Random 2D Spherical Particle Distribution

I would like to generate a random 2D spherical particle distribution in a 245mm wide and 100mm high rectangle

Particles must vary in size from 1.5mm to 20mm and not intersect one another.

The particles must occupy 50% of the total volume.

Once generated, id like to export the geometry as a .mph file.

Any guidance on how to achieve this would be greatly appreciated.

Referance image atached.