Biodiesel

Methods of production

The main raw material for the production of biodiesel, besides oilseeds, is also the waste (used) oils and animal fats from the mass caterers. It is known that fats are esters of trivalent alcohol glycerol and three molecules of higher fatty acids, which is why they are also known as triglycerides (triacylglycerols).

For the production of biodiesel from oils and fats mainly three processes are used - catalysed by transesterification of the oil, direct acid catalyzed transesterification of the oil, conversion of the oil into its fatty acids and then - in biodiesel. Most of the biodiesel produced today is a transesterification-catalyzed base. The reasons for the preference of this process are primarily its economy, its flow at low temperatures and pressure, and the provision of a conversion rate of up to 98%.

Equipment for production

Biodiesel plants include several major facilities in which the processes involved in the production and processing of biodiesel occur. Different types of reactors are used to carry out the transesterification process and can generally be classified into two main groups - reactors with non-continuous operation (batch reactors) and continuous reactors with continuous operation. The second group of reactors can be categorized as ideally blending reactors with continuous mixing of the mixture and reactors with ideal displacement, also known as tubing or flow reactors.

In the batch reactors, a certain amount of reagents are placed in the reactor, then closed and the conditions necessary for the reaction (temperature, pressure and agitation) are created. After the reaction time has elapsed, the resulting chemicals are removed from the reactor and sent for subsequent treatment.

In continuous reactors, the flow of reagents entering the reactor is continuous as well as the process of discharging the finished products. Typical of these reactors is that once they have reached a steady state of operation, the composition of the leaving products remains constant. In ideal mixing reactors, individual parameters such as temperature, pressure, concentration, rate of chemical reaction remain constant throughout the reactor volume. In contrast, in the case of tubular reactors, these parameters change along the reactor, changing the chemical composition of the mixture as it moves through the reactor.

Biodiesel as a fuel

Biodiesel is a biofuel produced from vegetable oils (raw or used) or animal fats. It is a clear liquid and has characteristics similar to those of diesel oil, which is why it is considered to be particularly suitable as a fuel for standard diesel engines without the need for further modifications. Biodiesel can be used both in pure form and in addition to conventional diesel. Adding biodiesel to ordinary diesel does not degrade the quality of the diesel, and even leads to its improvement, experts say. One reason for this claim is the better lubricating properties of biodiesel than the oil. In the biodiesel composition there is no sulfur, which eliminates the need for the use of synthetic potassium hydroxide based lubricants to limit engine corrosion caused by condensation of sulfuric acid and sulfur dioxide and trioxide. Biodiesel contains 11% of oxygen, which helps to burn it better. When using biodiesel as an alternative to oil, similar power and torque properties are observed. Biodiesel has a more cetane number (a value between 45.8 to 56.9) and nearly the same calorific value. The use of biodiesel leads to a reduction in carbon dioxide emissions, as it, like other biofuels, produces only as much carbon dioxide as is needed for plant growth and therefore is also environmentally neutral.

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