ETHANOL-PRODUCTION - A PROCESS-BASED MATHEMATICAL-MODEL

Two ethanol production models were developed as a function of microbial growth, metabolism, and the chemical and physical processes occurring in a fermentation system. The first equation, which considered a monosaccharide as the substrate, fit measured data well (R2 > 0.98). This function considered lag time through a microbial population increase component and fit all physical boundary conditions. Because of the theoretical basis for the equation and the excellent fit to measured data, it was concluded that the model fully explained the fermentative conversion of a monosaccharide to ethanol. The upper boundary condition for the monosaccharide substrate equation was modified to include effects of the chemical and physical processes that convert starch and/or cellulose to a sugar. This starch-based equation also closely fit measured data reported in the literature. The four coefficients in the general starch equation were related to carbohydrate concentration, percent saccharification, and temperature. A physical explanation was given for each coefficient. Independent verification of the second model using 18 data sets reported in the literature predicted measured results with an R2 value of 0.89 and was highly significant (alpha = 0.001).34397798

Energy and exergy evaluation of ice production by absorption refrigeration

This article presents an energetic and exergetic analysis of absorption refrigeration and the results from tests of ice production by absorption refrigeration using steam as the principal energy input at the UNICAMP hospital. The analysis found the UNICAMP absorption refrigeration system COP to be 0.36 and the exergetic efficiency to be about 10.4%, both similar to reported values, but less than desired. Exergy analysis further identified the generator strong solution pre-heater and absorber subsystems for additional performance improvement evaluation due to the high irreversibilities of these components.40239540

Effect of container opening area on air distribution during precooling of horticultural produce

An existing research tool was used to investigate air distribution in horticultural produce containers during forced-air precooling. This tool consisted of an instrumented produce simulator that allowed indirect measurement of surrounding air velocity at different positions inside a package. Using this new research tool for different forced-air cooling conditions, the surrounding air velocity was inferred as a function of the simulator's location in reference to the air entrance. The air pathway during the cooling process was investigated for three total package-opening areas (0.67%, 2%, 6%) at airflow rates ranging from 0.125 to 3.9 L s(-1) kg(-1). The air approach velocity at each position inside a package rose as the opening area increased More vented area also enhanced the cooling efficiency. However increasing the airflow rate resulted in a greater air pressure drop. Opening areas more than 6% of the package surface should be tested to achieve the maximum necessary vented configuration that meets the structure constraints and generates air distribution and cooling efficiency not significantly different from fully open.4762033203

Selecting the most adequate bedding material for broiler production in Brazil

Broiler chicken production is widely dispersed across the globe, and one important issue for growers is the selection of adequate bedding material, as the availability and price of substrates varies among countries and regions within a same country. This study aimed at applying a multiple criteria analysis approach for the selection of the most appropriate bedding material for broiler production. Based on field research data and growers' experience, the most desirable characteristics of a litter material were chosen as the main criteria. The selected materials were wood shavings, rice husks, chopped Napier grass (Pennisetum pupureum), 50% sugar cane bagasse (Saccharum L.) plus 50% wood shavings, 50% sugar cane bagasse (Saccharum L.) plus 50% rice husks, and pure sugar cane bagasse (Saccharum L.). The analytical hierarchy process (AHP) was applied for selecting the most suitable bedding material. Validation was performed using data from previous studies carried out in central-western Brazil on the effects of different types of bedding material on broiler carcass quality. Considering the selected criteria, several bedding materials were tested and ranked, and the results showed that wood-shavings litter was the best option (weight = 0.28), followed by rice husks (weight = 0.24). All other tested alternatives presented lower scores and were, therefore, not considered for use. The AHP approach was found to be an efficient tool to select the most appropriate litter material under specific scenarios

ENERGY ANALYSIS - ESSENTIAL TO EFFECTIVE ENERGY MANAGEMENT

Energy management which considers quality or capability as well as quantity can better identify appropriate and cost effective use of energy. Energy analysis utilizing the first and second laws of thermodynamics, termed exergy analysis, considers both energy degradation and loss to provide most effective, not just most efficient, management solutions. This article summarizes the basis for exergy analysis and presents examples which demonstrate the benefits of exergy management in agricultural engineering applications.3841173117

Potential for the use of pyrolytic tar from bagasse in industry

Tar From pyrolyzed bagasse was characterized according to its main structural features. Its solubility in NaOH solutions results in an alkaline tar solution (ATS) that exhibits surface active properties. The prepared ATS was successfully used as a foam flotation agent in copper mining, as a foaming agent in foam concrete formation, and as a fluidization agent for Portland cement manufacture. The potentialities of by-products of conventional pyrolysis and carbonization processed are stressed. (C) 1997 Elsevier Science Ltd.12536336

Towards ProAlcool II - A review of the Brazilian bioethanol programme

Since the creation of the National Alcohol Programme (NAP) in 1975, commonly known as 'ProAlcool', it has gone through a number of fluctuations reflecting Brazilian political, economic and energy priorities. In 1996-1997 over 175 Mt of sugarcane (65% of 270 Mt harvested) was converted to ethanol fuel. The ProAlcool started as a highly innovative programme, but in recent years has lost part of its technological zeal and in certain areas is becoming stagnant. This is due to a combination of reasons, e.g. unclear energy policy, high sugar prices in the international market and lower investment in ethanol production as a result of low international oil prices. A new impetus is needed to reflect changing economic and energy policy in Brazil. This paper reviews the implications for ProAlcool of the new economic policies and the possibilities for restructuring the programme to guarantee its survival as a pioneering and sustainable renewable energy source. This will bring new challenges, costs and opportunities to Brazilian society. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.14211512