Turndown studies for utility fluidized-bed boilers. Final report

This report contains a series of analyses that evaluate the turndown potential of the EPRI 6 x 6 test facility and the TVA 20 MW FBC pilot plant by variation of the fluidization velocity. The basis of the analyses is a heat balance program that incorporates basic principles of thermodynamics and fluidization. The heat balance program is used to explain the interrelationship of operating variables of a fluidized-bed boiler and to predict the steady state operating conditions of the boilers over a range of loads. Turndown analyses were performed on two tube bundle designs for the EPRI 6 x 6 test unit including a nine drawer tube bundle designed for 8 ft/sec operation and a twelve drawer bundle for operation up to 12 ft/sec. This twelve drawer bundle was found to have reasonable turndown characteristics between 4 and 12 ft/sec. At a 20 inch static bed depth, for example, this bundle should operate between 1545 and 1620/sup 0/F at 3.2% O/sub 2/ for loads from 4 to 12 ft/sec. In addition to the two bundles studies, a tube bundle capable of a 3:1 turndown range with a minimum temperature variation was designed for the 6 x 6 test facility. Themore » tube bundle for the TVA 20 MW pilot plant was found to have excellent turndown characteristics between 4 and 8 ft/sec. For example, a 21 inch static bed should allow operation between 1541 and 1575/sup 0/F bed temperature at 3% O/sub 2/.« less