SO - Rheinkalk

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Dry processes have become standard in modern flue-gas cleaning since they offer the user decisive advantages. In addition to the safe compliance with mandatory limiting values and high flexibility, they also lead to lower investment and operating costs, low personnel expenditures as well as a simple concept and space-saving design. The reaction products are produced in the dry state. Examples for its use can be found in almost all fields of application, e.g.: • wood and biomass-fired power stations, • municipal waste incineration plants, • hazardous waste incineration plants, • conventional power stations, • non-ferrous metal processing, • glassworks, • ceramics industry, • process firing. In addition to the reduction of acid-forming pollutants, the removal of ecotoxic substances, such as heavy metals (e.g. Hg, Pb, Zn) and dioxins/furans (PCDD/PCDF), is of particular interest. These adsorption processes are carried out advantageously in the low-temperature range using suitable mixed products. For this application, the Lhoist Group can supply products tailored to the customer's requirements and which are based on Spongiacal ® , hydrated lime and limestone powder. The adsorption materials used are, for example, lignite coke and activated carbon. The products offered by Lhoist for this purpose offer a higher inherent safety. They can be used, if necessary, without additional apparatus and personnel expenditures. This fulfils the demand for more simple and more reliable plant engineering. specific surface (BET) [m²/g] 60 50 40 30 20 10 0 Normal hydrated lime Spongiacal® Hydrated lime with 3% lignite coke Graph 3: Lime Carbon Mixtures adsorptive carbon surface Spongiacal® with 3% lignite coke 3
The use of products that are optimally customised to the process provide particular advantages for the operator of semi-dry and dry processes. Therefore, highly reactive hydrated lime (Spongiacal ® ) is generally used since this • minimises the consumption of operating materials, • allows a safe compliance with mandatory limiting values, • reduces the amount of residual waste (requirement to minimise residual waste!). In the low-temperature range, the highly reactive hydrated lime products (WÜLFRAsorp ® A and Spongiacal ® ) have been used successfully for some time. An important further development was the combination of semi-dry and dry process steps with high porous products (MCD process).The medium temperature range offers very good application conditions for the use of special hydrates, particularly those to remove SO2. For example, in the glass industry, flue-gas cleaning has been very successful using WÜLFRAsorp ® A at 350 – 500 °C 4 . In the high-temperature range at approx. 850 –1000 °C, products with high surface areas that were specially developed for flue-gas cleaning (e.g. WÜLFRAsorp ® A) have also been used successfully. WÜLFRAsorp ® A Spongiacal ® WÜLFRAsorp ® A NHL / Milled Limestone ~ 1200 - 1000 °C ~ 1000 - 850 °C SO2 NHL ~ 850 - 450 °C ~ 300 - 220 °C ~ 220 - 80 °C ~ 450 - 300 °C SO 2 + HCl WÜLFRAsorp ® D SP NHL SO 2 + HCl Max. 180°C PCDD/DF + Hg Graph 4: Temperature application range of lime based products In addition to the temperature a number of other factors influence the removal of pollutant gases. They can be summarised under the headings gas properties (given), process engineering (can be influenced) and adsorbent (can be influenced). The influence of temperature for the use of hydrated lime in semi-dry and dry process is discussed here, in particular. Results and operating experience are discussed on the basis of practical examples from the field of thermal waste treatment. 4
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SO - Rheinkalk

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