• 펄프종이기술
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• 제36권3호
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• pp.15-34
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• 2004

Diverse benefits such as reduction of fresh water consumption and effluent discharge, efficient use of raw materials and energy savings can be obtained by papermaking system closure. Closure of papermaking processes, however, causes many problems including reduction of the efficiency of additives, decrease of retention and dewatering, felt plugging, poor Paper quality, generation of slime and odor, poor vacuum efficiency, etc, and it has been recognized that accumulation of Inorganic and organic substances in the process white water is the prime cause of these problems. Therefore, technological developments for preventing accumulation of these detrimental substances are urgently required for Implementing papermaking system closure. Understanding of the accumulation phenomena of the inorganic and organic substances in the papermaking process white water is prerequisite for papermaking system closure. In this study a process simulation method was used to analyze the accumulation phenomena of anionic starch In the process white water as the closure level of a fine paper making process is increased. A pilot paper machine was used as a model process. Starch adsorption and desorption models were developed based on the concept of starch adsorption ratio, which was not considered in previous studies. Steady state simulation studies were carried out based on this model using a commercial simulator. In steady state simulation, the variation of dissolved starch concentration in each process unit was monitored as a function of white water usage for wire shower. The result of the steady state simulation showed that dissolved starch concentration and its increase ratio in Process units increased as white water usage ratio for wire shower increased.

• 펄프종이기술
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• 제36권1호
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• pp.16-23
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• 2004

Recently the increased concerns about the cost reduction and environmental protection make the paper industry increase the closure level of papermaking system, which results in the buildup of organic and inorganic materials in the papermaking process water. Increase of the system closure causes deterioration of additive performance and provokes diverse problems in papermaking process and product quality. To investigate the effects of process water quality on the physical properties of fine papers handsheets were prepared with process water containing various amounts of inorganic and organic contaminants including calcium or sodium ions and oxidized or cationic starches. Inorgainc and organic materials did not show any significant effect on the physical properties of handsheets. Recycled GCC showed the same trends as inorganic and organic materials. The performance of cationic starch was deteriorated, however, in the recycled white water, which resulted in the reduction of tensile index of handsheets.

• 펄프종이기술
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• 제33권2호
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• pp.1-7
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• 2001

Use of high yield pulp and recycled fiber as raw materials and water system closure result in higher fines content and buildup of organic and inorganic contaminants in white water. These are detrimental for the effectiveness of chemical additives including retention aids. Thus it is imperative to employ a retention systems that maintains its efficiency in closed papermaking system for reducing fresh water consumption. The performance of four different microparticle retention systems including cationic polyacrylamide (C-PAM)/bentonite, highly charged cationic starch (HCS)/silica, C-PAM/micropolymer, cationic guar gum (CGG)/silica was evaluated and compared at three different levels of papermaking system closure. Buildup of detrimental substances in a closed white water system increased cationic demand and finally reduced the performance of retention systems. Cationic starch and guar gums maintained their effectiveness in retention in closed white water systems contaminated with anionic trashes because of their structural rigidity and hydrogen bonding ability. Particularly, cationic guar gums, due its stiffness of molecular structure, appeared perform better than catinonic starch.

• 펄프종이기술
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• 제36권3호
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• pp.35-43
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• 2004

Reduction of fresh water consumption and effluent discharge provide diverse advantages in raw materials and energy savings. Papermaking system closure, however, reduces the efficiency of additives, decreases retention and dewatering, and causes many other Problems in papermaking. Accumulation of inorganic and organic substances in the process white water is the prime cause of these problems. Understanding of the accumulation phenomena of the detrimental substances in the papermaking process is of great importance for papermaking system closure. In this study a process simulation method was employed to analyze the accumulation phenomena of anionic starch in the process white water as the reuse rate of dry broke and pick up of surface sizing agent is increased. Steady state simulation studies were carried out based on the model developed in previous study. The variation of dissolved starch concentration in each process unit was monitored as a function of reuse rate of dry broke and surface sizing agent pick up rate. The result showed that dissolved starch concentration Increased as reuse rate of dry broke and surface sizing agent pick up rate was increased.

• 펄프종이기술
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• 제36권4호
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• pp.16-24
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• 2004

The reduction of paper machine water usage is precursor to the water system closure of any mills. This reduction in water consumption reduces the loss of solids; especially fine particulates and their surface adsorbed chemical additives, from mills, which causes an inevitable increase of fine materials in papermaking systems. Also the reduction of paper machine water usage causes substantial increase of organic and inorganic substances in process water. The deterioration of the papermaking process water quality accompanying the reduction of papermaking system closure can be a prime source of the aggravation of paper quality and process efficiency. It is of great importance for paper mills to investigate the influence of the level of papermaking system closure on the paper properties and process runnabililty before implementing process closure. To predict the changes in paper properties at different levels of system closure, highly cotaminated white water was prepared using reverse osmosis technology and used to prepare handsheets from fine paper and newsprint stocks. Results showed that the quality of process water affects the strength. Preparation of highly contaminated process water and handsheet forming with headbox stocks provided important criteria to determine the relationship between the qualities of process water and paper products.

• 펄프종이기술
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• 제30권4호
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• pp.11-17
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• 1998

Reducing the effluent discharge from a paper mill is urgently needed due to tightening environmental regulations and economic reasons. For a paper mill to respond to system closure it is required to adopt the best practical retention system that enables the mill to improve fines retention and drainage. In this study, effects of various retention agents on fines retention, drainage and formation were examined using linerboard stock in the laboratory. Among the retention aids tested, high molecular weight cationic polyacrylamides showed good efficiency both in retention and drainage. On the other hand, high charge density, low molecular weight polymeric retention aids showed little improvement both in retention and drainage. The best retention system selected from the laboratory experiment was applied on a paper machine producing linerboard to evaluate its effect on papermaking system closure.

• 펄프종이기술
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• 제31권1호
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• pp.52-60
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• 1999

Drainage rate in wet-end, which has significant influences on the production capacity, product quality and process economics in papermaking, becomes an important factor in the modern high speed papermaking processes owing to increased level of fines contained in today's pulp materials and increased papermaking system closure. A study was carred out to investigate the influence of beating and fines content on natural and vacuum dewatering using a vacuum drainage tester. Increase in beating and accumulation of fines in the stock decreased natural dewatering, Vacuum dewatering effect, however, increased substantially as beating and fines content were increased. But this increase in vacuum dewatering decreased again when a stock is severely beaten or fines content is greater than 35%. Above this level of fines content, mobile fines migrates to the interstices of the forming web to cause sealing or plugging which restrict fluid movement through the web.

• 펄프종이기술
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• 제30권4호
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• pp.12-12
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• 1998

• 펄프종이기술
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• 제31권1호
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• pp.31-38
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• 1999

Adsorption of polymeric flocculants and dry strength agents onto the surface of papermaking fibers is critical for their effective utilization since the polymeric substances not adsorbed on fibers or fines keep recirculating in the papermaking system to cause various operational difficulties and loss of raw materials. Problems associated with the unadsorbed polymeric substances generate great attention because unprecedent interests in utilization of recycled papers and papermaking system closure. In this study, to understand the effects of recycling on the adsorption propensity of cationic polyacryamide (PAM) dry strength resin onto hardwood bleached kraft pulp fibers and fines a systematic approach was followed. Never dried bleached hardwood kraft pulp was recycled in two different ways. In mode one recycling experiment never dried pulp was beaten then recycled three times by employing simple drying and disintegrating steps. In mode two recycling experiment beating of the recycled pulp was carried out after each recycling step. Adsorption of cationic PAM on fibers and fines was evaluated employing Kjeldahl nitrogen analysis method. The influence of recycling on water retention value, carboxyl content, sheet density and tensile strength of the pulp was examined. As the number of recycling increased, water retention value of the fiber was reduced due to hornification and this in turn caused a decrease in adsorption of cationic PAM. On the other hand, the carboxyl content of the recycled fibers increased because of the oxidation of fibers occurred during drying, and this caused an increase in adsorption of cationic PAM. Because of these two opposing factors the adsorption of the cationic PAM on the recycled fibers decreased and then increased slightly at third recycling step. Increase of PAM adsorption, however, did not provide did not provide and strength improvement for the recycled pulp fibers indicating greater influence of the honification on interfiber bonding.

• 펄프종이기술
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• 제33권4호
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• pp.1-6
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• 2001

Today's paper industry tries to use greater amount of high yield pulp and recycled fiber and to close mill water system, which results in higher fines content and buildup of organic and inorganic contaminants in white water system. Researches are being focused to develop chemical additives that provide good retention and drainage in a closed papermaking system. A microparticle retention system consisted of cationic guar gum and anionic colloidal silica so has been developed to meet the requirements for improving machine speed and product quality. The objective of this investigation was to determine the effects of the degree of cationic guar gums, charge density and structure of anionic colloidal silica sols, and the degree of system closure on the performances of this microparticle retention system. Cationic guar gums and anionic colloidal silica sols with higher charge densities showed better retention performance. Particularly, wider maximum in retention was obtained when structure colloidal silica was used suggesting as mechanism of microparticle bridging is functioning in this system.