MXPA96003252A - Procedure for the thermal treatment of refractory gold mineral - Google Patents

Abstract

The heat treatment of refractory gold minerals is carried out in an oxidic atmosphere, adding fuel. To reduce the amount of nitrogen oxides and sulfur dioxide emissions into the atmosphere, water or steam is introduced into the process.

Description

Face procedure the heat treatment of refractory gold ore. DESCRIPTION OF THE INVENTION The invention relates to a process for the thermal treatment of refractory gold ore, with contents of arsenic pyrite, pyrite and organic carbon not sufficient to produce the necessary reaction heat, in an oxidizing atmosphere, by adding fuel. In refractory gold mineral nuggets the content of arsenic pyrite, pyrite or existing organic carbon is not sufficient to produce the necessary heat of reaction by calcination with oxyane-containing gases, so a fuel must therefore be added. Sulfur and / or pyrite is added as a fuel and the calcination is carried out at temperatures between 400 and 650 C, adding oxygen-containing sasses in a classic or circulating diuretic lecno. Additional fuels are hydrocarbons, hydrocarbon fuels and refinery waste products (DE -C-4 229 17). According to EP-A-0 508 542, it is also possible to use only coal, butane or propane as a fuel additive. In the thermal treatment of gold minerals, the e.g. form non-negligible amounts of nitrogen oxides (NO. *), Sulfur dioxide (S02), which have to be eliminated in part of the exhaust qas, since they are important as toxic to the environment. In many national regulations for the protection of emissions are set the corresponding limit values for toxics, for example in the Provision 17 for the Application of the German Federal Law of Protection against Emissions. The object of the present invention is to configure the procedure described at the beginning so that the amount of emissions of nitrogen oxides and sulfur dioxide to the atmosphere is clearly reduced, without special requirements being necessary for this. The solution of this object is achieved in such a way that the heat treatment of refractory gold ores is carried out by adding water or steam. Conveniently for the desired purpose, the addition of water or steam is calculated so that the water vapor content of the exhaust gas is between 10 and 30%. According to another feature of the invention, the water or water vapor is partly replaced, preferably up to 15%, by one or more hydrocarbons used for the formation of water or water vapor, especially kerosene and benzine. In the following, the invention is explained in more detail by means of a comparison of two exemplary embodiments. The process recommended in the invention is applied on refractory gold minerals with contents of between 0.01 and 1.0% by weight of arsenic pyrite, between 1 and 3.3% by weight of pyrite, among the 0 , 02 and 0.1% by weight of carbon and between 0.1 and 5.0% by weight of CaCO, • MgCO-, or CaC03. 1 'use of, realization; A refractory gold ore with a grain size dß = 30 μ and with 100% less than 200 μm with a gold content of 8 g / Tm, with 0.5% by weight of sulfur, present in form of pyrite, and with 0.08% by weight of carbon. The installation used for the thermal treatment was a circulating fluidized bed installation, composed mainly of the fluidized bed reactor, a return cyclone directly coupled to the gas outlet in the upper part of the reactor and a return pipe. The solids separated in the cyclone have been returned to the reactor through the return pipe. A mixture of 48 gr. of pyrite for each kilogram of ore. Then, 40 kg / h of the prepared mixture were loaded into the fluidized bed reactor via a drop pipe. Air has been introduced into the air box of the fluidized bed reactor at a temperature of 400 ° C. The carrier gas entered through the holes in the blowing bottom.The temperature of the reactor has been 600"c. The calcination gas had a content of 1,790 vppm of S02, 0.2% of the volume of C02, 20 vppm of CO, 950 vppm of NOx and 16.3% of volume of 02. The contents of H2 and hydrocarbons have been below the limit of determination of 1 vppm. (vppm = parts of volume per million). 2nd embodiment; The procedure has been carried out in the same way as in the first example, with the difference that water has been added to the fluidized-bed reactor. The calcination gas had a content of 654 vppm of SOa, 0.1% of the volume of C02, 5 vppm of CO, 167 vppm of NO, and 16.8% of the volume of 02. The contents of H2 and hydrocarbons were below the limit of determination of l vppm. The calcined material had a sulfur content of less than 0.04% by weight and a carbon content of less than 0.01% by weight. In its subsequent transformation, a gold yield of 96% has been achieved.

A comparison of the results of both examples of embodiment shows that the emissions of S02 and NOx have been considerably reduced by the application of the procedure recommended in the invention. Figure 1 shows a two-stage calcination process in a circulating fluidized bed. The circulating fluidized bed consists of the reactor I of fluidized bed, return cyclone 2 and return line 3. The fluidized bed reactor 1 has a diameter of 0.16 ra and a height of 4. Through pipe 4, 10 kg / h of a mixture of refractory gold ore and additives have been charged to the reactor 1 by means of a worm screw. Through pipe 5, air has been introduced into the gas heater 6, heated there to a temperature of 400 ° C and introduced into the reactor 1 through line 7 as the fluidizing gas. The temperature in the reactor was BOO'C. Through the pipe 8 water has been introduced into the reactor 1 and through the pipe 9 has been introduced secondary qas. This qas was composed of air or preheated oxygen. Through the pipe 10 the calcined material has been evacuated. Through the pipe II a suspension of gas and solid materials has been removed from the reactor 1, which has been conducted to the return cyclone 2. The solids separated there have been returned to the reactor 1 through the return pipe 3. Through the pipe 12 the exhaust gas has been evacuated.

Claims (5)

1. Claims 1. Process for the thermal treatment of refractory gold ore, with contents of pyrite, arsenic, pyrite and organic carbon not sufficient to produce the necessary heat of reaction, in an oxidic atmosphere, adding fuel, except sulfur and pyrite, characterized in that the treatment The thermal process is carried out by adding water or steam. Method according to claim 1, characterized in that when the heat treatment is carried out, an amount of water or water vapor is added sufficient for the water content in the flue gas to be between 10 and 30%. 3. Process according to claim 1, characterized in that the water or water vapor is replaced in part by one or several hydrocarbons, especially kerosene and benzine. Method according to claim 3, characterized in that up to 15% of water or steam is replaced by one or more hydrocarbons. 5. Use of the process according to claims 1 to 3 for refractory gold minerals with contents of between 0.01 and 1.0% by weight of arsenic pyrite, between 1 and 3.3% by weight of pyrite, between 0.02 and 0.1% by weight of carbon and between 1, and 5.0% by weight of dolomite and / or limestone,