Mixture Of Steam Research Articles

Experimental Study on Influencing Factors of Aerosol Retention by Pool Scrubbing

During the process of containment depressurization venting, a high-temperature and high-pressure carrier gas with aerosol may be released into the spent fuel pool by a multihole injector. This aerosol in the carrier gas can be removed by pool scrubbing. A small-scale pool scrubbing facility was built to study the aerosol pool scrubbing phenomenon using a multihole injector. In this study, a gaseous mixture of nitrogen and steam is used to simulate a carrier gas, and insoluble solid particles of TiO2 are used to simulate aerosols in the carrier gas. Seven tests were performed to examine the dependence of the decontamination factor (DF) on the pool depth, particle diameter, and steam mass fraction. The results show that log(1/(1–Xm)) has a linear relationship with log(DF). DF varies exponentially with the pool depth, which has an influence on the retention of aerosols with a larger particle diameter. Particle diameters in the range of 0.2–0.52 μm have little effect on the DF. For a low-depth pool scrubbing, the steam condensation mechanism is dominant and the particle diameter does not have a significant effect on the DF. Moreover, the pool scrubbing model is discussed, and an empirical correlation is proposed to evaluate the DF of a pool.

Galvanodynamic Electrochemical Impedance Spectroscopy on a Solid Oxide Cell Stack for In-Operando Diagnostics

Introduction Lifetime expectations and uncertainties regarding end-of-life performance hinder widespread deployment of fuel cell technology. Conventional cell performance diagnostic methodologies rely upon either ex-situ measurements, which lack an immediate connection with the physical degradation phenomena, or upon single cell in-operando electrochemical impedance spectroscopy (EIS), which often is troubled by challenges of feature identification of the spectra and uncomplete representation of the full stack operating conditions in large scale systems [1]. To address these problems, we propose to use electrochemical impedance spectroscopy techniques as diagnostic and prognostic tools to predict the cause-effect relationship between degradation phenomena and stack operating conditions. This experimental methodology can be potentially integrated into commercial systems for stack state of health monitoring during continuous operation. Experimental methods Through experimental study on a solid oxide fuel cell (SOFC) short stack, we explore the potential use of electrochemical impedance spectroscopy (EIS) for in-operando diagnosis. We identify the mechanisms contributing to this system EIS, by carrying out pristine cell/stack tests at different operating conditions (gas partial pressure, current, temperature).We collect experimental data on a 6-cell short-stack with active area of 80 cm2 per cell. Each anode-supported cell features a Ni-YSZ fuel electrode (240 μm), a Sr-doped LaMnO3 (LSM) oxygen electrode (40 μm) and an 8 mol% Y2O3 stabilized Zirconia (YSZ) electrolyte (8 μm). In our experimental setup, the first (reference electrode, i.e., cathode of cell no.1) and last (i.e., anode of cell no.6) electrodes are connected to the counter and working electrode leads of the potentiostat, respectively. This allows connecting the diagnostic system in parallel with the load and the stack, while performing floating ground galvanodynamic EIS measurements. This configuration enables the load to impose the operating current of the stack, while the potentiostat modulates the signal without any current in its main circuit. Reference and working sensing connections to individual cells in the stack are independent on the potentiostat leads.We operate the stack with mixtures of hydrogen, nitrogen and steam at the fuel electrode and mixtures of oxygen and nitrogen/helium at the oxygen electrode. We control the operating temperature via an electric furnace, while monitoring the stack temperatures with a set of six thermocouples, as reported in [2]. Discussion Figure 1 compares the measured EIS spectra for each cell in the short stack at beginning of life and after a major degrading event. With continuous stack monitoring, we are able to identify how degradation phenomena differently impact the state of health of the cells during the stack normal operation. This allows identifying the most degrading operating conditions of the system in real-time, hence informing the operational planning and lifetime maximization strategies of the system. Conclusions Preliminary results suggest that our methodology can provide meaningful insights regarding the cause and nature of the physical processes at the origin of degradation phenomena in solid oxide cells. This process is particularly interesting as a non-disruptive diagnostic and prognostic tool for commercial scale systems that need to optimize their operating conditions to either maximize their lifetime or meet a performance target at end-of-life.Figure 1 – (left) Beginning of life and (right) degraded cell plot comparison of experimental EIS for a 6-cell short stack at 1 A. Tstack=750°C, Anode flow=1.2 Nl min-1 (N2/H2=50/50%), Cathode flow=18.9 Nl min-1 (Air)[1] A. Baldinelli, L. Barelli, G. Bidini, A. Di Cicco, R. Gunnella, M. Minicucci, A. Trapananti, 2019, p. 020012.[2] L. Mastropasqua, S. Campanari, J. Brouwer, J. Power Sources 2017, 371, 225–237. Figure 1

Biomass gasification using mixtures of air, saturated steam, and oxygen in a two-stage downdraft gasifier. Assessment using a CFD modeling approach

This work proposes and employs a mixed-complexity modeling approach to creating a 3D computational fluid dynamics (CFD) model to predict the syngas production from Miscanthus briquettes in a two-stage downdraft gasifier operating with different gasification fluids. The study was performed at steady state regime in the Ansys Fluent environment considering the non-premixed combustion model. A probability density function is also included as a tool for the description of the chemical kinetics to predict the syngas composition following the main chemical reactions involved in the gasification process. The goal of this approach is to reduce the computational cost while still providing accurate predictions. In comparison to experimental gasification with air, the model correctly predicts the temperature profile inside the reactor, the composition of the syngas (CO, H2 and CH4), and therefore the lower heating value (LHV). For cases involving the use of saturated steam and oxygen as gasification fluids, the model predicted key species concentrations in the gasification zone and the reactor core and accurately described the significant increase in the LHV of the syngas. This approach opens the possibility of studying the gasification process in moving-bed reactors using different gasification fluids and feedstocks based on their elemental and proximate analysis.

Equilibrium Simulations of Coal Gasification – Factors Affecting Syngas Composition

Purpose Coal gasification is complex technology, which results depend on many variables, connected among others with fuel, the converting agent and the process itself. The paper aims to analyze, by means of simulations, the influence of the following factors – temperature, pressure, characteristic parameters of coal and gasifying agent, on the composition and heating value of the obtained syngas. The other aim of this paper is the determination of gasification efficiency (based on the definition of cold gas efficiency) for various process conditions. Methods Computer simulations were used as the research method for the work presented. An equilibrium model, based on the stoichiometric method with four independent reactions, was formulated and used in this paper. This model was implemented in Mathematica software. The influence of temperature (in a range from 500 to 1500°C), pressure (changed from atmospheric to 35 atm), three types of gasifying agent (mixtures of air, pure oxygen and steam) and the composition of four Polish coals (lignite and three hard-coals) on syngas parameters were analyzed in this paper. Results Concentrations of CO2, CO, CH4, H2O, H2, N2 in the equilibrium syngas, for the chosen temperature, pressure and parameters of the fuel and converting agent were the results of the simulations carried out. Subsequently, the lower heating value and process efficiency for each syngas composition was calculated. Practical implications: The simulations indicated the thermodynamic limits of gasification and allowed for the formulation of the general principles ruling this process. Results presented in this paper may be useful in the preliminary optimization and analysis of coal gasification. They also can be a point of reference for more advanced simulations. Originality/value This paper presents own results obtained from equilibrium simulations of coal gasification. The author implemented a mathematical model, based on the method of Deringer and Traustel, presented earlier in literature, to carry out the calculations.

PdAu and PdAuAg composite membranes with reduced film thickness using YSZ as a stainless-steel support modifier

PdAu and PdAuAg alloy membranes were synthesized on top of YSZ-modified planar porous stainless steel supports by electroless deposition. A uniform, continuous and smooth coverage was observed after three YSZ deposition calcination cycles, with neither uncovered zones nor detachment after calcination at 673 K. Through this modification procedure, we could obtain thinner and more robust PdAu and PdAuAg alloy membranes. These membranes showed higher hydrogen permeance during the evaluations (623–723 K) and high thermal stability during the long-term stability test. The PdAu and PdAuAg membranes exhibited a good performance during the exposure to CO/H2O steam mixture. Contrary to the PdAu membrane, where no significant change on the atomic surface composition was observed, silver segregation was evidenced on the PdAuAg membrane after exposure to CO/H2O steam mixture.

Mathematical model of the energy consumption calculation during the pine sawn wood (Pinus sylvestris L.) drying process

The article presents a modification of the existing mathematical model to calculate energy consumption during conventional drying process. Apart from energy consumption, the model permits to estimate the time of high-temperature drying process. The drying medium is air and superheated steam mixture. The obtained calculation results were compared with conducted experimental tests of drying square-edged sawn sapwood timber (Pinus sylvestris L.). The pine sawn wood samples were dried according to three different drying modes, namely mild, normal and intense. The experiments were performed in a semi-industrial scale drying chamber. On the basis of the experimental research available, existing mathematical models of drying wood have been improved. The developed model included the following changes: a different drying time for each mode and type of drying medium (moisturized air or air and superheated steam mixture). The use of an intensive drying mode significantly reduced the drying process time. The developed mathematical model revealed that the energy consumption of the drying process increases with the intensity of the mode used.

Regime Design for Gold Ore Flotation by Air and Steam Mixture

Regime Design for Gold Ore Flotation by Air and Steam Mixture

Exergy and exergoeconomic analysis of hydrogen and power cogeneration using an HTR plant

This paper proposes using sodium-cooled fast reactor technologies for use in hydrogen vapor methane (SMR) modification. Using three independent energy rings in the Russian BN-600 fast reactor, steam is generated in one of the steam-generating cycles with a pressure of 13.1 MPa and a temperature of 505 °C. The reactor's second energy cycles can increase the gas-steam mixture's temperature to the required amount for efficient correction. The 620 ton/hr 540 °C steam generated in this cycle is sufficient to supply a high-temperature synthesis current source (700 °C), which raises the steam-gas mixture's temperature in the reactor. The proposed technology provides a high rate of hydrogen production (approximately 144.5 ton/hr of standard H2), also up to 25% of the original natural gas, in line with existing SMR technology for preparing and heating steam and gas mixtures will be saved. Also, exergy analysis results show that the plant's efficiency reaches 78.5% using HTR heat for combined hydrogen and power generation.

INVESTIGATION OF EVAPORATION AND CONDENSATION PROCESS OF INDUCED FLOW USING STEAM EJECTOR

The research aims to understand the design parameters of steam ejector nozzle on the performance of flash evaporation induced by the effect of a steam jet passing through it. The research concentrates on studying the effect of ejector nozzle outlet diameter on induced flow from preheated water in a specified evaporator using a subsonic ejector. The thermal energy extracted from the condensed steam mixture in the condenser is used to heat the water in the evaporator. The experimental tests investigate the effect of nozzle geometry on the induced evaporation process by changing nozzle outlet diameter while keeping the pressure of evaporator, condenser and primary steam constant. The experimental results proved that both primary and secondary steam mass flow rates increase versus nozzle outlet diameter, while the entrainment ratio of secondary to primary steam flow rates decreases due to the restricted increase of the secondary steam mass flow rate. The mathematical model prepared to simulate the behaviour of the subsonic ejector is validated using the comparison between experimental and theoretical results. The mathematical model showed that maximum entrainment of 0.57 is obtained at a primary steam pressure of 2 bars when the nozzle outlet diameter is fixed at 1.5 mm, while minimum entrainment ratio of 0.17 is estimated at 1.5 bar pressure related to primary steam when the nozzle outlet diameter is fixed at 2.5mm. The authors recommend defining nozzle geometrical parameters according to the operating conditions of the experimental test rig to enhance ejector efficiency.

Enhanced Coke Gasification Activity of the Mn1.5Cr1.5O4 Spinel Catalyst during Coking in Ethylene–Steam Mixtures

Mn–Cr–O spinel catalysts (MnCr2O4 and Mn1.5Cr1.5O4) and single oxides of Mn and Cr are coked under ethylene and ethylene–steam mixtures to simulate reaction conditions occurring in steam cracker fu...

Comprehensive study on hydrogen production via propane steam reforming inside a reactor

In the proton exchange membrane fuel cells, the required hydrogen must be produced in some way. The power generators in the path of these fuel cells generally include a steam reactor that, through other fuels, provides the needed energy to produce hydrogen. This study investigates a steam reactor powered by propane fuel consisting of a shell and tube heat exchanger. The shell contains a catalyst that receives the mixture of propane and steam, and the tubes embedded inside the reformer contain hot gases that provide a suitable substrate for the reaction. Velocity and temperature fields inside the reformer, species concentration control, and reaction rate are studied. The conversion of reactants and yield of products are investigated according to the reaction rate. The results show that the hydrogen production yield can vary from 77.5 % to 92.2 %. The reaction rate can be controlled by the velocity and temperatures of the hot gases. However, for the T=900 K, full propane consumption is achieved at the reformer outlet.

A linear cascade tunnel for flow investigations of steam turbine rotor tip blades in subsonic nucleating flows

The paper presents details of a unique experimental facility along with necessary accessories and instrumentation for testing steam turbine cascade blades in wet and nucleating steam. A steam turbine rotor tip cascade is chosen for flow investigations. Cascade inlet flow measurements show uniform conditions with dry air and steam and dry air mixture of different ratios. Exit flow surveys indicate that excellent flow periodicity is obtained. Blade surface static pressure and exit total pressure distributions are also presented with dry air and with steam and dry air mixture of different ratios as the working medium at an exit Mach number of 0.52.

Effect of reactant types (steam, CO 2 and steam + CO 2 ) on the gasification performance of coal using entrained flow gasifier

This study investigates the gasification behaviour of bituminous coal using different reactants of CO2, steam and a mixture of CO2 and steam under entrained flow gasification conditions at temperatures of 1000°C and 1200°C with atmospheric pressure. The major gas constituents of the syngas were measured using online micro-GC with a model number Varian 490, whereas the minor pollutant gases were analysed using Kitagawa gas detection tubes. A maximum carbon conversion of 86% was achieved under steam gasification at a temperature of 1200°C compared to 74% from CO2 gasification. The higher carbon conversion from steam gasification is due to the higher gasification reactivity than CO2 gasification. At 1000°C, the lower heating value (LHV) from steam gasification was determined to be 60%, 70% and 80% higher than that of CO2 gasification using the reactant concentrations of 10, 20 and 40 vol.%, respectively. Using a stoichiometric 50/50 ratio of CO2 and steam, the yield of H2, CO and CH4 were increased by 56%, 106% and 35% compared to that of pure CO2 gasification. At 1000°C, the LHV under mixed reactant condition is close to the LHV from the pure steam gasification at 1200°C. In steam gasification, increasing the temperature by 200°C from 1000°C decreases the LHV by 17 and 10% using 10 and 20 vol.% steam. The higher heating value from steam gasification is due to the H2 and CH4-rich syngas compared to CO-rich syngas in CO2 gasification. The BET surface area of the solid char from steam gasification is about 17 and two times higher than that of CO2 gasification at 1000°C and 1200°C, respectively.

Investigation of Flashing Flow in a Siphon to Extract Condensate in Paper Dryer Application

Abstract The paper industry uses steam to dry paper web through cylinder dryers. As steam condenses inside the dryer, the condensate is removed by means of either a stationary or a rotary siphon. However, during the siphoning process for transporting the condensate, flashing of the condensate occurs, which could cause backflow or discontinuity in the siphoning process. To resolve this flashing issue, two approaches have been employed: (a) increasing the amount of steam supplied to the cylinder to “blow-through” the stalled condensate–steam mixture and (b) reducing the back pressure by inducing “suction” through a thermocompressor from downstream. The objective of this study is to investigate and improve understanding of the flashing phenomena during condensate transport through the siphon and piping system in order to develop means to reduce the excessive steam consumption during the paper drying process. A computational fluid dynamics (CFD) simulation is performed that uses the Eulerian–Eulerian multiphase method. The steady-state case is first solved to obtain the flow field without flashing. Then, the transient method is initiated by employing evaporation and condensation model. The results show that reduction of local pressure triggers flashing; however, flashing in turn reduces local temperature and subsequently induces condensation, resulting in an alternating flashing and condensation behavior. To maintain continuity of the siphon flow, the inlet pressure fluctuates corresponding to the variation of total vapor volume ratio inside the siphon. The results will be used to modify the current siphon system design and operating practices to reduce the steam consumption.

Aero Engine Concepts Beyond 2030: Part 1—The Steam Injecting and Recovering Aero Engine

Abstract Recognizing the attention currently devoted to the environmental impact of aviation, this three-part publication series introduces two new aircraft propulsion concepts for the timeframe beyond 2030. This first part focuses on the steam injecting and recovering aero engine (SIRA) concept. Exhaust heat generated steam is injected into the combustion chamber. By use of a condenser, installed behind the steam generator, the water is recovered from the exhaust gas–steam mixture. Both lead to a noticeable increase in specific power compared to a conventional gas turbine and, foremost, to a significant increase in thermodynamic efficiency. The proposed concept is expected to reduce fuel burn and carbon dioxide (CO2) emissions by about 15% and nitrogen oxides (NOx) formation can be almost completely avoided compared to state-of-the-art engines of the same technology level. Moreover, the described concept has the potential to drastically reduce or even avoid the formation of condensation trails. Thus, the SIRA concept operated with sustainable aviation fuels offers the potential for climate-neutral aviation. Based on consistent thermodynamic descriptions, preliminary designs and initial performance studies, the potentials of the concepts are analyzed. Complementarily, a detailed discussion on concrete engineering solutions considers the implementation into aircraft. Finally, the impact on emissions is outlined.

Design and computational fluid dynamics analysis of the last stage of innovative gas-steam turbine

Research regarding blade design and analysis of flow has been attracting interest for over a century. Meanwhile new concepts and design approaches were created and improved. Advancements in information technologies allowed to introduce computational fluid dynamics and computational flow mechanics. Currently a combination of mentioned methods is used for the design of turbine blades. These methods enabled us to improve flow efficiency and strength of turbine blades. This paper relates to a new type turbine which is in the phase of theoretical analysis, because the working fluid is a mixture of steam and gas generated in a wet combustion chamber. The main aim of this paper is to design and analyze the flow characteristics of the last stage of gas-steam turbine. When creating the spatial model, the atlas of profiles of reaction turbine steps was used. Results of computational fluid dynamics simulations of twisting of the last stage are presented. Blades geometry and the computational mesh are also presented. Velocity vectors, for selected dividing sections that the velocity along the pitch diameter varies greatly. The blade has the shape of its cross-section similar to action type blades near the root and to reaction type blades near the tip. Velocity fields and pressure fields show the flow characteristics of the last stage of gas-steam turbine. The net efficiency of the cycle is equal to 52.61%.

Study of a gas turbine unit energy efficiency

The method of the gas turbine unit and the waste heat boiler gas-air duct circuit modernization is considered. The operation scheme of a gas turbine unit and a waste heat boiler with the use of a catalytic afterburner has been shown. There is also a decrease in nitrogen and carbon oxides in the exhaust steam-and-gas mixture due to a deeper cleaning process of the exhaust steam and gas mixture, which leads to an increase in the service life of the waste heat boiler [1]. A more complete process of heat transfer to the coolant in the furnace section of the boiler is performed due to the cleaner steam and gas mixture in the waste heat boiler and due to a decrease in the boiler tubes growth formation by the combustion products. This makes it possible to reduce the cost of fuel consumption by gas burners of the waste heat boiler. Also, as a result of this process, it is possible to reduce fuel consumption for the needs of heating the feed water and the auxiliary needs of a power unit. This article proposes to use lattice devices in the afterburner, treated with active substances by the ion implantation method, as one of the most promising ways of modifying lattice surfaces [2 – 6]. These processes occurring when the steam-and-gas mixture passes through the afterburner, allow increasing the cycle efficiency factor and limit of maximum allowable concentrations (MAC) emissions for various options for the exhaust steam-and-gas mixture utilization of a gas turbine unit (GTU) and heat supply to the waste heat boiler.

Regime Design for Gold Ore Flotation by Air and Steam Mixture

Regime Design for Gold Ore Flotation by Air and Steam Mixture

High efficiency steam-gas mixture condenser

The process of development of steam condenser for steam-gas mixture has been described. The construction is based on idea to maintain a constant steam-gas mixture speed along the steam condensation channel. The shape of the channel with constant speed is described. To research the heat-mass transfer of gas- steam mixture the test plant with tubes dissected by thermocouples, have been realized. In the process of testing there where changes of gas- steam mixture speed, pressure and air concentration from 0% to 18%. The experimental results have been summarized by dimensionless equation. The pressure drop and increase of air concentration also contributes to the decrease in a saturation temperature. So there Is optimal speed when the surface area of channel in condenser will be minimal. The optimal speed value is about 30 – 50 m/s. The research results are implemented in the experimental model of high-efficiency condenser. The heat transfer coefficient in this model is equal about 4500 – 2700 W/(m2K), if the air concentration at inlet is 0–8 %. The design of high-efficiency condenser for gas-steam turbine plant 25 MW capacity and condenser with vertical tubes have been presented.

Heat transfer calculation under film and drop condensation on tube with heat intensifiers

This article discusses well-known models and equations for calculating the heat transfer gain during film and drop condensation on a pipe, which need to be improved. Film condensation heat transfer on horizontal pipe made from brass with knurling is analyzed. The heat transfer data for investigated steam mixture condensation on horizontal tube with spikes heat intensifiers is analyzed. It is noted that the functions of drop growth for various conditions and their distribution must be known for calculating heat transfer during drop condensation. The maximum droplet radius, droplet size distribution, and then condensation heat transfer performance could be adjusted with special condensing surfaces, such as gradient, superhydrophobic, grooved, hydrophobic-hydrophilic patterned and hybrid surfaces. Now the nanoscale structures can by nanotechnologies.