1,721,295 research outputs found
Coal-fired power plant with calcium oxide carbonation for post-combustion CO2 capture.
No full textAbstractIn the plant configuration discussed in this paper, CO2 rich flue gas from an air fired coal boiler is contacted with CaO in a fluidized bed reactor (carbonator) generating CaCO3 and capturing more than 90% of the CO2 generated. Sorbent is regenerated in a second fluidized bed (calciner) via oxyfuel combustion of coal, generating a CO2 rich stream ready for compression and sequestration. Kunii–Levenspiel model, together with correlations for the estimation of sorbent performance after a number of carbonation–calcination cycles were used, in order to estimate carbonator dimensions and pressure losses. A net LHV efficiency of 37.4% was predicted for the selected reference case, with 97% of CO2 captured. As a comparison, for full oxy-combustion and amine based plants, net efficiency of 36.3% and 32.6% were obtained respectively
Zecomix: a zero-emissions coal power plant, based on hydro-gasification, CO2 capture by calcium looping and semi-closed high temperature steam cycle
No full textAbstractThis paper analyzes various aspects of the Zecomix cycle, a novel coal fired power plant, based on various innovative processes to achieve elevated efficiency and zero-emissions. A coal hydro-gasification process, using recycled steam and hydrogen as gasifying agents, converts carbon to CH4, which is then processed by two carbonator reactors where CH4, mixed with steam and contacted with calcium oxide, is converted to an H2/H2O based syngas while CO2 is absorbed by the solid sorbent generating CaCO3. The synthetic fuel produced in the chemical island is burned with oxygen in a semi-closed high temperature steam cycle, with a rather complex supercritical heat recovery steam cycle.The main relevant operating parameters for the chemical island are varied in order to evaluate their effect on plant performance and to optimize the process. In addition, the paper presents a rather detailed analysis of some critical issues, often neglected in previous works from the literature. Net plant efficiency of 44–47% with a virtually complete carbon capture was predicted, a very interesting results with respect to other proposed coal power plants with carbon capture. The high complexity of the chemical island and the importance of a good sorbent performance in the critical conditions typical of this plant should be however taken into account for a fair comparison with other plant concepts
Development of metal/ceramic membranes for hydrogen purification at medium/high temperatures
Full text linkThe aim of the PhD activity (completely developed at CNR-ICMATE, Padova Research Area) was the development of planar and thin membranes for hydrogen separation for high temperature processes (400°C, metal membranes) and medium temperature processes (< 150°C, zeolite membranes), supported by porous ceramic substrates. Metallic membranes were deposited by PVD processes and zeolite membranes were grown onto ceramic substrate by hydrothermal synthesis. Advantages of PVD techniques are exposed in the PVD chapter of the thesis. PVD deposition is particularly useful in case of metal alloys, since co-sputtering of metals can hinder the inter-metallics formation in the alloy and allows a fine tuning of the chosen stoichiometry.
A goal of the work was to develop new composite membranes combining porous substrates, having fine pore size and smooth surfaces, with a new deposition technique, HiPIMS (High Power Impulse Magnetron Sputtering), to deposit very thin and dense palladium-based membranes (Pd-Ag 77-23 wt%) to reduce the thickness and thus the palladium content, in order to fulfil the targets of the U.S. Department of Energy (DoE), in term of costs of membranes and hydrogen flux.
A further goal of the activity was the investigation of new and promising alloys, mainly palladium-free alloys, with a focus on vanadium based alloys, to meet the new guidelines established by European Community about critical elements. We studied a binary alloy (V90Pd10) and a ternary alloy (V84.2Ni10.5Ti5.3, an alloy whose properties have been predicted by a computational screening approach), both prepared for the first time by PVD processes (the main preparation process involve arc melting).
In order to compare different membranes and flow mechanism, a parallel research activity involved the preparation of thin membranes of zeolites, grown directly onto a porous ceramic substrate. Among the various zeolite structures available, hydroxy-sodalite is the best choice to prepare hydrogen separation membranes, thanks to the pore size compatible with the size of hydrogen molecule. Hydroxy-sodalite membranes are already reported in literature, but our aim was the preparation of reliable zeolite membranes in only one hydrothermal step, simplifying the synthetic approach.
Once membranes were prepared, hydrogen permeation measurements were performed in test station entirely developed at CNR-ICMATE (experimental layout and Labview interface), to gather information about the hydrogen permeance and H2/N2 selectivity of membranes
Ultra-high CO2 capture efficiency in CFB oxyfuel power plants by calcium looping process for CO2 recovery from purification units vent gas
No full textGenerazione di elettricità da gas naturale ad emissioni nulle di CO2 tramite Chemical Looping Combustion
No full textLONG-TERM COAL GASIFICATION-BASED POWER PLANTS WITH NEAR-ZERO EMISSIONS. PART A: ZECOMIX CYCLE
No full textLONG-TERM COAL GASIFICATION-BASED POWER PLANTS WITH NEAR-ZERO EMISSIONS. PART B: ZECOMAG AND OXY-FUEL IGCC CYCLES
No full textA thermodynamic study of a novel zero-emissions power plant, based on hydrogasification of coal
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Flexible sorption enhanced gasification (SEG) of biomass for the production of synthetic natural gas (SNG) and liquid biofuels: Process assessment of stand-alone and power-to-gas plant schemes for SNG production
No full textA flexible sorption enhanced gasification (SEG) process is assessed in this work, where CaO-based material circulating between gasifier and combustor reactors is adjusted for fulfilling the syngas composition requirements according to the downstream fuel synthesis process. A case study of a synthetic natural gas (SNG) production plant based on this SEG process is presented, which has been analysed under different conditions of gasification temperature or solid circulation. A possible integration of this plant with an electrolysis system for power-to-gas application for balancing the electric grid is also proposed and assessed. SNG production efficiencies as high as 62% (LHV-based) have been found for the production of SNG with final CH4 content of 98%. Excess energy recovered from the process streams can be used for producing electricity in a steam turbine, covering the electric demand in the plant. If credits associated to electricity production are considered, equivalent SNG production efficiencies higher than 70% have been calculated. Efficiencies reported in this work are in the upper limit of the range found in the literature for non-SEG concepts, which require an intermediate conditioning step of WGS and CO2 removal. When coupled with an electrolyser, power-to-gas efficiencies of about 60% have been calculated, in line with stand-alone power to gas methanation systems
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