Papers by Keyword: Superheater

Abstract: Superheater pipes in boilers generally experience failure due to extreme operating conditions, such as high temperatures and pressures, often leading to ruptures on the pipe surface. These failures reduce the boiler system’s efficiency and increase the risk of further, costly damage. Therefore, it is important to conduct a failure analysis on the ruptured pipe area to enhance the reliability and operational lifespan of the boiler superheater pipes. This study uses several methods to analyze superheater pipe failure, including visual observation and chemical composition testing, which showed a carbon content of 0.228%, classifying the material as low carbon steel. This was also confirmed by microstructure analysis. Hardness testing revealed an average hardness value of 140.9 HV, whereas the expected hardness should be around 180 HV. In the hardness test, there is a difference of 40 HV from the hardness value that meets the standard, which is an indication of material failure. Additionally, in the SEM test, fine defects were found along the grain, and the tested pipe that experienced rupture was already very thin, with many deposits found on the pipe walls.

Abstract: In order to solve the problems of strong coupling and nonlinear parameters of superheater model, in this paper, we aimed at a 600MW subcritical drum boiler high temperature superheater as the object of study .On the basis of mechanism analysis and its dynamic characteristics I built a dynamic model of high superheater contains 9 typical working conditions .I optimized the model parameters by using field data. A continuous nonlinear model is obtained by curve fitting. The simulation results show that superheater model built by this method can better simulate the field characteristic. This model provides a reference design of automatic control system of main steam temperature .This paper aims to provide the basis for the application of advanced control algorithms in the field. Furthermore, this model can provide higher accuracy for on-site training to improve training effect.

Abstract: According to the basic mechanism of the supercharged boiler superheater, a superheater simulation model was established. The simulation about a whole superheater system including the flue gas,steam and tube wall was conducted according to the simulation model.Therefore, the internal working laws of superheater system are revealed by the simulation results.

Abstract: Austenitic stainless steel grade UNS S31035 (Sandvik Sanicro® 25) has been developed for the next generation of 700°C A-USC power plant. This paper will mainly focus on the study of low cycle fatigue behavior and damage mechanisms of the material at room temperature, 600C to 700C by using electron back scatter diffraction and electron channeling contrast image techniques. At room temperature, the material shows a hardening and softening behavior as usual. At high temperature, however, it shows only a cyclic hardening behavior. Dynamic strain ageing can be one of the mechanisms. The damage and fatigue crack initiation mechanisms due to cyclic loading at different temperatures and loading conditions have been identified. The interactions between dislocations or slip bands with grain boundary or twin boundary are the main damage mechanism at low temperature or at high temperature with large strain amplitudes. Strain localization due to dislocation slipping is the main mechanism for the damage in grain.

Abstract: Oxide scales have negative effects on the security and economy of supercritical and ultra-supercritical units.The finite volume method was exploited to simulate oxide scales growth temperature on the inside of superheater tube,then the appropriate time and spatial intervals were selected to calculate oxide scales thickness along the circumferential direction with the correspond growth temperature.At last,the stress response of the oxides was simulated with finite element method.The simulated temperature is closed to the analytical temperature, confirming that the simulation results are credible.The results show that the growth temperature rises fast at the beginning and drops in the circumferential direction,which changes rapidly at the 90°. Oxide scales thickness is thinner and thinner in the circumferential direction and changes fast at approximately 90°.Though the magnitude of circumferential stress and axial stress is different, but the trend same.The simulation results can provides a theoretical basis for the failure research of the oxide scales.

Abstract: Traditional models of power plant boiler superheater are incapable of simulating the operating conditions under large disturbances with high precision. To resolve this challenging problem, this paper presents a nonlinear lumped-parameter dynamic model of power plant boiler superheater. The present model describes the dynamic processes of the pressure-flowrate and the enthalpy-temperature channels with sufficient consideration of their coupling effect. To better capture the distributed-parameter property of superheater temperature, the multi-segment lumped-parameter modeling method is employed for modeling the enthalpy-temperature channel. Dynamic responses of the last-stage superheater of a 600 MW controlled circulation boiler to disturbances of the spray water flowrate, the superheater inlet enthalpy, and the absorbed heat flux are simulated. Simulation results show that dynamic responses of the present model are reasonable, and the model has high precision, which can meet the requirements for full scale simulation and control system simulation.

Abstract: In order to control the attemperation water demand, the superheater heating ability is calculated by enthalpy increment. According to the changed enthalpy of the superheater outlet, the attemperation water demand is estimated. To simplify calculation, the changing steam flow is regarded as linear process during a certain time. Thus, the attemperation water calculation method is obtained. Basis on this, Matlab software is used to perform computer simulation to the system.

Abstract: In response to the deposition problem in biomass-fired boiler, inert addictive was tested to inhibit the possibility of coking. The deposition samples collected from final and primary superheater of biomass-fired CFB (circulating fluidized bed) boiler were grinded into fine powder. The inhibitive ability of additive was tested by mixing the deposition sample with different proportions of inhibitor under high temperature. By means of scanning electron microscope (SEM), X-ray diffraction (XRD) and other analytical procedures, the properties of the samples with inhibitor such as microstructure, composition were studied. The inhibitor was also introduced to the industrial biomass CFB boiler to verify its inhibition effect on superheater deposition. Unfortunately, the effect of adding inhibitor in industrial boiler is not certain, though the inhibitor added to the samples is obviously effective in weakening coking in the laboratory scope.

Abstract: Boiler failure is the main power plant boiler operation fault. And boiler superheater tube is one of the important reasons for boiler failure, which affects the safe and stable operation of power generation equipment. Structure design and calculation of boiler superheater has important influence on performance and life of boiler, so three-dimensional structural model of boiler superheater is built in this paper. Based on the finite element method boiler superheater in temperature and stress coupled field are analyzed. The highest temperature, maximum stress, and distribution characteristics of stress and temperature couple field of boiler superheater including straight and elbow section are computed. The date on the actual operation of a power plant was used in the process of analysis. And thermal physics and mechanical properties of the boiler superheater tube were taken full consideration. It provides a reliable basis for reasonable design and safety evaluation of the boiler superheater.

Abstract: Fireside corrosion is since a long time the main limitation to increase efficiency of energy recovery boilers of waste to energy (W-t-E) facilities. Nevertheless, the increase of steam conditions in addition with the variation of feeding fuels composition imply greater risks of fouling and corrosion along with heat exchanger failure, loss of plant availability and high maintenance costs. Fireside corrosion mechanisms had already been widely treated in the literature and this paper will review the main critical factors that enhance fireside corrosion of superheater. Recent failure cases will be developed in regards with recent studies that provide interesting routes to predict corrosion failure and develop maintenance strategy.