Pure Steam Research Articles

Effect of surface conditions and alloying elements on the early oxidation behaviour of two austenitic alloys in the pure steam environment

The early oxidation behaviour of 347 SS and Alloy 800H with various surface preparation methods, including grinding, mechanical polishing (M−polishing), and electropolishing (E−polishing), were investigated in 650 °C pure steam. For the ground specimens, a protective Cr-rich oxide layer was formed at the M/O interface and lowered the oxidation rate owing to the presence of a nano-crystalline subsurface layer which provided the fast Cr outward diffusion path. On the other hand, M− and E−polished specimens showed significant spallation for 347 SS, while larger weight gain for 800H. Low Cr in 347 SS resulted in the formation of Fe2O3 nodules due to easier Cr2O3 degradation for ground specimen and the absence of Cr-rich oxide at the internal oxidation zone (IOZ)/matrix interface for M− and E−polished specimens. Higher Cr in 800H contributed to duplex Cr2O3 for ground specimen and Cr-rich oxide at IOZ/matrix interface for M− and E−polished specimens. Higher Ni in 800H enhanced Cr outward diffusion and Cr activity at the M/O interface, which improved the oxidation resistance. Low Al content in Alloy 800H showed no positive effect on oxidation resistance due to the Al internal intergranular oxidation.

Marangoni condensation of steam-ethanol mixtures on a horizontal smooth tube

Experiments were conducted to measure condensation heat transfer of steam-ethanol mixtures on a horizontal smooth tube. Heat flux and vapor-to-surface temperature difference were accurately measured over a wide range of mass concentration of ethanol (0.001%, 0.005%, 0.01%, 0.025%, 0.05%, 0.1%, 0.5% and 1.0%.) at atmospheric pressure. The present work extends earlier data of Murase et al. (2007) and Ali et al. (2013) to lower mass concentration of ethanol and higher vapor-to-surface temperature difference. Visual observations, the appearance of condensate, show the condensation modes and their transitions of pseudo-dropwise, rivulets and filmwise. Heat flux and heat-transfer coefficient are found to increase, reach to a peak and decrease as vapor-to-surface temperature difference increases for all mass concentrations of ethanol and vapor velocities. The maximum heat-transfer coefficients appear in the range of mass concentration of ethanol from 0.01% to 0.025%. The highest heat-transfer coefficient values are 112.4 kW/m2 K and 93.9 kW/m2 K at ΔT = 3.43 K and 4.46 K, respectively. The maximum enhancement ratio of 5.5 is achieved at vapor-to-surface temperature difference of 4 K and mass concentration of ethanol 0.01%. The results also show that heat-transfer coefficient of filmwise eventually approaches to a value slightly higher than that of pure steam.

Hydrogen-rich syngas production from biomass in a steam microwave-induced plasma gasification reactor

Substitution of fossil fuels by sustainable practices must be rapidly implemented to mitigate the impacts of climate change. The conversion of biomass into combustible gas is investigated in a microwave-induced plasma reactor using pure steam as the plasma working gas for the first time. The optimum results are achieved at the highest forward microwave power of 6 kW with biomass carbon conversion efficiency over 98% and complete biomass energy recovery in syngas. Unreacted steam is simply condensed out, leading to the production of a syngas with low inert dilution and high calorific value in the range 10.5–12 MJ/Nm3. The syngas produced is rich in hydrogen, exceeding 60% by volume. The proposed process could aid in the transition to a carbon neutral economy as it has the potential to efficiently convert biomass to syngas that can be used for the sustainable generation of fuels, chemicals and energy.

Effect of the effects of different doses of mineral fertilizers on the number of ecological-trophic groups of microorganisms

The results of studies on the effect of mineral fertilizers on the number of ecological and trophic groups of microorganisms and the yield of winter wheat in the zone of unstable moisture in the Stavropol Territory are presented. The soil of the experimental site is ordinary chernozem, a powerful low-humus heavy-loam, the precursor is pure steam. Mineral fertilizers have been applied in various doses for 30 years, and the aftereffect of fertilizers has been studied since 2006. The total number of microorganisms in the aftereffect of nitrogen or phosphorus fertilizers alone was low (5.53–8.0 mln columnforming units). The number of microorganisms that transform organic forms of nitrogen in the aftereffect of nitrogen or phosphorus nutrition alone ranged from 2.62 to 4.16 mln column-forming units, and using mineral forms of nitrogen from 2.91 to 4.32 mln column-forming units. The full dose of fertilizers significantly increased the number of microorganisms that transform nitrogen compounds in the soil by an average of 15.5 mln column-forming units. The maximum total number of microorganisms was obtained in the aftereffect of high doses of nitrogen against the background of P 120 K 120 and phosphorus together with N 120 K 120 — 28.58 mln column-forming units and 30.21 mln column-forming units, respectively. The coefficient of mineralization in the studied soils is greater than one. With the unilateral introduction of nutrients in the soil, the intensity of microbiological processes decreases, сoefficient of microbiological transformation of organic matter — 3,94–8,64.

Vapor condensation with low air mass fraction inside water seal branch tube under free convection

The pressure vessel has used a newly designed water seal structure, and the sealed water is from condensation at low hydrogen concentration. To get the condensation capacity of the water seal branch tube under the pressure vessel normal operation, the experimental loop named WASETEL was constructed, which is aimed at studying the heat transfer during the process of air-steam mixture condensation inside the inclined branch tube at the condition of low air mass fraction. The inner tube is diameter 0.134 m with length 0.68 m which is connected with diameter 1.4 m, high 2.5 m pressure vessel. A canon camera was set to record the images and videos of the condensate height through glass tube in communicating vessel liquidometer. The experiment was conducted under the pressure ranged from 0.2 to 0.6 MPa, air mass concentration ranged from 0.49 to 6.42% and wall subcooling ranged from 11 to 40 K. The test showed HTC (heat transfer coefficient) would sharply deteriorate with the small air fraction, compared with pure steam condensation, about 0.49% mass fraction of the air will reduce heat transfer coefficient by 70–80%. When air concentration is relatively small, those widely used relations can not predict the condensation well, therefore, a new heat transfer empirical correlation with air mass fraction, pressure and subcooling is proposed, covered all the experimental data within the error band ±13%.

К вопросу о диагностике и защите почв от дефляции в Ставропольском крае

Abstract. The research aim is to assess the degree of deflation when comparing traditional crop cultivation technology using soil treatment and no-till. Object of research is located on the territory of the Ipatovsky district of the Stavropol territory, where the method of evaluating the deflation of ordinary chernozems (WRB 2006 Voronic Chernozems Pachic) by morphometric indicators and properties of the soil profile has been tested on the example of 2 farms using different technologies. Methods. In this research, a morphometric method for estimating deflation was used, based on measuring the capacity of the humus horizon of soils based on data from manual drilling of wells fixed by GPS in 5-fold repetition. Results and practical significance. The obtained data revealed a decrease in the capacity of the humus horizon in the treated soils (on average by 19-21 cm) compared to the soils of the farm that has been using no-till technology for the past 13 years. The forest belt serves as a buffer zone, it accumulates the dusty material of chernozems carried out during deflation with a capacity of up to 40-50 cm. Deflation of arable soils is caused by cultivation and use of pure steam in crop rotations (every third year). It leads to the transformation of the soil profile as a whole, changing the species composition of chernozems by one gradation from medium and carbonate (no-till) to low-power and high-carbon (traditional technology). The reduction or cessation of deflation of chernozems in the no-till technology is associated with its anti-deflation feature – the distribution of crop residues on the soil surface, the refusal to use pure steam, which together leads to the restoration of degraded properties of chernozems. Scientific innovation consists in testing a field morphometric method for estimating deflation in time and space, which can be used for monitoring soil cover (soil mapping, agrochemical surveys, etc.) or targeted research.

Bioinspired Hydrophilic-Hydrophobic Janus Composites for Highly Efficient Solar Steam Generation.

Solar energy has received extensive attention as a renewable and sufficient energy source. Herein, inspired by the Janus wettability of lotus leaves, we have constructed a bioinspired hydrophilic-hydrophobic Janus hybrid system of carbonized carrot powder (CC powder)-modified cotton cloth with Nafion coating on one side (cotton cloth-NCC) for highly efficient solar steam generation. In cotton cloth-NCC, CC powder functions as a light absorber to achieve high light absorption, whereas the hydrophilic cotton cloth ensures efficient water transport. Meanwhile, the coating of Nafion establishes a hydrophobic-hydrophilic Janus structure, which can not only modulate water supply but also prevent salt deposition even with the high-concentration salt solution. The cotton cloth-NCC has been further shaped into a waved structure (w-cotton cloth-NCC) to increase the water evaporation area and achieve high light absorption (95%). Under 1 sun irradiation, w-cotton cloth-NCC yields a pure water steam generation rate of 1.88 kg m-2 h-1 and a seawater evaporation rate of 1.52 kg m-2 h-1. Furthermore, the w-cotton cloth-NCC also has a good purification effect on sewage: Escherichia coli can be completely removed, and the removal rate of Rhodamine B reaches 98.3%. The simple approach presented here for the construction of a high-efficient, low-cost, environmentally sustainable, long-term stable hydrophobic-hydrophilic Janus solar steam evaporator holds great promise for application in both environmental purification and photothermal conversion.

Experimental research on steam condensation in presence of non-condensable gas under high pressure

With a great level of safety and reliability, an integrated steam-gas pressurizer is applied in the NHR-200 reactor. This work provided a solid experimental database regarding the pure steam, steam-Nitrogen and steam-Argon condensation under high pressure, which could be used to support the thermohydraulic analysis in steam-gas pressurizers of small modular reactor. The pressure ranged from 0.21 to 4.12 MPa. Benchmark experiments with pure steam found that the condensation heat transfer coefficient increased with pressure, but the response characteristics to specific pressure ranges were inconsistent. As is the case at low pressures, the introduction of non-condensable gas would weaken the steam condensation heat transfer. In particular, under high pressure, the effects of pressure on steam condensation depends highly on the species of non-condensable gas. A significant increase of 92.1% in condensation heat transfer coefficient of steam with 10% Ar was obtained as the pressure increased from 1.76 to 3.12 MPa.

Analysis of potential energy and environmental impact from coal gasification through simulation of plasma gasification process of Indonesian low-rank coal

Indonesia's coal reserve is abundant with its lower price and widely distributed than oil and natural gas. However, the coal emits high carbon dioxide gas (CO2) and sulfur compounds (H2S, SOx) to the environment during utilization. Plasma gasification can overcome those lacks using the external electric energy through a plasma torch. The chemical properties of coal have impacts on the energy content and environmental benchmarking. Using steam as a gasifying agent should be adequate to produce H2 and CO syngas. A research has been carried out to analyze and understand the benefit of using different gasifying agent for maximizing the H2 production and minimizing the environmental impact. Pure Steam (PS) gasifying agent to coal ratio of 0.4 has shown 43.76% H2 composition in syngas and cold gasification efficiency (CGE) with 37.71%. The PS to coal ratio of 0.2 has a significant carbon conversion efficiency of 4.75% and the PS to coal ratio of 0.6 has a gross energy potential of 86.5 kW. Using such the PS is significantly better than the mixture of steam oxygen (SO) as the gasifying agent since it needs to have a greater SO flow rate to have the SO to coal ratio of 1.00.

Crop rotation yield depending on from the receptions of biologization

Among the methods of cultivation that increase the productivity of crops, a prominent role is assigned to crop rotation. In a properly constructed crop rotation, the efficiency of all agrotechnical methods aimed at improving the use of land increases, the biological needs of crops are satisfied, the rational use of technology is achieved, and the cost of production is reduced [1]. The soils are low in nitrogen, medium in phosphorus and high in potassium. The humus content is 1.2–2.0%, pH = 7–8. Studies have shown that green manure (sweet clover, oats, phacelia) have a positive effect on the balance of organic matter. The negative balance of organic matter is noted for pure steam. The stock of productive moisture in the 0–0.3 cm soil layer varied from 4.1 to 29.5 mm for winter wheat, 28.1–32.7 mm for chickpea and 28–35.3 mm for spring barley, depending on the weather conditions. conditions and methods of biologization. On average, over three years, the highest yield was in winter wheat for a busy fallow (phacelia) and amounted to 1.0 t/ha, which depended on weather conditions. A reliable correlation was revealed for the factors of yield-precipitation; temperature; batteries, etc.

Material selection and design of shell and tube heat exchanger for thermos-syphon steam generator

Pure steam generated by conventional boiler is not devoid of chemical additives, rust or other undesirable materials and fails to meet essential quality of steam needed for pharmaceutical and health care process industries for WFI(Water for Injection), sterilization of medical equipment and clean room humidification on account of the limitations in achieving desired standards needed by the qualities of ideal pure steam such as pH value, conductivity, bacteria count etc. as prescribed by the International Society of Pharmaceutical Engineers (ISPE). Dry and pure steam is produced by ‘pure steam generators’ using purification process of the plant steam and doesn’t contain any liquid droplets, any anti scaling additives and corrosion inhibitors. - Thermo siphon type Pure Steam Generator has been chosen in the present project for its extremely good heat transfer performance at low temperature differences, less sensitivity to large changes in process condition and more stable operation. In this paper design of the heat exchanger for generation of pure steam has been discussed. Here shell and tube type heat exchanger has been selected due to its flexibility of design, which allows wide range of pressures and temperatures. Standards laid out in ASME BPE for selection of material, CGMP and TEMA for design and manufacturing methods are followed for efficient and safe steam generation. Parameters given by the industry to meet customers’ requirements have been considered while designing the HE, its accessories, piping, valves and instruments. Thermal design of the two phase shell and tube heat exchanger has been done manually and validated using HTRI suite. The mean % error between HTRI results and manual results is 12.05%.

Hierarchical microcavity topography for enhancement of water vapor condensation heat transfer by regulating droplet dynamics and droplet size distribution

Manipulating droplet dynamics is of great importance in condensation heat transfer enhancement. Cavity topography was believed to be able to regulate droplet merging and self-removal via Laplace force imbalance by the cavity wall and the effect of spatial confinement and isolation. However, the size effect of the microcavity on the droplet dynamics behavior, droplet size distribution and condensation heat transfer performance are not sufficiently understood. In this paper, hierarchical microcavity-arrayed superhydrophobic surfaces with a nominal cavity diameter of 20, 35, 50 and 70 μm were fabricated. Condensation experiments were first carried out in the atmosphere under an optical microscope, and then in pure steam in a self-designed environmental chamber at 4000 Pa. Local dynamic behaviors and time-lapsed evolutions of droplets during condensation were observed. Droplet size distribution and jumping rate were statistically analyzed using ImageJ software. It was proved the smaller cavity size of 20 μm is beneficial to facilitate condensate droplet jumping and increase the density of small droplets. The surface coverage ratio on the microcavity-arrayed superhydrophobic surfaces was only half of that on the hydrophobic surface at steady state. Enhancement of pure steam condensation heat transfer can be realized by effectively regulating droplet dynamics using microcavity topographies at limited subcooling degrees.

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.

Thermochemical Conversion of Coal and Coal-Biomass Blends in an Autothermal Moving Bed Gasifier: Experimental Investigation

A unique laboratory scale auto-thermal moving bed gasifier was designed for studying the thermochemical conversion of coal-biomass blends. For this purpose, two coals (lignite and sub-bituminous), two biomass materials (corn stover and switchgrass), and their respective blends were used. Gasification characteristics of the fuels were evaluated with an emphasis on improving the producer gas composition. The efficiency and product gas compositions reveal that utilizing the inner stainless-steel tubing better promotes heat transfer upwards in the axial direction when compared to utilizing quartz insulation. The H2/CO ratio at the same operating conditions is much higher due to the increase in bed temperature and heat transfer upwards in the axial direction. This improved the overall efficiency by at least 20%. Using pure oxygen and steam, efficiency greater than 50% was obtained for blends with corn stover at steam to oxygen ratio of 2:1. Also, using air as the gasifying agent greatly improved the H2/CO ratios and overall efficiency in blends with corn stover. In contrast, blends with switchgrass were not very effective with respect to the overall gasification characteristics. Blending switchgrass with coal may not be viable option from the viewpoint of generating high quality producer gas for downstream operations.

ЭФФЕКТИВНОСТЬ БИОМОДИФИЦИРОВАННЫХ МИНЕРАЛЬНЫХ УДОБРЕНИЙ ПРИ ВОЗДЕЛЫВАНИИ СЕЛЬСКОХОЗЯЙСТВЕННЫХ КУЛЬТУР НА ЧЕРНОЗЕМАХ ЛЕСОСТЕПИ ПОВОЛЖЬЯ

Research on the effectiveness biomodified mineral fertilizers were carried out on the basis of Ulyanovsk SRIA – SamSC RAS branch during the rotation grain fallow five fields crop rotation: pure steam – winter wheat – spring wheat – barley – oats in 2013-2018. The field experiment scheme included options (except control): with the introduction of biologics BisolbiFit (introduction with seeds that were treated before sowing), azofoski N15P15K15, in pure form, modified with biopreparation azofoski in the same dose N15P15K15, half a dose of modified azofoski (N7, 5 P7, 5 K7, 5). The effectiveness of fertilizers and biopreparations in crop cultivation was studied on three backgrounds: natural (control), ammonium nitrate at a dose of 40 kg ai/ha (NH4NO3), and modified ammonium nitrate at a dose of 20 kg DW/ha. It was established that modification of azofoski with Bisolbifit biopreparation can significantly increase the coefficients of use of elements from it by plants. The latter allows to reduce the dose of fertilizer, without reducing the productivity of cultivated crops, twice. Long-term cultivation of crops using only mineral fertilizers and biological products led to a relative decrease in the humus content in the soil and its acidification. For 6 years, the content of humus in the arable layer of leached chernozem decreased by 0.12 %, and the acidity of the soil solution increased by 0.5 pHKCI units. In the conditions of the Volga forest-steppe, when cultivated on chernozems, the highest-yielding winter wheat is (up to 4.00 t / ha or more, in our experiments 3.88-4.80 t / ha). The average yield of spring wheat was 2.68-3.31 t / ha, spring barley 2.67-3.21 t / ha, oats 2.15-2.71 t / ha. The highest productivity of crop rotation was observed against a background with modified ammonium nitrate at a dose of 20 kg ai/ha (½NH4NO3) when applying modified azofoski (N15P15K15). Grain harvest for 2013-2018 in this variant was 13.36 t / ha, exceeding the control variant on this background by 1.31 t / ha.

Cross verification of a simplified model of pure steam condensation in a tube bundle using experimental and CFD-simulation data

This paper presents an analysis of a simplified model of pure steam condensation in a bundle of smooth horizontal tubes. The model was based on classical recommendations for calculating the condensation process in tube bundles. Two different approaches were used to calculate the condensation heat transfer coefficient in the model. First, the inundation effect was not considered, and the average heat transfer coefficient was calculated for condensation on a single cylinder using the Nusselt equation. Second, condensation drainage which is asymmetric to the vertical diameter of the tube was considered. The results of these calculations were verified using available experimental data. The analysis of distributions of condensation local characteristics was presented. The results of detailed CFD simulation using a previously developed author’s model was employed for additional cross-verification of closing equations used in the simplified model.

Experimental study of heat transfer processes during the operation of WWER steam generator in emergency mode on a single-tube model

The paper presents the results of experimental research of the heat transfer processes during the operation of a WWER steam generator in emergency condensation mode. The experiments are carried out at a research facility with a test section in the form of a single-tube model of a steam generator. The geometric characteristics of the tube and the main research parameters, such as temperature and pressure, are similar to the real steam generator. Several stages of research are planned: with pure water steam, with a fixed concentration of boiling boric acid and with a variable concentration of acid in the solution. The results of the first series of experiments performed on pure water steam are presented. As a result of research, the heat flux density is determined, and the values of the heat transfer coefficient during steam condensation in a single horizontal tube are calculated.

Solution‐processed graphene oxide coatings for enhanced heat transfer during dropwise condensation of steam

AbstractHydrophobic coatings have the ability to promote dropwise condensation on metal surfaces. In this work, reduced graphene oxide coatings are fabricated by dip coating copper substrates into a graphene oxide colloidal suspension, followed by thermal reduction. The formation of reduced graphene oxide is demonstrated by Raman and X‐ray photoelectron spectroscopy characterizations, while scanning electron microscopy, atomic force microscopy and dynamic water contact angle analyses are employed to verify the morphology and the wettability of the coatings. The prepared coatings demonstrate applicability in the promotion of dropwise condensation of pure steam, with an 8‐fold enhancement of the heat transfer coefficient compared to film‐wise condensation. In addition, durability of the reduced graphene oxide coatings of more than 100 hours in the tested condition is reported.

Model development and simulation on dropwise condensation by coupling absorption theory in the presence of non-condensable gas (NCG)

Various methodologies have been proposed in literatures to simulate pure steam filmwise/dropwise condensation and filmwise condensation in the presence of non-condensable gas (NCG). However, simulation methodology for dropwise condensation in the presence of NCG is rarely to be studied. In this paper, theories related to chemical gas-liquid absorption are referred, coupling with the widely used pure steam dropwise condensation model, a new methodology for heat transfer calculation of dropwise condensation in the presence of NCG is finally developed. After comparing experimental data from literatures with simulation results based on the proposed model, the new developed methodology gets validated. Heat transfer performance is found to be coordinately controlled by capacities of absorption mass transfer and surface condensation. Then, the effect of two practical easy to be controlled operation variables of Re number and sub-cooling degree on dropwise condensation process in the presence of NCG are investigated. Results indicate that sub-cooling degree is more sensitive than Re number, and the key to improve total heat flux is to accelerate the rate-determining step. Finally, 133° is found to be the optimal contact angle, under which the maximum heat flux could be achieved.

Experimental investigation on improved vertical sweep efficiency by steam-air injection for heavy oil reservoirs

Steam injection is one of the most widely used technique for heavy oil recovery. There are few laboratory experiments to investigate how to decrease the negative effect of steam override in thick heavy oil reservoirs, thus increasing the vertical sweep efficiency and further improving oil recovery. In this paper, a three-dimensional physical model was introduced to study the sweep efficiency of steam injection and steam/air injection in reservoirs with different rhythms. The mechanisms of improved vertical sweep efficiency by the hybrid injection of steam and air were also analyzed by monitoring the real-time temperature and liquid production of the 3D model. The experimental results indicated that as pure steam was injected, the sweep area mainly located in the upper part of the model. The sweep area decreased from the top to the bottom, and the same to liquid production. The steam override was most serious in negative-rhythm reservoir, followed by the homogeneous and positive-rhythm reservoirs. As steam and air were coinjected, the vertical sweep efficiency of different-type reservoirs was improved to different degrees. The liquid production of in the upper part decreased while that in the lower part increased, among which the liquid production increase at the bottom of negative-rhythm reservoir was most significantly. The investigation of this paper was beneficial to visually recognize steam override by steam injection and provided a guidance to improve the vertical sweep efficiency with the hybrid injection of steam and air in thick heavy oil reservoirs.