Volatilization/Condensation of Alkali Salts in a Pressurized Fluidized Bed Coal Combustor/Gas Turbine Combined Cycle

Spacil, H. S.; Luthra, Krishan L.

doi:10.1149/1.2124391

Cited by 30 publications

(21 citation statements)

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“…However, the new model shows that the Superoxides 4.0 X 10"' 1.6 X 10"'^N ew code 16.4 X 10"' 5.3 X 10"' 1.8 X 10"' 1.0 X 10"" 31.0 X 10"' 7.3 X 10"' 3.2 X 10"' 2.6 X 10"'m ake a significant contribution, being intermediate in concentration between the chlorides and the hydroxides.…”

Section: Calculations For a High Chlorine Coalmentioning

confidence: 93%

“…Gas turbines normally operate with clean fuels such as natural gas whereas coal-derived gases contain various impurities including alkali salts, which can deposit on the turbine blades causing corrosion [4,5]. In some gasification systems, principally those using oxygen-blown gasifiers, the fuel gas is cooled and cleaned with aqueous solvents before combustion; in these systems, most of the alkali salts are removed before the gas turbine.…”

Section: Introductionmentioning

confidence: 99%

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Deposition of Corrosive Alkali Salt Vapors on the Blades of Gas Turbines Fueled by Coal-Derived Syngases

Young

Tabberer

Fackrell³

2013

Journal of Engineering for Gas Turbines and Power

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Many proposed clean coal technologies for power generation couple a gasification process with a gas turbine combined cycle unit. In the gasifier, the coat is converted into a syngas which is then cleaned and fired before entering the turbine. A problem is that coat-derived syngases may contain alkali metal impurities that combine with the sulfur and chlorine from the coal to form salts that deposit on the turbine blades, causing corrosion. This paper describes a new model, applicable to most types of coal, for predicting the dewpoint temperatures and deposition rates of these sodium and potassium salts. When chtorine is present the main atkati species in the mainstream gas flow are the chtorides; but when chlorine is absent, the Superoxides dominate. However, because the high-pressure turbine blades are film-cooled, they are at much lower temperatures than the mainstream gas flow and analysis then shows that the deposit is composed almost entirely of the sulfates in either liquid or solid form. This is true whether or not chlorine is present. Detailed calcutations using the new model to predict the alkali salt deposition rates on three stages of an example utility turbine are presented. The calculations show how the dewpoint temperatures and deposition rates vary with the gas-phase chlorine and sulfur levels as well as with the concentrations of sodium and potassium. It is shown that the locations where corrosion is to be expected vary considerably with the type of coal and the levets of impurities present.

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Section: Calculations For a High Chlorine Coalmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Deposition of Corrosive Alkali Salt Vapors on the Blades of Gas Turbines Fueled by Coal-Derived Syngases

Young

Tabberer

Fackrell³

2013

Journal of Engineering for Gas Turbines and Power

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“…However the condensed salt is very corrosive. Numerous studies have been conducted concerning the formation, vapor pressure, and condensation of sodium sulfate in gas turbine engines (26)(27)(28)(29)(30)(31).…”

Section: Salt Depositionmentioning

confidence: 99%

Advanced turbine design for coal-fueled engines. Topical report, Task 1.6, Task 1.7

Bornstein¹

1992

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Section: Salt Depositionmentioning

confidence: 99%

Advanced turbine design for coal-fueled engines

Bornstein¹

1992

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The objective of this task is to perform a technical assessment of turbine blading for advanced second generation PFBC conditions, identify specific problems/issues, and recommend an approach for solving any problems identified. A literature search was conducted, problems associated with hot corrosion defined and limited experiments performed. (1) The conditions that favor sulfidation corrosion are present in PFBC turbines. Sulfidation corrosion occurs in industrial, marine and aircraft gas turbine engines and is due to the presence of condensed alkali (sodium) sulfates. The principle source of the alkali in industrial, marine and aircraft gas turbine engines is sea salt crystals. The principle source of the sulfur is not the liquid fuels, but the same ocean born crystals. Moreover deposition of the corrosive salt occurs primarily by a non-equilibrium process. Sodium will be present in the cleaned combusted gases that enter the PFBC turbine. Although equilibrium condensation is not favored, deposition via impaction is probable. (2) Accelerated oxidation associated with the presence of chlorine or chlorides is not anticipated. Marine gas turbines operate in sodium chloride rich environments without experiencing the accelerated attack noted in coal fired boilers where condensed chlorides contact metallic surfaces. Gaseous mixtures of sodium chloride and air are reported to mitigate sufidation corrosion. (3) Calcium sulfate can be an aoaressive corrodent, The sulfates of calcium and magnesium are the products of the reactions used to control sulfur. Based upon industrial gas turbine experience and laboratory tests, calcium and magnesium sulfates are, at temperatures up to 1500°F (815°C), relatively innocuous salts. In this study it is found that at 1650°F (900°C) and above, calcium sulfate becomes an aggressive corrodent. (4) The ternary sulfates of calcium, magnesium and sodium are very aggressive corrodents. Calcia and magnesia are used to capture the oxides _,I sulfur. The presence of sodium and the formation of sulfates can lead to the formation of corrosive salts which will attack turbine components. (5) The anticipated materials for advanced DOE engines are the high temperature single crystal alloys used in advanced aircraft gas turbines. A noteworthy observation is that th6 single crystal alloy appears to be more resistant to the combined calcium-magnesium-sodium sulfate corrosion that the industrial alloys developed to resist sulfidation corrosion. The resistance of the current families of coatinas with respect to the mixed sulfate corrodentis not v known, (6) Engine manufacturers establish parameters that relate turbine ai,"foil life with laboratory data. The data when used to rank materials is generally in agreement. However, the deposition of the corrosive salt is a non-controllable variable which differs from machine to machine. Therefore improvements in life associated with material selection by one manufacturer need not translate to another manufacturer. Improvements in life are related to the understa...

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Volatilization/Condensation of Alkali Salts in a Pressurized Fluidized Bed Coal Combustor/Gas Turbine Combined Cycle

Cited by 30 publications

References 0 publications

Deposition of Corrosive Alkali Salt Vapors on the Blades of Gas Turbines Fueled by Coal-Derived Syngases

Deposition of Corrosive Alkali Salt Vapors on the Blades of Gas Turbines Fueled by Coal-Derived Syngases

Advanced turbine design for coal-fueled engines. Topical report, Task 1.6, Task 1.7

Advanced turbine design for coal-fueled engines

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