Biodiesel production process

Modifications in the production of biodiesel can result in valuable glycerol as a byproduct and in fewer separation steps. The modifications studied or considered include combining etherification of glycerol into the biodiesel production process, etherification in situ within the biodiesel process and a biodiesel process with heterogeneous catalyst. 

Figure 7 depicts a simplified block flow diagram (BFD) for a typical biodiesel production process using base catalysis. In the first step, methanol and catalyst (NaOH) are mixed with the aim to create the active methoxide ions (Figure 4, step 1(b)). Then, the oil and the methanol-catalyst solution are transferred to the main reactor where the transesterification reaction occurs. Once the reaction has finished, two distinct phases are formed with the less dense (top) phase containing the ester products and unreacted oil as well as some residual methanol, glycerol, and catalyst. The denser (bottom) layer is mainly composed of glycerin and methanol, but ester residues as well as most of the catalyst, water, and soap can also be found in this layer. 

Generally, alkali-catalyzed transesterification is performed near the boiling point of the alcohol, but several researchers have reported high conversion yield at room temperature (8,14). Low reaction temperature was desirable, since reaction temperature was closely related to the energy cost of the biodiesel production process. 

Reaction temperature and time were significant operating parameters, which are closely related to the energy costs, of the biodiesel production process. Figure 7 shows the effect of reaction time on the transesterification of rapeseed oil at a catalyst concentration of 1%, molar ratio of 1 6, and 60°C. Within 5 min, the reaction was rapid. Rapeseed oil was converted to above 85% within 5 min and reached equilibrium state after about 10 min. Several researchers reported that the conversion of vegetable oils to FAME was achieved above 80% within 5 min with a sufficient molar ratio (8,11). For a reaction time of 60 min, linoleic acid methyl ester was produced at a low conversion rate, whereas oleic and linolenic methyl ester were rapidly produced. 

Figure 2.48 Current biodiesel production process by transesterification of vegetable oils.

The biodiesel production process has three basic routes from fats and oils to produce esters or biodiesel, according to the National BioDiesel Board [14] ... 

Shrivastav and co-workers [26] attempted to isolate PHA-producing bacteria from soil and marine environments using a Jatropha biodiesel by-product generated from the biodiesel production process which uses Jatropha curcas seeds as the carbon source. The Nile red... 

Urbani, F., Freni, S., Galvagno, A., and Chiodo, V. (2011) MCFC integrated system in a biodiesel production process. 

In many cases, the conversion at the reactor is low and the unreacted species need to be recycled. Duran and Grossmann [19] proved that we can improve the conversion of the recycled systems by simultaneous optimization and heat integration if the conversion of the reaction is variable compared to sequential approaches. Recently, this concept was used in the design of biodiesel production processes where methanol or ethanol was used in excess in the transesterification reaction to move the equilibrium toward biodiesel, which needs to be recycled. The recovery of the alcohol determines the energy consumption of the process and thus the operating conditions at the reactor must be adjusted to reduce the energy needed in the recovery of the alcohol. The optimal operating conditions at the reactor differ from the ones reported where the reactor is evaluated alone [20,21]. 

The use of methanol offers the best results in the trans-esterification of oils and fats. Compared with other alcohols, methanol requires shorter reaction times and smaller catalyst amounts and alcohol/oil molar ratios [10,12,15,16,51,52]. These advantages lead to reduced consumption of steam, heat, water, and electricity, and use of smaller processing equipment to produce the same amount of biodiesel. Biodiesel applications continue to expand. Thus, in addition to its use as fuel, biodiesel has been employed in the synthesis of resins, polymers, emulsifiers, and lubricants [53-64]. Concerning the range of applications, new biodiesel production processes should be considered as alternatives to the production based on methanol. Currently, methanol is primarily produced from fossil matter. Due to its high toxicity, methanol may cause cancer and blindness in humans, if they are overexposed to it. Methanol traces are not desired in food and other products for human consumption [15]. In contrast, ethanol emerges as an excellent alternative to methanol as it is mainly produced from biomass, is easily metabolized by humans, and generates stable fatty acid esters. Additionally, fatty acid ester production with ethanol requires shorter reaction times and smaller amounts of alcohol and catalyst compared to the other alcohols, except methanol, used in transesterification processes [11,15,16]. 

D Ippolito SA, Yori JC, Itmria ME, Reck CL, Vera CR. Analysis of a two-step, noncatalytic, supercritical biodiesel production process with heat recovery. Energy Fuels 2007 21 339-346. 

Crude glycerol is a cheap substrate, a readily available waste byproduct of current biodiesel production processes. Its potential as a carbon source for microbial fermentation in the production of industrially important chemicals is currently being exploited [37, 38]. Glycerol is a reduced, three-carbon compound like 3-HP, so the reaction steps for the conversion of glycerol into 3-HP are generally... 

Mootabadi, H., Salamatinia, B., Bhatia, S., and Abdullah, A. Z. Ultrasonic-assisted biodiesel production process from palm oil using alkaline earth metal oxides as the heterogeneous catalysts. Fuel 89,1818-1825 (2010). 

Figure 6.6 A simplified biodiesel production process. Reproduced with permission from D. Co. 

Using the simulated biodiesel production process as case study, basically Jeerawongsuntom and team (2011) integrated the human-machine interface with HAZOP analysis for safety protection. Safety instmmented system was developed to create interlocks such as automatic shutdown to prevent the system from being exposed to extreme or... 

Lee, S., Posarac, D., Elhs, N. Process simulation and economic analysis of biodiesel production processes using fresh and waste vegetable oil and supercritical methanol. Chemical Engineering Research and Design. 89 (2011) 2626-2642. 

Narayanan, D., Zhang, Y. Mannan, M. S. Engineering for sustainable development (ESD) in biodiesel production. Process Safety and Environmental Protection 85 (2007) 349-359. 

Dhar, B.R., Kirtania, K., 2009. Excess methanol recovery in biodiesel production process using a distillation column a simulation study. Chemical Engineering Research Bullettin 13,55-60. 

Baroi, C., Dalai, A.K., 2015. Process sustainabihty of biodiesel production process from green seed canola oil using homogeneous and heterogeneous acid catalysts. Fuel Processing Technology 133, 105—119. 

Li, Y.H., Ye, B., et al., 2013. Optimization of biodiesel production process from soybean oil using the sodium potassium tartrate doped zirconia catalyst under microwave chemical reactor. Bioresource Technology 137, 220—225. 

Lee, H.V., Taufiq-Yap, Y.H., 2015. Optimization study of binary metal oxides catalyzed transesterification system for biodiesel production. Process Safety and Environmental Protection 94, 430—440. Available at http //www.sciencedirect.com/science/article/pii/ S0957582014001529 (accessed 27.04.15.). 

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