Andrey V. Zenkov

This study presents a method for controlling the shape of the spray plume during the atomization of coal-water slurries by introducing helical swirl of the atomizing gas in an external mixing pneumatic atomizer. Coal-water slurries obtained from coal preparation waste were investigated using two processing routes: with and without treatment in a rotary hydrodynamic cavitation reactor. Atomization experiments were conducted on a dedicated test rig modified to introduce air tangentially into the annular channel, thereby producing a swirling flow. Droplet size was measured using interferometric particle imaging, while droplet velocity was determined by particle tracking velocimetry. The experiments were performed at slurry flow rates of 100 and 200 g/s and atomizing gas pressures of 0.6 and 0.9 MPa (gauge). Cavitation treatment reduced the dynamic viscosity of the slurry at shear rates above 50 s–1 and increased the fraction of particles smaller than 100 μm by 10 %. Atomization of the treated slurry produced average droplet diameters ranging from 87.8 to 112.3 μm, which were 29–42 % smaller than those obtained with the untreated slurry. As the slurry flow rate increased from 100 to 200 g/s, the proportion of fine droplets decreased by 5–18 %, depending on the pressure, whereas the fraction of larger droplets increased. The velocity of droplets obtained from the treated slurry was 10–15 % higher than that of droplets produced from the untreated slurry. The introduced helical swirl of the atomizing gas increased the spray cone angle from 21.1° to 25.8°, while causing only a modest (18 %) increase in average droplet diameter compared with straight gas injection. The proposed atomizer modification provides effective control of spray geometry while maintaining acceptable atomization quality. In addition, cavitation treatment significantly improves the rheological properties of coal-water slurries and their atomization characteristics, which is important for efficient combustion of coal-water fuels in power generation systems.

Relevance. Modern environmental and power challenges dictate the need to switch to clean energy technologies. This is the basis for an active search and creation of innovative sources of energy and fuel. One of the most promising approaches to meeting such requirements while maintaining electricity production at thermal power plants is the use of multicomponent fuel mixtures, for example, coal-water slurries. Aim. Experimental studies of the fragmentation processes of the coal-water slurries jet (quantity, size, shape) at short distances from the nozzle, depending on the spraying parameters and the slurry properties. Object. Experimental studies were carried out with coal-water slurries based on lignite (2B grade) with addition of 1 and 2% by weight of carbon black. A slurry consisting of coal and water, without the addition of the third component, was used as a reference sample. Methods. Coal-water slurries were prepared using a homogenizer with a cavitation effect. A pneumatic nozzle with an internal mixing of the slurry and the spraying agent were used to spray the coal-water slurries. The average size of fuel droplets after spraying was determined using the Interferometric Particle Imaging method. Droplet velocities were determined using the Particle Image Velocimetry method. Results and conclusions. The effect of spraying parameters and the component composition of the slurries on droplet shape, size and velocity was experimentally proven. It was found that the third component, nano dispersed carbon black, contributes to a significant increase in the kinematic viscosity of the slurry and a slight change in its density. Large (more than 1 mm) slurry fragments were proved to be present in a jet in the immediate vicinity of the nozzle at low air pressure (0,1 MPa). Fuel droplets have the shapes of spheres, elongated ellipsoids, and droplets. The spray mode at air pressure of 0,2 MPa is transitional – from a coarse-dispersed gas droplet jet to a finely dispersed one. The number of large droplets and fragments of the slurry increases to 88% with the addition of 2% by weight of nano dispersed carbon black. For citation: Gvozdyakov D.V., Zenkov A.V. Impact of the spraying parameters of coal-water slurries and their properties on droplet primary atomization in a jet. Bulletin of the Tomsk Polytechnic University. Geo Assets Engineering, 2026, vol. 337, no. 7, pp. 36-48. https://doi.org/10.18799/24131830/2026/7/5324

The results of experimental studies of the spraying characteristics of coal-water slurries based on lignite and pyrogenetic liquid are presented. The introduction of pyrogenetic liquid into the slurries was carried out by replacing it with a similar amount of coal and water by weight (from 10 to 20%). The substitution of only water with pyrogenetic liquid leads to a significant increase in the viscosity of the slurry and turns it into a non-flowing substance. As the concentration of pyrogenetic liquid in the slurry increased, the value of kinematic viscosity changed by 51 and 45%, respectively, in comparison with two-component coal-water slurry due to a decrease in the concentration of both water and coal. A slight effect (changes of no more than 3%) of the pyrogenetic liquid on the density of slurries was found. The average size of slurry droplets in the study area on the 226-350 mm segment from the nozzle decreases by 8% compared to the 0-100 mm segment. After replacing 10% and 20% of coal and water in the fuel with a similar amount of pyrogenetic liquid, the average droplet size of coal-water slurries decreased by 10%. In general, droplets of the largest size are typical for the slurries with addition of 10% by weight of pyrogenetic liquid. The jet spraying angle for the studied compositions varied slightly. Its average value was 19°. The substitution of coal and water in the composition of lignite-based slurries with a similar amount of pyrogenetic liquid by weight allows spraying such coal-water slurries quite effectively. Представлены результаты экспериментальных исследований характеристик распыления водоугольных суспензий на основе бурого угля и пирогенетической жидкости. Введение в состав суспензий пирогенетической жидкости осуществлялось путем замещения ею аналогичного по массе (от 10 до 20%) количества угля и воды. Замещение только воды пирогенетической жидкостью приводит к значительному увеличению вязкости суспензии и превращает ее в не текучую субстанцию. По мере роста концентрации пирогенетической жидкости в составе суспензии значение кинематической вязкости изменялось на 51 и 45%, соответственно, в сравнении с двухкомпонентной водоугольной суспензией за счет уменьшения концентрации и воды, и угля. Установлено незначительное влияние (изменения составляют не более 3%) пирогенетической жидкости на плотность суспензий. Средний размер капель суспензии в области исследования на отрезке 226-350 мм от сопла форсунки снижается на 8% в сравнении с отрезком 0-100 мм. После замещения в составе суспензии 10% и 20% угля и воды на аналогичное по массе количество пирогенетической жидкости снижение среднего размера капель водоугольных суспензий составляет по 10%. В целом, капли наибольшего размера характерны для суспензий с добавкой 10% по массе пирогенетической жидкости. Угол раскрытия струи для исследовавшихся составов изменялся незначительно. Его усредненное значение составило 19°. Замещение угля и воды в составе суспензий на основе бурого угля аналогичным по массе количеством пирогенетической жидкости позволяет достаточно эффективно распылять такие водоугольные суспензии.

Relevance. Transition to environmentally friendly energy technologies, due to modern requirements for environmental protection, involves the search and creation of new energy sources, including fuels. One of the ways to meet these requirements and maintain the same level of energy production by thermal power plants is the transition to multicomponent fuels. The most promising and affordable boiler fuels from the point of view of energy, ecology and economy are coal-water slurries. In this regard, the study of the properties and characteristics of such fuels is relevant in many countries. Aim. Experimental studies of the effect of the coal-water fuel cavitation treatment duration on a droplet average size in a jet after spraying with a pneumatic nozzle and substantiation of the efficiency of such approach for practical application. Object. Experimental studies were carried out with coal-water slurries based on long-flame coal (D grade) with addition of 10 and 20 wt % by weight of pyrogenetic liquid. A slurry, consisting of just coal and water, without the addition of pyrogenetic liquid, was used as a reference sample. Method. The coal-water slurries were prepared in a rotary hydrodynamic cavitation generator. A pneumatic nozzle with external mixing was used to spray the coal-water slurries. The average size of fuel droplets after spraying was determined using the Interferometric Particle Imaging method. Results. Experiments on the preparation of coal-water slurries with pyrogenetic liquid showed an increase in the dynamic viscosity of the fuel. An increase in the duration of treatment of the slurries in a rotary hydrodynamic cavitation generator reduced the viscosity by 54%. The average size of droplets in the jet was reduced by 22%.

This work presents a review of modern devices for spraying coal–water fuels. The efficiency of their operation was analyzed according to several criteria: the simplicity of their design (A), the fuel channel’s predisposition to clogging (B), durability in terms of the erosive wear of the nozzle channel (C), and dispersion of the jet—the average size of droplets in the jet (D). It was established that, from the point of view of operational efficiency, the most preferred devices for spraying coal–water fuels are those with a quasi-internal mixing of fuel and spraying agents. In combination with refractory or ceramic materials and the large diameter of the fuel channel, its rapid erosion wear and the likelihood of clogging with large particles of coal or agglomerates of viscous coal–water fuel are excluded. At the same time, the possibility of forming a fine-dispersed jet remains. The cooling of the nozzle with an external mixing of fuel and spraying agents during its operation also reduces the rate of erosion wear. Narrowing the fuel channel was proven to be an undesirable solution when creating a coal–water fuel nozzle. This review will be useful for both researchers studying the processes of spraying coal–water fuels and designers involved in the creation of coal–water fuel injectors or the transfer of existing boilers to coal–water fuel.

RELEVANCE. A review of the current state of research on coal-water slurries in Russia and abroad is presented. Coal-water slurries are promising alternative types of energy fuels. Their use in the energy sector will allow generating thermal and electrical energy. It is possible to use a fairly wide range of substances as components of such fuels. One of the preferred types are various waste. The analysis of modern literature has shown a fairly wide range of directions for the study of multicomponent coal-water slurries.THE PURPOSE. To provide information on the current state of research in the field of technologies for the preparation, spraying and combustion of coal-water fuels, as well as on existing and promising additives to such slurries.METHODS. The study was carried out by the method of collecting and structuring information.RESULTS. The review of the current state of research in the field of technologies for the preparation, spraying and combustion of coal-water fuels, as well as existing and promising additives to such slurries, was carried out. It was found that additives of liquid combustible waste and biomass contribute to reducing the ignition delay time. At the same time, such additives do not reduce the quality characteristics of spraying multicomponent coal-water slurries. A number of components reduces the amount of emissions of combustion products of such fuels into the atmosphere. The influence of additives and components of coal-water slurries on their characteristics and properties was analyzed. It was shown that liquid components contribute to the intensification of ignition and combustion processes. In addition, their introduction into the fuel composition has a positive effect on the rheological properties of slurries, the characteristics of their spraying, combustion and the concentration of harmful emissions.CONCLUSION. Coal-water slurries are promising alternative types of energy fuels. The introduction of combustible components into the composition of coal-water slurries can significantly improve the rheological properties, which can improve the storage and transportation characteristics of such fuels. The established positive characteristics and properties of coal-water slurries provide prerequisites for the full-scale introduction of such fuels into industrial power engineering.

Experimental studies were conducted to investigate the rheological properties and atomization characteristics of coal-water slurries sprayed by a pneumatic nozzle with addition of pyrogenetic liquid. The research object was coal-water slurries prepared on the basis of long-flame coal using a rotary hydrodynamic cavitation generator. The dynamic viscosity of samples was investigated using a Reotest-2 rotary viscometer. The droplet size of atomized slurries was determined by the interferometric particle imaging method. A pneumatic nozzle designed for spraying of coal-water slurry fuels was used. The calorific value of coal-water slurry compositions was estimated by a theoretical method using Mendeleev's equation for calculating the lower heating value of combustion of organic substances with a certain elemental composition. It was found that cavitation treatment of a two-component coal-water fuel for 90 s leads to a 48% decrease in its viscosity. It was shown that substitution of water with a similar amount of pyrogenic liquid (5 to 20%) leads to an increase in the viscosity of coal-water fuels. The cavitation treatment of such slurries reduces the viscosity of the respective three-component coal-water fuels by 27–45%. According to the results of static sedimentation studies, coal particles start to precipitate 24 h after the onset of cavitation treatment. The treatment of the slurries under consideration for 27 and 90 s in a rotary hydrodynamic cavitation generator was established to reduce the average droplet size in the jet after spraying with a pneumatic nozzle by 5.5% and 6.5%, respectively. The introduction of pyrogenetic liquid into the composition of coal-water fuels increases their calorific value by 6.9%. It can be concluded that the use of pyrogenetic liquid in the composition of coal-water slurry fuels followed by their treatment in a rotary hydrodynamic cavitation generator can solve the problem of low reactivity of coal-water slurries.

The effect of metal nitrates on the activation of anthracite combustion process has been studied. Fe(NO₃)₂ · 9H₂O and Cu(NO₃)₂ · 3H₂O were used as nitrates in an amount of 5 wt% applied to anthracite powder (fraction less than 0.1 mm) by incipient wetness impregnation. Using scanning electron microscopy and EDX mapping, it was found that using this method of applying the additive makes it possible to achieve high dispersion and uniform distribution in the fuel composition. The characteristics of oxidation, ignition, and combustion were studied using thermal analysis methods and high-speed video recording in the combustion chamber at a temperature of 800°C. It was found that the use of metal nitrates contributes to an increase in the reactivity of anthracite as evidenced by a decrease in the temperature of the intensive oxidation beginning (ΔT_i) by 23–84°C and the ignition delay time (Δt_i) by 0.9–2.2 seconds. The greatest effect of changing the reactivity of anthracite was recorded in the case of using copper nitrate additive. The use of nitrates also contributed to the decrease in the resulting fuel underburning (from 3.5 to 0.4 wt%) and gas-phase CO compounds (by 31–53%). At the early stages, combustion process of modified samples was accompanied by periodic formation of micro-explosions, which led to the activation and development of the particle surface.

Experimental studies of the steam pyrolysis of oil sludge were performed using a flow-type pilot plant with 300 kg/h capacity (raw material) to obtain energy-valuable products, such as liquid hydrocarbons (30.4 wt%), semi-coke (39.6 wt%), non-condensable gas-phase compounds (26.5 wt%), and bitumen (3.5 wt%). The pyrolysis process was conducted at a temperature of 650 ° C and with a steam flow rate of 150 kg/h. Liquid hydrocarbons were considered a target product. Comprehensive studies of their physicochemical characteristics, atomization process, droplet ignition, and combustion were carried out. The studied sample had physicochemical characteristics similar to traditional fuel oil (calorific value—42.6 MJ/kg, sulfur content—0.8 wt%). The jet spraying angle was 25° in view of the improved rheological properties of the test sample, with a homogeneous jet structure and a predominant droplet diameter of no more than 0.4 mm. The flame combustion process was accompanied by the formation of microexplosions, the frequency and intensity of which depended on the temperature of the air (T_g = 450–700 °C). This study, in view of its applied nature, is of interest in the design of new installations and technological systems for hydrocarbon pyrolysis.