Primary Energy Consumption For CO2 Research Articles

Lignite-fired air-blown IGCC systems with pre-combustion CO2capture

Detailed analyses based on mass and energy balances of lignite-fired air-blown gasification-based combined cycles with CO2 pre-combustion capture are presented and discussed in this work. The thermodynamic assessment is carried out with a proprietary code integrated with Aspen Plus® to carefully simulate the selective removal of both H2S and CO2 in the acid gas removal station. The work focuses on power plants with two combustion turbines, with lower and higher turbine inlet temperatures, respectively, as topping cycle. A high-moisture lignite, partially dried before feeding the air-blown gasification system, is used as fuel input. Because the raw lignite presents a very low amount of sulfur, a particular technique consisting of an acid gas recycle to the absorber, is adopted to fulfill the requirements related to the presence of H2S in the stream to the Claus plant and in the CO2-rich stream to storage. Despite the operation of the H2S removal section representing a significant issue, the impact on the performance of the power plant is limited. The calculations show that a significant lignite pre-drying is necessary to achieve higher efficiency in case of CO2 capture. In particular, considering a wide range (10–30 wt.%) of residual moisture in the dried lignite, higher heating value (HHV) efficiency presents a decreasing trend, with maximum values of 35.15% and 37.12% depending on the type of the combustion turbine, even though the higher the residual moisture in the dried coal, the lower the extraction of steam from the heat recovery steam cycle. On the other hand, introducing the specific primary energy consumption for CO2 avoided (SPECCA) as a measure of the energy cost related to CO2 capture, lower values were predicted when gasifying dried lignite with higher residual moisture content. In particular, a SPECCA value as low as 2.69 MJ/kgCO2 was calculated when gasifying lignite with the highest (30 wt.%) residual moisture content in a power plant with the advanced combustion turbine. Ultimately, focusing on the power plants with the advanced combustion turbine, air-blown gasification of lignite brings about a reduction in HHV efficiency equal to almost 1.5 to 2.8 percentage points, depending on the residual moisture in the dried lignite, if compared with similar cases where bituminous coal is used as fuel input. Copyright © 2016 John Wiley & Sons, Ltd.

CO2 capture in integrated steelworks by commercial-ready technologies and SEWGS process

Integrated steelworks are a significant source of anthropogenic CO2 emissions. In integrated steelworks, which are large stationary plants suitable for application of carbon capture processes, a large fraction of total CO2 is emitted from the power plant, where carbon-rich blast furnace gas (BFG) and other steel mill off-gases are burned to produce electricity by means of a steam cycle or a gas-steam combined cycle. One option to considerably reduce CO2 emission from integrated steelworks without affecting the main iron and steel manufacturing process is hence to apply carbon capture and storage (CCS) technologies on the power plant section either in pre-combustion or in post-combustion configurations.The aim of the present paper is to assess the potential of Sorption Enhanced Water Gas Shift (SEWGS) process for pre-combustion CO2 capture from steel mill off-gas fed to the power plant. The application of the SEWGS process on steel mill off-gas is here investigated and compared to reference monoetanolamine (MEA) and methyldiethanolamine (MDEA) based post-combustion and pre-combustion absorption processes. Different configurations, both for SEWGS and MEA-based cases, have been evaluated and compared from the energy and the environmental point of view. Technical issues associated to the use of the unconventional fuels in state-of-the-art turbines and the effects of steel mill gas blending with natural gas are also discussed.From the mass and energy balances, results show that the MDEA and SEWGS-based plants allow achieving high CO2 capture efficiencies (of the order of 85–90%), while MEA-based plants need a significant additional heat input through natural gas blending to achieve high capture levels. In terms of efficiency and specific primary energy consumption for CO2 avoided (SPECCA), the SEWGS technology with the most advanced sorbent developed allows achieving the highest efficiencies (about 37.7%) and the lowest SPECCA (around 2.2 MJ/kgCO2) among the cases assessed.

Ultra-high CO2 capture efficiency in CFB oxyfuel power plants by calcium looping process for CO2 recovery from purification units vent gas

This work presents a new option for the recovery of the CO2 losses from CO2 purification units in oxyfuel plants, by means of the Ca-looping process. The idea is to capture the CO2 in the vent stream from purification units by reaction with CaO sorbent in a carbonator reactor, where CaCO3 is formed. Sorbent is then regenerated in a calciner reactor by oxyfuel combustion of a fraction of the coal fed to the power plant. Since the Ca-looping process requires a continuous purge of exhaust sorbent and make-up of fresh limestone, the system is best coupled with a CFB boiler, where the exhausted Ca-rich sorbent can be used for in-furnace sulfur absorption.In this work, detailed mass and energy balances of the system proposed are reported, including a preliminary sizing of the reactors of the Ca-looping unit. A sensitivity analysis was also performed, by considering two types of coal as feed (mainly differing in sulfur content), two levels of non-condensable gases in the impure CO2 stream to be purified and different behaviors of the exhausted Ca-based sorbent injected in the CFB boiler, where it can experience different levels of recarbonation.Interesting results were obtained for this new system, which can capture about 90% of the CO2 vented from the purification unit in a reasonably compact reactors system, allowing an overall CO2 avoidance of the order of 99% with respect to conventional coal-fired steam plants without capture. As far as energy penalties are concerned, they were evaluated by the specific primary energy consumption for CO2 avoided index (SPECCA). Small differences with respect to reference oxyfuel plants without CO2 recovery were obtained, with either slightly better or slightly worse performances, depending on the sulfur content of the coal used. Penalties are associated to the export of CaO in the final exhausted sulfated sorbent from the CFB boiler, which increases when a higher sulfur coal is used. However, experimental analysis on the recarbonation level which can be attained by the CaL exhaust sorbent in the CFB boiler and further process optimization are needed to correctly account for these penalties and possibly minimize them.

CO2 capture in natural gas combined cycle with SEWGS. Part A: Thermodynamic performances

An innovative process for CO2 capture named SEWGS (sorption enhanced water gas shift) was investigated from technical and economic point of view when applied to natural gas power plants. This activity was carried out under the FP7 project CAESAR financed by the EU community. The SEWGS working conditions were optimized in terms of carbon capture ratio and purity of the CO2 separated as well as number of vessels adopted. Moreover, two different types of sorbent, Sorbent Alfa and Sorbent Beta, were considered in order to evaluate the impact of sorbent cyclic capacity on system performances. Results show that SEWGS with Sorbent Alfa can avoid 91% of CO2 emissions reducing the efficiency penalty of amine scrubbing technologies from 8.4% to 7.2%with a CO2 avoided of 91%. No significant impact of CO2 purity on system performances was determined.The adoption of Sorbent Beta, which has an improved capacity of 60% than Sorbent Alfa, can further reduce specific primary energy consumption for CO2 avoided together with vessel number.The best overall performance in terms of specific primary energy consumption for CO2 avoided has a net electrical efficiency of 51.93% and CO2 avoided of 86%. Part B presents the economic assessment of the investigated cases together with three reference cases selected for electricity production with and without CO2 capture in order to benchmark the innovative solution.

97/01313 A solar thermochemical power plant using ammonia as an attractive option for greenhouse-gas abatement

This work deals with CO2 capture plants for an advanced air-blown gasification-based combined cycle where a coal with high sulphur content, which is really relevant for the coal market, is used as feedstock. The sulphur removed as H2S from the coal-derived gas enters a wet sulphuric acid process. Later, the resulting acid is used to control ammonia slip in a post-combustion CO2 capture plant based on ammonia scrubbing and designed for a reduced energy demand. Thus, limiting the energy impact of the CO2 capture technology will improve the power plant efficiency, according to a presumable lower cost of the generated electricity, as a high-sulphur coal is used as fuel input.In detail, a cooled ammonia-based process is found to be more attractive than a more conventional chilled ammonia-based solution: in case of 90% of CO2 avoided, the overall power plant efficiency is equal to 41.7% and the SPECCA (specific primary energy consumption for CO2 avoided) as low as 2.3MJ/kgCO2. Moreover, the calculation results show the SPECCA for CO2 avoided ranging from 80% to 90% is almost constant, even though the power plant efficiency increases if lower levels of CO2 capture are considered.