Distillation Column Heat Pump With Compressor Inlet Superheating

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Solution Overview

Problem

The use of heat pumps in distillation columns for separating C5 and C6 components is not economically viable due to high temperature differences between overhead and bottoms streams, requiring higher compression ratios and leading to partial condensation of the overhead vapor stream, which necessitates steam superheating, further increasing costs.

Innovation Solution

A distillation column with a side reboiler and heat pump system where the compressed overhead stream is used to heat the reboiler and superheat the overhead stream, reducing the temperature difference and eliminating the need for external steam, thereby reducing compression requirements and improving process economics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a heat pump is used in a distillation column for separating C5 and C6 components, then energy recovery from the overhead stream is achieved, but the high temperature difference between overhead and bottoms streams requires higher compression ratios leading to increased compression costs

Engineering Contradiction:

Improveenergy recovery from overhead streamVSAvoidcompression costs

Core Design Contradiction:

Loss of energyVSUse of energy by moving object

Solution Approach 1:

The overhead vapor stream is superheated before entering the compressor to prevent condensation during compression. This preliminary heating action ensures the vapor remains in gas phase throughout the compression process, enabling effective heat pump operation despite the high temperature difference between overhead and bottoms streams

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The temperature of the overhead stream is increased above its dew point temperature before compression. This parameter change (temperature elevation) allows the heat pump system to operate effectively by preventing condensation while recovering energy from the overhead stream

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If the overhead vapor stream is compressed without superheating, then compression costs are reduced, but partial condensation of the stream occurs which undermines the heat pump effectiveness

Engineering Contradiction:

Improvecompression costsVSAvoidheat pump effectiveness

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The overhead stream is heated to a temperature above its dew point before compression to counteract the condensation tendency that would occur during compression. This preliminary anti-action prevents the harmful condensation effect before it can undermine the heat pump effectiveness

Inventive Principle:

Principle #9Preliminary anti-action

3Reliability

If steam is used to superheat the overhead stream before compression, then condensation is avoided, but steam consumption increases further eroding the economics of the heat pump

Engineering Contradiction:

Improveprevention of condensationVSAvoidsteam consumption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The heat pump system itself provides the superheating function by using the compressed overhead stream to heat the incoming overhead vapor stream. This self-service approach eliminates the need for external steam superheating, as the system uses its own compressed output to perform the required preheating action

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The superheating function is merged with the heat pump cycle by using the compressed overhead stream to heat the incoming vapor stream. This combines two functions (compression and superheating) into a single integrated system, eliminating the separate steam superheating step and its associated energy consumption

Inventive Principle:

Principle #5Merging (Combining)

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 design reduces energy consumption by lowering the heat pump compressor requirements, eliminates the need for external steam superheating, and improves the overall economic viability of the process by optimizing heat recovery and usage within the distillation column.

Implementation Method 1

compression of the C5 and C6 overhead vapor stream results in partial condensation of the stream

Methodology Applied

Scientific EffectCompression: Compression

Implementation Method 2

A portion of the compressed overhead stream is used to heat a portion of the bottoms stream

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 3

compression of the C5 and C6 overhead vapor stream results in partial condensation of the stream

Methodology Applied

Scientific EffectCondensation: Condensation

Data Source

PatentUS20130227986A1Distillation column heat pump with compressor inlet superheater

Publication Date: 2013.09.05 UOP LLC

AI summary

Hydrocarbon distillation columns with heat pumps and methods of operating them are described. The overhead stream is compressed to increase temperature so that it can be used both to heat the reboiler and to superheat the overhead stream before it enters the heat pump compressor.