*Article* **Impact of Primary Air Separation in a Grate Furnace on the Resulting Combustion Products**

**Michał Kozioł 1,\* and Joachim Kozioł 2,†**


**Abstract:** When burning fuel in grate furnaces, supplying the right amount of air to them is as important as the method of air supply. In a furnace with a fixed grate, the supply method of primary air is determined by the distribution of the supplied air stream over time, and in a furnace with a movable grate, the said method involves the distribution of the stream along the active length of the grate. The need to account for air distribution is attributable to complex processes that occur during the combustion process. The paper describes experimental studies aimed at determining the influence of the distribution of the supplied primary air on the emission of CO2, CO, SO2, NOx, and on the content of combustible parts in the slag. In all cases, the total amount of primary air supplied to the process as well as other process control parameters was identical, and only the distribution of primary air was different. The paper proposes the use of a generalized function to describe the distribution of air, defined by its total demand and the relative time R that fuel remains on the grate until the maximum air stream is obtained. The quantity R was accepted at the value ranging from 1/6 to 2/3. With the rise of R, the emissions of CO2, CO, and SO2 increased by 53%, 125%, and 27%, respectively, and the emissions of NOx and the share of combustibles in the slag decreased by 12% and 79%, respectively.

**Keywords:** grate furnaces; combustion process control; primary air distribution; co-combustion; emission of gaseous pollutants
