Experimental investigations of long stick wood gasification in a bottom lit updraft fixed bed gasifier

Based on the experience of the gasifier users on the efforts and energy for wood chip preparation in a typical gasifier, we have embarked on the development of a gasifier suitable to work with long stick woody biomass as the feed materials. In the context of the impact of gasifiers, as decentralized energy delivery devices such an approach, it is hoped, would be an attractive option in rural areas both in domestic and industrial sectors. In the present paper in the gasifier operation, there is a fixed quantity of char that is combusted to gasify a fixed amount of wood, and the gasifier does not operate in a steady state manner. In this present work, focus is made on the development of a gasifier using long sticks of wood as feed materials. With this concept, a 10 kW thermal output power gasifier is designed and constructed. The gas and airflows can be converted to the air/fuel ratio, the most important aspect of gasifier operation. The air/fuel ratio shows operation in a combustion mode at start up, a gasification mode for the middle part of the run and a charcoal gasification mode at the end of the run. Since the interest here is exploring and validating of this concept, a bottom lit updraft gasifier is designed mainly to look at the gas yield and other favourable factors and to use this gas so obtained for thermal applications. The rate of feed was between 9 and 10 kg/h and continuous operation for 5 h was made in a couple of runs to study the performance. In this paper we report the salient features of our efforts and results, yielding a gasifier efficiency of 73%.     

Measurement of 40k as an indicator of body potassium: implication for diabetes and other disease conditions

Potassium (K) content in 408 male workers of a rare earths processing plant was estimated using a shadow shield whole body counter. The average K content in the non-vegetarian and vegetarian group was found to be 1.5 g kg(-1) and 2.1 g kg(-1) respectively. The absorbed dose due to 40K is determined as 0.18 +/- 0.02 mGy. While the K content was found to be proportional to body build index, it is inversely proportional to slenderness. Body K was maximum in the middle aged group (35-45 y) and a minimum in younger and older persons. The correlation of potassium content with some disease patterns was also studied. Diabetes mellitus patients were observed to have low K content of 0.9 +/- 0.2 g kg(-1) and those who suffer from cardiovascular disorders were found to have high K content 2.7 +/- 0.3 g kg(-1). The studies showed that the depletion of body K content takes place a few years prior to the clinical detection of diabetes and it builds up a few years before the clinical detection of cardiovascular disorders. It is stressed that the medical information is preliminary as the number of subjects studied was not very large. Wider and in depth study by various groups can hopefully strengthen the observation.     

Wind energy potential at Palkalainagar

This paper uses the Weibull's distribution function to describe the wind speed frequency distribution at Palkalainagar (geographical co-ordinates N : 9°54′, E : 78°54′), Madurai, India using the one year data available. Weibull's parameters are used to estimate the wind data parameters for the site. Of the wind data parameters the most important one is the annual specific output (T_A). This is used in determining the annual energy output of a Wind Energy Conversion System (WECS) and in conducting cost-benefit analysis of wind-electricity generation. The parameter is used in evaluating the efficiency of WECS in the same site. Results show the possibilities of harnessing wind energy towards electricity generation.     

Natural radionuclides in zircon and related radiological impacts in mineral separation plants

The activity concentration of uranium and thorium present in zircon obtained from mineral sand industries are presented. External gamma radiation levels and inhalation of airborne dust are found to be the significant routes of radiation exposure to occupational workers. The annual average dose attributed to zircon processing is estimated to be 2.3 mSv in the plants under study. This paper presents the results of external gamma measurements, estimation of airborne radioactivity in zircon process locations and radon and thoron in the occupational environment of two mineral separation plants in India. Analyses of the solid wastes and liquid effluent generated and resultant environmental impacts are indicated.     

Impact of acceptor-type substitution on electrical transport properties of zircon-type EuVO4

Magnesium-substituted europium vanadate ceramics, Mg_xEuVO_4 ± δ (x = 0–0.5), were prepared by solid state method and characterized by XRD, SEM/EDS, dilatometry, UV–vis spectroscopy, impedance spectroscopy, and measurements of oxygen-ion transference numbers ($\overline{{\text{t}}_{\text{o}}}$). Magnesium was found to substitute preferentially into vanadium sublattice of zircon-type EuVO₄ with limited solubility of ～5 at.%. Additions of magnesium increase slightly coefficients of thermal expansion (3.2–6.0 ppm/K at 150–400 °C) and have negligible effect on the optical properties. Undoped EuVO₄ is predominantly an oxygen-ionic conductor with $\overline{{\text{t}}_{\text{o}}}$ = 0.96–0.99 at 700–900 °C under oxidizing conditions. Acceptor-type substitution suppresses total conductivity and oxygen-ionic transport. The variations of electrical transport properties are discussed in terms of interstitial oxygen diffusion in the parent EuVO₄ and oxygen vacancy diffusion in Mg-substituted vanadate. Humidified atmosphere has negligible impact on the electrical properties of substituted ceramics but results in increased electrical conductivity of EuVO₄ indicating a protonic contribution to the total electrical transport.     

Flaming pyrolysis model of the fixed bed cross draft long-stick wood gasifier

The future industrial development of biomass energy depends on the application of renewable energy technology in an efficient manner. Of all the competing technologies under biomass, gasifiers are considered to be one of most viable applications. The use of biomass fuel, especially biomass wastes, for distributed power production can be economically viable in many parts of the world through gasification of biomass. Since biomass, is a clean and renewable fuel, gasification gives the opportunity to convert biomass into clean fuel gas or synthesis gas for industrial uses. The preparation of feedstock for a gasifier requires time, energy and labour and this has been a setback for gasifier technology development. The present work is focused on gasification of long-stick wood as a feed material for gasifiers. This application makes reduction not only in the cost but also on the power consumption of feed material preparation. A 50 m³/h capacity gasifier was fabricated in the cross draft mode. The cross draft mode makes it possible to produce low tar content in producer gas. This cross draft mode operates with 180 W of blower supply for air to produce 10 kW of thermal output. The initial bed heights of the long-stick wood and charcoal are 58 cm and 48 cm respectively. Results were obtained for various flow conditions with air flow rates ranging from 20 to 30 m³/h. For modelling, the flaming pyrolysis time for long-stick wood in the gasifier is calculated to be 1.6 min. The length of the flaming pyrolysis zone and char gasification zone is found to be 34 cm and 30 cm respectively. The rate of feed was between 9 and 10 kg/h. Continuous operation for 5 h was used for three runs to study the performance. In this study we measured the temperature and pressure in the different zones as a function of airflow. We measured the gas flow and efficiency of the gasifier in order to determine its commercial potential for process and power industries.     

The impact of metallization thickness and geometry for X-band tunable microwave filters

The impact of dc resistance on the performance of X-band filters with ferroelectric varactors was investigated. Two series of combline bandpass filters with specific geometries to isolate sources of conductor losses were designed and synthesized. Combining the changes in filter geometry with microwave measurements and planar filter solver (Sonnet software) simulations quantitatively identified the dependency of insertion loss on overall metallization thickness and local regions of thin metallization. The optimized 8-GHz bandpass filters exhibited insertion losses of 6.8 dB. These filters required 2.5 µm of metal thickness (or 3 effective skin depths) to achieve this loss. The trend of loss with thickness indicates diminishing return with additional metal. The integration scheme requires thin regions of metal in the immediate vicinity of the varactors. It is shown through experiment and simulation that short distances (i.e., 15 µm) of thin metallization can be tolerated provided that they are located in regions where the resonant microwave current is low.