IDENTIFICATION OF NEEDS

The highest consumption rate in today’s world is of fossil fuel. Fossil fuels are created

by the decomposition of dead plant and animal life that existed in the Earth millions of years ago.

Petroleum, coal, and natural gas are major fossil fuels that are most people need. In 1997, the

world produced approximately 130 quadrillion Btu of energy from oil, 80 quadrillion Btu from

coal, and 70 quadrillion Btu from  natural gas (Alison et al., n.d). 

During the industrial revolution, fossil fuels seemed to be the ideal energy source. The

fairly low cost of converting natural resources to energy causes most countries to use fossil fuels

as their main source of energy, but there is a major problem that arises out of this natural

resources are limited and non-renewable. From the day it has been extracted and discovered, they

have served the mankind and are still one of the most useful tools for human existence. In fact,

the whole world is dependent on fossil fuels to fulfill their daily energy needs.

The consumption of these fossil fuels is going at an high rate which means once we have

used up all of them, we need to rely on alternative sources of energy such as solar, wind and

hydro power to meet our daily needs. Though fossil fuels have their own advantages but the

damage that they cause to the environment can affect entire ecosystem. According to The

National Academies of Science, Engineering and Medicine the United States gets 84% of its

total energy from oil, coal, and natural gas, all of which are fossil fuels. The uses the fossil fuels

to heat homes, run the vehicles, power industry and manufacturing, and produce electricity.

Thus, there is a need in order to find a new type of energy source to replace and reduce

the usage of fossil fuels. The whole world is the potential customers as the fuel is a very popular

type of energy that people use in their daily life.

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IDENTIFICATION OF IDEAS BASED ON NEEDS

Based on the community need of fuels there are ten ideas that we introduce in order to produce

fuel:

1. Producing of fuel from plastic waste

2. Producing fuel from animals fat

3. producing biofuel from waste cooking oil

4. producing fuel from mix carbon dioxide

5. producing fuel from lignocellulosic biomass

6. producing fuel from algae

7. producing of fuel using rubber

8. use water steam as a fuel

9. coconut oil as a fuel

10. producing fuel from animal waste (Biomass)

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SELECTION OF THE IDEAS

From the ten IDEAS that our group presented, the selection of IDEAS are the best by using

concept screening and scoring method.

a) Concept Screening

IDEAS number 10 act as references in this method because that process have similar

with industrial practicing in produce the fuel.

Some of the criteria is consider in select the best ideas such as:

Criteria 1: The availability of the feed stock

Criteria 2: The cost of the feed stock

Criteria 3: The ratio of the product to the feed stock

Criteria 4: Environmental friendly of the process.

Criteria 5: The quality of the feed stock

Criterion IDEAS

1 2 3 4 5 6 7 8 9 10

1 + 0 + + 0 - + + 0 0

2 + 0 + + 0 - 0 + + 0

3 + - 0 - - 0 + - 0 0

4 0 0 0 + - + - 0 - 0

5 + 0 + 0 + - + 0 + 0

Score +4 -1 +3 +2 +1 0 +3 +1 +1 0

Rank 1 6 2 3 4 5 2 4 4 5

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b) Concept Scoring

From 10 IDEALS stated above, we took the best 3 rank from concept screening to do

concept scoring method to determine the IDEA that most best to serve the need for

further study.

Criterion Weight

IDEAS

1 3 4 7

1 30% 4 3 3 3

2 30% 3 2 3 3

3 20% 2 2 1 2

4 10% 2 2 3 1

5 10% 3 2 2 2

Total Score 3.0 2.3 2.5 2.5

Rank 1 3 2 2

By using this method, idea 1 that is converting waste plastic to fuel was chosen to be as our

product that is best serve for our need. In recent years, the using of plastic have increasing

drastically, as plastic waste has created serious social and environmental arguments. At the

present landfilling and incineration of plastics wastes are widely practiced. The production of

plastics in the world has been in steady increasing trend since 1980 from 60 million tonnes to

more than 230 million tonnes in 2005. Figure 1 shows the market and demand for plastics that

has tremendous across the world.

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Figure 1: world plastics production.

Waste plastics composition in Malaysia like other Asian countries as shown in Table 1 is

dominated by organic waste, followed by plastic and paper. Thus, the management of plastics in

Municipal Solid Wastes (MSW) stream in Malaysia is very crucial.

Table1: solid waste composition in Malaysia and other Asian countries.

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Currently in Malaysia, most of the recyclable plastics are being collected via the 3R

programs initiated by the Alam Flora Shd Bhd (central and eastern region, covering Kuala

Lumpur, Selangor and Pahang), SWM Environment Shd Bhd (southern region, covering Negeri

Sembilan, Melaka and Johor) and Environmental Idaman Sdn Bhd (northern region, covering

Kedah, Perlis and Pulau Pinang) which are the appointed concessionaire companies. There are

also some local council that run the 3R programs.

As a conclusion, the feedstock in order to develop the process to achieve the desired product

can be done as there is a lot of plastic production and consumption every year. Table 2 shows the

type of polymer as the feedstock for fuel production and Table 3 shows the product types of

some plastics pyrolysis.

Sources : converting waste plastics into a resource. ( Compendium of Technologies)

Table 2: polymer as feedstock for fuel production.

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Sources : converting waste plastics into a resource. ( Compendium of Technologies)

Table 3: Product types of some plastics pyrolysis

The definition of pyrolysis is the chemical decomposition of condensed organic substances by

heating. The word ‘pyrolysis” is derived from Greek word which is pyro”fire” and lysis

“decomposition”. Pyrolysis is usually the first chemical reaction that involve in the burning of

many solid organic fuels, like wood, cloth, and paper, and also of some kinds of plastic.

For the pyrolysis of plastic, it takes the long chain polymer molecules and then breaks them

into shorter chains by heating and by applying pressure. Essentially, the process will take

million of years to break down carbon into oil naturally. The pyrolysis process does this with

intense heat in a closed system in a short amount of time.

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The conditions that needed to produce pyrolysis oil are more likely to include virtually no

oxygen. The pyrolysis oil can be used directly as fuel or further refined into diesel or jet fuel.

Plastics are durable and its degrade very slow, the molecular bonds of plastic is very durable and

make it hard to undergo process of degradation. Since the 1950’s, there are one billion tons of

untreated plastic has been discarded and it may persist for hundreds or even thousands of years.

The plastics pyrolysis can provide an alternative for the disposal of plastics wastes into

valuable gasoline – range hydrocarbons. In the pyrolysis process, the polymeric materials will

be heated to a high temperatures, so their macromolecular structures are broken down into

smaller molecules and wide spectrum of hydrocarbon will be form. These pyrolytic products

can be classified into a gas fraction, a liquid fraction conssiting of paraffins, olefins, naphtenes

and aromatics, and solids residues.

Liquids fuel can be derived from the plastics wastes undergo normal temperature and

pressure. There will be only some types of thermoplastics undergo thermal decomposition to

yield liquids hydrocarbons used as liquid fuel. PE (Polyethylene) was preferred for the feedstock

of the production of liquids hydrocarbons. With the addition of thermosetting plastics, wood,

and paper will leads to the formation of carbonous substance. As a result, it will lower the rate

and yields of liquids products. It is also depends on the components of the waste plastics being

used as feedstock for fuel production, the resulting liquids fuel may contain other contaminants

such as amines, alcohols, waxy hydrocarbons and some inorganic substances. Unexpected

contamination and high water will lower the products yields and shorten the lifetime of a reactor

for pyrolysis.

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TYPICAL PROCESS FLOW FOR PYROLYSIS

Sources : European Plastics Recyclers Association (2010)

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1) Collection and segregation of polyethylene plastic wastes.

2) Storing of plastic wastes.

3) Shredding of wastes.

4) Feeding and hopper.

5) Flow of wastes into heating vessel in presence of catalyst.

6) Liquid / movement of liquid-vapour into condenser.

7) Tapping of liquids fuel as product.

CHEMICAL REACTIONS IN PYROLYSIS

There are four stages of reactions that occur during the plastic pyrolysis process: initiation,

propagation, hydrogen transfer, and termination reaction.

A) Initiation

in the figures, G represents the side group in the polymer unit, which can be H, CH3 or others.

Figure 2: Sketch of random sciccion reaction in plastic pyrolysis.

B) Propagation reactions

Β-scission was known to be the main propagation reaction which including the end chain

scission reactions and mid-chain random scission reactions. The products from the reaction are

mainly 1-alkenes.

Figure 3: Illustration of mid chain β-scission reaction.

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Figure 4: Illustration of end chain β-scission reaction

C) Hydrogen chain transfer reactions

In this reaction, the molecular weight of the polymer is decrease, which can be found in many

polymerization systems. Hydrogen chain transfer is when the proton is being transfer to other

location. Below are the intermolecular transfer reaction in the polymer chains.

Figure 5: Intermolecular transfer reaction on to the end chain radical.

Figure 6: Intermolecular transfer reaction on the mid-chain radicals.

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Figure 7: Intra-molecular transfer isomerization via (1,6) hydrogen transfer.

D) Termination reactions

This reaction occurs due to dispropotionation of the free radicals or the combination of two free

radicals as shown below. This reaction directly affects the product chain length.

Figure 8: Sketch of the termination reaction or radical combination reaction.

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STOICHIOMETRIC EQUATION

When the Polyethylene molecule undergoes pyrolysis reaction, it will convert into n 1-alkene

molecules, there are n-1 C-C bonds broken in the long chain. Each secondary C-C bond is

broken and turned into one C=C double bond. At the same time, C-H bond dissociation energy

on the carbons with double bond and at the other end also been changed. This process can be

explained as figure below.

Figure 9: Formation of a 1-alkene from PE molecule pyrolysis.

TYPE OF CATALYST USED

The type of catalyst that is used in the process is zeolite. As zeolite catalyst can increase

the production of fuel product. There was a reaction that carried out in a locally manufactured

reactor, with the volume of 1L. During the process, the production of condensable vapor and

fuel gases exerted pressure on the pressure valve and the valve opened at certain pressure to

release the products into condenser and collection system. As a result, it produced 48.6 wt% of

oil, 40.7 wt% of gases, and 10.1 wt% of char at 275 ˚C. But in the other hand, by using zeolite

as catalyst, it has increase the conversion to 51.19 wt% of oil, 35.88 wt% gases, and 12.50 wt%

of waxes. The oil was identified in a mixture of hydrocarbons in a range of kerosene and petrol,

and it can be used after the upgrading the fuel.

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Figure 10: Framework types of zeolite.

PRODUCTION METHOD

Figure 11: Schematic diagram of the production plant of the plastics-derived fuel.

The plastic (PE) pyrolysis is by subjecting plastic to a special condition of temperature

which is a high temperature of 400 degree celcius in the absence of oxygen . After pyrolysis,

deposit will removed from the reactor in order to maintain the heat conduction efficiency of the

reactor. The liquid oil (mixture of liquid hydrocarbons) is continuously distilled.

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The single pass conversion of PE into hydrocarbon was over 99% and a very little char was

produced during the pyrolysis. As pyrolysis of hydrocarbon polymers is a very complex process,

which undergo hundreds of reaction and products, the pyrolysis reactions is a kinetic-

controlled as there are a number of factors that will affect the process and the reactions such as

catalyst, reactor type.

Items Contents

Feed PE (Plastic film, plastic wrap)

End products Fuel oil, carbon black, combustible gas

Heating material Coal, charcoal, wood, fuel gas, fuel oil

Catalyst Zeolite NKC-5 (ZSM-5)

Table 4: items description for the process

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Items (products) Application Sales market

Pyrolysis oil 1. Add into heavy oil

generator to produce

electricity

2. Used as heating

material

3. Sell it into oil

refining factory for

further process

For ceramic factory, glass

factory, electric power

factory, boiler factory, etc.

Carbon black 1. Make into pellet for

burning

2. Further process it

into color master

batch as basic

material to make

pipes, cable jacket.

For coal briquette factory,

plastic factory, cable

factory, etc.

Waste gas Recycle into the fire furnace

for heating the reactor in

order to minimize fuel

material

Table 5: Products of the pyrolysis reaction.

Fuels LPG Petrol Kerosene Diesel Heavy Fuel

Oil

Hydrocarbons C3 to C4 C4 to C12 C12 to C15 C12 to C24 C12 to C70

Table 6: Hydrocarbon range in commercial fuels

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BATCH AND CONTINUOUS REACTOR

Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures in the

absence of oxygen (or any halogen). It involves the simultaneous change of chemical

composition and physical phase, and is irreversible. The word is coined from the Greek-

derived elements pyro "fire" and lysis "separating". In this process we used batch and semi-batch

reactor. Batch reactor because most of researchers utilized batch reactor for thermal and catalytic

pyrolysis of virgin plastic and for post-consumer plastic waste (Wong, et.al. 2014) We chose

batch reactor because it is easy to control the process parameters. The temperature that needed

for the reaction ranged from 300 ˚C – 900 ˚C, and the reaction time is 30 – 90 min.

The batch process is a single- or multi-stage process in which a certain quantity of inputs (raw

materials, auxiliary materials, energy, etc.) are fed into the chemical reaction unit (of the entire reaction) under

conditions suitable for obtaining the desired reaction (temperature, pressure, required time, etc.). In the batch

process, in the reactor and at any given period of time, various actions take place in the wake of which a

concentration of reactants and products varies so long as the reaction progresses. At the conclusion of the

process the mixture is removed from the reactor and it then undergoes the appropriate separation and

processing stages (either physical or chemical) at the required level of cleanliness. This is generally dictated by

the customers for whom the specific product is manufactured.

In the batch process, so long as the batch has not undergone the entire series of actions, there is no

possibility of preparing a further batch. The batch process can be undertaken in one reactor in which all the

actions are carried out one after the other, or in a series of reactors in each of which a different stage of the

process is carried out. The quality of the end product can also be controlled by the addition of appropriate

separation stages between the various other stages as required. Reactants that do not react and which are

separated from the reaction mixture can be returned for a further reaction (usually after they have undergone

treatment or cleaning for by-product contamination), thus fully exploiting the process.

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IDENTIFICATION OF THE INPUT/OUTPUT STRUCTURE OF THE REACTOR

The input structure to the batch reactor is polyethylene with is react with catalyst zeolite at 255

°C. It is capable to produce 51.19 wt% of oil, 35.88 wt% of gases, and 12.50 wt% of waxes

(Wong, et.al. 2014). The influence of zeolite catalytic upgrading of the pyrolysis gases derived

from the pyrolysis of polyethylene has been investigated. The yield and composition of the

derived hydrocarbon gases and oils have been investigated in terms of the temperature of the

catalyst.

Polyethylene was pyrolysed in a batch reactor and the pyrolysis gases passed to a

secondary reactor containing Y-zeolite or zeolite ZSM-5 catalyst. The polyethylene was

pyrolysed at 500°C and the temperature of the catalyst bed was 400, 450, 500, 550 or 600°C. The

oils consisted of mainly aliphatic compounds represented by alkadiene, alkene and alkane

hydrocarbons and their branched chain derivatives. The uncatalysed pyrolysis oil also contained

low concentrations of aromatic hydrocarbons. 

After the reaction is complete in the batch reactor the product produce is Propene,

Octane, Hexadecene and Octacosene. This outlet product is in the form of gas phase. Physical

properties of the chemical element involve in this process is shows in the table below :

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Inlet Reactant Physical Properties

Name Polyethylene

Molecular formula (C2H4)n

Density 0.975 g/cm3

Boiling point 115–135 °C (239–275 °F; 388–408 K) (239–275 °F)

Melting point 110 oC (230 oF)

Viscosity -

Molecular weight average Mw 3,000,000-6,000,000

Outlet Product Physical Properties

Name Propene

Molecular formula C3H6

Density 1.81 kg/m³

Boiling point -47.6°C

Melting point -185.2°C

Viscosity 8.34 µPa·s at 16.7 °C

Molecular weight 42.07974 g/mol

Name Octane

Molecular formula C8H18

Density 703 kg/m³

Boiling point 125.1 to 126.1 °C

Melting point −57.1 to −56.6 °C

Viscosity 542 μPa s (at 20 °C)

Molecular weight 114.23 g/mol

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MATERIAL BALANCE IN THE REACTING SYSTEM

Products Proportion Mass flow (g/s) MW (g/mol) Mol Volume flow

at 400 ˚C

(L/s)

C3H6 10 % 0.96 30 0.0319 1.76

C8H16 30 % 2.87 112 0.0256 1.41

C16H32 40 % 3.82 224 0.0171 0.94

C28H56 19% 1.91 392 0.0049 0.27

Total 100 % 9.56 189.5 0.0794 4.38

The reaction is in liquid form at initial then the product is gases form. We call this type of

reaction is heterogeneous reaction. Plastic wastes enter the reactor in liquid form at standard

temperature and pressure that is 27 oC and 1 atm respectively.

Because the polyethylene is in the form of liquid, then the density of polyethylene is constant.

When the density is constant then the volume metric is constant at the final and initial reaction.

But because the product reaction is gases form, then the change of phase is take into account.

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10 wt/wt % C3H6

30wt/wt% C8H16

40wt/wt% C16H32

19wt/wt% C28H56

All in the gases form

Plastic waste100 wt/wt% Liquid form at 27 ˚C

DESIGN OF REACTOR

Heuristics for Reactor ( Table 11.17)

Rule 3 : The optimum proportions of stirred tank reactor are with liquid level equal to the tank

diameter, but at high pressures slimmer proportions are economical.

Rule 6 : Batch reactions are conducted in stirred tanks for small daily production rates or when

the reaction times are long or when some condition such as feed rate or temperature must be

programmed in some way.

Rule 11 : The effect of temperature on chemical reaction rate is to double the rate every 10 oC.

Rule 12 : The rate of reaction in a heterogeneous system is more often controlled by the rate of

heat or mass transfer than by the chemical reaction kinetics.

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