Low Cloud Point Diesel via Segmented Hydrotreatment
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Solution Overview
Problem
Current refinery processes face challenges in reducing sulfur content in diesel fuels to meet stringent regulatory requirements without increasing hydrogen pressure, which can lead to higher energy costs and catalyst degradation, and often require expensive equipment upgrades.
Innovation Solution
A two-stage process involving hydrotreatment and dewaxing stages, using a divided wall column fractionator to separate and process feedstocks, reduces sulfur content to below 15 wppm while improving cold flow properties, utilizing catalysts with Group VIII metals on bound zeolites and operating at lower pressures to minimize energy expenditure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrogen pressure is increased to reduce sulfur content in diesel fuels, then sulfur removal efficiency is improved, but energy costs increase and catalyst degradation accelerates
Solution Approach 1:
The hydroprocessing reaction is divided into two sequential stages: hydrotreatment stage followed by dewaxing stage. Each stage operates at optimized pressure levels with specific catalysts, allowing sulfur removal to be achieved without requiring excessively high hydrogen pressure throughout the entire process. The segmentation enables tailored operating conditions for each functional stage.
Solution Approach 2:
The process utilizes parameter changes by operating the hydrotreatment stage at lower pressure (300-800 psig) compared to conventional single-stage high-pressure processes. The divided wall column fractionator also enables parameter changes by separating fractions at different pressures and temperatures, optimizing the overall energy efficiency while achieving the required sulfur content reduction.
2Manufacturing precision
If hydrogen pressure is increased to reduce sulfur content in diesel fuels, then sulfur removal efficiency is improved, but catalyst lifetime decreases
Solution Approach 1:
The catalytic process is segmented into two stages with different catalyst functions. The hydrotreatment catalyst operates at lower pressure to perform sulfur removal, preserving catalyst lifetime. The dewaxing catalyst then handles the remaining processing requirements. This segmentation protects the sulfur-removal catalyst from excessive pressure stress while still achieving the required sulfur content reduction.
Solution Approach 2:
By changing the pressure parameter to operate in the lower range (300-800 psig) during hydrotreatment, the process reduces mechanical stress and chemical degradation on the catalyst. This parameter optimization extends catalyst lifetime while maintaining effective sulfur removal through the two-stage configuration.
3Manufacturing precision
If conventional single-stage hydroprocessing is used, then process simplicity is maintained, but sulfur content reduction to below 15 wppm is difficult without high pressure
Solution Approach 1:
The hydroprocessing unit is segmented into two functional stages: hydrotreatment and dewaxing. Each stage has its own optimized catalyst and operating conditions. The divided wall column fractionator further segments the product separation, allowing simultaneous production of multiple fractions with different sulfur contents. This segmentation enables achieving sulfur content below 15 wppm without requiring a single high-pressure stage.
Solution Approach 2:
The divided wall column fractionator performs multiple functions: it separates the hydroprocessed effluent into multiple fractions (light ends, diesel fraction, heavy fraction), recycles appropriate fractions back to the reactors, and produces final products meeting different sulfur specifications. This multi-functionality achieves high sulfur removal efficiency while managing process complexity through integrated design.
4Manufacturing precision
If expensive equipment upgrades are implemented to meet sulfur standards, then sulfur content reduction capability is improved, but capital costs increase
Solution Approach 1:
The process achieves sulfur content reduction to below 15 wppm by changing operating pressure parameters to the lower range (300-800 psig) and utilizing the two-stage configuration with divided wall column fractionation. This parameter optimization allows existing equipment to meet stringent sulfur standards without requiring expensive high-pressure equipment upgrades or new capital investments.
Solution Approach 2:
The divided wall column fractionator enables discarding of light ends fractions and recovering/recycling of intermediate fractions back to the hydroprocessing reactors. This recycling approach maximizes sulfur removal efficiency from the available feedstock without requiring additional expensive processing equipment, thereby reducing capital costs while meeting sulfur content targets.
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 allows for the production of low sulfur diesel fuels with improved cold flow properties at lower costs, reducing the need for expensive equipment upgrades and maintaining catalyst longevity, while effectively meeting current and future regulatory sulfur content standards.
Implementation Method 1
fractionating the hydroprocessed liquid fraction to produce at least a product fraction and a common fraction that is passed to an upper undivided volume of the fractionator
Implementation Method 2
hydroprocessing at least a portion of the separated liquid fraction under effective dewaxing conditions in the presence of a catalyst including at least one Group VIII metal on a bound zeolite
Implementation Method 3
hydrotreating a feedstock having a sulfur content of at least about 1500 wppm under effective hydrotreating conditions to produce at least a liquid fraction
Data Source
AI summary
A diesel fuel product with beneficial cold flow properties can be produced. A suitable feedstock for forming a diesel boiling range product can be hydrotreated to have a sulfur content of at least about 100 wppm and then dewaxed. This two stage process can allow for production of an arctic or winter diesel without use of high pressures. Optionally, a divided wall column fractionator can be used to allow a single separation stage to handle the effluent from both the hydroprocessing and the dewaxing stages.