Study On The Treatment Of Oil-field Produced Water With Cavitating Water Jet

Cavitating water jet is a new type of high-efficiency jet. The technical idea of using cavitating water jet to treat oilfield produced water is proposed on the basis of researches on wastewater treatment by ultrasonic cavitation and hydraulic cavitation, and this idea is testified actually practicable by experiment.The main mechanism of treatment on oil field produced water by cavitating water jet is analyzed through theoretical investigation. Based on the view of engineering application, three simple and practical types of cavitation nozzles are optimized for designing nozzle structure from all cavitation nozzles, which are Helmholtz Oscillator cavitation nozzle, organ pipe resonator cavitation nozzle and angle cavitation nozzle. Assembled nozzle, a new type of cavitation nozzle, is designed from making use of characteristics of angle cavitation nozzle and Helmholtz cavitation nozzle.The flow fields in these four optimized cavitaion nozzle are simulated by Fluent software under the designed experimental conditions, and the simulation results are well consistent with the experimental results, so it testifies that the simulation method established on N-S equation with cavitation model and Standard k-εmodel is high credible. The distributions of pressure field, velocity field and vapor volume fraction are analysed, and the primary optimization of better cavitation nozzle structure for the technique is made based on the use of vapor volume fraction as the evaluation parameter, and the simulating result indicates that the assembled cavitation nozzle is much more feasible for following experiment study. Influence of the inlet pressure and the liquid temperature on the cavitation degree in assembled cavitation nozzle is also investigated.The experiment is carried out on the specialized suit of experimental device, which is designed for the treatment of oilfield produced water by cavitaing water jet. Based on the result that the technique is proved feasible by the experiment, the crucial optimization of available cavitation nozzle structures for the technique is made. By using of the optimized nozzle structure, the influence of inlet pressure, circulation number and length/diameter ratio of nozzle on the COD removal ratio is investigated by the experiment.On the basis of experimental results, the multi-stage cavitation nozzle design proposal by the tandem-connect of several assembled cavitation nozzles is proposed. By optimizing the design proposal using the Fluent software, it is found that the function of multi-stage cavitation in the multi-stage cavitation nozzle can be achieved only by the design of adopting the single-stage nozzle diameter from small to big, and each single cavitaton nozzle has good cavitation effect. The three-stage cavitation system is designed in detail as an example of muliti-stage. The primary design of the device for oil field produced water treatment by cavitating water jet is proposed at last.