Vortex Regulator Staging for CNG Pressure Drop Without Freeze-Up
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Solution Overview
Problem
Current methods for reducing the pressure of compressed natural gas (CNG) are inefficient due to substantial cooling caused by the Joule-Kelvin effect, leading to equipment failures and safety concerns, especially when high-pressure CNG needs to be depressurized for delivery to customers with varying flow rates.
Innovation Solution
A system comprising a vortex regulator, a heat exchange device, and a pressure-reducing regulator is used to decrease the pressure and temperature of CNG, employing a vortex tube to separate the gas into hot and cold fractions, with the heat exchange device warming the gas to prevent freezing and ensure safe delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If conventional pressure reduction methods are used on CNG, then pressure is reduced from 3000 PSIG to delivery pressure, but substantial cooling occurs causing equipment freeze-up and safety issues
Solution Approach 1:
The pressure reduction process is divided into multiple stages using a two-stage regulator system. The first regulator reduces pressure from 3000 PSIG to an intermediate pressure, and the second regulator further reduces it to the final delivery pressure. This segmentation prevents excessive temperature drop at any single stage, avoiding equipment freeze-up while achieving the required pressure reduction.
2Productivity
If high-pressure CNG is depressurized rapidly to meet high flow demands, then delivery rate increases, but temperature drops significantly exposing equipment to unsafe operating ranges
Solution Approach 1:
The regulatory process is segmented into two stages, allowing high flow rates to be maintained while preventing excessive temperature drop. Each regulator handles a portion of the pressure reduction, ensuring the gas remains within safe operating temperature ranges even at high delivery rates up to 5500 SCFH.
Solution Approach 2:
An intermediate pressure stage is introduced between the high-pressure CNG source and the final delivery pressure. This intermediary pressure level acts as a buffer, allowing rapid depressurization to occur in controlled increments rather than as a single large pressure drop, thereby maintaining equipment safety while supporting high flow demands.
3Productivity
If expensive electric or electronic pressure control devices are used to depressurize CNG at high rates, then delivery capability improves, but system cost increases reducing profitability
Solution Approach 1:
The patent employs simple, mechanically-based two-stage pressure regulators instead of expensive electric or electronic pressure control devices. These mechanical regulators achieve the required high-rate delivery capability (up to 5500 SCFH) through purely mechanical means, significantly reducing system cost and maintaining profitability of truck-delivered CNG while avoiding the need for costly controlled depressurization equipment.
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 reduces CNG pressure from 3000 PSIG to 45 PSIG while maintaining a temperature above -28.9°C, preventing equipment freeze-up and ensuring reliable, uninterrupted gas delivery with varying flow rates.
Implementation Method 1
The at least one vortex regulator may include a vortex tube and may have at least one inlet to receive natural gas and at least one outlet for releasing the natural gas at a substantially decreased pressure and temperature
Implementation Method 2
The heat exchange device may be configured to receive the natural gas from the at least one vortex regulator and to increase the temperature of the natural gas
Implementation Method 3
The pressure-reducing regulator may be in fluid communication with the heat exchange device and may be configured for further reducing the pressure of the natural gas
Data Source
AI summary
Methods and systems for reducing a pressure of compressed natural gas and for delivering natural gas are disclosed. A regulator comprising a vortex tube may be used to reduce the pressure of compressed natural gas while a temperature thereof is also reduced. The temperature reduction associated with a pressure drop in the compressed natural gas is achieved by throttling the gas at constant enthalpy from 3,000 PSIG to 150 PSIG through the regulator. At least one heat exchanger may be utilized to increase the temperature of the compressed natural gas to a temperature suitable for injection delivery. A pressure-reducing regulator may be used to further reduce a pressure of the gas to about 45 PSIG for delivery to an end-user.