Research On Solid-liquid Two-phase Flow Of Deep-water Shallow Hydrate Crushing And Ore Gathering Recovery

The deep water shallow layer of the ocean is rich in natural gas hydrate resources.Solid-state fluidization is the first method to effectively exploit shallow non-diagenetic and weakly cemented natural gas hydrates in China,and it has been successfully tested in the Shenhu area of the South China Sea.At present,solid-state fluidized exploiting still exist problems such as low gas production and unable to meet commercial exploiting requirements.The hydrate crushing and high-efficiency ore collection recovery are the key to the smooth entry of the pulp into subsequent separation and lifting,and it is also the main factor affecting the efficiency of hydrate exploitation.Therefore,the replacement sample test of hydrate breaking by water jet is carried out in this paper,and the breaking efficiency and particle size distribution of hydrate are obtained.on this basis,referring to the deep-sea metal manganese nodule ore-gathering method,the method of negative pressure ore-gathering recovery of hydrate slurry is put forward.The influence of different perforation arrangements on the concentrating efficiency of hydrate particles was analyzed by CFD software.Based on experimental device for crushing recovery in solid-state fluidized mining,negative-pressure ore-gathering recovery test was carried out to verify the reliability of simulation results,which laid a foundation for the design and optimization of subsequent gas hydrate particle-gathering recovery device.The main work of this paper is as follows:In order to study the particle size distribution after hydrate jet breaking,based on single nozzle breaking hydrate substitute sample test,collecting the particles in the process of breaking test,obtaining the particle size distribution of the broken particles with jet pressure of 10 MPa,12.5 MPa and 14 MPa by screening the standard sample.The particle size range of hydrate particles after jet breaking was determined,and the jet pressure of 10 MPa was obtained.The fragmentation efficiency curve fitted the influence of pullback velocity on hole diameter and particle fragmentation and peeling boundary,which provided particle size distribution parameters for subsequent ore collection and recovery,separation and lifting.In order to improve the exploitation efficiency of natural gas hydrate,the technology of equal displacement negative pressure suction for ore collection and recovery is put forward.Based on the particle size distribution,analyzing the velocity attenuation law of the crushed cavity under the condition of single recovery hole,the same inlet displacement and different aperture,and the velocity attenuation law of the crushed cavity under the action of porous coupling by CFD simulation.The influence of pore size on the broken cavity is obtained,which provides a basis for the selection and optimization of the hole in the ore collection and recovery device.In order to find out the factors affecting the recovery efficiency of negative pressure ore-gathering,the simulation analysis of the influence of different broken cavity diameter,recovery hole size and hole arrangement on recovery efficiency was carried out under the condition of jet excitation based on CFD simulation.In order to verify the reliability of the proposed ore recovery method and device,a collection recovery test was carried out based on the solid state fluidized mining and crushing recovery experimental device.Under the condition of equivalent suction flow rate,the difference between the hole area of different recovery holes and the solid content of the collected particles was obtained,and the main factors affecting the recovery of negative pressure collection were obtained by the size of the hole and the arrangement of the holes.The reliability of CFD simulation was verified.In summary,this paper obtains the ash formation efficiency and particle size distribution of the hydrate under different working conditions through the hydrate replacement sample crushing and ore collection recovery test,and provides the particle distribution basis for separation and lift.A method of collecting and recovering ore is established and a set of simulation models and analytical methods are established to improve the mining efficiency,which provides a new idea for the design and optimization of the ore recovery unit in hydrate solid state fluidized mining.