The KLT-40S is a small modular reactor developed by Russia based on the KLT-40 reactor with two fuel assembly designs: a four-ring and a five-ring. Few studies have been published on fuel assembly and power-flattening designs for the KLT-40S. In this paper, the effects of different fuel assembly designs on burnup and power flattening are investigated. This paper compares the effects of the two fuel assembly designs of the KLT-40S on its burnup characteristics, analyzes the effects of fuel rod diameter on burnup characteristics, and conducts a computational study on the ideal power-flattening design. The results show that the five-ring fuel assembly design has better burnup characteristics than the four-ring fuel assembly design. At a fuel rod diameter of 0.62 cm, the optimal burnup lattice is obtained. The 15.84% + 19.75% power-flattening design (uranium enrichment in the innermost and outermost rings + uranium enrichment in inner rings) reduces the local power peaking factor of the fi... [more]

Hitachi is advancing their designs for a conceptual reactor called the resource-renewable boiling water reactor (RBWR), a concept reactor similar to the advanced boiling water reactor with a harder neutron spectrum. This design aims to minimise construction costs and waste production as well as to utilise separated plutonium and minor actinide fuel. However, the axial heterogeneity of the design poses calculation difficulties. The aim of this work is to use a known method, reactivity-equivalent physical transformation (RPT), for calculating fuel with double heterogeneity and apply it to a BWR-type fuel pin. This could reduce the calculation time needed for optimisation of the design of the RBWR. The objective of the study is to use SCALE 6.2 to produce an equivalent axial pin model by comparison with the burnup and neutron spectra of a radial model of the fuel. This model can then be used for 2D burnup calculations, and in future work will be used for the generation of two-group and mu... [more]

Geological restrictions and the low energy density of compressed air energy storage (CAES) plants constitute a technical and economic barrier to the enablement of variable and intermittent sustainable sources of energy production. Liquid air energy storage (LAES) and pumped thermal energy storage (PTES) systems offer a promising pathway for increasing the share of renewable energy in the supply mix. PTES remains under development while LAES suffers from low liquefaction unit efficiency, although it is at a higher technology readiness level (TRL) than PTES. The most significant element of large-scale EES is related to the discharge features of the power plants, especially the energy storage unit. Here, a novel multi-aspect equation, based on established codes and thermodynamic principles, is developed to quantify the required storage capacity to meet demand consistent with the design parameters and operational limitations of the system. An important conclusion of the application of the... [more]

The paper presents the impact of different methods of sewage sludge conditioning on the improvement of sludge dewatering during pressure filtration processes. The following conditioning methods were tested for sludge preparation: sonication, addition of organic and inorganic chemicals (Zetag 8180, PIX 113 and the combined action of both substances). The research covered: physical and chemical analysis of sewage sludge, measurement of capillary suction time as an indicator of sludge dewaterability, some technical parameters of sludge pressure filtration process and the analysis of filtrate to assess the degree of contamination. The results of the research showed that the final water content of the prepared sludge decreased, while the specific filtration resistance increased. Among the tested methods the best results of sludge dewatering effects were obtained for sonicated sludge and its preparation with inorganic coagulant PIX 113. The combined effect of sonication with the addition of... [more]

Comparative tests in air and oxy-fuel combustion were conducted in a 30 kWth circulating fluidized bed (CFB) pilot plant for waste sludge combustion. General combustion characteristics of the CFB, such as pressure profiles, temperatures along the bed, and flue gas composition, were different under the air and oxy-fuel conditions. At the bottom and in the fly ash, alkali and heavy metals had different distributions under the air and oxy-fuel combustion conditions. The particle size distribution in fly ash from air combustion was dominated by coarse particles, over 2.5 μm in size, whereas with oxy-fuel combustion, most particles were submicron in size, approximately 0.1 μm, and a smaller quantity of coarse particles, over 2.5 μm in size, formed than with air combustion. Mass fractions of Al, Ca, and K, below 2.5 μm in size, were found in the ashes from oxy-fuel combustion and in higher quantity than those found in air combustion. Submicron particle formation from Cr, Ni, Cu, and Zn in th... [more]

The generation and emission characteristics of fine particulates (PM2.5) from three 300 MW power plant circulating fluidized bed boilers were investigated. One boiler had an external bed and used an electrostatic precipitator, the other two used an electrostatic filter precipitator and fabric filter, respectively. The particle size distribution of fine particles was performed by an electrical low-pressure impactor. PM2.5 samplers were used at the same time to collect fine particles for subsequent laboratory analysis. The results show that the number size distributions of fine particles presented one single peak, but there was no peak in mass size distributions. The mass concentrations of three CFB boilers were similar, but the number concentration of the external bed CFB boiler was much higher than that of the general CFB boiler. The minimum removal efficiencies of the precipitator appeared between 0.1~1 μm, but the locations of the minimum point were different. The morphology of fine... [more]

This study aimed to evaluate the effects of mechanical disintegration of waste activated sludge (WAS) on full scale anaerobic digestion, considering the possibility of obtaining a positive energy balance. The results showed that an increase in energy density (εL) used in disintegration was accompanied by an increase in the release of organic compounds from sludge (SCOD increased from 211 ± 125 mg O2/L for εL = 0 kJ/L to 6292 ± 2860 mgO2/L for εL = 180 kJ/L). Some of them were volatile fatty acids. The percentage share of WAS subject to disintegration was also documented as a crucial parameter affecting the efficiency of biogas production. An increase in the value of this parameter from 25% to 100%, even at much lower εL used in disintegration (therefore with much smaller amounts of organic compounds released from sludge flocs) resulted in an increase in biogas production. Conducting disintegration of the entire stream of WAS directed to the fermentation tank at εL 30 kJ/L resulted in a... [more]

Degraded lands are potential areas for obtaining biomass which can serve as an energy source after its conversion into biogas. Thus, the studies on biogas production from maize and cocksfoot biomasses obtained from degraded soil supplemented with additions of new zeolite substrate (Z-ion as the nutrient carrier) and on arable soil (reference soil) were carried out during batch digestion tests. It was found that the biogas and biomethane potentials and specific energy of the test species growing in degraded soil enriched with Z-ion additions (1% and 5% v/v in the cases of cocksfoot and maize, respectively) did not differ significantly from the values of these parameters that were found for the plants growing in arable soil. The application of Z-ion to the degraded soil (especially in a dose of 5% v/v) resulted in an increase in the nitrogen content and decrease (below the lower optimum value) in the C/N ratio in the plant biomass. However, these changes did not negatively influence the... [more]

A novel experimental method for the lateral mixing of binary solids in bubbling fluidized beds was developed based on the capacitance probe technique. The evolutions of local mixing ratios in a fluidized bed which can be assumed as one mixing cell were analyzed in detail. The solids mixing within one mixing cell was resolved and the effect of convection and diffusion mechanism on lateral mixing was evaluated individually. The results show that at lower part of the fluidized bed, convection plays a more important role in the mixing process near the wall; meanwhile, diffusion is very important for the mixing around the center line. This is opposite with that at the higher part. A lateral micro dispersion coefficient was proposed to characterize the lateral mixing within the mixing cell and the value is generally between 0.005 and 0.025 m/s. A new mixing index was proposed to evaluate the lateral mixing quality of binary solids. It was found that at the lower part of the fluidized bed, th... [more]

This paper presents the results of measurements of vibrations of the pipes of the steam superheater installed in the convection pass of the 235 MWe Circulating Fluidized Bed boiler (CFB) induced using sonic soot blowers of the Nirafon NI-100 type. The measurements were made using two ICP Triaxial 356A16 accelerometers allowing the analysis of accelerations in the maximum range of ±490 m/s2. Simultaneously with vibration measurements, the sound pressure level was recorded using the G.R.A.S. 40BH high-pressure microphone. The measurements and spectral analysis of the recorded signals showed that the acoustic wave of 148 dB is safe for the steam superheater pipes causing vibrations of maximum amplitude not exceeding 1 mm. The field tests confirmed the supposition that the dominant mechanism for cleaning the surfaces of the superheater’s heating pipes are not pipe vibrations, but the breakage of cohesion forces between dust particles.

This is a reply to the paper by Variny et al. [...]

Systems of two immiscible liquid phases—aqueous phase (i.e., distilled water (dH2O) or phosphate-buffered saline (PBS)) and liquid perfluorochemical (i.e., perfluorodecalin (PFD))—were subjected to wave-assisted agitation, i.e., oscillatory rocked, in a disposable bag-like container in a ReadyToProcess WAVETM25 bioreactor, to recognize oxygen transfer effects and effectivity of the surface aeration. According to the DoE methodology, values of the volumetric liquid-side mass transfer (kLa) coefficient for dH2O, PBS, dH2O-PFD, and PBS-PFD systems were determined for the whole range of operating parameters of the WAVE 25 bioreactor. A significantly higher maximal value of kLa was found for waving dH2O than for dH2O-PFD (i.e., 0.00460 s−1 vs. 0.00331 s−1, respectively) compared to more equal maximal values of kLa reached for PBS and PBS-PFD (0.00355 s−1 vs. 0.00341 s−1, respectively). The interface development factor (f) depended on the interfacial area a, and the enhancement factor (EPFD)... [more]

The transverse vibration frequency of conveyor belts is an important parameter describing the dynamic characteristics of a belt conveyor. This parameter is most often identified from theoretical relationships, which are derived on the basis of an assumption that the belt is a stationary elastic string. Belt vibrations have a number of analogies to other tension member systems, such as, for example, power transmission belts. Some research findings suggest that in the case of a limited length of the belt section, a more accurate description of its vibration can be obtained with a beam model rather than with a string model. Experimental research has so far mostly revolved around measurements of stationary belts. This article presents the results of vibration measurements performed for a moving belt and obtained for various operating parameters of the conveyor, as well as for several configurations of the distance between idler supports. The analysis was conducted on a moving steel-cord be... [more]

Value Stream Mapping (VSM) is a popular and easy tool for visualizing production processes in enterprise. It allows one to eliminate or reduce waste, i.e., activities that do not create added value for the customer. The versatility of this tool allows it to be used in industry. There are theoretical, methodological, and practical aspects encountered by practitioners in developing Value Stream Mapping (VSM) for a specific manufacturing industry, but they are not fully resolved and require clarification. This paper presents a case study that describes the use of Value Stream Mapping (VSM) in the production of steel pipes. Relevant data from this process were collected and analyzed at the start of the project. An initial process was mapped, associated waste was identified, and then future processes were mapped. The financial results were estimated. Consequently, the process was improved, and savings were achieved. The article should constitute the basis for further development of an impro... [more]

For self-entrainment venturi nozzles, the effects of nozzle shapes and operating conditions on the water−air two-phase flow pattern, and the characteristics of the air entrainment rate have been investigated. A rectangular venturi nozzle with width and height dimensions of 3 mm and 0.5 mm was used with a vertically downward flow direction. The pressure ratio, which is the ratio of the inlet and outlet pressures, water flow rate, and diverging angle were set as experimental parameters. From the flow visualization, annular and bubbly flows were observed. In the case of bubbly flow, the more bubbles that are generated with a higher water flow rate, the smaller the pressure ratio. In the case of annular flow, the increased pressure ratio and water flow rate induce the breakup of air core in the diverging area and make the interfacial oscillation stronger, which finally causes the flow transition from annular to bubbly flow, by accompanying a sharp increase in the air entrainment rate. Duri... [more]

An experimental investigation of single Taylor bubbles rising in stagnant and downward flowing non-Newtonian fluids was carried out in an 80 ft long inclined pipe (4°, 15°, 30°, 45° from vertical) of 6 in. inner diameter. Water and four concentrations of bentonite−water mixtures were applied as the liquid phase, with Reynolds numbers in the range 118 < Re < 105,227 in countercurrent flow conditions. The velocity and length of Taylor bubbles were determined by differential pressure measurements. The experimental results indicate that for all fluids tested, the bubble velocity increases as the inclination angle increases, and decreases as liquid viscosity increases. The length of Taylor bubbles decreases as the downward flow liquid velocity and viscosity increase. The bubble velocity was found to be independent of the bubble length. A new drift velocity correlation that incorporates inclination angle and apparent viscosity was developed, which is applicable for non-Newtonian fluids... [more]

Unstable flow structures cause inevitable energy losses in all power energy systems, including turbomachines. In this study, a set of analyses was conducted with the use of spectral maps on the pressure signals obtained from an industrial centrifugal compressor. The spectral maps provide one a detailed visualization of the flow conditions present in the machine along the performance curve and to distinguish the flow phenomena present prior to the surge. The method accuracy is especially useful in detecting the inlet recirculation. The study was conducted at four impeller rotational speeds with varying loads imposed by a valve at the outlet. At each speed, the machine experienced different stages of unstable flow conditions prior to the surge. Five main frequency peaks that appeared in all cases were identified and discussed. The surge was observed at all impeller speeds. At lower ones, however, it appeared at higher valve closures. At higher speeds, the surge was much more intense. The... [more]

Industrial hemp stands out as a promising candidate for clean and sustainable biomass-to-bioenergy systems due to its multipurpose, high biomass yield and resource efficiency features. In this study, different hemp biomass residues (HBRs) were evaluated as a potential feedstock for renewable biomethane production through anaerobic digestion (AD). The biochemical methane potential (BMP) of the raw and pretreated fibers, stalks, hurds, leaves and inflorescences was investigated by means of batch anaerobic tests. The highest BMP was obtained with the raw fibers (i.e., 422 ± 20 mL CH4·g VS−1), while hemp hurds (unretted), making up more than half of the whole hemp plant dry weight, showed a lower BMP value of 239 ± 10 mL CH4·g VS−1. The alkali pretreatment of unretted hurds and mechanical grinding of retted hurds effectively enhanced the BMP of both substrates by 15.9%. The mix of leaves and inflorescences and inflorescences alone showed low BMP values (i.e., 118 ± 8 and 26 ± 5 mL CH4·g VS... [more]

A process for obtaining ethyl levulinate through the direct esterification of levulinic acid and ethanol using AlCl3·6H2O as a catalyst was investigated. AlCl3·6H2O was very active in promoting the reaction and, the correspondent kinetic and thermodynamic data were determined. The reaction followed a homogeneous second-order reversible reaction model: in the temperature range of 318−348 K, Ea was 56.3 kJ·K−1·mol−1, whereas Keq was in the field 2.37−3.31. The activity of AlCl3·6H2O was comparable to that of conventional mineral acids. Besides, AlCl3·6H2O also induced a separation of phases in which ethyl levulinate resulted mainly (>98 wt%) dissolved into the organic upper layer, well separated by most of the co-formed water, which decanted in the bottom. The catalyst resulted wholly dissolved into the aqueous phase (>95 wt%), allowing at the end of a reaction cycle, complete recovery, and possible reuse for several runs. With the increase of the AlCl3·6H2O content (from 1 to 5 mol%), t... [more]

Various kinds of pilot burners were experimentally investigated to examine the effects of their geometry and their location relative to the main burner of a real size combustor. In addition, a wide range of fuel equivalence ratios were investigated to analyze the feasibility of the novel pilot burner for the conventional burner application. From the results, it is shown that the novel pilot burner with multi air holes had a thin, straight, long and stable pilot flame, while the conventional pilot burner had a thick, lifted, short and unstable flame. It is also shown that the novel pilot burner with an upper air flow hole had a straight pilot flame which led to less thermal damage to the burner combustor. This study suggests that not only pilot burner flame shape but also the vertical location of the pilot burner from the main burner combustor has a significant effect on combustor durability.

In this study, Kraft lignin was depolymerised by hydrothermal liquefaction in near-critical water (290−335 °C, 250 bar) using Na2CO3 as an alkaline catalyst. Isopropanol was used as a co-solvent with the objective of investigating its capping effect and capability of reducing char formation. The resulting product, which was a mixture of an aqueous liquid, containing water-soluble organic compounds, and char, had a lower sulphur content than the Kraft lignin. Two-dimensional nuclear magnetic resonance studies of the organic precipitates of the aqueous phase and the char indicated that the major lignin bonds were broken. The high molar masses of the char and the water-soluble organics, nevertheless, indicate extensive repolymerisation of the organic constituents once they have been depolymerised from the lignin. With increasing temperature, the yield of char increased, although its molar mass decreased. The addition of isopropanol increased the yield of the water-soluble organic products... [more]

A review on the rotating stall in the vaneless diffuser of centrifugal compressors is presented showing that different stall modes characterized by different numbers of cells can be detected within the diffuser even if the operating condition remains unchanged. The interaction between the inlet perturbation and the stall cells near the diffuser outlet is supposed to be the trigger of the stall mode transformation. In order to determine if the inlet perturbation will interact with the downstream stall cells, a characteristic time analysis is proposed to estimate the characteristic time of the perturbation in radial and tangential directions. An additional theoretical model which focused on the development of the vaneless diffuser rotating stall is presented to determine the propagation velocity of the cells. The comparison between the characteristic time in two directions shows that one stall mode is able to evolve into another stall mode if a critical condition is met, and the stall mo... [more]

In this study, hydrothermal liquefaction (HTL) of wheat straw (WS) in sub (350 °C) and supercritical (400 °C) water with and without alkali catalyst was performed to investigate the potential of WS for the production of biocrude. The influences of temperature and catalyst were studied for the HTL products. Results showed that maximum biocrude yield (32.34 wt. %) with least solid residue (4.34 wt. %) was obtained at subcritical catalytic condition, whereas the carbon content was slightly higher in biocrude at supercritical. The higher heating value (HHV) for biocrude is around 35 MJ/kg for all four conditions. The major compounds in biocrude were observed as ketones, alcohols, acids, and hydrocarbons. At 350 °C, 44−55% of the carbon recovered into biocrude. The products were characterized in terms of elemental composition, higher heating values, organics, and inorganic compounds in different phases. To keep in consideration the scale-up of HTL process for continuous plant, aqueous phase... [more]

The aim of this study was the performance evaluation of anaerobic digestion of dairy wastewater in a multi-section horizontal flow reactor (HFAR) equipped with microwave and ultrasonic generators to stimulate biochemical processes. The effects of increasing organic loading rate (OLR) ranging from 1.0 g chemical oxygen demand (COD)/L·d to 4.0 g COD/L·d on treatment performance, biogas production, and percentage of methane yield were determined. The highest organic compounds removals (about 85% as COD and total organic carbon—TOC) were obtained at OLR of 1.0−2.0 g COD/L·d. The highest biogas yield of 0.33 ± 0.03 L/g COD removed and methane content in biogas of 68.1 ± 5.8% were recorded at OLR of 1.0 g COD/L·d, while at OLR of 2.0 g COD/L·d it was 0.31 ± 0.02 L/COD removed and 66.3 ± 5.7%, respectively. Increasing of the OLR led to a reduction in biogas productivity as well as a decrease in methane content in biogas. The best technological effects were recorded in series with an operating... [more]

In this research, we present a novel design for a large scale spectral splitting concentrator photovoltaic system based on double flat waveguides. The sunlight concentrator consists of a Fresnel lens array and double waveguides. Sunlight is firstly concentrated by Fresnel lenses then reaches an upper flat waveguide (UFW). The dichroic mirror-coated prisms are positioned at each focused area to divide the sunlight spectrum into two bands. The mid-energy (mid E) band is reflected at the prism surface and coupled to the UFW. The GaInP/GaAs dual-junction solar cell is attached at the exit port of the UFW to maximize the electrical conversion efficiency of the mid E band. The low-energy (low E) band is transmitted and reaches a bottom flat waveguide (BFW). The mirror coated prisms are utilized to redirect the mid E band sunlight for coupling with the BFW. The GaInAsP/GaInAs dual-junction solar cell is applied to convert the low E band to electricity. The system was modeled using the commerc... [more]