529618
research-article2014
WMR0010.1177/0734242X14529618Waste Management & ResearchMałgorzata
Original Article
Optimization of fuels from waste composition with application of genetic algorithm
Waste Management & Research 2014, Vol. 32(5) 423–433 © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0734242X14529618 wmr.sagepub.com
Wzorek Małgorzata
Abstract The objective of this article is to elaborate a method to optimize the composition of the fuels from sewage sludge (PBS fuel – fuel based on sewage sludge and coal slime, PBM fuel – fuel based on sewage sludge and meat and bone meal, PBT fuel – fuel based on sewage sludge and sawdust). As a tool for an optimization procedure, the use of a genetic algorithm is proposed. The optimization task involves the maximization of mass fraction of sewage sludge in a fuel developed on the basis of quality-based criteria for the use as an alternative fuel used by the cement industry. The selection criteria of fuels composition concerned such parameters as: calorific value, content of chlorine, sulphur and heavy metals. Mathematical descriptions of fuel compositions and general forms of the genetic algorithm, as well as the obtained optimization results are presented. The results of this study indicate that the proposed genetic algorithm offers an optimization tool, which could be useful in the determination of the composition of fuels that are produced from waste. Keywords Cement industry, fuel from waste, genetic algorithm, optimization, sewage sludge
Introduction The basic element of modern waste management involves the use of substances, materials and energy produced from waste. Legal provisions encourage the use of waste as an energy source; and the Council Directive 99/31/EC 99/31/EC introduces restrictions on waste disposal and prohibits storage of biodegradable waste in any landfills. Besides, it is necessary to bear in mind the guidelines in the section on electricity production from renewable energy sources included in Directive 2001/77/EC of the European Parliament and of the Council. The waste materials, owing to their origin, are characterized by variable yet advantageous properties and composition, so we can note an increased interest in using such waste materials as an energy source in the form of fuels. Processing of waste into fuels offers the possibility of obtaining a product of specific quality requirements, tailored to the process where they will be used, thus avoiding the technical and operational problems associated with the instability and heterogeneity of the composition of the unprocessed waste. Fuels from waste can be produced from municipal, industrial and other types of waste that have non-hazardous properties and required energy properties. The waste types that are used for fuels production are: municipal waste, paper, plastics, rubber, waste solvents, waste oil, tyres, shredded tyres, sewage sludge, animal waste and textiles. Wastes suitable for fuel production were identified in the list of waste and in the European Commission Decision 2000/532/EC. Properties of selected wastes that are often used for fuels production are shown in Tables 1 and 2. In Europe, different terms for fuels from waste are used, such as secondary fuel and alternative fuel. In Germany, for example,
the fuels from waste are known as SBS (Sekundärbrennstoffe) and EBS (Ersatzbrennstoffe) (Glorius, 2000; Schückes, 2007), and in Italy, CDR (Combustibili Derivato di Rifiutti) or CSS (Combustibili Solido Secondario) (Mariotti and Iannantuoni, 2011). While in other European countries, the fuels from waste are referred to as RDF (refused derived fuel) (Caputo et al., 2004; Genon and Brizo, 2008; Kara et al., 2009) or as SRF (solid recovered fuel) (Garg et al., 2007; van Tubergen et al., 2003), for which the notation has been introduced by the European Committee for Standardization (Technical Committee on Solid Recovered Fuels, 2006). In Poland they are known as alternative fuel (pali-wo alternatywne) (Mokrzycki et al., 2003; Polish Cement Association, 2010) and formed fuel (paliwo formowane) (Wandrasz and Wandrasz, 2006).
Required quality parameters for fuels from waste Fuels from waste can be used in processes of co-combustion with coal in boilers in the electricity production industry (Garg et al., 2011; Kakaras et al., 2005; Thiel and Thomé-Kozmiensky, 2012; Waglanda et al., 2011) and cement industry (CEMBUREAU, 2009; Opole University of Technology, Opole, Poland Corresponding author: Wzorek Małgorzata, Department of Process Engineering, Opole University of Technology, ul. Mikołajczyka 5, 45-271 Opole, Poland. Email: [email protected]
Downloaded from wmr.sagepub.com at UNIV OF CALIFORNIA SANTA CRUZ on April 5, 2015
424
Waste Management & Research 32(5)
Table 1. Energy properties of selected waste used for fuel production. Parameter
Unit
MSWa
Proximate analysis LHV Water % % Volatilesd % Ashd Ultimate analysis wt% of dry matter C % H % O % N % S % Cl %
6–17.70 15–40 40–60 10–30 32.88–38.25 4.41–4.65 23.11–2.23 0.67–1.02 0.15–0.6 0.6–1.02
Sewage sludgeb
Paperc
Plasticc
11.32–12.90d 79.25–82.50 47.55–56.94 35.51–40.28
12.70–19.72 4.11–5.83 66.39–84.20 1.1–22.47
21.81–38.97 8.00 n.d. 1.38–7.94
23.75–27.24 3.37–3.72 26.57–27.90 3.98–4.37 1.11–1.18 0.85–0.17
32.91–44.90 5.41–6.17 n.d. 0.01–0.18 0.08–0.21 0.00–0.002
37.56–88.48 4.94–12.37 38.55–47.84 0.42–33.10 0.71–1.92 0.16–4.43
aSource:
Garg et al. (2011); Tchobanoglous et al. (1993). Wzorek and Król (2009). cSource: Wandrasz and Wandrasz (2006). dIn dry matter. LHV: low heat value; MSW: municipal solid waste; n.d.: no data. bSource:
Table 2. Trace elements in selected waste used for fuels production (in dry mass). Parameter
MSWa
Sewage sludgeb
Paperc
Plasticc
Fe Cr Zn Pb Co Ni Cu As Hg Tl Cd
n.d. 8–612 245–2875 3–152 3–22 1–240 8.7–3.906 1.2–2.3 0.01–0.5 n.d. 1–19
1236–5794 28.0–53.56 1931–3503 36.34–64.89 2.88–9.30 1.96–33.39 104–193.5 2.77–6.72 0.91–2.57 0.15–0.64 1.03–3.09
1.276 54.49 146.69 1221 5.38 3.19 21.56 n.d. n.d. n.d. 230.5
603–5903 5.35–64.84 3.8–735.4 40.06–3059 3.45–14.16 4.23–28.54 16.25–68.22 n.d. n.d. n.d. 5.44–126.9
aSource:
Król (2012). Wzorek and Król (2009). cSource: Wandrasz and Wandrasz (2006). MSW: municipal solid waste; n.d.: no data. bSource:
Kaantee et al., 2004; Thomanetz, 2012). Otherwise, it is possible to use such types of materials in the facilities dedicated for combustion of alternative fuels (Rotter, 2012; van Tubergen et al., 2003). Each of these processes determine other requirements for the parameters of fuels. Therefore determining the quality criteria for fuels from waste is a common subject of discussion and studies undertaken by research centres, producers and users of fuels. Some countries in Europe, such as Germany, Italy, Switzerland and Finland, have established their standards with regard to the quality of fuels from waste, which account for the energy parameters and content of hazardous substances. Table 3 contains a summary of values and limit regulations according to different national regulations. Italian and Finnish standards contain a classification of fuels with regard to their quality, which became a proposal under preparation for the European Standardization Committee (CEN) standard for SRF. In order to unify the existing quality standards for the fuels produced from waste, quite recently CEN established a new system of classifying SRF on three parameters of
fuels, i.e. based on calorific value, chlorine and mercury content. The selection of these parameters is associated with three aspects used for the assessment of fuel: economic, technological and emission-based ones (Technical Committee on Solid Recovered Fuels, 2006). However, quality standards are also imposed by the manufacturers of fuels from waste since industry norms define the quality classes of fuels described, which fuels are applied in the particular industry branches. The main users of fuels from waste are the companies in the cement and electricity production. The power industry is interested in obtaining fuels from waste with the following parameters (Wasilewski and Sobolewski, 2007): – Constant characteristic of energy, emission and corrosive parameters (calorific value, sulphur and chlorine content). – Uniform size and bulk density, which should be determined individually for each type of the boiler installations. – Lack of metallic and mineral impurities damaging the grinding and dosing systems.
Downloaded from wmr.sagepub.com at UNIV OF CALIFORNIA SANTA CRUZ on April 5, 2015
425
Małgorzata Table 3. Quality systems for SRF according to different national standards. Parameter
Unit
Italya
LHV Water Ash Cl S N Hg Hg + Cd Cd As Co Cr Cu Mn Ni Pb Sb Sn Tl V
MJ/kg % % % % % mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge
Finlandb
Standard
High quality
>15.0
research-article2014
WMR0010.1177/0734242X14529618Waste Management & ResearchMałgorzata
Original Article
Optimization of fuels from waste composition with application of genetic algorithm
Waste Management & Research 2014, Vol. 32(5) 423–433 © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0734242X14529618 wmr.sagepub.com
Wzorek Małgorzata
Abstract The objective of this article is to elaborate a method to optimize the composition of the fuels from sewage sludge (PBS fuel – fuel based on sewage sludge and coal slime, PBM fuel – fuel based on sewage sludge and meat and bone meal, PBT fuel – fuel based on sewage sludge and sawdust). As a tool for an optimization procedure, the use of a genetic algorithm is proposed. The optimization task involves the maximization of mass fraction of sewage sludge in a fuel developed on the basis of quality-based criteria for the use as an alternative fuel used by the cement industry. The selection criteria of fuels composition concerned such parameters as: calorific value, content of chlorine, sulphur and heavy metals. Mathematical descriptions of fuel compositions and general forms of the genetic algorithm, as well as the obtained optimization results are presented. The results of this study indicate that the proposed genetic algorithm offers an optimization tool, which could be useful in the determination of the composition of fuels that are produced from waste. Keywords Cement industry, fuel from waste, genetic algorithm, optimization, sewage sludge
Introduction The basic element of modern waste management involves the use of substances, materials and energy produced from waste. Legal provisions encourage the use of waste as an energy source; and the Council Directive 99/31/EC 99/31/EC introduces restrictions on waste disposal and prohibits storage of biodegradable waste in any landfills. Besides, it is necessary to bear in mind the guidelines in the section on electricity production from renewable energy sources included in Directive 2001/77/EC of the European Parliament and of the Council. The waste materials, owing to their origin, are characterized by variable yet advantageous properties and composition, so we can note an increased interest in using such waste materials as an energy source in the form of fuels. Processing of waste into fuels offers the possibility of obtaining a product of specific quality requirements, tailored to the process where they will be used, thus avoiding the technical and operational problems associated with the instability and heterogeneity of the composition of the unprocessed waste. Fuels from waste can be produced from municipal, industrial and other types of waste that have non-hazardous properties and required energy properties. The waste types that are used for fuels production are: municipal waste, paper, plastics, rubber, waste solvents, waste oil, tyres, shredded tyres, sewage sludge, animal waste and textiles. Wastes suitable for fuel production were identified in the list of waste and in the European Commission Decision 2000/532/EC. Properties of selected wastes that are often used for fuels production are shown in Tables 1 and 2. In Europe, different terms for fuels from waste are used, such as secondary fuel and alternative fuel. In Germany, for example,
the fuels from waste are known as SBS (Sekundärbrennstoffe) and EBS (Ersatzbrennstoffe) (Glorius, 2000; Schückes, 2007), and in Italy, CDR (Combustibili Derivato di Rifiutti) or CSS (Combustibili Solido Secondario) (Mariotti and Iannantuoni, 2011). While in other European countries, the fuels from waste are referred to as RDF (refused derived fuel) (Caputo et al., 2004; Genon and Brizo, 2008; Kara et al., 2009) or as SRF (solid recovered fuel) (Garg et al., 2007; van Tubergen et al., 2003), for which the notation has been introduced by the European Committee for Standardization (Technical Committee on Solid Recovered Fuels, 2006). In Poland they are known as alternative fuel (pali-wo alternatywne) (Mokrzycki et al., 2003; Polish Cement Association, 2010) and formed fuel (paliwo formowane) (Wandrasz and Wandrasz, 2006).
Required quality parameters for fuels from waste Fuels from waste can be used in processes of co-combustion with coal in boilers in the electricity production industry (Garg et al., 2011; Kakaras et al., 2005; Thiel and Thomé-Kozmiensky, 2012; Waglanda et al., 2011) and cement industry (CEMBUREAU, 2009; Opole University of Technology, Opole, Poland Corresponding author: Wzorek Małgorzata, Department of Process Engineering, Opole University of Technology, ul. Mikołajczyka 5, 45-271 Opole, Poland. Email: [email protected]
Downloaded from wmr.sagepub.com at UNIV OF CALIFORNIA SANTA CRUZ on April 5, 2015
424
Waste Management & Research 32(5)
Table 1. Energy properties of selected waste used for fuel production. Parameter
Unit
MSWa
Proximate analysis LHV Water % % Volatilesd % Ashd Ultimate analysis wt% of dry matter C % H % O % N % S % Cl %
6–17.70 15–40 40–60 10–30 32.88–38.25 4.41–4.65 23.11–2.23 0.67–1.02 0.15–0.6 0.6–1.02
Sewage sludgeb
Paperc
Plasticc
11.32–12.90d 79.25–82.50 47.55–56.94 35.51–40.28
12.70–19.72 4.11–5.83 66.39–84.20 1.1–22.47
21.81–38.97 8.00 n.d. 1.38–7.94
23.75–27.24 3.37–3.72 26.57–27.90 3.98–4.37 1.11–1.18 0.85–0.17
32.91–44.90 5.41–6.17 n.d. 0.01–0.18 0.08–0.21 0.00–0.002
37.56–88.48 4.94–12.37 38.55–47.84 0.42–33.10 0.71–1.92 0.16–4.43
aSource:
Garg et al. (2011); Tchobanoglous et al. (1993). Wzorek and Król (2009). cSource: Wandrasz and Wandrasz (2006). dIn dry matter. LHV: low heat value; MSW: municipal solid waste; n.d.: no data. bSource:
Table 2. Trace elements in selected waste used for fuels production (in dry mass). Parameter
MSWa
Sewage sludgeb
Paperc
Plasticc
Fe Cr Zn Pb Co Ni Cu As Hg Tl Cd
n.d. 8–612 245–2875 3–152 3–22 1–240 8.7–3.906 1.2–2.3 0.01–0.5 n.d. 1–19
1236–5794 28.0–53.56 1931–3503 36.34–64.89 2.88–9.30 1.96–33.39 104–193.5 2.77–6.72 0.91–2.57 0.15–0.64 1.03–3.09
1.276 54.49 146.69 1221 5.38 3.19 21.56 n.d. n.d. n.d. 230.5
603–5903 5.35–64.84 3.8–735.4 40.06–3059 3.45–14.16 4.23–28.54 16.25–68.22 n.d. n.d. n.d. 5.44–126.9
aSource:
Król (2012). Wzorek and Król (2009). cSource: Wandrasz and Wandrasz (2006). MSW: municipal solid waste; n.d.: no data. bSource:
Kaantee et al., 2004; Thomanetz, 2012). Otherwise, it is possible to use such types of materials in the facilities dedicated for combustion of alternative fuels (Rotter, 2012; van Tubergen et al., 2003). Each of these processes determine other requirements for the parameters of fuels. Therefore determining the quality criteria for fuels from waste is a common subject of discussion and studies undertaken by research centres, producers and users of fuels. Some countries in Europe, such as Germany, Italy, Switzerland and Finland, have established their standards with regard to the quality of fuels from waste, which account for the energy parameters and content of hazardous substances. Table 3 contains a summary of values and limit regulations according to different national regulations. Italian and Finnish standards contain a classification of fuels with regard to their quality, which became a proposal under preparation for the European Standardization Committee (CEN) standard for SRF. In order to unify the existing quality standards for the fuels produced from waste, quite recently CEN established a new system of classifying SRF on three parameters of
fuels, i.e. based on calorific value, chlorine and mercury content. The selection of these parameters is associated with three aspects used for the assessment of fuel: economic, technological and emission-based ones (Technical Committee on Solid Recovered Fuels, 2006). However, quality standards are also imposed by the manufacturers of fuels from waste since industry norms define the quality classes of fuels described, which fuels are applied in the particular industry branches. The main users of fuels from waste are the companies in the cement and electricity production. The power industry is interested in obtaining fuels from waste with the following parameters (Wasilewski and Sobolewski, 2007): – Constant characteristic of energy, emission and corrosive parameters (calorific value, sulphur and chlorine content). – Uniform size and bulk density, which should be determined individually for each type of the boiler installations. – Lack of metallic and mineral impurities damaging the grinding and dosing systems.
Downloaded from wmr.sagepub.com at UNIV OF CALIFORNIA SANTA CRUZ on April 5, 2015
425
Małgorzata Table 3. Quality systems for SRF according to different national standards. Parameter
Unit
Italya
LHV Water Ash Cl S N Hg Hg + Cd Cd As Co Cr Cu Mn Ni Pb Sb Sn Tl V
MJ/kg % % % % % mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge mg/kge
Finlandb
Standard
High quality
>15.0
