EP0278843B1 - Apparatus for chemically cleaning heat generators - Google Patents

Description

The present invention relates to an apparatus for the continuous chemical sweeping of heat generators, of the type in which a liquid chemical reagent is introduced into the hearth of the generator to be treated, whether this generator operates on domestic, heavy or special fuel oil, coal or wood, or whether it is an incinerator of household waste, industrial waste or plant residues.

The systems proposed hitherto in this field are most often extremely simplified, since it involves blowing the product into the flame using compressed air, therefore very irregular spraying. Often, these known systems are devoid of automatisms, so that they require human intervention which is tedious, often irregular in its frequencies of intervention and not devoid of risks of burns due to the manipulation of worn injection systems. at very high temperature.

It has already been recommended, of course, a process for cleaning boilers and heat exchangers in which the injection of the liquid purification agent is carried out, at various time intervals, for durations and with predetermined flow rates, with purging by pressurized air (patent DE-A 2 810 725). However, the recommended injection system is not sufficiently reliable and does not ensure the regularity and homogeneity of the liquid reagent.

The invention therefore aims to provide a continuous chemical sweeping apparatus with an improved system for the injection of liquid reagent and a set of means for automatic cleaning of boilers or similar devices. In accordance with the invention, the apparatus for implementing the abovementioned method is characterized in that it comprises a lance which is surrounded coaxially by a tube for the circulation of a cooling fluid and which opens into the hearth of the heat generator to be treated, means for predetermined supply of the chimney sweeping reagent to the lance in question, means for circulating a cooling fluid between the latter and the tube specified above, and means for supplying predetermined a purge fluid to the lance for injecting sweeping reagent.

Preferably, the means for supplying, in a predetermined manner, the chimney-sweeping reagent to its injection lance comprise a conduit which brings the reagent from a delivery barrel to a hydropneumatic cabinet and an electrical cabinet which controls the passage of the reagent to the end of its injection lance.

The delivery barrel can be connected directly to the hydropneumatic cabinet which distributes the sweeping reagent, but, in an advantageous embodiment of the present invention, it is connected to it by means of a buffer tank whose level of liquid is controlled by a transfer pump and a level controller, this arrangement facilitating the operation of the method according to the invention.

Preferably, the tube which surrounds the lance for injecting sweeping reagent and which is intended for the circulation of a cooling fluid is in turn surrounded by a secondary air nozzle which is another means of cooling the lance, or by a specially fitted sheath.

Advantageously, the lance for injecting the sweeping reagent ends, on the side of the hearth of the generator to be treated, by a nozzle-shaped enlargement having, preferably, a polygonal section whose outer edges are in contact with the circulation tube. cooling fluid, thus leaving a passage for this fluid between it and the internal circular wall of this tube. Any other means of centering the nozzle can however be used.

Preferably, the electrical control cabinet of the device according to the invention is provided with light and / or sound signaling devices indicating the progress of the operations and the faults which may occur, as well as devices to interrupt the injection. chimney sweep reagent in case of an incident. Thus, indicator lights which may or may not be flashing or which may consist of flashing beacons, or alternatively audible signals such as rings or "klaksons" can indicate to the personnel the lack of fluid under pressure of purge and cooling, the lack of sweeping reagent, obstruction of the reagent injection line or non-functioning of the reagent injection pump.

Finally, and also according to the invention, it is preferable that the lance for injecting sweeping reagent and / or the pumps and valves which serve to supply it are made of stainless steel, which increases the reliability of the device. and reduces its maintenance.

• - La figure 1 représente, en vue en coupe axiale, la lance d'injection de réactif de ramonage de l'appareil selon l'invention ; et :
• - La figure 2 montre un diagramme schématique qui indique le mode d'alimentation de cette lance d'injection.

The description which follows will make it possible to understand clearly how the present invention can be put into practice. It should be read against the accompanying drawings, among which:

• - Figure 1 shows, in axial section view, the lance for injecting sweeping reagent of the device according to the invention; and:
• - Figure 2 shows a schematic diagram which indicates the mode of supply of this injection lance.

This lance is designated as a whole by the reference 1 in FIG. 1. As can be seen on the latter, the injection lance or injection pipe itself, 2, is mounted coaxially in a tube 3 which is intended for the circulation of 'a peripheral cooling fluid and which, in turn, is installed coaxially in a nozzle 4 of secondary air. The lance 2, the tube 3 and the nozzle 4 all open into the hearth 5 of the heat generator to be swept through a refractory wall 6, and they are sealed relative to each other at their opposite end by a plug annular 7 interposed between the nozzle 4 and the tube 3 and by an annular plug 8 interposed between this tube 3 and the lance 2. A secondary air inlet 9 opens into the annular space which is thus formed between the nozzle 4 and the tube 3, however that a peripheral cooling air inlet 10 is present on this tube 3, between the plugs 7 and 8, to bring air between it and the lance 2. On the side of the hearth 5, the latter widens into an injection nozzle 11 of polygonal cross section, for example hexagonal, the edges of which are in contact with the cylindrical inner surface of the tube 3, the cooling air thus being able to pass through the free space which is present between two consecutive edges. On the other side, the lance 2 passes through the plug 8 mounted in the end of the tube 3, and its projecting end 12 is connected by any suitable means to a source of sweeping reagent.

Of course, if it is desired to prevent the cooling air circulating between the lance 2 and the tube 3 from entering the hearth 5, it would be possible, without departing from the scope of the present invention, to obstruct the passage between the injection nozzle 11 and the tube 3 and to provide on the latter, in the vicinity of the refractory wall 6, a cooling air outlet.

At this point in the presentation, it should be emphasized that the embodiment which has just been described and which is represented in FIG. 1 assumes that a lance 2 for injecting chimney-sweeping reagent surrounded by it is installed. by a tube 3 intended for the passage of cooling air in a pre-existing secondary air nozzle 4 or in a specially fitted sheath. Without departing from the scope of the invention, such a lance and its cooling tube could be mounted directly through the refractory wall 6 of the heat generator to be swept.

In Figure 2, we find the free end 12 of the lance 2, as well as the inlet 10 of peripheral cooling air, these bodies of Figure 1 being shown here very schematically. They are connected to a hydropneumatic cabinet 20 for distributing the fluids which is supplied, respectively, at 21 by the chimney sweep reagent and at 22 by purge air and cooling under pressure which comes from a tank not shown.

The reagent inlet 21 is connected to a delivery barrel 23, either directly by a conduit 24, or by means of a conduit 25 immersed in a buffer tank 26 which is provided with a level controller and which is supplied with reagent by a transfer pump 28 sucking the reagent from the barrel 23 through a conduit 29. An electrical control cabinet 30, possibly equipped with a beacon 31 indicating incidents, controls the operation of the hydropneumatic cabinet 20 through an electric line 32.

The operating mode of this installation is as follows: at regular intervals, chimney sweeping reagent is injected into the hearth 5 for a predetermined duration and with a flow rate, the injection being produced by the hydropneumatic cabinet 20 from information supplied by the control cabinet 30 where the necessary data have been recorded. The reagent flows either directly from the barrel 23 through the conduit 24, or from the buffer tank 26 through the pipe 25, the level of the liquid in the tank 26 being kept substantially constant by virtue of the transfer pump 28, the starting and stopping are controlled by an operator or automatically with the help of the level controller 27. This reagent then enters the lance 2 through its end 12 and it is injected into the hearth 5 by the nozzle 11.

Between the injection periods of the sweeping reagent, purge and cooling air can be injected into the lance 2 from the inlet 22 of pressurized air, the air flow and the duration of its injection being controlled by the hydropneumatic cabinet 20 as a function of the information recorded in the control cabinet 30.

It is in the same way that peripheral cooling air can be injected periodically at 10 (FIG. 1) between the lance 2 and the tube 3 also coming from the inlet 22 of compressed air under pressure. Finally, the secondary combustion air is introduced at 9, in a conventional manner, between the nozzle 4 and the tube 3.

The control cabinet 30 includes a clock system which starts and stops the injection cycles, as well as several timers each having a precise function, namely, for example, the timing of the pre-ventilation of the periphery of the lance d injection and that of the operating time of the injection pump, the purging time of the latter, and the duration of the periodic flushes with compressed air which ensure the permanent cleanliness of the spray nozzles, these flushes not being moreover not in operation during the course of an injection cycle.

This cabinet 30 also includes the electrical accessories necessary for the proper functioning of the assembly, as well as the light and sound signals indicating the progress of the injection cycle and the faults of the installation.

For its part, the hydropneumatic cabinet 20 for distributing the fluids includes the injection pump, the solenoid valves of the air circuit, the transfer lines which are each provided with non-return valves to protect the solenoid valves and the pump, as well that the safety devices, such as a compressed air presence detector, an overpressure detector in the injection lance, such overpressure possibly coming from an obstruction of the injection nozzle, and a circuit discharge valve pumping.

These various automatisms are well known to those skilled in the art, so they will not be described here in detail.

It is important that the pumps, non-return valves and the injection lance (s) are made of stainless steel. On the other hand, the lances specified above could be cooled by a fluid other than air, and in particular by water, in certain particular cases.

Various variants and various adaptations of the device are possible. For example, a single electrical control cabinet can be used to simultaneously treat several generators in operation and / or when stopped. Such a cabinet, which can be mobile or to be placed fixed on a generator, can be connected to a computer providing the dosing instructions for the chemical reagent (s).

On the other hand, the reagent can be introduced at a other than the hearth, for example in any part of the smoke path, such as the overheating beam or the convection beam or any other zone where the temperature is higher than the evaporation temperature of the liquid reagent. Spraying of the reagent can be done mechanically or using pressurized steam. In addition, the injection lance (s) can be made retractable by means of a jack or any other means.

Finally, it should be noted that, during the implementation of the method and the device according to the present invention, the chemical reagent used, which is for example an aqueous solution of an oxidizing agent, has a film-forming effect on the exchange surfaces. The deposited film acts over time, its action being therefore preventive and curative. Thus, in the subsequent treatments of the same generator, it is possible to use quantities of reagent lower than the stoichiometry.

Claims (8)

1. Apparatus for the continuous cleaning of heat generators by chemical reagent, characterized by the fact that it comprises a lance (2) which is coaxially surrounded by a tube (3) for the circulation of a cooling fluid and which opens into the hearth of the heat generator to be treated, means (20, 30) for leading on a predetermined manner the cleaning reagent to said lance (2), means (22, 10) for circulating a cooling fluid between the latter and said tube (3), and means (22, 12) for leading on a predetermined manner a draining fluid to said lance (2).

2. Apparatus according to claim 1, characterized by the fact that said means for leading on a predetermined manner the cleaning reagent to said lance (2) comprise a duct (24, 25) which leads the reagent from a delivery cask (23) to a hydropneumatic cabinet (20), and a switch cupboard (30) for controlling the flow of the reagent towards the end (12) of the injection lance (2).

3. Apparatus according to claim 2, characterized by the fact that said delivery cask (23) is connected to said hydropneumatic cabinet (20) through a buffer tank (26) the liquid level of which is controlled by a transfer pump (28) and a level controller (27).

4. Apparatus according to any of claims 1 to 3, characterized by the fact that said tube (3) for the circulation of a cooling fluid is coaxially surrounded by a nozzle (4) for secondary air or by a specially arranged sheath.

5. Apparatus according to any of claims 1 to 4, characterized by the fact that said lance (2) for the injection of reagent ends as a nozzle-shaped enlargement (11) in the direction of the hearth of the heat generator to be treated.

6. Apparatus according to claim 5, characterized by the fact that said enlargement (11) presents a polygonal cross-section the outer edges of which are in contact with said tube (3) for the circulation of cooling air, so that a passage is left for this cooling air between itself and the internal circular wall of this tube (3).

7. Apparatus according to any of claims 2 to 6, characterized by the fact that its electric switch cupboard (30) is provided with devices for transmitting light and/or sound signals in order to indicate the course of the operations and the defects which may occur, as well as with devices for interrupting the injection of the cleaning fluid in case of incident.

8. Apparatus according to any of claims 1 to 7, characterized by the fact that said lance (2) and/or the pumps and valves which are used to feed it are made of stainless steel.

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