Feed Nozzle Purging Orifices Prevent Catalyst Suction
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Solution Overview
Problem
In catalytic cracking processes, the interruption of hydrocarbon feed can cause catalyst particles to be sucked into the feed nozzle due to reduced pressure areas, leading to conduit blockage and slurry formation, especially when steam flows without hydrocarbon supply.
Innovation Solution
A feed nozzle assembly with an inner and outer tube configuration, featuring purging orifices in the inner tube to allow fluid passage between the tubes, ensuring dispersion gas flows through the liquid conduit even when hydrocarbon supply is stopped, and a second nozzle for uniform atomization of the gas-liquid mixture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steam flows through the gas conduit without hydrocarbon feed supply, then the gas conduit remains clear, but reduced pressure areas cause catalyst to be sucked into the hydrocarbon conduit leading to blockage
Solution Approach 1:
A purging nozzle is introduced as an intermediary device that directs a purging stream into the hydrocarbon conduit during steam-only flow conditions. This purging stream acts as a mediator to prevent catalyst particles from being sucked into and blocking the hydrocarbon conduit, while not interfering with normal co-flow operation of steam and hydrocarbon feed.
2Reliability
If hydrocarbon feed is interrupted during emergency situations, then safety is improved, but catalyst defluidization and slurry formation occur due to suction into the nozzle
Solution Approach 1:
The system performs preliminary action by activating the purging nozzle before catalyst blockage can occur. During emergency shutdown conditions when hydrocarbon feed is interrupted but steam continues to flow, the purging nozzle preemptively introduces a purging stream that maintains positive pressure in the hydrocarbon conduit, preventing catalyst suction and slurry formation before they can happen.
3Reliability
If a purging nozzle is added to prevent catalyst suction, then conduit reliability improves, but device complexity increases
Solution Approach 1:
The purging nozzle is designed with multi-functionality to minimize added complexity. It serves multiple purposes: preventing catalyst suction during steam-only flow, maintaining positive pressure in the hydrocarbon conduit, and not interfering with normal co-flow operation. The nozzle can be integrated into the existing feed nozzle structure, sharing common mounting and control systems.
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
Prevents catalyst entry into the nozzle during hydrocarbon feed interruption, maintaining normal operation and ensuring continuous steam flow through the liquid conduit, thus preventing conduit blockage and ensuring efficient distribution of the feed in catalytic cracking reactors.
Implementation Method 1
steam flows through the gas supply nozzle without hydrocarbon feed being supplied to the annular conduit. This seems to create areas of reduced pressure inside the feed nozzle which in turn cause catalyst to be sucked into the hydrocarbon conduit
Implementation Method 2
a second nozzle attached to the outlet end of the outer tube and arranged downstream of the first nozzle
Data Source
AI summary
A feed nozzle assembly for co-currently introducing gas and liquid into a reactor vessel which feed nozzle assembly comprises (a) an inner tube defining a gas conduit and an outer tube arranged around the inner tube, wherein the outer surface of the inner tube and the inner surface of the outer tube define an annular liquid conduit, and wherein each of the tubes have an inlet end and an opposite outlet end; (b) a first nozzle attached to the outlet end of the inner tube; (c) a second nozzle attached to the outlet end of the outer tube and arranged downstream of the first nozzle, wherein the inner tube contains purging orifices.