US1103082A - Process of preparing pyritiferous zinc-blende for magnetic separation. - Google Patents

Description

UNTTED STATES PATENT @FFTCE.

GILBERT RIGG, 0F PALMERTON,

PENNSYLVANIA, ASSIGNOR TO NEW JERSEY ZINC COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

ioness,

N 0 Drawing. I

Specification of Letters Patent.

Application filed March 27, 1911.

Patented uly Mt, rare. Serial No. 617,211.

To all whom it may concern Be it known that I, GILBERT RIGG, a subject of the King of Great Britain, residing at Palmerton, county of Carbon, State of Pennsylvania, have invented certain new and useful Improvements in Processes of Preparing Pyritiferous Zinc-Blende for Magnetic Separation; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to a process for separating pyrite from zinc blende and other minerals with which it is associated, by first converting the pyrite into pyrrhotite or magnetic sulfid, with the simultaneous recovery of the sulfur in elementary form, and thereupon withdrawing the pyrrhotite from the zinc blende or other non-magnetic material by means of magnetic attraction.

In the usual method of converting pyrite F e8 into pyrrhotite, the ore is partially roasted in a current of air, and the endeavor is made to interrupt the roasting at a point when suliicient sulfur has been driven off to effect the desired conversion into pyrrhotite, whose formula varies somewhat but is usually given as from Fe,S to Fe s If the roasting is not continued long enough, a certainamount of non-magnetic pyrite is left unchanged, and if carried too far, nonmagnetic ferric oxid is produced, which is equally undesirable from the standpoint of effecting its subsequent separation. Moreover, there is a further objection to converting thepyrite of the ore into pyrrhotite by partially roasting in a current of air, in that the sulfur is driven off as SO mixed with large volumes of fire gases, so that the gas mixture is too dilute and too impure to be available for sulfuric acid manufacture. The gas mixture is, therefore, usually delivered into the air, and not only is the sulfur Wasted, but the gases thus discharged are very injurious to vegetation and cause much trouble.

By the practice of my invention, as hereinafter described, it is impossible to pass beyond the point of converting the pyrite into pyrrhotite or magnetic sulfid, and the sulfur is. recovered in the form of elementary sulfur or brimstone, all loss and nuisance being practically obviated.

In carrying the process into effect, I heat the pyritiferous ore ina mufile, or in a shaft, from which the fire gases and air are excluded. At temperatures ranging from 600 C. to 800 C. the pyrite gives up part of its sulfur, which passes over as sulfur vapor, and, leaving the muflie or shaft by suitable exit openings, is recovered in the form of elementary sulfur in a suitable condenser. The pyrite by this treatment, is converted into pyrrhotite or magnetic sulfid and may thereupon be separated from the zinc blende or other non-magnetic minerals with which it is associated, by means of a magnetic separator. As hereinbefore noted, it is a char acteristic feature of this method of treatment that it is impossible to pass beyond the point of converting the pyrite into pyrrhotite or magnetic sulfid. After it has been so converted, further heating has no effect upon it, unless the temperature is carried to such a degree as to fuse the charge, and this is easily avoided. Consequently, the heating'can be continued long enough to insure the complete conversion of the pyrite into pyrrhotite Without incurring any danger from over-roasting. his insures the ultimate withdrawal by the magnetic separator from the zinc blende or other non-magnetic constituent of the ore of practically all of the pyrite originally contained therein, with the incidental recovery of the elementary sulfur as a valuable by-product and the avoidance of injury to vegetation whichwould be involved in discharging the sulfurin the form of SO into the atmosphere.

Having thus described my invention, what I claim is:

1. The process of treating zinc blende associated with pyrite, so as to render said constituents capable of magnetic separation, which consists in expelling a portion of the sulfur of the ,pyrite by heating the pyritiferous ore at a temperature below the fusing point of the pyrite and below the dissociation point of the zinc blende, thereby converting the pyrite constituent of the ore into a magnetic condition as pyrrhotite, and without altering the zinc blende constituent; substantially as described.

2. The process of treating zinc blende associated with pyrite, so as to render said constituents capable of magnetic separation,

which consists in heating the pyritiferous carry the pyrite beyond the magnetic con- 10 ore, with the exclusion of air, thereby exdition; substantially as described.

pelling a portion of the sulfur of the pyrite In testimon whereof I aflix my signature, constituent of 318 ore and collliverting ithinto in presence of two witnesses.

a magnetic con ition as pyrr otite, the eating operation being conducted at atempera- GILBERT RIGG' ture below the fusing point of the pyrite, Witnesses: whereby said conditions of the operation HENRY HARDENBERGH, insure against such desulfurization as would E. G. TAOY.