Mercury Sampling Critical Orifice Pressure Reduction
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Solution Overview
Problem
Existing mercury sampling systems for high-pressure natural gas face challenges in reducing pressure effectively without contamination, as diaphragm regulators can accumulate contaminants and are difficult to clean, while also requiring the gas to be below the dew point for accurate testing.
Innovation Solution
A system utilizing a critical orifice with a heater to reduce pressure and a parallel configuration with a control loop and heated sorbent trap section, which maintains the gas temperature above the dew point and minimizes contamination by isolating the control loop components from the sorbent trap pathway.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a diaphragm regulator is used to reduce pressure, then pressure reduction is achieved, but contamination accumulates in the regulator and it becomes difficult to clean
Solution Approach 1:
The harmful function of contamination accumulation is extracted from the pressure reduction function. Instead of using a diaphragm regulator where contamination accumulates, the patent uses a critical orifice that prevents contamination buildup while maintaining pressure reduction capability. The control loop is separated into a parallel configuration where contamination-prone components are isolated from the sorbent trap pathway.
Solution Approach 2:
The critical orifice is designed as a simple, easily replaceable component compared to a diaphragm regulator. When contamination occurs, the critical orifice can be quickly replaced rather than requiring complex cleaning procedures, effectively treating it as a disposable or easily renewed component.
2Stress or pressure
If pressure is reduced for sorbent trap operation, then sorbent trap can function, but gas temperature may drop below dew point causing condensation
Solution Approach 1:
The gas stream is heated before entering the sorbent trap to prevent temperature drop below dew point during pressure reduction. This preliminary heating action ensures that even as pressure drops across the critical orifice, the gas remains above the dew point and condensation is avoided.
Solution Approach 2:
The patent changes the temperature parameter of the gas stream by introducing heating elements. The gas is heated to a temperature above the dew point before pressure reduction, and the heating is maintained during the pressure reduction process to prevent condensation while allowing the sorbent trap to operate at reduced pressure.
3Stress or pressure
If control loop components are placed in the sample gas stream path, then pressure control is achieved, but contamination builds up in the components
Solution Approach 1:
The system is segmented into two parallel paths: one path for the sample gas stream that goes directly to the sorbent trap without passing through control loop components, and another control loop path that handles pressure control separately. This segmentation isolates the contamination-prone control components from the critical sample path.
Solution Approach 2:
The critical orifice serves as an intermediary element that performs pressure reduction without the contamination accumulation problems of diaphragm regulators. It mediates between the high-pressure source and the low-pressure sorbent trap while maintaining a clean sample stream.
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
This solution ensures consistent and clean sample delivery to sorbent traps, reducing contamination risks and maintaining accurate mercury level measurements across varying gas pressures, while being easier to maintain and less prone to contamination buildup compared to traditional diaphragm regulators.
Implementation Method 1
The pressure reduction section has a critical orifice
Implementation Method 2
a heater configured to heat the critical orifice
Implementation Method 3
the heated sorbent trap section is configured to receive a first portion of the sample gas stream
Data Source
AI summary
A system according to an exemplary aspect of the present disclosure includes a probe configured to collect a sample gas stream, a pressure reduction section, a heated sorbent trap section, and a control loop. The pressure reduction section has a critical orifice and a heater configured to heat the critical orifice. The heated sorbent trap section is configured to receive a first portion of the sample gas stream, and the control loop is configured to receive a second portion of the sample gas stream.