CA1314149C - Methods of recovering arsenic values from waste - Google Patents
Methods of recovering arsenic values from wasteInfo
- Publication number
- CA1314149C CA1314149C CA 554182 CA554182A CA1314149C CA 1314149 C CA1314149 C CA 1314149C CA 554182 CA554182 CA 554182 CA 554182 A CA554182 A CA 554182A CA 1314149 C CA1314149 C CA 1314149C
- Authority
- CA
- Canada
- Prior art keywords
- arsenic
- arsenic trioxide
- particles
- trioxide
- values
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B30/00—Obtaining antimony, arsenic or bismuth
- C22B30/04—Obtaining arsenic
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B5/00—General methods of reducing to metals
- C22B5/02—Dry methods smelting of sulfides or formation of mattes
- C22B5/16—Dry methods smelting of sulfides or formation of mattes with volatilisation or condensation of the metal being produced
Abstract
ABSTRACT
A process for the recovery of arsenic values from arsenic containing material which may also contain sulphur, the process comprising the step of evaporating the arsenic values from the arsenic containing material into a gas stream which gas stream does not react with the arsenic values. A
process for the recovery of arsenic values from arsenic containing material which may also contain sulphur, the process utilizing electrical energy for evaporation of arsenic trioxide in an evaporator into a gas stream and after separation of arsenic trioxide and any residue, the clean gas may be recycled to the evaporator thus minimizing possible emissions permitting the process to be carried out in a closed circuit thus substantially eliminating emissions.
A process for the recovery of arsenic values from arsenic containing material which may also contain sulphur, the process comprising the step of evaporating the arsenic values from the arsenic containing material into a gas stream which gas stream does not react with the arsenic values. A
process for the recovery of arsenic values from arsenic containing material which may also contain sulphur, the process utilizing electrical energy for evaporation of arsenic trioxide in an evaporator into a gas stream and after separation of arsenic trioxide and any residue, the clean gas may be recycled to the evaporator thus minimizing possible emissions permitting the process to be carried out in a closed circuit thus substantially eliminating emissions.
Description
131414q FIELD OF INVENTION
This invention relates to methods of recovering arsenic values from arsenic bearing materials.
BA,C~OUND OF THE INVENTION
Ores containing arsenic have to be subjected to an arsenic removal step prior to the extraction of other values. A typical example is gold ore -arsinopyrite.
The removal of arsenic is most often accomplished by roasting.
When roasted, Arsenic is oxidized to As203, and at the roasting temperature leaves the Roaster as a vapour together with the oxidation products of Sulphur, - Sulphur Dioxide and Sulphur Trioxide. The presence of Sulphur oxides with Arsenic complicates the subsequent Gas Cleaning step, resulting in an impure (crude) Arsenic Trioxide dust being trapped in a bag-house, following precipitation from the gas stream by the addition of cold air.
The off-gas is usually discharged to the atmosphere with consequent environmental problems.
A major consumer of Arsenic Trioxide (As203) is the wood preservative industry. Since As203 from the roasting operation is not of a sufficient purity, a further refining step has to be employed.
Refining is usually accomplished by one of two approaches:
(a) Hot Water Leach, by one of two approaches.
(b) Ammonia Leach (a~ Hot Water Leach:
Approach 1 Hot water is used to dissolve the As203 from the crude feed material. Undissolved solids are separated from the solution by filtration, and the filtered solution is either cooled or evaporated in a crystallizer to form As203 crystals.
~k Approach 2 Due to the positive effect of temperature on solubility of As203, pressure leaching may be employed with a higher water temperature hence obtaining a higher solubility of As203. The cost of energy with this approach S is improved over Approach 1 but still remains very high.
(b) Ammonia Leach:
The Ammonia Leach process has an advantage over the hot water leach approach in that the solubility of As203 is higher in amrnonia solution.
However the only user of this process of which the inventor is presently aware has presently ceased operations due to technical difficulties.
Both approaches additionally have a common problem. Re-contamination of the residue is caused by a reaction between dissolved Arsenic and the Iron content of the residue, resulting in a slimy material which is difficult to filter. Since this residue contains in some cases significant amounts of precious metals, this is a serious problem. Further these approaches are generally complicated and have a high operating and capital cost.
U.S. patent 3923478 teaches pyrites-roast gas at 350-400 degrees C composed mainly of S02 with As203, iron oxide dust, S03, and other impurities being scrubbed in a closed system with a solvent (preferably aqueous) for As203. The product is obtained by concentration and crystallization and unwanted deposits formed are removed by dissolution in unsaturated As203 solution. Using systems in parallel and switching liquid flows makes possible continuous operation, it is alleged, with minimal solid or liquid effluent.
Thus a process and an apparatus is asserted as having been provided for recovering arsenic trioxide from a gas by washing out the oxide from the gas with a liquid having the ability of dissolving arsenic trioxide.
The purported invention is characterized that non-desired deposits in the apparatus formed in connection with a saturated solution are removed by ... ..... .
3 l 5 1 4 1 4 9 dissolution with an unsaturated solution of arsenic trioxide. See also corresponding Canadian Letters patent 1033538.
U.S. patent 4588564 relates to a process for recovering arsenic trioxide from scrubbing water used to scrub the flue gas of sulfide ore 5 smelting. The crude arsenic trioxide crystals collected from the scrubbing solution which contains plaster as an impurity are purified by treating with hydrochloric acid of a concentration of 50-150 g/l at a temperature not higher than 30C.
U.S. patent 4605812 purports to teach a process for the removal 10 of arsenic from gases whereby arsines are removed from streams of hydrocarbons or inert gases by contacting the streams with copper (II) chromite catalyst.
U.S. patent 4615731 purports to teach a hydro metallurgical process for treating a feed comprising an aqueous acidic solution containing 15 dissolved therein one or more precious metals selected from the group, platinum group metals and gold and one or more of the nuisance elements bismuth lead, tin, arsenic and antimony, to separate the precious metals from the nuisance elements comprising:
(i) treating the aqueous acidic solution with sulfur dioxide in 20 the presence of selenium and a halide to reduce and precipitate selectively selenium and precious metals, and (ii) separating the precipitated components from the remaining solution; thereby separating selenium and precious metals from the nuisance elements.
U.S. patent 4489046 purports to teach a method for converting an arsenic-containing waste product to a depositable, substantially arsenic-free form by fuming-off the arsenic content thereof. The method comprises melting the waste product under oxidizing conditions in a furnace to form an oxidic slag melt; causing turbulence of the melt, while maintaining a reducing ` 30 atmosphere supporting the formation of arsenic (III) oxide at the furnace temperature driving-off arsenic content of the waste product substantially in the form of gaseous arsenic (III) oxide; separating the formed oxide by condensation and recovering the same and removing from said furnace a substantially arsenic-free depositable slag.
U.S. patent 4244735 purports to teach a process for the hydrometallurgical recovery of metals, such as, lead, silver, gold, antimony, and bismuth from materials such as flue dust in the presence of arsenic, comprising precipitating arsenic as an insoluble ferric-arsenic compound in the first processing step, carrying the insoluble arsenic compound through a chloride leach step, in which it is insoluble, to recover the metals, and disposing of the residue in which the arsenic has been fixed with ferric ions torender it non-polluting, or alternatively, recovering the arsenic by caustic leach and crystallization.
Swiss patent 273779 purports to teach a continuous refining process which it is purported, can be done more intensively and is carried out in equipment which consists of a lined vessel, screw feeder with a rotating discmounted on it and bearing fixed knives, screening plates. Silite heaters and a discharging screw, moving inside the vessel. The product to be refined is fed on to the rotating disc of the screw feeder having a sealed hopper. The distance between the cover and the disc is relatively small (i.e. 1/5 to 1/8 of the diameter of the disc), as a result of which uniform heating of the reaction zone is obtained and dust-formation of the incoming material is eliminated.
The product to be refined is fed on to the disc, which is red-hot (500-600 degrees C), and the Arsenic trioxide is purported to immediately begin to evaporate, which causes the original thickness of the layer of material to diminish. The solid residue, which comprises about 10% of the original material put on the disc, is removed by the fixed knife and the screw being conveyed to the hopper. In this way the disc is cleaned ready for the fresh deposit of material. The vapours of the trioxide go along into a crystallizer of ~ .
-s 1 31 4 1 4q the usual type. The device operates under minimum vacuum (0.5-1.0 mm of water column).
German reference 131850 purports to teach that Sulphur dioxide gases containing As203, halides and dust, are cleaned by washing with 5 circulating H2S04 solution of which the concentration is adjusted to such a low value that the halides are being dissolved, separating the H2S04 solution and subjecting this solution to a vacuum evaporation to evaporate the halides and crystalize As203. The purified H2S04 is recycled.
Once again these approaches are generally complicated and have 10 high operating costs and capital costs.
It is therefore an object of this invention to provide an improved process for the recovery of Arsenic values.
It is a further object of the invention to provide such process at reduced operating and reduced capital costs.
Further and other objects of the invention will be realized by those skilled in the art from the following Summary of the Invention and Detailed Description of Embodiments thereof.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a process is provided 20 for the recovery of Arsenic values from Arsenic containing material which may also contain Sulphur in one embodiment the Arsenic being in the form of As203, the process comprising the step of evaporating (in a wet or dry state) the Arsenic values from the Arsenic containing material into a gas stream which gas stream does not react with the Arsenic values. The gas stream is 25 then cooled to precipitate the Arsenic. The residue from which the arsenic was evaporated may then be treated for removal of the metal values. The simplicity of the process is reflected in relatively low operating costs and relatively low capital expenditures. Without the presence of Sulphur, the As203 vapour can be well cleaned of any carry-over solids (prior to 30 precipitation) giving a high purity As203 product, acceptable to for example the wood preserving industry. Preferably the evaporation of the Arsenic values is as arsenic trioxide (As203) near its boiling point.
According to another aspect of the invention the evaporation of the arsenic trioxide is performed in:
S (a) A chamber heated by a combustion of oil or hydrocarbon gas.
(b) Fluid bed heated by combustion of oil or hydrocarbon gas or by electrical energy.
(c) Electrical plasma reactor.
According to another aspect of the invention the arsenic values (for example the arsenic trioxide) are precipitated from the clean arsenic trioxide vapour containing gas in a fluidized bed of arsenic trioxide particles cooled by water evaporation. Thus the As203 is deposited on the surface of a cold particle causing it to grow to a form of little balls. The size of the balls of As203 may be controlled by the amount of precipitation onto the coarse particles. Thus "dusting" during handling of the "balled" material is reduced.
According to another aspect of the invention the process may be carried out u~ilizing electrical energy for evaporation of arsenic trioxide in an evaporator into a gas stream and after separation of the residue and precipitation of arsenic trioxide, the clean gas stream may be recycled back to the evaporator thus minimizing possible atmospheric emissions.
Thus, according to another aspect of the invention the process may be carried out in a closed circuit thus substantially eliminating emissions giVillg rise to substantial and significant environmental benefits.
According to another aspect of the invention the process may be carried out utilizing combustion of oil or hydrocarbon gas for evaporation of arsenic trioxide in the evaporator. Due to production of combustion products with this process the gas after cleaning can be vented.
-7- l 31 41 49 The invention will now be illustrated with reference to the following drawings of embodiments of the invention and the detailed description of the embodiments thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
S Figure 1 is a flow sheet illustrating a process carried out according to an embodiment of the invention.
Figure 2 is a flow sheet illustrating another process according to another embodiment of the invention.
Figure 3 is a flow sheet illustrating another process according to another embodiment of the invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
With reference to Figures 1 and 2, two processes are disclosed schematically according to the flow sheets. The difference between the processes relate to the energy source used to generate the heat in the evaporator to evaporate the Arsenic trioxide (As203).
With reference to Figures 1 and 2, the crude material containing arsenic trioxide 10 is exposed to heat in the evaporator 50. The arsenic trioxide vapour is transported from the evaporator 50 by a stream of other gas e.g. Nitrogen (See Figure 3) and the mixture leaves at a temperature of 250 - 500 degrees C (preferably 350 - 450 degrees C.) 12.
The evaporator 50 could be a:
(a) heated chamber - (for example for fine material which wouldn't stay in a fluid bed) (b) fluid bed heated by oil or hydrocarbon gas combustion, (Figure 1), or by electrical energy (Figure 2). The carry-over solids (residue) 24 are removed from the hot gas stream in a solids separator 52, preferably in a double filtration baghouse.
The separated residue 24, usually containing other metallic values is then available for further treatment as the major portion of arsenic was -8- l 31 41 49 removed. The clean gas 14 containing As203 vapour, or As203 vapour and water vapour and other gases, depending on the source of energy used in the evaporator, is then cooled in cooling and As203 removal section S4 by injection of water, preferably condensate 20 from the scrubbing circuit to a temperature:
(a) above boiling point of water (110-200 degrees C.) and the precipitated Arsenic trioxide is then removed in the cold baghouse.
b) just above point of Arsenic trioxide precipitation (depending upon concentration of arsenic trioxide in the vapour), generally between 300 degrees C. to 460 degrees C., and the precipitation is accomplished by further cooling in a fluid bed of Arsenic trioxide by spray of water (preferably condensate from scrubbing circuit) 20, to produce a desirable coarse product 26. (See Figure 3). The remaining gas is then scrubbed of Arsenic trioxide in a scrubber - cooler 56 and excess water vapour is condensed. The condensate 20 is recycled for cooling of the hot clean gas 14. The surplus 22 will be disposed of. The scrubbed cooled gas is then:
(a) recycled to the evaporator as Arsenic trioxide vapour carrier via 18 - if electric energy is utilized for heating of the evaporator.
(b) sent to stack. (See 18 of Figure 2).
With reference to Figures 1 and 2, equipment suitable for use (1) as the evaporator 50 may comprise:
(a) Fluid bed heated by an electrically preheated circulating gas.
(b) Fluid bed heated by inserted electrical heaters.
(c) Fluid bed heated by combustion of oil or hydrocarbon gas.
(d) Evaporation chamber heated by either electricity or by combustion of oil or hydrocarbon gas fine grained crude.
This invention relates to methods of recovering arsenic values from arsenic bearing materials.
BA,C~OUND OF THE INVENTION
Ores containing arsenic have to be subjected to an arsenic removal step prior to the extraction of other values. A typical example is gold ore -arsinopyrite.
The removal of arsenic is most often accomplished by roasting.
When roasted, Arsenic is oxidized to As203, and at the roasting temperature leaves the Roaster as a vapour together with the oxidation products of Sulphur, - Sulphur Dioxide and Sulphur Trioxide. The presence of Sulphur oxides with Arsenic complicates the subsequent Gas Cleaning step, resulting in an impure (crude) Arsenic Trioxide dust being trapped in a bag-house, following precipitation from the gas stream by the addition of cold air.
The off-gas is usually discharged to the atmosphere with consequent environmental problems.
A major consumer of Arsenic Trioxide (As203) is the wood preservative industry. Since As203 from the roasting operation is not of a sufficient purity, a further refining step has to be employed.
Refining is usually accomplished by one of two approaches:
(a) Hot Water Leach, by one of two approaches.
(b) Ammonia Leach (a~ Hot Water Leach:
Approach 1 Hot water is used to dissolve the As203 from the crude feed material. Undissolved solids are separated from the solution by filtration, and the filtered solution is either cooled or evaporated in a crystallizer to form As203 crystals.
~k Approach 2 Due to the positive effect of temperature on solubility of As203, pressure leaching may be employed with a higher water temperature hence obtaining a higher solubility of As203. The cost of energy with this approach S is improved over Approach 1 but still remains very high.
(b) Ammonia Leach:
The Ammonia Leach process has an advantage over the hot water leach approach in that the solubility of As203 is higher in amrnonia solution.
However the only user of this process of which the inventor is presently aware has presently ceased operations due to technical difficulties.
Both approaches additionally have a common problem. Re-contamination of the residue is caused by a reaction between dissolved Arsenic and the Iron content of the residue, resulting in a slimy material which is difficult to filter. Since this residue contains in some cases significant amounts of precious metals, this is a serious problem. Further these approaches are generally complicated and have a high operating and capital cost.
U.S. patent 3923478 teaches pyrites-roast gas at 350-400 degrees C composed mainly of S02 with As203, iron oxide dust, S03, and other impurities being scrubbed in a closed system with a solvent (preferably aqueous) for As203. The product is obtained by concentration and crystallization and unwanted deposits formed are removed by dissolution in unsaturated As203 solution. Using systems in parallel and switching liquid flows makes possible continuous operation, it is alleged, with minimal solid or liquid effluent.
Thus a process and an apparatus is asserted as having been provided for recovering arsenic trioxide from a gas by washing out the oxide from the gas with a liquid having the ability of dissolving arsenic trioxide.
The purported invention is characterized that non-desired deposits in the apparatus formed in connection with a saturated solution are removed by ... ..... .
3 l 5 1 4 1 4 9 dissolution with an unsaturated solution of arsenic trioxide. See also corresponding Canadian Letters patent 1033538.
U.S. patent 4588564 relates to a process for recovering arsenic trioxide from scrubbing water used to scrub the flue gas of sulfide ore 5 smelting. The crude arsenic trioxide crystals collected from the scrubbing solution which contains plaster as an impurity are purified by treating with hydrochloric acid of a concentration of 50-150 g/l at a temperature not higher than 30C.
U.S. patent 4605812 purports to teach a process for the removal 10 of arsenic from gases whereby arsines are removed from streams of hydrocarbons or inert gases by contacting the streams with copper (II) chromite catalyst.
U.S. patent 4615731 purports to teach a hydro metallurgical process for treating a feed comprising an aqueous acidic solution containing 15 dissolved therein one or more precious metals selected from the group, platinum group metals and gold and one or more of the nuisance elements bismuth lead, tin, arsenic and antimony, to separate the precious metals from the nuisance elements comprising:
(i) treating the aqueous acidic solution with sulfur dioxide in 20 the presence of selenium and a halide to reduce and precipitate selectively selenium and precious metals, and (ii) separating the precipitated components from the remaining solution; thereby separating selenium and precious metals from the nuisance elements.
U.S. patent 4489046 purports to teach a method for converting an arsenic-containing waste product to a depositable, substantially arsenic-free form by fuming-off the arsenic content thereof. The method comprises melting the waste product under oxidizing conditions in a furnace to form an oxidic slag melt; causing turbulence of the melt, while maintaining a reducing ` 30 atmosphere supporting the formation of arsenic (III) oxide at the furnace temperature driving-off arsenic content of the waste product substantially in the form of gaseous arsenic (III) oxide; separating the formed oxide by condensation and recovering the same and removing from said furnace a substantially arsenic-free depositable slag.
U.S. patent 4244735 purports to teach a process for the hydrometallurgical recovery of metals, such as, lead, silver, gold, antimony, and bismuth from materials such as flue dust in the presence of arsenic, comprising precipitating arsenic as an insoluble ferric-arsenic compound in the first processing step, carrying the insoluble arsenic compound through a chloride leach step, in which it is insoluble, to recover the metals, and disposing of the residue in which the arsenic has been fixed with ferric ions torender it non-polluting, or alternatively, recovering the arsenic by caustic leach and crystallization.
Swiss patent 273779 purports to teach a continuous refining process which it is purported, can be done more intensively and is carried out in equipment which consists of a lined vessel, screw feeder with a rotating discmounted on it and bearing fixed knives, screening plates. Silite heaters and a discharging screw, moving inside the vessel. The product to be refined is fed on to the rotating disc of the screw feeder having a sealed hopper. The distance between the cover and the disc is relatively small (i.e. 1/5 to 1/8 of the diameter of the disc), as a result of which uniform heating of the reaction zone is obtained and dust-formation of the incoming material is eliminated.
The product to be refined is fed on to the disc, which is red-hot (500-600 degrees C), and the Arsenic trioxide is purported to immediately begin to evaporate, which causes the original thickness of the layer of material to diminish. The solid residue, which comprises about 10% of the original material put on the disc, is removed by the fixed knife and the screw being conveyed to the hopper. In this way the disc is cleaned ready for the fresh deposit of material. The vapours of the trioxide go along into a crystallizer of ~ .
-s 1 31 4 1 4q the usual type. The device operates under minimum vacuum (0.5-1.0 mm of water column).
German reference 131850 purports to teach that Sulphur dioxide gases containing As203, halides and dust, are cleaned by washing with 5 circulating H2S04 solution of which the concentration is adjusted to such a low value that the halides are being dissolved, separating the H2S04 solution and subjecting this solution to a vacuum evaporation to evaporate the halides and crystalize As203. The purified H2S04 is recycled.
Once again these approaches are generally complicated and have 10 high operating costs and capital costs.
It is therefore an object of this invention to provide an improved process for the recovery of Arsenic values.
It is a further object of the invention to provide such process at reduced operating and reduced capital costs.
Further and other objects of the invention will be realized by those skilled in the art from the following Summary of the Invention and Detailed Description of Embodiments thereof.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a process is provided 20 for the recovery of Arsenic values from Arsenic containing material which may also contain Sulphur in one embodiment the Arsenic being in the form of As203, the process comprising the step of evaporating (in a wet or dry state) the Arsenic values from the Arsenic containing material into a gas stream which gas stream does not react with the Arsenic values. The gas stream is 25 then cooled to precipitate the Arsenic. The residue from which the arsenic was evaporated may then be treated for removal of the metal values. The simplicity of the process is reflected in relatively low operating costs and relatively low capital expenditures. Without the presence of Sulphur, the As203 vapour can be well cleaned of any carry-over solids (prior to 30 precipitation) giving a high purity As203 product, acceptable to for example the wood preserving industry. Preferably the evaporation of the Arsenic values is as arsenic trioxide (As203) near its boiling point.
According to another aspect of the invention the evaporation of the arsenic trioxide is performed in:
S (a) A chamber heated by a combustion of oil or hydrocarbon gas.
(b) Fluid bed heated by combustion of oil or hydrocarbon gas or by electrical energy.
(c) Electrical plasma reactor.
According to another aspect of the invention the arsenic values (for example the arsenic trioxide) are precipitated from the clean arsenic trioxide vapour containing gas in a fluidized bed of arsenic trioxide particles cooled by water evaporation. Thus the As203 is deposited on the surface of a cold particle causing it to grow to a form of little balls. The size of the balls of As203 may be controlled by the amount of precipitation onto the coarse particles. Thus "dusting" during handling of the "balled" material is reduced.
According to another aspect of the invention the process may be carried out u~ilizing electrical energy for evaporation of arsenic trioxide in an evaporator into a gas stream and after separation of the residue and precipitation of arsenic trioxide, the clean gas stream may be recycled back to the evaporator thus minimizing possible atmospheric emissions.
Thus, according to another aspect of the invention the process may be carried out in a closed circuit thus substantially eliminating emissions giVillg rise to substantial and significant environmental benefits.
According to another aspect of the invention the process may be carried out utilizing combustion of oil or hydrocarbon gas for evaporation of arsenic trioxide in the evaporator. Due to production of combustion products with this process the gas after cleaning can be vented.
-7- l 31 41 49 The invention will now be illustrated with reference to the following drawings of embodiments of the invention and the detailed description of the embodiments thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
S Figure 1 is a flow sheet illustrating a process carried out according to an embodiment of the invention.
Figure 2 is a flow sheet illustrating another process according to another embodiment of the invention.
Figure 3 is a flow sheet illustrating another process according to another embodiment of the invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
With reference to Figures 1 and 2, two processes are disclosed schematically according to the flow sheets. The difference between the processes relate to the energy source used to generate the heat in the evaporator to evaporate the Arsenic trioxide (As203).
With reference to Figures 1 and 2, the crude material containing arsenic trioxide 10 is exposed to heat in the evaporator 50. The arsenic trioxide vapour is transported from the evaporator 50 by a stream of other gas e.g. Nitrogen (See Figure 3) and the mixture leaves at a temperature of 250 - 500 degrees C (preferably 350 - 450 degrees C.) 12.
The evaporator 50 could be a:
(a) heated chamber - (for example for fine material which wouldn't stay in a fluid bed) (b) fluid bed heated by oil or hydrocarbon gas combustion, (Figure 1), or by electrical energy (Figure 2). The carry-over solids (residue) 24 are removed from the hot gas stream in a solids separator 52, preferably in a double filtration baghouse.
The separated residue 24, usually containing other metallic values is then available for further treatment as the major portion of arsenic was -8- l 31 41 49 removed. The clean gas 14 containing As203 vapour, or As203 vapour and water vapour and other gases, depending on the source of energy used in the evaporator, is then cooled in cooling and As203 removal section S4 by injection of water, preferably condensate 20 from the scrubbing circuit to a temperature:
(a) above boiling point of water (110-200 degrees C.) and the precipitated Arsenic trioxide is then removed in the cold baghouse.
b) just above point of Arsenic trioxide precipitation (depending upon concentration of arsenic trioxide in the vapour), generally between 300 degrees C. to 460 degrees C., and the precipitation is accomplished by further cooling in a fluid bed of Arsenic trioxide by spray of water (preferably condensate from scrubbing circuit) 20, to produce a desirable coarse product 26. (See Figure 3). The remaining gas is then scrubbed of Arsenic trioxide in a scrubber - cooler 56 and excess water vapour is condensed. The condensate 20 is recycled for cooling of the hot clean gas 14. The surplus 22 will be disposed of. The scrubbed cooled gas is then:
(a) recycled to the evaporator as Arsenic trioxide vapour carrier via 18 - if electric energy is utilized for heating of the evaporator.
(b) sent to stack. (See 18 of Figure 2).
With reference to Figures 1 and 2, equipment suitable for use (1) as the evaporator 50 may comprise:
(a) Fluid bed heated by an electrically preheated circulating gas.
(b) Fluid bed heated by inserted electrical heaters.
(c) Fluid bed heated by combustion of oil or hydrocarbon gas.
(d) Evaporation chamber heated by either electricity or by combustion of oil or hydrocarbon gas fine grained crude.
(2) for Solids separation 52 may comprise:
(a) High temperature bag-house, preferably two in series.
9 1 ~ 1 4 1 4 9 (3) For cooling and As~03 removal referred to at 54, the equipment may comprise:
(a) A fluid bed of coarse As203 particles cooled by spraying with a scrubber solution or water 20. As203 deposits on the cold particles thus allowing the production of a coarse particle As203 product. The remaining As203 dust is removed in a cold bag-house and can be sent to either product storage or back for evaporation.
(b) Injection of scrubber condensate directly to hot gas-adiabatic cooling. The precipitated As203 is removed from the gas stream in a cold bag-house and sent to product storage.
(c) combination of both - cooling to temperature of As203 saturation by injection of condensate or water, then precipitation of As203 as per (a).
(a) High temperature bag-house, preferably two in series.
9 1 ~ 1 4 1 4 9 (3) For cooling and As~03 removal referred to at 54, the equipment may comprise:
(a) A fluid bed of coarse As203 particles cooled by spraying with a scrubber solution or water 20. As203 deposits on the cold particles thus allowing the production of a coarse particle As203 product. The remaining As203 dust is removed in a cold bag-house and can be sent to either product storage or back for evaporation.
(b) Injection of scrubber condensate directly to hot gas-adiabatic cooling. The precipitated As203 is removed from the gas stream in a cold bag-house and sent to product storage.
(c) combination of both - cooling to temperature of As203 saturation by injection of condensate or water, then precipitation of As203 as per (a).
(4) As Scrubber and Water Condenser shown at 56:
(a) Scrubbing traces of As203 from the gas stream is accomplished in a tower or a venturi using the condensate from the following condenser. The amount of condensate to be used for scrubbing is determined by the consumption of Arsenic bearing scrubber solution used for gas cooling.
(b) As a Water condenser:
The water condenser can be a tray or preferably a packed tower which is cooled, depending on scrubber efficiency, by:
- directly injected cooling water - recycled, indirectly cooled condensate Depending on the temperature of the cooling water, the Gas Cooling-Water Condenser may employ an additional cooling (for example, heat pump) so that a minimum of water vapour is recycled to evaporate.
The operating conditions may be as follows:
(1) Evaporator 50 !; ~
-lo- 1314149 Temperature 300-600 degrees C., preferably 350-450 degrees C.
Pressure in freeboard - approximately minus 1 inch of H20.
(2) Hot bag-house Temperature 300-400 degrees C. Pressure - approximately minus .5 psig.
(3) Precipitator Temperature 80-150 degrees C. Pressure - approximately minus 1 psig.
(4) Cold bag-house Temperature 80-150 degrees C., preferably 110-120 degrees C.
(a) Scrubbing traces of As203 from the gas stream is accomplished in a tower or a venturi using the condensate from the following condenser. The amount of condensate to be used for scrubbing is determined by the consumption of Arsenic bearing scrubber solution used for gas cooling.
(b) As a Water condenser:
The water condenser can be a tray or preferably a packed tower which is cooled, depending on scrubber efficiency, by:
- directly injected cooling water - recycled, indirectly cooled condensate Depending on the temperature of the cooling water, the Gas Cooling-Water Condenser may employ an additional cooling (for example, heat pump) so that a minimum of water vapour is recycled to evaporate.
The operating conditions may be as follows:
(1) Evaporator 50 !; ~
-lo- 1314149 Temperature 300-600 degrees C., preferably 350-450 degrees C.
Pressure in freeboard - approximately minus 1 inch of H20.
(2) Hot bag-house Temperature 300-400 degrees C. Pressure - approximately minus .5 psig.
(3) Precipitator Temperature 80-150 degrees C. Pressure - approximately minus 1 psig.
(4) Cold bag-house Temperature 80-150 degrees C., preferably 110-120 degrees C.
(5) As203 Scrubber Temperature 65-80 degrees C., preferably 71 degrees C.
Pressure - approximately minus 2.1 psig.
Pressure - approximately minus 2.1 psig.
(6) Water Condenser Temperature 5-10 degrees C., preferably lowest possible.
As many changes can be made to the embodiments without departing from the scope of the invention, it is intended that all material contained herein be interpreted as illustrative of the invention and not in a limiting sense.
. .
As many changes can be made to the embodiments without departing from the scope of the invention, it is intended that all material contained herein be interpreted as illustrative of the invention and not in a limiting sense.
. .
Claims (27)
1. A process for the recovery of arsenic values from arsenic containing material which may also contain sulphur, the process comprising the step of evaporating the arsenic values from the arsenic containing material into a gas stream which gas stream does not react with the arsenic values.
2. The process of Claim 1, wherein the arsenic is ill the form of As2O3.
3. The process of Claim 1, wherein the gas stream is, after solids separation, cooled to precipitate the arsenic.
4. The process of Claim 2, wherein the gas stream is, after solids separation, cooled to precipitate the arsenic.
5. The process of claim 2, 3, or 4, wherein the evaporation of the arsenic values is as arsenic trioxide (As2O3) near its boiling point.
6. The process of Claim 1, wherein the evaporation of the arsenic as arsenic trioxide is performed in:
(a) A chamber heated by a combustion of oil, hydrocarbon gas or by electrical energy; or (b) Fluid bed heated by combustion of oil, hydrocarbon gas or by electrical energy.
(a) A chamber heated by a combustion of oil, hydrocarbon gas or by electrical energy; or (b) Fluid bed heated by combustion of oil, hydrocarbon gas or by electrical energy.
7. The process of Claim 2, wherein the evaporation of the arsenic as arsenic trioxide is performed in:
(a) A chamber heated by a combustion of oil, hydrocarbon gas, or by electrical energy; or (b) Fluid bed heated by combustion of oil, hydrocarbon gas or by electrical energy; or (c) Electrical plasma reactor.
(a) A chamber heated by a combustion of oil, hydrocarbon gas, or by electrical energy; or (b) Fluid bed heated by combustion of oil, hydrocarbon gas or by electrical energy; or (c) Electrical plasma reactor.
8. The process of Claim 3, wherein the evaporation of the arsenic as arsenic trioxide is performed in:
(a) A chamber heated by a combustion of oil, hydrocarbon gas, or by electrical energy; or (b) Fluid bed heated by combustion of oil, hydrocarbon gas or by electrical energy.
(a) A chamber heated by a combustion of oil, hydrocarbon gas, or by electrical energy; or (b) Fluid bed heated by combustion of oil, hydrocarbon gas or by electrical energy.
9. The process of Claim 4, wherein the evaporation of the arsenic as arsenic trioxide is performed in:
(a) A chamber heated by a combustion of oil, hydrocarbon gas, or by electrical energy; or (b) Fluid bed heated by combustion of oil, hydrocarbon gas or by electrical energy.
(a) A chamber heated by a combustion of oil, hydrocarbon gas, or by electrical energy; or (b) Fluid bed heated by combustion of oil, hydrocarbon gas or by electrical energy.
10. The process of Claim 1 further comprising the step of the arsenic values (for example the arsenic trioxide) being precipitated from the clean arsenic trioxide vapour containing gas in a fluidized bed of arsenic trioxide particles cooled by water which allows production of coarse particles.
11. The process of Claim 2, further comprising the step of wherein the arsenic values (for example the arsenic trioxide) being precipitated from the clean arsenic trioxide vapour containing gas in a fluidized bed of arsenic trioxide particles cooled by water which allows production of coarse particles.
12. The process of Claim 3, further comprising the step of wherein the arsenic values (for example the arsenic trioxide) being precipitated from the clean arsenic trioxide vapour containing gas in a fluidized bed of arsenic trioxide particles cooled by water which allows production of coarse particles.
13. The process of Claim 4, further comprising the step of wherein the arsenic values (for example the arsenic trioxide) being precipitated from the clean arsenic trioxide vapour containing gas in a fluidized bed of arsenic trioxide particles cooled by water which allows production of coarse particles.
14. The process of Claim 6, further comprising the step of wherein the arsenic values (for example the arsenic trioxide) being precipitated from the clean arsenic trioxide vapour containing gas in a fluidized bed of arsenic trioxide particles cooled by water which allows production of coarse particles.
15. The process of Claim 7, further comprising the step of wherein the arsenic values (for example the arsenic trioxide) being precipitated from the clean arsenic trioxide vapour containing gas in a fluidized bed of arsenic trioxide particles cooled by water which allows production of coarse particles.
16. The process of Claim 8, further comprising the step of wherein the arsenic values (for example the arsenic trioxide) being precipitated from the clean arsenic trioxide vapour containing gas in a fluidized bed of arsenic trioxide particles cooled by water which allows production of coarse particles.
17. The process of Claim 9, further comprising the step of wherein the arsenic values (for example the arsenic trioxide) being precipitated from the clean arsenic trioxide vapour containing gas in a fluidized bed of arsenic trioxide particles cooled by water which allows production of coarse particles.
18. The process of Claim 10, wherein the size of the particles of As2O3 may be controlled by the amount of precipitation of the arsenic onto coarse particles.
19. The process of Claim 11, wherein the size of the particles of As2O3 may be controlled by the amount of precipitation of the arsenic onto coarse particles.
20. The process of Claim 12, wherein the size of the particles of As2O3 may be controlled by the amount of precipitation of the arsenic onto coarse particles.
21. The process of Claim 13, wherein the size of the particles may be controlled by the amount of precipitation of the arsenic onto coarse particles.
22. The process of Claim 14, wherein the size of the particles of As2O3 may be controlled by the amount of precipitation of the arsenic onto coarse particles.
23. The process of Claim 15, wherein the size of the particles may be controlled by the amount of precipitation of arsenic onto coarse particles.
24. The process of Claim 16, wherein the size of the particles may be controlled by the amount of precipitation of arsenic onto coarse particles.
25. The process of Claim 17, wherein the size of the particles may be controlled by the amount of precipitation of arsenic onto coarse particles.
26. A process for the recovery of arsenic values from arsenic containing material which may also contain sulphur, the process utilizing electrical energy for evaporation of arsenic trioxide in an evaportor into a gas stream and after separation of arsenic trioxide and any residue, the clean gas may be recycled to the evaporator thus minimizing possible emissions permitting the process to be carried out in a closed circuit thus substantially eliminating emissions.
27. The process of Claim 1, wherein the process utilizes combustion of oil or hydrocarbon gas for evaporation of arsenic trioxide in an evaporator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 554182 CA1314149C (en) | 1987-12-11 | 1987-12-11 | Methods of recovering arsenic values from waste |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 554182 CA1314149C (en) | 1987-12-11 | 1987-12-11 | Methods of recovering arsenic values from waste |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1314149C true CA1314149C (en) | 1993-03-09 |
Family
ID=4137061
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 554182 Expired - Fee Related CA1314149C (en) | 1987-12-11 | 1987-12-11 | Methods of recovering arsenic values from waste |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1314149C (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006042898A1 (en) * | 2004-10-22 | 2006-04-27 | Outokumpu Technology Oyj | A process for reprocessing oxidic by-products containing arsenic |
| CN101587064B (en) * | 2009-06-09 | 2010-09-29 | 扬州高能新材料有限公司 | Sulfur dioxide concentration detection method in detecting sulfur contained in high-purity arsenic trioxide |
| WO2018120406A1 (en) * | 2016-12-30 | 2018-07-05 | 焱鑫环保科技有限公司 | Precisely controlled arsenic trioxide sublimating purification furnace using low-melting point alloy as floatation body |
| CN109502874A (en) * | 2018-11-16 | 2019-03-22 | 西北矿冶研究院 | Device and method for strengthening evaporation crystallization of arsenic trioxide |
| CN111569903A (en) * | 2020-05-29 | 2020-08-25 | 常熟理工学院 | Method for preparing ruthenium-based catalyst by directly utilizing arsenic ruthenium ore, product and application thereof |
| CN114314657A (en) * | 2022-02-18 | 2022-04-12 | 郑州德凯科技有限公司 | Production device and method for continuously preparing arsenic trioxide |
-
1987
- 1987-12-11 CA CA 554182 patent/CA1314149C/en not_active Expired - Fee Related
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006042898A1 (en) * | 2004-10-22 | 2006-04-27 | Outokumpu Technology Oyj | A process for reprocessing oxidic by-products containing arsenic |
| EA011214B1 (en) * | 2004-10-22 | 2009-02-27 | Ототек Оюй | A process for reprocessing oxidic by-products containing arsenic |
| CN101587064B (en) * | 2009-06-09 | 2010-09-29 | 扬州高能新材料有限公司 | Sulfur dioxide concentration detection method in detecting sulfur contained in high-purity arsenic trioxide |
| WO2018120406A1 (en) * | 2016-12-30 | 2018-07-05 | 焱鑫环保科技有限公司 | Precisely controlled arsenic trioxide sublimating purification furnace using low-melting point alloy as floatation body |
| CN109502874A (en) * | 2018-11-16 | 2019-03-22 | 西北矿冶研究院 | Device and method for strengthening evaporation crystallization of arsenic trioxide |
| CN109502874B (en) * | 2018-11-16 | 2021-11-16 | 西北矿冶研究院 | Device and method for strengthening evaporation crystallization of arsenic trioxide |
| CN111569903A (en) * | 2020-05-29 | 2020-08-25 | 常熟理工学院 | Method for preparing ruthenium-based catalyst by directly utilizing arsenic ruthenium ore, product and application thereof |
| CN114314657A (en) * | 2022-02-18 | 2022-04-12 | 郑州德凯科技有限公司 | Production device and method for continuously preparing arsenic trioxide |
| CN114314657B (en) * | 2022-02-18 | 2023-09-22 | 郑州德凯科技有限公司 | Production device and method for continuously preparing arsenic trioxide |
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