Combustion characteristics and kinetic analysis of co-combustion between bag dust and pulverized coal

The combustion characteristics of blast furnace bag dust(BD) and three kinds of coal—Shenhua(SH) bituminous coal, Pingluo(PL) anthracite, and Yangquan(YQ) anthracite—were obtained via non-isothermal thermogravimetry. The combustion characteristics with different mixing ratios were also investigated. The physical and chemical properties of the four samples were investigated in depth using particle size analysis, Scanning electron microscopy, X-ray diffraction, X-ray fluorescence analysis, and Raman spectroscopy. The results show that the conversion rate of the three kinds of pulverized coals is far greater than that of the BD. The comprehensive combustion characteristics of the three types of pulverized coals rank in the order SH > PL > YQ. With the addition of BD, the characteristic parameters of the combustion reaction of the blend showed an increasing trend. The Coats–Redfern model used in this study fit well with the experimental results. As the BD addition increased from 5 wt% to 10 wt%, the activation energy of combustion reactions decreased from 68.50 to 66.74 k J/mol for SH, 118.34 to 110.75 kJ/mol for PL, and 146.80 to 122.80 kJ/mol for YQ. These results also provide theoretical support for the practical application of blast furnace dust for blast furnace injection.

Comparison of kinetic models for isothermal CO_2 gasification of coal char–biomass char blended char

This study investigated the isothermal gasification reactivity of biomass char （BC） and coal char （CC） blended at mass ratios of 1：3, 1：1, and 3：1 via isothermal thermogravimelric analysis （TGA） at 900, 950, and 1000℃ under CO2. With an increase in BC blending ra- tio, there were an increase in gasification rate and a shortening of gasification time. This could be attributed to the high specific surface area of BC and the high uniformity of carbon structures in CC when compared to those in BC. Three representative gas-solid kinetic models, namely, the volumetric model （VM）, grain model （GM）, and random pore model （RPM）, were applied to describe the reaction behavior of the char. Among them, the RPM model was considered the best model to describe the reactivity of the char gasification reaction. The activa- tion energy of BC and CC isothermal gasification as determined using the RPM model was found to be 126.7 kJ/mol and 210.2 kJ/mol, re- spectively. The activation energy was minimum （123.1 kJ/mol） for the BC blending ratio of 75%. Synergistic effect manifested at all mass ratios of the blended char, which increased with the gasification temperature.

Basic characteristics of Australian iron ore concentrate and its effects on sinter properties during the high-limonite sintering process

The basic characteristics of Australian iron ore concentrate (Ore-A) and its effects on sinter properties during a high-limonite sintering process were studied using micro-sinter and sinter pot methods. The results show that the Ore-A exhibits good granulation properties, strong liquid flow capability, high bonding phase strength and crystal strength, but poor assimilability. With increasing Ore-A ratio, the tumbler index and the reduction index (RI) of the sinter first increase and then decrease, whereas the softening interval (Delta T) and the softening start temperature (T (10%)) of the sinter exhibit the opposite behavior; the reduction degradation index (RDI+3.15) of the sinter increases linearly, but the sinter yield exhibits no obvious effects. With increasing Ore-A ratio, the distribution and crystallization of the minerals are improved, the main bonding phase first changes from silico-ferrite of calcium and aluminum (SFCA) to kirschsteinite, silicate, and SFCA and then transforms to 2CaO center dot SiO2 and SFCA. Given the utilization of Ore-A and the improvement of the sinter properties, the Ore-A ratio in the high-limonite sintering process is suggested to be controlled at approximately 6wt%.

Effect of ash on coal structure and combustibility

Four bituminous coals and one anthracite were used in this study.On the basis of the similar volatile matter contents of the four bituminous coals,the effects of ash in coal on the microstructure,carbonaceous structure,and chemical composition of pulverized coal were studied.Thermogravimetric analysis was used to study the effect of the addition of anthracite on the combustibility of four different bituminous coals.The results showed that with the increase of ash content in pulverized coal,the microstructure of carbon particles in coal was not much different.However,the analysis results of Raman spectroscopy and X-ray diffraction pattern showed that as the ash content increased,the degree of graphitization of coal carbonaceous structure gradually decreased.The combustibility of the four bituminous coals were better than that of the anthracite.When bituminous coal and anthracite were mixed and burned,the combustibility of the mixed sample decreased as the ash content increased.

Reduction behavior and kinetics of vanadium–titanium sinters under high potential oxygen enriched pulverized coal injection

In this work, the reduction behavior of vanadium–titanium sinters was studied under five different sets of conditions of pulverized coal injection with oxygen enrichment. The modified random pore model was established to analyze the reduction kinetics. The results show that the reduction rate of sinters was accelerated by an increase of CO and H2contents. Meanwhile, with the increase in CO and H2contents, the increasing range of the medium reduction index (MRE) of sinters decreased. The increasing oxygen enrichment ratio played a diminishing role in improving the reduction behavior of the sinters. The reducing process kinetic parameters were solved using the modified random role model. The results indicated that, with increasing oxygen enrichment, the contents of CO and H2in the reducing gas increased. The reduction activation energy of the sinters decreased to between 20.4 and 23.2 kJ/mol. © 2017, The Author(s).

Kinetics of petroleum coke/biomass blends during co-gasification

The co-gasification behavior and synergistic effect of petroleum coke, biomass, and their blends were studied by thermogravimetric analysis under CO2 atmosphere at different heating rates. The isoconversional method was used to calculate the activation energy. The results showed that the gasification process occurred in two stages： pyrolysis and char gasification. A synergistic effect was observed in the char gasification stage. This effect was caused by alkali and alkaline earth metals in the biomass ash. Kinetics analysis showed that the activation energy in the pyrolysis stage was less than that in the char gasification stage. In the char gasification stage, the activation energy was 129.1–177.8 k J/mol for petroleum coke, whereas it was 120.3–150.5 k J/mol for biomass. We also observed that the activation energy calculated by the Flynn–Wall–Ozawa（FWO） method were larger than those calculated by the Kissinger–Akahira–Sunosen（KAS） method. When the conversion was 1.0, the activation energy was 106.2 k J/mol when calculated by the KAS method, whereas it was 120.3 k J/mol when calculated by the FWO method.

Infiltration behavior of sintering liquid on nuclei ores during low-titanium ore sintering process

Sinter strength is dependent not only on the self-intensity of the residual rude and bonding phase but also on the bonding degree between them. The infiltration behavior of sintering liquid on nuclei ores influences the bonding degree, which ultimately determines the sinter strength. Infiltration tests were conducted using micro-sinter equipment. The infiltration area index of original liquid（IAO）, infiltration volume index of secondary liquid（IVS）, and sinter body bonding strength（SBS） were proposed to study the melt infiltration behavior. The results show that the IVS first increases and then decreases with increasing TiO2 content in adhering fines, whereas the IAO exhibits the opposite behavior. Compared with the original liquid, the secondary liquid shows lower porosity, smaller pores, and more uniform distribution. The SBS increases first and then decreases with increasing IAO and TiO2 content, and reaches a maximum when the IAO and TiO2 contents are approximately 0.5 and 2.0wt%, respectively. The SBS first increases and then tends to be stable with increasing IVS. The TiO2 content is suggested to be controlled to approximately 2.0wt% in low-titanium ore sintering.

Combustion characteristics and kinetics of anthracite with added chlorine

The combustion process of Yangquan anthracite（YQ） with the addition of 0.045wt%, 0.211wt%, 1.026wt%, and 2.982wt% chlorine was investigated using a thermogravimetric method from an ambient temperature to 1173 K in an air atmosphere. Results show that the YQ combustion characteristics are not significantly affected by an increase in chlorine content. Data acquired for combustion conversion are then further processed for kinetic analysis. Average apparent activation energies determined using the model-free method（specifically the KAS method） are 103.025, 110.250, 99.906, and 110.641 k J/mol, respectively, and the optimal kinetic model for describing the combustion process of chlorine-containing YQ is the nucleation kinetic model, as determined by the z（α） master plot method. The mechanism function of the nucleation kinetic model is then employed to estimate the pre-exponential factor, by making use of the compensation effect. The kinetic models to describe chlorine-containing YQ combustion are thus obtained through advanced determination of the optimal mechanism function, average apparent activation energy, and the pre-exponential factor.

Recombination-induced voltage-dependent photocurrent collection loss in CdTe thin film solar cell

Recently, the efficiency of CdTe thin film solar cell has been improved by using new type of window layer Mg_(x)Zn_(1-x)O(MZO). However, it is hard to achieve such a high efficiency as expected. In this report a comparative study is carried out between the MZO/CdTe and CdS/CdTe solar cells to investigate the factors affecting the device performance of MZO/CdTe solar cells. The efficiency loss quantified by voltage-dependent photocurrent collection efficiency(ηC(V′)) is 3.89% for MZO/CdTe and 1.53% for CdS/CdTe solar cells. The higher efficiency loss for the MZO/CdTe solar cell is induced by more severe carrier recombination at the MZO/CdTe p-n junction interface and in CdTe bulk region than that for the CdS/CdTe solar cell. Activation energy(Ea) of the reverse saturation current of the MZO/CdTe and CdS/CdTe solar cells are found to be 1.08 e V and 1.36 e V, respectively. These values indicate that for the CdS/CdTe solar cell the carrier recombination is dominated by bulk Shockley-Read-Hall(SRH) recombination and for the MZO/CdTe solar cell the carrier recombination is dominated by the p-n junction interface recombination. It is found that the tunneling-enhanced interface recombination is also involved in carrier recombination in the MZO/CdTe solar cell. This work demonstrates the poor device performance of the MZO/CdTe solar cell is induced by more severe interface and bulk recombination than that of the CdS/CdTe solar cell.

Benefits of Daily Intake Tea on Human Health

The recent research achievements about the mechanisms of beneficial health effects of tea polyphenols and the epidemiological investigation on anti-cancer,anti-cardiovascular diseases,and anti-obesity through tea consumption were reviewed.It is proved that reactive oxygen species is the main reason to induce cell mutation,DNA damage,obesity,high blood pressure and many kinds of cancers.Tea catechins and theaflavins have excellent bioactivity on scavenging ROS due to their characteristic structure feature of phenolic hydroxyl group,which means drinking tea could prevent diseases.Epidemidogical investigations also showed that tea consumption could reduce the risk of lung cancer,gastric cancer,bladder cancer,and so on.However,the frequency of tea drinking or tea consumption amounts significantly affected the prevention efficiency.The epidemiologic investigations also find that drink green tea,especial black tea is useful to modify the cardiovascular diseases.In vivo and vitro tests showed that tea supplement could moderate the metabolism of blood lipid and prevent obesity.These indicated that tea and tea extracts might reduce the risk of many diseases.

Effects of Brewing Conditions on Quality of Pu'erh Tea Infusion

To brew tea correctly is very important to absorb the tea nutrition for people.The dynamic changes of the main compositions in brewing Pu'erh tea processing with different conditions were studied.Three different temperatures and eight times were designed to study the effects on the tea infusion quality.The index t0.5min(50%concentration of compounds in tea infusion) was used to evaluate the extract speed of compound in this experiment.The results showed that caffeine solubility speed at 80℃ was the highest to compare with tea polyphenols,amino acid,caffeine,soluble sugar,theaflavins and theabrownine,t0.5min of caffeine was 4.8 min,amino acid 10.3min was the second,the third one was tea polyphenols,soluble sugar was the lowest.We also found in different infusion temperature the t0.5min of compounds was distinguishing.With increasing the temperature all t0.5min of six compounds were shorter.However,the change regulations of t0.5min for all compounds in 90℃ and 100℃ were similar to in 80℃.Total quality score(TQS) were applied to evaluate the quality of tea infusion.The results found the TQS score of infusion was higher with the temperature rising,and the temperature to brew best quality infusion was 100℃ for 4-5min.According to the multiple regression analysis between sensory assessments and chemical components of Pu'erh tea we suggested the TQS was mainly affected by theaflavins,amino acid,soluble sugar and theabrowine four factors in 100℃.

Comprehensive evaluation of sintering basic characteristics of iron ore based on grey relational analysis

Sintering basic characteristics of fourteen iron ores were comprehensively evaluated using micro-sinter and grey relational analysis methods. The results show that magnetite has a low assimilability, high bonding phase strength, and high crystal strength. Hematite presents a good assimilability, while limonite exhibits a strong assimilability, but the bonding phase strength and crystal strength of these two kinds of iron ores are comparatively low. Great difference in liquid flowability exists for the same kind of iron ores. When the assimilation temperature of the sinter mixture is too high, limonite can be added;when the bonding phase strength or crystal strength of the sinter mixture is too low, magnetite can be added. The liquid fluidity of the sinter mixture can be adjusted according to the ratios of corresponding iron ores. Grey relational analysis is an effective method to evaluate the comprehensive sintering characteristics of iron ores, which can provide theoretical basis for the purchasing department of the steel enterprises.

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 heat- ing rate （A）, non-isothermal multiple heating rate （B）, and isothermal test （C）, were conducted to calculate the ki- netic 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 combus- tion temperature, the combustion process changed from kinetic control to diffusion control. For isothermal combus- tion, the combustion process was kinetically controlled at temperature lower than 580 ℃ for bituminous coal char and at temperature lower than 630 ℃ for anthracite char.

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

According to different energy utilization in different regions, blast furnace is divided into raceway zone, bottom heat exchange zone （BHZ）, thermal reserve zone （TRZ）, and top heat exchange zone （THZ）, and a mathe- matical 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 recy- cling top gas in lower area of 295 ma/t. Energy balances are reached in different regions. Theoretical combustion temperature （TCT） in raceway zone is largely affected by different 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 tradi- tional blast furnace, in NF-BF, the emission of CO2 would be reduced by 45.91% and 49.02G 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.

The application of digital technology in BEPCII RF system

Background The Beijing Electron Positron Collider(BEPCII)is a high-brightness collider and operates in compatible mode of synchronous light source.This summer,BEPCII spare cavity,which was all made in China,had been put into BEPCII operation,and the LLRF system for the spare cavity was also upgraded at the time.Purpose The purpose is to stably control the amplitude and phase of the spare cavity and apply digital technology to achieve some intelligent functions.Methods The digital method is applied in the superconducting cavity feedback control of the accelerator and it introduces the digital technology of the RF low-level control system that has been stably applied to the BEPCII spare cavity operation.In addition,some functions such as quench detector and input protection as well as horizontal test have been realized in the RF system operation.Results The amplitude and phase stabilities of cavity voltage with beam in the digital LLRF have reached±0.09%(RMS)and±0.055°(RMS),respectively.Conclusion The BEPCII spare cavity with digital LLRF system has been stably operated for 2 months.The DLLRF system has been reliable and stable,and the performance of the spare cavity with beam was very good.

Experimental research on semi-coke for blast furnace injection

The combustion properties and grindability of Shenmu low-rank coal(SM)and its four different semi-cokes were studied by the self-designed equipment and Hardgrove method.The four semi-cokes were obtained under the pyrolysis temperature of 400,500,600 and 700℃,named as SM-400,SM-500,SM-600 and SM-700,respectively.The analyses of nitrogen adsorp-tion,Fourier-transform infrared spectroscopy(FTIR)spectra and Raman spectra were carried out to explain the change in combustion ratio and grindability.The result showed that the specific surface area of samples had an essential effect on the combustion ratio of SM-400 and SM-500.Meanwhile,the grindability depended on the strength of coal matrix,and the augment of pore amounts would increase the grindability.The functional groups and graphitization degree of the same sam-ple were identical with the combustion ratio.With the pyrolysis upgrading temperature increasing,the combustion ratio of sample decreased,corresponding to the decrease in the benzene ring and the increase in graphitization degree.In addition,the thermogravimetric analysis was carried out,and the result was compared against what was shown in the data of com-bustion ratio.For pulverized coal injection,the combustion ratio was more intuitive and more accurate than combustibility.

Non-isothermal study of gasification process of coal char and biomass char in CO_2 condition

Non-isothermal method was used to study gasification characteristics of three coal chars and one biomass char.Four chars were made from anthracite coal（A）,bituminous coal（B）,lignite coal（L）,and wood refuse（W）,respectively.The gasification process was studied by random pore model（RPM）,unreacted core model（URCM）and volumetric model（VM）.With an increase in metamorphic grade,the gasification reactivity of coal char decreased,and the gasification reactivity of biomass char was close to that of low metamorphic coal char.With an increase in heating rate,the gasification of all samples moved towards high temperature zone,and the whole gasification time decreased.It was concluded from kinetics analysis that the above-mentioned three models could be used to describe the gasification process of coal char,and the RPM fitted the best among the three models.In the RPM,the activation energies of gasification were193.9,225.3 and 202.8 kJ/mol for anthracite coal char,bituminous coal char and lignite coal char,respectively.The gasification process of biomass char could be described by the URCM and VM,while the URCM performed better.The activation energy of gasification of wood refuse char calculated by the URCM was 282.0 kJ/mol.

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 thermogravimetrie 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.

Gasification reactivity and kinetic parameters of coal chars for non-isothermal steam gasification

The gasification reactivity and kinetic parameters of coal chars for non-isothermal steam gasification were investigated.One kind of lignite and three kinds of bituminous coals were used as the samples,and their coal ranks follow the ascending order:XB<KL<ZJ<GD.As characterized by the comprehensive gasification index,the gasification reactivity of coal chars follows the descending order:XB>KL>ZJ>GD.Through systematically analyzing factors affecting gasification reactivity,it was ascertained that the gasification reactivity is mostly determined by the carbonaceous structure.The gasification reactivity is inversely proportional to the coal rank,and the higher the coal rank,the lower the gasification reactivity.A new kinetic model was proposed to calculate the kinetic parameters,in which the reaction order was considered as an unknown kinetic parameter.The reaction order n follows the ascending order:XB<KL<ZJ<GD,which are n=1.00,n=1.34,n=1.83,and n=2.63,respectively.It is proved that the reaction order is proportional to the coal rank,and the higher the coal rank,the higher the reaction order.