Delivering technology solutions for spray coating systems and applications...

 

 

Solvent Mixture Optimization Case Study

Problem

Solvent mixture in coating solutions is usually determined by the solubility of the coating substrate.  However within the solubility range, there is some freedom to choose the optimal solvent mixture that results in reduced cycle times.  Determine the solvent mixture of water and methanol and the process condition that will result in exhaust condition of 38°C and less than 17% RH.  The spray rate is to be maximized while keeping the LEL below 20%.  The process air flow rate limit is 3000 SCFM, and the maximum expected dew-point of inlet air is 5°C.

Problem Categories

Thermodynamics, formulation, engineering, and thermocoat, PCTSUni and PCTSWurster.
Solution
Enter the exhaust temperature and RH, and inlet air dew-point set points into the thermodynamics screen.  Change the composition of the water and ethanol until close to 20% LEL is achieved as shown below.  Increase the spray rate until 3000 SCFM is reached.
Results

The maximum spray rate under the conditions specified is ~1670 g/min, which occurs at 12%/88% by weight water/methanol mixture.