FR2519962A1 - PROCESS FOR PRODUCING TUNGSTEN OXIDE - Google Patents

Abstract

A.PROCESS OF MANUFACTURING TUNGSTENE OXIDE. B. PROCESS CHARACTERIZED BY HEATING THE CONCENTRATE IN REACTOR 2 TO A TEMPERATURE HIGHER THAN THE BOILING POINT OF TUNGSTEN OXIDE. C. THE INVENTION APPLIES TO THE MANUFACTURE OF TUNGSTEN.

Description

1996 2

  The present invention relates to a process for producing

  of making tungsten oxide from a

  centered of an ore containing tungsten.

  Nowadays, the main source of tung-

  stene in the United States is the mineral scheelite which is

  a double oxide of formula Ca WO 4 (or Ca O 3 W 3 O)

  which can contain up to several percent of W 03, is converted using conventional crucible and flotation processes into a concentrate which can contain up to 70% of W 03. The theoretical concentration of W 03 in the compound Pure WO 4 is 80.52% Tungsten is traditionally separated from this concentrate according to one of the various processes such as acid removal,

  alkali roasting, caustic soda

  tick, a reaction with calcium carbonate and the

  These processes characteristically

  tick a solution of tungsten acid or a tungstate

  sodium; these compounds are then transformed into

  Pure ammorium tungstate (APT) according to a three step process Such processes are not only multi-step and long but often uneconomical processes.

  especially for low grade ores.

  In order to manufacture metallic tungsten, the APT compound is first converted to tungsten oxide (either W 03, W 02, or W 401 1) by heating in air at a temperature greater than 250 ° C. The oxide is then reduced with hydrogen to give the pure metal in form

  of powder in cla-ir, one could increase so

  the economic interest by developing a more direct path between the concentrate of scheelite in pure tungsten or in tungsten oxides.

  According to the invention, a method of manufacturing

  Tungsten oxide from a tungsten-containing ore concentrate consists of heating the concentrate in a reactor at a higher temperature.

  at the boiling point of tungsten oxide.

  Advantageously, the concentrate vaporizes the tungsten oxide while leaving the compounds in the solid or liquid state. The process according to the invention is less expensive than the known processes and thus it can be used to recover tungsten from minerals.

  of low quality where tungsten could not be ex-

  previously described economically While the known methods require several steps and discontinuously, the method according to the invention can be done

  continuously during a step, which simplifies

  the manufacturing process.

  An object of the invention is that the product may be better than the tungsten oxide obtained by the

  known processes in that it is thinner and purer.

  A doctoral thesis defended at the University of Limoges

  by Pierre Chaussade in December 1980 describes the evaporation

  tungsten from ores containing

  tungsten using a plasma arc.

  An article published by I G Sayce in International Symposium on Advances in Metallurgy and Refining Extractives, London, October 1971, describes the use of the so-called "fusion-quenching" plasma process.

  to break down various mixed oxide systems

  taking zirconium sand (Zr O 2 * Si O 2), rhodo-

  nite (Mn Of Si O 2) and ilmenite (Ti O * Fe O).

  The invention will be described hereinafter with the aid of an example with reference to the accompanying drawing consisting of

of a seple figure.

  According to the figure, the ore concentrate 1 containing tungsten enters the reactor 2 through the injector 3 The concentrate passes into the arc 4 formed by the arc heater 5 which releases

  tungsten oxide leaving a liquid coproduct.

  The liquid coproduct 6 is grouped at the bottom of the reactor and can be evacuated via the pipe 7. The oxide W 3 gas evolved by the arc passes through the pipe 8 to reach the quench chamber 9 which cools the gas and gives a solid powder. The solid product passes through the conduit 10

  to be collected in the filter 11.

  The process according to the invention can be used with any ore concentrate containing tungsten. A concentrate is obtained by crushing the ore to a particle size of less than 1 millimeter and floating the crushed ore on water. The

  ore that is sinking is then dried and serves as

  centered A typical concentrate contains between

  viron 30 and 70% W 03 (all percentages used

  in this description are percentages

  tungsten oxide in combination with oxides of iron, manganese,

  calcium and to a limited extent lead and copper.

  The main source of tungsten ore in the United States is scheelite which is a double oxide of calcium

  and tungsten Another important source of tungsten

  is not wolframite which is a double oxide of iron and tungsten Any ore containing tungsten can

  serve according to the invention if at least 50% of the co-product -

  tungsten concentrate is a solid or

  quide at the boiling point of the oxide W 03 cor-

  around 17001 C. In the practice of the invention, it is

  desirable that at least half of all co-produced products

  heated above the melting points,

  that a molten coproduct is easier to handle and to extract from the reactor Similarly, a liquid is less likely than the solid powder to be driven by the gaseous vein of W O because the droplets of liquid are subjected to

  coalescence phenomena and fall to the bottom of the reactor.

  For this reason, it is preferable to add a flux to the concentrate to lower the melting point

  of the co-product-melt blend and reduce the energy required

  As a non-fluxing example, the calcium oxide in scheelite melts at more than 2580 ° C. while with an agent melting at 30% P 205, the melting point Ca O-melt is lowered up

  about 18000 C Since it is also necessary to heat this

  However, it is necessary to relate the advantage of a point of

  lower melting and the disadvantage of the heating required.

  of the flux and the cost of the flux.

  product is calcium oxide, it is possible to use

  melting silicon dioxide, titanium dioxide, alumina, chromium dioxide, P 205 and other oxides. If the co-product is an iron oxide, it is not

necessary to use a fondant.

  The concentrate can be heated using a variety of means including fuels

  fossils and radiation, but it is better to use

  This means is the most efficient. A gas stream heated by an electric arc is used to heat the concentrate.

  air is the preferential arc heating gas then

  that the least expensive; other arc-heating gases such as nitrogen, argon, oxygen, dry steam, carbon dioxide could also be used. For air, the flow of gas arc heating is of the order of 3 to 8 normal cubic meters per minute and per megawatt (MW) preferably at a flow rate too low or too high that would result in heat loss The maximum temperature in the gas vein Arc heating may be of the order of 5,000 C but the most important temperature range is that of tungsten concentrate and the reactor collection chamber. These temperatures are set by

  the exact nature of the mixture introduced but must

  pass substantially 17001 C to vaporize the oxide W 03.

  The pressure is generally of the order of 0.5 to 5 bars.

  The concentrate may be introduced into the heating device with a carrier gas. Air is the carrier gas chosen preferably since it is the least expensive; however, it is also possible to use nitrogen, argon, oxygen, dry steam

or carbon dioxide.

  The quenching chamber transforms the oxide

  gaseous oxide WO 3 WO 3 The particle size

  of solid oxide W 03 can in some

  This means that larger oxide particles W 03 are obtained if the residence time in the liquid state is large. and small particles if the residence time of WO 3 oxide in the state

liquid is short.

  The oxide WO 3 collected can be treated in the form of metallic tungsten used in the filaments

  lamp or other high temperature applications.

  The oxide W 03 can also be treated with tungsten carbide which can be used as an abrasive and for cutting tools. Calculations have been made to substantially determine the energy required to obtain tungsten-35 oxide according to the process of the invention by means of an arc heater having a 75% yield, assuming that 80% of the tungsten oxide has been recovered and only 50% of the gas energy

  heated with the bow was exchanged with the ore

  terminated only for a 50% concentration of W 03 oxide of the scheelite type and without fluxing, a reaction temperature exceeding 26000 C is required; the energy demand is of the order of 6 KW hour / 1 kilogram of oxide W 03 If 30% of a suitable flux is added to the 50% concentration of oxide WO 3 of the scheelite type, the temperature can be lowered reaction at 1600-2000 C and the demand for

  energy is of the order of 8 KW hour / l kg W 03 If the

  Concentrated scheelite contains only 20% of W 03 oxide, and with a natural flux, the reaction temperature is between 1600 and 20000 C and the energy

  is of the order of 16 KW hour / l kg W 03.

Claims (2)

R E V E N D I C A T IO N S   1) Process for producing tungsten oxide from a tungsten-containing ore concentrate, characterized in that the   concentrated in a reactor (2) at a higher temperature   above the boiling point of tungsten oxide.   Method according to claim 1,   characterized in that the concentrate is heated in a   gas vein (4) heated by an electric arc (5).   Method according to claim 2,   characterized in that the gas heated by the electric arc   (4, 5) is air, nitrogen, oxygen, water,   gon, carbon dioxide, steam or mixtures of these gases.   The method of claim 2, wherein   in that the gas heated by the electric arc to a temperature which exceeds at least 1700 ° C and a pressure of the order of 0.5 to 5 bar.   Process according to any one of the   1 to 4, characterized in that the ore containing tungsten is scheelite.   Process according to claim 5, characterized   in that scheelite contains between 30 and 70% oxide weight W 03.   7) Process according to any one of the   Claims 1 to 4, characterized in that the ore is wolframite.   Process according to any one of the   dications 1 to 7, because it is acted upon by mixing a fondant ore concentrate.   90) Process according to any one of the   1 to 8, characterized in that the concentrate is mixed to a carrier gas.    The method of claim 9, wherein   characterized in that the carrier gas is air.   1 l) Process according to any one of the   1 to 10, characterized in that the heating temperature of the concentrate exceeds the melting point of at least   less than half of any coproduct present.   ) Process according to any one of   Claims 1 to 11, characterized in that it comprises   less an additional step of cooling the oxide W 03 in the solid state and in that the particles are collected W 03 solid.   ) Characterized in that it is   obtained by carrying out the process according to any one that claims 1 to 12. 4.