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Faïçal Larachi - One of the best experts on this subject based on the ideXlab platform.

  • prospect of open cell solid foams for Floating platform multiphase reactor applications maldistribution susceptibility and hydrodynamic behavior
    Chemical Engineering Journal, 2018
    Co-Authors: Amir Motamed Dashliborun, Alexander Fussel, Faïçal Larachi
    Abstract:

    Abstract Open-cell solid foams are tested for the first time as prospective structured packings in Floating columns to evaluate their potential for offshore multiphase reactor applications. Using a hexapod ship motion simulator and low-intrusive wire-mesh sensors, the effect of Floating Vessel motions on the hydrodynamic behavior of SiSiC foam packed beds operated with concurrent descending gas-liquid flow was comprehensively investigated. The response of gas-liquid distribution, overall bed pressure drop, and liquid axial dispersion to column tilts as well as translational and rotational motions was acquired and compared to their corresponding stationary (onshore) analog configuration. Maldistribution sensitivity and susceptibility of solid-foam packed beds subject to ship tilts and accelerations were interpreted in terms of fluid uniformity factor. Moreover, a stimulus-response tracer pulse technique and a macro-mixing model were used to estimate the liquid mean residence time and Peclet number. Similar to random packings, fluid maldistribution was found to prevail in solid-foam beds with deviations from uniformity greater for rotational than for translational perturbations. Vessel tilts and oscillations adversely affect open-cell foam bed hydrodynamic performance yielding transient gas-liquid segregated flow regimes, oscillations of pressure drop and uniformity factor, as well as notable deviation from liquid plug flow.

Amir Motamed Dashliborun - One of the best experts on this subject based on the ideXlab platform.

  • 110th Anniversary: Marinization of Multiphase Reactors through the Prism of Chemical Engineers
    2019
    Co-Authors: Amir Motamed Dashliborun, Jian Zhang, Seyed Mohammad Taghavi, Faïçal Larachi
    Abstract:

    Offshore oil/gas industries have been employing multiphase scrubbers and reactors to treat hydrocarbons extracted from undersea reservoirs. Operation of Floating scrubbers and reactors on nonstationary platforms undergoes remarkable technical and operational challenges stemming from the complex sea states. Indeed, ship tilts and motions affect the reactor hydrodynamics and consequently its chemical performance. Therefore, imperatives for predicting and controlling the performance of offshore reactors by accounting for the contribution of marine swells have opened up considerable opportunities for research. This contribution presents an extensive chemical engineering overview on experimental and theoretical studies related to the effect of Floating Vessel motions on the performance of multiphase reactors and scrubbers. Cocurrent downflow, cocurrent upflow, and countercurrent gas–liquid packed beds, spinning gas–liquid packed beds, gas–solid fluidized bed, and bubble columns are reviewed with an emphasis on their hydrodynamic, mass and heat transfer, mixing behaviors, and their impact on catalytic and noncatalytic reactions for the marine applications

  • prospect of open cell solid foams for Floating platform multiphase reactor applications maldistribution susceptibility and hydrodynamic behavior
    Chemical Engineering Journal, 2018
    Co-Authors: Amir Motamed Dashliborun, Alexander Fussel, Faïçal Larachi
    Abstract:

    Abstract Open-cell solid foams are tested for the first time as prospective structured packings in Floating columns to evaluate their potential for offshore multiphase reactor applications. Using a hexapod ship motion simulator and low-intrusive wire-mesh sensors, the effect of Floating Vessel motions on the hydrodynamic behavior of SiSiC foam packed beds operated with concurrent descending gas-liquid flow was comprehensively investigated. The response of gas-liquid distribution, overall bed pressure drop, and liquid axial dispersion to column tilts as well as translational and rotational motions was acquired and compared to their corresponding stationary (onshore) analog configuration. Maldistribution sensitivity and susceptibility of solid-foam packed beds subject to ship tilts and accelerations were interpreted in terms of fluid uniformity factor. Moreover, a stimulus-response tracer pulse technique and a macro-mixing model were used to estimate the liquid mean residence time and Peclet number. Similar to random packings, fluid maldistribution was found to prevail in solid-foam beds with deviations from uniformity greater for rotational than for translational perturbations. Vessel tilts and oscillations adversely affect open-cell foam bed hydrodynamic performance yielding transient gas-liquid segregated flow regimes, oscillations of pressure drop and uniformity factor, as well as notable deviation from liquid plug flow.

Wittingen Martijn - One of the best experts on this subject based on the ideXlab platform.

  • Offshore Wind Turbine Monopile Foundation Installation with a Dynamic Positioned Vessel: A feasibility study by modeling
    2018
    Co-Authors: Wittingen Martijn
    Abstract:

    After years of using fossil fuel, the transition to renewable energy sources need to be made to limit the increase in temperature and to support the future energy demand. To support and speed up the transition phase from fossil fuels to renewables it is necessary to decrease the costs. Offshore Wind Turbines are widely used for the production of renewable energy and several Offshore Wind Turbine projects are planned for the future. Most of the Offshore Wind Turbines are founded by monopile, large steel tube, to support the wind turbine. Nowadays, these monopile be installed by either jack-up Vessel or moored Floating Vessel. However, these installation method come with a major drawback: the installation procedure is time consuming. A new installation method is propose to reduce the installation time. This thesis focus of the feasibility to install the monopile with a dynamically positioned (DP) Vessel. Therequired station keeping situation is faster achieved with a DP Vessel. Due to the footprint of the DP Vessel relative to an earth fixed position, a Vessel motion compensated pile gripper is used to maintain the upright position of the monopile and to decrease the interaction forces between Vessel and monopile. Adding the monopile to the Vessel is an off-design condition for the DP controller. During the early hammering phase of the monopile, the monopile have limited interaction with the soil and is unstable. The upright position is maintain by the gripper frame. The forces from the gripper frame on the monopile are reaction forces on the Vessel. Beside these forces, environmental forces are acting on the monopile and via the gripper frame acting on the Vessel. The forces on the Vessel could lead to unstable behavior and/or increased Vessel footprint. A simulation model is build to investigate the behavior of the DP Vessel during the operation. A industry used DP simulator and a simulation model of the Bokalift1 is used. A model of a typical shallow water and deep water monopile is build. A hydraulic based gripper frame is simulated with an inclination controller and a induced Vessel motion controller which needto maintain the upright position of the monopile. The inclination controller is tuned with a higher bandwidth compare to the bandwidth of the DP controller to prevent motions of the monopile is the same frequency range as the linear motions of the Vessel. The forces from the gripper frame are fed into the Kalman filter of the DP controller. This is done to prevent a drift of the Vessel when the gripper frame starts acting on the Vessel. In all simulation cases with governing environmental conditions, the Vessel could maintain stable behavior. The rotations of the monopile are in the same frequency as the first order wave forces on the Vessel. This relative high frequency motions to not significantly amplify the position of the DP Vessel. However, despite the fact of feeding the Kalman filter, a larger drift is observed in case of the large, deep water monopile in the operation stage when the gripper frame force is introduced to the Vessel. This increase the requirement on the envelope of the gripper frame. The requirement on the gripper frame is given in terms of power, force and envelope based on governing environmental conditions. The requirements on the gripper frame are assumed to be within an acceptable magnitude. The operation seams to be promising in the future.Ship Design, Production and Operation

  • Offshore Wind Turbine Monopile Foundation Installation with a Dynamic Positioned Vessel: A feasibility study by modeling
    2018
    Co-Authors: Wittingen Martijn
    Abstract:

    After years of using fossil fuel, the transition to renewable energy sources need to be made to limit the increase in temperature and to support the future energy demand. To support and speed up the transition phase from fossil fuels to renewables it is necessary to decrease the costs. Offshore Wind Turbines are widely used for the production of renewable energy and several Offshore Wind Turbine projects are planned for the future. Most of the Offshore Wind Turbines are founded by monopile, large steel tube, to support the wind turbine. Nowadays, these monopile be installed by either jack-up Vessel or moored Floating Vessel. However, these installation method come with a major drawback: the installation procedure is time consuming. A new installation method is propose to reduce the installation time. This thesis focus of the feasibility to install the monopile with a dynamically positioned (DP) Vessel. Therequired station keeping situation is faster achieved with a DP Vessel. Due to the footprint of the DP Vessel relative to an earth fixed position, a Vessel motion compensated pile gripper is used to maintain the upright position of the monopile and to decrease the interaction forces between Vessel and monopile. Adding the monopile to the Vessel is an off-design condition for the DP controller. During the early hammering phase of the monopile, the monopile have limited interaction with the soil and is unstable. The upright position is maintain by the gripper frame. The forces from the gripper frame on the monopile are reaction forces on the Vessel. Beside these forces, environmental forces are acting on the monopile and via the gripper frame acting on the Vessel. The forces on the Vessel could lead to unstable behavior and/or increased Vessel footprint. A simulation model is build to investigate the behavior of the DP Vessel during the operation. A industry used DP simulator and a simulation model of the Bokalift1 is used. A model of a typical shallow water and deep water monopile is build. A hydraulic based gripper frame is simulated with an inclination controller and a induced Vessel motion controller which needto maintain the upright position of the monopile. The inclination controller is tuned with a higher bandwidth compare to the bandwidth of the DP controller to prevent motions of the monopile is the same frequency range as the linear motions of the Vessel. The forces from the gripper frame are fed into the Kalman filter of the DP controller. This is done to prevent a drift of the Vessel when the gripper frame starts acting on the Vessel. In all simulation cases with governing environmental conditions, the Vessel could maintain stable behavior. The rotations of the monopile are in the same frequency as the first order wave forces on the Vessel. This relative high frequency motions to not significantly amplify the position of the DP Vessel. However, despite the fact of feeding the Kalman filter, a larger drift is observed in case of the large, deep water monopile in the operation stage when the gripper frame force is introduced to the Vessel. This increase the requirement on the envelope of the gripper frame. The requirement on the gripper frame is given in terms of power, force and envelope based on governing environmental conditions. The requirements on the gripper frame are assumed to be within an acceptable magnitude. The operation seams to be promising in the future.Marine Technology | Ship Design, Production and Operation

Unegbu Ihuaku - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of Ballast Failures during operations of Semi-submersible rigs
    University of Stavanger Norway, 2017
    Co-Authors: Unegbu Ihuaku
    Abstract:

    Offshore drilling is an operation performed to explore for and extract hydrocarbon beneath the seabed. The drilling operation is a very sensitive and extremely risky task and can be carried out from a Floating Vessel, semi-submersible and so on. Because of the high risk involved in drilling operations, the structural integrity and stability of the platform on which the drilling operation is performed are of uttermost importance to the success of the operation. In recent times, drilling operations are performed on mobile platforms most especially on semi-submersibles, thus the stability of this platform as well as the risk involved are worth given careful considerations and evaluations. In the past couple of years, the PSA has focused on hazards relating to Floating installations and thus requested that more attention should be made by the industry on hazards relating to buoyancy loss and stability. Ballast systems play a very vital role to ensure Vessel stability. The main function of the ballast system is to maintain stability and sufficient draft, and also to retain the sheer forces and bending moments within required limits. The ballast system comprises ballast tanks, different network of pipes, pumps and valve, hydraulic power system, electric power system and ballast control system. Failure to properly ballast may lead to accidents which could lead to loss of Vessel, death of personnel and environmental disasters as in the case of Ocean Ranger accident in 1982, and Petrobras P-34 FPSO in 2002 (Sobena, 2007). This thesis is aimed at evaluating the risks involved in ballast operations, by identifying the various failure modes of semi-submersible ballast systems and we will consider possible barriers and consequences due to the ballast system failure during drilling operation. The thesis focuses primarily on the failure mode effect and criticality analysis (FMECA) of the main components of the semi-submersible’s ballast system by determining the failure causes and failure modes that could influence each components performance, and thus identifying the most critical component(s). Also the Structured What-If Technique (SWIFT) is used to compensate for hazard identification for the unidentified hazards (i.e., human errors), in the FMECA. By studying the most critical system components, a qualitative risk analysis is conducted to model accidental sequences by using the fault tree method to establish the chain of failure events. In addition to this, a stability analysis of a typical semi-submersible based on ballast system is performed to assess the criticality of different ballast failure conditions such as damage condition, and ballast failure under different environmental conditions such as under harsh environment, polar low occurrence. In achieving these objectives, both qualitative risk analysis and evaluation methods are adopted

  • Evaluation of Ballast Failures during operations of Semi-submersible rigs
    University of Stavanger Norway, 2017
    Co-Authors: Unegbu Ihuaku
    Abstract:

    Master's thesis in Risk managementOffshore drilling is an operation performed to explore for and extract hydrocarbon beneath the seabed. The drilling operation is a very sensitive and extremely risky task and can be carried out from a Floating Vessel, semi-submersible and so on. Because of the high risk involved in drilling operations, the structural integrity and stability of the platform on which the drilling operation is performed are of uttermost importance to the success of the operation. In recent times, drilling operations are performed on mobile platforms most especially on semi-submersibles, thus the stability of this platform as well as the risk involved are worth given careful considerations and evaluations. In the past couple of years, the PSA has focused on hazards relating to Floating installations and thus requested that more attention should be made by the industry on hazards relating to buoyancy loss and stability. Ballast systems play a very vital role to ensure Vessel stability. The main function of the ballast system is to maintain stability and sufficient draft, and also to retain the sheer forces and bending moments within required limits. The ballast system comprises ballast tanks, different network of pipes, pumps and valve, hydraulic power system, electric power system and ballast control system. Failure to properly ballast may lead to accidents which could lead to loss of Vessel, death of personnel and environmental disasters as in the case of Ocean Ranger accident in 1982, and Petrobras P-34 FPSO in 2002 (Sobena, 2007). This thesis is aimed at evaluating the risks involved in ballast operations, by identifying the various failure modes of semi-submersible ballast systems and we will consider possible barriers and consequences due to the ballast system failure during drilling operation. The thesis focuses primarily on the failure mode effect and criticality analysis (FMECA) of the main components of the semi-submersible’s ballast system by determining the failure causes and failure modes that could influence each components performance, and thus identifying the most critical component(s). Also the Structured What-If Technique (SWIFT) is used to compensate for hazard identification for the unidentified hazards (i.e., human errors), in the FMECA. By studying the most critical system components, a qualitative risk analysis is conducted to model accidental sequences by using the fault tree method to establish the chain of failure events. In addition to this, a stability analysis of a typical semi-submersible based on ballast system is performed to assess the criticality of different ballast failure conditions such as damage condition, and ballast failure under different environmental conditions such as under harsh environment, polar low occurrence. In achieving these objectives, both qualitative risk analysis and evaluation methods are adopted

Adebayo Addayo - One of the best experts on this subject based on the ideXlab platform.

  • Steel catenary risers supported by subsurface buoy
    University of Stavanger Norway, 2011
    Co-Authors: Adebayo Addayo
    Abstract:

    Master's thesis in Offshore technologyOil and gas exploration and production activities in deep and ultra deep waters in hostile environments necessitates the need to develop innovative riser systems capable of ensuring transfer of fluids from the seabed to a Floating Vessel and vice versa, with little or no issues with respect to influences of environmental loads and Vessel motions. Over the years, studies have shown that the conventional flexible riser and steel catenary riser configurations cannot function effectively under such environmental and Vessel motion influences as a result of issues such as collapse (predominant in flexible risers when used in deep waters), and fatigue (predominant in steel catenary risers). Nevertheless, a riser system known as the hybrid riser which is a combination of a vertical rigid riser and a flexible riser has been used effectively under these seeming adverse conditions and has been found effective. However, it is regarded as an expensive option considering the cost of its components, in addition to its limitation in terms of step-out distance between the Floating Vessel and a subsea well. The limitations of the aforementioned riser systems are conveniently accommodated by a riser system presently undergoing development. It is known as “steel catenary risers supported by subsurface buoy”. This riser solution combines the best properties of flexible risers (ability to uncouple a system from Vessel motions) and steel catenary risers (usability in deep waters). In addition to this, it offers flexibility in terms of achievable step-out distance between a floater and a subsea well. This riser system is the thrust of this thesis. This write-up begins with a review of the previously mentioned riser solutions, pros and cons related to their usage in harsh deep water environments, and some essential design code requirements to be fulfilled in a riser design activity. This is followed by design analysis of the thesis example riser system. In-depth analysis is done with two different buoy types (rectangular buoy and H-shaped buoy) by conducting sensitivity studies to understand the contribution of factors such as the buoy size and submerged weight, flowline content density, riser anchor length, and so on, to the performance of the riser system in a typical North Sea environment. Observation was made that whilst both buoy shapes result in good flexible risers and steel catenary risers strength performance, the H-shaped buoy had line clashing issues when subjected to cross flow environmental loads. This was however eradicated through the use of another buoy shape referred to as the modified H-buoy. The rectangular and H-shaped buoys were further studied for possibility of resonance with peak waves obtainable in the North Sea environment and were found to have satisfactory sway and heave periods. In addition, a brief fatigue assessment was carried out with the rectangular buoy to show that the riser system helps in alleviating fatigue issues prominent in conventional steel catenary risers. The study concludes by showing that while both the conventional buoy and the H-shaped buoy offer appreciable strength performance and stability to the riser system, the latter has better stability in comparison with the former while the former offers better strength performance to the steel catenary risers. Keywords: Steel Catenary Riser, Rectangular buoy, H-shaped buoy

  • Steel catenary risers supported by subsurface buoy
    University of Stavanger Norway, 2011
    Co-Authors: Adebayo Addayo
    Abstract:

    Oil and gas exploration and production activities in deep and ultra deep waters in hostile environments necessitates the need to develop innovative riser systems capable of ensuring transfer of fluids from the seabed to a Floating Vessel and vice versa, with little or no issues with respect to influences of environmental loads and Vessel motions. Over the years, studies have shown that the conventional flexible riser and steel catenary riser configurations cannot function effectively under such environmental and Vessel motion influences as a result of issues such as collapse (predominant in flexible risers when used in deep waters), and fatigue (predominant in steel catenary risers). Nevertheless, a riser system known as the hybrid riser which is a combination of a vertical rigid riser and a flexible riser has been used effectively under these seeming adverse conditions and has been found effective. However, it is regarded as an expensive option considering the cost of its components, in addition to its limitation in terms of step-out distance between the Floating Vessel and a subsea well. The limitations of the aforementioned riser systems are conveniently accommodated by a riser system presently undergoing development. It is known as “steel catenary risers supported by subsurface buoy”. This riser solution combines the best properties of flexible risers (ability to uncouple a system from Vessel motions) and steel catenary risers (usability in deep waters). In addition to this, it offers flexibility in terms of achievable step-out distance between a floater and a subsea well. This riser system is the thrust of this thesis. This write-up begins with a review of the previously mentioned riser solutions, pros and cons related to their usage in harsh deep water environments, and some essential design code requirements to be fulfilled in a riser design activity. This is followed by design analysis of the thesis example riser system. In-depth analysis is done with two different buoy types (rectangular buoy and H-shaped buoy) by conducting sensitivity studies to understand the contribution of factors such as the buoy size and submerged weight, flowline content density, riser anchor length, and so on, to the performance of the riser system in a typical North Sea environment. Observation was made that whilst both buoy shapes result in good flexible risers and steel catenary risers strength performance, the H-shaped buoy had line clashing issues when subjected to cross flow environmental loads. This was however eradicated through the use of another buoy shape referred to as the modified H-buoy. The rectangular and H-shaped buoys were further studied for possibility of resonance with peak waves obtainable in the North Sea environment and were found to have satisfactory sway and heave periods. In addition, a brief fatigue assessment was carried out with the rectangular buoy to show that the riser system helps in alleviating fatigue issues prominent in conventional steel catenary risers. The study concludes by showing that while both the conventional buoy and the H-shaped buoy offer appreciable strength performance and stability to the riser system, the latter has better stability in comparison with the former while the former offers better strength performance to the steel catenary risers. Keywords: Steel Catenary Riser, Rectangular buoy, H-shaped buoy