Hydroprocessing Reactor Cooling via Temporary Heat Exchanger
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Solution Overview
Problem
Hydroprocessing reactor shutdown processes are inefficient below 400° F (204° C.), leading to slow cooling and increased risk to personnel and equipment, as existing methods are cumbersome and pose hazards during catalyst removal.
Innovation Solution
Implementing a temporary heat exchanger in the recycle gas circulation system to accelerate cooling below 400° F (204° C.), combined with nitrogen purging and water flooding, allowing for safer and faster catalyst removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional cooling methods are used below 400° F (204° C.), then the cooling process is slow and unsafe, but implementing a temporary heat exchanger increases device complexity
Solution Approach 1:
A temporary heat exchanger is introduced as an intermediary device in the recycle gas circulation system to accelerate cooling. The heat exchanger acts as a mediator between the hot reactor and the cooling medium, enabling faster heat removal without permanently modifying the reactor itself. This resolves the contradiction by providing enhanced cooling capability only when needed during shutdown.
Solution Approach 2:
The patent employs a temporary heat exchanger that is installed only during the cooling phase and then removed. This disposable approach allows the use of specialized cooling equipment without permanent installation costs or ongoing maintenance complexity. The heat exchanger serves its purpose during the critical cooling period and is then discarded, resolving the complexity issue.
2Productivity
If cooling is accelerated below 400° F (204° C.), then catalyst removal can be performed faster, but the risk to personnel and equipment increases without proper safety measures
Solution Approach 1:
The patent implements preliminary safety actions before accelerating the cooling process. Nitrogen purging is performed beforehand to create an inert atmosphere, and water flooding is prepared in advance. These preliminary actions ensure that when the accelerated cooling is initiated, the environment is already safe for rapid temperature reduction, thus enabling faster catalyst removal without compromising safety.
Solution Approach 2:
The patent converts the potential harm of rapid cooling (thermal shock and safety risks) into a benefit by using controlled water flooding. The water, when introduced, provides both cooling and protective functions simultaneously. The rapid temperature reduction that could cause thermal stress is transformed into a controlled process that facilitates quick catalyst removal while the water protects against overheating and creates safe working conditions.
3Reliability
If the cooling process is extended to ensure safety, then personnel and equipment are protected, but the shutdown duration increases
Solution Approach 1:
The patent employs periodic action through staged cooling and alternating operations. The cooling process is divided into phases: initial conventional cooling, then accelerated cooling with the temporary heat exchanger, followed by nitrogen purging periods, and finally water flooding. This periodic approach maintains safety through controlled intervals while minimizing total shutdown time by switching between different cooling intensities and methods.
Solution Approach 2:
The patent changes the cooling parameters dynamically throughout the shutdown process. Initially, standard cooling rates are used to bring the reactor to a safe threshold. Then, parameters are changed by introducing the temporary heat exchanger to dramatically increase the cooling rate. Finally, additional parameters are adjusted by introducing nitrogen and water. These parameter changes enable the process to maintain safety while minimizing total shutdown duration.
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 significantly accelerates the cooling process, enabling faster catalyst changes, reducing equipment damage and personnel risk, while ensuring safe and efficient shutdown procedures.
Implementation Method 1
routing at least a portion of a gaseous medium flowing to the reactor through a heat exchanger cooling the gas to not less than 40° F. (4.4° C.)
Implementation Method 2
mixing the cooled gas with gas medium flowing to the reactor. Continue routing and cooling at least a portion of the gas medium flowing to the reactor, and then mixing the cooled gas with the flow to the rector
Implementation Method 3
cooling the reactor to a first threshold reactor temperature in the range of from 375-425° F. (190-218° C.)
Implementation Method 4
The reactor is then purged with N2 gas
Implementation Method 5
introducing water into the reactor via a quench gas distribution system
Implementation Method 6
introducing water into the reactor via a quench gas distribution system
Data Source
AI summary
A process for shutting down a hydroprocessing reactor and for removing catalyst from the reactor, wherein the reactor includes a quench gas distribution system. The process comprises shutting off hydrocarbon feed to the reactor, stripping hydrocarbons from the catalyst, and cooling the reactor to a first threshold reactor temperature in the range of from 375-425° F. (190-218° C.). At least a portion of circulating gaseous medium flowing to the reactor is then routed through a temporary heat exchanger and cooling the gas to not less than 40° F. (4° C.). Once cooled, mixing the cooled gas with the circulating gaseous medium flowing to the reactor. Continuing steps routing and cooling until a second threshold temperature is reached wherein the reactor temperature is in a range between 120° F. and 250° F. (49° C.-121° C.). The reactor can then be purged with N2 gas, followed by introducing water into the reactor via the quench gas distribution system. The catalyst can then be safely removed from the reactor.