Study of sodium chloride scaling in salt dissolver of a chlor-alkali plant / Estudo da incrustação em saturador de cloreto de sódio em unidade de produção de cloro-soda.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

In the chlor-alkali industry, a Salt Dissolver has the objective of producing brine saturated in sodium chloride to feed electrolytic cells. However, the Dissolver studied in this work presented an incrustation of 1.5 meters of thickness, formed during nine years of operation. Many samples were collected in distinct positions of the equipment to allow proper characterization of the incrustation and to compare differences. The crystal size of the samples taken from the top was bigger than those from the bottom, where diluted brine is injected. X-ray diffraction analysis determined that samples at the bottom are less crystalline, hence, relatively more soluble. Normal operation and particular situations were examined to identify conditions which allow the incrustation formation. A fluid dynamic program, CFX-5, was used to evaluate brine flow inside the Dissolver, while the Pitzer model provided the phase equilibrium for each case. The latter was developed for Na+-H+-Cl--SO4 =- OH--H2O system. Although the pH varies from 2,5 to 10,5 in the Dissolver, it does not cause a change in solubility. Based on the results obtained with the Pitzer model, temperature and sulfate content are the main factors. The incrustation mechanism is driven by the temperature coupled to equilibrium changes. Situations checked with the model and crystal size difference denotes that Ostwald ripening and agglomeration happens in the Dissolver

ASSUNTO(S)

pitzer sodium chloride engenharia quimica cloreto de sódio incrustation ostwald ripening saturador de cloreto de sódio incrustação ostwald ripening pitzer desenvolvimento e otimização de processos industriais

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