Energy production from coal-fired boilers currently contributes to 14% of total U.S. energy production. We expect that coal will continue to have a sizeable share of the energy market for the foreseeable future. Therefore, it is imperative that these existing coal-fired boilers reach a high efficiency to limit the emissions per unit of energy produced. This can be achieved through improved knowledge of the spatial distribution of temperature inside the boiler, which can be used for the tuning and validation of detailed models of combustion within the coal-fired boilers. One way this temperature measurement can be achieved is by co-feeding coated pyrotechnic particles with the pulverized coal. The particles need to be designed to emit an optical signal at a certain temperature. Given the reddish-yellow background in coal-fired boilers, a green color would yield a distinct and detectable signal. The most commonly used green colorant in pyrotechnics is Ba(NO3)2. Additionally, to achieve high flame temperatures metallic fuels such as Al, Mg, MgAl are used. Recently, studies have also shown boron can serve a dual purpose of ‘fuel’ as well as ‘colorant.’ So, would the addition of boron to a Ba(NO3)2 based system lead to enhancement in green color emission in terms of intensity or color? In this study, different compositions containing KClO4, Ba(NO3)2, fuels (B, Mg), and PVC and Parlon as chlorine source and binder, respectively were made and analyzed using TGA and burner tests. The flame intensity was captured using a photocell attached with a green color filter. It was observed that the ratio of B to Mg strongly influenced the overall burn time, ignition temperature, and the green color emission intensity. Compositions having a higher amount of Boron were found to decompose faster and had a slightly less intense flame as can be seen from Table 1. This might be due to the higher volatility of ‘B’ compared to ‘Mg’ and causing the overall composition to react faster. Thus, although ‘B’ is slightly lowering the intensity of the flame, it is providing a more tunable composition that can be used to tune the ignition temperature and burn time for a green light-emitting pyrotechnic.

Effect of boron to magnesium ratio on green color emissions in pyrotechnics

ACS Fall 2021

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