Phosphonates as additives in kraft pulping--a preliminary investigation.Application: Kraft mills may be able to apply phosphonates as additives in the digester di·gest·er n. 1. One that makes a digest. 2. Chemistry A vessel in which substances are softened or decomposed, usually for further processing. Noun 1. to achieve higher yield, shorter cooking times and better bleaching response. We investigated the performance of phosphonates as additives in kraft pulping of aspen using hydroxyethylidene diphosphonic acid (HEDP HEDP High-Energy-Density Physics HEDP 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid (organophosphoric acid corrosion inhibitor) HEDP High-Explosive Dual-Purpose ) and diethylenetriamine pentamethylenephosphonic acid (DTMPA). Phosphonate addition in kraft cooking resulted in considerable reduction in kappa number The Kappa number is an indication of the lignin content or bleachability of pulp. It measures the amount of bleach required during digestion of a wood pulp (part of the process of paper making) in order to obtain a pulp with agiven degree of whiteness. (4-8 points), while pulp yield was increased by 3%-5% at a given degree of delignification. Extended lignin lignin (lĭg`nĭn), a highly polymerized and complex chemical compound especially common in woody plants. The cellulose walls of the wood become impregnated with lignin, a process called lignification, which greatly increases the strength and removal and pulping uniformity led to remarkable decrease in rejects especially at low H-factors. For comparison, we used anthraquinon under identical cooking conditions, but it proved inferior to phosphonate in all cases. Application of HEDP or DTMPA in the digester is able to yield pulps of higher initial brightness and viscosity at given degrees of delignification, or to produce pulps of comparable kappa number with much shorter cooking cycle time. Pulps cooked with 0.1%-0.2% phosphonates at H-factor 600 are comparable in kappa number to pulps processed without additive at H-factor 1000. In other words Adv. 1. in other words - otherwise stated; "in other words, we are broke" put differently , for a target kappa number (e.g. 21) at a cooking temperature of 170[degrees]C application of 0.1%-0.2% phosphonates would mean a 27 min. savings in total cooking time. H-factor reduction also can be achieved by reducing cooking temperature while maintaining time. This will result in energy savings and should further improve yield. The bleaching responses of phosphonate treated pulps to DEDED and OPD OPD Tape symbol showing either the first transaction of the day in a security after a delayed opening or the opening transaction in a security whose price has experienced a large rise or fall from the previous day's closing price. sequences were significantly improved, allowing lower chemical application or higher final brightness. In addition to enhanced lignin removal, the improved bleachability is likely extended by an appreciable decrease in metal content of pulp fibers. S! Li is research assistant and Tschirner is associate professor in the Department of Wood & Paper Science, University of Minnesota (body, education) University of Minnesota - The home of Gopher. http://umn.edu/. Address: Minneapolis, Minnesota, USA. , 2004 Kaufert Laboratory, St. Paul, MN 55108; email Tschirner at ulrike@unm.edu. |
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