Session: 04-47 Combustor Design V

Paper Number: 127690

127690 - Water-Based Yttrium Additive for Hot Corrosion Inhibition in a Gas Turbine 

Hot corrosion is a substantial challenge for operating gas turbines (GT) running on vanadium-laden liquid fuels. Vanadium exists with significant concentration in low-grade fuels (crude oil and heavy fuel oil) in an organometallic form. This prevents its elimination through upstream fuel treatment via water wash. Upon combustion, vanadium combines with oxygen forming vanadium pentoxide (V2O5) which is highly corrosive and has a melting point (681°C) below the hot gas path (HGP) operating temperature. This causes V2O5 to melt down and attack the HGP parts in what is so called hot corrosion. In order to mitigate the potential hot corrosion of vanadium on gas turbine parts, a corrosion inhibitor is injected upstream with the fuel. The role of the corrosion inhibitor is to chemically react with V2O5 by preferentially combine with the inhibitor and form non-harmful chemical molecules “ash” with a higher melting point.

Magnesium-based inhibitors are commonly used in gas turbine application. Magnesia (MgO) typically reacts with V2O5 to form magnesium vanadate Mg3V2O8, which has a higher melting point (1212°C) than V2O5. However, Mg3V2O8 melting point is lower than the operating point of the HGP of gas turbines, thus magnesium vanadate sticks on the HGP blades causing the output of the gas turbine to deteriorate with longer operation. Consequently, water wash for the turbine is required to remove the stuck ash off the turbine blades to recover the output. This results in a decrease in the gas turbine availability. In addition, to enable water wash, the gas turbine performance must be derated by decreasing its firing temperature to reduce the stickiness of the ash, which results in a significant loss of gas turbine output and efficiency.

To overcome the degradation and derate challenges that accompany the use of Mg-based inhibitors, a yttrium-based inhibitor was developed and tested. The byproduct of yttrium reaction with vanadium is yttrium orthovanadate (YVO4) which is an ash with melting point of 1810C. This increased melting point warrants less ash accumulation on the turbine blades, thus avoiding output degradation, and reducing the water-wash cycle, i.e., improving availability. In addition, the derate is not required, thus avoiding output and efficiency penalties.

A water-based version of the yttrium-based inhibitor was manufactured and tested in the laboratory under temperatures that mimic GT conditions. Ash and hot corrosion tests were conducted for the Y-based inhibitor, and the results were compared with the results obtained from using Mg-based inhibitor. The results proved that yttrium inhibitor achieved superior performance in comparison with magnesium inhibitor in terms of less ash formation and higher hot corrosion resistance.

Furthermore, yttrium-based inhibitor was tested in an E-class gas turbine pilot. The performance data was acquired for two gas turbines, one that utilizes Y-inhibitor, and another that utilizes Mg-inhibitor, for comparison purposes. The performance results proved the superiority of yttrium as an inhibitor in comparison to magnesium. In this paper, we will present the Y-inhibitor corrosion and ash accumulation lab testing. In addition, we will present Y-inhibitor pilot testing including discussion about injection arrangement, testing planning and results.

Presenting Author: Hatem Selim GE Gas Power

Presenting Author Biography: Ph.D. in mechanical engineering from University of Maryland College Park
Lead engineer combustion and fuels at GE Gas Power since 2016

Authors:

Hatem Selim GE Gas Power
Baha Suleiman GE Gas Power
Alaaeldin Dawood GE Gas Power
Pierre Montagne General Electric Company
Sundar Amancherla General Electric Company
Abdurrahman Khalidi Covanta