In Vietnam, since domestic solid waste (DSW) has not been separated at-source, only about 20 – 30% of domestic waste generated is used for composting, and the rest, which is difficult for biodegradation, is dumped in landfills.
Trang 1APPLICATION OF THE PYROLYSIS PROCESS IN RECYCLING NON-BIODEGRADBLE ORGANIC COMPONENTS OF
MUNICIPAL SOLID WASTE IN HOT-MIX ASPHALT CONCRETE
Le Anh Kien*
Abstract:In Vietnam, since domestic solid waste (DSW) has not been separated
at-source, only about 20 – 30% of domestic waste generated is used for composting, and the rest, which is difficult for biodegradation, is dumped in landfills Aiming at reducing the amount of solid wastes landfilled and enhancing waste recycling and natural resources reserving, the research team of ITE and University Putra Malaysia (UPM) has carried out a research on applying pyrolysis process in recycling non-biodegradable organic components of DSW in hot-mix asphalt concrete Primary results indicated that with an appropriate pyrolyzing condition, the final pyrolyzed product has an asphalt content of about 15%, and bitumous ability that can be mixed with other aggregate to make asphalt concrete This saved about 10 – 15% in the amount of asphalt used in producing the asphalt concrete The asphalt concrete produced has characteristics that comply with Vietnamese standards by Ministry of Transport for materials used in road construction
Keywords: Pyrolyis process, Non-biodegradble organic, Municipal solid waste, Hot-mix asphalt concrete
1 INTRODUCTION
About 5,000 ton of DSW is generated daily in HCMC The increasing amount
of DSW generated is contributing to serious problems of air, soil, and water pollution There are still difficulties in treatment of solid waste in HCMC as well
as in Vietnam In the near future, HCMC is going to implement some projects on using DSW for composting, in which the biodegradable organic components of DSW is used for producing compost However, since DSW is not yet at-source separated, only 20 – 30% of DSW can be used for composting About 70 – 80% of DSW remained (including both organic and inorganic components) containing organic components that is not biodegradable, has to be treated by landfilling [1, 2] Aiming at reducing the amount of waste landfilled as well as enhancing recycling solid waste and reserving natural resources, some research on recycling DSW has been carried out, mainly for recycling construction solid wastes and rubber and plastic in domestic wastes There was a research by Nguyen Minh Chau
on recycling inorganic components of DSW from Cau Dien Solid Waste Treatment Plant in producing concrete Hoang Dai Company (Hai Phong) is producing an organic solvent, which can be used as fuel, from rubber and plastic There was another research by Mai Ngoc Tam on recycling nylon and other plastics (PET and PVC bottles, plastic boxed, sponge, etc…) in making board In Ho Chi Minh City, there are a number of agencies working on recycling rubber and plastic, however, there have not been any researchs converting the DSW to asphalt concrete yet
In 2007, Akbulut, H and C Gürer presented a study of “Use of aggregates produced from marble quarry waste in asphalt pavements” The test results indicated that the physical properties of the aggregates were within specified limits and these waste materials could potentially be used as aggregates in light to medium trafficked asphalt pavement binder layers [3]
Trang 2In another research, Bassani, M., E Santagata, et al had published "Use of vitrified bottom ashes of municipal solid waste incinerators in bituminous mixtures
in substitution of natural sands" The investigation was carried out by considering performance related compaction, volumetric and mechanical properties, which were assessed in the laboratory by employing a number of different characterisation techniques [4]
In 2013, Abbas, A R., U A Mannan, et al Presented the study of "Effect of recycled asphalt shingles on physical and chemical properties of virgin asphalt binders" The results in the laboratory showed that a virgin asphalt binder meeting the Superpave specifications for PG 58-28 was mixed with varying percentages (0%, 5%, 7%, and 10%) of recycled asphalt shingles (RAS) binder recovered from post-manufactured asphalt shingles The physical properties of the blended binders were measured using the rotational viscometer (RV), dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), and bending beam rheometer (BBR) tests The chemical properties of the binders were determined using the Fourier transform infrared spectrometry (FTIR) and gel-permeation chromatography (GPC) tests The physical test results showed an improved resistance to permanent deformation (or rutting) with the addition of RAS, but higher susceptibility to early low-temperature (thermal) cracking [5]
Moon, K H., A C Falchetto, et al had studied the "Using recycled asphalt materials as an alternative material source in asphalt pavements" in 2014 The results concluded that most of the mixtures prepared with combinations of RAP and RAS perform similarly to standard mixtures at low temperature [6]
In 2016, M Abukhettala published the study on “Use of Recycled Materials in Road Construction” in the Conference on Civil, Structural and Transportation Engineering This study presented a literature review on the most viable recycled materials currently in practice by the industry and it aims towards developing a noble idea on better inclusion of a recycled material in the road industry [7]
In this paper, there have been some results of the study on applying pyrolysis process in recycling non-biodegradable organic componentsof DSW in hot-mix asphalt concrete will be introduced The research object includes solid waste discarded from composting plant and from municipal landfills
Table 1 Composition of solid waste remained after composting
Note: Sampled at Tan Thanh Composting Plant, Ba Ria – Vung Tau
Trang 32 EXPERIMENT 2.1 Producing material from solid waste
2.1.1 Equipment
The experiment is carried out on a pilot pyrolytic incinerator (Figure 1) with
the chamber size of 35 cm x 30 cm x 30 cm The temperature in the pyrolyzing chamber is regulated by an automatic program
Figure 1.The pilot pyrolytic incinerator used for waste pyrolyzing experiment
2.1.2 Materials
Materials for pyrolyzing experiment are taken from composting plants with the composition presented in Table 1 Waste is primarily cut into small bits of 1cm x 1cm x 1cm with a cutting machine
2.1.3 Procedure
Material is dried and then pyrolyzed at various pyrolyzing temperatures and times to determine the optimal pyrolyzing conditions to produce material with high asphalt content and low gasification
The optimal pyrolytic conditions for making material has been determined in previous research [1] Results indicate that at the temperature of 350oC (± 15oC) and pyrolyzing time of about 30 min (± 5 min) the pyrolyzed product have high content of asphalt and gasified rate of 10 – 15% as expected
Therefore, in this experiment, we chose the pyrolyzing temperature and time of
350oC and 30 min The pyrolyzed product achieved, hereafter called “material” is used for follow-up experiments as follows:
- Determine the optimum asphalt content in the “material” and measure its physicochemical characteristics in comparison with those of bitumen on Vietnam market for producing asphalt concrete (hereafter called conventional bitumen);
- Replace the conventional bitumen with the asphalt from the “material” at different ratio and estimate the physicomechanical ability of achieved asphalt concrete
2.2 Determinationof asphalt content and testification of asphalt physicocheical characteristic
2.2.1 Materials
- “Material” achieved from pyrolyzing DSW (section 2.1)
Trang 4- Solvents for extracting asphalt from the “material”: light gasoline: toluene:
methanol: acetone =40: 50: 5: 5 (weight)
2.2.2 Procedure
To determine the asphalt content in the “material”, the “material” is steeped in the mixture of solvents for two hours, and then the liquid containing asphalt is filtered, distilled, and dried at 160oC to achieve a mixture of asphalt Physicochemical characteristics of the asphalt are measured at Universiti Putra Malaysia
2.3 Testing experiment for physicochemical characterstics of the asphalt concrete made from the “material”
2.3.1 Experimental Objectives
The experiment measures physicomechanical characteristics of the asphalt concrete produced with different replacement percentages of the “material” in order to determine the appropriate mixing ratio of the “material” in asphalt concrete
2.3.2 Equipment
Facilities and equipments for the experiments were employed from University Putra Malaysia The machine is the Accu-Tek Touch 250 Automatic Compression Machine 110V/60Hz This machine is designed to meet the need for reliable and consistent concrete testing It is fully compliant to ASTM C39 and AASHTO T22 standards
2.3.3 Materials
- Aggregate for the road surface application under 22 TCN 249-98 [8]
- Bitumen type 60/70
- “Material” from pyrolyzing non-biodegradable organic component of DSW
at 350oC in 30 minutes
2.3.4 Procedure
The experiment procedure is followed the construction standard 22TCN 62-84 [9] Indicators to be determined are air void, stability, and deformability
3 RESULTS ANDDISCUSSION 3.1 Result of determination of asphalt content and testification of asphalt physicocheical characteristic
The asphalt content in the “material” makes up from 14 to 15% of the
“material” weight Results of testing physicochemical characteristics of the asphalt
extracted from the “material” are presented in Table 2
Results of the experiment indicate that the dissolubility in CCl4 and the ignition point of the asphalt achieved from pyrolyzed “material” are equivalent to those of conventional bitumen currently used in producing asphalt concrete However, the density, the flexing temperature and the extension ability of the asphalt from the
“material” is lower than those required for asphalt 60/70
Trang 5Table 2 Physicochemical characteristics of asphalt
3.2 Result of testing experiment for physicochemical characterstics of the asphalt concrete made from the “material”
Experiment results is presented in Table 3 and Figure 2, 3, and 4
The experiment results can be summarized as follows:
- Stability: asphalt concrete samples has compactability strength varies from 5.5 to 16.1 kN; there are 12/18 samples are conformed to standards of stability (AASHTO-T22 or ASTM-C39) which specify a compactability strength 8 kN It
is noted that the samples of asphalt concrete that meet standards for Marshall stability are those with replacement percentage of less than 15%
- Deformability: the samples of asphalt concrete have deformability varies from 2.8 mm to 6.4 mm There are 6/18 samples that meet the standard for deformability 22 TCN 249-98 (4mm) It is noted that the asphalt concretes with replacement percentage of 10% meet 22 TCN 249-98 for deformability
- Air void: the samples of asphalt concrete have the air voids varies from 14.1% to 27.3% There are 9/18 samples meet the standards for air void 22 TCN 249-98 (14 – 18%) It is noted that the asphalt concretes with replacement percentage of 10% meet 22 TCN 249-98 for air void
Table 3 Results of marshall experiment
Asphalt
from the
“material”
Conventional
bitumen
Sample height
Asphalt concrete density
Air void Deformability Stability
Construction standard 22TCN
249-98
Trang 6Figure 2 The stability of the asphalt concrete
for different replacement percentages
Figure 3 The air void of the asphalt concrete for different replacement percentages
Figure 4 The deformability of the asphalt concrete
for different replacement percentages
There are some remarks from the testing results, as follows:
- The increase of the replacement percentage result in the decrease of physicomechanical abilities (decrease in stability and deformability and increase in air void
- Even though the asphalt concrete produced has high stability, its
Trang 7deformability is also relatively high, particularly when increasing proportion of the
“material” Therefore, in order to assure the required physicomechanical characteristics of asphalt concrete, replacement percentage of the asphalt from
“material” for conventional bitumen is recommended to be 5 – 10%
In conclusion, it is feasible to apply pyrolysis processes in recycling non-biodegradable organic component of DSW in producing asphalt concrete for road construction, and the appropriate replacement percentage of asphalt from the
“material” in the blend is determined to be 10 %
4 CONCLUSIONS
Pyrolyzing non-biodegradable organic components of DSW at an appropriate condition (350oC, 30 minutes), we achieve a material with high content of asphalt (15%) and bituminous ability that can be mixed with aggregate to produce asphalt concrete;
The asphalt extracted from the “materials” has physicochemical characteristics (ignition point,tensile strength, dissolubility in solvent, etc…) that equivalent to bitumen and can be used to replace conventional bitumen in producing asphalt concrete;
The achieved “material” can replace by 5 – 10% in aggregate and 10 – 15% in bitumen used in asphalt concrete The asphalt concrete produced conforms to technical standards by Ministry of Transport However, to assure a long-term stability for road surface, the asphalt concrete should first be used for rural roads or grade 2 roads
It is clearly from the experimental study that it is feasible to recycle non-biodegradable organic components of DSW in road surface application This contributes to reducing the amount of solid wastes dumped in landfills, which in turn contribute to land and natural resources saving as well as reducing environmental pollution
However, it is recommended to have follow-up research on reusing heat from pyrolyzing process as well as have a project of producing the “material” in pilot scale before mass production in practice
Acknowledgement: The data for this study was collected from the research of Dr Nguyen Quoc
Binh Thanks for analysis results that were carried out at the lab of Mr Zurina Zainal Abidin and Prof M Halim S Ismail in the Putra University, Malaysia
REFERENCES
[1] N Q Bình, "Applying pyrolysis for organic waste treatment in MSW",
Hochiminh City for recycling material, 2006
[2] G A.-H.- AIT, "Training, management of MSW, South of Vietnam," 2005 [3] H Akbulut and C Gürer, "Use of aggregates produced from marble quarry waste in asphalt pavements," Building and Environment, vol 42, pp
1921-1930, 2007
[4] M Bassani, E Santagata, O Baglieri, M Ferraris, M Salvo, and A Ventrella,
"Use of vitrified bottom ashes of municipal solid waste incinerators in
Trang 8bituminous mixtures in substitution of natural sands," Advances in Applied Ceramics, vol 108, pp 33-43, 2009/01/01 2009
[5] A R Abbas, U A Mannan, and S Dessouky, "Effect of recycled asphalt shingles on physical and chemical properties of virgin asphalt binders," Construction and Building Materials, vol 45, pp 162-172, 2013
[6] K H Moon, A C Falchetto, M Marasteanu, and M Turos, "Using recycled asphalt materials as an alternative material source in asphalt pavements," KSCE Journal of Civil Engineering, vol 18, pp 149-159, 2014
[7] M Abukhettala, "Use of Recycled Materials in Road Construction," in
Proceedings of the 2nd International Conference on Civil, Structural and Transportation Engineering (ICCSTE’16), Ottawa, Canada – May 5 – 6, 2016
[8] M o Transport, "Professional standard 22 TCN 249:98," 1998
[9] M o Transport, "Professional standard 22 TCN 62: 84," 1984
TÓM TẮT
ỨNG DỤNG QUÁ TRÌNH NHIỆT PHÂN TRONG TÁI CHẾ THÀNH PHẦN HỮU CƠ KHÔNG PHÂN HUỶ SINH HỌC CỦA CHẤT THẢI RẮN ĐÔ THỊ
TRONG BÊ TÔNG NHỰA TRỘN NÓNG
Tại Việt Nam, chất thải rắn đô thị không được phân loại tại nguồn, chỉ khoảng 20 đến 30% chất thải nội địa được sử dụng cho việc ủ phân, phần còn lại khó phân huỷ sinh học và được chôn tại các bãi chôn lấp rác Nhằm mục đích giảm lượng chất thải rắn chôn lấp và tăng cường tái chế chất thải
và giữ gìn tài nguyên môi trường tự nhiên, nhóm nguyên của của Viện Nhiệt Đới Môi Trường và Đại học Putra Malaysia đã thực hiện một nghiên cứu về tính ứng dụng của quá trình nhiệt phân trong tái chế thành phần hữu cơ không phân huỷ sinh học của chất thải rắn đô thị trong bê tông nhựa trộn nóng Các kết quả quan trọng chỉ ra rằng với điều kiện nhiệt phân thích hợp, sản phẩm nhiệt phân của cùng có hàm lượng nhựa khoảng 15% và khả năng nhựa hoá có thể trộn với các chất kết tự khác để tạo bê tông nhựa Điều đó
sẽ tiết kiệm được khoảng 10-15% lượng nhựa sử dụng trong sản xuất bê tông nhựa Bê tông nhựa được sản xuất có các đặc điểm phù hợp với các tiêu chuẩn Việt Nam được ban hành bởi Bộ Giao Thông Vận Tải đối với vật liệu
sử dụng trong xây dựng đường giao thông
Từ khóa: Bê tông nhựa, Không phân huỷ sinh học, Nhiệt phân, Chất thải đô thị
Received date, 25 th January 2017
Revised manuscript, 16 th March 2017 Published on 28 th April 2017
Address: Institute for Tropical Technology and Environment (ITE),
Academy of Military Science and Technology
*
E-mail: leanhkien@vnn.vn