Integration and Operation of Post-combustion Capture System on Coal-fired Power Generation: Load Following and Peak Power

Integration and Operation of Post-combustion Capture System on Coal-fired Power Generation: Load Following and Peak Power
Author: Robert David Brasington (S.M.)
Publisher:
Total Pages: 87
Release: 2012
Genre:
ISBN:

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Coal-fired power plants with post combustion capture and sequestration (CCS) systems have a variety of challenges to integrate the steam generation, air quality control, cooling water systems and steam turbine with the capture system. A variety of engineering studies have been completed that cover these aspects when a plant is operating at full load while operating at a 90 percent capture rate. These studies investigate the basic integration of the these systems, the energy penalty and the effect of capital costs; however, none of these studies comprehensively explore the ability of the capture plant and the balance of the integrated system to respond dynamically to changes in load or capture rate. These load changes occur due to a change in demand for electricity in the system, generation by variable, intermittent resources, or if the plant is equipped with the ability to store solvent to implement price arbitrage. The integrated carbon capture system can be broken down into three general modes: full capacity, load following and peak power generation. Each of these modes presents unique challenges to integration with the CCS system. The load following mode requires the ability to accommodate different ramp rates that are reflected in flue gas flow and composition. Operation at partial load will affect the quality of steam sent to the solvent regeneration unit. Depending on the setup of the steam turbine system, at lower loads multiple extractions points may be necessary or an increase of the amount of extraction steam will be required due to the reduction in steam quality. Using Aspen Dynamics, a CO2 capture system using a monoethanolamine (MEA) absorption process is simulated at various plant loads to determine the overall effects on the efficiency of the CCS unit and the balance of the system. In addition, the dynamic behavior of the CCS unit on power output and emissions is shown to demonstrate that the capability of a coal-fired power plant to load follow is not hindered by the addition of a carbon capture unit. The solvent storage mode can be further broken to two operation modes. The first is peak power production, which occurs when the solvent is capturing CO2 from the flue gas, but is minimizing or delaying regeneration to a future time through storage. This mode is used to take advantage of peak power prices by maximizing power output of the plant and maintaining a 90 percent capture rate. The regeneration mode entails the solvent being released from the storage tanks and sent to the reboiler column. Solvent storage has been shown in previous studies to have the ability to increase operating profits, but these studies have neglected to incorporate the capital costs associated with this type of operation mode and the operational issues and complexity associated with the large swings in quantities of steam required for the solvent regeneration. By including the capital costs, this study determines that a system with large duration solvent storage is not economically viable given the flexible demands of the system and current electricity price spreads. This thesis presents a framework for considering the flexible operations of a coal-fired power plant with an integrated carbon capture and sequestration system. By exploring the operational limitations of the integrated system and the economic costs, an evaluation is made of the viability of different CCS operational schemes. This study finds that the CCS unit can match the dynamics of the base coal plant and also increase the operational flexibility of the system. The increased capital expenditure to meet peak demand is viable for larger steam turbine configurations in electricity systems with high peak prices and plants with short duration solvent storage.

Investigation of Thermal Integration in a Coal-Fired Power Plant with MEA Post-Combustion Carbon Capture

Investigation of Thermal Integration in a Coal-Fired Power Plant with MEA Post-Combustion Carbon Capture
Author: Erony Whyte Martin
Publisher:
Total Pages: 183
Release: 2011
Genre:
ISBN: 9781124657424

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One option for capturing CO2 from pulverized coal power plants is to use a MEA scrubber, with the captured CO2 then being compressed to high pressure. Between them, the capture and compression processes will result in approximately 33% less net unit power. The compression process generates heat which can be recycled within the plant to reduce the energy penalty. This report describes the effect of compressor selection and thermal integration on heat rate. The power plant, MEA scrubber and compressors were modeled with Aspen Plus software and Ramgen, an inline and two integrally geared compressors and five thermal integration cases were evaluated.

Efficient Carbon Capture for Coal Power Plants

Efficient Carbon Capture for Coal Power Plants
Author: Detlef Stolten
Publisher: Wiley-VCH
Total Pages: 0
Release: 2011-07-05
Genre: Technology & Engineering
ISBN: 9783527330027

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Carbon Capture and Storage is a key technology for a sustainable and low carbon economy. This book unites top academic and industry researchers in search for commercial concepts for CCS at coal power ploants. This reference focuses on power plant technology and ways to improve efficiency. It details the three principal ways of capturing the CO2 produced in power plants: oxyfuel combustion, postcombustion and precombustion, with the main part concentrating on the different approaches to removing carbon dioxide. Wtih an eye on safety, the authors explain how the three parts of the CCS chain work - capture, transport and storage - and how they can be performed safely. The result is specific insights for process engineers, chemists, physicists and materials engineers in their relevant fields, as well as a sufficiently broad scope to be able to understand the opportunities and implications of the other disciples.

Thermal Integration of CO{sub 2} Compression Processes with Coal-Fired Power Plants Equipped with Carbon Capture

Thermal Integration of CO{sub 2} Compression Processes with Coal-Fired Power Plants Equipped with Carbon Capture
Author:
Publisher:
Total Pages:
Release: 2012
Genre:
ISBN:

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Coal-fired power plants, equipped either with oxycombustion or post-combustion CO2 capture, will require a CO2 compression system to increase the pressure of the CO2 to the level needed for sequestration. Most analyses show that CO2 compression will have a significant effect on parasitic load, will be a major capital cost, and will contribute significantly to reduced unit efficiency. This project used first principle engineering analyses and computer simulations to determine the effects of utilizing compressor waste heat to improve power plant efficiency and increase net power output of coal-fired power plants with carbon capture. This was done for units with post combustion solvent-based CO2 capture systems and for oxyfired power plants, firing bituminous, PRB and lignite coals. The thermal integration opportunities analyzed for oxycombustion capture are use of compressor waste heat to reheat recirculated flue gas, preheat boiler feedwater and predry high-moisture coals prior to pulverizing the coal. Among the thermal integration opportunities analyzed for post combustion capture systems are use of compressor waste heat and heat recovered from the stripper condenser to regenerate post-combustion CO2 capture solvent, preheat boiler feedwater and predry high-moisture coals. The overall conclusion from the oxyfuel simulations is that thermal integration of compressor heat has the potential to improve net unit heat rate by up to 8.4 percent, but the actual magnitude of the improvement will depend on the type of heat sink used and to a lesser extent, compressor design and coal rank. The simulations of a unit with a MEA post combustion capture system showed that thermal integration of either compressor heat or stripper condenser heat to preheat boiler feedwater would result in heat rate improvements from 1.20 percent to 4.19 percent. The MEA capture simulations further showed that partial drying of low rank coals, done in combination with feedwater heating, would result in heat rate reductions of 7.43 percent for PRB coal and 10.45 percent for lignite.

Research and Education of CO{sub 2} Separation from Coal Combustion Flue Gases with Regenerable Magnesium Solutions

Research and Education of CO{sub 2} Separation from Coal Combustion Flue Gases with Regenerable Magnesium Solutions
Author:
Publisher:
Total Pages:
Release: 2013
Genre:
ISBN:

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A novel method using environment-friendly chemical magnesium hydroxide (Mg(OH)2) solution to capture carbon dioxide from coal-fired power plants flue gas has been studied under this project in the post-combustion control area. The project utilizes the chemistry underlying the CO2-Mg(OH)2 system and proven and well-studied mass transfer devices for high levels of CO2 removal. The major goals of this research were to select and design an appropriate absorber which can absorb greater than 90% CO2 gas with low energy costs, and to find and optimize the operating conditions for the regeneration step. During the project period, we studied the physical and chemical characteristics of the scrubbing agent, the reaction taking place in the system, development and evaluation of CO2 gas absorber, desorption mechanism, and operation and optimization of continuous operation. Both batch and continuous operations were performed to examine the effects of various parameters including liquid-to-gas ratio, residence time, lean solvent concentration, pressure drop, bed height, CO2 partial pressure, bubble size, pH, and temperature on the absorption. The dissolution of Mg(OH)2 particles, formation of magnesium carbonate (MgCO3), and vapor-liquid-solid equilibrium (VLSE) of the system were also studied. The dissolution of Mg(OH)2 particles and the steady release of magnesium ions into the solution was a crucial step to maintain a level of alkalinity in the CO2 absorption process. The dissolution process was modeled using a shrinking core model, and the dissolution reaction between proton ions and Mg(OH)2 particles was found to be a rate-controlling step. The intrinsic surface reaction kinetics was found to be a strong function of temperature, and its kinetic expression was obtained. The kinetics of MgCO3 formation was also studied in terms of different pH values and temperatures, and was enhanced under high pH and temperatures.