Plant Fund Scope: Ash Fouling Free Regenerative Air Pre-heater for Deep Cyclic Operation

To improve power plant efficiency and reliability, UKy-CAER is proposing a self-cleaning ash fouling free air pre-heater to increase the capacity of coal-fired power plants for load following due to the use of alternative energy sources, deep cyclic operation in particular. The proposed technology is transformative from the state-of-art regenerative heater with hot-air recycling or steam injection, and it will be accomplished by installing three sets of auto-controlled blind valves at the air inlet of the air preheater without any additional duct or blower. With program set with boiler load, whenever the load is below 50%, the inlet blind valve will be rotationally closed to provide a hot-temperature non-heat changing zone inside the air-preheater for condensate ammonia bisulfite/bisulfate re-evaporation, then transfer the adhesive fouling ash to loose dry ash, which will be cleaned by high temperature flue gas. The objective of the proposed project is to design, build and test a 0.25 MWth regenerative air heater at a coal-fired power plant. The effectiveness of auto-control blind valves will be investigated in terms of flue gas pressure drop across the air heater and the flue gas exhaust temperature versus the operating time. The optimal blind valves opening frequency and sequence will be determined during a year-long operation. If successful, the potential benefit to existing coal-fired power plants will be threefold with (1) the turn-down ratio of a coal-fired power plant could be as low as 25-30% of baseload to better position itself for grid load handling; (2) the high efficiency de-NOx can be achieved and maintained by relative high ammonia injection flowrate without the concern of air-preheater blockage resultant from ammonia bisulfite/bisulfate formation due to high ammonia slip; and (3) lower metal corrosion rate caused by ash fouling and SO2/SO3 condensation.