Modeling and Evaluation of a Coal Power Plant with Biomass Cofiring and CO2 Capture

Coal-fired power plants are the largest source of anthropogenic carbon dioxide (CO2) emissions into the atmosphere, with more than 9.5 billion tonnes of CO2 emitted annually. In order to mitigate the emissions of CO2 from coal-fired plants, several measures were proposed, such as increasing the efficiency of the plants, cofiring biomass with coal, and capturing and storing CO2 deep underground. Among these measures, the use of biomass, which is considered one of the most cost-effective renewables and, in addition, carbon neutral, combined with CO2 capture and storage will play an important role toward reducing the fossil-based CO2 emissions. In this study, we investigated in detail the performances of pulverized coal combustion plants with direct cofiring of biomass and integrated with an amine-based postcombustion capture technology. All the systems were modeled and simulated using the process simulation software Aspen Plus. The results indicate that cofiring 10% of biomass in a coal-based power plant only slightly affects the energy performance of the plant, reducing the net efficiency by 0.3% points. The addition of an amine capture system to both the coal-fired and biomass cofiring plants further reduces the efficiency of the plants by more than 10% points. Analyzing the effect of various CO2 capture process parameters on the heat, solvent and cooling water requirements, and on the overall plant performance, it was found that the concentration of amine in the solution is the most important parameter. The results showed that the net electrical efficiency increases for systems using higher amine concentrations. Further, we investigated the effect of systems with lower heat requirement for solvent regeneration on the plant gross/net power output and also analyzed the plant performances under a flexible CO2 capture efficiency

Environmental management of the sewage sludge: case study – the wastewater treatment plant of Timisoara

Kad govorimo o otpadu iz kanalizacije mislimo na suvišni otpad iz postrojenja za preradu otpadnih voda. EEC Uputstvo 91/271, koje se odnosi na preradu otpadnih voda u gradovima, modificirano EEC Uputstvom 98/15 primjenjuje se i u Rumunjskoj. Prema njemu do 31. prosinca 2018. sva mjesta s populacijskim ekvivalentom (p.e.) većim od 2000 moraju imati mreže kanalizacije i postrojenja za preradu otpadnih voda u kojima će se nastale otpadne tvari ekološki tretirati. Potrebno je stoga hitno primijeniti strategiju ekološkog gospodarenja otpadnim vodama. Ekološke studije o upravljanju kanalizacijskim otpadom u kratkom (2013), srednjem (2020) i dugom (2040) vremenskom periodu su u EU provedene 2008. godine, a u Rumunjskoj 2012. I u EU i u Rumunjskoj osnovna opcija je korištenje otpadnih tvari kao organskih gnojiva na poljoprivrednim površinama, ali i njihovo korištenje kao izvora energije dobivene izgaranjem. Za učinkovito upravljanje, i u jednom i u drugom slučaju potrebno je odstranjivanje vode i sušenje. Tako će se količina taloga smanjiti, troškovi prijevoza i skladištenja znatno reducirati, a niža vrijednost topline (ul) će porasti. Glavni je zaključak da treba podržati ideju o potrebi prethodne provjere iznosa udjela termodinamičke energije u kanalizacijskom otpadu kako bi se prikazala i odabrala globalna vizija postupka te osigurao razvoj optimalnog iznosa energije i postupci obrade ekološki prihvatljivi.When we talk about the sewage sludge, we refer to the excess of the sludge resulting from the wastewater treatment plants. The EEC Directive 91/271, referring to the Urban Waste Water Treatment, modified by the EEC Directive 98/15 is implemented in Romania also. This requires that until 31 December 2018, all localities with more than 2000 population equivalent (p.e.) must be served by sewerage networks and wastewater treatment plants where the resulting sludge should be managed ecologically. Therefore it is necessary to implement urgently an environmental management strategy of the sludge. The ecological studies on the sewage sludge management in short (2013), medium (2020) and long (2040) term were made in the EU in 2008 and in Romania in 2012. Both in the EU and in Romania the main option is to use the sludge on agricultural land as organic fertilizer but also to use the sludge as an energy source recovered by combustion. For an efficient management, in both cases there is a need for the sludge dewatering and drying. Thus the sludge volume will decrease, the transport and storage costs will be significantly reduced, and the lower heat value (ul) will increase. As a main conclusion one will support the idea that it is necessary to make a preliminary assessment of the thermodynamic energy content of the sewage sludge in order to depict and select the global vision of the process, assuring both the optimal energy development and environmental friendly treatment processes