Fall 2015 /

Process Modelling and Optimization. 

The Process Ecology Newsletter includes updates and news relevant to the energy industry regarding regulatory updates for air emissions, technical information related to process simulation as well as case studies and best practices in process engineering.
This issue
  • The Water-Energy Nexus in the Oil & Gas Industry
  • Sizing PSVs in the Supercritical region
  • FlareAdvisor: A new way to track and manage Flaring and Venting emissions and identify opportunities to reduce emissions.

The Water-Energy Nexus in the Oil & Gas Industry

It has now long been recognized that the demand for energy and water are tightly interconnected and that interventions to increase the efficiency on the use of one of these resources will impact the other, often in unintended ways.

Unconventional hydrocarbon extraction plays an increasingly important role in the global energy system. The most common methods for unconventional oil and gas extraction include hydraulic fracturing and mining and in situ techniques (oil sands). A common theme on these developments is the public concern with the energy (and therefore, GHG emissions) and water intensive nature of these operations. Produced water treatment operations, required to protect the environment and recycle more water, increase the cost and the energy requirements to extract these resources. Process design and operating decisions related to minimizing environmental impacts from these operations are complicated by these important trade-offs. A number of researchers have been exploring these questions for some time using modeling and optimization tools, with limited success in industrial deployment. 

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Sizing of Pressure Safety Valves in the Supercritical Region

By Samaneh Hajipour, PhD, EIT

Pressure safety valves (PSVs) on vessels containing liquid hydrocarbon may relieve a supercritical fluid during a fire, if the relieving pressure is higher than the critical point. The typical method for sizing an orifice area for supercritical fluids is presented in API 521, Section [1]. As stated in the API text, this method is based on the physical properties of air, the ideal-gas law, no change in fluid temperature, and an uninsulated vessel with no mass. This standard cautions the reader to review these assumptions to ensure that they are appropriate for any particular case.
Supercritical fluids exhibit characteristics of both liquids and vapours and their physical properties can be strong functions of pressure and temperature and may deviate appreciably from ideal-gas behaviour. These deviations from both ideal-gas law and incompressible fluid behaviour present challenges for relief valve sizing. Furthermore, the compressibility factor and the fluid temperature are not constant while the vessel is relieving. The API-recommended method with ideal-gas behaviour simplification is conservative and may lead to improperly sized valves with larger orifice areas than required [2], [3]. Two main problems with over-sized valves are destructive chattering and cost.  

The relieving condition depends on the relation between the critical pressure of the fluid and the relieving pressure. In fire case scenario, for example, if the relieving pressure is less than the critical pressure, the liquid will boil when the valve opens and the relieving will continue until all liquid is vaporized. If the fluid is multi-component the temperature will vary during the relieving process. On the other side, if the relieving pressure is greater than the critical pressure, the liquid will not boil. The fluid becomes supercritical when heated until the pressure reaches the valve relieving pressure and the valve opens. Full text

 Training and Events
  • Process Ecology displayed FlareAdvisor at the  Natural Gas Star Implementation Workshop in Pittsburgh, PA describing the value of the software for tracking and reporting flared and vented volumes. The USEPA Workshop showcased a number of technologies for methane emissions reduction. 
  • A new paper with contributions from the University of Calgary and Process Ecology has been published in the Journal for Applied Thermal Engineering 87 (2015) 788-802 . "Evaluation of energy efficiency options in steam assisted gravity drainage oil sands surface facilities via process integration ". Access the paper at  Applied Thermal Engineering.
Easily track and report accurate flared and vented gas volumes using the FlareAdvisor web-based system.

FlareAdvisor is an innovative web-based software that is designed to assist the Upstream Oil & Gas sector estimate and manage flaring and venting volumes and associated air emissions from operating facilities. FlareAdvisor brings together the benefits of a modern user interface with rigorous engineering calculations that will meet the most stringent requirements for reporting.

Register for an evaluation trial today. Please visit www.methaneadvisor.com or send us an email

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