Evaluation of Failsafe Performance for Hot Gas Filtration

Abstract

The Power Systems Development Facility (PSDF) is an engineering-scale demonstration facility of advanced coal-fired power systems and high-temperature, high-pressure gas filtration systems. The PSDF was designed at sufficient size so that system components can be evaluated and assessed in an integrated fashion to provide data for commercial scale-up. The PSDF is funded by the U.S. Department of Energy, the Electric Power Research Institute, Southern Company, Siemens Power Generation, Kellogg Brown & Root (KBR), Peabody Energy, Burlington Northern Santa Fe Corporation, and the Lignite Energy Council. Coal gasification at the PSDF is achieved with the KBR Transport Gasifier. Particulate laden gas exiting the gasifier is filtered by a downstream particulate control device (PCD). The PCD is a hot-gas filter that can hold up to 91 filter elements arranged in two tiers, with 36 elements in the top cluster and up to 55 elements in the bottom cluster. More than 30 different types of sintered metal powder, metal fiber, and ceramic filter elements have been tested. As of October 2006, the longest exposure of an individual element was approximately 8550 hours, which was achieved with a Pall iron aluminide sintered metal powder element. The outlet particle loading during normal operation has been reliably maintained within the lower limit of measurement resolution (routinely less than 0.1 ppmw). Downstream of each filter element is a failsafe device to prevent particulate leakage in the event of a filter element failure. The failsafe device is a small filter element or other type of particle collector and serves as a backup to the primary filter element. Demonstration of reliable failsafes is a critical factor in advancing hot gas filtration technology and increasing readiness for commercialization. A failsafe test program was developed at the PSDF to identify failsafe devices that would provide satisfactory protection of a gas turbine from particulate damage. In tests that simulated the failure of a single filter element, both metallic and ceramic failsafe devices were typically able to produce an outlet particle loading below 0.1 ppmw after an initial period of seasoning. From the overall particulate collection efficiency point of view, the failsafes tested showed promising results of protecting a gas turbine from being damaged by particles in the event of a filter failure. This paper focuses on failsafe performance and effectiveness in preventing particulate leaking through the PCD in the event of a filter element failure.