Los rellenos de malla en la absorción de gases nitrosos

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, leída en 1976.Fac. de Ciencias QuímicasTRUEProQuestpu

Characterisation of agricultural residues used as a source of fibres for fibre-cement production

Nowadays, certain components of non-wood annual plants such as corn stalk and industrial hemp core are considered waste materials or used in low value applications; both by-products have a very low cost. On the other hand, given the large quantities of these materials generated worldwide and their renewable character, it is reasonable to explore new routes for their exploitation. The aim of this paper is to study the potential of both corn stalk (Zea Mays L.) and industrial hemp core (Cannabis Sativa L.) fibres as a renewable source of cellulose fibres in the production of fibre-cement. For each source of fibres, a number of chemical cooking treatments were studied. The morphological properties of the fibres were determined using a scanning electron microscope and a fibre and pulp morphological analyser. Pulp refining was carried out in a PFI mill to improve the characteristics of the fibres. In the case of corn fibres, different degrees of refining were applied. The fibre flocculation process was investigated using several polyacrylamides. The process was studied by monitoring the chord size distribution in real time by means of a focused beam reflectance measurement probe. The results indicated both pulps can be used for the production of fibre-cement, having the two types of pulp morphological similarities with the pine fibres currently used. Through the flocculation process it was concluded the floc size depends on the length of the fibres

Pitch adsorption on natural and modified talcs

Talc is used traditionally for pitch control in papermaking. The effectiveness of talcs as control agent of dissolved and colloidal pitch depends on its structural and surface characteristics of minerals. Talcs are modified by thermal and surface treatments to obtain different properties e.g specific surface, surface energy, surface charge and ratio lypophilic/hydrophilic surface. Five commercial talcs have been tested to determine its capacity to adsorb the lypophilic contaminants by experiments of adsorption isotherms. The talcs correspond to two groups of different mineralogical compositions: one with high concentration of talc and some dolomite; and the other, with medium concentrations of talc and chlorite. Colloidal dispersions of extractives were obtained by extraction of Eucalyptus globulus wood at pilot plant scale with acetone, evaporation of the solvent and reextraction with hexane to increase the selectivity of lypophillic compound extraction. The isotherms of adsorption of the pitch dispersions were carried out at 50ºC on the different talcs. The adsorption took place by a mechanism of colloidal adsorption and the results obtained were adjusted to the Langmuir equation. Results show that talc addition to bleaching waters or process waters can produce high reductions of colloidal pitch concentrations, at comparatively low doses

Pitch detackification with natural and modified talcs

Pitch deposition in the pulp or in different parts of the manufacturing system can lead to a decrease in the quality of the final paper produced and to manufacturing efficiency problems. Tackiness is the property of pitch which related to the deposit formation. One of the methods to control pitch deposition in the pulp and paper industry is the use of the talc. The talc acts primarily by a detackification mechanism and hence must be part of the deposit to control further deposition. The effectiveness of talc as control agent depends on its structural and surface characteristics, e.g. specific surface, surface energy, surface charge and ratio lypophilic/hydrophilic surface, being these related to its mineral composition and the thermal and surface treatments it has undergone. Five commercial talcs, corresponding to two groups of different mineralogical compositions, have been tested to determine their detackification capacity using the deposition tester developed by the Complutense University of Madrid. In this method, the quantification of the deposits is carried out by an image analysis (IA) of stainless steel collectors on which the deposit has formed. After IA a qualitative analysis to determine the deposit organic fraction is carried out by gas chromatography (CG) after deposit extraction. The detackification capacity is expressed as the reduction of the deposits formed on the collectors when the different talcs at several concentrations are added to the pulp suspensions. The results show that pitch detackiness by talc addition is related to talc concentration and surface properties of mineral, as for example chlorite proportion, surface area and surface treatment and to the adsorption capacity of pitch on talcs. The general conclusions are that the talc having the highest quantity of mineral talc presents the best detackification capability and that all talcs studied have an appreciable detackification reduction at low proportion of addition

Stickies removal in a deinking line of a newsprint mill: efficiency of the different process stages

The study evaluates stickies removal efficiency of the different process stages in a deinking line of a newsprint paper mill, using 100% recovered paper as raw material. Two different situations have been considered, namely, a normal one, with a low level of stickies at the beginning of the line, and a critical situation with a high level of stickies. Removal efficiencies have been compared with data available in the literature. Although results show a high efficiency of the process for contaminants removal in both cases (80-90%), residual stickies levels at the end of the line are very different (a double initial stickies content causes four times higher stickies content at the end of the line). The first loop is the most critical step, removing 72% of the inlet stickies to the line. The most efficient units are preflotation and the second thickening stage (disc filter 2)

Development of a methodology to predict sticky deposits due to dissolved and colloidal material destabilization in papermaking - Application to different systems

Due to trends in papermaking like closed water systems or higher use of recovered paper as raw material, a large number of contaminants are accumulated in the system as dissolved and colloidal material (DCM). When the DCM is destabilized by a sudden change in the system conditions, it produces sticky deposits called secondary stickies that affect the papermaking processes and the quality of the final product. The laboratory methods existing to predict DCM destabilisation have limitations as low reproducibility or they do not distinguish between sticky and non-sticky materials and/or high volumes are necessary to perform the test, etc. In order to solve these problems, a methodology to predict the depositability potential of DCM has been developed by the Complutense University of Madrid. The methodology is based, first, on the destabilisation of the DCM by polymer addition, second, on its deposition on the collector surfaces and, third, on the quantification of the formed deposits by image analysis. Results show that the methodology has a good reproducibility with an error below 10%. Validation was carried out by application of the method to different cases. Results demonstrate that the developed methodology is a useful tool for researchers and papermakers to predict deposit problems due to the destabilisation of DCM in papermaking

Improving deposition tester to study adherent deposits in papermaking

Conventional methods used for the quantification of adherent material contained in a pulp suspension propose either filtration of the sample, which may lead to loss of sticky material in the filtrate, or dilution of the pulp, which may cause destabilization of the dissolved and colloidal material; thus, leading to unreliable results. In 1998, the Cellulose and Paper Group of University Complutense of Madrid developed a deposition tester which aimed to quantify the adherence of material (microstickies and secondary stickies from dissolved and colloidal material) that was present in white waters generated during papermaking processes. In this paper, an improved deposition tester capable of directly studying the deposition tendency of total stickies in pulps without dilution is described and validated. The design of this device prevents the rotor system from being clogged and blocked by pulps, hence, being able to quantify deposits without having to apply any filtration and/or dilution stages. In addition, the study provides determination of the equipment optimum operating conditions as well as comparison between the improved deposition tester and the one previously developed. Results show that this deposition tester can determine the adherent material contained in pulps with a consistency up to 1%. The comparison of results obtained after applying both deposition quantification methods shows that the quantities of deposits that were measured with the improved tester are slightly lower than those obtained with the application of the conventional method; however, they are in the same order of magnitude. Therefore, it is possible for the improved tester to determine total stickies in all cases, including cases that it is not convenient to apply a filtration and/or a dilution stage

Innovation tools for Chem-E-Car Competition in Spain

Desarrollo de herramientas docentes para la adquisición de la capacidad de controlar de forma segura una reacción química, concibiendo, diseñando y ejecutando un sistema cumpliendo los estándares de seguridad y medioambientales. Las herramientas desarrolladas son de aplicación a un posible implantación de la competición desarrollada por AIChE: "Chem-E-Car".Development of teaching tools to acquire the ability to safely control a chemical reaction, conceiving, designing and implementing a system meeting the safety and environmental standards. The tools developed are designed for a possible implementation of the competition developed by AIChE, "Chem-E-Car".Depto. de Ingeniería Química y de MaterialesFac. de Ciencias QuímicasFALSEsubmitte