Process and installation of air conditioning for grain drying

Description

1 / 11 AIR CONDITIONING PROCESS AND EQUIPMENT FOR GRAIN DRYING Technical sector

[001] The present invention belongs to the agribusiness technology sector, more specifically it refers to an air conditioning process and equipment for grain drying, which improves biomass combustion, optimizes the mixing of gases with ambient air and makes grain drying more effective, reducing biomass consumption and the emission of carbon monoxide, smoke and sparks. State of the art

[002] In the context of agribusiness, the different types of planted grains exhibit a large variation in moisture content when harvested from the fields, which must be corrected to bring these grains into line with appropriate relative moisture levels for storage and / or processing.

[003] One of the main processes used by cereal processing plants is mechanized drying in equipment specifically designed for this purpose, using biomass combustion to condition the drying air. To achieve these objectives, the industry has developed equipment called a grain dryer or furnace. This technology uses the principle of biomass combustion to generate heat that will treat a certain amount of air drawn in by the dryer's exhaust fans to promote the dehydration of the grains.

[004] To dry products such as corn, soybeans, wheat, and coffee, firewood is frequently used as fuel. Fuels are substances rich in carbon and hydrogen that react chemically in the presence of oxygen to release CO2, water vapor, and energy in the form of heat and light. The combustion of organic fuels, such as firewood, is an exothermic process in which the fuel and combustion air are consumed to produce combustion gases and solid substances (ash / slag) as byproducts.

[005] Combustion can be complete or incomplete depending on the volume of Petition 870260049388, dated 05 / 25 / 2026, page 16 / 46 2 / 11 primary air is needed to oxidize the fuel during the combustion process. If the fuel supplied is greater than the volume of air, or vice versa, there will be an incomplete combustion process or pyrolysis, producing CO (carbon monoxide) known as soot.

[006] For complete combustion, the fuel temperature must also be observed (in the case of firewood, temperature > 300°C), retention time in the furnace for combustion to occur, and air movement within the furnace in order to provide a homogeneous mixture between air and fuel, that is, fully meeting the stoichiometric conditions.

[007] Furnaces can be classified as direct or indirect heating and consist of a combustion chamber formed by a grate, primary and secondary air intake openings, and an ash pan. In direct heating, the gases from combustion are mixed with ambient air blown by a fan directly onto the grain mass. In indirect combustion, the gases from combustion pass through a heat exchanger that heats the drying air.

[008] In conventional air conditioning processes for grain drying, to obtain a larger volume of gases (hot air), the configuration used adopts an excess of air passing inside the furnace, causing incomplete combustion, which limits the burning temperature inside the furnace, preventing the "burning of volatiles" that occurs in the range of 550 to 800°C, in addition to smoke emission, risk of fire due to the production of incandescent sparks, low drying yield and high allocation of labor because of the high consumption of firewood.

[009] This condition of spark production inside the furnace generates the need for a supplementary post-combustion system to mitigate the continued carryover of sparks into the dryer body, thus avoiding the risk of fire in the grain mass. Therefore, equipment called cyclones is used, in which the sparks enter a spiral motion and are separated from the gas flow by the action of centrifugal force, falling through the flow. Petition 870260049388, dated 05 / 25 / 2026, page 17 / 46 3 / 11 lower and letting the gases out through the upper flow.

[010] Furthermore, in systems with incomplete combustion of organic matter, contamination of the grains occurs with toxic chemical agents, Polycyclic Aromatic Hydrocarbons (PAHs) which are generated under high temperature, released in the form of vapors and with high carcinogenic and mutagenic potential.

[011] Patent document BRPI0800527 describes a grain drying system with a continuous cross-flow dryer. There are 3 air inlets in the dryer. In this drying system, the volume and speed of the air passing through the grate are high. This configuration causes combustion at low temperatures inside the furnace, in addition to promoting the generation of sparks and smoke, making it necessary to attach a cyclone to retain the sparks, reducing the risk of fire.

[012] Patent document BR202015010001 describes a drying equipment applied in the grain drying system. In this drying system, the volume and speed of the air passing through the combustion chamber are high, therefore it is necessary to use equipment (flame arrester and swirler) to retain sparks and reduce the risk of fire.

[013] Patent document BR102021002378 describes a grain drying system comprising a furnace formed by three zones: combustion, afterburner, and ambient air intake positioned before the grain dryer inlet. In this furnace, the volume and speed of air passing through the combustion chamber are high, resulting in incomplete combustion and failing to meet stoichiometric conditions. The ambient air mixing chamber is open, causing a very rapid passage of the mixture and generating insufficient air path and residence time to promote adequate homogenization of the ambient air with the hot gas and to retain sparks before reaching the dryer body. Thus, the non-homogeneous air mixture, with sparks and a high CO content, promotes ineffective grain drying, with high contamination of toxic chemical agents, in addition to increasing Petition 870260049388, dated 05 / 25 / 2026, page 18 / 46 4 / 11 the risk of fire.

[014] In this context, it is necessary to develop an air conditioning process and equipment for grain drying that promotes efficient biomass combustion, with greater generation of thermal energy, spark retention and stabilization of the drying air temperature. New features and purpose of the invention

[015] The present invention aims at a process and air conditioning equipment for grain drying, which achieves a higher energy yield from biomass combustion, makes the mixture of gases with ambient air more homogeneous, resulting in reduced consumption of firewood and emission of smoke and sparks.

[016] The equipment of the invention consists of a combustion chamber, a post-combustion chamber and an air mixing chamber. The combustion chamber is equipped with air inlet openings, a grate area and a gas outlet; the post-combustion chamber has at least one baffle to increase the passage time of the gases and to abate sparks and the air mixing chamber has at least three baffles for homogenizing the gases with the ambient air.

[017] Ambient air intake openings are positioned immediately after the after-combustion chamber. In this way, the largest volume of ambient air is introduced after the combustion chamber and not inside the furnace. This makes it possible to reduce the rate of air passing through the firewood, without excess air and dragging of sparks into the dryer body, avoiding the risk of fire in the grain mass and eliminating the need for equipment to retain sparks (cyclone, flame arrester or swirler).

[018] Furthermore, the presence of a complete combustion area increases the air path and improves the homogenization of the drying air that reaches the dryer, providing ideal conditions for grain drying, culminating in optimized drying efficiency, lower firewood consumption, less release of polluting gases into the atmosphere, and a lower quantity of agents. Petition 870260049388, dated 05 / 25 / 2026, page 19 / 46 5 / 11 toxic chemicals. Advantages and technical effects of the invention

[019] The air conditioning process and equipment for drying grains, the subject of the invention, results in the following advantages and achieves the following technical effects on those incorporating prior art: • The equipment configuration provides an ideal atmosphere for the complete combustion of firewood, producing superheated gases; • Reducing air turbulence inside the equipment; • Improved biomass combustion, generating gases at higher temperatures; • With warmer gases, it is possible to mix a larger volume of ambient air, generating a larger volume of drying air with the same volume of biomass; • Reduction of grain drying time; • Reducing temperature variation during the drying process, thus reducing the frequency of firewood replenishment, which establishes a less tiring and more ergonomic working condition for employees in grain processing plants; • Increasing the path traveled by the combustion air, optimizing the mixing with ambient air in order to provide drying air with a homogeneous temperature to be inserted into the dryer; • Optimized grain drying, consequently producing grains with higher nutritional value, less smoke odor, and reduced contamination by chemical compounds; • Reduction of grain contamination by Polycyclic Aromatic Hydrocarbons (PAHs); • Reduction in the emission of toxic gases and particulate matter by the equipment; • Drying process that adheres to environmental, social, and corporate governance (ESG) practices; Petition 870260049388, dated 05 / 25 / 2026, page 20 / 46 6 / 11 • Reduction in spark production and minimization of fire risk; • Eliminates the need for equipment to dissipate sparks from the airflow; • Lower firewood consumption and grain drying costs; • Reduction in smoke and soot production; • Reduced labor costs, as it requires less frequent firewood replenishment. List of attached drawings

[020] In order that the present invention may be fully understood and put into practice by any technician in this technological sector, it is described in a clear, precise and sufficient manner, based on the attached drawings listed below, which illustrate preferred embodiments of the process and air conditioning equipment for grain drying: Figure 1 - Flowchart of the air conditioning process for grain drying; Figure 2 - Side view in section of the air conditioning equipment for grain drying. Detailed description of the invention

[021] The process and equipment of the invention produce superheated gases, heating a larger volume of drying air and promoting optimized grain drying, consequently producing grains with higher nutritional value, less smoke smell in the grain and reduced contamination by chemical compounds.

[022] Figure 1 illustrates the air conditioning process for grain drying, which comprises the following steps: Stage A - biomass combustion on a fixed grate, generating hot air in the range of 550 to 800 °C, which will treat a certain quantity of air to be carried away by the dryer exhaust fans; the biomass can be firewood logs or wood chips, fed manually or on a conveyor belt driven by chains - the combustion process has an excess Petition 870260049388, dated 05 / 25 / 2026, page 21 / 46 7 / 11 of air in the range of 1.4 to 1.6 times above the theoretical combustion air volume, with the stoichiometric combustion air volume in the range of 3.095 to 4.15 m3 per kg of biomass; Stage B - post-combustion - deflector panels promote spark suppression, being divided into at least three sub-stages: (B1) entry, (B2) suppression and (B3) exit; Stage C - mixing of hot gases with ambient air - deflector panels promote the mixing of hot gas from the combustion chamber and post-combustion with the fraction of ambient air from the louvered windows; being divided into at least five mixing sub-stages: (C1) hot gas inlet, (C2) ambient air inlet, (C3) incomplete mixing, (C4) complete mixing and (C5) outlet - with the volume ratio of hot gases to ambient air volume in the range of 6 to 11% and the mixture of hot gases with ambient air in the range of 70 to 100°C; Stage D - feeding the grain dryer with the hot gas mixture, with the energy required ranging from 785 to 950 kcal for each kilogram of water evaporated from the material being dried and introduced into the dryer.

[023] Figure 2 illustrates the equipment for generating hot air for grain drying, comprising a combustion chamber (1) with biomass (firewood logs, wood chips or similar) supplied to the fixed grate (12) through the feed opening (11). The combustion chamber (1) also has ash pan openings (14) for removing combustion residues. The combustion of biomass, under the conditions of the invention, generates hot gases in the range of 550 to 800 °C, which are drawn out by the dryer exhaust fans (5). An excess of air is introduced into the combustion chamber (1) in the range of 1.4 to 1.6 times above the theoretical volume of combustion air. The stoichiometric combustion air volume is in the range of 3.095 to 4.15 m3 per kg of biomass.

[024] The hot gases generated in the combustion chamber (1) flow to the Petition 870260049388, dated 05 / 25 / 2026, p. 22 / 46 8 / 11 aftercombustion chamber (2) through the gas outlet opening (13). The aftercombustion chamber (2) has at least two deflectors (21) that assist in defusing the sparks released during the agitation of the wood during the furnace feeding cycles. The hot gases flow through the lower passage (22) and reach the mixing chamber (3) through the gas outlet opening (23).

[025] The mixing chamber (3) has a louvered window (32) that allows ambient air to enter and at least three deflectors (31) arranged to form alternating openings (33) that optimize the mixing of the hot gas with the ambient air that will be fed into the dryer (5). The ratio of hot gas volume to ambient air volume is in the range of 6 to 11%.

[026] Finally, the mixture of hot gas with ambient air is directed to the grain dryer (5) through the gas outlet chamber (4). The energy required is in the range of 785 to 950 kcal for each kilogram of water evaporated from the material being dried inside the dryer.

[027] The maintenance of the volume of air flowing through the furnace occurs due to the grain dryer's exhaust system, which has fans that draw air through the chambers (2, 3 and 4). The system promotes a column of drying air pressure that passes through the grain mass in the dryer body (5), causing mechanical resistance and natural restriction to the airflow.

[028] As the fans respect a manufacturing architecture that correlates pressure and flow rate, whenever there is an excess of restrictions in the airflow path inside the furnace, there will be an increase in pressure and consequently the total flow rate will be reduced, generating a loss of drying air fed into the dryer proportional to the total volume of air that will pass through the grain mass. Thus, in the equipment of the invention, the arrangement of the deflectors (21 and 31) defines openings (22 and 33) that optimize the conditioning of the drying air without restricting the volume of air flowing through the equipment.

[029] The combustion chambers (1), post-combustion chambers (2) and mixing chambers (3) provide conditions for complete combustion of the wood, which is burned to its fullest extent respecting a previously established volume. As. Petition 870260049388, dated 05 / 25 / 2026, page 23 / 46 9 / 11 combustion chambers (1) and post-combustion chambers (2) must have an equal volume to provide a condition for the emission of volatiles generated from the temperature reached inside the combustion chamber (550 to 800°C). This configuration of the combustion chambers (1), post-combustion chamber (2) and mixing chamber (3) ensures complementary biomass combustion along the equipment's path, allowing for complete combustion with few sparks released during wood agitation during furnace feeding cycles and a reduced amount of CO. EXAMPLE 1

[030] Evaluation of the reduction of chemical substances in corn kernels during drying using the invention. An effective reduction in the amount of chemical agents found in the mass of kernels analyzed after drying with and without the invention was verified (Table 1). The sum of PAHs found in the kernels after drying without the invention totaled 9.1 pg / kg of kernels. In the kernels dried with the invention, the amount of PAHs found was 3.5 pg / kg. Table 1. Presence of Polycyclic Aromatic Hydrocarbons (PAHs) in grains after drying with and without the invention. Parameters Without the invention (pg / Kg) With the invention (pg / Kg) Difference (pg / Kg) Reduction (%): Benzo[a]anthracene B(a)A 3.7 1.1 2.6 70.3 Benzo[a]pyrene B(a)P 0.7 0.2 0.5 71.4 Benzo[a]fluoranthene B(b)F 1.1 0.4 0.7 63.6 Chrysene (ChR) 3.6 1.8 1.8 50.0 Sum of PAHs 9.1 3.5 5.6 61.5 EXAMPLE 2

[031] Evaluation of the efficiency of the air conditioning process for grain drying (Table 2). Regarding the efficiency of the air conditioning process for grain drying, it was observed that the process Petition 870260049388, dated 05 / 25 / 2026, page 24 / 46 The combustion of firewood using the invention is more effective, since a smaller quantity of firewood (in kilograms) is needed per hour to generate the same drying air temperature as conventional equipment. Thus, there is a 77% reduction in firewood consumption, decreasing from 806 m3 to 178 m3 in absolute quantity of firewood that was not burned. Following the same line of reasoning, drying without the invention had an energy yield of 2,848 kcal / kg of evaporated water, consuming 806 m3 of firewood to dry 5,881 tons of corn (Table 2). With the invention, a new energy yield of 729 kcal / kg of evaporated water was achieved, reducing the amount of firewood burned to 178 m3 to dry 6,313 tons of corn. It is important to note that in both cases analyzed, the calorific value adopted for burning the firewood was 2800 kcal / kg of firewood.

[032] Regarding productivity gains, it was observed that the actual drying yield increased from 18.7 t / h of grain to 26.0 t / h of grain. This operational efficiency is estimated from the average volume of moisture entering the grain drying process, which corresponds to the average amount of water to be evaporated. In drying without the invention, the operational yield achieved was 78%, while in drying with the invention, the yield achieved was 96% operational efficiency, which corresponds to a 39% gain in drying productivity in tons per hour (Table 2). Table 2. Efficiency of the air conditioning process of the invention. Corn crop drying Without the invention With the invention Dry grain volume 5,881 t 6,313 t Actual yield 18.7 t / h 26.0 t / h Operational efficiency 78% 96% Firewood consumption 806 m3 178 m3 *Thermal efficiency 2,848 kcal / kg water 729 kcal / kg water Inlet temperature 102.3 °C 90.0 °C Mass temperature 33.4 °C 38.2 °C Input unit 21.1% 18.8% Petition 870260049388, dated 05 / 25 / 2026, page 25 / 46 11 / 11 Output unit 15.4% 14.2% EXAMPLE 3

[033] Drying yield and quantitative measurement of chemical agents released into the atmosphere. A reduction of more than 5 times in the amount of carbon monoxide (CO) released into the atmosphere was observed, decreasing from 2474 ppm to 473 ppm, characterizing the low environmental impact of the invention, mitigating greenhouse gases.

[034] A significant increase in the temperature of the gases measured at the combustion chamber outlet was observed (from 323.6°C to 707.2°C). This allows for the effective combustion of volatiles and a reduction in the amount of smoke and sparks released in the drying system due to the greater efficiency in the wood combustion process, in addition to the drying air temperature, which directly impacts the quality of the grains in terms of their germination capacity and dry matter content during storage. This temperature reduction is directly related to the increase in grain stock, by mitigating losses caused by evaporation and excessive degradation due to the high drying temperature (Table 3).

[035] It was also verified that the temperature variation during the drying process was reduced. This greater thermal stability achieved by the invention drastically reduces the frequency of firewood replenishment, which establishes a less tiring and more ergonomic working condition for the employees of the cereal processing plants during the harvest season. Table 3. Drying yield and carbon monoxide (CO) emission Parameter Without the invention With the invention Process gain CO (ppm) 2474 473 5.2 times reduction Gas temperature (°C) 323.6 707.2 218% gain Drying temperature (°C) Average 95°C Average 70°C 25°C reduction Temperature variation (°C) 25°C in 15 min 5°C in 20 min 45% reduction in firewood Petition 870260049388, dated 05 / 25 / 2026, page 26 / 46

Claims

1 / 2 CLAIMS 1 - AIR CONDITIONING PROCESS FOR GRAIN DRYING comprising the stages of combustion, post-combustion, mixing of hot gases with ambient air and feeding the grain dryer with the mixture of hot gases and ambient air through suction from the dryer fans, characterized by comprising the following stages: A. biomass combustion stage in a fixed grate that generates hot gases in the temperature range of 550 to 800°C; B. post-combustion stage with spark suppression, divided into at least three sub-stages: gas inlet (B1), spark suppression (B2) and post-combustion region outlet (B3); C. hot gas mixing stage with ambient air, divided into at least five sub-stages: hot gas inlet (C1), ambient air inlet (C2), incomplete mixing (C3), complete mixing (C4) and outlet (C5); D.Feeding stage of the grain dryer with a mixture of hot gases and ambient air at a temperature in the range of 70 to 100°C. 2 - AIR CONDITIONING PROCESS FOR GRAIN DRYING, according to claim 1, characterized by having in the combustion stage (A) an excess of air in the range of 1.4 to 1.6 times above the theoretical volume of combustion air. 3 - AIR CONDITIONING EQUIPMENT FOR GRAIN DRYING, which performs the process defined in claim 1, comprising a combustion chamber (1) formed by an opening for feeding biomass (11), a fixed grate (12), openings for ash pans (14) and a gas outlet opening (13); a post-combustion chamber (2) and a mixing chamber (3) for hot gases with ambient air, characterized by: - ​​the post-combustion chamber (2) having at least two deflectors (21) equipped with alternating passages (22) and a gas outlet opening (23) to the mixing chamber (3); - the mixing chamber (3) for hot gases with ambient air having at least three deflectors (31) that form alternating openings (33) and windows of Petition 870260049388, dated 05 / 25 / 2026, page. 39 / 46 2 / 2 Venetian blind (32) for ambient air intake and - an outlet chamber (4) for mixing hot gases with ambient air and intake into the grain dryer (5). Petition 870260049388, dated 05 / 25 / 2026, page.40 / 46.

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