System and method for removal of volatile hydrocarbons from a water stream
A system for separating a volatile hydrocarbon from a water stream includes a lead mixer-injector device that receives an untreated water stream including a volatile hydrocarbon, injects compressed air into the untreated water stream and mixes the injected air with the untreated water stream to form a first injected fluid stream. A shear mixing device receives the first injected fluid stream from the mixer-injector device and shear gas bubbles within the received first injected fluid stream so that a frothed stream is formed. A lead degas separator receives and separates the frothed stream from the shear mixing device into a volatile hydrocarbon stream and a partially treated water stream based on difference in density. A compressor directs clean and oil free compressed air to the lead mixer-injector device.
1 . A system for separating a volatile hydrocarbon from a water stream comprising:
a lead mixer-injector device configured to receive an untreated water stream including a volatile hydrocarbon, inject compressed air into the untreated water stream and mix the injected air with the untreated water stream to form a first injected fluid stream;
a shear mixing device configured to receive the first injected fluid stream from the lead mixer-injector device and shear gas bubbles within the first injected fluid stream so that a frothed stream is formed;
a lead degas separator configured to receive and separate the frothed stream from the shear mixing device into a volatile hydrocarbon stream and a partially treated water stream based on difference in density;
a compressor configured to direct clean and oil free compressed air to the lead mixer-injector device;
a lag mixer-injector device configured to receive second compressed air and the partially treated water stream from the lead degas separator including a remaining volatile hydrocarbon, inject the second compressed air into the partially treated water stream and mix the second injected air with the partially treated water stream to form a second injected fluid stream; and
a lag degas separator configured to receive and separate the second injected fluid stream from the lag mixer-injector device into a second volatile hydrocarbon stream and a treated water stream based on a difference in density.
2 . The system of claim 1 wherein the lead mixer-injector device and the lag mixer-injector device each has a diffuser including a plurality of openings or a mesh.
3 . The system of claim 1 further comprising a first line reducer positioned upstream of the lead mixer-injector device, a first line expander positioned downstream of the lead mixer-injector device, a second line reducer positioned upstream of the lead degas separator and a second line expander positioned downstream of the lag degas separator.
4 . The system of claim 1 wherein the lead degas separator includes a lead degas relief valve configured to open when a pressure of a volatile hydrocarbon within the lead degas separator is raised and the lag degas separator includes a lag degas relief valve configured to open when a pressure of a volatile hydrocarbon within the lag degas separator rises above a pre-determined level.
5 . The system of claim 1 wherein the lag mixer-injector device receives the second compressed air from the compressor.
6 . The system of claim 1 wherein the lead degas separator includes a lead degas relief valve configured to open when a pressure of a volatile hydrocarbon within the lead degas separator is raised.
7 . The system of claim 1 wherein the lead mixer-injector device includes a diffuser having a plurality of openings or a mesh.
8 . The system of claim 1 wherein the shear mixing device includes a plurality of flash reactors.
9 . The system of claim 1 further comprising a line reducer positioned upstream of the lead mixer-injector device and a line expander positioned downstream of the lead mixer-injector device.
10 . The system of claim 1 further comprising a throttling valve downstream from the lead degas separator.
11 . A method for separating a volatile hydrocarbon from a water stream comprising:
pumping an untreated water stream from a pump positioned at a wellhead;
injecting compressed air into the untreated water stream;
mixing the injected air and the untreated water stream to form a first injected fluid stream;
shearing gas bubbles within the first injected fluid stream so that a frothed stream is formed;
separating the frothed stream into a volatile hydrocarbon stream and a partially treated water stream based on a difference in density;
injecting second compressed air into the partially treated water stream;
mixing the second injected compressed air and the partially treated water stream to form a second injected fluid stream; and
separating the second injected fluid stream into a volatile hydrocarbon stream and a treated water stream based on a difference in density.
12 . The method of claim 11 where the volatile hydrocarbon includes methane.
13 . The method of claim 11 further comprising throttling the partially treated water stream.
14 . The method of claim 11 wherein a ratio of the injected air to untreated water during the injecting is in a range of 0.80 to 1.50.