Wet High Gradient Magnetic Separator Research Articles

Recovery of Metals from Heat-Treated Printed Circuit Boards via an Enhanced Gravity Concentrator and High-Gradient Magnetic Separator.

The recovery and reuse of waste printed circuit boards (PCBs) has attracted more and more attention from global researchers, as recycling of waste PCB metals is of great significance to the rational utilization of metal material resources. This study puts forward a clean and economical method in which enhanced gravity separation and wet high-gradient magnetic separation were combined to recover waste PCBs with heat treatment at a temperature of 240 °C. The heat treatment could improve the metal liberation effect of the PCBs, and the thermal behavior was measured by thermogravimetric analysis (TGA). The pyrolysis of the non-metal fraction (NMF) began around 300 °C, and the glass transition temperature of epoxy resin was 135.17 °C. The enhanced gravity separation technique was used for the separation of metals and NMF under the compound force field. The metals grade of the gravity concentrates fraction (GRF) was 82.97% under the optimal conditions, and the metals recovery reached 90.55%. A wet high-gradient magnetic separator was applied to classify the GRF into magnetic (MA) and non-magnetic (NMA) fractions, which could achieve iron and copper enrichment. After the three stages combined process, the copper and iron grades of the NMA and MA fractions were 70.17% and 73.42%, and the recovery reached 74.02% and 78.11%, respectively.

Removal of Impurities from Shungite Via a Combination of Physical and Chemical Treatments

This study investigated the removal of sulfur and iron from shungite rocks through different methods after fine grinding: flotation, magnetic separation, microwave treatment, and chemical leaching. In this work, first, a mineralogical study of shungite was conducted. The carbon, silica, iron, and sulfur compositions in the as-received shungite were 45.4%, 38.3%, 4.6%, and 2.4%, respectively. In flotation, a sulfur grade of 1.4% was obtained. In the wet high-gradient magnetic separation at a magnetic flux density of 1 tesla, the iron and sulfur grades in the nonmagnetic fraction were 2.8% and 1.9%, respectively. Furthermore, the sulfur reduced to 0.2% by the 9 min microwave irradiation. In addition, chemical leaching using chelating reagents and inorganic acids was utilized to remove iron and sulfur. Nitrilotriacetic acid (NTA) could reduce the iron and sulfur grades to 2.0% and 0.9%, respectively. For leaching using reverse aqua regia, the iron and sulfur grades were reduced to 0.9% and 0.23%, respectively. For leaching using a 6N HCl with H2O2 aqueous solution, the iron and sulfur grades were reduced to 0.8% and 0.34%, respectively. Overall, chemical leaching using HCl with H2O2 was the most effective for iron and sulfur removal from shungite.

On Improving the Separation Efficiency of a Wet High Gradient Magnetic Separator for the Removal of Pyrite from Egyptian Coal

ABSTRACTWet high gradient magnetic separation (WHGMS) of an Egyptian coal sample was carried out to minimize its pyritic-sulfur content reaching 1.60% (2.9% total sulfur). Optimization of the process using the Boxmag Rapid separator included feeding rate, pulp density, applied magnetic field, and the canister loading %. This was conducted through the CCRD and RSM, using Design Expert 6.0 software. Results showed that, at the optimum separation conditions, i.e., 10 l/h feeding rate, 5% pulp density, 2200 Gauss, and 0.6% canister loading, a coal concentrate assaying 0.57% pyritic sulfur was obtained with a recovery 58% and separation efficiency 79.34%.

焼却灰中のレアメタルリサイクルのためのチタンおよびクロム化合物の超電導高勾配磁力選別

In order to recover Ti and Cr compounds from the incinerated bottom ash, the wet high gradient magnetic separation (HGMS) was investigated by using a superconducting magnet. To separate Ti and Cr from Fe particles, it is necessary to weaken the magnetic force, which is acting on Ti and Cr particles. At first, basic tests using a pure sample of Ti or Cr compound were performed in order to minimize the amount of captured fraction of Ti and Cr compounds. As a result, the minimum amount of captured fraction of each compound was obtained by varying the magnetic susceptibility of the fluid. As for Ti compound (TiO2, CaTiO3), iron tri-chloride and manganese sulfate were used to change the magnetic susceptibility. Likewise, as for Cr compound (Cr2O3), water based magnetic fluid was used. By applying the condition, which gives the minimum captured fraction, to a mixture sample of Ti (or Cr) and Fe compounds, Ti and Cr compounds were efficiently recovered as nonmagnetic products.Furthermore, the conditions obtained from basic tests were applied to the bottom ash from an industrial waste incinerator, which has a high content of TiO2. As a result of wet HGMS after leaching ash with HCl, the TiO2 grade was increased from 10wt% to 28wt%, whereas the TiO2 recovery reached 64 wt%.

The Removal of Iron From Hard Pulverised Kaolin by Dry High–Gradient Magnetic Separation

Deposits of hard kaolin are abundant in China, with kaolin content in the ore exceeding 95%. It is, however, rather difficult to remove iron from the ore. It was demonstrated that wet high–gradient magnetic separation is very efficient in removing the iron compounds from kaolin. For hard kaolin, however, dry high–gradient magnetic separation (HGMS) may be more suitable. To this end, we have developed a new type of dry HGMS device for laboratory use. The separation performance of the device was tested as a function of the iron concentration in the ore, gas velocity, magnetic induction and the intensity of the vibrating current. The following results were achieved: for sample no. 1 of hard kaolin, the content of Fe2O3 was reduced from about 2.20% to .082%, with the yield of the concentrate of 86.5%. For no. 2 sample of hard kaolin, the content of Fe2O3 was reduced from about 0.60% to 0.48%, with the yield of the concentrate 83.15%. The removal of the iron oxide from hard kaolin by dry HGMS proved to be feasible. Industrial–scale dry HGMS device was built and installed at a mine at the end of 1993.

Carrier Coagulation of Chromite Fines in Wet Magnetic Separation

A "carrier" or "piggy–back" coagulation process was applied to improve the separation efficiency of chromite slimes in wet high–gradient magnetic separation. This was achieved by the addition of a coarse chromite fraction to the slime fraction (< 10 mm). Three coarse chromite fractions were investigated in the present study with size ranges <106>75, <75>53 and <53>38 μm. The results suggested that the <53>38 μm coarse fraction was the most effective in improving the process efficiency. Superior performance was also found to occur between pH 5 and 6. The results were discussed by computing the various components for potential energy of interaction between the slime particles and the "carrier" or "piggy‐back" particles at a range of surface potentials in the absence or presence of the magnetic field.

The influence of pH on the high gradient magnetic separation of < 10 μm particles of hematite and quartz

This paper presents the influence of surface interaction on wet high gradient magnetic separation (WHGMS) for hematite and quartz particles (<10 μm), by controlling the pH value of the slurry flow. This influence is discussed by computing the net interaction energies for the particle-particle and particle-matrix element systems at various pH values. Such an approach leads to an improvement in the efficiency of separating the mineral ultrafines by WHGMS.

High gradient magnetic separation applied to tin minerals

The present work reports the application of wet High Gradient Magnetic Separation, HGMS, to the recovery of weakly paramagnetic particles of very small dimensions. Pure minerals of different iron content were recovered magnetically with applied magnetic field intensities of up to 19 kOe under various conditions of flow velocity and separating matrix density. Tourmaline mineral, the main impurity in tin ore, can be recovered with a maximum of 63% efficiency in a single passing of HGMS at maximum field and 6 cm/sec flow velocity whereas cassiterite mineral (SnO 2 ) from the same ore deposit and particle size can be recovered with 37% efficiency. With a second passing of HGMS tourmaline was recovered with an increase of 14% in efficiency. From these results it seems possible that one could separate tourmaline minerals from cassiterite minerals with the appropriate conditions of magnetic field intensity, flow velocity and separating matrix density.