3-D Simulation of Methanol-steam Reforming for Hydrogen Production in Microreactor

In order to investigate the effects of inlet temperature,velocity and water methanol molar ratio on methanol- steam reforming for hydrogen production in microreactor, we carry out 3-D simulation of methanol-steam reforming for hydrogen production in self-designed plate microreactor with the application of general finite reaction rate model in CFD software of FLUENT, The kinetics used are DE and SR model, The results show that, At the conditions of inlet velocity, temperature and water methanol molar ratio are 2.88 m/s, 493 K and 1.3 respectively, methanol conversion at the reactor outlet reaches 79.8%. Through the simulation, we can see that in microreactor it can be maintain higher hydrogen molar fraction and methanol conversion at high reactant flow rate.     

Numerical Simulation of Catalytic Combustion of Extremely Low Concentration CH4

This paper used FLUENT to simulate the Catalytic combustion characteristics of extremely low concentration methane in microchannel of honeycomb combustor which was coated with catalyst Pt/Al2O3.It analyzed the effect of inlet CH4 concentration, temperature of catalyst wall and inlet fuel velocity on CH4 conversion ratio. The results show that CH4 conversion rate is increases with the increase of inlet CH4 concentration and catalyst wall temperature and the decrease of inlet fuel velocity. When inlet fuel velocity is 0.1 m/s, CH4 volume concentration is 1%, catalyst wall temperature is 950 K, the conversion ratio of CH4 can achieve to 97.0%.     

Optimization analysis of methanol steam reforming for hydrogen production

In order to intensify the process of methanol steam reforming, this paper studies the effect of equally and gradiently distributed catalytic bed on methanol conversion and H2 content at reactor outlet. With the application of general finite reaction rate model in CFD software of FLUENT,2 D simulation of this process is carried out.The results show that methanol conversion and outlet H2 content can be increased through gradiently distributed catalytic bed with higher catalytic activity at inlets and lower at outlets. Compared with the equally distributed catalytic bed, the cold spot temperature difference in the microreactor reduces by 10 K, experiment results prove that H2 content at outlets increases about 8.5% and CO decreases by about 0.19%.     

Study on Optimum Design of Rectangular Sedimentation Tanks

In this paper,the flow velocity fields,suspended solids concentration fields and flow-through curves in rectangular sedimentation tanks with different reaction baffles location,inlet horizontal velocity and length height ratio are simulated in detail using a developed mathematical model given in Reference 2.According to the numerical results,the influence of different reaction baffles location,inlet horizontal velocity and length height ratio on the operating efficiency is analyzed.Finally,the rational reaction baffles location,inlet horizontal velocity and length height ratio are presented.     

Numerical simulation of hydrogen air combustion in meso scale IC engine

The burning rate of hydrogen air pre mixture on meso scale is mainly determined by its chemical reaction rate. So a Laminar Finite Rate Model, the gas phase reaction mechanism for the combustion of hydrogen air mixture which consists of 19 reversible elementary reactions and the dynamic mesh method are adopted to simulate the combustion of hydrogen air mixture in a meso scale IC engine which operates a quasi gas power cycle under ultrahigh combustion load. The combustion of hydrogen air mixture on meso scale in the micro combustion chamber with moving boundary can be stable. The complete thermodynamic process of heat addition, internal energy increasing, and a boundary work output producing during expansion can be perfectly achieved in the closed combustion system of the meso scaled IC engine igniting the hydrogen air mixture by wire surface of high temperature. However, running parameters such as cycle period, initial pressure and fuel/air ratio have complex effects on the hydrogen air combustion of micro closed container with moving boundary.     

Investigation on the reaction characteristics of methane catalytic partial oxidation in a micro-channel

The reaction characteristics of fuel-lean CH4 catalytic partial oxidation over Rh are investigated numerically in a micro-channel, by using detailed elementary mechanism, focusing on the effects of inlet temperature, equivalence ratio of CH4/O2 and added H2O on catalytic partial oxidation of CH4. The results show that over Rh surface reaction of CH4 is kinetically controlled, while that of O2 is controlled by mass transport. Duo to the high reactivity of O2, CH4 is firstly oxidized and both complete and partial oxidation products are generated. After O2 is consumed, steam reforming begins, however, CO2 reforming does not appear. Increase of the equivalence ratio of C/O leads to increase of carbon deposition at reforming zoon, as thus both conversion of CH4 and production of syngas decrease, even the reforming process is stopped. The added H2O could dramatically inhibit carbon deposition, and promote the formation of H2 and CO2.     

The influencing factors of N2O emission and denitrification in the soil of water-level-fluctuation zone in the Three Gorges Reservoir area

In order to study the influences of water filled pore space (WFPS), temperature, the addition of nitrate (NO -3) and carbon source on N2O emission and denitrification in the soil of water-level-fluctuation zone in the Three Gorges Reservoir area, C2H2 in hibition incubation experiments are applied. Results from experiments in laboratory and in situ field are analyzed. Results show that the WFPS is a main factor determining N2O emission and denitrification. Denitrification rate increases while the WFPS increases, and the maximum denitrification rate and the maximum N2O emission rate appear when the WFPS is 100% and 60%, respectively. In addition, while the temperature is between 10 ℃ and 40 ℃, the increase of temperature contributes to the increase of the N2O emission and denitrification rates. Furthermore, it is found that the N2O emission and denitrification rates are significantly and positively correlated with temperature. The addition of carbon source could increase denitrification performance in soil. However, the addition of nitrate has a negative impact on the denitrification performance, because nitrogen source is not the main factor determining denitrification performance and excessive nitrate could inhibit the denitrification in these experiments. The addition of glucose, which is a carbon source easily be utilized by denitrifying bacteria, could significantly increase the denitrification rate in soil, and the maximum denitrification rate takes place while the carbon content in per kilogram soil is 240 mg.     

Modeling and Performance Analysis of Unglazed Solar Collector/Regenerator

An analytical model of the unglazed solar collector/regenerator(C/R) was presented. There was an optimum flow rate per unit collector area at normal temperature which led to the maximum evaporation rate. The inlet temperature of absorbent solution and the wind velocity are key parameters to determine the optimum flow rate, in addition, the concentration of solution and solar radiation intensity have obvious effects on the maximum evaporation rate. When the outlet temperature of solution is higher than the inlet temperature, there is not an optimum flow rate, which reflects that the more the flow rate of solution is, the better regeneration efficiency is. With the 2m/s of wind speed, the evaporation rate reaches the peak. In this paper, kinds of factors influencing the performance of solar C/R were evaluated as well.     

Experiments of the influencing factors on dissolution rate of rock salt

The influence of different factors on dissolution rate of rock salt is studied by a series of experiments, such as dissolution obliquity, solution concentrations, solution temperatures and solution flows. The laws of rock salt dissolution shown in the experiments are as follows: it isn’t obvious that the effect of the dissolution rate on different dissolution area. Temperature, velocity of flow and dissolution obliquity is in an exponential relationship with rock salt dissolution. Dissolution rate decreases with the increase of solution concentration of rock salt. Gray correlation analysis is adopted to study the dissolution obliquity, solution concentration, temperature and solution flow rate. It is found that solution temperature is the main factor, followed by dissolution obliquity, solution flow rate, and solution concentration. The findings can provide theoretical foundation and experimental basis for rapidly create cavity.     

Experimental Study of Preparation of Calcium Sulfide from Thermal Decomposition of Phosphogypsum

In this paper, it was carried out for reduction decomposition of phosphogypsum to calcium sulfide under N2 atmosphere. The size of phosphogypsum was measured by Nano-ZS90 Zetasizer. Scanning electron microscopy and XRD-ray diffraction were used to analyze the raw-material and decomposition solid production. These conditions were also studied on a carbon to CaSO4 molar ratio, reaction temperature, reaction time, and reaction atmosphere in the N2 atmosphere. The results showed that the optimal conditions for production of CaS are found to be a carbon to CaSO4 molar ratio of 2.4 to 1, a temperature of 900～1000 ℃,a reaction time of 2 h, and reductive atmosphere. Under these conditions the conversion rate of CaS from phosphogypsum amount to no less than 97.60%.     

Thermogravimetric study on the pyrolysis performance and its impactfactors of several kinds of typical industrial sludge

Thermogravimetric analysis is used to determine the pyrolysis performance of three types of industrial sludge and their mixed samples at different pyrolysis temperature,sample diameter,heating rate,pyrolysis pressure and adding different metal element compounds.At the same time,the pyrolysis mechanism equations and pyrolysis reaction parameters are obtained.The results indicate that the pyrolysis temperature,sample diameter,heating rate,pyrolysis pressure play an important role in the pyrolysis process for industrial sludge.The metals element compounds can improve the pyrolysis performance of industrial sludge.The pyrolysis reaction progression is respectively 1,1.5,and 2.0 in low,medium and high temperature segment for three types of industrial sludge,the pyrolysis character of mixed sludge isn't obviously changed.The pyrolysis characters of the industrial sludge are alike as the coal residue,the activation energy and the frequency factors are smaller at the initial pyrolysis process,they are increased with the increase of the pyrolysis temperature.The activation energy and the frequency factors are enhanced at the end of pyrolysis.     

The emission of N2O during single SBBR completely autotrophic nitrogen removal system

Three single autotrophic denitrification biofilm reactors with artificial water are applied to study the influence of aeration treatments and carbon source on the N2O emission and N2O emission characteristics. The results show that the accumulative N2O emission amount and the conversion rate of N2O of reactor 1,2 and 3 in an operation cycle are 13.69,14.28,2.51 mg,and 1.36%,1.49%,0.236%,respectively. The comparative results of reator 1(continuous aeration) with reactor 2(intermittent aeration) show their accumulative N2O emission amounts and N2O conversion rates are similar. The accumulative N2O emission amount and the N2O conversion rate of reactor 3(organic carbon) are about 1/6 of those of reactor 2(without organic carbon). Aeration treatments have great influence on N2O emission characteristics,for reactor 1,the accumulative N2O emission amount increases persistently,the mean N2O emission rate and dissolved N2O concentration performance continue to decline after the first rise to the maximum. For reactor 2,N2O emissions are mainly in aeration period. The mean N2O emission rate and dissolved N2O concentration reduce after first increase. The N2O conversion rate of single autotrophic nitrogen removal process is lower than those of other biological denitrification processes.     

Optimization of Subway Indirect Evaporative Cooler Water Distribution Methods

In conventional indirect evaporative cooler, the lack of uniformity and integrity of water film surface results in low thermal efficiency. To solve the problem,an indirect evaporative cooler with rotating water on both sides is put forward. The experiment was carried out to explore the heat transfer performance of heat exchanger under three types of arrangement and the factors influence the performance were studied by orthogonal experiment. The study results show that when the hole is on the direction of air flow, the thermal performance of heat exchanger is optimal and the recommended rate of rotating water distribution installation 76 r/min. Heat exchange increases with the increase of water spray quantity, air velocity, cooling water flow rate, cooling water inlet temperature and decrease with increase of water temperature, air temperature cooling water inlet temperature has the most significant effect on the performance of heat transfer. And when the temperature increases form 35 ℃ to 39 ℃, the heat transfer improved 37.62%, Heat transfer in per unit area is about 1.14 kW. The heat exchanger can be installed in exhaust tunnel of underground stations, which can effectively solve the subway station cooling tower installation location problem.     

Effect of space velocity on the performance of methane steam reforming in a plate micro channel reactor

A 2 D numerical simulation is conducted on the steam reforming reaction in a plate micro reactor by applying the general finite reaction rate model in the CFD software FLUENT and a detailed surface reaction kinetics mechanism. Catalyst space velocity(CSV) and gas space velocity(GSV) inlet mixture impact on the reaction is discussed. During the calculations, the space reaction effect is ignored and only the reaction of CH4 on catalytic surface is taken into account. Calculation results show that lower CSV or GSV can achieve high efficiency conversion of CH4 and H2 output; besides CSV and GSV, channel height is an important factor for the reforming performance of plate micro reactors.     

Hydraulic Characteristics and Energy Efficiency of An Air Conditioning Chilled Water System With Primary Pumps

The hydraulic characteristics and energy-saving performance of a chilled water system with primary pumps is analyzed. It is proved that the hydraulic characteristics of the system with terminal of the air conditioners tends to large temperature differences and small flow rate, while the hydraulic characteristics of the system with terminal of the combination of fan coil units and air conditioners tends to large flow rate and small temperature differences. When the cooling load is reduced, in order to ensure the energy-saving performance of the primary pump system, the fixed chilled water flow is required. If the fixed water flow system is adopted to regulate the outlet water temperature,the bypass water flow rate should be decreased as much as possible. If the pump frequency regulation is selected, and the proportion of energy consumption of the pump accounts for 30% of the total at the same time, the more the system’s hydraulic characteristics approaches that of air conditioners, the higher the energy-saving rate will be, which could be markedly greater than 10%. By regulating the water temperature and cold water quantity, over flow of chilled water still exists. Therefore, bypass water flow should be provided. And the bypass pipe diameter is determined respectively by the water flows which are 1.2 ~ 1.8 or 0.2 ~ 1.0 times larger than that of a single chiller when the pump works in frequency conversion and constant frequency.     

Experimental Analysis on Function of Free Cooling Unit with a Pump-driven Loop Heat Pipe for Internet Data Center

A free cooling unit with a pump-driven loop heat pipe was designed for internet data center (IDC), and its components and working processes were described. The experiment system for the developed prototype was built and the comprehensive studies were conducted. The experimental results demonstrate that the coefficient of performance (COP) of the unit can reach to 5.88 when the temperature difference between IDC indoor and outdoor is 10℃, and it will be 10.41 when the temperature difference is 18℃. When mass flow rate of the working fluid in the unit changes within a certain range, namely the gasification rate of the fluid being between 2% and 50%, there is no significant changes for the heat transfer capacity. And there is an approximately linear relationship between the capacity and the temperature difference. Meanwhile, with the increase of the system resistance, both temperature difference of the fluid between inlet and outlet of the evaporator and the proportion of the sensible heat to the capacity also increase.     

Recent Advances in Synthesizing Single-walled Carbon Nanotubes

The main synthesis of single-walled carbon nanotubes (SWCNTS) on a large scale and in higher purity is investigated. To analyse the characteristic of different synthesis and the major parameters whose variety influence the product. The kinds and ratio of carbon source and catalyst influence the preparation of SWCNTS obviously.The factors such as current and voltage,the kind of inert gases and pressure and the cooling rate of electrodes play important roles in synthesis of SWCNTS by arc discharges. The intensity of laser bean,environmental temperature,the kind and the velocity of flow of catalyst and the frequency and interval of impulse act important parts in SWCNTS produced by laser evaporation. The flow rate of carbon resource, the grain sizes of catalyst,reaction temperature,the gases pressure and flux and matrix materials etc play key parts in SWCNTS synthesized by chemical vapor deposition.     

Analysis for Heat Transfer in Micro-annular Channel with Unsymmetrically Heated Walls in Slip Flow Regime

A theoretical analysis is presented for heat transfer in micro-annular channel with an adiabatic wall and a heated wall with uniform wall temperature in slip flow regime. The energy equations with the boundary conditions of temperature jump are solved for the hydrodynamical and thermal fully developed laminar flow of the incompressible fluid in this microchannel. The influences of the Kn number, the ratio of inner diameter to outer diameter on the heat transfer characteristics are discussed respectively. The results show that the Nusselt number in microchannel decreases with the increasing of Kn number comparing with that in macrochannel.     

Analysis of Nitrite Accumulation During Denitrification

To realize the purpose of enhanced nitrogen removal (TN<5 mg·L-1) in step feed process treating urban wastewater, by using SBR reactor, the nitrite accumulation, variation of pH and ORP as well as dynamic properties during denitrification with methanol and glucose as the sole carbon sources are investigated in details. The results show that for both carbon sources, serious nitrite accumulations are observed during denitrification under different ratios of nitrogen and carbon (C/N). With identical C/N, when glucose is used as carbon source there is more maximum NO2--N accumulation concentration. However, NO3--N reduction rate is faster than NO2--N reduction rate for both carbon sources. Furthermore, with the increase of C/N, the maximum NO2--N concentration increases and the time in which the NO2--N achieves the highest concentration is accordingly shortened. For glucose, however, under high C/N ratio (C/N=29.3) both the denitrification rate and NO2--N accumulation concentration decrease. Besides, the changes of pH and ORP reflect the variation of NO2--N accumulation concentration well because pH and ORP have the significant relationship with NO2--N concentration. The second inflexion on curves indicates the real end of denitrification process.     

Physical simulation on burden movement in COREX melter gasifier

Based on the actual size and operation parameters of COREX melter gasifier and the similarity theory,as caled COREX melter gasifier model is established to study the burden movement.The polyethylene particles and mung bean are used as the packed burden and traceparticles,respectively.The effects of blast volume and discharging rate on flow pattern and trajectory are studied in detail. The results reveal that with the increase of discharging rate,the residence time decreases,the top position of deadman reduces,and the descending of burden movement becomes uneven.With the increase of the blast volume,the upper burden descends more even.Under abnormally discharging condition,the burden movement in meltergasifier would become uneven,which would cause uneven gas distribution in the furnace.The flow behavior in one half of the model appears to be independent of the other half.Particles under deadman descending at the slowest velocity tend to bend to the outlet.Particles above the raceway descend at the fastest velocity,and the blast causes the residence time to be reduced.Particles being close to the furnace wall descend along the wall until they get close to the outlet and then bend.