Case Study of the APC Maintenance Project at Zhenhai Refining & Chemical
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Maintenance Work Example
The bottom temperature of the distillation column in the gas separation unit at Zhenhai Refining & Chemical is controlled by the thermal oil flow rate. Following modifications to the upstream unit, fluctuations in the thermal oil temperature have increased and become more difficult to stabilize, resulting in significant variations in the column’s bottom temperature and poor control performance. The temperature profile is shown in Figure 1.
After analyzing historical data, it was found that both the flow rate and temperature of the hot oil influence the reboiler temperature; however, the underlying factor governing the reboiler temperature is the heat transfer between the hot‑oil temperature and flow rate and the reboiler temperature. Accordingly, the hot‑oil energy term Q was calculated through process‑engineering analysis using the hot‑oil flow rate and temperature. By replacing the manipulated variable with Q and rebuilding the model, the disturbance caused by fluctuations in hot‑oil temperature was mitigated, enabling stable control of the reboiler temperature. Following maintenance, the standard deviation of the reboiler temperature decreased by 45% compared with the pre‑maintenance level, as shown in Figure 2.
Maintenance performance
During the APC maintenance period at Zhenhai Refining & Chemical, Bangye Technology responded to 35 fault‑handling requests in the first quarter, most of which were APC faults that had accumulated due to prolonged lack of maintenance on the controllers.
Following the implementation of maintenance and support activities, the total number of fault responses decreased to 11, fault frequency dropped by 70%, and the level of automation improved significantly.
Maintenance benefits
The advantage of APC maintenance services lies in ensuring the safe and stable operation of the plant, continuously optimizing controller models and parameters, providing uninterrupted issue tracking and resolution, and submitting and implementing improvement recommendations—thereby sustaining high levels of economic performance. To date, Bangye Technology has deployed APC maintenance at multiple plants, achieving consistently excellent results.
Bangye Technology boasts a dedicated APC team and extensive experience in project maintenance, and remains committed to the execution and ongoing support of APC projects, ensuring that plant‑level APC performance is visualized, sustained, and optimized.
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