Study on the Dynamic Viscoelasticity of Bamboo Kraft Black Liquor

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.

Section: Introductionmentioning

confidence: 99%

Green liquor desilication via black liquor combustion process for bamboo pulping

Zhang

Pei

et al. 2022

“…The silicide in raw materials reacts with alkali to produce Na2SiO3 dissolved into the black liquor, which will cause a series of trouble, named "silicon interference" problems. One of the problems is that the viscosity of BKBL will increase rapidly with the increase in silicon content, which brings problems to black liquor pumping and atomization and then has an influence on the evaporation and combustion efficiency (Zaman and Fricke 1996;Liu et al 2013;Xu et al 2016aXu et al , 2016b. The black liquor forms a liquid film when hitting the splash-plate nozzle at a higher speed by accelerating in the barrel of spray gun, and this process is defined as an atomization (Barreras et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Spray atomization simulation of bamboo kraft black liquor with high solid content at splash-plate nozzle

Chen

et al. 2021

Self Cite

Increasing the solids content of pulping black liquor burned in a furnace is a development trend of the alkali recovery system in the pulp and paper industry. However, the viscosity of kraft black liquor increases exponentially with an increase in solids content, especially in the case of non-wood pulping black liquor, such as bamboo. This brings great difficulties to the pulping system and atomization of black liquor at the splash-plate nozzle, which is a complete atomization unit constituted of a splash nozzle and a splash plate. To obtain instructive results for industry, a simulation of the atomization process was made using Fluent software for the bamboo kraft black liquor with solids contents of 70 wt% and 80 wt%, which flowed through splash nozzles with the diameter of 22 or 20 mm. The studies were conducted on the distribution of flow field in the nozzle and atomization region through changing the injection pressure and nozzle diameter. The variation of atomization characteristic parameters, such as liquid film thickness, and breakup length, were elucidated. The results reveal the relationship between spray atomization with injection pressure and nozzle diameter, which provides a theoretical basis for improving the concentration of black liquor entering alkali recovery in the future.

“…The quality of bamboo kraft paper is superior to that of straw pulp paper. Hence, bamboo is considered a favorable papermaking material (Xu et al 2016a).…”

Section: Introductionmentioning

confidence: 99%

Rheological properties of thick kraft black liquor at high temperature with the addition of sodium aluminate

Yue

2017

In kraft recovery systems, there is a trend toward increasing solids content of the black liquor injected to the furnace. Higher solids contributes to combustion efficiency and stable boiler operations. However, the presence of silica can adversely affect the viscosity of the mixture in such cases. Sodium aluminate, which was used as a desilicating agent during the black liquor combustion, had an excellent effect on the removal of silicon from the bamboo kraft black liquor (BKBL) to solve the problems presented by silicon. The apparent viscosities of thick BKBL with the addition of varied sodium aluminate loading were studied with a rotational rheometer. The thick BKBL behaved as a pseudo-plastic fluid that exhibited shear-thinning. However, shear-thickening appeared when the shear rate exceeded 30 s-1 at 98 °C, which would influence the flow stability of BKBL in pipelines. When the loading was 1.5 wt.%, sodium aluminate promoted the flow and droplet formation of thick BKBL by reducing its structural strength. The Ostwald-de Waele model provided an ideal fit to the apparent viscosity data. Hence, it could be used to accurately predict apparent viscosity changes in thick BKBL.