Technical method for producing light diesel oil by hydrogenation of coal tar

With the sustained and rapid development of social economy, the demand for light diesel oil in China is increasing. However, oil belongs to non-renewable energy and is facing a depletion crisis. In contrast, China's coal reserves are abundant, and the preparation of liquid fuels (light diesel oil, gasoline, diesel oil and intermediate oil) from coal has become a basic direction of coal processing and utilization.

On the other hand, with the rapid growth of iron and steel industry at home and abroad, the industry is showing a trend of rapid growth, and the output of coal tar is increasing, so the clean processing and effective utilization of coal tar is becoming more and more important. At present, the conventional treatment method is to obtain various fractions through pretreatment distillation, and then treat the fractions with acid-base washing, distillation, polymerization and crystallization to extract pure products. However, a large amount of sewage will be produced in the process of acid-base refining, which will seriously pollute the environment. Therefore, with coal tar hydrotreating technology and hydrocracking technology, naphtha and light diesel oil (coal-based light diesel oil) that we commonly use are finally obtained through hydrogenation.

Method for producing light diesel oil by hydrogenation of coal tar;

Crude oil distillation refers to the separation of crude oil by distillation to obtain two or more fractions including heavy oil fractions;

The catalyst is made of slurry oil, and the slurry oil is made by uniformly mixing a part of heavy oil fraction, hydrogenated heavy fraction oil after catalyst removal, hydrofining tail oil fraction, catalyst and vulcanizing agent;

Hydrocracking, that is, the remaining heavy oil fraction except for preparing catalyst slurry and a part of bottom outflow oil obtained by separating hydrocracking products are used as raw materials and catalyst slurry for hydrocracking reaction in a suspended bed, slurry bed or bubbling bed hydrogenation reactor;

Separation of hydrocrack products: that hydrocrack products are separated to obtain top outflow oil and bottom outflow oil, wherein the bottom outflow oil contains a catalyst;

Catalyst separation: solid-liquid separation is carried out on a part of oil flowing out from the bottom to obtain catalyst residue and hydrogenated heavy fraction oil;

Hydrorefining: distilling the raw oil to obtain other fractions except the heavy oil fraction and the oil flowing out from the top of the tower as raw materials, and mixing hydrogen to carry out hydrofining reaction;

Product fractionation is to distill and fractionate the reactants obtained from hydrofining reaction to obtain fuel oil fraction and tail oil fraction.

In that method, the mix slurry of the distilled heavy oil fraction and the catalyst is subject to hydrocracking reaction in a suspended bed, a slurry bed or a bubbling bed reactor, so that the problem that the heavy oil hydrocracking reaction is easy to coke in a fixed bed reactor is avoided to a certain extent.