Economic Optimization of Inlet Air Filtration for Gas Turbines

Abstract

Selecting the appropriate level of filtration for a gas turbine helps to minimize overall unit costs and maximize net revenue. When selecting a filter type and configuration, one must consider the initial costs, operational costs, and ongoing maintenance costs for both the filter and corresponding impacts on unit performance. Calculations are complex, and a fully functional framework is needed to properly account for all aspects of the life cycle and provide an opportunity to optimize filter selection and water wash scenarios for specific plant operating conditions. Decisions can generally be based on several different criteria. For instance, one may wish to minimize maintenance costs, maximize revenue, minimize fuel consumption, etc. For criteria that can be expressed in monetary terms, Life Cycle Cost Analysis (LCCA) is a means to simultaneously consider all criteria and reduce them to a single parameter for optimization using present value arithmetic. To be practically applied, the analysis must include all the significant inputs that would have an impact on the relative comparison between alternatives, while excluding minor inputs that would unduly add to complexity. This paper provides an integrated, quantitative, and transparent approach to life cycle cost analysis for gas turbine inlet filtration. Most prior art tends to focus either on how to perform the life cycle cost analysis (with simplified assumptions on the impact of filtration on performance), or on a specific technical aspect of filtration such as filter efficiency and performance, the impact of dust on compressor blading and fouling, or the impact of fouling on overall gas turbine performance. Many of these studies provide useful insight into specific aspects of gas turbine degradation due to fouling, but make simplifying assumptions that can lead to inaccuracies in application. By heavily leveraging prior work, this paper provides the reader with an overview of all aspects of the functionality required to perform such a life cycle analysis for gas turbine filtration. This work also serves as a technical summary of the underlying physics models that lead to the development of EPRI’s Air Filter Life-Cycle Optimizer (AFLCO) software. The software tool provides a method to account for the influence of gas turbine type, operating conditions, load profile, filtration choices, and wash type and frequency on overall life-cycle costs. The AFLCO tool is focused on guiding the user to make optimum filter selections and water wash scheduling, accounting for all the significant parameters that affect the economic outcome. Revenue and cost quantities are considered simultaneously to determine the net present value of gross revenue minus filtration and water wash costs over a multiple year analysis period. The user defines the scenarios and the software displays the net present value (NPV) and present value difference between the scenarios. The preferred configuration from an LCCA perspective is that which yields the highest present value for net revenue. The user can iterate on multiple scenarios to seek further increases in NPV. The paper provides relevant example case studies to illustrate how LCCA evaluations of inlet air filters and water wash frequency can be applied to optimize gas turbine economic performance. The intent of the paper is to provide the user with a summary of prior work that can be integrated to provide a more holistic, complete life cycle cost analysis and describes the framework used within the AFLCO software. The underlying technical analysis in this paper can be applied to any life cycle cost analysis.