Decarbonising the Portland and Other Cements—Via Simultaneous Feedstock Recycling and Carbon Conversions Sans External Catalysts

Abstract

The current overarching global environmental crisis relates to high carbon footprint in cement production, waste plastic accumulation, and growing future energy demands. A simultaneous solution to the above crises was examined in this work. The present study focused on decarbonizing the calcination process of the cement making using waste plastics and biowastes as the reactants or the feedstock, to reduce the carbon footprint and to simultaneously convert it into clean energy, which were never reported before. Other studies reported the use of waste plastics and biowastes as fuel in cement kilns, applicable to the entire cement making process. Calcination of calcium carbonate and magnesium carbonate is the most emission intensive process in cement making in Portland cements and Novacem-like cements. In the Novacem process, which is based on magnesium oxide and magnesium carbonates systems, the carbon dioxide generated is recycled to carbonate magnesium silicates at elevated temperatures and pressures. The present study examined the Novacem-like cement system but in the presence of waste plastics and biomass during the calcination. The carbon dioxide and the methane produced during calcination were converted into syngas or hydrogen in Novacem-like cements. It was established that carbon dioxide and methane emissions were reduced by approximately 99% when plastics and biowastes were added as additives or feedstock during the calcination, which were converted into syngas and/or hydrogen. The reaction intermediates of calcination reactions (calcium carbonate–calcium oxide or magnesium carbonate–magnesium oxide systems) can facilitate the endothermic carbon conversion reactions to syngas or hydrogen acting as non-soot forming catalysts. The conventional catalysts used in carbon conversion reactions are expensive and susceptible to carbon fouling. Two criteria were established in this study: first, to reduce the carbon dioxide/methane emissions during calcination; second, to simultaneously convert the carbon dioxide and methane to hydrogen. Reduction and conversion of carbon dioxide and methane emissions were facilitated by co-gasification of plastics and bio-wastes.

Simulation and Modelling of Hydrogen Production from Waste Plastics: Technoeconomic Analysis

“…Another study by Pravin et.al [ 33 ] accomplished the conversion of PE (polyethylene) to syngas through pyrolysis then gasification using Aspen plus. The results were not validated by the experiment due to the lack of resources; however, they claimed that the most convenient temperature, and equivalence ratio for the pyrolysis unit were 0.4–0.6, and 500–750 , respectively The catalytic approach has advantages over the thermal one in terms of reducing the sulfur content when special catalysts are used (i.e., CaS, and MgS) [ 34 , 35 , 36 ]. Several studies have been performed on the conversion of waste plastics to hydrogen along with other feedstocks [ 37 , 38 ].…”

Security Concerns for Using Deep Learning Models in Predicting Hydrogen Production: A Comparative Study on Adversarial Attack

“…Simultaneously, in the quest to convert carbon into sustainable energy sources like hydrogen and syngas, the utilization of plastics and biowastes holds the potential to reduce the environmental impact of industrial processes found in sectors such as iron, steel, and cement [9] [10]. The co-gasification of mixtures containing plastic and biomass, achieved through dry and steam reforming of CO2, results in the production of H2, with factors such as feed composition and catalyst selection influencing the conversion of waste plastics into valuable fuel products [11][12][13][14][15].…”

“…The co-gasification of mixtures containing plastic and biomass, achieved through dry and steam reforming of CO2, results in the production of H2, with factors such as feed composition and catalyst selection influencing the conversion of waste plastics into valuable fuel products [11][12][13][14][15]. Various variables, including temperature, the ratio of polymers to biomass, CO2/CH4 ratios, and the choice of catalyst, all contribute to the H2 production process [9][16]- [18]. Waste polymers like polyethylene and polypropylene exhibit low moisture and ash contents but possess high volatile content, viscosity, and heating value.…”

Evaluation of Explainable Deep Learning Models in Predicting Hydrogen Production

“…While simultaneously transforming carbon into sustainable energy sources such as hydrogen and syngas, the utilization of plastics and biowastes can reduce the environmental impact of industrial processes found in sectors like iron steel, and cement [8] [9]. The cogasification of plastic and biomass mixtures through dry and steam reforming of CO2 generates H2, with factors like feed composition and catalyst type influencing the conversion of waste plastics into fuel products [10] [11].…”