Studies On Nuclear Hydrogen Production By Steam Coal Gasification In Argentina.

FOUGA G. G.; NASSINI H.; NASSINI D.; BOHÉ A. E

Viena

Encuentro; IAEA´s Technical Meeting to Examine the Role of Nuclear Hydrogen Production in the Context of Hydrogen Economy.; 2017

International Atomic Energy Agency

            In thepresent framework of worldwide reevaluation of nuclear energy, the hydrogenproduction using nuclear energy is receiving a great attention, since thedemand of hydrogen is rapidly increasing as a result of decreased availabilityof light crude oils that do not require extra H2 for conversion togasoline, with a corresponding increased use of heavy crude oils that requiremassive amounts of H2 for conversion to gasoline. Furthermore, ifthe cost goals for automotive fuel cells are reached, the transportation sectormay be also fueled by H2 in the near future in which case the H2consumption is expected to grow one of two orders of magnitude over a period ofseveral decades. The current and projected H2 demands aresufficient to justify massive investments in new methods to produce H2that would be more cost-efficient than the actual large-scale productionmethods.            Coal gasification technologies offer the potential ofa cleaner and more efficient energy than conventional combustion processes.Nuclear coal gasification is a process that uses nuclear energy for providingindirect heating to the gasification reactors, in order to replace the partialcombustion of the feed material that is needed to drive the endothermicgasification reactions, contributing then to the saving of fossil fuelresources and lowering the specific carbon emissions to the environment.            Argentinais presently exploring the application of nuclear coal gasificationtechnologies to domestic solid fuel materials such as a low-rank coal extractedfrom the Río Turbio minefield, asphaltites and petroleum residues. Since thechemical composition, the heating value and, then, the future use of thesynthesis gas produced by the gasification process are strongly dependent onthe solid fuel composition and rank, the gasification technology to be appliedshould be primarily matched to the properties of the feed material availablefor gasification.            Inthis framework, a comprehensive research program is being implemented tocharacterize the behaviour of our domestic solid fuels under typicalgasification conditions, with the objective of identifying the most suitablegasification process to be implemented for nuclear hydrogen production. Theresearch program comprises both theoretical and experimental studies onlaboratory scale which were designed to provide the necessary information aboutthe fundamental mechanisms and kinetics of gasification reactions, as aprevious step for a further scaling up of experimental facilities.            Inorder to simulate properly the gasification conditions occurring in alarge-scale commercial gasifier and, then, achieve the kinetics/mechanism ofthe gasification, it is essential to reproduce, at least: (1) the rapid heatingof solid fuel particles, and (2) the gas convection around individual particleswith definable intensity. The experimental approach followed to achieve bothobjectives is the so-called two-stagesexperiments in which the gasification reactivities are measured on charsamples prepared in a previous pyrolysis step under inert atmosphere, wheresolid fuel particles are heated in a drop tube furnace at high-heating ratesand short residence times.            Inthis reasearch, recent results of studies on gasification of Argentine solidfuels in presence of steam and CO2 as gasifying agents arepresented. The kinetics of the CO2 gasification has been studied bythermogravimetry between 800 and 950 ºC and CO2 partial pressuresfrom 28 to 82 kPa, using isothermal and non-isothermal measurements to studythe influence on the reaction rates of several parameters such as the gaseousflow rate, sample mass, temperature, and CO2 partial pressure. Theexperimental conditions under which the reaction rate is controlled by chemicalreaction were established for the setup used, and a theoretical model todescribe the evolution of the reaction degree as a function of time wasdeveloped.            Steamgasification was also investigated using a specially designed experimentalsetup, which is able to produce different partial pressures of steam.Gasification reactions were produced in a tubular flow reactor heated by anelectrical furnace that can reach temperatures up to 950 ºC. The overallreaction rates under different experimental conditions of gaseous flow rate andsample mass were determined by following the temporal evolution of the gaseousproduct concentration by gas chromatography.             Finally,based on own capabilities developed for more than 50 years in CNEA, relatedwith both nuclear and hydrogen technologies, the production of hydrogen byusing nuclear energy is being seriously considered as an alternative for thecountry, with the conviction that nuclear production of hydrogen has thepotential to contribute significantly to the national energy supply in asustainable, competitive and environmentally friendly manner.