Document Type:Technical Results
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This report analyses public domain availability data from Integrated Gasification Combined Cycles (IGCC) and other significant coal gasification facilities, backed up with additional data gained from interviews and discussions with plant operators. Predictions for the availability of future IGCCs are made based on the experience of the existing fleet and anticipated improvements from the implementation of lessons learned.
ObjectiveA simple "checklist" approach to the elimination of problems identified in existing plants is insufficient to achieve availability levels of 85 to 90%. It is necessary to include availability as a key objective of the project team from the inception. Key plant operations and maintenance personnel must be identified at an early stage and must be involved at every stage of the design. The design process must recognize the "chemical plant" nature of an IGCC and include many of the features common in the chemical industry (HAZOP, Process Safety Management etc.).
ApproachData were first gleaned from more than 90 reports or presentations on gasification plants available in the public domain. These reports are listed in the literature references section of this report. These data were supplemented by private interviews with gasification plant operations staff and plant visits to selected gasification facilities. The compiled data were then analyzed to identify underlying trends or cause of unavailability.
ResultsBeginning in the mid-1990's, a number of IGCC plants were built and operated so that a base of experience has begun to develop. These plants have confirmed the exceptionally low (SOx, NOx, particulate matter and, if required, mercury) or less toxic (waste water and slag) emissions from this technology. They have also confirmed the expectations of improved thermal efficiency, even if parallel advances in other coal-based technologies have not allowed this to be translated into the competitive advantage originally contemplated.
However, the reliability and availability of demonstration IGCC's has not been as high as desired by the power industry or as actually achieved by gasification plants operating in the chemical and refining industries. The success of IGCC in realizing its potential is therefore also dependant on establishing the reasons for this reduced reliability and taking appropriate steps to improve it.
It is striking that much of the causes for reduced availability originate in areas where it could be assumed that the technology was established. The data for four IGCC units over the period 2001–2003 shows that on average the units were out of service 17.2% of the time due to issues with the combined cycle power block, 6.2% of the time due to the gasification equipment, 3.3% of the time due to issues with the air separation units, and 1.6% of the time due to gas treating equipment, for a total outage time of 28.2%. This corresponds to an average availability of 71.8%.
Furthermore in the gasification area there is a mixture of issues which might have been avoidable and others that are inherent to the process (for example, syngas cooling).
Based on the state of current technology, it is expected that an availability of at least 85% could be reached. An increase in the availability of gas turbines could increase this further to about 90%.
Application, Value and UseThe report will be a great value to any organization considering the deployment of IGCC technology. It is also of use to organizations considering the deployment of other advanced coal generation technologies who wish to conduct a "due diligence" review of the alternatives in order to defend their technology choice for a coal power plant.
EPRI PerspectiveThe CoalFleet IGCC RD&D Augmentation Plan (EPRI Technical Update 1013219 issued in Jan. 2007) identified improvement in IGCC availability as a key near-term RD&D task. The Augmentation Plan also called for more detailed quantification of the causes of IGCC unavailability as the first step in the plan to improve availability. One must first know what is causing the problem before a solution can be developed.
This report, the first of a two-part set which will address reliability-availability-maintainability (RAM) expectations for new IGCCs, fulfills the first step in the CoalFleet IGCC RAM improvement strategy. It compiles the availability experience of existing coal-based IGCCs and supplements that with relevant availability information from IGCCs designed for liquid petroleum residues and coal gasification plants which produce chemicals rather than power. EPRI believes it is the most comprehensive compilation of IGCC availability data ever assembled.
A companion report, being assembled by Strategic Power Systems, Inc. (SPS), will develop predictions for the reliability and availability of new IGCC designs based on a section-by-section model of the IGCC. The models rely on the database of availability information compiled in this first report as well as the extensive ORAP® database on combustion turbines and combined cycle maintained by SPS. The IGCC design reflect the standard configurations for a nominal 600 MW IGCC defined in the CoalFleet User Design Basis Specification – Version 4 (EPRI Technical Report 1012227 issued in Dec. 2006) for both GE Energy and Shell coal gasification technology.
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