Cleaning Storage Vessels by Emulsifying Trace Hydrocarbons
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Solution Overview
Problem
Cleaning and degassing oil storage vessels are challenging due to the presence of sludge, which contains volatile organic compounds (VOCs) that are difficult to remove, especially when conventional methods leave residual VOCs that gradually release into the atmosphere, violating air quality standards like those set by Rule 1149.
Innovation Solution
A method involving a two-stage or one-stage treatment regime using surfactants to separate and emulsify oil from sludge, with the first stage using an oil release agent to float oil on the surface and the second stage employing an emulsifying agent to reduce VOC levels to 5,000 ppmv, measured as methane, before allowing atmospheric exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional cleaning techniques are used, then the cleaning process is simple and quick, but volatile organic compounds gradually release into the atmosphere violating air quality standards
Solution Approach 1:
The patent applies preliminary action by injecting a cleaning composition into the storage vessel before degassing to pre-treat the sludge and reduce VOC content. The composition is introduced and allowed to act on the sludge for a period before the vessel is opened, preventing harmful VOC release during the cleaning process while maintaining operational simplicity.
Solution Approach 2:
The cleaning composition acts as an intermediary substance that mediates between the sludge and the atmosphere. It chemically interacts with the VOC-containing sludge to transform harmful compounds into less volatile forms, thereby preventing direct release into the atmosphere while allowing the vessel to be opened for cleaning.
2Ease of operation
If the vessel is opened to atmosphere for cleaning, then cleaning access is improved, but VOC emissions increase violating regulatory standards
Solution Approach 1:
The cleaning composition is injected and allowed to act on the sludge before the vessel is opened to the atmosphere. This preliminary treatment reduces the VOC content and volatility of the sludge, enabling the vessel to be opened for cleaning operations while maintaining emissions below regulatory thresholds.
Solution Approach 2:
The cleaning composition changes the chemical parameters of the sludge, specifically reducing VOC concentration and volatility. This parameter transformation allows the sludge to remain in the vessel during opening without exceeding emission limits, while still permitting effective cleaning access.
3Productivity
If sludge is removed without treatment, then cleaning efficiency is high, but regulatory compliance fails due to excessive VOC levels
Solution Approach 1:
The cleaning composition is injected into the vessel before sludge removal to pre-treat the sludge in situ. This preliminary chemical treatment reduces VOC content and alters sludge properties, enabling efficient mechanical removal while ensuring the remaining sludge and emissions meet regulatory compliance standards.
Solution Approach 2:
The patent replaces purely mechanical sludge removal with a combined chemical-mechanical approach. The cleaning composition chemically modifies the sludge properties before mechanical removal, substituting the need for extensive mechanical processing while ensuring regulatory compliance through chemical transformation of harmful compounds.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively reduces VOC levels in the vessel to meet regulatory standards without exposing the interior to the atmosphere prematurely, ensuring safe degassing and compliance with air quality regulations.
Implementation Method 1
an oil release agent is initially mixed with the sludge to separate the oil from solids in the sludge. The separated oil floats on the surface of water
Implementation Method 2
a predetermined amount of an emulsifying agent is added to substantially emulsify the trace hydrocarbons, so the level of volatile organic compounds remaining in the interior of the vessel is no greater than 5,000 ppmv
Data Source
AI summary
A sealed storage vessel containing volatile organic vapor over a bottom sludge layer is cleaned by (a) determining the level of free oil in the vessel and then using (b) either a two-stage or one-stage treatment regime, adding a cleaning agent thereto. If the free oil is greater than 2 volume percent the two-stage regime is used where an oil release agent is initially mixed with the sludge to separate the oil from solids in the sludge. The separated oil floats on the surface of water and is removed without substantially exposing the vessel's interior to the atmosphere, leaving within the vessel a mixture of water, solids, and trace amounts of hydrocarbons. Next, a predetermined amount of an emulsifying agent is added to substantially emulsify the trace hydrocarbons, so the level of volatile organic compounds remaining in the interior of the vessel is no greater than 5,000 ppmv, measured as methane, at least one hour after adding the emulsifying agent. If the free oil is less than 2 volume percent, the one-stage treatment regime is employed by only adding the emulsifying agent to achieve this same level of volatile organic compounds.