Biomass to oil : fast pyrolysis and subcritical hydrothermal liquefaction

International audienceThe present abstract deals with the comparison of two biomass-to-oil processes: fast pyrolysis and subcritical hydrothermal liquefaction. Using the same biomass (beech sawdust), fast pyrolysis was led thanks to the cyclone reactor (wall temperature between 870 and 1040 K) and subcritical hydrothermal liquefaction thanks to a 150-ml-batch-reactor (temperature between 420 and 600 K). Mass balances and analysis (ultimate analysis, HHV, pH, Karl-Fischer, gas chromatographies, H 1 NMR) allow the comparison of both processes and the characterization of the main fractions of pyro-oils (heavy oils, light oils and aerosols) and liq-oils (heavy oils and water soluble organics)

Les procédés de gazéification comme alternative pour la valorisation de boues de stations d'épuration des eaux usées

International audienceThe problem of wastewater treatment plant sewage sludge is becoming crucial. Indeed the quantity of sewage sludge will increase with the population and the economic developments, the rise of the number of treatment plants and their better performance. Sewage sludge treatment is at the moment realized in limited ways. Whatever the future of those ways and without creating polemics, they will not be able, to absorb this increasing volume. It consequently becomes necessary to diversify the methods of treatment to answer the problems arising from the management of this waste. Within this framework, the new thermochemical ways of treatment by valorization seems more interesting. Indeed, they present in addition to the advantage of the possibility of processing, the capacity to easily produce "storable" and valuable compounds. Thus will treat, in this article, the interest to develop the processes of gasification of waste water sewage sludge.Le devenir des boues de stations d'épuration des eaux usées (Step) est un problème crucial posé aux pays industrialisés. En effet la quantité de boues produite en Step ne va cesser d’augmenter avec les croissances démographique et économique, ainsi que le nombre et la performance des Step des eaux usées. Actuellement, le traitement des boues de Step se fait par différentes filières, dont le nombre est limité. Quel que soit le devenir de ces filières et sans créer de polémiques particulières elles ne pourront, dans tous les cas, pas absorber ce volume croissant. Il devient dès lors nécessaire de diversifier les méthodes de traitement pour répondre aux problèmes posés par la gestion de ce déchet. Dans ce cadre, les nouvelles filières de traitement par valorisation thermochimiques semblent des plus intéressantes. En effet, elles présentent en plus de la capacité de traitement, l’avantage de produire des composés « stockables » et facilement «valorisables». Nous traiterons ainsi, dans cet article, de l'intérêt de développer les procédés de gazéification des boues de Step

Modélisation de la gazéification de boues de station d’épuration dans un réacteur à lit fluidisé

International audienceno abstrac

Sewage sludge valorisation for the mechanical energetic needs of a wastewater treatment plant

International audienceno abstrac

Dynamic optimization of heat exchanger using entropy generation minimization

International audienceIn order to reduce fossil fuel consumption for heat and cold generation, different lowtemperature heat sources have been considered for heat pump operations such as sewagesystems, sea water, ground water and drinking water. Raw water systems can also beused as a heat source for heat pump, heat sink for chiller, or for direct cooling. These systemsrepresents a high thermal potential for some clients, according to their activity. In this study,the thermal potential of a raw water system (made up of 5000 km of piping and carrying 200million m3 annually in the south of France) is investigated. To this day, this source has notbeen used. The main problem is the optimisation of the equipment sizing according to thetemporal variability of water flow, temperature and heat (or cold) demand. The dynamicbehaviour of heat exchanger between network and user is the key parameter to enhance theperformance of the system.For the raw water source, temperature, flow, and heat demand are highly time dependent.The method is based on the minimization of entropy generation in the heat exchangersbetween the water pipes and the users. The optimisation of the sizing and the location indicatewhere to install direct heat exchange systems. In order to calculate entropy generation in theheat exchanger, a dynamic model of a simple heat exchanger (concentric tube) is developed.It determines the pressure and temperature profile along the heat exchanger according to time.Temperature is calculated for water and for the heat exchanger partition wall. By integratingthe terms of entropy generation due to temperature difference and to pressure drop along theheat exchanger, the value of total entropy generation is obtained under transient operation.Total entropy generation is used as an objective function to optimize heat exchanger geometry(length and diameters) and control mechanism.The method has been used to model direct cooling of a datacenter using a raw waternetwork as a heat sink. Optimization is done considering a year of operation; seasonal anddaily fluctuations for water flow and temperature are considered. Results show that entropygain is important when the heat exchanger optimal size is chosen. The use of the raw waternetwork connected to reversible heat pump for building heating and cooling have also beenstudied and achieves high gain compared to air-source heat pump

Influence of mineral matter on sewage sludge thermo chemical conversion kinetics obtained by TGA-FTIR analysis

International audienceno abstrac