PLASTIC PYROLYSIS - PROCESS ANALYSIS

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ABSTRACT

This document lay down the process

analysis for plastic pyrolysis. This analysis is

a key for determining parameters, such as

reaction temperature, reaction pressure,

and time.

It is necessary for observing parameters

effect and considering the effect of

catalysis in upgrading product.


CONTENT

Process FlowChart...................................................... 4

Chemical Composition............................................. 5 Reaction Temperature & Heating Rate.......... 6

Reaction Time & Pressure Inside Reactor......8 Catalysis............................................................................. 10

Catalytic Reaction Temperature......................... 11

Resources......................................................................... 12


PROCESS FLOWCHART 1. Thermal Processing Thermal Cracking

2. Catalytic Process Thermal Cracking + Catalytic Reforming

• Plastic pyrolysis process (thermal or catalytic) classified as batch, semi-batch, or continuous.

a. Batch Process : Time cycle is composed of reactor feeding time (mechanical feeding system), processing time , cooling time , and carbon ash removing time (mechanical discharging system).

b. Semi-Batch Process : During a batch cycle, after processing time is completed , a new PE/PP batch is fed to reactor instead of proceding to cooling step. Heat residue is utilized. However, carbon ash accumulation is a drawback.

c. Continuous Process : Used for high capacity , established using continuous mechanical feeding system , and continuous discharging system for carbon ash.


CHEMICAL COMPOSITION

Feed Chemical Composition

Thermal cracking of (PE/PP) occurs through exposing to high temperatures in an oxygen free ambient resulting in random polymer chain rupture proceeding decomposition into a range of (sulfur–free) paraffins and olefins.

Product Distribution Of (PE/PP) After Thermal Cracking


REACTION TEMPERATURE AND HEATING RATE

1. REACTION TEMPERATURE

For (PE/PP) thermal process, optimum range for producing pyrolysis gas that condenses in a product within L.G.O fraction (450 C째 - 500 C째).

Parameter : Increasing Temperature Within A Specific Range

Temprature @ (450 C째 - 500 C째)

Observed Response (Quantities)

P.Oil (Liquid)

Lighter Fraction (Gas)

C.Ash (Solid)

Increasing temperature above specific range leads to product within kero sene + naphtha fraction.

Decreasing temperature below specific range leads to product within f.oil fraction.


2. HEATING RATE

For (pe/pp) thermal process, optimum range observed within (7C°/min) .

Parameter : Increasing Heating Rate (Reaching Optimum Temperature Range Quickly)

Observed Response (Quantities)

Heating Rate @ (450 C° - 500 C°)

C.Ash (Solid)

Increasing temperature above specific range leads to product within kero sene + naphtha fraction.

Decreasing temperature below specific range leads to product within f.oil fraction.

Parameter : Decreasing Heating Rate (Reaching Optimum Temperature Range Slowly)

Observed Response (Quantities)

Heating Rate @ (450 C° - 500 C°)

C.Ash (Solid)


REACTION TIME AND PRESSURE INSIDE REACTOR

1. REACTION TIME

For (PE/PP) thermal process, optimum processing time observed to be within 70 min.

Parameter : Increasing Reaction Time (Reaching Optimum Temperature Range Slowly)

Observed Response (Quantities)

Reaction Time @ (450 C° - 500 C°)

C.Ash (Solid)

For (PE/PP) thermal process, short processing time means reduction of secondary conversion (aromatics) of primary products (L.G.O).


2. PRESSURE INSIDE REACTOR

For (PE/PP) thermal process, optimum pressure inside reactor observed to be within 1.0 atm.

Parameter : Increasing Reaction Time (Reaching Optimum Temperature Range Slowly)

Observed Response (Quantities)

Reaction Time @ (450 C° - 500 C°)

C.Ash (Solid)

For (PE/PP) thermal process, low pressure means reduction of secondary conversion (aromatics) of primary products (L.G.O).


CATALYSIS

•For (PE/PP) catalytic process, which is basically thermal process plus catalytic reforming, optimum reforming catalyst inside fixed bed reactor observed to be a natural Zeolite.

•Zeolite structure consists of 3 dimensional micro-porous, crystalline solid that contains [AL] , [SI] , [O] framework , cations prefer to fill pores (active sites).

•zeolite should be activated –prior to be used as a catalyst- in order to eliminate impurities.

•Activation is done by increasing surface area (increasing active sites), and increasing acidity so that active site is a proton donor (Bronsted acid) and electron acceptor (Lewis acid),an advantage of using natural zeolite is the ease of modification (activation). natural zeolite is an optimum choice due to its activity, availability, and cost.

Common Zeolites Used For Plastic Pyrolysis

•Catalyst pellets (5mm diameter, 10mm length) composed of 70% natural zeolite 30% bentonite (mass%) packed inside fixed-bed reactor , an optimum range of catalyst mass to feed ratio observed (7% ~ 11% ).


CATALYTIC REACTION TEMPERATURE

For (PE/PP) catalytic process, optimum range for producing pyrolysis gas that condenses in a product within L.G.O fraction is below that range of thermal process (450 c° - 500 c°).

Parameter : Increasing Temperature Within Reacting Time

Observed Response (Quantities)

Temperature @ (450 C° - 500 C°)

P.Oil (Liquid)

Lighter Fraction (Gas)

C.Ash (Solid)

Due to extensive cracking within catalyst bed, pyrolysis gas is reformed resulting in an increase in lighter fractions and decrease in P.Oil.

Also, It Was Observed That HHV (P.Oil Catalytic) > HHV (P.Oil Thermal)

(PE/PP) P.Oil Characteristics

Extensive cracking within catalyst bed eliminates H.G.O production, also it seems that increasing catalyst to feed ratio even beyond observed range can compensate for a lower reaction temperature inside pyrolysis reactor leading to more cost reduction. Catalyst Mass

=

Reaction Temperature


REFERENCES

•Walter Kaminsky, John Scheirs. 2006. Feedstock Recycling and Pyrolysis of Waste Plastics: Converting Waste Plastics Into Diesel and other Fuels, Wiley

•Felder, Roussea .2005. Elementary Principles of Chemical Process. 3rd edition. Wiley

•Ferdianta Sembiring, et al. 2018. “Catalytic Pyrolysis of Waste Plastic Mixture”. IOP conference series: Materials Science and Engineering.

•Marcilla, J.C., Quesada, G.S., et al. 2005. “Study of The Catalytic Pyrolysis Behavior of PE-PP Mixtures”. Journal of Analytical and Applied Pyrolysis, V.74, PP.386-392.

•Seo, Y.Y., Lee, K.H., et al .2003. “Investigation of Catalytic Deg radation of HDPE by HC Group Type Analysis”. Journal of Analytical and Applied Pyrolysis, V.70 , PP.383-398.

•Abadi, M.S.A., Haghighi, M.N., et al .2014. “Evaluation of Pyrolysis Process Parameters on PP Degradation Products”. Journal of Analytical and Applied Pyrolysis, V.109 , PP.272-277.