Jiu-gang Shao

Study on CO2 gasification properties and kinetics of biomass chars and anthracite char

The CO2 gasification properties and kinetics of three biomass chars (WS-char, RL-char and PS-char) and anthracite char (AC-char) were investigated by thermogravimetric analysis method. Three nth-order representative gas-solid reaction models, random pore model (RPM), volume reaction model (VM) and unreacted core model (URCM) were employed to describe the reactive behavior of chars. Results show that gasification reactivity order of different chars from high to low was WS-char, PS-char, RL-char and AC-char. In addition, the chemical components as well as physical structures of four chars were systematically tested. It was found that gasification properties of char were determined by carbonaceous structure. It was concluded from kinetics analysis that RPM model was the best model for describing the reactivities of biomass chars and VM was the model that best fitted the gasification process of anthracite char. The activation energies obtained for the biomass and anthracite char samples lie in the range of 236.4-284.9 kJ/mol.

Thermogravimetric Analysis of Coal Char Combustion Kinetics

Four chars prepared from pulverized coals were subjected to non-isothermal and isothermal combustion tests in a thermogravimetric analysis (TGA) device. Three different test methods, i. e., non-isothermal single heating rate (A), non-isothermal multiple heating rate (B), and isothermal test (C), were conducted to calculate the kinetic parameters of combustion of coal char. The results show that the combustion characteristics of bituminous coal char is better than that of anthracite char, and both increase of heating rate and increase of combustion temperature can obviously improve combustion characteristics of coal char. Activation energies of coal char combustion calculated by different methods are different, with activation energies calculated by methods A, B and C in the range of 103. 12–153. 77, 93. 87–119. 26, and 46. 48–76. 68 kJ/mol, respectively. By using different methods, activation energy of anthracite char is always higher than that of bituminous coal char. In non-isothermal tests, with increase of combustion temperature, the combustion process changed from kinetic control to diffusion control. For isothermal combustion, the combustion process was kinetically controlled at temperature lower than 580 °C for bituminous coal char and at temperature lower than 630 °C for anthracite char.

Comprehensive Mathematical Model and Optimum Process Parameters of Nitrogen Free Blast Furnace

According to diferent energy utilization in diferent regions, blast furnace is divided into raceway zone, botom heat exchange zone (BHZ), thermal reserve zone (TRZ), and top heat exchange zone (THZ), and a mathematical model of nitrogen free blast furnace (NF-BF) is established. The optimum process parameters of two kinds of nitrogen free blast furnaces are calculated by the new mathematical model. The results show that for the nitrogen free blast furnace with a single row of tuyeres, the optimum process parameters are coke ratio of 220 kg/t, coal ratio of 193 kg/t, and volume of recycling top gas of 577 m3/t; for two rows of tuyeres, the process parameters are coke ratio of 202 kg/t, coal ratio of 211 kg/t, volume of recycling top gas in upper area of 296 m3/t, and volume of recycling top gas in lower area of 295 m3/t. Energy balances are reached in diferent regions. Theoretical combustion temperature (TCT) in raceway zone is largely afected by diferent processes, and a lower TCT should be adopted for the single row of tuyeres, but for two rows of tuyeres, a higher TCT should be maintained Compared with traditional blast furnace, in NF-BF, the emission of CO2 would be reduced by 45.91% and 49.02% for a single row of tuyeres and two rows of tuyeres, respectively, and combined with CO2 sequestration technology, zero emission of CO2 could be realized.

Combustion Property and Kinetic Modeling of Pulverized Coal Based on Non-Isothermal Thermogravimetric Analysis

Non-isothermal combustion kinetics of two kinds of low volatile pulverized coals (HL coal and RU coal) were investigated by thermogravimetric analysis. The results show that the combustibility of HL coal was better than that of RU coal, and with increasing heating rate, ignition and burnout characteristics of pulverized coal were improved. The volume model (VM), the random pore model (RPM), and the new model (NEWM) in which the whole combustion process is considered to be the overlapping process of volatile combustion and coal char combustion, were used to fit with the experimental data. The comparison of these three fitted results indicated that the combustion process of coal could be simulated by the NEWM with highest precision. When calculated by the NEWM, the activation energies of volatile combustion and coal char combustion are 130.5 and 95.7 kJ • mol−1 for HL coal, respectively, while they are 114.5 and 147.6 kJ • mol−1 for RU coal, respectively.

Pulverized Coal Combustion of Nitrogen Free Blast Furnace

The efficiency of coal combustion is an important factor for the blast furnace process. The influence of low xo/xc on coal combustion performance under nitrogen free blast furnace condition was researched through the self-developed pulverized coal burning device. The results show that the coal combustion rate reduces with xo/xc decreasing, and the combustion rate of bituminous coal is higher than that of anthracite. The coal combustion rate ascends with the rise of volatile matter, but when volatile matter of pulverized coal is more than 18%, the combustion rates will not increase correspondingly. Small amount of CaCO3 and CO2 additions can promote coal combustion, and the effect of CaCO3 is more apparent, which can increase the pulverized coal combustion rate by 15%–18% or so.

A Modified Random Pore Model for Gasification Kinetics of Coal Char and Biomass Char

Gasification is a well-known reaction owing to its relevance to generation of sustainable energy from biomass. The present paper attempts to experimentally investigate the kinetics of coal char (CC) and biomass char (BC) gasification using carbon dioxide (CO2) in a controlled environment using Thermo Gravimetric Analyzer (TGA) at different temperature. The random pore model (RPM) and a modified random pore model (MRPM) proposed in this paper were used to investigate gasification kinetics of CC and BC. It was clarified that gasification reactivity of BC is superior to that of CC and gasification reactivity of both chars were improved with increase of temperature, while the influence of temperature on biomass char gasification reactivity is more obvious. Kinetic analysis showed that, since the CC particles were approximately spherical in the shape, the RPM model and the MRPM model could both be used to characterize its gasification process, but flake-like BC gasification process could only be explained by the MRPM. The activation energy for CC and BC using the MRPM are 194.3kJ/mol and 123.3kJ/mol, respectively.

Rules of Assimilation of Single Ore and Mixed Ores

Assimilation behaviors of 7 kinds of iron ores from Australia, Brazil, India, South Africa and China were evaluated and analyzed. On the basis of that, four ore blending principles were proposed, and seven groups of iron ore powder blending schemes were designed. The ores of different types or from different places are shown apparently different in assimilation. The assimilation of hematite in Australia, Brazil and India is relatively high, but the assimilation of magnetite in South Africa and China and specularite in China is relatively low. The assimilation of the ores has negative correlation with MgO content and binary basicity, while the assimilation of the ores has positive correlation with porosity, SiO2 and Al2O3 contents, and crystal water. The iron ores with smaller crystal size and microstruc ture looseness have relatively higher assimilation. Assimilation of mixed ores has relationship of linear, arch and “S” types to the ratio of single iron ore powder. When the charge ratio of ore is less than 25%, it possesses additivity, providing theoretical basis for optimization of ore matching.

Experiments and Kinetics Modeling for Gasification of Biomass Char and Coal Char under CO2 and Steam Condition

Gasification behaviors of biomass char and coal char were analyzed by thermal gravimetric method, and influences of gasification temperature and different gasifying agents were investigated. At the same time, kinetics of char gasification under CO2 condition and steam condition were investigated by Chou model. Under the same condition, gasification characteristics of biomass char are better than that of coal char, and meanwhile performance of steam is better than CO2 as gasifying agent. From kinetics analysis, among 1173~1323K range, gasification of biomass char and coal char is under chemical reaction control both for steam and CO2 condition. Gasification process of biomass char could be simulated by flat particle gas-solid reaction of Chou model, with activation energy as 113.7kJ/mol and76.4kJ/mol for CO2 and steam condition respectively; gasification of coal char could be simulated by spherical particle gas-solid reaction of Chou model, with activation energy 182.6kJ/mol and160.9kJ/mol for CO2 and steam condition respectively.

Study for Influence of Prereduction Degree on the Softening and Melting Properties of Sinter

Softening and melting properties of sinter depends not only on the composition and nature of the iron ore itself, but also by the degree of prereduction. In this paper, according to the curve of reduction degree changes over time at temperature of 900°C, flow of reaction gas, composition of reaction gas, reaction time and reaction temperature were got in order to make the sinter different prereduction degree. Then, on this basis, influence of prereduction degrees on the softening and melting properties of sintering ore was studied using the method of continuous test in the same container by metallurgical properties of softening temperature, melting temperature, softening interval, melting interval and air permeability.