Effect of potassium fluorozirconate addition on properties of fly ash based cordierite ceramics

Li Jiayi, Liu Yangqiao, Chang Qibing, Gu Yajie, Sun Shengrui, Sun Ke, Chang Xinglan, Xi Shuang

2022, (6): 461-466. doi：10.3969/j.issn.1001-1935.2022.06.001

In order to prepare high-performance cordierite ceramics from fly ash,fly ash (d₅₀=4.03 μm) from a power plant,talc (≤2.6 μm),α-alumina (≤5 μm) and nano magnesia (0.1 μm) were used as raw materials to prepare fly ash-based cordierite ceramics at 1 100-1 350 ℃.The effects of the potassium fluorozirconate (K₂ZrF₆) addition (0,0.5%,1% and 1.5%,by mass) on cordierite phase transition,the physical properties and the microstructure of fly ash based cordierite ceramics were studied.The results show that with the firing temperature of 1 300 ℃,as the K₂ZrF₆ addition increases from 0 to 0.5%,the bulk density of samples increases from 1.82 g·cm^-3 to 2.02 g·cm^-3,the cold compressive strength increases from 342 MPa to 511 MPa,and the average thermal expansion coefficient from room temperature to 800 ℃ reduces to 2.48×10^-6℃^-1 from 3.12×10^-6℃^-1.K₂ZrF₆ promotes the phase transformation and improves the sintering performance for the reason that the reaction of K₂ZrF₆ to form zircon promotes the formation of magnesium aluminate spinel and the conversion to cordierite.In addition,the hydrogen fluoride gas generated in the decomposition process reacts with some solid phases,which improves the fluidity of the hot melt produced in the calcination process and promotes the liquid-phase sintering of the material.

Effect of nano-CaCO₃ addition on properties of corundum based dispersive purging plugs

Su Yuqing, Zhu Yening, Yu Baisong, Xi Zijian, Wei Juncong, Tu Junbo, Zhang Houxing, Wang Yilong

2022, (6): 467-471. doi：10.3969/j.issn.1001-1935.2022.06.002

Abstract ( ) PDF (1675KB)( )

In order to improve the properties of corundum based dispersive purging plugs,dispersive purging plug specimens were prepared using tabular corundum (1-0.15 mm and ≤0.15 mm) as the aggregates,tabular corundum (≤0.044 mm) and α-Al₂O₃ micropowder (d₅₀=0.6 μm) as the matrix,Secar 71 cement as the binder,introducing different amounts of nano-CaCO₃,casting into shapes,and firing at different temperatures (1 200 ℃ or 1 600 ℃) for 4 h.The effects of the nano-CaCO₃ extra-addition (0,0.5%,1%,1.5%,and 2%,by mass) on the fluidity of castables,the properties and the microstructure of the dispersive purging plug specimens were studied.The results show that:(1)with the fixed water addition,the flow value of the corundum castables decreases as the nano-CaCO₃ addition increases;(2)with the increasing nano-CaCO₃ addition,the bulk density of the specimens fired at different temperatures for 4 h decreases,the apparent porosity,the cold strength and the hot modulus of rupture all increase,the air permeability does not change significantly;(3)the specimens fired at 1 600 ℃ for 4 h have obviously better cold physical properties than those fired at 1 200 ℃ for 4 h;(4)when the nano-CaCO₃ addition is 1.5%,the comprehensive performance of the specimen is the optimal.

Performance of adsorbents for NO₂ in furnace flue gas

Liu Wei, Cui Xinghui, Gao Zhengxia, Tao Mengya, Suo Dong, Tian Shishuai, Ma Chengliang

2022, (6): 472-476. doi：10.3969/j.issn.1001-1935.2022.06.003

Abstract ( ) PDF (1887KB)( )

In order to meet the emission standard of nitrogen oxides (NO_x) in the flue gas of batch furnaces through dry adsorption,calcia silica inorganic adsorbents were prepared with limestone and quartz as raw materials.Sample Cu-BTC 1^# was obtained by solvothermal synthesis,drying and purification in vacuum at 120 using trimesic acid (H₃BTC) and copper nitrate trihydrate (Cu(NO₃)₂·3H₂O) as raw materials; likewise,sample Cu-BTC 3^# was obtained at 200 ℃.Sample Cu-BTC 2^# was obtained by hydrothermal synthesis,drying and purification in air (metal organic skeleton MOFs materials,1,3,5-benzenetricarboxylic acid copper).The two types of materials were tested in terms of the NO₂ adsorption,and then the specific surface area,the pore volume,the NO₂ adsorption performance,the phase composition,the microstructure,and the thermal stability of adsorbent materials were explored via N₂ physical adsorption-desorption,SEM,XRD and TG characterization.The results show:(1)the Cu-BTC samples have higher adsorption capacity than the calcia silica adsorbent,in which sample Cu-BTC 3^# has the largest specific surface area and pore volume,thus adsorption capacity for NO₂;(2)the calcia silica adsorbent has better thermal stability and lower total mass loss during the entire process than the Cu-BTC samples;sample Cu-BTC 2^# has better thermal stability than the other two Cu-BTC samples,and the metal Cu active sites of the Cu-BTC samples can be exposed at least above 150 ℃.

Effect of ferric nitrate loading mode on properties of Si₃N₄ composite MgO-C refractories prepared by nitridation

Chen Yang, Deng Chengji, Ding Jun, Yu Chao, Lou Xiaoming

2022, (6): 477-480. doi：10.3969/j.issn.1001-1935.2022.06.004

Abstract ( ) PDF (1390KB)( )

In order to investigate the effect of the catalyst loading mode on the mechanical properties of Si₃N₄ composite MgO-C refractories prepared by nitridation,fused magnesia,flake graphite,silicon powder,and phenolic resin were used as the main raw materials,and ferric nitrate as the catalyst to prepare refractories by nitriding at 1 350 ℃.The effects of different catalyst supports (silicon powder,silicon powder+phenolic resin) on the formation of Si₃N₄ in MgO-C refractories and the properties of refractories were studied.The results show that the silicon powder+phenolic resin catalyst support promotes the participation of α-Si₃N₄ in the reaction to generate β-Si₃N₄ and MgSiN₂,and generates more SiC.However,this loading mode causes more gas to escape from the refractories and loosens the material structure,which reduces the mechanical properties.On the contrary,MgO-C refractories prepared by nitridation with silicon powder-supported catalysts under the same conditions show higher density and better mechanical properties.

Pore structure and performance of tabular corundum aggregates

Wu Pei, Han Bingqiang, Wei Jiawei, Wang Huijun

2022, (6): 481-484. doi：10.3969/j.issn.1001-1935.2022.06.005

Abstract ( ) PDF (2156KB)( )

In order to investigate the relationship between the properties and the pore structure of tabular corundum aggregates,two commercial tabular corundum aggregates (A and B) of 3-5 mm were selected as the research objects.The chemical composition,the phase composition,the microstructure and the physical properties of the two tabular corundum aggregates were analyzed,while their three-dimensional structure and pore size distribution were characterized by X-ray computed tomography (CT).The results show that the chemical composition of the two tabular corundum aggregates is similar,and their grain size ranges from 20-100 μm.There is no significant difference in the physical properties of the two tabular corundum aggregates,except for the cylinder compressive strength.Tabular corundum B has smaller average pore size,less large-sized pores and more uniform pore distribution than tabular corundum A.The microstructure and the CT results indicate that the average pore size and the large pore amount are the main factors to influence the strength of the tabular corundum aggregates: the larger the pore size and the more the large pores,the lower the strength of tabular corundum aggregates.

Effect of SiO₂ micropowder on rheological behavior of alumina magnesia gunning mixes

Liu Mengxuan, Nie Jianhua, Li Hongbo, Wang Yongjin, Liang Yonghe, Cai Manfei

2022, (6): 485-488. doi：10.3969/j.issn.1001-1935.2022.06.006

Abstract ( ) PDF (1507KB)( )

Alumina magnesia gunning mixes were prepared using sintered tabular alumina,α-Al₂O₃ micropowder,cement and fused magnesia as raw materials,adding SiO₂ micropowders (0,0.5%,1%,1.5% and 2%,by mass).The effects of the SiO₂ micropowder addition on the cold properties of gunning mixes and the rheological behavior of gunning mix slurries (matrix) were investigated.The results show that:(1)the rheological behavior of the alumina magnesia gunning mix slurries conforms to the De-Kee Fluid Equation,and the SiO₂ micropowder addition reduces the linear viscoelastic range of the slurries;when the SiO₂ addition is 0.5%,the slurry has the lowest yield stress and viscosity in the flow state,showing the best pumping performance;in the gel state,with the increase of the SiO₂ micropowder addition,the storage modulus G′ of the gel increases,and the elasticity of the slurry increases;(2)an appropriate introduction of SiO₂ micropowder in the alumina magnesia gunning mix can improve the rheological behavior of the slurry,and improve the flow properties as well as the densification degree after construction.

Effect of TiO₂ addition on performance of Al₂O₃-SiC-C taphole clay

Ju Maoqi, Liang Yonghe, Nie Jianhua, Cai Manfei, Guo Mengzhen

2022, (6): 489-494. doi：10.3969/j.issn.1001-1935.2022.06.007

Abstract ( ) PDF (2671KB)( )

In order to improve the properties of Al₂O₃-SiC-C taphole clay,the effects of TiO₂ additions (0,1%,2%,3%,and 4%,by mass) on the performance of samples after hot treatment were studied,including the permanent linear change,the density,the cold strength,the oxidation resistance and the slag resistance,etc.The results show that:(1)after heat treatment at 1 100 ℃ for 3 h,all samples shrink and the linear shrinkage rate increases with the TiO₂ addition increasing,the density and the cold strength also increase with the increase of TiO₂ addition;(2)after heat treatment at 1 450 ℃ for 3 h,all samples expand due to the volume expansion caused by the formation of mullite;with the TiO₂ addition increasing,the linear expansion rate increases,the density decreases,and the cold strength increases first and then decreases and reaches the maximum with 3% of TiO₂;(3)adding TiO₂,the oxidation resistance and the slag corrosion resistance of the taphole clay are slightly improved.

Effect of BN micropowder addition on high temperature oxidation resistance of Si₃N₄-BN composites

Niu Shicheng, Wu Jiguang, Liang Pengpeng, Xiang Yubo, Zheng Han, Bu Xiangjuan, Luo Tian

2022, (6): 495-498. doi：10.3969/j.issn.1001-1935.2022.06.008

Abstract ( ) PDF (2275KB)( )

In order to explore the effect of BN micropowder addition on the high temperature oxidation resistance of Si₃N₄-BN composites,Si₃N₄-BN composites with different BN micropowder additions (0,12%,26%,and 41%,by mass) were prepared using Si powder,Si₃N₄ powder,and h-BN micropowder as main raw materials by reaction sintering technology.The oxidation test was carried out at 1 200 ℃ in a static air atmosphere for 2-20 h.The apparent porosity,the cold modulus of rupture,the cold compressive strength of the samples before and after oxidation were detected,and the samples were investigated by XRD and SEM.The results show that: when the BN micropowder addition is 41%,the oxidation resistance of the reaction sintered Si₃N₄-BN sample is the best,which is significantly better than that of the reaction sintered Si₃N₄ sample;the B containing glass phase formed in the oxidation product forms a dense protective layer on the sample surface,which is the key factor for the excellent oxidation resistance of the composites.

Influence of alumina-rich spinel micropowder on key performances of corundum-spinel castables

Xiao Xiong, Wei Yaowu, Zhou Hui, Yan Lin, Chen Zhiqiang, Shao Changbo

2022, (6): 499-504. doi：10.3969/j.issn.1001-1935.2022.06.009

Abstract ( ) PDF (2686KB)( )

The study aims to research the influence of alumina-rich spinel micropowders with different alumina contents on the key performances of corundum-spinel castables.The corundum-spinel castables were prepared using tabular corundum particles (6-3,3-1,≤1 mm) and spinel particles (≤1 mm) as the aggregates,tabular corundum fines (≤0.074 mm),spinel fines (≤0.032 mm ),active α-Al₂O₃ micropowder (d₉₀=10.0 μm) and magnesium aluminate spinel micropowders with different alumina contents as the fine powder,Secar 71 cement as the binder.The mass ratio of aggregates to fines was 66.5∶33.5.Fixing the addition of alumina-rich spinel micropowders at 7 mass%,the effects on the microstructure and the key performances of the corundum-spinel castables were studied.The results show that:(1)the addition of aluminum-rich spinel micropowder is helpful to improve the hot modulus of rupture,the thermal shock resistance,and the slag resistance of the castables;a large amount of calcium hexaluminate forms and uniformly distributes on the slag-castables boundaries,hindering the penetration of ladle refining slag to the castables;(2)when the alumina content in alumina-rich spinel micropowder is 90%,the developed sample has good slag penetration resistance.

Characteristics of refractory patent technology

Wang Jiezeng

2022, (6): 505-510. doi：10.3969/j.issn.1001-1935.2022.06.010

Abstract ( ) PDF (1305KB)( )

This paper used R language + Excel,and data cleaning,data merging,data pivoting,text analysis,correlation analysis,expert analysis and other operations to analyze 4 410 patents downloaded from CNKI from the beginning of 2019 to the end of 2021,focusing on 958 patents of 17 typical units.These patents belonged to 12-sub items with the main classification of C04B35.It was interpreted from the perspectives of patent category,country and applicant,hot words,service industry and technical characteristics.It is found that:(1)China has become a leader to promote the development of refractory technology;(2)the high-temperature ceramic technology providers such as the Chinese Academy of Sciences,the integrated refractory application technology provider such as Wuhan University of Science and Technology,the professional refractory technology providers such as Beijing Lirr High Temperature Materials Co.,Ltd.have become the leaders in China;(3)through the science conrergence,the technology integration,and the great combination of technology and markets,China’s refractory industry is breaking through the bottleneck and undergoing upgrading.

Current air pollutant emission situation and control measures of refractory industry in Henan Province

Zhang Aiqin, Wang Haozhao, Cao Xia, Deng Huaxiang, Pang Long, Cao Jiahui

2022, (6): 511-514. doi：10.3969/j.issn.1001-1935.2022.06.011

Abstract ( ) PDF (927KB)( )

Based on the investigation of over 1 400 refractory enterprises in Henan Province,the current situation of air pollutant emission was analyzed from the aspects of online monitoring and detection of air pollutant emission amount and concentration,and the pollution control process of refractory enterprises using different types of furnaces was summarized and analyzed.According to the survey results,the problems existing in the prevention and control of air pollutants in refractory enterprises in Henan Province were discussed.Simultaneously,corresponding pollution control measures were proposed,which could provide references and ideas for promoting the pollution reduction of refractory industry in Henan Province and formulating relevant pollutant emission standards.

Application of Si₃N₄ bonded SiC bricks in vertical zinc-smelting furnaces

Xu Haiyang, Cao Huiyan, Zheng Han, Gong Jianfeng, Shi Huiying, Li Jie, Yang Kui, Zhu Chong

2022, (6): 515-518. doi：10.3969/j.issn.1001-1935.2022.06.012

Abstract ( ) PDF (2521KB)( )

The problems,the measures and the results of Si₃N₄ bonded SiC bricks to replace fireclay bonded SiC bricks in a vertical zinc-smelting furnace of Dongling Zinc Industry Co.,Ltd.,were introduced,and the damage of two kinds of bricks after 20 months service was compared.The results show that:(1)compared with the fireclay bonded SiC bricks,the Si₃N₄ bonded SiC bricks present higher thermal conductivity,which can lower the temperature in the high temperature area by about 30 ℃;(2)the Si₃N₄ bonded SiC bricks show better corrosion resistance than fireclay bonded SiC bricks,the residual thickness of which in the high temperature area is 40-50 mm thicker than that of the fireclay bonded SiC bricks after 20 months of service;(3)during service,long cracks and leak-spot occurbecause the thermal stress of the Si₃N₄ bonded SiC bricks is not fully released,which can be relieved to a certain degree by adjusting the firing schedule during the removing of furnace accretion.If more efficient leak-spot repairing technology can be developed,the service life of Si₃N₄ bonded SiC bricks can be prolonged.

Corrosion of fly ash from domestic waste incineration and CaO to refractories

Xia Min, Wang Qinqin

2022, (6): 519-522. doi：10.3969/j.issn.1001-1935.2022.06.013

Abstract ( ) PDF (1578KB)( )

The corrosion resistance and the permeability resistance of typical refractories (corundum-mullite bricks,chrome corundum bricks and high chrome bricks) for fly ash high temperature melting furnaces to fly ash from domestic waste incineration and pure CaO at 1 400 ℃ were studied.The results show that:(1)high chrome bricks perform the best corrosion resistance and permeability resistance to fly ash and CaO,followed by chrome corundum bricks and corundum-mullite bricks;(2)calcium aluminosilicate,calcium aluminate and calcium silicate are formed in the test bricks corroded by fly ash and CaO;but the fly ash corrosion is more serious,because chlorine in the fly ash reacts with Al₂O₃ in the bricks to form gaseous substances such as AlCl₃,Al₂Cl₆ and NaAlCl₄,leading to the decreasing Al₂O₃ content;(3)when fly ash melts,all the bricks are corroded by both high chlorine and high alkali.

Wettability of silica sol modified multilayer graphene

Yu Baisong, Zhu Yening, Li Yangzhe, Su Yuqing, Wei Juncong, Tu Junbo, Wang Yilong

2022, (6): 523-526. doi：10.3969/j.issn.1001-1935.2022.06.014

Abstract ( ) PDF (2297KB)( )

To expand the application of multilayer graphene in water-based systems,modified multilayer graphene was prepared by vacuum impregnation with silica sol and carbon-embedded heat treatment at 300,500 or 700 ℃ for 3 h.The phase composition,the microstructure and the wettability of the modified multilayer graphene heat treated at different temperatures were studied.The results show that the water wettability of the modified multilayer graphene is improved after vacuum impregnation with silica sol and carbon-embedded heat treatment;the optimum heat treatment temperature is 300 ℃,and the modified multilayer graphene has the water wetting angle of 64.7°.

Corrosion of ladle refractories and its influencing factors during production with high scrap ratio

Xiao Tongda, Li Muyun, Kong Yongjiang, Hu Bo, Xu Guotao

2022, (6): 527-529. doi：10.3969/j.issn.1001-1935.2022.06.015

Abstract ( ) PDF (909KB)( )

The influence of production process changes on application of ladle refractories during production with high scrap ratio was summarized.The corrosion reasons of ladle slag line bricks,wall bricks and gas supply bricks as well as their influencing factors were analyzed.It is pointed out that the increase of ladle heating ratio is the main reason for the abnormal performance of refractories,and the requirements of the steelmaking process changes can be satisfied through local thickening of ladle wall bricks,regular maintenance and repair,quality improvement of refractories,and optimization of operation processes and maintenance modes.

Effect of natural magnesite on properties of environment-friendly water-based magnesia repair mixes for converters

Dai Chenchen, Nie Bohua, Zhang Wanpu, Huang Yu, Lu Yang, He Lijie

2022, (6): 530-534. doi：10.3969/j.issn.1001-1935.2022.06.016

Abstract ( ) PDF (994KB)( )

To further improve their properties,based on the formulation of 93 mass% fused magnesia (5-3,3-1,≤1 and ≤0.088 mm),5 mass% SiO₂ micropowder,2 mass% sodium metasilicate nonahydrate,and extra 0.15 mass% superplasticizer SD-80,the environment-friendly water-based magnesia repair mixes for converters were prepared by replacing the ≤0.088 mm fused magnesia fines in the equal amount with high-quality natural magnesite powder from southern Liaoning (0,1%,2%,3%,4%,5%,6%,7%,8%,and 9%,by mass).The effects of the natural magnesite addition on the fluidity,the bulk density,the apparent porosity,the mechanical properties,and the slag resistance of the repair mixes were studied.The results show that:(1)the introduction of natural magnesite powder has no obvious effect on the fluidity of the repair mixes and the bulk density and the apparent porosity of the samples dried at 110 ℃ for 24 h;(2)the samples fired at 1 500 ℃ for 3 h have significantly improved bulk density,cold strength,hot modulus of rupture,slag resistance and other properties,achieving the best performance with 4%-5% natural magnesite powder;(3)the application test proves that the sample with 5% natural magnesite powder has long service life and the shortest sintering time;under the same smelting conditions,the service life of the sample increases by 100% and the sintering time shortens by 70% compared with the traditional asphalt bonded magnesia carbon repair mixes,which is the most ideal technical scheme.

Cementitious property of ferrovanadium slag and preparation of ferrovanadium slag castables

Hao Jianzhang, Zeng Guanwu

2022, (6): 535-538. doi：10.3969/j.issn.1001-1935.2022.06.017

Abstract ( ) PDF (1258KB)( )

Ferrovanadium slag was crushed and ball milled into micropowders with the specific surface area of 324,359,406 and 448 m²·kg^-1,respectively.The cementitious property of the prepared micropowders and calcium aluminate cement CA-70 was compared.It is found that the cementitious property of the ferrovanadium slag micropowder with the specific surface area of 406 m²·kg^-1 is equivalent to or even better than that of calcium aluminate cement CA-70.On this basis,cement-free ferrovanadium slag castables were developed.The effect of the addition of the ferrovanadium slag micropowder (the specific surface area of 406 m²·kg^-1) on the properties of the castables was studied.The on-site application of the castables was carried out at blast furnace slag spouts,slag hole nozzles and hot metal tanks.The results show that the ferrovanadium slag castable with 25 mass% ferrovanadium slag micropowder has better properties than the high alumina castables,achieving good on-site application effects.

Influence of spinel micropowder on properties of alumina-magnesia dry ramming mixes

Jiang Guangsen, Nie Jianhua, Li Hongbo, Liang Yonghe, Cai Manfei

2022, (6): 539-542. doi：10.3969/j.issn.1001-1935.2022.06.018

Abstract ( ) PDF (1963KB)( )

Alumina-magnesia dry ramming mixes were prepared using white fused corundum (5-3,3-1,≤1 and ≤0.074 mm) and fused magnesia (≤1 and ≤0.074 mm) as the main raw materials to achieve excellent mechanical properties and appropriate expansion.The effects of different spinel micropowders (MA90,MA70,MA66 and MA60) on the properties and the microstructure of the samples were studied.The results show that:(1)the spinel micropowder addition can effectively reduce the expansion during the formation of in-situ spinel and improve the mechanical properties of the samples;MA90 performs better effect than other spinel micropowders;(2)after heat treatment at 1 600 ℃ for 3 h,the expansion of the sample added with MA90 significantly reduces,achieving a denser structure and greatly improved cold compressive strength.

Research progress of infrared radiation coatings for industrial kilns

Wu Qi, Wang Guangyang, Sun Yiran, Wang Xueqing, Sang Shaobai, Wang Qinghu, Li Yawei

2022, (6): 543-547. doi：10.3969/j.issn.1001-1935.2022.06.019

Abstract ( ) PDF (950KB)( )

Radiation heat transfer is the dominant factor affecting the thermal efficiency of high-temperature kilns.High-emissivity infrared radiation coatings can realize energy saving of industrial kilns by enhancing the radiation heat transfer.The energy saving mechanism and the coating methods of infrared radiation coatings for industrial kilns were mainly introduced.Related research progress of infrared radiation coatings was reviewed.The problems existing in the application of infrared radiation coatings at present were analyzed,and the future development was prospected.

Effect of sintering aids on thermal conductivity of Si₃N₄ ceramics

Guo Hongli, Yao Can, Cheng Benjun, Gu Qiang

2022, (6): 548-552. doi：10.3969/j.issn.1001-1935.2022.06.020

Abstract ( ) PDF (960KB)( )

The effects of single,binary and ternary sintering aids on the thermal conductivity of Si₃N₄ ceramics were reviewed.The comprehensive analysis shows that the introduction of sintering aids can reduce the sintering temperature of Si₃N₄ ceramics,increase the density,and reduce the glass phase and oxygen contents,so that the Si₃N₄ grains grow up and contact more closely,thus effectively improving the thermal conductivity of Si₃N₄ ceramics.The binary sintering aids have the greatest influence on the thermal conductivity,and Si₃N₄ ceramics with high thermal conductivity can be obtained by appropriately adjusting the sintering aids addition or the ratio of sintering aids.

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