Transform kiln head electrostatic precipitator into bag filter dust collector

1. System calibration and program analysis

Inviting relevant qualified manufacturers to calibrate the kiln head system to understand the current system resistance, actual air volume and other related parameters, and then provide a basis for the bag filter modification and the existing kiln head exhaust fan changes. The calibration parameters of the dust removal system before transformation are shown in Table 1. The parameters of the kiln exhaust fan and motor are shown in Table 2.

Experience in transforming kiln head electrostatic precipitator into bag filter

The system calibration air volume is 441,592m3/h, and the rated air volume of the fan is 740,000m3/h. In order to ensure that the filtered wind speed is below 0.90m/min, we require the manufacturer to calculate the rated air volume. The filtration rate is the ratio of the filtered gas flow to the filtered fabric area. The maximum filtration area is 740 000 ÷ 60 ÷ 0.9 = 13 704 (m 2 ).

In addition, according to the existing space of the original electrostatic precipitator, the design bag filter is a double row 16 air chamber, the filter bag size is Φ160mm×7 500mm, and the material is Nomex + microfiber. To this end, we have determined to use the KDM13740-2×8 large low-pressure jet pulse bag filter.

According to Table 1 and Table 2, it can be seen that the actual operating pressure of the dust removal system before the exhaust fan renovation is 1 200Pa, which is much smaller than the original design pressure of 2 550Pa (220 °C). The original exhaust fan has a certain margin when it is selected. After the transformation, the total pressure required by the exhaust fan = the system resistance before the change + the resistance after the change (1 + surplus factor) = 1 200 + 800 × (1 + 20%) = 2 160 (Pa).

At present, the amount of flue gas is much smaller than that of the design, so the exhaust fan and the electric motor can meet the design requirements of the transformation.

2. Improvement measures

1) The electric dust removal part retains the ash bucket, the wallboard, the ash conveying equipment, the inlet and outlet head and the equalizing device;

2) Remove the internal cathode and anode system and its rapping device, inner top and outer top;

3) Adding the top beam, the inner tube support of the shell, the inlet and outlet air duct, the upper tank body, the blowing system, the gas path system and the poppet valve, etc., and adding an equal air panel in front of the filter bag;

4) Renovate existing ladders, cable trays and housing insulation;

5) Add 2 cold air valves and 1 set of rapid spray cooling device to the inlet pipe to adjust the temperature of the flue gas;

6) Add a bag filter control system;

7) According to the actual situation of the site, the construction period node, construction plan and acceptance process are formulated;

8) In order to reduce the occupation of construction sites, the disposal of waste materials was done in advance.

3. Operation of equipment during the transformation process

See Table 3 for comparison of relevant parameters before and after the renovation of dust removal equipment .

Experience in transforming kiln head electrostatic precipitator into bag filter

It can be seen from Table 3 that in the case of the same speed of the kiln head exhaust fan, the electric dust removal pressure difference before the transformation is 291Pa, and the bag dust removal pressure difference after the transformation is 546Pa, which is 255Pa higher than that before the transformation, and the dust collector pull-down chain machine current is about liter. At about 3A high, the flue gas flow rate and rate have dropped significantly; when the kiln feed rate reaches 400t/h, the kiln head exhaust fan speed reaches 630r/min, and the current is about 530A. In summer, the opening and closing of the one- and two-chamber fan valves in the cold room are about 65%, and the fan valves in the other rooms are basically fully open. (In the winter, the opening of the one- and two-chamber fan valves in the cold room is about 60%, and the other rooms are Fan valve opening degree is 40%~60%). From the current operating conditions, the bag filter is operating normally and the kiln exhaust fan can meet the production needs.

We have been tracking and analyzing the operation of the bag filter. At the beginning of use, the system pressure difference is 623Pa. The relevant electrical parameter setting values are: injection chamber injection interval time 10s, cycle period interval 40min, pulse width 0.2s, injection gap time 5s, injection pressure 0.35MPa (pressure The fluctuation range is 0.25 to 0.35 MPa). After the groping in the later stage, we separately introduced the injection pipe on each side of the bag filter to ensure that the injection pressure is sufficient and the fluctuation is small. In addition, under the premise of not increasing the resistance, the cleaning pressure is minimized and the cleaning cycle is extended to achieve the purpose of prolonging the service life of the filter bag and reducing the use cost of the high pressure wind. The injection chamber injection interval was changed to 150s, the cycle interval was adjusted to a maximum of 80 minutes, and the injection pressure was adjusted to 0.30 MPa (pressure fluctuation range was 0.25 to 0.30 MPa). Now the system pressure difference is about 550Pa, and the actual filtered wind speed is 0.66m/min. After the environmental monitoring department determined that the particulate matter emission value was kept at <20mg/m3 (standard state), the expected effect was achieved.

Due to the cold weather in winter, the water inside the pipe cooled by the spray is very easy to freeze. Therefore, in addition to the insulation on the pipeline, the anti-air blower is installed on the 8 water guns (4 water pipes) that are cooled by the spray. The air blower will drain the water after each use of the spray to ensure that the system works normally during emergency use.

4, the running effect

Before and after the renovation, the clinker power consumption of the kiln head system was reduced by 0.5kWh/t on average, calculated according to the annual clinker output of 1,161,300 tons, and the annual electricity saving was 800,000 kWh (see Table 4). Compared with the electrostatic precipitator, the bag filter has the characteristics of simple maintenance, small maintenance and easy operation. After the change, the measured particulate matter emission value is in line with national standards. In addition, the kiln head exhaust fan in this transformation has not changed, and it can meet the normal use requirements from the actual use.

Experience in transforming kiln head electrostatic precipitator into bag filter

It should be noted that, because the bag dust collector has higher requirements on the inlet temperature, the temperature should be lowered in time through the cold air valve and the spray cooling method.