Fig. 1: Participants of the seminar ”Membrane technology in the paperindustry“

Fig. 2: State of the art: Application sites of membrane systems in thewater circuits of paper mills (lecture by B. Simstich, PTS)

Membrane technology in thepaper industry: A success,despite critical conditions

Although membrane systems havebecome state of the art in many industries,they continue to be an exception in thepaper sector. This may be due to the highvolume flows or sometimes difficult watercompositions involved, for example calci-um concentrations of > 300 mg / L. Theseminar, which has been organized for thefourth time in a row by PTS, nonethelessdemonstrated that membrane systems canbe used economically and successfully

also in the paper industry. Widely known,but of constant interest, is the MBR tech-nology (Ingulf Schroeter lecture, Hager +Elsässer GmbH), which is currently usedin nine large-scale installations in Euro -pean paper mills. The technique of coatingpigment recovery from the wastewater ofhigh-quality paper coating processes hasbeen known for more than 20 years aswell. The presentation of Ms Tuija Kuula(Metso Paper Inc.) showed that it can beused very economically with an ROI of< 0.5 years. This was confirmed by a refer-ence list of 40 full-scale plants worldwide.The applied ultrafiltration technologyfrom Metso Paper Inc. is also suitable forthe treatment of so-called white waters andthus the actual circuit water of a papermill. Mr Thomas Boehme (Propapier PM2GmbH) presented one of these systems,which has been operated very successfullyand without technical problems in the millfor some time.

Recovery of recyclable materialsfrom wastewater

Applications, where membrane tech-nology is not only used to treat water, butcreates direct economic benefits for theoperator by recovering another valuablematerial, were of particular interest. In thiscontext, the seminar participants discussedongoing developments of membrane tech-niques for the concentration of lignin andhemicelluloses. Dr. Frank Lipnizki (AlfaLaval - Business Centre Membranes A / S)presented an industrial plant for the extrac-tion of hemicellulose from the wastewaterof a pulp mill that will soon be put intooperation. A variety of uses are conceivablefor both lignin and hemicelluloses, e.g. toproduce biopolymers or alternative fuels.

A presentation about anaerobic MBRtechnology met with great interest as well(lecture by Dr. Benjamin Simstich, PTS).In principle, the procedure is the same asin a conventional (aerobic) MBR, butmembrane operation is linked to an anaer-

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Water management in the paperindustry: Solving scaling problems andrecovering recyclable materials bymeans of membrane processesB. Simstich, H. Jung*

Paper production requires large amounts of water. To produce 1 ton of paper, a paper machine needs several hundredm3 of water. Skillful circuit design and re-use have brought the fresh water demand of an average paper production unitdown to around 10 m3 / t today. Water extraction and treatment play an important role in the economic efficiency of thepaper industry. For this reason, Papiertechnische Stiftung (PTS) in Munich organized two seminars on the topic of waterfrom 11 to 13 June 2012, under the headings “Membrane technology in the paper industry” and “Water circuits in paperproduction”. The first one was carried out in cooperation with the Deutsche Gesellschaft für Membrantechnik DGMTe.V., supported and represented by Dr. Ines Bettermann (CUT Membrane Technology GmbH & Co.KG). With around 50participants mainly from paper mills and plant construction companies, each of the two events attracted great interest.Lectures were presented by experts from the industry, universities and PTS.

* Dr.-Eng. Benjamin SimstichDipl.-Eng. Holger Jung

Papiertechnische StiftungHess-Str. 134, 80797 Munichbenjamin.simstich@ptspaper.deholger.jung@ptspaper.dePhone: +49 (0)89 12146 388Fax: +49 (0)89 12146 36www.ptspaper.de

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obic reactor here. The advantage of the process is that it generatesbiogas with at the same time minimal energy demand and residueproduction. The technology is currently under development in sev-eral companies and several full-scale plants have already beenimplemented, though so far not (yet) in the paper industry.

Innovative applications

Mr Buurmann-Behne (Pall GmbH) presented a cost-effectivealternative to traditional sand filters for freshwater treatment inpaper mills: a dead-end ultrafiltration system with minimal flush-ing water volume. Other technological developments that provedto be of interest to the professional audience included a pretreat-ment process for water softening (PhD Marie-Pierre Denieul,Veolia Environnement Recherche & Innovation) as well as theZELIX membrane system of PANTREON GmbH (lecture by Dr.Andreas Lüer, see Fig. 3) with practical examples of biomass ultra-filtration from anaerobic digestion.

Future workshop: Results of ongoing R & D activities

The development of a ceramic nanofiltration membrane havinga separation limit of 200 D enables entirely new applications ofmembrane technology. The known advantages of ceramic materi-als, especially their high resistance, make it possible to use this

membrane in highly demanding areas, e.g. processes with very hotpartial streams (lecture by Dr. Hannes Richter, Fraunhofer-Institutfür Kerami sche Technologien und Systeme IKTS, InstitutsteilHermsdorf and Ms. Daniela Roemer, PTS).

The last three lectures of the seminar were devoted to otherongoing research and development projects. Organizer Dr.Simstich presented his research on the use of submerged MBRtechnology at 50° C. This unusual membrane use indeed poses achallenge to biology and materials, but opens up opportunities andpossibilities that cannot be offered by conventional mesophilicMBR operation. Ms Daniela Roemer (PTS) presented the goalsand first results of the EU research project “CapWa”, which inves-tigates the use of gas permeation membranes for water recoveryfrom the moist exhaust air of paper machines. The event was con-cluded by the lecture of Mr Sebastian Tews (GKU Gesellschaft fürkommunale Umwelt technik mbH), who introduced a project aboutconcentrate treatment conducted by the University of Stuttgart(Department of Sanitary Engineering, Water Quality and WasteManagement).

Re-definition of aims for the use of membraneprocesses: Valuable materials instead of only H2O

To sum up, three central statements can be made about thefuture of membrane technology in the paper industry:

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Highlights 2012

Fig. 3: Effectively staged: Views of membrane systems (lecture by A.Lüer, PANTREON GmbH)

Fig. 4: Pilot plant trials performed in the EU research projectAquaFit4Use (lecture by B. Simstich, PTS)

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- Membrane processes used for watertreatment only have certainly potentialfor further development; but on accountof their lower economic efficiency theyonly have a chance in isolated casestoday.

- The biggest opportunities for furtherdevelopments and new installations areoffered by membrane processes thatrecover recyclable materials in additionto water treatment. The followingprocesses have proved to be particularlypromising here: coating pigment recov-ery, the anaerobic MBR process and theextraction of lignin and hemicelluloses.

- Membrane processes for fresh watertreatment offer advantages and will bedeveloped further.

Against this background, it was decidedto organize the seminar again in 2014,focusing on the “Recovery of recyclablematerials from wastewaters of the pulp andpaper industry “.

Scaling problems in the watercircuits of paper production

The seminar “Water circuits in paperproduction“, which has been held by PTSevery two years for many decades, had anentirely different focus this year: Scaling

problems, focusing especially on the caus-es and possible avoidance strategies. Theuse of CaCO3 as filler and coating pigmentis standard practice in papermaking.Recovered paper, the main raw materialused for papermaking today, introduceslarge amounts of calcium in the mill watercircuit. In recent decades, it has becomeincreasingly evident that closed loop recy-cling management and the multiple recy-cling of papermaking fibers tend to raisethe calcium concentrations in the circula-tion waters of paper mills (lecture byGeorg Hirsch, TU Darmstadt, PMV).

There are basically three options to pre-vent lime deposits: avoiding the introduc-tion of calcium, targeted precipitation andremoval of calcium, or avoiding the disso-lution of CaCO3 from recovered paper toretain most of it on the fibers and removeit from the circuit with the new paper prod-uct. Based on the carbonate balance, pH isthe central parameter here. The fact thatmicrobial activity has a major influence onthe pH of complex water circuits as wellwas highlighted by two presentations onbiocide use given by Ms Elke Tiedtke(Kolb Distribution Ltd.) and Mr RolandFliegen (Ashland Industries DeutschlandGmbH). The relationships between pHand anaerobic microbial activity as causes

of odor problems and scaling as well as anoptimized water circuit design wereexplained by Mr Holger Jung (PTS) (see.Fig. 6). His presentation was based on theexperience and data gained by consultancyand research projects on water circuit opti-mization, a service PTS has been provid-ing to its customers from the paper indus-try for many years. Together with theproject partners from industry, PTS regu-larly develops customized solution con-cepts to reduce odor or scaling problems.

The lectures by Mr Bernd Mueller(Siemens AG) and Mr Frank Wiemeyer(KOWITEC Ingenieurgesellschaft fürWassertechnik mbH) introduced varioustechnological possibilities for the specificelimination of calcium carbonate fromwater. Dr. Torsten Richter (BK GiuliniGmbH) showed in his presentation thatlime deposits can also be prevented withthe help of chemical additives (see Fig. 5).

To sum up: Even though scaling prob-lems have been an issue in the paper indus-try for decades, they continue to be highon the agenda to date. In particular thetrend towards increasingly closed watercircuits and the higher calcium contents ofrecovered paper contribute to this develop-ment.

Well informed with continuingeducation offers of PTS

All seminar proceedings (only inGerman) can be purchased from PTS.Most of the presentations can also befound in other publications or documents.Feel free to contact the authors of this arti-cle for further details. PTS organizes sev-eral other seminars and symposia on thesubjects of environmental and processengineering in the paper industry. Pleasevisit our website www.ptspaper.com forfurther details.

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Fig. 5: Calcium carbonate deposits on a membrane: The effect of antiscalants is clearly visible inthe SEM image (lecture by T. Richter, BK Giulini GmbH)

Fig. 6: An optimized water loop makes it possible to reduce anaerobic microbial processes as well as the formation of organic acids. This raises thepH and reduces the dissolution of calcium carbonate, causing its concentration in the water circuit to decrease (lecture by H. Jung, PTS)

without anti-scalant with anti-scalant

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