Experimental study of bottom feed updraft gasifier

The updraft biomass gasifiers currently available produce a gas with high tar content. For almost all downstream applications a substantial reduction of the tar concentration is required. The gravimetric tar concentration behavior in producer gas, obtained at a modified updraft fixed bed gasifier, was studied. The feedstock feeding system was modified respect to the traditional updraft gasification design in order to decrease the tar concentration in the producer gas; the material is feeding continuously through a conduit in the base of the reactor over the grate. The caloric power of the syngas obtained was slightly lower than the typical value for this type of reactor and the highest efficiency obtained for the woodchip gasification was 77%. The highest tar concentration obtained during the experiments was 1652.7 mg N m-3 during the first our of experiments, comparable with the smaller value reported for the updraft reactors, this value is reduced significantly after the stabilization of the gasification process in the reactor. The smaller value obtained was 21 mg N m-3. © 2013 Elsevier Ltd

Tar reduction in downdraft biomass gasifier using a primary method

This work present a novel primary method, for tar reduction in downdraft gasification. The principle of this new technology is to change the fluid dynamic behaviour of the mixture, formed by pyrolysis product and gasification agent in combustion zone; allowing a homogeneous temperature distribution in radial direction in this reaction zone. To achieve the change in the fluid dynamic behaviour of the mixture; the entry of gasification agent to combustion zone is oriented by means of wall nozzles in order to form a swirl flow. This modification in combination with the extension of the reduction zone, will allow, to increases the efficiency of the tar thermal cracking inside the gasifier and the extension of the Boudouard reactions. Consequently, the quantity of tar passing through the combustion zone without cracking and the concentration of tar in the final gas, decrease significantly in relation with the common value obtained for this type of reactor, without affecting significantly the heating value of the producer gas. In this work is presented a new design for 15 kW downdraft gasification reactor, with this technology implemented, the tar content obtained in the experiments never overcome 10 mg/Nm3, with a lower heating value of 3.97 MJ/Nm3

Comparative analysis between a PEM fuel cell and an internal combustion engine driving an electricity generator: Technical, economical and ecological aspects

In the recent years the fuel cells have received much attention. Among various technologies, the Proton Exchange Membrane Fuel Cell (PEMFC) is currently the most appropriate and is used in several vehicles prototype. A comparative technical, economical and ecological analysis between an Internal Combustion Engine fueled with Diesel driving an electricity Generator (ICE-G) and a PEMFC fed by hydrogen produced by ethanol steam reforming was performed. The technical analysis showed the advantages of the PEMFC in comparison to the ICE-G based in energetic and exergetic aspects. The economic analysis shows that fuel cells are not economic competitive when compared to internal combustion engine driving an electricity generator with the same generation capacity; it will only be economically feasible in a long term; due to the large investments required. The environmental analysis was based on concepts of CO2 equivalent, pollution indicator and ecological efficiency. Different to the ICE-G system, the Fuel Cell does not emit pollutants directly and the emission related to this technology is linked mainly with hydrogen production. The ecological efficiency of PEMFC was 96% considering the carbon dioxide cycle, for ICE-G system this parameter reach 51%. (C) 2013 Elsevier Ltd. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Hydrogen production by biogas steam reforming: A technical, economic and ecological analysis

Fuel cells are electrochemical energy conversion devices that convert fuel and oxidant electrochemically into electrical energy, water and heat. Compared to traditional electricity generation technologies that use combustion processes to convert fuel into heat, and then into mechanical energy, fuel cells convert the hydrogen and oxygen chemical energy into electrical energy, without intermediate conversion processes, and with higher efficiency. In order to make the fuel cells an achievable and useful technology, it is firstly necessary to develop an economic and efficient way for hydrogen production. Molecular hydrogen is always found combined with other chemical compounds in nature, so it must be isolated. In this paper, the technical, economical and ecological aspects of hydrogen production by biogas steam reforming are presented. The economic feasibility calculation was performed to evaluate how interesting the process is by analyzing the investment, operation and maintenance costs of the biogas steam reformer and the hydrogen production cost achieved the value of 0.27 US$/kWh with a payback period of 8 years. An ecological efficiency of 94.95%, which is a good ecological value, was obtained. The results obtained by these analyses showed that this type of hydrogen production is an environmentally attractive route. © 2013 Elsevier Ltd

Techno-Economic and Environmental Assessment of Municipal Solid Waste Energetic Valorization

In 2019, Chile generated 20 million tons of waste, 79% of which was not properly disposed of, thereby providing an attractive opportunity for energy generation in advanced thermochemical conversion processes. This study presents a techno-economic and environmental assessment of the implementation of Waste-Integrated Gasifier-Gas Turbine Combined Cycle (WIG-GTCC) technology as an alternative for Municipal Solid Waste (MSW) treatment. The studied case assesses the conversion of 14.61 t·h−1 of MSW, which produces a combustible gas with a flow rate of 34.2 t·h−1 and LHV of 5900 kJ·kg−1, which, in turn, is used in a combined cycle to generate 19.58 MW of electrical power. The proposed economic assessment of the technology uses the energy generation processes as a reference, followed by a model for an overall economic evaluation. The results have shown that the profit could be up to USD 24.1 million, and the recovery of investment between 12 and 17 years would improve the environmental impacts of the current disposal technology. The WIG-GTCC has the most efficient conversion route, emitting 0.285 kg CO2eq/kWh, which represents 48.21% of the potential yield of global warming over 100 years (GWP100) of incineration and 58.51% of the GWP100 of the standard gasification method. The WIG-GTCC would enable the energetic valorization of MSW in Chile, eliminate problems associated with landfill disposal, and increase opportunities for decentralized electricity generation

Sugarcane Bagasse Torrefaction for Fluidized Bed Gasification

Sugarcane bagasse has a great potential to be used as biofuel; however, its use as feedstock in fluidized bed reactors is hampered due to its fibrous nature, low apparent density, high moisture content, and difficulties with its fluidization. The present study evaluated the torrefaction of sugarcane bagasse to propose suitable process conditions that balance the properties of the fuel obtained in the torrefaction and the process’s energy requirements. Based on the thermogravimetric analysis and previous reports, two final process temperatures (230 °C and 280 °C) and residence times (35 and 45 min) for the same heating rate (5 °C/min) and nitrogen flow (1 L/min) were evaluated. Within the experimental conditions evaluated, it can be concluded that for 30 min of residence time, the average target temperature of 230 °C should be high enough to produce a stable torrefacted bagasse with a 3.41% reduction in the volatile content and obtain 98.85% of energy yield. Higher temperatures increase the feedstock’s carbon content and energy density, but the reduction in energy yield and the fraction of volatiles do not justify higher temperatures or longer residence times for pretreating the sugarcane bagasse