Skip to main content Accessibility help

We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.

Close cookie message
×
Hostname: page-component-669899f699-2mbcq Total loading time: 0 Render date: 2025-05-02T08:32:56.907Z Has data issue: false hasContentIssue false

14 - The Wurster coater

Published online by Cambridge University Press:  04 February 2011

By
Sarah Palmer ,
Andrew Ingram  and
Jonathan Seville
Edited by
Norman Epstein  and
John R. Grace
Norman Epstein
Affiliation:
University of British Columbia, Vancouver
John R. Grace
Affiliation:
University of British Columbia, Vancouver
Get access

Summary

Introduction: particle coating techniques

The Wurster coater is a special variant of a fluidized or spouted bed (Figure 14.1) that resembles a spouted bed in being of conical-cylindrical construction, but normally has a gas distributor at its base, through which an upfacing spray nozzle projects. This nozzle is usually of the two-fluid type and is used to introduce a coating material – usually a solution, but sometimes a suspension or melt. It is customary to install a draft tube into the column, so particles are constrained to circulate upward inside the draft tube and downward in the annulus surrounding the draft tube. In this respect, Wurster coaters have similarities to spout-fluid beds containing draft tubes. Their main use is for coating pharmaceutical tablets and pellets, for which this is one of the most common methods.

Within the pharmaceutical industry, particulate materials are coated for a number of reasons: to produce controlled release dosage forms, to mask unpleasant tastes, to protect ingredients within the tablet/pellet from the environment (light, moisture, air, or undesirable pH), for aesthetic appeal, and to protect the consumer from toxic compounds that may cause gastric distress or nausea.

In industrial practice, particle coating is accomplished using several types of equipment, most notably rotating drum (or perforated pan) and fluidized bed coaters. (Fluidized beds are also used to agglomerate particles, but agglomeration is undesirable in coaters, which are therefore designed to minimize it.)

Type
Chapter
Information
Spouted and Spout-Fluid Beds
Fundamentals and Applications
 , pp. 238 - 249
Publisher: Cambridge University Press
Print publication year: 2010

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Book purchase

Temporarily unavailable

References

Cole, G. Tackling the tablet. Chem. Engr., 618 (1996), 22–31.
Hogan, J.. Coating of tablets and multiparticulates. In Pharmaceutics: The Science of Dosage Form Design, ed. Aulton, M. E. (London: Churchill Livingstone, 2002), pp. 441–448.Google Scholar
Tzika, M., Alexandridou, S., and Kiparissides, C.. Evaluation of the morphological and release characteristics of coated fertilizer granules produced in a Wurster fluidized bed. Powder Technol., 132 (2003), 16–24.CrossRefGoogle Scholar
Subramanian, G., Turton, R., Shelukar, S., and Flemmer, L.. Effect of tablet deflectors in the draft tube of fluidized/spouted bed coaters. Ind. Eng. Chem. Res., 42 (2003), 2470–2478.CrossRefGoogle Scholar
Teunou, E. and Poncelet, D.. Batch and continuous fluid bed coating – review and state of the art. J. Food Eng., 53 (2002), 325–340.CrossRefGoogle Scholar
Jones, D.. Air suspension coating. In Encyclopedia of Pharmaceutical Technology, ed. Swarbrick, J. and Boylan, J. (New York: Dekker, 1988), pp. 189–216.Google Scholar
Wurster, D. E.. Means for applying coatings to tablets or like. J. Amer. Pharmaceutical Assoc., 48 (1950), 451.Google Scholar
Jono, K., Ichikawa, H., Miyamoto, M., and Fukumori, Y.. A review of particulate design for pharmaceutical powders and their production by spouted bed coating. Powder Technol., 113 (2000), 269–277.CrossRefGoogle Scholar
Cheng, X. X. and Turton, R.. The prediction of variability occurring in fluidized bed coating equipment. I. The measurement of particle circulation rates in a bottom-spray fluidized bed coater. Pharmac. Dev. & Technol., 5 (2000), 311–322.CrossRefGoogle Scholar
Geldart, D.. Types of gas fluidization. Powder Technol., 7 (1973), 285–292.CrossRefGoogle Scholar
Crites, T. and Turton, R.. Mathematical model for the prediction of cycle-time distributions for the Wurster column-coating process. Ind. Eng. Chem. Res., 44 (2005), 5397–5402.CrossRefGoogle Scholar
Christensen, F. N. and Bertelsen, P.. Qualitative description of the Wurster based fluid bed coating process. Drug Develop. & Ind. Pharm., 23 (1997), 451–463.CrossRefGoogle Scholar
Turton, R. and Cheng, X. X.. The scale-up of spray coating processes for granular solids and tablets. Powder Technol., 150 (2005), 78–85.CrossRefGoogle Scholar
Palmer, S. E.. Understanding and optimisation of pharmaceutical film coating using the Wurster coater. Ph.D. thesis, Univ. of Birmingham, UK (2007).
Mann, U., Rubinovitch, M., and Crosby, E. J.. Characterization and analysis of continuous recycle systems, AIChE J. 25 (1979), 873–882.CrossRefGoogle Scholar
Mann, U.. Analysis of spouted-bed coating and granulation. 1. Batch operation. Ind. Eng. Chem. Proc. Des.Dev., 22 (1983), 288–292.CrossRefGoogle Scholar
Cheng, X. X. and Turton, R.. The prediction of variability occurring in fluidized bed coating equipment. II. The role of nonuniform particle coverage as particles pass through the spray zone. Pharm. Dev. & Technol., 5 (2000), 323–332.CrossRefGoogle ScholarPubMed
Shelukar, S., Ho, J., Zega, J., Roland, E., Yeh, N., Quiram, D., Nole, A., Katdare, A., and Reynolds, S.. Identification and characterization of factors controlling tablet coating uniformity in a Wurster coating process. Powder Technol., 110 (2000), 29–36.CrossRefGoogle Scholar
Mann, U. and Crosby, E. J.. Cycle time distribution measurements in spouted beds. Can. J. Chem. Eng., 53 (1975), 579–581.CrossRefGoogle Scholar
Wesdyk, R., Joshi, Y. M., Jain, N. B., Morris, K., and Newman, A.. The effect of size and mass on the film thickness of beads coated in fluidized bed equipment. Int. J. Pharmaceutics, 65 (1990), 69–76.CrossRefGoogle Scholar
Choi, M.. Hydrodynamics of commercial-scale Wurster coaters. Presented at annual AIChE meeting (1998).
Fitzpatrick, S., Ding, Y., Seiler, C., Lovegrove, C., Booth, S., Forster, R., Parker, D. J, and Seville, J. P. K.. Positron emission particle tracking studies of a wurster process for coating applications. Pharmaceutical Technol., 27 (2003), 70–78.Google Scholar
Seville, J. P. K., Tüzün, U., and Clift, R.. Processing of Particulate Solids (Glasgow: Chapman and Hall/Blackie, 1997).CrossRefGoogle Scholar
Turton, R.. Challenges in the modelling and prediction of coating of pharmaceutical dosage forms. Powder Technol., 181 (2008), 186–194.CrossRefGoogle Scholar
Sherony, D. F.. A model of surface renewal with application to fluid bed coating of particles. Chem. Eng. Sci., 36 (1981), 845–848.CrossRefGoogle Scholar
Liu, L. X. and Litster, J. D.. Coating mass distribution from a spouted bed seed coater: experimental and modelling studies. Powder Technol., 74 (1993), 259–270.CrossRefGoogle Scholar
KuShaari, K., Pandey, P., Song, Y., and Turton, R.. Monte Carlo simulations to determine coating uniformity in a Wurster fluidized bed coating process. Powder Technol., 166 (2006), 81–90.CrossRefGoogle Scholar
Seiler, C., Fryer, P. J., and Seville, J. P. K.. Statistical modelling of the spouted bed coating process using positron emission particle tracking (PEPT) data. Can. J. Chem. Eng., 86 (2008), 571–581.CrossRefGoogle Scholar
Heng, P. W. S., Chan, L. W., and Tang, E. S. K.. Use of swirling airflow to enhance coating performance of bottom spray fluid bed coaters. Int. J. Pharmaceutics, 327 (2006), 26–35.CrossRefGoogle ScholarPubMed

Save book to Kindle

To save this book to your Kindle, first ensure [email protected] is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.

Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Available formats
×

Save book to Dropbox

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.

Available formats
×

Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

Available formats
×