Synthetic SO2 Sorbents for Fluidized-Bed Coal Combustors

The information presented in this paper is directed to engineers who are involved with environmental emissions from coal conversion plants. Synthetic sorbents were investigated as an alternative to natural sorbents (limestone) for the removal of SO₂ from the combustion gas in a fluidized-bed coal combustor. The sulfation rate of a synthetic sorbent, CaO in α-AI₂O₃, was determined as a function of gas composition, temperature, and calcium concentration in the sorbent. The reaction was found to be diffusion-controlled above 850°C and kinetically controlled at lower temperatures. The physical characteristics of the support material have a major effect oh the sulfation kinetics. Porosity measurements indicated that supports containing large pores (>0.2 µm) produced sorbents having high sulfation rates and that pores with diameters less than 0.2 µm did not contribute significantly to the capture of SO₂. The sorbents SrO in α-AI₂O₃ and BaO in α-AI₂O₃ had lower SO₂ capture rates than did CaO in α-AI₂O₃. The alkali metal oxide sorbents K₂O and Na₂O in α-AI₂O₃ captured SO₂ much faster than did the alkaline earth metal oxides.     

MEASURING IMPACTS OF URBAN WATER DEVELOPMENT1

ABSTRACT The role of water resources in the urban economic and social environment, particularly in the inner city, has never been established to the degree necessary for making informed decisions on investments in urban waterway and shoreline improvements. The basic tools for measuring psychological and social impacts of waterway and shoreline developments in the inner city have not been fully developed and utilized to date. However, through a detailed analysis of the water resources in the urban core area of Cleveland, it appears that deliberate development of water-based recreation and other environmental resources can lead to improvement in some of the social problems of the inner city. In recreation analysis, there is currently a great gap between methodologies that are conceptually sound and those that have been applied by urban and water-resources planning agencies. New tools and methodologies can only be used successfully when public agencies are given the institutional and policy means for using them equitably in light of social needs. Present urban-water planning practices have been found to be biased against the inner city, often unintentionally.     

Long-term projections of non-fuel minerals: We were wrong,but why?

This article revisits global projections made in 1981 of eight metallic and fertilizer minerals for the year 2000. The principal objectives of the present study are to quantify the differences between the projected and observed levels of consumption for the year 2000 for eight of the 26 non-fuel minerals covered in the earlier study, and, then, to attempt to attribute these (often) large differences to the major determinants of minerals demand: income, technological, regulatory and other public policy changes, and changes in the recycling rates of the metallic minerals. The eight minerals are: aluminum, copper, iron, mercury, nickel, phosphate rock, potash and tin.This follow-up study begins with a discussion of the need for long-term projections of minerals. This section also includes a summary of the major determinants of the long-term demand for, and supply of, minerals, and a review of some of the earlier assessments of mineral needs and availability.Section 3 of the article begins with a short summary of the World Input–Output Model, the main methodological tool used in the earlier study that was developed by Prof. Wassily Leontief, the 1973 Nobel laureate in economics, and the way in which non-fuel minerals were represented in that system. This section also provides a summary of other global modeling efforts of non-fuel minerals that were carried out at a similar point in time for a similar interval.Section 4 presents the actual population, GDP and per capita GDP changes over the 1970–2000 time interval compared with the projected rates for these important determinants of mineral use, along with the projected and observed growth rates of minerals consumption for the eight non-fuel minerals included in this study. When the projections are compared to the observed global consumption rates for the year 2000, the differences range from +43% for nickel to +229% for potash.Section 5 discusses the apparent reasons for the differences between the projected and observed global consumption rates of these non-fuel minerals that include differences in the growth of GDP and GDP per capita, changes in recycling rates (for the metallic minerals), technological change, and regulatory or other public policy changes that have affected mineral use over the 30-year-interval ending in 2000.In light of the data and analysis presented in Sections sec# and sec#, the article concludes with some remarks, made almost a quarter of a century ago, by Prof. Leontief on the need and justification for long-term projections.