Energy - Efficiency in the Cement Industry

ENERGY EFFICIENCY IN THE CEMENT INDUSTRY

Proceedings of a seminar organised by the Commission of the European Communities, Directorate-General for Energy and CIMPOR Cimentos de Portugal E.P. with the co-operation of Cembureau European Cement Association, and held in Oporto, Portugal, 6–7 November 1989. Particular thanks are due to Mr V.Teixeira Lopo, President of CIMPOR, and to Mr A.Soares Gomes, Director, for help in the organisation of this symposium, and to NIFES Consulting Group for editorial assistance.

ENERGY EFFICIENCY IN THE CEMENT INDUSTRY Edited by

J.SIRCHIS Directorate-General for Energy, Commission of the European Communities, Brussels, Belgium

ELSEVIER APPLIED SCIENCE LONDON and NEW YORK

ELSEVIER SCIENCE PUBLISHERS LTD Crown House, Linton Road, Barking, Essex IG11 8JU, England This edition published in the Taylor & Francis e-Library, 2005. “To purchase your own copy of this or any of Taylor & Francis or Routledge’s collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk.” Sole Distributor in the USA and Canada ELSEVIER SCIENCE PUBLISHING CO., INC. 655 Avenue of the Americas, New York, NY 10010, USA WITH 26 TABLES AND 55 ILLUSTRATIONS © 1990 ECSC, EEC, EAEC, BRUSSELS AND LUXEMBOURG British Library Cataloguing in Publication Data Energy efficiency in the cement industry. 1. European Community countries. Industries. Energy. Conservation I.Sirchis, J. 658.26 ISBN 0-203-21565-6 Master e-book ISBN

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PREFACE

The existence of significant uncertainty as to the long-term prospects for energy supply and demand following the rapid fall in oil prices, has stimulated both the international energy situation as well as that of the Community and made it essential that the substantial progress already made in restructuring the Community’s energy economy be maintained and, if necessary, reinforced. The European Energy Policy objectives for the year 1995 call for adequate energy supply, controlled energy prices and increased environmental concern. All of these constraints necessitate the rational exploitation of the primary energy forms by the EEC Member States. The above objectives can be attained either by energy saving or by increased energy efficiency, or finally through the development of new technologies to augment both saving and efficiency. Better insulation, heat and material recycling, or application of improved processes, are typical examples. Cement production is one of the most energy intensive sectors and requires a great quantity of energy. Although much progress has already been achieved today in the field of the energy economy in the cement industry in EEC countries, some stages of cement production still offer opportunities for further improvement.

CONTENTS

PREFACE

v

OPENING SESSION Chairman: V Teixeira Lopo, President CIMPOR OPENING ADDRESS—ENERGY POLICY OF THE COMMISSION OF THE EUROPEAN COMMUNITIES F KINDERMANN, Commission of the European Communities

2

OPENING SPEECH—A POLICY OF ENERGY EFFICIENCY NUNO RIBEIRO DA SILVA, Secretary of State for Energy

6

FIRST SESSION Chairman: Professor Veiga Simao, President of LNETI ENERGY SAVING AND ENVIRONMENTAL IMPACT IN THE CEMENT INDUSTRY A SOARES GOMES, CIMPOR, Cimentes de Portugal, Portugal

16

ENERGY OUTLOOK IN WEST GERMANY’S CEMENT INDUSTRY A SCHEUER and S SPRUNG, Forschungsinstitut der Zementindustrie, Düsseldorf 30, Federal Republic of Germany

20

OUTLOOK OF LATIN AMERICAN CEMENT INDUSTRY JESUS GARCIA DEL VALLE and ALEJANDRO TORRES Asland Tecnologia SA, Madrid, Spain

29

ENERGY OUTLOOK IN THE JAPANESE CEMENT INDUSTRY YUKIO NAKAJIMA, Nihon Cement Co Ltd., Tokyo, Japan

42

DISCUSSION

49

SECOND SESSION—PART 1—SPECIFIC TECHNOLOGIES AND CEC DEMONSTRATION PROJECTS Chairman: J Sirchis, Commission of the European Communities TRADITIONAL AND ADVANCED CONCEPTS OF WASTE HEAT RECOVERY IN CEMENT PLANTS E STEINBISS, KHD Humboldt Wedag AG, Cologne, Federal Republic of Germany

52

DISTRICT HEATING BASED ON WASTE HEAT FROM CLINKER COOLER BO AHLKVIST, Cementa AB, Sweden

64

vii

HEAT RECOVERY ON THE SMOKE OF THE CEMENT KILN AND UTILIZATION OF THE RECOVERED ENERGY J-F BOUQUELLE, Département Projets Ciments d’Obourg, Obourg, Belgium

69

UTILIZATION OF WASTE HEAT FROM THE CEMENT ROTARY KILN K-H WEINERT, Interatom GmbH, Bergisch Gladbach, Federal Republic of Germany

74

ENERGY SAVING BY UTILISATION OF HIGH EFFICIENCY CLASSIFIER FOR GRINDING AND COOLING OF CEMENT ON TWO MILLS AT CASTLE CEMENT (RIBBLESDALE) LIMITED, CLITHEROE, LANCASHIRE, UK P F PARKES, Castle Cement, Clitheroe, United Kingdom

81

DISCUSSION

86

SECOND SESSION—PART 2—ENGINEERING AND ENERGY MANAGEMENT ‘HOLDERBANK’S’ ENERGY MANAGEMENT IN THE 1990s M BLANCK, ‘Holderbank’ Management and Consulting Ltd, Holderbank, Switzerland

90

ENGINEERING AND ENERGY SAVINGS J DUMAS, CITEC, Guerville, France

102

ENERGY SAVINGS IN CEMENT KILN SYSTEMS E BIRCH, F L Smidth and Co AS, Valby, Denmark

112

HIGH ENERGY SAVINGS THROUGH THE USE OF A NEW HIGH-PERFORMANCE HYDRAULIC COMPONENT THE K-TECH PROCESS M PALIARD and M MAKRIS, CLE, Paris La Defense, France G MENARDI and M BAILLY, Ciments de Champagnole, Dole, France

125

ENERGY MANAGEMENT IN THE UK CEMENT INDUSTRY T M LOWES and K W BEZANT, Blue Circle Industries plc, Greenhithe, Kent, United Kingdom

136

WASTE GAS HEAT RECOVERY IN CEMENT PLANTS M NETO, Souselas Cement Plant, CIMPOR, Portugal

144

DISCUSSION

148

THIRD SESSION—RODND TABLE DISCUSSION 152 Chairman: Professor Mario Nina, University of Lisbon K W Bezant, BLUE CIRCLE, United Kingdom F Aellen, HOLDERBANK, Switzerland Professor G Parisakis, University of Athens, Greece J Sirchis, Commission of the European Communities E Steinbiss, KHD, BR Deutschland H Takakusaki, NIHON CEMENT CO, Japan CLOSING SESSION Chairman: V Teixeira Lopo, President of CIMPOR CONCLUSIONS D QUIRKE, CEMBUREAU CEC, Ministry of Industry

158

viii

LIST OF PARTICIPANTS

160

INDEX OF AUTHORS

189

OPENING SESSION Chairman: V Teixeira Lopo, President CIMPOR

OPENING ADDRESS “ENERGY POLICY OF THE COMMISSION OF THE EUROPEAN COMMUNITIES” F.KINDERMANN Head of Division Commission of the European Communities Directorate-General for Energy Technology Directorate Programme Management: Solid Fuels and Energy Saving

If one goes back to the roots of the European Community, one discovers that two of the three Treaties deal, partly of completely, with energy. – The Treaty establishing the EUROPEAN COAL AND STEEL COMMUNITY (ECSC) was signed in Paris in 1951. – The Treaty establishing the EUROPEAN ATOMIC ENERGY COMMUNITY (EAEC or EURATOM) was signed in Rome in 1957. Therefore, one could say that, from the beginning, the founders of Europe regarded energy as a very important brick for the construction of a real Community and one could even say that a good deal of the integrated Common Market has already been realised for coal, steel and uranium. In spite of this, I must admit that there was virtually no real common energy policy existing before the first oil crisis back in 1973. Until then, the energy sector in the Community was characterised by twelve distinct national markets with a matching number of national policies which were more or less coordinated on the European level. It was only under the influence of the 1973 shock that quantified targets for selected, energy carriers in the Community were defined. Of course, the main concern was, at that time, to substitute oil and to reduce the dependency of the Community. Therefore, alternative energy sources, solid fuels and energy efficiency, played a very important role, and it should be noted that the latter two are of very great Importance to the cement industry, which is characterised by a high energy demand. Anyway, once the European Energy Policy was established, it led very quickly to tangible results. In fact, the consumption of imported oil was halved within 10 years, from 62% in 1973 to 31% in 1985, and energy efficiency raised by ±20%. This forced the Commission to propose new targets for 1995, which were adopted by the Council in September 1986.

OPENING ADDRESS

3

I will not go into these in great detail as we all know very well that, since then, conditions on the energy market have changed drastically: oil prices went down, as did coal prices on the world market; natural gas is pressing for a higher market share; and in some countries, nuclear energy continues to expand. In addition to this, there is more and more concern about the environment and particularly about the so-called greenhouse effect. For these reasons, I would like to mention today only three of the present targets which are of importance to industry and will remain vaild in future too: – Energy efficiency will remain one of the most important topics of Energy Policy, for the reasons of economy as well as of environment. – Solutions are needed to establish a well-balanced relationship between Energy and the Environment. This will certainly become even more important in future and will require adequate developments. – Technology will have to play an extremely important role in achieving the targets. It is quite interesting to see that these three items were amongst the Community’s targets from the beginning. Yet, importance shifted from aspects of substitution and economics to the protection of the environment. In addition, there are the requirements of the integrated Market for Energy or, in short, 1992. In fact, National as well as Community policies have to change to meet the situation that will exist after 1992. Energy is an area where this transition now has to be made in order to have the integrated European energy market followed by a true common energy policy at Community level. The integration of Europe’s internal energy market is already underway, and a number of new initiatives in this field have been launched since the beginning of 1989. These include new schemes for greater crossfrontier trade and competition in the gas and electricity sectors, a mechanism for taking into account the European dimension In the planning of major energy investments, and a new system allowing the transparency of gas and electricity prices. Other measures to ensure the 1992 deadline will follow. In the longer term, however, it will be the Commission’s task to propose to the Member States, a concise framework for an effective Community energy policy. Therefore, a new review of longterm energy prospects is at present underway, i.e., the 2010 study. A first disscussion paper, entitled “Major Themes in Energy to 2010” was realised by the Commissioner for Energy, Mr Antonio Cardoso e Cunha, at the World Energy Conference in Montreal last September. As the Commissioner said in Montreal, the essential question facing all of us is the following: “Can we continue to develop the world’s energy supplies, on a secure and economic basis, sufficient to maintain economic growth while at the same time ensuring that the global environment is protected and indeed improved?” The “Major Themes in Energy” shows possible alternative paths for our energy future. One is a “convential route” with continuing growth in energy consumption and CO2 emissions. Another path suggests a way of controlling energy consumption and its environmental impact whilst maintaining economic growth—in other words, meeting the challenge of sustainable energy growth. In the months ahead, the Commission will refine its analysis, taking into account the reactions in the Community and Internationally, to this document. However, the preliminary findings were already communicated to the international press in early October. In this context, it is quite clear that the major constraint, or challenge, facing energy policy in the next few years will be the environmental one. We have seen, for example, how much attention was focused on this issue recently at the world Energy Conference in Montreal. But we cannot afford either to neglect the more traditional concern of energy policy makers, that of security of supply. This is particularly true at a time when the world’s need for oil and other energy supplies continues to grow steadily month by month. Action

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ENERGY EFFICIENCY IN THE CEMENT INDUSTRY

must be taken to curb this trend in order to preserve as far as possible our energy resource base and to protect the global environment. With these two fundamental concerns in mind, it is quite clear that the major priority will have to be given to energy efficiency. In order to reduce the growth in energy consumption and the associated pollution. Thus, the political target is set, and all possible actions have to be put in hand to reach it. Of course, this covers political and financial measures as well as technology but for reasons of time, I would like to concentrate on the latter one. An excellent technical base to build upon has been created by the Community’s energy demonstration programme which was set up in 1978 and concentrated on three major areas: – Energy saving or energy efficiency; – New and renewable energy sources; – Solid fuels. I feel I shouldn’t go into too much detail because the area of interest to your industry will be presented during the course of the next two days. But, in order to let you have an idea of what is involved, I would like to give you some figures on the total programme and on the part devoted to energy saving. 1978–1989

Total Programme

Energy Saving

%

Number of projects Total aid (MECU)

1,698 881.7

738 327.7

43.5 37.2

These figures prove that in the past, the Community already gave the appropriate attention to all the possibilities of saving energy and improving energy efficiency. Let me just say that the main technical areas were, and still are: – Buildings – Transport – Industry The demonstration programme, as it stands now, has pratically come to an end. An independent evaluation was carried out last year which highlighted the remarkable results obtained in the different areas, but also said that much more should be done to assure a widespread use of the results, and to match the new targets for energy at the beginning of the next century. The Commission adopted this line and, consequently, proposed to the Council that the replacement for the existing demonstration and hydrocarbon technology scheme should be the THERMIE programme, a new programme for demonstrating new energy technologies and promoting their commercialisation in the European market. As for the current programmes, THERMIE will concentrate on the state beyond R&D by providing risk finance for the testing of new energy technologies on a nearly commercial scale. It will however, be more selective than its predecessor schemes and give more emphasis to the promotion and replication of successfully demonstrated technologies. The current plan is that the Energy Council and the European Parliament should give their consent to this new programme in time for it to start at the beginning of next year.

OPENING ADDRESS

5

THERMIE will cover a wide range of energy technologies including most renewable energies and energy efficiency technologies, as well as clean coal combustion and hydrocarbon projects. These technologies will certainly have a key role to play in assuring the Community’s energy future and preserving its environment. They will also be of benefit to other countries outside Europe, particularly in the Third World where the Community has cooperation and technology transfer programmes. I have no doubt that companies, universities, and all those working in the Community in the energy saving field will find that THERMIE provides a valuable new impetus to, and support for their pioneering activities. In addition, the launching of THERMIE proves that the Community in conscious of tomorrow’s problems and is ready to take its responsability.

A POLICY OF ENERGY EFFICIENCY SPEECH OF HIS EXCELLENCY THE SECRETARY OF STATE FOR ENERGY NUNO RIBEIRO DA SILVA

The aim of the Common Energy Policy in Portugal for the period up to 1995 is a 20% saving energy consumption. If this is accomplished, it will represent: – An annual saving of at least 2 million tons equivalent of oil (14 million barrels), corresponding to something like Esc. 45bn at today’s prices. – A consequent drop in the emission of CO2 into the atmosphere of around 6 million tons annually. Such an increase in energy efficiency will have repercussions in the balance of payments and will lead to improvements in the quality of the environment; there will, moreover, be an increase in the competitiveness of the economy in general. To these results would have to be added the internal and external effects of these moves to diversify sources, above all those which aim to maximise the use of natural and renewable resources. These were, and indeed are, the fulcral points in the search for technical and financial instruments for a concerted policy of energy efficiency, set up with the consumer in mind. The first element which ties these instruments together is the fact that they aim to support operations, systems and sectors which are highly diversified and made up of a large number of distinct, financially limited activities. This is a broad characterisation of the system of energy demand, a system requiring not only special attention but also a framework for the unavoidable “confrontation” with the supply side. The complementary nature of the various instruments should also of course be mentioned: Firstly, as already mentioned, they open the door to all forms of rational association of the three most important components of a logical use of energy in the widest sense: – the management of energy at the level of the company or the region;

A POLICY OF ENERGY EFFICIENCY

7

– the conservation of energy in the widely differentiated systems used by the consumer; – the diversification of sources of energy with all those possible forms available for its use and transformation. Secondly, within the purview of these instruments, as in no other, we find all those Involved in economic activities which it is really important to mobilize, from central and local administration to companies, cottage industries and services. The only exception here is the domestic consumer, who of course demands a very different type of action. Finally, the new Instruments contribute even more to efficient and continuing support at all stages of the prjects, beginning at R.D. & D. or in studies of project potential, continuing through the legal framework and feasibility studies and ending at the point of incentives to investment. But perhaps the most important of the aspects referred to here is the fact that the new instruments contribute overall to providing a reply to many of the questions which are raised in a continuing policy of energy efficiency: – A more exhaustive study of the resources of the country, including not only renewable energy but also the potential of economy of energy at end-user level; – Diffusion of tried and tested energy technology and useful equipment into all areas of production and use of energy: – Increase in production and quality of equipment, systems and energy services; – Development of decentralised means of electrical energy production with a resultant drop in the costs and thereby the creation of profit potential at local or company level. – Breaking down of legal barriers which hinder full use of resources, along with rulings on the contractual conditions of supply of energy to the public network: – Increase in the viability, through financial support of energy projects, which may otherwise be of only minor interest from the narrow vieuwpoint of the consumer: – Creation of incentives and opportunities for new forms of financing, over and above supports and loans, all with a view to maximising results. Here specifically we can refer to the suppliers of energy, who finance their system through third parties. From among these instruments, of a somewhat varied nature, the following can be pointed out: I) SYSTEMS OF FINANCIAL INCENTIVES 1. 2. 3. 4.

SIURE incentive system for the rational use of energy The Community programme VALOREN The Community programme of pilot studies in the field of energy PEDIP

II) REGULATORY INSTRUMENTS 1. Regulation of independant production of electrical energy 2. Regulation on the management of energy consumption 3. Regulation on the thermal characteristics of buildings

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ENERGY EFFICIENCY IN THE CEMENT INDUSTRY

III) SYSTEM OF ALTERNATIVE FINANCING – Financing by third parties I would like to take advantage of the present occasion, albeit in a necessary summary fashion, to take stock of the situation regarding these instruments in the two years of a coherent energy policy which has gone hand in hand with a community policy for this sector. 1. SIURE incentive system for the rational use of energy This is “par excellence” the national system of support for the rational use of energy, having taken over in May 1988 from the previous system (SEURE) which had been operative since August 1986. From among the alterations introduced the following are worthy of mention: – An open door policy for all sectors of activity (with the exception of domestic consumption); – Application to operations and cost centres as diversified as pilot studies, projects and R & D operations—over and above investment in fixed assets; – Articulation with regulations in force for major consumers (to the standa&rd of the RGCE norms); – Probality of application to the system of “financing by third parties); – Increase in joint participation when operations can be included in the VALOREN programme; – Progressive increase in the incentives for R.D. & D. operations with those of the existing Community programme of demonstration projects and with the THERMIE programme in the future. With three applications already accepted (August and September 1988 and January 1989) and two underway (May and September of this year) the system has already proved that it is much better adapted to the requirements and characteristics of its potential beneficiaries. The situation is at present as follows: . The total investment made up to now (Esc. 17.8bn.) has already way outstripped the values of the old systems, as indeed has the number of applications, already up to 217, as compared with 245 in the two years of SEURE. . The 82 operations approved in the three phases already completed is more than those of SEURE (75); moreover approvals represent 66% acceptance of the projects proposed, whereas in SEURE the rate was a mere 31%. . There are already 30 applications in the area of feasibility studies (an area not considered before). There have been 8 approvals and 10 are under consideration. Of the 30, 25 relate to cost control and plans for rationalization of energy; The diversification of sectors and activities is manifest in those projects which have been approved, with emphasis on textiles and clothing, ceramics and glass, foodstuffs, agrilture and fishing. . From the total of applications approved, the forecast of annual energy economy is around 40.500 tons of oil, corresponding to Esc. 911m in foreign currency. In geographical terms, it is the regions of the centre and the north which show a more entrepreneurial spirit, if we consider the level of investment and subsidies which have been given. Stange to say, it is the Lisbon region that has seen most operations (28), possibly because there are many pilot studies included, and projects with a high level of energy economy.

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. As a final point, the Esc. 1.16bn in subsidies already given represent nearly 29% of the total investment associated with the same companies; by comparison, during the period of SEURE the total was 19%. As has already been mentioned, increases in the subsidies may be possible, as well as joint financing through the VALOREN programme, as long as the operations come within the terms of reference of the programme. I would like to take this opportunity to announce that the whole community and national process has been completed, allowing for joint financing of SIURE through PEDIP, in the case of applications which cannot be included in the VALOREN programme, but which relate to the operations to be developed in the extracting and transformation industries. In this way, there will be close on Esc. 2.2bn available between 1989 and 1992 as reinforcement of the budget available for SIURE, and Esc. 2.4bn through the country’s Budget applications for the same period. 1.2) THE COMMUNITY VALOREN PROGRAMME This programme is available to provide finance for operations which aim at rational use of energy in small and medium industrial and services companies. The aim is above all to stimulate regions of various potential renewable energy sources. The programme has been operative from October 1987 for applications for public or comparable infrastructures. The VALOREM programme can, as has been seen, provide joint finance for incentives which are taken through SIURE, as long as the operation is included among its objectives, in terms of investment, budget and others regulations. The joint financing began in 1988, immediately after the first applications for SIURE funding. The committed funds in this operation of the VALOREM programme valid until the end of 1991, were Esc. 5.6bn up to the end of this past September, and this has already gone beyond the 50% of the Esc. 10. 5bn earmarked for these specific projects. On this situation the following points can be made: The VALOREM programme has already supplied close on Esc. 915m through SIURE, in terms of the 3 applications which have already been processed. This sum corresponds to approximately 79% of the subsidies provided by SIURE and up to 26% of funds available through the VALOREM programme for these projects up to December 1991. Given that SIURE only started in August 1988, this information should be more widely known, with a view to attracting more applications. . The commitments undertaken in participation in energy projects relating to the public or comparable infrastructures represent already 68% ot the total allowed for. There are in fact regions, such as the North and Centre, wich show greater dynamism and which have already gone beyond the forecats, while the Alentejo, the Algarve and above all the Azores are still considerably behinhand. In terms of type of energy or sector of activity, it is found that the use of biomass (kindling wood, stalks from vines, biogas…) is the source of the largest number of applications. These have already gone beyond the forecast limit and have made it necessary to reappraise the distribution of available funds. The projects for the use of water have not been confirmed, because the authorisation for such use has not come through yet. These projects are already sufficient to take up all of the funds available for this area. For this reason, and also because the average duration of these investments goes beyond the end of 1991 have meant that studies are underway with the Portuguese Small Hydro-Power Association to find alternative

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ways for the VALOREM programme to be associated with the investment which was caused by the new legislation regarding the independent producer. The VALOREN programme has been available as finance for important actions involving energy sources which are part of the country’s natural resources and the technologies which are associated with them, as well as information relating to the possibilites of rational use of energy (for example, through finance for the IAPMEI “Energy-bus”). The steady increase in the proportion of energy consumption in the GPD, as well as the recent boom in consumption, bearing especially on domestic consumption and services, has led to the VALOREN programme becoming actively involved in a major campaign to inform the public— in fact all consumers— that energy must be used sparingly and that there should be greater awareness of the need for its rational use. 1.3) COMMUNITY PROGRAMME FOR DEMONSTRATION PROJECTS This programme was created and is run by the Office of the Director-General of Energy (DG XVII) of the European Community Commission. It is at the heart of this seminar and since 1975 has been responsible for financing important projects in various energy sectors during the precompetition stage. It is also the Community programme which is best-known among Portuguese industrialists, according to a survey conducted by the Ministry of Energy and industry. This is by no means by chance. Since 1986, the date of the our accession to the Community, we have participated—in the sense that the Portuguese entrepreneurs, in conjonction with Universities or national laboratories have made applications to the programme. Since great care always been given to the choice and preparation of good projects, the percentage of approvals has always been high, and this has allowed us to get support for a percentage which has always been higher than our overall weight in the total. In the four competitions which have taken place, a total of Esc. 2.55bn in support has been given to Portuguese projects, representing 22% of the total investment of nearly Esc. 11.5bn. However, in the last two years alone, the support has totalled Esc. 1.8bn, out of a total of Esc. 9.8bn of total project costs. In terms of the “quota” received, and without taking into account the part of the competitions relating to solid fuels (that is, carbon fuels), in which, understandably, we saw only 3 out of the 4 projects approved, the grants awarded represented in the last two years 8.5% and 7.7% of the available funds. For the values relating to the past years, a large proportion is taken up by the CIMPOR project which is presented here today. Apart from its innovation in European and Community terms, there are two aspects to the projects which are worthy of mention here. Firstly, there is the adoption and adaptation of a Japanese technology for the cement industry which is of great interest in the energy sector. Secondly, there is the system of recovery of heat from gases from the furnace exhausts, which will also contribute to diminishing pollution in terms or dust and the combustion products of coal. Next year, the present demonstration programme will be replaced by the recently approved THERMIE programme, which draws on a different philosophy, due in large measure to the suggestions which we put forward. In this way, innovatory projects will continue to be supported, with an assessment procedure which is more rigorously controlled. Moreover, THERMIE will open up the possibility of support to projects already presented, where these are put forward in new contexts, geographical, economic, social and energy oriented within, and in some cases outside the EEC.

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This new approach will undoubtedly bring in its train more and better opportunities for Portuguese projects and for the diffusion of the results obtained through the present programme. Less widely-known, but capable of being very interesting at the level of back-up for these Community programme is the part of SIURE which allows for incentives for demonstration projects and pilot studies, as well as research and development of new forms of production and distribution of energy. From among 14 applications presented for this tranche of SIURE, 4 to date have already been approved, 3 are under review, 2 were rejected and another 3 were asked to reformulate their terms and resubmit. From among the projects already approved, the CIMPOR project already referred to looms largest. Exceptionally, this project will receive an additional grant of 100m escudos, not only in view of the risk involved but also the great scope for reproduction, even if only at a national level. II.1) REGULATION FOR INDEPENDENT PRODUCTION OF ELECTRICITY The launch of this regulation in May 1988 was a real success, such was the interest among individuals, companies and local authorities. The conviction that decentralised production by agents independent from EDP would reduce production costs for small units and stimulations could lead to 6.500GWh/year being made available. This led to the new legislation, which is innovatory above all in terms of the full and rational legal framework in which this activity can now be undertaken. The recent law on production is applicable to all forms of the production electricity from any renewable source, or from recycled thermal effluents. However, in the early days up to the present, the speediest and most exciting reply has been in the area of water resources. The main characteristics of this legislation are well known, and I consider it more interesting on this occasion to refer to some points which give an idea of the interest it has awoke. The right to use any water, as indeed any utility in the public domain, is subject to specific authorisation. Up to now, 702 requests to produce electrical energy have been put in to the Office of the Director General of SEARN. The difficulties in the management of water resources which this avalanche has created are not difficult to imagine. The 370 requests which have a solid foundation and obvious know-how of the field and his use represent close on 1.015MW, greater than the biggest power station In Portugal (Alto Lindoso, which generates 625MW). Forecasts point to a production of approximately 4.025GWh, i.e. around 20% of the domestic electricity production in 1988. The authorisation process is not limited to the use to which the water is to be put. Among other things, it is essential that the interested parties cleraly justify their technical and economic aims; that there should be no other intentions for the same site; and that different uses are not being considered for the same water resources. As for any overlaps, in terms of requests made by different groups for the same site, the decision on which takes priority should not be based simply on legal points. We have found that in many cases a solution has been or is being found through discussions with the interested parties. There have also been examples or collaboration from the official services involved. Given the large number of interested parties—companies, local authorities and individuals—and given the variety of motives know-how and financial capacity, I consider it of paramount importance to encourage all forms of collaboration which are being found. This applies to the equating of interests, technical expertise and management of the resources in question.

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ENERGY EFFICIENCY IN THE CEMENT INDUSTRY

I would like here to draw attention to the creation of the Portuguese Association of Small Hydro Producers. This I consider to be indicative of the dynamism of the sector and the professionalism and enthusiasm of those involved. The initial members of the Association bear the responsability of making it a real partner In the dialogue between the various entities in the sector. The Association must consider all applications from would-be members, and should even encourage those who work in the sector and are interested in their activities for widely differing reasons. The question of how representative the Association happens to be is fundamental to relations with third parties and for this reason, with in the Association, mutual understanding and interchange of ideas among the members become much more important. Should this spirit prevail I have no doubt at all the Small Hydro-Electric scheme will be of benefit to everybody involved. This whole process shwows how business peopple are reacting to the liberalization of the energy sector which is underway in our country. As far as the use of small power stations for the production of electricity is concerned, all the 6 requests for authorisations which have been handed in to the Office of the Director General of Energy relate to premises destined for the generation of heat and electricity. The fuels to be used are forest waste in 4 cases and gas in each of the other two. The total power potential is around 130MW, with a forecast annual production of the order of 800GWh. This demonstrates how much greater is the potential of these systems than those in the field of Small Hydro- Power. We know of a large number of other new projects of the same type as these, among them the CIMPOR project, with its total close on 9MW, For theses projects, no authorisation for electrical installations was necessary and they therefore do not figure in this survey. II.2) REGULATIONS FOR THE MANAGEMENT OF ENERGY CONSUMPTION This legislation dates from 1982, altough it only reached the statute books in 1987. Its objective was to lay down the structures for operations which will hopefully be undertaken by the major electrical energy producers, in the sense of rationalising consumption and bringing about a progressive drop in energy use. This legislation, which covers all sectors, is based on two ideas: one, that the energy problems of the country will not just go away; and two, that the entitles involved are not just the State and those on the supply side. Major consumers must also bear the responsability of bringing about a dowturn in consuption and a diversification of sources. Seen from this angle, there are 106 rationalisation plans which have been submitted for approval to the Office of the Director General of Energy. The period of validity for these schemes is 5 years, from the total, 33 have already been approved and 15 were considered inadequate in terms of the targets established. After 5 years of use, these 33 will bring out an annual saving of at least 30,000 tons equivalent of oil, i.e. Esc. 675m in foreign exchange. The approach of the Secretary of State is not bound by the mere wording of the regulations. It is rather to awake the spirit of collaboration among those who run the companies in the sector, since they are the ones who will benefit first and foremost from the new procedures for management of energy deriving from the legislation. The fact that applicants for state aid must fulfil the regulations has also helped to spread on them regulations. It has been recognised that the greatest possible cost control should be exercised over investment and development plans in the energy field. For this reason, the costs of auditing can be in part offset by

A POLICY OF ENERGY EFFICIENCY

13

subsidies from SIURE, as long as methods and content correspond to the models prepared by the Office of the Director General of Energy. In this field, as has already been noted, there have been 25 applications to SIURE. As an immediate consequence of the enrgy audits undertaken, SIURE is in a position to support further studies relating to the creation and implementation of measuring systems, the recording and cost control of consumption and the infrastructures necessary for the management of energy in premises where it is consumed. This control exists as a parallel to the managemment of production, raw materials and personnel. II.3) REGULATIONS ON THE THERMAL PROPERTIES OF BUILDINGS This legislation is still at the review stage, and is in the hands of various Ministries involved. The legislation represents the first step towards standardisation of the regulations for buildings with the aim both of lowering the heating and cooling requirements and of improving the quality of the environment. With this in mind, are plans for cheking the minimal thermal characteritics of office and residential buildings and the other passive systems used their construction. As a first approach, using simple, easily understood and easily applied calculations, a start is to be made on improving buildings which have a life span of 20–30 years. The reason for this is to avoid mortgaging the future of energy. These regulations, which should be on the statute books from January 1991, draw in their train further regulations on the characteristics and dimensioning of active systems of air conditioning in the same buildings. These regulations are being drawn up in the Council of Public Works, Transport and Communications. The great challenge now is to get them known among owners, designers and builders, and also in the training of teams in Local Authorities, who will oversee and approve the regulations. III) FINANCING BY THIRD PARTIES The projects for rational use of energy require consistent technical and financial support based on turnkey principles and to this and the Office of the Secretary of State of Energy is actively promoting the creation in Portugal of service companies which provide what is known as “financing by third parties”. At this point in time there are at least 4 Portuguese companies of thie type operating in the market or in the process of setting up. A system of finance specifically for projects which generate energy savings is different from leasing operations, from credit operations involving suppliers of equipment and from other forms of finance. The fundamental differences are threefold: . The contract is specific to the supply of a consultancy service and technical assistance, a financial package for the total investment and the guarantee of concrete results; . The financing entity takes responsability not only for turning the project into a reality but also for operating the system on site for the duration of the contract; . The investment, along with associated services and charges, is paid off through the measurement of energy saved, taking the initial situation as a point of departure. The return is normally within the parameters of the savings achivied.

14

ENERGY EFFICIENCY IN THE CEMENT INDUSTRY

Altough there are no public funds for this, the Office of the Secretary of State, along with the European Commission, is actively seeking the structure and support mechanisms for this system of financing. To this end, these groups can apply for support through SIURE, and it is hoped, through the VALOREN programme. At this time, ways of channelling venture capital available through PEDIP are also being actively sought for this type of company. This then is the situation regarding the major instruments created by the Office of the Secretary of State for Energy with a view to improvements in energy efficiency. And over and above this attempt to show the country what is happening—as well as the European Community represented here—I wished to take advantage of the fact that CIMPOR is also tied in with events. If there was a “Portuguese Nobel prize for energy savings” it should be awarded, in our opinion, to CIMPOR. This company realised at a very stage that is needed to manage its energy consumption efficiently, and to this has: a) diversified its energy sources by using old tyres and even coal (which was then made available for other consumers); b) recovered thermal effluents from furnaces, not only in absorption systems for air conditioning but also recovery boilers where electricity is now generated; c) exercised systematic control over consumption; and d) made savings in electrical energy through management of overheads and control of heavy electrical equipment used for ventilation and crushing. CIMPOR now has a body of knowledge and experience in these matters which I am sure would ne made available to other companies and other countries. Moreover, the company has used in the best possible way the domestic and community financial instruments available to it. If you will forgive the play on words, I should like to end by expressing my heartfelt wish that the same spirit should become a concrete reality in other companies and consumers in Portugal. By the same token I hope that the work begun today will be crowned with success.

FIRST SESSION Chairman: Professor Veiga Simao, President of LNETI

ENERGY SAVING AND ENVIRONMENTAL IMPACT IN THE CEMENT INDUSTRY ANGELO SCARES GOMES CIMPOR, Cimentos de Portugal, Portugal

Summary Since 1986 CIMPOR’s Maceira cement plant has had a tyre burning installation working regularly in two dry-process kilns, each with a capacity of clinker production of 1350 ton/day. The amount of tyres consumed per year could be doubled, at least, but the factory is now facing many obstacles in the acquisition of used tyres, due to the lack of appropriate legislation and mechanisms. The low amount of tyres burned is the main cause of the present reduced economic profitability of the installation. 1. INTRODUCTION The subject of this address has been deliberately requested within the context of the general outline conceived in the initial stages of organisation of this Seminar. The concern to include this subject in the programme is understandable. Currently questions related to the environment are of great importance, and they are not separate from the problems involved in energy saving. It is an incontestable fact that the greatest contribution of the cement industry to the improvement of the environment has always been, and still remains, the resolution of the problems raised in the industry itself. The great progress recorded in this matter over the past 20 or 30 years is also incontestable. So, for the cement industry the use of derivatives from other industries or activities is a question of relative importance, but it is still one more contribution on behalf of the environment. This utilization, which has been common practice for several years, has been even further increased in recent years as a result of the 1973 and 1978 oil crises.

ENERGY SAVING AND ENVIRONMENTAL IMPACT

17

For this reason we now propose to meet the request that has been made by presenting below some considerations on this subject, starting with the recent experience of a tyre burning installation at CIMPOR’s Maceira cement plant. In the course of several years of work it has become apparent that in various sectors the ability of the cement industry to absorb certain waste which would affect the environment or demand considerable costs to be eliminated has been regarded with extreme optimism and in too simplistic a way. What we intend to point out is that this ability is far more limited than is sometimes thought, and it always presents great economic and technical difficulties. 2. TYRE BURNING INSTALLATION AT MACEIRA CEMENT PLANT The tyre burning installation has been erected at our Maceira cement plant. This factory has two similar dryprocess kilns, with a four stage cyclone tower, each with a capacity of 1350 ton/day. In 1982 studies regarding the erection of this installation began. At that time the experience already in existence in Europe indicated the possibility of consumption of used tyres in the kilns in the near future at 15% of the total thermal energy, which meant a consumption of between 7500 and 8000 tons per year, in each kiln. It was foreseen that a sufficient quantity of used tyres would be available to use regularly with one kiln and that eventually the burning of tyres would be extended to the second kiln. This was based on the fact that the quantity of tyres produced in Portugal was calculated at about 20000 t, with an upward trend. In economic terms, the scenario envisaged at the date that the decision was made (1984) was as follows: Coal price (at factory prices) Tyre cost (at factory prices) Annual Saving (Gross) Installation Costs Payback

9760 Esc/ton 5000 Esc/ton 30 million Esc 90 million Esc 3 years

So from the economic point of view the investment appeared quite interesting. The decision for its accomplishment was taken in 1984. Basically, the installation comprises: – – – – – – – –

a tyre park where tyres are stored; 43 m reception metallic hopper, tyres supplied by a load shovel; horizontal belt conveyor; tyre elevator, 26 m high; belt conveyor with deflector for kilns Nos. 5 and 6; roller conveyor with incorporated weighing station, which feeds the tyres into the kiln; pendular double trapdoors pneumatically driven, which limit the admission of air into the kiln.

The installation became operational at the end of 1986. Following the start-up and adjustment period, normal work practice was established.

18

ENERGY EFFICIENCY IN THE CEMENT INDUSTRY

The factory has now been working for two and a half years, regularly burning used tyres in kiln No. 5. The quantity of tyres burned corresponds to 13% of the total thermal consumption in long periods of stable work, although the annual average is slightly lower at 10%. The kiln has a stable working pattern and the quality and daily clinker production have not been affected at all. The problems reported are as follows: – Thermal consumption is slightly aggravated, at a level of approximately 18 Kcal/kg of clinker (about 2%). – A greater degree of corrosion than is normal has occurred inside the gas conditioning tower, as a consequence of the presence of SO2 and NOx in the outlet gases from the cyclone tower. 3. ECONOMIC OUTLOOK During 1988 kiln No. 5 produced 395748 tons of clinker and burned 57893 tons of coal, 118 tons of fuel-oil and 5848 tons of tyres. TABLE 1. Tyre burning economic situation Clinker output Thermal ton consumption kcal/kg

COAL

Cost ×1000 Esc/ton

Consumption ton

Cost ×1000 Esc/ton

Consumption ton

1984 100% COAL Forecast (based 1984) COAL & TYRES 1988 REAL FIGURES

392300

825

400000

825

9.76 (1) 9.76 (1)

395748

843

7.98 (2)

TYRES

Operating profit Payback ×1000 Esc

51000

–

–

–

–

45200

5.0 (1)

7000

30000

3 years

52091

6.69 5848 (2)

2 280

38 years

(1) Factory price (2) Cost at loading into the furnace

Table 1 summarizes the economic analysis of the present working year, comparing it with the provisional estimations made in 1984. It can be seen that in 1988 the annual profit resulting from tyre burning was below the level forecast in 1984, and did not allow recovery of the investment. What is the reason for such a drastic reduction of profit? It is basically due to the following factors. – The significant reduction of the quantity of tyres burned each year compared to the expected level. Instead of 7500 to 8000 tons per year, or even 15000 tons if tyres were burned in both kilns, the factory burned only 5848 tons, due to lack of supply of tyres. – Increase in the thermal consumption of 18 Kcal/kg of clinker.

ENERGY SAVING AND ENVIRONMENTAL IMPACT

19

– Reduction of the coal price in the international market. The priority now must be to secure the supply of tyres to the factory. 4. TYRE COLLECTING The collecting of tyres in our country is being made by a few small road transport companies. CIMPOR negotiates with those companies a certain price for the acquisition of tyres, delivered to the factory, as well as the quantities required. Unfortunately, those quantities are never achieved. It is impossible to find such an enormous quantity of tyres concentrated in one place. Tyres are scattered widely by geographical location and are available from companies and organisations, thus making collection difficult, slow and inevitably inefficient. However, a curious situation is now happening. Some of the organisations that until recently gave the tyres freely are now demanding to be paid for the same tyres. The factory’s demand itself has led to the attribution of a certain commercial value to a product that before had absolutely no value. In practical terms this development is gradually reducing the quantities of tyres likely to be collected. As has been shown, the economics of the installation do not allow for an increase in the cost of acquisition of the tyres, but even if it were possible to pay the suppliers, it is still doubtful whether, in the medium term, the quantities would increase. Probably it would only cause an increase of the prices at the origin. So far, CIMPOR has not been able to acquire the necessary quantities to achieve viability of the installation, nor has the country been able effectively to reduce the pollution caused by the old tyres. The problem is that we are only burning 15% or 20% of the tyres produced in the country every year. It is quite clear that although the interests of the country and those of CIMPOR are identical in this matter, the desired result will only be accomplished if the state takes part, through the Central Administration, or Autarchys, regarding the concentration of the tyres in specific places. The economics of the process can support, at least partially, the cost of the transport. However it cannot bear the costs involved in the complex organization of collection of the tyres which are spread all over the country.

ENERGY OUTLOOK IN WEST-GERMANY’S CEMENT INDUSTRY A.SCHEUER and S.SPRUNG Forschungs institut der Zementindustrie, Tannenstraße 2, 4000 Düsseldorf 30 Federal Republic of Germany

Summary Through the construction of advanced rotary kilns and the shutting down of old kilns the fuel consumption in the Federal Republic fell from 4.8 GJ/t of cement in 1960 to 3.0 GJ/t of cement in 1988. To a limited extent, energy savings are today possible by the use of secondary constituents in cement grinding or by optimizing the process technology in the preheating, burning and cooling of the cement clinker. The technological possibilities for waste heat utilization, on the other hand, are already largely exhausted. Sophisticated process technology should therefore aim at a reduction in the heat loss through the kiln wall, e. g. by the construction of short rotary kilns with tertiary air duct and precalciner. Due to increased automation and measures for an improved environmental protection the electrical energy consumption rose from 0.32 GJ/t of cement in 1960 to 0.42 GJ/t of cement in 1988. When modern roll mills are used energy savings of up to 50 % are conceivable in the grinding of the raw materials and of up to 35 % in the grinding of cement. Further savings are possible with the modern cyclone air separator, the vertical impact crusher, the optimum design of electrical drives as well as a sophisticated energy management. 1. INTRODUCTION The manufacture of cement is very energy-intensive. Already in the past great efforts have therefore been made to lower the energy consumption in the manufacture of cement (1). By using advanced rotary kilns and shutting down older kilns the fuel consumption fell for instance from 4.8 GJ/t of cement in 1960 to 3.0 GJ/t

ENERGY OUTLOOK IN WEST-GERMANY’S CEMENT INDUSTRY

21

of cement in 1988. Due to a greater degree of automation and measures to improve environmental protection the demand for electrical energy, on the other hand, rose from 0.32 GJ/t of cement to 0.42 GJ/t of cement (s. table 1). Table 1: Cement production and average energy requirement of the cement industry in the FRG from 1960 to 1988, (Source: Bundesverband der Deutschen Zementindustrie).

Cement manufacture Fuel energy requirement per ton of cement Electrical energy requirement per ton of cement

Unit

1960

1970

1980

1988

106

24,6

37,5

33,1

24,4

GJ/t

4,8

3,8

3,4

3,0

GJ/t

0,32

0,34

0,39

0,42

t

The most important process stages where energy savings are constantly sought are a) the preparation (combined drying and milling) of the raw material components, b) the burning of the kiln feed to cement clinker and c) the preparation (milling) of the clinker to cement. Under the headings a) energy savings through product innovation b) energy savings through process optimization and c) energy savings through waste heat utilization are discussed the possibilities the German cement industry either already exploited in the past or may still have at its disposal to fulfil the demand for an optimum use of energy, a demand which is, after all, of the greatest importance to the economics of both the individual business and the national economy as a whole. However, the realization of measures should not only be judged on whether these are technologically feasible or not. Decisive are also cost considerations in relation to the results achieved. Furthermore, in future greater care has to be taken to ensure that a branch of industry is not put under cost pressure by governmental regulations impairing its competitive power on the European as well as the non-European market. 2. ENERGY SAVINGS THROUGH PRODUCT INNOVATION Portland cement is produced by intergrinding cement clinker and about 5 % of gypsum. Already since the turn of the century portland-slag cement and blastfurnace cement have existed as further standardized types of cement containing as a third component 6 to 35 % or 36 to 80 % of glasslike set and latent hydraulic granulated blastfurnace slag. Nowadays also limestone and flyash are used as constituents for manufacturing portland composite, portland filler and port land flyash cements. In addition, in the Federal Republic of Germany oil-shale and portland pozzolana cements have been made for some time. But table 2 shows that in 1988 owing to market demands portland cement still accounted for 71.7 % of the total production. Only 28.3 % of the cements contained other main constituents besides clinker. Altogether for this about 4 Mio. tons of secondary constituents were needed. In principle, the use of secondary constituents

22

ENERGY EFFICIENCY IN THE CEMENT INDUSTRY

instead of clinker brings about significant savings in fuel energy as well as electrical energy in the clinker production. On the other hand, cements with secondary constituents have to be ground to a greater fineness than a portland cement of the same strength class. Furthermore, the secondary constituents must be dried and additional transportation costs are incurred, in turn lowering the energy savings. It also has to be borne in mind that the market demands on the utility properties of the cements and an increased quality awareness regarding durability of concrete do not allow an unlimited use of secondary constituents and added materials in the manufacture of cement and concrete. Table 2: Cement type percentage of total sales on the home market in 1988. Portland cement Portland-slag cement Blastfurnace cement Oil-shale cement Portland-pozzolana cement Other cements

71,7 % 7,3 % 15,4 % 1,7 % 0,5 % 3,4 %

3. ENERGY SAVINGS THROUGH PROCESS OPTIMIZATION Fuel energy savings The major part of the fuel energy consumption is used up for the burning of the cement clinker, which in the Federal Republic of Germany is mainly produced in three types of kilns, namely a) kilns with cyclone preheater and grate cooler (type A) b) kilns with cyclone preheater and counter-current cooler (type B) c) kilns with grate preheater and grate cooler (type C). Of type A are at present 32 plants in operation, of type B 11 and of type C 22. Merely 6 plants of type A or B are equipped with a calcinator, 3 in addition with a tertiary air duct. The average throughput of the various kiln types ranges from 1,000 to 3,050 t/d, that of the individual kilns even from 500 to 3,800 t/d. This especially results in different specific heat losses through the wall of the rotary kiln, but also of the cooler and the preheater and thus in the total also in different mean specific fuel energy consumptions (s. table 3). Table 3: Average energy expenditures of cement kilns operated in the FRG. Preheater type

Cyclone

Cyclone

Grate

Cooler type

Grate

Counter-flow

Grate

Mean capacity in t/d

1700

3050

1000

Energy loss in kJ/kg cli Rotary kiln Cooler

400 500

315 500

500 500

ENERGY OUTLOOK IN WEST-GERMANY’S CEMENT INDUSTRY

Preheater type

Cyclone

Cyclone

Grate

Cooler type

Grate

Counter-flow

Grate

Mean capacity in t/d

1700

3050

1000

Preheater Theor. heat requirement Total heat requirement

875 1760 3535

855 1760 3430

350 2220 3570

23

Table 4 shows how the fuel energy consumption of a rotary kiln with cyclone preheater increases or decreases with the source of the energy loss becoming bigger or smaller. Accordingly, a waste gas enthalpy loss of the preheater rising by 10 kJ/kg cli must be compensated with approximately 8 to 9 kJ/kg cli of fuel energy. Heat losses through the wall of the preheater affect the fuel energy consumption less and require only 0.2 to 0.8 times the fuel energy. In contrast, losses of heat through the wall in the burning zone (the lowest stage of the preheater and the Table 4: Relative alteration in the fuel energy consumption when different sources of energy loss are influenced. Eloss Waste gas energy loss Energy loss through wall of cyclone stage 2 3 4 Energy loss through wall of rotary kiln and theor. heat requirement Energy loss of the cooler

1

0,87 0.22

0,44 0,76 1.18 1,18 1,46

rotary kiln) have to be compensated with about 1.2 times the fuel energy. This factor is also to be used for assessing altered reaction enthalpies of the clinker. However, with the usual design of the kiln the greatest influence on the fuel energy consumption is exerted by the cooler. In relation, a change in the cooler energy loss leads to a change in the fuel energy consumption by almost 1.5 times (2). Thus, heat recovery in the cooler is the most important parameter for fuel energy consumption. For this reason, most optimization measures are nowadays directed towards the clinker cooler. Clinker cooler Since all rotary kilns in the Federal Republic of Germany are fed with fuel via silos or tanks, the percentage of primary air in the total combustion air is normally smaller than 10 %. Measures to improve heat recovery in the clinker cooler therefore aim at a further drop in the primary air proportion to about 5 % with at the same time low NOx emissions through the use of advanced rotary kiln burners as well as at lowering the proportion of the false air through the installation of sophisticated kiln seals. In grate coolers heat transfer may be further improved by a higher clinker bed in the recuperation zone, e.g. by narrowing the grate width or by lowering the number of thrusts. Furthermore, heat transfer may also be improved by grate plates with horizontal air outlet. If there is a chance to use the enthalpy of the cooler waste air, the design of the cooler should be such that recuperation zone and cooling zone are separated and each zone is optimized

24

ENERGY EFFICIENCY IN THE CEMENT INDUSTRY

Fig. 1: Related heat loss through the wall of rotary kilns in dependence on the clinker capacity of the kiln plant for kilns with and without tertiary air duct.

individually. On the other hand, with coarse clinker or clinker with a wide grain size distribution the optimization of tube coolers or planetary coolers still presents difficulties. Cooler optimization is at present carried out in practically all plants, normally with the aim of achieving cooler efficiency rates of 70 %. Rotary kiln Especially in smaller capacity kilns heat losses through the wall of the rotary kiln may constitute a substantial proportion of the total energy losses. Accordingly, to compensate the heat losses through the wall of rotary kilns different proportions of fuel energy are needed. Due to higher energy inlet, high heat loss through the wall therefore also leads to higher waste gas energy loss of the kiln (2). An increase in the energy loss through the wall of the rotary kiln must therefore be compensated by an overproportionally high amount of fuel energy. Heat loss through the wall of the rotary kiln is mainly governed by the kiln design and its specific burning process. Fig. 1 (2) gives the heat losses through the wall of various kilns found in field tests in dependence on their clinker throughput. The figure illustrates that kilns with large clinker throughputs show smaller specific heat losses through the wall than kilns of smaller capacity. These heat losses are also smaller in kilns with tertiary air duct than in those without tertiary air duct, since in the former the operation process allows substantially smaller dimensions. Thus figure 1 makes it quite plain that by shutting down smaller kiln units and/or by installing sophisticated pre-calcination kilns savings in fuel energy may be achieved. The shutting down of smaller kilns makes especially in those cases economical sense where through this the capacity of already existing bigger plants can be better utilized. Preheater The operational behaviour of cement kilns is also determined by the cyclone preheater, in which part of the waste gas enthalpy is transferred to the kiln feed and thus recovered for the process. In addition to the gas mass flow, which in turn is governed by the fuel energy demand as well as by the air rate, the efficiency of the preheater is mainly dependent on the dust cycles in the preheater. It is normally between 50 to 65 % and may be markedly increased by the installation of additional dip tubes. Fig. 2 (2) indicates that by increasing the separation efficiency of both lower cyclone stages from 60 to 80 % each, the preheater energy loss may be cut by about 0.15 MJ/kg of clinker. In the past the installation of dip tubes was successfully effected in numerous plants.

ENERGY OUTLOOK IN WEST-GERMANY’S CEMENT INDUSTRY

25

Fig. 2: Energy loss of a cyclone preheater with four cyclone stages in dependence on the separation efficiency of both lower cyclones.

Savings in electrical energy The main part of the electrical energy requirements is accounted for by the milling of the cement (3), in addition, the preparation of the raw materials and the burning of the clinker are also of importance (s. table 5). Table 5: Mass-related electrical energy requirement for the production of cement in the FRG. (Source: Bundesverband der Deutschen Zementindustrie). Energy requirement in kWh/t Raw material preparation Clinker burning Cement grinding Other

10 to 30 15 to 25 30 to 80