1,721,176 research outputs found
Thermoeconomic evaluation of CO2 alkali absorption system applied to semi-closed gas turbine combined cycle
No full textA new carbon dioxide separation system based on CO2 absorption in aqueous solutions of alkaline salts (sodium and potassium carbonate) was studied with reference to semi-closed gas turbine/combined cycle (SCGT/CC), and compared to results obtained with existing technologies. Use of calcium hydroxide for the regeneration of the exhaust solution was studied in order to obtain a tail-end product, calcium carbonate in the form of precipitated calcium carbonate (PCC) with a wide spread and continuously growing market. The alkali CO2 absorption process was compared with a conventional amine absorption process (DEA + MDEA), referring to the same SCGT/CC based on the same CO2 removal efficiency. The comparison allows foregrounding of the possible goals of the CO2 alkali absorption process with respect to previous amine cycle analyses. The modeling approach focuses on a thermodynamical and economical first comparison of the proposed cycle to previous studies carried out on CO2 absorption
Efficiency of different types of landfill covers and comparison of CH4 emission monitoring campaigns.
No full textComparison of two different possibilities for biogas recovery: power production vs. up-grading.
No full textCarbon Dioxide Capture: Technical Review and Proposal of an Alternative Absorption Process.
No full textEnergy recovery from waste: Comparison of different technology combinations
No full textEnergy recovery from waste can follow several routes. The most common one is waste direct combustion associated with conventional energy recovery in a steam turbine cycle. The combustion can be applied directly to Municipal Solid Waste or can be applied to a stream of selected waste obtained by means of mechanical sorting of Municipal Solid Waste, using several technologies for the combustion, the most common of which is mobile grate combustor. Besides the direct combustion of waste, alternative possibilities for thermal treatment are gasification and pyrolysis. These processes require being fed by a homogeneous combustible fraction obtained by mechanical sorting and supply as output one or more combustible streams, available for energy recovery. When Municipal Solid Waste mechanical sorting is applied, besides the combustible fraction stream, a humid fraction is also obtained, characterised by a high presence of organic biodegradable fraction. At present the fate for this stream is biological aerobic stabilisation, but another option, to push energy recovery also from this stream, is biological anaerobic digestion, which can be applied through different technologies (wet and dry digestion). Through this process a biogas with elevated content of methane can be produced and supplied to engines for energy recovery. The above-mentioned technologies can be combined in several schemes to optimise the overall energy recovery. The combination of schemes will be analysed in this chapter in reference to a study case characterised by an average waste material composition. The comparison will be carried out using some indicators of the overall energy recovery for each scheme
Biodegradation of poly(vinyl alcohol) with different molecular weights and degree of hydrolysis
No full textThe biodegradability of poly(vinyl alcohol) (PVA) was investigated under different conditions by respirometric determinations, iodometric analysis, and molecular weight evaluation. Microbial inocula derived from the sewage sludge of municipal and paper mill wastewater treatment plants were used. A rather active PVA-degrading bacterial mixed culture was obtained fr om the paper mill sewage sludge. Significant biodegradation levels within quite short incubation times were obtained in liquid cultures in the presence of acclimated microbial populations. The influence of some polymer properties such as molecular weight and degree of hydrolysis on the biodegradation rate and extent was investigated in the presence of either the acclimated mixed bacterial culture or its sterile filtrate. Kinetic data relevant to PVA mineralization and to the variation of PVA concentration, molecular weight, and molecular weight distribution revealed a moderate effect of the degree of hydrolysis. The molecular weight appeared to be not a limiting factor of microbial attack. Comparison of the degradation process in the presence of either bacterial cells or their culture filtrate highlighted the ability of some microbial strains to utilize polymer chains having 5-10 kD molecular weight. This result suggests the occurrence of two PVA degradation mechanisms: a random-type attack and a terminal unzipping depolymerization process of polymer chains
Reference procedure definition for accumulation chamber measurements of landfill cover emissions through field experimental campaigns.
No full textA new respirometric test simulating soil burial conditions for the evaluation of polymer biodegradation
No full textA new convenient and reliable method is described for assessing the biodegradation properties of polymeric materials under simulated soil burial conditions, which makes it possible to test with nutrient-rich soils. This method consists of the utilization of a minimum amount of a soil layer, in which the samples to be tested are set in close contact, sandwiched between two layers of perlite, a natural porous aluminosilicate. The biodegradation level is monitored by determining the carbon dioxide evolution derived from the test samples. The limited amount of soil used limits carbon dioxide evolution from the blanks, due to the corresponding limited overall amount of soil carbon. This experimental setup allows for an extremely satisfactory level of confidence in the analytical results, permitting a wider variety of soil types to be tested
Management conditions and diffused gas emission monitoring correlation in four non-hazardous waste landfills
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