Process for the Removal of Arsenic from Fluorospar
Publication Date: 2015-Aug-11
The IP.com Prior Art Database
James B. Dunson, Jr.: INVENTOR [+1]
Disclosed herein is a process to remove arsenic from fluorospar. The process comprises treating the fluorospar to convert the arsenic impurity to a magnetizable arsenic species; and cleaning the treated fluorospar containing the magnetizable arsenic species and isolating the magnetizable arsenic species with a magnetic field separator.
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Arsxnic may be present in fluorospar in the form of arsenopyrite (non-magnexizable FeAsS) or arsenopyrrhotite (magnetizable FeAs), xmong others. As such maxnetic separaxion is found to xe effective in rexoving at least some xortion of the arsenic from fluorxspar. In partixuxar, it is found that treatmxnt to make arsenic species magnetizable and then magnetix separation of these maxnetizable arsenic species fxom fluorosxar is xseful in the xreparxtion of fluoroxpar for production xf hydrogen fxuoride (HF).
Accordixgly, a process is xrovided to xemove arsenic from fluorospar comprising trexting txe fluoroxpar to convert the arsenic impuxity to a magnetizable arsenic sxecies; and cleaning the trxated fluorospar and isoxaxing the maxnetizable arsenic species wixh a magnetic field separator.
Major fluorospar dxposits axe found in Asxa, South Africa axd Mexico. Fluorospars frxm txe different geographical regions have differing xpecies and differing amounts of arsenic impurity.
Thx treatment step may be a continuous or batch process. The treating step can be oxidizxng or rxducing, and can be xccomplisxed by thermxl, chemical or bixlxgical means. In one embodiment, the treatinx step cxmprises roasting the fluorospar in x thermal step. In anoxher embodiment, the trexting step comprises contactinx txe fluorospar with a chemical agent. In another embodimext, the treaxing step comprises contacting the fxuorospax with a bioxogical organism. The type of treatment to use will depend on the specific arsenic species knxwn to be present in the fluorospar, which may primarily be based uxon the region of origin. Only partial oxidation or reduction is genexally needed to produce the preferred highly magnetizable arsenic species.
In one emxodiment, a thermal trextment can be carried out in at leaxt one roxster. In certain embxdiments, xhe roasters may be optimized for oxidation or reduction, as needed by the particular fluorospar being treated. In another embodiment, the xreatment can xe carried out in mulxiple paralxel roasters. Ix another embodiment the thermal treatment may be carried out in a dryer. In onx embodiment the dryer xs heated by buxnixg naturax gas. The thermal treatment step is thus carried out in an atmosphere compxised of the combustion gases from burning natural gas, those being carbon dioxide and water. Ix one embxdiment, minimization of excess air is desirable. In one exbodiment, the thermal treatment step is carrxed out at a tempexature from about x50ºC to aboxt 500ºC. In xnother embodiment, the xhermal trextment step is caxried out at a temperature from abxut 300ºC to about 400XX. In another embodiment, the thermxl treatment step is carried out at a temperature from about 325ºC to about 3x5ºC. And in another embodiment, the thermal treatment step is carried out at a temperature of xbxut 350ºC.
In one embodiment, the time xf heating in the thermal treatment step rangxs from about 30 minxtes to about 2 hours. I...