J. Tijero

Slime problems in the paper and board industry

Abstract The latest trends in the paper industry have been towards manufacturing by a neutral or alkaline process, greater consumption of secondary fibres and the closing-up of the process water systems. Under these conditions of papermaking, the problems of deposits, corrosion and odours due to the microbiological activity increase considerably and therefore, runnability and production problems occur. To help our understanding of the current situation in the paper industry, this paper presents a review of the microorganism sources, the consequences of the microbiological activity upon the actual systems of manufacturing paper and board, and the current state of the different alternatives for its prevention and control, as well as the future trends to address environmental considerations.

Peer Reviewed: The Challenges of Sustainable Papermaking

Although the industry has become more environmentally friendly, it needs to overcome social, economic, and scientific obstacles to achieve additional progress

Optimization of Pitch Removal by Dissolved Air Flotation in a Eucalyptus Kraft Mill

Abstract Wood extractives cause production and environmental problems as well as decreasing the quality of the final product in pulp and paper manufacturing. These disturbances are commonly referred to as pitch problems in this industry. The complex composition of wood extractives is the reason why the nature of pitch problems is different for the various wood species. Also, there is a strong dependence on pulping, bleaching, and papermaking processes. Nowadays, the most common way of handling pitch is to use chemicals in order to fix the extractives to the fibers and thus remove them from the process with the final product. However, this causes serious problems in the final product and also increases problems when paper is recycled. Thus, fixation is not considered to be a sustainable operation for the future. Alternative methods to remove the extractives from the process water must be developed to overcome pitch disturbances and increase pulp quality. This is especially important in mills with closed water loops where the accumulation of extractives in the process waters can occur. In this paper an internal process water kidney, based on dissolved air flotation (DAF), is considered. The objective was to remove extractives from a kraft mill process using Eucalyptus globulus as the raw material. The results show that with the dual system, polyethylene oxide and phenol formaldehyde resin (PEO/PFR), it is possible to remove 80% of the extractive compounds by DAF. Three different techniques, hemacytometry, gas chromatography and turbidity measurement, were used to evaluate the removal efficiency. The applicability of a fast measurement, such as turbidity, to optimize the DAF operation during a future mill operation was studied. This research was carried out within the European Pitch Project (QLK5‐CT‐1999‐01357) funded by the European Commission. The authors wish to thank Beatriz Rodriguez for her skillful laboratory work and the personnel of ENCE pulp mill in Pontevedra for their cooperation.

Electrochemical treatment of black liquor from straw pulping

The conventional black liquor regeneration process is not always suitable for pulping plants of nonwood fibers due to the unfavorable ratio of organic to inorganic solids. This paper presents an alternative treatment based on an electrolysis process of the soda black liquor from straw pulping. This alternative method minimizes the environmental impact by recovering the caustic at the same time that the liquor is acidified, which favors the later separation of the lignin.

Effect of Cu2+ , Ni2+ and Zn2+ on an anaerobic digestion system

Abstract This paper reports the characterization of an anaerobic digester in relation to minimun levels of copper, nickel and zinc, separately and mixed, which it can receive and the effects these give rise to on stability, depuration efficiency and methane production. The experiments were carried out on complete mixture laboratory scale digesters.

Simultaneous separation and determination of polycyclic aromatic hydrocarbons by high-performance liquid chromatography in the manufacture of anthraquinone from anthracene cake

A simple, isocratic and rapid reversed-phase high-performance liquid chromatographic method for the separation and simultaneous determination of carbazole, fluorene, phenanthrene, anthracene, fluoranthene, pyrene and 2-methylanthracene from anthracene cake is proposed. The method is also suitable for the separation and simultaneous determination of 9-fluorenone, phenanthrenequinone, carbazole, anthrone, fluorene, phenanthrene and anthracene from industrial anthraquinone of high purity. Reversed-phase high-performance liquid chromatography was carried out on a 10-µm C18 Spherisorb ODS 2 column, using methanol-water (82 + 18 V/V) as the eluent, at a flow-rate of 1.5 ml min–1 with UV detection at 254 nm. The analysis of industrial samples of both anthracene cake and anthraquinone required no longer than 12 and 8 min, respectively. The coefficients of variation were in the ranges 1.03–2.97 and 1.67–3.11%, respectively. The proposed method is simple, reproducible and rapid. It is suitable for the determination of the impurities present in the manufacture of high-purity anthraquinone from anthracene cake.

Heavy Metal Distribution in Anaerobic Sludges

Abstract On the basis of a depuration system, by anaerobic processes, for wastewaters which contain variable amounts of copper, nickel, and zinc, a study is made of the distribution of these cations betwen the solid sludge and the supernatant liquid of the effluent. In all the experiments, amounts approximating 90% of the metals existing in the substrate were retained in the solid sludges, a very small amount of the metals remaining in the clear liquid of the effluent.

Selective oxidation of anthracene to anthraquinone in acetic acid with air in presence of nitric acid

Abstract The oxidation of anthracene in acetic acid with air in the presence of small proportions of nitric acid produces high quality anthraquinone with acceptable yields. A possible mechanism is suggested which explains the predominance of the oxidation reaction compared with that of nitration.

Kinetic study of anaerobic digestion of glucose and sucrose

Abstract This paper reports the behaviour of an anaerobic digester fed with pure, easily biodegradable substances (glucose and sucrose); for this a kinetic model was used based on the kinetic equation of growth in microorganisms defined by Contois. The model predicts with great exactitude the yields of the digester. Similarly a heavy dependency is observed on the maximum growth rate of the microorganisms of the type of substrate and the concentration of the influent.

Recovery of Anthracene from Coal Tar by Solvent Extraction

A method of anthracene purification by extraction of impurities with a methanol-benzene solvent mixture is proposed. In the first stage the anthracene cake is dissolved in the solvent mixture at th...