The tailings are significant geological environments in mining and industrial regions. They represent special engineering-geological zones of anthropogenic sediments that require specific engineering-geological investigation. In particular, it is important to examine the sites in detail with regard to their potential heterogeneity. The article deals with an important engineering-geological issue of burning in coal mine and coal tailing dumps. A case study was implemented in a tailing dump in Heřma-nice located in Ostrava which is a major industrial city of the Czech Republic. In this urban agglomeration, anthropogenic sediments form 20 % of all foundation soils. Thermometric monitoring in Heřmanice detected a thermally active coal tailing dump with burning as deep as 9 m. The burning is predominantly related to the content of oxygen in the body of the tailing. It belongs to the limiting conditions of the pyrophoric and consequently self-sustained burning. Other factors are sufficient contents and quality of coal mass and capacity to accumulate thermal energy of exothermal reactions. Dynamics of changes in the burning processes were identified in dependence on time, depth and distribution. There was a considerable heterogeneity of thermal activity as for all parameters, and changes were observed from the point of view of time. Considering the depth, burning gradually spread deeper. However, in the depth of 12 m, no significant thermal activity was observed within the overall studied locality. It may be stated that thermal activity is observed as much as 40 % of the studied area. Directionally, there was a progression of the process from west to east. The identified facts may be applied in final designed levels of coal tailing dumps where observational experiences identified intense cooling up to the height of 5 m preventing higher stages of self-ignition process (best situation). Tailing dumps from 5 to 12 m may already be thermally active (meeting other boundary conditions), and in tailing dumps over 12 m, it is clear that there is no thermal activity below 12 m.
This paper focuses on increasing quantities of digestate, a final product of anaerobic digestion, in biogas stations being built as alternative sources of energy. The potential use of digestate is limited due to its rather specific physical properties. This paper presents current approaches to digestate and digestate management. The objective is to compare the properties of digestate and the products of its separation via centrifuging, i.e. the liquid phase known as digestate liquor, and the solid phase referred to as digestate fibre. Its focus is mainly laid on techniques for dewatering digestate in low-solid anaerobic processes only, which have been tested for the effectiveness of the basic physical and chemical methods including their combinations. The measured results show that the use of coagulants and flocculants for this purpose would be very problematic in practice with regard to their high consumption as well as the need to input other elements into the process.
AbstraktPředložený článek se zabývá problematikou narůstajícího množství digestátu jako konečného produktu anaerobní digesce v bioplynových stanicích, budovaných jako alternativní zdroje energie. Digestát má v současné době omezené využití, které je dáno jeho specifickými fyzikálními vlastnostmi, zejména extrémně problematickou separací jednotlivých složek, ale také chemickým a mikrobiologickým složením. Jeho vlastnosti jsou z největší části ovlivněny druhem zpracovávané biomasy. V úvodní části tato studie předkládá současné možnosti nakládání s digestátem. Předmětem experimentální části je popis odběru a analýzy vzorků digestátu včetně jeho zpracování v laboratorních podmínkách použitím odstředění a následné posouzení vlastností digestátu a produktů separace, tj. fugátu a separátu a dále testování koagulačních a flokulačních činidel pro účinnější separaci tuhé fáze z digestátu, resp. fugátu. Použití koagulantů a flokulantů pro tyto účely v praxi by bylo značně problematické s ohledem na jejich vysokou spotřebu a vnos dalších prvků do procesu.
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