Evaporative Loss from Storage Tank Floating Roof Landings
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This technical report investigates and quantifies evaporative losses from the floating roof landings of storage tanks.
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Research summary
Key Insights: Evaporative Loss from Storage Tank Floating Roof Landings
This research provides engineers with a more accurate method to quantify evaporative losses from floating roof storage tanks, particularly when the roof is landed.
Research Focus
This technical report addresses the critical question of how to accurately estimate volatile organic compound (VOC) emissions from the landing and refloating of floating roofs in storage tanks. These emissions are significant for environmental compliance and product loss in the petroleum refining, chemical manufacturing, and bulk liquid storage industries. The study developed and refined calculation methodologies to account for various tank configurations and operating scenarios, moving beyond simplified assumptions.
What the Research Found
Finding 1: Landing Scenarios Significantly Impact Emissions
The research differentiates between tanks that are drained dry and those that retain a liquid heel when the floating roof is landed. This distinction is crucial because the presence of a liquid heel alters the vapor space and evaporation dynamics, leading to different emission rates.
Finding 2: Specific Models for Different Landing Conditions
Distinct models were developed for "standing idle" losses and "filling" losses under various landing conditions. This includes accounting for breathing losses in internal floating roof tanks with a heel, wind effects on external floating roof tanks with a heel, and clingage-related losses in dry tanks.
Finding 3: Refined Calculation Methods for Practical Application
The report presents detailed equations and calculation methods for estimating these losses, including considerations for tank bottom geometries like cone-down bottoms. This provides engineers with the tools to perform more precise loss estimations than previously available.
Why It Matters for Practice
This research challenges the assumption that floating roof tanks inherently minimize emissions under all conditions. It highlights that landing the roof, especially with a residual liquid heel, can be a significant source of VOCs. The findings empower environmental and process engineers to move from generalized estimates to data-driven calculations, enabling more accurate emissions reporting, better process optimization, and potentially identifying opportunities for emission reduction strategies. This can also inform tank design and operational procedures.
Putting It Into Practice
Based on these findings, professionals should consider:
- • Implementing the specific landing loss calculation methods presented in the report for tanks with and without liquid heels.
- • Re-evaluating existing emission inventories to incorporate these more refined calculations, especially for tanks where roofs are frequently landed.
- • Incorporating these methodologies into tank design and operational guidelines to minimize product loss and environmental impact during landing and refloating cycles.
Limitations to Note
The methodologies are based on specific assumptions and may require validation for unique tank designs or stored products not extensively covered. The report focuses on evaporative losses from the landing event itself, and other emission sources should be considered separately.