Obiettivo
A two-step scheme of the gas-to-liquid (GTL) process is proposed, which includes syngas (hydrogen + carbon monoxide) production as the first step followed by Fischer-Tropsch synthesis (FTS) as the second. Conventional catalytic technology, which is currently used in the first step has serious drawbacks because of relatively low specific productivity and high equipment costs. These problems maybe overcome by a novel plasma-catalytically chemical process of methane steam reforming, where a non-equilibrium plasma allows an attractive alternative forcing production. For the second stage of the process (FTS) we propose to study anew type of catalytic reactors - a reactor with a regular catalyst packing. We expect that this will dramatically improve the process productivity and avoid the problem of catalyst-product separation.
As part of the planned two-step Gas-to-liquid conversion process, plasma-catalytic steam reforming was achieved in three different plasma reactors. The results obtained in the project indicate that the non-equilibrium plasma can indeed enhance the methane partial oxidation (POM) or steam reforming (STM). However, for practical applications, further research and development towards lowering the specific energy requirement will be needed. Pulsed microwave plasma: methane partial oxidation into syngas was carried out with a pulse reactor and with a stationary coaxial reactor. At the stationary reactor conversion degrees of 60 - 80% were obtained at plasma energy cost of 0,7 - 0,9 KW·h/m3 syngas. At the pulsed reactor conversion were 40 - 55% at energy costs of about KW·h/m3. In the oxidation of methane, discharge influence is more efficient than thermal one, i.e. thermal heating with the same value of energy input does not have the same effect. Dielectric barrier discharge: The POM and steam assisted POM in a dielectric barrier discharge was considerably enhanced by the plasma at temperatures between 100°C and 400°C. This is considerably lower than in pure catalytic conditions. In POM the effect of the catalyst is solely to promote the oxidation of CO to CO2, without an effect on the methane conversion.
The results for steam-assisted POM indicate an activation of the Ni-catalyst at low temperatures and higher yields of hydrogen. Also the low energy requirement indicates a promising synergy between plasma activation and catalysis. Gliding discharge: The first studies indicated that the gliding discharges reactors must be improved in order to obtain better conversions. Nevertheless, selectivity was quite high (60-80%) at low energy costs (0.4 and 0.2 Wh/l H2). The second technical approach lead to a new three-phases reactor which has been proposed with good results, the conversion increasing up to 60% with an hydrogen production energy cost of 1-2 Wh/l of H2.We have modelled the chemical processes occurring in the gliding discharge reactor starting from conclusions drawn from our experimental studies. Taking into account the specific energy consumption, there are hopes that the final cost of the produced hydrogen could be lowered to about 0.1 /m3 which would become competitive with the classic technologies. Numerical modelling of plasma reforming: Both the simulation of steam conversion of methane and the methane reforming in air-steam mixtures assisted by the microwave discharge was carried out. Modelling of two types of experiments (pulse and continuous MW discharge) in respect of dependence of limits of methane-air-steam mixture ignition on air-methane stoichiometric ratio was made.
Simulations shown that plasma affects of chain propagation processes in methane oxidation. This leads to an essential acceleration of methane conversion in a preliminary stage and to a reduced ignition time of the mixture. The mechanism of chain methane decomposition by pure radical mechanism and by methane dissociation on the soot particles surface are in good agreement with experiments. It was shown that the continuous MW discharge stimulates methane conversion more then pulsed discharge. This is due to a different mechanism of active species generation in the streamer body. Fisher-Tropsch synthesis: Catalyst samples for the novel Regular Catalyst Packing Reactor (RCPR) were developed. The key technology, a permeable composite monolith (PCM) allows high catalyst loading and good temperature control and mechanical strength at reasonable permeability. The catalytic tests at laboratory scale showed a three times higher performance compared to a traditional slurry bed reactor design. A numerical model of a gas?to-liquid plant combining plasma reforming with RCPR- Fisher-Tropsch synthesis was developed.
Campo scientifico
- natural scienceschemical scienceselectrochemistryelectrolysis
- engineering and technologyenvironmental engineeringenergy and fuelsfossil energynatural gas
- natural scienceschemical sciencescatalysis
- natural scienceschemical sciencesorganic chemistryaliphatic compounds
- engineering and technologyenvironmental engineeringenergy and fuelsrenewable energyhydrogen energy
Argomento(i)
Data not availableInvito a presentare proposte
Data not availableMeccanismo di finanziamento
CSC - Cost-sharing contractsCoordinatore
17489 GREIFSWALD
Germania