Pig Receiver Emissions Characterization via Grab Sampling
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Solution Overview
Problem
There is a need for systems and methods to determine air emissions associated with the depressurization of pig receivers and launchers in hydrocarbon pipeline systems, which include methane, ethane, higher alkanes, volatile organic compounds, and hazardous air pollutants, as existing methods do not effectively characterize these emissions during the depressurization process.
Innovation Solution
A system and method that involves isolating pressurized gas flow, controlling valve releases, measuring mass flow rate and pressure, obtaining and analyzing exhaust gas samples at various pressures, and using interpolation and extrapolation to determine gas compositions and potential emissions, utilizing a grab sample collection train with multiple containers and sensors to characterize emissions throughout the depressurization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pig receiver depressurization is performed to enable safe pig removal, then operational safety is improved, but air emissions of hydrocarbons increase
Solution Approach 1:
The patent captures the harmful hydrocarbon emissions during depressurization and redirects them through a series of processing steps (condensate knockout, flare combustion, gas recovery) to convert the harmful emissions into useful energy or safe byproducts, thereby eliminating the harm while maintaining the necessary depressurization operation
2Measurement precision
If comprehensive gas sampling and analysis is conducted at multiple pressure points, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the continuous depressurization process into discrete pressure segments (high-pressure, medium-pressure, low-pressure ranges) and collects gas samples at each segment using separate sampling containers. This segmentation allows comprehensive characterization of gas composition changes throughout depressurization while organizing the complex sampling process into manageable discrete steps
3Loss of information
If real-time emissions monitoring is implemented during depressurization, then loss of information is reduced, but use of energy increases
Solution Approach 1:
The patent performs gas sampling and analysis at predetermined pressure points before, during, and after depressurization. By collecting compositional data in advance at key pressure segments, the system enables accurate emissions calculations without requiring continuous real-time monitoring, thereby reducing energy consumption while maintaining complete emissions information
Data Source
AI summary
System, method, and apparatus embodiments characterize potential air emissions during the pig receiver depressurization. The mass flow rate, pressure, and temperature of exhaust gas released from the pig receiver are ascertained using a mass flow meter, pressure gauge, and temperature gauge, respectively. A flow meter and control valve regulate flow of exhaust gas through a sampling line and into a grab sample collection train. The grab sample collection train includes grab sample containers (e.g., piston cylinders, double-ended cylinders, and evacuated canisters) that collect exhaust gas samples over a range of pressures. The exhaust gas samples are used to determine the concentrations of gas components in the exhaust gas over the range of pressures. These concentrations are interpolated and/or extrapolated to provide a concentration versus pressure curve for each identified component in the exhaust gas. The ascertained mass flow rate and gas concentration curve are used to characterize potential mass emissions of each gas component during pig receiver depressurization.