US1018609A - Process for roasting ores. - Google Patents

Description

UNITED STATES PATEN OFFICE.

CHARLES GABRIELLI, OF PARIS, FRANCE.

YROCESS FOR BOAS'IING OBES.

1,018,609. No Drawing.

is a sulfid, it is generally necessary to first roast the ore so that a compound of the metal will be formed which is soluble in water or in a solution of an acid. In other cases, the ore is first roasted to obtain the metalloid combined with the metal and the residue is then treated to recover the metal contained therein. Let us take for examplethe more complex case of copper pyrites, which is roasted with a View to the production of sulfuric acid and consider the general operations: employed for the recovery of the copper. As is known in the manufacture of sulfuric acid either by the lead chamber process or by the contact process, the copper pyrites is usually roasted in Maletra or mechanical furnaces, the Maletra-furnaces -being used for ores which are poor in sulfur. To obtain a good yield of acid, it is necessary to carry on the roasting in a manner which will give a fixed composition of gas, but in this case the residue is not in a good condition for the recovery of the copper. Thus when the residue of the copper pyrites from the furnace is treated by the wet-' process, after being roasted in any usual manner it still contains some quantity of copper in an insoluble state and also a quan tityof iron passes into the liquor and adds to the amount of iron which is precipitated so that a very impure precipitate is obtained. To avoid these inconveniences many processes are employed in practice such as treatment with a chlorid or with a sulfate such as ferric sulfate or ferrous sulfate, or with sulfuric acid and the like. These treatments consist in grinding the residue of Specification of Letters Patent. Application filed. November 15, 1910. Serial No. 592,587.

Patented Feb. 27, 1912.

the roasted pyrites to either mix it with a chlorid having a lower temperature of dissociation than the temperature of the formation of cupric chlorid CuCl or to mix it with ferric or ferrous sulfate or with sulfuric acid or the like. The mixture is then placed in a special furnace where the reaction takes place at a temperature between 400 and 500 C. These known methods assist in giving a better yield of metal, but they leave nevertheless a considerable quantity of the metal in the residues; besides the carrying out of.the difl'erent operations is very expensive.

The object of the present invention is a process of roasting the pyrites or sulfid ores, matte, or the like which will give, at the same operation and direct from the pyrites residue, a compound of the metal which is soluble in water or acid solution and thus nearly all the metal can be extracted by the wet process without submitting the pyrites residue to any further reactions, treatment or roasting.

This process consists in adding a certain quantity of green pyrites to the dead roasted pyrites on a hearth or at a part of the roasting furnace where thetemperature is between that which is necessary for the formation of the sulfates of the metal to be sepa rated and that at which the said sulfates decompose. Thus in the case where greater heat is required for the formation of the sulfate which it is desired to dissolve than is necessary for the formation of the sulfate to be kept insoluble, the hearth or that part of the furnace where the green pyrites is added to bring about the production of the sulfate, must be at a lower temperature than that which would decompose the sulfate of the metal which it is desired to dissolve in water or in an acid solution but it must have a higher temperature than that at which the sulfate of the metal which it is desired to keep insoluble will decompose. In the opposite case that is to say, when less heat is required for the formation of the sulfate of the metal to be dissolved than is necessary for the formation of the sulfate ofthe metal desired to remain insoluble, the

temperature of the hearth or of thepart of the furnace at which the formation\of the sulfates takes place, should be higher than the temperature required for the formatlon of the sulfate of the metal to be dissolved but lower than the temperature required for recovering from it the metals contained in the residue.

The process described produces a particular chemical action by the, introduction and bringing about of a new reaction during the roasting of the .pyrites, z. e., the production of a sulfate at a particular point of the furnace and at a temperature which is determined by thetemperatures at which the sulfates of the metal to be separated are formed or decomposed. Moreover this rocess produces new technical results an has the following practical and industrial advantages. The yield from the pyrites thus roasted is higher than at present as practically the whole is converted into sulfate and almost all the metal contained therein is extracted and recovered by the wet process, the yield varying from 90% to 100% according to the nature of the ore. There is no need of any further treatment of the residue as is the case with the other processes but the sulfate is separated by the wet process -directly from the residue obtained by asingle roasting. It does not disturb the arrangement of the chambers when it is desired to obtain the metalloid. Moreover in consequence of the elimination of the costly processes and the increased yield this process is very economical and advantageous.

To better explain the idea of the invention I will hereinafter describe by way of example the application of the process, to the complex case of the roasting of copper pyrites in a Maletra-furnace with the ob ect of obtaining sulfuric acid or recovering the copper.

Practlcally all the metals can be turned directly into sulfates in the furnace if the reaction obtained by the addition of green pyrites is carried out at the right temperature.

In order to obtain the copper as a sulfate the residue of the pyrites must not be heated to the decomposing point but the temperature has to be kept at the degree at which the sulfate of iron will decompose while the sulfate of the copper will not be influenced. Thus practically all the copper can be changed into sulfate by adding green pyrites to the dead roasted pyrites at a determined the sul ur is practically complete and where the pyrites 1s heated to the temperature which is necessary for the artial change into sulfate, 2'. e., into the su fate of one of the two metals to be separated, it is possible to carry out this rocess in any ordinary roasting furnace. suppose that in a furnace of the Maletratype the favorable place for obtaining the sulfate ofsthe copper is the fifth hearth. This reaction can therefore take place at this precise part.

The roasting carried out according to this invention will result in obtaining nearly all the copper as a sulfate in water or in an acid solution, nearly all the ironremaining insoluble. By this process the iron and copper in the pyrites are first changed into oxids and from the oxids the sulfates are produced by adding green pyrites on the hearth or the part of the furnace where the temperature is higher than that at which the sulfate of iron will decompose but lower than that bus for example let us treatment of the residue as the reaction takes place in the furnace during roasting without interfering with the working of the chambers.

I claim 1. A process for roasting pyrites, ores, matte, residues and the like containing sulfur in order to separate one or more of the metals contained therein, consisting in adding green pyrites to the dead roasted pyrites at a part of the furnace where the temperature is between that required for the formation of the sulfates of the metals to be separated, and the temperature at which said sulfates decompose, substantially as described and set forth.

2. Process for separating copper from perature at which the sulfate of iron is pyrites, matteand the like, consisting in formed, substantially as described and set adding green pyrites during the roasting to forth.

the dead roasted'pyrites when the same is at CHARLES GABRIELLI. 5 a part of the furnace where the temperature In presence of is lower than that at which the sulfate of the H. G. Coxn,

copper decomposes but higher than the tem- VICTOR MARENDOWSKI.