Airflow arrangement method of high static pressure flue-cured tobacco house

Abstract

The application discloses a kind of high static pressure tobacco house's air flow arrangement method, it is related to solve the problem of uniform heating and control exhaust speed in tobacco chamber, and effectively improve the quality of curing tobacco.Circulating air duct is designed in the lower part of tobacco chamber with exhaust channel on both sides, and exhaust electric damper and exhaust regulating induced draft fan are designed on the outside end of exhaust channel.The function is to discharge or lead out part of hot and humid gas from tobacco chamber, and can control the size of static pressure in tobacco chamber, control the transpiration speed of tobacco moisture, control the exhaust speed of tobacco house, reduce the air flow speed in tobacco chamber, make the tobacco in upper and lower shed be heated uniformly, and maximize the retention of tobacco aroma substance.The opening is on both ends of circulating air duct, and the function is to lead part of hot and humid gas from the rear part of tobacco chamber to the air return inlet of heating chamber, and enter the heating chamber with other parts of hot and humid gas to heat and circulate, to avoid the formation of air flow stagnation in the rear part of tobacco chamber.The application is suitable for all intensive tobacco houses, such as heat pump, coal-fired, etc.

Description

Technical Field

[0001] This invention relates to an airflow arrangement method for a high static pressure tobacco curing barn. In particular, it addresses how to solve problems related to pressure uniformity, temperature uniformity, airflow short-circuiting, airflow stagnation, dehumidification rate, and transpiration rate of tobacco leaves during the curing process, which are crucial to the curing quality of the tobacco leaves. Background Technology

[0002] Intensive tobacco curing barns have a history of over 30 years in my country and offer significant advantages in improving tobacco production efficiency. However, their curing quality is not fully recognized by industry professionals, who generally believe it is inferior to older, smaller curing barns. Applying basic principles of fluid mechanics, the problems with traditional intensive curing barns are readily apparent.

[0003] The main problems are as follows:

[0004] 1. In intensive tobacco curing barns, the tobacco leaves at the back of the loading chamber take longer to dry than those at the front.

[0005] This is due to a short circuit in the airflow arrangement. Especially after the later stages of color change, the tobacco leaves gradually wither, and increasingly larger gaps begin to appear between the dense leaves. Because the air outlet and return air inlet of the heating chamber are designed on the same partition wall of the tobacco curing barn, it does not conform to the basic principle of parallel flow arrangement of fluid circulation. This inevitably leads to a short circuit between the supply and return air, resulting in reduced airflow at the rear of the loading chamber and difficulty in returning air, even causing near-stagnant airflow. That is, the air delivered by the circulating fan to the rear of the loading chamber through the heating chamber outlet cannot smoothly circulate back to the heating chamber return air inlet. Only during dehumidification, the accumulated hot and humid air is removed through the rear dehumidification louvers, and even then, the dehumidification capacity is weaker compared to the front of the loading chamber.

[0006] 2. There is a significant difference in the color-changing period of tobacco leaves between the upper and lower sheds, meaning the color-changing time is different.

[0007] The tobacco leaves on the upper rack always turn yellow first, then the middle rack turns yellow, and finally the lower rack turns yellow last. In order to ensure that the lower rack tobacco leaves have completed the color change, the curing time for the entire tobacco leaf color change period must be extended.

[0008] 3. The dehumidification speed cannot be controlled.

[0009] When the fresh air inlet is opened, the dehumidification process begins. The hot and humid gas is quickly expelled from the tobacco loading chamber. The wet-bulb temperature of the tobacco loading chamber can only be controlled intermittently, and cannot be maintained at a constant wet-bulb temperature for a sustained period. This is because the rate of evaporation of moisture in the tobacco leaves cannot be effectively controlled, which is very detrimental to the formation of chemical substances in the tobacco leaves.

[0010] 4. It is impossible to determine the control value of wet-bulb temperature based on the different qualities of tobacco leaves at different harvesting periods.

[0011] The control system lacks data analysis capabilities for wet-bulb temperature, cannot determine the quality of tobacco leaves at different times of the year, and cannot automatically adjust and accurately control the appropriate wet-bulb temperature based on the quality of the tobacco leaves. It relies solely on experience or regulations to control the wet-bulb temperature.

[0012] 5. Outdated technical measures to reduce wind speed.

[0013] To preserve the aroma compounds in tobacco leaves, the traditional approach is to reduce the fan speed, including lowering the frequency of variable frequency fans, to minimize the impact of airflow on the leaves. However, this often reduces the flow rate of circulating gas, resulting in more uneven curing temperatures throughout the tobacco curing chamber, particularly affecting the leaves at the back of the chamber. For heat pump-type tobacco curing barns, reduced circulating gas flow will significantly increase the heat pump exhaust pressure, increase the compression ratio, and raise energy consumption. It may also cause electromechanical malfunctions such as compressor overpressure and motor overcurrent. Summary of the Invention

[0014] In order to overcome the shortcomings described in the background art above, the present invention discloses an airflow arrangement method for a high static pressure tobacco curing barn.

[0015] This invention includes a smoke loading chamber, a heating chamber outlet, a circulating fan, a heating chamber, heating equipment, a circulating air duct, a dehumidification regulating fan, a dehumidification electric damper, a heating chamber return air inlet, an electric fresh air damper, a dehumidification channel, a dehumidification inlet, and a pressure equalizing circulating air duct. The circulating fan is designed above the heating equipment in the heating chamber. The dehumidification channel is designed on both sides of the ground circulating air duct in the smoke loading chamber. The pressure equalizing circulating air duct is designed inside or on the side of the dehumidification channel. On the upper surface and inlet end face of the dehumidification channel, several dehumidification inlets with progressively increasing cross-sectional areas are designed from front to back. An electric dehumidification damper and a dehumidification regulating fan are installed at the inlet end. Utilizing the high static pressure inside the tobacco loading chamber, some of the hot and humid gas inside the chamber enters the dehumidification channel through the dehumidification inlet and is then discharged from the tobacco curing barn. A pressure equalization circulation duct is installed inside or on the side of the dehumidification channel. Its outlet end is designed at the front of the dehumidification channel inside the tobacco loading chamber and leads out to a location near the return air vent of the heating chamber. The inlet end is located near the rear door of the tobacco loading chamber. Utilizing the pressure difference between the higher static pressure at the rear and the lower static pressure at the front of the tobacco loading chamber, some of the hot and humid gas at the rear of the tobacco loading chamber is sent to the return air vent of the heating chamber through the pressure equalization circulation duct.

[0016] A further invention is that the circulating fan is installed at an angle greater than 25° to the horizontal plane, and is lower near the air outlet.

[0017] A further invention is to adjust the opening of the electric fresh air damper and differentially control the amount of fresh air entering the smoke chamber.

[0018] A further invention is to adjust the opening of the dehumidification electric damper and differentially control the static pressure of the smoke chamber.

[0019] A further invention is that the electric fresh air damper is linked with the dehumidification electric damper, and differentially controls the evaporation rate of moisture in the tobacco leaves and the dehumidification rate of the tobacco loading chamber.

[0020] The beneficial effects of this invention are: by using the airflow arrangement method of this invention, a higher static pressure is generated in the tobacco loading chamber, allowing the tobacco leaves to be cured under pressure. Specifically, the static pressure in the middle and rear part of the tobacco loading chamber is controlled at 40-60 Pa (2-3 times that of ordinary dense tobacco curing barns). Furthermore, it effectively solves the problems of uneven pressure, uneven temperature and humidity, airflow short circuit, airflow stagnation, and uncontrollable dehumidification speed when curing tobacco leaves in a tobacco curing barn.

[0021] Installing the circulating fan at an angle greater than 25° to the horizontal plane can increase the air supply pressure at the heating chamber outlet by 30% compared to a horizontally installed circulating fan. 40%, longer air delivery distance, which is conducive to airflow circulation.

[0022] The design of the pressure-equalizing circulating air duct is based on the fundamental principle of fluid flow path alignment. It guides the airflow from the rear of the tobacco loading chamber (far from the heating chamber outlet) back to the heating chamber return air inlet via the pressure-equalizing circulating air duct. During actual operation, the rear of the tobacco loading chamber has the highest static pressure, lowest wind speed, and smallest gas flow rate; conversely, the area near the heating chamber inlet has the lowest static pressure, highest wind speed, and largest gas flow rate. Utilizing the pressure difference between the front and rear sections of the loading chamber, the high-static-pressure airflow at the rear is smoothly guided back to the heating chamber, thus solving the problem of longer drying times for the rear tobacco leaves compared to the front tobacco leaves—in other words, resolving the "airflow stagnation" problem at the rear of the tobacco curing chamber.

[0023] The design of the pressure equalization circulation air duct and dehumidification channel can eliminate the influence of the resistance generated by the vertical pressure of each fluid micro-particle, and avoid the situation where the resistance of each micro-particle increases from front to back, which would increase the resistance of the fluid micro-particles at the rear of the smoke loading chamber. This allows the circulating airflow at the rear to return to the return air inlet smoothly, and allows the hot and humid gas at the rear to be discharged smoothly from the smoke loading chamber.

[0024] The linkage differential control of the electric fresh air damper and the dehumidification electric damper creates a higher static pressure and a lower airflow velocity in the tobacco loading chamber. This allows the tobacco leaves to be cured under high static pressure, enabling dynamic differential control of the wet-bulb temperature and controlling the rate of moisture evaporation from the tobacco leaves, which is more conducive to improving the curing quality of the tobacco leaves.

[0025] The design of the dehumidification regulating fan can cope with special situations, mainly the failure of the circulating fan and the occurrence of high moisture tobacco leaves during special periods.

[0026] The airflow arrangement method of the above high static pressure tobacco curing barn is based on the law of conservation of mechanical energy in fluid mechanics.

[0027] The design concept is as follows: Along the airflow direction within the tobacco curing barn, the airflow is divided into numerous ideal gas particles, each with equal total energy. Since the curing barn is entirely composed of gas, the potential energy of each particle can be eliminated, retaining only pressure and kinetic energy. Based on the physical characteristics of tobacco curing, the airflow particles can be assumed to be in steady flow at a given moment, leading to Bernoulli's theoretical expression:

[0028] C = Pj + V 2 (1)

[0029] In the formula: C Represents the total energy constant of the airflow element.

[0030] Pj This refers to the static pressure (intensity) of a gas flow element.

[0031] The mass density of airflow particles

[0032] V Indicates the airflow velocity of a micro-particle.

[0033] As can be seen from formula (1), since the total energy of each micro-element is a constant, increasing the static pressure energy of the micro-element will decrease the kinetic energy of the micro-element, that is, increasing the static pressure of the micro-element will decrease the airflow velocity of the micro-element.

[0034] When tobacco leaves are roasted, the transpiration of the tobacco leaves themselves will have some impact on the values, but the trend of the changes of each physical quantity in formula (1) remains unchanged.

[0035] In actual tobacco curing, the relationship between static pressure and airflow velocity can be described as follows:

[0036] When the dehumidification electric damper is closed, the total energy of the airflow in the tobacco curing barn remains unchanged, but the static pressure will increase. Under the action of a larger static pressure (pressure energy), the gaps between the tobacco leaves will increase, and the dynamic pressure will inevitably decrease. For all micro-clusters that are ideally fluidized, the airflow velocity will inevitably decrease if the flow rate and mass remain unchanged.

[0037] In summary, by utilizing the fundamental law of conservation of mechanical energy in fluid mechanics, and through the design of electric fresh air dampers, pressure equalization circulation ducts, dehumidification channels, dehumidification electric dampers, and dehumidification regulating fans, it is possible to increase the static pressure and reduce the airflow velocity within the tobacco curing barn, without reducing the circulating air volume within the barn.

[0038] This has further led to the following beneficial effects:

[0039] 1. Increased static pressure, especially during the tobacco leaf color-changing stage, widens the gaps between the dense tobacco leaves, reducing airflow resistance and causing the tobacco leaves on the upper and lower racks to change color almost simultaneously.

[0040] 2. Reducing the airflow speed without reducing the circulating air volume can retain the aroma substances of the tobacco leaves to the greatest extent and ensure that the circulating air volume, heat and temperature at all points in the tobacco curing room are as uniform as possible, thereby ensuring the curing quality.

[0041] 3. The electric fresh air damper and the dehumidification electric damper are linked. While controlling the high static pressure in the tobacco loading chamber, the wet bulb temperature can be dynamically controlled by differential control. By using data analysis technology, the precise wet bulb temperature to be controlled in each baking section can be automatically adjusted according to the moisture content of tobacco leaves in different seasons and different parts, and the dehumidification speed (transpiration rate of tobacco leaves) can be adjusted to ensure baking quality. Attached Figure Description

[0042] Figure 1 This is a perspective view of the airflow arrangement method for the high static pressure tobacco curing barn of the present invention.

[0043] Figure 2 This is a plan sectional view of the airflow arrangement method of the high static pressure tobacco curing barn of the present invention.

[0044] Figure 3 This is a front elevation sectional view of the airflow arrangement method for the high static pressure tobacco curing barn of the present invention.

[0045] In the attached diagram: 1. Smoke chamber; 2. Heating chamber air outlet; 3. Circulating fan; 4. Heating chamber; 5. Heating equipment; 6. Circulating air duct; 7. Dehumidification regulating fan; 8. Dehumidification electric damper; 9. Heating chamber return air inlet; 10. Electric fresh air damper; 11. Dehumidification passage; 12. Dehumidification air inlet; 13. Pressure equalizing circulating air duct. Detailed Implementation

[0046] like Figure 1 As shown, the airflow arrangement method of the invented high static pressure tobacco curing barn is achieved through the following equipment and facilities: a tobacco loading chamber 1, a heating chamber outlet 2, a circulating fan 3, a heating chamber 4, a heating device 5, a circulating air duct 6, a dehumidification regulating fan 7, a dehumidification electric damper 8, a heating chamber return air inlet 9, an electric fresh air damper 10, a dehumidification channel 11, a dehumidification air inlet 12, and a pressure equalizing circulating air duct 13. The circulating fan 2 is designed inside the heating chamber 4, above the heating device 5; the dehumidification channel 11 is designed on both sides of the ground circulating air duct 6 inside the tobacco loading chamber 1; and the pressure equalizing circulating air duct 13 is designed inside or to the side of the dehumidification channel 11.

[0047] like Figure 2 , Figure 3As shown, several exhaust air inlets 12 with progressively larger cross-sectional areas are designed on the upper surface and inlet end face of the exhaust channel 11. An electric exhaust damper 8 and an exhaust regulating fan 7 are installed at the outlet end of the exhaust channel 11. A portion of the hot and humid gas, indicated by the thin dashed arrow, enters the exhaust channel 11 through the exhaust air inlets 12 and is then discharged from the smoke chamber 1 via the electric exhaust damper 8 and the exhaust fan 7.

[0048] like Figure 2 , Figure 3 As shown, a pressure-equalizing circulating air duct 13 is installed inside or on the side of the dehumidification channel 11. The outlet end is led out from the front of the dehumidification channel 11 in the smoke loading chamber 1 near the return air inlet 9 of the heating chamber, and the inlet end is located near the rear door of the smoke loading chamber 1. Among them, a portion of the hot and humid gas indicated by the thin solid arrow enters the heating chamber 4 through the circulating air duct 6 and the return air inlet 9 of the heating chamber for continuous circulation; a portion of the hot and humid gas indicated by the thick solid arrow enters the heating chamber 4 through the pressure-equalizing circulating air duct 13 and the return air inlet 9 of the heating chamber for continuous circulation.

[0049] The function of the pressure equalization circulation air duct 13 is to arrange the airflow in the tobacco loading chamber 1 in the same direction, so as to solve the problems of "airflow stagnation" at the rear end of the tobacco loading chamber 1 and slow tobacco drying.

[0050] The above airflow arrangement method can control the dehumidification rate of the smoke chamber 1 and regulate the static pressure inside the smoke chamber 1.

[0051] This invention takes the downward airflow tobacco curing barn as an example. The upward airflow tobacco curing barn works on the same principle, except that the dehumidification channel and the pressure equalization circulation channel are designed at the top of the tobacco loading chamber, and the circulating fan is designed below the heating equipment.

[0052] This invention is not limited to the above-described embodiments. Any design that produces equivalent results based on the design principles described in this invention, made by those skilled in the art, is included within the scope defined by the claims of this application, such as arranging the dehumidification channel underground or on the outside of the smoke chamber.

Claims

1. A method for airflow arrangement in a high static pressure tobacco curing barn, characterized in that, The system includes a smoke loading chamber, a heating chamber outlet, a circulating fan, a heating chamber, heating equipment, a circulating air duct, a dehumidification regulating fan, a dehumidification electric damper, a heating chamber return air inlet, an electric fresh air damper, a dehumidification passage, a dehumidification inlet, and a pressure equalizing circulating air duct. The circulating fan is located above the heating equipment in the heating chamber. The dehumidification passage is located on both sides of the ground circulating air duct in the smoke loading chamber. The pressure equalizing circulating air duct is located inside or on the side of the dehumidification passage. Several dehumidification inlets with progressively larger cross-sectional areas are arranged from front to back on the upper surface and inlet end face of the dehumidification passage. A pressure equalizing circulating air duct is located at the outlet end of the dehumidification passage. The system is equipped with an electric dehumidification damper and a dehumidification regulating fan. Utilizing the high static pressure inside the tobacco loading chamber, some of the hot and humid gas inside the chamber enters the dehumidification channel through the dehumidification inlet and is then discharged from the tobacco curing barn. A pressure-equalizing circulating air duct is installed inside or on the side of the dehumidification channel. Its outlet is located at the front of the dehumidification channel inside the tobacco loading chamber and leads out to a location near the return air vent of the heating chamber. The inlet is located near the rear door of the tobacco loading chamber. Utilizing the pressure difference between the higher static pressure at the rear and the lower static pressure at the front of the tobacco loading chamber, some of the hot and humid gas at the rear of the tobacco loading chamber is sent to the return air vent of the heating chamber through the pressure-equalizing circulating air duct.

2. The airflow arrangement method for a high static pressure tobacco curing barn according to claim 1, characterized in that, The circulating fan is installed at an angle greater than 25° to the horizontal plane, and is positioned lower near the air outlet.

3. The airflow arrangement method for a high static pressure tobacco curing barn according to claim 1, characterized in that, Adjust the opening of the electric fresh air damper and use differential control to control the amount of fresh air entering the smoke chamber.

4. The airflow arrangement method for a high static pressure tobacco curing barn according to claim 1, characterized in that, Adjust the opening of the dehumidification electric damper and differentially control the static pressure of the smoke chamber.

5. The airflow arrangement method for a high static pressure tobacco curing barn according to claim 1, characterized in that, The electric fresh air damper and the dehumidification electric damper are linked, and the differential control is used to control the evaporation rate of moisture in the tobacco leaves and the dehumidification rate of the tobacco loading chamber.

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