THE EFFECT OF LIGNIN CONTENT OF WOOD FIBERS ON PULP SCREENING/SEPARATION

An experimental investigation of the effect of lignin content of wood fibers on pulp screening is conducted. A non-uniform lignin distribution may exist in wood pulp due to variations in wood chip characteristics, and/or cooking conditions in a digester. Pulp screening was conducted in a modified Williams Freeness tester at different fiber lignin contents and pulp consistencies. The study indicated a large drop in pulp accepts fraction, thus a substantial fiber loss, with an increase in lignin content. The fiber loss was more significant at higher consistencies of pulp. This study suggests that the fiber lignin content should be considered an important process variable affecting the efficiency of pulp screening processes.     

INFLUENCE OF PULP PULSATION ON THE BATCH FLOTATION OF GALENA

An experimental investigation into the effect of pulp pulsation on the flotation of an artificial mixture of galena and quartz has been conducted. Laboratory experiments have shown that the recovery and kinetics of lead flotation can be improved significantly by pulsating the pulp, while the grade and selectivity of the lead remained virtually unchanged. Pulsation of the pulp led to structural change of bubbles. An increase in the number of bubbles and a decrease in the bubble size resulted in an increase in the gas holdup in the pulp and a likely increase in the bubble-particle collision rate. Likewise, the viscosity of the slurry could be decreased by means of pulp vibration, enhancing mass transfer between the slurry phase and froth phase. At the same time, the energy input by pulp pulsation could help to lower the energy barrier for bubble-particle attachment by lowering the induction time of the attachment. In addition, non-selectively attached particles could be stripped off the bubble surface by the inertial forces acting on the particles during pulsation of the pulp. Image analysis of the froth showed that pulsation resulted in a more stable froth, with more numerous, smaller bubbles with higher loadings.     

Effects Of Ozone On Kraft Process Pulp Mill Effluent

Effluent from a kraft process pulp mill was studied in a batch reactor for ozone doses between 50 and 200 mg O₃/L to identify the relative suitability of ozone application locations in the treatment process and see the improvements in biotreatability of wastewaters from a kraft process pulp mill. Laboratory acclimatized seed were used for BOD tests for ozonated and unozonated samples. The inhibitory effects were minimized by using optimum dilutions. The studies were divided into three major sections: characterization of mill effluent; ozone system calibration, and reactor design; and ozonation of mill effluent. Seed for Biochemical Oxygen Demand tests were acclimatized in batch units for primary, bleach and secondary effluents separately. The inhibitory effects which were noted with unacclimatized seed, were reduced by using laboratory acclimatized seed and optimum dilution which were determined during the characterization phase.

The batch reactor designed for the studies consisted of a cylindrical section for holding effluent, and a top spherical section for ozone/oxygen mixture. The reactor proved to be effective for controlling ozone dose. The variation in the applied ozone dose was less than 5 mg/L.

Bleach and primary effluents were treated with 50 and 100 mg/L ozone doses. Duplicate experiments were conducted for these effluents. Secondary effluent was studied for 50,100,150 and 200 mg/L ozone doses. Six replicate experiments were conducted for 50 and 100 mg/L ozone doses, whereas two experiments were carried out for 150 mg/L and one experiment for 200 mg/L ozone dose.

The results were analyzed using 't' test for paired experiments and ANOVA table for statistical confirmation. Residuals were plotted to check the assumptions of constant variance and normal distribution. The results indicated that 50 and 100 mg O₃/L effectively removed color from bleach effluent and primary effluent, but did not significantly change the BOD. Ozone was found to be effective for secondary effluent, as BOD₅ was increased by 65% for 50 and 100% for 100 mg O₃/L doses. The corresponding reduction in color was 62% and 82%, respectively. K_e and L_o values for the BOD equation were calculated by using the non-linear least square method for the BOD equation, giving joint confidence regions for the calculated parameters. It was concluded that ozone is most effective for the removal of color and the increase of BOD in secondary effluent.     

Effect of physico-chemical conditions on the properties of zeolite microparticles used in pulp and paper applications

Zeolites are framework aluminosilicates that have been proposed as a replacement for bentonite in microparticle retention systems. It has been claimed in many patents that zeolite can improve sheet formation in fine paper manufacturing. However, this improvement was not observed in mechanical grades. These experimental results, and also theoretical evidence, suggest that papermaking pH plays an important role in zeolite efficiency. In consequence, the effect of pH and temperature on the chemical properties of zeolite and bentonite microparticles was determined. Streaming potential, conductivity, and pH were measured while microparticle solutions were gradually acidified to pH 5. Samples were also taken at specific pH values to measure the cationic demand. Results showed that a gradual reduction of pH caused several modifications to zeolites. The first step was the neutralization of free hydroxyl ions in solution. The second step was an irreversible exchange of the charge-compensating sodium ions by hydrogen ions on the inner and outer surface of microparticles. Finally, dealumination of the zeolites occurred. It was determined that neutralization must be completed before ion-exchange can begin. However, ion-exchange and dealumination occurred simultaneously. Between pH 7.5 and 9, zeolites had more anionic sites than bentonite (around 0.8 meq/g vs. 0.5 meq/g). The higher surface charge of zeolites might partly explain their efficiency in microparticle systems. On the other hand, under pH 7.5, the anionic charge of zeolite samples rapidly decreased while that of bentonite was stable. The effect of temperature was also studied in the 25 to 55 °C range. Generally, a temperature rise promoted a greater dissociation of the surface hydroxyl groups and an acceleration of ion-exchange and dealumination processes.     

造纸行业的清洁生产技术与措施分析

分析了我国造纸行业的污染现状,提出了推行清洁生产是造纸行业可持续发展的必要条件。然后从革新工艺与降污减废以及污染治理与废物利用两个方面系统阐明了推行造纸行业清洁生产的技术、措施及其环境经济效益,归纳了推行清洁生产的政策与管理方法,旨在对造纸业发展及实施污染治理工程技术有借鉴作用。     

Ozonation Dynamics and Its Implication for Off-Gas Ozone Control in Treating Pulp Mill Wastewaters

Ozonation of biologically pretreated pulp mill wastewaters was studied using both bench and pilot scale fine bubble contactors to determine the oxidation efficiencies, mass transfer coefficients (k_La) and enhancement factors (E) due to the occurrence of chemical reactions. A sensitivity analysis based on the measured process parameters was then used to reveal the interrelated effects of key factors on off-gas ozone concentrations. It was shown that the removal efficiencies of color and AOX were simply related to the amount of utilized ozone, regardless of variation of other operating conditions. Furthermore, the rate of absorption fell within the fast or instantaneous kinetics regimes due to the occurrence of rapid chemical reactions. The Ek_La values were found to vary substantially during the course of ozonation, indicating that the enhancement factors were not only affected not only by operating conditions but also by wastewater characteristics. To effectively control the off-gas ozone emission, measures should be taken to minimize the backmixing, use a counter-current flow arrangement and provide adequate contact time.     

Selective Removal of Lipophilic Wood Extractives from Paper Mill Water Circulations by Ozonation

Circulation waters from paper mills and TMP production were treated by selective ozonation to remove lipophilic wood extractives (LWE's). In the reaction model, ozone was assumed to react with overall organic matter measured as COD with one global reaction rate coefficient. The target compounds, LWE's, are a part of the overall organic matter and they react with ozone with a specific reaction rate coefficient. Reaction selectivity, defined as the ratio of reaction rate coefficients of the reactions of ozone with the LWE's and COD, describes how efficiently ozone is used to remove the LWE's compared to removal of COD. The reaction selectivity was determined from experimental results and it was found to vary from 3 to 20 for different sets of water and for different fractions of LWE's. However, the ozone dose needed for removal of extractives was found to be rather high, about 100–300 mg/dm³ for 50% removal. The reason is the high concentration of organic matter in the waters leading to excessive usage of ozone despite the high selectivity of the reaction. A reactor model was developed to predict the behavior of industrial ozonation reactors. The reactor model takes into account the variation in the rate coefficient with respect to the reaction extent.     

SRMC-Ⅰ型打浆度自动在线检测仪

本文介绍了SRMC-Ⅰ型纸浆打浆度自动在线检测仪的组成、原理、性能指标、功能和使用。实际应用表明，该检测仪工作稳定可靠，使用方便，提高了打浆度检测的实时性，可在造纸厂推广使用。     

中国造纸工业六十年的光辉历程——纪念中华人民共和国成立六十周年

文章简要地回顾了我国制浆造纸工业在过去60年的发展历程,取得的成绩,以及存在的问题,还为进一步取得更大的进步和发展,作者提出了他的有益的建议和策略。     

草浆造纸黑液改性制备木质素酚醛树脂结合剂

以草浆造纸黑液为研究对象,通过对木质素的分离、提纯及对其酚羟基、羟甲基化改性,制备了木质素酚醛树脂结合剂。选择双氧水+稀土为催化剂,确定了其最佳的制备反应条件和试样成型工艺条件。所合成的木质素酚醛树脂结合剂,可以用于A1