Canadian Journal of Chemical Engineering最新文献

Appropriately evaluating the gas–solid hydrodynamics and reaction kinetics of reactors within process simulation approach can provide more accurate and comprehensive techno-economic and environmental assessments, as well as more effective design and optimization for new processes and technologies. In this study, a one-dimensional process simulation of biomass and coal oxy-co-firing in a 100 kW_th circulating fluidized bed was developed, with the models for gas–solid hydrodynamics and synergistic reactions of two fuels being established in Aspen Plus software. The effects of fuel properties, gas atmosphere, and operating parameters on the combustion process, flue gas products, and heat distributions in the bed were studied. Results show that the proposed process models can successfully describe the oxy-co-firing of coal and biomass in the furnace including the pyrolysis and the combustions of gaseous volatile and char. Increasing the oxygen concentration and biomass blending ratio will improve the combustions in dense phase region and obviously increase the heat release in this region. More heating surfaces should be arranged in the dense phase region when retrofitting an existing circulating fluidized bed (CFB) boiler with air combustion to be the oxy-fuel one. Additionally, the increase of oxygen concentration could reduce the emissions of pollutants such as CO and NO_X, while the addition of biomass may bring a slight increase in NO_X emission.

In order to handle the overwhelming effects of the removed hydrogen sulphide (H₂S) from natural gas and industrial waste gases on the environment, H₂S can be converted to elemental sulphur. Among the available processes for sulphur recovery, the most widely employed process is a modified Claus process. In this work, first, least square version of support vector machine (LS-SVM) approach is utilized for determining the properties of sulphur including heat of vaporization, heat of condensation (S₆, S₈), heat of dissociation (S₆, S₈), and heat capacity of equilibrium sulphur vapours as a function of temperature. An illustrative example is given to show the usefulness of the presented computer-based models with two parameters for designing and operation of the Claus sulphur recovery unit (SRU). According to the error analysis results, predicted values by the proposed intelligent models are in excellent agreement with the reported data in the literature for the aforementioned sulphur properties where the coefficient of determination (R²) is higher than 0.99 for all developed models. The average absolute relative deviation percent (%AARD) is less than 1.3 while predicting the heat capacity of equilibrium sulphur vapours. Other proposed models' predictions show less than 0.2% AARD from the target values. In addition, a mathematical algorithm on the basis of the Leverage approach is proposed to define the domain of applicability of the developed LS-SVM models. It was found that the presented models are statistically valid and the employed data points for developing the models are within the range of their applicability.

This review paper explores the transition from thermochemical to electrochemical processes in clean energy technologies, particularly focusing on hydrogen-containing fuels, namely hydrogen, ammonia, and methanol. The main characteristics of the thermochemical and electrochemical technologies are compared, followed by a focus on specific approaches in production of each of these e-fuels. Steam methane reforming, partial oxidation of hydrocarbons, coal and biomass gasification, as well as thermal decomposition and autothermal reforming processes are discussed for hydrogen thermochemical production. Electrochemical technologies for green hydrogen production are then described, including water electrolysis based on alkaline, proton exchange membrane, anion exchange, and solid oxide cells. The paper further compares the Haber–Bosch process with the electrochemical synthesis of ammonia, and discusses thermochemical technologies for methanol synthesis from syngas, comparing them to the two electrochemical approaches-electrochemical CO₂ reduction and methane oxidation reaction. Additionally, approaches for extracting hydrogen from ammonia and methanol by electrochemical reforming are briefly discussed. The paper closes with the future prospects and challenges of the transition from the traditional thermochemical technologies to the more sustainable electrochemical processes. Despite the promising prospects of the electrochemical technologies, challenges such as high initial capital costs, the need for advanced materials, and scalability must be addressed. Ongoing research, policy incentives, and collaborative efforts are essential to overcome these barriers and facilitate the transition to a low-carbon economy. In the meantime, the integration of these technologies represents a transformative approach to chemical manufacturing and energy management, offering a pathway towards more sustainable and versatile industrial practices.