This study investigates by experiment the global characteristics of both moderate or intense low-oxygen dilution (MILD) oxy-combustion and air combustion of firing light oil and pulverized coal in a pilot-scale furnace. There are three burner configurations used, i.e., (I) central straight (primary) jet + swirl (secondary) jet, (II) central straight (primary) jet + two side symmetrical (secondary) jets, and (III) central straight (primary) jet + side asymmetrical jet. The furnace centerline temperature, species concentrations, and exhaust emissions are measured and compared for the MILD and conventional combustion cases. For light oil and pulverized coal, the MILD air combustion or oxy-combustion occurs with burner II or III, while the conventional combustion takes place when using burner I. For the light oil, the MILD oxy-combustion can be reached even using pure oxygen. As the MILD combustion is reached, a fairly uniform temperature distribution and low emissions of NO and CO are obtained. Note that burner III produces the largest internal recirculation of the flue gas, lowest peak temperature, and most uniform temperature, whereas the opposite occurs for burner I. Importantly, the MILD combustion is found to reduce the NO emission much more effectively in the oxy-combustion case than in the air combustion case. Moreover, the appearance of the MILD combustion of light oil and pulverized coal differs from the invisible MILD combustion of gaseous fuels. Dark sparks from burning oil droplets or char particles are present in the MILD combustion of light oil or pulverized coal. It is also revealed that the char burnout under the MILD combustion is weaker than that under the conventional combustion.

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Abstract. Improving the ability of global models to predict concentrations of black carbon (BC) over the Pacific Ocean is essential to evaluate the impact of BC on marine climate. In this study, we tag BC tracers from 13 source regions around the globe in a global chemical transport model, Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4). Numerous sensitivity simulations are carried out varying the aging timescale of BC emitted from each source region. The aging timescale for each source region is optimized by minimizing errors in vertical profiles of BC mass mixing ratios between simulations and HIAPER Pole-to-Pole Observations (HIPPO). For most HIPPO deployments, in the Northern Hemisphere, optimized aging timescales are less than half a day for BC emitted from tropical and midlatitude source regions and about 1 week for BC emitted from high-latitude regions in all seasons except summer. We find that East Asian emissions contribute most to the BC loading over the North Pacific, while South American, African and Australian emissions dominate BC loadings over the South Pacific. Dominant source regions contributing to BC loadings in other parts of the globe are also assessed. The lifetime of BC originating from East Asia (i.e., the world's largest BC emitter) is found to be only 2.2 days, much shorter than the global average lifetime of 4.9 days, making the contribution from East Asia to the global BC burden only 36 % of that from the second largest emitter, Africa. Thus, evaluating only relative emission rates without accounting for differences in aging timescales and deposition rates is not predictive of the contribution of a given source region to climate impacts. Our simulations indicate that the lifetime of BC increases nearly linearly with aging timescale for all source regions. When the aging rate is fast, the lifetime of BC is largely determined by factors that control local deposition rates (e.g., precipitation). The sensitivity of lifetime to aging timescale depends strongly on the initial hygroscopicity of freshly emitted BC. Our findings suggest that the aging timescale of BC varies significantly by region and season and can strongly influence the contribution of source regions to BC burdens around the globe. Therefore, improving parameterizations of the aging process for BC is important for enhancing the predictive skill of global models. Future observations that investigate the evolution of the hygroscopicity of BC as it ages from different source regions to the remote atmosphere are urgently needed.

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(125)I brachytherapy is a feasible and effective modality for the treatment of locally advanced unresectable or recurrent ACC.