Biodiesel is a methyl ether received as a result of a chemical reaction of any vegetable oils and animal fats. Chemically biodiesel is a mixture of methyl or ethyl ethers of fatty acids. The fats are the glycerin ethers of fatty acids. It is known that the molecules of fats consist of so called triglycerides: the connections of trivalent alcohol of glycerin with three fatty acids. Seven mass units of vegetable oil are added to one mass unit of methanol to receive the methyl ether (there is a ratio 7:1). It is necessary to change glycerin to methanol in the glycerin ethers. This change (re-etherification) is carried out by means of the reaction between the fat and alcohol with the formation of methyl ether and precipitation of the dense glycerin that is insoluble in the methyl ether.

It is possible to receive a necessary speed of the reaction and degree of conversion by means of increasing of the temperature, surplus alcohol and catalysts application. Alkalis NAOH, KOH forming alcolates with alcohols, can be used as catalysts. The limited mutual solubility of alcohol and fat influences onto heterogeneous two-phase character of the reaction and significantly decreases the speed of the re-etherification process. This difficulty is easy to overcome by means of intensive mixing and dispersing. The quantity of the catalysts and the alcohol surplus are determined by the material characteristics and the results of the test reactions. The glycerin containing phase and ether phase received after the product separation need to be cleaned from the unreacted alcohol and catalyst. The ether received has a high flammability provided with the high cetane number. If cetane number of a mineral fuel is 42-45, cetane number of biodisel is not less than 51. It causes the possibility of its application in the diesel engines without any other substances stimulating inflammation. Owing to this characteristic methyl ether was called biodiesel.

Biodiesel can be independently used in the traditional engines of internal combustion and with mixture with traditional diesel fuel without any changes to the engine construction.

     EXON PLANT consists of: block of methoxide – for the automatic preparation and dosing of methoxide ( fluid of NAOH in methanol), block of oil dosing , block of heat exchangers and condensers, block of transetherification, separator, recuperative evaporate apparatus (of biodiesel and glycerine), block of filters sorbers.

     The block of preparation and dosing of methoxide consists of mixing and metering device, buffer capacity and volumetric measuring device with the filter of the current fluctuations. Methanol is given into the capacity of mixing and metering device in a quantity determined by the level sensors. The catalyst is also given there with the help of a screw batcher. The dose of catalyst is measured by automatic weight batcher and is added to methanol. The mixing (dissolution) of reagents by mixer during the determined time is carried. Prepared fluid is pumped into the buffer capacity. The automatic preparation of methoxide allows to avoid errors and considerably decreases the labor inputs. Methoxide is periodically sent to the measuring device (which is  the cylindrical container with the sensors of level ) by the pump and the system of magnetic valves. Determining the volume of measuring device and the frequency of filling it is possible to obtain the required value of the average volumetric flow rate of methoxide with the high exactness. From the measuring device methoxide is sent to the filter of the current fluctuations which is the capacity with the float flow regulator. The filter of the current fluctuations allows to convert the periodic flow  into the continuous one with the small variations, necessary for the optimum work of  the heat exchangers and evaporators.

     The block of oil  dosing consists of the measuring device and filter of the current fluctuations, they are analogically constructed as the same for methanol, the given volumetric flow rate of oil is obtained at the end. The control system of the components consumption by the measuring devices is simple, reliable, it ensures the high exactness of the components consumption determination, sufficient for the compliance with any given formula. Oil is preheated to the reaction temperature in the lamellar heat exchangers and is sent to the module of transesterification. The module of transesterification consists of the block of the series-connected reaction volumes equipped with mixers. Methoxide and oil are given to the entrance of module The series-connected volumes ensure the impossibility of the penetration of the unreacted components to the exit of module at continuous mixing and the flowing nature of the work of module. The glycerin mixture obtained in the module is given into the gravitational separator.

     Separation is carried by precipitating of the denser glycerin phase under the action of gravitational force in the long horizontal cylindrical capacity - separator. Mixture is given from the input end of the capacity through the distributor- damper of the current. The capacity of separator is constructed in such a way, that the movement of mixture from one end of cylinder to another one takes about 12 hours, during this time the mixture is divided into the glycerin and ether layer. At the output end of the separator the float level regulators to remove the separation products are installed. In comparison with the centrifugal separators, gravitational one is simple, it does not have moving parts, it is reliable and is characterized by the predictable separation. Horizontal separator works in the flowing regime and is characterized by clearer separation in the comparison with the vertical capacities- sumps of periodic action. Glycerin and ether phases are sent to the recuperative apparatuses for the removal of dissolved excess methanol.

     In the recuperative evaporators of a film type the film of fluid flows over the heat surface, the temperature of the surface grows with the movement from top to bottom. Hot glycerin or ether after the evaporation along the special channels in the heat surface move from bottom to top returning the  acquired thermal energy to the evaporating fluid (heat recuperation). Glycerin and ether leave  the evaporator with practically the same temperature as the primary fluids, thus energy is expended only on the evaporation of methanol, in contrast to the non-recuperative evaporators and the boiling capacities, where the energy is taken away by the hot liquid going out the apparatus. The construction of the film evaporator with the counter flows of liquid and steam makes it possible to work in the continuous mode and to obtain the high degree of cleaning of the products from methanol. The application of evaporators allows to use any ratio of alcohol and oil necessary for the optimum reaction of transesterification, because the surplus of alcohol will be removed. After the evaporation of methanol the glycerin is directed to the stock.

     Ether (Biodiesel) is sent to the lamellar heat exchanger, where gives back the heat to the counterflow of oil (this allows to shorten the consumption of electric power 5-6 times). Methanol steams are condensed in the exchanger-condenser returning the heat of condensation to the flow of oil. Thus heat regeneration is achieved, external energy is not expended to preheat the oil. The uncondensed methanol steams finally are condensed in the water condenser.

     Further ether (biodiesel) is being filtered and cleaned in the unit of filters - sorbers. Block consists of two containers filled with sorbent. The filter -sorber detains mechanical pollution and deletes catalyst (alkali) and other admixtures from ether. They periodically substitute the worked out sorbent to the new one  through the hatchways. One of the devices is to be disconnected for replacing of the sorbent. The application of sorbents  guarantees the high quality of biodiesel purification.The micro-controller manages all processes, it determines the parameters of the technological process. Manual labor is necessary only for the loading of alkali into the bunker of the mixing and metering device of the block of methoxide preparation and for replacing of the sorbent in the filters.

Links on this topic:
What is biodiesel or biodiesel fuel?
The technology to produce biodiesel fuel in a stream from BIODIESEL CRIMEA LTD
The benefits of using biodiesel in comparison with traditional diesel fuel
Product Range of EXON biodiesel plants
Advantages of the equipment manufactured by BIODIESEL CRIMEA LTD
Photos and technological scheme of biodiesel production in stream
The quality of biodiesel produced by EXON biodiesel plants
Application of glycerin produced by EXON plants