Vertical warehouse grain pile cooling and ventilating system, ventilating method and fan type selection method

Abstract

The invention discloses a vertical warehouse grain pile cooling and ventilating system, a ventilating method and a fan type selection method, and aims to solve the problems of high fan noise, high fan compression heat and non-thorough grain pile cooling and ventilating due to the fact that a large centrifugal fan is adopted in an existing vertical warehouse for pressing-in type ascending grain pile cooling and ventilating. The ventilation system comprises a vertical reinforced concrete silo and four low-power fans, wherein four longitudinally distributed air ducts are uniformly arranged on the inner wall of a cylinder of the silo along the height direction; a transverse flow ventilation mode is adopted, based on the fact that long axes of grains are mainly arranged in the horizontal direction when grains enter the silo, the airflow resistance in the horizontal direction is 0.6 time of the resistance in the vertical direction, a ventilation fan with small power is used, and the equipment cost and the operation cost are reduced; the total ventilation quantity is larger, the grain pile cooling and ventilation time is shorter, and the energy consumption is lower; meanwhile, an alternate airflow ventilation mode is provided, and the problem of a dead zone in the center of a grain pile is effectively solved; the invention further provides a ventilation fan type selection method.

Description

Technical Field

[0001] The present application relates to the technical field of grain storage and circulation, and in particular to a cooling and ventilation system for grain piles in an upright warehouse, a ventilation method and a fan selection method. Background Art

[0002] During the natural storage of grain, due to the combined influence of the external environment and the respiration of grain particles inside the grain pile, the temperature and moisture in the local area of ​​the grain pile will rise, causing insects and mildew, resulting in a decline in grain quality and endangering safe grain storage. Therefore, the temperature and moisture in the grain pile are two parameters that need to be paid attention to during the natural storage process. In order to ensure safe grain storage, the grain storage ventilation system is used to reduce the temperature and moisture inside the grain pile.

[0003] In 1998, my country's grain output exceeded 510 million tons, and the national and local storage capacity was seriously insufficient, making it difficult for farmers to sell grain. Therefore, the country began to build modern reserve grain warehouses, mainly tall flat warehouses. 2003-2016 was an important period for the construction of modern grain reserve warehouses. At present, the various types and proportions of my country's reserve grain warehouses are: 85% tall flat warehouses, 7% vertical silos, 5% shallow round silos, and 2.5% other types of warehouses. Grain storage is to control the moisture content and temperature of stored grain to inhibit the growth of insects and molds, maintain the activity of grains, prolong the deterioration of quality, and improve the processing quality. In temperate and subtropical grain storage areas, based on the two major physical properties of grain piles, namely porosity of 0.35-0.55 and poor heat conductor, the basic grain temperature of dry grain piles is reduced by using natural cool air to cool and ventilate in autumn and winter, and the growth and development of stored grain pests and the quality of grain are controlled by grain surface temperature control and grain pile chemical fumigation in summer and autumn. The height of the vertical silos and shallow circular silos currently designed in my country does not exceed 27 meters. In autumn and winter, large centrifugal fans are used at the base of the warehouse to cool and ventilate the upward grain pile. The fan noise is loud, the fan compression heat is high, the thickness of the grain pile temperature migration front and the moisture migration front is wide, resulting in a large loss of moisture in the grain pile, and it is impossible to fully seize the effective ventilation opportunity. In addition, with the shortage of land in urban suburbs in China, the construction of vertical tall warehouses is a trend. China cannot design and build 28-45 meter high concrete silos, mainly because of the lack of research on ventilation theory in China. This patent proposes a method for cooling and ventilating vertical tall concrete circular silos. Summary of the invention

[0004] To this end, the present application provides a vertical warehouse grain pile cooling and ventilation system, ventilation method and fan selection method to build grain silos and shallow circular silos with a height of 28 to 50 meters, and at the same time solve the problems of existing vertical warehouses using large centrifugal fans for pressure-type ascending grain pile cooling and ventilation, which have high fan noise, high fan compression heat and high energy consumption.

[0005] In order to achieve the above objectives, this application provides the following technical solutions:

[0006] In a first aspect, a vertical warehouse grain pile cooling and ventilation system comprises a vertical warehouse, a first fan, a second fan, a third fan and a fourth fan, the warehouse is a reinforced concrete silo, four longitudinally distributed air ducts are evenly arranged on the inner wall of the cylinder of the warehouse along the height direction, and are respectively recorded as air duct A, air duct B, air duct C, and air duct D in the clockwise direction of the circumference, wherein the air duct A and the air duct C are two opposite air intake ducts, the air duct B and the air duct D are two opposite exhaust ducts, the first fan and the second fan are located at the outer bottom of the warehouse, the third fan and the fourth fan are located at the top of the warehouse, and the first fan, the second fan, the third fan, and the fourth fan are respectively connected to the air duct A, the air duct B, the air duct C, and the air duct D;

[0007] The air inlet duct and the air exhaust duct are perforated plates, and the diameter of the holes punched therein is smaller than the minimum grain particle diameter.

[0008] Optionally, the diameter of the warehouse is 6 to 12 meters, and the height of the grain pile in the warehouse is 26 to 50 meters;

[0009] The straight-line distance between the centers of the two air intake ducts is 1.0 times the diameter of the warehouse; the distance from the air intake duct to the two exhaust ducts is 0.7 times the diameter of the warehouse.

[0010] Optionally, the air intake duct and the air exhaust duct have the same air duct size;

[0011] The cross-sectional shape of the air inlet duct and the exhaust duct is a semicircular duct with a radius of 0.3-0.5m, and the material is a 1.5-2mm thick cold-rolled punching plate. The hole type used is a bridge-type double-hole hole with an opening rate of 25%-30%.

[0012] Optionally, the first fan, the second fan, the third fan and the fourth fan are centrifugal fans.

[0013] Optionally, the first fan, the second fan, the third fan and the fourth fan are axial flow fans.

[0014] Optionally, the air duct A and the air duct C are respectively provided with a vent and a cover on one side close to the first fan and the third fan;

[0015] The air duct A, air duct B, air duct C and air duct D are all composed of multiple air duct units, adjacent air duct units are fixedly connected, and the length of each air duct unit is 1m.

[0016] Optionally, the ventilation system is a suction-type airflow system, the air duct A or the air duct C is provided with negative air pressure, and the other three air ducts serve as air intake supply ducts.

[0017] In a second aspect, a method for cooling and ventilating a grain pile in a vertical warehouse is provided, wherein the vertical warehouse grain pile cooling and ventilating system is used, and the air duct A or the air duct C is used alternately as an air inlet duct, and the ventilation method comprises:

[0018] Step 1: Load the grain in the warehouse and select a fan type that provides uniform temperature ventilation after loading the grain;

[0019] Step 2: Turn on the first and third fans. At this time, both air duct A and air duct C serve as air inlet channels. Low-temperature cold air enters the interior of the warehouse through air duct A and air duct C respectively, enters the center of the grain pile horizontally from the side of the grain pile, contacts the hot air in the grain pile, pushes the hot air flow to turn to air duct B and air duct D to be discharged outside the warehouse, and performs ventilation for t1 time.

[0020] Step 3: turn off the third fan, and keep the first fan on. At this time, air duct A serves as an air inlet channel, and air duct C serves as an exhaust channel to the atmosphere. Low-temperature cold air enters the interior of the warehouse through air duct A, and enters the interior of the grain pile horizontally from the side of the grain pile, contacts the hot air in the grain pile, and pushes the hot air to be discharged out of the warehouse from air ducts B, C, and D, and ventilation is performed for t2 time.

[0021] Step 4: Turn on the third fan and turn off the first fan. At this time, air duct A is used as an exhaust channel and leads to the atmosphere, and air duct C is used as an air inlet channel; low-temperature cold air enters the interior of the warehouse through air duct C, enters the interior of the grain pile horizontally from the side of the grain pile, contacts the hot air in the grain pile, and pushes the hot air to be discharged out of the warehouse from air duct A, air duct B, and air duct D, and ventilation is carried out for t3 time;

[0022] Step 5: Repeat steps 2 to 4.

[0023] In a third aspect, a method for cooling and ventilating a grain pile in a vertical warehouse is provided, wherein the vertical warehouse grain pile cooling and ventilating system is used, and the air duct A or the air duct C is used alternately as an air inlet duct, and the ventilation method comprises:

[0024] Step 1: Load the grain in the warehouse and select a fan type that provides uniform temperature ventilation after loading the grain;

[0025] Step 2: Turn on the first fan and turn off the third fan. At this time, air duct A serves as an air inlet channel, and air duct C serves as an exhaust channel to the atmosphere. Low-temperature cold air enters the interior of the warehouse through air duct A, and enters the interior of the grain pile horizontally from the side of the grain pile, contacts the hot air in the grain pile, and pushes the hot air to be discharged out of the warehouse from air ducts B, C, and D, and ventilation is performed for t1 time.

[0026] Step 3: turn off the first fan and turn on the third fan. At this time, air duct A is used as an exhaust channel and leads to the atmosphere, and air duct C is used as an air inlet channel. Low-temperature cold air enters the interior of the warehouse through air duct C, enters the interior of the grain pile horizontally from the side of the grain pile, contacts the hot air in the grain pile, and pushes the hot air to be discharged from the warehouse through air duct A, air duct B, and air duct D, and ventilation is carried out for t2 time.

[0027] Step 4: Repeat steps 2 and 3.

[0028] In a fourth aspect, the vertical warehouse grain pile cooling and ventilation system is adopted, and the fan selection method includes:

[0029] Step 1: Determine the unit ventilation volume for cooling and ventilation according to the local cold weather conditions in autumn and winter and the working conditions: Determine the relevant parameters of the warehouse and grain pile;

[0030] Step 2: Determine the effective ventilation bed length and static pressure;

[0031] Step 3: Estimate fan power: Calculate total power requirement based on grain pile weight and unit power requirement;

[0032] Step 4. Select the fan model: According to the ventilation volume and static pressure requirements, consult the fan manufacturer's catalog and select the appropriate fan model.

[0033] Compared with the prior art, this application has at least the following beneficial effects:

[0034] Based on further analysis and research on the existing technical problems, the present application solves the ventilation problem of reinforced concrete silos with a diameter of 6 to 12 meters and a grain pile height of 26 to 50 meters, which is helpful to promote the construction of such warehouses in my country and save land in urban suburbs; the ventilation system of the present application includes an upright reinforced concrete silo and four low-power fans. The warehouse is a reinforced concrete circular silo. Four longitudinally distributed semicircular air ducts with a radius of 0.3 to 0.5m are evenly arranged along the height direction on the inner wall of the cylindrical body of the silo. The ducts are symmetrical in pairs and have an opening rate of 25% to 30%; the present application adopts a cross-flow ventilation method, with small horizontal airflow resistance and horizontal airflow. The path is short, and a smaller-power ventilation fan can be used, which reduces noise, equipment cost and operating cost; a lower-power fan is used, and the fan compression heat rise is lower; the total ventilation volume is higher, the grain pile cooling and ventilation time is shorter, and the energy consumption is lower; the horizontal airflow can provide a higher airflow through the central core grain pile of the circular silo or other non-circular silo, quickly cool down the grain pile with high content of deposits or impurities, and the ventilation effect is good; at the same time, it also provides a ventilation method of alternating airflow, which effectively solves the problem of the dead zone in the center of the grain pile and further improves the ventilation effect; in addition, a method for selecting a ventilation fan is also provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more intuitively illustrate the prior art and the present application, exemplary drawings are given below. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing the present application; for example, those skilled in the art are capable of easily making conventional adjustments or further optimizations to the addition / reduction / attribution division, specific shapes, positional relationships, connection methods, dimensional ratios, etc. of certain units (components) based on the technical concepts and exemplary drawings disclosed in the present application.

[0036] Figure 1 A schematic longitudinal cross-sectional view of the air duct distribution of a vertical warehouse grain pile cooling and ventilation system provided in one embodiment of the present application;

[0037] Figure 2 A schematic cross-sectional view of the air duct distribution of a vertical warehouse grain pile cooling and ventilation system provided in one embodiment of the present application;

[0038] Figure 3 Schematic diagram of static pressure of different unit ventilation volume of ventilated wheat grain pile provided in one embodiment of the present application Figure 1 ;

[0039] Figure 4 Schematic diagram of static pressure of different unit ventilation volume of ventilated corn grain pile provided in one embodiment of the present application Figure 2 ;

[0040] Figure 5 for Figure 1 Illustration of air flow isobars on the cross section of the silo in the middle second air duct Figure 1 (A is the air intake duct, C is the exhaust duct);

[0041] Figure 6 for Figure 1 The shadow area of ​​the cross section of the silo in the middle second air duct shows the minimum area of ​​grain pile cooling and drying Figure 2 (A is the air intake duct, C is the exhaust duct);

[0042] Figure 7 for Figure 1 Schematic diagram of air flow distribution in the middle four air duct silo Figure 1 (Schematic diagram of air flow isobars on the cross section);

[0043] Figure 8 for Figure 1 Schematic diagram of air flow distribution in the middle four air duct silo Figure 2 (Schematic diagram of the minimum cooling and drying area of ​​the grain pile shown in the shaded area of ​​the cross section);

[0044] Fig. 9 Schematic diagram of ventilation mode of a four-air duct cross-flow ventilation system provided in an embodiment of the present application Figure 1 (Air duct A is the air intake duct);

[0045] Fig.10 Schematic diagram of ventilation mode of a four-air duct cross-flow ventilation system provided in an embodiment of the present application Figure 2 (Air duct C is the air intake duct).

[0046] Description of reference numerals:

[0047] 1. Silo wall; 2. Air duct A; 3. Air duct B; 4. Air duct C; 5. Air duct D; 6. Grain pile; 7. Silo bottom; 8. Silo top space; 9. First fan; 10. Third fan. DETAILED DESCRIPTION

[0048] The present application is further described below in detail through specific embodiments in conjunction with the accompanying drawings.

[0049] In the description of this application: unless otherwise specified, the meaning of "plurality" is two or more. The terms "first", "second", "third", etc. in this application are intended to distinguish the objects referred to, and do not have special meanings in terms of technical connotations (for example, they should not be understood as emphasizing the importance or order, etc.). Expressions such as "including", "comprising", "having", etc. also mean "not limited to" (certain units, components, materials, steps, etc.).

[0050] The terms such as "upper", "lower", "left", "right", "middle", etc. cited in this application are usually used to indicate the general relative position relationship for the purpose of intuitive understanding by referring to the drawings, and are not absolute limitations on the position relationship in the actual product.

[0051] In an embodiment of the present application, a vertical warehouse grain pile cooling and ventilation system is provided. Figures 1 to 10 As shown, it includes a vertical warehouse, a first fan 9, a second fan, a third fan 10 and a fourth fan. The warehouse is a reinforced concrete silo. The bottom of the warehouse is recorded as the silo bottom 7, the top is recorded as the silo head space 8, the cylindrical inner wall of the warehouse is recorded as the warehouse wall 1, and the warehouse diameter is 6 to 12 meters, and the grain loading height is 26 to 50 meters; four longitudinally distributed air ducts are evenly arranged on the warehouse wall 1 along the height direction, and are recorded as air duct A2, air duct B3, air duct C4, and air duct D5 in the clockwise direction along the circumference, among which the air duct A2 and air duct C4 are two opposite air inlet ducts, and face each other from the front, and air duct B3 and air duct D5 are two opposite exhaust ducts, and the positions of the two exhaust ducts are 90° with the air inlet duct on the circumference; the first fan 9 and the second fan (not shown) are located at the outer bottom of the warehouse, and the third fan 10 and the fourth fan (not shown) are located at the top of the warehouse, and the first fan 9, the second fan, the third fan 10, and the fourth fan are respectively connected to the air duct A2, the air duct B3, the air duct C4, and the air duct D5 through the ventilation holes;

[0052] The air inlet duct and the exhaust duct are perforated plates, and the diameter of the holes is smaller than the minimum grain diameter, that is, the size of the holes is limited to prevent grains from leaking.

[0053] Preferably, the straight-line distance between the centers of the two air inlet ducts is 1.0 times the diameter of the warehouse; the distance from the air inlet duct to the two exhaust ducts is 0.7 times the diameter of the warehouse.

[0054] Preferably, the air intake duct and the air exhaust duct have the same air duct size;

[0055] The cross-sectional shape of the air inlet duct and the exhaust duct is a semicircular duct with a radius of 0.3 to 0.5 m, and the material is a 1.5 to 2 mm thick cold-rolled punched plate. The hole type used is a bridge-type double-hole hole with an opening rate of 25% to 30%.

[0056] Preferably, the air duct A2 and the air duct C4 are provided with a vent and a cover on one side close to the first fan 9 and the third fan 10 respectively.

[0057] Preferably, the first fan 9, the second fan, the third fan 10 and the fourth fan are centrifugal fans.

[0058] Preferably, the first fan 9, the second fan, the third fan 10 and the fourth fan are axial flow fans.

[0059] Preferably, the air duct A2, the air duct B3, the air duct C and the air duct D5 are all composed of a plurality of air duct units, the adjacent air duct units are fixedly connected, and the length of each air duct unit is 1 m.

[0060] Preferably, the ventilation system is a suction-type airflow system, and negative air pressure is provided on the air duct A2 or the air duct C4, and the other three air ducts serve as air intake supply ducts.

[0061] The working principle of the above embodiment is as follows: based on the horizontal distribution of the long axis of grains when they are put into the warehouse, the air flow resistance along the horizontal direction is 0.6 times the air flow resistance in the vertical direction, and the traditional silo ventilation duct is arranged at the bottom of the warehouse to be distributed longitudinally along the height of the inner wall of the warehouse, and the longest air flow path is changed to be along the warehouse diameter, that is, 0.6 times of 6 to 12m. Therefore, natural ventilation, axial flow fans and low-speed centrifugal fans can be used to ventilate the silo with a height of 26 to 50 meters for the grain pile 6. The air volume, power, type and number of fans used for ventilation can be selected based on the relationship between the static pressure of different grain piles 6, the effective ventilation length of the grain pile 6 and the unit ventilation volume.

[0062] Based on the above-mentioned vertical warehouse grain pile cooling and ventilation system, the cross-flow ventilation methods provided in this application include the following three methods:

[0063] The first method is a method for cooling and ventilating a grain pile in a vertical warehouse, which is as follows:

[0064] Step 1: Load the grain in the warehouse and select the fan type for uniform temperature ventilation after loading. The fan type is selected by checking the ventilation volume and calculated static pressure in the fan manufacturer's catalog;

[0065] Step 2, turn on the first fan 9 and the third fan 10, and the low-temperature cold air enters the interior of the warehouse through the air duct A2 and the air duct C4, enters the center of the grain pile 6 horizontally from the side of the grain pile 6, and after contacting the hot air in the grain pile 6, pushes the hot air to turn to the air duct B3 and the air duct D5 and be discharged outside the warehouse.

[0066] Air flow distribution: Figure 7 , Figure 8 As shown, the fastest air flow rate will be along the straight line between each inlet and each outlet duct, very close to the walls on each side of the inlet duct; the slowest moving air should move directly along the straight line between the two inlets. It splits at the center of the bin near the intersection of the two 0.16-inch water column pressure lines and turns to the two outlets. Since the length of this air flow path is approximately twice the shortest air flow path between the inlet and outlet, the slowest air flow speed is approximately half of the shortest air flow path. There is an area around the center of the bin where the two straight pressure lines intersect, and little or no air flow may occur, especially when the center of the bin contains a higher proportion of grain dust, broken particles and impurities.

[0067] Figure 7 The pressure drop across the bin is about 0.15 inches of water column. For a common airflow pattern per unit ventilation, these pressure differences can be compared using the shortest and longest airflow paths. The shortest airflow path is 0.7 bin diameters. The longest airflow path approaches the center of the bin first. Based on the characteristics of this type of four-channel bin, the airflow path turns 90 degrees at the bin center to reach the outlet duct. Logically, a lot of cooling or drying will occur near the center of this four-channel pattern of round or cylindrical bins, such as Figure 8 shown.

[0068] During ventilation, the silo with these four ducts should have a diamond-shaped central dead zone or core, which cannot be fully cooled and cools down very slowly. Due to the temperature difference between the center of the grain pile 6 and the already cooled grain pile 6 1 to 2 meters away, the central core of the grain pile 6 may cool down slowly through heat conduction and may not be ventilated and cooled to a level that prevents grain deterioration. In response to the problem of these stagnant air zones, the present application also proposes a second method of using alternating airflow. In the silo four-duct system, one of the two intake ducts is used as an exhaust duct (one intake duct and three exhaust ducts) during part of the ventilation time, and the central dead zone can be ventilated through the silo by direct airflow; the specific ventilation method is as follows:

[0069] The second method is a method for cooling and ventilating a grain pile in a vertical warehouse. The system is designed as a forced-in ventilation system. Four air ducts are always in use. At the same time, air duct A2 or air duct C4 is used alternately as an air intake duct. One of the air ducts is used as an air intake duct, and the other opposite air duct is used as a central exhaust duct for the grain pile 6. Fig. 9 , Fig.10 The ventilation method is as follows:

[0070] Step 1: Load grain in the warehouse and select the fan type for uniform temperature ventilation after loading. The fan type is selected by checking the unit ventilation volume and calculated static pressure in the fan manufacturer's catalog;

[0071] Step 2: Turn on the first fan 9 and turn off the third fan 10. At this time, the air duct A2 serves as the air inlet channel, and the air duct C4 serves as the exhaust channel and leads to the atmosphere. The first fan 9 pushes the low-temperature cold air into the interior of the warehouse through the air duct A2, and enters the interior of the grain pile 6 horizontally from the side of the grain pile 6. After contacting the hot air in the grain pile 6, the hot air is pushed out of the warehouse through the air duct B3, the air duct C4, and the air duct D5, and ventilation is performed for t1 time.

[0072] Step 3: turn off the first fan 9 and turn on the third fan 10. At this time, the air flow direction is opposite, the air duct A2 is used as an exhaust channel and leads to the atmosphere, and the air duct C4 is used as an air inlet channel; the third fan 10 pushes the low-temperature air into the interior of the warehouse through the air duct C4, and enters the interior of the grain pile 6 horizontally from the side of the grain pile 6, and after contacting the hot air in the grain pile 6, pushes the hot air to be discharged out of the warehouse from the air duct A2, the air duct B3, and the air duct D5, and ventilates for t2 time;

[0073] Step 4: Repeat steps 2 and 3.

[0074] Preferably, the ventilation time of step one and step two may be equal.

[0075] The reverse airflow in the second ventilation method eliminates the dead zone in the cooling ventilation mode, because the airflow will flow through all four areas between the intake duct and the adjacent exhaust duct. The direct distance between the intake duct and the adjacent exhaust duct is a ratio of 0.7D to 1.0D (D is the bin diameter). According to the length of the airflow path, duct C4 is the same as duct B3 and duct D5, and each duct receives about 70% of the exhaust volume.

[0076] The direct distance from the center of duct A2 to the center of duct C4 is 1.0 times the diameter of the warehouse, while the distance from duct A2 to ducts B3 and D5 is only 0.7 times the diameter of the warehouse. The grain ventilated through ducts B3 and D5 first gets more airflow relative to the airflow flowing through the center of grain pile 6 to duct C4. If the supply air flow is reversed from duct A2 to duct C4, the airflow along paths C-D and C-B is greater than the previous case when the airflow comes from duct A2; the longer airflow distances along the A-C and C-A paths are compensated by having continuous alternating airflow throughout the ventilation process.

[0077] The inlet duct switches periodically from duct A2 to duct C4 to cool the grain along the walls of the area between ducts C4 and B and duct C4 and duct D5. The four-duct crossflow ventilation system is physically designed with all four ducts of equal size, and the only mechanical adjustment is to reverse the inlet or conveying air ducts A2 and C4 through the silo. There are valves on these ducts, and when the two fans switch, the first inlet duct is opened to the atmosphere as the reverse exhaust duct while the second inlet duct is pressurized.

[0078] In summary, for the first method, two relative intake and two relative exhaust ducts are used in the four-duct model, and there is a ventilation dead zone problem between the central and side exhaust ducts of the grain pile 6. If the second method is adopted, the advantage of the reverse intake airflow with one intake duct and three exhaust ducts is that the airflow moves in all directions and through the center of the grain pile 6. The key factor is that the air must be forced to flow in all directions of the silo, and the use of alternating airflow with three exhaust ducts into the ducts to obtain a satisfactory cooling effect, the airflow directly passes through the center of the silo to the exhaust duct on the opposite side, and the problem of the dead zone in the center of the grain pile 6 is effectively solved.

[0079] The present application also provides a third method, which combines the first method with the second method, first turning on the first fan 9 and the third fan 10, selecting a two-in-two-out mode, performing transverse ventilation for a certain period of time, then switching the first fan 9 and the third fan 10, using alternating airflows to perform transverse ventilation for a certain period of time, to ensure that the center of the grain pile 6 can be effectively ventilated and heat-dissipated. The ventilation method is as follows:

[0080] Step 1: Load the grain in the warehouse and select the fan type for uniform temperature ventilation after loading. The fan type is selected by checking the ventilation volume and calculated static pressure in the fan manufacturer's catalog;

[0081] Step 2: Turn on the first fan 9 and the third fan 10. At this time, the air duct A2 and the air duct C4 are both used as air inlet channels; the low-temperature air enters the interior of the warehouse through the air duct A2 and the air duct C4 respectively, and enters the center of the grain pile 6 from the side of the grain pile 6. After contacting the hot air in the grain pile 6, the hot air is pushed to turn to the air duct B3 and the air duct D5 to be discharged outside the warehouse, and ventilation is carried out for t1 time;

[0082] Step 3, turn off the third fan 10, and the first fan 9 is in the open state. At this time, the air duct A2 serves as the air inlet channel, and the air duct C4 serves as the exhaust channel and leads to the atmosphere; the first fan 9 allows the low-temperature air to enter the interior of the warehouse through the air duct A2, and enter the interior of the grain pile 6 laterally from the side of the grain pile 6. After contacting with the hot air in the grain pile 6, the hot air is pushed out of the warehouse through the air duct B3, the air duct C4, and the air duct D5, and ventilation is performed for t2 time;

[0083] Step 4, turn on the third fan 10, turn off the first fan 9, at this time, the air duct A2 is used as an exhaust channel and leads to the atmosphere, and the air duct C4 is used as an air inlet channel; the third low-temperature air enters the interior of the warehouse through the air duct C4, enters the interior of the grain pile 6 from the side of the grain pile 6, and after contacting with the hot air in the grain pile 6, pushes the hot air to be discharged from the warehouse through the air duct A2, the air duct B3, and the air duct D5, and ventilates for t3 time;

[0084] Step 5: Repeat steps 2 to 4.

[0085] In addition, the ventilation system can also be designed as a suction-type airflow system, with negative air pressure set on duct A2 or duct C4, and the other three ducts can be used as air intake supply ducts; the negative air pressure generated by the fan on duct A2 or duct C4 sucks the low-temperature cold air in the other three ducts from the side of the grain pile 6, and then after coming into contact with the hot air in the grain pile 6, pushes the hot air to pass through duct A2 or duct C4 and be discharged out of the warehouse.

[0086] Compared with traditional vertical ventilation, the advantages of cross-flow ventilation provided by the present application are: ① The horizontal airflow resistance is about 50% to 60% of the vertical airflow resistance of the grain pile; ② The horizontal airflow path is generally about 20% to 30% of the vertical airflow path; ③ Smaller power ventilation fans can be used to reduce equipment costs and operating costs; ④ Lower power fans are used, and the fan compression heat rise is lower; ⑤ The total ventilation volume is higher, the grain pile cooling and ventilation time is shorter, and the energy consumption is lower; ⑥ The horizontal airflow can provide a higher air flow through the central core grain pile of the silo or silo (depending on the duct pattern), and quickly cool down the grain pile with high content of accumulation or impurities; ⑦ The use of cross-flow suction ventilation technology in tropical and subtropical regions eliminates the compression heat of maximum cooling.

[0087] In addition, the present application also provides a method for selecting a ventilation fan for a grain pile in a vertical warehouse, comprising the following steps:

[0088] Step 1: Determine the unit ventilation volume requirement; determine the relevant parameters of the warehouse and the grain pile. The relevant parameters of the warehouse include the diameter and height of the warehouse, and the relevant parameters of the grain pile include volume, weight, bulk density, ventilation volume, etc.

[0089] Step 2: Determine the effective ventilation bed length and static pressure; the effective ventilation bed length is calculated based on the geometric shape of the grain pile and the airflow coefficient, and the static pressure is determined based on the grain pile density, ventilation length and airflow rate. The required static pressure is determined by checking the diagram;

[0090] Step 3: Estimate the fan power; calculate the total power requirement based on the grain pile weight and unit power requirement;

[0091] Step 4. Select the fan model; refer to the fan manufacturer's catalog and select the appropriate fan model based on the ventilation volume and static pressure requirements.

[0092] Example 1:

[0093] (1) For a vertical reinforced concrete circular silo with a diameter (d) of 6 to 12 m and a grain pile height (h) of 26 to 50 m, four semicircular air ducts with a radius of 0.3 to 0.5 m are evenly arranged along the height direction of the inner wall of the silo (e.g. Figure 1 The ducts A, B, C, D) are made of 1.5-2mm thick cold-rolled high-quality perforated plate. The size of the punching holes is limited to the size of the grains. The hole type used is a bridge-type double-hole hole with an opening rate of 25%-30%. Each section of the duct is 1m long, with consistent specifications and fixed together. Before the round silo is loaded with grain, it is installed in place as required. The ducts A, B, C, D can be connected to low-power axial flow fans or centrifugal fans A, B, C, D through the vents.

[0094] (2) After loading, select a fan type that provides uniform temperature ventilation. When the circular silo is designed with d of 8m and h of 30m, and loaded with secondary wheat (bulk density 770kg / m 3 ) is 1161 tons. Using 6 (m 3 / h) / t unit ventilation volume, the effective ventilation length of the grain pile bed is 8m×0.6 (horizontal airflow coefficient)=4.8m. Figure 3 is the static pressure and fan power requirement for different airflow rates in ventilated wheat pile (pile density 830 kg / m 3 , fan static efficiency 50%) Figure 3 , static pressure is 0.36kPa, estimated power is about 0.13kW / 100t, for the whole grain pile it is 0.13kW / 100t×1161t=1.5kW. 3 / h) / t ventilation rate, the total ventilation rate of 1161t wheat is 6966m 3 / h. The fan selection should be made by checking the airflow rate and calculated static pressure in the fan manufacturer's catalog. When the fan efficiency is about 50%, the ventilation volume is 6966m 3 / h, at 0.36kPa, the fan power should be close to 1.5kW. According to Table 1, you can choose power 2.24kW, diameter 45.7cm, speed 3500rpm, and air volume 7815m 3 / h axial flow fan, or power 2.24kW, speed 1750rpm, air volume 7340m 3 One low-speed centrifugal fan with a capacity of / h is used. This fan is connected to the air inlet duct A. The other ducts B, C, and D are used as exhaust ducts and do not need to be connected to ventilation fans.

[0095] If the local low temperature weather conditions are rare, use 12 (m 3 / h) / t unit ventilation volume, 8m×0.6 (horizontal airflow coefficient) = 4.8m is the effective ventilation grain bed length. Figure 3 , the static pressure is about 0.48kPa, the estimated power is about 0.3kW / 100t, and the power required for the entire grain pile is 3.5kW. At 0.48kPa, the total air flow required is 12×1161t=13932m 3 / h. Check Table 1 to select power 3.73kW, diameter 61cm, speed 3500rpm, air volume 15291m 3 One axial flow fan with a capacity of / h is used. This fan is connected to the air inlet duct A. The other ducts B, C, and D are used as exhaust ducts and do not need to be connected to ventilation fans.

[0096] When the circular silo is designed with d of 12m and h of 50m, and loaded with secondary corn (bulk density 690kg / m 3 ) is 3900 tons. 3 / h) / t unit ventilation volume, the effective ventilation length of the grain pile bed is 12m×0.6 (horizontal airflow coefficient)=7.2m. Figure 4 Static pressure and fan power requirements at different airflow rates for ventilated corn piles (pile density 764 kg / m 3 , fan static efficiency 50%) Figure 4 The static pressure is 0.18 kPa, and the estimated power is about 0.06 kW / 100 t, which is 0.06 kW / 100 t×3900 t=2.34 kW for the whole grain pile. 3 / h) / t ventilation rate, the total ventilation rate of 3900t corn is 23400m 3 / h. When the fan efficiency is about 50%, the total ventilation volume is 23400m 3 / h, at 0.18kPa, the fan power should be close to 2.34kW. Table 1 can be used to select power 3.73kW, diameter 61cm, speed 3500rpm, air volume 17840m 3 Two axial flow fans with a capacity of / h are connected to the air inlet ducts A and C respectively, and the exhaust ducts B and D do not need to be connected to fans ( Figure 5 ).

[0097] According to the local limited low temperature weather conditions, 12 (m 3 / h) / t unit ventilation volume, 12m×0.6 (horizontal airflow coefficient) = 7.2m is the effective ventilation grain bed length. Figure 4 , the static pressure is about 0.25kPa, the estimated power is about 0.17kW / 100t, and the power required for the entire grain pile is 6.63kW. At 0.25kPa, the total ventilation volume required is 12×3900t=46800m 3 / h. Check Table 1 to select power 7.46kW, diameter 66cm, speed 3500rpm, air volume 26335m 3 Two axial flow fans with a capacity of / h are connected to the air inlet ducts A and C respectively, and the exhaust ducts B and D do not need to be connected to fans ( Figure 5 ).

[0098] Table 1 Ventilation fan performance data (static pressure)

[0099]

[0100] (3) Ventilation scheme optimization

[0101] When one fan is used for forced ventilation, the schematic diagram of the air flow isobars on the cross section of the silo is as follows: Figure 5 , where A is the air intake duct, C is the exhaust duct, and the static pressure is expressed in inches of water column, 1 inch of water column equals 0.322 Pa. From the air inlet to the outlet, the static pressure gradually decreases, and the ventilation dead zone is the fan area along the air outlet end, such as Figure 6 The solution is to use A as the exhaust duct and C as the intake duct during the second half of the cooling and ventilation period.

[0102] When two fans are used for forced ventilation, the schematic diagram of the air flow isobars on the cross section of the silo is as follows: Figure 7 , where A and C are the air intake ducts, and B and D are the exhaust ducts. From the air inlet to the outlet, the static pressure gradually decreases, and the ventilation dead zone is the area along the BD diameter, such as Figure 8 The solution is that in the first half of the cooling and ventilation period, A is the air intake duct, and B, C, and D are the exhaust ducts. In the second half of the cooling and ventilation period, C is the air intake duct, and A, B, and D are the exhaust ducts.

[0103] Example 2:

[0104] Using a reinforced concrete circular silo with a diameter of 7.6m and a height of 30m, the static pressure and fan power requirements for the crossflow ventilation fan system of a 1000t grain pile are developed. Four equally spaced vertical ducts are used for crossflow ventilation, and the air supply ducts are alternated. First, 6 and 12m are proposed for the wheat grain pile. 3 / h / t fan design. Second, for these two types of cross flow ventilation, compare the static pressure and power of wheat grain pile push-pull type and full-depth bed type cross flow ventilation.

[0105] Method: Use Fig. 9 , Fig.10 In the four-duct cross-flow ventilation system, one duct is used as the air inlet duct, and the other three ducts are used as exhaust outlet ducts. For the airflow from two adjacent ducts, the airflow distance changes from 0.75D to 0.9D (D is the warehouse diameter), and the longest path to the opposite duct is 1.0D to 1.3D. For approximate calculations, it is assumed that the ventilation duct is flush with the warehouse wall, and the average airflow distance of all three exhaust ducts is assumed to be 1.0D, that is, 7.6m.

[0106] For small grain wheat, the resistance to the horizontal component of airflow is Figure 7 (Note: Bulk density 0.83t / m 3 , fan static efficiency 50%), check the 7.6m distance of the wheat grain pile deep bed, and multiply it by the static pressure or air flow resistance coefficient of 0.6. From Table 1, select 6 and 12 (m 3 / h) / t fan type and size.

[0107] (1) Cross flow ventilation: for 6 (m 3 / h) / t unit ventilation volume, the effective depth of the grain pile bed is 7.6m×0.6 (horizontal airflow coefficient)=4.6m. Figure 7 The static pressure is 0.33 kPa, and the estimated power is about 0.13 kW / 100 t, which is 0.13 kW / 100 t×1000 t=1.3 kW for the entire grain pile. 3 / h / t unit ventilation volume, the total ventilation volume of 1000t wheat is 6000m 3 / h. The fan selection should be made by looking at the ventilation volume and calculated static pressure in the fan manufacturer's catalog. If the fan efficiency is about 50%, then for 6000m 3 / h, at 0.33kPa, the fan power should be close to 1.3kW.

[0108] 12m 3 / h / t unit ventilation volume, 7.6m×0.6 (horizontal airflow coefficient) = 4.6m is the effective grain bed depth. Figure 7, the static pressure is about 0.45kPa, the estimated power is about 0.3kW / 100t, and the power required for the entire grain pile is 3.0kW. At 0.45kPa, the total air flow required is 12×1000t=12000m 3 / h.

[0109] (2) Comparison with vertical push-pull ventilation fans

[0110] At unit ventilation volume 6(m 3 / h) / t, for a grain pile with a half depth of 30 / 2 = 15m and a grain mass of 1000t, a push-pull cooling and ventilation system is used. Figure 7 Total ventilation volume in wheat pile is 6000m 3 / h, and a static pressure of 1.55kPa is required at a grain pile depth of 15m. The estimated power is about 0.50kW / 100t, with a total power of 5kW, and two 2.5kW fans.

[0111] At unit ventilation volume 12(m 3 / h) / t, from Figure 7 , total ventilation volume of wheat grain pile is 12000m 3 / h, 3.13kPa is required at a grain bed depth of 15 meters. The estimated power is about 2.0kW / 100t, the total power is 20kW, and there are 2 10kW fans.

[0112] (3) Comparison with full-depth ventilation fans in vertical grain piles

[0113] At unit ventilation volume 6(m 3 / h) / t, from Figure 7 Total ventilation volume in wheat pile is 6000m 3 / h, the airflow at a depth of 30m in the grain pile requires 5.86kPa. The estimated power is about 2.0kW / 100t, and the total power is 20kW. This exceeds the rated fan pressure rating in the ventilation monograph table, but there are fans on the market with higher pressures than those stated in the ventilation monograph table.

[0114] At unit ventilation volume 12(m 3 / h) / t, 12(m 3 / h) / t of wheat volume with a ventilation depth of 30m is impractical. The fan and static pressure requirements are beyond practical limits.

[0115] The comparison of the three cases above shows that crossflow ventilation has great potential to increase the cooling rate of high grain piles in a silo with a diameter of 7.6m and a height of 30m while maintaining low operating costs. For slender grains such as wheat, horizontal airflow ventilation effectively reduces static pressure by about 40% compared to vertical vertical ventilation of the same grain type and grain pile depth. Slender grains tend to be arranged horizontally with the long axis of the grain, which can reduce horizontal airflow resistance. However, for generally spherical grains such as soybeans, sorghum and millet, there is not much difference in static pressure when horizontal airflow is compared with vertical airflow. The stacking factor is the main difference between horizontal and vertical airflow for round grains.

[0116] Table 2 Comparison of fan power and static pressure of three ventilation methods for 30-meter-high wheat grain pile in silo

[0117]

[0118] Table 2 summarizes the results of the above examples. 3 / h) / t unit ventilation volume for wheat cross flow ventilation, at the same airflow rate as vertical push-pull ventilation, only about 1 / 5 of the fan power and static pressure are required. 3 The fan power and static pressure required for in-line or push-pull vertical ventilation of a wheat pile with an airflow of 1.5 / h / t are about 7 times that of the same wheat pile with cross-flow ventilation.

[0119] When using 6m 3 / h / t airflow for full depth push-in or pull-out ventilation, the selected fan power is consistent with the unit ventilation volume of 12 (m 3 / h) / t push-pull ventilation is almost the same, but the static pressure is increased by 87%. From a practical point of view, using 12 (m 3 / h) / t airflow requires too much power and static pressure to push air through a 30m pile of wheat, but this is physically possible. Therefore, the airflow at the bottom of the silo or at the top is significantly higher than 6 (m 3 It seems not feasible to carry out full-depth vertical ventilation with a unit ventilation rate of / h) / t.

[0120] The technical features of the above embodiments may be arbitrarily combined (as long as there is no contradiction in the combination of these technical features). To make the description concise, not all possible combinations of the technical features in the above embodiments are described; these embodiments that are not explicitly written should also be considered to be within the scope of this specification.

Claims

1. A vertical warehouse grain pile cooling and ventilation system, characterized in that: It comprises a vertical warehouse, a first fan, a second fan, a third fan and a fourth fan, the warehouse is a reinforced concrete silo, four longitudinally distributed air ducts are evenly arranged on the inner wall of the cylinder of the warehouse along the height direction, and are respectively recorded as air duct A, air duct B, air duct C, and air duct D in the clockwise direction of the circumference, wherein the air duct A and the air duct C are two opposite air intake ducts, the air duct B and the air duct D are two opposite exhaust ducts, the first fan and the second fan are located at the outer bottom of the warehouse, the third fan and the fourth fan are located at the top of the warehouse, and the first fan, the second fan, the third fan, and the fourth fan are respectively connected to the air duct A, the air duct B, the air duct C, and the air duct D; The air inlet duct and the air exhaust duct are perforated plates, and the diameter of the holes punched therein is smaller than the minimum grain particle diameter.

2. The vertical warehouse grain pile cooling and ventilation system according to claim 1 is characterized in that: The diameter of the warehouse is 6 to 12 meters, and the height of the grain pile in the warehouse is 26 to 50 meters; The straight-line distance between the centers of the two air intake ducts is 1.0 times the diameter of the warehouse; the distance from the air intake duct to the two exhaust ducts is 0.7 times the diameter of the warehouse.

3. The vertical warehouse grain pile cooling and ventilation system according to claim 1 is characterized in that: The air intake duct and the air exhaust duct have the same air duct size; The cross-sectional shape of the air inlet duct and the exhaust duct is a semicircular duct with a radius of 0.3-0.5m, and the material is a 1.5-2mm thick cold-rolled punching plate. The hole type used is a bridge-type double-hole hole with an opening rate of 25%-30%.

4. The vertical warehouse grain pile cooling and ventilation system according to claim 1 is characterized in that: The first fan, the second fan, the third fan and the fourth fan are centrifugal fans.

5. The vertical warehouse grain pile cooling and ventilation system according to claim 1 is characterized in that: The first fan, the second fan, the third fan and the fourth fan are axial flow fans.

6. The vertical warehouse grain pile cooling and ventilation system according to claim 1 is characterized in that: The air duct A and the air duct C are respectively provided with a vent and a cover on one side close to the first fan and the third fan; The air duct A, air duct B, air duct C and air duct D are all composed of multiple air duct units, adjacent air duct units are fixedly connected, and the length of each air duct unit is 1m.

7. The vertical warehouse grain pile cooling and ventilation system according to claim 1 is characterized in that: The ventilation system is a suction-type airflow system, the air duct A or the air duct C is provided with negative air pressure, and the other three air ducts serve as air intake supply ducts.

8. A method for cooling and ventilating a grain pile in a vertical warehouse, characterized in that: The vertical warehouse grain pile cooling and ventilation system according to any one of claims 1 to 7 is adopted, wherein the air duct A or the air duct C is used alternately as the air inlet duct, and the ventilation method comprises: Step 1: Load the grain in the warehouse and select a fan type that provides uniform temperature ventilation after loading the grain; Step 2: Turn on the first and third fans. At this time, both air duct A and air duct C serve as air inlet channels. Low-temperature cold air enters the interior of the warehouse through air duct A and air duct C respectively, enters the center of the grain pile horizontally from the side of the grain pile, contacts the hot air in the grain pile, pushes the hot air flow to turn to air duct B and air duct D to be discharged outside the warehouse, and performs ventilation for t1 time. Step 3: turn off the third fan, and keep the first fan on. At this time, air duct A serves as an air inlet channel, and air duct C serves as an exhaust channel to the atmosphere. Low-temperature cold air enters the interior of the warehouse through air duct A, and enters the interior of the grain pile horizontally from the side of the grain pile, contacts the hot air in the grain pile, and pushes the hot air to be discharged out of the warehouse from air ducts B, C, and D, and ventilation is performed for t2 time. Step 4: Turn on the third fan and turn off the first fan. At this time, air duct A is used as an exhaust channel and leads to the atmosphere, and air duct C is used as an air inlet channel; low-temperature cold air enters the interior of the warehouse through air duct C, enters the interior of the grain pile horizontally from the side of the grain pile, contacts the hot air in the grain pile, and pushes the hot air to be discharged out of the warehouse from air duct A, air duct B, and air duct D, and ventilation is carried out for t3 time; Step 5: Repeat steps 2 to 4.

9. A method for cooling and ventilating a grain pile in a vertical warehouse, characterized in that: The vertical warehouse grain pile cooling and ventilation system according to any one of claims 1 to 7 is adopted, wherein the air duct A or the air duct C is used alternately as the air inlet duct, and the ventilation method comprises: Step 1: Load the grain in the warehouse and select a fan type that provides uniform temperature ventilation after loading the grain; Step 2: Turn on the first fan and turn off the third fan. At this time, air duct A serves as an air inlet channel, and air duct C serves as an exhaust channel to the atmosphere. Low-temperature cold air enters the interior of the warehouse through air duct A, and enters the interior of the grain pile horizontally from the side of the grain pile, contacts the hot air in the grain pile, and pushes the hot air to be discharged out of the warehouse from air ducts B, C, and D, and ventilation is performed for t1 time. Step 3: turn off the first fan and turn on the third fan. At this time, air duct A is used as an exhaust channel and leads to the atmosphere, and air duct C is used as an air inlet channel. Low-temperature cold air enters the interior of the warehouse through air duct C, enters the interior of the grain pile horizontally from the side of the grain pile, contacts the hot air in the grain pile, and pushes the hot air to be discharged from the warehouse through air duct A, air duct B, and air duct D, and ventilation is carried out for t2 time. Step 4: Repeat steps 2 and 3.

10. A method for selecting a ventilation fan for a vertical grain warehouse, characterized in that: The vertical warehouse grain pile cooling and ventilation system according to any one of claims 1 to 7 is adopted, and the fan selection method comprises: Step 1: Determine the unit ventilation volume for cooling and ventilation according to the local cold weather conditions in autumn and winter and the working conditions: Determine the relevant parameters of the warehouse and grain pile; Step 2: Determine the effective ventilation bed length and static pressure; Step 3: Estimate fan power: Calculate total power requirement based on grain pile weight and unit power requirement; Step 4. Select the fan model: According to the ventilation volume and static pressure requirements, consult the fan manufacturer's catalog and select the appropriate fan model.

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