Particles size optimization

Catalyst Particle Size Optimization and Dispersion Uniformity 87... 

An in-depth investigation of the grinding operation has been done, together with a precise balance of all incoming material flow in the pilot hne (see the examples of a material balance and a diagram of the particle size optimization). 

Homogeneity Aggregates Particle Sizes Optimal Size for optics... 

Another example is the purification of a P-lactam antibiotic, where process-scale reversed-phase separations began to be used around 1983 when suitable, high pressure process-scale equipment became available. A reversed-phase microparticulate (55—105 p.m particle size) C g siUca column, with a mobile phase of aqueous methanol having 0.1 Af ammonium phosphate at pH 5.3, was able to fractionate out impurities not readily removed by hquid—hquid extraction (37). Optimization of the separation resulted in recovery of product at 93% purity and 95% yield. This type of separation differs markedly from protein purification in feed concentration ( i 50 200 g/L for cefonicid vs 1 to 10 g/L for protein), molecular weight of impurities (<5000 compared to 10,000—100,000 for proteins), and throughputs ( i l-2 mg/(g stationary phasemin) compared to 0.01—0.1 mg/(gmin) for proteins). 

The cmde copper phthalocyanine must be treated to obtain a satisfactory pigment in regard to the crystal modification and optimal particle size... 

The large majority of activated alumina products are derived from activation of aluminum hydroxide, rehydrated alumina, or pseudoboehmite gel. Other commerical methods to produce specialty activated aluminas are roasting of aluminum chloride [7446-70-0], AIQ calcination of precursors such as ammonium alum [7784-25-0], AlH2NOgS2. Processing is tailored to optimize one or more of the product properties such as surface area, purity, pore size distribution, particle size, shape, or strength. 

Some special requirements of continuous systems are (1) Metering the feed. A continuous system must be fed at a precise, uniform rate. (See Sec. 21.) (2) Dust collection. This is a necessary part of most diy-processing systems. Filters are available that can effectively remove dust down to 10 mg/m or less, and operate automatically. (Dust collection is covered in Sec. 17.) (3) Ondine analysis. For more precise operation, on-line analysis of product particle size and composition may be desirable. (4) Computer control. SiiTuilation can aid in optimizing system design and computer control. 

If individual controllers are used instead of optimal computer control, several strategies are possible. In one strategy (Lynch and Fiber, 3rd IFAC Symposium on Automation of Mining, Mineral and Metal Proce.ssing, 25-32, 1980) the sluri y-pump rate is controlled to maintain sump-level constant, which results in smooth cyclone operation. The water-feed rate is ratioed to the ore-feed rate, which keeps the circiilating load from oscillating. The ore-feed rate is then controlled to maintain product-particle size. 

Adsorption efficiency can be optimized by using finer particle size products which will improve the diffusion rate to the surface of the activated carbon. However, there is a tradeoff in using finer particles with pressure drop and, hence energy use. Note that during start-up of an activated carbon filter bed, a bed expansion of 25 to 35 % is recommended in order to remove soluble matter and to stratify particles in order to ensure that the MTZ is maintained when future backwashing is performed. 

As mentioned above, among many possible process variables, industrial crystallization frequently focuses on the optimization of particle size. In many cases this may be fixed by market demands, in others it may be a variable e.g. during the processing of intermediates. 

Irrespective of the development of media, many of the traditional media are successfully defending their position. This is due to their hydrophilic nature, preserving biological function of the separated molecules, but also the fact that columns may be prepared easily and, finally, some of the classical media, e.g., Sephadex, have a selectivity that is so far unsurpassed and therefore very fit for use. Intersting enough, Sephadex is still the premiere gel filtration medium for desalting due to the optimal pore size and particle size of this medium (see Section II,C). 

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