PLASMA PYROLYSIS FOR RECOVERY OF ENERGY FROM PLASTIC WASTE
B.Ruj1*, P.K.Chatterjee1, and A.K.Goel2
1 CSIR-Central Mechanical Engineering Research Institute (CMERI), Durgapur-713209, West Bengal, INDIA
2 Petroleum Conservation Research Associations, Ministry of Petroleum & Natural Gases, New Delhi, INDIA

e.mail: biswajitruj@yahoo.co.in ; bruj@cmeri.res.in
Phone: +91-343-6452156; Fax: +91-343-2544567

Abstract
The problem of safe disposal of plastic waste, together with the increasing cost of petroleum products, has encouraged researchon the possibility of their conversion into useful forms of energy or chemical products. Plasma pyrolysis is an innovativetechnology for transforming high calorific plastic waste into a valuable synthesis gas (syngas) by means of thermal plasma. The
process developed is a drastic non-incineration thermal process, which uses extremely high temperature in an oxygen-starved
environment to completely decompose input plastic waste into syngas, composed of very simple molecules viz : CO, H2 andhydrocarbons. A 20 kg/hr capacity plasma arc pyrolyser for treatment of plastic waste as well as energy recovery options fromwaste plastic has been indigenously designed, developed, installed and studied its performance. After pyrolysis of plastic waste
in the plasma arc reactor, generated hot gases (syngas) are quenched through water scrubbing. The Syn gas produced fromplasma reactor has been used in an IC-Engine Generator combination for generation of electrical power. Syngas composition
has been characterized by Gaschromatograph, residue/ash collects at the bottom of the pyrolyser has been characterized by
Neutron Activation Analyzer (NAA). Techno-economic study and research results indicated that the developed plasma pyrolyser
may be a useful way of plastic waste treatment for energy recovery.

Keywords: plasma pyrolysis, plastic waste, syngas, energy

1. Introduction
Plastics have been one of the materials with the fastest
growth because of their wide range of applications due toversatility and relatively low cost. Since the duration of lifeof plastic products is relatively small, there is a vast plastics
waste stream that reaches each year to the final recipient
creating a serious environmental problem. So, the plastic
waste management is an important issue in bothdeveloped and developing countries nowadays [1-4]. To
alleviate part of our energy crisis and environmental
degradation, it has become imperative to make use ofBlock diagram- Plasma pyrlysis systemappropriate technologies for recovery of resources fromplastic waste. The present approach in this study ie,
plasma pyrolysis has a number of unique advantages overconventional pyrolysis. When carbonaceous solids areinjected into plasma, they are heated up very rapidly andthe volatile matter is released and cracked giving rise toCO, H2, CH4, C2H2 and other hydrocarbons. It is thereforeof considerable interest to study plastic waste pyrolysis inplasma processes for gaseous fuel or chemical production
purposes.

2. Materials and Methods

Experimental setup of plastic waste plasma arc pyrolyser

The experimental set-up consists of mainly feeding, plasmaarc reactor and cleaning & cooling sections. Graphite andcarbon electrodes have been fixed inside the plasma
reactor in such a way so that supply of voltage throughtransformer generates high temperature at the sparking
zone. Carbon electrode (-ve) is fixed upon a tripodarrangement at the bottom of the reactor and the graphite
electrode is fixed at the top of reactor. The gap in between
the electrodes is adjusted through a lead screw
arrangement to facilitate the continuous arc discharge. The
plastic waste beads are gasified at high arc temperature
and a combustible gas resembling a synthetic natural gas(syngas) is produced. The syngas generated is passed
through a water scrubber for cleaning and quenching thehot syngas. An ID fan is used to draw the syngas from thereactor. The syngas produced from plasma reactor has
been used in an IC-Engine Generator combination forgeneration of electrical power. Techno-economic study ofthis process has also been carried out.

3. Results and Discussion
Performance study of the developed plasma pyrolyser has
been carried out with the plastic waste as feeding material.
The major gas components of the product gas arehydrogen, carbon monoxide, methane, acetylene, ethylene
and other hydrocarbons which are combustible in nature

Chromatogram of syngas
It is observed from the experimental study that 1 kg/hr
plastic requires roughly 1 kWe power in a plasma gasifier.
The calorific value of plastic is 43.5 MJ/kg. If the overall
efficiency of conversion is 30 % then the output electricalenergy is 13.05 MJ which is equivalent to 3.6 kWe for 1
kg/hr plastic conversion. Considering 1.2 kWe for auxiliary
power requirement the net recovery is 2.4 kWe .

4. Conclusions
The present study reveals that there is a great potential fordevelopment of thermal plasma pyrolysis technologies
applicable to plastic waste disposal management withenergy recovery. Again, considering the fact that the raw
material used in this process is plastic waste which is asource of pollution and governments across the globe havespend huge amount of money to handle them. Thisdeveloped process will be a handy and economic one inthat perspective.

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