What Is the Difference Between Diesel and Biodiesel?

The physical and chemical properties of biodiesel fuels are closer to those of petrochemical diesel fuels, and large-scale use can reduce greenhouse gas emissions. At present, they have been widely accepted as alternative fuels for petrochemical diesel fuels. Biodiesel can be blended with diesel in any proportion or used directly on the diesel engine without major adjustments to the diesel engine. In addition, biodiesel is also free of sulfur and aromatics, has a high cetane number, and is biodegradable.

Biodiesel engine

The physical and chemical properties of biodiesel fuels are closer to those of petrochemical diesel fuels, and large-scale use can reduce greenhouse gas emissions. At present, they have been widely accepted as alternative fuels for petrochemical diesel fuels. Biodiesel can be blended with diesel in any proportion or used directly on the diesel engine without major adjustments to the diesel engine. In addition, biodiesel is also free of sulfur and aromatics, has a high cetane number, and is biodegradable.

Chinese name

Biodiesel engine

Field

car

The "12th Five-Year Plan" outlines the construction of a resource-saving and environment-friendly society as an important focus for accelerating the transformation of economic development. The Twelfth Five-Year Plan energy conservation and emission reduction targets established by the outline are: non-fossil energy accounts for 11.4% of primary energy consumption. Energy consumption per unit of GDP is reduced by 16%, and carbon dioxide emissions per unit of GDP are reduced by 17%. The total emission of major pollutants has been significantly reduced. The chemical oxygen demand and sulfur dioxide emissions have been reduced by 8%, and the ammonia nitrogen and nitrogen oxide emissions have been reduced by 10%.

Because the physical and chemical characteristics of biodiesel and ordinary petrochemical diesel are different, the combustion characteristics of biodiesel, such as flame retardation period, ignition temperature, and penetration distance of spray, are different from ordinary petrochemical diesel. In general, due to the relatively large cetane number of biodiesel, the use of biodiesel in diesel engines will shorten the flame retardation period, thereby reducing the premix peak of the heat release rate curve, and the oxygen content of the fuel promotes diffusion combustion Small burning duration.

Similar to ordinary petrochemical diesel, the main emissions from burning biodiesel are carbon monoxide, unburned hydrocarbons, nitrogen oxides, and particulate emissions. After using biodiesel or a mixture of biodiesel and ordinary diesel,

Although biodiesel can be applied directly without major adjustments to the engine, because biodiesel is a mixture of saturated fatty acid methyl esters and unsaturated fatty acid methyl esters, which is significantly different from diesel, the large-scale application of biodiesel will inevitably require In-depth research on engine reliability, optimization of combustion and emissions, economics of production and use of biodiesel, and carbon dioxide emissions. Therefore, the application of biodiesel to diesel engines still has some key scientific issues to be resolved:

(1) Nitrogen oxide control strategy for biodiesel engines: Biodiesel engines can significantly reduce CO, HC, and PM emissions, but because biodiesel molecules contain 12% oxygen, biodiesel engines are usually started

Compared with conventional diesel engines, NOx emissions from engines have increased by about 10% to 12%.

(2) The influence of the physical characteristics of biodiesel on the spraying law, the formation of mixed gas and the mechanism of PM generation:

The viscosity of biodiesel is higher than that of commercial diesel, and the compressibility of fuel is significantly different from that of diesel. Therefore, when biodiesel is directly applied to diesel engines, the fuel spray characteristics change significantly.

(3) Unconventional emissions of biodiesel engines: Although biodiesel can significantly reduce CO, PM and HC emissions, biodiesel contains a small amount of methanol (or ethanol), and alcohols will inevitably be generated during the combustion process. Various harmful unconventional emissions, such as formaldehyde, acetaldehyde, olefins and alkynes.

(4) Particulate Matter Emissions from Biodiesel Engines: Biodiesel can reduce particulate matter emissions (mass), but the impact on the amount and concentration of particulate matter remains to be explored in depth.

(5) The impact of the micro-molecular structure of biodiesel on the combustion and emission characteristics of engines: The molecular structure of different methyl esters in biodiesel includes the length of carbon chain, the number of double bonds, and the branched structure formed by the preparation of different alcohols, which will cause combustion emissions. influential. ^[2]