Captura de dióxido de carbono (CO2) em processos de carbonatação mineral
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Data
2021-12-02
Autores
Galina, Natalia Ribeiro
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Universidade Estadual Paulista (Unesp)
Resumo
A tecnologia de carbonatação mineral mostra-se como um processo promissor para reduzir as emissões de CO2 na atmosfera. Entretanto, apresenta um alto custo de operação devido ao consumo de elevadas quantidades de energia e produtos químicos no processo. Para que o processo de carbonatação mineral possa ser implantado em escala industrial é necessário reduzir os custos energéticos. Assim, a presente pesquisa investiga o processo de carbonatação mineral indireta aquosa por balanço de pH, composto de três etapas principais: (1) dissolução ácida da matéria-prima, (2) purificação e (3) precipitação de carbonatos. Para isto, um planejamento experimental de superfície de resposta foi aplicado na etapa de dissolução ácida com o objetivo analisar a influência dos fatores de controle do processo na resposta de extração de Mg, Fe e Ca. Os resultados mostraram que o fator temperatura exerce influência significativa sobre a extração dos minerais, sendo que a maior extração de Mg registrada (96%) foi obtida quando o processo foi ajustado com temperatura de 100°C e concentração de HCl de 2,5 M em 120 min de reação. Observou-se que nessa condição, 91% de Mg pode ser extraído, ao reduzir o tempo de reação para 30 min. Desta forma, é possível reduzir o tempo da reação de dissolução do serpentinito utilizado de 120 min para 30 min mantendo-se níveis de extração de Mg acima de 90%. Na etapa de carbonatação hidromagnesita (Mg5(CO3)4(OH)2·4H2O) foi formada e precipitada. A máxima eficiência da conversão de íons de Mg em carbonatos foi de aproximadamente 66 % em condições de pressão atmosférica e 90% em ambiente com 150 bar de pressão.
Mineral carbonation technology shows itself as a promising process to reduce CO2 emissions into the atmosphere. However, it has a high operating cost due to the consumption of high amounts of energy and chemicals in the process. For the mineral carbonation process to be implemented on an industrial scale, it is necessary to reduce energy costs. Thus, the present research investigates the process of aqueous indirect mineral carbonation by pH balance, composed of three main steps: (1) acidic dissolution of the raw material, (2) purification and (3) precipitation of carbonates. For this purpose, an experimental response surface design was applied in the acid dissolution step in order to analyse the influence of process control factors on the Mg, Fe and Ca extraction. The results showed that the temperature factor influences the extraction of minerals, and the highest Mg extraction recorded (96%) was obtained when the process was adjusted with a temperature of 100°C and 2.5 M HCl concentration in 120 min of reaction. It was observed that in this condition, 91% of Mg can be extracted reducing the reaction time to 30 min. In this way, it is possible to reduce the time of the used serpentinite dissolution reaction from 120 min to 30 min, keeping Mg extraction levels above 90%. In the carbonation step hydromagnesite (Mg5(CO3)4(OH)2·4H2O) was formed and precipitated. The maximum efficiency of converting Mg ions into carbonates was approximately 66% under atmospheric pressure conditions and 90% in an environment with 150 bar of pressure.
Mineral carbonation technology shows itself as a promising process to reduce CO2 emissions into the atmosphere. However, it has a high operating cost due to the consumption of high amounts of energy and chemicals in the process. For the mineral carbonation process to be implemented on an industrial scale, it is necessary to reduce energy costs. Thus, the present research investigates the process of aqueous indirect mineral carbonation by pH balance, composed of three main steps: (1) acidic dissolution of the raw material, (2) purification and (3) precipitation of carbonates. For this purpose, an experimental response surface design was applied in the acid dissolution step in order to analyse the influence of process control factors on the Mg, Fe and Ca extraction. The results showed that the temperature factor influences the extraction of minerals, and the highest Mg extraction recorded (96%) was obtained when the process was adjusted with a temperature of 100°C and 2.5 M HCl concentration in 120 min of reaction. It was observed that in this condition, 91% of Mg can be extracted reducing the reaction time to 30 min. In this way, it is possible to reduce the time of the used serpentinite dissolution reaction from 120 min to 30 min, keeping Mg extraction levels above 90%. In the carbonation step hydromagnesite (Mg5(CO3)4(OH)2·4H2O) was formed and precipitated. The maximum efficiency of converting Mg ions into carbonates was approximately 66% under atmospheric pressure conditions and 90% in an environment with 150 bar of pressure.
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Palavras-chave
Carbonatação mineral, Balanço de pH, Serpentinito, Metodologia de superfície de resposta, Mineral carbonation, pH-swing, Serpentinite, Response surface methodology, Dióxido de carbono, Rochas metamórficas, Extração mineral