Hongyu Huang

Facile synthesis of MoS2/B-TiO2 nanosheets with exposed {001} facets and enhanced visible-light-driven photocatalytic H2 production activity

Cocatalysts have been extensively used to accelerate the rate of hydrogen evolution in semiconductor-based photocatalytic systems; however, the influence of interface states between the semiconductor and cocatalyst has rarely been investigated. Herein, we demonstrated a feasible strategy of heterogeneous structure to enhance visible light hydrogen generation of the MoS2/B-TiO2 system. Loading of MoS2 nanosheets on the surface of anatase boron doped TiO2 (B-TiO2) nanosheets with exposed {001} facets considerably increases the interfacial contact. At an optimal ratio of 1.0 wt% MoS2, the MoS2/B-TiO2 hybrid photocatalyst showed the highest H2 evolution rate of 0.50 mmol h−1 g−1, which is almost 6 times higher than that of pure B-TiO2 nanosheets. More importantly, the MoS2/B-TiO2 hybrid photocatalyst exhibited photocatalytic activity much higher than that of Pt/B-TiO2 nanosheets and the simple mechanical mixing of B-TiO2 and MoS2 nanosheets photocatalysts. The decisive factor in improving the photocatalytic H2 production activity is an intimate and large contact interface between the light-harvesting semiconductor and cocatalyst. The effective charge transfers from B-TiO2 to MoS2 was demonstrated by the significant enhancement of the photocurrent responses in MoS2/B-TiO2 hybrid electrodes. This study created new opportunities for designing and constructing highly efficient visible light photocatalysts by surface modification or doping.

Modelling of ammonia combustion characteristics at preheating combustion: NO formation analysis

In order to improve the combustion characteristics and flame stability of NH3-air flame, preheating the reactants at different temperature was proposed in this study. We focused on the formation of NO at NH3 preheated combustion because NH3 is a typical fuel-nitrogen. The NO formation characteristics of premixed NH3-air mixtures at various preheating temperatures of the reactants were numerically analysed. The Miller and Bowman mechanism was applied in the numerically calculation of all species. The results show that the formation reaction rates of thermal NO from N + O2 → NO + O, and N + OH → NO + H increase with the increase of preheating temperatures of the reactants at fuel lean condition. Higher decomposition reaction rate of N + NO → N2 + O at stoichiometric condition finally results in a lower formation of NO comparing to that at fuel lean condition. At fuel rich condition, the reactions of NH2 + NO → N2 + H2O, NH + NO → NNH + OH have grate effect on the decomposition of NO at all preheating temperatures of the reactants, which results in an extremely low formation of NO, showing a potential for reducing NO formation in NH3 combustion.

Effect of Adsorbent Diameter on the Performance of Adsorption Refrigeration

Adsorbents are important components in adsorption refrigeration. The diameter of an adsorbent can affect the heat and mass transfer of an adsorber. The effect of particle diameter on effective thermal conductivity was investigated. The heat transfer coefficient of the refrigerant and the void rate of the adsorbent layer can also affect the effective thermal conductivity of adsorbents. The performance of mass transfer in the adsorber is better when pressure drop decreases. Pressure drop decreases with increasing permeability. The permeability of the adsorbent layer can be improved with increasing adsorbent diameter. The effect of adsorbent diameter on refrigeration output power was experimentally studied. Output power initially increases and then decreases with increasing diameter under different cycle time conditions. Output power increases with decreasing cycle time under similar diameters.

Heat Transfer during Microwave-Assisted Desorption of Water Vapor from Zeolite Packed Bed

This study attempted to quantify the effect of microwave-assisted desorption of water vapor from a zeolite packed bed. Specifically, an experiment was carried out comparing water vapor desorption using hot air and microwave heating. In the experiment, the temperature in the zeolite packed bed and humidity at the inlet and outlet of the adsorption column were measured.Then, the heat transfer behavior was quantified by calculating the heat balance of a zeolite packed bed, and the effect of microwave irradiation was examined. The results showed that microwave heating is effective for desorption at the beginning.

On the Pyrolysis of Sewage Sludge: The Influence of Pyrolysis Temperature on Biochar, Liquid and Gas Fractions

Pyrolytic conversion of sewage sludge to biochar, oil and gas is an environmentally and economically acceptable way comparable to conventional options for sewage sludge disposal. The aim of this paper is to investigate the influence of pyrolysis temperature on production of biochar fraction for agronomic application, oil and gas fractions for energy utilization. Sewage sludge samples collected from an urban sewage treatment plant were pyrolysed in a bench–scale quartz tubular furnace over the temperature range of 300-700°C.The results indicated that the biochar fraction yield decreased, the yields of liquid (oil and water) fraction and gas fraction increased by evaluating the pyrolysis temperature. Concentration of heavy metals and nutrient elements present in biochar varied with pyrolysis temperature, the heating value of oil from liquid fraction fluctuated between 26938.3 and 30757.9kJ/kg, the heating value of gas fraction increased from 4012kJ/Nm3 to 12077 kJ/Nm3 with the increasing pyrolysis temperature.

Development of a compact MnO2 filter for removal of SO2 from diesel vehicle emissions

Increasing concern about sulfur dioxide (SO2) from diesel vehicle exhausts causing detrimental effects on NOx removal catalysts has resulted in the development of dry desulfurization filters for complete removal of SO2. In this study, a compact MnO2 filter was developed for diesel emission control. The SO2-capture behavior of the compact MnO2 filter was investigated by using a volumetric device in a low temperature range (200–400 °C) and low SO2 pressure conditions. The maximal capacity of the MnO2 filter was 304.1 mgSO2 per gMnO2 at 400 °C. Based on the experimental results, the required volume of the MnO2 filter was estimated as only 0.6 L for a diesel car with 30u2006000 km distance traveled per year. The thickness of the MnO2 filter had significant influence on its SO2-capture performance. The sulfate reaction mechanism was also discussed by using a grain model under four reaction temperature conditions for improving the efficiency of the design of the desulfurization filter. The sulfate process can be divided into two control stages (the chemical reaction control stage and the solid diffusion control stage) and the prediction models fit the experimental data well for both control stages, indicating that the two-stage grain model is suitable for the sulfate reaction between the MnO2 filter and SO2. The calculated apparent activation energy of 18.8 kJ mol−1 indicates that the MnO2 filter exhibits high activity for SO2 adsorption in a pure SO2 atmosphere.

A Facile Method to Construct Graphene Oxide–Based Magnesium Hydroxide for Chemical Heat Storage

ABSTRACT Mg(OH)2 nanoparticles anchored on graphene oxide (GO) were facilely prepared by a hydrothermal method. The main diameter scale of nanoparticles on the graphene sheet was about 25–50 nm shown by transmission electron microscopy characterization results. X-ray diffraction results indicated that the nanoparticles are in accordance with the data on magnesium hydroxide. This material exhibited significantly improved heat storage capacity and a higher hydration rate than pure magnesium oxide, and the introduction of GO leads to greatly increased thermal conductivity of the nanocomposites. As a novel thermochemical heat storage material, Mg(OH)2/GO has huge potential for high-efficiency energy systems.

Study and Theoretical Calculation on New Type of Adsorption Chiller

One of improving refrigeration performance of adsorption chiller methods is optimizing adsorption chiller structure. A new type of adsorption chiller was proposed in this paper, which obtained two adsorbers, evaporator, condenser and vapor valves between adsorber and evaporator and between adsorber and condenser. The vapor valve was the very important component of the adsorption chiller, which was controlled by pressure difference of both sides of vapor valve. Compared with normal adsorption chiller, the vapor valve replaced the tubes and vacuum valves between adsorber and evaporator and between adsorber and condenser. It can reduce the total equipment size, and decrease the pressure loss of refrigerant flowing in the refrigeration system. Working mechanism of vapor valve and working process of adsorption chiller were investigated, and the theoretical calculation of adsorption chiller was carried out. These works were important foundation for design of adsorption chiller.

Study on Adsorption Desiccant Based Hybrid Air Conditioning System

The desiccant based hybrid air conditioning system can control temperature and humidity separately, which consists of adsorption desiccant system and compression type refrigeration system. The adsorption desiccant system obtains the moisture power, and the compression type refrigeration can obtain sensible heat load. Generally, the regenerated energy consumption of the desiccant wheel is very large in the total energy consumption, using electric power, waste heat or renewable energy (solar etc). Heat recovery from the condenser considered as only regenerated energy in the new type adsorption desiccant based hybrid air conditioning system is proposed and discussed in this paper. This method can reduce much energy consumption, and make the air conditioning system structure simple.

Microwave Irradiation Effect in Water-vapor Desorption from Zeolites

In recent years, humidity control has been recognized as one of the important technologies in various fields; e.g., the system is required to maintain comfortable indoor air quality in household sector, and to improve the quality of products in industrial sector. In general, controlling the humidity through temperature, as in the case of conventional systems, appears to be an energy consuming process, and, depending to the operation conditions, does not assure the demand levels for humidity and temperature. Under these circumstances, desiccant humidity conditioner, which makes use of adsorption/desorption phenomena of porous adsorbent, has been gaining a great attention as an environmental friendly humidification/dehumidification system because of its advantages in the following points: 1. It consumes very little electrical energy, and for regeneration process it allows the use of solar energy and waste energy. 2. It is efficient when latent heat load is larger than the sensible load. 3. It is a clean technology, which can be used to condition the internal environment of buildings and operates without the use of harmful refrigerants. 4. The achieved control of humidity is better than that when using vapor compression systems. 5. In some cases the cost of energy to regenerate the desiccant is less than that when compared with the cost of energy to dehumidify the air by cooling it below its dew point. 6. Improvement in indoor air quality is more likely due to the normally high ventilation. 7. It has the capability of removing airborne pollutants. The technology of adsorptive desiccant cooling presents interesting prospects as regards market penetration (Ando & Kodama, 2005; Davanagere et al., 1999; Elsayed et al., 2006, 2008; Ge et al., 2008; Halliday et al., 2002; Hamed, 2003; Kabeel, 2007; Kodama et al., 2001; Mavroudaki et al., 2002; Oshima et al., 2006). The desiccants are natural or synthetic substances capable of absorbing or adsorbing watervapor due to the difference of water-vapor pressure between the surrounding air and the desiccant surface. Typical adsorptive desiccant cooling process mainly consisting of a rotary dehumidifier (D-hum) and heat exchanger can be driven with low-temperature heat energy