I have been pyrolysing my biomass 3 times under the same conditions using microwave technology to compare the yield. I have noticed that the yield of the biochar changed every time. I am wondering what could be the reasons for this to happen?
What do you mean by "same conditions". Has the temperature, for example, not been changed? or did you get Biochar yield at different pyrolysis temperatures?
Your findings would make sense if the temperatures were changed. In this case, the observed decrease in yield with the increase of temperature could probably be attributed to the thermal dehydration of hydroxyl groups as moisture is lost through evaporation and the volatilisation of organic fractions.
For this, please refer to Koetlisi and Muchaonyerwa, (2017), and Liu et al. (2014).
Regards
How big is the variation in yield between runs? Calculate the mean and deviation, are you within these values for the next runs? Biomass is not a homogenous material, can there be variation in the composition?
The answer is simple. Even if the pyrolysis conditions are identical, the yield behaviour is different because "biomass" is dofferent. There is vaiation in several compositional features whether the material benonged to the core of the tree or midway or in the outer region simply because the lifetimes over which they have grown are different. The density can vary by 10 to 50 % and the finer aspects of the composition, namely, cellulose, hemicellulose, or lignin can be slightly different and the pyrolysis behaviour can be different. There are earlier studies in this regard.
There are 13 independent and inter-dependent process parameters in pyrolysis. Its impossible to fix them every time and hence there will always ben inherent variation in the results. Do 1000 experiments and then assess the errors in the results. They will still be there.
heterogeneity of biomass may be the reason, second thing is the biomass grain size - was it the same each time?repeat the experiment 20-50 times, then you can calculate the average yield... three times is not enough
good luck! :)
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials Chemistry
- Polymer Chemistry