From: NOMAD Power Comes to Texas
How the NOMAD Evaporator Works
A gallon of water involved in fracturing a rock formation deep underground to release natural gas has a harrowing journey. First it receives a mixture of chemical additives: a friction reducer (a polymer to reduce the viscosity of the water and improve its flowability so it’s easier to pump down the well), a special grade of light sand, and a cross-linked guar gel that helps to carry the sand down into the well.
This “fraccing fluid” is injected into a gas hole at a high flow rate and pressure to break up the formation, increasing the permeability of the rock and helping the gas flow toward the surface. As the water cracks the rock formation, it deposits the sand. As the fractures try to close, the sand keeps them propped open. Fraccing typically occurs once when a well is newly drilled and again after a couple of years, when the rate of gas flow begins to decline.
Underground, the fraccing fluid picks up other contaminants present in the rock formation, including barium, calcium bicarbonate, iron, magnesium sulfate, sodium chloride, and strontium.
During the next couple of days, 75% of the injected fraccing fluid returns to the surface, where it collects in holding tanks. Then water-hauling trucks transport it to a deep-well injection site several hundred miles away—or to treatment in a NOMAD 2000 Mobile Oilfield Evaporator located within a few miles of the gas well.
The NOMAD evaporator, manufactured by Aqua-Pure Ventures Inc. of Calgary, AB, receives the wastewater in holding tanks or a surface pit, then pumps it through the pretreatment module to remove additives and other impurities that could foul and plug the evaporator. These include organic materials (bacteria present in the rock formation, and fraccing chemicals), polymers (the friction reducers and cross-linked gels), residual hydrocarbons (trace oil and volatile organic compounds such as benzene and toluene), and suspended solids (clay, iron oxides, and silica).
“Aqua-Pure uses a chemical/mechanical separation process for this primary treatment,” explains Patrick Horner, Aqua-Pure’s process engineer. “We mix chemical additives with the water to alter the charge balance, causing much of the suspended and organic material to break from solution. A mechanical separation process removes this material, leaving behind dissolved solids, primarily from underground, to be removed by secondary treatment with the evaporator.”
Energy Efficiency
After pretreatment, the wastewater enters the evaporator, where the feedwater stream divides and flows through heat exchangers that recapture process heat from the exiting distillate and concentrated brine. “Due to the heat exchangers, we recover about 95% of the heat energy in the system,” Horner says.
From the exchangers, the feedwater goes into a de-aerator column where dissolved gases are vented. Then the feedwater enters a recirculation loop that moves a large volume of fluid from a separator vessel through a circulation pump to the evaporator exchanger, then back to the separator vessel. The evaporation exchanger receives 1,200 gallons of fluid per minute and boils 60 gallons per minute to produce steam. Then steam and fluid return to the separator vessel, where a compressor draws the steam off the top and boosts its pressure and temperature. This superheated steam provides the energy that evaporates the fluid in the evaporator exchanger.
“If you boil water on a stove, producing one pound of steam takes 1,000 BTUs,” Horner says. “Because of the heat recovery, we can theoretically produce one pound of steam with 25 to 40 BTUs per pound—about 1/40th of the energy required to boil water on the stove.”
The evaporator exchanger contains more than 100 cassettes, each consisting of two thin metal plates laser-welded together with a half-inch gap between them. The cassettes are aligned in a series and pressed together like an accordion with its bellows compressed. Inside the cassettes, the high-pressure steam condenses to distilled water, while transferring its latent heat through the cassettes to boil the brine flowing outside.
Reusing the Residue
From the evaporator exchanger, clean water is pumped into the distillate tank, where noncondensible gases such as carbon dioxide are vented outside. Then it is pumped to the distillate exchanger to transfer its heat to the incoming feed water, and continues on to an outdoor frac pit where gas producers draw water for a frac job.
As the steam rises to the top of the separator vessel, concentrated brine sinks to the bottom, where it is drawn off and pumped to the blowdown exchanger to transfer its heat to the incoming feed water. Then it continues outside for disposal, or for use by drilling and well-service companies as a “kill fluid.” The gas pressure in the Barnett Shale formation is 4,000 psi. When drilling is done, concentrate injected into a gas well acts as a cork to keep the gas from flowing to the surface. Other productive uses for the concentrated brine, and for solids crystalized from it, are being explored.
A Service Company
The NOMADs are owned and operated by Fountain Quail Water Management LLC of Jacksboro, TX, an oil-field service company that is a joint-venture partnership with ownership shared equally between Aqua-Pure and a group of local investors, the Elenburg family. Aqua-Pure builds the units and sells them to Fountain Quail for about $2.5 million apiece.
“Fountain Quail does all the work,” Horner explains. “It transports, operates, and maintains the plant, charges a fee for each barrel of wastewater it treats, and then sells distilled water back to the producers. In addition to saving the producers money, this service reduces their freshwater demand, the trucking of both fresh and contaminated water, and the disposal volume.
“It also provides a broader environmental benefit. Any time you take water from surface sources or wells that tap a freshwater aquifer, if you inject it deep underground, it’s out of the hydrological cycle forever. We’re keeping it on the surface and cleaning it so it can be reused and remain part of the hydrologic cycle.”
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July-August 2006
From: NOMAD Power Comes to Texas
How the NOMAD Evaporator Works
A gallon of water involved in fracturing a rock formation deep underground to release natural gas has a harrowing journey. First it receives a mixture of chemical additives: a friction reducer (a polymer to reduce the viscosity of the water and improve its flowability so it’s easier to pump down the well), a special grade of light sand, and a cross-linked guar gel that helps to carry the sand down into the well.
This “fraccing fluid” is injected into a gas hole at a high flow rate and pressure to break up the formation, increasing the permeability of the rock and helping the gas flow toward the surface. As the water cracks the rock formation, it deposits the sand. As the fractures try to close, the sand keeps them propped open. Fraccing typically occurs once when a well is newly drilled and again after a couple of years, when the rate of gas flow begins to decline.
Underground, the fraccing fluid picks up other contaminants present in the rock formation, including barium, calcium bicarbonate, iron, magnesium sulfate, sodium chloride, and strontium.
During the next couple of days, 75% of the injected fraccing fluid returns to the surface, where it collects in holding tanks. Then water-hauling trucks transport it to a deep-well injection site several hundred miles away—or to treatment in a NOMAD 2000 Mobile Oilfield Evaporator located within a few miles of the gas well.
The NOMAD evaporator, manufactured by Aqua-Pure Ventures Inc. of Calgary, AB, receives the wastewater in holding tanks or a surface pit, then pumps it through the pretreatment module to remove additives and other impurities that could foul and plug the evaporator. These include organic materials (bacteria present in the rock formation, and fraccing chemicals), polymers (the friction reducers and cross-linked gels), residual hydrocarbons (trace oil and volatile organic compounds such as benzene and toluene), and suspended solids (clay, iron oxides, and silica).
“Aqua-Pure uses a chemical/mechanical separation process for this primary treatment,” explains Patrick Horner, Aqua-Pure’s process engineer. “We mix chemical additives with the water to alter the charge balance, causing much of the suspended and organic material to break from solution. A mechanical separation process removes this material, leaving behind dissolved solids, primarily from underground, to be removed by secondary treatment with the evaporator.”
Energy Efficiency
After pretreatment, the wastewater enters the evaporator, where the feedwater stream divides and flows through heat exchangers that recapture process heat from the exiting distillate and concentrated brine. “Due to the heat exchangers, we recover about 95% of the heat energy in the system,” Horner says.
From the exchangers, the feedwater goes into a de-aerator column where dissolved gases are vented. Then the feedwater enters a recirculation loop that moves a large volume of fluid from a separator vessel through a circulation pump to the evaporator exchanger, then back to the separator vessel. The evaporation exchanger receives 1,200 gallons of fluid per minute and boils 60 gallons per minute to produce steam. Then steam and fluid return to the separator vessel, where a compressor draws the steam off the top and boosts its pressure and temperature. This superheated steam provides the energy that evaporates the fluid in the evaporator exchanger.
“If you boil water on a stove, producing one pound of steam takes 1,000 BTUs,” Horner says. “Because of the heat recovery, we can theoretically produce one pound of steam with 25 to 40 BTUs per pound—about 1/40th of the energy required to boil water on the stove.”
The evaporator exchanger contains more than 100 cassettes, each consisting of two thin metal plates laser-welded together with a half-inch gap between them. The cassettes are aligned in a series and pressed together like an accordion with its bellows compressed. Inside the cassettes, the high-pressure steam condenses to distilled water, while transferring its latent heat through the cassettes to boil the brine flowing outside.
Reusing the Residue
From the evaporator exchanger, clean water is pumped into the distillate tank, where noncondensible gases such as carbon dioxide are vented outside. Then it is pumped to the distillate exchanger to transfer its heat to the incoming feed water, and continues on to an outdoor frac pit where gas producers draw water for a frac job.
As the steam rises to the top of the separator vessel, concentrated brine sinks to the bottom, where it is drawn off and pumped to the blowdown exchanger to transfer its heat to the incoming feed water. Then it continues outside for disposal, or for use by drilling and well-service companies as a “kill fluid.” The gas pressure in the Barnett Shale formation is 4,000 psi. When drilling is done, concentrate injected into a gas well acts as a cork to keep the gas from flowing to the surface. Other productive uses for the concentrated brine, and for solids crystalized from it, are being explored.
A Service Company
The NOMADs are owned and operated by Fountain Quail Water Management LLC of Jacksboro, TX, an oil-field service company that is a joint-venture partnership with ownership shared equally between Aqua-Pure and a group of local investors, the Elenburg family. Aqua-Pure builds the units and sells them to Fountain Quail for about $2.5 million apiece.
“Fountain Quail does all the work,” Horner explains. “It transports, operates, and maintains the plant, charges a fee for each barrel of wastewater it treats, and then sells distilled water back to the producers. In addition to saving the producers money, this service reduces their freshwater demand, the trucking of both fresh and contaminated water, and the disposal volume.
“It also provides a broader environmental benefit. Any time you take water from surface sources or wells that tap a freshwater aquifer, if you inject it deep underground, it’s out of the hydrological cycle forever. We’re keeping it on the surface and cleaning it so it can be reused and remain part of the hydrologic cycle.”