Solvent Injection in LNG Feed to Prevent Heavy Component Freezing

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Solution Overview

Problem

LNG plants face frequent shutdowns due to freezing of heavy hydrocarbon components during the liquefaction process, leading to pressure drops and fouling in heat exchangers, which disrupts production and requires frequent de-riming cycles.

Innovation Solution

The implementation of solvent injection into the natural gas feed to condense and separate heavy components, preventing them from freezing in heat exchangers, and the use of a solvent recovery unit to recycle and minimize solvent import, ensuring a continuous and efficient LNG production process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If natural gas is cooled through multiple cooling stages to achieve liquefaction, then the natural gas is converted to convenient transportation and storage form, but heavy hydrocarbon components freeze and cause fouling in heat exchangers

Engineering Contradiction:

Improveliquefaction temperatureVSAvoidfreezing of heavy components

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by injecting solvent into the natural gas feed stream before the cooling process begins. This preliminary solvent injection modifies the feed composition to prevent heavy component freezing during subsequent cooling stages, eliminating the need for shutdowns and de-riming operations while maintaining continuous liquefaction production

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses solvent as an intermediary substance that mediates between the heavy hydrocarbon components and the cooling process. The solvent interacts with the heavy components to prevent their freezing and deposition on heat exchanger surfaces, allowing the cooling process to proceed without fouling issues

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the cooling process continues until liquefaction temperature is reached, then natural gas is successfully liquefied, but pressure drop increases beyond system constraints requiring shutdown

Engineering Contradiction:

ImproveLNG productionVSAvoidpressure drop in heat exchanger

Core Design Contradiction:

ProductivityVSStress or pressure

Solution Approach 1:

The solvent injection is performed as a preliminary action before cooling to prevent the pressure drop issue from occurring in the first place. By modifying the feed composition upfront, the system maintains acceptable pressure drop levels throughout the cooling process, enabling continuous operation at full productivity without shutdowns for de-riming

Inventive Principle:

Principle #10Preliminary action

3Reliability

If solvent is injected into natural gas feed to prevent freezing, then fouling in heat exchangers is eliminated, but solvent import and recovery costs increase

Engineering Contradiction:

Improvecontinuous operation without shutdownVSAvoidsolvent import

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The patent implements a solvent recovery system that captures and recycles solvent from the process stream. This recovery mechanism significantly reduces the net solvent import requirement, making the reliability improvement economically viable by minimizing continuous solvent consumption while maintaining continuous operation without shutdowns

Inventive Principle:

Principle #34Discarding and recovering

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 approach effectively eliminates freezing in chilling and liquefaction areas, reduces solvent import, and provides a customizable system adaptable to various LNG train architectures, enhancing operational reliability and efficiency.

Implementation Method 1

The condensed liquid contains a fouling portion of the heavy components condensed by the solvent during chilling

Methodology Applied

Scientific EffectCondensation: Condensation

Implementation Method 2

A mixed feed is produced from a dispersal of the solvent into the feed of natural gas

Methodology Applied

Scientific EffectDispersion: Dispersion (of waves)

Implementation Method 3

A chilled feed is produced by chilling the mixed feed

Methodology Applied

Scientific EffectCooling: Cooling

Implementation Method 4

The liquid containing the fouling portion of the heavy components is separated from the vapor

Methodology Applied

Scientific EffectPhase separation: Two-Phase Flow

Data Source

PatentUS20240310118A1Solvent injection and recovery in a LNG plant

Publication Date: 2024.09.19 CONOCOPHILLIPS CO

AI summary

Implementations described and claimed herein provide systems and methods for processing liquefied natural gas (LNG). In one implementation, a solvent is injected into a feed of natural gas at a solvent injection point. A mixed feed is produced from a dispersal of the solvent into the feed of natural gas. The mixed feed contains heavy components. A chilled feed is produced by chilling the mixed feed. The chilled feed includes a vapor and a condensed liquid. The condensed liquid contains a fouling portion of the heavy components condensed by the solvent during chilling. The liquid containing the fouling portion of the heavy components is separated from the vapor. The vapor is directed into a feed chiller heat exchanger following separation of the liquid containing the fouling portion of the heavy components from the vapor, such that the vapor being directed into feed chiller heat exchanger is free of freezing components.