What does the Firozabad profile's saving of 48 million cubic metres of gas from better tank furnaces mean for one furnace?

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At the profile's 30 to 35% saving, 48 million standard cubic metres (scm) a year would mean tank furnaces burning 137 to 160 million scm if it covers all 55, about 6,800 to 8,000 scm a day each. That fits smaller tank melt rates, not the 52,000 scm a day printed for a tank unit. The Energy and Resources Institute (TERI) Firozabad profile says an improved tank furnace, with better bricks, burners, heat recovery from the exhaust and controls, would save 30 to 35% of gas, equal to 48 million scm a year at cluster level, with an estimated investment of rupees (Rs) 400 lakh for each tank furnace. A lakh is 100,000. A standard cubic metre (scm) is the amount of gas that fills a one metre cube, counted at a fixed temperature and pressure. If 48 million is 30% of the gas, the gas is 48 / 0.30 = 160 million scm a year. If it is 35%, it is 137 million. Per day that is 375,700 to 438,400 scm, over 365 days. Divided over 55 tank furnaces, the profile's count in its first table, that is 6,800 to 8,000 scm a day each. Over 45 furnaces, its second count, it is 8,350 to 9,740. Against the cluster's printed 879,280 scm a day, which is 320.9 million scm a year, the 137 to 160 million is 43% to 50% of all the gas. That is plausible for the furnaces that make most of the glass. The profile says tank furnaces melt 25 to 40 tonnes a day, and that melting furnaces use 0.20 to 0.35 scm for each kilogram of melt, depending on type. That is 25,000 x 0.20 = 5,000 up to 40,000 x 0.35 = 14,000 scm a day for the melter alone. The melter is about 60 to 70% of a tank unit's energy, as the live 52,000 page applies it, so a whole unit burns about 7,100 to 23,300 scm a day. The implied 6,800 to 9,700 sits at the low end of that band. It fits 25 tonne tanks, not 40 tonne ones, which the live page puts at 11,400 to 23,300. The profile's table also prints 52,000 scm a day for a tank furnace unit. At that figure 30% saved would be about 313 million scm a year, about 6.5 times the printed 48 million, so the 48 million does not rest on 52,000. The linked page on the 52,000 checks that figure against melt rates and the cluster total. How many furnaces the 48 million covers. It may mean every tank furnace, but it does not say so, and the sums above only hold if it does. The price of gas it used, so the money value of the saving is not in the text. Whether the 30 to 35% is measured on furnaces rebuilt in the cluster or taken from a design. It gives no test result. Work out your own gas for each kilogram of glass drawn, from the furnace meter and the tonnes packed. If it is already near 0.20, the room to save is smaller. Ask the builder for a guaranteed gas figure at your pull rate, in writing, and what it pays if the figure is missed. Take twelve months of gas before and twelve after, with tonnes, so the saving is yours. Check the quota effect on the gas bill: savings first come off gas above quota.

What does the Firozabad profile's saving of 48 million cubic metres of gas from better tank furnaces mean for one furnace?

What the profile claims

Working backwards from 48 million

Does it fit the furnaces' melt rates?

What the profile does not say

Before you rebuild

One tank furnace, example numbers

What Senseible does here