Integrated Newsprint Mill Research Articles

BUSINESS MODEL FRAMEWORK FOR USING REAL-TIME PROCESS DATA FOR DESIGN DECISION MAKING

In recent years real-time data management systems have become commonplace at pulp and paper mills, and mills seek to use this important resource for improved operation of production facilities as well as for business decision-making. This paper presents a comprehensive and holistic approach to business modeling in which real-time process data, cost data, and environmental data are used in a “bottom-up” manner to exploit their potential for process decision-making. The paper describes a hypothetical case study in which the business model concept is illustrated by application to a process design problem at an integrated newsprint mill.

Energy decision making in a pulp and paper mill: selection of LCA system boundary

Background, aim, and scope North American pulp and paper mills are facing tremendous challenges, which may necessitate major mill modernizations. An example is process modification to reduce dependency on purchased power, which is an expensive resource. Such modifications may have environmental implications at the mills’ sites, on their product life cycle, and on other interconnected systems, and therefore, systematic tools such as life cycle assessment (LCA) need to be applied. Different LCA system boundary approaches can be used for such process design applications, and these approaches need to be compared to determine their respective benefits and limitations in this context. This study compares setting the system boundary according to a cradle-to-gate approach [attributional LCA (ALCA)] and a system expansion [consequential LCA (CLCA)] approach using a case study, which deals with implementing cogeneration and increased de-inked pulp production at an integrated newsprint mill.

Potential Impact on Activated Sludge Treatment from the Implementation of Cellulosic Ethanol Production at a Pulp and Paper Mill

The potential impacts of additional flow and organic loads resulting from the production of cellulosic ethanol on an existing integrated newsprint mill were simulated in this paper. It was found that depending on the ethanol production rate and the existing spare capacity for additional biochemical oxygen demand (BOD), treatment plant modifications may be required. In terms of operating costs, it was found that nutrients use could increase by 50% to 150%, while aeration flow could increase by 5% to 140% depending on the desired level of dissolved oxygen in the aeration basin. Significant increases in polymer use for mixed sludge dewatering could result due to additional biosolids production. Additional capital costs for air blowers could also be necessary unless the mill has existing spare capacity. It was also found that ethanol recovery efficiency and production rate had little impact on BOD removal up to a certain ethanol production level, and that the impact on operating costs decreased with increasing recovery.

Implications of choices and interpretation in LCA for multi-criteria process design: de-inked pulp capacity and cogeneration at a paper mill case study

Retrofit process design can be seen as a multi-criteria decision-making (MCDM) problem aiming at selecting the best alternative for improving the performance of a chemical process. There is a growing consensus that environmental considerations, including the environmental impact associated with all life cycle stages of materials, should be integrated in chemical process design. Life cycle assessment (LCA) is a technique that allows quantification of those impacts. However, implementing this technique would increase the decision-making complexity and thus would necessitate systematic tools and methods. The analogy between LCA and MCDM has been recognized, but the systematic evaluation of LCA methodological choices and interpretation in this context is rarely discussed. The importance of those is demonstrated in this paper using a case study involving the implementation of de-inked pulp capacity and cogeneration and an integrated newsprint mill.

Spatial and Temporal Resolution in Data-Driven Process Modeling of an Integrated Newsprint Mill

Like many globalized industries, the pulp and paper sector finds itself with an increasingly demanding clientele, who continually expect a better and cheaper product. An important design strategy being employed to address this objective is through an analysis of the vast quantity of process and product data accumulated in plant-wide data historians, in order to improve operations. Mill processes are multivariate, meaning that the interactions between the variables are as important as the variables themselves. Process relationships must therefore be modeled as a group, using an appropriate simulation technique like Multivariate Analysis (MVA), with suitable data pre-processing to account for process upsets and other disturbances. In a previous paper, using an Eastern Canadian newsprint mill as an industrial case study, we showed that it was possible to find statistically significant correlations between wood chip refiner operation, intermediate pulp quality, and final paper quality using data-driven models. This was true even though some important process parameters went unmeasured, process lags changed with time, and the operation of key equipment items changed gradually with use. The present study compares the use of different timescales and combinations of unit operations to determine which ones yield the best MVA simulations. Because plant operating data were used, and experimental design was not practical, it is possible that some of the correlations found could be attributable to coincidence. We therefore added and removed variables and time periods to explore the validity of the models. The best MVA models were obtained by using a shorter (1-hour) data timescale, although use of a weighted-average filter helped to bridge the gap between these faster readings and the slower paper quality trends.

OPPORTUNITY FOR REAL-TIME OPTIMIZATION IN A NEWSPRINT MILL: A SIMULATION CASE STUDY

Real-time optimization (RTO) is applied for the broke recirculation in the stock approach system of an integrated newsprint mill simulation. New optimal broke ratio profiles are set for the paper machine recipes each time the process is confronted with an important disturbance. The variability in the four paper machine headboxes is minimized while the inventory management is handled. The proposed approach is compared to the actual mill operation, making use of a detailed plant simulation. While maintaining broke tank level within an acceptable range, RTO brings the pulp variability down about an order of magnitude. It is expected that it could significantly reduce the sheet break occurrence in a real plant and therefore enhance its economical efficiency.

Model-based direct search optimization of the broke recirculation system in a newsprint mill

This work is concerned with the dynamic modelling of the papermaking section of an integrated newsprint mill, and the subsequent application of two direct search methods in a proof-of-concept optimization study of broke recirculation strategies. The effect of the current broke recirculation policy on the mixed pulp properties at the paper machine headboxes was quantified using a dynamic simulation generating data for an objective function which reflected the rate of change in measurable (flow, consistency and temperature) and immeasurable (total dissolved solids and fibre length distribution) parameters. Genetic Algorithm and the Nelder–Mead simplex methods were then linked dynamically to the simulation and used to find improved ways of recirculating broke pulp. Specifically, the profile of the changes to the broke ratio was modelled using a quadratic function and a second-order transfer function, and the coefficients of these functions were optimized. The optimized broke recirculation resulted in a significant reduction in the value of the objective function, thus, suggesting that the fluctuations in the properties of the mixed pulp stream could be dampened and paper machine headbox stability improved. It is expected that this process enhancement strategy would contribute to an increase in production yield (via a reduction in the occurrence of paper machine breaks), and thus an overall reduction in the waste of materials and energy.

Physiological effects of thermomechanical newsprint mill effluent on Atlantic salmon ( Salmo salar L.)

Anadramous Atlantic salmon ( Salmo salar L.) returning to Exploits River, Newfoundland, Canada, to spawn encounter low concentrations of thermomechanical pulp (TMP) effluent as they migrate upstream past an integrated newsprint mill. Various physiological responses of adult Atlantic salmon from the Exploits River were studied under laboratory conditions. The effects of a 6-h exposure to 0%, 6%, 12%, or 25% (v/v) TMP effluent or an increasing concentration gradient of effluent (0–25%) on cardiac output ( Q ˙ ) , critical swimming performance ( U crit), hematocrit, and blood glucose, cortisol, lactate, and osmolality were examined. Relative to other treatment groups, Q ˙ during routine and low-level activity was 7–10% higher in fish exposed to at least 12% effluent. The 25% exposure group had a distinctly lower U crit and scope for increase in Q ˙ than the other treatment groups. These findings suggest that effluent exposure elevates physiological maintenance and repair costs, resulting in a reallocation of energetic resources.

Applying controllability techniques to analyze a white water network for improved productivity in integrated newsprint mills

Abstract Techniques such as controllability analysis and resiliency studies integrate concepts of process design and process control, with the goal of increasing productivity and preventing pollution by maintaining the stability of steady state and dynamic operation. In this paper, a preliminary controllability and resiliency analysis has been completed for a whitewater network of an integrated newsprint mill. In Canada, pulp and paper is by many measures the most important industry sector, and of particular importance is newsprint production from mechanical pulps (TMP, CTMP, groundwood, etc.). In recent years, the use of process information systems has become widespread in newsprint mills, so that accurate and reliable information has become available to analyze the real dynamics of the process. Effective management strategies for pulp, white water and broke are critical for the efficient operation of integrated newsprint mills. In this paper, a methodology is developed for a specific system within an integrated newsprint mill—the so-called ‘short loop’ around the paper machine. In addition, a more general approach is proposed for the application of plantwide control and controllability theory to an entire newsprint mill network.

Water network analysis in pulp and paper processes by pinch and linear programming techniques

Two water network optimization methods are presented. Both can be utilised to establish, without detailed design, whitewater network configurations that would minimize fresh water requirements and waste-water rejects while respecting critical contamination constraints. The essentially graphic pinch-type analysis is partially automated; it is only applicable to one contaminant system. Linear programming appears to be a more powerful tool because it can be applied simultaneously to several contaminants to be removed and fine fibers to be retained in the system while fresh water consumption is minimized. It is fully automated and particularly well adapted to large size problems. Both methods have been applied to industrial case studies with interesting results. In the case of the water network of the alkaline zone of a de-inking plant no fresh water consumption reduction was obtained, but it was shown that network rearrangement could eliminate the need for a filtration step. In the case of the complete whitewater network of an integrated newsprint mill, it was shown that it is possible to reduce the fresh water consumption by two thirds.

Experimental Field Exposure of Brown Trout to River Water Receiving Effluent from an Integrated Newsprint Mill

Effects of effluents from mechanical pulp production on brown trout were studied for 8 weeks at environmentally relevant concentrations. The exposure took place in laboratory-based pools upstream and downstream of the effluent discharge point of an integrated newsprint mill using ground wood/thermomechanical pulp. The mill had no secondary treatment of the wastewater. The pools were supplied with water pumped directly from the river. To determine the relevance of this approach, wild fish were also caught at the respective sites upstream and downstream from the mill. Sublethal effects were assessed using physiological and biochemical parameters including liver histology, hematology, serum biochemistry, and hepatic enzyme assays. Exposure was verified by analyzing water samples, fish bile, and tissues for resin acid concentrations. The downstream experimental fish and captured feral fish displayed responses and changes in physiological parameters similar to those previously observed in laboratory experiments with untreated effluents. The most obvious effects were liver damage and growth inhibition.

Treatment of integrated newsprint mill wastewater in moving bed biofilm reactors

Wastewaters from three integrated newsprint mills have been treated in a pilot plant Moving Bed Biofilm Reactor (MBBR). In the MBBR the biomass adheres to small plastic elements which move freely along with the water in the reactor. A reduction of 65-75% for COD and 85-95% for BOD was obtained at HRT of 4-5 hours. By prolonging the HRT the removal efficiencies of COD and BOD increased to about 80% and 96%, respectively. With a subsequent chemical precipitation a removal efficiency of COD up to 95% was achieved. The amount of chemicals needed for precipitation of the biologically treated wastewater was only a quarter to a third of that needed for chemical treatment of the untreated wastewater. The results showed the MBBR process to be competitive with conventional biological treatment systems and that treatment objectives can be met at short HRTs.

Treatment of integrated newsprint mill wastewater in moving bed biofilm reactors

Wastewaters from three integrated newsprint mills have been treated in a pilot plant Moving Bed Biofilm Reactor (MBBR). In the MBBR the biomass adheres to small plastic elements which move freely along with the water in the reactor. A reduction of 65–75% for COD and 85–95% for BOD was obtained at HRT of 4–5 hours. By prolonging the HRT the removal efficiencies of COD and BOD increased to about 80% and 96%, respectively. With a subsequent chemical precipitation a removal efficiency of COD up to 95% was achieved. The amount of chemicals needed for precipitation of the biologically treated wastewater was only a quarter to a third of that needed for chemical treatment of the untreated wastewater. The results showed the MBBR process to be competitive with conventional biological treatment systems and that treatment objectives can be met at short HRTs.

Uptake and elimination of resin acids and physiological responses in rainbow trout exposed to total mill effluent from an integrated newsprint mill

AbstractThe effects of thermomechanical pulping effluents from an integrated newsprint mill were tested on rainbow trout (Oncorhynchus mykiss). Continuous‐flow exposures under laboratory conditions were conducted at three dilutions (1:200, 1:400, and 1:1,000) for 8 weeks, followed by a 4‐week recovery period. Sublethal effects were assessed using physiological and biochemical parameters including liver histology, hematology, serum biochemistry, and hepatic enzyme assays. Exposure was verified by analyzing water column, fish bile, and fish tissues for resin‐acid concentrations. The effluent was found to be lethally toxic to rainbow trout within 3 to 4 weeks at a dilution of 1:200. Resin‐acid concentrations in bile, muscle, gill, and liver showed a clear‐cut positive dose response. However, relatively few responses and changes in the physiological parameters analyzed were found when comparing exposed and reference fishes. The small differences in physiological parameters between the reference group and an exposure group (1:400) after a 4‐week recovery period show that the observed responses were reversible. It is noteworthy that the difference between the lowest acutely toxic concentration and the concentration at which only slight physiological responses occurred was very narrow for this effluent.

UPTAKE AND ELIMINATION OF RESIN ACIDS AND PHYSIOLOGICAL RESPONSES IN RAINBOW TROUT EXPOSED TO TOTAL MILL EFFLUENT FROM AN INTEGRATED NEWSPRINT MILL

The effects of thermomechanical pulping effluents from an integrated newsprint mill were tested on rainbow trout (Oncorhynchus mykiss). Continuous-flow exposures under laboratory conditions were conducted at three dilutions (1:200, 1:400, and 1:1,000) for 8 weeks, followed by a 4-week recovery period. Sublethal effects were assessed using physiological and biochemical parameters including liver histology, hematology, serum biochemistry, and hepatic enzyme assays. Exposure was verified by analyzing water column, fish bile, and fish tissues for resin-acid concentrations. The effluent was found to be lethally toxic to rainbow trout within 3 to 4 weeks at a dilution of 1:200. Resin-acid concentrations in bile, muscle, gill, and liver showed a clear-cut positive dose response. However, relatively few responses and changes in the physiological parameters analyzed were found when comparing exposed and reference fishes. The small differences in physiological parameters between the reference group and an exposure group (1:400) after a 4-week recovery period show that the observed responses were reversible. It is noteworthy that the difference between the lowest acutely toxic concentration and the concentration at which only slight physiological responses occurred was very narrow for this effluent.