CNG Tank Purging System with Two-Stage Expansion
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Solution Overview
Problem
Current methods for purging CNG tanks during maintenance result in methane discharge into the atmosphere, posing environmental risks and discomfort for nearby industrial installations, and lack efficient recovery and reuse options.
Innovation Solution
A system comprising a flexible pipe connected to the tank with a discharge circuit, buffer capacity circuit, compressor filling circuit, and a two-stage expansion system, allowing for pressure equilibrium and gas transfer between tanks without atmospheric release, utilizing a transportable metal frame for easy installation and operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If CNG tanks are purged in open air during maintenance, then the purging operation is simple and quick, but methane is discharged into the atmosphere causing environmental pollution and safety risks
Solution Approach 1:
The patent introduces a flexible pipe as an intermediary component that connects the CNG tank vent to a discharge circuit. This pipe serves as a mediator to redirect the methane flow from direct atmospheric discharge to a controlled recovery system, eliminating pollution while maintaining operational simplicity.
Solution Approach 2:
The invention converts the harmful methane discharge into a beneficial resource by capturing the purged gas and transferring it to other CNG tanks. The previously wasted methane becomes reusable fuel, transforming an environmental hazard into a valuable asset for refilling vehicles.
2Object-affected harmful factors
If a complex gas recovery system is installed to prevent methane discharge, then environmental pollution is reduced, but the system complexity and installation difficulty increase
Solution Approach 1:
The gas recovery system is segmented into distinct functional modules: a flexible pipe for connection, a discharge circuit with barrier valves for controlled flow, a compressor filling circuit for gas compression and transfer, and a two-stage expansion system for pressure regulation. Each module performs a specific function, making the overall system manageable and maintainable despite its complexity.
Solution Approach 2:
The system is designed with multi-functional components that serve multiple purposes. For example, the compressor filling circuit both compresses the purged gas and prepares it for transfer to other tanks. The barrier valves control flow in multiple directions and at different stages of the process, reducing the need for separate dedicated components.
3Ease of operation
If a portable purging system is used to enable autonomous operation, then ease of deployment is improved, but the system requires multiple circuits and components increasing complexity
Solution Approach 1:
The system incorporates dynamic elements including a movable flexible pipe that can be connected to different tank vents, and barrier valves that can be opened or closed to control gas flow paths. The portable metal frame allows the entire system to be moved and repositioned as needed, providing adaptability for different maintenance scenarios while maintaining autonomous operation.
Solution Approach 2:
The purging system is designed to be autonomous and self-sufficient. The portable metal frame with all mounted components can be independently deployed and operated without external infrastructure. The system performs its own gas compression, pressure regulation, and transfer operations automatically, requiring minimal external intervention during maintenance operations.
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
Enables ecological purging of CNG tanks, facilitating the recovery and reuse of natural gas, reducing environmental impact, and allowing for autonomous, convenient, and efficient operation.
Implementation Method 1
a two-stage expansion system, the first stage of which provides an expansion between a pressure between 200 and 250 bar and a pressure between 5 bar and 20 bar while the second stage of the expansion system provides an expansion between a pressure between 20 bar and 5 bar and a pressure between 15 and 25 mbar
Implementation Method 2
a compressor interposed between the fourth and fifth barrier valves
Implementation Method 3
a reheating loop comprising a heat recovery member at the level of a ventilation system of the compressor and means for transferring the recovered heat to a section of pipe located between the first and second stages of the expansion system
Data Source
Figure 1~3
Figure 2
Figure 4~6
AI summary
The system has a discharging circuit (182) connected to a flexible conduit (181) that is connected to a vent hole of a reservoir of a vehicle to be purged. A connection circuit (189) connected to the discharging circuit has a buffering capacity (131). A filling circuit has lines (183, 186) with respective sectional valves (V2, V3) between which a triggering system with two-stages (105, 106) and a compressor (107) are intercalated. A supply pipe (184) has a filling nozzle (121) to fill a reservoir of another vehicle and is connected in downstream to the discharging circuit and the line (186). An independent claim is also included for a method of purging a natural gas reservoir installed in a vehicle.