Objetivo The project is focused on the low energy conversion of :I. low NOX fly ash, andII. moist fly ash from disposal sites into lightweight aggregates for the building industry. The purpose of the project is to demonstrate that the processing of these residues of coal-fired power stations is technically feasible on a near-commercial scale of 25 tph.Most important parameter of the product quality is the compressive strength of the pellets. Pellet strength is the maximum force that can be applied before the pellet is damaged. The minimum as laid down in the licence contract for this installation is 3 N/mm2. First indications are that this standard can be reached and maintained. The pellets will have to be subjected to certifcation before they can be sold. Therefore, it is of primary importance that the quality remains constantly up to standard and the production process is fully controlled. Aardelite was granted certification on 17 November 1994. For this reason the plant has not produced at its full capacity up till now. Indications are, however, that the production capacity of the plant will exceed the design specifications.On the basis of market surveys in many countries in Europe and elsewhere the following observations can be made with regard to the commercial outlook for future Aardelite projects :- a potential site for the plant has to be selected close to the ash producer;- the gravel must be marketed at close range from an AArdelite plant to reach prices comparable with existing (natural) aggregates.SUCCESS OF THE PROJECTTaken the first-in-business character into account, it can be concluded that no major setbacks have been encountered so far. Component performance indicated that it is almost certain that the design capacity of the plant can be reached and the quality of the final product is up to specifications.Technically speaking, the project can therefore be qualified as successful.This success paves the way for many other commercial Aardelite projects in different parts of the world.PROCESSThe Aardelite process is relatively simple. No high temperatures are required. The aggregates are formed in a continuous cold-bonded process, using the pozzolanic properties of the fly ash. The fly ash can be processed both in its dry and moist form. This allows for the economical storage of moistened fly ash at times when the amount of dry fly ash produced, exceeds the demand for Aardelite gravel.The Aardelite demonstration plant has been erected near the town of Geertruidenberg, in the south-central part of the Netherlands within three miles from the AMER power plant, the largest conglomeration of coal-fired units in the country.The first batch of the final product left the installation in November 1993. The installation was designed to process 257,000 tons of fly ash annually in dry and moist conditions. It will be able to turn out 330,800 tons of lightweight aggregate per year.INSTALLATION AND PRODUCTIONThe bulk solids (fly ash, bottom ash, sand and lime) are stored in daybins. From the respective daybins, the ash and the lime can be dosed and weighed in continuous flow. When the plant is in normal operation, the different streams of solids are transported jointly towards one of two powerful process mixers, where water is added until a sticky "green mix" is formed. Two large disk pelletizers which are steeply inclined rotating pans, form spherical pellets, due to the adhesiveness of the mixture. To strengthen the still vulnerable "green pellets", they are embedded in a constant stream of fly ash.After transportation to two large curing silos just outside the production building, low pressure steam is allowed to expand to atmospheric pressure and is saturated in these silos. The steam condensates on the embedding material around each pellet. The energy released indirectly warms the pellets to a temperature of 85 deg. C.After 15 hours they leave the silo and as a result of a reaction between lime, fly ash and water, the pellets have by thattime turned into rock-hard gravel. The mixture of hardened pellets and the now moistened embedding material is used to make new pellets. The hardened pellets are divided into different fractions on a vibrating screen. The oversized material is crushed to a suitable size. In accordance with the demonstration character of the project, facilities are also incorporated in the installation for converting bottom ashes and residual products from gasification into useful aggregates. Programa(s) ENG-ENDEMO C - Programme (EEC) of demonstration projects and industrial pilot projects (EEC) in the energy field, 1985-1989 Tema(s) 8.5 - USE OF WASTE Convocatoria de propuestas Data not available Régimen de financiación DEM - Demonstration contracts Coordinador VLIEGASUNIE BV Aportación de la UE Sin datos Dirección POSTBUS 3254 5203 DG 'S-HERTOGENBOSCH Países Bajos Ver en el mapa Coste total Sin datos
