Liquid Slag Removal Research Articles

Strength and deformation characteristics of slag crushed stone of coal thermal power plants

Mechanical properties of the slag crushed stone (coarse-grained ASM), formed in the course of coal combustion at Kansk-Achinsk, Kuznetsk coal deposits (in boilers equipped with liquid and dry slag removal facilities) and the application of the slag crushed stone in roadbuilding are considered. In the course of the research, the crushability and the deformation modulus of particular fractions of slag crushed stone samples taken from the dumps of Novosibirsk TPP-3 (that consumes the coal of the Kansk-Achinsk coal mining field) and from Novosibirsk TPP-2 and Seversk TPP (that consume the coal of the Kuznetsk coal mining field) were identified. To assess the factors influencing the mechanical strength of the slag crushed stone, ignition losses, the content of flaky and acicular particles, dust and clay particles and clay lumps was made. The difference in the mechanical strength of samples having different genesis was identified. The graphs obtained in the course of testing were assessed and deformability characteristics were calculated (for materials having different fineness values). The factors influencing the mechanical strength of slag crushed stone were determined. Dependencies between deformation parameters and crushability of the slag crushed stone were obtained. Some mechanical and physical parameters of the slag crushed stone were identified; they were applied to outline potential areas of the slag crushed stone application in road building. The mathematical relationship needed to project the deformation modulus of the slag crushed stone was identified. This relationship will be used to design structures to be made of this material.

Calculation of a Direct-Flow Anthracite Culm Gasification Process with Liquid Slag Removal

Abstract A program for calculating the gasification process based on a mathematical model of direct-flow coal gasification with liquid ash removal, in which a mixture of oxygen and water vapor is used as a blast, is considered. Calculations were carried out for anthracite culm from the Eastern Donbass coal basin as a raw material.

Modification of ash fusion behavior of high ash fusion temperature (AFT) coal by textile dyeing sludge addition and its mechanism

To address the slagging problem during coal entrained-flow bed (EFB) gasification, the influences of textile dyeing sludge (TDS) addition on the fusing characteristics of high ash fusion temperature (AFT) coal were explored under a reducing atmosphere. And the change mechanisms were investigated by X-ray diffraction, Fourier Transform Infrared Spectroscopy (FT-IR) and FactSage calculation. The results showed that the flow temperature of high ash fusion temperature (AFT) coal decreased below 1380 deg;C when the TDS addition reached 20%–25%, which met the requirements of liquid-slag removal for EFB gasification. With the content of TDS increasing, the formations of low-melting minerals (e.g., hercynite, anorthite, and albite) decreased AFT. The bridging oxygen bonds of the network structure were destroyed by metal ions (e.g., Fe2+, Ca2+, Na+), formation of much non-bridged oxygen (NBO) bonds relaxed the silicate network, thus decreasing the AFT. The formations of NBO bonds were confirmed by gradual decreases in the peak strengths of Si–O–Si and Si–O–Al bonds and intensified the vibration of Fe–O and Si–O–M (M: Ca2+ or Na+) bonds. FactSage calculation results were in good agreement with the experimental ash fusion behavior.

Formation features of benz(a)pyrene and nitrogen oxides when burning brown coal in boilers with liquid slag removal system

In the article, the authors examine the experience of burning Kansk-Achinsk coal (KAC) in the boilers of the BKZ-320-140PT type at the CHPP-6 in Bratsk. The article considers the results of the experiments carried out at two boilers (b.u.No.5 and No.7), where the organization of aerodynamic processes is significantly different. These results are presented as the dependences of the concentrations of nitrogen oxides (NOx) and benz(a)pyrene (BaP), as well as the content of combustibles in fly-ash (Cf) on several parameters simultaneously, namely, the boiler load, the number of working dust collecting systems, and excess air. The following conclusions have been drawn: 1) two parameters have the most significant effect on the amount of BaP emissions – the scheme of entering drying gases into the combustion chamber and the excess air in the combustion chamber; 2) there is a certain relationship between BaP emissions and the content of combustibles in fly-ash: a lower Cf value corresponds to the mode with a lower concentration of BaP. It follows that BaP emissions can be reduced by measures reducing chemical and mechanical underburning (q3 and q4), primarily the turbulization of flue gases. The formula is proposed that clarifies the values of BaP emissions during vortex combustion. It is shown that the formation of NOx is also significantly affected by the same parameters as the formation of BaP, as well as the load of the boiler. The effect of these parameters is explained. Various technological measures are proposed to reduce pollutant emissions comprehensively by providing vortex combustion in the boilers with both liquid and solid slag removal systems.

Mathematical support for the control system for nitrogen oxide emissions in boilers with furnaces with liquid slag removal

When burning high-calorie low-volatile brands of coal in furnaces with liquid slag removal to achieve the standard concentration of nitrogen oxides in the outlet gases of the boiler, it is necessary to use two methods of reducing the concentration, for example, staged combustion and selective non-catalytic reduction. For optimal control of the two-stage process of successive concentration reduction, it is necessary to develop appropriate mathematical support that guarantees the maintenance of the standard concentration at any load of the boiler and minimizes the operating costs of reducing emissions. The scheme of mathematical support functioning is presented, which is an information processing system, the input of which is a signal from the steam load sensor of the boiler, and the output is a tasks for the regulators of the degree of stepwise combustion of fuel and urea supply, which ensure the optimal mode of operation of the emission control subsystem. The key issues of system development and operation are considered.

DESIGN BY PROGRAM ANSYS FLUENT PROCESSES IN HEATING OF CALDRON OF TPP-210А

Numerical modeling of processes in the furnaces of power boilers serves as a tool for assessing the impact of the proposed structural or operational changes on the ongoing processes and characteristics of the boiler. Using the ANSYS FLUENT program, three-dimensional numerical simulation of anthracite combustion processes in the furnace of a TPP-210A boiler with liquid slag removal was performed. The initial data for the calculation — component costs, composition and calorific value of coal — are taken from the boiler passport for the nominal operating mode. Air suction into the furnace has been taken into account. As the boundary conditions on the walls of the furnace, their thermal resistances are set, the values of which are determined by the results of the zone calculation of the furnace by the normative method. The turbulence model was used in the modification of a realizable, non-premixed combustion model of particle combustion in a single mixture fractions formulation, discrete phase model of the movement of coal particles, P-1 emission model, two-competing-rates model of volatile output, kinetics/diffusion-limited model of coal combustion. Obtained as a result of the distribution of heat flux densities and wall surface temperatures («contaminants») within each of the zones is substantially uneven, which confirms the validity of the type of boundary condition used on the walls. The change in the height of the furnace of the mass-average temperature of the flow, the heat flux densities into the walls, the distribution of the mechanical underburning of the fuel along the height of the furnace according to the simulation results are compared with the data of a well-known experimental study of S.L.Shagalova and I.N.Shnitser processes in the boiler under consideration, as well as with the data of the zone calculation of the boiler by the normative method. On this basis, a conclusion was made about satisfactory simulation results. Ref. 12, Fig. 7, Tab. 3.

Calculation of a Direct-Flow Coal Gasification Process with Liquid Slag Removal

A program for the calculation of a gasification process based on a mathematical model of direct-flow coal gasification with liquid slag removal is proposed. Calculations were performed for Chinese gas coals. A good agreement between the experimental and calculated data of the process is demonstrated.

Mechanical strength of slag crushed stone generated at coal-fired thermal power plants

Introduction. Production waste is used in the construction industry worldwide as it helps to cover a considerable portion of the industry’s demand for building materials. Coarse-grained slag deposits (slag crushed stone and sand), formed in the slag washout zone, have more potential for application than other ash and slag mixtures (coarse ASM), but they need more research. Mechanical properties of the slag crushed stone (coarse-grained ASM), formed in the course of coal combustion at Kansk-Achinsk, Kuznetsk coal deposits (in boilers equipped with liquid and dry slag removal facilities) and the application of the slag crushed stone in roadbuilding are considered.
 Materials and methods. In the course of the research, the crushability and the deformation modulus of particular fractions of slag crushed stone samples (in dry and water-saturated conditions) taken from the dumps of Novosibirsk TPP-3 (that consumes the coal of the Kansk-Achinsk coal mining field) and from Novosibirsk TPP-2 and Seversk TPP (that consume the coal of the Kuznetsk coal mining field) were identified. To assess the factors influencing the mechanical strength of the slag crushed stone, ignition losses, the content of flaky and acicular particles, dust and clay particles and clay lumps was made.
 Results. The difference in the mechanical strength of samples having different genesis was identified. The graphs obtained in the course of testing were assessed and deformability characteristics were calculated (for materials having different fineness values). The factors influencing the mechanical strength of slag crushed stone were determined. Dependencies between deformation parameters and crushability of the slag crushed stone were obtained.
 Conclusions. Some mechanical and physical parameters of the slag crushed stone were identified; they were applied to outline potential areas of the slag crushed stone application in road building. The mathematical relationship needed to project the deformation modulus of the slag crushed stone was identified. This relationship will be used to design structures to be made of this material.

Investigation of the interaction of turbulent jets in furnaces with direct-flow burners for high-power boilers

The aim of the study is to develop a highly efficient scheme of combustion of low-grade solid fuels with the realization of regulatory requirements for emissions of hazardous substances into the atmosphere. One of the directions of practical application of such a scheme is conversion of boilers with liquid slag removal to solid slag removal. Liquid slag removal boilers have a number of disadvantages that make their use in modern conditions impractical: reducing the reliability of the liquid slag at low loads and high emissions of NOx nitrogen oxides, which exceed the standard values 2-3 times. In light of amendments to the environmental legislation of the Russian Federation, changing the order and rates of payment for emissions of hazardous substances from 2020, thermal power plants will be forced to implement environmental measures to ensure normative values of specific emissions. The basic principles of effective solid fuel burning organization with the application of direct-flow burners have been formulated on the basis of the conducted research.

Features of formation and reduction of sulfur dioxide emissions when burning brown coal in boilers with liquid slag removal

The paper considers the influence of technological factors (design of the boiler-unit, load, air excess, the number of working dust collecting systems) on the formation and reduction of sulfur dioxide emissions in boilers with liquid slag removal. Understanding of this influence can be used both at many operating heat and power sources, and in the development of new combustion technologies. The long-term experience of burning brown coals of the Kansk-Achinsk basin (KAC) at CHPP-6 in Bratsk in boilers of the BKZ-320-140 PT type is studied and analyzed. The analysis uses the results of various thermodynamic and industrial studies of the sulfur dioxide formation during the combustion of KAC, including those carried out by the authors. They identified the temperature and structural zones of the boiler unit, where the resulting reaction of the sulfur dioxide transition to calcium sulfate occurs. It was found that such a zone is the upper part of the cooling chamber, where the indicated transition occurs at temperatures of 1500 ÷ 1400 K. It was found that SO2 emissions rise with an increase in the boiler load and air excess. They also depend on the number of dust systems and their combination (determining the turbulization of combustion processes). A technological mechanism for the sulfur dioxide transition to calcium sulfate for the operation of boilers with liquid slag removal is proposed. Regime and constructive measures are proposed to reduce emissions of sulfur dioxide.

MECHANICAL STRENGHT’S RESEARCH OF THE THERMAL POWER STATION’S SLAG

Introduction. The use of the thermal power station’s (TPS) waste in the construction industry becomes the norm in world practice of recent decades. Basically, the researches use ash and slag in the construction of automobile roads as a material for filling the subgrade or in the form of a cement-bound material in industrial and civil construction as a material for planning work, when filling inconveniences and quarries. However, the potential of the ash and slag’s usage is much wider. Coarse-grained slag deposits that form in the zone of slag erosion have a greater potential for application than other ash and slag mixtures, however, these mixtures have been less studied by both domestic and foreign researchers. The paper discusses the use of the boiler slag formed at power plants with boilers involving liquid slag removal for the construction of road pavement bases with the position of its mechanical properties.Materials and methods. The author studied samples of boiler slag from Novosibirsk TPS-2, operating (Kuznetsk coal basin) and Novosibirsk TPS-3 (Kansko-Achinsk coal basin). Moreover, the author determined the crushing losses of individual fractions of the investigated materials in a dry and water-saturated state. The author determined the modulus of deformation of boiler slag.Results. The researcher found the difference in mechanical strength of the different genesis material. The crushing values of the investigated materials are determined.The author estimated the graphs obtained during testing and calculated the deformability characteristics of the material.Discussion and conclusions. The author determines possible directions of the studied materials’ usage in the road construction.The author has read and approved the final manuscript. Financial transparency: the author has no financial interest in the presented materials or methods. There is no conflict of interest.

Ash Composition of Lignite

Five lignite samples from Russia’s Itatsky, Munai, Arkharo-Boguchansky, and Kangalassky fields and the Mongolian Baganuur field are characterized on the basis of technical analysis, their elemental composition, calorific value, petrographic composition, and the properties of their mineral component. Experimental data regarding the chemical composition of their ash residues permit empirical calculation of temperatures characterizing ash fusibility, the temperature of normal liquid slag removal, and the temperature of slagging onset. The melting temperatures are found to rise with increase in content of the acidic oxides SiO2 and Al2O3 in the ash residues but to fall with increase in the concentration of Fe2O3, CaO, and MgO.

Analysis of Combustion of Coal-Water Fuel in Low-Power Hot-Water Boiler via Numerical Modeling and Experiments

The paper presents an experimental and computational study of various regimes of firing coal-water fuel in a low-power hot-water boiler that enable both dry and liquid slag removal. The experimental studies were carried out on a pilot industrial boiler adapted for firing coal-water fuel. The fuel was prepared using flotation products of beneficiation of K grade hard coal. The experiments were accompanied by numerical modeling of combustion processes. The mathematical model includes description of the carrier phase motion (based on the RANS approach with the two-parameter Menter SST k-ω turbulence model), radiation transfer (based on the P1 approximation of the spherical harmonics method for a two-phase two-temperature gray medium), particle motion (based on the Lagrange approach), and gas phase combustion (based on a combination of the kinetic model of combustion of gas components with the vortex break model). The physico-mathematical model was tested on the problem of combustion of coal-water fuel (CWF). One of the goals of the work was verification of a complex mathematical model. A comparative analysis of the results of the numerical modeling and experimental data showed that the model reliably described the process of burning in a combustion chamber. An advanced design of hot-water boiler enabling regimes of both dry and liquid slag removal was investigated. The chamber was shown to provide the necessary conditions for firing CWF in terms of reliability and economy.

Трансформация и снижение выбросов диоксида серы при сжигании канско-ачинских углей на котлах с жидким шлакоудалением

Трансформация и снижение выбросов диоксида серы при сжигании канско-ачинских углей на котлах с жидким шлакоудалением

ANALYSIS OF METHODS FOR INCREASING THE OPERATING TERM OF THE BOILER UNIT TP-100A OF THE POWER UNIT № 10 BURSHTYN TPP

Boiler units with a view to prolonging their work are being reconstructed and modernized by carrying out qualitative repair works, replacement and restoration of worn out and spent resources of the most responsible units and parts of the units themselves and associated pipelines. When choosing a reconstruction project, it is important to consider the possibility of placing new equipment within the existing boiler units, minimizing the cost of the reconstruction with the achievement of maximum effect, the possibility of performing works for reconstruction and subsequent maintenance. Consequently, methods of increasing the life of the boiler unit, increasing its efficiency and maneuverability characteristics are extremely relevant. Therefore, we have stated the requirements for maneuverability. The power unit should be designed to work in a maneuverable mode that is to participate in primary and secondary regulation of frequency and power under normal and emergency modes of operation of the electric power system of Ukraine. When working on boiler plants, an adjustment range for loading, minimum and maximum permissible load should be provided. The lower boundary of the adjustment range of the load of the power unit shall be established, proceeding from the conditions of maintaining the unchanged composition of the operating equipment and the reliability of the boiler screen system and the operation of the automatic control system in all specified load ranges without personnel interference. The boiler must operate in the range of load of 50–100 % of nominal without the use of fuel for stabilizing combustion (gas, fuel oil). Expansion of the lower limit of the operating range of the control of the load of the power unit up to 50 % at the combustion of solid fuel without the use of backlighting fuel and providing a liquid slag removal taking into account the expected maneuvering mode of the power unit at the nominal boiler pressure, without backlighting of reserve fuel and the need for emergency injections. In course of the research a fundamentally new system of supplying (transporting) highly concentrated deodorized coal dust (PVKr) with steam ejectors is introduced, instead of existing transport systems, a highly concentrated coal dust feed from piles to burners by pneumatic transport under pressure of a blower fan, and the design speed at the outlet of the burner is: 1) secondary air – 25–30 m/s; 2) gas-air mixture during transportation of dust МВ – 25–28 m/s; 3) aerosomes for transportation of dust PVКr – 18–20 m/s. A steam-ejector burner is installed in a direct-current burner, in a branch pipe of a primary air, a pipe of 377 mm in diameter, in which a dust-air mixture is produced (discharging of a dusty, dusty exhaust dryer (gas-air mixture) by a single-ventilated closed-circuit sawing boiler). The device is a pipe with a diameter of 133×9 mm, at the end of the pipe, which is included in the furnace, a nozzle mounted is a stainless steel cutter, which provides a wide-conic leakage of a dust-vapour-steam mixture and a reliable aerodynamic mixing with secondary air. Thus, we have come to the following conclusions. The reconstruction of the boiler unit TP-100A enables achieving an increase in the installed electric power of the power unit to a value not less than 210 MWt without increasing the cost of fresh steam, improving the technical and economic performance of the equipment, restoring the steam resource of the boiler elements, boosting the boiler efficiency to a value not lower than 90 %, as well as prolongation of the operation life of the boiler elements, pipelines within the boiler, steam lines, pressure vessels, which are not subject to replacement, up to a minimum of 40 thousand hours.

Numerical simulation of submicron particles formation by condensation at coals burning

The thermodynamic analysis of the composition of the combustion products of 15 types of coals was carried out with consideration for the formation of potassium and sodium aluminosilicates and solid and liquid slag removal. Based on the results of the analysis, the approximating temperature dependences of the concentrations of condensed components (potassium and sodium sulfates) were obtained for the cases of two-phase and single-phase equilibriums; conclusions on the comparative influence of solid and liquid slag removal on the probability of the formation of submicron particles on the combustion of coals were made. The found dependences was make it possible to perform a numerical simulation of the bulk condensation of potassium and sodium sulfate vapors upon the cooling of coal combustion products in a process flow. The number concentration and size distribution of the formed particles have been determined. Agreement with experimental data on the fraction composition of particles has been reached at a reasonable value of a free parameter of the model.

Environmental and economic evaluation of selective non-catalytic reduction of nitrogen oxides

There are two groups of atmosphere protecting measures: technology (primary) and treatment (secondary). When burning high-calorie low-volatile brands of coals in the furnaces with liquid slag removal to achieve emission standards required joint use of these two methods, for example, staged combustion and selective non-catalytic reduction recovery (SNCR). For the economically intelligent combination of these two methods it is necessary to have information not only about the environmental performance of each method, but also the operating costs per unit of reduced emission. The authors of this report are made an environmental-economic analysis of SNCR on boiler Π-50P Kashirskaya power station. The obtained results about the dependence of costs from the load of the boiler and the mass emissions of nitrogen oxides then approximates into empirical formulas, is named as environmental and economic characteristics, which is suitable for downloading into controllers and other control devices for subsequent implementation of optimal control of emissions to ensure compliance with environmental regulations at the lowest cost at any load of the boiler.

Сравнительные исследования процессов жидкого шлакоудаления при разных технологиях пылеподачи на горелки котла ТПП-210А

We present some results of studies of a TPP-210A boiler, burning ASh coal, under loads of the units of 200–300 MW at two technologies of dust feed to the burners: the traditional pneumatic dust transport with primary air and highly-concentration dust feed under pressure (PVKd) with estimating the influence of these technologies on the modes of liquid slag removal. The degree of influence of the main factors on the stability of liquid slag yield and the expenditure of fuel oil for lighting was determined. The results of studies have revealed the possibility of increasing the economical efficiency of boiler operation by reducing the fuel oil consumption for lighting with the use of PVKd technology, which should be considered as a method for improving furnace conditions in boilers, burning low-reaction coal at liquid slag removal.

Solution of Problems with the Burning of Coals from the Kansk-Achinsk Basin in the P-49 Boiler of a 500 MW Unit at the Nazarovo State Regional Electric Power Plant

Experience with the burning of coals from the Kansk-Achinsk Basin in a P-49 boiler with different burner and furnace configurations is examined. Problems in running the boiler with liquid slag removal are noted. Some studies of boiler operation with low-temperature vortex coal firing following technical renovation are discussed.

Thermodynamic analysis of the formation of submicron particles on the combustion of coals

The thermodynamic analysis of the composition of the combustion products of 15 types of coals was carried out with consideration for the formation of potassium and sodium aluminosilicates and solid and liquid slag removal. Based on the results of the analysis, the approximating temperature dependences of the concentrations of condensed components (potassium and sodium sulfates) were obtained for the cases of two-phase and single-phase equilibriums; conclusions on the comparative influence of solid and liquid slag removal on the probability of the formation of submicron particles on the combustion of coals were made. The found dependences will make it possible to perform a numerical simulation of the bulk condensation of potassium and sodium sulfate vapors upon the cooling of coal combustion products in a process flow.