Boiler Furnace Research Articles

Assessment of the influence of thermal characteristics of non-design lignite on their suitability for combustion in the furnace of an energy boiler

The possibility of burning various brown coals (LC) in the furnace of the BKZ-420-140-6 boiler was studied using numerical simulation. To check the compiled numerical model of solid fuel combustion, it was previously validated in relation to the combustion of BU of a certain composition by comparing the calculation results with data obtained during the operation of a real boiler. A method was developed for averaging the characteristics of coal and dependencies were obtained that determine the composition of coal based on an analysis of the composition of 14 types of coal in the range of values of the lower calorific valueQnr from 7.5 to 16 MJ/kg. Based on the obtained dependencies for 4 values of Qnr, the theoretical average composition (ATC) of coals was determined. For one of the TUSs, the humidity varied by 10% up and down. As indicators of the efficiency of the combustion chamber of the boiler, the temperature of the gases at the exit from the combustion chamber, mechanical underburning and the concentration of nitrogen oxides in the flue gases are taken. The results of numerical modeling show that with the calorific value of the fuelQnr ≤10 MJ/kg, the mechanical underburning q4 exceeds the permissible standards. The highest concentration of nitrogen oxides at the level of 800–900 mg/nm3 is observed for brown coals with highQnr and the highest carbon content. It is also shown that the use of direct-flow burners with the organization of staged fuel combustion makes it possible to reduce the formation of nitrogen oxides in the furnace by 3.25 times compared to the original combustion scheme using existing vortex burner devices. The influence of the lower calorific value of fuel on the gas temperature at the exit from the combustion chamber in the rangeQnr from 11.75 to 16.45 MJ/kg is insignificant. The effect of increasing fuel humidity on the gas temperature at the outlet of the combustion chamber and on mechanical underburning is insignificant up to a working fuel humidity of approximately 45%. In general, studies have shown that the firebox under consideration allows the combustion of various brown coals with changes in the physico-chemical composition and thermal characteristics within a wide range.

Improved method for calculating fuel burnout in pulverized coal furnaces

An improved method of engineering calculation of the degree of burnout of pulverized solid organic fuel in the flare furnaces of steam boilers is proposed, taking into account the kinetics of the processes of moisture evaporation, the release of volatile substances with a separate assessment of individual gaseous components and tar release and their combustion, secondary cracking of tars, combustion and gasification of coke residue, conversion of mineral part of the fuel, which allows for assessment and control of the implementation of material balances of individual stages, stages and, in general, the entire gross process of coal combustion, and ultimately an adequate determination of the magnitude of heat losses with mechanical and chemical incompleteness of combustion. Methodological provisions have been developed to take into account the kinetic and diffusion processes of the thermochemical transformation of coal to establish a quantitative relationship between the temperature-time characteristics of the combustion of pulverized coal particles and the local parameters of the combustion process. The technique is implemented in the form of specialized algorithmic and software and makes it possible to assess the degree of fuel burnout, both for the active combustion zone and for zones located in the cooling chamber of the combustion space during design and operational adjustment work.

Experimental Study of Sawdust Syngas Gasification in Bench-Scale Gasifier and Three-Dimensional Numerical Analysis for Syngas Cocombustion in a 600 MW Coal-Fired Boiler Furnace.

To comprehensively explore syngas cocombustion technology, gasification experiments in a bench-scale circulating fluidized bed (CFB) and three-dimensional (3D) numerical simulations of a coal-fired boiler furnace have been conducted. In the amplification experiment of biomass gasification, sawdust has been gasified using air, oxygen-enriched air, and steam. The highest heating value of the syngas products reaches 12.3 MJ/m3 when the equivalence and steam/biomass ratios are adjusted in the ranges of 0.21-0.31 and 0.1-0.5, respectively. Subsequently, 3D numerical simulation has been performed with several kinds of syngas product to analyze the cocombustion characteristics of the boiler furnace. Results demonstrate that the velocity field of the boiler furnace exhibits a well-formed tangential velocity circle and full degree of streamlines. Syngas cocombustion in the coal-fired furnace reduces the temperature extremum in the combustion zone. Radiant heat flux accounts for >88% of the total heat flux in the furnace. The outlet NO concentration in the case of syngas cocombustion is less than that of pure coal combustion, and it is reduced approximately 25 and 40 mg/m3 at cocombustion ratios of 0.1 and 0.15, respectively.

Study on On-line Monitoring method for Local Slagging in the Coal-Fired Boiler Furnace

Abstract Slag formation in coal-fired boiler furnaces is an unavoidable issue, which is further exacerbated by the combustion of Zhundong coal. The accumulation of slag in the furnace can reduce the heat exchange capacity of the boiler, leading to a decrease in power generation efficiency and operational economy. However, there is currently a dearth of monitoring techniques to evaluate the local slagging status in the furnace. To address this gap, this study proposes an innovative approach by installing multiple thermocouples on water wall tubes and fins to establish an online monitoring model for local slagging based on temperature differences. The effectiveness of this model has been validated on a 660 MWe utility boiler. The monitoring results reveal that the slagging in the furnace is uneven and asymmetrical in both the circumferential and longitudinal directions. The central region of the water wall in the circumferential direction is particularly prone to slagging, and the main combustion zone exhibits the highest slagging rate, while the burnout zone experiences the lowest. Moreover, the slagging rate in various regions is influenced by the unit load. It is directly proportional to the load in the main combustion zone, inversely proportional in the furnace bottom zone, and relatively unaffected by the load in the burnout zone.

A new approach to reducing slagging based on laser modification of heating surfaces: Field tests and mathematical modeling

The article presents the results of field tests of a new approach to reducing slagging of a boiler furnace. The approach involves laser radiation treatment of metal surfaces to obtain a coating with a high degree of passivation and a special texture (microchannel or anisotropic). Due to the texture and formation of the oxide layer, the resistance of the heating surfaces to adhesion of hydrocarbon fuel combustion products, including slag, is increased. Field tests were conducted over 60 days in an operating boiler burning brown coal, the combustion products of which form solid ferrous and sulfate–calcium deposits. The study used scanning microscopy, X-ray fluorescence spectral analysis and mass analysis of slag deposits. The results showed that steel samples with the Microchannels texture formed by laser radiation are characterized by increased resistance to adhesion of brown coal slag. Using the original software code, a mathematical model has been developed to describe the slag deposition process on heat exchange surfaces modified by laser radiation. A numerical simulation was performed under conditions of dynamic change in the thickness of the slag layer on the surface of the heat exchanger pipe to assess the heat transfer characteristics in the “hot flue gases – slag layer – pipe wall – liquid coolant” system. The results showed that the steel surface modified by laser radiation, compared to the untreated surface, is resistant to slagging at the initial stages of interaction with molten ash from different types of fuel. The use of laser-modified surfaces in boiler furnaces will increase the intervals between procedures for cleaning the furnace from slag by up to 64 %. Also, due to the increase in absorbed heat per unit area by 1.6–2.2 times, the use of laser-modified surfaces increases the efficiency of energy production.

Impact of excess air factor on performance and NOx emissions of an industrial water tube boiler with hydrogen enrichment

This study investigates the impact of excess air factor (λ) on performance and NOx emissions of a 207-MW boiler furnace, used for steam generation in an industrial water tube boiler installed at Saudi Aramco, at fixed volumetric fuel composition of hydrogen/methane of 10%/90%. The numerical approach employed for this investigation utilized ANSYS-Fluent software. The findings of the study revealed robust correlations between λ, temperature, and NO emissions. An increase in λ led to a decrease in both the average furnace temperature and average NO emissions at the boiler exit. Specifically, increasing the value of λ from 1.05–1.45 consistently reduces the average NO emissions from 1541 ppm to 653 ppm. In other words, a 27% increase in λ resulted in approximately a 55% reduction in NOx emissions. As λ increases, the volumetric absorbed of radiation decreases owing to the reduced concentrations of CO2 and H2O. Notably, the maximum combustion efficiency, reaching 37.88%, is achieved at a λ value of 1.35, corresponding to the lowest average flue gas temperature. The results show that to achieve the best performance with high efficiency and low NO emissions, the boiler needs to be operated at an excess air factor of about 1.35.

The combustion biased dual cross-limited control strategy for industrial boiler furnaces

Abstract The combustion process in boilers is a crucial aspect of industrial boiler operation, and the quality of this process is closely related to the industrial boiler’s operational efficiency and pollutant emissions. This paper focuses on furnace combustion control within the industrial boiler control system and proposes an improved variable bias control method to address the issues associated with over-oxygen and oxygen-deficient combustion, which are prevalent in current double-closed-loop cascade proportional control technologies. First, the working principle of the variable bias double cross-limit combustion process is analyzed, and the variable bias cross-limit combustion control system is designed. Second, by introducing a bias variable, the paper addresses the problem that fixed bias parameters in the double cross-limit control system cannot accommodate the variable loading and rapid response requirements. Finally, the range of bias coefficients is estimated using the trial-and-error method. Experimental results demonstrate that the variable bias double cross-limit control strategy resolves the issues of oxygen deficiency and over-oxygen combustion, along with the slow response speed of conventional combustion control modes, enhances fuel heat utilization efficiency, and reduces pollutant and harmful gas emissions.

Effect of coal suspension concentration and gas-air medium temperature on liquid droplets collisions

Relevance. Understanding the mechanisms of liquid droplets interaction with each other is important for many industrial and technical applications related to solving a range of problems like slag removal in a high-temperature environment, obtaining components of the desired fraction in the food industry, etc. Aim. Establishment of the main patterns of suspension droplets interaction in a gas-air environment with temperature variation. Methods. Using shadow high-speed video recording, the main patterns of the binary collision of suspensions droplets were determined. The paper introduces the results of experimental studies of the characteristics of collisions of droplets of coal-water suspensions in a gas-air environment with a temperature of 90–120°C. Parameters of the generated droplets: radius 1.0–2.2 mm, velocity 0.5–2.0 m/s. Results and conclusions. The authors have determined the modes of collision of droplets of suspensions (coagulation and separation) and the main characteristics of secondary fragments and constructed the maps of the modes of interaction of drops of suspensions with each other when varying the concentration of solid particles in the suspension, the temperature of the gas-air environment and the time the target drop spent in a gas-air environment with an elevated temperature. The conditions were established for the coagulation of droplets, as well as their intensive secondary grinding to intensify their drying, ignition and combustion in boiler furnaces. It was established that an increase in the temperature of the gas-air environment leads to a significant change in the size and properties of droplets, as well as to the occurrence of oscillatory phenomena in the system. It is substantiated that collision of droplets of suspensions in a gas-air environment with elevated temperature is complex and multi-parametric. Its characteristics depend on a combination of factors (surface tension and liquid viscosity, size and shape of droplets, speed of their movement, density and viscosity of gas-air environment). The authors obtained mathematical expressions to describe the boundaries of the modes of the studied processes and schemes for using the results obtained in order to increase the efficiency of the corresponding technological processes.

Experimental study on combustion characteristics of a 40 MW pulverized coal boiler based on a new low NOx burner with preheating function

In this study, a novel low NOx burner is proposed and tested on a 40 MW pilot pulverized coal combustion system, aiming to experimentally investigate the impact of preheating temperature, air ratio distribution, and thermal power on furnace combustion characteristics. The experimental results demonstrate that the pulverized coal could be preheated stably above 700 °C in the designed burner. Furthermore, an increase in preheating temperature from 500 °C to 750 °C corresponds to a proportional rise in the total volume fraction of combustible pyrolysis gases released from pulverized coal, ranging from 18.34 % to 22.85 %. Consequently, the release and combustion of pyrolysis gases effectively improve the combustion characteristics within the boiler furnace and lead to reduced NOx emissions at the furnace outlet. When the thermal power is increased from 22.5 MW to 37.5 MW, the NOx emissions at the furnace output range from 46.8 mg/Nm3 to 98.3 mg/Nm3 (at 9 % O2). Under a specific thermal power of 25MWth, the boiler furnace output NOx emissions are reduced to 47.9 mg/Nm3 (@9 % O2) without any additional NOx reduction equipment. These findings offer valuable insights for advancing cleaner and more efficient low-NOx pulverized coal combustion technology.

The Influence of Burning Ratios Based on Coal Characteristics on its Combustion in the Boiler Furnace

The Influence of Burning Ratios Based on Coal Characteristics on its Combustion in the Boiler Furnace

Boiler furnace temperature and oxygen content prediction based on hybrid CNN, biLSTM, and SE-Net models

Boiler furnace temperature and oxygen content prediction based on hybrid CNN, biLSTM, and SE-Net models

Experimental Combustion of Different Biomass Wastes, Coals and Two Fuel Mixtures on a Fire Bench

When designing settlements according to the “Green Building” principle, it is necessary to develop a heating system based on climatic conditions. For example, in areas with a sharply continental climate (cold and prolonged winters), it is sometimes necessary to use solid fuel boilers (in the absence of gas). However, to use these, it is necessary to use biomass or biomass-coal blends as fuel to increase their combustion heat. The addition of biomass waste to coal can be aimed at achieving various objectives: utilization of biomass waste; reduction of solid fossil fuel consumption; improvement of environmental performance at coal-fired boiler houses; improvement of the reactivity of coals or to improve the technical and economic performance of heat-generating plants due to the fact that biomass is a waste from various types of production, and its cost depends only on the distance of its transportation to the boiler house. In this work, combustion of various biomass wastes, including sewage sludge, was carried out on a fire bench emulating the operation of a boiler furnace. Fuel particles were ignited by convective heat transfer in a stream of hot air at a velocity of 5 m/s in the temperature range of 500–800 °C, and the experimental process was recorded on a high-speed, color video camera. The obtained values were compared with the characteristics of different coals used in thermal power generation (lignite and bituminous coal). The aim of the work is to determine the reactivity of various types of biomass, including fuel mixtures based on coal and food waste. The work presents the results of technical and elemental analysis of the researched fuels. Scanning electron microscopy was used to analyze the fuel particle surfaces for the presence of pores, cracks and channels. It was found that the lowest ignition delay is characteristic of cedar needles and hydrolyzed lignin; it is four times less than that of lignite coal and nine times less than that of bituminous coal. The addition of hydrolysis lignin to coal improves its combustion characteristics, while the addition of brewer’s spent grain, on the contrary, reduces it, increasing the ignition time delay due to the high moisture content of the fuel particles.

Numerical modeling of hydrodynamics of spouted bed in solid fuel boiler

The issues of numerical modeling of hydrodynamics of a spouted fuel bed in the furnace of a solid-fuel boiler are considered. At present, solid-fuel boilers are widely used in the power industry of the Russian Federation, with the share of coal-fired generation to remain significant in the projected terms. Therefore, the study of the efficiency of thermal and hydrodynamic processes that ensure the implementation of clean coal technologies is a relevant task both today and in the long term. The article presents the following main stages of numerical modelling of the hydrodynamics of the spouted bed: problem formulation with selection of boundary and initial conditions, methods of solving the Navier-Stokes and continuity equations for the air flow, Newton's equations and diffusion equations for particles. The k-omega turbulence model was used in the calculations that is described by means of two partial differential equations for the variables k (kinetic energy of turbulence) and omega (specific dissipation rate). A comparative analysis of environmental advantages and disadvantages of existing methods of combustion of low-grade coal in schemes with in-cycle gasification (ICG) is carried out. Advantages and difficulties of switching to structures with CFB in the spouted bed mode are shown. Numerical modeling of the cold spouted bed created by means of particle injection is performed, a set of initial settings and boundary conditions is presented, the adequacy of the obtained results is verified by hydrodynamic characteristics of the isothermal process. The obtained results allow us to proceed to the next stages with non-isothermal models, with heat exchange and combustion reactions in the spouted bed of coal taken into account. The following refinement of the physical model will allow to achieve more accurate and reliable results and to ensure their correct scaling.

Modeling of Unburned Carbon in Pulverized Coal-Fired Supercritical Steam Generators

ABSTRACT In coal-fired boilers, one of the most important metrics for optimizing combustion is the proportion of unburned carbon (UC) in the ash. In most Indian power plants, it is still assessed offline through manual sample collection and laboratory analysis. The laborious processes of sample collection, preparation, analysis, and reporting require at least five to eight hours of work. The delayed results may not be useful to optimize combustion in the boiler furnace, as the boiler operating conditions may be completely different from the conditions when the samples were collected. Instead, the use of prediction algorithms may bring timely corrective action if the UC goes high. The present experimental study is taken up to obtain a correlation between UC and corresponding relevant boiler operational parameters and on the residence time of coal particles in the boiler furnace. Multiple regression analysis is performed using ANOVA tools. One hundred and ninety-four sets of coal, ash samples and boiler operating parameters are collected from 07 supercritical units. Coal proximate, coal fineness and ash UC analysis are carried out. The analyzed results and collected boiler operational data are statistically analyzed using Microsoft Excel’s ANOVA tool to understand the dependent behavior of UC on the boiler operational parameters and fired coal characteristics. The empirical equations are proposed for the prediction of UC in bottom and fly ash for supercritical boilers. Additionally, fresh 20 sets of coal, ash samples, and related operating data are gathered for the validation of the proposed empirical equations. For additionally collected samples, the predicted results are compared with the offline measured laboratory results. The maximum deviation between the predicted and laboratory results are within the range of ± 0.40% and ± 0.24% for bottom and fly ash samples, respectively.

Simultaneous Reconstruction of Gas Concentration and Temperature Using Acoustic Tomography.

Acoustic tomography utilizes sensor arrays to collect sound wave signals, enabling non-contact measurement of physical parameters within an area of interest. Compared to optical technologies, acoustic tomography offers the advantages of low cost, low maintenance, and easy installation. Current research in acoustic tomography mainly focuses on reconstruction algorithms for temperature fields, while monitoring the composition and concentration of gases is significant for ensuring safety and improving efficiency, such as in scenarios like boiler furnaces and aviation engine nozzles. In excitable gases, the speed of sound exhibits an S-shaped curve that changes with frequency, a characteristic that could be potentially useful for acoustic tomography. Therefore, this study primarily discusses the quantitative calculation of gas concentration and temperature based on the dispersion of the speed of sound. By employing graphic processing and pattern matching methods, a coupled relationship of the dispersion of the speed of sound with gas concentration and temperature is established. The projection intersection method is used to calculate the concentration and temperature of binary and ternary gas mixtures. Combined with the inversion method, a joint reconstruction method for gas concentration fields and temperature fields based on the dispersion of the speed of sound is developed. The feasibility of the proposed simultaneous reconstruction method for temperature and concentration fields is validated using numerical simulations. Additionally, an acoustic tomography experimental system was set up to conduct reconstruction experiments for binary gas concentration fields and temperature fields, confirming the effectiveness of the proposed method.

Numerical Study on Combustion Characteristics of Biogas Cocombustion in a 300MW Coal-Fired Boiler Furnace.

To further explore cocombustion technology with biogas and coal, a series of numerical simulations have been carried out to analyze the effects of the cocombustion ratio ξ, height of biogas nozzle HGN, and tilt angle of burner θBN on combustion characteristics in a 300 MW four-corner tangential boiler furnace. Three types of biogas are gasified from straw, sawdust, and raw wood when air serves as the gasification agent. The velocity field, temperature field, and NO emissions have been comprehensively analyzed when the values of ξ, HGN, and θBN range, respectively, from 0.02 to 0.12, from 17.3 to 20.3 m, and from -15° to +15°. Results showed that the NO concentration at the furnace outlet monotonously decreased with ξ. The injection of biogas reduces both the peak temperature of the entire boiler furnace and the NO concentration at the furnace outlet. The NO emission concentration decreases with the increased ξ value for all types of biogases. The cocombustion with sawdust biogas indicates the least NO emission at a fixed cocombustion ratio. Furthermore, reducing the furnace height at HGN = 17.3 m or titling down the burner at θBN = -15° contributed to a greater NO concentration at the furnace outlet.

Numerical Analysis of the Co-firing Combustion of Coal and Palm Shell Kernel In Stoker Boiler

The United Nations Framework Convention on Climate Change (UNFCCC) states that Indonesia is committed to contributing to global climate change solutions. The government will also continue to encourage the development of a number of renewable energy (EBT)-based power generation projects. This is based on the use of renewable energy which is still low, namely around (1.9%) 8215.5 MW. Meanwhile, the potential for EBT to become energy can be around 443,208 MW. One source of EBT in Indonesia that can be utilized is Biomass. Co-firing of biomass is a relatively cheaper option and does not require investment in new power plants. However, Co-firing combustion has several aspects that need to be studied, such as temperature combustion and the generation of gas emissions. Therefore, this study aims to determine the temperature and the emissions resulting from co-firing of palm kernel shell biomass. This research was conducted using the Computational Fluid Dynamics method on stoker boiler model. The test parameters of the research was the maximum and average temperatures in the furnace, and the average and maximum fractions of CO2, SO2 in the stoker boiler furnace. From the research conducted, it was found that the resulting combustion temperature decreased as the co-firing fraction of the biomass increased. However, CO2 gas emissions increased and SO2 decreased with increasing fraction of co-firing biomass which showed a decrease in harmful gas emissions and complete combustion that occurred in the furnace.

Fast reconstruction of boiler numerical physical field based on proper orthogonal decomposition and conditional deep convolutional generative adversarial networks

ABSTRACT Obtaining real-time physical field data inside the boiler furnace is crucial for combustion diagnostics and optimization. In this work, we propose a fast reconstruction technique for the physical fields in a tangentially-fired coal boiler. The method combines the Proper Orthogonal Decomposition (POD) and Conditional Deep Convolutional Generative Adversarial Networks (cDCGAN) based on the boiler physical field obtained by computational fluid dynamics (CFD). Firstly, CFD simulations are performed using data from the boiler Distributed Control System (DCS). After verifying the CFD results, we expanded the simulation to 105 operational condition cases sample sets. Then, the physical fields of the sample set undergo POD to determine the appropriate number of POD bases, thereby ensuring the accuracy of the reconstruction. Finally, the cDCGAN method is employed to establish the correlation between the POD bases and the operational conditions of the boiler. Results show that the POD-cDCGAN method achieves rapid and accurate reconstruction of temperature and velocity fields, with mean relative error (MRE) below 1.5% and root relative squared error (RRSE) below 5.7%. The reconstruction time is reduced to 10.57s, significantly faster than direct CFD methods. The POD-cDCGAN method offers an efficient approach for online operational diagnosis and digital twin construction of boiler equipment.

Numerical analysis of flow and combustion of Coal-Ammonia blend in coal-fired furnace

Co-firing ammonia (NH3) in coal-fired power plants presents an attractive method to expedite the global decarbonization process. Nevertheless, the challenge lies in reconciling the need for higher temperatures within the furnace with the imperative of maintaining low nitrogen oxides (NOx) emissions, which limits the widespread use of NH3 as a fuel. In this article, the flow and combustion of coal-NH3 blends in a 3 × 700 MW tangentially-fired utility coal boiler furnace are investigated using Computational Fluid Dynamics (CFD). The impact of NH3 blending ratios is examined through numerically simulated combustion involving five co-firing ratios (CRs) of NH3, including 0%, 10%, 20%, 30%, and 50%. Various combustion properties are assessed, including the furnace’s temperature profile, flow distribution, species emissions, pollutant formation, and heat generation. To validate the approach, single coal and coal blend simulations performed depicted reasonable agreement in predicting furnace flame temperatures. The predicted flue gas temperature exhibited a decrease with an increase in NH3 CR, leading to a reduction in the furnace’s heat generation. Regarding flow characteristics, there was a notable increase in velocity as the concentration of NH3 was raised. The elevated NH3 content correlated with an observed rise in oxygen (O2) residue in the rear pass, coupled with a decrease in both carbon dioxide (CO2) and carbon monoxide (CO) concentrations. Pollutant formation, assessed in terms of nitrogen oxide (NO) emissions, revealed an increase in concentration with the rise in NH3 CR. Indeed, these findings suggest a promising strategy for adopting NH3 as a viable alternative to coal, representing an effective carbon-neutral fuel for the future.

Combined Combustion of Various Industrial Waste Flows in Boiler Furnaces. Part 3

To solve the problem of useful utilization (by combustion in heat generators) of liquid and gaseous industrial waste (that was defined in Part 1 of the present article), heat transfer processes in heat generating units were considered in Part 2. The main equipment for the effective solution of this process is a burner device and a combustion chamber with heat transfer to an external heat carrier, for example, a boiler furnace or a heat recovery boiler. The present article considers an example of calculating such a process for a distinctive mixture of waste from a chemical industry enterprise using modeling of possible schemes of a flame combustion system for a characteristic combination of various types of gaseous and liquid combustible products. For this purpose, the CFD (Computational Fluid Dynamics) computational hydrodynamics method was applied, which is determined to be the most effective one, in analyzing the behavior of media flows and combustion processes. CFD analysis makes it possible to predict hydrodynamic and thermal processes (especially in complex multicomponent systems) and optimize them to achieve the best results. The most important factor in high-quality combustion is the atomization process (fine atomization) of highly viscous liquids with high surface tension coefficients. The ultrasonic me-thod has been adopted as the most effective for such liquids. Besides, the quality of the distribution of flows of combustion mixtures and flue gases in the combustion chamber is considered. For doing this, it is necessary to arrange separate flows of axial and peripheral air, which make it possible not only to change the configuration of the flame, but also to direct convective flue gas flows to the most efficient areas of the combustion chamber. The article considers various options for heat transfer (convective and radial) depending on various factors, taking into account the degree of probability of formation of pollutants (primarily NOx) in combustion products. The results of the numerical solution of the problem are presented. The analysis of the results on the optimal ratio of the shares of primary and secondary air flows for combustion was carried out. In conclusion, a comparative analysis of the options for burning fuel directly in the boiler and in the pre-combustion chamber is presented. The efficiency of direct combustion has been demonstrated.