Caustic Treating

With the improved electrolytic property packages available in ProMax, caustic treating may be modeled to predict the absorption of acid gas compounds and sulfur species such as H₂S, CO₂, and mercaptans from liquid or vapor streams.

Absorption of Acid Gas

ProMax can predict the absorption of acid gas compounds and sulfur species such as CO₂, H₂S, and mercaptans from liquid or vapor streams by caustic (NaOH) solutions.
A caustic wash can be used to remove acid gas from either natural gas or liquid hydrocarbon streams.
Sodium Hydroxide solution is a very effective but usually non-regenerable absorbent for CO₂ and H₂S, forming stable salts such as sodium carbonate and sodium sulfide.
The actual salt compound is not shown in ProMax, however, the stream ionic information is used to determine the amount of salt formed. The amount of species [HS-] corresponds to the amount of NaHS formed, [S--] corresponds to Na₂S, [CO3--] correspnds to Na₂CO₃, etc.
Caustic solutions can be used to selectively remove H₂S from vapor streams in the presence of CO₂ provided that extremely short contact times of about 0.01 to 0.02 seconds are maintained as described by Hohlfeld (1979) and by Kent (1985).

Absorption of Mercaptans

A caustic wash can be used to remove mercaptans from either natural gas or liquid hydrocarbon streams. When used to absorb mercaptans only, the caustic solution is usually regenerable either by thermal means or by oxidative regeneration.
Thermal regeneration is achieved in a stripping column by the addition of open steam or by steam internally generated by a column heating element. About 6 lb steam per gal of NaOH solution is required for stripping. Although this steam rate seems high compared to typical amine unit stripping steam requirements, the amount of caustic solution required to pick up the mercaptans is much lower than amount of amine solution that would be used in a comparable amine sweetening system.


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Free SixxacMenu module license Capabilities Amine Sweetening Glycol Dehydration Heat Exchanger Rating Crude Oil Refining LPG Recovery NGL Fractionation Caustic Treating Sulfur and TGCU Reactors Sour Water Stripper Pipelines Vessel Sizing Other Processes Interface Flowsheet Drawing Multiple Flowsheets Project Viewer Reporting Property Packages Extensibility TSWEET PROSIM Client List Sales Information Testimonials	Caustic Treating With the improved electrolytic property packages available in ProMax, caustic treating may be modeled to predict the absorption of acid gas compounds and sulfur species such as H₂S, CO₂, and mercaptans from liquid or vapor streams. Absorption of Acid Gas ProMax can predict the absorption of acid gas compounds and sulfur species such as CO₂, H₂S, and mercaptans from liquid or vapor streams by caustic (NaOH) solutions. A caustic wash can be used to remove acid gas from either natural gas or liquid hydrocarbon streams. Sodium Hydroxide solution is a very effective but usually non-regenerable absorbent for CO₂ and H₂S, forming stable salts such as sodium carbonate and sodium sulfide. The actual salt compound is not shown in ProMax, however, the stream ionic information is used to determine the amount of salt formed. The amount of species [HS-] corresponds to the amount of NaHS formed, [S--] corresponds to Na₂S, [CO3--] correspnds to Na₂CO₃, etc. Caustic solutions can be used to selectively remove H₂S from vapor streams in the presence of CO₂ provided that extremely short contact times of about 0.01 to 0.02 seconds are maintained as described by Hohlfeld (1979) and by Kent (1985). Absorption of Mercaptans A caustic wash can be used to remove mercaptans from either natural gas or liquid hydrocarbon streams. When used to absorb mercaptans only, the caustic solution is usually regenerable either by thermal means or by oxidative regeneration. Thermal regeneration is achieved in a stripping column by the addition of open steam or by steam internally generated by a column heating element. About 6 lb steam per gal of NaOH solution is required for stripping. Although this steam rate seems high compared to typical amine unit stripping steam requirements, the amount of caustic solution required to pick up the mercaptans is much lower than amount of amine solution that would be used in a comparable amine sweetening system.