Hello there,

I'm currently designing a Continuously operated Slow Pyrolysis Reactor for one of my classes and have reached a point where all the kinetics are modelled.

A key factor of Pyrolysis is the heating rate, with a a lower heating rate yielding more Biochar than a higher heating rate. (This is what my kinetics show and this agrees with literature.)

My kinetics were modelled using a constant heating rate in MATLAB, I then used this model to evaluate how long it would take to convert all of the biomass, using the heating rate and residence time, I was able to calculate the final temperature within the pyrolysis reactor.

My confusion comes when trying to select the correct heating rate to maximise cost effectiveness.

Below is some data which may be useful to understand my problem;

As an example, at a heating rate of 0.1 degrees celcius/minute, my time to reach full conversion of the biomass is 1630 minutes, the final temperature is 302 degrees celsius. At a heating rate of 1 degrees celcius/minute, my time to reach full conversion is 222 minutes and the final temperature is 361 degrees celcius. Lower heating rates produce more char and as char is my intended product I want to maximise its production.

If I use the general energy balance equation,

Q=mc_{p}(T_{2}-T_{1}) with m being 1, c_{p} also being 1 (assuming constant over temperature range), T_{2} being the final temperature and T_{1} being the starting temperature (139 degrees celcius)

I get;

Q=163kJ for the first scenario and Q=222kJ for the second scenario, converting these to power, by dividing by the total residence time in the reactor I get 0.0016kW for the first scenario and 0.016kW for the second scenario.

Surely there will be a higher energy/power requirement to keep biomass in the reactor for longer, even though it reaches a lower final temperature? Am I overlooking something? I feel like I've been staring at this for an eternity.

Any help is greatly appreciated,

Niall.

**Edited by NiallS, 08 March 2019 - 01:38 PM.**