Furnace Chamber Research Articles

Комплексное использование отходов деревообрабатывающей и сельскохозяйственной промышленности в энергетике Сибири

The article considers the methods of increasing technoeconomic and ecological indices of boilers of little and average power by the means of vertical-way combustion of alternative fuels (eg. husks, chips, wood waste). We analyzed the technology of combustion of solid fuels from plant biomass and revealed several issues in the combustion of light sailing particles. The article is dedicated to the investigation of the properties of alternative fuels, to the generation and refinement of furnace arrangements for combustion of low-grade fuels. The results of our work represent a new construction design of the furnace chamber for effective combustion of alternative fuels. The new construction design of the furnace chamber is obtained via the aerodynamic modelling with the use of the «SigmaFlame» software.

Numerical Simulation of Temperature Fields in a Three-Dimensional SiC Crystal Growth Furnace with Axisymmetric and Spiral Coils

Three-dimensional numerical simulation platform for silicon carbide crystal growth furnace was established using C programing language, where a physical model of the furnace was built based on cylindrical coordinates; governing equations for electromagnetic and temperature fields were discretized by finite volume method; radiation characteristics were studied with the help of S2S model (surface to surface radiation model); and the least distance method was proposed to check radiation faces visibility efficiently. LU decomposition algorithm based on graphic processing unit (GPU) technology was developed to accelerate the solving process of surface to surface radiation. Then the radiation heat transfer in silicon carbide crystal (SiC) growth chamber and temperature field of silicon carbide growth furnace were studied quantificationally at I = 1250 A and F = 16 kHz. The effects of coil structures (axisymmetric and spiral) on temperature field and its gradient distributions were investigated by standard deviation method. The simulation results demonstrate that spiral electromagnetic coil generates non-axisymmetric temperature field easily; the radiation heat flux is 102~103 times more than conduction heat flux, radiation heat transfer is helpful to increase temperature evenness; the spiral temperature field on the SiC crystal cross-section reduces the poor homogeneity of temperature gradient, which will cause crystal to generate large defects.

Modified DHTT Equipment for Crystallization Studies of Mold Slags

The double hot thermocouple technique (DHTT) enables simulations of the temperature gradient at near-service conditions during continuous casting of steel. With the equipment applied so far, a rectangular slag film of even thickness often cannot be achieved. Further, the minimum temperature frequently lies within the slag film. Modified equipment can avoid these disadvantages via the following design features. The entire furnace chamber is heated to the selected temperature of the cold wire, and the minimum temperature is not located within the slag film. Furthermore, the shape of the heating wire is improved, which enables mounting of a thin, rectangular slag film between four platinum wires. This modification allows for investigations on transparent and translucent slags. So far, the results from DHTT investigations were represented via snapshots of the samples at certain experimental times. Therefore, appropriate methods for the graphical representation of the results were suggested: the maximum crystallinity, the time related to certain crystallinities with a dependence on the position within the slag film, and the crystal growth rate. The CaO-MgO-Al2O3-SiO2 slag investigated with this equipment was mineralogically examined additionally, and based on thermodynamic calculations, the allocation of temperatures to certain positions within the crystallized slag film was possible.

Intelligent sensor in control systems for objects with changing thermophysical properties

The control of heat devices in a wide temperature range given thermophysical properties of an object is a topical issue. Optimal control systems of electric furnaces have to meet strict requirements in terms of accuracy of production procedures and efficiency of energy consumption. The fulfillment of these requirements is possible only if the dynamics model describing adequately the processes occurring in the furnaces is used to calculate the optimal control actions. One of the types of electric furnaces is the electric chamber furnace intended for heat treatment of various materials at temperatures from thousands of degrees Celsius and above. To solve the above-mentioned problem and to determine its place in the system of energy-efficient control of dynamic modes in the electric furnace, we propose the concept of an intelligent sensor and a method of synthesizing variables on sets of functioning states. The use of synthesis algorithms for optimal control in real time ensures the required accuracy when operating under different conditions and operating modes of the electric chamber furnace.

THE INNOVATIVE CONTROL OF THE HEATING UP PROCESS OF THE METAL IN THE FURNACE USING SPATIAL ELECTRIC FIELD

Context. The actual task of developing an innovative control system for the process of metal heating up in the chamber furnace has been solved in the work.Objective is a creation of an algorithm for the controlling of the heating up of the metal with additional use as the controlling influence of a spatial electric field in the furnace chamber.Method. A regression model of a real chamber furnace was obtained using well-known experimental design techniques. The model is the basis of the algorithm and takes into account the magnitude of the voltage between the burner and the metal cage.Results. A control system for the chamber furnace has been developed, in which the optimal values of control actions at each step of the heating cycle are determined according to the created algorithm. The proposed control system is universal, it gives the dynamics of the change in the constant voltage and the gas supply in steps in time j to perform any given mode of heat treatment of the metal. The carried out experiments on a real chamber furnace with a withdrawable hearth at OOO «Zaporizhzhya Titanium and Magnesium Plant» have confirmed this. Analysis of the obtained graphs of the annealing temperature of the metal. There is a high uniformity and a better quality of metal heating when implementing the optimal values of control actions obtained with the help of the algorithm. The dynamics of gas consumption by the chamber furnace during the heating cycle is shown in accordance with the optimization performed without the supply of voltage and with the supply of voltage. The obtained data testify to the possibility of a significant increase in the energy efficiency of the furnaces in question.Conclusions. For the first time, the possibility and efficiency of using a spatial electric field in the furnace chamber as a control action has been proved, which confirms the scientific novelty of the results obtained. The developed control algorithm is universal from the viewpoint of thermal treatment of metal and can be used in chamber furnaces of any industrial enterprise. During one heating cycle, natural gas consumption is reduced by more than 10%, which confirms the practical importance of research.

INFLUENCE OF ISOTHERMAL OXIDATION ON CORROSION RESISTANCE OF TITANIUM IN BOVINE SERUM

The thermal oxidation treatment is an innovative and simple method for modifiying the surface properties of titanium such as enhance corrosion and wear resistance. The effects of isothermal oxidation immersion time on the surface properties and corrosion behavior under bovine serum of cp-Ti were studied in this paper. The treatment was done at 700<sup>o</sup>C for 0 to 36 hours in furnace chamber. The surface microhardness, surface roughness, wettability and polarization potentiodynamic corrosion of cp-Ti were determined. The result shows the surface microhardness, surface roughness, wettability and corrosion resistance of the cp-Ti enhanced by isothermal oxidation treatment. The presence of the oxide layer on the surface in the form of TiO<sub>2</sub> rutile and Ti<sub>3</sub>O are responsible to enhance the surface properties and corrosion behavior

A study of burning processes of fossil fuels in straitened conditions of furnaces in low capacity boilers by an example of natural gas

The aim of this work is to research operations of modern combined low-emission swirl burner with a capacity of 2.2 MW for fire-tube boiler type KV-GM-2.0, to ensure the effective burning of natural gas, crude oil and diesel fuel. For this purpose, a computer model of the burner and furnace chamber has been developed. The paper presents the results of numerical investigations of the burner operation, using the example of natural gas in a working load range from 40 to 100%. The basic features of processes of fuel burning in the cramped conditions of the flame tube have been identified to fundamentally differ from similar processes in the furnaces of steam boilers. The influence of the design of burners and their operating modes on incomplete combustion of fuel and the formation of nitrogen oxides has been determined.

INVESTIGATION CORROSION AND MECHANICAL PROPERTIES OF CARBURIZED LOW CARBON STEEL

In this research, Taguchi method is used (S/N) ratio for measuring the variations in experimental design. Taguchi designs used in converting the multi-performance problem into a single-performance problem for experiments which will are in building (Taguchi (L27) orthogonal array) for carburization operation. The main variables that had a great effect on carburizing operation are Carburization temperature (o C), carburization time (hrs.) and tempering temperature (oC). It was focused also on calculating the amount of carbon penetration, the value of hardness, wear rate, corrosion rates and optimal values obtained during the optimization by (Taguchi) approach method for multiple parameters. In this study, the carburization process was done in temperature between (850 to 950 ᵒC) for (2 to 6 hrs.). Quenching process was done for the specimens after heat treatments in furnace chamber by different quench solution (water, salt and polyvinyl alcohol). Taguchi design used to achieve maximum hardness and depth penetration, Minimum wear and corrosion rates.

Investigation of inner aerodynamics of the four-vortex furnace model

The internal aerodynamics of a perspective vortex furnace chamber of a pulverized coal boiler with a diagonal arrangement of burners is studied using the non-contact optical method of flow diagnostics. The results of laser Doppler anemometry, characterizing the complex spatial structure of a swirling flow in an isothermal laboratory model of the furnace device, are presented. The velocity distribution in the vortex chamber volume is obtained, and the flow structure in the form of four conjugate closed vortices with curved axes is visualized.

Computational modeling of the combustion of coal water slurries containing petrochemicals

The combustion predictive model was developed based on the results of experiments with coal water slurry and coal water slurry containing petrochemicals. Unlike other known models, it takes into account the effect of liquid flammable component (in particular, engine oil waste) on the main mass and heat transfer as well as other physical and chemical processes in the combustion chamber. The main differences, conditions and characteristics of the combustion of coal water slurries containing petrochemicals and without additives have been studied theoretically with different defining parameters: fuel composition, component properties, and furnace chamber temperature. Temperature fields and volumetric concentration distribution of combustion products in the furnace chamber are established for fuel compositions based on water, coal, and industrial oil waste. Temperatures and concentrations for both the initial fuel components and their combustion products are established at different points of the furnace chamber for various component concentrations, properties, and furnace air temperatures. The main research findings are the quantitative differences between the characteristics of ignition and combustion of slurries with and without a liquid fuel component. These differences are critical to illustrate the benefits of using coal water slurries containing petrochemicals in heat and power plants. Adding as little as 10% (relative mass fraction) of waste industrial oils was shown to significantly reduce the ignition delay times and improve the combustion efficiency of fuel compositions. Possible ranges, in which the ignition delay of slurry fuels can be reduced, and the displacement of their ignition zones in the combustion chamber were determined when changing the temperature and the main fuel component – coal (as illustrated by brown and bituminous coals, as well as anthracite).

Review of the literature discussing the problem of uneven thermal stresses in the furnace chamber

Uneven thermal stresses occurring in the walls of the furnace chamber in high power boilers are the reason for the occurrence of significant thermal stresses. The occurrence of excessive stress leads to serious damage to the waterwall tubes, which result in the necessity of more frequent repairs of the boiler. Therefore, finding a way to reduce stress values is one of the key challenges in improving productivity and increase the service life of boilers.In this paper will be presented the review of the literature concerning the problem of uneven temperature distribution on the surface of the combustion chamber walls. There will also be presented studies that discuss the methods of modifying the furnace chamber to reduce the values of the stresses occurring in it.

Characterization and properties of cordierite – mullite refractories from raw materials and Narathiwat clay (in Thailand)

In the present study, the relationship between characterization and properties of mullite-cordierite refractory were investigated. Talc, alumina oxide and kaolin (Narathiwat clay, Thailand: NRT) were mixed by varying the ratio of MgO+Al2O3+SiO2 as NRT1 (31:66:3), NRT2 (45:54:1), NRT3 (13:86:1) and NRT4 (50:49:1). The mixture was pressed into rectangular shape by a hydraulic press under a pressure of 150 kg/cm2 and sintered at 1300 °C with a heating rate of 5 °C/min for 1 hour of soaking time and cooled down to room temperature in a furnace chamber. Sample dimensions, density, water absorption, porosity, shrinkage, and mechanical properties were measured as a function of firing temperature. The chemical composition and loss on ignition (LOI) of the raw materials were performed using X-ray fluorescence spectrometer (XRF). Effects on the phases formation and morphology that capable to improve mullite and cordierite in samples were performed using X-ray diffractometer (XRD). The results revealed that mullite was the major phase in sintered samples and cordierite was also found which formed during expense of the other phases with talc. SEM pictures exhibited the role of talc in the grain growth of mullite and also showed the formation of pseudohexagonal cordierite which was observed by Scanning electron microscope (SEM).

Economical and ecological assessment of hot-water boilers substitution or modernization within district heat supply systems across the Republic of Kazakhstan

This paper describes significance and necessity of PTVM hot-water boilers modernization and substitution by hot-water boilers with higher efficiency rates and improved ecological indexes. It also describes an analysis performed in relation to different ways of PTVM-100 boilers modernization across CIS countries, which were aimed at extension of boiler’s heat efficiency period working on natural gas and fuel oil. Results of this analysis showed that the issue of ash and soot formation on convective surfaces during operation of boiler on fuel oil, which is directly connected with high exhaust temperatures of PTVM-100 furnace chamber, is still remains to be unsolved.Designs of new hot-water boilers KV-GM-42 and KV-GM-145 with bi-radiated screens and optimized convective heating surfaces, suggested by authors of this paper, are considered to fit the old series of boilers, and allow to have efficiency rate at about 93% level. This paper contains assessment of economical and ecological effects, which are going to be used as grounds for substitution of hot-water boilers that have come to the end of their service lifetime. Assessment was performed based on current tariffs and normative acts and in accordance with statistics data across the Republic of Kazakhstan.

Interaction between a hollow‐cone spray and the co‐axial swirling stratified flow in a novel spray pyrolysis furnace

Pressure‐swirl nozzles producing hollow‐cone sprays are widely used in many engineering applications, but the induced high‐speed stream along the centreline of the spray cone was ignored in designing spray chambers. The high‐speed stream influences the flow field especially in minimized spray chambers, but it is difficult to characterize experimentally. Hence, computational fluid dynamics was applied to investigate the multi‐phase flow interactions inside a novel spray pyrolysis furnace for liquid ore exploitation. The mass flow rate distribution of the co‐axial swirling stratified flow inside the furnace, the gas‐solid separation efficiency, particle size distribution, and residence time were investigated under different positions and directions of the hollow‐cone spray. The results proved that different spray operations would cause variation in the air mass flow rate distribution and gas‐solid separation efficiency, which should be paid attention to in the design of process intensification. The distribution of particles sized from 30 to 40 μm were most sensitive under different flow rates. The recommended operating conditions of the spray pyrolysis process were confirmed as the inlet velocity of 5 m/s and downward spray from the top of the furnace chamber.

BOILER HOUSE BASED ON IMPROVED FURNACE OF HIGH EFFICIENCY

Forecasting the further development of the economics and power engineering on the basis of modern effective technologies we can conclude that it is possible to replace nuclear and fossil fuels with renewable energy sources. The results of calculation of the amount of wood that is needed for the boilers with different efficiency are presented in the paper. We found that the main advantage of a solid fuel boiler over a gas boiler is the low cost of non-traditional types of fuel (wood and its wastes) compared to natural gas. It is necessary to take into account physical-mechanical and heat-engineering characteristics of fuel in order to increase the energy efficiency of biomass combustion and to reduce the level of pollutants. We analyzed the wood breeds which are widely used as fuel in the solid fuel boilers particularly pine, birch, aspen, alder, fast growing willow (Salix Viminalis). The mathematical modelling of combustion process of various wood breeds was carried out. The modelling results and the experimental values of the kinetic parameters of individual wood breeds are the basis for the investigation of the process of burning both pure breeds and their mixtures. The design of chamber furnace for burning of chopped wood biomass is developed by the authors in order to ensure the efficient and complete combustion. It has two protrusions to create a whirl in the main combustion chamber and the additional burner in the post-combustion chamber which creates an additional whirl of the wood mixture. The proposed furnace allows to increase the time of staying of fuel particles in the combustion volume. The applying of the improved furnace design as well as the modular construction principle make it possible to build an efficient boiler-house based on combustion of chopped wood biomass.

Design and robust optimization of a novel industrial continuous heat treatment furnace

This paper designs and robustly schedules a novel AAHP (air to air heat pump) based ICHTF (industrial continuous heat treatment furnace) which is driven by a solar Stirling engine and a wind turbine. The proposed flame-making process equipped with two inside and outside air fans, an expansion valve, compressor, condenser, and an evaporator to supply the heating demand with the high-temperature more than 1000 K.The heating energy obtained from the AAHP is not produced during the combustion reactions but is transferred from the ambient air to the furnace chamber. Therefore, use of solar, wind and AAHP in an industrial furnace with no need to fossil fuels not only reduces the stack pollutant emissions and ozone-depleting substances, but also increases the economic savings in the consumptions of petroleum products and electricity, significantly. In this study, an energy-exergy based mathematical framework is comprehensively presented to model the proposed ICHTF in the presence of renewable energy sources such as air, solar, and wind. Moreover, an interval robust economic optimization strategy is introduced to minimize total energy procurement cost using the forecasted wind speed as inputs and taking into account the upper and lower limits of the wind power for modeling its uncertainties. In the robust model, the range of wind power is divided into several consecutive nested subintervals. The proposed ICHTF is simulated on a benchmark small-scale industrial sector which is located in a tropical region in order to minimize total electricity cost considering the operational constraints of Stirling cycle and AAHP considering the wind generation uncertainties. Simulation results reveal the feasibility and strength of the proposed ICHTF by solving a RNLP (robust nonlinear programming) problem using the CONOPT solver under GAMS (general algebraic mathematical system) environment.

Synthesis process and microstructure of carbon fibres/graphite/copper composites by spark plasma sintering

ABSTRACTCarbon fibres/graphite/copper composites are prepared by mechanical alloying and spark plasma sintering at different temperature in this study, and the microstructure evolution is investigated during sintering. The curves of punch displacement, mould temperature, furnace chamber vacuum, and voltage against time were recorded and discussed. The results show that the carbon fibre/graphite/copper composite presents neat and pure interface. Copper element is found in carbon fibres and graphite, which may be due to discharge. The microhardness of the obtained composites is up to 160 HV. The highest relative density in this test is 96.5%. The microstructure evolution process during SPS is associated with sparking, joule heat, pressure, and deformation. The sintering process is uneven at initial stage.

Distinctive features of high-ash bituminuos coals combution with low milling fineness in furnace chambers with bottom blowing

Nowadays the problem of improvement of pulverized coal combustion schemes is an actual one for national power engineering, especially for combustion of coals with low milling fineness with significant portion of moisture or mineral impurities. In this case a big portion of inert material in the fuel may cause impairment of its ignition and combustion. In addition there are a lot of boiler installations on which nitrogen oxides emission exceeds standard values significantly. Decreasing of milling fineness is not without interest as a way of lowering an electric energy consumption for pulverization, which can reach 30% of power plant’s auxiliary consumption of electricity. Development of a combustion scheme meeting the requirements both for effective coal burning and environmental measures (related to NOx emission) is a complex task and demands compromising between these two factors, because implementation of NOx control by combustion very often leads to rising of carbon-in-ash loss. However widespread occurrence of such modern research technique as computer modeling allows to conduct big amount of variants calculations of combustion schemes with low cost and find an optimum. This paper presents results of numerical research of combined schemes of coal combustion with high portion of inert material based on straight-flow burners and nozzles. Several distinctive features of furnace aerodynamics, heat transfer and combustion has been found. The combined scheme of high-ash bituminouos coals combustion with low milling fineness, which allows effective combustion of pointed type of fuels with nitrogen oxides emission reduction has been proposed.

Modelling of nitrogen oxides distribution in the hearth of gas-fired industrial furnace

A model is proposed for calculating the formation and transportation of nitrogen oxides in the combustion chamber of an industrial furnace heated by gaseous fuels burning. The calculations use a three-dimensional stationary description of turbulent flow and mixing of fuel and oxidizer flows in the presence of heat transfer, mass transfer, and momentum between them transfer. Simulation of the spatial pattern of nitrogen oxides formation in the working space of the furnace is performed in the programming and computing suite SCAN. It is shown that the temperature non-uniformity over the hearth surface is not too pronounced due to the organization of the inclined flow inlet in the direction of the hearth, which is a desirable feature of the furnace operation. The highest concentration of combustion products is observed in the zone of maximum temperatures. In addition, the existence of two zones of the highest generation of oxides has been determined. The first zone is located approximately in the center of the hearth, and the second is located on the far external surface of the furnace. The possibility of using the developed model in the SCAN complex for carrying out parametric studies and engineering calculations, as well as for modification in the direction of adjusting and adapting the model to the regime-constructive features of specific energy technological devices, is noted.

Furnace devices aerodynamics optimization for fuel combustion efficiency improvement and nitrogen oxide emission reduction

MPEI conducts researches on physical and mathematical models of furnace chambers for improvement of power-generation equipment fuel combustion efficiency and ecological safety. Results of these researches are general principles of furnace aerodynamics arrangement for straight-flow burners and various fuels. It has been shown, that staged combustion arrangement with early heating and igniting with torch distribution in all furnace volume allows to obtain low carbon in fly ash and nitrogen oxide emission and also to improve boiler operation reliability with expand load adjustment range. For solid fuel combustion efficiency improvement it is practical to use high-placed and strongly down-tilted straight-flow burners, which increases high-temperature zone residence time for fuel particles. In some cases, for this combustion scheme it is possible to avoid slag-tap removal (STR) combustion and to use Dry-bottom ash removal (DBAR) combustion with tolerable carbon in fly ash level. It is worth noting that boilers with STR have very high nitrogen oxide emission levels (1200-1800 mg/m3) and narrow load adjustment range, which is determined by liquid slag output stability, so most industrially-developed countries don’t use this technology. Final decision about overhaul of boiler unit is made with regard to physical and mathematical modeling results for furnace and zonal thermal calculations for furnace and boiler as a whole.Overhaul of boilers to provide staged combustion and straight-flow burners and nozzles allows ensuring regulatory nitrogen oxide emission levels and corresponding best available technology criteria, which is especially relevant due to changes in Russian environmental regulation.