Two-stage series-connected Fischer-Tropsch synthesis system and process thereof

Abstract

The invention discloses a two-stage series-connected Fischer-Tropsch synthesis system and a process thereof. The system comprises at least one first-stage high-temperature Fischer-Tropsch synthesis slurry reactor, at least one low-carbon olefine separator and at least one second-stage low-temperature Fischer-Tropsch synthesis slurry reactor or fixed-bed reactor, wherein synthesis gas is subjected to high-temperature Fischer-Tropsch synthesis reaction in the at least one first-stage high-temperature Fischer-Tropsch synthesis slurry reactor to mainly generate gasoline and low-carbon olefine; the at least one low-carbon olefine separator is used for separating the low-carbon olefine generated in the first-stage reactor; the tail gas of the synthesis gas from the first-stage reactor is directly subjected to low-temperature Fischer-Tropsch synthesis reaction in the second-stage reactor without being subjected to any component adjustment or conversion to mainly generate diesel and Fischer-Tropsch wax; and the Fischer-Tropsch wax or paraffin is supplemented or circulated into the first-stage high-temperature slurry reactor so as to maintain the stable liquid level in the gas-solid-liquid reaction system in the first-stage high-temperature slurry reactor.

Description

technical field [0001] The invention relates to a two-stage series Fischer-Tropsch synthesis system and its process, in particular to a two-stage series Fischer-Tropsch synthesis system and its process in which reaction products and reaction raw materials are complementary. Background technique [0002] The Fischer-Tropsch synthesis reaction refers to the synthesis gas (H 2 +CO) is converted into hydrocarbons and other chemicals under the action of a catalyst at a certain temperature and pressure. In recent years, due to the increasing shortage of petroleum resources and the continuous rise of crude oil prices, Fischer-Tropsch synthesis has attracted extensive attention from researchers all over the world. Generally, the reaction of Fischer-Tropsch synthesis to generate hydrocarbons can be represented by the following reaction formula: [0003] mCO+(2m+1)H 2 →C m h 2m+2 +mH 2 O (1) [0004] mCO+2mH 2 →C m h 2m +mH 2 O (2) [0005] 2mCO+(m+1)H 2 →C m h 2m+2 +mC...

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Problems solved by technology

[0022] (2) The unconverted tail gas of the first Fischer-Tropsch synthesis reaction contains a certain amount of C 1 -C 4 hydrocarbons, and, at this point, the H in the unconverted tail gas 2 The / CO volume ratio does not meet the requirements for continuing the Fischer-Tropsch synthesis reaction. In order to make the H in the unconverted tail gas 2 The / CO volume ratio meets the conditions for continuing the Fischer-Tropsch synthesis reaction, and the H in the unconverted tail gas needs to be adjusted 2 / CO volume ratio, one of the ways is to combine the above C 1 -C 4 Hydrocarbons undergo CO and H in specific conversion units 2 Transformation to make it into syngas, which undoubtedly increases equipment investment and process complexity;

[0026] But the slurry bed reactor also has some insurmountable shortcomings, for example, the catalyst abrasion therein is very serious, which will cause a considerable proportion of catalyst fine powder or dust in the liquid product, and such fine powder or dust is quite difficult to remove from the liquid. In addition, the reaction system of the slurry bed reactor is a gas-solid-liquid three-phase reaction system. In order to ensure the continuous and smooth progress of the reaction, the liquid level in the slurry bed reactor must be kept constant Or stable, that is to say, the liquid level or liquid level of the gas-solid-liquid three-phase reaction system in the slurry bed reactor should be kept stable, which determines that the reaction temperature of the slurry bed reactor should not be too high, because the reaction temperature Once it is too high, the liquid substance at low temperature will either become gaseous or be cracked into gaseous substance at high temperature. Therefore, generally speaking, once the reaction temperature of the slurry bed reactor exceeds 285 ° C, it is difficult to ensure the slurry bed reaction. Therefore, in the prior art, the reaction temperature of the Fischer-Tropsch synthesis slurry bed reactor is generally not higher than 285°C

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