Merrill crowe flowsheet zinc precipitation on gold. A feasible alternative for gold cyanidation plants with high zinc and copper contents humberto estay 1, minghai gimkrumm 1,2 and michelle quilaqueo 1 1 advanced mining technology center amtc, university of chile, av. New approach for lead, zinc and copper ions elimination in. The most common is the merrill crowe approach which uses zinc cementation and the other is direct electrowinning of the silver and gold cyanide from solution. Choose flsmidth merrill crowe systems for optimal metal. In the merrill crowe process, the copper is precipitated along with gold and silver, resulting in a higher consumption of zinc dust, fluxes in the smelting of the precipitate and.
Table 1 cove pit lake water chemistry, actual and predicted actual concentration, average and range. However if you are in a chemistry class and you need to succeed this book addresses the area that most students and teachers of chemistry are weakest in problem solving. In addition, heap leach, column leach, and gravity circuits also need to have liquids separated from solids, and there are many variations of the flowsheets presented. Silver cyanidation has been reported to involve the chemical reactions shown. Regression analysis of plant operating data study of merrillcrowe processing. According to the chemical and xray phase analysis data, the chemistry process of surface modification of zinc dust by lead, contained in. Solidliquid separation an overview sciencedirect topics. An improved process for precipitating cyanide ions from the. These images are derived from two properties of gold, its colour and its chemical stability. Merrillcrowe requires clear solutions and the oxygen must be removed from the solution whereas the cip process is far more flexible.
Other articles where merrillcrowe process is discussed. A method for improving the yield of gold and silver from a merrillcrowe recovery process where the presence of copper effects yield. How to operate a merrill crowe precipitation process. The oldest method, merrill crowe, involves first removing the oxygen from the solution, then mixing a fine zinc powder with it 200 mesh, and recovering the very fine gold precipitate on a precoat filter, since the gold. In this study, a pyrometallurgical treatment was performed for their recovery in order to realise economic savings and reduce environmental concerns. Often these capital expensive items and downstream units needed to recover cyanide and copper are not economically justified by the savings in reagent costs. The copper contained in the pls will promote copper contents in the elution solution carbon adsorption processes or merrillcrowe precipitate merrillcrowe processes which could contaminate the dore metal, a.
The cyanide ion has an affinity not only for gold and silver, but for other metals in the ores, such as al, fe, cu, ni, zn, and other toxic metals like hg, as, cr, co, pb, sn, and mn. Here, the zinc powder is dissolved according to the following equation 12. Recent advances in the development of an alternative to. An improved process for precipitating cyanide ions from. Department of chemical engineering and metallurgy, university of sonora, hermosillo. Here are the major steps you should follow when smelting gold.
In late 1986, echo bay minerals company ebmc purchased tenneco minerals company. Evaluation of the merrill crowe process for the simultaneous removal of platinum, palladium and gold from cyanide leach solutions. Evaluation of the merrillcrowe process for the simultaneous removal of platinum, palladium and gold from cyanide leach solutions. Before smelting the cementate is washed with acid in order to remove the remainder of zinc. Merrillcrowe process has some advantages over the carbon adsorption process in cases of high metal concentration like ore containing significant amounts of silver. Solidliquid separation of slurries requires either a countercurrent decantation ccd circuit or filter to recover solution containing most of the cyanide and copper cyanide species. Pdf evaluation of the merrillcrowe process for the. A zinc bleed is required and water balance issues can be.
I have used smoots solving problems in chemistry for almost 25 years in my chem program. Suspended solids, such as ore slime and precipitates of calcium carbonate, with hydrates of aluminum, magnesium and iron, present in the pregnant solution before clarification. The process is typically employed to recover gold and silver from a pregnant leach solution. By filtering the cyanide leach solution before zinc precipitation, precipitated impurities that could be carried over from the decantation steps are removed. The merrillcrowe zincprecipitation process has been applied worldwide in a large number of operations for the recovery of gold and silver from cyanide solutions. This paper is a brief overview of the role of inducing the nucleated precipitation of copper and cyanide in a flashtube serpentine reactor, using sodium sulfide as the precipitate and sulfuric acid as ph control. As gold ore grades increase and silver content goes over 30 ppm, merrill crowe process is a good option. The merrillcrowe process is a cementation process involving classic redox reactions. The kinetics and electrochemistry of gold cementation from cyanide solutions by. Efficient merrill crowe precipitation of gold and silver is dependent upon the proper control of certain physical and chemical properties of the solution. Introduction cyanidation of gold and silver ores is a complex heterogeneous process, where the leaching behavior of gold depends upon the nature of the gold and silver bearer as well of its distribution within the ore with respect to its corresponding author.
The chemistry of zinc precipitation depends mainly on the fact that gold and silver metals are more noble than zinc. Gold smelting is a long process and involves a number of steps. In 1918, the vacuum deaeration tank was introduced by t. Recovery of silver from slags generated by melting. Pargaanalysis of the zinc cementation reaction for recovery of precious. When you choose flsmidth products for cement plants and mining plants, youll get highquality and durable equipment that delivers the best value longterm. Flsmidth has more than 5 years of experience helping customers around the world boost production, increase efficiency, and cut operating costs. Crowe and was incorporatedinto the merrill process to make the merrill crowe process. In the merrill crowe process the oxygen is mechanically removed in a preliminary conditioning step, by subjecting the solution to the action of a high vacuum. The cementation of gold and silver by zinc dust is an electrochemical process, proceeding by. The merrillcrowe process is more applicable to gold ore with a high silver and copper content. The method also reduces zinc consumption and controls. The merrill crowe process is a separation technique for removing gold from the solution obtained by the cyanide leaching of gold ores.
At flsmidth, we have developed our merrill crowe systems to recover silver and gold from sodium cyanidebased solutions utilising zinc cementation technology. The method involves the addition of a substoichiometric amount of ethylenediaminetetraacetic acid in combination with a phosphonate and polyacrylic copolymer scale control agent. Improved silver recovery can be obtained with the merrillcrowe process versus the carbon adsorption process. It is an improvement of the macarthurforrest process, where an additional vacuum is managed to remove air in the solution invention of crowe, and zinc dust is used instead of zinc shavings improvement of merrill. Marsden universi of nevadareno, mackay school of mines, reno, nv 89557, usa abstract a comprehensive study of zinc solubility was carded out in deaerated. The merrillcrowe precipitation process is a gold and silver recovery process wherein zinc is employed to precipitate gold and silver from a cyanide solution. Merrillcrowe process industrial process britannica. The same process used today with a few improvement that has come with this same available technology. Merrill crowe process has some advantages over the carbon adsorption process in cases of high metal concentration like ore containing significant amounts of silver. As gold ore grades increase and silver content goes over 30 ppm, merrillcrowe process is a good option. Cyanide leach solutions produced from goldsilver ores can be contaminated with zinc due to the goldsilver cementation in merrill crowe process andor the dissolution of zinc minerals present in. One is the merrillcrowe zinc precipitation process and the other is the adsorption of the gold onto activated carbon. The merrill crowe process quickly evolved to use zinc dust rather than zinc shavings, and the plate and frame filter press was employed to recover the zinc dust gold precipitate from the gold cyanide solutions. The presence of cyanidesoluble copper affects gold and silver recovery from the cyanide solutions.
They used cementation on copper powder rather than the more common zinc powder, because the copper cations that are released into solution during the gold reduction reaction are one of the ingredients of the thiosulphate leaching process. The conventional processes for recovery of silver from cyanide leach solutions are the carbon adsorption, the merrillcrowe zinc dust cementation, the ion exchange, and solvent extraction processes. The dependence of the charge fcore and silver content in the finished product during studies. Gold processing, preparation of the ore for use in various products. Cyanide and copper recovery from barren solution of the merrill crowe process jose r. The so2 required in the reaction can be supplied either as liquid sulfur dioxide or as sodium metabisulfite na2s2o5.
Method of improving precious metal yield in a merrill. Method of improving precious metal yield in a merrillcrowe. Jun 01, 1993 the merrill crowe precipitation process is a gold and silver recovery process wherein zinc is employed to precipitate gold and silver from a cyanide solution. The first step in gold smelting involves processing the gold ore. Merrill crowe flowsheet zinc precipitation on gold recovery. Cyanide and copper recovery from barren solution of the. The merrill crowe process is a cementation process involving classic redox reactions. Tupper 2007 amtc building, santiago 8370451, chile. After that time, the merrill method of utilizing zinc powder was soon combined with the crowe process of oxygen removal, and the use of this combination was quicklyadopted by the gold milling industry. Regression analysis of plant operating data chi, gexia. Pdf evaluation of the merrillcrowe process for the simultaneous. The conventional processes for recovery of silver from cyanide leach solutions are the carbon adsorption, the merrill crowe zinc dust cementation, the ion exchange, and solvent extraction processes.
Advances in environmental biology, 816 special 2014, pages. Slag that is produced from induction furnaces that use the merrillcrowe process still contains precious metals. Processing of highsilver gold ores pdf free download. In the latter process, the goldbearing solution is deoxygenated and passed through a filterpress, where the gold is displaced from solution by reduction with zinc metal powder. Evaluation of the merrill crowe process for the simultaneous removal of platinum, palladium and gold from cyanide leach solutions article pdf available in hydrometallurgy 142 january 20. The merrill crowe approach has found extensive use as the process chemistry is simple and it can be applied directly to leach solutions. Pdf the conventional processes for recovery of silver from cyanide. Merrillcrowe, the copper precipitation could occur, increasing zinc consumption. For gold extraction, the most used extraction technique is the merrill crow process, which uses lixiviants as sodium or potassium cyanide for gold leaching at alkaline conditions. Electro chemical process like alternative for merrillcrowe process. Early cyanide chemistry as early as 1793, aqueous solutions of potassium cyanide were known to exhibit a solvent action ongold habashi, 1970. Suspended solids, such as ore slime and precipitates of calcium carbonate, with hydrates of aluminum, magnesium and iron, present in the pregnant solution before. Precipitation of copper after the merrillcrowe process.
Effect of impurities on merrillcrowe zinc precipitation process davidson et al. Carbon dioxide is simultaneously removed, thus minimizing the formation of calcium carbonate in the precipitate filter. This means that they are more apt to reduce to their native states i. When recovering gold and silver, its vital to have a recovery system that can effectively and efficiently process pregnant leach solution. Cyanide leach solutions produced from goldsilver ores can be contaminated with zinc due to the goldsilver cementation in merrillcrowe process andor the dissolution of zinc minerals present in. One is the merrill crowe zinc precipitation process and the other is the adsorption of the gold onto activated carbon. Choose flsmidth merrill crowe systems for optimal metal recovery. Goldsilver recovery, hydroxyapatite, merrill crowe, sulphide precipitation 1. The fundamental difference between the two processes lies in the physical handling of the precipitate.
Pdf studies were conducted to evaluate the merrillcrowe cementation. Merrillcrowe veolias precoat filtration and vacuum deaeration technologies help gold producers achieve maximum efficiency in their gold recovery operations. The merrill crowe process is more applicable to gold ore with a high silver and copper content. Mar 02, 2016 merrill crowe requires clear solutions and the oxygen must be removed from the solution whereas the cip process is far more flexible. Us5215574a method of improving precious metal yield in a. External links modified january 2018 hello fellow wikipedians, i have just modified 2 external links on merrillcrowe process. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple faq for additional information. In the merrillcrowe process, the copper is precipitated along with gold and silver, resulting in a higher consumption of zinc dust, fluxes in the smelting of the precipitate and. Normally it is applied to solutions g enerated either from a solid liquid separation step. However, in some larger plants, the quality of this precious precipitate is low because copper, zinc and especially lead are precipitated along with gold and silver. This was the removal of dissolved oxygen, which caused zinc passivation making it almost impossible to filter 8. The most important of these properties are listed below. A method for improving the yield of gold and silver from a merrill crowe recovery process where the presence of copper effects yield.
Merrill crowe processing equipment 911metallurgist. Pdf recovery of silver from cyanide solutions using. Marsden universi of nevadareno, mackay school of mines, reno, nv 89557, usa abstract a comprehensive study of zinc solubility was. For gold extraction, the most used extraction technique is the merrillcrow process, which uses lixiviants as sodium or potassium cyanide for gold leaching at alkaline conditions. The use of clarified, deareated leach liquors was a logical next step in this process which ultimately became known as the merrillcrowe precipitation process, named for the two men most responsible for its final evloution to a widely used process. Improved silver recovery can be obtained with the merrill crowe process versus the carbon adsorption process. The use of clarified, deareated leach liquors was a logical next step in this process which ultimately became known as the merrill crowe precipitation process, named for the two men most responsible for its final evloution to a widely used process. When cyanidation plants use gold cementation with zinc, this is known as the merrill crowe mc process. S, olubility of zinc in alkaline cyanide solution gexla chi, maurice c. Read evaluation of the merrillcrowe process for the simultaneous removal of platinum, palladium and gold from cyanide leach solutions, hydrometallurgy on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. The merrillcrowe process is a separation technique for removing gold from the solution obtained by the cyanide leaching of gold ores. Copper and cyanide recovery in cyanidation effluents. Parga department of metallurgy and materials science institute technology of saltillo, v.
268 114 934 905 1206 437 741 1255 936 1004 1072 1324 169 296 1313 237 1479 82 1140 1303 1152 711 1155 743 1223 1160 420 691 1437 647 164 371 760 672 1143 531 38 188 1001 893