Carbon screening

The carbon case for a dividing wall column

Enter the reboiler duties you run today. Read back the CO₂e avoided, what it is worth, and how it measures against the whole refinery.

Basis—

USD is the base — rate fixed at 1.

The refinery you are comparing against

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Reboiler duty of the columns today

30 %
10 %typically 30 %50 %

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What it means

CO₂e avoided
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tonnes per year
Money saved
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Share of refinery
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The sequence becomes one column

A sequence of conventional columns replaced by one dividing-wall column

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The same carbon, in everyday terms

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cars off the road for a year
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hectares of forest, absorbing all year
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Indian homes powered for a year
Notes, assumptions and sources

Carbon. Avoided CO₂e follows steam mass — tonnes per hour × operating hours × the steam carbon factor. Reboiler duty converts to steam through the latent heat set in the basis.

Money. The steam figure values the saving at the site's internal steam transfer price. The fuel-gas figure prices the same heat as the fuel a boiler would otherwise have burned — heat saved ÷ boiler efficiency × fuel gas price. The two differ because a transfer price carries water treatment, distribution and capital recovery that raw fuel does not; quote whichever basis the client's economics team uses. Prices are entered and shown in the currency chosen in the basis, and the arithmetic runs in US dollars, so switching currency re-expresses the same price rather than changing it.

Refinery totals. No Indian refiner publishes a verified refinery-by-refinery CO₂e figure — the majors disclose company-wide Scope 1 and 2 only. One exception sets the yardstick: HMEL Bathinda, whose Sustainability Report FY2023-24 gives 4.30 Mt Scope 1 against 12.6 MMT throughput; a single-refinery company, so the corporate disclosure is the refinery. Every other figure in the list comes from the Climate TRACE 2024 asset inventory, which computes throughput × an emission factor assigned by refinery archetype rather than measuring, and which flags its own refining data as low confidence; against HMEL's disclosure it reads 16 % low. Treat every modelled figure as ±20 %. Reliance Jamnagar carries a further caveat: DTA and SEZ are lumped into a single asset and cannot be separated. Each refinery is shown as capacity × carbon intensity so the arithmetic stays visible — change either and the total follows, or type the total and the intensity follows. Published Indian refinery intensities run about 0.22 to 0.34 tonnes of CO₂e per tonne of crude, against a global volume-weighted average of 0.30 (Jing et al., Nature Climate Change 2020). For a refinery not listed, an audited total is always the figure to prefer; failing that use capacity × intensity, taking 0.22 for a simple refinery, 0.28 typical, 0.34 for deep conversion.

Everyday equivalents. 4.6 t CO₂e per car-year, 2.08 t per hectare of forest per year, 0.85 t per Indian household's annual electricity. Indicative, for communication only.

Dividing wall column CO2e savings calculator

A dividing wall column does in one shell what a conventional sequence needs two or three columns to do. Because the wall stops the middle-boiling component being remixed and re-separated, the reboiler duty for the same separation falls — typically by 25 to 40 per cent, with 30 per cent a fair screening figure. This tool turns that duty saving into the three numbers a revamp study actually has to report: tonnes of CO2e avoided per year, the money value of the steam or fuel gas no longer raised, and the size of the saving set against a whole refinery's annual emissions.

It is a screening tool, not a design. Enter the reboiler duties of the one to three columns you run today, choose the saving your basis supports, and read the answer back. Nothing is stored and nothing is sent anywhere — the arithmetic runs in your browser.

How the calculation works

  1. Duty saved. The reboiler duties you enter are summed, then multiplied by the dividing wall saving you select (10 to 50 per cent).
  2. Steam mass. The saved duty is divided by the latent heat of the steam level — 417 kcal/kg by default — to give tonnes of steam per hour no longer raised.
  3. Carbon. That steam mass is multiplied by 0.2515 tonnes of CO2e per tonne of steam, the factor implied by DWC Innovations' delivered projects, over 8,000 operating hours a year.
  4. Money. The same steam mass is priced at your steam cost, or the equivalent duty is priced as fuel gas, in any of ten currencies.
  5. Refinery share. The annual tonnes are divided by the total annual CO2e of the refinery you pick, and expressed both as a percentage and as days of refinery operation.

Common questions

How much CO2e does a dividing wall column save?

On a two-column sequence drawing 63.9 MMkcal/h of reboiler duty, a 30 per cent saving is about 46 tonnes per hour of steam, or roughly 92,000 tonnes of CO2e a year at 8,000 hours. Your own answer depends entirely on the duties you run — that is what the tool is for.

What emission factor is used for steam?

0.2515 tonnes of CO2e per tonne of steam. It is back-calculated from DWC Innovations' own delivered projects, where the same factor holds across all three. Substitute your own site factor if you have one.

Can I price the saving in my own currency?

Yes — US dollars, Indian rupees, euros, pounds sterling, Saudi riyals, UAE dirhams, Singapore dollars, Chinese yuan, Japanese yen and Korean won. Steam and fuel gas prices are both editable.

Which refineries can I compare against?

Thirty-seven refineries across India, Asia and the Middle East, each shown as capacity × carbon intensity so the arithmetic stays visible. You can also type your own capacity, intensity or audited total. Sources and their uncertainty are set out in the notes above.

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