FR3087457A1 - PROCESS AND DEVICE FOR RECOVERING HEAT FROM WASTEWATER - Google Patents

Abstract

The present invention relates to a device 1 and a method for recovering energy from waste water. The device 1 comprises a storage tank 10 intended to receive waste water coming from an inlet pipe 11, a heat exchanger 20 placed within the tank 19 and intended to be passed through by a fluid, for example. cold sanitary water, and a siphon 30 capable of emptying the storage tank 10 into an outlet pipe 12 by self-priming when the volume of waste water stored in the tank 10 is greater than a threshold Vmin and the flow rate of waste water arriving in the tank 10 through the inlet pipe 11 is greater than a threshold Dmin. The invention thus proposes a particularly compact and economical device as well as a very efficient process thanks to the automatic and natural emptying of the storage tank 10 by the self-priming siphoid effect.

Description

Description Title of the invention: Process and device for heat recovery from wastewater Technical field

The invention relates to the field of improving the energy efficiency of buildings, and more particularly the recovery of energy from wastewater.

Prior art

[0002] In recent years, significant efforts have focused on the energy efficiency of residential and tertiary buildings.

In France in 2014, residential buildings represented 26% of final energy consumption, more than industries and slightly less than transport.

This share rises to nearly 50% if we add tertiary buildings.

The unit consumption of buildings, expressed in kilowatt-hours per square meter, has been significantly reduced thanks to the improvement in the insulation of buildings and the generalization of technological progress in heating systems (heat pumps, condensing boilers, and cætera).

[0003] One of the objectives is, for example, for positive energy buildings to quickly become the standard for new residential buildings.

[0004] In order to continue improving the energy efficiency of buildings, attention has recently focused on other renewable energy resources, in particular on the recovery of fatal heat from wastewater.

Fatal energy represents the energy produced by a process whose purpose is not the production of this energy.

It is most often lost if it is not recovered or valued.

In the field of buildings, part of the injected energy is fatal because it is evacuated without being valued, for example in the air at the ventilation outlet or in the form of hot waste water (baths, showers, dishes).

[0006] Devices and methods for recovering heat from wastewater were first designed for industrial contexts rejecting wastewater at high temperature.

Then other processes for recovering heat from wastewater have been developed for large buildings or buildings, such as hospitals, or even neighborhoods, by means of wastewater recovery plants, the power of which is frequently. between 1 and. 8 megawatts.

For use in individual dwellings or in small collective buildings, two types of devices and methods are known.

They focus on recovering heat from wastewater to reduce energy consumption linked to the production of domestic hot water.

[0008] A first type groups together recuperators without storage which make it possible to preheat cold water by circulating it within a heat exchanger within which the waste water also circulates.

In some vertical models, the cold water inlet pipe wraps around the wastewater drain pipe (also called gray water), in order to have a ratio between the contact area and the volume as high as possible , to extract a maximum of heat from gray water.

This type of process and. This device is for example used in collective residential buildings at the foot of the fall of the wastewater evacuation pipes.

Even more compact wastewater heat recovery systems without storage have been developed so as to be placed directly under a shower tray or under a bathtub.

Of course, they only allow heat to be recovered from the wastewater produced by the sanitary equipment under which they are installed.

The main advantages of these storage-less systems are their simplicity of design and use, and their low cost to install and use.

The main drawback is the instantaneous heat recovery which leads to significant losses.

[0011] A second type groups together wastewater heat recovery units with storage, making it possible to use the potential of gray water at any time, most often for collective applications.

In these recuperators, the wastewater is stored in at least one tank.

A heat exchanger is used to preheat cold water supplying, for example, the domestic hot water production system.

Heat pumps are frequently used.

The main advantage of these methods and devices is to make the energy resource available over time, the drawbacks being the use of additional pumps and the need to clean and maintain the tank, which increases installation costs and in use.

These systems are therefore of a much more complex design and use than systems without storage.

Objectives of the invention

The invention aims in particular to overcome all or part of the drawbacks of the prior art, by providing a method and a device for recovering heat from wastewater with storage, compact, both efficient and simple in its design and use.

[0014] More precisely, an objective of the invention is to provide a device for the recovery of heat from waste water comprising a storage tank intended to receive waste water coming from an inlet pipe, a heat exchanger placed within the tank and intended to be passed through by a fluid.

According to the invention, the device also comprises a siphon capable of emptying the storage tank into an outlet pipe by self-priming when the volume of waste water stored in the tank is greater than a threshold Vmin and the water flow rate. waste arriving 3 in the tank via the inlet pipe is greater than a threshold Dmin.

Thus the device is both efficient and simple in its use, while being very compact.

An advantageous embodiment comprises a siphon external to the tank and placed on the outlet pipe, which facilitates maintenance interventions.

A particularly compact embodiment comprises a bell siphon placed inside the tank, comprising a discharge tube covered with a bell.

Advantageously, part of the heat exchanger is a coil which can then be wound around the bell siphon to improve the efficiency of the device while retaining its great compactness.

In a particular embodiment, the heat exchanger comprises a second part, placed above the bell of the bell siphon and on which flows the waste water arriving in the tank through the inlet pipe.

Thus the heat exchanger makes it possible to recover heat by convection and by trickling.

Advantageously, this second part comprises a coil placed above at least one conical-shaped surface having a slight inclination with respect to the horizontal and on which flows the waste water arriving in the tank through the inlet pipe, which makes it possible to obtain an improvement in heat exchange by trickling.

In an alternative embodiment, the device according to the invention comprises a second self-priming siphon capable of emptying the storage tank into an outlet pipe when the volume of waste water stored in the tank is greater than a second threshold Vmin2 and the flow of waste water arriving in the tank through the inlet pipe is greater than a second threshold Dmin2.

The device is thus perfectly suited for use in a known context in which different configurations of volumes and of waste water flows arriving through the inlet pipe 1 have been clearly identified.

The invention also relates to an installation for recovering heat from waste water comprising a device according to the invention, the fluid passing through the heat exchanger being sanitary water.

Such an installation is extremely simple.

Alternatively, the fluid passing through the exchanger can be “heating quality” water or a refrigerant or a heat transfer fluid, to meet specific health requirements.

The invention also relates to a method for recovering heat from wastewater according to which the wastewater from a building is collected and stored in a tank, and a fluid circulates in a heat exchanger placed within the tank .

According to the invention, emptying of the tank into an outlet pipe is automatically carried out by self-priming siphoid effect when the volume of waste water stored in the tank exceeds a threshold Vmin and the flow of waste water arriving in the tank. tank 4 via an inlet pipe exceeds a threshold Dmin.

Advantageously, the threshold Dmin is substantially. equal to 0.1 liter per second.

Optionally, the emptying of the tank (10) is partial and concerns only 50% to 75% of the volume Vmin.

Brief description of the drawings

Other characteristics and advantages of the invention will emerge more clearly on reading the following description of particular embodiments, given by way of simple illustrative and non-limiting examples, and from the accompanying drawings, among which:

[0022] FIG. 1 schematically represents a device for recovering heat from waste water in accordance with the invention;

[0023] FIG. 2 schematically shows different types of siphons that can be used to implement the invention;

[0024] FIG. 3 schematically represents a siphon of the siphon-bell type;

[0025] FIG. 4 and Fig. 5 schematically show different configurations of use of a heat recovery device according to the invention;

Fig.6 schematically shows a bell siphon;

[0027] FIG. 7 schematically shows an embodiment comprising two external siphons.

[0028] FIG. 8 schematically shows an embodiment comprising a bell siphon and a heat exchanger composed of a first and a second part.

[0029] FIG. 9 and Fig. 10 schematically represent cross sections of the device shown in FIG. 10.

[0030] FIG. 11 schematically shows another embodiment with a heat exchanger comprising a second part.

[0031] FIG. 12 schematically shows another embodiment of a device for recovering heat from waste water in accordance with the invention.

Description of Embodiments 100321 With reference to the figures, FIG. 1 to Fig. 12, different embodiments according to the invention.

100331 An example of a device 1 for recovering heat from wastewater in accordance with the invention is shown schematically in FIG.

I.

The device 1 is intended for use in individual dwellings or collective buildings.

The device 1 comprises a storage tank 10 intended to receive, via an inlet pipe 11, the gray water coming from the baths, showers or even sinks and sinks as well as washing machine or dishwasher type devices.

This gray water is generally at a temperature close to 36 ° for showers and baths and between 30 ° and 90 ° for washing machines and dishwashers depending on the program chosen by the user.

The capacity of the tank 10 is typically between 75 liters and 150 liters and its shape is arbitrary, for example cylindrical or parallelepiped.

Advantageously, the tank 10 is thermally insulated in order to limit energy losses.

A heat exchanger 20 is placed within the tank 10.

Conventionally, cold sanitary water, the temperature of which is typically between 12 ° and 18 ', is sent to the inlet 21 of the heat exchanger 20.

During circulation within the heat exchanger 20, the water is heated by the transfer of heat recovered from the gray water contained within the tank.

At the outlet of the heat exchanger 22, the heated water can be used in different ways.

The heat exchanger 20 can be of different types, for example plate type.

In a particularly advantageous embodiment, the heat exchanger takes the form of a coil, as illustrated schematically in FIG. 1, made of a material having good thermal conductivity, for example copper.

An outlet pipe 12 makes it possible to evacuate gray water from the tank 10.

They join a collector 40 ensuring their evacuation in the traditional way.

The device 1 also comprises a self-priming siphon 30.

The siphoid effect of the siphon 30 is triggered automatically when, the volume of water contained in the tank 10 exceeding a threshold Vmin, there is an arrival of gray water in the tank 10 via the inlet pipe 11 with a flow rate exceeding a minimum threshold Dmin.

The siphon 30 thus makes it possible to empty the tank 10 naturally and passively, without any additional mechanical, electrical and / or electronic device.

In particular, the absence of a pump simplifies installation and saves energy, and the absence of a valve reduces maintenance interventions.

The flow rate Dmin threshold for triggering an emptying, the frequency of emptying, the volume of gray water emptied, and the flow rate of the gray water discharged from the tank 10 during an emptying are determined by the dimensions and the shapes of the tank 10 and the siphon 30.

Preferably, the trigger threshold flow rate is greater than 0.1 liter per second.

For a given threshold Vmin, many types of siphons 30 can be used in accordance with the invention, as shown schematically in FIG. 2.

In certain embodiments, the siphon 30 is external to the tank 10, which provides the advantage of greater ease of access and disassembly to possibly clean the siphon 30 and facilitate maintenance.

The drawback is an increase in the size of the device 1.

[0040] Other embodiments propose a device 1 with a siphon 30 mainly or even totally placed within the tank 10, which makes the device 1 more compact.

In the exemplary implementation shown schematically in FIG. 3, the siphon 30 is of the bell siphon type, comprising an evacuation tube 31 placed within 6 of a bell 32.

This particularly advantageous embodiment makes it possible to place a heat exchanger 20 of the coil type wound around the bell 32 of the bell siphon 30, the discharge tube 31 passing through the base of the storage tank 10.

The device 1 is thus extremely compact.

The lukewarm sanitary water 55 available at the outlet 22 of the heat exchanger 20 can be used in many different ways.

In the examples of use shown schematically in FIG. 4 and Fig. 5, it supplies respectively a plurality of individual boilers 50 or a collective collective boiler 50 producing domestic hot water 56.

In both cases are shown three dwellings on three floors, each equipped with a shower 51, a sink 52, a sink 53 and a washing machine or dishes 54.

As the boilers 50 are supplied with sanitary water 55 which is already warm instead of being supplied in a conventional manner with cold sanitary water 57, they consume less energy to reach the desired temperature for domestic hot water 56.

In the examples of installations shown schematically in FIG. 4 and Fig. 5, the shower mixers 51 are supplied with lukewarm sanitary water 55 and hot sanitary water 56.

As water 55 that is already lukewarm is used instead of cold sanitary water 57, the consumption of sanitary hot water 56 produced by the boiler or boilers is reduced in the mixing valves.

The sinks 52, sinks 53 and washing machines 54 are, in these examples, supplied with hot sanitary water 56 and cold sanitary water 57.

Naturally, multiple uses can be envisaged, combining the supply of boilers 50, and / or shower mixers 51, sink 52, sink 53, or washing machines 54 which then need less energy to reach the temperature of the program selected by the user.

The wastewater is collected at the outlet of the showers 51, sink 52, sinks 53 and washing machines 54, in an evacuation pipe 58 connected to the inlet pipe 11 of the device 1.

At the outlet of the device 1, the waste water is evacuated to a collector 40 ensuring their evacuation in the traditional way.

Counters 59 make it possible to measure the consumption of warm 55, hot 56 and cold 57 sanitary water.

Optionally, the dimensions of the siphon 30 and its positioning in the storage tank 10 make it possible to drain only a part of the volume of waste water contained in the tank 10, for example 50% or 75% of the volume of water .

Such a configuration thus makes it possible to optimize the heat recovery by adapting the volume of a drain to the average volume of a gray water inlet in the device 1, and by ensuring that there is always a level of water. minimum to recover heat.

Advantageously, when the siphon 30 is of the bell siphon type, the shape of the top 7 of the discharge tube 31 and the shape of the top of the bell 32 can be adapted in order to facilitate the flow of waste water during the automatic drain.

As shown schematically in Fig. 6, by flaring the top of the discharge tube 31, it is for example possible to facilitate the priming of the siphon 30, and therefore to lower the value Dmin of the threshold flow rate for triggering the siphoid effect.

In some cases, the device 1 for recovering heat from wastewater can be used in a known context in which different configurations of volumes and flows of wastewater arriving through the inlet pipe 1 have been clearly identified.

For example a bath type configuration with a large volume of waste water at about 38 ', and a washing machine type configuration, with a lower volume of much hotter waste water.

In such a case, the device 1 may comprise a second self-priming siphon 35, as shown schematically in FIG. 7.

The characteristics of the first siphon 30 and of the second siphon 35 make it possible to define two threshold flow rates Dmin, two volumes of drained water and two separate drain flow rates in order to optimize the heat recovery at the two identified configurations and thus to present a greater self-priming flow range.

[0048] For example, one of the two siphons 30 and 35 constructed with a small diameter will trigger emptying with a low threshold flow rate Dmin and a low emptying flow rate.

In the event of a strong flow of wastewater arriving through the inlet pipe 11, the water level in the tank 10 will continue to rise until the automatic triggering of the siphoid effect of the second siphon 35 or 30, built with a larger diameter and then triggering by self-priming an emptying with a high emptying rate.

The wastewater heat recovery devices according to the invention have the common features of being extremely easy to use and compact with high efficiency, but the exemplary embodiment shown schematically in FIG.

S to Fig. 10 is particularly advantageous in these two areas

In this example, the tank 10 has a parallelepipedal shape and it is provided with an optional overflow discharge pipe 13.

The siphon 30 is of the bell siphon type, the discharge tube 31 of which has an optional flared top.

A coil-type heat exchanger 20 comprises a first part 25 having a substantially cylindrical profile placed around the bell 32 of the bell siphon 30.

When the tank 10 contains used water, this first part 25 of the heat exchanger 20 heats, by convection, the sanitary water which passes through it.

In the extension of the first part 25, the heat exchanger 20 also comprises a second part 26 placed above the bell 32 of the bell siphon 30, and having an angulation relative to the horizontal.

When the used water arrives in the tank 10 through the inlet pipe 11, it trickles onto the second part 26 by heating the sanitary water which passes through it.

This heating is the result of countercurrent trickle exchange, which is one of the most efficient heat exchanges.

In the exemplary embodiment shown in FIG. 8 to Fig. 10, the second part 26 is also of the serpentine type, the turns of which have decreasing diameters so as to present a profile favoring runoff, for example a conical profile.

In an alternative embodiment not shown, the second part 26 of the heat exchanger 20 consists of two substantially parallel surfaces between which circulates the sanitary water.

These two surfaces can then define a profile favoring runoff, for example a conical profile, and have a very low angulation with respect to the horizontal so as to maximize the heat exchange by runoff while reducing the size of the device.

This alternative embodiment is particularly suitable for high flow rates of waste water inlet into the tank.

A device 1 as shown in FIG. 8 to Fig. 10 is very compact and makes it possible to heat domestic water in a particularly efficient manner both by countercurrent trickling and by convection in a tank 10, which is automatically emptied by the self-priming siphon 30, thus providing a great ease of manufacture, installation and use.

[0056] FIG. 11 schematically shows a particularly advantageous embodiment, in which the second part of the heat exchanger 26 comprises a coil 27 placed above a plurality of surfaces 28 of conical shape having a slight inclination with respect to the horizontal.

[0057] The waste water arriving in the tank 10 via the inlet pipe 11, trickles successively over the different surfaces 28 by heating the sanitary water which passes through the coil 27, thanks to a heat exchange by counter streaming. -running.

In the embodiment shown in FIG. 11, the inclination of the surfaces 28 is alternately positive and negative so as to optimize the heat exchange by increasing the duration of the runoff.

[0058] Optionally, the surfaces 28 can be constructed from a thermally conductive material.

The surfaces 28 are then also heated by the waste water which runs off.

The surfaces 28 being in contact with the coil 27, they then also participate in the heating of the sanitary water which passes through it.

In the examples of implementation of the invention presented above, sanitary cold water 57 feeds the heat exchanger 20 placed in the tank 10 within which is the waste water.

However, for sanitary treatment reasons, it may be desirable that the tank 10 does not contain both drinking sanitary water passing through the heat exchanger 20, and waste water arriving through the inlet pipe 11.

The installation shown schematically in FIG. 12 responds to this problem by using a device 1 having a structure identical to that of the devices 9 previously described, but the heat exchanger 20 of which is not supplied by its inlet 21 with cold sanitary water 57, but with fluid to warm up.

This fluid can for example be “heating quality” water which is then used in an exchanger 60 to preheat the domestic cold water 57, or else a refrigerant from a thermodynamic system 60 of the heat pump type, or else again a heat transfer fluid alternating vaporization and condensation in a sealed closed circuit forming a two-phase loop or a thermosiphon loop 60.

The invention also relates to a process for recovering heat from waste water, according to which the waste water is stored in a tank 10 in which a heat exchanger 20 is placed.

A fluid being sent to the inlet 21 of the heat exchanger 20, it is reheated at the outlet 22 of the heat exchanger.

The method according to the invention comprises automatic draining phases by self-priming siphoid effect triggered when the volume of waste water stored exceeds a threshold Vmin, and when the flow of waste water arriving in the tank 10 exceeds a threshold Dmin d initiation of the siphoid effect.

Advantageously, Dmin is greater than 0.1 liter per second.

Optionally, the emptying of the tank 10 is partial and concerns only 50% to 75% of the Vrnin volume. 10

Claims (1)

Claims [Claim 1] Device (1) for heat recovery from waste water comprising a storage tank (10) intended to receive waste water from an inlet pipe (11), a heat exchanger (20) placed within of the tank (19) and intended to be traversed by a fluid, characterized in that it also comprises a siphon (30) capable of emptying the storage tank (10) in an outlet pipe (12) by self-priming when the volume of waste water stored in the tank (10) is greater than a threshold Vmin and the flow of waste water arriving in the tank (10) through the inlet pipe (11) is greater than a threshold Dmin. [Claim 2] Device (1) for heat recovery from wastewater according to claim 1 characterized in that the heat exchanger (20) comprises a coil. [Claim 3] Device (1) for heat recovery from waste water according to claim 1 characterized in that the siphon (30) is a siphon outside the tank (10) and placed on the outlet pipe (12). [Claim 4] Device (1) for recovering heat from waste water according to claim 1 characterized in that the siphon (30) is a bell siphon placed inside the tank (10), comprising a discharge tube (31) covered with a bell (32). [Claim 5] Device (1) for heat recovery from waste water according to claims 2 and 4 characterized in that the coil (20) forms a first part (25) of the heat exchanger (20) wound around the bell siphon (30) . [Claim 6] Device (1) for heat recovery from waste water according to claim 5 characterized in that the heat exchanger comprises a second part (26), placed above the bell (32) of the bell siphon (30) and on which runs off the waste water arriving in the tank (10) through the inlet pipe (11). [Claim 7] Device (1) for heat recovery from wastewater according to claim 6 characterized in that the second part (26) comprises a coil (27) placed above at least one surface (28) of conical shape having a slight inclination with respect to the horizontal and over which the waste water flowing into the tank (10) flows through the inlet pipe (11). [Claim 8] Device (1) for heat recovery from waste water according to one of the preceding claims, characterized in that it comprises a second self-priming siphon (35) capable of emptying the storage tank (10) into an outlet pipe (15) when the volume of waste water stored in the tank (10) is greater than a second threshold Vmin2 and the flow rate waste water arriving in the tank (10) via the inlet pipe (11) is greater than a second threshold Dmin2. [Claim 9] Waste water heat recovery installation comprising a device 1 according to one of the preceding claims, characterized in that the fluid is domestic water. [Claim 10] Installation for recovering heat from waste water comprising a device 1 according to one of claims 1 to 8, characterized in that the fluid is "heating quality" water or a refrigerant or a heat transfer fluid. [Claim 11] Method for recovering heat from waste water according to which the waste water from a building is collected and stored in a tank (10), and a fluid circulates in a heat exchanger (20) placed within the tank (10) , characterized in that an emptying of the tank (10) in an outlet pipe (12) is automatically carried out by self-priming siphoid effect when the volume of waste water stored in the tank (10) exceeds a threshold Vmin and the flow rate d waste water arriving in the tank (10) via an inlet pipe (11) exceeds a threshold Dmin. [Claim 12] Process for recovering heat from waste water according to claim 11, characterized in that the threshold Dmin is substantially equal to 0.1 liters per second. [Claim 13] Process for recovering heat from waste water according to claim 11 or 12, characterized in that the emptying of the tank (10) is partial and only concerns 50% to 75% of the volume Vmin. 1/9