J. Sánchez-Oneto

Advanced thermal hydrolysis: optimization of a novel thermochemical process to aid sewage sludge treatment.

The aim of this work was to study in depth the behavior and optimization of a novel process, called advanced thermal hydrolysis (ATH), to determine its utility as a pretreatment (sludge solubilization) or postreatment (organic matter removal) for anaerobic digestion (AD) in the sludge line of wastewater treatment plants (WWTPs). ATH is based on a thermal hydrolysis (TH) process plus hydrogen peroxide (H(2)O(2)) addition and takes advantage of a peroxidation/direct steam injection synergistic effect. On the basis of the response surface methodology (RSM) and a modified Doehlert design, an empirical second-order polynomial model was developed for the total yield of: (a) disintegration degree [DD (%)] (solubilization), (b) filtration constant [F(c) (cm(2)/min)] (dewaterability), and (c) organic matter removal (%). The variables considered were operation time (t), temperature reached after initial heating (T), and oxidant coefficient (n = oxygen(supplied)/oxygen(stoichiometric)). As the model predicts, in the case of the ATH process with high levels of oxidant, it is possible to achieve an organic matter removal of up to 92%, but the conditions required are prohibitive on an industrial scale. ATH operated at optimal conditions (oxygen amount 30% of stoichiometric, 115 °C and 24 min) gave promising results as a pretreatment, with similar solubilization and markedly better dewaterability levels in comparison to those obtained with TH at 170 °C. The empirical validation of the model was satisfactory.

Supercritical Water Oxidation for Wastewater Destruction with Energy Recovery

Abstract Supercritical water oxidation (SCWO) is a promising technology that respecting the environment destroys wastes definitely and allows an energy recovery. This process has been applied to many model compounds and real wastewaters at laboratory scale. However SCWO treatments at pilot plant scale of real wastewaters are much more limited in literature. Furthermore, the application of this technology to industrial wastewaters has some drawbacks as corrosion, salt deposition, management of biphasic wastes, presence of suspended solids and high costs, so nowadays the industrial scale-up is scarce and it is being delayed. As an attempt to reduce process costs, energy recovery from the effluent of the reactor has been studied by several authors. In this chapter, the main aspects of the SCWO are briefly described and the studies regarding energy recovery are summarized.

Chapter 10 – Supercritical Water Gasification of Organic Wastes for Energy Generation

Nowadays, numerous studies are focused on finding nonpolluting energy sources. Among others, wet biomass waste is one of the most promising renewable resource and its conversion into a suitable form of energy, usually electricity or fuel, can be achieved using different routes, each one with specific advantages and disadvantages. A review of the main conversion processes is presented, among which it is possible to highlight those which use high pressure. In Supercritical Water Gasification, the supercritical water is not only a solvent for organic materials but also a reactant. In this way, besides the destruction of wastewaters, it is aimed to harness their energy potential by burning the gas effluent generated in the process to produce electrical power, due to its high content in hydrogen and light hydrocarbons.

Supercritical water gasification: a patents review

Abstract Supercritical water gasification (SCWG) is a very recent technology that allows conversion of organic wastewaters into a fuel gas with a high content of hydrogen and light hydrocarbons. SCWG involves the treatment of organic compounds at conditions higher than those that define the critical point of water (temperature of 374°C and pressure of 221 bar). This hydrothermal process, normally operated at temperatures from 400 to 650°C and pressures from 250 to 350 bar, produces a gas effluent with a high hydrogen content. SCWG is considered a promising technology for the efficient conversion of organic wastewaters, mainly wet biomass, into fuel gas. This technology has received extensive worldwide attention, and many research groups have studied the effect of operation conditions, reaction mechanisms, kinetics, etc. There are some recent reviews about the research works carried out in the last decades, but there is no information or analysis of almost 100 patents registered in relation with this new technology. A revision of the current status of SCWG patents and technologies has been completed based on the Espacenet patent database. The objective of this revision was to set down the new perspectives toward the improvement of this technology efficiency. Patents have been published with regard to process or device improvements as well as to the use of different catalysts. More than 71% of these patents were published since 2009, and a substantial climb in the number of patents on SCWG is expected in the coming years. One of the most important aspects where research is particularly interesting if the integration of renewable energy recovery systems with SCWG processes.

Energy Production by Hydrothermal Treatment of Liquid and Solid Waste from Industrial Olive Oil Production

This work studies the use of olive oil mill waste ( OMW ) treated as subcritical or supercritical water to produce both, a biofuel by liquefaction and a gas fuel by gasification. The increasing amount of OMW , both liquid and solid, is becoming a serious environmental problem. This wastewater is highly resistant to biodegradation and contains a wide variety of compounds such as polyphenols, polyoils, organic acids, etc, that require depuration treatments to remove the odour and pollutant load before being discharged. This work studies both, liquefaction and gasification of OMW streams in subcritical and supercritical water in different batch reactors at temperatures between 200 and 530 ÂoC and pressures between 150 and 250 bar. This study also tests the effectiveness of various types of homogeneous (KOH 0.01 g/g sample dry ) and heterogeneous catalysts (TiO 2 , V 2 O 5 and Au-Pd 0.1-0.5 g/g sample dry ) for supercritical water gasification (SCWG) and studied the way they affect biomass conversion yields. It also covers the effect that the use of different organic compound concentrations (23, 35, and 80 g O 2 /l of chemical oxygen demand concentration (COD)) and compositions (mixtures of solid and liquid OMW ) has on energy production results. A maximum of 82% oil yield was obtained from the hydrothermal liquefaction of OMW under optimum conditions (330 ÂoC, 150 bar, 23 g O 2 /l as initial concentration and 30 minutes reaction time). Meanwhile, a yield of 88.6 mol H 2 /kg OMW dry was obtained when Au-Pd was used as a catalyst for the gasification of OMW supercritical water.

Supercritical Water Oxidation

Abstract Supercritical water oxidation (SCWO) is a powerful green technology to treat hazardous wastewaters. This process has been extensively studied for decades from laboratory scale studies of model compounds to several demonstration and industrial plants under construction worldwide. However, SCWO treatments at pilot plant scale of real wastewaters are much less extensive in literature. Furthermore, the application of this technology to industrial wastewaters has two main drawbacks such as corrosion and salt deposition, and some other problems to be solved related to management of biphasic wastes, presence of suspended solids, high costs, etc.; and therefore, currently, the industrial scale-up and commercialization of this process is still subject to difficulties.

Depressurization System by Coiled Pipes Applied to a High Pressure Process: Experimental Results and Modeling

Received: February 10, 2017 Revised: May 24, 2017 Accepted: June 02, 2017 Abstract: Background: The use of backpressure regulator valves is widespread in high-pressure processes both at laboratory and pilot plant scales, but being a single step for effluent depressurization, such valves may have some limitations at industrial scale. In an effort to improve the depressurization step, this work studies a system based on the pressure drop of a fluid that circulates through coiled pipes.