Emerging CO2-Mineralization Technologies for Co-Utilization of Industrial Solid Waste and Carbon Resources in China

CO2 mineralization (aka mineral carbonation) is a promising method for the chemical sequestration of CO2 via reaction with oxides of alkaline or alkaline-earth metals to form carbonates. It has documented advantages over similar technological solutions to climate change. The huge amount of industrial solid waste, as a serious environmental issue confronted by China, can provide additional alkalinity sources for CO2 mineralization. In this study, we present an overview of the latest advances in the emerging technologies of CO2-mineralization via industrial solid waste in China, from the perspective of both theoretical and practical considerations. We summarize the types of industrial solid waste that are used (mainly coal fly ash, steel slag, phosphogypsum, and blast furnace slag) and the technological options available in the literature, with an emphasis on the discussion of the involved process-intensification methods and valuable chemicals produced. Furthermore, we illustrate the current status of pertinent policies, and research and development activities in China. Finally, we identify the current knowledge gaps, particularly in understanding the overall sustainability performance of these CO2-mineralization technologies, and indicate that the technical, economic, and environmental challenges of promoting and commercializing these technologies for the co-utilization of industrial solid waste and carbon resources call for, amongst other things, more joint efforts by chemists, chemical engineers, and environmental scientists, and more feedback from the energy and industrial sectors.

Flotation of Chromite as Pre-Treatment of Olivine Before Carbonation for CO2 Sequestration

Background and Objective:For the sake of optimal beneficiation of the products formed in the chemical sequestration of CO2on silicates, extraction of the chromite has been carried out prior to carbonation, by flotation in a lab-scale column.Method:Industrial-grade olivine and serpentine were tested. Flow conditionse.g. gas flow rate, stirring, particle diameter of silicates, and physicochemical considerations (composition if the electrolyte solution) have been examined to optimize the separation efficiency in terms of chromite recovery or enrichment factor.Result:The high performance observed with chromite-enriched olivine allows a multistage flotation process from low-chromite minerals blends to be designed.Conclusion:The lower performance with native olivine was attributed to the existence of mixed chromite-silicate particles.

Design and Thermoeconomic Evaluation of a Waste Plant With an Integrated CO2 Chemical Sequestration System for CH4 Production

Object of this paper is the modelling, process design and simulation of a waste incineration plant integrated with a novel CO2 chemical sequestration system for CH4 production. The main components of the proposed system are: the incineration plant (whose operational data are considered known here), a Sabatier reactor for CH4 production, a post-combustion monoethanolamine (MEA) chemical absorption unit and a H2O electrolyser. Carbon dioxide captured from the waste plant stack gases and hydrogen from water electrolysis feed the Sabatier chemical reactor in a temperature range of 250–450°C. Through the exothermic methanation reaction (CO2 + 4H2 = CH4 + 2H2O + Heat), methane is produced with a conversion yield of 90–95%. Through a perm-selective membrane, hot steam can be extracted from the reactor and recycled to cover about 40% of the MEA regenerating re-boiler duty. The methanation of CO2 is an established carbon capture technique, profitably suitable for waste plants. When the produced methane is burned, the CO2 absorbed in the process returns to the environment, enacting in a global sense a quasi-zero-emissions cycle. The possible integration of the electrolyser with renewable-generated electricity has been investigated to evaluate the storage capacity of electrical energy as “renewable methane”, which from a technical point of view is more suitable than hydrogen to be stored, burned or sent into natural gas pipelines. A thermo-economic analysis is presented to evaluate the exergetic performance of the proposed system and the final cost of products.