Hexaammonium wolframate

Manufacture

Documents

Ammonium metatungstate as an intermediate in the production of catalysts

Manufacture

Contributing activity / technique for the environment

Environmental release category (ERC):

ERC1: Manufacture of the substance

Contributing activity / technique for workers

Contributing activity / technique for workers 1

Process category (PROC):

PROC 2: Chemical production or refinery in closed continuous process with occasional controlled exposure or processes with equivalent containment conditions

Contributing activity / technique for workers 2

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

Contributing activity / technique for workers 3

Process category (PROC):

PROC 8b: Transfer of substance or mixture (charging and discharging) at dedicated facilities

Related assessment:

use assessed in a joint CSR

Manufacture of ammonium metatungstate

Manufacture

Contributing activity / technique for the environment

Name of activity / technique:

Manufacture of ammonium metatungstate

Environmental release category (ERC):

ERC1: Manufacture of the substance

Contributing activity / technique for workers

Contributing activity / technique for workers 1

Name of activity / technique:

Step 1: Raw material handling - Ammonium paratungstate is received and stored in sealed containers. A container of APT is transferred to a metering station, where the raw material is transferred through an enclosed loading system into a furnace (e.g., a rotary furnace).

Process category (PROC):

PROC 8b: Transfer of substance or mixture (charging and discharging) at dedicated facilities

Contributing activity / technique for workers 2

Name of activity / technique:

Step 2: Furnace operation - Ammonium paratungstate is heated in a furnace (e.g., a rotary furnace) at 400°C to thermally decompose the APT. The product discharge (partially decomposed APT) is collected in a container which is fixed to the furnace discharge outlet.

Process category (PROC):

PROC 22: Potentially closed processing operations with minerals/metals at elevated temperature. Industrial setting

Contributing activity / technique for workers 3

Name of activity / technique:

Step 3: Transfer to the dissolving reactor / dissolution process - The partially decomposed APT is conveyed in a closed container to a metering station, where the material is dosed into a dissolving tank using a closed, automated system (such as an enclosed conveying screw). Dust emission from the transfer container is minimised, for example, by using a top cover with a filter cloth. The closed dissolving reactor is filled with water. Dissolution is performed at 80 - 100 °C for approximately 2 hours. Ascending vapour is condensed in a cooling unit and returned to the vessel. AMT forms in the water.

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

Contributing activity / technique for workers 4

Name of activity / technique:

Step 4: Transfer of dissolved material to sedimentation tank or filtration - Since the dilution contains marginal amounts of insoluble components, the suspension is pumped into a sedimentation tank or it may be filtered. The pumping lasts approximately 0.5 hour. The temperature of the suspension is 70 - 80 °C. Sedimentation takes place in a closed system for approximately 10-12 hours. If filtration is used, it also takes place in a closed system.

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

PROC 8b: Transfer of substance or mixture (charging and discharging) at dedicated facilities

Contributing activity / technique for workers 5

Name of activity / technique:

Step 5: Transfer of the dilution to an evaporator - After sedimentation or filtration is completed, the supernatant is pumped into an evaporator.

Process category (PROC):

PROC 8b: Transfer of substance or mixture (charging and discharging) at dedicated facilities

Contributing activity / technique for workers 6

Name of activity / technique:

Step 6: Evaporation of water / concentration - A high fraction of the water is evaporated to reach a certain concentration of AMT solution. Temperature: 100 - 105 °C Time: 6 - 8 hours

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

Contributing activity / technique for workers 7

Name of activity / technique:

Step 7: Filtration - The concentrated dilution is filtered for approximately 0.5 hours.

Process category (PROC):

PROC 8b: Transfer of substance or mixture (charging and discharging) at dedicated facilities

Contributing activity / technique for workers 8

Name of activity / technique:

Step 8: Crystallisation of AMT - To crystallise the AMT, the filtered concentrate is cooled at a temperature less than 25°C for approximately 5 - 6 hours.

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

Contributing activity / technique for workers 9

Name of activity / technique:

Step 9: Filtration - The crystalline suspension is released to a band filter. The mother liquor is filtered out of the suspension. The filtration period is approximately 5 - 6 hours at a temperature < 25 °C.

Process category (PROC):

PROC 8b: Transfer of substance or mixture (charging and discharging) at dedicated facilities

Contributing activity / technique for workers 10

Name of activity / technique:

Step 10: Drying of AMT Sludge - The AMT sludge is dried (for example, in a flow dryer). The dust-loaded air is released from the dryer over a filter system using an exhaust air fan. De-dusting of the filters occurs automatically. The incurring dust is returned to the process.

Process category (PROC):

PROC 2: Chemical production or refinery in closed continuous process with occasional controlled exposure or processes with equivalent containment conditions

Contributing activity / technique for workers 11

Name of activity / technique:

Step 11: Transfer to a mixer - The dried AMT is conveyed to a mixer using a bucket conveyer. The transfer is conducted at room temperature.

Process category (PROC):

PROC 8b: Transfer of substance or mixture (charging and discharging) at dedicated facilities

Contributing activity / technique for workers 12

Name of activity / technique:

Step 12: Mixing operation - Blending of the AMT powders in a batch at room temperature. Duration is less than 5 min. A sample of AMT may be collected for subsequent laboratory analysis.

Process category (PROC):

PROC 2: Chemical production or refinery in closed continuous process with occasional controlled exposure or processes with equivalent containment conditions

Contributing activity / technique for workers 13

Name of activity / technique:

Step 13: Quality control - The finished AMT powder may be analyzed in a laboratory.

Process category (PROC):

PROC 15: Use as laboratory reagent

Contributing activity / technique for workers 14

Name of activity / technique:

Step 14: Packaging and shipping of AMT - The homogenised AMT powder is transferred into drums or big bags; each type of packaging is connected to the mixer discharge over a dust-proof collar. For certain grades of AMT (eg laboratory reagent grade), the AMT powder is packed in smaller containers. The sealed containers are shipped to the customer

Process category (PROC):

PROC 8b: Transfer of substance or mixture (charging and discharging) at dedicated facilities

PROC 9: Transfer of substance or mixture into small containers (dedicated filling line, including weighing)

Contributing activity / technique for workers 15

Name of activity / technique:

Step 15: Maintenance and cleaning - Various maintenance and cleaning operations inside and outside the equipment.

Process category (PROC):

PROC28: Manual maintenance (cleaning and repair) of machinery

Related assessment:

use assessed in a joint CSR

Ammonium metatungstate as an intermediate in the production of catalysts

Manufacture

Contributing activity / technique for the environment

Contributing activity / technique for the environment 1

Environmental release category (ERC):

ERC6a: Use of intermediate

Contributing activity / technique for the environment 2

Environmental release category (ERC):

ERC1: Manufacture of the substance

Contributing activity / technique for workers

Contributing activity / technique for workers 1

Process category (PROC):

PROC 1: Chemical production or refinery in closed process without likelihood of exposure or processes with equivalent containment conditions

Contributing activity / technique for workers 2

Process category (PROC):

PROC 2: Chemical production or refinery in closed continuous process with occasional controlled exposure or processes with equivalent containment conditions

Contributing activity / technique for workers 3

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

Contributing activity / technique for workers 4

Process category (PROC):

PROC 8b: Transfer of substance or mixture (charging and discharging) at dedicated facilities

Contributing activity / technique for workers 5

Process category (PROC):

PROC 9: Transfer of substance or mixture into small containers (dedicated filling line, including weighing)

Contributing activity / technique for workers 6

Process category (PROC):

PROC 14: Tabletting, compression, extrusion, pelletisation, granulation