Optimization-based decision support systems for planning problems in processing industries
Claassen, G.D.H. - \ 2014
Wageningen University. Promotor(en): Jack van der Vorst. - Wageningen : Wageningen University - ISBN 9789462572089 - 171
operationeel onderzoek - logistiek - voedselverwerking - voedselindustrie - pulp- en papierwarenindustrie - beslissingsondersteunende systemen - optimalisatie - procesoptimalisatie - wiskundige modellen - operations research - logistics - food processing - food industry - pulp and paper industry - decision support systems - optimization - process optimization - mathematical models
Optimization-based decision support systems for planning problems in processing industries
Nowadays, efficient planning of material flows within and between supply chains is of vital importance and has become one of the most challenging problems for decision support in practice. The tremendous progress in hard- and software of the past decades was an important gateway for developing computerized systems that are able to support decision making on different levels within enterprises. The history of such systems started in 1971 when the concept of Decision Support Systems (DSS) emerged. Over the years, the field of DSS has evolved into a broad variety of directions. The described research in this thesis limits to the category of model-driven or optimization-based DSS.
Simultaneously with the emergence of DSS, software vendors recognized the high potentials of available data and developed Enterprise Systems to standardize planning problems. Meanwhile, information oriented systems like MRP and its successors are extended by the basic concepts of optimization based decision support. These systems are called Advanced Planning Systems (APS). The main focus of APS is to support decision making at different stages or phases in the material flow, i.e. from procurement, production, distribution to sales (horizontal-axis), on different hierarchical aggregation levels (vertical-axis) ranging from strategic (long-term) to operational (short- term) planning. This framework of building blocks decomposes planning tasks hierarchically into partial planning problems. This basic architecture of the planning processes in APS is known as the Supply Chain Planning Matrix (SCPM).
Compared to, for instance, discrete parts manufacturing, planning tasks are much more complicated in processing industries due to a natural variation in the composition of raw materials, the impact of processing operations on properties of material flows, sequence dependent change-over times, the inevitable decline in quality of product flows and relatively low margins. These specific characteristics gave rise to focus on optimization-based decision support in the domain of processing industries. The problems to be addressed in this field call for (inter-related) decisions with respect to the required raw materials, the production quantities to be manufactured, the efficient use of available resources, and the times at which raw materials must be available.
Although different APS modules can interact directly, coordination and integration is often restricted to the exchange of data flows between different modules. Given the need for specific integrated decision support, the research presented in this thesis focusses particularly on medium to short term decision support at production stage in processing industry, including the vertical and horizontal integration and coordination with adjacent building blocks in the SCPM.
Extensive reviews from literature show that the gap between research and practice of DSS is widening. As the field of DSS was initiated as an application oriented discipline, the strategy of what is referred to as “application-driven theory” was taken as the preferred approach for this thesis. “Application-driven” refers to a bottom-up approach which means that the relevance of the research should both be initiated and obtained from practice. The intended successful use of the proposed approaches should, where possible, be represented by tests of adequacy. Simultaneously, the contribution to “theory” aims to be a recognizable part of the research effort, i.e.
obtained understanding and insights from problems in practice should provide the basis for new approaches. Based on the preceding considerations we defined the following general research objective:
General research objective
To support medium- to short term planning problems by optimization-based models and solution techniques such that:
i) The applicability and added value of (prototype) systems is recognized and carried by decision makers in practice
ii) The proposed approaches contribute to knowledge, understanding and insights from a model building and – solving point of view.
In order to link the general objective with the different studies in the thesis, we defined five, recurring research premises, i.e. Professional relevance and applicability (P1), Aggregation (P2), Decomposition and reformulation (P3), Vertical integration at production level (P4), and Horizontal coordination and integration (P5).
The overarching premise P1 refers to the first part of the research objective. All other premises refer to the second part of the research objective, i.e. model building and/or – solving. Several planning issues are studied to give substance to the research objective and each study is connected to at least two research premises.
Study 1: Planning and scheduling in food processing industry
The main question in Chapter 2 was:” How to apply aggregation, decomposition and reformulation in model-based DSS at planning and scheduling level such that the aspect of decision support is recognized and appreciated by decision makers in practice, and which level of aggregation is needed to integrate production planning (i.e. lot-sizing) and scheduling problems in a single model?
The study consists of two parts. The first part of the study refers to a case study for the bottleneck packaging facilities of a large dairy company. The goal was to develop, implement and test a pilot DSS which was able to deliver solutions recognized and carried by decision makers at lower decision levels. The latter aim implied that a straight-forward aggregation on time, product type, resources or product stage, was not preferred. The key to develop an approach for regular use was to identify and take advantage of specific problem characteristics. Clustering of numerous jobs, while retaining information at order level, could be exploited in a reformulation approach. The inclusion of (combined) generalized- and variable upper bound constraints gave very tight lower bounds and sparse search trees.
An extensive test phase in daily practice showed that the main benefit of the DSS was the initial quality of the generated plans including the time needed to generate these schedules. Hence, decision makers could i) postpone their planning tasks, ii) conveniently cope with rush orders or planned maintenance and iii) easily generate
alternatives or revised plans when unforeseen disturbances occur. Moreover, the graphical presentation and overview of the (future) working schedule enabled order acceptance to make use of remaining capacity.
The study also showed that planning problems in practice cannot be captured exhaustively by a (simplified) model. Decision makers need the opportunity to modify automatically generated plans manually and use human judgement and experience such that the solution is tuned to the actual situation. Hence, the DSS should not be considered as an optimizer but rather as a tool for generating high quality plans to be used for further analysis. Within this context the various options of a user-friendly, graphical, and fully interactive user interface, were of major importance.
Although the case study clearly demonstrates the validity of earlier case based DSS research for current days APS, the proposed approach is hardly a generic solution for a complete vertical integration between lot-sizing and scheduling. If lot-size decisions are strongly affected by the sequence of jobs, production planning and scheduling should be performed simultaneously.
As the described case refers to an earlier study and today’s APS do not provide modules for integrated lot-sizing and scheduling, the second part of the study gives an overview of developments in literature regarding lot-sizing and scheduling models and assess their suitability for addressing sequence-dependent setups, non-triangular setups and product decay. The review shows a tendency in which so-called Big Bucket (BB) models are currently proposed for short term time horizons too. However, we argue that segmentation of the planning horizon is a key issue for simultaneous lot-sizing and scheduling. The advantage of BB models may become a major obstacle for i) the effectiveness of simultaneous lot-sizing and scheduling, and ii) addressing specific characteristics in food processing industry.
Study 2: Vertical integration of lot-sizing and scheduling in food processing industry
Chapter 3 focused on a complete integration of lot-sizing and scheduling decisions in a single model. The main question was:” How to integrate production planning (i.e. lot- sizing) and scheduling problems in a single model, such that common assumptions regarding the triangular setup conditions are relaxed and issues of product decay and limited shelf lives are taken into account?”
The literature research in Chapter 2 revealed that the computational advantage of time oriented aggregation in BB models may become a major obstacle in addressing the identified characteristics in FPI. In addition, product decay is primarily associated with the “age” of products and consequently relates to the segmentation of the time- horizon. Therefore, two SB models are developed to demonstrate the impact of non- triangular setups and product decay on the generated solutions. Small scale examples were used to demonstrate how a small change in the balance between inventory - and
changeover costs may generate significantly different solutions, especially when the triangular setup conditions do not hold.
The developed models are potentially very large formulations and, as expected, hard to solve. Exploratory research was conducted with a Relax-and-Fix (R&F) heuristic. The heuristic is based on a decomposition of the time horizon. Numerical results of small to medium sized problem instances are promising. However, solving real-size problem instances is not possible yet.
Study 3: Integrated planning between procurement and production
The case study in Chapter 4 focussed on the need for horizontal coordination and integration between the phases procurement and production, which is of particular importance in inter-organizational supply chains. The main question was:” How to model and solve an integrated planning problem between procurement and production, both on a mid-term and short-term planning level, in an inter-organizational supply chain? The research question was projected on an illustrative milk collection problem in practice.
The aim was to develop a pilot DSS that lifted decision support for a “weaker” partner in a food supply chain to a higher level, and to illustrate the importance of horizontal integration between the phases procurement and production in an APS framework.
Problem analysis revealed that the problem can be classified as an extension of the Periodic Vehicle Routing Problem (PVRP). The problem was decomposed into more tractable sub problems on different hierarchical levels, i.e. the daily (vehicle) routing problem was separated from a medium-term planning problem. On the higher planning level, numerous suppliers were aggregated such that total supply within a cluster met (multiple) vehicle loading capacities. The continuous supply of relatively small amounts from many suppliers had to be balanced with strict delivery conditions at processing level. A model was developed to assign a single (stable) collection rhythm to each cluster such that the total, weighted deviation of desired processing levels on various days in the planning horizon was minimized.
The applied aggregation on the higher planning level turned out to be very beneficial for the required disaggregation at the lower planning level. Once supplier farms were geographically grouped into clusters and the aggregated supply within a cluster was assigned to a single collection rhythm with fixed collection days, the (initial) daily routing problem was considerably easier to solve for vehicle schedulers.
The computational complexity of the problem was reduced by exploiting application-based properties algorithmically in a specific branch-and-bound scheme, i.e. a customized approach of Special Ordered Sets type 1 (SOS1) This approach made it possible to solve the generated problems exactly for real-size problem instances.
The various facilities of a user-friendly and interactive man-machine interface (i.e. an input, planning, simulation and analysing module) turned out to be essential. Decision makers could easily change the data, and the generated plans, in a separate simulation module. However, the impact of any modification was immediately visualised by several (conflicting) indicators in the output screens, both on supply and demand level.
Study 4: Mixed Integer (0-1) Fractional Programming in Paper Production Industry
The study in Chapter 5 focussed on the impact of technical settings of production units on material flows. The main question was:” How to support decision-makers in practice if crucial properties of end products simultaneously depend on (endogenous) types of raw materials with different chemical or physical properties and (endogenous) technical settings of processing units?
The goal of the study was to revise and upgrade an existing, locally used DSS, to a tailored and flexible tool for decision support within the enterprise. The study revealed that the aimed extension towards multi-objective decision support, together with new physical insight for calculating properties of end products due to process operations, had a substantial impact on the optimization module.
The proposed solution procedure takes advantage of the problem characteristics and gives rise i) to apply and extend a classical reformulation approach for continuous linear fractional programming (FP) problems to a more general class of mixed integer (binary) FP problems and ii) to exploit the special structure between the original non- linear mixed integer model and the continuous, linear reformulation by applying the concept of Special Ordered Sets type 1 (SOS1).
Although Chapter 5 focusses in particular on the reformulation and solution approach, the DSS consists of four main building blocks, i.e. the user interface, a scenario manager, a simulation- and optimization routine. The optimization module provides a powerful tool to find feasible solutions and the best (unexpected) recipes for any available set of raw materials. Moreover, it provides an innovative way of decision support for purchasing (new) pulps on the market, for assigning available pulps to different paper grades, and for attuning available stock levels of raw materials to (changing) production targets for different paper grades. The results of the optimization routine are mainly used to obtain alternative recipes for different paper grades. Usually, these recipes are stored as base scenarios and adapted to daily practice in the simulation module.
Main conclusions and future research
Based on the studies in the Chapters 2 and 3 we conclude that no generically applicable models and/or solution approaches exist for simultaneous planning and scheduling in processing industries. More industry-specific solutions are needed incorporating specificities of different production environments into those models. The key to develop solvable approaches for contemporary practice may be i) to use knowledge and experience from practice and take advantage of specific characteristics in different problem domains during model construction, and/or ii) to identify and exploit special problem structures for solving the related models.
We conclude that surprisingly little research has been devoted to issues of coordination and integration between “procurement” and “production”. The studies in the chapters 4 and 5 confirm that sourcing of (raw) materials flows needs more attention in processing industries, particularly in push-oriented, inter-organizational networks. The valorisation of raw materials can be improved even more if the composition of raw materials is considered too in future planning problems at production level.
In the second part of this thesis we focused on extensions for the applicability of Special Ordered Sets type 1 (SOS1), both from an algorithmic (Chapter 4) and modelling (Chapter 5) point of view. We conclude that the concept of SOS1 can extend a classical reformulation approach for continuous fractional programming (FP) problems, to a specific class of mixed integer (0-1) FP problems. Moreover, we conclude that a natural ordering of the variables within the sets is not necessary to make their use worthwhile. A separate (user defined) reference row or weights associated to the variables in the sets might be omitted for an efficient use of SOS1 in commercially available mathematical programming packages. However, this requires further research and extensive computational tests.
Lignin as a renewable aromatic resource for the chemical industry
Gosselink, R.J.A. - \ 2011
Wageningen University. Promotor(en): Johan Sanders, co-promotor(en): G. Gellerstedt; Jan van Dam. - [S.l.] : S.n. - ISBN 9789461731005 - 191
vervangbare hulpbronnen - lignine - lignocellulose - lignocellulosehoudend afval - pulp- en papierwarenindustrie - chemicaliën uit biologische grondstoffen - chemie op basis van biologische grondstoffen - renewable resources - lignin - lignocellulose - lignocellulosic wastes - pulp and paper industry - biobased chemicals - biobased chemistry
Valorization of lignin plays a key role in the further development of lignocellulosic biorefinery processes for biofuels and biobased materials production. Today’s increased demand for alternatives to fossil carbon-based products expands the interest and the need to create added value to the unconverted lignin fraction. The aim of the research was to study the potential of lignin to become a renewable aromatic resource for the chemical industry. Lignin can be considered as an abundantly available and cheap raw material for the manufacturing of an array of products. Development of applications needs to go hand in hand with the anticipated increased production of technical lignins derived from the pulp and paper industry and the emerging lignocellulosic biorefinery industry. Two promising lignin applications are studied in this thesis:
1) the use of lignin in wood adhesives
2) the use of lignin for the production of aromatic chemicals
PCA modeling was performed aimed at the prediction of the application potential of different technical lignins for wood adhesive production. The lignins and their fractions could be classified in different clusters based on their structure dependent properties. Lignins exhibiting sufficient reactive sites, medium molar mass and low level of impurities are most promising candidates for the development of lignin based wood adhesives. Both lignin reactivity and formaldehyde-free crosslinking agents are needed to develop emission-free adhesives. Periodate oxidation was studied as method to improve the lignin reactivity. Alternatives to formaldehyde- based glues are under investigation and a combination of lignin and furans might be an interesting concept to develop renewable adhesives.
In this research a reliable SEC methodology was developed for the analysis of the molar mass distribution of a wide range of different lignins. The major drawback of this method is that the molar masses are calculated on a relative basis to sulfonated polystyrenes. Using MALDI-TOF-MS and prior fractionation of lignin did not solve all problems associated with the determination of the absolute molar mass of lignin.
Supercritical depolymerisation of lignin using a carbon dioxide/acetone/water fluid resulted in a depolymerised lignin oil. In this oil some monomeric compounds are present in relatively high amounts up to 3.6% (based on dry lignin). These products maybe further isolated by downstream processing to obtain purified fine chemicals. For continuous operation of this supercritical process, the formation of char should be further limited.
The results presented in this thesis are expected to contribute - together with the many on-going activities worldwide - to the increased commercial utilisation of lignin in the future. Moreover, the obtained results contribute to the increasing knowledge on lignin analysis, chemistry and reactivity.
A pilot constructed treatment wetland for pulp and paper mill wastewater: performance, processes and implications for the Nzoia River, Kenya
Abira, M.A. - \ 2008
Wageningen University. Promotor(en): P. Denny, co-promotor(en): J.J.A. Bruggen. - [S.l.] : S.n. - ISBN 9789085048152 - 151
afvalwaterbehandeling - pulp- en papierwarenindustrie - helofytenfilters - proefprojecten - kenya - waste water treatment - pulp and paper industry - artificial wetlands - pilot projects - kenya
Sustainable water pollution control calls for effective enforcement of regulations and adoption of cleaner production technology as well as effective end-of-pipe treatment of effluents. The final effluent quality of many municipalities and industries in Kenya seldom comply with government-prescribed effluent discharge guidelines. There is, therefore, a need for a sustainable technology that can reliably achieve acceptable effluent quality for discharge into the environment at minimal cost. Natural and artificial wetland systems have been used as a cost-effective alternative to conventional wastewater treatment methods for improving final effluent quality. Data and information on pulp and paper mill wastewater treatment in constructed wetlands are few while performance data that can guide design and operation under tropical environment conditions are lacking.
This study was undertaken to explore the potential of a constructed wetland to improve the quality of the final effluent from Pan African paper mills (E.A.) Limited (PANPAPER) in western Kenya in order: 1) to be in compliance with national discharge regulations, and 2) to protect the receiving aquatic environment, the River Nzoia, and downstream riparian users. In this thesis the problematic wastewater components were characterised (Chapter 2). The data were used to evaluate the performance of the PANPAPER Mills wastewater treatment ponds and the wetland system with respect to removal of nutrients, organic matter (BOD, COD), suspended solids (TSS), and phenols (Chapters 4-6) under various operational conditions.
A pilot-scale constructed wetland covering a total area of 48.5 m2 was located in the tree nursery just below the final stabilization pond of PANPAPER Mills. It consisted of eight subsurface flow (SSF) cells each of dimensions 3.2 m (length) x 1.2 m (width) x 0.8 m (depth) cells and two cells of dimensions 6.2 m (length) x 1.5 m (width) x 0.8 m (depth). The latter were initially operated as free water surface flow and later as subsurface flow systems. The subsurface flow cells were planted in pairs with Cyperus immensus, Typha domingensis, Phragmites mauritianus and Cyperus papyrus. The Cyperus immensus did not establish well due to frequent attacks by vermin monkeys and were therefore removed after eight months and the cells left implanted. The larger cells were planted with Typha domingensis. All cells were filled with gravel to a depth of 30 cm.
The experimental systems operation was dynamic and ran for a total period of 3 years from 2002 to 2005. It involved different operation modes, hydraulic loading rates and retentions in order to optimise pollutant removal while maintaining good plant vitality. Initially the wetland was operated on a batch load-drain mode starting with 5-day retention time (batch phase 1). It was assumed that this format would enhance organic matter degradation. Plant vitality was relatively poor and was partly attributed to low nitrogen loading at a long retention time. A shorter retention time of 3 days (batch phase 2) was subsequently used. Although plant vitality increased, there was a reduction in treatment efficiency with respect to TSS. It was therefore decided to use a continuous flow operation mode. The results of batch phase 2 had shown better wetland performance at 3 days than at 5 days. A third phase of batch operation was undertaken as a repeat of the first phase when the wetland was considered to be mature. In all there were three phases of batch operation and two of continuous flow. In the first phase of continuous flow plant growth was at steady stage while in the second phase the plants were at an exponential growth stage. A tracer study using lithium chloride was conducted in the first phase.
The study revealed that the PANPAPER Mills pond system was actually performing well as per its type and design. However, the concentration of pollutants in the final effluent (average 45±3,
394±340, 52±6, and 0.64±0.09 for BOD, COD, TSS and phenols, respectively) discharged into the Nzoia River does not comply with the national discharge limits. Mean total nitrogen and phosphorus were about 3 mg/1 and 0.7 mg/1, respectively giving a low N:P ratio.
Evapotranspiration (8-16 mm/day) was found to be an important component of outputs in the water budget of the wetland system making up to 15-32 %, depending on the system type. ET rates were different for the aquatic plant species studied. It was not possible to deduce the actual retention time and other hydraulic parameters (efficiency and number of "tanks in series") under continuous flow, as there was no discernable tracer concentration curve for all wetland cells. For this wastewater, which has high organic matter content, the study should be conducted with a different tracer. Alternatively, lithium chloride may still be used but with continuous feed instead of pulse feed, as was the case in this study.
Plant tissue nutrient concentrations were lower than in healthy natural wetland plants. Nitrogen concentrations based on dry weights in Phragmites, Typha and papyrus were 9.2±0.7, 7.4±0.5, and 6.1±0.2 mg/g, respectively while phosphorus concentrations were 1.7±0.12, 1.9±0.11, 1.6±0.14 mg/g, respectively. Despite this, Typha and Phragmites had satisfactory aboveground biomass production (10896 g/m and 3015 g/m2 dry weight, respectively) when compared to natural wetlands. The growth of papyrus was sub-optimal with an aerial biomass of 3075 g/m2. In general, plant vitality and growth was lower during batch mode wetland operation. Below ground root and rhizome growth was variable. Typha roots penetrated the entire bed depth (approx. 30 cm) while Phragmites and papyrus rooting depths were in the top 20 cm and 10 cm, respectively.
Plant uptake of nutrients exceeded inputs by influent in the exponential growth stage. Nutrient mass flows indicated that in this low loaded system mineralisation and cycling of nutrients in accumulated sediments and/or in senescing/decaying plant organs are important for sustaining plant growth.
Mean removal efficiency for total nitrogen was in the range of 49 - 75 % for planted cells and 42 - 49 % for unplanted ones in continuous flow. For phosphorus removal efficiencies were 30 - 60 % in planted cells and (minus) 4 - 38 % in unplanted ones. Removal efficiency of up to 25 % may be attributed to uptake into plant shoots. Harvesting of plant shoots should be appropriately timed to avoid depletion of the nutrient pool. The removal efficiencies were lower during batch operation modes.
The constructed wetland effectively removed BOD (up to 90 %) and TSS (up to 81 %) from the wastewater to concentrations below that prescribed by the regulating authority in Kenya. However, COD removal was low (up to 52 %). The non-zero background concentration for BOD varied between 4.3 and 7.4 mg/1 for the different cells while areal BOD reaction rate constants varied from 0.055 - 0.114 m/day (20 - 42 m/yr). The reaction rates are reported for pulp and paper mill wastewater for the first time. Typha cells had consistently higher TSS removal efficiency than Phragmites and papyrus in continuous flow. Besides TSS removal in the wetland bed with developed plant roots, the presence of macrophytes does not seem to enhance BOD and COD removal when compared to unplanted cells. However, the presence of plants is essential for nutrients and phenol removal.
Mean phenol removal efficiencies based on mass flows ranged from 73 % to 96 %. Good buffering was achieved even during the highest inflow phenol concentration of 1.3 mg/1 and the highest hydraulic loading rate (HLR) of 9.8 cm/day in the wetland. For batch operation, optimal removal was achieved at 5-day hydraulic retention time with a mean outflow concentration of 0.053 ± 0.004 mg/1. The major processes of phenol removal are microbial breakdown (60 %) followed by sedimentation/adsorption (up to 30 %). However, ultimate biodégradation in a mature wetland may be higher as some of the sedimented and/or adsorbed phenols may be re-cycled and microbially degraded. The removal was enhanced by wetland age and presence of aquatic macrophytes especially when they were at an exponential growth stage. During this stage plant uptake rates were
5.4 - 12.7 mg phenol/day accounting for 10 - 23 % of phenol removed in SSF cells. The study reports, for the first time, phenol reduction rates (k values) in a constructed wetland. Average k, for SSF cells was 27 m/yr and 44 m/yr respectively at hydraulic loading rates of 4.1 - 4.9 cm/day and 9.8 cm/day, respectively. The reduction rate was 38 m/yr for the free water surface flow cells at a HLR of 9.3 cm/day. Mean volumetric removal rate for batch operation was 0.57 d' for Phragmites and papyrus cells.
Water quality of Nzoia River
PANPAPER Mills's effluent discharge in a "business-as usual" scenario causes an increase in the concentration of pollutants downstream (3 km) compared to an upstream location (500 m). The increase is highest during low flow in the River, usually in the dry season (January to March). This was reflected in an increase in the concentration of various pollutants by between 20 % and 120 % at the downstream sampling point during the month of March. From the findings of this study I predict that the quality of water in River Nzoia downstream of the discharge point would improve significantly if a full-scale constructed wetland with similar performance as that in the pilot study were to be integrated with the existing treatment ponds as a tertiary stage. Such an intervention would decrease pollution by more than 90 % for phenols. TSS, COD and BOD would be reduced by 44 %, 30 % and 63 %, respectively. Nitrogen concentration downstream of discharge would remain the same as that in the upstream location (100 % pollution reduction) while phosphorus concentrations would reduce by 50 % of the current level.
An appraisal of these findings is given in Chapter 7, which also includes recommendations for design, set-up and maintenance of a full-scale wetland.
Ontwikkelingen in vraag en aanbod van rondhout in Nederland en aangrenzend gebied en mogelijke knelpunten en kansen voor de bos- en houtsector in de periode 2005 - 2025
Oosterbaan, A. ; Berg, C.A. van den; Schelhaas, M.J. - \ 2007
Wageningen : Alterra (Alterra-rapport 1510) - 35
bosbouw - rondhout - hout - houtproducten - pulp- en papierwarenindustrie - vraag - marketing - markten - houtvoorziening - grensgebieden - nederland - forestry - roundwood - wood - wood products - pulp and paper industry - demand - marketing - markets - timber supply - frontier areas - netherlands
In opdracht van het Ministerie voor LNV is een verkennende studie uitgevoerd naar de vraag en het aanbod van rondhout in de komende 20 jaar in ons land en het aangrenzende gebied van België, Nordrhein Westfalen en Niedersachsen. Als eerste stap is gekeken naar ontwikkelingen in vraag en aanbod gedurende de afgelopen 20 jaar. Vervolgens zijn voor verschillende scenario’s berekeningen gemaakt voor de te verwachten vraag en het te verwachten aanbod in de komende 20 jaar. De mogelijke kansen en knelpunten, die verschillen in verwachte vraag en aanbod kunnen opleveren voor zowel de bossector als de houtsector, worden besproken
An environmental systems analysis of the Kraft pulp industry in Thailand
Warit, J. - \ 2006
Wageningen University. Promotor(en): L. Hordijk, co-promotor(en): Carolien Kroeze; W. Soontaranun. - [S.l.] : S.n. - ISBN 9789085045106 - 203
pulp- en papierwarenindustrie - pulpfabrieksafvalwater - verzuring - eutrofiëring - industrieel afval - papierfabrieksslib - eucalyptus - thailand - pulp and paper industry - pulp mill effluent - acidification - eutrophication - industrial wastes - paper mill sludge - eucalyptus - thailand
The pulp industry in
Structural Characterisation and Enzymatic Degradation of Exopolysaccharides involved in Paper Mill Slime deposition
Verhoef, R.P. - \ 2005
Wageningen University. Promotor(en): Fons Voragen, co-promotor(en): Henk Schols. - Wageningen : Wageningen University - ISBN 9789085041412 - 154
polysacchariden - enzymen - degradatie - pulp- en papierwarenindustrie - bacteriën - bacteriële producten - chemische structuur - biofilms - polysaccharides - enzymes - degradation - pulp and paper industry - bacteria - bacterial products - chemical structure - biofilms
Bacteria that adhere to the surface of a paper machine form a biofilm that entraps the fibres and additives used as raw material to form a slime deposit. The formation of these slime deposits can result in serious problems with respect to the papermaking process itself and the end product. Traditionally more or less toxic biocides are used to prevent this problem. However, due to more strict environmental legislation there is growing interest in alternative methods for slime control. One of these methods could be the use of enzymes that degrade the exopolysaccharides (EPSs) that form the major structural element of a biofilm. To obtain these enzymes it is important to know which EPSs to target for enzymatic degradation. Therefore the EPSs produced by several species isolated from different paper mills within Spain, Finland or France were subjected to a (detailed) chemical structure elucidation. From these studies several EPSs were selected as target substrates for enzymatic degradation. The enzyme able to degrade one of these substrates was subjected to purification and characterisation studies.
Aim and technologies for fibre upgrading
Westenbroek, A.P.H. - \ 2004
paper - pulp and paper industry - management - recycling - fibres - quality - upgrading - biobased economy
Improved level and control of stiffness
Sinke, R.J. - \ 2004
paper - pulp and paper industry - paperboard - sizing - quality - cooperation - compressive strength - tensile strength - bending strength - applications - biobased economy - supply chain management
|Kringloopsluiting in de papierfabriek door middel van thermofiele proceswaterzuivering
Vogelaar, J.C.T. ; Klapwijk, A. ; Lier, J.B. van - \ 2002
Afvalwaterwetenschap 1 (2002)4. - ISSN 1568-3788 - p. 25 - 38.
afvalwaterbehandeling - afvalwater - warmte - geactiveerd slib - aërobe behandeling - voorbehandeling - anaërobe behandeling - pulp- en papierwarenindustrie - waterzuivering - waste water treatment - waste water - heat - activated sludge - aerobic treatment - pretreatment - anaerobic treatment - pulp and paper industry - water treatment
Dit artikel beschrijft het onderzoek naar de thermofiele aerobe nazuivering van anaeroob voorgezuiverd papier proceswater. In batch experimenten vond een proceswater karakterisering plaats met mesofiel en thermofiel actief slib. In tweede instantie werd de toepasbaarheid van een conventioneel actiefslibsysteem onder thermofiele condities bestudeerd
Thermophilic aerobic post treatment of anaerobically pretreated paper process water
Vogelaar, J.C.T. - \ 2002
Wageningen University. Promotor(en): G. Lettinga; A. Klapwijk; J.B. van Lier. - S.l. : S.n. - ISBN 9789058087133 - 152
pulp- en papierwarenindustrie - pulpperswater - anaërobe behandeling - warmtebehandeling - aërobe behandeling - pulp and paper industry - pulp press water - anaerobic treatment - heat treatment - aerobic treatment
Thermophilic waste- or process water treatment increases in importance as industries shift from end-of-pipe treatment towards integrated process water treatment. The need for process water treatment becomes evident as the levels of pollutants in industrial water circuits need to be controlled whereas the intake of fresh water generally diminishes. In the paper and board industry, high process water temperatures prevail and thus water treatment needs to take place under thermophilic conditions. In many cases, an anaerobic pretreatment method can be used but aerobic post treatment is required for polishing of the anaerobic effluent. This thesis describes research in which the aerobic post treatment of anaerobic effluent of a board mill was investigated under thermophilic conditions.
As a boundary condition for aerobic conversions, sufficient oxygen needs to be transferred from the gas phase to the liquid in which the bioconversion takes place. It was shown that although the oxygen saturation concentration decreases with a rise in temperature, this effect is fully compensated by the increased oxygen diffusion rate with the same temperature increase. The overall oxygen transfer rate thus remains constant in the temperature range of 20-55 °C.
Post treatment of anaerobic effluent in activated sludge reactors revealed several fundamental differences between mesophilic and thermophilic treatment. Firstly, batch and continuous experiments showed a lesser removal of complex soluble COD under thermophilic conditions when compared to mesophilic reference experiments. This could not be attributed to a higher production of soluble microbial products (SMP) at elevated temperatures. It is therefore expected that thermophilic biomass is unable to oxidize the same variety of complex soluble components as the mesophilic biomass is capable of.
Secondly, thermophilic effluents are often cloudy while effluents of mesophilic activated sludge reactors are generally clear. This is caused by smaller cohesion forces within thermophilic activated sludge flocs resulting in a higher sensivity towards shear forces and smaller floc sizes. Furthermore, fewer colloidal particles from the influent are adsorbed on the thermophilic sludge flocs and are washed out with the effluent. However, a clear thermophilic effluent can be obtained provided the influent contains little colloidal material.
The underlying causes for the weaker cohesion forces within the flocs are still unclear. The absence of protozoa at 55 °C was shown to be of minor importance regarding the effluent turbidity and could not account for this effect. Binding of hydrophobic pollutants on a hydrophobic surface was hardly affected by temperature and could not explain the observed effects either. Based on calculations using the DLVO theory it was shown that bacterial exo-polymers are of crucial importance in the flocculation process. These interactions are highly temperature dependant and are therefore expected to be the underlying cause for the differences in flocculation behavior.
Besides differences in removal efficiencies and flocculation behavior, also the kinetics of mesophilic and thermophilic activated sludge treatment differ. The maximum growth (and thus conversion rate) of biomass cultivated at 55 °C was a factor 1.4 higher than for a similar type of biomass cultivated at 30 °C. Decay rates are doubled with the same temperature increase whereas the gross biomass yields were similar. As a result, higher substrate conversion rates can be obtained under thermophilic conditions provided that a high concentration of thermophilic biomass is cultivated in the reactor by application of a high organic loading rate.
These kinetic advantages are however of little use when polishing the effluent of an anaerobic bioreactor. Under thermophilic conditions biomass growth will be limited since the organic loading rate is restricted by the need to retain and convert particulates from the anaerobic effluent and by the absence of readily biodegradable COD. Furthermore, biomass decay rates have doubled under thermophilic conditions. The combination of these factors diminishes the amount of active biomass in the thermophilic reactor and can not be compensated fully by the intrinsic higher conversion rates. Overall conversion rates in a thermophilic bioreactor can thus be lower as compared to a mesophilic reference system, depending on the applied loading rates.
Nevertheless, for application in the board industry these disadvantages can be dealt with as the water quality demands are relatively low. Additional treatment methods are however required in case higher water quality demands prevail.
Identification and quantification of nitrogen nutrient deficiency in the activated sludge process using respirometry
Ning, Z. ; Patry, G.G. ; Spanjers, H. - \ 2000
Water Research 34 (2000)13. - ISSN 0043-1354 - p. 3345 - 3354.
afvalwaterbehandeling - pulp- en papierwarenindustrie - geactiveerd slib - stikstof - voedingsstoffentekorten - respirometrie - waste water treatment - pulp and paper industry - activated sludge - nitrogen - nutrient deficiencies - respirometry
Experimental protocols to identify and quantify nitrogen nutrient deficiency in the activated sludge process were developed and tested using respirometry. Respirometric experiments showed that when a nitrogen nutrient deficient sludge is exposed to ammonia nitrogen, the oxygen uptake rate (OUR) of the sludge increases while an initial nitrogen nutrient uptake takes place at the same time. Our investigation suggests that this initial nitrogen uptake is metabolically mediated. The protocols developed in this study can be used: (a) to assess whether a sludge sample is nitrogen nutrient deficient or not; and (b) to estimate the amount of nitrogen required to remedy a nutrient deficient condition in the sludge. Finally, a respirometry-based strategy to control nutrient addition to the activated sludge process is proposed. (C) 2000 Elsevier Science Ltd. | Experimental protocols to identify and quantify nitrogen nutrient deficiency in the activated sludge process were developed and tested using respirometry. Respirometric experiments showed that when a nitrogen nutrient deficient sludge is exposed to ammonia nitrogen, the oxygen uptake rate (OUR) of the sludge increases while an initial nitrogen nutrient uptake takes place at the same time. Our investigation suggests that this initial nitrogen uptake is metabolically mediated. The protocols developed in this study can be used: (a) to assess whether a sludge sample is nitrogen nutrient deficient or not; and (b) to estimate the amount of nitrogen required to remedy a nutrient deficient condition in the sludge. Finally, a respirometry-based strategy to control nutrient addition to the activated sludge process is proposed.
|The development of a corrugated board container for seed potatoes
Sman, R.G.M. van der - \ 1997
Aardappelwereld (1997)8. - ISSN 0169-653X - p. 30 - 33.
Solanum tuberosum - aardappelen - verpakken - ruwe grondstoffen - vezels - karton - bordpapier - pulp- en papierwarenindustrie - potatoes - packing - raw materials - fibres - paperboard - cardboard - pulp and paper industry
Fibres in the European Union; Availability and prices of fibrous raw material for packaging in the EU-1 2
Meeusen-Van Onna, M.G.J. ; Boers, G.J. - \ 1996
Den Haag : LEI-DLO (Mededeling / Agricultural Economics Research Institute (LEI-DLO) 553) - ISBN 9789052423326 - 61
bordpapier - kosten - landen van de Europese Unie - vezelgewassen - vezelplaten - vezels - bosbouw - hardboard - karton - prijsvorming - prijzen - pulp- en papierwarenindustrie - ruwe grondstoffen - cardboard - costs - European Union Countries - fibre plants - fibreboards - fibres - forestry - hardboard - paperboard - price formation - prices - pulp and paper industry - raw materials
Vezelhennep als papiergrondstof : teeltonderzoek 1990 - 1993 = Fibre hemp as a raw material for paper : agronomic research 1990 - 1993
Werf, H.M.G. van der; Geel, W.C.A. van - \ 1994
Lelystad : PAGV (Verslag / Proefstation voor de Akkerbouw en de Groenteteelt in de Vollegrond nr. 177) - 62
Cannabis sativa - bordpapier - hennep - industrie - papier - karton - pulp- en papierwarenindustrie - textielvezels - Cannabis sativa - cardboard - hemp - industry - paper - paperboard - pulp and paper industry - textile fibres
Afzetperspectieven voor Nederlandse hennep en henneppulp in de papiersector
Onna, M.J.G. van; Ent, E.J. van den - \ 1994
Den Haag : Landbouw-Economisch Instituut (LEI-DLO) (Onderzoekverslag / Landbouw-Economisch Instituut (LEI-DLO), Afdeling Landbouw 118) - ISBN 9789052422367 - 103
Cannabis sativa - hennep - ruwe grondstoffen - papier - plantenvezels - bosbouw - pulp- en papierwarenindustrie - cellulose - cellulosevezels - handel - markten - marketing - marktconcurrentie - aanbodsevenwicht - Nederland - Cannabis sativa - hemp - raw materials - paper - plant fibres - forestry - pulp and paper industry - cellulose - cellulosic fibres - trade - markets - marketing - market competition - supply balance - Netherlands
The role of natural wood constituents on the anaerobic treatability of forest industry wastewaters
Sierra - Alvarez, R. - \ 1990
Agricultural University. Promotor(en): G. Lettinga. - S.l. : Sierra-Alvarez - 128
bosbouw - houtpulp - pulpbereiding - afvalwaterbehandeling - waterzuivering - anaërobe behandeling - pulp- en papierwarenindustrie - chemische behandeling - forestry - wood pulp - pulping - waste water treatment - water treatment - anaerobic treatment - pulp and paper industry - chemical treatment
Anaerobic treatment has been shown to be an efficient and energy conserving method for treating various types of readily biodegradable non-inhibitory forest industry wastewaters. However, the high toxicity of paper mill effluents derived from chemical wood processing operations has hampered the wide spread application of anaerobic treatment in the forest industry.
This dissertation describes research on the anaerobic treatment of inhibitory wastewaters from the forest industry. The main objective was to determine the role of natural woodderived organic constituents on the methanogenic toxicity of these wastewaters.
Lignocellulosic feedstocks were pulped by processes commonly applied in the forest industry, namely thermomechanical (TMP) and alkaline pulping processes, to determine which factors are responsible for the extraction of toxic substances. Batch anaerobic biodegradability and methanogenic toxicity assay results indicated that the pulping conditions applied had a significant effect on the anaerobic treatability of the resulting wastewaters. TMP effluents were highly biodegradable and non-inhibitory. Soda pulping liquors contain important fractions of recalcitrant organic matter and exerted severe toxicity. Wood resin constituents were shown to be the major inhibitors present in pulping wastewaters. Wood resin is composed of fatty constituents which are poorly soluble in water at neutral to acid pH values. The increased solubility of resin at high pH values, indicates that the contact of alkali with wood contributes strongly to producing toxic wastewaters by extracting resinous compounds. The alkali promotes lignin solubilization and thereby also contributes to a lowered biodegradability of the wastewater.
Compounds representative of the major wood resin constituents were assayed for methanogenic toxicity. The high toxicity of a variety of resin compounds including volatile terpenes, resin acids and apolar phenols was demonstrated. Concentrations causing 50% inhibition ranged from 20 to 330 mg/l.
Aside from the resinous wood constituents, lignin derived compounds are also potential sources of toxicity in pulping wastewaters. The methanogenic toxicity of lignin mixtures isolated from paper mill effluents was determined. Experiments with ultrafiltered lignins revealed that the toxicity of various wastewater lignins originated from the low molecular weight (MW) fraction. Studies with selected low MW lignin model compounds showed that their inhibitory activity was related to the functional groups on the aromatic ring. Compounds with aldehyde groups or apolar substituents were highly toxic; whereas, those with carboxylic groups were distinctly less toxic.
The effect of chemical structure on the methanogenic toxicity of aromatic compounds was investigated. Some basic structure- toxicity relationships were evident. In general, the toxicity increased with increasing the length of aliphatic side-chains and increasing the number of alkyl or chlorine groups. On the other hand, the toxicity decreased as polar 'functional groups were introduced on the alkylic side chains. The partition coefficient n-octanol/water, an indicator of hydrophobicity, was observed to be positively correlated with the methanogenic inhibition. The results indicate that hydrophobicity is an important factor contributing to the high toxicity of numerous aromatic compounds. Therefore, highly hydrophobic compounds such as resin constituents, apolar lignin derivatives and chlorinated aromatics and are the primary suspect toxicants in forest industry effluents.
The susceptibility of important organic toxins in forest industry effluents to anaerobic biodegradation was assessed. The results indicated that anaerobic treatment technologies have a limited capacity to mineralize natural wood toxins. Although the degradation of a lignin derivative, guaiacol, and long chain fatty acids was demonstrated, other important wood toxins such as volatile terpenes and resin acids were persistent.
Finally, the treatability of TMP and soda pulping effluents was evaluated in lab-scale upward-flow anaerobic sludge blanket (UASB) reactors. TMP wastewaters were found highly suitable for anaerobic treatment. Despite the inhibitory character of soda pulping liquors, anaerobic systems were feasible for removing the biodegradable COD if, prior to biological treatment, the wastewaters were diluted to subtoxic levels or detoxified by pretreatment with the adsorbent Amberlite-XAD-2.
Milieu-effecten van papierslibtoediening op landbouwpercelen in de gemeente Apeldoorn
Pankow, J. ; Toorn, A. van de; Hoeks, J. - \ 1987
Wageningen : ICW (Nota / Instituut voor Cultuurtechniek en Waterhuishouding 1797) - 26
bordpapier - gezondheid - zware metalen - industrie - papier - karton - pulp- en papierwarenindustrie - rioolwater - bodem - bodemverontreiniging - nederland - gelderland - veluwe - cardboard - health - heavy metals - industry - paper - paperboard - pulp and paper industry - sewage - soil - soil pollution - netherlands - gelderland - veluwe