The Oxidation of Sulphur Dioxide and the Formation of Sulphuric Acid in Situ at Atmospheric Pressure in the Leaching of a Uranium Ore

Abstract

The oxidation of SO₂ to form H₂SO₄ in situ, at atmospheric pressure and temperatures from 25 to 80°C, was examined by passing a mixture of SO₂ dioxide and air for 7 hrs through a reaction vessel containing quartz- or uranium-bearing solids moistened with H₂O to 85% solids. At the end of the contact period the solution was analyzed for free acid and other constituents of SO₂ and extraction of Uranium.

In tests with quartz at 80°C, the addition of Fe₂(SO₄)₃ or Fe₂O₃ increased the amount of SO₂ converted to H₂SO₄. E.g. without Fe₂(SO₄)₃ added the conversion obtained was 2% with 0.7 and 2.3 1b/ton quartz of Fe₂(SO₄)₃ the conversions were 18 and 24% respectively.

Tests were conducted on a mixture of flotation tailings, and a residue, which contained 24.3 per cent Fe⁺⁺⁺ as oxide, derived from the roasting of a sulphide concentrate at 500°C. The tailings and sulphide concentrate were obtained from the flotation of a uranium ore containing brannerite and about 9 per cent pyrite Roasting of the sulphide concentrate yielded "160 to 180 lb per ton of ore of sulphur dioxide of which 80,to, 100 lb was introduced into the conversion system over a 7-hour period. At 80°C, 40 per cent of the sulphuric dioxide introduced was converted to sulphuric acid which dissolved 93 per cent of the uranium in the mixturet of solids.     

Investigations into dioxin emissions at Italian iron ore sintering plant

Abstract

The paper presents the results of tests performed on an existing iron ore sintering plant to evaluate the limiting capability of dioxins releases to air and of measures and technologies adopted. These measures and technologies are in line with the best available techniques as stated in the Integrated Pollution Prevention and Control Directive 96/61/EC, so a measurement campaign was planned to determine the operating conditions capable of complying with the legislation in force. In this paper, the authors define the running conditions tested and the manner in which the testing campaign was performed. The results are presented and analysed in the light of the aims of the study.     

Modelling of Charpy V test rejection probability

Abstract

The purpose of this study was to develop a product design model for estimating the impact toughness of low alloy steel plates. The rejection probability in a Charpy V test is predicted with process variables and chemical composition. Joint modelling of the mean and deviation was used in order to improve the results. The proposed method is suitable for the whole production line, including all grades of steel in production and it is not restricted to a few test temperatures. Using the proposed model the product design group could have recognised most of the rejections before production. Next, the developed model will be implemented into a graphical simulation tool that is in daily use in the product planning department and already contains some other mechanical property models. The model will guide designers in predicting the related risk of rejection and in producing desired properties in the product at lower cost.     

Relationship between physical structure and machinability of green compacts

Abstract

The dependence of green machinability on compact density and strength was investigated for room temperature and warm compacted steel powder compacts containing two different types of lubricant. Brazilian disc compression tests were employed to determine green strength, while machinability was assessed in terms of response to drilling.

For the room temperature compacted materials, it was found that high compact densities and strength were not, in most cases, associated with improvements in machinability. Furthermore, it was shown that lubrication (both type and quantity) and compaction pressure plays a critical role in determining the level of breakouts observed. In contrast, the use of warm compaction, in conjunction with specially designed lubricants, has been shown to be a suitable method of producing high density, high strength compacts while retaining good green machining characteristics. Mechanisms responsible for the observed behaviours of both the room temperature and warm compacted specimens have been forwarded in the present paper.     

Starch consolidation of M3/2 high speed steel powder – influence of microstructure on mechanical properties

Abstract

The influence of microstructure on the mechanical properties of starch consolidated super solidus liquid phase sintered AISI type M3/2 high speed steel powder has been evaluated. Hardness measurements, Rockwell C indentation and scratch testing were used to evaluate the mechanical properties and light optical microscopy and scanning electron microscopy were used for post-test characterisation. The results show that it is possible to starch consolidate and sinter large particle size high speed steel powder to obtain microstructures with high mechanical strength. However, the results show a strong correlation between the as sintered microstructure and the resulting mechanical properties and illuminate the importance of having a dense and isotropic microstructure in order to meet engineering requirements in demanding applications. Consequently, the failure mechanisms observed during indentation and scratch testing can be related to residual pores, present in the low temperature sintered samples, and a coarse microstructure with eutectic carbides, present in the high temperature sintered samples.     

Test performance as an involuntary function of interpersonal relationships.

The hypothesis that tension aroused by making a new acquaintance might adversely affect test performance is here investigated. Two person teams of subjects are given the Vigotsky Blocks Tests. In the control group, the subjects knew each other before the experiment and knew the experimenter. In the experimental group, the subjects were unacquainted before the experimental session. Analysis of the results shows that the experimental groups took significantly longer to complete the test. Although this result tends to support the hypothesis, several alternate explanations are proposed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)