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  3. jeudi 29 avril 2004
POST 00668E : WASTE MANAGEMENT Follow-up on Post 00657E and 00664E 29 April 2004 __________________________________ Note Those who could not attend the recent TechNet Consultation in Antalya can still receive the meeting CDRom by sending a request to Paul Mallins ( from WHO. Do not forget to give a full postal address with your request. ------------------------------------------------------ In this posting Ville Lehto ( from Finland discusses the issue of toxic emissions during incineration, __________________________________ Thank you for these important documents! I already posted my comments to Yves too. As stated, the main problem with incineration has been the formation of dioxins and furans. The issue of proper operation is related to the same problem. Bad operation results in incomplete burning and toxic emissions. It was also written that "Even in high temperature incinerators (>800 °C), temperatures are not uniform and dioxins and furans can form in cooler pockets or during start up or shut down periods. Optimization of the incineration process can reduce the formation of these substances by, e.g., ensuring that incineration takes place only at temperatures above 800°C, and that flue gas temperatures in the range of 250 to 450°C are avoided." We are afraid that the temperature of 800°C might not be enough, and minimum of 850°C should be preferred. When it comes to cooler pockets it is better to take a look how these emissions are created. There are three mechanisms that result in PCDD/PCDF emissions: 1. The fuel/burned material contains PCDD/PCDF, and it doesn't decompose during the burning process 2. In temperatures 300-800°C organic compounds that contain chlorine form PCDD and PCDF 3. In temperatures 250-400°C inorganic chlorine and organic compounds form PCDD and PCDF (De-Novo-synthesis). Burning at temperatures over 850°C prevents the formation of dioxins and furans, and the residence time min. 2 seconds make the existing ones decompose. By ensuring sufficient preheating and burning time, also the problems with start up and shut down periods can be avoided. It was also said that "WHO has not established an acceptable limit for dioxins and furans emissions since: • most incinerators are unlikely to meet existing standards; • most incinerators cannot easily be equipped with emission reduction and control devices;" My comments are: - The existing standards are for 50MW plants. For example, the power of our gas burner is 72 kW. -- There are no standards for small scale incinerators. - However, there are incinerators that meet existing (50MW) standards for PCDD and PCDF, and as the technology takes steps forward we believe that there will be more and more of them. - Emission reduction devices are not a solution to the problem. The toxic emissions could be collected e.g. in some filter, but then the problem would be: What to do with the filters? Instead we should aim at a clean process. Some best practices were also listed. I would like to comment the operation part. The key is that the products must be user friendly. It is inappropriate to expect that every operator in the field is an expert of burning theories. With automation it is possible to reduce the demands for the operator to the level that can be achieved with very little training. Another point of the user friendliness is that the products should be so safe to use that the protective equipment is not needed. I would like to hear everyone's opinions and comments. The issue is important. Let's keep the discussion alive! Best regards, Ville Lehto Marketing Manager Mediburner Ltd. Oulu, FINLAND ______________________________________________________________________________ Visit the TECHNET21 Website at You will find instructions to subscribe, a direct access to archives, links to reference documents and other features. ______________________________________________________________________________ To UNSUBSCRIBE, send a message to : Leave the subject area BLANK In the message body, write unsubscribe TECHNET21E ______________________________________________________________________________ The World Health Organization and UNICEF support TechNet21. The TechNet21 e-Forum is a communication/information tool for generation of ideas on how to improve immunization services. It is moderated by Claude Letarte and is hosted in cooperation with the Centre de coopération internationale en santé et développement, Québec, Canada ( ______________________________________________________________________________

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