The startup and shutdown times and operation time of a GE coal water slurry gasifier lined with phosphate containing high chrome brick were real-time tracked.The inner chamber diameter of the gasifier in different operation stages was measured,the thickness of residual brick was calculated,the damage rate of high chrome brick during the whole operation cycle and the microstructure,composition distribution and phase composition of residual brick were analyzed.The results show that the damage rate of phosphate containing high chrome brick in the coal water slurry gasifier is not uniform,which is slow in the early stage,fast in the middle stage,and slow again in the final stage; erosion,penetration and spalling are the main factors resulting in the damage of phosphate containing high chrome brick lining;the specific damage factors are dominant in different stages,which is the reason for the uneven damage rate;the phosphate in high chrome brick inhibits the penetration of silicate glass slag,reduces spalling and prolongs the service life of the furnace lining.

In order to reduce the thermal energy loss of high temperature kilns and furnaces and lower the surface temperature of the kiln body,magnesia insulation materials were prepared using self-made magnesia porous aggregates (using high purity magnesia powder as starting material and potassium oleate as foaming agent),middle grade magnesia powder,calcium aluminate cement,and SiO₂ micropowder as starting materials,introducing walnut shell powder impregnated with silica sol (short for Sws) as a pore-making agent.The effect of the Sws addition (0,10%,15%,and 20%) and the sintering temperature (1 300,1 350,1 400,and 1 480 ℃) on the properties of magnesia insulation materials was studied.The results show that (1)when the Sws addition is 10 mass%,the compressive strength is 22 MPa;when the Sws addition is 20%,the thermal conductivity is 0.368 W·m^-1·K^-1(350 ℃);(2)nano-silica in the silica sol reacts with MgO in the matrix to form forsterite,which encapsulates the pores volatilized from the walnut shell powder and forms closed pores.

To improve the sintering quality of Al₂O₃-C tubes for continuous temperature sensors of molten steel,firstly,the temperatures in different positions in the furnace during sintering were measured,and the variations of the temperature field were analyzed;then,the thermal stress model of the Al₂O₃-C tube head during sintering was established;according to the calculated thermal stress nephogram and the stress,the temperature,the strain curve corresponding to the maximum thermal stress position,the most vulnerably damaged positions were determined and the damage reasons were analyzed;finally,the firing schedule was optimized based on the analysis of the damage reasons and then applied in on site production.The results show that: the actual furnace temperatures in not consistent with the set temperatures;the upper temperatures are higher than the lower temperatures,and the temperatures below the exhaust ports are higher than those at other parts;the three maximum stress positions predicted by the stress model are consistent with the damage positions in the actual sintering;the heating rate in the range of 300-600 ℃ is reduced from 3.3 ℃·min^-1 to 2 ℃·min^-1,which decreases the failure rate from 8/1 000 to 1/10 000.

Silicon carbide castables of different SiC contents (86% and 71%,by mass) were prepared using fused white corundum,silicon carbide particles and fines,activated alumina powder,silica powder and pure calcium aluminate cement as main starting materials,heat treating at 1 000 ℃ for 3 h,oxidizing in steam atmosphere at 1 000 ℃ for different durations (100,200,300,400 and 500 h).The mass and volume before and after oxidation,the bulk density,the apparent porosity and the cold compressive strength were tested.The phase composition and the microstructure before and after oxidation were analyzed by XRD and SEM.The results indicate that: (1)within 300 h of oxidation duration,silicon carbide shows an increasing oxidation rate;however,the oxidation rate is low during 300-500 h of oxidation duration;2)the oxidation rate of the specimen with 71% SiC is slightly higher than the one with 86% SiC;3)with the increasing oxidation degree of silicon carbide,the apparent porosity of the specimens tends to increase,followed by the declining bulk density and cold compressive strength.

Commercial high purity corundum brick,corundum-mullite brick,mullite brick and calcium hexaluminate brick and calcium hexaluminate-corundum brick were studied to investigate their reaction state and alkali vapor corrosion resistance mechanism at 1 370 ℃ and 1 500 ℃.The results show that:1)served in hot alkali vapor,high-purity corundum brick has no obvious slag layer and reaction-expands obviously;2)corundum-mullite brick shows obvious reactive expansion at 1 370 ℃ and melting corrosion happens at 1 500 ℃;3)at 1 370 ℃,alkali vapor and mullite brick react and form a slag layer without volume effect;when the temperature is increased to 1 500 ℃,the reaction melting corrosion is intensified;4)calcium hexaluminate brick and calcium hexaluminate-corundum brick form a thin slag layer under alkali vapor,and its surface absorbs Na⁺ to form a dense layer with small volume effect.

In order to improve the comprehensive utilization of fly ash resources,porous mullite materials were prepared by solid sintering using fly ash as the silicon source,alumina hydroxide as the aluminum source,AlF₃ as the crystal whisker accelerator,and V₂O₅ as the sintering aid.The effects of the ratio of fly ash to aluminum hydroxide (28.2:71.8,34.2:65.8,40.2:59.8,46.2:53.8 and 52.2:47.8,respectively) on the properties,the phase composition and the microstructure of the prepared porous mullite materials were studied.The results show that with the ratio of fly ash to aluminum hydroxide increasing,the apparent porosity gradually increases,the compressive strength and bulk density gradually reduce,the diffraction peaks of mullite gradually strengthen,while those of corundum gradually weaken and disappear;when the mass ratio of fly ash to aluminum hydroxide is 52.2:47.8 the sample shows an apparent porosity of 53.1%,the bulk density of 1.12 g·cm^-3,the compressive strength of 22.8 MPa,and the length to diameter ratio of 30.

Corundum spinel aggregates were prepared using magnesium hydroxide and α-Al₂O₃ micropowder as starting materials,dry mixing,molding and reaction sintering at 1 750 ℃.The effect of the particle size of magnesium hydroxide (average size of 55,36.4 and 10.6 μm) on the bulk density,the porosity and the microstructure of corundum-spinel materials was studied.The results show that with the decreasing particle size of magnesium hydroxide,(1)the bulk density of corundum-spinel materials increases,the apparent porosity decreases,the closed pores increase,and the total porosity and the pore size decrease gradually;(2)the distribution of magnesium hydroxide and Al₂O₃ is more uniform and the effective contact area increases,which can promote the solid reaction and form finer,more uniform and extensive closed pores;(3)the thermal conductivity at 500 ℃ of the sample increases.

Based on the proposal of “micro-pored aggregates and dense-packed matrixes” and the particle dense packing theory,the Dinger-Funk Equation was modified to establish a prediction model of matrix packing density for lightweight refractories.Lightweight alumina magnesia castables were prepared using micro-pore corundum,bauxite and magnesia as starting materials.The micro-pore corundum used has low apparent density,high closed porosity,low thermal conductivity (20%-50% lower than the common corundum),similar slag resistance of the common corundum and micro- or nano-sized intracrystalline pores.The results show that the lightweight alumina magnesia castables not only have good thermal shock resistance and low thermal conductivity,but also have the same slag resistance as the common alumina magnesia castables.The onsite application shows that the service life of the alumina magnesia precast blocks for the ladle working lining prepared with the microporous corundum as aggregates are better than that of the current materials with the same conditions.

Silicon nitride ceramics were prepared using different amounts of MgO or Y₂O₃ powder as sintering aids (2%,4%,6%,8%,and 10%),ball milling,granulating,shaping and sintering at 1 750 ℃ under 6 MPa nitrogen.The relative density of the specimens was determined,the phase composition and microstructure were explored.The results show that (1)the maximum relative density reached 96.5% or 98% with 6% MgO or 8% Y₂O₃,respectively;(2)with the same addition,the relative density of the sample with Y₂O₃ powder is higher than that with MgO powder,indicating that Y₂O₃ preforms better than MgO in promoting sintering densification;(3)MgO and Y₂O₃ powder both can promote the transition from α-Si₃N₄ to β-Si₃N₄.

In order to study the possibility of recycling waste sagger from cordierite-mullite lithium battery cathode material sagger,cordierite-mullite specimens were prepared using waste sagger powder (≤0.044 mm),cordierite particles (1.25-0.5 mm),M70 mullite particles (2-1,≤1 mm),fused magnesium aluminate spinel (≤0.5,≤0.045 mm),alumina micropowder and Guangxi white mud as main raw materials,using 0,4%,8% and 12% waste sagger powder to substitute alumina micropowder and spinel fine powder.After fired at 1 320,1 350 and 1 380 ℃ for 3 h,the physical properties such as bulk density,apparent porosity and cold strength were tested,and the microstructure of the specimnes was analyzed by SEM.The results show that with the waste sagger powder addition increasing,the bulk density and the apparent porosity of the specimens change little,and the strength decreases slightly.In conclusion,the addition of 4% or 8% waste sagger powder has little effect on the properties of cordierite-mullite specimens.

Nitride bonded silicon carbide bricks after used in a 170 t·h^-1 coke dry quenching oven for 6 years in inclined channel area (up and down) were researched.The changes of chemical composition,bulk density,cold strength,hot strength,pore size distribution,phase makeup and microstructure were discussed.The results show that:(1)both the contents of SiC and Si₃N₄ decrease,while the content of SiO₂ increases substantially (up 291.3% to 722.5%),the pore size enlarges (d₅₀ increases 22%-239%);the CMOR and HMOR for up brick decrease substantially (47.9% and 48.5%,respectively);the CMOR and HMOR for down brick decrease slightly (8.6% and 11.0%,respectively);(2)such change is aroused by the oxidation of nitride bonded silicon carbide.The oxidation for up brick is more serious than that of down brick,and also the oxidation for surface is more serious than inner.

The influences of different antioxidants (Al powder,Al powder+Si powder,Al powder+Si powder+CaB₆ powder) and carbon sources (flake graphite,granulated graphite,and expanded graphite) on the properties of taphole pipe bricks for converter prepared using fused magnesia,flake graphite as raw materials were investigated.The results show that:(1)the oxidation resistance and hot modulus of rupture of magnesia-carbon taphole pipe bricks are significantly improved when using Al powder+Si powder+ CaB₆ powder;(2)the introduction of granulated graphite is beneficial for the improvement of thermal shock resistance and oxidation resistance;although the addition of expanded graphite can significantly improve the thermal shock resistance,it reduces their oxidation resistance;(3)the developed taphole pipe bricks were applied in the converters in a steel plant with the average service life of 181 cycles,enhancing by 45%.

Taking the flue gas treatment of tunnel kilns for firing magnesia-calcia brick as an example,the treatment process of dry desulphurization and SCR denitrification technology was put forward.The ultra-low emission standards of sulfur dioxide,dust and nitrogen oxide lower than 10,35 and 50 mg·m^-3,respectively were realized.The process has been put into use in a magnesia-calcia brick enterprise in Shanxi Province,and the operation effect was good,but the cost of per ton product increased about CNY13.5.

The effect of silicon source on properties silica calcia materials prepared by hydrothermal method using fused quartz powder,white carbon black and silica sol as silicon sources,calcium hydroxide as calcium source was researched.The results show that no xonotlite phase forms when using fused quartz as the silicon source,and the xonotlite fiber forms in the materials with the white carbon black or silica sol as the silicon source.Silica sol has higher activity,leading to higher xonotlite content with a needle-like structure.The formation of xonotlite determines the cold and high temperature properties of silica calcia materials.In the specimen with silica sol,the xonotlite needle-like fiber intertweares,leading to an excellent high temperature strength.

On the basis of preparing corundum-cordierite-mullite composite phase materials,the specimens were prepared using sludge in aluminum profile plant,kaolin and French chalk as main raw materials,adding ZrO₂(1.0%,1.5%,2.0%,2.5%,and 3.0%,by mass) as the mineralizer,to improve the performance of the composite phase materials.The results show that with the increase of ZrO₂ mineralizer,the cold modulus of rupture and its residual value of the specimens after thermal shock firstly increase and then decrease,while other properties fluctuate.All specimens include three main crystal phases:corundum,mullite solid solution and cordierite.When ZrO₂ addition is 2.5%,the cold modulus of rupture of the specimens after thermal shock and the retention ratio are the highest,and the specimen has obviously developed particles,dense structure and few glass phase,which can form a complete network structure.Therefore,the optimal addition of the ZrO₂ mineralizer is 2.5%.

BN nanotubes (BNNTs) are tubular structural materials similar to carbon nanotubes.Owing to their excellent mechanical strength,high thermal conductivity,good thermal and chemical stability,super hydrophobicity and excellent electrical insulation,they have broad application prospects in the fields of metallurgy,chemical industry,environment,catalysis and biomedicine,etc.The advantages,shortcomings and influencing factors of arc discharge method,chemical vapor deposition method and ball milling nitridation reaction method to prepare BNNTs were briefly summarized.In addition,the future research focus and direction of BNNTs were proposed.

The current research status of preparing MgAlON materials by carbon thermal nitriding method,solid phase reaction method,direct nitriding method and discharge plasma sintering method was reviewed in China and overseas,and the development direction of MgAlON materials was prospected.

Oxide-based refractories are widely used in high temperature industrial equipment fields such as ceramic manufacturing,petroleum and energy due to their excellent high temperature mechanical properties,good thermal shock stability and slag corrosion resistance.But slag penetration and chemical corrosion are the main factors leading to their destroy.The corrosion and penetration mechanisms of molten slag to single-phase oxides,multi-phase oxides and oxide-carbon composite refractories were reviewed.The changes in the properties and microstructure of refractories after corrosion were also analyzed.The future research direction of oxide-based refractories against corrosion by molten slag was prospected.

Hydrogen metallurgy is a technology during which carbon is partially or completely replaced by hydrogen as the reducing agent of iron ore to realize the deoxidation.It is not fixed in a particular process,and direct reduction of iron process is one of the key processes of hydrogen metallurgy.In this paper,the direct reduction iron technology was introduced,combined with the hydrogen metallurgy project in China and overseas,the hydrogen metallurgy methods and hydrogen source were discussed,and finally the promotion of hydrogen metallurgy technology was prospected in the iron and steel industry.

The adhesion of inclusions in molten steel in the inner wall of the submerged entry nozzles is the main cause of the nodules and blockage of nozzles.Controlling the migration and aggregation of inclusions to the nozzle wall is an important technical measure to inhibit the nodules and blockage.The electrophoresis theory of inclusion migration under current was introduced,the application and the mechanism of external current to inhibit the nodules and blockage were summarized,and the future research was prospected.The external current was expected to be a new metallurgical technique for controlling the migration of inclusions and inhibiting blockage.