Since the modification and capacity expansion of the ethylene cracker at Sinopec Guangzhou Company in 2003, the process water system was seriously blocked. After adding new coalescers and heat exchangers and adopting toluene extraction technology, the blockage problem in process water system was successfully solved, and the stable operation of process water system throughout one overhaul cycle, i.e. 4 to 5 years, can be guaranteed, thus eliminating the risk of unit shutdown due to the blockage in process water system,  laying a foundation for the long-term operation of the unit, and reducing the maintenance cost of process water system in one overhaul cycle by more than 600,000 yuan.