Developing an optimum maintenance policy by life cycle cost analysis - a case study

This paper focuses on developing maintenance policies for critical assets to improve the production performance based on life cycle cost (LCC) analysis. A general approach is adopted for conducting the LCC analysis. The investigation is based on a case study to demonstrate how an optimum maintenance policy is determined. The relevant LCC structure in the case study is defined for the decision process which involves determination of the optimum life, repair limit and selection of materials, and trade-off between repair and replacement. The LCC analysis is based on statistical data modelling which facilitates decision-making on the optimal replacement of an asset and its remaining life. Based on the optimization and remaining life criterion, the optimal maintenance policy can be made. The results obtained from this case study include selection of the best lining material for use, determination of the optimal time for refractory lining replacement, the hot repair sequence required for maintaining the optimum condition and the repair limit for doing cold repairs before replacement, for one type of electric arc furnaces used in the steel industry

Fundamental aspects of alloy smelting in a DC arc furnace

DC arc furnaces have been applied to a number of smelting processes, including the reductive smelting of chromite ore fines to produce ferrochromium, the smelting of ilmenite to produce titania slag and pig iron, the recovery of cobalt from non-ferrous smelter slags, stainless steel dust smelting, battery recycling, and nickel laterite smelting. The recovery of base metals and platinum group metals (PGMs) in a reductive smelting process is a function of the recovery of iron (which indicates the extent of reduction). A recovery equation has been developed that is characterised by a single parameter (Ky) for each metal that can either be fitted empirically to the data, or expressed in terms of the equilibrium constant and the ratios of the activity coefficients involved. The DC arc furnace has been modelled electrically as an arc in series with a layer of slag. The voltage is non-linear with respect to the current. Equations have been developed (and confirmed by measurement) to describe how the arc voltage varies as a function of arc length and current. The voltage distribution across a molten slag bath requires the solution of Laplace’s equation for a geometry that includes the depression in the molten slag caused by the impingement of the arc jet. Aspect ratios of the arc depression were determined photographically. Equations have been developed for the calculation of the mean residence time in a continuously-fed batch-tapped furnace, and this has been illustrated using a novel graphical depiction. The mean residence time is directly proportional to the tap-to-tap time, and is increased by increasing the volume of material retained in the furnace between taps. The ConRoast process treats dead-roasted nickel sulfide or PGM concentrates by reductive smelting in a DC arc furnace, where an ironbased alloy is used to collect the valuable metals. This process results in much lower sulfur dioxide emissions, the ability to accept high chromite contents, and improved furnace containment. The ConRoast process has been demonstrated by smelting 50 000 tons of PGM-containing feed materials at Mintek over a period of operation of about five years

Best Available Techniques (BAT) Reference Document:for:Iron and Steel Production:Industrial Emissions Directive 2010/75/EU:(Integrated Pollution Prevention and Control)

The BREF entitled ‘Iron and Steel Production’ forms part of a series presenting the results of an exchange of information between EU Member States, the industries concerned, non-governmental organisations promoting environmental protection and the Commission, to draw up, review, and where necessary, update BAT reference documents as required by Article 13(1) of the Directive. This document is published by the European Commission pursuant to Article 13(6) of the Directive. This BREF for the iron and steel production industry covers the following specified in Annex I to Directive 2010/75/EU, namely: • activity 1.3: coke production • activity 2.1: metal ore (including sulphide ore) roasting and sintering • activity 2.2: production of pig iron or steel (primary or secondary fusion) including continuous casting, with a capacity exceeding 2.5 tonnes per hour. The document also covers some activities that may be directly associated to these activities on the same site. Important issues for the implementation of Directive 2010/75/EU in the production of iron and steel are the reduction of emissions to air; efficient energy and raw material usage; minimisation, recovery and the recycling of process residues; as well as effective environmental and energy management systems. The BREF document contains 13 chapters. Chapter 1 provides general information on the iron and steel sector. Chapter 2 provides information and data on general industrial processes used within this sector. Chapters 3 to 8 provide information on particular iron and steel processes (sinter plants, pelletisation, coke ovens, blast furnaces, basic oxygen steelmaking and casting, electric arc steelmaking and casting). In Chapter 9 the BAT conclusions, as defined in Article 3(12) of the Directive, are presented for the sectors described in Chapters 2 to 8.JRC.J.5-Sustainable Production and Consumptio

Annual Report 1984-1985

It contains the statement of R&D works undertaken, achivement made and the expenditure by the laboratory during the financial year 1984-1985

Energy recovery systems based on high temperature phase change materials

Energy recovery from the waste heat released by industrial processes represents one of the greatest opportunity to reduce the consumption of primary energy and the related emission of greenhouse gases. Nevertheless, the fluctuating and/or intermittent nature of many energy-intensive processes (e.g. electric arc furnace in steel industry) hinders the deployment of current energy recovery systems. Thus, the development of technologies able to minimize the thermal power fluctuations released by such processes is required to enable the deployment of affordable energy recovery systems. With the aim of developing such type of technology, this thesis explores the potential of latent heat storage systems based on phase change materials (PCMs) to minimize the thermal power fluctuations of high-temperature waste heat sources. In particular, three significant areas of investigation characterised by different types of thermal power fluctuations are investigated: electric arc furnace, billet reheating furnace and waste-to-energy plant. An interdisciplinary approach is adopted to face the crucial issues of developing a PCM-based technology (e.g. thermo-mechanical stresses, transient heat transfer). Chapter 1 includes the background, the motivation, the aim, the methodology and the structure of thesis. In chapter 2, a general overview on the thermal energy storage systems with a particular focus on latent heat storage systems based on PCMs is provided. Chapter 3 addresses the issues related to the energy recovery from the electric arc furnace and proposes three different configurations of a PCM-based device to increase the efficiency and the capacity factor of the downstream energy recovery system. In Chapter 4 an existing waste heat recovery system of a steel billet preheating furnace is retrofitted by adding a PCM-based device. In Chapter 5 a refractory brick technology based on PCMs is proposed for the protection of the radiant superheaters against high temperature corrosion and temperature fluctuations. At the end of each chapter a series of conclusions are reported, concerning the performed investigations and the obtained results