Molten salt electrolysis is currently the main process for the preparation of rare earth metals and their alloys.There are many studies on rare earth electrolysis technology and equipment at home and abroad,but there are few studies on the tapping technology.At present,a method of manually using a titanium spoon to cut out or using a stainless steel jaw clamp is still widely used in practical production.This method makes electrolysis discontinuous,workers work hard and the environment is bad.In this paper,the tapping technology of rare earth electrolysis is studied,and the extraction process of vacuum suction casting method is studied by using computational fluid dynamics(CFD)method,taking the way of tapping in small electrolytic cell as the object of study.A simple static press-out furnace device is designed and numerical simulation of its absorption process is carried out.The specifics as follows:(1)The unsteady extraction process of rare earth metals by vacuum suction casting is analyzed.The computational fluid dynamics model and the fluid properties of each phase are determined.According to the parameters of electrolytic process in 8KA cell,the shape of suction channel is determined,and the two-dimensional geometric model of the flow channel is established.The transient simulation of the flow field of rare earth metal by negative pressure suction was carried out with Fluent software.It was found that the liquid metal rose in the vertical pipe with a plunger full pipe flow,the annular flow formed at the tail end due to electrolyte inclusions,and the wave formed in the horizontal section of the bend tube.The metal liquid outflow velocity is larger,the suction tube inlet negative pressure is the largest,the speed is the largest,the entrance pipe wall has metal residue caused by blockage;The influence of suction flow under loading negative pressure is studied.It is found that the inlet and outlet velocity of suction pipe increase with the increase of load negative pressure,and the outlet at start-up.The velocity of flow was not related to the size of negative pressure.The influence of insertion depth and eccentric center position on the flow field is studied.It is found that when the insertion depth is off the bottom 30 mm,the flow of liquid metal is more concentrated and stable,and the deviation from the center will lead to uneven extraction of liquid metal and excessive loss of electrolyte.Comparing the metal flow under negative pressure suction under three kinds of curved pipe shapes,it is found that the large circular arc bending pipe is the best bending pipe shape.(2)In order to solve the problems of fast metal outflow rate and horizontal flow impact in vacuum suction casting process,a static press-out furnace device is designed,and the geometric model of the suction passage is established,and the flow field distribution is obtained by simulation of the suction process.It is found that the liquid metal can flow through the block at a relatively fast velocity and form a symmetrical eddy current above the block.When the pressure is balanced,a large amount of liquid metal in the suction tube is concentrated on the block,and the electrolyte is above the liquid metal.A small amount of metal liquid and gas exist in electrolyte liquid in the form of bubbles and flocs.The shape of conical block and cylindrical block are selected respectively to analyze the flow field in the process of absorption.The comparison shows that the metal liquid can all rise to the top of the block and concentrated in the center of the suction tube wrapped by electrolyte,and the pressure difference between the upper and lower surfaces of the block is smaller than that of the top and bottom surfaces of the block.The cone-shaped block is more favorable for the metal to get out of the furnace.The influence of block size and loading negative pressure on furnace exit is studied.It is found that the small diameter of 68 mm diameter under suction tube is the best 38 mm cone block.The loading negative pressure is proportional to the suction height,independent of the time of reaching pressure balance,the negative pressure is larger,the bigger the negative pressure is,the more the negative pressure is.The more electrolytes in the straw,the more metal dispersed in the electrolyte.(3)In this paper,the self-made static pressing furnace device is tested and analyzed.The test results show that the design scheme is feasible and the small diameter 38 mm cone block is the best.Compared with man-made lifting pot and vacuum suction casting,this scheme has higher stability and faster efficiency. |