Three kinds of biochars (called poplar branch biochar (PBC), water hyacinth biochar (WHC), and corn straw biochar (CSC)) were prepared in a fixed-bed pyrolyzer at different pyrolysis temperature of 300-700 °C. The effects of biochar species, pyrolysis temperature and biochar addition on adsorption characteristics of typical heavy metals (HMs) of Pb and Zn in vegetable soil (collected from lead-zinc-silver mining area, Nanjing, China) were investigated. The obtained results indicate that WHC presents the best adsorption ability at the same experimental conditions, whose adsorption efficiency on HMs of Zn and Pb is 21.83% and 44.57%, and the relative adsorption capacity of Zn and Pb is 227.65 μg/g and 363.76 μg/g, respectively. The adsorption efficiency of biochar on HMs of Zn and Pb in soil increases gradually with the increasing of pyrolysis temperature. The increasing of biochar addition is beneficial to increase adsorption efficiency of soil HMs, but unhelpful for adsorption capacity.

The effects of biomass types (including cotton stalk, wheat straw, rice husk, and rice straw), the stoichiometric ratio in the reburning-zone (SR2), the reaction temperature in the reburning-zone (t2), the particle sizes of biomass reburning fuels (dp), and the reburning fuel fraction (Rff) on NO reduction efficiency during biomass reburning were investigated systematically in an entrained flow reactor. The NO heterogeneous reduction mechanism resulting from the reburning of wheat straw and its char was analyzed. The results indicated that cotton stalk has the best performance of NO reduction, wheat straw is in second place, and rice husk and rice straw are less effective. In the range of t2 = 900–1100 °C NO reduction efficiency increases when the reburning-zone reaction temperature is increased at the same SR2. NO reduction efficiency increases insignificantly with a decrease in the particle size of the biomass with dp < 425 μm. NO reduction efficiency follows a pattern of first increasing and then decreasing with the decreasing of the SR2 or the increasing of the Rff. The higher NO reduction efficiency (more than 50%) can be achieved in the range of SR2 = 0.7–0.8 or Rff = 20–25% during reburning with the four types of biomass. The contribution of NO heterogeneous reduction by wheat straw char to the total NO reduction was in the higher range of 59–68%, whereas the Rff was in the range of 10–26%.

•Temperature window of NO reduction in a SNCR process with NH3 is at 875–1050 °C.•Water vapor can improve NO reduction and optimal water vapor content is at 4–8%.•Na/K additives can improve NO reduction and the promoting order is Na2CO3 > KCl > NaCl.•Molar concentration of additives has little effect on NO reduction while it above 50 ppm.•Flyash and Na/K additives have a coupling effect on NO reduction in a SNCR process.An experimental study of Na/K additives and flyash on NO reduction during the selective non-catalytic reduction (SNCR) process were carried out in an entrained flow reactor (EFR). The effects of reaction temperature (Tr), water vapor, Na/K additives (NaCl, KCl, Na2CO3) and flyash characteristics on NO reduction were analyzed. The results indicated that NO removal efficiency shows a pattern of increasing first and decreasing later with the increase of the temperature at Tr = 850–1150 °C. Water vapor can improve the performance of NO reduction, and the NO reduction of 70.5% was obtained while the flue gas containing 4% water vapor at 950 °C. Na/K additives have a significant promoting effect on NO reduction and widen the SNCR temperature window, the promoting effect of the test additives is ordered as Na2CO3 > KCl > NaCl. NO removal efficiency with 125 ppm Na2CO3 and 4% water vapor can reach up to 84.9% at the optimal reaction temperature. The additive concentration has no significant effects on NO reduction while its concentration is above 50 ppm. Addition of circulating fluidized combustion (CFB) flyash deteriorates NO reduction significantly. However, CFB flyash and Na/K additives will get a coupling effect on NO reduction during the SNCR process, and the best NO reduction can reach 72.3% while feeding Na2CO3-impregnated CFB flyash at 125 ppm Na2CO3 and Tr = 950 °C.