Cake Strength Research Articles

Measurement of Cake Strength in Potash Using a Centrifuge

When a water-soluble granular fertilizer, such as potash fertilizer, is wetted and then dried, clumps or cakes often form in the material. A centrifugal loading method has been developed to determine cake strength in a ring of potash fertilizer. This method determines the area-average tensile stress at the speed of the centrifuge when the specimen fractures. The cake strength was measured for a series of tests in which the initial moisture content and drying time of each sample was varied. The results show that the cake strength increases linearly with greater initial moisture content. It was also found that a slower drying process produces a stronger cake.

Application of Binder in Stamp Charge Coke Making

Successful and sustainable implementation of Stamp Charging Technology in Tata Steel has given it an edge over conventional Top Charging Technology in terms of production of superior quality of Blast Furnace grade coke from a wide range of coal base, even permitting use of inferior coals. But, the stability of stamped coal cake and the additional thermal energy necessary to drive the extra quantity of water (3-4 %), added intentionally to the coal blend to impart requisite coal cake strength, have always been the two haunting issues associated with this technology. This paper describes the role of coal tar pitch, used as a binder to the coal blend that not only imparts required strength and stability to the coal cake even at lower moisture level and thereby, reducing energy consumption, but also improves the rheological properties of coal blend that contributes to the quality of coke produced from inferior coals. This paper also describes the laboratory scale experimentation and its results followed by commercial plant-scale trials that confirmed the R & D findings on the use of coal tar pitch.

Factors affecting the tensile strength of hot-gas filter dust cakes

The University of North Dakota Energy and Environmental Research Center is determining some of the fuel-, sorbent- and operations-related conditions that lead to blinding or bridging of hot-gas particle filters in pressurized fluidized bed combustion systems. Several mechanisms contribute to the stickiness of dust particles within a filter cake: electrostatic and van der Waals attractions, and mechanical, liquid and solid bridging. The magnitudes of these mechanism impacts depend on the size and composition distributions of the dust particles, cake porosity, gas composition and system temperature. High-temperature tensile strength measurements of filter dust cakes have shown that only a small amount of liquid is necessary to double the tensile strength of a cake. The amount of strength increase is related more to the wettability of the dust than to the liquid's viscosity or air-liquid surface tension. Also, if the tensile strength of a filter cake is less than approximately 50 N/m 2, the cake re-entrains after being pulsed off and can lead to blinding of the filters. If the cake strength is over approximately 300 N/m 2, it can bridge between filters, in some cases forcing them apart and causing them to break. However, the factors affecting cake strength are not independent variables and laboratory measurements have shown that the tensile strength of filter dust does not adequately explain its propensity to bridge across filters in a hot-gas filter system. A better measurement is the tensile strength divided by the density of the cake, or its specific strength. The authors have defined the cake specific strength as its critical thickness index (CTI) because it indicates the maximum thickness for which a cake would build before failing or shedding under its own weight. Laboratory measurements show that the CTI is a better indicator of the observed propensity of a particular dust to form bridges between filters than its simple tensile strength.

重炭酸ナトリウムの固結メカニズ

Sodium bicarbonate easily forms cakes during the storage and / or transport process after production, due to the influence of conditions such as humidity, temperature, compaction etc. Caking causes serious degradation of the material in the commercial value. To overcome the problem, the caking mechanism must be clarified first, and thereafter the effective treatment should be considered to avoid caking. Weak caking strength of sodium bicarbonate powder at the initial stage of caking was measured and evaluated in relation to amounts of various components and physical properties of the powder. Caking under the high humidity (RH80%) of sodium bicarbonate found to occur due to the bridging among particles during the process of changing of sodium carbonate to sodium sesquicarbonate. The caking under the conditions of low humidity (RH40%) and high temperature (40 ∼ 50 °C) however owes bridging accompanied by the change from sodium carbonate to Wegscheider's salt. Caking strengths measured for sodium bicarbonate samples with various particle sizes were correlated with contacting numbers among particles. The caking strength, BL, was found to be expressed with the equation: BL = k·Sc·F, where Sc is the contact area per unit surface area of sodium bicarbonate particles, and F is the formation quantity per the unit surface area, of the double salts such as sodium sesquicarbonate and Wegscheider's salt. We have found finally an effective method to avoid caking through the process of analyzing the caking mechanism of sodium bicarbonate.

Expression behaviour of fine particle suspensions and the consolidated cake strength

The high-level expression of suspensions up to 50 bar is concerned with the recovery of finest particles, e.g. submicron particles. A so-called Press-Shear-Cell was designed, constructed and tested to measure the most important filtration process parameters. In a first filtration stage, a compressible filter cake builds up from a fine particle suspension. The following cake consolidation is applied to reduce the liquid amount in the small pores of the particle packing. To describe the two-stage expression process of fine sludge, a new dynamic model is introduced. In contrast to the common Tiller–Shirato model, which assumes constant average material properties of particle pressure p s, packing density ε s and permeability k inside the cake during constant pressure expression, the new dynamic expression model considers the time and local variation of these material properties. Furthermore, the wall friction resistance is taken into account with the wall friction angle ϕ W and the lateral pressure ratio λ of the cake. The pressure-dependent constitutive functions of kaolin and titanium dioxide filter cakes are shown. Yield loci in a water saturated particle packing were in situ measured with comparatively high normal loads of 100–1000 kPa.

Measurement of powder cohesive strength with a penetration test

An assessment was made of the utility of a cone penetrometer technique for measurement of the cohesive caking strength of a powder. Results from a shear cell were compared with those from a penetrometer using five different types of powder. Simple theory shows that the unconfined compression strength f c should be related to the penetration force F and penetration depth d by f c = a fc (μ, Φ k ) F d 2 where a fc is a proportionality coefficient dependent on both the interfacial friction coefficient μ, and the internal friction angle Φ k . Comparison of shear cell and penetrometer data showed that there was a reasonable correlation between the two techniques, with a fc = 1.4.

LITERATURE ABSTRACTS

General Principles: Viscoelastic Properties of Plant Cell Walls I. Mathematical Formulation for Stress Relaxation with Consideration for Pre‐Extension Rate. S. Fujihara, R. Yamamoto and Y. Masuda (Sci. Ed. Inst. of Sakai City, Mozu ak ah ata, Sakai 591, and Dept. of Biology, Faculty of Sci., Osaka City Univ., Sumi‐yoshi‐ku, Osaka 558, Japan) Biorheology 15, (1978) 63–75.General Principles: II. Effect of Pre‐Extension Rate on Stress Relaxation, ibid. 77–85.General Principles: III. Hysteresis Loop in the stress‐Strain Curve at Constant Strain Rate. Y. Masuda (Dept. of Biology, Faculty of Sci., Osaka City Univ., Sumiy oshi‐ku, Osaka 558, Japan), ibid. 87–97.General Principles: Rheology of Polyelectrolyte‐Stabilized Emulsions. II. Dynamic Measurements. T. Van Vliet, J. Lyklema and M. van den Tempel (Lab. for Phys. & Colloid Chem., Agric. Univ., de Dreyen 6 Wageningen, The Netherlands). J. Colloid and Interface Sci. 65, (1978) 505–508.General Principles: Evaluating the Caking Strength of Powders. T. Tanaka (Dept. of Chemical Process Engineering, Hokkaido Univ., Sapporo, Japan). Ind. Eng. Chem. Prod. Res. Dev., 17, (1978) 241–246.General Principles: Dynamics of Insoluble Monolayers. I. Dilational or Elastic Modulus, Friction Coefficient and Marangoni Effect for Dipalmitoyl Lecithin Monolayers. D. S. Dimitrov, I. Panaiotov, P. Richmond and L. Ter‐Minassian‐Saraga (last author's address, Laboratoire de Physico‐Chimie des Surfaces et des Membranes, UER Biomedicale, 45 me des Saints Peres, 75270 Paris Cedex 06, France). J. Colloid and Interface Sci. 65, (1978) 483–494.General Principles: Measuring the Texture of Cooked Spaghetti. I. Sensory and Instrumental Evaluation of Firmness. P. W. Voisey, E. Larmond and R. J. Wasik (Res. Branch, Agric. Canada, Ottawa, Ontario K1A OC6). Can Inst. Food Sci. Technol. J. 11, (1978) 142–148.General Principles: Laboratory Measurements of Eggshell Strength. I. An Instrument for Measuring Shell Strength by Quasi‐Static Compression, Puncture and Non‐Destructive Deformation. P. W. Voisey and D. C. MacDonald (Eng. Res. Service, Res. Branch, Agriculture Canada, Ottawa, Ontario K1A OC6. Canada) Poultry Sci. 57, (1978) 860–869.General Principles: Milk Gel Structure VIII. Effect of Drying on the Scanning Electron Microscopy of Some Dairy Products. M. Kalab (Food Research Inst., Research Branch, Agriculture Canada, Ontario, Canada K1A OC6) Milch wissenschaft 33, (1978) 353–358.General Principles: Texture‐Structure Relationships in Texturized Soy Protein. III. Textural Evaluation of Extruded Products. T. J. Maurice, L. D. Burgess and D. W. Stanley (Dept. of Food Science, Univ. of Guelph, Guelph, Ontario, Canada). Can. Inst. Food Sci. Technol. J. 9, (1976) 173–176.General Principles: Texture‐Structure Relationships in Texturized Soy Protein. IV. Influence of Process Variables on Extrusion Texturization. T. J. Maurice and D. W. Stanley (Dept. of Food Science, Univ. of Guelph, Guelph, Ontario, Canada) Can. Inst. Food Sci. Technol. J. 11, (1978)1–6.General Principles: Studies of Some Properties of Milk/Soymilk Mixture. W. M. Abou El‐Ella, S. M. Farahat and M. A. Ghandour (Dept. of Food Science, Ain Shams and Zagazig Univ., Egypt) Milch wissenschaft 33, (1978) 295–297.General Principles: Differences in Baking Quality Between Wheat Flours. F. MacRitchie (CSIRO Wheat Research Unit, North Ryde, NSW, 2113, Australia) J. Food Technol. 13, (1978) 187–194.

Evaluating the Caking Strength of Powders

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEvaluating the Caking Strength of PowdersTatsuo TanakaCite this: Ind. Eng. Chem. Prod. Res. Dev. 1978, 17, 3, 241–246Publication Date (Print):September 1, 1978Publication History Published online1 May 2002Published inissue 1 September 1978https://doi.org/10.1021/i360067a013RIGHTS & PERMISSIONSArticle Views216Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (589 KB) Get e-Alerts

The Relationship between Caking and Changes in Surface Properties of Urea Particles due to Moisture Absorption

The thickness of adsorbed water layers required to cause changes in the surface properties of urea was determined by comparing the mesured values of surface area, surface conductivity and X-ray diffraction peak intensity on the urea particles, in varying humidity with the water vapor adsorption isotherm. An adhesive force among the particles by water layers adsorbed and a change in the caking strength of the shaped urea with increasing water vapor pressure were also estimated.The caking tendency and a change in the surface area were recognized at humidities above ca. 20%rH, at which water molecules with thickness 1.2 layer were adsorbed. This fact suggests that the adsorbed water layers dissolve partially the surface of the salt and some deposits are formed in the neighborhood of contacting points among the particles, making salt-bridges. On the other hand, a cohesive force could appeared above 30%rH, at that humidity the two layer adsorption was completed. At water vapor pressures above 60%rH, such the bridge formation occurred in a macro-scale, therefore the caking cecame remarkable.