Biogas is composed of CH₄ and CO₂ which are produced by the action of anaerobic microorganisms on raw materials such as garbage, livestock excretion, and sewage sludge. It is expected to source for renewable H₂. This study proposes the biogas dry reforming membrane reactor to produce H₂ for use in fuel cells. Pd/Cu alloy (Cu of 40 wt%) membrane is used to enhance the performance of the biogas dry reforming reactor by H₂ separation. The purpose of this study is to understand the effect of operating parameters such as feed ratio of sweep gas, pressure in the reactor, and reaction temperature on the performance of the biogas dry reforming membrane reactor. As a result, it is revealed that H₂ selectivity and CO selectivity increases and decreases respectively, when the reaction temperature increases, irrespective of molar ratio of supplied CH₄:CO₂. It has been found that the optimum feed ratio of sweep gas to produce H₂ is 1, irrespective of molar ratio of supplied CH₄:CO₂.

In a conventional periodic inspection of a steam turbine, the amount of clearance change during turbine assembly is obtained by temporary assembly and used in alignment adjustment. Because this temporary assembly takes several days to a week, this paper proposed a virtual assembly method using 3D shape measurement and finite element analysis (FEA) as an alternative to the temporary assembly for the purpose of skipping it and extending the plant operation term. In the virtual assembly, the shape of the horizontal flange surface of the turbine casing is firstly measured by high-precision laser measurement, and the continuous surface of Non-Uniform Rational B-Spline (NURBS) is automatically generated from the measured shape. Then, the horizontal flange surface of analysis mesh is adjusted to the generated NURBS surface to reflect the actual distorted shape. Finally, the FEA simulates the casing assembly and estimates the amount of clearance change during turbine assembly. The effectiveness of the proposed method was confirmed by evaluating the prediction accuracy in actual turbines. The proposed method makes it possible to shorten the total term of the periodic inspection by omitting the temporary assembly with maintaining the appropriate clearance.

The Mitsubishi Heavy Industries Group has found the business direction based on multiple scenarios that can be envisioned from a medium to long-term perspective in changing the business environment. In particular, the thermal power generation business is reaching a great turning point. As progress of technological innovations in renewable energy and energy storage, further high efficiency and flexible operation of large-scale thermal power is required, and the role of centralized power sources will shift to power grid stabilization. As our solution for these predictable changes, Mitsubishi Power suggests developing highly efficient and reliable products, modifications and repair technologies that meet the various needs of customers with existing thermal power plants, and operation improvement technology that optimizes the customer's plant operation and maximizes the asset value.

Torrefaction is one of the promising treatments for reforming conventional solid biofuels, and torrefied solid biofuels have come to attract attention as an alternative to coal. When torrefied solid biofuels are utilized or produced, energy properties such as higher heating value (HHV) and energy yield of torrefied solid biofuels are quite important. There are two aims of the study. One is to present the HHV evaluation method by lumped-parameter pyrolysis kinetic models with high evaluation accuracy. The other is to present the simple correlation to evaluate HHV without depending on three biomass species. From the comparison between the HHV evaluation method and experimental data, it is clarified that the proposed HHV evaluation method based on the two-step pyrolysis kinetic model can be useful to evaluate the HHV of torrefied biomass for three biomass samples with high evaluation accuracy, 5% or less. The linear correlation between HHV enhancement factor and mass yield of torrefied biomass is found regardless of three biomass species in the range of torrefaction mass yield larger than 0.6.

Wind power has been developed rapidly under the administrative encouragement policy in recent decade. Wind-power heating system has been a promising low carbon emission approach in context of 4th Generation District Heating that more renewables and energy saving technologies can access to energy supply system conveniently. Instead of the conventional central circulating pump configuration, an alternative configuration of Distributed Variable-Speed Pumps proposed to be suitable for the fluctuating wind-power heating system. Moreover, the advanced Model Predictive Control method can also be employed to relieve the hydraulic imbalance in the proposed configuration. Then, a new mathematical model is proposed here to adapt fluctuating wind-power heat sources in urban DH system with consideration of pipe blockages. It is also applied to a real looped DH system with one CHP heat source and 3 wind-power heat sources. The result shows that the wind share can be 40.81% while the wind curtailment rate reaches 6.75%. The proposed model can be developed to simulate onsite operation to save more wind power.

In this paper a source term inversion model is built to study the source release during severe accident in nuclear power plant. The model is based on the combination of genetic algorithm and Nelder-Mead simplex algorithm and the dispersion model is Gaussian plume model. It uses the off-site monitor data and the meteorological data to estimate the amount of radiological materials released into environment during severe accident. This method can support the rapid obtain of source term during nuclear emergency and become a supplement to the core damage evaluation method. Three validation cases are present in this paper, which are indoor wind tunnel experiments. According to the wind tunnel experiment, the average inversion error is within 10%, which shows that the source term inversion model established in this paper can give the accident release source term very accurately. This model can be used in the consequences evaluation of nuclear accidents, provide suggestions to accident emergency decision-making.

Compared with steam cycle systems, supercritical carbon dioxide(s-CO2) power cycle system, which is more compact and efficient, can achieve rapid response and multiple start and stop. A high-efficiency turbine, one of the key equipment of s-CO2 power cycle, is being developed by Shanghai Power Equipment Research Institute. Its rotor design is checked by finite element analysis results of rotor dynamics and strength during scheme optimization. By adjusting the flow path scheme, shaft seal scheme and balance piston scheme, the balance disk length and the length of the high temperature section of the rotor is reduced, the system efficiency and safety performance can be greatly improved. The improvement of turbine rotor layout and cooling gas system greatly shorten the overall span of the rotor.

Municipal solid waste incineration (MSWI) is currently the main method of harmless treatment of waste. The high moisture content of municipal solid waste (MSW) is one of the important reasons that affect the capacity of MSWI power plants. Therefore, this paper proposes a waste drying system which uses the waste heat of flue gas and steam to dry the MSW. This system includes a combined drying waste component built by Ebsilon software and is applied to MSWI power plants in China. Meanwhile, in order to make the power plant system more optimized, the original system is reformed from two aspects of steam extraction point and condensate return point, and four systems are put forward. Finally, the thermal economy of the four systems is compared and analyzed under pure condensing conditions, it is determined that the system with the extraction steam before the deaerator as the heat source and the return water before the heater is the best system for the waste drying power plant system. The efficiency of the whole plant has been increased from 22.8% of the original power plant system to 28.7%, bringing greater economic benefits to the MSWI power plants.

Municipal solid waste (MSW) incineration power generation technology has been widely used in China and abroad, and the technology has become increasingly mature. However, the high water content of MSW reduces the efficiency of MSW incineration power plants. At present, there is a major problem of reducing the water content of MSW. Steam is used as a heat source to reduce the water content of MSW before incineration. In this paper, Ebsilon software was used to simulate and transform a MSW incineration power plants, and a steam drying MSW system was constructed. The MSW was dried before entering the furnace by steam. Two improved systems based on the original system are proposed from the steam extraction point, and the pure condensation condition and heating condition were simulated and analyzed. Through the analysis, the best system of steam drying MSW system under two working conditions is the system with the steam of the deaerator as the heat source. Under the pure condensing condition, the overall efficiency in plant is 18.0 % higher than that of the original system, and under the heating condition, the overall efficiency in plant is 16.5 % higher than that of the original system.

Shirai, et al (2016) theoretically investigated on the universal trade-off relation between the power, P, and the thermal efficiency, η, for heat engines. They indicated that P became 0 at both η = 0 and η_C (Carnot efficiency) and became the maximum at (1/2)η_C. The present study explored this subject though a model on piston-cylinder thermal cycle system with finite period, τ. State change of the gas was characterized by the Tv-diagram. The present model brought qualitatively the same trade-off relation by Shirai et al. (2016).

Carbon capture and storage (CCS) is an important technical option to reduce CO₂ emissions and chemical absorption by amine solutions is the most mature post-combustion carbon capture technology. Reducing costs is critical to accelerate large-scale deployment of CCS. Cost estimates of CCS vary markedly depending on the CO₂ capture performance, CO₂ transport method, characteristics of CO₂ storage site, and the like. This study estimated the cost of CCS by amine-based CO₂ capture integration into thermal power plants in Japan. The thermal power plant system with CO₂ capture process was modeled on a process simulator, and CO₂ capture cost was calculated based on the modelling results. The CCS chain feasible in Japan at this time is transportation by ship and injection onshore into subseafloor storage sites. Transport cost was estimated via bottom-up analysis of each transportation sub-process. Injection cost was based on the values reported by the Tomakomai demonstration project. In total, transport and storage costs were roughly equivalent to capture costs. Full chain CCS implementation is likely necessary to markedly reduce costs through learning-by-doing.

We study experimentally so-called "microbubble emission boiling (MEB)," which occurs under high subcooled conditions. We especially focus on the correlation among the heat transfer characteristics, the oscillating behaviors of the vapor bubbles on a horizontal circular heating surface, and the boiling sound in the developing and developed states of the MEB in the pool. Spatial-temporal behaviors of the vapor bubbles oscillation and characteristics of boiling sound are investigated through the Fourier spectra of the temporal variations of the oscillation obtained by high-speed imaging and the boiling sound obtained by sheathed microphone, respectively. We indicate that the vapor bubbles exhibit non-uniform oscillation in the radial direction at the early stage of the MEB, whereas they oscillate uniformly in the radial direction in phase above the heating surface at the fully developed state of the MEB. We find that the uniformity of the vapor bubbles oscillation is the essence of the heat transfer characteristics and the accompanying boiling sounds.

Aqueous glycerol was used in this study as a liquid-phase hydrogen source for the hydrogenation of CO₂. It was found that hydrogen could be efficiently evolved from aqueous glycerol upon highly dispersed Ru on layered double hydroxide (LDH), inducing the transformation of CO₂ into formaldehyde under base-free conditions at low temperature.

We suggest new CO₂ absorption processes with biphasic phase separation type for reducing consumption energy. the CO₂-rich solution liquid was separated hydrophilic liquid and hydrophobic liquid. In this work, we studied some kind of amine and ether mixture solvents, and observed phase separation phenomena. From the results of phase separation characteristics, we selected with 2-Amino-2-methyl-1-prophanol (AMP), diethylene diethyl ether (DEGDEE) and water pair. We measured the CO₂ solubility at different temperature and CO₂ patricidal pressure conditions, and evaluated the effect of component concentration in the solvents on CO₂ absorption characteristics and phase separation phenomena. We adjusted the biphasic solvents. AMP, DEGDEE and H₂O of biphasic solvent weight-composition ratio are 30, 20 and 50 wt% respectively. The CO₂ solubility of absorption at 40℃, 0.1atm was obtained 0.647 mol-CO₂/mol-AMINE. The CO₂ solubility of desorption at 90℃, 1.0 atm was obtained 0.177 mol-CO₂/mol-AMINE. The difference of CO₂ loading of this solvent was high performance of CO₂ capture compared with that of other solvents. These result is attributed to the additive phase assisting in the regeneration of CO₂ by extracting the regenerated amine. The results of the present study show reduction of desorption temperature and high CO₂ absorption performance.

In order to reduce environmental pollution, improve energy structure and realize rational development and utilization of energy, the distributed system including Brayton cycle, HRSG and lithium bromide absorption refrigeration is determined in this paper according to the energy consumption of gas, cold, heat and electricity in large integrated community. Then, the equipment selection and system optimization are carried out. Ebsilon, a power station simulation software, is used to build the system, and the transformation process of LNG cold energy utilization, waste heat boiler backpressure heating and natural gas secondary preheating are carried out. The results show that when the inlet temperature of natural gas is raised from -30℃ to 60℃, the power capacity of the whole unit increases by 0.362MW.When the air temperature decreases from 20℃ to 0℃, the overall power generation power of the CHD system increases by 1.2MW, the heating capacity per unit flue gas increases by 2.05kJ/kg, and the work capacity per unit flue gas increases by 30.01 kJ/kg, which improves the overall efficiency of the system.

By combining flue gas waste heat utilization technology with multi-effect evaporation and vacuum cooling technology, the concentration and crystallization system of magnesium oxide desulfurization wastewater is optimized, which reduces the cost of desulfurization product production process and increases the extra income of coal-fired power plants. First, the forward-flow benchmark system and the parallel-flow benchmark system are compared. The results show that the specific flue gas heat, specific heat transfer area, specific cooling water and annual profit of the parallel-flow benchmark system are about 83%, 92%, 90% and 101% of those of the forward-flow benchmark system, respectively. Then, different optimization processes are added to the parallel-flow benchmark system and compared. The results show that the specific flue gas heat, specific heat transfer area, specific cooling water and annual profit of the 7-process parallel-flow optimization system are about 94%, 94% ,94% and 101%, respectively, compared with the parallel-flow benchmark system. Finally, the 7-process parallel-flow optimization systems of 300, 600 and 1000 MW coal-fired power plants are compared. The results show that the annual profits of 300, 600 and 1000 MW coal-fired power plants are about 7 million yuan, 15 million yuan and 22 million yuan respectively.

Some ash particles in municipal and industrial waste adhere to heat exchanger tube surfaces, which causes problems such as heat-transfer inhibition and operational problems in Waste-to-Energy (WtE) plants. The objective of this study is to provide further understanding of ash-deposition mechanisms for various metal surfaces in WtE plants. First, the adhesion force between an ash pellet, which was sampled from a WtE plant, and an alloy specimen was measured to investigate the mechanisms that increase ash deposition. Second, the adhesion interfaces of the specimens were analyzed after the adhesion force measurement. The result was that the adhesion forces of all specimens increased with the interface temperature, and there was a clear temperature dependency on the force. The adhesion force of the ash pellet to austenite stainless steel AISI 304 was larger than to AISI 310S or to a surface-modified AISI 304 due to a lower Cr content. Moreover, analysis of the adhesion interface and the thermodynamic equilibrium calculation supported the results of the adhesion measurements.

Experimental absorption refrigeration equipment with a generator driven by waste heat was manufactured and tested, with 2,2,2-trifluoroethane/1-methylpyrrolidine as the working-fluid pair. A plate generator was used to reduce the amount of solution in the equipment and to decrease the start-up time. However, the flow paths of the plate generator were not large enough to separate the refrigerant vapor from the two-phase flow. Therefore, a gas–liquid separator was introduced and a cooling coil as a partial condenser was embedded in the separator to cool the refrigerant vapor, which contained some absorbent, and condense the absorbent, and thus increase the concentration of the refrigerant vapor. The separator separated the refrigerant from the solution at lower solution flow rates, but at higher flow rates, the refrigerant vapor was accompanied by liquid droplets that flowed out of the vapor outlet. The cooling rate of the partial condenser was varied from 143 to 222 W by changing the flow rate of the cooling water, decreasing the refrigerant vapor temperature.

Kawasaki Heavy Industries had started a comprehensive program as New Energy and Industrial Technology Development Organization subsidy project finished successfully. Based on the result of the program, KHI has launched the upgraded model of L30A gas turbine, rated output of 32.6MW, 39.9% of thermal efficiency, and 517 ℃ of exhaust temperature at standard site condition. In spite of employing higher turbine inlet temperature, the NOx emission is controlled to be same level as that of original model which is less than 15 ppm with improved dry low emission combustor. The combined heat and power plant has started operation in 2020, the plant generates 107MW of power at the specific site condition, the overall plant thermal efficiency was validated to be reached to 90.3%.This paper mentions in-house gas turbine validation test result, and also introduces the CHP plant employed L30A GT and its performance validated at site.

In pulverized coal-fired boilers, coal-ash deposition on heat transfer surfaces can cause operational problems. It is important to predict ash-deposition characteristics based on the ash composition of the raw coal in advance. However, general prediction methods do not always agree with actual ash deposition under co-combustions. In this study, we investigated the relationship between the mineral particles in raw coal samples analyzed with CCSEM and the ash-deposition characteristics in an actual boiler collected with the newly designed sampling system. The main conclusions drawn were as follows: (1) iron components were condensed in the early-stage ash deposition of the secondary superheater-tube area, and the amount of iron components affected the ash-adhesion properties; and (2), these ash-adhesion properties had a positive correlation with the new index based on included minerals, which were iron oxide, iron-aluminum silicate, iron silicate, and pyrite; (3) this index was able to predict ash-deposition characteristics with high accuracy.

In this study, a simplified model equation is presented to analytically model the rotational speed of a rotor disk of a small wind turbine. Specifically, the response of the rotational speed to changes in the inflow wind speed is examined. First, the governing equations for the rotation speed of a small wind turbine are obtained in a dimensionless form using characteristic quantities. Therefore, the present analysis targets the non-dimensional inflow wind speed and rotation speed. Then, the profile of the tip speed ratio of the aerodynamic torque coefficient is used. Here, the profiles of aerodynamic torque coefficients for two small wind turbines are used. Using the first and second derivatives of the aerodynamic torque coefficient, the profile of the aerodynamic torque coefficient is described by a series expansion. Here, based on previous studies, it is not necessary to include the value of the second-order derivative. In view of the above, a simplified model equation using the aerodynamic torque coefficient and its first-order derivative is presented. The use of a reduced-order modeled accurate governing equation, such as that presented in this study, may provide a mathematical solution to describe the response of the rotational speed as a future study.

In this work, we analyse the potential grid stabilizing effects of the advanced double-effect adsorption thermal energy storage in decentralized and on-site domestic use. As the adsorption and thermochemical heat storage systems can provide both hot and cold, relative to the environment, the usage can be projected as continuous through the whole year for both air conditioning as well as hot water preparation. We show that the adsorption systems have the capability to elevate part of the immediate electric demands used for “hot and cold” preparation in the domestic and commercial environment as independent systems or in combination with other interactive parts of the electric grid. The adsorption thermal energy storage system introduced in this work can operate with high COP of >0.7 depending on the conditions and shows good energy stability over time. Additionally, the adsorption systems use thermal energy or electricity mainly for charging and only a negligible amount during the discharge. Hence, they can mitigate the adverse effects on the grid during the high demand periods and still deliver the necessary work while providing the grid operators with another stabilizing tool that can substantially enhance the effective utilization of renewable sources of energy.

The purpose of this study is to understand the shear rate of cooling water and silicone oil when they are stirred by up-and-down motion. For this purpose, an experiment and simulations using a Moving Particle Semi-implicit (MPS) method were conducted. The stirring experiment was performed under the same condition as in the simulation, and the validity of the simulation was examined by comparing the results. The liquid surface deformation was observed in the experiment, and it was confirmed that the behavior expressed in the simulation was in good agreement with the experimental one. The simulations were performed at three different velocity of reciprocating motion of 0.04m/s, 0.07m/s, and 0.1m/s, and the shear rates in each case were compared and discussed. As a result, the relationship between the velocity of reciprocating motion and the shear rate, and the relationship between the up-and-down motion and the shear rate were clarified.

This study aimed to elucidate the relationship between the spray characteristics and cooling performance in a suction air cooling system. The sprays from pin jet nozzles and hole nozzles are evaluated under several supply-water temperature conditions. The droplet diameter and spray velocity are measured using a phase doppler anemometer (PDA). The air temperatures at the upstream and downstream of test section are recorded via thermocouples to estimate the cooling efficiency. The cooling efficiency of both nozzles increases continuously once the supply-water temperature reaches 60°C. The PDA measurements reveal that the atomization activates in high-temperature supply water because the droplets are smaller and slower under this condition. The cooling performance was ascertained to be connected to the spray characteristics.

In order to improve the thermal performance of natural draft wet cooling tower under crosswind, a three-dimensional numerical model for heat and mass transfer of cooling towers was established. The comparison with the design parameters of the cooling tower shows that this model satisfies the requirements of the thermal performance computation of cooling tower. According to the numerical calculation of the cooling tower and the analysis of the temperature, humidity and velocity field under various crosswinds velocities, a scheme of partition water distribution of cooling tower was proposed to deal with the effect of crosswind. Using this scheme, the influence of various spray water density ratio k on the thermal performance of cooling tower were researched, and the results show that the heat transfer performance of the cooling tower can be effectively improved under a certain comparing with uniform water distribution. When the crosswind speed is in the range of 2-6 m/s and this partition water distribution scheme is applied, maximum reduction of the outlet water temperature will reach 1.01K comparing with uniform water distribution.

In the present paper, the blade vibration monitoring (BVM) method and the system products based on blade tip timing were studied and demonstrated in detail in the following four aspects: (1) Based on the finite elemental method (FEM) simulation calculations, the variation principle of the vibration characteristics after blade cracks, bumps and other faults was investigated to verify the feasibility of the BVM method. (2) Based on the simulation calculation of the test blade, the blade vibration monitoring experiment was conducted on a small rotor test bench. The effectiveness of the current monitoring system function is verified by the blade spectrum identification. (3) Based on the real long blade of a steam turbine unit, the vibration monitoring test verification of the long blade of steam turbine was conducted. The key problems such as sensor installation, signal conditioning, data acquisition and data analysis were experimentally studied, providing a technical support for product engineering. (4) Combined with the demonstration power plant, the on-site debugging and verification test of the BVM system were conducted to confirm the reliable application of the BVM system.

Type IV creep voids are creep voids that originate inside the weld zones of high-chromium steel piping. The voids occur in main piping structures for ultra-supercritical pressure coal-fired power generation equipment. The damage of the high-chromium material will start with the increase of creep voids density and grows to the micro-cracks and at last grows to the macro-cracks to relate for the rupture accidents. Since these damage considered serious in power generation industry, the mechanism of the Type IV creep damage have been studied all over the world. Tough conventional nondestructive inspection methods, including advanced phased-array ultrasonic system, applied for the damage detection of piping structure with deep-zone creep voids, any methods cannot satisfy the resolution to estimate the creep damaged at the periodic inspection of power plant. Thus, new nondestructive evaluation techniques to detect the microstructural creep damage of concentration of creep voids on grain boundaries have been required. The authors focused on water immersion acoustic imaging technique, which has the highest spatial resolution among the commercial ultrasonic inspection systems, to estimate initial stage of Type IV creep void. We developed a new measurement system with designing a high-focusing aspherical angle acoustic lens, and with its scanning pitch modified with high precision. As a result, we have discovered that the new measurement system which we have developed can lead to the evaluation of Type IV creep void density in deep areas of the material.

The high-temperature corrosion behaviors of Ni-based alloys including Hayness 230, Hayness 282, Inconel 740H, Inconel 617, Inconel 625 in CO₂ environment at 800 ℃ for 1000 h were studied. The corrosion performance of the alloys was measured by Mettler electronic balance, and the surface behavior of oxide were characterized by X-ray diffraction, scanning electron microscope, and energy dispersive spectrometry. The results show that the oxidation kinetics of Ni-based alloys in high-temperature carbon dioxide environment obeyed a parabolic oxidation law. The weight gain of investigated alloys followed in order: Hayness 282 > Inconel 740H > Inconel 617 > Inconel 625 > Hayness HR230. The external oxide scales of alloys of Ni-based alloys were mainly Cr₂O₃ and MnCr₂O₄. But the alloys (282, 740H, 617) containing Ti were composed of TiO₂ and Cr₂O₃. Internal oxidation was observed, which consisted of TiO₂ and Al₂O₃. The mass change of 282 and 740H were higher due to internal oxidation caused by high Al and Ti contents, and this phenomenon had also been observed in air, wet air and water vapor. There is almost no carburization of Ni-based alloys in CO₂ environment. Ni-based alloys have excellent performance in high temperature CO₂ environment, mainly due to the high Cr content of investigated alloys, which will form a protective chromia-rich scale.

This paper presents the attempt made to develop a new configuration of a thermally driven pumping system. A vertical narrow evaporation channel and displacer unit concepts were introduced to implement the TPP cycle in a liquid piston configuration. An experimental setup was developed to investigate the performance and characteristics of the system. For a heat source temperature of 60 °C, it was possible to attain the delivery pressures up to 174kPa using isopentane as a working fluid. The corresponding thermal efficiency of the system was in the range of 0.5 - 0.7%, which is found to be higher than the literature. The effect of introduction of preheating times (PHT) on the system performance was investigated and it was found that for a short critical PHT, the efficiency of the system improves by the order of 2%. However, longer periods were observed to deteriorate the system performance. The results seem to suggest that the boiling process in the evaporation channel may be in the subcooled pool boiling regime when the system is operating without the preheating periods, as the thermal demand of the system is lower, and it operates at a higher frequency in such conditions.

The fluctuating power output of renewable energy sources (REs) renders the electric grid unstable, and thus, a realistic approach must be established to compensate for the load fluctuations associated with RE-based power generation. The gas turbine combined cycle power generation (GTCC) with a rapid start-up and high ramp rate is a potential solution to solve the problem. This study presented the feasibility of an advanced GTCC focused on the rapid load following operation through dynamic simulation. A dynamic model of an advanced GTCC was constructed with the Modelica-based tool. It was found that the load-following capability of the GTCC can be improved by increasing the operational performance of the GT, but the steam condition fluctuation such as steam temperature in the steam bottoming system becomes larger. A simulation for increasing the temperature of the exhaust gas at the inlet of the heat recovery steam generator during low load band operation was conducted. The potential of this approach to suppress the steam temperature fluctuation was highlighted through this simulation.

The superheater is a critical component in a coal-fired power plant because it sustains the highest tube wall (metal) temperature point in the boiler. The steam flowing in the superheater tubes is heated by thermal radiation and convection from the combustion gas in the radiant zone. To prevent melting and bursting of the tubes and to ensure normal plant operation and maintenance, accurately predicting complex heat transfer characteristics, estimating local temperature, and assessing the heat flux of the superheater are all essential. In this study, a computational fluid dynamics model of the boiler and superheater is developed using radiation and turbulence models. The local metal temperature and heat flux of the superheater are evaluated by calculating the heat exchanged between the combustion gas flow and steam flow in the tubes. The calculated values of the steam outlet temperature accurately reproduce the values measured using the equipment in the plant, and thermal radiation was confirmed to be dominant in the boiler. In addition, it was found that the heat flux of the outermost heat transfer tube, which receives the most thermal radiation, was more than 11–15% higher than those of the other inner tubes.

With the increasing capacity of thermal power units in China, due to the influence of Coal mixed combustion, peak load regulation and combustion conditions and other factors, the boiler burst accident has not yet reached the design life. Considering the factors of coal quality, heat transfer mechanism, equipment deterioration, material aging and off-line data, on-line model combined with off-line data is used to monitor the pipeline life damage. A boiler monitoring system based on digital twin technology is developed to realize the mapping of key equipment states in boiler spatial structure. By displaying the status of digital twin, operators can directly perceive the weak links of boiler equipment and accurately locate the high-risk parts of the equipment. Put forward condition based maintenance opinions or operation optimization measures three days before the occurrence of risk to avoid unnecessary shutdown of the unit and effectively ensure and improve the reliability of boiler equipment.

Hydrogen production from alkaline water electrolysis is a promising solution for the intermittency problem of solar and wind energy. Compared with the expensive Pt-based electrode for hydrogen evolution reaction (HER), it is highly desirable to develop earth-abundant electrocatalysts with high activity and durability for practical implementation. Herein, we report a facile method to synthesize hierarchically porous NiCo-P nanostructures anchored on nickel sheets (NiCo-P@Ni) as the HER electrode. The NiCo-P@Ni are prepared by a dynamic hydrogen bubble template cathodic electrodeposition of honeycomb porous NiCo microspheres on nickel sheets and subsequential phosphatization. The superaerophobic surface of the hierarchically porous NiCo-P@Ni accelerates the bubble detachment during water electrolysis due to the discontinuous three phase contact line caused by the compact nanowires and honeycomb macropores, leading to more sufficient exposure of active sites on the electrode surface, thus increased the HER activity. As a result, the NiCo-P@Ni electrode exhibits a lower overpotential of 69 mV at 10 mA cm−2 with a Tafel slope of 39 mV dec− in 1 M KOH compared with the CoP and Ni5P4 catalysts growing on the same substrate. This work provides a novel avenue to construct hierarchically porous transition metal phosphides based electrode for highly efficient HER.

Boiling heat transfer characteristics of HFC-245fa in a horizontal tube bundle with a staggered arrangement were experimentally investigated. Thermal spray coated tubes as a boiling heat transfer enhancement tube were installed only at the first row of the tube bundle to form homogeneous bubble flows. In our previous results with the thermal spray coated tube, it was shown that uniform heat transfer enhancement factor to the single tube heat transfer could be obtained independent of the tube position. Since the effect will depend on the relative size of the tube gap to the size of vapor bubbles, the tube gap was reduced to 4.5 from 7.5 mm with the same tube pitch of 22.5 mm of the previous study. The experiments were carried out at the saturation temperature of 18 °C. Heat flux was varied from 1.33 to 50 kW/m2 with the mass flux at the minimum gap of 18.5 and 30.8 kg/(m2·s). As a result, it was confirmed that higher heat transfer enhancement factor could be obtained by the reduction of the tube gap in the case with the thermal pray coated tubes at the 1st row. The increase in heat transfer coefficient by installing the thermal spray coated tubes was larger under the lower mass flux condition of 18.5 kg/(m²·s).

Ever since the Paris Agreement, efforts to decarbonize have been underway around the world. Similarly, Japan has declared that it will become carbon neutrality by 2050, and thermal power plants that use fossil fuels are required to reduce their CO₂ emissions using CO₂ capture and storage (CCS). However, the cost of CO₂ capture in CCS is high, and the reduction of this capture cost is required. Kawasaki Heavy Industries, Ltd. has developed a novel CO₂ capture system, named the Kawasaki CO₂ Capture (KCC) system. This system uses an amine solid sorbent comprising a porous solid and a liquid amine. CO₂ is captured by this material and subsequently released by low-temperature steam. Furthermore, the low-temperature steam can be generated from using waste heat in various industries. Therefore, the KCC system can be expected to enable energyefficient capture of CO₂ and reduce the CO₂ capture costs. So far, KHI has developed a fixed-bed and movingbed of the KCC system. In this context, KHI believes that the moving-bed system is suitable for large-scale plants, such as thermal power stations. KHI has been evaluating the feasibility of the KCC moving-bed system by conducting CO₂ capture tests at its in-house bench-scale test facility. In recent years, we have been participating in a national project, and have succeeded in capturing 7.2 t/d CO₂ using the bench-scale test facility. Currently, based on the results of the bench test, after having designed a 40 t/d scale demonstration test facility, we started its construction at a thermal power plant.

Prime Minister Suga announced that Japan should achieve carbon neutral society by 2050. To achieve this goal, it is important to have a concrete plan on renewable energy use. So far, biomass has been utilized mainly for electricity generation through the feed-in tariff system. Already more than 2.2 GW of power generation plant using biomass is in operation, but the power generation cost has not been decreased. This is mainly due to the high cost of biomass feedstock. On the other hand, price of solar panels and wind turbines are getting lower and proliferation of electric cars with battery is expected. Considering this situation, the role of biomass in the carbon neutral society in 2050 should not be power generation any more. Three utilization of biomass as carbon resource is proposed. The first one is coke in steel production. The second use is jet fuel. The third use is bioplastic. However, the availability and technology to achieve this goal has not been concretely discussed. In this study, present technology of biomass utilization for these uses as carbon resource is introduced and quantitative discussion is made.

MgAl layered double hydroxide (LDH), with the advantages of low cost and wide employment in commercial applications, has been regarded as the promising catalyst for CO₂ photocatalytic conversion into fuels. To improve the visible light absorption and electron separation efficiency of MgAl LDH, metalloporphyrin (Co-TCPP) was used for the surface modification of MgAl LDH to prepare the noble-metal-free nanocomposite (Co-TCPP@LDH). The Co-TCPP@LDH composite exhibits obviously increased photocatalytic activity under visible light compared with pure MgAl LDH. Experiment results show that 20%Co-TCPP@LDH exhibits highest photocatalytic activity with CO yield of 0.40 umolg⁻¹_cat, which is about 4.1 times and 3.3 times than these of MgAl LDH and Co-TCPP. The excellent visible light absorption of porphyrin molecules can effectively widen the light absorption edge to low energy region (600-800 nm). The intramolecular heterogeneous interface and the highly dispersed cobalt metal sites can facilitate charge separation.

Hydrogen is one of the most promising elements to accelerate the realization of low carbon society. Today many countries mention that the demand of hydrogen will be increased in coming decades. Although green hydrogen, produced from renewable energy using water or steam electrolysis (power to gas) is preferable, it is expected to be still costly in coming decade and also it requires enormous and rapid increase in the capacity of power generation facility for satisfying the increased hydrogen demand. Because of that, hydrogen produced from fossil fuels with carbon capture and storage (CCS) which is so called blue hydrogen (cf. without CCS is called grey hydrogen) is considered to play an important role. It should be noticed that even CCS is applied, certain amount of CO₂ is released during the blue hydrogen production due to the cost limitation of CCS. Therefore the present study focuses on analyzing the cost of blue hydrogen, grey hydrogen and green hydrogen, taking into account the amount of CO₂ emission and CO₂ price. The results show that blue hydrogen may be cost competitive to green hydrogen as CO₂ price would be higher than the long term expectation reported by IEA.

In the present study, the temperature dependence of luminescence properties of 9 different metal complex temperature sensitive luminophores (Eu(hfc)₃, Eu(tfc)₃, EuTTA, Ru(phen)₃, Ru(dpp)₃, PtTFPP, PtOEP, PdTFPP, PdOEP) were investigated at cryogenic temperatures (0 °C ~ -190 °C). Luminescence was excited by the third harmonics of a pulsed Nd:YAG-laser (355 nm) and recorded by a compact size CMOS spectrometer. The luminescence decay after excitation was detected by a photodiode and temporally recorded by an oscilloscope. Common to all investigated luminescent materials, the emission intensity tended to increase as the temperature decreased. It was found that the emission intensity was extremely high, and temperature measurement with a high signal-to-noise ratio was achievable, because there was no noise caused by radiated heat at cryogenic temperatures. The rate of change in emission intensity at the peak wavelength of the emission spectrum of all luminophores, while temperature changed from 0 °C to -190 °C, exceeds 100 %. Two-color ratiometric method, which uses the ratio of integral of relative intensity at two wavelength bands, can also be applied for high precision temperature determination by some of these luminophores. The investigated luminescent materials with particularly high temperature sensitivity for two-color ratiometric method were Ru(phen)₃ and Ru(dpp)₃. The tested luminophores, which are suitable for the lifetime-based method, were Eu(hfc)₃, Eu(tfc)₃, EuTTA and PtTFPP.

The flow resistance and wear of the pipeline system are jointly influenced by pipe structure, fluid flow pattern, and fluid composition. When two local resistance components are connected, the upstream component will affect the fluid flow pattern into the downstream component. In other words, the interaction of two components will affect the flow resistance and wear of the pipeline system. In this study, numerical models for the flow and wear of the elbow-reducer pipe connection were developed and validated. When the elbow is directly connected with the reducer pipe, great flow resistance and large wear occur. The local entropy generation model of gas-solid flow was developed to evaluate the irreversible loss of the flow field. The existence of solid particles will affect the average entropy generation, turbulent entropy generation and wall entropy generation. The results may provide some guidance for the design and optimization of pipeline system.

Coal takes a big portion of power generation in many developing countries, and efficiency enhancement of coal utilization is very important for the sustainable development. Combined heat and power (CHP) is an effective way to enhance the efficiency of coal-fired power plants. Moreover, the cogeneration of heat and power can bring remarkable economic benefits for power stations. The energy consumption evaluation to express the efficiency of CHP plants is a traditional but also a reserved issue that needs to be addressed, which is very important for the design, operation, and energy saving evaluation of CHP plants. In this study, the off-design calculation models of CHP unit were developed. With a reference case, efficiency to produce thermal energy and power under variable heat and power loads were studied. Three tradition energy consumption evaluation methods were compared when the unit operates under the off-design conditions. The exergy loss and dissipation of the case unit under the off-design conditions are shown. This study may provide a reference for the development of energy consumption method for CHP plants.

To develop a real-time temperature estimating method for a gas turbine blade and a header of heat recovery steam generator, surrogate models that can estimate transient changes in temperature under arbitrary operation conditions were obtained by applying Gaussian process regression to results of numerical simulations. The predicted temperatures by the surrogate model adequately agreed with the numerical results under various operating conditions. The surrogate model was found to be robust against the noise in operating condition data and setting error of initial temperature. In addition, the surrogate model for predicting thermal stress was also obtained and accuracy of the model was validated.

Halogenated activated carbon adsorbent has exhibited superior mercury capture efficiency in the flue gas. Not only the fabrication of effective adsorbents, but the used adsorbents stability is also crucial, which is essentially determined by product bonding nature. Here, Density functional theory was employed to investigate spent halogenated activated carbon adsorbents bonding nature at the electronic level. Seven possible mercury-containing product geometries and effects of halogen species (X = Cl / Br / I) were all considered. Precisely, bond length value, and Mayer bond order of Hg-C, Hg-X and C-X bonds were calculated to indicate product stability in the gaseous phase. It was found that mercury was bonded on the carbonaceous surface with C-Hg Mayer bond order around 0.5 in product structures G and H, suggesting a weak interaction. Moreover, effects of halogen species in X-Hg and C-X bond strength follow the order of I > Br > Cl. Additionally, electron localization function and localized orbital locator were employed to determine electron high localization regions. In summary, this study analyzed the bonding nature of used halogenated activated carbon adsorbents. The results are beneficial for fabricating more environmental-friendly mercury removal adsorbents in the future.

The hydration characteristics of calcium chloride/silica microcapsule composite cell have been investigated. Especially, this paper focused on the effect of encapsulation ratio of calcium chloride in microcapsules and gap fraction of composite cell on power density of composite cell based on hydration reaction experiments. The mass of sodium polymethacrylate (Na-PA) in the microcapsule generation process was changed for controlling the encapsulation ratio. The gap fraction of the cell was also controlled by the concentration of sodium silicate used for bonding material between microcapsules. From the results, it was found that thermal storage density of composite cells when the gap fractions of cells were set constant at 0.69 could optimize the power density of cell, which reached 0.52 kW/L when the encapsulation ratio of calcium chloride was 69.9 wt%. It was also revealed that the reaction rate is not severely affected by the encapsulation ratio. When the encapsulation ratio of calcium chloride was at 69.9 wt%, the power density increased with the increasing gap fraction from 0.64 to 0.71 and reached 0.56 kW/L at 0.71. It showed that low gap fraction hindered the penetration of water into cell and reduced the hydration reaction rate.

Power supply system optimization, in which the installed capacity and power output from variable renewable energy (VRE) and thermal power are obtained by minimizing the total cost of power supply, provides conditions for lower-cost integration of high shares of VRE. However, power transmission and distribution (PTD) companies operate on a partially optimized system in which the installed power capacities are fixed and the amount of power acquired is primarily driven by the price of electricity from the various power sources. In this study, we analyze the effect of electricity pricing on the amount of power acquired by the PTD companies from the power supply sources using a power supply mix model. The model has an optimization objective function aimed at minimizing the cost of power acquired and the cost of operating the power transmission and storage facilities by the PTD companies. The power system of Hokkaido, Japan, is taken as the case study for this analysis. The results show that the electricity pricing can affect the amount of power purchased by the PTD company and increase or decrease the VRE share of a total system optimization scenario.

As a result of the expansion process within low pressure steam turbines, the last stages typically operate in the two-phase flow regime. Consequently, water droplets are carried with the steam flow leading to the potential risk of water droplet erosion on rotating blades. This operation situation overtime leads to performance degradation, reduction of service lifetime and thus increased product costs. In order to improve reliability and safety of steam turbine modules, special design features can be applied to reduce the erosion risk. One common approach utilizes suction slots on the stationary airfoils of guide vanes, intending to drain the deposited water from the vane surface and consequently diminish the amount of coarse water droplets. This paper presents the development and validation of a model using numerical and experimental methods to determine and assess the performance accuracy as a design and optimization approach for hollow vane suction slots. The analysis focuses on previous investigations for a flat-plate arrangement and is extended to a vane nozzle setup intending to consider surface curvature effects on water rivulets paths. Based on steady-state and transient multiphase Eulerian-Lagrangian framework simulations for different operating conditions, the suction slot performance for both applications is derived by means of collection rate and air leakage considering predominant multiphase flow phenomena (film building, transport, stripping of droplets and wall impingement of droplets). The resulting numerical dataset is used in comparison to available measurement data (air flow and film conditions) and for validation as well as calibration of the prediction accuracy of the simulation model. Results for flat-plate and nozzle setup show that the numerical approach is able to predict the main phenomena of film flow and breakup into droplets. Comparison with test data illustrates that an error of less than 15% is achieved for the slot efficiency based on the water film collection rate and water film properties. Overall, the ability of the modelling approach to predict the performance of suction slots is confirmed. Results thus lead to the conclusion that the numerical model is sufficiently accurate to represent geometric changes relevant during design procedure of hollow guide vane suction slots.

The combustion process of carbon-based fuels will produce CO. If CO can be used as a reducing agent to remove NO, the goal of removing NO and unburned carbon (UBC) simultaneously can be achieved. When rice husk ash (RHA) rich in amorphous SiO₂ is used to support Fe-Cu metal oxides, its huge specific surface area and non-lattice microstructure can reduce the reaction temperature, so that Fe-Cu/RHA catalyst has a high performance of selective catalytic reduction of NO by CO (CO-SCR). The paper used honeycomb ceramic to support Fe-Cu/RHA catalyst, and studied the effects of preparation method, active ingredient loading and reaction conditions on the CO-SCR performance of integral catalyst. The experimental results showed that the integral catalyst obtained by the heating and stirring method was better than the room temperature method. The conversion rates of CO and NO of the integral catalyst increased with the increase of the active ingredient loading. Besides, the oxygen concentration had little effect on the conversion rates of NO and CO. The conversion rate of CO to CO₂ increased with the increase of temperature, and it could reach up to 98%. The conversion rate of NO to N₂ fluctuated slightly as the temperature increased.

To achieve clean and efficient coal utilization, various gasification processes were modelled and simulated to obtain their energy potential degrees in this study. Effects of reaction conditions on the product composition, exergy efficiency, and energy potential change were evaluated. The energy potential matching degrees of coal gasification processes were compared. Results show that high temperature, low pressure, low oxygen coal ratio and high water coal ratio are beneficial to increasing the amount of effective gas, i.e., H₂ and CO. Low oxygen and water coal ratio can enhance the exergy efficiency of coal gasification processes, because they can improve the output gas energy potential. The exergy efficiency of coal conventional gasification process peaks as the gasification temperature reaches 900℃. The exergy efficiency of coal chemical looping gasification process peaks as the gasification pressure reaches 1.5 MPa. The results may provide some guidance on the selection and optimization of process operation parameters.

Wind turbine wakes reduce the power generation and life of the downstream wind turbines. Accurately predicting the impact of wind turbine wakes is very important for evaluating the feasibility of large wind farms. We have recently proposed a computational fluid dynamics (CFD) porous disk (PD) wake model as an intermediate method between engineering wake models and CFD wake models in order to predict accurately the time-averaged wind speed deficits in the wind turbine wakes. In this study, to further evaluate the validity of the CFD PD wake model, we additionally measured the wind turbine wakes of 2 MW‐class downwind turbines installed on the coastal area using a vertical profiling lidar (ZephIR ZX300), and considered them including the data in the previous report to clarify its airflow characteristics in detail. Based on the measurement results by the lidar, we reproduced the wind turbine wake using the CFD PD wake model. The simulated vertical distribution of wind speed by the CFD PD wake model corresponded with the measurement result of the lidar.