R.D. Pascoe

Influence of path length and slurry velocity on the removal of iron from kaolin using a high gradient magnetic separator

Abstract The influence of path length and slurry velocity on the performance of a reciprocating canister type super-conducting magnetic separator has been investigated. The canister train of a Carpco 5 T separator was removed and replaced with seven test cells each with a different length of stainless steel matrix, varying from 25 to 500 mm. A kaolin sample from the St. Austell area in Cornwall was dispersed and pumped through each matrix. The resultant product was analysed for iron. The longer the path length, at a fixed flowrate, the greater was the removal of iron from the kaolin. Shorter path lengths, however, offer the potential advantage of multiple paths within a canister of fixed length. The optimum path length for the kaolin was found to be within the range 25–100 mm, depending on percentage iron removal. The optimum path length increased as the required iron removal rate was increased. Increasing the slurry velocity through the matrix reduced particle capture, with the effect being more significant at 2 T than at 5 T. The higher throughput achieved at the increased velocity however more than compensates for the reduction in performance.

Investigation of the importance of particle shape and surface wettability on the separation of plastics in a LARCODEMS separator

Abstract The sorting of plastic types on the basis of differing density has important industrial application in the recycling industry. Some important packaging plastics, such as PVC and PET have similar densities, making density separation either unsuitable or requiring very careful control. The behaviour of PVC and PET in a LARCODEMS dense medium separator has been investigated using calcium chloride solutions as the medium. It has been shown that particle thickness and surface conditioning can have a significant influence on the plastics behaviour within the separator. The results can be explained by considering the forces acting on the particles, with surface tension and buoyancy being of particular importance. The possibility of controlling the wettability of the plastic to improve the separation of PET and PVC is discussed.

Development of a method for separation of PVC and PET using flame treatment and flotation

Abstract Flame treatment can be used to modify the surface of plastics to allow water-based coatings to be attached. The effect of the treatment is to produce hydrophilic species on the surface of the plastic. The process is therefore potentially useful for the separation of plastics by froth flotation, provided that the production of the hydrophilic surface can be achieved selectively. Polyvinyl chloride (PVC) and polyethylene terephthalate (PET) were selected for investigation as they are found as a co-mingled product from the recovery of beverage containers. In this paper we report on the development of a simple, but effective, flame treatment method for flaked plastics. The treatment involves the use of an acceleration chute that delivers the flakes through the flame of an angled burner. In experiments with virgin plastics the PVC was found to be less susceptible to surface modification than PET, as indicated by contact angle measurement. Separation of the treated virgin plastic by froth flotation was found to be possible, using careful control of frother addition. The technique was then considered for the treatment of post-consumer plastic bottles. It was demonstrated that flame treatment was effective in rendering the surface of both plastics hydrophilic, although the process alone was not sufficiently selective. Hydrophobic recovery of the PVC, but not the PET, was achieved by raising the temperature of the material to 140 °C for a period of 10 min. A two-stage flotation process was tested for the separation of the plastics. In the first stage the PET was floated away from the PVC utilising differences in particle thickness and surface contamination. The float product was then subjected to flame treatment and hydrophobic recovery prior to the second stage of flotation. In this stage the PVC reported to the float product leaving a PET-rich sinks fraction.

Capital and operating costs of minerals engineering plants - a review of simple estimation techniques

Abstract The production of order of magnitude estimates of both capital and operating costs for mineral processing plants is extremely useful when evaluating projects. This paper reviews the many techniques that can be employed to produce these cost estimates.

Method for near infrared sensor-based sorting of a copper ore

Sorting of minerals based on near infrared (NIR) analysis is promising because many minerals have distinct “fingerprints” in the NIR region. An experimental system was customised in order to obtain accurate NIR reflectance spectra. As a test application, the NIR spectra of transects across pre-classified copper ore particles were measured. Matrices containing correlation coefficients of particle pixel–pixel spectra were subjected to principal component analysis. In addition to providing insight into the homogeneity of the particle surface, the results were used to identify key spectral features which could be used to sort product from waste particles. With a selected spectral range, it was found that the classification improved when two standard pixels relating to product and waste were inserted into the transects. While testing an equal number of particles from each rock type, it was found that a correct classification was made in 82% of all rocks. It was found that moisture had little to no effect on the sorting method.

Selective aggregation of ultrafine hematite and quartz under high shear conditions with conventional flotation collectors

Abstract Recovery of ultrafine minerals, of less than 10 microns in size, remains one of the most difficult problems faced by the minerals engineer. Shear flocculation is one technique that can be applied to minerals in this size range. The technique involves aggregating mineral particles, made hydrophobic with flotation collectors, under high shear conditions. The work presented considers the use of primary aliphatic amines and sodium oleate for the selective aggregation of hematite and quartz. Sodium oleate was shown to offer potential for selective aggregation of hematite whereas the amines tested could not provide the desired selectivity. Factors that affect the size of the aggregates formed were investigated. Collector concentration and pH were found to be the most important with each system tested.