What is the Hydrocracker unit and what is the process of hydrocracking

 

Hydrocracking is a refining process used to convert heavy petroleum fractions, such as vacuum gas oil (VGO), into lighter, higher-value products, such as gasoline, diesel fuel, and jet fuel. The process involves breaking apart large hydrocarbon molecules in the presence of hydrogen gas and a catalyst, which leads to the formation of smaller, more useful molecules.

The Hydrocracker unit in an oil refinery is a high-pressure, high-temperature reactor that operates at elevated temperatures and pressures, typically around 150-250 bar and 260-425°C. The unit consists of three main sections: the reactor section, the separation section, and the hydrogen recovery section.

The reactor section is where the hydrocracking reaction takes place. The feedstock, which is typically a heavy, high-boiling point fraction of crude oil, is mixed with hydrogen gas and sent into the reactor vessel, which contains the catalyst. The catalyst is typically made up of a mixture of metals, such as nickel, cobalt, and molybdenum, that promote the breaking of carbon-carbon bonds in the heavy hydrocarbons.

As the feedstock and hydrogen gas pass through the catalyst bed, the large hydrocarbon molecules are broken apart into smaller molecules, such as alkanes and alkenes. The reaction also produces some side products, such as sulfur compounds and nitrogen compounds, which need to be removed in the subsequent separation section.

The separation section is where the products of the hydrocracking reaction are separated from the unreacted feedstock, as well as any byproducts or impurities that may have been formed during the reaction. The products are typically separated into light gases, naphtha, kerosene, diesel, and vacuum gas oil, depending on their boiling points.

The hydrogen recovery section is where the hydrogen gas that was not consumed in the reaction is separated from the other products and recycled back into the reactor section. This helps to maintain the proper hydrogen-to-feedstock ratio in the reactor and ensures that the hydrocracking reaction can proceed at an optimal rate.

Overall, the hydrocracking process is a highly efficient way to convert heavy, low-value petroleum fractions into lighter, higher-value products. It is particularly useful for producing diesel fuel, which has become increasingly important as demand for transportation fuels has grown in recent years. Additionally, the use of hydrogen gas in the process helps to reduce the environmental impact of refining by lowering the sulfur content of the final products and reducing emissions of greenhouse gases.