Use of a solar steam generator for the extraction of essential oils.
Steam generation is an energy-intensive process and is invariably based on fossil fuels, briquettes or biomass. In this context, a recent study carried out by a team of Indian researchers (Pise & Thorat, 2023) proposed the use of a sustainable system, based on solar technologies, to be applied to the extraction process of an essential oil (Betel leaf). In particular, for the tests, opto-geometric optimisation and concentrating solar collectors (CSC) area calculation were carried out.
The analysis was performed considering the following three different types of CSC: Linear Fresnel reflector (LFR), parabolic plate collector (PDC) and parabolic trough collector (PTC). According to the results, a collection area of 78, 122 and 139 m2 for LFR, PDC and PTC, respectively is necessary to meet the required steam generation (250 kg per batch of biomass processed). The test als allowed to determine a given steam requirement of 750 g/ml of extracted oil.
Finally, the study carried out a detailed techno-economic analysis showing that the cost associated with unit steam generation through CSC technologies is lower than a for a conventional briquette-based steam generation. Even if the initial cost seems to be high, the payback period of LFR and PTC systems are 1.10 and 2.45 years, respectively. In conclusion, CSC technology can provide a sustainable green solution for the generation of steam to be used for the extraction of essential oils.
Use of filter cake and bagasse as fuel for the production of steam in sugar mills.
Filter cake is a by-product from sugar production and estimated to be about 4% of input biomass (sugar cane). This residue is a dark brown fine particle with a 65-75% moisture content. The aim of a recent study, carried out by a team of Thai researchers (Pajampa & Wongwuttanasatian, 2023), was to turn this by-product to energy by pelletisation and using the pellets as fuel in a steam generator. For the test, the filter cake was fed to the plant with bagasse in different ratios (in the range of 1–5 % by mass).
The results showed that 1% and 2% filter cake pellets gave approximately 91% combustion efficiency, which is similar to that of pure bagasse, without impacting the pressure and temperature of the steam produced. However, when using 5% pellets, the combustion efficiency dropped to 87%, due to feeding systm problems. According to the authors, in this case the fuel spreading system should be modified using higher ratio of the pellets. In summary, the study revealed that filter cake pellets can be used without any problem as a fuel for steam generators to support the sustainable zero-waste campaign in sugar industry.
References: V.H. Pise and B.N. Thorat, Energy Nexus, 9, 2023, 100175. Pajampa and T. Wongwuttanasatian, Energy Reports, 9, 2023, 422-430.
