Effects of aqueous suspension properties on the atomization and dispersibility of spray dried cellulose nanocrystallite granules

加拿大是全球主要的林产品国家，并引领下一代高附加值木材衍生产品的商业化：纤维素纳米晶体（CNC）和纤维素纳米原纤维（CNF）。为了加速木质纳米纤维的商业化进程并保持全球领先地位，加拿大林业行业领先的研究机构FPInnovations确定了需要解决的六大挑战。其中之一是纤维素纳米晶体在水介质中的分散，这在本提案中得到了解决。CNC通常首先通过铣削，然后酸水解硫酸盐纸浆纤维素来生产。采用浓硫酸（65%）去除无定形区域，释放均匀和无缺陷的纤维素纳米晶体（CNC）。生产出来的浆料先进行离心、过滤，然后进行CNC分散浆料喷雾干燥。因此，CNC颗粒以自由流动的干燥颗粒材料的形式回收。在喷雾干燥中，水分的蒸发往往会导致CNC颗粒的不可逆聚集。粉末状态的CNC必须重新分散在水溶液中，以获得精确的最终产品应用。因此，在干燥过程中需要适当控制聚集，以保持CNC颗粒在再分散过程后的单个颗粒大小和表面特性。本文研究了电解液、表面活性剂和聚合物在CNC水悬浮液中如何影响喷雾干燥机操作过程中CNC颗粒的液滴形成和形态，以及它们在水介质中的分散性。本研究的目的是了解过滤后的CNC悬浮液性能如何影响喷雾干燥和干燥后CNC颗粒的形貌。这反过来又有助于形成聚集体和CNC颗粒在水中的再分散。CNC悬浮液的喷雾干燥将在不同的CNC悬浮液浓度、电解质（NaCl）、表面活性剂（具有12-14碳链的非离子型线性二次醇）和防絮凝剂（聚丙烯酸铵）的存在下进行，并在不同的喷雾干燥机操作条件下进行。

Canada is a major global forest products country and leads the commercialization of next generation high-value added wood derived products:cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF). To accelerate the commercialization process of wood based nanofibers and maintain global leadership, Canadian forest industries leading research organization, FPInnovations identified six (6) main challenges to be solved. One of them is the dispersion of cellulose nanocrystals in aqueous media which is addressed in this proposal. CNC is typically produced first by milling and then acid hydrolyzing of kraft pulp cellulose. Employing concentrated (65%) sulfuric acid removes the amorphous regions and releases homogenous and defect free cellulose nanocrystals (CNC). The produced slurry is first centrifuged, filtrated and then CNC dispersion slurry is spray dried. Thus, CNC particles are recovered in the form of free flowing dry granular material. In spray drying, evaporation of water often causes an irreversible aggregation of CNC particles. CNC in powder state must be redispersed in aqueous solutions for accurate end product applications. Hence, proper control of aggregation during drying is needed to preserve individual particles sizes and surface properties of CNC particles after the redispersion processes.This proposal deals with how electrolytes, surfactants and polymers in aqueous CNC suspensions influence the droplet formation and the morphology of dried CNC granules during the spray drier operations and their dispersibility in aqueous media. The objective of this research is to understand how CNC suspension properties after filtration influences the spray drying and morphologies of dried CNC granules. This in turn contributes to the formation of aggregates and redispersion of CNC granules in water. Spray drying of CNC suspensions will be carried out at various CNC suspension concentrations, electrolyte (NaCl), surfactant (non-ionic linear secondary alcohol with 12-14 carbon chain), and deflocculant (ammonium polyacrylate) presence and operating at different spray dryer operating conditions.