The invention relates to a convection oven, a thermal energy system and a process according to the preambles of the independent claims.

Preferably, the invention relates to the technical field of baking ovens for the industrial production of baked products by baking a baking mass like a dough, in particular by baking cut out or punched out cookie dough pieces.

According to the state of the art, convection ovens generate a convection flow by moving heated air through a baking chamber. The air is usually heated by a gas burner. While passing the baking chamber, the heated air bakes the dough and absorbs the moisture, which evaporates from the dough. Thereafter the hot airflow leaves the oven through an exhaust pipe.

To improve the efficiency of this kind of convection ovens, it is known to provide a heat exchanger, which uses the heat of the exhaust gas to preheat the air, which is being heated by the gas burner. However, according to the state of the art, there are limitations for the recuperation of the heat energy of the exhaust gas. For example, the exhaust gas contains baking moisture, which has to be exhausted from the baking oven. Therefore, the exhaust temperature has to be higher than the dew temperature of the exhaust gas to prevent condensation of the moisture in the exhaust pipe. Further, other volatile substances such as evaporated fat or even particles have to be removed from the baking chamber by exhausting the convection flow to prevent pollution of the baking chamber.

Another important measure to enhance the efficiency of a baking oven is to improve the uptime of the oven. In particular, it is important to maintain a continuous production without a service downtime as long as possible.

It is now the object of the invention to improve conventional convection ovens for the production of baked products. This comprises in particular, that the energy efficiency of the convection oven is further improved by using an efficient heating system and an efficient uptime of the baking process.

The object of the invention is solved in particular by the features of the independent patent claims.

The invention in particular concerns a convection oven comprising a baking chamber, a heating system, and a blower. The convection oven preferably comprises a thermal energy system. Preferably, the thermal energy system can on the one hand generate a heated convection flow and on the other hand recuperate energy, like thermal energy and latent energy, from the convection flow.

The convection oven preferably is a baking oven for the industrial production of baked products by baking a baking mass like a dough, in particular by baking cut out or punched out cookie dough pieces.

Preferably, the blower and the heating system generate a convection flow, which convection flow is being heated by the heating system up to a baking temperature, flows through the baking chamber and thereby, in a baking mode of the convection oven, bakes a baking mass to baked products and absorbs baking moisture evaporating from the baking mass.

Preferably, a flow channel is provided, along which the convection flow circulates in the convection oven and in particular through the baking chamber.

Preferably, along the flow channel after the baking chamber but before the heating system, a condensation heat exchanger is provided, which extracts baking moisture from the convection flow through condensation and which is connected to the heating system to supply the thermal energy, in particular the latent thermal energy, of the condensed baking moisture to the heating system.

In particular, in all embodiments “along the flow channel” or “along the convection flow” “before” or “after” means along the direction of the convection flow before or after, as shown in the drawings. In particular before means upstream and after means downstream with regard to the direction of the convection flow.

Preferably, the heat exchanger temperature of the condensation heat exchanger is at or below the dew temperature of the convection flow entering the condensation heat exchanger.

Preferably, the convection oven comprises a heat pump system with a working fluid.

Preferably, the condensation heat exchanger is connected to the heat pump system as a thermal energy source of the heat pump system.

Preferably, along the flow channel after the condensation heat exchanger but before or in the baking chamber, a baking heat exchanger is arranged.

Preferably, the baking heat exchanger is a heat sink of the heat pump system and heats the convection flow to the baking temperature.

Preferably, the baking heat exchanger is a part of the heating system.

Preferably, the heat pump system comprises an evaporator for evaporating the working fluid.

Preferably, the evaporator is a part of the condensation heat exchanger.

Preferably, the heat pump system comprises a condenser for condensation of the working fluid.

Preferably, the condenser is a part of the baking heat exchanger.

Preferably, the heat pump system comprises a first heat pump stage and a second heat pump stage. Preferably, the first heat pump stage has a lower working temperature as the second heat pump stage.

Preferably, the first heat pump stage and a second heat pump stage are thermally connected, in particular via at least one intercooler.

The intercooler can comprise or be one or more heat exchangers, to exchange thermal energy between two or more heat pump stages.

The intercooler can comprise a thermal storage reservoir for the storage of thermal energy. The thermal storage reservoir can comprise a container, in which the working fluid of the heat pump(s) can be arranged, in order to store thermal energy. The working fluid can be provided in the container in a two phase form, in particular in a liquid phase and in a vapor phase. One, both or all heat pump stages can directly use the working fluid, which is stored in the container. The intercooler thereby may serve as a liquid thermal storage system for quick start-up and load variations. The intercooler may be an open intercooler. A separate heating, in particular an electric heating, can be provided to heat the working fluid, which is stored in the container.

Preferably, the evaporator is a part of the first heat pump stage and the condenser is a part of the second heat pump stage.

Preferably, a first convection flow heat exchanger is provided.

Preferably, the first convection flow heat exchanger cools the convection flow with a cooling section along the flow channel after the baking chamber but before the condensation heat exchanger.

Preferably, the first convection flow heat exchanger preheats the convection flow with a heating section along the flow channel after the condensation heat exchanger but before the baking heat exchanger.

Preferably, a second convection flow heat exchanger is provided.

Preferably, the second convection flow heat exchanger cools the convection flow with a cooling section along the flow channel after the cooling section of the first convection flow heat exchanger but before the condensation heat exchanger. Preferably, the second convection flow heat exchanger preheats the convection flow with a heating section along the flow channel after the condensation heat exchanger but before the heating section of the first convection flow heat exchanger.

Preferably, along the flow channel after the baking chamber but before the condensation heat exchanger, in particular after the cooling section of the first convection flow heat exchanger but before the cooling section of the second convection flow heat exchanger, a filter system for filtering out contaminations like particles from the convection flow is arranged.

Preferably, the filter system comprises or is an electrostatic precipitator.

Preferably, a water collector is arranged at the condensation heat exchanger to collect the condensed water, which was extracted from the convection flow in the condensation heat exchanger.

Preferably, the convection oven comprises a conveyor system, which moves the baking mass through the baking chamber while being baked to baked products and which ejects the baked products through a removal opening.

Preferably, the convection flow circulates in a substantially closed loop through the flow channel of the convection oven, wherein leak air can eventually escape or enter the convection flow through the removal opening.

Preferably, the heat pump system comprises at least one compressor for compressing the working fluid.

Preferably, the first heat pump stage and the second heat pump stage each comprise at least one compressor for compressing the respective working fluid.

Preferably, a thermal startup source is provided.

Preferably, the thermal startup source comprises a thermal storage reservoir and/or a heating device. The thermal startup source can be a part of the intercooler. In particular, the thermal startup source can be thermal storage reservoir of the intercooler.

Preferably, in a startup mode of the convection oven, the thermal startup source is a thermal energy source of the heat pump system.

Eventually, the invention concerns a process for operating a convection oven, comprising the following steps:

- generating a convection flow, which convection flow is being heated up to a baking temperature by a heating system, flows through a baking chamber and thereby, in a baking mode of the convection oven, bakes a baking mass to baked products and absorbs baking moisture evaporating from the baking mass,

Preferably, the convection flow circulates in the convection oven along a flow channel.

Preferably, along the circulating convection flow after the baking chamber but before the heating system, a condensation heat exchanger extracts baking moisture from the convection flow through condensation and supplies the thermal energy, in particular the latent thermal energy, of the condensed baking moisture to the heating system.

Preferably, the convection flow is being cooled in the condensation heat exchanger to or below the dew temperature of the convection flow entering the condensation heat exchanger.

Preferably, the thermal energy, being absorbed by the condensation heat exchanger from the convection flow, is transferred to a working fluid of a heat pump system and in particular evaporates the working fluid of the heat pump system.

Preferably, a baking heat exchanger of the heating system heats the convection flow up to a baking temperature.

Preferably, the thermal energy for the baking heat exchanger is delivered by a working fluid of the heat pump system and in particular by condensing the working fluid in a condenser of the heat pump system.

Preferably, a first convection flow heat exchanger: - cools the convection flow with a cooling section along the flow channel after the baking chamber but before the condensation heat exchanger,

- and preheats the convection flow with a heating section along the flow channel after the condensation heat exchanger but before the baking heat exchanger.

Preferably, a second convection flow heat exchanger:

- cools the convection flow with a cooling section along the flow channel after the cooling section of the first convection flow heat exchanger but before the condensation heat exchanger,

- and preheats the convection flow with a heating section along the flow channel after the condensation heat exchanger but before the heating section of the first convection flow heat exchanger.

Preferably, along the convection flow after the baking chamber but before the condensation heat exchanger, in particular after the cooling section of the first convection flow heat exchanger but before the cooling section of the second convection flow heat exchanger, contaminations and in particular particles are filtered out from the convection flow.

Preferably, the contaminations are filtered by a filter system comprising for example an electrostatic precipitator.

Preferably, condensed water, which was extracted from the convection flow in the condensation heat exchanger, is collected by a water collector.

Preferably, the baking mass is conveyed through the baking chamber while being baked to baked products, and the baked products are ejected through a removal opening.

Preferably, the convection flow circulates in a generally closed loop through the convection oven, wherein leak air can eventually escape or enter the convection flow through the removal opening.

Preferably, more than 90%, in particular more than 95%, of the vaporization enthalpy or the latent energy, applied by the heating system to evaporate baking moisture from the baking mass is recuperated by the condensation heat exchanger and in particular by the heat pump system. To improve the efficiency of the convection oven, the convection flow is preferably circulated in or through the convection oven along a substantially closed loop. The circulation of the convection flow can be regarded as closed loop, but there might be inevitable leakage and/or dilution along the flow channel, in particular in the area of the baking chamber. For example, the baked products have to be removed from the convection oven through an opening and leak air can eventually escape and/or enter through this removal opening. The leakage is preferably less than 5%, more preferably less than 3% or less than 1% of the flow rate of the convection flow.

Moreover, it might be advantageous to add small amounts of fresh process gas or air to the circulating convection flow, for example to dilute the circulating process gas. The dilution is preferably less than 5%, more preferably less than 3% or less than 1% of the flow rate of the convection flow.

In all embodiments, the process gas can be air, but eventually the process gas contains a modified composition like an increased CO2 or N2 content.

By circulating the convection flow in the convection oven, the energy loss and thereby the energy efficiency can be optimized. Nevertheless, it is not possible to circulate the convection flow without processing the process gas, in particular without removing moisture and other contaminations from the gas.

When baking a dough in the convection oven, for example for the production of cookies, the water of the dough evaporates from the dough almost completely. For this reason, the convection flow of a convection oven for industrial applications has to absorb hundreds of liters of water during a baking cycle.

To remove this baking moisture from the convection flow, the convection oven comprises a condensation device, on which the moisture form the convection flow condenses. In order to remove further containments from the convection flow, a filter system can be provided to filter out particles or other contaminations.

To improve the efficiency of the convection oven even further, the condensation device is or comprises a heat exchanger, which allows it to use the thermal energy of the condensed moisture. When evaporating water from the dough, it is of course important to heat the dough up to a temperature above the evaporation temperature of the water. However, in addition, it is a known physical law that also the evaporation enthalpy has to be overcome by providing even more energy. In known baking ovens this latent energy is lost when the gas and the moisture are being exhausted through the exhaust pipe. With the current invention, it is possible to use this latent energy and to recuperate this energy to improve the energy efficiency of the convection oven even further.

Therefore, with the convection oven according to the invention, it might be possible not only to minimize the energy loss through circulating the convection flow through the convection oven, but also to use the latent energy of the evaporated baking moisture. This energy can be used as an energy source to reheat the convection flow up to a baking temperature.

To enhance the efficiency of the convection oven even further, it can comprise a heat pump system. The heat pump system has a thermal energy source and a thermal energy sink. In a preferred embodiment, the heat pump system uses the condensation heat exchanger as thermal energy source. This allows the heat pump system to use the thermal energy of the process gas as well as the latent energy from the condensation of the baking moisture.

According to a preferred embodiment, the heat pump system uses the baking heat exchanger as a heat sink in order to heat up the convection flow to the baking temperature. The heat pump system might use a working fluid, which is being evaporated in an evaporator and condensed in a condenser. In a preferred embodiment, the evaporator is a part of the condensation heat exchanger and/or the condenser is a part of the baking heat exchanger. The baking heat exchanger and the condensation heat exchanger might be gas-liquid heat exchangers.

The heat pump system may comprise several heat pump stages, for example, a first heat pump stage and a second heat pump stage. The heat pump stages might be thermally connected, for example with an intercooler.

To improve the efficiency of the convection oven further, convection flow heat exchangers may be provided, which exchange heat energy of the convection flow between different stages of the convection flow. For example, one or more convection flow heat exchangers may be provided along the convection flow channel after the condensation heat exchanger and before the baking heat exchanger, in particular to preheat the convection flow. The thermal energy for the convection flow heat exchangers may be thermal energy from the convection flow itself, in particular from the convection flow, which leaves the hot baking chamber and flows along the convection flow channel to the condensation heat exchanger. Through these convection flow heat exchangers the convection flow is being cooled after the baking chamber but before the condensation heat exchanger and preheated after the condensation heat exchanger and before the baking heat exchanger.

According to a preferred embodiment of the invention, two convection flow heat exchangers are provided to cause a two-stage cooling and/or heating of the convection flow. Eventually it is provided, that the filter system is located between the two cooling sections of the two convection flow heat exchangers.

According to an alternative embodiment of the invention, only one convection flow heat exchanger is provided. This convection flow heat exchanger can also cool the convection flow after leaving the baking chamber and can preheat the convection flow between the condensation heat exchanger and the baking heat exchanger. Preferably, the filter system is located after this convection flow heat exchanger but before the condensation heat exchanger.

The baked products, which can be manufactured in the convection oven, might be end products like baked cookies or intermediate products like baked bodies, which are further processed in a station, for instance a coating station for coating cookies or wafers with edible cream like chocolate cream.

The baking chamber is preferably an elongated chamber, having the shape of a channel and forming part of the flow channel.

In a preferred embodiment, a conveyor is provided which transports the dough or the baked products through the baking chamber. For example, the conveyor can be an endless belt conveyor for transporting cut or punched out biscuit dough. Alternatively, the conveyor can be an endless conveyor, which transports different baking moulds like baking tongues or the like.

The convection flow is being heated by a heating system up to a baking temperature and flows through a baking chamber to bake the baking mass to baked products.

According to a preferred embodiment, the convection flow is directly directed at the baking mass. For this purpose, at least one nozzle or a plurality of nozzles are directed at the baking mass or a conveyor, which transports the baking mass. According to a preferred embodiment, a nozzle bar is provided, which extends along the baking chamber and which comprises a plurality of nozzles along its extension or along the conveyor. This nozzle bar works as a manifold and might comprise a manifold space from which the nozzles extend towards the inside of the baking chamber.

According to an embodiment of the invention, the nozzles and in particular the nozzle bar can be movably provided in the baking chamber so that the direction of the nozzles and/or the distance between the nozzles and the baking mass and/or the conveyor can be adjusted. By adjusting the nozzles, the heat transfers from the convection flow to the baking mass can be improved and thereby the efficiency of the convection oven can be improved further.

To improve the efficiency of the convection oven even further, a cleaning device for at least one of the heat exchangers can be provided. The cleaning device preferably allows cleaning in place (CIP) without the need to remove the cleaned component from the convection oven.

For example, a cleaning device can be attached to the convection flow heat exchanger. The cleaning device dispenses water through the heat exchanger channels. Especially the convection flow heat exchanger, in particular the first convection flow heat exchanger, contains channels through which unfiltered process air from the baking chamber flows. For this reason, these channels can be cleaned more often than heat exchanger channels, which are located along the convection flow and the flow channel after the filter system.

However, generally all heat exchangers can be provided with a cleaning device, which dispenses water through the channels to clean these channels. This cleaning can be done in service mode or also while baking baked products.

The water, which is used for cleaning the channels, can be collected on the other side to avoid contamination of the baked products. In a preferred embodiment, the cleaning device sits on top of the heat exchanger and the water runs through the channels of the heat exchanger to be collected on a lower part of the heat exchanger.

Preferably, one or both convection flow heat exchangers are provided with a cleaning device.

It is also possible that parts of the flow channel are provided and are being cleaned by a cleaning device. According to a preferred embodiment of the invention, the convection flow flows along the flow channel through the following components:

- a blower and a heating system, wherein the heating system can comprise a baking heat exchanger and eventually a preheating exchanger, for example preheating by one or more convection flow heat exchangers;

- eventually through one or more nozzles, in particular a manifold space and a nozzle bar;

- the baking chamber,

- eventually through a pre cooling heat exchanger, in particular the cooling sections of one or more convection flow heat exchangers;

- eventually a filter system;

- the condensation heat exchanger to extract the baking moisture from the convection flow;

- and back to the blower.

In a preferred embodiment of the process, the process air, in particular the convection flow, passes a blower, a heating system, the baking chamber, a cooling system, in particular a condensation heat exchanger and then again the blower.

According to another preferred embodiment of the process, the convection flow passes the baking chamber, the cooling section of a first convection flow heat exchanger, a filter system, the condensation heat exchanger, the blower, the heating section of the first convection flow heat exchanger, the baking heat exchanger and again the baking chamber.

The heat pump powered convection oven can utilize the latent heat in the process gas as an energy source for the heat pump. Lower quality thermal energy could be extracted in the working fluid and upcycled using electric energy though a compressor and applied in the condenser to reheat the process air.

To capture the latent heat, driving the heat pump evaporator, the process air need to be at or below the dew point. This temperature is preferably reached using a high performance air/air heat exchanger. After latent heat has been captured, the process air could be reheated in the heat exchanger and passed along to the heat pump condenser for a final temperature lift before it enters the baking chamber. To ensure the systems, three heat exchangers do not block, fail or foul (become inefficient) the process air circuit can contain a filter and cleaning system.

According to a preferred embodiment of the invention, the convection oven is powered by electricity, in particular only by electric power. Although the components of the convection oven act together to improve the efficiency, also the components as such can eventually improve the efficiency of the convection oven and/or the thermal energy system. For example, the convection flow heat exchanger(s), the heat pump system, the condensation heat exchanger, the heating system, the filter system and/or the cleaning device can individually improve the efficiency of an convection oven and the thermal energy system.

Eventually, the invention also relates to a thermal energy system for a convection oven, wherein the thermal energy system can be used as a retrofit kit to replace a heating system like a gas burner heating system of an existing or conventional convection oven.

The thermal energy system can comprise the convection flow heat exchanger(s), the heat pump system, the condensation heat exchanger, the heating system, the filter system and/or the cleaning device. In particular, the thermal energy system can comprise all components of the described embodiments, but not the baking chamber and not the conveyor system. Eventually, also the nozzles can be optimized and/or replaced by a moveable nozzle bar to improve the efficiency further.

The thermal energy system comprises an inlet and an outlet. The convection flow, which is being generated by the blower and the heating system, leaves the thermal energy system through the outlet in order to flow through the baking chamber of the convection oven.

The thermal energy system comprises a flow channel in which the convection flow circulates through the thermal energy system, but in particular also through the baking chamber. The flow channel thereby extends through the thermal energy system but preferably also through the baking chamber. To process gas of the circulating convection flow, the thermal energy system comprises an inlet to allow the convection flow to enter the thermal energy system after the baking chamber.

Preferably, the thermal energy system is the thermal energy system of the described convection oven.

Preferably, the thermal energy system comprises the heating system and the blower. Preferably, the blower and the heating system generate a convection flow, which convection flow is being heated by the heating system up to a baking temperature.

Preferably, the convection flow leaves the thermal energy system through an outlet in order to flow through a baking chamber and thereby, in a baking mode of the convection oven, bakes a baking mass to baked products and absorbs baking moisture evaporating from the baking mass.

Preferably, a flow channel is provided, along which a circulating convection flow flows through the thermal energy system and enters the thermal energy system through an inlet.

Preferably, a baking heat exchanger is arranged along the flow channel after the condensation heat exchanger but before or in the outlet.

Preferably, the thermal energy system comprises a heat pump system with a working fluid, and the condensation heat exchanger is connected to the heat pump system as a thermal energy source of the heat pump system.

Preferably, the baking heat exchanger is a heat sink of the heat pump system and heats the convection flow to the baking temperature, and the baking heat exchanger is a part of the heating system.

Preferably, a first convection flow heat exchanger is provided, which cools the convection flow with a cooling section along the flow channel after the inlet but before the condensation heat exchanger. Preferably, the first convection flow heat exchanger preheats the convection flow with a heating section along the flow channel after the condensation heat exchanger but before the baking heat exchanger.

Eventually, a second convection flow heat exchanger is provided, which cools the convection flow with a cooling section along the flow channel after the cooling section of the first convection flow heat exchanger but before the condensation heat exchanger. Eventually, the second convection flow heat exchanger preheats the convection flow with a heating section along the flow channel after the condensation heat exchanger but before the heating section of the first convection flow heat exchanger. Preferably, along the flow channel after the inlet but before the condensation heat exchanger, in particular after the cooling section of the first convection flow heat exchanger but before the cooling section of the second convection flow heat exchanger, a filter system for filtering out contaminations like particles from the convection flow is arranged.

Eventually, the filter system comprises or is an electrostatic precipitator.

Subsequently, the invention is described further by means of exemplary embodiments.

Fig. 1 shows a schematic diagram of components of the convection oven.

Fig. 2 shows a schematic view of a sectional view of components of an convection oven.

Unless otherwise indicated, the numerals correspond to the following components: baking chamber 1, heating system 2, blower 3, convection flow 4, compressor 5, baking mass 6, baking moisture 7, flow channel 8, condensation heat exchanger 9, heat pump system 10, baking heat exchanger 11 , evaporator 12, condenser 13, first heat pump stage 14, second heat pump stage 15, intercooler 16, first convection flow heat exchanger 17, cooling section 18, heating section 19, second convection flow heat exchanger 20, cooling section 21, heating section 22, filter system 23, water collector 24, conveyor system 25, removal opening 26, drain 27, thermal startup source 28, cleaning device 29, nozzle 30, nozzle bar 31, manifold space 32, outlet 33, inlet 34.

Fig. 1 shows a schematic diagram of a possible convection oven comprising a thermal energy system. The convection oven comprises a baking chamber 1, which is heated by a heating system 2, and in particular by a convection flow 4. The convection flow 4 is generated by a blower 3, which moves process gas, in particular process air, along a flow channel 8 (not shown in fig. 1). The convection flow 4 preferably circulates in a substantially closed loop. When passing the baking chamber 1, the convection flow 4 absorbs baking moisture 7 from the baking mass 6. This baking moisture 7, at least partly, has to be removed from the convection flow 4 in order to maintain a constant baking process while circulating the convection flow 4 in a substantially closed loop.

For this purpose, a condensation heat exchanger 9 is arranged along the convection flow 4 after the baking chamber 1. The exchanger temperature of the condensation heat exchanger 9 is at or below the dew temperature of the convection flow 4, so that the temperature of the convection flow 4 is lowered beneath the dew temperature and the baking moisture 7 can be extracted from the convection flow 4 by a condensation process. The thermal energy of the convection flow 4 is transferred to the condensation heat exchanger 9 and is preferably recuperated to use it as a thermal energy source of the heating system 2. Apart from the thermal energy of the convection flow 4, in particular of the process gas, also the latent heat of the condensing baking moisture 7 is transferred to the condensation heat exchanger 9 and can be reused to act as a heat source for the heating system 2.

Preferably in all embodiments of the invention, the convection oven and the thermal energy system comprises a heat pump system 10. The heat pump system 10 comprises at least one heat pump, a compressor 5, a heat sink and a thermal energy source. In the preferred embodiment, the thermal energy source of the heat pump system 10 is or comprises the condensation heat exchanger 9. The heat sink of the heat pump system 10 is or comprises the baking heat exchanger 11. The baking heat exchanger 11 is a heat changer, which heats up the convection flow 4 up to a baking temperature to bake products in the baking chamber 1. Preferably, the baking heat exchanger 11 is arranged along the convection flow 4 and the flow channel 8 right before and consequently upstream the baking chamber 1.

The heat pump system 10 comprises a working fluid, which preferably is vaporized and condensed in the course of the heat pump’s cycle. For this reason, the heat pump system 10 comprises an evaporator 12 for evaporating the working fluid, wherein the evaporator 12 is preferably part of the condensation heat exchanger 9. The heat pump system 10 preferably comprises a condenser 13 and this condenser 13 preferably is part of the baking heat exchanger 11.

In the present configuration of fig. 1, the heat pump system 10 comprises two heat pump stages 14, 15, in particular a first heat pump stage 14 and a second heat pump stage 15. The two heat pump stages 14, 15 are thermally connected via an intercooler 16.

In this configuration, the heat pump system 10 comprises two heat pumps, respectively two compressors 5.

The convection oven and the thermal energy system of fig. 1 comprises a first convection flow heat exchanger 17. This first convection flow heat exchanger 17 comprises a cooling section 18 and a heating section 19. The convection flow 4 leaves the baking chamber 1 and enters the cooling section 18 of the first convection flow heat exchanger 17, which pre cools the convection flow 4 before the condensation heat exchanger 9. The thermal energy, which is extracted from the convection flow 4 in this section, is transferred to a heating section 19 of the first convection flow heat exchanger 17. This heating section 19 preheats the convection flow 4 after the condensation heat exchanger 9 but before the baking heat exchanger 11. According to an alternative embodiment, a two-stage convection flow heat exchanger can be used which then comprises a first and second convection flow heat exchanger 17, 20.

To maintain a constant and efficient baking process, the convection oven and the thermal energy system can comprise a filter system 23, which can filter out particle or other contaminations from the convection flow 4. The heating sections of the convection flow heat exchangers 17, 20 can preferably be regarded as part of the heating system 2.

The filter system 23, respectively one of the filters of the filter system 23, can preferably be arranged after the baking chamber 1 but before the condensation heat exchanger 9.

The convection oven and the thermal energy system uses or recuperates the thermal energy of the convection flow 4 after the baking chamber 1 as a thermal energy source for the heating system 2, in particular for the heat pump system 10.

When starting up the convection oven and the thermal energy system, this thermal energy source is not available, because on the one hand, the convection flow 4 in the baking chamber 1 does not have a high temperature, and on the other hand, there is no latent energy of a baking moisture 7, which could be recuperated. The heat pump system 10 is optimized for the regular baking process to ensure an efficient and in particular an energy-efficient baking process.

For this reason, a thermal startup source 28 is connected to the convection oven and the thermal energy system to act as a thermal energy source when starting up the convection oven. This thermal startup source 28 can be a thermal energy storage or an active heating system. In a preferred embodiment, the thermal energy of the thermal startup source 28 is connected via a heat exchanger to the heat pump system 10 as an addition or as a replacement for the condensation heat exchanger 9.

Fig. 2 shows a schematic cross-sectional view of a convection oven comprising the thermal energy system. The components described in fig. 1 can be the same components shown in fig. 2. The convection oven comprises a baking chamber 1, through which baking mass 6, in particular pieces of baking mass 6 are transported. For the transport of the baking mass 6 through the baking chamber 1, a conveyor system 25 is provided. The conveyor system 25 can be or can comprise a conveyor belt, in particular a conveyor system 25 with a metal band.

The baking chamber 1 , and in particular the baking mass 6, is heated by a heating system 2 to produce baked products from the baking mass 6. In particular, a convection flow 4 is generated by a blower 3 in combination with the heating system 2. The convection flow 4 flows along a flow channel 8 through the convection oven.

According to a preferred embodiment, the convection flow 4 circulates in a substantially closed loop. The baking chamber 1 comprises at least one removal opening 26 for removal of the baked products. Eventually leak air or leaking process gas can escape or get into the baking chamber 1 in this area. The process gas acts as a convection flow 4, which is transported by a blower 3 to the heating system 2 in order to be heated up to a baking temperature. The heated convection flow 4 further streams through the baking chamber 1 to heat up the baking mass 6.

While baking, baking moisture 7 evaporates from the baking mass 6 and is being absorbed by the convection flow 4. Because of the circulation of the convection flow 4, it is important to remove baking moisture 7 from the convection flow 4. For this reason, the convection flow 4, together with the baking moisture 7, flows to a condensation heat exchanger 9. This condensation heat exchanger 9 cools the convection flow 4 beneath the dew temperature to extract and in particular to condensate the baking moisture 7 out of the convection flow 4. The baking moisture 7 can be collected by a water collector 24 and can be removed as liquid water through a drain 27. After that, the substantially dry convection flow 4 can again flow through the heating system 2 to enter the baking chamber 1 again.

To improve the efficiency of the convection oven and the thermal energy system, the thermal energy of the condensation heat exchanger 9 can be used and/or recuperated as an energy source for the heating system 2.

Preferably, the heat pump system 10 of fig. 1 can be used also with the convection oven and the thermal energy system of fig. 2. The heat pump system 10 might comprise one, two or more stages and is connected to the condensation heat exchanger 9 as well as to the baking heat exchanger 11. The convection oven according to fig. 2 comprises two convection flow exchangers 17, 20, in particular a first convection flow heat exchanger 17 and a second convection flow heat exchanger 20.

Preferably in all embodiments, the convection flow heat exchangers 17, 20 comprise a crossflow arrangement through which the convection flow 4 passes through the heat exchanger in two different stages along the flow channel 8. In particular, both heat exchangers contain a cooling section 18, 21 and a heating section 19, 22 as for example described in fig. 1.

In an alternative embodiment, the convection oven and the thermal energy system according to fig. 2 can also comprise only one convection flow heat exchanger 17, 20.

The heating system 2 comprises the baking heat exchanger 11, which is preferably the component, which heats up the condensation flow 4 up to the baking temperature. Eventually the heating sections of the convection flow heat exchangers 17, 20 can also be regarded as part of the heating system 2, as they preheat the convection flow 4 after the condensation heat exchanger 9 and before the baking heat exchanger 11.

The convection oven and the thermal energy system according to fig. 2 comprises a filter system 23, which is provided to filter out particles or other contamination from the convection flow 4. In the present embodiment, the filter system 23 is at least provided between the cooling sections of the first convection flow heat exchanger 17 and the second convection flow heat exchanger 20.

In an alternative embodiment, the filter system 23 can also comprise a filter, which is arranged between the baking chamber 1 and the cooling section 18 of the first convection flow heat exchanger 17 and/or a filter, which is arranged after the cooling section 21 of the second convection flow heat exchanger 20 but before the condensation heat exchanger 9.

A water collector 24 and a drain 27 allow to collect and drain the baking moisture 7 from the condensation heat exchanger 9.

Preferably, in all embodiments, a cleaning device 29 is provided in the convection oven and eventually in the thermal energy system. The cleaning device 29 is preferably a cleaning in place (CIP) device, which allows to clean components of the convection oven. As an example, a cleaning device 29 can be attached to the first convection flow heat exchanger 17 to be able to clean the elements of this heat exchanger. For example, the cleaning device 29 can dispense water, which flows through the channels of the heat exchanger, to clean the walls of the heat exchanger. This cleaning water can be collected and eventually recycled. Preferably, the cleaning device 29 cleans only the cooling section 18, 21 of the first and/or the second convection flow heat exchanger(s) 17, 20. A cleaning device 29 can also be provided at the flow channel 8 to clean the channel wall, at the condensation heat exchanger 9 and/or at the baking heat exchanger 11.

The heated convection flow 4 is preferably blown at the baking mass 6 through at least one nozzle 30 and in particular through a plurality of nozzles 30.

According to a preferred embodiment, a nozzle bar 31 can be provided, which comprises a manifold space 32 from which several nozzles 30 lead in the direction of the conveyor of the conveyor system 25 and/or the baking mass 6.

According to the configuration of fig. 2, two nozzle bars 31 are provided, wherein the convection flow 4 flows through both nozzle bars 31 and is directed through nozzles 30 at the baking mass 6 and in particular at the section of the conveyor system 25, on which the baking mass 6 is transported.

To improve the heating efficiency of the convection oven, the direction and/or the position of the nozzles 30 can be optimized. For example, the nozzle bar 31 can be movably attached to the convection oven, wherein the distance between the nozzle bar 31 and/or the nozzles 30 and the baking mass 6 and/or the conveyor system 25 can be adjusted and optimized. In particular, it might be advantageous, if the nozzles 30 are as close as possible to the baking mass 6. An adjustment of the position of the nozzles 30 can allow the optimization of the convection oven for different products, in particular for products with different product heights. In case of only one produced product, the position of the nozzles 30 can be optimized for this particular product.

A process or method for operating a convection oven can be described based on fig. 1 and fig.2, but is not limited to these special configurations of convection ovens.

In the convection oven, a convection flow 4 bakes a baking mass 6 or a dough to baked products. The convection flow 4 is generated by heating up process gas with a heating system 2 and by moving the process gas by a blower 3 through a flow channel 8. The heated convection flow 4 flows through the baking chamber 1 along the conveyor system 25 and thereby heats up and bakes the baking mass 6. While baking the products, the baking moisture 7 evaporates from the baking mass 6 and gets absorbed by the convection flow 4.

As the convection flow 4 preferably circulates in the convection oven, the baking moisture 7 has to be removed from the convection flow 4 in order to be able to bake the products with the right temperature and moisture content. To remove the baking moisture 7 from the convection flow 4, a condensation heat exchanger 9 is arranged after the baking chamber 1. The condensation heat exchanger 9 cools the convection flow 4 below the dew temperature so that the baking moisture 7 condenses and can be easily removed, preferably using a water collector 24 and a drain 27.

After removing the baking moisture 7 from the convection flow 4, the convection flow 4 can be reheated by the heating system 2 and be blown into the baking chamber 1.

To improve the efficiency of the system, the thermal energy, which is transferred from the convection flow 4 to the condensation heat exchanger 9 when cooling down the convection flow 4, gets used or is recuperated for the heating system 2. For this reason, the condensation heat exchanger 9 is terminally connected to the heating system 2.

To improve the efficiency of the system further, a heat pump system 10 is arranged, which uses the condensation heat exchanger 9 as a heat source and the heating system 2 as a heat sink. In particular, the heating system 2 comprises a baking heat exchanger 11 , which heats up the convection flow 4 up to the baking temperature.

In the heat pump system 10 a working fluid passes an evaporator 12 and a condenser 13, wherein the heat pump system 10 can be a one-stage or a more-stages heat pump system. If the heat pump system 10 for example has two heat pump stages, in particular a first heat pump stage 14 and a second heat pump stage 15, an intercooler 16 can be used to connect the two heat pump stages 14, 15. Each heat pump stage 14, 15 comprises at least one compressor 5. The working fluid of the heat pump system 10 circulates and gets evaporated by the evaporator 12 through the thermal energy of the convection flow 4 in the condensation heat exchanger 9. Further, the working fluid of the heat pump system 10 gets condensed in a condenser 13, in particular in the baking heat exchanger 11. To improve the efficiency of the system further, the convection flow 4 can be precooled after the baking chamber 1 but before the condensation heat exchanger 9. The thermal energy, which gets picked up by the convection flow heat exchanger 17, 20, can also be reused, in particular to preheat the convection flow 4 after the condensation heat exchanger 9 and before the baking heat exchanger 11.

This precooling and/or preheating can be done by one convection heat exchanger, as shown in fig. 1 or by two convection heat exchangers, as shown in fig. 2.

To improve the efficiency of the convection oven, a filter system 23 can be provided, which filters out particles or other contamination from the convection flow 4.

In a preferred embodiment of the process, the process gas, in particular the convection flow 4, passes a blower 3, a heating system 2, the baking chamber 1, a cooling system, in particular a condensation heat exchanger 9 and then again the blower 3. According to a preferred embodiment, the convection flow 4 passes a filter system 23, which is preferably located after the baking chamber 1 but before the condensation heat exchanger 9.

According to another preferred embodiment of the process, the convection flow 4 passes the baking chamber 1, the cooling section 18 of a first convection flow heat exchanger 17, a filter system 23, the condensation heat exchanger 9, the blower 3, the heating section 19 of the first convection flow heat exchanger 17, the baking heat exchanger 11 and back to the baking chamber 1.

According to a preferred embodiment of the process and/or the convection oven and the thermal energy system, the baking temperature is higher than 190°C, in particular 190°C to 290°C, preferably around 200°C.

Preferably, the temperature of the return air leaving the baking chamber 1 is lower than 180°C, in particular lower than 150°C, preferably around 120°C.

Preferably, the convection flow 4 gets cooled down below the dew temperature, which may lie in the range of approximately 60°C.

The temperature of the convection flow 4 entering the condensation heat exchanger 9 may be below 120°C, in particular below 100°C, preferably below 70°C or about 70°C. If one or more convection flow heat exchangers 17, 20 are provided, the convection flow heat exchangers 17, 20 might precool or preheat the convection flow 4. In a preferred embodiment, the convection flow heat exchangers 17, 20 might work in a range of about 60°C to 100°C, so that the convection flow 4 gets precooled from for example approximately 120°C to 70°C and might get preheated from around 60°C to around 90°C or 100°C.

When using a two-stage convection flow heat exchanger system, the first convection flow heat exchanger 17 can be a plate heat exchanger with a 6mm plate gap.

A possible second convection flow heat exchanger 20 might also be a plate heat exchanger, but with a lower plate gap, for example a 3mm plate gap.

The convection ovens of fig. 1 and fig. 2 comprise a thermal energy system. The thermal energy system is provided to heat of the convection flow but also to use the energy of the convection flow. The thermal energy system in particular extends along the flow channel 8 and/or the convection flow 4 from the inlet 34 to the outlet 33.

Figs. 1 and 2 show schematic diagrams of the use of the thermal energy system in a convection oven.

Alternatively, the thermal energy system can also be used as a retrofit kit with a known baking chamber and can replace a heating system like a gas burner heating system. In order to create a circulating convection flow, the exhaust opening of a known baking chamber can be connected to the inlet 34 of the thermal energy system and the opening for the replaced heating system can be connected to the outlet 33 of the thermal energy system.