Multi-stage system for heating air for drying by means of concentrated solar energy

Abstract

The present invention relates to a multi-stage system for heating air for drying in general, applied to the field of thermal engineering and methods, more specifically TO the area of heat transfer and energy efficiency using solar concentrators (3) for heat a fluid, which is stored in a thermal reservoir (1), connected to a main heat exchanger (11) that performs heat exchange with the drying air, which is injected into a dryer (2). In addition to reusing residual air, by heating a secondary heat exchanger (10), it operates with a support system (16) that may be activated when necessary. The system discloses the advantages of using renewable energy for drying without affecting the environment.

Description

[0001] Multistage air heating system for drying using concentrated solar energy.

[0002] Field of invention

[0003] This patent application refers to a multi-stage air heating system for drying ores, drying agricultural products, animal welfare and comfort, as well as processes in other sectors that require heated air for a given thermal system. It is applied in the field of thermal engineering and processes, more specifically in the area of ​​heat transfer and energy efficiency, with the aim of reducing or eliminating fuel consumption and pollutant generation, in addition to the resulting benefits such as greater energy availability for the process, with the advantage of providing lower operating costs compared to other sources of thermal energy, using clean and renewable energy.

[0004] Fundamentals of the invention

[0005] The ever-increasing search for sustainable solutions in the industrial sector has driven research and development of new technologies based on renewable energy. In this scenario, the use of solar energy as a source stands out due to being an innovative and effective alternative. Solar energy-based systems, such as the one in this patent, not only provide thermal heating for industrial processes but are also aligned with environmentally friendly principles and the ESG agenda, reducing the consumption of fossil fuels and consequently the emission of pollutants.

[0006] Industrial processes that utilize heating have high operational costs. By employing solar energy as a thermal source, these processes can reduce dependence on conventional energy sources, thus reducing economic and environmental impact. Furthermore, the use of solar concentrators for indirect air heating improves the utilization of solar energy, increasing efficiency in applications such as agriculture and livestock farming, where temperature control is essential for product quality and animal welfare.

[0007] However, multistage systems based on concentrated solar energy, such as the one in this patent, present some disadvantages that need to be considered. Industrial environments with limited space can be a problem, since these systems are more robust and require more space for installation. Furthermore, they depend on backup systems for initial support, such as gas heaters, which can impact short-term economic viability. Even with these challenges, the sustainability and reduction in operating costs show that these systems present themselves as a promising option for industries seeking solutions based on energy efficiency and ecological innovations, as already demonstrated in many national and international prior art inventions.

[0008] Searches conducted in Brazilian and international patent databases revealed the following findings.

[0009] The subject of patent KR20210061819A describes a system / equipment for solar energy storage that uses dual heat collection tubes with a mixture of thermal oils. This system / equipment can track the sun's movement, maximizing heat absorption.

[0010] Although the system in this patent proves to be quite efficient, the mixture of thermal oils applied in the system can increase the risk of leaks and equipment degradation, as well as the viscosity and specific heat of the mixture, thus compromising the equipment's performance. It has a heat exchanger inside the reservoir, which can lead to a decrease in the system's thermal efficiency, and it also lacks a solution for reusing the thermal energy from residual vapors in a drying process.

[0011] The object of patent GR20180200175U presents a dual-axis solar reflector system that rotates on a rail and heats a specific oil, assisting in the water evaporation process and energy generation.

[0012] Although this patent presents efficient solutions to the problem of energy generation, the mechanical complexity of the two-axis movement can lead to failures and premature wear of the moving components, which can generate high maintenance costs. Furthermore, the arrangement of the concentrators, even with minimal distance between them, can cast shadows on the reflectors themselves, which can also affect the system's effectiveness.

[0013] The subject of patent CN106123363A discloses a nano-fluid-based energy generator that uses solar concentrators to heat and store the nano-fluid in a reservoir containing fins and a mixer at the bottom. The nano-fluid is composed of nanoparticles that include Cu (copper), ZnO (zinc oxide), TiCf (titanium dioxide), graphene, and CNTs (carbon nanotubes).

[0014] Despite its high effectiveness in converting solar energy into thermal energy, the invention, due to its distinct application field, does not reveal the use of residual air reuse after the air treatment with the use of a secondary heat exchanger. Furthermore, it does not utilize a system that adjusts the internal pressure of the piping, preventing damage on days with higher solar incidence.

[0015] The subject of patent CN114353343A discloses a rock dryer and cleaner using a fluid that performs both rock cleaning and drying. This process occurs by heating the fluid as it passes through solar concentrators, returning to a condensation chamber, and after that it passes through the material cleaning tank, performing the cleaning and drying process.

[0016] The disadvantage of this process is that it cannot operate at high drying temperatures, as the solar concentrator system cleans the solvent, separating impurities and sending the purified and vaporized solvent to a condensation chamber, restarting its cycle.

[0017] Patent CN103584270A discloses a device designed to dry tobacco leaves using solar energy. It utilizes a cylindrical parabolic solar energy reflector with an evacuated annular receiver. The system works by concentrating sunlight onto this vacuum tube using highly reflective mirrors. Heat transfer oil circulating through the tube is heated to a pre-defined temperature and then used to dry the tobacco via a controlled airflow. The drying system has a closed air circulation system.

[0018] Although it has a drain to remove internal moisture from the piping, because it is a closed air circulation system, the moisture removed from the leaves during drying can directly affect the internal components of the product, requiring more frequent maintenance. Furthermore, it lacks a support system for periods of low sunlight. The invention also does not include a system to regulate the internal pressure of the heated piping, preventing damage on days with higher sunlight intensity.

[0019] The prior art presents the following problems and technical shortcomings that have been resolved by the present invention, shown below: a. Mixing thermal oils to perform heat exchange can increase the risk of leaks and degradation, in addition to altering the viscosity and specific heat of such a mixture, which can compromise the equipment's performance. This is resolved by using thermal oils with stabilizing additives that improve resistance to degradation, maintain adequate viscosity across different temperature ranges, and minimize the risk of leaks through high-performance sealing materials; b. Mechanical complexity of movement on two axes that can generate failures and premature wear of moving components, resulting in high maintenance costs.a. Solved by a configuration that uses a linear focus parabolic reflector system for simplified solar tracking on a single axis, minimizing wear, maintenance costs, and maintaining process efficiency; b. Some prior art uses only one system for drying ores or grains, limited to gas or wood-fired furnaces. Solved by developing a system that, in addition to using more than one energy source (one of them renewable), adopting a hybrid system, reuses residual heat using a second heat exchanger; c. Some prior art uses a closed system to reuse drying air, which can lead to problems with humidity and maintenance. Solved by using a duct to collect residual drying air, passing it through a filter to eliminate airborne particles, and passing this still-heated air through a secondary heat exchanger; and d.The internal pressure in the oil heating system does not have a self-adjusting system, which can lead to leaks on days with high levels of sunlight. This is resolved by inserting an expansion tank, which adjusts the internal pressure of the piping, thus preventing further problems with leaks.

[0020] The inventor faced a rather challenging technical problem in the mining sector: the need for an efficient and sustainable industrial drying system. After 13 years of experience in research and development (R&D), including master's and doctoral research where he developed a bench with a solar concentrator and a furnace, and another bench with a solar concentrator and a system for measuring the solar energy flux curve in the image of the solar concentrator's focus, respectively, the author noted that solar energy could be a viable solution for reducing fossil fuel consumption and minimizing pollutant emissions, as well as increasing the availability of thermal energy for industrial thermal processes. Furthermore, when concentrated, solar energy could enhance these factors.

[0021] From this, the inventor sought to develop a heating system that utilized solar concentrators, thermal fluids, heat exchangers, and other components. In this way, the system would combine the possibility of reducing operational costs with environmentally friendly practices, contributing to the achievement of sustainability goals.

[0022] After implementing the first prototype during his master's degree, the inventor continued to refine his invention, adding variables that would allow for more effective control, through automated systems, for example. This could ensure a more efficient and safer operation of the system.

[0023] Finally, the entire research and development process not only resulted in an innovative solution for the sector but also consolidated the inventor as an expert in the field, focused on sustainable heating technologies and proposing / solving contemporary challenges in this market.

[0024] Brief description of the drawings

[0025] For a better understanding of the present patent, the following figures are attached: / 9

[0026] Figure 1 schematically illustrates the thermal fluid heating cycle with cylindrical parabolic solar concentrators, including: thermal reservoir, expansion tank, heat exchangers, and support system;

[0027] Figure 2 schematically illustrates the thermal fluid heating cycle with: cylindrical parabolic solar concentrators, expansion tank, heat exchangers and support system;

[0028] Figure 3 schematically illustrates the thermal fluid heating cycle with fixed-focus solar concentrators, a thermal reservoir as an expansion tank, heat exchangers, and a backup system with gas generation; and

[0029] Figure 4 illustrates a perspective view of the plant with the thermal fluid heating cycle including: cylindrical parabolic solar concentrators, expansion tank, heat exchangers, and support system.

[0030] Description of the invention

[0031] According to Figure 1, the plant in its most complete version has in its hydraulic heating circuit equipped with a thermal reservoir (1); containing a plurality of temperature sensors (22), positioned vertically along the side, but which could be any other internal temperature monitoring system; equipped with a temperature sensor (22), connected to the piping at the outlet of the thermal reservoir (1); equipped with a pressure sensor (21), connected to the piping at the outlet of the thermal reservoir (1); equipped with a temperature sensor (22), connected to the piping at the outlet of the thermal reservoir (1); equipped with a main pump (5) downstream of the thermal reservoir (1), connected by a pipe at the bottom of the same; equipped with a flow sensor (23) downstream of the main pump (5), connected through a pipe; equipped with an inlet valve (2) downstream of the flow sensor (23), connected through a pipe;equipped with temperature sensors (22), connected to both pipes at the outlet of the inlet valve (2); equipped with pressure sensors (21), connected to both pipes at the outlet of the inlet valve (2); equipped with a plurality of solar concentrators (3) downstream of the inlet valve (2), connected via a pipe; equipped with temperature sensors (22), connected to the pipe at the outlet of the thermal reservoir (1); equipped with pressure sensors (21), connected to both pipes at the outlet of the solar concentrators (3); equipped with an outlet valve (4) downstream of the solar concentrators (3) and upstream of the thermal reservoir (1), connected via a pipe, at the top of the thermal reservoir (1); equipped with a temperature sensor (22), connected to the pipe at the inlet of the thermal reservoir (1); equipped with a pressure sensor (21), connected to the pipe at the inlet of the thermal reservoir (1);equipped with a main heat exchanger (11) downstream of the thermal reservoir (1), connected via a pipe to the top of the thermal reservoir (1); equipped with temperature sensors (22), connected to the pipe at the outlet of the thermal reservoir (1); one positioned near the thermal reservoir (1) and another near the main heat exchanger (11); equipped with pressure sensors (21), connected to the pipe at the outlet of the thermal reservoir (1); one positioned near the thermal reservoir (1) and another near the main heat exchanger (11); equipped with an expansion tank (7) downstream of the main heat exchanger (11); equipped with a temperature sensor (22), connected to the pipe at the outlet of the main heat exchanger (11); equipped with a pressure sensor (21), connected to the pipe at the outlet of the main heat exchanger (11);equipped with a nitrogen tank (8), which can be replaced by any gas from a higher pressure reservoir or a compressor or, alternatively, a mechanical pressurization system; upstream of the expansion tank (7); equipped with a pressure sensor (21), connected to the piping at the outlet of the nitrogen tank (8); equipped with a temperature sensor (22), connected to the side of the expansion tank (7); equipped with a pressure sensor (21), connected to the side of the expansion tank (7); equipped with an expansion tank pump (6); downstream of the expansion tank (7); equipped with a flow sensor (23) downstream of the expansion tank pump (6), and upstream of the thermal reservoir (1), connected by a pipe at the bottom; equipped with a temperature sensor (22), connected to the lower inlet of the thermal reservoir (1); equipped with a pressure sensor (21), connected to the lower inlet of the thermal reservoir (1);in its air intake and supply circuit for drying it is equipped with a secondary heat exchanger (10), upstream of the primary heat exchanger (11), equipped with four temperature sensors (22), connected to the ambient air inlet, the residual air inlet, the residual air outlet and the heating air outlet of the secondary heat exchanger (10); equipped with a main fan (9), upstream of the secondary heat exchanger (10); equipped with a temperature sensor (22), connected to the air outlet of the lower primary heat exchanger (11); equipped with a dryer (12), positioned downstream of the primary heat exchanger (11); equipped with a filter (13) positioned at the end of the dryer (12), at the top; equipped with an exhaust fan (14), positioned downstream of the filter (13); equipped with a temperature sensor (22), connected to the exhaust fan outlet (14);equipped with a wet air valve (15), positioned downstream of the exhaust fan (14) and upstream of the secondary heat exchanger (10); equipped with a backup dryer (16), installed at the initial end of the dryer (12); equipped with a PLC or similar device, which controls all the sensors and actuators of the plant.

[0032] The internal temperature of the thermal reservoir (1) is higher at the top than at the bottom, therefore the main pump (5) collects the fluid through a connection at the bottom and feeds the solar concentrators (3) through a branch in the inlet valve (2).

[0033] The heating of the fluid by the solar concentrators (3) occurs due to solar incidence on the parabolic mirrors, after the fluid passes through the receivers of the solar concentrators (3), mixing in the outlet valve (4), returning to the thermal reservoir.

[0034] (I) by the upper part of the same.

[0035] The main heat exchanger (11) is fed with the fluid with the highest temperature from the thermal reservoir (1), collected from the top. After the fluid performs heat exchange with atmospheric air in the main heat exchanger (11), it loses thermal energy and returns to the expansion tank (7). The expansion tank (7) is necessary due to the variation in fluid volume as a function of temperature due to variations in solar radiation incidence throughout the day. The tank with higher pressure, which can be a nitrogen tank (8), or another gas in a reservoir or pressurized by a compressor, or even a mechanical system, maintains the internal pressure of the expansion tank (7) constant and, consequently, of the entire thermal fluid cycle so that it remains within the thermodynamic conditions of the process.

[0036] Atmospheric air is vented into the secondary heat exchanger (10) where it is heated by the residual humid air from the dryer (12). Upon exiting the secondary heat exchanger (10), the previously heated atmospheric air passes through the main heat exchanger.

[0037] (II) where its temperature is raised before passing through the dryer (12). If the air temperature at the outlet of the main heat exchanger (11) is below the temperature required to enter the dryer (12), a support system (16) is activated to complete the heating.

[0038] This support system (16), which is a final heater for the air, can use any fuel available on site, or it can be any type of heating system.

[0039] In the dryer (12), the heated air gives off thermal energy to the drying material. Therefore, its temperature decreases. After exiting the dryer (12), the air enters one or more filters (13), with the aid of an exhaust fan (14), where residual particles dispersed due to interactions inside the dryer (12) are separated from the air.

[0040] If the air temperature at the outlet of the filters (13) is above the ambient air temperature, the air recirculation valve (15) is adjusted to direct the airflow to the secondary heat exchanger (10). If, on the other hand, the air temperature at the outlet of the filters (13) is equal to or lower than the ambient air temperature, the air recirculation valve (15) directs the airflow to the environment.

[0041] The plant is equipped with global solar radiation meters, diffuse radiation in the horizontal plane and direct radiation in the plane orthogonal to the incidence, wind speed and direction meter, ambient humidity meter, pressure, temperature and flow meters, in addition to the control and automation system. The thermal reservoir (1) has a pressure sensor (21) and several temperature sensors (22) arranged vertically for monitoring and controlling the temperature gradient. There is a temperature sensor (22) and a pressure sensor (21) in the pipe between the reservoir (1) and the main pump (5). There is a flow sensor (23), a temperature sensor (22) and a pressure sensor (21) between the main pump (5) and the solar concentrators (3). There is a temperature sensor (22) and a pressure sensor (21) between the solar concentrators (3) and the thermal reservoir (1).

[0042] If the temperature of the thermal fluid at the outlet of the solar concentrators (3) is greater than the temperature at the inlet of the solar concentrators (3), the system remains set for heating. If the temperature of the thermal fluid at the outlet of the solar concentrators (3) is equal to or less than the temperature of the thermal fluid at the inlet of the solar concentrators (3) for a pre-set time, there is not enough solar radiation to heat the system, and therefore the solar concentrators (3) are defocused and the main pump (5) is switched off. If there is uninterrupted solar radiation for a pre-set time, the main pump (5) is switched on and the solar concentrators (3) are positioned for focusing.If the temperature of the thermal fluid at the outlet of the solar concentrators (3) reaches a pre-established maximum limit for the thermal fluid temperature, the main pump (5) is adjusted to increase the flow rate so that the temperature difference between the outlet and inlet of the solar concentrators (3) decreases. If the system flow rate adjustment reaches the maximum flow rate and the temperature of the thermal fluid reaches the pre-established limit for its maximum temperature, the solar concentrators (3) are defocused and the main pump (5) is switched off. If the pressure sensors (21) show values ​​different from the expected operating levels for a given flow and a given temperature, the programmed safety system is activated, the solar concentrators (3) are defocused and the hydraulic pump is switched off.

[0043] If the air temperature at the heat exchanger outlet (11) is below the temperature specified in the design, the hydraulic pump (6) is adjusted to increase the flow rate of the thermal fluid to reduce the temperature difference of the thermal fluid between the inlet and outlet of the heat exchanger (11) and thus increase the air temperature difference between the inlet and outlet of this heat exchanger (11). If the air temperature at the heat exchanger outlet (11) is above the maximum temperature pre-established in the design, the hydraulic pump (6) is adjusted to reduce the flow rate of the thermal fluid to decrease the heat transferred between the thermal fluid and the drying air.

[0044] The pressure sensor between the expansion tank (7) and the pressurized gas reservoir (8), or other gas from a reservoir or compressor or even a mechanical system, assists in controlling the thermal fluid pressure throughout the system to maintain the design thermodynamic conditions.

[0045] If the temperature sensor (22) of the thermal fluid at the inlet of the heat exchanger (11) indicates a temperature below a pre-established limit in the design, the system is switched off, as it is understood that the thermal reservoir has reached the minimum operating temperature.

[0046] The system can be controlled by a PLC, a microcontroller system, or a similar controller.

[0047] Examples of embodiments of the invention

[0048] According to Figure 2, the plant, in a reduced variation, without containing the thermal reservoir (1), using only the expansion tank (7) to store the fluid; in its hydraulic heating circuit it is equipped with an expansion tank (7); equipped with a pressure sensor (21), connected to the side of the expansion tank (7); equipped with a temperature sensor (22), connected to the side of the expansion tank (7); equipped with a main pump (5) downstream of the expansion tank (7) and connected by a pipe at the bottom of the same; equipped with a flow sensor (23) downstream of the main pump (5), connected through a pipe; equipped with an inlet valve (2) downstream of the flow sensor (23), connected through a pipe; equipped with temperature sensors (22), connected to both pipes at the outlet of the inlet valve (2); equipped with pressure sensors (21), connected to both pipes at the outlet of the inlet valve (2);equipped with a plurality of solar concentrators (3) downstream of the inlet valve (2), connected via a pipe; equipped with temperature sensors (22), connected to the pipe at the outlet of the thermal reservoir (1); equipped with pressure sensors (21), connected to both pipes at the outlet of the solar concentrators (3); equipped with an outlet valve (4) downstream of the solar concentrators (3) and upstream of the thermal reservoir (1), connected via a pipe, at the top of the thermal reservoir (1); equipped with a temperature sensor (22), connected to the pipe at the inlet of the main heat exchanger (11); equipped with a pressure sensor (21), connected to the pipe at the inlet of the main heat exchanger (11); equipped with a main heat exchanger (11) downstream of the outlet valve (4) and upstream of the expansion tank (7), connected via a pipe, at the bottom of the thermal reservoir (1);equipped with a temperature sensor (22), connected to the piping at the outlet of the main heat exchanger (11); equipped with a pressure sensor (21), connected to the piping at the outlet of the main heat exchanger (11); equipped with a nitrogen tank (8), which can be replaced by any gas from a higher pressure reservoir or a compressor or a mechanical pressurization system; upstream of the expansion tank (7); equipped with a pressure sensor (21), connected to the piping at the outlet of the nitrogen tank (8); in its air intake and supply circuit for drying, it is equipped with a secondary heat exchanger (10), upstream of the primary heat exchanger (11), equipped with four temperature sensors (22), connected to the ambient air inlet, the residual air inlet, the residual air outlet and the heating air outlet of the secondary heat exchanger (10); equipped with a main fan (9), upstream of the secondary heat exchanger (10);equipped with a temperature sensor (22), connected to the air outlet of the lower primary heat exchanger (11); equipped with a dryer (12), positioned downstream of the primary heat exchanger (11); equipped with a filter (13) positioned at the end of the dryer (12), at the top; equipped with an exhaust fan (14), positioned downstream of the filter (13); equipped with a temperature sensor (22), connected to the exhaust fan outlet (14); equipped with a humid air valve (15), positioned downstream of the exhaust fan (14) and upstream of the secondary heat exchanger (10); equipped with a backup dryer (16), installed at the beginning end of the dryer (12); equipped with a PLC or similar device, which controls all the sensors and actuators of the plant.

[0049] According to Figure 3, the plant with a gas generation system, in its hydraulic heating circuit, is equipped with a thermal reservoir (1); containing a plurality of temperature sensors (22), positioned vertically along the side; containing a pressure sensor (21) positioned on the side opposite the temperature sensors (22); equipped with a temperature sensor (22), connected to the piping at the outlet of the thermal reservoir (1); equipped with a pressure sensor (21), connected to the piping at the outlet of the thermal reservoir (1); equipped with an expansion tank (7), downstream of the thermal reservoir (1); equipped with a nitrogen tank (8), which can be replaced by any gas from a higher pressure reservoir or from a compressor or, alternatively, a mechanical pressurization system; positioned upstream of the expansion tank (7); equipped with a temperature sensor (22), connected to the side of the expansion tank (7);equipped with a pressure sensor (21), connected to the side of the expansion tank (7); equipped with an oil filter (24) downstream of the expansion tank (7), connected by a pipe to the bottom of the same; equipped with a main pump (5) downstream of the oil filter (24) and connected by a pipe; equipped with a flow sensor (23) downstream of the main pump (5), connected by a pipe; equipped with a pressure sensor (21) and a temperature sensor (22), both connected to the pipe downstream of the flow sensor (23); equipped with a solar concentrator (3) downstream of the flow sensor (23) and upstream of the thermal reservoir (1), connected by a pipe and connected at the top to the inlet of the thermal reservoir (1); equipped with a valve (2); downstream of the thermal reservoir (1), connected by a pipe to the top of the expansion tank (7); equipped with a temperature sensor (22), connected to the pipe at the outlet of the thermal reservoir (1);equipped with a pressure sensor (21), connected to the piping at the outlet of the thermal reservoir (1) upstream of the valve (2); equipped with a valve (4), downstream of the valve (2); equipped with a heat exchanger (18), downstream of the valve (4); equipped with a dryer (12), downstream of the heat exchanger (18); connected via duct; equipped with a flow heater (17); downstream of the valve (2) and upstream of the valve (4), forming a bypass; in its air intake and supply circuit for drying it is equipped with a main fan (9) upstream of the heat exchanger (18); equipped with a flow sensor (23), downstream of the main fan (9); equipped with a temperature sensor (22), connected to the ambient air inlet equipped with a dryer (12), positioned downstream of the heat exchanger (18); equipped with a biodigester (19), positioned downstream of the dryer (12) and upstream of the flow heater (17), equipped with a filter (13) downstream of the biodigester (19);equipped with an exhaust fan (14), positioned downstream of the filter (13); equipped with a condensate water tank (20), downstream of the biodigester (19) at the bottom; equipped with a flow sensor (23), downstream of the biodigester (19) and upstream of the flow heater (17) connected by a pipe at the bottom; equipped with a pressure sensor (21); connected to the pipe downstream of the biodigester (19) and upstream of the flow sensor (23) connected to the pipe; equipped with a gas burner as a support system (16), fixed at the bottom of the dryer (12) and connected downstream of the flow sensor (23) of the biodigester (19); equipped with a gas burner as a support system (16), fixed at the bottom of the thermal reservoir (1) and connected downstream of the flow sensor (23) of the biodigester (19); equipped with a return valve (25), connected to a pipe downstream of the heat exchanger (18) and downstream of the dryer inlet (12);equipped with a heat exchanger return pump (26) connected downstream of the return valve (25) and upstream of the thermal reservoir (1) connecting to the bottom of the same; equipped with a dryer return pump (27) connected downstream of the dryer outlet (12) and upstream of the thermal reservoir (1) connecting to the bottom of the same; equipped with a pressure sensor (21) and a temperature sensor (22), both connected to the piping upstream of the dryer return pump (27); equipped with a pressure sensor (21) and a temperature sensor (22), both connected to the piping upstream of the heat exchanger return pump (26); equipped with a pressure sensor (21) and a temperature sensor (22), both connected to the piping downstream of the dryer (12) return valve (25) and upstream of the thermal reservoir (1) and equipped with a PLC or similar device, which controls all the sensors and actuators of the plant.

[0050] Solar concentrators (3) can be of the following types:

[0051] 1. With parabolic profile reflectors with a cylindrical tube receiver, enclosed or not by a glass tube. The receiver is a tube with an external surface treatment, specific paint, thermal or thermochemical treatment, and may have intensified viscosity. Inside the receiver tube circulates a thermal fluid, which can be water, oil, or saline solution. Inside this tube, there may or may not be a system for intensifying heat exchange by increasing the Reynolds number. This equipment can be a twisted ribbon, spring, or internal fins.

[0052] 2. Fresnel type, with flat reflectors and cylindrical receivers, possibly with or without a secondary reflector, of the CPC type. The receiver is analogous to the previous one, with a tube treated on the outer surface to increase the absorptivity of solar radiation. On the inner side, there may or may not be a heat transfer intensification system.

[0053] 3. With fixed-focus paraboloidal geometry reflectors (Scheffler type). The receiver has a similar treatment to the receiver of previous solar concentrators, although with a different geometry. The receiver also has a thermal insulation system.

[0054] 4. Of the central tower type, in which there is a field of heliostats that reflects solar radiation to a specific region, where there is a receiver at the top of a tower. Or, alternatively, instead of a tower with a receiver, there is a secondary reflector to redirect solar radiation downwards, where there is a receiver.

[0055] All the solar concentrator models (3) mentioned must be equipped with a tracking system that articulates the structure to keep the mirrors aligned with the incidence of solar radiation constantly or for predefined periods in order to keep the incident solar radiation concentrated on the receiver. This system can be powered by means of an electric motor with reduction, it can be gravitational, pneumatic, by means of springs, by lighting sensors or photovoltaic panels. According to figure 3, the plant with gas generation system can present a variation using the thermal reservoir (1) in a pressurized form with the expansion tank (7), eliminating the use of a second tank.

Claims

MODIFIED CLAIMS Received by the International Secretariat on March 27, 2026 (27.03.2026) 1. Multistage air heating system for drying using concentrated solar energy, characterized by the plant having:

5. Thermal fluid heating hydraulic circuit containing: at least one thermal reservoir (1); at least one hydraulic pump (5); a flow sensor (23); one or more solar concentrators (3) configured to heat a thermal fluid; thermal fluid cooling circuit containing at least one thermal reservoir (1); at least one main heat exchanger (11); at least one expansion tank (7); a nitrogen tank (8), which may be replaced by any gas. 10 from a higher pressure reservoir or from a compressor or, alternatively, a mechanical pressurization system; at least one hydraulic pump (6); a flow sensor (23); air intake and supply circuit for drying and containing at least one secondary heat exchanger (10); containing at least one main fan (9); containing at least one main heat exchanger (11); containing at least one dryer 15 (12); containing at least one filter (13); containing at least one exhaust fan (14); containing at least one humid air valve (15); containing at least one auxiliary heater (16), installed at the initial end of the dryer (12); containing a programmable logic controller (PLC).

2. A multi-stage air heating system for drying using concentrated solar energy, according to claim 1, alternatively the plant is characterized by: 20 Hydraulic heating and cooling circuit containing an expansion tank (7); containing a main pump (5); containing a flow sensor (23); containing an inlet valve (2); containing one or more solar concentrators (3), equipped with a solar radiation incidence tracking system; containing an outlet valve (4); containing a main heat exchanger (11); containing a nitrogen tank (8), which can be replaced by any gas from a higher pressure reservoir or from a compressor or, alternatively, a mechanical pressurization system; 25 Air intake and supply circuit for drying contains a secondary heat exchanger (10); containing a main fan (9); containing at least one main heat exchanger (11); containing at least one dryer (12); containing a filter (13); containing an exhaust fan (14); containing a humid air valve (15); containing a backup heater (16); equipped with a programmable logic controller (PLC), which may be any process control and / or automation system.

3. Multistage Air Heating System for Drying Using Solar Energy 30 CONCENTRATED, according to claim 1, alternatively the plant is characterized by: The hydraulic heating circuit shall contain at least one thermal reservoir (1); containing a plurality of temperature sensors (22), positioned vertically along the side; containing a pressure sensor (21); containing at least one expansion tank (7); containing at least one nitrogen tank (8); containing at least one oil filter (24); containing to less than one main pump (5); containing flow sensor (23); containing at least one or a plurality of solar concentrators (3), equipped with a system for tracking the incidence of solar radiation; In its thermal fluid cooling circuit containing valve (2); containing valve (4); containing at least one flow heater (17); downstream of valve (2) and upstream of valve (4), forming a bypass; 5. Its air intake and supply circuit for drying contains a main fan (9); containing a flow sensor (23); containing at least one heat exchanger (18); containing at least one dryer (12); containing at least one biodigester. (19); containing at least one filter (13); containing at least one exhaust fan (14); containing at least one condensate water tank (20); containing flow sensor (23); containing at least one gas burner as a backup system (16); containing return valve (25); containing heat exchanger return pump (26); containing dryer return pump (27); containing a 10. Programmable logic controller (PLC).

4. MULTISTAGE AIR HEATING SYSTEM FOR DRYING BY MEANS OF CONCENTRATED SOLAR ENERGY, according to claims 1, 2 or 3, characterized by having a plurality of temperature sensors (22) and pressure sensors (21) along the plant piping.

5. Multistage Air Heating System for Drying Using Solar Energy 15 CONCENTRATED, according to claims 1, 2 or 3, characterized in that the plant control is alternatively carried out by a microcontroller system or a similar controller.

6. MULTISTAGE AIR HEATING SYSTEM FOR DRYING BY MEANS OF CONCENTRATED SOLAR ENERGY, according to claims 1, 2 or 3, characterized in that the heating fluid is water or oil or a saline solution. 20 7. MULTISTAGE AIR HEATING SYSTEM FOR DRYING BY MEANS OF CONCENTRATED SOLAR ENERGY, according to claims 1, 2 or 3, characterized in that the expansion tank (7) is associated with a pressurization system containing pressurized gas or compressor, configured to maintain stable thermodynamic conditions of the thermal fluid, if necessary.

8. Multistage Air Heating System for Drying Using Solar Energy 25 CONCENTRATED, according to claims 1, 2 or 3, characterized in that the recirculation valve (15) is controlled according to the temperature of the residual air, allowing recirculation when the temperature is higher than the ambient temperature and discharge to the environment otherwise.

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