Industrial Systems and Environment Gas Turbine System - Example

Industrial Systems and Environment – Gas Turbine System Name: Professor: Institution: Date: Table of Contents Introduction 3 Background Information 3 Selection of the system 5 Characterization of the GT System 6 System Purpose 6 Environment 6 Sub-systems Purpose 6 Elements of the Sub-systems and their attributes 6 System Relationships 10 System Complexity 10 Dynamics of the system 10 Challenge identification 11 Challenge Description 11 Problem context 11 Stakeholders/Players 12 Selection of System Methodology 12 Application of System methodology 13 Stage 1: Problem Situation 13 Stage 2: Formulation of the conceptual models of the discharging cooling water 14 Stage 3: Comparing conceptual models with reality 14 Stage 4: Taking Action 14 Implementation Issues 15 Conclusions 15 Introduction Background Information A gas turbine (GT) or combustion turbine is an internal combustion engine that utilizes the burning of air-fuel mixture to produce mechanical energy. It is the mechanical energy produced by hot gases that s a turbine to produce power, hence, the term “gas turbines”. The types of fuels utilized in gas turbines include natural gas, synthetic fuels, and fuel oils. Generation of electricity using gas turbine is dated back to late 1930`s, but it was until the 1960`s that gas turbine started playing a significant role in generation of electricity (Langston & Opdyke, 1997). Penetration into the market has been steadily rising, although initially, the application of this technology was limited to low running hours, such as, emergency duty and peaking, due to high operation costs (Gareta, et al., 2004). Today, gas turbine engines have become one of the technologies that are widely used in generation of electricity after power output and thermal efficiency of the engine were improved. At present, GTs for generation of electricity account for over 50% of the world thermal electricity market share. GTs operating on combined cycles are gradually replacing steam power generator plants because they require a relatively low capital cost, reduced manufacturing lead time, and also, statutory environment regulations. The powering assembly which comprises of a compressor, a turbine and a combustor is considered as the main functioning unit of the gas turbine system. To help in governing system performance in a typical power generation system, the gas turbine is modelled into various supporting systems that are structurally or functionally related (MacIsaac & Langton, 2011). These supporting sub-systems include: a) Air inlet sub-system b) Gas fuel sub-system c) Liquid-fuel sub-system d) Fire protection sub-system e) Exhaust sub-system f) Lubrication sub-system g) Water cooling sub-system h) Atomizing air sub-system i) Powering unit sub-system j) Starting and sub-system k) NOx abatement sub-system l) Ventilation and enclosure sub-system m) Water wash sub-system n) Control sub-system All the above sub-systems are interrelated with varying degree of functional relationship, and either directly or indirectly contribute to the output of the entire system. This report details the analysis of the first eight of the sub-systems listed above; their application concepts and ideas, and how they contribute to characterization of gas turbine engine. Selection of the system In recent times, gas turbine technology has greatly advanced to become one of the most efficient and reliable devices for conversion of energy from fossil fuel to electricity. Their development has evolved to focus on smaller systems that are more powerful and efficient despite other technologies that address clean energy. The study of the gas turbine sub-systems enable improved development, performance and maintenance strategies for the power generation sector. The subsystems are developed based on the relationship of a number of factors that affect the performance of the gas turbine system. Gas turbines use fossil fuels, meaning that there is emission of greenhouse gases into the environment. This is the major environmental issue associated with gas turbine systems. Another common issue that causes alteration of the ecosystem is the intake and discharge of cooling water used in the cooling system of the gas turbine engine. One of the side effects of greenhouse gases is global warming, which brings with it rising sea levels, climatic change, and altered natural ecosystems. Research has shown that 80% of greenhouse emissions come from fossil fuels, which are the fuels used in the gas turbine power generators. Characterization of the GT System System Purpose The main purpose of GT system is to convert the chemical energy stored in a fuel into an energy form that is most desirable and of maximized use, depending on the type of application. In power plants, fuel energy is converted into mechanical energy that is then used to a power generator. The type of system application determines its most appropriate design. The energy produced is used to power trains, aircraft, electric generators, tanks, ships etc. Environment The environment comprises external factors, such as the atmosphere and gases, climate, water, soil and light. All this factors affect the biodiversity in different ecosystems. Operation of gas turbine has a larger effect on the atmosphere, and the ocean of air used by living organisms. Without doubt, gas turbines are quickly becoming important sources of power in the current and future years. For continued acceptance, there is need to control greenhouse gas emissions into the environment. Sub-systems Purpose There are various sub-systems that form the whole extremely sophisticated gas turbine device. All these sub-systems require precise modelling to ensure that they are structurally and functionally interrelated to operate with maximum efficiency and performance. All the sub-systems play a role that contributes to the outcome of the system. The purpose of these sub-systems is to govern the best matching system performance in power generation.41 Elements of the Sub-systems and their attributes Each sub-system comprises of elements that have different functions in the sub-system to ensure that the desired output of the sub-system is delivered as desired. Here, we will discuss the elements that form the first eight subsystems listed earlier on, and also their functions in the subsystem. a) Air inlet sub-system The air inlet sub-system comprises of the following elements: i. Air filter compartment – Ambient air entering through the air inlet is first passed through a filter before entering the compressor inlet plenum to remove solid particles, such as dust. ii. Compressor inlet plenum– The filtered air is compressed before it is pumped into the power unit iii. Compressor discharge - This element pumps air into the filter compartment with a reversed flow to intermittently clean the filter segment. iv. Chiller coil – The chiller coil is used to cool the air that enters the compressor inlet to reduce the air temperature. This helps to improve power augmentation of the system. v. Anti-icing module – Anti-icing features are also included in the system for all weather conditions. The module contains an inlet manifold that is controlled using a valve, and is used to filter the inlet compartment. It has a split thrash screen to protect it against thrashing and ingestion of ice. In addition, a pressure switch is fitted to indicate any alarming situation and trigger controlled switch off when the inlet pressure drop reaches a certain pre-determined value (Yadav, et al., 2012). b) Gas fuel system The gas fuel sub-system comprises the following elements: i. Valves – There are three valves; the speed ratio valve where the gas fuel enters before it passes to the gas fuel control valve via the gas stop valve. Each of the three valves is used to control gas flow through the system. ii. Fuel measuring device – The temperature and pressure of the gas fuel are measured as they flow through this device and the signals are transmitted to the actuators for the required corrective measures to be taken. iii. Gas intake – After the temperature and pressure of the fuel gas has been measured, it enters the intake manifold in the nozzle assembly, fitted on the outer casing of the combustion chamber (Lefebvre, 1998). c) Liquid-fuel sub-system This sub-system comprises of the following elements: i. Fuel conditioning unit: The conditioning unit is fueled by the liquid fuel to remove any contaminants that may be in the liquid fuel. ii. Fuel pump – A pump is provided to the conditioned fuel through a stop valve. Across the pump, a bypass line is also fitted. iii. Flow measuring device – The fuel from the pump is fed through a flow measuring device which is connected to the GT control panel to initiate the required corrective actions, if any, to monitor the set values of temperature and temperature drop, and pressure and pressure drop etc. iv. Selector valve unit and flow divider – The fuel out of the flow measuring device is fed through a flow divider into selector valve assembly, so that equal fuel flows into each combustor for uniform combustion. v. Intake manifold – In the combustion chamber, there is an intake manifold in which the fuel from the selector valve assembly is passed through to feed the dual fuel nozzle. d) Fire protection sub-system The fire protection system comprises of the following elements: i. Temperature detectors – The temperature detectors are used to sense temperature rise and signal the control panel, which triggers the control valves to release CO2 in the turbine compartment, accessory compartment, and the load-gear compartment. ii. CO2 bottle bank – The CO2 bottle bank supplies and control CO2 by separating flooding pipelines, and also extended discharge to all the three compartments mentioned above. For the purpose of fire extinguishing, a minimum amount of CO2 is maintained through the compartments. e) Exhaust sub-system The exhaust sub-system comprises the following elements: i. Exhaust plenum – The exhaust gases released from the exhaust of the turbine move into the exhaust plenum. ii. Guillotine dumper – A guillotine dumper or a diverter dumper is used to control the flow of the exhaust gases, or they are directed towards the stack, or directed into the guillotine damper then into the HRSG. iii. The HRSG unit – In this element, the heat energy contained in the exhaust gases is used to produce steam through indirect heating of the water released from the steam power cycle. iv. Steam turbine unit – In the steam turbine unit, the steam from HRSG is fed here and is used to run the power generator to produce electricity energy. A fraction of the steam flows into the compressor inlet for limiting NOx and augmentation in the GT system. v. The duct unit – After the exhaust gases have released their thermal energy, they are then allowed to escape into the atmosphere through the duct unit (Yadav, et al., 2012). f) Lubrication sub-system The lubrication sub-system comprises the following elements: i. Lube oil pumps – There is the main pump that is n an accessory shaft, an auxiliary pump run by an AC motor, and then there is an emergency oil pump. These pumps control the flow of oil through the filters from the reservoir to the seals, bearings, and gear meshes within the circuit of the GT. After the oil flow completes the circuit, it is drawn back to the reservoir, which is big enough to maintain the properties of the lube oil. ii. Temperature and pressure measuring devices – These devices regulate the flow of oil using the response of the control panel. g) Water cooling sub-system The water cooling sub-system comprises the following elements: i. Filtration and deionization unit – In this unit, the water from the supply intake is conditioned by: first, filtering, then followed by deionization process. ii. Water coolers – After conditioning, the water is passed over lube coolers, and then through atomizing air coolers. The circulation of water through the coolers is controlled by 3-way by-pass valves. Further cooling takes place by using an industrial heat exchanger that operates in a closed loop, or the open system cooling tower (Gotoh, et al., 2011). h) Atomizing air sub-system This sub-system comprises the following elements: i. Heat exchanger – The heat exchanger or a pre-cooler unit receives the high pressure air that comes from the compressor. ii. Atomizing air compressor – The main atomizing air compressor further increases the pressure of the cooled air. When the speed of the atomizing compressor is not sufficient enough to boost the air pressure during the start-up, the air compressor at the suction of the atomizing compressor provides the required pressure. iii. Drain points and isolation valves – There are drain points alongside isolation valves provided to allow the flowing out of condensed water. iv. Fuel nozzles – The atomized air passes through the fuel nozzles, where it is split into smaller droplets to aid in efficient combustion System Relationships a) System: Between Each of the Sub-systems The sub-systems are both functionally and structurally interrelated to contribute to the systems performance and output. The air inlet takes air into the system that combines with the fuel to be conditioned in the liquid gas fuel sub-system before combustion. The liquid fuel is atomized through the atomizing sub-system for easy combustion. Burning of the hot gases produce exhaust gases that are released through the exhaust sub-system (Yadav, et al., 2012). The resulting high temperatures due to hot gases are cooled by the cooling water system, and the system is protected by a fire protection system. b) Sub-System: Between each of its Elements Each of the elements in a particular sub-system performs a different function on the input to ensure that the desired output is achieved. Like the sub-systems, the elements are related both functionally and structurally. The output of a sub-system is the sum output by each of the elements in the sub-system. System Complexity The gas turbine systems are very complicated. There are many sub-systems that are interrelated both functionally and structurally. All these sub-systems work in coordination and contribute to the system’s power output. The sub-systems are connected to the control panel using actuators and sensors to ensure that optimum operation conditions are maintained within the system. Dynamics of the system To understand the complex GT system, the graph theoretic model with a matrix representation can be used. In the graph theoretic model, a diagraph is used to represent the whole system in terms of the interrelationships between the sub-systems. Since it may be difficult to directly process all the required logical information in a diagraph, a matric representation is developed. The matrix representations allow for incorporation of functional and structural information of the various sub-systems within the gas turbine. The matrix model contains information about interdependencies of sub-system attributes as well as inheritance levels, and can serve the function of characterization of the GT system. For characterization to be realistic, the effect of every single sub-system should contribute to the desired system output to its maximum (Kulikov & Thompson, 2013). Challenge identification Challenge Description The biggest challenge for gas turbine generators are air quality and greenhouse gas emissions, and noise pollution. With the current push for development of green energy sources that do not depend on the use of fossil fuels like natural gas and other fuel gases, the gas turbine technology faces a challenge in this area. The pollutant gases produced by fossil fuels include NOx, and GHGs (Lieuwen & Yang, 2013). Other environmental issues associated with gas turbine generators include noise pollution, and intake and discharge of cooling water into the system and out into the environment. Gas turbines produce noise during the operation of the machine. There is need to control the high levels of noise pollution if this power generation technology is to be fully accepted and competitive with other alternative energy sources. The temperature of the cooling water discharged into the environment also affect the environment’s natural ecosystem. Problem context Fossil fuels are non-renewable energy resources that impact the ecosystem through greenhouse gas emissions and airborne particulates. The greenhouse effect describes how the atmosphere plays a role in insulating the surface of the earth by building an ozone layer in the atmosphere. The continued use of fossil fuels has been increasing the level of CO2 in the atmosphere by about 0.4% annually. The theories of global warming have been greatly linked to the ozone layer. Global warming impacts on climate change, crop production, and rise in seal level, all of which come with adverse secondary effects. The cooling water discharged into the environment from the system cause thermal pollution on the natural ecosystem. Some of the environmental effects of thermal pollution include: loss of biodiversity, reduction in reproductive systems, migration, and increased metabolic rate (Lefebvre, 1998). Noise levels that exceed the safe levels may reduce the sensitivity of the ear to sound. Stakeholders/Players The main stakeholders to address these challenges are the gas turbine engineers and environmental pollution experts. The role of gas turbine engineers is to design gas turbine engines that produce minimum amount of pollutants, minimal noise level and a safe intake and discharge of the system’s cooling water. The environmental experts provide the guiding standards to be met by such designs. Selection of System Methodology There are two methodologies that can be used; hard systems methodologies (HSM) and soft system methodologies (SSM). HSM is a problem solving approach to real-world problems in science and engineering. The approach assumes that the problems in hard systems are well-defined, have an optimum solution, can be solved by a scientific approach, and technical factors predominate in the system. SSM on the other hand is an approach that deals with problem situations that are characterized by pluralism and complexity. The approach assumes that all the problems are ill-defined and cannot easily be quantified (Jackson, 2003). We used the soft systems methodology to solve the problem caused by the cooling water discharged from gas turbines. Application of System methodology Stage 1: Problem Situation Rich picture Figure 1: Possible rich picture of the system’s cooling water problem situation Root Definitions The effects of discharging the system’s cooling water into the ecosystem affects the survival of both aquatic plants and animals. This leads to altered food web and ultimately, loss of biodiversity. The manufactures of gas turbine power generators can prevent this feature by designing an engine that can utilize the thermal energy in the cooling water to produce more power. Most of these power plants discharge into river streams, and this affects the biodiversity of the natural ecosystems of the world. This problem situation can only be prevented by changing the design of the gas turbine engine. This must be done in a way that meets the required legal and environmental standards (Zlatanović, 2015). Stage 2: Formulation of the conceptual models of the discharging cooling water Based on the root definitions, the system of managing the situation involves a number of activities represented in the conceptual model shown in the figure below: Figure 2: Conceptual model of the GT design (adapted from Checkland and Sholes, 2007) Stage 3: Comparing conceptual models with reality To assess the relevance of the activities in the conceptual models above, a sample of the cooling water from the system is collected at intervals to measure the temperature. This temperature is likely to be above any survival temperature of an organism. The temperature at the exhaust of the gas turbine is about 370 – 590oC. With a modified engine system, thermal energy from the cooling water can be used to produce a steam that can another turbine, and be recycled back to the cooling chamber through a closed loop. Stage 4: Taking Action By implementing a design that will provide the desired output, and at the same time utilize the thermal energy in the cooling water, or discharging cooling water that is within tolerable temperatures, the gas turbine engineers will minimize the problem of thermal pollution in the ecosystem. This means re-designing the current gas turbine models. The design selected has to be thoroughly tested to ensure that it does not compromise system efficiency. Implementation Issues The gas fuel refiners may not be ready to adapt to a refining process that can produce suitable quality gas turbine fuel using liquids derived from oil shale, coal, or tar sands. The increased heteroatom content as well as high carbon-hydrogen ratios in these liquids may imply a need for hydrogen processing, which is viewed as increase in cost. Due to economic reasons, the manufacturer of the gas turbine may prefer the use of gas fuels of low quality. Considering the quality difference in fuels from alternative sources implies that the system designs need to change, and more improved materials to be used in the system design. Conclusions In this paper, a study has been done to characterize, and integrate different concepts of a typical gas turbine system. The study also identifies some of the challenges that come with operation of these systems. The system is made up of several sub-systems that are functionally and structurally linked together to ensure that the whole system works as desired. Within each sub-system, there are elements with different functions that also work in relation to ensure that sub-system works appropriately. Despite their increased applications, gas turbine systems have challenges; GHGs emissions, air and noise pollution and discharge of cooling water to the environment. Some of these challenges have been partially addressed, but some need a more improved system designs. There is also competition from other sources of energy, especially green energy sources. The methodology used in the study of the system is flexible and can accommodate most of the typical system designs. References Read More

Gas turbines use fossil fuels, meaning that there is emission of greenhouse gases into the environment. This is the major environmental issue associated with gas turbine systems. Another common issue that causes alteration of the ecosystem is the intake and discharge of cooling water used in the cooling system of the gas turbine engine. One of the side effects of greenhouse gases is global warming, which brings with it rising sea levels, climatic change, and altered natural ecosystems. Research has shown that 80% of greenhouse emissions come from fossil fuels, which are the fuels used in the gas turbine power generators.

Characterization of the GT System System Purpose The main purpose of GT system is to convert the chemical energy stored in a fuel into an energy form that is most desirable and of maximized use, depending on the type of application. In power plants, fuel energy is converted into mechanical energy that is then used to a power generator. The type of system application determines its most appropriate design. The energy produced is used to power trains, aircraft, electric generators, tanks, ships etc.

Environment The environment comprises external factors, such as the atmosphere and gases, climate, water, soil and light. All this factors affect the biodiversity in different ecosystems. Operation of gas turbine has a larger effect on the atmosphere, and the ocean of air used by living organisms. Without doubt, gas turbines are quickly becoming important sources of power in the current and future years. For continued acceptance, there is need to control greenhouse gas emissions into the environment.

Sub-systems Purpose There are various sub-systems that form the whole extremely sophisticated gas turbine device. All these sub-systems require precise modelling to ensure that they are structurally and functionally interrelated to operate with maximum efficiency and performance. All the sub-systems play a role that contributes to the outcome of the system. The purpose of these sub-systems is to govern the best matching system performance in power generation.41 Elements of the Sub-systems and their attributes Each sub-system comprises of elements that have different functions in the sub-system to ensure that the desired output of the sub-system is delivered as desired.

Here, we will discuss the elements that form the first eight subsystems listed earlier on, and also their functions in the subsystem. a) Air inlet sub-system The air inlet sub-system comprises of the following elements: i. Air filter compartment – Ambient air entering through the air inlet is first passed through a filter before entering the compressor inlet plenum to remove solid particles, such as dust. ii. Compressor inlet plenum– The filtered air is compressed before it is pumped into the power unit iii.

Compressor discharge - This element pumps air into the filter compartment with a reversed flow to intermittently clean the filter segment. iv. Chiller coil – The chiller coil is used to cool the air that enters the compressor inlet to reduce the air temperature. This helps to improve power augmentation of the system. v. Anti-icing module – Anti-icing features are also included in the system for all weather conditions. The module contains an inlet manifold that is controlled using a valve, and is used to filter the inlet compartment.

It has a split thrash screen to protect it against thrashing and ingestion of ice. In addition, a pressure switch is fitted to indicate any alarming situation and trigger controlled switch off when the inlet pressure drop reaches a certain pre-determined value (Yadav, et al., 2012). b) Gas fuel system The gas fuel sub-system comprises the following elements: i. Valves – There are three valves; the speed ratio valve where the gas fuel enters before it passes to the gas fuel control valve via the gas stop valve.

Each of the three valves is used to control gas flow through the system. ii. Fuel measuring device – The temperature and pressure of the gas fuel are measured as they flow through this device and the signals are transmitted to the actuators for the required corrective measures to be taken. iii.

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