Conversion efficiency of pyrolysis = (Weight of bio-char + bio-oil + gas)/*100/Weight of initial biomass

The factors affecting efficiency of pyrolysis are temperature, time. inert gas flow rate and heating rate.

Liquefaction produces liquid products, mainly. But pyrolysis produces solid, liquid and gaseous products.

Dear Omkar,

If you found out the energy balance of the biomass pyrolysis we will get the answer of conversion efficiency.

Dear Dr. Omkar,

Temperature is the most significant factor affecting pyrolysis yield. Since its a thermo-chemical process. However, additional parameters including heating rate, residence time, moisture content of feedstock and gas flow rate.

With regards to the conversion efficiency calculations,

conversion efficiency = (weight of all products formed)/initial weight of biomass*100

liquefaction is quite different from pyrolysis.

1. The operating temperature for liquefaction is lower than that of pyrolysis ranges between 150oC to 350oC

2. moisture content of feedstock does not hinders liquefaction unlike in the case of pyrolysis, where moisture is greatly hindering the process.

3. Solvents or medium like water are required in liquefaction and not in pyrolysis.

4. Although in both cases liquid products are formed, scientists are using heavy oil and pyrolysis oil to differentiate the products of liquefaction and pyrolysis respectively.

Thank you all for answering.

These questions are  not easy to be answered in a short time and should take time.

Briefly there are several biomass liquefaction pahthways :

- Fast pyrolysis with or without catalyst : In Fast pyrolysis the biooil yied is optimized (typically 60 to 70 wt % with about 15% gas and 15% biochar but the oxygene content of the biooil is not decreased v/s the initial dry biomass (about 40-45 wt%O). In catalytic fast pyrolysis the oxygen content is decreaded, typically  down to 15-30%, but the biooil yield is also decreased . Typically temperature is about 500-550°C for both processes and biomass vapor residence time very short : 1 to 2 s.

Torrefaction is another pyrolysis pathway at a lower temperature (150-260°C) with a longer residence time (15-60 mn) but this is not a liquefaction process : the objective is to produce a dried , partially modified solid biomass.

Liquefaction through hydrothermal conversion using high pressure water (typically 150 to 180 b or even superctitical water at P > 220 b) is performed at a much lower temperature, about 350°C and 15-20 mn typical residence time. Yield is about 45-50% of an oxygenate biocrude (less oxygen than in fast pyrolysis biooil similar to catalytic fast pyrolysois oils). The obtained  biocrude is far from a crude oil in term of chemical structure.

Hydroliquefaction using hydroconversion catalyst (such as the CRI/GTI IH2 process or  processes derived from direct coal liquefaction using a hydrogen donnor solvent  is a 3rd pathway using medium to high pressure hydrogen and medium to high temperature (350 to about 500°C) to directly hydroconvert the oxygenate compounds towards hydrocarbons.

Economic comparison and overall enegertic and weight material balance is a specific field , quite complicating, feed stock  and market dependant with condifdential aspects.

IFPEN published a rewiew 2 years ago relating to biomass conversion (2hd & 3rd Generation Biofuels) and also concerning biomass thermal conversion : OGS&T 2013/July-August / Vol. 68 / N°4 and OGS&T 2013/Sept.-AOct./ Vol. 68 / N°5 .

Thank you all for giving valuable insights!!

What are the hot/promising areas of Pyrolysis these days ?

Alain Quignard Y. Alhassan Vivek Khambalkar Selvaraju Sivamani

Thank you all for deep insights towards determining the conversion efficiency of Biomass by pyrolysis . Your contributions are highly appreciated.

May I ask, is there anyone working on or know about method known to control the biomass products ?

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