عنوان مقاله
مدلسازی و ارزیابی بوزدایی ناپیوسته روغن آفتابگردان
فهرست مطالب
مقدمه
مدل انتقال گرما
مقدار D
مواد و روشها
نتایج و بحث
نتیجه گیری
بخشی از مقاله
مواد و روشها
فرایند مورد مطالعه در بوزدای ناپیوسته ای متشکل از یک مخزن استوانه ای عمودی با ابعاد کلی ، قطر 2 متر، ارتفاع 1. 4 متر و سطح گرمایش کویل های بخار F=25𝑚^2 اجرا گردید. جرم و ظرفیت گرمایی ویژه جسم فولادی با کویل بخار به ترتیب Mm=1900kg و Cm=0.46kg-1 ℃- 1 بود.
شکل 1- بوزدای ناپیوسته: (1) کویل لوله و حرارت داخلی؛ (2) توزیع کننده لوله ستاره ای شکل؛ (A) خنثی کننده روغن ورودی ؛ (B) مانع ورودی بخار؛ (C) بوزدایی خروجی روغن؛ (د) خروجی بخار؛ (E) ورودی بخار گرم. (F) خروجی میعانات.
کلمات کلیدی:
g and evaluating the batch deodorization of sunflower oil S. Akterian * University of Food Technologies, Division Vegetable Oils, 26 Maritza Boulevard, BG-4002 Plovdiv, Bulgaria article info Article history: Received 12 December 2007 Received in revised form 10 June 2008 Accepted 1 August 2008 Available online 9 August 2008 Keywords: Batch deodorization Oleic acid Steam distillation Sunflower oil Vacuum abstract An engineering approach for evaluating the oil temperature during the batch deodorization is proposed. This approach employs a quasi-steady model including equations of steady-state heat transfer for consecutive time steps of computation. A new index – De-value – for assessing the efficacy of batch deodorization is proposed. The De-value represents the reduction of a key volatile component. It was established that the oleic acid is better to be used as a key component for assessing the deodorization of high oleic sunflower oil conducted at low temperature conditions – below 200 C. The deodorization process of sun- flower oil may be accepted as efficient if the De-value reaches a value 2 ± 0.2. The engineering approach proposed for evaluating De-value can be used as a tools for: (i) estimating the efficacy of process conditions applied at present; (ii) specifying eligible values of process parameters when a new process design will be established. 2008 Elsevier Ltd. All rights reserved. 1. Introduction Deodorization is a crucial refining stage with an important effect on the quality of oil refined. Principally, it is a steam distillation under vacuum. The purpose of this process is the removal of undesired volatile odoriferous components in vegetable oils, namely aldehydes, ketones, carbohydrates, and free fatty acids. Among them the heavier free fatty acids have the lowest vapor pressure and therefore they are the least volatile components (Bockisch, 1998). The saturated stearic acid C18:0 with a molecular mass of 284.5 Da, the saturated palmitic acid C16:0 with a molecular mass of 256.4 Da, the unsaturated oleic acid C18:1 with a molecular mass of 282.4 Da and linoleic acid C18:2 with a molecular mass of 280.4 Da are of the biggest interest because their concentrations in crude sunflower oil and in the oils before deodorization are the highest (Vasileva, 2003) and their vapor pressures are the lowest. The deodorized oils can be considered as a binary mixture including triglycerides (non-volatile in practice) and a key component – a volatile free fatty acid (Bockisch, 1998). The free stearic acid is used as a key component in the cases when the deodorization process is carried out at temperatures exceeding 200 C (Vasileva, 2003). It is not found any criterion or an index cited in the specialized literature for assessing the reduction of undesired volatile components of the oil when the deodorization is carried out under variable temperature conditions. At present, three types of deodorizers – batch, semi-continuous and continuous – are used in the practice. Semi-continuous and continuous deodorizers are best suited for large plants. These deodorizers enable the residence time of oil and the consumption of stripping steam to be reduced (Brekke, 1980). They can gain a heat recovery up to 50% and 85%, respectively (Carson, 1988). The batch deodorizers are more suitable for small plants because of their flexibility and very low instatement costs (Bockisch, 1998). A large part of Bulgarian refineries are small and medium enterprises and for that reason the batch deodorizers are widespread. The temperature of the oil in these batch deodorizers is variable throughout the process and it is low due to the technical background of these small refineries. Two stages can be specified during the batch deodorization: (i) indirect heating up to temperatures 145–160 C, and (ii) indirect heating up to temperatures 175–210 C under high vacuum conditions (with a residual pressure 0,3...1...15 kPa) and a simultaneous injection of stripping superheated steam. The deodorization is a complex heat and mass transfer process. During deodorization some degradation reactions such as hydrolysis of triglycerides and cis–trans isomerization reactions of free fatty acids (Ceriani et al., 2008; Kemeny et al., 2001; Tasan and Demirci, 2003) take place as well. The equation of Bailey (1941) for the requirement of stripping steam is recognized all over the world (Bockisch, 1998; Brekke, 1980; Gavin, 1978; Leniger and Beverloo, 1975; Molchanov, 1965). The vaporization efficiency included in this equation can be determined more accurately if the approach presented by Ceriani and Meirelles (2005), Decap et al. (2004) and MacFarland et al. (1972) is taken into consideration. Dijksra (1999) showed that Bailey’s equation is eligible for batch and crow-flow deodorizing systems but it is not suitable for evaluation of the stripping requirement of countercurrent continuous 0260-8774/$ - see front matter 2008 El
