HTL reactor system consideration Table HTL performance comparison
The typical final cell concentration from mass-cultivation facilities such as racing open-pond is too low to be used for a subsequent step of oil extraction; therefore Radezolid concentration, namely harvesting, is rather of absolute necessity. Unfortunately, however, harvesting is one of the most energy-intensive steps, consuming around 20% of total biodiesel production cost (Wei et al., 2014). There are a good many harvesting methods available at the moment, such as centrifugation (Schenk et al., 2008), various filtration methods including membrane modification in micro-, ultra-filtration(Hwang et al., 2013 and Kim et al., 2014a), and forward osmosis filtration (Buckwalter et al., 2013), flotation (Kwon et al., 2014), electro-floatation (Kim et al., 2012), coagulation/flocculation (Ahmad et al., 2011 and de Godos et al., 2011), and simple pH control (Nguyen et al., 2014). Even though each has its own advantages, the practical application has been limited due to its own inherent issues like energy consumption and scaling-up. Lipid extraction is an equally heavy burden to the industrial-scaled production of algal biodiesel: one obvious and critical issue is the prior requirement of biomass drying (Halim et al., 2012). Though laboratory-scale protocols of lipid extraction are well established and routinely practiced for the purpose of lipid analysis, no technology is being implemented at an industrial level (Cheng et al., 2014). Direct extraction of oil from wet biomass omitting a drying step might be a promising or even necessary route of improving overall efficiency in terms of both time and cost (Yoo et al., 2014). In addition, it would become even more competitive if harvesting and oil extraction processes can share energy consumption or chemical use. In the previous study, we developed a new method for cell disruption based on FeCl3 as catalyst and applied it to oil extraction, and achieved noticeable results of high extraction yield and good lipid quality (Kim et al., 2014b). In the present study, an attempt was made to integrate the harvesting step with the cell disruption step, especially in a way that FeCl3 (and also Fe2(SO4)3) was used both as a coagulant in harvesting step and as a catalyst for cell disruption in oil extraction step. This combined and simplified process was anticipated to improve the economic feasibility of the algal biodiesel production, by way of consuming less chemicals and energy.