Renewable Energy Technology 3(2+1)

Lesson 29. Performance evaluation of biodiesel transesterification system

As per the capacity of the reactor, the quantity of vegetable oil to be added can be measured.  Various factors considered for the variables can be listed below.

Reaction temperature : The reaction temperature of the teansesterification process will be decided based on the temperature of vapourization of selected alcohol.  If methanol is selected for the process, the temperature considered for the transesterification may be from 50 to 70°C.      

Agitator speed : The rate of mixing of the chemicals and vegetable oil has a significant effect on the production of biodiesel.  This can be decided based on the viscosity of the oil, capacity of the reactor etc.  The mixing speed has to be optimized to assure proper mixing of the oil and chemical, lesser the agitation speed will lead to improper mixing of reactants and higher rpm may cause the disturbance of the reactants which may hinder the reaction. 

Alcohol addition : Theoretically the addition of alcohol is in 3:1 molar ratio.  Where as for proper completion of reaction, this will be increased upto 6:1 molar ratio.  This will be about 15 – 20 per cent of weight of oil used in the reaction.  Lesser addition of alcohol will lead to incomplete reaction.  Whereas, higher addition of alcohol is unnecessarily increase the cost of operation and also make segregation of ester and glycerol more difficult.

Catalyst : Potassium hydroxide and sodium hydroxide are the most common catalyst used in transesterification process.  The optimized dosage of alkaline catalyst concentration is in the range of 0.5 to 1% by weight.  The effect and suitability of catalyst and dosage of catalyst are to be assessed for maximum biodiesel production.    

Performance evaluation studies can be taken up by varying the above parameters to optimize them for maximum biodiesel recovery.

The calculated amount of oil is pumped into the reactor.  The measured quantity of alcohol and catalyst is fed into the chemical tank and is mixed thoroughly.  After proper mixing, the chemical is fed into the reactor and is agitated in the predetermined rpm.  After allowing the reaction for about 1 ½ to 2 h, the products will be pumped into the sedimentation tank.  It will be sedimented for 4 to 6 h.  The sedimented glycerol will be collected initially and the esters, biodiesel will be collected in separate tank.  The quantity of biodiesel produced will be measured.  The following calculations can be made for the reactor.

Observation table

Sl. No.	Input			Output
	Oil (kg)	Alcohol (kg)	Catalyst (kg)	Biodiesel (kg)	Glycerol (kg)

 

Similarly, by varying the type of alcohol, quantity of alcohol, type of catalyst, quantity of catalyst etc., the experiments can be repeated and the biodiesel production may be observed.

                                                              Biodiesel production, kg

            Biodiesel recovery                  = ----------------------------------

                                                                    Oil used, kg