Numerička studija izrađena pomoću ChemKin za rasplinjavanje vodene pare ugljene prašine i transformacije žive unutar rasplinjača s vodenom parom

Zero-emission coal (ZEC) technology has been actively studied recently. It aims to achieve zero emission of CO2 and other pollutants and the efficiency of this system can reach no less than 70%. Hydro-gasification of pulverized coal is a core process of ZEC. However, the mechanism of gasification and transformation of mercury speciation in the hydro-gasification is has not been understood precisely up until now. This restrains the ZEC’s commercialization. The purpose of this paper is to study the mechanism of hydro-gasification and mercury speciation transformation for coal in the gasifier with high temperature and pressure. Detailed chemical kinetics mechanism (CKM) has been proposed for hydro-gasification for pulverized coal in an entrained flow hydro-gasifier. The effects have been studied for different reaction conditions on hydro-gasification products and evolution of Hg in terms of the chemical reaction kinetics method. The CKM mechanism includes 130 elementary reactions and is solved with commercially available software, ChemKin. The calculation results are validated against the experimental data from literature and meaningful predictions are finally obtained. In addition, the chemical equilibrium calculation (CEC) is also used for predictions. Although the CEC method assumes all the reactions have reached chemical equilibrium, which is not the case in industrial reality, the calculation results are of value as reference.Tehnologija korištenja ugljena bez emisija (ZEC) se od nedavno aktivno proučava. Njezin cilj je postizanje nulte stope emisija CO2 te ostalih štetnih tvari dok efikasnost sustava mora biti minimalno 70%. Rasplinjavanje ugljene prašine vodenom parom je temeljni proces ZEC-a. Međutim, mehanizam rasplinjavanja i transformacije žive u rasplinjavanju vodenom parom još nije u potpunosti shvaćeno. To ograničava mogućnost komercijalne primjene ZEC-a. Cilj ovog rada je proučavanje mehanizama rasplinjavanja vodenom parom i transformacije žive za rasplinjavanje ugljena u rasplinjaču s visokim temperaturama i tlakom. Predloženi su detaljni kemijski kinetički mehanizmi (CKM) za rasplinjavanje ugljene prašine u fluidiziranom sloju sa zajedničkim tokom tvari. Proučeni su utjecaji raznih uvjeta pod kojim su se odvijale reakcije na produkte rasplinjavanja i evoluciju žive u uvjetima kemijskih reakcija kinetičke metode. CMK mehanizam sadrži 130 elementarnih reakcija i rješava se s komercijalno dostupnim programom, ChemKin. Rezultati simulacije se uspoređuju s eksperimentalnim iz literature te su konačno dobivena smislena predviđanja. Jednadžbe kemijske ravnoteže (CEC) su također korištene za predviđanja. Iako CEC metoda pretpostavlja da su sve reakcije postigle ravnotežu, što nije uvijek slučaj u industriji, rezultati tog proračuna mogu poslužiti kao referenca

Impact of Porphyromonas gingivalis-odontogenic infection on the pathogenesis of non-alcoholic fatty liver disease

AbstractAim: Non-alcoholic fatty liver disease is characterized by diffuse hepatic steatosis and has quickly risen to become the most prevalent chronic liver disease. Its incidence is increasing yearly, but the pathogenesis is still not fully understood. Porphyromonas gingivalis (P. gingivalis) is a major pathogen widely prevalent in periodontitis patients. Its infection has been reported to be a risk factor for developing insulin resistance, non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), and metabolic syndrome. The aim of this review is to evaluate the association between P. gingivalis infection and NAFLD, identify the possible etiopathogenetic mechanisms, and raise public awareness of oral health to prevent and improve NAFLD.Methods: After searching in PubMed and Web of Science databases using ‘Porphyromonas gingivalis’, ‘non-alcoholic fatty liver disease’, and ‘hepatic steatosis’ as keywords, studies related were compiled and examined.Results: P. gingivalis infection is a direct risk factor for NAFLD based on clinical and basic research. Moreover, it induces systematic changes and systemic abnormalities by disrupting metabolic, inflammatory, and immunologic homeostasis.Conclusion: P. gingivalis-odontogenic infection promotes the occurrence and development of NAFLD. Further concerns are needed to emphasize oral health and maintain good oral hygiene for the prevention and treatment of NAFLD

Self-healing hydrogels based on reversible noncovalent and dynamic covalent interactions: A short review

The self-healing capability of a material refers to its ability to autonomously heal fractures or defects and restore its original structures and functionalities. Self-healing hydrogels, with enhanced lifespan and mechanical performances compared to traditional fragile hydrogels, can serve as ideal synthetic analogues of living tissues, holding great promise in a wide range of biomedical, electrical and environmental applications. Reversible interactions play crucial roles in the construction of self-healing hydrogel networks. A deep understanding of these bonds is critical for the rational design of hydrogels with desirable properties. In this short review, we first introduce the experimental tools for the direct measurements of reversible intermolecular interactions, followed by discussing the self-healing hydrogels via diverse noncovalent interactions (i.e., hydrogen bonding, ionic interaction, metal-ligand coordination, hydrophobic association and π-interactions) and dynamic covalent bonds (i.e., imines, boronic esters, hydrazones and disulfide bond). Challenges and our opinions on future development of self-healing hydrogels are also provided

Dynamic and Static Multiobjective Topology Optimization for Gears of Directional Drill Transmission System

Aiming at the multiobjective topology optimization design of the structure, this paper proposes a method to establish the comprehensive objective function based on the normalized subobjective of the compromise programming method and to determine the weight coefficient of the subobjective of the comprehensive objective function by the analytic hierarchy process (AHP). By using statistical analysis and modal analysis, the static and dynamic characteristics of the gear can be obtained. The single objective topology optimization is used to reduce the compliance of the gear and elevate the low-order natural frequency, and the frequency weighting method is used to suppress the oscillation phenomenon in the frequency-single-objective optimization. AHP was used to determine the weight coefficient of each subtarget. The compromise programming method is used for multiobjective topology optimization, and the gear design is improved according to the optimization results. By analyzing the improved gear structure, the weight of the optimized gear is reduced by 25.3%. The overall stiffness performance and strength performance are enhanced, and the natural frequencies of each order are improved to different degrees

Numerical Research on Biomass Gasification in a Quadruple Fluidized Bed Gasifier

Utilization of bioenergy with carbon capture can realize carbon-negative syngas production. The quadruple fluidized bed gasifier (QFBG) integrates a chemical looping oxygen generation process and a dual fluidized bed gasifier with limestone as bed material. It is one promising device that can convert biomass to H2-rich syngas whilst capturing CO2 with little energy penalty. However, experimental or numerical simulation of QFBG is rarely reported on due to its complex structure, hindering the further commercialization and deployment of QFBG. In this work, a new computational fluid dynamics (CFD) solver is proposed to predict the complex physicochemical processes in QFBG based on the multi-phase particle in cell (MPPIC) methodology with the assistance of the open source software, OpenFOAM. The solver is first validated against experimental data in terms of hydrodynamics and reaction kinetics. Then, the solver is used to investigate the QFBG property. It is found that the QFBG can operate stably. The cold gas efficiency, H2 molar fraction, and CO2 capture rate of the QFBG are predicted to be 87.2%, 93.3%, and 90.5%, respectively, which is promising. It is believed that the solver can give reliable predictions for similar fluidized bed reactors

Efficient Remediation of <i>p</i>-chloroaniline Contaminated Soil by Activated Persulfate Using Ball Milling Nanosized Zero Valent Iron/Biochar Composite: Performance and Mechanisms

In this study, efficient remediation of p-chloroaniline (PCA)-contaminated soil by activated persulfate (PS) using nanosized zero-valent iron/biochar (B-nZVI/BC) through the ball milling method was conducted. Under the conditions of 4.8 g kg−1 B-nZVI/BC and 42.0 mmol L−1 PS with pH 7.49, the concentration of PCA in soil was dramatically decreased from 3.64 mg kg−1 to 1.33 mg kg−1, which was much lower than the remediation target value of 1.96 mg kg−1. Further increasing B-nZVI/BC dosage and PS concentration to 14.4 g kg−1 and 126.0 mmol L−1, the concentration of PCA was as low as 0.15 mg kg−1, corresponding to a degradation efficiency of 95.9%. Electron paramagnetic resonance (EPR) signals indicated SO4•−, •OH, and O2•− radicals were generated and accounted for PCA degradation with the effect of low-valence iron and through the electron transfer process of the sp2 hybridized carbon structure of biochar. 1-chlorobutane and glycine were formed and subsequently decomposed into butanol, butyric acid, ethylene glycol, and glycolic acid, and the degradation pathway of PCA in the B-nZVI/BC-PS system was proposed accordingly. The findings provide a significant implication for cost-effective and environmentally friendly remediation of PCA-contaminated soil using a facile ball milling preparation of B-nZVI/BC and PS

Energy and Exergy Analysis on a Blast Furnace Gas-Driven Cascade Power Cycle

Blast furnace gas is the major combustible by-product produced in the steel industry, where iron ore is reduced by coke into iron. Direct combustion of blast furnace gas after simple treatment for power generation is a common utilization method nowadays. However, this method suffers from low efficiency and high carbon intensity. The use of gas-steam combined cycle is an excellent method to improve the efficiency of blast furnace gas for power generation. However, there is a problem of insufficient utilization of low product heat, and the addition of CCS system can further reduce the power efficiency. To solve these issues, a new blast furnace gas power generation system with a Brayton cycle with supercritical CO2 and a Rankine cycle with transcritical CO2 is proposed in this work. The new system is then thermodynamically simulated by Aspen Plus, after the sub-modules are validated. The effects of molar ratio of steam to carbon, selexol/CO2 mass ratio, compression ratio, turbine import temperature and turbine inlet pressure on the system are investigated. A comparison is also performed between the new combined cycle system and the traditional combined cycle power generation system. The results show that in the new power generation system, net power efficiency of 53.29%, carbon capture efficiency of 95.78% and sulfur capture rate of 94.46% can be achieved, which is significantly better than the performance of the conventional combined cycle