Research On Microwave Drying Mechanism For Oil-based Mud Cuttings And Treating System Design

Due to the advantages of powerful inhibition,strong anti-pollution,low drag force and low filtrate volume,the oil-based mud(OBM)is widely used for horizontal drilling operation.However,produced oily cuttings contain petroleum hydrocarbons,heavy metal and other harmful substances,which may profoundly influence natural ecosystems if not treated appropriately.At Present,some representative national demonstration areas,such as Fuling and Changning-Weiyuan shale gas field,have made a major breakthrough in the development of shale gas.But the scant processing capacity,complex technics flow and high-cost,it has become the mutual problem that current shale gas field faces.Therefore,it is necessary to develop a new and low-cost method to solve the problem.For this purpose,this paper proposed the microwave thermal desorption technology to carry on the harmlessization handle for oily cuttings.The degreasing mechanism of oily cuttings using microwave heating was investigated deeply and the optimization design of the processing system are also carried out in terms of this.The primarily work and achievements of the paper are as follows:(1)Based on the experimental data of oily cuttings,an experimental apparatus.on evaluating the oil-removal effect of microwave heating is developed.The.degreasing mechanisms of oily cuttings are revealed,including vaporization and entrainment,and its main desorption mechanism is manifest as vaporization.The effects of oil-water ratio,heating time,microwave power and particle size distribution on the degreasing effect of are examined by orthogonal experiment.The oil-removal effect in an order from strong to weak are oil-water ratio,heating time,microwave power and particle size distribution.The ranges of microwave thermal desorption parameters are given out on the basis of this.(2)According to the resonant circuit model and the field distribution theory in the waveguide,a new microwave cavity with multi-mode is designed.The dimension of microwave cavity and the feeding mechanism of microwave source are optimized based on the simulation results.The uniformity of electromagnetic field distribution in the resonant cavity can be improved,and then realizing the continuous processing of oily cuttings.(3)From the basic method of transmission line and impedance matching,a three pins tuner simulation model is established to study the dynamic matching relations between microwave source and reactor chamber.The algorithm of measuring standing wave ratio of microwave voltage by using three probe method is derived.The real deployment system have been successfully trial-produced and the system’s reliability have also been validated through experimental method.(4)After accomplishing the design of resonant cavity and automatic matching system,a microwave thermal desorption disposal system for oily cuttings degreasing is designed.The special designed apparatus can realize the real-time control of temperature.It can also adjust microwave power dynamically depending on the temperature under the cooperation of automatic triple pins.This eliminates the power matching problems caused by variation of oily cuttings composition The working parameters of the system are determined by experiments,meanwhile the evaluation results of the system performance is affirmative.The concept of industrial microwave thermal desorption system for oily cuttings is given at last based on our design and experiments..