The report gives results of an evaluation of the performance (over a 2-year period) of a full-scale flue gas desulfurization (FGD) unit to demonstrate the Wellman-Lord/Allied Chemical process. The process is regenerable, employing sodium sulfite wet scrubbing, thermal regeneration of the spent scrubber solution, and reduction to elemental sulfur of the recovered SO2. Tests indicate that 89-90% of the SO2 can be removed readily from the flue gas in a long-term dependable manner. However, best performance of the regeneration system for 1 year was limited to only 61% of the time called upon to operate. Major operating limitations were reduction unit problems, but unscheduled evaporator and booster blower outages, as well as start-ups and shutdowns, also contributed to downtime. As expected, process energy requirements, primarily for thermal regeneration of the scrubber solution and subsequent recovery of SO2, were quite large, amounting to 12% of the boiler heat input derived from fuel. Actual annualized operating cost was 14.9 mills/kWh, at 1978 prices for raw materials and utilities. Credits for the sale of byproduct sulfur were only 0.2 mills/kWh. The reported operation and performance occurred after some modification to the boiler to increase inlet flue gas temperature and after implementing FGD plant improvements identified during initial operation.