Method for preparing ethylene by steam cracking in pipe type cracking furnace

Abstract

A method of producing ethylene by using refinery C4 comprising: a refinery C4 as a first raw material which comprises 45%-55% isobutane, 5%-10% n-butane, 15%-20% isobutene, 10%-15% 1-butylene and 5%-10% 2-butylene based on the total weight percentage of the refinery C4, the weight average molecular weight thereof being 55-60, an alkane-rich light hydrocarbon as a second raw material which comprises 40%-50% linear alkane, 25%-35% branched alkane, 15%-25% cyclane, less than or equal to 1% alkene and less than or equal to 10% arene based on the total weight percentage of the alkane-rich light hydrocarbon, the weight average molecular weight thereof being 90-100; the refinery C4 being in amount of about 10% to about 30% of the total weight percentage of the refinery C4 and alkane-rich light hydrocarbon; introducing the mixture of said first raw material and said second raw material into the upper part of the convection section of a cracking furnace, after diluted with steam, passing the diluted mixture through the lower part of the convection section to enter into the radiation section of said cracking furnace, distributing the diluted mixture to manifolds to carry out copyrolysis reaction therein so as to produce ethylene, wherein the cracking temperature is about 840°C to about 860°C, and the dilution ratio of steam / total raw materials is about 0.30 to about 0.60 wt / wt. According to the method provided in the present invention, the yield of ethylene attributed to the refinery C4 of the total raw materials can be greatly increased as compared with the separate cracking of refinery C4, while the cracking performance of light hydrocarbon can be maintained. In this way, the use value of refinery C4 and also other C4-rich products can be effectively improved, thus notable economic bendfits can be brought to the oil refinery.

Description

technical field [0001] The invention relates to a method for producing ethylene by steam cracking in a tubular cracking furnace. Background technique [0002] The C4 output of the refinery can reach 300,000 to 400,000 tons / year. At present, this part of C4 is mainly used as civil liquefied gas, and its utilization value is extremely low. If this part of C4 products are used as raw materials for cracking equipment, it can The utilization value of C4 products is greatly improved, which not only expands the source of raw materials for the cracking unit, but also solves the problems of excess C4 products and difficulties in leaving the factory. [0003] At present, the research reports on the use of C4 as ethylene raw material are mostly in the catalytic cracking of C4 raw material and the thermal cracking of C4 alone, but the co-cracking of C4 and other raw materials has not been reported yet. [0004] When the C4 raw material is used alone as a cracking raw material, the ethy...

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Problems solved by technology

[0003] At present, the research reports on the use of C4 as ethylene raw material are mostly found in the catalytic cracking of C4 raw material and the thermal cracking of C4 alone, but the research on the co-cracking of C4 and other raw materials has not been reported yet.