Reducing Flared Gas by Generating Water

Physical Sciences : Mechanical

Available for licensing

Inventors

  • Vaibhav (VB) Bahadur , University of Texas at Austin
  • Enakshi Wikramanayake , Mechanical Engineering

Background/unmet need

Natural gas flaring is a commonly employed and global practice, especially in regions that lack gas storage and transport infrastructure and where demand for natural gas is lower. Overall, the worldwide amount of gas flared equals about a quarter of U.S. gas consumption. Flaring represents a significant waste of natural resources, in addition to creating significant nighttime light pollution near residential areas.

There are no easy solutions to reducing natural gas flaring. Natural gas capture and transportation involves the construction of capital-intensive pipelines or liquefaction systems. At the currently depressed prices and lower demand for natural gas and in the absence of any regulated limits on flaring, the most economical solution for unwanted gas is to flare it off.

Invention Description

Researchers at The University of Texas at Austin have developed a new system that uses the energy of natural gas to extract moisture from air. The system thus converts a product that would have been wasted (natural gas) into a useful commodity (fresh water).

The energy produced by burning natural gas is used to power vapor compression refrigeration units which provide the cooling power to condense water. Specialized coatings covering the condensers increase the efficiency of water condensation significantly, leading to compact natural gas-powered water harvesters. The water collected can be used for oilfield operations or domestic consumption at oil-gas production sites. Preliminary calculations indicate that up to a thousand barrels of water can be harvested per well per day, based on the natural gas flare rates and atmospheric conditions in South Texas. 

Benefits/Advantages

  • New concept for natural gas utilization
  • Converts waste (flared gas) into a valuable commodity (water)
  • Low CAPEX system compared to alternative natural gas capture and transport systems (e.g., pipelines, liquefaction plants)
  • Modular and retrofittable design
  • Provides fresh water for oilfield operations on-site (alternative to trucking in water)
  • Reduces negative public perception associated with flaring, including light pollution

Features

  • Enabling system to convert the energy of natural gas to cooling power for water condensation
  • Modular water harvesting units that can be retrofitted in existing production facilities
  • Mobile water harvesting units that can service many wells in a given producing field 
  • On-demand ability to turn the water harvesting module on and off

Market potential/applications

Local U.S. flare rates can be significant; it is estimated that up to one-third of the natural gas being produced as a result of hydraulic fracturing in North Dakota is flared off. In Texas, commercial exploitation of the Eagle Ford Shale led to a 400% increase in flaring from 2009 to 2012. In a 2014 investigation of flaring of natural gas in the nation’s two most prolific shale oil formations, North Dakota’s Bakkan Shale and Texas’ Eagle Ford Shale, Earthworks found that North Dakota oil companies have flared more than $854 million worth of natural gas since 2010.

A recent study by NASA reports that from 2005 to 2015, nitrogen dioxide and black carbon levels rose by 1.5% to 2% per year in North American flaring sites. These pollutants present health hazards and act as agents of global warming. The proposed waste conversion system can reduce the rate at which these pollutants are increasing in Earth’s atmosphere.