MINING CHEMICALS
while improving precious metal recoveries for gold mines , it said .
It does this by combining chemical sensing technology with a cloud-based data visualisation and analysis solution for “ holistic monitoring and optimisation .” Its patented single-use test cartridge changes in colour instantaneously based on cyanide concentration in the sample solution , delivering accurate results in less than 30 seconds anywhere on the spot , without any lab equipment or training , according to the company .
CyanoGuard ’ s Head of Mining Solutions Sales , Margarita Zvezda , says the company ’ s technology removes the need to overdose cyanide , which has a direct impact on lixiviant costs as well as environmental impacts .
“ Adding the right amount of cyanide is critical in gold production because it directly impacts recovery ratios ,” she told IM .
This is a challenging task as the cyanide control methods prevalent in the gold mining industry – in particular , those based on silver nitrate titration – are highly unreliable , she said . As a result , mines tend to overdose cyanide to be on the safe side .
“ This turns out to be an expensive choice though ,” Zvezda said .
CyanoGuard ’ s solution addresses this problem by offering much more accurate and reliable cyanide measurement technology , which has almost no interferences and is digital , thus minimising any potential human error .
“ It is also a very fast method , allowing management decisions related to cyanide control to be taken very promptly ,” Zvezda said .
This same reliability issue with cyanide control methods can also see companies underdeliver cyanide during the cyanidation process – directly impacting recoveries .
“ With CyanoGuard ’ s solution , such situations can be identified and resolved within minutes , thus helping to achieve better gold recovery ratios ,” Zvezda said .
The savings on the solution go beyond simply cyanide use .
“ Excessive cyanide usage implies higher water consumption as well as detox reagent costs ,” Zvezda explained . “ Not only does CyanoGuard ’ s technology automatically address both of those cost categories , but it also proves efficient in cutting the less obvious expenses : in particular , those related to downtime .” The latter point is particularly true as CyanoGuard ’ s devices require no maintenance or calibration .
With CyanoGuard ’ s platform , gold mining companies can reduce cyanide consumption during the gold mining process by 15-20 % through improved process control and lower detoxification costs , while detox reagent savings of 20 % can be achieved along with improved recovery rates , the company claims .
The CyanoGuard solution is ‘ plug and play ’ and very easy and intuitive to use , Zvezda added .
“ It does not require any changes to the production process , or any special preparation / training from the team who uses it ,” she said . “ You can implement it in just a couple of days and start seeing a positive impact on costs and operational efficiency almost immediately .”
Australia-based Orica has also devised a cyanide measuring system to optimise the chemical ’ s use .
With the mining industry primarily relying on lab experiments and plant trials to optimise gold leaching processes , Orica said it felt the need to provide a different option with its LeachIT™ solution .
Designed to support metallurgists in optimising recovery in continuous leaching , LeachIT simulation software allows customers to visualise and predict gold leaching outcomes based on a mine ’ s unique requirements . In doing so , it does away with the time consuming and uncharacteristic results that can come with these lab and plant tests , and enables customers to see just how the given process will respond to changes .
It does this by using historical data from a myriad of sources to form the model . Once the model is set up , it takes very little effort and time to perform multivariable analysis , according to Orica .
Aimed at enabling best practice leaching , LeachIT simulates changes to the process and presents the impact on tails grade . The software harnesses this information not only to calculate but also visualise gold recovery and cyanide consumption .
Recent updates to LeachIT are aimed at improving customers ’ ability to process gold more efficiently and reduce overall cyanide costs and consumption .
With the latest upgrades , LeachIT is now able to ingest data from sources such as laboratory experiments and pilot plant trials , according to Orica ’ s Paul Martin , Global Cyanide Customer Solutions Manager , and Greg Zwolak , Senior Metallurgist .
“ By enabling data inputs beyond that of plant data , the overall model fit can be vastly improved ,” Martin and Zwolak agreed .
LeachIT can also now output optimum cyanide to oxygen ratios for each tank , as well as predict the impact of the changes on concentration of Weak Acid Dissociable cyanide in plant tails , the pair said . This allows cyanide detox costs to be accurately predicted , resulting in more precise knowledge of the overall costs and benefits of any changes .
The final enhancement to LeachIT is its ability to model systems that have a number of ore types processed at the same time . This allows for optimisation of process conditions for various ore mixtures that require different optimum process conditions .
Martin and Zwolak concluded : “ With customers already taking advantage of the improvements , Orica believes customers can substantially improve profit by increasing the percentage of gold recovered from the ore and reducing operating expenditure . This is all achieved by reducing the time , cost and accuracy of the predictions .”
Chemical challenges
Beyond cyanide use , there are a plethora of chemical companies looking to solve industry challenges , with one of the frontrunners in this sector-wide problem-solving being Belgiumbased Solvay .
The company has made a living off providing clean chemicals that improve recoveries and environmental impact , while reducing impurities .
It has recently been advancing the commercialisation of its next-generation sodium hydrosulphide replacement technology , the AERO ® NR 7361 depressant , which has a role to play in today ’ s and tomorrow ’ s copper operations .
It explained : “ Copper mines contain valuable by-products within their ore that contribute to a mine ’ s overall economic performance . Ores with both copper and molybdenum need to be concentrated together into a bulk flotation concentrate before being separated from one another prior to further processing .”
Molybdenum is commonly separated from copper using sodium hydrosulphide ( NaSH ), yet mining operations often dislike the use of NaSH due to the smell , risk of exposure to highly toxic hydrogen sulphide gas , high treatment cost , performance deficiencies when treating difficult ores and logistical challenges in handling large volumes , according to Solvay .
Eammon Guitard , Mineral Processing Marketing Manager at Solvay , said : “ The mining industry is continually looking to reduce hazards in the workplace and minimise potential exposures for employees . Sustainability is clearly a driver for major mining companies as they look to reduce risk around hazardous chemicals .”
Solvay previously introduced its AERO 7260 HFP depressant technology as a safer and sustainable alternative to NaSH . While well received and in commercial use globally , the depressant was only able to replace up to 60 % of the NaSH , the company admitted .
The industry wanted more , according to Esau Arinaitwe , Mineral Processing Innovation
52 International Mining | MAY 2021