A systems study of waste paper recovery and recycling

This thesis investigated the technological economics of waste paper recovery and recycling in UK. The major problem in waste paper recycling is still the removal of contraries, although technological developments have so far been able to remove some of them. The costs incurred by the local authorities in recovering waste paper were investigated. Local authority costing was found to be inconsistent and many of them did not include all the relevant indirect costs and savings, so that many local authorities claimed to be making heavy losses in their operations. Full accounting incorporating all the relevant indirect costs and savings have shown that most local authorities incurred much smaller losses and in some cases profited from their waste paper recovery operations. A general computer model was developed to allow local authorities to check the viability of their on-going operations and another computer model was developed for an investment appraisal of a proposed waste paper recovery operation. Multiple regression models were developed to forecast the demand of waste paper in the short term and the long term. The cost to the mill in recycling waste paper was also examined. Waste paper recycling can only be increased by improving demand for waste paper based products. Various alternatives for diversifying the markets for waste paper were investigated, particularly those outside the paper and board industry. The government's role in helping to inc~ease waste paper recovery and recycling was examined and some government actions that could be taken were proposed

Evaluation of hazardous airborne carbonyls in five urban roadside dwellings: A comprehensive indoor air assessment in Sri Lanka

Indoor hazardous airborne carbonyls were quantified in five natural-ventilated roadside dwellings in Colombo, Sri Lanka. The total concentrations of all targeted carbonyls ranged from 13.6 to 18.6 mu g/m(3). Formaldehyde (C1) was the most abundant carbonyl, followed by acetaldehyde (C2) and acetone (C3K). The concentrations of C1 and C2 ranged from 3.3 to 8.5 mu g/m(3) and 2.3 to 4.4 mu g/m(3), respectively, which accounted for 23 to 42% and 18 to 26% respectively, to the total quantified carbonyls. The highest carbonyls levels were obtained in the dwelling located in an urban district with a mixture of industrial, commercial and residential areas. Much lower concentrations of carbonyls were measured in a light local traffic value was counted. Moderate correlations between individual combustion markers from vehicular emissions suggest the strong impacts from traffics to the indoor airs. The concentrations of C1 and C2 were compared with international indoor guidelines established by different authorities. A health assessment was conducted by estimation of inhalation cancer risk, implementing the inhalation unit risk values provided by Integrated Risk Information System (IRIS), associated with C1 and C2, which were 6.2 x 10(-5) and 7.7 x 10(-6), respectively. Even though the risks did not reach the action level (1 x 10(-4)), their health impact should not be overlooked. This kick-off indoor monitoring study provides valuable scientific data to the environmental science community since only limit data is available in Sri Lanka

Microstructural Characteristics and Hardness Enhancement of Super Duplex Stainless Steel by Friction Stir Processing

In the present study, microstructural evolution and hardness of the friction stir processed (FSPed) SAF 2507 super duplex stainless steel fabricated at a rotational speed of 650 rpm and a traverse speed of 60 mm/min were investigated. A scanning electron microscope (SEM) equipped with an electron backscatter diffraction (EBSD) detector was used to study the microstructure of the stir zone. The grain sizes of austenite and ferrite in the FSPed 2507 were found to be smaller (0.75 and 0.96 μm) than those of the substrate (6.6 and 5.6 μm) attributed to the occurrence of continuous dynamic recrystallization (CDRX) in both phases. Higher degree of grain refinement and DRX were obtained at the advancing side of the FSPed specimens due to higher strain and temperature. A non-uniform hardness distribution was observed along the longitudinal direction of the SZ. The maximum hardness was obtained at the bottom (407 HV1)