Investigation of the direct-flow burners and nozzles arrangement at the direct-flow-vortex coal combustion in a furnace with solid slag removal

The paper presents results of the furnace aerodynamics investigation using direct-flow burners and air nozzles (DFBAN) with solid slag removal (SSR). The studies were performed using the computational fluid dynamics software ANSYS Fluent. The paper includes recommendations for the development of effective solid fuel combustion schemes with DFBAN, methods for researching and optimization of the combustion aerodynamics with the use of DFBAN, optimization criteria, initial data for the study. The scheme for burning Kuznetsk lean coal with the use of DFBAN and SSR was developed. Several series of calculations were performed for the developed scheme. In these calculations, the dependencies of the indicators of efficiency, furnace ecological safety and reliability on the nozzles and burners positions, which are located in the first zone of the scheme, were found. The first stage of the optimization of the developed scheme burning solid fuel with the SSR was made.

Integrated research of slaging intensityof the boilerunit heating surfaceswhen burning non-project fuels

THE PURPOSE. Comprehensive research of the slagging intensity is the heating surfaces of the BKZ-420-140 boiler unit with solid slag removal at the Abakan CHP when burning non-project fuels. The relevance of the work is due to the technical necessity and economic feasibility of conversion boiler units to combustion of non-design coals. METHODS. The problem has been analyzed by methodology for conducting complex tests, measurements and processing of experimental data, as well as the results of experimental and computational studies of a boiler unit when operating on coals of various qualities. RESULTS. Qualitative and quantitative parameters for assessing the properties of off-design coals and their behavior in real operating conditions of radiation, semi-radiation and convective conditions, taking into account their modes and design functions, have been obtained. CONCLUSION: A computational analysis of the operating modes of boiler units when burning non-design fuels showed that a promising technology for involving non-design coals in the fuel and energy balance of a thermal power plant is providing a scientifically based mixture of design and nondesign fuels.Analysis of the slagging and polluting properties of non-design coals makes it possible to predict changes in the characteristics of the thermal efficiency of heating surfaces and to develop many practical recommendations for optimizing the parameters of the cleaning equipment installed on the boiler.Also, mixtures of fuels were determined for which the wall temperatures of the metal of the outlet stack of the superheater increase, which significantly reduces the strength characteristics of the surface.The assessment and prediction of the reliability of the heating surface is carried out by calculating the temperature of the metal wall in the most heat-stressed place.

Image-Based Iron Slag Segmentation via Graph Convolutional Networks

Slagging-off (i.e., slag removal) is an important preprocessing operation of steel-making to improve the purity of iron. Current manual-operated slag removal schemes are inefficient and labor-intensive. Automatic slagging-off is desirable but challenging as the reliable recognition of iron and slag is difficult. This work focuses on realizing an efficient and accurate recognition algorithm of iron and slag, which is conducive to realize automatic slagging-off operation. Motivated by the recent success of deep learning techniques in smart manufacturing, we introduce deep learning methods to this field for the first time. The monotonous gray value of industry images, poor image quality, and nonrigid feature of iron and slag challenge the existing fully convolutional networks (FCNs). To this end, we propose a novel spatial and feature graph convolutional network (SFGCN) module. SFGCN module can be easily inserted in FCNs to improve the reasoning ability of global contextual information, which is helpful to enhance the segmentation accuracy of small objects and isolated areas. To verify the validity of the SFGCN module, we create an industrial dataset and conduct extensive experiments. Finally, the results show that our SFGCN module brings a consistent performance boost for a wide range of FCNs. Moreover, by adopting a lightweight network as backbone, our method achieves real-time iron and slag segmentation. In the future work, we will dedicate our efforts to the weakly supervised learning for quick annotation of big data stream to improve the generalization ability of current models.

Research on drilling process technology and parameter optimization in soft coal seam

Due to the low firmness coefficient of soft coal seam and the influence of formation pressure and in-situ stress, it is easy to cause hole collapse in bedding drilling, resulting in low hole forming rate and insufficient hole forming depth, so the drilling technology needs to be improved. This paper focuses on the study of hole forming technology and parameters of bedding drilling in soft coal seam. The research results show that: the key to improve the construction efficiency of bedding drilling in soft coal seam is to improve the slag removal ability of drilling engineering, and the drilling technology of spiral drilling and pressure air slag removal is conducive to improve the drilling depth and drilling effect. The hole forming process and parameters of spiral drilling and pressure air slag removal are systematically described. The drill pipe speed, the coal conveying capacity in the hole, the minimum wind speed of pressure air slag removal and the air supply pressure of slag removal are determined. It is of great practical significance to develop and improve the drilling technology of bedding hole drilling in soft coal seam to improve the gas drainage capacity of coal mine and the drilling depth and rate of bedding hole drilling in soft coal seam.

Numerical Simulation Analysis Based on the Study of the Slag discharge Mechanism of the Triangular-shaped Drill Pipe

According to the characteristics of high efficiency and high hole forming rate of the triangular-shaped drill pipe in the process of drilling in soft outburst coal seam, the slag discharge model of annular gap between the triangular-shaped drill pipe and hole wall is established by using the basic theory of computational fluid dynamics.Using the finite volume element method, the flow field characteristics of the annular flow area between drill pipe and hole wall are analyzed.Through the numerical simulation analysis, the velocity fluctuation effect of the annular flow field of the slag removal model is put forward, that is, the velocity fluctuation zone is formed between the sides of the arc edge of the triangular-shaped drill pipe, which causes the precipitated coal cinder to rise under the vortex action of the flow field, and is quickly discharged out of the hole under the coordination of the axial velocity, which effectively improves the slag removal efficiency and pore forming rate of the drill pipe.Finally, the comparative test of the triangular-shaped drill pipe and wide-blade spiral drill pipe was carried out in the soft outburst coal seam of 31021 lower auxiliary roadway in a mine. The drilling depth was increased by 19.4%, the hole forming rate was increased by 17.4%, and the drilling efficiency was increased by 26.4%. There was no drill drop and broken phenomenon.

Emissions of sulfur dioxide and dust at coal power plants of Ukraine

We developed an algorithm for the estimation of harmful emissions depending on the amount of supplied electricity and heat at coal-fired TPP. By this algorithm, we calculated the emissions of SO2 and dust at Ukrainian TPP in 2017 and 2018. The values of SO2 concentrations in dry flue gases at Ukrainian TPP in 2017 and 2018 depending on fuel brand, sulfur content, and method of slag removal in the boiler were in the range of 1520–5900 mg/Nm3, and the general gross emissions of SO2 were about 620 thousand t. The specific emissions of SO2 were at a level of 14–15 g/kWh of supplied electric energy as compared with 1.2 g/kWh – the level for coal-fired plants of EU countries. At Ukrainian TPP, about 100 thousand t of dust were thrown away. The dust concentrations in flue gases at Ukrainian TPP were equal to 300–1800 mg/Nm3. The values of specific dust emissions per 1 kWh of supplied electricity constituted 0.8-5.1 g against 0.2 g/kWh characteristic of present-day coal-fired TPP of EU countries. The level of gross emissions of SO2 and dust at the TPP of Ukraine did not exceed the maximum possible according to the National Emission Reduction Plan of Pollutants from Large Combustion Plants.

INFLUENCE OF THE RECIPES ON THE STRENGTH OF STRENGTH OF GEOPOLYMER COMPOUNDS WHEN CEMENTING LRW

The influence of the composition of geopolymer binders (blast furnace slag, removal ash, liquid glass and KOH) on the properties, namely the compressive strength of the compounds formed during LRW cementation, is studied. To perform the work, compounds were made in which the masses of the components varied according to the plan of the factorial experiment in 23 – three factors on two levels. The factors chosen were: liquid glass, a mixture of slag with ash in a ratio of 1: 1 and potassium hydroxide. The mass of LRW imitation did not change in all experiments. The experiments were not duplicated, and the random error was assessed analytically. The calculations gave the equation that relates the compressive strength of the compounds to the mass of liquid glass, slag and ash, and potassium hydroxide. When constructing the equation, it was found that the variance of the batch of measurements by the Cochren’s criterion is homogeneous, the coefficients of the equation by the Student’s criterion are statistically significant, and the model (equation) by the Fisher criterion is adequate. The analysis of the equation showed that the strength limit is influenced by slag and ash, but the greatest influence is exerted by the pair interaction of liquid glass with ash and slag. The consequence of the interaction is the formation of a geopolymer network, which strengthens the compounds. The addition of potassium hydroxide reduces the strength of the samples due to excess potassium and sodium cations, for which there is no functional place (combination with Al atoms to change the electronic configuration to tetrahedral). For this case, an equation with a correlation coefficient R = 0.86 is obtained. The application of the method of steep ascent showed the possibility of increasing the strength limit by 1.5 times or more. In the future, it is planned to reduce the amount of ash in the binder or replace it with temperature-activated kaolin. Mechanical activation of the slag powder had a positive effect on increasing the compressive strength.