Diamond Vault

Project Diamond Vault is a large-scale post-combustion carbon capture project developed by Cleco Power to retrofit Madison Unit 3 at the Brame Energy Center in Boyce, Louisiana, a 635 MW coal and petroleum coke-fired power plant. The project was designed to capture CO₂ from the full flue gas stream of two circulating fluidized bed boilers using Mitsubishi Heavy Industries’ KM CDR Process with KS-21 amine solvent technology. At design conditions, the system targeted a 95 percent capture rate, processing approximately 15,429 tonnes of CO₂ per day and capturing about 4.28 million tonnes of CO₂ per year assuming an 80 percent capacity factor. Captured CO₂ would be compressed to dense phase and prepared for onsite geological sequestration, although transport and storage infrastructure were outside the FEED scope. The project advanced through feasibility, pre-FEED, and partial final FEED phases under a U.S. Department of Energy grant, with engineering led by Cleco, Mitsubishi Heavy Industries America, and Sargent & Lundy. The design included new flue gas ducting, absorber and regenerator systems, steam extraction from the host turbine for solvent regeneration, a dedicated once-through cooling water system sourced from Lake Rodemacher, new electrical substations and control systems, and full balance-of-plant integration. The capture facility was designed to operate across full-load and single-boiler turndown conditions while maintaining stable capture performance The FEED study produced an AACE Class 3 cost estimate with a total project capital cost of approximately $1.30 billion (2023 dollars), including contingency. Annual operating and maintenance costs were estimated at $121 million, resulting in a calculated cost of capture of $66 per tonne of CO₂, excluding transportation and storage costs and without applying 45Q tax credits. Despite technical feasibility and engineering maturity, Cleco halted the project during the final FEED phase due to unfavorable market conditions and project economics at the time of evaluation