Brief introduction of the development of the most

2022-08-01
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Brief introduction to the development of grain pneumatic conveying (grain suction machine)

I. technical and economic indicators that must be paid attention to in the development of grain pneumatic conveying technology (I) grain damage: grain damage is an important indicator of grain grading, and the number of damaged grains directly affects the economic benefits and food quality of grain storage and transportation. China's "technical conditions for fixed grain suction machine" stipulates that the increase rate of grain damage during the whole process shall not exceed 0.3%, and the increase rate of grain damage during the operation of the grain suction machine produced by Christensen company shall not exceed 0.1%, which is higher than China's industry standard. The domestic trial production of grain suction machine should pay attention to and improve the control technology of increasing rate of grain damage

(II) fan selection: fan is the key component of grain suction machine. The design and selection of fan directly affect the performance of grain suction machine. At present, the selection of fans mainly includes eddy current fans and roots fans. The performance of vortex fan is low wind pressure and high air volume. In the process of grain transportation, the wind speed is high, and the impact force of grain on the pipe wall is large. The resulting problem is that the increase rate of grain damage is high, and the wall thickness and pipe diameter of the pipe must be increased. The performance of Roots blower is high pressure and low air volume. During transportation, the wind speed is low, the impact of grain on the pipe wall is small, and the concentration ratio of transported grain is high, which reduces the increase rate of grain damage, reduces the wall thickness and diameter of the pipe, and reduces the labor intensity of the operator

(III) equipment service life: service life is an important factor to evaluate the value of equipment. Christensen company guarantees that the service life of its main equipment components is about 5 years, while domestic products are in the process of trial production, and there is no relevant report

(IV) flexibility and output: the flexibility of the grain suction machine is closely related to its performance. If the pipe is equipped with multi-purpose hose, the flexibility of the grain suction machine can be increased, and its output and efficiency will inevitably be affected. Otherwise, some flexibility will be lost. Both manufacturers and users should seek a balance between the two

(V) energy consumption: the energy of the grain suction machine is from the motor or diesel engine. For the user, if the reservoir area is equipped with high-power cables, the motor should be selected as far as possible; If there are no users equipped with high-power cables, diesel engines can be preferred

(VI) dust control: the quality of dust control is an important indicator for selecting grain suction machine. Poor dust control will pollute the environment and endanger the health of the operator. Excessive dust entering the roots blower will easily cause impeller wear, which will directly affect the service life of the blower. Therefore, high-efficiency dust removal and filtration system is the key

(VII) performance and cost: in the performance formula of the equipment, ha is shore a hardness Energy is closely related to its cost. The better the performance, the higher the cost and the higher the sales price. The manufacturer shall, on the premise of ensuring the good performance of the equipment, reduce the cost to meet the production needs of different consumers

(VIII) scope of application: the grain suction machine can not only be used for ship unloading at the wharf, delivery from the warehouse and warehousing in the shallow circular warehouse, but also for clearing the warehouse, sucking out local hot grain, and cleaning and dedusting materials during transportation

II. The grain sucking machine equipment and its characteristics of Christensen company of the United States

Christensen company of the United States has decades of experience in designing and manufacturing grain sucking machines, and continuously carries out technical transformation on grain sucking machines. Its production and sales volume has reached more than 7000, and its users are distributed all over the world, including China's Dalian beiliangguo storage depot and Anhui mechanized grain depot. At present, the company's grain suction machine equipment includes: special products for grain in and out of the warehouse (mobile, production capacity: T/h), dual-purpose products for out of the warehouse and ship unloading (heavy mobile, production capacity: T/h), special products for ship unloading (ultra heavy, production capacity: T/h), etc

(I) key components

1. Roots blower is used in the grain suction machine of Christensen company. It uses very little air flow to form a strong wind pressure. In the process of operation, it can not only save energy (the oil consumption of the third generation vb series grain suction machine per 100 tons of output is only 12 liters), but also minimize grain damage and equipment wear, improve the quality and efficiency of grain handling, and greatly extend the service life of the equipment

2. Kjeldahl AFS patented air flow dust filtering system: the main function of the system is that when the grain and dust impurities carried by the high-speed air flow are sucked into the equipment, the dust impurities are immediately collected into the dust removal box by the dust filtering system, so that the air flow into the fan can be purified, so as to greatly reduce the wear of the equipment caused by the dust impurities, prolong the service life of the equipment, and maintain the long-term stability of the equipment performance. Equipped with high-quality silencing devices, the working conditions of equipment operators have been greatly improved and environmental pollution has been reduced

3. Hydraulic drive system: Ha series adopts advanced built-in hydraulic drive system to directly transmit power. For example, 1 ton or more reduces the load of bearings. At the same time, it avoids the possibility of shutdown and maintenance caused by blocking the drive chain when the wood, stone, iron flakes and grains with high oil or moisture content mixed in the grain enter the equipment, greatly reducing the equipment maintenance rate and prolonging the service life of the equipment

(II) technical advantages

Christensen has many significant advantages in the design of resistance of grain suction system, the selection of fans, the design of air shutoff, grain damage control, dust control, energy consumption and production capacity

according to the introduction, the third generation product uses the roots blower designed by the company itself. This kind of blower has high pressure and low speed, which can not only reduce the damage degree of grain (less than 0.1%), but also reduce the diameter of the system pipeline to more than 120 mm. Its material concentration is high, the operation is simple, and the labor intensity is reduced. It is suitable for the warehouse in and warehouse out operations of the room type warehouse and the shallow round warehouse; The resistance of the system is 15 inch mmHg, and the resistance of the microporous tube filtration system is only 1 inch mmHg, which has a significant energy-saving effect; Through the use of the microporous tube filtration system, the dust recovery rate can reach 99.97%, effectively avoiding the possibility of decreasing the capacity and efficiency of the equipment due to the dust wear during the continuous operation all the year round, and making the equipment maintenance rate drop linearly

due to the adoption of mxene nano sheet developed by Drexel University, several major technological innovations have been made, such as the integration of cyclone dust Valley separation kettle and filtration system, which reduces the volume and weight of the equipment and improves the overall mobility; The installation of wind speed reducer with air shutter greatly reduces the damage of wind speed to grain and improves the equipment efficiency; With the negative pressure intermittent operation function, it is convenient to move the suction nozzle and other operations without stopping the machine

due to the use of quick clip type conveying pipe interface, the pipe orifice is seamlessly connected, further reducing the damage during grain conveying. No tools are required for pipe installation and disassembly, and the operation is easy and labor-saving

III. Development and current situation of China's grain pneumatic conveying equipment (grain suction machine)

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grain suction machine was used in China's grain industry in the early 1960s, and was first used for grain delivery in underground warehouses. In 1992, China formulated the industrial standard of technical conditions for fixed grain suction machine, and in 1994 formulated the industrial standard of test methods for fixed grain suction machine

at present, China is carrying out the construction of large-scale national reserve grain depots. Pneumatic conveying equipment is required for the delivery of room type warehouses, the transportation of shallow round warehouses and the "four scattered" circulation of grain. However, there is still a big gap between China's grain suction machine and foreign countries, and it is in the trial production stage. The key technologies to be further studied and solved include:

fans: accelerate the research and development of multi-stage centrifugal fans, and adopt high-quality silencing devices for roots fans to reduce noise pollution; Reduce the impact of dust on the impeller and prolong the service life of the equipment

unloader: appropriate wear-resistant materials shall be selected for the inner wall of the unloader to reduce grain friction noise

air shutter: reliable anti-jamming and overload protection devices shall be adopted, and advanced materials and sealing technology shall be applied to the production of air shutter to improve the sealing performance and service life of air shutter

dust removal: develop effective dust collectors to control dust

operating accessories: develop the multi-function of the equipment, meet the requirements of various jobs, improve the utilization rate of the equipment, and improve the manufacturing accuracy of the whole set of equipment. (end)

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