# Caustic Merox Extraction > >- - **Type:** Skill - **Install:** `agentstack add skill-jskherman-engg-skills-caustic-merox-extraction` - **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior - **Seller:** [jskherman](https://agentstack.voostack.com/s/jskherman) - **Installs:** 0 - **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills) - **Latest version:** 0.1.0 - **License:** Apache-2.0 - **Upstream author:** [jskherman](https://github.com/jskherman) - **Source:** https://github.com/jskherman/engg-skills/tree/main/skills/caustic-merox-extraction ## Install ```sh agentstack add skill-jskherman-engg-skills-caustic-merox-extraction ``` Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent. ## About # Caustic / Merox Mercaptan Extraction Screening ## Overview Thin mass-balance helpers built around the chemistry of mercaptan extraction with aqueous NaOH: RSH + NaOH → RS-Na + H2O and the subsequent regeneration (oxidation): 2 RS-Na + 0.5 O2 + H2O → RSSR + 2 NaOH Provides: - Stoichiometric RS-Na loading at steady extraction. - Kremser-style stage performance with a user-supplied distribution coefficient `K = C_LPG / C_caustic`. - Risk-score heuristic for disulfide carryback to product LPG (caustic disulfide loading + caustic age + separator dP). These are screening and troubleshooting tools, not licensor design calculations. ## Prerequisites 1. `uv` available. 2. On first use, the script writes `LICENSE_NOTIFICATION.txt`. ## When to Use - Troubleshooting a Merox unit (rising RSH slip, caustic age question, carryback suspicion). - Sanity-checking caustic circulation rate vs RS-Na uptake. - Order-of-magnitude operator discussion. ## Don't use for - Licensor design (UOP Merox package and successors are proprietary; use the licensor's calculations). - Amine treating: use `sour-gas-amine-treating`. - Exact prediction of product disulfide concentration — the carryback score is directional, not quantitative. ## Utility Scripts - `uv run scripts/merox.py loading --rsh-ppmw 500 --lpg-kg-s 10 --caustic-kg-s 0.5 --naoh-wt 0.12 --output /tmp/load.json` - `uv run scripts/merox.py kremser --K 0.02 --lpg-vol 0.014 --caustic-vol 0.0006 --stages 3 --rsh-in 500 --output /tmp/k.json` - `uv run scripts/merox.py carryback --caustic-disulfide-ppmw 300 --caustic-age-days 60 --separator-dp-kpa 8 --output /tmp/risk.json` ## Procedure 1. Compute RS-Na loading from inlet RSH and current caustic circulation. 2. Compare with the bound-alkalinity available in lean caustic (total alkalinity − free alkalinity). 3. If loading is approaching available bound alkalinity, regeneration is not keeping pace — investigate the oxidizer / separator side. 4. Use the Kremser estimate to bracket required stages for a given RSH removal. 5. Use the carryback risk score to triage process data when product disulfide is rising. ## Pitfalls - Treating `K` as a constant when it depends on caustic concentration, T, and RSH chain length. - Confusing "free alkalinity" with "total alkalinity" — RS-Na consumption reduces free alkalinity. - Ignoring water carryover between the LPG and caustic phases (and the reverse): the coalescer / sand filter is part of the design envelope. - Treating the carryback heuristic score as quantitative. - Treating disulfide rise in product solely as a Merox issue when it could be feed (DMS / DEDS / DMDS passthrough). - Forgetting that caustic age increases mercaptide loading even at constant RSH inlet; bound alkalinity climbs over time. - Sizing without considering the disulfide-separator (Stelter/Hsu-style) performance. ## Fallback Strategies - If the Kremser estimate predicts unachievable removal at any reasonable stage count, the dominant problem is likely K (poor distribution) rather than stages; revisit caustic strength and contactor design. - If disulfide carryback score is "high" but product disulfide is low, there may be a strong DMS feed passthrough; surface to `vle-flash-calculations` or product-sulfur speciation skill. ## Verification - Run the listed script with representative inputs and an `--output` file when a deterministic calculation is available. - Confirm the JSON result contains `ok: true`, expected units, and no unhandled warnings. - Check result magnitudes against the stated assumptions, references, and a hand calculation or known operating range before reporting them. ## References - `references/merox_chemistry.md` — chemistry, regeneration, and the practical role of free alkalinity. - Kohl & Nielsen, *Gas Purification*. - UOP Merox descriptive literature (public). ## Anti-Patterns - Reporting "Merox is the cause" without considering feed sulfur speciation. - Treating the carryback score as a value to optimise on rather than a triage indicator. - Using these helpers for licensor design or rerate. ## Source & license This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code. - **Author:** [jskherman](https://github.com/jskherman) - **Source:** [jskherman/engg-skills](https://github.com/jskherman/engg-skills) - **License:** Apache-2.0 Install and usage instructions live in the source repository linked above. ## Pricing - **Free** — Free ## Security capabilities Automated source analysis of v0.1.0 — what this tool can access: - **Network access:** no - **Filesystem access:** no - **Shell / process execution:** no - **Environment & secrets:** no - **Dynamic code execution:** no *"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.* ## Versions - **0.1.0** — security scan: passed — Imported from the upstream source. ## Links - Listing page: https://agentstack.voostack.com/l/skill-jskherman-engg-skills-caustic-merox-extraction - Seller: https://agentstack.voostack.com/s/jskherman - Browse the marketplace: https://agentstack.voostack.com/browse --- Listed on AgentStack — the marketplace for AI agent skills and MCP servers. 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