Computuerized process control systems are applied in diverse range of industries in order to improving productivity, product quality, and efficiency of a production line which also help reduce energy consumption directly (e.g. by reducing residence time) or indirectly (by reducing defects). While process control for energy efficiency of a glass melting tank is highly important, it is also difficult as the necessary sensors need to be resistant to the agressive environments and high temperatures in the melting tank (Worrell et al., 2008. p.57).
The use of modern, computerized process control systems in the glass industry is relatively low but is increasing with various producers placing new systems in the market. The energy saving potential of these systems, however, is not very clearly defined. Some of the computerized process control systems developed for the glass industry include the following:
Expert system II™is a system that controls the glass melter, the working end, the forehearth, and forming equipment. Its important features include having multi–input multi–output options, incorporation of several set parameters and points, and having a model based dynamic predictive control system. The systems enables fuel savings due to continuously optimized heat input distribution. In addition, the furnace can operate continuously with little action from operators, and resulting stability leads to fewer defects, increased yields, increased product quality, more stable crown and bottom glass temperatures (with less risk for corrosion), and increased lifetime.
Melting Expert is another control system which reduces the need for electric boosting – rather than specific energy savings. Reportedly, the system also increases throughput due to reduced downtime and improved temperature stability, which may lead to additional energy savings.
GlassMax system controls the furnace but also the forehearth, leading to reduced downtime, improved product quality, and reduced product losses. (Cassidy 2000). The developers Universal Dynamics claims a 4% increase in annual production. The payback period was estimated at less than 1 year with an investment of $150,000 (Universal Dynamics 2003).
SIGlas and SIMATIC are control systems supplied by Siemens and are used in various float, container and hollow glass, and fiber glass plants around the world. The systems typically control not just the furnace but also the forehearth and other parts of the production (Worrell et al., 2008. pp.58-59).