DE29720148U1 - Thermal oil baking system - Google Patents

Description

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14 November 1997

MIWE GmbH MIW-036

97450 Arnstein Boe/mac

Thermo oil baking system

The invention relates to single- or multi-level thermal oil baking systems for the production of baked goods. In such thermal oil baking systems, heating modules are arranged which can be heated using thermal oil and serve to heat the baking system.

Such baking systems are used in particular for the so-called hearth baking of bread or similar baked goods. During hearth baking, the baking system is initially loaded from one side until the entire baking surface of the baking system is completely covered. This is followed by the baking process with a defined baking temperature curve. The baking process ends with the so-called baking, in which the temperature in the baking system is lowered to a defined final temperature that is below the baking temperature. Baking serves to improve the quality of the baked goods. After baking is complete, the baking system is emptied by removing the finished baked goods and then loaded with the next batch of goods.

Since the final temperature of the baking process is below the starting temperature, the baking system must first be heated up to the starting temperature before it can be loaded again. During this heating

During the heating time, baking cannot take place in the baking system, which results in an idle time that leads to performance losses in the baking system.

These performance losses are unavoidable if the baking system is loaded with baked goods from a batch in one go and then emptied again in one go. In conventional thermal oil continuous baking ovens, however, the loading does not take place in one go, but in successive loading cycles. During each loading cycle, new baked goods from a batch are fed into the baking system and existing baked goods are fed further into the baking system. There are so many loading cycles in succession until the entire baking area of the baking system is occupied and the entire batch of goods is therefore within the system. With each individual loading cycle, the baking time for the partial quantity of baked goods fed in begins. So that all baked goods in a batch have essentially the same residence time within the baking system, i.e. have essentially the same baking time, the baked goods from the various loading cycles are also fed out of the baking system in a timed manner according to the first-in-first-out principle. If only one baking temperature can be set in the system, the baking system must therefore wait to heat up again until the baked goods from the last loading cycle have left the baking system. Only then can the system be heated up again and then reloaded.

A baking system is known from the German utility model DE 296 16 692 Ul, which has two heating zones in which different temperatures can be set in the individual heating zones by regulating the amount of thermal oil flowing through the individual heating zones. The separate temperature control in the two heating zones allows the first heating zone, which has already been emptied, to be heated up to the starting temperature while baked goods are still in the second heating zone and are being baked at a low temperature. After the last baked goods of a batch have been emptied, the first loading cycle of the following batch can immediately begin in the first heating zone of the

Baking system, as this heating zone is already heated to the starting temperature. This measure eliminates dead times during which the normally empty baking system is heated up, as the heating begins in the already empty area of the system, while baked goods from the previous batch are still in another area of the system and are being baked. This means that the performance of the baking system can be increased.

In DE 296 16 692 Ul, it is proposed to arrange an adjustable valve in the flow of the second heating zone in order to regulate the heating temperature in the two heating zones, with the feed starting at the first heating zone. There is no actuator in the flow of the first heating zone to influence the flow rate. By adjusting the valve in the flow of the second heating zone, the flow rate flowing through the second heating zone can be reduced, which is associated with a reduction in temperature in the second heating zone. Adjusting the valve is associated with an increase in the flow resistance in the second heating zone. Since the thermal oil flows flowing through the first heating zone and the second heating zone are connected in parallel, this increase in the flow resistance in the second heating zone is also associated with an increase in the flow rate flowing through the first heating zone. The result is that as soon as the flow rate in the second heating zone is reduced by controlling the throttle valve to reduce the temperature, this increases the flow rate in the first heating zone, causing the temperature in this area to rise. The disadvantage of such a system is that the temperatures in the two heating zones are very difficult to regulate independently of one another, since both control variables are influenced simultaneously and in conjunction with one another by the actuator in the second heating zone. Independent control of the temperatures in both heating zones is only possible to a limited extent with such an arrangement. The temperatures in the two heating zones cannot therefore be set independently of one another.

The object of the present invention is therefore to create a thermal oil baking system with which the temperatures in at least two heating zones can be controlled independently of one another using simple control technology.

This object is achieved by a thermal oil baking system with the features of claim 1.

Advantageous embodiments are the subject of the subclaims.

According to the invention, the thermal oil baking system has one or more actuators, each of which has a direct effect on the thermal oil flow of each individual heating zone. The amount of thermal oil flowing through the individual heating zones can thus be controlled directly by the actuators, which makes independent temperature control in the individual heating zones possible using simple control technology. If the temperature in a heating zone is too high or too low, the respective actuator can be opened or closed, which changes the thermal oil flow and thus allows the temperature to be increased or reduced. As a result, independent temperature control circuits can be set up for each heating zone. These separate temperature control circuits can be controlled particularly easily if each heating zone is provided with not only its own flow but also an independent return and an independent circulation pump. Thanks to these measures, an intervention in one temperature control circuit of one heating zone essentially no longer influences the flow rate of the other temperature control circuit.

According to the invention, the thermal oil baking system can have any number of separately controllable heating zones. However, the cost-benefit ratio is particularly favorable if the baking system can be operated in exactly two heating zones with different temperatures. This is because two independent temperature zones mean that the already emptied first heating zone can be heated up to the starting temperature again, while

Baked goods from the previous batch are still being baked in the second heating zone.

Many types of actuators are known from control technology with which the thermal oil flow in the individual heating zones can be controlled. This can be achieved particularly cost-effectively by arranging an adjustable flow valve in the thermal oil flow of each heating zone. By controlling the individual flow valves, the flow rate in each heating zone can be reduced and thus the temperature in the heating zone can be lowered.

Instead of individual flow valves for each thermal oil supply line, it is also possible for the thermal oil supply line of the individual heating zones to be fed from a total supply line via a multi-way, adjustable distributor valve. This means that the entire available thermal oil quantity flows into the distributor valve and is distributed to the supply lines of the individual heating zones, regulated depending on the temperature in the individual heating zones.

The individual heating modules in the heating zones can be connected in series in a manner known per se so that a single thermal oil flow flows through them one after the other, or can alternatively be connected in parallel so that individual thermal oil flows flow through them in parallel.

In principle, it is irrelevant how the baking system is supplied with energy via the thermal oil. However, it is particularly advantageous to connect the system to a primary oil circuit in which the thermal oil can be heated up and thus supplies the system with energy, and to also provide a circulating secondary circuit for the thermal oil in the system. If the system is not to be heated up any further, but rather to be gradually cooled down, the primary oil circuit is separated from the system and the thermal oil in the system is circulated in the secondary circuit using a circulation pump. Since no new energy is supplied, the baking system cools down

gradually. By controlling a bypass between the primary and secondary circuits, energy can be supplied to the system from the primary circuit as required.

According to the invention, an actuator is arranged in the flow of each individual heating zone to regulate the amount of thermal oil in the respective heating circuit. By opening the individual valves, the respective flow rate can be increased, whereby a larger amount of hot thermal oil flows through the heating zone. However, this measure can only heat the individual temperature zones. The heating zones are only cooled by the release of thermal energy via the baking system and can therefore only be influenced indirectly by the control system by not adding any further thermal energy. If the last loading cycle of a batch of goods is in the first heating zone and the baking of this loading cycle has been completed, the temperature in the first heating zone should be reduced as quickly as possible to the baking temperature as set in the second heating zone. If only one control valve is provided on the flow line of the first heating zone, the only way to reduce the temperature is to close the valve and wait until the hot thermal oil in the first heating zone has cooled down. This cooling down takes a long time, as energy can only be released as baking heat and waste heat. The cooling down time therefore depends essentially on the type and quantity of baked goods in the first heating zone and their respective heat absorption.

It is therefore advantageous if the first heating zone and the second heating zone can be connected to form a common thermal oil circuit. This can be achieved, for example, by overflow lines that connect the return of the first heating zone with the flow of the second heating zone and the return of the second heating zone with the flow of the first heating zone. The overflow lines must be able to be closed off by shut-off devices. If the two thermal oil circuits are connected to form a common circuit by reversing the corresponding valves,

connected together, the thermal oil quantities of the different temperatures mix. This results in a rapid reduction in the temperature in the first heating zone, as cooler thermal oil is fed in from the return of the second heating zone. The temperature in the second heating zone only increases insignificantly due to the hotter thermal oil from the return of the first heating zone, as the thermal oil on the return has already cooled down slightly. This is all the more true if the first heating zone is relatively small compared to the second heating zone, as the thermal oil quantity in the first heating zone is therefore relatively small. A short-term, slight increase in the temperature in the overall circuit has no noticeable effect on the baking result.

If the two circuits are connected to form an overall circuit, the temperature in the overall circuit can be regulated uniformly for the entire system after the transient processes have subsided.

In terms of design, there are basically many ways to combine the two secondary circuits into one overall circuit. This is particularly easy if the thermal oil circuit in the first heating zone and the thermal oil circuit in the second heating zone can be connected by at least two overflow lines that can be shut off by shut-off devices. If the shut-off devices are closed, no thermal oil can flow from one of the secondary circuits into the other. The two secondary circuits are therefore independent of one another and can be controlled independently of one another. If the shut-off devices are open, thermal oil can flow from one of the secondary circuits into the other. Since there are at least two overflow lines, this creates an overall secondary circuit that flows through all the heating modules one after the other, resulting in an essentially uniform baking temperature in all the heating modules.

In the overflow lines, all types of components that can influence and shut off the flow in the overflow lines can be used as shut-off devices, for example through-flow shut-off valves.

Shut-off valves. It is advantageous if additional shut-off devices are provided in the individual secondary circuits, so that when the overflow lines are open, all the thermal oil must flow through the overflow lines and does not flow uncontrollably directly in the lines of the same secondary circuit. This can be achieved in particular if the shut-off devices are designed as three-way valves, to which the inlet and outlet of a secondary circuit and an overflow line are connected. In the first position of the three-way valves, the overflow lines are each closed and the secondary circuits of both heating zones are closed independently of one another. In the second position of the three-way valves, the overflow lines are each open and the outlet of the secondary circuits is each closed off at the three-way valves. All the thermal oil in the secondary circuits therefore flows through the overflow lines. The same function can of course also be achieved by combining two through-flow shut-off valves.

The size of the individual heating zones is in principle irrelevant. However, it is particularly advantageous if the length of the first heating zone corresponds approximately to the length required for baking the baked goods that are fed into the system during a certain number of loading cycles. This means that the first heating zone is just large enough that the baked goods fed in during the first loading cycles of a batch already find the starting temperature required for baking in the first heating zone, while at the same time the baking process of the baked goods from the last loading cycles of the previous batch, which are still in the second heating zone, continues and is only minimally influenced by the heating of the first heating zone.

If a batch of goods corresponds to more than two loading cycles, the already heated first heating zone can be separated from the area of the second heating zone in which baked goods are still being baked, for example

separated by an area that has been introduced as an idle cycle in order to minimize the influence of the different temperature zones on the baking process of the successive batches of goods. However, since such idle cycles reduce the baking performance of the baking system, it is better if the atmosphere in the baking chamber can be divided into two areas by a separating device between the first and second heating zones. Such a separating device can, for example, be designed in the form of a separating curtain. A separating curtain prevents the atmospheric temperature exchange between the zones and can be easily passed through by the baked goods. A higher temperature for baking in the first heating zone then does not influence the baking process in the second heating zone.

The invention is explained in more detail below using drawings showing only preferred embodiments. They show:

Fig. 1 shows a first embodiment of a baking system;

Fig. 2 shows a second embodiment of a baking system;

Fig. 3 shows a third embodiment of a baking system;

Fig. 4 shows a fourth embodiment of a baking system;

Fig. 5 shows a fifth embodiment of a baking system.

In the baking systems shown in Fig. 1, Fig. 2, Fig. 3, Fig. 4 and Fig. 5, only the heating modules with the associated thermal oil supply are shown. All other known system components are not shown.

In Fig. 1 you can see the heating modules 1, 2, 3, 4, 5 and 6, which are used to heat the baking system. The individual heating modules are flowed through by thermal oil, which is heated in a heating system (not shown), fed into the system via the flow line 7 of the primary circuit and discharged from the system via the return line 8 of the primary circuit. In addition to the primary oil circuit with the flow line 7 and the

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The system has a secondary oil circuit in the return line 8, in which the thermal oil can be pumped in a circle using the circulation pump 9. The primary oil circuit and the secondary oil circuit are connected via the bypass connection 10 and the bypass connection 12, which can be controlled using the adjustable distributor valve 11. This means that, depending on the energy requirement in the baking system, heated thermal oil can be fed from the primary circuit into the system and otherwise the thermal oil can only be circulated in the secondary oil circuit.

The temperature gauge 14 can be used to measure the temperature in the entire flow of the individual heating zones. The temperature gauges 15 and 16 provide the temperatures at the outlet of the two heating zones. It can be seen that the heating module 1 and the heating module 2 together form the first heating zone. The second heating zone is formed by the heating modules 3 to 6. The individual heating modules in the two heating zones are each connected in series and one of the two thermal oil streams flows through them one after the other. The baked goods are fed in a timed manner in the area of the heating module 1 and removed in the area of the heating module 6. A conveyor device (not shown) is present within the system, with which the baked goods are conveyed through the system. The heating modules can be arranged in the oven as top and/or bottom heat.

The flow 17 of the first heating zone can be controlled with the adjustable flow valve 18. Similarly, the flow 19 of the second heating zone can be controlled with the adjustable flow valve 20. If the temperature in one of the heating zones deviates from the specified target value, the thermal oil flow rate in the respective flow can be immediately reduced or increased by operating the corresponding flow valve 18 or 20, so that the actual temperature can be adjusted to the target temperature. The control circuits of the two heating zones can be operated independently of one another, since the actuators have a direct effect on the control variables to be controlled.

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Heating modules 1 and 2 form the first heating zone in which the temperature can be set to a higher level for baking the baked goods. Once the entire system has been loaded with baked goods and the baking of the last loading cycle has been completed, the temperature of heating modules 1 and 2 is regulated down to the baking temperature.

Once the baking process of a loading cycle is completed, it is conveyed out of the system from the area of heating module 6 and the other loading cycles remaining in the system are subsequently conveyed. As soon as the first two loading cycles have left the system, there is no more baked goods in the area of heating modules 1 and 2. The heating modules 1 and 2 can then be heated up to the starting temperature again without having to wait for the baking process for all loading cycles to be completed. It is advisable to arrange a separating curtain 13 between the heating module 2 and the heating module 3, which does not hinder the flow of the baked goods, but prevents the atmospheric heat exchange between the two temperature zones.

Once baking in the area of heating modules 3 to 6 has been completed and the baked goods from the first batch have been completely removed from the system, the first loading cycle of the next batch of goods can begin immediately, as heating modules 1 and 2 have already reached the starting temperature. The other heating modules are then heated up during the ongoing loading cycles. In particular, with baked goods with almost the same baking temperature, the next batch of goods can begin to be loaded immediately after heating modules 1 and 2 have heated up, even if baked goods from the previous batch are still in the area of heating modules 3 to 6, which are then fed out at the same time as the new batch of goods is fed in.

The system shown in Fig. 2 corresponds in its essential parts to the system shown in Fig. 1. The heating modules 1 and 2 again form the first heating zone and the heating modules 3 to 6 form the second heating zone. In this embodiment too, the flow 17 of the first heating zone

via the adjustable flow valve 18 and the flow 19 of the second heating zone via the adjustable flow valve 20. The individual heating modules in the two heating zones are not connected in series, but are arranged parallel to one another.

The system shown in Fig. 3 essentially corresponds to the system shown in Fig. 2. However, in this system the thermal oil supply 17 and 19 of the first heating zone and the second heating zone is fed from the total supply 22 via a three-way, adjustable distributor valve 21. The flow rate to the individual heating zones can thus be controlled separately and the baking temperature in the two heating zones can be controlled independently of one another.

The system shown in Fig. 4 corresponds essentially to the system shown in Fig. 3. However, the individual heating modules in the two heating zones are not connected in parallel, but are arranged one behind the other.

In the system shown in Fig.5, the first heating zone with heating modules 1 and 2 and the second heating zone with heating zones 3, 4, 5 and 6 can be controlled separately or together. The first heating zone is supplied with thermal oil via the three-way valve 23 from the flow line 7 of the primary circuit. The circulation pump 24 of the first secondary circuit pumps the thermal oil in the circuit through the heating modules 1 and 2 and through the three-way valve 25 set to throughflow back to the circulation pump 24. When heat is required in the first heating zone, i.e. when the actual temperature is lower than the target temperature, the three-way valve 23 previously set to branch opens to throughflow and feeds a portion of hotter thermal oil from the flow line 7 of the primary circuit to the circulation of the secondary circuit in front of the circulation pump. The same amount of colder thermal oil flows from the secondary circuit via the open shut-off valve 26 to the return 8 of the primary circuit. Depending on the degree of opening and the duration of the opening of the three-way valve 23 on passage, more or less hot thermal oil flows from the primary circuit 7 to the suction line of the pump 24 of the first

Secondary circuit, with which the temperature of heating modules 1 and 2 can be regulated.

The temperature in the second heating zone is regulated in principle in the same way as in the first heating zone. The secondary circuit of the second heating zone is supplied with thermal oil via the three-way valve 27 from the flow line 7 of the primary circuit. The circulation pump 28 conveys the thermal oil through the three-way valve 29, which is set to branch, to the heating modules 3, 4, 5 and 6 and then through the line 30 to the return line 8 of the primary circuit. The three-way valve 27 can be adjusted so that part of the return flow or the entire return flow flows back into the flow line of the thermal oil circuit for the second heating zone.

The two thermal oil circuits are connected to each other by the overflow lines 31 and 32. If the two thermal oil circuits are to be operated at different temperatures, the shut-off valves 25 and 29, designed as three-way valves, are placed in the position in which the connecting lines 31 and 32 are closed. In this state, the two thermal oil circuits can be controlled independently of each other, since both the thermal oil supply and discharge of both circuits are independent of each other.

If the two thermal oil circuits are to be connected together in order to regulate the entire system to a common temperature, the shut-off valves 25 and 29, designed as three-way valves, are placed in the position in which the connecting lines 31 and 32 are open. The line connections 33 and 34 of the two secondary circuits are shut off in this position of the three-way valves 25 and 29, so that all the thermal oil in the secondary circuits must flow via the overflow lines. In this state, a common thermal oil circuit is created to supply all heating modules. If necessary, the three-way valves 25 and 29 can also take on intermediate positions.

The thermal oil circuit can be supplied with thermal oil in a regulated manner by adjusting valve 27 and cooled thermal oil can be discharged into the return line 8 of the primary circuit via line 30. In this operating state, valves 23 and 26 are closed to the flow line 7 and the return line 8, respectively, since there is an increased pressure between pumps 28 and 24, which would cause an undesirable backflow in a parallel circuit via the lines of the primary circuit. Instead of the three-way valves, as shown for the embodiment in Fig. 5, combinations of through-flow shut-off valves can also be used. This does not affect the function of the system.

Claims (1)

f ft·« « « M ftf« 14 November 1997 MIWE GmbH MIW-036 97450 Arnstein Boe/ste Protection claims 1. A single- or multi-level thermal oil baking system for producing baked goods with heating modules that can be heated by thermal oil, the system having at least two heating zones in which different temperatures can be set by regulating the amount of thermal oil flowing through the individual heating zones, characterized in that
that the thermal oil flow rate in each heating zone (1, 2) (3, 4, 5, 6) can be changed by an actuator (18, 20, 21, 23, 27) acting directly on the thermal oil supply of each heating zone (1, 2) (3, 4, 5, 6). 2. Thermal oil baking system according to claim 1,
characterized, that the temperature in a first heating zone (1,2) and in a second heating zone (3, 4, 5, 6) can be set differently. 3. Thermal oil baking system according to claim 1 or 2, characterized in that that an adjustable flow valve (18, 20, 23, 27) is arranged in the thermal oil supply line of each individual heating zone. • »··« * « t« t*tt 4. Thermal oil baking system according to claim 1 or 2, characterized in that that the thermal oil feed lines of the individual heating zones are fed from a total feed line (22) via a multi-way, adjustable distributor valve (21). 5. Thermal oil baking system according to one of claims 1 to 4, characterized in that that the heating modules in a heating zone (1, 2) (3, 4, 5, 6) are connected one after the other so that a ■ 10 thermal oil flow flows through them one after the other. 6. Thermo-baking system according to one of claims 1 to 4, characterized in that that the heating modules in a heating zone (1, 2) (3, 4, 5, 6) are each connected in parallel so that individual thermal oil streams flow through them in parallel. 7. Thermal oil baking system according to one of claims 1 to 6, characterized in that that the thermal oil supply of the heating zones (1, 2) (3, 4, 5, 6) can be fed proportionally from a primary oil circuit (7, 8) for supplying energy to the system and a secondary circuit circulating in the system. 8. Thermal oil baking system according to one of claims 1 to 7, characterized in that that the first heating zone (1, 2) and the second heating zone (3, 4, 5, 6) can be connected together to form a common thermal oil circuit. 9. Thermal oil baking system according to one of claims 1 to 8, characterized in that that the thermal oil circuit in the first heating zone (1, 2) and the thermal oil circuit in the second heating zone (3, 4, 5, 6) can be connected to one another by at least two overflow lines (31, 32), and the overflow lines (31, 32) can be shut off by shut-off devices (25, 29). 10. Thermal oil baking system according to claim 9,
characterized, that the shut-off devices are designed as three-way valves (25, 29). 11. Thermal oil baking system according to one of claims 1 to 10, characterized in that that the length of the first heating zone (1, 2) corresponds approximately to the length required for baking the baked goods that are fed into the system during a certain number of loading cycles. 12. Thermal oil baking system according to one of claims 1 to 11, characterized in that that the atmosphere in the baking chamber can be divided into two areas by a separating device (13) between the first heating zone (1, 2) and the second heating zone (3, 4, 5, 6).