| Palladium carbon is a catalyst made by loading metal palladium powder onto active carbon.Because of its high hydrogenation reducibility,good selectivity,stable performance,small feed ratio,repeatable application,convenient production and other characteristics,it is widely used in fine chemical industry,petrochemical industry,pharmaceutical industry,electronics industry,automobile catalyst and other fields.China is a country with scarce platinum group metals,among which there is less palladium ore reserves available for mining,and palladium metal external dependence exceeds 95%.Nowadays,supply and demand of palladium metal of our country is already in serious imbalance state.From a long-term perspective,our country’s heavy dependence on foreign palladium metal imports will not change.In order to offset the adverse effect caused by the rising international palladium metal price,we must start from applied basic research,focus on promoting the recycling of palladium metal,and spread the production costs of palladium catalysts to offset the adverse effect of the price rise of palladium metal on the fine chemical industry,medicine and environmental protection industries.The roasting stage is the most important step to affect the recovery of palladium in carbon catalyst,especially the selection of roasting equipment and pretreatment of waste catalyst.The recovery of palladium can be increased by improving the roasting process and equipment because some roasting equipment will lose palladium ash along with the tail gas.In this paper,on the basis of a model roaster furnace of Shanghai Songping Electric Furnace Co.,LTD.,FLUENT simulation software was used to simulate the roaster furnace,and the flow trace diagram and flow field slice cloud diagram of the furnace were obtained,and the distribution law of airflow velocity amplitude at the opening position of the material plate was analyzed and studied.The selection of air inlet structure and the optimization of size parameters of air inlet and air outlet are completed.A prototype of roaster was developed for experimental verification,and the recovery rate of carbon-based precious metal under different binder conditions was studied.The main research contents of this paper include:(1)According to the structure of a certain type of roaster of Shanghai Songping Electric Furnace Co.,LTD.,the whole simulation and analysis process is simplified,the simplified three-dimensional simulation model of the furnace is constructed,the mesh is divided,the boundary conditions are set up,the appropriate turbulence model and numerical calculation method are selected,and the mathematical model of the flow field of the furnace of the roaster is established.(2)In FLUENT software,the same area and flow of air inlet and air outlet are adopted.According to the flow track diagram of the roaster furnace,four different air inlet and air outlet layout modes are studied,and the final structure of the furnace is determined: the furnace size is 30×40×30cm,the intake holes are arranged symmetrically,the number is 8,the spacing is 5cm and the aperture is 2.8cm.On this basis,the flow field distribution of the final furnace structure scheme at different firing rates is analyzed.Finally,the velocity amplitude distribution law at the open section of the material plate of the roaster furnace is analyzed by means of average and variance method.The results show that the velocity amplitude distribution uniformity of the furnace flow field in the X-axis direction is good,while the velocity amplitude distribution uniformity of the furnace flow field in the Y-axis direction is poor.(3)Based on the numerical simulation results,a prototype prototype of roaster was developed.Due to the high price of palladium carbon catalyst,the ruthenium carbon catalyst with lower price was first used in this paper to optimize the roasting conditions.The effects of binder type,ratio of catalyst to binder,gas supply flow,roasting time and other factors on the recovery rate of ruthenium carbon catalyst were investigated by orthogonal experiment.The results show that the factors affecting the recovery rate of ruthenium carbon catalyst are adhesive type > gas supply flow >roasting time > ratio of catalyst to adhesive.The type of binder has the most significant effect on the recovery of ruthenium,and the ratio of catalyst to binder has the least effect on the recovery of ruthenium.The optimal conditions are as follows: adhesive is glutinous rice flour,catalyst/adhesive ratio is 6:1,roasting time is 1h,and airflow is2m~3/h.According to the optimum conditions,the ruthenium and palladium carbon catalysts were tested respectively.The average ruthenium recovery was 97.65%,and the average palladium recovery was 95.07%.This paper mainly takes the overall flow field of the furnace and the velocity amplitude uniformity of the predetermined opening position of the material plate at the bottom of the furnace as the research object to create a more uniform flow field on the surface of the material.A non-standard roaster was developed and its roasting conditions were optimized by orthogonal experiment.Experimental results show that under optimal roasting conditions,the recovery rate of palladium carbon catalyst is improved by about 10% compared with that of a certain type of roaster made by Shanghai Songping Electric Furnace Co,LTD and the roasting time is shortened from2 h to 1h.The research results of this paper provide a new idea for the recovery of carbon-based precious metals and have a positive significance for reducing the recovery cost of carbon-based precious metals waste.At the same time,the roasting equipment designed in this paper is suitable for the recovery of most supported noble metal catalysts. |
PDF Full Text Request