How much charcoal does an efficient 60 kg reheating furnace save a brass unit?

About 7,880 kg a year, 91% of the 8,640 kg a 60 kg unit burns, in Bureau of Energy Efficiency (BEE)'s Bhubaneswar report. A furnace with a recuperator lifts efficiency from 1.32% to 15%. Cost Rs 2.45 lakh, saving Rs 1.76 lakh a year, payback 1.39 years. The report leaves charcoal CO2 out because the fuel is wood based.

Why reheating is the big bill

In Bhubaneswar's brass units about 15% of energy cost is melting and 84% is reheating. The pit is dug in the ground, 30 to 50 cm wide and 30 to 90 cm deep, at about 800 C. A batch of 60 kg takes 6 hours, and the unit does 144 batches a year, burning 60 kg of charcoal per batch, 1 kg for every kg of brass.

How low the efficiency is

Heating 60 kg of brass from 35 C to 800 C needs about 5,140 kcal. The charcoal burned supplies 390,000 kcal. So the pit's efficiency is about 1.3%. The report's redesigned furnace has an insulated enclosure and a recuperator that warms combustion air to about 180 to 200 C using flue gas at 450 to 500 C, and a small blower. It takes the efficiency to about 15%.

The charcoal after the change

At 15% instead of 1.32% the unit needs 8,640 x 1.32 / 15 = 760 kg a year, so it saves 7,880 kg. The blower is 0.75 kW for 864 hours, 648 kWh a year.

CO2

The report does not count the CO2 from charcoal for credit purposes because charcoal is made from wood. That fits how the GHG Protocol treats biomass CO2: reported on its own line. Only the 648 kWh of blower power adds a fossil figure, about 0.4 tonnes (t). The saving is mainly in rupees; the fossil CO2 effect is small.

Before you commit

• Charcoal at Rs 22.5 a kg is a 2010 price. Check what you pay.
• The report allows 15 years of life, new refractory every 5 years and 2 days of downtime.
• The furnace is built by a local fabricator to the report's drawing, so ask for a performance test, not just a quote.

The sums

• Heat needed per batch: 60 x 0.112 x (800 minus 35) = 5,141 kcal. Heat in charcoal: 60 x 6,500 = 390,000 kcal. Efficiency 1.32%
• Charcoal after: 8,640 x 1.32 / 15 = 760 kg. Saved: 8,640 minus 760 = 7,880 kg, which is 91.2%
• Money: 7,880 x Rs 22.5 = Rs 1,77,300, less blower power 648 x Rs 2.3 = Rs 1,490, so about Rs 1,75,800 a year. Payback 2.45 / 1.76 = 1.39 years
• Blower CO2: 648 x 0.675 = 437 kg, about 0.4 t a year

Report figures at the report's prices. Power at Central Electricity Authority (CEA)'s financial year (FY) 2025-26 grid factor.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records. Fuel used per kg of brass, taken from your production register, is the figure to track before and after. The green loan check shows what a lender asks for on a furnace loan.

• Green loan readiness check
• The Bhubaneswar brass cluster and its melting furnace
• A 60 kg rice husk gasifier
• Biogenic CO2 in a GHG report

Sources: BEE, Detailed project report: energy efficient reheating furnace, 60 kg, Bhubaneswar brass cluster (2010, SAMEEEKSHA), CEA CO2 Baseline Database, version 22.0, GHG Protocol Corporate Accounting and Reporting Standard, revised edition, Chapter 9

Last reviewed 2026-11-04. Report figures are from a BEE SME programme project report; costs and paybacks are at the report year's prices. Check today's prices and a current quote before you rely on the payback. Re-check the grid factor when CEA publishes a new edition.