Hybrid rotary oven and method of baking using a hybrid rotary oven

Abstract

Hybrid rotary oven for use with a method for baking food products using the hybrid rotary oven, the method comprising: - rotating a removable vertical unit (15) containing multiple food products positioned above each other around a vertical axis within a baking chamber (14); - simultaneously applying convection heating, using heating unit (7), by circulating hot air (13) through the removable vertical unit (15) and applying infrared radiation by operating one or more infrared heating units (1, 2); - controlling the one or more short-wave infrared heating lamps (1) to direct infrared radiation onto the food products as the removable vertical unit (15) rotates.

Description

HYBRID ROTARY OVEN AND METHOD OF BAKING USING A HYBRID ROTARY OVEN

[0001] The invention relates to a hot air rotary oven for heating food products to high temperatures, such as baking bread and pastry products.

[0002] Motivation for the invention: Due to the high energy consumption of these installations, which in most cases are heated by a fuel such as natural gas, it is often not possible to switch to fully electrically heated ovens because of EnergieNed (i.e. power grid) regulations. To somewhat achieve energy transition goals, it would be beneficial to combine different energy sources to obtain an energy-efficient installation and alleviate the burden on the energy grid.

[0003] A hybrid rotary oven is known where electric heating elements are placed near the combustion chamber, but due to the energy-absorbing capacity of the oven and because heat energy transfer takes place through convection heat, it is necessary to use higher air temperatures than when using radiant heat on the baking product, i.e. the food product to be baked, such as an unbaked, parbaked or baked food product. This results in longer baking times and higher energy consumption.

[0004] From publication WO8701186A1 , a hot air oven with infrared heating tubes placed in the oven chamber is known, which ensures that the heating temperature and heating time can be lower due to the heated air and infrared radiation. However, because the unit with products in the oven remains stationary, many infrared heating tubes are needed to distribute the radiant heat evenly over the quantity of baking products. This is not feasible for a large number of baking products that need to be baked simultaneously. Due to the very high heat energy density of the infrared heating tubes continuously exerted on the baking product, this is a problem for delicate baking products, making this technique unsuitable for large ovens where many products need to be baked simultaneously.

[0005] However, the state of the art according to the invention is different; in the baking chamber of the industrial hot air rotary oven with removable baking trolleys, according to the invention, a number of infrared heating tubes are fixed above each other in such a way that the rotating baking trolley with a quantity of baking products positioned above each other repeatedly passes the infrared heating tubes. The infrared radiation heats the baking products evenly in combination with hot air heated by the heating unit. The airflow passing through the heating unit can be heated by means of fuel and / or electric heating. The hot air from the heating unit heats the baking trolley with baking products, and the infrared radiation from the infrared heating tubes radiates directly onto the baking product. This allows the hot air temperature and baking time to be significantly reduced, resulting in much lower consumption of conventionalheating, which can also apply to fully electric ovens. By being able to switch the various infrared heating tubes on and off, you can create an infrared heat zone in the oven, so that part of the baking trolley is not heated with infrared radiation. This is beneficial, for example, for a partially loaded baking trolley, or if part of the baking trolley needs less heat due to different baking products and these do not need to be baked separately. All these advantages lead to significant energy savings and more efficient baking.

[0006] This technique also provides a considerable improvement in baking quality. Because part of the heat is transferred directly to the baking product, the baking product gets a crispier crust and a nice crust color, which corresponds to that of a traditional deck oven.

[0007] By using infrared heating tubes in the baking chamber of the rotary oven in combination with conventional heating, you can create a very effective baking result with less mass and kilowatts of power in the oven, resulting in less energy spent on heating the oven and baking the product.

[0008] Due to the high heat energy density of the infrared heating tubes, which have a very intense heat radiation transfer to the baking product, it may be necessary when using a lot of power in infrared heating tubes for delicate baking products to convert part of the energy into convection heat. This can be done, for example, by placing the infrared heating tubes in or near the air inlet unit of the air circulation system, and using a heat-absorbing grid to convert part of the infrared radiation into convection heat, so that the air blown into the baking chamber is additionally heated by means of the infrared radiation-heated grid.Embodiments

[0009] 1 . A Hybrid rotary oven for baking food products; consisting of an oven section where heated hot air from a heating unit (7) with active heating is blown into the baking chamber (14), and the hot air (13) flows through a removable vertical rotating unit (15) with multiple baking products positioned above each other, and the cooled air then returns to the heating unit (7) through the forced air flow (8) to be reheated and recirculated, where the baking products repeatedly pass one or more optionally switched active infrared radiation units (1 resp. 2) while rotating in the baking chamber (14), characterized in that in the baking chamber (14) of the oven (20-21) a quantity of heated hot air (13) circulates, and a quantity of electrically generated infrared radiation (1), and a vertically rotating removable unit (15) to evenly heat a quantity of baking products positioned above each other through convection heat and infrared radiation.

[0010] 2. Hybrid rotary oven according to embodiment 1 , characterized in that in the baking chamber (14) of the hot air rotary oven, a number of infrared heating tubes (1) are installed from bottom to top, and can optionally be switched separately during the heating and rotation of the removable unit (15) with baking products positioned above each other.

[0011] 3. Hybrid rotary oven according to embodiment 2, characterized in that in the baking chamber (14) the infrared heating tubes (1) can be provided with a reflector (2), for directed infrared radiation on the rotating removable unit (15) with baking products positioned above each other.

[0012] 4. Hybrid rotary oven according to embodiment 2, characterized in that the infrared radiation unit (1) can also be multiple units as needed, so that the baking products have multiple contact moments during a rotation cycle of the removable unit (15) with baking products positioned above each other.

[0013] 5. Hybrid rotary oven according to embodiment 1 , characterized in that in the air flow supply unit (11 resp. 12) present in the baking chamber (14), the infrared radiation unit (1 resp. 2) can be placed in such a way that part of the generated heat energy of the infrared heating tubes (1) can be converted into convection heat, which is carried along with the air flow (8) flowing through the rotating removable unit (15) with baking products positioned above each other.Detailed description

[0014] The present invention relates to a hybrid rotary oven for heating food products to high temperatures, such as baking bread and bakery products. The invention addresses the challenge of high energy consumption in conventional rotary ovens, which are typically heated by fossil fuels such as natural gas, by combining different energy sources to achieve energy efficiency while supporting energy transition goals.

[0015] Conventional rotary ovens rely primarily on convection heating, where heat energy transfer occurs through heated air circulation. This approach requires higher air temperatures than direct radiant heating methods, resulting in longer baking times and higher energy consumption. The hybrid approach disclosed herein combines convection heating with infrared radiation to provide more efficient heat transfer directly to baking products.

[0016] The hybrid rotary oven system combines circulated hot air heating with electrically generated infrared radiation. The infrared radiation provides direct heat transfer to baking products while the rotating mechanism ensures uniform heat distribution. This combinationallows for reduced air temperatures and shorter baking times compared to conventional convection-only systems.

[0017] The system can achieve a 10-25% reduction in baking time compared to conventional ovens. The infrared radiation can accelerate starch gelatinization in baking products by directly heating starch granules, which normally occurs through longer conventional heating processes. This direct heating mechanism enables faster processing while maintaining product quality.

[0018] The energy efficiency benefits include approximately 25% reduction in fossil fuel consumption and similar reduction in CO2 emissions for gas-fired rotary ovens. The hybrid approach allows for selective use of different energy sources, enabling operators to optimize energy consumption based on availability and cost considerations.

[0019] The infrared heating elements can be selectively controlled to create heating zones within the baking chamber, allowing different products with varying heat requirements to be processed simultaneously. This flexibility reduces the need for separate baking cycles and further improves overall energy efficiency.

[0020] The hybrid rotary oven provides a combination of convection heating and infrared radiation heating to achieve enhanced baking performance with reduced energy consumption and improved baking quality. The oven configuration integrates multiple heating technologies to optimize the baking process for various food products.

[0021] The baking chamber comprises a, preferably removable, vertical rotating unit for holding multiple baking products positioned above each other. The removable vertical rotating unit is arranged to rotate around a vertical axis within the baking chamber and can be removed from the baking chamber for loading and unloading of baking products. Such a removable vertical rotating unit for holding multiple baking products positioned above each other may also be detachable from the hybrid rotary oven. This rotating configuration ensures that baking products receive uniform heat exposure as the unit rotates during the baking process. In particular, the removable vertical rotating unit may be a baking trolley, which is a mobile wheeled rack system designed for industrial baking operations. It comprises of metal frame structure mounted on casters or wheels and multiple horizontal shelves or rails positioned at regular vertical intervals. The trolley may accommodates numerous baking trays, pans, or product containers arranged spaced apart vertically across its multiple levels, enabling efficient batch processing of large quantities of baked goods. Constructed from heat-resistant materials such as stainless steel or aluminum, the trolley is engineered to withstand high oven temperatures and can be easily wheeled in and out of commercial ovens. In rotary ovenapplications, the entire loaded trolley is positioned within the oven chamber where it rotates around a vertical axis during baking, ensuring uniform heat distribution to all products across all shelf levels simultaneously.

[0022] A circulated hot air heating unit provides convection heating throughout the baking chamber. The circulated hot air heating unit includes a heating unit with active heating and an air inlet unit that extends in the vertical direction over substantially the largest part of the height of the baking chamber. In some examples, the air inlet unit extends over the full height of the baking chamber. It is noted that circulated hot air heating unit is typically positioned separate from the baking chamber. The circulated hot air heating unit is arranged for flowing hot air from the heating unit, through the air inlet unit, to the baking chamber and through the removable vertical rotating unit. The system causes cooled air to return to the heating unit by means of a forced air flow, creating a continuous circulation pattern that maintains consistent temperature distribution throughout the baking chamber. By arranging the inlet unit to extend in the vertical direction over substantially the largest part of, preferably the full, height of the baking chamber, an at least partial, preferably mostly or substantially fully, horizontal flow of hot air through the removable vertical rotating unit in the baking chamber may be achieved. Preferably, an air outlet unit is arranged at a different location in the baking chamber, preferably at an opposing side of the baking chamber, wherein the air outlet unit is arranged for receiving cooled air flow from the baking chamber and for guiding the cooled air flow towards the heating unit with active heating for re-heating the airflow, such that it may be recycled to back into the baking chamber. By arranging both the air inlet unit and air outlet unit to extend in the vertical direction over substantially the largest part of, preferably the full, the height of the baking chamber, an improved horizontalness of the flow of the circulated air flow through the baking chamber may be achieved. The air outlet may also be arranged at an upper section of the baking chamber, to create also a partial vertical upward flow to improve the heat transfer at the bottom of the baking products.

[0023] One or more optionally switched active electrical infrared radiation units provide electrically generated infrared radiation that radiates directly onto the baking products. The active electrical infrared radiation units can be selectively activated or deactivated to control the infrared heating zones within the baking chamber. The infrared radiation units generate electromagnetic radiation that is absorbed directly by the surface of the baking products, providing rapid heat transfer that complements the convection heating from the circulated hot air system.

[0024] The oven may optionally include a steam generator for providing steam during the baking process. When present, the steam generator can introduce controlled amounts ofsteam into the baking chamber to achieve desired moisture conditions for specific baking applications.

[0025] The combination of circulated hot air and infrared radiation creates a hybrid heating environment where baking products receive heat through both convection and direct radiation. As the removable vertical rotating unit rotates, the baking products are exposed to the infrared radiation units at regular intervals, ensuring uniform heating while the continuous hot air circulation provides consistent background heating. This dual heating approach reduces baking time compared to conventional convection-only systems while improving energy efficiency through more direct heat transfer to the baking products. The enhanced heat transfer also improves baking quality by promoting better crust formation and more uniform internal heating of the baking products.

[0026] In a preferred embodiment, the hybrid rotary oven employs multiple infrared heating tubes arranged in a vertical configuration within the baking chamber. The infrared heating tubes are installed from bottom to top and are arranged to be switched separately during the heating and rotation process of the removable vertical rotating unit. This individual switching capability enables precise control over the infrared radiation distribution and allows for the creation of selective infrared heating zones within the baking chamber. Hereby, different baking products having, for instance, different sizes and / or requiring different baking conditions (i.e. the combination of heat and time) may be placed on a single removable vertical rotating unit and simultaneously baked (under different baking conditions) in the hybrid rotary oven.

[0027] The infrared heating tubes may comprise various types of electrical infrared radiation elements depending on the specific application requirements.

[0028] In a preferred embodiment, the infrared heating tubes comprise short-wave infrared lamps that operate in the IR-A wavelength range of approximately 0.75-1.4 micrometers. These IR-A infrared lamps provide optimal performance in combination with circulating hot air systems due to their resistance to air flow interference and efficient energy transfer characteristics.

[0029] In alternative embodiments, the infrared heating tubes may comprise a combination of IR-A lamps with other infrared radiation types. However, IR-B wavelength range (approximately 1.4-3 micrometers) and IR-C wavelength range (approximately 3-10 micrometers) infrared radiators are susceptible to interference from high wind speeds and are therefore not ideal for combination with circulating hot air systems. When used, such longerwavelength infrared radiators should be positioned to minimize exposure to air circulation patterns.

[0030] The IR-A infrared lamps offer superior compatibility with the hybrid rotary oven's circulating hot air system, maintaining consistent infrared radiation output despite the presence of forced air circulation. This compatibility ensures reliable heat transfer performance and optimal energy efficiency in the combined convection and infrared heating environment.

[0031] The infrared heating elements typically have power ratings ranging from 500-3000W per element, allowing for scalable heating capacity based on the size and requirements of the baking chamber. The infrared heating elements may have different IP ratings for various environmental conditions, such as IP65 rating for applications requiring protection against dust and water ingress.

[0032] The infrared heating elements are designed for extended operational life, with lifespans ranging from 5,000 to 10,000+ hours depending on the type and operating conditions. This extended lifespan reduces maintenance requirements and operational costs.

[0033] The individual switching capability of the infrared heating tubes enables the creation of infrared heating zones within the baking chamber. By selectively activating specific infrared heating tubes, different sections of the rotating unit can receive varying levels of infrared radiation. This zonal control allows for simultaneous baking of different products with varying heat requirements, eliminating the need for separate baking cycles.

[0034] The combination of circulated hot air heating and selectively controlled infrared radiation achieves substantial improvements in energy efficiency and baking performance. Testing has demonstrated that this hybrid approach results in approximately 25% reduction in gas consumption compared to conventional rotary ovens. Additionally, baking times are reduced, on average, by approximately 12%, leading to increased throughput and energy savings.

[0035] The selective infrared heating zones also enable partial loading scenarios where only a portion of the rotating unit contains baking products. In such cases, the infrared heating tubes corresponding to the loaded sections can be activated while the tubes corresponding to empty sections remain deactivated, further optimizing energy consumption.

[0036] In a preferred embodiment, the active electrical infrared radiation units are provided with a reflector for directing infrared radiation that is emitted by the active electrical infrared radiation units onto the removable vertical rotating unit. The reflector serves to focus andconcentrate the infrared energy in a specific direction, thereby increasing the efficiency of heat transfer to the baking products.

[0037] The reflector may be constructed from materials with high infrared reflectivity, such as polished aluminum or stainless steel with reflective coatings.

[0038] The reflector is positioned behind or around the active electrical infrared radiation units to capture infrared radiation that would otherwise be dispersed in unwanted directions and redirect the infrared radiation toward the baking products in the removable vertical rotating unit. Alternatively, the reflector may be integrated within the infrared heating tube itself.

[0039] The active electrical infrared radiation units are positioned to direct infrared radiation in at least a horizontal direction toward the removable vertical rotating unit. The one or more active electrical infrared radiation units are preferably arranged in a substantially vertical orientation to achieve this. This at least horizontal direction of radiation allows the infrared radiation to penetrate directly onto the surfaces of the baking products as the removable vertical rotating unit rotates around the vertical axis. The at least horizontal direction of radiation ensures that the infrared energy reaches the baking products at an optimal angle for heat absorption and surface heating.

[0040] The combination of the reflector and the at least horizontal direction of radiation of the active electrical infrared radiation units creates a focused beam of infrared radiation that follows the rotating baking products. As the removable vertical rotating unit rotates, each baking product receives direct infrared exposure multiple times during each complete rotation cycle, resulting in uniform heat distribution across all surfaces of the baking products.

[0041] This reflector configuration provides enhanced heat distribution compared to conventional hot air circulation alone. The directed infrared radiation penetrates the surface of the baking products more effectively than convection heating, leading to improved crust formation and browning characteristics. The focused infrared energy creates surface temperatures that promote the Maillard reaction and moisture evaporation at the product surface, resulting in crust properties comparable to those achieved in traditional deck ovens.

[0042] The reflector also contributes to energy efficiency by preventing infrared radiation from being wasted on heating the baking chamber walls or other non-productive surfaces. By concentrating the infrared energy onto the baking products, the reflector configuration reduces the overall energy consumption while maintaining or improving baking performance.

[0043] In an embodiment, a plurality of active electrical infrared radiation units are arranged at different angular coordinates around the vertical axis in the baking chamber. This configuration enables the baking products to receive infrared radiation multiple times during a single rotation of the removable vertical rotating unit.

[0044] The angular positioning of multiple infrared radiation units provides enhanced heating uniformity compared to a single infrared source. As the removable vertical rotating unit rotates around the vertical axis, each baking product passes by each infrared radiation unit sequentially. This sequential exposure creates multiple heating events during each complete rotation cycle.

[0045] The multiple radiation exposure pattern contributes to more uniform heating distribution across all baking products. Each product receives infrared energy at regular intervals as the rotating unit moves through its rotation cycle. The timing and intensity of these multiple exposures can be controlled by selectively operating individual infrared radiation units.

[0046] Short-wave infrared heating lamps positioned at different angular coordinates around the vertical axis provide direct energy transfer to the food products at multiple points during rotation. The short-wave infrared radiation penetrates into the surface layers of the baking products, promoting rapid heating and enhanced starch gelatinization. The multiple exposure points ensure that all surfaces of the rotating products receive adequate infrared energy.

[0047] The starch gelatinization process benefits from the repeated infrared exposure cycles. Each exposure event contributes to the breakdown of starch granules and the formation of the desired texture and crust characteristics. The multiple infrared sources operating at different angular positions create overlapping heating zones that promote uniform starch transformation throughout the baking process.

[0048] The angular distribution of infrared radiation units can be configured based on the specific requirements of different baking products. The spacing between units and their individual power levels can be adjusted to optimize the heating pattern for particular product types or batch compositions.

[0049] In a preferred embodiment, the hybrid rotary oven includes an infrared-to-convection heat conversion system that addresses the challenge of managing heat intensity for delicate baking products while maintaining energy efficiency. This system provides a mechanism to modulate the direct infrared radiation by converting a portion of the infrared energy into gentler convection heat.

[0050] The air flow supply unit and infrared radiation unit may then be arranged such that part of the generated heat of the infrared heating tubes is converted into convection heat carried along with the air flow. This arrangement allows the system to harness the high energy density of infrared radiation while providing a more controlled heating environment for sensitive baking products that may be adversely affected by intense direct infrared exposure.

[0051] A heat-absorbing grid may therefore be positioned in the air flow path to convert infrared radiation into convection heat. The heat-absorbing grid functions as an intermediary component that intercepts a portion of the infrared radiation emitted by the infrared heating tubes and absorbs the radiant energy. The absorbed energy heats the material of the heatabsorbing grid, which then transfers the thermal energy to the air flowing past the grid through convective heat transfer mechanisms.

[0052] Converting a portion of the infrared radiation into convection heat by positioning the short-wave infrared heating lamps adjacent to an air flow path provides operational flexibility in the heating process. When the infrared heating lamps are positioned near or within the air circulation system, the air stream flowing past the lamps absorbs thermal energy both from direct contact with the heated lamp surfaces and from the heat-absorbing grid that has been warmed by intercepted infrared radiation.

[0053] This infrared-to-convection conversion system enables the oven to operate with reduced direct infrared intensity while maintaining overall energy efficiency. The system allows operators to utilize high-power infrared heating elements while protecting delicate baking products from excessive radiant heat exposure. The converted convection heat is distributed more uniformly throughout the baking chamber via the circulating air flow, providing supplemental heating that complements both the direct infrared radiation and the primary hot air circulation system.

[0054] The heat-absorbing grid may be constructed from materials with high thermal conductivity and infrared absorption properties to maximize the conversion efficiency from radiant to convective heat transfer. The positioning and design of the heat-absorbing grid can be optimized to intercept a predetermined portion of the infrared radiation while allowing the remaining direct infrared energy to reach the baking products for surface browning and crust development.

[0055] In a preferred embodiment, the hybrid rotary oven employs short-wave infrared heating lamps as the active electrical infrared radiation units. Short-wave infrared heating lamps emitinfrared radiation in a wavelength range of 0.75 to 1.4 micrometers, which corresponds to the near-infrared spectrum. This wavelength range provides enhanced heat penetration characteristics compared to longer wavelength infrared radiation.

[0056] The short-wave infrared heating lamps are arranged in a vertical configuration within the baking chamber to provide uniform radiation coverage as the removable vertical rotating unit rotates. The majority of the emitted infrared radiation from these lamps falls within the 0.75 to 1.4 micrometer wavelength range, enabling direct energy transfer to the baking products without requiring intermediate heating of the surrounding air.

[0057] In a specific implementation, the active electrical infrared radiation units comprise halogen infrared heating lamps. Halogen infrared heating lamps utilize a tungsten filament enclosed within a quartz glass envelope filled with halogen gas. The halogen gas enables the tungsten filament to operate at elevated temperatures while maintaining structural integrity through a regenerative halogen cycle. This configuration allows halogen infrared heating lamps to achieve the high operating temperatures necessary to produce short-wave infrared radiation in the desired 0.75 to 1.4 micrometer range.

[0058] The short-wave infrared radiation provides rapid heat penetration into the surface layers of baking products. This direct energy transfer mechanism accelerates the heating process compared to conventional convection heating alone. The rapid heat penetration contributes to faster starch gelatinization within the baking products, as the infrared energy is absorbed directly by the starch molecules and converted to thermal energy. This accelerated gelatinization process can occur without extended baking times that would typically be required to achieve similar results through convection heating.

[0059] The short-wave infrared radiation also enhances crust formation properties of baking products. The direct energy transfer to the product surface promotes rapid moisture evaporation and protein denaturation at the surface, leading to improved crust texture and coloration. The combination of rapid surface heating and controlled moisture removal produces crust characteristics similar to those achieved in traditional deck ovens.

[0060] In a preferred embodiment, at least one of the active electrical infrared radiation units (1 ,2) comprises two or more halogen infrared heating lamps, in particular longitudinal halogen infrared heating lamps, that are arranged directly adjacent and parallel to each other. When two infrared tubes are positioned directly adjacent to each other and activated simultaneously, they influence each other's operating position and emit a lower wavelength due to mutual heating effects. This configuration achieves the same effect as twin-tube designs, which arespecifically engineered to achieve higher temperatures within the tube, thereby reducing the wavelength and achieving higher intensity radiation output. The mutual heating effect between adjacent infrared heating lamps creates enhanced thermal conditions that shift the emission spectrum toward shorter wavelengths, resulting in more efficient energy transfer to the baking products and improved heating performance compared to individually spaced infrared heating elements.

[0061] In a further preferred embodiment, the hybrid rotary oven may comprise a multi-tier infrared heating configuration with enhanced zonal control capabilities. This configuration may include three larger infrared heating tubes positioned vertically above each other, with each tier comprising two infrared heating tubes arranged directly adjacent to each other in parallel rows, creating a total of six infrared heating tubes. The six infrared heating tubes may be optionally housed within reflectors to optimize radiation distribution and may be configured for three-phase electrical distribution to provide balanced power loading.

[0062] This multi-tier arrangement enables the oven to be divided into three distinct baking layers, where each baking layer can be independently controlled with three different baking power levels. The three-tier configuration provides operational flexibility by allowing different heating intensities to be applied to different vertical zones within the baking chamber as the removable vertical rotating unit rotates.

[0063] The three different baking power levels for each layer may comprise: a first level with no infrared radiation where only convection heating is applied, a second level with one infrared heating tube activated to provide moderate infrared radiation combined with convection heating, and a third level with two infrared heating tubes activated to provide maximum infrared radiation intensity combined with convection heating. This graduated power control system allows for precise thermal management across different vertical zones of the baking chamber.

[0064] The multi-tier infrared heating configuration enables simultaneous processing of different product types with varying heat requirements within a single baking cycle. Products requiring gentle heating may be positioned to pass through zones with reduced or no infrared radiation, while products requiring intensive heating may be positioned to pass through zones with maximum infrared radiation. This zonal heating capability optimizes energy utilization and allows for customized baking profiles without requiring separate baking cycles.

[0065] The three-phase electrical distribution of the six infrared heating tubes provides balanced electrical loading and may reduce electrical infrastructure requirements compared tosingle-phase configurations. The three-phase arrangement also enables more precise power control and may provide improved electrical efficiency for the infrared heating system.

[0066] Reflectors may be positioned adjacent to the halogen infrared heating lamps to direct and concentrate the emitted infrared radiation toward the rotating baking products. The reflectors enhance the efficiency of the infrared heating system by reducing radiation losses and focusing the energy output onto the target area where the baking products are located during rotation.

[0067] Preferably, the hybrid rotary oven includes individual switching control means for each of the active electrical infrared radiation units. The individual switching control means comprises electrical switching circuits configured to selectively activate and deactivate individual active electrical infrared radiation units. The electrical switching circuits enable independent control of each infrared heating element, allowing operators to switch individual short-wave infrared heating lamps on and off according to specific baking requirements.

[0068] The selective activation and deactivation capability can create infrared heating zones within the baking chamber. By controlling which active electrical infrared radiation units operate during a baking cycle, different thermal zones can be established within the baking chamber. For example, infrared heating elements positioned at upper (i.e. higher) vertical positions may be activated while those at lower positions remain deactivated, creating a concentrated heating zone in the upper portion of the baking chamber.

[0069] The zone creation functionality provides technical advantages for simultaneous baking of different products. When the removable vertical rotating unit contains different types of baking products requiring varying heat levels, the individual switching control means allows customization of the infrared radiation pattern. Products requiring higher infrared exposure can be positioned to pass through activated heating zones, while products requiring gentler heating can be positioned to avoid direct infrared radiation from deactivated units.

[0070] The individual control system also optimizes energy consumption for partially loaded baking trolleys. When the removable vertical rotating unit is not fully loaded with products, corresponding active electrical infrared radiation units can be deactivated to prevent unnecessary energy consumption. The electrical switching circuits enable precise matching of active heating zones to the actual product distribution within the baking chamber.

[0071] The plurality of active electrical infrared radiation units with individual switching control means enables flexible operation modes. Each infrared heating element can be controlledindependently through dedicated electrical switching circuits, allowing for complex heating patterns that adapt to specific baking requirements. The switching control means may include electronic controllers, relays, or solid-state switching devices that provide reliable on-off control for each active electrical infrared radiation unit.

[0072] The hybrid rotary oven incorporates a heating unit that comprises both fuel-based heating elements and electric heating elements that can be operated independently or in combination. This dual-energy configuration addresses energy transition requirements while maintaining operational flexibility and reducing electrical grid burden.

[0073] The fuel-based heating elements may include gas burners, oil burners, or other combustion-based heating systems that utilize conventional fuels such as natural gas, propane, or heating oil. Possible fuels may thus be fossil fuels (e.g., oil, natural gas and / or fuels derived therefrom), hydrogen, and / or synthetic fuels, such as ethanol and / or bio-fuels. These fuel-based heating elements provide high-capacity heating suitable for rapid temperature increases and sustained high-temperature operation. The electric heating elements may include resistance heating coils, electric heating strips, or other electrically- powered heating components that convert electrical energy directly into thermal energy.

[0074] The heating unit allows independent operation of either the fuel-based heating elements or the electric heating elements, enabling operators to select the most appropriate energy source based on availability, cost, or environmental considerations. Additionally, the heating unit supports combined operation where both fuel-based and electric heating elements operate simultaneously, providing enhanced heating capacity and improved temperature control precision.

[0075] A control unit is configured to coordinate operation of the circulated hot air heating unit and the one or more active electrical infrared radiation units. The control unit manages the interaction between the conventional heating system and the infrared heating system to optimize energy consumption and baking performance. The control unit may include programmable logic controllers, temperature sensors, flow sensors, and communication interfaces that monitor operating conditions and adjust heating parameters accordingly.

[0076] The control unit coordinates the timing and intensity of both heating systems to achieve desired baking profiles while minimizing energy consumption. For example, the control unit may reduce the output of the fuel-based or electric heating elements in the heating unit when the infrared radiation units are providing supplemental heating to the baking products. This coordinated approach prevents overheating while maintaining consistent baking temperatures.

[0077] A temperature sensor, such as a thermocouple, may be arranged in the baking chamber to monitor the actual temperature conditions during the baking process. The temperature sensor may be used in a feedback control loop by the control unit for controlling a temperature in the baking chamber. The control unit may receive temperature readings from the temperature sensor and automatically adjust the operation of the circulated hot air heating unit and the active electrical infrared radiation units to maintain desired temperature setpoints. This feedback control system may enable precise temperature regulation and may compensate for variations in ambient conditions, product loading, or energy source fluctuations to ensure consistent baking performance.

[0078] The temperature sensor may be arranged within reach of the infrared radiation from the active electrical infrared radiation units, allowing the sensor to detect both the convection heat from the circulating air and the radiant heat from the infrared heating elements. This positioning enables the control unit to account for the additional thermal energy contributed by the infrared radiation units when determining the required output from the circulated hot air heating unit. When the temperature sensor detects elevated temperatures due to infrared radiation exposure, the control unit may correspondingly reduce the fuel or electric heating input to the circulated hot air system, resulting in additional fuel savings and improved energy efficiency.

[0079] In some aspects, a plurality of temperature sensors may be arranged throughout the baking chamber, with some temperature sensors positioned to receive direct infrared radiation while others may be shielded from infrared radiation exposure. The shielded temperature sensors may provide readings that reflect primarily the convection heating temperature, while the exposed sensors may provide readings that incorporate both convection and radiant heating effects. The control unit may be configured to determine a control temperature based on readings from the different temperature sensors using various calculation methods, such as weighted linear interpolation schemes or non-linear interpolation algorithms. This multisensor approach may enable more precise temperature control by accounting for the varying thermal conditions throughout the baking chamber and optimizing the balance between convection and infrared heating systems.

[0080] The control unit coordinates the timing and intensity of both heating systems to achieve desired baking profiles while minimizing energy consumption. For example, the control unit may reduce the output of the fuel-based or electric heating elements in the heating unit when the infrared radiation units are providing supplemental heating to the baking products. This coordinated approach prevents overheating while maintaining consistent baking temperatures.

[0081] The hybrid heating configuration enables compliance with energy transition goals by allowing gradual migration from fossil fuel dependence to increased electrical utilization without requiring complete infrastructure replacement. The system reduces electrical grid burden by utilizing fuel-based heating for base load requirements while employing electric heating and infrared radiation for precision control and enhanced baking characteristics.

[0082] The flexible energy source utilization provided by the hybrid heating unit allows operators to respond to energy price fluctuations, supply constraints, or regulatory requirements by adjusting the proportion of fuel-based versus electric heating. This adaptability extends equipment service life and provides operational continuity during energy supply disruptions.

[0083] The hybrid rotary oven operates through a method that combines convection heating and infrared radiation to achieve enhanced baking performance. The operational method involves rotating a removable vertical unit containing multiple food products positioned above each other around a vertical axis within a baking chamber. This rotation ensures uniform exposure of all food products to both heating methods throughout the baking process.

[0084] The method simultaneously applies convection heating by circulating hot air through the removable vertical unit and applies infrared radiation by operating one or more short-wave infrared heating lamps. The hot air circulation provides consistent temperature distribution throughout the baking chamber, while the infrared radiation delivers direct energy transfer to the food products. Hot air is supplied to the baking chamber through an air inlet unit that extends in the vertical direction over substantially the largest part of, preferably the full, height of the baking chamber. This vertical air distribution arrangement ensures uniform convection heating across all levels of the vertically spaced apart food products.

[0085] A distinguishing feature of the operational method involves selectively controlling individual short-wave infrared heating lamps to direct infrared radiation onto the food products as the removable vertical unit rotates. This selective control enables the creation of infrared heating zones within the baking chamber, allowing different sections of the rotating unit to receive varying levels of infrared energy. The selective switching capability accommodates different product types or partially loaded baking units, optimizing energy usage and baking conditions for specific requirements.

[0086] The short-wave infrared heating lamps emit radiation in a wavelength range of 0.75 to 1.4 micrometers, which corresponds to the IR-A spectrum. This wavelength range provides efficient energy transfer directly to the food products, resulting in faster heating compared toconvection heating alone. The infrared radiation can be positioned at different angular coordinates around the vertical axis, ensuring that food products receive infrared radiation multiple times during each complete rotation cycle.

[0087] The combined heating approach produces several technical advantages over conventional rotary ovens. Baking times are reduced, on average, by approximately 12% compared to standard convection-only rotary ovens. This time reduction results from the direct energy transfer provided by infrared radiation, which supplements the convection heating and accelerates the baking process.

[0088] Energy efficiency improvements are achieved through the hybrid heating system. Gas consumption in gas-fired rotary ovens is reduced by approximately 25%, leading to corresponding reductions in CO2 emissions. For electric rotary ovens, the hybrid system enables lower connection requirements and reduced energy costs through more efficient heat transfer.

[0089] The infrared radiation enhances starch gelatinization in baking products. Starch gelatinization occurs when starch granules absorb moisture and swell when heated, transforming from a crystalline to an amorphous state. The direct energy transfer from infrared radiation accelerates this process, achieving better starch conversion in shorter baking times compared to convection heating alone.

[0090] Crust formation and quality are improved through the hybrid heating method. The infrared radiation provides direct surface heating that promotes better crust development, resulting in improved texture and color formation. The enhanced crust characteristics are comparable to those achieved in traditional deck ovens, while maintaining the production efficiency of rotary ovens.

[0091] The selective control capability enables simultaneous baking of different product types within the same baking cycle. By switching individual infrared heating lamps on or off, different heating zones can be created to accommodate products with varying baking requirements. This flexibility allows bakeries to process mixed product loads efficiently without requiring separate baking cycles for different product types.

[0092] The method may include converting a portion of the infrared radiation into convection heat by positioning short-wave infrared heating lamps adjacent to an air flow path. This conversion provides additional flexibility in balancing direct infrared heating with convection heating, particularly for delicate products that may require gentler heating conditions.

[0093] The invention will be further explained below, with reference to the fictitious figures shown in the examples of a hot air oven with a rotating removable baking trolley, and active infrared heating that directly heats the baking products in combination with hot air heating.

[0094] Fig. 1 shows a schematic front cross-sectional view of a hot air oven with a rotating baking trolley and, according to the invention, infrared heating tubes 1 , where the circulation fan 8 resp. 9 sucks the air from the baking chamber 14, and then transports it to the heating unit 7. The heating unit 7 can consist of (i.e. may comprise) a heat exchanger section 6 resp. 5 with combustion burner 4 or electric heating elements 3 or a combination of both heat sources, where the different heat sources 3-6 in the heating unit 7 can optionally be switched separately. After this, the heated air 13 enters the baking chamber 14 through the air inlet unit 11 , and then flows through the baking trolley 15. The baking trolley 15 rotates during baking by means of a suspension system 16 and the rotation motor 17. The heated air 13 in combination with the infrared heating tubes 1 according to the invention heats the baking products evenly, after which the cooled air returns to the heating unit 7 through the circulation fan 8 to circulate. The suspension and rotation system 16 for the baking trolley 15 can also be a fixed rotating carousel into which or onto which the baking trolley 15 is driven, after which the baking trolley 15 rotates and ensures that the baking products repeatedly pass the infrared heating tubes 1 during the baking and heating process.

[0095] Fig. 2 shows a schematic top cross-sectional view of a hot air oven with a rotating baking trolley and, according to the invention, infrared heating tubes 1. By opening the oven door 21 , the baking trolley 15 can be driven into or onto a stationary rotating carousel or suspension system 16 in the baking chamber 14. By closing the oven door 21 and starting the baking and heating process through the control unit 22, with optional steam from the steam generator 18 resp. 19 and the heated hot air from the heating unit 7 flowing through the rotating baking trolley 15, the baking products in the rotating baking trolley 15 are, according to the invention, directly heated each time they pass by and through the optionally switched infrared heating tubes 1 in combination with hot air from the heating unit 7. After the baking process, the baking trolley 15 can be removed from the oven 20 by opening the oven door 21.

[0096] According to Fig. 2, the infrared heating tubes 1 can optionally be attached to a reflector 2 to give better direction to the infrared radiation, where multiple rows of infrared heating tube units 1 resp. 2 can be placed in different locations in the baking chamber 14 as needed.

[0097] Fig. 3 shows a possible schematic top cross-sectional view of Fig. 1-2, of a hot air oven with rotating baking trolley 15, and according to the invention, infrared heating tubes 1 , wherethe heated hot air 13 from the heating unit 7 flows into the baking chamber 14 via the air inlet unit 11 , and where the heated air passes the infrared heating tubes 1 , and part of the infrared radiation can be converted into convection heat by means of a heat-absorbing grid 12, which together with the infrared radiation evenly heats the baking product in the rotating baking trolley 15.

[0098] The figures further illustrate the vertical arrangement of the infrared heating tubes 1 within the baking chamber 14, showing how they are positioned from bottom to top to provide uniform infrared radiation coverage as the removable vertical rotating unit 15 rotates around its vertical axis. The infrared heating tubes 1 are strategically positioned to ensure that baking products positioned above each other on the rotating unit 15 receive consistent infrared exposure during rotation.

[0099] The figures demonstrate the vertically extending longitudinal arrangement of the infrared heating tubes 1 , which direct infrared radiation substantially horizontally towards the removable vertical rotating unit 15. This vertically extending longitudinal arrangement ensures optimal infrared energy transfer to the surfaces of the baking products as they rotate past the heating elements, maximizing the effectiveness of the direct radiant heating.

[0100] The air inlet unit 11 is shown extending in the vertical direction over substantially the full height of the baking chamber 14, providing uniform hot air distribution across all levels of the positioned baking products. This vertical air distribution arrangement works in conjunction with the infrared heating system to create the hybrid heating environment that combines convection and radiant heat transfer.

[0101] The figures illustrate the individual switching capability of the infrared heating tubes 1 , showing how different heating zones can be created within the baking chamber 14 by selectively activating or deactivating specific infrared heating elements. This zonal control feature enables customized heating patterns for different product types or partially loaded baking trolleys.

[0102] The reflectors 2 are shown positioned to focus and direct the infrared radiation emitted by the heating tubes 1 toward the rotating baking products, enhancing the efficiency of the infrared heating system by concentrating the radiant energy where it is most needed and reducing energy losses to the surrounding chamber walls.

Claims

Claims1 . Hybrid rotary oven (20) for baking food products comprising:- a baking chamber (14) comprising a removable vertical rotating unit (15) for holding multiple baking products positioned above each other, wherein said removable vertical rotating unit (15) is arranged to be rotated around a vertical axis in the baking chamber (14) and is arranged to be removed from the baking chamber (14);- a circulated hot air heating unit for reheating and recirculating a forced air flow (8), the circulated hot air heating unit comprising a heating unit (7) with active heating and an air inlet unit (11) that extends in the vertical direction over substantially the largest part of the, preferably the full, height the baking chamber (14), and wherein the circulated hot air heating unit is arranged for flowing hot air (13) from the heating unit (7), through the air inlet unit (11), to the baking chamber (14) and through the removable vertical rotating unit (15), and for causing the cooled air to return to the heating unit (7) by means of the forced air flow (8);- one or more, optionally switched, active electrical infrared radiation units (1 , 2); such that, when in use, in the baking chamber (14) of the oven (20) a quantity of heated hot air (13) circulates, and a quantity of electrically generated infrared radiation (1) radiates onto the baking products that are rotated around by vertically rotating removable unit (15) to heat a quantity of baking products positioned above each other through convection heat and electrically generated infrared radiation.

2. Hybrid rotary oven (20) according to claim 1 , wherein the one or more active electrical infrared radiation units (1 , 2), in particular a number of electrical infrared heating tubes (1) that are installed from bottom to top, are arranged to be switched separately while heating and rotating the removable vertical rotating unit (15).

3. Hybrid rotary oven according to any of the preceding claims, wherein the one or more active electrical infrared radiation units (1 , 2) are provided with a reflector (2) for directing infrared radiation that is emitted by the one or more active electrical infrared radiation units (1 , 2) on removable vertical rotating unit (15).

4. Hybrid rotary oven according to any of the preceding claims, characterized in that the one or more active electrical infrared radiation units (1 , 2) are a plurality of active electrical infrared radiation units (1 , 2) arranged at different angular coordinates around the vertical axis in the baking chamber, so that, when in use, the baking products are radiated multiple times during a single rotation a removable vertical rotating unit (15).

5. Hybrid rotary oven according to any of the preceding claims, characterized in that in the air flow supply unit (11 , 12) and the infrared radiation unit (1 , 2) are arranged such that part of the generated heat of the infrared heating tubes (1) is converted into convection heat, which is carried along with the air flow (8) flowing through the rotating removable unit (15) with baking products positioned above each other.

6. Hybrid rotary oven according to any of the preceding claims, wherein one or more, optionally switched, active electrical infrared radiation units (1 , 2) are one or more short-wave infrared heating lamps (1) arranged in a vertical configuration; wherein the majority of the emited infrared is in the wavelength range of 0.75 to 1 .4 micrometers.

7. Hybrid rotary oven according to any of the preceding claims, wherein the active electrical infrared radiation units (1 ,2) are halogeen infrared heating lamps, in particular longitudinal halogeen infrared heating lamps.

8. Hybrid rotary oven according to any of the preceding claims, wherein at least one of said active electrical infrared radiation units (1 ,2) comprises two or more halogen infrared heating lamps, in particular longitudinal halogen infrared heating lamps, that are arranged directly adjacent and parallel to each other.

9. Hybrid rotary oven according to any of the preceding claims, wherein the active electrical infrared radiation units (1 ,2) comprise one or more reflectors (2) for directing the infrared radiation.

10. Hybrid rotary oven according to any of the preceding claims, comprising a plurality of active electrical infrared radiation units (1 , 2) and individual switching control means for each of the active electrical infrared radiation units (1 , 2), wherein the individual switching control means comprises electrical switching circuits configured to selectively activate and deactivate individual active electrical infrared radiation units (1 , 2) to create infrared heating zones.

11. Hybrid rotary oven according to any of claims 1 to 10, wherein the heating unit (7) comprises both fuel-based heating elements and electric heating elements that can be operated independently or in combination.

12. Hybrid rotary oven according to any of the preceding claims, further comprising a control unit (22) configured to coordinate operation of the circulated hot air heating unit and the one or more active electrical infrared radiation units (1 , 2).

13. Hybrid rotary oven according to any of the preceding claims, wherein the one or more active electrical infrared radiation units (1 , 2) are positioned to direct infrared radiation in at least a horizontal direction toward the removable vertical rotating unit (15).

14. Hybrid rotary oven according to any of the preceding claims, further comprising a heatabsorbing grid (12) positioned in the air flow path to convert infrared radiation into convection heat.

15. A method of baking food products using a hybrid rotary oven, the method comprising:- rotating a removable vertical unit (15) containing multiple food products positioned above each other around a vertical axis within a baking chamber (14);- simultaneously applying convection heating, using heating unit (7), by circulating hot air (13) through the removable vertical unit (15) and applying infrared radiation by operating one or more short-wave infrared heating lamps (1);- controlling the one or more short-wave infrared heating lamps (1) to direct infrared radiation onto the food products as the removable vertical unit (15) rotates.

16. The method according to claim 15, wherein the step of controlling comprises switching individual short-wave infrared heating lamps (1) on and off to create infrared heating zones within the baking chamber (14).

17. The method according to claim 15 or 16, wherein the short-wave infrared heating lamps (1) are positioned at different angular coordinates around the vertical axis such that the food products receive infrared radiation multiple times during each complete rotation.

18. The method according to any of claims 15 to 17, further comprising converting a portion of the infrared radiation into convection heat by positioning the short-wave infrared heating lamps (1) adjacent to an air flow path.

19. The method according to any of claims 15 to 18, wherein the short-wave infrared heating lamps (1) emit infrared radiation in a wavelength range of 0.75 to 1 .4 micrometers.

20. The method according to any of claim 15 to 19, wherein the step of simultaneously applying convection heating, using heating unit (7), by circulating hot air (13) comprises supplying hot air (13) to the baking chamber (14) through an air inlet unit (11) that extends in the vertical direction over substantially the largest part of the, preferably the full, height the baking chamber (14).

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