Method for combining coal tar fractional distillation and hydro-conversion

Abstract

The invention relates to a method for combining coal tar fractional distillation and hydro-conversion. Initial coal tar extracts a first fraction and a second fraction which have different boiling ranges in coal tar extraction parts; and the first fraction enters a first hydro-conversion part and the second fraction enters a second hydro-conversion part. By selecting each suitable hydro-conversion operation condition on fractions with different boiling ranges, the method has the advantages of optimized operation condition, stable operation, catalyst usage reduction, and operation period extension, and is particularly suitable for the large-scale hydro-conversion of full fraction coal tar.

Description

technical field [0001] The invention relates to a coal tar hydrogenation conversion method; in particular, the invention relates to a coal tar fractionation and hydrogenation conversion combined method. 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 light and heavy fractions, the properties of the light and heavy fractions (such as hydrogen content, density, viscosity , residual carbon content, metal content, oxygen content, sulfur content, nitrogen content, aromatic hydrocarbon coke asphaltene content) are very different, when they are hydrogenated and converted to produce diesel fractions, the reaction process, reaction pressure conditions, catalyst configuration, hydrogen The consumption, operation cycle and product quality are all different or even very different. For small-scale processing, it is more suitable for combined proces...

AI Technical Summary

Problems solved by technology

[0004] ②Because the content of reactants such as oxygen-containing phenols and small molecular unsaturated hydrocarbons in the light fraction is much higher than that in the heavy fraction, the light fraction needs to be reacted at a lower temperature to prevent the local temperature of the catalyst bed. However, at a lower reaction temperature, the heavy distillate is difficult to react and dilutes the light distillate, reducing the concentration of the reactant and increasing the amount of hydrodeoxidizer; what is more, the heavy distillate with high viscosity The fluidity is very poor at low reaction temperature, and the liquid holding capacity in the catalyst bed is very large, which greatly reduces the void ratio of the catalyst bed, resulting in excessive pressure drop, making the device unable to operate normally;

[0005] ③Because the average molecular size and shape of the light fraction and the heavy fraction are very different, the most suitable catalyst formulations for the same function (such as hydrodenitrogenation) must be different, and the combined processing cannot select the catalyst with the best performance and operating conditions;

[0006] ④Because the average molecular size and shape of light distillate and heavy distillate are very different, if the heavy distillate is hydrotreated to a suitable depth during combined processing, it will inevitably form excessive hydrogenation of light distillate, which will increase hydrogen consumption and reduce Liquid Product Yield

[0007] ⑤Industrial experience shows that for full fraction or wide fraction coal tar, there is coal tar stratification in its storage tanks. Although forced circulation in the tank is used to achieve homogenization, the problem of unstable properties of full fraction or wide fraction coal tar is difficult. Complete elimination, which will lead to unstable raw material properties of the whole fraction or wide fraction coal tar hydrogenation unit, unstable hydrogenation reaction operation, and unstable operation of the separated part of the hydrogenation reaction effluent

[0008] There is no report about the method of separating initial coal tar to obtain light fraction and heavy fraction and hydrogenating them separately