Why does one Indian cluster profile print about 1,030 kilocalories per kilogram for a tunnel kiln and another 1,740?

The Energy and Resources Institute (TERI) profiles print 1,030 kilocalories (kcal) per kilogram of ware for Khurja tunnel kilns and 1,740 for Virudhachalam ones, yet shuttle kilns agree at 3,748 and 3,779. Neither profile explains the tunnel gap. Product mix is one possible cause, my reading, not stated.

The two sets of figures

• Khurja: tunnel 4.3 megajoules (MJ) a kilogram or 1,030 kcal; shuttle 15.7 MJ or 3,748 kcal. The profile says shuttle is about 3.6 times tunnel.
• Virudhachalam: tunnel 7.3 MJ or 1,740 kcal; shuttle 15.8 MJ or 3,779; rotary 5.9 MJ or 1,413; downdraft 17.6 MJ or 4,200.
• Conversion check: 1,030 x 4.1868 = 4,312 kilojoules, 4.3 MJ; 1,740 x 4.1868 = 7,285, 7.3 MJ.

Where they agree and where they do not

Shuttle kilns sit 0.8% apart: 3,779 / 3,748 = 1.008. Tunnel kilns sit 69% apart: 1,740 / 1,030 = 1.69. So the shuttle-to-tunnel ratio is 3.6 in Khurja and 2.2 in Virudhachalam (3,779 / 1,740).

What the profiles say about the kilns

• Khurja tunnel kilns fire crockery and insulators at 1,050 to 1,200 degrees Celsius (°C), mostly on oil, at 2 to 9 tonnes a day.
• Virudhachalam tunnel kilns include three on ceramics (oil, about 7.5 tonnes a day) and two on high alumina refractory bricks (pet coke and coal dust, about 20 tonnes a day, up to 1,260 °C). Its table gives one tunnel kiln figure, while its typical-unit table splits ceramic and refractory tunnel kilns into 138 and 633 tonnes of oil equivalent a year of thermal energy.

A possible cause, not a stated one

The Virudhachalam figure may be an average over refractory and ceramic kilns, and the Khurja figure over ceramic kilns alone. The profiles do not say. I cannot split it further from what is printed, so I do not give a separate figure for each group.

What to use as your benchmark

• Your own fuel in megajoules divided by your own good ware in kilograms, over a full year.
• If you must quote a cluster figure, quote the profile and the year, and say the other profile differs for the same kiln type.
• Do not mix: do not set a Khurja shuttle figure beside a Virudhachalam tunnel figure and read a ratio.

The same 100 tonnes of ware under each profile

• Khurja tunnel: 100,000 kilograms x 4.3 MJ = 430,000 MJ
• Virudhachalam tunnel: 100,000 kilograms x 7.3 MJ = 730,000 MJ
• Difference: 300,000 MJ, 70% more under the second profile (730 / 430 = 1.70)

The 100 tonnes is an example. Heat per kilogram is each profile's average, not a measurement.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so the fuel and power lines of a furnace or kiln are on file. A kiln comparison is worked from your own fuel records and ware weights.

• Khurja fuels and the green loan route
• Virudhachalam kiln fuel and carbon
• Tunnel kiln against shuttle kiln emissions
• Virudhachalam firing temperature by product

Sources: TERI, Cluster profile: Khurja potteries, Uttar Pradesh (SAMEEEKSHA), TERI, Cluster profile: Vriddhachalam ceramics and refractory industries (SAMEEEKSHA)

Last reviewed 2026-11-06. Figures are from TERI's 2015 cluster profile, which describes the cluster at that time; fuels, kiln counts and prices have moved since. Treat them as typical, and check your own records before quoting.