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The coal/ammonia co-firing technology for thermal power generation is a feasible method to effectively reduce CO 2 emissions. However, the easy formation of NO x is one of the challenges faced by this technology owing to the high nitrogen content in ammonia. This study proposes a novel swirl burner with a scalable dual-channel ammonia pipe, and evaluates the combustion and NO x formation under different extension lengths of the dual-channel ammonia pipe (i.e., 0 m, 0.4 m, 0.8 m, 1.0 m, 1.2 m). The results show that the extension length of the dual-channel ammonia pipe significantly affects the flow, combustion, and NO x formation. When the extension length of the dual-channel ammonia pipe is above 0.8 m, the ammonia stream can completely penetrate the internal recirculation zone into the high CO environment, which contributes to promoting the ammonia pyrolysis and inhibiting the ammonia oxidation to form NO x. NO x emissions significantly decrease from 846 ppm to 146 ppm as the extension length of the dual-channel ammonia pipe from 0 m to 0.8 m, but change slightly as further increases from 0.8 m to 1.2 m. The carbon content in fly ash decreases from 4.53% to 3.40% as the extension length of the dual-channel ammonia pipe increases from 0 m to 1.0 m. Still, it increases from 3.40% to 3.70% as the extension length of the dual-channel ammonia pipe rises to 1.2 m. Overall, it is reasonable to set the extension length of the dual-channel ammonia pipe at 1.0 m in this studied condition, which can obtain low NO x and low carbon content in fly ash. [Display omitted] • A novel swirl burner with a scalable dual-channel NH 3 pipe is proposed. • Effect of NH 3 pipe extension length on combustion and NO x formation is investigated. • NH 3 pipe extension length significantly affects flow, combustion, and NO x formation. • 1.0 m for NH 3 pipe extension length is reasonable with good performance. [ABSTRACT FROM AUTHOR]

Cofiring of coal slime in existing utility boilers is a promising approach to the disposal of coal slime. However, reports about cofiring coal slime with anthracite in the down-fired utility boiler are still few. This work presents a comprehensive study on the combustion characteristics, slagging potential, and NOx emissions of cofiring coal slime and anthracite through lab-scale experiments, numerical simulations, and full-scale industrial measurements in a 600MW down-fired utility boiler. The lab-scale experiments show combustion interactions between anthracite and coal slime, which have both a promotive effect on the ignition of anthracite and inhibitive effect on the combustion and burnout of anthracite. Especially, the inhibitive effect is greater than the promotive effect when the blending ratio of coal slime is above 5%. The addition of coal slime can effectively improve the ash fusion temperature of blended samples. In addition, simulations and full-scale industrial measurements of anthracite cofiring with coal slime are performed in a down-fired utility boiler. The results show that as the blending ratio of coal slime increases, the carbon content in fly ash increases and the boiler efficiency and NOx emissions decrease. A 5% ratio is validated to be a reasonable cofiring ratio of coal slime in the actual operation without no slagging phenomenon. These results provide more insights into the cofiring behavior of coal slime and anthracite and guide the application of blending coal slime in a down-fired boiler. [ABSTRACT FROM AUTHOR]

Coal blends are commonly used in thermal power plants and oxy-fuel combustion also attracts great concerns recently. However, little has been done on oxy-fuel combustion of coal blends. In this paper, combustion tests are performed in a drop tube furnace for various coal blends under O 2 /CO 2 mixtures, which are also reproduced numerically. Strong combustion interactions between the parent coals in a blend are observed. The ignition of the low-volatile coal is promoted due to the rapid combustion of the volatiles from the high-volatile coal. However, the char burnout of the low-volatile coal is compromised due to the rapid O 2 consumption by the large amount of volatiles. The interactions under oxy-fuel conditions are more sensitive to the excess O 2 , inlet oxidizer temperature and coal particle size. 1) The increase in the excess O 2 tends to weaken the combustion interactions, in which both the ignition promotion and burnout inhibition effects on the low-volatile coal become less apparent. 2) The increase in the inlet oxidizer temperature further promotes the ignition of the low-volatile coal whereas weakens the burnout inhibition of the low-volatile coal. 3) The effects of reducing particle size on the combustion interactions are similar to those of increasing inlet oxidizer temperature. Since biomass often contains a high volatile content, the findings may shed light on the synergistic effects in oxy-fuel co-combustion of biomass and coal. [ABSTRACT FROM AUTHOR]

Co-incineration of sludge in the existing coal-fired utility boilers is a promising sludge disposal approach, but study on the combustion characteristics and the economic impacts of co-firing sludge in full-scale utility boilers is in absence. In this study, a series of full-scale field experiments and numerical experiments were conducted to study the coal-sludge co-combustion characteristic in a 100 MW coal-fired utility boiler. The effects of sludge blending ratio and moisture content in sludge are concerned. Subsequently, the economic impacts of co-firing sludge is presented. The results demonstrate that the combustion characteristics is acceptable when co-firing 10% sludge. The ignition property and the flame stability are significantly affected when the mass content of co-fired sludge is over 10%. Decreasing the moisture content in sludge is beneficial to the combustion characteristics but the improvements are limited. Co-firing sludge is profitable for power plants as the savings from coal and sludge disposal allowance is quite substantial. Considering both the combustion characteristics and the economic impacts, co-firing 10% sludge with moisture content ranging from 40% to 56% is optimal. The annual profit from co-firing sludge can reach 4.2 million to 5.5 million Chinese yuan (CNY), which is remarkable for the power plant. [ABSTRACT FROM AUTHOR]