The EPA’s recently published Affordable Clean Energy (ACE) Rule identifies heat rate improvements as the Best Source for Emissions Reductions (BSER) to control CO2. ACE does not set any emissions limits, rather it outlines the framework for states to use to set achievable unit level heat rate improvements (HRI) at the plants.
The ACE Package includes three distinct, separate, and independent actions:
States must set source-specific standards of performance - based only on emissions limitations achievable by six candidate technologies and best O&M practices. See the chart below:
| HRI Measure | <200 MW | 200-500 MW | > 500 MW | |||
| Min | Max | Min | Max | Min | Max | |
| Neural Network / Intelligent Sootblowers |
0.5 | 1.4 | 0.3 | 1.0 | 0.3 | 0.9 |
| Boiler Feed Pumps | 0.2 | 0.5 | 0.2 | 0.5 | 0.2 | 0.5 |
| Air Heater & Duct Leakage Control |
0.1 | 0.4 | 0.1 | 0.4 | 0.1 | 0.4 |
| Variable Frequency Drives |
0.2 | 0.9 | 0.2 | 1.0 | 0.2 | 1.0 |
| Blade Path Upgrade (Steam Turbine) |
0.9 | 2.7 | 1.0 | 2.9 | 1.0 | 2.9 |
|
Redesign / Replace |
0.5 | 0.9 | 0.5 | 1.0 | 0.5 | 1.9 |
| Improved Operating & Maintenance (O&M) Practices |
Can range from 0 to > 2.0% depending on the O&M practices |
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Source: EPA
2018 – EPA published proposed ACE Rule
2019 – EPA published final ACE Rule
2022 – States are required to establish standards of performance for each designated facility within their jurisdiction and submit state plans to EPA for approval
2019 to 2024 – Compliance schedules for designated facilities must initiate within 24 months after a state plan submission. If completeness schedule initiates beyond 24 months, increments of progress must be included for those designated facilities.
Plant owners may choose any means to improve heat rate, not just the State’s recommendations, nor the six listed Best System of Emissions Reduction (BSER) technologies. B&W can help you support ACE Rule requirements and other efficiency improvements with the technologies shown below.
Units that are cycled or operate under low load conditions present unique challenges in optimizing plant heat rate. Retrofits and modifications are available to minimize the impacts of cycling on boiler systems.
Optimizes boiler heat absorption and sootblower steam consumption; minimize exit gas temperature and stack losses
Reduces boiler exit gas temperature; may affect SCR operation
Performance testing can identify various O&M improvements at the plants
Air heater and boiler setting leakage degrades AH performance, increases UBC, and requires operation at higher total excess air
Allows fans to operate more efficiently; most significant efficiency gain potential during low load operation
Reduces power consumption
Improves coal fineness, reduces motor power consumption
Permits increased load change rate capability; extends reheat steam temperature control range (better low load heat rate)
Extends steam temperature control range and fuel flexibility
Reduces total excess air and unburned carbon levels; maintains or reduces NOx and CO emissions
