Electrostatic Precipitators (ESPs) are widely used in sugar plants after biomass/agricultural waste-fueled boiler process to capture fly ash before escaping through the stack.
There are two rapping system designs of ESPs based on how the dust is cleaned from collecting electrodes (CE) and discharge electrodes (DE)—tumbling hammers and MIGI (Magnetic Impulse Gravity Impact) rapping system.
Tumbling hammers are rotating mechanical rappers and located inside the ESP casing, while the MIGI design is located outside and uses rod plungers that are lifted and dropped to create the rapping impact.
It is not only the location related to the ESP that tumbling hammers and MIGI rappers differ, but also how they are operated and maintained. Tumbling hammers rotate in motion driven by gear motors while MIGI rappers move vertically in motion energized by electrically induced magnets that lift the plungers. Tumbling hammers can only be maintained when ESP is in a shutdown condition while MIGI rappers can be maintained or replaced even when ESP is in operations.
MIGI rapping systems for collecting electrodes and discharge electrodes both require another separate controller apart from the automatic voltage controller of the transformer/rectifier (T/R) sets. New MIGI rapper controllers are also able to control the intensity of the rapping force through the lifting height of the plunger, frequency as well as cycle of rapping.
MIGI RAPPING CONTROL UPGRADE - Case Study
A sugar plant in Kalasin, Thailand has an ESP with MIGI rapping system that had been operating since 2012. In 2018, the plant started experiencing problems on their MIGI rapping system, which resulted in dust build up on CE and DE causing high rate of sparking.
Some MIGI rappers were found to be disabled and some whose height could not be adjusted. Some others even rapped at the same time causing higher emission or puffing at the chimney.
To remedy these problems on the MIGI rappers, upgrading MIGI rapper controller was recommended. The new MIGI rapper controller ERC1001 has been installed, and not only addressed the problems on rapper control but also provided the users with more features beneficial to operations.
The ERC1001 provides group parameters setting which separates the setting of field 1, field 2 and so on. This feature enables the anti-coincident rapping group (ACG) which prevents the MIGI rapping system in one field to be energized at the same time with the other MIGI rapper group. This anti-coincident rapping prevents puffing incidences.
ERC1001 can also adjust the lifting height of each MIGI plunger by changing the current input to the MIGI rapper based on the rapping force needed to dislodge dust on both CE and DE systems. Each MIGI rapper can be turned on manually for checking and maintenance purposes while ESP is still in operation.
With the new ERC1001 controller, operators can easily monitor the MIGI rappers, change parameters and adjust rapper intensity and sequence according to operation conditions through HMI.
When ESP is in operations, it is only on the electrical aspect that one can do any adjustments. Having a user-friendly automatic voltage controller and rapper controllers can make a big difference not only for maintaining stable operations but also impact on emission levels.