Multi-objective Optimization of Supercritical Water Gasification of Leftover Brazilian Ginseng Roots After Phytochemical Recovery Steps

The present study aims at studying the supercritical water gasification (SCWG) of the leftover Brazilian ginseng roots after phytochemicals extraction for synthetic natural gas (SNG) production, envisioning the development of a promising Brazilian ginseng roots valorization route using sub/supercritical fluids in different steps. A multi-objective energetic-economic-environmental optimization of the proposed SCWG process was assessed through the use computational simulation tools. The results showed that for a given leftover biomass input of 20MW a specific cost of 62-66 USD/MWh of SNG is obtained, which is higher than the average price in Brazilian market. On the other hand, the production process of SNG from this residue showed to be a promising option, being energetically self-sufficient and environmentally friendly. In order to become more economically attractive this alternative process we proposed the construction of the SCWG and the sub/supercritical extraction units in the same location, sharing part of the same high-pressure equipments

Thermo-economic and environmental model of microalgae-to-SNG conversion process through hydrothermal gasification

Kevin Arrandel, François Maréchal, Alberto Mian, Adriano Viana Ensinas

Due to its high photosynthesis conversion efficiency, microalgae are currently considered as a serious feedstock for next-generation biofuels production. One possible conversion process is the production of synthetic natural gas (SNG) through catalytic hydrothermal gasification which uses a supercritical water-processing for the gasification and has the advantage to avoid drying of the biomass. The whole system includes four steps of production: microalgae cultivation, dewatering, gasification and product separation. In this paper the SNG production from microalgae is analyzed considering algal biomass cultivation system with open-ponds technology. To do so, a mathematical model based on mass and energy balances has been developed in order to represent microalgae growth process, and regarding culture temperature, solar-radiation incidence, CO2 and nutrients supply. The complete physical model of the biomass conversion system is developed including the dewatering system with settling ponds and centrifuges, catalytic hydrothermal gasification with salt separation unit and the SNG separation and purification system. An economic model is carried out for investment and operation cost of the process, from the biomass cultivation to the final product, including possibilities of nutrients, CO2 and water recovery. Finally, the environmental impact regarding the CO2 emission of this process and the avoided emission from the replacement of fossil natural gas is estimated in a complete life cycle analysis. A multi-objective optimization methodology is used to find the trade-off between the total cost of the system and the environmental impact that can be linked with the equipment size and the energy conversion efficiency.

2013

Integration of Supercritical Water Gasification in Combined 1G/2G Ethanol Production

François Maréchal, Alberto Mian, Adriano Viana Ensinas

The present study investigates the potential conversion of sugarcane into ethanol and synthetic natural gas. The considered conversion path consists in combining ethanol first and second generation ethanol production plant with a catalytic supercritical water gasification system. The main steps of the ethanol conversion consider fermentation of sugars (1G) and enzymatic hydrolysis of bagasse (2G). Enzymatic hydrolysis is selected since it represents a promising alternative for 2nd generation biofuels due to its high conversion efficiency. Among streams that are leaving the ethanol production plant are some high watered streams, whose carbon/energy content is not negligible. These streams should be valorised in an efficient way in order to improve the energy conversion efficiency. In this context supercritical gasification process allows to valorise these flows leaving the ethanol plant. Using supercritical water gasification it is in fact possible to avoid the drying the ethanol production leftovers, thus performing a direct gasification. The conversion of ligno-cellulosic residues into synthetic natural gas is modelled considering a catalytic supercritical gasification plant. Since the goal is to achieve high energy and exergy conversion efficiencies, the potential use of an additional set of utilities, such as burners, steam injected gas turbines or steam networks, is added to the sizing problem. The mathematical nature of the optimal utility selection problem deals with mixed integer linear programming (MILP) model, in which the type and size of utilities represent the independent variables, having fixed the process size. The results of the integration are showed in terms of Composite and Grand Composite Curves, economic indicators and local CO2 balance. Finally, having identified the ratio of sugarcane that goes to second generation ethanol plant as key dependent variables, the results of a sensitivity analysis are presented. The sensitivity analysis results are shown accounting economics for the Brazilian market, energy conversion performance indicators and considering local carbon dioxide balance.

Aidic Servizi Srl2014

Comparison of extraction techniques for product diversification in a supercritical water gasification-based sugarcane-wet microalgae biorefinery: Thermoeconomic and environmental analysis

François Maréchal, Adriano Viana Ensinas

This study presents a thermoeconomic and environmental assessment of the extraction of lipids and proteins from wet microalgal biomass in a 3G biorefinery by two different technologies: supercritical fluid extraction (SFE) and low-pressure solvent extraction (LPSE). Simulation tools were used to study a sugarcane biorefinery producing ethanol from sugarcane juice (1G) and bagasse (2G); the microalgal growth in an open pond; and the processing of microalgal biomass into lipids, proteins and synthetic natural gas (SNG). Supercritical water gasification (SONG) of microalgal biomass enables an increase in biofuel production of 10.2% MJ when no extraction process is considered and of 1.9% MJ when LPSE is considered. The heat demand of the proposed biorefinery with LPSE was increased by 87.8% compared with the demand of the sugarcane biorefinery without microalgal growth and processing. When the SFE process is considered, the heat demand of the overall process increased 3.2 times. SFE for wet microalgae processing is not economically attractive, as it increases the total investment by 71%. The CO2 flow used in the SFE process demonstrated to be a key factor in the thermoeconomic viability of the process. Regarding the wet processing of microalgae prior to SCWG, the best alternative studied was the use of LPSE technology. (C) 2018 Elsevier Ltd. All rights reserved.

ELSEVIER SCI LTD2018

Integration of Supercritical Water Gasification in Combined 1G/2G Ethanol Production

François Maréchal, Alberto Mian, Adriano Viana Ensinas

Aidic Servizi Srl2014