Short-term Evaporative Loss Estimation from Atmospheric Storage Tanks
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This API Technical Report provides methods for estimating short-term evaporative losses from atmospheric storage tanks.
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Research summary
Key Insights: Short-term Evaporative Loss Estimation from Atmospheric Storage Tanks
This API Technical Report introduces a standardized methodology for estimating peak, short-term evaporative emissions from atmospheric storage tanks, crucial for accurate risk assessment and regulatory compliance.
Research Focus
This research addresses the limitations of traditional annual or monthly averaged emission calculations, which can significantly underestimate peak emissions during short durations like hours or days. For industries like oil and gas, petrochemical, and fuel storage, accurately quantifying these high-emission events is vital for process safety assessments, determining the need for control technologies, and ensuring compliance with air permitting requirements. The report develops a methodology specifically for estimating "reasonable worst-case" short-term hourly emissions from individual tanks and tank batteries.
What the Research Found
Finding 1: Need for Short-Term, Worst-Case Emission Data
Traditional emission estimation methods often rely on long-term averages, failing to capture the higher emission rates that can occur over short periods. This report introduces a standardized approach to calculate these peak emissions, which are critical for scenarios like process safety analyses and siting evaluations.
Finding 2: Methodology for Individual and Battery Emissions
The report provides distinct methodologies for estimating short-term losses from both single tanks and collections of tanks (batteries). This allows for more granular assessments, enabling engineers to pinpoint potential high-risk sources within a facility.
Finding 3: Focus on Routine Operations, Not Upset Conditions
The developed methodology is designed for routine tank operations with properly functioning equipment. It explicitly excludes emissions related to maintenance, roof landings, or equipment malfunctions, ensuring the estimates reflect expected worst-case scenarios under normal operating conditions.
Why It Matters for Practice
This report fundamentally shifts how engineers should approach short-term emission assessments. It moves beyond average-case scenarios to provide a framework for understanding potential peak events. This is particularly important for:
- • Process Safety: Identifying potential risks from elevated hazardous air pollutants (HAPs) or approaching lower explosive limits (LEL) during specific, high-emission periods.
- • Regulatory Compliance: Providing a defensible methodology for demonstrating compliance with air permits that may require worst-case hourly emission rates, especially for New Source Performance Standards (NSPS) and New Source Review (NSR) applicability.
- • Control Technology Justification: Quantifying the need for additional emission controls by demonstrating the impact of worst-case short-term events.
Putting It Into Practice
Based on these findings, professionals should consider:
- • Re-evaluating existing emission estimates: Determine if current annual averages adequately represent short-term risks.
- • Implementing the API TR 2576 methodology: Utilize the standardized approach for estimating reasonable worst-case short-term hourly emissions for process safety reviews and air permit applications.
- • Integrating with dispersion modeling: Use these short-term emission estimates as inputs for