Search

Po Valley in Italy is characterized by severe air pollution problems in terms of particulate matter (PM) and nitrogen oxides (NOx). The study focuses on small mountain municipalities in this territory that are not connected to the natural gas grid and F-climate zones that are eligible for liquefied petroleum gas (LPG) subsidies. The sustainability of the main two residential heating fuel alternatives in the area (i.e., biomass and LPG) is investigated in terms of primary PM and NOx emissions by studying two emission reductions scenarios where the heating demand currently provided by solid biomass combustion is hypothesized to be covered with advanced wood pellet appliances or by LPG. The associated equivalent CO2 emissions are also calculated. The study concluded that the turnover of biomass appliances reduces significantly the PM emissions but may not be an effective way to reduce NOx emissions in the area. Gaseous fuel (e.g., LPG) combustion may bring more benefits in this respect. Both wood pellets and LPG cause fossil CO2 emissions to some extent. [ABSTRACT FROM AUTHOR]

The CLEANKER (CLEAN clinKER production by calcium looping process) project got EC support from October 2017 to September 2021 under the Horizon 2020 call LCE 29 – 2017. CLEANKER (www.cleanker.eu) aims at demonstrating at TRL7 (Technology Readiness Level) the Calcium Looping (CaL) concept in a configuration highly integrated with the cement production process, making use of entrained flow reactors. There are currently no feasible methods to produce clinker, and thus cement, without releasing CO2 from CaCO3, and, given the lifetime of a cement plant, the technologies to be developed have to be retrofittable. In addition to oxyfuel combustion and post-combustion solvent-based capture technologies, which have attracted most of the research efforts up to now, Calcium Looping is recognized as another very promising emerging technology for CO2 capture in cement plants. The core activity of the project is the design, construction and operation of a CaL demonstration system including the entrained-flow carbonator (the CO2 absorber) and the entrained-flow oxyfuel calciner (the sorbent regenerator). This demonstration system, connected to the Buzzi Unicem kiln of the Vernasca cement plant (Italy), will capture the CO2 from a portion of the flue gases of the kiln, using as CO2 sorbent the same raw meal that is used for clinker production. The CLEANKER implementation plan spans four years from October 2017 to September 2021.The project is in its crucial phase: the erection of the demo plant is going to be completed by the end of August 2020 and the experimental campaigns will start immediately after.

Chemical-Looping Combustion (CLC) is a process where fuel oxidation is carried out through an intermediate agent--a metal oxide--circulated across two fluidized bed reactors: a reduction reactor, where an endothermic reaction reduces the metal oxide and oxidizes the fuel, and an oxidation reactor, where an exothermic reaction oxidizes the metal oxide in air. Overall, the system carries out the same job of a conventional combustor, with the fundamental advantage of segregating the oxidation products (C[O.sub.2] and [H.sub.2]O) into an output flow free of nitrogen and excess oxygen. The flow exiting the reduction reactor consists of water and C[O.sub.2], the latter readily available for liquefaction, transport and long-term storage. The hot, vitiated air from the oxidation reactor is the means to produce power through a thermodynamic cycle. This paper reports of a study supported by the ENI group to assess the potential of the integration between CLC and combined gas-steam power cycles. More specifically, we focus on four issues: (i) optimization of plant configuration; (ii) prediction of overall efficiency; (iii) use of commercial gas turbines; (iv) preliminary economic estimates. The CLC system is based on iron oxides which, to maintain their physical characteristics, must operate below 900-1000[degrees]C. Given the crucial importance of the temperature of the vitiated air generated by CLC on the performance of the combined cycle, we consider two options: (i) 'unfired' systems, where natural gas is fed only to the CLC system, (ii) 'fired' systems, where the vitiated air is supplementary fired to reach gas turbine inlet temperatures ranging 1000-1200[degrees]C. Results show that unfired configurations with maximum process temperature 850-1050[degrees]C and zero emissions reach net LHV plant efficiencies ranging 43%-48%. Fired cycles where temperature is raised from 850 to 1200[degrees]C by supplementary firing can achieve 52% net LHV efficiency with C[O.sub.2] emission about one half of those of a state-of-the-art combined cycles. Fired configurations allow significant capital cost and fuel cost savings compared to unfired configurations; however, a carbon tax high enough to make them attractive (close to 50 [euro]/ton) would undermine these advantages. [DOI: 10.1115/1.1850501]

This paper assesses performances and economic viability of [CO.sub.2] removal by chemical absorption from the flue gases of natural gas-fired Combined Cycles, more specifically for two configurations: one where [C0.sub.2] is removed ahead of the stack without modifying the power cycle; the other where part of the flue gases is recirculated to the gas turbine, thereby reducing the flow to be treated by chemical absorption. In both cases sequestered [C0.sub.2] is made available at conditions suitable to storage into deep oceanic waters. Performances and cost of electricity are evaluated for systems based on large, heavy-duty turbines representative of state-of-the-art 'FA' technology. Carbon sequestration reduces net plant efficiency and power output by about 10 percent and increases the cost of electricity from 36 to about 50 mills/kWh. Flue gas recirculation warrants slightly higher efficiencies and lower costs. [C0.sub.2] removal is eventually compared with other strategies for the reduction of [C0.sub.2] emissions, like switching existing coal-fired steam plants to natural gas or replacing existing steam plants with conventional CCs. At current fuel prices the latter appears the option of choice, with a cost of about $25 per tonn of avoided [C0.sub.2] emission. [S0742-4795(00)02803-9]

Black liquor, the lignin-rich byproduct of kraft pulp production, is burned in boiler/steam turbine cogeneration systems at pulp mills today to provide heat and power for onsite use. Black liquor gasification technologies under development would enable this fuel to be used in gas turbines. This paper reports preliminary economics of 100-[MW.sub.e] scale integrated black-liquor gasifier/combined cycles using alternative commercially proposed gasifier designs. The economics are based on detailed full-load performance modeling and on capital, operating and maintenance costs developed in collaboration with engineers at Bechtel Corporation and Stone & Webster Engineering. Comparisons with conventional boiler/steam turbine systems are included. [S0742-4795(00)00402-6]