Process Control in Flotation Plants

The processing of ores often entails use of unit opera-tions such as grinding and flotation. Typical production requirements in mineral processing plants include the maximisation of throughput, maintenance of desired product quality and reduction of operating costs. For optimising plant performance, redesigning a process route is often impractical and the problem is best addressed through on-line optimisation which involves controlling key process parameters to achieve the desired production requirements. Process control, thus, plays a key role in on-line optim-isation. However, given the number of constraints/ variables and targets to be maintained simultaeously in a typical operation such as grinding or flotation, optimal performance can almost never be ensured through manual control. Automatic control is then the answer. There are several level of abstraction in automatic cont-rol. This paper describes various on-line anlysis system and automatic control systems available for various unit operations. Some of the process control systems adopted in HZL beneficiation plants to optimise the concentrator returns and more development efforts in pipeline to acq-uire model-based expert control systems to quest the thirst for modernisation by HZL are described in this paper

World radiocommunication conference 12 : implications for the spectrum eco-system

Spectrum allocation is once more a key issue facing the global telecommunications industry. Largely overlooked in current debates, however, is the World Radiocommunication Conference (WRC). Decisions taken by WRC shape the future roadmap of the telecommunications industry, not least because it has the ability to shape the global spectrum allocation framework. In the debates of WRC-12 it is possible to identify three main issues: enhancement of the international spectrum regulatory framework, regulatory measures required to introduce Cognitive Radio Systems (CRS) technologies; and, additional spectrum allocation to mobile service. WRC-12 eventually decided not to change the current international radio regulations with regard to the first two issues and agreed to the third issue. The main implications of WRC-12 on the spectrum ecosystem are that most of actors are not in support of the concept of spectrum flexibility associated with trading and that the concept of spectrum open access is not under consideration. This is explained by the observation that spectrum trading and spectrum commons weaken state control over spectrum and challenge the main principles and norms of the international spectrum management regime. In addition, the mobile allocation issue has shown the lack of conformity with the main rules of the regime: regional spectrum allocation in the International Telecommunication Union (ITU) three regions, and the resistance to the slow decision making procedures. In conclusion, while the rules and decision-making procedures of the international spectrum management regime were challenged in the WRC-12, the main principles and norms are still accepted by the majority of countries

The increasing risk of space debris impact on Earth: case studies, potential damages, international liability framework and management systems

Since the beginning of space colonization, the number of space objects in orbit around the Earth has increased exponentially. It is currently estimated that around 15,000 satellites or other types of space vehicles are orbiting from the lower (LEO or above the stratosphere up to 10,000 km from Earth) to the higher (GEO or more than 10,000 km from Earth) orbital planes, for a total mass of more than 5000 tons. Consequently, uncontrolled space “debris” is produced for a total of 150 million pieces, from submillimetric items (propellant dust, paint flakes) to golf ball sizes and above (20,000). Besides the risks of collision with flying space vehicles, there is now growing concern for Earth impacts, since debris, by definition, is uncontrolled and may survive atmospherical re-entry friction falling almost anywhere when eventually reattracted by gravity. US NASA and NORAD statistics account for almost 17,000 large and small debris that have fallen until 2000, and 1 piece of debris a day is falling as a current average. This study aims at describing the framework for damage liability according to the International Treaty on Outer Space and its accessory protocols, giving an overview of the cases happened so far and the outlook for the future, together with examples of insurance models for damage coverage and mitigation systems (route diagnostics, radar surveillance, onboard protection, etc.)

Routing Optimization of Small Satellite Networks based on Multi-commodity Flow

As the scale of small satellite network is not large and the transmission cost is high, it is necessary to optimize the routing problem. We apply the traditional time-expanded graph to model the data acquisition of small satellite network so that we can formulate the data acquisition into a multi-commodity concurrent flow optimization problem (MCFP) aiming at maximizing the throughput. We use an approximation method to accelerate the solution for MCFP and make global optimization of routing between satellite network nodes. After the quantitative comparison between our MCFP algorithm and general augmented path maximum flow algorithm and exploring the detail of the algorithm, we verify the approximation algorithm’s reasonable selection of routing optimization in small satellite network node communication

Graphite rejection in a lead concentrate using gravity concentration techniques

During the sequential flotation of the ore from Dariba-Rajpura mines of Hindustan Zinc Limited (India), graphite reports in considerable amounts into the lead concentrate. Graphite above a stipulated limit of 2.5% decreases the sinter strength to a great extent. Reports on flotation routes for graphite rejection from lead concentrate showed limited success. In the present study, attempts were made for exploiting the specific gravity differential between graphite and lead-bearing minerals using gravity techniques. Lead rougher concentrate collected from the operating plant was treated in a laboratory model multi-gravity separator and in a 75mm water-only cyclone. The metallurgical data obtained at different test conditions was analysed. The results indicated that lead concentrates with a graphite could be obtained using both the techniques. The concentrate grade and recovery values obtained in multi-gravity separator were better than water-only cyclone. However, considering the capacity of both the units. The possibility of a hybrid circuit with water-only cyclone as a pre-concentrator and multi-gravity separator for graphite rejection from water-only cyclone overflow product is discussed