Preheater Research Articles

A novel silicon carbide plate-fin heat exchanger and its thermal and hydraulic performance for SOFC cathode air preheater application

This paper focuses on a novel silicon carbide (SiC) plate-fin heat exchanger (PFHE) for the cathode air preheater application of Solid Oxide Fuel Cells (SOFCs). An innovative assembly method and a reliable connection structure with the system's metal pipelines were proposed, and then a prototype of the SiC PFHE with offset strip fins was developed. Additionally, a performance testing apparatus for the SOFC cathode air preheater was built. Based on this testing setup, experimental studies and application validation on the heat transfer and flow characteristics of the SiC PFHE were conducted. Finally, the application prospect of SiC PFHE in SOFC systems was further evaluated and compared with metallic plate heat exchangers. The results indicate that the assembly structure and test procedure of the SiC PFHE not only realize the reliable high temperature sealing, but also effectively reduce the thermal stress of SiC ceramic material. Essential parameters such as overall heat transfer coefficient, Colburn factor, and friction factor reveal consistent trends with existing literature under various operating conditions at average Reynolds number in the range from 84 to 361. The SiC PFHE has significant advantages in upper operating temperature limit and high temperature structural integrity and reliability.

Chemical kinetics of Lean − Rich − Lean fuel-air staged NH3/H2-air combustion for emission control

Ammonia has garnered considerable attention among researchers as a carbon–neutral fuel option. Addressing the challenge of its inherently slow combustion kinetics, significant research efforts have been directed toward mitigating NOx emissions, which represents a critical hurdle in advancing the commercial viability of ammonia as a sustainable fuel. The rich-lean combustion approach has been advocated and demonstrated as the primary means to keep NOX within acceptable emission limits. However, in the current study, a distributed fuel and air injection strategy is proposed and investigated as a superior alternative compared to the traditional rich-lean method for NOX reduction for NH3/H2-air mixtures with higher ammonia fuel fraction (XNH3 = 50 − 90 %). The proposed lean-rich-lean strategy with multi-staging of fuel and air supply is achieved by injecting NH3-air mixtures into H2-air combustion products followed by a downstream supply of preheated dilution air. Such an injection strategy manages the surge of NHi and O/H radicals while avoiding local temperature peaks by implementing a two-stage ignition pattern of NH3/H2 blends combustion in series. NOX reductions of approximately 48 % and 7 % forXNH3 = 50 % and 70 %, respectively, is achieved with the lean-rich-lean combustion strategy compared to the rich-lean strategy over a wide range of global equivalence ratios(ϕG = 0.3 to 0.7). The lean-rich-lean combustion strategy for atmospheric NH3/H2-air swirl flames, when integrated with advanced SCR technology, is anticipated to demonstrate a viable approach to achieving zero carbon and low NOX emissions in industrial applications.

Interplay Between Unburned Emissions and NOx Emissions From a Dual Swirl Hydrogen Air Injector

Abstract OH planar laser induced fluorescence (OH-PLIF) and particle image velocimetry (PIV) are employed to analyze the structure of hydrogen/air flames stabilized by a dual swirl injection system under globally lean and atmospheric conditions with preheat air temperature varied from ambient up to 673 K. The flames exhibit two distinct reaction branches. The first, located in the central recirculation zone (CRZ), is a diffusion-controlled reaction layer characterized by a relatively large thickness associated with low strain rates. The second branch, stabilized in the shear layer of the swirling jet, is strongly influenced by large coherent structures. Depending on operating conditions, this front may adopt either the form of a fully diffusive strained reaction layer anchored to the hydrogen injector lip or a lifted diffusion front with a leading-edge flame evolving into a partially premixed flame at high air injection velocities. Flue gas analysis indicates NOx emission levels, typically below 10 ppm at 15% O2, for sufficiently large air injection velocities. Air preheating barely increases NOx emissions at lean operating conditions. The injector operational range is constrained only by the ultralean blowout limit reached for global equivalence ratios below 0.02. Furthermore, it demonstrates remarkable resilience to large and rapid drop in fuel flow rate. However, combustion efficiency drops close to the lean blowout (LBO) limit due to intermittent fragmentation of the flame wings that progresses further upstream as the equivalence ratio drops. The results demonstrate that fragmentation arises from the combined effects of a temperature drop in the central recirculation zone and the flame wings being exposed to high shear stress. Additionally, it is shown that combustion efficiency under ultralean conditions improves significantly with an increase in air preheat temperature.

Optimizing Organic Rankine Cycle (ORC) configurations integrated with transient industrial waste heat: a multi-objective approach

Decarbonizing heat-intensive industries by reusing the waste heat for power or combined heat and power systems is becoming increasingly important to address global warming. The Organic Rankine Cycle has shown a high level of feasibility and performed efficiently for utilizing medium-to-low-grade heat from renewable resources and heat-intensive industries for direct power generation. This study contributes to the field by conducting a techno-economic investigation of various Organic Rankine Cycle configurations to enhance energy conversion when real-life transient waste heat sources are available. These configurations were optimized to maximize energy output along with economic benefits. The non-linear programming by quadratic Lagrangian, a computational unintensive yet accurate optimization algorithm, was utilized for the multi-objective optimization. The optimized cycle configurations showed a 12.57% enhancement of turbine efficiency. Combining regeneration and recuperation enhanced the superheating by 32%, and the optimized air preheater cycle improved the overall objective by 64.2% compared to the pre-optimized conventional cycle, leading to a feasible 1.72-year payback period.

Study of Steam Turbine Unit Operation Using Natural Gas Combustion in Pure Oxygen to Ensure Decarbonisation through Gas Path Modernization (using the Example of a TGM-94 (EP-500/140) steam boiler)

The research is aimed at substantiating the technical use of natural gas combustion in an environment with a high oxygen content and, in the long-run objective - in pure oxygen in a steam turbine power unit. To achieve this aim, the following problems were solved: the development of a mathematical model of a steam turbine power unit for operation when burning natural gas in pure oxygen, a numerical study of the power unit operation when replacing air with oxygen from 0 to 100%, and an assessment of the efficiency of the equipment in these modes. The most important result is an increase in the efficiency of the steam turbine power unit when switching to burning natural gas in an environment with a high oxygen content. The significance of the results obtained is to ensure the efficiency of CO2 capture from flue gases without a complete reconstruction of the facility. The object of the study was the Krasnodar Thermal Power Plant. In the study, the previously verified mathematical model of the power unit was modified. The model was created using the Boiler Designer software product. The mathematical model was modified by zeroing air leaks into the boiler gas path, replacing the regenerative air heater with a tubular one, and bypassing the air heater along the flue gases when operating on an oxygen-air mixture. The maximum increase in the boiler unit efficiency is 0.6% and is in the range of air substitution with oxygen from 40 to 60%.

Effect analysis on the low-temperature preheating performance of a novel micro-combustor air preheater for the cold start of the Li-ion battery packs

In this work, a micro-combustor (MC) air preheater as the heat source is developed. This novel air preheater has a compact size and outputs hot air with a wide range of temperatures with high temperature uniformity, which can well meet the preheating needs of Li-ion batteries in cold environments. Numerical studies are carried out to investigate the effects of baffle height, number of fins Nfin, hot air inlet velocity, cold air inlet velocity and combustor inlet velocity on the performance of the air preheater. The heating power of the air preheater can be adjusted by changing combustor inlet velocity Vcombustor, the outlet temperature can be easily adjusted by changing cold air inlet velocity Vcold and hot air inlet velocity Vhot, and the addition of baffles makes the outlet temperature very uniform. The results show that the height of the baffle of 20 mm and 30 mm makes ΔTair not exceed 1.5 K. The air preheater performance is better with fin number 6, and the maximum air temperature of 309.8 K is obtained with fin number and Vhot of 6 and 0.3 m/s respectively. Tair can vary between 287.8 K and 309.8 K when Vcombustor = 12 m/s.

Design and performance analysis of a coupled burner for the Solid Oxide Fuel Cell system

The Solid Oxide Fuel Cell (SOFC) system is characterized by high energy conversion efficiency and low emissions. The energy supply and recovery of the SOFC system are facilitated through the ignition burner and the off-gas burner, respectively. This study proposes a coupled design of the ignition burner and the off-gas burner to reduce the burner volume, thereby enhancing the power density of the SOFC system. The ignition burner employs radially opposed jet combustion with fully premixed natural gas, while the off-gas burner uses swirl diffusion combustion with the anode off gas. When the premixed gas and lean anode off gas are unable to sustain the flame, catalytic combustion is initiated. Simulation and experiment methods are utilized to analyze the performance of the coupled burner in this paper. The results indicate that uniform mixing is achieved with a high swirl number (s1 = 2.6) for the premixed gas, and the maximum excess air coefficient for stable flame combustion at 400 °C is 2.47. As the temperature of the cathode off gas increases, the flameout boundary for the premixed gas gradually increases; conversely, with increasing burner power, the flameout boundary gradually decreases. The intersection cooling effect of mixed air and circumferential high-temperature flue gas is effective, and the flame does not exceed the tolerance temperature of the catalytic carrier. The diffusion combustion of anode off gas with a swirl number (s2 = 0.5) exhibits great gas mixing uniformity without a high-temperature core region. When transitioning from flame to catalytic combustion with premixed natural gas and anode off gas, there is a temperature lag of approximately 60 s. The isotropic cylindrical cordierite catalytic carrier with a 400 mesh and a coating of 60 g/ft3 Pt0.1Pd0.5 achieves stable catalytic combustion in an environment with preheated air temperatures ranging from 400 to 600 °C and H2 concentrations of 0.25–2.91 %.

Studies into Ash Deposition Propensities in the Vicinity of Economizer and Air Preheater of Coal-Fired Power Utility

Studies into Ash Deposition Propensities in the Vicinity of Economizer and Air Preheater of Coal-Fired Power Utility

Recovering Low-Grade Heat from Flue Gas in a Coal-Fired Thermal Power Unit

To achieve the goals of carbon peaking and carbon neutrality, the retrofitting of existing coal-fired power plants is crucial to achieving energy-saving and emission reduction goals. A conventional recovery system of waste heat typically occurs downstream of the air preheater, where the energy quality in flue gas is low, resulting in limited coal-saving benefits. This study proposes a scheme involving a flue gas exchanger bypassing the air preheater and low-temperature economizers, which is used to transfer the waste heat from flue gas to primary and secondary air (System I). Additionally, a heat pump can be introduced to provide supplementary energy for primary and secondary air, as well as the condensate from the steam turbine (System II). The coal consumption rate and exergy efficiency are used to evaluate the two schemes. The results show that both waste heat recovery systems can increase the power output of the coal-fired unit by recovering waste heat. System II can boost power output by approximately 13.98 MW. The power increase in both waste heat recovery systems show a declining trend as the unit load decreases. This increased power is primarily attributed to the medium- and low-pressure cylinders, while the contributions from ultra-high-pressure and high-pressure cylinders are negligible. The increased power output for the medium-pressure cylinder ranges from approximately 3.49 to 3.58 MW, while the low-pressure cylinder has an increased power output of around 10.10 to 10.19 MW. The coal consumption rate is decreased from 250.3 g/(kW·h) to 247.5 g/(kW·h) under a full load condition for both systems, which can be augmented at lower load conditions. System II outperforms System I at 30% load condition, achieving a reduced coal consumption rate of 3.36 g/(kW·h). System I has an exergy efficiency of 40%, while System II shows a higher efficiency of 44%.

Numerical Simulation Study on Rotary Air Preheater Considering the Influences of Steam Soot Blowing

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.

Ultrasonic atomization technique for enhancing humidification process in thermal desalination

The need for desalination is expected to evolve, and interests in novel techniques to enhance thermal desalination are developing. Research studies on ultrasonic atomization for desalination application has been observed in the last few years. Hence, this study aims to examine humidification process enhancement using ultrasonic atomization and interaction of atomized droplets with hot air in the humidifier. In the Humidification and Dehumidification (HDH) desalination system examined, the humidifier is equipped with a single ultrasonic atomizer unit which operates continuously with preheated hot air entering the humidifier chamber. The system is investigated for different air flowrates (40 – 100 LPM) and hot air temperatures (40, 50, and 60 °C). The average relative humidity at the humidifier outlet was maximum reaching 94 % for the highest flowrate. The results indicate that increasing hot air temperatures have significant improvement in droplet evaporation which causes higher relative humidity at the outlet, and increasing hot air flowrates have significant impact on the faster response of the humidification process to reach equilibrium.

Investigation of safe operating conditions for reducing acid corrosion and ABS deposition in rotary air preheater using computational fluid dynamics

Investigation of safe operating conditions for reducing acid corrosion and ABS deposition in rotary air preheater using computational fluid dynamics

Numerical investigation to predict the impact of pre-heated air on the tar formation of cocoa pod husk gasification in a fixed bed downdraft gasifier

Tar production is a critical aspect of gasification thermochemistry, and it hinders the widening of biofuel utilisation in several applications. Both the gasifier configuration and the operating conditions influence the quantity of tar in PG. Since temperature plays a major role, this study examines the performance parameters of a gasifier across a spectrum of input air temperatures, from 27 to 627 °C, utilising computational fluid dynamics with species transport and porous media models. Since the deviation of numerical predictions from experimental results is within 10 %, the model's validity is confirmed. CO and H2 gas production increased from 19.23 % to 27.12 % and 9.23 %–16.2 %, respectively, over the tested air temperature range; however, the variation in methane content was not significant. Furthermore, the higher heating values of PG and cold gas efficiency were found to be 5–6.8 MJ/Nm3 and 65–69 %, respectively. The study also investigates reaction rates for gasification, combustion, and volatiles' breakdown under various operating conditions. Among the tar species studied, benzene is the most concentrated at 1.6 g/Nm3, followed by toluene at 0.9 g/Nm3, with naphthalene and phenol present in comparatively smaller amounts. Furthermore, the research indicates that an appropriate temperature of gasifying medium can control tar in PG.

Comprehensive pollutant emission prediction models from hydrogen-enriched methane combustion in a gas-fired boiler based on box-behnken design method

Hydrogen-enriched methane (HEM) combustion is an effective method for reducing the consumption of carbonaceous fuels. However, high adiabatic flame temperature of H2 can cause large NO emissions. To reduce the NO and CO2 emissions from HEM combustion, the Box-Behnken design (BBD) method combining response surface experimental design, analysis of variance, and multi-nonlinear regression models was adopted. The effects of the H2 doping ratio (XH2), preheated air temperature (Tair), excess air coefficient of burners arranged at the bottom (Ex,b), and their interactions on the NO, N2O, and CO2 emissions of a gas-fired boiler were investigated. According to the BBD method, the NO, N2O, and CO2 emissions prediction models with R2 exceeding 0.98 were proposed, respectively. The results showed that the increase of Tair had a positive effect on reducing NO emissions, as the NO exhausted from HEM combustion is mainly thermal NO. Compared with Tair and Ex,b, XH2 was the most significant factor affecting N2O and CO2 emissions, indicating that an increase in XH2 can significantly reduce greenhouse gas emissions. Additionally, the formation and consumption of N2O emissions presented a competitive mechanism at XH2 increased from 0 to 0.8, and CO2 emissions reduced with the increase of XH2, Tair, and Ex,b. Furthermore, a comprehensive emission prediction model with NO, N2O, and CO2 emissions was proposed. With the target of minimizing total NO, N2O and CO2 emissions, three groups of combinations for XH2, Tair, and Ex,b were obtained from the equal weight, entropy weight method, and criteria importance through the inter-criteria correlation method as 1:1:1, 24:9:17, and 21:11:18. The results showed that for minimize emissions, there is not much difference in the results calculated based on the optimal boundary conditions under different weights. For various reduction targets for nitrogen, carbon, and greenhouse gases, three groups of optimal combinations of XH2, Tair, and Ex,b were obtained and their accuracies were verified based on numerical calculations with relative errors below 6%. The proposed comprehensive pollutant emission prediction models are conducive to calculating the pollutant emissions of HEM combustion and guiding the investigation of prediction models considering other operating conditions.

Lean Blowout Proximity Sensing in a Low Emission Liquid-Fueled Combustor

ABSTRACT Advanced aircraft engine combustor designs, intended for achieving low NOx emissions, necessitate lean combustion with small operating margins above the LBO boundary, posing a high risk of exhibiting lean blowout (LBO) problems. Employing active LBO controllers receiving input from LBO proximity sensors can allow for narrower margins, thereby yielding multiple performance gains. Although several previous studies investigated LBO proximity sensing, they predominantly focused on premixed gas-fueled combustors. The application of proximity sensing approaches to liquid-fueled combustor designs, relevant to aircraft engines have not received adequate attention. Therefore, this study investigates LBO proximity sensing in a low emission lean direct injection (LDI) liquid-fueled combustor design developed by NASA. The combustor operates at atmospheric pressure with preheated air. The proximity sensing is examined by analyzing both OH* and CH* chemiluminescence signals, with a focus on assessing their relative performances. The signal analysis approaches include spectral, partial extinction event (LBO precursor) detection, signal RMS, and the CH*/OH* ratio, with an emphasis on the first two methods. Both steady-state and transient operating conditions have been examined. The combustor did not exhibit large-scale flame partial extinction and re-ignition events near LBO, as commonly observed in gas-fueled combustors. However, an increase in flame unsteadiness and partial extinction events with very subtle signatures in optical signals, have been observed. Low-pass filtering has been observed to considerably enhance the precursor signatures enabling their improved detection. With a reduction in LBO margin, an increase in signal low-frequency power, RMS, and precursor event occurrence rate have been observed, which were utilized for providing LBO proximity measures. A key finding from this study is that CH* signals provide significantly superior performance compared to OH* for the proximity sensing in all the approaches, and the potential reasons are discussed.

Exergy assessment of a semi-transparent building integrated photovoltaic facade for mild weather conditions of Srinagar

Abstract Effective utilization of solar energy reduces the dependence on fossil fuel usage along with achieving the objective of carbon neutrality. The current work aims to numerically assess the performance of a facade based semi-transparent BIPVT system while considering four different weather conditions in a month for the climate of Srinagar, India. In the proposed configuration, the BiSPVT facade serves the dual purpose of generating electrical power gain and providing pre-heated air for space heating. PV module surface was cooled by flowing air through the air channel. Movement of air through the cavity takes away the heat from the PV module back surface reducing the temperature of the solar cells resulting in enhanced module efficiency. System performance has been evaluated in terms of obtained energy and exergy using a 1-D numerical model developed in MATLAB. The Exergy analysis presented shows an informative means of estimating system functioning based on qualitative aspect of useful energy gained. For a mild cold weather condition of Srinagar, with minimum ambient temperature dropping to 1.2 °C, useful daily exergy gain of 0.0545 kWh/m2 has been achieved signifying the increase of space heating during winters of cold climatic regions. Maximum temperature difference between room and ambient was obtained as 9.76 °C using the BiSPVT façade. Results shows that the proposed BiSPVT system was able to produce monthly electrical and thermal exergy gain of 12.56 kWh/m2 and 16.81 kWh/m2 respectively. Exergy efficiency of the system was determined in the range of 18.2%-19%. Further, environmental assessment of the PV façade system based on CO2 emission gave an estimated amount of 0.387-ton CO2 emission reduction for the month of November leading to environmental cost reduction of 5.615$/month.

PROMISING TYPES OF HEAT STORAGE ELEMENTS FOR REGENERATIVE AIR HEATERS OF BLAST FURNACES

The paper considers the problem of improving the efficiency of operation of blast furnace air supply systems, which are equipped with regenerative heat exchangers with fixed refractory nozzle for heating hot blast. The existing methods of improving the performance of air heaters are analyzed. It is shown that further growth of thermal efficiency of regenerative heat exchangers by optimization of operation parameters or replacement of nozzles is impossible without increasing the overall parameters. As a perspective measure the use of heat storage elements with phase transition is proposed, where as a fusible insert compounds with a certain melting point are used, which corresponds to the operating modes of blast furnace air heaters. They have found application for heat storage in solar systems. Due to the "residual" thermal effect, the nozzles accumulate additional heat. This will increase the heat capacity of the heat exchanger and increase the hot blast heating temperature without changing the dimensional parameters. Operating conditions of air supply systems of blast furnaces are characterized by high temperature level, which is 1200–1350 °С, significant flow rates and speeds of hot and cold coolants, their increased pressure. Therefore, there is a question of choosing appropriate heatacumulative elements taking into account their properties and operating parameters of blast furnaces. Operation of such nozzles has revealed a number of problems, the solution of which requires additional research. For this purpose it is necessary to carry out modeling of quasi-stationary heat-exchange processes in the nozzle chamber of regenerative air heaters in order to select chemical compounds or their mixtures, which meet the operating conditions of blast furnace air supply systems, and to determine the optimal combinations of nozzle materials. Application of this technology will make it possible to obtain higher hot blast heating temper- ature, reduce metallurgical coke consumption or increase blast furnace productivity.

CLIMATE AND ENVIRONMENTAL BACKGROUNDS OF FUEL UTILIZATION, INFLUENCING UPON ALTERATION THE EUROPEAN AND UKRAINIAN TRENDS OF GAS SUPPLY. PART 2. PROVIDING THE EFFICIENCY OF FUEL USE IN CONDITIONS OF DECARBONIZATION OF ENVIRONMENT

The paper is dedicated to power and environmental aspects of option the most appropriate types of fuel for supplying the economics of European countries and Ukraine. Accordingly notions about influence of C-containing fuels on greenhouse effect and on warming of environment, the existing tendency of substitution the fossil fuels — generally — and the natural gas — particularly — for methane-hydrogen mixtures is discussed as a controversial point. The problem of advancement the national fuel complexes is under consideration and has been studied with approach based upon the example of Ukrainian pre-war state of economics. An attention has been paid up on reduction of production and consumption of all types of the fossil fuels in the last decades, mainly due lowering the industrial using constituent. An enhancement of fuel using efficiency due improvement of furnace equipment basis provides an successive solution the fuel problems. The thermodynamic background for evaluation the efficiency of fuel using with account of the furnace’s non-ideality has been developed. The problem of “wet combustion” takes of special significance by the reason of weather and climate conditions’ account, on the one hand, and an opportunity to control the efficiency of fuel using, on the other hand, with new combined technique. The contemporary approach consists in combination the direct method of decrease the CO2 emission due exclusion of using the C-containing fuels (firstly — the fossil fuels) and with enhancement the efficiency of using the fossil fuels, for example due erection the recuperative heat recovery facilities with preliminary preheating of combustion air, in some advanced cases by combination with an air, humidification. The perspective ways of provision the decarbonization of environment consists in substitution the fossil fuels (mainly the natural gas NG) for hydrogen or H2-containing gas mixtures. The thermodynamic analysis of relevant technique has been carried out to estimate the opportunities of control the efficiency of hydrogen admixture to NG. Taking into account the variety of technologies of hydrogen production, the engineering method with giving of conditional coloration of hydrogen as a fuel has been considered. The “green” H2 makes the most valuable type of fuel (compared with “blue”, “turquoise”, “yellow”, “rose” colored and especially to the “grey” H2) as a substituting fuel from the standpoint of H2 fitness to process and plant. Particularly for high-temperature melting furnaces a provision of maximum emissivity of flame requires an using of carbon containing fuels to organize thermal pyrolysis of gas and soot formation within the combustion zone. Ref. 44, Fig. 5, Tab. 3.

A novel data-driven approach for coal-fired boiler under deep peak shaving to predict and optimize NOx emission and heat exchange performance

Coal-fired boilers considering deep peak shaving operate under wide and variable load requirements with complex and varying working conditions, making the prediction and optimization of combustion target variables challenging. This study proposed a data-driven approach for the prediction model building, tuning and combustion optimization. In this approach, a neural network for prediction based on Gaussian kernel and long short-term memory (LSTM), which captured and fused the working condition and temporal information, was first proposed. To address incomplete historical data coverage of working conditions, a fine-tuning framework with the idea of transfer and few-shot tuning was then introduced. Finally, an improved fitness function considering both optimization objectives and combustion adjustment limitations was designed to mitigate the risks associated with large-scale adjustments of operable variables. By conducting experiments on a 1000 MW boiler, targeting NOx concentration and the outlet temperature of the air pre-heater, the proposed method demonstrated high prediction accuracy with R2 values of 0.979 and 0.989, and significantly reduced mean squared error (MSE) by 98.05% and 97.37% on new conditions compared to untuned models. It achieved the reductions in NOx and temperature of 24.70 mgm−3 and 2.013 ∘C, and decreased the average changes of operable variables by 9.66% and 11.24% compared to using only rigid constraints.

Redesigning the Element Profile of Air Preheater in Coal-fired power plants for Emission Reduction and Efficiency Improvement

PT PLN Nusantara Power Unit Pembangkit Tanjung Awar-Awar (UPTA) is a state-owned company that supplies electricity to areas of Java and Bali. Using coal as the main fuel, UPTA currently has two mills that each has capacity of 350 MW in coal-fired mode. Since the last few years, UPTA has been focusing on bringing efficiency into its overall operations, maximizing efforts for an improved output, modernizing machinery, and reducing emissions. After conducting routine inspection and examinations, UPTA decided to improve the air preheating element, so-called air preheater (APH), as an enabling condition to heat both the primary and secondary air to a temperature required for effective combustion in a boiler. To seek for an optimal APH, a redesign project was initiated to primarily change the element profile from a distorted wavy flow path to a linear flow path. The profile surface was coated with an added "enamel" layer, which prevents ash from adhering readily. Our measurements and calculations were based upon the data collected in October 2022 (pre- implementation) and within the periods of February to June 2023 (post-implementation). As a result, the average power consumption was reduced: from over 1740 kWh per month to become around 1377 - 1535 kWh per month, or 11% - 21%, for the induced draft fan (ID Fan) and from over 1900 kWh per month to become around 1450 - 1542 kWh per month, or 19% - 29%, for the primary air fan (PA Fan).