Our worldwide references emphasise the global nature of our company. Experience gained from more than 100 completed installations provides the necessary resources for offering the total solution for the optimal treatment of a vast array of different waste streams. Bart Gevaerts works at SOLIDS + AIR division as Design Engineer for the Mechanical Design Department and as Project Engineer Your Project: Description The Seghers Sludge Pelletiser is a device developed to dry and palletise (make pellets) sludge. This is principally done by transporting the sludge over trays, heated internally by thermal oil to typically 250 °C. The device therefore consists of a vertical tower structure in which the trays are stacked. Centrically a shaft which drives a scraping mechanism to transport the sludge is placed. Typical data: nr of trays in 1 Pelletiser: up to 23 Diameter of tray: 5200/6200 mm Weight of 1 tray: 7500 kg Weight of driving shaft + scrapers: 30 tons Weight of shell structure: tons Height of pelletiser: up to 20 m This design was firstly used at the BESOS-plant (Spain), for 4 Pelletisers of 17 trays each This means a total of 17*4 = 68 trays! The shell structure of the Pelletiser 1. Structural design Basic structure, which was designed using ESA-Prima WIN consists of a steel structure, covered by flat plating: this part carries the trays of the Pelletiser. Bottom part is a cylindrical and conical structure, supported on steel columns. On the central conical structure, the driving shaft and main drive is supported. A complete analysis model could be made because of the possibility in PRIMA WIN to make a combination of 2D, 3D and 1D elements. Because a complete model was built during the design, this was a very interesting basis for making up scaling models (by very easily copying existing modelled structure and loadings) in later projects: eg. Model of 5200 pelletiser for BESOS-plant was upgraded to 6200 pelletiser for TAY plant (Scotland). 2. Loading data Design of the device consists of calculation and evaluation of a number of load cases and their complex combinational effects: Own weight of shell structure Loading by trays Sludge loading on trays Internal pressure of the shell during operation Loading of bottom by shaft and main drive Wind loading during erection Temperature loading: shell structure obtains a higher temperature as column supports during operation, which leads to thermal stresses. · Top loading: on top of pelletiser a hopper, sludge coater and thermal expansion tank are mounted Using this model evaluation was made of deformations of plated structure, stresses in plates, stress concentrations at support-points … Thermal trays 1. Deformation characteristics of thermal tray Design of the thermal trays is determined to a high degree by the amount of deformation (by own weight, thermal oil, loading of the tray with sludge). This is investigated by means of a complete F.E.M. model to calculate, evaluate and minimise these deformations. In 2000, a new design of thermal tray was made, and a test stand was built in workshop to measure the deformations of the tray; a very accurate agreement between realisation and calculations was found. Calculation of behaviour of the tray at operation temperatures was done by reducing the E-modulus of the material in the calculation and recalculation. 2. Thermal tray as pressure vessel Since the tray is heated by thermal oil at a pressure of typically 3 bar, the tray actually is a pressure vessel. Therefore, during design, model of tray is also loaded with pressure-load case to calculate resulting stresses and obtain information on behaviour of stress-concentrations in the tray-structure. Corrosion calculations were easily possible by graphically selecting elements considered as being corroded, reducing their wall-thickness and recalculate structure. Tray supports Because of the high importance of the very limited deformations of the trays, naturally also a very strict analysis is done on the tray supports. Torque Reaction arm of main drive A reaction arm balances the drive torque of the main drive. Due to the high mechanical power of the main drive and the low speed of rotation of the main shaft, this leads to high reaction forces to be distributed via the reaction arm. This arm is also designed by using a FEM model: Use of ESA-Prima Win Pelletiser Shell structure: 3D shell + 3D frame EC3-code check Tray: 3D shell Supports: 3D shell Torque Arm: 3D shell 35 SCIA User Contest Catalog
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