Abstract

Ultrafine particles are object of main health concern, but its concentration is challenging to be continuous monitored in mineral and metallurgical industrial processes. This paper shows the development of an empirical regression model correlating the ultrafine particles concentration measured by two continuous analyzers, electrodynamic (EDA) and optical scatter (OSA) with meteorological and process parameters. The analyzers were installed at stack of an industrial mineral fertilizer plant over 4 seasons. The results showed that EDA have poor correlation with process or meteorological parameters (r-squared less than 10%) what can be caused by particles not being charged evenly on the stream as its better accuracy for particles over 10µm, as previous studies had suggested. The OSA ultrafine particles concentration model showed r-squared of 45% correlation with meteorological parameters and raw material feed. The model presented and standard error of 0.21 mg/Nm3 which is considered adequate for industry compliance purposes. OSA shows promising application if meteorological parameters are included, as already in practice for ultrafine particles monitoring outdoors.

Highlights

  • The mineral fertilizer industry produced in 2018 around 62 million tons of ammonium nitrate/ calcium ammonium nitrate (AN/CAN) over the world [1]

  • The process is based on reaction from phosphate rock and nitric acid and after some separation steps the called mother liquor is mixed with potassium chloride and ammonia, generating a melt in high temperature which is pumped to a centrifugal bucket with small holes inside the Prilling Tower (PT) [5]

  • The best regression model found for EDA using transformed response was optimal lambda equal to -40 giving a r-squared equal to 9.49%, F-value of 53.91 (p-value of 0) and standard error of 2 mg/Nm3

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Summary

Introduction

The mineral fertilizer industry produced in 2018 around 62 million tons of ammonium nitrate/ calcium ammonium nitrate (AN/CAN) over the world [1]. When producing AN/ CAN there is emission of ultrafine particles (UFP) mainly formed in gas phase, no matter which production process is employed but, when using prilling towers (PT) the issue becomes critical due to the high air flow needed. Besides that, their health impact is significant once the human exposure to particulate matter (PM) is correlated with an increase in cardiac and respiratory morbidity and mortality [2]. Séquier et al [4] when prilling molten lipids, have obtained spherical prills when adjusting prilling melt temperature and have observed coalescence of liquid droplet during their fall, what they assumed was caused by turbulence into the air column

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