Demonstration and Assessment of Purification Cascades for the Separation and Valorization of Hemicellulose from Organosolv Beechwood Hydrolyzates

Hemicellulose and its derivatives have a high potential to replace fossil-based materials in various high-value-added products. Within this study, two purification cascades for the separation and valorization of hemicellulose and its derived monomeric sugars from organosolv beechwood hydrolyzates (BWHs) were experimentally demonstrated and assessed. Purification cascade 1 included hydrothermal treatment for converting remaining hemicellulose oligomers to xylose and the purification of the xylose by nanofiltration. Purification cascade 2 included the removal of lignin by adsorption, followed by ultrafiltration for the separation and concentration of hemicellulose. Based on the findings of the experimental work, both cascades were simulated on an industrial scale using Aspen Plus®. In purification cascade 1, 63% of the oligomeric hemicellulose was hydrothermally converted to xylose and purified by nanofiltration to 7.8 t/h of a xylose solution with a concentration of 200 g/L. In purification cascade 2, 80% of the lignin was removed by adsorption, and 7.6 t/h of a purified hemicellulose solution with a concentration of 200 g/L was obtained using ultrafiltration. The energy efficiency of the cascades was 59% and 26%, respectively. Furthermore, the estimation of specific production costs showed that xylose can be recovered from BWH at the cost of 73.7 EUR/t and hemicellulose at 135.1 EUR/t.

Controle do Processo TCPSD para Separação da Mistura Acetonitrila/Benzeno/Metanol

Visando uma maior economia em custos operacionais, a inclusão de correntes de reciclo e integrações térmicas são rotineiras nos processos químicos, gerando a necessidade de estruturas de controle mais robustas, capazes de impedir perdas devido a distúrbios rotineiros e proporcionar segurança operacional. A separação via Triple-Column Pressure-Swing Distillation (TCPSD) pode ser utilizada para separar diferentes solventes da indústria de química fina, e devido ao grande número de variáveis envolvidas, juntamente a integrações térmicas e correntes de reciclo, a definição de uma estrutura de controle eficaz se torna um problema complexo. Neste contexto, este trabalho tem como principal objetivo o desenvolvimento e avaliação de estruturas de controle plantwide para o processo TCPSD, utilizado para separação da mistura acetonitrila/benzeno/metanol. Utilizando os softwares Aspen Plus© e Aspen Plus Dynamics©, foram avaliadas duas estruturas de controle, nas quais as composições dos produtos são controladas por inferência, através do controle da temperatura de pratos sensíveis. A principal diferença entre as duas estruturas é que a Estrutura de Controle 1 possui uma malha de controle de soma dual de temperatura de pratos sensíveis na coluna de baixa pressão, manipulando a razão de refluxo. Ao avaliar os resultados das composições dos produtos ao atingir estado estacionário e valores de ISE, concluiu-se que ambas as estruturas são capazes de controlar distúrbios do tipo degrau na vazão e composição de alimentação do processo. Contudo, observaram-se melhores resultados na Estrutura de Controle 1.

Process Simulation of Oxy-Fuel Combustion for A 120 MW Coal-Fired Power Plant Using Aspen Plus

Oxy-fuel Combustion is a technology with the potential of drastically reducing the amount of CO2 emission, it relies on the use of oxygen and recycled CO2 instead of air as the oxidant. This helps to reduce the amount of the CO2 and NOx emissions. This study focuses on the components of flue gas produced and their amounts for oxy-fuel combustion in a coal-fired power plant (CFPP) and also the boiler efficiency using the direct (input-output) method. The combustion process of pulverized coal in a 120MW power plant is studied using Aspen Plus 11. The amount of each component in flue gas in coal-fired processes with air or O2/ CO2 (using recycle of 20%, 40%, 60% and 80% of CO2) as oxidizer was obtained. From the process simulation, as the recycle % of CO2 was increased, the flame temperature, CO and NOx emissions were reduced. The simulation results of air combustion were compared with that of oxy-fuel combustion with 80% recycle and it was seen that the flame temperature dropped from 1894oC when air was used as oxidizer to 1679oC for oxy-fuel combustion with 80% recycle. Also, there was a reduction in the amount of NOx produced, but the SOx levels were constant for both combustion processes. The Gross Calorific Value (GCV) of the coal was calculated from its Proximate Analysis using Dulong’s formula and it was used to estimate the Boiler Efficiency using the Direct (Input-Output) method and a value of 83.6% was obtained.