Classification of Technology:
Air Pollution Control Type of Industry:
Petroleum Refining Subject:
Reduction of Dust Discharged from Catalyst Regenerator
1. Purpose
To reduce the dust in the exhaust gas discharged from the catalyst regenerator of the fluidized catalytic cracker from 0.30 g/Nm3 to 0.03 g/Nm3 according to the discharge regulation of the Air Pollution Control Law.
2. Details and the Time of Introduction
The dust concentration is high in the exhaust gas discharged from the catalyst regenerator since it contains scattered catalysts. The electric precipitator was therefore installed to collect the dust and to clean the exhaust gas. ( March, 1974 )
3. Principle and Structure
The basic structure of the electric precipitator consists of 1) electric discharging poles, 2) dust collecting poles to collect the dust charged by corona current, 3) striking devices to release the dust adhering to the pole plates, 4) discharge device ( conveyor ) to process the dust collected and 5) shielding of the dust collecting unit and high voltage insulating mechanism.
The dust particles in the discharge gas are charged by corona discharge from the discharging pole and are attracted to the dust collecting pole by Coulomb force. The dust that has collected and grown on the dust collecting pole is separated from the pole by the impact of the striker and is removed after falling down by the gravity.
The general outline of the process flow is shown on the next page.
4. Effect and Achievement
Before the Countermeasure
After the Countermeasure
Dust density in exhaust gas ( equipment outlet ) g/mN3
0.29
0.05
5. Future Subject
It will be necessary to grasp the optimum processing conditions to the exhaust gas as the measures of improving dust collecting efficiency such as 1) increasing corona discharge by maintaining a high load voltage, 2) maintaining gas temperature higher than the dew point but not too high ( normally 230 ~ 300°C ), 3) adjusting strike time appropriately and 4) refraining from storing excessive dust in the hopper of the electric dust collector.
