Method for separating air by cryogenic distillation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional air separation devices by cryogenic distillation face inefficiencies in energy usage due to significant pressure drops required to ensure gas flow, leading to partial condensation and potential safety risks from liquid stagnation, and subcooling configurations that fail to fully utilize available cold recovery.
Innovation Solution
The method involves deepening the cooling of fluids within the distillation system to maintain air flow above its dew point, optimizing the subcooling process, and rearranging the heat exchanger configuration to minimize pressure drops and enhance cold recovery, ensuring the air entering the first column is at least 1° C. or 2° C. above its dew point, and using a subcooler to cool both liquids against nitrogen flows from the second column.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If significant pressure drops are applied to ensure sufficient gas speed in the exchange line, then liquid transport is improved and safety is enhanced, but energy consumption increases
Solution Approach 1:
The patent changes the temperature parameter of the air flow by maintaining it at least 1°C or 2°C higher than the dew point throughout the exchange line. This parameter change prevents condensation, eliminates the need for high gas speeds to transport liquid, and thereby reduces pressure drops and energy consumption while maintaining safety
Solution Approach 2:
The patent applies preliminary anti-action by pre-heating the air flow to stay above the dew point before it enters the exchange line. This prevents the harmful condensation effect from occurring in the first place, eliminating the need for subsequent liquid transport measures and associated energy costs
2Loss of energy
If air is cooled deeply in the heat exchanger to maximize cold recovery, then energy efficiency is improved, but condensation occurs causing safety risks
Solution Approach 1:
The patent optimizes the temperature parameter of the air flow to maintain it at least 1°C or 2°C higher than the dew point. This parameter optimization allows the system to recover maximum cold energy while preventing condensation, thereby resolving the contradiction between energy efficiency and safety
3Productivity
If the subcooler cools oxygen-enriched liquid to lower temperatures, then distillation efficiency is improved, but available cold recovery is reduced
Solution Approach 1:
The patent optimizes the temperature parameter of the oxygen-enriched liquid in the subcooler to find the optimal balance point. By controlling the liquid temperature and flow rates, the system achieves sufficient distillation efficiency while maximizing cold recovery from the nitrogen-rich gas, resolving the contradiction between productivity and energy loss
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 by minimizing pressure drops, prevents condensation in the exchange line, and maximizes cold recovery from distillation fluids, ensuring safe and efficient operation by maintaining air in a gaseous state and optimizing the cooling process.
Implementation Method 1
an air flow purified of water and carbon dioxide is cooled in a heat exchanger and sent to the first column in gaseous form
Implementation Method 2
a separation device generally comprises an exchange line wherein the air to be distilled cools against at least two products of the distillation and a column system
Implementation Method 3
During cooling, from the bottom up in the main exchange line, this air partially condenses
Implementation Method 4
a nitrogen-enriched liquid is withdrawn from the upper part of the first column and sent to the second column having been subcooled in the subcooler
Data Source
AI summary
In a method for separating air by cryogenic distillation in a system of columns comprising a first column operating at a first pressure and a second column operating at a second pressure which is lower than the first column, the temperature T1 at which an airflow leaves, after cooling, the heat exchanger by rising towards the cold end of said heat exchanger and enters the first column is at least 1° C., preferably at least 2° C., higher than the dew point of the airflow.