Neste trabalho, se estudou o comportamento de partículas no interior de um reator termoquímico com o intuito de desenvolver uma grelha que maximizasse o movimento e homogeneização do leito fluidizado. Este reator é utilizado para a geração de gás de síntese, uma mistura multifásica de gás e partículas suspensas, por meio da termodegradação de biomassa. Para entender o comportamento dessas partículas, realizou-se um estudo numérico no software ANSYS® Fluent, considerando um modelo multifásico DPM (Discrete Phase Model) e o modelo de turbulência k-ômega-SST. Os resultados demonstraram um comportamento satisfatório das partículas, já que foi verificado a ausência de acúmulo de partículas na grelha e nas bordas do dispositivo, além de comprovar a eficácia dos ciclones filtrantes no seu interior.

For the first time, the mass yields of products and the composition of synthesis gas (syngas) from pyrolysis of Brazilian plastic solid waste were evaluated for a reactor processing 20g of plastic at 800oC. Combustion of the syngas was simulated, evaluating the levels of COx and CxHy emissions, and a burner was designed to minimize emissions during combustion. The main findings highlighted the importance of performing thermogravimetric analyses of waste materials. Higher thermal degradation temperatures (530-900oC) were obtained for all the plastics, compared to values reported in the literature (300-600oC). Between 46.7 and 98.0wt.% of syngas was produced, with lower heating values ranging from 10390 to 45684kJkg−1, due to differences between the plastics in the fractions of inorganic and hydrocarbon gases produced. The maximum temperatures for syngas combustion, simulated using ANSYS software, were 2000 and 800oC inside the burner and combustion chamber, respectively. In the burner, higher COx and CxHy levels were related to the syngas composition and incomplete chemical reactions in the flame zone. The CO and CxHy levels decreased towards the combustion chamber, where CO2 was less than 8wt.%, in compliance with the CONAMA 316/2002 regulation.

This study is motivated by the production of synthesis gas (syngas) from gasification of refused-derived fuel (RDF) in thermochemical reactors. For this purpose, a reactor with a circulating fluidized bed transforms RDF into synthesis gas at temperatures around 850°C. The syngas consists of a biphasic mixture, containing fuel gas and solid particles that are dragged during the gasification process. The gas flows into an axial cyclone positioned inside the upper part of the reactor, so that non-gasified particulates, inert residues and particles from the bed can be removed. Due to the size and density of the solid particles and the residence time inside the thermochemical reactor, the cyclone must be designed to clean the gas, improving its quality and reducing costs with scrubbers. Therefore, in this study, a vertical cylindrical reactor with 10.57 m height and 0.95 m diameter was modeled computationally, with an axial cyclone inside measuring 9.3 m in height and 0.6 m in the largest diameter region. The model does not consider thermochemical reactions inside the reactor. For the solid phase, 0.425 m³ of 100 mesh sand particles with a constant density equal to 1500 kg/m³ were considered. For the gas phase an air flow of 800 kg/h at 500°C was adopted. Numerical-computational models were solved using the ANSYS® software, based on the classical equations of mass conservation, momentum and energy. The k-omega SST turbulence model has been applied. From the analysis of pressure gradient, velocity profiles and the particulate removal rate in the cyclone, the cyclone efficiency and the pressure drop were determined. An efficiency of 99.83% in the cleaning process carried out by the axial cyclone was observed. The obtained results also allowed analyze the distribution of particles inside the reactor and their passage in the axial cyclone.

Devido ao fato de serem muito leves e pequenas, moléculas de hidrogênio podem facilmente penetrar materiais, gerando desafios no que diz respeito ao armazenamento desse gás. O objetivo deste estudo é analisar a permeabilidade ao hidrogênio do bag comercial de fluoreto de polivinila (PVF), além de desenvolver e testar a permeabilidade ao hidrogênio de um recipiente de policloreto de vinila (PVC). Para isso, foi utilizada a cromatografia gasosa, além da Equação de Clapeyron para determinar as concentrações de cada gás de uma mistura de H2 + CH4 + CO ao longo de vários dias. Foi constatado que o bag comercial de PVF não é uma boa opção para o armazenamento de gases que contêm alta concentração de H2, visto que ele é altamente permeável, de modo que a amostra perdeu suas características iniciais rapidamente. No entanto, o recipiente de PVC desenvolvido no laboratório provou-se uma alternativa viável, pois foi capaz de manter praticamente constante, por vinte dias, as concentrações dos gases da mistura citada anteriormente. Tal resultado oferece uma aplicação prática, no sentido de facilitar o trabalho laboratorial na questão do armazenamento de amostras que contêm gás hidrogênio.

. Heat exchangers are intended to increase heat transfer between fluids, with or without mixture between them, making thermal processes more efficient and reducing energy demand. This study aims to analyze the heat transfer that occurs inside shell-and-tube heat exchangers (recuperators) with baffles, to verify their efficiency through models related to the first law of thermodynamics. For this, the influence of the baffles was analyzed, as elements to direct the flow, expanding time and the area of contact between cold fluid with the hot one, thus allowing an increase in the exchange efficiency. To carry out this study, three-dimensional numerical simulations were performed using the ANSYS ® Fluent software. The turbulence model used was the 𝑘 - 𝜔 𝑆𝑆𝑇 and the energy equation was considered. The main objective of this study is to understand the physical, fluid dynamic and thermal phenomena of the heat exchanger, as well as to evaluate the variables involved.

Simulations of a fluidised bed reactor for gasification of municipal solid refuse-derived fuel were performed using OpenFOAM software. Firstly, evaluation was made of a simplified gas-solid two-phase model, considering sand and air as the components, according to a transient Eulerian-Eulerian approach. A scale-up study was also performed to obtain thermal-fluid dynamic parameters. Then, a real dimensions non-reacting model was developed, based on the experimental information from a semi-industrial gasification plant with capacity for processing 7.1 t day−1 of municipal refuse-derived fuel, producing 16.9 t day−1 of syngas. The fluidising regime was mapped for different inlet conditions, at 1,123 K, with air velocities ranging from 0.01 to 1.25 m s−1, and the continuous operation of the reactor was analysed, where in the solid particles packing remained at approximately 88% from maximum, with bed height of 2.05 m. The results were in good agreement with data available in the scientific literature, and the computational model was able to provide consistent results when compared to the experimental information for the semi-industrial reactor. The authors’ major remark was the hability of this computational model in obtaining consistent results from simulations of the semi-industrial scale reactor, with good prediction of the internal fluid dynamics characteristics.

Temperature is the main parameter measured in industry. It allows identification of the operational status of equipment and helps to predict maintenance. However, electric motors, bearings and hydraulic pumps do not have thermal sensors in their internal parts. Therefore, a numerical and experimental technique to determine the internal temperature and the thermal properties (thermal conductivity and diffusivity) of industrial equipment was developed. The proposed technique uses a one-dimensional transient thermal model, inverse heat conduction and generalised impedance method. Polyvinyl chloride flat plate (in a laboratory scale and under controlled conditions) was used to evaluate the technique. Based on the results and compared with experimental data and information from the literature, this technique demonstrates to be feasible and applicable in flat surfaces. However, further work is still needed to confirm the feasibility of the technique when applied to metallic, curved or thicker surfaces. Graphical abstract

This is the first study to investigate the use of municipal refuse-derived fuel for gasification in pilot plant scale aiming at urban waste treatment and energy generation. Energy and mass balances were applied to the thermochemical reactor based on the experimental data obtained during pilot scale operation to calculate thermal efficiency associated to the process. Volumetric composition, lower heating value, and density of the resulting syngas were determined using calorimetric tests and chromatographic analyses. The pilot plant gasification system processed 7.1 tonnes day?1 of municipal refuse-derived fuel producing 16.9 tonnes day?1 of syngas with a lower heating value of 4.6 MJ kg?1, along with 26 wt.% ash. No tar was generated during the process. According to results of this study, the pilot plant is able to generate sufficient electricity for nearly 800 small houses if connected to a steam power cycle. Pollutants emitted from syngas combustion (performed by accredited agencies) were analyzed and levels were below legal standards established in Brazil and in the United States, thus demonstrating the feasibility of this technology for conversion of municipal solid waste into a renewable energy source. ? 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.