2/2019
Optical assessment of ash melting behavior of solid fuels
Ash fusion characteristics of solid fuels are key practical information for co-firing options and further thermochemical conversion processes. The study investigated the optical assessment techniques currently available for ash fusibility analysis, initially developed for characterization of coal ashes, later modified suitable for solid biofuels. Though the standardized procedures are quite similar, but the difference between the common used guidelines were significantly identified with ash conditioning temperatures of 815±10 °C and 550±10 °C, respectively. The setting up for ash determination regarding to the shapes of specimens, ash preparation, test sample binding, particle size, and constant heating rates were reviewed. Several variations of definition on characteristic temperatures according to available standard methods for solid fuels were discussed. The initial deformation temperature (DT) was highlighted as an indicative parameter in ash melting determination for main fuel and supplemental biofuels in co-firing options. Further examinations concerning ash contents, transformations of elemental compositions, morphological structural changes are essential for better understanding practical phenomena occurs.
Utilization of waste from the production of phosphoric acid while expanding cypress clay
The article deals with the use of waste from the production of phosphoric acid. It follows from the laboratory experiments that one of the monitored wastes is very well usable as an expanding agent in the production of expanded aggregates. Its use can significantly reduce the amount of landfilled waste from the production of phosphoric acid. The bases for the pilot plant verification of waste from the production of phosphoric acid were obtained by means of samples taken in its production, respectively landfill. Their genesis is as follows: decontamination sludge, resp. so-called dearzenization sludge - a by-product that is formed in the process of purifying the phosphoric acid thermal. Calcium phosphate sludge is the waste product from superphosphate production. Through the laboratory study, it has been demonstrated that calcium phosphate sludge deposition is a very promising product from phosphoric acid waste products. Already 3.3% wt. this component to the cypress clay guarantees the possibility of achieving a better bulk density of the product compared to the expanded aggregate produced without the additive. With regard to the total volume of the existing production of expanded aggregates, it is justifiable to dispose of a significant amount of this waste in compliance with all valid ecological and technological conditions. Hundreds of tons of VPF per year could be destroyed by the monitored technology, which means that mining of the already long-term dump substance is also offered.
Coal Combustion Residuals from Brown Coal of the Sokolov Coal Basin and their unique composition
Fly ash and bottom ash samples resulting from combustion of brown coal of the Sokolov Coal Basin were studied for the contents of ten minor elements (Ge, Ti, V, Rb, Cs, Ga, Nd, La, Ce, Pr), where titanium was considered as the most important component. The samples were analysed first by means of the AES technique for the target elements concentrations, which was followed by scanning electron microscope and optical microscope examination. All the samples analysed showed quite a high concentrations of titanium with the highest one reaching 92 000 mg.kg-1 for a sample taken in Tisová power station in November 2014. Observation through scanning electron microscope showed that this sample contained the particles having up to about 35% of titanium.
Nickel-based catalysts for hydrotreating of fatty acids triglycerides
Using of nickel-based catalysts in a reduced (metallic) form for hydrotreating of fatty acids triglycerides seems to be a promising way to produce a renewable component of fuels. This form of the catalyst is more suitable for low sulphur feedstock in comparison with sulphided catalysts commonly used for the processing of petroleum fractions. Another significant advantage of reduced nickel catalysts is their price, especially if compared to the very active noble metal catalysts. Noble metal catalysts have strong cracking and methanization activity. But there are still some problems, for example their rapid deactivation due to the formation of coke deposits on their surface. However, these aspects can be suppressed to some extent by the optimization of preparation process and nickel loading and by using of suitable type of the support. Furthermore, the use of polymetallic nickel catalysts, which are still affordable but can exhibit significantly higher stability compared to monometallic nickel catalysts, is possible also. The development of nickel catalysts in the form of phosphides, nitrides or carbides is the last modern perspective for increasing the stability and activity of nickel-based catalysts, however, these types of catalysts are complicated and so on expensive to prepare, which is the considerable problem for their common using.
Continuous monitoring of landfill gas
The original design of a landfill gas monitoring unit is presented together with the observations and results from the continuous testing operation. The monitoring unit included the gas flow meter, a set of sensors and supporting electrotechnical components in total price of about five hundred EUROS. The monitoring unit showed very good performance characteristics and durability in current operational conditions of a municipal waste landfill. The results collected within the six days continuous testing run clearly proved the advantages of this long-termed approach over simple individual measurements according to current Czech technical standards. The landfill gas extraction well selected for the testing run showed relatively poor performance as far as gas production and methane concentration were concerned. It was evidenced that the waste deposited around the extraction well was in the final stage of its stabilization.