Conversion of Municipal Waste Plastic into Liquid

Journal of Environmental Science and Engineering A 1 (2012) 721-726 Formerly part of Journal of Environmental Science and Engineering, ISSN 1934-8932

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Conversion of Municipal Waste Plastic into Liquid Hydrocarbon Fuel Using a Stainless Steel Reactor Moinuddin Sarker, Mohammad Mamunor Rashid, Mohammad Molla and Ashiquz Zaman Department of Research & Development, Natural State Research Inc., Stamford CT-06902, USA Received: January 10, 2012 / Accepted: February 9, 2012 / Published: May 20, 2012. Abstract: Plastic wastes from milk containers, soft drink bottles, plastic wraps, plastic flatware, etc. have been successfully converted into fuel. Two approaches for the conversion of waste post consumer plastic into fuel have been investigated: (1) muffle furnace to reactor liquefaction system; (2) direct liquefaction system. Majority of used plastics are derived from ethylene, propylene, butadiene and benzene. Waste plastics are plastics that are used by the people in their daily life. It is collected from outside and city municipalities. Some of them are coded and rests are non-coded. A developed process discussed in this paper works with most of the waste plastic, both coded and non-coded. The plastics are heated up at 120-380 °C temperature to melt. The gaseous vapor is then condensed into liquid fuel. Key words: Polyethylene, fuel, waste plastic, condensation, thermal, hydrocarbon, liquefaction.

1. Introduction Plastics are “one of the greatest innovations of the millennium” and have certainly proved their reputation to be true. There are a numerous ways that plastic is and will be used in the years to come. An analysis of plastic consumption on a per capita basis shows that consumption has now grown to over 100 kg/y in North America and Western Europe and has the potential to grow to up to 130 kg/y per capita by 2010 [1]. Hindu business line, January 21, 2006 reveals that India will be the third largest plastics consumer by 2010 after USA and China. The reason of this high growth rate in last few years in India is due to the fact that one third of the population is poor and may not have the disposable income to dispose of the large amount of waste plastic properly. The rising needs of the middle class, and abilities of plastics to satisfy them at a cheaper price as compared to other materials like glass metal, have contributed to an increase in consumption of plastics in Corresponding author: Moinuddin Sarker, Ph.D., research fields: high temperature and superconductivity of oxides and waste plastics conversion into liquid fuel. E-mail: [email protected].

the last few years [2]. Plastics have become a major threat due to their non-biodegradability and high visibility in the waste stream. Littering also results in secondary problems such as clogging of drains and animal health problems. Their presence in the waste stream poses serious problem when there is lack of efficient end of life management of plastic waste. Some countries have too much of plastic rubbish for them to dispose of, due to the high cost of the disposal of plastic rubbish. The environmental issues due to plastic waste arise predominately due to the throwaway culture that is plastic transmit, and also the lack of an efficient waste management system [3]. Plastics wastes can be classified as industrial and municipal plastic wastes according to their origins; these groups have different qualities and properties and are subject to different management strategies [4]. Plastic wastes represent a considerable part of municipal wastes; furthermore huge amount of plastic waste arise as a by-product or faulty product in industry and agriculture [5]. Of the total plastic waste, over 78 wt% of this total corresponds to thermoplastics and the

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Conversion of Municipal Waste Plastic into Liquid Hydrocarbon Fuel Using a Stainless Steel Reactor

remaining to thermosets [6]. Thermoplastics are composed of polyolefins such as polyethylene, polypropylene, polystyrene and polyvinyl chloride [7] and can be recycled. On the other hand thermosets mainly include epoxy resins and polyurethanes and cannot be recycled. The research work described in this paper deals with conversion of thermoplastics into a renewable source of energy in the form of hydrocarbon fuel. The process of conversion used in our research is thermal degradation of waste thermoplastics. Researches have shown that catalytic thermal degradation is found to have the greatest potential to be developed into a commercialization process [8]. The process described uses a state of the art stainless steel reactor technology to produce high quality liquid hydrocarbon fuel.

2. Description of Experimental Process 2.1 Raw Materials and Sample Preparations The average consumption of municipal plastics in United States is shown in Fig. 1. Based on the composition of this average plastic mixture, waste plastics such as HDPE (high density polyethylene), LDPE (low density polyethylene), PP (poly propylene) and PS (polystyrene) are used as raw materials in our production process. These raw materials are collected from households and municipal waste collection sectors,,, brought to our site and at our sites they are manually separated. After separation the raw materials are washed and they are grinded to small pieces with an average diameter 12 to 13 mm2. The pieces are then loaded in the reactor vessel in a non-proportion mixture. 2.2 Specifications of the Stainless Steel Reactor Reactor height up to neck = 22 inch round reactor body = 46 inch, reactor chamber diameter = 21 inch, reactor chamber height = 15.5 inch, inner diameter = 6 inch, insulator & cover (outside of reactor chamber) = 46 inch – 21 inch = 25 inch, condenser length = 49 inch,

Fig. 1 Western Europe plastic production percentage per year.

condenser angle = 70°, reactor neck to angle height = 10 inch, reactor top main neck diameter = 2 inch. Top of reactor surrounding has four necks and each neck is = 1.5 inch. Top of reactor surrounding has 2 monitoring glass necks, one for thermocouple, one gas pressure checking and another 1.5 inch neck for monitoring inside temperature. Condenser diameter = 2 inch, condenser angle diameter = 2 inch, total reactor coil used = 3, 1st coil = Bottom of reactor, 2nd coil = Middle of reactor, 3rd coil = Top of reactor. Three connections are connected with three coils separately. Temperature monitoring device from watlow and this temperature reading can go up to 500 °C. Reactor chamber thickness = 0.16 inch. All parts of reactor are made by 316 grade stainless steel and all information is proprietary (patent pending) information. A visual diagram of the improved steel reactor has been presented in Fig. 2 for visual understanding. 2.3 Process Description Thermal degradation process has been performed with the stainless steel reactor shown in Fig. 2 using various types of randomly mixed waste plastics: HDPE—95%, LDPE—2%, PP—2% and PS—1%. The process of conversion involves heating the waste plastic to form a liquid slurry (thermal liquefaction in the range 120-380 °C), distilling the slurry in the presence of oxygen, thermal cracking without catalyst,


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Fig. 2 Waste plastic to fuel production process using stainless steel reactor (” = inch).

condensing the liquid slurry with distillate to recover the liquid hydrocarbon fuel materials. No additional chemicals are used in the thermal degradation process. In the mini scale process, the weight of a single batch of input plastics for the fuel production process ranges from 1-2 kg. Also, during the production process, light gases are produced. Light gases are ranging from C1-C4. 7% and about 4% residue is leftover from the production process. The residue is colored black and contains high Btu (British thermal unit) value. The yield content is almost 89% conversion which consists of liquid and gaseous product. About 1.5 kg waste plastics convert to ~ 1,335 gm of liquid fuel, ~105 gm of light gas and residue is ~60 gm.

3. Results and Discussion The effect of the cracking parameters (temperature, residence time, chemical structure of raw materials) on

the yields and structures of products was investigated by the properties of three different products formed in the laboratory cracking reactions, gas, liquid and residue with components of different length of hydrocarbon chains. The composition of liquid fraction formed in the cracking reactions of municipal plastic waste was analyzed by GC/MS. The liquid product’s chemical composition mostly consisted of n-alkanes and n-alkenes, which were evenly distributed by carbon number. The evenly distribution of the carbon number indicates an optimum burning quality of the fuel. The improved burning quality and the presence of heavy hydrocarbon groups will make the fuel suitable for heavy engines. A GC/MS chromatogram of the produced liquid fuel is presented on Fig. 3 for visual understanding. The chromatograms were individually analyzed using the Perkin Elmer GC library and the results are presented in Table 1. The liquid fuel was also analyzed by FT-IR using a


Intensity (a.u.)

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0

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45

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R e t e n t io n T im e ( M )

Fig. 3 GC/MS chromatogram of waste plastic to fuel by using steel reactor. Table 1

GC/MS chromatogram detection compound list of waste plastic to fuel.

Retention time (M) 1.53 1.65 1.95 2.54 3.66 3.78 5.21 5.35 6.05 6.93 7.08 7.72 8.65 8.80 10.30 10.44 11.85 11.98 13.31 13.43 14.69 14.80 15.99 16.10 17.22 17.32 18.38 18.48 19.49 19.58 20.54 20.62 21.55 21.62 23.49 28.45

Compound name Propene Butane Pentane 1-Hexene 1-Heptene Heptane 1-Octene Octane 2,4-Dimethyl-1-heptene 1-Nonene Nonane Cyclopentane, butyl1-Decene Decane 1-Undecene Undecane 1-Dodecene Dodecane 1-Tridecene Tridecane 1-Tetradecene Tetradecane 1-Pentadecene Pentadecane 1-Hexadecene Hexadecane E-14-Hexadecanal Heptadecane 1-Nonadecene Octadecane 9-Nonadecene Nonadecane 1-Docosene Eicosane Heneicosane Octacosane

Compound formula C3H6 C4H10 C5H12 C6H12 C7H14 C7H16 C8H16 C8H18 C9H18 C9H18 C9H20 C9H18 C10H20 C10H22 C11H22 C11H24 C12H24 C12H26 C13H26 C13H28 C14H28 C14H30 C15H30 C15H32 C16H32 C16H34 C16H30O C17H36 C19H38 C18H38 C19H38 C19H40 C22H44 C20H42 C21H44 C28H58

Molecular weight 42 58 72 84 98 100 112 114 126 126 128 126 140 142 154 156 168 170 182 184 196 198 210 212 224 226 238 240 266 254 266 268 308 282 296 394


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110.0 105 100 95 90 1976.64

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2026.80 3617.98

80 75

1780.53 2330.69

469.29

70 65

464.80

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40 634.96

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2730.76

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1302.26

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1641.69

1377.68

2899.96

965.06 888.02 909.39

1444.06

721.83

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3600

3200

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2400

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Fig. 4

FT-IR spectrum of waste plastic to fuel.

NaCl (0.05 mm) cell. The operation system was the Perkin Elmers Spectrum 100 series. The IR spectrums were analyzed by the Perkin Elmer Spectrum 100 library. The web numbers were input in the E = hcw equation where, E = energy, h = plank’s constant (6.626 × 10-39 j/s), c = speed of light (299,792,458 m/s), w = the wave number of the spectrums. The wave energies obtained from the equation reveal that the fuel can yield substantial amount of energy and this energy can be used to power combustion engines. A visual diagram of the IR spectrum is presented in Fig. 4 and Table 2 presents the identifying the individual spectrums.

ASTM tests were performed on liquid hydrocarbon fuel. The results were obtained from fuel produced in the steel reactor. The result of the fuel obtained from the steel reactor has a gross heat of combustion (ASTM D240): 19,807 Btu/lb; IBP recovery rate (ASTM D86): 97.0 Vol% and electrical conductivity (ASTM D2624): 6 pS/M. These tests were performed by Intertek at New Jersey. In comparison with the commercial fuel available in the market, the reactor fuel compares fairly well with commercial diesel. Commercial diesel has a high gross heat of combustion than other commercial fuels due to the presence of larger and complex hydrocarbon compounds.

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Table 2 FT-IR spectrum of produced fuel functional group compound list. Band wave number 1 2 3 4 5 9 10 11 12 13 17 18 19 20 22

Wave number (cm-1) 3617.00 3077.35 2899.96 2730.76 2671.31 1821.49 1780.53 1641.69 1444.06 1377.68 991.97 965.06 909.39 888.02 721.83

Functional group name Free OH (Sharp) H Bonded NH C-CH3 C-CH3 C-CH3 Non-Conjugated Non-Conjugated Conjugated CH3 CH3 Secondary Cyclic Alcohol -CH=CH- (trans) -CH=CH2 C=CH2 -CH=CH- (cis)

4. Conclusion

References

The produced hydrocarbon material was investigated using standard testing method and analyzing equipments. The produced fuel contains hydrocarbon compounds as the composition base and also contains several functional groups. ASTM studies performed on the fuel showed that the fuel does not contain much heavy metals or high amount of toxic carcinogens; also by analyzing the different parameters it can be seen that the fuel can be utilized for energy source and it can have the potential to compete with the commercial fuel available in the market specifically diesel category. The production method utilizing the stainless steel reactor gives better efficiency in the conversion rate, as less amount of raw materials are lost in the conversion process, and higher efficiency is maintained. Overall the current conversion process is an efficient and sustainable conversion process that can be utilized in commercial scale.

[1]

Acknowledgments The author acknowledges the support of Dr. Karin Kaufman, the founder of Natural State Research, Inc (NSR). The author also acknowledges the valuable contributions of NSR laboratory team members during the preparation of this manuscript.

[2]

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[4]

[5]

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[7]

[8]

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