SRFl, Pyrolysis and Gasification Flashcards
Incentives for SRF
Increased CV by 2.5x
Reduced moisture content
Fuel for cement kilns
How is SRF produced
shredded, screened, metal removal, dried, pelletised
What does the UK do with SRF
do not have enough capacity so export to Germany, sweden, denmark
What needs to be known for producing SRF
Composition variation of waste from each district.
What is pyrolysis
Thermal degradation of organic waste in the absence of oxygen to produce carbonaceous char, oil and combustible gas.
Residence time, heating rate, temp and products for:
a.) slow
b.) conventional
c.) fast
a.) Hours+, low, 400C, Char
b.)Minutes, medium, range depending on products to produce
c.) second, high, 800+, liquid and syngas
Heating rate for:
Cyclonic
Fluidised
Entrained
Fixed
RK
Depends on wall heating or product gas combustion
HIgh
high
low
low
How does Mogami operate small scale pyrolysis
1 tonne of plastics per day
External heating from combustion of product oil or gas
Internal heating produces Hcl rich off gas due to decomposition of PVC.
After dechlorination, pyrolysis gases are switched and product gas are condensed to produce a medium and light oil - non combustible gas are flared.
Rotary kiln Sapporo
1.) Shredder, dryer, pelletiser
2.) Initial heating for HCl gas, combusted to get acid
3.)RK pyrolysis
4.) Condenser, oil drum
5.) Distillation column
6.) Waste gas combustor.
What is gasfication?
Partial oxidation of waste where organic compounds are converted to syngas comprising CO, H2, CH4, tar and ash.
Advantages and disadvantages of Updraft gasifier
+High thermal efficiency
+High moisture fuels
+Simple and can scale up
-High tar content (must be removed which requires energy)
-Lower H2 and CO generation
Advantages and disadvantages of downdraft gasifiers
+High C conversion
+Low tar and ash
+High solid residence time
- Slag formation on grate
-Requires dry fuels
-Poor turndown capability
Advantages and disadvantages of bubbling fluidised bed
+Good contact and mixing
+Good temperature control
+easy start up and shut down.
+Variable fuel quality
-Carbon loss with ash
- Pre - processing required
-Limited scale
How does an Updraft Fixed bed reactor work?
- Feed at top gas at bottom, moves down where it dries, pyrolyzed reduced then oxidised.
-Volatiles are released quickly in pyrolysis zone and partly leaves gasifier, without being combusted.
-Leads to high tar content.
How do downdraft fixed bed reactors work?
Feed and air move in same direction. Volatiles from pyrolysis pass through the oxidation zone, where tar is partially cracked. Gas leaves the bottom with a low tar content.
