Online Carbon Concentration Measurement for Gold Processing Plants
Online Carbon Concentration Measurement for Gold Processing Plants: Optimal Gold Adsorption.
A critical parameter for efficient operation of CIL/CIP processes is accurate measurement and control of carbon concentration. Traditional measurement methods are manual, time-consuming and inaccurate, leading to poor process control and gold loss. The C2 Meter is a probe designed to continuously measure adsorption in the tank pulp. Comprising of a matched transmitter/receiver pair of piezoelectric ceramic transducers, it generates and measures ultrasonic signal attenuation.
Activated carbon is commonly used for the adsorption of gold cyanide complexes in the gold leaching extraction process. The measurement of the carbon concentration in the gold-bearing solution is of critical importance to the efficient operation of the process. If too little carbon is added to the tanks, there is not enough carbon available to adsorb the gold, resulting in decreased recovery and increased soluble gold lost to tailings (waste). If too much carbon is added, the carbon breakage rate increases, resulting in increased carbon loss and increased soluble gold losses. Gold mines in South Africa are faced with increasingly higher operating costs with lower grade ores, and it is therefore imperative that the extraction process is executed as efficiently as possible.
In most gold operations, the measurement of carbon concentration is done manually and routinely by plant operators. Unfortunately, this process is rarely done frequently enough and is often inaccurate due to human error. Accurately managing carbon profile levels in the tank is extremely challenging using infrequent and inaccurate data obtained from manual samples. Automating carbon profile levels is only possible when accurate, frequent carbon concentration measurements are accessible. These can only be obtained from an automated analyser. As a result, Mintek has developed an ultrasonic-based carbon concentration meter (C2 Meter) consisting of a probe which is mounted directly into the leaching tanks. This system provides an accurate and continuous online measurement of carbon concentration within the tanks.
Accessibility to a continuous, reliable online measurement makes it possible to automate the management of carbon concentration profiles in the tanks, resulting in an efficient gold extraction process. Preliminary research has indicated that it may be possible to reduce the amount of soluble gold losses by 30% by implementing an effective automated controller in conjunction with a stand-alone carbon concentration meter, resulting in savings of over R1 million in a 6-month period on a typical South African gold plant.
Presently, there are no online carbon concentration analysers commercially available capable of measuring carbon concentration at a frequency as high as Mintek’s C2 Meter. The instrument also has no moving parts, which minimises maintenance.
The C2 Meter probe submerged in the tank consists of an ultrasonic transmitter and receiver. Variations in carbon concentration are evident in the nature of the received ultrasonic signal, which in turn is used to quantify the carbon concentration within the tank.
Mintek was established through an act of parliament to meet a national imperative of promoting mineral technology and to foster the establishment and expansion of industries in the field of minerals and products derived therefrom, through research, development and technology transfer. The organization is divided into 10 technical divisions, each targeting different areas of the minerals extraction, processing and beneficiation chain. The Measurement and Control (MaC) division is one of these technical divisions. MaC is an international leader in developing and supplying advanced process control and instrumentation for the mineral processing industry. MaC covers the full product development lifecycle, from discovering and understanding the needs of industry, developing and testing products, through to transferring, commissioning and servicing of the products. Operations of interest to the division are mineral processing, hydrometallurgical and smelting plants. It is in this division where the Carbon Concentration Meter was developed.