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Simple Indirect Determination of Syngas Purging Success by Temperature Measurement

IP.com Disclosure Number: IPCOM000184141D
Original Publication Date: 2009-Jun-25
Included in the Prior Art Database: 2009-Jun-25
Document File: 3 page(s) / 113K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

Certain parts of a gas turbine system (such as fuel gas piping, combustor, combustion chamber, combustion turbine, exhaust etc.) have frequently to be cleaned from residual fuel gas in order to prevent the existence of flammable or even explosive gas mixtures. Such a cleaning is necessary after introduction of fuel gas into the mentioned parts of the engine, mainly after shutdown or failed starts of the engine. For some parts of the engine like the fuel injectors a “self-cleaning” capability has been proposed and implemented. The cleaning of piping and other larger cavities is usually carried out by purging, more specifically by "flow purging", where an inert gas is pumped through the system to be cleaned, thereby displacing the fuel gas. This results in a system filled with the aforementioned inert gas at a well-defined pressure, which therefore has frequently been used as an indicator. Such purging procedures are especially important for gas turbines fired with synthesis gases, since those fuel gases are highly toxic due to their CO content and highly explosive over a wide range of fuel/air mixture ratios due to their hydrogen content.

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Simple Indirect Determination of Syngas Purging Success by Temperature Measurement

Idea: Dr. Peter Kury, DE-Muelheim; Holger Hesse, DE-Muelheim; Dirk Haensel, DE-Muelheim

Certain parts of a gas turbine system (such as fuel gas piping, combustor, combustion chamber, combustion turbine, exhaust etc.) have frequently to be cleaned from residual fuel gas in order to prevent the existence of flammable or even explosive gas mixtures. Such a cleaning is necessary after introduction of fuel gas into the mentioned parts of the engine, mainly after shutdown or failed starts of the engine. For some parts of the engine like the fuel injectors a "self-cleaning" capability has been proposed and implemented.

The cleaning of piping and other larger cavities is usually carried out by purging, more specifically by "flow purging", where an inert gas is pumped through the system to be cleaned, thereby displacing the fuel gas. This results in a system filled with the aforementioned inert gas at a well-defined pressure, which therefore has frequently been used as an indicator. Such purging procedures are especially important for gas turbines fired with synthesis gases, since those fuel gases are highly toxic due to their CO content and highly explosive over a wide range of fuel/air mixture ratios due to their hydrogen content.

In order to achieve a sufficient purging the inert gas must be pumped sufficiently fast through the system to be cleaned in order to ensure a plug flow with as little intermixing of the inert gas and the fuel gas as possible. As a rule of thumb, a system is considered to be clean after three volume exchanges, i.e., after an amount of inert gas of three times the volume of the system to be cleaned has been pumped through that system.

This rule of thumb, however, is valid if the displacement of the fuel gas has been carried out fast enough not to allow significant interdiffusion. Therefore, an adaptation of the purge times to varying purge media supply pressure is desirable instead of using fixed values determined for nominal or minimum supply pressures.

In order to keep the purging time as short as possible for low inert gas consumption and engine operation delays, but long enough for a complete inertization of the piping and engine, a measurement is desirable that allows to check for the absence of fuel gas in the system to be cleaned. Such a measurement allows in addition a straightforward adaptation of purging parameters to varying purge media pressures.

A direct gas analysis would fulfill all requirements, yet it is technically very demanding (H2, N2, CO, H2O), cost-intensive, and potentially very slow if gas chromatographs with gas cooling and drying sequences are used. Therefore an indirect determination of the absence of the fuel gas by the measurement of any gas property that is distinctly different betw...