Multi-Stripper Hydroprocessing for Heater Duty Reduction
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Solution Overview
Problem
Hydroprocessing, particularly hydrocracking, is energy-intensive due to high temperature and pressure conditions, leading to significant heater duty requirements in product fractionation columns, necessitating more efficient recovery methods to reduce energy consumption and capital costs.
Innovation Solution
Implementing a process with two or three strippers instead of a single stripper in hydroprocessing units to separate hydroprocessing effluent streams by temperature, reducing heater duty by at least 40% and counterintuitively lowering capital costs by optimizing the design of the product fractionation column.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If a single stripper column is used to strip hydroprocessed effluent, then the process is simpler with lower capital cost, but the heater duty for the product fractionation column is excessively high
Solution Approach 1:
The single stripper column is divided into multiple stripper columns (typically two or three) that operate in series. Each stripper column handles a specific temperature range of the hydroprocessed effluent stream, with the first stripper handling the hottest stream and subsequent strippers handling progressively cooler streams. This segmentation allows each stripper to be optimized for its specific temperature range, reducing the overall heater duty required for the product fractionation column while distributing the complexity across multiple simpler units rather than one complex unit
2Loss of energy
If multiple stripper columns are implemented to reduce heater duty, then energy consumption decreases, but capital costs increase due to additional equipment
Solution Approach 1:
The multiple stripper columns are merged with the product fractionation column system in an integrated configuration where the stripped streams from multiple strippers feed into the fractionation column. The stripping mediums (steam or other gases) and the hydroprocessed effluent streams are combined and processed together through the fractionation column, creating a unified system that achieves energy savings while consolidating equipment functions rather than simply adding independent units
3Reliability
If the hydroprocessed effluent is stripped at high temperature, then hydrogen sulfide removal is more effective, but the heater duty for subsequent fractionation increases significantly
Solution Approach 1:
The stripping process is segmented into multiple stages with decreasing temperature levels. The first stripper column operates at the highest temperature to effectively remove hydrogen sulfide from the hot hydroprocessed effluent. Subsequent stripper columns operate at progressively lower temperatures to remove remaining contaminants from cooler streams. This segmentation maintains high hydrogen sulfide removal efficiency in the first stage while avoiding the energy penalty of heating all streams to high temperatures
Solution Approach 2:
The stripping process is performed as a preliminary action before the product fractionation step. By removing hydrogen sulfide and other contaminants in the stripper columns before the effluent enters the product fractionation column, the subsequent fractionation process operates with cleaner feedstock, reducing the heater duty required and improving overall process 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
The multi-stripper approach reduces energy consumption and capital expenditures by enhancing energy efficiency in hydroprocessing units, specifically by minimizing the heater duty required for the product fractionation column, while maintaining or improving product recovery efficiency.
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 before entering a product fractionation column to separate and recover products
Implementation Method 3
the stripped effluent then is heated in a fired heater to fractionation temperature
Data Source
AI summary
Two or three strippers are used to strip three hydroprocessed effluent streams, perhaps from a slurry hydrocracking reactor, separated by temperature instead of a single stripper to preserve separations previously made and conserving energy and reducing vessel size. A cold stripped stream may be taken as a diesel blending stock without further fractionation.