We will explore the ever-popular subject of how to make money the easy way. Well, better stated: How to save some money, but at the end of the year the result is the same.
This column is a Combustion Corner feature written by John Clarke, technical director at Helios Electric Corporation, and appeared in June 2022 Heat Treat Buyers Guide print edition.
If you have suggestions for savings opportunities you’d like John to explore for future columns, please email Karen@heattreattoday.com.
Technical Director
Helios Electric Corporation
Source: Helios Electric Corporation
For our discussions, we will assume that we are operating a continuous heat treat furnace that processes work at 1600°F. The furnace currently consumes 2,000 SCFH of 1000 BTU/SCF natural gas and operates 8,000 hours per year. With today’s natural gas at 8.00 USD per 1 mmBTU (1 mmBTU = 1,000 SCF of natural gas), our furnace’s annual operating cost is:
Using our trusty combustion analyzer that provides a readout of the oxygen present in the flue products, we quickly determine the fuel contains 6% O2 (measured by volume, dry basis). The “volume/dry basis” is the most common value measured by handheld combustion analyzers. We measure the temperature of the flue products at 1700°F. Our burner and/or furnace specifications say the system should be operated at 3% O2. How much can we save by adjusting the burner(s) on this furnace?
Table 1 below provides savings numbers that result when non-recuperated burners are returned to 3% O2.
If we read where the exhaust temperature row intersects with our column for our starting O2 volume in the flue products, we see the resultant savings will be 13.9%:
We chose 3% O2 in the flue products (around 15% excess air) because radiant tubes and direct fired systems can commonly operate at this level with little CO or soot generation. A simple combustion analyzer can be purchased for a few thousand dollars and the labor required to make these adjustments is generally under a day. The payback period for this maintenance investment is measured in weeks, even if it requires the purchase of new tools.
There may be an added benefit we receive when adjusting the furnace. We may have an opportunity to increase the throughput, so perhaps production can be increased while fuel costs are reduced.
Table 1 can be used for other specific conditions, so keep it handy. Next month, we will explore the savings resulting from recuperation or pre-heating the air.
Recuperation projects are more complicated and require greater investments, but they are becoming increasingly critical for heat treaters working to stay competitive in our new reality of dramatically higher natural gas prices.
About the Author:
John Clarke, with over 30 years in the heat processing area, is currently the technical director of Helios Corporation. John’s work includes system efficiency analysis, burner design as well as burner management systems. John was a former president of the Industrial Heating Equipment Association and vice president at Maxon Corporation.
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