Selection of dust collectors
From the external literature and industrial theoretical experience, there are currently four types of equipment for metal dust pollution recovery:
① Bag type dust collector
② electrostatic precipitator
③ wet venturi tube dust collector
④ Multi-tube cyclone dust collector
From the aspects of technology and economy, stop comparing the above-mentioned several types of dust removal equipment
, and according to the characteristics of flue gas in this project, choose explosion-proof high-pressure pulse bag dust collector
as the equipment for dust treatment and recycling, and choose anti-static nylon needle felt Filter material. This type of dust collector
has the following characteristics:
① The operation fluctuates, it is easy to clean the ash, and the maintenance is convenient;
② Low resistance to spray installation, large disposal capacity, and high dust removal efficiency;
③ The equipment weight is light, the investment is low, the construction cost is low, and the area is small.
Calculation of rare earth hydrogen storage alloy powder flue gas volume The amount of flue gas generated during the smelting of rare earth hydrogen storage alloy powder is the amount of air entering from the vacuum state to the normal pressure state during the opening process of the intermediate frequency vacuum induction melting furnace. According to the "Design Standards for Heating Ventilation and Air Conditioning", the wind speed of the air inlet is taken as 0.6m / s, the cross-sectional area of the air inlet is 0.314m2, and the air volume is: Q1 = 0.6 x 0.314 x 3600 = 678m3 / h; a total of 4 Smelting furnace, so the total air volume is: Q2 = 678 × 4 =
2712m3 / h, thinking about the fractional air leakage, multiplying the safety factor of 1.1 to 1.15 as the basis for the total amount of flue gas for dust removal and the selection of induced draft fans. Therefore, the amount of flue gas for pulse dust removal is Q = 2712 × 1.1 = 2983m3 / h. The filter area of the dust collector and the
filter area of the filter wind speed dust collector
can be calculated according to the following formula: F = Q60V (1) where: F is dust removal
Filter area, m2; Q is the fractional flue gas volume, m3 / h; V is the filtering wind speed, m / min. The size of the filtering wind speed and the cleaning method, cleaning system, dust characteristics, dust concentration at the inlet, etc. close relationship. According to experience, when the filtering wind speed is V = 1.0m / min, the filtering area of the dust collector
is F = 49.7m2.
Based on the above calculations, the LDM-50 explosion-proof high-pressure pulse bag filter
was selected in the design, with a smoke volume of 3000m3 / h and a filtering area of 50m2. Process flow clarification and secondary technical measures The melting furnace flue gas enters the bag dust collector
through the stainless steel air duct, and then is discharged through the ground of the induced draft fan. The dust
collected by the dust collector
hopper enters the bucket and is stored in the material warehouse for reuse as raw materials. An electric valve is installed in the suction hood of each melting furnace, and its signal is connected to the inverter, so that the inverter can automatically adjust the fan's air volume according to the number of electric valve openings. It is very convenient to operate. In the rare earth hydrogen storage alloy powder flue gas dust removal and fragmentation, the key is to deal with the flammable and explosive performance of the rare earth hydrogen storage alloy dust in the air. The following technical measures have been taken to prevent this fragmentary design:
① Use stainless steel pipes as ventilation ducts, which will not cause extinction.
② The explosion-proof high-pressure pulse bag type dust collector is
adopted. The explosion-proof door is provided in the box of the dust collector
, and the pressure can be quickly opened and released when the event occurs, and the equipment is safe.
③ Use anti-static nylon needle felt as filter material to prevent dust explosion caused by sparks caused by electrostatic discharge.
④ The use of condensed N2 as a pulse gas to prevent dust and air from causing friction.
Bag type dust removal and fragmentation process characteristics In this fragmentation, because the hydrogen storage alloy powder is flammable and explosive metal dust, the dust removal is stopped by partial ventilation. In this project, tightening N2 is used as a maintenance gas, and a nitrogen production unit with a capacity of 40m3 / h is configured. Therefore, tightening N2 is used as a pulsed ash cleaning gas in this fragmentation. The anti-static nylon needle felt is used as a filter material to prevent dust explosion caused by sparks caused by electrostatic discharge. In addition, an explosion-proof door is provided in the middle box, which improves the safety and reliability of the normal operation of the equipment. At the same time, a programmable controller (PLC) is used to stop automatic control and short-range operation, which makes this piecemeal operation convenient.
① The filter material has high filtering efficiency and functional fluctuation. Needle felt is a three-dimensional structure (planar structure) filter material. The filter unit is a single fiber. Several single fibers are intertwined together. The pores are very small, and its filtering process not only occurs outside. The surface layer can also occur outside the filter. Therefore, the filtration efficiency of the needle felt felt material is high, and the filtration efficiency can reach more than 99.0% in this project. In addition, the tasks fluctuate and are not affected by changes in the operating conditions of consumer technology equipment. The outlet concentration is constantly less than 20 mg / Nm3, which effectively invalidates the environmental protection standards for smoke and dust.
② High level of automation. Automatic control is one of the key measures for the normal operation of the dust removal system. This system adopts a BMC bag type dust removal system computer control cabinet and uses the Japanese original programmable controller (PLC) as the host. The task function fluctuates and the automation level is high. . The programmable controller (PLC) can automatically control the fan speed and the amount of induced air through the inverter according to the opening and closing of the furnace valve, so as to complete the automatic control of the air volume entering the dust collector
, which is invalid. At the same time, the programmable controller can automatically control the dust
removal time and distance according to the pressure difference at the inlet and outlet of the dust collector
. Economic benefits of dust removal and fragmentation The economic benefits of recycling dust are calculated as 6 kg of dust recovered per hour, and the amount of dust recovered each year is: 6 × 24 × 300 = If the value of each kilogram is calculated as 70 yuan, the economic benefits of annual dust recovery are: 43200 × 70 = 3024000 yuan.
② The operation cost of bag-type dust removal system is calculated as 0.50 yuan per kWh. The annual operation cost of bag-type dust removal system is: 7.8 × 0.50 × 24 × 300 = 28080 yuan
③ The maintenance cost of bag-type dust removal and piecemeal equipment is calculated by changing a set of filter bags
every one year. Assuming that the price of each set of filter bags is 10,000 yuan, the annual filter bag maintenance cost is increased by 10,000 yuan; the annual machine maintenance cost is added by 0.2 million yuan. The annual piecemeal maintenance costs add 12,000 yuan