Effects of Flame Temperature and SiCl_4 Concentration on Particle Characteristics for Synthetic Silica Glass

Effects of flame temperature and SiCl4 concentration on the particle characteristics were studied.The flame temperature distributions were measured using modified sodium line-reversal technology.The particles were collected by quartz supports and were analyzed by scanning electron microscope（SEM） at different locations along the flame centerline.When the SiCl4 concentration is 16 g/min,the particles first grow and then shrink with the flame temperature increasing.When the SiCl4 concentration is 26 g/min,the flame temperature has little influence on the particle characteristics along the flame and many large spherical particles exist all the way.

A Modified Model for Calculating Theoretical Flame Temperature in Blast Furnace and Its Application

The theoretical flame temperature （TFT） before tuyere, always highly concerned by blast furnace （BF） operators, is one of the most important parameters for evaluating the thermal state of hearth. However, some influ- encing parameters, for example, the SiO2 reduction by carbon, were always neglected or inaccurate when calculating the TFT. According to the definition of TFT, the temperature of coke into raceway and the reduction rate of SiO2 in ash of coke and pulverized coal were obtained by analyzing the samples before tuyere in blast furnace. Taking full ac- count of different factors, a modified model for calculating the TFT in blast furnace was established. The effects of the oxygen enrichment rate, the reduction rate of SiO2 in raceway, the ash content in coke and pulverized coal and the pulverized coal injection （PCI） rate on TFT were determined quantitatively. The modified model was applied to selecting the used coal for PCI in blast furnace. Considering the different SiO2 contents of mixed coal, the calculated TFT remained a stable level. This showed that the selected coal could be suitable for PCI in blast furnace.

Effect of CO_(2) dilution on laminar burning velocities,combustion characteristics and NO_(x) emissions of CH_(4)/air mixtures

The laminar combustion characteristics of CH_(4)/air premixed flames with CO_(2) addition are systemically studied.Experimental measurements and numerical simulations of the laminar burning velocity(LBV)are performed in CH_(4)/CO_(2)/Air flames with various CO_(2) doping ratio under equivalence ratios of 1.0–1.4.GRI 3.0 mech and Aramco mech are employed for predicting LBV,adiabatic flame temperature(AFT),important intermediate radicals(CH_(3),H,OH,O)and NO_(x) emissions(NO,NO_(2),N2O),as well as the sensitivity analysis is also conducted.The detail analysis of experiment and simulation reveals that as the CO_(2) addition increases from 0%to 40%,the LBVs and AFTs decrease monotonously.Under the same CO_(2) doping ratio,the LBVs and AFTs increase first and then decrease with the increase of equivalence ratio,and the maximum of LBV is reached at equivalence ratio of 1.05.The mole fraction tendency of important intermediates and NO_(x) with equivalence ratio and CO_(2) doping ratio are similar to the LBVs and AFTs.Reaction H+O_(2)⇔O+OH is found to be responsible for the promotion of the generation of important intermediates and NO_(x) under the equivalence ratios and CO_(2) addition through sensitivity analysis.The sensitivity coefficients of elementary reactions that the increasing of CO_(2) doping ratio promotes or inhibits formation of intermediate radicals and NO_(x) decreases.

Investigation over the recirculation influence on the combustion of micro organic dust particles

This paper investigates the role of recircnlation and non-unity Lewis number on the combustion of organic dust particles. Since recirculation effect is more noticeable in micro-combustors, it is necessary to propose a modeling approach of this phenomenon to better simulate the performance of micro-combustors. In this research, in order to model the combustion of organic dust particles, it is assumed that the dust particles va- porize first to yield a known chemical structure which is oxidized in the gas phase, and the chemical structure of this gaseous fuel is assumed methane. To study the flame structure and solve the governing equations, it is considered that the flame structure consists of three zones titled the preheat-vaporization zone, the narrow reaction zone and finally the post flame zone. The recirculation phenomenon is evaluated by entering the exhausted heat from the post flame zone into the preheat zone. The solution is based on the follow- ing approach. First, the governing equations in each zone are nondimensionalized. Then the needed boundary and matching conditions are applied in each zone. After that, these equations and the required boundary and matching conditions are simultaneously solved with the analytical model. Consequently, the remarkable effects of recirculation and non- unity Lewis number on the combustion characteristics of the organic dust particles such as burning velocity and temperature profiles for different particle radii are obtained. The results show reasonable agreement with published experimental data.

Thermodynamic Analysis of Burning Resistivity of Ti-Cr-V-Mo Alloys

Burning resistivities of the Ti Cr V Mo alloys were investigated by means of their adiabatic flame temperatures. Calculated results show that the adiabatic flame temperature of the Ti Cr V Mo alloys is lower than that of the Ti Cr V alloys, most probably due to that the gas products of molybdenum oxide can be easily formed and the sublimation of more oxides leads to the reduction of T af . Therefore, the Ti Cr V Mo alloys would have better burning resistivity and their optimal composition is presented.

Optimization of Flow Parameters for Waste Lubricating Oil Combustion

The global energy demand has continued to skyrocket, exacerbating the already severe energy problem and environmental pollution, prompting researchers to look for alternative energy sources. Exploration of waste lubricating oil (WLO) as an alternative source of fuel has gained prominence among researchers due to its availability at low cost and the potential to generate energy while providing a safer means of disposal. The main challenge with WLO combustion is proper regulation of fuel and oxidizer during combustion to realize a near stoichiometric result. Additionally, WLO has high viscosity, hence preheating of the oil is necessary to lower the viscosity and enhance atomization, for a more efficient combustion process. This paper presents the optimization of flow parameters for combustion of WLO in a burner system by use of response surface methodology (RSM). The effects of air flow rate, injection pressure and fuel flow rate on combustion performance of a WLO burner were investigated. The highest flame temperature recorded was 1200°C at an air flow rate of 1 m3/min, fuel flow rate of 0.08 m3/hr and injection pressure of 20 bar. Tests on physical and chemical properties of WLO were conducted and characterized according to ASTM standard to ascertain its potential as an alternative fuel. The calorific values of WLO from petrol and diesel engines were found to be 41.23 MJ/kg and 42.65 MJ/kg respectively. Therefore, recycling of WLO by utilizing it as a fuel for burners has double benefits of mitigating environmental pollution and harnessing energy for process heating and power generation.

Experimental Study of H_(2)and/or N_(2)Addition Effects on CO/CO_(2)-Air Flames using a Combustion Diagnostic System

In this work,the effects of H_(2)(0–8 vol%)addition,N_(2)(0–8 vol%)addition,and H_(2)/N_(2)(4 vol%/4 vol%)addition in CO/CO_(2)gas flow on the flame structure,flame temperature,and CO_(2)concentration in flames were investigated.A combustion diagnostic system based on tunable diode laser absorption spectroscopy(TDLAS)was utilized to measure the flame temperature and CO_(2)concentration in flames simultaneously.This work simulated the combustion of converter gas(CO/CO_(2)/H_(2)/N_(2))in an industrial turbulent partly premixed burner.The results show that with the addition of H_(2)(0–8 vol%)in CO/CO_(2)flame and the addition of H_(2)(4 vol%)in CO/CO_(2)/N_(2)(4vol%)flame,the flame length is longer than that with the same volume addition of N_(2).The added reactions caused by the addition of H_(2)(4 vol%)in CO/CO_(2)flame and CO/CO_(2)/N_(2)(4 vol%)flame result in a larger high-temperature reaction zone.The enrichment of H_(2)(8 vol%)in CO/CO_(2)/H_(2)(4 vol%)flame,the dilution of N_(2)(0–8 vol%)in CO/CO_(2)flame,and the dilution of N_(2)(4 vol%)in CO/CO_(2)/H_(2)(4 vol%)flame make little difference on the high-temperature reaction zone.The promotion effects of H_(2)addition on CO_(2)formation are more prominent than the dilution effects of N_(2)addition on CO_(2)concentration in flames.

Numerical study of effects of hydrogen addition on methane combustion behaviors

The methane combustion with hydrogen addition can effectively reduce carbon emissions in the iron and steel making industry,while the combustion mechanism is still poorly understood.The oxy-fuel combustion of methane with hydrogen addition in a 0.8 MW oxy-natural gas combustion experimental furnace was numerically studied to investigate six different combustion mechanisms.The results show that the 28-step chemical reaction mechanism is the optimal recommendation for the simulation balancing the numerical accuracy and computational expense.As the hydrogen enrichment increases in fuel,the highest flame temperature increases.Consequently,the chemical reaction accelerates with enlarging the peak of the highest flame temperature and intermediate OH radicals.When the hydrogen enrichment reaches 75 vol.%,the flame front is the farthest,and the flame high-temperature zone occupies the largest proportion corresponding to the most vigorous chemical reactions in the same oxygen supply.

Theoretical Approach to Change Blast Furnace Regime With Natural Gas Injection

The operation of blast furnace using natural gas and oxygen enriched blast （composite blast technology） is considered in many countries to be standard operation for a modern blast furnace particularly in certain countries with cheap and stable supply of natural gas. The theoretical flame temperature （TFT） of combustion and the degree of di-rect reduction of iron oxides （rd） are considered as the main controlling parameters of composite blast technology. The calculated values of these parameters are mainly dependent on the amount of air blast consumption. This amount of air blast is measured before entering into blast stoves, Actually, some of air blast is lost through valves of air stoves. Consequently, the real volume of air blast in the furnace is less than the recorded value by amounts of 5%-15% which is not considered in the estimation of rd and TFT. The purpose is to analyze the different methods for es-timation of air blast inside the blast furnaces and develop a theoretical model to calculate air blast eonsumption with high accuracy. Based on the calculation of air blast consumption, a complete roadmap is demonstrated to change the operation regime parameters of blast furnaces working on composite blast technology.