The Chromium Resources Of Zimbabwe

An IMR report on Zimbabwe's chromium resources

Combustion of Pulverized Biomass Crop Residues and Their Explosion Characteristics

Two Pakistani crop residues bagasse (B) and wheat straw (WS), both with high ash content, were milled to <63µm and the ISO 1 m3 explosion equipment was used to investigate flame propagation in the dispersed cloud of pulverised biomass. Their turbulent flame speed was measured and the Kst (dP/dtmaxV1/3) and comparison was made with two pulverised coal samples. Minimum Explosion Concentration (MEC) values for B and WS were, in terms of the burnt dust mass equivalence ratio (Ø) 0.2Ø to 0.3Ø , which was leaner than for the coal samples. These MEC were lower than had previously been determined using the Hartmann explosion tube, and this was considered to be due to the 10 kJ ignition energy in the 1 m3 equipment and 4J spark energy in the Hartmann explosion tube, which extended the lean limit in the 1 m3 equipment. Peak turbulent flame speeds were 3.8 m/s for B and 3.0 m/s for WS compared with 3.5–5.2 m/s for the two coal samples. The peak Kst was 103 bar m/s for bagasse and 80 bar m/s for wheat straw and the two coal samples had peak Kst of 78 and 120 bar m/s. Overall the agricultural biomass and coal samples had a similar range of reactivity. Thus these agricultural crop residues are a viable renewable fuel for co-firing with coal or as 100% biofuel operation of steam power plants

Flame Propagation of Pulverised Biomass Crop Residues and their Explosion Characteristics

Pulverised agricultural crop residues were investigated using the ISO 1 m3 turbulent explosion vessel. This was modified to enable the spherical flame propagation flame speed and the heat release rate in MW/m2 to be determined. From the turbulent flame speed, the laminar flame speed and laminar burning velocity and global heat release, MW/m2, were determined. In addition the equipment was used to determine the biomass explosibility, Kst (= dP/dtmaxV1/3), and the minimum explosion concentration (MEC). Two Pakistani crop residues bagasse (B) and wheat straw (WS) were investigated. Particle size distribution, elemental and proximate analysis and surface morphology for the raw powders and for their post explosion residues were carried out. It was found that these crop residues have explosibility characteristics comparable to wood biomass powders. MEC values as low as equivalence ratios of 0.18 to 0.3 were found which were lower than for gaseous hydrocarbons, but similar to other measurements for biomass using the Hartmann explosibility equipment. Peak turbulent flame speeds were measured at 3-4 m/s. There was a significant post explosion residue of unburned material which was shown to have an increase in char content relative to the raw biomass, while the volatile content was reduced. The BET surface area of the post explosion residue of bagasse was higher than that of the wheat straw residue, showing a higher release of volatiles for bagasse with a more porous char residue in the burnout indicating higher reactivity. These crop residues are a viable renewable fuel for existing coal power plants or as a basis for a new generation of small scale steam power generators in Pakistan

The role of private rental brokerage in housing outcomes for vulnerable Australians: Final report

This Final Report outlines the findings of research investigating the role of private rental brokerage in supporting housing outcomes for vulnerable households in the private rental market. In the last two decades the private rental market has become increasingly important in providing homes for Australians. It has also become increasingly competitive, particularly at the lower-end, where supply has fallen significantly behind demand. Given the lack of affordable ownership options in many local housing markets, and the contraction of public housing, many households with low or moderate means must now look to the private rental sector for their housing over the longer term. Government policy has encouraged renters who would otherwise be eligible for social housing to move into the private rental market. This tenure shift has been supported by the provision of several assistance measures for private renters. Those best known and understood are Commonwealth Rent Assistance (CRA) and state and territory Private Rent Assistance (PRA) programs, which provide bond and rent loans to eligible people. Two other elements also exist alongside the best known private rental supports: the National Rental Affordability Scheme (NRAS) (although as the planned further expansion of this scheme was halted by the newly elected Abbott Government in budget 2014/15 thereby limiting its future potential as a supply-side private rental assistance measure) and private rental brokerage. This report is concerned specifically with private rental brokerage; a previously underresearched measure among private rental supports nationally. Conceptually, we describe private rental brokerage as the 'third pillar' of supports nationally, sitting alongside the much larger CRA measure and, as the research findings reported here note, reinforcing the reach and impact of PRA.Selina Tually, Michele Slatter, Debbie Faulkner and Susan Oakley for the Australian Housing and Urban Research Institute at The University of Adelaid

Applying experimental micro-tool wear measurement techniques to industrial environments

Productivity in micro-milling is hindered by premature fracture of tools and difficulty predicting wear. This work builds upon previous investigations into tool wear mechanisms and coatings for micro-mills.The technology readiness level of this work exceeds previous studies by investigating the micro-mills for practical applications and comparing this data. 0.5 mm micro end mills are tested with different coatings on CuZn38, and wear curves produced both in the case of simple straight slot testing and milling of complex parts representing industrial applications. The results show that curves produced using straight slots can be used to predict the behaviour of tools used to machine industrial parts. Due to interrupted cutting, tools used in straight slot tests reach the end of steady state wear after approximately 12 s of cutting as compared with 170 s in continuous milling. Typical cutting forces seen for the tools are in the order of 2–4 N. Catastrophic failure is seen towards the end of tool life for a TiAlN tool with a cutting force of over 30 N seen. For the first time a comparison has been made between fundamental tool wear studies and tool wear observed when producing test pieces representative to micro-industrial parts. This presents a novel perspective on tool wear and facilitates the integrating of existing micro-milling research into industr

Tool life and wear mechanisms of CVD coated and uncoated SiAlON ceramic milling inserts when machining aged Inconel 718.

In this study, an investigation has been conducted to fully characterise for the first time the tribological benefits of adding two different types of chemical vapour deposition (CVD) coatings to silicon aluminium oxynitride milling inserts with a chemical composition of (Si3N4+Al2O3+Y2O3), known by the trade abbreviation “SiAlON”, typically used to cut difficult to machine materials such as Inconel 718. The experimental tests compared the tool life, material removed and wear resistance of the two different CVD coated inserts against that of uncoated SiAlON ceramic milling inserts. Coating A was a multilayer CVD coating and had a composition of (TiN+TiCN+Al2O3), Coating B was a bilayer CVD coating and had a composition of (Al2O3+TiN). It was determined that at 900m/min the uncoated SiAlON ceramic milling inserts exhibited the least amount of wear and variation in cutting force when milling precipitation hardened Inconel 718 samples. Coating A demonstrated significantly lower adhesion to the SiAlON substrate but had higher tool life and material removal rates, Coating B demonstrated excellent adhesion to the SiAlON substrate. The interfacial bonding of Coating B allowed for much higher adhesion to the substrate, but it suffered from much lower tool life and higher rates of rake and flank face wear. The flank wear measurements concluded a cutting speed of 900m/min to be the optimum cutting speed for machining Inconel 718 with uncoated SiAlON ceramic milling inserts

Corporate governance and financial constraints on strategic turnarounds

The paper extends the Robbins and Pearce (1992) two-stage turnaround response model to include governance factors. In addition to the retrenchment and recovery, the paper proposes the addition of a realignment stage, referring specifically to the re-alignment of expectations of principal and agent groups. The realignment stage imposes a threshold that must be crossed before the retrenchment and hence recovery stage can be entered. Crossing this threshold is problematic to the extent that the interests of governance-stakeholder groups diverge in a crisis situation. The severity of the crisis impacts on the bases of strategy contingent asset valuation leading to the fragmentation of stakeholder interests. In some cases the consequence may be that management are prevented from carrying out turnarounds by governance constraints. The paper uses a case study to illustrate these dynamics, and like the Robbins and Pearce study, it focuses on the textile industry. A longitudinal approach is used to show the impact of the removal of governance constraints. The empirical evidence suggests that such financial constraints become less serious to the extent that there is a functioning market for corporate control. Building on governance research and turnaround literature, the paper also outlines the general case necessary and sufficient conditions for successful turnarounds