Crude Argon Column Closed-Loop Standby for Faster Restart

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Solution Overview

Problem

The crude argon column in air separation units requires a long time to start up and is sensitive to upsets, particularly due to the difficulty in separating argon and oxygen, which can lead to interruptions and high nitrogen ingress, resulting in energy inefficiencies and prolonged downtime.

Innovation Solution

Implementing a closed-loop operation mode for the crude argon column using an argon-enriched gas cycle to maintain reboil, allowing the column to operate independently during cold stand-by or upsets, with the cycle stream being used to warm and condense within the column, maintaining liquid levels and purity profiles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the crude argon column operates in conventional mode dependent on the double column, then it can maintain stable separation, but it requires long restart time and is sensitive to upsets in the second column

Engineering Contradiction:

Improvecolumn operation stabilityVSAvoidrestart time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-establishing a cold standby configuration where the crude argon column is kept ready with frozen liquid argon in the reboiler before any upset occurs. This allows the column to immediately resume operation after disturbances without requiring lengthy restart procedures, directly addressing the long restart time issue while maintaining operational stability through the pre-prepared cold standby state

Inventive Principle:

Principle #10Preliminary action

2Loss of time

If the crude argon column is kept running at reduced load in closed loop mode, then restart time is reduced and operational readiness is improved, but energy consumption increases

Engineering Contradiction:

ImprovedowntimeVSAvoidenergy cost

Core Design Contradiction:

Loss of timeVSUse of energy by moving object

Solution Approach 1:

The patent implements periodic action through a cyclical operational pattern where the crude argon column alternates between full operation mode and reduced load closed loop mode. The system performs a sequence of operations including normal separation, cold standby preparation, upset response, and recovery, creating a periodic cycle that optimizes both downtime reduction and energy management by switching between operational states based on process needs

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies parameter changes by dynamically adjusting operational parameters such as reboil duty, feed flow rates, and pressure conditions to transition between different operational modes. The system changes parameters to maintain a frozen liquid argon state in the reboiler during cold standby, and adjusts these parameters during upsets to enable rapid recovery while managing energy consumption through optimized parameter selection in each operational phase

Inventive Principle:

Principle #35Parameter changes

3Reliability

If nitrogen ingress occurs from the second column, then the temperature at the top of the crude argon column decreases, but this blocks the top condenser and interrupts flow

Engineering Contradiction:

Improveseparation continuityVSAvoidnitrogen ingress effect

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies beforehand cushioning by preparing a frozen liquid argon charge in the reboiler before nitrogen ingress can cause harmful effects. This pre-positioned cold reserve acts as a buffer that can immediately compensate for temperature drops caused by nitrogen ingress, preventing condenser blockage and maintaining separation continuity without interrupting the process flow

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 reduces energy costs and allows the crude argon column to remain operational and ready for use during interruptions, with the cycle stream maintaining liquid levels and purity profiles, making it economical to run for extended periods rather than restarting, thus enhancing operational efficiency and reducing downtime.

Implementation Method 1

at least part of the cycle stream is used to warm a bottom reboiler of the crude argon column being thereby condensed to form a condensed cycle stream

Methodology Applied

Scientific EffectCondensation: Condensation

Implementation Method 2

Argon volatility being between those of oxygen and nitrogen, for a pure argon product, two argon columns are required to get on specification

Methodology Applied

Scientific EffectCryogenic distillation: Distillation

Implementation Method 3

The first column (called crude argon column in the remaining description) removes oxygen from argon and nitrogen, this separation is the more difficult one due to the close volatility of oxygen and argon

Methodology Applied

Scientific EffectVolatility difference:

Data Source

PatentEP4455588A1Process and apparatus for the separation of air by cryogenic distillation

Publication Date: 2024.10.30 LAIR LIQUIDE SA POUR LETUDE & LEXPLOITATION DES PROCEDES GEORGES CLAUDE

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AI summary

During shut-down of a double column, the argon column (K10) keeps functioning or is in a ready to function state, using a cycle stream (3) to heat a bottom reboiler (E2) of the argon column.