Paper Machine Process Research Articles

Effects of tissue additives on copy paper forming and properties

Laboratory tests were conducted in an effort to determine the effects on paper machine process attributes and the properties of paper made from recycled copy paper furnish upon the addition of chemical agents that are commonly used in the production of hygiene tissue products. Due to continuing growth in tissue and towel grades of paper, such agents are experiencing greater usage. Charge titration test results revealed that certain dry strength agents associated with tissue manufacturing have the potential to shift the balance of charge in papermaking furnish to less negative or even positive values. Creping adhesive was found to contribute to fine particle retention, especially when present at relatively high levels. Release aid and a polyacrylate dispersant had the opposite effect. Low addition levels of both a creping adhesive and a debonding agent surprisingly increased a wide range of strength attributes of paper handsheets in comparison to sheets prepared from unaltered recycled copy paper furnish. The debonding agent decreased paper strength at higher levels of addition. Such effects appear to depend not only on the expected effects of agents themselves, but also on how they affect the charge balance of the wet-end system.

Improving monochloramine performance with innovative sensor-controlled dosing

Monochloramine (MCA) has become one of the major oxidant chemistries for biological control in the paper industry. Feedback control, such as oxidative-reductive potential (ORP), is often used to provide better control of a dosing scheme. The trademarked Ackumen MCA-i is a chemical-digital solution that uses artificial intelligence with actionable insights to stabilize the wet-end process, providing improved performance and reduction in overall chemical costs. Accurate sensor-controlled dosing can be tied to multiple inputs, such as production rates, grade changes, pH, ORP, chlorine residual, freshwater usage, and more. In this study, a case history will be presented to demonstrate how this technology provided a more consistent MCA molecule throughout the process, resulting in a higher level of efficacy and reduction in chemical costs. Application: Through advanced multiparameter dosing controls, monochloramine feed rates can be adjusted as the paper machine process changes. This leads to the right amount of chemistry being applied at the right time, maximizing efficiency of the biocide program.

Effect of nanofiber addition on the physical–mechanical properties of chemimechanical pulp handsheets for packaging

The effect of nanofiber addition on the physical–mechanical properties of industrial chemimechanical pulp handsheets was evaluated. The nanofibers (3 wt%) were added to industrial pulps taken from two positions of the approach flow, trying to reproduce the real paper machine process. Significant correlations between the characteristics of the cellulose nanofibers, the drainability of pulp suspensions, and the physical–mechanical properties of handsheets were found. The increase in the degree of fibrillation decreased significantly the drainability of the pulp suspensions. Nanofibrillation yield, transmittance, viscosity at 0.5% consistency, and carboxylic content positively correlated with °SR, whereas turbidity, and ξ-potential correlated negatively. Nanofiber incorporation increased Tensile Index (up to 21%), Burst Index (23–37%), E modulus (up to 17%), concora medium test (up to 27%), ring crush test (up to 28%), and short-span compression test values up to 23% in the handsheets where nanofibers from bleached kraft pulp were added. A positive correlation was found between the Tensile Index and nanofibrillation yield, and between E modulus and viscosity at 0.5% consistency for all pulps and a high linear relationship between both variables was found for nanofibers from pine pulps. Finally, the values of air permeability decreased up to 80% respect to the control.

A General Robust MPC Design for the State‐Space Model: Application to Paper Machine Process

AbstractApplying model predictive control (MPC) in some cases such as complicated process dynamics and/or rapid sampling leads us to poorly numerically conditioned solutions and heavy computational load. Furthermore, there is always mismatch in a model that describes a real process. Therefore, in this paper in order to prevail over the mentioned difficulties, we design a robust MPC using the Laguerre orthonormal basis in order to speed up the convergence at the same time with lower computation adding an extra parameter “a” in MPC. In addition, the Kalman state estimator is included in the prediction model and accordingly the MPC design is related to the Kalman estimator parameters as well as the error of estimations which helps the controller react faster against unmeasured disturbances. Tuning the parameters of the Kalman estimator as well as MPC is another achievement of this paper which guarantees the robustness of the system against the model mismatch and measurement noise. The sensitivity function at low frequency is minimized to tune the MPC parameters since the lower the magnitude of the sensitivity function at low frequency the better command tracking and disturbance rejection results. The integral absolute error (IAE) and peak of the sensitivity are used as constraints in optimization procedure to ensure the stability and robustness of the controlled process. The performance of the controller is examined via the controlling level of a Tank and paper machine processes.

Membrane Process Design for the Reduction of Wastewater Color of the Mazandaran Pulp-Paper Industry, Iran

The aim of this study is evaluate the use of membrane bioreactor for wastewater treatment Mazandaran pulp and paper Industry. The qualification of wastewater is case study and Characteristics of this industry wastewater were determined by different experiments such as: COD, BOD, Color, densitometry, viscometry and TG/DTA analyzer. Also, the color creating agents in the investigated wastewater was characterized. Then In this study, flux, retention, and permeate quality of various Nanofiltration and low-pressure reverse osmosis membranes were investigated at two temperatures and by using a low shear (DSS Labstak M20®) and a high shear (CR250/2) filter. The overall aim was to study the suitability of Nanofiltration in purification of the discharge water from external activated sludge processes in the pulp and paper industry for reuse in the paper manufacturing process and to compare the results to Nanofiltration of paper machine process waters. The discharge waters were nanofiltered at a higher flux than paper machine process waters. The permeate was almost free of color and organic compounds but contained significantly more inorganic compounds than the permeate from the filtration of process waters. To successfully remove monovalent anions and inorganic carbon from the discharge water a low-pressure reverse osmosis membrane such as the TFC ULP membrane is needed. With that membrane the permeate flux is lower than for Nanofiltration membranes but the permeate quality is significantly better when considering inorganic ions such as sodium, chloride, nitrate and inorganic carbon (bicarbonate). The permeate flux was two times higher in the high shear filter than in the low shear filter but the retentions were significantly lower. The result of this study: decrease pollutants parameter in Tajan Rivers that is effluent because attention to surface water quality has limited in Iran.

Chemical surface modification of glass beads for the treatment of paper machine process waters

Adsorption of detrimental contaminants on a solid sorbent is proposed to remove these contaminants from process waters to increase water recycling and reduce effluent loads in the papermaking industry. A self-assembly process of attaching (covalent grafting) cationic aminosilane molecules to glass beads was investigated. The existence and the hydrolytic stability of self-assembled monolayers and multilayers were confirmed by X-Ray Photoelectron Spectroscopy and contact angle measurements. Effects of reaction time and curing on aminosilane layer structures are also discussed. The curing step after silanization seems to be crucial in the hydrophobization of the quaternary ammonium silane coated onto glass beads, and curing could affect the final chemical structure of the ammonium groups of grafted organosilane. Results indicated that modified glass beads have a strong hydrophobicity, which is attributed to the hydrophobic property of the longest carbon chain grafted onto the glass surface. Adsorption of a model contaminant (stearic acid) onto chemically modified glass beads was determined using colloidal titration. Hydrophobic interactions could be the main driving force involved between the long carbon chains of stearic acid and the carbon chains of the aminosilane layers on glass bead surfaces. Finally, self-assembly processes applied onto glass beads may have two promising applications for papermaking and self-cleaning systems.

Direct injection analysis of fatty and resin acids in papermaking process waters by HPLC/MS

A novel HPLC-atmospheric pressure chemical ionization/MS (HPLC-APCI/MS) method was developed for the rapid analysis of selected fatty and resin acids typically present in papermaking process waters. A mixture of palmitic, stearic, oleic, linolenic, and dehydroabietic acids was separated by a commercial HPLC column (a modified stationary C(18) phase) using gradient elution with methanol/0.15% formic acid (pH 2.5) as a mobile phase. The internal standard (myristic acid) method was used to calculate the correlation coefficients and in the quantitation of the results. In the thorough quality parameters measurement, a mixture of these model acids in aqueous media as well as in six different paper machine process waters was quantitatively determined. The measured quality parameters, such as selectivity, linearity, precision, and accuracy, clearly indicated that, compared with traditional gas chromatographic techniques, the simple method developed provided a faster chromatographic analysis with almost real-time monitoring of these acids.

The effect of transmembrane pressure and pH on treatment of paper machine process waters by using a two-step nanofiltration process: Flux decline analysis

In this work, the treatment of paper machine whitewater obtained from paper production by using loose and tight Nanofiltration (NF) membranes in a lab-scale plant with a plate and frame module was investigated. The NF membranes were evaluated for fouling, flux decline due to concentration polarization and their suitability for removing of components present in wastewater. The loose NF membrane was used for the first step under different transmembrane pressure (8 to 32bars) and pH (3, 5.6 and 10) values. The best filtration performances were provided under a pressure of 32bar and a pH of 5.6. The fouling mechanism at different transmembrane pressures and pH values was investigated by “Hermia's model”. Also, fouling on pores and on the surface of NF membranes was characterized by Scanning electron microscopy (SEM) and contact angle measurements, respectively. For the advanced treatment of permeate obtained from the loose NF membrane that provided the lowest fouling and flux decline, a tight NF membrane was used in the second step. Even better retentions were achieved from experiments with this NF membrane. Results obtained in this study showed that the combination loose and tight NF membranes achieved reuse of paper machine white water for use as shower water of paper machine.

CAUSAL MODEL BASED FAULT DIAGNOSIS APPLIED ON A PAPER MACHINE SIMULATOR

The aim of the work presented in this paper is to evaluate the ability of the causal digraph method to detect and isolate faults on a simulated paper machine process. A causal digraph model for the short circulation process of the paper machine was constructed, identified and used to detect and isolate artificial faults in the simulation environment. The fault of headbox slice opening was studied and diagnosed.

Nanofiltration of biologically treated effluents from the pulp and paper industry

In this study, flux, retention, and permeate quality of various nanofiltration and low-pressure reverse osmosis membranes were investigated at two temperatures and by using a low shear (DSS Labstak M20 ®) and a high shear (CR250/2) filter. The overall aim was to study the suitability of nanofiltration in purification of the discharge water from external activated sludge processes in the pulp and paper industry for reuse in the paper manufacturing process and to compare the results to nanofiltration of paper machine process waters. In this study the discharge waters were nanofiltered at a higher flux than paper machine process waters. The permeate was almost free of colour and organic compounds but contained significantly more inorganic compounds than the permeate from the filtration of process waters. To successfully remove monovalent anions and inorganic carbon from the discharge water a low-pressure reverse osmosis membrane such as the TFC ULP membrane is needed. With that membrane the permeate flux is lower than for nanofiltration membranes but the permeate quality is significantly better when considering inorganic ions such as sodium, chloride, nitrate and inorganic carbon (bicarbonate). The permeate flux was two times higher in the high shear filter than in the low shear filter but the retentions were significantly lower.

Structured uncertainty analysis of robust stability for multidimensional array systems

This paper considers one of the fundamental issues in design and analysis of sampled multidimensional systems - that of uncertainty modeling and robust stability analysis. Methods of structured uncertainty analysis (/spl mu/-analysis) are extended toward systems with dynamical and noncausal spatial coordinates. The stability is understood in a broad sense and includes decay (localization) of system response along the noncausal spatial coordinates. Robustness of dynamical stability and spatial localization of response and boundary effects are addressed in a unified way. The main technical condition enabling the technical results of the paper is that the feedback loop including a multidimensional plant and controller does not have a feedthrough in the dynamical (time) coordinate sense. As an example, this paper applies the multidimensional structured uncertainty analysis to closed-loop control of a cross-directional paper machine process. The paper formulates multidimensional models of the process, its controller, and a structured uncertainty. The uncertainty corresponds to a combination of errors in the actuator mapping, the cross-directional response gain, and the response width.

Multimodel‐based minimum bias control of a benchmark paper machine process

AbstractThis paper presents a multimodel‐based minimum bias (MB), long‐range predictive control algorithm that minimizes the bias in the output using a multiobjective optimization method.To enhance the robustness of the control system, the MB control scheme is extended to the multimodel‐ or multicontroller‐ based MB control scheme, which establishes several models simultaneously. Models with relatively small prediction errors are selected to form a group of acceptable models. The final control is chosen to be the weighted average of the MB controls. Models with significant or large errors are reinitialized.The proposed MB control scheme is evaluated by application to a paper machine benchmark problem and its performance is compared with that of other controllers.

Development of Speed Sensorless Control System for Multimotor Drive in Steel Plant.

In industrial plants such as those for iron and steel process, paper machine process and others, multimotor drive system are very popular. Speed sensorless vector control is most suitable for those system with high performance, high reliability, low cost and less maintenance. Very few papers about multimotor drive system, however, have been reported. This paper describes such a drive system.In case of unbalanced load among the motors, the phase differences between their vectors cause insufficient performance, especially during regenerating at low speed. In this paper, we propose an advanced sensorless control for multimotor drives. The proposed control system estimates the axis of the motors with heavy load and follows it.The proposed drive system are now operating with good performance in steel and other plants.

短周期坪量変動の解析

The technology to analyze the short-term basis weight variation and the long-term variation of relevant paper machine process variables was developed. A number of measured data were stored in a database for several weeks. By the proper interpretation of accumulated data, it was found that the paper quality problem derived from the interaction of short-term and long-term process variation. The developed system quickly identified the causes of the problem and appropriate corrective action was taken to eliminate the bottlenecks in optimum paper machine operation.

Inorganic Impurities in Cationised Starch Granules

AbstractWhen cationised starch containing inorganic water‐soluble salts is used in manufacture papermaking, salts that are not retained in the fibre web will accumulate in the white water of the paper machine. When the white water is recirculated, the inorganic salts are carried into the paper machine's process water. The presence of these salts in the process water constitutes a potential detrimental factor in paper‐making.Point analysis of cross‐sections of granules of dry and wet‐cationised starch with a scanning electron microscope (SEM) and an energy‐dispersive X‐ray microanalyser (EDXA) revealed that the Cl content in dry‐cationised granules was lowest in the central part of the granule (0.8%), higher at the layer under the surface (1.3%) and highest in the surface of the granule (2.5%). The starch sample contained on average (chemical analysis) 1.21% Cl, 0.43% Si and 0.58% Ca. The Cl content in cross sections of starch granules cationised in a water slurry proved to be the same in both the centre and the surface of the granule (0.4%). Chemical analysis of the starch sample revealed no Si and Ca, but 0.2% S.

Studies on Pitch Trouble of News Paper Stocks

Causes of the pitch trouble in the news paper machine process were found out and the preventative treatment for them were established. Troublesome pitch in the process comes mostly from unbleached sulfite pulp. The pitch of sulfite pulp is more fluid and sticky than that of ground pulp and chemi-ground pulp. Those characteristics are due to insufficient seasoning of wood in winter. The same results are obtained also in ground pulp. The pitch trouble caused by sulfite pulp is avoided by means of converting the wood species, red pine to Japanese cedar. In the case of ground pulp, the trouble is apt to appear when the wood contains amount of sticky pitch. The depositing pitch of ground pulp is remarkably reduced when oxidation agent is used to accelate the seasoning effect. For this effect, permanganate is most intensive and peroxide or calcium hypochlorite are also considerably effective.