Emission losses and dispersion of volatile organic compounds from tank farm of petroleum refinery complex

Photochemical loss with consequential underestimation in active VOCs and corresponding secondary pollutions in a petrochemical refinery, China

The photochemical loss of volatile organic compounds (VOCs) significantly alters the capturing source profiles in high-reactivity VOC species and results in an underestimation of secondary pollutants such as ozone (O3) and secondary organic aerosol (SOA). Utilising speciated VOC data from large petrochemical refineries, the research assesses the photochemical loss of various VOC species. Air samples from multiple sites revealed over 99 VOCs, with initial concentrations estimated via a photochemical age-based parameterisation method. The comparative analysis of initial and measured VOC values provided insights into the VOCs' photochemical degradation during transport. Findings highlight that the average photochemical loss of total VOCs (TVOCs) across different refinery process areas varied between 4.9 and 506.8 ppb, averaging 187.5 ± 128.7 ppb. Alkenes dominated the consumed VOCs at 83.1 %, followed by aromatic hydrocarbons (9.3 %), alkanes (6.1 %), and oxygenated VOCs (OVOCs) at 1.6 %. The average consumption-based ozone formation potential (OFP) and SOA formation potential (SOAP) were calculated at 1767.3 ± 1251.1 ppb and 2959.6 ± 2386.3 ppb, respectively. Alkenes, primarily isoprene, 1,3-butadiene, and acetylene, were the most significant contributors to OFP, ranging from 19.9 % to 95.5 %. Aromatic hydrocarbons, predominantly monocyclic aromatics like toluene, xylene, styrene, and n-dodecane, were the primary contributors to SOAP, accounting for 5.0 % to 81.3 %. This research underscores the significance of considering photochemical losses in VOCs for accurate secondary pollution assessment, particularly in high-reactivity VOC species. It also provides new detection methods and accurate data for the characterization, source analysis and chemical conversion of volatile organic compounds in the petroleum refining industry.

Integrated Sustainable Management of Petrochemical Industrial Air Pollution

The emission inventory, emission factor, and spatial concentration distribution of volatile organic compounds (VOCs) from a petrochemical industry (aromatics plant) were intensively evaluated in this study to elucidate the potential sources of BTX emission and their contribution to ambient concentrations. Five emission groups were quantified through direct measurement and emission models. These data were then used as input for the AERMOD dispersion model for the source apportionment analysis. The source to ambient contribution analysis revealed that a wastewater treatment facility and organic liquid storage tank were major contributors accounting for about 20.6-88.4% and 10.3-75.4% to BTX environmental concentrations, respectively. The highest annual ambient concentrations of benzene (B), toluene (T), and xylenes (X) were predicted as 9.0, 2.8, and 57.9 µg/m³ at the fence line of the plant boundary, respectively. These findings assist policymakers in prioritizing the appropriate control measures to the right source by considering not just the amount released but also their contribution to ambient concentrations. This study suggested that the wastewater treatment unit should be changed to the closed system which will benefit reduction in its emission (45.05%) as well as effectively minimizing ambient VOC concentration by 49.96% compared to its normal operation.

Characteristics and Impact of VOCs on Ozone Formation Potential in a Petrochemical Industrial Area, Thailand

In this study, the ambient concentrations of volatile organic compounds (VOCs) were intensively measured from January 2012 to December 2016 using an evacuated canister and were analyzed using a gas chromatography/mass spectrophotometer (GC/MS) based on the US EPA TO-15 in the community and industrial areas of the largest petroleum refinery and petrochemical industrial complex in Map Ta Phut Thailand. The ternary diagram was used to identify the source of VOCs. Reactivity of VOCs on their ozone formation potential (OFP) were quantified by the maximum incremental reactivity coefficient method (MIR) and propylene-equivalent concentration methods. Results from the study revealed that aromatic hydrocarbon was the dominant group of VOCs greatly contributing to the total concentration of measured VOCs. Among the measured VOCs species, toluene had the highest concentration and contributed as the major precursor to ozone formation. The ternary analysis of benzene:toluene:ethybenzene ratios indicated that VOCs mainly originated from mobile sources and industrial processes. Within the industrial area, measured VOC concentration was dominated by halogenated hydrocarbons, and alkene was the highest contributor to ozone formation. The propylene-equivalent concentration method was also used to evaluate the reactivity of VOCs and their role in ozone formation, and secondly to support findings from the MIR method.

A Modeling Framework to Quantify Routine VOC Emissions and Concentrations from Organic Liquid Tanks

The oil industry has been a primary source of energy for years but it can also lead to the emission of Volatile Organic Compounds (VOC). VOCs play a major role in the formation of photochemical oxidants and can be harmful to the ecosystem. Thereupon, effective mitigation and control strategies of air pollution have recently become more prominent for the oil industry. To orchestrate these strategies, the understanding of how air pollutants disperse from organic storage tanks should be improved. In this study, a modeling framework was developed to estimate in-field two-month average VOC concentrations caused by crude oil tanks. Firstly, United States Environmental Protection Agency's (US-EPA) Tanks 9b software was used to estimate emission rates from tanks. Then, Gaussian Dispersion Formulation was applied to simulate VOC dispersion. Following this, an in-house equation was used to represent the average VOC concentration at selected receptor locations. Moreover, in-field VOC measurement (passive sampling method) was also conducted to evaluate model performance. The normalized root-mean-square deviation between the measured and estimated VOC concentration was found to be 0.15. There was also a strong correlation between the two data with a correlation coefficient of 0.96. Overall, the results suggest the model statistically performed well with a 95% confidence interval. Due to its effectiveness and time-saving application, the method described in this study can be used to develop air pollution mitigation plans for organic storage facilities.

Improved speciation profiles and estimation methodology for VOCs emissions: A case study in two chemical plants in eastern China

Volatile organic compounds (VOCs) poses a serious health risk through not only their own toxicity but also their role as precursors of ozone and secondary organic aerosols. The chemical industry, as one of the pillar industries in eastern China, is a key source of VOCs emissions. In this study, speciated VOCs emissions were measured in two chemical plants in eastern China. Oxygenated VOCs and aromatics were found to be the dominant species categories in both plants. The ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) of VOCs from dedicated resin production were both higher than general resin production. Three process-based models were used for the estimation of VOCs emissions from the two tested plants as a case study. The comparison between the emission factor model and the model with best available estimation methods (e.g., the measurement-based method, the mass balance method, the empirical formula method, and the correlation equation method) implied possible overestimation of the widely used emission factor model for the chemical industry. The probabilistic model developed in this study incorporated probability distribution of key parameters and proved to be a promising tool for emission inventory development and uncertainty analysis. The overall uncertainties of VOCs emissions based on the model were (-48%, +147%) and (-48%, +139%) for the two tested plants. In this study, the speciation profiles and estimation methodology for VOCs emissions from the chemical industry in China were both improved, which could benefit the accurate evaluation of the impacts of VOCs emissions.

Estimation of Emission Factors for Hazardous Air Pollutants from Petroleum Refineries

The hazardous air pollutants (HAPs) group is composed of 187 chemicals that are known to be potentially carcinogenic and dangerous for human health. Due to their toxicological impact, HAPs are an increasingly studied class of compounds. Of the different HAPs sources, refineries are one of the major sources. In order to obtain a preliminary assessment of the impact of a refinery in terms of emissions, a useful instrument is the determination of the emission factor (EF). For this reason, this work, focusing on the USA refining scenario, aims to provide evidence for a generic trend in refinery emissions to evaluate a correlation between the plant size and the amount of its emissions, in particular the HAPs emissions. Based on the analysis of the data collected from the U.S. Environmental Protection Agency (US EPA), a general trend in the emissions from refinery plants was established, showing a positive correlation between the HAPs emissions and the refinery size, represented by a value of the Pearson correlation coefficient r close to 1. Once this correlation was highlighted, a purpose of this work became the estimation of an organic HAPs emission factor (EF): from a whole refining plant, the EF of the total organic HAPs is equal to 10 g emitted for each ton of crude oil processed. Moreover, it was also possible to undertake the same evaluation for two specific HAP molecules: benzene and formaldehyde. The benzene and formaldehyde EFs are equal to, respectively, 0.8 g and 0.2 g for each ton of processed crude oil. This work provides a simple rule of thumb for the estimation of hazardous substances emitted from petroleum refineries in their mean operating conditions.