A Brief Discussion on the Practical Impact of FRP Fans in Ventilation
Release time:
2021-05-27
The governance plan consists of two main systems: exhaust and supply air. (1) Exhaust system. Due to the large three-dimensional space of the workshop and the lack of partition walls with the ore dressing workshop, if unified extraction is considered, with a minimum ventilation rate of 8 times/h for the workshop, an exhaust volume of 130,000 m3/h would be required. This not only involves high investment but also high energy consumption. Based on the actual situation, a main exhaust duct is designed to be placed in the upper space where the sources of exhaust pollution are concentrated; a fume hood is used above the dosing tank to collect exhaust gases, and movable guide plates are left at the dosing and maintenance areas for the tank. The exhaust gas is controlled by a butterfly valve through the hood body, entering the main exhaust duct along the branch pipe; the slurry discharge trough is uniformly covered with movable fiberglass panels, and the cover panel on top.
The governance plan consists of two main systems: exhaust and supply air. (1) Exhaust system. Due to the large three-dimensional space of the workshop and the lack of partition walls with the ore dressing workshop, if a unified exhaust is considered, with a minimum ventilation rate of 8 times/h, an exhaust volume of 130,000 m3/h would be required. This not only involves high investment but also high energy consumption. Based on the actual situation, a main exhaust duct is designed to be placed in the upper space where the sources of waste gas pollution are dense; a gas collection hood is used above the dosing pool to collect waste gas, with movable guide plates left at the dosing and maintenance areas. The waste gas is controlled by a butterfly valve through the hood and enters the exhaust main duct via branch pipes. The slurry discharge trough is uniformly covered with movable fiberglass plates, with an exhaust port set every 6m on the cover plate, and the air volume is controlled by a butterfly valve, also entering the exhaust main duct through branch pipes, creating a negative pressure state in the trough to ensure that harmful gases from the slurry do not escape. The entire exhaust system is designed for an air volume of 32,712 m3/h and a resistance of 680 Pa. The waste gas is discharged through the fan via pipes along the outer wall of the workshop to the top of the workshop. A BF4-72-11.No12 centrifugal fan is selected for the system, with an air volume of 35,650 m3/h, air pressure of 921 Pa, and a power of 22 kW. (2) Supply air system. Since this workshop is connected to the flotation workshop, the discharged gas needs a certain amount of fresh air to supplement; otherwise, it will be polluted again by the harmful gases from the flotation workshop. A rectangular duct with a short pipe supply air outlet is designed above the maintenance passage, with a total supply air volume greater than the exhaust volume, set at 45,000 m3/h. The duct is evenly equipped with 15 adjustable multi-leaf supply air outlets measuring 600mm×300mm, with each outlet having an air volume of 3,000 m3/h and a spacing of 6m. The intake of the supply air system is opposite to the exhaust outlet of the exhaust system. This ventilation project was completed after more than two months of equipment manufacturing, installation, and debugging, and was officially put into operation in September 1998, achieving good ventilation effects, with all indicators meeting design requirements, thoroughly improving the working environment for employees. After nearly three years of operation, the fan, pipes, and hood remain intact, and the corrosion resistance of the FRP material has not been affected.
Application of ventilation in the acid washing workshop of the metal wire factory. This workshop has four wire drawing racks, with acid washing tanks on both sides, each tank measuring 9m in length and 0.5m in width. Since the acid tanks are open, they sometimes need to be heated, and during the wire drawing process, the wire reels are in motion within the acid tanks. After drawing, the residual acid liquid on the wire passes through a fixed pulley along the entire wire drawing rack and then enters the cleaning tank, resulting in a particularly high concentration of acid mist emitted from the workshop, with concentrations exceeding 400mg/L at the working interface. In summer or during low atmospheric pressure conditions, the entire workshop is filled with acid mist, forcing workers to wear wet masks soaked in tap water to continue working, creating a very poor working environment that severely affects production and workers' health. The steel frame roof at the top of the entire workshop is severely corroded, and electrical equipment has been damaged. The mining department had no choice but to dismantle the entire steel frame roof in early 2000 to eliminate safety hazards. Through the redesign of the waste gas treatment system by Zhonghui Company, the goal of thorough treatment was achieved. The design is based on the GB16297-1996 acid mist emission standard, aiming to ensure that the workshop's waste gas is completely extracted and treated, while avoiding the possibility of secondary pollution caused by the treatment process and selected equipment. At the same time, the ventilation materials and equipment should consider corrosion resistance requirements. The overall treatment plan is divided into two aspects: first, the acid washing tanks and the sides of the wire drawing racks, as well as the front section before entering the cleaning tank, use hoods for centralized extraction, which are then discharged through waste gas purification devices. The four lines are divided into two treatment systems; second, a roof exhaust fan is installed at the upper part of the workshop to expel acidic gases that escape during non-production states, preventing the accumulation of waste gas at the top.
Extraction and treatment of acid mist through hoods. Based on the evaporation area of the acid mist from the acid washing tanks, the extraction volume for each production line is determined to be 12.5 km3/h. The suction hood adopts a strip seam type side suction hood, with a seam width of 10mm and a designed wind speed of 6m/s; the main duct wind speed is selected at 9m/s, and the vertical pipe wind speed is 7.6m/s; the resistance of the pipe network system is 350 Pa. (2) Fans. Two BF4-72-11.No10C glass centrifugal fans are selected, each used for two purification devices, with a power of 15 kW per unit and a speed of 1000 r/min. (3) Waste gas purification devices. Two sets of FBSJ-25 type fiberglass acid mist purification devices are selected, with a processing air volume of 25,000 m3/h per set, a designed empty tower wind speed of 1.5m/s, a neutralizing liquid contact reaction time of 2.5s, and a total resistance of the purifier of 509 Pa. Each set is equipped with a neutralization circulation pump with a flow rate of 25 m3/h per unit, a lift of 24m, and a power of 3 kW per unit.
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