Evaluation of Air Filtration Options for an Industrial Gas Turbine

Abstract

Gas turbines ingest large quantities of air during operation. As a result, large quantities of foreign particles ranging in size from smoke (0.01 to 1.0 micron) to pollen (10 micron) enter the unit and can contribute to both fouling and erosion depending on particle size. Fouling and erosion both lead to reductions in unit output and efficiency resulting in increased operational cost. Operators have historically combatted fouling through a combination of online water washes, more effective off-line water washes, and air filtration. As is the case with almost all engineering problems, the trade-off between the cost and effectiveness of these methods must be evaluated. Online washing is somewhat effective but has led to first stage blade erosion and unit trips in some cases. Off-line washing is more effective at cleaning the unit, but requires the unit to be shut down for extended periods of time. Air filtration can help prevent foreign particles from entering the unit, but higher efficiency filters are generally associated with a larger inlet pressure drop, leading to decreased unit output; this is balanced against reduced fouling rates. These tradeoffs between the costs associated with higher efficiency filters and the frequency of compressor washing need to be evaluated on a plant-by-plant basis to determine the best combination of air filtration and compressor washing programs. This paper presents a field study carried out to determine the effectiveness of high efficiency filters in preventing compressor fouling. Fourteen units at four sites were monitored over a 9 month to 3 year time period to determine the changes in unit performance and the impact of water washes on unit performance for both pre and final filters of lower and higher efficiency ratings. Results to date indicate that higher efficiency filters are effective at reducing the need for off-line water washes and potentially reduce life-cycle cost. Reduced output from the higher pressure drop, high efficiency filters is offset by the better performance retention offered from reduced fouling rates.

Experimental Assessment of Fouling Effects in a Multistage Axial Compressor

“…Looking at the data, the pressure ratio values appear randomly dispersed and very similar to the data reported in the literature related to on-field detections [7,8]. The linear trend used for interpolating the data is adopted according to the literature [13] and allows the definition of the compressor performance drop.…”

“…This technique is adopted mainly for studying the deposition phenomenon of cold and hot gas turbine sections [2 -4]. For this reason, the exposure time adopted in the present investigation is 30 min that covers about 500 operating hours of an actual installation [8].…”

“…Due to this, power units are affected by deposits that develop over time, reducing the operability of the engine [6,7]. On-field detections have revealed that the fouling issue affects the unit performance despite the presence of filtration systems [8] and, only with a periodic (frequent) online washing operation, the reliability of the engine remain acceptable. During the machine overhaul, inspections of the deposits are rarely reported [1, 9 -11], and, when provided, the details useful for relating the pattern to the operating conditions of the units are missed.…”

Off-line washing effectiveness on a multistage axial compressor

“…The concentration of natural and/or artificial micro-sized particles, together with the air humidity, are those of the most critical variables on the fouling rate [7]. Literature data have revealed that the fouling issue affects the unit performance despite the presence of filtration systems [8,9] and, only with a periodic (frequent) online washing operation [5,10,11], the reliability of the engine remains acceptable.…”

A Compressor Fouling Review Based on an Historical Survey of ASME Turbo Expo Papers

“…These applica- 103 tions are characterized by the contemporary presence of erosion 104 and fouling phenomena [6][7][8]. 105 One of the first reports on gas turbine operation in a power plant 106 can be found in Carameros's study [9]. This is a summary of El 107 Paso Natural Gas Company's operating experience, covering the 108 design and operating problems encountered during the period 109 between September 1952 and January 1956.…”