Application of a nanosecond corona discharge generator for electrical separation of ores

The use of a pulsed nanosecond voltage source in a corona separator was investigated. Measurements of the distribution of corona discharge current were obtained. The influence of the interelectrode distance on the distribution of the corona discharge current was investigated. Experiments with gold-bearing quartz-sulfide ore and ilmenite ore were carried out. A concentrate was obtained with a gold content of 48 g/t, a mass equal to 18.7% of the original, which corresponds to the extraction of 92% of gold. The titanium content of ilmenite was enriched from 2.87% to 18.1%.

Modeling Pulsed High-Power Spikes to Drive Piezoelectric Broadband Transducers Improving SNR in Ultrasonic Imaging & NDE

Ultrasonic imaging & NDE applications can greatly improve their signal-to-noise ratios (SNR) by driving each transducer (composing piezoelectric arrays) with a spike giving pulsed power of k-Watts, repetitively at a PRF = 5000 spikes/s, by using a HV capacitive-discharge generator. However very-high levels, of pulsed intensities (3-10 A) and voltages (300-700 V) must be considered for a rigorous spike modeling. Even though the consumed "average" power will be small, the intensity through each transducer achieves several amperes, so the pulsed powers delivered by each HV generator can attain levels higher than in CW high-power ultrasonic applications: e.g., up to 5 kW / spike. This is concluded here from a transient modeling of the loaded generator. Then, unforeseen phenomena rise: intense brief pulses of driving power & emitted force in transducers, and non-linearities in driver semiconductors, because their characteristic curves only include linear ranges. But fortunately, piezoelectric devices working in this intense regime do not show serious heating problems, because the average power remains being moderate. Intensity, power and voltage, driving a broadband transducer from a HV capacitive pulser, are calculated to drastically improve (in ≅ 40 dB) the ultrasonic net dynamic range available, with emitted forces ≅ 250 Newtons pp and E/R received pulses of 70 V pp.