Staged Co-Hydrotreating for Low-Sulfur Diesel from Mixed Feedstocks
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Solution Overview
Problem
Current processes for producing diesel fuels from biocomponent feedstocks face challenges such as high sulfur levels, poor cold flow properties, and increased reaction temperatures due to exothermic hydrodeoxygenation reactions, which result in decreased yield and undesirable side products, and require significant additional equipment for separate processing of mineral and biologically derived feedstocks.
Innovation Solution
A staged co-hydrotreating process that initially reduces the sulfur content of a mineral hydrocarbon feedstock to 50 ppm or less in a first reaction zone, then combines it with a biocomponent feedstock for further hydrotreatment in a second zone to achieve a diesel product with sulfur levels of 10 ppm or less, using existing catalyst technology without increased pressures or hydrogen consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrodeoxygenation reactions are used to convert biocomponent feedstocks to hydrocarbon liquids, then oxygen is removed and unsaturated bonds are saturated, but the highly exothermic nature of these reactions leads to undesirably high reaction temperatures and low hydrogen availability
Solution Approach 1:
The hydrotreating process is divided into two separate stages: a first hydrotreating stage that processes mineral hydrocarbon feedstock to reduce sulfur to 50 ppm or less, and a second hydrotreating stage that processes the combined stream with biocomponent feedstock. This segmentation allows temperature and hydrogen conditions to be optimized for each stage independently, preventing the exothermic hydrodeoxygenation reactions from causing excessively high temperatures that would harm catalyst performance and product quality.
Solution Approach 2:
The mineral hydrocarbon feedstock undergoes preliminary hydrotreating to reduce its sulfur content to 50 ppm or less before being combined with the biocomponent feedstock. This preliminary action ensures that when the biocomponent feedstock undergoes hydrodeoxygenation in the second stage, the overall hydrogen consumption is better managed and temperature control is improved, avoiding the formation of unwanted side products and catalyst coking.
2Adaptability or versatility
If biocomponent feedstock is co-processed with mineral diesel feedstocks, then renewable diesel fuel is produced, but significant additional equipment footprint is required for separate processing trains
Solution Approach 1:
The process merges the processing of mineral hydrocarbon feedstock and biocomponent feedstock into a single integrated hydrotreating system. The mineral feedstock is treated in a first reaction zone, then combined with biocomponent feedstock and treated together in a second reaction zone. This merging eliminates the need for separate dedicated process trains for each feedstock type, reducing equipment footprint and capital costs while maintaining the ability to handle up to 20 wt% biocomponent feedstock.
Solution Approach 2:
The hydrotreating system is designed with multi-functionality to handle both mineral hydrocarbon feedstocks and biocomponent feedstocks (such as vegetable oils and animal fats) within the same reaction zones. The catalysts and process conditions are optimized to perform both hydrodesulfurization of mineral feedstock and hydrodeoxygenation of biocomponent feedstock, making the system universally applicable to mixed feedstock processing without requiring separate specialized equipment.
3Reliability
If separate processing of mineral and biologically derived feedstocks is performed, then preferred conditions can be selected for each feedstock, but significant additional equipment footprint is required
Solution Approach 1:
The processing is segmented into two distinct stages within an integrated system: a first hydrotreating stage for mineral feedstock optimization and a second hydrotreating stage for combined processing. This segmentation allows preferred conditions to be selected for each stage while maintaining a compact footprint through vertical integration rather than separate parallel trains.
Solution Approach 2:
The process merges the optimized processing of mineral feedstock with the treatment of biocomponent feedstock in a combined second reaction zone. This merging allows the benefits of separate processing (optimized conditions) to be achieved while avoiding the penalties of separate equipment trains, as the two streams are combined and processed together in shared reactor volume.
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 process effectively produces diesel fuel with low sulfur content and improved cetane number, reducing the formation of unwanted side products and maintaining desired temperature conditions, while utilizing existing refinery infrastructure.
Implementation Method 1
hydrotreating a mineral hydrocarbon feedstock in a first reaction zone to reduce the sulfur content to 50 ppm by weight or less
Implementation Method 2
the combined feedstock is then hydrotreated in a second reaction zone to produce a diesel boiling range product with a sulfur content of 10 ppm by weight or less
Implementation Method 3
hydrodeoxygenation reactions are highly exothermic relative to hydrodesulfurization and also require relatively large amounts of hydrogen
Data Source
AI summary
Processes are provided for producing a diesel fuel product having a sulfur content of 10 ppm by weight or less from feed sources that include up to 20% by weight of a biocomponent feedstock. The mineral hydrocarbon portions of the feed sources can be distillate or heavier feed sources.