Dry Steam Research Articles

Solvent and Catalyst-Free Depolymerization of Polylactic Acid Waste to Lactide Enabled by Dry Steam

Solvent and Catalyst-Free Depolymerization of Polylactic Acid Waste to Lactide Enabled by Dry Steam

Thermodynamics to economic analyses of geothermal-driven hydrogen energy systems

This paper investigates geothermal energy's potential for hydrogen production, addressing fossil fuel limitations, climate change, and the need for integrated simulations and financial assessments tailored to specific geological contexts. We compare the energy efficiency and economic feasibility of geothermal-driven hydrogen production systems through simulations of flash cycles, organic Rankine cycle (ORC), and hybrid flash-ORC systems. Optimal operational parameters for energy efficiency are identified under various geothermal conditions. Our analysis reveals that the system efficiency strongly depends on temperature and geofluid type. For dry steam over 200 °C, the energy efficiency of the system is estimated to be roughly 15 %. For wet steam in a fully liquid state, combining ORC with flash cycles can extract more than 10 % of energy from the geofluid. The levelized cost of hydrogen (LCOH) production using dry steam is estimated at 1.26 USD/kg, which is even lower than that of using natural gas. When feeding the hybrid flash systems with fully liquid wet geofluid, the lowest LCOH is 5.23 USD/kg. Economic viability depends on geological and technological variables, including well depth and pressure constraints. The results highlight the strategic potential of integrating geothermal energy into the clean energy matrix, balancing economic and environmental sustainability for carbon neutrality.

Effects of different postharvest drying processes on flavonoid content and enzymatic activity of Styphnolobium japonicum (L.) Schott flowers for industrial and medicinal use

Traditionally, fresh S. japonicum flowers (SJF) and S. japonicum flowers buds (SJFB) are dried prior to further processing and use. Here, we investigated the ways in which drying techniques, including sun drying (SD), steam drying (STD), microwave drying (MD), hot air drying (HAD, 40 °C, 60 °C, 80 °C, 100 °C), and freeze drying (FD), alter the flavonoid composition of freshly-harvested SJF and SJFB. The flavonoid content of dried samples was determined by Ultra High Performance Liquid Chromatography-Diode Array Detector (UPLC-DAD). Overall, different drying techniques had significantly different effects on the RU content, ranging from 10.63 % (HAD-80 °C) to 34.13 % (HAD-100 °C) in SJF and from 18.91 % (HAD-100 °C) to 29.16 % (HAD-40 °C) and 30.53 % (SD) in SJFB. To clarify the mechanism by which drying affects the RU content of S. japonicum flowers, we studied the activity of a rutin-hydrolyzing enzyme (RHE) isolated from SJF and SJFB using multiple separation and assay methods. According to the Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) results, the apparent molecular weight of the purified RHE was approximately 38 kDa. According to UPLC-DAD, RHE catalyzes the production of quercetin (QU) from rutin (RU), but not from other flavonoid glycosides. Drying fresh SJF and SJFB at low and high temperatures can inhibit RHE activity and prevent RU hydrolysis. Therefore, subjecting freshly-harvest SJF to HAD-100 °C, and freshly-harvest SJFB to SD or HAD-40 °C, can greatly increase the RU content. In particular, HAD is viable for large-scale application due to its simplicity and industrial feasibility.

Energy and exergy analysis of dry and steam external reformers for a power cycle based on biogas-fueled solid oxide fuel cell

In the present research a cogeneration cycle based on a solid oxide fuel cell (SOFC), and Organic Rankine Cycle (ORC) is proposed. The cycle is fed with biogas in different molar ratios of carbon dioxide to methane (RCTC). In addition, the cycle is examined for both dry reforming (DR) and steam reforming (SR). A thermochemical model is presented for both cycles of SR–SOFC–ORC, and DR–SOFC–ORC. The model is coded in MATLAB coupled with Engineering Equation Solver software. The model was verified with both experimental and theoretical research and agreement was achieved. The energy and exergy performance of the cycle is presented and carbon deposition on the cathode due to different reactions of methane cracking, Boudouard reaction, and vapor formation are studied. The results show that for RCTC<1.2 steam reforming produces more hydrogen, while for RCTC>1.2 dry reforming is advantageous. At RCTC = 1.2 the DR and SR work the same. The overall thermal efficiency of DR-SOFC and SR-SOFC has reached 67 % and 70 %. Carbon deposition due to the Boudouard reaction, and vapor formation for both SR and DR are negligible while due to methane cracking is serious. The DR-SOFC deposits less carbon because of methane cracking due to higher operating temperatures.

Numerical investigation of discharge pressure effect on steam ejector performance in renewable refrigeration cycle by considering wet steam model and dry gas model

Abstract In recent times, steam ejectors have garnered significant interest among researchers due to their environmental friendliness and the utilization of low-grade energy sources. However, a key drawback of the ejector refrigeration cycle (ERC) is its relatively low coefficient of performance (COP). Understanding the behavior of ejectors under various operating conditions is crucial for addressing this concern. This study specifically focuses on investigating the flow characteristics of ejectors in the single-choking mode. Both dry steam model (DSM) and wet steam model (WSM) are employed to analyze and evaluate the performance in this study. Based on the findings, it is evident that the discharge pressure (DP) significantly influences the flow characteristics. With increasing DP, there is a decrease in the Mach number and liquid mass fraction (LMF) within the ejector, while the temperature distribution shows an upward trend. Additionally, as the DP increases, there is a notable decline in the entrainment ratio (ER) and production entropy. With an increase in the DP, both the DSM and WSM exhibit similar trends. However, in the DSM, the ER reaches zero at an earlier stage compared to the WSM. Specifically, when the DP rises from 5000 Pa to 5600 Pa, there is a 12.6 % increase in the production entropy in the WSM, while the DSM experiences a slightly higher increase of 12.9 %.

Dry reforming of methane at high temperature and elevated pressure over nickel spinellized powder catalyst and pellets prepared from a metallurgical residue

AbstractThe coke deposition on catalysts is a significant problem in the dry reforming of methane at elevated pressures. Understanding and controlling the mechanisms of such deposition is essential in developing a techno‐economically viable industrial application for the production of synthesis gas and/or hydrogen. The patent‐pending nickel‐supported upgraded slag oxide (Ni‐UGSO) catalysts, in powder form, have demonstrated excellent performance and achieved equilibrium in dry reforming, steam reforming and mixed methane reforming in a gram‐scale laboratory packed bed reactor under barometric pressure. In this extended study, Ni‐UGSO pellets were prepared using the wet impregnation method. The pelletized form of said catalyst was studied under elevated pressure to imitate the industrial operating conditions in a kilogram‐scale laboratory packed bed reactor. The characterization of the fresh and used catalytic formulation produced data allowing the investigation of the physicochemical properties of catalysts and the effects of metal dispersion, reaction pressure and crystallite size, as well as the role of side reactions on the nature of the coke. The metal support nature favored the interaction between the Ni metal and spinels (UGSO), and the presence of the clay binder (kaolinite, quartz) improved the pellet morphology, provided higher Ni dispersion, maintained the crystallite size, reduced the coke formation and achieved similar or higher performance with respect to Ni‐UGSO powder despite having 85% less surface area. The Ni‐UGSO pellet showed negligible coke deposits from 1 to 6.5 atm and operated successfully for 24 h at 5.5 atm, 800°C and gas hourly space velocity 810 L/(h kg cat). This study provides new insight into the design of a more efficient and robust catalyst for methane dry reforming at elevated pressures, which is critical for potential future transfer at the industrial level.

Emerging trends in hydrogen and synfuel generation: a state-of-the-art review.

The current work investigated emerging fields for generating and consuming hydrogen and synthetic Fischer-Tropsch (FT) fuels, especially from detrimental greenhouse gases, CO2 and CH4. Technologies for syngas generation ranging from partial oxidation, auto-thermal, dry, photothermal and wet or steam reforming of methane were adequately reviewed alongside biomass valorisation for hydrogen generation, water electrolysis and climate challenges due to methane flaring, production, storage, transportation, challenges and opportunities in CO2 and CH4 utilisation. Under the same conditions, dry reforming produces more coke than steam reforming. However, combining the two techniques produces syngas with a high H2/CO ratio, which is suitable for producing long-chain hydrocarbons. Although the steam methane reforming (SMR) process has been industrialised, it is well known to consume significant energy. However, coke production via catalytic methane decomposition, the prime hindrance to large-scale implementation of these techniques for hydrogen production, could be addressed by coupling CO with CO2 conversion to alter the H2/CO ratio of syngas, increasing the reaction temperatures in dry reforming, or increasing the steam content fed in steam reforming. Optimised hydrogen production and generation of green fuels from CO2 and CH4 can be achieved by implementing these strategies.

Combined effects of low pressure superheated steam drying and vacuum drying on sugar reduction and quality attribute in mango (Mangifera indica L.) slices

Abstract Consumers paying more attention to physical health has led to an increasing market demand for low-sugar dried fruit products. The quality of products dried via low pressure superheated steam drying (LPSSD) is not only superior to those dried via conventional hot air or vacuum drying (VD), but also has the potential to reduce sugar content. In order to elucidate the mechanism of reducing the sugar of mango slices by LPSSD and obtain low-sugar dried mango slices, the combined effect of LPSSD–VD on mango slices was studied and an evaporation experiment of a sugar solution in a low pressure superheated steam environment was performed. This study revealed that the sugar reduction of mango slices was mainly due to the superheated steam carryover phenomenon in the second half of the constant-temperature stage and the occurrence of Maillard reaction during LPSSD. The quality attributes of mango slices dried using LPSSD–VD was improved compared with LPSSD and VD. As a result, LPSSD–VD could be used to regulate the sugar content in dried fruit and provide a theoretical basis for the production of low-sugar preserved fruits.

The effects of dry heat and steam on germination of dry and imbibed seeds of the invasive garden lupine (Lupinus polyphyllus Lindl.)

Abstract Regularly mown road verges are an important habitat for conservation of grassland vegetation. Disturbance and movement of seed-contaminated soil during road construction and maintenance makes road verges susceptible to the establishment of invasive alien plants such as garden lupine (Lupinus polyphyllus Lindl.). To combat spread of L. polyphyllus via seeds, we tested methods for seed destruction using heat. This study aimed at developing heat eradication methods for dry and imbibed L. polyphyllus seeds applying dry heat (88, 93, 98, 103 C at 1, 3, 5, 10 min) in a laboratory, steam (85, 90, 95 C at 3, 5, 10 min) in a test-box steaming device and (97 C at 10-17 min; dry seeds only) in a stationary soil-steaming machine (S30). In order to speed up water absorption and post-treatment germination, the imbibed seeds were manually scarified before the heat treatment and the dry seeds afterwards. Additionally, germination of two different age seed batches was tested applying dry heat (88, 98 C at 3, 5 min). The results showed that steam treatments inhibited seed germination more than dry heat in both dry and imbibed seeds. Germination dropped to &lt; 5% when steamed at ≥ 90 C or dry-heated at &gt; 100 C. Seed germination decreased with higher temperatures and longer exposure times. Imbibed seeds exhibited lower germination compared to dry seeds for dry and steam heat. Approximately 0.5% of dry seeds germinated when steamed using S30. 2022-collected seeds were less sensitive to dry heat than seeds from 2020. In conclusion, hot steam is more effective in reducing L. polyphyllus seed germination than dry heat. Thus, to successfully eradicate L. polyphyllus seeds in soil masses, we recommend steaming them at 97 C for at least 10 minutes.

Experimental and Numerical Study of Superheated Steam Drying for Sliced Avocado

AbstractSuperheated steam drying (SSD) of sliced avocado is studied by both experiment and theory. An experimental system is built to evaluate the effects of drying temperature and gas velocity on the evaporation rate and color change of the product. Experiments are conducted for ripened Booth avocado from Daklak province of Vietnam. Experimental results show that evaporation is faster at higher temperatures and velocities, but the effect of temperature decreases at higher velocities. At temperatures below 130 °C, the product is not brown, but at a temperature in the range of 130–150 °C, the dried sample is burned. The experimental model is fitted with high accuracy to predict the moisture rate as a function of time. The evaporation processes of SSD are also compared with hot air drying at the same drying conditions. To extend the application ability of the result, the theoretical model is developed on the basis of Fick's law in which the spatial distributions of temperature and moisture are taken into account. The effective diffusivity is determined by an optimization tool with good agreement. This parameter is constant for all drying conditions, so the model can be applied to a huge range of drying conditions. The numerical results show that the temperature is almost uniform in the sample because of high thermal conductivity, but the moisture gradient is significant.

Oxidation and mechanical properties of SiC fibers after high temperature exposure in air and steam

SiC fibers are widely used in composites exposed to high temperature oxidizing environments. The present study compares the oxidation behavior of SiC fibers and the associated changes in tensile strength upon their exposure to dry air and steam for up to 50 hours at temperatures from 950°C to 1350°C. In both cases, the scale thickness and oxide microstructure were analyzed by scanning electron microscopy. When the SiC fibers were oxidized in air, a crack-free amorphous oxide layer formed at temperatures up to 1200°C, whereas a cracked, crystallized oxide layer was found at 1350°C. By contrast under steam environment, a crystalline oxide forms at 950°C for oxidation times longer than 30 h. In both environments, the fiber strength decreased with increasing exposure time and temperature, the degradation being faster after oxidation in steam compared to dry air. This appears to relate to residual stress in the oxide scale and a reduction in the cross section of the load-bearing unoxidized SiC. An increase in defect size may also contribute to the loss of strength. The oxide scale follows parabolic growth kinetics in both dry air and in steam from 950°C to 1350°C, except at 1350°C for over 30 hours. The oxidation rate in steam is faster than that in dry air, with activation energies of 79.8±1.4 kJ/mol in steam and 153.6±3.4 kJ/mol in dry air, respectively. This work is relevant to the application of SiC fibers and SiC fiber reinforced composites in air and steam environments at high temperature.

Effect of generator temperature on steam ejector performance in renewable refrigeration cycle considering wet steam model and dry steam model

The rise in global warming has led to an increased utilization of cooling systems. High energy consumption associated with common refrigeration cycles not only contributes to air pollution but also intensifies the consumption of fossil fuels. Consequently, the imperative to conserve energy has become paramount in today's world. One of the methods to decrease energy consumption involves employing systems capable of harnessing waste heat from industries, solar energy, and other sources. The ejector refrigeration cycle (ERC) stands as an example of such systems. In present study, the impact of elevating the generator temperature on various aspects such as flow behavior in the ejector, aerodynamic shocks, entrainment ratio (ER), and entropy production was examined. The investigation encompassed both wet steam model (WSM) and dry steam model (DSM). Based on the findings, it was observed that with an increase in generator temperature, the ER decreases while the production entropy increases. In the WSM, the liquid mass fraction (LMF) also experiences an increase. Additionally, the Mach number distribution in the DSM surpasses that of the WSM and the temperature drop in the DSM is greater compared to the WSM. With the rise in generator temperature from 388 K to 418 K, both the DSM and WSM exhibit a decrease in ER by 52.9% and 58.7%, respectively. Furthermore, the production entropy experiences a substantial increase of 180% and 206% for the DSM and WSM, respectively.

Preparation of Cr2AlC powder and its isothermal oxidation behavior in dry air and pure steam

As a promising candidate ceramic for using in harsh environments, Cr2AlC ternary carbide possesses numerous unique properties at elevated temperatures. Herein, high-purity Cr2AlC powders had been synthesized by using a facile method with a mixture of Cr7C3, Cr3C2 and Al powders at 1200 °C for 3 h. Subsequently, the oxidation behaviors of Cr2AlC powders were investigated in dry air and pure steam at temperatures ranging from 900 to 1100 °C, respectively. In addition, the oxidation products were characterized and the mass gain curves were analyzed via the real physical picture (RPP) kinetic model. As a result, thicker Al2O3-rich oxide scale and porous Cr7C3 subscale were generated during dry air oxidation compared to pure steam oxidation. Notably, the oxidative active energy of Cr2AlC was 446.5 kJ/mol in pure steam, while in dry air it was decreased by 14.4%. Theoretical calculations further verified that Cr2AlC oxidizes more sluggishly in steam than in dry air.

Development of Sustainable Dust Compression System for Coal Yard Safety

A sustainable water mist spray system for a closed coal yard. The project aims to address the need for dust suppression in the coal yard to mitigate environmental and health risks. The design specifications will be determined by considering the coal yard's size, layout, and specific requirements. The system will utilize a pneumatic air vane motor powered by residual dry steam from the plant's operation and, coupled with a fan for effective mist dispersion. Ro Reject water, a byproduct of reverse osmosis water treatment, will be used as the water source. The project will involve collaboration with mechanical engineering, fluid dynamics, and environmental studies to develop an optimized system design. Field tests will be conducted to validate the system's functionality, mist spray effectiveness, and coverage area. Safety features will be installed to ensure operator protection, and training programs will be developed to educate operators on safe system operation. The effectiveness of the mist spray system will be evaluated and monitored through regular assessments and data collection. Maintenance activities will be conducted to ensure system functionality, and safety features will be updated as necessary. The successful implementation of this sustainable water mist spray system will contribute to dust suppression, environmental sustainability, and safety in the coal yard.

Impact of inlet steam state on ejector internal flow and performance considering non-equilibrium condensation

Most of the numerical studies adopted dry gas model to predict transonic and supersonic flow in steam ejectors, but it cannot accurately reflect flow characteristics in ejectors, since the condensation and evaporation of wet steam is ignored. The current work develops and validates a CFD model describing spontaneous condensation to simulate complicated flow behaviors and phase transition inside an ejector, and illustrates the impact of initial state of primary fluid including wet, saturated and superheated state on flow characteristics, mass and heat exchange and ejector performance. It is found that the initial steam wetness obviously impacts the average liquid fraction in the ejector. Both the superheated and wet initial primary steam suppress the process of mass and heat exchange during nucleation, and the position and intensity of nucleation are influenced by the inlet steam state. Compared with the case of dry saturated inlet steam, the superheated inlet steam improves entrainment ratio by 3.7%, and decreases compression ratio by 2.5%.

Energy comparison analysis between direct and indirect dry saturated steam generation, thermally powered by EFPCs’ solar fields

Steam is a key energy vector in the industrial sector and each application requires it at a specific pressure and temperature. In this paper the production of low pressure dry saturated steam for industrial use through high-vacuum flat plate solar collectors (HVFPCs) is discussed. This technology can produce steam from solar energy, hybridizing it with existing fossil powered steam generators to obtain significant energy savings and reduce CO 2 emissions. An energy comparison using the 0-D TRNSYS® software between numerical results of different plant configurations is made, which differ in the type of dry saturated steam production device. These devices are necessary as it is not possible to produce steam directly inside collectors. Two possible steam generation methods were analysed: direct steam production, using a Flash vessel, and indirect steam production, using a Kettle reboiler. Finally, each configuration was simulated by imposing a solar field ΔT of 10 °C and 20 °C. Dynamic results show that flash vessel configurations are generally the most efficient, with the same operating parameters, compared to the configurations with Kettle reboiler. Furthermore, configurations with certain ΔT, such as to determine lower operational solar field temperatures, lead to the best results due to the higher HVFPCs’ efficiency.

Retracted: Kinetics of Sludge Superheated Steam Drying and Optimization of Process Parameters

Retracted: Kinetics of Sludge Superheated Steam Drying and Optimization of Process Parameters

Simulation and experimental study on the effect of deformation on heat and mass transfer in potato chips during superheated steam drying

AbstractSuperheated steam drying is a drying technology with enormous potential and numerous advantages. Volume change and substantial deformation will occur on the materials to be dried during the superheated steam drying, which would affect the heat and mass transfer of the sample. However, the influence mechanism is not clear. Therefore, the nonuniform volume change of potato slices was studied, and the deformation model (DM) and the non‐DM (NDM) were constructed and verified to study the heat and mass transfer processes of the sample. The results showed that there was little difference between the measured and simulated temperatures based on DM and NDM with a maximum error of 4.22% and 5.03%, respectively, but there was obvious difference between simulated moisture contents with a maximum error of 5.76% and 12.21%, respectively. The volume in DM was in good agreement with the experimental data. Temperature distribution and moisture distribution in potato chips during superheated steam drying were nonuniform and the maximum temperature gradient and moisture gradient appeared in the early period. The moisture gradient existed in the whole drying process, and the stress caused by the moisture gradient was the main factor causing the drying deformation.Practical applicationsThis work can reveal that the volume change and substantial deformation have a significant impact on the heat and mass transfer during drying. In production practice, there are many similar phenomena. The results would be helpful to understand the heat and mass transfer mechanism, optimize quality parameters to obtain better products in potato drying industry, and expand the applied range of the superheated steam drying technology.

Ayurvedic intervention in the management of Amavata (Rheumatoid Arthritis): A Case Series

The present case series documents the successful management of five cases of confirmed Amavata (Rheumatoid Arthritis). A retrospective analysis of five patients with Rheumatoid Arthritis (RA) symptoms was conducted in this study at the Arogyashala Rugnalaya Panchavati Nashik, Maharashtra. The patients were between the age of 39 to 70 years, were diagnosed as RA positive through a blood investigation, in July-August 2023, and were managed through Ayurveda interventions. The interventions include Anshanrupi Langhana (Fasting), Sunthisiddha Jala (Medicated water) in a dosage of 250-500 ml a day, Ruksha Waluka Pottali Swedana (Dry steam), and Shothahara Lepa (Medicinal paste) were prescribed for five days. Symptomatic assessment was done every day and blood investigations were conducted after 5 days. Significant relief in all the cases was observed as per RA classification criteria 2010 and DAS28-P index scores. However, large-scale randomized controlled trials are required to further validate the same.

Problem of Injection of Dry Steam into a Reservoir without Condensation in the Well

Problem of Injection of Dry Steam into a Reservoir without Condensation in the Well