Development of a simplified methodology for furnace aerodynamics with vortex combustion of organic fuel modeling

This paper describes the process of developing a simplified methodology for furnace aerodynamics during the development or modernization of combustion schemes with direct-flow burners. This technique is based on the use of numerical modeling of air movement and turbulence phenomena in the furnace volume and allows for a relatively short period of time to analyze a large number of options for the burners and nozzles location. This is its advantage in comparison with the use of experimental modeling or numerical simulation with combustion when analyzing a variety of schemes. The model was developed on the basis of validated results of combustion processes numerical simulation in the K-50 boiler furnace. The paper presents the results of calculations performed for several variants of the simplified methodology. For further use, the option that best corresponds to full-scale studies taking into account the fuel combustion process has been selected. The main states of the methodology are formulated.

Management of the Torch Structure with the New Methodological Approaches to Regulation Based on Neural Network Algorithms

A method for evaluating the thermophysical characteristics of the torch is developed. Mathematically the temperature at the end of the zone of active combustion based on continuous distribution functions of particles of solid fuels, in particular coal dust. The particles have different average sizes, which are usually grouped and expressed as a fraction of the total mass of the fuel. The authors suggest taking into account the sequential nature of the entry into the chemical reactions of combustion of particles of different masses. In addition, for the application of the developed methodology, it is necessary to divide the furnace volume into zones and sections. In particular, the initial section of the torch, the zone of intense burning and the zone of afterburning. In this case, taking into account all the thermophysical characteristics of the torch, it is possible to make a thermal balance of the zone of intense burning. Then determines the rate of expiration of the fuel-air mixture, the time of combustion of particles of different masses and the temperature at the end of the zone of intensive combustion. The temperature of the torch, the speed of flame propagation, and the degree of particle burnout must be controlled. The authors propose an algorithm for controlling the thermophysical properties of the torch based on neural network algorithms. The system collects data for a certain time, transmits the information to the server. The data is processed and a forecast is made using neural network algorithms regarding the combustion modes. This allows to increase the reliability and efficiency of the combustion process. The authors present experimental data and compare them with the data of the analytical calculation. In addition, data for certain modes are given, taking into account the system’s operation based on neural network algorithms.

Numerical modeling of peat burning processes in a vortex furnace with countercurrent swirl flows

The paper presents the process of peat burning in a swirl furnace with countercurrent swirl flows and the results of a numerical study. The cyclone-vortex technology of solid fuel combustion allows the furnace volume of a boiler unit, its dimensions and weight to be reduced. The aim of the work is a numerical study of the combustion of pulverized peat in a cylindrical vortex furnace with countercurrent swirl flows. The results of computer simulation of the combustion of pulverized peat with a moisture content of 40%, an ash content of 6% and a higher heat of combustion Q?? = 12.3 MJ/kg are presented. The results of the influence of the design parameters of the furnace and heat load (from 100% to 15%) are given as well. When the heat load is reduced to 15%, the entrainment of unburnt particles increases. The cooled and adiabatic furnace is studied. A significant entrainment of unburned particles is observed n a cooled furnace. The fields of temperature distribution, gas velocity and particle trajectory in the volume and at the outlet of the furnace are determined. The three-dimensional temperature distribution in the furnace volume indicates the combustion of peat particles at temperatures (1300-1450?C). Values of the tangential velocity of a swirl flow near the furnace outlet reach 150 - 370 m/s, which ensures the efficiency of separation of fuel particles and a reduction in heat loss due to mechanical underburning (up to 0.06%). The results of a numerical study show that the diameter of peat particles affects the combustion process, namely coke of particles with an initial diameter from 25 microns to 250 microns burns out by 96%, and particles with a diameter of about 1000 microns are carried away from the furnace and do not burn. The furnace provides a complete combustion of dust particles of peat by 99.8% and volatiles by 100%.

WATERTUBE SMOKE TUBE BOILER: NUMERICAL COMPUTER SIMULATION AND EXPERIMENT

The improvement of natural gas use technologies in water-heating boilers is considered. The concept of a new watertube smoke tube boiler, created on the basis of the screen radial tube bundle placement in the space of a cylindrical heat pipe-furnace. The results of numerical computer simulation of the furnace process in the 630 kW watertube smoke tube boiler are compared with the corresponding data obtained during the experiment. The analysis of the results of numerical computer simulation reveals the efficiency of the installed tube radial bundle: the total heat perception in the furnace increased by 56 %, while the growth of the part of the heat transferred by convective heat exchange occurred by 22 %; the temperature level in the furnace volume has decreased, while the concentration of nitrogen oxides has decreased by 45–51 %. It is experimentally established that the presence of the cooled screen tube radial bundle in the furnace of the watertube smoke tube boiler makes it possible: to increase heat release rate in the furnace volume by 10 %; to reduce the concentration of nitrogen oxides and carbon monoxide in flue gases by 24–40 % and 25–67 % respectively (resulting in a compliance of the level of pollutant emission to the requirements of the Ukrainian national regulations, viz. GOST 30735–2001); reduce the excess air in the furnace by 3 % and increase the efficiency of the boiler by 0.5 %. The pre-production prototype of the water-heating smoke tube boiler (KVVD-0.63 Gn) has passed the certification tests, state registration; the boiler has been adopted in permanent operation. The boiler is not complicated in manufacturing, and producible in the conditions of municipal heating network companies. The reliability of the boiler's design has been confirmed by the experience of many years of functioning.

Viscosity and structure evolution of the SiO2-MgO-FeO-CaO-Al2O3 slag in ferronickel smelting process from laterite

The SiO2 fractions in laterite-nickel ores are quite high, thus certain amount of lime should be used as fluxing material to achieve good fluidity and desulfurization capacity in industrial smelting process. However, this operation leads to an additional cost of lime. In addition, the increase of slag volume decreases the effective furnace volume. To avoid such problem, partial reduction of FeO has been suggested. Therefore, the high SiO2, low MgO and FeO and very little CaO slag is formed, which was less studied in the previous literature. Therefore, the viscosity and slag structure are investigated in the present study through FT-IR and Raman analysis methods. Experimental results show that the slag is a mixture of liquid and solid phases under the experimental temperature. The FT-IR and Raman spectra show that the fractions of the complex polymerization structure decrease significantly with the increase of FeO content and slag basicity, resulting in the decrease of apparent viscosity.

Conventionally Heated Microfurnace for the Graphitization of Microgram-Sized Carbon Samples

A new type of miniaturized, externally heated graphitization reaction furnace, the microconventional furnace (MCF), was constructed following our development of the laser heated furnace (LHF). The MCF is comprised of a gas reactor, a cold finger cooling system, and a compact resistive heater, which can raise the temperature of the hot finger to 850°C. The gas reactor is provided with three integrated valves to connect with the hydrogen/vacuum manifold, to isolate the reactor, and to connect with sample vessels. We made two types of MCF: the type 1 furnace (volume of 0.9 mL), with an integral stainless steel cold finger, and the type 2 furnace (volume from 1.3 to 10 mL), with a changeable glass cold finger. The MCF is designed for above atmospheric pressure (up to 2500 mbar) operation to decrease the overall graphitization time and improve the carbon yield. The MCF provides an effective solution for producing graphite from carbon dioxide (CO2) sample gas from 5 to 2000 µg of carbon with only 0.083 μg of 100 pMC extraneous carbon added. Cross-contamination tests show that the MCFs have no memory effect from previous samples.

Preparation of Both Reactive α-Si3N4 and SiC Mixed Powder in Flame-Isolation Nitridation Shuttle Kiln

α-Si3N4 possesses excellent sintering activity, which is used to prepare high performance Si3N4-based ceramics and composite refractory. Si3N4 powder is always synthesized by nitriding silicon in controlled-atmosphere furnace whose furnace volume is very small(effective volume: 1840×1420×1660mm), the extreme reaction heat is difficult to diffuse, which leads to high reaction temperature and conversion of α-Si3N4 to β-Si3N4, thus α-Si3N4 is difficult to be obtained in controlled-atmosphere furnace. While flame-isolation nitridation shuttle kiln has much larger furnace volume to conduct reaction heat (effective volume: 11500×4190×1684mm), so it owns homogeneous temperature field and stable low-temperature environment which benefits the preparation of α-Si3N4. Thermodynamic analysis of Si-N system is shown that Si3N4 can be formed by two formats: direct nitridation of Si(s) and indirect nitridation of SiO(g); to ensure completely nitridation, the particle size of silicon powder should be less than 88μm. With reclaimed powder from polysilicon cutting slurry as starting materials, both reactive α-Si3N4 and SiC mixed powder were successfully prepared in flame-isolation nitridation shuttle kiln. Because of the gas-gas reaction between SiO(g) and N2(g), α-Si3N4 is fiber-like and in favor of processing high quality Si3N4-based materials.