Conversion of biomass to energy does not contribute to the net increase of carbon dioxide in the environment, therefore the use of biomass waste as a clean and renewable fuel source is an attractive alternative to the use of fossil fuels. Biomass can be converted to energy via direct combustion or via thermo-chemical conversion to liquid or gas fuels. This study focuses on employing gasification technology to convert biomass waste to producer gas, which is then cleaned and fed as gaseous fuel into the gas turbine. Since the producer gases are usually low caloric values, the power plants performance under various operating conditions has not yet been proven. In this study, system performance calculations are conducted for a 5MWe and a 20MWe power plants using commercial software ThermoFlow. The power plants considered including simple gas turbine systems, steam turbine systems, combined cycle systems, and steam injection gas turbine systems (STIG) using the producer gas with low caloric values at approximately 30% and 15% of the natural gas heating value. The low caloric value fuels are shown to impose high back compressor pressure and increased power output due to increased fuel flow. Power augmentations under four different weather conditions are also calculated by employing gas turbine inlet fog cooling. Different capacity options for the heat recovery steam generator (HRSG) that provides the steam for STIG are analyzed.

The pulp- and paper production is a very energy intensive industry sector. Both Sweden and the U.S. are major pulpandpaper producers. This report examines the energy and the CO2-emission connected with the pulp- and paperindustry for the two countries from a lifecycle perspective.New technologies make it possible to increase the electricity production in the integrated pulp- andpaper mill through black liquor gasification and a combined cycle (BLGCC). That way, the mill canproduce excess electricity, which can be sold and replace electricity produced in power plants. In thisprocess the by-products that are formed at the pulp-making process is used as fuel to produce electricity.In pulp- and paper mills today the technology for generating energy from the by-product in aTomlinson boiler is not as efficient as it could be compared to the BLGCC technology. Scenarios havebeen designed to investigate the results from using the BLGCC technique using a life cycle analysis.Two scenarios are being represented by a 1994 mill in the U.S. and a 1994 mill in Sweden.The scenariosare based on the average energy intensity of pulp- and paper mills as operating in 1994 in the U.S.and Sweden respectively. The two other scenarios are constituted by a »reference mill« in the U.S. andSweden using state-of-the-art technology. We investigate the impact of varying recycling rates and totalenergy use and CO2-emissions from the production of printing and writing paper. To economize withthe wood and that way save trees, we can use the trees that are replaced by recycling in a biomassgasification combined cycle (BIGCC) to produce electricity in a power station. This produces extra electricitywith a lower CO2 intensity than electricity generated by, for example, coal-fired power plants.The lifecycle analysis in this thesis also includes the use of waste treatment in the paper lifecycle. Both Sweden and theU.S. are countries that recycle paper. Still there is a lot of paper waste, this paper is a part of the countries municipalsolid waste (MSW). A lot of the MSW is landfilled, but parts of it are incinerated to extract electricity. The thesis hasdesigned special scenarios for the use of MSW in the lifecycle analysis.This report is studying and comparing two different countries and two different efficiencies on theBLGCC in four different scenarios. This gives a wide survey and points to essential parameters to specificallyreflect on, when making assumptions in a lifecycle analysis. The report shows that there arethree key parameters that have to be carefully considered when making a lifecycle analysis of wood inan energy and CO2-emission perspective in the pulp- and paper mill in the U.S. and in Sweden. First,there is the energy efficiency in the pulp- and paper mill, then the efficiency of the BLGCC and last theCO2 intensity of the electricity displaced by BIGCC or BLGCC generatedelectricity. It also show that with the current technology that we havetoday, it is possible to produce CO2 free paper with a waste paper amountup to 30%. The thesis discusses the system boundaries and the assumptions.Further and more detailed research, including amongst others thesystem boundaries and forestry, is recommended for more specificanswers.

Orientador: Prof° Dr. Marcelo Modesto da Silva / Dissertação (mestrado) - Universidade Federal do ABC. Programa de Pós-Graduação em Energia, 2016. / Existe um crescente interesse mundial pelo uso de biocombustíveis devido à preocupação com impactos ambientais provenientes do uso de fontes não-renováveis, além da busca por diversificação da matriz e redução da dependência em relação aos combustíveis fósseis. Diante desse contexto, destaca-se a biomassa de cana-de-açúcar, que pode ser aproveitada nas usinas para atender as demandas elétrica e térmica do processo. No Brasil quase todas as usinas sucroalcooleiras são autossuficientes em energia térmica, mecânica e elétrica, mas geralmente estes sistemas de cogeração possuem baixa eficiência. No que se refere a novas tecnologias de geração de energia, a gaseificação do bagaço, integrada a um ciclo combinado, se apresenta como uma alternativa promissora para aumentar a eficiência de geração de energia elétrica. Assim sendo, o objetivo principal desta dissertação foi desenvolver um módulo computacional para a simulação do comportamento termodinâmico de sistemas de cogeração BIGCC (Biomass Integrated Gasification Combined Cycle) através da metodologia de análises energética, exergética e custo exergético. A etapa inicial foi executada descrevendo-se um breve panorama do setor sucroalcooleiro brasileiro e uma visão geral do processo de gaseificação. A implementação de um modelo de equilíbrio químico não estequiométrico através da minimização da Energia Livre de Gibbs, utilizando o método dos Multiplicadores de Lagrange, foi realizada no software EES®, bem como versões modificadas desse modelo incluindo a quantidade de carbono não convertido e fração de metano, através do uso de equações empíricas de modo a melhorar os resultados do modelo. Os resultados obtidos foram comparados com outros trabalhos da literatura e mostraram boa concordância. Comparou-se também com simulações realizadas no software Thermoflex®, obtendo bons resultados. A modelagem também foi realizada no software EMSO. Em seguida, realizou-se a implementação de um ciclo de potência BIGCC em quatro etapas: a implementação da configuração proposta no softwareThermoflex® para a realização dos balanços de massa e energia; aplicação da mesma configuração no software EES® para validação e inserção das análises exergética e de custo exergético, utilizando modelo de equilíbrio puro; implementação do modelo modificado para comparação dos resultados e, por fim, simulação com inserção de palha ao gaseificador. / There is a growing interest worldwide for the use of biofuels due to concerns about environmental impacts from the use of non-renewable energies, and the search for diversification of the energy matrix and reducing dependence on fossil fuels. In this context, there is biomass sugarcane, which can be utilized in power plants to meet the electrical and thermal demands of the process. In Brazil almost all sugar and ethanol mills are self-sufficient in thermal, mechanical and electrical energy, but usually these cogeneration systems have low efficiency. With regard to new power generation technologies, gasification of bagasse, integrated with a combined cycle, is presented as a promising alternative to increase the efficiency of power generation. Therefore, the main objective of this thesis was to develop a computer module for the simulation of thermodynamic behavior of BIGCC cogeneration systems (Biomass Integrated Gasification Combined Cycle) using the methodology of energy, Exergy and exergetic cost analysis. The initial step was performed by describing a brief overview of the Brazilian sugar and alcohol sector and an overview of the gasification process. The implementation of a non-stoichiometric chemical equilibrium model by minimizing the free energy of Gibbs, using the method of Lagrange multipliers, was held at EES® software, as well as modified versions of this model including the amount of unconverted carbon and methane fraction, through the use of empirical equations to improve the model results. The results obtained were compared with other work from literature and shown good agreement. It is also compared with simulations in Thermoflex® software, getting good results. The modeling was also performed in EMSO software. Then, the implementation of a BIGCC power cycle in four steps are carried out: the implementation of the proposed configuration in Thermoflex® software for the realization of mass and energy balances; application of the same configuration in EES® software for validation and integration of Exergy and exergetic cost analysis using pure equilibrium model; implementing the modified model to compare the results and finally simulation with straw inserting the gasifier.

This thesis describes the development and experimental testing of a 100 kW dual fluidized bed biomass gasifier (also called a Fast Internally Circulating Fluidized Bed (FICFB) biomass gasifier). This steam-blown gasifier is being studied for its suitability within combined heat and power plant systems for the New Zealand forest products industry. This advanced design of gasifier has the ability to generate producer gas with a lower heating value (LHV) of 11.5-13.4 MJ/Nm3, which is two to three times higher than yielded by conventional gasification systems. This is accomplished because the gasification and combustion processes occur in two physically separated reactors. Several modifications to the gasifier were required after it was first constructed in order to achieve stable and reliable operation. Producer gas yields were measured through the use of helium as a tracer gas. A new simultaneous producer gas and tar sampling system was developed, allowing accurate samples to be obtained in a matter of minutes. Experimental testing included a cold testing exercise which provided valuable information on the circulation behaviour of the bed material and char within the gasifier. This helped in achieving stable and reliable operation of the plant. Producer gas yields of 14.6 Nm3/h were recorded with a fuel (radiate pine wood pellets) feed rate of 18.9 kgdry/h. The cold gas efficiency ranged from 16-40 % with limited heat recovery in place, but depended noticeably on the plant operating conditions especially gasification temperature. The amount of polycyclic aromatic hydrocarbon (PAH) tars measured in the producer gas ranged between 0.9-4.7 g/Nm3 with naphthalene and acenapthylene being the most abundant compounds. The moisture content of the producer gas was determined to be 0.9-1.2 g/gdry gas. It was found that a steam to biomass ratio of 0.45-0.7 kg/kgdry was most favourable for generating a 12-13.4 MJ/Nm3 producer gas while limiting the amount of steam generation. Gasification temperatures above 750 °C encouraged higher producer gas yields and higher cold gas efficiencies. The catalytic bed material olivine (forsterite olivine) was found to increase the producer gas yield by approximately 20 % compared to the non-catalytic bed material greywacke. The use of olivine meant higher cold gas efficiencies were achieved for a given wood feed rate.