http://digibuo.uniovi.es/dspace/bitstream/10651/38378/3/TFGSaraSolisRUO.pdf

http://cdn.intechopen.com/pdfs/45639/InTech-The_overview_of_thermal_decomposition_of_cellulose_in_lignocellulosic_biomass.pdf

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.387.9448&rep=rep1&type=pdf

https://fortress.wa.gov/ecy/publications/documents/1107017.pdf

http://www.vtt.fi/Documents/P731.pdf

Hi Teo,

Hydrogen is a highly volatile element in many organic materials and renewable wastes. Thus, it's not surprising that the H/C atomic ratio in the solid residue (char) decreases with increasing pyrolysis severity (i.e. higher temperature, longer residence time). However, the H content in the char remains quite high; a dramatic decrease in the hydrogen content in the char will not happen until very high temperature (>1000°C). I've seen many examples that in the solid residues from many pyrolytic processes, including fast/flash pyrolysis and thermal cracking in the medium temperature range (450-600°C), the H/C atomic ratio in the char remain above 0.2, even though the pyrolysis process has achieved "completion" for good engineering reason - because higher temperature and longer residence time don't mean better yield, especially when high added value chemicals (e.g. BTX) or bio-oil (for production of liquid fuels) are the intended products. Therefore, unless the intended product is char, the H/C atomic ratio or "complete pyrolysis" is not a good metric of the performance of a pyrolytic process, sometimes even totally irrelevant.

That's said, I haven't seen a case where the hydrogen content in the char is literally higher than that in the original dry feed. I don't think that the char contains "more hydrogen" is what the author really meant.

Hi dear,

Pyrolysis, or thermolysis, is the chemical decomposition of an organic compound by a significant increase in its temperature to obtain other products (gas and matter) that it did not contain. The operation is performed in the absence of oxygen or in a low oxygen atmosphere to prevent oxidation and combustion (the operation therefore does not produce a flame). This is the first stage of thermal transformation after dehydration.

It generally makes it possible to obtain a carbonaceous solid, an oil and a gas. It starts at a relatively low temperature level (from 200 ° C) and continues to about 1000 ° C. Depending on the temperature, the proportion of the three resulting compounds is different1. It can in particular be produced in a solar oven, as was shown in Odeillo.

One of the first concerns of analytical chemistry since Antoine Lavoisier has been to determine the elements, that is to say the products of which are composed all the bodies. It was necessary to find methods to divide the complex bodies, then to characterize the elementary bodies resulting from this decomposition.

Pyrolysis, hydrolysis or electrolysis are the tools of analytical chemistry for the determination of these bodies. From pure Greek, puros and the suffix -lyse (λύσις) "dissolution", pyrolysis means analysis (in its primary sense of separation) by fire. In the same way, hydrolysis means analysis or separation by water and electrolysis, separation by electricity3.

From the eighteenth century, before the term exists, pyrolysis or carbonization operations are carried out in industry to obtain among others charcoal from wood, coke from coal, peat coal from peat or manufactured gases (Essentially coal gas but experiments will also be attempted, by similar processes, with varying success, from wood (wood gas), resins (resin gas), oils (oil gas), oil shale (compressed portable gas), petroleum industry waste (petroleum gas), etc., referred to as "distillation" or "dry distillation". These operations must be more properly called pyrolysis: in modern acceptance, distillation is a process for separating the constituents of a homogeneous mixture whose boiling temperatures are different; pyrolysis is the decomposition of an organic compound by heat to obtain other products (gas and matter) that it did not contain. In pyrolysis, the material is destroyed (the same difference exists between separating the cards from a game (distillation), and cutting cards with scissors (pyrolysis)). It can be assumed that, by analogy, the glass retort used in distillation operations will give its name to refractory retorts used in industry, in pyrolysis operations, although there is not much of common between the two.

Pyrolysis should not be confused with combustion (or incineration): oxidation-reduction processes carried out by fire in the presence of oxygen.

or complex organic bodies are composed of chains of molecules (polymer, for example plastics, rubber, wood, paper, etc.). The heat breaks this chain and produces smaller organic molecules, for example methane CH4.

When a solid body, like wood, burns, it is often done in the following way:

Any moisture is evaporated (dehydration).

The heat of the flame breaks down the matter into light molecules.

the light molecules, of the methane type, burn with the oxygen of the O2 air.

There is thus a combination pyrolysis / combustion of a gas, the combustion maintaining the pyrolysis until disappearance of the organic body.

Most of the time, we talk about pyrolysis for flameless decomposition (for example the decomposition of grease in the process of cleaning a furnace called "pyrolysis").

In the face of peak oil and the danger of the greenhouse effect, renewable energies are of increasing interest, and pyrolysis could be an interesting process to valorize certain forms of biomass currently used in a little effective or even simply burned in open field (straw, sugar cane bagasse, leaves, bark, wood and agricultural waste including coconut husks, peanuts, etc.) 4.

Pyrolysis of this type of biomass produces vapors, a combustible gas (synthesis gas), solid minerals (recyclable in agriculture) and a kind of charcoal that can be used as an amendment (Biochar or agrobiochar) or as a fuel (biochar). from an ecological point of view if the products were not contaminated by salt, radionuclides or certain pesticides.

With my best regards!

Biomass has a composition of CH1.6O0.7 or around that. Good char has a composition of CH0.05 to CH0.1. The char from pyrolysis may go up to CH0.2. Poor pyrolytic process can generate compositions with higher H fraction.

What Mr Radwan Alkhatib (2015) said is high hydrogen content in the bio-char (pyrolysis char). Typically a higher biomass conversion would produce a higher bio-oil content with high water content. High water content in the bio-oil as a result of a higher hydrogen from biomass decomposition react to form water. Hence , the amount of hydrogen would decrease in bio-char. By increase the pyrolysis temperature up to 450-500oC would favour a higher bio-oil yield.

There are several techniques for measuring the conversion efficiency of the pyrolysis process. The presence of hydrogen in the char is one way of determining how much of the volatile matter (VM) portion of the starting material were converted to syngas and/or pyrolytic oil and how much was left in the char. The char is typically composed mainly by fixed carbon (FC) and ash but VM and other inorganic materials usually remain in the char depending on the pyrolysis condition used. Therefore, when there is a high elemental H remaining in the char, it may indicate the presence of high VM which were not thermally converted. The higher the H/C ratio (IBI uses >0.7), the lower the conversion efficiency.

It is a preposterous statement. State of pyrolysis based on the thermal and design conditions of experiment. Presence of more char means the heating rate was low. If Volatile content is very high, it insinuates the heating rate was very high. Does it implies torrefaction and carbonisation which take place at low and high temperature respectively, is not kind of pyrolysis? I think if you are not getting the good composition of producer gas, or CO +H2 for biofuels at end point, it means thermal decomposition did not happen properly and the stoichiometric ratio is quite imbalance.

Having more H_2 in Char is related to characteristic of fuel, not pyrolysis.