Soot Blowing Research Articles

Improvement of slagging monitoring and soot-blowing of waterwall in a 650MWe coal-fired utility boiler

Owing to the lack of direct measurement on the slagging extent of the waterwall, random or empirical soot-blowing strategies practiced in many power plants can result in untimely or excessive soot-blowing operations. In this research, a dynamic slagging monitoring model was established based on the heat balance principle and GA-BP (genetic algorithm and backpropagation) neural networks. A soot-blowing optimization strategy was formulated by adopting the model of the maximum net heat profit and setting the accumulated system heat loss as the assessment variable. The applicability of the proposed monitoring model and optimization strategy was evaluated for the waterwall in a 650MWe coal-fired utility boiler. The monitoring results have verified that the change of system heat loss is in line with the actual slagging trend and the influence of the electric load change on the monitoring results is weakened greatly. The optimization results have shown that activating all soot blowers of the waterwall in every soot-blowing operation can achieve the higher net heat profit per unit time and the shorter duration for each pair of soot blowers. Using the optimized soot-blowing strategy can also realize the dynamic adjustment of the moment and the duration of soot-blowing, and improve the heat transfer performance of the waterwall remarkably.

Operating characteristics and ultra-low NOx emission of 75 t/h coal slime circulating fluidized bed boiler with post-combustion technology

Coal slime was a kind of industrial solid waste and it was hard to utilize. To realize the resource utilization of coal slime, a 75 t/h circulating fluidized bed (CFB) boiler with post-combustion technology was built. The operating and emission characteristics during mono-combustion of coal slime were investigated in detail. The fuel characteristics of coal slime and feeding from the top of the furnace resulted in the temperatures at the top and the bottom were higher than the middle of the furnace. When the furnace differential pressure increased, the furnace temperature and the main steam temperature both decreased, but the main steam flow increased. The main steam temperature could significantly increase after the soot blowing. The post-combustion air (PCA) was an effective means to adjust the main steam parameters. The main steam temperature increased as PCA increasing. The average SO2 emissions were only 8.4 mg·m−3 benefited from the excellent desulfurization effect of the combination of dry and semi-dry desulfurization. Nevertheless, due to the fluctuations of coal slime characteristics, the standard deviation of SO2 emission reached 8.6 mg·m−3. Under the conditions without desulphurization and SNCR, the NOx emissions of coal slime could be decreased to 38 mg·m−3 and reach the ultra-low NOx emission when post-combustion technology was used.

Soot Blower Optimization Technique in Recovery Boiler

The Chemical Recovery boiler is the profit earning section of Paper Industry. By properly reutilizing the resources like wood, water and steam for manufacturing, there would be a chance of the paper cost can be reduced. To be the proper functioning of the boiler Soot blowers is necessary. There are 28 Soot blowers available in Seshasayee Paper Board Ltd., Pallipalayam, procured from Clyde Bergemann Inc., Atlanta, USA. Optimization of High-Pressure steam during soot blowing saves green energy and effectively controls the plugging tendency. The fouling management of the boiler was enhanced and the soot blowing steam consumption was reduced. Soot Blowing performed only where and when needed. This project focuses on how to reduce the high-pressure steam during Soot blowing process. Heat transfer from flue gas to water and steam to get maximum potential. This will increase the efficiency of the Recovery Boiler.

Peningkatan Ketersediaan Waktu Operasi Pada Mesin Boiler Berdasarkan Down Time Dengan Pendekatan Metode Reliability Centered Maintenance (RCM) (Studi Kasus PT. Dian Swastika Sentosa, Tbk

This study aims to (1) determine the subsystem or component that causes the main failure in boiler unit 2 and the effect on production efficiency. (2) Determine the maintenance interval at boiler unit 2 with the Reliability Centered Maintenance method. This research was conducted by processing downtime data from each sub-system or component, which was converted into time data between failures. Thus, testing of the distribution data is to determine the appropriate distribution. Based on the parameters obtained, it is used to determine the reliability function of each subsystem or component. Thus, the reliability value of each component over a certain period of time can be calculated. From the results of the research, the most damage has reliability including ballmill a (29.01%), ballmill b (37,250%), bottom ash a (41,604%), coal feeder a (35,282%), boiler (38,275%), hydraulic (20,236%), soot blower l3 (16,019%), coal feeder b (35,915%). So that reliability is focused on these components or subsystems. Then the maintenance time intervals are arranged as a group maintenance strategy to achieve the targeted system reliability.

Understanding effect of phosphorus-based additive on ash deposition characteristics during high-sodium and high-calcium Zhundong coal combustion in drop-tube furnace

Zhundong coal as a high quality steam coal has not been widely utilized due to severe fouling and slagging problems during combustion. To promote clean utilization of Zhundong coal, combustion experiments of Zhundong coal were carried out in the drop tube furnace (DTF). The influence of novel phosphorus-based additive on ash deposition characteristics of Zhundong coal was studied. The appearance and phase composition of the raw coal and mixed coal ash deposits at different flue gas temperatures were researched respectively. The new prediction index of slagging tendency containing phosphorus was proposed, and the balance calculation were performed by FactSage thermodynamic software in different flue gas temperatures, including experimental temperatures selected. The results showed that the values of new indexes for predicting slagging tendency had obvious changes, and the phosphorus-based additive had a significant effect on the ash deposition behavior during the combustion process of Zhundong coal in DTF. Compared with the raw coal, the mixed coal with additive had higher ash fusion points and were in the form of loose, crisp, and porous powder, which was beneficial for soot blowing. When the flue gas temperature was 1000 °C or 1150 °C, there was much phosphate complex salt as the skeleton in the ash deposits of the mixed coal, such as Na2CaMg7(PO4)6. Phosphate captured Na and Ca, and effectively inhibited the low temperature eutectic mixtures of Ca with Si and Al, indicating that phosphorus-based additive had good effect on improving ash deposition characteristics of Zhundong coal.

Cracking Failure Analysis on 316L Stainless Steel Elbow

The 316L stainless steel elbow used in the pulse soot blower cracked during service, and the cracking occurred at the maximum bending radius of the elbow. There is no obvious plastic deformation at crack and there is much rust deposit on the inner elbow wall of cracked elbow. In order to avoid similar accidents, the methods such as chemical composition analysis, microstructure analysis and crack pattern scanning are adopted to analyze crack reason. The results show that stress corrosion is the main reason to cause crack of 316L stainless steel elbow.

The sensitivity of failure analysis of boiler tubes to the shape of elliptical external erosion flaws

Localized erosion is one of the most common failure mechanisms associated with boiler tubes, driven by impaction of the tube surface by fly ash, soot blowing steam, falling slag or other abrasive substances from the boiler’s combustion chamber. The tubes may experience significant localized reduction in their wall thickness, becoming susceptible to plastic collapse and bursting. The replacement of failed tubes is one of the leading causes of unplanned and forced boiler outages in process and power plants. In this study, geometric functions to enable the accurate modelling of boiler tubes with localized erosion flaws were developed from conceptualized models and finite element analyses were conducted on the modelled flawed tubes. The effect of geometry on the stress concentration in the tubes and on the failure pressure associated with the tubes was investigated. Linear elastic stress analysis is sensitive to the flaw geometry – for a representative problem stresses vary 38% as the flaw shape is varied. However, nonlinear elastic-plastic analysis shows significantly reduced sensitivity to flaw shape. The collapse pressure of the same representative problem now varies only 2.45% as the flaw shape is varied. This finding was demonstrated for various failure thresholds sourced from the literature, based either on plastic strain or Von Mises equivalent stress, which demonstrates that the failure of the tubes is insensitive to the specific choice of shape parameterization, as long as the minimum remaining wall thickness is matched. The outcome of these investigations gives further insight into the behaviour of tubes with localized external flaws while in service.

Failure Investigation of a High-Temperature Cast Soot Blower Lance Tube Nozzle

Failure in the form of stress corrosion cracking has occurred on the SS304 lance tube soot blower. The hardness test showed high value for the area close to the failed region. The SEM test showed formation of heterogonous and porosity film on the surface. XRD indicated that the oxides determined were Fe2O3 and Fe3O4. Metallographic of the lance tube revealed pitting as the stress concentrator. Pitting is caused by chloride (as chlorine) and SO2− from the flue gas. SO2− reacts with water to form acidic sodium bisulfate (NaHSO4). Stress is generated from exposure of lance tube parts to high and low temperature during its service.

Failure analysis and fatigue performance assessment of titanium diaphragms used in sonic soot blowers

Sonic soot blower, utilizing an oscillating diaphragm, generates acoustic waves for cleaning of equipment such as boiler and furnace to increase their efficiency. Based on earlier research by NRI (Niroo Research Institute), one of the main reasons disrupting the regular function of sonic soot blower is the failure of the diaphragm. The failure of circular Ti-6Al-4V sheets employed as the diaphragms is investigated by using SEM images. Based on these images, fatigue failure is found in the governing failure mechanism. A modification to the arrangement of the blower is proposed by introducing a gap between the diaphragm and its seat to improve the fatigue performance. A computational fluid dynamics (CFD) analyses are performed using the Ansys CFX software for estimation of pressure distribution on the diaphragm during service loading, and the results are introduced to the finite element (FE) model developed by the Abaqus software for calculation of stresses induced in the diaphragm. Variation of Mises stress at the center of the diaphragm, where the maximum stress developed, is extracted from the FE model for one period as a stress spectrum for one operation interval. A stress-life approach is employed to assess the fatigue life of the diaphragm subjected to estimated stress spectra. According to the prediction, increasing the gap size by 0.1 mm results in extension of life up to 2.75e10 spectrum passes, which are significantly higher than the desirable lifetime (5 years) of the diaphragm. Further increase of gap size leads to higher fatigue life, however, considering the decrease of efficiency as the gap size is increased, the gap size of 0.1 mm would be the optimum configuration.

Research on the Mechanism of Slagging and Fire-off for different capacity boilers

For slag extinguishing process of different capacities boilers (1000MW, 670MW, 300MW, 150MW), the slag extinguishing mechanism is analysed in terms of equipment, slagging characteristics, coal quality, furnace heat load, and operation mode. Prevention measures for slag extinguishing are put forward in terms of fire coal controlling, operation optimization, and technical transformation. Analyses results show that there are mainly three types of furnace pressure change during the slag extinguishing process. The common feature is that the furnace pressure goes up first, which is because of combustible gas explosion in the lower part of the furnace (primary reason) and the entry of a large amount of water vapor into the furnace (secondary reason). The degree of slagging for these four boilers is aggravated by the factors such as high ash content and sulfur content, the low input frequency of soot blower, and the large fineness of the pulverized coal.

Energy and Exergy Analysis of Steam Source Optimization for Boiler Soot Blowing System

In order to improve the economy of boiler soot blowing system, the steam source position of boiler soot blowing system should be optimized. For a 1000MW ultra-supercritical coal-fired unit, the thermodynamic process of soot blowing steam in temperature and pressure reducing station was studied through energy analysis and exergy analysis in this paper, and it was revealed that the annual water and energy consumption of boiler soot blowing system was independent of the steam source position, the change of steam source position only affected the annual exergy loss of soot blowing system. The comparion results indicated that the annual exergy loss of soot blowing system with cryogenic reheater outlet as steam source was minimal. After adopting cryogenic reheater outlet as the steam source position of soot blowing system, it would be more economical than the original soot blowing system with platen superheater outlet as steam source. The annual exergy loss would be reduced by about 2.183×1010kJ, and it was equivalent to an annual increase of power generation revenue by about 2486000CNY.

Online Ash Fouling Prediction for Boiler Heating Surfaces based on Wavelet Analysis and Support Vector Regression

Depending on its operating conditions, traditional soot blowing is activated for a fixed time. However, low-frequency soot blowing can cause heat transfer efficiency to decrease. High-frequency soot blowing not only wastes high-pressure steam, but also abrades surface pipes, reducing the working life of a heat exchange device. Therefore, it is necessary to design an online ash fouling monitoring system to perform soot blowing that is dependent on the status of ash accumulation. This study presents an online monitoring model of ash-layer thermal resistance that reflects the degree of ash fouling. A wavelet threshold denoising algorithm was applied to smooth the thermal resistance of the ash layer calculated by the heat balance mechanism model. Thus, the variation in thermal resistance becomes more visible, which is more conducive to optimizing the operation of soot blowing. The designed Support Vector Regression (SVR) model could achieve the online prediction of thermal resistance denoising for low-temperature superheaters. Experimental analysis indicates that the prediction accuracy was 98.5% during the testing phase. By using the method proposed in this study, online monitoring of heating surfaces during the ash fouling process can be realized without adding complicated and expensive equipment.

Investigation of high temperature corrosion resistance of Ni25Cr coated and bare 347H SS in actual husk fired boiler atmosphere

This paper presents the experimental investigation of corrosion occurring at elevated temperatures in various critical constructional components of husk-fired boiler. In order to reduce the impact of high operating temperatures on boiler components, some protection, in the form of high temperature resistant coating becomes necessary. The critical components of a boiler are generally made of stainless steel. In this work an attempt has been made to determine experimentally the corrosion resistance performance of 347H SS components coated with 75Ni25Cr. Specimens of 75Ni25Cr coated 347H SS and bare 347H SS were hung in an actual husk fired boiler near superheater region through soot blower dummy points. The temperature recorded by an industrial pyrometer near superheater region was about 750 ± 50 °C. These samples were hung for about 150 h in the above-mentioned environment and it was found that 75Ni25Cr coating offers substantial protection as the bare metal underwent severe corrosion.

CFD를 이용한 선박용 이코노마이저 Soot Blower 유동 해석에 관한 연구

In the recent high oil era, fuel reduction, energy saving and environmental pollution reduction are the main tasks of this era. Even though it has a lot of heat in the exhaust gas of marine engines and boilers, it is discharged through the atmosphere, and the energy loss is very large. To this end, Economizer is essential for waste heat recovery, and there is a “Soot Cleaning System” to increase efficiency. The purpose of this paper is to verify the efficiency by analyzing the flow of exhaust gas inside the mill with the automatic soot blower installed in the mill. In this study, soot blowing inside the economizer was simulated using ANSYS CFX(V.18.1), a general-purpose flow analysis engineering program, and the temperature, pressure and velocity fields in the economizer were analyzed.

On Line Dirt Based Soot Blowing System using Fuzzy Logic for Utility Boilers

Soot is a byproduct of burning coal in thermal power plants. The soot accumulates in the boilers tubes. It gradually spoils the heating surface which reduces the heating efficiency. Hence it has to be cleaned. This process is called soot blowing. The existing soot blower control system in the old boiler is composed of relays, timers and contactors which are not efficient. In order to improve the efficiency, an intelligent system is proposed which estimates the dirt in the boiler tube periodically and initiates soot blowing process to improve the thermal efficiency. Simulation results demonstrate the superiority of the proposed scheme when compared to relay logics.

Soot Blowing Optimization for Frequency in Economizers to Improve Boiler Performance in Coal-Fired Power Plant

Because of the present ineffective method of soot blowing on a boiler’s heating surface in a coal-fired power plant, and to improve the economic benefit of the boiler in the power plant, weigh the improvement of boiler efficiency and steam loss brought by soot blowing, and ensure the safe operation of the unit, an optimization model of soot blowing on the boiler’s heating surface is established. Taking the economizer of the 300 MW coal-fired power plant unit as the research object, the measurement data and basic thermodynamic calculation data of the Distributed Control System (DCS) of the thermal power plant are used to calculate the fouling rate of the heated surface in real time. By analyzing the multi-group fouling rate under the same working conditions, the incremental distribution of the same measuring point at different times is obtained, and the expectation is obtained according to the distribution curve. The state of heating of the heated surface at a time in the future is predicted by the known initial cleaning state. By analyzing the trend of the fouling rate and combining the soot blowing optimization model, a set of soot blowing optimization strategies are proposed. The method proposed in this manuscript can be applied to the guidance of boiler soot blowing operation.

Modeling and linear analysis of sound generation mechanism in sonic soot blowers

Sonic soot blowers (SSBs) are nondestructive tools to prevent ashes and particle build-up on the surfaces of boilers or other similar instruments. For higher performance, sonic soot cleaners should generate a high level-low frequency sound wave. In this article, the sound generation mechanism in these tools has been modeled. Firstly, the governing equations of the diaphragm and the horn and coupling between them are derived. By linearization, a parametric study is performed to find the optimum design points. Based on the eigenvalue analysis, it is shown that the sound generation in sonic soot cleaners is due to instability of the interaction between the diaphragm and the horn. Moreover, it is found that the sound wave frequency is approximately equal to the lowest fundamental frequency of the horn or diaphragm. Finally, the frequency content of an SSB voice is investigated.

Optimization Fuzzy Controller Parameters for Soot Blower in Power Plant

In power plant, soot blower operation plays important role in efficiency. Most soot blowing process on the power plants is using fixed schedule of time. In many instances, certain boiler stages are blown unnecessarily, resulting in efficiency loss. The Target of this research is to optimize the control of soot blowing fuzzy logic techniques.

Optimization of Boiler Soot Blowing Based on Hamilton-Jacobi-Bellman Equation

In this paper, the optimization of the boiler soot blowing is investigated based on the Hamilton-Jacobi-Bellman (HJB) equation and from the standpoint of the equipment health management. The mathematical model of the boiler soot blowing is built by a Markov process with two modes: soot deposition mode and soot blowing mode. In order to obtain the optimal soot blowing strategies via the HJB method, a cost function is constructed according to the proposed boiler soot blowing model. Considering the solution's existence of the HJB equation, the elementary properties of the value function are described and proved. It is difficult to solve the HJB equation analytically, so Kushner's method is applied to get the numerical solution of the HJB equation. Moreover, the sensitivity analyses for the effects of different parameters are shown via a set of numerical simulations.

The algorithm of steam soot blowers operation based on the monitoring of fouling factors of heating surfaces of a coal-fired boiler under operating conditions

The article deals with the problem of optimizing the operation of soot blowers in a pulverized coal-fired boiler based on the instantaneous degree of cleanliness of heating surfaces, determined in real time. The elaborated methodology of calculations and the algorithm that determines the optimal configuration of the blowers operation has been implemented and tested on a boiler with a capacity of 380 t/h. The indicator defining the degree of cleanliness of a given heating surface is calculated using available measurements of process parameters based on the epsilon-NTU method. The calculations are carried out in the DCS system for each surface individually (air and water heaters, evaporator, superheaters). During the standard operation of the boiler, the adopted methodology was verified, having analysed the usefulness of the tool to assess the boiler cleanliness under operating condition.