Mixing and metering

The metering operation is considered to be critical with regard to the economics of the plant. If the metering of the reactants is not controlled within precise limits, then excess of carbon monoxide must be used to prevent dichlorine contamination of the final product. This is wasteful not only of carbon monoxide, but also of phosgene product in the condenser 

The mixing ratio of the reactants is either analysed constantly, or regulated manually or automatically. However, since the CO quality may vary within limits, it is recommended that the CO excess in the phosgene be monitored continuously, for example by infrared 

---

Metering can be done either by weight using a balance, or by volume using a calibrated vessel, pipette, disposable syringe or an automatic mixing and metering device. 

Pourable and spreadable products can be mixed by hand with a spatula or, for larger amounts, with a mechanical stirrer or automatic mixing and metering equipment. 

The equipment required ranges from bottle-based, hand-held dispensers through simple pressure-operated applicators to complex mixing and metering equipment. The latter is used in mass production or where viscous/thixotropic, mixed formulations have to fill large gaps. 

For small output, mixing and metering of the two components can be done by hand, for instance with a small blade mixer. If the products contain solvents, the mixer should he spark proof,... 

Mixing and Metering Machine Kontimix from Oest Mineralolwerk, Germany... 

Fig. 20 shows an example of a mixing and metering machine for 2 components A and S. 

---