Investigation of Different Operation Strategies to Provide Balance Energy With an Industrial Combined Heat and Power Plant Using Dynamic Simulation

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Steffen Kahlert ◽  
Hartmut Spliethoff
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Dynamic Simulation ◽  
Process Model ◽  
Power Plants ◽  
Control Valve ◽  
Combined Heat And Power ◽  
Combined Cycle ◽  
Water Steam ◽  
Load Change

Intermittency of renewable electricity generation poses a challenge to thermal power plants. While power plants in the public sector see a decrease in operating hours, the utilization of industrial power plants is mostly unaffected because process steam has to be provided. This study investigates to what extent the load of a combined heat and power (CHP) plant can be reduced while maintaining a reliable process steam supply. A dynamic process model of an industrial combined CHP plant is developed and validated with operational data. The model contains a gas turbine (GT), a single pressure heat recovery system generator (HRSG) with supplementary firing and an extraction condensing steam turbine. Technical limitations of the gas turbine, the supplementary firing, and the steam turbine constrain the load range of the plant. In consideration of these constraints, different operation strategies are performed at variable loads using dynamic simulation. A simulation study shows feasible load changes in 5 min for provision of secondary control reserve (SCR). The load change capability of the combined cycle plant under consideration is mainly restricted by the water–steam cycle. It is shown that both the low pressure control valve (LPCV) of the extraction steam turbine and the high pressure bypass control valve are suitable to ensure the process steam supply during the load change. The controllability of the steam turbine load and the process stability are sufficient as long as the supplementary is not reaching the limits of the operating range.

Investigation of Different Operation Strategies to Provide Balance Energy With an Industrial CHP Plant Using Dynamic Simulation

2016 ◽  
Author(s):  
Steffen Kahlert ◽  
Hartmut Spliethoff
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Dynamic Simulation ◽  
Process Model ◽  
Power Plants ◽  
Thermal Power ◽  
Control Valve ◽  
Combined Cycle ◽  
Water Steam ◽  
Load Change

Intermittency of renewable electricity generation poses a challenge to thermal power plants. While power plants in the public sector see a decrease in operating hours, the utilization of industrial power plants is mostly unaffected because process steam has to be provided. This study investigates to what extent the load of a CHP plant can be reduced while maintaining a reliable process steam supply. A dynamic process model of an industrial combined CHP plant is developed and validated with operational data. The model contains a gas turbine, a single pressure HRSG with supplementary firing and an extraction condensing steam turbine. Technical limitations of the gas turbine, the supplementary firing and the steam turbine constrain the load range of the plant. In consideration of these constraints, different operation strategies are performed at variable loads using dynamic simulation. A simulation study shows feasible load changes in 5 min for provision of secondary control reserve. The load change capability of the combined cycle plant under consideration is mainly restricted by the water-steam cycle. It is shown that both the low pressure control valve of the extraction steam turbine and the high pressure bypass control valve are suitable to ensure the process steam supply during the load change. The controllability of the steam turbine load and the process stability are sufficient as long as the supplementary is not reaching the limits of the operating range.

Steam Injected Gas Turbine (STIG) for Load Flexible CHP: Aspects of Dynamic Behaviour, Control and Water Recovery

2019 ◽  
Author(s):  
Thorsten Lutsch ◽  
Uwe Gampe ◽  
Guntram Buchheim
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Power Plants ◽  
Operating Cost ◽  
Combined Cycle ◽  
System Response ◽  
Water Recovery ◽  
Operating Range ◽  
Demand Fluctuations ◽  
Wide Operating

Abstract Industrial combined heat and power (CHP) plants are often faced with highly variable demand of heat and power. Demand fluctuations up to 50% of nominal load are not uncommonly. The cost and revenue situation in the energy market represents a challenge, also for cogeneration of heat and power (CHP). More frequent and rapid load changes and a wide operating range are required for economic operation of industrial power plants. Maintaining pressure in steam network is commonly done directly by a condensation steam turbine in a combined cycle or indirectly by load changes of the gas turbine in a gas turbine and heat recovery steam generator arrangement. Both result in a change of the electric output of the plant. However, operating cost of a steam turbine are higher than a single gas turbine. The steam injected gas turbine (STIG) cycle with water recovery is a beneficial alternative. It provides an equivalent degree of freedom of power and heat generation. High process efficiency is achieved over a wide operating range. Although STIG is a proven technology, it is not yet widespread. The emphasis of this paper is placed on modeling the system behavior, process control and experiences in water recovery. A dynamic simulation model, based on OpenModelica, has been developed. It provides relevant information on system response for fluctuating steam injection and helps to optimize instrumentation and control. Considerable experience has been gained on water recovery with respect to condensate quality, optimum water treatment architecture and water recovery rate, which is also presented.

Effects of Steam Reheat in Advanced Steam Injected Gas Turbine Cycles

1998 ◽  
Author(s):  
A. Hofstädter ◽  
H. U. Frutschi ◽  
H. Haselbacher
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Power Plants ◽  
Steam Injection ◽  
Combined Cycle ◽  
Back Pressure ◽  
Turbine Efficiency ◽  
Pressure Steam ◽  
Additional Improvement ◽  
Gas Turbine Exhaust

Steam injection is a well-known principle for increasing gas turbine efficiency by taking advantage of the relatively high gas turbine exhaust temperatures. Unfortunately, performance is not sufficiently improved compared with alternative bottoming cycles. However, previously investigated supplements to the STIG-principle — such as sequential combustion and consideration of a back pressure steam turbine — led to a remarkable increase in efficiency. The cycle presented in this paper includes a further improvement: The steam, which exits from the back pressure steam turbine at a rather low temperature, is no longer led directly into the combustion chamber. Instead, it reenters the boiler to be further superheated. This modification yields additional improvement of the thermal efficiency due to a significant reduction of fuel consumption. Taking into account the simpler design compared with combined-cycle power plants, the described type of an advanced STIG-cycle (A-STIG) could represent an interesting alternative regarding peak and medium load power plants.

scholarly journals Simulation of Producer Gas Fired Power Plants with Inlet Fog Cooling and Steam Injection

2006 ◽  
Vol 129 (3) ◽  
pp. 637-647 ◽  
Author(s):  
Mun Roy Yap ◽  
Ting Wang
Keyword(s):  
Natural Gas ◽  
Steam Turbine ◽  
Gas Turbine ◽  
Power Output ◽  
Power Plants ◽  
Steam Injection ◽  
Combined Cycle ◽  
Producer Gas ◽  
Turbine Inlet ◽  
Cycle Systems

Biomass can be converted to energy via direct combustion or thermochemical conversion to liquid or gas fuels. This study focuses on burning producer gases derived from gasifying biomass wastes to produce power. Since the producer gases are usually of low calorific values (LCV), power plant performance under various operating conditions has not yet been proven. In this study, system performance calculations are conducted for 5MWe power plants. The power plants considered include simple gas turbine systems, steam turbine systems, combined cycle systems, and steam injection gas turbine systems using the producer gas with low calorific values at approximately 30% and 15% of the natural gas heating value (on a mass basis). The LCV fuels are shown to impose high compressor back pressure and produce increased power output due to increased fuel flow. Turbine nozzle throat area is adjusted to accommodate additional fuel flows to allow the compressor to operate within safety margin. The best performance occurs when the designed pressure ratio is maintained by widening nozzle openings, even though the turbine inlet pressure is reduced under this adjustment. Power augmentations under four different ambient conditions are calculated by employing gas turbine inlet fog cooling. Comparison between inlet fog cooling and steam injection using the same amount of water mass flow indicates that steam injection is less effective than inlet fog cooling in augmenting power output. Maximizing steam injection, at the expense of supplying the steam to the steam turbine, significantly reduces both the efficiency and the output power of the combined cycle. This study indicates that the performance of gas turbine and combined cycle systems fueled by the LCV fuels could be very different from the familiar behavior of natural gas fired systems. Care must be taken if on-shelf gas turbines are modified to burn LCV fuels.

An Integrated Steam/Gas Turbine-Generator for Combined-Cycle Applications

1989 ◽  
Author(s):  
J. H. Moore
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Power Plants ◽  
Combined Cycle ◽  
Gas Temperature ◽  
Turbine Generator ◽  
Fully Integrated ◽  
Reheat Steam ◽  
Exhaust Gas Temperature ◽  
Steam Cycle

Combined-cycle power plants have been built with the gas turbine, steam turbine, and generator connected end-to-end to form a machine having a single shaft. To date, these plants have utilized a nonreheat steam cycle and a single-casing steam turbine of conventional design, connected to the collector end of the generator through a flexible shaft coupling. A new design has been developed for application of an advanced gas turbine of higher rating and higher firing temperature and exhaust gas temperature with a reheat steam cycle. The gas turbine and steam turbine are fully integrated mechanically, with solid shaft couplings and a common thrust bearing. This paper describes the new machine, with emphasis on the steam turbine section where the elimination of the flexible coupling created a number of unusual design requirements. Significant benefits in reduced cost and reduced complexity of design, operation, and maintenance are achieved as a result of the integration of the machine and its control and auxiliary systems.

Repowering: An Option for Refurbishment of Old Thermal Power Plants in Latin-American Countries

2010 ◽  
Author(s):  
Washington Orlando Irrazabal Bohorquez ◽  
Joa˜o Roberto Barbosa ◽  
Luiz Augusto Horta Nogueira ◽  
Electo E. Silva Lora
Keyword(s):  
Power Plant ◽  
Natural Gas ◽  
Steam Turbine ◽  
Gas Turbine ◽  
Power Plants ◽  
Thermal Power ◽  
Rankine Cycle ◽  
Combined Cycle ◽  
Fuel Oil ◽  
Thermal Power Plants

The operational rules for the electricity markets in Latin America are changing at the same time that the electricity power plants are being subjected to stronger environmental restrictions, fierce competition and free market rules. This is forcing the conventional power plants owners to evaluate the operation of their power plants. Those thermal power plants were built between the 1960’s and the 1990’s. They are old and inefficient, therefore generating expensive electricity and polluting the environment. This study presents the repowering of thermal power plants based on the analysis of three basic concepts: the thermal configuration of the different technological solutions, the costs of the generated electricity and the environmental impact produced by the decrease of the pollutants generated during the electricity production. The case study for the present paper is an Ecuadorian 73 MWe power output steam power plant erected at the end of the 1970’s and has been operating continuously for over 30 years. Six repowering options are studied, focusing the increase of the installed capacity and thermal efficiency on the baseline case. Numerical simulations the seven thermal power plants are evaluated as follows: A. Modified Rankine cycle (73 MWe) with superheating and regeneration, one conventional boiler burning fuel oil and one old steam turbine. B. Fully-fired combined cycle (240 MWe) with two gas turbines burning natural gas, one recuperative boiler and one old steam turbine. C. Fully-fired combined cycle (235 MWe) with one gas turbine burning natural gas, one recuperative boiler and one old steam turbine. D. Fully-fired combined cycle (242 MWe) with one gas turbine burning natural gas, one recuperative boiler and one old steam turbine. The gas turbine has water injection in the combustion chamber. E. Fully-fired combined cycle (242 MWe) with one gas turbine burning natural gas, one recuperative boiler with supplementary burners and one old steam turbine. The gas turbine has steam injection in the combustion chamber. F. Hybrid combined cycle (235 MWe) with one gas turbine burning natural gas, one recuperative boiler with supplementary burners, one old steam boiler burning natural gas and one old steam turbine. G. Hybrid combined cycle (235 MWe) with one gas turbine burning diesel fuel, one recuperative boiler with supplementary burners, one old steam boiler burning fuel oil and one old steam turbine. All the repowering models show higher efficiency when compared with the Rankine cycle [2, 5]. The thermal cycle efficiency is improved from 28% to 50%. The generated electricity costs are reduced to about 50% when the old power plant is converted to a combined cycle one. When a Rankine cycle power plant burning fuel oil is modified to combined cycle burning natural gas, the CO2 specific emissions by kWh are reduced by about 40%. It is concluded that upgrading older thermal power plants is often a cost-effective method for increasing the power output, improving efficiency and reducing emissions [2, 7].

Integrating HRSG Technical Dimensioning in Overall CCPP Cycle Optimization of Performance and Cost

2009 ◽  
Author(s):  
Camille Pedretti ◽  
Tobias Kjellberg ◽  
Tjiptady Nugroho
Keyword(s):  
Steam Turbine ◽  
Design Methodology ◽  
Process Model ◽  
Pareto Front ◽  
Combined Cycle ◽  
Heat Integration ◽  
Water Steam ◽  
Initial Design ◽  
And Performance ◽  
Steam Cycle

This article presents an initial design methodology of the water/steam cycle of combined-cycle power plants. From prescribed boundary conditions such as the GT type or ambient conditions, the water/steam cycle process model performs a computation and initial design of all key components, leading to cycle performance and cost. Particular focus is given here to the Heat Recovery Steam Generator (HRSG), a key component for heat integration having a large impact on both plant cost and performance. With the assistance of an optimization toolbox, optimal designs are found with respect to cost and performance. The process model allows a number of water/steam cycle configurations. Features include the number of pressure levels, the choice of single or double reheat, options for supplementary firing in the HRSG, heat integration with GT coolers, fuel gas preheating and steam extraction from the steam turbine. From prescribed thermodynamic inputs, the model computes and/or selects key components and systems from the Original Equipment Manufacturer (OEM) portfolio: HRSG, piping, steam turbine, condenser and generator. For each key component and system, the performance and cost are derived. The initial design of the HRSG fully integrates all interfaces and is supported by a sub-optimization step, which provides proper surfacing and sequencing of heat exchanger components with the target of minimizing cost. To achieve the required accuracy, the HRSG is first designed technically in detail, namely dimensioning and material selection of finned tubes, structural steel, casing and insulation. The resulting partial bill of quantities is then converted into cost, applying appropriate material rates. This approach guarantees full sensitivity of the model to mass flow, pressure or temperature changes at any location in the HRSG. Coupled to this process model, the multi-objective optimization toolbox allows identifying the pareto front for plant net performance and plant cost, clearly two conflicting objectives. In the example application of a KA26–1 combined-cycle power plant, steps are identified on the pareto front, which can be associated with the number of HRSG modules. For selected project economic conditions and plant operation profile, the pareto front can be post-processed to identify the design with minimum COE or maximum project NPV. Simultaneous optimization of the complete cycle ensures the best possible integration of all key components. Flexibility, speed and effectiveness of the methodology allow exploring many cycle variants, maximizing the chances of finding the global plant optimum in less time. Having been thoroughly validated, the initial design methodology is applicable for development of standard plants as well as integration of specific customer requirements.

Prediction of Gas Turbine Trip Due to Electro Hydraulic Control Valve System Failures

2010 ◽  
Author(s):  
Y. B. Ravi ◽  
Achalesh Pandey ◽  
Vinay Jammu
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Control Valve ◽  
Combined Cycle ◽  
Hydraulic Control ◽  
Current Application ◽  
System Failures ◽  
Thermal Transients ◽  
Valve System

Gas turbines are the main power producing components in combined cycle and simple cycle power plants. A gas turbine trip is a rapid uncontrolled shutdown of the turbine that is initiated by the turbine controller to protect it from failures. The turbine loses significant amount of life due to strong thermal transients during a trip and the utility company loses revenue because of lost power generation. Therefore, prediction of trips has significant financial impact. This paper presents a method to predict gas turbine trips due to electro hydraulic control valve system failures. This paper also provides methods to detect gas control valve system failures in their incipient phase and methods to identify various failure signatures for diagnostics. The methodology presented here could be extended beyond the current application to other causes of trips in the gas turbine, thereby impacting availability and reliability of the turbine.

Low CO2 Emission Combined Cycles With Natural Gas Reforming, Including NOx Suppression

2001 ◽  
Author(s):  
Giovanni Lozza ◽  
Paolo Chiesa
Keyword(s):  
Natural Gas ◽  
Gas Turbine ◽  
Power Plants ◽  
Flame Temperature ◽  
Combined Cycle ◽  
Water Steam ◽  
First Case ◽  
Order Of Magnitude ◽  
Combined Cycles ◽  
Pressure Swing

The present paper addresses the plant configuration, the thermodynamic performance and the economics of combined cycle power plants, having the following characteristics: (i) CO2 emissions reduced by at least one order of magnitude, (ii) utilization of hydrogen produced by natural gas as the fuel for the gas turbine, (iii) acceptable NOx emissions. Two plant configurations are discussed, based on high pressure reformers heated up by: (i) gas turbine exhausts with hydrogen firing, (ii) oxygen combustion of carbonated purge gases from a pressure-swing-absorber. In the first case CO2 is separated by a chemical absorption plant, in the second from the reformer exhausts after water condensation. The fuel dilution by water/steam or nitrogen was properly kept into account, to achieve NOx emission of about 30-45 ppmvd with a flame temperature of 2300 K. The two plant schemes show a net efficiency of about 48% (including CO2 liquefaction) vs. 56% of the reference combined cycle having the same gas turbine and cycle technology, with a remarkable increase of the net power output (based on the same gas turbine unit). The ability of removing CO2 from the exhausts yields to a 25-30% increase of the cost of electricity, i.e. 40-45 $/ton of CO2 sequestrated.

Effect of Inlet Steam Temperature on the HP Section Efficiency of a Steam Turbine

2015 ◽  
Author(s):  
Yiping Fu ◽  
Thomas Winterberger
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Pressure Ratio ◽  
Control Valve ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Steam Temperature ◽  
Load Range ◽  
Lp Turbine ◽  
The Relationship

Steam turbines for modern fossil and combined cycle power plants typically utilize a reheat cycle with High Pressure (HP), Intermediate Pressure (IP), and Low Pressure (LP) turbine sections. For an HP turbine section operating entirely in the superheat region, section efficiency can be calculated based on pressure and temperature measurements at the inlet and exhaust. For this case HP section efficiency is normally assumed to be a constant value over a load range if inlet control valve position and section pressure ratio remain constant. It has been observed that changes in inlet steam temperature impact HP section efficiency. K.C. Cotton stated that ‘the effect of throttle temperature on HP turbine efficiency is significant’ in his book ‘Evaluating and Improving Steam Turbine Performance’ (2nd Edition, 1998). The information and conclusions provided by K.C. Cotton are based on test results for large fossil units calculated with 1967 ASME steam tables. Since the time of Mr. Cotton’s observations, turbine configurations have evolved, more accurate 1997 ASME steam tables have been released, and our ability to quickly analyze large quantities of data has greatly increased. This paper studies the relationship between inlet steam temperature and HP section efficiency based on both 1967 and 1997 ASME steam tables and recent test data, which is analyzed computationally to reveal patterns and trends. With the efficiencies of various inlet pressure class HP section turbines being calculated with both 1967 and 1997 ASME steam tables, a comparison reveals different characteristics in the relationship between inlet steam temperature and HP section efficiency. Recommendations are made on how the results may be used to improve accuracy when testing and trending HP section performance.

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