Katja Ohenoja

High-strength nanocellulose-talc hybrid barrier films.

Hybrid organic-inorganic films mimicking natural nacre-like composite structures were fabricated from cellulose nanofibers obtained from sequential periodate-chlorite oxidation treatment and talc platelets, using a simple vacuum-filtration method. As a pretreatment, commercial talc aggregates were individualized into well-dispersed talc platelets using a wet stirred media mill with high-shear conditions to promote the homogeneity and mechanical characteristics of hybrids. The nanofiber-talc hybrids, which had talc contents from 1 to 50 wt %, were all flexible in bending, and possessed tensile strength and Youngs modulus values up to 211 ± 3 MPa and 12 ± 1 GPa, respectively, the values being remarkably higher than those reported previously for nanofibrillated cellulose-talc films. Because of the lamellar and well-organized structure of hybrids in which the talc platelets were evenly embedded, they possessed a small pore size and good oxygen barrier properties, as indicated by the preliminary results. The talc platelets decreased the moisture adsorption of highly talc-loaded hybrids, although they still exhibited hydrophilic surface characteristics in terms of contact angles.

Partial Replacement of Portland-Composite Cement by Fluidized Bed Combustion Fly Ash

AbstractFly ash from fluidized bed combustion differs greatly from that of pulverized coal firing. The most noticeable differences are in morphology, reactivity, and chemical composition. The use o...

Fly ash classification efficiency of electrostatic precipitators in fluidized bed combustion of peat, wood, and forest residues.

The increasing use of biomasses in the production of electricity and heat results in an increased amount of burning residue, fly ash which disposal is becoming more and more restricted and expensive. Therefore, there is a great interest in utilizing fly ashes instead of just disposing of it. This study aimed to establish whether the utilization of fly ash from the fluidized bed combustion of peat, wood, and forest residues can be improved by electrostatic precipitator separation of sulfate, chloride, and some detrimental metals. Classification selectivity calculations of electrostatic precipitators for three different fuel mixtures from two different power plants were performed by using Nelsons and Karniss selectivity indices. Results showed that all fly ashes behaved similarly in the electrostatic separation process SiO2 resulted in coarse fractions with Nelsons selectivity of 0.2 or more, while sulfate, chloride, and the studied detrimental metals (arsenic, cadmium, and lead) enriched into fine fractions with varying selectivity from 0.2 to 0.65. Overall, the results of this study suggest that it is possible to improve the utilization potential of fly ashes from fluidized bed combustion in concrete, fertilizer, and earth construction applications by using electrostatic precipitators for the fractionating of fly ashes in addition to their initial function of collecting fly ash particles from flue gases. The separation of the finer fractions (ESP 2 and 3) from ESP 1 field fly ash is recommended.

Increasing the utilization potential of fly ashes from fluidized bed combustion by mechanical treatments

The increasing use of biomasses in the production of electricity and heat delivers an increased amount burning residue, fly ash that disposal is becoming more and more restricted and expensive. Therefore, there is a great interest to utilize fly ash in other means than disposal. This study aimed to determine the suitability of air jet sieving and air classification to separate detrimental elements, such as sulfate, chloride and some heavy metals, into fine fractions. Furthermore, the effect of fly ash deagglomeration on classification selectivity was studied. Experiments were conducted using two fly ash samples originated from fluidized bed combustion of peat, forest residues and wastes. The results showed that it is possible to significantly improve the utilization potential of fly ashes using air jet classification. In classification, calcium is concentrated into a fine fraction and silica and aluminum are concentrated in coarse fractions. Sulfate, chloride and studied detrimental metals (cadmium, copper, lead and zinc) enrich to the fine fraction with high selectivity. Deagglomeration had a minor effect, as it slightly improved the classification selectivity for some elements.