Displacement dewatering. Project 3680, report 1: a progress report to the member companies of the Institute of Paper Science and Technology

 Investor Relations

 4 views
of 45
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Description
SUMMARY A displacement dewatering process for paper dewatering has been experimentally evaluated. The process uses a pressurized air or steam phase to expel free liquid water from paper while the paper is simultaneously under mechanical pressure. The
Share
Tags
Transcript
  DISPLACEMENT DEWATERING Project 3680 Report 1 to MEMBER COMPANIES OF THE INSTITUTEOF PAPER SCIENCE ANDTECHNOLOGY April 1992 Atlanta, Georgia science fish'Weoa PaperIc )hnBgy88b  NOTICE & DISCLAIMER The Institute of Paper Science and Technology (IPST)hasprovided a high standard of professional serviceand has put forth itsbest efforts within the timeand fundsavailable for this project. The information and conclusions are advisory and are intended only for internal useby any company who may receive this report.Each company must decide for itself the best approach to solvingany problems it may have and how, or whether, this reported information should be considered in its approach.IPST does not recommend particular products, procedures, materials,or service. These are included only in the interest of completeness within a aboratory context andbudgetary constraint. Actual products, procedures,materials, and services used may differ andare peculiar to the operations of each company. In no event shall IPSTorits employees and agentshave any obligation or liability for damages including, but notlimited to, consequentialdamages arising out of or in connection with any company's use of or inability to use the reportedinformation. IPST provides no warranty or guaranty of results.  INSTITUTE OF PAPER SCIENCEAND TECHNOLOGY Atlanta,GeorgiaDISPLACEMENT DEWATERING Project 3680 Report 1 A Progress Report to MEMBER COMPANIES OFTHE INSTITUTE OF PAPER SCIENCE AND TECHNOLOGY By Jeffrey D. Lindsay Assistant ProfessorApril 1992  TABLE OF CONTENTS Summary ......................................................................................... 1 Background .................................................................................... 2 Previous Work ......................................................... ...................... 3 Theory of Displacement Dewatering ......................... ............. 4 The Physics of Gas-Liquid Displacement .................................. 4 InterfaceStability ................................................................. 5 Experimental Approach .................................................................... 7 Equipment ............................................................................ 7 Run Procedures ..................................................................... 9 Results and discussion........................................................................ 10 Revision of Previous Data Analysis ......................................... 10 Recent Results for Dewatering and Densification ....................... 13 Strength Properties ....................................................... 19 Path-Dependent Consolidation in Pressing ............................... 21 Discussion.................................... .................................................... 25 Opportunities for Displacement Dewatering.............................. 25 Theory forPath-DependentConsolidation ................................ 25 Conclusions ......... ....... .. ......... .......... ................................................ 28 Bulk Preservation ......... .................. ........................28 Process Needs ................................................. 28 Sheet Properties ......... ............ ............................ 28 Path-Dependent Consolidation................................................. 28 Possible Problems to Overcome ........................................... 29 Future W ork .........2....... .......... ................................. 29 Acknowledgments......... .................................................................... 29 Literature Cited....................................... ................................... 30 Appendix: A ChronologicalDescription of the "Unconfined" Displacement Dewatering Results ............................................ 32 · II  DISPLACEMENT DEWATERING Jeffrey D. Lindsay Institute of PaperScience and TechnologyAtlanta, Georgia SUMMARY A displacement dewatering process for paper dewatering has been experi-mentally evaluated. The processuses a pressurized air or steamphase to expel free liquidwaterfrom paper while the paper is simultaneously under mechanical pres- sure.The objective is to efficiently dewaterpaper while maintainingbulk, in con- trast to conventionalpressing operations which remove watersolelythrough vol- ume reduction of the web. Displacement dewateringalsodiffers fromthrough- drying, inwhich a gas phase blows through the paper to evaporate water. In dis- placement dewatering, a true displacement process is desired in which a gas-liquid interface is maintained. The results to date suggest that displacement dewatering can be a useful dewatering process for some grades of paper and for some specialty products. It has the potential to increase water removalwithoutsignificantly increasing sheet den- sification. Bulk increaseson the order of 5-20% maybe possible, allowing less fiber to be used for some in ordertoachieve a specifiedsheet thickness for some grades. For some other grades, displacement dewatering could yield an increase of several percent in solids levels, resulting in energy savings orpossibly speed im- provement. Displacement dewateringis most likely tosucceed in highlypermeable webs for productswherebulk is desirable. In the past period we have examineddisplacement dewatering processes in bleached kraft hardwood and softwoodpulps, extendingourpreviousresults for unbleached furnishes. Wehave demonstrateddecoupling of dryness and density in all pulp typesexamined, provided the degree of refining is low. We have also exam- ined strength properties in displacement dewateredsheets. As expected, sheetstrength properties are correlated with sheet density for both wetpressed and dis-placement dewatered sheets.We have alsoshown that somedecoupling of density-dryness is possible in wet pressing operations,without the use of a gas phase, by changing the pressing process variables. Very long-nip, low-pressure wet pressing can result in higher bulkat a given dryness than is possiblein conventional wet pressingorin commer- cial shoe presses. Displacement dewateringcan further decoupledryness andden- sity through the application of a gas phase to increasehydraulic pressure in the sheet. Our next major step is transferring the lab-scale technologyto a feasible pilot scale operation.To do this, manyengineeringchallenges must be overcome. 1
Related Search
Similar documents
View more...
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks