Vol.65, No.9 Abstracts

Trend of Pulp Bleaching Research in Oji Paper

Makoto Iwasaki
Advanced Technology Laboratory, Oji Paper Co., Ltd.

  In this paper three topics which I was concerned to the development were briefly described.
  1) Medium consistency Oxygen bleaching
  This method was applied to NUKP fiber line in Tomakomai mill as the first installation of medium consistency oxygen bleaching in Japan in 1986. At first the delignification rate at O2 stage was lower than the target. After many trials, we could overcome this problem with developing two stages oxygen bleaching method. However several years ago three stage oxygen bleaching system was started by the effort of young power.
  2) Xylanase treatment of LOKP
  LOKP was treated by xylanase produced on-site in order to reduce the amount of chlorine using for delignification. This method was first installation in Japan and the first xylanase on-site production and application of it directly to LOKP. This method was stopped after ECF bleaching started, however, new method to utilize the effluent from xylanase treatment of LOKP for health care etc was investigated by young researchers.
  3) Yellowing problem brought by ECF bleaching and the discovery of solution method
  We met yellowing problem aroused from ECF bleaching of LUKP. After struggle we could find the cause of it and proposed ways to remove it during the bleaching stage. The causing chemical was considered to be Hexenuronic acid formed by pulping stage from xylan in hardwood. A young researcher found the effective chemical to remove it and its on-site production method was installed in a mill.

Recent Report on Kraft Pulping Process in Japan
(Phase 1) Brown Stock Process

Pulping Technical Committee, JAPAN TAPPI
Tsukasa Watanabe and Yosuke Uchida
Oji Paper Co., Ltd.
Tetsuya Tanaka
Hokuetsu Kishu Paper Co., Ltd.

  In order to provide and share the technical information among Japanese pulp and paper industries, Pulping Technical Committee surveyed Kraft pulping operations in all domestic KP mills. We received the answers from all mills equivalent to 30 mills. This report summarizes results of the above investigation, concerning operational conditions and equipment of brown stock process which covers from cooking to post oxygen delignification.

Recent Report on Kraft Pulping Process in Japan
(Phase2) Bleaching and Treatment after Bleaching

Yasuo Asano
Nippon Paper Industries Co., Ltd.
Pulping Technical Committee, JAPAN TAPPI

  We report on the bleaching and the treatment after bleaching among the KP operation technology questionnaire results that Pulping Technical Committee executed. There were 48 BKP lines in 28 mills (L:29 lines, N:15 lines, and LEN switches: 4 lines). The process of the oxygen delignification was set up by all lines.
  In the ECF bleaching, there were 40 lines, and the conversion has advanced from three lines of the last investigation greatly. The main ECF bleaching sequence were three or four stages and in both accounts for almost 80%. First bleaching stage was D stage (25 lines), A stage (9 lines) and Z stage (7 lines). The alkali extraction stages were strengthened with hydrogen peroxide or hydrogen peroxide and oxygen in the line of 80%, and hydrogen peroxide was used in the line of 90% or more. On the other hand, it was limited to a conventional bleaching though there were 11 line of hypochlorite.
  The average kappa number of UKP was 10.0 (LUKP) and 12.0 (NUKP), and it was not different from the last investigation. The total available chlorine in the ECF bleaching was 33.4kg/t (LBKP) and 47.0kg/t (NBKP), and a numerical value that was higher than a conventional bleaching. The average COD discharge was 11.8kg/t (LBKP) and 12.7 kg/t (NBKP), and it has improved from the last investigation.

Optimization of a Continuous Digester Operating with Low Bulk Density Chips

Yan Ju
Fiber Business Line, Process Technology, Metso Paper Japan Co., Ltd.

  In operation of a continuous digester with low bulk density chips, there is a problem that liquor level in chip cute becomes to be unstable which may affect on a digester operation. To modify an existing feed system to COMPACT FEEDTM is a good way to solve this problem. On the other hand, in order to obtain a homogenous cooking it is important to even both alkali profile and temperature profile in a digester, and to make even chip column formation in a digester top. By utilizing DiConnTM system it can save steam consumption by means of producing more flash steam, increasing dry solid content in black liquor which decrease steam consumption in an evaporator.

Andritz Technical Solution for Mill Survey Report of Japanese Kraft Mill

Kanji Hagiwara and Hiromi Kida
Capital System Sales Group 1, Andritz K.K.

  Refer to Mill Survey Report of Japanese Kraft Mills, there are mills put new fiber lines with bigger capacity during recent 10 years. But also many mills are still using very old equipment. Also raw material of chip has been changed due to cost reduction. Most of the mills have spent a lot of effort to decrease mill energy consumption. But still mills are strongly requested to decrease the energy cost due to const increase of oil price. This paper presents recent Andritz recent technology of Kraft Pulp process, and technical solutions for the energy saving based on the Mill Survey Report.

Producing Polysulfide by Electrolysis of White Liquor, Integrated with Kraft Pulping Process

Kazuhiro Kurosu
Research Laboratory, Nippon Paper Industries Co., Ltd.

  An electrolytic oxidation process to produce polysulfide (PS) liquor from the white liquor, and application of this process to the kraft pulping (KP) process is introduced.
PS cooking and modified cooking process has been realized because it is valuable to increase yield of KP, but it is not practical to simply combine these processes. We have been developed the electrolytic process as a much more accomplished technology to increase KP yield from 1996. Highly concentrated PS liquor is available with good efficiency, and pure sodium hydroxide is available simultaneously in the electrolytic process. Integration of the electrolytic process with modified cooking process, in which cooking liquor is split and charged into the multistage of cooking digester, provide ideal method to increase KP yield. Moreover, sodium hydroxide obtained from the electrolytic oxidation of white liquor is useful to other process than cooking in KP, such as oxygen delignification, so this electrolytic process is expected to realize quite advanced KP process.
Concrete illustration and idea of above contents are proposed in this article. Technical issue and solution to the problem is also stated.

On-site Production of New Bleaching Agent gPeroxymonosulfuric Acidh and Application of It to Pulp Bleaching

Tetsuo Koshitsuka
Tokyo Research Laboratory, Mitsubishi Gas Chemical Company, Inc.

  In Japan, full-scale ECF bleaching started at the Niigata Mill of Hokuetsu Paper Company in 1998. After that, other companies also began to change from chlorine bleaching to ECF bleaching. The ECF bleaching methods is a combination of chlorine dioxide, ozone, oxygen, and hydrogen peroxide.
The problem of this ECF bleaching became clear that discoloration of product increased. In particular, we noticed discoloration of paper became worse when three factors exist at the same time. Three factors are hexenuonic acid, aluminium sulfate, and acidic papermaking. We researched chemicals that have the ability to remove hexenuronic acid efficiently, we knew that peroxymonosulfuric acid can remove hexenuronic acid efficiently. Peroxymonosulfuric acid can be produced by the reaction between conc. hydrogen peroxide and conc. sulfuric acid. But, continuous production method of peroxymonosulfuric acid was not popular because of the large amount of reaction heat that was produced by the reaction and severe corrosion.
We overcame many difficulties, and established industrial methods and equipment to produce peroxymonosulfuric acid in continuous ways. This method and equipment was first adopted in the world at the Tomioka Mill of Oji Paper Company. After that, a bleaching sequence that introduced peroxymonosulfuric acid revealed some performance like 1) resolution method for the discoloration problem, 2) cost performance, 3) high brightness, and 4) increase in production. This method is being used at two mills and two more mills will adopt this same method in the future.

GL&V/Kawanoe Energy Saving Technologies
-Minimum Investment and Faster Payoff-

Junichi Yano

  Energy saving projects has been becoming one of the most important and urgent matter within the Pulp & Paper industry in order to enhance competitiveness and improve their earnings. Today, many Japanese paper companies will particularly or completely fund energy saving projects depending on the project scope, amount of energy reduction, and the return on investment. Many customers have been successful claiming energy saving incentives by GL&V energy saving technologies, such as by upgrading disk refiners with spline technology and by Luthi rotor.

Metsofs New Rotating Consistency Transmitter Adopts Patented gMetal to Metalh Process Seal

Kiyoyuki Doi
Sales Division, Process Automation Systems, Metso Automation Co., Ltd.

  Metso has developed Metso Rotating Consistency Transmitter to better meet user needs. This universal transmitter suits all pulp and papermaking applications. It is based on Metsofs long, in-depth experience in developing world-class consistency transmitters featuring several patents.
Metso Rotating Consistency Transmitter features shear force measurement principle, but with a new approach. It features Direct Torque? technology, which replaces traditional force balance technology and gives improved measurement stability and faster response.
The new consistency transmitter has an optimal design, which results in higher reliability, easier maintenance, longer lifetime and lower lifetime costs.
One of the factors behind the longer lifetime is the patented Metal-to-Metal Precision? sealing construction that replaces the conventional structure with rubber components. The lighter design with fewer parts lowers the maintenance need to the minimum. It is easy to maintain it onsite by the mill staff, partly even when the process is running.
Metso Rotating Consistency Transmitter is fast to install, and its installation costs are low. In case of replacements, the costs are even lower because the existing installation set-up can be used. Calibration tuning and recipe change can easily be done during production. These new solutions increase the transmitterfs availability time and reliability compared with traditional technology.

Theoretical Study of Shear Wrinkles in Web Span

Takao Kobayashi
Core Technology Laboratory, Oji Paper Co., Ltd.

  In many cases, when the web is transported in a paper machine or a rotary press, the mechanism of wrinkle trouble by paper factor is not clear. Then, theoretical consideration was done by using FEM from the viewpoint of traveling performance of web about the condition that shear wrinkle which run on the roller and causes the trouble is generated by paper factor.
  As a result, the possibility of causing the lateral motion of running web turned out depending on the factor of paper origin like orientation angle and tension profile. The reason is that the web is transported with shear deformation done on driving roller according to the load of tension.
  In addition, the technique for analyzing the process that shear wrinkle caused by tension and lateral motion of web runs on the roller was examined. Although a huge number of element meshes was needed to express wrinkle by simulation, it was shown to be able to analyze the generation of wrinkle by using elastic-plastic analysis.