Chemical Processing - April 2008 - (Page 30)

speeds (and rotor tip speed is what’s important here) often are far higher than on the larger units. So, interpreting results requires a degree of experience. A rule often applied at the start of testing is that if the task can be completed on the lab scale relatively quickly it can be replicated in bulk manufacture — but it follows that if poor results are ob- tained at this initial stage simply hitting the problem with larger, more powerful equipment may not be the answer. Once laboratory scale testing has established the viability of the task, calculations for sizing the right mixer for an application typically are carried out based on vessel geometry and required throughput for in-line devices or tank OUR MISSION YOUR SAFETY GOES TO EXTREMES Gas Detection System SafEye™ Xenon 800 For operational reliability within severe environments. • Detects combustible gases up to 120 meters over open path • Immunity to solar radiation, hydrocarbon ﬂames and external IR radiation • Low-proﬁle stainless steel housing • Heated detector and source optics • Simple installation, alignment and maintenance VISIT US ONLINE MSANET.COM | M U LT I G A S D E T E C T O R S | G A S M O N I T O R S | | HEAD/EYE/FACE PROTECTION | SCBA | 1.800.MSA.INST | www.MSANET.com/chemprocess.html turnover rate in terms of immersion machines, which reflects the common need by end users to achieve a result in a given timescale. These calculations are made with allowance, based almost entirely on experience, for the characteristics of the product being mixed. This guessology has worked well enough for many years. Increasingly however, end users of the equipment expect a level of technical data to be provided — as is the case with agitators — to allow them to make better informed decisions when specifying a mixing system. Technical data sheets more and more frequently accompany quotations for new machinery and equipment manufacturers often must assist with validation and the provision of process guarantees. This has led a number of mixer manufacturers to take a more scientific approach to their customer service and R&D activities. Most already operate testing facilities where clients can carry out trials on laboratory or even production scale equipment (Figure 1). Many tests are purely subjective and it’s often difficult to produce definitive, comparable results, especially in terms of particle size of suspensions and emulsions or the degree of particle size reduction obtained by various means. Recently the trend has been to augment these test centers with analytical capabilities (Figure 2). In the past, samples may have been sent to outside agencies or returned with the customer for testing — a delay that can adversely affect results, particularly where products have characteristics that change on cooling, when shear forces are removed or where hydration continues over time. Immediate on-site analysis of samples during trials allows great accuracy and repeatability of test results and scale-up forecasts. In addition, some mixer manufacturers have been working with academic organizations to further the understanding of the processes involved in high shear mixing. To date limited research has been carried out in this field and still less has been published. Only a couple of institutions have turned their www.chemicalprocessing.com http://www.MSANET.com/chemprocess.html http://www.MSANET.com/chemprocess.html http://www.MSANET.com/chemprocess.html http://www.chemicalprocessing.com

Table of Contents Feed for the Digital Edition of Chemical Processing - April 2008

Chemical Processing - April 2008 Contents From the Editor ChemicalProcessing.com Field Notes In Process Energy Saver Compliance Advisor Is It a Tragedy or Comedy for Engineers? Better Understanding Boosts Mixer Scale-up Don't Err With Air Compressors Control Performance Supervision Enhances Revamp Process Puzzler Plant InSites Equipment & Services Product Spotlight/Classifieds Ad Index End Point

Chemical Processing - April 2008

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