The stability limit of extremely low calorific gas combustion in a cone-shape two-section burner with the preheaters

• Published in: International communications in heat and mass transfer Vol. 140; p. 106524
• Main Authors: Shi, Junrui, Kong, Xiangjin, Lv, Jinsheng, He, Fang, Qi, Xiaoni
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2023
• Subjects: Divergent two-layer burner; Heat recirculating; Heat recovery; Low calorific gas; Preheater; Divergent two-layer burner; Preheater; Heat recirculating; Low calorific gas; Heat recovery
• ISSN: 0735-1933; 1879-0178
• DOI: 10.1016/j.icheatmasstransfer.2022.106524

The current lean flammability limit (LFL) for methane/air mixture in two-layer burner is generally greater than the equivalence ratio of 0.4–0.5. We introduce a divergent two-section burner with preheaters to significantly extend the LFL for low calorific gas (LCG). The idea is realized by heat recovery using preheaters embedded in the downstream of porous media to effectively preheat fresh mixture before entering the burner, thus the temperature of fresh mixture is increased through heat recover without any external heat source, and the extremely LCG achieves stable combustion. It is confirmed by numerical studies with two-dimensional axial symmetry model that the LFL for methane/air can be extended to equivalence ratio of 0.15 for the developed burner with inlet temperature of 800 K. Results show that the stability limit is strongly dependent on the mass flow ratio, inlet temperature and equivalence ratio. Thermal efficiency of the porous burner varies between 0.45 and 0.54 with equivalence ratio. It is advantageous to choose a moderate velocity to achieve stable combustion of LCG. The presented stability limit offers guideline for the use of LCG without any external energy. •A divergent two-section burner with preheaters to extend lean flammability limit is proposed.•The developed burner can operating at equivalence ratio of 0.15 for CH4/ air mixture.•The thermal efficiency is descended from 0.54 to 0.45 with the equivalence ratio.•Combustion stability is improved with increasing the mass flow rate of the reactants.•The the root mean square of preheating temperature decreases from 15.9 K to 13.6 K with inlet temperature.