The selection of bag filter is not only a technology but also an art. The design and selection of bag filter need to consider many factors. The design of bag filter must know the processing parameters of the dust gas handled. Including many factors such as gas flow, temperature, humidity, dust concentration, gas and dust characteristics, etc.) The main considerations in design are:
1. Pressure loss of dust collector
The designer can make different choices for the baghouse dust removal mechanism, and the cleaning process parameters can be implemented in different designs. Therefore, it is sometimes possible to reduce the pressure loss of the dust collector filter bag to a level close to the pressure drop of the clean fabric in some cases by increasing the intensity and frequency of the dust cleaning. However, the dust removal of the dust remover will bring about a reduction in the dust removal efficiency, and damage the fabric and the excessive power consumption of the cleaning mechanism. On the other hand, the lack of clean dust and the large pressure difference will increase the power consumption of the blower. Therefore, in the design of bag filter, the best pressure loss should be selected based on practical experience or field test.
Experience has shown that for low dust filter filter speed, loose dust, the pressure loss can choose 784 ~ 1176Pa (80 ~ 120mmH2O). When the dust collector adopts a high filtration rate, or a dust layer with low viscosity and porosity, the pressure loss can reach 1960 (200mmH2O).
The pressure loss of the bag filter accounts for 70% to 80% of the pressure loss of the entire ventilation and dust removal system. Therefore, the pressure loss of the bag filter will affect the economical efficiency and reliability of the entire ventilation and dust removal system, often resulting in unnecessary energy waste. Must be taken seriously.
2、Filter speed of bag filter
The filter speed V of the bag filter is the ratio of the filtered gas flow rate (m3/min) to the filter fabric area (m2), so the order of times is m/min, also called the filtration speed, it only represents the passage of gas The average speed of the dust bag does not take into account that many areas are occupied by the fibers of the fabric, and is therefore referred to as the “apparent flow velocity.”
The filtration rate is a very important factor in determining the performance of the filter. Too high a filtration rate will cause excessive pressure loss, reduce dust collection efficiency, and clog and rapidly damage the dust filter bag. However, increasing the filtering speed can
In general, baghouse dust removal methods have an impact on the choice of filtration speed. For high-energy cleaning (pulse, gas ring cleaning, etc.), the filtration rate can be higher than low-energy cleaning (swing, anti-hair dryer cleaning, etc.).
In the cement plant, bag filters should be carefully and carefully selected when selecting the filtration speed. The reason is that the dust concentration is high and the powder is fine, and the gas contains a certain amount of moisture. Therefore, for high-energy dust-removing bag filters such as pulses, the filtration speed is also preferably 1 to 2 m/min, and for low-energy types it is less than 1.0 m/min.
3, the determination of dust filter bag area
1 dust filter bag specifications
For the large blowback dust bag filter, the filter bag size (length and diameter) is determined by the following factors. The length and diameter of the dust filter bag are related to two factors.
(1) The strength of dust bag. The relationship between the actual load of the dust filter bag (ie the weight of the dust filter bag, the weight of dust attached to the dust filter bag and other forces) and the dust bag should be taken into consideration in use. When the actual load exceeds the allowable strength of the dust bag, the dust filter bag will burst due to insufficient strength. Obviously, it is more important whether the tensile strength of the dust bag can meet the requirements for use.
(2) The inlet flow velocity V1 (m/s) into the dust filter bag. When the dust-laden gas enters and deposits each dust filter bag, the inlet velocity V1 is too fast. On the one hand, it accelerates the secondary flying of dust removal and dust reduction. On the other hand, due to the friction of the dust, the wear of the dust bag increases rapidly. V1 cannot be greater than 2.5m/s.
The filter speed V (m/min) of the bag filter is related to the inlet flow velocity V1. The relationship between length and diameter is calculated as follows:
From the above formula, it can be concluded that when V is high, L/D should be in a smaller range; when V is low, L/D is in a larger range. According to relevant data, the L/D of the bag filter is generally 10 to 23, and the L/D of the fiber bag filter can reach 50 to 60.
When the glass fiber bag filter chooses the filter speed V = 0.5m/min inlet flow velocity V1 ≤ 1.5m/s. Therefore, the dust filter bag diameter can be 150 ~ 300mm, the length of the bag can also be selected within 3 ~ 12m (reverse hair cleaning dust bag filter)
2 Determination of the filter area of the dust collector;
3 The number of filter bag filter N;
4 reverse suction (blow) air cleaning bag dust collector;
In actual selection, as long as the total filtration area is calculated, the selected bag filter can be determined according to different cleaning methods through product samples, and the ventilation and dust removal system and installation design can be carried out according to product samples.
