This paper presents the results of thermodynamic and economic analysis of a coal-fired combined heat and power plant (CHP) working at supercritical parameters, integrated with a carbon dioxide capture unit based on membrane technologies. Two membrane system configurations are described, compared and optimized. Both consist of a twostage membrane unit, but in the first variant (Case 1) no recirculation is performed while in the second one (Case 2), retentate from behind the second membrane is recirculated before the first membrane. The economic analysis includes a comparison of the systems with a unit working without CO2 capture (reference unit). The main thermodynamic (annual generation of the products, efficiencies) and economic (break-even price of electricity, break-even price of membranes) indices are presented in this paper. The results show that the profitability of the investment in CHP units integrated with CO2 capture is strongly dependent on the annual operation time and price of emission allowances. Better thermodynamic and economic characteristics are obtained for the system with retentate recirculation than for the system without recirculation.
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In this paper the application and the performance of a membrane unit for preliminarily removing CO2 from the product gas mixture in the Oxidative Coupling of Methane (OCM) process based on a mini-plant scale experimental facility are presented and discussed. The model for the membrane unit is validated via experiments based on the comparison of concentrations and recoveries, respectively, with a brilliant agreement <5% under operating pressure up to 5 and 10 bar. It is found that the C2H4 loss rate could not be reduced less than 5% with the CO2 removal rate of 50% in a given membrane module. Since ethylene (C2H4) is the target product in OCM process, a two-stage membrane system is therefore proposed to enhance the C2H4 recovery. This configuration could further reduce the product loss rate while keeping the same CO2 removal rate as that of the single stage process.
PL
W artykule niniejszym zaprezentowano i omówiono zastosowanie oraz wydajność pojedynczej membrany dla wstępnego usuwania CO2 z mieszaniny gazowej w procesie oksydacyjnego sprzężenia metanu (OCM) w oparciu o skalę mini-aparatury doświadczalnej. Model pojedynczej membrany weryfikowany jest drogą eksperymentów opartych odpowiednio na porównaniu stężeń i odzysków przy bardzo dobrą zgodności <5% i ciśnieniu operacyjnym do 5 i 10 barów. Ustalono, że tempa strat C2H4 nie można ograniczyć o mniej niż 5% przy tempie usuwania CO2 wynoszącym 50% w danym module membrany. Ponieważ docelowym produktem procesu OCM jest etylen (C2H4), zaproponowano dwuetapowy system membranowy, który ma zwiększyć jego odzysk. Konfiguracja taka mogłaby w dalszej perspektywie zmniejszyć tempo strat produktu przy niezmienionym tempie usuwania CO2, właściwym dla procesu jednoetapowego.
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This paper deals with the construction of a CO2 membrane separation system and the fundamental processes at work. Results from research testing of membranes with low flows are discussed. The aim of the tests was to check the apparatus and how it performs for the needs of research into the characteristics of ceramic and polymer membranes with the use of gas-simulant mixtures of combustion gases - typical for power systems. Selected results of research into ceramic and polymer membranes conducted on the experimental stand are presented.
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