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Perspectives for pilot scale study of RDF in Istanbul, Turkey
Waste Management 29 (2009) 2976–2982
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Perspectives for pilot scale study of RDF in Istanbul, Turkey Mustafa Kara a,*, Esin Günay a, Yasemin Tabak a, Sß enol Yıldız b a b
TUBITAK MRC (Marmara Research Center) Materials Institute, Gebze, P.O. Box 21, 41470 Kocaeli, Turkey _ ISTAÇ, Istanbul Metropolitan Municipality Environmental Protection and Waste Materials Valuation Industry and Trade Co., Kasımpasßa, Istanbul, Turkey
a r t i c l e
i n f o
Article history: Accepted 29 July 2009 Available online 25 August 2009
a b s t r a c t Municipal solid waste (MSW) is one of the most important environmental problems arising from rapid urbanization and industrialization. The use of alternative fuels in rotary kilns of cement plants is very important for reducing cost, saving fossil fuels and also eliminating waste materials, accumulated during production or after using these materials. Cement industries has an important potential for supplying preferable solutions to the waste management. Energy recovery from waste is also important for the reduction of CO2 emissions. This paper presents an investigation of the development of refuse derived fuel (RDF) materials from non-recycling wastes and the determination of its potential use as an alternative fuel in cement production in Istanbul, Turkey. RDF produced from MSW was analyzed and its effects on cement production process were examined. For this purpose, the produced RDF was mixed with the main fuel (LPG) in ratios of 0%, 5%, 10%, 15% and 20%. Then chemical and mineralogical analyses of the produced clinker were carried out. It is believed that successful results of this study will be a good example for municipalities and cement industries in order to achieve both economic and environmental benefits. Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction Waste and waste management, which are realities of our daily lives, have been ignored for many years. Nonetheless, increasing population, technological developments and industrialization cause ever increasing solid waste problems, with a negative impact on environment and public health. Nowadays, treatments of municipal solid wastes (MSW) possess a serious problem in countries where the population density is very high and space for land filling is limited. Land filling is the simple and inexpensive method for disposal of non-recyclable solid wastes. However land filling causes many serious problems, such as groundwater pollution due to the leaching of toxic components from landfill solids, emission of odour and soil contaminants. Incineration of MSW has many advantages including a significant reduction in volume (about 70–90%), recovery of energy and complete disinfection. Therefore, incineration of MSW has been adopted in many countries, such as Japan and several European countries (Saikia et al., 2007). Municipal solid waste is a major environmental problem in Turkey, as in many developing countries. Problems associated with municipal solid waste are difficult to address, but efforts towards more efficient collection and transportation and environmentally acceptable waste disposal continue in Turkey. Although strict regulations on the management of solid waste are in place, primitive * Corresponding author. Tel.: +90 262 677 30 33; fax: +90 262 641 23 09. E-mail address: [email protected] (M. Kara). 0956-053X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2009.07.014
disposal methods such as open dumping and discharge into surface water have been used in various parts of Turkey. In many cities in Turkey, deficiencies in the provision of waste services are the result of inadequate financial resources, management, and technical skills of municipalities and government authorities to deal with the rapid growth in demand for services (Turan et al., 2009) Solid waste issue may be evaluated also as a management problem which requires developing collection, transportation and disposal practices for wastes; raising awareness among local authorities and public. In addition, the main goal which aims to carry on solid waste servicing in management organization is to collect and dispose waste in the most effective and suitable economic way to address environmental, social and technical issues. Furthermore, urbanization in Turkey has two important characteristics with respect to solid waste management issues. First one is fast and chaotic urbanization. This leads to more acceptable urban solid waste production; the second is the accumulation of garbage in rural areas that becomes a major problem for cities. Increasing solid wastes, both in mass and volume, forces municipalities to carry on solid waste management in limited capacity and this will be a major concern for city as well as rural areas (Kara et al., 2008). Solid waste management strategies and targets in Istanbul are determined until 2025 with ‘‘Integrated Waste Management Strategic Plan compatible with EU Environment Regulation for Istanbul”. Solid waste strategy plan in Istanbul is given in Fig. 1 (ISTAÇ Co., 2009). Municipal solid waste (MSW) can be processed as refuse derived fuel (RDF) and then used as a fuel in a cement kiln. But the
M. Kara et al. / Waste Management 29 (2009) 2976–2982
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Fig. 1. Solid waste strategy plan in Istanbul.
cement industry faces significant challenges in reducing CO2 emissions because the majority of CO2 emissions result from the process of calcinations, and are not solely based on the type of fuel or plant operational efficiencies. Higher fossil fuel prices are increasingly forcing cement plants to consider the use of alternative fuels for clinker production. It is well known that RDF saves large amounts of money, based on various experiences mostly in European countries, where well developed waste collection and disposal systems combine with high disposal costs. For example, in Germany in 2007, more than 54% of the industry’s heat demand was met using RDF, and some plants now operate with ‘‘zero fuel costs” or even earn money through their ability to offer environmentally friendly utilization of appropriate wastes (Lechtenberg and Partner, 2008). Refuse-derived fuel typically consists of pelletized or fluff MSW that remains after the removal of non-combustible materials such as ferrous materials, glass, grit, and other non-combustible materials. The remaining material is then called as RDF and used in clinker production as a secondary fuel. However, the environmental concerns of incineration also apply to RDF combustion facilities. Air emission limit values for dust, NOx and SO2 emissions are less stringent for cement kilns than for incinerators. This process should be carried out according to the related Directives where in emission control requirements are indicated. The composition of MSW varies significantly from country to country, due to cultural differences and to the level of source separation and other recycling and processing of wastes carried out in different countries. In general terms, the quality of the MSW also reflects the level of industrialization, and the quantities of paper and plastic sheet used in packaging. The MSW quality also varies with time, e.g. the inclusion of grass cuttings hedge trimmings and other plant materials and seasonal features can have a significant impact. Different countries had different rates of substitution of secondary fuel not only RDF but also other wastes, from 72% in The Netherlands to 2% in Spain, including 5% in Italy and 30% in Germany. In Italy, there have been two principal experiences with the use of RDF in cement kilns. In 2005, the Holcim group in Lombardia was authorized to use 15,000 tonnes/year of RDF for one plant (Merone) and 60,000 tonnes/year of animal meal together with 130,000 tonnes/year fossil fuels for another plant (Ternate). The other experience, in the province of Cuneo (northwest Italy), signif-
icant experience was gained through a collaboration between an important cement manufacturer and the Waste Disposal Company in Cuneo in the southern part of Piedmont, Italy. The most important aspect of this case is that of the three rotary kilns in the plant, the biggest one (3500 tonnes/day of clinker) used a substitution of 24.5% in 2004, and the second (1900 tonnes/day) had a substitution of 7% (Genon and Brizio, 2008). The main problem regarding the use of RDF by cement kilns is the chlorine content. When chlorine content is high, it weakens the concrete in terms of 2, 7 and 28 days compressive strength. The chlorine compounds and alkali–silica reactions occur salts. These salts generate microcracks and because of this compressive strength decreases (TS EN 197-1, 2002). However, the cement industry estimates that up to 20% of the heat load of a cement kiln could be produced by RDF, and the cement kiln could also burn other wastes such as tyres at the same time. The aim of this study is to produce RDF materials from nonrecycled plastic wastes as an alternative fuel in cement kilns. The wastes that are separated from non-recyclable plastic wastes are sent to the land filling areas in current systems after being pro_ cessed at ISTAÇ Co. Compost and Recovery Facilities. This study is carried out to research manufacturing process of RDF Material and developing the process of using alternative or additional fuels (instead of the fossil fuels). It is expected that, by means of this study, the continuous collecting of wastes as a respectful behaviour to the environment will be realized and the recycle of these wastes by granulating will be provided. As environmental concerns have become more important nowadays, Turkey signed the Kyoto Protocol by affirmation of the Turkish Great National Assembly (TBMM) in 5th February 2009. Thus, the usage of fossil fuel will be reduced and alternative fuels will be much preferred. This experimental pilot scale work is a pioneer study for Turkey in the means of applying Kyoto Protocol rules.
2. Experimental studies 2.1. RDF manufacturing and characterization Solid wastes larger than 80 mm obtained by sieving were taken to recycling bands and recyclable plastic, metal, paper and derived _ materials were sorted at ISTAÇ Co. Compost and Recovery Plant.
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Wastes different from these recyclable wastes treated in decomposing unit (non-recyclable plastic wastes, nappies, wood pieces, paper wastes, textile wastes, organics, etc.) were collected and transported to regular storage areas. The amount of these wastes is 300 tonnes per day and creates an intensive operation and occupies large volumes. RDF manufacturing process is explained along with the flow diagram given in Fig. 2. RDF is produced from municipal solid waste. Process steps are given as follows: separating at source; sorting or mechanical separation; size reduction (shredding, chipping and milling); separation and screening; blending; drying and pelletizing. Firstly, MSW is treated in pre-shredder followed by magnetic separator. Then, it is sent to a ballistic separator to separate the low calorific value wastes. The rest of the waste material is screened to remove the recyclable fractions (e.g. metals), the inert fractions (e.g. glass) and the fine wet putrescible fractions (e.g. food) before being pulverized. The metal free part is sent to fine (final) crushers for an appropriate size that can be used in cement factories. In this way, the fuel produced from wastes is called RDF. The waste is then sent to RDF stock area. Calorific value of RDF is about 4000 kcal/kg. The reason for high calorific value is due to plastic, paper or cardboard contents. In addition RDF has also high biomass value. This technology is generally applied only at very large MSW facilities. Non-recyclable wastes coming from compost facility’s recycling band such as plastic bags, textile wastes, nappies, paper wastes, wood pieces, plastics are converted into RDF products at the Refuse Derived Fuel Plant. The composition of the waste sent to RDF plant is given in Table 1. RDF was obtained from decomposition of organic parts and recyclable solid wastes (paper, metals, plastic, etc.). The most important criteria in selecting alternative fuels used in cement factories are humidity and calorific value. Values of these parameters are used to determine the ratio of alternative fuels into actual fuels during the process. Total humidity value of produced RDF was determined as 25% but needs to be decreased to approximately 10–15% before feeding into rotary cement kiln. The developments in this system provided a reduction in the amount of organic waste and the required limit value of humidity. The specimens generally include nylon pack, paper and tetra pack cover. The lower calorific value of the produced RDF in this study is 3500 kcal/kg. The picture of the produced RDF is given in Fig. 3. Chemical and trace element analysis of RDF are indicated respectively in Tables 2 and 3. There are no standards regarding physical and chemical characteristics of this product since RDF production is being realized in Turkey for the first time. However, there are
Table 1 The composition of waste sent to RDF plant. Waste
Composition of input (%)
Composition of output (%)
Textile Paper Organic fraction Plastic bag Napkin Other combustible PET-plastic Wood Bone Tetra Pak Sack Tin Glass Aluminium Stone
17,1 25.4 22 15.2 7.0 3.7 3.2 1.9 0.3 1.2 0.5 0.6 0.7 0.4 0.8
66.0 17.1 0 13.3 0 0 3.6 0 0 0 0 0 0 0 0
Total
100
100
Fig. 3. The picture of produced RDF.
limit values established for characteristics of RDF since significant progress regarding this issue was made in Germany. As it is indicated in Tables 2 and 3, the characteristics of RDF produced at _ ISTAÇ Co. are compared with the limit values of RDF produced at MVW Lechtenberg in Germany.
Fig. 2. Flow diagram of RDF manufacturing process.
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M. Kara et al. / Waste Management 29 (2009) 2976–2982 Table 2 Chemical analysis of RDF.
*
Parameters
RDF analyses
Total carbon, % Inorganic carbon, % Organic carbon, % Ash, % Volatile matter, % pH Humidity, % Bulk density, gr/cm3 Lower calorific value, kcal/kg Conductivity, us/cm Sulphur, % Chlorine, %
58 0.5 57.5 7.7 92.3 6.7 25 0.154 3500 3.04 0.46 0.9519
Standardized limits*
8–12 50–80 <20
<0.5 <1
Lechtenberg (2008).
3. Pilot scale test work
Table 3 Trace element analysis of RDF.
*
as other elements are provided from clay, shale and other materials. All the natural materials mentioned above also contain a wide variety of other elements in small quantities. Component and module of raw meal used in this study are given in Table 4, physical characteristics of raw meal is given in Table 5. LPG–propane gas has been selected for this study as a fuel. The composition of LPG–propane gas is 4% butane, 96% propane. The calorific value of the LPG is 11,200 kcal/kg. LPG has been used in pilot scale study because of LPG is more friendly to the environment and emits less emission than other fuels. Also LPG has high calorific value, easy transport and storage advantages. LPG comes out to high temperature in the kiln in a short time and can be converted to fuel in an amount of 100%.
Element
RDF analysis (ppm)
Standardized limits* (ppm)
As Cd Cu Hg Ni Pb Sb
0.9 1.6 18.4 0.3 54.6 26.5 2.9
10 5 150 1 50 100 20
Lechtenberg (2008).
There are some specifications about RDF in the literature. Minimum calorific value of 4000 kcal/kg, bulk density of 0.7 g/cm3, minimum density of 1.3 g/cm3, less than 15% ash content and approximately 10% moisture are defined as the characteristics of fuel pellets in a Indian pilot plant. The results of ultimate analysis for RDF pellets are 3–8% moisture, 15–25% mineral matter, 35–40% carbon, 5–8% hydrogen, 1–1.5% nitrogen, 0.2–0.5% sulphur and 25–30% oxygen. The fuel pellets can be efficiently used in fixed grate, traveling grate, fluidized-bed and multi fuel packaged boilers (Sika, 2000). The pelletized RDF specifications for Greve in Chianti plant (Italy) are determined as the bulk density of 0.5–0.7 g/cm3, the net calorific value of 4,108.149 kcal/kg, 71.1% volatile matter, 6.5% moisture, 11.4% fixed carbon, 0.5% sulphur, 0.4–0.6% chlorine and total 11% non-combustible. The fuel pellets can be used in fluidized-bed gasifiers, combustor and boiler (Granatstein, 2003). RDF analysis of Lomellina II RDF Plant (Italy) are defined as the calorific value of 2,507.88–3,988.72 kcal/kg, 20–30% water, 3.7– 17.3% ash, 0.7% chlorine, 0.1% sulphur, 5% inert, less than metals, less than 1% glass and 0.5% metallic aluminium, e.g. folio. The RDF pellets can be used in a circulating fluidized-bed boiler for electricity generation (Holopainen, 2006). Refuse-derived fuel facility (Phoenix) for making RDF from general household waste was built, and operations began in April 1999. Tosoh is cooperating with the city’s environmental administration by using the RDF as raw material and fuel for its cement plant. Heating value of 4.060 kcal/kg, less than 10% moisture and bulk density of 0.6 g/cm3 are defined as the RDF properties (TOSOH, 2000).
A pilot scale rotary cement kiln was manufactured for the purpose of conducting pilot scale test work within the scope of project. A view of pilot rotary cement kiln is shown in Fig. 4 and temperature field in rotary kiln is given in Fig. 5. Several parameters of preheating and firing kilns are fixed during clinker production and given in the below. Clinker production capacity: 125 kg/h Clinker production time: approximately 60 min Incline of pre-heating and firing kiln: 3.4° Rotating speed of pre-heating kiln: 4 rpm Rotating speed of firing kiln: 3.2 rpm Dimensions of pre-heating kiln: height: 4000 mm, inner–outer diameter: 275 mm–325 mm Dimensions of firing kiln: height: 6000 mm, inner–outer diameter: 380 mm–700 mm Solid retention time is approximately 60 min
Table 4 Component and modules of raw meal. Component and module
Amount (%)
CaO SiO2 Al2O3 Fe2O3 MgO K2O Cl Na2O TiO2 SO3 MnO LOI Total Standard of lime Silica module Hydraulic module
42.89 13.14 3.11 2.15 0.81 0.65 0.06 0.19 0.19 0.08 0.00 36.71 99.98 102.46 2.50 2.33
Table 5 Physical characteristics of raw meal. Physical property
Value
Distribution of composition
81% limestone 15% schist 1.5% magnetic materials 2.5% sand 0.4% 925–975 kg/m3 Under 150 lm 100% Under 59 lm 90% Under 15 lm 50%
2.2. Other inputs The main raw material of clinker production, the raw meal, has been supplied from AKÇANSA Cement Industry and Trade Co. The components are the oxides of calcium, silicon, aluminium and iron. Calcium mainly originates from raw materials such as limestone, marl or chalk. The silica, aluminium and iron components as well
Amount of humidity Density Particle size
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Fig. 4. A view of pilot cement kiln.
Solid/gas ratio (RDF/LPG) in pilot scale study is 0/100, 5/95, 10/ 80, 15/75 and 20/80. In this study, the investigation of clinker production by using different RDF ratios in pilot scale rotary cement kiln was studied. The purpose of this study is to use RDF as a supplementary fuel and to determine RDF performance by assessing RDF’s effect on clinkering process followed by the characterization of clinker obtained. Clinker production studies are started by feeding RDF and all other inputs by spiral and vibratory feeders into pilot scale rotary cement kiln. RDF, which was produced in this study, was added to the main fuel (LPG) in ratios of 0%, 5%, 10%, 15% and 20%. These fuel mixtures were used to produce clinker in pilot cement rotary kiln. After heat treatment work in the rotary kiln, clinker product is obtained. Bulk density tests are conducted in order to understand whether or not clinker is achieved. The density is determined by 5.6 mm and 12.2 mm sieves. Hot clinker is poured freely into a one litter beaker and the weight of clinker was measured. This value is used to determine density of clinker. The ideal density range is 1.26–1.28 g/cm3. If the density value is lower than 1.2 g/cm3 this indicates the presence of free lime in clinker. Clinker production was tested based on the results of bulk density tests made during clinker production. Then chemical and mineralogical analyses of produced clinker were carried out. It is confirmed that the values obtained from chemical analysis fall within limit values of Portland
cement; these test results reveal that Portland cement clinker is produced. In cement kilns, combustion takes place under very high flame temperatures and relatively long residence times. These conditions are favourable for the burning of refuse waste. Based on technical and environmental considerations, the analysis of burning RDF in a cement kiln shows that no special firing technology has to be installed except that of the RDF handling system, that there is an upper limit to the total fuel consumption (no more than 30%) for firing RDF and that there is no increase in the emission levels of air pollutants (including acid gases, dioxins, furans, etc.) (Lockwood and Ou, 1993). In the light of all these evidence obtained in pilot scale, a test of one-to-one dimension will be conducted at AKÇANSA Cement Industry and Trade Co. Emission measurements are not required during experimental studies since the pilot rotary kiln is manufactured for experimental purposes. Because there is not any dust suppression and other cyclone units which are present in industrial scale cement rotary kiln. In this study, the investigation of clinker production by using different RDF ratios in pilot scale rotary cement kiln was studied. The purpose of this study is to use RDF as a supplementary fuel and to determine RDF performance by assessing RDF’s effect on clinkering process followed by the characterization of clinker obtained. The cement industry faces significant challenges in reducing CO2 emissions because the majority of CO2 emissions result from the process of calcinations, and are not solely based on the type of fuel or plant operational efficiencies. CO2 emissions will be considerably reduced since RDF, as a renewable resource, reduces consumption and consequently the emissions of fossil fuels. Emission measurements will be required during experimental study at industrial scale rotary cement kiln. Result of the emission will be available in cement industry. Also emission values will below the limit values given in directives named as ‘‘Directive 2000/ 76/EC of The European Parliament and of the Council of 4 December 2000 on the Incineration of Waste”.
4. Results and discussion RDF, which was produced in this study, was added to the main fuel (LPG) in ratios of 0%, 5%, 10%, 15% and 20%. Chemical and mineralogical analyses of produced clinker were made according to the standard of TS EN 197/1. Clinker production was achieved
Fig. 5. Temperature field in rotary kiln.
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M. Kara et al. / Waste Management 29 (2009) 2976–2982 Table 6 Summary – chemical analysis of clinker. Compound and modules
CaO SiO2 Al2O3 Fe2O3 MgO K2O Cl Na2O TiO2 SO3 MnO Undefined Lime standard Lime saturation factors (L.S.F.) Silica modules Aluminium modules (T.M) Hydraulic module (H.M.) Free lime Density (g/cm3) Liquid phase (%)** * **
Amount (%) % 0 RDF + % 100 LPG test
% 5 RDF + % 95 LPG test
% 10 RDF + % 90 LPG test
% 15 RDF + % 85 LPG test
% 20 RDF + % 80 LPG test
Standard limits*
66.28 21.04 5.68 3.96 1.23 0.27 0.0102 0.22 0.28 0.14 0.05 0.84 97.19 0.97
66.24 20.90 5.66 3.94 1.22 0.28 0.0125 0.23 0.28 0.13 0.05 1.06 97.75 0.98
65.92 21.31 5.38 3.91 1.19 0.26 0.0256 0.24 0.28 0.13 0.05 1.12 95.84 0.96
66.08 21.26 5.67 3.92 1.22 0.27 0.0242 0.24 0.28 0.13 0.05 0.85 96.09 0.96
66.37 21.13 5.83 3.98 1.24 0.27 0.0228 0.25 0.28 0.13 0.05 0.44 96.70 0.97
60–67 17–25 3–8 0.5–6 0.1–4 0.2–1.3 Max. 0.1 0.2–1.3
2.18 1.43 2.16 2.82 1.28 27.81
2.18 1.43 2.17 3.82 1.25 27.70
2.25 1.43 2.14 2.76 1.35 27.34
2.21 1.45 2.14 3.06 1.21 27.71
2.15 1.46 2.15 3.60 1.19 28.37
2.3–2.7 1.3–1.6
1–3
% 92–96
Max. 2 1.2–1.3 25–27
The values taken from reference Erdog˘an (2004). Material phase changing ratio (%) was found by ampric formula at 1338 °C.
Table 7 Summary clinker compostion of main phases produced in pilot rotary. Modules
C3S C2S C3A C4AF *
Amount (%) % 0 RDF + % 100 LPG test
% 5 RDF + % 95 LPG test
% 10 RDF + % 90 LPG test
% 15 RDF + % 85 LPG test
% 20 RDF + % 80 LPG test
AKÇANSA values* (%)
54.20 19.44 8.35 12.06
51.23 21.28 8.31 12.00
51.73 22.06 8.18 11.89
50.88 22.56 8.40 11.94
49.71 23.08 8.71 12.11
51.33 20.60 6.36 11.25
Values of CEM I 42.5 R Portland cement commercially produced by AKÇANSA (June 2008 average).
according to the results of bulk density tests made during clinker production. A summary chemical analysis of clinker is given in Table 6; summary clinker composition of main phases produced in Pilot Rotary Kiln is given in Table 7. The standard limit values given in Table 6 were taken from Oxide and Quantities Occurring Portland Cement Table (Erdog˘an, 2004). After clinker production, only type of CEM I 42.5 R cement has been obtained by 95% clinker and 5% limestone mixture. It is confirmed that the values obtained from chemical analysis fall within limit values of Portland cement. The results of the tests show that Portland cement’s clinker is produced. Possibilities of using RDF material, which was derived from domestic wastes with high organic waste contents as supplementary fuel in cement factories in Turkey, were investigated in this study. As a result of these studies, it is confirmed that clinker quality conforms to the standards when RDF material is used. Calorific value, chlorine content and humidity are the most important parameters of RDF used in cement factories. According to studies chlorine value of 0.9% is below the level specified as 1% in the literature and humidity value of 25% is above the literature values. In the next study, a drying process will be performed to lower the humidity value additionally.
5. Conclusions In this study, it has been investigated the potential use of RDF materials from wastes leaving the isolation unit and not being recycled wastes as a supplementary fuel (instead of fossil fuels) in cement kilns. Results obtained in this study are given below:
The process of alternative fuel usage and combustion technology is developed in Turkey for the first time under the financial support of TUBITAK (The Scientific and Technical Research Council of Turkey) for Istanbul Metropolitan Municipality. This study is carried out by ISTAÇ Co., AKÇANSA Co and TUBITAK MRC. This is a model work and will be generalized to other municipalities in overall Turkey. Recycling processes will provide protection of natural resources. The use of RDF as an alternative fuel in cement production is an economically viable option to reduce fuel costs and landfill disposal. Thus, the amount of fossil fuel imported from abroad will be reduced. The use of alternative fuels in cement manufacturing is helping the cement industry to reduce effects on the environment and to improve its overall environmental performance. Alternative fuels provide a waste management solution for the community and reduce the use of non-renewable resources, without adverse environmental effects. RDF produces a more homogeneous fuel which burns more evenly at a higher temperature thereby making combustion control easier. Emission measurements are not required during experimental studies since the pilot rotary kiln is manufactured for experimental purposes; because of the pilot scale rotary kiln has not dust suppression and cyclone units which are present in industrial scale cement rotary kiln. In the light of these evidence obtained in pilot scale, a test of one-to-one scale will be conducted at Cement Industry. Since emission control has became more important because of
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environmental concerns, Turkey signed the Kyoto Protocol by affirmation of the Turkish Great National Assembly (TBMM) in 5th February 2009. Emission measurements are planned to be carried out during these industrial studies.
Acknowledgements The authors wish to acknowledge the financial support of TUBITAK (The Scientific and Technical Research Council of Turkey), Project: 105G108, 1007 – Support Programme for Research Projects of Public Institutions. We thank the project steering group members for their inputs. References Erdog˘an, T.Y., 2004. Questions and Answers of Concrete Materials (Cements, Aggregates, Water). Turkish Ready-Mixed Concrete Association. Genon, G., Brizio, E., 2008. Perspectives and limits for cement kilns as a destination for RDF. Waste Management 28, 2375–2385. Granatstein, D.L., 2003. Case study on waste-fuelled gasification project, Greve in Chianti, Italy. Natural Resources Canada/CANMET Energy Technology Centre (CETC).
Holopainen, H., 2006. Lomellina II – A New Generation RDF Power Plant in Italy, Foster Wheeler Power Group Europe Finland. In: Presented at Power-Gen Europe 2006.. ISTAÇ Co., 2009. . Kara, M., Günay, E., Tabak, Y., Yıldız, Sß ., Enç, V., 2008. The usage of refuse derived fuel from urban solid waste in cement industry as an alternative fuel. In: The 6th IASME/WSEAS International Conference on Innovation Heat Transfer, Thermal Engineering and Environment (HTE’08), 20–22 August 2008, Rhodes, Greece, pp. 172–177. ISBN: 978-960-6766-97-8. Lechtenberg, D., 2008. MVW Lechtenberg. . Lechtenberg, D., Partner, 2008. Alternative fuels in developing countries. MVW Lechtenberg. Reprinted from World Cement, Germany. Lockwood, F.C., Ou, J.J., 1993. Review: burning refuse-derived fuel in a rotary cement kiln. 207 (1), 65-70. Saikia, N., Kato, S., Kojima, T., 2007. Production of cement clinkers from municipal solid waste incineration (MSWI) fly ash. Waste Management 27, 1178–1189. Sika, P., 2000. Energy from MSW, RDF Pelletization, A Pilot Indian Plant, Department of Science & Technology, Government of India. . TOSOH, 2000. Responsible Care Activities Report Environment, Safety & Health. . TS EN 197-1, 2002. Cement, Composition, Specifications and Conformity Criteria for Common Cements (March). Turan, N.G., Çoruh, S., Akdemir, A., Ergun, O.N., 2009. Municipal solid waste management strategies in Turkey. Waste Management 29, 465–469.
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Perspectives for pilot scale study of RDF in Istanbul, Turkey Mustafa Kara a,*, Esin Günay a, Yasemin Tabak a, Sß enol Yıldız b a b
TUBITAK MRC (Marmara Research Center) Materials Institute, Gebze, P.O. Box 21, 41470 Kocaeli, Turkey _ ISTAÇ, Istanbul Metropolitan Municipality Environmental Protection and Waste Materials Valuation Industry and Trade Co., Kasımpasßa, Istanbul, Turkey
a r t i c l e
i n f o
Article history: Accepted 29 July 2009 Available online 25 August 2009
a b s t r a c t Municipal solid waste (MSW) is one of the most important environmental problems arising from rapid urbanization and industrialization. The use of alternative fuels in rotary kilns of cement plants is very important for reducing cost, saving fossil fuels and also eliminating waste materials, accumulated during production or after using these materials. Cement industries has an important potential for supplying preferable solutions to the waste management. Energy recovery from waste is also important for the reduction of CO2 emissions. This paper presents an investigation of the development of refuse derived fuel (RDF) materials from non-recycling wastes and the determination of its potential use as an alternative fuel in cement production in Istanbul, Turkey. RDF produced from MSW was analyzed and its effects on cement production process were examined. For this purpose, the produced RDF was mixed with the main fuel (LPG) in ratios of 0%, 5%, 10%, 15% and 20%. Then chemical and mineralogical analyses of the produced clinker were carried out. It is believed that successful results of this study will be a good example for municipalities and cement industries in order to achieve both economic and environmental benefits. Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction Waste and waste management, which are realities of our daily lives, have been ignored for many years. Nonetheless, increasing population, technological developments and industrialization cause ever increasing solid waste problems, with a negative impact on environment and public health. Nowadays, treatments of municipal solid wastes (MSW) possess a serious problem in countries where the population density is very high and space for land filling is limited. Land filling is the simple and inexpensive method for disposal of non-recyclable solid wastes. However land filling causes many serious problems, such as groundwater pollution due to the leaching of toxic components from landfill solids, emission of odour and soil contaminants. Incineration of MSW has many advantages including a significant reduction in volume (about 70–90%), recovery of energy and complete disinfection. Therefore, incineration of MSW has been adopted in many countries, such as Japan and several European countries (Saikia et al., 2007). Municipal solid waste is a major environmental problem in Turkey, as in many developing countries. Problems associated with municipal solid waste are difficult to address, but efforts towards more efficient collection and transportation and environmentally acceptable waste disposal continue in Turkey. Although strict regulations on the management of solid waste are in place, primitive * Corresponding author. Tel.: +90 262 677 30 33; fax: +90 262 641 23 09. E-mail address: [email protected] (M. Kara). 0956-053X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2009.07.014
disposal methods such as open dumping and discharge into surface water have been used in various parts of Turkey. In many cities in Turkey, deficiencies in the provision of waste services are the result of inadequate financial resources, management, and technical skills of municipalities and government authorities to deal with the rapid growth in demand for services (Turan et al., 2009) Solid waste issue may be evaluated also as a management problem which requires developing collection, transportation and disposal practices for wastes; raising awareness among local authorities and public. In addition, the main goal which aims to carry on solid waste servicing in management organization is to collect and dispose waste in the most effective and suitable economic way to address environmental, social and technical issues. Furthermore, urbanization in Turkey has two important characteristics with respect to solid waste management issues. First one is fast and chaotic urbanization. This leads to more acceptable urban solid waste production; the second is the accumulation of garbage in rural areas that becomes a major problem for cities. Increasing solid wastes, both in mass and volume, forces municipalities to carry on solid waste management in limited capacity and this will be a major concern for city as well as rural areas (Kara et al., 2008). Solid waste management strategies and targets in Istanbul are determined until 2025 with ‘‘Integrated Waste Management Strategic Plan compatible with EU Environment Regulation for Istanbul”. Solid waste strategy plan in Istanbul is given in Fig. 1 (ISTAÇ Co., 2009). Municipal solid waste (MSW) can be processed as refuse derived fuel (RDF) and then used as a fuel in a cement kiln. But the
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Fig. 1. Solid waste strategy plan in Istanbul.
cement industry faces significant challenges in reducing CO2 emissions because the majority of CO2 emissions result from the process of calcinations, and are not solely based on the type of fuel or plant operational efficiencies. Higher fossil fuel prices are increasingly forcing cement plants to consider the use of alternative fuels for clinker production. It is well known that RDF saves large amounts of money, based on various experiences mostly in European countries, where well developed waste collection and disposal systems combine with high disposal costs. For example, in Germany in 2007, more than 54% of the industry’s heat demand was met using RDF, and some plants now operate with ‘‘zero fuel costs” or even earn money through their ability to offer environmentally friendly utilization of appropriate wastes (Lechtenberg and Partner, 2008). Refuse-derived fuel typically consists of pelletized or fluff MSW that remains after the removal of non-combustible materials such as ferrous materials, glass, grit, and other non-combustible materials. The remaining material is then called as RDF and used in clinker production as a secondary fuel. However, the environmental concerns of incineration also apply to RDF combustion facilities. Air emission limit values for dust, NOx and SO2 emissions are less stringent for cement kilns than for incinerators. This process should be carried out according to the related Directives where in emission control requirements are indicated. The composition of MSW varies significantly from country to country, due to cultural differences and to the level of source separation and other recycling and processing of wastes carried out in different countries. In general terms, the quality of the MSW also reflects the level of industrialization, and the quantities of paper and plastic sheet used in packaging. The MSW quality also varies with time, e.g. the inclusion of grass cuttings hedge trimmings and other plant materials and seasonal features can have a significant impact. Different countries had different rates of substitution of secondary fuel not only RDF but also other wastes, from 72% in The Netherlands to 2% in Spain, including 5% in Italy and 30% in Germany. In Italy, there have been two principal experiences with the use of RDF in cement kilns. In 2005, the Holcim group in Lombardia was authorized to use 15,000 tonnes/year of RDF for one plant (Merone) and 60,000 tonnes/year of animal meal together with 130,000 tonnes/year fossil fuels for another plant (Ternate). The other experience, in the province of Cuneo (northwest Italy), signif-
icant experience was gained through a collaboration between an important cement manufacturer and the Waste Disposal Company in Cuneo in the southern part of Piedmont, Italy. The most important aspect of this case is that of the three rotary kilns in the plant, the biggest one (3500 tonnes/day of clinker) used a substitution of 24.5% in 2004, and the second (1900 tonnes/day) had a substitution of 7% (Genon and Brizio, 2008). The main problem regarding the use of RDF by cement kilns is the chlorine content. When chlorine content is high, it weakens the concrete in terms of 2, 7 and 28 days compressive strength. The chlorine compounds and alkali–silica reactions occur salts. These salts generate microcracks and because of this compressive strength decreases (TS EN 197-1, 2002). However, the cement industry estimates that up to 20% of the heat load of a cement kiln could be produced by RDF, and the cement kiln could also burn other wastes such as tyres at the same time. The aim of this study is to produce RDF materials from nonrecycled plastic wastes as an alternative fuel in cement kilns. The wastes that are separated from non-recyclable plastic wastes are sent to the land filling areas in current systems after being pro_ cessed at ISTAÇ Co. Compost and Recovery Facilities. This study is carried out to research manufacturing process of RDF Material and developing the process of using alternative or additional fuels (instead of the fossil fuels). It is expected that, by means of this study, the continuous collecting of wastes as a respectful behaviour to the environment will be realized and the recycle of these wastes by granulating will be provided. As environmental concerns have become more important nowadays, Turkey signed the Kyoto Protocol by affirmation of the Turkish Great National Assembly (TBMM) in 5th February 2009. Thus, the usage of fossil fuel will be reduced and alternative fuels will be much preferred. This experimental pilot scale work is a pioneer study for Turkey in the means of applying Kyoto Protocol rules.
2. Experimental studies 2.1. RDF manufacturing and characterization Solid wastes larger than 80 mm obtained by sieving were taken to recycling bands and recyclable plastic, metal, paper and derived _ materials were sorted at ISTAÇ Co. Compost and Recovery Plant.
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Wastes different from these recyclable wastes treated in decomposing unit (non-recyclable plastic wastes, nappies, wood pieces, paper wastes, textile wastes, organics, etc.) were collected and transported to regular storage areas. The amount of these wastes is 300 tonnes per day and creates an intensive operation and occupies large volumes. RDF manufacturing process is explained along with the flow diagram given in Fig. 2. RDF is produced from municipal solid waste. Process steps are given as follows: separating at source; sorting or mechanical separation; size reduction (shredding, chipping and milling); separation and screening; blending; drying and pelletizing. Firstly, MSW is treated in pre-shredder followed by magnetic separator. Then, it is sent to a ballistic separator to separate the low calorific value wastes. The rest of the waste material is screened to remove the recyclable fractions (e.g. metals), the inert fractions (e.g. glass) and the fine wet putrescible fractions (e.g. food) before being pulverized. The metal free part is sent to fine (final) crushers for an appropriate size that can be used in cement factories. In this way, the fuel produced from wastes is called RDF. The waste is then sent to RDF stock area. Calorific value of RDF is about 4000 kcal/kg. The reason for high calorific value is due to plastic, paper or cardboard contents. In addition RDF has also high biomass value. This technology is generally applied only at very large MSW facilities. Non-recyclable wastes coming from compost facility’s recycling band such as plastic bags, textile wastes, nappies, paper wastes, wood pieces, plastics are converted into RDF products at the Refuse Derived Fuel Plant. The composition of the waste sent to RDF plant is given in Table 1. RDF was obtained from decomposition of organic parts and recyclable solid wastes (paper, metals, plastic, etc.). The most important criteria in selecting alternative fuels used in cement factories are humidity and calorific value. Values of these parameters are used to determine the ratio of alternative fuels into actual fuels during the process. Total humidity value of produced RDF was determined as 25% but needs to be decreased to approximately 10–15% before feeding into rotary cement kiln. The developments in this system provided a reduction in the amount of organic waste and the required limit value of humidity. The specimens generally include nylon pack, paper and tetra pack cover. The lower calorific value of the produced RDF in this study is 3500 kcal/kg. The picture of the produced RDF is given in Fig. 3. Chemical and trace element analysis of RDF are indicated respectively in Tables 2 and 3. There are no standards regarding physical and chemical characteristics of this product since RDF production is being realized in Turkey for the first time. However, there are
Table 1 The composition of waste sent to RDF plant. Waste
Composition of input (%)
Composition of output (%)
Textile Paper Organic fraction Plastic bag Napkin Other combustible PET-plastic Wood Bone Tetra Pak Sack Tin Glass Aluminium Stone
17,1 25.4 22 15.2 7.0 3.7 3.2 1.9 0.3 1.2 0.5 0.6 0.7 0.4 0.8
66.0 17.1 0 13.3 0 0 3.6 0 0 0 0 0 0 0 0
Total
100
100
Fig. 3. The picture of produced RDF.
limit values established for characteristics of RDF since significant progress regarding this issue was made in Germany. As it is indicated in Tables 2 and 3, the characteristics of RDF produced at _ ISTAÇ Co. are compared with the limit values of RDF produced at MVW Lechtenberg in Germany.
Fig. 2. Flow diagram of RDF manufacturing process.
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M. Kara et al. / Waste Management 29 (2009) 2976–2982 Table 2 Chemical analysis of RDF.
*
Parameters
RDF analyses
Total carbon, % Inorganic carbon, % Organic carbon, % Ash, % Volatile matter, % pH Humidity, % Bulk density, gr/cm3 Lower calorific value, kcal/kg Conductivity, us/cm Sulphur, % Chlorine, %
58 0.5 57.5 7.7 92.3 6.7 25 0.154 3500 3.04 0.46 0.9519
Standardized limits*
8–12 50–80 <20
<0.5 <1
Lechtenberg (2008).
3. Pilot scale test work
Table 3 Trace element analysis of RDF.
*
as other elements are provided from clay, shale and other materials. All the natural materials mentioned above also contain a wide variety of other elements in small quantities. Component and module of raw meal used in this study are given in Table 4, physical characteristics of raw meal is given in Table 5. LPG–propane gas has been selected for this study as a fuel. The composition of LPG–propane gas is 4% butane, 96% propane. The calorific value of the LPG is 11,200 kcal/kg. LPG has been used in pilot scale study because of LPG is more friendly to the environment and emits less emission than other fuels. Also LPG has high calorific value, easy transport and storage advantages. LPG comes out to high temperature in the kiln in a short time and can be converted to fuel in an amount of 100%.
Element
RDF analysis (ppm)
Standardized limits* (ppm)
As Cd Cu Hg Ni Pb Sb
0.9 1.6 18.4 0.3 54.6 26.5 2.9
10 5 150 1 50 100 20
Lechtenberg (2008).
There are some specifications about RDF in the literature. Minimum calorific value of 4000 kcal/kg, bulk density of 0.7 g/cm3, minimum density of 1.3 g/cm3, less than 15% ash content and approximately 10% moisture are defined as the characteristics of fuel pellets in a Indian pilot plant. The results of ultimate analysis for RDF pellets are 3–8% moisture, 15–25% mineral matter, 35–40% carbon, 5–8% hydrogen, 1–1.5% nitrogen, 0.2–0.5% sulphur and 25–30% oxygen. The fuel pellets can be efficiently used in fixed grate, traveling grate, fluidized-bed and multi fuel packaged boilers (Sika, 2000). The pelletized RDF specifications for Greve in Chianti plant (Italy) are determined as the bulk density of 0.5–0.7 g/cm3, the net calorific value of 4,108.149 kcal/kg, 71.1% volatile matter, 6.5% moisture, 11.4% fixed carbon, 0.5% sulphur, 0.4–0.6% chlorine and total 11% non-combustible. The fuel pellets can be used in fluidized-bed gasifiers, combustor and boiler (Granatstein, 2003). RDF analysis of Lomellina II RDF Plant (Italy) are defined as the calorific value of 2,507.88–3,988.72 kcal/kg, 20–30% water, 3.7– 17.3% ash, 0.7% chlorine, 0.1% sulphur, 5% inert, less than metals, less than 1% glass and 0.5% metallic aluminium, e.g. folio. The RDF pellets can be used in a circulating fluidized-bed boiler for electricity generation (Holopainen, 2006). Refuse-derived fuel facility (Phoenix) for making RDF from general household waste was built, and operations began in April 1999. Tosoh is cooperating with the city’s environmental administration by using the RDF as raw material and fuel for its cement plant. Heating value of 4.060 kcal/kg, less than 10% moisture and bulk density of 0.6 g/cm3 are defined as the RDF properties (TOSOH, 2000).
A pilot scale rotary cement kiln was manufactured for the purpose of conducting pilot scale test work within the scope of project. A view of pilot rotary cement kiln is shown in Fig. 4 and temperature field in rotary kiln is given in Fig. 5. Several parameters of preheating and firing kilns are fixed during clinker production and given in the below. Clinker production capacity: 125 kg/h Clinker production time: approximately 60 min Incline of pre-heating and firing kiln: 3.4° Rotating speed of pre-heating kiln: 4 rpm Rotating speed of firing kiln: 3.2 rpm Dimensions of pre-heating kiln: height: 4000 mm, inner–outer diameter: 275 mm–325 mm Dimensions of firing kiln: height: 6000 mm, inner–outer diameter: 380 mm–700 mm Solid retention time is approximately 60 min
Table 4 Component and modules of raw meal. Component and module
Amount (%)
CaO SiO2 Al2O3 Fe2O3 MgO K2O Cl Na2O TiO2 SO3 MnO LOI Total Standard of lime Silica module Hydraulic module
42.89 13.14 3.11 2.15 0.81 0.65 0.06 0.19 0.19 0.08 0.00 36.71 99.98 102.46 2.50 2.33
Table 5 Physical characteristics of raw meal. Physical property
Value
Distribution of composition
81% limestone 15% schist 1.5% magnetic materials 2.5% sand 0.4% 925–975 kg/m3 Under 150 lm 100% Under 59 lm 90% Under 15 lm 50%
2.2. Other inputs The main raw material of clinker production, the raw meal, has been supplied from AKÇANSA Cement Industry and Trade Co. The components are the oxides of calcium, silicon, aluminium and iron. Calcium mainly originates from raw materials such as limestone, marl or chalk. The silica, aluminium and iron components as well
Amount of humidity Density Particle size
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Fig. 4. A view of pilot cement kiln.
Solid/gas ratio (RDF/LPG) in pilot scale study is 0/100, 5/95, 10/ 80, 15/75 and 20/80. In this study, the investigation of clinker production by using different RDF ratios in pilot scale rotary cement kiln was studied. The purpose of this study is to use RDF as a supplementary fuel and to determine RDF performance by assessing RDF’s effect on clinkering process followed by the characterization of clinker obtained. Clinker production studies are started by feeding RDF and all other inputs by spiral and vibratory feeders into pilot scale rotary cement kiln. RDF, which was produced in this study, was added to the main fuel (LPG) in ratios of 0%, 5%, 10%, 15% and 20%. These fuel mixtures were used to produce clinker in pilot cement rotary kiln. After heat treatment work in the rotary kiln, clinker product is obtained. Bulk density tests are conducted in order to understand whether or not clinker is achieved. The density is determined by 5.6 mm and 12.2 mm sieves. Hot clinker is poured freely into a one litter beaker and the weight of clinker was measured. This value is used to determine density of clinker. The ideal density range is 1.26–1.28 g/cm3. If the density value is lower than 1.2 g/cm3 this indicates the presence of free lime in clinker. Clinker production was tested based on the results of bulk density tests made during clinker production. Then chemical and mineralogical analyses of produced clinker were carried out. It is confirmed that the values obtained from chemical analysis fall within limit values of Portland
cement; these test results reveal that Portland cement clinker is produced. In cement kilns, combustion takes place under very high flame temperatures and relatively long residence times. These conditions are favourable for the burning of refuse waste. Based on technical and environmental considerations, the analysis of burning RDF in a cement kiln shows that no special firing technology has to be installed except that of the RDF handling system, that there is an upper limit to the total fuel consumption (no more than 30%) for firing RDF and that there is no increase in the emission levels of air pollutants (including acid gases, dioxins, furans, etc.) (Lockwood and Ou, 1993). In the light of all these evidence obtained in pilot scale, a test of one-to-one dimension will be conducted at AKÇANSA Cement Industry and Trade Co. Emission measurements are not required during experimental studies since the pilot rotary kiln is manufactured for experimental purposes. Because there is not any dust suppression and other cyclone units which are present in industrial scale cement rotary kiln. In this study, the investigation of clinker production by using different RDF ratios in pilot scale rotary cement kiln was studied. The purpose of this study is to use RDF as a supplementary fuel and to determine RDF performance by assessing RDF’s effect on clinkering process followed by the characterization of clinker obtained. The cement industry faces significant challenges in reducing CO2 emissions because the majority of CO2 emissions result from the process of calcinations, and are not solely based on the type of fuel or plant operational efficiencies. CO2 emissions will be considerably reduced since RDF, as a renewable resource, reduces consumption and consequently the emissions of fossil fuels. Emission measurements will be required during experimental study at industrial scale rotary cement kiln. Result of the emission will be available in cement industry. Also emission values will below the limit values given in directives named as ‘‘Directive 2000/ 76/EC of The European Parliament and of the Council of 4 December 2000 on the Incineration of Waste”.
4. Results and discussion RDF, which was produced in this study, was added to the main fuel (LPG) in ratios of 0%, 5%, 10%, 15% and 20%. Chemical and mineralogical analyses of produced clinker were made according to the standard of TS EN 197/1. Clinker production was achieved
Fig. 5. Temperature field in rotary kiln.
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M. Kara et al. / Waste Management 29 (2009) 2976–2982 Table 6 Summary – chemical analysis of clinker. Compound and modules
CaO SiO2 Al2O3 Fe2O3 MgO K2O Cl Na2O TiO2 SO3 MnO Undefined Lime standard Lime saturation factors (L.S.F.) Silica modules Aluminium modules (T.M) Hydraulic module (H.M.) Free lime Density (g/cm3) Liquid phase (%)** * **
Amount (%) % 0 RDF + % 100 LPG test
% 5 RDF + % 95 LPG test
% 10 RDF + % 90 LPG test
% 15 RDF + % 85 LPG test
% 20 RDF + % 80 LPG test
Standard limits*
66.28 21.04 5.68 3.96 1.23 0.27 0.0102 0.22 0.28 0.14 0.05 0.84 97.19 0.97
66.24 20.90 5.66 3.94 1.22 0.28 0.0125 0.23 0.28 0.13 0.05 1.06 97.75 0.98
65.92 21.31 5.38 3.91 1.19 0.26 0.0256 0.24 0.28 0.13 0.05 1.12 95.84 0.96
66.08 21.26 5.67 3.92 1.22 0.27 0.0242 0.24 0.28 0.13 0.05 0.85 96.09 0.96
66.37 21.13 5.83 3.98 1.24 0.27 0.0228 0.25 0.28 0.13 0.05 0.44 96.70 0.97
60–67 17–25 3–8 0.5–6 0.1–4 0.2–1.3 Max. 0.1 0.2–1.3
2.18 1.43 2.16 2.82 1.28 27.81
2.18 1.43 2.17 3.82 1.25 27.70
2.25 1.43 2.14 2.76 1.35 27.34
2.21 1.45 2.14 3.06 1.21 27.71
2.15 1.46 2.15 3.60 1.19 28.37
2.3–2.7 1.3–1.6
1–3
% 92–96
Max. 2 1.2–1.3 25–27
The values taken from reference Erdog˘an (2004). Material phase changing ratio (%) was found by ampric formula at 1338 °C.
Table 7 Summary clinker compostion of main phases produced in pilot rotary. Modules
C3S C2S C3A C4AF *
Amount (%) % 0 RDF + % 100 LPG test
% 5 RDF + % 95 LPG test
% 10 RDF + % 90 LPG test
% 15 RDF + % 85 LPG test
% 20 RDF + % 80 LPG test
AKÇANSA values* (%)
54.20 19.44 8.35 12.06
51.23 21.28 8.31 12.00
51.73 22.06 8.18 11.89
50.88 22.56 8.40 11.94
49.71 23.08 8.71 12.11
51.33 20.60 6.36 11.25
Values of CEM I 42.5 R Portland cement commercially produced by AKÇANSA (June 2008 average).
according to the results of bulk density tests made during clinker production. A summary chemical analysis of clinker is given in Table 6; summary clinker composition of main phases produced in Pilot Rotary Kiln is given in Table 7. The standard limit values given in Table 6 were taken from Oxide and Quantities Occurring Portland Cement Table (Erdog˘an, 2004). After clinker production, only type of CEM I 42.5 R cement has been obtained by 95% clinker and 5% limestone mixture. It is confirmed that the values obtained from chemical analysis fall within limit values of Portland cement. The results of the tests show that Portland cement’s clinker is produced. Possibilities of using RDF material, which was derived from domestic wastes with high organic waste contents as supplementary fuel in cement factories in Turkey, were investigated in this study. As a result of these studies, it is confirmed that clinker quality conforms to the standards when RDF material is used. Calorific value, chlorine content and humidity are the most important parameters of RDF used in cement factories. According to studies chlorine value of 0.9% is below the level specified as 1% in the literature and humidity value of 25% is above the literature values. In the next study, a drying process will be performed to lower the humidity value additionally.
5. Conclusions In this study, it has been investigated the potential use of RDF materials from wastes leaving the isolation unit and not being recycled wastes as a supplementary fuel (instead of fossil fuels) in cement kilns. Results obtained in this study are given below:
The process of alternative fuel usage and combustion technology is developed in Turkey for the first time under the financial support of TUBITAK (The Scientific and Technical Research Council of Turkey) for Istanbul Metropolitan Municipality. This study is carried out by ISTAÇ Co., AKÇANSA Co and TUBITAK MRC. This is a model work and will be generalized to other municipalities in overall Turkey. Recycling processes will provide protection of natural resources. The use of RDF as an alternative fuel in cement production is an economically viable option to reduce fuel costs and landfill disposal. Thus, the amount of fossil fuel imported from abroad will be reduced. The use of alternative fuels in cement manufacturing is helping the cement industry to reduce effects on the environment and to improve its overall environmental performance. Alternative fuels provide a waste management solution for the community and reduce the use of non-renewable resources, without adverse environmental effects. RDF produces a more homogeneous fuel which burns more evenly at a higher temperature thereby making combustion control easier. Emission measurements are not required during experimental studies since the pilot rotary kiln is manufactured for experimental purposes; because of the pilot scale rotary kiln has not dust suppression and cyclone units which are present in industrial scale cement rotary kiln. In the light of these evidence obtained in pilot scale, a test of one-to-one scale will be conducted at Cement Industry. Since emission control has became more important because of
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environmental concerns, Turkey signed the Kyoto Protocol by affirmation of the Turkish Great National Assembly (TBMM) in 5th February 2009. Emission measurements are planned to be carried out during these industrial studies.
Acknowledgements The authors wish to acknowledge the financial support of TUBITAK (The Scientific and Technical Research Council of Turkey), Project: 105G108, 1007 – Support Programme for Research Projects of Public Institutions. We thank the project steering group members for their inputs. References Erdog˘an, T.Y., 2004. Questions and Answers of Concrete Materials (Cements, Aggregates, Water). Turkish Ready-Mixed Concrete Association. Genon, G., Brizio, E., 2008. Perspectives and limits for cement kilns as a destination for RDF. Waste Management 28, 2375–2385. Granatstein, D.L., 2003. Case study on waste-fuelled gasification project, Greve in Chianti, Italy. Natural Resources Canada/CANMET Energy Technology Centre (CETC).
Holopainen, H., 2006. Lomellina II – A New Generation RDF Power Plant in Italy, Foster Wheeler Power Group Europe Finland. In: Presented at Power-Gen Europe 2006.