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Item type:Publication, Access status: with files , Energetic evaluation of different flow sheet modifications of post-combustion CO₂ capture plant at coal and natural gas fired power plant for a generic improved solvent(2014-10); ; ; ; The post-combustion capture (PCC) technology is a promising possibility to reduce CO₂ emissions of fossil fuel fired power plants. One of the main concerns for the PCC is the loss in electric power output. A reduction in efficiency penalty for solvent based PCC can be achieved by improving the solvent properties as well as by improving the process design. There are many different process flow sheet modifications with an improvement in process design reported in literature. In this work two of these modifications for a capture plant are evaluated. To be able to compare these process modifications it is necessary to evaluate them on identical solvent and process conditions. The modified processes are compared to base cases processing the flue gas from a supercritical pulverised coal fired power plant as well as a natural gas combined cycle power plant. The solvent used in the capture plant is a generic improved solvent, representing possible future solvents. The main advantages of the flow sheet modifications are pointed out. Subsequent, the specific reboiler heat duty, the specific cooling duty and the specific auxiliary power for the capture plant are shown for the flow sheet modifications. The overall efficiency penalties for the flow sheet modifications are compared and differences are highlighted.Publicationtype: Conference PaperScopus© Citations 4 389 218 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Optimisation potentials for the heat recovery in a semi-closed oxyfuel-combustion combined cycle with a reheat gas turbineSemi-closed oxyfuel-combustion combined cycle plants are one possibility to realise CCS technologies with natural gas-fired power plants. Due to the recirculation of exhaust gas the working fluid in the gas turbine consists mainly of CO2. This leads to the necessity for an increased pressure ratio to achieve the efficiency and the exhaust gas temperatures of conventional gas turbines. In this work a conventional natural gas-fired combined cycle plant with a reheat gas turbine modified for oxyfuel operation will be presented. As it is assumed that the necessary pressure ratio is not realisable with axial compressors two different scenarios are considered. On the one hand the pressure ratio is the same as in the conventional process and on the other hand the pressure ratio is set to an assumed maximum of 60. The exhaust gas temperature lies significantly above the values of the conventional plant. Generally the higher pressure ratio results in a higher net efficiency of the plant. An unchanged heat recovery process results in a loss of efficiency of at least 9.3 to 10.8 %-pts. depending on the pressure ratio. Increasing the steam parameters can achieve a reduction of this loss ranging from 0.5 %-pts for the high pressure ratio to 1.0 %-pts for the low pressure ratio. An alternative approach for the heat recovery is the application of an internal recuperator in the gas turbine. When the achievable pressure ratio is far from the optimum value, as in the low pressure ratio case, this approach can lead to significantly lower losses of 9.1 %-pts. With a higher pressure ratio the effects of the optimisation options are similar.Publicationtype: Conference PaperScopus© Citations 9 316 235 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Benchmarking and comparing first and second generation post combustion CO₂ capture technologies(Elsevier, 2014-10); ; ; ; The Octavius FP7 project focuses on demonstration of CO2 capture for zero emission power generation. As part of this work many partners are involved using different rate based simulation tools to develop tomorrow's new power plants. A benchmarking is performed, in order to synchronize accuracy and quality control the used modeling tools. The aim is to have 6 independent partners produce results on simulation tasks which are well defined in this work. The results show the performance of a typical simulation tool ranging from in-house process simulator to Aspen Plus® and combination of the two, using CAPE-Open. Definitions of the models are outlined describing the used assumptions on mass transfer correlations, hydraulics, thermodynamic models, kinetics, and property packages. A sensitivity study is carried out for absorption and desorption which shows the performance of capture percentage, specific reboiler duties, loading of rich and lean solutions, pressure drop, flooding, concentration and temperature profiles, product purity, and condenser performance. The overall conclusion is that most predicted properties vary in the order of 5-10% percent, often more than accuracy in experimental pilot plant measurements. There is a general good resemblance between modeling results. A few important properties like specific reboiler duty and reboiler temperature plus concentration and temperature profiles vary more than expected. Also high flooding scenarios in the stripper are difficult cases. Efficiencies are discussed as part of the summary. Recommendations for modeling principles and best practice are given.Publicationtype: Conference PaperScopus© Citations 16 264 160 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , The coal-fired Oxyfuel-process with additional gas treatment of the ventgas for increased capture ratesThe Oxyfuel-process could be a solution to lower the high specific CO2 emissions of coal-fired power plants. The carbon capture rate (CCR) in current research is usually set to 90% due to the increasing specific energy demand of the capture process (GPU) and lower CO2 purity of the product stream at higher CCR. The remaining CO2 and most of the impurities escape to the environment with the ventgas downstream of the GPU. In current literature it is recommended to increase the CCR from 90% to higher values of up to 98-99%. This can be achieved by adding an additional gas treatment to capture the CO2 contained in the ventgas downstream of the GPU. At high CCR like 99% the necessary recycle of the captured CO2 into the basic GPU process leads to an increase of the specific energy demand of the GPU and an efficiency decrease of the overall process. It is possible to lower this efficiency penalty by recycling the remaining impurities downstream of the additional gas treatment to the ASU to regain the contained oxygen. The feasibility of the recycle strongly depends on the capture rate of the additional gas treatment, because it influences the CO2 concentration in the recycled exhaust gas. In this work an overall process of a coal-fired Oxyfuel power plant with cryogenic ASU and externally cooled GPU as a basic process is modelled. This process is adapted to higher CCR by adding an additional gas treatment by a polymeric membrane (PM) downstream of the GPU. The ASU is modelled as a triple column process. This process enables an exhaust gas recycle downstream of the PM. The GPU is a two stage partial condensation. Furthermore the influence of the additional gas treatment on the GPU process and the overall process for different CCR is examined and the resulting exhaust gas concentrations are calculated to evaluate the possibility for an exhaust gas recycle. This evaluation is necessary, because the remaining CO2 in the exhaust gas that is recycled to the ASU has to be removed upstream of the ASU. This leads to an additional energy demand to regenerate the molecular sieves upstream of the ASU.Publicationtype: Conference PaperScopus© Citations 5 303 300