Propylene Propane Separation Using Absorption Refrigeration
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Solution Overview
Problem
The separation of propylene from propane is challenging due to their close boiling points, requiring high-pressure distillation columns and significant reflux, which increases energy consumption and costs, and existing solutions like using a compressor are inefficient.
Innovation Solution
The method employs an absorption refrigerator cooled by chilled water from a waste heat source to reduce condenser pressure, utilizing hot water for heat in the reboiler and optionally low-pressure steam, thereby improving energy efficiency and reducing the need for high-energy compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a distillation column operates at high pressure with cooling water at 20-30°C, then the separation of propylene from propane can be achieved, but the condenser pressure becomes high (16 bar a), which limits the feed stream capacity and requires large column diameter
Solution Approach 1:
The invention changes the temperature parameter of the cooling medium from conventional cooling water at 20-30°C to chilled water at -10 to +10°C. This parameter change allows the condenser to operate at lower pressure (9 bar a instead of 16 bar a) while maintaining the same separation performance, thereby increasing feed stream capacity without requiring larger column diameter
Solution Approach 2:
The invention replaces the conventional mechanical compression system (compressor requiring electricity or steam turbine) with a thermodynamic absorption refrigeration system that uses waste heat to produce chilled water. This substitution eliminates the need for high-energy compression while achieving the same pressure reduction effect
2Stress or pressure
If a compressor is used to decrease condenser pressure, then the pressure can be reduced, but high value energy such as electricity or high pressure steam is required
Solution Approach 1:
The invention converts waste heat (a harmful or wasted resource) into a useful resource by using it to drive the absorption refrigeration cycle. The waste heat at 80-90°C provides the thermal energy needed to generate chilled water, thereby achieving pressure reduction without consuming high-value energy like electricity or steam turbine power
Solution Approach 2:
The system uses its own waste heat output to power the refrigeration cycle that produces chilled water for cooling. The process is self-sufficient, using internally generated thermal energy rather than requiring external high-value energy inputs
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 decreases the condenser pressure, allowing for increased feed stream capacity and reducing energy consumption and installation costs by leveraging waste heat for chilling, resulting in a more efficient and economical separation process.
Implementation Method 1
an absorption refrigerator (Y-301) is used to cool chilled water (331)
Implementation Method 2
The distillation column C-301 produces 214 t/h of vapor 304 at the top that is condensed against chilled water in a condenser H-302
Implementation Method 3
A reboiler H-301 has a duty of 21 MW th and produces 226 t/h of vapor 303
Implementation Method 4
separation of propylene (propene) from propane... Propylene fractionation separates propylene as a chemical-grade overhead product
Data Source
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AI summary
A separation system for separating a feed stream comprising propylene and propane and a method for separating such feed stream. The separation system includes a distillation column for producing a light stream comprising propylene and a heavy stream comprising propane; a reboiler for reboiling a part of the first heavy stream to produce a boiled heavy stream; a condenser for cooling the light stream to produce a condensed light stream; and an absorption refrigerator for receiving water and providing chilled water, for receiving hot water from a waste heat source and providing a cooled hot water and for receiving cooling water and providing a heated cooling water. The absorption refrigerator is arranged such that the cooling of the water and the hot water occurs by the cooling water. The condenser is arranged such that the cooling of the light stream occurs by the chilled water from the absorption refrigerator.