Slurry Bubble Column Reactor Shutdown Nozzle Protection
Solution Overview
Problem
During the shutdown of a three-phase slurry bubble column reactor, maintaining the minimum pressure drop across the gas distributor is challenging, leading to slurry ingress into the nozzles and potential blockages, as the flow of gas decreases and eventually stops, causing uneven gas distribution and catalyst issues.
Innovation Solution
Abruptly stopping the gas flow to the gas distribution nozzles while trapping inert gas within them to prevent slurry ingress, using a fast response valve and replacing reactive gas with inert gas like nitrogen to maintain pressure and prevent catalyst reaction, and introducing a quench fluid to cool the reactor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gas flow rate is reduced during shutdown, then reactor shutdown is achieved, but pressure drop across nozzles decreases causing slurry ingress
Solution Approach 1:
A fast response valve is installed in the gas feed line to abruptly stop gas flow to the gas distributor nozzles during shutdown. This preliminary action traps inert gas within the nozzles before slurry can ingress, preventing blockages. The valve responds rapidly to shutdown signals, closing the gas supply path before pressure drop reduction can cause slurry backflow into the nozzles.
2Ease of operation
If downwardly directed gas distribution nozzles are used, then uniform gas distribution is achieved during operation, but slurry ingress occurs during shutdown when gas flow stops
Solution Approach 1:
Inert gas (such as nitrogen) is introduced into the gas distributor system before shutdown to replace the reactive synthesis gas. This preliminary anti-action prevents catalyst reactions during shutdown and maintains positive pressure in the nozzles. When the fast response valve closes, the trapped inert gas creates a pressure barrier that prevents slurry from entering the nozzles, counteracting the harmful effect of shutdown conditions.
3Stress or pressure
If synthesis gas is fed to gas distributor during shutdown, then pressure is maintained, but catalyst reactions may occur causing thermal runaway
Solution Approach 1:
The synthesis gas in the gas distributor system is replaced with an inert gas (nitrogen) before shutdown. This creates an inert atmosphere that prevents any catalyst reactions from occurring during the shutdown period. The inert gas maintains positive pressure in the system to prevent slurry ingress, while its non-reactive nature eliminates the risk of exothermic reactions and thermal runaway that would occur if reactive synthesis gas remained in the system.
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 method effectively inhibits slurry ingress into the gas distributor nozzles during shutdown, maintaining reactor integrity and preventing thermal runaway, allowing for safer and more efficient shutdown and startup processes by maintaining pressure and cooling the reactor.
Implementation Method 1
Replacing the synthesis gas in the gas distributor with an inert gas, such as nitrogen, before shutting down the reactor prevents any catalyst reactions from occurring during the shutdown period
Implementation Method 2
abruptly stopping flow of gas from the gas feed line to the gas distribution nozzles to trap gas in the gas distribution nozzles thereby to inhibit slurry ingress upwardly into the gas distribution nozzles
Implementation Method 3
Due to the exothermic nature of Fisher-Tropsch hydrocarbon synthesis reactions it is very important to keep the catalyst in suspension in order to avoid hot spots and subsequent deterioration of the catalyst activity
Data Source
AI summary
A method is provided of shutting down an operating three-phase slurry bubble column reactor (10) having downwardly directed gas distribution nozzles (30) submerged in a slurry body (19) of solid particulate material suspended in a suspension liquid contained inside a reactor vessel (12), with the gas distribution nozzles (30) being in flow communication with a gas feed line (26) through which gas is fed to the gas distribution nozzles (30) by means of which the gas is injected downwardly into the slurry body (19). The method includes abruptly stopping flow of gas from the gas feed line (26) to the gas distribution nozzles (30) to trap gas in the gas distribution nozzles (30) thereby to inhibit slurry ingress upwardly into the gas distribution nozzles (30).