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Manufacture, use & exposure

Manufacture

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Manufacture

Contributing activity / technique for the environment
Name of activity / technique:
Manufacture of ammonium paratungstate powder
Environmental release category (ERC):
ERC1: Manufacture of the substance
Contributing activity / technique for workersopen allclose all
Name of activity / technique:
Step 1: Transfer to silica precipitation - After pressure leach, impure sodium tungstate solution is transferred through a pipe system in a closed tank to the silica precipitation
Process category (PROC):
PROC 1: Chemical production or refinery in closed process without likelihood of exposure or processes with equivalent containment conditions
Name of activity / technique:
Step 2: Filtration / silica precipitation - Silicate ions are precipitated by adding aluminium sulphate or magnesium sulphate to the sodium tungstate solution. Also, mixtures of both reagents are used. After the precipitation, the solution is filtered in a filter press. The filtration residue is sent off-site as waste. The tungstate solution is transferred through a pipe system to the molybdenum precipitation, or if the Kryolith-precipitation is necessary, to the Kryolith-precipitation step.
Process category (PROC):
PROC 3: Manufacture or formulation in the chemical industry in closed batch processes with occasional controlled exposure or processes with equivalent containment conditions
Name of activity / technique:
Step 3: Kryolith-(fluorine) precipitation - Aluminium sulphate and sulfuric acid are added to the tungstate solution. The sodium tungstate solution is filtered in a filter press. After the precipitation, the filtration residue is sent off-site as waste. The tungstate solution is transferred through a pipe system to the molybdenum precipitation.
Process category (PROC):
PROC 3: Manufacture or formulation in the chemical industry in closed batch processes with occasional controlled exposure or processes with equivalent containment conditions
Name of activity / technique:
Step 4: Moybdenum precipitation - Sodium sulfide is added to the sodium tungstate solution, the molybdate ion is converted to thiomolybdate. The addition of sulfuric acid to change the pH converts the thiomolybdate to insoluble molybdenum trisulfide. The H2S evolved during acidification has to be scrubbed by NaOH. The sodium tungstate solution is filtered again. The residue from the filtration is sent off-site as waste. The tungstate solution is transferred in pipes to the solvent extraction process.
Process category (PROC):
PROC 3: Manufacture or formulation in the chemical industry in closed batch processes with occasional controlled exposure or processes with equivalent containment conditions
Name of activity / technique:
Step 5: Solvent extraction -
This stage extracts isopolytungstate species from slightly acidic aqueous solution by the reagent dissolved in the organic phase, thus separating the tungstate from sodium ions. Kerosene and the modifier are part of the organic phase.
1) Re-extraction from the organic into aqueous phase is performed by aqueous ammonia solution. The organic solvent circulates from the extraction to scrubbing, stripping regeneration and back to extraction. The aqueous phase leaves the process as raffinate.
2) Extraction: The slightly acidic polytungstate solution is contacted with the regenerated organic phase, whereby the isopolytungstate reacts with the protonated cationic amine to form an ion associate complex. The equivalent amounts of sulphate and sodium ions, as well as any surplus of these ions applied in excess during digestion and acidification, remain in the aqueous phase and leave the extraction as raffinate.
Scrubbing: Some entrainment of the organic phase after extraction cannot be avoided. By scrubbing, the main portion will be removed. The scrubbing raffinate contains low concentrations of sodium sulphate. A combination of coalescer and settler are used for entrainment removal besides mixer settlers.
3) Stripping: In this step, the loaded organic is contacted with aqueous ammonia solution. The ion associate complex is decomposed, and the isopolytungstate is re-extracted into the aqueous phase as ammonium salt solution.
4) Solvent regeneration: In this process step, the stripped organic phase is contacted with an aqueous sulfuric acid solution. Then the amine is again protonated and at the same time the organic phase is cleaned from the entrainment of the ammoniacal salt solution.
The ammonium isopolytungstate solution is transferred in a pipe system to the crystallisation and filtration process.
Process category (PROC):
PROC 1: Chemical production or refinery in closed process without likelihood of exposure or processes with equivalent containment conditions
Name of activity / technique:
Step 6: Crystallization / filtration - The ammonium isopolytungstate solution is evaporated, water and ammonia are distilled, the pH of the solution decreases, and the sparingly soluble ammonium paratungstate (APT) crystallises. The ammonia – water mixture is condensed and recycled to the solvent extraction process. The process is carried out in a continuously recirculating crystalliser. The crystal slurry is separated from the mother liquor by filtration and washing with deionized water. Filtrate and wash water are recycled.
Process category (PROC):
PROC 1: Chemical production or refinery in closed process without likelihood of exposure or processes with equivalent containment conditions
PROC 22: Potentially closed processing operations with minerals/metals at elevated temperature. Industrial setting
Name of activity / technique:
Step 7: Transfer to tungsten trioxide (WO3) and tungsten blue oxide (TBO) production
Process category (PROC):
PROC 3: Manufacture or formulation in the chemical industry in closed batch processes with occasional controlled exposure or processes with equivalent containment conditions
Related assessment:
use assessed in a joint CSR

Manufacture

Contributing activity / technique for the environmentopen allclose all
Environmental release category (ERC):
ERC6a: Use of intermediate
Environmental release category (ERC):
ERC1: Manufacture of the substance
Contributing activity / technique for workersopen allclose all
Process category (PROC):
PROC 1: Chemical production or refinery in closed process without likelihood of exposure or processes with equivalent containment conditions
Process category (PROC):
PROC 2: Chemical production or refinery in closed continuous process with occasional controlled exposure or processes with equivalent containment conditions
Process category (PROC):
PROC 3: Manufacture or formulation in the chemical industry in closed batch processes with occasional controlled exposure or processes with equivalent containment conditions
Process category (PROC):
PROC 4: Chemical production where opportunity for exposure arises
Process category (PROC):
PROC 9: Transfer of substance or mixture into small containers (dedicated filling line, including weighing)
Process category (PROC):
PROC 14: Tabletting, compression, extrusion, pelletisation, granulation

Manufacture

Contributing activity / technique for the environmentopen allclose all
Environmental release category (ERC):
ERC6a: Use of intermediate
Environmental release category (ERC):
ERC1: Manufacture of the substance
Contributing activity / technique for workersopen allclose all
Process category (PROC):
PROC 3: Manufacture or formulation in the chemical industry in closed batch processes with occasional controlled exposure or processes with equivalent containment conditions
Process category (PROC):
PROC 8b: Transfer of substance or mixture (charging and discharging) at dedicated facilities
Process category (PROC):
PROC 22: Potentially closed processing operations with minerals/metals at elevated temperature. Industrial setting

Manufacture

Contributing activity / technique for the environment
Environmental release category (ERC):
ERC1: Manufacture of the substance
Contributing activity / technique for workersopen allclose all
Process category (PROC):
PROC 3: Manufacture or formulation in the chemical industry in closed batch processes with occasional controlled exposure or processes with equivalent containment conditions
Process category (PROC):
PROC 8b: Transfer of substance or mixture (charging and discharging) at dedicated facilities
Process category (PROC):
PROC 22: Potentially closed processing operations with minerals/metals at elevated temperature. Industrial setting
Related assessment:
use assessed in a joint CSR

Manufacture

Contributing activity / technique for the environment
Environmental release category (ERC):
ERC1: Manufacture of the substance
Contributing activity / technique for workersopen allclose all
Process category (PROC):
PROC 1: Chemical production or refinery in closed process without likelihood of exposure or processes with equivalent containment conditions
Process category (PROC):
PROC 3: Manufacture or formulation in the chemical industry in closed batch processes with occasional controlled exposure or processes with equivalent containment conditions
Process category (PROC):
PROC 22: Potentially closed processing operations with minerals/metals at elevated temperature. Industrial setting

Manufacture

Contributing activity / technique for the environment
Name of activity / technique:
Manufacture of ammonium paratungstate
Environmental release category (ERC):
ERC1: Manufacture of the substance
Contributing activity / technique for workersopen allclose all
Name of activity / technique:
Step 1: Transfer to silica precipitation - After pressure leach, impure sodium tungstate solution is transferred through a pipe system in a closed tank to the silica precipitation
Process category (PROC):
PROC 1: Chemical production or refinery in closed process without likelihood of exposure or processes with equivalent containment conditions
Name of activity / technique:
Step 2: Filtration / silica precipitation - Silicate ions are precipitated by adding aluminium sulphate or magnesium sulphate to the sodium tungstate solution. Also, mixtures of both reagents are used. After the precipitation, the solution is filtered in a filter press. The filtration residue is sent off-site as waste. The tungstate solution is transferred through a pipe system to the molybdenum precipitation, or if the Kryolith-precipitation is necessary, to the Kryolith-precipitation step.
Process category (PROC):
PROC 3: Manufacture or formulation in the chemical industry in closed batch processes with occasional controlled exposure or processes with equivalent containment conditions
Name of activity / technique:
Step 3: Kryolith-(fluorine) precipitation - Aluminium sulphate and sulfuric acid are added to the tungstate solution. The sodium tungstate solution is filtered in a filter press. After the precipitation, the filtration residue is sent off-site as waste. The tungstate solution is transferred through a pipe system to the molybdenum precipitation.
Process category (PROC):
PROC 3: Manufacture or formulation in the chemical industry in closed batch processes with occasional controlled exposure or processes with equivalent containment conditions
Name of activity / technique:
Step 4: Moybdenum precipitation - Sodium sulfide is added to the sodium tungstate solution, the molybdate ion is converted to thiomolybdate. The addition of sulfuric acid to change the pH converts the thiomolybdate to insoluble molybdenum trisulfide. The H2S evolved during acidification has to be scrubbed by NaOH. The sodium tungstate solution is filtered again. The residue from the filtration is sent off-site as waste. The tungstate solution is transferred in pipes to the solvent extraction process.
Process category (PROC):
PROC 3: Manufacture or formulation in the chemical industry in closed batch processes with occasional controlled exposure or processes with equivalent containment conditions
Name of activity / technique:
Step 5: Solvent extraction -
This stage extracts isopolytungstate species from slightly acidic aqueous solution by the reagent dissolved in the organic phase, thus separating the tungstate from sodium ions. Kerosene and the modifier are part of the organic phase.
1) Re-extraction from the organic into aqueous phase is performed by aqueous ammonia solution. The organic solvent circulates from the extraction to scrubbing, stripping regeneration and back to extraction. The aqueous phase leaves the process as raffinate.
2) Extraction: The slightly acidic polytungstate solution is contacted with the regenerated organic phase, whereby the isopolytungstate reacts with the protonated cationic amine to form an ion associate complex. The equivalent amounts of sulphate and sodium ions, as well as any surplus of these ions applied in excess during digestion and acidification, remain in the aqueous phase and leave the extraction as raffinate.
Scrubbing: Some entrainment of the organic phase after extraction cannot be avoided. By scrubbing, the main portion will be removed. The scrubbing raffinate contains low concentrations of sodium sulphate. A combination of coalescer and settler are used for entrainment removal besides mixer settlers.
3) Stripping: In this step, the loaded organic is contacted with aqueous ammonia solution. The ion associate complex is decomposed, and the isopolytungstate is re-extracted into the aqueous phase as ammonium salt solution.
4) Solvent regeneration: In this process step, the stripped organic phase is contacted with an aqueous sulfuric acid solution. Then the amine is again protonated and at the same time the organic phase is cleaned from the entrainment of the ammoniacal salt solution.
The ammonium isopolytungstate solution is transferred in a pipe system to the crystallisation and filtration process.
Process category (PROC):
PROC 1: Chemical production or refinery in closed process without likelihood of exposure or processes with equivalent containment conditions
Name of activity / technique:
Step 6: Crystallization / filtration - The ammonium isopolytungstate solution is evaporated, water and ammonia are distilled, the pH of the solution decreases, and the sparingly soluble ammonium paratungstate crystallises. The ammonia – water mixture is condensed and recycled to the solvent extraction process. The process is carried out in a continuously recirculating crystalliser. The crystal slurry is separated from the mother liquor by filtration and washing with deionized water. Filtrate and wash water are recycled.
Process category (PROC):
PROC 1: Chemical production or refinery in closed process without likelihood of exposure or processes with equivalent containment conditions
PROC 22: Potentially closed processing operations with minerals/metals at elevated temperature. Industrial setting
Name of activity / technique:
Step 7: Transfer to tungsten trioxide and/or tungsten oxide production
Process category (PROC):
PROC 3: Manufacture or formulation in the chemical industry in closed batch processes with occasional controlled exposure or processes with equivalent containment conditions
Related assessment:
use assessed in a joint CSR but not a lead’s own use

Manufacture

Contributing activity / technique for the environment
Name of activity / technique:
Manufacture of ammonium wolframate solution
Environmental release category (ERC):
ERC1: Manufacture of the substance
Contributing activity / technique for workers
Name of activity / technique:
Manufacture of ammonium wolframate solution
Process category (PROC):
PROC 3: Manufacture or formulation in the chemical industry in closed batch processes with occasional controlled exposure or processes with equivalent containment conditions

Manufacture

Contributing activity / technique for the environment
Environmental release category (ERC):
ERC1: Manufacture of the substance
Contributing activity / technique for workersopen allclose all
Process category (PROC):
PROC 1: Chemical production or refinery in closed process without likelihood of exposure or processes with equivalent containment conditions
Process category (PROC):
PROC 2: Chemical production or refinery in closed continuous process with occasional controlled exposure or processes with equivalent containment conditions
Process category (PROC):
PROC 3: Manufacture or formulation in the chemical industry in closed batch processes with occasional controlled exposure or processes with equivalent containment conditions
Process category (PROC):
PROC 4: Chemical production where opportunity for exposure arises
Process category (PROC):
PROC 9: Transfer of substance or mixture into small containers (dedicated filling line, including weighing)
Process category (PROC):
PROC 14: Tabletting, compression, extrusion, pelletisation, granulation
Related assessment:
use assessed in a joint CSR