Shaped Insulating Refractory Products——Determination of Cold Crushing Strength

1 Scope This standard specifies a method for determination of the cold crushing strength of shaped insulating refractory products.

Experimental study on crushing strength and Young's modulus of granules in iron ore sintering using Taguchi method

The contributions of three operating parameters(moisture content,hydrated lime addition,magnetite concentrate substitution)to the crushing strength and Young's modulus of granules in each stage of iron ore sintering were studied by applying the Taguchi method.The results indicated that the strength properties of the iron ore granules were greatly affected by its structure,which is composed of inner nuclei and an outer adhering layer.The granules with a thick adhering layer showed a clear changing trend in strength with increasing temperature,whereas those with a thin adhering layer showed additional fluctuations as their force-displacement responses were greatly determined by the nuclei.The granules with a thick adhering layer were gen erally more deformable and easier to break than that those with the thin adhering layer in most states.The signal-to-noise ratio and variance analysis indicated that moisture was the dominant parameter affecting the strength properties of the iron ore granules,as this factor controls the primary granule structure and material distribution.With the progress of sintering,the contribution of moisture to the quality characteristics gradually decreased(from〜80%to 50%),whereas the contributions of hydrated lime and magnetite concentrate increased correspondingly(from〜5%to 20%).

Effects of Al_(2)O_(3)-SiO_(2) Raw Material Types on Properties of Anorthite Based Insulation Refractories

To optimize their Al_(2)O_(3)-SiO_(2) raw materials,anorthite based insulation refractories were prepared by the in-situ sintering process combined with the foaming method after sintering at 1350℃for 3 h,using green and pollution-free kaolin,kyanite,andalusite and sillimanite as Al_(2)O_(3)-SiO_(2) raw materials,respectively,and industrial CaCO_(3) as the CaO source.Effects of Al_(2)O_(3)-SiO_(2) raw material types on the physical properties,phase composition and microstructure were investigated.The results are as follows.All samples prepared by different Al_(2)O_(3)-SiO_(2) raw materials have hexagonal flake anorthite and a small amount of mullite and corundum.Their bulk density and thermal conductivity decrease in the order of using kaolin,andalusite,kyanite and sillimanite as the Al_(2)O_(3)-SiO_(2) raw material,but their apparent porosity increases.Moreover,in the sample with kaolin,the bonding between anorthite crystals on the pore walls is closer than that of the other samples,which is conducive to increasing the cold crushing strength.The bonding between anorthite crystals on pore walls gradually decreases in the order of using kyanite,andalusite and sillimanite as the Al_(2)O_(3)-SiO_(2) raw material,thus their cold crushing strength decreases accordingly.In comprehensive consideration,the properties of the sample from kyanite are the optimal.Its apparent porosity,thermal conductivity and cold crushing strength are 84.6%,0.141 W·m^(-1)·K^(-1) and 1.89 MPa,respectively.

Fabrication and Properties of Aluminabased Reticulated Porous Ceramics

The primary impregnation slurry was prepared using active alumina(56.25 mass%),kaolin(15 mass%),zirconia(3.75 mass%),deionized water(25 mass%),and extra adding FS(0.2 mass%)and CMC(0.4 mass%).The effects of the active alumina particle size(d50=5.043,2.934,and 1.629μm)on the rheology and the thixotropy of the slurry were researched.It was found that the bimodal activeα-Al2O3(AMA-10)with d50=1.629μm was optimum.The secondary impregnation slurry was prepared using AMA-10,kaolin and zirconia as the main raw materials.Then the alumina-based reticulated porous ceramics were fabricated by the organic foam impregnation method combined with a secondary vacuum impregnation process.The influence of the AMA-10 content on the properties of the ceramics was studied.The residual stress of the specimens was analyzed by finite element analysis.The results show that the smaller alumina particle size and multimodal distribution are beneficial to the thixotropy of the primary impregnation slurry.The secondary vacuum impregnation technique can significantly improve the mechanical properties,the thermal shock resistance and the residual strength of the alumina-based reticulated porous ceramics.With the decrease of alumina content in the secondary impregnation slurry,the residual stress of the external layer of ceramic reinforcement gradually changes from tensile stress to compressive stress,which effectively inhibits the expansion of the surface crack,and remarkably improves the crushing strength retention ratio of alumina reticulated porous ceramics.

Influence of Addition of ZnO on Property of Fe_2O_3-K_2O System Catalyst for Ethylbenzene Dehydrogenation to Styrene

The incorporation of ZnO into Fe2O3-K2O system increases its activity, enhances its moisture stability and mechanical strength. The origin of the enhancement in activity and moisture stability is discussed in the light of experimental results obtained by BET, XRD, XPS. It was found that the addition of ZnO to Fe2O3-K2O system strengthens the interaction between Fe2O3 and K2O, reduces the formation temperature of KFe11O17 at least by 50 oC, and promotes the transformation of Fe3+ to Fe2+ further.

Experimental and statistical assessments of the mechanical strength reliability of gamma alumina catalyst supports

The mechanical strength of solid catalysts is considered an important factor in terms of ensuring the reliable performance of industrial reactors. In this work, a pelletizing method was used to form gamma alumina support for catalysts. Response surface methodology （RSM） was employed to analyze and model the effects of various manufacturing parameters on the crushing strength of the supports. These parameters were binder concentration, compaction pressure, calcination temperature, and drying mode. The suggested model was verified by applying an analysis of variance to assess its validity with regard to crushing strength. The mechanical reliability of various supports was also determined by calculating their Weibull modulus values through linear regression of the Weibull equation. The material with the highest mechanical strength reliability will have both a high mean crushing strength and a high Weibull modulus, and the best values obtained for a support in this work were 70.7 MPa and 6.63, respectively. The conditions used to form this sample were： 20mass% binder concentration, 861 MPa compaction pressure, 466 ℃ calcination temperature, and gentle drying.

Interaction between Weibull parameters and mechanical strength reliability of industrial-scale water gas shift catalysts

A fundamental step in the production of an industrial catalyst is its crushing strength assessment. Limited literature exists in which the strength reliability of supported catalysts is investigated from production to their application in a reactor. In this work, cylindrical supports were prepared by pelletizing high poros- ity γ-alumina powder, and Cu-Znf/γ-Al2O3 catalysts were prepared by impregnation of the pelletized γ-alumina supports with an aqueous solution of copper and zinc nitrates. The support-forming variables, such as binder concentration, compaction pressure, calcination temperature, and drying procedure were investigated. The Weibull method was used to analyze the crushing strength data of the supports, and the fresh and used catalysts before and after the low-temperature water gas shift reaction. Support formation at a 50 wt% binder concentration, 1148 MPa compaction pressure, 500 ℃ calcination temperature, and rapid drying （100 ℃, 8 h） led to the maximum support mechanical reliability. The most reliable catalyst with respect to simultaneous appropriate catalytic performance and mechanical strength was prepared from a support with the lowest mean crushing strength （26.25 MPa）. This work illustrates the impor- tance of the Weibull modulus as a useful mechanical reliability index in manufacturing a supported solid catalyst.

Comparative performance of different urea coating materials for slow release

Approximately 70%of the applied urea fertilizer may be lost into the environment.This loss is due to leaching,decomposition and ammonium volatilization in soil,water and air.Through coating,the slow release technology can be used to reduce losses and to increase the fertilizer efficiency.Sulfur has been used as a coating material,but the coating cracks easily because of its friability,sometimes being peeled off from the urea surface.In this study,four types of materials,namely,gypsum,cement,sulfur and zeolite,were mixed and used as coating materials to search for the most effective and cheap coating materials.The primary reasons for selecting these materials were improving fruit quality and preventing plant diseases,providing a plant nutrient,increasing soil fertility and water retention.The materials were also selected based on their availability,processiblity and price.The effects of the coating materials,thickness,drying time,sieving and sealant on the crushing strength and dissolution rate of urea were investigated.Coated urea with the same proportion of gypsum-sulfur exhibited high crushing strength and lower dissolution rate.However,the performance was further enhanced by applying molten paraffin wax on the hot urea surface.SEM images demonstrated that the micro-structure of gypsum-sulfur coated urea after sieving resulted in a smoother coated layer.The efficiency of the coated urea was improved by26%using gypsum-sulfur（20%total coating）,3%paraffin wax and sieving the coating materials before application.

New coating formulation for the slow release of urea using a mixture of gypsum and dolomitic limestone

The use of urea and urea-based fertilizers has increased considerably over the past 15 years. They cur- rently account for approximately 51% of the world＇s agricultural nitrogen consumption. However, about 20-70% of the applied urea fertilizer is lost to the environment, causing serious pollution and increasing costs. These losses come from leaching, decomposition, and ammonium volatilization in the soil during handling and storage. Controlled release by coating can be used to increase urea fertilizer efficiency. We studied the use of gypsum, sulfur, and ground magnesium lime as cost-effective coating materials. All these coating materials contain nutrients required by plants. The effects of the coating composition and proportion of sealant on the rate of urea release and the crushing strength of the coated urea were investigated. We found that coated urea with the same proportion of gypsum-ground magnesium lime （GML） exhibited low urea release and high crushing strength. The performance was enhanced when using polyols as a sealant on the surface of the coated urea. A surface morphology analysis indicated a uniform and smooth surface on the coated film. The efficiency of the coated urea improved by 34.2% when using gypsum-GML （ 1：1 ratio） containing 1.1% oolvols.

PRESSURE DROP ACROSS A FIXED BED REACTOR WITH MECHANICAL FAILURE OF CATALYST PELLETS DESCRIBED BY SIMPLIFIED ERGUN'S EQUATION

The pressure drop across a laboratory-scale catalyst packed bed with mechanical failure of catalyst pellets has been examined. It was found that the increased pressure drop can be described by a simplified model deduced from Ergun's equation. The pressure drop is determined mainly by the term of viscous energy loss.