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Waste Heat Recovery

ControlGlobal.com
01/13/2012

By IDEC

Process Description

My application involves waste heat recovery projects. While performing energy assessments for various companies and industries, during the follow-up process, I discovered that most of the waste heat recovery projects designed or that I assisted with were not being implemented. After subsequent questioning during the follow-up for the projects, I discovered that most plant managers and their financial people were not grasping the concept of the projects even though on paper the project was a "no brainer" from a financial point of view. Secondly, and admittedly so, waste heat recovery is difficult to quantify or at least is a very time consuming endeavor. For example, it is not the same as a lighting project in that the savings is easily measurable by utilizing an amp probe prior to the upgrade and again after the up-grade, perform the math and there are the savings; visible and upfront. In addition, in most cases there is usually more and brighter light. Everyone is happy. The light is usually much better and the facility is saving money and at the same time there is now a good story to tell.

PLC Process Design

With waste heat recovery, I believe what we need, as in any other type of energy reduction project, is a method to quantify and monetize the savings, both in MMBTU's and/or dollars and to design with the all important visual in mind. This is what I have done using IDEC's Slim CPU model FC5A-D12S1E and an IDEC HMI. I chose the Slim Line with the Ethernet and USB model capabilities as most facilities are now waking up to the opportunities to incorporate all of their building energy systems to whatever SCADA system the facility may have, be it a BAS, EMS or any of the many remaining acronyms available in the market today. Along with a couple of analog expansion modules for temperature measuring and flow sensing, coupled with a secondary discrete expansion module, a method was devised to control all aspects of any designed waste heat recovery system. Being that there are all types of waste heat projects; gas-to-gas, liquid-to-liquid and all combinations thereof, we would now have the ability to accommodate those differing styles of systems either by controlling a VFD or contactor on both sides of a heat exchanger if one or both is needed. In addition, there is also the ability to monitor the velocity of the various flows in and out of the systems and the temperatures in and out so that BTU's could be accounted for along with their costs and savings. The design of the program is being intended to act much like a CNC controller where as a series of variables can be entered to match the type of waste heat recovery project is at hand for each particular project. These variables will determine the type of thermal energy and the content of the thermal energy expected.

Features and Benefits of using the embedded Ethernet MicroSmart Pentra

Along with the control of the system, alarms have been designed in to aid the facility in determining if there is an issue with the system. With the Slim Line models, the capabilities to email faults or alarms to maintenance or management personnel was a much added bonus especially if the waste heat recovery system was attached to an intricate or important piece of equipment for which the project was integrated with; e.g., a thermal oxidizer, heat treat oven, boiler or any other heat source or process end user within the facility. And with that in mind, the ability to trend any of the sensors we use for control also might tell a story regarding the health of the source heat system or possibly the recipient thermal energy end-user.

A successful pilot has been completed for an air-to-water waste heat recovery system. I am currently rewriting to accommodate the remaining types of waste heat recovery systems. Following, is a print screen of a few of the screenshots that a facility would utilize.