Deinked Pulp Research Articles

Recovering fibers from fine-prescreening reject at deinking mills

The yield of recycled paper production can be as low as 75%. The reject losses at deinked pulp mills are high compared to the small amount of ink applied to paper during printing. Thus, plenty of sufficiently clean fibers, fiber fines, and fillers are also rejected. This study provided proof of concept for recovery of long fibers from fine-prescreening rejects that contain a considerable amount of contaminants, such as stickies and dirt specks. The recovery of long fibers was studied by means of laboratory flotation experiments for untreated (fine-prescreening reject without dispersing) and dispersed (fine-prescreening reject after low-consistency dispersing) rejects. The pos¬sibility of recycling dispersed fine-prescreening rejects directly back into the preflotation feed also was considered; however, this technique was found to be unworkable. Instead, these results showed that low-consistency dispersion before flotation enabled a high level of contaminant removal at the separate flotation unit. Thus, there seems to be an opportunity to purify fine-prescreening rejects to a level that enabled reuse of the long-fiber fraction without degrading the quality of the end product.

Deinking of Different Furnishes of Recycled MOW, ONP, and OMG Pulps in Silicate-Free Conditions Using Organic Complex of PHASS

Sodium silicate causes problems in papermaking such as deposit formation, decreased retention, and lower sheet strength. Due to these problems, chemical deinking of different recycled papers furnishes including 100% ONP, 80% ONP, and 20% OMG, and a combination of 70% ONP/ 20% OMG/ 10% MOW was accomplished using an organic complexing agent which included poly-hydroxyl acrylic acid and sodium salt (PHAAS) in silicate-free conditions. PHAAS was utilized at four levels of 0.3, 0.5, 0.7, and 1% (based on oven-dry weight of recycled paper) rather than sodium silicate. The optical and physical properties of deinked pulp were compared to control pulp (conventional deinking containing 2% sodium silicate). The results showed that the paper brightness was improved and the yellowness, dirt count, and dirt area were decreased significantly by increasing PHAAS charge up to 0.9%. Also, in different recycled paper furnishes above mentioned, using different charges of PHAAS had different effects on paper opacity. Using different charges of PHAAS (especially 0.7 to 0.9%) decreased paper caliper, increased paper air resistance, increased freeness, and gave similar or slightly better paper tear indices. Differences of tear indices were not significant at confidence level of 99%. Based on the present research, the use of 0.7 to 0.9% PHAAS in place of sodium silicate is advisable because of the better quality of final papers compared to conventional deinking process.

Effects of Flotation Deinking on the Removal of Main Colors of Oil-Based Inks from Uncoated and Coated Office Papers

This paper presents the results of trials to evaluate the color-stripping behaviour of offset printing colors and the effect of coating on deinking performance. Oil-based four-color inks were separately printed as base printing on coated and uncoated white poster paper, and then extensive pulping and deinking processes were carried out. Standard offset printings were conducted on paper samples using cyan, magenta, yellow, and black colors (CMYK), and the effects of deinking efficiency on the removal of each color were analysed. The pulps were made at Micro-Maelstrom Laboratory Pulper at specified conditions with and without bleaching agents. Formamidin sulfinic acid and hydrogen peroxide formulation were used as reductive and oxidative bleaching agents, respectively. Flotation deinking and thickening of pulp were practiced using Degussa flotation and thickening cell. The changes in the optical properties, such as brightness, whiteness, and color value (CIE L⃰, a⃰ b⃰) of deinked pulp were determined. It was found that optical properties of color-stripped pulps from coated papers were better than that of uncoated office papers. However, yield was quite low in coated papers since fillers were lost during flotation process. Cyan color was found to be the most difficult one in four main color printing inks stripping out in the deinking process.

PAPER PHYSICS .The effect of newsprint furnish composition and sheet structure on wet pressing efficiency

Abstract The dewatering ability and wet sheet structure after pressing was studied using a dynamic wet pressing simulator in combination with electron microscopy and image analysis. Deinked pulp (DIP) that contains 5% ash dewaters more easi ly than thermomechanical pulp (TMP) when pressed with single roll pulse. The in-plane moisture flow ( crushing) in DIP samples started at higher peak pressure and higher solids content compared to TMP samples. The TMP sample showed higher springback after wet pressing compared to DIP samples. When both TMP and DIP samples were designed to have a higher amount of small pores at the dewatering side surface layers, the samples with coarser TMP pulp could achieve similar dryness as DIP samples when pressed with higher nip pressure. In addition, the DIP samples with higher number of small pores in the outermost I 0 11m thick surface layer in the dewatering side resulted in lower dryness after pressing with a single roll pulse. The effect of filler distribution in paper zdirection on dryness and sheet structure after wet pressing using an 8 milliseconds roll pulse was also studied. In this study the distribution of filler does not affect the maximum achievable dryness (4 1 %) after wet pressing when the total amount of filler in the sheets remains constant, 1 3 .5%. In addition, the samples with more filler in the dewatering layer dewater more easily and yield the maximum achievable dryness ( 40%) after wet pressing at lower nip pressure (2 . 5 MPa) when compared to samples made from TMP (3 6% at 4.4 MPa) and DIP pulps (40% at 4 . 9 MPa).

Evaluation of Applicability of Bottom Ash as Inorganic Filler

ABSTRACT The disposal of the bottom ash originated from a thermoelectric power plant which used the pulverized coal, has been an important issue of the power plants. In order to find the possibleway of recycling of the bottom ash, the applicability of the bottom ash as an inorganic filler for papermakingwas investigated in this study. The pretreatment with acid were applied for upgrading the properties of bottom ash. The effects of the addition of the bottom ash to the different pulp stocks, Sw-BKP, DIP(Deinked Pulp), Sw-UBKP were evaluated in terms of the change in paper properties. The brightness and tensile strength decreased as the increase of the amount of the bottom ash addition. The bulk and the opacity were in-creased by the addition of bottom ash. The pretreatment of bottom ash resulted in the increase of improve-ment of the brightness and the strength properties comparing with those of untreated bottom ash. Keywords : filler, bottom ash, bulk, pretreatment, brightness 1. 서 론

The influence of pulp refining on de-inking potential and strength properties of ink jet printed paper

The effect of laboratory refining on de-inking potential of inkjet printed handsheets was investigated. Pulp samples containing 80% short fiber and 20% long fiber were beaten in a PFI mill to reach four predetermined freeness levels of 650 (unrefined), 550, 430, and 340 mL CSF, and then handsheets were made. Handsheets were identically inkjet printed and then de-inked. Results revealed that, at lower freeness value, the brightness of de-inked pulps was higher, but the opacity decreased. The surface roughness of handsheets produced using different refined pulp before de-inking was reduced. Our results showed that refining will impart a positive effect on handsheets’ de-inking potential, and de-inking printed papers produced from pulps refined to lower freeness generated the highest brightness. The results revealed that both tensile and tear strength indices of de-inked pulp were lower. However, the tear strength index of unrefined sample and the tensile strength index of pulp refined to 430 ml CSF were higher than for undeinked samples.

Study of Flotation Deinking of Old Magazine and Mixed Office Waste Paper

The effect of flotation parameters such as flotation consistency, temperature, flotation time, air to pulp ratio, and velocity of pulp flow (turbulence level) on OMG/MOW deinking efficiency was studied by using a high-consistency laboratory pulper and a laboratory deinking cell. The optimized flotation conditions were: flotation consistency 1.1%, 40°C, 8min, air to pulp ratio 40%, velocity of pulp flow 3.5m/s and pH 9.0. By using the optimized flotation conditions, the deinked pulp brightness could reach 70.56%ISO, 11.78%ISO higher than that of the control, the effective residual ink concentration was 108.46 mg/kg, which less than 378.14mg/kg of the control, theoretic deinking efficiency was up to 88.41%.

An ecofriendly cost effective enzymatic methodology for deinking of school waste paper

Efficiency of xylano-pectinolytic enzymes in deinking of school waste paper for its reuse has been investigated in the present study. Enzymatic deinked pulp decreased the requirement of chemicals to nearly 50% and gave same optical properties of pulp as obtained by conventional deinking process. This biodeinking plus chemical deinking approach resulted in a decrease of 20.15% and 22.64% in BOD and COD values of effluents and a gain of 10.71% in viscosity, 7.49% in breaking length, 10.52% in burst factor and 6.25% in tear factor as compared to conventional chemical deinking. This is the first report mentioning the use of xylanase and pectinase produced from a cellulase free alkalo-thermotolerant bacterial strain in the same cost effective agricultural residues based production medium for deinking and will help in making the process ecofriendly with 50% reduction in chemicals, commercially viable with better paper quality.

Specks masking by the coating layer in coated paper made from deinked pulp

Abstract Production of lightweight coated paper (LWC) utilises more and more deinked pulp (DIP), for both economical and environmental reasons. A critical requirement on DIP quality for such grades is the cleanliness of the pulp. Indeed, the coating layer may not fully cover specks in the base paper. The objective of this work was to determine the required specifications of the coating layer to produce LWC with DIP base paper. The specks masking phenomena by the coating layer was studied from both optical measurements on coated handsheets made from DIP, and computer simulations of specks contrast reduction. The impact of coating layer parameters (coat weight and optical properties), base paper parameters (grammage and optical properties) and specks nature (grammage and optical properties) on specks masking is studied.

Application of Image Enhancement Technology in Bubble Dimension Measurement of Deinked Pulp Flotation Column

A substantial increase in demand of paper causes a severe shortage of wood, paper recycling have become increasingly important; Deinked pulp flotation column has the features of less site area, good treatment efficiency, easily control and so on, which can be wildly used in fiber recycling in abroad. This thesis uses the working principle of ore dressing to recycle secondary fiber in order to apply flotation column in wastepaper recycling. And meanwhile this article primarily study on deinked pulp flotation column which is imported from Canada, and drawing 2D maps of flotation column, Meanwhile comparing the application of image enhancement techniques in bubble dimension measurement of deinked pulp flotation column.

DecolorizatioDecolorization of process waters in deinking mills and similar applications: A reviewn of process waters in deinking mills and similar applications: A review

Process waters in deinking mills often feature a strong coloration, due to dyes and pigments released from the recovered paper. This can usually be remediated by pulp bleaching treatment with appropriate chemicals. However, the red shade (from rhodamine dye) is resistant to conventional bleaching treatments. This largely limits the use of deinked pulp in white paper grades. In this review, the available technologies for process water decolorization are discussed (chemical methods, physico-chemical methods and biological treatments). Ozonation of the process water appears to be the most promising technique for decolorization of process water in deinking mills. Other emerging technologies such as photo-catalytic treatment or mineralization by white-rot fungi (after adsorption on low-cost agricultural residues) should be considered as well.

PP composites based on mechanical pulp, deinked newspaper and jute strands: A comparative study

In the present work, polypropylene-based composites reinforced with three types of randomly distributed short lignocellulosic fibers, namely mechanical pulp (MP), deinked pulp (DIP), and jute strands, were prepared and analyzed. Addition of 6% (wt/wt) of MAPP resulted in a significant enhancement in the tensile strength in line with the improvement of the fiber–matrix interfacial adhesion making more effective the transfer of stress from the matrix to the rigid reinforcement. The mechanical properties of these composites were analyzed in terms of Bowyer–Bader and Hirsch models to fit the obtained experimental data. From the stress/strain curves and the fiber length distributions, it was possible to access to the orientation factor, the interfacial shear strength, the intrinsic tensile strength and the modulus of the fibers.

Deinking of Thermal Inkjet Newsprint

The advantages of digital printing are emerging into commercial printing. Deinking of inkjet prints is important because they will become a sizable portion of the waste stream. Thermal inkjet ink dispersions are water-based and under certain chemical environments can remain suspended in the process water during flotation, potentially causing discoloration in a closed-loop water system during deinking [1]. Newsprint has not been a major inkjet printing category for digital commercial inkjet prints but the recycling industry has expressed concern about the deinkability of this combination. Also, while newsprint is rarely used in the office, the advent of the commercial inkjet web press will see increasing interest in the recyclability of inkjet on newsprint media, since it provides the option for deployment of newsprint media for short-life (non-archival) printing. When inkjet inks are printed on newsprint, made from wood-containing pulp with lignin, which is then included in the papermaking furnish, the problem of process water darkening can be exacerbated under some chemical conditions. Ideally, the individual sub-micron pigments and molecular dyes in inkjet ink dispersions should be collected to form larger particles of the appropriate size and also made hydrophobic for efficient flotation.In this paper, we show that inkjet-printed newsprint can be satisfactorily deinked via chemistry based on our near-neutral HPES deinking chemistry, described previously [2]. Two kinds of chemicals are used; the “E” in HPES is ethoxylated fatty alcohol, which interacts with the ink and fibers, separates them and prevents the ink from reattaching, while aggregating small ink particles into larger ones. The “S” in HPES is a small amount of an ionic surfactant added into the flotation cell, which facilitates the creation of bubbles which carry particles to the top where they can be skimmed off with the froth, leaving the clean pulp fibers to be recovered. We studied the effect of pH, collecting and clarifying agents, water hardness, chemical loading, and bleaching chemistry on filtrate darkening. In particular, we have found that the color shade and brightness of the deinked pulp and the process water can be significantly enhanced with the addition of a suitable collector or flocculating agent, in this case aluminum sulfate.

GC-MS study of the removal of dissolved and colloidal substances in recycled papermaking by flocculation with nano-size TiO2 colloids

In the papermaking process, the removal and control of dissolved and colloidal substances (DCS) is a key issue for reducing the usage of fresh water. Nano-size TiO2 is an excellent capturing and flocculating agent for DCS due to its large surface area and positive charge. The composition of dissolved and colloidal substances in a system and the removal of these substances by flocculation with nano-size TiO2 colloids were determined by gas chromatography and mass spectrometry (GC-MS). The samples were obtained from non-deinked pulp (non-DIP), deinked pulp (DIP), and whitewater. The research results indicated that the removal efficiencies of the DCS, which are associated with the molecular structures, were sequenced from large to small as follows: resin acids and sterols, benzene derivatives containing carboxyl, fatty acids, and the phthalic acid esters. Then, the mechanism of flocculation removal of DCS was considered. With hydrogen bonding between the surface hydroxyl (Ti4+-OH) and the functional groups containing oxygen, the nano-size TiO2 particles can capture dissolved substances (DS), and bridge colloidal substances (CS) and complexes to induce agglomerate flocculation. The flocculating removal efficiencies were influenced by the functional groups and alkyls of the DCS. Greater numbers and polarities of functional groups produced higher removal efficiencies. Long alkyl chains shield functional groups, thereby inhibiting the formation of hydrogen bonding, which results in a decrease in removal efficiencies.

Study of Flotation Deinking Efficiency of Old Newspaper and Old Magazine

The effect of flotation parameters such as flotation consistency, temperature, flotation time, air to pulp ratio, velocity of pulp flow (turbulence level), and pH on old newspaper/old magazine deinking efficiency was studied by using a laboratory deinking cell developed by ourselves. The optimized flotation conditions were: flotation consistency 1.2%, 50°C, 6min, air to pulp ratio 50%, velocity of pulp flow 3.5m/s and pH 8.5. By using the optimized flotation conditions, the deinked pulp brightness could reach 59.15%ISO, 10.18%ISO higher than that of the control, the effective residual ink concentration was 234.65 mg/kg, which less heavily than 875.56 mg/kg of the control, theoretical deinking efficiency was up to 84.42%.

Study on Bleaching of De-Inked Pulp

FAS bleaching (F) and conventional H2O2 bleaching (P) as well as TAED activated H2O2 bleaching (PT) of wastepaper de-inked pulp (DIP) were studied in this paper. The results showed that the optimum conditions for FAS bleaching of DIP at 10% consistency were FAS 0.6%, NaOH 0.3%, reaction time 30min, temperature 70°C. Under the same conditions of H2O2 3.0%, NaOH 2.0%, Na2SiO3 3.0％, MgSO4 0.05％, the optimum temperature was 80°C and reaction time 90min for conventional hydrogen peroxide bleaching; the optimum TAED dosage was 1.5%, reaction time 60min, temperature 60°C for TAED activated hydrogen peroxide bleaching. Finally a comparison was made between PTF and PF two-stage bleaching for DIP. The performance of PTF was better than PF.

OMG Neutral Deinking Technical Conditions and Mechanism

Single factor experiment was used to investigate neutral deinking technology of old magazine paper (OMG) by self-compounded NTM-2 deinking agent. Olympus inverted biological microscope were used to research distribution state of ink particles in the secondary pulp before and after deinking treatment. Scanning electron microscopy (SEM) was used to analyze fiber surface changing during neutral deinking and ink particles dispersing behaviors in the paper. The results showed that NTM-2 deinking agent had a good deinking effect to OMG, optimum operation conditions of neutral deinking was NTM-2 0.5%, deinking temperature 50°C, deinking time 40min, repulper time 25s, pulp consistence 1.0%, and floatation time 6 min. Under these conditions, brightness of the deinked pulp increased 8.4%SBD, and the ink removal efficiency reached by 90%. Olympus inverted biological microscope images showed that there were a large number of ink particles in the un-treated pulp, and these ink particles integrated with fibers tightly. After treated by neutral deinking, most of ink particles were separated from the fiber, dispersed and suspended in the pulp evenly. SEM images indicated that there were little ink particles in the secondary paper, the fiber surface turned more smoother, and the clean degree would nearly corresponding to the effect of alkaline deinking.

Effect of Flotation Parameters on Old Book Paper Deinking Efficiency

The effect of flotation parameters such as flotation consistency, temperature, flotation time, air to pulp ratio, and turbulence level (velocity of pulp flow) on old book paper deinking efficiency was studied by using a high-consistency laboratory pulper and a laboratory deinking cell. The optimized flotation conditions were: flotation consistency 1.2%, 50°C, 6min, air to pulp ratio 40%, velocity of pulp flow 5.0m/s. By using the optimized flotation conditions, the deinked pulp brightness could reach 77.01%ISO, 9.69%ISO higher than that of the control, the effective residual ink concentration was 175.26 mg/kg, which less than 437.84mg/kg of the control, deinking efficiency was up to 59.97%. After washing process, pulp brightness could reach 84.27%ISO, the effective residual ink concentration was 93.71 mg/kg, deinking efficiency was up to 78.60%.

Control of sticky contaminants with cationic talc in deinked pulp

In this study a cationic talc was applied to deinked pulp for control of sticky contaminants. Effects of the cationic talc on stickies and dissolved and colloid substances were investigated and compared with those of a conventional talc. Characteristics of wet-end chemistry were examined for the pulp with addition of both kinds of talc samples. Furthermore, influences on paper properties were also compared. The results showed that the addition of cationic talc can effectively decrease the content of stickies and DCS, while reducing the cationic demand of the pulp, and the turbidity of the filtrate. Deposition of stickies can be reduced by about 63% with the addition of 2.0% cationic talc into the pulp, and the DCS was reduced from 1989 mg/L to 1927 mg/L. Addition of cationic talc significantly increased the ash content of the paper, but it negatively influenced the paper strength properties.

Neutral Deinking Process Optimization and Comparison with Alkaline Deinking of Old Newsprint

Pulping parameters in neutral deinking of old newsprint (ONP) and its impacts on deinking efficiency were investigated as well as comparison with alkaline deinking was carried out in this paper. The results showed that the low pulping consistency and short pulping time mostly contributed to the removal of ink in neutral pulping stage. The optimum pulping conditions of ONP were as follows: deinking agent, 0.6%~1.0%; pulping consistency, 6%~8%; pulping time, 15min; pulping temperature, 40°C. The low temperature in pulping stage of ONP neutral deinking process could greatly improve the deinking efficiency and reduce heat energy consumption. The comparison of neutral deinking and alkaline deinking of ONP showed that low pulping consistency contributed to the ink removal for neutral deinking, however, high pulping consistency benefit the alkaline deinking. Neutral deinked pulp had better H2O2bleachability than alkaline deinked pulp, and could save 60% H2O2, when the brightness was similar to that of alkaline pulp.