Three-Dimensional Computation Fluid Dynamics Simulation of CO Methanation Reactor with Immersed Tubes

CO methanation is an exothermic process, and heat removal is an essential issue for the methanation reactor. Numerical studies were carried out to investigate the performance of a 3D fluidized bed methanation reactor with immersed cooling tubes. The simulations were carried out in the frame of the Euler–Euler model to analyze the performance of the reactor. The influences of operating temperatures were studied to understand the reaction characteristics. The temperature increases rapidly neared the inlet due to the reactions. The immersed tubes were effective at removing the reaction heat. The chemical equilibrium state was achieved with an operating temperature of 682 K for the case with immersed tubes. Different control mechanisms can be found during the process of increasing and decreasing the temperature. The reaction kinetic is the dominate factor for the cases with lower temperatures, while the chemical equilibrium will play a more important role at high temperature conditions. The configuration with staggered tubes is beneficial for heat removal.

Slurry-Phase Carbonation Reaction Characteristics of AOD Stainless Steel Slag

Argon oxygen decarburization stainless steel slag (AOD slag) has high mineral carbonation activity. AOD slag carbonation has both the resource utilization of metallurgical waste slag and the carbon reduction effect of CO2 storage. This paper aimed to study carbonation reaction characteristics of AOD slag. Under the slurry-phase accelerated carbonation route, the effect of stirring speed (r) and reaction temperature (T) on AOD slag’s carbonation was studied by controlling the reaction conditions. Mineral composition analysis and microscopic morphology analysis were used to explore the mineral phase evolution of AOD slag during the carbonation process. Based on the unreacted core model, the kinetic model of the carbonation reaction of AOD slag was analyzed. The results showed that the carbonation ratio of AOD slag reached its maximum value of 66.7% under the reaction conditions of a liquid to solid ratio (L/S) of 8:1, a CO2 partial pressure of 0.2 MPa, a stirring speed of 450 r.min−1, and a reaction temperature of 80 °C. The carbonation reaction of AOD slag was controlled by internal diffusion, and the calculated apparent activation energy was 22.28 kJ/mol.

The Delivery of Nitric Oxide in the Cardiovascular System: Implication for Clinical Diagnosis and Therapy

Nitric oxide (NO) is a key molecule in cardiovascular homeostasis and its abnormal delivery is highly associated with the occurrence and development of cardiovascular disease (CVD). The assessment and manipulation of NO delivery is crucial to the diagnosis and therapy of CVD, such as endothelial dysfunction, atherosclerotic progression, pulmonary hypertension, and cardiovascular manifestations of Coronavirus (COVID-19). However, due to the low concentration and fast reaction characteristics of NO in cardiovascular system, the clinical applications centered on the NO delivery are challenging. In this tutorial review, we first summarized the methods to estimate the in vivo NO delivery process based on the clinical images and mathematical modeling to assess the endothelial function and vulnerability of atherosclerotic plaque. Then, the emerging bioimaging technologies that have the potential to directly measure the arterial NO concentration were discussed, including the Raman spectroscopy and electrochemical sensor. Aside from the diagnostic methods, therapies aimed at controlling NO delivery to regulate CVD were reviewed, including the inhaled NO therapy to treat the pulmonary hypertension and COVID-19, stem cell therapy and NO-releasing platform to treat endothelial dysfunction and atherosclerosis.

Investigation on the Reaction Behaviour of Partially Reduced Iron under Blast Furnace Conditions

The reaction behaviour of partially reduced iron (PRI) was studied to understand the effect of PRI utilisation in the blast furnace process. For quantitative analysis, the reaction behaviour of PRI under typical operating conditions of a blast furnace was measured using the thermogravimetric method along with the reduction behaviour of hematite and sinter. Experimental results indicated that the reoxidation behaviour of the PRI under the conditions of the upper shaft of the blast furnace retarded the indirect reduction rate in the lower shaft. The rate constants derived from the grain model, experimental results of scanning electron microscopy, and porosimetry analysis indicated that the phenomenon of reduction retardation of PRI under the conditions of the lower shaft originated owing to the reoxidation of PRI, resulting in the blockage of pores. The reaction behaviour considering the reaction characteristics of PRI was derived under conventional blast furnace conditions.

Characteristics of Pyrolysis and Low Oxygen Combustion of Long Flame Coal and Reburning of Residues

To further understand the problems of coal combustion and coalfield fire reignition, this paper researched the reaction characteristics of coal pyrolysis and low oxygen combustion and the reburning oxidation characteristics of residual structure by thermal analysis methods. The results show that temperature promotes both pyrolysis and low oxygen combustion reactions, but low oxygen combustion reaction is more sensitive to temperature changes. As the constant temperature rises, the mass reduction rate of low oxygen combustion of coal samples reaches 80% on average, which is 4 times that of pyrolysis, and the variations of thermogravimetric parameters are also significantly higher than those of pyrolysis. However, the higher the pyrolysis degree of the residues, the stronger their oxidizability, which greatly enhances the intensity and concentration of the secondary combustion, and the mass of residues is reduced by 90% on average. Conversely, because the combustible components are continuously consumed during low oxygen combustion, the reburning characteristics of residues become less obvious. For instance, the weight loss rate slows down, the burning becomes dispersed, and the burning intensity is weakened. In addition, the heat release is reduced from 8662 to 444.5 J/g, and the change trend is just opposite to that of pyrolysis. The above results show that as the constant temperature rises, the pyrolysis reaction greatly shortens the reburning process, while the low oxygen combustion reaction largely inhibits the reburning.