Coal-fired power plant with calcium oxide carbonation for postcombustion CO2 capture

n/

Experimental investigation on free surface vortices driven by tangential inlets

Particle Image Velocimetry (PIV) measurements have been carried out in order to analyze the structure of free surface vortices in a promoting geometry with two tangential inlets. Velocity fields associated to the free surface vortex have been obtained at different horizontal planes and Reynolds numbers. Average velocity fields have been calculated and tangential velocity profiles have been compared at different vortex stages and measurement planes. The results show that tangential flow is uniform along the vortex axis and it scales well with the average exit velocity. The tangential velocity profiles, in comparison to the potential behavior, show discrepancies especially at large distances from the vortex axis. Vorticity fields and circulation profiles have been also derived from the measured velocity fields and discussed. The circulation profiles increase along the vortex radius even at large distances from the vortex axis, so that the potential solution is not applicable at all. The comparison of tangential velocity and circulation profiles between promoted and free vortices, the last presented in a previous paper, shows that the tangential motion in a driven vortex is more intense and predominant over the sink effect (radial motion), except very close to the tank bottom, as in a forced configuration (i.e. rotating cylindrical tank)

Application of Sorption Enhanced Water Gas Shift for Carbon Capture in Integrated Steelworks

Abstract In integrated steelworks a large fraction of total CO2 is emitted from the power plant, where carbon- rich blast furnace gas (BFG) is burned to produce electricity by means of a steam cycle or a gas-steam combined cycle. The aim of the present paper is to assess the potential of Sorption Enhanced Water Gas Shift (SEWGS) process for CO2 capture from blast furnace gas. Firstly, a reference combined cycle applied to blast furnace steel plant is defined. Mass flow rate and composition of the steel plant off-gas used as fuel in the combined cycle have been derived from a large integrated steel plant. Then, the application of the SEWGS process is investigated and compared to a reference monoethanolamine (MEA)-based post-combustion absorption option. Two different SEWGS plant layouts are proposed together with two different sorbents. SEWGS achieves 85% of CO2 avoided with electric efficiency of 39% with the advanced sorbent

Zecomix: A zero-emissions coal power plant, based on hydro-gasification, CO2 capture by calcium looping and semi-closed high temperature steam cycle

n/

Impact probability computation of Near-Earth Objects using Monte Carlo Line Sampling and Subset Simulation

This work introduces two Monte Carlo (MC)-based sampling methods, known as line sampling and subset simulation, to improve the performance of standard MC analyses in the context of asteroid impact risk assessment. Both techniques sample the initial uncertainty region in different ways, with the result of either providing a more accurate estimate of the impact probability or reducing the number of required samples during the simulation with respect to standard MC techniques. The two methods are first described and then applied to some test cases, providing evidence of the increased accuracy or the reduced computational burden with respect to a standard MC simulation. Finally, a sensitivity analysis is carried out to show how parameter setting affects the accuracy of the results and the numerical efficiency of the two methods

CO2 Capture from Industrial Sources by High-temperature Sorbents

Among the emerging CO2 capture technologies, systems based on high temperature (HT) regenerable sorbents had a significant development in recent years. In addition to power plants, HT sorbents technologies can be particularly promising for CO2 capture in carbon intensive industrial processes such as cement plants, steel mills and hydrogen plants. Calcium looping (CaL) is a combined post-combustion and oxyfuel combustion technology which uses calcium oxide (CaO) as CO2 sorbent. In this process, CO2 in combustion flue gases is absorbed in a carbonator reactor by forming calcium carbonate (CaCO3) through the exothermic carbonation reaction. Carbonated sorbent is then regenerated to CaO through the reverse calcination reaction in a calciner, where reaction heat is provided by oxyfuel combustion. A CO2 concentrated stream is therefore released from the calciner, which can be purified and compressed as in conventional oxyfuel product gas. Calcium looping is particularly promising for application in cement plants, because the raw materials used for the production of clinker (the energy intensive process in cement manufacturing) are rich of CaCO3, which is also the starting material of the CaL CaO sorbent. Therefore, no additional material needs to be imported or is released as waste when CaL is integrated in a cement plant. Two main configurations can be assumed to integrate the CaL process into a cement burning line: (i) the tail-end configuration, where the CaL process is used as a post-combustion, end-of-pipe capture process and (ii) a highly integrated configuration, where the CaL reactors are integrated into the raw meal preheating tower of the clinker production process and the CaL oxyfuel calciner coincides with the raw meal pre-calciner. Another class of processes where CaO is used as CO2 sorbent is sorption enhanced reforming (SER) technologies, where CO2 is absorbed within a steam methane reforming (SMR) reactor. The advantage of this class of processes is that the heat released by sorbent carbonation reaction matches very well with the steam methane reforming reaction. Moreover, the removal of the CO2 reaction product allows a greater advancement of the reforming and water gas shift (WGS) reactions. As a result, with a SER reactor, a H2 production and CO2 separation are performed in a single adiabatic reactor operating at moderate temperature (~650°C) instead of a sequence of reactors for steam reforming (~900°C), WGS (200-400°C) and CO2 separation (~30°C) operating in a wide temperature range as in conventional H2 production processes. In addition to material development, the main challenge in SER technologies is in the endothermic sorbent regeneration step. Several process schemes have been proposed for sorbent calcination, such as: (i) oxyfuel combustion, (ii) high temperature heat exchangers, (iii) direct contact heating with hot solids from a chemical looping combustion loop. Both fluidized bed and packed bed reactors are proposed for SER processes operating at different temperature and pressure range. If a CO2 sorbent is active at intermediate temperatures (~400°C), such as in the case of hydrotalcite-based sorbents, it can be adopted in sorption enhanced WGS (SEWGS) processes. As in the SER principle, the in-situ removal of CO2 form the gas phase allows a higher advancement of the WGS reaction. Therefore, H2-rich gas production and CO2 separation can be performed in a single pressurized reactor. While this concept can be adopted in hydrogen production plants, a promising application is in steel mills, where most of the CO2 emissions are associated to the combustion of the blast furnace gas (BFG) in the steel mill power plant. BFG is a byproduct of the pig iron production process and is a low calorific value fuel rich of CO, CO2 and N2. By processing BFG in a SEWGS reactor, a H2-N2 stream is produced, which can be burned at high efficiency in a low emission combined cycle. CaL, SER and SEWGS processes illustrated above for CO2 capture in industry, are being developed in the three ongoing EU FP7 and H2020 projects Cemcap (G.A. 641185), Ascent (G.A 608512) and Stepwise (G.A. 640769). In this work, the potential of these processes in terms of CO2 capture efficiency and energy efficiency will be discussed and compared with benchmark technologies, based on process integration and simulation studies