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Researchers
Abstract
Abbreviations
Introduction
Materials and methods
Results and discussion
Conclusions
References
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Linda Yousef1, Aber Mohamad2
1 Environmental Engineer, Homs, Syria
lindamouniryoussuf@gmail.com
2 Dr. Eng. Department of Environmental Engineering, Faculty of Civil Engineering, Al-Baath University, Homs, Syria
dr.aber.mohammad@gmail.com
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Abstract
Municipal solid waste (MSW) management is one of the most important challenges facing many developing countries like Syria, especially that today in Syria the waste is disposed of in landfills without any pretreatment. Therefore, this waste requires effective treatment methods and technologies considering the environment protection and public health. The aim of this research is to study the possibility of using solid waste as a substitute fuel RDF (Refuse - Derived Fuel) in cement plants as an effective contribution to the process of managing a part of the generated solid waste. This treatment focuses on the portion of the non-degradable components of MSW, this includes industrial waste (packaging waste), commercial waste, and the dry portion of municipal waste collected and sorted from landfills. Samples are refused combustible components of solid waste with low moisture: plastic, textiles, and paper. These samples were shredded, dried and finally burned in order to calculate the calorific value. Waste samples were taken from Wadi Al-Haddaeh factory in Tartous city - Syria. The calorific value rises as the moisture content of the RDF components decreases, the conducted thermal energy for plastic was 27,512 KJkg-1, and 14,390 KJkg-1 for textiles, and 17,912 KJkg-1 for paper. Therefore, RDF components with high calorific value would make it more suitable for use as an alternative fuel, which will save natural gas and reduce carbon dioxide emissions, and waste treatment costs.
Keywords: Municipal solid waste, Refuse - Derived Fuel, Cement industry, combustible, calorific value, Syria.
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Abbreviations
RDF: Refuse Derived Fuel; MSW: Municipal Solid Waste
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Introduction
It is well recognised that numerous types of consumption occur in contemporary communities, and that waste production has been steadily rising. The entities in charge of these communities' hygiene face a significant challenge as a result of the generated waste, especially since organic content will decay and massive amounts of bacteria and insects will grow when the waste is exposed to the air, causing undesirable odors and the spread of diseases in surrounding environment [1].
waste is currently disposed of in random landfills without any pretreatment or even separation at the source, which makes it difficult to deal with waste through recycling and recovery processes, and the most dangerous of that is generating a rise in the level of greenhouse gas emissions (CO2, CH4, N2O), which results from the decomposition of the organic part of the waste as well as the water content, especially that the organic part has the largest proportion of the household solid waste composition. On the other hand, the massive usage of non-renewable energy sources leads to a significant issue that has negative effects on the environment and public health, especially natural gas, fuel, coal, and oil... as a fuel source in sectors that demand a lot of energy, like the steel, cement, and electricity producing industries.
Moreover, the accumulation of waste quantities without treatment, which will lead to the occupation of large areas of land, which prevents its use in agriculture, construction or others activities. Wrong waste management affects communities and the economy 5 to 10 times more than what proper management of this sector can cost [4].
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Materials and methods
Composition of municipal solid waste (MSW)
MSW is materials with solid and semi-solid properties that are produced by homes and residential communities, as well as other wastes similar in nature and composition and originating from any activity (offices, public institutions, commercial and industrial activities, etc.) [4]. Table 1 shows what waste consists of [1].
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Solid waste content of papers and wrappings used for preserving food and other items increases as a result of high levels of living, economic development, and commercial activity [1].
The waste hierarchy principle
Waste must be avoided as a matter of priority in accordance with the waste hierarchy. If possible, unavoidable waste must be reused (preparation for reuse), otherwise it must be recycled. Non-recyclable waste shall then be recovered elsewhere, in particular by energy recovery or backfilling, or, if recovery is not possible, disposed of in an orderly manner. In the cement industry, the use of waste-derived fuels (stage 4 – energy recovery) and raw materials (stage 3 – recycling) serves to conserve primary resources. In 2017, the German cement industry recycled around 3.6 million metric tons of waste or waste-derived fuels and raw materials [5].
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RDF
RDF, or waste-derived fuel is defined as a renewable energy source that ensures waste is used constructively rather than being disposed of untreated in landfills. This fuel is produced from MSW’s combustible components. Waste treatment activities that are commonly used in the whole sector. For example, techniques used for repackaging, crushing, sieving, drying, blending or sorting [4]. This waste which will be extracted as fuel, must have a recoverable calorific value to be burned as an alternative fuel in cement plant kilns after being treated under certain conditions to replace part of the traditional fossil fuels (coal, oil and gas).
RDF production
Waste is separated, shredded, dried, packed and finally burned to produce energy.
• Separation: separating non-combustible wastes such as metal and glass from combustibles.
• Screening and Shredding (size reduction): that different materials need to be separated into a high- and a low-calorific fraction.
• Drying: to reduce the moisture content of waste and prevents the leachate production.
Finally, the residual waste is mixed to produce the final product (RDF) [4].
RDF co-combustion in cement plants
The co-incineration of waste-derived fuels and raw materials has been an established and proven measure for years to conserve natural resources such as fossil fuels or primary raw materials [6]. Therefore, RDF co-combustion in cement plants aims to:
• Minimizing the environmental impacts of solid waste management
• Reducing emissions of greenhouse gas
• Reducing waste treatment costs
• Reducing landfill waste without treatment
• Conservation of natural resources such as fossil fuels or primary raw materials
Many studies showed that RDF has:
• A high calorific value
• Low moisture
which makes it more suitable for use as an alternative fuel in the cement industry [3].
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Sampling and laboratory experiments
Different samples of rejected waste were taken from Wadi Al-Haddaeh factory located in Tartous city - Syria. The samples then were prepared for the incineration process in the laboratory, this included separation and shredding using simple cutting tools (scissors – metal cutter). Combustible components were taken by manual sorting.
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| Laboratory analysis was carried out in the laboratory of Al Baath University to determine the moisture content by placing the samples in an oven at 77°C for 24 hours [1]. The moisture was obtained by using Equation (1): |
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The energy content (J kg-1) of the combustibles (Plastic, paper, textiles) can be obtained after determining moisture.
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Results and discussion
By knowing the rate of solid waste generation per capita in a city and waste composition, the amount of RDF components can be determined. Then waste sorting helps to determine the appropriate treatment type to be selected for each type of waste (recycling, composting, incineration (RDF) or landfill).
RDF utilization reduces the waste quantities for landfilling and the CO2 emissions. Many feasibility studies showed:
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Moreover, the potential of using the remaining ash as a material that might be added to the cement plant's manufacturing line will be considered, it means material recovery of waste-derived fuels, in particular their inert content (ashes), in clinker production is also considered, or be transported with the rest of the inert materials to the landfills [7].
It is required to consider the emission generated by using RDF in cement plants, so it has to be procedures and techniques for emission control, like exhaust gas cleaning techniques, their applications and limitations. In addition to pay special attention to dust, nitrogen oxides and ammonia, sulphur dioxide, mercury as well as carbon monoxide [5]. For example, it must be in Syria legal bases for the use of waste-derived fuels in the cement industry. And these legal bases must include determining measuring equipment for continuous emission measurements with automated measuring systems.
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Conclusions
Potential production and utilization of RDF derived from mixed municipal solid waste to be used as an alternative fuel aim at:
• Environmentally: MSW can be a vital source of energy rather than a source of pollution, if it is managed and used properly. Thus, reducing the proportion of landfill waste without pre-treatment and reducing greenhouse gas emissions.
• Economically: Saving non-renewable natural energy and material resources and reducing waste treatment costs
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References
[1] SOLID WASTE TREATMENT. (1995). (Prof. Haytham Shahin, Tishreen University)
[2] Refuse-derived fuel potential production for co-combustion in the cement industry in Algeria.
https://orcid.org/0000-0002-8012-3136
[3] Potential Utilization of RDF as an Alternative Fuel to be Used in Cement Industry in Jordan.
www.mdpi.com/journal/sustainability
[4] Design and feasibility study of RDF preparation and utilization in Cement Industry. Dipl.-Ing. Markus Gleis - Federal Environment Agency (UBA)
[5] Abfallmitverbrennung in Zementwerken - Sachverständigengutachten
http://www.umweltbundesamt.de/publikationen
[6] Schönberger, H. (2020): State of the art of the co-incineration of waste-derived fuels in cement plants, Habilitationsschrift, in Vorbereitung
[7] Best Available Techniques (BAT) Reference Document for Waste Incineration Industrial Emissions Directive.
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