Simulação computacional de gaseificação de madeira de pequeno prte empregando um gaseificador downdraft

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Analise técnico-econômica de um gaseificador Downdraft e de filtros para limpeza de gás de síntese

The biomass gasification systems have been used for a long time and prove to be a good alternative to the generation of energy problems. This type of management requires a simple installation and maintenance which gives them a high availability. In Biomass project via Call CTEnerg 33/2006-1, funded by the Ministry of Science and Technology - MCT - Brazil, the Group Energy Systems Optimization – GOSE - at FEG - UNESP built and tested two prototypes of gasifiers. These is fed with 25 kg / h of dry wood (chips), and 50 Nm3 / h of air to produce gas at a flow rate of approximately 70 Nm3 / h of wood (syngas) at a temperature approximately 600 ° C. In this work of graduation, studies were conducted on the materials used in both the gasifier as well as cleaning the filter synthesis gases. The system of gas cleaning and conditioning is vital to ensure the life of the Internal Combustion Engine. In this case the studies of different filters for small gasification systems (properties, materials used, characteristics, types, etc.) are very relevant to its use in the prototype of the college campus. Were also performed a technical and economic analysis of a cogeneration system that consists in the combination of the downdraft gasifier studied in this work, an internal combustion engine, two heat exchangers and a SRA (absorption system refrigerator). Were calculated the costs of electricity generation, hot water and cold water. Finally, we analyzed the economic feasibility of the project

Caracterização de um gaseificador do tipo downdraft

A gaseificação é uma conversão termoquímica da biomassa em gás combustível, que pode ser usado como combustível em motores de combustão interna ou como gás de síntese para a indústria química. Para checar o desempenho de um gaseificador temos de quantificar a energia contida no gás produzido e a quantidade de carbono convertido por meio dos cálculos de eficiência energética e de conversão de carbono através dos dados obtidos experimentalmente. A eficiência energética é uma relação entre os fluxos de gás e biomassa e de suas respectivas quantidades de energia, no mesmo sentido, a conversão de carbono é a quantidade de compostos carbonáceos presentes no gás convertido a partir da quantidade de carbono presente na composição da biomassa. O presente documento avalia a eficiência energética e de carbono na conversão de um protótipo de um gaseificador indiano do tipo downdraft produzido por uma empresa local (Floragás). Os parâmetros nominais do gaseificador são: capacidade de produção de gás de 45 kWt, consumo de biomassa (caroço de açaí) de 15 kg/h. As dimensões do gaseificador são: DI 150 mm e altura de 2000 mm). A eficiência energética e a taxa de conversão de carbono foram quantificados, a queda de pressão devido ao leito do reator e a temperatura dos gases também foram medidos na saída do reator e também, a concentração de alcatrão, partículas e gases não condensáveis (CO, CO², CH⁴, SO², N² e NO^x) nos gases de combustão após a sistema de limpeza.

Estudo experimental de um reator de gaseificação em um leito fixo de açaí

Um leito de gaseificação de pequena escala foi projetado, construído e operado com o objetivo de investigar os parâmetros que influenciam o processo de gaseificação de um leito fixo de caroço de açaí. O reator é do tipo topo aberto downdraft estratificado, de dimensões de 15 cm de diâmetro interno por 1,5 m de altura, com isolamento térmico. O gás produzido foi coletado a jusante do leito de gaseificação e condensado para remoção de alcatrão, o qual foi posteriormente quantificado em titulador Karl Fisher. Após remoção do alcatrão o gás foi introduzido em um Micro GC para quantificação dos percentuais molares de H², CO, N² e CH⁴. O perfil de temperatura do leito foi medido com termopares tipo K posicionados ao longo do eixo longitudinal do leito em distâncias de 10 cm. A vazão de ar foi medida com auxilio de um tubo de Pitot e um micromanômetro. As aquisições dos dados de temperatura foram feitas por um data logger e vazão mássica do ar sendo feita usando comunicação RS232 do micromanômetro. Os procedimentos experimentais foram feitos ao longo de 4 horas de operação do leito de gaseificação, com consumo médio de biomassa de 1,6 kg/h, com 6 dados do perfil de temperatura, vazão mássica de ar, perda de carga do leito e concentração dos gases obtidos no processo de gaseificação e quantificação do teor de alcatrão condensável presente no gás. Verificou-se que o gaseificador de leito de açaí pode ser operado através de uma gama bastante ampla de taxas de fluxo de ar de 2 a 5 kg/h, com a quantidade de energia do gás produzido variando de 5 a 15 MJ/h. As concentrações típicas dos gases obtidos no leito foram de 13% de H², 11% de CO, 1,3% de CH⁴. A eficiência máxima de gás frio de 57% e teor médio de alcatrão de 155 g/m³.

Análise técnica econômica de um gaseificador de biomassa de 100 kg/h para acionamento de um motor de combustão interna

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Tar characterisation in new generation agro-residue gasifiers - Cyclone and downdraft open top twin air entry systems

This paper deals with the characterisation of tar from two configurations of bioresidue thermochemical conversion reactors designed for producer gas based power generation systems. The pulverised fuel reactor is a cyclone system (R1) and the solid bioresidue reactor (denoted R2) is an open top twin air entry system both at 75-90 kg/h capacity (to generate electricity similar to 100 kVA). The reactor, R2, has undergone rigorous test in a major Indo-Swiss programme for the tar quantity at various conditions. The former is a recent technology development. Tars collected from these systems by a standard tar collection apparatus at the laboratory at Indian Institute of Science have been analysed at the Royal Institute of Technology (KTH), Sweden. The results of these analyses show that these thermochemical conversion reactors behave differently from the earlier reactors reported in literature in so far as tar generation is concerned. The extent of tar in hot gas is about 700-800 ppm for R1 and 70-100 ppm for R2. The amounts of the major compounds - naphthalene and phenol-are much lower that what is generally understood to happen in the gasifiers in Europe. It is suggested that the longer residence times at high temperatures allowed for in these reactors is responsible for this behavior. It is concluded the new generation reactor concepts extensively tried out at lower power levels hold promise for high power atmospheric gasification systems for woody as well as pulverisable bioresidues.

Oxy-steam gasification of biomass for hydrogen rich syngas production using downdraft reactor configuration

The paper focuses on the use of oxygen and steam as the gasification agents in the thermochemical conversion of biomass to produce hydrogen rich syngas, using a downdraft reactor configuration. Performance of the reactor is evaluated for different equivalence ratios (ER), steam to biomass ratios (SBR) and moisture content in the fuel. The results are compared and evaluated with chemical equilibrium analysis and reaction kinetics along with the results available in the literature. Parametric study suggests that, with increase in SBR, hydrogen fraction in the syngas increases but necessitates an increase in the ER to maintain reactor temperature toward stable operating conditions. SBR is varied from 0.75 to 2.7 and ER from 0.18 to 0.3. The peak hydrogen yield is found to be 104g/kg of biomass at SBR of 2.7. Further, significant enhancement in H-2 yield and H-2 to CO ratio is observed at higher SBR (SBR=1.5-2.7) compared with lower range SBR (SBR=0.75-1.5). Experiments were conducted using wet wood chips to induce moisture into the reacting system and compare the performance with dry wood with steam. The results clearly indicate the both hydrogen generation and the gasification efficiency ((g)) are better in the latter case. With the increase in SBR, gasification efficiency ((g)) and lower heating value (LHV) tend to reduce. Gasification efficiency of 85.8% is reported with LHV of 8.9MJNm(-3) at SBR of 0.75 compared with 69.5% efficiency at SBR of 2.5 and lower LHV of 7.4 at MJNm(-3) at SBR of 2.7. These are argued on the basis of the energy required for steam generation and the extent of steam consumption during the reaction, which translates subsequently in the LHV of syngas. From the analysis of the results, it is evident that reaction kinetics plays a crucial role in the conversion process. The study also presents the importance of reaction kinetics, which controls the overall performance related to efficiency, H-2 yield, H-2 to CO fraction and LHV of syngas, and their dependence on the process parameters SBR and ER. Copyright (c) 2013 John Wiley & Sons, Ltd.

Hydrogen-rich gas production from biomass air and oxygen/steam gasification in a downdraft gasifier

Biomass gasification is an important method to obtain renewable hydrogen, However, this technology still stagnates in a laboratory scale because of its high-energy consumption. In order to get maximum hydrogen yield and decrease energy consumption, this study applies a self-heated downdraft gasifier as the reactor and uses char as the catalyst to study the characteristics of hydrogen production from biomass gasification. Air and oxygen/steam are utilized as the gasifying agents. The experimental results indicate that compared to biomass air gasification, biomass oxygen/steam gasification improves hydrogen yield depending on the volume of downdraft gasifier, and also nearly doubles the heating value of fuel gas. The maximum lower heating value of fuel gas reaches 11.11 MJ/ N m(3) for biomass oxygen/steam gasification. Over the ranges of operating conditions examined, the maximum hydrogen yield reaches 45.16 g H-2/kg biomass. For biomass oxygen/steam gasification, the content of H-2 and CO reaches 63.27-72.56%, while the content Of H2 and CO gets to 52.19-63.31% for biomass air gasification. The ratio of H-2/CO for biomass oxygen/steam gasification reaches 0.70-0.90, which is lower than that of biomass air gasification, 1.06-1.27. The experimental and comparison results prove that biomass oxygen/steam gasification in a downdraft gasifier is an effective, relatively low energy consumption technology for hydrogen-rich gas production.

Electricity, hot water and cold water production from biomass. Energetic and economical analysis of the compact system of cogeneration run with woodgas from a small downdraft gasifier

Wood gasification technologies to convert the biomass into fuel gas stand out. on the other hand, producing electrical energy from stationary engine is widely spread, and its application in rural communities where the electrical network doesn't exist is very required. The recovery of exhaust gases (engine) is a possibility that makes the system attractive when compared with the same components used to obtain individual heat such as electric power. This paper presents an energetic alternative to adapt a fixed bed gasifier with a compact cogeneration system in order to cover electrical and thermal demands in a rural area and showing an energy solution for small social communities using renewable fuels. Therefore, an energetic and economical analysis from a cogeneration system producing electric energy, hot and cold water, using wooden gas as fuel from a small-sized gasifier was calculated. The energy balance that includes the energy efficiency (electric generation as well as hot and cold water system; performance coefficient and the heat exchanger, among other items), was calculated. Considering the annual interest rates and the amortization periods, the costs of production of electrical energy, hot and cold water were calculated, taking into account the investment, the operation and the maintenance cost of the equipments. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.

Atendimento de energia elétrica domiciliar para comunidades isoladas de baixa potência do interior do estado do Pará através de um gaseificador de 1kw

No Pará, quase 21% de sua população, não tem acesso ao uso da energia elétrica na sua residência. Neste universo está o público alvo deste trabalho que são as comunidades isoladas. Dado a extensão territorial e a extensa bacia hidrográfica do Estado do Pará, estas comunidades dificilmente serão atendidas por extensão da rede de distribuição. A proposta deste trabalho consiste na sugestão de uso do caroço de Açaí como biomassa para um gaseificador indiano de 1 Kg/hora, co-corrente e topo aberto, adaptado e adequado às especificidades da região; o sistema de gaseificação é acoplado a um gerador de 2 KVA (Diesel ou Gasolina), para suprir com energia elétrica as comunidades isoladas, onde já existe a biomassa como resultado do processamento do Açaí e que vem sendo tratada como lixo. Neste contexto, foram pesquisados os programas governamentais que podem respaldar esta proposta, utilizando-a como uma das muitas opções de atendimento de energia elétrica através das fontes alternativas.

Aumento da oferta de eletricidade no setor sucroalcooleiro: incorporação de ciclo combinado associado à gaseificador de leito fluidizado

Pós-graduação em Engenharia Mecânica - FEG

Thermochemical equilibrium modeling of a biomass downdraft gasifier: Constrained and unconstrained non-stoichiometric models

The objective of this work is to develop a non-stoichiometric equilibrium model to study parameter effects in the gasification process of a feedstock in downdraft gasifiers. The non-stoichiometric equilibrium model is also known as the Gibbs free energy minimization method. Four models were developed and tested. First a pure non-stoichiometric equilibrium model called M1 was developed; then the methane content was constrained by correlating experimental data and generating the model M2. A kinetic constraint that determines the apparent gasification rate was considered for model M3 and finally the two aforementioned constraints were implemented together in model M4. Models M2 and M4 showed to be the more accurate among the four developed models with mean RMS (root mean square error) values of 1.25 each.Also the gasification of Brazilian Pinus elliottii in a downdraft gasifier with air as gasification agent was studied. The input parameters considered were: (a) equivalence ratio (0.28-035); (b) moisture content (5-20%); (c) gasification time (30-120 min) and carbon conversion efficiency (80-100%). (C) 2014 Elsevier Ltd. All rights reserved.

Thermochemical equilibrium modeling of biomass downdraft gasifier: Stoichiometric models

The aim of this work is to develop stoichiometric equilibrium models that permit the study of parameters effect in the gasification process of a particular feedstock. In total four models were tested in order to determine the syngas composition. One of these four models, called M2, was based on the theoretical equilibrium constants modified by two correction factors determined using published experimental data. The other two models, M3 and M4 were based in correlations, while model M4 was based in correlations to determine the equilibrium constants, model M3 was based in correlations that relate the H-2, CO and CO2 content on the synthesis gas. Model M2 proved to be the more accurate and versatile among these four models, and also showed better results than some previously published models. Also a case study for the gasification of a blend of hardwood chips and glycerol at 80% and 20% respectively, was performed considering equivalence ratios form 0.3 to 0.5, moisture contents from 0%-20% and oxygen percentages in the gasification agent of 100%, 60% and 21%. (C) 2013 Elsevier Ltd. All rights reserved.

Thermodynamic analysis and comparison of downdraft gasifiers integrated with gas turbine, spark and compression ignition engines for distributed power generation

The objective of the present article is to assess and compare the performance of electricity generation systems integrated with downdraft biomass gasifiers for distributed power generation. A model for estimating the electric power generation of internal combustion engines and gas turbines powered by syngas was developed. First, the model determines the syngas composition and the lower heating value; and second, these data are used to evaluate power generation in Otto, Diesel, and Brayton cycles. Four synthesis gas compositions were tested for gasification with: air; pure oxygen; 60% oxygen with 40% steam; and 60% air with 40% steam. The results show a maximum power ratio of 0.567 kWh/Nm(3) for the gas turbine system, 0.647 kWh/Nm(3) for the compression ignition engine, and 0.775 kWh/Nm(3) for the spark-ignition engine while running on synthesis gas which was produced using pure oxygen as gasification agent. When these three systems run on synthesis gas produced using atmospheric air as gasification agent, the maximum power ratios were 0.274 kWh/Nm(3) for the gas turbine system, 0.302 kWh/Nm(3) for CIE, and 0.282 kWh/Nm(3) for SIE. The relationship between power output and synthesis gas flow variations is presented as is the dependence of efficiency on compression ratios. Since the maximum attainable power ratio of CIE is higher than that of SIE for gasification with air, more research should be performed on utilization of synthesis gas in CIE. (C) 2014 Elsevier Ltd. All rights reserved.

Tar reduction in downdraft biomass gasifier using a primary method

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)