A new generation of incinerators is required for shipboard waste disposal to enable Navy ships access to ports and bodies of water around the world without operational constraints related to environmental laws and regulations. The present practice of over-board discharge and storage/off-loading will be unacceptable. Thermal destruction is considered the ultimate solution beyond the year 2000 for all types of waste.

This project established the science and technology basis for a compact, closed-loop-controlled waste incinerator using resonant acoustics for enhanced waste pyrolysis and controlled vortex dynamics for enhanced and controlled afterburning. The afterburning process is closed-loop controlled using newly-developed control components, including diode-laser based sensors for real-time and continuous emission monitoring, new types of actuators, and a non-standard controller based on fuzzy logic or neural nets. A second SERDP project, WP-887: Demonstration of a Compact, Closed-Loop Controlled Waste Incinerator, applied this new technology to two Navy incinerator programs.

The S&T studies consisted of the following: (1) control component development, including separate tasks for the development of advanced sensors, actuators, a process model, and an adaptive controller; (2) sub-scale evaluation of advanced laser diagnostics conducted to evaluate both the trapped-vortex and periodic-vortex concepts and to validate and integrate control components; and (3) comparison of the effectiveness of the new closed-loop controlled system to existing incinerator technologies for compactness and emission characteristics. Sub-scale integration tests further defined the requirements and design criteria for full-scale demonstration and optimization of the sludge incinerator and the plasma arc afterburner.

This project developed two technologies to improve the combustion characteristics of solid and liquid wastes. The first technology applied resonant acoustics to the primary combustion chamber to enhance the burning rate of solid beds and improve the burning characteristics of liquid sprays. The advantages of resonant acoustics for enhancing the pyrolysis processes were demonstrated in simulated solid-waste experiments. The second technology applied active combustion control to the secondary combustion chamber to achieve efficient and controlled afterburning in acoustically stabilized vortices. The active control technology significantly increased the destruction and removal efficiency while greatly reducing emissions of unburned hydrocarbons, carbon monoxide, and nitrogen oxides. The controlled afterburner concept is applicable to a variety of waste treatment and combustor systems. This project was completed in FY 1999.

Successful demonstration of a compact incinerator with real-time exhaust monitoring for active combustion control represents a significant step towards assured waste incineration and can be the basis for the next-generation incinerators. The closed-loop active control of the incineration process will ensure, for the first time, proper incineration. Assured waste incineration onboard ships will result in significant cost savings by avoiding cost for waste off-loading and on-shore destruction, particularly in foreign countries.