Cascades: Heat Recovery Steam Generator | Cascades
“This is a good example of a waste heat recovery project. The team navigated a challenging problem to successfully implement a new process with a reasonable payback that integrates with their sustainability plan. Demonstrated results are promising, particularly the generation of high enough quality steam to be used in process on site.”
--Energy Manager Today Awards judge
The Cascades Tissue Group – NY Inc. (Mechanicville) mill has a machine that makes 100 percent recycled fiber white and brown paper towel sold on the commercial and industrial markets. In a typical plant like this, energy consumption represents 20 percent to 30 percent of our products’ total cost, so the company turned its attention to improving efficiency. The steam generator project consists of recovering and reusing the energy in the exhaust gases of the hood used to dry out the paper, by means of a system fitted with a steam-generating heat exchanger. Initiated in 2014, this project aimed to produce an average of 4,450 lb/h of steam at 125 psig, or about 15 percent of the steam required by the mill. The objective was to reduce the amount of natural gas consumed without impacting the production negatively—part of an effort to decarbonize our operations. This million-dollar project would save the plant $240,000 per year
This was the first project of its kind carried out by the Cascades energy efficiency team and also a first for the industry in North America, Cascades says. This means there were no comparables to help the company predict the potential risks. Unlike most energy recovery projects, which re-inject heat into the process by means of a lower-temperature medium, this project sought to maximize the quality of the energy by producing high-pressure steam that could be used by all equipment requiring steam in the plant.
The project also raised unique challenges related to control and automation to make the system autonomous, going beyond what the supplier proposed, in order to maximize the system’s operation and overall performance without operators having to intervene even when there are major variations in the process.
A rigorous feasibility study examined the incorporation of this technology into the existing process including cost-benefit and risk analyses, paying special attention to ensuring that there would be no negative impacts on or prolonged stoppage of the paper machine. Energy efficiency specialists worked closely with team members to make sure all aspects were understood and that the system was compatible at each deployment stage. The supplier of the equipment (technology) was chosen based on the limitations of the existing facilities (lack of space, evacuation capacity). As this system is pressurized and involves very high temperatures, there were several risks associated with workers’ health and safety which needed to be addressed.
Today the project is operational and achieving the expected results. Savings associated with the energy recovery steam generator project are estimated at approximately 41,888 GJ/year, which is equal to nearly 10% of the company’s total reduction target of 450,000 GJ/year for 2014, Cascades says.