Risk Assessment Of Sulphur Recovery (1)

ENVIRONMENTAL RISK ASSESSMENT TERM PAPER RISK ASSESSMENT OF SULPHUR RECOVERY (SRU) IN THE OIL AND GAS INDUSTRY Members of the group Precious Eledu – 201693242 Tejas Shah- 201690213 Terrence Ijeomah – 201793756

Table of Content Abstract…………………………………………………………………………………………………………………. Introduction………………………………………………………………………………………………………………… Sources of risks involved in process of sulphur recovery ……………………………………………. Risk assessment (Routes of exposure)…………………………………………………………………….. Adverse human and environmental effect ……………………………………………………………. Statutory standards of sulphur content level……………………………………………………………… Risk characterization and risk management ………………………………………………………………….

Risk assessment of Sulphur recovery (SRU) in the Oil and Gas Industry Abstract This paper discusses the sources of risks involved in the process of sulphur recovery such as leakage of hydrogen sulphide from the equipment required for the processes. It also talks about the risks assessment involved, and the environmental and adverse human health effects. In the Oil and Gas Industry, there is a sulphur content level in fuelwhich is considered as a dangerous pollutant and refineries need to upgrade their processes to meet the statutory standards so that emission of it could be reduced. The Claus process is majorly used to convert the produced hydrogen sulphide to elemental sulphur. This paper would also entail the advantages and applications of Sulphur Recovery Unit in the Oil and Gas Industry as well as therisk characterization and risk management involved in the processes.

Introduction Sulphur recovery refers to the process of converting hydrogen sulphide (H2S) to elemental sulphur. Hydrogen sulphide occurs naturally as an impurity in natural gas. Gases which contain sulphur elements are referred to as sour gas. It is also a by-product of refinery processes such as gas treatment units for crude oil containing sulphur. It is important to remove sulphur bearing compounds from the gas to reduce corrosion in pipelines and to preserve public safety. Several guidelines have been set by government bodies around the world for the maximum sulphur level allowed in diesel, fuel, kerosene and other crude oil products. The Claus process is the most common method used for sulphur recovery. 90 to 95 percent of recovered sulphur is produced by the Claus process. Sulphur recovery unit (SRU) is sometimes referred to as the Claus process. The Claus process is a two-step chemical reaction as shown in the equation below. 2 H2S +3 O2 → 2 SO2 + 2 H2O  4 H2S +2 SO2 → 3 S2 + 4 H2O A portion of the total H2S is burned in the reaction furnace to form SO2. The rest of the H2S then reacts with the formed SO2 at a 2:1 ratio to form elemental sulphur. The Claus process involves a three steps; thermal, catalytic and thermal reactions. Hazard Identification and properties of contaminant Hydrogen sulfide (H2S) is a clear, colorless, extremely toxic gas that has a rotten egg smell at low concentrations that also cause irritation of eyes. The human nose can detect H2S at concentrations below 100 parts per billion. Hydrogen sulfide has a Chemical Abstracts Service (CAS) Number of 7783-06-4. It has a boiling point is -60.2oC and a density (liquid) of 0.995 g/ cm3. Sulphur gas has a boiling point of 445oC and a melting point of 120oC (amorphous). It has a density of 2.1 g/cm3 and is not soluble in water. It has an auto-ignition temperature of 232oC. Find CAS Number or sulphur Statutory standards of sulphur content level The typical sulphur content level usually ranges between 5 ppm to 15 ppm in the Union Gas system, including the 4.9 mg/m3 of sulphur in the odorant (mercaptan) added to gas for safety reasons. By 2007 in Canada, the new regulations for ultra-low sulphur diesel was set a maximum limit of 15 ppm of sulphur in on-road diesel fuels [10]. A recent review of the sulphur content carried out by the US EPA came out with the following limits; Distillate fuel oil (15 ppm (0.0015%) by weight), Residual oil/residual oil-biodiesel blend (3000 ppm; (0.3%) by weight), Aviation fuel (3000 ppm; (0.3%) by weight), Kerosene (15 ppm; (0.0015%) by weight) [11]. These new limits are to be in effect from July 1, 2018. Advantages of Sulphur recovery unit.   

Recovery of Sulphur from Hydrogen sulphide (H2S) reduces the amount of sulfur oxide (SO2) that can be emitted when end users burn the refined petroleum products that contain the compound. This helps reduce the chances of acid rain as Sulphur oxide is a precursor to acid rain. (2) Sulphur recovery units are inherently low energy consumers and can be a net producer of medium pressure steam which can be used in other parts of the plant. (2) The elemental Sulphur produced from a traditional Sulphur recovery unit can be used for commercial and industrial applications and is used in rubber products, detergents, paints, pharmaceuticals, fertilizers, tyres etc. (2)

Sources of risks and Risk Management

Sources of risks Leakage through the tube in the condensers:Porosity from welding defects between joints and tubes might lead to leakage of H2S gas. This can be as a result of the gasket not properly placed or the flanges stud bolts not tightened properly. This leads to the possible mixture of condensed water/steam with H2S or sulphur elements which is undesirable in the recovery process. Sulfur fire:The main known risk is sulfur fire due to accumulated liquid sulfur and fire take place if the concentration of air or oxygen is higher (>10%). A sulfur fire can also lead to corrosion that is higher than normal condition. It might result in higher pressure and equipment failure and contaminant release to the air or soil through different pathways. Risk management  Perform hydro test pressure at the time of erection and after regular interval and monitor shell or tube side pressure  Auto ignition temperature of sulfur is 232 °C so monitor the temperature of the process through temperature element. Risk assessment Routes of Exposure Inhalation - The major route of hydrogen sulphide exposure is through inhalation and it is readily absorbed by the lungs. The odour can be identified but at high concentrations and at continuous low concentrations olfactory fatigue occurs. This means odour is not a reliable indicator of H2S. H2S is heavier than air so it will accumulate in enclosed and low-lying areas. For this reason, children are exposed to higher levels of H2S since they are closer to the ground. Skin and eye contact – Long exposures to H2S leads to dermatitis and burning eyes even at low levels. Direct contact with the liquefied gas can cause frostbite. Ingestion – Ingestion is unlikely to occur because it is a gas at room temperature Standards and Guidelines Table 1: Standards and guidelines for H2S exposure through inhalation [1, 3, 4] Human 20 ppm

Rat -

Mouse -

-

-

NIOSH IDLH LC50 (ppm) LCLo(ppm) NOAEL LOAEL

50 ppm for 10 minutes Immediately dangerous to life at 100 ppm 800 for 5 minutes 13.9 mg/m3 (10 ppm) 41.7 mg/m3 (30 ppm)

713 ppm for 1 hr -

673 ppm for 1 hr -

-

-

LEL RfC UF

4.0% (10% LEL, 4,000 ppm) 2E-3 mg/m3 300

-

-

OSHA ceiling OSHA maximum peak

Adverse human and environmental effect Acute Exposure – Acute exposures to H2S leaves the cardiac tissues and the nervous system vulnerable to oxidative metabolism which often leads to death resulting from respiratory arrest. It also causes irritation to the respiratory tract, mucous membranes eyes and skin.

Chronic Exposure –Prolonged exposure can lead to low blood pressure, headache, chronic cough, nausea, weight loss, loss of appetite as a result of chronic exposure. Table 2: Effects and Toxicity of H2S in the human body Concentration Percentage Symptoms (ppm) (%) 1 0.0001 Detected by odour 10 0.001 Occupational Exposure Level, Threshold Limit Value (TLV) 100 0.01 Kills sense of smell in 3 to 5 minutes. May burn eyes and throat 200 0.02 Kills sense of smell rapidly. Burns eyes and throat after one hour. 500 0.05 Dizziness, loses sense of reasoning, breathing ceases in few minutes. Needs prompt artificial resuscitation. 700 0.07 Will become unconscious quickly. Breathing will stop, death will result if not rescued promptly. Immediate artificial resuscitation 1000 0.1 Unconscious at once; followed by death.

Effect N/A N/A Slight symptoms after several hours exposure 1 hour without serious effects Dangerous after 30 mins to 1 hour Fatal in less than 30 minutes.

Death

Conclusion References 1. Agency for Toxic Substances and Disease Registry (ATSDR). Medical Management Guidelines for Hydrogen Sulfide, (2014). Toxic Substances Portal - Hydrogen Sulfide. 2. Ernst, N., (2014, April 9). Benefits of Sulphur Recovery. Chem Info. Retrieved from https://www.chem.info/article/2014/04/qa-benefits-sulfur-recovery 3. Hydrogen sulphide; 7783-06-4 (2003). Integrated Risk Information System (IRIS). U.S. Environmental Protection Agency. 4. Hydrogen sulphide, (1994). National Institute for Occupational Safety and Health (NIOSH). Centers for disease control and prevention. 5. Mahmud Mohammadi and MaryaZadeh (2016). Assessing environmental risks using Equipment Failure Mode and Effect Analysis (EFMEA) and modelling emissions using AERMOD in sulphur recovery unit (SRU). International Journal of Advanced Biotechnology and Research (IJBR), 7(2), 12781285. 6. Bohme Gerald and Sames John (1999). The Seven Deadly Sins of Sulphur Recovery. Sulphur Experts Inc. 7. Ticheler-Tienstra, E.et. al., (2014). Risks of accumulated sulphur in sulphur recovery units. Jacobs Nederland B.V. 8. Al-Sarawy, A. A, Raslan W. E. and Tawfeek M. A., (2016). Environmental Impact Assessment for Sulfur Recovery Unit in Natural Gas Liquids Plant. International Journal of Scientific & Engineering Research (IJSER), 7(1), 2229-5518 9. Alaei, R. et al., (2014). Safety assessment approach of hazard and operability (HAZOP) for sulfur recovery unit Claus reaction furnace package; blower; heat exchanger equipment in South Pars gas processing plant. Journal of Natural Gas Science and Engineering, 20(2014), 271-284. 10. Environment Canada, (2001). Reducing the level of sulphur in Canadian on-road diesel fuel. A Discussion Paper on Designing Canadian Regulations to Align with the New U.S. Standard.

11. Connecticut Department of Energy and Environmental Protection, (2014). Fuel Sulphur Content Limitations for Stationary Sources. New RCSA Section 22a-174-19b.