Apparatus and method for separating air by cryogenic distillation
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Solution Overview
Problem
Existing air separation processes face inefficiencies due to large turbine sizes and non-standardized, low-efficiency cryogenic turbines, requiring complex regulation and high energy consumption, especially when producing oxygen-enriched gases.
Innovation Solution
A double-column air separation apparatus with a single-stage compressor and optimized expansion ratios, utilizing a single-stage blower and a turbine for air purification at reduced pressures, minimizing energy consumption and turbine size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If all the air flow going to the second column is expanded in the turbine to maximize energy gain, then energy efficiency is improved, but the turbine size becomes at least 4 to 5 times larger due to the volume flow rate
Solution Approach 1:
The air flow to the second column is divided into two separate streams: one stream (first flow rate) is expanded in the turbine to generate energy, while the other stream (second flow rate) bypasses the turbine and enters the second column directly. This segmentation allows the turbine to be sized for a smaller, manageable flow rate rather than handling the entire air flow, thus reducing turbine size while still capturing energy from a portion of the stream.
2Quantity of substance
If the cooling capacity is fixed and remains low, then the turbine expansion ratio becomes very low, but this results in an inefficient turbine and non-existent standardized turbines among cryogenic turbine suppliers
Solution Approach 1:
The invention changes the operating parameters of the turbine by adjusting the expansion ratio to fall within the conventional range of 4:1 to 10:1, despite the fixed low cooling capacity. This is achieved by carefully controlling the first flow rate through the turbine and the second flow rate bypassing it, allowing the turbine to operate at an optimized expansion ratio that ensures efficiency and compatibility with standardized turbine designs.
3Ease of operation
If the scrubbing pressure is regulated by adjusting the pressure upstream of the turbine, then cooling capacity regulation is achieved, but the regulation process becomes significantly complicated and necessitates sizing the scrubbing system for the lowest possible pressure
Solution Approach 1:
The air flow is segmented into two independent paths: one through the turbine and one bypassing it. This allows independent control of each stream, simplifying the regulation of cooling capacity by adjusting the split between the two streams rather than complicating the overall pressure regulation system.
Solution Approach 2:
The invention introduces an intermediary flow distribution mechanism that separates the air stream into two paths, allowing the turbine to operate at a fixed optimized pressure while the bypass stream handles pressure variations. This intermediary segmentation decouples the complexity of pressure regulation from the turbine operation.
4Quantity of substance
If the expansion ratio is low between 1.2:1 and 3.8:1, then the turbine operates outside the conventional range, but this significantly degrades turbine efficiency
Solution Approach 1:
The invention changes the expansion ratio parameter to fall within the conventional efficient range of 4:1 to 10:1 by adjusting the flow distribution between the turbine stream and bypass stream. This parameter optimization ensures the turbine operates at peak efficiency while still handling the required air flow rates for the air separation process.
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 apparatus achieves a 1-2% reduction in energy consumption and avoids inefficient turbine operation by using a smaller, standardized turbine, ensuring efficient air separation with optimized airflow distribution.
Implementation Method 1
cooled in a heat exchanger
Implementation Method 2
expanded in a turbine coupled to the blower
Implementation Method 3
purified of water and carbon dioxide in a purification unit
Implementation Method 4
separating air by cryogenic distillation
Data Source
Figure 1
AI summary
An apparatus for separating air, comprising a double column (K3, K4), means (B) for sending air to the purification unit at a pressure that is no more than 1 bar higher than atmospheric pressure, a pipe for sending a first air flow (8), which has been purified in the purification unit, to the heat exchanger at a fourth pressure that is no more than 1 bar higher than the second pressure, a pipe for sending the first purified air flow, which has been cooled in the heat exchanger, to the second column for separation, and a booster compressor (E), the apparatus not comprising any means for depressurising the first flow.