Regarding Fly ash, Bottom Ash, Coal, Stoichiometry, Biomass, Gasification, how do i calculate bottom ash and fly ash for Biomass gasification theoretically? I have already calculated the ash content.
The ration of fly ash versus bottom ash will depend on two factors: 1/the gas velocity 2/the density (and -distribution) of the ash AFTER gasification. If I would have this situation I think I would do some experiments with coal particles in a small scale system, perhaps a TGA device and measure the densitiy of ash after the carbon part was reacted out. Molten ash will have a silica-like density of perhaps 2200 kg/m3 but when it is highly porous after carbon has reacted, particle density it can easily be 10 or more time lower. So, experiments and perhaps relevant literature may be the best way out.
It is generally very difficult to predict the ratio of bottom ash to fly ash. As stated earlier, it depends on gas and particle properties. It also depends strongly on gasifier design. For a slagging gasifier, a rule of thumb is that ash that impacts a wall will flow to the bottom, with the remainder flowing out of the gasifier. If you can estimate the fraction of the ash that impacts a wall, that would be a good place to start.
I agree with the other experts. It is hard to predict the ratio of fly ash vs. bottom ash theoretically. If you can't do any experiments or CFD calculations (which are very hard without validation), I suggest you do a very profound literature on these ratios for different cases and try to find a correlation between the named factors and the experimentally determined Ratio.
Greetings,
You are considering a hard and a very important problem. I think that the estimation of the fly ash should be done experimentally by analysing the flue gaz emission using for example the ELPI technique (electrical low pressure impactation). The partition between flay and bottom ash dépends on many factors: the nature of the biomass, the conversion system and the conversion protocol (slow, fast or flash pyrolysis). Some minerals like chlorine, potassium and sulfure are crucial in the kinetic of ash release. Without experimental runs, one should considered the dominant reactions and their kinetic models for assessing the yields.
Even the most sophisticated CFD have not yet considered this question.
for more information, you can learn the latest publications of Garcia Maraver et al.
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