Moving Bed Reactors: Challenges and Progress of Experimental and Theoretical Studies in a Century of Research

Introducing a Linear Empirical Correlation for Predicting the Mass Heat Capacity of Biomaterials

This study correlated biomass heat capacity (Cp) with the chemistry (sulfur and ash content), crystallinity index, and temperature of various samples. A five-parameter linear correlation predicted 576 biomass Cp samples from four different origins with the absolute average relative deviation (AARD%) of ~1.1%. The proportional reduction in error (REE) approved that ash and sulfur contents only enlarge the correlation and have little effect on the accuracy. Furthermore, the REE showed that the temperature effect on biomass heat capacity was stronger than on the crystallinity index. Consequently, a new three-parameter correlation utilizing crystallinity index and temperature was developed. This model was more straightforward than the five-parameter correlation and provided better predictions (AARD = 0.98%). The proposed three-parameter correlation predicted the heat capacity of four different biomass classes with residual errors between -0.02 to 0.02 J/g∙K. The literature related biomass Cp to temperature using quadratic and linear correlations, and ignored the effect of the chemistry of the samples. These quadratic and linear correlations predicted the biomass Cp of the available database with an AARD of 39.19% and 1.29%, respectively. Our proposed model was the first work incorporating sample chemistry in biomass Cp estimation.

An Extensive Review and Comparison of Modern Biomass Torrefaction Reactors vs. Biomass Pyrolysis—Part 1

Major efforts are currently being made in the research community to address the challenges of greenhouse gas emissions from fossil fuel combustion by using lignocellulosic biomass, agricultural waste, and forest residues as cleaner energy sources. However, its poor qualities, such as low energy density, high moisture content, irregular shape and size, and heterogeneity, make it impossible to utilize in its natural state. Torrefaction, a simple heat treatment method, is used frequently with natural bioresources to improve their thermal characteristics so that they may be used as energy sources in domestic power plants. The quality of the resulting torrefied solids (biochar) is determined by the heat condition settings in the absence of oxygen, and it may be enhanced by carefully selecting and altering the processing parameters. The comprehensive overview presented here should serve as a useful toolkit for farmers, combined heat and power plants, pulp and paper installations, and other industrial plants that use biomass as a substrate for biofuel production. This research focuses on torrefaction product properties, reaction mechanisms, a variety of technologies, and torrefaction reactors. It is impossible to determine which torrefaction technology is superior as each reactor has unique properties. However, some suggestions and recommendations regarding the use of torrefaction reactors are given.

CO2 Capture From Air in a Radial Flow Contactor: Batch or Continuous Operation?

The capture of CO2 from the atmosphere via Direct Air Capture using solid supported-amine sorbents is an important option to reduce the atmospheric concentration of CO2. It addresses CO2 emissions from dispersed sources and delivers a location independent, sustainable carbon source. This study evaluates the possibility for a continuous adsorption process for direct air capture in a radial flow contactor, using both batch and continuous mode of operation. Gas and solid flow were varied to determine hydrodynamic feasible operating conditions. The operation modes are compared by their capture efficiencies in the optimal adsorption time range of 0.5 tstoB and 1.5 tstoB. A 15–25% lower capture efficiency is found for a continuous process compared to a batch process in the relevant range for direct air capture. This decline in gas-solid contact efficiency is more pronounced at longer adsorption time and higher superficial gas velocity. Overall, a batch process is preferred over a continuous process in the majority of operating conditions.