Investigation of combustion reactivity and NO emission characteristics of chars obtained from the devolatilization of raw and partially dried lignite

Abstract

In an attempt to achieve the clean and efficient utilization of lignite, drying pre‐treatment was performed in this study before lignite combustion. The combustion reactivity and NO emission characteristics of the partially dried lignite samples in the char combustion stage were investigated by means of TG and isothermal combustion tests, and the reactivity could be summarized as the following order: L1>L0.5>raw>L3>LT>L5 (chars obtained from the devolatilization of the raw and partially dried coals at 378 K for 0.5, 1, 3, 5, and 120 minutes) and the NO conversion ratio of L1 was the lowest. When the moisture content in the coal particles was relatively high (19.68%‐35.84%), the drying treatment could increase the combustion reactivity and inhibit NO emission in the char combustion stage; When the moisture content was within a relatively low range (0.17%‐19.68%), the moisture removal had negative effects on the reactivity and NO emission in the char combustion stage. The surface behaviour and microstructure of the raw coal char and chars derived from the partially dried coals were clarified by temperature programmed desorption/reduction (TPD/TPR) and Raman spectroscopy. The results illustrated that L1 derived from Lc1 (19.68%) was the most reactive sample with the largest amount of C(O) on the particle surface. There were also more reactive aromatic structures in L1 than other samples. Compared with direct combustion or excessive drying treatment, lignite should be dried to a certain degree (19.68%) for optimized lignite combustion.

Comparison of three methods for the sequential extraction of lignite pretreated by ionic liquid

“…Lignite is one of the important energy sources in China, but it has the characteristics of low‐rank coal, such as high moisture content and difficulty in denitrification and desulphurization. [ 1,2 ] When coal is used as fuel, only C and H are effective elements, while elements such as O, S, and N and other elements are ineffective or harmful. It also provides the possibility of using lignite as a raw material for the production of “scarce chemicals.” [ 3 ] With a full understanding of the occurrence structure of lignite and making use of the characteristics of low‐rank coal that are rich in condensed aromatic nuclear structure, terpenoids, and oxygen, which can be used to produce oxygen‐containing chemicals such as phenols and ketones with high added value, as well as polycyclic aromatic hydrocarbons and hopanes, it will gradually develop a fine coal chemical industry with broad prospect.…”

“…Lignite is one of the important energy sources in China, but it has the characteristics of low-rank coal, such as high moisture content and difficulty in denitrification and desulphurization. [1,2] When coal is used as fuel, only C and H are effective elements, while elements such as O, S, and N and other elements are ineffective or harmful. It also provides the possibility of using lignite as a raw material for the production of "scarce chemicals."…”