Experimental measurements for Polish lignite combustion in a 1 MWth circulating fluidized bed during load changes

Abstract

The conventional design of circulating fluidized beds mainly focuses on high process efficiency, while electricity markets increasingly target operating flexibility due to the increased penetration of renewable energy sources. In this work, the operational flexibility of the CFB furnace when applied to compensate for the feed-in fluctuations from renewable energies has been investigated experimentally. Employing a 1 MWth CFB test facility, Polish lignite was combusted over a wide range of transient operating conditions. The profiles of temperatures and pressures along the riser, the flue gas concentration and the temperature developments in the bed zone, and the outlet of the cyclone that identify the basis for operational flexibility and scale-up studies were shown. It was found that the circulating fluidized bed furnace can be operated with higher positive and negative load change rates up to ±25%/min, maintaining high combustion efficiency and low emissions. Furthermore, the temperature distribution along the riser was almost homogeneous at higher loads. By reducing the load, the temperature difference in the bed zone and after the cyclone was decreased and heterogeneous temperature distribution along the riser can be observed, resulting in a slight decrease in the combustion efficiency.