Boiler Model Research Articles

SCRN: A Complex Network Reconstruction Method Based on Multiple Time Series

Complex network reconfiguration has always been an important task in complex network research. Simple and effective complex network reconstruction methods can promote the understanding of the operation of complex systems in the real world. There are many complex systems, such as stock systems, social systems and thermal power systems. These systems generally produce correlated time series of data. Discovering the relationships among these multivariate time series is the focus of this research. This paper proposes a Spearman coefficient reconstruction network (SCRN) method based on the Spearman correlation coefficient. In the SCRN method, we select entities in the real world as the nodes of the network and determine connection weights of the network edges by calculating the Spearman correlation coefficients among nodes. In this paper, we selected a stock system and boiler equipment in a thermal power generation system to construct two complex network models. For the stock network model, we used the classic Girvan–Newman (GN) algorithm for community discovery to determine whether the proposed network topology is reasonable. For the boiler network model, we built a predictive model based on an support vector regression (SVR) model in machine learning, and we verified the rationality of the boiler model by predicting the amount of boiler steam.

Effects of moisture and its input form on coal combustion process and NOx transformation characteristics in lignite boiler

Effects of moisture content in lignite (MCL) and its input form (IFMC), i.e. liquid water or water vapor, on coal combustion behavior and NOx transformation characteristics were studied in this paper. For this, 6 cases were numerically investigated within a previously validated 660 MW lignite-fired pulverized boiler model, where coal properties were defined by simplified coal compositions method. Among cases, MCL and IFMC were artificially altered while the relative contents of other coal components remain unchanged. Results show that when MCL is increased as H2O(l), coal combustion process deteriorates heavily and thus results in decreases in combustion temperature and fuel utilization rate. Meanwhile, the weakened in-furnace reductive atmosphere leads to a monotonic increase of NOx emission with liquid MCL increasing. Besides, IFMC is found to greatly affect NOx emission, and an increased proportion in water vapor tends to significantly lower the final NOx emission. Based on this, the operating cost of pre-drying system is correlated to that of the post-furnace denitrification process. Considering the potential widespread use of high moisture lignite in future power plants, these findings can be of great theoretical help in guiding the practical operation of lignite boilers.

Quantitative Feedback Theory design of valve position control for co-ordinated superheater control of main steam temperatures of power plant boilers

Abstract This paper presents an application of a Single-Input Single-Output (SISO) controller and a Valve Position Controller (VPC) using robust Proportional-Integral (PI) controllers designed using Quantitative Feedback Theory (QFT) specifications to control superheater outlet steam temperatures of a 600MW once-through boiler. To illustrate the methodology, a dynamic model of a tower-type boiler was modelled using Flownex® to test the VPC design application with structured uncertainty under varying load and disturbance conditions. The results show that the valve position controller application is more efficient than the SISO technique, allowing the final attemperator more bandwidth to deal with unexpected temperature changes.

Determination of the Working Parameters of the Biomass Boiler

The modern day trend is associated with the green energy. Thermochemical conversion is the commonly used way of extraction energy from the biomass. Nevertheless, the thermochemical processes of the combustion are not totally known. The simulation model of the woodchips boiler was made to understand the processes inside. Simulation model was made for Ansys Fluent 2019. Combustion model consist of two combustion stages: 1st – combustion of volatile compounds, 2nd – combustion of the solid parts. The simulation was validated by the series measurements at the boiler HERZ firemytic 80 BioControl.

Evaluation and Simulation on the Reserve Capacity of Thermal Storage Electric Boiler Clusters

After providing a better service for nearby heating loads, a thermal storage electric boiler system can use the heat storage tank to participate in the peak-shaving and reserve services of the power grid. Current researches focus on its peak-shaving capacity, but ignores the use of its reserve capacity, which is important to the random fluctuations of renewable energy sources. Facing the actual analyzing demands on power system adequacy, this paper starts with the discussion of typical operation modes, and builds the powersystem- adequacy model of a thermal-storage electric boiler based heating system. Based on the presented model, the concept of feasible domain for heat charging and discharging is proposed. By implementing the concept, the quantitative evaluation method to calculate the reserve capacity of a thermal storage electric boiler system is proposed. The verification of the method is also given. Based on the planning data of an actual power grid, the short-term reserve capacity as well as the effect on promoting renewable energy consumption is estimated according to the given size of the provincial thermal storage electric boiler clusters. Finally, the influences of different choices of peak-shaving strategies, heat storage tank capacity on its reserve capacity are simulated and analyzed.

Application of waste oil purification technology on a heating installation of an industrial hall

The paper proposes the development of an experimental model of boiler using waste oil revitalized with bentonite, for heating an industrial hall. The main objective is to present a new perspective on the use of waste oils, a framework in which it no longer presents a danger to the environment and to human health, as well as their energy use from an economic and ecological point of view. Experiments were performed to determine the adsorption of the impurities from the waste oil. One of the experiments is to compare the combustion of the revitalized waste oil with the combustion of raw waste oil. The results show improvements in the combustion process and decreases of the pollutant emissions for revitalized waste oil. The CO concentration decreased on average by 52% when and the NOx concentration increased by 57% due to the increase of temperature in the furnace in the case of burning purified oil. The experimental installation is adapted on an industrial hall.

Enhancing peak shaving capability by optimizing reheat-steam temperature control of a double-reheat boiler

Double-reheat coal-fired power plants elicit much research attention due to their high efficiency and low emissions. However, steam temperatures fluctuate heavily, especially in transient processes, thereby compromising the load cycling capacity of these power plants and even threatening their stable operation. To overcome these challenges and optimize the operations of double-reheat boilers, a dynamic boiler model was established and validated with values measured from a real power plant. A revised reheat steam control logic was proposed that considers the heat storage variation in boiler metals and the deviation of steam temperatures during peak shaving transient processes. The performance of the original and revised reheat steam control logics in terms of temperature control and energy delivery characteristics was compared and discussed. Calculation results show that the revised control logic performs better than the original logic in large-range load cycling processes. The steam temperature fluctuations are alleviated, and the overshoots are reduced substantially. The revised reheat steam control logic ensures that the accessible maximum load variation rate is 4.0% BMCR min−1, which cannot be safely guaranteed by the original logic. These improvements are beneficial to increasing the threshold of the load variation rate and improve the flexibility of the power plant. The average thermal (ηI) and exergetic (ηII) efficiencies of the original and revised control logics in load cycling are compared. For loading up processes, ηI and ηII decrease by 1.04% and 0.28% at the most, respectively. For the loading down processes, the maximum increments in ηI and ηII are 1.44% and 0.77%, respectively.

Heat transfer calculation methods in three-dimensional CFD model for pulverized coal-fired boilers

Computational fluid dynamics (CFD) has been used extensively to study the combustion characteristics of coal-fired boilers. However, very limited of the boiler CFD studies were used to quantitatively predict the heat transfer distributions in practical boiler applications. This paper presents a systematic description on the heat transfer calculation methods in three-dimensional CFD model for coal-fired boilers. The primary objective is to provide a set of heat transfer submodels that can be easily employed to solve and analyze large scale practical boiler problems. All types of boiler heating surfaces are considered with particular focus on the heat transfer calculation of furnace water wall. It is implemented in the CFD model in terms of a thermal boundary condition (B.C.) describing the energy balance between the boiler’s fire side heat transfer and water side heat absorption. The physical significance of the associated B.C. parameters and their accurate prescription are discussed in detail in this paper. It is found that furnace wall heat transfer is largely affected by the wall ash deposit conditions such that the heat transfer coefficient of furnace wall can be determined based on the thermal properties of ash. Although ash thickness may vary dramatically over furnace wall and is extremely difficult to predict, its thermal conductance was found to only vary within a small range for normally operated coal-fired boilers. Establishing the connection between the thermal conductance of wall ash deposits and the heat transfer calculation of furnace wall bypasses the tremendous difficulty and uncertainty incurred in predicting the ash thickness, and thereby, greatly simplifies the wall heat transfer calculation process. The heat transfer calculation methods introduced in this study embody the key physics associated with boiler’s heat transfer process while making a reasonable balance between the level of model complexity and their applicability to practical boiler problems. In this paper they are illustrated and validated on a 330 MW tangentially-fired subcritical boiler. The results show that the predicted boiler heat transfer distributions are in close agreement with the boiler’s operating data.

Modeling and simulation of a natural circulation water-tube steam boiler

In the present work, the overall behavior of a steam boiler is investigated using RELAP5/MOD3.2 system code at three different operating loads. Main thermal–hydraulic parameters are analyzed at steady-states corresponding to 60%, 100% and 110% of the boiler nominal load. RELAP5 system code is widely used in the design and safety analysis of nuclear reactor installations as well as for conventional facilities in recent years. The steam boiler studied herein is a water-tube natural circulation type used in a natural gas liquefaction complex for superheated steam production purposes. A complete model of the steam boiler has been developed for the RELAP5 code. This model, that is also suitable for transient simulation, has been used for the reconstruction of three steady-state tests in order to assess the steam boiler safety features during the operation. The model includes all parts that can eventually influence the safety of the steam boiler particularly the control and regulation system. A qualification process has been undertaken in the aim to verify the capability of the model to reproduce the main parameters of the steam boiler. This process revealed that RELAP5 system code results matches significantly the experimental data of the steam boiler. Finally, it should be mentioned that the results obtained so far are very encouraging for studying the general behavior of the steam boiler in transient operating conditions, as well as for evaluating its safety under hypothetical scenarios. This step will be undertaken in the near future and will allow the check of the code capability to simulate thermal–hydraulic phenomena occurring in the steam boiler during transient operation.

Integration of continuous restricted Boltzmann machine and SVR in NOx emissions prediction of a tangential firing boiler

The NOx emissions prediction modeling of a coal-fired boiler is a complicated problem because of its highly nonlinear and strongly correlated multi-variables. To address this problem, this paper presents a novel deep structure using continuous restricted Boltzmann machine (CRBM) with support vector regression (SVR). A new steady-state identification method is first established by applying kernel principal component analysis (KPCA). Subsequently the stationary samples are subjected to the stacked CRBM network for extracting implied features. The combination of the optimal features and target NOx values are further utilized for training SVR to establish the regression pzmart of the CRBM-SVR prediction model. Additionally, particle swarm optimization (PSO) is applied for optimizing hyper-parameters of SVR, and weights of CRBMs are fine-tuned with gradient descent on account of prediction errors. Compared with the existing state of the art, the proposed structure achieves a good performance of 4.83 mg/m3, 3.55 mg/m3 and 0.963 of RMSE, MAE and R2.

Parametric identification of integrated model of a coal-fired boiler in a thermal power plant

Retrofit or replacement of few units in a subcritical facility may not only improve overall efficiency of conversion of energy in a power plant but also support sustainability issues. The primary objective of this article is to identify model parameters of a coal-fired integrated boiler and to present a comparative study on three different identification methods. This leads to select most suitable models that are applied for the developed model of the boiler of 210 MW coal-fired thermal power plants. The mathematical models of economizer, drum, and super-heater assembly are derived using mass balance and energy balance equations. The derived multi input–multi output model is then validated, and the model parameters are identified using three different identification methods namely nonlinear least square technique, maximum likelihood estimation, and expectation maximization algorithms. Identification of the plant model will essentially help to frame a good controller. In this article, parameter estimation has been carried out from real-time plant as it provides selective tool through quantitative comparative study of the three methods. The expectation maximization method has been found to provide suitable results compared to the other two methods. Model parameters of integrated boiler of a comprehensive structure have been obtained for the first time using expectation maximization method.

A data-driven approach for industrial utility systems optimization under uncertainty

Energy optimization of utility system helps to reduce the operating cost and save energy for the industrial plants. Widespread uncertainties such as device efficiency and process demand pose new challenges for this issue. A hybrid modeling framework is presented by introducing the operating data into mechanism model to adapt the changes of device efficiency and operating conditions. Mathematical models of boilers, steam turbines, and letdown valves are then developed in the framework. Based on the process historical data of a real-world plant, a Dirichlet process mixture model is used to capture the support information of uncertain parameters. Bridging data-driven robust optimization (DDRO) and utility system optimization under uncertainty, a robust mixed-integer nonlinear programming (MINLP) model is developed by utilizing the derived uncertainty set. The robust counterpart of the developed model can be reformulated as a tractable MINLP problem including conic quadratic constraints that could be solved efficiently. A real-world case study is carried out to demonstrate the effectiveness of the proposed approach in protecting against uncertainties and achieving a good trade-off between optimality and robustness of the operational decisions for industrial utility systems.

Effects of the Distribution of Heating Surface Areas on the Performance of Bagasse Boiler

Main components of a bagasse boiler are furnace, evaporator, superheater, boiler bank, economizer, and air heater. Combustion of fuel and air in the furnace produces thermal energy that is used to evaporate feed water in the evaporator. Hot flue gases from the furnace also contribute to increasing steam temperature in the superheater. Hot flue gases then pass through the boiler bank, resulting in additional water evaporation. After that, they pass successively through the economizer, in which feed water temperature is increased, and the air heater, in which air temperature is increased, before being exhausted to the atmosphere. It is known qualitatively that the boiler efficiency is increased with the heating surface area of each component. Quantitative effects of increasing heating surface areas, however, require a bagasse boiler model that takes into account their effects. The unavailability of a suitable model in the open literature is the main reason why this paper is written. The proposed model assumes the superheater is a radiative-convective heat exchanger, whereas boiler bank, economizer, and air heater are convective heat exchangers. The model is then used to determine how the boiler efficiency is affected by the heating surface areas of superheater, economizer, and air heater. It is found the boiler efficiency is most sensitive to change in economizer surface area.

Modeling of a steam boiler operation using the boiler nonlinear mathematical model

The subject of this paper is the steam boiler nonlinear mathematical model. The furnace chamber heat transfer is modelled assuming that the flue gas temperature across the entire furnace chamber is constant. Only radiation heat transfer to the boiler waterwalls is modelled. Distributed parameter mathematical models are developed of the steam superheater individual stages: the superheater first stage, the platen superheater, the second and third stage of the superheater. In the same way, the boiler two-stage economizer is modelled. The flue gas and air temperatures downstream the air heater individual stages are determined using the ε-NTU method (effectiveness ε - the number of transfer units NTU).Due to such arrangement of the boiler heating surfaces and the heat transfer nonlinear character, iterative calculations of the steam, flue gas, and air temperatures are necessary. The developed mathematical model makes it also possible to determine temperatures of the tube outer and inner surfaces and external fouling for all heating surfaces of the boiler.The developed non-linear mathematical model of the entire boiler has high practical importance. The proposed mathematical model can be used to simulate the boiler operation in various conditions, allowing to determine and correct selection the parameters of boiler operation. A non-linear mathematical model of the boiler can also be used to design the individual stages of the superheater properly so as to achieve the desired temperature behind the individual stages. Determination of the local temperature of the tube wall allows selecting an appropriate grade of steel for the individual stages of the superheater. Also, the developed non-linear mathematical model can be used for boiler operation monitoring in on-line mode.

Simulation of Legionella concentration in domestic hot water: comparison of pipe and boiler models

The energy needed for the production of domestic hot water (DHW) represents an important share in the total energy demand of well-insulated and airtight buildings. DHW is produced, stored and distributed above 60°C to kill Legionella pneumophila. This elevated temperature is not necessary for DHW applications and has a negative effect on the efficiency of hot water production units.In this paper, system component models are developed/updated with L. pneumophila growth equations. For that purpose, different existing Modelica pipe and boiler models are investigated to select useful models that could be extended with equations for simulation of bacterial growth. In future research, HVAC designers will be able to investigate the contamination risk for L. pneumophila in the design phase of a hot water system, by implementing the customized pipe and boiler model in a hot water system model. Additionally it will be possible, with simulations, to optimize temperature regimes and estimate the energy saving potential without increasing contamination risk.

Mathematical model of a supercritical power boiler for simulating rapid changes in boiler thermal loading

This paper presents a new online-ready mathematical model of a supercritical power boiler, which enables comprehensive analysis of the boiler dynamics. The model allows generating modified sliding curves for a power unit that is currently under construction in one of a Polish power plant. The modified sliding curves illustrate the transients of the steam at the turbine inlet, which varies depending on the power unit load. The developed model allows analysing the boiler operation during start-up from cold, warm, and hot states. Moreover, the model allows simulating the boiler operation when the power unit output increases by 7.5% and 5% in a specified period.To satisfy the requirement of increasing the power unit load by 5% in a set period, the live steam mass flow rate must be increased at the boiler outlet. For this purpose, the live steam pressure at the turbine inlet is reduced, and the fuel mass flow rate is increased simultaneously. This results in an increase in the live steam mass flow rate at the boiler outlet. The total increase in the live steam mass flow rate can be determined using the developed model. After the pressure decrease process is stopped, the required level in the steam mass flow rate at the boiler outlet should be achieved only by firing more fuel. The only approach to obtain the appropriate values of the target decrease in the pressure at a set load, in the range of the power unit loads from 40% to 80%, is to develop a mathematical model of the entire boiler and perform the simulations.All the simulations are performed using an in-house developed computer program.

Research and Simulation of Boiler Combustion System Based on Convolution Neural Network

This paper developed a coal-fired boiler modeling method based on CNN (convolutional Neural Network). In recent years, the deep learning using CNN has made remarkable achievements in image research field. This paper combined the image convolution method and the signal system convolution theory in coal-fired boiler modeling, which regards the DCS records as time series signal. This network is consisted of two convolutional layers which map the input to the feature map, followed by two fully connected layers to model the feature to the output. All the parameters in the network, including the convolution kernel parameter are optimized by minimizing the cost function. This model provided a good solution of modeling coal-fired boiler system with characters of time delay, highly nonlinear and multi-variable coupling.

Perancangan Boiler untuk Proses Sterilisasi pada Baglog Jamur Tiram

The production process is the core of an industry that certainly relies on a variety of equipment to help the process run. Oyster mushroom baglog industry is one of the agricultural industries that needs to be developed in its production equipment because of its good market prospects and high economic potential with a clear market segment. But there is a problem that often faced by the baglog farmers, the problem is the sterilization process from baglog itself is not good, so the quality of the oyster mushroom will decrease or worse is the crop failure. Therefore an appropriate boiler is needed that it can increase the yield and quality of a baglog oyster mushroom industry. Boilers that are designed will follow the existing standards, which are in accordance with the ASME (American Society of Mechanical Engineers) Boiler and Pressure Vessel Code (BPVC) standards and coupled with simulations in the form of adding loads to the boiler model using Pro Engineer Wildfire 4.0 software.

Simulation of rapid increase in the steam mass flow rate at a supercritical power boiler outlet

The paper presents selected results of simulations of a rapid increase in the supercritical power boiler thermal load. The simulations concerned the possibility of obtaining the required increase in the live steam mass flow rate at the boiler outlet in a set period. This condition must be met to achieve the required increase in the power unit load, of the order of a few dozen MW in a few dozen seconds. For this purpose, it is necessary to decrease the boiler pressure and increase the fired fuel mass flow rate at the same time. The pressure reduction is carried out by opening, at a constant rate, the control valves installed on the pipeline at the turbine inlet. Assuming that the rate is known, the unknown parameters are the values of the target pressure reduction and the time of the pressure decrease process duration. The values vary depending on the power unit initial load. After the pressure decrease process is stopped, the required increase in the power unit load (the increase in the live steam mass flow rate) should be maintained only by firing more fuel. The required values of the target reduction in pressure within a specific range of the power unit load can only be determined by developing a precise mathematical model of the entire boiler and performing simulation computations. The obtained results are of fundamental practical importance because they are used by the boiler manufacturer to generate the power unit modified sliding curves. The results presented in the paper relate to a supercritical power unit now being constructed in one of the Polish power plants. An in-house mathematical model was developed for the power unit boiler. The model comprises all heating surfaces of the boiler and enables simulation of the boiler operation in conditions of rapid changes in loads.

Dynamic modeling and optimization of a coal-fired utility boiler to forecast and minimize NOx and CO emissions simultaneously

Increasing penetration of renewable energy sources to the power grid has prompted new ramping scenarios to dispatchable thermal power plants to balance the variability caused by intermittent renewable supplies. With many thermal power plants designed to be base-loaded, ramping of the power output results in increased emission of pollutants. This study develops a dynamic data-driven model of a coal-fired utility boiler that estimates NOx and CO emissions simultaneously. Given a production schedule of a power plant, estimation of NOx and CO emissions for 3 h into the future is performed that can be further utilized in a dynamic optimization algorithm to minimize the emissions over a horizon. It is observed that a dynamic model always has a higher prediction accuracy than a static model, when training and forecasting of the models are concerned. Application of dynamic and steady-state optimization also results in reduced emissions as compared to historical plant emissions.