Green liquor desilication via black liquor combustion process for bamboo pulping

Abstract

The presence of silicon in non-wood raw materials is known to interfere with the causticization of green liquor and the calcination of white mud, which has provided motivation for advances in alkali recovery technology. Therefore, reducing the silicon content of green liquor is the fundamental way to solve the problem. However, there are certain defects in conventional green liquor desilication, so this study provides a basis for desilication from green liquor via black liquor combustion and studies the desilication effect of a compound desilication agent on bamboo pulping black liquor. The results show that the desilication effect was better and the desilication rate could reach 84% when the Mg/Al proportion in compound desilication agent was 1:0.6. Meanwhile, the content of residual aluminum in green liquor decreased, which can avoid the influence of residual desilication agent on subsequent stages. Scanning electron microscopic images show that green-liquor-silicon-insoluble (GLSI) substance is a granular precipitate, and the X-ray diffraction analysis shows that GLSI substance has a complex structure similar to 3Al2O3•2SiO2•MgO. This implies that the desilication mechanism consists of chemical precipitation and physical adsorption.