Cryogenic Distillation Column Reflux for Peak Nitrogen Demand

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Solution Overview

Problem

Conventional air separation processes using cryogenic distillation face high costs due to prohibitive investment and labor costs for autonomous production units, and inefficient energy use in vaporizing liquid nitrogen for peak demand, leading to significant refrigeration energy loss.

Innovation Solution

Recover refrigeration power by redirecting vaporized liquid nitrogen to the distillation column during peak consumption, increasing reflux and allowing for additional nitrogen production, which is then stored to reduce or eliminate the need for conventional liquid nitrogen injection, thereby reducing operating costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If liquid nitrogen is vaporized in an atmospheric heater to top up nitrogen molecules during peak consumption, then nitrogen demand is met, but refrigeration energy is lost

Engineering Contradiction:

Improvenitrogen moleculesVSAvoidrefrigeration energy

Core Design Contradiction:

Quantity of substanceVSLoss of energy

Solution Approach 1:

The invention converts the harmful energy loss from vaporizing liquid nitrogen in an atmospheric heater into a beneficial process by redirecting the liquid nitrogen through the distillation column where it is efficiently vaporized, transforming the waste refrigeration energy loss into useful cooling effect that maintains column temperature and produces additional nitrogen.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Temperature

If liquid nitrogen is continuously injected to keep the apparatus cold, then refrigeration is maintained, but operating costs increase

Engineering Contradiction:

Improveapparatus temperatureVSAvoidliquid nitrogen consumption

Core Design Contradiction:

TemperatureVSUse of energy by moving object

Solution Approach 1:

The distillation column serves itself by using the incoming liquid nitrogen feed as both a cooling agent and a production feedstock. The liquid nitrogen vaporizes within the column, providing the necessary refrigeration to maintain low temperatures while simultaneously contributing to nitrogen production, eliminating the need for separate liquid nitrogen injection for cooling purposes.

Inventive Principle:

Principle #25Self-service

3Stability of the object's composition

If the distillation column operates at nominal extraction level, then steady production is maintained, but additional nitrogen cannot be produced during peak demand

Engineering Contradiction:

Improveproduction stabilityVSAvoidnitrogen production capacity

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The invention introduces dynamic operation to the distillation column by allowing the liquid nitrogen feed rate to vary according to demand. During peak consumption, the liquid nitrogen feed is increased and redirected through the column, enabling the system to dynamically adjust production capacity while maintaining stable operation through controlled reflux adjustments.

Inventive Principle:

Principle #15Dynamics

4Quantity of substance

If an evaporator with large capacity is used to meet nitrogen demand, then nitrogen availability is improved, but investment cost and energy efficiency worsen

Engineering Contradiction:

Improvenitrogen availabilityVSAvoidevaporator capacity

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The distillation column is made multi-functional by serving both as the primary nitrogen production unit and as an emergency vaporizer for liquid nitrogen. This eliminates the need for a separate large-capacity evaporator, as the column can handle both steady-state production and peak-demand vaporization functions, reducing overall system complexity and investment cost.

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

This approach significantly reduces operating costs by minimizing liquid nitrogen consumption and maintaining apparatus refrigeration using stored rich liquid, allowing for flexible production to meet variable demands without continuous liquid injection.

Implementation Method 1

In the distillation column, this inflow of liquid increases the level of reflux into the column... The column therefore acts as a 'vaporizer' for liquid coming from the storage tank.

Methodology Applied

Scientific EffectVaporization: Evaporation

Implementation Method 2

The present invention relates to an air separation process and apparatus using cryogenic distillation.

Methodology Applied

Scientific EffectCryogenic distillation: Distillation

Data Source

PatentUS8776546B2Air separation process and apparatus using cryogenic distillation

Publication Date: 2014.07.15 LAIR LIQUIDE SA POUR LETUDE & LEXPLOITATION DES PROCEDES GEORGES CLAUDE

AI summary

An air distillation unit comprises an air distillation column (10) suitable for producing a nominal flow of gaseous nitrogen, the top of said column being connected to a liquid nitrogen source (8), and operates by carrying out the following steps: a flow of compressed, cooled and purified air is sent to an exchanger (11) and then to the column, a flow of gaseous nitrogen is withdrawn from the column, the level of liquid at the bottom of the column is controlled; and injection liquid (20), sent from the source to the column, is no longer sent if the required production reduces to at most the nominal production. Application to the separation of air by cryogenic distillation.