We all know the detrimental effects of the exploration of crude oil and also of its use in the global industry. Crude oil is recognized as a major pollutant in terrestrial, atmospheric, and aquatic water ecosystems. The severity of hydrocarbon contamination is directly proportional to the scale of oil processing. The more we have well-to-refinery operations, the more would the contamination be.
Moreover, the adverse effects of crude oil pollution are not limited to the operations areas only as hydrocarbons within the crude oil mass are what is known as ‘volatile substances’ or VOCs, in technical parlance – with low boiling points and evaporates or sublimates at room temperature or even below it and thus escape into the surrounding atmosphere and create public health problems. Crude oil processing contributes to 16% of the total VOC emissions into the atmosphere in the late 20th century. Certain VOCs like BTEX ( benzene, toluene, ethylbenzene, and xylenes) are the main hazards always found in crude oil processing zones.
The effect of VOCs on human health
The hydrocarbons denoted by BTEX attack the human nervous system and cause dizziness, nausea, and headaches. Even short term exposure to hydrocarbons results in eye and throat irritations, vertigo, and dizziness. Prolonged exposures bring on irreversible damages to the ear and kidney. Living and working in environments that contain toxic amounts of these elements may lead to unconsciousness and even death.
Policies and regulations
Regional as well as international regulations define VOCs and lay down rules to control indoor air quality (IQA) and outdoor air pollution (OAP). These standards aim to impose restrictive policies on specific industries to (i) reduce their VOC emissions, and (ii) to protect their VOC-exposed workers by effective personnel protective equipment (PPEs).
Emission inventories of the crude oil industry
Emission inventory (EI) as a monitoring catalogue of atmospheric pollutants is usually produced as an annual or regular report prepared by the international bodies and individual industrial organizations.
VOC dispersion phenomena and also source appointments are highly affected by meteorological factors like wind and temperature or and the surface of the terrain.
Temporal variations in the VOCs originated from petroleum industries are highly sensitive to seasonal changes – usually with higher concentrations in summer and lower during autumn or spring. This can be a result of an increase in the evaporation of volatile compounds at higher temperatures. For highly volatile compounds such as benzene and toluene, lower temperature and wind speed in cold months led to their high concentrations and atmospheric lifetime.
Methods of Study
Differences in analytical methods and apparatus types were taken into consideration when reporting the range of VOCs detected. This was important as some apparatus may have limitations of range. Vacuum pumped canisters that are VOC adsorbent and simple gas-sampling non-reactive canisters with flow-limiting valves were found to be the most common types of sampling equipment installed.
Gas Chromatograph-Mass Spectrometry (GC–MS) and Gas Chromatography with Flame-Ionization Detection (GC-FID) were found to be normally used in the labs for analysing the specimens or as online/offline analyser attached to the sampling apparatus.
Control measures of crude oil VOC emissions
The most common strategies in Common Vulnerabilities and Exposures (or CVE) controlling systems are vapour recovery (pressure and temperature swing adsorption) and vapour suppression.
Based on a recent statistical report by the International Tanker Owners Pollution Federation (ITOPF), approximately 50% of major crude oil incidences (incidents with oil spillage larger than 700 t) between 1970 and 2017 have happened in open water. This significance of total spillage proportion can hardly be minimised and restricted using controlling/recovering CVE systems.
The rest of the oil spillage is related to inland transportation incidences (17%), loading/discharging (15%), and unknown sources (18%). Moreover, the major amounts of CVEs which should be controlled are emitted through charging/discharging and transportation of crude oil, especially in ocean tankers due to their high capacities.
Most control methods are derived from VOC abatement procedures which can be broadly classified as ‘recovery’ methods and ‘destruction’ techniques:
Recovery procedures aim to collect, store and reuse VOCs and include membrane separation, condensation (including refrigeration condensation and cryogenic condensation, adsorption, and absorption.
Destruction methods aimed at converting VOCs into simpler and safe compounds (CO2 and H2O) are thermal incineration, catalytic incineration, photo-catalytic oxidation, plasma technology, electron beam technology, bio-filtration, and flares.
Inherent limitations in the used analytical approaches, discrepancies in types of crude oil, and meteorological influences on crude oil VOC emissions (CVEs) were the main challenges to accurately quantify the VOC. Among all VOCs emitted from crude oil, toluene, benzene, hexane, heptane, cyclohexane, and pentane were found to be high-detected high-concentrated compounds. The majority of the detected VOCs have relatively high boiling points which emphasise the importance of implementing control measures at the early stages of crude oil extraction.
Restrictive policies and regulations are vital to control the VOC emissions worldwide, with immediate and special attention to be paid to those related to the oil and gas industry. The reported oral/inhalation toxicity and carcinogenic effects from VOCs in crude oil production sites are still a matter of debate and should be further explored for the benefit of all and the health and safety of our planet.
This is the vital area where refineries can and have to go beyond their utmost efforts to find the earliest and most effective solutions.