Bagasse is waste material from sugarcane, which sugar plants nowadays are using it as a value-added biofuel for electricity generation. However, the by-product of combustion must be addressed and dealt with so as not to pose a threat to the environment.
Today, Electrostatic Precipitator (ESP) is being applied in many sugar and biomass industries in order to control the emission from the stack. ESP has been considered to be more efficient than multi cyclone, wet scrubber or any other emission control devices. In the meantime, baghouse is less preferable due to its risk of fire and high maintenance cost.
Sugar plant case study in Thailand
One of the sugar plants in the northeastern part of Thailand encountered a problem of seriously corroded ESP internal parts especially Collecting Electrode (CE) and Rigid Discharge Electrode (RDE) in the entire 3 fields. CE and DE are the mechanical components involved in the charging and collecting of dust particles. They are then cleaned by rapping systems, where dust is collected in the hoppers and eventually transported to silos or designated areas.
Upon inspection of the ESP in this plant, it had been found that the root causes of its dust collection inefficiency and CE corrosion were the leakage of air from the access doors and insulator compartments including bending / deformed DE.
Some ESP fields tripped and were malfunctioned as DE and CE had either fallen off or severely bent resulting in almost near contact. These issues all contributed to lower ESP dust collection efficiency and resulted in air pollution.
Furthermore, leakage was found in the multi cyclone that led to inlet temperature drop to less than 100 degree Celsius, allowing moisture to easily form inside the ESP. Severely damaged condition of the ESP internal parts are shown in photo 1 and 2 below.
Problems observed from the ESP inspection were addressed and solved as part of the scope of work of this project. CE and RDE were replaced for the entire 3 fields, where CE material for the 1st and 2nd fields had been changed to Corten steel to withstand corrosion. Maintenance and replacement of some internal parts like rapping system and manhole gasket were also carried out. With good project management and proper supervision of installation, replacement of CE and DE was successfully completed within the plant’s period of shutdown.
After replacement, all three fields of the ESP were up and running normally without any tripping issue. The plant had not yet experienced any emergency shutdown due to ESP problems after 5 months of operation straight. Inspection had been done on the ESP and its internal parts were found to be in good condition still.
Expertise on ESP together with good quality products are elements to solutions of ESP problems. Improving an ESP to be efficient is not necessarily expensive as long as solutions are based on the root causes found. Good emission control not only portrays environmental awareness but also expresses social responsibility and well-being.