Dick Bennett was president of Janus Technology Group Inc., Rockford, Ill., a consulting firm specializing in industrial heating and energy technology. He is a veteran of the heat processing industry with a total of 35 years experience with well-known combustion equipment companies. In 2012, Dick Bennett retired and closed his consulting business.
With most plants now searching for ways to
minimize energy waste, one of the most common questions I hear is whether
there’s enough heat in an oven or furnace exhaust stream to make it worth
recapturing. Obviously, everything has to be approached on a case-by-case
basis, but here are some facts, figures and guidelines that may help you make
an informed decision.
Over the years of writing columns for Process Heating, I’ve had a number of items worth communicating
that are just too brief to fill an entire column. This is a collection of those
little bits and pieces. Just because something is small doesn’t mean it
shouldn’t see the light of day.
2006, as part of its “Save Energy Now” program, the U. S. Department of Energy
funded “Energy-Savings Assessments” of process heating applications in many
industrial plants. The assessments are conducted by engineering professionals
who have completed the DOE’s training to become BestPractices Qualified
Over the last few columns, I’ve beaten the energy conservation drum pretty hard. But energy costs remain fairly high, and many companies are still struggling with their impact on profitability, so please indulge me one more swing of the drumstick.
We all know that in convection ovens and furnaces, air is heated by a burner or electrical elements and then is pushed or pulled over and through the workload by a circulating fan. Coming into contact with the workpieces, the air transfers some of its heat to the product before going out the exhaust or being recirculated to the heating chamber.
It's a well-established fact that setting up combustion systems for too much excess air (or dilution air) wastes fuel. You can use this relationship to calculate just how much you can save by decreasing excess air:
% Fuel Savings = 100 x [1- (Available Heat, High XS Air/Available Heat, Low XS Air)]
Check out the November 15, 2020 edition of Process Heating: Adapt to changing emissions regulations, optimizing operating efficiency in a forced convection dryer or roaster, most read Process Heating Products of 2020 and more!