Data acquisition is one of the most important factors in the waste-to-energy industry. With access to accurate and reliable data, plant managers can easily predict operating costs, forecast their spending and minimise downtime.
To provide their managers with this kind of information, American Ref-Fuel chose to make the hub of its waste to energy plant’s control systems a PC based Citect Scada system, running on a Windows NT platform. This enables its engineers to monitor real time operations in the northeastern US from a PC in the company’s Houston, Texas, head office.
Like most cogeneration plants in the waste to energy industry, power plants operated by American Ref-Fuel use a distributed control system (DCS) for boiler combustion control and PLCs for peripheral systems. The problem is, once these types of system have been assembled and wired, additions and design changes can be very expensive.
One way to get around this problem would be to use a configurable interface with a CRT display rather than hardwired panel boards. However, early versions of non-PC based HMI packages could not handle large I/O counts, while PC based ones capable of handling the I/O counts were limited by the DOS environment. To overcome this dilemma, American Ref-Fuel installed Omron PLCs and Citect industrial automation software for Windows NT in all its plants, providing the flexibility to develop modular growth.
At Ref-Fuel’s Niagara Resources Facility, the PCs that run its initial Citect installation are networked to a Bailey Infi 90 DCS with a common database. This configuration allows PLC control, comprehensive real time plant monitoring and data acquisition. Previously, the corporate engineering staff had to travel across the country to each plant to troubleshoot process problems. Now, with Citect system, they can view plant data in real time from their desktops PCs, saving travel and engineering time.
Three Citect Manager nodes are in the corporate office in Houston with one Citect Manager node at each plant. The I/O servers continually collect data and store it on the local hard drive. Citect software creates DBF file reports, which are easily manipulated and distributed throughout the Windows environment. Every twelve hours the Citect SCADA system exports the data into the DBF file format, then automatically opens Microsoft Excel and pastes these files into an Excel workbook. Calculations are automatically performed within Excel and a formal end-of-shift report is printed on a laser printer. Plant personnel save a copy of this report on the local plant file server for review, while the manager at each plant can call into the I/O server from home to check on operations. The report gives the plant manager a comprehensive evaluation of how well the plant is operating, including the number of tons of refuse on hand.
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