On March 23, it was reported that the steam turbine driving the diesel hydrotreating unit at Daqing Refining & Chemical Company achieved stable operation under high-load conditions—running at 9,000 rpm with the steam valve opening stabilized at 86%—while all core operating parameters fully returned to design standards. This marks the complete success of a two-month application of on-stream steam turbine desalting technology, serving as a demonstration case for PetroChina in successfully resolving salt deposition issues without shutting down the turbine.
As the core power equipment for the diesel hydrotreating unit, the steam turbine's operational status directly impacts the unit's continuous, stable production and the quality of the diesel product. Previously, severe internal salt deposition had significantly degraded equipment performance, making it difficult to meet the urgent need to increase the production of low-pour-point diesel for winter use. Resorting to a traditional shutdown for maintenance would have entailed risks of equipment freezing and production losses, thereby disrupting the company's overall production schedule.
Faced with this formidable challenge, the company’s team—grounded in thorough research and scientific validation—innovatively introduced on-stream chemical desalting technology. This process involved continuously injecting a specialized cleaning agent into the steam inlet line to chemically dissolve and physically flush away the internal salt deposits. Breaking away from conventional thinking and adhering to the principles of "proactive risk control and precise execution," the technical team conducted a comprehensive risk assessment. They developed multiple contingency plans for potential issues—such as parameter anomalies triggering safety interlocks or chemical leaks—and tightened alarm thresholds for critical parameters (like shaft vibration and axial displacement) by 30% relative to original standards. Additionally, they upgraded the injection line to a hard-piped connection, significantly enhancing safety and controllability.
During implementation, the team established a refined management mechanism characterized by "phased progression, dynamic optimization, and closed-loop control," scientifically dividing the cleaning operation into five stages and gradually increasing the dosage of the cleaning agent. Steam samples from the turbine inlet and outlet were analyzed every four hours to closely monitor levels of sodium and chloride ions as well as fluctuations in steam flow; real-time data enabled precise assessment of cleaning effectiveness and flexible adjustment of operational plans. Additionally, the steam sampling method was independently improved through the development of a rapid-condensation sampler, significantly enhancing analysis efficiency.
Following two months of continuous, stable cleaning and monitoring, the issue of internal salt deposition in the turbine was thoroughly resolved; the equipment's power generation capacity and operational efficiency saw fundamental improvements, and all key parameters returned to normal levels.
Moving forward, the company will consolidate the experience gained from this application, continue to advance research into condition monitoring and state-of-the-art maintenance technologies for critical equipment, and provide reliable technical solutions for addressing turbine salt deposition in similar facilities.
