Method for CFD facilitated pressure rise calculation due to deflagration in heat recovery steam generator

Abstract

For combined cycle operations, especially during startup and shutdown, safety concerns have always been the top priority. Residual fuels can escape to and accumulate in the downstream heat recovery steam generator (HRSG) if appropriate purge is not taken, which may cause deflagration, an explosion at subsonic condition, during startup when heat source exists. Residual fuel deflagration will lead to pressure rise and therefore, structural and or tube damages depending on the level of pressure increase. Therefore, a careful study of the residual fuel distribution in HRSG and the pressure rise due to possible deflagration is wanted.Historically, thermodynamics relationships and chemical equilibrium calculations are used to estimate the pressure rise. These approaches either assume that all fuel energy is converted into heat, or make assumptions on the amount of fuel in chemical equilibrium that contributes to the pressure rise. These assumptions tend to overestimate the pressure rise. With the development of computational fluid dynamics (CFD) simulation, a more accurate prediction of the fuel concentration in HRSG during transient startup and/or shutdown process is possible. The local fuel concentrations can now be calculated and therefore, how much fuel that are within the explosion limits and contribute to the pressure rise can be detected readily.This article presents the transient CFD modeling results of residual fuel concentration in a typical HRSG configuration during a gas turbine/combined cycle startup failure process. The article then refines the adiabatic mixing model with the predicted local fuel concentrations to provide a better estimation of the pressure rise due to deflagration.

A comprehensive review to study and implement solar energy in dairy industries

“…Since dairies routinely keep running for the duration of the day, reliably, the enthusiasm for cooling is high and driving forward ideal things for CHP. For instance, the heat from sources, the fumes gas would be utilized a bit of a tri-generation plan to make cooling from waste heat [70].…”