Stochastic variability of output levels in a pulp mill

Quite often, in the construction of a pulp mill involves establishing the size of tanks which will accommodate the material from the various processes in which case estimating the right tank size a priori would be vital. Hence, simulation of the whole production process would be worthwhile. Therefore, there is need to develop mathematical models that would mimic the behavior of the output from the various production units of the pulp mill to work as simulators. Markov chain models, Autoregressive moving average (ARMA) model, Mean reversion models with ensemble interaction together with Markov regime switching models are proposed for that purpose.

Sorption of metal ions to wood, pulp and bark materials

Ett huvudmål med denna avhandling var att erhålla ny information om växelverkan mellan metalljoner i vattenfas och träbaserade material såsom olika pappersmassor, ved och bark. Material av gran, tall och björk har studerats. En ny känslig kolonnkromatografisk metod utvecklades för bestämning av affinitetsordningar för 17 olika metalljoner. Av dessa bands trevärt järn och de mycket toxiska tungmetallerna bly, koppar och kadmium starkast till de studerade materialen. Växelverkan i dessa tvåfas system sker som jonbyte, huvudsakligen via komplexbildning av metalljoner till funktionella grupper i den fasta fasen. Vattenfasens pH är den viktigaste parametern som bestämmer totala halten av metalljoner som binds till materialen. Resultatet i denna avhandling kan delvis betraktas som grundforskning. En ny kunskap om metalljoners förekomst och kemiska reaktioner i dessa system är även av stor ekonomisk och ekologisk, betydelse, när man strävar till allt mera slutna system i moderna massafabriker. Avhandlingen visar också att trädbark har stor potential för biosorption av tungmetaller t.ex. från avfallsvatten. Trädbark har nästan lika stor bindningskapacitet som dyra syntetiska jonbytare.

Ultrafiltration of pulp mill bleaching effluents

Main objective of this research was to find suitable polymeric ultrafiltration membranes with high retentions, good capacities and low fouling tendencies for the E2- and EP-effluent ultrafiltration. Purpose was to treat alkaline bleaching effluents with ultrafiltration in a way that permeates of the filtrations could be recycled back to process and the consumption of fresh water in the pulp mill could be reduced significantly. In the theoretical part of this work the challenges set by the pulp and paper indus-try processes for membranes were examined. An overview of the membrane tech-nology in the pulp industry was also provided. In addition process conditions in the chemical pulp bleaching and properties of bleaching effluents were discussed in literature study. In experimental part the E2- and EP-stage bleaching effluents from Stora Enso Imatra kraft pulp mill were ultrafiltered with CR250- and CR200-filters. Suitable membranes for ultrafiltration were chosen after screening experiments. Concentra-tion experiment was made for the E2-effluent in order to estimate water saving potential. The E2-effluent was finally ultrafiltered in the pulp mill in order to test the feasibility of ultrafiltration in a real industrial environment. Good membrane for the EP-effluent ultrafiltration based on the EP-screening ex-periments was polyethersulfone membrane UP020 with cut-off value of 20 000 Da. Polysulfone membrane UFX05 with cut-off value of 5 000 Da was promising membrane for the ultrafiltration of the E2-effluent. Based on the concentration filtration of the E2-effluent with UFX05 membrane the water saving potential could be 2.2 m3/Adt for the industrial scale ultrafiltration process. Retention re-sults, such as average COD retention of 60 %, from the trial filtration at the pulp mill with UFX05 membrane were modest compared to the screening experiments, where average COD retention was 75 %. Therefore tighter ultrafiltration mem-branes should be tested for the ultrafiltration of the E2-effluent. The UP020 mem-brane seemed to be suitable for the ultrafiltration of the EP-effluent however con-centration and pilot scale ultrafiltration experiments are needed to verify this.

Characterization of fiber and vessel elements in pulp suspension images

The thesis is related to the topic of image-based characterization of fibers in pulp suspension during the papermaking process. Papermaking industry is focusing on process control optimization and automatization, which makes it possible to manufacture highquality products in a resource-efficient way. Being a part of the process control, pulp suspension analysis allows to predict and modify properties of the end product. This work is a part of the tree species identification task and focuses on analysis of fiber parameters in the pulp suspension at the wet stage of paper production. The existing machine vision methods for pulp characterization were investigated, and a method exploiting direction sensitive filtering, non-maximum suppression, hysteresis thresholding, tensor voting, and curve extraction from tensor maps was developed. Application of the method to the microscopic grayscale pulp images made it possible to detect curves corresponding to fibers in the pulp image and to compute their morphological characteristics. Performance of the method was evaluated based on the manually produced ground truth data. An accuracy of fiber characteristics estimation, including length, width, and curvature, for the acacia pulp images was found to be 84, 85, and 60% correspondingly.

Risk management measures for REACH registered intermediate substances in pulp mill

Tämän työn tavoitteena on antaa kuvaus riskinhallintamenetelmistä viidelle välituotekemikaalille, joita käytetään Stora Enson Imatran tehtailla. Välituotekemikaalit ovat mustalipeä, viherlipeä, valkolipeä, natriumbisulfiitti ja natriumsulfiitti. Nämä kemikaalit ovat jo rekisteröityjä ECHA:an ja rekisteröintiin liittyen ECHA:an on toimitettava myös kuvaus riskinhallintamenetelmistä. Työn alussa kuvaillaan työn kannalta olennaiset säädökset ja viranomaiset, jotka valvovat kemikaalien käyttöä ja valmistusta Euroopan Unionin alueella. Tämän jälkeen kerrotaan yleisesti välituotekemikaalien rekisteröintikriteereistä. Työn loppuosa käsittää kuvauksen riskinhallintamenetelmistä jokaiselle kemikaalille. Riskinhallintamenetelmät sisältävät eristyksen teknisin keinoin, menettelytapa- ja valvontatekniikat, johtamistavat ja henkilökunnan koulutuksen ja välituotekemikaalien kuljetuksen. Myös jokaisen kemikaalin ominaisuudet on kuvattu ja lyhyt prosessikuvaus kemikaalien valmistuksesta ja käytöstä on esitetty helpottamaan ymmärtämistä.

Electro-Oxidation Treatment of Pulp and Paper Mill Circulating Waters and Wastewaters

Interest in water treatment by electrochemical methods has grown in recent years. Electrochemical oxidation has been applied particularly successfully to degrade different organic pollutants and disinfect drinking water. This study summarizes the effectiveness of the electrochemical oxidation technique in inactivating different primary biofilm forming paper mill bacteria as well as sulphide and organic material in pulp and paper mill wastewater in laboratory scale batch experiments. Three different electrodes, borondoped diamond (BDD), mixed metal oxide (MMO) and PbO2, were employed as anodes. The impact on inactivation efficiency of parameters such as current density and initial pH or chloride concentration of synthetic paper machine water was studied. The electrochemical behaviour of the electrodes was investigated by cyclic voltammetry with MMO, BDD and PbO2 electrodes in synthetic paper mill water as also with MMO and stainless steel electrodes with biocides. Some suggestions on the formation of different oxidants and oxidation mechanisms were also presented during the treatment. Aerobic paper mill bacteria species (Deinococcus geothermalis, Pseudoxanthomonas taiwanensis and Meiothermus silvanus) were inactivated effectively (>2 log) at MMO electrodes by current density of 50 mA/cm2 and the time taken three minutes. Increasing current density and initial chloride concentration of paper mill water increased the inactivation rate of Deinococcus geothermalis. The inactivation order of different bacteria species was Meiothermus silvanus > Pseudoxanthomonas taiwanensis > Deinococcus geothermalis. It was observed that inactivation was mainly due to the electrochemically generated chlorine/hypochlorite from chloride present in the water and also residual disinfection by chlorine/hypochlorite occurred. In real paper mill effluent treatment sulphide oxidation was effective with all the different initial concentrations (almost 100% reduction, current density 42.9 mA/cm2) and also anaerobic bacteria inactivation was observed (almost 90% reduction by chloride concentration of 164 mg/L and current density of 42.9 mA/cm2 in five minutes). Organic material removal was not as effective when comparing with other tested techniques, probably due to the relatively low treatment times. Cyclic voltammograms in synthetic paper mill water with stainless steel electrode showed that H2O2 could be degraded to radicals during the cathodic runs. This emphasises strong potential of combined electrochemical treatment with this biocide in bacteria inactivation in paper mill environments.

Tertiary Treatment and Re-use of Kraft Pulp Mill Effluent

The efficient use of materials and natural recourses, for ecological and economic reasons, has become more and more important in all industries. In the forest industries this means higher levels of closure in the material circulations of the mills. One possibility to reduce wastewater discharge is to re-use part of the 2nd clarifier effluent as process water. The main target of this thesis was to evaluate the technical suitability of several mechanical and chemical tertiary treatment methods for water re-use. Some of the tested methods seemed to have high potential for the removal of some specific constituents from the wastewater. Tertiary treatment is needed because higher levels of closure may cause problems with increasing amounts of non-process elements in different points of kraft pulp process. The aspect of sustainable development was taken into account by evaluating positive and negative environmental effects of the treatment processes. Environmental benefits can be gained by using some of the tertiary treatment methods tested. These methods should still be researched more for system optimization.

Additional revenue opportunities in pulp mills and their impacts on the kraft process

Although the concept of multi-products biorefinery provides an opportunity to meet the future demands for biofuels, biomaterials or chemicals, it is not assured that its implementation would improve the profitability of kraft pulp mills. The attractiveness will depend on several factors such as mill age and location, government incentives, economy of scale, end user requirements, and how much value can be added to the new products. In addition, the effective integration of alternative technologies is not straightforward and has to be carefully studied. In this work, detailed balances were performed to evaluate possible impacts that lignin removal, hemicelluloses recovery prior to pulping, torrefaction and pyrolysis of wood residues cause on the conventional mill operation. The development of mill balances was based on theoretical fundamentals, practical experience, literature review, personal communication with technology suppliers and analysis of mill process data. Hemicelluloses recovery through pre-hydrolysis of chips leads to impacts in several stages of the kraft process. Effects can be observed on the pulping process, wood consumption, black liquor properties and, inevitably, on the pulp quality. When lignin is removed from black liquor, it will affect mostly the chemical recovery operation and steam generation rate. Since mineral acid is used to precipitate the lignin, impacts on the mill chemical balance are also expected. A great advantage of processing the wood residues for additional income results from the fact that the pulping process, pulp quality and sales are not harmfully affected. For pulp mills interested in implementing the concept of multi-products biorefinery, this work has indicated possible impacts to be considered in a technical feasibility study.

Characterisation of Functional Brown Adipose Tissue In Adult Humans

The white adipose tissue mainly serves the purpose of energy storage, while brown adipose tissue (BAT) has the capacity to generate heat under cold conditions in mammals and in human infants. BAT is controlled by the central nervous system, and BAT function is accompanied by increased energy expenditure. However, it was not previously certain whether adult humans also have functional BAT. The aim of this doctoral work was to identify functional BAT in adult humans and to characterise its glucose uptake and blood flow under cold and insulin stimulation conditions in lean and in obese humans, by using positron emission tomography. Further, the impact of weight loss on BAT glucose uptake was assessed. Cerebral glucose uptake was also studied in relation to BAT function and cold exposure. The results showed that healthy adult humans have functional BAT, as assessed by the intense cold-induced glucose uptake and by biopsies. BAT was also found to be a highly insulinsensitive tissue in lean humans, but the effects of insulin and cold exposure were attenuated in obese humans, although the glucose uptake capacity of cold-activated BAT might be increased by weight loss. Blood flow in the BAT of lean humans was associated with whole-body energy expenditure. The presence of cold-activated BAT was related to lower body mass index and higher insulin sensitivity. Finally, BAT activation was linked to the activity of the cerebellum, the thalamus and certain neocortical regions. The cold-induced cerebral glucose uptake was also lower in obese than in lean adult humans.

The Effect of Plant Closures on Market Value: Empirical Evidence from Pulp and Paper Industry 2004-2012

The aim of this study was to research how plant closure announcements affect the market value of the largest pulp and paper industry companies in the world. Also the effect of announcements on competitors was researched and whether the location of plants, timing, reasons for the closures, and characteristics of the closing firms and competitors have an impact on the results. The overall sample included 57 events in the years 2004-2012 and event study was used as a research method. Main theories were signaling theory and spillover effect. According to empirical results, investors consider plant closure announcements as a positive signal for market value. The spillover effect on competitors was, on average, positive and characteristics of the firms and closures had an effect on the results. Furthermore, the market generally predicted the closures and overreacted to them on the announcement day and after it. It is possible for corporate management and investors to learn from the results and use them as support for their decision making.

Effects of the partial removal of wood hemicelluloses on the properties of kraft pulp

The objective of this work was to study the effects of partial removal of wood hemicelluloses on the properties of kraft pulp.The work was conducted by extracting hemicelluloses (1) by a softwood chip pretreatment process prior to kraft pulping, (2) by alkaline extraction from bleached birch kraft pulp, and (3) by enzymatic treatment, xylanase treatment in particular, of bleached birch kraft pulp. The qualitative and quantitative changes in fibers and paper properties were evaluated. In addition, the applicability of the extraction concepts and hemicellulose-extracted birch kraft pulp as a raw material in papermaking was evaluated in a pilot-scale papermaking environment. The results showed that each examined hemicellulose extraction method has its characteristic effects on fiber properties, seen as differences in both the physical and chemical nature of the fibers. A prehydrolysis process prior to the kraft pulping process offered reductions in cooking time, bleaching chemical consumption and produced fibers with low hemicellulose content that are more susceptible to mechanically induced damages and dislocations. Softwood chip pretreatment for hemicellulose recovery prior to cooking, whether acidic or alkaline, had an impact on the physical properties of the non-refined and refined pulp. In addition, all the pretreated pulps exhibited slower beating response than the unhydrolyzed reference pulp. Both alkaline extraction and enzymatic (xylanase) treatment of bleached birch kraft pulp fibers indicated very selective hemicellulose removal, particularly xylan removal. Furthermore, these two hemicellulose-extracted birch kraft pulps were utilized in a pilot-scale papermaking environment in order to evaluate the upscalability of the extraction concepts. Investigations made using pilot paper machine trials revealed that some amount of alkalineextracted birch kraft pulp, with a 24.9% reduction in the total amount of xylan, could be used in the papermaking stock as a mixture with non-extracted pulp when producing 75 g/m2 paper. For xylanase-treated fibers there were no reductions in the mechanical properties of the 180 g/m2 paper produced compared to paper made from the control pulp, although there was a 14.2% reduction in the total amount of xylan in the xylanase-treated pulp compared to the control birch kraft pulp. This work emphasized the importance of the hemicellulose extraction method in providing new solutions to create functional fibers and in providing a valuable hemicellulose co-product stream. The hemicellulose removal concept therefore plays an important role in the integrated forest biorefinery scenario, where the target is to the co-production of hemicellulose-extracted pulp and hemicellulose-based chemicals or fuels.

e-Business and collaboration: A case study of pulp supply chain

This thesis studies how the case company could digitalize its supply chain and what kind of advantages this would create in the light of supply chain efficiency. The case company manufactures several pulp products that are used for paper, fabrics and packaging products by customers worldwide. The paper and pulp industry has been paying more and more attention to increasing supply chain efficiency with new operating and service models made possible by today’s information technology. The main focus of this study is on the supply chain between the case company and its key customers and the goal is to find ways to make the operations between them as efficient as possible. The study relays heavily on collaboration techniques and digitalization technologies. In addition to a theoretical framework, the study includes several empirical studies that offer real-life examples of how these theories and technologies are applied in operating environments similar to the case company. A plan with strategic and operational levels is created according to the findings of the previous sections to support the case company’s future operations. The plan is based on an RFID-supported collaboration model that aims to advance information sharing between the supply chain partners. The time for an RFID-investment is sought to be very optimal and the benefits of such system to be noteworthy, but challenging to measure in monetary terms.

Production planning and optimization of a pulp mill: introduction of the optimisation based scheduling software for pulp industry

The objective of this project was to introduce a new software product to pulp industry, a new market for case company. An optimization based scheduling tool has been developed to allow pulp operations to better control their production processes and improve both production efficiency and stability. Both the work here and earlier research indicates that there is a potential for savings around 1-5%. All the supporting data is available today coming from distributed control systems, data historians and other existing sources. The pulp mill model together with the scheduler, allows what-if analyses of the impacts and timely feasibility of various external actions such as planned maintenance of any particular mill operation. The visibility gained from the model proves also to be a real benefit. The aim is to satisfy demand and gain extra profit, while achieving the required customer service level. Research effort has been put both in understanding the minimum features needed to satisfy the scheduling requirements in the industry and the overall existence of the market. A qualitative study was constructed to both identify competitive situation and the requirements vs. gaps on the market. It becomes clear that there is no such system on the marketplace today and also that there is room to improve target market overall process efficiency through such planning tool. This thesis also provides better overall understanding of the different processes in this particular industry for the case company.