Evaporative Loss from the Cleaning of Storage Tanks
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This technical report addresses the issue of evaporative loss during the cleaning of storage tanks.
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Research summary
Key Insights: Evaporative Loss from the Cleaning of Storage Tanks
This API technical report provides engineers and operations personnel with a standardized methodology to quantify evaporative hydrocarbon losses during storage tank cleaning operations.
Research Focus
This research addresses the critical need for accurate estimation of volatile organic compound (VOC) emissions generated specifically during the cleaning of storage tanks, a process often associated with significant environmental releases. Understanding these emissions is crucial for compliance with environmental regulations, optimizing cleaning procedures, and accurately assessing the environmental footprint of tank maintenance activities. The study developed and validated a methodology for quantifying these losses across various tank types and cleaning stages.
What the Research Found
Finding 1: Distinct Emission Stages Identified
The report breaks down evaporative loss into distinct phases: standing idle emissions, vapor space purge emissions, sludge removal emissions, and refilling emissions. This segmentation is vital for targeted control strategies and accurate accounting.
Finding 2: Sludge Removal is a Major Emission Source
Sludge removal, particularly when involving diluents or free-standing liquid, is identified as a primary contributor to overall evaporative loss. The methodology provides specific equations to quantify these emissions based on vapor concentration.
Finding 3: Methodology for Quantifying Losses Developed
The report offers a detailed, step-by-step estimation method, including specific calculation procedures and necessary input parameters for different tank configurations and cleaning scenarios. This provides a consistent framework for practitioners.
Why It Matters for Practice
This research moves beyond generalized emission factors for tank storage by focusing specifically on the dynamic and often higher-emission events of tank cleaning. It challenges the assumption that emissions are solely a function of tank type and fill level, highlighting the significant impact of the cleaning process itself. This provides an opportunity to develop more precise environmental impact assessments and to justify the implementation of specific emission control technologies during cleaning.
Putting It Into Practice
Based on these findings, professionals should consider:
- • Segmenting emission calculations: Treat each cleaning phase (idle, purge, sludge removal, refilling) separately for more accurate total emission estimates.
- • Prioritizing sludge removal controls: Recognize sludge removal as a critical emission point and implement appropriate vapor capture or control measures during this phase.
- • Utilizing the proposed methodology: Adopt the standardized estimation method for consistent and defensible emission calculations, particularly for regulatory reporting.
- • Considering diluent impact: Evaluate how the use of cleaning diluents can affect vapor generation and associated emissions.
Limitations to Note
The report focuses on estimation methodologies and does not prescribe specific control technologies. The accuracy of the estimations is dependent on the quality of input data regarding tank conditions, product properties, and cleaning procedures.