Gas Turbines Fired on Coal Derived Gases - Modelling of Particulate and Vapour Deposition

Abstract:

<p>This document is the final report for the project titled 'Gas Turbines Fired on Coal Derived Gases - Modelling of Particulate and Vapour Deposition'. This report is titled 'Alkali Salt Vapour Deposition on Gas Turbine Blades.'</p> <p>The following report describes the development of a computer program for calculating deposition rates of alkali salts from two-dimensional turbulent boundary layer flows on turbine blades. The description of the program was originally submitted as the Milestone 1 Report of the project. This description is included here, but with additional sections summarising the background and theoretical approach of the work and the application of the code to an example cleaner-coal turbine.</p> <p>The development and testing of the new code involved: <ol> <li>Conducting a literature search for thermochemical data on the alkali oxide/hydroxide system;</li> <li>Deriving appropriate thermochemical constants and parameters;</li> <li>Revising the existing models to incorporate the alkali oxides and hydroxides;</li> <li>Incorporating the new model into a computer program to estimate the boundary layer diffusion and surface deposition rates of the alkali salts;</li> <li>Performing sample test calculations with the new computer program.</li> </ol></p> <p>There is considerable potential for exploitation of the existing computer code. As it stands, the code should be of interest to those companies involved in the design and manufacture of the type of heavy-duty industrial gas turbine which will be required in the future for coal-fired operation. The main companies operating worldwide are General Electric in the United States, Alstom in the United Kingdom, Siemens in Europe, and Mitsubishi and Hitachi in Japan. The Whittle Laboratory at Cambridge University has close contact with most of these (and other) companies and it is proposed to investigate the possibilities for marketing of the code and establishing other consulting arrangements.</p> <p>There is also potential for further scientific development of the thermochemical modelling. Although attention has been confined in the present project to the salts of sodium and potassium and their behaviour in high temperature gas flows, the method of analysis is fairly general and could be extended to encompass other situations. For example, two problems of current interest which might respond to similar modelling techniques are the transport of corrosive vanadium salts to gas turbine blades in conventional gas turbines and corrosion of steam turbine blades by sodium salts present in the feedwater. In the United Kingdom, companies such as Rolls-Royce, Alstom and Siemens will be approached for discussion on the possibility of extending the modelling to deal with these and other technical problems.</p> This report is divided into the following sections: <ol> <li>Introduction</li> <li>Outline of the Theory</li> <li>The Computer Program 'VAPOURDEP'</li> <li>Testing and Validation of the Program</li> </ol> <p> The remainder of the report consists of a user manual for VAPOURDEP written by J.B. Young, and Appendices: <ul> <li>Appendix 1 - Equilibrium of Sodium and Potassium Species in the Gas Phase</li> <li>Appendix 2 - Species Conservation Equation</li> <li>Appendix 3 - Grid Generation</li> <li>Appendix 4 - Finite Volume Solution of the Species Continuity Equations</li> <li>Appendix 5 - Specification of the Initial Concentration Profiles</li> <li>Appendix 6 - Calculation of Mass Transfer Coefficients</li> <li>Appendix 7 - Equilibrium at the Gas-Deposit Interface</li> <li>Appendix 8 - Thermodynamic Properties</li> </ul></p>

Author(s):

Fackrell, J.E., Tabberer, R.J., Young, J.B. & Wu, Z