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H2S in the Alberta Petroleum Industry

H2S is always a topical subject in the Oil and Gas Industry in Alberta as it tends to form in areas where the geological formation was covered by tropical seas. In Alberta, workers are exposed to hydrogen sulphide during drilling and production of natural gas, crude oil and petroleum products Therefore, employers must do a hazard assessment of these workplaces and determine risks and controls.

 

Historicallly , tunnel workers, miners and divers would die when entering confined spaces when encountering underground pockets of H2S.  Some of it was formed from where anerobic  conditions with bacteria were prevalent such as mines and caves. These deaths were called heart attacks or a lack of oxygen, since they did not conduct proper evaluations of the incidents.

Hydrogen Sulphide also occurs naturally in the earth in  crude petroleum, hot springs ,natural gas reservoirs, and volcanic gases .Hydrogen sulphide is also produced from  the breakdown of human and animal wastes by bacteria. Alberta has manyƒ industrial activities  that can create H2S as a side effect.  Examples are  food processing,  kraft paper mills,  coke ovens, rayon textile manufacturing, sulphur production , wastewater treatment facilities,ƒ, tar and asphalt manufacturing plants, ƒ tanneries, and ƒ refineries. Hydrogen sulphide can accumulate in sewers, or hide storage pits in the tanning industry and  sewage treatment plants.    It can be encountered as a  raw material used to manufacture inorganic sulphides,  sulphuric acid and  mercaptans to odorize natural gas

One of the safety concerns  with hydrogen sulphide is  that it has very poor warning signs to trigger its presence. It is a colourless and poisonous ,flammable gas that can become explosive and corrosive. People tend to rely on their sense of smell, since it produces a nasty rotten egg odor at low concentrations,. Relying solely on its odour  is a poor idea because at concentrations above 100 ppm   it deadens a person’s sense of smell within a few minutes .  While It can be detected by smell at concentrations ranging from 0.01-0.3 parts per million , it tends to overload a person’s olfactory sense and then, they lose their ability to smell it.  Workers tend to believe it as gone away, but it is likely to be increasing in concentration.

Understanding its physical properties can help to predict its presence..  The pure gas is heavier than air and can collect in low areas such as  sewers  , tunnels , gullies  and   pits,. It can spontaneously combust since Hydrogen sulphide  can react with rust or corrosion deposits on equipment to form iron sulphide scale. This reaction occurs in an oxygen free atmosphere where H2S gas is present or where the concentration is greater than that of oxygen. This happens most often in closed tanks ,vessels or pipelines. Iron sulphide is a pyrophoric material, which means that it can ignite spontaneously when it is exposed to air. concentrations (between 4.3% and 46% of gas by volume in air) can catch fire and explode if there is a source of ignition. Having a flammable range of 42% is one of the most widespread ranges of the gases, making it exceedingly dangerous when welding, having open flames, grinding and chipping activities.  When the gas is burned it can form other environmentally and toxic gases such as sulphur dioxide are formed.

Training in what it can react with should be emphasized and the Safety Data Sheets noting safe work activities must be clearly outlined.  Hydrogen sulphide is incompatible with strong oxidizers, such as chlorine trifluoride and nitric acid , and may  ignite spontaneously  or react violently .Flaring activities should be reduced, when possible, as  releasing it  into the air, it will form sulphur dioxide and sulphuric acid in the atmosphere  This can become a danger to the public and air quality, resulting in fines and costs of remediation. .

Foremost, workers must understand the toxic  health effects  from Hydrogen sulphide is extremely poisonous by inhalation.  This toxic gas is quickly absorbed by the lungs and may preventsthe brain from using oxygen by inhibiting the enzyme cytochrome oxidase. Once breathing  stops, brain damage can occur rapidly. Knowing the initial response strategy to rescue workers is essential, as it can knock people down in a couple seconds.  They must be removed to a safe area and resuscitation efforts started immediately to prevent brain damage or death.

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