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Questions and Answers
What reaction occurs when aluminum alkyls are mixed with heated circulating caustic in M-340?
Aluminum alkyls react with water to form n-paraffins and aluminum hydroxide.
What is the purpose of maintaining the circulating caustic strength between 12% and 30%?
This range ensures that sodium aluminate remains in solution.
What happens to the vapor that rises through T-340 (Caustic Wash Vapor Scrubber)?
The vapor gets washed free of any entrained caustic by fresh process water.
What two liquid phases are produced after the separation in D-340 (Caustic Wash Settler)?
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Where is excess caustic routed after being separated in D-340?
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What is the primary function of D-345 (Continuous Skim Drum)?
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What negative impact does the rag layer have on product quality?
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Describe the function of the level sensor in D-345.
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What precaution must be taken before maintenance on the nuclear source of D-345?
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Where do the oily water and waste water from D-345 get routed to?
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Study Notes
Caustic Wash System Overview
- Liquid streams from several drums (D-310A/B, T-330, D-330, D-344) mix with streams from the Ethylene Feed Section (D-110, D-120A/B).
- The mixture is processed in M-340 (Caustic Wash Static Mixer) with heated circulating caustic.
Reactions and Catalyst Removal
- Aluminum alkyls react with water, yielding n-paraffins and aluminum hydroxide.
- Caustic reacts with aluminum hydroxide, forming soluble sodium aluminate, facilitating catalyst removal.
- Nickel catalyst from the saturate reduction system also reacts with caustic, producing a nickel salt eliminated with spent caustic.
Caustic Strength Maintenance
- Circulating caustic strength is maintained between 12% (minimum) and 30% (maximum) to keep sodium aluminate in solution.
Phase Separation and Treatment
- The resultant three-phase stream from M-340 moves to T-340 (Caustic Wash Vapor Scrubber) for separation of vapor and liquid phases.
- Vapor dusts through a packed bed in T-340, washed of entrained caustic by contact with fresh water.
Hydrocarbon and Caustic Separation
- The liquid phases separate in D-340 (Caustic Wash Settler) into hydrocarbon and caustic streams.
- Hydrocarbon stream, along with water from T-340, is directed to T-350 (Water Wash Vapor Scrubber) for additional washing.
Caustic Makeup and Recycling
- Most caustic from D-340, along with fresh caustic from TK-342, mixes in M-341 and is recycled by P-340A/B.
- Recycled caustic is heated in E-340 using 100 psig steam before returning to M-340.
Handling Spent Caustic and Wastewater
- Excess caustic is sent to T-344 (Degassing Tower) while wastewater goes to D-353 (Waste Water Degassing Drum).
- D-340 features a continuous skim system to manage rag layers, which negatively impact NAO product quality.
Rag Layer Management
- Continuous skim system extracts rag layer from D-340 into D-345 (Continuous Skim Drum).
- Lighter components from the rag layer undergo further stripping in T-350, while oily water goes to T-344.
- Wastewater is channeled to D-353 for treatment.
Safety Measures and Maintenance
- D-345 contains a sophisticated level sensor with a nuclear source for accurate measurements.
- Specific protocols are mandated for maintenance of the nuclear source to minimize personnel exposure risks.
- Qualified technicians must shutter the nuclear source before initiating maintenance tasks.
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Description
This quiz explores the Caustic Wash System and its components, including reactor effluent separators and scrubbers. Understand the process of combining liquid streams and the chemical reactions involved in treating the effluents. Test your knowledge of the equipment and their functions in the Ethylene Feed Section.
