by
Victoriano B. Ocon
1
, Alexis T. Belonio
2
, and Antonio H. Co
3
1
CEO, Suki Trading Corporation, Lapu-Lapu City, Cebu
2
Project Director, CRHET- CLSU Rice Husk Project, Central Luzon State University
Science City of Munoz, Nueva Ecija
3
Project Coordinator, GIFO Project – Kanvar Enterprise, Paranaque City, Metro Manila
ABSTRACT
A batch-type plastic pyrolyzer was designed and tested to provide a locally-built
technology for proper disposal of sando-bag plastics that are commonly found dumped in landfill
areas. The plastics are shredded, washed, and thermally cracked to produce liquid fuel or
crude oil suitable as fuel blend for diesel.
The pyrolyzer consists of: a reaction chamber equipped with electric heater to vaporize
volatile matters; a condensing chamber to liquefy the gas to produce pyrolysis liquid; a catalyst
reactor to dilute the chloride that produces furan and dioxin; and a bio-filter to eliminate
unpleasant odor from the gas. The pyrolyzer cracks the plastics at a rate of 10 kilogram per
batch in 1 hour. The equivalent amount of liquid fuel produced per batch ranges from 1.5 to 2.0
liters, with residual liquid of 0.2 to 0.5 liter collected from the deodorizer. The temperature of the
pyrolyzing chamber ranges from 200° to 300°C while the temperature of the gas coming out of
the pyrolyzer ranges from 105° to 150°C. The weight of the char produced after pyrolyzing
varies from 0.8 to 1 kilogram. Moreover, it was also found out that the liquid produced from the
pyrolyzer when blended with diesel fuel at 30:70 ratio can successfully run a compression
ignition engine for a continuous test period of more than 4 hours.
Economic analysis of a larger unit of the technology installed in LGUs showed that the
pyrolyzer can contribute to saving in terms of hauling and tipping fees in disposing raw plastics
on a conventional municipal landfill or dump site and in terms of the value of the liquid fuel
produced.
Keywords: Plastic, Pyrolyzer, Pyrolysis Liquid Fuel
Paper presented at the 62
nd
PSAE Annual National Convention and 23
rd
Agricultural
Engineering Week held at Puerto Princesa City, Palawan on April 23 – 27, 2012.
INTRODUCTION
Disposal of garbage, especially sando-bag plastics which contain a mixture of low- and
high-density polyethylene plastics, is one of the major problems in the Philippines. This is
because plastics are generally non-biodegradable and there is an excessive amount disposed
of day after day. Wherever one goes, scattered sando-bag plastics are commonly seen on
roadsides, vacant lots, and even in market places. They are very visible litters which are
eyesores and which cause environmental pollution. The worst scenario, they are hazardous to
human health especially when burned and inhaled. Furthermore, not only that littered plastics
spoil the attractiveness of a municipality but worse they clogged its drainage system. When
mixed with garbage, plastics inter fere in waste processing facilities and cause problems in
landfill operations.
On the average, Local Government Units (LGUs) in the country produces about 1 to 2
tons of garbage daily. Of th is amount, 70% are biodegradable while the remaining 30% are
non-biodegradable. And, sando-bag plastics constitute about 50% of the non-biodegradable
wastes. In a month time, an average of about 4.5 to 9 tons of sando-bag plastics is
accumulated.
Recent development, on the other hand, has shown potential to address this problem.
With this new technology, sando-bag plastics can now be properly disposed by converting them
to liquid fuel. The process is called pyrolysis where the plastics are subjected to a moderate
temperature to break the polymer structure into smaller hydro carbon molecules in the absence
of air [1,4,6, & 7]. The advantages of pyrolysis over the other methods of disposing plastics are:
(a) the process has low energy requirement; (b) it can handle plastics which cannot be
efficiently recycled by other process; (c) the process operates at low pressure thus not needing
air; (d) the by-products have economic utilization; and (e) it does not generate pollutants since
the process is conducted in a closed environment. Several studies [1,3,4,& 5] pointed out that
pyrolyzing plastics can produce liquid fuel, which can be used as fuel blend for diesel. Per
kilogram, liquid oil from plastics at a density of 0.79 g per cc, contains a heat energy of 41,858
kJ [3].
In December 2011, the SUKI Trading Corporation , in collaboration with the Garbage-In
Fuel-Out (GIFO) Project, has come up with a design of a batch-type pyrolyzer that converts
sando-bag plastics into liquid fuel [2]. Tests were conducted to determine the performance of
the machine fueled with diesel-liquid-fuel blend. Tests were likewise conducted to assess the
usefulness of the pyrolyzer technology as an alternative means in disposing sando-bag plastics
properly, which is a primary environmental concern of Local Government Units (LGUs).
Objectives of the Study
The objectives of the study are:
(1) To design a batch-type pyrolyzer that can convert sando -bag plastics to liquid fuel;
(2) To test and evaluate the performance of the pyrolyzer in terms of loading capacity,
pyrolyzing temperature, energy consumption, volume of liquid fuel, and weight of
char produced;
(3) To determine whether the liquid fuel produced from the pyrolyzer can be burned and
used as fuel blend for diesel; and
(4) To determine its economic advantage over the present practice of disposing sando bag plastics.
METHODOLOGY
The design of the batch-type plastic pyrolyzer was carried out at Suki Trading
Corporation, Lapu-lapu City in Cebu in December 2011 . It was based on a German technology
developed at Maiden. The design criteria used were as follows: Process – Slow Pyrolysis,;
Capacity – 10 kg per load; Heat Source – Electricity; Loading and Unloading – Manual; and
Construction Materials – Stainless Steel.
The design concept of the pyrolyzer included a reaction chamber, which has a cubical
shape for ease of loading plastics and of removing burnt char. The heat source to pyrolyze
plastics was with the use of a strip electric heater so the temperature can be controlled and
uniform heating can be achieved. A condenser was included in the design of the system to
collect the liquid fuel from the gas generated during the process. In order to eliminate the odor
and, at the same time, to collect the residual oil, a deodorizer or catalyst reactor was integrated
in the system. A bio-filter was also included in the system to further eliminate the odor from the
gas.
The pyrolyzer was fabricated using stainless steel plates and bars to minimize chemical
and heat corrosion problems. The pryrolyzing chamber was made of thicker plates to withstand
increase in temperature. The condenser and the deodorizer as well as the bio-filter were built
using thinner stainless steel sheets. Stainless steel bars were used as support frames for these
different devices.
The performance of the pyrolyzer was tested using assorted sando-bag plastics as
feedstock. The samples were shredded into uniform sizes of about 1 cm by 1 cm. Shredded
plastics were then washed in a dipping vat and subsequently sprayed with water to remove
impurities. Before loading into the reaction chamber, the samples were allowed to dry for 1
hour.
The weight of shredded plastic samples was taken before loading into the reaction
chamber using a 25-kg capacity weighing scale. During the tests, the temperature of the
reaction chamber was measured by installing a type-K thermocouple wire sensor at the bed of
the samples at one end and attaching to a digital thermometer at the other end. The same
measuring device was used in recording the temperature of the gas generated from the reaction
chamber. The volume of liquid fuel collected from the condenser and from the bio-filter was
also taken using a 1000-ml volumetric flask. After pyrolyzing the plastics, the weight of char
produced was also measured using a spring scale. The pyrolysis oil obtained was blended to
diesel fuel at a ratio of 30 to 70 and then fed into the diesel engine to determine whether the oil
produced can be used as supplementary fuel.
The cost of pyrolyzing plastics against that of the conventional method of dumping
plastic wastes on a landfill was also compared.
RESULTS AND DISCUSSIONS
Design Description of the Pyrolyzer
The plastic pyrolyzer, as shown in Figure 1, is a batch type consisting of the following
major components: (a) Reaction Chamber, (b) Condenser, (c) Deoderizer, and (d) Bio-Filter.
The Reaction Chamber is where shredded plastics are thermally cracked by heating them at a
relatively low temperature for a period of one hour. The chamber is made of two layers of
stainless steel, serving as the inner and outer layers, with a total volume of 0.5 m
3
. The inner
layer is 3-mm thick while the outer layer is 1 mm. Between the inner and the outer layers is a
10-cm thick rock wool serving as heat insulation. A 3-kW electric strip heater is embedded
inside the reaction chamber to heat the plastics during the process. The gas produced from the
pyrolysis exits through a 2-in. diameter stainless steel pipe located at the upper end of the
reaction chamber. Moreover, the reaction chamber can be opened from the top to load the
feedstock and to discharge the char.
Figure 1. The Batch-Type Plastic Pyrolyzer Showing the Various Major Components.
The condenser, on the other hand, is a 1-mm thick stainless steel cylinder with an inlet
at the top and an outlet at the bottom to facilitate passage of the gas. The function of the
condenser is to liquefy the moisture in the gas to produce pyrolysis oil or liquid fuel. A 1-in.
diameter drip pipe with ball valve is provided at the bottom of the condenser to facilitate
discharge of the oil in every operation. The deodorizer, which has a 0.5-m
3
volume and is
situated next to the condenser, is made of a 1-mm thick stainless steel box with mixture of rice
husks and a catalyst as filter to eliminate the odor from the gas. As the gas passes through the
filter layer, the catalyst dilutes the chlorides that produce furans and dioxins thus eliminating the
odor from the gas. The residual oil is collected from the bottom of the deodorizer through a drip
pipe with ball valve. The bio-filter is a 0.3-m
3
cylindrical chamber made of 1-mm thick stainless
steel sheet. It has an activated carbon inside to further filter the gas thereby removing
unpleasant odor from the gas. The gas generated is released through a 2-in. chimney and is
subsequently flared.
Test Performance
Results of three separate runs for the performance testing of the pyrolyzer are shown in
Table 1 below. Using 10 kilograms of shredded plastics, which were loaded in the reaction
chamber and then thermally cracked for one hour, in each run, 1.8, 1.5 and 2.0 liters of liquid
fuel was obtained from the condenser for the 1
st
, 2
nd
and 3
rd
run, respectively. The resultant
volume of the residual liquid collected from the deodorizer was 0.3, 0.2, and 0.5 liter for the 1
st
,
2
nd
, and 3
rd
run, respectively. On the other hand, the temperature at the reaction chamber was
measured from 230 to 250C for the first run, 200 to 225C for the second run, and 240 to
300 for the third run. The temperature of the gas coming out of the pyrolyzer was measured at
110 to 125C for the first run, 105 to 115C for the second run, 130 to 150C for the third run.
Results also showed that the weight of char produced after pyrolyzing was 0.9, 0.8, and 1 kg for
the 1
st
, 2
nd
, and 3
rd
run, respectively.
Table 1. Results of the Performance Testing of the Pyrolyzer.
Run 1 Run 2 Run 3
Weight of Shredded Plastics (kg) 10 10 10
Operating Time (hr) 1 1 1
Temperature of the Reactor (C) 230-250 200-225 240-300
Gas Temperature (C) 110-125 105-115 130-150
Volume of Oil Produced (liter) 1.8 1.5 2.0
Volume of Residual Oil (liter) 0.3 0.2 0.5
Weight of Char Produced (kg) 0.9 0.8 1
Specific Liquid Fuel Produced (liter/kg) 0.21 0.17 0.25
Percentage Liquid Fuel Produced (%) 16.6 13.4 25.0
Percentage Char Produced (%) 9 8 10
1/ Computed as Total Volume of Oil Produced x Density of Oil x 100 / Weight of Plastic
2/ Computed as Weight of Char Produced x 100 / Weight of Plastic
The percentage amount of oil obtained from plastics was calculated at 13.4 to 25.0% per
unit weight of pyrolyzed plastics and, the percentage weight of char produced per kg of plastics
ranges from 8 to 10%.
The pictorials of the shredded plastics used as samples as well as the liquid fuel
obtained from the condenser and from the deodorizer including the char produced from the
reaction chamber are shown in Figure 2 below.
Separate tests of the pyrolysis oil obtained from the pyrolyzer revealed that the liquid
fuel is combustible and can be used as fuel b lend for diesel. By blending liquid fuel and diesel
at 30:70 ratio, a 4-stroke, single-cylinder 16-hp diesel engine can be continuously run for more
than 4 hours. No smoke emission was observed from the engine when liquid fuel is blended
with diesel.
(a) (b) ( c )
Figure 2. The Sample of: (a) Shredded Plastics, (b) Liquid Fuel, and (c) Char Produced from
the Pyrolyzer.
Operating Cost
Economic analysis of the plastic pyrolyzer was based on the larger models of the
machine, which are presently installed and operated in two Local Government Units. The
pyrolyzer has a loading capacity of 50 kg per load and can process 150 kilos of plastics (i.e.,
equivalent to three loads) a day and subsequently produces 30 liters of liquid fuel. It requires 6
kW of electricity to heat the plastics for a period of 1 hour. Moreover, the shredder which was
used to chop the plastics has a capacity of 80 to 100 kg per hour and is driven by a 12-hp diesel
engine.
The total investment cost for the technology is P1.1 million (i.e., P680,000.00 for the
pyrolyzer and P420,000 for the plastic shredder). As shown in Table 2, the total operating cost
per day to pyrolyze shredded plastics and turn them into liquid fuel is P1,147.34. In terms of per
Table 2. Operating Cost Analysis of Using the Pyrolyzer (As of April 2012).
1/ Life Span - 7 years
2/ Straight line with 10% salvage value
3/ 24% of the total investment cost
4/ 10% of the total investment cost
5/ 3% of the total investment cost
6/ 1.2 liters per hour at P47 per liter
7/ 6 kW at P10 per kw-hr, 3 hours operation per day
8/ Two (2) persons @ P250.00 per 8 hour-day
unit basis, the cost to pyrolyze plastics, which includes fuel, electricity and labor, is P7.65 per kg
and the cost to produce liquid fuel is P38.24 per liter.
The payback period analysis (Table 3) was done to determine whether the investment is
worthwhile. As shown in the table, the total cost incurred per day for the conventional method of
garbage disposal is P114.38 for one ton and P228.75 for two tons. Considering the volume of
liquid fuel produced of 30 and 60 liters per day at P 47.00 per liter, the investment costs for the
pyrolyzer and for the shredder can be recovered for a period of 2 years for a garbage production
of one ton per day. For two tons of garbage production per day, the total investment cost can
be recovered in just one year.
Load Per Batch (kg) 50
Loading Frequency per day 3
Loading Capacity per Day (kg) 150
Expected Oil Produced (liter/day) 30
Investment Cost (P) 1/
Pyrolyzer 680,000.00
Shredder 420,000.00
Total 1,100,000.00
Fixed Costs (P/day)
Depreciation 2/ 271.23
Interest on Investment 3/ 72.33
Repair and Maintenance 4/ 30.14
Insurance 5/ 9.04
Sub-Total 382.74
Variable Costs (P/day)
Fuel Shredder 6/ 84.60
Electricity 7/ 180.00
Labor 8/ 500.00
Sub Total 764.60
Total Costs (P/day) 1,147.34
Operating Cost per Hour 254.96
Pyrolyzing Cost (P/kg of Plastic) 7.65
Oil Production Cost (P/liter) 38.24
Table 3. Payback Period Analysis of the Pyrolyzer.
Garbage Production (Tons per day) 1 2
Weight of Sando-Bag Plastics (Tons per
day) 0.15 0.3
Tipping Fee for Sando-Bag Plastics (P) 1/ 105 210
Hauling Fee for Sando-Bag Plastics (P) 2/ 9.38 18.75
Total Cost Per Day (P) 114.38 228.75
Total Cost Per Month (P) 3431.25 6862.50
Volume of Liquid Fuel Produced (liter) 30 60
Value of the Liquid Fuel Produced (P) 3/ 1410.00 2820.00
Payback Period (Year) 2 1
1/ At P700.00 per ton tipping fee
2/ At P2,500 per truck hauling fee, one truck at 4 tons per load
3/ Valued at P47.00 per liter of liquid fuel
CONLUSIONS AND RECOMMENDATIONS
Based on the above results of the study, the following are concluded:
1. The pyrolyzer performs according to the design. Shredded plastics can be converted
into liquid fuel employing the process of thermal cracking combined with condensing
and filtering of gas to eliminate toxic gases and unpleasant odor.
2. The liquid fuel produced from the pyrolyzer can be successfully blended with diesel
to run compression ignition engines. Since it is also combustible, it can also be
used for other applications such as heating boilers, industrial cooking, kiln firing, and
many others.
3. The pyrolyzer is an effective means of disposing sando-bag plastics over the
conventional method, which is disposing plastics on dump sites. It is also an
effective means of converting sando-bag plastics into fuel, which helps address the
fuel shortage.
It would be more advantageous to integrate the pyrolyzer in the garbage gasification
system in order to further degrade burnt plastics, which can still be used to produce heat or
electricity. Designing the system to operate on a continuous-mode can minimize the problem of
loading plastics and unloading of char.
REFERENCES
[1] Behzadi, S. and M. Farid. Liquid fuel from Plastic Wastes in New Zealand. Department of
Chemical and Material Engineering. The University of Aukland. 30pp
[2] Belonio, A.T., Ocon, V. B., and A. H. Co. SUKI Garbage-to-Energy Processing Technology.
Paper presented during the Symposium on Peso from Waste ++ (Mitigating Measures for
Climate Change) hel d at Legislative Building, Provincial Capitol, Matti, Digos City on February
10, 2012.
[3] Guntur, R., Deva Kumar, M.L.S., and K. Vijaya Kumar Reddy. Experimental Evaluation of a
Diesel Engine with Blends of Diesel-Plastic Pyrolysis Oil. International Journal of Engineering
Sciece and Technology. Vol. 3 No. 6. June 2011. Pp 5033-5040.
[4] Osueke, C.O. and I.O. Ofonda. Conversion of Waste Plastics (Polyethylene) to Fuel By
Means of Pyrolysis. International Journal of Advanced Engineering Sciences and Technologies.
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[5] Sadaka, S. Pyrolysis. Center for Sustainable Environmental Technologies/Department of
Agricultural and Biosystem Engineering. Iowa State University. Nevada, IA 50201, USA. 25pp.
[6] UNEP. 2009. Converting Waste Plastic into a Resource: Compendium of Technology.
United Nations Environmental Program. Division of Technology, Industry and Economics.
International Environmental Technology Center. Osaka/Shigg. Japan. 51pp.
[7] Wikipedia. Pyrolysis. http://en.wikipedia.org/wiki/pyrolysis
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