Physical Properties of Crushed Air-cooled Blast Furnace Slag and Numerical Representation of Its Morphology Characteristics

Physical properties and geometrical morphologies of crushed air-cooled blast furnace slag （SCR） and crushed limestone （LCR） were comparatively investigated. The shape, angularity, surface texture and internal pore structure of aggregate particles for different size and gradation were numerically represented by sphericity （ψ） and shape index （SI）, angularity number （AN）, index of aggregate particle shape and texture （IAPST）, porosity and pore size, respectively. The results show that SCR is a porous and rough aggregate. Apparent density, void, water absorption and smashing index of SCR are obviously higher than those of LCR with the same gradation, respectively. However, bulk density of SCR is lower than that of LCR with the same gradation. SI, AN, IAPST and porosity of SCR are obviously higher than those of LCR with the same gradation, respectively. The smaller particle size of SCR, the larger of its AN, IAPST and porosity.

Application of Air-cooled Blast Furnace Slag Aggregates as Replacement of Natural Aggregates in Cement-based Materials：A Study on Water Absorption Property

The influence of air-cooled blast furnace slag aggregates as replacement of natural aggregates on the water absorption of concrete and mortar was studied, and the mechanism was analyzed. The interface between aggregate and matrix in concrete was analyzed by using a micro-hardness tester, a laser confocal microscope and a scanning electron microscope with backscattered electron image mode. The pore structure of mortar matrixes under different curing conditions was investigated by mercury intrusion porosimetry. The results showed that when natural aggregates were replaced with air-cooled blast furnace slag aggregates in mortar or concrete, the content of the capillary pore in the mortar matrix was reduced and the interfacial structure between aggregate and matrix was improved, resulting in the lower water absorption of mortar or concrete. Compared to the concrete made with crushed limestone and natural river sand, the initial absorption coefficient, the secondary absorption coefficient and the water absorption capacity through the surface for 7 d of the concrete made from crushed air-cooled blast furnace slag and air-cooled blast furnace slag sand were reduced by 48.9%, 52.8%, and 46.5%, respectively.

Effect of Crushed Air-cooled Blast Furnace Slag on Mechanical Properties of Concrete

Morphology characteristics of mix aggregates with crushed air-cooled blast furnace slag（SCR） and crushed limestone（LCR） with 5-20 mm and 20-40 mm gradation were represented by numerical parameters including angularity number（AN） and index of aggregate particle shape and texture（IAPST）.The effect of mix aggregates containing SCR on compressive strength and splitting tensile strength of concrete was investigated.Fracture characteristics of concrete,interfacial structure between aggregates and matrix were analyzed.The experimental results show that porous and rough SCR increases contact area with matrix in concrete,concave holes and micro-pores on the surface of SCR are filled by mortar and hydrated cement paste,which may increase interlocking and mechanical bond between aggregate and matrix in concrete.SCR can be used to produce a high-strength concrete with better mechanical properties than corresponding concrete made with LCR.The increase of AN and IAPST of aggregate may enhance mechanical properties of concrete.

Study on the removal of Hg^0 from flue gas by coal dry powder gasification coarse slag

The prevention and treatment of mercury in coal-fired power plants has always been the focus and difficulty.How to control the pollution of mercury to human body and ecological environment quickly and effectively is a hot research topic nowadays.As a low cost and potential adsorbent,there is a huge space for the development of coal dry powder gasification coarse slag.In this paper,Mercury osmotic tubes are heated by water bath tank as mercury source,and the scavenging effect of adsorbent on Mercury monomer under different influence conditions is explored.The adsorbent plays an important role in adsorption of mercury monomer because of its special active sites on the surface.The reason is that the adsorbent surface is rich in carboxyl group,hydroxyl functional group,combined with mercury to form complexes.This shows that chemical adsorption facilitates the adsorption process.

电弧炉配加直接还原铁对炼钢的影响

通过开展全废钢及配加10%、20%、30%比例直接还原铁(DRI,direct reduced iron)试验研究了Consteel电弧炉配加不同比例DRI对冶炼技术经济指标、钢水洁净度和电弧炉终渣成分的影响,并根据试验情况对金属料加入、吹氧喷碳、造渣辅料加入、排渣等冶炼控制要点进行分析。结果表明,随着DRI加入比例增加,电耗、钢铁料消耗、造渣辅料消耗和渣量等逐渐增加。且DRI加入比例在30%时,因炉渣量较大,在冶炼过程中后期有炉渣从炉门溢出。同时,电弧炉配加DRI后钢水洁净度明显升高,电弧炉冶炼终点氮、磷、硫和残余元素质量分数降低,且随着DRI加入比例增加,电弧炉终点钢水氮质量分数下降速率变小。此外,随着DRI加入比例增加,电弧炉终渣FeO质量分数呈降低趋势。DRI加入比例20%时效果较好,冶炼周期较短,与全废钢炉次相比电耗增加不高,且氮和残余元素含量较低,满足大部分钢种要求。

新型蒸压加气混凝土砌块性能研究

基于容重轻、强度高以及成本低的新型蒸压加气混凝土砌块,通过分析脱硫渣、陶瓷抛光废料、煤化工业固体以及工程泥浆干化泥的化学成分和基本性能,研究了上述工业废弃物制备的新型蒸压加气混凝土的各项基本物理力学性能及其应用前景,合理配合比下的新型蒸压加气混凝土砌块的各项技术指标满足建筑材料的标准要求,存在较为可观的潜在应用前景,对推动建材绿色循环利用具有重要意义。

利用熔铁浴高温粗煤气冶炼DRI的能耗估算

为降低炼铁能耗,本文提出熔铁浴煤制气加热循环还原气生产直接还原铁(DRI)的新工艺,并对过程能耗进行了估算。新工艺流程:DRI炉顶气经除尘、CO变换H2、洗涤降温至25℃后脱S和CO2后,被转化成H2体积分数>90%的循环还原气;利用熔铁浴产生的1300~1700℃的高温粗煤气加热25℃循环还原气至850℃,使V(H)/V(C)(体积比)>1.3,并将还原气送入竖炉冶炼DRI。能耗估算结果表明:新工艺的能耗为329.4 kg标煤/tDRI;若利用转炉富余热量全流程加入30%DRI用于炼钢,与2018年的全国炼钢平均技术指标相比,其能耗降低225.84 kg标煤/t,能源成本降低459元/t;此外,30%DRI加入转炉炼钢比DRI直接加入电炉的能耗降低135.46 kg标煤/t,能源成本降低162元/t。由于利用了高温粗煤气的显热、压力,新工艺的能耗、排放和成本大幅降低。此外,该工艺可低成本回收纯净CO2,利用绿色H2(核能或可再生电力生产的H2)将CO2合成尿素或甲醇后,可以实现CO2零排放。

Self-adaptive PID controller of microwave drying rotary device tuning on-line by genetic algorithms

The control design, based on self-adaptive PID with genetic algorithms(GA) tuning on-line was investigated, for the temperature control of industrial microwave drying rotary device with the multi-layer(IMDRDWM) and with multivariable nonlinear interaction of microwave and materials. The conventional PID control strategy incorporated with optimization GA was put forward to maintain the optimum drying temperature in order to keep the moisture content below 1%, whose adaptation ability included the cost function of optimization GA according to the output change. Simulations on five different industrial process models and practical temperature process control system for selenium-enriched slag drying intensively by using IMDRDWM were carried out systematically, indicating the reliability and effectiveness of control design. The parameters of proposed control design are all on-line implemented without iterative predictive calculations, and the closed-loop system stability is guaranteed, which makes the developed scheme simpler in its synthesis and application, providing the practical guidelines for the control implementation and the parameter design.

Influence of Thermally Treated Flue Gas Desulfurization(FGD) Gypsum on Performance of the Slag Powder Concrete

The feasibility of flue gas desulphurization （FGD） as concrete admixture was studied. A combined concrete admixture of the thermally-treated FGD gypsum and slag powder was explored. The FGD gypsum was roasted at 200℃ for 60 min and then mixed with the slag powder to form FGD gypsum-slag powder combined admixture in which the SO3 content was 3.5wt%. Cement was partially and equivalently replaced by slag powder alone or FGD gypsum-slag powder, at concentration of 25wt%, 40wt%, and 50wt%, respectively. The setting times, hydration products, total porosity and pore size distributions of the paste were determined. The compressive strength and drying shrinkage of cement mortar and concrete were also tested. The experimental results show that, in the presence of FGD gypsum, the setting times are much slower than those of pastes in the absence of FGD gypsum. The combination of FGD gypsum and slag powder provides synergistic benefits above that of slag powder alone. The addition of FGD gypsum provides benefit by promoting ettringite formation and forms a compact microstructure, increasing the compressive strength and reduces the drying shrinkage of cement mortar and concrete.

DRI钛渣制备钛白粉新工艺研究

DRI钛渣活性强,品位较高,便于实现钛的回收利用,可以代替钛铁矿生产钛白粉,是硫酸法钛白的发展趋势。然而,相对于钛铁矿来说,DRI钛渣的铁含量明显减少,钙镁铝含量提高明显,不能直接应用于现有的硫酸法钛白工艺。针对DRI工艺钛渣的工艺矿物学特征进行钛白粉制备新工艺的探索试验,成功开发了原料预除杂与硫酸法钛白相结合、以及酸解液沉铝与硫酸法钛白相结合的新工艺,均可制得高品质的钛白粉。

DRI钛渣制备高钛渣新工艺研究

传统高炉工艺流程处理钒钛磁铁矿,钛资源回收率低。针对气基竖炉还原—电炉熔分的非高炉冶炼工艺得到熔分钛渣,开展DRI钛渣提质生产高钛渣的方案探索和尝试,成功开发了HCl加压浸出—碱浸工艺和NaOH/Na_2CO_3活化焙烧—浸出分离工艺,均可获得满足氯化钛白要求的高钛渣。

Distribution optimization of circulating water in air-cooled heat exchangers for a typical indirect dry cooling system on the basis of entransy dissipation

The flow and heat transfer of air-cooled heat exchangers play important roles in the performance of indirect dry cooling systems in power plants,so it is of benefit to the design and operation of a typical indirect dry cooling system to optimize the thermo-flow characteristics of air-cooled heat exchangers.The entransy dissipation method is applied to the performance optimization of air-cooled heat exchangers in this paper.Two irreversible heat transfer processes in air-cooled heat exchangers,the heat transfer between circulating water and cooling air and the mixing of circulating water,are taken into account and analyzed by means of the entransy dissipation method.The total entransy dissipation rate,which connects the geometrical parameters of air-cooled heat exchanger sectors and the heat capacity rates of the fluids to the heat flow rate in every sector,is obtained.Based on the mathematical relation and the conditional extremum method,an optimization equation group is derived,by which the air-cooled heat exchanger with known air-side parameters is optimized,showing that the entransy dissipation based optimization approach can contribute to the distribution optimization of circulating water in air-cooled heat exchangers of a typical indirect dry cooling system.

Thermo-Flow Performances for the Main-Auxiliary Integrated Natural Draft Dry Cooling System

Recently,natural draft dry cooling system with the main-auxiliary integrated air-cooled heat exchangers in the up and lower layers,has drawn attention to the electric power industry.This research firstly develops two physical models for the integrated cooling system,namely Case A and Case B.In Case A,the main air-cooled heat exchanger is arranged in the upper layer and the auxiliary air-cooled heat exchanger arranged in the lower layer,while in Case B,the two heat exchanger systems are arranged in the opposite way.And then,directing at the engineering TMCR and TRL 1 working conditions,the unit-local-overall thermo-flow characteristics of Case A and Case B are obtained and compared by numerical simulation.The findings show that,for the auxiliary air-cooled exchanger,Case A has obviously higher cooling performances than Case B,with the difference varying from 5.46%to 7.55%.Whereas,for the main air-cooled exchanger,Case B shows the recovered cooling performances,with the difference changing from 1.15%to 2.99%.Case A is preferably recommended to the engineering application in consideration of more strict cooling demand of the auxiliary cooling system.Conclusively,this research will provide some theoretical guidelines for the design and construction of the main-auxiliary integrated natural draft dry cooling system.

直接还原铁作为废钢替代品在电弧炉中的应用

为了满足用户对优质钢和纯净钢的要求,直接还原铁作为废钢的替代品用于电弧炉炼钢应是一种可行的选择。概述了直接还原铁的特点,指出高比例使用DRI可以得到N、Cu、Cr、Ni、As、Sn等含量低的钢,直接还原铁可认为是一种较好的电弧炉炼钢原料。

炼钢渣和炭的混合物用于微波辅助甲烷干气重整反应(英文)

The use of steel-making slag as catalysts for microwave-assisted dry reforming of CH4 was studied. Two carbon materials (an activated carbon and a metallurgical coke), mixtures of the carbon materials and Fe-rich slag, and mixtures of the carbon materials and Ni/Al2O3 were tested as catalysts. The mixtures of slag with carbons gave rise to higher and steadier conversions than those achieved over the carbon materials alone. In addition, the use of the metallurgical coke mixed with metal-rich catalysts gave rise to remarkable results. Thus, no CH4 and CO2 conversions were achieved when coke was used alone, whereas high conversions were obtained when it was mixed with the metal-rich catalysts.

150t超高功率电炉直接还原铁炼钢工艺分析

通过对国内天津某厂150t超高功率电炉炼钢过程中的跟踪观察与纪录结果进行综合分析整理，结果表明，在碱度CaO／SiO2＝1．8～2．0和吹氧流速为4000～5000Nm3／h时，要保证渣中FeO20％左右这一理想泡沫渣形成条件的关键是生铁的配入量应为21％（35t）左右，电极“穿井”后进入熔化期加入直接还原铁（DRI）是降低电耗的关键。对于以连续加料的方式从炉盖第5孔加入的15％（25t）DRI，在3篮料的熔化潮时，分别加入4．2％（7t）、4．8％（8t）、6．0％（10t）左右DRI的加料方式较佳。

铁尾矿砂与干化污泥制备免压免烧砖的研究

利用铁尾矿砂和城市污泥为原料制备免压免烧砖,以碱性激发剂NaOH和水玻璃激发矿渣微粉替代水泥作为胶凝材料。研究结果表明:免烧砖的强度随矿渣微粉掺量的增加而增大,矿渣微粉掺量为24%~30%与铁尾矿砂掺量为70%~76%或矿渣微粉、铁尾矿砂、污泥的掺量为45:50:5,均可制备出强度满足《非烧结垃圾尾矿砖》(JC/T422-2007)MU25国家建材行业标准的免压免烧砖。

锅炉干排渣系统运行调整

自大港电厂一期机组试运投产以来,锅炉炉底干排渣系统多次出现严重积渣、堵渣现象。直接造成锅炉超温、效率降低、甚至限负荷运行,给锅炉的安全、稳定运行造成了相当大的影响。文中通过对锅炉运行稳定性、锅炉结焦防范、大渣冷却等运行技术进行研究,分析并得到了干排渣系统结渣、堵渣的原因以及渣量对负荷变化的影响。针对本厂机组,采取了一系列控制措施应对大渣量对锅炉机组造成的影响,以及结渣、堵渣后的处理方法。实践表明,干排渣系统运行良好,有效的保证了锅炉机组的运行。