Modeling packed bed reactor

Hi

I am a beginner of COMSOL. I would like to design packed-bed reactor. The reactor diameter is 1 mm, and the particle size is about 1 micro meter. The porosity of packed bed is about 60%. If I want to fill reactor with this small particle, I need about 1000 particles, it take too long time for me. Is it possible to mimic this reactor using other method?

Thank you for your help