Temperature Flow Research Articles

Multi-objective optimal operation of a large deep reservoir during storage period considering the outflow-temperature demand based on NSGA-II

Thermal stratification occurs in deep reservoirs and causes an outflow temperature that is significantly different from the inflow temperature, which is harmful to the ecology of downstream reaches. Optimal operation of reservoirs using the multi-objective evolutionary algorithm (MOEA), which focuses on power generation, flood control, agricultural irrigation, navigation, etc., has been performed. However, the outflow temperature has not been considered. Focusing on this deficiency, we considered Sanbanxi Reservoir as a case study and used the non-dominated sorting genetic algorithm II (NSGA-II) by combining it with the calibrated 1-D General Lake Model. The trade-off relationships among three objectives, namely, total power generation (TPG), root-mean-square deviation between the inflow and outflow temperatures (RMSDtem) and weighted aggregate eco-index (EI) based on indicators of hydrologic alteration (IHAs) parameters, were estimated as Pareto frontiers during the storage period from March 15 to July 15. The results demonstrated the following. 1) Through reservoir re-operation, RMSDtem could be reduced by 1.60 °C from 5.99 to 4.39 °C at the expense of reducing TPG from 7.43 × 108 to 6.56 × 108 kW·h (–11.8%) during a normal year. 2)The optimized operating schemes were extracted as Pareto frontiers, and the slope of the outflow discharge curve (SODC) could be a useful parameter for determining the operating scheme in practice. A large SODC yielded high TPG, a small SODC resulted in low RMSDtem, and a medium SODC yielded minimum EI. The medium SODCs ranged from –0.1 to 0.4 m3/(s·d), –0.4 to 0.6 m3/(s·d), and –0.6 to 1.2 m3/(s·d) for dry, normal, and wet years, respectively. 3) As the yearly inflow increased, the absolute value of the SODC for the best individuals for a single objective became larger. The range of TPG and RMSDtem in the Pareto frontier expanded, and that of EI remained basically unchanged. The results of the Sanbanxi Reservoir can be applied to other reservoirs to support reservoir re-operation, especially for the deep reservoirs in southwest China that suffer from outflow-temperature problems.

Influence of non-uniform inflow swirl and hot streak on turbine vane

The turbine vane bears higher and higher temperature of upstream flow with the higher requirements for the engine thrust. The heat resistance of turbine vanes is a severe problem for the lifetime of turbine vanes. Therefore, it is essential to study the flow field and heat transfer of the vane to find better ways to improve the heat resistance of the turbine and increase the thrust of the engine. To improve the efficiency of the turbine vanes, the present paper conducted researches on the heat transfer and the pressure loss of turbine vanes under different radius ratio of swirl and hot streak. The numerical applies CFD 3D RANs solver with the SST turbulent model to get the influence of non-uniform inflow velocity and temperature distribution on turbine vanes. The present numerical model utilizes turbine vane C3X. Considering the viscosity of the fluid causes shear stress on the wall, the paper set the boundary layers mesh in the numerical model. The size of the first boundary layer mesh is 10–6 m. The results show that the hot fluid on the suction side migrates towards the hub, and the hot fluid on the pressure side migrates towards the shroud while there are coupling effect of the swirl and hot streak. The larger the radius ratio of the hot streak and the swirl (RHS) is, the higher the temperature of the local high-temperature regions exist on the suction side of leading edge and the pressure side of the trailing edge is, and the higher the pressure loss is.

A numerical study on gasification of a single char particle in supercritical water for hydrogen production

Supercritical water gasification technology provides a promising way for the efficient and clean utilization of coal. Char conversion in supercritical water is a complex coupled process of flow, heat transfer and reaction, and particle-scale study can provide important details for its in-depth understanding. A numerical work was conducted in this paper to investigate the influence of multiple factors on the gasification behavior of a single char particle in supercritical water. The results showed that the increase of temperature significantly benefited the char conversion and hydrogen production. Convection promoted the char gasification mainly by enhancing the heat transfer, and its improvement on effective mass transfer was quite limited. The existence of radiation is conducive to the char conversion, and cannot be ignored in some cases. The results derived from surface Damköhler number indicated that the gasification lied in kinetically controlled regime and tended to move towards diffusion controlled regime with larger inflow temperature, lower Reynolds number and larger particle size.

Application of biomass leachate in regulating the fusibility of coal ash

Biomass leachate was rich in water-soluble alkali and alkali earth metals (AAEM) species, which can effectively reduce the ash fusion temperatures (AFTs) of coal ash. In this study, a high silicon-aluminium coal (SA) with high AFTs and typical agricultural biomasses were selected to investigate the application of biomass leachate in regulating the fusibility of coal ash. The results showed that with the addition of biomass leachate, the AFTs of high silicon-aluminium coal with high-melting temperatures could be effectively reduced by greater than 70 °C, and the effect of biomass leachate on reducing the AFTs of coal ash is stronger than that of biomass. The ash chemical composition of the biomass alone could not fully reflect the ability of biomass leachate in regulating the fusibility of coal ash, the content of water-soluble AAEM and the evaporation of alkali metal elements in ashing process also had a significant influence. By adding biomass or biomass leachate into the SA, low-melting leucite and gehlenite, which would react with anorthite to generate low-melting eutectic, formed, resulting in the remarkable decrease of AFTs of SA. Exothermic peak temperature (EPT) and flow temperature (FT) showed an approximate linear relationship as FT ≈ EPT + 65 °C. The prediction results of FactSage were basically correspond to the experimental results.

High-Frequency Dynamics of Water Quality and Phytoplankton Community in Inflowing River Mouth of Xin'anjiang Reservoir, China

The tail of the reservoir is the unstable zone regarding water quality and phytoplankton community. Therefore, it is the crucial zone in aquatic ecosystem transitions. To understand the transition characteristics and driving mechanisms of water environment dynamics, high-frequency monitoring of the water environment and phytoplankton community in the tail of a deep and large reservoir, the Xin'anjiang Reservoir in southeast of China, was conducted using a water quality monitoring buoy and three-day interval water sampling during 18 months. Results show clear seasonal thermal and oxygen stratification in the river mouth of the reservoir. The nutrient and chlorophyll-a concentrations also show stratifying phenomena during the thermal stratification period. Heavy rain and inflow quickly consume the stratification. Nutrient concentrations were highly dynamic in the river mouth. The total phosphorus ranges from 0.011 mg·L-1 to 0.188 mg·L-1, and total nitrogen ranges from 0.75 mg·L-1 to 2.76 mg·L-1. Dissolved phosphorus comprised 56% of total phosphorus, and dissolved nitrogen occupied 88% of total nitrogen, respectively. Nutrient concentrations were influenced strongly by rainfall intensity and inflow rate. Total phosphorus and nitrogen concentrations were significantly related to the three-day accumulated rainfall. Nutrient concentrations in the flood season (March to June) were significantly higher than in the non-flood season (P<0.001). Seasonal phytoplankton proliferation also significantly influenced by total phosphorus concentration. The phytoplankton community changes significantly with seasons and flood events. Bacillariophytea was generally dominant throughout the year, with the predominant genus of Fragilaria spp., Cyclotella spp., Synedra spp., and Melosira spp. Cyanophyta biomass peaked in July, August, and September, with the dominant genus of Aphanizomenon spp., Microcystis spp., and Oscillatoria spp. Apart from the high temperature, storm inflow events also triggered Cyanophyta proliferation. The proliferation of Chlorophyta was similar to Cyanophyta, with the predominant genus of Pediastrum spp. and Closterium spp.. While the Cryptophyta biomass peaked during March to May, with the predominant genus of Cryptomonas spp.. Redundancy analysis shows that the influence factors of phytoplankton community dynamics include the inflow rate, temperature, water level, water transparency, total nitrogen, total phosphorus, and nitrogen to phosphorus ratio. The meteorological and hydrological factors were major factors for phytoplankton dynamics during later autumn and winter, while the nutrient will be the co-driving factors of phytoplankton community dynamics during summer and early autumn. The research confirmed the huge influence of the intensity rainfall event on the water environment in reservoirs and described the key environmental conditions for phytoplankton community dynamics. The research is useful for the design of the monitoring and forecasting system for water safety in drinking water source reservoirs.

Mechanisms Driving the Interannual Variability of the Bering Strait Throughflow

AbstractThe Bering Strait throughflow has important implications for the Arctic freshwater, heat, and nutrients. By keeping the interannual variabilities of the atmospheric forcing only inside or outside the Arctic Ocean in numerical simulations, we can quantify their relative contributions to the interannual variability of the throughflow. We found that winds play a much more important role for the throughflow interannual variability than buoyancy forcing. Winds over the western Arctic Ocean and North Pacific determine the direction of Ekman transport, thus changing the sea surface height gradient between the two basins, and consequently influencing the volume transport strength. Although winds over the two basins are similarly important for the variance of ocean volume transport, the North Pacific winds cause stronger variability in freshwater and heat transports through modifying the inflow temperature and salinity. After 1994, winds over the western Arctic Ocean explain a larger part of the variability of Bering Strait volume transport than the winds outside the Arctic Ocean.

Fuel distribution and evaporation characteristics downstream of an integrated flameholder

The vapor- and liquid-phase fuel distributions play critical roles in the combustion processes of augmented/ramjet combustors. In this study, the fuel distribution and evaporation characteristics downstream of an integrated flameholder in a fan-shaped test section are investigated under different inflow and fuel conditions using physical and optical methods. The experimental results denote that the Sauter mean diameter (SMD) and liquid equivalence ratio Φliquid at the cross-sections decrease with the increasing inflow temperature T1, inflow velocity V1, fuel temperature Tf or flow distance, while increase with an increasing global equivalence ratio ϕ. The total equivalence ratio Φtotal is conserved at all cross-sections; thus, the evaporation rate η at the measurement points increase with increasing inlet conditions and flow distance, similar to the vapor-phase equivalence ratio Φvapor. Under a given condition, along the radial direction from the outer wall to the central axis of the fan-shaped test section, the Φvapor and η initially increase, then decrease, and finally increase again, and reaching their maximum at a radius of 10/11, whereas Φliquid always increase; note that these trends are not affected by the inlet conditions. In any given cross-section, the SMD and Φvapor variations are significant for increasing V1 or Tf, whereas they are relatively small for increasing T1 or ϕ. This indicates that increasing the V1 or Tf is more conducive for promoting fuel atomization and evaporation than increasing the T1 or ϕ.

Potential influence of sewer heat recovery on in-sewer processes.

Heat recovery from combined sewers has a significant potential for practical renewable energy provision as sources of heat demand and sewer pipes are spread across urban areas. Sewers are continuously recharged with relatively hot wastewater, as well as interacting with heat sources from surrounding air and soil. However, the potential effects of modifying sewage temperature on in-sewer processes have received little attention. The deposition of fats, oils and greases (FOGs) and hydrogen sulphide formation are biochemical processes and are thus influenced by temperature. This paper utilises a case study approach to simulate anticipated temperature reductions in a sewer network due to heat recovery. A laboratory investigation into the formation of FOG deposits at temperatures varying between 5 °C and 20 °C provided mixed results, with only a weak temperature influence, highlighting the need for more research to fully understand the influence of the wastewater composition as well as temperature on FOG deposit formation. A separate modelling investigation into the formation of hydrogen sulphide when inflow temperature is varied between 5 °C and 20 °C showed considerable reductions in hydrogen sulphide formation. Hence, heat extraction from sewers could be a promising method for managing some in-sewer processes, combined with traditional methods such as chemical dosing.

Influence of the Direct Coal Liquefaction Residue on the Fusion Characteristics of Jincheng Coal with a High Ash Fusion Temperature

Nowadays, entrained flow bed gasification technology is the foundation of the modern coal chemical industry, while its liquid slag discharge process generally requires the flow temperature (FT) of ...

Fracture diagnostic using distributed temperature measurements during a pause in flow-back period

The significant temperature difference between the fractured and non-fractured regions during the stimulation fluid flow-back period can be very useful for fracture diagnosis. The recent developments in downhole temperature monitoring systems open new possibilities to detect these temperature variations to perform production logging analyses. In this work, we derive a novel analytical solution to model the temperature signal associated with the shut-in during flow-back and production periods. The temperature behavior can infer the efficiency of each fracture. To obtain the analytical solution from an existing wellbore fluid energy balance equation, we use the Method of Characteristics with the input of a relevant thermal boundary condition. The temperature modeling results acquired from this analytical solution are validated against those from a finite element model for multiple cases.Compared to the warm-back effect in the non-fractured region after shut-in, a less significant heating effect is observed in the fractured region because of the warmer fluid away from the perforation moving into the fracture (after-flow). Detailed parametric analyses are conducted on after-flow velocity and its variation, flowing, geothermal, and inflow temperature of each fracture, surrounding temperature field, and casing radius to investigate their impacts on the wellbore fluid temperature modeling results.The inversion procedures characterize each fracture considering the exponential distribution of temperature based on the analytical solutions in fractured and non-fractured regions. Inflow fluid temperature, surrounding temperature field, and after-flow velocity of each fracture can be estimated from the measured temperature data, which present decent accuracies analyzing synthetic temperature signal. The estimations are independent on each cluster, which can be combined to analyze the entire production section. The outputs of this work can contribute to production logging, warm-back, and wellbore storage analyses to achieve successful fracture diagnostic.

Effect of CaO/Fe2O3 ratio on fusibility of coal ashes with high silica and alumina levels and prediction

Ash fusibility which is usually investigated and evaluated by the ash chemical compositions is widely used to guide the coal selection in boiler and gasifier. Calcium and iron are the main basic oxides in coal ash, which tend to decrease ash fusion temperatures (AFTs). However, the change of AFTs varied with CaO/Fe2O3 mass ratio is not yet revealed. In this work, effect of CaO/Fe2O3 ratio on the fusibility of ash with high silica and alumina levels was explored under weak reducing atmosphere (CO: CO2 = 3/2, volume ratio). Thermodynamic calculations were applied to investigate the fusion behavior. A general rise of AFTs with the increasing CaO/Fe2O3 ratio was verified, especially for the coal ash with low SiO2 + Al2O3 level and SiO2/Al2O3 mass ratio. Mullite and anorthite are main refractory minerals phase of the ash samples with high SiO2 and Al2O3 levels. The fusion of the ash in anorthite primary phase is the “soft-melting” mechanism, and liquidus temperature was well used to predict flow temperature (FT). However, the liquidus temperature should not be used to predict FT of the ash in mullite primary phase due to the “melting-dissolve” mechanism. A Tmullite model was proposed to predict FT for the ashes in mullite primary phase. The deviation of predicted and measured FT was within the measuring error range (±40 °C), which was supported by 25 real coal ashes.

The influence mechanism research of inflow temperature in different time scale on the water temperature structure

A 3D hydraulic-thermodynamic mathematical model is established to predict the temporal and spatial distribution of temperature in a large reservoir in different time scale inflow temperature condition, and a further research on the influence mechanism of inflow temperature on the water temperature structure is made. it is found that the convection current between the upper and the lower of the reservoir always appear when the storage heat in a reservoir decreases; the stratification phenomenon appears in most time of a year in a large reservoir which is controlled by the climate, and there is a close relationship between the water temperature distribution and the inflow temperature. Different inflow temperature has different affected area where the density current propagates, in the affected area, the difference of water temperature distribution occurs by the cumulative effect of the previous months, for the other area, the more detailed the inflow temperature is, the more accurate the simulation results are.

Developing a framework for assessment of climate change impact on thermal stratification of dam reservoirs

According to the impact of climate change on the thermal stratification which results in a quality change of dams outflow, this study aims to present a framework to assess the impacts of climate change on altering thermal regimes of dam reservoirs. Therefore, five Atmosphere–Ocean Global Circulation Models (AOGCM-AR5 models) under two emission scenarios (RCP2.6 and RCP8.5) are used to investigate the change of air temperature, precipitation, wind speed, relative humidity, dam inflow and water temperature in 2020–2039. To quantify these impacts, three models are used, namely rainfall–runoff IHACRES, hydrodynamic model CE-QUAL-W2 and a downscaling model of LARS-WG. The efficiency of the proposed framework was evaluated in Latian Dam in Iran. Results show an increment of long-term air temperature average by 0.7 °C and, consequently, water surface temperature by 0.59 °C in 2020–2039 relative to the baseline period (1990–2009). Precipitation, wind speed and relative humidity decrease due to climate change in the future by 57%, 17% and 11%, respectively. The simulated dam inflows show that the maximum of 89% of the dam inflow decreases in the future period relative to the baseline period. The results indicate that the water temperature will increase in the coming period as the air temperature increases and this will lead to the extension of thermal stratification period up to 52 days.

Effects of heat transfer on separated boundary layer behavior under adverse pressure gradients

Separated boundary layers in a converging-diverging channel under two different wall heat transfer conditions, including the adiabatic wall and the cooled isothermal wall, have been investigated by using a large eddy simulation (LES) code coupled with a wall heat transfer module. The wall temperature of the cooled isothermal wall is 0.8 times of the inflow temperature, which is a typical value in a low-pressure turbine. The pressure distribution of the converging-diverging channel bottom wall is similar to that of a typical low-pressure turbine blade suction surface. The flow conditions are set as the exit isentropic Reynolds number (Re = 60,154) and the exit isentropic Mach number (Ma = 0.402). The results show that the cooled isothermal wall condition can increase the static pressure rise coefficient significantly, accelerate the transition process of the separation boundary layer, and suppress the separation. Furthermore, the cooled isothermal wall condition can decrease the frequency of the large-scale spanwise vortex rolled-up, reducing the influence of the spanwise vortex on the separated shear layer and decreasing the scales of the downstream hairpin vortex. In addition, the instability of the separated shear layer can be regarded as the superposition result of both the Tollmien-Schlichting (T-S) instability mechanism and the Kelvin-Helmholtz (K-H) instability mechanism, while the K-H instability mechanism on the whole is slightly more dominant in the presence of separation and reattachment. This trend is more obvious under the cooled isothermal wall condition.

Measurement of the vapor-phase and liquid-phase fuel distributions downstream of an integrated flameholder in heated stream

Understanding the vapor-phase and liquid-phase fuel distributions are necessary for conducting combustion performance research, especially under high-temperature inflow or fuel conditions. In this study, we propose physical and optical quantitative methods for measuring the total fuel distribution in the dual-modal (afterburner/ramjet) combustor with an integrated flameholder. The vapor-phase equivalence ratio is deduced from the n-decane (C10H22) concentration (determined using an n-decane detector). Raw images of the fuel spray field are captured using a high-speed camera. The droplets Sauter mean diameter (SMD) can be obtained using an image processing technology. The liquid-phase equivalence ratio is further derived by analyzing the droplet size and distribution. Finally, the total equivalence ratio can be obtained by adding the equivalence ratios of the vapor and liquid phases. The vapor-phase and liquid-phase fuel distributions were measured on different cross-sections downstream of an integrated flameholder. The global equivalence ratio, inflow velocity, inflow temperature, and fuel temperature were set to ∅=0.3–0.6,V1=50m/s, T1=450K, and Tf=373K, respectively. Further, the vapor- and liquid-phase equivalence ratios for the measurement points increased and decreased, respectively, with increasing flow distance. The flow characteristics and the vapor-phase fuel distribution were consistent behind the flameholder, confirming the rationality of deducing the vapor-phase fuel concentration from the n-decane concentration. The maximum error of the SMD obtained using the image processing technology was lower than the value reported in the literature (5.1%). Finally, the total equivalence ratio was almost conserved along the flow distance, proving the credibility of the proposed measurement methods.

Synergistic effect of CaO and MgO addition on coal ash fusibility in a reducing atmosphere

AbstractDuring coal gasification in entrained‐flow slagging gasifiers, the addition of additives is a promising method to improve coal ash fusibility. In some cases, mixed additives are more effective in decreasing ash fusibility than single additive addition with the same content added. However, mechanisms of mixed additive addition for improving ash melting are scarce. In this study, the effect of CaO, MgO, and their mixtures on the ash flow temperature (FT) of Chinese bituminous coal was investigated. The results show that the single addition of CaO or MgO influenced the ash FT of the test coal sample. The addition of CaO and MgO mixture synergistically decreased the ash FT relative to their single addition. When the ratio of CaO to MgO was 5:5 (mass ratio) in the mixture, the FT decreased to 1297°C, which is 69°C and 110°C lower than that of the single addition of CaO and MgO, respectively. The formation of a low‐temperature eutectic from the interactions between anorthite and olivine caused such synergistic effects.

Improved prediction of critical-viscosity temperature by fusion behavior of coal ash

Coal ash slag viscosity is critical for slag tapping in entrained-flow coal gasifiers, so the accurate prediction of slag viscosity and the critical temperature of viscosity (Tcv) will help the coal selection, flux addition and gasifier operation. Many empirical correlation models based on ash fusion temperature have been proposed to calculate Tcv. In order to correlate the viscosity with the fusion behavior and then improve the prediction of Tcv, we measured the viscosity of several synthetic coal ash slags with a high-temperature rotary viscometer and studied their ash fusion behavior through thermomechanical analysis. X-ray diffraction was used to compare the mineral transformation before and after Tcv combined with the FactSage calculation. The viscosity measurement shows that the viscosity above Tcv of glassy slags is higher than that of the crystalline type. The mineral transformation from FactSage also demonstrates that the precipitation rate of solid phase is lower for glassy slags. The fusion behavior for the glassy and the crystalline slag is also distinctly different.The fusion range from deformation temperature (DT) to flow temperature (FT) of the ash for the glassy slag was larger than that of the crystalline one, and the shrinkage above FT in TMA trace slopes gently. The correlation between the fusion behavior and viscosity-temperature behavior for the glassy slag is reasonable, because the large temperature range from DT to FT and the low shrinking rate of the stage III indicate the high viscosity of the liquid phase formed and the slow melting of the remained solid phase respectively, which are also the correlative condition prefer for the formation of glass as mentioned above. For the crystalline slag, the small fusion range from DT to FT means the rapid melting of the solid phase and the high flowability of the liquid phase which are indicative for the rapid precipitation during cooling. The slow rate of the stage III indicates the slow melting of the remained solid which can be the crystal nucleus. When the viscosity of the liquid phase is low, it also benefit for the formation of crystalline slags. The characteristic in fusion behavior for different type of slag also suggested that the predicting Tcv by applying one method to all the crystalline slags and non-crystalline slags is not appropriate.

Toward a new method for the design of combined sensible/latent thermal-energy storage using non-dimensional analysis

Placing an encapsulated phase-change material (PCM) on top of a packed bed of sensible filler material is an effective way of reducing the drop in the heat-transfer fluid (HTF) outflow temperature during discharging associated with a sensible thermal-energy storage (TES). So far, the literature lacks guidelines for the design of a combined sensible/latent TES. This study aims at developing a new method for the design of combined TES based on non-dimensional analysis. The method will provide a designer with non-dimensional plots, produced from quasi-steady-state results of simulations with a one-dimensional model, that relate performance parameters to geometrical, thermophysical, and operational parameters of the combined TES. In this paper, a simplified version of the method is demonstrated that allows the selection of a metallic PCM and its amount such that a specified drop in the HTF outflow temperature is attained during discharging, assuming a fixed sensible section of natural rocks and air as HTF. The plots show that the drop in the outflow temperature during discharging is minimized by selecting a PCM with a melting temperature equal to 98% of the HTF inflow temperature during charging. The plots also show that the heat of fusion, provided it exceeds a threshold, has a subordinate effect on the drop in the outflow temperature. Finally, the plots show that a smaller heat of fusion can be compensated with a larger height of the latent section. The method is illustrated with a specific example.

Effect of Hydrogen Refueling Parameters on Final State of Charge

The state of charge (SOC) is a key indicator to show whether a compressed hydrogen tank meets refueling requirements, so it is worth to study effects of the refueling parameters on it. A new SOC analytical solution is obtained based on a simple thermodynamic model. By applying a mass balance equation and an energy balance equation for a hydrogen storage system, a differential equation was obtained. An analytical solution of hydrogen temperature was deduced from the solution of the differential equation, then an analytical solution of hydrogen mass was further deduced based on the analytical solution of hydrogen temperature with some mathematical modifications. By assuming the hydrogen density inside the tank is uniform, the SOC, which defined as a ratio of hydrogen density to the full-fill density, can be transformed to be the ratio of hydrogen mass to the full-fill mass. The hydrogen mass can be calculated from analytical solution of hydrogen mass, while the full-fill mass is supposed to be a constant value. The full-fill density of 35 MPa and 70 MPa tanks at 15 °C are respectively 24.0 g/L and 40.2 g/L, and if the volume of the tank is known, the full-fill mass can also be calculated. The analytical solution of SOC can be unitized to express the reference data, the contributions of inflow temperature and mass flow rate on SOC are presented for a Dynetek type III tank (40 L, metallic liner) and a Hexagon type IV tank (29 L, plastic liner). In addition, the two-parameter effect of inflow temperature and mass flow rate on SOC are presented. The Nusselt number and Reynolds number are utilized to modify the analytical model, the relationship between SOC and refueling parameters can be obtained through the method of fitting. The fittings show a good agreement. The SOC can be determined from the refueling parameters based on the model with more physical meaning. The method developed in this research can be applied to the control algorithm of refueling stations to ensure safety and efficiency.

Regulation of ash fusibility for high ash-fusion-temperature (AFT) coal by industrial sludge addition

The effects of an industrial sludge (IS) on three high ash-fusion-temperature (AFT) coals (Jincheng coal (JC), Fuxing coal (FX) and Jiaozuo coal (JZ)) were investigated by an AFT detector, X-ray diffraction (XRD) analyzer, and thermo-physical modeling software. The results showed that IS could reduce the AFTs of three high AFT coals. The effect of IS on the AFTs of JC and JZ coals was clearly different from its effect on FX coal. When adding 18% IS ash to three coal ashes, the flow temperatures (FTs) of JC-IS and JZ-IS mixtures were reduced to below 1380 °C, which met the requirement of entrained-flow bed gasification, and the FT of FX-IS mixture was still higher than 1380 °C. After adding iron-rich IS ash (Fe2O3 > 41%) into three coal ashes, under reducing atmosphere, the Fe3+ was converted into Fe2+, the interactions of Fe2+ and Al2O3 led to the formation of a large amount of low melting-point (MP) hercynite (FeAl2O4). And some CaO could easily react with Al2O3 and SiO2 in the mixed ashes to produce anorthite (CaAl2Si2O8), restraining the formation of high MP mullite, which decreased the AFTs of these three mixtures. At 1100 °C, no mullite was detected in JC-IS and JZ-IS mixed ashes, and some mullite still existed in FX-IS mixed ash when the IS ash mass ratio even reached 30%, which might be the main reason for the decrease in the AFTs of JC and JZ was different from that of FX.