CO2 Capture for Power Plants: An Analysis of the Energetic Requirements by Chemical Absorption

Author(s):  
Ana R. Diaz

The tendency in the world energy demand seems clear: it can only grow. The energetic industry will satisfy this demand-despite all its dialectic about new technologies-at least medium term mostly with current fossil fuel technologies. In this picture from an engineer’s point of view, one of the primary criterions for mitigating the effects of increasing atmospheric concentration of CO2 is to restrict the CO2 fossil fuel emissions into the atmosphere. This paper is focused on the analysis of different CO2 capture technologies for power plants. Indeed, one of the most important goal to concentrate on is the CO2 capture energy requirements, as it dictates the net size of the power plant and, hence, the net cost of power generation with CO2 avoidance technologies. Here, the Author presents a critical review of different CO2 absorption capture technologies. These technologies have been widely analyzed in the literature under chemical and economic points of view, leaving their impact on the energy power plant performance in a second plan. Thus, the central question examined in this paper is the connection between abatement capability and its energetic requirements, which seriously decrease power generation efficiency. Evidencing that the CO2 capture needs additional technical effort and establishing that further developments in this area must be constrained by reducing its energy requirements. After a comprehensive literature revision, six different chemical absorption methods are analyzed based on a simplified energetic model, in order to account for its energetic costs. Furthermore, an application case study is provided where the different CO2 capture systems studied are coupled to a natural gas cogeneration power plant.

2006 ◽  
Vol 10 (3) ◽  
pp. 71-80
Author(s):  
Nikolaos Koukouzas ◽  
Paraskevas Klimantos ◽  
Prokopis Stogiannis ◽  
Emmanouel Kakaras

The aim of this paper is to examine the possibilities for the abatement of CO2 emissions in the Greek fossil fuel power generation sector. An overview of CO2 capture, transportation, and storage concepts, on which the R&D community is focused, is presented. The implementation of post-combustion CO2 capture options in an existing fossil fuel power plant is then examined and the consequences on the overall plant performance are determined. Finally, the possibilities of transportation and then underground storage of the pure CO2 stream are analyzed taking into account both technical and economical factors. The results of this analysis show that CO2 sequestration is technically feasible for existing fossil fuel fired power plants in Greece. However, substantial reduction in plant efficiency is observed due to increased energy demand of the technologies used as well as in electricity production cost due to capital and operation costs of capture, transport, and storage of CO2. .


Author(s):  
Stuart M. Cohen ◽  
John Fyffe ◽  
Gary T. Rochelle ◽  
Michael E. Webber

Coal consumption for electricity generation produces over 30% of U.S. carbon dioxide (CO2) emissions, but coal is also an available, secure, and low cost fuel that is currently utilized to meet roughly half of America’s electricity demand. While the world transitions from the existing fossil fuel-based energy infrastructure to a sustainable energy system, carbon dioxide capture and sequestration (CCS) will be a critical technology that will allow continued use of coal in an environmentally acceptable manner. Techno-economic analyses are useful in understanding the costs and benefits of CCS. However, typical techno-economic analyses of post-combustion CO2 capture systems assume continuous operation at a high CO2 removal, which could use 30% of pre-capture electricity output and require new capacity installation to replace the output lost to CO2 capture energy requirements. This study, however, considers the inherent flexibility in post-combustion CO2 capture systems by modeling power plants that vary CO2 capture energy requirements in order to increase electricity output when economical under electricity market conditions. A first-order model of electricity dispatch and a competitive electricity market is used to investigate flexible CO2 capture in response to hourly electricity demand variations. The Electric Reliability Council of Texas (ERCOT) electric grid is used as a case study to compare plant and grid performance, economics, and CO2 emissions in scenarios without CO2 capture to those with flexible or inflexible CO2 capture systems. Flexible CO2 capture systems can choose how much CO2 to capture based on the competition between CO2 and electricity prices and a desire to either minimize operating costs or maximize operating profits. Coal and natural gas prices have varying degrees of predictability and volatility, and the relative prices of these fuels have a major impact on power plant operating costs and the resulting plant dispatch sequence. Because the chosen operating point in a flexible CO2 capture system affects net power plant efficiency, fuel prices also influence which CO2 capture operating point may be the most economical and the resulting dispatch of power plants with CO2 capture. Several coal and natural gas price combinations are investigated to determine their impact on flexible CO2 capture operation and the resulting economic and environmental impacts at the power plant and electric grid levels. This study investigates the costs and benefits of flexible CO2 capture in a framework of a carbon-constrained future where the effects of major energy infrastructure changes on fuel prices are not entirely clear.


Author(s):  
S. Can Gülen ◽  
Indrajit Mazumder

Cost of electricity (COE) is the most widely used metric to quantify the cost-performance trade-off involved in comparative analysis of competing electric power generation technologies. Unfortunately, the currently accepted formulation of COE is only applicable to comparisons of power plant options with the same annual electric generation (kilowatt-hours) and the same technology as defined by reliability, availability, and operability. Such a formulation does not introduce a big error into the COE analysis when the objective is simply to compare two or more base-loaded power plants of the same technology (e.g., natural gas fired gas turbine simple or combined cycle, coal fired conventional boiler steam turbine, etc.) and the same (or nearly the same) capacity. However, comparing even the same technology class power plants, especially highly flexible advanced gas turbine combined cycle units with cyclic duties, comprising a high number of daily starts and stops in addition to emissions-compliant low-load operation to accommodate the intermittent and uncertain load regimes of renewable power generation (mainly wind and solar) requires a significant overhaul of the basic COE formula. This paper develops an expanded COE formulation by incorporating crucial power plant operability and maintainability characteristics such as reliability, unrecoverable degradation, and maintenance factors as well as emissions into the mix. The core impact of duty cycle on the plant performance is handled via effective output and efficiency utilizing basic performance correction curves. The impact of plant start and load ramps on the effective performance parameters is included. Differences in reliability and total annual energy generation are handled via energy and capacity replacement terms. The resulting expanded formula, while rigorous in development and content, is still simple enough for most feasibility study type of applications. Sample calculations clearly reveal that inclusion (or omission) of one or more of these factors in the COE evaluation, however, can dramatically swing the answer from one extreme to the other in some cases.


Author(s):  
S. Can Gu¨len

Increasing the thermal efficiency of fossil fuel fired power plants in general and the gas turbine power plant in particular is of extreme importance. In the face of diminishing natural resources and increasing carbon emissions that lead to a heightened greenhouse effect and greater concerns over global warming, thermal efficiency is more critical today than ever before. In the science of thermodynamics, the best yardstick for a power generation system’s performance is the Carnot efficiency — the ultimate efficiency limit, set by the second law, which can be achieved only by a perfect heat engine operating in a cycle. As a fact of nature this upper theoretical limit is out of reach, thus engineers usually set their eyes on more realistic goals. For the longest time, the key performance benchmark of a combined cycle (CC) power plant has been the 60% net electric efficiency. Land-based gas turbines based on the classic Brayton cycle with constant pressure heat addition represent the pinnacle of fossil fuel burning power generation engineering. Advances in the last few decades, mainly driven by the increase in cycle maximum temperatures, which in turn are made possible by technology breakthroughs in hot gas path materials, coating and cooling technologies, pushed the power plant efficiencies to nearly 40% in simple cycle and nearly 60% in combined cycle configurations. To surpass the limitations imposed by available materials and other design considerations and to facilitate a significant improvement in the thermal efficiency of advanced Brayton cycle gas turbine power plants necessitate a rethinking of the basic thermodynamic cycle. The current paper highlights the key thermodynamic considerations that make the constant volume heat addition a viable candidate in this respect. First using fundamental air-standard cycle formulas and then more realistic but simple models, potential efficiency improvement in simple and combined cycle configurations is investigated. Existing and past research activities are summarized to illustrate the technologies that can transform the basic thermodynamics into a reality via mechanically and economically feasible products.


Author(s):  
Rodney R. Gay

Traditionally optimization has been thought of as a technology to set power plant controllable parameters (i.e. gas turbine power levels, duct burner fuel flows, auxiliary boiler fuel flows or bypass/letdown flows) so as to maximize plant operations. However, there are additional applications of optimizer technology that may be even more beneficial than simply finding the best control settings for current operation. Most smaller, simpler power plants (such as a single gas turbine in combined cycle operation) perceive little need for on-line optimization, but in fact could benefit significantly from the application of optimizer technology. An optimizer must contain a mathematical model of the power plant performance and of the economic revenue and cost streams associated with the plant. This model can be exercised in the “what-if” mode to supply valuable on-line information to the plant operators. The following quantities can be calculated: Target Heat Rate Correction of Current Plant Operation to Guarantee Conditions Current Power Generation Capacity (Availability) Average Cost of a Megawatt Produced Cost of Last Megawatt Cost of Process Steam Produced Cost of Last Pound of Process Steam Heat Rate Increment Due to Load Change Prediction of Future Power Generation Capability (24 Hour Prediction) Prediction of Future Fuel Consumption (24 Hour Prediction) Impact of Equipment Operational Constraints Impact of Maintenance Actions Plant Budget Analysis Comparison of Various Operational Strategies Over Time Evaluation of Plant Upgrades The paper describes examples of optimizer applications other than the on-line computation of control setting that have provided benefit to plant operators. Actual plant data will be used to illustrate the examples.


Author(s):  
S. Can Gülen ◽  
Indrajit Mazumder

Cost of electricity (COE) is the most widely used metric to quantify the cost-performance trade-off involved in comparative analysis of competing electric power generation technologies. Unfortunately, the currently accepted formulation of COE is only applicable to comparisons of power plant options with the same annual electric generation (kilowatt-hours) and same technology as defined by reliability, availability and operability. Such a formulation does not introduce a big error into the COE analysis when the objective is simply to compare two or more baseloaded power plants of the same technology (e.g., natural gas fired gas turbine simple or combined cycle, coal fired conventional boiler steam turbine, etc.) and the same (or nearly the same) capacity. However, comparing even the same technology class power plants, especially highly flexible advanced gas turbine combined cycle units with cyclic duties, comprising a high number of daily starts and stops in addition to emissions-compliant low-load operation to accommodate the intermittent and uncertain load regimes of renewable power generation (mainly wind and solar) requires a significant overhaul of the basic COE formula. This paper develops an expanded COE formulation by incorporating crucial power plant operability and maintainability characteristics such as reliability, unrecoverable degradation, and maintenance factors as well as emissions into the mix. The core impact of duty cycle on the plant performance is handled via effective output and efficiency utilizing basic performance correction curves. The impact of plant start and load ramps on the effective performance parameters is included. Differences in reliability and total annual energy generation are handled via energy and capacity replacement terms. The resulting expanded formula, while rigorous in development and content, is still simple enough for most feasibility study type of applications. Sample calculations clearly reveal that inclusion (or omission) of one or more of these factors in the COE evaluation, however, can dramatically swing the answer from one extreme to the other in some cases.


2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Shimin Deng ◽  
Rory Hynes ◽  
Brian Drover

In this paper, the issues and challenges of capturing CO2 from a pulverized coal (PC) power plant have been summarized and assessed and a hybrid power generation configuration is developed, which features a gas-turbine cogeneration unit supplying steam for stripping CO2, thereby decoupling the CO2 capture from the steam cycle of PC units. The hybrid power generation cases are modeled by using GTProTM and SteamProTM. The performance of the hybrid power plant is compared with the base case that uses extraction from the steam cycle. Retrofitting existing power plants by this hybrid concept is also assessed; performance comparison and economic analysis indicate that this kind of retrofitting is attractive to utilities with PC power generation fleet.


2016 ◽  
Vol 13 (1) ◽  
pp. 53
Author(s):  
Siti Nabihah Jamaludin ◽  
Ruzitah Mohd Salleh

Anthropogenic CO2 emissions has led to global climate change and widely contributed to global warming since its concentration has been increasing over time. It has attracted vast attention worldwide. Currently, the different CO2 capture technologies available include absorption, solid adsorption and membrane separation. Chemical absorption technology is regarded as the most mature technology and is commercially used in the industry. However, the key challenge is to find the most efficient solvent in capturing CO2. This paper reviews several types of CO2 capture technologies and the various factors influencing the CO2 absorption process, resulting in the development of a novel solvent for CO2 capture.


Author(s):  
Shane E. Powers ◽  
William C. Wood

With the renewed interest in the construction of coal-fired power plants in the United States, there has also been an increased interest in the methodology used to calculate/determine the overall performance of a coal fired power plant. This methodology is detailed in the ASME PTC 46 (1996) Code, which provides an excellent framework for determining the power output and heat rate of coal fired power plants. Unfortunately, the power industry has been slow to adopt this methodology, in part because of the lack of some details in the Code regarding the planning needed to design a performance test program for the determination of coal fired power plant performance. This paper will expand on the ASME PTC 46 (1996) Code by discussing key concepts that need to be addressed when planning an overall plant performance test of a coal fired power plant. The most difficult aspect of calculating coal fired power plant performance is integrating the calculation of boiler performance with the calculation of turbine cycle performance and other balance of plant aspects. If proper planning of the performance test is not performed, the integration of boiler and turbine data will result in a test result that does not accurately reflect the true performance of the overall plant. This planning must start very early in the development of the test program, and be implemented in all stages of the test program design. This paper will address the necessary planning of the test program, including: • Determination of Actual Plant Performance. • Selection of a Test Goal. • Development of the Basic Correction Algorithm. • Designing a Plant Model. • Development of Correction Curves. • Operation of the Power Plant during the Test. All nomenclature in this paper utilizes the ASME PTC 46 definitions for the calculation and correction of plant performance.


2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Bilal Hassan ◽  
Oghare Victor Ogidiama ◽  
Mohammed N. Khan ◽  
Tariq Shamim

A thermodynamic model and parametric analysis of a natural gas-fired power plant with carbon dioxide (CO2) capture using multistage chemical looping combustion (CLC) are presented. CLC is an innovative concept and an attractive option to capture CO2 with a significantly lower energy penalty than other carbon-capture technologies. The principal idea behind CLC is to split the combustion process into two separate steps (redox reactions) carried out in two separate reactors: an oxidation reaction and a reduction reaction, by introducing a suitable metal oxide which acts as an oxygen carrier (OC) that circulates between the two reactors. In this study, an Aspen Plus model was developed by employing the conservation of mass and energy for all components of the CLC system. In the analysis, equilibrium-based thermodynamic reactions with no OC deactivation were considered. The model was employed to investigate the effect of various key operating parameters such as air, fuel, and OC mass flow rates, operating pressure, and waste heat recovery on the performance of a natural gas-fired power plant with multistage CLC. The results of these parameters on the plant's thermal and exergetic efficiencies are presented. Based on the lower heating value, the analysis shows a thermal efficiency gain of more than 6 percentage points for CLC-integrated natural gas power plants compared to similar power plants with pre- or post-combustion CO2 capture technologies.


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