Mixing speeds

Variations in viscosity of both the incoming and finished products have a dramatic effect on mixer performance. Standard operating procedures should include specific operating guidelines for the range of variation that is acceptable for each application. The recommended range should include adjustments for temperature, flow rates, mixing speeds, and other factors that directly or indirectly affect viscosity. 

Reactor Conditions for Experimental Runs. Operating conditions for the continuous, stirred tank reactor runs were chosen to study the effects of mixing speed on the monomer conversion and molecular weight distribution at different values for the number average degree of polymerization of the product polymer. 

Experimental Procedure. For the initial start-up of the continuous tirred tank reactor, the mixing speed and bath temperature were adjusted with the reactor full of solvent. The polymer seed and monomer feed rates were then adjusted simultaneously. 

Initial comparison of CFSTR runs with similar feed conditions indicates conditions for which the monomer conversion may be dependent on mixing speed. However, when the effects of experimental error in monomer conversion and differences in reaction temperature are considered, the monomer conversion is seen to be relatively independent of mixing speed for rpm equal to or greater than 500. Comparing Run 14 with Run 12 reveals a small decrease in monomer conversion in spite of a rise in reactor temperature of 2°C. This indicated the presence of a small amount of bypassing or dead volume at the lower mixing speed. This imperfect mixing pattern would also be present in Run 15. 

To differentiate between the micro-mixed reactor with dead-polymer and the by-pass reactor models in this investigation, the effect of mixing speed on the value of "( )" was observed. As illustrated in Table V, the value (j>" is not observed to increase with decreasing mixing speed as would be expected for a by-pass reactor. This rules out the possibility of a by-pass model and further substantiates the dead-polymer model. 

The mixing speed had little or no signficant effect on the monomer conversions or the shape of the molecular weight distributions for mixing speeds of 500 rpm or greater. 

Control mixing speed, time, temperature, and vacuum until drying is complete. 

Mix the solution of wastewater, bentonite, alum, caustic, and polymer for 10 minutes and then flocculate at a mixing speed of about 10 rpm for 30 minutes. 

Capacity of Blender, Mixing time, mixing speed... 

Flood tank with nitrogen, increase mixing speed and slowly add sodium citrate. Add tartaric acid. Mix for at least 30 minutes or until dissolved. 

Sunflower Seed. Emulsion capacity of defatted sunflower meal was investigated by Huffman et al. (45) at three pH levels (5.2, 7.0, 10.8), blender speeds (4500, 6500, 9000 rpm), and oil addition rates (30, 45, 60 ml/min). With low mixing speeds and rapid rates of oil addition, optimum emulsion capacity occurred at pH 7.0. These authors related the observed emulsification properties to protein solubility, surface area and size of oil droplets, and rate of protein film formation. 

Add sodium hypochlorite to the mixture. Reduce the mixing speed to prevent splashing as a sudden drop in viscosity will occur. 

The validation protocol should be prepared after the master batch record is approved and signed by responsible parties (i.e., the manufacturer and NDA or ANDA holder). The batch directions should be detailed and easily understood. For example, mixing speeds and times, mixer positions, and method of adding ingredients should be explained clearly. The protocol must agree in process descriptions and flowcharts and be specific enough to remove any ambiguities on process conditions, decisions, or product specifications. For these reasons, it is usually beneficial to prepare a production-sized, prevalidation batch with the proposed final batch record. This batch should also be completely tested and meet finished product specifications. 

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