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Questions and Answers
What is the primary factor limiting the catalyst flow in the reactors currently?
The limiting factor is the capacity of the catalyst pumps P-201-205.
How does the amount of 5 wt% TEA fed to each reactor vary?
The amount of TEA varies based on the reactor temperature.
What is the purpose of routing boiler feed water from H-530 to the reactors?
The boiler feed water removes heat generated by the NAO reactions, ensuring a constant reaction temperature.
What happens to the reactor effluent after it exits from each reactor?
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What is the effect of manipulating the average coil temperature in the reactors?
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What is the main purpose of the reactor section in this context?
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Why is there a 10% non-availability in the reactor system?
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What factors must be controlled to achieve the operating objectives of the reactor section?
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What is the function of the catalyst injection header in each reactor?
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How often are the reactors taken off-line for solvent washing, and why?
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Study Notes
Reactor Section Overview
- Converts compressed ethylene using Triethylaluminum (TEA) catalyst to produce Normal Alpha Olefins (NAO).
- Five reactors operate in parallel, aiming for 90% online availability with four typically in service and one under solvent washing.
Operational Dynamics
- Each reactor undergoes monthly solvent washing to remove waxy polymer buildup caused by the reaction, impacting heat transfer.
- Approximately 50% of ethylene converts to NAO in each reactor with product quality focused on high alpha olefin content and vinylidene specifications.
Process Control
- Reactor operations are finely tuned through control of pressure, temperature, ethylene feed rate, purity, and catalyst feed rate.
- It is critical to avoid upsets that may lead to temperature fluctuations.
Feed and Reaction Mechanism
- Ethylene feed from C-120A/B enters R-201-205 reactors and is preheated in four internal tubes.
- TEA catalyst injected at 5 wt% from D-210, with precautions in place to prevent ethylene backflow into catalyst injection headers.
- Mixture flows isothermally through 212 reactor tubes, with an average residence time of approximately 50 minutes.
Catalyst Management
- Conversion efficiency is managed by adjusting the TEA feed amount, which is dependent on reactor temperature.
- High catalyst flow rates are desired to maintain stable operations; catalyst pump capacity currently limits further increase in catalyst dilution.
Future Expansion
- Installation of P-200 catalyst pump on R-205 aims to alleviate pump capacity limitations, with plans for similar equipment on R-201-204.
Thermal Regulation
- Boiler feed water from H-530 (Dowtherm Heater) maintains a constant reaction temperature by removing heat generated from NAO reactions.
- Pressure adjustments in the reactor shell help control the average coil temperature to align product composition with market demands.
Steam Management
- Generates approximately 220 psig steam, which is reduced and routed to the 100 psig steam header for process use.
Purge and Effluent Management
- An ethylene purge continually flows through valve inlets to maintains pressure stability; purged gas treated before entering reactors to remove impurities.
- Reactor effluent is flashed through control valves to minimize reactions before heading to E-201-205 for cooling, where they combine into a common header, excluding R-205’s effluent, which has a separate routing plan for future reactor integration.
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Description
This quiz covers the purpose and operation of reactors used in the conversion of compressed ethylene to Normal Alpha Olefins (NAO) using an aluminum alkyl catalyst. It emphasizes the production rates, reactor availability, and the operational management during solvent washing. Test your understanding of the key processes involved and their implications in chemical engineering.
