Volume 40, Issue 4

Coal and biomass are important feedstocks for carbon energy from thermochemical conversion process. Fully understanding the analytical technology that characterizes the changes in physicochemical properties and structural characteristics of coal and biomass during the thermochemical reactions is a key prerequisite for the realization of appropriate utilization of energy fuels. Modern in-situ process analysis technology can accomplish the in-situ detection of the experimental process, and therefore reflect the experimental process more accurately. Moreover, it is developing towards automation, intelligentization, and comprehensive detection. Based on the characteristics of each detection technology, this paper summarizes the basic principles, application scope and performance characteristics of the three advanced in-situ process analysis technologies: hyphenated technology, synchrotron radiation, and online analysis. The practicability and accuracy of each detection technology in coal and biomass research are compared and analyzed, and its latest application and development trend are elucidated. These tools not only make up for the shortcomings of traditional detection techniques in characterizing the in-situ reaction, but also provide complementary information on molecular microscopic changes during fuel thermal conversion. This review paper can provide insights for relevant researchers in the selection of analytical techniques, and promote in-depth study on microcosmic mechanism of fuel conversion.

This paper assesses various approaches that use captured greenhouse gases (GHG) as feedstocks for chemical synthesis. The analysis focuses mainly on the two most abundant anthropogenic GHG, such as carbon dioxide (CO 2 ) and methane (CH 4 ), as well, their conversion technologies to obtain methanol (MeOH), formic acid (FA) and dimethyl carbonate (DMC). These GHG conversions to chemicals technologies are compared with the conventional industrial methods based on fossil feedstocks. The essential information, such as the ranges of energy requirements, environmental footprint and economic production aspects, are summarised. According to the collected information and analysis, the conventional, non-GHG conversion methods are still more environmentally sustainable. Chemicals production technologies based on CO 2 , such as direct catalytic synthesis to obtain both MeOH and FA, as well as transesterification with MeOH to obtain DMC, are relatively good candidates for implementation on a large scale when a good source of co-reactants such as hydrogen, ethylene carbonate and urea will be provided. In turn, electrochemical methods to synthesise the target chemicals are less feasible due to energy consumption related to the concentration and purification stages of products being the main hotspots. Chemical synthesis based on captured CH 4 is currently difficult to evaluate as too little information is available to draw a credible conclusion. However, it may be a trend in future. The limitations of GHG-based conversion for application are related to the capture and transport stages.

Congo red (CR) dye, due to its structural stability and non-degradable nature, is hazardous for humans and the aquatic environment. Among various methods used for degradation of CR, photocatalysis have been widely reported as a cost effective and environment-friendly method. Besides, extensive studies have been carried out regarding the use of nanomaterial-based photocatalyst for degradation of CR. This review describes the basics of photocatalysis along with the factors affecting the process, mechanism, and kinetics in detail. Additionally, literature related to synthetic and bio-based stabilizing mediums in photocatalytic assemblies have been arranged in a systematic manner. Advanced hybrid materials, i.e., metal–organic frameworks (MOFs) have also been described briefly. Future directions are discussed to address existing shortcomings in this field and also to expand research in this area.

In multiphase particulate systems, the turbulence of the continuous phase (gas or liquid) is modulated due to interactions between the continuous phase and the suspended particles. Such phenomena are non-trivial in the essence that addition of a dispersed phase to a turbulent flow complicates the existing flow patterns depending on the physical properties of the particles leading to either augmentation or attenuation of continuous phase turbulence. In the present study, this aspect has been comprehensively analysed based on the available experimental data obtained from the well-studied turbulent flow systems such as channel and pipes, free jets and grids. Relevant non-dimensional parameters such as particle diameter to integral length scale ratio, Stokes number, particle volume fraction, particle momentum number, and particle Reynolds number have been utilised to characterise the reported turbulence modulation behavior. Some limitations of these commonly used dimensionless parameters to characterise turbulence modulation are discussed, and possible improvements are suggested.

The natural vortex length is a complex turbulent dynamic phenomenon of cyclone separator, which can provide reference for the height design. It is calculated by the axial distance between the vortex end and the bottom of vortex finder. At present, scholars mainly attribute the influencing factors of natural vortex length to cylinder diameter, inlet area and vortex finder diameter, ignoring the influence of other structural parameters and operating parameters, so the accuracy and applicability of empirical formula are poor. This study described the mechanism of the vortex end and analyzed the PVC phenomenon. Then, an example was provided to illustrate the limitations and shortcomings of empirical formula. In addition, the influences of some geometric parameters and operating parameters on natural vortex length were summarized. Therefore, this work could provide an important reference for design optimization of cyclone separator height.