Apr-2020

Environmental monitoring and management in the downstream oil and gas sector

Keeping it clean, keeping it green. Ground water, rain water run-off and effluent. Contaminated soil replacement in spillage areas, excavated soil disposal during site improvements and end-of-life site remediation.

Stephen B Harrison
Nexant Energy and Chemicals Advisory

Article Summary

Vapour, flare and smoke stack emissions to air. In the downstream oil & gas sector there’s plenty to keep us busy with when it comes to environmental monitoring and protection. In the upstream sector the potential for pollution is significantly more severe, with crude tanker wrecks, such as the Exxon Valdez in 1989, and the BP Deepwater Horizon oil spill in 2010 still painful memories in many peoples’ minds. However, refineries, tank farms, oil terminals and the barge, road and rail distribution network all have a significant custodial role to play to protect the land and waterways around which they operate and to maintain ambient air quality.

Environmental monitoring costs are material
Putting the costs of crude oil and other essential chemical inputs to one side, a high proportion of the residual refinery operating costs will be in the areas of labour, utilities, insurance and laboratory expenses. Within the utilities bill, the costs of process waste-water and site rain water run-off management will appear. And, in the laboratory costs there will be product assay in addition to multiple environmental related analysis work to be done. So, putting it all together, the price-tag for environmental management on the refinery can be significant.

In the worst case, if the finger is ever pointed to indicate that regulations have been breached, consent levels exceeded, or laws broken then the costs of litigation can be high. And, the fines, impact on company reputation and share price erosion can be devastating, as we have observed in the recent environmental case of VW in Germany related to diesel vehicle air emissions. The VW share price has somewhat recovered since it lost approximately 30 percent of its value within one month of the scandal coming into the public domain. However, the company now faces a €9.2 billion legal claim involving 1 670 investors who attest that they wrongfully suffered financial losses due to VW malpractice.

Also, in the news as recently as November 2018, has been the case related to Chemours in Fayetteville, North Carolina. Chemours have denied any violation of any regulation, law or permit and have simultaneously offered to settle a pollution case with a $13 million payment to avoid further legal process costs and to address community concerns about the Fayetteville facility. The legal case is still open and relates to emissions of fluorocarbon chemicals to air and in to the Cape Fear river which flows through the city of Wilmington. Whilst these examples are taken from industries outside the refining sector, the lessons are directly transferrable to hydrocarbon processing operations and paint a picture of the potential negative consequences that can follow from actual, or perceived, poor execution of environmental management policies.

Diversity of monitoring and measurement required
Environmental monitoring on the refinery has implications all around the facility and in all three physical states: air, soil and water. For example, most refineries will have stack emissions from combustion processes which are monitored for regulatory compliance. The most common solution is to use a continuous emissions monitoring system (CEMS) to ensure that the air pollution is controlled within defined emissions limit values (ELV’s) for species such as NOx and CO, as laid out in the EU Industrial Emissions Directive. Direct-read Fourier transform infra-red (FTIR) and non-dispersive infra-red (NDIR) instrumentation with a high up-time target are commonly employed for this CEMS application. After the initial capex related to the equipment purchase and installation, the cost of CEMS operation is low because the system is automated and requires only occasional maintenance and calibration, perhaps through a service contract from the instrumentation supplier.

Perimeter ambient air quality monitoring is also regularly undertaken. In this case, it is common to collect air samples intermittently and take them off-site to a highly specialised contract laboratory for analysis using a gas chromatograph with a flame ionisation detector (GC-FID). This device can speculate and detect very low levels of volatile organic compounds (VOC’s) which are a typical air-born environmental concern associated with hydrocarbon processing operations. Often, the services of an environmental contractor will be used for this type of environmental monitoring. The samples must be transported in specially designed gas containers that have an extremely inert internal surface treatment to ensure that the collected sample is delivered correctly to the gas analysis instrumentation without any of the pollutant molecules adsorbing to the surface of the gas container.

Water quality monitoring will focus on core issues such as pH and total organic carbon (TOC). pH measurement equipment is one of the most simple and robust types of water quality instrumentation. TOC analysers, on the other hand, are a sophisticated black box that will use an oxidation process (e.g. chemical oxidation with hydroxyl radicals or catalytic combustion) to convert the organic chemicals to carbon dioxide, which is then measured using a gas-phase instrument such as an NDIR sensor. Additionally, for refinery effluent the possibility exists that certain carcinogenic aromatics, such as benzene, may be present in the water. So, additional specific checks for chemicals within the BTEX (Benzene, Toluene, Ethyl-Benzene and Xylene) group may also be undertaken.

Analysis of soil samples can have much in common with water analysis, and it is often the case that soil is mixed with water in the laboratory and the eluate is analysed, in addition to the soil solids. The relationship between soil contamination and groundwater pollution also binds the water and soil environmental issues. When conducting environmental soil analysis, it is therefore common to run similar tests to those conducted on water. Additionally, the scope for soil will generally include a search for trace metals such as lead and mercury and salt ions such as cyanide and sulphates.

For the trace metal species, inductively coupled plasma with various detectors such as mass spectrometry (ICP-MS) or atomic emissions spectroscopy (ICP-AES) is often used. The flame technique known as atomic adsorption spectroscopy (AAS) is an alternative. Various methods will be used for measuring the range of salts. One standard method for total cyanide analysis, as laid out in the US EPA Contract Laboratory Program (CLP) document ILM05.3 - Exhibit D, references a type of liquid phase colorimetry known as UV-VIS spectrophotometry. This CLP document also covers mercury measurement using AAS and gives guidance on the ICP-AES and IC -MS techniques.

On-site laboratory or outsourced contract lab?
With so much measurement to be done, the trade-off between using an on-site laboratory versus outsourcing is extensively debated. The inputs to the decision making generally focus around cost which are driven by the complexity and frequency of the measurement and the capital cost of the instrumentation. For risk mitigation, insurance or legal reasons, it might also be prudent, or required, that an independent accredited third-party laboratory make the analysis.

We have already noted that for CEMS systems with a 100 percent on-line measurement target the instrumentation will exist in situ. The same is not always the case for occasional samples. And, whilst refineries will have a sophisticated production, QC or R&D laboratory on site where some occasional environmental monitoring analysis may be done, smaller downstream operations such as tank farms or terminals will rarely have on-site analytical capability that stretches beyond a few key fuels physical property metrics such as flash point for gasoline and cloud point and pour point for aviation kerosene and diesel. These methods are laid out in the relevant ISO, ASTM or other national standards documents.

The idea that a tank farm would have the sophisticated, expensive instrumentation required to complete a full groundwater analysis or perimeter air quality analysis is unrealistic. The expertise required to conduct the analysis is also highly specialised and with a low frequency of measurement, retaining staff with this level of competence is simply not cost effective. And, even in larger refineries the specialism towards organic analytical chemistry for hydrocarbon analysis would generally mean that they would have neither the inorganic analytical equipment nor expertise to conduct the broad range of soil and water sample analysis that may be required. So, this work is also often outsourced to an environmental contract laboratory by major refineries.