Generation Of High-temperature Steam Research Articles

Water-free surface silanization on composite zeolite 13X/MgSO4 in a direct-contact adsorption heat pump for stable steam generation

Direct-contact method has been utilized in an open-loop adsorption heat pump based on composite adsorbent for high-temperature steam generation. Deliquescence problem arisen from the loss of salt in adsorbent under high humidity environment limits the stable performance during adsorption process. The composite zeolite was functionally modified with octyltrimethoxysilane (OTMOS) agent during water-free process based on liquid chemical grafting method. Measurement results from XRF (X-Ray Fluorescence) confirm the stable amount of salt is kept inside the modified zeolite. Characterization results from BET (Brunauer-Emmett-Teller) reveal the facts that pore volume and diameter are reduced simultaneously with the decrease in surface area. During regeneration dry air at 130 °C is used for removing water out of the packed bed filled with S8-7.5 (the composite adsorbent modified with 7.5 % OTMOS). During generation process superheated steam at 200 °C is obtained directly from hot water at 72 °C. GTL (Gross Temperature Lift) reaches 115 °C. COPh (coefficient of performance for heating) and SHP (specific heating power) for steam generation are increased by 16.2 % and 10.4 %, respectively after modification. The corresponding increases in system indicators stem from the promotion of steam mass, as adsorption abilities for composite zeolite are maintained well during direct contact with liquid water after modification.

Bifunctional photothermal membrane for high-temperature interfacial solar steam generation and off-grid sterilization

High-temperature solar steam generation is a promising sustainable strategy to alleviate the global clean water shortage. However, it is challenging to scale up the high-temperature steam generation under ambient conditions for water purification and steam sterilization simultaneously. Herein, we develop a solar-powered steam generating system to produce high-temperature steam for interfacial solar steam evaporation and off-grid sterilization. A three-layered photothermal membrane made of polystyrene foam, bubble wrap, and reduced graphene oxide (rGO) coated cloth produces high-temperature steam that can be condensed to clean water as well as sterilize microbes efficiently. The hybrid device configuration and higher solar light-absorbing capability of rGO result in high temperature steam generation (∼90 °C) to sterilize microorganisms such as S.aureus, E.coli, and G.stearothermophilus. Such a bifunctional device with high temperature steam generation and solar-steam evaporation capability could be a promising development for sustainable clean water generation and sterilization in remote areas.

Heat generation in a packed bed of zeolite particles using moist air

This work investigated the generation of high-temperature steam by feeding saturated moist air through a steam generation system containing a zeolite 13X packed bed. The use of moist air was a unique aspect, which demonstrated a novel approach to steam generation system design. The issue with the steam generation system in previously existing published research works is that it needs high regeneration energy. In order to solve this issue, it is desirable to employ moist air as the working medium. In order to better understand the physical processes involved, numerical modeling of zeolite energy storage was also performed in addition to the experimental work. As the result, when the temperature of the moist air was raised from 30 to 95 °C, the maximum temperature of the resulting water vapor reached to about 200 °C. The maximum temperature of the water vapor was not greatly affected by the superficial velocity of the moist air between 0.108 and 0.216 mN/s. In the case that the moist air temperature was high, the maximum temperature of water vapor could be predicted based on correlations between the heat balance and adsorption equilibrium, assuming that temperatures of the moist air and zeolite were identical. The numerical technique also included a comparison between Arrhenius and linear driving force models. At higher temperature input moist air, both models resulted the close tendency.

Cavity-shaped direct solar steam generator employing conical helical tube for high-temperature application: Model development, experimental testing and numerical analysis

Concentrating solar thermal technologies are drawing more attention since it can substantially contribute to a carbon-neutral society. The solar receivers are essential in this technology to convert solar energy efficiently into thermal energy. Moreover, high-temperature steam generation is the promising application for concentrated solar power plants or industirial processes. Therefore, the direct solar steam generator has been gaining more attention due to its advantages of low operation and maintenance costs. Most solar steam generator designs consist of a tube with helical configuration because of its high heat exchange performance and compactness. However, only few studies address solar steam generators with conical helical tubes. Thus, both experimental and simulation data of this design are scarce. This paper shows the successful development and experimental testing of a solar steam generator with a conical helical tube. The experimental results proved that the developed solar steam generator can produce high-temperature steam of 600 °C at an inlet pressure and mass flow rate of 150–200 kPa and 2.5 kg/h, respectively. The overall calculated energy efficiency (thermal and optical efficiency) was 60–62%. In addition, a coupled 1D-3D numerical model was implemented to analyze the solar steam generator’s performance. The model consists of a 3D cavity heat transfer model and a 1D two-phase fluid flow model. The numerical analysis demonstrated the ideal generator’s performance (energy efficiency of 68–69%) and the great impact of convection in the heat losses (50% of the total energy losses). Although more research of the convection is required, the presented results provide a basis for designing further, upscaled solar steam generators employing conical helical tubes.

DETERMINATION OF THERMAL EFFICIENCY AND COOKING POWER OF PARABOLIC SOLAR CONCENTRATING SYSTEM WITH THERMAL COMPENSATOR FOR DOMESTIC APPLICATIONS

Energy and the environment have a strong relationship. The production and consumption of energy is one of the biggest causes of environmental damage on earth. Therefore, the rapid increase in the level of CO2 and other greenhouse gases are given out during burning fossil fuel rise or unsteady of fuel prices are the main purposes led to a search to more effectively utilize a different sources of renewable energy. To reduce the consequences of greenhouse gases emitted by burning fuel for energy, which course depletion of the ozone layer and global warming. Therefore, the use of solar radiation directly as a source of energy has proved in the past to be less economical and affordable. The paper was aimed at determination of the performance of a parabolic solar concentrating system with a thermal compensator for domestic applications using thermal efficiency and cooking power. The parabolic dish solar collector (PDSC) with a focal point of 6.15 m, aperture area of 5.8 m2 and rim angle (φo) of 45O was designed and constructed for the determination of the variables. The PDSC was made of stainless steel reflector sheet in such a way that both the manufacturing and assembly method do not require complicated skilled techniques and cost. Since the PDSC is for high temperature steam generation, hot water and cooking application. A finite element stress test analysis was conducted to determine the thermal efficiency and cooking power of the system under various weather conditions. A simple manual solar tracking mechanism was employed, and the results of the system performance were also reported. The efficiency according to thefinding depends on the optical properties of the materials involved, the geometry of the collector, and the various imperfections arising from the construction of the collector. The thermal efficiency and cooking power of the system were determined and obtained to be 54.4% and 543.1W respectively.

Enhanced Steam Temperature Enabled by a Simple Three-Tier Solar Evaporation Device.

Interfacial water evaporation technology by using solar energy provides one of the promising pathways for freshwater shortage management. However, current research mainly focuses on the improvement of evaporation efficiency by macro or microregulations, ignoring the steam temperature, which is a manifestation of the quality of water. Herein not only is a high‐rate solar evaporation achieved but also steam temperature is enhanced by a simple three‐tier (wet absorber–air gap–dry absorber) device. In a routine interfacial evaporation test, the evaporator achieves a stable evaporation rate up to 2.15 kg m−2 h−1 under one sun, demonstrating a competitive evaporation rate compared with other reports. With the three‐tier device, the steam temperature can increase 33.7%, 41.13%, and 47% without dry absorber under one sun, two sun, and three sun illumination, respectively. At the same time, the steam temperature can be as high as 95.5 °C under three sun intensities. This work provides the possibility of using a simple three‐tier device for high‐temperature steam generation without extra energy input, which contributes to an idea for future research on the production high‐quality water.

Surface Superhydrophobic Modified Zeolite 13X for High-Temperature Steam Generation in an Open-Loop Adsorption Heat Pump

Surface Superhydrophobic Modified Zeolite 13X for High-Temperature Steam Generation in an Open-Loop Adsorption Heat Pump

고온수 온도에 따른 축열식 판형 열교환기의 축/방열 특성

Heat pump systems for high-temperature steam generation using waste heat generated in industrial sites are attracting attention. However, the disadvantage of waste heat is that it fluctuates quantitatively and qualitatively during the acquisition process. This study proposes the combination of the heat exchanger and thermal storage tank in a high-temperature heat source system to enhance the use of industrial waste heat as an energy source. The developed thermal storage type heat exchanger has a plate type heat exchange structure and allows mutual heat transfer between three mediums, including a phase change material (PCM). Named a thermal storage type plate heat exchanger (TSPHE), it comprises 16 kg of a PCM, with a phase change temperature of 68.8℃ to provide heat storage function. The heat storage and release characteristics of the PCM according to the temperature of hot water and cold water were verified through a heat transfer experiment using the TSPHE. Also, because of the structural characteristics of the TSPHE, the phenomenon of the three-medium heat exchange was verified during the experimental process. The heat storage and heat dissipation characteristics according to the supply temperature conditions of the heat medium used in the TSPHE were analyzed. The results of this study will be used as basic data for applying a thermal storage type evaporator to a high-temperature heat pump that generates steam using industrial waste heat.

Pre‐adsorption of low‐grade waste steam for high‐temperature steam generation by using composite zeolite and long‐term heat storage salt of MgSO 4

Adsorptive heat transformer is a promising technology for waster heat recovery and global energy conservation. A novel cyclic adsorption heating system based on direct contact heat exchange method has been established for the purpose of high-temperature steam generation from hot water. Pre-adsorption is originally proposed before generation phase to enhance the system performance with composite zeolite 13X and MgSO4 in the open-loop adsorption heating system. Composite zeolite is prepared by impregnation method. Experimental results show steam with temperature higher than 200°C is generated from inlet water at 72.0°C. During regeneration phase, dry air at 130°C and relative humidity of 7.37% is employed. Gross temperature lift is 95.0°C to 103°C for different pre-adsorption conditions. The effective steam generation time with pre-adsorption temperature at 90.0°C is prolonged by 27.4%. Meanwhile, the mass of steam is elevated by 16.2% compared with the cycle without pre-adsorption. Exergy coefficient of performance is upgraded by 14.7% and specific heating power for steam generation is increased by 16.0%. The pre-adsorption operation achieved the goal of recovery of low-grade waste steam on adsorbents to enhance the subsequent high-temperature steam generation. After pre-adsorption operation, the packed bed reaches adsorption and thermal equilibrium more quickly during generation phase. Thus, dynamic steam generation is significantly intensified and then system performance is improved correspondingly.

Experimental study of heat and mass recovery on steam generation in an adsorption heat pump with composite zeolite-CaCl2

High-temperature steam generation in adsorption heat pump with composite zeolite-CaCl2 has been experimentally investigated by introducing heat and mass recovery. A direct contact heat exchange method is utilized to enhance the overall heat transfer rate. Composite zeolite (CZ) is prepared by immersing zeolite particle in CaCl2 solution at mass concentration of 40%. Cyclic experiment consists of two processes: regeneration with 130 °C dry air and steam generation with 80 °C hot water. The heat and mass recovery with steam below 90 °C is added before generation process. Mass of generated steam above 200 °C is increased by 9.12%. The effective time for steam generation is dramatically extended by 18.33%. Adsorption and thermal equilibriums inside the packed bed are achieved more quickly with heat and mass recovery. Gross temperature lift for one-stage adsorption heat pump is above 100 °C. Coefficient of performance for heating (COPh) and specific heat power (SHP) are elevated by 9.55% and 9.23%, respectively. The increase in mass of generated steam contributes to the improvement of COPh. Meanwhile, only a short time used for heat and mass recovery enables the rise in SHP.

High-temperature steam generation from low-grade waste heat from an adsorptive heat transformer with composite zeolite-13X/CaCl2

High-temperature adsorptive heat transformer for steam generation has been experimentally investigated by introducing composite zeolite/CaCl2-water working pair based on a direct contact method. Composite adsorbents are prepared by immersing zeolite into different mass concentrations of CaCl2 solutions. SEM (Scanning Electron Microscope) is used to observe the surface structure of the composite zeolite. XRF (X-Ray Fluorescence) is selected to analyze the element mass ratios in adsorbents. BET (Brunauer-Emmett-Teller models) is employed to calculate the pore characteristic of pores inside zeolite. Characterization results confirm the success of preparation for composite zeolite. Adsorption properties including equilibrium water uptake and integral adsorption heat are measured for basic evaluation. Overall volumetric adsorption heat is increased by 13.1% for CA40% (immersion of zeolite in CaCl2 solution concentration at 40%) compared with that for 13X. Cyclic experiments are conducted to test the design of system. Superheated steam above 200 °C is generated for 13X and different composite zeolites from hot water below 80 °C. Dry gas at 130 °C is used for regeneration. Gross temperature lift is more than 100 °C for single stage zeolite adsorptive heat transformer. Dynamic steam generation on interface between water and zeolite is enhanced with more heat released by using composite zeolite. Subsequently, adsorption equilibrium is easier to be achieved inside the whole range of the packed bed. Effective time ratio for steam generation is elevated by 18.6% for CA40% compared with that for 13X. Mass of generated steam is raised by 12.9% simultaneously. Both the time and mass of generated steam have been obviously promoted with the increase of CaCl2 impregnated in zeolite. COPex (Exergy Coefficient of Performance) is kept constant while SHP (Specific Heating Power for steam generation) is increased by 12.6%.

Solar-driven high-temperature steam generation at ambient pressure

This paper demonstrates a facile solar steam generator for the generation of high-temperature steam at ambient pressure. The steam generator consists of a coiled copper tube (CCT) that serves as both solar collector and vapor heater. Both the inner and outer surfaces of the CCT are coated with black superhydrophobic copper oxide layer to improve the solar absorption, and such superhydrophobic layer prevents the condensation and clogging of water vapor during the heating process. Solar vapor is generated at the inlet of CCT through interfacial evaporation and subsequently heated inside the CCT as the vapor travels from the inlet to the outlet. By employing this approach, steam temperature that exceeds 100 °C under 1-sun illumination is demonstrated. Furthermore, steam temperature could reach as high as 250 °C under 10-sun illumination at ambient pressure. Successful sterilization experiment was also performed in this work to demonstrate the potential application of the high temperature steam generated. Such demonstrated approach helps open up the potential usage of solar-driven interfacial evaporation in applications that involve high-temperature steam, including medical sterilization, chemical manufacturing and food processing.

Floating rGO-based black membranes for solar driven sterilization.

This paper presents a new steam sterilization approach that uses a solar-driven evaporation system at the water/air interface. Compared to the conventional solar autoclave, this new steam sterilization approach via interfacial evaporation requires no complex system design to bear high steam pressure. In such a system, a reduced graphene oxide/polytetrafluoroethylene composite membrane floating at the water/air interface serves as a light-to-heat conversion medium to harvest and convert incident solar light into localized heat. Such localized heat raises the temperature of the membrane substantially and helps generate steam with a temperature higher than 120 °C. A sterilization device that takes advantage of the interfacial solar-driven evaporation system was built and its successful sterilization capability was demonstrated through both chemical and biological sterilization tests. The interfacial evaporation-based solar driven sterilization approach offers a potential low cost solution to meet the need for sterilization in undeveloped areas that lack electrical power but have ample solar radiation.

The potential of SO2 for reducing corrosion in WtE plants

Due to the high-temperature boiler corrosion induced by chloride-rich fly ash deposits, steam generation in today’s Waste-to-Energy (WtE) plants is typically designed only for 40 bar/400 °C as an economic compromise between acceptable corrosion rate and maximum power generation. The high-corrosive metal chlorides in the fly ash can react with SO2 forming low-corrosive sulfates. The sulfation efficiency is enhanced by high SO2 levels and sufficient residence time of the flue gas at high-temperatures (700–900 °C). The fly ash sulfation was tested in full scale in a Swedish WtE plant by applying the economic sulfur recirculation method. Probes of several alloys (16Mo3, Inconel 625, Sanicro 28) were exposed for 1000 h at controlled material temperatures in the superheater position, at normal and during sulfating operation respectively. Analyses of the fly ash showed that the molar Cl/S was decreased to values well below 1 and the corresponding corrosion rates of the individual material samples were less than half when sulfur recirculation was in operation. These positive findings demonstrate that the sulfur recirculation process has high potential for low-corrosive high-temperature steam generation (T ≈ 500 °C) and improved electricity production. Further steam superheating can be realized by staged superheating using small amounts of secondary fuel.

Probabilistic creep rupture life evaluation of T91 alloy boiler superheater tubes influenced by steam-side oxidation

A systematic probabilistic evaluation method for the long‐term creep rupture life (LCL) of T91 alloy superheater tubes is proposed in this work. The effects of steam‐side oxidation on the effective load‐bearing thickness and temperature of tube wall are taken into account, and the latest assessment results of the creep rupture strength of T91 alloy are utilized. Since the uncertain factors including not only the geometry dimensions but also the operational conditions may hinder a reliable analysis, instead of usual deterministic methods, probabilistic life evaluation employing Monte Carlo simulation method is performed. The effects of initial inner tube diameter, steam temperature, and steam flow on the LCL of superheater tubes are analyzed, and simple fitting functions formulating the analysis results are obtained. The survival probability of the tubes, which reflects the possibility for the LCL to be longer than a given time, is calculated. It is found that when the initial inner tube diameter or the steam temperature increases, the survival probability of the tubes exhibits a decrease trend. However, the steam flow has an opposite effect. Based on the conclusions, feasible measures that can be adopted to improve the survival probability of high temperature steam generation components in coal‐fired power plants are introduced.

Development of a double-stage heat pump: experimental and analytical surveys

A double-stage heat pump using three different kinds of metal hydrides was developedto demonstrate the practical applicability of the hydriding-dehydriding reactions to the generation of high temperature heat through the dehydriding reaction, under lower temperature conditions, with high operational performance. Extensive research was carried out on the design, construction and operation,and the operating performance of two experimental demonstration units with different capacities (7.72 kW and 77 kW) was analysed. The emphasis of this work was the generation of high temperature steam in thetemperature range 120–150°C using a low grade heat source at a temperature of 80°C and ambient air as the cooling medium. Experimental and analytical results of the operational performance of thetesting unit was 7.72kW capacity are described in detail.

Behavior of Superheater Tubing Materials in Contact With Combustion Atmospheres at 1350 F

Abstract With steam temperature of central-station boiler plants advancing to 1050 F in new installations today, and with indications that steam temperatures of 1200 F are not too far in the future, selection of suitable materials for superheater and reheater tubing requires special consideration. Alloys having good service characteristics in the range of 1100 F to 1350 F are required to meet the foregoing steam conditions. While mechanical properties of such alloys are not too serious a problem, the matter of corrosion resistance is a critical one. The ASME Special Research Committee on High-Temperature Steam Generation, recognizing the importance and the complexity of the corrosion problems, undertook sponsorship of a comprehensive program to evaluate commercially available alloys for suitability as superheater and reheater tubing at metal temperatures up to 1350 F. (The program is divided into two broad parts.) One is concerned with the reaction of high-pressure high-temperature steam on such materials. The other deals with corrosion by flue gases and slag-forming ash on the external surface of the tubing, and is divided in turn into two phases. The specific objective of one phase is the evaluation of the alloys with respect to resistance toward corrosion by the combustion products of the various fuels used for boilers, under actual field conditions. The objective of the other phase, carried out in the laboratory, is the investigation of the effect of certain components of a combustion atmosphere on the rate of corrosion of the same alloys. This paper is concerned with the field-test phase of the program which was carried out at Battelle. The laboratory work done at Battelle will be the subject of a future paper.