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DESCRIPTION

The present invention relates to a sensible and latent heat recovery condensing apparatus from boilers.

More specifically, the invention relates to a heat exchanger which, when installed between a hot water or steam heating boiler and its gas expulsion flue, can intercept the combustion flue gases thus recovering and re-using the thermal power they contain.

Normal boilers, even those known as "high-efficiency boilers" (91- 93% nominal thermal power), can use only part of the sensitive heat of combustion flue gases; furthermore, they cannot use the latent vaporization heat due to the need to avoid heat condensation in the flue gases, which gives rise to corrosion phenomena. The aqueous vapor generated in the combustion process is thus totally dispersed into the atmosphere through the flue: the amount of heat contained therein, referred to as latent heat, is about 1 1% of the energy released by the combustion.

Condensation boilers can instead recover part of the latent heat contained in the flue gases expelled through the flue. Indeed, the particular condensation technology allows to cool the flue gases to return them to the saturated liquid state (or in some cases to the humid vapor state) and the recovered heat is used to pre-heat the return water in the system. Thereby, the output flue gas temperature maintains a very low value, close to the return temperature of the water.

As mentioned, the latent condensation heat is equal to 1 1% of the total combustion heat of methane. For this reason, assuming a boiler without any dispersion, a thermodynamic efficiency of 1 1 1% could be obtained compared to 100% of the lower heating value (100% sensitive heat + 1 1% of latent condensation heat).

However, these apparatuses achieve very high efficiencies only when they are used in low temperature systems with a temperature of the heat transfer fluid (water) of 30-40°C, or by applying some specific solutions (increasing the At between delivery and return, slowing down the heat transfer fluid flow, limiting the power of the boiler). Nevertheless, if the temperature of such boilers is maintained at a value of 60-80°C (in these cases, a system with appropriate radiators or fan coil units must be provided), the condensation boiler cannot recover the latent vaporization heat because the input water temperature is either higher than or too close to the flue gas dew point temperature (about 55°C with methane): in this case, the condensation boiler acts as a standard, high-efficiency boiler (85-95%).

A module communicating with a boiler is known from patent WO- 2006067820, such a module being suitable to intercept the flow of flue gases output from the boiler in order to recover part of the sensitive heat and part of the latent vaporization heat of the flue gases. This allows the boiler to consume less energy to increase the temperature of the fluid to the set temperature, thus obtaining a saving of fuel with the same power obtained from the system.

In view of the prior art, it is the object of the present invention to present an apparatus which allows to increase the recovery of sensitive heat and latent vaporization heat contained in large amount of vapors produced by combustion in high-efficiency boilers, thus improving efficiency.

In accordance with the invention, such an object is achieved by a heat recovery condensing apparatus from a boiler comprising a heat exchanger, said apparatus being provided with an inlet for receiving the flue gases leaving the boiler and an output, connected to a flue, characterized in that the flow of flue gases through the apparatus is through a vertical path, and the inlet of the apparatus is provided with at least one flow detector of flue gases suitable to send a signal to a control unit, said control unit being configured for driving a modulating extractor device of the flue gases at the output of the apparatus. These and other features of the present invention will become more apparent from the following detailed description of an embodiment thereof, shown by way of non-limitative example in the accompanying drawings, in which:

figure 1 shows a vertical partial section view of the heat recovery condensing apparatus according to the present invention;

figure 2 shows an axonometric view of a plate heat exchanger included in the heat recovery condensing apparatus;

figure 3 shows a detail of the heat exchanger in figure 1 ;

figure 4 shows a first diagram with a heat recovery condensing apparatus according to the present invention installed between a boiler and a flue;

figure 5 shows a second diagram with a heat recovery condensing apparatus according to the present invention installed between a boiler and a flue.

A heat recovery condensing apparatus 1 according to the present invention is shown in Figure 1. Apparatus 1 comprises a U-shaped frame 7 in which a heat exchanger 2 of the sealed plate type is placed within a descending chamber 4.

Apparatus 1 is provided with an inlet 5, arranged at the top of apparatus 1, suitable to receive the flue gases leaving a (water or steam) boiler 6, such an apparatus 1 being installed between the boiler 6 and a flue 19 (see diagram in Figure 4).

The descending chamber 4 is the path that, through the plates 3 of heat exchanger 2, conveys the flue gases towards a bottom 70 of the frame 7 suitable to collect the acid condensation (see Figure 1). A flue gas lifting chamber 8 vertically departs from the bottom 70 of frame 7, such a lifting chamber 8 being separated from the descending chamber 4 by means of an inner wall 9. A modulating extractor device 11 suitable to expel the flue gases is placed at the upper end 80 of the lifting chamber 8. For example, such a modulating extractor device 1 1 may be a stainless steel fan. The fan 11 is suitable to push the flue gases from the lifting chamber 8, conveying them to a metal box 12 provided with a siphon outlet 13 which will be coupled to the outer flue 19 (see Figures 4 and 5). The metal box 12 further comprises a bottom output 16 suitable to dispose of acid condensation from flue 19.

In order to allow monitoring the flow of flue gases at the inlet of apparatus 1, at least one detector 17 is placed close to inlet 5, as diagrammatically shown in Figure 1. Specifically, it may be a pressure sensor. Such a sensor 17 is suitable to send a signal to a control unit 18 suitable in turn to drive fan 11, said control unit 18 being capable of switching the fan 1 1 on/off and also adjusting the rotation speed thereof by means of an inverter 22 connected to fan 11.

By virtue of the flue gas flow adjustment, a particulate filter (not shown in the figures) may be used downstream of apparatus 1.

Each plate 3 of the heat exchanger 2 (see Figures 2 and 3) has a substantially rectangular surface and comprises a passage chamber 10 suitable to receive a heat transfer fluid. An input conduit 15, suitable to introduce the heat transfer fluid into the passage chambers 10 of each plate 3, is positioned at the bottom of apparatus 1 (see Figures 1, 2 and 3). Similarly, an output conduit 14, suitable to flow the heat transfer fluid out from the heat exchanger 2, is placed at the top of apparatus 1. A hydraulic circuit 21, connected to said inlet 15 and output 14 conduits of the heat exchanger 2, is suitable to transport the heat transfer fluid either through the boiler 6 to a heating system 23 (Figure 4), or through a boiler for the accumulation of domestic water 25 (Figure 5), or to other devices to which the recovered energy is to be given.

In use, Figure 4 shows a diagram with a heat recovery condensing apparatus 1 installed between the boiler 6 and the flue 19. Apparatus 1 intercepts at its inlet 5 the flue gases expelled from boiler 6, recovering the thermal power in the form of sensitive heat and latent vaporization heat, and giving it to the hydraulic circuit 21 where the heat transfer fluid circulates. Heat is given by means of the heat exchanger 2, where the large contact surface with the flue gases, the optimal distance between plates 3, and the turbulent surface facilitate the incorporation (both by solution and by surface activity) of part of the polluting substances in the produced condensation itself. The flue gases thus cross the heat exchanger 2, travelling through a vertical downward path (see the arrows in Figure 1), and are conveyed towards the bottom 70 of frame 7. The acid condensation formed both in the descending chamber 4 with the heat exchanger 2 and possibly in the lifting chamber 8 are collected by gravity at the bottom 70. The flue gases are condensed only inside apparatus 1. Acid condensation is disposed of by preventing it from returning into boiler 6, thus protecting the latter from corrosion. This may occur by virtue of the shape of apparatus 1, with the flue gases flowing vertically.

The extractor fan 1 1 aspirates the flue gases through the lifting chamber 8 pushing them towards the metal box 12. The bottom output 16 has the purpose of recovering and disposing of the acid condensations should they flow back from the outer flue 19 and/or fan 1 1. The flue gases are conducted to the outer flue 19 through the siphon output 13.

Apparatus 1 is automatically activated without needing to be electrically connected to boiler 6; indeed, the control unit 18 checks the ignition of the boiler 6 by means of the pressure sensor 17 which detects the movement of the input flue gases 5. When the boiler 6 turned on, before the flame is lit, the modulating extractor device 1 1 of apparatus 1 is activated to keep the flue gas pressure in the boiler 6 unchanged.

The control unit 18, by adjusting the rotation speed of fan 11 by means of the inverter 22, adapts the flow rate of the flue gas circulating in apparatus 1 so that the flue gas pressure at the inlet 5 is equal to the normal, primitive pressure of the flue gases exiting from the boiler 6. This occurs in order to avoid subjecting the boiler 6 to a stress caused by possible load losses caused by known heat recovery apparatuses. Creating an although minimal load loss on flue gas side of the boiler 6 (i.e. creating a counter- pressure) would cause a variation of the combustion supporter/fuel ratio, and thus a loss of efficiency, and the exponential production of pollutants and unburnt substances.

In the present invention, the fan 1 1 placed at the output of the chamber 8 accurately moves the amount of flue gases produced by the boiler 6, and especially cancels the load losses determined upstream by the heat exchanger 2 and downstream by possible other apparatuses, such as particulate filters for flue gas purification. This is a very important opportunity because the particulate filter will increasingly obstruct in use, thus continuously increasing load loss on flue gas side. Normally, such a filter must not be installed directly at the flue gas output of the boiler 6. Checking the flue gas pressure instead allows these filters to be used because it maintains the flue gas pressure constant, thus increasing the speed of the fan 1 1 as the filter obstruction increases, thus overcoming the load loss.

By adopting the same principle, apparatus 1 allows to expel the cold flue gases in lack of draw from the flue 19, and to use small passage section flues (in the case of re-lining of an old flue).

An advantage of the presence invention is that, in the heat exchanger 2, the plates 3 have no gasket or braze welding with soft metals; this aspect and the presence of an opening flange 20 in the outer body of apparatus 1 (see Figure 2) allows cleaning on flue gas side without needing to remove the heat exchanger 2 from apparatus 1 or disassembling plate by plate; additionally, no gaskets need to be replaced between plates 3.