Process Simulation and Optimization of Fluid Catalytic Cracking Unit’s Rich Gas Compression System and Absorption Stabilization System

In a fuel-based refinery, rich gas in the fluid catalytic cracking (FCC) unit is further processed to separate dry gas and refinery products (i.e., stabilized gasoline and liquified petroleum gas). The process is utility-intensive and costly and includes a two-stage compressor, pumps, an absorber, a stripper, a stabilizer, and a re-absorber. The optimization was conducted with respect to the compressor outlet pressure from the gas compression system (GCS) and the flow rate of absorbent and supplementary absorbent from the Absorption-stabilization System (ASS) using the process simulation software Aspen Plus. Compared to the base case of a 725 kt/a rich gas FCC unit, a refinery can save 2.42% of utility costs under optimal operation. Through optimized operation, medium-pressure steam consumption has been reduced by 2.4% compared to the base case, resulting in a significant improvement in total operational cost. The optimization strategy can provide insightful guidance for the practical operation of GCS and ASS.</p

SoC-Cluster as an Edge Server: an Application-driven Measurement Study

Huge electricity consumption is a severe issue for edge data centers. To this end, we propose a new form of edge server, namely SoC-Cluster, that orchestrates many low-power mobile system-on-chips (SoCs) through an on-chip network. For the first time, we have developed a concrete SoC-Cluster server that consists of 60 Qualcomm Snapdragon 865 SoCs in a 2U rack. Such a server has been commercialized successfully and deployed in large scale on edge clouds. The current dominant workload on those deployed SoC-Clusters is cloud gaming, as mobile SoCs can seamlessly run native mobile games. The primary goal of this work is to demystify whether SoC-Cluster can efficiently serve more general-purpose, edge-typical workloads. Therefore, we built a benchmark suite that leverages state-of-the-art libraries for two killer edge workloads, i.e., video transcoding and deep learning inference. The benchmark comprehensively reports the performance, power consumption, and other application-specific metrics. We then performed a thorough measurement study and directly compared SoC-Cluster with traditional edge servers (with Intel CPU and NVIDIA GPU) with respect to physical size, electricity, and billing. The results reveal the advantages of SoC-Cluster, especially its high energy efficiency and the ability to proportionally scale energy consumption with various incoming loads, as well as its limitations. The results also provide insightful implications and valuable guidance to further improve SoC-Cluster and land it in broader edge scenarios

Highly Efficient Liquid-Phase Hydrogenation of Naringin Using a Recyclable Pd/C Catalyst

A highly efficient liquid-phase hydrogenation reaction using a recyclable palladium on carbon (Pd/C) catalyst has been used for the transformation of naringin to its corresponding dihydrochalcone. The effects of various solvents on the hydrogenation process were studied, with water being identified as the optimal solvent. The analysis also revealed that sodium hydroxide (NaOH) can accumulate on the surface of the Pd/C catalyst in alcoholic solvents, leading to its inactivation. The higher solubility of NaOH in water implies that it remains in solution and does not accumulate on the Pd/C catalyst surface, ensuring the catalytic activity and stability

Self-Calibration Sensor for Contactless Voltage Measurement Based on Dynamic Capacitance

Noncontact voltage measurement has the advantages of simple handling, high construction safety, and not being affected by line insulation. However, in practical measurement of noncontact voltage, sensor gain is affected by wire diameter, wire insulation material, and relative position deviation. At the same time, it is also subject to interference from interphase or peripheral coupling electric fields. This paper proposes a noncontact voltage measurement self-calibration method based on dynamic capacitance, which realizes self-calibration of sensor gain through unknown line voltage to be measured. Firstly, the basic principle of the self-calibration method for noncontact voltage measurement based on dynamic capacitance is introduced. Subsequently, the sensor model and parameters were optimized through error analysis and simulation research. Based on this, a sensor prototype and remote dynamic capacitance control unit that can shield against interference are developed. Finally, the accuracy test, anti-interference ability test, and line adaptability test of the sensor prototype were conducted. The accuracy test showed that the maximum relative error of voltage amplitude was 0.89%, and the phase relative error was 1.57%. The anti-interference ability test showed that the error offset was 0.25% when there were interference sources. The line adaptability test shows that the maximum relative error in testing different types of lines is 1.01%

Reaction mechanism of oxidative desulfurization of heterocyclic organic sulfides: A computational study

The potential energy surfaces of the oxidation of two model heterocyclic organic sulfides thiophene and benzothiophene were examined using H2O2 and HCO3H as oxidants adopting CCSD(T), ωB97X-D, M06-2X and B3LYP at the 6-311+G (d,p) level of theory. Stationary points on the potential energy surfaces for the first and second oxidation reaction were fully optimized and characterized. The natural orbital population analysis was also performed to understand the charge distribution. The results suggest that the oxidation of benzothiophene is faster than that of thiophene using both oxidants, and HCO3H is more efficient than H2O2 in oxidation of both sulfides, which are in accordance with the experimental observation. Such results may assist in understanding the reaction mechanism of the oxidative desulfurization of sulfides. © 2014 Springer-Verlag Berlin Heidelberg

Long-term trend of O-3 in a mega City (Shanghai), China: Characteristics, causes, and interactions with precursors

In recent years, ozone (O-3) is often the major pollutant during summertime in China. In order to better understand this problem, a long-term measurement of ozone (from 2006 to 2015) and its precursors (NOx and VOCs) as well as the photochemical parameter (UV radiation) in a mega city of China (Shanghai) is analyzed. The focus of this study is to investigate the trend of O-3 and the causes of the O-3 trend in large cities in China. In order to understand the relationship between the O-3 precursors and O-3 formation, two distinguished different sites of measurements are selected in the study, including an urbanization site (XJH-Xujiahui) and a remote site (DT-Dongtan). At the XJH site, there are high local emissions of ozone precursors (such as VOCs and NOx), which is suitable to study the effect of O-3 precursors on O-3 formation. In contrast, at the DT site, where there are low local emissions, the measured result can be used to analyze the background conditions nearby the city of Shanghai. The analysis shows that there were long-term trends of O-3 and NOx concentrations at the urban site (XJH) from 2006 to 2015 (O-3 increasing 67% and NOx decreasing 38%), while there were very small trends of O-3 and NOx concentrations at the background site (DT). The analysis for causing the O-3 trend suggests that (1) the large O-3 increase at the urban area (XJH) was not due to the regional transport of O-3; (2) the measurement of solar radiation had not significant trend during the period, and was not the major cause for the long-term O-3 trend; (3) the measurement of VOCs had small change during the same period, suggesting that the trend in NOx concentrations at the urban site (XJH) was a major factor for causing the long-term change of O-3 at the urban area of Shanghai. As a result, the O-3 and NOx concentrations from 2006 to 2015 at the urban area of Shanghai were strongly anti-correlated, suggesting that the extremely high NOx concentration in the urban area depressed the O-3 concentrations. It is interesting to note that the anti-correlation between O-3 and NOx was in an un-linearly relationship. Under high O-3 concentration condition, the ratio of Delta[O-3]/Delta[NOx] was as large as - 1.5. In contrast, under low O-3 concentrations, the ratio of Delta[O-3]/Delta[NOx] was only - 0.2. This result suggested that when O-3 concentration was high, it was more sensitive to NOx concentration, while when O-3 concentration was low, it was less sensitive to NOx concentration. This study provides useful insights for better understanding the causes of the long-term-trend of regional O-3 pollution nearby Shanghai, and has important implication for air pollution control in large cities in China. Due to the fact that NOx and VOCs are not only precursors for O-3, but also are important precursors for particular matter (PM). If reduction of NOx leads to decrease in PM, but increase in O-3, the NOx emission control become a very complicated issue and need to carefully design a comprehensive control method. (C) 2017 Elsevier B.V. All rights reserved

Process Simulation and Integration of Natural Gas Condensate Recovery Using Ethane–Propane Refrigerant Mixture

Separating heavy components from natural gas not only enhances safety, improves pipeline transportation, ensures product quality, and addresses environmental considerations, but it also exerts an influence on global energy trends. Therefore, separating heavy components is necessary and can result in beneficial goods. This article presents a comprehensive study on the process simulation and optimization of the recovery of natural gas condensate via the combined refrigeration of a mixture of ethane and propane as a refrigerant. The optimization objectives include maximizing the recovery of ethane and propane, minimizing energy consumption, and achieving desired product quality targets. A sensitivity analysis was performed to assess the impact of key parameters on process performance. Using Aspen HYSYS software, the influence of the cooler outlet stream temperature and expander outlet stream pressure on the shaft power and profit of a dry gas compressor was analyzed based on the operating conditions of the case plant, which has a processing capacity of 2988 kmol/h. The profitability of the plant is at a maximum when the cooler’s outlet stream temperature is −61 °C and the expander’s outlet stream pressure is 2500 kPa. After optimization, the refrigeration cycle system can reduce the plant’s energy consumption by 1516.4 kW. An optimized process design can lead to enhanced recovery efficiency, reduced energy consumption, and improved profitability in the natural gas industry

Characteristics of black carbon aerosol during the chinese lunar year and weekdays in xi’an, china

Black carbon (BC) aerosol plays an important role in climate forcing. The net radiative effect is strongly dependent on the physical properties of BC particles. A single particle soot photometer and a carbon monoxide analyser were deployed during the Chinese Lunar Year (CLY) and on weekdays at Xi'an, China, to investigate the characteristics of refractory black carbon aerosol (rBC). The rBC mass on weekdays (8.4 mu g center dot m(-3)) exceeds that during the CLY (1.9 mu g center dot m(-3)), presumably due to the lower anthropogenic emissions during the latter. The mass size distribution of rBC shows a primary mode peak at ~205 nm and a small secondary mode peak at ~102-nm volume-equivalent diameter assuming 2 g center dot cm(-3) in void-free density in both sets of samples. More than half of the rBC cores are thickly coated during the CLY (f(BC) = 57.5%); the percentage is slightly lower (f(BC) = 48.3%) on weekdays. Diurnal patterns in rBC mass and mixing state differ for the two sampling periods, which are attributed to the distinct anthropogenic activities. The rBC mass and CO mixing ratios are strongly correlated with slopes of 0.0070 and 0.0016 mu g center dot m(-3)center dot ppbv(-1) for weekdays and the CLY, respectively