Tuesday, March 22, 2011

CONVERSION OF PLASTICS INTO FUELS

Conversion of

Plastics into Fuels

Abstract

Plastic have become an integral part of our lives. Since plastics are relatively low cost and being easily available have brought a use and throw away culture. Each year more than 100 million tones of plastics are produced worldwide because of use and throw culture so plastics waste management has become a problem worldwide.

In this paper, the process of converting waste plastic into value added fuels are explained which a solution for recycling of plastics become. Thus two universal problems such as

§ Problems of waste plastic.

§ Problems of fuel shortage are being tackled simultaneously.

The waste plastics are subjected to depolymerisation, fractional distillations to obtain different value added fuels such as petrol, kerosene, and diesel, lube oil, furnace oil traction and coke.

The process of waste plastic into fuels can literally change the economic scenario of our country. Thus, the process of converting plastics to fuel has now turned the problems into an opportunity to make wealth from waste.

KEY WORDS: Waste plastics, Reactors, Depolymerisation, Fractional distillation.

CONVERSION OF WASTE PLASTICS INTO FUELS

INTRODUCTION:

Plastics play an important role in day-today life, as in certain application they have an edge over conventional materials. Indeed, their light weight, durability, energy efficiency, coupled with a faster rate of production and more design flexibility, have allowed breakthroughs in fields ranging from non-conventional energy, to horticulture and irrigation, water-purification systems and even space flight.

How ever one has to accept that virtues and vices co-exist. Plastics are relatively cheaper and being easily available has brought about use and throwaway culture. Plastics waste management has become a problem world over because of their non-degradable property. A majority of landfills, allotted for plastic waste disposal, are approaching their full capacity. Thus recycling is becoming increasingly necessary.

PLASTICS IN ENVIRONMENT:

Three million tones of waste plastics are produced every year in the U.K.alone, only 7% of which is recycled. In the current recycling process usually the plastics end up at city landfills or incinerator. As with any technological trend, the engineering profession plays an important role in the disposal of plastic waste. Discarded plastic products and packaging materials make up a growing portion of municipal solid waste.

The global environment protectional agency [GEPA] estimates that by the year 2004 the amount of plastic throw away will be 65% greater than that in the 1990’s. The recycling of the plastic is only about one percent of waste plastic in the stream of waste in developing countries as compared to a rate of recycling of aluminum which is about 40% & 20% for paper, where as recycling rate in India is very high up to 20% of waste plastic.

In a short span of five years plastics have captured 40% of total 6.79 billion USD packaging market in India. This situation may grow further in the coming years with more and more US and European companies entering the market. It would be very interesting to note the type of litter we generate and the approximate time it takes to degenerate.

TABLE: Degradability of different waste materials

S.NO

TYPE OF LITTER

TIME TAKEN TO DEGENERATE

1

Organic waste, etc.

1 to 3 weeks

2

Paper

1 to 3 weeks

3

Cotton cloth

8 to 20 weeks

4

Wood

10 to 15 years

5

Wooden items.

10 years

6

Tin, aluminium&metals

100 to 500 years

7

Plastics

A million years?

India has been used as a dumping ground for plastic waste, mostly from industrialized countries like Canada, Denmark, Germany, UK, Netherlands, Japan, France and the United States.

Each year more than 100 million tones of plastic are produced worldwide. Though plastics have opened the way for a plethora of new inventions and devices it has also ended up clogging the drains and becoming a health hazard. The plastic waste accounts to about 5600 tons per day in India. At these alarming levels of waste generation, India needs to set up facilities for recycling and disposing the waste.

Process technology:

Several processes and means have been attempted to fight against the alarming levels of waste generation. However each process had its drawbacks and operational, economical and financial limitations for practical implementation. We have to set up a process to overcome the above-mentioned drawbacks and limitations.

process DESCRIPTION:

Sorting operation:

Generally any waste plastic treatment involves sorting operation, which is a time & energy consuming process .In this process waste plastic can be utilized without any sorting (or) cleaning operation.

The process consists of following operations

A. DEPOLYMERISATION:

1. Loading of waste into the reactors.

2. Depolymerisation of the waste plastic.

3. Collecting the liquid distillate

4. Collecting the combustible gases.

B. FRACTIONAL DISTILLATION:

1. Loading of distillate into the distillation furnace

2. Collecting the fraction of liquid distillate from the distillation tower

The waste plastic from the landfills are segregated and stored in the storage tank. Using hot air to the reactor where depolymerisation takes place conveys it. The depolymerisation of waste plastic under control batch reactor results in conversion of waste plastic in a mixture of fuels at atmospheric pressure and ambient room temperature.

Liquid fuels consist of fraction of gasoline, diesel, and lubricating oil. In the process of conversion, by-products such as gases and cokes are also formed. Gases are tested and majority of them are proved to be in the range of LPG. Coke is available as residue in the process, which is again a saleable product.

PROPERTIES AND PURITY OF FUELS:

The properties of liquid distillate match with properties (Ex: specific gravity and pour points) of high quality imported crude.

The fuels obtained in the waste plastic process are virtually free from contaminants such as lead, sulphur and nitrogen .In the process (i.e.) the conversion of waste plastic into fuels, the properties mentioned above of petrol & Diesel fractions obtained are of superior quality with respect to regular commercial petrol and diesel purchased locally and has been proved by the performance test.

During the process, hazards related to health and safety is reduced to 90% as compared to regular refinery process.

QUALITY OF FUELS:

The quality of gasoline and diesel fractions obtained in the process is not only at par with regular fuels in tests like sp – gravity is 0.7365 /150C CCR (conradson carbon Residue) Ash, calorific value etc but it is also better in terms of quality in test like flash point, API gravity.

ADDITIVES:

Regular fuels obtained from crude oil like gasoline and diesel are subjected to many reactions and various additives are added to improve combustion and meet BIS characteristics before it is introduced to market. However the fuel (Gasoline, Diesel) fractions obtained in the process can be utilized without much processing.

YIELD:

The average percentage output yield of the products in the first phase of reaction depending on the composition of the waste plastic is as follows

Name of the product

Amount in percentage

Liquid Distillate

110 % - 115 %

Coke

05% - 10%

Gas

18 % - 22%

LPG

14% - 16%

Hydrogen etc

01% - 02 %

The percentage of liquid distillate is mentioned in terms of weight by volume whereas percentage of coke & gas are mentioned in terms of weight by weight.

During the second phase of reaction (i.e.) fractional distillation, the average percentage yields of various fuel fractions depending on the composition of the waste plastic are follows

Fuels

Percentage

Gasoline

60%

Diesel

30%

Lubricating Oil

8 –10 %

COMPARISON OF PETROL FROM WASTE PLASTICS WITH REGULAR PETROL

s.no

SPECIFICATIONS

REGULAR

PETROL

PETROL FROM WASTE

PLASTIC

1.

specific gravity at 280 c

0.7423

0.7254

2.

specific gravity at 150 c

0.7528

0.7365

3.

gross calorific value

11210

11262

4.

net calorific value

10460

10498

5.

api gravity

50.46

60.65

6.

aniline point in 0 c

48

28

7.

aniline point in 0 f

118.4

82.4

8.

flash point

23

22

9.

pour point

< -20 0 c

< -20 0 c

10

cloud point

< -20 0 c

< -20 0 c

11.

reactivity with ss

nil

nil

12.

reactivity with ms

nil

nil

13.

reactivity with cl

nil

nil

14.

reactivity with al

nil

nil

15.

reactivity with cu

nil

nil

16.

octane rating

83

95

17.

mileage

44.4

44.0

18.

time for 0-60 kph

22.5 sec

18.1 sec

19.

co % at 400 rmp/hc

2.8

3.5

20.

comments on engine noise

more

less

FEASIBILITY:

The production of the fuels from the waste plastic of various sorts has been carried out a number of times to arrive at the unit cost of production. The break - up of the cost for per kg input of the plastic and the related output for the same is depicted in the table below.

Process brief for 1 KG input and the yield of output

input

qty

rate

per kg

amount

(rs).

output

qty

(liter)

rate

per

liter

amount

(rs).

plastic

1.00

2.00

2.00

petrol

0.600

37.50

22.50

labour

5.00

diesel

0.300

25.50

7.65

service

charge

2.50

lube oil

0.100

15.00

1.50

total

1.00

9.50

1.00

31.65

Conclusion:

Since, the plastics are non-biodegradable, the development in biodegradable plastics are still lagging behind. So it is essential to convert the plastics for some useful purposes in order to reduce the waste plastics to environment. . Thus, the process of converting plastics to fuel has now turned the problems into an opportunity to make wealth from waste.

This paper is of greater importance in the present Indian scene in view of the serious energy crisis and is in the interest of national economy.

References:

Ø Outlines of chemical engineering by Drydens.

Ø Shreeve’s Handbook of chemical engineering.

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