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Edreder E.A.,Libyan Petroleum Institute | Mujtaba I.M.,University of Bradford | Emtir M.M.,Academy of Graduate Studies
Chemical Engineering Transactions | Year: 2012

The middle vessel column (MVC) is a combination of a batch rectifier (conventional column) and a batch stripper (inverted column). Therefore it is possible to obtain a light and a heavy fraction simultaneously from the top and the bottom of the column while an intermediate fraction may also be recovered in the middle vessel. Several researchers in the past have proposed the esterification of lactic acid (impure) with alcohol to obtain lactate ester which is then separated by distillation. To the best of our knowledge, simulation of middle vessel batch reactive distillation column for hydrolysis system has not yet been explored. In this work, the hydrolysis reaction of methyl lactate to produce lactic acid (LA) is carried out in a middle vessel column with fixed batch time while control variables are treated as a piecewise constant reflux ratio (multiple time intervals) and a single reboil ratio. For MVC, the LA being the heaviest in the reaction mixture, reflux and reboil ratios policy plays an important role to achieve high purity of LA. Copyright © 2012, AIDIC Servizi S.r.l. Source

Sibi G.,Academy of Graduate Studies
Research Journal of Environmental Toxicology | Year: 2015

Autotrophic cultivation of microalgae induces low biomass and lipid production and is difficult to be used in pilot scale production. Heterotrophic and mixotrophic algae allows higher growth rate, which in turn can accumulate higher biomass and lipid. Enhanced biomass and lipid production is crucial to use oleaginous microalgae for industrial application of biodiesel production. A fresh water microalga was isolated from waste water treatment plant and identified as Scenedesmus obliquus. The isolate was grown under varying cultural and nutrient conditions to increase biomass and lipid production. For this purpose, CO2 (10-160 mL min-1), temperature (20-45°C), fructose, maltose, glucose, sucrose and starch (10-50 g L-1), urea, sodium nitrate, potassium nitrate, ammonium nitrate and ammonium chloride (0.2-1.0 g L-1) were used. Optimum conditions were found by calculating specific growth rate and used to determine their influence on biomass and lipid production. At 40 mL minG1 (0.51%) CO2 concentration, 18.17 g L-1 biomass and 64.2% lipid production was obtained from the isolate. Glucose at 20 g L-1 have produced 18.62 g L-1 and 62.6% whereas sodium nitrate at 0.8 g L-1 resulted in 14.64 g L-1 and 65.1% of biomass and lipid production at the end of 20 days culturing period. Temperature of 25°C was found optimum where 12.38 g L-1 and 60.9% of biomass and lipid were obtained. Based on the results, by choosing optimum cultural conditions and nutrient composition of the growth medium it is possible to increase both biomass and lipid production in microalgae. © 2015 Academic Journals Inc. Source

Edreder E.A.,Libyan Petroleum Institute | Mujtaba I.M.,University of Bradford | Emtir M.,Academy of Graduate Studies
Chemical Engineering Journal | Year: 2011

Hydrolysis of methyl lactate to lactic acid in a reactive distillation column is widely used in the purification of lactic acid. In this work, optimal operations of conventional and inverted batch reactive distillation columns undergoing the hydrolysis reaction are presented. Minimum time optimisation problem is formulated incorporating a process model within gPROMS software and is solved for different range of lactic acid purity and the amount of product using both columns. For a given column type and configuration the minimum operation time is obtained by optimising the reflux ratio profile. For conventional column, the lactic acid being the heaviest in the reaction mixture, reflux ratio policy plays an important role in removing the light product methanol from the top of the column while ensuring the presence of both reactants in the reaction zone to maximise the conversion to lactic acid. For inverted column, reboil ratio policy plays an important role in removing the lactic acid from the bottom of the column while ensuring the presence of both reactants in the reaction zone to maximise the conversion to lactic acid. For some cases (although limited) it is observed that for low lactic acid product purity the conventional column outperforms the inverted column while for high product purity the inverted column outperforms the conventional column in terms of batch time. © 2011 Elsevier B.V. Source

Mujtaba I.M.,University of Bradford | Edreder E.A.,Libyan Petroleum Institute | Emtir M.,Academy of Graduate Studies
Applied Energy | Year: 2012

Lactic acid is widely used as a raw material for the production of biodegradable polymers and in food, chemical and pharmaceutical industries. The global market for lactic acid is expected to reach 259 thousand metric tons by the year 2012. For batch production of lactic acid, the traditional process includes the following steps: (i) esterification of impure lactic acid with methanol in a batch reactor to obtain methyl lactate (ester), (ii) separation of the ester in a batch distillation, (iii) hydrolysis of the ester with water in a batch reactor to produce lactic acid and (iv) separation of lactic acid (in high purity) in a batch distillation. Batch reactive distillation combines the benefit of both batch reactor and batch distillation and enhances conversion and productivity (Taylor and Krishna, 2000 [1]; Mujtaba and Macchietto, 1997 [2]). Therefore, the first and the last two steps of the lactic acid production process can be combined together in batch reactive distillation (Fig. 1) processes. However, distillation (batch or continuous) is an energy intensive process and consumes large amount of thermal energy (via steam). This paper highlights how significant (over 50%) reduction in thermal energy consumption can be achieved for lactic acid production process by carefully controlling the reflux ratio but without compromising the product specification. In this paper, only the simultaneous hydrolysis of methyl lactate ester and the separation of lactic acid using batch reactive distillation is considered. © 2010 Elsevier Ltd. Source

Sibi G.,Academy of Graduate Studies
Journal of Environmental Science and Technology | Year: 2015

The aim of this study was to evaluate the hydrolysates from crop residues as low cost carbon and nitrogen source for algal cultivation. The enzymatic hydrolysates of sweet sorghum (SSH) and rice straw (RSH) were used for heterotrophic cultivation of Chlorella vulgaris and Scenedesmus obliquus. Sugar concentration of 36.5 and 30.3 g LG1 were obtained in SSH and RSH, whereas, the nitrogen content was 10.6 and 19.5 mg LG1. Basal media with glucose was used as control and hydrolysates medium was used alone and in combination to determine its efficiency on microalgal biomass and lipid production. Maximum biomass was achieved in combined hydrolysates medium in C. vulgaris (4.8 g LG1) followed by S. obliquus (4.3 g LG1). Total lipid content of Chlorella was ranged from 11.26-29.36 and 15.43-27.24% in Scenedesmus. The qualitative analysis of fatty acids showed very high values of stearic acid (28.41 and 31.01%) and palmitic acid (23.54 and 26.21%) in both microalgae. This study could establish that the hydrolysates from sweet sorghum stem and rice straw can be used as growth medium for microalgal cultivation and opens new possibilities of exploiting crop residues for industrial applications. © 2015 Asian Network for Scientific Information. Source

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