This study focuses on the use of slow pyrolysis with controlled temperature increase for the thermal decomposition of pre-dried wastewater sludge. A combination of two significantly different methods was applied to investigate the pyrolysis process. The first of the experimental approaches was based on laboratory apparatus with a vertical batch retort equipped with external electrical heating. Samples of the liquid and gaseous products of the pyrolysis were taken at defined intervals throughout the pyrolysis process and were subsequently analysed. The second method involved the application of thermal analysis to the identical sludge, completed by online analysis of the pyrolysis products generated. This second method included thermogravimetry (TG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The results obtained by both methods demonstrate that waste water sludge can be effectively converted into pyrolysis gas and oil with good combustion properties.
This paper focuses on the laboratory experiments of low-temperature adsorption of CO2 at elevated pressure and on the validation of our mathematical model with the data obtained. The numerical approach uses fitting of adsorption isotherm parameters and sensitivity analysis of parameters influencing the breakthrough curve shape and onset time. We first evaluate the results of breakthrough experiments for zeolite 13X. Then, we use the results obtained to design a dynamic mathematical model to predict the breakthrough curve profile. Experimental results show that zeolite 13X possesses high adsorption capacities (over 10 % of its weight at adsorption temperatures of 293 K and below), as expected. The mathematical simulation was accurate at predicting the breakthrough onset time; however, this prediction accuracy declined with the outlet CO2 concentration exceeding 75 %, which is discussed. The sensitivity analysis indicated that the choice of different estimates of mass transport and bed porosity, as well as the choice of numerical scheme, can lead to a more accurate prediction, but the same set of parameters is not suitable for all process conditions.
In the years 2017-20, the research on the use of fly ashes and bottom ashes from power plants for the preparation of adsorbents for carbon dioxide capture from flue gases was carried out at the involved institutes. As part of the research, adsorbents were prepared by alkali fusion and hydrothermal processes. The obtained products were subjected to cyclic adsorption and desorption tests simulating their industrial use. One of the partial tasks was to evaluate how the worn adsorbents can be subsequently utilized. In the study presented here, the materials collected after the adsorption testing were subjected to several procedures, which aim was to verify the applicability of these materials as substrates for the reclamation of excavated brown coal and lignite quarries. The basic property assessed was the ability to retain humidity and thus contribute to the water balance in the reclaimed landscape. A hydration test followed by slow drying of the sample in a thermogravimetric analyzer was proposed for this purpose. With regard to the raw materials from which the adsorbents were prepared, attention was also paid to the risk of undesired leaching of toxic substances. The last measured parameter was the course of CO2 desorption from the pores of the used adsorbent. It answers the question of whether the adsorbent is usable for terrain reclamations in the state after the last adsorption (i.e. CO2 saturated), or whether it requires thermal desorption as the final step. Based on the results of hydration tests of the spent adsorbents, it can be concluded that they could be applied in the reclamation of closed lignite quarries, and these materials would allow a more sophisticated application than just as a stabilizer. In the tested samples, the high retention of water and its slow release was confirmed by the TGA method, which (in the case of the mentioned use) could improve the management of soil humidity and its distribution to woody plants used in the biotechnical reclamation phase. Another, but as yet unproven, possibility is to use the porous structure of the materials as a suitable substrate for colonization by nitrifying bacteria. These bacteria would subsequently improve the self-cleaning ability of the water tank created in the case of the hydraulic reclamation method. Due to the results of measurements of carbon dioxide desorption from saturated adsorbents, it is necessary to recommend that thermal desorption should be included in their preparation before the use in reclamation. Tests of toxic elements leaching have not identified any potential risk from their mobilization into groundwater or surface water.
The article deals with the issue of waste plastics pyrolysis leading to the industrially applicable liquid and gaseous products. The problem of thermally labile halogenated compounds, present in the feedstock, is discussed. The introductory part focuses mainly on halogenated flame retardants and their toxicological and environmental risks. In comparison with the standard recycling of waste plastics, pyrolysis with subsequent material utilization of the liquid product is mentioned as a promising method capable to solve the problem with the presence of halogen derivatives. The following second part of the article summarizes studies searching suitable methods for removing inorganically and organically bound chlorine and bromine from pyrolysis organic condensates - i.e. pyrolysis oils. Dehalogenation processes are divided into several categories according to the nature of the process and also according to the method of application of the respective reagent, catalyst or sorbent. Within each group, the results published in the available literature are briefly summarized. When commenting on them, the main emphasis is placed on the applicability of the obtained pyrolysis oils as raw materials for refinery processing and new polymers production. At the end of the article, a plan of experiments is outlined, which will be carried out during the research of the issue by the authors team. The space is mainly dedicated to the construction of two laboratory apparatuses that has been developed for this purpose.The first batch apparatus working with a vertical retort allows studying of gaseous, liquid and solid pyrolysis products at various temperatures. The second, continuously operating apparatus, is designed to test the efficiency of hydrogen halides adsorption from gaseous mix-tures at high temperatures. The third apparatus designed for the research purposes is a catalytic continuous system enabling to study the decomposition of organic halogen derivatives. The results of the experiments will be published continuously after their verification with sufficient reproducibility.
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