Hydro-conversion combination method for coal tar fraction with different boiling ranges

Abstract

The invention relates to a hydro-conversion combination method for a coal tar fraction with different boiling ranges, which comprises the following steps that: a first hydrogen fraction mainly comprising a coal tar light fraction is converted at a first hydrogen refining reaction part; a second hydrogen fraction mainly comprising a coal tar heavy fraction is converted at a second hydrogen refining reaction part; and a first hydrogen refining reaction effluent and a second hydrogen refining reaction effluent are mixed, separated and reclaimed. The method can select respective proper hydrogen refining reaction conditions for the coal tar fraction with different boiling ranges, has the advantages of improving the quality of products, stabilizing the operation, simplifying the flow and the like, and is particularly suitable for medium-scale classified combined hydro-conversion of medium-high temperature coal tar wide fractions.

Description

technical field [0001] The invention relates to a combined method for hydrogenation conversion of coal tar fractions with different boiling ranges, which is particularly suitable for medium-scale classification joint hydrogenation conversion of wide fractions of medium and high temperature coal tar. Background technique [0002] It is well known that the initial coal tar from coal pyrolysis or coal gas production or other processes, if the coal tar suitable for hydroconversion contains different boiling range fractions (such as naphtha fraction, diesel fraction, heavy fraction), The properties (such as hydrogen content, density, viscosity, residual carbon content, metal content, oxygen content, sulfur content, nitrogen content, aromatics content, coke content, asphaltene content, boiling point) of different boiling range fractions are very different. When they are hydroconverted to produce clean oil, the reaction process, reaction pressure and temperature conditions, catalys...

AI Technical Summary

Problems solved by technology

[0004] ②Because the content of reactive substances such as oxygen-containing phenols and small molecular unsaturated hydrocarbons in the light fraction of coal tar is much higher than that in the heavy fraction of coal tar, the light fraction of coal tar needs to be heated at a lower temperature The reaction is carried out at a lower temperature to prevent the local temperature rise of the catalyst bed from being too large; but at a lower reaction temperature, the heavy fraction of coal tar is difficult to react, and it forms a dilution effect on the light fraction of coal tar, which reduces the concentration of reactants and increases The amount of hydrodeoxidation agent; for the heavy fraction of coal tar with high viscosity, the fluidity is poor at low reaction temperature, resulting in too large pressure drop in the catalyst bed, and normal reaction operation cannot be carried out;

[0005] ③Because the average molecular size and shape of naphtha fraction, diesel fraction, and heavy fraction are very different, the most suitable catalyst formulations for the same function (such as hydrodenitrogenation) must be different, and it is impossible to choose the most suitable catalyst for combined processing. Optimal catalyst and operating conditions;

[0006] ④Because the average molecular size and shape of naphtha fraction, diesel fraction, and heavy fraction are very different, in the joint processing, if all of them realize the hydrotreating at a suitable depth, it will inevitably cause excessive processing of a certain fraction. Hydrogen, increasing hydrogen consumption and reducing liquid product yield;

[0007] ⑤Because of the "cracking" effect in the hydrofining process of coal tar, naphtha fraction and diesel fraction are "cracked" in the hydrofining process of heavy fractions, but the time for "cracking" to produce smaller molecules is inconsistent. The hydrofining process time is also long and short, and its refining effect is inconsistent. If the hydrofining effect of the smaller molecules produced by "cracking" is guaranteed, that is, more stringent hydrofining conditions are selected, and other fractions will be overhydrogenated. Reduce liquid yield or reduce product quality, and increase hydrogen consumption and catalyst consumption;

[0008] ⑥ After the mixed hydrogenation conversion of different boiling range fractions, the naphtha fraction, diesel fraction and heavy fraction need to be separated by distillation, which consumes a lot of energy;

[0009] ⑦Industrial experience shows that the mixed oil of naphtha fraction, diesel fraction and heavy fraction, in most cases, has a certain layering phenomenon in the storage tank, although forced circulation in the tank is used to achieve homogenization, However, the problem of unstable properties of mixed coal tar is difficult to completely eliminate, which will lead to unstable raw material properties of full-fraction or wide-fraction coal tar hydrogenation units, unstable hydrogenation reaction operation, and operation of the separated part of the hydrogenation reaction effluent unstable

[0011] There is no report about the method of separating the initial coal tar to obtain coal tar fractions with different boiling ranges and hydrogenating them separately