Avaliação térmica de placas de argamassa de cimento e casca de arroz aquecidas por resistência elétrica

An alternative proposal for floor heating system by means of electric resistance for both chick and piggy installation is presented in this work. Several formulations of rice husk and cement mortar boards were used. An electronic device controlled all board temperature. This system presented a good efficiency design. The conventional cement mortar mixed with rice husk showed a better performance.

Características físicas e mecânicas de misturas de solo, cimento e casca de arroz

The main objective of this work is the study of the effect of rice husk addition on the physical and mechanical properties of soil-cement, in order to obtain an alternative construction material. The rice husk preparation consisted of grinding, sieving, and the pre-treatment with lime solution. The physical characteristics of the soil and of the rice husk were determined. Different amounts of soil, cement and rice husk were tested by compaction and unconfined compression. The specimens molded according to the treatments applied to the mixtures were subsequently submitted to compression testing and to tensile splitting cylinder testing at 7 and 28 days of age and to water absorption testing. After determining its physical and mechanical characteristics, the best results were obtained for the soil + 12% (cement + rice husk) mixture. The results showed a promising use as an alternative construction material.

Efeito da adição de cinza da casca de arroz em misturas cimento-casca de arroz

The rice husk and its ash are abundant and renewable and can be used to obtain alternative building materials. An increase in the consumption of such waste could help minimize the environmental problems from their improper disposal. This study aimed to evaluate the use of ashes as a cargo mineral (filler). However, the rice husk chemically interferes in the conduct of the based cement mixtures. Thus, different mixes cement-rice husk with and without the addition of ash were evaluated in order to highlight the influence of its components (husk; ash), which could otherwise be excluded or be underestimated. Cylindrical samples (test of simple compression and traction by diametrical compression) and samples extracted from manufactured pressed board (test of bending and parallel compression to the surface), were used to evaluate the behavior of different mixtures of components (rice hush; RHA - rice husk ahs). The results of the mechanical tests showed, in general, there is not a statistical difference between the mixtures, which are associated with the chemical suppressive effect of the rice husk ash. The mixture of rice husk of 10 mm, with an addition of 35% of the rice husk ash, is notable for allowing the highest consumption of rice husk and rice husk ash, to reduce 25% the consumption of cement and to allow the storage (without emissions to the atmosphere), around 1.9 ton of CO2 per ton of cement consumed, thus contributing to the reduction of CO2 emissions, which can stimulate rural constructions under an ecological point of view.

Caracterização física e mecânica de argamassas à base de cimento Portland e cinza de casca de arroz residual

Rice husk, employed as an energy source at milling industries in Brazil generates, after burning, a dark ash. This residue is not yet conveniently disposed, being currently dumped on large areas, causing environmental problems. This research intended to evaluate the applications of residual rice husk ashes (RHA) as a partial replacement of cement for mortar production. Rice husk ash was chemically characterized through X-ray fluorescence, determination of carbon content, X-ray diffraction, and laser granulometric analysis. Mortar specimens were submitted to two different exposure conditions: internal and external environments at a maximum period of five months. Physical-mechanical testing were compressive strength and ultrasonic pulse velocity (UPV). Although presenting good mechanical performance, the mortar based on ash (RHA) did not present pozolanicity but it can be employed in cement matrices as inert material (filler).

Preparação e caracterização de carvão ativado quimicamente a partir da casca de arroz

This work consists in a study about the chemical activation of charred rice hulls using NaOH as the activation agent. The influence of the naturally-occurring silica was particularly evidenced. X-ray diffraction patterns showed the formation of sodium carbonate and silicates in the activated samples, whereas thermogravimetric curves revealed a strong reduction in the ash content of these samples after washing with water. Nitrogen adsorption data indicated a microporosity development only in the washed samples, with BET surface area values of 450 and 1380 m2/g achieved for the samples activated at 800 °C starting from the precursor with or without silica, respectively.

Argamassas com base em cal aérea e cinzas de casca de arroz para conservação do património construído

2º Congresso Nacional de Argamassas de Construção, APFAC, Lisboa, 2007 (CD-ROM)

Atributos físicos e químicos de substratos compostos por biossólidos e casca de arroz carbonizada

O objetivo deste trabalho foi estudar os atributos físicos e químicos de substratos com diferentes doses de biossólido (BIO) e de casca de arroz carbonizada (CAC), com vistas em obter um meio de crescimento adequado para o desenvolvimento de mudas. Desta forma, utilizando biossólido proveniente da SABESP, estação de Franca (SP), estabeleceu-se um ensaio com os seguintes tratamentos (proporções BIO/CAC): 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, 20/80, 10/90 e 0/100, os quais foram comparados ao substrato comercial Multiplant®. Foram realizadas análises para determinação dos atributos físicos, como: densidade aparente do substrato, macro e microporosidade, porosidade total, capacidade máxima de retenção de água, e dos atributos químicos dos substratos, como: teores totais de macro e micronutrientes, pH, relação C/N e condutividade elétrica. Com a elevação da dose de BIO no substrato houve aumento da densidade e do percentual de microporos e, conseqüentemente, da capacidade de retenção de água. O BIO apresentou teores razoáveis de nutrientes com destaque para N e P, mas baixos teores de K. Não foram detectados teores de metais pesados superiores aos limites estabelecidos pela Legislação Brasileira no biossólido usado. Comparando-se os valores considerados adequados para o desenvolvimento de mudas encontrados na literatura com os obtidos neste trabalho, encaixaram-se na faixa adequada os substratos cujas doses de biossólido variaram de 30 a 60 %. Nenhum substrato testado, incluindo o do tratamento com substrato comercial, apresentou valores ideais em todas as propriedades estudadas.

Hidrólise enzimática de casca de arroz utilizando-se celulases: efeito de tratamentos químicos e fotoquímicos

In the present work we reported the study of rice hull enzymatic hydrolysis using a commercial cellulase preparation. The results showed that previous treatment with light and sodium chlorite inhibits the enzymatic process (31.4 and 11.8%, respectively) while hydrogen peroxide and ozone favoured the enzymatic production of reducing sugars (5.9 and 54.9%, respectively). Studies performed by quimiluminescence showed that the chlorite treatment produced the most significant change in the structure of rice hull. Nevertheless, this treatment did not favour the subsequent enzymatic process. Photomicrographs obtained from rice hull hydrolysates showed that pre-treatment changed mainly the inner epidermis and parenchyma cell and that they did not change cellular organization of the hull.

Caracterização de cinza de casca de arroz para uso como matéria-prima na fabricação de refratários de sílica

The characterization of rice husk ash, a deriving by-product of the burning of the rice husk during the rice processing is the object of this study. This by-product, for being rich in silica, can be an important raw material for the production of siliceous ceramics, such as thermal insulators and refractory. A combination of surface analysis, thermal analysis and microscopy analysis techniques was used for the characterization. The characterized by-product presented as main component the silica, under amorphous form, with a maximum content of alkalis around 1%, features that become it potentially interesting for the production of ceramic materials.

Aplicabilidade das cinzas da casca de arroz

Currently, the accumulation of rice husk is a serious environmental problem. The burning of rice husk generates a considerable volume of ash, that falls to the ground and gets into the air and the rivers, causing a disequilibrium in the ecosystem. This motived research into solutions that aim to exploit the husks for energy generation and the ashes for developing diverse technological products. This work presents the possibilities of using rice husks and their ashes after burning.

Estudo comparativo entre sílica obtida por lixívia ácida da casca de arroz e sílica obtida por tratamento térmico da cinza de casca de arroz

A comparison between silica by acid leaching of rice husk (RH) and silica obtained from thermal treatment of rice husk ash (RHA) is presented. The best leaching results were obtained using 10% hydrochloric acid followed by washing with water. The alternative method, calcination of RHA at 700 ºC for 6 h followed by grinding for 80 min, was more effective. Silica obtained from RH was about 97% amorphous, had a 17.37 µm mean particle size, and a specific surface area of 296 m²/g. On the other hand, for silica obtained from RHA the values were about 95% amorphous material 0.68 µm, and 81 m²/g.

Preparação e caracterização de carvão ativado quimicamente a partir da casca de arroz

This work consists in a study about the chemical activation of charred rice hulls using NaOH as the activation agent. The influence of the naturally-occurring silica was particularly evidenced. X-ray diffraction patterns showed the formation of sodium carbonate and silicates in the activated samples, whereas thermogravimetric curves revealed a strong reduction in the ash content of these samples after washing with water. Nitrogen adsorption data indicated a microporosity development only in the washed samples, with BET surface area values of 450 and 1380 m²/g achieved for the samples activated at 800 °C starting from the precursor with or without silica, respectively.

Caracterização de cinza obtida por combustão de casca de arroz em reator de leito fluidizado

The rice husk combustion in a bubbling and atmospheric fluidized bed reactor was investigated. This paper presents the rice husk ash characterization employing the techniques of X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM) among others. After combustion, a rice husk ash containing 93% amorphous silica and <3% unburned char was produced. Methods usually applied to fixed bed considering external sources of energy and high reaction times were employed. Thus, the potential of this type of reactors with respect to speed, continuity and self-sufficiency energy of the process was shown.

Uso da cinza da casca do arroz (CCA) obtida da geração de energia térmica como adsorvente de Zn(II) em soluções aquosas

The removal study was conducted using 1.00 g of the rice husk ash (RHA) and 20.0 mL solution with concentrations in the range of 10-1000 mg/L of Zn(II). The influence of contact time, initial metal concentration, agitation and pH of the removal process was investigated. Superior removals to 95% were obtained at the end of 24 h of contact. The agitation increased in 20% the removal of Zn(II), being needed only 5 min to reach the equilibrium. The adsorption process was studied by the models of isotherms of Langmuir, Freundlich and BET, obtaining results of R L and 1/n for a process favorable of adsorption. BET isotherm best represents the equilibrium adsorption. The results showed that the RHA has the largest capacity and affinity for the removal of Zn(II).

Aplicação da casca de arroz na adsorção dos íons Cu2+, Al3+, Ni2+ e Zn2+

The potential use of rice husk as biosorbent to remove Cu2+, Al3+, Ni2+ and Zn2+ ions from aqueous solutions was investigated under both noncompetitive and competitive conditions. The biosorbent was used in the form of particles with size smaller than 0.5 &#956;m and in the concentration of 500 mg L-1 (dry weight). The experiments were performed using batch adsorption technique for concentrations of 10, 30 and 70 mg L-1 of metal ions at pH 4.0 and 5.0. The chemical speciation of metals in the experimental conditions used in this work was predicted by the software Visual MINTEQ 2.6.