Industrial Steam Generator Research Articles

Analysis and improvement of gas flow behaviour at the inlet duct of an industrial HRSG boiler through CFD modelling

This work analyses and improves the distribution of the flow of flue gases along the inlet duct of two industrial Heat Recovery Steam Generation (HRSG) boilers. The inlet duct connection with the boiler casing presents a special configuration, being axial for one boiler and radial for the other. The study was carried out using a 3D Computational Fluid Dynamics (CFD) modelling. The flow uniformity improvement is studied considering the introduction of baffles, perforated plates and the Part Elimination and Lattice Search (PELS) method. The Root Mean Square (RMS) axial velocity is used to determine uniform flow distribution. Its value must be equal to or below 0.2 m/s. Nevertheless, the pressure drop in the boiler must not increase by 1 mbar as compared to the standard case. After analysing the 3D CFD modelling results, our conclusion is that, in an axial configuration, the PELS method and a perforated plate (TAD44A65) located at the inlet of the recovery zone can improve the fluid flow uniformity to 40 %. For the radial configuration, only a perforated plate (TAD44A65) located at the inlet of the recovery zone improves fluid flow uniformity to 43 %.

Energy, exergy, economic, and environmental analysis of a high-temperature heat pump steam system

Industrial steam is widely recognized as a valuable form of heat currency, possessing considerable social and economic significance. As the industry shifts to low carbon emissions, there is an urgent need to reduce CO2 emissions from industrial steam generation. The analysis of a high-temperature heat pump steam system (HTHPSS), which recovers industrial waste heat to produce high-temperature steam at 170 °C, includes evaluations of its energy, exergy, economic, and environmental (4E) to determine whether it can replace a coal-fired boiler. The economic analysis considered the recovery value of waste heat and the effect of CO2 trading prices. Optimization calculations were performed to investigate changes in the waste heat temperature and condenser outlet temperature. The study also offers recommendations for operational conditions and optimization strategies for the HTHPSS. The results indicate a positive correlation between the system coefficient of performance (COP) and the waste heat utilization rate with waste heat temperature and condenser outlet temperature. The maximum COP value is 2.73. The total exergy efficiency initially increases and then decreases as waste heat temperature increases. It also decreases as the condenser outlet temperature increases, reaching a peak value of 43.26 %. The waste heat temperature needs to be at least 59 °C to generate a net profit, with a corresponding payback period (PBP) of 4.40 years. The minimum PBP is 0.03 years, independent of waste heat temperature. The annual emission reduction increases as waste heat temperature increases and decreases as condenser outlet temperature increases. These results indicate that a HTHPSS could replace a coal-fired boiler and offer guidance for design optimization.

Explainable multimodal learning for predictive maintenance of steam generators

Prognostics and Health Management (PHM) is identified as an important lever for enhancing the development of predictive maintenance to ensure the reliability, availability, and safety of industrial systems. However, the efficiency of data- driven PHM approaches is dependent on the quality and quantity of data. Therefore, exploiting multiple data sources can provide additional, useful information than single-modal data. For instance, by incorporating multiple data sources, including condition monitoring data, images from cameras, and texts from maintenance technicians’ reports, multi-modal learning can provide a more comprehensive and accurate understanding of the system’s health. However, multi-modal deep learning is complex to understand. To address this complexity, it is crucial to incorporate explainable artificial intelligent techniques to provide clear and interpretable insights into how the model makes decisions. In this light, this paper proposes the application of the model-agnostic-explanation approach, i.e., SHAP, to explain the working mechanism of multimodal learning for the prediction of industrial steam generator degradation. Particularly, we determine the important features of each data modality and investigate how multimodal learning can overcome the issues of low-quality data from a single modality due to the additional information from other data modalities.

Integration of Dynamic Models and Virtual Reality for the Training of Steam Generator Operators

Abstract The goal of the PITSTOP (Immersive platform for structured operator training) project is to overcome the limits of traditional workplace training on dangerous systems and reduce the related risks, using an innovative integration of engineering simulation models and virtual reality (VR) tools. This article specifically presents the first VR platform for training on small-scale industrial steam generators, representative of a vast class of hazardous industrial equipment. The dynamic model of the steam generator was developed in matlab-simulink using a mixed physics-based and data-driven approach. The generator model includes the main engineering components, actuators and measuring equipment, as well as control logic and emergency procedures. It can simulate normal operations and emergency situations. The model was calibrated using experimental data collected from the real system at various operating conditions to align simulated performance with the real behavior. The VR environment was developed in Unity, a graphics engine widely adopted by the videogame industry, using three-dimensional computer-aided design models of the steam generator and its surroundings. The user can access this immersive system wearing an HTC Vive headset. Unlike most existing training systems, learners can interact with the actuators using bare hands gestures, without controllers, making the experience intuitive and easily accessible. By connecting the dynamic model with the VR environment, the user's interactions are directly provided to the steam generator model, which in turn directly outputs the steam generator response to the VR environment, providing audio and visual feedback to the user, as if they were actually acting on the real generator. The results from this study could boost the further development of training platforms to safely train operators and certify their competence.

Techno-economic comparative analysis of solar thermal collectors and high-temperature heat pumps for industrial steam generation

Industrial heat production is responsible for around 20% of total greenhouse gas emissions in Europe. To achieve the climate change goals defined in the Paris Climate Agreement, the EU commission has shifted its focus on sustainable means to generate heating. Moreover, global dependencies are leading to a re-organization of natural gas supplies. Therefore, there is a need for less vulnerable and less price-volatile solutions for heating. This paper focuses on two decarbonization technologies for industrial process heat supply: a) electricity-driven steam-generating high-temperature heat pumps (HTHP), a technology that is more efficient than fossil fuel boilers in generating steam, and b) solar parabolic trough collector (PTC), which can produce heat economically and at a minimal carbon footprint compared to other technologies. The main aim of this paper is to evaluate the levelized cost of heat (LCOH) of these technologies to fulfill a comparative techno-economic analysis. A maximum PTC collector's solar fraction limit (SFlimit) is defined to indicate when the LCOH for these two technologies is equal. This allows for distinguishing between the economic stronghold of each technology. The evaluation is carried out through the annual energy simulations using TRNSYS and Excel spreadsheets for HTHPs, while TRNSED and OCTAVE are used for the solar thermal part. Boundary conditions for European geographical constraints have been applied to establish use cases for the analysis. The result shows that the design of a PTC system with optimal SF can reach cost parity with HTHP for most of the analyzed locations. The developed methodology serves as a valuable guide to quickly determine a preferred lower carbon heat solution, thus easing the decision-making for industries.

CFD SIMULATION COMPARISON OF BOILER COMBUSTION TEMPERATURE USING CONVENTIONAL COMBUSTION AIR AND OXY-FUEL COMBUSTION

The burning of fossil fuels is the cause of the largest carbon dioxide (CO2) emissions in the world today. CO2 emissions may cause the greenhouse effect and global countermeasures. Boilers are steam generators that use fossil fuels such as coal and natural gas in their environment. The boiler itself is commonly used in power plants and industrial steam generators. In its operation, conventional boilers fueled by natural gas use air for the combustion system where the content of Nitrogen (N2) gas in ordinary air reaches 79% which dissolves CO2 gas in the exhaust gas so that the CO2 gas is carried into the atmosphere. Several technologies that aim to reduce CO2 emissions include pre-combustion, post-combustion, and combustion of oxygen fuel. Numerical methods such as Computational Fluid Dynamics (CFD) are used because the oxy-fuel technology has limited use in the industrial and utility world, and requires large procurement costs. Based on the simulation results, the combustion temperature in the fire system in 1917 o C originating from the combustion system, the resulting temperature is 1857 o C. Even so, the temperature distribution in the oxyfuel combustion system is more even in the combustion system so that the combustion system will be better. This is evidenced by the comparison of temperature comparison graphs on each furnace wall. The result was an increase in the temperature of the wall furnace by 5 o C to 20 o C.

Critical Deposit Loading Thresholds for Under Deposit Corrosion in Steam Generators

Significant industrial facilities typically operate a steam system with multiple steam generators (or boilers) that are potentially vulnerable to under deposit corrosion (UDC). This mechanism begins with the deposition of a porous layer of magnetite particles on the waterside heat transfer surfaces. Beneath this layer, wick-boiling causes the concentration of contaminants (such as chlorides) until the concentration exceeds some critical threshold that results in rapid corrosion. Industry practice to mitigate this risk includes monitoring the extent of deposition and then chemically cleaning the equipment before the deposits reach the critical level. One significant factor in this mechanism is the heat flux, which drives both the magnetite deposition and the wick-boiling processes. This paper investigates the relationship between heat flux and the critical deposit thickness for the initiation of chloride-driven UDC. Ex-service samples from industrial steam generators have been examined, an electrochemical method has been developed for in situ measurement of the deposit loading, and a wick-boiling model has been used to estimate the local conditions beneath the porous deposits during the progress of UDC. For 1.0 Cr 0.5 Mo steel coils from a steam generator operating at approximately 75 bar(a) under an all volatile treatment regime, the threshold for the onset of rapid UDC was determined to be at a heat flux of 350 kW/m2, deposit loading of approximately 50 mg/cm2, and deposit thickness of approximately 95 µm, corresponding to a local chloride concentration beneath the deposits of approximately 80 ppm and a local at-temperature pH below ∼2.7.

Multi-domain Vibrations Response of Externally Excited Fluid Conveyer Pipe in Industrial Steam Generator

Electric power is an indispensable consumer commodity for a little over a century now as all electric equipment in dwellings, commercial, and industry sectors are essentially dependent on electricity. Heat recovery steam generator, HRSG is an important system in combined cycle power plants. Indeed, excess vibrations induced on such devices may gradually lead to fatigue failure that affect the process of power output. This work investigates, models, and simulates the vibrations response of a fluid carrier pipe housed inside the cavity of the system while experiencing highly pressurized nearly perpendicular external force of extremely hot flue gas on the outside and pressurized water and water vapour from the inside. Transient and steady-state vibrations from initial conditions and the forcing function analysis are performed to account for the variation of damping, amplitude, and frequency responses of the system. Initial parameters used in the systems’ model are from industry subsequent to the OEM instructions. However, we introduce a new set of parameter values so as to observe the vibrational behaviour by varying these parameters. The purpose of performing a parameter-based vibration analysis is that parameter variation may point to different responses in the system. Indeed, this in turn indicates which set of parameters are suitable for rectifying the primary causes of undesired vibrations. To account for the consequence of mass flowrate, the model covers low pressure, intermediate pressure, and high-pressure constituents. The results obtained from the model are for the relationships of amplitude and phase angle as functions of frequency of the system. From these data, different interactions of quantities such as force, damping ratio, and number of dampers and vibration supports are observed. These results implores the implementation of new set of parameters to improve the agility of the system and minimize the impact of excess vibrations.

A computationally efficient method for the prediction of fretting wear in practical engineering applications

A method for simulating fretting wear using the Modified Simplex Method for a contact solution has been developed. The initial separation between two contacting bodies was used as an input to solve the contact force distribution. An average cycle pressure distribution was calculated for the stationary surface over a displacement cycle. The wear depth was calculated for each body based on the modified Archard’s wear equation using the force distributions and the gross sliding distance. The initial separation was updated and the force distribution was solved for the next iteration. Methods for optimizing computational time are presented using a combination of linear jumping and adaptive cycle jumping for the wear depths, and an interpolation weighting method for reducing the grid size. It was found that computational time can be reduced by at least 98% compared with other simulation methods, making this method a viable tool for design. Fretting wear scars and depths were simulated for a cylinder on flat in contact and were found to agree with experimental results and Finite Element modeling results from previous literature. To show the capability of the fretting wear model, three practical applications were simulated: automotive seat sliding rails, steel wire ropes for industrial applications and steam generator tubes for nuclear power stations.

Design Factors in Concentrating Solar Power Plants for Industrial Steam Generation

The importance of energy consumption for industrial steam generation justifies the need to promote new renewable and environmentally friendly energy sources, such as concentrated solar energy, for its integration in this sector. In this work, the different alternatives currently available and their advantages and disadvantages are discussed, as well as the main parameters that influence the design of solar installations for industrial steam production. Besides, a guidance procedure is proposed and applied to a real solar plant design.

Estimating the Steam Quality in Power-Generating Boilers from Electrical Conductivity and pH Measurements

The quality of steam produced by boilers is strictly standardized and must be maintained whatever the quality of makeup water and whatever the composition of the boiler unit’s thermal cycle equipment. Under the conditions of constantly improved instruments for chemical monitoring, it becomes possible to develop measurement systems using which the main standardized and diagnostic steam quality indicators can be monitored by measuring the electric conductivity and pH of cooled samples. Unlike boilers operating at a pressure of 13.8 MPa and higher, steam boilers for steam pressures equal to 9.8 and 3.9 MPa—and also industrial heat recovery steam generators—operate with steam that has a higher content of salts and carbon dioxide; in addition, it contains ammonia, which enters into steam from boiler water. Steam quality is often estimated using the two-quadrant nomographic chart of Mostofin, who proposed it more than 50 years ago. In using certain computation algorithms, it is possible to calculate the standardized and diagnostic steam quality indicators, such as concentrations of sodium, chlorides, ammonia, carbon dioxide, and salt content. The article presents an algorithm for estimating the concentrations of the above-mentioned impurities for cooled live steam samples of power-generating boilers operating at pressures below 10.0 MPa, and boilers for superhigh and supercritical pressures, and industrial heat recovery steam generators, including the combined-cycle power plant units. Examples of using the calculation procedure for analyzing the steam quality in industrial boilers are given.

Analysis and Perspective on Heat Pump for Industrial Steam Generation

Sustainable Manufacturing In article number 2000108, Ruzhu Wang and co-workers study possible steam generation paths based on heat pump and propose a novel path to turn water into high-temperature steam by an air-source heat pump with a temperature lift over 100 °C, which could be a sustainable solution for industrial heating decarbonization. The “AIR for STEAM” in the picture illustrates the concept that utilizing heat from ambient air for steam generation, where the heat pump “O” in the middle of “for” is the key. The dial in the middle of the heat pump symbolizes the temperature scale. It shows that the air source heat pump can abstract heat from the ambient surroundings to heat water up to 120–150 °C high temperature steam. The water tap on the right side is connected to the heat pump through the pipeline, which symbolizes the water input and is used to generate steam. The red fluid below symbolizes high-temperature and high-pressure steam, which is sent to the corresponding factory for industrial uses.

Analysis and Perspective on Heat Pump for Industrial Steam Generation

Steam generation process is closely related to energy conversion and cleaner energy utilization, and the industrial steam is even regarded as the currency of heat with significant social and economic value. Herein, the possible industrial steam generation paths are analyzed based upon thermodynamics analysis, in which fossil fuel, electric, and heat‐pump heating are considered. The large‐temperature‐lift heat‐pump heating for steam generation is proved to be a most reasonable way with high‐efficiency and wide adaptability. Furthermore, a possible system sketch is proposed, in which the heat pump is used for preheating for low‐temperature evaporation and the generated steam can be thus compressed with a steam compressor to the expected high‐temperature (pressure) steam. The key parameters of the heat pump for steam generation are ascertained and the subsequent optimization space is discussed. The results show that the proposed steam‐generation path has clear performance advantages and potential for industrial steam generation, which could be a sustainable heating system for industry.

Complex for the production of compressed carbon dioxide based on an industrial furnace for food production

Today, the problem of the use of energy is the most common. In order to increase energy efficiency could be used at food enterprises. A new scheme of combined main production and auxiliary production has been developed. In particular, on the basis of industrial furnaces for the production of compressed carbon dioxide. In this system, the coolant is supplied from an industrial furnace. In addition, it is shown that the coolant may be a rotary kiln or an industrial steam generator. The developed scheme is universal and can be used at the enterprise for various purposes.

Evaluation of the efficiency of a heat recovery steam generator via computational simulations of off-design operation

This work investigates the flow and heat transfer on the gas side of a heat recovery steam generator. During the operation of a power plant, off-design conditions that significantly impact the steam generator efficiency, caused by variations in the gas flow, corrosion and fouling of tube walls, may be encountered. In addition, passages around the heat exchanger modules develop along the equipment lifetime, allowing the bypass of flowing gas into zones of the boiler of low heat transfer effectiveness. These issues are here addressed via computational simulations, using a commercial software application for solving the mass, momentum, and energy conservation equations. The boiler geometry and the boundary conditions for the simulations are taken from a real, typical industrial heat recovery steam generator fed by gas turbines exhaust gases. Flow turbulence is modeled using the k- $${\epsilon}$$ model, and heat exchanger modules are considered as porous media, through which the exhaust gases flow while supplying heat to the water. The water flow properties are specified from process data. Numerical results for thirteen realistic off-design conditions are compared to those for the boiler normal operation point. It is found that the cases considering deviation of gas to the trapdoors and lateral passages have the greatest impact on the boiler efficiency. Results indicate an efficiency drop from 86% for the base case to 48% for the case with gas deviations. In addition, a reduction in the gas flow or the plugging of the low-pressure economizer tubes may decrease the boiler efficiency by more than 10% points.

Advanced Study of the Parabolic Trough Collector Using Aluminum (III) Oxide Seal

Solar energy is the main source of all sorts of energy present in nature, i.e. all energy produced from it. So the direct use of solar energy as a useful energy is very important. There are numerous solar thermal projects in which the concentrated type collector heats up to 100 to 400 degrees Celsius. It is used in a wide range of applications, including power generation, industrial steam generation and hot water supply. Parabolic trough collector is chosen for steam production, since high temperatures can be achieved. The temperature of the inlet and outlet water, the mass flow rate, the usable heat gain and also the thermal efficiency of the collector are calculated. Theoretical values for heat loss of vacuum as the annulus gas is measured and compared with other values for heat loss of air as the annulus gas. In order to help preserve the vacuum within the annulus gap, a substitute glass-metal seal was created. The seal helped increased the heat loss and thereby improve the overall efficiency of the collector. It can be deduced from the band structure and density of the states of Al2O3 and is an outstanding insulator content. In addition, the assessment of the absorption coefficient showed a low energy range of 5.34 eV to 11.88 eV, with a median value of 11.50 eV and 11.88 eV respectively for parallel and perpendicular polarizations.

Fuel choice in industrial steam generation: Empirical evidence reveals technology preferences

Scenario analysis of the energy system relies largely on model calculation and underlying techno-economic data. In the industrial context, the influence of behavioral aspects has been neglected or is subject to expert-judgment. Empirical evidence on technology preferences is scarce. In this publication, we present original survey results for preferences in industrial steam generation technologies in Germany. Additionally, we compare the performance of a set of preference parameters derived from these results with expert-judgment. We find that in the sample, coal- and oil-based generation is perceived as less attractive than biomass- and natural gas-based generation by a value equivalent to 4.40 €ct/kWh and 2.26 €ct/kWh, respectively, for experienced users. This effect is stronger for inexperienced users (+55%). Different results were obtained in an energy system model using these stated preferences and expert judgment (considering revealed preference data). This might hint at a shift of preferences.

Calcium and magnesium ion removal from water feeding a steam generator by chemical precipitation and flotation with micro and nanobubbles

ABSTRACT This work summarises the results of calcium and magnesium ion removal from raw water feeding an industrial steam generation system. The cations were precipitated with sodium phosphate before separation of the solids by dissolved air flotation, with micro and nanobubbles. Studies were done at bench scale and validated at pilot scale (raw water feed = 1 m3 h−1; air-to-solids ratio = 0.046 mg of air mg−1 of solids; residence time = 11 min). Results indicated that chemical precipitation followed by flotation significantly improved the quality of the boiler water. Best results were obtained after precipitating the cations with 50 mg L−1 of sodium phosphate at pH 11.5 and flotation with a saturation pressure (P sat) of 4 bar, a recycling ratio of 30% and a sodium oleate concentration of 20 mg L−1 as an hydrophobizing reagent. The latter assisted the adhesion of the nanobubbles (100–500 nm) generated at 4 bar with a numeric concentration of about 2.5 × 108 NBs mL−1. At pilot scale, the total hardness in the solution decreased by 80%; the residual calcium and phosphate ion concentrations were 12 and 2 mg L−1 respectively. This cell was designed including lamellae and perforate plate to improve the superficial loading capacity (up to 9 m h−1). The results were explained by chemical and interfacial phenomena and it is believed that this technique has great potential in water softening processes.

New Theoretical and Methodological Approaches to the Study of Heat Transfer in Coal Dust Combustion

The existing theories of heat transfer in combustion chambers of boiler units fail to take into account a number of important factors that affect the reliability of results, and the methodological approaches to optimizing combustion processes can be revised in view of the spatial and temporal parameters of flame. Hence, the research aimed to improve the fundamental theoretical and methodological principles of studying heat transfer in coal dust combustion in the combustion chambers of industrial steam generators. The authors proposed to extend the theory of heat transfer with the mathematical description of particle size distribution of coal dust. In addition, the authors used the developed mathematical model of coal dust combustion based on a continuous curve of the particle size distribution in the ensemble. The mathematical model is consistent with the aeromechanical and thermal characteristics of flame. This work introduced a concept of flame continuum as a continuous medium, where the processes of combustion and heat transfer are studied. To achieve the research aim, in this paper, the methods of combustion chamber zoning, the equations of stationary and non-stationary heat conduction, radiation, and convective heat transfer, were used. These methods were tested on a number of high-temperature units.

Simulation of flow field and carbon monoxide emission in an industrial scale heat recovery steam generator

Computational simulation is performed for flow field and carbon monoxide (CO) emission in an industrial scale heat recovery steam generator (HRSG) by ANSYS Fluent v13. The geometrical details are reproduced with burner holes and swirler blades simplified to avoid excessive computational burden. Turbulence-chemistry interaction is modeled by the steady laminar flamelet model (SLFM) and the unsteady laminar flamelet model (ULFM) through a lookup table without time consuming integration of stiff elementary reaction steps. The ULFM showed good agreement with measured CO mass fractions near the extinction limit for Sandia Flame D in Turbulent Nonpremixed Flame (TNF) Workshop. The proper trends of variation and the same order of magnitude of CO mass fractions were reproduced by the ULFM for the three reference cases of varying HRSG loads. Parametric investigations were performed to identify the factors influencing exhaust CO with respect to the number and layout of activated burners and flow correction device (FCD). Results showed two competing factors for CO emission, rich mixture by undermixing and lean mixture by overmixing, which may lead to local extinction below the flammability limit.