Effects of S and Al on K Migration and Transformation during Coal and Biomass Co-combustion

Numerical Study on Combustion Characteristics of Biogas Cocombustion in a 300MW Coal-Fired Boiler Furnace

To further explore cocombustion technology with biogas and coal, a series of numerical simulations have been carried out to analyze the effects of the cocombustion ratio ξ, height of biogas nozzle HGN, and tilt angle of burner θBN on combustion characteristics in a 300 MW four-corner tangential boiler furnace. Three types of biogas are gasified from straw, sawdust, and raw wood when air serves as the gasification agent. The velocity field, temperature field, and NO emissions have been comprehensively analyzed when the values of ξ, HGN, and θBN range, respectively, from 0.02 to 0.12, from 17.3 to 20.3 m, and from -15° to +15°. Results showed that the NO concentration at the furnace outlet monotonously decreased with ξ. The injection of biogas reduces both the peak temperature of the entire boiler furnace and the NO concentration at the furnace outlet. The NO emission concentration decreases with the increased ξ value for all types of biogases. The cocombustion with sawdust biogas indicates the least NO emission at a fixed cocombustion ratio. Furthermore, reducing the furnace height at HGN = 17.3 m or titling down the burner at θBN = -15° contributed to a greater NO concentration at the furnace outlet.

Screening of Potential Additives for Alleviating Slagging and Fouling during MSW Incineration: Thermodynamic Analysis and Experimental Evaluation

The formation of slagging and fouling during municipal solid waste (MSW) incineration not only significantly affects heat transfer, but also results in shortened operating cycles. In order to solve the issues, the effect of different additives on the migration and transformation patterns of alkali/alkaline earth metals (AAEM) and chlorine during MSW incineration is screened based on the Gibbs energy minimization method. The effect of potential additives on the ash fusion temperature and combustion reactivity of MSW char is subsequently verified and evaluated by experimental methods. The thermodynamic equilibrium analysis shows that Al(NO3)3, Ca(NO3)2, and Mg(NO3)2 have great potential to increase the ash fusion temperature. The experimental investigation confirms that the addition of Al(NO3)3, Ca(NO3)2, and Mg(NO3)2 significantly increases the ash fusion temperature. The order of increasing the ash fusion temperature by different additives is Mg(NO3)2 > Ca(NO3)2 > Al(NO3)3. The addition of Mg(NO3)2 significantly increased the initial deformation temperature, softening temperature, hemispheric temperature, and flow temperature of ash from 1180, 1190, 1200, and 1240 °C to 1220, 1230, 1240, and 1260 °C, respectively. The addition of Cu(NO3)2, Fe(NO3)3, and KMnO4 significantly decreases the temperature at the maximum weight loss rate of MSW char, while increasing the maximum weight loss rate. Additionally, Cu(NO3)2 shows the best performance in improving the combustion reactivity of MSW char. The addition of Cu(NO3)2 evidently increases the maximum weight loss rate from 0.49 to 0.54% °C−1. Therefore, it is concluded that Mg(NO3)2 and Cu(NO3)2 are supposed to be the most potential candidates for efficient additives. This study presents an efficient and economical method to screen potential additives for alleviating slagging and fouling during MSW incineration.