Research On Protective Corrosion Product Film Of REAC Exit Pipelines And Its Erosion Corrosion Critical Characteristics

Reactor effluent air cooler (REAC) systems withstand the long-term erosion effects of the corrosive multiphase flow. The erosion occurs with an obvious local, sudden and risky failure and the critical characteristics exist in the erosion failure, the quantitative calculation of the erosion damage can be obtained by fluid-structure interaction analysis of the corrosion product film. While, there was not a fundamental breakthrough of the prediction and erosion-control technology of the REAC system due to the lack of performance indicators of actual protective film and the test of the critical characteristics in the erosion prediction.The thesis targets at the frequent cases of erosion failure of the export piping system of REAC. According to analyse of technical process and the mechanism of erosion failure, sulfur-containing wastewater is comformed as the main corrosive phase. A rotary single-phase flow erosion experimental device is developed and an electrochemical testing system is design innovatively. Based on these services, the erosion simulation experiments, the performance test of the corrosion product film and the experimental research of critical characteristics erosion are carried out. According to the corrosion impact factors in the actual environment, alter such factors as NH₄HS concentration in sulfur-containing wastewater, temperature, velocity and etc, the performance and critical characteristics of corrosion product film on the surface of 20 carbon steel is studied. The study showed that the NH₄HS concentration has a large influence on the anti-erosion performance of protective film. Under a static condition, when NH₄HS concentration is 6 wt% and temperature ranges from 40℃to 60℃, the protective film is looser with a higher temperature, so the corrosion will occurs easily. When NH₄HS concentration is 8 wt% and the temperature is 50℃, the protective performance of corrosion product film indicates the cracks is larging with increasing of rotating velosity. If the temperature is 50℃and the NH₄HS concentration ranges from 4 wt% to 8 wt%, the performance of protective film is worsing with the increasing of the NH₄HS concentration in flow state. When NH₄HS concentration is 8 wt% (suggested by API formerly), the critical speed of corrosion product film occurring erosion damages is between 50 rpm to 100 rpm. When NH₄HS concentration is 4 wt% (control index suggested by NACE now), the critical speed of corrosion product film occurring erosion damage is between 150 rpm to 200 rpm. The NH₄HS concentration of REAC system which was controled to reduce from 8 wt% to 4 wt%, can significantly improve the erosion-resistant running reliability of REAC system.The innovative work in this paper is concluded as following: A rotary single-phase flow erosion experimental device and the electrochemical test system is developed, which is utilized to achieve the research of corrosion product film and the transient characteristics of erosion. The corrosion environment of REAC outlet piping system is simulated, the product film performance formed in the sulfur containing wastewater and 20 carbon steel and the variation of its critical characteristics is studied under the different temperatures, NH₄HS concentration, pH, velocity and other conditions. The results above will provide a theoretical basis and technical support for erosion failure prediction of REAC system.