Drying of paper by impinging jets of superheated steam was studied in an apparatus which closely simulates conditions for a potential industrial impingement dryer. / Drying was found to consist in a constant rate period, followed by a falling rate period where the drying rate decreases linearly with moisture content. The relation found between the constant rate and Reynolds number and temperature of the jet is consistent with a previous correlation for air impingement heat transfer, suitably modified for conditions in a steam environment. For a given mass flux, steam drying is slower than air drying below an inversion temperature of 175$ sp circ$C and faster above. The specific blower power for steam drying is much lower than for air drying at temperatures in the industrial range. / Equilibrium moisture content measurements showed that complete drying can be obtained at steam temperatures only slightly above the boiling point. Expressions for the critical moisture content in impingement drying in steam and in air were obtained. In steam drying, the falling rate period was found to be determined more by internal transport resistance than by adsorption of water on the fibers. / A new arrangement for drying paper, in which the first half of the drying is done by a conventional dryer to which steam is supplied from a steam impingement dryer handling the second half, was analyzed. In regions with low electricity cost, recirculation of steam around the impingement dryer circuit by a mechanical fan is much more economical than by a thermocompressor. However, this advantage is only marginal where electricity cost is high. The overall performance is optimized by using the highest temperature and lowest jet velocity possible. The drying cycle proposed is a realistic and attractive means to increase drying capacity and reduce energy consumption.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.41047 |
| Date | January 1991 |
| Creators | Bond, Jean-François |
| Contributors | Douglas, W. J. M. (advisor), van Neiningen, A. R. P. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001384360, proquestno: NN91667, Theses scanned by UMI/ProQuest. |
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