Chemical Processing - July 2008 - (Page 41)

process puzzler deal with dryer drizzle Readers suggest ways to solve a spray interference problem this month’s puzzler our spray dryer is fed from two booms. These booms have a dozen tiny spray nozzles each. each set of nozzles is set into a head, one to each boom. it is a new design that our management hopes will increase throughput. The result has been completely opposite. one of our engineers thinks that some of the droplets collide where the streams of the booms strike together. conversations with the spray nozzle company and calculations confirm that this is the case. our vendor suggests going with only one boom but this will cut our rate and the spray won’t be centered in the dryer. The droplets must fall at a specific rate to crystallize properly. is there anything we can do that will allow us to work with the existing heads? ing viscosity of the liquid; and increasing the liquid temperature or gas temperature. A centered stream is best for maximizing the rate To avoid droplet collisions, change to larger and performance of the dryer. This necessitates the nozzles for the part of the heads facing away from the presence of the two opposite streams; that is also booms and smaller nozzles for the nozzles pointed at what management wants to keep. With this as a start, I would suggest considering including a chemi- each other. Or eliminate all the interfering nozzles. Another possible approach may be to rebuild the cal solution that incorporates an additive to alter the spray heads to reduce the angles between the jets, givsurface tension so as to promote small particle size ing them more time to evaporate before eventually colon falling. I assume economics and product quality liding. This combined with other improvements, e.g., a will not be adversely affected. The second alternahotter dryer, may be enough to improve the situation. tive would be to increase the upstream air flow to Dirk Willard, senior process engineer enhance particle breakdown. Ambitech Engineering, Hammond, Ind. Emilio Malaguti, technical manager, Chemtron, Hialeah, Fla. Use an additive september’s puzzler talk to a specialist Without a complete redesign of the spray dryer, the best option is to keep the nozzle streams from mixing before evaporation has occurred. If the distance between the booms can’t be adjusted because of chamber diameter restrictions, a nozzle orifice change is probably needed. Reduce the spray angle for each small nozzle in the head to eliminate the droplet collisions. When reducing the spray angle, the feed pressure will have to be adjusted to keep the same atomization. After you’ve developed a better understanding of the problem, get some help. Talk with a company specializing in spray nozzles to design the correct system. John Kelsoe, process engineer Polyone, Peoria, Ill. RUn some tests To perform well, the spray must be atomized to an optimum droplet diameter and evenly dispersed to allow good evaporation. Several options exist for increasing evaporation, including: improving gas flow within the dryer; increasing the height the liquid must drop; reduc- our pressure filter suffers from excessive cake build-up. after a few hours we must tear down the filter so the media can be cleaned. as a result, the media often are damaged during the maintenance and must be replaced at considerable expense. also, because of the extremely high pressure used, the operators must follow a strict procedure for switching the filters; a few accidents have occurred along with several near-misses. although some caking is necessary for efficient filtering, it would be desirable to extend the running time. What do you suggest? also, do you have any ideas on how we can lengthen media life or reduce operating costs? send us your comments, suggestions or solutions for this question by august 11, 2008. We’ll include as many of them as possible in the June 2008 issue and all on cp.com. send visuals — a sketch is fine. e-mail us at processpuzzler@putman.net or mail to process puzzler, Chemical Processing, 555 W. pierce road, suite 301, itasca, il 60143. Fax: (630) 467-1120. please include your name, title, location and company affiliation in the response. and, of course, if you have a process problem you’d like to pose to our readers, send it along and we’ll be pleased to consider it for publication. 41 chemicalprocessing.com July 2008 http://CP.com http://chemicalprocessing.com

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

Chemical Processing - July 2008 Contents From the Editor ChemicalProcessing.com Field Notes In Process Energy Saver Compliance Advisor Who’s a Big Hit? Succeed with Condensate Control Take Some Basic Steps with pH Measurements Steam Projects Provide Fast Payback Process Puzzler Plant InSites Equipment & Services Product Spotlight/Classifieds/Ad-Lits Ad Index End Point

Chemical Processing - July 2008

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