What in the world is a Condensing Economizer, and why would I want one?

August 20th, 2021

A non-technical person’s look at what why and how of economizers, saving money and reducing emissions.

So, as you might have guessed I write articles for the Associated Steam, Air & Hot Water website, but do not spend any time actually out in the field dealing with the nuts and bolts of Steam, Air & Hot Water installations.  As my ex liked to say, “don’t give her a tool unless you want to end up with more parts than you started with”.  Granted, at eighteen I did take apart the engine of my ’76 VW Bug and put it back together with only one extra piece. But it still ran… just not very well.

So when Condensing Economizers were suggested as a website topic, I knew I had to go to the experts at Combustion & Energy Systems Limited and BMR Thermal Inc. for help.

Let’s start with some basic information from the US Department of Energy’s (USDoE) publication Quadrennial Technology Review 2015 and the article “Waste Heat Recovery Systems” which I downloaded from their website.

Waste heat is generated from a variety of industrial systems distributed throughout a manufacturing plant.  The largest sources of waste heat for most industries are exhaust and flue gases and heated air from heating systems such as high-temperature gases from burners in process heating; lower temperature gases from heat treating furnaces, dryers, and heaters; and heat from heat exchangers, cooling liquids and gases.  While waste heat in the form of exhaust gases is readily recognized, waste heat can also be found within liquids and solids.

In industrial heating processes, a large amount of the heat energy that is produced through fuel combustion is underutilized and wasted in exhaust gas streams.  This can be high- or low- grade heat energy, both of which are valuable and can be reused. It was explained to me that typical efficiency of process fuel use is 80% (+/- 5%).  The best way I can visualize this is to think of a pie that I purchased, warm from the oven.  If someone told me I had to leave a slice in the oven I would think they were crazy.  I paid for a whole pie.

Isn’t that the same concept as waste heat?  Someone has to pay for the fuel – whether it is natural gas, electricity, steam or apple pie.  Do your customers want to pay for this kind of waste? Is this inefficiency built into their annual budget?

On the flip side, do your think that any of these processes could benefit from not sending dollars “up the stack,” so to speak?

In Steam Tip Sheet #26A, the USDoE states that “The key to a successful waste heat recovery project is optimizing the use of recovered energy.”

That is where the Condensing Economizer comes in

A condensing economizer system can complete the task of recovering the latent energy and will also recover the sensible heat energy above the water dew point as well. The condensing economizer gathers the waste heat from singular or multiple heat sources and transfers this energy to a heat sink in the facility.  This offsets the part of the process that would otherwise consume purchased or live energy to provide the heating.  By utilizing waste heat for this purpose, less fuel consumption is required, and an overall fuel cost savings and emission reduction target is achieved.

Traditional heat recovery methods are limited in the amount of heat than can be recovered because of the concerns inherent in cooled flue gases. If you cool it far enough to recover most of the latent heat, the temp can hit the dew point and the gases condense – leading to corrosive effects within the flue. So, while the process may recover some additional heat and there may be a fuel cost savings, what will the corrosive effect of the condensed flue gas cost your customer?

At Associated Steam, Air & Hot Water we are pleased to offer the next generation in heat recovery.  The CONDEX Condensing economizer System is a fully condensing system.  Advancements in metallurgy and heat recovery methodology now allow for this energy to be recovered and the fuel cost saving more fully realized. 

The CONDEX System can recover both sensible and latent heat and put it to substantive work that would otherwise require the use of purchased energy to heat cold process liquids. The CONDEX system is not limited by the dew point of the exhaust gas, allowing for a significantly higher recovered temperature return.

Please visit their website, where I was directed to the following information ( http://www.condexenergy.com/heat-recovery-perfected.html):

When incoming cold fluid enters the ConDex exchanger and the hot exhaust gases pass through the proprietary ConDex exchanger unit, so much energy is exchanged that the gases are cooled beyond the point where the water vapor condenses out of the exhaust gas, releasing and recovering the heat it took to vaporize the water initially.

This phase change from vapor to liquid recovers 980 Btu’s of energy for every pound of water condensed.

So even from a non-technical standpoint, it is obvious that adding a CONDEX Condensing Economizer System in almost any plant process provides higher efficiency, lower fuel costs, decreased wear from corrosive gases and several other facility specific, benefits.  To determine how this system can provide your facility or customers with this benefit, contact your Associated Steam, Air & Hot Water salesperson or our main office at (800) 477-1620.

And yes, please.  I would like that last slice pie. 😊