(A little preview) Oil Draining process
PCBs waste in temporary storage will be moved to oil draining area. In oil draining process, PCBs oil will be pumped out from transformers or drums and collected in PCBs oil storage tank. The capacity of this tank is 5 m3. Oil draining is conducted above oil pan box as a kind of preventive action if there is any spill occurred during process. All of this activity is carried out in a controlled area. Furthermore, pumped PCBs oil will be processed in dechlorination and oil regeneration units. The empty transformers will be dismantled and segregated into several types of materials.
PCBs oil that has been drained from transformers in oil draning process will be processed in dechlorination unit. This process is carried out in closed system and vacuum condition. Dechlorination process is the removal of one or more chlorine atoms in PCBs molecule using alkali metal. The reagent used in this process is sodium metal (Na). Sodium metal will form ionic bond with chlorine atom and combine into NaCl salt. Furthermore, PCBs molecule will turn into simply biphenyl (non-chlorinated). The chemical reaction occured as follow:Sodium metal will be dissolved in PCBs oil (in small quantity) in reagent tank as a preparation step before being put into dechlorination tank. Reagent tank and dechlorination tank will be heated using diathermic oil boiler and maintained its temperature at 110 C. After that, sodium mixture will be pumped into dechlorination tank which containings PCBs oil and the reaction proceed. Dechlorination process is conducted in batch system.
The dechlorination reaction process takes approximately 30-60 minutes and periodically sampling is carried out to determine the concentration of PCBs in the dechlorination tank. When the process is complete (the PCBs concentration has reached the set target), the oil is ready to be filtered. Bleaching earth is added before the oil enters the filtering unit. Oil free PCBs from the dechlorination tank, after the temperature is lowered then filtered using a filter press. The filtered oil free PCBs will be further processed in the oil purification unit. The filtered cake or sludge is processed by Stabilization before being stockpiled in landfills.
Oil free PCBs from the dechlorination process after the filtering process are pumped into the purification unit to reduce the water content to 10-15 ppm and remove dissolved gases. After this series of processes is completed, the oil free PCBs have been purified and ready to be used again in the transformer and have met the transformer oil standard/ specification.(atp)