(613a) A "Green" Pilot Plant Process Cooling Alternative

The Xerox Research Centre of Canada (XRCC) Pilot Plant is a multi-purpose specialty chemicals pilot plant. Originally designed and built in early 1980s, the pilot plant has the mission of enabling pre-manufacturing R&D and commercialization of specialty materials, including organic, inorganic, and composites, for use in document printing and other applications.

To satisfy temperature requirements of different types of chemical processes, dedicated heat transfer systems, containing media including steam, water, glycol and hot oil, were installed in the pilot plant to cover temperature ranging from -25oC to 350oC. Common to these heat transfer systems had been domestic water supply, which was the primary source of process cooling. Domestic water in distribution headers was piped to heat transfer systems for removing heat generated by chemical processes and was immediately discharged to the sewer systems. As the plant grew in size and increased in utilization, more systems were connected and more domestic water was consumed. In recent year, the plant had been using significantly more water. The open water cooling system was costly and it warranted a greener and more innovative alternative.

As part of XRCC's long standing commitment to ?Green? and ?Sustainable? technologies and solutions, a team representing operations, plant support and facilities engineering was commissioned to design a new eco-friendly pilot plant cooling system that would offer better environmental benefits and provide improved operational features.

Based on thermodynamic and heat transfer studies carried out on existing equipment and processes, the team estimated that the plant's peak demand for process cooling would be close to two million BTU/hr. HVAC suppliers contacted suggested that a 200-refrigeration ton Closed-loop Chilled Glycol Circulation System, which consists of a 200-ton chiller, heat exchangers, pumps, a reservoir and dedicated process control system, would be required to handle heat loads of this magnitude.

After review systems designed by HVAC suppliers, the plant's engineering team made the following proposals to further improve the efficiency of the system and to reduce installation and operating costs:

- Incorporate a roof-mounted air cooler for cooling glycol medium with outside air, taking advantage of the plant's location in Southern Ontario, where winters tend to be long and cold, and average daily temperature frequently drops below 8oC. - Use variable speed motors and compressors, and to control temperature and flow rate of the new chilled glycol circulation system with the plant's exiting distributed control system - Tie in the chilled glycol system to the existing building automation system which is programmed weekly to start up and shut down plant utilities based on operation requirements - Purchase components instead of a packaged system and utilize as much as possible, in-house engineering, project management and installation capabilities

The project took about a year to complete from concept and design to commissioning and start up. Sizing and selecting the system's components to work adequately and efficiently under different demand conditions was a major challenge. Installing the system and keeping the plant in operation was another. Once completed, chilled glycol was first fed to major consumers of domestic water, including the plant's hot glycol and hot oil circulation systems. Heat exchangers for reactors, receivers and dryers would soon follow.

The new chilled glycol circulation system has been in operation for over a year. The project has proven successful and has dramatically reduced the plant's consumption of domestic water and sewage discharges. From late Fall to early Spring, the system was able to supply chilled glycol at 5oC to 8oC by circulating glycol to the roof-mounted air cooler without running the 200-ton chiller, a practically ?free? cooling for optimum performance and less downtime. This and other built-in energy saving features has made the system more efficient and the project more ?Green?.