Search

Since 1869, when the first synthetic polymer began replacing natural materials, industrial polymer use has grown dramatically. This increased the number of polymer materials that became waste after reaching the end of their products' lifespans. The overall composition of discarded waste is different, thus, suitability for recovery needs to be analysed individually. Material recovery is the preferred waste management solution. However, it is applicable only for sorted and clean mono-fractions. Here pyrolysis stands out as one of the most environmentally sustainable energy recovery options for multi- material plastic waste. Through a technological assessment of 30 pyrolysis plants, the applicability of pyrolysis for the recovery of multi-layered plastics (MLP) is reviewed. Acceptable feedstock composition and additional feedstock requirements are identified. According to Resin Identification Code (RIC) system, MLP is classified as other (7). Only 40% of existing plants accept other (7) waste stream, and acceptance of polymer materials that are not classified by the RIC system is even lower. This represents a problem as MLP is commonly used in the food industry and accounts for over 14% of packaging waste. Currently, the recovery is challenging because the available technologies cannot identify and separate the individual layers of MLP. The feedstock composition is an important parameter in setting the operating conditions (temperature, residence time, catalyst) of the pyrolysis process. Since the composition of the MLP waste stream is not sufficiently investigated, it was decided to conduct the identification of its average composition from the discarded plastic waste by Fourier transform infrared (FTIR) microscopy. The obtained average MLP mixture was examined using thermogravimetric and kinetic analysis and pyrolyzed in a fixed bed reactor. Pyrolysis products (oil and gas) were analysed using FTIR spectroscopy and Nuclear Magnetic Resonance.

Pyrolysis Kinetic Study of the Plastic Food Packaging Waste Stream

Multi-layered plastics are a great challenge for the waste recycling industry. The majority of multi-layered plastics consist of two or more types of polymers, making it difficult to recycle mechanically, which leads to landfill or incineration plant. As a way of thermochemical recycling, pyrolysis is a promising cleaner technology that could use multi-layered waste plastics potential and convert it into valuable products like fuels and chemicals. To better understand the pyrolysis process of multi-layered plastics, thermogravimetric analysis was carried out to determine their thermochemical behaviour and kinetic parameters. Thermogravimetric measurements were conducted in a nitrogen atmosphere at heating rates of 5, 10, 15 and 20 °C/min in the temperature range 40−600 °C. Kinetic analysis was done using the isoconversional model- free Friedman method in combination with an advanced statistical approach. Thermogravimetric analysis revealed how decomposition occurs in the range 350−510 °C and the weight loss >90% indicating high volatile matter content, hence potential for pyrolytic oil production. The results of the kinetic analysis showed how pyrolysis of multi-layered plastics is a complex process consisting of three decomposition stages. The activation energy values determined by Friedman were rising with the degree of conversion from 127 kJ/mol at 0.01 to 219 kJ/mol at 0.95.

Plastična prehrambena ambalaža veliki je izazov za reciklažnu industriju. Većina prehrambene ambalaže sastoji se od dvije ili više vrsta polimera. Takva višeslojna plastična ambalaža pruža dobra mehanička svojstva s barijerama protiv vlage, svjetlosti i kisika kako bi se osigurao dulji vijek trajanja proizvoda. Međutim, zbog različitog sastava ambalaže, zahtjevno je provesti mehaničko ili kemijsko recikliranje tih materijala, što ih dovodi do odlagališta ili postrojenja za spaljivanje otpada. Piroliza je alternativna tehnologija kojom se termokemijski recikliraju miješani plastični otpad i polimerni materijali koje je teško reciklirati mehanički. Stoga se piroliza javlja kao obećavajuća, ekološki prihvatljiva metoda obrade otpadne prehrambene plastične ambalaže. U usporedbi sa spaljivanjem, u pirolizi se ulazni materijal ne koristi za izravnu proizvodnju energije već se dobiva pirolitičko ulje, plin i kruti ostatak, koji se dalje mogu koristiti za proizvodnju goriva, energije i kemikalija. Za bolje razumijevanje procesa pirolize prehrambene plastične ambalaže, provedena je termogravimetrijska analiza kako bi se utvrdilo termokemijsko ponašanje i kinetički parametri. U ovom istraživanju odabran je skup reprezentativnih uzoraka prehrambene ambalaže s poznatim omjerima polimera. Termogravimetrijska mjerenja provedena su u atmosferi dušika pri brzinama zagrijavanja od 5, 10, 15 i 20 °C/min u temperaturnom rasponu 40- 600 °C. Kinetička analiza provedena je bezmodelnom izokonverzijskom Friedmanovom metodom u kombinaciji s naprednim statističkim pristupom.

World plastic materials production has increased 240 times in the last 70 years and now consists of hundreds of different polymers but only a few of them are used in everyday products and account for the production of the majority of all polymers. The biggest share of polymers use is in packaging production (around 40%) followed by construction (20%), while other significant consumption of polymers can be found in electronic, electrical, automotive, sports, household leisure and agriculture industry. The life cycle of material is determined by its use, where some products lifespan is measured in decades while others reach the end of the life in less than a year. Some of the most problematic plastic products and co- products are packaging waste which is discarded soon after product sale, thus they reach waste streams very quickly. These wastes are mainly used for material recovery while residual waste can be used in energy recovery technologies. Because of this, it is important to know the characteristics of waste streams that consist of such wastes. This research analyses composition and morphological characteristics of separately collected packaging waste stream, but puts emphasis on residual waste fraction after each sequential separation. Residual fraction of packaging waste stream, which is not used for material recovery, is sampled during the municipal waste separation and recovery chain, thus, the efficiency of primary and secondary waste separation, as well as of tertiary, i.e. during refuse-derived fuel production, are tracked. Material characterisation and composition analysis results show that primary waste separation results in material with only 7% of contaminants and manual secondary waste separation efficiency ranges between 45 and 55%, while physico-chemical comparison results show very high level of separation quality of tertiary separation in RDF production step, thus produced RDF properties can be approximated through the use of input residual waste composition and technological characteristics of RDF production facility. Results show that both analysed MRF facilities produce residual waste fraction suitable for production of RDF usable in wide range energy recovery and fuel production technologies. Results of this analysis can be used by decision makers for planning the both environmentally and economically sustainable system for recovery of residual waste fractions from packaging waste management systems.

Otpadna plastika krajnjih potrošača koja se ne može mehanički reciklirati predstavlja zabrinjavajuće ekološko pitanje. Prema najnovijim dostupnim podacima za Europu (Plastics-the Facts 2019), čak 25% sakupljene otpadne plastike nakon konzumiranja odlaže se na odlagališta, 43% se energetski oporabljuje i 32% reciklira. Jedan od mogućih načina obnavljanja plastike koja se ne može reciklirati (NRP) je piroliza koja se smatra ekološki prihvatljivom tehnologijom za dobivanje goriva ili kemikalija iz plastičnog otpada. Da bi se riješio izazov oporavka NRP-a pirolizom, potrebno je odrediti njegov stvarni sastav. Izvedeno je vizualno odvajanje sakupljenog NRP, a korištena je infracrvena spektroskopija s Fourierovom transformacijom (FT-IR) kako bi se potvrdila točnost vizualnog odvajanja. Pronađena je značajna količina plastike koja je označena kao "ostalo". Budući da sastav te otpadne plastike nije dovoljno istražen, pronađeno je vrlo malo studija o njenoj pirolizi. Stoga je karakterizirana i dodana smjesi s drugim pronađenim polimernim vrstama NRP. Termogravimetrijska analiza (TGA) provedena je kako bi se utvrdilo termokemijsko ponašanje i kinetički parametri, što je potrebno za laboratorijska ispitivanja pirolize. TGA mjerenja provedena su pri brzinama zagrijavanja od 5, 10 i 15 ° C/min u temperaturnom rasponu 40-600 ° C s protokom dušika. Kinetička analiza provedena je izokonverzijskom bezmodelnom Friedmanovom metodom i metodom nelinearne multivarijatne regresije. Cilj ovog rada bio je analizirati kinetiku procesa pirolize NRP uz zeolitne katalizatore (Fe-ZSM i FCC). Otkriveno je kako se razgradnja NRP odvija u dva stupnja. Energija aktivacije NRP-a iznosila je 144 kJ/mol u prvoj fazi razgradnje i 262 kJ/mol u drugoj fazi razgradnje i smanjila se za 34% i 6, 5% nakon dodavanja FCC katalizatora, a za 41% i 18, 3% s dodatkom Fe-ZSM katalizatora.

Tijekom ručnog razvrstavanja plastičnog otpada krajnjih potrošača, u značajnoj količini je pronađena plastika označena kao tip sedam. Većina plastičnog otpada tipa sedam je višeslojna plastika koja se sastoji od dvije ili više vrsta polimera, što otežava mehaničku reciklažu, pa se obično spaljuje. Piroliza, kao način termokemijske reciklaže, danas je široko korištena tehnologija za pretvaranje otpadne plastike u vrijedne proizvode poput goriva i kemikalija. Da bi se dobio optimalni pirolitički proizvod, potrebno je kontrolirati sastav sirovine. Sastav otpadne plastične struje tipa sedam još nije dovoljno istražen. Stoga je karakterizacija te struje izvršena upotrebom infracrvene spektroskopije s Fourierovom transformacijom (FT-IR) za identifikaciju vrsta polimera. Nadalje, provedena je termogravimetrijska analiza (TGA) kako bi se utvrdilo termokemijsko ponašanje i kinetički parametri, što je potrebno za daljnja istraživanja u laboratorijskom reaktoru. TGA mjerenja provedena su u atmosferi dušika pri brzinama zagrijavanja od 5, 10 i 15 ° C/min u temperaturnom rasponu 40-600 ° C na zeolitnim katalizatorima. Kinetička analiza provedena je pomoću izokonverzijske Friedmanove metode u kombinaciji s multivarijantnom metodom nelinearne regresije. Rezultati kinetičke analize pokazali su složeni mehanizam razgradnje otpadne plastike tipa sedam. Vrijednosti prividne energije aktivacije za fleksibilne plastične folije snižene su dodatkom željezovog (III) oksida na ZSM-5 katalizatoru. Isto je postignuto i za krutu plastiku s dodatkom FCC katalizatora.

In most countries, waste management systems are modelled as a systems that provide a public waste management service and thus must be able to meet environmental sustainability requirements at a cost which is acceptable to system users/citizens. This study analyses the link between economic and environmental sustainability. The environmental sustainability of different waste management systems was analysed using a Cumulative Energy Demand indicator which analyses sustainability from a lifecycle perspective and whose application in waste management system analysis is more appropriate from conducting full-scale LCA analysis. The model used to carry out this environmental analysis was also extended with economic functions to analyse the economic sustainability of the system. The relation between the two calculated indicators defines the Economic Efficiency of Resource Recovery (EERR) index which shows the specific cost of the system for achieving identified resource recovery. This index can be used for benchmarking overall (environmental and economic) sustainability of the waste management systems, while its graphical representation can be used for easier comparison of possible solutions, easier presentation of the results, and easier decision making. The results show that the quality decision-making process needs to take into account the impact of expected changes on the overall sustainability of the systems under consideration and evaluate how they will affect the current perception of used technologies. In this context, it can be concluded that planning of sustainable waste management system needs to ecomaps not only waste management system itself but also the connecting systems which can provide support in meeting legislation goals in an economically sustainable way.

The biggest producer of plastic products today is the packaging industry which makes up for almost 40% of European plastic converter demand. In one year roughly 80% of produced plastic packaging in Europe turns into waste. In 2016, for the first time, a larger share of overall collected post- consumer plastic waste in Europe was recycled (31%) than landfilled (27%), while the rest was energy recovered (42%) mostly by incineration. Pyrolysis, a thermochemical degradation, is a promising technology used to valorise plastic waste by converting it into valuable products, such as fuels and chemicals. Most common polymers used in the packaging industry are high and low- density polyethylene (HDPE and LDPE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC) and polyethylene terephthalate (PET). From those, PVC and PET are not preferable components in the feedstock for pyrolysis process because of the formation of corrosive and toxic compounds. As pyrolysis reactor design is conditioned by prediction of the thermochemical behaviour and kinetic parameters of feedstock, in this research thermogravimetric analysis (TGA) was carried out on various mixtures of waste plastics containing HDPE, LDPE, PP, and PS in ratios that are determined by the actual plastic mix in Europe. TGA was carried out in a nitrogen atmosphere over a set of heating rates (5, 10, 15 and 20 °C/min) within a temperature range 40−600 °C. Kinetic analysis was performed using the isoconversional (Kissinger–Akahira–Sunose) method. Aim of this paper was to investigate the kinetics of the pyrolysis process of polymer mixtures using Ni- or Fe- based catalysts on γ- Al2O3 as a support. The results of the kinetic analysis showed that degradation mechanism of the polymer mixtures was complexed because of the variation in apparent activation energy with the conversion. The value of apparent activation energy for actual plastic mix (22% HDPE, 31% LDPE, 35% PP, 12% PS) was in range 180.8−208.3 kJ/mol. With the addition of catalyst Fe/γ-Al2O3 it lowered to 161.5−182.8 kJ/mol, and to 170.6−183.9 kJ/mol with Ni/ γ- Al2O3 catalyst.

Kontinuirano praćenje svojstava izolacije transformatora, koja zbog različitih utjecaja stari, vrlo je važno kako bi se osigurala pouzdana opskrba električnom energijom koja je neophodna u industriji i svakodnevnom životu. Provođenjem laboratorijskih eksperimenata starenja izolacijskih materijala i analizom njihovih fizikalno–kemijskih svojstava omogućuje se procjena preostalog vijeka trajanja transformatora i trenutnog stanja njegove izolacije. Bitno je pratiti i održavati izolacijski sustav transformatora kako ne bi došlo do kvarova te kako bi se pravovremeno mogli obnoviti ili zamijeniti. U ovom radu je istražena primjenjivost metode određivanja kontaktnog kuta i slobodne površinske energije s tri ispitne tekućine na izolacijskom kraft papiru koja predstavlja još jedan parametar kojim se može procijeniti stanje transformatora. Također se provela ATR–FTIR analiza kako bi se utvrdile promjene u strukturi kraft papira tijekom različitih vremena starenja u ulju. Dobiveni uzorci koji su bili ubrzano stareni u transformatorskom izolacijskom ulju u laboratorijskim uvjetima podvrgnuti su ispitivanju metodom mjerenja kontaktnog kuta kako bi se pratila promjena slobodne površinske energije (γ) papira tijekom različitih vremena starenja. Određeni su korelacijski pravci slobodnih površinskih energija uvrštavanjem izmjerenih vrijednosti kontaktnog kuta u različite modele. Rezultati mjerenja metodom kontaktnog kuta su pokazali da površina papira starenjem postaje hidrofobnija, odnosno nepolarnija. Iz korelacijskih pravaca slobodnih površinskih energija može se uočiti da brzina opadanja slobodne površinske energije kraft papira ovisi o temperaturi starenja pri čemu je brzina veća na višoj temperaturi. ATR−FTIR analizom utvrdilo se koje se vrpce javljaju na spektrima starenog papira. Continuous monitoring of transformer isolation, which degrades for a variety of influences, is very important to ensure a reliable supply of electricity which is essential in industry and everyday life. Laboratory experiments and the analysis of physical−chemical properties of aged insulating paper enable the evaluation of the remaining service life of the transformer and the current state of its isolation. It is essential to monitor and maintain the transformer insulation system to avoid damage and to organize replacement or reconstruction if needed. This thesis examined the applicability of the contact angle method using three test liquids on insulating kraft paper. Surface free energy of the paper was also calculated. ATR−FTIR analysis was implemented in order to determine changes in the structure of kraft paper during different times of aging in oil. Samples, which were artificially aged in transformer insulating oil in laboratory conditions, were investigated using the contact angle method to monitor changes of the surface free energy (γ) of paper during different times of aging. The correlation curves of the free surface energy were determined by including the contact angle method values in different calculation models. The contact angle method results showed that the surface of paper becomes more hydrophobic, or non–polar by aging. By looking at the correlation curves of the surface free energy it can be noticed that the rate of decline of the surface free energy of kraft paper depends on the aging temperature whereby the rate is greater at higher temperatures. By implementing ATR−FTIR analysis it was determined which bands appear in the spectra of aged paper.