ALes gaz issus des procédés de pyrolyse-gazéification de la biomasse doivent être épurés. Ils contiennent des vapeurs condensables (goudrons), des aérosols, des particules solides fines, des composés soufrés et des métaux alcalins qu’il s’agit d’éliminer avant leur utilisation sur des turbines (production d’électricité) ou comme gaz de synthèse. Les expériences rapportées dans ce travail concernent les vapeurs condensables et leur conversion par craquage thermique. Les vapeurs sont produites par pyrolyse de la biomasse dans un premier réacteur (RP) à 540°C. Elles sont ensuite craquées dans un réacteur parfaitement auto-agité par jets gazeux (RPAA) associé en série avec le RP. Le RPAA fonctionne à plus haute température (550-1030°C) et le temps de séjour de la phase gazeuse dans le craqueur est compris entre 0,1 et 1 s. Tous les produits de réaction (charbon, vapeurs condensables et gaz permanents) sont récupérés et analysés. Le RPAA étant uniforme en température et en concentration, la détermination de constantes de vitesse à temps de séjour donné est assez aisée à partir de bilans de matière en vapeurs et gaz. Des schémas réactionnels globaux rendant compte du craquage des vapeurs en gaz mais aussi de leur possible maturation en composés plus réfractaires sont proposés et leurs constantes de vitesse optimisées à partir des résultats expérimentaux. Ces modèles permettent de simuler le craquage thermique d’une charge type issue d’un gazogène. On détermine les conditions optimales de fonctionnement (température, temps de séjour) du réacteur de craquage qui aboutissent à une concentration en vapeurs condensables la plus faible possible. On comparera ainsi l’efficacité du craquage thermique à celle des autres procédés d’épuration des goudrons. / Pyrolysis and gasification processes give rise to gases containing by-products such as condensable vapors (tars), aerosols, dust, sulfur compounds and inorganics which may considerably lower the efficiency of catalysts (if chemical synthesis is foreseen) or cause severe damages to motors and turbines (in case of electricity production). Hence, efficient gas treatments are needed. The experiments reported in the present work are related to thermal cracking of condensable vapors. These vapors are produced in a first reactor by biomass pyrolysis (PR) at 540°C. They undergo further cracking in a second vessel, a continuous serf stirred tank reactor (CSSTR), assembled in series with the PR. The CSSTR is operated at temperatures ranging from 550 to 1030°C and gas phase mean residence times ranging from 0,1 to 1 s. Reaction products (char, condensable vapors and permanent gases) are recovered and analyzed. Temperature as well as composition are uniform at any point of the CSSTR. Therefore, it is easy to derive values of kinetic constants from mass balances at a given residence time. Global vapor cracking schemes including gas formation as well as possible maturation into more refractory compounds are proposed. Their kinetic constants are optimized from the experimental results. These models are used to simulate the thermal cracking of a typical load flowing out from a gasifier. Optimal operating conditions of the cracking reactor (in terms of temperature and residence time) are determined to reach the lowest condensable vapors concentration. Thus, efficiency of thermal cracking can be compared to other gas treatment processes.

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<p>The present work is focused on the synthesis of small-scale (modular processes) to produce olefins from light alkane resources in shale gas.</p> <p>Olefins, which are widely used to produce important chemicals and everyday consumer products, can be produced from light alkanes - ethane, propane, butanes etc. Shale gas is comprised of light alkanes in significant proportion; and is available in abundance. Meanwhile, shale gas wells are small sized in nature and are distributed over many different areas or regions. In this regard, using shale gas as raw material for olefin production would require expensive transportation infrastructure to move the gas from the wells or local gas gathering stations to large central processing facilities. This is because existing technologies for natural gas conversions are particularly suited for large-scale processing. One possible way to take advantage of the abundance of shale resource for olefins production is to place small-sized or modular processing plants at the well sites or local gas gathering stations.</p> <p>In this work, new process concepts are synthesized and studied towards developing simple technologies for on-site and modular processing of light alkane resources in shale gas for olefin production. Replacing steam with methane as diluent in conventional thermal cracking processes is proposed to eliminate front-end separation of methane from the shale gas processing scheme. Results from modeling studies showed that this is a promising approach. To eliminate the huge firebox volume associated with thermal cracking furnaces and allow for a compact cracking reactor system, the use of electricity to supply heat to the cracking reactor is considered. Synthesis efforts led to the development of two electrically powered reactor configurations that have improved energy efficiency and reduced carbon footprints over and compare to conventional thermal cracking furnace configurations.</p> <p>The ideas and results in the present work are radical in nature and could lead to a transformation in the utilization of light alkanes, natural gas and shale resources for the commercial production of fuels and chemicals.</p>