Energy Systems Engineering / Enerji Sistemleri Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4752
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Article Citation - WoS: 52Citation - Scopus: 60Applied Machine Learning for Prediction of Waste Plastic Pyrolysis Towards Valuable Fuel and Chemicals Production(Elsevier, 2023) Cheng, Yi; Yang, Yang; Coward, Brad; Wang, Jiawei; Yıldız, Güray; Ekici, Ecrin; Yıldız, GürayPyrolysis is a suitable conversion technology to address the severe ecological and environmental hurdles caused by waste plastics' ineffective pre- and/or post-user management and massive landfilling. By using machine learning (ML) algorithms, the present study developed models for predicting the products of continuous and non-catalytically processes for the pyrolysis of waste plastics. Along with different input datasets, four algorithms, including decision tree (DT), artificial neuron network (ANN), support vector machine (SVM), and Gaussian process (GP), were compared to select input variables for the most accurate models. Among these algorithms, the DT model exhibited generalisable and satisfactory accuracy (R2 > 0.99) with training data. The dataset with the elemental composition of waste plastics achieved better accuracy than that with the plastic-type for predicting liquid yields. These observations allow the predictions by the data from ultimate analysis when inaccessible to the plastic-type data in unknown plastic wastes. Besides, the combination of ultimate analysis input and the DT model also achieved excellent accuracy in liquid and gas composition predictions. © 2023 The AuthorsArticle Citation - WoS: 8Citation - Scopus: 10Spray Analysis of Biodiesels Derived From Various Biomass Resources in a Constant Volume Spray Chamber(American Chemical Society, 2022) Ulu, Anılcan; Yıldız, Güray; Rodriguez, Alvaro Diez; Özkol, ÜnverThis research aimed to analyze the spray characteristics of various biodiesels, which have rarely been investigated in terms of spray analysis in the literature compared to fossil diesel. For this purpose, four different methyl ester-type biodiesels were produced from canola, corn, cottonseed, and sunflower oils. These feedstocks were selected due to their wide availability in Turkey and being among the significant resources for biodiesel production. Measured physical properties of biodiesel samples showed that biodiesel fuels had, on average, 1.7 to 1.9 times higher viscosities, 5.3 to 6.6% larger densities, and 37 to 39.1% higher contact angle values than the reference diesel fuel. Spray characteristics of all fuels were experimentally examined in a constant volume spray chamber under chamber pressures of 0, 5, 10, and 15 bar and injection pressures of 600, 800, and 1000 bar. All tested biodiesels performed, on average, 3 to 20% longer spray penetration lengths, 5 to 30% narrower spray cone angles, and 5-18% lesser spray areas than the reference diesel fuel under chamber pressures of 5 and 10 bar. No significant differences occurred at 15 bar ambient pressure between biodiesels and diesel. In addition, analytical and empirical predictions showed that biodiesels had around 21.2-35.1% larger SMD values and approximately 7% lower air entrainment.Article Citation - WoS: 9Citation - Scopus: 11Experimental Investigation of Spray Characteristics of Ethyl Esters in a Constant Volume Chamber(Springer, 2022) Ulu, Anılcan; Yıldız, Güray; Özkol, Ünver; Rodriguez, Alvaro DiezAbstract: Biodiesels are mainly produced via the utilization of methanol in transesterification, which is the widespread biodiesel production process. The majority of this methanol is currently obtained from fossil resources, i.e. coal and natural gas. However, in contrast with methanol, biomass-based ethanol can also be used to produce biodiesels; this could allow the production line to become fully renewable. This study aimed to investigate the spray characteristics of various ethyl ester type biodiesels derived from sunflower and corn oils in comparison to methyl esters based on the same feedstocks and reference petroleum-based diesel. Spray penetration length (SPL) and spray cone angle (SCA) were experimentally evaluated in a constant volume chamber allowing optical access, under chamber pressures of 0, 5, 10 and 15 bar and injection pressures of 600 and 800 bar. Sauter mean diameter (SMD) values were estimated by using an analytical correlation. Consequently, ethyl esters performed longer SPL (2.8–20%) and narrower SCA (5.1–19%) than diesel under ambient pressures of 5 and 10 bar. Although the SMD values of ethyl esters were 48% higher than diesel on average, their macroscopic spray characteristics were very similar to those of diesel under 15 bar chamber pressure. Moreover, ethyl esters were found to be very similar to methyl esters in terms of spray characteristics. The differences in SPL, SCA and SMD values for both types of biodiesels were lower than 4%. When considering the uncertainty (± 0.84%) and repeatability (±5%) ratios, the difference between the spray characteristics of methyl and ethyl esters was not major.Article Citation - WoS: 77Citation - Scopus: 95Sustainable Use of Apple Pomace (ap) in Different Industrial Sectors(MDPI, 2022) Gołębiewska, Ewelina; Kalinowska, Monika; Yıldız, GürayIn many countries, apple pomace (AP) is one of the most produced types of agri-food waste (globally, it is produced at a rate of ~4 million tons/year). If not managed properly, such bio-organic waste can cause serious pollution of the natural environment and public health hazards, mainly due to the risk of microbial contamination. This review shows that AP can be successfully reused in different industrial sectors—for example, as a source of energy and bio-materials—according to the idea of sustainable development. The recovered active compounds from AP can be applied as preservatives, antioxidants, anti-corrosion agents, wood protectors or biopolymers. Raw or processed forms of AP can also be considered as feedstocks for various bioenergy applications such as the production of intermediate bioenergy carriers (e.g., biogas and pyrolysis oil), and materials (e.g., biochar and activated carbon). In the future, AP and its active ingredients can be of great use due to their non-toxicity, biodegradability and biocompatibility. Given the increasing mass of produced AP, the commercial applications of AP could have a huge economic impact in the future.Article Citation - WoS: 27Citation - Scopus: 29The Utilization of Plum Stones for Pellet Production and Investigation of Post-Combustion Flue Gas Emissions(MDPI, 2020) Dolzynska, Magdalena; Obidzinski, Slawomir; Piekut, Jolanta; Yıldız, GürayAgri-food waste is generated at various food cycle stages and is considered to be a valuable feedstock in energy systems and chemical syntheses. This research identifies the potential and suitability of a representative agri-food waste sample (i.e., plum stones) as a solid fuel. Ground plum stones containing 10, 15, and 20 wt.% of rye bran were subjected to pelletization. The pelletizer was operated at 170, 220, and 270 rpm, and its power demand for the mixture containing 20 wt.% of rye bran was 1.81, 1.89, and 2.21 kW, respectively. Such pellets had the highest quality in terms of their density (814.6 kg.m(-3)), kinetic durability (87.8%), lower heating value (20.04 MJ.kg(-1)), and elemental composition (C: 54.1 wt.%; H: 6.4 wt.%; N: 0.73 wt.%; S: 0.103 wt.%; Cl: 0.002 wt.%; O: 38.2 wt.%). Whole plum stones and pellets were subjected to combustion in a 25 kW retort grate boiler in order to determine the changes in the concentrations of NO, SO2, CO, CO2, HCl, and O-2 in the post-combustion flue gas. Collected results indicate that plum stone-rye bran pellets can serve as effective substitutes for wood pellets in prosumer installations, meeting the Ecodesign Directive requirements for CO and NO.Article Citation - WoS: 15Citation - Scopus: 19Ex Situ Catalytic Fast Pyrolysis of Lignin-Rich Digested Stillage Over Na/Zsm-5, H/Zsm-5, and Fe/Zsm-5(American Chemical Society, 2020) Priharto, Neil; Ghysels, Stef; Opsomer, Wim; Ronsse, Frederik; Prins, Wolter; Pala, Mehmet; Yıldız, GürayThe global increase in lignocellulosic ethanol production goes in tandem with an increase in lignin-rich stillage that remains underutilized to date. Anaerobic digestion could valorize residual (biodegradable) organic fractions into biogas, leaving a lignin-rich digested stillage (LRDS). This LRDS from the lignocellulosic ethanol production has been assessed as a feedstock for slow and fast pyrolysis in earlier studies, with the intention to increase the overall output of useful products or energy carriers from the starting material. While using this lignin-rich feedstock, ex situ catalytic vapor-phase upgrading (VPU) of fast pyrolysis vapors with fractional condensation was conducted over Na/ZSM-5, H/ZSM-5, and Fe/ZSM-5 catalysts. Semicontinuous fast pyrolysis experiments have been carried out at a reaction temperature of 480 degrees C in a mechanically stirred sand bed, which was connected directly to a fixed bed of catalyst particles for ex situ upgrading of the fast pyrolysis vapors. The carbon and mass yields in heavy phase liquids decreased after catalytic VPU (mass: ca. 8-11 wt %; carbon: ca. 11-15 wt %), compared to noncatalytic pyrolysis (mass: ca. 18 wt %; carbon: ca. 23 wt %). However, the yield in specific compounds, that is, alkylphenols and aromatics such as BTX, increased much upon catalytic VPU (especially for Fe/ZSM-5). For Fe/ZSM-5, the concentration in alkylphenols and aromatics was 20.8 wt % on liquid basis and the yield was 1.7 wt % on as-received (a.r.) feedstock basis. For noncatalytic pyrolysis, the concentration in alkylphenols and aromatics was 2.1 wt % (liquid basis) with a yield of 0.4 wt % (a.r. feedstock basis). This study thus demonstrates the potential of (modified) catalysts to upgrade lignin pyrolysis vapors.