Does running a POP calciner on more shifts cut energy per tonne?
Yes. TERI measured Bikaner calciners at 472 kcal per kg of plaster on one shift, 438 on two and 403 on three: 1.98, 1.84 and 1.69 GJ per tonne. Firing round the clock uses about 15% less per tonne, because a furnace kept hot loses less heat than one restarted each day.
Three real units side by side
- 3,600 t a year: 95,000 kWh and 216 t of petcoke, 170 toe. About 60 kg of petcoke per tonne of plaster.
- 6,000 t a year: 175,000 kWh and 330 t of petcoke, 263 toe. About 55 kg.
- 7,800 t a year: 250,000 kWh and 390 t of petcoke, 314 toe. About 50 kg.
- Worked through, these are 1.98, 1.84 and 1.69 GJ per tonne: the one, two and three shift rates. TERI's text calls the 7,800 t unit a two shift plant with a larger drum, but its figures match the three shift rate.
Why the third shift pays
Each batch takes about 1½ hours in a 1 or 2 t drum. A cold start needs a pilot flame, and every stop lets the furnace walls, built from plain red brick, cool and soak up heat again. Of the 75 working units, 65 already run three shifts; 10 run one shift on a 1 t drum.
Before you add a shift
- Only add one if you can sell the plaster; idle hot running wastes fuel too.
- Insulate first. Uninsulated walls lose heat on every shift.
- Fix feeding. Petcoke goes in at a fixed rate while air is set by hand, so unburnt fuel clogs the burner orifices and shows as black smoke.
- Log petcoke per batch for a month at your current pattern, then again after the change, so the saving is measured rather than assumed.
CO2 per tonne of plaster, by unit (estimate)
- 3,600 t: 216 t petcoke x 3.17 = 685 t, plus 95,000 kWh x 0.675 = 64 t: 749 t, or 208 kg per tonne
- 6,000 t: 330 x 3.17 = 1,046 t, plus 118 t: 1,164 t, or 194 kg per tonne
- 7,800 t: 390 x 3.17 = 1,236 t, plus 169 t: 1,405 t, or 180 kg per tonne
- Making 3,600 t at the three shift rate instead: about 28 kg less per tonne, roughly 100 t CO2 a year
Unit energy from TERI's Bikaner plaster of Paris profile. Petcoke at 3.17 t CO2 per tonne from the IPCC 2006 default (32.5 GJ per tonne, 97.5 kg CO2 per GJ); grid factor CEA FY 2025-26.
What Senseible does here
The calculators turn a month's kWh into CO2 at the CEA grid factor; petcoke has no factor in Senseible, so add it from the IPCC default shown here to compare one shift pattern with another.
Sources: TERI, Cluster profile: Bikaner plaster of Paris industries (SAMEEEKSHA), IPCC 2006 Guidelines, Volume 2 Energy, CEA, CO2 Baseline Database for the Indian Power Sector, version 22.0
Last reviewed 2026-10-31.