Method and apparatus for recovering C2—C4 components in methane-containing industrial gas
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Solution Overview
Problem
Current methods for recovering C2-C4 components from methane-containing industrial gases, such as dry gas, face challenges including high energy consumption, large equipment investments, and significant steam usage, particularly in cryogenic separation and shallow cold oil absorption processes.
Innovation Solution
A method and apparatus that compress and cool the gas, followed by gas-liquid separation, absorption with C4 or C5 fractions as absorbents, and subsequent methane desorption at low pressure, reducing energy consumption and eliminating the need for dryers and propylene refrigeration compressors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If cryogenic separation method is used, then high recovery rate and high purity for ethylene are achieved, but large equipment investment and high energy consumption are required
Solution Approach 1:
The patent changes the operating parameters from cryogenic temperatures to ambient or mildly elevated temperatures. The absorption process operates at temperatures above 0°C, eliminating the need for cryogenic refrigeration while maintaining effective separation through pressure-swing absorption mechanisms
Solution Approach 2:
The patent replaces the mechanical cryogenic refrigeration system with a thermal absorption-desorption system. Instead of using mechanical compressors and heat exchangers for cooling, the process uses temperature and pressure changes to drive absorption and desorption cycles, significantly reducing mechanical equipment requirements
2Use of energy by stationary object
If pressure swing adsorption method is used, then low energy consumption is achieved, but low product purity and low recovery rate for C2 components are obtained
Solution Approach 1:
The patent introduces an absorbent liquid as an intermediary medium between the gas phase and the separation process. The absorbent selectively absorbs C2-C4 components from the dry gas, enabling high-purity separation that simple pressure swing adsorption cannot achieve alone
Solution Approach 2:
The patent employs a composite separation approach combining absorption and pressure swing mechanisms. The system uses absorbent materials with specific selectivity for C2-C4 components, creating a composite process that achieves both high purity and high recovery rate simultaneously
3Productivity
If shallow cold oil absorption method is used, then high recovery rate for C2 and C3 components is achieved, but large amount of low-pressure steam is consumed
Solution Approach 1:
The patent implements periodic absorption and desorption cycles. During absorption, C2-C4 components are captured; during desorption, the absorbed components are released by changing pressure and temperature conditions. This periodic operation allows continuous high recovery rate with reduced steam consumption compared to continuous shallow cold oil absorption
Solution Approach 2:
The patent utilizes pressure and temperature parameter changes to drive the absorption-desorption cycles. By changing pressure from high to low and adjusting temperature, the process achieves efficient component recovery without requiring large amounts of steam for continuous heating
4Manufacturing precision
If pressure swing adsorption tower operates below 0°C, then separation is achieved, but cooling, phase separation, dehydration and drying treatment are required, increasing apparatus investment
Solution Approach 1:
The patent performs preliminary heating and phase separation before the absorption process. By ensuring the feed gas is above 0°C and properly phased before entering the absorption tower, the need for subsequent cooling equipment, dehydration systems, and drying treatments is eliminated, reducing overall apparatus complexity
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
Achieves high purity and recovery rates for C2-C4 components with reduced energy consumption, specifically lowering steam usage and equipment costs by optimizing the absorption and desorption processes.
Implementation Method 1
contacting the gas phase with an absorbent to absorb the C2 components to obtain an absorption tail gas and an absorption rich liquid
Implementation Method 2
subjecting the depressurized stream to methane desorption to obtain a desorbed gas and a rich absorbent
Data Source
AI summary
A method for recovering C2 components in a methane-containing industrial gas includes the steps of (1) cooling a compressed methane-containing industrial gas and performing gas-liquid separation; (2) absorbing C2 components in the gas phase by using an absorbent to obtain an absorption rich liquid; (3) returning the absorption rich liquid to the compression in step (1) or mixing the absorption rich liquid with the liquid phase obtained in step (1) to obtain a mixed liquid, and depressurizing the mixed liquid or the absorption rich liquid; (4) performing methane desorption on the depressurized stream to obtain a rich absorbent, or performing second gas-liquid separation on the depressurized stream, followed by methane desorption on the second liquid phase to obtain a rich absorbent; and (5) desorbing and separating the rich absorbent to obtain a lean absorbent and an enriched gas, and recycling and reusing the lean absorbent.