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Boiler room for apartment building is in operation since 2009 and data are collected for cost evaluation. Question arises after a minor reconstruction. How much energy has been saved? The article selects and processes data that was available. It shows that the importance of the heating circuit pump control cannot be underestimated or overestimated. The article derives savings from gathered data.

— The HG-2100/25.4-YM16 boiler, manufactured by Harbin Boiler Co., operates as part of the 660‑MW power unit at the Troitsk district power plant (DPP). An analysis of the boiler design showed that many technical solutions adopted in the boiler differed from those commonly used by Russian manufactures. The aim of the study is to simulate and optimize the boiler startup technology without using the circulation pump (CP) but with ensuring reliable operation of the boiler components. For achieving this aim, the following main tasks must be solved: to substantiate reliable operation criteria of boiler components during the startup, to develop adapted static and adapted dynamic boiler analysis models (SM and DM, respectively), and to study the possibility of boiler starting without using the CP. The main criteria for reliable operation of the boiler’s lower and upper radiant parts (LRP and URP, respectively) are the absence of a scale formation process (the design temperature of the metal outer surface must be below its permissible value) and stable motion of medium. However, the results of predicting the steam superheating surface metal temperature in a dynamic mode are not sufficiently accurate. Therefore, the reliability criterion adopted for these surfaces was the steam flowrate downstream of the separator, the values of which in the boiler starting modes with and without the pump should be close to each other. The reliable operation criterion of the low-pressure steam superheater outlet stage (LPSS2) is the gas temperature at the furnace outlet, which shall not be higher in starting without the CP. The numerical analyses were carried out using the Boiler Designer software package. The boiler adapted static model was developed taking into account the authors' previous works and with comparing them with the results of manufacturer’s calculations. After that, the boiler adapted dynamic model was developed on the basis of its static model. To this end, the trends of real startup modes with participation of the circulation pump provided by Troitsk DPP specialists were used. Based on these data, taken together with the experience gained from the authors' previous numerical analyses and expert estimates, the dynamic model tuning was performed. Three boiler starting modes from its cold state were studied in detail: one with the pump (at the feed water temperature t f.w = 104°С) and two modes without the pump (at t f.w = 104 and 150°С). In all cases, the following startup stages were considered: hot flushing, turbine kicking, kicking mode end, and reaching the boiler once-through operation mode. The last stage corresponded to 30% of the boiler maximum continuous rating (BMCR). An analysis of the obtained results has shown that the adopted reliability criteria are fulfilled for all boiler operation modes and stages.

The higher the unit parameters, the more sensitive water-wall tubes are to the impurity ions in the feed water, especially when the feed water contains aggressive ions such as Cl−, SO42-, etc., which often cause severe corrosion to equipment. A great deal of research has been carried out to understand the characteristics of power plant boiler water wall tubes corroded by Cl−/SO42-, which is essential to keep industrial boilers running and power stations safe.In this paper, the author firstly elaborates on the furnace water treatment condition and the source of Cl−/SO42- in power plant furnace water; then, the development of water-wall tubes of the power plant corrosion study in Cl−/SO42- solution is summarized and discussed.

With sustainable energy being the key to reaching climate neutrality, the utilization of non-wooden biomass is a necessity. This article compares the emissions and efficiency of combusting a number of types of agrobiomass and wood pellets. A comparison was made on a moving grate pellet burner mounted in a boiler, where flue gas had a vertical flow via two pass heat exchangers with turbulization elements. Tests were conducted on wood pellets (ENPlus), miscanthus straw pellets, sunflower husk pellets, and corn stover pellets. During combustion, both wood and miscanthus pellets met the PN-EN 303-5:2012 emission and efficiency requirements. Corn stover pellets met the requirement on the nominal capacity. Sunflower husk pellets are characterized by excessive CO and particulate matter emissions. Sunflower husk pellets were the most problematic fuel from the point of view of the results of this research. During combustion of the miscanthus straw pellets there was a need to decrease the nominal heating capacity due to ash sintering.

Russia is one of the world leaders in the production of sunflower oil, and the utilization of sunflower husks seems to be a very pressing problem. The husk has low humidity (4.4‒12.2%) and a fairly high calorific value (16–19 MJ/kg), but its ash contains a significant amount of potassium, calcium, and magnesium compounds, which cause slagging of the boiler furnace and rapid growth of ash deposits on its convective heating surfaces. Agglomeration and slagging are especially acute when burning crop waste in a fluidized bed of quartz sand, causing defluidization of the layer. This leads to frequent boiler shutdowns to clean the furnaces. Alternative materials to quartz sand are known, but the literature contains little data on their commercial application. The operation of a combustion device with a fluidized bed of quartz sand and olivine as part of a 2-MW heat-generating installation when burning sunflower husks is analyzed. The chemical composition of agglomerates is studied and the mechanism of their formation is described. The experiment on burning husks in a layer of olivine lasted continuously for 600 h. When carrying out periodic measurements of the fractional composition of the olivine layer, the concentrations of carbon oxide, dioxide, and oxygen in the flue gases and the formation of agglomerates was not detected.

The continuous slagging problem occurred in the operation of a 660 MW supercritical opposed firing boiler, which seriously affected the safe operation of the boiler. From the analysis of coal composition, combustion air distribution mode and other equipment factors, it is considered that the main reasons for the slagging of the boiler include the large proportion co-combustion of Shenhua coal and Philippine coal with strong slagging and the strong swirl of the external secondary air of the central burner. According to the actual situation of boiler slagging, the corresponding solutions are put forward to ensure the safe and stable operation of the unit.

A boiler economizer is in continuous operation during several burst pipes. Burst tubes are located near the elbow below the weld, and the weld on both sides of the tube wall is thinning seriously. There is a flue gas formation vortex in the furnace chamber; the outer wall of the tubes is thicker ash, and fins and tubes are corroded to varying degrees. This study employed meticulous macroscopic observation, precise chemical composition analysis, detailed metallography, advanced scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) to determine the causes of the coal economizer tube burst and tube wall thinning, ensuring the accuracy of the findings. The chemical composition, microstructure, and grain size of the base material met the requirements of the relevant standards. The heat-affected zone and weld seam show the Widmannstatten structure, a superheated tissue caused by excessive heat input during welding. The outer wall of the pipe corrosion is more serious, resulting in serious wall thinning, and ultimately, the pipe bursts, unable to withstand the pressure inside the pipe. It was eventually determined that the cause of the pipe burst was that the operating temperature of the economizer was close to the dew point, and the flue gas contained sulfur dioxide, sulfur trioxide, and hydrogen chloride that met water vapor at that temperature to form acid. Acid on the outer wall of the pipe was caused by flue gas dew point corrosion, seriously causing the pipe wall to thin. When the pipe wall is thinned to a certain extent due to corrosion, it cannot withstand the pressure inside the pipe, and rupture will occur.

— The computational studies carried out previously taking as an example the BKZ-210-140 boiler installed at Tomsk-2 state-owned district power plant (SDPP) have shown that, given the existing scatter in the characteristics of coals fired at the power plant, the temperature of gases at the boiler furnace outlet may vary in a wide range (more than 100°С). Such variability of the operational parameters entails a number of problems, including difficulties with keeping a stable superheated steam temperature, increased risk of heating surfaces becoming slagged, and less efficient fuel combustion. A conclusion has been drawn based on the obtained computation results that the possibility of adjusting the flame’s initial section vector by ±15° will make it possible to solve the above-mentioned problems to a significant extent. A tiltable burner is the key component of the combustion system with adjusting the flame position. Based on an analysis of the current operation conditions of the Tomsk-2 SDPP BKZ-210-140 boiler, technical solutions were developed on the design of a tiltable vortex burner intended for combusting pulverized coal as well as natural gas and fuel oil. The burner’s outlet part is made so that it is possible to tilt it by ±15° in the vertical plane and by ±5° in the horizontal plane, which will make it possible to adjust the combustion mode in an efficient manner. The furnace process is simulated in the ANSYS Fluent software package under different boiler operation conditions. The simulation results show that, in the case of using the new burners, it is possible to improve the furnace process efficiency. By tilting the burner by ±15° in the vertical plane, it becomes possible to obtain the temperature adjustment range at the furnace outlet equal to 120°С. Based on the adopted technical solutions, design documentation for the burner has been developed. An experimental sample of the low-toxic tiltable vortex burner installed in the Tomsk-2 SDPP BKZ-210-140 boiler has been manufactured.

PurposeIndia's textile industries play a vital role in the Indian economy. These industries consume the highest thermal energy (steam power). The demand of the steam in process industries is increasing rapidly, and this demand can be met by increasing the capacity utilization of steam boilers. The purpose of this paper is to present a new approach for reliability analysis by expert judgment method.Design/methodology/approachA lack of adequate life data is one of the biggest challenge in the reliability analysis of mechanical systems. This research provides an expert judgment approach for assessing the boiler's reliability characteristics. For this purpose, opinions of experts on time to failure and time to repair data were elicited in the form of statistical distributions. In this work, reliability analysis of the boiler system is carried out by expert judgment method and by using best-fit failure model. The system reliability along with preventive maintenance intervals of all components is also evaluated.FindingsIt is observed that the reliability analysis results obtained by expert judgment method and best-fit failure model method indicate that there are no significant differences. Therefore, in case when insufficient data are available, the expert judgment method can be effectively used. The analysis shows that the feedwater tank, feedwater pump, supply water temperature sensor, strainer, return water temperature sensor, condensate filter, mechanical dust collector, coal crusher and fusible plug are identified as critical components from a reliability perspective, and preventive maintenance strategy is suggested for these components.Originality/valueIn this research paper, a system reliability model by the expert judgment method is developed, and it can be effectively used where insufficient failure data are available. This paper is useful for the comparative evaluation of reliability characteristics of a boiler system by expert judgment method and best-fit failure model method.

Ammonia (NH3), as a derivative of hydrogen and energy carrier, is regarded as a low-carbon fuel provided that it is produced from a renewable source or a carbon abated process of fossil fuel. Co-firing ammonia with coal is a promising option for pulverized coal-fired power plants to reduce CO2 emission. Applying the co-firing in an existing pulverized coal-fired boiler can achieve satisfying combustion performance in the furnace but may affect the boiler performance. In the present work, a thermal calculation method was employed to evaluate the impact of ammonia co-firing on the boiler performance of an existing 600 MW supercritical utility boiler, covering the co-firing ratio range up to 40% (on heat basis). The calculations indicated that, as compared to sole coal combustion, co-firing ammonia changed the volume and composition and consequently the temperature and heat transfer characteristics of the flue gas. These resulted in increased variations in the heat transfer performance of the boiler with increasing of the co-firing ratio. The evaluations revealed that co-firing up to 20% ammonia in the existing boiler is feasible with the boiler performance not being considerably affected. However, the distribution of the heat transferred from the flue gas to boiler heat exchangers is significantly deteriorated at higher ratios (30% and 40%), resulting in over-temperature of the superheated steam, under-temperature of the reheated steam and considerable reduction in boiler thermal efficiency. It implies retrofits on the heat exchangers required for accommodating higher ratio co-firing in the existing boiler. The comparison study showed that co-firing 20% ammonia provides a superior boiler performance over co-firing 20% biomass producing gases and blast furnace gas.