Expert control system–based multimode hybrid switching control strategy for microwave lignite drying

ABSTRACT

Thermal runaway is a critical feature of microwave lignite drying, which leads to the combustion of lignite. An expert control system (ECS)-based multimode hybrid switching control strategy is developed to solve it. The control strategy has three control modes, which contain two proportional integral derivative modes and a zero mode. Two knowledge-based ECS interface machines of the hybrid switching control strategy are built for mode switching and auxiliary decision. Experimental results demonstrate that fixed microwave power levels lead to the thermal runaway phenomenon during lignite drying process. Using the proposed hybrid switching control strategy, the wet lignite can be safely and efficiently dried to achieve the objective (moisture content 7%). Finally, based on the drying curves, the microwave lignite drying behaviors are adequately represented by the Wang and Singh model, which provides the best description (R² = 0.9913) for the experimental results.

KEYWORDS:

• Expert control system
• hybrid switching control
• microwave drying
• thermal runaway

Additional information

Funding

This work is supported by the National Basic Research Program of China (Grant no. 2013CB328903) and the Fundamental Research Funds for the Central Universities (Grant no. CDJXS12171104).