Objective The aim of the project is to substitute the existing conventional wet bottom ash extraction and handling system of the 300 MWe lignite burning boiler of the Unit IV of Ptolemaida Power Station with a new, non polluting and more efficient dry bottom ash extraction and handling system, the Magaldi Ash Conveyor {MAC} System.The MAC System is entirely innovative technology in the field of bottom ash extraction from Solid Fuels burning boilers. At present the bottom ash falls from the furnace into a water basin located beneath the boiler and is extracted by a submerged chain conveyor. The dry ash extraction gives a lot of benefits mainly from environmental and efficiency viewpoints. Improvements can also be demonstrated in auxiliary power and water consumption requirements.By installing this system it will be possible to use the bottom ash, having a high unburned carbon content of around 50%, as fuel by recycling it to the mills and furnace thus recovering a high percent of the energy lost.Furthermore, the possibility of usage of both the bottom and fly ash in the cement and concrete industry is examined by way of laboratory testing.Summarizing the results of the measurements, it is concluded that there is a decrease in efficiency losses rated about 1,6% depending on the fuel used as well as on the mode (recycling or no recycling of the bottom ash) of operation of the system. This decrease coincides with a correspondent improvement in boiler efficiency, i.e. an increase in power production to 4,5 mWe. The power consumption of the system in recycling mode is 41,41 kW or 158,4 kW without recycling, contrary to previous system consumption which was 35,6 kW.Furthermore, laboratory testing showed that it was possible to use both fly and bottom ash in the cement and concrete industry.The project has a definite positive impact against environmental pollution which is primarily due to the following reasons :a) the new system installed, practically eliminates the need for water whereas the conventional systems require about 800000 tn/y of water for bottom ash cooling.b) the total amount of ash produced and disposed is reduced by 35000 tn/y with the system operating in recycling mode and 8400 tn/y with the system operating in no recycling mode.The Public Power Corporation of Greece who is also the owner of the system intends to operate it continuously in recycling mode which provides a sufficient efficiency improvement of the Power Plant, thus using the pneumatic transportation line only in case of emergency.The installed system consists of a metal conveyor made of a steel wire mesh type belt, overlapping pan type plates (MAC extractor). The belt is driven by a pulley mechanism which transfers the force strictly by friction similar to a standard rubber belt drive. The return drum at the tail station is equipped with an automatic tensioning device to observe the changes in the belt length due to temperature variations during operation. The intermediate belt sections are equipped with support and return idlers. The belt continuously runs under the throat of the boiler, thus continuously receiving the heavy ashes failing from the furnace. The belt is totally enclosed in a tight envelope so as to avoid uncontrolled air leackage from the outside atmosphere. A fine recovery drag chain is underneath the belt, in the same enclosures transferring small ash particles dropping down from the belt.Between the belt and the boiler throat, a transition hopper equipped with bottom valves can be used for storing the bottom ash for a few hours enabling the possibility for minor maintenance operations of the MAC extractor and downstream avoiding boiler shutdown. Other parts of the system are the following :- a hydraulic seal consisting of a water channel, in which the edges of the boiler are merged, is used to ensure that no air from the environment is inserted in the boiler.- a primary crusher is provided at MAC discharge for size reduction of big ash lumps.- an Ecomag conveyor, receiving the ash from the crusher, conveys and cools the ash at the same time, to an intermediate hopper. The Ecomag conveyor is a belt conveyor completely enclosed in a tight container with a fine recovery drag chain at its bottom; it is a mechanism very similar to the MAC extractor, the main difference being the different construction material.An intermediate hopper is installed at the Ecomag discharge as a temporary surge bin. Programme(s) ENG-THERMIE 1 - Programme (EEC) for the promotion of energy technology in Europe (THERMIE), 1990-1994 Topic(s) 7.12 - USE OF WASTE Call for proposal Data not available Funding Scheme DEM - Demonstration contracts Coordinator PUBLIC POWER CORPORATION (PPC) EU contribution No data Address HEP DEV. DEPT 56-58 AGISIALOU STR. 10436 Athens Greece See on map Total cost No data
