Numerous models have been developed in Aspen Plus for the combustion of different coal types in fluidized bed reactors. However, these models are case‐specific, particularly with respect to coal type and bed reactor type, implying limitations to general application of these models. Moreover, these processes were generally developed step‐wisely by employing a series of model blocks to simulate fluidized bed reactors in Aspen Plus. In this study, a novel hybrid approach for modelling coal combustion has been implemented to comprehensively design a model for conversion of low‐grade coal under various operating conditions. The proposed model combines sequential modelling of drying/pyrolysis (devolatilization) and combustion of coal by means of conventionally used units (RYIELD and RGIBBS), and a newly used unit (FLUIDBED) in Aspen Plus. The model validation was performed by experiments on the combustion of low‐grade coal in a pilot‐scale circulating fluidized bed reactor (CFBR). Experimental data were used to further calibrate the Aspen Plus model and decrease model uncertainties. The results obtained from the developed simulation model were found to be in good agreement with the experimental data. Discrepancies of less than 15% were observed, in most of the predictions of molar fractions for the resultant flue gas composition, including NOx and SOx, emissions which were at ppm levels. As a result, the model can easily be used for design, scale‐up, and simulation of coal combustion as well as for other feedstock like biomass in fluidized bed with process optimization based on sensitivity analysis.

Ethanolamines have traditionally been used for capturing CO 2 in a postcombustion carbon capture column. However, the use of ethanolamines, due to their high volatility and solvent losses, is not sustainable. One of the ways in which the solvent loss occurs is in the form of aerosols from the top of the column. The mechanism, rate of nucleation, growth rate, and interaction leading to the formation of aerosols, although essential for better process design, remain obscure. Using molecular dynamics simulations, we herein, analyze the formation of aerosols in columns based on aqueous monoethanolamine (MEA), aqueous methyldiethanolamine (MDEA), and their mixtures, using reference, pilot-scale, and industrial-scale data. In particular, the nucleation rate and cluster growth analyses were performed for five different cases. The results show that CO 2 concentration had a strong influence on the rate of aerosol formation, a factor that can be easily controlled for better process design. Moreover, the interactions within the formed aerosols were mainly dominated by CO 2 −water interactions. Taken together, our results and analysis contribute toward a better understanding of aerosol formation and present some practical value, namely, calculated nucleation rates and particulate growth rates can be used in process simulators to account for solvent losses, factors that were identified as contributing to formation of particulate matter can be controlled and adjusted in design process simulations and in real plants, providing better performance of postcombustion carbon capture columns and thus suggest ways to prevent solvent loss.

The designer concept of ionic liquid (ILs) allows combination of different types of cation with anion to manipulate desire sets of physico-chemical properties. The additional degree of freedom to improve these properties is addition of second IL, i. e. mixture of two pure ILs, known as "Double Salt Ionic Liquids (DSILs)". Depending on variation in physico chemical properties, DSILs could be ideal or non-ideal solution. The present study was explores non-ideal behaviour of three novel combination of imidazolium based DSILs using physico-chemical properties. The proposed DSILs are homogeneous mixtures of two pure ILs with common cation and two different anions: ethylsulfate and bis(trifluoromethylsulfonyl)imide / trifluoromethanesulfonate / thiocyanate. The densities, 1 and speeds of sound, u for proposed DSILs were determined at different temperatures. The excess molar volumes V m E and excess molar isentropic compressibilities K S,m E were calculated and discussed in view of chemical structures of pure ILs, nature of anions and type of interaction between ions. The V m E were found to be positive for all cases, whereas positive or negative K S,m E were observed for studied DSILs. The behaviour of DSILs was explained by molecular dynamics simulations in terms of interaction energies and hydrogen bonds between components of DSILs as well as 1 H NMR results. The results indicate random distribution of anions around imidazolium cation and structural changes during formulation of DSILs.[a] Dr.

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With ever-increasing usage of biomass to curb environmental pollution, it is imperative to develop new insights into coal combustion processes, for efficient and optimal usage. Many process models have been developed for combustion process, including fixed and fluidized bed combustion for different types of coal; however, they are designed for specific process and lack generality. More recently, Aspen Plus has introduced new tools, and particularly featured a built-in unit operation model, to design fluidized bed processes. Herein, we comprehensively apply the novel tool to analyze the low grade coal combustion with varying process conditions such as: temperatures, fuel/air ratio, pressure, and other. The model developed in Aspen Plus was validated with our experimental data performed in a pilot-scale fluidized bed combustor. The fuel type of combustion used in the experiments is Ekibastuz coal (a type of low-grade Kazakhstan coal). The data from experiments were used to fine-tune the Aspen Plus model. Eventually, results indicate accuracy of the model in predicting the gas compositions and the reactor hydrodynamics. Furthermore, sensitivity analyses were performed in order to analyze the effect of temperature and feed flow rate on the combustion efficiency and flue-gas compositions. Taken together, the model developed can be ubiquitously used for process design of fluidized bed reactor co-combustion of coal and biomass.