Alternative fuels for the cement industry

Applied Energy 74 (2003) 95–100www.elsevier.com/locate/apenergyAlternative fuels for the cement industryEugeniusz Mokrzycki*, Alicja Uliasz- Bochen´ czykMineral and Energy Economy Research Institute of the Polish Academy of Sciences,Wybickiego 7 Str, 30-950 Krakow 65, PO Box 49, PolandAbstractOne of the main methods for utilising waste is its use as an energy source. Waste is onlysuitable for use as a fuel if it has a chemical energy content. This energy content depends mostof all on the size of the (organic) combustible fraction and on the moisture content. To betteremploy the chemical energy contained in wastes, alternative fuels have been developed whichare mixtures of different wastes. Some of these alternative fuels are: RDF, BRAM, SIBRCOM,INBRE, PAKOM, etc. Research carried out for a number of years in cement plants all overthe world has clearly shown the advantages of waste utilisation in clinkering processes andcement production. The decisive factors promoting the use of cement kilns for the utilisationof wastes are: the high incineration temperature, the large area of the furnace, the significantlength of the kiln and the alkaline environment inside the kiln.# 2002 Elsevier Science Ltd. All rights reserved.Keywords: Alternative fuels; Municipal and industrial waste; Cement plants1. IntroductionHighly-developed countries use low-waste or waste-free technologies as well askeep searching for waste treatment methods that would be (i) friendly to the environmentand (ii) helpful in recovering energy from waste. The cement industry alsoparticipates in the efforts to find a solution to the problem of waste management.The energy-intensiveness of cement production processes and increasing fuel prices,combined with fuel deficit, force the cement industry to search for technologiesbased on waste-derived and alternative fuels.Depending on local conditions, such as incineration technology, access to wasteand economic calculation, cement plants use various types of alternative fuels.* Corresponding author. Fax: +48-12-632-35-24.E-mail address: mokrzy@min-pan.krakow.pl (E. Mokrzycki).0306-2619/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.PII: S0306-2619(02)00135-6

96 E. Mokrzycki, A. Uliasz-Bocheńczyk / Applied Energy 74 (2003) 95–1002. Use of alternative fuels in rotary cement kilnsThe process of clinker burning in a rotary kiln creates favorable conditions for theuse of alternative fuels. These include [1]: high temperature, alkaline environment,oxidizing atmosphere, the lack of incineration wastes as all metallic and non-metallicincineration products undergo a complete absorption, large heat-exchange surface,good mixture of gases and products, and sufficient time (over 2 s) for thedisposal of hazardous wastes.Other advantages of a cement kiln are the following:waste treatment does not require any additional source of heat (as in the caseof a traditional incineration plant),there is no increase in discharges to the atmosphere,it is much cheaper to adapt a cement kiln to waste incineration than build anewincineration plant, andclinker burning process complies with all requirements of the EU Directive92/C130/01 concerning hazardous waste incineration.A diagram of temperatures of gases and materials (Fig. 1) shows the required timefor waste disposal (over 2 s).The use of waste-derived fuel in the process of clinker production also has certainlimitations, such as [2]:technological limitations related to the volume of waste-derived fuel, whichmay be at one time fed to the kiln. The waste volume depends on the effectiveincineration surface, i.e. the kiln’s length and capacity The use of waste-derivedfuel must not have a negative impact on the kiln running or clinker quality [3];limitations related to environmental safety. Waste-derived fuels should be used inaccordance with strictly defined rules so as to ensure that incineration productsdo not have an adverse impact on the process of clinker production, that is do notaffect cement quality or cause pollution of gases discharged to the atmosphere.3. Alternative fuels used in the cement industryAlternative fuels are the solid, liquid, municipal or industrial wastes used inindustrial and power plants as a substitute for conventional fuels. Alternative fuelshave been in use for more than 10 years nowand are gaining an increasing share inthe global energy market [3].Alternative fuels used in the cement industry are usually classified according to theconcentration criterion into [4,5]:gaseous (examples: landfill gas, pyrolysis gas),liquid (examples: pasty wastes, solvents, waste oils, greases),solid (examples: animal powder, bark, paper, tyres, ruber wastes, plastics, fluff).

E. Mokrzycki, A. Uliasz-Bocheńczyk / Applied Energy 74 (2003) 95–100 97Fig. 1. A diagram of the temperatures of gases and materials in a cement kiln [1,12,18].According to the classification by Cembureau, alternative fuels are divided intothe following five classes [6]:class 1: gaseous alternative fuels (examples: refinery waste gas, landfill gas),class 2: liquid alternative fuels (examples: lowchlorine spent solvents,hydraulic oils),

98 E. Mokrzycki, A. Uliasz-Bocheńczyk / Applied Energy 74 (2003) 95–100class 3: pulverized, granulated or finely-crushed solid alternative fuels (examples:sawdust, dried sewage sludge, granulated plastic, animal flours, finecrushed tyres),class 4: coarse-crushed solid alternative fuels (examples: crushed tyres, rubber/plastic waste, wood waste, reagglomerated organic matter),class 5: lump alternative fuels (examples: whole tyres, plastic bales).Solid alternative fuels may be divided into four groups [7]: group 1: solid, dry fuels of relative fine size, which do not adhere (dimensions:

E. Mokrzycki, A. Uliasz-Bocheńczyk / Applied Energy 74 (2003) 95–100 99content volatiles,calorific value,physical properties (scrap size, density, homogeneity),grinding properties,humidity content,proportioning technology.As a mixture of various wastes, alternative fuels must be produced in conformitywith certain rules [10]:the chemical quality of the fuel must meet regulatory standards assuringenvironmental protection,the calorific value must be stable enough to allowthe control of the energysupply to the kiln; the objective being to arrive at a fairly homogeneouscomposition, andthe physical form must alloweasy handling of the material for transporationand a stable, adjustable flowof material in the cement plant.In Western Europe and in Poland, special types of alternative fuels derived from amixture of wastes have been developed. These include [11–15]:RDF fuel (Refuse Derived Fuel),BRAM fuel (Brennsteff aus Mu¨ ll),INBRE fuel (Industrial Brennsteff),PAKOM fuel,other fuels: oil-derived, alternative, hybrid, etc.4. ConclusionsWhile cement plants do not themselves produce wastes, they use wastes fromother branches of industry as additives or alternative fuels. This is possible owing tothe technological conditions in rotary kilns.Many years of experience have shown that the use of wastes as alternative fuels bycement plants is both ecologically and economically justified. The use of alternativefuels will help reduce the costs of cement production. The average energy demandfor the production of 1 ton of cement is about 3.3. GJ, which corresponds to 120 kgof coal with a calorific value of 27.5 MJ per kg [16]. Energy costs account for30–40% of the total costs of cement production. The substitution of alternative fuelsfor fossil fuels will help reduce energy costs, providing a competitive edge for acement plant using this source of energy. Furthermore, thanks to waste management,less waste will have to be dumped or burnt, which will mean less dumpingsites. Therefore, the use of waste-derived alternative fuels by cement plants will bealso beneficial to the environment. The conditions in rotary kilns, such as high

100 E. Mokrzycki, A. Uliasz-Bocheńczyk / Applied Energy 74 (2003) 95–100temperature, the high speed of the gas stream and the long particle-storage period,guarantee that the use of alternative fuels is ecologically safe.According to the European Cement Association, CEMBUREAU [17], the figuresfor the proportion of alternative fuels used in clinker kilns between 1990 and 1998 inparticular countries were as follows: Belgium—18%; France—52.4%; Italy—4.1%;Portugal—1.3%; Spain—1%; Sweden—2%; Switzerland—25%; Czech Republic—9.7%; Great Britain—20%; Germany—15%; Poland—1.4%.References[1] Duda J. Energetyczne i ekologiczne aspekty wykorzystanie odpadówprzemys•owych i komunalnychwprocesie produkcji cementu. Mieˆ dzynarodowa Konferencja ‘‘Wykorzystanie odpadówprzemys•owychi komunalnych w procesie produkcji cementu’’. Opole, Poland, 1998.[2] Kowalik T. Spalanie odpadówwpiecu cementowym. S´ rodowisko 1997:22.[3] Syrek H, Nowak E. Ekologicznie czyste spalanie w cementowniach jako alternatywna metoda utylizacjiprodukto´ wodpadowych. Cz I Cement, Wapno, Gips 1993;5:153–8.[4] Jenkins BG, Mather SB. Fuelling the demand for alternatives. The Cement Environmental Yearbook1997:90–7.[5] Pizant J, Gauthier JC. Burning alternative fuels in rotary kilns. World Cement 1997;9:64–75.[6] Best available techniques for the cement industry. Brussels: Cembureau, 1999.[7] Paulin F. Conveying, dosing and combustion of solid alternative fuels. World Cement 1998;7:81–4.[8] Grosse-Daldrup H, Scheubel B. Alternative fuels and their impact on refractory linings. WorldCement 1996;3:94–8.[9] Greco C. Fresh alternatives. International Cement Review1996;11:24–6.[10] Lemarchand D. Burning issues. International Cement Review2000;2:65–7.[11] Żygad•o M. Gospodarka odpadami komunalnymi. Wydawnictwo Politechniki S´ wiêtokrzyskiej,Kielce, 1999. p. 281.[12] Duda J. Paliwa alternatywne w przemyœle cementowym. IV Szko•a Gospodarki Odpadami. Rytro,Poland; 2001.[13] Wandrasz JW, Wandrasz AJ. Przetwarzanie krajowych odpadówkomunalnych wpaliwo energetyczne.Eko-Problemy 1995;1:22–9.[14] Nowak E. Unieszkodliwianie odpadówwcementowym piecu obrotowym. Cement Wapno Gips1995;2:42–6.[15] Utylizacja odpadówniebezpiecznych wpiecach cementowych. Praca zbiorowa pod red. L.Paw•owskiego, Wydawnictwo Politechniki Lubelskiej, Lublin, 1997. p. 164.[16] Substytucja paliw w piecach do wypalania klinkieru cementowego. Przegla¸d sytuacji wœwietle propozycjiDyrektywy Unii Europejskiej dotycza¸cej spalania niebezpiecznych odpadów. EnviromentalResources Managment, 1994.[17] Informator 2001. Wydany przez Stowarzyszenie ProducentówCementu i Wapna. Kraków; 2001.p. 77.[18] Alternative fuels in cement manufacture. Technical and environmental review. Brussels: Cembureau,1997.