Offshore Gas Turbine Research Articles

Modelling and analysis of offshore energy hubs

Clean offshore energy hubs may become pivotal for efficient offshore wind power generation and distribution. In addition, offshore energy hubs may provide decarbonised energy supply for maritime transport, oil and gas recovery, and offshore farming, while also enabling conversion and storage of liquefied decarbonised energy carriers for export. In this paper, the role of offshore energy hubs is investigated in the transition of an offshore energy system towards zero-emission energy supply. A mixed-integer linear programming model is developed for investment planning and operational optimisation to achieve decarbonisation at minimum cost. We consider offshore wind, solar, energy hubs and subsea cables. A sensitivity analysis is conducted on CO2 tax, CO2 budget and the capacity of power from shore. The results show that: (a) a hard carbon cap is necessary for stimulating a zero-emission offshore energy system, (b) offshore wind integration and power from shore can more than halve current emissions, but offshore energy hubs with storage may be necessary for zero-emission production, and (c) at certain CO2 tax levels, the system with offshore energy hubs can potentially reduce CO2 emissions by 49% and energy losses by 10%, compared to a system with only offshore renewables, gas turbines and power from shore.

(Digital Presentation) Offshore Gas Turbines

Offshore gas turbines are the main power drivers for offshore production facilities; they are used for gas lifting, pumping, power generation and compression due to their high power to weight ratio and size. It is therefore imperative to minimize their downtime to prevent production losses. The need to examine the how deposits formed on the blade surface limits the life and performance of the engine cannot be overemphasized.In this study the Rolls Royce RB211, an aero derivative engine commonly used offshore was selected and its performance data obtained from PYTHIA engine simulation and diagnostic software. These values were used to calculate the rate of mass deposition of potassium sulphate (K2SO4), a potential corrosive salt.In order to determine rate of mass deposition, contaminant levels for a clean gas and good filter were obtained from General Electric’s fuel specification while a higher contaminant level was assumed.It was found that at high temperature corrosive salt tend to deposits on the blade surface when concentration of contaminants was calculated for both low and high impurity levels. It was also observed that the rate of mass deposition was high at the first stage of the turbine section where high gas temperature and pressure is usually experienced and drops as hot gas travel along the turbine and leaves as exhaust gas at very low temperature and pressure.In order to minimize the risk of damage to turbine hot section components like nozzle guide vanes and blades, fuel purity specifications and an appropriate inlet air filtration system must be used. This keeps contaminants in the combusted gas below allowable contaminant levels as recommended by original equipment manufacturers.

Utilizing the evidential reasoning approach to determine a suitable wireless sensor network orientation for asset integrity monitoring of an offshore gas turbine driven generator

This research proposes the most ideal Wireless Sensor Network (WSN) topology for remote integrity monitoring of an offshore gas turbine driven generator. The intention is to design the structure of a number of WSNs within the electrical generation system with varying connection types and methods of relaying data. The research is concerned only with the design of the WSNs, i.e. the hardware and orientation of the sensor nodes and not the software, programming or data protection. This will potentially provide a good base, once an ideal WSN design is determined, to expand the network further incorporating more criteria and develop the necessary software to complete the WSN. The work applies the Evidential Reasoning approach to a number of WSN topologies in order to determine the most suitable based upon an outlined set of performance criteria. Axiom based validation of the methodology is also provided within the analysis.

Modelling and Analysis of Offshore Energy Hubs

Clean, multi-carrier Offshore Energy Hubs (OEHs) may become pivotal for efficient offshore wind power generation and distribution. In addition, OEHs may provide decarbonised energy supply for maritime transport, oil and gas recovery, and offshore farming while also enabling conversion and temporary storage of liquefied decarbonised energy carriers for export. Here, we investigate the role of OEHs in the transition of the Norwegian continental shelf energy system towards zero-emission energy supply. We develop a mixed-integer linear programming model for investment planning and operational optimisation to achieve decarbonisation at minimum costs. We consider clean technologies, including offshore wind, offshore solar, OEHs and subsea cables. We conduct sensitivity analysis on CO$_2$ tax, CO$_2$ budget and the capacity of power from shore. The results show that (a) a hard carbon cap is necessary for stimulating a zero-emission offshore energy system; (b) offshore wind integration and power from shore can more than halve current emissions, but OEHs with storage are necessary for zero-emission production and (c) at certain CO$_2$ tax levels, the system with OEHs can potentially reduce CO$_2$ emissions by 50% and energy losses by 10%, compared to a system with only offshore renewables, gas turbines and power from shore.

Advanced methodology for screening of novel adsorption materials for cost-efficient CO2 capture

Adsorption is a promising technology to develop cost-effective carbon capture solutions for the energy and industrial sectors. The PrISMa project aims to develop a technology platform to allow translating specific carbon abatement requirements for CO2 source-sink combinations into key performance indicators (KPIs) that will further translate into property targets for the design of novel materials. This is possible by using materials such as metal organic frameworks (MOFs) which can be tailor-made according to the requirements of the separation process. This work presents the progress on the development of one of the main building blocks for the PrISMa technology platform: a computer-based techno-economic screening tool for the screening of novel adsorption materials. The developed screening tool provides the user with a suite of fit-for-purpose models of adsorption processes that allow to co-optimize the material and process domains. The techno-economic screening tool utilizes the effective carbon price (ECP) as the ultimate metric for the identification of the most promising adsorbent materials, either readily existing, or still to be synthesized. This work presents a preliminary screening of novel adsorption materials for cost-effective CO2 capture for two different applications – a waste to energy plant and an offshore gas turbine combined cycle.

Improvement design and analysis of a supercritical CO2/transcritical CO2 combined cycle for offshore gas turbine waste heat recovery

The supercritical CO2 (S–CO2) and transcritical CO2 (T-CO2) combined cycle is considered a promising technology for offshore gas turbine waste heat recovery. To further improve the thermodynamic and economic performances of the S–CO2/T-CO2 combined cycle for offshore gas turbine waste heat recovery, a new system layout is proposed in this paper. The net power output and net present value (NPV) are chosen as the objective functions of thermodynamic and economic performances, respectively. Compared to the basic systems presented by previous researchers, the new proposed S–CO2/T-CO2 combined cycle layout is modified in two aspects. One is that the residual heat of the topping S–CO2 cycle can be recovered by the bottoming T-CO2 cycle. The other is that a split flow branch is added in the bottoming T-CO2 cycle. The sensitivity analysis of different systems is carried out to explore the allowable ranges of independent parameters. Compared with the two basic layouts (Basic-I and Basic-II), the simulation results at the design point reveal that the proposed system has more than 10.53% increment on the net power output and 7.87% increment on the net present value (NPV). Besides, the multi-objective optimization results indicate the proposed system attains at least 8.30% increment on the optimized net power output and 3.79% increment on the optimized NPV at the same time. It is proved that the proposed system can be applied in some practical cases from the thermodynamic and economic views.

Thermo-economic analysis and multi-objective optimization of a novel waste heat recovery system with a transcritical CO2 cycle for offshore gas turbine application

In this paper, a novel power cycle for the cascade utilization of waste heat from an offshore gas turbine is presented. Carbon dioxide is selected as the single working fluid to further simplify the power conversion system. Mathematical models for the heat recovery system are developed to investigate the improvement in thermodynamic and economic performance. Moreover, a comprehensive parametric analysis is carried out and discussed to evaluate the effects of key cycle parameters on system performance. Further, a multi-objective optimization of the system based on Artificial Bee Colony algorithm is conducted to obtain the optimal operating parameters, considering net power output and levelized energy cost as objective functions simultaneously. The results show that the presented waste heat recovery system operating at the design point can increase the net power output by 30.1% compared with the gas turbine alone. The presented cycle demonstrates superior performance than the typical cycle layout with the improvement in net power output by 5.3% and the decrease in levelized energy cost by 1.2% at optimal condition. The findings so far revealed that the proposed CO2 power cycle has potential for waste heat recovery in the offshore platform application.

Evolving ANN-based sensors for a context-aware cyber physical system of an offshore gas turbine

An adaptive multi-tiered framework, that can be utilised for designing a context-aware cyber physical system to carry out smart data acquisition and processing, while minimising the amount of necessary human intervention is proposed and applied. The proposed framework is applied within the domain of offshore asset integrity assurance. The suggested approach segregates processing of the input stream into three distinct phases of Processing, Prediction and Anomaly detection. The Processing phase minimises the data volume and processing cost by analysing only inputs from easily obtainable sources using context identification techniques for finding anomalies in the acquired data. During the Prediction phase, future values of each of the gas turbine’s sensors are estimated using a linear regression model. The final step of the process— Anomaly Detection—classifies the significant discrepancies between the observed and predicted values to identify potential anomalies in the operation of the cyber physical system under monitoring and control. The evolving component of the framework is based on an Artificial Neural Network with error backpropagation. Adaptability is achieved through the combined use of machine learning and computational intelligence techniques. The proposed framework has the generality to be applied across a wide range of problem domains requiring processing, analysis and interpretation of data obtained from heterogeneous resources.

Performance evaluation of a twin-shaft gas turbine engine in mechanical drive service

This study aimed at quantifying the effect of mechanical load on the performance of an 18.7 MW offshore gas turbine engine. The targeted engine is of two-shaft free power turbine configuration that operates as a mechanical driver for a process compressor in the gas compression service. The study is a part of a comprehensive performance health monitoring program to address the diagnostic and prognostic requirements in oil and gas offshore platforms and is motivated by the need to provide in-depth knowledge of the gas turbine engine performance. In this work, only the context of some design point key performance parameters and a limited set of collected operational data from the gas turbine in the real plant are available. Therefore, three major tasks, namely design point calculation, characteristic map tuning and off-design performance adaption, were needed to be performed. In order to check the validity of the proposed model, the obtained simulation results were compared with the operational data. The results indicate the maximum inaccuracy of the proposed model is 3.04 %. Finally, by employing the developed model, the engine capability for power generation when exposed to various load speeds is investigated. The obtained result demonstrates at the maximum gas generator speed, every 3 % decrease in mechanical speed leads to 1 % decline in the gas turbine power output. Moreover, when the gas turbine operates under design power load and mechanical speed is lower than 80 % of design speed, every 1 % decrease in load speed results in 0.2 % loss in thermal efficiency. The established relationship will assist proper assessment of mechanical drive gas turbines for performance health monitoring.

Power and Thermal Efficiency Study of Offshore Gas Turbines under Various Ambient Temperatures

Gas turbines offer a reduced weight and compact solution for installation on offshore platforms and floating facilities. The purpose of this study is to examine the influence of various parameters on offshore gas turbines performance. Operating measurements of a 23MW gas turbine installed at an offshore oil and gas plant in east of Peninsular Malaysia was used for model verification and evaluation. The results showed that the gas turbine performance improvements involve the study of a wide range of different parameters including ambient temperature, compression ratio, fuel-air ratio and operating load. These achieved relations will help in appropriate assessment of offshore gas turbines thermal efficiency.

Selection of Power From Shore for an Offshore Oil and Gas Development

With a step-out distance of 161 km and a design power of 55 MW, Martin Linge offshore gas field will be the longest ac submarine cable power supplying an entire offshore oil and gas platform from the shore. This field development comprises a platform with a jack-up rig and a floating storage offloading unit. This paper discusses the criteria that have been considered to select a power-from-shore concept instead of an offshore gas turbine power plant, which is the current practice in the offshore oil and gas industry. Since in a first approach, for such a long step-out distance, the choice of power from shore would be to select a dc transmission line, this paper discusses the design and the main technical challenges of this long step-out ac transmission development. Finally, the system approach that is required for the development of the onshore and offshore parts of the project is described.

CO2 Capture from Off-shore Gas Turbines Using Supersonic Gas Separation

CO2 capture from gas turbine based off-shore application face challenges such as size (foot-print), weight and stability (wave motion) in addition to the challenges faced by on-shore industry. Space- and weight challenges are given priority, and the size of the capture installations will be of importance when selecting capture technology rather than process efficiency alone. In this work, CO2 capture from an FPSO turbine exhaust gas using a supersonic separator is investigated. To assess the operational performance of the capture process, a Laval nozzle (converging- diverging geometry) model is implemented and successfully integrated in a steady-state process flow sheet simulator. The model includes equilibrium thermodynamics describing freeze-out of dry ice from a gas mixture containing CO2. To determine under which conditions this process is thermodynamically and fluid dynamically feasible, different boundary conditions are explored. By integrating the supersonic separator unit in a flow sheet model, the interaction between the capture and the rest of the process is studied. The results indicate that supersonic expansion is a viable strategy for capturing CO2 from off-shore gas turbines.

A MODEL-BASED MIXED DATA APPROACH FOR OPTIMIZING THE PERFORMANCE OF AN OFFSHORE GAS TURBINE COMPRESSOR

Gas turbines play prominent role in aviation, power generation, marine, mining, petrochemicals, onshore and offshore oil and gas industries. Environmental factors result to degradation mechanics of the overall performance of the engine. Industrialist therefore face unplanned equipment and manufacturing downtime which is undesirable because it leads to economic losses and costly repairs. While condition monitoring is used to obtain early warning of impending equipment failure, optimization techniques such as water washing (online and offline) are used to bring the engine/equipment back to lime-light. In this work, several schedule visits were made to a gas turbine plant on industrial duty for electricity generation in an offshore thermal station at Ibeno, near Eket, Akwa Ibom State in Nigeria. Continuous monitoring of the aerothermodynamics and vibration data were taken for a period of twelve months on hourly basis to examine the state of health of the engine due to adverse offshore environmental factors. The diagnostic approach of vibration analysis, trend and performance monitoring were used with a model-based mixed data approach for optimizing the performance of the offshore gas turbine plant.A software code-named VANCANAL written in C++ programming language was used to proactively monitor the gas turbine plant. The software displayed the operational (actual) values of all the parameters of the engine against their designed (reference) values. Once a set limit is exceeded, the software is capable of giving an alarm, signifying the need for maintenance.

Failure Investigation of a Gas Turbine Inlet Weatherhood

AbstractAnalytical and experimental methods have been used to investigate fatigue failures in the weatherhood protecting the air inlet to an offshore gas turbine power generation unit. A simple method for modelling transverse vibration of the leading edge is described, and the results are compared with experimental measurements made on a prototype installation. Calculation of the stresses induced at the critical locations, where cracking has been observed, suggests the failure should be attributed to aerodynamic excitation of the leading edge.

Separation of carbon dioxide from offshore gas turbine exhaust

Abstract The introduction of a CO 2 -tax in 1991, on offshore combustion of natural gas has led to an increased interest in both energy conservation and the possibility of separating CO 2 from gas turbine exhaust. In this paper a possible process will be presented. The result of the assessment is that an amine absorption process using membrane gas/liquid contactors in both the absorber and the desorber, in combination with a combined cycle power generation unit with 40% recycling of the exhaust gas and a CO 2 compression unit, is best suited for CO 2 removal among the options studied.

96/02173 Separation of carbon dioxide from offshore gas turbine exhaust

96/02173 Separation of carbon dioxide from offshore gas turbine exhaust

Separation of carbon dioxide from offshore gas turbine exhaust

The introduction of a CO 2-tax in 1991, on offshore combustion of natural gas has lead to an increased interest in both energy conservation and the possibility of separating CO 2 from gas turbine exhaust. In this paper a possible process will be presented. The result of the assessment is that an amine absorption process using MEA and a gas absorption membrane, in combination with a combined cycle power generation unit with 40% recycling of the exhaust gas and a CO 2 compression unit, is best suited for CO 2 removal among the options studied.

Industrial Type Gas Turbines for Offshore Applications

The paper discusses, with reference to the power generating gas turbines on the FRIGG TCP-2 platform, the specific and general requirements for offshore gas turbines, and how those sometimes conflicting requirements are met. Furthermore, interesting details of the particular installation on the FRIGG TCP-2 platform are described. The gas turbines on the FRIGG TCP-2 platform are the first ones to be installed in Norwegian water after the Norwegian regulations for “Production and auxiliary systems on production installations, etc.” were officially issued in April 1978. Some of these special regulations and their influence on the gas turbine design are discussed.