Development of a Dynamic Model and Control System for Load-Following Studies of Supercritical Pulverized Coal Power Plants

Traditional energy production plants are increasingly forced to cycle their load and operate under low-load conditions in response to growth in intermittent renewable generation. A plant-wide dynamic model of a supercritical pulverized coal (SCPC) power plant has been developed in the Aspen Plus Dynamics® (APD) software environment and the impact of advanced control strategies on the transient responses of the key variables to load-following operation and disturbances can be studied. Models of various key unit operations, such as the steam turbine, are developed in Aspen Custom Modeler® (ACM) and integrated in the APD environment. A coordinated control system (CCS) is developed above the regulatory control layer. Three control configurations are evaluated for the control of the main steam; the reheat steam temperature is also controlled. For studying servo control performance of the CCS, the load is decreased from 100% to 40% at a ramp rate of 3% load per min. The impact of a disturbance due to a change in the coal feed composition is also studied. The CCS is found to yield satisfactory performance for both servo control and disturbance rejection

The National Energy Technology Laboratory Annual Site Environmental Report for Calendar Year 2000

This Site Environmental Report was prepared by the Environment, Safety, and Health Division at the National Energy Technology Laboratory (NETL) for the U.S. Department of Energy. The purpose of this report is to inform the public and Department of Energy stakeholders of the environmental conditions at the NETL sites in Morgantown, West Virginia, and Pittsburgh, Pennsylvania. This report contains the most accurate information that could be collected during the period between January 1, 2000, through December 31, 2000. As stated in DOE Orders 5400.1 and 231.1, the purpose of the report is to: Characterize site environmental management performance; Confirm compliance with environmental standards and requirements and Highlight significant facility programs and efforts

Milliken Clean Coal Demonstration Project: A DOE Assessment

The goal of the U.S. Department of Energy's (DOE) Clean Coal Technology (CCT) program is to furnish the energy marketplace with a number of advanced, more efficient, and environmentally responsible coal-utilization technologies through demonstration projects. These projects seek to establish the commercial feasibility of the most promising advanced coal technologies that have developed beyond the proof-of-concept stage

US Liquefied Natural Gas (LNG) exports: boom or bust for the global climate?

Due to surging natural gas production, the United States is now a growing exporter of liquefied natural gas (LNG) to overseas destinations. However, the potential greenhouse gas implications from increased US natural gas remain unclear. Through a hybrid lifecycle energy strategy analysis, we investigate potential greenhouse gas scenarios of US LNG exports to Asia, the largest source of global LNG demand. We find that the climate impacts of US exports to China, Japan, India, and South Korea could vary tremendously. Annual global lifecycle emissions range from -32 to +63 million metric tons CO2e per billion cubic feet (Bcf) per day of exports. Despite this range, emissions are not likely to decrease and may increase significantly due to greater global energy consumption, higher emissions in the US, and methane leakage. However, international climate obligations are a critical uncertainty underlying all emissions estimates. Our results indicate the need for further research into quantifying the climate impacts of LNG exports, and energy exports more generally

Durable Zinc Oxide-Based Regenerable Sorbents for Desulfurization of Syngas in a Fixed-Bed Reactor

A fixed-bed regenerable desulfurization sorbent, identified as RVS-land developed by researchers at the U.S. Department of Energy's National Energy Technology Laboratory, was awarded the R&D 100 award in 2000 and is currently offered as a commercial product by Sued-Chemie Inc. An extensive testing program for this sorbent was undertaken which included tests at a wide range of temperatures, pressures and gas compositions both simulated and generated in an actual gasifier for sulfidation and regeneration. This testing has demonstrated that during these desulfurization tests, the RVS-1 sorbent maintained an effluent H2S concentration of <5 ppmv at temperatures from 260 to 600 C (500-1100 F) and pressures of 203-2026 kPa(2 to 20 atm) with a feed containing 1.2 vol% H{sub 2}S. The types of syngas tested ranged from an oxygen-blown Texaco gasifier to biomass-generated syngas. The RVS-1 sorbent has high crush strength and attrition resistance, which, unlike past sorbent formulations, does not decrease with extended testing at actual at operating conditions. The sulfur capacity of the sorbent is roughly 17 to 20 wt.% and also remains constant during extended testing (>25 cycles). In addition to H{sub 2}S, the RVS-1 sorbent has also demonstrated the ability to remove dimethyl sulfide and carbonyl sulfide from syngas. During regeneration, the RVS-1 sorbent has been regenerated with dilute oxygen streams (1 to 7 vol% O{sub 2}) at temperatures as low as 370 C (700 F) and pressures of 304-709 kPa(3 to 7 atm). Although regeneration can be initiated at 370 C (700 F), regeneration temperatures in excess of 538 C (1000 F) were found to be optimal. The presence of steam, carbon dioxide or sulfur dioxide (up to 6 vol%) did not have any visible effect on regeneration or sorbent performance during either sulfidation or regeneration. A number of commercial tests involving RVS-1 have been either conducted or are planned in the near future. The RVS-1 sorbent has been tested by Epyx, Aspen Systems and McDermott Technology (MTI), Inc for desulfurization of syngas produced by reforming of hydrocarbon liquid feedstocks for fuel cell applications. The RVS-1 sorbent was selected by MTI over other candidate sorbents for demonstration testing in their 500-kW ship service fuel cell program. It was also possible to obtain sulfur levels in the ppbv range with the modified RVS-1 sorbent

Carbon capture and storage: The ten year challenge

Carbon capture and storage (CCS) could play a significant role in reducing global CO2 emissions. It has the unique characteristic of keeping fossil carbon in the ground by allowing fossil fuels to be used, but with the CO2 produced being safely stored in a geological formation. Initial versions of the key component technologies are at a sufficient level of maturity to build integrated commercial-scale demonstration plants. If CCS is to reach its full potential to contribute to global efforts to mitigate the risk of dangerous climate change, it is urgent that a number of actions begin now in order to be ready for CCS deployment from around 2020 using proven designs that can be built in large numbers. This article discusses some key challenges for CCS, with a focus on development in the next decade, highlighting the potential benefits of a two tranche programme for integrated commercial-scale demonstration to develop proven reference plant designs and reviewing the importance of distinguishing between different classes of CCS according to their ability to significantly reduce CO2 emissions associated with fossil fuel use. It also identifies some ongoing CCS projects and initiatives and examines some possible implications of current policy discussions for technology development

Coordination of converter and fuel cell controllers

Load following fuel cell systems depend on control of reactant flow and regulation of DC bus voltage during load (current) drawn from them. To this end, we model and analyse the dynamics of a fuel cell system equipped with a compressor and a DC–DC converter. We then employ model-based control techniques to tune two separate controllers for the compressor and the converter. We demonstrate that the lack of communication and co-ordination between the two controllers entails a severe tradeoff in achieving the stack and power output objectives. A co-ordinated controller is finally designed that manages the air and the electron flow control in an optimal way. We demonstrate our results during specific and critical load changes around a nominal operating point. Although our analysis does not cover wide operating region, it provides insight on the level of controller co-ordination necessary in non-hybridized fuel cell power supply. The shut-down and start-up procedures will be investigated in future work. Copyright © 2005 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48762/1/1146_ftp.pd