Effects of CaO‐K₂CO₃ on combustion behavior and emission properties of SO₂ and NO_X during coal sludge combustion

Abstract

The purpose of this work is to investigate the effect of CaO-K 2 CO 3 on the coal sludge combustion and the emission properties of SO 2 and NO X . The combustion characteristics of coal sludge with or without catalysts were studied in a thermogravimetric analyzer, and the experiments were conducted from the ambient temperature to 1000°C at a heating rate of 10°C min À1 . Ignition index, burnout index, and general combustion parameter had been put forward to describe further the combustion characteristics of coal sludge. Combustion experiments were carried out in a quartz tubular fixedbed reactor, and the NO x and SO 2 released during combustion were monitored continuously using a flue gas analyzer. The results show that adding K 2 CO 3 accelerates the release of volatile matter and the combustion of partial fixed carbon. The reduction of ignition temperatures and burnout temperature followed the increase of the concentration of K 2 CO 3 . When the coal sludge is loaded with CaO and 1% K 2 CO 3 , the general combustion parameter is the maximum, and the activation energy (E) is the smallest. Meanwhile, when the coal sludge is loaded with CaO and 1% K 2 CO 3 , it emits less SO 2 and NO X . Therefore, it is concluded that CaO-1% K 2 CO 3 facilitates the clean and efficient combustion of coal sludge. Figure 6. Effect of CaO-K 2 CO 3 on the emission of NOx during the combustion of coal sludge. J. Wu et al. Asia-Pacific Journal of Chemical Engineering 742

Mechanism of NOx Formation from Nitrogen in the Combustion of the Coals Used in Sintering Process

“…The effect of the heating rate on X NO was evaluated by applying five different heating rates (20,30,40,50 and 80 K/min) at constant oxygen content (21 vol pct) and flow rate (600 mL/min). The tests were performed non-isothermally.…”

“…CaO acted as a catalyst for the formation of NO x at temperatures below 1273 K (1000°C). [26][27][28][29][30] Since the experiments were non-isothermally conducted, the catalytic effect of CaO in low temperature region could not be avoided. When the NO x formation pattern was analyzed at temperatures above 1473 K (1200°C), NO x formation was decreased when compared to anthracite combustion, which is in agreement with previous results.…”

“…[6,24] NO x increased when oxygen content increased-more O 2 was available to react with fuel-N. [23,25] Some studies showed that CaO could enhance the conversion ratio of nitrogen providing a non-desirable effect. [6,[26][27][28][29][30] Wu et al [31] found that FeO played a significant role in decreasing NO concentration formed during coal combustion at 1273 K (1000°C). His research also showed that FeO ability to reduce NO gas increases with experiment temperature.…”