Biodiesel is an alternative diesel fuel consisting of fatty acid alkyl monoesters from vegetable oils or animal fats. At present, most biodiesel is produced from soybean oil, methanol and an alkaline catalyst (cholinesterase). However, most of the cheap oils that are not easily digested by human body can be converted into biodiesel.
(1) physical refining: first, oil or water can be treated by hydration or phosphoric acid to remove phospholipids, colloids and other substances. Then the fat is preheated, dehydrated and degassed into the deacidification tower to maintain the residual pressure, and excess steam is introduced. At the steam temperature, free acid and steam are evaporated together. After condensation, the net loss of free fatty acid is removed. The free acid in the oil can be reduced to a very low level, and the pigment can be decomposed to make the color lighter. Crude fatty acid methyl esters were synthesized by esterification and alcoholysis of various waste animal and vegetable oils with DYD catalyst.
(2) Methanol pre-esterification: first of all, the oil is degummed by hydration, then the flocculent substance formed by hydration of phospholipid and glue is removed by centrifuge, and then the oil is dehydrated. In the presence of acidic catalysts, excessive methanol is added to the raw oil to pre-esterify the free acid into methyl ester. After distilling methanol water, C12-16 palmitic acid methyl ester and C18 methyl oleate were separated without any free acid.
(3) Transesterification reaction: The pretreated oil and methanol, together with a small amount of NaOH as a catalyst, transesterification reaction at a certain temperature and atmospheric pressure, that can produce methyl ester, two-step reaction, through a specially designed separator to continuously remove the glycerol generated in the primary reaction, so that the transesterification reaction continues.
(4) Gravity sedimentation, water washing and stratification.
(5) Separation of glycerol and the extraction of crude methyl esters.
(6) Water withdrawal, methanol release, catalyst removal and refined biodiesel production.
The whole process is closed loop, and the raw materials are comprehensively utilized to achieve cleaner production. The general description is as follows: raw material pretreatment (dehydration, deodorization, purification) – – reaction kettle (adding alcohol + catalyst + 70 () – – stirring reaction for 1 hour – – – precipitation separation and impurity removal – – – recovery of alcohol – – – Filtration – – – finished product
Biodiesel can be used as fuel for boilers, turbines, diesel engines and so on. Fatty acid methyl esters are mainly used in industry.
Biodiesel is a kind of high quality clean diesel, which can be extracted from various biomass, so it can be said that it is inexhaustible, inexhaustible energy, in the increasingly exhausted resources today, it is expected to replace oil as a substitute fuel.
Diesel oil is the main power fuel for many large vehicles such as trucks and diesel locomotives and generators. It has the advantages of large power and low price. There is a great demand for diesel oil in China. The main problem of diesel application is “smoking black smoke”. We often see smoking trucks on the road. The main cause of black smoke is incomplete combustion, serious air pollution, such as a large number of particulate dust, high CO2 emissions.
Air pollution from engine fuel combustion has become a major problem of air pollution, such as nitrogen oxides accounting for half of emissions from other industries, carbon monoxide accounting for two-thirds of emissions from other industries, and toxic hydrocarbons accounting for half of emissions from other industries. Nitrogen oxides and sulfides emitted from the tail gas combine with water in the air to form acid rain. Too much carbon dioxide and carbon monoxide in the tail gas will raise the temperature of the atmosphere, which is often called the “greenhouse effect”. In order to solve the problem of fuel exhaust pollution and worsening environmental pressure, people began to study the use of other fuels such as fuel alcohol instead of gasoline. At present, fuel alcohol has a considerable proportion in North America, such as the United States and Canada, and South America, such as Brazil, Argentina and so on. Market. Fuel alcohol is not suitable for most large power vehicles that require diesel fuel, such as buses, diesel locomotives and agricultural vehicles, such as tractors, which are mainly diesel-fueled engines. Moreover, diesel fuels cause much more pollution than gasoline, so people have developed biodiesel as a substitute for diesel fuels.