Comparative Analysis of Models of the Combustion Process of Coal Dust in a Turbulent Flow of a Torch of a Charcoal Boiler

This article provides an overview of existing turbulence models. The scheme of combustion of pulverized coal fuel, the construction of a pulverized coal boiler unit and the process of burning coal in the furnace of a boiler unit BKZ-420-140 are considered. We analyzed the existing turbulence models and selected the most optimal mathematical model to study the combustion process of pulverized coal fuel in order to increase the efficiency of the CHPP.

How water vapor and carbon dioxide additives affect oxygen gasification of pulverized coal fuel

The paper analyzes entrained-flow high-oxygen gasification of pulverized coal (a Shell type process)is considered. Water vapor is commonly added to increase the yield of combustible components. This research uses a mathematical model in a one-dimensional stationary approximation to see how adding carbon dioxide and a mixture of carbon dioxide and water vapor to the oxygen flow will affect the process. The paper presents estimates of thermochemical conversion rate (cold gas efficiency), combustible gas content, and completeness of fuel carbon conversion for all the tested configurations. Calculations show that adding carbon dioxide can reduce the specific oxygen consumption of the gasification process whilst ensuring more complete fuel conversion. Adjustments in the water vapor to carbon dioxide ratio help control the gas composition (albeit in a rather narrow range) and the temperature of the raw produced gas at the reaction zone outlet.

Mathematical modelling of the oxyfuel gasification of pulverized coal fuel

In this work, we studied the efficiency of the coal gasification process under oxyfuel conditions. Using mathematical modelling one-dimensional stationary statement, the optimal parameters of coal processing were determined, air and oxyfuel conditions are compared. The calculated dependences of the characteristics of the gasification process on the stoichiometric ratio at different initial temperatures are constructed. The optimal values of oxygen stoichiometric ratio and the maximum values of cold gas efficiency in the selected range of parameters are determined. The contribution of the thermophysical and reactive properties of the gasification agent to the change in the cold gas efficiency is estimated.

DIAGNOSTIC OF THE COMBUSTION PROCESS USING THE ANALYSIS OF CHANGES IN FLAME LUMINOSITY

Monitoring of the combustion process is carried out in order to ensure its efficiency and stability. Selected aspects of the combustion process diagnostics using the analysis of changes in flame luminosity for two configurations: 100% pulverized coal fuel and a mixture of 80% coal and 20% biomass were presented in the article. The analysis of measurement data was conducted using selected statistical tools and a multiresolution analysis of signals.

Mastering technology of blast furnace iron smelting using pulverized-coal fuel in the PAO NLMK BF shop № 2

Application of pulverized-coal fuel (PCF) for coke saving is strategic direction of energy costs decreasing for iron smelting in PAO NLMK blast furnaces, which allows to change the structure of coals supply to the plant and to decrease their summarized consumption. Stages of the technology mastering considered, including period of adjusting the PCF preparation and their supplying to the blast furnaces and at the stage of charging system selection and blast regime adjustment ensuring the maximum degree of CO utilization and the specified performance. Analysis of the dynamics of coke consumption and fuel additives showed that the consumption of total carbon fuel remained almost unchanged, despite the difference in the amount of carbon supplied with natural gas and with the PCF. Calculations made by the mathematical model showed that with an increase in the PCF consumption and a decrease in the consumption of natural gas, the replacement rate of coke with natural gas increased by an average of 0.09 kg of coke per 1 cubic meter of natural gas. As a result of the iron smelting technology mastering, in the PAO NLMK BF № 2 a specific coke consumption decrease reached by more than 80 kg/t of iron and natural gas consumption decrease by more than 60 m3/t of iron. The conditions were revealed for the blast furnaces to operate as with minimum coke consumption and with maximum intensity. The blast furnaces operation in the determined regime parameters allow to decrease the fuel costs for iron production.

Exergy analysis of silicon content in hot metal and its temperature influence on energy efficiency of “BF shop – BOF shop” complex operation

Application of pulverized-coal fuel in BF production results in changes of blast furnace heat operation, in particular, in hot metal temperature and silicon content in it changes, that effects the energy efficiency of “BF shop – BOF shop” complex operation. Isolated consideration of energy utilization by facilities (blast furnace, basic oxygen furnace) without taking into account their energy-technological ties does not provide steel smelting rational solutions obtaining. An exergy analysis of silicon content in hot metal and its temperature influence on energy efficiency of “BF shop – BOF shop” complex operation accomplished by application of the elaborated method of calculation of complete energy balance of “BF shop – BOF shop” system under existing conditions of pulverized-coal fuel application in Ukraine. It was shown, that silicon content decreasing down to level, which does not allow malfunctions of BF heat operation is strategically important for improving of energy efficiency of “BF shop – BOF shop” complex operation under conditions of pulverized-coal fuel application in BF production. It was determined, that under conditions of pulverized-coal fuel application in “BF shop – BOF shop” system, silicon content in hot metal decrease by 0.1% results in decreasing of exergy losses by 18–180 MJ/ton of steel, which is equivalent to standard fuel consumption decrease by 0.5–6.0 kg/ton of steel, increase of hot metal production by ~0.3–1.2 %. Hot metal temperature in blast furnace increase by 50 °С results in exergy losses decrease by 26–29 MJ/ton of steel, which is equivalent to standard fuel decrease by 0.9–1.0 kg/ton of steel.

Method for determining blast furnace tuyere zone blackness degree on pulverized coal fuel injection

Pulverized coal fuel (PCF) supply is one of the modern methods of improving the cast iron production technology in blast furnaces (BF). It has a significant effect on the heat exchange in the tuyere zone (TZ). The known method of radiant heat transfer calculation in TZ accounts only for the ash particle effect on the TZ blackness degree. The aim of this work is to develop a method for determining TZ blackness degree and to investigate the effect of different factors on this value. The work was based on the elements of the proven method of calculating heat exchange in boiler furnaces. Parametric sensitivity was investigated by alternately simulating an error in each of the input values and determining its effect on the sought value. By analysing the processes, the authors have derived dependences for obtaining the concentration of ash particles and triatomic gases and determined the degrees of TZ blackness by Bouguer’s law simultaneously taking into account the radiation of the burning coke and ash particles, and triatomic gases. It has been established that an increase in the PCF consumption from 0 to 250 kg/t of pig iron changes the TZ blackness degree from 0,067 to 0,243; and a 1 % increase in the pressure, concentration of triatomic gases, ray effective length, TZ temperature and ash particle size changes the TZ blackness by 0,714 %, 0,151 %, 0,72 %, –1,557 % and –0,176 %, respectively. The calculations have shown that the effects of coke particles, triatomic gases and ash particles on the sought value are approximately equal. In contrast, when the conventional method is applied, it results in an approximately 2-time underestimation of the values, while even for evaluation calculations, the maximum permissible error is 10–15 %. The developed method accounting for all factors has the maximum error of 5 %. It is important for designing tuyeres and TZ refrigerators.