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Copy of Pyrolysis

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on 24 December 2013

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Transcript of Copy of Pyrolysis

Towards Cleaner,Greener Fuels
Pyrolysis of Rice Straw
What is Pyrolysis ?
A process that chemically decomposes oragnic matter by heat in the absence of oxygen.

Organic materials are transformed into gases, small quantities of liquid, and a solid residue containing carbon and ash.

The off-gases may also be treated in a secondary thermal oxidation unit.
Why Rice Straw ?
Rice straw contains Lignin-an unusual biopolymer, because of its heterogeneity and lack of a defined primary structure. Its most commonly noted function is the support through strengthening of wood (xylem cells) in trees
Lignin: Structure
# Alcell lignin can be valorised by BFB pyrolysis at 400°C in a phenolic bio-oil and biochar.

#Typical yields (d.b.) are 15 wt% gas, 40 wt% oil and 45 wt% char. The bio-oil is a mixture of monomeric and oligomeric phenolic compounds, water and low boiling components like methanol.

#The phenolic compounds can be used as petrochemical substitution options for applications as wood-adhesives (resins), bio-plastics, chemicals, bio-fuels, etc.

#The porous biochar has potential as soil improver to decrease the amount of fertiliser.
Since Rice Straw contains 12.3% lignin and nearly 3 million tonnes of it is generated annually, it makes a good choice as the feed for pyrolysis.
Process Design:
Handling and Preparation
Bales of rice straw are opened and transferred to
the milling area using a set of appropriate conveyors.
The straw is then passed below a magnetic separator before it is directed to knife mills. The milled straw is then sieved using mechanically vibrating screens with 2mm openings.
The milled straw of size <2mm is then fed to a storage bin equipped with rotary air locked feeder to ensure the regular and steady feed to the
Fast Pyrolysis in a FBR
The bubbling fluidized bed reactor contains a bed
of silica sand which is fluidized using clean gases
produced from the pyrolysis as well as inert nitrogen gas. The milled rice straw is introduced at the bottom of the reactor where it is mixed with the hot agitated sand particles and transformed to three basic phases:
§ A solid phase comprising small carbon
particles and ash (char)
§ Condensable vapours which essentially
constitute the biooil product
§ Non- condensable gases
The fluidized silica sand, which withstands a temperature of about 1500 C and is in a state of
continuous turbulence, promotes fast and homogeneous heat transfer to the rice straw particles ensuring high efficiency of the pyrolysis process and the continuous and rapid evacuation of the produced vapours. The reactor is indirectly heated using the gases produced from the char burning, as well as the non- condensable gases which have been cleaned using electrostatic precipitator and are burnt in the pyrolyzer to get rid of all combustible matters. The fast pyrolysis process is completed in about 1-5 seconds at
450-550 C.
Solid Phase Separation
& Combustion
The char is separated from condensable vapour and gases in high efficiency cyclones and is temporarily stored before being directed to a combustor using pneumatic conveyor. The char is combusted at about 1600-1800 oC and the hot gases are used for heating the pyrolyzer
Cooling & Storage
After separating the char, the condensable
vapours and non-condensable gases are cooled to about 100 C by a condenser using chilled water at 4 C. The condensed vapours are further cooled to about 40 C to form the bio-oil which is then stored.
Cleaning and Reusing the Non-Condensable
After condensing the bio-oil, the resulting gases
and residual vapours are directed to electrostatic
precipitators before being reused in the fluidized bed reactor.
Simulation Using Aspen HYSYS
Fluid Package: Kabadi-Danner
Elemental Analysis of Bio-Oil at various temperatures:
The calorific value has been found to have an average value of about 29kJ/kg.
•Hydroxides at wave length 3150-3600 cm-1
•Esters and carboxylic acid derivatives at wave length 1720-1780 /cm
•Methyls and methylene groups at wave length 2930-2980 /cm
•Aromatic compounds at wave length 700-900 /cm
•Amines at wave length 2361cm-1 for biooil prepared at 500-600 but not at 450 C indicating that amines are not formed at lower temperatures.
•Confirms the presence of the phenyl, phenolic, ethanol, methyl and methylene groups
Economic Factors:
Bio-oil with adequate characteristics has been produced by fast pyrolysis of rice straw which is currently an environmental nuisance. Experimental results indicate that bio-oil with relatively high yield could be could be obtained at 550 C.
The produced bio-oil has composition of 54% C, 9.55% H2, 1.76% N2 and 34.56% O2 with calorific value of 29 kJ/ kg.
Based on process design and basic engineering for an integrated scheme, techno-economic appraisal indicated that the process is viable.
However, production facilities have to take into consideration storage and transport requirements. Also, it is necessary to ensure steady production using other ligno-cellulosic materials along the whole year.
For Rice Mills in CBE
#Rice Mills can consider employing this pyrolysis setup to use the bio-oil for minor needs.
#This not only reduces wastage of straw, but also provides an economic, clean, green fuel.
A Project by:
Keshav Narayan CSE11421
Padminy Kurdekar CSE11434
Shabala Natarajan CSE11449
Shruthi Krithika J CSE11451
Sukriti Bharti CSE11455

Let's Build A Greener Planet!
Key Design Factors:
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