The variability of the incoming materials shows considerable changes and due to a nervous and competitive market the gold refinery must be flexible in order to respond to qualitative and quantitative variations. This effect tends to modify and change the perspective of gold refineries. According to some market studies, the gold quantity of gold extracted on the planet is close to 150 millions of tonnes and every year adds a new quantity. There is a primary gold recycled from refineries and the production per year is around 500 tonnes. The current capacity of gold refining tends to exceed the total production and this consideration leads to an important competitive situation in the market and especially in the refineries located outside of the gold operations. Probably, this is the situation of some refineries in Europe that are used to treat and recycle precious metals scraps, dishoarded bars, low purity bars and non-accredited bars.
The production of Dore bars produced in North America, South America and Africa has grown the last years. The terms of high grade mine Dore are relatively close to the production costs. This very poor profitability is not acceptable on long term and gold refineries must look for more complex and profitable materials to be refined. In this way, gold refineries have to improve constantly their equipment in order to maintain high levels of efficiency; otherwise the profitability will not be optimum.
It has been noted that the added value of the gold refining operation is low compared to the real value of the refined material. Basically, the immobilization cost is important and can be as high as the operating costs themselves. Gold interest rates can fluctuate largely as a consequence of international market conditions over which a refiner lacks control. Normally, a gold refinery has to operate in such way that financing of the precious metals inventory does not become an uncontrolled cost when gold interest rates are very high. For this reason is important to study and analyze the lowest mean residence time for the most valuable metals. For example, a three week turn-around is the usual market requirement for high grade Dore and the system must follow quickly the changes in volume. The tools required to have lower residence time are overcapacity, on-line controls, working time flexibility and no stocks between the steps.
Other factor involved is the environment. Essentially, the treatment costs for liquid and gaseous effluents have been more significant the last years. Probably, landfill costs for solid wastes produced by the refining operations. It has been noted that as the limits of emissions to the air and the water are more rigorous and the costs of landfilling becomes high, the waste plants are not of primary importance. For example, oxidation and reduction reactions of material in a gold refinery are performed using electrical energy and no chemical energy. Wet dissolution process with aqua regia has the main inconvenience to load the waste stream with nitrates and chlorides. Some metallurgists consider limiting this type of material and it could possible to apply other process such as evaporation or osmosis. In this way, emanation of nitrous gases will be limited. Gold refineries are used to produce large quantities of sludge with metallic hydroxides mixed with insoluble salts such as calcium sulphate. When a gold refinery plans to add new stages oriented to recover selectively precious metals, their cost must be lower than waste disposal. The idea is to minimize the production of residues and to maximize the output of valuable by-products.