I have four zones in my reactor body ;drying, pyrolysis, oxidation and reduction ( a typical gasifier reactor). In reality , biomass particle feedstock is initially loaded in the entire first zone (pyrolysis) and then when gasification/combustion takes place, the amount which is consumed is added from the upper part .In this way , we do have very low mass flow rate ,for instance, 5 kg/hr. Now in case of fluent, I am using discrete phase model to inject particles with the same flow rate but here I don't have a facility that all the feedstock is initally loaded. If I am using same flow rate like in experiment (5kg/hr), then nothing prominent reactions taking place. I am pondering, is it because I have no initial mass loaded and the flow rate is too low. 

Now, Can I load the particles initially in the zone and then just add required when consumed with specific flow rate? or what can be the problem in my case not getting result?