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Waste Plastics as an Alternative Energy Source

JOANNA POŁOMSKA*, JERZY BARON**, JADWIGA ZABAGŁO**, WITOLD ŻUKOWSKI**

Waste Plastics as an Alternative Energy Source
Keywords
waste utilization – energy recovery – thermal destruction – alternative fuel – air pollutants
Abstract
Current trends of technique and technology result in a wide of application of plastic materials. However,
the growth in production causes also a lot of waste plastics consequently. Among lots of methods of
utilization, thermal decomposition methods of waste plastics, as materials produced from the same stock as
natural high calorific fossil fuels, are undoubtedly very suitable methods for a total removal of waste plastics
from the environment with simultaneously the thermal energy recovery. But improper plastic combustion
processes, what are very complicated processes, may contribute to the serious environment contamination.
Thus, it is very important, that combustion chemical processes are studied properly, and then industrial
technology processes may be controlled. It is particularly important when we consider high costs of complex
operations on exhaust gases form large incineration plants. Public awareness of possible environment and
health hazards contributed to not only the more restricted emission standards but also to the interest on crucial
aspects of physical and chemical phenomena of industrial combustion processes. Nevertheless, complexity of
combustion processes of polymeric materials is not the argument against the environmentally-friendly energy
recovery possibility form plastic waste with the mandatory policy of a sustainable development satisfied.
There is a necessity that each parameter that has an influence on the combustion process progress is considered and most of the toxic products of the incomplete combustion are identified by available analytical
methods and successfully eliminated. In the following work some experiments of the co-combustion process

of bisphenol A polycarbonate with propane and 50 % air excess in the fluidised bed reactor filled with the
quartz sand or the limestone in the different temperature conditions are presented. The results confirmed the
general thesis about the influence of such parameters as the temperature value and the kind of the reactor bed
on the combustion progress and the flue gas components. The higher temperature value affected in positive
way the whole process because lower emissions of the incomplete combustion compounds were registered in
the flue gases then. There was also observed that the combustion in the presence of the different fluidising
materials filled the reactor may considerable change the character of the whole process. In case of the
limestone bed smaller temperature variations were registered in the reactor freeboard space when compared
with the quartz sand bed what may indicate different chemical reactions occurred.

*
**

mgr inż., Wydział Inżynierii Środowiska, Politechnika Krakowska, asiapolomska@gmail.com
dr inż. Jerzy Baron, mgr inż. Jadwiga Zabagło, dr hab. inż. Witold Żukowski, prof. PK, Wydział Inżynierii i Technologii
Chemicznej, Politechnika Krakowska, baron@pk.edu.pl, zabaglo@chemia.pk.edu.pl, pczukows@pk.edu.pl
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Połomska J., Baron J., Zabagło J., Żukowski W.: Waste Plastics as an Alternative Energy Source

1. Waste Incineration
Waste incineration is commonly used to reduce the volume and the toxicity of municipal solid
waste. And as in other combustion processes, the principal gaseous products of waste incineration
are carbon dioxide and water vapour. But waste incineration also produces by-products such as ash
and some amounts of organic and inorganic compounds. Other contaminants that are released in
exhaust gases from waste incineration plants may contain lots of harmful chemical compounds,
like particulate matter, carbon monoxide, nitrogen oxides, sulphur oxides, volatile organic
compounds, polycyclic aromatic compounds, dioxins and furans. The presence of these harmful
substances in the exhaust gases is determined by the waste stream composition, by the combustion
process itself and by the reactions occurring in the flue gases after combustion. The amount of
toxic products of incomplete combustion may be successively limited by the enough time of
combustion processes, the effective mixing of gases in combustion chambers and high combustion
temperature. When the gases in the combustion chamber mix continuously with air and proper
temperature values are maintained, then optimal conditions are achieved. In correctly designed
chambers the hazardous pollutants may be completely destroyed. Because all of the crucial issues
are in the public awareness nowadays, so environmentally-friendly technologies of waste
incineration may be realized [4].
In many countries incineration is widely used not only to reduce the volume of municipal-solid
waste but also to produce some forms of energy like heat, steam or electric energy. Firstly in 1960

combustion in low-efficiency incineration plants without energy recovery or advanced pollutioncontrol technology burned several percent of the municipal solid waste generated. In 1980 waste
incineration was decreased. Nevertheless, because there has been more and more interest about
waste-to-energy policy, by 1990 waste incineration had increased again. There were a few reasons
that had caused the decreasing in the municipal-waste incineration [4]:
− some alternative low-cost methods of waste disposal like land-filling,
− local people resistance what resulted in other locations of waste incineration plants,
− reusing of products and obligatory programs for waste recycling and so reduction of amount of
waste,
− some amount of municipal waste that can not be monitored.
Individual owners of houses and hotel managers had practised uncontrolled combustion of
municipal solid waste in their small waste incinerators for many years. But, from that time, waste
incineration technology and emission control have improved considerably. Nowadays large-scale
incineration plants are specially designed furnaces. Today, it is known, that the first step to reduce
the emissions of harmful substances have to start from the limiting of formation of them in the
incinerators by the reduction of pollutant precursors (e.g. chlorine, metals, nitrogen, sulphur) in the
waste stream. Formerly, typical waste incineration plants might be fed a heterogeneous mixture of
various-component municipal solid waste including toxic elements that were transformed into or
catalyzed the formation of pollutants. The combustion processes had been carried out with no
respect to temperature and oxygen control so consequently some waste components were often not
completely burned. Today, not only the volume but also the toxicity are considered during planning of waste incineration [4].
2. Fuel Properties of Plastics
Plastics have a widespread usage in our community today and the market of plastics has
increased rapidly over the past few decades. They are used in the construction of many items in the
development of numerous industrial, commercial and domestic applications. All plastics are
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polymers with long chain molecules. Generally, they are flexible and unbreakable materials, but
there are many rigid and brittle plastics and these physical features depend on the particular
plastic’s chemical characteristics. There are two basic kinds of plastics: thermoplastic materials
which can be re-melted, reformed and reused, and thermosetting materials which cannot be
reformed [3].
Plastics are produced from petroleum sources. Several percent of all the petroleum extracted
from the earth each year is intended to the petrochemical industry and from some of this amount of
petroleum plastics are produced. Petrochemical plants produce the basics of plastics and these
basics are then processed to final products [3].
The quantity of plastics in municipal solid waste is growing rapidly nowadays. The content of
plastics in a typical waste is directly proportional to the plastic consumption. The increase of plastic
waste may cause many problems with the disposal. Presently, the most common methods of the
disposal of solid waste including plastics are land-filling and incineration. However, there are many
drawbacks of land-filling of waste plastics, because covering waste plastics with soil simply removes
their visibility since plastics do not decompose. Most plastics are resistant to chemical corrosion and
biological attack and thus waste plastics may remain undamaged for many years. Dumping plastics
to sea does not result in their degradation as well. However, the increase of the content of plastics in
municipal solid waste brings about the higher heating value of these waste [3, 14, 15].
Waste incineration provides considerably reduction of the volume of waste and the heat
generated during the process may be utilized, but there are many unresolved problems when
combustion of municipal solid waste with waste plastics is considered. Application of conventional incinerators is usually not effective because combustion of plastics is often incomplete. Low
temperature of the combustion, below 760°C, may result in the emission of a lot of smoke because
of the burning of organic plastic waste. Grate systems may be found unsuccessful because heavier
thermoplastic polymers melt and create a sticky mass that block the air supply and inhibit the
process. Probably the most important problem with conventional incineration plants that burn
waste plastics is the high calorific value of plastic materials, which is approximately 24 MJ/kg to
43 MJ/kg. Most municipal sold waste incinerators are designed to burn materials that generate
much less heat then plastics, between 11 MJ/kg and 23 MJ/kg. However, plastics with their
chemical differences, high molecular weights and hydrocarbon natures may sometimes inhibit the
efficiency of the combustion of waste materials in conventional incineration plants. [3, 14].
3. Plastic Combustion Basis
Incineration of waste plastics, like other combustion processes, is a very complex phenomenon.
In a fire mass and heat fluxes to and from the combustible substance and the surrounding
atmosphere are occurred. The whole combustion process consists of a few stages and depends on
mainly the kind of the polymer [13].
The kind and the amount of the products what are created during the thermal decomposition of
the specific material substantially depend on the physical conditions under which the material is
decomposed. When the surrounding atmosphere is low in oxygen then a pyrolysis occurs but the
oxygen-rich atmosphere results in an oxidative pyrolysis or a flaming combustion. All natural and
synthetic polymers contain carbon so when they are burnt carbon monoxide and carbon dioxide
are generated. But, in fact, the smoke from polymer combustion processes is a very complex
mixture of solid particles and aerosols, there are lots of saturated and unsaturated hydrocarbons,
partially oxidized fragments of particles and more complex aromatics [7].
The combustion of polymers is an extremely interesting process so it is examined in different
ways in many special controlled flammability standards. For these purposes some appropriate
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Połomska J., Baron J., Zabagło J., Żukowski W.: Waste Plastics as an Alternative Energy Source

devices and apparatus are used. The most common parameters for testing and measurements
during small-scale flammability tests include [1]:
− the sample size, the dimensions and the orientation,
− the sample exposure to small flame or radiant heat,
− the sample environment (the oxygen concentration),
− the test measurements (the ignition time and the flame extinguishment, the dripping of the
burning or non-burning polymer melt and the ignition of the combustibles in the close
proximity to the test sample, the light obscuration by the smoke, the release rate of the smoke,
the heat release and the rate and the extent of the flame spread and the surface charring).
The process of the polymer burning can be started by setting a fire that may be initiated by the
exposure of the polymer to heat with or without using of a pilot flame. The burning proceeding
depends on the kind of the polymer. The exposure of thermoplastics to external or internal heat
fluxes in a fire brings about the polymer softening and the melting, and next the release of some
vapours to the environment but without the significant surface charring, whereas the exposure of
thermosets to external or internal heat fluxes in a fire generally results in the surface charging and
the release of some vapours to the environment. The mixture of the polymer vapours with air is
created and a combustible or a non-combustible zone around the polymer sample can be formed.
The combustible mixture ignites the polymer surface and some flames are then observed, while the
non-combustible mixture does not ignite. Because of the vapour ignition, the continuous process
of the polymer burning can be maintained. The expansion of the fire ignites the polymer surface
ahead and the release of some heat and smoke take place. The mass of the polymer sample is
reduced. The heat generated is transferred ahead and the growth of the polymer surface
temperature to the ignition temperature takes place and this temperature is maintained until the
polymer vapours ignite. During the whole thermal decomposition process including the ignition,
the combustion and the fire propagation, the incomplete and the complete combustion products
and the heat are generated. Considering more exactly of the polymer burning process, after when a
part of the sample melts, the molten and burning drips flow away from the heat source and they
burn as a liquid fire and also they ignite other parts of the polymer and other materials located
close to the fire. All the physical processes (so the softening, the melting and the flow of the
molten burning drips) and also the chemical processes (so the kind of the reactions in the flame),
what are carried out during the polymer burning process, depend on the polymer morphology [1].
The incineration of waste plastics have to be maintained by the energy released during the
combustion process, so the amount of the energy have to be sufficient to heat the air, that is needed
to oxidative reactions, and also the incoming waste plastic materials to the ignition temperature,
otherwise some fuel, that sustains the burning, have to be added. Beyond the air excess, the
combustion process is influenced also by the temperature and the time in the following way: while
higher temperature values, then shorter time is needed to attain the same effect of the oxidation
rate, and as the reverse, with lower temperature values the oxidation process is slower and the
combustion time is longer. It should be mentioned that the appropriate mixing conditions are also
very important because every mass of the waste plastics have to come in contact with the oxygen
form the air supplied [11]. There are some methods available to improve the mixing of the air and
the waste streams, e.g. fluidised bed reactors.
4. Experimental Data and Discussion
Among lots of various plastic materials, the special attention should be devoted to those which
are characterized by a complex chemical structure, so to those plastics which particles include not
only carbon and hydrogen molecules but also oxygen molecules or some other molecules like
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nitrogen or sulphur, and to those plastics which particles are composed of molecules that are
combined together not only by linear bonds but also by highly energetic aromatic bonds, what
makes those chemical compounds very stable and difficult to decompose. To break such chemical
structure during a combustion process a lot of energy and a high temperature are needed. Often, it
may be impossible to decompose thermally such compounds without using special methods.
In the following work a few experiments of the co-combustion process of some
bisphenol A polycarbonate samples with propane in the fluidised bed reactor, filled with the quartz
sand or the limestone, are presented with the results below in some graphs. Polycarbonate is a
thermoplastic polymer with a very high oxygen index equal to 26 (what indicates the minimum
volumetric concentration of oxygen in an oxygen – nitrogen mixture which will just support
combustion; higher OI values represent better flame retardation) and besides it is classified as V-2
by Underwriters’ Laboratory what means a material which have to be exposed to a relatively high
temperature before it will ignite [10, 12]. Because of the specific properties of polycarbonate, it is
commonly used in lots applications. It is an engineering polymer used in many everyday-usage
utensils in housewares, in laboratories and in industry as well. Polycarbonate typical engineering
applications may be presented in e.g. electrotechnical and electronic industry (switch and lamp
enclosures, connectors, plugs, sockets, loudspeakers, electrical insulation films, mobile phone
enclosures, identity cards, credit cards, compact discs and digital versatile discs), automotive
industry (streetlights, traffic signals, automotive windows, lampshades, reflectors, headlights,
taillight covers, interior lights, motorcycle windshield visors and helmets), a great deal of food
package and domestic utensils (drinking bottles, drinking glasses, egg boilers, coffee makers,
coffee filters, plastic dishes and trays, beverage pitchers, wine carafes, electrical kettles,
attachments for electrical grills and microwave ovens, electric shavers, hair-dryer, tanks for flat
irons), laboratory equipment (tubes, rods, microscope parts and flash-light instruments), medical
industry (some apparatus like blood oxygenators, dialysis machines, and also optical glasses and
diverse kinds of lenses), leisure devices (like ski carriers or binoculars), research animal enclosures
and lots of other technical employment and practical usage [2,10]. All these devices at the final
stage of their usage become waste components and consequently there is a need of the utilization
of them. Waste materials containing polycarbonate or creating from polycarbonate may cause
some serious problems while municipal waste combustion processes in industrial incineration
plants. The specific chemical construction of polycarbonate makes the polymer very thermally
stable. The results of the following presented laboratory-scale experiments are the prove that the
thermal decomposition of polycarbonate in combustion processes is possible and may be applied
in industrial waste incineration plants as well.
The whole laboratory position, which was used for the performance of the few experiments, is
schematically presented in the figure 1. The combustion processes that are realized in this bubbling
fluidised bed reactor can generate the heating power about from 5 kW to 15 kW, what depends on
the combustible substance applied. The reactor is the horizontal oriented cylindrical quartz tube,
which diameter equals to 96 mm, the height equals to 500 mm and the wall thickness is equal to
3 mm. The tube is resting on a flat perforated Cr/Ni steel distributor which thickness is equal to
1 mm. The perforation is made as a sequence of circular holes of 0.6 mm in their diameters in the
quantity of 6.25/cm2. The reactor principle operation arises from its construction and there are
three main zones if physical and chemical processes are considered. The first zone, the plenum
chamber, is located at the bottom, the air and some propane were mixed there. The streams of
gases supplied to the reactor plenum chamber were equal to 1.650 dm3/s of air and 0.046 dm3/s of
propane, measured at the ambient temperature. The mixture of the gases were then supplied
by the distributor to the bed, the second zone, and the fluidising flow of the bed was maintained.

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Połomska J., Baron J., Zabagło J., Żukowski W.: Waste Plastics as an Alternative Energy Source

HORIBA VA-3000 - PG-250
CO2 ,CO,N2O,SO2 (IR)
O2 (EC), NO,NOx (CLA)
24
22

23 MRU VarioPlus
O2 ,CO,NO,NO2 ,SO2 (EC)
CO2 ,VOCs (IR)

ECOM SG Plus
O2 ,CO,NO,NO2 ,SO2 (EC)
25

J.U.M. 3-200
VOCs (FID)
20

26

6

17
5
19
3
18
9

21

11

16

8
2

10

7

21

4
21

12
13

1

1 - plenum chamber
2 - bubbling fluidised bed
3 - freeboard space
4 - perforated distributor
5 - reactor cover
6 - pilot flame
7 - bed thermocouples
8 - freeboard thermocouples
9 - insulating sleeve
10 - air rotameter
11 - propane rotameter
12 - propane container
13 - air blower
14 - air blower contoller
15 - air pipe
16 - propane pipe
17 - flue gas sampling probe
18 - ash trap
19 - cyclone
20 - exhaust fan
21 - valve
22 - ECOM SG Plus gas analyser
23 - MRU VarioPlus gas analyser
24 - HORIBA VA-3000 - PG-250 gas analyser
25 - J.U.M. FID 3-200 gas analyser
26 - data storage system

15

14

Figure 1. The fluidised bed reactor with the measuring devices and the data logging system
Rysunek 1. Reaktor fluidyzacyjny wraz z zestawem urządzeń pomiarowych oraz systemem rejestracji danych

The chemical reactions of the combustion processes were just observed mainly in the fluidising
bed, which porosity and temperature altered all the time. The air in the quantity of 50 % excess,
was responsible for the ensuring of the special oxidizing conditions, what were required for the
particular arrangement of the combustion processes, and the propane, as a high calorific
hydrocarbon fuel, heated the sand or the limestone fluidising bed in the reactor. As a result, the
concentration of oxygen in the flue gases was about seven percent during the propane combustion
process and the temperature of the bed depended on the position of the moveable insulating sleeve,
which covered the reactor tube partially at the height of the freeboard location or was removed
completely, and that is why, the different bed temperature values, 960°C and 900°C, were
achieved appropriately at the same fuel distribution to the reactor. In the following few
experiments the mass of the fluidising bed was equalled to 300 g in each case, and the diameters of
the sand particles were about from 0.385 mm to 0.430 mm and the diameters of the limestone
particles were about from 0.500 mm to 0.600 mm. The temperature in the bubbling bed was
measured by the set of two Cr/Ni-Ni thermocouples located 20 mm and 50 mm above the
perforated distributor. The whole space of the fluidising bed had almost the same temperature
during each specific experiment. Above the bed, in the freeboard space, the third zone, the pilot
flame used for the ignition initiation was located, and through the freeboard space the parts of the
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solid fuel, the samples of polycarbonate, were inserted to the hot fluidising bed, where afterwards
they were ignited by the combustible air-propane mixture and then were heterogeneously burned
bombarding by the particles of the fluidising bed material. The temperature in the freeboard space,
above the fluidising bed, was monitored by the set of eight Cr/Ni-Ni thermocouples, the first one
180 mm above the distributor and the others: 187 mm, 195 mm, 204 mm, 214 mm, 224 mm,
235 mm and 245 mm located in the sequence on the axis of the reactor. The temperature values in
the freeboard space depended on the height above the distributor and these temperature values
were higher for the points located closer to the fluidising bed (and so closer to the distributor and
so closer to the main zone of the combustion processes, because in the bed the highest temperature
values were observed) and were equalled to about from 800°C to 750°C in case of the limestone
bed and from 830°C to 770°C in case of the sand bed. The values of the temperature growths in
the freeboard space, that are mentioned in the further description of this work, are the mean values
form these eight values of the temperature growths in the listed points. Next to the reactor, the
exhaust fan was located and it contributed to creating a small subatmospheric pressure, so that the
flue gases were not spread in the laboratory room but were taken outside into the atmosphere. The
laboratory position was equipped with four devices for the measurements of the concentrations of
the selected compounds in the flue gases:
− MRU Vario Plus gas analyser with some electrochemical sensors for detecting of O2, CO, NO,
NO2 and SO2 and some IR sensors for identification of CO2 and VOCs,
− Ecom-SG Plus gas analyser with some electrochemical sensors for detecting of O2, CO, NO,
NO2, SO2,
− Horiba VA-3000 - PG-250 gas analyser with some IR sensors for CO2, CO, N2O, SO2
identification, some electrochemical sensors for detecting of O2 and some chemiluminescent
acid sensors to monitor NO and NOx concentration,
− and J.U.M. 3–200 gas analyser for monitoring of the total concentration of VOCs with FID
method applied.

Figure 2. The propane combustion
(960°C, sand bed)
Rysunek 2. Spalanie propanu
(960°C , złoże piaskowe)

Figure 3. The polycarbonate co-combustion
process with propane (960°C, sand bed)
Rysunek 3. Współspalanie poliwęglanu
z propanem (960°C, złoże piaskowe)

The emissions of all nitrogen oxides that were monitored (NO, NO2, N2O, often given as NOx
and calculated as NO2) and sulphur dioxide (SO2) were almost negligible during the whole time of
the experiments because neither propane nor bisphenol A polycarbonate without some specific
pigments include nitrogen and sulphur in their chemical compound structures. All the data from
the measurements of the concentrations of the monitored components in the flue gases (O2, CO2,
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CO, VOCs, NO, N2O, NO2 or NOx and SO2) and of the temperature values in the fluidising bed
and in the freeboard space were registered in the frequency of 1 Hz and were saved on the
computer hard disc.
During the experiments, firstly, some propane was used to initiate the ignition and to heat up
the fluidising bed (the sand bed or the limestone bed as well). Some photos, which were made,
confirmed the fact that the combustion of propane in the fluidised bed reactor was a process
without flames and so the oxidative reactions between the air and the fuel were nearly complete.
Thus, the emissions of carbon monoxide and volatile organic compounds were very low then. The
appearance in the hot fluidising bed of some samples, from two to five pieces, of polycarbonate of
the masses about from 40 mg to 100 mg, which were thrown from the top of the reactor, was
resulted in some periodic blazing flames above the fluidising sand bed, in the freeboard of the
reactor, and at that time sudden temporary growths in the measured emissions of carbon dioxide,
carbon monoxide and volatile organic compounds in the flue gases were observed. The
concentration of oxygen in the flue gases decreased then. During this part of the experiment the
reactor quartz tube was also covered with a very thin layer of some soot, what is the prove, that the
combustion process of polycarbonate was incomplete. The emission of the carbon dioxide and the
water vapour, that are the main products of the combustion process of the specific mass of the
polycarbonate sample can be easily approximately calculated from the following formula (1):
CH3
C

O C O

CH3

O

+ n18O 2 + n18
n

79
79
N 2 ⇒ n16CO 2 + n7 H 2 O + n18
N2
21
21

(1)

but it should be noticed that the oxidation reactions during combustion of polycarbonate never
goes in this way exactly, and besides carbon dioxide and water vapour there are usually some byproducts, like carbon monoxide and volatile organic compounds, what was experimentally proven
and it is showed in the following graphs (figures 4 and 5). The experiments were realized in
different conditions, because both the kind of the fluidising material (the quartz sand or the
limestone) and its temperature were depended on the authors and therefore some crucial
conclusions can be stated.
A. CO (900 oC)
B. CO (960 oC)

CO [mg]

40

12

A.

C. VOCs (900 oC)

C.

D. VOCs (960 oC)
VOC [mg]

50

30
B.
20

8
D.
4

10

0

0
0

100

200 300
PC [mg]

400

0

500

100

200 300
PC [mg]

400

500

Figure 4. The carbon monoxide emissions during
the polycarbonate co-combustion process with
propane in the sand bed fluidised bed reactor in
different temperatures

Figure 5. The volatile organic compounds
emissions during the polycarbonate
co-combustion with propane in the sand bed
fluidised bed reactor in different temperatures

Rysunek 4. Emisja tlenku węgla (II) podczas
współspalania poliwęglanu z propanem w
reaktorze fluidyzacyjnym ze złożem piaskowym
w różnych temperaturach

Rysunek 5. Emisja lotnych części organicznych
podczas współspalania poliwęglanu z propanem
w reaktorze fluidyzacyjnym ze złożem
piaskowym w różnych temperaturach
322


Some observations, which were made, confirmed general theoretical theses about combustion
of polymers. The higher temperature values influenced in a positive way the combustion process
of polycarbonate because the lower emissions of the incomplete combustion compounds were
registered in the flue gases then. The results of the measured carbon monoxide and volatile organic
compounds emissions during the polycarbonate co-combustion process with propane in the two
experimentally realized cases, so while the temperature of the fluidised sand bed was equal to
900°C and 960°C, are presented in the figures 4 and 5. It was observed that the relations between
the emissions of the mentioned two parameters monitored in the flue gases were very similar when
the temperature dependence is considered. It should be also notice that in the two discussed
experiments both the oxygen access and so the turbulence and the time of the combustion process
were at the same level in each case.

25

20

20

15

15

a.

10

10

5

5
0

100

200 300
PC [mg]

30

30

b.

400

25

500

c.

T limestone

d.

T freeboard

25

20

20
c.

15

15

d.
10

10

5

5
0

100

200 300
PC [mg]

400

deltaT freeboard [oC]

deltaT bed [oC]

25

30

T sand
T freeboard

deltaT bed [oC]

a.
b.

deltaT freeboard [oC]

30

500

Figure 6. The growths of the temperature of the sand
bed and in the freeboard during the polycarbonate
co-combustion process with propane at 960°C in the
fluidised bed reactor

Figure 7. The growths of the temperature of the
limestone bed and in the freeboard during the
polycarbonate co-combustion process with propane
at 960°C in the fluidised bed reactor

Rysunek 6. Wzrost temperatury piaskowego złoża
oraz przestrzeni nadzłożowej podczas współspalania
poliwęglanu z propanem w temperaturze 960°C
w reaktorze fluidyzacyjnym

Rysunek 7. Wzrost temperatury wapiennego złoża
oraz przestrzeni nadzłożowej podczas współspalania
poliwęglanu z propanem w temperaturze 960°C
w reaktorze fluidyzacyjnym

There was also observed that the polycarbonate combustion process itself highly depends on
the kind of the material filled the reactor. The hot fluidising bed heated up the polymer samples
when they appeared in it and also maintained constant mixed conditions of air provided oxygen
and the gaseous and solid fuels so propane and polycarbonate. Despite the fact that the emissions
of carbon monoxide and volatile organic compounds in the next two discussed experiments were
in the very comparable levels, because the temperature of the combustion process was almost the
same and equalled to about 960°C, however there were different temperature growths in the bed
and in the freeboard when the sand bed and the limestone bed are compared. The analysis of
figures 6 and 7 gives the obvious conclusion that the difference between the reactions in the
freeboard zone of the fluidised bed reactor in both two cases was considerable. The higher
temperature growths in the reactor freeboard space while combustion with the sand bed as the
fluidising material may indicate to creating some more diffusive flames than in the analogous
temperature and hydrodynamic conditions during the combustion process with using the limestone
to mix the fuels with air. Because of this fact limestone is suggested to be more appropriate bed
while polycarbonate thermal decomposition processes by combustion. Diffusive blazing flames
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are very unwanted physical phenomena and they accompany aromatic products of incomplete
combustion and soot particle aggregation [9].
Summarising all these experimental data results, limestone may be assumed to be more
recommended fluidised reactor bed when the combustion of polycarbonate is deliberated. The
industrial processes of the incineration of waste, especially containing plastic waste, which are
very common in municipal solid wastes, should be carried out in high temperature, which is
defined in the prevailing standards [5,6]. The high calorific value of plastics, giving polycarbonate
as an example, which is in fact a hydrocarbon fuel, was also experimentally proven, because the
increase of the temperature of the fluidising bed causing by the additional amount of the fuel,
which warmed the bed up, was also undoubtedly confirmed the alternative fuel properties.

References
[1] Andrady A. L., Plastics and the Environment, Wiley-Interscience, Hoboken, 2003.
[2] Bottenbruch L., Anders S., Engineering thermoplastics: polycarbonates, polyacetals, polyesters,
cellulose esters, Hanser Verlag, New York, 1996.
[3] Cheremisinoff P. N., Morresi A. C., Energy from Solid Wastes, Marcel Dekker, New York, 1976.
[4] Committee on Health Effects of Waste Incineration, Board on Environmental Studies and
Toxicology, Commission on Life Sciences, National Research Council, Waste Incineration and
Public Health, National Academy of Sciences, Washington, 2000.
[5] Directive 2000/76/EC of the European Parliament and of the Council of 4 December 2000 on the
incineration of waste.
[6] Directive 2001/80/EC of the European Parliament and of the Council of 23 October 2001 on the
limitation of emissions of certain pollutants into the air from large combustion plants.
[7] Gad S. C., Anderson R. C., Combustion Toxicology, CRC Press, Florida, 1990.
[8] Hilado C.J., Flammability Handbook for Plastics, Technomic Publishing Company, Basel 1998.
[9] Jankowska G., Przygocki W., Włochowicz A., Palność polimerów i materiałów polimerowych, WNT,
Warszawa, 2007.
[10] Krajewski B. (red., praca zbiorowa), Poliwęglany, WNT, Warszawa, 1971.
[11] Reynolds J. P., Jeris J. S., Theodore L., Handbook of Chemical and Environmental Engineering
Calculations, Wiley-Interscience, New York, 2002.
[12] Seymour R. B., Engineering polymer sourcebook, McGraw-Hill, New York, 1990.
[13] Troitzsch J., Plastics Flammability Handbook: Principles, Regulations, Testing and Approvals,
Hanser, Kempten, 2004.
[14] Wandrasz J. W., Wandrasz A. J., Paliwa formowane. Biopaliwa i paliwa z odpadów w procesach
termicznych, Wyd. Seidel-Przywecki, Warszawa, 2006.
[15] http://www.wte.org/ (10.06.2010).

JOANNA POŁOMSKA, JERZY BARON, JADWIGA ZABAGŁO, WITOLD ŻUKOWSKI

Odpadowe tworzywa sztuczne źródłem alternatywnej energii
Słowa kluczowe
utylizacja odpadów – odzysk energii – rozkład termiczny – paliwo alternatywne –
– zanieczyszczenia powietrza

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V Krakowska Konferencja Młodych Uczonych, Kraków 2010

Streszczenie
Obecne trendy rozwojowe techniki i technologii przyczyniają się do coraz szerszego zastosowania
tworzyw sztucznych. Jednak wzrostowi ich produkcji towarzyszy także wzrost ilości powstających z nich
materiałów odpadowych. Tworzywa sztuczne są materiałami wytworzonymi z tych samych surowców, co
wysokoenergetyczne paliwa naturalne. Spośród wielu możliwych metod ich dalszego wykorzystania, procesy
termicznej utylizacji tworzyw sztucznych są z pewnością najlepszym sposobem na całkowite usunięcie ich ze
środowiska przy jednoczesnym wykorzystaniu ich potencjału energetycznego. Nieodpowiednie prowadzenie
wielce złożonego procesu spalania tworzyw sztucznych może jednak stanowić poważne zagrożenie dla
środowiska. Należy zatem szczegółowo poznać zjawiska zachodzące podczas termicznego rozkładu tworzyw
mogących stanowić alternatywne, użyteczne źródło energii, aby następnie móc sterować całością procesu
technologicznego. Jest to szczególnie ważne mając na uwadze wysokie koszty oczyszczania gazów odlotowych ze spalarni odpadów oraz stopień skomplikowania składających się na to oczyszczanie operacji
jednostkowych. Świadomość społeczna możliwych zagrożeń środowiskowych i zdrowotnych przyczyniła się
nie tylko do zaostrzenia obowiązujących przepisów, w tym standardów emisyjnych, ale także do wzrostu
zainteresowania przebiegiem całości procesu spalania oraz odpowiednim projektowaniem jego parametrów
technologicznych. Każde zjawisko zaobserwowane makroskopowo jest sumą sekwencji zdarzeń na poziomie
molekularnym, co z pewnością stanowi niebagatelną przeszkodę nad możliwością całkowitego zapanowania
nad procesem spalania. Złożoność procesu spalania takich odpadów jak tworzywa sztuczne nie stanowi
jednak przeszkody do coraz szerszego rozpowszechniania przyjaznych środowisku technologii termicznej ich
utylizacji, a użyteczne wykorzystanie generowanej w ten sposób energii cieplnej jest zgodne z obowiązującym prawem i zasadą zrównoważonego rozwoju. Niestety, stuprocentowa eliminacja wszystkich produktów
niecałkowitego spalania nie wydaje się możliwa, dlatego istotne i celowe jest zwrócenie uwagi na każdy
parametr procesu mający wpływ na jakość przebiegu procesów spalania. W artykule przedstawiono wyniki
eksperymentów współspalania poliwęglanu z propanem z nadmiarem powietrza w ilości 50 %, przeprowadzonych w reaktorze fluidyzacyjnym wypełnionym piaskiem lub wapieniem, eksperymenty te zrealizowano
w różnych warunkach temperaturowych. Uzyskane wyniki potwierdzają ogólne tezy dotyczące wpływu
takich paramentów jak temperatura czy środowisko reakcji na rodzaj zachodzących zjawisk oraz jakość
otrzymanych produktów procesu spalania. Zaobserwowano, że prowadzenie procesu termicznego rozkładu
oraz utleniania w wyższych temperaturach jest korzystniejsze ze względu na niższe stężenia składników
niecałkowitego lub niezupełnego spalania w gazach odlotowych. Wykazano również, że rodzaj zastosowanego złoża stanowiącego wypełnienie reaktora może mieć istotne znaczenie dla przebiegu procesu spalania.
W przypadku zastosowania złoża z wapienia zarejestrowano mniejsze wahania temperatury w strefie
nadzłożowej reaktora niż dla eksperymentów przeprowadzonych w analogicznych warunkach z zastosowaniem złoża z piasku kwarcowego, co może świadczyć o odmiennym charakterze zachodzących reakcji
chemicznych.

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