Self-drying process

The cement content in deflocculated castables is low. Hence, the amount of heat they produce during setting is low. The time of installation can therefore be limited to 24 h. There are special ULCC castables, which are installed in blast furnace trough systems. They contain metallic additives and catalysts. Because of these, an intensive exothermal reaction takes place after the addition of water. Hydrogen is produced out of this reaction. It creates capillaries as it escapes from the structure. These capillaries help in the self-drying process because they increase the surface area from which heat is remov. Because of the fast reaction and drying, the furnace can be put into operation in a short time. 

As described already, many practical applications in dry process surface modification concern the interaction of particles. Figure 13.3.13 shows a schematic drawing and a fabrication model of blending particles. Under self or mutual harmonization during the dry impact blending treatment, final arranging and controlled composites can be obtained. 

Put 400ml of sample into a 500ml dewer vessel. Put on the lid of the heat insulator. Put the vessel in a constant temperature chamber. Measure the temperature to indicate the start of self-heating and the self-accelerating decomposition. The method is very useful but it cannot apply to a substance which has a high vapor pressure, such as 5—CT. Chemical and pharmaceutical companies in Europe use a method to measure heat stability of solid deposit 3 >. The method applies to the drying process of powder products to avoid accidents. It is not yet used in Japan. 

The outcome of this self-accelerating process was a strong increase in condenser temperature (up to - 0°C) and an elevation of product temperature by a few degrees (up to -30°C). However, the difference of temperature between the product and the condenser temperature was still sufficient to ensure a very rapid drying of the product, much faster than in freeze-dryers equipped with an effective coil condenser cooled at -80°C. The observation that the primary drying was... 

The dry thickness is directly related to the wet thickness and always depends on suspension properties such as volume fraction solids and colloidal stability. In this respect self-metered and pre-metered coating flows do not differ. The self-metered process is much more complex, because the wet thickness also depends on the suspension properties. 

The effect of mixtures on the detachment conditions was also evaluated by dr)dng pastes made by a mixture of maltodextrin MOR-REX 1910 and sucrose, with a total solid content of 61.5%, but with increasing amount of sucrose (5, 10, and 15% sucrose, dry weight basis (dwb)). Results in Figure 21.3 indicate that for a defined drying temperature, the moisture content at the moment of self-detachment of the dried film decreased with the increase in sucrose addition. Thus the addition of sucrose made the detachment of dried films of maltodextrin from an inert solid surface during the drying process more difficult. The larger the amount of sucrose added. 

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