Derates and Outages Analysis - A Diagnostic Tool for Performance Monitoring of SaskPower’s Boundary Dam Unit 3 Carbon Capture Facility

Abstract

Establishing carbon capture and storage (CCS) as a viable carbon dioxide (CO2) emission mitigation strategy for various industries will require identifying and eliminating existing barriers to achieving desired performance. SaskPower’s Integrated Carbon Capture and Storage Project on Boundary Dam’s Unit 3 (BD3) began operations in October of 2014. By early December 2020, the facility had captured over 3.8 million metric tonnes of CO2. Although no small feat, the cumulative volume of CO2 captured by late 2020 does not reflect the expected cumulative capture volume considering the five-year operational window and the size of the capture facility. As with many “first of a kind” facilities, unforeseen barriers hindered the performance of the capture facility. A couple of challenges with CCS application to coal-fired power plants have been the lost capture potential due to power plant outages and derates (which limits flue gas availability to the capture island) and the performance of capture island. Capture operations stop during all outages of the power plant; this presents a constraint to be accommodated when applying CCS. Minimizing costs by improving capture island performance while also satisfying outage constraints is key. As CCS technologies seek increased deployment, not limited to electricity generation but to other industries as well, it is necessary to identify, review, and eliminate existing barriers of capture system performance. Performance evaluation is becoming increasingly important. Derate and outage analysis identifies areas of concern and provides a means for reporting performance. Such analysis helps to better understand how the process works and to identify process bottlenecks, for daily operation decisions as well as long term impacts.

This paper presents and explains fundamental concepts of data analysis to improve derates and outage analysis at BD3. An analytic model to evaluate the outages and derates of the coal-fired unit and the carbon capture facility is presented. The proposed model accounts for hourly data from the CO2 capture plant which was extracted from the OSI PI historian during the six-year operating period (October 2, 2014- October 1, 2020). The model describes how basic Microsoft Excel analysis can be used to detect outage and derate problems. Data analysis included: flue gas flow estimation; CO2 mol fraction; CO2 emissions, maximum theoretical amount of CO2 captured by the plant; and actual amount of CO2 capture by the plant.

Keywords: Boundary Dam, SaskPower, Microsoft Excel, Derates, Outages, Carbon Capture and Storage, Post Combustion Capture