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Abstract When high-temperature steam is used as a medium to pyrolyze organic-rich shale, water steam not only acts as heat transfer but also participates in the chemical reaction of organic matter pyrolysis, thus affecting the generation law and release characteristics of gas products. In this study, based on a long-distance reaction system of organic-rich shale pyrolysis via steam injection, the effects of steam temperature and reaction distance on gas product composition are analyzed in depth and compared with other pyrolysis processes. The advantages of organic-rich shale pyrolysis via steam injection are then evaluated. The volume concentration of hydrogen in the gas product obtained via the steam injection pyrolysis of organic-rich shale is the highest, which is more than 60%. The hydrogen content increases as the reaction distance is extended; however, the rate of increase changes gradually. Increasing the reaction distance from 800 to 4000 mm increases the hydrogen content from 34.91% to 69.68% and from 63.13% to 78.61% when the steam temperature is 500 °C and 555 °C, respectively. However, the higher the heat injection temperature, the smaller the reaction distance required to form a high concentration hydrogen pyrolysis environment (hydrogen concentration > 60%). When the steam pyrolysis temperature is increased from 500 °C to 555 °C, the reaction distance required to form a high concentration of hydrogen is reduced from 3800 to 800 mm. Compared with the direct retorting process, the volume concentration of hydrogen obtained from high-temperature steam pyrolysis of organic-rich shale is 8.82 and 10.72 times that of the commonly used Fushun and Kivite furnaces, respectively. The pyrolysis of organic-rich shale via steam injection is a pyrolysis process in a hydrogen-rich environment.

When high-temperature steam is used as a medium to pyrolyze organic-rich shale, water steam not only acts as heat transfer but also participates in the chemical reaction of organic matter pyrolysis, thus affecting the generation law and release characteristics of gas products. In this study, based on a long-distance reaction system of organic-rich shale pyrolysis via steam injection, the effects of steam temperature and reaction distance on gas product composition are analyzed in depth and compared with other pyrolysis processes. The advantages of organic-rich shale pyrolysis via steam injection are then evaluated. The volume concentration of hydrogen in the gas product obtained via the steam injection pyrolysis of organic-rich shale is the highest, which is more than 60%. The hydrogen content increases as the reaction distance is extended; however, the rate of increase changes gradually. Increasing the reaction distance from 800 to 4000 mm increases the hydrogen content from 34.91% to 69.68% and from 63.13% to 78.61% when the steam temperature is 500 °C and 555 °C, respectively. However, the higher the heat injection temperature, the smaller the reaction distance required to form a high concentration hydrogen pyrolysis environment (hydrogen concentration > 60%). When the steam pyrolysis temperature is increased from 500 °C to 555 °C, the reaction distance required to form a high concentration of hydrogen is reduced from 3800 to 800 mm. Compared with the direct retorting process, the volume concentration of hydrogen obtained from high-temperature steam pyrolysis of organic-rich shale is 8.82 and 10.72 times that of the commonly used Fushun and Kivite furnaces, respectively. The pyrolysis of organic-rich shale via steam injection is a pyrolysis process in a hydrogen-rich environment. [ABSTRACT FROM AUTHOR]

Li/SF6 energy system is a new type of high energy power source, which can support the construction of a closed cycle power system for underwater equipment due to its high energy density and no product emission. As a key feedback parameter that affects the reaction process, the helical tube outlet temperature in the energy system will impact the precision and stability of the system control under the disturbance of measurement noise and system noise, bringing a negative effect on the reliability of the vehicle. In this paper, the steam outlet temperature curve was obtained by one-dimensional distributed parameter simulation. In view of the shortcomings of common noise reduction methods, an online noise reduction method based on Kalman filter principle was proposed. By comparing with the conventional sliding average filtering and first-order low-pass filtering methods, it can be seen that the proposed method has distinct advantages in terms of error probability distribution and signal-to-noise ratio. Besides, it can shorten the stable time and improve the dynamic characteristics of the system.

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Steam superheaters experience various defects that can affect the system's operation differently. Maintaining a constant temperature and pressure of the steam at the turbine input is crucial for optimal steam turbine running conditions. This is achieved by regulating the steam temperature in the superheater, which is divided into three parts with devices mounted at each connection point to allow for the injection of condensates to cool the steam. The steam pressure is controlled by adjusting the fuel flow command. However, controlling the output temperature can be challenging because of the transfer time delay between the points where the water is sprayed and the points where the steam temperature is measured. To address this challenge, a temperature control system was developed and tested in three different environments using an electronic simulator, the block-oriented simulation hardware BORIS, data acquisition board dSpace, and a MATLAB R2020a Simulink with a PI controller model. These simulations allowed for the study of the superheater's function in both normal and fault conditions, with the possibility of controlling the system structure and detecting faults through the proper implementation of weighting matrices. [ABSTRACT FROM AUTHOR]

• A segmented model of ultra supercritical boiler water-cooled wall is established for dynamic simulation. • The uneven heat flux distribution on the water-cooled wall is considered. • The step response characteristics of different flow loops are compared under different load conditions. • The influence of combustion instability on the water-cooled wall is studied under different load conditions. The dynamic characteristics of water-cooled wall are of great significance to the evaluation of the safety and flexibility for the boiler during peak shaving process. However, few dynamic studies considered the uneven heat flux distribution on the water-cooled wall, let alone the variable heat load caused by the combustion instability. In this paper, a segmented dynamic model is developed for the water-cooled wall of a 660 MW ultra supercritical boiler. The model is validated under steady and dynamic working conditions, respectively. Then, the step responses of the steam temperature in different flow loops under different load conditions are comparatively studied under the disturbances of single-parameter changes. In the cases of 10 % step decrease of either the feedwater temperature, the heat load or the feedwater mass flowrate, the outlet steam temperature is influenced greatly by the step decreased feedwater temperature under 100 % BMCR condition, while it is impacted most by the step decreased feedwater mass flow under 50 % THA condition. Under these disturbances, the outlet steam temperature of the tube with higher heat loads has larger variation and longer response time. In addition, the simulated combustion instability by the sinusoidal fluctuating heat load on the water wall is employed to explore the influences of the flame fluctuation amplitude and frequency to the water wall. The maximum steam temperature rises with the increase in amplitude but drops with the frequency of flame fluctuation. The thresholds for the flame fluctuation amplitude and frequency are obtained under different load conditions. [ABSTRACT FROM AUTHOR]

Steam superheaters experience various defects that can affect the system’s operation differently. Maintaining a constant temperature and pressure of the steam at the turbine input is crucial for optimal steam turbine running conditions. This is achieved by regulating the steam temperature in the superheater, which is divided into three parts with devices mounted at each connection point to allow for the injection of condensates to cool the steam. The steam pressure is controlled by adjusting the fuel flow command. However, controlling the output temperature can be challenging because of the transfer time delay between the points where the water is sprayed and the points where the steam temperature is measured. To address this challenge, a temperature control system was developed and tested in three different environments using an electronic simulator, the block-oriented simulation hardware BORIS, data acquisition board dSpace, and a MATLAB R2020a Simulink with a PI controller model. These simulations allowed for the study of the superheater’s function in both normal and fault conditions, with the possibility of controlling the system structure and detecting faults through the proper implementation of weighting matrices.

The article provides a computational analysis and comparison of the thermal efficiency of various measures for adjusting the steam temperature during the process steam extraction (P-extraction). Methods for adjusting the steam temperature in the P-extraction are presented following the given initial conditions for a specific version of a steam turbine plant. [ABSTRACT FROM AUTHOR]

This paper presents a coupled heat transfer model for coal-fired boilers that integrates boiler’s fire side computational fluid dynamics (CFD) solution with the boiler’s steam cycle, and thus, can predict the boiler steam temperatures subject to different boiler design and operation conditions. In this coupled model, the heat transfer submodels describing the gas-steam heat exchange for each part of boiler heating surfaces are integrated by exchanging the steam temperatures iteratively. This coupled heat transfer model is self-consistent since it ensures the fire side heat transfer solution to always coincide with the steam temperature changes across each boiler heating surface. This model is specifically designed to provide efficient computational solutions to engineering boiler problems in which the changes of boiler steam temperatures subject to different boiler design and operation conditions are of the major concerns. This model is applied to a 320 MW subcritical boiler to evaluate the impacts of coal switching and boiler operation adjustment on boiler’s heat transfer distributions and steam temperatures. The simulation results demonstrate that this model can effectively capture the complex coupled heat transfer behavior between the fire and steam sides of boiler and serve as an efficient predictive tool for engineering boiler problems.

This research investigated the effects of heat transfer using vacuum insulation over a pipe for industrial application compared to fiberglass insulation for steel pipe. In this study, an experiment was conducted at various steam temperature. The experimental test was performed with 1 m length and 80 mm diameter of steel pipe at 27 ∘ C temperature and 1 atm pressure working condition. The vacuum space created by single stage vacuum pump was having an ultimate vacuum pressure of 0.05 mbar. The performance of vacuum and fiberglass insulation had been studied. The basic concept of thermodynamics and heat transfer equations were applied to explain the experimental results. From the results, the performance of vacuum insulation was higher than fiberglass insulation. The cost of fiberglass insulation material was 0.05 US dollars per unit length and the vacuum insulation material was 0.34 US dollars per unit length 80 mm pipe diameter. The heat loss cost of fiber was 156.54 US dollars/yr per unit length and the vacuum insulation was 4.08 US dollars/yr per unit length. The net saving cost from vacuum insulation was 152.46 US dollars/yr per unit length of pipe. In general, the report on the performance of vacuum insulation was higher than fiberglass insulation in efficiency, cost, and environmental aspect for industrial application of pipes system. [ABSTRACT FROM AUTHOR]

Abstract A solar‐aided coal‐fired power generation (SAPG) system is a new type of power generation system in the field of solar thermal power generation. However, the instability of solar radiation will cause fluctuations in steam temperature, which is unfavorable for the operation of boilers and steam turbines. Based on a 600 MW subcritical coal‐fired power generation unit, TRNSYS software is applied to establish a transient simulation model of SAPG in this paper. A dynamic feedforward control system for steam temperature is set up. Some essential parameters, such as the fuel consumption rate, solar‐heated steam extraction rate, water spraying flow rate, and flue gas damper opening, are under the control of direct normal irradiance (DNI). Then, the dynamic characteristics of SAPG are analyzed using typical weather data. The simulation results show that under the fuel‐saving mode, when solar irradiation changes, the SAPG system achieves a coal reduction of 4.9% by using the steam temperature control system with DNI feedforward control, and the main steam temperature fluctuation is less than 5°C with the reheat steam temperature reduced within a reasonable range. The power generation fluctuation is less than 10 MW, and the solar‐to‐electricity efficiency reaches 22.5%. Some parameters on both the flue gas side and the water/steam side in the utility boiler are simulated to demonstrate the effectiveness of DNI control.

This paper presents a coupled heat transfer model for coal-fired boilers that integrates boiler's fire side computational fluid dynamics (CFD) solution with the boiler's steam cycle, and thus, can predict the boiler steam temperatures subject to different boiler design and operation conditions. In this coupled model, the heat transfer submodels describing the gas-steam heat exchange for each part of boiler heating surfaces are integrated by exchanging the steam temperatures iteratively. This coupled heat transfer model is self-consistent since it ensures the fire side heat transfer solution to always coincide with the steam temperature changes across each boiler heating surface. This model is specifically designed to provide efficient computational solutions to engineering boiler problems in which the changes of boiler steam temperatures subject to different boiler design and operation conditions are of the major concerns. This model is applied to a 320 MW subcritical boiler to evaluate the impacts of coal switching and boiler operation adjustment on boiler's heat transfer distributions and steam temperatures. The simulation results demonstrate that this model can effectively capture the complex coupled heat transfer behavior between the fire and steam sides of boiler and serve as an efficient predictive tool for engineering boiler problems. [ABSTRACT FROM AUTHOR]

Industrial-scale experiments were conducted to study the effects of tertiary air declination angle (TDA) on the coal combustion and steam temperature characteristics in the first 350-MW supercritical down-fired boiler in China with the multiple-injection and multiple-staging combustion (MIMSC) technology at medium and high loads. The experimental results indicated that as the TDA increased from 0° to 15°, the overall gas temperature in the lower furnace rose and the symmetry of temperature field was enhanced. The ignition distance of the fuel-rich coal/air flow decreased. In near-burner region, the concentration of O2 decreased while the concentrations of CO and NO increased. The concentration of NO decreased in near-tertiary-air region. The carbon in fly ash decreased significantly from 8.40% to 6.45% at a load of 260 MW. At a TDA of 15°, the ignition distances were the shortest (2.07 m and 1.73 m) at a load of 210 MW and 260 MW, respectively. The main and reheat steam temperatures were the highest (557.2°C and 559.4°C at a load of 210 MW, 558.4°C and 560.3°C at a load of 260 MW). The carbon in fly ash was the lowest (4.83%) at a load of 210 MW. On changing the TDA from 15° to 25°, the flame kernel was found to move downward and the main and reheat steam temperatures dropped obviously. The change of TDA has little effect on NOx emissions(660–681 mg/m3 at 6% O2). In comprehensive consideration of the pulverized coal combustion characteristics and the unit economic performance, an optimal TDA of 15° is recommended. [ABSTRACT FROM AUTHOR]

A wide area for application of vapor in heat power industry has been shown. Due to this, the problem of maintaining and controlling the dryness of steam during its transportation through steam pipelines remains of current importance. Quite detailed theoretical investigations into the steam parameters during its flow in the pipe have been carried out. A comparative analysis of steam velocity and temperature epures as a function of certain parameters and assumed approximations has been conducted. All calculations have been brought to quantitative results. As a result of the implemented analysis, it has been shown that the uncertainty of exact values of some quantities does not play a crucial role in common patterns of the formation of a dropping liquid. As a result of numerical investigations into the kinetics of steam condensation, the specific volume and density of the droplet condensate across the pipe have been identified. The obtained results and the proposed methodological approach to identifying steam parameters have been used in the development and further improvement of a device to measure dryness of steam whose original design was proposed earlier by one of the authors. The functional diagram and the prototype model of the batchbox of the measuring device are given in this investigation. [ABSTRACT FROM AUTHOR]

A solar‐aided coal‐fired power generation (SAPG) system is a new type of power generation system in the field of solar thermal power generation. However, the instability of solar radiation will cause fluctuations in steam temperature, which is unfavorable for the operation of boilers and steam turbines. Based on a 600 MW subcritical coal‐fired power generation unit, TRNSYS software is applied to establish a transient simulation model of SAPG in this paper. A dynamic feedforward control system for steam temperature is set up. Some essential parameters, such as the fuel consumption rate, solar‐heated steam extraction rate, water spraying flow rate, and flue gas damper opening, are under the control of direct normal irradiance (DNI). Then, the dynamic characteristics of SAPG are analyzed using typical weather data. The simulation results show that under the fuel‐saving mode, when solar irradiation changes, the SAPG system achieves a coal reduction of 4.9% by using the steam temperature control system with DNI feedforward control, and the main steam temperature fluctuation is less than 5°C with the reheat steam temperature reduced within a reasonable range. The power generation fluctuation is less than 10 MW, and the solar‐to‐electricity efficiency reaches 22.5%. Some parameters on both the flue gas side and the water/steam side in the utility boiler are simulated to demonstrate the effectiveness of DNI control. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article considers the possibility of achieving more efficient performance of a TP-13B industrial steam boiler fitted with a spray desuperheater and operating in the mode of buffer consumption of blast-furnace gas as applied to the superheated steam temperature automatic closed-loop control system. The main problem stems from the fact that the superheated steam temperature increases essentially due to large blast-furnace gas flowrates and displacement of the flame when shifting to operation with a large fraction of blast-furnace gas (with respect to the natural gas fraction). The usual injection adjustment range turns out to be insufficient for stabilizing the steam temperature downstream of the second-stage convection steam superheater (CSS2). In addition, the steam temperature downstream of the first-stage convection steam superheater (CSS1) increases significantly, because this section is not protected by injections. For solving the problem, it is proposed to use a combined system, which uses, in addition to the conventional steam temperature controller downstream of the CSS2, which adjusts the injection, a controller of steam temperature downstream of the CSS1, which adjusts the flame position by turning the air-control registers. With the steam temperature downstream of the CSS1 stabilized by adjusting the air-control registers, it becomes possible to pose less demanding requirements to the injections; in addition, with such stabilization, the CSS1 metal is protected from overheating. This is an advantage in comparison with the well-known arrangement in which such control is only performed when the injection valve position approaches the specified limit values. The functional and structural diagrams of the proposed control system are given. The parameters of the plant model channels' transfer functions are determined proceeding from the known experimental data for the TP-13B boiler. The system has been studied by carrying out computations in the environment of the MathCad software system and the MatLab/Simulink modular simulation software package. The simulation model includes nonlinearities typical for the automation equipment used in thermal power engineering. The effectiveness of the proposed combined control system during operation with essential variations of the blast-furnace gas flowrate has been demonstrated. The information presented in the article can be used in fitting the industrial steam boilers operating with buffer consumption of gaseous production waste with means for automatic control of superheated steam temperature. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Solar Aided Power Generation (SAPG) technology has been proved to be one of the most efficient ways to integrate solar energy into a coal-fired power plant. However, previous studies on SAPG systems have mainly focused on their design and design optimization. There are few studies on their operation. In an SAPG plant, solar heat is used to replace the extracted steam to preheat feedwater. However, the introduction of solar energy inevitably affects the steam flow rate through the boiler, especially when the SAPG plant is in fuel-saving operation mode, thus affecting the boiler's operation. Namely, the steam parameters at the boiler outlets would change with various solar inputs if no control mechanism were applied. A mechanism for adjusting the burners' tilt and attemperation flows in the boiler is therefore proposed in this study, in order to stabilize the temperature of the steam at the outlet of the boiler. To simulate the effectiveness of the mechanism, a transient model of the SAPG plant, including a series of modules for key components in the plant, has been developed in this study. The simulation results in a case study of a 300 MW e SAPG plant, showing the proportion of heat that was absorbed in the boiler was redistributed due to the solar input, without adjusting the burners' tilt and attemperation flows, resulting in temperature drops of superheated/reheated steam when in a fuel-saving mode. However, the simulation in the case study also shows that by swinging the burner tilt angle up to 22.7° and adjusting the attemperation flows in the super-heaters and re-heaters in the boiler, the superheated/reheated steam temperature can be restored from 523 °C and 510 °C respectively back to 543.0 °C, the desired temperature. Highlights • A sophisticated model for SAPG plant simulation has been developed. • Drops of steam temperature at boiler outlets and the reasons were revealed. • A remedial control measure was developed to restore/stabilize the temperatures. [ABSTRACT FROM AUTHOR]

Hydrogen is a clean energy source, and its use helps to mitigate climate change. Underground coal gasification for hydrogen production is a promising method for countries with abundant coal resources and high hydrogen demand. However, the existing coal-to-hydrogen process underground exhibit low production efficiency. This work proposes the use of swirl flow injection to improve hydrogen production efficiency, and also explores the influence of other injection conditions (oxygen flow rate, steam mass flow and steam temperature) on hydrogen production. For straight flow injection, the effect of steam addition on gasification performance depends on the oxygen flow rate, and the highest H 2 production is 14.6 L under 1 L/min oxygen and 1 g/L steam. With a swirl flow injection, H 2 production increases with steam addition for both 1 L/min and 2 L/min oxygen, which shows a larger H 2 production than straight flow injection. The highest H 2 production for swirl flow injection is 19 L under 2 L/min oxygen and 1 g/L steam. An increase in steam temperature barely affects the composition of products but apparently increases the amount of products. The fracture effect of high temperature steam might cause a sudden increase of H 2 and CH 4 at the late stage. [Display omitted] • Hydrogen production behavior with swirl flow injection was studied. • Effects of oxygen flow rate and steam mass flow were analyzed. • Temperature field and gas products at different steam temperature were discussed. [ABSTRACT FROM AUTHOR]

Stream temperature is an important control of many in-stream processes. There is rising concern about increases in stream temperature with projected climate changes and human-related water activities. Here, we investigate the responses to climate change and water diversions in Eel River basin. The increase in stream temperatures is considered to be the result of changes in air temperature, the proportion of base flow and the amount of stream flow derived from historical and future simulations using the integrated VIC hydrologic model and ANN stream temperature model. The results show that stream temperature will increase throughout the basin in the future under two climate change representative concentration pathways (RCPs 4.5 and 8.5) and will also be influenced by the water diversion activities schedules. Specifically, the stream temperature increases, in the late twenty-first century under RCP8.5 scenarios, from 1.20 to 2.40 °C in summer and from 0.58-3.46 °C in winter respectively; Water diversion activities in Eel River Basin can increase nearly 1 °C in stream temperature. Therefore, both climate change and water diversion activities can substantially cause the rise of more than 2 °C in stream temperature. In conclusion, stream temperature is mainly sensitive to the proportion of base flow in summer, but also the change of the amount of stream flow in winter in our case study area. In addition, it should be noted that the low intensity irrigation schedule has lower impacts on increasing stream temperature, whereas the high intensity irrigation schedule will further exacerbate the rise of stream temperature. Understanding the different impacts of climate change scenarios and irrigation schedules on stream temperature can help identify climate-sensitive regions, climate-sensitive seasons and water diversion schedules as well as assist in planning for climate change and social adaptive management. [ABSTRACT FROM AUTHOR]

For producing wood products without fractures based on thermo-hygro-mechanical (THM) treatments, it is essential to understand how steaming and compression change the wood softening and cell wall components. In this paper, the effects of compression combined with steam treatment (CS) on the viscoelasticity of the in-situ lignin of Chinese fir has been investigated through dynamic mechanical analysis (DMA) under fully saturated conditions. Several variations were studied, such as the softening temperature (Tg) and apparent activation energy (ΔHa) of the softening process in response to CS treatment conditions (such as steam temperature and compression ratio) under separate consideration of earlywood (EW) and latewood (LW). No difference between EW and LW with respect to the viscoelasticity was noted. Tg and ΔHa of the lignin softening were nearly unaffected by the compression ratio, but were highly influenced by the steam temperature. The Tg decreased significantly with CS treatments at or above 160°C, but showed no appreciable change, compared to the native wood, at the lower steaming temperature of 140°C. ΔHa increased at higher steam temperatures, while ΔHa showed a decreasing tendency with decreasing Tg. This indicates that lignin undergoes a simultaneous depolymerization as well as a condensation during CS treatment. [ABSTRACT FROM AUTHOR]