Method for performing combining hydro-conversion on coal tar distillate having different boiling ranges

Abstract

The invention relates to a method for performing combining hydro-conversion on coal tar distillate having different boiling ranges. A first hydrocarbon distillate containing the coal tar light distillate is converted by performing a first hydrofining reaction; the effluent of the first hydrofining reaction and a second hydrocarbon distillate containing the coal tar heavy distillate are converted by performing a second hydrofining reaction; the effluent of the second hydrofining reaction is separated and recycled. The method of the invention performs combining hydro-conversion on the coal tar distillate having different boiling ranges so as to form a suitable temperature distribution of the hydrofining reaction. The method can improve the quality of the products, have stable operation, can prolong the operating period, and is specially fit for small-scale classification combining hydro-conversion for middle and high temperature coal tar distillate.

Description

technical field [0001] The invention relates to a method for combined hydrogenation conversion of coal tar fractions with different boiling ranges, which is particularly suitable for small-scale classified combined 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, catalyst ...

AI Technical Summary

Problems solved by technology

[0003] ①Because 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 Start the reaction 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 (including hydrogenation saturation reaction), which will dilute the light fraction of coal tar and reduce Increased reactant concentration, increased hydrodeoxygenation agent consumption;

[0004] ② The light fraction of coal tar needs to start to react at a lower temperature, but at a lower reaction temperature, it is difficult for the heavy fraction of coal tar to react (including hydrogenation saturation reaction), and at the same time, a thermal condensation reaction is formed in the catalyst bed. Or the time condition of coking speeds up the coking speed of the catalyst; for the heavy fraction of coal tar with high viscosity, the fluidity is poor at low reaction temperature, which leads to the excessive pressure drop of the catalyst bed and the normal reaction operation cannot be carried out;

[0005] ③ When combined processing, the same hydrorefining catalyst must be used. Because the average molecular size and shape of the light fraction of coal tar and the heavy fraction of coal tar are very different, and the depth of hydrogenation is different, sometimes the residence time of the fractions is quite different. , such as when the residence time required to complete the denitrification index of the light fraction of coal tar or the naphtha fraction of coal tar is longer than the residence time required for the completion of the refining index of the heavy fraction of coal tar, such as ensuring that the light fraction of coal tar or the coal tar stone The residence time required to complete the denitrification index of the naphtha fraction will cause excessive hydrogenation to the heavy fraction of coal tar or the diesel fraction of coal tar, reduce the liquid yield or reduce the product quality, and increase the consumption of hydrogen and catalyst;

[0006] ④Due to the "cracking" effect of the coal tar hydrofining process, the heavy fraction of coal tar or the diesel fraction of coal tar is "cracked" to produce light fractions or naphtha fractions during the hydrofining process, but the "cracking" yields smaller fractions. The molecular time is inconsistent, and the hydrofining process time of smaller molecules is also long or short, and the refining effect is inconsistent. If the hydrofining effect of the smaller molecules produced by "cracking" is to ensure the hydrofining effect, more stringent hydrofining conditions are selected. Excessive hydrogenation of other fractions, reducing liquid yield or product quality, and increasing hydrogen consumption and catalyst consumption;

[0007] ⑤Industrial 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

There is no report on the method of separating the initial coal tar to obtain coal tar fractions with different boiling ranges and combined hydroprocessing