Effects of Alkali and Alkaline Earth Metals on N-Containing Species Release during Rice Straw Pyrolysis

Abstract

Abstract:To study the effects of inherent and external alkali and alkaline earth metallic species (AAEMs, i.e., K, Ca and Mg) on the behavior of N-containing species release during rice straw (RS) pyrolysis, different pretreatments were applied in numerous experiments. Results indicate that ammonia (NH 3 ) and hydrogen cyanide (HCN) are the major N-containing species and that the yields of isocyanic acid (HNCO) and nitric oxide (NO) are relatively low. The removal of inhert AAEMs shifts N-containing species release to a high-temperature zone according to volatile release behavior because of the increase in activation energy. The formation selectivity of NH 3 , HNCO, and NO increases by demineralized pretreatment, whereas HCN selectivity decreases. The formation of HNCO is mainly affected by alkaline earth metal. N-containing species release occurs in low temperatures with the addition of external AAEMs. The activation energy of samples impregnated with CaCl 2 and MgCl 2 sharply decreases compared to the original RS. The total yields of N-containing species are reduced significantly in the presence of KCl, CaCl 2 , and MgCl 2 as additives. The inhibition ability of AAEMs follows the sequence MgCl 2 > CaCl 2 > KCl. The inhibition effect of MgCl 2 can be improved by solution immersion compared with solid powder mixing. The clean biomass pyrolysis and gasification technology with low N-containing species content may be developed according to the results.

Comparing the Thermo-Physical Properties of Rice Husk and Rice Straw as Feedstock for Thermochemical Conversion and Characterization of their Waste Ashes from Combustion

“…on the thermogravimetric characterization of RH or RS (Worasuwannarak et al 2007;Sun et al 2010;Chen et al 2014;Gao et al 2015;Moliner et al 2016). For example, Moliner et al (2016) studied the thermal and thermo-oxidative characterization of rice straw for its use in energy valorization processes, as well as the influence of carrier gas (Ar and O2) on its pyrolysis.…”

“…For example, Moliner et al (2016) studied the thermal and thermo-oxidative characterization of rice straw for its use in energy valorization processes, as well as the influence of carrier gas (Ar and O2) on its pyrolysis. Gao et al (2015) investigated the effects of alkali and alkaline earth metals on N-containing species released during RS pyrolysis. There also is much research concentrating on the dynamics models that predict the kinetics during pyrolysis (Arora et al 2009;Cai et al 2013;Mishra and Bhaskar 2014;Wang et al 2016).…”

Effect of Temperature and Mineral Matter on the Formation of NOx Precursors during Fast Pyrolysis of 2,5-Diketopiperazine

“…However, the yields of different gaseous products changed significantly. Magnesium and calcium promoted the formation of HCN and HNCO and inhibited that of NH3 [37].…”

“…Minerals are important components of biomass [36,37]. Minerals have an important influence on the distribution of nitrogen-containing compounds released from biomass pyrolysis [29,[38][39][40][41][42].…”

The Effect of Rice Straw Gasification Temperature on the Release and Occurrence Modes of Na and K in a Fluidized Bed

“…Gasification temperature is a significant factor affecting volatile form and combustible gas composition [27][28][29][30]. As shown in Figure 2, with an increase in gasification temperature, the concentrations of CO and H 2 gradually increased in the gas produced, while the concentration of CO 2 significantly decreased and that of CH 4 slightly increased.…”