Fidel Mato

Energetic approach of biomass hydrolysis in supercritical water.

Cellulose hydrolysis can be performed in supercritical water with a high selectivity of soluble sugars. The process produces high-pressure steam that can be integrated, from an energy point of view, with the whole biomass treating process. This work investigates the integration of biomass hydrolysis reactors with commercial combined heat and power (CHP) schemes, with special attention to reactor outlet streams. The innovation developed in this work allows adequate energy integration possibilities for heating and compression by using high temperature of the flue gases and direct shaft work from the turbine. The integration of biomass hydrolysis with a CHP process allows the selective conversion of biomass into sugars with low heat requirements. Integrating these two processes, the CHP scheme yield is enhanced around 10% by injecting water in the gas turbine. Furthermore, the hydrolysis reactor can be held at 400°C and 23 MPa using only the gas turbine outlet streams.

Vapor-liquid equilibrium data at 25°C for six binary systems containing methyl acetate or methanol, with dichloromethane, chloroform, or 1,2-trans-dichloroethylene

Isothermal vapor-liquid equilibrium (VLE) data, at 25° C were determined by a saturation method for each of the six methanol or methyl acetate binary systems with dichloromethane, chloroform, and 1,2-trans-dichloroethylene. The experimental data satisfy the Redlich-Kister consistency test, and were correlated with five Gibbs free energy models. All the binary mixtures of methanol with the chlorinated compounds exhibit strong positive deviations from ideality while the mixtures of methyl acetate with the chlorinated compounds present negative deviations from ideal behavior.

Vapor-liquid equilibrium data, at 298.15 K, for six binary systems containing methyl acetate or methanol, with acetonitrile, nitromethane or nitroethane

Abstract Martin, M.C., Cocero, M.J. and Mato, F., 1992. Vapor-liquid equilibrium data, at 298.15 K, for six binary systems containing methyl acetate or methanol, with acetonitrile, nitromethane or nitroethane. Fluid Phase Equilibria , 74: 243-252. Isothermal vapor-liquid equilibria were measured at 298.15 K for the systems containing methyl acetate or methanol with the three nitrogen compounds acetonitrile, nitromethane and nitroethane. The experimental data satisfy the Redlich-Kister thermodynamic consistency test. The liquid-phase activity coefficients were fitted by using the van Laar, Mato, NRTL, Wilson and UNIQUAC equations. The systems with methyl acetate present slight positive deviations from ideality while the systems containing methanol exhibit strong positive deviations.

Understanding bottom-up continuous hydrothermal synthesis of nanoparticles using empirical measurement and computational simulation

Continuous hydrothermal synthesis was highlighted in a recent review as an enabling technology for the production of nanoparticles. In recent years, it has been shown to be a suitable reaction medium for the synthesis of a wide range of nanomaterials. Many single and complex nanomaterials such as metals, metal oxides, doped oxides, carbonates, sulfides, hydroxides, phosphates, and metal organic frameworks can be formed using continuous hydrothermal synthesis techniques. This work presents a methodology to characterize continuous hydrothermal flow systems both experimentally and numerically, and to determine the scalability of a counter current supercritical water reactor for the large scale production (>1,000 T·year–1) of nanomaterials. Experiments were performed using a purpose-built continuous flow rig, featuring an injection loop on a metal salt feed line, which allowed the injection of a chromophoric tracer. At the system outlet, the tracer was detected using UV/Vis absorption, which could be used to measure the residence time distribution within the reactor volume. Computational fluid dynamics (CFD) calculations were also conducted using a modeled geometry to represent the experimental apparatus. The performance of the CFD model was tested against experimental data, verifying that the CFD model accurately predicted the nucleation and growth of the nanomaterials inside the reactor.

Supercritical Water Oxidation (SCWO) of Solid, Liquid and Gaseous Fuels for Energy Generation

The SCWO (Supercritical Water Oxidation) process is well known for being able to destroy any kind of compound without producing prejudicial byproducts. This fact together with the high potential for energy production (because the high pressure high temperature effluent generated in the process) makes it a good candidate for generating energy from bio-fuels, especially those which valorization by conventional combustion can be problematic. In this work, different literature energetic studies of the SCWO process are analyzed. When comparing the heat produced by direct expansion of the effluent and by indirect heating steam generation it is observed that when direct expansion is used, the energetic efficiency is much higher than when the effluent is used to heat an auxiliary fluid of a Rankine or Brayton cycle. Nevertheless, the production of energy by direct expansion of the SCWO is not technically available in the short term. In any case, obtaining a high temperature effluent it is a key point for optimizing energy utilization. To do so, reactors in which the effluent is not diluted or reactor working at hydrothermal flame regime are desirable. Also the lay-out of the plant is important for energy utilization and factors as preheating scheme must be thoroughly studied. In addition to all of this, SCWO process has the additional advantage of the possibility of CO2 sequestration.

Two-parameter model for correlating liquid phase activity coefficients of binary systems

Abstract A new two-parameter model for the activity coefficients of binary liquid systems is derived from the general expansion of Wohl. The model admits curves that exhibit maxima or minima in the activity coefficients and predicts well the liquid-vapor equilibrium from a restricted information : azeotropic condition, activity coefficients at infinite dilution or mutual solubilities.

Reactors for Supercritical Water Oxidation Processes

Supercritical water oxidation (SCWO) process can utilize different reactors to reduce the operation problems related with solids precipitation and corrosion. Tubular reactors are one of the most frequently used but its use is limited by plugging problems. Industrial plants operate with two parallel reactors. While one is under operation, the other is being cleaned to avoid obstruction due to salt precipitation. Transpiring wall reactor avoids plugging problems but dilution water reduces effluent temperature, reducing in this way the energy quality content of the effluent. Vessel reactors are under application to minimize corrosion by the control the wall temperature and the materials of construction. The implementation of the hydrothermal flame as internal heat source reduces the residence time and opens the way to reduce the reactor volume. Other reactors offer specific solution for some SCWO processes.

Behavior of the LEMF equation for vapor-liquid equilibrium data treatment of systems with negative deviations from ideality

Abstract Mato, R.B., Mato, F.A. and Mato, F., 1991. Behavior of the LEMF equation for vapor-liquid equilibrium data treatment of systems with negative deviations from ideality. Fluid Phase Equilibria, 68: 115-130. The local effective mole fraction (LEMF) equation shows abnormally poor performance in correlating and predicting vapor-liquid equilibrium data of binary and ternary systems when a binary pair exhibits negative deviations from ideality. This abnormal performance becomes progressively worse as the negative deviations from ideality increase, and it is a mathematical consequence of the negative value used in the LEMF equation for the non-randomness parameter αij.