Problem
A food processing facility
installed a new Regenerative Thermal Oxidizer (RTO) for odor
control from its roasting operation. The oxidizer was
designed for 95% thermal rate of efficiency and included
supplemental fuel injection (SFI) which is used during low VOC
loading conditions, to help save fuel cost. The customer was
looking at additional ways to further reduce their operating
cost.
Action
Recovering waste heat is one of the
easiest and most effective means of reducing operating cost.
Exhaust heat from energy consuming processes and exhaust stacks is
returned through a metal heat exchanger it as process air,
preheated combustion air or plant comfort heat.
The critical design factors for any
energy recovery product is the airflow rate, temperature of
the air stream, permissible pressure drop of the application
and the desired heat to be transferred to the heat
exchanger.
Anguil analyzed the application
data with a Heat Exchanger Performance Modeling Program which
models temperatures from ambient to 1,800°F and flow rates.
The program performs a boundary layer analysis for the specific
application and adjusted the plate thickness and spacing of the
heat exchanger to maximize performance.
Solution
A secondary plate type heat
exchanger was chosen for this application because of its' ,
versatility and rugged , yet cleanable plates. The
plate style heat exchanger has a low pressure drop, small foot
print and low capital cost , making it the best economical
option for this application.
The RTO exhaust heat was used
to preheat 7,000 SCFM of air to approximately 190°F. This hot air
mixes with outside air to provide 30,000 SCFM of heated air to the
makeup air unit. The secondary heat exchanger transfers
approximately 1.5 MMBTU/hr of heat from the RTO exhaust to the air
going back to the makeup air unit and the estimated yearly savings
for the project was approximately $45,000.00.
REPORTED VALUES
PROJECTED VALUES WITH ENERGY RECOVERY SYSTEM
| ESTIMATED HOURLY SAVINGS OPPORTUNITY |
$8.91 /HOUR
|
| ESTIMATED YEARLY SAVINGS OPPORTUNITY |
$44,906.40 /YEAR
|
NOTES/RECOMMENDATIONS:
1. An adjustment factor of 60% is used because of the assumption
that recovered heat will be used for comfort heat.
Job Pictures
