Hydrotreating Process with Separation Zone for Ultra-Low Sulfur Diesel
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Solution Overview
Problem
Current hydrotreating processes for hydrocarbon streams, such as coker kerosene, require high pressures to meet sulfur, nitrogen, and Bromine Index specifications, leading to high energy consumption and capital costs, and often necessitate additional reactors to achieve desired product quality, particularly for ultra-low sulfur diesel production.
Innovation Solution
A process involving a separation zone between two hydroprocessing reactors, where a partially hydrotreated stream is separated into vapor and liquid streams, with the liquid stream being further hydrotreated in a second reactor using a noble metal catalyst, and sulfur and nitrogen are stripped using hydrogen or steam, allowing for reduced operating pressures and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high pressure hydrotreating is used to meet sulfur and nitrogen specifications, then sulfur and nitrogen removal is improved, but energy consumption and operating costs increase
Solution Approach 1:
The hydrotreating process is divided into two separate reactors: a first reactor for bulk desulfurization and denitrification, and a second reactor for achieving final sulfur specifications. This segmentation allows each reactor to operate under optimized conditions, with the first reactor handling the majority of heteroatom removal at moderate pressure, thereby reducing overall energy consumption while meeting product specifications.
Solution Approach 2:
The first reactor performs preliminary desulfurization and denitrification to remove the bulk of sulfur and nitrogen compounds before the stream enters the second reactor. This preliminary action reduces the load on the second reactor, allowing it to operate at lower pressure and energy input while still achieving the final ultra-low sulfur specification.
2Manufacturing precision
If high pressure hydrotreating is used to achieve desired Bromine Index, then olefin saturation is improved, but capital cost of hydrotreating unit increases
Solution Approach 1:
The process uses two separate reactors with different catalysts and operating conditions. The first reactor uses a conventional hydrotreating catalyst for bulk treatment, while the second reactor uses a noble metal catalyst specifically optimized for olefin saturation at lower pressures. This segmentation allows the capital-intensive noble metal catalyst to be used only where needed for Bromine Index control, reducing overall capital costs.
Solution Approach 2:
Different regions of the process (the two reactors) have different catalyst compositions and operating parameters tailored to their specific functions. The second reactor is specifically designed with noble metal catalyst and lower pressure operation to address the Bromine Index requirement locally, rather than requiring the entire process to operate at high pressure.
3Manufacturing precision
If a post-treatment reactor is added to meet Bromine Index specification, then olefin saturation is improved, but device complexity and operating costs increase
Solution Approach 1:
The process combines bulk desulfurization/denitrification and olefin saturation functions into a two-reactor sequence where the second reactor serves dual purposes: finishing sulfur removal and achieving Bromine Index specification. This merging of functions into a sequential process reduces overall device complexity compared to having separate units for each function.
4Manufacturing precision
If single stage hydrotreating with high catalyst volume is used for ultra-low sulfur diesel production, then sulfur removal is improved, but reactor dimensions and site requirements increase
Solution Approach 1:
The hydrotreating function is segmented into two reactors with different catalyst types and volumes. The first reactor uses conventional catalyst for bulk sulfur removal, while the second reactor uses high-activity noble metal catalyst to achieve ultra-low sulfur levels with much smaller catalyst volume. This segmentation dramatically reduces the total reactor volume required compared to a single-stage process using only conventional catalyst.
Solution Approach 2:
The process changes the catalyst parameter from conventional hydrotreating catalyst to noble metal catalyst in the second reactor, which provides significantly higher activity per unit volume. This parameter change enables the same sulfur removal function to be achieved with much smaller reactor dimensions, accommodating site constraints.
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 effectively reduces sulfur and nitrogen levels, achieves the desired Bromine Index, and produces ultra-low sulfur diesel at lower costs by decoupling bulk desulfurization and denitrification reactions, enabling efficient processing and reducing capital and operating expenses.
Implementation Method 1
hydrotreating a hydrocarbon stream in a hydrotreating zone comprising a hydrotreating catalyst and being operated under conditions sufficient to hydrotreat the hydrocarbon stream
Implementation Method 2
hydrotreating a hydrocarbon stream in a hydrotreating zone comprising a hydrotreating catalyst
Implementation Method 3
separating the partially hydrotreated stream in a separation zone into a vapor stream and a liquid stream
Implementation Method 4
stripping at least one of sulfur and nitrogen from at least a portion of the partially hydrotreated stream in a stripping zone
Implementation Method 5
stripping at least one of sulfur and nitrogen from at least a portion of the partially hydrotreated stream
Implementation Method 6
hydrotreating the liquid stream in a second hydrotreating zone comprising a hydrotreating catalyst and being operated under conditions sufficient to hydrotreat the hydrocarbon stream
Implementation Method 7
hydrotreating the liquid stream in a second hydrotreating zone comprising a hydrotreating catalyst
Data Source
AI summary
Processes for hydrotreating a hydrocarbon stream in which a separation zone and a stripping zone is disposed between two hydrotreating reactors. The stripping zone may comprise a portion of the second hydrotreating reactor. The separation zone may comprise two separator vessels. A separator vessel may include the scrubbing zone to receive a scrubbing fluid, for example, steam, hydrogen, or heated effluent, and remove H.sub.2S and NH.sub.3. A divided wall separator may be used. Vapor from the separator vessels can be recycled in the system.