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Combining mine exhaust waste heat with existing heat pump technology is a promising technical route to realise the efficient extraction and scientific use of low-grade waste heat resources in mines and to solve the problem of insufficient heat supply in remote mining areas. This study proposes a new type of mine-exhaust-air heat exchange coupled with heat-pump waste-heat-utilisation system based on deep enthalpy heat extraction. Using a mining area in Northwest China as a representative case, this study establishes a systematic exergy analytical model and a thermo-economic model. Through an in-depth analysis of the different evaporation temperatures and condensing temperatures, the system's energy efficiency ratio (COP) reaches its optimal performance, with the total exergy efficiency surpassing 90%. The minimum efficiency of the subsystem return air heat exchanger is 35%. The unit thermal costs of the mine exhaust air waste heat utilisation system and a conventional coal-fired boiler system are 0.1291 and 0.1573 million RMB/kW·h, respectively. This is a thermal economics cost saving of 21%. The studied system demonstrates great economic viability and the potential for energy saving throughout its life cycle. [ABSTRACT FROM AUTHOR]

Rural areas in Northeast China present a large demand for heating energy in winter, but there are problems in such areas with poor thermal performance of building envelopes and poor indoor thermal comfort. In addition, coal-fired boilers are still widely used. China's "Dual-Carbon Goals" and "Clean Heating" policy call for the creation of a green and comfortable living environment for rural residential buildings. This paper considers the impact of the improvement of the thermal performance of envelope structures on the initial investment of the transformation program and the rated power of the ASHP and proposes an energy-saving transformation method to replace traditional coal-fired boilers with the ASHP on the basis of the improvement of the thermal performance of envelope structures. By establishing a typical rural residential building model in Northeast China, this energy-saving method is simulated based on TRNSYS. The results show that the payback period of investment of the transformation method of "envelope structure + heating system" is not superior to that of the transformation method of only improving the thermal performance of the envelope structure, but it has advantages in the comprehensive life-cycle benefits and it has great advantages in improving the satisfaction of rural residents in the use of heating systems. [ABSTRACT FROM AUTHOR]

High-temperature furnaces and coal-fired boilers are widely employed in the petrochemical and metal-smelting sectors. Over time, the deterioration, corrosion, and wear of pipelines can lead to equipment malfunctions and safety incidents. Nevertheless, effective real-time monitoring of equipment conditions remains insufficient, primarily due to the interference caused by flames generated from fuel combustion. To address this issue, in this study, a through-flame infrared imager is developed based on the mid-wave infrared (MWIR) radiation characteristics of the flame. The imager incorporates a narrowband filter that operates within the wavelength range of 3.80 μm to 4.05 μm, which is integrated into conventional thermal imagers to perform flame filtering. This configuration enables the radiation from the background to pass through the flame and reach the detector, thereby allowing the infrared imager to visualize objects obscured by the flame and measure their temperatures directly. Our experimental findings indicate that the imager is capable of through-flame imaging; specifically, when the temperature of the target exceeds 50 °C, the imager can effectively penetrate the outer flame of an alcohol lamp and distinctly capture the target's outline. Importantly, as the temperature of the target increases, the clarity of the target's contour in the images improves. The MWIR through-flame imager presents considerable potential for the real-time monitoring and preventive maintenance of high-temperature furnaces and similar equipment, such as detecting the degradation of refractory materials and damage to pipelines. [ABSTRACT FROM AUTHOR]

Under the dual carbon target, circulating fluidized bed boilers are not only a coal-fired power generation technology with great commercial value and development potential for refining enterprises, but also the main source of carbon emissions in refining enterprises. With the development of CFB boiler technology and the increasing capacity of boilers, the problem of poor air-fuel mixing caused by the position and method of inletting feedstock and air during the operation of large industrial CFB boilers has gradually become prominent. In order to improve the combustion efficiency and stability of coal-fired circulating fluidized bed boilers and reduce CO2 emissions, this study developed an Fe-based oxygen carrier based on the principle of OCAC technology, and analyzed the performance of the oxygen carrier on a bubbling bed reactor and a 0.3 MW/h CFB coal-fired reactor. Fe-based oxygen carrier has excellent performance of oxygen absorption and oxygen release, the CO conversion rate can reach more than 88% on the bubbling bed reactor, and reach 52% ~65% on the 0.3 MW/h CFB reactor. The emissions of pollutants such as NOx and SO2 in the flue gas have been reduced. [ABSTRACT FROM AUTHOR]

The high-pressure and high-temperature super heater tubes are critical in circulating fluidized bed combustion coal-fired boilers. The intention of this paper is to avoid the failure of platen super heater tubes by careful boiler operation and inspection, thereby improving the reliability of boiler equipments. [ABSTRACT FROM AUTHOR]

The ash deposition is a general problem that needs to be solved effectively for the rotary air preheater of the coal-fired boiler. Taking the rotary air preheater of a 600 MW power station as the object, the mesh model of the flue gas side of the air preheater, considering the influences of steam soot blowing, is established using the Gambit 2.4.6 software. Based on the SIMPLE algorithm, the velocity field and the temperature field in the air preheater under varied working conditions are simulated using the software of Ansys Fluent 2021R1, and the influences of the boiler load, the operation parameters of the steam soot blower, and the running and outage of the soot blower on the flue gas velocity distribution in the depth direction of the corrugated plates, the soot-blowing coverage area, the inlet flue gas velocity, and the inlet flue gas temperature of the corrugated plates are analyzed. Under the base working condition, the flue gas velocity on the axis of the steam nozzle first decreases rapidly with increasing the corrugated plate depth (Z < 1.0 m), and then it decreases slowly with an almost equal slope. The longitudinal flue gas velocity has a positive correlation with the boiler load. The longitudinal flue gas velocity obviously decreases when the boiler load is decreased, and its reduction increases as the corrugated plate depth increases. It is one reason that the ash deposition is prone to occur on the cold end surface of corrugated plates under the condition of low boiler load. The longitudinal flue gas velocity increases with the soot-blowing steam velocity increasing when the corrugated plate depth is less than 1.5 m, but after that, it is almost not affected by the change in soot-blowing steam velocity. The soot-blowing coverage area has a negative correlation with the boiler load but a slight positive correlation with the steam velocity of the soot blower on the whole. The inlet flue gas velocity of the corrugated plates has a positive correlation with the boiler load and the inlet steam velocity of the soot blower. The average inlet flue gas velocity decreases by 21.7% when the boiler load is reduced by 50%. For every 5 m/s variation in the inlet steam velocity, the inlet flue gas velocity changes by about 10–14% whether the steam soot blower is put into operation or not, which has an obvious effect on the inlet gas velocity of the corrugated plates. The inlet flue gas temperature of the corrugated plates is, respectively, positively correlated with the boiler load and the inlet steam temperature of the soot blower. When the boiler load is reduced from 100% BMCR to 50% BMCR, the average inlet flue gas temperature of the corrugated plates is reduced by 44.2 K; however, when the soot-blowing steam temperature varies by 20 K, the average inlet flue gas temperature of the corrugated plates varies by only about 1.8 K. It means that it is difficult to enhance the cold end flue gas temperature of the corrugated plates only by raising the soot-blowing steam temperature at low boiler load. Adding a soot blower using high-temperature steam or hot air at the outlet of the corrugated plates may be an option to solve the ash deposition of the corrugated plates. [ABSTRACT FROM AUTHOR]

The temperature of the water wall in the furnace chamber is extremely important for the daily operation of a boiler. Considering the high temperature and dusty environment in the furnace, a temperature measurement device mainly composed of four parts (armored temperature sensor, in-furnace heat-collecting block, out-furnace fixing base, and protective cannula) was designed in this study, which could be used to directly obtain the temperature of the in-furnace water-wall. Numerical simulations of temperature measurement devices with different heat-collecting block structures were carried out using the computer fluid dynamics method. After comparing the measurement accuracy and considering the practical application scenarios, the optimized heat-collecting block structure with a specific expansion gap (0.5 mm wide and 4 mm deep) was selected for practical application. Such a temperature measurement device was then applied to a 1000 MW ultra-supercritical coal-fired boiler in China, and the tested in-furnace water-wall temperature data were in good agreement with relevant research. Compared with the conventional temperature measurement device arranged outside the furnace, the in-furnace water-wall temperature-measurement device adopted in this study has a more sensitive response characteristic and can directly reflect the temperature of the water wall inside the furnace. In addition, it can also reflect the local slag formation state of the water wall and has a long service life. [ABSTRACT FROM AUTHOR]

To meet the Chinese government's energy-saving and emission-reduction policies, flexible peak regulation is necessary for traditional coal-fired boilers. Flexible peaking leads to large changes in boiler load, which affects the safety of the boiler water wall. In this paper, a 1000 MW ultra-supercritical unit was tracked for three years, and effective data were selected to study the temperature characteristics of the water wall under flexible peak regulation. The results show that the lower the load, the greater the temperature fluctuation of the water wall. The temperature distribution of the spiral water wall is more uniform. The position of the temperature valley value of the rear spiral water wall was found, and the load of more even temperature distribution was also found. The temperature change of the front vertical water wall was the most complex of all the water walls. The 643.9 MW load case showed different behavior to the temperature distribution of the water wall. The side water walls were heated evenly under the different loads. The characteristics of the temperature distribution of the side vertical water wall were found through statistical analysis. The fitting equation for the change rule of the temperature is presented. The higher the load, the better the equations. Finally, this paper gives some advice on how to avoid temperature deviation in the water wall, and the detailed research highlights the safe running of water walls. [ABSTRACT FROM AUTHOR]

To mitigate global warming, phasing out coal in the global energy system orderly and rapidly is an important near-term strategy. However, the majority of coal-fired plants in China have operated for less than 15 years. Accelerated coal power plant retirements would lead to substantial asset stranding. Coal-to-nuclear (C2N) technology offers a potential solution by replacing coal boilers in existing coal-fired plants with nuclear reactors. In this study, the G4-ECONS model was used to assess the economics of repowering a 600 MW supercritical coal-fired power plant with two 272 MWe high-temperature gas-cooled reactors. The timeline for the C2N project and the additional cost of dispatching electricity from the grid during retrofitting were discussed. Results showed that the C2N total capitalized costs are 19.4% (baseline estimate, USD 5297.6/kW) and 11.1% (conservative estimate, USD 5847.2/kW) lower than the greenfield project (USD 6576.5/kW), respectively. And C2N projects need to reduce LUEC by at least 20% to become competitive. This study can inform engineering design decisions leading to more precise and cost-effective C2N projects. [ABSTRACT FROM AUTHOR]

Flue gas recirculation technology and air-staged combustion technology are both effective methods for reducing the production of NOX in coal-fired boilers. However, the synergistic effect of air-staged combustion technology and flue gas recirculation technology on NOX generation characteristics in S-CO2 boilers needs further study. The formation characteristics of NOX in the main combustion zone of coal combustion were studied experimentally when flue gas recirculation and air-staged combustion were combined. The results indicate that as the recirculation flue gas is injected at deeper levels, there is a gradual decrease in the concentration of NOX along the path, And the concentration of O2 also decreases gradually. The concentration of NOX decreases as the excess air coefficient decreases. The concentration of O2 increases as the excess air coefficient increases. Additionally, the NOX concentration at the furnace outlet increases with the increase of the excess air coefficient. Along the axial direction of the one-dimensional flame combustion furnace, the NOX production along the way and the NOX concentration at the outlet decrease with the increase of the flue gas recirculation position. Flue gas recirculation in air-staged combustion is an effective method for reducing NOX emissions. The positioning of flue gas recirculation significantly impacts NOX emissions. The NOx concentration is lowest when the flue gas recirculation rate is 27% and the mixing position of the recirculated flue gas is 300 mm with an excess air coefficient of 0.8. [ABSTRACT FROM AUTHOR]

The basic national condition that is dominated by coal will not alter in the foreseeable future. Coal-fired boiler is the main equipment for coal utilization, and cyclone burner is a practical type of burner. There is a cyclone formation, a primary air duct inside the center air duct, and a secondary air duct. Introducing a small stream of pulverized coal gas or oil mist stream or gas directly into the reflux zone in the center duct ignites first a stable combustion and a small fluctuation of ignition pressure. In this paper, the variation of furnace temperature for cyclone pulverized coal burner corresponding to different excess air factors and the composition of gases such as O2, CO, CO2, and NOX produced by combustion were investigated using fluent software. A single cyclone pulverized coal burner from an actual coal-fired boiler is used, and a combustion zone applicable to the study of a single pulverized coal burner is established to study the actual operation of a single pulverized coal burner at different excess air coefficients. The findings indicate that the ignition position of pulverized coal combustion advances with decreasing α (Excess Air Factors); however, the length of the produced high-temperature flame gets shorter. As the value of α decreases, the burnout in the furnace decreases and the CO emission concentration increases, with a maximum CO mole fraction of 0.38% at α = 1.2 and a maximum CO mole fraction of 3.13% at the axial position when α decreases to 0.8. The furnace's concentration of NOX, the NOX emission level decreases significantly with decreasing α. The NOX mole mass increases gradually with increasing α, and in the bottom portion of the primary combustion zone, more NOX is produced. The concentration of NOX in the chamber changes significantly after α exceeds 1.0, and the NOX at the outlet surges from 417.25 ppm to 801.07 ppm, which is attributed to the increase in the average temperature of the chamber, which promotes the generation of thermophilic NOX. The distribution pattern of O2 mole fraction along the furnace height cross-section at different excess air factors is basically the same, with a maximum at the burner inlet and a gradual decrease in the O2 content as it enters the combustion chamber to react with the pulverized coal in a combustion reaction. The value of α = 0.8 when the air supply is obviously insufficient, the fuel cannot be fully combusted, and only a small amount of CO2 is produced. [ABSTRACT FROM AUTHOR]

To improve the low-load stable combustion capacity of a low-grade coal-fired boiler, this study proposed to reform C-layer secondary air, which was then used to improve the ignition and combustion stability of coal/airflow of a 600 MWe Foster Wheeler down-fired boiler. Cold airflow experiments and industrial measurements were carried out to investigate the influence of the new C-layer secondary air on the aerodynamic and combustion characteristics at low load under different C-layer secondary air ratios and damper openings, respectively. The flow and mixing characteristics of the C-layer secondary air and coal/airflow, the flue gas temperature and NOx, O2, and CO concentration distributions in the furnace at low load were examined. With increase in the C-layer secondary air ratio, the flow range of coal/airflow gradually expanded. The mixing distance first increased and then decreased. At an air ratio of 25%, the mixing distance was the longest. Industrial measurements showed that compared with that at the C-layer secondary air damper opening of 0%, the coal/airflow ignited earlier at 40% (corresponding to the C-layer secondary air ratio of 23.73%), and the flue gas temperature in the furnace increased substantially. At C-layer secondary air damper opening of 0%, 20%, and 40%, carbon content in the fly ash was 4.62%, 5.32%, and 4.20%, respectively. The respective NOx emissions at the furnace exits were 450 mg/Nm3, 378 mg/Nm3, and 427 mg/Nm3, (O2 = 6%). In actual operation, 40% is recommended as the optimal C-layer secondary air damper opening. [ABSTRACT FROM AUTHOR]

Coal-fired thermal power plants are currently converting their technology to supercritical and ultra-supercritical in order to meet the world's energy demands. An important component in this technology is the superheater of the boiler, which operates at higher temperatures and above the critical pressures. For the design and reliable operation of a superheater tube bundle, thermal and structural analyses are crucial. This study focuses on the superheater tubes bundle of a 660 MW coal-fired supercritical boiler. The superheater model is simulated to investigate the thermal characteristics such as temperature distribution, total heat flux and directional heat flux and structural parameters such as von Mises stresses, equivalent strains and total deformations. Different materials such as martensitic steel, austenitic steel and nickel–titanium are compared based on thermal and structural analysis. It is claimed that thermal performances of martensitic steel are more impressive as compared to superheater materials. The lower strain appeared for austenitic steel as compared to martensitic steel. [ABSTRACT FROM AUTHOR]

The price of coal used by a pineapple processing plant has increased from 3.90 Php/kg in 2018 to 8.60 Php/kg in 2022, thus increasing steam generation costs. This study conducted an energy audit on the two 22-TPH coal-fired boilers of the pineapple processing plant to determine boiler efficiency, quantify sources of heat loss, identify energy conservation measures, and calculate energy and coal savings. The coal-fired boilers investigated were fluidized bed combustion boilers with a reverse osmosis feedwater system. The boiler efficiency was calculated using an indirect method, considering energy losses from sensible heat in refuse and blowdown water. Of the three performance tests conducted, the average boiler efficiency is at 80.655%. The top five sources of heat loss were dry flue gas, hydrogen in coal, moisture in coal, surface radiation and convection, and boiler blowdown. These sources account for 18.322% of the energy input. The identified energy conservation measures include the installation of an automatic oxygen trim control, the installation of an economizer, the installation of a caustic injection system, and the insulation of uninsulated surfaces. These measures have a total potential energy savings of 52,494,974 MJ/yr and coal savings of 2,594,579 kg/yr. While a caustic injection system is not yet installed, setting blowdown TDS to 2,090 ppm can reduce energy consumption by 1,656,496 MJ/yr and coal consumption by 81,873 kg/yr. Using coal with lower hydrogen and moisture content can also reduce energy loss by 6,096,810 MJ/ yr per 0.5% reduction in hydrogen content and 6,816,813 MJ/yr per 5% reduction in moisture content. [ABSTRACT FROM AUTHOR]

In the technical literature examining P92 steel grade, a common material used for elements of power equipment with enhanced operating parameters, there are numerous studies on creep tests. However, there is a lack of information on the fatigue processes of such materials, especially thermo-mechanical fatigue. The presented article investigates certain aspects of this phenomenon, focusing on the behavioral aspect of P92 steel under time-varying mechanical and thermal load conditions. The analysis of the behavior of the high-pressure elements of power equipment focused on the operating parameters. These parameters lead to various stress and strain fields in the elements, allowing the determination of their fatigue life. The issue of selecting fatigue life criteria for materials and forecasting the durability of elements operating under mechanical loads and time-varying elevated temperatures was also examined. In this case, the material characteristics determined under laboratory conditions and the applicable standard used by designers of power equipment were utilized. [ABSTRACT FROM AUTHOR]

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At present, there’s a lack of combustion visualization in the combustion control of heating boilers. To understand the combustion of coal in the furnace, only experienced workers can observe it through visual inspection. Using infrared thermal imaging technology to monitor the combustion can realize combustion visualization. This paper analyzed and solved two problems: the installation position and number of infrared cameras, and the infeasible of using infrared cameras observing the combustion condition in the furnace through heat-resistant glass. Monitored parameters such as oxygen content, furnace temperature and smoke exhaust temperature, and monitored the concentration of PM, NOx, and SO2 in the main atmospheric pollutants in the flue gas. After calculation, the air leakage coefficient when the inspection doors are opened for observation is 0.04. This value still includes the sum of air leakage from coal hopper, furnace door, grate side seal, peep holes and other parts. The monitored average emission concentration of PM decreased by 16.28%, from which we can concluded that the use of thermal imaging technology to monitor the combustion in the furnace is conducive to emission reduction. The application of thermal imaging technology implementation of coalfired boiler combustion visualization is feasible. [ABSTRACT FROM AUTHOR]

This study is a numerical study to predict the temperature of the heat exchange tubes inside the pulverized coal-fired boiler through the conjugate heat transfer analysis. Due to the aspect ratio and number of tubes inside the pulverized coal-fired boiler, actual tube modeling analysis has rarely been conducted. Most of the research has been conducted through the porous media method, resulting in limited information on the temperature distribution of each tube. However, for the development of a digital twin model for improving the performance of the boiler and reducing maintenance costs, information on the local temperature of the tubes is required. In this study, all the tubes inside the boiler were modeled, and conjugate heat transfer analysis was performed to confirm the local temperature distribution. For this purpose, the analysis was conducted using Fluent 2020 r2, and the analysis model was constructed using more than 300 million structured grids. The calculation was performed considering conjugate heat transfer in the pulverized coal-fired boiler, heat exchange by steam inside the tubes, and conductive heat transfer of the tubes. As a result, it was confirmed that there is a significant deviation in the local temperature for each tube position. Furthermore, the maximum temperature of the PrSH tube ranges widely, between 492 and 532 degrees, depending on the tube's position. It was observed that the point of the highest temperature inside the tubes also varies for each tube due to the flow of external combustion gas. Based on these results, it is expected that strategic approaches to boiler design and maintenance can be achieved. Furthermore, it is anticipated to contribute to the high efficiency of power facilities by being utilized as basic data for the development of a digital twin model for the boiler. [ABSTRACT FROM AUTHOR]

Low‐nitrogen burners and air‐staging system, which would generate a large amount of CO and H2S in the furnace, are frequently adopted in the coal‐fired boilers in China. This is one of the main reasons for the high‐temperature corrosion of the water‐cooled wall, while the other is the high wall temperature. In this study, the influences of boiler load, burner tilt angle and near‐wall air (NWA) nozzles numbers on the high‐temperature corrosion of water‐cooled wall in a 600 MW opposed firing boiler are numerically investigated. The results show that the H2S concentration does not decline monotonously with the decreasing boiler load. The H2S concentration declines from 443 to 396 ppm while the average wall temperature decreases by 146 K dramatically when the load descends from 100% BMCR to 50% BMCR. When the effect on both side walls are considered, it is confirmed that the high‐temperature corrosion of the water‐cooled wall would not be alleviated significantly by adjusting the burner tilt angle in this study. Compared with standard condition, the average temperature drops moderately and the maximum H2S concentration drops dramatically from 434 to 367 ppm in the main combustion zone near the left wall when the angle is set at 5°. The reducing atmosphere could be significantly alleviated when NWA nozzles are put into operation. Moreover, a sharp drop of the average CO concentration from 7.8% to 2.1% occurs when only the lower two layers of NWA nozzles are operating. [ABSTRACT FROM AUTHOR]

Slagging and fouling of boilers are typical technological problems in the combustion of solid fuels (especially coal and biomass). This study proposes a novel approach based on laser texturing of the near-surface layer of steel used to make heating surfaces of coal-fired boilers. This approach is aimed at improving the resistance of metal surfaces to slagging. The formation of slag deposits on the surfaces of AISI 310 S steel modified by laser radiation has been experimentally studied. The formation of slag melt was analyzed on the surface of modified and polished steel plates during heating to 1400 °C. High-temperature heating and interaction with slag led to a change in the chemical composition of the steel. A significant increase in the chromium content (up to 47%) of the steel surface and the transformation of its texture with the formation of grains up to 2.5 µm in size were established. Laser surface treatment significantly increased the resistance of the steel to such changes and also reduced the grain size to 1.5 µm. As a result of laser modification of surfaces, the temperature of slag formation shifts to higher values (higher by 60–75 °C compared to the unmodified polished surface). The anisotropic texture (cauliflower type) contributed to a decrease in the size of the slag spreading front, and also had by self-cleaning properties from the mineral melt. The latter allows to increase the reliability and energy efficiency of boiler equipment. [Display omitted] [ABSTRACT FROM AUTHOR]

Aiming at the problem that the energy consumption of the boiler system varies greatly under the flexible peaking requirements of coal-fired units, an energy consumption prediction model for the boiler system is established based on a Least-Squares Support Vector Machine (LSSVM). First, the Mean Impact Value (MIV) algorithm is used to simplify the input characteristics of the model and determine the key operating parameters that affect energy consumption. Secondly, the Snow Ablation Optimizer (SAO) with tent map, adaptive t-distribution, and the opposites learning mechanism is introduced to determine the parameters in the prediction model. On this basis, based on the operation data of an ultra-supercritical coal-fired unit in Xinjiang, China, the boiler energy consumption dataset under variable load is established based on the theory of fuel specific consumption. The proposed prediction model is used to predict and analyze the boiler energy consumption, and a comparison is made with other common prediction methods. The results show that compared with the LSSVM, BP, and ELM prediction models, the average Relative Root Mean Squared Errors (aRRMSE) of the LSSVM model using ISAO are reduced by 2.13%, 18.12%, and 40.3%, respectively. The prediction model established in this paper has good accuracy. It can predict the energy consumption distribution of the boiler system of the ultra-supercritical coal-fired unit under variable load more accurately. [ABSTRACT FROM AUTHOR]

To deal with environmental problems caused by NOx production in thermal plants, it is imperative to establish a reliable model to predict NOx concentration in the combustion process. NOx formation in a coal‐fired boiler is complex, and many variables affect NOx emissions. The effective information fusion of these variables can improve the accuracy of NOx concentration prediction. However, the existing NOx prediction algorithms based on thermal parameters rarely consider the mechanical knowledge of the boiler operation, and it is not easy to incorporate the topological information of production into modelling. Therefore, a graph convolutional network is proposed for NOx emission prediction. First, the key variables affecting NOx generation are selected according to the knowledge and the random forest‐based variable importance. Then, the model structure is designed by exploring the topological information among thermal variables to capture the complex spatial dependence. The model inputs are constructed by coding different operation variables, and the adjacency matrix is generated according to the correlation information between variables, which can fuse data information and reduce redundancy. On this basis, the prediction model of NOx concentration is established. Historical data from a 660 MW coal‐fired boiler are used in the experiment. The prediction results show that the proposed model can effectively fuse the information of characteristic variables and fully exploit the non‐linear mapping relationship between process variables and NOx emission. When compared with three typical models in NOx modelling, the proposed model has better performance with a determination coefficient of 0.906. [ABSTRACT FROM AUTHOR]

In this study, a portable spectral analysis instrument based on spontaneous emission spectroscopy (SES) was developed for the in situ, non-intrusive, and quantitative measurement of gaseous Na inside ZD coal-fired boilers, which is mainly applied for predicting slagging in furnaces. This technology is needed urgently because the problem of fouling and slagging caused by high alkali metals in ZD coal restricts the rational utilization of this coal. The relative extended uncertainty for the measurement of gaseous Na concentration is Urel = 10%, k = 2, which indicates that measurement data are reliable under working conditions. It was found that there is a clear linear relationship between the concentration of gaseous Na and fouling in high-alkali coal boilers. Therefore, a fast and efficient method for predicting the slagging and fouling of high-alkali coal boilers can be established by using this in situ online real-time optical measurement. [ABSTRACT FROM AUTHOR]

Hydrogen blending of pulverized coal in boilers is a promising technology. However, there are few studies on hydrogen blending in coal-fired boilers. In order to reduce CO2 emissions from coal-fired boilers, this study investigates the co-combustion of pulverized coal and hydrogen in a swirl pulverized coal burner by numerical simulation. Itis shown that the burnout rate of fuel is 5.08% higher than that of non-hydrogen blended coal when the percentage of hydrogen blended is 5%. The water vapor generated by hydrogen blending not only leads to the formation of a low-temperature zone near the burner outlet; it also results in a prolonged burnout time of moist pulverized coal and a high-temperature zone near the furnace outlet. The greater the amount of hydrogen for blending, the higher the water produced. When 1–3% hydrogen is blended, the water vapor in the furnace reacts with the carbon to produce a large amount of CO. When the amount of hydrogen added to the furnace is more than 3%, the water content in the furnace rises, resulting in a lower temperature at the burner outlet and a decrease in the amount of CO produced. When 1–3% hydrogen is blended, the CO2 emission rises. The CO2 emission decreased by 1.49% for 5% hydrogen blending compared to non-hydrogen blending and by 3.22% compared to 1% hydrogen blending. [ABSTRACT FROM AUTHOR]

It is of great importance to obtain the exact location and severity of slagging deposits on the waterwall surface of an operational boiler to avoid aimless soot-blowing and reduce steam consumption. In this paper, an effective waterwall surface temperature monitoring method is proposed to determine the slagging locations. It has been noted that the temperature difference of the waterwall surface before and after soot-blowing varied with the waterwall location, with more than 80 °C covered with slag and less than 20 °C found clean. According to this, a slagging temperature index was developed to describe the severity of slagging deposits on the waterwall surface. Results indicated that the process of slagging deposit growth included four stages, with the slagging temperature fluctuating in the range of about 90–110 °C in stage III, followed by a rapid drop below 60 °C in stage IV. Furthermore, a digital image monitoring system was used to validate the slag growth process and study the relationship between deposit thickness growth and area expansion. This novel approach provides automated and accurate guidance for each soot blower around the furnace, which reduces soot-blowing steam consumption and avoids serious slagging on the waterwall surface. [ABSTRACT FROM AUTHOR]

With the increase in the proportion of new energy power generation in grids, there is an urgent need for the flexible operation of coal‐fired power plants. However, as the most efficient commercial coal‐fired power generation technology, the flexibility of double‐reheat ultra‐supercritical units is limited due to the steam temperature fluctuation in transient processes. To inhibit the steam temperature fluctuations, a data‐driven method, called long short‐term memory (LSTM) was introduced to model the dynamics of the steam temperatures of a 1000‐MW double‐reheat coal‐fired boiler. Moreover, an advanced controller was proposed by combining the LSTM‐based dynamic model and the model predictive control architecture. The results demonstrate that the LSTM model can be used to capture the time delay, multivariable coupling and non‐linear dynamics of the steam temperatures and the proposed controller exhibits excellent performance in steam temperature regulation. The superheated steam temperature fluctuation decreases from 15.4 to 9.8°C, the primary reheat temperature fluctuation decreases from 34.6 to 8.3°C, and the secondary reheat temperature fluctuation decreases from 41.4 to 8.8°C. The proposed method has good potential to stabilize steam temperatures during transient processes of wide‐range load cycling, and finally improves the flexibility of the double‐reheat ultra‐supercritical unit. [ABSTRACT FROM AUTHOR]

In order to evaluate the environmental risk of heavy metals in fly ash during the co-processing of pharmaceutical residues in coal-fired boilers, the distribution and leaching characteristics of heavy metals in fly ash with different particle sizes were investigated. The results showed that the distribution rates of Pb and Zn in the overall fly ash all reached more than 95%, and the distribution rates of Cd, Cu and As in the overall fly ash all reached more than 75%, while the distribution rate of Mn in the overall fly ash was only 40%. Along the flue gas flow, the median particle size of the fly ash captured by different electric fields of the dust collector gradually decreased, and the surface of the fly ash particles was smoother. With the decrease of the fly ash particle size, the mass fraction of Pb, Zn, Cd and Cu in the fly ash gradually increased, while the mass fraction of As gradually decreased. The mass fraction of Mn in the fly ash of different particle sizes fluctuated above and below 300 mg/kg. The leaching concentration of Pb, Cd and Cu gradually increased as the particle size of fly ash decreased. The median particle size of fly ash decreased from 20.2 μm to 5.0 μm, and the leaching concentration of Zn increased by 687%, the environmental risk increases sharply; the leaching concentration of As in different particle sizes of fly ash is less than 0.05 μg/L, and the leaching concentration of Mn is less than 0.01 μg/L. In the process of co-processing of pharmaceutical residues, the environmental risk of Pb, Zn, Cd, Cu, Mn gradually increases as the particle size of fly ash decreases, but the environmental risk of heavy metals in different particle sizes of fly ash samples in this test meets the environmental requirements. [ABSTRACT FROM AUTHOR]

Cofiring sludge with coal based on existing power plants is a promising method to realize harmless recycling treatment for sludge disposal. However, the influences of sludge addition on NOx emission are still controversial. Moreover, the optimal operating strategies for the cocombustion boiler need further investigations. In this study, the influences of sludge blending ratio, moisture content, sludge inlet position, and air-staging parameter on the combustion characteristics and NOx emission behaviors in a 330-MW boiler were analyzed numerically. The results show that with the increase of sludge blending ratio, the flue gas temperature in the primary zone decreases. The overall burnout ratio declines with the addition of sludge due to the higher ash and moisture contents. Although the sludge contains more N than coal, the NOx emissions in the cofiring case are lower than those in the coal-fired case due to the lower temperature and stronger reducing atmosphere in the primary zone. Reducing the moisture in the sludge is beneficial to the combustion within the furnace. Nevertheless, because of the higher temperature and lower CO concentration within the furnace, the NOx concentration at the furnace outlet increases. For wall-fired boilers, feeding the sludge from the lower burners should be avoided considering the potential surge in NOx emission. When the excess air ratio in the primary zone increases from 0.74 to 0.96, the NOx concentration at the furnace outlet rises by 58%. Hence, although relatively lower excess air ratio in the primary zone could bring adverse impacts on the burnout behaviors, air-staging combustion is still necessary when cofiring sludge in the coal-fired boiler. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3), as a potential carbon-free alternative fuel, can be blended into coal-fired boiler to achieve significant pollution reduction and carbon reduction, but there are concerns about high NOx emissions due to high nitrogen content. According to the characteristics of coal/NH 3 co-combustion, a dual-fuel co-combustion model with strong adaptability and high accuracy was established in this study through Chemkin software to study the influence of different injection positions and blending ratios on combustion characteristics and NOx generation process. Then, the co-combustion model was applied to the three-dimensional CFD calculation process of a 330 MWe front-fired boiler, and the combustion characteristics, NOx distribution and reaction process were calculated when cal. 20% NH 3 was blended in the primary air. The results show that when cal. 20% NH 3 is blended, the change of NO content mainly occurs in ignition zone and flame zone, and the transformation behavior of N in NH 3 is optimized to a 15-step elementary reaction; The temperature distribution in the furnace is similar, and the average temperature at the furnace outlet decreases from 1033 °C to 988 °C, while NH 3 have a preferential combustion reaction with air than coal, resulting in a decrease in the burnout rate of coal; The NOx concentration at the furnace outlet decreases from 355 mg/Nm3 to 281 mg/Nm3, which is 20.85% lower than that under the pure coal burning condition, and the variation range of O 2 concentration and unburned NH 3 concentration is small. • The NO transformation behavior was optimized to a 15-step elementary reaction. • The change of NO content mainly occurred in the IZ and FZ when blending cal. 20% NH 3. • The burnout rate of pulverized coal was reduced by blending NH 3. • NOx concentration at the furnace outlet reduced by 20.85% when blending cal. 20% NH 3. [ABSTRACT FROM AUTHOR]

The external heat exchanger (EHE) can solve the problem of the insufficient heating surface due to the large‐scale circulating fluidized bed (CFB) boiler effectively; furnace temperature and bed temperature can be regulated quickly and accurately with the adjustment of the solids circulation rate (SCR). The ash differs from coal‐fired boilers in particle size, density, and other physical parameters, so the circulation and heat transfer characteristics are not identical. The results of SCR and pressure distribution in a cold CFB experimental system with an EHE in which the height of the partition (HP) could be adjusted were analyzed. Experiments studied the effect of fluidized air velocity in the riser (Ug), HP of the EHE, and the pressure of the supply air chamber (PSA) in the EHE on SCR using quartz sand with an average size of 0.239 mm. It was noted that SCR increased with Ug and PSA in the range of 7.01–28.37 g/s with the increase in Ug, and the maximum value of SCR was obtained when PSA was 750 Pa and the HP was 80 mm. The experiments also noted that the increase in SCR significantly affected the pressure distribution in the region of high solids content (EHE and the region above 600 mm in the riser). A reference to the above characteristics of SCR and pressure distribution variations can be considered for operating commercial CFB waste incinerators. [ABSTRACT FROM AUTHOR]

With the era of big data, data-driven models are increasingly vital to just-in-time decision support in pollution emission management and planning. This article aims to evaluate the usability of the proposed data-driven model to monitor NOx emission from a coal-fired boiler process using easily measured process variables. As the emission process is highly complex, process variables interact with each other, and they cannot guarantee that all the variables in the actual operation obey the Gaussian distributions. As conventional principal component analysis (PCA) can only extract variance information, a novel data-driven model is proposed, called survival information potential-based PCA (SIP-PCA) model, is proposed in this work. First, an improved PCA model is established based on the SIP performance index. SIP-PCA can extract more information in the latent space from the process variables following the non-Gaussian distributions. Then, the control limits for fault detection are determined based on the kernel density estimation method. Finally, the proposed algorithm is successfully applied to a real NOx emission process. By monitoring the operation of process variables, possible failures can be detected as soon as possible. Fault isolation and system reconstruction can be implemented in time, preventing NOx emissions from exceeding its standard. [Display omitted] • Survival information potential based PCA (SIP-PCA) for fault detection is proposed. • The SIP-PCA method does not have any distribution assumptions and it is robust. • The SIP-PCA algorithm is successfully applied to the real NOx emission detection. • The timeliness and effectiveness of the NOx emission fault are detected. • SIP-PCA outperforms conventional algorithms. [ABSTRACT FROM AUTHOR]

In order to improve the utilization rate of coal generation and reduce carbon emissions from coal-fired boilers, the operation parameters of power plant boilers should be matched with the actual burning coal. Due to the complex and high-risk blending process of multiple coal types, the actual application of coal types inconsistent with expectations may lead to low combustion efficiency of boilers, cause disturbances to the normal operation of thermal power units, increased energy waste and carbon emissions, and even lead to serious explosion accidents. Therefore, the online identification of coal types for thermal power units is of great significance. To obtain the precise type of coal online, in the present work, a data-driven coal identification method is proposed based on convolutional networks that do not necessitate additional hardware detection equipment and are easy to implement. Experimental results indicate that the proposed method exhibits superior performance in comparison to traditional methods, thus ultimately improving the performance of thermal power plant. [ABSTRACT FROM AUTHOR]

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Coal is expected to be an important energy resource for some developing countries in the coming decades; thus, the rapid classification and qualification of coal quality has an important impact on the improvement in industrial production and the reduction in pollution emissions. The traditional methods for the proximate analysis of coal are time consuming and labor intensive, whose results will lag in the combustion condition of coal-fired boilers. However, laser-induced breakdown spectroscopy (LIBS) assisted with machine learning can meet the requirements of rapid detection and multi-element analysis of coal quality. In this work, 100 coal samples from 11 origins were divided into training, test, and prediction sets, and some clustering models, classification models, and regression models were established for the performance analysis in different application scenarios. Among them, clustering models can cluster coal samples into several clusterings only by coal spectra; classification models can classify coal with labels into different categories; and the regression model can give quantitative prediction results for proximate analysis indicators. Cross-validation was used to evaluate the model performance, which helped to select the optimal parameters for each model. The results showed that K-means clustering could effectively divide coal samples into four clusters that were similar within the class but different between classes; naive Bayesian classification can distinguish coal samples into different origins according to the probability distribution function, and its prediction accuracy could reach 0.967; and partial least squares regression can reduce the influence of multivariate collinearity on prediction, whose root mean square error of prediction for ash, volatile matter, and fixed carbon are 1.012%, 0.878%, and 1.409%, respectively. In this work, the built model provided a reference for the selection of machine learning methods for LIBS when applied to classification and qualification. [ABSTRACT FROM AUTHOR]

Simplicity, efficiency and precision are basic principles for modeling and analyzing of coal-fired boilers data. However, the load fluctuations, system delay, multi-variable coupling pose great challenges to the high-precision modeling for NOx emission. A hybrid feature selection method for boiler data is proposed to predict accurately NOx emission. Firstly, the mechanism analysis is used to narrow the feature scope, and the feature set is selected preliminarily. Secondly, maximum information coefficient (MIC) method is introduced to calculate the correlation between features and NOx information to eliminate boiler system delay. Thirdly, a combined feature evaluation method is developed, which integrates Filter and Embedded method to obtain feature ranking, then the ranking information is regarded as priori knowledge to improve the genetic algorithm. Finally, a fitness function to maximize prediction accuracy and minimize feature dimension is constructed based on hybrid method to realize feature subset selection and NOx emission prediction. Original data are collected from one 1000 MW coal-fired unit in the Guangdong province of China. Experimental results show that the number of features is reduced by nearly 70%, the MAPE of LightGBM regression model is no more than 2%. Higher prediction accuracy can be obtained using the features extracted through the proposed hybrid method. [ABSTRACT FROM AUTHOR]

In a thermal plant, the combustion system of the coal-fired boiler is a nonlinear time-varying system, which leads to undesired responses, if traditional proportional-integral-derivative controllers are utilized. Internal process delay is an important characteristic of the steam pressure in the boiler of coal-fired power plants, which affects the closed-loop dynamics. To compensate for this significant delay and reach the desired performance, a novel control strategy based on a combination of an optimal fractional-order proportional-integral-derivative (OFOPID) controller with a Smith predictor (SP) structure is suggested in this paper that achieves the desired control performance required for the optimal operation of the boiler. The simulation results of a coal-fired power plant boiler with the power of 300 MW show that the performance is improved considerably by having lower overshoot and lower rise and settling times, as well as a lower mean square error during the operation of the power plant Boiler. [ABSTRACT FROM AUTHOR]

Coal‐fired thermal power must be flexible to enable the grid absorption of inconsistent photovoltaic (PV) and wind power. Combined heat and power (CHP) coal‐fired plants are the primary source for district heating systems. This paper uses a 330 MW subcritical CHP unit as an example to carry out the study. With the promotion of building energy efficiency, when the thermal index is reduced to below 20 W/m2, the low‐load operation of CHP can meet the wind power and PV feed‐in demand and guarantee residential heating without the need for flexibility modification. Meanwhile, more renewable energy generation can reduce carbon emissions from the power supply, further contributing to reducing carbon emissions from buildings. The impacts of different envelope parameters and supplementary heat sources on building carbon emissions are also studied. The conclusion shows that the degree of their impact on carbon emissions ranks as ESMs (energy supply modes) > Factor D (infiltration N50) > Factor A (external wall heat transfer coefficient) > Factor C (window heat transfer coefficient) > Factor B (roof heat transfer coefficient). When the building's heating energy consumption gradually decreases, the distributed heat pump unit can replace the coal‐fired boiler to supply the peak heat load demand. In the future, China's district heating systems can be gradually changed from the current CHP and coal‐fired boilers to CHP and distributed heat pumps. [ABSTRACT FROM AUTHOR]

Multi-fuel operation of the coal-fired boiler is considered as a promising option for boiler reformation to reduce carbon emissions while recycling solid waste. In this work, co-combustion characteristics of sugarcane bagasse, Nanning meager-lean coal and petroleum coke under different conditions were investigated in detail. And the interaction between raw materials was analyzed. Finally, the kinetic parameters were estimated by using the first-order response model. The results show that differences in petroleum coke content affect the appearance of weight loss peaks in the DTG curve. When the proportion of sugarcane bagasse is between 40 and 60%, the ignition and burnout characteristic indexes are particularly sensitive to variations in sugarcane bagasse content. Additionally, the interaction between the three raw materials is promoted as the proportion of petroleum coke is less than 40%. The kinetic analysis suggests that the increase of heating rate is conducive to the precipitation of volatiles, but there is an optimal heating rate for the fixed carbon combustion stage. The change of particle size combination has little effect on the activation energy of the volatile fraction combustion stage. This study provides a reference to ensure the stable and high-efficient operation of the coal-fired boilers during the multi-fuel combustion. [ABSTRACT FROM AUTHOR]

Copyright of Safety & Fire Technology (2657-8808) is the property of Centrum Naukowo-Badawcze Ochrony Przeciwpozarowej and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Boilers using different fuels like HSD, LDO, coal, PNG and propane were taken into consideration in this study. Different parameters associated with boilers like economic factor, efficiency factor and the environmental impact factor were being calculated by taking measurements and collecting data from different plants in Odisha with variety of fuels. It is found that the most economical fuel is coal with a price index of 4.69 Rs/megacalorie and the most expensive fuel is LDO with a price index of 9.83 Rs/megacalorie. The most efficient boilers are propane‐fired boilers with an efficiency of 95.1% and least efficient boilers are coal‐fired boilers with an efficiency of 88.8%. PNG‐fired boilers had the lowest environmental impact around 1.0 and coal‐fired boilers had the highest around 6.0. A new concept of EEE impact index has been introduced which denotes the combined impact of Economic factor, Efficiency and Environmental factor. PNG was found to be the best fuel, having an EEE impact factor of 0.06 and LDO is the worst, having an EEE impact factor of 0.43. A case study was also carried out to convert a boiler from HSD‐fired to PNG‐fired, which was found to be very encouraging with a payback period of approximately 1 year. The IRR also calculated, it was around 120% making it very appealing to invest for a good financial gain. This can be used as a reference and guiding document for the industries to take decisions for fuel switching and achieve better sustainability by implementing this initiative. [ABSTRACT FROM AUTHOR]

This study is focused on the high-temperature corrosion evaluation of selected thermally sprayed coatings. NiCoCrAlYHfSi, NiCoCrAlY, NiCoCrAlTaReY, and CoCrAlYTaCSi coatings were sprayed on the base material 1.4923. This material is used as a cost-efficient construction material for components of power equipment. All evaluated coatings were sprayed using HP/HVOF (High-Pressure/High-Velocity Oxygen Fuel) technology. High-temperature corrosion testing was performed in a molten salt environment typical for coal-fired boilers. All coatings were exposed to the environment of 75% Na2SO4 and 25% NaCl at the temperature of 800 °C under cyclic conditions. Each cycle consisted of 1 h heating in a silicon carbide tube furnace followed by 20 min of cooling. The weight change measurement was performed after each cycle to establish the corrosion kinetics. Optical microscopy (OM), scanning electron microscopy (SEM), and elemental analysis (EDS) were used to analyze the corrosion mechanism. The CoCrAlYTaCSi coating showed the best corrosion resistance of all the evaluated coatings, followed by NiCoCrAlTaReY and NiCoCrAlY. All the evaluated coatings performed better in this environment than the reference P91 and H800 steels. [ABSTRACT FROM AUTHOR]

The coal ash fusion characteristics are a significant factor to consider while designing a boiler to match a coal or different coal range. Characterization of coal ash provides the fundamental mechanism that controls the heating efficiency of the coal in a pulverized coal-fired boiler, regarding the coal minerals association. Changes in coal properties could lead to changes in ash properties, i.e., ash fusion temperatures (AFT) and ash elemental composition, which could lead to slagging or fouling issues inside the boiler. The main cause could be attributed to the high temperature of the combustion process and the low melting point of ash, or vice versa. This study aimed to develop AFT prediction models using coal samples from different coalfields to predict the initial deformation temperature (DT), softening temperature (ST), hemispherical temperature (HT) and fluid temperature (FT) of coal ash. The artificial neural network (ANN), Gaussian process regression (GPR) and support vector regression (SVR) are the three machine learning tools used in this modeling. The resulting AFT predictive models indicated that the ANN model predicted DT, ST, HT and FT more adequately and reliably than the GPR and SVR. The Taylor's diagram, which enabled easy identification of the closeness of the model predictions to the measured data, also indicated that the ANN outperformed all the other models. [ABSTRACT FROM AUTHOR]

This study focuses on the emission characteristics of NOx under oxy-fuel combustion conditions. A comparative analysis with air combustion was performed. NOx emission, control measures and influence factors under different working conditions were studied. Experiments were carried out on a 3-MWth test platform and a laboratory platform. The 'π'-type furnace was adopted, with the furnace width of 2.6 m, depth of 2.0 m and height of 10.5 m for the 3-MWth coal-fired boiler. NOx emissions at different oxygen concentrations and different air distribution were investigated; the effects of H2O and CO2 concentration on denitrification efficiency and SO2/SO3 conversion rate were explored. Experiment results suggest that, compared with air combustion, NO concentration (volume basis) at the furnace outlet under oxy-fuel combustion is higher than that of air combustion, but the amount of NOx emissions in the discharged gas significantly decrease compared to the air combustion conditions. In addition, the formation of NOx can be effectively controlled through staged combustion. Furthermore, the selective catalytic reduction (SCR) denitrification efficiency and the conversion rate of SO2 to SO3 decreases when the CO2 concentration and the H2O content increase, indicating that CO2 and H2O have an adverse effect on the performance of the catalyst. Additionally, compared with CO2 concentration, H2O content has a greater effect on catalyst performance. [ABSTRACT FROM AUTHOR]

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)