FR2547024A1 - Method and installation for producing hot water or other liquid continuously, in particular for industrial requirements - Google Patents

Abstract

The invention relates to a method and an installation for continuously producing a hot liquid. According to the invention, a tank 2 is used, containing a bath of liquid to be heated 4 which is heated by means of a heat generator 18 of the pre-mixing gas burner type, working in submerged combustion. The temperatures of the bath are measured by probes 25, 26 which determine the instants when the generator has to operate. The invention applies especially to producing industrial hot water.

Description

 The subject of the invention is a process and an installation for the production of hot water or other liquid, continuously, in particular for industrial needs.

 The continuous supply of hot water in the industrial sector is very often carried out from a steam boiler requiring a significant investment and working with yields which hardly exceed 65%, due to the use in such installations. of intermediate exchangers.

 The temperatures required are usually in the range of 850 ° C. to 1100 ° C., starting with water at a temperature close to 10 ° C.

 It has also been proposed to use immersed heat exchangers known as "compact" equipped with gas burners with total premix and which are used for heating latent baths contained in tanks. Such installations which are used in particular in the metallurgical industry for the surface treatment of various products are advantageous in that the heating efficiency can frequently reach 90% on lower calorific value (PCI), while the installation is compact and relatively simple, therefore inexpensive. However, these installations are only well suited to the preparation of latent baths, in particular not allowing the production of water at a temperature above 1000C and being ill-suited to intermittent demands except provide for the addition of a hot buffer hot water tank which may be pressurized, which results in very significant additional installation costs and a drop in thermal efficiency.

 The object of the invention is to solve the above-mentioned difficulties by proposing a simple inexpensive installation having very good thermal efficiency and great flexibility of use.

 The invention uses an installation of the latent bath type heated by a submerged heat exchanger.

In accordance with the process for operating the installation in accordance with the invention, with a view to satisfying a request at all times while optimizing the operating conditions of the installation
the temperature of the liquid is continuously measured at at least one point in the tank near the hot liquid withdrawal pipe,
the liquid level in the bath is continuously measured around an optimal filling level and / or the flow rate of the hot liquid withdrawn,
the heating of the installation is controlled when the temperature measured as indicated above drops below a first determined threshold and the heating is stopped when this temperature exceeds a second determined threshold higher than the first,
- the supply of cold water to the bath is controlled when there is a flow of hot liquid drawn off or when the liquid level in the bath drops below a first determined height and the supply is stopped in cold water when said level rises above a second determined height situated at a level greater than said first height.

 The installation according to the invention thus essentially comprises inside a thermally insulated tank at least one submerged heat generator of the type supplied by a burner with a premix air / combustible gas and the various organs for controlling the operation of the installation such as temperature probes, level detectors and / or control of draw-off flow and bath supply.

 The invention, its implementation and its advantages will appear more clearly with the aid of the description which follows, made with reference to the appended drawings illustrating schematically by way of example an embodiment.

In these drawings
Figure 1 is a schematic sectional view of an installation according to the invention;
Figure 2 is a sectional view taken substantially at the plane II-II of Figure 1;
FIG. 3 is an electrical diagram relating to the control of the operation of the burner.

 Referring first to Figures 1 and 2, we see an installation identified as a whole 1 essentially comprising a tank 2 thermally isolated from the outside by a wall 3 containing the bath 4 of the liquid to be heated, such as water example. The level of the bath appears at 5 and above the volume of vapor 6 connected to the atmosphere by a vent 7 possibly ending with a stop valve 8 if the bath must be heated to a temperature above 1000C.

 The bath 4 is heated by a heat generator identified as a whole 9 essentially comprising a burner 10 with total premix supplied with air + fuel gas melanosis as indicated by the arrow 11 by a duct 12 a combustion chamber 13 in which takes place most of the combustion is a plate heat exchanger 14 which follows the combustion chamber -13 and leads into a manifold 15 connected to the flue gas evacuation pipe 16. In the combustion chamber 13 are also provided as it appears more clearly in FIG. 2 different conduits 16 crossing from top to bottom the chamber and which are traversed by currents of convection of the water to be heated as indicated by the arrows 17. In the plate exchanger part 14, convection currents 18 circulating between the plates also ensure good heating and homogenization of the bath temperature. Figure 2 simply schematically illustrates the installation, the number of conduits and plates being generally significantly greater than illustrated schematically.

 In 19, the ultraviolet radiation control cell for the correct functioning of the burner has been depicted, which "looks" at the plate 20 on which the flames of the burner are attached by means of a conduit 21 protecting the cell 19 from the hot and humid atmosphere.

 The installation further comprises an inlet 22 for cold liquid preferably at the bottom towards the end of the tank adjacent to the outlet side 15 of the heat generator, and a hot water outlet 23 at upper part of the bath towards the end opposite to the relief of the burner 10. Thus the circulation of cold water takes place substantially in the bath against the current with the circulation of the fumes as indicated by the arrow 24.

 The installation further comprises for controlling its operation a probe 25 which measures in the upper part in the vicinity of the hot water withdrawal duct the temperature of the bath. Advantageously, a second probe of the same type 26 is provided at a lower level but also towards the end of the hot water outlet as indicated in FIG. 1.

 The installation is completed by probes 27,28,29 measuring three levels of water in the bath.

 The operation of the installation will now be described.

 When the installation is started up, the probes 25 and 26 measure the temperature of the bath in the respective regions 30 and 31. Assuming that the bath is at too low a temperature, each of these probes controls an associated relay respectively RTî T2 and RIZ1, T2 at closing controlling the start-up of the programmer 32 of the installation burner. At this stage of the operations, the control cell 19 checks the correct ignition of the burner, and assuming the bath is filled to a suitable level, the bath is heated.

The heating persists, as long as the two probes 30 and 31 have not each measured the exceeding of a maximum temperature threshold T'2 and T2 respectively. For example, the threshold T2 measured by the probe 30 can be 95 ° C., while the threshold T′2 measured by the probe T1 can be 800C. If these two temperatures are exceeded, then this means that the whole bath is sufficiently hot and the two relays
and
Rut1, T2 RUT, 1 T'2 opening the circuit of the programmer 30 control the heating off.

 As for the probe 29, it identifies the level of the bath in the tank. It controls a slave valve 33 ensuring the supply of cold water to the bath if the level tends to drop and closing this supply if the level tends to rise too high. This automatically compensates for hot water withdrawals at 23.

 The probe 27 is a safety sensor which will control the stopping of the installation if the bath tends to reach this level, which can be caused for example by a malfunction of the solenoid valve 33 or of the probe 29. the same way the probe 28 detects a lack of water in the installation if the level tends to drop below this probe, also ordering the shutdown of the installation. In this way it is ensured that the level of the bath 5 above the heat generator 18 will always be maintained substantially at the desired value h measured by the probe 29.

 It will be noted that in place of the probe 29 measuring the level of the bath, it is possible to place on the outlet orifice 23 of hot water a flow meter measuring the withdrawal and controlling in correlation the admission of cold water to the solenoid valve 33.

 From the above description, it appears that the construction and the general design of the invention are very simple and also very advantageous, in that they allow to benefit from the particularly good conditions of performance of an installation of the type described operating in submerged combustion. In addition, in such an installation, the volume of the tank ensures instant withdrawal of hot water forming hydro-accumulation without additional installation cost.

The temperature detections at the low level T1, T'1 which can for example be chosen respectively at 850C and 700C also protect the user against excessive cooling of the bath as a result for example of a long period of non-use. In fact, if after a long period of non-use the water tends to cool, first in the lower layers, the probe 26 will detect a drop in temperature, for example below 700C controlling the start-up of the burner and consequently the reheating of the entire bath due to the convection movements that this start-up causes. Of course the adjustment of the bath temperature is done at the desired level by playing on the setting of the probes 30 and 31. Finally if one wants to obtain hot water baths at a temperature above 1000C, for example for production of steam, it suffices to program the probes 30 and 31 in correspondence and to calibrate the valve 8 of the vent 7 to the corresponding pressure.

Claims (7)

 1. A method of operating a hot water or other liquid production installation continuously using a heat exchanger immersed in a tank containing a bath of liquid to be heated, characterized in that in order to satisfy at all times a request while optimizing the operating conditions of the installation  the temperature of the liquid is continuously measured at at least one point 60} of the tank (2) adjacent to the pipe (23) for drawing off the hot liquid,  the liquid level in the bath (4) is continuously measured around an optimal filling level (29) and / or the flow rate of hot liquid withdrawn,  the heating of the installation is controlled when the temperature measured as indicated above descends below a first determined threshold T1 and the heating is stopped when this temperature exceeds a second determined threshold T2 higher than the first,  - The supply of cold water (22) to the bath is controlled when there is a flow of hot liquid drawn off or when the level of liquid in the bath (4) drops below a first determined height and we start; and stop cold water supply when said level rises above a second determined height situated at a level higher than said first height.  2. Method according to claim 1 characterized in that the temperature of the bath is measured at two points (30, 31) located at different levels in the vicinity of the withdrawal pipe (23) of the hot liquid to control the start-up or the '' heating stops according to the temperature levels reached T1, T2, T'1, T'2.  3. Method according to claim 1 or claim 2 characterized in that a high level probe is provided (27) stopping the operation of the installation and in particular its heating and the cold water supply if this level is exceeded  4. Method according to one of the preceding claims, characterized in that a low level probe 28 is provided, stopping the operation of the installation and in particular its heating if the level of the bath drops below this level.  -5. Installation for producing hot water or other liquid, continuously using a heat exchanger immersed in a tank containing a bath of liquid to be heated for the implementation of the method according to one of the preceding claims, characterized in that it comprises interior of a thermally insulated tank (2) at least one submerged heat generator (18) of the type supplied by an air / combustible gas premix burner and the various plant operating control members such as temperature probes temperatures (25,26), level detectors (27,28, 29) and / or control of withdrawal and supply flow.  6. Installation according to claim 5, characterized in that the withdrawal of hot liquid takes place towards one end of the tank in the upper part, the supply of cold liquid taking place towards the opposite end of the tank in the lower part, and the circulation of liquid in the tank being made substantially against the current of the burnt gases in said heat generator (18).  7.Installation according to the claims 5 or 6 characterized in that the tank (2) is closed in leaktight manner by a calibrated valve (8).