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Öğe Generalizability of empirical correlations for predicting higher heating values of biomass(Taylor & Francis Inc, 2024) Daskin, Mahmut; Erdogan, Ahmet; Gulec, Fatih; Okolie, Jude A.Designing efficient biomass energy systems requires a thorough understanding of the physicochemical, thermodynamic, and physical properties of biomass. One crucial parameter in assessing biomass energy potential is the higher heating value (HHV), which quantifies its energy content. Conventionally, HHV is determined through bomb calorimetry, but this method is limited by factors such as time, accessibility, and cost. To overcome these limitations, researchers have proposed a diverse range of empirical correlations and machine-learning approaches to predict the HHV of biomass based on proximate and ultimate analysis results. The novelty of this research is to explore the universal applicability of the developed empirical correlations for predicting the Higher Heating Value (HHV) of biomass. To identify the best empirical correlations, nearly 400 different biomass feedstocks were comprehensively tested with 45 different empirical correlations developed to use ultimate analysis (21 different empirical correlations), proximate analysis (16 different empirical correlations) and combined ultimate-proximate analysis (8 different empirical correlations) data of these biomass feedstocks. A quantitative and statistical analysis was conducted to assess the performance of these empirical correlations and their applicability to diverse biomass types. The results demonstrated that the empirical correlations utilizing ultimate analysis data provided more accurate predictions of HHV compared to those based on proximate analysis or combined data. Two specific empirical correlations including coefficients for each element (C, H, N) and their interactions (C*H) demonstrate the best HHV prediction with the lowest MAE (similar to 0.49), RMSE (similar to 0.64), and MAPE (similar to 2.70%). Furthermore, some other empirical correlations with carbon content being the major determinant also provide good HHV prediction from a statistical point of view; MAE (similar to 0.5-0.8), RMSE (similar to 0.6-0.9), and MAPE (similar to 2.8-3.8%).Öğe Low-temperature chemical looping oxidation of hydrogen for space heating(Elsevier Sci Ltd, 2023) Gulec, Fatih; Okolie, Jude A.; Clough, Peter T.; Erdogan, Ahmet; Meredith, Will; Snape, Colin E.Chemical looping combustion (CLC) is an advanced combustion process in which the combustion reaction splits into two parts; in the first reaction metal oxides are used as oxygen suppliers for fuel combustion and then in the second reaction, reduced metal oxides are re-oxidised in an air reactor. Although this technology could be applicable for the safe implication of low-temperature oxidation of hydrogen, there is limited understanding of oxygen carrier reduction stages and the oxidation mechanism of hydrogen throughout the process. The novelty of this research lies in its pioneering investigation of low-temperature oxidation of hydrogen through chemical looping technology as a safe and alternative heating system, using three distinct metal oxide oxygen carriers: CuO, Co3O4, and Mn2O3. The oxidation of hydrogen over these oxygen carriers was comprehensively studied in a fixed-bed reactor operating at 200-450 degrees C. XRD analysis demonstrates that CuO directly reduced to metallic Cu at 200-450 degrees C, instead of following a sequential reduction step CuO & RARR;Cu4O3 & RARR;Cu2O & RARR;Cu throughout the temperature. Co3O4 was reduced to a mixture CoO and Co at 450 degrees C, which may refer to a sequential reduction step Co3O4 & RARR;CoO & RARR;Co with increasing the temperature. Decreasing the reduction temperature led to an elevation in CoO formation. Mn2O3 can also reduce to a mixture of Mn3O4 and MnO at temperatures between 250 and 400 degrees C. Compared to temperature, the increase in the residence time did not show any further reduction in Mn2O3. SEM results showed that most of the metal oxide particles were evenly dispersed on the supports. Based on the experimental results, a potential reduction stage of CuO, Co3O4 and Mn2O3 was proposed for low-temperature hydrogen oxidation, which could be a potential application for space heating using safe hydrogen combustion.Öğe Techno-economic feasibility of fluid catalytic cracking unit integrated chemical looping combustion - A novel approach for CO2 capture(Pergamon-Elsevier Science Ltd, 2023) Gulec, Fatih; Okolie, Jude A.; Erdogan, AhmetOil refineries are collectively responsible for about 4-6% of the global CO2 emissions, largely because of the regenerator part of the Fluid Catalytic Cracking (FCC) unit (25-35%). An advanced combustion technology, also called chemical looping combustion (CLC), has been recently presented as a novel CO2 capture process for FCC units; however, no study provides the economic feasibility of a CLC-FCC unit. In this study, a techno-economic feasibility of the novel CLC-FCC unit was presented for the first time based on a case study with 50,000 barrels feed per day. A rigorous mass and energy balance estimation shows that 96 vol% of coke regeneration (com-bustion) was achieved in the FCC regenerator by using a stoichiometrically required amount of metal oxide (CuO modified catalysts) at 750 C-degrees for 45 min. The preliminary energy penalty calculations of the proposed CLC-FCC unit (0.21 GJ/ton CO2) is relatively lower compared to the post-combustion (3.1-4.2 GJ/t CO2) via amine solvent and oxy-fuel combustion (1.8-2.5 GJ/t CO2) units reported in the literature. The equipment purchase cost (EPC) is 1.1 times higher than a standalone FCC unit due to the increase in the number of processing equipment required. The cash flow analysis results reveal a yearly basis average CO2 capture cost of 0.0106 US$/kg of CO2 (10.6 US$/ton CO2) for the CLC-FCC unit, which is lower compared to the other conventional CCS technologies i.e. oxy-fuel combustion and post-combustion. Factors such as EPC, capital expenditure (CAPEX), and discount rate significantly influenced the capture cost. In contrast, the CO2 capture cost is not influenced by a change in oxygen carrier and electricity cost.
