|2010 February JAPAN TAPPI JOURNAL
Vol.64, No.2 Abstracts
Water Removal and the Latest Felt Design
Nippon Felt Co., Ltd.
With a technological innovation in press section such as shoe press, paper machine performance has been rapidly improved．At the same time, press felts, a paper machine clothing, has been developed and its function has become higher and higher．A theory of water removal at press section was systematized by the 1980’s, and pressure uniformity, rewetting and flow resistance are the key words in the theory．This report introduces Nippon Felt’s latest press felts developed in consideration of these key words aiming at performance improvement.
The Latest Development and Trend for Forming Fabrics
-The Situation of Latest Triple Layer Fabric-
Albany International Japan Corporation
Paper machine clothing suppliers have experienced greater change in the last few years than at any time since the industry converted from metal to synthetic fabrics. During recent years the share of SSB (Sheet Support Binder) multilayer fabrics has increased rapidly. Nowadays almost all major forming fabric suppliers in the world are selling more SSB fabrics than other styles all together. Depending on the paper grade, for Albany International, the biggest PMC (Paper Machine Clothing) supplier in the world, SSB forming fabrics cover up to 80% of the sales for the segment. Although this rapid evolution has been mainly customer-driven, it has been assisted by development in weaving technology. The latest developments in forming fabric technologies use ULTRAPLANE surface processing, ULTRAPRINT yarn technology (both MD and CD yarns have been reduced to 0.10 mm in diameter) and Inline warp binder concept technology. The focus of Albany International is the continued development of new technologies in both products and processes to target these objectives and provide the highest possible value to the papermaker. This article provides an overview of Albany International’s newest SSB and In-line developments.
Ceramics Applied to Various Formers
Technical Department, Horikawa Engineering Works Ltd.
For many years alumina, oxide ceramic, has been mainly used for dewatering blades. However by increased paper machine operating speed in accordance with improvement of plastic wires further anti-ablation and thermal shock resistance properties are required to dewatering blade materials. In case of alumina it has enough anti-ablation property but sometimes major cracks are created by thermal shock at the time of dry run just ahead of stock on wire. Such thermal shock is generated between plastic wires and surface of blades under high speed with high wire tension. Surface of blades are heated up over 180 degree C in a few minutes by dry run condition and they are cooled down suddenly by stock on wire.
To avoid above, numbers and amount of water shower must be increased but depending on design of a former still dry area can be appeared. Therefore, it is essential selecting ceramic material, which has both anti-ablation and thermal shock resistance properties.
HORIKAWA has been working on ceramic blades in different former types over 40 years. A huge applications and data are available. We are trying to standardize such information as far as possible. We wish to contribute to customers for selecting ceramic material and its maintenances.
Operating Experience of Ishinomaki PM N6
-Headbox, Former and Press-
Ishinomaki Mill, Nippon Paper Industries Co., Ltd.
The wet end of a paper machine contains the initial steps of the paper making process, including dispersion of the stock (pulp fibres) by the headbox, dewatering and sheet formation by the forming section, and mechanical dewatering in the press section. This is the part that determines most of the fundamental properties of the paper sheet, such as basis weight, formation, strength, fibre orientation and paper ply structure. The strength of the sheet is at its lowest here due to the high water content, while on the other hand it removes a large amount of water, also containing fibre. Thus, the wet end has the highest number of contaminant sources, and countermeasures against defects and paper breaks are of great importance. Further, aside from mechanical equipment, paper machine clothing is an important factor affecting paper quality and runnability. Since all clothing that runs on the paper machine, apart from dryer canvases, is concentrated in the wet end, it is a section in which clothing design selection and daily management is extremely important.
Ishinomaki PM N6 commenced commercial production on Nov 1st 2007, and since then had a smooth startup to now principally produce LWC and MWC at 1600 mpm. This report gives an outline of the latest equipment, and our recent operating experiences in the wet section of PM N6.
Operating Experience of Niigata N9 Wet Section
No.7 Production Department, Niigata Mill, Hokuetsu Kishu Paper Co., Ltd.
Niigata N9 has produced A3 grade as the paper machine focused on wide width, high speed and low base weight, since September 1, 2008. N9 has become a competitively cost performed paper machine with its high productivity brought by wide and high speed. Remarkable and distinctive equipments are a gap former which is new for us, tandem shoe press put 2-stacks shoe press in series, 4-stacks hot soft nip calendar bringing us on-line gloss paper, tail threading equipments for steady tail threading with high speed, and so on. This paper reports outline and operating experiences of N9 focused on wet section from headbox to press.
Operating Experience of Mishima PM N10
Mishima Mill, Daio Paper Corporation
N10 paper machine introduced state-of-the-art technologies to realize its design concept of high speed on-machine coater which combines lighter paper with high DIP composition. We began the commercial operation in September 2007.
It can switch the coating process with blade coater and roll coater, and has online multi-nip calender. Therefore our products have higher quality compared with an existing machine and have achieved our first target.
After two-year operation, we report the comparison about quality and runnability with an existing machine, and the improvement of the productivity for lighter paper with high DIP composition.
Operating Experience of Tomioka PM N1
Tomioka Mill, Oji Paper Co., Ltd.
PM N1 in Tomioka mill started the trial operation from November 2008 and has produced commercial paper since February 2009. We successfully achieved the continuous operation at 1,600mpm and the production of 1,000t/day in last June.
This report presents the outline of troubles we experienced since commercial production started and the countermeasures.
Introduction of Total Tail Handling System for Paper Machine
-From Wetend to Reel-
Paper Machinery Sales Dept., Kobayashi Engineering Works, Ltd.
In recent years, according the speed increase of paper machine, the most reliable paper threading methods are required for entire parts of paper machine from wetend to reel.
The shortening of paper threading time contributes to not only direct reduction of production loss, but also progress of operation efficiency of paper machine. Easier paper threading which everybody can do it without experience, resulting in labor saving which means the reduction of operators who touch the tails of paper threading, offers you finally a great safety.
Considering kind of paper products, operational conditions, machine arrangements, etc., we prepare sophisticated paper threading facilities, coping with the various applications required for each part of paper machine.
Total tail handling system introduced this time, is the result of combination of process know-how, and manufacturing expertise obtained from our long experience in Japanese pulp and paper industry, and those of paper machine, who is a technical licensor in USA, succeed to and developed in the technology of former Beloit Corporation. This combination has succeeded in the epoch making improvement of tail handling system for whole parts of paper machine.
Board Machine Technology of Andritz
-New Board Machine Started the Operation in China-
Andritz AG (Austria Graz) had manufactured and sold paper machines under license from Escher Wyss until 1995. From 1996 Andritz started to focus on tissue paper machines and from 2000 made joint research projects in cooperation with Voith. Since then, Andritz installed more than forty high speed tissue paper machines mainly in Europe, North America and China. In 2005 Andritz restarted board machine business. As a result, an integrated board production facility that consists of recycled fiber line and board machine were ordered in 2007 by Hebei Yongxin Paper in China and started up in April 2009. The machine type is three-ply Fourdriniers and multi-dryer cylinders. The wire width is 6,200 mm, the design speed is 1,100 m/min and the production capacity is 350,000 ton/year. This paper reports the specifications, the machine concept and the start-up of the recycled fiber line as well as board machine.
Development of a New Cooking System using Highly Concentrated Polysulfide (II)
-Application to Modified Cooking with Multi Charges of Cooking Liquor-
Keigo Watanabe, Masahiro Shimizu, Kazuhiro Kurosu, and Yasunori Nanri
Nippon Paper Industries Co., Ltd.
Graduate School of Life and Environmental Science, University of Tsukuba
Polysulfide (PS) cooking is one of the most efficient technologies available today to increase pulp yields. The PS has to be produced from Na2S in the white liquor (WL) to keep Na+ and S2- balance in the WL recovery cycle. To produce the PS in high efficiency, a WL electrolysis using ion-exchange membranes has been developed by Nippon Paper Industries CO., LTD.
Modified cooking is characterized by sequential charges of WL to the cooking digester. Recently, Iso-thermal cooking (ITC), which is one of the modified cooking, characterized by low temperatures and long-cooking times has been industrialized and installed in a lot of kraft pulping processes. However, not only NaOH concentrations but also Na2S concentrations at a start of the cooking are decreased, because the initial charge of WL was decreased by the modified cooking.
In this study, the combinatorial use of ITC cooking and PS cooking were evaluated, expecting a process in which the mill scale pilot electrolyzers were installed. A yield gain caused by the PS cooking was decreased in cases of the modified cooking conditions. However, when the PS was produced by the electrolyzers, the yield gain was increased contrary to the case by the air oxidation. By the electrolyzers, the PS concentrations became double and a lack of initial Na2S concentration was minimized.
In addition, the electrolyzers, which have a function of electro dialysis using ion-exchange membranes, enabled sulfide elements in WL to be concentrated as PS and Na2S. Consequently, much more yield gain was expected by using the new modified cooking.
Keywords: Polysulfide, Sulfidity, Na2S, Pulp yield, Electrolysis
Relationship between Hexenuronic Acid and Brightness Reversion of ECF-bleached Hardwood Kraft Pulp Part 1
Ayano Kawae and Yosuke Uchida
Oji Paper Co., Ltd., Pulp and Paper Research Div.
Yellowing of ECF (Elementally Chlorine Free) or TCF (Totally Chlorine Free) bleached pulp has became a significant problem since 1990s. This brightness reversion tends to occur around pH 4.5. Acid-sized paper decreases brightness significantly. Many researchers have studied the causes of brightness reversion of softwood bleached kraft pulp having brightness of around ISO 90%. Affects of cellulose, hemicellulose, hexenuronic acid (HexA) and metal ions were reported. Some factors will probably affect each other. Although the mechanism is still unknown, it has been shown that HexA is a main cause. To remove it, acid treatment, hot chlorine dioxide bleaching, powerful ozone bleaching were introduced. However, they need a huge amount of energy, and decrease pulp yield and strength.
In Japan, brightness of bleached pulp is usually around ISO 86%, and it is rare to produce bleached kraft pulp having brightness of ISO 90%. We have to consider affect of lignin besides HexA. The purpose of this report is making the affect of HexA in Japanese kraft pulp clear, and finding the way to avoid the yellowing by an efficient method.
It was shown that HexA was also a main cause of heat and moisture induced yellowing of Japanese hardwood bleached kraft pulp (LBKP). Compared with reactivity of chlorine dioxide to lignin, that of HexA was low. Therefore HexA tended to remain in D-ECF bleached pulp. We concluded that reducing HexA and lignin ratio of the pulp entering into D-ECF bleaching is important to decrease HexA content of LBKP. The ratio of unbleached hardwood kraft pulp (LUKP) had a maximum value toward kappa number of the pulp. As one of the ways to avoid the yellowing, the cooking kappa number should be fixed higher or lower than the kappa number that gives the maximum HexA content.
Keywords : Hexenuronic acid, Brightness reversion, Yellowing, Kraft pulp, Hardwood, ECF, ECF bleaching