Summaries of January 2005 peer-reviewed papers.

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RECOVERY BOILERS

EXPERIENCES WITH LOWER FURNACE TUBE CRACKING IN A RECOVERY BOILER

APPLICATION: By making modifications to the recovery boiler, mills can alleviate temperature variations that lead to cracking in boiler tubes.

The recovery boiler at the DMI Peace River Pulp Mill was experiencing severe cracking of stainless steel 304L/SA210 composite tubes. Cracking was occurring in tubes on the furnace floor, at primary air ports, at smelt spout openings, and at composite-to-composite butt welds in the lower furnace.

The problem was found to be related to frequent temperature excursions in the tubes. These temperature variations were caused by the location and configuration of the tertiary air system and by the operation of the six-on-six interlaced secondary air system.

The personnel at the DMI Peace River Pulp Mill reduced the cracking problem to an acceptable level by making a number of modifications over a number of years. They reconfigured the secondary air interlacing and changed the air splits between the primary, secondary, and tertiary levels. The tertiary air ports were moved to a higher elevation. Moreover, a number of SS304L/SA210 composite tubes were replaced with co-extruded Inconel 825 tubes. View this paper online at http://www.tappi.org/index.asp?pid=31490&ch=1

Rob Vesak, Bill Downing, Mike Gauthier, Sally Howard, Doug Spirig, and Laura Neels are with the Daishowa-Marubeni International Peace River Pulp Mill, Peace River, AB, Canada. Honghi Tran is with the Pulp & Paper Centre. University of Toronto, Toronto, ON, Canada. Email Veska at [e-mail].

EMISSIONS CONTROL 

ABATEMENT OF MALODOROUS PULP MILL EMISSIONS BY CATALYTIC OXIDATION--PILOT EXPERIMENTS IN STORA ENSO PULP MILL, OULU, FINLAND

APPLICATION: Catalytic incineration is a feasible technology for removing volatile organic compounds and malodorous sulfur-containing emissions at low operating temperatures.

Emissions from a pulp mill contain volatile organic compounds (VOCs) as well as malodorous mercaptanes and other organic sulfides. Although malodorous emissions are usually treated in the soda recovery boiler, some of these emissions are released to the atmosphere in different parts of the pulping process. One emission source is a chip bin in which wood chips are treated with malodorous gases and water vapor.

Catalytic oxidation has proven to be a feasible technology in the abatement of VOC emissions. In addition, earlier short-term experiments have shown that catalytic oxidation can be used to abate the odorous emissions from pulp mills. We carried out experiments to study the catalytic incineration of chip bin emissions. We monitored the operation of the catalytic pilot incinerator by measuring emissions, and we also tested the activities of the catalysts in the laboratory.

The activity measurements showed that high end-conversions of pinenes can be achieved by catalytic oxidation at relatively low operating temperatures. In the pilot experiments, the deactivation of the catalyst was not a problem, contrary to what we had been expected to find. However, some problems occurred as a result of a black deposit that blocked the heat exchangers of the pilot incinerator.

Catalytic incineration was found to be feasible in the pilot experiments. The conversions of odorous emissions can even be close to complete oxidation. Under the operating conditions, the formation of the black deposit was an obstacle, and further studies are needed to overcome this problem. View this paper online at http://www.tappi.org/index.asp?pid=31491&ch=1

At the time of this research work, Satu Ojala, Ulla Lassi, Reeta Ylonen, and Riitta Keiski were with the University of Oulu, Dept. of Process and Environmental Engineering, P.O. Box 4300, 90014 University of Oulu, Finland. Lassi is currently with Central Ostrobothnia Polytechnic, Dept. of Technology, Talonpojankatu 2, 67100 Kokkola, Finland. Ilkka Laakso is with Stora Enso Fine Paper Oy, Nuottasaarenkatu 24, 90120 Oulu, Finland. Teuvo Maunula is with Ecocat Oy, P.O. Box 171, 90101 Oulu, Finland. Reijo Silvonen is with Ehovoc Oy, Hankasentie 6, 90560 Oulu, Finland. Email Ojala at [e-mail].

SIZING

THE EFFECT OF PRESS DRAW AND BASIS WEIGHT ON WOODFREE PAPER PROPERTIES DURING HIGH-SOLIDS SURFACE SIZING

APPLICATION: Reducing the press-to-dryer draw to 2% or less can help compensate for a loss of internal strength in high-solids surface sizing.

Papermakers can reduce drying requirements by increasing the starch solution solids in surface sizing. However, higher solids content limits the liquid penetration of starch into the sheet. This side effect can lead to problems with reduced internal sheet strength. How can we compensate for this loss?

To answer this question, we studied the possibility of increasing the basesheet's internal strength through reducing the press-to-dryer draw. Base paper produced on a pilot paper machine was surface sized on a pilot coater at starch solids contents of 10% and 25%. The press-to-dryer draw was set at various levels--1%, 2%, and 3%.

The results showed that the internal strength of surface-sized paper can be increased by reducing the press draw to 2% or lower. This improvement partly compensates for the loss of internal strength caused by reduced starch penetration at solids contents up to 25%.

Starch penetration was further reduced, however, when the press draw decreased. The lower press draw decreased the porosity of the basesheet. It also decreased the elastic modulus of the fiber network and reduced the bending stiffness of the sheet.

The press draw can be optimized for high-solids surface sizing based on the results of this study. Papermakers could minimize the press draw to 2% when internal strength and air permeability are critical. On the other hand, the press draw could be maximized when the bending stiffness of the sheet is more important. View this paper online at http://www.tappi.org/index.asp?pid=31492&ch=1

When this research was carried out, Juha Lipponen and Johan Gron were with Metso Paper, Inc., Jarvenpaa, Finland. Gron is now with StoraEnso, Finland. Email Lipponen at [e-mail].

FIBER SUPPLY

PROFILING THE WOOD AND PULPING PROPERTIES OF SOUTHERN PINE THINNING RESOURCES

APPLICATION: This study provides a road map for kraft pulping southern softwood thinnings and mature wood. It shows the effects of using different mixtures of this valuable wood resource to produce pulps of differing physical properties.

This study established the chemical and physical properties of chips and kraft pulps made from southern softwood thinnings and mature wood. Differences in physical pulp properties were established and shown to be due to the effects of the wood furnish. Carbohydrate analysis demonstrated distinct differences in wood carbohydrates, including increased levels of glucose and reduced levels of xylan for mature wood samples. When we used constant kraft pulping conditions, the mature wood samples provided a 1% increase in screened pulp and 13% reduction in pulp kappa number. Mixtures of thinnings and mature wood provided pulps that were a composite average between the two extremes of 100% mature and 100% thinning wood fiber resources. The differences in wood carbohydrates were shown to influence pulp carbohydrate profiles, hexenuronic acids, and fiber charge. Fiber quality analysis indicated that the kraft pulps prepared from wood thinnings were ~30% shorter; this yielded handsheets that were denser and had higher tensile strengths. View this paper online at http://www.tappi.org/index.asp?pid=31493&ch=1

Dong Ho Kim, Lenong Allison, Blair Carter, Qingxi Hou, Charles Courchene, and Arthur J. Ragauskas are with the Institute of Paper Science and Technology, Georgia Institute of Technology, 500 10th St., NW, Atlanta GA, 30332-0620, USA; James Sealey is program manager with Weyerhaeuser Company, Federal Way, WA 98003, USA. Email Ragauskas at [e-mail].

OXYGEN DELIGNIFICATION

PILOT SCALE TRIALS OF A LOW CONSISTENCY OXYGEN DELIGNIFICATION SYSTEM PERFORMED WITH A HYDRO DYNAMICS SHOCKWAVE POWER[TM] REACTOR

APPLICATION: The type of system tested in this pilot study could be retrofit into existing mill operations to help address environmental requirements relating to pulp bleaching.

An 8 ton/day, low capital, pilot low consistency oxygen delignification system employing a Hydro Dynamics ShockWave Power[TM] Reactor (SPR) in the place of a high-pressure retention tower and high shear mixer was installed in the Rumford, Maine, kraft mill. The system was run with both hardwood and softwood pulps. Several potential process variables have been explored. The effect of the technology on fiber integrity has also been determined.

Operational conditions and system performance are discussed. Potential operational pitfalls are reviewed. In general, excellent delignification results have been achieved in the low consistency, short residence time reactor system. View this paper online at http://www.tappi.org/index.asp?pid=31494&ch=1

Peter W. Hart is senior research engineer, MeadWestvaco Research, Chillicothe, Ohio, USA; Melany Gilboe is production engineer, MeadWestvaco Corporation, Rumford, Maine; George Adusei is lead engineer, BOC, Process Gas Solutions Technology, Murry Hill, New Jersey, USA; Doug Mancosky is research scientist, Hydro Dynamics, Inc., Rome, Georgia, USA; Daniel A. Armstad is director of technical and engineering support, Hydro Dynamics, Inc., Rome, Georgia, USA. Email Hart at [e-mail].

ONLINE EXCLUSIVE PROCESS CONTROL

PERFORMANCE MONITORING AND ADVANCED PROCESS CONTROL IN THE PULP AND PAPER INDUSTRY 

APPLICATION: The program maintenance tools described in this paper can help mills realize the benefits of well-functioning distributed control systems.

Modern, user-friendly tools are needed in process control, so that mill engineers are able to achieve high-quality product specifications via reduction of variability, as well as increased throughput and reduced energy consumption. This paper addresses the main features and implementation issues of two of those tools: a loop monitoring package and a multivariable advanced process controller. For each of these tools, we provide a mill-based case study with analyses of the benefits obtained. The use of the loop monitoring tool for predictive maintenance has eliminated most of the problems associated with control loop malfunctions and their lack of performance. The advanced process controller increased the throughput of a lime kiln while maintaining product quality, with an estimated annual savings of about US$120,000. View this paper online at http://www.tappi.org/index.asp?pid=31497&ch=1

This paper was originally published in O Papel 65(8): 55(2004), the official publication of the Brazilian Technical Association of Pulp and Paper (ABTCP). It is being reprinted by TAPPI JOURNAL through a cooperative agreement between TAPPI and ABTCP.

Leonardo C. Kammer and Bruce J. Allison are with Paprican in Vancouver, and Alain A. Roche is with Paprican in Pointe-Claire, Canada. Email Kammer at [e-mail].