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Trends in kiln systems for the cement industry
Abstract
Recent years have seen an increasing standardization of cement kiln lines. This is due firstly to the current construction boom and limited plant engineering capacities and secondly to new, modular solutions for preheaters, calciners, rotary kilns and grate coolers. Standardized kiln lines provide significant cost benefits compared to non-standardized systems while still permitting tailor-made solutions. This report provides an insight into this subject and discusses the current development trends.
Some of the significant trends in process filter technologies in the cement industry are discussed. Process filters are installed in cement factories to prevent the uncontrolled dust emissions. It is being observed that electrostatic precipitators (ESP) and fabric filters, or combinations of two processes are gaining recognition in the cement industry for preventing uncontrolled dust emissions. There is a trend towards the installation of bag filters, which enable compliance with lower emission limit values than ESPs and are independent of operating conditions and plant starting and stopping phases. The dust collection in ESPs depends on the raw gas temperature and the electrical resistance of the dust particles that fluctuate, depending on the temperature or the humidity. The cement industry also prefers jet-pulse filters to be used as process filters in place of filters cleaned by rapping or shaking.
Cement plants are operating continuously for 24 hours a day and when possible for about 330 days a year without interruption. The rest of the year the plants have their annual shutdown for major repairs. Accordingly when using benchmark methods for the comparison of actual cement production costs it will be best if the latest energy and other production costs of other cement plants in the same region are known. If not, average cost breakdowns could help. The average Lafarge 2012 production cost for cement is 33% energy, 29 % for raw materials and consumables, 26 % other costs, and 12 % depreciation. In larger cement groups auditing has become a part of the normal routine of performance management in cement plants and individual kiln lines. A professional plant audit is a powerful tool in analyzing current plant performance, identifying current limitations on the productivity of the plant, developing improvement measures and eventually justifying necessary modernizations and plant upgrades.
Some important interrelationships between the cement producers and the suppliers and changes in the market situation in the wake of cement boom are discussed. Due to the increase in new clinker production capacities in China, numerous established mechanical and plant engineering companies expanded their activities in China and Asia in order to improve their competitive situation compared to Chinese low-cost vendors. The expansion of manufacturing capabilities and engineering capacities in China, India, and other low-cost countries brought advantages for suppliers such as FLSmidth, Polysius, KHD Humboldt Wedag, and ABB etc. Some mechanical and plant engineering companies whose core competence was in cement grinding, were originally active on the sector of plant modernization. The established cement plant suppliers are all working practically to full capacity and have full order books. The demand for used plants is increasing because some customers are not prepared to accept the long delivery times and the prices of new plants.
Alternative fuels have become a trend topic all over the world. This is partly due to the increase in price of conventional fuels and partly to the discussion about resource conservation and climate change.What contribution can the cement industry make? This report presents background facts and experience gained in the cement industry. Its purpose is not only to deal with the technological aspects but rather to explore the economic and ecological considerations. It particularly discusses the cost-effectiveness and ecological benefit of waste co-processing in cement plants and what developments are currently taking place.
An overview and the situation of the cement markets in Latin America, which is dominated by the Asian economies, is presented. The cement consumption of the TOP 10 countries accounts for almost 91% of the Latin America's total consumption. Brazil, the largest cement market in Latin America, has experienced an increase in cement plant capacity utilization to 77%, while cement prices rose to 12.5% in the period 2006 to 2007. Mexico, with a per capita cement consumption of 346 kg, has experienced an increase in cement investments from foreign investors, including US$24 billion investment in 2007 from the US. The cement industry has experienced an upswing in Columbia due to the implementation of overdue private and public construction projects. The cement industry in Venezuela has shown a remarkable development, with annual growth rates exceeding 30%.
Cement producers are taking effective measures to use the refractory materials to compensate for fluctuations in the composition of the fuels and raw materials. The expenditure on refractories materials accounts for 1% of the cement production operating cost. The quantity of refractory materials is increasing significantly to 1.59 millions of tonnes per year (Mta) after a increase of production plants in China and world, and is expected to increase 10% to 1.75 Mta by 2010. With the increasing demand of specific consumption, the use of alternative fuels the chemical attacks and stress on the refractory material is increasing. In Europe the use of alternative fuels increased from 10% in 1995 to 30% and In Germany it is increased from 10.8% in 1995 to 50% in 2007. The refractories industry for the cement industry achieved a growth rate of 3-4% despite of falling specific consumption rates.
There is an increasing trend towards using benchmarking methods for deciding modernization and maintenance measures on the basis of cost considerations. When cement producers decide on a modernization project, they are usually aiming to increase efficiency, either by eliminating a bottleneck, modernizing the entire plant, a plant section or just individual machines and components. Although ready-made concepts exist for all these projects, individual projects are generally approached in a customerspecific manner. The situation with respect to maintenance and servicing of cement plant is similar. Here, too, the possibilities are numerous and therefore very company-specific. This article deals with current topics on this sector.
G. Bernard Huybens, IKN GmbH, Singapore, describes the benefits of the company's Pendulum cooler technology and recent successes in the Arabian Gulf. The pendulum cooler is a highly reliable and efficient cooler that delivers the lowest operating cost when considering the specific electrical kWh/t and the low yearly wear parts usage as compared to all other new generation clinker coolers. In a pendulum cooler it is not necessary to push and shear clinker layers over each other in the horizontal or the vertical plane, and the friction and hydraulic forces are low. IKN pendulum cooler of line 3 at Union cement's plant, started in September, 2002, has operated with remarkable success till now. A new cooler for line 4 with a capacity of 10, 000 tpd has been erected which will utilizes the new linear pendulum system (LPS).
Precalcining technology offers the advantage of carrying out the calcining of limestone to a great extent outside the rotary kiln so that the kiln can be designed with smaller dimensions or it can be operated with higher outputs if the dimensions are maintained. Additionally, it is possible to limit the emission of nitrogen oxides and to burn secondary fuels using modern calciners. It took four generations to develop the modern calciners we know today. They are described in this paper and, for the first time, the market shares of the various processes and bidders are presented. Finally it is shown in which regions and countries most of the calciners have been commissioned until now.