The Plasma Arc Waste Destruction system (PAWDS) uses a plasma torch to rapidly and efficiently destroy combustible waste aboard ships. After eight years of development under the support of the US Navy and after two and a half years of operation aboard a commercial cruise ship, PAWDS has proven itself to be a viable alternative to traditional incinerators. In the PAWDS, the waste is first shredded and then milled into a lint-like material. This milled waste is then rapidly gasified in a patented plasma fired eductor. The resulting synthesis gas is then mixed with air in the combustion chamber to produce a fully combusted off-gas. This off-gas is then rapidly cooled, preventing the reformation of dioxins and furans. The high energy density of the plasma flame and the use of a unique wall design for the thermal destruction section results in a system that can be rapidly started-up and shutdown within minutes and that is compact and lightweight, fitting into a single deck aboard a commercial cruise vessel or a Navy ship. PyroGenesis with the support of the US Navy, continued to make improvements to the PAWDS over the last two years with the focus of making it a fully automated, operator-friendly system. This paper focuses on several improvements made to the automation and process control of the PAWDS during 2004 and 2005. These improvements include: implementing single button automatic start-up and shutdown sequences, designing and implementing independent control loops for maintaining favorable combustion and waste feed rates, and simplifying the operator interface. Several descriptive pop-up screens have been added to the operator interface to help guide the operator to either rapidly troubleshoot the system or to provide a reminder that maintenance is required on a specific item. Most importantly, the automation program has been designed so that these multiple regulatory control loops work together to intelligently control the system operation in order to compensate for variations in the waste composition. In the event of an abnormal system operation, the control system guides the operator to the action(s) required to bring the system back into normal operating conditions. If no response from the operator is detected when an operator intervention is required, the control system is also designed to take action to safely initiate an automatic shutdown sequence. The system is also designed to allow for remote access over the internet.
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