At what temperature and for how long does a Firozabad pot or tank furnace melt glass, and what does it mean for gas records?

The Energy and Resources Institute (TERI) profile says a Firozabad tank furnace holds its melt at about 1,450 degrees Celsius (°C), while open pot furnaces run at 1,250 to 1,280 °C and take about 20 to 22 hours to melt a charge. Both run non-stop, so gas keeps burning when output stops (my reading).

Tank furnace

• An end-fired tank furnace melts continuously, at about 1,450 °C. The melt passes a refiner zone to lose air bubbles.
• Zirconium-based electro-cast refractory blocks sit where the melt touches; sillimanite blocks serve the other high-temperature zones.
• About 80% of the combustion air is secondary air, preheated to about 600 °C in a two-chamber regenerator, reversed by a manual valve.
• The tank furnace is about 60 to 70% of the unit's energy.

Open pot furnace

• Ten to twelve pots sit around the furnace, heated to 1,250 to 1,280 °C. Total melting time is about 20 to 22 hours.
• Each pot is charged consecutively three times. The text gives refill gaps of about 8 hours, about 5 hours after the previous filling, and the third filling about 3 hours after the second. Those do not give one clean timeline, since the last two statements put the third filling at 11 or at 13 hours. I would not build a log from them.
• The pot furnace is about 60% of the gas in a pot unit. Other steps run about 9 hours a day.

Never switched off

The profile says: "If a melting furnace is shut down in the middle of operation, charge material and fuel worth several tens of thousands of rupees is irretrievably lost." So a large part of the gas is a standing load that does not move with output. Record the month's gas, the tonnes of glass drawn and the idle days, and divide a full year of gas by a full year of good glass. This is my reading of what the profile implies for records.

Muffle furnaces

The profile says the coal-fired muffle furnaces that anneal bangles have no control or monitoring systems and depend on operator skill. For them the record is coal and firewood bought each month.

A 7 tonne a day pot furnace on the profile's heat range

• The profile gives 0.20 to 0.35 standard cubic metres (scm) of gas per kilogram of melt
• Low: 7,000 kilograms x 0.20 = 1,400 scm a day
• High: 7,000 kilograms x 0.35 = 2,450 scm a day
• Over a 30 day month: 42,000 to 73,500 scm

The 7 tonnes is the profile's open pot capacity. The range is the profile's, for melting furnaces generally; check it against your meter. The Bureau of Energy Efficiency (BEE) pot furnace figure on the glass furnace gas benchmark page is 300 to 350 scm a tonne, which is 0.30 to 0.35 a kilogram, above the profile's low end of 0.20.

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. In the self-serve product it does not read furnace temperatures or melt cycles; custom sensors are available on request. Gas bought each month can be set beside your own tonnes drawn.

• Firozabad glass cluster gas use and carbon
• Glass furnace gas per tonne benchmark
• Glass bangle furnace emissions per tonne
• Firozabad glass unit gas evidence for buyers

Sources: TERI, Cluster profile: Firozabad glass 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.