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Evaluation of VPA Filtration Tests to Determine Relevant Scale-up Factors
2015 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In the mining industry dewatering by vertical plate airblow (VPA) filtration is commonly used as a last stage before shipping or producing agglomerates of the concentrate. The installations of VPA filters worldwide by Metso Minerals have led to a growing demand for on-site dewatering test work and, in order to do so, Metso Minerals has developed a new pilot scale pressure filter, the VPA04. Several test units have been produced and will be placed on different continents to be easily available for customers around the world. Before the VPA04 filters are shipped, an evaluation of the VPA04 filter is needed. This has led to this master thesis. The aim of this thesis has been to evaluate the pilot filter and develop a new scale-up approach for the VPA filters at Metso Minerals in Sala.The focus of the scale-up is between three different chamber sizes (33, 42 and 53 mm) and between laboratory, pilot and full-scale VPA filters. An experimental approach was developed from a literature survey and experiences provided by Metso. The approach was consider dolomite, lead and a zinc concentrate on laboratory (LabVPA) and pilot scale with full-scale samples for the lead and zinc concentrate. A material characterisation was made on each material and a determination of the residual moisture content distribution over the filter cake on the VPA04 was made. The scale-up was developed for the effective filling time, air blowing time and the dry cake density (kg/l) using three different models, a linear-, exponential- and an implicit additive moisture model.The results from determination of the residual moisture content on the VPA04 showed higher moisture content in the centre of the filter cake and further up close to the feed inlet. This was performed with dolomite and is probably true for other materials.The results of the dry cake density showed a loss of 5 to 11 % between the LabVPA and the full-scale filter, where a factor of 0.95 and 0.89 was established in a linear model for the lead respectively zinc concentrate. The verification and validation showed a very low spread and the factors are considered as reliable to be used for scale-up between the machines and the chambers.The verification of the scale-up models for the effective filling time showed a small spreading for each material and the models were validated between the chambers and the machines with limited amount of measured values. The conclusion is that the scale-up factors should be used with precautions between different equipment sizes and chambers as the filling time is very short on the LabVPA using the lead concentrate. A rule of thumb having a filling time shorter than 2 minutes, the sizing is set to 2 minutes and a scale-up factor of 1.26 is implemented to be used after 2 minutes of effective filling time on the LabVPA to reach the full-scale filling time.The analyse of the three models for scale-up of the air blowing time showed a good fit in the verification. However the validation of the models in other datasets showed a spreading of the measured values for the lead concentrate with a slightly better fit and consistency for the zinc concentrate. The moisture model turned out to have the best fit and to be most suitable for scaling- up the air-blowing for both the materials with a moisture model factor of 1.3 to 2 % between the LabVPA and full-scale filter for the zinc and lead concentrate, respectively.However, the general conclusion is that the filter machines appear to give slightly different results due to the variation in design, feeding procedure and filtration area. The results of VPA04 showed higher correlation with the full-scale for all investigated variables than the LabVPA did. The main reason is the similarity in the design between the pilot and full-scale filters.

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Keyword [en]
Keyword [sv]
URN: urn:nbn:se:ltu:diva-49744Local ID: 70eae366-d0a4-45e5-8747-3edd09c3faa7OAI: diva2:1023091
Subject / course
Student thesis, at least 30 credits
Educational program
Sustainable Process Engineering, master's level
Validerat; 20150402 (global_studentproject_submitter)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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