Hydrocracking and Hydroisomerization Reactor Quenching
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Solution Overview
Problem
Current hydrocracking processes face challenges in reducing diesel fuel's cold flow property temperatures without lowering the diesel cut point, which limits diesel yield and requires additional dewaxing operations, especially for winter fuel specifications.
Innovation Solution
A process where the hydrocracked effluent is quenched with a recycle oil stream to cool the hydroisomerization catalyst bed, allowing for integrated hydrocracking and hydroisomerization in the same reactor, and the hydroisomerization catalyst can be inactivated during warmer months to conserve diesel product.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a lower diesel cut point is used to meet cold flow specifications, then cold flow properties are improved, but diesel yield is reduced
Solution Approach 1:
The process divides the hydrocarbon conversion into two distinct functional zones within a single reactor: a hydrocracking zone that operates at higher temperatures to maximize diesel yield, and a hydroisomerization zone that operates at lower temperatures to improve cold flow properties. This segmentation allows each zone to be optimized for its specific function without compromising the other, resolving the contradiction between yield and cold flow properties.
Solution Approach 2:
Different catalysts with specific local qualities are placed in different zones of the reactor. The hydrocracking zone uses catalysts optimized for high-temperature cracking activity to maximize diesel production, while the hydroisomerization zone uses catalysts optimized for low-temperature isomerization activity to improve cold flow properties. This local quality differentiation allows simultaneous optimization of both yield and cold flow properties.
2Temperature
If a separate dewaxing unit is added to improve cold flow properties, then cold flow properties are improved, but device complexity is increased
Solution Approach 1:
The patent merges the hydrocracking and hydroisomerization functions into a single reactor system with two distinct zones. The first zone performs hydrocracking while the second zone performs hydroisomerization, eliminating the need for separate dewaxing units and reducing overall process complexity while still achieving improved cold flow properties.
Solution Approach 2:
The single reactor system performs multiple functions: it conducts both hydrocracking and hydroisomerization reactions, and can operate in different modes (e.g., activating or deactivating the hydroisomerization zone) to adapt to different product specifications. This multi-functionality reduces the need for separate dedicated units for each function.
3Temperature
If the hydroisomerization catalyst is always active, then cold flow properties are continuously improved, but diesel product is lost during warmer months
Solution Approach 1:
The hydroisomerization catalyst zone can be periodically activated or deactivated based on seasonal demands and product specifications. During warmer months when cold flow properties are not critical, the zone can be deactivated to preserve diesel product. During colder months or when winter fuel specifications are required, the zone is activated to improve cold flow properties, thus resolving the contradiction between continuous improvement and seasonal product preservation.
Solution Approach 2:
The process incorporates dynamic control of the hydroisomerization zone, allowing operators to adjust catalyst activity levels or flow distribution to match changing product requirements. This dynamic capability enables the system to adapt between maximizing diesel yield during warm periods and optimizing cold flow properties during cold periods, preventing unnecessary product loss.
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 meets Arctic Diesel Specifications with a Cloud Point Temperature of -40°C and Pour Point of -45°C while increasing distillate yield by 4 to 5 wt% compared to alternative methods that reduce the diesel cut point.
Implementation Method 1
the hydrocracked effluent stream is quenched with a recycle oil stream
Implementation Method 2
Hydroisomerization or dewaxing is a hydroprocessing process that increases the alkyl branching on a hydrocarbon backbone in the presence of hydrogen and hydroisomerization catalyst
Implementation Method 3
Hydrocracking is a hydroprocessing process in which hydrocarbons crack in the presence of hydrogen and hydrocracking catalyst to lower molecular weight hydrocarbons
Data Source
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AI summary
A process and apparatus for quenching a hydrocracked stream to prepare it for hydroisomerization. A fractionated hydroisomerized stream is recycled to quench a hot hydrocracked stream prior to hydroisomerization. Sufficient quenching can inactivate the hydroisomerization catalyst bed. The hydroisomerization catalyst bed can be heated back to hydroisomerization temperature and can actively hydroisomerize again.