Dual Stripper Column Apparatus for Hydroprocessing Energy Reduction
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Solution Overview
Problem
Conventional hydroprocessing units with single stripper columns are inefficient due to the mixing of hot and cold flash drum liquids, leading to increased energy consumption and operational costs, as they undo the separation achieved in the hydroprocessing reactor, necessitating a more energy-efficient method for separating and recovering products.
Innovation Solution
A dual stripper column apparatus is introduced, comprising a hot flash stripper column and a cold flash stripper column, each with multiple trays, where the hot flash drum liquid is fed into the hot flash stripper column, and the cold flash drum liquid is fed into the cold flash stripper column, with the overhead vapor from the hot flash column combined and separated in a receiver to provide reflux to the cold flash column, optimizing the separation process and reducing the need for reflux in the hot flash column.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single stripper column is used to process both hot and cold flash drum liquids, then the device complexity is reduced, but the energy consumption increases and separation efficiency deteriorates due to mixing of different temperature streams
Solution Approach 1:
The single stripper column is segmented into two separate stripper columns - a hot stripper for hot flash drum liquid and a cold stripper for cold flash drum liquid. This segmentation prevents mixing of temperature streams, maintains separation efficiency, and reduces the energy required by the fractionator feed heater by approximately 50% compared to single stripper arrangements.
2Device complexity
If a single stripper column is used to process both hot and cold flash drum liquids, then the device complexity is reduced, but the product separation quality deteriorates due to mixing of different compositions
Solution Approach 1:
The stripper system is divided into separate hot and cold stripper columns that process different feed streams independently. This prevents the mixing of hot and cold flash drum liquids that have very different compositions, thereby maintaining the separation quality achieved in the hydroprocessing reactor and avoiding the need to redo the separation.
Solution Approach 2:
Each stripper column is optimized for its specific feed stream - the hot stripper handles hot flash drum liquid at elevated temperatures while the cold stripper handles cold flash drum liquid at lower temperatures. This localized optimization ensures each column operates at its optimal conditions for the specific composition and temperature range of its feed, improving overall product separation quality.
3Loss of energy
If overhead vapor from hot stripper is used as vapor inlet to cold stripper, then the energy efficiency is improved, but the device complexity increases due to additional vapor transfer equipment
Solution Approach 1:
The overhead vapor outlet of the hot stripper and the vapor inlet of the cold stripper are connected through a vapor transfer line, merging the vapor streams. This allows the hot stripper overhead vapor to serve dual purposes - exiting the hot stripper and simultaneously providing vapor input to the cold stripper, thereby improving energy efficiency while integrating the vapor flow paths.
Solution Approach 2:
The hot stripper overhead vapor automatically serves the cold stripper vapor requirement through the vapor transfer connection. The system utilizes its own internal vapor production to meet the vapor needs of another unit within the same system, reducing external energy input requirements and improving overall energy efficiency.
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 significantly reduces the fractionator feed heater duty by approximately 50% compared to single stripper column arrangements and 15% compared to original two stripper column designs, achieving better energy efficiency and product separation while maintaining the desired dewpoint margins and product quality.
Implementation Method 1
a stripper for stripping hydroprocessed effluent with a stripping medium, such as steam, to remove unwanted hydrogen sulfide
Implementation Method 2
The stripped effluent then is heated in a fired heater to fractionation temperature
Implementation Method 3
The effluent 15 from the reactor 10 is partially cooled and sent to a hot separator 20 where it is separated into a vapor stream 25 and a liquid stream 30
Implementation Method 4
The liquid stream 30 from the hot separator 20 is sent to a hot flash drum 35 which operates at a lower pressure
Data Source
AI summary
Dual stripper column arrangements are described in which hot flash drum liquid is sent to one column and cold flash drum liquid is sent to a second column. Methods of operating the dual stripper column apparatus are also described.