Process parameters particle size

Strong effects of the ionic conductivity on the lattice parameter caused by the dopant type and content upon processing parameters (particle size, sintering temperature, and microstructure) and operating temperature (defect formation and transport) were also reported for nanopowder ceria-based electrolytes. 

Properly controlling the different steps of the production process requires knowledge of the API concentration throughout the process (from the raw materials to the end product). The characteristics of the NIR spectrum require the use of multivariate calibration techniques in order to establish a quantitative relationship between the spectrum and the chemical (composition) and/or physical parameters (particle size, viscosity and density). 

In the case of suspension PVC, processing parameters and product structure are affected by particle size distribution. Morphology and particle size distribution determine preparation of dryblends and parameters of processing. The particle size also determines the minimum thickness of a product as well as surface gloss. 

The Q8 guideline emphasises the importance of understanding the formulation and the method of preparation, as well as preparation process control that is based on scientific data and risk analysis of the preparation process (see also Chap. 21). Identification of all relevant sources of variability will result in a window (the design space) for all adjustable parameters (particle size, pH, mixing time, etc.). Practically, the QbD approach will lead to a robust formulation and preparation process that is stUl flexible enough to adapt to necessary modifications. Detailed documentation of the development research will help limiting time- and resourceintensive follow-up studies in order to explain process deviations or applying process modifications. 

Minimum Fluidizing Velocity U,nj, the minimum fluidizing velocity, is frequently used in fluid-bed calculations and in quantifying one of the particle properties. This parameter is best measured in small-scale equipment at ambient conditions. The correlation by Wen audYu [A.l.Ch.E.j., 610-612 (1966)] given below can then be used to back calculate d. This gives a particle size that takes into account effects of size distribution and sphericity. The correlation can then be used to estimate U, at process conditions, if U,nj cannot be determined experimentally, use the expression below directly. 

The concentration of K2TaF7 in the initial melt is the main parameter controlling the particle size and surface area of the reduced primary powder [598]. Typically, the increased concentration of K2TaF7 leads to the formation of coarse tantalum powder. According to Yoon et al. [599], the diluent prevents a strong increase in the temperature of the melt that is caused due to the exothermic effect of the reduction process. Based on the investigation of the reduction process in a K2TaF7 - KC1 - KF system, it was shown that increased amounts of diluent lead to a decrease in particle size of the obtained tantalum powder. 

The uniformity of tantalum powder is also a veiy important parameter of capacitor-grade tantalum powder. The loss of powder uniformity can initiate during the regular reduction process due to varying conditions at the beginning and end of the reduction process. At the end of the process, the concentration of tantalum in the melt is very low, while the sodium content increases. Based on the complex structure model of melts, it should be noted that the desired particle size of the powder is formed at the veiy beginning of the process, while the very fine fraction forms at the end of the process, independent of the initial content of the melt. The use of special equipment enables to perform a continuous reduction process with simultaneous loading of K TaFy and sodium, which can influence the improved uniformity of the primary powder [592,603,604],... 

Situation There are two vendors for a particular bulk chemical who meet all written specifications. The products are equally useful for the intended reaction as far as the chemical parameters are concerned both comply in terms of one physical parameter, the size distribution of the crystals, but on the shop floor the feeling prevails that there is a difference. Because the speed of dissolution might become critical under certain combinations of process variables, the chemical engineers would favor a more finely divided raw material. On the other hand, too many fine particles could also cause problems (dust, static charging). 

Basket-type reactor (CSTR) for gas-phase reactions) High temperature, high pressure catalytic processes High transport rates, easy variation of parameters Limited particle size, high equipment cost, difficult to operate under a wide range of conditions without creating flow maldistribution... 

A mechanistic model for the kinetics of gas hydrate formation was proposed by Englezos et al. (1987). The model contains one adjustable parameter for each gas hydrate forming substance. The parameters for methane and ethane were determined from experimental data in a semi-batch agitated gas-liquid vessel. During a typical experiment in such a vessel one monitors the rate of methane or ethane gas consumption, the temperature and the pressure. Gas hydrate formation is a crystallization process but the fact that it occurs from a gas-liquid system under pressure makes it difficult to measure and monitor in situ the particle size and particle size distribution as well as the concentration of the methane or ethane in the water phase. 

---