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Eingeladener Vortrag
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The recycling of refractory materials in the chemical, metallurgical and glass industry has only had minor relevance until now because of the high performance required from these materials (stability against corrosion, inert when coming into contact with the glass melt, etc.). Refractory lifetimes are limited because of corrosion at higher temperatures. The best furnace lifetimes has been achieved with chromium oxide and chromium oxide corund refractories. Waste from the production and use of refractory material is generated in three main forms: as residues from cutting and grinding, as refractories which have limited or no contact with glass melts, and as refractories with infiltration of sublimation residues or condensates. The waste material is classified as hazardous waste due to its chromium content. In this study, arc furnace technology was used for thermal treatment of the waste materials to enable recycling of refractory materials. (author abst.)
Commercial native lipase A from Candida antarctica was used to produce alkyl esters through the alcoholysis of (waste) fats with 2-ethyl-1-hexanol. The process was carried out in batch stirred tank reactors (from 100 mL up to 3000 L).
The content of alkyl esters in reaction mixtures was determined by gradient HPLC using an evaporative light scattering detector and the reaction progress was controlled by determining the ratio of the palmitic acid ester peak area to the oleic acid ester peak area in HPLC chromatograms.
The results show that alcoholysis is the favoured reaction in presence of excess water and water-insoluble alcohols in comparison with hydrolysis (fatty acid content <5%). The optimum amount of water for the alcoholysis was found to be 80-100% of the amount of fat. In the presence of low quantities of water both alcoholysis and hydrolysis are slow.
Conversion rate increases with increasing temperature to 65-70 °C.
Based on these results a large-scale test to produce 3000 L of alkyl ester (to be used as lubricant coolant) was carried out. The experiments have proved that alcoholysis is completed after about 7-10 h depending on temperature.
The Rietveld method was used to reliably interpret severely superimposed diffraction patterns of a sewage sludge ash before and after being turned into an ecologically desirable, high-quality fertilizer by a newly-developed method of thermochemical treatment. The thermochemical treatment causes severe changes in the phase composition of the ash, which can be described as a mixture of a large number of solid solution phases.
Municipal sewage sludge is a carrier of nutrients most important phosphorus (P) but also contains organic pollutants and heavy metals. A two steps thermal treatment is suggested based on 1. mono-incineration of sewage sludge under destruction of organic pollutants and 2. thermochemical treatment of the resulting ashes to remove heavy metals and increase P-bioavailability. The targeted products are marketable P-fertilisers. The thermochemical treatment was investigated in a gas tight lab-scale rotary furnace. Seven sewage sludge ashes of different origin and composition and one residue from gasification of sewage sludge were mixed with a chlorine donor (e.g. MgCl2) and thermochemically treated under systematic variation of operational parameters. The distributions of the heavy metals between solid and gas phase were determined. The heavy metals concentrations of the treated ashes met the legislative limits in most cases. The products from thermochemical treatment are suited raw materials for P-fertiliser production. Relevant process parameters such as temperature, type and concentration of Cl-donor and retention time were optimised for the thermochemical treatment step.