Preventing Air Pollution in Wastewater Evaporation
Resource West Enhanced Evaporation’s system cuts evaporation costs by up to 80 percent.
Due to the high cost of transporting and disposing of produced water, oil and gas producers are turning to evaporation instead. Evaporating up to 80 percent of produced water before sending it to SWD wells is also more environmentally friendly because it greatly reduces the amount of water sent to underground formations.
But improperly designed evaporation units can, surprisingly, pollute the air for miles around the site because the droplets they create are so small that they float away from the evaporation pond, carrying with them toxic contaminants. These systems, based on snowmaking machines or fire sprinklers, also are inefficient and costly to operate.
In 2016, Grand Junction CO-based RWI Enhanced Evaporation began the development and testing process that led to the creation of RWI APEX 2.0. This system can concentrate produced water 10-20 times, at a power cost of just .006 per barrel, down from the standard .20 per barrel. Studies have shown that most injection formations can accept water concentrates at these levels, allowing producers to save 80-90 percent of injection costs.
But efficiency was not enough for RWI Enhanced Evaporation, says RWI’s Director of Research and Development Robert Ballantyne. They needed to also solve the issues that were allowing suspended solid particles to drift into the air, polluting the surrounding area.
The main issue was that the machines were creating droplets so small that they dried out in flight, allowing formerly dissolved solids (toxic salts and compounds) to float in the air, polluting the air and damaging nearby property. It would be better for them to stay large enough to fall back into the evaporation pond, where the now concentrated water that remains can be injected. Here are the top two issues involved:
- Some droplets start out too small (particles of less than 50 microns are likely to dry out in flight)
- Spray trajectory from snowmakers allows droplets to collide, breaking them into tiny “daughter” particles.
Resource West Enhanced Evaporation solved those issues by designing their evaporation machines from the ground up. They create larger droplets (average of 150-300 microns), small enough to allow sufficient evaporation, but large enough to fall back onto the evaporation pond instead of drying out and releasing toxins into the air.
Second, Resource West’s sprayers inject droplets into the flow at a trajectory that prevents collisions, eliminating daughter particles.
This prevents producers from having their evaporation procedures subject to warnings and fines.
The system is also designed to accomplish this “clean” evaporation at .006 per barrel, 80 percent less than the standard of .20 per barrel. Field tests have proven this to be the case.