Hydrodynamics and recovered papers deinking in an ozone flotation column

This work was aimed at investigating the potential use of ozone flotation for recovered papers deinking. The mixing characteristics and the bubble size of a Venturi aerated laboratory flotation column were studied in the presence of simplified model systems and of an industrial pulp slurry. Experimental results showed that surfactants dissolved in the pulp slurry stabilized air bubbles while cellulose fibers promoted coalescence. Moreover, bubble buoyancy was sufficient to fluidize the fiber suspension generating perfect mixing. The gas–liquid transfer coefficient of ozone (k_La) estimated from gas hold-up, air bubble size and k_La measured in water was high enough (0.84 1/s) for the complete transfer of ozone in the pulp slurry and the generation of ozone-free gas effluent. With O₃ dosage of 0.8 mg O₃/mg COD, ozone flotation allowed increasing chemical oxygen demand removal from 41 to 63% with no effect on the ink flotation efficiency, which remained close to that obtained with air flotation, i.e. ～92%.     

复配生物酶废纸脱墨剂的制备与应用研究

制备了复配生物酶废纸脱墨剂,得到了脱墨剂中纤维素酶与脂肪酶的合适配比(3:2).通过实验,考察了脱墨剂用量,纸浆浓度,溶液pH值,脱墨温度,脱墨时间等工艺条件对脱墨效果的影响.实验结果表明,最佳的生物酶用量为0.3％(对绝干废纸),SDBS用量为1.0％(对绝干废纸),碎浆浓度为10％,pH值为6.0,熟化时间30mi...     

影响酶法脱墨效果的主要因素

研究了含纤维素酶和半纤维素酶的混合酶液对进口美国废报纸的脱墨效果及影响油墨去除率的主要因素。在所研究的 5个主要因素中 ,废纸碎浆时间、酶处理浆浓的影响最显著。     

Modeling and simulation of ozone formation from a propene-nitrogen oxide-wet air mixture in a smog-chamber

Ozone formation from a propene-nitrogen oxide-wet air mixture was modeled and simulated by using a detailed reaction model to characterize ozone formation in air pollution. Effects of reaction parameters such as light intensity, initial concentrations of propene and nitrogen oxides, temperature and humidity were investigated. The loss reactions of N₂O₅ by H₂O were incorporated in the model developed in the present study. Results of simulations showed good agreement with smog-chamber experimental data. From the results of simulations it was found that the maximum ozone concentration was little affected by humidity. The model proposed in the present study can be used to predict the amount of ozone formation successfully.     

The influence of frother types and concentrations on fine particles’ entrainment using column flotation

Entrainment which is the characteristic feature of fine particles is closely related to water recovery. It is based on the changes depending on the establishment of linear relationship between water recovery and solid recovery. This paper deals with the investigation of the effect of frother types and concentrations on fine particles’ entrainment using column flotation. Entrainment of fine particle using a mixture of artificial ore (celestite:calcite; 1:1) was investigated in column flotation. In a two-phase system (water/air), the variation of bubble diameters and gas hold-up with a superficial air rates using different frother types and concentrations were tested. The results showed that the frother types and concentrations had significant effect on the grade and recovery, superficial air rate, gas hold-up and fine gangue entrainment. Entrainment factors for frother types and concentrations were compared in flotation column. Kirjaveinen^[11] model was used for describing the specific entrained factor (P_i) of hydrophilic particles. It has been found that Kirjaveinen model supports the results of this study.     

混合酶用于激光打印废纸脱墨的研究

将生物脱墨技术应用于惠普激光打印废纸脱墨工艺中,在尽量减少碱的用量或完全不用碱的情况下,达到了脱墨的效果和环保的目的。比较了纤维素酶、淀粉酶和脂肪酶以及它们的混合酶对脱墨的影响。分别研究了酶种类和混合酶的配比、温度、pH值对脱墨效果的影响。实验结果表明:纤维素酶和淀粉酶的混合使用有较好的脱墨效果,能使脱墨浆白度达到76.93%(ISO),接近白纸的白度80.48%(ISO)。其最佳工艺条件为:反应温度40℃、pH=9—10、纤维素酶与淀粉酶质量比=1∶1.5。为脱墨工艺的研究提供了理论依据。     

Modeling and simulation of separation process in flotation system

In order to design a flotation circuit to remove ink and contaminants from slushed old corrugated container (OCC) pulp suspension, a model based on mass balance was developed. The model is a five fractional model, which handles mass flow rate of ink, fiber, fines, filler and dichloromethane (DCM) extractives. A detailed method of calculating the deinking selectivity of a material from experimental data, described in terms of reject ratio, is presented. Three flotation deinking systems were simulated. In a single stage flotation system, increasing the number of flotation cells improved cleanness of the accept pulp suspension while it decreased yield at the same time. Yield can be increased by adding a second stage and by introducing the accept flow of the second stage into the feed flow of the first stage. However, the cleanness of the accept pulp was deteriorated. It was shown that yield can be increased without compensating the cleanness of the accept pulp by utilizing the accept pulp from the second stage for another paper machine line instead of sending back to the feed flow of the first stage.     

On Fiber Rejection Loss in Flotation Deinking

Reducing fiber rejection loss in flotation deinking is very important to conserve natural resources and reduce the cost of secondary fibers in paper recycling. This study examined two aspects of the problem, fiber consistency in the rejection stream and rate of froth (or wet stream) rejection. Flotation experiments were conducted using both nylon and wood fibers in column and commercial bench‐scale flotation deinking cells. It was found that increased froth stability resulted in a lower fiber consistency in the wet reject stream. However, it also increased rejection rate of the wet stream. As a result, the total fiber rejection loss was increased with the increase of froth stability. The results obtained suggest that controlling froth stability through reducing frother application and froth rejection are effective ways to reduce fiber yield loss in flotation deinking. This study also experimentally measured water and fiber drainage in fiber suspended froth to explain the effect of froth stability on fiber consistency in the reject stream using froth drainage dynamics.     

Enhancing Phosphate Grade Using Oleic Acid–Sodium Dodecyl Sulfate Mixtures

Upgrading of calcareous phosphate ores by reverse flotation in acidic media depends mainly on the chemical reagents used, especially the collectors. Anionic collectors are commonly used in phosphate flotation circuits; however, in the most cases each collector was tested separately. Although using the mixture of the anionic collectors in salt-type minerals flotation is very limited, it has several advantages over using each collector alone. Therefore, in the present paper, the mixture of oleic acid and sodium dodecyl sulfate (SDS) was tested and compared to the usage of each collector individually. A number of experiments were conducted to find out the optimal reverse flotation conditions for each collector in terms of collector dose, pH, and oleic acid to SDS (Ol:SDS) mixing ratio as main variables using factorial design. The design results showed that the Ol:SDS mixture, particularly at 1:1 mixing ratio, improves the phosphate grade with slight decrease in recovery in comparison with using each collector separately. The highest concentrate grade (>33% P₂O₅), with a recovery of 85%, was obtained at pH 6, 1:1 Ol:SDS mixing ratio, and collector dose 3.5 kg/t. In addition, using 1:1 mixing ratio drastically lowers the collector dose from 3.5 to 2 kg/t or even lower depending on the pH to achieve the concentrate grade required by phosphate industry (30% P₂O₅).     

Vapor phase oxidation of dimethyl sulfide with ozone over V2O5/TiO2 catalyst

The removal of volatile and odorous emissions from pulp and paper industrial processes usually generates secondary pollution which is treated further by scrubbing, adsorption, and catalytic incineration. Studies using a flow reactor packed with 10% vanadia/titania (V₂O₅/TiO₂) catalyst showed complete conversion of dimethyl sulfide (DMS) in the presence of ozone. The molar yields of partial oxidation products were only 10–20%. Small amounts of partial oxidation products, such as and dimethyl sulfone (DMSO₂), dimethyl disulfide (DMDS), and dimethyl sulfoxide (DMSO), were also formed. The results of the oxidation of DMS using ozone only, ozone plus catalyst, and oxygen plus catalyst suggest that the combined use of O₃ with catalyst is essential for the complete destruction of DMS to CO₂ and SO₂. A Box-Behnken design was used to determine the factors that have a significant effect on the conversion and selectivity of the products. It was concluded that product selectivity is strongly influenced by temperature, gas hourly space velocity (GHSV), and ozone concentration. The catalysts were characterized using XRD, surface area measurements, and SEM techniques. Time-on-stream studies carried out in a 500 ppmv gas stream held at 150 °C for 6 h, using 2 g of the catalyst, an ozone-to-DMS molar ratio of 0.9, and a GHSV of 37,000 h⁻¹, yielded 99.9% conversion of DMS. A plausible reaction mechanism has been proposed for the oxidation of DMS based on reaction product distribution and possible intermediates formed.     

Effects of Ozone on Resin Acids in Thermomechanical Pulp and Paper Mill Circulation Waters

The present study investigated ozonation as means to remove resin acids from pulp and paper mill circulation waters. Ozone selectively oxidizes resin acids in debarking, thermomechanical pulping (TMP), and newsprint machine (PM) circulation waters. The relative ozone dose of 0.2 mgO₃/initial mgCOD eliminated over 90% of total resin acid concentration in all tested waters, despite the initial resin acid or organic matter concentration. With that ozone dose, the removal of organic material (measured as COD) was only about 30%. Because of the different COD concentrations of tested waters, the absolute amount of ozone needed for over 90% resin acid reduction was 2000 mg/1 for debarking water, 600 mg/1 for TMP water, and 300 mg/1 for PM water, when initial COD concentrations were 10,000, 3000, and 1500 mg/1, respectively. In theory, abietane type resin acids should be more susceptible to ozone attack than pimarane type resin acids, because of their conjugated double bond structure. In the experiments, a high oxidizability of pimarane type resin acids, as compared to abietane type resin acids, was found.     

造纸制浆和废纸脱墨用表面活性剂

综述了表面活性剂在造纸制浆和废纸脱墨中的应用。讨论了用于纸浆脱脂、洗涤脱墨、浮选脱墨和浮选洗涤脱墨中的表面活性剂。研究表明，在纸浆脱墨中，乙氧基化壬基酚和乙氧基化二壬基酚以及磷酸酯能提供好的脱脂作用，而用于洗涤脱墨和浮选脱墨的表面活性剂类型是不同的。     

Inkjet ink behaviors and its implication in adsorption deinking

The deinking process of inkjet deinking was evaluated by following INGEDE Method 11 and the influence of the pulping chemistry was studied. The inkjet ink behavior during pulping and papermaking was also investigated to distinguish between redeposited ink and bound ink, which has shown that redeposited ink is the major concern during paper recycling. In order to prevent the ink redeposition, adsorption has been used to improve inkjet removal during pulping. Chitosan was selected as an effective adsorbent, and the ISO brightness was improved by 5 points compared with flotation deinking.     

Vapor phase oxidation of dimethyl sulfide with ozone over V2O5/TiO2 catalyst

The removal of volatile and odorous emissions from pulp and paper industrial processes usually generates secondary pollution which is treated further by scrubbing, adsorption, and catalytic incineration. Studies using a flow reactor packed with 10% vanadia/titania (V₂O₅/TiO₂) catalyst showed complete conversion of dimethyl sulfide (DMS) in the presence of ozone. The molar yields of partial oxidation products were only 10–20%. Small amounts of partial oxidation products, such as and dimethyl sulfone (DMSO₂), dimethyl disulfide (DMDS), and dimethyl sulfoxide (DMSO), were also formed. The results of the oxidation of DMS using ozone only, ozone plus catalyst, and oxygen plus catalyst suggest that the combined use of O₃ with catalyst is essential for the complete destruction of DMS to CO₂ and SO₂. A Box-Behnken design was used to determine the factors that have a significant effect on the conversion and selectivity of the products. It was concluded that product selectivity is strongly influenced by temperature, gas hourly space velocity (GHSV), and ozone concentration. The catalysts were characterized using XRD, surface area measurements, and SEM techniques. Time-on-stream studies carried out in a 500 ppmv gas stream held at 150 °C for 6 h, using 2 g of the catalyst, an ozone-to-DMS molar ratio of 0.9, and a GHSV of 37,000 h⁻¹, yielded 99.9% conversion of DMS. A plausible reaction mechanism has been proposed for the oxidation of DMS based on reaction product distribution and possible intermediates formed.     

角质酶/表面活性剂体系对混合办公废纸的协同脱墨作用

角质酶能够水解可溶性酯、不溶性甘油三酯和各种聚酯，因此可以水解油墨中的连接料，有代替脂肪酶应用于废纸脱墨领域的潜能。利用角质酶和实验室复配得到的表面活性剂协同应用于混合办公废纸脱墨领域，探讨其脱墨效果和最优工艺，并与常用商业脂肪酶进行脱墨效果比较。结果表明，角质酶在酶用量10 U·g^-1，酶处理时间30 min，酶处理温度50℃，表面活性剂用量0.2%的条件下可以达到最优效果。与脂肪酶/表面活性剂以及单独用表面活性剂脱墨相比，角质酶脱墨后纸页的白度与油墨去除率更高，纸页的机械强度也较好。通过纸页性能的对比和扫描电镜（SEM）观察，角质酶的脱墨效果较脂肪酶更佳，角质酶/表面活性剂体系对混合办公废纸脱墨效果较好。     

Coal gasification by a mixture of air and carbon dioxide in the filtration combustion mode

This paper presents the results of a numerical and experimental study of gasification of carbonaceous materials in the filtration combustion mode using mixtures of air with CO₂ as an oxidizer. The results obtained are compared with the results on gasification of carbonaceous materials by a steam–air mixture. It is shown that the replacement of steam in the gaseous oxidizer by an equal volume CO₂ leads to a marked reduction in the combustion temperature. The maximum calorific values of the product gas in coal gasification by a mixture of air and CO₂ are close to the values obtained for steam–air gasification.     

Separation of Water and Nitric Acid with Porous Hydrophobic Membrane by Air Gap Membrane Distillation (AGMD)

Abstract

This study investigates the effect of operation parameters on the separation of nitric acid‐water mixture using air gap membrane distillation (AGMD). Porous hydrophobic PTFE membrane was used. The performance was evaluated based on the permeate flux and the nitric acid selectivity. Operating parameters such as feed solution temperature, feed concentration, flow rate, and air gap width were varied. Nitric acid selectivity was found to increase with the increase in feed solution temperature, feed concentration, flow rate, and air gap width. Permeate flux increased, when the feed temperature and the flow rate were increased. The effect of recirculation of the feed solution was also studied. With the recirculation mode, at different initial solution volumes, it was observed that the nitric acid concentration in the feed and the permeate, increased. The rate of flux decline was greater, when the initial feed solution volume was lower.     

Decomposition of ozone on Ag/SiO2 catalyst for abatement of waste gases emissions

A silica-supported Ag system made by the incipient wetness impregnation method was investigated in the reaction of heterogeneous catalytic decomposition of ozone. It was established that the catalytic ozone decomposition on Ag/SiO₂ proceeded in the temperature interval −40 °C to 25 °C as a first order reaction with activation energy of 65 kJ/mol (pre-exponential factor 5.0 × 10¹⁴ s⁻¹). Based on the results from the instrumental methods (SEM, XRD, XPS, EPR, TPD) it can be concluded that in presence of ozone the silver is oxidized to a complicated mixture of Ag₂O₃ and AgO. Due to the high activity and stability of the Ag/SiO₂ catalyst, it is promising for neutralization of waste gases containing ozone.     

Molecular design of nanohybrid gas separation membranes for optimal CO2 separation

Organic-inorganic materials comprising CO₂-philic components may yield superior CO₂ transport properties and good CO₂/H₂ gas selectivity. We report that a fine balance in size heterogeneity in the silicon-based structures is essential and a mixture of sizes up to 50 nm surrounded by 5–15 nm silicon-based nanostructures is the preferred inorganic phase morphology that yields optimal nanohybrid membranes. The combination of optimal synthesis conditions i.e. water/silicon ratio, condensation and ozone pre-treatment durations yields a nanohybrid membrane with a CO₂ permeability of 2000 Barrer while achieving a CO₂/H₂ selectivity of 11. The findings of this work are important for the design of gas separation membranes using green materials.