DECEMBER 2020 www.fe.um.si/en/jet.html 2 JET VOLUME 13 / Issue 4 Revija Journal of Energy Technology (JET) je indeksirana v bazah INSPEC© in Proquest’s Technology Research Database. .quest’s Technology Research Database. 4 JET JOURNAL OF ENERGY TECHNOLOGY Ustanovitelj / FOUNDER / R Izdajatelj / PUBLISHER / R Glavni in odgovorni urednik / EDITOR-IN-CHIEF C Souredniki / CO-EDITORS Bruno CVIKL Miralem HADŽISELIMOVIC Gorazd HREN Zdravko PRAUNSEIS Sebastijan SEME Bojan ŠTUMBERGER Janez USENIK Peter VIRTIC Ivan ŽAGAR Uredniški odbor / EDITORIAL BOARD Dr. Anton BERGANT, a Izr. prof. dr. Marinko BARUKCIC, a Prof. dr. Goga CVETKOVSKI, a Prof. dr. Nenad CVETKOVIC, a Prof. ddr. Denis ĐONLAGIC, a Doc. dr. Brigita FERCEC, a Prof. dr. Željko HEDERIC, Josip Juraj Strossmayer University of Osijek, Croatia Prof. dr. Marko JESENIK, University of Maribor, Slovenia Izr. prof. dr. Ivan Aleksander KODELI, Jožef Stefan Institute, Slovenia Izr. prof. dr. Rebeka KOVACIC LUKMAN, University of Maribor, Slovenia Prof. dr. Milan MARCIC, University of Maribor, Slovenia Prof. dr. Igor MEDVED, Slovak University of Technology in Bratislava, Slovakia Izr. prof. dr. Matej MENCINGER, University of Maribor, Slovenia Prof. dr. Greg NATERER, Memorial University of Newfoundland, Canada Prof. dr. Enrico NOBILE, University of Trieste, Italia Prof. dr. Urška LAVRENCIC ŠTANGAR, University of Ljubljana, Slovenia Izr. prof. dr. Luka SNOJ, Jožef Stefan Institute, Slovenia Izr. prof. dr. Simon ŠPACAPAN, University of Maribor, Slovenia Prof. dr. Gorazd ŠTUMBERGER, University of Maribor, Slovenia Prof. dr. Anton TRNIK, Constantine the Philosopher University in Nitra, Slovakia Prof. dr. Zdravko VIRAG, University of Zagreb, Croatia Prof. dr. Mykhailo ZAGIRNYAK, Kremenchuk Mykhailo Ostrohradskyi National University, Ukraine Prof. dr. Marija ŽIVIC, University of Slavonski Brod, Croatia 6 JET Tehnicni urednik / TECHNICAL EDITOR Sonja Novak Tehnicna podpora / TECHNICAL SUPPORT Tamara BRECKO BOGOVCIC Izhajanje revije / PUBLISHING Revija izhaja štirikrat letno v nakladi 100 izvodov. Clanki so dostopni na spletni strani revije -www.fe.um.si/si/jet.html / The journal is published four times a year. Articles are available at the journal’s home page - www.fe.um.si/en/jet.html. Cena posameznega izvoda revije (brez DDV) / Price per issue (VAT not included in price): 50,00 EUR Informacije o narocninah / Subscription information: http://www.fe.um.si/en/jet/ subscriptions.html Lektoriranje / LANGUAGE EDITING Terry T. JACKSON Oblikovanje in tisk / DESIGN AND PRINT Fotografika, Boštjan Colaric s.p. Naslovna fotografija / COVER PHOTOGRAPH Jurij AVSEC Oblikovanje znaka revije / JOURNAL AND LOGO DESIGN Andrej PREDIN Ustanovni urednik / FOUNDING EDITOR Andrej PREDIN Spoštovani bralci revije Journal of energy technology (JET) Procesi hlajenja in ogrevanja so izjemnega pomena za celotno družbo, saj vplivajo na pocutje cloveka, kot tudi na procese v industriji. Eden od sodobnejših nacinov hlajenja je gotovo uporaba tehnike magnetnega hlajenja, zato smo v aktualno številko revije Journal of energy technology uvrstili kar dva clanka s tega podrocja. Raziskave magnetnega hlajenja, opisane v obeh clankih, so potekale na Gheorghe Asachi technical University of Iasi, Fakulteti za elektrotehniko, v Romuniji, pod okriljem prof. dr. Adriana Traiana Plesce. Imel sem privilegij, da sem prof. Plesco osebno spo­znal in ga tudi povabil, da je leta 2019 preko projekta Erasmus+ obiskal Fakulteto za energetiko. Žal je prof.Plesca v mesecu februarju 2021 preminil v starosti 49 let. Odšel je na višku svoje uspešne strokovne poti in za seboj pustil veliko nedokoncanega dela. Kot profesor in raziskovalec je delo-val na podrocju elektricnih naprav, modeliranja in simulacijah ter toplotnih analizah v elektricnih napravah. Je avtor 13 knjig, 29 patentov in velikega števila znanstvenih clankov. Bil je tudi clovek z veliko energije in pozitivne naravnanosti do življenja, zato je njegov odhod velika izguba tako po cloveški kot tudi strokovni plati. Jurij AVSEC odgovorni urednik revije JET 8 JET Dear Readers of the Journal of Energy Technology (JET) Cooling and heating processes are extremely important for the whole of society, as they affect both individual people as well as processes in industry. One of the more modern cooling methods is the magnetic cooling technique; we have included two articles about in the current issue of the Journal of energy technology. The research on magnetic cooling described in both articles was conducted at Gheorghe Asachi Technical University of Iasi, Faculty of Electrical Engineering, Romania, under the auspices of Prof. Adriana Traian Plesca. I had the privilege of meeting Prof. Plesca in person and also hosted him when he visited the Faculty of Energy in 2019 through the Erasmus+ project. Unfortunately, he passed away in February 2021 at the age of 49. He passed away at the height of his successful career and left behind a lot of unfinished work. As a professor and researcher, he worked in the field of electrical devices, modelling and simulations, and thermal analysis in electri­cal devices. He was the author of 13 books, 29 patents and a large number of scientific articles. He was also a man full of energy and a positive attitude towards life, so his departure is a great loss from both the human and professional points of view. Jurij AVSEC Editor-in-chief of JET Table of Contents / Kazalo Analysis of combustible fractions in mixed municipal waste and packaging and calculation of energy value Analiza gorljivih frakcij v mešanih komunalnih odpadkih in embalaži ter izracun energijske vrednosti Buble Ivana, Jerina Simon, Seme Sebastijan, Stergar Janja . . . . . . . . . . . . . . . . . . . . . . . . .11 Analysis and efficiency of a gadolinium magnetocaloric material plate Analiza in ucinkovitost gadolinijske magnetokaloricne plošce Botoc Dorin, Rusu Ionut-Bogdan, Plesca Adrian, Avsec Jurij . . . . . . . . . . . . . . . . . . . . . . . .29 Cost-benefit analysis of frost protection methods Analiza stroškov in koristi metod za zašcito proti pozebi Matej Fike, Mateja Fekonja, Miha Smrekar. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39 Production of artificial cold for industry, based on the magnetocaloric effect Proizvodnja umetnega hladu, osnovana na magnetokaloricnem ucinku Botoc Dorin, Rusu Ionut-Bogdan, Plesca Adrian, Avsec Jurij . . . . . . . . . . . . . . . . . . . . . . . .51 Instructions for authors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63 10 JET JET Volume 13 (2020) p.p. 11-28 Issue 4, December 2020 Type of article 1.01 www.fe.um.si/en/jet.html ANALYSIS OF COMBUSTIBLE FRACTIONS IN MIXED MUNICIPAL WASTE AND PACKAGING AND CALCULATION OF ENERGY VALUE ANALIZA GORLJIVIH FRAKCIJ V MEŠANIH KOMUNALNIH ODPADKIH IN EMBALAŽI TER IZRACUN ENERGIJSKE VREDNOSTI Buble I.1, Jerina S.R,2, Seme S.2, Stergar J.3,4 Keywords: mixed municipal waste, mixed municipal packaging, combustible fractions, energy value, solid recovered fuel, TGA analysis Abstract The present article analyses combustible fractions in mixed municipal waste and packaging and the calculation of energy value. Methods of thermal treatment of waste and methods of preparation of alternative fuels and classifications are presented and described. The article describes the method of analysis of caloric values with which we determined the energy values of individual fractions. For the research, we also used two thermal analyses, with which we considered individual fractions, ther­mogravimetric analysis, and differential dynamic calorimetry. The article presents the results of both thermal analyses, with which we observe the responses of individual types of plastics at different R Corresponding author: Simon Jerina, University of Maribor, Faculty of Energy Technology, Hocevarjev trg 1, Krško, Tel.: +386 40 453 805, E-mail address: simon.jerina@gmail.com 1Kostak d.d., Leskovška cesta 2a, Krško 2University of Maribor, Faculty of Energy Technology, Hocevarjev trg 1, Krško 3University of Maribor, Faculty of Chemistry and Chemical Technology, Smetanova ulica 17, Maribor, Slovenia 4University of Maribor, Faculty of Medicine, Taborska ulica 8, 2000, Slovenia temperatures and the change in physical and chemical properties. The problem we have analysed in this article is mainly recyclable plastic that can no longer be reused due to various factors. The results of the structural analysis of household waste collection are also presented and described; on the basis of the analysis, the energy value of the container of mixed municipal waste and the reasonableness of waste reuse are recalculated. Povzetek Clanek obravnava analizo gorljivih frakcij v mešanih komunalnih odpadkih in embalaži ter preracun energijske vrednosti. Predstavljeni in opisani so nacini termicne obdelave odpadkov ter metode priprave alternativnih goriv in klasifikacija. V clanku je opisana metoda analize kaloricnih vrednosti, s katero smo dolocali energijsko vrednost posameznih frakcij. Za namen raziskave smo uporabili tudi dve termicni analizi, s katerimi smo obravnavali posamezne frakcije, termogravimetricno analizo in diferencno dinamicno kalorimetrijo. V clanku so predstavljeni rezultati obeh termicnih analiz, s katerimi opazujemo odzive posameznih vrst plastike pri razlicnih temperaturah ter spremembo fizikalnih in kemijskih lastnosti. Problematiko, ki smo jo analizirali v tem clanku, predstavlja predvsem plastika, ki se lahko reciklira, vendar je zaradi razlicnih dejavnikov ni mogoce vec ponovno uporabiti. Predstavljeni in opisani so tudi rezultati strukturne analize zbiranja odpadkov v gospodinjstvih in na podlagi analize preracuna energijska vrednost zabojnika mešanih komunalnih odpadkov ter smiselnost ponovne uporabe odpadkov. INTRODUCTION Waste overcrowding is a major issue today. Ways to prevent the accumulation of waste material effectively are being sought. Utility companies collect waste in their collection centres. Waste material is classified according to its usability (and non-usability). At the same time, great emphasis is placed on the field of recycling. For the most part, the public is insufficiently aware of waste separation and the method of proper separation. There are several types of waste separation and collection. Collection begins with an ordinary household, for which purpose mixed municipal waste and mixed packaging. In some cases, bio-waste is separated in the first phase. With the right approach to waste management, we can contribute significantly to reducing the accumulation of waste and waste materials. Through detailed analyses and studies, waste can be separated to such an extent that it is reused, and disposed of as little as possible. Waste is also strictly defined according to legislation, and the consequent management of all types of waste differs at local, regional, and national levels. These classifications help in planning and defining methods of waste separation and collection. The reuse or recycling of waste requires precise information on the source and composition, the means and strategy of management can be determined. The definition of waste, of course, facilitates its classification into different groups, but such classification extremely demanding due to the diversity of waste, but only in this manner can it be handled consistently. Due to the heterogeneity of the waste material, we must strive for further homogenization. 1.1 Waste issues in Slovenia In Slovenia, the amount of waste is increasing every year; about 8 million tons of waste are generated annually. The largest share is accounted for by construction waste, specifically, 59%; waste from thermal processes represents about 13%, waste from metal and wood processing accounts for 7%, and waste is also generated in waste management facilities themselves (about 4%). Other types represent 5% of all generated waste. Municipal waste represents approximately one million tons, which is 12.5% of all waste and means that the population of Slovenia generates an average of 495 kilograms per person of waste per year. In the past, most waste was disposed of in dedicated landfills. With municipal waste management centres, the trend of waste disposal is significantly reduced as the recycling rate has increased. In Slovenia, about 59% of all municipal waste is recycled, [1]. 1.2 Types of waste that can be used for alternative fuels Annex 7 of the Waste Management Regulation (1358), page 3194, [2], describes the division of waste into individual types. The waste classification list is divided into 20 groups, as can be seen in Table 1. The source of the waste must be identified for classification. Table 1: Waste classification [2] Wastes from prospecting, mining, quarrying, physical and chemical processing of mineral resources Wastes from agriculture, horticulture, aquaculture, forestry, hunting and fishing, food preparation and processing Wastes from wood treatment and processing and production of particleboard and furniture, fibre, paper, and board Wastes from the leather, fur, and textile industries Wastes from oil refineries, natural gas refining, and coal pyrolysis Wastes from inorganic chemical processes Wastes from organic chemical processes Wastes from manufacture, formulation, supply and use of surface preservatives (paints, varnishes and enamels), adhesives, sealants, and printing inks Wastes from the photographic industry 10 Wastes from thermal processes 11 Wastes from chemical treatment and surface protection of metals and other materials; hydrometallurgy of non-ferrous metals 12 Wastes from shaping processes and physical and mechanical surface treatment of metals and plastics 13 Oil wastes and wastes from liquid fuels (excluding edible oils referred to in points 05 and 12) 14 Waste organic solvents, refrigerants and propellants (excluding 07 and 08) 15 Packaging waste; absorbents, cleaning cloths, filter media and protective clothing not elsewhere specified or included 16 Wastes not otherwise specified in the classification list 17 Construction and demolition wastes (including excavations from contaminated sites) 18 Wastes from health or veterinary medicine and/or related research (excluding wastes from kitchens and restaurants not directly derived from health or veterinary medicine) 19 Wastes from waste treatment facilities, treatment plants and from the preparation of drinking water and water for industrial use 20 Municipal waste (household and similar wastes from trade, industry and the public sector), including separately collected fractions Wastes that can be used in processing for alternative fuels are in groups: • 04 01 09 wastes from finishing and finishing of fur and leather, • 07 02 13 Waste plastics, • 15 01 01 Paper and paperboard packaging, • 15 01 02 Plastic packaging, • 15 01 06 Mixed packaging, • 17 09 04 Mixed construction and demolition wastes other than those mentioned in 17 09 01, 17 09 02, and 17 09 03, • 19 12 12 Other wastes (including mixtures of materials) from mechanical treatment of waste other than those mentioned in 19 12 11 • 20 01 01 Paper and paperboard • 20 01 39 Plastic, • 20 03 01 Mixed municipal waste, • 20 03 07 Bulky waste, [3]. Products of alternative fuel production are most often classified as: • 19 12 10 Combustible waste (fuel derived from waste), . 19 12 12 Other wastes (including mixtures of materials) from mechanical treatment of wastes other than those mentioned in 19 12 11, [3]. WASTE MANAGEMENT AND TREATMENT The preparation of an alternative fuel requires a multi-stage treatment to achieve the desired quality. High-calorie fuel is used in primary kilns or cement plants. The preparation of this fuel takes place in the process of sorting waste material. To achieve the efficiency of the sorting process, it is necessary to reduce the dimensions of the material and then separate it into 2D and 3D material. 3D material often contains several impurities in the form of heavy metals and larger pieces of building material. Also, 3D material is more demanding for mechanical processing. In the first step, magnetic separation, it is necessary to eliminate materials containing iron (Fe). This is followed by Eddy current separation to remove non-ferrous metals. Prior to the grinding process, air separation in an air separator is required to maintain the quality of the solid fuel, as all remaining heavy fraction is eliminated in this process. The particle size of the solid fuel is determined by the acquirer. Materials are usually ground to a size >30 mm. A similar separation procedure is used for 2D materials, [4]. 2.1 Heat treatment of waste Incineration or co-incineration is used for different types of waste. Heat treatment is only part of the complex waste treatment technology used to generate energy or reduce waste. From the chemical point of view, the waste incineration process can be divided into three phases. In phase one, drying and degassing takes place. This phase does not require oxygen, as it depends only on the supplied heat, [5]. Evaporation starts in the first phase, mainly of hydrocarbons and water; it occurs between 100 °C and 300 °C. The second phase is the pyrolysis and gasification of alternative fuels or waste. Pyrolysis represents further decomposition without the presence of oxygen at a temperature between 250 °C and 700 °C. Gasification of carbon residues with water vapour and CO in residues occurs at temperatures between 500 °C and 1000 °C. In the third stage, the flammable gases formed in the first and second stages are oxidized and burned at a temperature between 800 °C and 1450 °C. This phase is called oxidation, [5]. 2.2 Heat treatment technologies Different types of waste also require the use of different types of heat treatment. The most common heat treatment technologies are: • grate incinerators, • rotary kilns, • fluidized beds, • pyrolysis and gasification systems. ALTERNATIVE FUELS FROM WASTE Alternative fuels and the qualification system can be defined in several ways. In addition to the values and restrictions set by the legislation for the different uses of solid fuels from waste, in practice, the composition and properties of the fuel are determined by the supplier and the user. The most important parameters for fuel are fraction size, net calorific value, sulphur, fluorine, ash content, moisture, organic carbon content as well as material density and heavy metal content in the fuel, [6]. Regardless of its use and method, alternative fuel from waste must meet several criteria: • caloric values, • low chlorine content, • quality control, • particle size, • density, • a sufficient amount of fuel with the required properties, [6]. 3.1 Solid Recovered Fuel Solid Recovered Fuel (SRF) is a solid fuel from waste with calorific values ranging from 11 to 25 MJ/kg. Typically, fuel is produced from high-calorie sorted mixed municipal waste and industrial waste. The size of individual fuel particles is between 5 and 300 mm, [4]. Table 2: Classification of solid alternative fuels, [7] PARAMETERS SHARE UNITS 1. Class 2. Class 3. Class 4. Class 5. Class Net calorific arithmetic MJ/kg = 25 = 20 = 15 = 10 = 3 value mean Chlorine (Cl) arithmetic % (m/m) = 0.2 = 0.6 = 1.0 = 1.5 = 3.0 mean Mercury (Hg) median mg/MJ = 0.02 = 0.03 = 0.08 = 0.15 = 0.5 Mercury (Hg) 80th mg/MJ = 0.04 = 0.06 = 0.16 = 0.30 = 1.0 percentile value Cadmium arithmetic mg/kg = 1.0 = 4.0 = 5.0 = 5.0 = 5.0 (Cd) mean Sulphur (S) arithmetic % (m/m) = 0.2 = 0.3 = 0.5 = 0.5 = 0.5 mean There are several types of solid SRF fuel classification. They can be divided by quality (Table 3) or by using heat treatment technology (Table 4). Of course, each classification needs verified fuel quality parameters and properties. Table 3: Classification of different SRF-qualities, [4] Parameters SRF . specifications Coal- Calciner Grate Fluidized HOT DISC Primary Blast fired firing bed cement kiln burner furnace power station Utility boilers (HDF) cement kiln (PBF) (steel plant) Net calorific 11.15 11.18 11.16 11.16 14.16 20.25 <25 value MJ/kg] Particle size <50 <50.80 <300 <20. 100 <120 <10.30 <10 [mm] Oversize [%] 0 <1 <3 <2 * <1 0 Impurities <1 0 <3 <1.2*<1 0 (extraneous material) [w %] Chlorine (Cl) [w < 1.5 < 0.8 < < 1.0.0.8 0.8.0.6 < 1.0.0.8 < 2 %] 1.0.0. 8 Ash [w %] <35 * * <20 20.30 <10 <10 POLYMERS IN WASTE AND THEIR PROPERTIES There are many types of polymers. In waste, they are divided into seven subgroups. Some types of plastic can be recycled, while others are non-recyclable. The problem described in this article is mainly plastic that can be recycled, but due to various factors (incorrect separation, incorrect storage and use), it can no longer be recycled. Such waste in many cases ends in landfills. To reduce the disposal of non-degradable and non-reusable plastics, heat treatment is therefore essential. The largest share is represented by plastic in waste, which is used as an alternative fuel, and it also represents the raw material that in most cases has the highest net calorific value and thus increases the value of the fuel itself. Plastic is an extremely important component. Many substances are being investigated to replace it with other raw materials, but in the short term life without it will certainly not be possible. Therefore it is extremely important that it is used for other purposes, such as obtaining energy by heat treatment. Plastics are divided according to SPI labels, and these labels help individual and waste processors to classify plastics into groups for further sorting and processing. Data on different types of plastics are presented in Table 4. Table 4: Classification of plastics in waste by groups TYPE OF PLASTIC SPI LABEL USAGE Polyethylene terephthalate (PET or PETE) Drink bottles High-density polyethylene (HDPE) Packaging for milk, cosmetics Polyvinyl chloride (PVC) Plastic wrappers, various toys, spray bottles Low-density polyethylene (LDPE) Shopping bags, plastic covers, reusable plastic Polypropylene (PP) Food packaging Polystyrene (PS) Plastic cutlery, various food packaging Other Other packaging that cannot be classified in any of the above groups Polyethylene terephthalate (PET or PETE) or polymer PET is a type of polyester and represents one of the most important groups of packaging material, as it is widely used for packaging beverages. PET is primarily useful because of its properties. It has low density, good light transmission, resistance to elevated temperatures, good chemical resistance and dimensional stability and high toughness, [8]. High-Density Polyethylene (HDPE) and Low-Density Polyethylene (LDPE) are the simplest polymers, at least in terms of chemical structure, which ranks them among the most represented synthetic polymers also in terms of production. They generally have high toughness, are flexible and chemically resistant, but have lower thermal stability and strength. Low and high-density polyethylenes have a characteristic low melting point. They are distinguished by density, namely HDPE .= 0.940–0.965 g/cmł, and LDPE density . = 0.915–0.940 g/cmł, [8]. Polyvinyl chloride or PVC can be soft or hard. In connection with its properties, PVC has a high resistance to organic chemicals, and lower to heat, light and mechanical influences. PVC is an environmental problem mainly due to the content of phthalate-based plasticizers. An additional problem is the unreacted monomer in the form of vinyl chloride, which is considered to be carcinogenic, [8]. Polypropylene (PP) is one of the lightest synthetic polymers with a density of .= 0.90–0.91 g/cmł. It is similar in basic properties to LDPE but has higher strength, high gloss, and a higher melting point. It is resistant to water and most organic solvents. The problem is oxidation and decomposition at elevated temperatures, [8]. Polystyrene (PS), compared to other polymers, is slightly harder and stiffer, as well as more brittle. It is unsuitable for use at higher temperatures. It is highly susceptible to photochemical degradation in light, [8]. RESULTS 5.1 Structural analysis of mixed municipal solid waste and mixed packaging Mixed municipal solid waste (MSW) was classified into individual fractions: plastics, paper and cardboard, textiles and footwear, wood waste, rubber, glass, metals, construction waste, electronic devices, kitchen waste, including food scraps and other discarded waste, biological waste (mostly waste landscaping) and some other waste that we could not separate. Table 5 shows the percentage of waste. Table 5: Quantity of individual fractions in the analysed container in MSW Kitchen waste (food scraps and other) 17.5 Biological waste 7 Other 3 SUM 100 As part of the research, we also analysed the percentage of individual fractions in MP, using a 30 kg sample. From Table 6, we determine which fractions were in the container. Tetra packs of various packaged liquids appeared in the container to the greatest extent (31%), followed by bottles (25%), aluminium cans (22%). The fractions that remained were paper and cardboard (12%) and glass (3%). Some waste was also of biological and other origins, which belongs more to MSW (7%). We found that 43% of this packaging waste is recyclable, which means that no additional treatment is required. As much as 57% was dirty packaging that was not suitable for recycling and needed to be further processed for alternative fuels or reuse. Table 6: Structural analysis of MP Quantity FRACTION Suitable for recycling [%] Processing required [%] [%] Bottles 25 1510 Cans 22 220 Tetrapack 31 229 Paper and cardboard 12 39 Glass 3 12 Other (MSW) 7 07 SUM 100 43 57 In Table 7, the MP structure was further elaborated, according to the needs of analysis in the research. Plastics were divided into seven basic groups, as presented in Table 4. We see that most packaging waste has a PET composition (47%), followed by HDPE and LDPE with 16 and 17%. Other polymers are approximately evenly represented. Table 7: Polymers in MP Type of plastic in MP Quantity [%] Polyethylene terephthalate (PET or 47 PETE) High density polyethylene (HDPE) 16 Polyvinyl chloride (PVC) 3 Low density polyethylene (LDPE) 17 Polypropylene (PP) 5 Polystyrene (PS) 4 Other 8 SUM 100 5.2 Samples As part of the research, we analysed 50 samples of SRF fuel: 25 samples of fuel of lower quality and 25 samples of higher quality fuel. Gross and net calorific value and moisture content were analysed in the samples. We also performed a calorimetric analysis for the two individual most represented fractions in the structural analysis, plastic foil and cardboard. Thermogravimetric analysis and differential dynamic calorimetry were also performed for four plastic samples. In total, we analysed approximately 80 kg of waste. 5.3 Results of calorimetric analysis For the analysis of the calorific value of waste, we used 25 samples of SRF fuel of lower quality and 25 samples of SRF fuel of higher quality. We also analysed the calorific value of the foil and cardboard in Figure 1. Figure 1: Photos of foil (up) and cardboard (down) Figure 2 (below) shows the results of the calorimetric analysis of SRF fuel of lower quality. The graph presents the results of caloric values as a function of moisture. The samples had different moisture content; it is evident that those samples that contained more moisture have a slightly lower calorific value. Values range between 12 MJ/kg and 24 MJ/kg. According to the obtained results, the fuel can be classified into the classes given in Table 4 (Classification of solid fuels). Eight samples are thus classified into the fourth quality class, sixteen samples into the third quality class, and one sample exceeds the value of 20 MJ/kg and could be classified in the second quality class. Similarly, we analysed the calorific values of SRF fuel samples of higher quality. Figure 2 clearly shows how the moisture content reduces the calorific value of the fuel. The net calorific value of the samples ranged from 10 MJ/kg to 33 MJ/kg. These samples were also divided into quality classes. In the fourth class, we add one sample, in the third three, the second class comprises eleven, and the first ten samples. Figure 2: Calorific values compared to the moisture content of individual fuel samples of lower quality (up) and higher quality (down) 5.4 Results of thermogravimetric analysis and differential dynamiccalorimetry To facilitate the understanding of the behaviour of solid alternative fuels in heat treatment, we performed a laboratory analysis of the fractions that contribute the highest value of caloric energy to the fuel, namely plastics. We analysed four samples. The results of the analysis were compared with the research already conducted in this field. In the case of samples 1, 2 and 3, the measurement was carried out in the temperature range from 30 to 1000 °C with a temperature step of 20 K/min, in an inert nitrogen atmosphere, with a gas flow of 100 mL/min. In the case of sample four, the measurement was made in the range from 30 to 700 °C with a temperature step of 10 K/min, in an inert nitrogen atmosphere, with a gas flow of 100 mL/min. Plastic polymers in waste are composed of synthetic or natural materials, chemical building blocks of monomers are placed in high molecular weight chains, and the main element is carbon. Other elements are oxygen, hydrogen, nitrogen and other inorganic and organic elements. Research has shown that the thermal decomposition of plastics takes place at elevated temperatures. In a study of the thermal analysis of alternative fuel components, [9], it was found that plastics behave differently at elevated temperatures. Sample 1, plastic bottle belongs to the group of PET or PETE plastics. Figure 3 (left) shows that the sample decomposes almost completely. Weight drops by 84.3% or 8.45 g. The initial or initial weight of the sample was 10.0260 mg. The sample began to decompose at a temperature of 434.20 °C and completely decomposed to a temperature of 497.94 °C, which is consistent with the results from [9]. The decomposition temperature, at which the mass drop is 50%, is 1st 468.91 °C, determined by means of the lead function (DTG-curve = differential thermogravimetry, differential thermal gravimetry . 1st lead of the thermogravimetric curve over time). Figure 3 (left) shows only one jump, which indicates that the decay takes place in one step, as also found in [9]. Figure 3 (right) shows the energy changes of sample 1, which has a starting weight of the sample was 6.34 mg. For substances that are partially crystalline, the melting point and the glass transition temperature can be determined. In our case, we see that the glass transition temperature is 81.99 °C and the melting point is 250 °C, with the enthalpy of melting, being released during the melting process, 271.68 mJ or 42.25 J/g. Figure 3: TGA analysis of sample 1 (left), DSC analysis (right) Sample 2, yogurt packaging, belongs to the PS plastic group. Figure 4 shows that the initial weight of the sample was 8.101 mg; the sample disintegrated almost completely, and the mass decreased by 7.8204 mg, representing 96.54%. The decomposition process started at a temperature of 359.85 °C and lasted until a temperature of 554.61 °C. Compared to the TGA analysis in [9], depending on the composition of the crucible belonging to the PS group, the temperature change occurred earlier. We realized that for more accurate measurements, the exact chemical composition of individual plastics should also be determined, as these are very different from each other. The decomposition temperature, at which the mass has fallen by 50%, is 452.14 °C, determined by means of a DTG curve. Figure 4: TGA analysis of sample 2 Sample 3, foil packaging, belongs to the group of PP plastics. Figure 5 (left) shows that the initial weight of the sample was 6.5010 mg; the sample completely disintegrated and the mass decreased by 99.39% and 6.46 mg, respectively. The sample decomposed in the temperature range from 437.06 °C to 534.36 °C. The DTG curve showed a 50 % drop in mass at 486.90 °C. Compared to the analysis [9], we can see that the degradation occurred at a higher temperature, which means that our sample is more resistant to temperature changes. Figure 5 (right) shows that the sample melted and that the melting point was 169 °C, which is much lower than in the case of sample 1. 410.39 mJ of energy was released in the melting process. Figure 5: TGA analysis of sample 3 (left), DSC analysis (right) Sample 4, shampoo packaging, belongs to the group of HDPE plastics. Figure 6 (left) shows that this sample also completely disintegrated. The initial weight of the sample was 17.8210 mg, and the final weight was 17.6890 mg, representing a 98.7 1% decrease. The sample began to decompose at 474.27 °C and completely decomposed at 525.36 °C. Compared to the study in [9], the temperature range also differs slightly in this sample, but only by a few degrees; we can conclude that the results of the analysis are very similar. Figure 6 (right) shows that the initial weight of the sample was 11.7 mg, that this sample also melted and that the melting point was 133 °C, which is slightly lower than in the case of the Jamnica bottle and the flaxseed packaging. During the melting process, 1945.54 mJ of energy or 166.29 J/g was released.    Figure 6: TGA analysis of sample 4 (left), DSC analysis (right)  If we compare the samples, we see that they differ slightly from each other in terms of temperature resistance. For sample 1 (PET), decomposition begins at 434.20 °C, the first temperature change of sample 2 (PS) is at 359.85 °C; for sample 3 (PP) the temperature change occurs at 437.06 °C, and sample 4 (HDPE) is the most heat-resistant - the change starts at 474.27 °C. It is true that all samples decompose within a given temperature range. Based on the results of the analysis, we can determine the order of durability of the considered plastics, from the least to the most durable: PS