# Offshore Methanol Process Design — QA and Reconciliation Report

**Status:** Controlled supporting artifact  
**Reference:** Group T3 conceptual process-design report, 2026  
**Purpose:** Make numerical reconciliation visible rather than silently selecting convenient values.

## Executive QA conclusion

The public website and support workbook preserve the technical conclusion of the report: the flowsheet reaches the methanol specification but the base-case economics are negative. The review identified two material items that remain open for independent reconciliation: the reported steam-to-carbon ratio and the operating-labor cost basis.

The controlled hierarchy is:

1. controlling stream table or explicit equation;
2. detailed equipment or economic appendix;
3. narrative section and rounded executive values;
4. figure-only qualitative evidence.

## Control ledger

| ID | Topic | Source values | Controlled value | Logic | Status | Severity |
|---|---|---|---|---|---|---|
| QA-01 | Annual methanol production | 8.19 kt/y; 8.97 kt/y; 1,025.368 kg/h; 8,000 h/y | 8.203 kt/y | 1,025.368 × 8,000 / 1,000,000 | Reconciled | Medium |
| QA-02 | Reformer tube diameter | 4 m in narrative/table; 0.1016 m in catalyst sizing | 0.1016 m per tube | Detailed catalyst-volume basis controls | Reconciled | High |
| QA-03 | Synthesis conversion | 75.5% and 75.8% | 75.5% | Balance calculation and conclusion value used; 75.8% treated as narrative rounding | Rounded | Low |
| QA-04 | Distillation reflux ratio | 0.36 and 1.03829 | 0.36 DSTWU preliminary; 1.03829 final RadFrac | Values belong to different model stages | Clarified | Low |
| QA-05 | Product purity basis | 99.86 wt%; 99.89 mol% | Both retained with basis labels | Mass and molar fractions are not interchangeable | Clarified | Low |
| QA-06 | Steam-to-carbon ratio | Reported design value 2.78; stream table not fully reconciled | 2.78 reported assumption | Do not present as independently verified | Open | Medium |
| QA-07 | Operating labor cost | $0.160m/y executive table; approximately $0.994m/y appendix calculation | $0.160m/y in executive economics; discrepancy disclosed | Preserve official COMd result and avoid mixing cost bases | Open | High |
| QA-08 | Reformer furnace duty | 8,762 MJ/h actual note; 10,800 MJ/h CAPCOST input | Both retained with purpose labels | 10,800 MJ/h is the conservative CAPCOST regression minimum | Clarified | Low |
| QA-09 | Direct versus indirect emissions | 116 kg CO2/h indirect; 138 kg CO2/h direct | Separate bars and labels | Avoid false single-footprint claim | Passed | Low |
| QA-10 | Methane economic boundary | Methane purchase cost set to zero | Explicit boundary assumption | Opportunity cost would worsen economics | Passed with boundary | Medium |

## Open items

### QA-06 — Steam-to-carbon ratio

The report states a design steam-to-carbon ratio of 2.78. A direct recomputation from the public stream table is not fully reconciled with that statement. The value is therefore shown as a reported design assumption, not as an independently verified calculation.

### QA-07 — Operating-labor cost

The executive economic results use approximately $0.160m/y, while a detailed appendix calculation is near $0.994m/y. The public economics preserve the official COMd and NPV result from the executive table. The discrepancy is disclosed because mixing the two bases would create an internally inconsistent financial model.

## Passed and clarified controls

- Annual production is recalculated as 1,025.368 kg/h × 8,000 h/y = 8.203 kt/y.
- Reformer tube diameter is controlled at 0.1016 m per tube from the catalyst-volume calculation, replacing the conflicting 4 m narrative value.
- The 75.5% synthesis conversion is the controlled overall value; 75.8% is treated as rounding.
- Reflux ratios 0.36 and 1.03829 refer to DSTWU shortcut and final RadFrac models, respectively.
- Product purity values 99.86 wt% and 99.89 mol% are kept with their correct composition bases.
- Furnace duties 8,762 MJ/h and 10,800 MJ/h are retained with different purposes: process duty note and conservative CAPCOST regression input.
- Direct furnace and indirect steam emissions are shown separately.
- The zero methane purchase price is presented as a battery-limit assumption; an opportunity cost would worsen the economics.

## File integrity controls

- All download URLs correspond to physical files under `public/downloads/`.
- The model workbook contains formula checks and a dedicated QA sheet.
- The complete package includes the source JSON datasets used by the website.
- The website source code is included without changing the design or page behavior.

## Remaining project limitations

- No original Aspen Plus binary file was supplied in the website package.
- The XLSX is a structured support workbook, not a substitute for the original Aspen simulation.
- No FEED-level safety, operability, mechanical, offshore layout or vendor-cost validation has been performed.
- Environmental results are order-of-magnitude calculations rather than a verified life-cycle assessment.
