022] In the method claimed here, this adjustment of the power setting is carried out, in particular, also in a downstream direction, i.e., proactively for the heating zone following the temperature measurement point. In other words, the settings of the subsequent heat sources are adjusted in a way that takes into account the results already obtained and recognized from the previous heat treatment of the bulk material being treated, more precisely, the virtual subunits. Thus, the energy applied in a downstream second heating zone is adjusted to match the amount of energy still required, as determined by data comparison.It is advantageous if the individual heating zones are set so that a smaller proportion of the total energy input is deliberately transferred into the material in the earlier heating zones, i.e., a comparatively lower power output is set for the heat sources. This then allows the subsequent heating zones to react by adjusting the power output of the heat source(s) located there, thus adapting and adjusting the process with regard to the required amount of energy.
[0023] Naturally, the actual temperature value determined at the end of the first heating zone can and usually will also be used to adjust the power settings of the heat sources in that zone, in other words, to influence the heat treatment of subsequent virtual sub-units within that zone. This allows for adjustments to be made in both directions of the product flow, resulting in precise tracking and adjustment of the treatment parameters and thus an improved heat treatment outcome that meets the requirements.In the method according to the invention, the actual temperature value can be determined, in particular, by averaging the temperatures recorded for a predetermined number of virtual subunits, wherein the predetermined number of virtual subunits is less than or equal to the number of virtual subunits simultaneously located in a heating zone. Such averaging smooths the curve of the actual temperature used as a parameter for adjusting the heat sources in the subsequent heating zone, thus improving control and, in particular, preventing otherwise potential overshooting of the power setting. It is particularly advantageous that the predetermined number of virtual subunits is identical to the number of virtual subunits simultaneously located in a heating zone.However, for a good result, it should ideally be at least 50% of the number of virtual subunits simultaneously located in a heating zone.
[0024] The averaging process can be, in particular, a repeated and rolling averaging, in which a temperature value of a newly considered virtual subunit is included and a temperature value of a virtual subunit considered for the largest number of previously performed averaging calculations is excluded. This approach can lead to further smoothing and still results in a power setting of the heat sources in the subsequent heating zone that closely matches the result of the pretreatment in a preceding heating zone, thus improving the control of the heat treatment and consequently the result of this heat treatment.
[0025] The primary objective of this method is to regulate the heating power applied to each fraction of the bulk plant material being treated within a heating zone. In the case of averaging as described above, such a fraction is the number of virtual subunits considered for the averaging process. In practice, an operator will often set a treatment system based on a target temperature that the material being treated should reach at the end of a heating zone. In the method according to the invention, changes in the mass flow rate for each fraction are particularly taken into account when determining the heating power. This is because such fluctuations in mass flow rate inevitably result in temperature fluctuations at the outlet from the preceding heating zone, which are detected before entering the subsequent heating zone and taken into account according to the method disclosed herein.In particular, even if the fractions determined by the mean value contain only a comparatively small quantity, i.e. mass, of the bulk material to be treated, the mean value of the set power of the heat source in the subsequent heating zone is reduced pro rata.
[0026] In the method according to the invention, a multiple temperature measurements can be taken at various sections of the virtual subunit as it passes through a measuring range of the temperature sensor to determine its temperature, thus achieving a higher sampling and data density. The temperature assigned to the virtual subunit is then determined as an averaged value derived from the values of the multiple temperature measurements. This procedure essentially involves a two-stage cascaded averaging process. First, an average is calculated from temperature values recorded in close succession at different positions within a virtual subunit to determine the temperature assigned to that virtual subunit. Second, an average is calculated to determine the actual temperature value.This approach allows for the consideration of temperature in a closely monitored sequence without incurring excessive computational costs in the control system that would become unmanageable in continuous monitoring. The potential application of such cascaded averaging is not limited to the downstream control of the second heating zone based on temperature values determined at the outlet of the first heating zone, as is the focus here. It can also be used with similar advantages in a control system where only the upstream heating zones are monitored based on the actual temperature values determined in this way—in the nomenclature of this application, the first heating zone.Naturally, the actual values determined in this way can also be used for regulation in both directions, i.e., in the nomenclature of this application, for regulation of the first and second heating zones.
[0027] Within the scope of the invention, it may further be possible to monitor the values of the individual temperature measurements used to determine the temperature of the respective virtual subunits, as described above, or additionally or alternatively, to monitor the temperature values of the virtual subunits and compare them with predefined threshold values. Then, if predefined threshold values are exceeded or fallen below, the heat treatment can be adjusted. For example, if it is determined that one of the aforementioned values is significantly below a lower limit or threshold value for the temperature, the power of the heat sources can be increased accordingly to achieve rapid readjustment. Conversely, if a limit or threshold value for an upper temperature threshold is exceeded, the power can be reduced, or the treatment can even be stopped, to prevent loss of treated material, e.g.,to avoid charring of goods, which would otherwise be expected if overheated.
[0028] In the method according to the invention, the virtual subunits can be determined in particular according to fragments of a throughput time of the plant bulk material through the conveying system.
[0029] For example, the subunits can be determined based on throughput intervals of 0.2 to 4 s, preferably 0.5 to 2 s, and particularly 1 s. Alternatively or cumulatively, it is also possible to determine the subunits based on throughput intervals of a fraction of 0.01 to 2.0%, preferably 0.01 to 0.50%, of the total throughput time of the bulk plant material through the conveying system. The number of virtual subunits simultaneously present in a heating zone can be, for example, 500 to 2000, and particularly 900 to 1500. Accordingly, an equal number of data records are then generated and must be processed.
[0030] If a two-stage cascaded averaging process, as described above, is used, a high frequency of temperature measurements for a specific virtual subunit can be achieved, for example, every 1 to 50 ms, or every 20 ms. This allows for the highest possible resolution with a large number of measurement points per virtual subunit, which in turn leads to quasi-continuous monitoring and thus particularly reliable and accurate control. Since the computational effort required to process the recorded data is generally a limiting factor, these measured values are not included in the moving average calculation described above. Instead, an initial averaging is performed to determine the temperature values for the virtual segments, and only then are these temperature values averaged.
[0031] In the method according to the invention, the conveying system can have at least three, preferably at least four, sequentially arranged heating zones in the conveying direction. In each of the heating zones, separate heat sources, e.g., infrared radiators adjustable in terms of their output power, are arranged, and the temperature of the bulk plant material of the respective virtual subunits is directly measured by a temperature sensor after it leaves the heating zone.For each virtual sub-unit, the actual temperature determined before entering a second heating zone downstream of a preceding first heating zone is compared with a target temperature planned for heat treatment at the end of this first heating zone. If a deviation is detected, the power of at least the heat source in the second heating zone downstream is adjusted. If necessary, the power in the first heating zone, i.e., for the treatment of subsequent virtual sub-units, can also be adjusted. Providing multiple heating zones allows for the adjustment of heating power in several stages, enabling improved control. On the other hand, the number of heating zones must be kept within a reasonable range with regard to the design, operation, and acquisition costs of the conveying system.
[0032] In such a setup with multiple heating zones, it is particularly possible to design the individual heating zones with the same structure, especially with identical lengths in the conveying direction. Alternatively, a different design may include a shortened inlet heating zone located at the inlet of the conveying system, for example, only half the length of the subsequent heating zones. This inlet heating zone can then be used as a kind of learning zone, from which the control and regulation of the heat sources in the subsequent heating zones can be calibrated based on data acquired, particularly from the temperature sensor at the outlet of this zone.A shortened design of this inlet heating zone has the advantage that, although the data for controlling the subsequent heating zone and the heat sources arranged therein can be obtained, heat treatment without initial knowledge of the behavior of the bulk material to be treated is only of a comparatively short duration, so that any misjudgments with regard to setting the inlet heating zone do not have serious effects on the overall process.
[0033] The conveying system may in particular be a rotary tube system, especially one with an internal conveying loop.
[0034] In the inventive method, if the heat sources are infrared emitters, a dark zone can advantageously be provided between two sequentially arranged heating zones, whereby no infrared radiation is applied to the plant material in the dark zones. In particular, the temperature of the plant material can then be directly measured with the temperature sensors in the dark zones. This leads to higher accuracy of the temperature measurement, since the influence of the infrared radiation acting in the heating zones on the temperature sensors is eliminated, or at least significantly reduced. It should be clarified here that a dark zone does not mean that no visible light is present in these zones, i.e., that these zones actually appear dark or dimmed to the human eye. Rather, it means that the infrared radiation from the heating zones is blocked in the dark zones.If further sensors are to be placed in the dark zones that rely on measurement with visible light, such as optical cameras, it is even essential that reflected light is present in these dark zones, which can convey information about the treated bulk material.
[0035] The inventive method can be provided by using at least one color-sensitive optical sensor to detect the surface color of the bulk plant material in a virtual subunit and to derive the degree of heat treatment from this. In addition to temperature measurement, this approach provides a further control and, if necessary, regulation instrument for adjusting and optimizing the heat treatment. This approach can be particularly advantageous in roasting, as a color change indicating the degree of roasting can serve as an indicator of the roasting state. However, such sensor technology can also be advantageous for processes such as pasteurization or drying, where roasting is not desired. In such cases, for example, a detected color change could indicate a possible imminent onset of the roasting process, allowing intervention to prevent it.
[0036] To prevent roasting or over-roasting, the targeted introduction of water or steam, particularly finely atomized water, into the conveying system can directly lower the temperature of the treated bulk material, thus preventing overheating. When using color-sensitive optical sensors, it is advantageous to distribute several sensors along the conveying path, ideally positioned in a way that corresponds to the temperature sensors. This allows for the detection of color changes in the treated bulk material at various locations, especially for virtual subunits at the same position as the temperature sensors.
[0037] For the color-sensitive optical sensors, cameras for recordings in the visible light and / or infrared spectrum can be used in particular.
[0038] The color-sensitive optical sensors, or rather the images and data they capture, can also be used to control the power output of the heat sources. For example, the degree of heat treatment detected by at least one color-sensitive optical sensor can be compared with the degree of heat treatment expected at the sensor's location. If there is a discrepancy, the power output of at least one of the heat sources can be adjusted. When examining virtual subunits with one of the optical sensors, a single data acquisition can be performed for each virtual subunit, and the result or a measurement value can then be assigned to that subunit. However, it is also possible to perform multiple acquisitions.To take measurements with the optical sensor over different positions of a virtual subunit and to determine a value to be assigned to the virtual subunit viewed with the optical sensor by averaging the measurement results thus obtained.
[0039] To prevent the color-sensitive optical sensors and their measurement results from being affected by electromagnetic radiation emitted by the heat sources, these sensors can advantageously be arranged in the dark zones provided above as a possible embodiment of the method. If the amount of light in the dark zones is insufficient for image capture by the optical sensors, active illumination with visible light or other electromagnetic radiation adapted to the detection wavelength of the optical sensors can be provided there.
[0040] Pyrometers, in particular, can be used as temperature sensors for implementing the invention and the method described herein. This type of sensor operates without contact and can offer the high temporal and spatial resolution necessary for detecting temperature values in the comparatively small mass fractions of the virtual subunits. The temperature measurements or the recording of temperature values can then be timed by polling the output signals of the sensors, such as pyrometers, which continuously output signals corresponding to an observed temperature.
[0041] For monitoring and controlling the heat treatment process, in addition to the values recorded and considered as described above, the moisture content of the bulk plant material in the virtual subunits can also be directly measured using one or more sensors, which are arranged in the inlet area but can also be located at the same measuring points as the temperature sensors. In particular, if the moisture content of the material is measured at the inlet, i.e., in the area where the material enters the conveying position, the heat sources can be preset with an already adjusted power output, so that the control can be carried out with comparatively minor adjustments.This is advantageous because, in the case of a strong deviation and resulting large fluctuations in control, the risk increases of subjecting the material to be treated to excessive heat source power and, in the worst case, burning or charring it.
[0042] The moisture sensors proposed here for use typically determine the moisture content of the material being processed in percent by weight. To utilize the measured values, an average moisture content of a virtual sub-segment can be determined with high accuracy, for example, by taking multiple measurements at various points within that sub-segment and calculating an average value representing its moisture content. Since the mass contained in each virtual segment is known—derived from the mass flow rate set for feeding into the conveyor system and a time interval used to determine the sub-unit—the absolute amount of water contained in that sub-unit can then be calculated from the moisture values and the mass contained within it.If, analogous to the method described above, a moving average is calculated from the individual moisture values assigned to the subunits, the difference between the individual moisture values of the subunits and the moving average can also be determined. Fluctuations in the amount of water per virtual subunit primarily result in a correspondingly higher or lower amount of heat energy being required for evaporation. The energy of evaporation at 100°C is approximately 2088 kJ per kg of water.
[0043] These values allow for predictive adjustment of the heat energy to be supplied, especially if the moisture is already determined at the inlet of the conveying system and before entering an input heating zone, but also for each subsequent heating zone if additional moisture sensors are provided between the heating zones.
[0044] Even when examining virtual subunits with the humidity sensor(s), a single data acquisition can be performed for each virtual subunit examined by the sensor, and the result or value of this measurement can then be assigned to that subunit. However, it is also possible to perform multiple acquisitions or measurements with the humidity sensor at different positions within a virtual subunit and, by averaging the measurement results, determine a value to be assigned to the virtual subunit examined by the respective humidity sensor.Advantageously, the mass flow supplied to the conveying system at the beginning can also be recorded within the framework of the procedure, and the heat work generated in the first heating zone, i.e., located at the beginning of the conveying system, can then be determined by a product of the power output of the heat sources of the first heating zone and the exposure time to the bulk plant material passing through the first heating zone.This heat work, combined with a temperature increase determined by comparing the actual temperature of the bulk material entering the conveying system (as measured by the temperature sensor located at the entrance of the first heating zone) with the actual temperature at the end of the first heating zone (as measured by the temperature sensor located at the end of the first heating zone), allows for the determination of a heat capacity value for a specific fraction of the plant material being treated. This value can then be used to adjust the power output of the heat sources in the conveying system, particularly in an inlet heating zone located at the entrance of the conveying system.
[0045] This allows for further optimization of power correction, especially for fluctuating mass flow rates.
[0046] Even though the conveying systems in the inventive method are continuously fed with a predetermined mass flow, fluctuations in the mass flow can occur, for example, depending on the flow properties of the product. Therefore, it is advantageous to record and monitor the actual mass flow. If fluctuations in the mass flow occur, particularly for certain virtual subunits, and exceed the predetermined limits, the heat sources in the heating zones where the affected virtual subunits are located and heat-treated can be predictively adjusted up or down accordingly to prevent a significant over- or under-input of heat into the material being treated. This approach thus represents a kind of protective mechanism to prevent such mistreatment resulting from fluctuations in the mass flow.Such power adjustment can be implemented proportionally, for example. This means that when "zero mass" (i.e., no material to be processed) is detected in a virtual subunit, the power is completely reduced to 0. Conversely, when a fill level of 100% of the target is detected in a virtual subunit, the power is adjusted to the target power otherwise determined by this method, with a proportional adjustment for intermediate values. Alternatively, instead of reducing the power to 0 when "zero mass" is detected, a certain minimum value, e.g., 10 to 20% of the nominal power of the heat sources, can be reduced to protect the heat sources, e.g., in the form of IR emitters, from excessive wear caused by large fluctuations in power.
[0047] Advantageously, in the inventive method for controlling the power of the heat sources, control software with self-learning algorithms can be used. This allows for rapid and accurate adjustments, particularly with the large amounts of data to be processed, which continue to fine-tune over the course of the process. One can speak of a self-learning system or an AI application here, at least for the treatment of a batch of a starting product where fluctuations do occur, but precisely the kind for which the self-learning algorithms can make very good predictions and adjust the control accordingly. Such a self-learning function can, in particular, also take into account a heat capacity value of the bulk material determined as described above.
[0048] As already mentioned, the heat treatment carried out according to the inventive method can be a roasting process, a pasteurization process, or a drying process, wherein the conveying system can then be, in particular, a rotary kiln system, and preferably, for roasting operations, a rotary kiln roasting unit. In particular, the method can be used for roasting green coffee, wherein the bulk plant material to be subjected to the roasting process is coffee beans. However, other products can also be advantageously roasted using the inventive method, e.g., seeds, nuts, or nut kernels. In one possible embodiment, a method for the heat treatment of bulk plant material, e.g., for roasting coffee, can be carried out as follows:
[0049] A conveyor system is provided with several heating zones, for example four, arranged one after the other in the direction of conveyance. Each zone contains heat sources, such as infrared radiators extending along its length. The heat sources in different heating zones can be individually adjusted for their heating output, independently of the heat sources in other heating zones. However, the heat sources within a single heating zone are set together to a common and uniform output level.
[0050] Temperature sensors, such as pyrometers, are now arranged between the heating zones and in front of the first heating zone located on the inlet side of the conveyor system in the direction of flow.
[0051] To illustrate the procedure according to the method disclosed herein, the power setting of a second heating zone following the first heating zone described above will now be considered as an example. To control the power setting of the heat sources arranged in this second heating zone, the measured values of the temperature sensor, e.g., measured values of a pyrometer, located between the first and second zones are used.
[0052] The measured values from this temperature sensor are read at a predetermined sampling frequency, e.g., 50 Hz, meaning one query every 20 milliseconds. A number of such measured values, e.g., 50, are then assigned to a virtual subunit, which accordingly has a throughput time of 1 second. From the measured values recorded for this virtual subunit (e.g., 50), a temperature value assigned to the virtual subunit is then determined by averaging.
[0053] From the temperature values determined in this way for a plurality of virtual subunits, a moving average is then calculated over a predetermined number of temperature values, i.e., virtual subunits, in particular a number of virtual subunits that is less than or - ideally - equal to a number of virtual subunits simultaneously located in a heating zone of the conveying system.
[0054] A control system for adjusting the power output of the heat sources in the second heating zone processes this averaged temperature at a rate corresponding to the transit time of the virtual subunits summarized in the average value—in the example above, a rate of 1 Hz—and assigns the averaged temperature an actual value. From this actual value for the averaged temperature, a setpoint for the power to be supplied to the second zone is determined in a manner described in more detail below.
[0055] This procedure compensates for temperature fluctuations in the treated material, which arise because particles located on the surface of a product stream are heated more intensely by the heat source, particularly IR radiation emitted by an infrared heater, than the particles below. To minimize these differences, the product stream is also mixed within the conveying system, for example, by rotating a conveyor roller. Due to the aforementioned local variations in exposure to the heat source and the resulting temperature fluctuations, it is particularly advantageous to record temperature values at a high sampling frequency and then calculate an average value as input for controlling the heat source in the downstream zone.This ensures a more accurate picture and prevents erratic fluctuations in the temperature setting caused by the power setting, which, without such averaging, can easily reach 3 to 5 degrees and lead to a "flickering" of the control system. In an example where the conveyor system has four heating zones, each with a heat source (e.g., one or more infrared emitters extending across the entire zone), and where the temperature values of the virtual sub-units are acquired by averaging measurements taken at a sampling rate of 50 Hz at a 1-second interval, the entire conveyor system with all four heating zones can simultaneously handle a total of 1,600 virtual sub-units, i.e., 400 virtual sub-units per heating zone.Taking into account the temperature values for 400 virtual subunits, i.e., corresponding to the number of virtual subunits simultaneously located in a heating zone, the moving average taken over these 400 temperature values is derived based on 400 averaging calculations from the individual measurements.
[0056] For each virtual subunit that is newly included in the averaging process with a sampled temperature, a temperature value previously included in the averaging process for a now further advanced virtual subunit is removed from the calculation. The resulting average can therefore be described as a moving average.
Claims
Claims 1. A method for the continuous heat treatment of bulk plant material, in particular seeds, nuts, nut kernels and coffee beans, in a conveying system and by direct heating of the bulk plant material by a heat source, in particular by infrared radiation, wherein bulk plant material is continuously added to the conveying system at an inlet in a predetermined mass flow and is conveyed in the conveying system in a controlled manner through at least two sequentially arranged heating zones, each of which is equipped with its own heat source and which covers the respective heating zone in its flow length, and which is separately adjustable in each of the heating zones, but jointly adjustable for the respective heating zone with regard to the output power, until it reaches an outlet.wherein the temperature of the bulk plant material is measured by a temperature sensor as it leaves a first heating zone located upstream and before entering a second heating zone located downstream of the first heating zone, characterized in that, for monitoring and controlling the heat treatment process, the mass flow of the bulk plant material is continuously divided into virtual subunits and the temperature of the bulk plant material at the end of the first heating zone is measured for each virtual subunit by means of the temperature sensor, wherein an actual temperature value is derived from the temperature of the bulk plant material of each virtual subunit measured by the temperature sensor and compared with a target temperature value planned for the heat treatment at the end of the first heating zone, and if a deviation of the actual value from the target value is detected, the power of at least the heat source in the second heating zone is adjusted.
2. Method according to claim 1, characterized in that the actual value of the temperature is determined by averaging the temperatures recorded for a predetermined number of virtual subunits, wherein The specified number of virtual subunits is less than or equal to the number of virtual subunits simultaneously located in a heating zone.
3. Method according to claim 2, characterized in that the averaging is a repeated and moving averaging in which a temperature value of a newly considered virtual subunit is recorded and a temperature value of a virtual subunit considered for the largest number of previously performed averaging is excluded.
4. Method according to one of claims 2 or 3, characterized in that, for the purpose of detecting the temperature of the virtual subunit with the temperature sensor, a plurality of temperature measurements are carried out on different sections of the virtual subunit passing through a measuring range of the temperature sensor, and the value of the temperature of the virtual subunit is determined as an averaged value derived from the values of the plurality of temperature measurements.
5. Method according to claim 4, characterized in that the values of the individual temperature measurements from the plurality of temperature measurements and / or that the values of the temperature of the virtual subunits are monitored and compared with predetermined threshold values, wherein an intervention in the heat treatment takes place if predetermined threshold values are exceeded or fallen below.
6. Method according to one of the preceding claims, characterized in that the virtual subunits are determined according to fragments of a throughput time of the plant bulk material through the conveying system.
7. Method according to claim 6, characterized in that the virtual subunits are selected based on throughput intervals of 0.2 to 4 s, preferably 0.5 to 2 s, in particular 1 s, and / or based on a The fraction of 0.01 to 2.0%, in particular 0.01 to 0.5%, of the total throughput time of the bulk plant material through the conveying system can be determined.
8. Method according to one of the preceding claims, characterized in that the conveying system has at least three, preferably at least four, sequentially arranged heating zones in the conveying direction, wherein in each of the heating zones separate and independently adjustable heat sources with respect to the output power are arranged,wherein at the end of each of the heating zones the temperature of the plant material of the respective virtual subunits is directly recorded with a temperature sensor after leaving the heating zone, and wherein for the virtual subunits a comparison of the actual temperature determined before entering a second heating zone downstream of a preceding first heating zone with a target temperature planned for the heat treatment at the end of this first heating zone, and wherein if a deviation is detected an adjustment of the power of at least the heat source in the second heating zone downstream is made.
9. Method according to claim 8, characterized in that the heating zones, with the exception of an inlet heating zone located at the inlet of the conveying system, each have identical lengths in the conveying direction, wherein the inlet heating zone is shorter than the subsequent heating zones, in particular having only half the length compared to the subsequent heating zones.
10. Method according to one of the preceding claims, characterized in that the heat sources are infrared radiators extending over the length of the heating zone. 1 1 . Method according to claim 10, characterized in that a dark zone is provided between two sequentially arranged heating zones, wherein no infrared radiation is applied to the plant bulk material in the dark zones.
12. Method according to claim 1 1 , characterized in that the temperature of the plant bulk material is directly detected with the temperature sensors in the dark zones.
13. Method according to one of the preceding claims, characterized in that at least one color-sensitive optical sensor detects a surface color of the plant bulk material in a virtual subunit and a degree of heat treatment is derived from this.
14. Method according to claim 13, characterized in that several color-sensitive optical sensors are arranged distributed along the conveyor path of the conveyor system, in particular each in a positioning corresponding to the temperature sensors.
15. Method according to one of claims 13 or 14, characterized in that cameras for recordings in the visible light range are used as color-sensitive optical sensors.
16. Method according to one of claims 13 to 15, characterized in that a degree of heat treatment detected by means of the at least one color-sensitive optical sensor is compared with a degree of heat treatment expected at the position of the color-sensitive optical sensor and, in the event of a deviation, the power of at least one of the heat sources is adjusted.
17. Method according to one of claims 13 to 16, insofar as these are directly or indirectly related back to claim 11, characterized in that the color-sensitive optical sensors are arranged in the dark zones.
18. Method according to one of the preceding claims, characterized in that pyrometers are used as temperature sensors.
19. Method according to one of the preceding claims, characterized in that, for monitoring and controlling the heat treatment process, the moisture content of the plant bulk material in the virtual subunits is additionally directly detected by means of one or more sensors, in any case in the area of the feed, preferably at the same measuring locations as the temperature sensors.
20. A method according to one of the preceding claims, characterized in that a mass flow supplied to the conveying system is detected and that, for each of the virtual subunits, the heat work supplied to a first heating zone is determined, which is generated by a product of the power of the heat source set there in the first heating zone and the exposure time to the bulk plant material passing through the first heating zone, and a temperature increase is determined by comparing the actual temperature of the bulk material entering the first heating zone, as determined by temperature values recorded by a temperature sensor arranged before the inlet to the first heating zone, with the actual temperature at the end of the first heating zone, as determined by temperature values recorded by a temperature sensor arranged at the end of the first heating zone, and a heat capacity value of an affected fraction of the bulk plant material to be treated is derived therefrom.This is determined and taken into account for a power setting of the heat source, at least in the second heating zone following the first heating zone downstream.
21. Method according to one of the preceding claims, characterized in that the mass flow actually entering the conveying system is recorded and monitored, and that when fluctuations in the mass flow occur, particularly for certain virtual subunits, and exceed the predetermined limits, the heat sources in the heating zones, in which the affected virtual subunits are located and are heat-treated, their performance is predictably increased or decreased in order to avoid a significant over- or under-input of heat into the material being treated.
22. Method according to one of the preceding claims, characterized in that control software with self-learning algorithms is used for controlling the power of the heat sources.
23. Method according to one of the preceding claims, characterized in that the heat treatment is a roasting process, a pasteurization or a drying process and that the conveying system is a rotary tube system with an internal conveying helix, for a roasting process in particular a rotary tube roasting device.
24. Method according to claim 23, characterized in that the vegetable bulk material to be subjected to the roasting process is coffee beans, seeds, nuts or nut kernels to be roasted.