The present invention relates to an apparatus and a method for the thermal recovery from at least two thermal flows.

In particular, the present invention relates to an apparatus usable in industrial processes and in particular for the thermal recovery from at least two or more non-simultaneous thermal flows (batches).

Further, the present invention finds advantageous application for the thermal recovery from at least two or more thermal heating and cooling flows having compatible thermal levels where therefore the maximum temperature of the flow being cooled is greater than the minimum temperature of the flow being heated.

As is well known, industrial plants of various kinds, such as in the food or chemical field, have respective heating and cooling flows served by appropriate heat and cold generators independent of each other. Such a solution, which does not include any thermal recovery circuit, is however very expensive from the perspective of energy consumption and therefore, appropriate thermal recovery solutions have been adopted.

A first solution for heat recovery includes using heat exchangers to exploit only the simultaneous share of the heating and cooling flows. In fact, in this case the thermal recovery action occurs only in an operating condition of both flows and therefore without the possibility of accumulating the thermal value.

Therefore, such a solution is limited as it cannot be used for non- simultaneous thermal flows, commonly called “batches”, in which an accumulation step is necessary. Therefore, in accordance with a further known solution, thermal recovery systems with accumulations are provided, in which the heat dissipation does not occur in parallel with the thermal recovery. However, such a solution has important drawbacks and application limitations.

In fact, this solution involves problems in the management of excess heat dissipation. In the case where the available heat exceeds the needs of the utilities of the recovery system, the most relevant heat (which has a high temperature) is dissipated to balance the system, or the mass of hot fluid deemed unnecessary is eliminated.

For example, evaporative towers or other dissipation systems are provided in series with the (upstream) recovery system which dissipate high temperature heat and recover at a lower thermal level. This leads to a non- optimal sizing of the storage and pumping systems. In this case, the size of the two tanks, with the same accumulated energy, is inversely proportional to the temperature difference between the tanks themselves. The further the distance between the thermal levels, the more limited the accumulation volumes required (and the related investment costs). Furthermore, always with the same recovered energy, the flow rates from both sides of the system are lower as the thermal difference between the two tanks increases.

Further, especially in the food sector, the recovery plant requires periodic washing, which requires the complete emptying of the circuit, resulting in drawbacks in terms of maintenance costs derived from the volume of water necessary for washing.

In a further known solution, the dissipation system is not included and the available heat is completely recovered at the maximum available temperature. In this case, however, if the daily need does not exhaust the recovered heat, a part of the mass of hot water (reintegrated into the cold tank) is eliminated, causing a significant waste of water.

Furthermore, the known solutions do not include a predictive-type thermal adjustment system which does not allow to obtain the maximum recovery potential. In this case, the recovery systems are in fact managed with fixed settings on the temperatures of the tanks and/or with fixed settings on the temperatures at the outlet of the process fluids from the heat exchangers. Such a type of regulation does not allow correcting the management of the system to react to changes in the timing and/or the available/necessary thermal energy in the subsequent processing cycles, with consequent excess heat to be dissipated or a lack of heat to be integrated through backup generation systems, minimizing the share of thermal recovery on the flow to be heated.

In this context, the object of the present invention is to provide an apparatus and a method for the thermal recovery from at least two thermal flows capable of solving the aforementioned drawbacks of the known art.

In particular, the object of the present invention is to provide an apparatus and a method for the thermal recovery from at least two non-simultaneous thermal flows.

It is a further object of the present invention to optimize the structure of a thermal recovery apparatus in order to minimize the costs for the construction of the thermal recovery system and the operating/maintenance costs.

Another object of the present invention is to provide an apparatus and a method capable of optimally regulating the heat exchange in order to maximize the exploitation of the recovery potential.

Finally, an object of the present invention is also to provide an apparatus and a method for thermal recovery capable of providing a predictive strategy to make the entire recovery system more versatile.

The technical task mentioned and the objects specified are substantially achieved by an apparatus and a method for the thermal recovery from two, preferably non-simultaneous, thermal flows in accordance with the appended claims.

Further features and advantages of the present invention will become more apparent from the description of an exemplary, but not exclusive, and therefore non-limiting preferred embodiment of an apparatus and a method for the thermal recovery from two thermal flows. Such a description will be set out hereinafter with reference to the accompanying drawings given only for illustrative and, therefore, non limiting purpose, in which:

- figure 1 shows a schematic view of an apparatus for the thermal recovery from at least two thermal flows in accordance with the present invention;

- figure 2 shows a schematic view of the apparatus of figure 1 in accordance with a further embodiment solution.

With reference to the accompanying figures, the number 1 globally indicates an apparatus for the thermal recovery from at least two thermal flows.

In particular, with reference to figure 1 , the apparatus 1 comprises at least a first circuit 2 of a flow to be heated “L” also called a process flow, and at least a second circuit 3 of a flow to be cooled S.

It should be specified that in the present invention explicit reference is made to two thermal flows S, L respectively to be cooled and to be heated, not simultaneous.

However, the present invention can also be used for a greater number of thermal flows, both in a simultaneous and a non-simultaneous condition. The apparatus 1 further comprises a third circuit 4 of an exchange flow C, F interposed in parallel between the first and the second circuit 2, 3.

More in particular, the third circuit 4, which has a closed configuration, is provided with at least a first heat exchanger 5 operatively engaged to the first circuit 2 to transfer heat from the exchange flow C to the flow to be heated L. Similarly, the third circuit 4 further comprises at least a second heat exchanger 6 operatively engaged to the second circuit 3 to transfer heat from the flow to be cooled S to the exchange flow F.

At least one accumulation tank 5a, 6a of the exchange flow C, F is further included between the first and the second heat exchanger 5, 6. Preferably, the third circuit 4 comprises a first accumulation tank 5a arranged downstream of the second exchanger 6 and upstream of the first exchanger 5. Thereby, the first accumulation tank 5a accumulates the exchange flow C heated and exiting the second exchanger 6. Advantageously, the third circuit 4 further comprises a second accumulation tank 6a arranged downstream of the first exchanger 5 and upstream of the second exchanger 6. Such a second tank 6a accumulates the cooled exchange flow F exiting the first exchanger 5.

The third circuit 4 is further provided with a pair of pumps 5b, 6b, adapted to feed the exchangers 5, 6 with the exchange flow C, F withdrawn from the respective tanks 5a, 6a. More specifically, a first pump 5b is provided downstream of the first tank 5a to withdraw the heated exchange fluid C from the first tank 5a and feed it to the first exchanger 5.

A second pump 6b is arranged downstream of the second tank 6a to withdraw the cooled exchange fluid F from the second tank 6a itself and feed it to the second exchanger 6.

The apparatus 1 further comprises an auxiliary branch 7 arranged in parallel to the second circuit 3, to bypass the second exchanger 6 and disperse any excess heat of the flow to be cooled S.

In particular, the auxiliary branch 7 comprises a partition valve 8 arranged upstream of the second exchanger 6 for determining the fluid entering the second exchanger 6 and/or entering the auxiliary branch 7.

The auxiliary branch 7 further comprises a heat sink 9 arranged downstream of the partition valve 8.

In accordance with a further embodiment solution illustrated in figure 2, the first circuit 2 can comprise an auxiliary branch 10 for bypassing the first exchanger 5 and introducing the first heated fluid L downstream of the first exchanger 5.

Such an auxiliary branch 10 comprises a partition valve 11 arranged upstream of the first exchanger 5 for determining the fluid L entering the first exchanger 5 and/or entering the auxiliary branch 10. The auxiliary branch 10 further comprises a heat generating member 12, such as a heat pump, arranged downstream of the partition valve 11.

In use, the first heat exchanger 5 heats the process fluid L starting from the exchange flow C coming from the first tank 5a. The exchange fluid F cooled downstream of the first exchanger 5 is then introduced into the second tank 6a at a lower temperature.

Thereby, the cooled exchange fluid F is withdrawn from the second tank 6a, by means of the second pump 6b, and introduced into the second exchanger 6 where it is heated and then reintroduced into the first tank 5a. Such heating occurs by virtue of the cooling of the flow S of the second circuit 3. The cooled fluid flow S can be partitioned by the valve 8 before entering the second exchanger 6 and directed to the heat sink 9.

Thereby, a control device (of a known type and therefore not described in detail) detects the temperatures of the flows (flow to be cooled S, flow to be heated L and exchange flow C, F) and inside the two tanks 5a, 6a. The fluid level in the tanks 5a, 6a is also controlled to regulate the start of the pumps 5b, 6b for circulating the exchange fluid C, F and the partition of the fluid S to be cooled between the exchanger 6 and the heat sink 9. It should be specified that such a control involves detecting the fill level of the exchange fluid C, F inside the respective tanks.

Thereby, the constraints on the flow temperatures to be cooled S and heated L are respected and the recovery of thermal energy through the third circuit 4 is maximized.

The optimal regulation of the system comprises the prediction of the thermal loads, both the needs of the recovery heat utilities and the availability of heat from the sources. The predictive part of the regulation allows to optimize the management of the heat to be recovered, it allows to not dissipate potentially useful heat in the subsequent steps.

Such a predictive regulation is very useful for predicting thermal dispersions due to a long break in the cycle, for example in the event that the first tank 5a is filled during the last work cycle and the exchange fluid C reused in the first cycle of the following day.

In this case, the excess heat over the current cycle need would not be completely dissipated, but partially accumulated to compensate for the thermal dispersions up to the next cycle, thus allowing the maximum thermal quota to be recovered even in the first post-pause cycle (also introducing a saving on the heat dissipation system).

In the second embodiment of figure 2, the implementation of a heat generator 12 (heat pump) in parallel to the first exchanger 5 has significant advantages in terms of energy. In fact, the generator 12 has a very high efficiency under low temperature operating conditions.

Therefore, the present invention involves important advantages.

First, investment costs are minimized with respect to the known art, as the tanks and pumping systems are very limited in size. Furthermore, the flow rates circulating in the recovery system are lower, as is the demand to the excess heat dissipation system.

The thermal exchange is also optimally managed in order to maximize the exploitation of the recovery potential, also by virtue of the predictive regulation described above.

Finally, there is considerable water savings in the washing steps resulting from the small size of the plant which minimizes the waste of water for such washing steps.