DEM Investigation of separation performance and stress analysis of a five-deck industrial screen

In the Iron-making process, to achieve effective reducibility and porosity inside the blast furnace, pellets of definite size distribution i.e., (-16 +6.3) mm are required. For this, a multisizer screen made up of five decks with aperture sizes 25, 20, 17, 11 and 8 mm of wire mesh media are used. However, due to poor separation efficiency of screen, misplacement of fines increases in product. These excess fines return to the pellet making process reducing the net pellet production. So higher the fines, higher are the losses. Furthermore, wire mesh panels used in screens have a low average life leading to considerable loss of production hours. In screening, the ease of separation and particle flow is governed by particle-particle and particle-screen interactions. Therefore, a fundamental approach is required which can track these microscopic events and convert them into usable information to optimize the events at macroscopic level. The Discrete Element modelling (DEM) is such a technique used to simulate and predict bulk material trajectory flow. The current study started with modelling of existing process through Discrete Element Method (DEM) tool and validation of the model with plant data. For better reliability of the DEM model, the model input parameters were determined experimentally as well as through DEM calibration approach. Study of effects of vibration parameters (viz. amplitude and frequency) was done to find optimum values for maximum efficiency. On increasing frequency, overall efficiency of bottom deck increased. Due to increase in frequency, better percolation of fines through particle bed was observed which resulted in reducing the misplacement of fines. Total force calculations on each deck were carried out to identify areas which are more prone to damage. It was observed that feed part of top deck experienced the highest impact force and breakage mostly occurred in this part. This helped in better designing of screen panels for improved life.