Cement, Energy and Environment

Quality & Standards PRELIMINARY ASSESSMENTS [FOR A CEMENTPLANTPROPOSAW This article first appeared in International Cement Review in January 2011 and is reprinted with kind permission of Tradeship Publications Ltd , United Kingdom. Email: info@CemNet.com Website: www.CemNet.com Prior to expending large amounts of money, time and energy on detailed proposals for a cement plant, potential limestone deposits need to be assessed for compatibility and to identify any further materials required to make a cement clinker. Apart from limestone the other raw materials are usually a clay or shale, sand and iron oxide. Not all these are required in all cases, but their availability needs to be known to determine what qualities of cement can be made from the limestone deposit. Arthur Harrison, UK Initially, it is necessary to determine the quality of the limestone deposit in terms of factors, including: • Chemistry, found from any historical data available • Consistency, also found from historical data as well as a study of available geological information from national surveys, commercial explorations, etc • Determination of the deposit geometry. For example, is the deposit undulating or dipping or thinning in any direction? Are further • drillings necessary to discover this? Accessibility, including the depth of overburden, the presence of geological faults, the nature of the ground in terms of the ease of building quarry roads or whether transport by conveyor may be necessary etc • Will exploitation of the deposit have an effect on the water table in the location? This will have bearing on the ease of extraction, but also on the local area and liaison with local authorities will be necessary. Once the above are satisfactorily established a quarry plan needs to be created for two purposes. Firstly local authorities in most parts of the world will require a five year (or longer) plan of how the deposit is to be worked for environmental reasons and secondly the quarry manager needs to have a plan of how to exploit the deposit in order to provide the optimum quality of product to the cement plant over the life of the quarry. The following stages are proposed for an evaluation. 1. Desk study of the geological data available. This is to determine the extent of further data collection required and to provide an indication of what will be necessary further downstream in the project. 2. Analysis of data available on raw materials other than limestone. This is important in terms of costing of the project. If assumptions are made concerning the quality of the raw materials at this stage, which are incorrect, the extra expense required to correct the assumptions can be very high. 3. Collection of any further data which may be necessary. 4. Analysis of further data. At this stage an independent testing house will be used for the chemical analysis to ensure reliability of the information. 5. Proposal for the type of cement which may be possible and, if necessary, corrections for the required market conditions. 6. Production of a quarry plan, which will be needed for any local or national permission requirements. 7. Provision of a computer model of the deposit which will be used to provide the optimum raw material for the plant in terms of chemistry, handling properties and cost. Requirements for limestone for cement making The preliminary assessment covers stages one and two above. The primary requirement is a limestone with a calcium carbonate content sufficient to produce about 80 per cent calcium silicates when fired in combination with other raw materials. Cement clinker is generally characterized by the use of three chemical parameters, calculated from the following formula in Table-1. The value of these parameters is typically LSF from 15