FR2538093A1 - Method for supplying steam to apparatuses needing such a thermal energy source and installation for implementing such a method - Google Patents

Abstract

Method allowing the distribution of steam to an installation comprising a plurality of apparatuses 2 using this steam as an energy source. According to the invention, each apparatus functioning at the same pressure as the steam generator 1 is connected to the latter by a closed individual circuit comprising, on the one hand, a steam supply tube 8 extending from the boiler 1 to the top portion of the apparatus, and, on the other hand, a tube 10 returning the condensed products produced during the thermal exchange to the generator 1, this circuit being such that the circulation of steam is carried out at low speed, and such that the total head loss in the circuit is as low as possible.

Description

PROCESS FOR THE STEAM SUPPLY OF NEEDED DEVICES
LOCATING SUCH A SOURCE OF THERMAL ENERGY AND INSTALLA
TION IMPLEMENTING SUCH A PROCESS.

 The present invention relates to an improved process for supplying saturated steam to various devices requiring such a source of thermal energy for their implementation. It also relates to an installation implementing this method.

 In the following description, the invention will be described in the case of a laundry-including appliances (dryers, dryers-ironers, presses.

require steam as a source of thermal energy, but it is obvious that this is not limiting and that it could also be used in other technical fields.

 In general, industrial laundries use devices that require the use of saturated steam for their operation.

 Among these devices, a certain number, such as dryers or ironer-dryers are equipped with heat exchangers which therefore cause the production of condensate which should be eliminated. These condensates are returned to the boiler water tank through traps.

 The production of such condensates poses many problems. Indeed, it very often happens that the traps are out of adjustment, which results in an overconsumption of steam at the level of the exchanger which can be very significant. In addition, such installations require constant monitoring since if water accumulates in the exchangers, this can lead to a high reduction in the heat exchange coefficient and, also, an overconsumption of energy.

 However, we have found, and this is what is the subject of the present invention, a simple and effective process which not only makes it possible to obtain significant energy savings in such installations using steam but which, moreover, simplifies the circuits allowing the distribution of steam while reducing the maintenance and monitoring costs of such an installation.

 In general, the method according to the invention allowing the distribution of steam in a facility comprising a plurality of devices using this steam as a source of energy, is characterized in that each device operating under the same pressure that the steam generator is connected to this by an individual closed circuit comprising, on the one hand, a steam supply tube extending from the boiler to the upper part of the appliance (or exchanger) and on the other hand, a return tube which generates the condensates produced during the heat exchange, said circuit being such that the circulation of steam is carried out at low speed, preferably less than ten meters per second and that the total pressure drop in the circuit is as low as possible.

 According to the invention, the return of condensate to the generator will preferably be done directly, without expansion, by simple action of gravity, this being obtained by placing the boiler at a level lower than appliances using steam.

 This condensate return can be achieved either by connecting the device to the boiler directly by the return tube, or, optionally, by connecting the return tube to the steam supply tube on return of condensate to the boiler then against the flow of steam.

Advantageously and in practice
- the height in centimeters to be respected between the boiler level and the low condensate outlets on the exchangers must be greater than the total pressure drop expressed in grams per square centimeter: supply tube to the generator - exchanger + exchanger + possible collector of steam inlet + possible collector biphasic steam condensate outlet
- the condensate return tube to the generator preferably has no counter-slope and, if such a counter-slope is necessary, it has no higher point before it than the condensate outlet height minus the pressure drop total defined previously
- the condensate return tube to the generator is fitted with a valve with very low resistance to opening, a valve located near the generator and which prevents any accidental return of water heated by the condensate return tube. Optionally, such valves can be arranged on each tube connecting the low point of each element of the exchanger to the condensate collector, especially when each element has instantaneous energy needs very different from the others and if the sections used are unsuitable for such accidental needs or if one of the elements is put at atmospheric pressure for more or less time for specific needs (for example external vaporization).

 As said previously, in order that, in accordance with the invention, the pressure drops are reduced to the maximum, very low vapor velocities are used (usually less than 5 m / s), this being obtained by having, for each device or exchanger, a direct connection to the generator.

 In addition, since the steam generator is preferably located at a level lower than that of the operating devices, the tubes thus connected directly to the generator will have to rise, without a counter-slope, to the supply or to the collector exchanger power supply.

 Finally, in order to promote this very low speed of steam, the elbows of the steam supply should preferably have the largest possible radius and not have any roughness on their internal surface.

Of course, a valve, for example a ball valve is arranged on each tube near the device.

The implementation of the method according to the invention will however be better understood thanks to the example of re-realization given below for information but not limitation and which is illustrated by the attached diagrams in which
- Figure 1 schematically illustrates, in perspective, a steam circuit of an appliance supplied in accordance with the invention
- Figure 2 is a plan view of such a circu-it of steam, a variant in the way in which the return of the condensates can be produced being illustrated in dotted lines in this figure.

In the example of implementation illustrated by the appended diagrams, the # boiler (1), of conventional type, is intended to supply saturated steam to a plurality of devices, at least part of which are equipped with exchangers ( 2), such as for example dryers, dryers-ironers, and which operate at the same pressure as the generator (1). This generator (1) can also supply devices operating under reduced pressure or by direct injection (bubbling)
According to the invention, the supply of these various devices with steam is carried out by means of individual circuits, each circuit comprising a steam intake socket (3,435,6) opening at the upper part of the boiler (1) at the -above the water level (7), the return of condensate to said boiler (1) being obtained by individual pipes opening into (3a-4a-5a-6a ...) therein.

In the case of devices operating at reduced pressure, conventional traps are provided on the circuit and the condensates of the devices are brought back to the food cover of the generator to ensure the preheating of the cold water consumed by the bubbling heating devices.
In accordance with the invention, with regard to the devices (2) provided with exchangers and which operate at the same pressure as the generator such); the circuit of. steam consists only of a steam supply tube (8) extending from there. the boiler (1) up to the upper part (9) of the appliance (2) and by a return tube (10) allowing the condensates produced during # heat exchange to be returned to the generator (1) This tube return (10) may be constituted by a separate tube, and is in this case equipped with a check valve system (11) eliminating any accidental return of superheated water from the generator by said return tube (10).

Conventional valves (12-13) are also provided on each of the conduits (8-10).

 According to the invention, the steam circuit is designed so that the circulation of the steam is carried out at low speed, in general less than 10 m / s - and preferably less than 5 M / s, this circuit being such that. the total load part is as low as possible and is less than the height h between the base of the exchanger and the water level (7) in the boiler. In the present case; these conditions are obtained by placing the boiler (1) approximately three meters below the level (14) of the factory, the difference in level between the condensate outlet and the water body (7) being approximately The circuit is constructed in such a way that the tube (8) for supplying steam is connected to the generator (2) without having a slope and the inclination of the tube (10) for return is such that the condensate can drain directly.

 If the condensate return can be carried out by means of an independent tube (10), it can also be envisaged, as shown in FIG. 2, to connect said tube (10) to the supply tube (8) steam. In this case, the condensates will flow against the flow of steam inside the tube (8). Of course, in this case, the check valve (11) provided in the case of a return by a separate tube is eliminated.

 Thanks to such a process, in the two preceding cases, it is therefore possible to use only in a minute manner (pressure drop) the dynamism of the steam which works in a manner similar to a pressure cooker, at the limit static, in two-phase at almost identical pressure in all respects. Then, no energy expenditure is implemented except gravity, to bring about the permanent "rain", caused by the change of state in the exchanger towards the generator, thus allowing the complete return of the condensates to the generator practically without loss of temperature, a significant saving of primary energy implemented permanently of the order of 30 to 35% at least in practice.

 In addition, given the fact that the steam circuit does not include a trap, the drawbacks (losses by yield or malfunction) of these elements are eliminated. It also eliminates the phenomenon of re-vaporization in the food sheets which remain cold as well as the wear of the pumps. Finally, since the condensates are brought back to the generator at a temperature close to that of steam, it is possible, for a given installation, to reduce the capacity of said generator and, consequently, to reduce the price of said installation.

 In summary, in addition to a basic saving of the order of 25% of the energy used, such a method eliminates the sometimes high additional energy losses resulting from the malfunction of the state of the traps. Finally, this process simplifies and limits maintenance and monitoring problems.

 Of course, the invention is not limited to the embodiment described above, but it covers all the variants produced in the same spirit. Thus such a process can be adapted, certainly leading to lower savings, in the case of large and extensive installations for which the pressure drops to be taken into account could cause high level differences-between the exchangers and the generators .

 In these cases, it is possible, while retaining the same general characteristics as those set out above, to limit the level difference by providing, on each pressure network, at a low point.

unique for each of them, a small condensate storage tank, with an electro-level (top and bottom) after which, in the bottom part, a small centrifugal pump will be provided on the condensate return tube allowing the said condensates to be raised.

In this case, the condensate return tubes will open into the generator, preferably above the level of said generator. The tubes will be fitted with non-return valves and the same type of valve must isolate, on the condensate return side, each exchanger. It can even be envisaged, in this case, to bring back to the same generator, condensates coming from different pressure networks.

 This variant of recycling, independently of the cases where the boiler room cannot be installed at a sufficiently low level compared to the apparatus, can also be used in the case of existing conventional installations, without significant modification of plumbing, by eliminating the steam traps. and replacing them with one or more pumps each preceded by small electro-level tanks. Of course, in this adaptation, the thermal energy savings achieved are lower than when working by completely fulfilling the conditions according to the invention, but a significant saving is nevertheless obtained compared with a traditional installation with steam traps. condensate return on the generator food cover.

 Compared to conventional installations, in which the exchangers are fitted with traditional steam traps, in addition to the savings made in normal operation, a much faster heating-up and a better production yield of the apparatus are also obtained.

Claims (6)

 1 / Method allowing the distribution of steam in an installation comprising a plurality of devices (2) using this steam as a source of energy, characterized in that each appliance operating at the same pressure as the steam generator (1) is connected to the latter by an individual closed circuit comprising, on the one hand, a steam supply tube (8) rising from the boiler (1) to the upper part of the appliance and, d on the other hand, a return tube (10) to the generator (1) of the condensates produced during the heat exchange, said circuit being such that the circulation of vapor is carried out at low speed and that the total pressure drop in the circuit be as low as possible.  2 / A method according to claim 1, characterized in that the circulation of steam in the circuit is carried out at a speed less than 10 m / s and preferably less than 5 m / s.  3 / Method according to one of claims 1 and 2, characterized in that the return of condensate to the generator (1) is done directly, without expansion, by simple action of gravity, the boiler (1) being disposed at a -lower level for appliances (2) using steam.  4 / A method according to claim 3, characterized in that the condensate return tube (10) is independent and is connected directly to the boiler (1).  5 / A method according to claim 3, characterized in that the condensate return tube (10) to the boiler (1) is connected to the supply tube (8), the return being against the flow of steam.  6 / A method according to claim 4, characterized in that the return tube (10) is provided with a non-return valve (13).