ES1172383U - Device for recovery of the residual energy of the process of drying, or other thermal processes, using packed beds as captors, preheaters and accumulators (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Device for the recovery of residual heat from thermal processes, (such as that generated by drying, the manufacture/production of various products or the ventilation/dissipation of heat generated in buildings), characterized in that the enthalpy of the residual heat produced in the process (1) and extracted from (1) by a heat transfer fluid is recovered, and characterized in that it uses a set of blowers (s) and/or pumps (b), a set of conduits, valves and gates, a heater (6) and two beds filled with solid materials, the first acting as a residual heat sensor (2) receiving the heat transfer fluid from the process (1) and the second acting as a preheater (3) of the heat transfer fluid before entering the process (1) that generated the residual heat or another external process. (Machine-translation by Google Translate, not legally binding)

Description

D E S C R I P C I Ó N

RESIDUAL ENERGY RECOVERY DEVICE OF THE DRYING PROCESS, OR OF OTHER THERMAL PROCESSES, USING PACKED MILK AS RECEIVERS, PRE-HEATERS AND 5 ACCUMULATORS

SECTOR OF THE TECHNIQUE

 10

Thermal processes. Drying processes. Recovery of waste heat and water.

BACKGROUND OF THE INVENTION

Around 70% of the energy demand of European industry has 15 thermal purposes, of which about 30% is emitted into the atmosphere as waste heat. The residual heat dissipated in buildings is also of great importance. Within these processes, the drying process is one of the most prominent.

As a sign of the importance of energy consumption in drying processes, it is enough to point out that, in Spain, about 11% of the final energy used in the industry is used for drying. The drying of a product consists of totally or partially eliminating the liquids that impregnate it, usually water. The drying processes are used daily and extensively in many industrial sectors, from agriculture to the pharmaceutical industry or to the production of natural gas, with objectives such as the preservation of the properties of the food for long periods of time , the production of processed products or the elimination of the inconveniences associated with the presence of water for the transport or processing of the products.

The huge demand for drying processes and other thermal processes worldwide, has greatly boosted technological development, especially in reducing energy consumption by increasing its energy efficiency and reducing costs. In that sense, the implementation of technologies, such as that proposed in this report, capable of significantly reducing energy consumption in thermal processes is of great importance 35

Drying represents a good example of the need for heat recovery in the industry. At present, various technologies are used for drying from the sun drying of agricultural products, to conductive, convective or radiative drying in silos and ovens or to drying using adsorbent or absorbent materials. In most cases, drying is carried out thermally with air or gases, which carry away evaporated moisture, or without air by evaporation under vacuum or using materials that retain water vapor (adsorbents or absorbents). In the latter case, used for example in the drying of natural gas prior to transport and / or liquefaction, the adsorbent (or absorbent) material has to be regenerated to lose the captured water vapor, which is done through the application of heat. , which is still another variant of the drying process in the dryer, in this case the adsorbent or absorbent material. A good summary of the different drying technologies and associated problems can be found in “Drying handbook. Fourth edition ”, (Arun S. Mujumdar, 2014, CRC Press). Most of the energy contributed to drying is lost in the moist air that is expelled from the dryer or in the regeneration of adsorbent or absorbent materials. To date, most of the drying systems do not recover much of the enthalpy of the exhaust air and therefore the typical efficiencies are quite low. In the table below (“Energy Efficient Multistage Zeolite Drying for heat Sensitive Products”, Mohamed Djaeni, 2008, Doctoral Thesis University of Wageningen 20 (Netherlands)) we show the typical values:

Table 1: Comparison between the energy efficiency of various drying systems

 No.

 Type of dryer Energy efficiency (%) Steam consumption (kg of steam per kg of water extracted)

 one

 Chamber dryer 20-30% 3.0-5.0

 2

 Vacuum dryer 35-40% 2.5-3.0

 3

 Freezer dryer 10-20% 5.0-10.0

 4

 Spray dryer 30-60% 1.6-3.0

 5

 Rotary drum dryer 25-60% 1.6-4.0

 6

 30-70% fluidized bed dryer 1.5-3.0

Energy efficient drying systems usually incorporate, taking into account the characteristics of the product to be dried, one or more of the following mechanisms (see “Energy efficiency in boilers, steam generators, ovens and dryers”, Guillermo Escobar et al, chapter 5 of the energy efficiency wikibook 5, School of Industrial Organization,
http://www.eoi.es/wiki/)

 Present the product previously in natural or forced atmospheric air currents

 Dry the minimum possible in absolute terms.

 Reduction of the humidity of the air entering the dryer 10

 Dry air heating to the maximum possible temperature, if the objective is to reduce the drying times or to the minimum practical temperature if the drying time does not matter.

 Exchange of dry air with the product to dry

 Saturate the air or exhaust gases to maximum humidity 15

 Recovery of enthalpy of the outlet air from the dryer (e.g. recirculation of the drying air, fluidized beds with thermal tubes, tube and fin exchangers, heat pumps, ...)

 Air pressure reduction

 Recover the sensible residual heat of the dried product 20

For the recovery of waste heat from other industrial processes the usual approaches are:

 Heat recovery for external use to the installation where the process is located (for example, heating, cooling and DHW of a nearby neighborhood, see: http://pitagorasproject.eu/) through heat exchangers that transmit energy residual of the process to a distribution network.

 Heat recovery for internal use in the installation where the process is located or even in the same process. If the temperature available in the residual heat is lower than 70 ° C, it can be consumed directly, by means of exchangers, in lower temperature processes (eg ACS) or to increase its temperature by means of Heat Transformers by Absorption (AHT) for use in other processes . If the temperature available in the residual heat is higher than 70 ° C, it can be used to produce electricity with cogeneration engines or, if the temperature of the residual heat exceeds 300 °, by means of equipment that works, for example, with organic cycles 35

(ORC)

With regard to the recovery of waste heat generated in buildings, and given its reduced thermal level, it is usually used mainly for preheating the ventilation air and, in some cases, for the preheating of domestic hot water. 5

To reduce the environmental impact of drying and other thermal processes, in addition to improving the efficiency of the process, it is convenient to couple it with renewable energy sources. The combination with systems of thermal use of solar energy as a source of heat, is an objective that is present in numerous references especially for drying agricultural products in developing countries with a good solar resource (see for example “Solar Drying ”, W. Weiss & J. Buchinger, 2015. Training course within the project" Establisment of a Production, Sales and Consulting Infrastructure for Solar Thermal Plants in Zimbabwe ", AEE INTEC-Industry) .This combination can be favored when you have storage systems that filter the variability of the energy source and allow a more homogeneous energy supply.

Among the pending problems of the technology of recovery of the residual heat of the drying and other thermal processes, and that we intend to attack with the device of the invention, we can highlight:

 Low efficiency 20

 High energy consumption

 High investment costs of efficient systems

 Evaporated water loss

 Coupling with intermittent sources of heat, such as solar thermal installations 25

EXPLANATION OF THE INVENTION

The device of the invention uses the theoretical and experimental results of the doctoral thesis of the author of the device of the invention "Study of the exchanges of the invention" in a new device for its application in drying and other industrial thermal processes and in the construction heat between a greenhouse considered as a solar collector of moist air and a bed of rocks as an environmental control system ”(José Ignacio Ajona Maeztu, Faculty of Physics - Universidad Complutense de Madrid, 1990). In that study, without being related to heat recovery in the 35

thermal processes, a series of usable results were modeled and tested experimentally to understand how the device of the invention works, especially in the case of drying. When hot and humid air is introduced through the top of a packed bed (in that case boulders) colder, with a step jump in the temperature and humidity conditions of the 5-inlet air, the air gives its heat to the filling in form of sensible heat and phase change, producing condensation of part of the water contained in the air over the landfill and observing:

 Even with reduced flow rates and air velocities, the heat transfer between the air and the filling is excellent and therefore the temperature of the air and the filling are very similar at the points inside the bed.

 If the relative humidity of the inlet air is less than 100% with a humid temperature exceeding the initial filling temperature, the thermal evolution of the filling experienced two distinct stages. In the first stage, the filling reaches a temperature close to the humid temperature of the inlet air and condensation of water occurs on the filling and, subsequently, drainage or evaporation of the deposited water. When the water on the landfill is exhausted, either by evaporation or by the movement of the liquid water towards the bottom due to gravity, the second phase begins in which the bed evolves from the temperature close to that of the humid air 20 of the inlet air, until the dry temperature of the feed air is reached.

 If the air that is introduced is very dry, only the second temperature wave in which the bed evolves from the initial filling temperature to the dry temperature of the feed air is propagated. 25

 In the first stage, the thermal wave travels inside the bed at a speed, depending on the operating conditions, significantly faster than in the second and the faster the higher the wet temperature.

 The liquid water deposited on the landfill and descending to the bottom of the bed represented a very significant proportion of the liquid water introduced.

 During the first stage, the evolution of the humid air, represented on the psychrometric diagram, crosses the saturation curve until it approaches the humid temperature of the inlet air 35

In the device of the invention are used, coupled to the container with the product to be dried or to the process from which residual heat comes out, two packed beds to recover the residual heat of the process both in the form of heat of phase change and of sensible heat such as shown in Figure 1, 2 and 3 where the numbers refer to the different teams. 5

A packed bed is a multiphase reactor in which various materials are present in two or three phases (solid, liquid or gas). Inside there may be chemical reactions or, as in the case of the device of the invention in question, phenomena of heat and mass transfer between the solid (typically called bed filling) and a heat transfer fluid (eg humid air, 10 water, ...) that circulates inside and that serves to give or take away energy to the solid filling of the bed, depending on the mode of operation.

In the device of the invention, packed beds are used for the residual heat sensor (2) and the preheater (3) with a solid filling material with physical properties such that the product of the value of its specific heat, its density and of the fraction of the space occupied by the solid in the bed is greater than 200 kilojoules per degree centigrade and cubic meter (kJ / C / m3), being able to exceed 3000 kJ / C / m3. The fluid used as heat transfer fluid in the beds (2) and (3) (eg humid air) that has increased its enthalpy level by previously passing through the process (1), will yield a good part of the enthalpy gained in (1) when circulating to through beds 20 (2) and (3), according to the modes of operation described below, and thus recovering the energy applied (or generated) in the process (1), for the process itself (1) or for others applications.

For the circulation of the heat transfer fluid between the process (1) and the beds (2) and (3) the blower (S) is required and if it is necessary to heat it before it enters the process (1), 25 a heater is required (6). So that the flow of the heat transfer fluid is directed from the process (1) to the bed (2) or to the bed (3) and for which the flow of the heat transfer fluid enters the process (1) from the bed (3) or from the ( 2), valves or gates (a), (b), (c) and (d) actuated in conjunction with (a '), (b'), (c ') and (d') are required. To allow the entry and exit of fluid from outside the device, the valves or gates (e), (f) and (g) are required. Condensate extraction in the beds (2) or (3) requires a pump (B)

The meaning of the numbers in Figures 1, 2 and 3 is

1. Process that generates waste heat both in the form of phase change heat and sensible heat (eg, a dryer in which water vapor is produced) 35

2. Packed bed that captures the residual heat and transmits it to the filling material (eg condensing the steam extracted from a dryer)

3. Packed bed that takes advantage of the enthalpy of residual heat captured by (2) to preheat the fluid with which it feeds (1) or other equipment

4. Inlet of the fluid to the preheater (3), (in operation mode 1, described below 5)

5. Preheated fluid outlet of the preheater (3) (in operating mode 1 and 3, described below)

6. Preheated fluid heater, (in operating mode 1).

7. Fluid inlet to the process (e.g. dryer) (1) (in operating mode 1 and 10 2)

8. Output of the process fluid (1) to the waste heat sensor (2) in operating mode 1 and 3 or to the preheater (3) in operating mode 2, described below

9. Exit of the fluid to the outside, in the operation mode 1 and 3, from the residual heat sensor 15 (2).

10. Output of the distillate from the residual heat sensor (2) in the event that it occurs.

11. Fluid inlet from outside to the process (1), (in operation mode 3)

12. Exit of the fluid to the outside, in the mode of operation 3, towards the external process 20 of use of the residual heat.

The device of the invention can operate in three different modes of operation.

In the first (mode of operation 1), the product that is processed in (1) (eg product to be dried) is heated with an external source (6) (boiler, solar installation, ...) or internal 25 (chemical reaction) and It produces residual heat (eg hot and dry air enters the process (1) that evaporates the water from the product to be dried and produces hot and humid air) that is transferred by the heat transfer fluid to the residual heat sensor (2) and the preheater ( 3). The process fluid (1), at low temperature, enters (4) into the preheater (2) where it is preheated before entering the heater (6) through the conduit (5) and being introduced into the process (1) by conduction (7), producing a fluid with residual heat at its outlet (in the case of drying steam is produced, causing the air to reach an initially quasi-saturated state at a temperature close to that set in the heater and subsequently with a moisture content that will decrease as the product dries up to 35

approach the humidity of the inlet air). The fluid with high enthalpic content from the process (1) through the conduit (8), will transfer its enthalpy in contact with the filling material of the residual heat sensor (2)

 In the case of drying, the heat transmission will be carried out in the same way as described previously in the aforementioned Thesis and initially traveling a path, represented in the psychrometric diagram, or in the pressure-temperature diagram corresponding to the steam at condense, on the saturation curve, between a temperature close to that set in the heater (6) and that of the inlet air, or treatment gas, introduced by (4). The liquid condensed on the filling and which arrives by gravity at the bottom of the residual heat sensor (2) is extracted from the system by (10). The cooled fluid leaving the residual heat sensor (2) is expelled from the system by (9).

 In the case of other processes without changing the phase of the fluid, the heat transfer will be only by sensible heat between the heat transfer fluid and the solid. fifteen

In the second mode of operation (mode of operation 2) will be entered exclusively when you want to recover the sensible heat of the material inside the process (1); for example, in the case of drying a product when it is already dry to the established levels and at a temperature close to that set as a setpoint in the heater (6). In this mode of operation 2, the heater (6) is turned off, 20 keeping the fluid circulator (S) connected to recover the sensible heat of the product and transfer it to the upper part of the preheater (3). The fluid cooled to the outlet of the preheater (3) enters the process (1) by conduction (7). If the preheater outlet temperature is not cold enough to cool the product, cold fluid will be taken from the outside, for example, by properly positioning 25 (b) and (c), and it will be ejected by (e) once opened.

The third mode of operation (mode of operation 3) will be entered exclusively when you want to use the residual heat generated in the process (1), recovering it for use in a different process than the one that generated it (process (1)); for example, in the case of an exothermic process (or with internal sources of heat generation) 30 that it does not need the incoming fluid to provide it with energy and that in many cases is used to cool it. In this mode of operation 3, the heater (6) will normally be turned off (since the process (1) generates heat), keeping the fluid circulator (S) connected to move the fluid and recover the residual heat from the process (1) in the same way as in operating mode 1: The fluid with high 35

enthalpy content from the process (1) through the conduit (8), will transfer its enthalpy in contact with the material of the residual heat sensor filling (2), making the same change of roles with the preheater (3) with the same criteria described in the following paragraph. The difference with the operating mode 1 is that, in the operating mode 3, the fluid will enter the device 5 through the conduit (11) to direct it towards the process (1) and through the conduction (4) to direct it through from the conduit (12) towards the external use of the enthalpy from the preheater (3), instead of directing it towards the process (1), the fluid that enters through the conduction (11) can be the same or different from the one entering by driving (4). For this mode of operation 3, it is necessary that the gate (f) divert the fluid 10 towards the external process, preventing it from going towards the process (1) from the conduit (5) and that the gate (g) is open to allow the fluid inlet through (11). The process to which the heat recovered from the process is sent (1) will have all the necessary elements for the circulation of the fluid through it.

In operating modes 1 and 3, the fact that the preheater (3) can function as a preheat for the fluid is due to the residual heat sensor (2) and the preheater (3) exchanging their roles when the temperature evolution in the lower part of the residual heat sensor (2) it is such that it rises above the temperature of the fluid inlet by (4) the amount established as the operating criterion. This change is carried out by means of a set of 3-way gate valves (or 20 equivalent) whereby connections (a), (b), (c) and (d) of the residual heat sensor (2) change their function with (a '), (b'), (c ') and (d') of the preheater (3) and vice versa while the process exit gate (e) remains closed. The movement of the fluids is carried out, mainly, by the hydraulic group of condensate extraction pumps B, and by the circulator (blower for drying) S, in the duct (5) (it is also possible to locate it in the conduit (8)) to circulate the fluid between the preheater (3), the dryer (1) and the residual heat sensor (2). When the change occurs, the new preheater is in the conditions that the residual heat collector was, with a temperature in the high part close to that set in the heater (6) and a temperature in the low part close to the inlet 30 of the fluid by (4) so that it can preheat, yielding its heat, to the incoming fluid. In the same way, the new residual heat collector is in the conditions that the preheater was, which has been thermally discharged after being cooled by the passage of the feed fluid to the system, with a temperature in its lower part close to the of fluid input by (4) so, in 35 modes

operation 1 and 3, you can efficiently recover the residual heat from the process (1) as well as recover the sensitive heat of the processed product, in the second mode of operation. This change of roles is one of the most remarkable elements of the device of the invention. It is important to note that the change of roles between the residual heat sensor (2) and the preheater (3) will be carried out, 5 during modes of operation 1 and 3, the number of times necessary to recover the heat of the process as established as a setpoint and that mode of operation 2 will be used only if it is desired to extract the sensible heat from the product once it has been processed so that it can be used in the processing of a new product.

The efficiency of the device of the invention, understood as the ratio between the residual energy of the process (1) recovered, by using the residual heat sensor (2) and the preheater (3), and the residual heat generated in (1 ) will depend mainly on

 The temperature set as a setpoint in the heater (6), or produced by the process itself, and the working pressure: the higher, the more efficient. fifteen

 During operating modes 1 and 3, the temperatures that are near the high part of the residual heat collector (2) and the preheater (3) are close to those set in the heater (6) (or produced by the process) and the temperatures of the lower part of the residual heat collector (2) and the preheater (3) at the fluid inlet by (4): The closer, the greater the efficiency.

 Enthalpy at the exit of the process (1): In modes of operation 1 and 3 the higher, the more efficient and in mode of operation 2, the lower the temperature, the greater the efficiency

 The temperature of the distillate produced (if produced): The lower, the more efficient

 The temperature of the product to be processed, once processed: The lower, the more efficient.

 The level of thermal insulation of the residual heat sensor (2) and the preheater (3): The better the insulation, the better the efficiency of the device.

Applying these guidelines to control the working conditions that favor the energy efficiency of the device, the efficiency values attainable in most cases will be greater than 60%, and levels above 95% can be reached in many cases, provided that The level of thermal insulation is sufficient. 35

The design criteria of the beds for efficient operation, taking into account the amount of residual heat produced in the process (1) and the corresponding flow rates, is therefore the

 dimension the residual heat collector (2) and the preheater (3) with sufficient thermal capacity to change the roles of collector from residual heat (2) to preheater (3), and vice versa, (to be performed when the thermal wave caused by the entry of residual heat in the upper part of the residual heat sensor (2) begins to reach the lower part of the residual heat sensor (2), must be carried out with a reasonable frequency (eg every 2 -3 hr) and a recovery of almost all the residual energy 10 of the process (1) is guaranteed.

 dimension the beds to ensure adequate heat and mass transfer, which depends, among other things, on the speed of the fluid inside the bed.

Although the device of the invention can work with numerous filling materials, it is advisable to use materials with a high value of the product specific density and heat, small void fraction, low cost, local availability and resistance to temperature and corrosion . Therefore, the use of rocks (boulders, granite, ...) available locally, is an excellent (not unique) choice: It allows working at elevated temperatures and pressures with a very low cost so it can be sized with amplitude to be able to work with significant thermal jumps between the top and bottom of the fillings of the residual heat sensor (2) and the preheater (3)

The bed of the residual heat sensor (2) and the preheater (3) when using materials such that the product of the value of its specific heat, its density and the fraction of the space occupied by the solid in the bed is greater than 200 kilojoules per degree centigrade and cubic meter (kJ / C / m3), being able to exceed 3000 kJ / C / m3, in addition to as a residual heat collector (2) or preheater (3), it works as a storage system energy from heat sources (intermittent or not), efficient and, potentially, low cost. This is especially interesting if you want to provide with solar heat, or other sources of renewable or recovery heat, (alone or as a main contributor) the energy needed for the process (you have to take into account that you can always hybridize the system solar with another system of heat production with renewable or with conventional fuels to maintain a constant regime in the production of the process if 35

this is desired).

It is important to note that in the device of the invention thermodynamic balancing of the fluid flows and the filling of the beds is achieved, thanks to the coupling caused between the thermal behavior of the fluid and the filling, both in the residual heat sensor (2 ), as in the preheater (3), due to the good heat transfer achieved and the great thermal stratification between the upper part of the bed and the lower part of the bed, increased if filling materials with a high thermal inertia are used and low thermal conductivity.

BRIEF DESCRIPTION OF THE DRAWINGS 10

To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, a set of drawings is attached as an integral part of said description, where illustrative and non-limiting nature has been represented. next: 15

In Figure 1 we show a schematic view of the device of the invention with the main constituent elements, working in the mode of operation 1.

In Figure 2 we show a schematic view of the device of the invention with the main constituent elements, working in the mode of operation 2.

In Figure 3 we show a schematic view of the device of the invention with the 20 main constituent elements, working in the mode of operation 3.

In Figures 4, and 5 we show a detailed view, in plan from above and from below, for mode of operation 1 and in Figures 6 and 7 we show a detailed view in plan from above and from below for mode of operation 2 , of a possible preferred embodiment of the object of the invention in the case of a drying process, with its various components in which the device of the invention is shown including the devices for changing roles between the residual heat sensor ( 2) and the preheater (3) and the sensible heat recovery process (1).

In Figures 4, 5, 6 and 7 the elements designated by the lowercase letters refer to those of Figure 1, 2 and 3 as well as those designated by the numbers.

PREFERRED EMBODIMENT OF THE INVENTION

The device object of the invention can be realized in multiple ways, with

different sizes and materials and in numerous applications. We specify it in the case of a drying process,

In Figures 4, and 5 we show a detailed view, in plan from above and from below, for mode of operation 1 and in Figures 6 and 7 we show a detailed view in plan from above and from below for mode of operation 2 , of a possible preferred embodiment of the object of the invention with its various components in which the device of the invention is shown including the devices for changing roles between the residual heat sensor (2) and the preheater (3) and sensible heat recovery from the drying process (1). These figures show a possible preferred embodiment of the invention for dryers and with the same elements of Figures 1, 2 and 3 (except the fyg gates that are not necessary for this preferred embodiment) and a layout of the pipes and ducts in the that the pumps B, the blower S, the gates C, D1, D2, D3 and D4 and the 3-way valve, V, used for the operation of the device are observed.

In operation in operating mode 1, 15

 The blower S works as long as you want to dry the product in the dryer (1).

 Pump B works while you want to extract the distillate produced.

 The position of the gate C, directs the air from the dryer (1) to the residual heat sensor (2) and from the preheater (3) to the heater (6).

 D1 and D2 dampers are open and allow the entry of outside air 20 into the preheater (3) and the exit of air from the residual heat sensor (2)

 The position of the D3 and D4 gates allows the preheater outlet air (3) through the pipe (5) to reach the heater (6) and prevents air from circulating through the openings (b) and (b ’).

 Gate D5 remains closed 25

 The heater (6) receives the air through the pipe (5) and sends it hotter, at the designated temperature, through the pipe (7) to the dryer (1) whenever the blower S is running.

For the change of roles between the residual heat sensor (2) and the preheater (3) to be carried out when the temperature in the lower part of the residual heat sensor (2) 30 increases the set amount above that of the supply air to the preheater (3):

 Blower S is stopped and the residual heat collector (2) of water is emptied with pump B.

 The C gate is repositioned. When changing the gate (CC ’), located between the duct (5) and the (8), the preheater (3) is

transforms into the new residual heat sensor (32 ’) and the air moves between the new residual heat sensor (2’) and the dryer (1)

 When gate C has been repositioned, blower S is started and the new normal operating mode is entered

The operating mode 1 is maintained until the desired humidity level 5 is reached at the exit of the dryer (1); when it is reached, it goes into operating mode 2. In operation in operating mode 2,

 Blower S works while the product is to be cooled in the dryer.

 The heater (6) is off

 The position of the gate C, directs the air from the dryer (1) to the last 10 that has acted as a preheater (3)

 As long as the preheater outlet temperature (3) is low enough to cool the product in the dryer (1),

o The dampers D1 and D2 are closed and prevent the entry of outside air into the preheater (3) and the exit from the residual heat sensor 15 (2)

o The position of the D3 and D4 gates prevents the preheater outlet air (3) through the pipe (5) from reaching the heater (6), prevents air from circulating through the opening (b) and allows air to circulate through the openings (b '). twenty

 If the outlet temperature of the preheater (3) is not low enough to cool the product in the dryer (1), outside air will be taken (opening the passage, for example, through the gates D1 and D3) and after circulating it through the dryer (1) it will be expelled to the outside through an opening for the purpose after the dryer D5, in the pipe (8) 25

 The dryer (1) receives the cold air from the preheater (3) or from the outside through the pipe (7) whenever the blower S is running.

Both in operation mode 1 and in 2, if you want to make all or part of the energy supply with a solar installation, or another one with intermittent availability, you can, among other options, heat the air at the exit of the dryer. 30

The packed beds of the preferred embodiment shown in Figure 4, 5, 6 and 7, can be constructed with rocks of a homogeneous size and with a diameter, preferably, about 20 times smaller than the equivalent diameter of the container. The container will be thermally insulated, it can be made of a material capable of withstanding the pressure (or be contained in another container that supports it as it can

be the ground itself if it is buried), and the working temperature (e.g. polypropylene, steel, ..), and in addition to the landfill, it may have a lower and upper plenum / diffuser for adequate air distribution. The size of the packed beds will depend on the demand for dry product to be processed and on the desired modes of operation and can vary from a few liters 5 to many thousands of m3.

Equipment for the movement and control of fluids will be selected to withstand working conditions (e.g. temperature, pressure, pressure drop, ..)

It is noteworthy that, by changing the working fluids (air for any gas and water for any liquid), and maintaining the general concept, the number of applications 10 in which the device of the invention can be applied is enormous and could be shown a large number of embodiments essentially identical to the preferred embodiment described in this section.

Industrial Application 15

The industrial application of the device of the invention is inherent in the nature of the invention both in drying and other thermal processes in the industry and in construction and is deduced from the explanation thereof.

Claims (6)

1. Device for the recovery of waste heat from thermal processes, (such as that generated in drying, the manufacture / production of various products or the ventilation / dissipation of heat generated in buildings), characterized in that the enthalpy of waste heat produced in the process (1) and extracted from (1) by a heat transfer fluid is recovered, and characterized in that it uses a set of blowers (S) and / or pumps (B), a set of ducts, valves and gates , a heater (6) and two beds filled with solid materials, the first acting as a residual heat collector (2) receiving the heat transfer fluid from the process (1) and the second acting as a preheater (3) to the heat transfer fluid before 10 enter the process (1) that generated the residual heat or another external process. 2. Device according to claim 1 characterized in that the Residual Heat Collector (2) and the Preheater (3) exchange their roles when the residual heat collector (2) has been thermally charged, upon receiving the heat transfer fluid that drags the residual heat originated in the process (1) by means of the blower (S), up to the established thermal level. This change is carried out in a cyclic manner, each time the described change condition is reached, by using a set of valves and gates with interlocking performances between them so that, once operated, the Residual Heat Collector (2 ) will begin to act as a new 20 Preheater and the old Preheater (3) as a new Waste Heat Collector. In this way and with these operating cycles, the enthalpy captured by the residual heat sensor (2) can be used to preheat the fluid that feeds the process (1), or to another external process, when acting as a Preheater (3).  25 3. Device according to claim 1 characterized in that the Preheater (3) can recover the sensitive heat of the product once processed in the process (1), by using a set of gates with interlocking performances between them, thereby capturing heat captured by The preheater can be used to preheat the fluid that feeds the process in successive process cycles. 30 Device according to claim 1 characterized in that the bed filling materials (2) and (3) will preferably have physical properties such that the product of the value of its specific heat, its density and the fraction of the space occupied by the solid in the bed is greater than 200 kilojoules per degree 35 centigrade and cubic meter (kJ / C / m3), being able to exceed 3000 kJ / C / m3, which allows it to act as energy storage for heat sources, intermittent or not, such as solar thermal installations and other sources of renewable or recovery heat.  5 5. Device according to claim 1, characterized by an energy efficiency greater than 60%. 6. Device according to claim 6, characterized by an energy efficiency greater than 95%. 10