Hello guys, I am currently working on the characterization of bio-char produced from high temperature (>1000 °C) pyrolysis of biomass. Unfortunately, I find it difficult to determine the exact char yield.
Firstly, I tried the classic ash tracer method, which was introduced by Badzioch and Hawksley in 1970 and has often been used for determining char yield during coal/biomass pyrolysis. However, I found that the experimental error was a little bit too high.
I wonder are there any methods to correctly determine char yield for my experiments?
Why do you think that there will be an exact answer? It will surely depend a lot on the nature of the biomass, airflow etc.
I agree with Tony Maine that there can be various factors to consider. For example, if this is a batch process, the reaction rate will definitely vary with time due to the varying equivalence ratio and other coupled factors. At certain condition we could see something else such as gasification or combustion. Perhaps the reaction profile (versus time) can be useful for segregation of 'valid' char. Just my guess. Good luck.
Hi Nicola, recently we have developed a novel-double tube configuration that enables direct determination of char yield during biomass pyrolysis. Our experimental temperature is 1300 °C, slightly higher than yours. Below is the description of our design.
Briefly, a small alumina tube (19 mm OD) was inserted through the regular DTF. Sample particles are entrained into the inner tube by 1 L/min of ultrahigh-purity (UHP) argon. Another stream of argon flow (0.2 L/min) was introduced to prevent the backflow of volatiles into the reactor headspace. A stream of UHP nitrogen was added to the annulus space between the two alumina tubes. The reactor effluent is cooled in a water-cooled N2-quenched sampling probe before being directed to a DEKATI cyclone (aerodynamic cutoff diameter, 10 μm). What’s in the cyclone are all the char samples.
For detailed descriptions, you can refer to my papers.
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