Economic case study of ash reactivation for a generic 150 MWe Canadian circulating fluidized bed combustor

Abstract

Reactivation of circulating fluidized bed combustor (CFBC) ash (mainly spent Ca‐based sorbent) has received much attention over the past 25–30 years, because of the inefficiency of the sulphur capture process. A wet grinding reactivation process, developed by CANMET Energy Technology Centre‐Ottawa (CETC‐O) and University of Toronto, has recently shown promising results in pilot‐ and demonstration‐scale testing. The process is effective in improving CaO use and reducing limestone demand of the plant, while maintaining constant SO₂ capture in the combustor. Results of an Excel‐based economic analysis are presented for this wet grinding process used to reactivate CFBC ash for re‐injection into the combustor. AACE International Class 5 estimates are made of the capital, operating, and maintenance costs required for purchasing, installing and operating the off‐the‐shelf equipment. The impact of the system on limestone demand, ash production, and CO₂ generation is determined, and a financial comparison of the expected costs and benefits of the technology is made. The process is found to be economically attractive, with a conservative five‐year Internal Rate of Return of approximately 26%, without including potentially significant benefits from reduced CO₂ production. The paper presents a sensitivity analysis of key process variables and recommends future work to more accurately determine project costs.

Keywords:

• CFBC ash reactivation
• Wet grinding
• CaO utilization
• Sorbent reactivation economics