Heat Recovery Steam Generator Research Articles

Exergetic, economic and exergy-based sustainability analysis of a power generation system with CO2 capture and methanol production

This study proposes a new biomass-based Combined Heat and Power (CHP)/renewable methanol production through captured carbon dioxide. A liquid organic hydrogen carrier (LOHC) stores and releases hydrogen. Literature review shows that LOHC has been integrated into such a system for the first time. The exergetic, exergoeconomic, and economic performance are researched. On average, results show that the exergetic efficiency of the system is 6.6 %. Depletion ratio (DR) is the depletion rate of the exergy source given to the system, which is desired to have low values. The sustainability index (SI) is the DR's reverse, representing the required exergy source per exergy destruction (exergy depletion). High values of this index indicate less exergy source consumed in the system. Exergetic ecological index (EECI) compares the useful products or depleted exergy per consumed exergy source destruction. The negative value of EECI means that the depletion of the exergy source is more significant than the product exergy and vice versa. The exergy-based sustainability indices, including DR, SI, and EECI, are found as 0.934, 1.071, and −0.868, respectively. Exergoeconomic analysis reveals that the exergy destruction rate at the system's capital cost (REX) value is 0.087×102. Heat Recovery Steam Generator (HRSG), gasifier, and Heat Exchanger 1 (HE1) are obtained as 5.153×10−2 (kW/€), 1.707×10−2 (kW/€), 3.094×10−2 (kW/€) respectively. The payback period and the REX are 14.56 years and 0.087×10−2 (kW/€), respectively; it seems long for an engineering application, but these technologies are relatively new, and their costs might decrease soon. Exergy destruction or lost power per capita, which means depleted investment, costs much less than 1. Although the thermodynamic values of the system seem low because irreversibilities occurred in chemical reactions, CO2 saved and produced methanol and cannot be ignored in terms of its environmental and economic benefits, considering CO2 taxes and the methanol economy.

Optimization of steam parameters in double-pressure heat recovery steam generators

Double-pressure heat recovery steam generators are installed in medium-size combined cycle power plants. For a fixed total heating surface area of heat recovery steam generator, the net power output of the power plant depends on steam pressures and temperatures. This paper presents a method of determining the optimal set of steam parameters in double-pressure heat recovery steam generators without reheating and with reheating. The mathematical models of both heat recovery steam generators are presented, and the optimization procedure is described. For given exhaust gas temperature and total heating surface area, the optimal steam parameters of both heat recovery steam generators that maximize net power output can be found subjected to the constraint that the steam quality at turbine outlet is not less than 88 %. Simulation results show that reheating increases optimal net power output by 2.4 % and exhaust gas temperature by about 80 °C.

Power Augmentation of Gas Turbine Using Exhaust Flue Gas Operated Vapor Absorption Machine

Industrial gas turbines (GT) that operate at constant speed are constant-volume-flow combustion machines. As the specific volume of air is directly proportional to the temperature, an increase in air density results in a higher air mass flow rate at low air ambient temperatures. This results more mass of air is now passes through same volume gas turbine space. Consequently, the gas turbine power output increases proportionally with the increase in air mass flow rate. For geographic regions where warm and humid months are predominant throughout the year, significant power loss occurs during these months, and a higher rate of expensive fuel is fired at reduced power output. A gas turbine inlet air cooling technique is a useful option to enhance GT output. One of the innovative options for power augmentation of gas turbine is inlet air conditioning using a vapor absorption machine (VAM). Using VAM for GT intake air conditioning has the advantage over other systems in that it can be operated from waste heat. Many gas turbine machines, particularly natural gas pumping stations, are operated without heat recovery steam generator (HRSG) or heat recovery option. Valuable heat energy is escaped with exhaust flue gas in these systems. This paper demonstrates how GT exhaust waste heat can be utilized for its own power generation enhancement. In this study, a flue gas-based vapor absorption machine is selected for cooling the inlet air of a 26 MW gas turbine, which is used to drive the booster compressor of a natural gas pumping station. The capacity of the VAM for the required cooling effect has been calculated. The expected GT power enhancement from intake air gas conditioning has also been estimated in this paper.

Binary Vapor Cycle for Waste Heat Recovery from Marine Engine Exhaust

Abstract The considerable energy waste in maritime transport and the need to obtain alternatives to reduce emissions of polluting gases are factors that have motivated the study of waste heat recovery systems for marine engines. The system studied herein relies on a binary vapor cycle that uses water for the topping cycle while three organic fluids were investigated for the bottoming cycle: R601a, R134a, and R22. Each of these belongs to a different category of fluid, namely, dry fluid, isentropic fluid, and wet fluid, respectively. Two engines of different ratings and two different pressures of the heat recovery steam generator have been considered for each engine. Various outlet pressures for the topping turbine, which is the most liable to erosion and corrosion due to wet steam, have been investigated. The maximum efficiency achieved for the waste heat recovery system peaked at 21% while the maximum electric power accounted for 4.2% of engine brake power. Therefore, the employment of a waste heat recovery system based on a binary cycle seems a promising alternative to harnessing heat from the exhaust gases of marine engines.

Identification of acid phosphate corrosion in heat recovery piping of combined cycle power plants

Failure of heat recovery units in power plants is a serious problem that causes large economic losses. Accurate determination of the failure mechanism is critical to identify problems at an early stage and make recommendations to power plant operators to prevent equipment failures. These failures are due to tube breakage caused by various mechanisms such as acid corrosion (hydrogen attack), temperature damage, caustic corrosion, and acid phosphate corrosion. The present work aims to report a case study of four damaged tubes from a heat recovery steam generator from a unit of combined cycle power plants (HRSG). The techniques of simple and high-resolution transmission electron microscopy (TEM-HRTEM), scanning electron microscopy with elemental analysis (SEM-EDS) and X-ray diffraction (XRD) allowed to provide evidence of the presence of the acid phosphate corrosion mechanism in three of the four pipes analyzed.

Sensitivity and sustainability analysis of combined cycle plant with integrated LNG pressure energy recovery

Although combined cycle power plants (CCPPs) and liquefied natural gas (LNG) have arisen as solutions to the intermittent nature of renewable energy sources, they still need creative methods for performance enhancement and sustainability of the energy systems. Moreover, the energy efficiency of CCPPs is negatively impacted by environmental conditions, higher specific fuel consumption and a large quantity of waste heat released into the ambient. On the other hand, using seawater as a heating medium in LNG regasification circuits has a detrimental effect on the marine ecosystem. In this context, the LNG pressure energy recovery system through a direct expansion cycle (DEC) integrated with CCPP is proposed to improve sustainability, enhance exergetic performance and to reduce the heat recovery steam generator (HRSG) exhaust loss. To improve the cycle performance, low grade heat harnessed from CCPP is used as the heat source in the DEC rather than seawater. The system performance is analyzed by the energy and exergy method through a mathematical model. Moreover, the sensitivity analysis of the combined system is accomplished to examine the influence of LNG flow rate and ambient temperature on various performance indicators of the total system. It is observed that the integration of DEC boosts the HRSG performance by reducing the stack exergy loss and the efficiency is sensitive to LNG flow rate. The total integrated system energy efficiency ηtot, enhanced to 1.55% compared to the base case. Whereas, for ambient temperature in range of 15 – 45 °C, the system minimum and maximum exergetic efficiency ηex,tot is found to be 54.52 % and 55.94 %. Furthermore, the comparison of exergetic sustainability indicators is calculated and presented for three different simulation cases. The results demonstrate that increase in ηex,tot, affects the environment impact factor, ref and the sustainability index, θsi and improved 2.09 % compared to base case combined cycle.

Introducing and performance evaluation of a novel Multi-Generation process for producing Power, fresh Water, oxygen and nitrogen integrated with liquefied natural gas regasification and carbon dioxide removal process

The objective of this paper is to develop and evaluate a new integrated multigenerational system comprised of cryogenic air separation, hydrate-based desalination, combined cycle and oxyfuel power plants, carbon dioxide amine absorption, and transcritical carbon dioxide power cycle, employing liquefied natural gas cold energy. This integrated multi-generation system, applicable for liquefied natural gas importer terminals with access to seawater, produces approximately 2,533 MW net output power and 1,985 kg/h fresh water. In addition, this integrated multi-generation process produces 16,735,861 kg/h high-purity liquid oxygen (100 mol%), 4,773,633 kg/h liquid nitrogen with 99.71 mol% purity, more than 31,724,465 kg/h high-purity gaseous nitrogen (99.9 mol%), and 90,903,230 kg/h low-purity gaseous nitrogen (83.38 mol%). About 5907.3 MW of produced power is generated by liquefied natural gas expander. The performance of this system is evaluated by energetic methods. The results of energy analysis show the specific energy consumptions of the air separation products are 0.551 kW/kg and 1.93 kW/kg for liquid oxygen and nitrogen, respectively. Moreover, in the hydrate-based desalination subsystem, the specific energy consumption is 0.5 kW/m3 for produced pure water. The combined cycle power plant includes two gas turbines, three steam turbines, and a three-pressure level heat recovery steam generation. The thermal efficiencies of gas turbine cycles (Bryton), steam turbine cycles (Rankine) and combined power cycles are 26.3 %, 29.6 %, and 36.2 %, respectively. The flue gases from power plants enter the carbon dioxide amine absorption subsystem. The separated carbon dioxide is used as a working fluid to produce 372.1 MW power in transcritical carbon dioxide cycle. The results of energy analysis for carbon dioxide amine absorption subsystem show that the specific energy consumption, the ratio of captured carbon dioxide per unit mass of liquefied natural gas and the carbon dioxide removal efficiency are 6.60 kW/kg, 33.91 kg/tone, and 90.06 %, respectively. Approximately 2,905,000 kg/h of liquid carbon dioxide is obtained as the byproduct of this multi-generation process. Additionally, sensitivity analysis is conducted to determine key parameters influencing the main energetic indexes. Finally, the amount of attainable regasified natural gas reaches 257,523 tone/h by applying this multi-generation system with total 86 % energy efficiency.

Proposal and thermodynamic investigation of pressurized calcium looping integrated with chemical looping combustion for tail-end CO2 capture in a retrofitted natural gas combined cycle power plant

The integration of tail-end calcium looping into an existing natural gas combined cycle (NGCC) power plant has minimal impact on CO2 capture retrofits. However, a high volume of flue gas needs to be preheated before entering the carbonator, and the relatively high energy consumption of oxygen production exacerbates the energy penalty of the NGCC system with tail-end CO2 capture. This paper proposes the method of pressurized calcium looping integrated with chemical looping combustion (PCaL-CLC). It employs the PCaL-CLC method to reduce the energy penalty and energy consumption of the NGCC system with tail-end CO2 capture. Results show that the proposed system using the PCaL-CLC method achieves a 3.0% reduction in energy penalty, decreasing from 9.1% in the reference system employing the calcium looping method to 6.1% in the proposed system. Besides, the specific energy consumption for CO2 avoided (SPECCA) declines from 4.43 MJLHV/kg CO2 to 2.76 MJLHV/kg CO2. Exergy analysis and energy utilization diagrams reveal the underlying reason for improving system performance. Furthermore, by optimizing the operating parameters of the gas turbine and equipping it with advanced heat recovery steam generation, an energy penalty of 2.9% and a SPECCA of 1.21 MJLHV/kg CO2 are achieved without CO2 compression, which is superior to those of amine scrubbing and hot-end calcium looping CO2 capture technologies. The proposed PCaL-CLC method offers an alternative approach to reducing the energy consumption of tail-end CO2 capture in existing natural gas combined cycle power plants.

Thermal analysis of an integrated solar combined cycle power plant and its application in southern Iraq

Recently, simple cycle play a significant role in electric power production in Iraq. However, those units suffer from low thermal efficiency and low power output. In the present work, theoretical study is carried out aiming to improve the performance of (AL-Amara station 125MW). The present work includes three parts: the first part focus on the effect of ambient temperature on the performance of simple cycle including mass flow rate, power output, thermal efficiency and other parameters. In the second parts, a modification to simple cycle is implanted to be a combined cycle. The third part is studied the benefit of using solar unit for producing more steam to be supplied to the heat recovery steam generator wishing to produce more power and low emissing. Regarding, to simple gas turbine unit, the obtained results show that the mass flow rate is decreased nearly (10.8%) when the ambient temperature increased from (15-50) ºC. However, this reduction in mass flow rate of air is led to significant reduction in power output and thermal efficiency nearly (22.6%,13.2%) respectively. In the second parts, applying combine mode show a significant increase in power output and thermal efficiency nearly (32.5% and 32.3%) respectively. while the specific fuel consumption is decrease nearly (32.19%). Finally, the third parts when solar units are used, the gathered results show an acceptable increase for the amount of steam produced via solar units (21.02kg/s). The overall performance of the integrated cycle shows that the power output and the thermal efficiency increased nearly (11.28%and10%).

Tracing the carbon capture energy distribution in a natural gas combined cycle power plant under variable operating conditions

A thermodynamic analysis method with a new criterion was introduced to reveal and dynamic track the internal energy consumption distribution of natural gas combined cycle power plants with CO2 capture. The new method decomposes the capture energy consumption into separation energy consumption and system integration energy consumption caused by gas turbines, steam turbines, heat recovery steam generators and steam extraction. The results indicate that load variation has little effect on the energy penalty of the separation process, which accounts for over 50 % of the total capture energy consumption and is stable at around 0.8 MJe/kg CO2 for MEA-based cases, while the integration performance becomes better with load decreasing, since the superior matching between extraction steam and reboiler parameters. Besides, exhaust gas recirculation technology reduces energy consumption caused by steam extraction by around 67 %∼85 % and brings an additional penalty of 0.1–6 MW on the gas turbine under 40–100 % load conditions. Therefore, exploring new absorbents and optimizing the matching between extraction steam and reboiler parameters are the critical points for capture system without exhaust gas recirculation. In contrast, for capture system with exhaust gas recirculation, energy consumption caused by the deterioration performance of gas turbines is crucial under high operation load, while absorbent innovation is dominant at low load. With the aid of the thermodynamic analysis method introduced in this paper, a better understanding of CO2 capture systems under variable load conditions can be obtained, which may be helpful for reducing energy consumption in CO2 capture technologies.

Conventional and advanced exergy-based analyses and comparisons of two novel tri-generation systems based on solid oxide fuel cells and gas turbines

This study conducts conventional and advanced exergy, exergo-economic, and exergo-environmental analyses and comparisons of two tri-generation systems driven by solid oxide fuel cells (SOFCs) and gas turbines (GTs). The proposed systems mainly consist of SOFC, GT, heat recovery steam generator (HRSG), (organic) Rankine cycle, and heat exchanger. The analysis results indicate that the biggest cost rates of exergy destruction and component in both systems appear in SOFCs being 4.4333 $/h and 4.2760 $/h, while the highest environmental impact rates combined with exergy destruction and component in systems 1 and 2 are found in afterburner and HRSG, which are 645.9569 mPts/h and 849.2659 mPts/h. Compared to the conventional analyses, the advanced analyses demonstrate that air compressors own the largest avoidable-endogenous parts of cost rates, while HRSG of system 1 and steam turbine (ST) of system 2 own the highest avoidable-endogenous parts of environmental impact rates being 165.8482 mPts/h and 115.2299 mPts/h.

Zero carbon emission CCGT power plant with integrated solid fuel gasification

The development of a high-capacity power plant with zero CO2 emissions is an urgent task that will curb the increase in atmospheric temperature. It should have an efficiency comparable with existing TPPs, a low metal consumption rate, a high fuel versatility, and high flexibility. To meet these conditions, oxygen combustion is conducted in an environment of inert CO2, and most of the condensation heat from the combustion products is usefully utilized. This work presents a combined cycle gas turbine (CCGT) power plant with solid fuel gasification, oxy-fuel combustion, and a pressurized heat recovery steam generator (PHRSG). The two plant options are compared with the natural gas plant previously proposed. In the PHRSG, the low metal intensity is achieved by high average temperature differences, the pinch point value at 8–12 °C, and the intensification of heat transfer caused by the high pressure of combustion products and the condensation of water vapor in the tail surfaces. The developed plants are highly efficient when using coal, 51%, and 57.3% when using peat, and have acceptable CO2 avoidance costs of 72.7 €/t and 60.4 €/t. By combining these factors, and using well-developed materials, it will take less time to develop and implement this plant widely.

Efficiency Assessment of a Combined Heat and Power Plant Using Exergy Analysis

This study conducted an exergy analysis of a cogeneration power plant utilizing gas turbines, air compressors, combustion chambers, heat recovery steam generators, heat exchangers, and pumps. The study performed an extensive exergy analysis of the system, focusing on each component's process and calculating its base efficiency while tabulating the corresponding exergy degradation. Relevant equations for mass, energy, and exergy were identified to determine optimal control volume conditions for an optimal system and boundary conditions that would enhance the design and reduce exergy destruction. The research project developed revisions and modifications necessary to the base system, utilizing available parameters and boundary conditions, to enable a second law analysis, improve the overall efficiency, and reduce irreversibility and the loss of exergy. The proposed modifications included the remodelling of the cogeneration plant by applying additional processes to utilize the excessive waste heat in the plant. The study further optimized the plant's efficiency by modifying individual system elements that yielded minimal exergy destruction to the overall design. The proposed modifications explored the best-case alteration on optimizing overall plant efficiency with minimum irreversibility compared to the initial analysis done. The technical contributions of this research project are the revisions and modifications that enabled a second law analysis and improved the overall efficiency of the cogeneration power plant.

Effect of Exhaust Gas Flow Rate in Heat Recovery Steam Generator Duct Using Computational Fluid Dynamic Approach

Effect of Exhaust Gas Flow Rate in Heat Recovery Steam Generator Duct Using Computational Fluid Dynamic Approach

Energy and exergy analysis of a steam power plant to replace the boiler with a heat recovery steam generator

Energy and exergy analysis of a steam power plant to replace the boiler with a heat recovery steam generator

Thermodynamic Analysis of Once-through Heat Recovery Steam Generator in a Combined Cycle Power Plants Fueled with Biogas

The working principle of the combined cycle in the combined cycle power plant (CCPP) is to utilize a certain amount of waste heat in the gas turbine, which reaches temperatures of 1650°C, to generate steam in the steam turbine. Due to the high temperature of the exhaust gas in the gas turbine, a device is needed to recover this waste heat, known as a Heat Recovery Steam Generator (HRSG). Compared to conventional HRSG, a once-through heat recovery steam generator (OTHRSG) offers the advantages of faster design time (25% faster than conventional) and lower design costs because it does not require a drum which contributes to an increase in thermal efficiency. This study aims to model and simulate the CCPP system with an OTHRSG to achieve maximum thermal efficiency by using biogas from the degradation of organic waste as the input fuel for CCPP using Cycle Tempo software. The thermal efficiency of the CCPP system was achieved at 57% by applying turbine inlet temperature (TIT) of 1500°C and compression ratio of 46. These results proved that the CCPP system by using biogas as fuel could increase the thermal efficiency of a single cycle power plant.

Energy and exergy analysis of a steam power plant to replace the boiler with a heat recovery steam generator

Energy and exergy analysis of a steam power plant to replace the boiler with a heat recovery steam generator

Reliable AI models can reveal key processes of heat recovery steam generator operation in air pollutant emission

Artificial intelligence (AI) algorithms have been applied to air pollution prediction modeling, but assessment of their trustworthiness is lacking. This study aims to examine whether AI-based models can identify key operational processes of a Heat Recovery Steam Generator (HRSG) facility and predict the emission of target air pollutants, including nitrogen oxides (NOx), sulfur oxides (SOx), and total suspended particles (TSP). First, key operational variables are selected based on the feature importance of the Random Forest models (that is, data-driven input selection). Secondly, Bidirectional Long Short-Term Memory-based AutoEncoder (BiLSTM-AE) and Random Forest (RF) models with the data-driven input selection are trained and evaluated using multiple predictive performance metrics. Then, the BiLSTM-AE and RF models are trained and evaluated using the operational variables selected by experts. Results demonstrate that the data-driven and expertise-based methods select five common operational variables that are key factors to predict variations of target output variables. The results from the multi-metric evaluations show a skillful prediction of BiLSTM-AE and RF models for NOx and TSP, but not SOx. For TSP prediction, RF is more sensitive to the input selection method than BiLSTM-AE. This study underscores the dependency of the prediction skill of AI algorithm-based models on the target air pollutant and input selection method, and suggests the trustworthiness of selected key operational variables by RF's feature importance.

Comprehensive analysis of energy, exergy, economic, and environmental aspects in implementing the Kalina cycle for waste heat recovery from a gas turbine cycle coupled with a steam generator

This study introduces a transformative approach by integrating the Kalina Cycle System (KCS) within a cogeneration of heat and power (CHP) framework alongside a gas turbine (GT) cycle and a single-pressure heat recovery steam generator (HRSG). Through development of thermodynamic and thermo-economic models, a comprehensive assessment of the system's performance is conducted, emphasizing energy, exergy, and exergoeconomic considerations. The outcomes reveal a remarkable enhancement in both 1st and 2nd law efficiencies for the GT-HRSG/KCS-11 system compared to its conventional counterpart. Witnessing an ascent from 53.60 % to 54.31 % in efficiency and an increase from 50.59 % to 51.27 % in 2nd law efficiency underscores the profound impact of the proposed system. Furthermore, a parametric study scrutinizes the influence of diverse design parameters on critical objective functions, encompassing second law efficiencies and the total system cost rate. Findings spotlight the combustion chamber, heat recovery steam generator, and gas turbine as focal points of exergy destruction, revealing crucial insights for system optimization. The combustion chamber, heat recovery steam generator, and gas turbine emerge as pivotal contributors to the total cost rate, highlighting key areas for economic consideration. According to the results, the share of the environmental cost rates in the system cost rate is insignificant.

Determination of optimal total area of heat recovery steam generator

Heat recovery steam generator (HRSG) plays a critical role in recovering waste heat from exhaust gas in a combined cycle. The performance of the steam cycle in the combined cycle depends on total HRSG area. This paper presents a comprehensive study on the determination of the optimal total area of single-pressure HRSG considering various factors such as exhaust gas temperature, main steam temperature, main steam pressure, reheat steam pressure, and reheat steam temperature. The research methodology involves the development of a mathematical model of HRSG that considers the key parameters affecting the HRSG performance. It is shown that, for given exhaust gas temperature and total HRSG area, there exists the set of steam parameters that yields the maximum net power output of the steam cycle. Furthermore, the power output increases monotonically with total HRSG area. However, the power output increases at a decreasing rate as total HRSG area increases. The optimal total HRSG area is shown to depend on the unit selling price of electricity, the unit cost of heat exchanger, the capacity factor of the power plant, and the acceptable payback period for the investment in the installation cost of HRSG.