S.D. Probert

An integrated approach to municipal solid waste management

A theoretical model has been developed for the management of municipal solid waste streams (MSW), taking into account their rates and compositions, as well as their adverse environmental impacts. The model identifies the optimal combination of technologies for the handling, treatment and disposal of MSW in a better economic and more environmentally sustainable way.

Municipal solid waste: a prediction methodology for the generation rate and composition in the European Union countries and the United States of America

Abstract The economically-viable and environmentally-acceptable disposal of municipal solid waste (MSW) is a major concern in many industrialised countries. The main problem facing policy makers in the waste management sector is how to predict the amount and the composition of MSW that is likely to be generated in the near future in order to devise the most appropriate treatment/disposal strategy. Published data on MSW arisings in European countries during the period 1980–1993 and those for the USA between 1960 and 1993 have been correlated with the corresponding figures for the gross domestic product (GDP) and population. The typical composition of MSW has been expressed in terms of the fraction of the total consumer expenditure on goods and products resulting in the generation of MSW, i.e. related total consumer expenditure (RTCE). A model linking RTCE to GDP has been developed and utilised to estimate the amounts of the individual fractions in the total MSW generated. The correlations permit highly-accurate predictions of the total amount of MSW arisings to be obtained both for European countries and the USA. Deviations between the predicted and measured values are, however, much lower in the case of the USA, because the corresponding model is based on data for a single country. Good matches between the predicted and measured figures for the individual fractions of the MSW also ensue. However, the model for predicting the individual fractions in the MSW for the European countries is based solely on information available for the UK.

Thermal resistances of pressed contacts

Contacts between two surfaces under mechanical load occur frequently in numerous structures, yet their behaviour when heat is transferred across them is usually not fully appreciated. The present review is aimed at assisting the designer in understanding the intricacy of this problem and the factors involved.

Rankine-cycle systems for harnessing power from low-grade energy sources

Rankine-cycle systems, each employing a single organic compound as the working medium, are the most commonly used units for converting low-temperature heat into mechanical work. The performances of these systems have been analysed and simulated. The composed interactive computer programs (in BASIC) for predicting the properties of the candidate organic fluids, and for evaluating the behaviour of the simple and regenerative Rankine-cycle units, are listed. The accuracies of the estimated values of the thermodynamic properties have been assessed. Samples of the performance characteristics predicted, employing the routine developed, are given. The programs should help facilitate (i) choosing the most appropriate working fluid from amongst those considered, as well as (ii) predicting the optimal design and operating conditions of a proposed system for a particular application.

Pyrolysis and gasification kinetics of Jordanian oil-shales

Two Jordanian oil-shale samples have been pyrolysed and gasified, non-isothermally, using a thermogravimetric analyser. The controlling parameters studied were the final temperature and influence of particle size as well as the heating rate employed during the process of thermal degradation of the oil-shale sample. The integral method was used in the analysis of weight-loss data to determine the pyrolysis and gasification kinetics. Within experimental error, a slightly greater weight loss occurred during the devolitlization phase when carbon dioxide was used instead of nitrogen to purge the system. The magnitude of the weight loss was dependent on the final temperature, as well as, to a lesser extent, on the heating rate employed. Increasing the latter resulted in the reaction ensuing at higher temperatures. Gasification and pyrolysis of the investigated shales complied with first-order kinetics: the activation energy and temperature at which the maximum reactivity rate occurred decreased slightly as the shale-particle size was reduced.

Evaluation of oil yield from Jordanian oil shales

In this paper, the influences of particle size, grade and pyrolysis temperature on the oil yield have been evaluated in a laboratory scale reactor. Five categories of particle sizes from two different oil shale samples were pyrolyzed by employing a fixed bed retorting system. The reactor and the oil shale sample were heated at a constant rate and nitrogen gas was used to purge the sample, continuously, in order to remove the pyrolysis products from the reactor as well as to reduce secondary reactions. The liquid products were condensed and collected in a series of cold glass-traps and the off-gases analysed for their hydrocarbon and non-hydrocarbon species. Subsequent experiments were carried out, employing a thermogravimetric analyser, using only the four smallest particle sizes under similar conditions as applied to the fixed bed retort. The activation energy was determined by using the integral method. The pyrolysis of the investigated shales was found to comply with first-order kinetics within the limits of experimental error. Increasing the particle size resulted in a small rise in the liquid oil yield, but simultaneously the total gaseous production was decreased.

Heat transfers from pin-fin arrays experiencing forced convection

Steady-state heat-transfers from pin-fin arrays have been investigated experimentally for staggered and in-line arrangements of the pin fins, which were orthogonal to the mean air-flow. For the applied conditions, the optimal spacings of the fins in the span-wise and stream-wise directions have been determined. The dependences of the Nusselt number upon the Reynolds number and pin-fin pitch (in both directions) have been deduced.

Economic and Environmental Evaluations of Waste Treatment and Disposal Technologies for Municipal Solid Waste

MSW management can be defined as the discipline associated with the control of generation, storage, collection, transfer, processing and disposal of MSW, in a way which is governed by the best principles of public health, economics, engineering, aesthetics and other environmental considerations. The disposal of MSW has been the focus of environmental policy for several industrialised countries since the mid-1970s, when attempts were made to identify and categorise, in a systematic way, the waste fractions involved. This categorisation provided the policy makers with the necessary information, to determine the most appropriate option for dealing with the waste in a more economic and environmentally-sustainable way. This paper reviews the main economic costs and the environmental impacts of the widely-accepted waste treatment and disposal methods. Examples of successful waste-management schemes are presented and prospective future trends are assessed.

Heat-exchanger performance: Effect of orientation

For an extended-surface natural-convective type heat-exchanger in air, with its base at up to 40°C above the temperature of the ambient environment, the steady-state heat-transfer performances of the three most commonly employed orientations of the rectangular fins and base (namely vertical fins perpendicular to a vertical base, or protruding vertically upwards from a horizontal base, or horizontal fins attached to a vertical base) have been considered. The latter configuration is of no practical interest for the intended purpose because of its relatively inferior heat-transfer capabilities. If an optimal inter-fin separation of approximately 10 mm is adopted, all other conditions remaining invariant, a higher heat-transfer rate per unit base area is usually achieved from the array of fins when they are attached orthogonally to the vertical, rather than the horizontal, base; but this is not unequivocally so! More than 300 sets of experimental data, obtained from several different arrays of vertical rectangular highly polished duralumin fins protruding orthogonally either from a vertical, or upwards from a horizontal, rectangular highly polished duralumin base were assessed. The non-dimensional data correlations that emerged enable the average coefficient for heat-transfer from a finned surface to the ambient environment, for all the finned surfaces in these two types of configuration, to be easily predicted.

Environmental impacts of atmospheric nitrous oxide

Nitrous oxide (N2O) is an important trace gas in the atmosphere. Changes in the atmospheric concentration of N2O have evoked considerable concern because of its role in (i) regulating stratospheric ozone levels, (ii) contributing to the atmospheric greenhouse phenomenon and (iii) participating in the acid-rain formation process. The global concentration of N2O in the atmosphere has been rising since the start of the Industrial Revolution, before which it was almost constant at about 285 ± 5 ppbv (billion = 109). In 1990, the concentration reached about 310 ppbv and is now rising at a rate of 0·5-1·1 ppbv (i.e. 0·2-0·3%) per year. In this paper, the environmental impacts of the increasing atmospheric concentration of N2O are discussed.