Experimental Research on Heterogeneous N2O Decomposition with Ash and Biomass Gasification Gas

Junjiao Zhang,Qiang Lu,Xiaoying Hu,Yongping Yang,Wu Qin,Changqing Dong

doi:10.3390/en4112027

Abstract

In this paper, the promoting effects of ash and biomass gas reburning on N2O decomposition were investigated based on a fluidized bed reactor, with the assessment of the influence of O2 on N2O decomposition with circulating ashes. Experimental results show that different metal oxides contained in ash play distinct roles in the process of N2O decomposition with biomass gas reburning. Compared with other components in ash, CaO is proven to be very active and has the greatest promoting impact on N2O decomposition. It is also found that O2, even in small amounts, can weaken the promoting effect of ash on N2O decomposition by using biomass gas reburning.

Highlights

With the popularization of fluidized bed technology, the nitrous oxide (N2O) generated in the circulating fluidized bed (CFB) combustion process has aroused more and more attention.The concentration of N2O emissions from CFB is in the range from 20 to 300 ppm and sometimes400 ppm [1]
Heterogenous N2O decomposition in CFB boilers indicates that heterogenous reactions must happen between N2O and some components in solid fuels, ashes or catalysts [4,5]
Comparing the decomposition of N2O before and after adding circulating ash as bed material, the thermal decomposition proportion of N2O with bed material is about 5% larger than that seen with the bare bed conditions

Summary

Introduction

With the popularization of fluidized bed technology, the nitrous oxide (N2O) generated in the circulating fluidized bed (CFB) combustion process has aroused more and more attention. The conversion rate of the heterogenous decomposition of N2O in the CFB increases owing to the catalytic effect of oxides [6,7,8]. Debbagh et al [10] showed that N2O decomposition with CO at catalyst surface at the temperature range of 200–600 °C was expressed with following reactions: CO + O* → CO2 + *. Choosing the temperature range of 22–550 °C, with the effect of Fe-USY zeolite catalyst, and using selective catalytic reduction (SCR) method, Shen and co-workers [15] prepared a variety of mixed gases with CH4 (such as N2O/CH4, N2O/CH4/NO, N2O/CH4/O2, N2O/CH4/H2O, N2O/CH4/NO/O2, N2O/CH4/NO/O2/H2O) to study N2O decomposition, concluding that N2O conversion rate in N2O/CH4 system was much higher than that in other systems

Experimental Devices and Method

Influence of Biomass Gas Components without Oxygen in Flue Gas

Influence of Biomass Gas Components with Oxygen Content in Flue Gas

Influence of Ash and Metal Oxides on Heterogenous N2O Decomposition

Conclusions