Probing into Volatile Combustion Flame and Particulate Formation Behavior During the Coal and Ammonia Co-firing Process

Abstract

Co-firing ammonia in coal-fired utility boilers is a promising de-carbon technical route for power stations, yet currently, there is still no information on how co-firing ammonia would affect the release and conversion of volatiles. Here, coal pellets were burned with/without ammonia co-firing on a flat-flame burner facility in both fuel-lean and -rich conditions. Detailed information on time-resolved evolution of volatile flame, size evolution of soot particles in flame, and changes in their physiochemical structures was obtained. It was observed that co-firing ammonia promoted devolatilization of coal and release of volatiles, leading to an earlier ignition moment in both fuel-lean and -rich conditions. In the flame, massive soot particles were formed from volatiles, and co-firing ammonia affected the conversion of volatiles into soot and changed the flame radiation properties. Interestingly, both the number density of all soot and size of primary soot particles increased after co-firing ammonia in fuel-lean conditions (by 2.5 times and ∼10 nm, respectively), while they decreased in fuel-rich conditions. In fuel-lean conditions, co-firing ammonia promoted inception and surface growth of soot due to competitive consumption of O 2 and increased flame temperature, while in fuel-rich conditions, these effects were offset by partial consumption of soot precursors by forming nitrogencontaining species. Furthermore, when ammonia was co-fired, fringe length, tortuosity, and especially inter-fringe spacing of soot increased slightly, indicating that particles formed in co-firing flames might show higher oxidation reactivity than those formed without ammonia co-firing.

Probing into Volatile Combustion Flame and Particulate Formation Behavior during the Coal and Ammonia Cofiring Process: Further Study on the Chemical Structure and Oxidation Reactivity of Soot Particles

“…The entire capillary sampling device is installed on a stainless-steel connecting rod, which facilitates sampling at different heights of the flame. The gas flow control system, CCD camera system, temperature measurement system, gas collection system, and thermal sampling system are the same as those mentioned in our prior article; 23 detailed information on them can be found in it.…”

“…Through the analysis of the evolution process of flame morphology under four working conditions using a CCD camera system, it was found that the flame shape remained stable for a period of time. 23 It can be approximated that the chemical properties of soot also remained stable during this period, and soot can be accumulated for sampling. This article sets the sampling height to HAB = 24 mm, and the flame morphology of the four working conditions is shown in Figure 1.…”

“…Soot samplings and measurements of oxidation reactivity and physicochemical properties of soot generated in coal volatile flame with ammonia cofiring were carried out in this study, as a further study following our prior publication. 23 Experiments were performed on the same McKenna burner 37 combustion system, in which the flat flame formed by CH 4 − CO−O 2 −N 2 premixed gas combustion was used to provide a real hot flue gas environment for coal pyrolysis and combustion. A capillary sampling system was used to sample the fine particles in a volatile matter flame.…”

Mini Review of Ammonia for Power and Propulsion: Advances and Perspectives

“…Authors could not find very recent publications on NH 3 boilers and furnaces at a practical scale not already featured in review articles. However, fundamental or laboratory-scale research is very active, especially on NH 3 -coal ,− and NH 3 MILD ,− combustion (only including studies published in 2022 and 2023).…”

Oil Palm Wastes Co-firing in an Opposed Firing 500 MW Utility Boiler: A Numerical Analysis

“…Due to the huge reserves and affordability of coal, coal-fired thermal power plants produce a significant share of the world's primary electricity [2][3][4][5][6]. Since coal has a high carbon content, coal-fired thermal power plants generate more CO2 than any other form of power generation [7][8], and they are one of the main anthropogenic CO2 emission sources [2,4,9], contributing for 30.4% of global CO2 emissions in 2018 [10]. The reduction of greenhouse gas (GHG) emissions is essential for addressing climate change triggered by global warming, and the reduction of CO2 emissions is now a global consensus [7,[9][10][11][12][13].…”