CNG Compressor Pressure Let-Down for Flow Capacity

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Solution Overview

Problem

Conventional CNG stations are energy inefficient due to compressor design limitations, which require sacrificing gas pressure through an inlet regulator, limiting flow capacity and not allowing for adjustable operation to meet varying demand levels.

Innovation Solution

A reciprocating compressor system with a high-pressure storage vessel let down section that de-pressurizes gas from the storage vessel to increase and adjust inlet gas pressure, enabling higher and adjustable flow capacity by supplementing local gas utility inlet gas with pressure let down gas, utilizing components like shutoff valves, multi-stage depressurization regulators, and pressure transducers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an inlet regulator is used to de-pressurize gas before compression, then gas pressure is reduced to meet compressor design specifications, but energy efficiency deteriorates due to re-compression of already de-pressurized gas

Engineering Contradiction:

Improvecompressor design specification complianceVSAvoidenergy efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent applies preliminary action by de-pressurizing gas from high-pressure storage vessels before it enters the compressor, rather than de-pressurizing after compression. This reverses the conventional sequence and allows the compressor to handle gas at optimal pressure levels, avoiding the energy waste of compressing already de-pressurized gas.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent inverts the conventional approach by placing the de-pressurization function upstream of the compressor rather than downstream. Instead of compressing high-pressure gas and then regulating it down, the system blends de-pressurized high-pressure gas with incoming utility gas before compression, allowing the compressor to operate at design specifications while maintaining energy efficiency.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If conventional compressor design is used with inlet regulator, then compressor can operate within design specifications, but flow capacity is limited and cannot be adjusted to meet varying demand levels

Engineering Contradiction:

Improvecompressor operation within design specificationsVSAvoidflow capacity adjustability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies dynamics by making the system adaptable to varying demand levels through a controllable blending mechanism. The control system dynamically adjusts the proportion of de-pressurized high-pressure gas blended with incoming utility gas, allowing flow capacity to be increased or decreased based on demand while keeping the compressor operating within its design specifications.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent uses an intermediary blending mechanism that combines de-pressurized high-pressure gas with incoming utility gas before the compressor inlet. This intermediary blending allows the system to modulate the total flow capacity independently of the compressor's fixed design parameters, providing adaptability without compromising the compressor's operational integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If custom-designed CNG station is built for specific site conditions, then station can operate within predetermined inlet gas pressure and flow ranges, but construction time increases and flow capacity is limited by local gas utility inlet pressure

Engineering Contradiction:

Improveoperation within predetermined inlet gas pressure and flow rangesVSAvoidconstruction time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies universality by creating a modular system that can be adapted to different site conditions without custom design. The high-pressure storage vessels and blending mechanism serve multiple functions: they can supplement inlet gas pressure, increase flow capacity, and provide buffer storage. This multi-functional approach allows the same basic system configuration to work across various locations with different utility gas pressures and demand patterns, reducing the need for site-specific custom design and construction.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 enhances energy utilization and flow capacity, allowing for active management of gas supply and demand, reducing power draw and operating costs by providing higher flow during peak hours and slower flow during non-peak hours.

Implementation Method 1

a pressure let down section that depressurizes the high pressure gas from the high pressure storage vessel to the inlet of the compressor section

Methodology Applied

Scientific EffectPressure let down (depressurization): Depressurisation

Data Source

PatentUS8950441B2Reciprocating compressor with high pressure storage vessel let down for CNG station and refueling motor vehicles

Publication Date: 2015.02.10 CLEAN ENERGY FUELS CORP

AI summary

Embodiments of the present invention are directed toward a reciprocating compressor having a high pressure storage vessel let down for a CNG station for refueling motor vehicles, wherein the CNG station design utilizes inlet gas from a local gas utility. By supplementing the inlet gas with a pressure let down in order to de-pressurize the gas from a high-pressure storage vessel, the CNG station has the ability to increase and adjust its flow capacity.