Industrial drying installation using drying fluid

Abstract

A drying system for a wet product using a drying fluid, comprising several elements: a drying chamber (1), at least one boiler (7), at least one compressor (11), at least one injection heat exchanger (12), and at least one recovery heat exchanger (6). Figure for the abbreviated version: Fig. 1

Description

Title of the invention: Industrial drying installation using drying fluid. Field of the invention

[0001] The invention relates to the field of drying wet products using a drying fluid in industry. It potentially covers any drying installation that can be implemented, such as spray dryers, belt dryers, heating cylinders, ovens, drying furnaces, flash dryers, fluidized bed dryers, paddle dryers, screw dryers, silos, rotary drums, or tunnel dryers. These dryers are found in various industrial sectors, including food processing, chemicals, paper and cardboard, and non-metallic materials. This installation uses, for example, air as the drying fluid (a drying fluid is defined as a fluid that allows the evaporated water to be removed from the dryer and provides heat to the dryer to facilitate this evaporation), which serves as a transport medium for the evaporated water as well as a means of supplying heat to the dryer.

[0002] The invention is more particularly aimed at optimizing energy consumption in such installations by recovering heat from the drying fluid exiting (mists) of the drying chamber in particular, for reinjection into the intake air circuit or into said drying chamber.

[0003] In the context of this description, the term "approximately" preceding a numeric value means that the value can be changed by plus or minus 10%. In the specific case of a numeric value being an interval limit, the term "approximately" means that the lower limit can be decreased or increased by 10%, or the upper limit can be decreased or increased by 10%. It is also possible to omit the term "approximately" preceding a numeric value. Prior state of the art

[0004] Drying systems are very common in industry and represent a significant portion of industrial energy consumption: 10 to 20% of total industrial energy consumption in industrialized countries (according to the literature "Modern Drying Technology", Volume 4 by Evangelos Tsotsas and Arun S. Mujumdar - 2007). They generally consist of a drying chamber through which the wet product to be dried passes. A drying fluid, usually hot, flows through this chamber and absorbs moisture from the wet product. This moisture-laden drying fluid, commonly referred to as vapor, is then discharged from the chamber. This vapor has a relatively high temperature and humidity level.

[0005] The energy loss resulting from the temperature and humidity in the vapors is therefore easily understood, as is the corollary to the energy consumption required to ensure the effective evaporation of the moisture present in the product to be dried. It is indeed known that the enthalpy of vaporization at atmospheric pressure Ahvap is on the order of 630 kWh per tonne of water evaporated, requiring, in such a configuration where the vapors are simply released into the atmosphere, an energy consumption 2 to 4 times greater (according to the literature "Drying processes in industry", ADEME, CETIAT, 2017), often using fossil gas or coal, possibly via a heat transfer fluid such as steam, superheated water or hot water.

[0006] In other words, this mode of operation is a source of energy and exergetic inefficiency.

[0007] To reduce this consumption, solutions exist for recirculating some of the vapors back into the drying fluid inlet circuit, thereby transferring some of the relative heat from said vapors. While this recirculation does provide some energy savings, these savings are quite limited.

[0008] Drying installations combining the introduction of hot air, similar to that described previously, and heating cylinders located within the heating chamber have also been described. These heating cylinders are typically heated by steam or hot air.

[0009] Other solutions allow heat to be recovered by preheating the inlet drying fluid with the vapors, via an air / vapor heat exchanger.

[0010] Recently, there has been a growing interest in heat recovery from vapors by means of high temperature heat pumps (whose condenser has a temperature below 100°C), or even very high temperature heat pumps (whose condenser has a temperature above 100°C), for reinjection into the intake air or into other means of heat input, for example injector exchangers, in the dryer (for example heating cylinders).

[0011] Also, some manufacturers are working on closed loop drying systems, in which a heat pump allows the water from the vapors to condense at the heat pump evaporator, and then to reheat the dried vapors via the heat pump condenser.

[0012] Finally, superheated steam dryers make it possible to approach the minimum energy required for changing the drying fluid, and can be coupled with mechanical steam compressors to approach the minimum exergy required for the drying process, with consumption below 200 kWh / tonne of water evaporated. These types of dryers and configurations are the most efficient, but their intrinsic characteristics limit their scope of application. particularly with regard to the thermosensitivity of the products to be dried and the management of sealing.

[0013] It follows from these findings, particularly in a context where energy is becoming a particularly high expense item for manufacturers and where industry is strongly encouraged, or even forced, to reduce its carbon emissions to curb global warming, that there is an increasingly pressing need for rationalization of such drying facilities and more particularly for reducing energy consumption at the source.

[0014] This is the subject of the present invention. Brief description of the invention

[0015] To this end, the invention relates to a drying installation by means of a drying vector or fluid, and in particular by air, of a wet product, said installation comprising a drying chamber within which the wet product to be dried and the drying fluid ensuring the drying pass, this chamber being provided with at least one circuit for the introduction of said incoming drying fluid, and at least one evacuation of said drying fluid charged with moisture resulting from the exchange of water and energy with the wet product to be dried, referred to as vapors.

[0016] According to the invention, the installation comprises: - at least one boiler operating with a working fluid (typically water), this boiler being configured: • to recover heat from one or more heat sources consisting of the moisture-laden drying fluid (vapors) passing through the moisture-laden drying fluid exhaust, this heat recovery being carried out using a heat exchanger, and • to generate steam using the heat thus recovered, the boiling temperature of the working fluid within the boiler being adapted by means of the pressure in the boiler to the temperature of the heat source(s); - at least one means suitable for initiating the operation of the boiler(s) by supplying heat to the latter(s), - at least one compressor, capable of increasing the pressure, and therefore the temperature, of the steam generated in the boiler; - at least one injector exchanger capable of condensing the vapor from the compressor, this at least one injector exchanger being positioned within the inlet drying fluid introduction circuit, i.e. upstream of the drying chamber, and to ensure the heating of this drying fluid upstream of the drying chamber; - possibly, at least one condensate collector from the condensation of steam in said at least one injection exchanger, these condensates being returned to said at least one boiler.

[0017] In one embodiment, within the boiler, the working fluid is at a pressure less than approximately 1 bar, preferably less than approximately 0.9 bar, preferably less than 0.8 bar, preferably less than approximately 0.7 bar, preferably less than 0.6 bar, preferably less than approximately 0.5 bar, preferably less than 0.4 bar, preferably less than approximately 0.3 bar, of preferably less than 0.2 bar, preferably less than approximately 0.1 bar. In the For the purposes of this description, "Bar" means "Absolute Bar".

[0018] In one embodiment, said drying fluid is chosen from the group consisting of air, nitrogen, carbon dioxide, and mixtures thereof.

[0019] Depending on the situation, the initial heat input within the boiler(s) occurs directly in said boiler(s) by external input, or indirectly by heating the inlet drying fluid by an external source during the initiation of heat recovery.

[0020] In other words, the invention mainly consists of recovering the heat contained in the vapors and possibly in other heat sources present in the environment of the dryer, and, from this heat, generating steam within the boiler, said steam undergoing an increase in its pressure and temperature by means of a compressor so as to supply an injector exchanger to heat the drying fluid upstream of the drying chamber.

[0021] In the sense of the invention: - a boiler is defined as a reservoir containing a working fluid in a liquid / vapor phase equilibrium in which a heat input at the bottom allows the working fluid to boil; - a working fluid is defined as a fluid that carries heat from a source to a sink, through phase changes; - a heat recovery exchanger is defined as equipment that allows heat to be taken from the dryer's exhausts, in this case the vapors and / or from any other source; - an injection exchanger is defined as equipment that allows heat to be supplied directly to the product to be dried or via the drying fluid.

[0022] According to a variant of the invention, the drying chamber can itself integrate additional heat supply means, called additional injector exchangers, supplied with steam from the previously mentioned compressor.

[0023] These means of additional heat supply are classically heating cylinders, double walls of drying chambers, screws, pallets or even steam radiants.

[0024] In order to ensure the start of the boiling operation within the boiler, the means for initiating the operation of the boiler(s) by supplying heat consists of a heat source, that is to say, an energy flow from which additional heat can be recovered. This additional heat source is located in the boiler, in the inlet drying fluid, or even in the chamber itself, and may consist of any means of supplying heat, and in particular resistance or induction technology, by at least one electric immersion heater, by at least one heat exchanger supplied by a heat transfer fluid such as hot water, thermal oil, or steam, or by an external heat source available at start-up.

[0025] Furthermore, this additional starting heat source can also serve as a backup in the event of a mechanical, electrical, pneumatic, automation, or hydraulic failure in the installation, or as a supplementary source, assuming, for example, that the system is sized to cover 80% of the dryer's operating conditions. Consequently, the installation may also include a device for evacuating the boiler to enable the boiling process to begin within it.

[0026] In order to optimize the drying system of the invention, the compressor(s) are regulated according to the drying requirements defined by the drying kinetics of the different products: the system allows for adjustment of the steam condensation temperatures by varying the compression ratios of the compressor(s). This makes it possible to inject steam at different pressure levels for the same injection exchanger, depending on the product's drying requirements. This is achieved through measurements that allow for estimation of the drying kinetics in order to prevent over-drying. This regulation thus limits the electrical energy consumption required for compressor operation; when the drying temperature requirement is lower, the steam is compressed to lower pressure levels.

[0027] To this end, the electric motor equipping each compressor has a frequency converter that allows the vapor pressure setpoint at the compressor outlet to be regulated. This substantially limits electrical consumption by avoiding excessively high and unnecessary pressures. Thus, an online measurement of the product's moisture content or temperature variation, for example by infrared or thermal imaging, allows for monitoring the drying kinetics of the product in question and avoid over-drying by defining the appropriate pressure / temperature levels.

[0028] Furthermore, to facilitate the operation of the boiler, the installation may also include a heat pump (HP) designed to raise the temperature level obtained by the heat exchanger located in the steam discharge, particularly if the pressure at the obtained temperature is not achievable under satisfactory technical conditions. In the theoretical ideal, the evaporator of the heat pump is positioned directly in the steam flow, and the condenser in the boiler.

[0029] Nevertheless, a low temperature recovery loop (LT loop) to supply the evaporator of the heat pump can advantageously be implemented to take advantage of the calories present on other heat sources in the installation, and which are thus recovered on this LT loop.

[0030] A water loop (or glycol water) on the condenser side may also be of interest to facilitate the use of heat and / or the recovery of the latter on the same high temperature recovery loop (HT loop).

[0031] According to a particular closed-loop configuration of the invention, the intake drying fluid is derived from the vapors, after drying by means of a recuperating exchanger and then reheating by means of an injecting exchanger.

[0032] In other words, the installation may include a closed-loop configuration to allow for total or partial recycling of the vapors, where necessary by implementing means for filtering said drying fluid and managing waste heat. Brief description of the figures

[0033] The manner in which the invention can be implemented and the resulting advantages will be more apparent from the following examples of implementation, given by way of example and not limitation, in support of the attached figures.

[0034] Fig. 1 is a schematic representation illustrating the basic drying installation of the invention.

[0035] The [Fig.2] is a variant of the [Fig.1] incorporating an additional injector exchanger integrated into the drying chamber itself.

[0036] The [Fig.3] is a variant of the [Fig.2] comprising two injector exchangers integrated within the drying chamber.

[0037] Fig. 4 illustrates a more complex installation for large evaporative capacity dryers, incorporating several (n) drying chambers mounted in series, equipped with their respective drying fluid intake system.

[0038] Figure 5 illustrates a closed-loop drying installation, as described in the last paragraph of the prior art, implementing the principle of the invention.

[0039] [Fig.6] illustrates a variant of [Fig.4] in closed loop mode.

[0040] Figure 7 schematically illustrates a particular embodiment of the invention implementing a low-temperature (LT) loop and a high-temperature (HT) loop, in which the low temperatures of the LT loop necessitate the use of a heat pump to raise the temperature levels of the heat source. The evaporator of the heat pump is located on the LT loop and the condenser of the heat pump is located on the HT loop.

[0041] Fig. 8 illustrates a variant of Fig. 3 incorporating a first stage of pressure rise achieved by thermocompressors.

[0042] Fig.9 illustrates a variant of Fig.7 with water storage on the HT loop.

[0043] Fig. 10 illustrates a variant of Fig. 7 with heat recovery from several heat sources on the BT loop.

[0044] Fig. 11 illustrates a variant of Fig. 3, in which the operation of the dryer with the selected compressors requires the creation of inertia on the steam network to ensure the instabilities of steam consumption of the dryer, ensured by a steam accumulator.

[0045] Fig. 12 illustrates a variant of Fig. 3 with the use of a thermocompressor to have steam at an intermediate pressure level, between the outlet pressure levels of the two mechanical compressors of the installation.

[0046] Fig. 13 illustrates a variant of Fig. 3 with water injection into the superheated steam to desuperheat - to bring it back to the state of saturated steam - said steam downstream of the compressors which superheat the steam, in order to convey the steam at a temperature close to the saturation temperature.

[0047] Fig. 14 illustrates a variant of Fig. 7 with heat recovery from several heat sources on the HT loop.

[0048] Fig. 15 illustrates a variant of Fig. 7 with a recovery of the heat from the BT and HT loops on the drying air supply.

[0049] Fig. 16 illustrates a variant of Fig. 3 with heat recovery by exchanger on the vapors for preheating drying fluid. Detailed description of the invention

[0050] The various figures schematically illustrate different variants of the installation according to the invention. As mentioned in the preamble, this installation can be implemented for all types of dryers (except superheated steam dryers) and requires adaptation to meet the needs of the wet products to be dried.

[0051] The implementation of the present invention coupled with other drying methods (infrared, by dielectric losses such as microwaves or high frequencies) is possibly conceivable in order to ensure the best performance of the whole and to meet the drying needs of the products.

[0052] The invention therefore relates to a drying installation using a drying fluid, for a wet product comprising a drying chamber (1) within which the wet product to be dried (2) and the drying fluid ensuring the drying pass, said chamber comprising at least one inlet circuit (4) for the inlet drying fluid, and at least one outlet (5) for said drying fluid laden with moisture resulting from the exchange of water and energy with the wet product to be dried, characterized in that the installation comprises: - at least one boiler (7) operating with a working fluid, preferably water, configured: • to recover heat from one or more heat sources consisting of the moisture-laden drying fluid passing through said at least one outlet (5) by means of a heat recovery exchanger (6); and • to generate steam using the heat thus recovered, the boiling temperature of the working fluid being adapted by means of the pressure in the boiler (7) to the temperature of the heat source(s), possibly by means of an intermediate heat transfer loop; - at least one means suitable for initiating the operation of said heat recovery by input of third-party heat; - at least one compressor (11) capable of increasing the pressure, and therefore the temperature, of the steam generated in said (said) boiler(s) (7); - at least one injector exchanger (12) capable of condensing the vapor from said at least one compressor (11), positioned within the inlet circuit (4) of the inlet drying fluid, and of ensuring the heating of the latter upstream of the drying chamber (1).

[0053] In one embodiment, the wet product drying installation using a drying fluid according to the invention is characterized in that it further comprises at least one condensate collector (19) resulting from the condensation of the steam in said (said) injector exchanger(s) (12), said condensate being returned to said or said boiler(s) (7).

[0054] In one embodiment, the wet product drying fluid installation according to the invention is characterized in that said at least one boiler (7) operates with a working fluid being water.

[0055] In one embodiment, the wet product drying fluid installation according to the invention is characterized in that said at least one boiler (7) operates with a working fluid at a pressure less than about 1 Bar, preferably less than about 0.9 Bar, preferably less than 0.8 Bar, preferably less than about 0.7 Bar, preferably less than 0.6 Bar, preferably less than about 0.5 Bar, preferably less than 0.4 Bar, preferably less than about 0.3 Bar, preferably less than 0.2 Bar, preferably less than about 0.1 Bar.

[0056] In one embodiment, the wet product drying fluid installation according to the invention is characterized in that the heat input within the boiler(s) (7) occurs directly in said boiler(s), or indirectly through a low temperature recovery loop (25).1) which carries heat from at least one heat recovery exchanger (6), said low temperature recovery loop comprising one or more heat sources, said heat sources being selected from the group comprising additional heat recovery exchangers (27) on humid air, fumes, flash vapors, wastewater or industrial water requiring cooling, condensers of chillers, of an urban heating network, hot water from a geothermal borehole, of a solar thermal power plant, of a vacuum steam condenser inserted in a cogeneration steam cycle, of cooling water from electric motors, of voltage transformers, of data storage centers or electrical cabinets, of a compressed air plant, of a greasing or lubrication plant or of any other heat source.

[0057] In one embodiment, the wet product drying fluid installation according to the invention is characterized in that it further comprises a heat pump (8) capable of raising the temperature levels obtained at the level of the heat exchanger (6.1) to supply the boiler (7) or a high temperature recovery loop (25.2), said high temperature recovery loop comprising one or more heat sources, said heat sources being selected from the group comprising complementary heat exchangers (27) on humid air, fumes, flash vapors, wastewater or industrial water requiring cooling, from an urban heating network, hot water from a solar thermal power plant, cooling water from electric motors, from a compressed air power plant, or from any other heat source.

[0058] In one embodiment, the drying installation using a drying fluid for a wet product according to the invention is characterized in that it further comprises means for supplementary heat supply (14; 14.1; 14.2) positioned within the drying chamber (1), supplied with steam, consisting of injector exchangers complementary elements which are preferably chosen from the group consisting of heating cylinders, double walls of the drying chamber, screws, pallets and / or steam radiants.

[0059] In one embodiment, the wet product drying fluid installation according to the invention is characterized in that the means suitable for initiating the operation of said heat recovery by input of third heat is an additional start-up heat source chosen from the group comprising an electrical induction technology, electrical resistances, direct combustion or exchangers supplied by a heat transfer fluid such as hot water, superheated water, thermal oil, hot air, fumes or steam.

[0060] In one embodiment, the wet product drying fluid installation according to the invention is characterized in that the compressor(s) (11) are regulated according to the drying requirements defined by the drying kinetics of said wet product to be dried.

[0061] In one embodiment, the wet product drying fluid installation according to the invention is characterized in that it is equipped with a degassing device (35) to remove air that could enter the water / steam installation and a working fluid make-up device in a condensate collector (19).

[0062] In one embodiment, the wet product drying fluid installation according to the invention is characterized in that said auxiliary working fluid added in the condensate collector (19) is derived from the condensed water (23) in the vapors, possibly after water treatment as required.

[0063] In one embodiment, the wet product drying installation using a drying fluid according to the invention is characterized in that it further comprises a vacuum device (9) for the boiler(s) (7) in order to facilitate the start of the boiling operation.

[0064] In one embodiment, the wet product drying fluid installation according to the invention is characterized in that it further comprises a hot water storage tank (26) in communication with the high temperature recovery loop, intended to ensure a continuity of heat supply to said installation.

[0065] In one embodiment, the wet product drying fluid installation according to the invention is characterized in that it further comprises a steam accumulator (28), intended to respond to sudden variations in steam demand.

[0066] In one embodiment, the wet product drying fluid installation according to the invention is characterized in that it comprises two compressors, and in that it further comprises at least one thermocompressor (30) supplied with steam from the steam from the first compressor (11.1) and from the steam from the second compressor (11.2), so as to supply the injector exchanger(s) (14.1, 14.2) with steam at a pressure intermediate between the pressures of the steam collector (29) and the steam at the outlet of the second compressor (11.2).

[0067] In one embodiment, the wet product drying fluid installation according to the invention is characterized in that it further comprises desuperheaters (31.1, 31.2) capable of injecting water into the steam at the outlet of the compressors (11, 11.1, 11.2).

[0068] In one embodiment, the wet product drying fluid installation according to the invention is characterized in that it comprises a first compression stage consisting of one or more thermocompressors (24) located upstream of the compressor(s) (11; 11.1, 11.2).

[0069] In one embodiment, the wet product drying fluid installation according to the invention is characterized in that it comprises a heat exchanger (38) on said moisture-laden drying fluid resulting from the exchange of water and energy with the wet product to be dried, allowing the preheating of the inlet drying fluid.

[0070] In one embodiment, the wet product drying installation using a drying fluid according to the invention is characterized in that it operates in a closed loop, and in that the inlet drying fluid (4) is derived from the extraction drying fluid (5) of the drying chamber (1), which is dried by means of at least one recuperating exchanger (6), then reheated by means of at least one injecting exchanger (12).

[0071] The invention also relates to such a drying installation using a drying fluid for a wet product, comprising a plurality of drying chambers 1, 2, ..., n, connected in series, the most upstream chamber (1.1) receiving the product to be dried having the highest degree of moisture, and the most downstream chamber (ln) receiving the product to be dried (2) after transit through the upstream chambers, in which: - the inlet drying fluid (4.i) conveyed within the enclosure (li) upstream relative to the direction of progression of the wet product to be dried comes from the moisture-laden drying fluid (4.i+l) from the drying enclosure (l.i+1) mounted immediately downstream of said upstream enclosure after heating by an injector exchanger (12.i), i being an integer between 1 and n-2, - the steam from the boiler(s) and whose pressure (and therefore temperature) has been increased using the main compressor (11.1), is delivered primarily to an injector exchanger located in the drying fluid introduction circuit of the most upstream chamber (1.1), - part of this vapor is subjected to compression at an additional compressor (11.2) to convey a higher pressure vapor to an injection exchanger (12.1) provided within a drying fluid introduction circuit of said downstream chamber with possible addition of new drying fluid for mixing (20.1); this compression process to the downstream chamber being likely to occur 1, 2, ..., n-2 times, - the drying fluid of the chamber (1.n-1) is derived from the drying fluid exiting the chamber (ln), preheated by the hot product to be dried from the chamber (ln-1), which has cooled in the chamber (ln) by transferring its heat to the drying fluid and possibly drying the drying fluid (4.nl) by hygroscopicity of the product, - and the inlet drying fluid of the enclosure (ln), the most downstream, consists of dry drying fluid, possibly of vapors dried by the recuperating exchanger (6) in the case of closed loop operation on the drying fluid.

[0072] In one embodiment, the wet product is selected from the group consisting of strip products, for example paper, cardboard or textiles; pasty products, for example sewage sludge, process sludge, paint sludge, concentrated paint, moist cakes, infant flours, potato flakes, yeasts, gelatins or pulps; powdered or granular products, for example zinc oxides, metal oxides, silicon, cocoa, powdered milk, instant flours, lactose, pharmaceutical powders, paint powders, detergent powders, pigments, sand, sugar, starch powders, coffee, yeasts, oxides, proteins, wood particles, dyes, wood pellets, wood particleboard, carbon black, potassium chloride, talc, barley, peas Protein crops, sunflowers, wheat, corn, legumes,spelt, soybeans, rapeseed, oats, rice, beans, millet, buckwheat, quinoa, flocculants or powdered milk, products in pieces, for example vegetables, cereals, molded objects, ceramics, tiles, food products, plasterboard, hardwood or softwood, fries, pasta, animal feed, biscuits, bricks, roof tiles, latex mattresses or foams, fibrous products, for example wool, cotton, wood fiber, sawdust, paper pulp, herbs and medicinal plants, alfalfa or coconut, flat products, for example, insulation panels, wood or particle boards, and liquid products, for example PVC latex, aqueous solutions, milk or juices.

[0073] In one embodiment, the temperature of introduction of the drying fluid into the drying chamber is between about 40°C and about 200°C, preferably between about 40°C and about 150°C, preferably between about 40°C and about 100°C, preferably between about 40°C and about 80°C, preferably between about 40°C and about 60°C.

[0074] In one embodiment, the maximum pressure of the working fluid being water is between 0.2 and 20 Bars, preferably between about 0.2 Bar and about 15 Bars, preferably between about 0.2 Bar and about 10 Bars, preferably between about 0.2 Bar and about 6 Bars, preferably between about 0.2 Bar and about 3 Bars, preferably between about 0.2 Bar and about 1.5 Bars.

[0075] In one embodiment, the relative humidity in the drying chamber is between about 1% and about 90%, preferably between about 10% and about 90%, preferably between about 20% and about 90%, preferably between about 40% and about 90%, preferably between about 60% and about 90%, preferably between about 80% and about 90%.

[0076] Within [Fig. 1], the drying chamber (1) is intended to receive a wet product to be dried (2). Thus, the wet product (2) enters the chamber, undergoes drying within the chamber (1), and exits it in dry form (3).

[0077] Within this drying chamber (1), hot drying fluid is introduced via an inlet circuit (4). After exchange within the drying chamber resulting from the phenomenon of convection and mass transfer between the hot drying fluid and the wet product to be dried, drying fluid heavily laden with moisture, also referred to as vapors, exits said chamber through an outlet (5).

[0078] According to the invention, the vapors (5) emerge at a relatively high temperature and humidity, and part of the heat of said vapors (5) is recovered by means of a recuperative exchanger (6) by recovering the energy in the form of sensible heat as well as the latent energy of the vapors by condensing water, from the water of the evaporated product, which can be recovered (23), this heat being transferred to the working fluid in the boiler (7).

[0079] This working fluid can be demineralized or softened water. The heat supplied via the heat exchanger (6) will heat the working fluid to the saturation pressure temperature in the boiler. This working fluid, in liquid / vapor phase equilibrium in the boiler, thus generates steam at the saturation temperature.

[0080] In one embodiment, the working fluid is water treated by demineralization, softener, osmosis and mixtures thereof.

[0081] In one embodiment, the working fluid is water.

[0082] In one embodiment, the working fluid is water refrigerant fluid R718.

[0083] However, and in order to facilitate the boiling process of the working fluid within the boiler (7), a temperature rise may be necessary to limit the boiler depression.

[0084] This temperature rise can be achieved by a heat pump (8) (see [Fig.7]), taking heat from the evacuation (5) of vapors, possibly by means of two recovery loops ((25.1) for the BT loop and (25.2) for the HT loop), made up for example of water or glycol water.

[0085] Cold start-up of the installation requires an additional heat source to initiate system operation. This heat source can be provided by: - by a high-pressure steam boiler which initiates drying by injecting steam into the injection exchangers, and thus starts heat recovery before shutting down in favor of recovery; - by an energy source in the boiler; - by the installation itself which draws calories from heat recovery exchangers other than those on the dryer vapors which can have calories available when the dryer is not in operation, which represents an additional advantage of achieving multi-source recovery.

[0086] Furthermore, still with the same objective of initiating the boiling process of the working fluid within the boiler (7), the pressure may need to be adjusted to the temperature of the heat source. In this regard, the boiler can be connected to a vacuum device (9) (see [Fig. 11]) to lower the pressure within the boiler during the start-up phases. This device is subsequently switched off. The compressor (11) associated with the injection heat exchanger (12) ensures pressure maintenance in the boiler during normal operation, preventing excessive energy input through the heat recovery heat exchanger (6).

[0087] In stabilized operation, the steam produced in the boiler (7) is conveyed (10) to a main compressor (11) intended to increase the pressure, and therefore consequently the temperature of the steam thus generated, according to the well-known laws of thermodynamics.

[0088] This vapor, thus compressed, is conveyed superheated to an injector heat exchanger (12) positioned in the inlet circuit (4) of the drying fluid, in order to raise its temperature. It should be noted that, for reasons of achieving higher temperatures on the drying fluid by counter-current heat exchangers Currently, utilizing this superheat can be advantageous. However, it may require larger heat exchange surfaces due to the absence of condensation, which limits the heat transfer coefficients in the exchanger. This phenomenon is partially offset by the larger pinch points in the exchanger. Thus, once boiling has begun in the boiler (7), the only significant electrical consumption is for powering the main compressor (11), the regulation of which will be discussed below.

[0089] The compressor (11) associated with the injector exchanger (12) and with a pressure relief or purge device (37, 37.1, 37.2) ensures the maintenance of pressure in the boiler during normal operation.

[0090] The liquid condensates, possibly subcooled, have fallen below the saturation temperature of the working fluid resulting from the heat exchange occurring at the level of the injector exchanger (12) placed within the intake circuit (4) are returned (13) to the boiler (7).

[0091] The condensed water (23) in the heat recovery exchanger (6) can be reused in the installation after any necessary water treatment, such as pH adjustment, Biological Oxygen Demand (BOD), or Chemical Oxygen Demand (COD). This recovered water (23) helps limit industrial water consumption and is therefore an additional advantage of the invention, particularly relevant in a context of increasing water resource scarcity. Figure 2 illustrates a first variant of the drying installation according to the invention.

[0092] In this, the drying of the wet product (2) in the drying chamber (1) occurs not only due to the introduction of the drying fluid, as illustrated in [Fig.1], but also by at least one additional heat supply means (14) positioned inside the drying chamber (1).

[0093] For example, such a supplementary heat input source consists of one or more heating cylinders, the heating of which is ensured by steam. And in fact on [Fig.2], part of the steam, produced by the boiler (7), and whose pressure is increased by the compressor (11) is conveyed into an injection exchanger to be condensed (14), then is subcooled in another subcooler exchanger (15) preheating the drying fluid upstream of the injection exchanger (12), the condensate joining (16) the supply circuit (13) of the boiler (7).

[0094] Figure 3 illustrates a variant of the installation shown in Figure 2. In this variant, two injector heat exchangers (14.1) and (14.2) are shown, providing additional heat input, positioned within the drying chamber (1). Part of the steam from the compressor (11.1) is introduced at the first from these additional injection heat exchangers (14.1), is diverted and sent to a secondary or supplementary compressor (11.2), supplying the second supplementary heat supply means (14.2). This secondary compressor (11.2) is designed to further increase the pressure (and therefore the temperature) of the steam, compared to that supplying the first supplementary heat supply means (14.1). Indeed, in the example described, this second heat exchanger (14.2) is located downstream of the first heat exchanger (14.1) in the direction of the product flow by design, due to the actual progression of the wet product within the chamber, a configuration in which a higher temperature heat source is required downstream for the purpose of optimizing the drying process. The condensates from the injection heat exchangers (14.1) and (14.2) are returned to a tank (19), then subcooled in a subcooler heat exchanger (15) preheater of the inlet drying fluid before being returned (16) to the boiler feed circuit.

[0095] Figure 4 illustrates yet another embodiment of the invention. In this embodiment, the drying chamber is in fact subdivided into a number of chambers (1.1) to (ln), mounted in series with each other, each of said chambers being supplied with hot drying fluid, as described previously.

[0096] However, in this embodiment, the evacuation of vapors (5), i.e., in this case, the drying fluid with the highest moisture content, only occurs at the level of the most upstream chamber (1.1). For an integer i between 1 and n-2, the chamber (11) is supplied with drying fluid (4.i) from the heat exchange and water with the product to be dried from the chamber immediately downstream (1.i+1), and optionally with additional inlet drying fluid (20.i). This drying fluid undergoes a temperature increase by means of injector exchangers (12.i), which are themselves supplied with steam. The injector exchanger (12.1) of the inlet circuit (4.1) of the most upstream chamber (1.1) is supplied with steam from the main compressor (11.1). The injector exchangers (12.i) Downstream intake circuits are supplied with steam taken from the upstream circuit, and subjected to a pressure (and therefore temperature) increase by means of additional compressors (1 li). In fact, the further the wet product to be dried progresses within the chambers, the hotter and drier the drying fluid becomes. The most downstream chamber (ln) is supplied with fresh air (4.n), i.e., ambient air, and the preceding chamber (ln-1) is supplied with slightly humid air heated by the product passing through chamber (ln); the product cools upon contact with the fresh, dry air and may absorb moisture from the air according to its hygroscopic capacity and dry matter content.

[0097] It should be noted that the configuration shown in [Fig.4] could also include additional injector exchangers (14.i) in order to improve the supply of heat into the drying chambers, as shown in [Fig.3].

[0098] Figure 5 illustrates the adaptation of the invention to a loop drying installation closed. In this configuration, the heat recovery exchanger (6) is installed on the vapor circuit to dry the vapors by removing the water from the product (23). The dried vapors are recirculated to the injection exchanger (12) to generate hot inlet drying fluid (4) to supply the drying chamber (1).

[0099] This configuration potentially implies excess heat depending on the drying temperature regimes, compressor performance, product heat capacity, and system losses. This excess heat, called waste heat, can be recovered in a waste heat exchanger (21) so that the condensate can be redirected to the boiler (7).

[0100] This configuration is particularly interesting with regard to the evaporated water of the product, which is thus recovered at 100% as well as the absence of discharges in the form of vapors, only in liquid form.

[0101] Figure 6 illustrates an application equivalent to the operation of Figure 4. with closed loop recirculation of the drying fluid to reuse the dried vapors (5) in the recovery exchanger (6) to be redirected to the drying fluid inlet (4.n) of the downstream enclosure (ln).

[0102] Figure 7 illustrates a variant of the invention incorporating means for raising the temperature and pressure of the working fluid in the boiler (7).

[0103] These means consist of a heat pump (8). The latter makes it possible to raise the temperature level of the energy recovered from the vapors (5) by means of a heat exchanger on the vapors (6.1), supplying the evaporator of the heat pump, and a heat exchanger (6.2) in the boiler (7), by means of a BT recovery loop (25.1).

[0104] This low-temperature (LT) heat recovery loop is a loop of water, glycol water, or thermal fluid, which carries heat from the heat exchangers (6.1) to the evaporator of the heat pump. This loop has the capacity to recover heat from other heat exchangers (27) and may also supply injection heat exchangers (34) whose temperature in this LT loop is sufficient to supply the heat well in question.

[0105] Note that this solution facilitates assembly using a standard, mass-produced technological component (heat pump). However, it would be possible to install a compressor and an expansion valve between the heat exchangers (6.1) and (6.2) with a different working fluid, whose saturation temperatures are at the recovery temperature in the heat exchanger (6.1) and at the saturation temperature The working fluid in the secondary of the heat exchanger (6.2) in the boiler is adapted. This configuration has the significant advantage of facilitating an approach: - multi heat exchangers to recover heat available from several sources; - multi injector exchangers to make the heat available at the required temperature levels, as shown in figures 10, 14 and 15.

[0106] Moreover, this configuration is particularly suitable when the steam pressure inside the boiler (7) at the saturation temperature of the working fluid corresponding to the recovery temperature is not attainable under satisfactory conditions.

[0107] Thus, the heat pump (8) can directly supply the boiler (7) via its condenser, or via a High Temperature heat recovery loop, called the HT loop (25.2).

[0108] Like the low-temperature (LT) loop, this high-temperature (HT) recovery loop is a water, glycol water, or thermal fluid loop that carries heat from the heat pump condenser to the boiler (7) and possibly to injection heat exchangers (34). The temperature of this HT loop is sufficient to supply the heat sinks. This loop has the advantage of being able to act as a heat sink, as shown in [Fig. 14], with high-temperature heat sources that can supply it directly via heat recovery exchangers (32).

[0109] An advantageous feature of the invention lies in its ability to improve performance at reduced loads: the main compressor (11.1) and the auxiliary compressors (11.2) to (ll.n-2) are regulated according to the drying requirements defined by the drying kinetics of the products entering the drying chamber and online measurements. The incoming moisture content of said products may, for example, vary depending on the season or the recipe, requiring online adaptation of the dryer to the drying needs. The invention achieves this by reducing consumption per unit of evaporated water when the drying system is operating at low load through a decrease in the compression ratios of the steam compressors, and therefore their consumption per unit of evaporated water.

[0110] Typically, the invention optimizes drying performance when the tonnage of evaporated water is lower than the dryer's design value, which is very frequently the case in real-world applications due to initial oversizing and operation on various products, the most humid of which is the designed product. Thus, a regulated pressure increase of the steam from the boiler (7) via the compressors (11.1 to 1ll.n-2) allows: - to reduce the temperatures of the drying fluid when the latter does not need a very high temperature; - to reduce the temperature in the means of supplementary heat supply by injection exchangers; - to obtain reduced energy consumption when drying needs are lower, since vapor pressures are lower, resulting in lower electricity consumption of compressors as well.

[0111] This compressor management can be carried out by online measurement of the product's moisture content or by varying the temperature of the wet product to be dried at different points, for example. This temperature measurement can be performed by any measurement and acquisition method, for example infrared measurement or by means of thermal imaging cameras integrated into the drying chamber, depending on the dryer configurations and technologies adapted to the temperatures, humidity, and potential fouling, possibly with an outdoor drying chamber with a viewing window if the technologies allow.

[0112] Figure 8 illustrates the installation according to the invention, equipped with a first compression stage, in this case consisting of four thermocompressors (24), located upstream of the compressors (11.1, 11.2), which compress the very low-pressure steam from the boiler to a few tens of millibars absolute, thus achieving high specific volumes, under potentially satisfactory installation conditions. In this example, the thermocompressors use higher-pressure steam, resulting from compression by compressor (11.1), to compress the steam from the boiler (7), exiting the first thermocompressor, the second thermocompressor, and then the third thermocompressor. It should be noted that this configuration currently presents technical challenges with water as the refrigerant, given the significant volumetric flow rates involved and the resulting space constraints.Nevertheless, high-capacity models in terms of volumetric flow rates are installed in certain applications such as water desalination.

[0113] This configuration has the advantage of reducing the space required for mechanical compressors that must operate with high volumetric flow rates at these low pressure levels. Static compressors of the thermocompressor type minimize space requirements, with elongated designs that can be positioned lengthwise along the boiler, or vertically if ceiling heights permit in the case of indoor installation.

[0114] This figure also represents expansion, purging or calibrated orifice type devices (37, 37.1, 37.2) which are accessory devices enabling separation between vapor phase and liquid phase in the steam / condensate network.

[0115] Figure 8 incorporates a steam degassing means (35) for extracting air that may have infiltrated the steam circuits of the installation. This degassing means may be a vent, an air trap, or any other means for performing this function. Also shown in this diagram is the water make-up (36) which compensates for any losses in the water / steam circuit due to leaks, opening of safety valves, degassing, or the possible use of steam directly from the circuit.

[0116] The initial vacuum system, if necessary, and the vent(s) are used only as strictly necessary to minimize the use of the makeup water injection system. Indeed, the reality of industrial water / steam systems often results in circuits that are not completely sealed, which implies the presence of non-condensable gases and a potential need for a deaerator. Furthermore, some working fluid losses occur due to dry seals, loose flanges, or passage through valves, for example. Finally, some steam requirements necessitate the use of injected steam, leading to condensate return problems in the water / steam cycle. These three factors combined necessitate the installation of a makeup water system as described, with preliminary water treatment based on the industrial water quality of the sites, the makeup water flow rates, and the equipment suppliers' recommendations.

[0117] Figure 9 illustrates yet another variant of the installation of the invention. In this variant, heat storage in the form of a hot water tank (26) or superheated water is implemented on the HV loop (25.2). This heat storage allows for charging during periods when energy is available on the LV loop (25.1) and the heat pump (8) has sufficient power to supply energy for the drying process and to charge the water storage tank. The tank (26) discharges via a set of valves and pumps when the power on the LV loop (25.1) is no longer sufficient to supply the dryer. This allows the system to be resilient during these phases when the coupling between heat recovery and heat utilization is not ensured.In other words, the heat storage thus achieved ensures a continuous heat supply to the installation, including during short periods of interruption in the supply of heat to the heat exchangers.

[0118] Figure 10 illustrates a variant of Figure 7 in which additional heat recovery exchangers (27) are installed on the LV loop (25.1) to supplement the energy input from the heat recovery exchanger (6.1) on the vapors, and thus facilitate the reuse of waste heat in industry by means of the invention described herein. The additional heat recovery exchangers (27) are connected in series, in parallel, or in series-parallel as in Figure 10, depending on the levels of temperature, simultaneity, power and priority defined on each of these sources.

[0119] These heat recovery exchangers (27) are capable of recovering energy from humid air, fumes, flash vapors, wastewater or industrial water requiring cooling, from chiller condensers, an urban heating network, hot water from a geothermal borehole, from a solar thermal power plant, from a vacuum steam condenser inserted in a cogeneration steam cycle, from the cooling water of electric motors, voltage transformers, data centers or electrical cabinets, from a compressed air plant, from a greasing or lubrication plant or any other heat source at sufficiently high temperatures of techno-economic interest.

[0120] Figure 11 illustrates a variant of Figure 3, incorporating a vapor accumulator (28) which is a reservoir with a liquid / vapor phase equilibrium at the pressure into which vapor is injected. This allows for smoothing the peak demand of the drying process implemented by charging and discharging said accumulator, which tends to: - to lower the pressure, thus vaporizing some of the water contained, when the process requires a lot of steam, thus releasing the accumulator; - increase pressure, and therefore temperature, when the process requires less steam, therefore store the accumulator.

[0121] The inertial function performed by this accumulator (28) can prove advantageous, in order to avoid start / stop of the mechanical compressors (11.1 and 11.2) which could become problematic in the process for reasons of mechanical fatigue, inertia of the machines and longevity of the installations.

[0122] Figure 12 illustrates a variant of Figure 3 in which a thermocompressor (30) mixes steam from the first compressor (11.1) and steam from the second compressor (11.2) to supply the injector heat exchanger (14.1) with steam at a pressure intermediate between the pressures of the steam manifold (29) and the steam outlet of the second compressor (11.2). This thermocompressor optimizes energy consumption related to pressure buildup by supplying the desired pressure to the consumer.

[0123] [Fig. 13] illustrates a variant of [Fig. 3] in which the steam, superheated by non-isentropic compression at the compressor (11.1), is desuperheated at the outlet of the latter by injection of water (31.1 and 31.2), in particular if this desuperheating is not ensured by the compressors (11.1 and 11.2) in the design of the latter, which is sometimes the case to limit the temperatures reached in the compressors.

[0124] Figure 14 illustrates a variant of Figure 7 in which additional heat recovery exchangers (32) are installed on the high-temperature loop (25.2) to supplement the energy input from the heat pump condenser (8), thereby facilitating the reuse of high-temperature waste heat in industry through the innovation described in the present invention. The additional heat recovery exchangers (32) are connected in series, in parallel, or in series-parallel as in Figure 14, depending on the temperature, power, simultaneity levels, and priority defined for each of these sources.

[0125] Fig. 15 illustrates a variant of Fig. 7 in which injector exchangers (33, 34) are integrated into the BT (33) and HT (34) loops to enable the recovery of low-temperature heat on blow-drying fluid (4).

[0126] Fig. 16 illustrates a variant of Fig. 3 in which a heat exchanger (38) is positioned on the mist circuit (5), upstream of the recuperating exchanger (6) in order to preheat the inlet drying fluid (4).

[0127] The installation according to the invention constitutes a significant improvement over those known in the prior art. It offers a number of advantages, including: - a very significant increase in the energy performance of drying without degrading the quality of drying, allowing us to move towards the Minimum Energy Required through the electrification of dryers, allowing us to divide energy consumption by a factor of 2 to more than 10; - the extremely significant decarbonization potential of this arrangement, particularly in countries where electricity is low carbon-based, such as France; - the complete (closed loop) or large part recovery of the water extracted from the products to be dried, allowing to improve the water efficiency of the drying operations; - the implementation of a limited number of components, and allowing to limit the lengths of heat transport networks with a process self supplied by equipment present at the installation level, including start-up, backup and supplementary equipment; - the implementation of technological building blocks that are now perfectly mastered and implemented to achieve this objective; - the use of a potential working fluid, namely water, already present as an energy carrier in industry (therefore reassuring), facilitating refilling in case of leaks and non-polluting; - the flexibility to get closer to the minimum drying requirement without overconsumption by a variable supply temperature of the injection exchangers depending on the types of products to be dried.

[0128] The installation thus allows substantial gains compared to known prior art installations, particularly in terms of energy consumption and therefore greenhouse gas emissions, and water consumption.

Claims

Demands

1. A drying installation using a drying fluid, for a wet product comprising a drying chamber (1) within which the wet product to be dried (2) and the drying fluid ensuring the drying pass, said chamber comprising at least one inlet circuit (4) for the inlet drying fluid, and at least one outlet (5) for said drying fluid laden with moisture resulting from the exchange of water and energy with the wet product to be dried, characterized in that the installation comprises: - at least one boiler (7) operating with a working fluid, preferably water, configured: • to recover heat from one or more heat sources constituted by the drying fluid laden with moisture passing through said at least one outlet (5) by means of a heat recovery exchanger (6);and • to generate steam using the heat thus recovered, the boiling point of the working fluid being adapted by means of the pressure in the boiler (7) to the temperature of the heat source(s), possibly by means of an intermediate heat transfer loop; - at least one means suitable for initiating the operation of said heat recovery by input of third-party heat; - at least one compressor (11) suitable for increasing the pressure, and therefore the temperature, of the steam generated in said boiler(s) (7); - at least one injection heat exchanger (12) suitable for condensing the steam from said at least one compressor (11), positioned within the inlet circuit (4) of the inlet drying fluid, and for ensuring the heating of the latter upstream of the drying chamber (1).

2. A drying installation using a drying fluid for a wet product according to claim 1, characterized in that it further comprises at least one condensate collector (19) resulting from the condensation steam in said (said) injector exchanger(s) (12), said condensate being returned to said boiler(s) (7).

3. A drying installation using a drying fluid for a wet product according to any one of the preceding claims, characterized in that the temperature of introduction of the drying fluid into the drying chamber is between 40°C and 200°C, preferably between 40°C and 150°C, preferably between 40°C and 100°C, preferably between 40°C and 80°C, preferably between 40°C and 60°C and the relative humidity in the drying chamber is between 1% and 90%, preferably between 10% and 90%, preferably between 20% and 90%, preferably between 40% and 90%, preferably between 60% and 90%, preferably between 80% and 90%.

4. A wet product drying installation using a drying fluid according to any one of the preceding claims, characterized in that said at least one boiler (7) operates with a working fluid at a pressure of less than 1 Bar, preferably less than 0.9 Bar, preferably less than 0.8 Bar, preferably less than 0.7 Bar, preferably less than 0.6 Bar, preferably less than 0.5 Bar, preferably less than 0.4 Bar, preferably less than 0.3 Bar, preferably less than 0.2 Bar, preferably less than 0.1 Bar.

5. A drying installation using a drying fluid for a wet product according to any one of the preceding claims, characterized in that the heat input to the boiler(s) (7) occurs either directly in said boiler(s) or indirectly via a low-temperature heat recovery loop (25.1) which carries the heat from at least one heat exchanger (6), said low-temperature heat recovery loop comprising one or more heat sources, said heat sources being selected from a group comprising complementary heat exchangers (27) using humid air, fumes, flash vapors, wastewater or industrial water requiring cooling, condensers from chillers, a district heating network, hot water from a geothermal borehole, a solar thermal power plant, or a vacuum steam condenser inserted in a steam cycle. cogeneration, cooling water for electric motors, voltage transformers, data storage centers or electrical cabinets, compressed air plant, grease or lubrication plant or any other heat source.

6. A wet product drying installation using a drying fluid according to any one of the preceding claims, characterized in that it further comprises a heat pump (8) capable of raising the temperature levels obtained at the level of the heat exchanger (6.1) to supply the boiler (7) or a high-temperature recovery loop (25.2), said high-temperature recovery loop comprising one or more heat sources, said heat sources being selected from the group comprising complementary heat exchangers (27) on humid air, fumes, flash vapors, wastewater or industrial water requiring cooling, from an urban heating network, hot water from a solar thermal power plant, cooling water from electric motors, from a compressed air power plant, or from any other heat source.

7. A drying installation using a drying fluid for a wet product according to any one of the preceding claims, characterized in that it further comprises additional heat supply means (14; 14.1; 14.2) positioned within the drying chamber (1), supplied with steam, consisting of additional injector exchangers which are preferably selected from the group consisting of heating cylinders, double walls of the drying chamber, screws, paddles and / or steam radiants.

8. A drying installation using a drying fluid for a wet product according to any one of the preceding claims, characterized in that the means suitable for initiating the operation of said heat recovery by input of third-party heat is an additional start-up heat source selected from the group comprising electrical induction technology, electrical resistances, direct combustion or exchangers supplied by a heat transfer fluid such as hot water, superheated water, thermal oil, hot air, fumes or steam.

9. A drying installation using a drying fluid for a wet product according to any one of the preceding claims, characterized in that the compressor(s) (11) are regulated according to the drying requirements defined by the drying kinetics of said wet product to be dried.

10. A drying installation using a drying fluid for a wet product according to any one of the preceding claims, characterized in that it is equipped with a degassing device (35) and a device for supplying working fluid to a condensate collector (19), the drying fluid being air.

11. A drying installation using a drying fluid for a wet product according to claim 10, characterized in that said supplementary working fluid added in the condensate collector (19) is derived from the condensed water (23) in said moisture-charged drying fluid, optionally after water treatment as required.

12. A drying installation using a drying fluid for a wet product according to any one of the preceding claims, characterized in that it further comprises a vacuum device (9) for the boiler(s) (7) in order to facilitate the start of the boiling operation.

13. A drying installation using a drying fluid for a wet product according to claim 6, characterized in that it further comprises a hot water storage tank (26) in communication with the high-temperature recovery loop, intended to ensure a continuity of heat supply to said installation.

14. A drying installation using a drying fluid for a wet product according to any one of the preceding claims, characterized in that it further comprises a steam accumulator (28), intended to respond to sudden variations in steam demand.

15. A wet product drying installation using a drying fluid according to any one of the preceding claims, characterized in that it comprises two compressors, and in that it further comprises at least one thermocompressor (30) supplied with steam from the steam from the first compressor (11.1) and from the steam from the second compressor (11.2), so as to supply the injection exchanger(s) (14.1, 14.2) with steam at a pressure intermediate between the pressures of a steam collector (29) and the steam at the outlet of the second compressor (11.2).

16. A drying installation using a drying fluid for a wet product according to any one of the preceding claims, characterized in that it further includes desuperheaters (31.1, 31.2) capable of injecting water into the steam at the outlet of the compressors (11, 11.1, 11.2).

17. A drying installation using a drying fluid for a wet product according to any one of the preceding claims, characterized in that it comprises a first compression stage consisting of one or more thermocompressors (24) located upstream of the compressor(s) (11; 11.1, 11.2).

18. A drying installation using a drying fluid for a wet product according to any one of the preceding claims, characterized in that it comprises a heat exchanger (38) on said moisture-laden drying fluid resulting from the exchange of water and energy with the wet product to be dried, allowing the preheating of the inlet drying fluid.

19. A wet product drying installation using a drying fluid according to any one of the preceding claims, characterized in that it operates in a closed loop, and in that the inlet drying fluid (4) is derived from the outlet drying fluid (5) of the drying chamber (1), which is dried by means of at least one recuperating exchanger (6), and then reheated by means of at least one injecting exchanger (12).

20. A drying installation using a drying fluid for a wet product according to any one of claims 1 to 19, characterized in that it comprises a plurality of drying chambers 1, 2, ..., n, connected in series, the most upstream chamber (1.1) receiving the product to be dried having the highest degree of moisture, and the most downstream chamber (ln) receiving the product to be dried (2) after transit through the upstream chambers, and wherein: - the inlet drying fluid (4.i) conveyed within the upstream chamber (li) relative to the direction of progression of the wet product to be dried comes from the moisture-laden drying fluid (4.i+l) from the drying chamber (1.i+1) mounted immediately downstream of said upstream chamber after reheating by an injector heat exchanger (12.i), i being an integer between 1 and n-2, - the steam from the boiler(s) and whose pressure (and therefore temperature) was increased using a main compressor (11.1), is routed as a priority within an injector exchanger provided in the drying fluid introduction circuit of the most upstream enclosure (1.1), part of this vapor is subjected to compression at an additional compressor (11.2) to convey a higher pressure vapor to an injection exchanger (12.1) provided within a drying fluid introduction circuit of said downstream chamber with possible addition of fresh drying fluid for mixing (20.1); this compression process to the downstream chamber being likely to occur 1, 2, ..., n-2 times, the drying fluid of the chamber (ln-1) is from the drying fluid outlet of the chamber (ln), preheated by the hot product to be dried from the chamber (ln-1), which has cooled in the chamber (ln) by giving up its heat to the drying fluid and possibly drying the drying fluid (4.nl) by hygroscopicity of the product, and the drying fluid inlet of the chamber (ln), the most downstream, consists of dry drying fluid, possibly of vapors dried by the recuperating exchanger (6) in the case of closed loop operation on the drying fluid.

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