Corrosion leakages often occur in the air cooler of a hydrocracking unit,with the failure sites mainly located in the entrance area of the tubes.An analysis of the macroscopic morphology and corrosion products confirm...Corrosion leakages often occur in the air cooler of a hydrocracking unit,with the failure sites mainly located in the entrance area of the tubes.An analysis of the macroscopic morphology and corrosion products confirmed that the damage was caused by erosion-corrosion(E-C).Numerical and experimental methods were applied to investigate the E-C mechanism in the air cooler.Computational fluid dynamics(CFD)was used to calculate the hydrodynamic parameters of the air cooler.The results showed that there was a biased flow in the air cooler,which led to a significant increase in velocity,turbulent kinetic energy and wall shear within 0.2 m of the tube entrance.A visualization experiment was then performed to determine the principles of migration and transformation of multiphase flow in the air cooler tubes.Various flow patterns(pure droplet flow,mist flow,and annular flow)and their evolutionary processes were clearly depicted experimentally.The initiation mechanism and processes leading to the development of E-C in the air cooler were also determined.This study provided a comprehensive explanation for the E-C failures that occur in air coolers during operation.展开更多
The ammonium salt corrosion is a typical failure mode for the hydrogenation reaction effluent air cooler(REAC) system. In order to investigate the corrosion characteristics in the REAC system, numerical simulations we...The ammonium salt corrosion is a typical failure mode for the hydrogenation reaction effluent air cooler(REAC) system. In order to investigate the corrosion characteristics in the REAC system, numerical simulations were performed by using the mixture model, the heating transfer model, and the particles tracking model. The results show that the differences between the temperature and the velocity at each cross section of the first-row and second-row tubes are small. The inertia of the particles plays an important role in the particle’s deposition, and the smaller particles distribute more uniformly in the air cooler. However, for larger particles, they prefer falling from the inner side of the vertical elbow, and preferentially depositing at the inlet header and pipes before saturation. In the heat exchanger tubes, the particle deposition number is larger in the second-row tubes than that in the first-row tubes, and the high-risk tubes mainly concentrate on the middle and right side of the air cooler. The kinetic parameters of the particles are in accordance with the blocking-prone position in many real operating conditions.展开更多
Corrosion leakage occurred in the 14th tube bundle in the first row of a residual oil hydrotreating air cooler after operating for two years.The failure location was 0.5 m from the outlet header box.In this paper,the ...Corrosion leakage occurred in the 14th tube bundle in the first row of a residual oil hydrotreating air cooler after operating for two years.The failure location was 0.5 m from the outlet header box.In this paper,the erosion corrosion of the air cooler tube bundle was investigated by experimental and numerical methods.Visual inspection,scanning electron microscopy(SEM),and X-ray diffraction(XRD)experiments were performed,and the failure morphology and material composition confirmed that the damage was caused by erosion corrosion.The shear stress transport k–ωturbulence model(SST-k–ω)was then used to investigate the flow and erosion corrosion characteristics,combined with mass transfer,corrosion rate,and ionization equilibrium models.The numerical simulation results revealed that the water phase volume fraction increased with flow and heat transfer in the fluid,which increased the mass flow rate and concentration of hydrogen sulfide.The mass transfer coefficient and corrosion rate were proposed as important parameters to characterize erosion corrosion.Moreover,the local concentration of wall shear stress was found to increase the risk of erosion corrosion.The predicted high-risk area was consistent with the actual failure area,which verified that this failure incident was attributable to erosion corrosion by the water phase.展开更多
The air cooler is an important equipment in the petroleum refining industry.Ammonium chloride(NH4 Cl)deposition-induced corrosion is one of its main failure forms.In this study,the ammonium salt crystallization temper...The air cooler is an important equipment in the petroleum refining industry.Ammonium chloride(NH4 Cl)deposition-induced corrosion is one of its main failure forms.In this study,the ammonium salt crystallization temperature is chosen as the key decision variable of NH4 Cl deposition-induced corrosion through in-depth mechanism research and experimental analysis.The functional link neural network(FLNN)is adopted as the basic algorithm for modeling because of its advantages in dealing with non-linear problems and its fast-computational ability.A hybrid FLNN attached to a small norm is built to improve the generalization performance of the model.Then,the trained model is used to predict the NH4 Cl salt crystallization temperature in the air cooler of a sour water stripper plant.Experimental results show the proposed improved FLNN algorithm can achieve better generalization performance than the PLS,the back propagation neural network,and the conventional FLNN models.展开更多
An experiment was carried out to investigate the relation of the maximum velocity of air passing through narrowest passage, mass flux of spray water in one square meter in one hour and the pressure drop of tube bundle...An experiment was carried out to investigate the relation of the maximum velocity of air passing through narrowest passage, mass flux of spray water in one square meter in one hour and the pressure drop of tube bundles. Twelve equations were obtained for the relation. The results show that the pressure drop of the tube bundles increases with increase of the maximum velocity of air and the mass flux of spray water. Comparing the pressure drop of the bare tube bundles with that of the film-enhanced tube bundles, it is found that the pressure drop of the film-enhanced tube bundles is lower about 11% and the surface roughness of the film-enhanced plates is a main factor that influences the pressure drop. The data and method obtained in the paper can be used to compute the pressure drop of the film-enhanced tube bundles and is helpful for selection of fan.展开更多
基金supported by the National Key R&D Program of China(2021YFB3301100)Beijing University of Chemical Technology Interdisciplinary Program(XK2023-07).
文摘Corrosion leakages often occur in the air cooler of a hydrocracking unit,with the failure sites mainly located in the entrance area of the tubes.An analysis of the macroscopic morphology and corrosion products confirmed that the damage was caused by erosion-corrosion(E-C).Numerical and experimental methods were applied to investigate the E-C mechanism in the air cooler.Computational fluid dynamics(CFD)was used to calculate the hydrodynamic parameters of the air cooler.The results showed that there was a biased flow in the air cooler,which led to a significant increase in velocity,turbulent kinetic energy and wall shear within 0.2 m of the tube entrance.A visualization experiment was then performed to determine the principles of migration and transformation of multiphase flow in the air cooler tubes.Various flow patterns(pure droplet flow,mist flow,and annular flow)and their evolutionary processes were clearly depicted experimentally.The initiation mechanism and processes leading to the development of E-C in the air cooler were also determined.This study provided a comprehensive explanation for the E-C failures that occur in air coolers during operation.
基金supported by the National Key R&D Program of China(Grant No.2017YFF0210403)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LY17E060008)the Talent Project of Zhejiang Association for Science and Development Project of SINOPEC(No.318023-2)
文摘The ammonium salt corrosion is a typical failure mode for the hydrogenation reaction effluent air cooler(REAC) system. In order to investigate the corrosion characteristics in the REAC system, numerical simulations were performed by using the mixture model, the heating transfer model, and the particles tracking model. The results show that the differences between the temperature and the velocity at each cross section of the first-row and second-row tubes are small. The inertia of the particles plays an important role in the particle’s deposition, and the smaller particles distribute more uniformly in the air cooler. However, for larger particles, they prefer falling from the inner side of the vertical elbow, and preferentially depositing at the inlet header and pipes before saturation. In the heat exchanger tubes, the particle deposition number is larger in the second-row tubes than that in the first-row tubes, and the high-risk tubes mainly concentrate on the middle and right side of the air cooler. The kinetic parameters of the particles are in accordance with the blocking-prone position in many real operating conditions.
基金supported by the National Natural Science Foundation of China(Grant Nos.51876194,U1909216,and 52176048)the Fundamental Research Funds of Zhejiang Sci-Tech University(Grant No.2021Q020).
文摘Corrosion leakage occurred in the 14th tube bundle in the first row of a residual oil hydrotreating air cooler after operating for two years.The failure location was 0.5 m from the outlet header box.In this paper,the erosion corrosion of the air cooler tube bundle was investigated by experimental and numerical methods.Visual inspection,scanning electron microscopy(SEM),and X-ray diffraction(XRD)experiments were performed,and the failure morphology and material composition confirmed that the damage was caused by erosion corrosion.The shear stress transport k–ωturbulence model(SST-k–ω)was then used to investigate the flow and erosion corrosion characteristics,combined with mass transfer,corrosion rate,and ionization equilibrium models.The numerical simulation results revealed that the water phase volume fraction increased with flow and heat transfer in the fluid,which increased the mass flow rate and concentration of hydrogen sulfide.The mass transfer coefficient and corrosion rate were proposed as important parameters to characterize erosion corrosion.Moreover,the local concentration of wall shear stress was found to increase the risk of erosion corrosion.The predicted high-risk area was consistent with the actual failure area,which verified that this failure incident was attributable to erosion corrosion by the water phase.
基金supported by the National Natural Science Foundation of China(Grant No.51876194,U1909216)the China Petrochemical Corporation Research Project(318023-2)the Zhejiang Public Welfare Technology Research Project(LGG20F030007)。
文摘The air cooler is an important equipment in the petroleum refining industry.Ammonium chloride(NH4 Cl)deposition-induced corrosion is one of its main failure forms.In this study,the ammonium salt crystallization temperature is chosen as the key decision variable of NH4 Cl deposition-induced corrosion through in-depth mechanism research and experimental analysis.The functional link neural network(FLNN)is adopted as the basic algorithm for modeling because of its advantages in dealing with non-linear problems and its fast-computational ability.A hybrid FLNN attached to a small norm is built to improve the generalization performance of the model.Then,the trained model is used to predict the NH4 Cl salt crystallization temperature in the air cooler of a sour water stripper plant.Experimental results show the proposed improved FLNN algorithm can achieve better generalization performance than the PLS,the back propagation neural network,and the conventional FLNN models.
基金Acknowledgement： The study is supported by the National Nature Science Foundation. Patent code is 200620098211.4.
文摘An experiment was carried out to investigate the relation of the maximum velocity of air passing through narrowest passage, mass flux of spray water in one square meter in one hour and the pressure drop of tube bundles. Twelve equations were obtained for the relation. The results show that the pressure drop of the tube bundles increases with increase of the maximum velocity of air and the mass flux of spray water. Comparing the pressure drop of the bare tube bundles with that of the film-enhanced tube bundles, it is found that the pressure drop of the film-enhanced tube bundles is lower about 11% and the surface roughness of the film-enhanced plates is a main factor that influences the pressure drop. The data and method obtained in the paper can be used to compute the pressure drop of the film-enhanced tube bundles and is helpful for selection of fan.
