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C. Li et al.
fertilizer). The filtrate flows through the filter to enter the continuous gravity separator, separating the light phase (fatty acid and oil) and the heavy phase (crude
glycerol).
b. Re-esterification of oil phase. After filtration, the oil phase enters the esterification reactor. Add a specified amount of methanol and catalyst (concentrated
sulfuric acid) for continuous esterification. The reactants then enter the separation column, separating biodiesel from methanol and concentrated sulfuric acid.
The small amount of methanol returns to the raw material oil tank as RME.
The remaining methanol and sulfuric acid solution are collected for reuse in the
recycling process.
c. Recycling of methanol in crude glycerol. Crude glycerol is heated before entering
the two-effect falling film evaporator, separating crude glycerol from methanol
and aqueous methanol. The glycerol obtained has very little methanol (less than
0.1%), and has a glycerol content of more than 80% (13.3% water, 2% potassium
sulfate, and less than 3% impurities). The aqueous methanol separated is purified
and recycled through the rectification column for reuse.
5.2.7 Determination of Conditions for Biodiesel Production
Process
Based on kinetics principles in chemical reactions and researches by Peterson et al.,
the key factors affecting the conversion rate of transesterification are reaction temperature, methanol concentration, types and concentration of catalyst, fluid mechanics
conditions, and reaction time.
5.2.7.1 Impact of Methanol Concentration on Biodiesel Yield
Transesterification is a reversible reaction. Normally, an excessive amount of
methanol is used to drive the reaction equilibrium towards the forward direction, so
as to enhance the conversion rate of transesterification. However, here is an amount
issue [28]. A higher methanol concentration drives the reaction equilibrium towards
the forward direction. However, an excessive level of concentration has a lower
performance in this regard and leads to higher cost. Therefore, it is necessary to
determine the initial optimal concentration of methanol.
Below is the research result of how the molar ratio of methanol and soybean oil
affects the yield of biodiesel at 60 °C using 1.0% (wt%) NaOH as a catalyst with a
reaction time of 45 min. It is presented as follows:
Figure 5.6 shows that as the initial concentration of methanol increases, the reaction yield of biodiesel also sharply increases. At the methanol/soybean oil molar ratio
of 6:1, it reaches the highest point of 85.0%. But if the initial methanol concentration
further increases, the biodiesel yield remains almost the same. This demonstrates
C. Li et al.
fertilizer). The filtrate flows through the filter to enter the continuous gravity separator, separating the light phase (fatty acid and oil) and the heavy phase (crude
glycerol).
b. Re-esterification of oil phase. After filtration, the oil phase enters the esterification reactor. Add a specified amount of methanol and catalyst (concentrated
sulfuric acid) for continuous esterification. The reactants then enter the separation column, separating biodiesel from methanol and concentrated sulfuric acid.
The small amount of methanol returns to the raw material oil tank as RME.
The remaining methanol and sulfuric acid solution are collected for reuse in the
recycling process.
c. Recycling of methanol in crude glycerol. Crude glycerol is heated before entering
the two-effect falling film evaporator, separating crude glycerol from methanol
and aqueous methanol. The glycerol obtained has very little methanol (less than
0.1%), and has a glycerol content of more than 80% (13.3% water, 2% potassium
sulfate, and less than 3% impurities). The aqueous methanol separated is purified
and recycled through the rectification column for reuse.
5.2.7 Determination of Conditions for Biodiesel Production
Process
Based on kinetics principles in chemical reactions and researches by Peterson et al.,
the key factors affecting the conversion rate of transesterification are reaction temperature, methanol concentration, types and concentration of catalyst, fluid mechanics
conditions, and reaction time.
5.2.7.1 Impact of Methanol Concentration on Biodiesel Yield
Transesterification is a reversible reaction. Normally, an excessive amount of
methanol is used to drive the reaction equilibrium towards the forward direction, so
as to enhance the conversion rate of transesterification. However, here is an amount
issue [28]. A higher methanol concentration drives the reaction equilibrium towards
the forward direction. However, an excessive level of concentration has a lower
performance in this regard and leads to higher cost. Therefore, it is necessary to
determine the initial optimal concentration of methanol.
Below is the research result of how the molar ratio of methanol and soybean oil
affects the yield of biodiesel at 60 °C using 1.0% (wt%) NaOH as a catalyst with a
reaction time of 45 min. It is presented as follows:
Figure 5.6 shows that as the initial concentration of methanol increases, the reaction yield of biodiesel also sharply increases. At the methanol/soybean oil molar ratio
of 6:1, it reaches the highest point of 85.0%. But if the initial methanol concentration
further increases, the biodiesel yield remains almost the same. This demonstrates