Waste Heat Recovery Systems Using Thermal Fluid Systems (Thermal Oil Systems)

Waste heat recovery systems help manage, recover, and repurpose waste heat from various energy consuming systems in commercial, industrial, and municipal facilities. As machines run, processing systems prepare goods or products, they often put off heat as a waste product. That waste heat is typically either a result of the friction of moving parts or from the exhaust of various types of combustion equipment. While the heat of friction can be significant, waste heat from exhaust streams is typically the most practical to recover and utilize. Repurposing waste heat allows facilities to become more efficient, reduce thier fuel costs, and overall emissions to the environment.

How Do They Work?

One of the most common types of waste heat recovery systems is a closed-loop liquid phase system filled with a thermal fluid of some type: typically thermal oil or a water/glycol solution. Within a waste heat recovery coil located in the exhaust stack or in the exhaust gas ductwork, the circulated thermal fluid absorbs the waste heat from the exhaust stream. The heated fluid is then circulated to the the chosen waste heat consumer(s) within the closed-loop system, where it will offset the heat demand of the combustion system providing that particular system with its heat energy.

The challenge for the system designer is to match a heat energy consumer with a waste energy source. In order for the system to work the waste heat source must be hotter than the heat consumer with enough margin to drive the heat transfer from one system to the other. One of the biggest benefits of a closed loop liquid phase heat recovery system is it’s ability to connect multiple sources with multiple consumers that may not be physically close to one another. If, for example, if three exhaust stacks in one part of the plant collectively produce 450F exhaust, and a boiler feedwater system 200 yards away could utilize that waste heat to pre-heat the feedwater to 200F, the energy can be collected from the three sources, combined, and then circulated over to a feedwater heat exchange to heat the boiler feedwater. The cold thermal fluid simply recirculates from the heat exchanger outlet back to the waste heat sources, and the process repeats continuously.

Benefits of Using Waste Heat Recovery Systems

Manufacturing centers, processing facilities, and large buildings all benefit from the introduction of closed-loop waste heat recovery systems. Some of the core benefits include:

Cost Savings

Because the systems recover heat energy the facility has already generated, the facility can use that energy more intentionally instead of having to pay for heat that is rejected to the environment. Recovering energy can reduce operational costs by offsetting energy demand, and therefore fuel consumed, in gas or oil fired combustion equipment. Natural gas and/or diesel fuel costs can fluctuate and can be a significant portion of a plants total energy operating costs.

Waste heat boilers are often utlized as altneratives to closed loop liquid systems, but they can actually be less efficient to operate. Steam traps, blow down, and energy lost to condensate return cause inneffeciencies in the system that don’t exist in a closed loop liquid phase system. For those reasons, a closed loop liquid phase waste heat recovery system may allow you to utilize more of your waste heat and maximize your fuel cost offset.

In addition to fuel cost savings, there are frequently opportunities for government funding, tax credits, and other incentives at the federal, state, and local levels. These can be specific to waste heat recovery projects, or generalized incentives for sustainability and effeciency improvement initiatives. In many cases there are several incentives available at multiple levels that can all be utilized in tandem with one another: federal, state, and local. These incentive can significnat decrease the cost of installing a system, decreasing your investment payback period and maximizing your long term cost savings.

Waste Heat Recovery Systems From Sigma Thermal

At Sigma Thermal, we have the experience and expertise to design or select the right closed-loop waste heat recovery system for your facility’s needs. Our company is ISO 9001:2015-certified, and our signature process includes every step from initial system design to installation and complete project management. Contact us today to learn more or request a quote to start your project.


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