A method for preparing light olefins by cracking petroleum hydrocarbons under reduced pressure

Abstract

The invention belongs to the field of petrochemical engineering and provides a method for preparing a low-carbon olefin from petroleum hydrocarbon under reduced pressure conditions. The method comprises the following steps: (1) through use of a decompression device which is communicated with a cracking furnace, a convection section and a radiation section of the cracking furnace and a pipeline forflowing through of a petroleum hydrocarbon raw material in a waste heat boiler are in a negative pressure state; (2) the petroleum hydrocarbon raw material is heated under the reduced pressure conditions, and then the petroleum hydrocarbon raw material is mixed with superheated steam and then gasified, a gas-state material flow continues to be heated to a cross temperature in the convection section, and then enters a radiation section furnace tube; (3) the gas-state material flow is subjected to cracking reaction at a high temperature, enters the waste heat boiler for heat exchange and cooling after passing through the radiant section furnace tube, and then preliminarily separated through a pressure reduction separation tower into tar and a cracked gas; and (4) the cracked gas is furtherseparated to obtain the low-carbon olefin. According to the method disclosed by the invention, the problem that special heavy cracking raw materials such as crude oil cannot be sufficiently gasified in the convection section is effectively solved, the yield of the low-carbon olefin is obviously improved compared with the yield of the low-carbon olefin obtained by a normal-pressure cracking process.

Description

technical field [0001] The invention belongs to the field of petrochemical industry, and more specifically relates to a method for preparing low-carbon olefins by cracking petroleum hydrocarbons under reduced pressure. Background technique [0002] Low-carbon olefins usually refer to the general term of unsaturated hydrocarbons with carbon four or less, mainly including ethylene, propylene, isobutylene, butadiene and other organic chemical raw materials with high economic value, and with the development of my country's economy, these The demand for organic chemical raw materials is increasing year by year. Although the production scale of low-carbon olefins is also increasing year by year, it cannot meet the growing demand. For example: It is estimated that in 2020, my country's ethylene production capacity will reach 35.6 million tons, and the equivalent demand is expected to be around 47.6 million tons, leaving a demand gap of nearly 2 million tons. Therefore, the technolo...

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Problems solved by technology

However, the crude oil treatment process in the early stage of this technology is complicated, which increases the production cost of low-carbon olefins, making it difficult for the low-carbon olefins produced by this technology to have good market competitiveness

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