The Hazards and Risks Associated with Sour Gas - Case Study Example

Name Tutor Course Date Introduction Hydrogen Sulfide (H2S) is a colorless, highly flammable and toxic gas with a foul odor occurring naturally in crude petroleum, hot springs, natural gas and volcanic gasses. It can also be formed as a result of bacterial breakdown of organic matter. (Boschee 21-25). Sour gas is a natural gas containing a significant amount of Hydrogen Sulfide. It has more than 4ppm in the concentration of Hydrogen Sulfide. It is referred to as sour since its foul odor is similar that of rotten eggs Hydrogen Sulfide is toxic and can cause serious injuries that can be fatal at relatively low concentrations. Properties and characteristics of Hydrogen Sulfide Hydrogen Sulfide is slightly denser than air. It has a density of 1.363 g dm−.3. It has a boiling point of −60 °C with a melting point of −82 °C. When mixed with air, hydrogen sulfide can be very explosive. It burns in the presence of oxygen with a bright blue flame to form sulfur dioxide (SO2) and water. Therefore, hydrogen sulfide acts as a reducing agent (Shirai, Ikeda and Aramaki 114-119). Hydrogen sulfide is slightly soluble in water and forms a weak acid known as hydrosulfuric acid (Guo and Wang 98-107). Metal ions reacts with hydrogen sulfide to form metal sulfides which are considered salts of hydrogen sulfide. It also reacts with alcohols to form thiols which is an important class of organosulfur compounds (Boschee 21-25). In gaseous form, hydrogen sulfide is a strong reducing agent, and when it gets in contact with concentrated nitric acid, it reacts explosively to form SOX, NOX, nitrogen, and water. At high pressures (above 90 Gigapascals), hydrogen sulfide turns into a metallic conductor of electricity, and when cooled below a critical temperature, it exhibits superconductivity at this high-pressure phase. Processes within the oil and gas industry which handle sour gas streams Claus process Claus process is one of the most significant means for recovering sulfur in the industry. A Claus plant can remove 95% of the inlet sulfur. This process works along with an acid gas removal system which removes the hydrogen sulfide from the sour gas stream. The resultant acid gas steam which is rich in carbon dioxide, hydrogen sulfide, and moisture can be treated in the Claus unit. The plant oxidizes the valuable natural gas using the acid gas thus removing the hydrogen sulfide. The plant requires hydrogen sulfide concentration of more than 50% in the feed steam. Stretford process Stretford is a liquid redox process. It involves a liquid phase oxidation process which converts hydrogen sulfide into sulfur. Thiopaq process This process integrates purification of gas with sulfur recovery in one unit. The sour gas fed in first comes in contact with the lean solution in the absorber. Hydrogen sulfide is then absorbed by the solution and sweet gas exits from the absorber ready for use or further processing. This process uses naturally occurring bacteria known as Thiobacillus for oxidation of the hydrogen sulfide to elemental sulfur. CrystaSulf process This process uses a non-aqueous solution with a high solubility for sulfur. Since the elemental sulfur stays dissolved in the non-aqueous solution, no solids are present in the liquid circulated towards the absorber. The Crystasulf design avoids the process of making the system for the recovery of aqueous sulfur unsuitable for the direct treatment of sour gas at high pressure. Lo-Cat process This is a liquid redox process. It is a patented, wet scrubbing system that uses a chelated iron solution to convert hydrogen sulfide to innocuous elemental sulfur. This process does not use any kind of toxic chemicals and produces non-hazardous waste by-products. Incidents occurred involving sour gas In Canada, 175 oil and gas workers were exposed to hydrogen sulfide in Alberta, a region best known for sour gas wells associated with the oil & gas industries. 14 workers of the 175, who were exposed to the hydrogen sulfide, lost their consciousness due to inhalation of high concentrations of hydrogen sulfide.. In the United States, The Chemical Safety Board, which investigates chemical incidents, has a record of 8 fatalities for a period of one decade (1984-1994). In Belgium, on 2008, an incident occurred at a refinery in Antwerp. The company produces fuels like butane, propane, benzene, kerosene and gas oil. On the day of the incident, a power line failed to render the refinery without electric power supply. This caused a safety valve to open and release approximately 40m3 of hydrogen sulfide. In France, the year 2009, at a petroleum refining plant by the name GONFREVILLE-L'ORCHER, a release of carbon monoxide and hydrogen sulfide was detected in the refinery during maintenance and operations of a tank. During the incident, three employees were injured and transported to the hospital. In 2007, at the United States, during a treatment and disposal of hazardous waste, four employees died of asphyxiation by hydrogen sulfide in a landfill when they were a pump in the sewer (Asakura 328-334). In 2006, during an extraction of crude petroleum in Allentown, United States, two employees were poisoned, and one succumbed to hydrogen sulfide during standard maintenance on the valve of a tank. In 2007, during distillation, refining and processing mineral oil products in Nordrhein-Westfalen, hydrogen sulfide gas was released as a result of an imperfect weld of the dished end of a tank. However, no injuries were reported. Dissertation Assignment Sour Gas Operations in the Oil and Gas Industry Proposal on individual assignment This dissertation project investigates the hazards and risks associated with sour gas. The project highlights the toxicity of hydrogen sulfide, its properties and examines the safety challenges associated with hydrogen sulfide. The proposal is to study the hazards and risks of exposure to sour gas. The following aspects provide context on the factors that may contribute to such risk: Its explosive and flammability properties, Its sour and pungent odor that is dangerous to the respiratory system It is highly corrosive hence can damage properties. Due to these properties, one must have knowledge on how to handle it, dispose of it and control it. This dissertation identifies and examines different layers of protection built on a series of risk assessments which will include: several ways of controlling the gas, disposal methods, regulatory measures that should be followed in case of exposure, key guidances existing for eliminating, preventing and reducing H2S hazards at deferent stages. i.e. design stage (inherent safety), operation and maintenance stage. Guidance that exist for managing the hazards and risks from hydrogen sulfide Fundamental requirements at design stage Designing the systems and equipment to optimal/maximum pressure of subjection is advantageous in simplifying the plant/system by eliminating or reducing protection or relief systems. Facilities shouldn’t be protected with recognized relief devices discharging to an instrumented high integrity protection system. (HSE, Appendix 4) The duty holder should have arrangements for preventing under- and over-pressure of the process plant and equipment. Such extremes lead to rapid uncontrolled loss of the containment vent. Therefore, pressure systems should be designed for maximum and where relevant the minimum expected operating pressure under all modes of operation. (HSE, Appendix 4) A means of removing significant hazardous gasses from equipment to a safe location should be provided e.g. a blowdown, which can be used immediately following the detection of a loss of contaminant. (HSE, Appendix 4) Hazardous gasses being discharged from relief and blowdown events need to be safely conveyed to flares of effective dispersion and disposal. (HSE, Appendix 4) Fundamental requirements for operation and maintenance OSHA 29 CFR 1910.146 Permit-required confined spaces. Any work involving breaking containment on the system should require a permit to work and efficient removal and isolation of stored energy/H2S hazard. The only exception is where there are specific and explicit authorization and a written procedure to control the work by other means such as under an emergency management procedure. OSHA 29 CFR 1910.146 Permit-required confined spaces. Procedures should identify who should be involved in the authorizing breaking of containment work and additional authority levels, certificates or permits may be appropriate to manage these. Active dialogue should be conducted between the performing and authorizing officials. This is done to ensure the planned scope of work, associated hazards, and necessary controls to be worked on located, its identification labeling checked, the worksite visibly checked, and the break-in points agreed, to ensure that the risk of break-in to the wrong equipment is minimized. OSHA 29 CFR 1910.146 Permit-required confined spaces. The working environment and workflow should support active permit to work issues/preparations. Individuals should ideally be able to plan, discuss and issue permits t work away from noisy or sensitive environments such as workshops or process control rooms. OSHA 29 CFR 1910.165 Employee alarm systems. There should be a policy to describe how the plant should be brought back into post service maintenance. It should include steps such as a visual check to confirm the maintenance task is completed as expected and that equipment is in place as per design, a leak test with lower hazard fluid to ensure the risk of a leak on the reintroduction of fluids minimized. Key emergency preparedness regulations and standards to do with designing (response plans and refugee areas). According to the Health and Safety Executive (HSE) in the UK, OSHA standards in the USA, and the American Petroleum Institution (API). Implement and develop a written emergency response plan that includes: Pre-emergency planning and coordination, safe distance and refuge, site security and control, procedures for emergency alerting and response, response critiques and follow-up, evacuation routes and methods. Standard – 29 CFR 1917.25 Fumigants, pesticides, insecticides and hazardous preservatives. Provide backup and advanced first aid support personnel ready to provide rescue or assistance. According to OSHA Standard – 29 CFR 1917.95 Other protective measures. Provide equipment necessary for backup and first aid support and transportation for medical care. According to OSHA Standard – 29 CFR 1917.95 Other protective measures. Provide chemical protective clothing for emergency responders appropriate for site hazards. According to OSHA Standard – 29 CFR 1917.95 Other protective measures. Provide training to workers based on their expected duties. Responders should be trained to the following levels: first responder operations, first responder awareness, hazardous materials specialist, hazardous material technician, and on-scene incident commander. According to, OSHA Standard – 29 CFR 1910.120 Hazardous waste operations and emergency response. Directive – CPL 02-02-059 Inspection Procedures for the Hazardous Waste Operations and Emergency Response Standard, 29 CFR 1910.120 and 1926.65, Paragraph (q): Emergency Response to Hazardous Substance Releases. API 11.2.2.7. It is recommended that instruments for detecting hydrogen sulfide should be approved by a nationally recognized testing laboratory (NRTL) to meet the minimum performance requirements of ISA S92.0.01, Part I (formerly ISA S12.15, Part I). API 11.2.2.7. Where intelligent sensors are utilized, connection directed to the control system should be considered and sensor monitoring provided by the control system instead of a separate controller. During the processes of the production refining of oil, different gasses are emitted. This report focuses on the hazards of hydrogen sulfide (H2S) commonly known as sour gas, its properties and the disposal and regulatory measures to control it. Onshore sour gas production may happen in two ways: As a result of the anaerobic prokaryotic breakdown of organic matter such as in sewers and swamps. The hydrogen sulphide produced as a by-product ends up mixing with air to form sour gas. In oil refineries and geothermal plants where hydrogen sulphide comes in contact with natural gas. Offshore sour gas production During offshore drilling, a well bore is drilled below the seabed. This is typically carried out so as to explore for and subsequently extract petroleum lying in rock formations beneath the seabed. Hydrogen sulfide gas occurs naturallyin these rock and during the extraction process, it mixes up with the natural gases to form sour gas. (Toxicological Profile For Hydrogen Sulfide 6-11 ). Sour gas (H2S) hazards in operations and maintenance in the oil and gas industry. Hydrogen sulfide is a chemical asphyxiant and an irritant with effects on both utilization of oxygen and the central nervous system. Its effects to the health depend on the level and duration of exposure (Toxicological Profile For Hydrogen Sulfide 6-12). Low concentrations of hydrogen sulfide cause eye irritation, nose and throat irritation, and discomfort of the respiratory system e.g. burning, coughing, choking and shortness of breath. Moderate concentrations of hydrogen sulfide cause more severe irritation to the eyes and respiratory system. A person exposed to this level of concentration is prone to headaches, dizziness, staggering, vomiting, and excitability. High concentrations can cause convolutions, shock, extremely rapid unconsciousness, inability to breathe, coma and death. The effects can occur within few breaths. Hydrogen sulfide is a highly flammable gas especially when mixed with oxygen. It rapidly burns in the presence of oxygen with a bright blue flame. Hydrogen sulfide mixed with oxygen is dangerous since a single spark can light it up and could lead to an explosion that can be fatal to the workers. Hazards from sour water Hydrogen sulfide dissolves in water to form sour water. The health hazards of sour water include: It is poisonous when swallowed Causes skin irritation Coming into contact with the eyes, it causes inflammation and irritation or worse; it could lead to blindness (Milia et al. 791-798). Sour water is carcinogenic thus causing cancer when ingested. It may cause long-term harmful effects on the aquatic life. Venting and flaring Venting is the controlled release of gasses to the atmosphere during the production and operation of oil and gasses. Flaring is the controlled burning of natural gasses during the routine production of oil and gasses. It occurs at the end of the flare stack. Venting and flaring are involved with a wide range of operations and energy development activities, including disposal of gas associated with: Bitumen, oil and gas well completion, Bitumen, oil and well drilling, Routine bitumen or oil production, Unplanned non-routine de-pressuring of gas pipelines and process equipment due to upsets of processes or emergencies, and Facilities for managing oilfield waste management. Flaring is used to burn harmful gasses that present a safety problem such as hydrogen sulfide. It results in emissions of hydrogen sulfide if hydrogen sulfide is present in large amounts in the natural gas. During gas and oil development, huge gas quantities vents into the atmosphere. For instance, in the course of a well completion, after the well has fractured, the fluids and solids from the well go into pits, and the gasses escape into the atmosphere (Shirai, Ikeda and Aramaki 114-119). Flaring work hand in hand with venting since one cannot function without the other in the reduction of hydrogen sulfide from the natural gas. Hydrogen sulfide hazards due to microbial activities Sulfate-reducing bacteria such as Desulfovibrio vulgaris obtain energy by oxidizing molecular hydrogen (H2) while reducing sulfates to hydrogen sulfide. The hydrogen sulfide produced is a waste product and can be detected by its foul odor that resembles a rotten egg (Shirai, Ikeda and Aramaki 114-119). The hydrogen sulfide produced is usually in low concentration, and long-term exposure to it could be harmful to the respiratory system and the body itself. The sour gas is also corrosive and may lead to damage of property. Conclusion In the events where the toxic effects of hydrogen sulfide were experienced, it appeared that there had been lack of adequate knowledge of the toxic effects. Due to the lack of awareness of the occurrence of hydrogen sulfide, there was lack of appropriate preparedness to deal with the release of the gas Lack of suitable gas alarms and protective equipment led to fatal hydrogen sulfide exposure. Hydrogen sulfide is a life-threatening hazard, especially in the geothermal industry. Petroleum refining, chemical processing, and petrochemical industries do not appear to suffer fatal hydrogen sulfide consequences as compared to the geothermal and waste treatment industries. References OSHA. [Washington, D.C.]: U.S. Dept of Labor, Occupational Safety and Health Administration, 2011. Print. Asakura, Hiroshi. "Sulfate And Organic Matter Concentration In Relation To Hydrogen Sulfide Generation At Inert Solid Waste Landfill Site – Limit Value For Gypsum". Waste Management 43 (2015): 328-334. Web. Boschee, Pam. "Taking On The Technical Challenges Of Sour Gas Processing". Oil and Gas Facilities 3.06 (2014): 21-25. Web. Guo, Xiao and Qiao Wang. "A New Prediction Model Of Elemental Sulfur Solubility In Sour Gas Mixtures". Journal of Natural Gas Science and Engineering 31 (2016): 98-107. Web. Milia, Stefano et al. "Partial Nitritation Of Nitrogen-Rich Refinery Wastewater (Sour Water) With Different C I /N Molar Ratios". Desalination and Water Treatment 55.3 (2014): 791-798. Web. Shirai, Hiromi, Michitaka Ikeda, and Hiroshi Aramaki. "Characteristics Of Hydrogen Sulfide Formation In Pulverized Coal Combustion". Fuel 114 (2013): 114-119. Web. Stewart, Maurice and Ken Arnold. Gas Sweetening And Processing Field Manual. Amsterdam: Gulf Professional Pub., 2011. Print. Toxicological Profile For Hydrogen Sulfide. [Atlanta, Ga.]: U.S. Dept. of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry, 2006. Read More

In the United States, The Chemical Safety Board, which investigates chemical incidents, has a record of 8 fatalities for a period of one decade (1984-1994). In Belgium, on 2008, an incident occurred at a refinery in Antwerp. The company produces fuels like butane, propane, benzene, kerosene and gas oil. On the day of the incident, a power line failed to render the refinery without electric power supply. This caused a safety valve to open and release approximately 40m3 of hydrogen sulfide. In France, the year 2009, at a petroleum refining plant by the name GONFREVILLE-L'ORCHER, a release of carbon monoxide and hydrogen sulfide was detected in the refinery during maintenance and operations of a tank.

During the incident, three employees were injured and transported to the hospital. In 2007, at the United States, during a treatment and disposal of hazardous waste, four employees died of asphyxiation by hydrogen sulfide in a landfill when they were a pump in the sewer (Asakura 328-334). In 2006, during an extraction of crude petroleum in Allentown, United States, two employees were poisoned, and one succumbed to hydrogen sulfide during standard maintenance on the valve of a tank. In 2007, during distillation, refining and processing mineral oil products in Nordrhein-Westfalen, hydrogen sulfide gas was released as a result of an imperfect weld of the dished end of a tank.

However, no injuries were reported. Dissertation Assignment Sour Gas Operations in the Oil and Gas Industry Proposal on individual assignment This dissertation project investigates the hazards and risks associated with sour gas. The project highlights the toxicity of hydrogen sulfide, its properties and examines the safety challenges associated with hydrogen sulfide. The proposal is to study the hazards and risks of exposure to sour gas. The following aspects provide context on the factors that may contribute to such risk: Its explosive and flammability properties, Its sour and pungent odor that is dangerous to the respiratory system It is highly corrosive hence can damage properties.

Due to these properties, one must have knowledge on how to handle it, dispose of it and control it. This dissertation identifies and examines different layers of protection built on a series of risk assessments which will include: several ways of controlling the gas, disposal methods, regulatory measures that should be followed in case of exposure, key guidances existing for eliminating, preventing and reducing H2S hazards at deferent stages. i.e. design stage (inherent safety), operation and maintenance stage.

Guidance that exist for managing the hazards and risks from hydrogen sulfide Fundamental requirements at design stage Designing the systems and equipment to optimal/maximum pressure of subjection is advantageous in simplifying the plant/system by eliminating or reducing protection or relief systems. Facilities shouldn’t be protected with recognized relief devices discharging to an instrumented high integrity protection system. (HSE, Appendix 4) The duty holder should have arrangements for preventing under- and over-pressure of the process plant and equipment.

Such extremes lead to rapid uncontrolled loss of the containment vent. Therefore, pressure systems should be designed for maximum and where relevant the minimum expected operating pressure under all modes of operation. (HSE, Appendix 4) A means of removing significant hazardous gasses from equipment to a safe location should be provided e.g. a blowdown, which can be used immediately following the detection of a loss of contaminant. (HSE, Appendix 4) Hazardous gasses being discharged from relief and blowdown events need to be safely conveyed to flares of effective dispersion and disposal.

(HSE, Appendix 4) Fundamental requirements for operation and maintenance OSHA 29 CFR 1910.146 Permit-required confined spaces. Any work involving breaking containment on the system should require a permit to work and efficient removal and isolation of stored energy/H2S hazard.

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