Vent Stacks Research Articles

Origins of Oil and Gas Sector Methane Emissions: On-Site Investigations of Aerial Measured Sources.

Success in reducing oil and gas sector methane emissions is contingent on understanding the sources driving emissions, associated options for mitigation, and the effectiveness of regulations in achieving intended outcomes. This study combines high-resolution, high-sensitivity aerial survey data with subsequent on-site investigations of detected sources to examine these points. Measurements were performed in British Columbia, Canada, an active oil- and gas-producing province with modern methane regulations featuring mandatory three times per year leak detection and repair (LDAR) surveys at most facilities. Derived emission factors enabled by source attribution show that significant methane emissions persist under this regulatory framework, dominated by (i) combustion slip (compressor exhaust and also catalytic heaters, which are not covered in current regulations), (ii) intentional venting (uncontrolled tanks, vent stacks or intentionally unlit flares, and uncontrolled compressors), and (iii) unintentional venting (controlled tanks, unintentionally unlit/blown out flares, and abnormally operating pneumatics). Although the detailed analysis shows mitigation options exist for all sources, the importance of combustion slip and the persistently large methane contributions from controlled tanks and unlit flares demonstrate the limits of current LDAR programs and the critical need for additional monitoring and verification if regulations are to have the intended impacts, and reduction targets of 75% and greater are to be met.

Methane remote sensing and emission quantification of offshore shallow water oil and gas platforms in the Gulf of Mexico

Offshore oil and natural gas platforms are responsible for about 30% of global oil and natural gas production. Despite the large share of global production there are few studies that have directly measured atmospheric methane emanating from these platforms. This study maps CH4 emissions from shallow water offshore oil and gas platforms with an imaging spectrometer by employing a method to capture the sun glint reflection from the water directly surrounding the target areas. We show how remote sensing with imaging spectrometers and glint targeting can be used to efficiently observe offshore infrastructure, quantify methane emissions, and attribute those emissions to specific infrastructure types. In 2021, the Global Airborne Observatory platform, which is an aircraft equipped with a visible shortwave infrared imaging spectrometer, surveyed over 150 offshore platforms and surrounding infrastructure in US federal and state waters in the Gulf of Mexico representing ∼8% of active shallow water infrastructure there. We find that CH4 emissions from the measured platforms exhibit highly skewed super emitter behavior. We find that these emissions mostly come from tanks and vent booms or stacks. We also find that the persistence and the loss rate from shallow water offshore infrastructure tends to be much higher than for typical onshore production.

Occurrence and decay of SARS-CoV-2 in community sewage drainage systems.

The rapid spread of the coronavirus disease (COVID-19) pandemic in over 200 countries poses a substantial threat to human health. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes COVID-19, can be discharged with feces into the drainage system. However, a comprehensive understanding of the occurrence, presence, and potential transmission of SARS-CoV-2 in sewers, especially in community sewers, is still lacking. This study investigated the virus occurrence by viral nucleic acid testing in vent stacks, septic tanks, and the main sewer outlets of community where confirmed patients had lived during the outbreak of the epidemic in Wuhan, China. The results indicated that the risk of long-term emission of SARS-CoV-2 to the environment via vent stacks of buildings was low after confirmed patients were hospitalized. SARS-CoV-2 were mainly detected in the liquid phase, as opposed to being detected in aerosols, and its RNA in the sewage of septic tanks could be detected for only four days after confirmed patients were hospitalized. The surveillance of SARS-CoV-2 in sewage could be a sensitive indicator for the possible presence of asymptomatic patients in the community, though the viral concentration could be diluted more than 10 times, depending on the sampling site, as indicated by the Escherichia coli (E. coli) test. The comprehensive investigation of the community sewage drainage system is helpful to understand the occurrence characteristics of SARS-CoV-2 in sewage after excretion with feces and the feasibility of sewage surveillance for COVID-19 pandemic monitoring.

Elevated LNG Vapour Dispersion—Effects of Topography, Obstruction and Phase Change

The dispersion of vapour of liquefied natural gas (LNG) is generally assumed to be from a liquid spill on the ground in hazard and risk analysis. However, this cold vapour could be discharged at height through cold venting. While there is similarity to the situation where a heavier-than-air gas, e.g., CO2, is discharged through tall vent stacks, LNG vapour is cold and induces phase change of ambient moisture leading to changes in the thermodynamics as the vapour disperses. A recent unplanned cold venting of LNG vapour event due to failure of a pilot, provided valuable data for further analysis. This event was studied using CFD under steady-state conditions and incorporating the effect of thermodynamics due to phase change of atmospheric moisture. As the vast majority of processing plants do not reside on flat planes, the effect of surrounding topography was also investigated. This case study highlighted that integral dispersion model was not applicable as key assumptions used to derive the models were violated and suggested guidance and methodologies appropriate for modelling cold vent and flame out situations for elevated vents.

Determination of radionuclide composition of the Russian NPPs atmospheric releases and dose assessment to population

Original data on radionuclide activities in air emissions of Russian NPPs are presented based on direct on-site measurements in vent stacks of NPPs during an extensive survey in 2017–2018. For the first time, the detailed inventories of radionuclides in the air releases were directly measured for all types of nuclear reactors, employed in the Russian NPPs. Based on the results of measurements, annual doses for local populations around the Russian NPPs were estimated. The technogenic radionuclides, detected in the air emissions, were ranked according to their contribution in the annual dose. 14C is the major contributor for the annual dose from the atmospheric releases of LWGR reactors – almost 98% for Bilibino NPP's EGP-6 reactor, and up to 86% for RBMK-1000 reactors (Smolensk NPP). For PWR reactors (VVER) contribution to the annual dose from atmospheric releases is formed mostly by tritium, 14C and noble gases. Estimated annual doses for local populations in the vicinity of the Russian NPPs do not exceed 10−5 Sv/year. Atmospheric releases of 60Co, 134Cs, 137Cs and other aerosols, involved in the routine monitoring programs of Russian NPPs, do not contribute significantly to the annual dose. Based on these results, 14C and tritium will be included in the monitoring programs of atmospheric release control at all Russian NPPs; maximal permissible levels of annual releases for 14C and tritium will be established since 2019.

Special monitoring results for determination of radionuclide composition of Russian NPP atmospheric releases

Abstract Measurements of activity concentrations of radionuclides in atmospheric releases were performed in 2017–2018 at vent stacks of seven Russian nuclear power plants. The selected instruments and research methods, with detection limits significantly lower than the existing detection limit of Russian NPPs routine control, allowed to reliably determine up to 26 radionuclides. Analysis of experimental data allows to determine the list of radionuclides for calculation the effective dose rates to public and the permissible annual discharge levels for each Russian NPP. Radiocarbon is determined as major contributor for the dose from the atmospheric releases of LWGR reactors – up to 98% for EGP-6 and RBMK-1000 (Smolensk NPP) reactors. For PWR reactors (VVER) radionuclides contribution to the annual dose from atmospheric releases is more complicated, but, in general, dose is formed by tritium, 14C and noble gases. The special monitoring results with ranking of measured radionuclides according to their contribution to the effective dose makes it possible to optimize the list of controlled radionuclides in airborne releases of Russian NPPs from 94 to 8–16 for different NPPs.

Stench Sources and Impact Analysis in Automobile Making

Volatile organic compounds (VOCs) are an important source of industrial stench. This study was aimed at sampling and analyzing the stench source and its impact on the sensitive spot residential areas, concentrating on certain automobile manufacturing enterprise. The odor concentration and VOCs species of each vent stack, plant boundary, and sensitive spot in the enterprise were determined for November 15 and 17, 2016 via qualitative and quantitative analysis using the triangle odor bag method and gas pre-concentration system-gas chromatography-mass spectra. The results show that the odor concentrations of all vent stacks in the original equipment manufacturing plant and the engine plant were below the criterion level, those of the plant boundaries in the engine plant were below the limits, and those of the plant boundaries and sensitive spots in the original equipment manufacturing plant exceeded the allowed standards. A total of 54 VOCs species were identified, including aromatics, halogenated compounds, alkanes, alkene, cycloalkanes, ketones, esters, ethers, alcohols, sulfur compounds, and oxygen ring compounds. Halogenated compounds were the most abundant VOCs species, followed by aromatics. As a result, aromatics and halogenated compounds are the representative odorants in automobile making. 1,3-Butadiene and ethyl toluene were selected to be the typical odorants of sensitive spots according to mass concentration, detector odor threshold, and threshold dilution multiples of characteristic VOCs species in sensitive spots. The results show that the majority of characteristic VOCs species were from paint composition through the qualitative analysis based on paint used in coating shops. 1,3-Butadiene, which contributed the most to odor pollution, excluding the impact of other emission sources on sensitive spots, originates from spraying and drying processes of coating shops in the original equipment manufacturer. It is recommended that the enterprise should adopt environmentally friendly paints with low VOCs components or RTO purification equipment with higher processing efficiency to reduce the impact of stench on the sensitive residential areas from automobile making.

Developing nomograms using CFD results for predicting propagation of hazardous gases released through vent stacks to the atmosphere

A physico-mathematical model allowing predictions of propagation of clouds of hazardous gases in the atmosphere appearing after gas releases through gas vent stacks is developed. Results of calculations carried out with the use of the developed model are compared versus available experimental data. For allowing urgent predictions of gas propagations, nomograms are developed using results of the carried out numerical calculations.

H2S emissions from Cerro Prieto geothermal power plant, Mexico, and air pollutants measurements in the area

We measured meteorological parameters and environmental concentrations of hydrogen sulfide (H2S) and criteria pollutants at Cerro Prieto, Mexico, from May to July 2010. In addition, non-condensable gases from vent stacks at Cerro Prieto geothermal power plant were sampled and analyzed by gas chromatography–mass spectrometry. A dispersion model, which was validated with environmental measurements, was applied to H2S. Criteria pollutants never exceeded the Mexican air quality standards. Results from dispersion modeling were compared against measured concentrations showing acceptable agreements for Chi square goodness of fit (χ2) in the 95% significance level (α=0.05), at afternoons and evening events when boundary layer is decreasing and wind speed is less than 5.5ms−1. Determination coefficient of curve fitting for computed concentrations at less than 4km from the source was 0.513 and farther 0.568. This study was the first to measure criteria pollutants and H2S in Cerro Prieto area.

Oil Fallout in the Vicinity of an Onshore Blowout: Observations on a Field Case

Summary Oil deposition in the area surrounding a blowout is one of the most visible consequences of the loss of control over well flow. Less visible, but equally serious, are the short- to medium-term effects of oil coverage on the environment. Apart from the direct damage, studies indicate effects (e.g., reduced tree growth) that persist many years following the incident. Hence, oil fallout, in the case of loss of well control, is a factor to be taken into account in decisions on well locations, emergency procedures, contingency planning, etc. This requires an estimate of the area around the well likely to be affected by oil fallout, given the geomorphology of the terrain, prevailing winds, and expected outflow conditions. Models to obtain such an estimate have been proposed, but application of these models (e.g., for environmental impact assessment) has been limited. In part, this limitation can be attributed to a lack of validation of the models because this requires a combination of well-effluent data, outflow conditions, meteorological data, a detailed terrain description, and fallout maps. For the field case discussed in this paper, all the data necessary for validation were assembled from various sources ranging from the well operator and environmental agencies to meteorological and cartographic institutes. The relation between the observed pattern of oil deposition around the well and factors such as outflow conditions and wind speed and direction is analyzed with a simple model. This relationship demonstrates that the main factors determining the area affected by deposition of oil are the outflow conditions and the wind direction. To verify this result, a comparison with historical observations on oil fallout around gushers has been made. Although more sketchy, the same patterns emerge from this comparison, which strongly suggests that the methods developed to explain the fallout pattern of the field case discussed can be used over a wide range of conditions to predict the area affected by a blowout. This prediction can serve several purposes, such as site selection, definition of emergency procedures, environmental impact assessment, and contingency planning. Finally, it is noted that this method also applies in less dramatic situations (e.g., predicting droplet deposition around vent stacks).

Flare case histories demonstrating problems and solutions

AbstractA flare is an important safety device for control and disposal of combustible gases. They are designed in accordance with API, ASME, EPA, and other codes. However, many other details and possible oversights, not found in the recommended practices, standards, and codes, can lead to dangerous conditions—bottlenecks, equipment malfunction, overpressure, flameout, vapor clouds, liquid carryover (burning rain), internal burning, and explosions. These normally overlooked details are also covered in this article. Vents and vent stacks will also be reviewed since they are simply a flare without a flame. They also use much of the same technology as a flare, except for the pilots, ignitors, and flame retainers. Some of these unsafe conditions, their causes, and their initial warning signs are presented from actual field experience and discussed in order to educate the engineer (design, piping, process, operating), plant operators, and maintenance people. © 2006 American Institute of Chemical Engineers Process Saf Prog, 2006

Operating Parameters to Minimize Emissions During Rotary Kiln Emergency Safety Vent Openings

Certain designs of hazardous waste incinerator systems include emergency safety vents (ESVs). ESVs (also called dump stacks, vent stacks, emergency by-pass stacks, thermal relief valves, and pressure relief valves) are regarded as true emergency devices. Their purpose is to vent combustion gases directly from the combustion chambers to the atmosphere in the event of a failure of other system components. This is done for operator safety as well as to protect the incinerator and other downstream equipment from damage. ESVs are typically required for rotary kiln and hearth incinerators which process a portion of their waste load as bulk solids or contained liquids introduced continuously or in batch charges. Research has been performed at the U.S. EPA on a 73 kW (250,000 Btu/hr) rotary kiln incinerator simulator examining optimum settings of kiln operating parameters so as to minimize emissions during an ESV opening event. Experimental results are interpreted in the light of previous research results on transient "puffs." Mechanisms governing both the release of volatile matter during an ESV event and the subsequent pyrolysis and oxidation in the residual sorbent bed are identified. From a practical point of view, results indicate that alteration of operator-controllable kiln parameters during the onset of certain ESV opening events can have a significant effect on emissions of both organics and hydrogen chloride (HCl). A low air flow rate results in lower emissions of both organics and HCl. This hypothetical low air flow rate could possibly be equal to the flow rate induced by the natural draft coupled with air in-leakage. Rotational speed (RPM) appears to have slightly different effects on organics and HCl. Whereas emissions of HCl are minimized at a very low or non-existent RPM, emissions of organics exhibit a minimum at a low (but non-zero) RPM, with increasing emissions at both zero and high RPM. The use of a small afterburner to simulate an in-stack flare during an ESV event dramatically reduced organic emissions.

Reducing the purge in hydrocarbon vent stacks

Abstract The purging of hydrocarbon vent stacks is necessary to ensure that large flammable regions are not created within such facilities. In order to minimize the environmental impact of purging, it is vital that purge rates should be set at the lowest level consistent with safe operations. The methods which are currently available for determining these minimum rates are empirical and may be overly conservative; therefore, it is important to develop a more robust basis on which to calculate the required gas flows. To this end, a reduced-scale Rayleigh-scattering investigation of purging flows has yielded two-dimensional concentration maps for a range of purge rates and crosswind velocities. The results indicate that it may be possible to reduce the purge rate significantly without adversely affecting operational safety; full-scale testing must be performed to determine the potential hazards associated with such action.

An overview of equipment for containment and disposal of emergency relief system effluents

Abstract This paper presents an overview of the various types of equipment and systems used in the containment and disposal of effluents from emergency relief systems, i.e., safety valves and rupture discs. The paper discusses the design, sizing, safety considerations, mechanical aspects, and operational considerations for such equipment as containment/separation vessels (blowdown drums, knock-out drums, catchtanks and quench tanks) and disposal equipment such as vent stacks, flare stacks and systems, vent condensers and scrubbers (gas absorbers).

Comparison of an integral model for predicting the dispersion of a turbulent jet in a crossflow with experimental data

Abstract The safe design of high pressure plant and pipework requires the installation of adequate pressure relief and vent stacks. To ensure that any discharge is safety removed, it is necessary to consider how the gas disperses under a variety of atmospheric conditions. This is best achieved by developing a mathematical model that has been validated against reliable data. This paper gives details of a mathematical model for predicting the dispersion of a jet in a crossflow. The model is based upon well-tried similarity ideas, and contains a number of closure or entrainment coefficients whose values must be specified. Appropriate well-documented laboratory or field-scale tests are selected to enable these values to be chosen. The predictions of the resulting model are than compared with experimental results over a wide range of conditions, including free and wind-blown underexpanded sonic and subsonic jets of natural gas and other materials.

Environmental, Safety and Health Issues at U.S. Nuclear Weapons Production Facilities, 1946–1988

Public Revelations Serious environmental, safety and health problems at Department of Energy-supervised nuclear weapons production and processing facilities were revealed to the mass public in the October, 1988, joint hearings of the Senate Governmental Affairs Committee and the House Government Operations Subcommittee on Environment, Energy, and Natural Resources and by subsequent admissions by the U.S. Department of Energy. The problems had been accumulating during the thirty-five to forty years of operations of the facilities.' At the Savannah River Plant in Aiken, South Carolina, operated by E. I. Dupont de Nemours and Company until 1988, 30 incidents of greatest significance involving management and structural problems occurred between 1957-85 in the production of tritium and plutonium. Three reactors are temporarily shutdown because of management and fire safety problems or because of cracks found in the cooling systems.2 The Department of Energy estimates late 1990 as the earliest start-up date for the first of the three reactors. In Femald, Ohio at the Feed Materials Production Center operated by National Lead of Ohio from 1951-86 and subsequently by Westinghouse Materials Company of Ohio, tons of uranium and other radioactive wastes were found stored in leaky pits and cracked holding tanks contaminating surface and ground water. Management and safety problems exposed workers to excessive amounts of radiation, and filters in vent stacks remained unrepaired for years, permitting unknown amounts of uranium dust

Analysis of Power Plant Safety and Relief Valve Vent Stacks

Power plant safety and relief value vent stacks have generally been sized according to the methods and design criteria published by Max W. Benjamin in the 1940s. Although the method might have been satisfactory at that time utilizing basic flow dynamics, it not only requires laborious calculations, but also contains some inadequate approaches which may contradict the theory of compressible fluid mechanics available today. This paper presents a complete analysis of steam conditions and its properties from power plant safety/relief valve inlet through its vent stack to the atmosphere. The analysis is based on the theory of compressible fluid flow under irreversible adiabatic process to establish a method and criterion for vent stack design. The method developed herein is applicable to both choking and nonchoking conditions at the valve exit and/or vent stack outlet, and greatly reduces complex trial-and-error solution. Furthermore, an accurate determination of fluid conditions will facilitate the calculation of reaction forces on safety/relief valve and its stack. This paper also presents the results of sensitivity analyses to verify the validity of applying perfect gas equations to steam.

Closure to “Discussion of ‘Analysis of Power Plant Safety and Relief Valve Vent Stacks’” (1975, ASME J. Eng. Power, 97, pp. 492–493)

Closure to “Discussion of ‘Analysis of Power Plant Safety and Relief Valve Vent Stacks’” (1975, ASME J. Eng. Power, 97, pp. 492–493)