Dry Gas Seal Reverse Flow to Cut Methane Leakage
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Solution Overview
Problem
Centrifugal compressors in the petrochemical industry experience significant methane leakage, contributing to greenhouse gas emissions, as conventional dry gas seal systems allow process gas to escape into the atmosphere, with current solutions not effectively reducing emissions without costly component replacements.
Innovation Solution
A dry gas seal system that pumps a low-pressure, clean inert gas upstream into the process chamber to reverse the normal gas flow across the first seal stage, utilizing a grooved rotating ring to pressurize the inert gas and minimize process gas leakage between the compressor housing and rotating shaft, thereby reducing emissions to near zero levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional dry gas seal systems are used to prevent gas leakage, then frictional wear on rotating components is reduced, but process gas still escapes into the atmosphere causing greenhouse gas emissions
Solution Approach 1:
The patent reverses the conventional gas flow direction through the seal. Instead of process gas flowing from the high-pressure process cavity through the seal to the atmosphere, inert gas is introduced at the atmospheric side and flows upstream through the seal into the process cavity. This inverted flow direction creates a barrier that prevents process gas leakage while maintaining reliable sealing, thereby reducing greenhouse gas emissions without compromising sealing effectiveness
Solution Approach 2:
The patent introduces an intermediary inert gas (such as nitrogen) between the process gas and the atmosphere. This inert gas acts as a mediator that forms a protective barrier, preventing direct contact and mixing between the process gas and the external environment. The inert gas flows through the seal in reverse direction, creating a pressure barrier that effectively blocks process gas leakage while maintaining seal reliability
2Object-affected harmful factors
If inert gas is introduced to reverse flow and reduce emissions, then greenhouse gas emissions decrease, but system complexity increases
Solution Approach 1:
The patent designs the seal system to perform multiple functions: the same seal structure that prevents frictional wear also enables the inverted flow of inert gas to block process gas leakage. The seal faces and housing are configured to accommodate both the traditional wear-protection function and the new emission-reduction function through reverse flow, thereby reducing methane leakage without significantly increasing system complexity
Solution Approach 2:
The rotating ring with spiral grooves serves dual purposes: it maintains the gas lubrication function for wear protection while simultaneously acting as a pump to drive the inert gas upstream against the pressure gradient. The rotational motion naturally pressurizes the inert gas through the spiral grooves, eliminating the need for additional external pressurization equipment and keeping the system relatively simple while effectively reducing methane leakage
3Device complexity
If a single separation gas supply subsystem is used to serve both seal stages, then device complexity is reduced, but gas distribution control becomes more difficult
Solution Approach 1:
The patent segments the gas distribution function into two parts: the single separation gas supply subsystem provides the inert gas, and the rotating ring with spiral grooves on each seal stage independently distributes and pressurizes the gas to its respective seal interface. This segmentation allows a simple single-point gas supply to effectively serve both seal stages while maintaining proper gas flow control through the rotational pumping action of each rotating ring
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
The system effectively decreases methane production losses by inhibiting process gas emission, providing a more environmentally friendly solution that does not require replacing existing compressor components, and can be applied to other industrial segments like Enhanced Oil Recovery (EOR) for compressed carbon dioxide.
Implementation Method 1
The rotating ring can define grooves configured to pressurize gas passing between the interfacing portions of the rotating ring and the stationary ring to partially counteract the biasing force of the biasing mechanism
Implementation Method 2
The stationary ring can be operably coupled to the compressor housing via a biasing spring and a spring carrier ring, thereby enabling axial movement of the stationary ring relative to the rotating ring
Implementation Method 3
A dry gas seal system that pumps a low-pressure, clean inert gas upstream into the process chamber to reverse the normal gas flow across the first seal stage, utilizing a grooved rotating ring to pressurize the inert gas and minimize process gas leakage
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A dry gas mechanical seal system (200) configured to inhibit the emission of process gas. The mechanical seal system having tandem first and second stage seals, and a single separation gas supply subsystem configured to direct a supply of separation gas from an inlet (250) through interfacing portions (260, 262) of the first stage seal into a process cavity (206) and from the inlet through the interfacing portions (268, 270) of the second stage seal and out through an outlet (280) to the atmosphere, thereby inhibiting the emission of process gas between a compressor housing (204) and a rotating compressor shaft (202).