Guofu Ou

Numerical simulation and factor analysis of petrochemical pipe erosion-corrosion failure

Based on the behavior of carbon steel outlet tube in REAC pipes of Zhenhai Refining & Chemical Company, the mathematical model of fluid-solid interaction was established according to the mechanism of erosion-corrosion damage. The interaction between corrosion products protecting film and multiphase liquid was analyzed by numerical simulation method. The distribution of shearing stress on the inwall of elbow bend, and the distribution of principal displacement, stress and strain of corrosion products protecting film were disclosed, while the erosion-corrosion failure processes was studied. The simulation result coincides with that of the positioned thickness gauging which validated the reliability and feasibility of the finite element analysis software simulation method. The obtained results can be used in the erosion-corrosion failure analysis, structural optimization, in-service testing positioning, life prediction, risk assessment, safety and other security projects for multiphase flow pipeline.

Numerical investigation on cavitation in pressure relief valve for coal liquefaction

The pressure relief valve for regulating the level of the high-pressure separator works under a pressure difference up to 15 MPa in the temperature of 415 °C. Severe cavitation erosion and particle impact lead to the valve discs mass loss. In this paper, three-dimensional turbulent cavitating flows in the pressure relief valve are numerically simulated to reveal the mechanism of mass loss at valve disc. The RNG k- turbulence model and the mixture model with a mass transfer for cavitation are employed to simulate the cavitating flow in the pressure relief valve. The result shows that there is phase change in the pressure relief process and cavitation bubbles would be transported by high-velocity backflow to the head of valve disc. For the local pressure higher than the saturated vapor pressure, the bubbles collapse at the head of disc and cavitation erosion is formed at the head of the disc. By comparing the cases of opening of 40%, 50%, and 60%, backflow velocity and cavitation region in front of the disc decrease with the opening increase. Therefore, during the actual operation, the pressure relief valve should be kept to a relatively large opening.

Failure Analysis and Structure Optimization of Hydrogenation Air-Cooler System Based on Imbalanced Degree

Due to the prevalent leakage and rupture of a hydrocracking reactor effluent air cooler (REAC) pipes, the corrosion mechanism is studied based on the REAC operation mode and conditions. The mathematic model of imbalance degree is constructed according to the REAC structural property. The multiphase flow characteristics are obtained by a universal petrochemical software HYSYS; and the systemic imbalance of dynamic parameters, such as flux and volume fraction, is simulated using Computational Fluid Dynamics (CFD). Comparing with actual anatomical instances, failure analysis based on the imbalance criterion is achieved. Moreover, the optimum measures to enhance the running reliability are proposed.Copyright

Investigation on the Flow Induced Erosion-Corrosion Failure of Hydrocracking Air Cooler Systems and Optimization Study

The flow induced erosion-corrosion of a hydrocracking reactor effluent air cooler (REAC) system normally occurs locally and abruptly, which leads to the high risk of unplanned shutdown and even catastrophic accidents. To study the typical failure cases induced by the high-sulfur and chloride-containing raw oil in the process of refining, numerical simulation of technical process and fluid dynamics parameters are performed on softwares of HYSYS and CFD, and the rules of multiphase flow erosion and ammonium salts deposition are analyzed. Analytical results are in good agreement with actual failure instance and thus the reliability of the predictive method is validated. A corrosion-control research system, consisting of mechanism research, numerical simulation, experimental verification and similarity theory correction, is established. The critical characteristics of multiphase flow deposition and erosion are obtained. And the system to control the flow induced erosion-corrosion, which can be widely applied in various conditions, is formed on the basis of “avoiding blockage and controlling erosion” conception. Moreover, this paper proposes an optimum design based on the degree of unbalancedness and a frame of the REAC Real-time Diagnosis Expert Software for guiding the optimum design. The method above will be beneficial to the promotion and modification of related criteria and regulations in the future.Copyright

Multi-Scale Simulation of Fluid-Structure Interaction Induced Erosion on the Pipe Surface

Erosion results from interactions between the pipe surface and fluids traveling along the surface. Fluid-structure interactions have a profound influence on the erosion that takes place. The location, rate and extent of thinning or loss of a protective surface film depend strongly on the nature of the flow regime and interactions. Erosion-corrosion involves the modification, thinning and removal of protective films composed of corrosion product or scale deposits from a susceptible metal surface by fluid shear stress under high turbulence conditions. In the paper, multi-scale simulation of fluid-structure interactions between the flow and the protective films on the pipe surface is presented. The fluid shear stress and pressure of the flow in a pipe with a step is obtained by macro-fluid dynamic analysis. Viscous forces and the system’s pressure impose forces to the surface of the pipe. Using micro-simulation method, the fluid-structure interactions between the flow and the protective films is modeled. The deformation of the protective films is shown and changed with the different velocity and flow regime. Using the multi-scale simulation of fluid-structure interactions, the location, rate and extent of the erosion on the pipe surface can be predicted. The results are proved by the actual instances.Copyright

Microscale Numerical Simulation on Dynamic Damage for the Deflagrated Pressure Vessels

The defects on the surface of the deflagrated pressure vessels leading to damage are usually in the form of pits, scratches or machine marks. A microscale numerical simulation method is presented for the dynamic damage process under the instantaneous impacted shock. The surface defects are described as the rectangle gap, the round gap and the groove. For fcc and other close-packed metals material, the embedded atom method (EAM), which has proven particularly good at modeling bulk and defect properties of metals and metal alloys, is used to describe the interactions among the metal atoms. The Molecular Dynamics (MD) code named LAMMPS is used to calculate the velocity of atoms and the pressure distribution in dynamic damage process. The results show the different damage effects of the metal material with different surface defects under the instantaneous impacted shock by the deflagration.Copyright